SSPC-PS4.02 62&Z T ADOPTION NOTICE SSPC-PS4.02, "Vinyl Painting System, Three-And Four-Coatrn was adopted on October 3, 1994 for use by the Department of Defense (DoD). Proposed changes by DoD activities must be submitted to the DoD Adopting Activity: Commanding Officer, Naval Construction Battalion Center, Code 156, 1000 23rd Avenue, Port Hueneme, CA 93043-4301. DoD activities may obtain copies of this standard from the Standardization Document Order Desk, 700 Robbins Avenue, Building 4D, Philadelphia, PA 19111-5094. The private sector and other Government agencies may purchase copies from the Steel Structures Painting Council, 4516 Henry Street, Suite 301, Pittsburgh, PA 15213. Custodians: Adopting Activity Army -ME Navy -YD-1 Navy -YD-1 Air Force -99 FSC 8010 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS--`,,,,`-`-`,,`,,`,`,,`---
SSPC-PAINT25 ADOPTION NOTICE SSPC-PAINT25, "Primer, Raw Linseed Oil and Aleyd, Red Iron Oxide, Zinc Oxide," was adopted on October 3, 1994 for use by the Department of Defense (DoD). Proposed changes by DoD activities must be submitted to the DoD Adopting Activity: Commanding Officer, Naval Construction Battalion Center, Code 156, 1000 23rd Avenue, Port Hueneme, CA 93043-4301. DoD activities may obtain copies of this standard from the Standardization Document Order Desk, 700 Robbins Avenue, Building 4D, Philadelphia, PA 19111-5094. The private sector and other Government agencies may purchase copies from the Steel Structures Painting Council, 4516 Henry Street, Suite 301, Pittsburgh, PA 15213. Custodians: Adopting Activity Army-ME Navy -YD-1 Navy -YD-1 Air Force -99 FSC 8010 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS--`,,,,`-`-`,,`,,`,`,,`---
SSPC-PAINT 1 ADOPTION NOTICE SSPC-PAINT1, "Red Lead And Raw Linseed Oil Primer," was adopted on April 11, 1995 for use by the Department of Defense (DoD). Proposed changes by DoD activities must be submitted to the DoD Adopting Activity: Naval Construction Battalion Center, 1000 23rd Avenue, Code 156, Port Hueneme, CA 93043-4301. DoD activities may obtain copies of this standard from the Defense Printing Service Detachment Office, Bldg. 4D (Customer Service), 700 Robbins Avenue, Philadelphia, PA 19111-5094. The private sector and other Government agencies may purchase copies from Steel Structures Painting Council, 4516 Henry Street, Suite 301, Pittsburgh, PA 15213-3728. Custodians: Adopting Activity: Navy -YD1 Navy -YD1 (Project 8010-N998) unlimited. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS--`,,,,`-`-`,,`,,`,`,,`--FSC 8010 DISTRIBUTION STATEMENT A. Approved for public release; distribution is
W 2595532 0079382 T30 B SSPC-PAINT2 ADOPTION NOTICE SSPC-PAINT2, "Red Lead, Iron Oxide, Raw Linseed Oil And Alkyd Primer," was adopted on April 11, 1995 for use by the Department of Defense (DoD). Proposed changes by DoD activities must be submitted to the DoD Adopting Activity: Naval Construction Battalion Center, 1000 23rd Avenue, Code 156, Port Hueneme, CA 93043-4301. DoD activities may obtain copies of this standard from the Defense Printing Service Detachment Office, Bldg. 4D (Customer Service), 700 Robbins Avenue, Philadelphia, PA 19111-5094. The private sector and other Government agencies may purchase copies from Steel Structures Painting Council, 4516 Henry Street, Suite 301, Pittsburgh, PA 15213-3728. Custodians: Adopting Activity: Navy -YD1 Navy -YD1 (Project 8010-N997) FSC 8010 DISTRIBUTION STATEMENT A. Approved for public release; distribution is un1imited. --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
M 2575532 0079383 977 SSPC-PAINT 13 ADOPTION NOTICE SSPC-PAINT 13, "Red Or Brown One-Coat Shop Paint," was adopted on April 11, 1995 for use by the Department of Defense (DoD). Proposed changes by DoD activities must be submitted to the DoD Adopting Activity: Naval Construction Battalion Center, 1000 23rd Avenue, Code 156, Port Hueneme, CA 93043-4301. DoD activities may obtain copies of this standard from the Defense Printing Service Detachment Office, Bldg. 4D (Customer Service), 700 Robbins Avenue, Philadelphia, PA 19111-5094. The private sector and other Government agencies may purchase copies from Steel Structures Painting Council, 4516 Henry Street, Suite 301, Pittsburgh, PA 15213-3728. Custodians: Adopting Activity: Navy -YD1 Navy -YD1 (Project 8010-N996) --`,,,,`-`-`,,`,,`,`,,`--FSC 8010 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
LEAD PAINT REMOVAL GUIDES: SUPPLEMENT TO VOLUME 2 SSPC = GUIDE 61 (CON) Guide for Containing Debris Generated During Paint Removal Operations and SSPC = GUIDE 71 (DIS) Guide for the Disposai of Lead-Contaminated Surface Preparation Debris STEEL STRUCTURES SSPC 92-07 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS--`,,,,`-`-`,,`,,`,`,,`---
SSPC TITLESSYSTEM 91 W 8bè79LiO 0003359 T82 ~ ~~ DISCLAIMER These specifications, guides and recommendations have been developed in accordance with voluntary consensus procedures by SSPC Advisory Committees and are believed to present good current practice. They are monitored and revised as practices improve, and suggestions for revision are welcome. Other methods, materials, and specifications may be equally effective or superior. SSPC is not responsible for the application, interpretation, or administration of these specifications, guides and recommendations. Moreover, SSPC does not issue interpretations of its specifications, guides or recommendations; and no person is authorized to issue an interpretation of an SSPC specification, guide, or recommendation on behalf of the SSPC. SSPC specifically disclaims responsibility for the use or misuse of these specifications, guides and recommendations. The supplying of details about the patented formulations, treatments, or processes is not to be regarded as conveying any right or permitting the user of this manual to use or sell any patented invention. When it is known that the subject matter of the text is covered by patent, such patents are reflected in the text. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS--`,,,,`-`-`,,`,,`,`,,`--Copyright 1992by SteelSîructures Painting Council Ali Right Reserved This book or any pati thereof must not be reproduced in any form without the written permission of the publisher. First Edition March 1, 1992 STEEL STRUCTURES PAINTING COUNCIL 4400 Fifth Avenue Pittsburgh, PA 15213-2683
SSPC TITLE*A ** = 8627940 00034Lï 287 '1 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS--`,,,,`-`-`,,`,,`,`,,`---
SSPC TITLEXA XX 8627940 0003420 TT9 STEEL STRUCTURES PAINTING MANUAL Volume 1 GOOD PAINTING PRACTICE Third Edition Executive Editor John D. Keane Editors Dean Berger, Harold Hower, Bernard R. Appleman Assistant Editors Joseph Bruno, Kitti Condiff, Mark O DonneII, Janet Rex, Aimee Beggs, Vilma Macura, Terry Sowers, Monica Madaus STEEL STRUCTURES PAINTING COUNCIL 4516 HENRY STREET, SUITE 301 PITTSBURGH, PA 15213-3728 I Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC TITLE*A YS ôb2794O 0003421 935 Copyright, 1993, by Steel Structures Painting Council All Rights Reserved This book or any pari thereof must not be reproduced in any form without the written permission of the publisher. Third Edition First Printing, January 1994 IBSN 0-938477-81-1 --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS II
SSPC TITLESA *Y = 8627740 0003422 87% Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS--`,,,,`-`-`,,`,,`,`,,`--DISCLAIMER The techniques, procedures, regulations and other information presented in this volume have been reviewed by experts in each field and are believed to represent good current practice. They are monitored and revised as practices improve, and suggestions for revision are welcome. SSPC is not responsible for the application, interpretation, or administration of the information outlined here. SSPC specifically disclaims responsibility for the use or misuse of any product, procedure or technology or misinterpretations of any regulations referred to in this manual. The supplying of details about patented formulations, treatments, or processes is not to be regarded as conveying any right or permitting the user of this manual to use or sell any patented invention. When it is known that the subject matter of the text is covered by patent, such patents are reflected in the text. Ill
IV --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC TITLEXA XX Ab27940 0003424 b4V Table of Contents Page Foreword Chapter 1 .O INTRODUCTION SSPC Staff ............................................................... 1 Chapter 1.1 CORROSION OF STEEL -SIMPLIFIED THEORY byF.L.LaQue ............................................................. 3 Chapter 1.2 PAINTS FOR ANTI-CORROSION SERVICE byCliveH.Hare ............................................................ 10 Chapter 2.0 SU RFAC E PREPARATION byH.William Hitzrot ........................................................ 19 Chapter 2.1 MECHANICAL SURFACE PREPARATION byA.W.Mallory ............................................................ 22 Chapter 2.2 M ETALLI C ABRASIVES byEinarA.Borch ........................................................... 32 Chapter 2.3 NO N-M ETALLIC ABRASIVES by H. William Hitzrot.. ...................................................... 4 5 Chapter 2.4 ABRASIVE AIR BLAST CLEANING byJim Bennett ............................................................ 52 Chapter 2.5 WATER BLAST CLEANING byJim Bennett ............................................................ 64 Chapter 2.6 HAND AND POWER TOOL CLEANING by Preston S. Hollister and R. Stanford Short .................................. . --`,,,,`-`-`,,`,,`,`,,`--68 Chapter 2.7 FIELD SURFACE PREPARATION COSTS byRobertB.Roth .......................................................... 75 Chapter 2.8 OTHER METHODS AND FACTORS IN SURFACE PREPARATION by Bernard R. Appleman and John D. Keane .................................... 78 Chapter 2.9 CHEMICAL CLEANING by Melvin H. Sandler and Sam Spring. ......................................... 9 0 Chapter 3.1 SPECIAL PRE-PAINT TREATMENTS: PHOSPHATING bySamspring ............................................................. 98 Chapter 3.2 PICKLING STEEL SURFACES by D. W. Christofferson ..................................................... 10 4 Chapter 4.1 PAINT MATERIALS by Sidney B. Levinson and Saul Spindel. ....................................... 117 Chapter 4.2 ZINC-RICH PRIMERS byCharlesG.Munger ....................................................... 125 Chapter 4.3 CORROSION INHIBITIVE PIGMENTS AND HOW THEY FUNCTION
byArnoldJ.Eickhoff ........................................................ 138 Chapter 5.1 PAI NT APPLICATION by Sidney B. Levinson and Saul Spindel.. ...................................... 150 Chapter 5.2 SCAFFOLDING by Sidney B. Levinson and Saul Spindel. ....................................... 168 Chapter 5.3 SAFETY IN PAINT APPLICATION by Sidney B. Levinson and Saul Spindel. ....................................... 176 Chapter 6.0 INSPECTION by Kenneth B. Tator and Kenneth A. Trimber .................................... 181 V Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC TITLEXA Xt 8627940 0003425 580 Chapter 7.1 QUALITY CONTROL OF PAINTS -AS MANUFACTURED by John F. Montle and Mary Ann Stephens ..................................... 20 7 Chapter 7.2 QUALITY ACCEPTANCE OF PAINTS -AS RECEIVED BY THE USER by John R. O Leary and Garland W. Steele ...................................... 21 3 Chapter 8.0 COMPARATIVE PAINTING COSTS by M.R. Sline, G. H. Brevoort, R. B. Feinberg,and S.J. Oechsle ................. ... 222 Chapter 9.0 SHOP PAINTING OF STEEL IN FABRICATING PLANTS byW.J.Wallace,Jr. ........................................................ 242 Chapter 10.0 PAINTING OF RAILROAD BRIDGES AND STRUCTURES byRayeA.Fraser .......................................................... 263 Chapter 11 .O PAINTING OF HIGHWAY BRIDGES AND STRUCTURES by R. R. Ramsey and Bernard R. Appleman ..................................... 28 0 Chapter 12.0 PAINTING OF STEEL VESSELS FOR SALT WATER SERVICE by David T. Bloodgood ...................................................... 293 Chapter 13.0 PAINTING OF STEEL VESSELS FOR FRESH WATER SERVICE byJ.R.Foster ............................................................. 307 Chapter 14.1 PAINTING STEEL TANKS byW.J.Wallace,Jr. ........................................................ 315 Chapter 14.2 THE LINING OF STEEL TANKS by Wallace P. Cathcart and Albert L. Hendricks ................................. 320 Chapter 15.0 PAINTING HYDRAULIC STRUCTURES byJ.L.Kiewit .............................................................. 330 Chapter 16.1 COATINGS FOR PIPELINES AND OTHER UNDERGROUND STRUCTURES by R. N. Sloan and A. W. Peabody ............................................. --`,,,,`-`-`,,`,,`,`,,`--349 Chapter 16.2 CATH ODIC PROTECTION byA.W.Peabody ........................................................... 363 Chapter 17.0 PAINTING OF INDUSTRIAL PLANTS by William F. Chandler.. .................................................... 37 7 Chapter 17.1 WASTE TREATMENT PLANTS byThomasP.Delany ....................................................... 379 Chapter 17.2 PAINTING OF COKE AND STEEL PLANTS by Arthur R. Thompson and S. C. Frye ......................................... 3 90 Chapter 17.3 PETROLEUM REFINERY COATINGS byW.E.Stanford ........................................................... 396 Chapter 17.4 PAINTING CHEMICAL PLANTS by J. Roy Allen and David M. Metzger. ......................................... 412
Chapter 17.5 PAINTING PULP AND PAPER MILLS by C. Edwin Wilkins and William F. Chandler ................................... 420 Chapter 17.6 PAINTING FOOD PLANTS bySteven L.Schmidt ....................................................... 429 Chapter 17.7 POWER GENERATION FACILITIES byRonald R.Skabo ......................................................... 442 Chapter 18.0 GOVERNMENT PAINTING PRACTICES by Richard W. Drisko and Howard G. Lasser .................................... 4 48 Chapter 19.0 TRAINING PROGRAMS FOR PAINTING byJayl.Leanse ............................................................ 452 Chapter 20.0 THERMAL SPRAYED COATINGS by S.J. Oechsle and J. N. Childs, Jr. .......................................... . 456 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS VI
Chapter 21.O Chapter 22.0 Chapter 23.0 Chapter 24.0 Chapter 25.0 Chapter 26.0 Chapter 27.0 Chapter 27.1 Chapter 27.2 Chapter 27.3 Appendix A Appendix B Appendix C Appendix D Index ....... SSPC TITLEtA tt m 8b27940 000342b 417 HOT DIP GALVANIZING byErnestW.Horvick ........................................................ 465 PAINTING GALVANIZED STEEL by Richard W. Drisko ...................................................... 481 CAUSES AND PREVENTION OF PAINT FAILURE by Charles G. Munger ...................................................... 486 PAINTING NAVY SHIPS by Stephen D. Rodgers, Richard W. Drisko and John Tock ....................... 5 16 DESIGN OF CORROSION-SAFE STRUCTURES byV.RogerPludek ......................................................... 528 SAFETY AND HEALTH IN THE PROTECTIVE COATINGS INDUSTRY by Dan Adley, D. Brian Shuttleworth, Scott Ecoff, Sidney Levinson and Saul Spind el . . 538 ENVI RON MENTAL REG U LATIONS AFFECTING PROTECTIVE COATINGS by Bernard R. Appleman ................................................... 556 AIR QUALITY REGULATIONS by Bernard R. Appleman and Karen A. Kapsanis ................................ 56 0 WASTE HANDLING AND DISPOSAL by Bernard R. Appleman ................................................... 573 OTHER REGULATIONS AFFECTING PROTECTIVE COATINGS by Bernard R. Appleman and Monica Madaus .................................. 580 ABBREVIATIONS ............................................................ 595 DEFINITIONS ............................................................... 596 STANDARDS AND SPECIFICATIONS REFERENCED IN VOLUME 1 ................. 619 UNITS CONVERSION CHART ................................................. 629 ............................................................................ 630 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS--`,,,,`-`-`,,`,,`,`,,`---
SSPC TITLESA tX 9 8627940 0003427 353 FOREWORD Coatings for structural steel have been called the principal means of protecting our principal construction material-steel-from its principal weakness-corrosion. This technology has been the subject of an intensive program by the Steel Structures Painting Council since 1950. The purposes of the SSPC are to assess and advance the technology of surface preparation and coating of industrial structures by conducting research, developing standards, and disseminating information: More specifically: 1. To instigate and carry on laboratory and field investigations of techniques to mitigate corrosion through the use of protective coatings; 2. To develop standards, specifications, and guides covering techniques and materials of surface preparation and coating of structures; and 3. To organize and communicate information intended to further improve and make more effective the protection of industrial structures. I. THE THIRD EDITION The first undertaking of the Council was the preparation of Volume 1 of the Steel Structures Painting Manual. It has been revised since then to incorporate new information. This third edition of Volume 1, Good Painting Practice is primarily an editorial revision and update. A complete technical revision of the volume will take several years. In the interim, several chapters have been added and several have been revised to reflect changes in the industrial painting industry since 1982. One of the most important changes since that time has been the increased attention health and safety and environmental regulators have focused on the industry. In addition to their other duties, specifiers and users must now be familiar with hazardous waste, air pollution control and other regulations. Worker safety has also become a concern. In recognition of the increased importance of these issues to painting concerns, an environmental chapter and a health and safety chapter have been added to the third edition. Concern about environmental and health effects has also led to major changes in the kinds of paint the industry uses. Lead- and chromate-based paints, once a mainstay of the industry, are being rejected in favor of less toxic paints. Most military and federal specifications for lead- and chromatebased paints have been canceled. SSPC has recently proposed to withdraw its specifications for lead-based paint and is re-examining specifications for paints containing chromate pigments. At the same time, paints are being reformulated to meet air pollution control requirements, and the recent amendmentsto the Clean Air Act will accelerate this process. The tables in this volume have been revised in light of these new realities. Because the list of specifications in the back
of Volume 2, Systems and Specifications has been enthusiastically received, we have added such a list to Volume 1. Like its predecessors, the third edition is written from the coating end user s point of view and not that of the paint technologist or scientist. Volume 1 should be considered a companion to Volume 2. Volume 1 was intentionally designed to include some duplication between chapters. This tends to make each chapter as complete as possible for the industry being covered, to present shades of opinion with regard to various controversial matters, and to spare the reader the necessity of large amounts of cross-referencing. When such cross-referencing is necessary, however, it is expedited by the detailed Index, Glossary, Table of Contents and Specification list. Each chapter attempts to be a balanced presentation in which each author has been given the benefit of the viewpoints of the outstanding leaders in his particular specialty, usually representing buyer, supplier, applicator, manufacturer, contractor, maintenance engineer and engineer-architect. The focus, of course, has been on coatings for structural steel rather than factory-applied enamels. II. ABOUT THE SSPC The SSPC is a professional technical society whose primary objective remains to improve the technology and practice of protecting structures through the application of coatings. Headquarters and laboratories of the SSPC are located in Pittsburgh. SSPC membership is open to both individuals and organizations, but SSPC services are not restricted to its membership. These services include consensus standards developed by technical committees, to help industry define and use good painting practice, a wide range of publications, and annual national conference and specialty conferences and tutorials offered throughout the year. SSPC s laboratory evaluates new materials and application techniques and develops procedures for coating performance evaluation and surface characterization. SSPC s Painting Contractor Certification Program (PCCP) is a national, prequalification service developed for facility owners who hire contractors. The PCCP confirms that an industrial painting contractor has met the standards for quality set forth in SSPC-QP-1, Standard Procedure for Evaluating Qualifications of Painting Contractors: Field Application to Complex Structures . 111. ORGANIZATION The affairs of the Steel Structures Painting Council are managed by a Board of Governors composed of sixteen (16) elected members, a non-voting Secretary and Treasurer, and additional ex-officio members appointed by the President. The board of Governors annually elects a five-person ExecuCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS VIII
tive Committee, consisting of the President, President-Elect, c.1.2 METALLIC COA TINGS Vice President, and two additional members from the Board C.1.2.a Painting Galva nized Steel of Governors. C.1.2.b Thermal Spray (Metallizing) The 6-member Standards Review Committee determines whether a standard is consistent with the Bylaws, mission c.1.2.c Shop-Applied Zinc (inactive) and overall best interests of SSPC and the industry before C.1.3 SOLVENTBORNECOA TINGS the standard is sent to the Board of Governors for approval. C.1.3.a C.1.3.b Coal Tar Epoxy (inactive) Chlorinated Rubber (inactive) The Executive Committee of the Board of Governors is responsible for the policy matters of the Council. It is electc.1.3.c C.1.3.d C.1.3.d.l Epoxy Polyamide (inactive) Polyurethanes Thick Film Polyurethanes ed annually, and is currently made up of the following: C.1.3.e Vinyls (inactive ) C.1.3.f Silicone-Containing Coatings (inactive) R. Dale Atkinson John F. Montle Brock Enterprises, Inc. Carboline President President-Elect C.1.3.g C.1.3.h Alkyds LOW-VOC Alkyds William M. Medford North Carolina Vice President Department of Transportation c.1.4 WATERBORNE COATINGS Bernie Beethe R. Wayne Beason Bernie Appleman Company American Steel & Aluminum Co., Inc. Texas Eastman SSPC Secretary (Ex Officio) C.1.4.a C.1.4.b C.1.4.c Waterborne Epoxies Water Miscible Coatings Latex Coatings Richard Benton Bob Washburne Dave Watson Barbara Fisher SSPC Treasurer (Ex Officio) C.1.5 SPECIAL USE COATINGS The following also served as members of the Board of Governors at the time of publication:
C.1.5.a C.1.5.b C.1.5.c Aluminum-Pigmented Coatings Marine Coatings Weathering Steel coatings (inactive) Steve Delich Steve Draskovich Gary Tinklenberg Fred Beckmann Joseph L. Buerger Ed Darrimon Tom Dunkin, II The American Institute of Steel Construction Procter & Gamble Company Bay Area Coating Consulting Co Dunkin and Bush C.1.5.d C.1.5.e C.1.6 C.1.6.a C.1.6.b C.1.6.c Surface Tolerant Coatings Coatings Under Fireproofing (inactive) Coatings & Linings for Concrete Concrete Coatings Floor Toppings for Concrete Coatings For Secondary Containment Tim Race Tim Leise Tim Leise Bob Ketterlin Tim Hyde Alan Holub Marcel M. Gaschke CIBA-GEIGY (Ex Officio) c.2-SURFACE PREPARATION E. Crone Knoy Tank Industry Consultants, Inc c.2.0 Surface Preparation Steering Ken Trimber Richard Lavergne Transocean Anti- c.2.1 Abrasives Bill Hitzrot corrosion, Inc c.2.2 Abrasive Blast Cleaning (inactive) Michael J. Masciale Mark S. Schilling Steven L. Schmidt Kenneth A. Trimber Charles H. Wyatt Valspar Corporation Unocal Corporation Porter International KTA-Tator Enviro-Air Corporation C.2.3 C.2.4 C.2.5 C.2.6 Power Tool Cleaning
Wet Blast Cleaning Visual Standards Industrial Blast Cleaning Duane Bloemke Jerry Woodson Lydia Frenzel Ken Trimber Ken Trimber Technical Committees are standing or ad-hoc groups asC.2.7 C.2.7.a Soluble Salt Contamination Chloride Extraction Simon Boocock William Johnson signed to address a specific or general technical topic within the scope of SSPC. Activities of technical committees include developing consensus standards and providing fo-g&3 APPLICATION, INSPECT ION, AND QUALITY CONTROL rums for exchange of information on pertinent technical issues. Technical committees are open to those interested in participating in the above activities, including members and non-members of SSPC. C.3.0 C.3.1 C.3.2 c.3.3 Application Steering Application Methods Paint Thickness Measurement Inspection TBA TEA Forrest Couch Dean Berger Dick Drisko c.3.4 Quality Assurance Nick Kozuska COMMITTEES AND CHAIRMEN Stan Gillard (1993) c.3.5 Applicator Pre-Qualification Ralph Trallo Eric Kline Number Name Chair 0 METHODS FOR IMPROVED PERFORMANCE -c.1 COATING MATERIALS C.4.1 Maintenance Painting TEA c.1.0 Coatings Steering Mary McKnight C.4.2 Performance Evaluation Mary McKnight c.1.1 Zinc-Rich (Unit) Dan Griffin c.4.3 New Specifying Methods (inactive) C.l.l .a ZR Performance Specs (inactive) Gerald Evarts c.4.4 Economics AI Roebuc k C.l.1.b ZR Topcoating Systems Gary Tinklenberg Gordon Brevoort C.l.l .c ZR Preconstruction Primers (inactive) John Peart Dick Drisko Joe Butler AI Kay AI Roebuck AI Beitelman Dick Wakefield Dean Berger Dick Hergenrother Jeff Jarboe
Bill Johnson Clive Coady Susan Simpson Marcel Gaschke --`,,,,`-`-`,,`,,`,`,,`--SSPC TITLEfA ft m 8627940 0003428 2îT m Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS IX
SSPC TITLEmA ** 8b27940 0003429 126 c.4.5 C.4.6 c.4.7 C.4.8 c.4.9 c.5 C.5.0 C.5.1 C.5.1.a C.5.l.b C.5.1.c C.5.l.d C.5.1.e C.5.1.f C.5.2 c.5.3 C.5.3.a C.5.3.b C.5.3.d c.5.4 C.5.4.a -C.6 C.6.0 C.6.1 C.6.2 C.6.4 C.6.3 C.6.5 C.6.6 C.A C.A.l C.A.2
C.A.4 NACEISSPC JOINT TASK GROUPS SSPC/NACE TG A NACEISSPC TG B SSPCINACE TG C SSPCINACE TG D SSPCINACE TG E NACEISSPC TG F --`,,,,`-`-`,,`,,`,`,,`--Bridge Painting Research John Peart Protective Linings Wallace Cathcart Tank Painting (inactive) Pulp & Paper Industry Dennis Justice Accelerated Testing Simon Boocock ENVIRONMENTAL, HEALTH AND SAFETY COMPLIANCE Environmental, Health and Safety Steering Dan Adley IV. PUBLICATIONS The Council makes available the results of its research, surveys and specifications work in a wide range of reports, manuals, conference proceedings and training videotapes which are listed in its publications sheet and which include, in addition to Volumes 1 and 2, the following: Individual specifications from Volume 2 on surface preparation, painting systems, paints, application, safety, thickness and maintenance; Photographic standards for surface preparation and degree of rusting; SSPC National Conference proceedings, covering protective coatings, surface preparation and compliance with environmental and health and safety regulations; Reports on laboratory and full coating performance evaluation, influence of soluble salts, accelerated testing and maintenance of weathering steel; Lead paint removal manuals, conference proceeding and reports; Video tape training on Abrasives, Protective Coatings, and Application. Bernard Appleman John Keane Dean Berger Harold Hower September 1993 Safety and Health Worker Protection Task Group (TG) Guidelines for Contract Documents Respiratory Protection TG Safety and Health Guideline TG Technical Peer Review Lighting in Containment TG Regulations & Litigation
Hazardous Paint Removal and Disposal Lead Paint Containment Lead Paint Disposal Ambient Air Monitoring for Lead Paint Abatement VOC Performance Reg-Neg Task Group EDUCATION AND CERTIFICATION Education & Certification Steering Education Main Education Objectives & Curriculum Review Certification Requirements PCCP Advisory Local Chapter Education Policy Local and National Painter ComDetitions ADMINISTRATIVE Local Chapters National Conferences Volume 1 Revision Dan Adley Scott Ecoff Richard Thompson Bill Dixon Frank Pokrwyka Doug Stephens Richard C. Miller James A. Giese John Baker Lloyd Smith Ken Trimber Lloyd Smith Vincent Coluccio Bob Klepser Bob Klepser Steve Pinney Steve Pinney Harold Hower Ron Hayden Ralph Trallo Mark Schilling Richard LaVergne Ed Feige1
Rose Mary Surgent Terry Sowers Ken Trimber Fred Lichtenstadter Carroll Steely Jerry Woodson Carroll Steely Lydia Frenzel Sy Solomon TBA Tom Aldinger Abrasive Blasting Thermal Cleaning Wet Abrasive Blasting Water Jetting Solvent Cleaning Surface Preparation of Concrete Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS X
SSPC TITLEtA tt 8627740 0003430 948 BIOGRAPHY BIOGRAPHY Dr. Bernard R. Appleman has been the Executive Director of the Steel Structures Painting Council since 1984. In this position, he is responsible for organizing and managing operations of a technical society whose activities encompass research, development of industry standards, and dissemination of technical information via reports, presentations, training programs and conferences. He has directed and coordinated numerous projects in coatings performance evaluations, surface preparation techniques, development of specifications and guides, and lead paint removal and abatement. His past work experience includes work as a CorrosionlCoatings Specialist for Exxon Research and Engineering Company. From 1977 to 1982, he was Project Manager, Coatings, for the Federal Highway Administration. He also worked as a Research Chemist for the Naval Ship Research and Development Center. BIOGRAPHY de Nemours and Company. Mr. Keane is a member of various honorary societies, including Tau Beta Pi, Phi Lambda Upsilon, Pi Nu Epsilon and Alpha Chi Sigma. He has served as director of several civic and religious organizations and is the author of approximately 60 scientific and technical publications and 30 technical disclosures. He has represented the United States at three international symposia and conferences on coatings. He served as a consultant, advisor, chairman, or active committee member in many societies, including the American institute of Steel Construction, the American Iron and Steel Institute, the Canadian Institute of Steel Construction, the Painting and Decorating Contractors of America, the Steel Plate Fabricators Association, the Federation of Societies for Coatings Technology, the American Society of Association Executives, the National Paint and Coatings Association, the National Association of Corrosion Engineers (NACE), the American Society for Testing and Materials, the Transportation Research Board, the International Organization for Standardization, and the American National Standards Institute. He is a Certified Manufacturing Technologist (Coatings), a NACE Corrosion Specialist, and a registered professional engineer (by examination) in the states of Illinois, Pennsylvania and California. Dean M. Berger received his B.S. degree at North Central College and did advance studies
at the University of Wisconsin. He has had over 20 years of research experience at PPG Industries, and eight years at Union Carbide Research. Beginning in 1974, he worked for GilbetVCommonwealth, advising engineers and architects on the application and use of coatings. In 1988 Mr. Berger retired from Gilbert Associates and formed his own coatings consulting firm, Berger Associates Inc., of Leola, Pennsylvania. He has attained specific expertise in zinc rich coating technology, epoxy, coal tar epoxy, urethane, and vinyl coating systems. He has been a member of the Steel Structures Painting Council since 1960, chairman of the Epoxy Advisory Committee, and CoChairman of both the Research Committee and the Inspection Committee. He was chairman of the American Society for Testing and Materials (ASTM) Subcommittee 0-1.46 on Industrial Protective Coatings. He is the Executive Director of the Board of Registration of Nuclear Safety-related Coating Engineers and Specialists, and a member of ASTM Committee D-33 on Coatings for Power Generation Facilities. Mr. Berger is a recipient of the Man-of-the-Year Award from the Washington Paint Technical Group, and belongs to the Gallows Bird Society. In 1957 Mr. Berger was President of the Pittsburgh Society for Coatings Technology Corrosion Committee, and of the National Association of Corrosion Engineers (NACE). He is also a director of the Institute of Applied Technology, and a member of the American Water Works Association Committee D102. Mr. Berger is a licensed Professional Engineer in California, a Nuclear-Safety-Related Coatings Engineer, and a NACE Corrosion Specialist. He has published over 100 technical articles and presented many papers on coating technology. BIOGRAPHY Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS XI
SSPC TITLE*A Y* öb27940 0004097 T30 XII Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS--`,,,,`-`-`,,`,,`,`,,`---
CHAPTER 1.0 INTRODUCTION by SSPC Staff This Third edition of the Steel Structures Painting Manual, GoodPainting Practice, also known as Volume 1, carries forward the mission of the Steel Structures Painting Council: 1. To instigate and carry on laboratory and field investigations of techniques to mitigate corrosion through the use of protective coatings; 2. To develop standards, specifications, and guides covering techniques and materials of surface preparation and coating of structures; and 3. To organize and communicate information intended to further improve and make more effective the protection of industrial structures. The first edition appeared in 1954 and the revised issue in 1964.The new edition is a technical update and editorial revision of the work that for nearly 40 years has been the bible in protective anti-corrosion coatings. Its aims remain the same as that of the original: the manual is written from the viewpoint of paint users; it is not intended to be a scientific or highly technical treatise on paint formulation, but rather a practical encyclopedia on painting methods, equipment, and systems that in the recent past have proved to be both economical and satisfactory. The manual is still appropriate to the varied audiences using it: contractors, engineers, specifiers, formulators, inspectors, suppliers, technicians, maintenance painters, users, and manufacturers. Given this wide audience with different levels of understanding about the subjects of the manual, it is necessary to present some material in a general rather than a detailed way, although some chapters have always been more detailed than others because the subject demanded it. I. PRINCIPAL CHANGES Volume 1 is intended as a companion to Volume 2, Systems and Specifications . The latter was revised in 1991. Like Volume 2, it now includes a list of specifications referenced throughout the book. During the last decade, there has been a tremendous increase in the number and the complexity of environmental and health and safety regulations. These regulations now apply in some way to most coating operations. Often, many different aspects of the same omperation are affected by a number of different regulations. A new chapter has been added to cover the aspects of environmental regulations that affect suppliers, specifiers, and contractors most: air pollution issues, particularly the
recent Clean Air Act Amendments, hazardous waste disposal as well as the requirements of the Toxic Substances Control Act, and requirements of the Clean Water and Safe Drinking Water Acts. While worker safety regulations have not grown at the same rate as environmental regulations, greater attention has been focused on health and safety aspects of coating operations, particularly exposures to lead. A revised health and safety chapter addresses the most important health and safety regulations facing coating applicators. Issues associated with exposure to lead in industries such as the coating industry are sufficiently distinct from those in general industry that OSHA recently issued a standard specifically addressing such exposures in the construction industry. Those in the coating industry must also be concerned with exposures to solvents, safety when working at heights, the flammability of solvents and coatings and communicating chemical hazards to workers. II. THE EDITORIAL PROCESS All sections of the manual were reviewed to identify needed changes. Leading authorities in their fields were asked to review and update selected chapters. Some aspects of the coating industry have changed more than others. William D. Corbett revised Chapter 6.0, Inspection . Gordon Brevoort revised Chapter 8.0, Comparative Painting Costs and John Tock revised Chapter 24.0 Painting Navy Ships . Dick Drisko rewrote chapter 22.0, Painting of Galvanized Steel. All specifications that have been canceled or fallen into disuse have been deleted from tables recommending paint for particular uses. Several recent SSPC specifications have been added, and specification for paints using lead pigments have been deleted. 111. USING THE MANUAL The reader of the Manual may wish to take advantage of several features that may be helpful: the Table of Contents, Index, Glossary, Metric Conversion Table and List of Referenced Specifications. The Index, for example, makes it possible to find both specialized information on a particular industry, and information applicable to most or all coating operations. --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 1
SSPC CHAPTER*L.O 93 8627740 0003432 710 = --`,,,,`-`-`,,`,,`,`,,`--Definitions common to most industries and practices are scientific to engineerin g to jargon in legitimate use in spegiven in the Glossary. Even in these, considerable variation cial contexts. Prop rietary names have been avoided exists within the standardizing bodies in the VariOUS indus- whenever a term cou ld be described in any other way. tries involved. Whenever deemed necessary, definitions are included with the textual material, since terms range from Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 2
SSPC CHAPTER*L-L 93 8627940 0003433 b57 CHAPTER 1.1 CORROSION OF STEEL SIMPLIFIED THEORY by F.L. La Que This chapter describes how steel corrodes. Because corrosion is the fundamental problem of coatings technology, the discussion presents an explanation that will be useful to those who design and develop innovative protective coatings and to others who must put into practice the technology of coating systems. Let us examine first the processes involved in the corrosion reactions that paint coatings will be required to suppress. I. ENERGY EXCHANGE Steel corrodes in reaction with its environment because of the thermodynamically unstable condition of iron after it has been extracted from its ores. Reduction of iron from its state as an oxide in ore requires energy in the reduction process. The fundamental laws of nature governing conservation of energy require that, eventually, balance must be restored by return of the unstable metal to its oxidized state. In the case of iron (steel) the oxidized state usually appears as rust. Rust is similar in appearance and practically identical in composition (Fe,O,) to the most common form of iron ore (hematite). Appropriate conditions yield two other oxidized forms, one of which has the same chemical composition as a principal form of iron ore magnetite (Fe304). The other is the lowest oxide of iron, Feo. All three of these oxides are components of the mill scale formed on steel by oxidation at temperatures encountered in the manufacture of steel into structural shapes and plates. Effects of such mill scale must be taken into account in preparing and painting steel to prevent corrosion. The principal difference, in terms of energy, between reduction from ore and eventual conversion into rust by corrosion is not the amount of energy required but the rate of reaction. Fortunately, ambient environmental corrosion of iron proceeds much more slowly than high temperature oxidation. The principal function of a paint coating is to reduce the rate of corrosion in the environment and the area of the metal involved as much as possible, ideally to zero. II. CORROSION PROCESSES Understanding the process of corrosion provides the key to steps that may be taken to prevent the reaction from occurring and to identify the role that paint can play in
achieving this recul t. Obviously, if the metal can be isolated from a corrosive environment, no corrosion reaction can occur. Such isolation is the most important function of a paint coating. In addition, some constituents of a coating can suppress the rate of corrosion reactions where complete isolation is not achieved either generally or locally, as at pores, scratches or other discontinuities (holidays) in a coating. Consideration must be given, also, to the possibility that a constituent of a coating might actually accelerate a corrosion reaction. Experience has shown that corrosion in the presence of a paint coating is likely to be much more serious where it is localized at discontinuities in a coating rather than where it occurs in a more general attack under a coating. This is true even if a coating is unable to isolate the metal from its environment. Consequently, what happens at discontinuities in a coating as related to the processes of corrosion requires special consideration. 111. THE MECHANISM OF CORROSION It has been well established by experimental demonstrati~n(~,~.~.~.~.~.~) that corrosion is the result of an electrochemical process involving an anodic reaction. Here, the metal goes into solution as an ion, and acathodic reaction takes place where the electrons released by the anodic reaction are discharged to maintain electrical neutrality by reaction with ions in solution, e.g. hydrogen ions in acid solutions, or by reduction of oxygen in solution in neutral or alkaline solutions. The anode in a corrosion cell is analogous to the negative zinc electrode in an ordinary dry cell battery. The cathode is analogous to the positive carbon electrode in such a cell. The current flows in the electrolyte inside the battery cell from the anode, zinc, to the cathode, carbon. The electrons generated by the cell move in the external circuit from the zinc electrode (-) to the carbon electrode k(+). By convention, the flow of current in the external circuit is opposite the electron movement. Whether a particular area of a steel surface will act as an anode or a cathode will be determined by a number of factors. One factor is the condition of the thin, air-formed oxide films that exist on dry steel. Such films when they are intact induce a modest level of passivity that makes the film-covered surfaces more noble than, and therefore Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 3
cathodic to, adjacent surfaces where a less protective film may exist. Observations of steel surfaces after immersion in water for several days have shown that, ordinarily, about 50% of the surface has been corroding as an anode with the remaining cathodic surfaces showing little or no evidence of attack. As time progresses, there is breakdown of the protective films on the original cathodic surfaces so that corrosion spreads eventually over the whole surface. But a division between anodic and cathodic surfaces persists with the cathodic areas at any time being protected from corrosion by currents flowing from adjacent anodic areas. Other factors in establishing anodic areas are differences in crystal orientation, the presence of contamination on the surface of the steel, and, in exceptional cases, the effects of stresses above the elastic limit of the metal, which cause rupture of protective oxide films by plastic deformation. Anodic areas can be established also by variations in the dissolved oxygen concentration of a solution in different zones on the steel surface. These variations can give rise to what is called an oxygen concentration cell in which current will flow from an anodic area in contact with the solution having the low concentration of dissolved oxygen to a cathodic area in contact with the solution having the higher concentration. The difference in corrosion potential that can be created by this mechanism on a steel surface can exceed 100 mV. The anodic and cathodic reactions in the corrosion of iron can be written as follows: At the anode where the metal goes into solution Fe (solid) Fe++ (ion) + 2e- (electrons) +
At the cathode 2H' (hydrogen ions) + 2e--H, (gas) or 2H' + %O, (air) + 2e--.H,O or O, + 2 H,O + 4e--4 OH- (hydroxyl ion) The hydroxyl ions generated by cathodic reactions can contribute to degradation of paints subject to attack by alkali. Figure 1 helps to illustrate the process of corrosion. Iron ions (Fe++) released by the anodic reaction interact with hydroxyl (OH-) ions generated by cathodic reactions to form Fe(OH), near the boundaries of anodic and cathodic areas. Oxygen reaching the precipitated Fe(OH), reacts with it to form Fe(OH), and, eventually, rust Fe,O,. The essential requirements for the electrochemical reactions in corrosion are, therefore, a thermodynamically unstable metal, iron; an electrolytic conductor of ions, water or another conductive solution; an electrical conductor, the metal; and an electron acceptor, hydrogen ions or dissoIved oxygen. We have the metal that we wish to protect from corrosion. What we need to control, therefore, is the availability of an electrolyte. This is best accomplished by an isolating barrier such as paint, or by reducing the concentration of electron acceptors such as hydrogen ions or dissolved oxygen. 4 IcATHODE,Y \CATHODE FIGURE 1 It may be possible under some circumstances to pre--`,,,,`-`-`,,`,,`,`,,`--vent corrosion by interfering with the anodic reaction by a process called passivation or reduction of the tendency of the iron to go into solution. In the case of steel, passiva tion usually is accomplished by very thin adherent oxide films which change the corrosion potential of the iron in the more noble direction (towards gold in the electromotive series). Galvanic Corrosion Induced by Passivation The change in potential of steel as a result of passivation, achieved for example by contact with passivating pigments such as red lead and chromates, can create galvanic couples between the passivated iron under the paint film and adjacent unpassivated iron at bare spots. The result would be galvanic acceleration of corrosion of
the exposed iron. For this reason it Was been proposed that passivating pigments be excluded from paints used to protect steel under conditions of continuous or frequent, complete or partial immersion. However, with no more than the thin film of electrolyte with limited electrical conductivity that will exist on surfaces exposed only to the atmosphere, a significant galvanic effect on a bare spot need not be anticipated. The benefit of passivating the bare spot by a pigment will more than offset the galvanic effect of passivation under the paint film. For this reason passivating pigments such as zinc chromate are beneficial rather than harmful in paints used for protection of steel in atmospheric exposures. In view of the moisture) must cipal function penetration of surface.
fact that an electrolyte be present for corrosion of a paint coating is to water or moisture to the
(water or to occur, the prinprovide a barrier to underlying metal
Transfer of water or moisture through a paint coating can occur by water absorption by a coating or by transfer of water vapor through a coating. Details of these processes will be described in other chapters of this book. For the present it will suffice to note that penetration of water or moisture is accompanied by poor adhesion of the coating to the metal. This permits osmotic effects to operate through the coating acting as a membrane and thereby results in the development of blisters. Such action may be accentuated further by the superimposed effects of electrical currents created by corrosion, leading to the phenomenon of electroendosmosis5 with resulting blisters adjacent to cathodic areas. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*L.L 93 m 8627940 0003435 42T m IV. CORROSION AT DISCONTINUITIES IN A PAINT FILM As noted previously, corrosion of steel associated with paint films is most troublesome at, or adjacent to, pores, scratches or other bare spots. It is convenient, therefore, to examine the factors related to attack at bare spots. The most important of these factors is the location of the cathodic areas in the corrosion reaction. Possible locations of cathodic surfaces are shown diagrammatically in Figure 2. The extent of corrosion at an anodic area will be determined by the magnitude of the current generated by the local reactive corrosion cell. It will be governed by Ohm s law: Equation 1 where I = corrosion current E = difference in potential between anodic and cathodic surfaces R = resistance of the circuit When current flows in a corrosion cell, the initial potential difference E is reduced by what is called polariza tion. The potential of the anodic surfaces drifts towards that of the cathodic surfaces as a result of an accumulation of corrosion products. The potential of the cathodic surfaces drifts towards that of the anodic surfaces as a result of accumulation of the products of the cathodic reactions. The latter is affected by the rates of evolution of hydrogen as a gas or, more importantly in applications of steel, the rate at which oxygen in solution can react with
electrons reaching cathodic surfaces after release by the anodic reaction. In most applications of painted steel the extent of cathodic polarization will determine the rate of the overall corrosion reaction. Anodic corrosion cannot occur at a rate higher than that accommodated by the cathodic reaction. Figure 3 illustrates the potential shifts that result from polarization. As indicated, polarization limits the amount of current that can flow. It will be reduced further by an increase in the resistance of the circuit. POSSIBLE LOCATIONS OF CATHODES IN CORROSION CELLS AT BARE SPOTS IN A PAINT COATING ON STEEL ELECTROLYTE 7 1 AN OTHER METAL PRIMER (I) At Base Coating (2) At Surface of Coating (3)At Base of Primer (4) At Other Metal Surface FIGURE 2 EFFECTS OF POLARIZATION AND RESISTANCE ON CORROSION CURRENTS I I I il 1 I 1 1 Corrosion Current Corrosion CurrZnt Limited by Resistance Limited by Polarization and Polarization FIGURE 3 As a result of polarization the original potential of the anode PA will be reduced by a factor Ap, and the original potential of the cathode PC will shift towards that of the anode by a factor Cp. As a result, the effective potential difference (E) in equation 1 will become: (PA -Ap) -(PC + Cp) and equation 1 becomes:
I = (PA -Ap) -(PC + Cp) Equation 2 R Let us now examine the factors that determine the magnitude of the resistance A. These will include, in series, the resistance of the electrolyte or whatever else occupies the discontinuity (D) in the coating (RDt), the resistance of the solution or film of moisture outside the discontinuity (RL), and the resistance of the paint coating (C), (RCt). The resistance of the metallic electron path is sufficiently low to be neglected. The factor t in (RDt) and (RCt) takes into account the fact that the resistance of the electrolyte within a discontinuity and the resistance of a coating will increase as the thickness of the coating is increased. Combining all these component elements, the resistance factor R becomes: RDt + RL + RCt and equation 2 becomes: I = (PA -Ap) -(PC + Cp) Equation 3 RDt + RL + RCt Now let us examine possible effects of the location ot the cathode on the corrosion reaction at the base of the discontinuity. Location 1 in Figure 2 assumes that both the anodic and cathodic reactions will have to occur at the base of a pore or other discontinuity in a coating. This automatically limits the area that can act as a cathode and, consequently, by increasing the cathode current density, increases favorably the value of the term Cp in equation 3. Even more importantly, as the dimensions of the Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 5
SSPC CHAPTERsL-L 93 H 8627940 000343b 3bb discontinuity decrease and the thickness of the coating increases, the discontinuity resistance factor RDt may increase dramatically; especially when, as frequently occurs, the discontinuity becomes clogged with rust (Fe203) which has a very high electrical resistance. The positive effect of thick coatings is shown by sea water tests of steel covered with a paint of proper thickness, but subsequently found to have many very small pores. The steel showed no visible evidence of corrosion after immersion in sea water for more than a year. What has just been described supports the advantage of increasing the thickness of a paint film, especially if the application involves exposure under conditions of immersion. The factor RL covering the resistance of the solution or film of moisture explains why corrosion is likely to be more severe in sea water than in fresh water and under conditions of immersion as compared with atmospheric exposure. In the case of the latter, humid atmospheres containing chlorides, sulfur dioxide or other pollutants can promote more corrosion than dry, unpolluted atmosp heres. The rather startling 8500 to 1 range in corrosivities of atmospheres was demonstrated by a test program undertaken by ASTM.6 The factor RCt, the electrical resistance of the coating, becomes important only if the cathode of the corrosion reaction exists underneath the coating, (location 3, Figure 2). In such circumstances, favorable factors will be the thickness of the coating
t
and the resistance of the
coating to water absorption and moisture penetration as well as its basic electrical resistance characteristics. A cathode created under a coating by the passivating action of primers containing inhibitive pigments such as red lead or chromates will have a low potential, Cp, and a relatively large area with low cathodic polarization, Cp in equation 3. Thus, the effect is to increase the corrosion current I. This supports the recommendation that
passivating pigments should not be used in paints on steel in services involving continuous or frequent, partial or complete immersion. As another example, it is possible also to create a cathode under a paint film by migration of copper from an antifouling paint containing cuprous oxide or metallic copper. Copper ions reaching the steel surface from an antifouling paint can deposit on the steel by cementation and thereby become a powerful cathode to steel at the base of an adjacent discontinuity in a coating. Thus, an antifouling paint system based on copper must include an effective anti-corrosive film under the anti-fouling topcoat. Quite different from the thin invisible oxide films formed on steel by exposure to dry air, mentioned above, are the relatively thick oxide scales formed on steel during high temperature manufacturing operations. This mill scale has the composition Fe,O,. It exhibits a potential that in sea water can be more than 500 mV more noble than that of bare steel. Metal exposed at discontinuities in such mill scale becomes the anode in a powerful galvanic cell with resulting severe localized attack at such anodic areas. The possibility of such effects produced by mill scale under paint coatings and the generally poor adherence of mechanically disturbed mill scale account for the need to remove mill scale from steel in preparation of steel for painting. V. EFFECT OF ANODIC PIGMENTATION A very favorable condition can be achieved if a paint system includes zinc in either an organic or inorganic (silicate) matrix. Since zinc is anodic to steel, an anodic potential in the opposite direction is superimposed on the steel so that the factor in the numerator of equation 3 becomes zero or even negative and consequently the corrosion current I is eliminated. This accounts for the excellent performance of zinc-rich coatings used either as primers or alone for protection of steel in marine and other severely corrosive environments. An essential requirement is that the zinc pigment loading be extensive enough to achieve electrical contact between the zinc particles so that they can function as effective galvanic anodes for the cathodic protection of the steel. VI. EFFECT OF CATHODIC PIGMENT
It is unlikely that any paint system would create a cathode at location 2, Figure 2, at the outer surface of the coating; however, this could happen in the case of an antifouling paint sufficiently loaded with copper powder or flake to form an effective copper cathode. Dangers from this source have restricted the use of antifouling paints based on metallic copper pigment. Vil. EFFECT OF GALVANIC COUPLES The most dangerous location of a cathode is location 4, Figure 2. This would be the case of painted steel in electrical contact with a more noble (cathodic) metal such as a copper or nickel alloy or stainless steel, both being immersed in an electrolyte. Such a situation would provide a cathode much larger than the very small anodes exposed at discontinuities in a paint film and with a large potential difference between the anode and the cathode (EA -EC), over 500 mV between the steel and the more noble metal. The resulting galvanic corrosion would result in fairly rapid penetration (pitting) of the steel. Painting the anodic (steel) member of such a galvanic couple will aggravate rather than minimize galvanic corrosion of the steel. It would be much better to leave the steel bare and tolerate the extent of the broadly spread galvanic corrosion that would result. But the best practice would be to paint both metals in the galvanic couple so as to eliminate both galvanic and normal corrosion. The next best choice would be to paint the more noble (cathodic) member of the couple and leave the steel bare. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 6
SSPC CHAPTER*L.L 93 8b27940 0003437 2T2 = Discontinuities in a coating on the cathodic member can be tolerated in view of the small area of cathode that would become involved. Coatings to be used on cathodic surfaces must be able to tolerate the alkali generated by cathodic reactions. An interesting form of galvanic corrosion has been encountered in oil production systems in the North Sea. Here, steel drilling and production structures are associated with very large concrete vessels used for storage of oil. The reinforcing steel embedded in the concrete can develop films that make the reinforcing steel strongly cathodic to steel outside the concrete. The galvanic cell generated in this way can accelerate the corrosion of the outside steel. This can be particularly serious if the galvanic effect is concentrated at discontinuities in a paint coating. This could be a factor in deciding whether to use a paint coating as a supplement to cathodic protection and in determining the amount of current required for cathodic protection of the steel in the concrete. VIII. CATHODIC PROTECTION USED IN CONJUNCTION WITH PAINTS Cathodic protection can be achieved using either galvanic anodes (zinc, aluminum or magnesium) or impressed current systems as the source of the protective current. As in the case of cathodic protection from zinc incorporated in a paint, the effect of the impressed current is to eliminate or change the direction of the potential difference in the numerator of equation 3. Cathodic protection simply substitutes electrons from an external source for the electrons otherwise generated in a corrosion cell to accommodate reduction of hydrogen ions and oxygen at the cathodic surfaces. The electrical resistance of the coating (RCt) plays an important role in cathodic protection by increasing the throwing power of the usually relatively small anodes by enabling the protective current to extend for greater distances from the current source. It has been found that under severe service conditions a combination of a good paint system and cathodic protection is better than either one alone. In addition to the throwing power effect, a paint system reduces the current required for cathodic protection by as much as 100to 1, depending on the condition of the paint. Even when there may be no opportunity for renewal of a paint system, its use can be justified in conjunction with cathodic protection in sea water. This is based on the
probability that, in the course of time, the calcareous deposits created by cathodic reactions will replace the original paint system in achieving distribution of current and maintaining the level of current required for protection. O Paint systems used with cathodic protection not only must tolerate attack by cathodic alkali, but must be protected from the danger of blistering by hydrogen which can result from too high a cathodic current density. Cathodic protection is usually monitored and controlled by measurement of the potential of the protected metal. This potential is measured relative to that of an appropriate bench mark reference electrode. One such electrode is a saturated calomel half cell. It is assumed that protection of steel has been achieved when its normal potential in sea water of about -600 mV has been raised to -850 mV. Potential measurements can be used, as well, to avoid hydrogen blistering of paints by restricting the potential resulting from cathodic protection. A conservative maximum polarized potential would be about -1000 mV versus a saturated calomel half cell. IX. EFFECTS OF STRAY CURRENTS The advantage of a substantially intact paint film having high electrical resistance in connection with cathodic protection is reversed in situations, usually rare, where painted steel immersed in an electrolyte becomes involved in the passage of a stray electrical current. Under such circumstances the current is forced to leave the metal at discontinuities in the coating with consequent severe localized attack. This has been observed, for example, on painted ship hulls when an on-shore source of current for electrical welding on a floating ship has been provided with inadequate negative return cables. This leads to a substantial amount of current returning to ground through the water path in parallel with the return cable path. The effect is to increase greatly the anodic potential AP in equation 3 leading to a high corrosion current l concentrated at discontinuities in the coating. X. EFFECTS OF COMPOSITION OF STEEL Self-limiting forms of rust can offer protection to steel under certain conditions of atmospheric exposure. The protective qualities of such rust films are affected by alloying elements and other minor constituents of steel. Copper, chromium, nickel and phosphorus have beneficial effects. Sulfur has the greatest detrimental effect, which can be compensated for by the presence of copper in an amount greater than the sulfur content. Combinations of favorable alloying elements are more effective than the same content of a single beneficial element. This is the case with the so-called high-strength, low-alloy steels. As measured by weight loss after exposure in certain corrosive atmospheres for 10 years,
these steels showed an advantage over ordinary steel in a ratio of about 4 to 1or greater. The advantage of the low-alloy steels is even greater when the steels are painted, ,* as illustrated by Figure 4. Painted specimens of a steel of very low copper content have poor resistance to a marine atmosphere as compared with a better steel containing about 0.20% copper and an even better steel containing copper, nickel, chromium and phosphorus. The alloy steel suffered much less spreading of corrosion adjacent to the scribe marks in the paint. Further improvement was achieved by a phosphating Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 7
SSPC CHAPTERaL.1 93 = 8627940 0003438 139 = Untreoted Surface Open Heorth Iron 01% Cu Steei Cr-Ni-Si-Cu-P Steel Bonderito Troated Surface Open Hearth tron 0.2%Cu Steel Cr-Ni-Si-Cu-$ Steel FIGURE 4 Effect of Surface Treatment on Painted Steels Exposed Eight Months in Atmosphere 80 Feet from the Ocean at Kure Beach, N.C. pre-treatment of the steel before painting. As measured by weight loss of scribed panels the advantage of the alloy steel over the poorest steel was in the ratio of 10 to 1. The combination of the phosphate pre-treatment and alloying resulted in an improvement to a ratio of 20 to 1. The advantage of a low-alloy steel observed in atmospheric exposure is not duplicated under conditions of immersion. The better performance of the alloy steel in atmospheric exposure is based on the superior protective qualities of the thin film of rust that forms on the alloy steels, while the voluminous hydrated rusts that form on steels under conditions of immersion do not exhibit a similar difference in protective ability. Furthermore, the principal factors that influence corrosion under water, such as dissolved oxygen, effects of organisms and water velocity, are external to the steel rather than related to its composition. XI. CONCLUSION Knowledge of the reactions involved in the corrosion of steel combined with a knowledge of how a paint system can impede these reactions and the qualities of a paint system needed to achieve the desired results, as described in the following chapter, along with proper preparation of steel of desirable composition, can serve as an effective guide for using protective coatings to prevent corrosion. ACKNOWLEDGEMENT The author and editors gratefully acknowledge the active participation of the following in the review process for this chapter: Roy Boyd, Theodore Dowd, Richard Drisko, Arnold Eickhoff, W.P. Gallagher, Clive Hare, William Hitzrot, William Mathay, Chuck Munger, Bruno Perfetti, Percy Pierce, Melvin Sandler, and William Wallace. BIOGRAPHY The late Francis L. LaQue, former Vice President of inco Ltd., (formerly International Nickel Co. of Canada), was often called a pioneer in corrosion
research and had a distinguished career in metallurgy. He devoted half his life to the research and development interests of the company, retiring in 1968, as Vice President and Special Assistant to the President. An honored member of many technical societies, Mr. LaQue served as President of the National Association of Corrosion Engineers from 1948 to 1949, the American Society for Testing and Materials from 1959 to 1960, the Electrochemical Society from 1962 to 1963, the American National Standards Institute from 1966 to 1971, and the international Organization for Standardization (ISO) from 1971 to 1973. He was a Fellow and Honorary Member of the American Society for Metals. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 8
SSPC CHAPTER*Z.L 93 W 8627940 0003439 075 He influenced several professional areas within the scope of his diversified interests. He was instrumental in the formation of IS0 Technical Committee TC156, Corrosion of Metals , served as chairman of the U.S. Corrosion Research Council, and as a Deputy Assistant Secretary to the US. Department of Commerce. He was a senior lecturer at the Scripps Institute of Oceanography at the University of California, in LaJolla, California and a professor at the University of Hawaii. He is best remembered for his specialization in marine corrosion engineering and for the establishment in 1935 of the worldrenowned marine corrosion test site at Kure Beach, North Carolina. The LaQue Center for Corrosion Technology, Inc. Wrightsville Beach, North Carolina, (a corporate unit of Inco Ltd.) stands as a monument to his achievements. REFERENCES 1. W.R. Whitney, The Corrosion of Iron J. Am. Chem. Soc., Vol. 22, p. 394, 1903. 2. T.P. Hoar and U.R. Evans, The Velocity of Corrosion from the Electrochemical Standpoint, Part II Proc. Roy. Soc. (A) 137, 343, 1932. 3. G.D. Beniouah. U.R. Evans. T.P. Hoar and F. Wormwell. The , Corrosion of Metals by Salt Solutions and Natural Waters an Agreed Statement,
Chem. ind., p. 1043, 1938.
4. R.B. Mears and R.H. Brown, Causes of Corrosion Currents J. Ind. & Eng. Chem., Vol. 33, p. 1001, 1941. 5. W.W. Kettelberger and A.C. Elm, Water Immersion Testing of Metal Protective Paints , ind. & Eng. Chem, 39, 1947. 6. S.K. Coburn, C.P. Larrabee, H.H. Lawson and 0.8. Ellis, Corrosiveness of Various Atmospheric Test Sites as Measured by Specimens of Steel and Zinc, ASTM Metal Corrosion in the Atmosphere Symposium June 1967; published June 1968. 7. H.R. Copson and C.P. Larrabee, Extra Durability of Paint on Low Alloy Steels ASTM Bull. 242, 68, Dec. 1959. 8. F.L. LaQue and J.A. Boylan, Corrosion, 9, 1953, p. 237. --`,,,,`-`-`,,`,,`,`,,`--9 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*L-2 93 W 8627940 0003440 897 September 1993 (Editorial Changes) CHAPTER 1.2 PAINTS FOR ANTI-CORROSION SERVICE by Clive H. Hare The chapter on corrosion has been primarily concerned with the metallic side of the metal/paint film interface. Proceeding across this interface, review will now be made of some basic principles of paint technology as they apply to the design of protective coating systems. These principles underline the specifics discussed in the chapters on paint materials (Chapter 4.1), inhibitors (Chapter 4.3),and zinc rich (Chapter 4.2). Protective coatings may function by one or more of three mechanisms: (1) the barrier principle, (2) the inhibitive primer principle, Or(3) the galvanic or zinc-rich principle',*. Often, coating systems employ two of the three mechanisms in conjunction for improved effect. For instance, the barrier principle may operate in a finish coat while another principle operates in the primer. Inhibitive pigments are sometimes used in the finish coat as well as in the primer, and thick-film systems utilizing the barrier principle alone are widely used on buried structures. Zincrich coatings, to work at all, must be electrically contiguous with steel and are used only as primers, with or without barrier coats. I. ADHESION AND SURFACE PREPARATION The primer is the critical element in most coating systems because it is most responsible for preserving the metallic state of the substrate, and it must also anchor the total system to the steel. This it may do in one of two ways, depending upon the nature of the primer vehicle3. Most coatings adhere to metal via purely physical attractions (e.g. hydrogen bonds) that develop when two surfaces are brought closely together.' Paint vehicles with polar groups (-OH, -COOH, etc.) have good wetting characteristics and show excellent physical adhesion characteristics (epoxies, oil paints, alkyds, etc.). Much stronger chemically bonded adhesion is possible when the primer can actually react with the metal, as in the case of a WP-1 wash primer5 pretreatment (SSPC-Paint 27),or a phosphate conversion coating. For adhesion to take place, the coating and substrate must not be separated from one another by more than appro:iimately 5 8, -about three times the diameter of an oxygen atom. Any contaminant on the steel will increase the separation and decrease paint film adhesion. Moreover, reactive sites on steel at which adhesion can occur are masked not only by contamination, but also by chemically bound species which may themselves satisfy
sites on the steel that would otherwise be available for reaction with the paint vehicle. Thorough surface preparation removes such contamination, and exposes many more reactive sites, thereby dramatically increasing the amount of surface area where adhesion can occur. II. BARRIER PRIMERS The removal of surface contamination is important not only for adhesion, but also for good corrosion resistance. The barrier film prevents corrosion by increasing the electrical resistance (RCt) of the path of currents generated by slight differences in electrochemical potential between adjacent areas of the metal surface or between the underlying metal and another metal having a different potential. Paint films are not completely impermeable to the concentration of water and oxygen, and transmission of both is normally high enough so that prevention of the cathode reaction is impossible6.'.*. Penetration by water and oxygen does not produce a resistance low enough to maintain a corrosion current, and though most paint films take up water relatively quickly, they take up ion solutions only very slowly3. This keeps the electrolyte resistance relatively high and the corrosion low since corrosion is dependent upon ionic flow. However, even when the electrical resistance of penetrating moisture is reduced by absorption of ions, the resistance of a good barrier film remains high enough to achieve an important reduction in the magnitude of the corrosion current. Underfilm ionogenic ticularly chlorides surface preparation penetrate the film, crease corrosion.
(ion producing) materials (parand sulphates) that are left after poor can be dissolved as ion-free water, form conductive electrolytes, and in-
Also, under conditions of immersion, differences in ionic concentration between liquids beneath and outside the film give rise to osmotic migrations of water into the film. This promotes blistering and eventual film rupture. Further degradation and loss of protective value can result from electroendosmosis generated by differences in the electrochemical potential on the metal surface at and around the film disruption. Salts may also form from soluble matter within the film. The effect of corrosive salts such as chlorides is obvious. Inhibitive ions, themselves, however, may also cause problems. At the interface, the ionic solution from inhibitive pigments passivates the metal by increasing the polarization of the anode (Ap in equation 2 in Chapter 1.1). However, such passivation of underfilm surCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 10
SSPC CHAPTER*L=2 93 W 8627740 000344l 723 faces can have a detrimental effect under certain conditions by accelerating the corrosion at bare spots. There will be a considerable difference between the potential of the unpassivated metal at a bare spot (PA in equation 2) and the relatively large areas of passivated metal (PC in equation 2) under the paint film. This can result in accelerated corrosion at the bare spot. For this reason the use of inhibitive primers (containing passivating pigments) is avoided by some formulators on surfaces submerged in conductive electrolytes such as salt water. Unlike well cured films, insufficiently cured films allow the penetration of much more ionic materiallo,ll. Polymer groups such as carboxyls and hydroxyls tend to foster ionic penetrati~n~~~,~~.~~,~~'. As pigment volume concentration (P.V.C.)' is increased, these factors are overwhelmed because interstitial penetration dominates. Good barrier films, therefore, are high molecular weight films with uniform crosslink density, cured uniformly, formulated well below the critical pigment volume concentration (C.P.V.C.)** with low water solubility pigments. Lamellar pigments (leafing type aluminum) dramatically reduce ionic transmission rates. Care must always be taken in using metal flakes (such as copper or stainless steel) to ensure complete pigment encapsulation to avoid unwanted galvanic effects. Lamellar metallic pigmented barrier films are best used as finish coats, with a nonmetallic primer to improve adhesion. Similarly, tie coats should be used to improve adhesion between such metallic barrier films and zinc-rich primers. All things being equal in atmospheric service, thicker barrier systems give better protection, as shown in work by SSPC and the FSCTl8. In general, the more severe the environment, or the longer the requirement for protection, the greater will be the coating dry film thickness required. Care should be taken, however, in the application of high build systems to thin walled structures and other dimensionally unstable substrates. Thick films (particularly those of rigid thermosets) are less able to provide the necessary flexibility to substrate movement (e.g. expansion and contraction) than are thinner films, and can easily undergo adhesive and cohesive failure leading to subsequent disbondment. Such delamination has been found in rail car tank linings, for example. Vehicle choice for barrier primers is also important. High molecular weight thermoplastics (e.9. vinyls and chlorinated rubbers) are effective, particularly at high builds. Thermosetting systems such as epoxylphenolics and certain polyesters are also effective vehicles, as are the coal tar epoxies. Vehicles with high hydroxyl or carboxyl contents (oils, alkyds, acrylics, etc) tend to attract water into the film.
'Ratio of the volume of pigment to the volume of total hon-volatile material (¡.e., pigment and binder) present in a coating. "Level of pigmentation where just sufficient binder is present to fill the voids between pigment particles in the dry film. 11 High-build vinyl and chlorinated rubber systems of 8 mils and more make excellent barrier systems. Both polymers contain an inherent flexibility. They employ a moderately slow solvent system with an efficient thixatrope to produce high wet film builds. OrganomontmoriIlonites, pyrogenic si Ikas, hydrogenated caster oi I derivatives or high molecular weight polyolefins are often used as thixatropes. Minimum effect on viscosity is desirable for ease of application. Solvent systems with high boiling aromatics or mono ethyl ether acetate are used. Application of up to 20 wet mils (5-7 dry mils) in one coat is possible. High build epoxy systems are also effective. Such synthetics are more permeable than coal tar enamels applied in super thick films. One hundred mils of coal tar on buried pipelines or immersed structures used in combination with impressed current cathodic protection can reduce current requirements for cathodic protection ten thousandfold as compared to requirements for bare steeIl7. High solids thermosets produce good barrier films, but they bring their own problems. Urethanes and epoxies may suffer from an unfavorable potlifeldrytime ratio resulting from exotherms that tend to increase reaction rate in the can but which are dissipated from the applied film. High solids urethanes often have the additional problem of hygroscopicity. The successful use of multiple component systems is very dependent on the skill of the applicator. Mixing and application instructions must be followed exactly. 111. THE INHIBITIVE PRIMER In this type of primer, pigments are incorporated to provide a source of corrosion inhibitive ions which can be carried to the metal interface as water penetrates the film. Here they modify anode andlor cathode reactions, driving the steel potential into its passive region1a. There are two principal routes to such inhibition. The first, direct inhibition, relies on a controlled dissolution of ions from the pigment itself. At the interface, the ionic solutions passivate the metal by increasing the polarization of the anode (increasing Ap in equation 2), by increasing the polarization of the cathode (Cp), or by thickening the natural oxide layer and increasing the electrical resistance across anode and cathode (increasing R).
Perhaps the most efficient direct inhibitives are the salts of hexavalent chromium. (Chromate pigments are toxic substances. Follow all applicable health, safety and environmental requirements in applying, handling or disposing of these materials.) In paint films, chromate inhibition is provided from such pigments as zinc potassium chromate, strontium chromate, etc. Pigment solubility is most important. Highly soluble pigments (calcium chromate) are rapidly depleted, while those with very low solubility (lead chromate) provide too few hexavalent chromate ions for protection. Zinc chromate offers a moderate solubility and is extensively used. Other less toxic inhibitors, the molybdates, phosphates, phosphosilicates, borates, and borosilicates also protect by similar mechanisms. Both type and loading of pigment are important, as are the type of vehicle and its moisture vapor transmission rate (MVTR). Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*L*2 93 = 8627740 0003442 bbT tant, as are the type of vehicle and its moisture vapor transmission rate (MVTR). The ratio of the primer s pigment volume concentration (P.V.C.) to the critical pigment volume concentration (C.P.V.C.) of the pigment system is equally important. Very low ratios (low pigment content) give overly tight films and increase the tendency of the primer to blister. Filiform corrosion of the substrate can occur. Too high a ratio provides rapid dissolution of the inhibitor, and allows corrosive ions such as chlorides from the environment to penetrate the film. Chlorides and other depassivators compete with inhibitive ions for anodic adsorption, and can nullify inhibition, or at least increase the quantities of inhibitor needed. Inhibitive primers are best restricted to environments where the penetration of chloride ions is limited. Their use in immersion conditions is definitely not recommended because of the danger of osmotic blistering. The best pigment volume concentration: critical pigment volume concentration ratio is determined experimentally, but a level near 0.9: 1 is often used. Barrier type vehicles are less effective with inhibitive primers than the more permeable vehicles (oils, alkyds, etc.). Oils and alkyds do not, however, have the alkali resistance of vinyls, etc., and this is a disadvantage. Alkai generated at the cathode can rapidly saponify alkalisensitive coatings. Alkali attack occurs at cathode areas adjacent to or surrounding corroding areas (anodes). Vehicle saponification can render a film quite water-soluble in such areas. This frequently occurs in alkyd systems where adhesion is destroyed. For more information on corrosion inhibitive pigments, see Chapter 4.3. IV. ZINC-RICH PRIMERS Zinc, employed in coating films at loadings that insure the film conductivity, will form an efficient anode of a galvanic couple with steel, sacrificially corroding itself, and overriding local cell activity on the steel which becomes entirely cathodic and protected. The concept is easily adaptable to practical coating systems, and such primers are the most efficient of all. Zincrich primers based on both organic and inorganic vehicles are widely and successfully employed. For more information on zinc-rich primers, see Chapter 4.2. A. ORGANIC ZINC-RICH PRIMERS The organic zinc-rich primer may be considered a special case of a high pigment volume concentration (P.V.C.) paint. It must maintain zinc particle to zinc particle contact within its continuum and contact between pigment and substrate to ensure electrical conductivity within the film and across the interface. These re
quirements translate to a paint formulated at a pigment volume concentration slightly above the CPVC. The film must also display sufficient adhesion at these loadings to anchor the system to the steel. Because of cathodic alkali generation at the interface, the vehicle must resist alkalis. Chlorinated rubber, epoxylpolyamides, high molecular weight linear epoxies and epoxy ester systems are used as binders. Epoxy esters do not have quite the alkali resistance of other vehicles, but certain specific vehicles (high epoxy content) offer acceptable compositions. Primer films will vary and reflect the properties of the vehicle type. In adjusting the P.V.C. to levels slightly higher than C.P.V.C., the primer achieves its tightest zinc to zinc packing, and zinc encapsulation is minimized. Judicious mixing of zinc dust of different particle sizes will also assist here to provide more uniform packing, resulting in better particle contact and ultimate galvanic protection. Too high a P.V.C., produces a coating having poor physical and application properties. Were zinc the only pigment, the P.V.C. fixation of a zinc primer (and, therefore, its optimum zinc loading) would be simple. Formulations are complicated by pigment anti-gassing agents, thixotropes, anti-settling agents, extenders, etc. Small amounts of highly oil absorbent materials markedly depress the C.P.V.C., but not the P.V.C., and the coating becomes porous. Used in controlled amounts such materials may be employed to reduce zinc levels, and maintain a P.V.C.: C.P.V.C. ratio, thus obtaining a strong film. This provides enough film and filmlcubstrate conductivity for good protection. Up to 15% mica has been effectively used in this way1e. The use of conductive extenders (di-iron phosphide) is not related to P.V.C. effects, and high zinc replacements have been achieved with this type of pigmentz0. Careless application of any organic zinc-rich primer can severely change the P.V.C.: C.P.V.C. ration in the applied film. Even with the best thixotropes, zinc settlement is possible, particularly in single package coatings. In a nonhomogenous film, some areas must surely be underbound, and some low in pigment. Poor physical properties, or zinc encapsulation (resulting in a nullification of cathodic protection) are the result. Zinc encapsulation has ruined many jobs at the outset, although the coating system itself may have been quite satisfactory. Application of organic zincrich paints must involve continuous agitation throughout the application. B. INORGANIC ZINC-RICH PRIMERS Inorganic zinc-rich paints, unlike the organics, depart radically from conventional paint technology. These vehicles (generally silicates) do not bind zinc as do the organics, but chemically react with zinc ions on zinc particle surfaces forming primary bonded zinc silicate matrices. As presented in the SSPC-Paint 20 classification, vehicles may generally be classed as either alkaline
silicates (water solutions of sodium, potassium, lithium, or quaternary ammonium silicates) or alkyl silicates which may be ethyl silicate (the most common) or higher alkyl or alkoxy homologues. 1. Alkali Silicates Film formation of the alkali silicates involves water Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 12
SSPC CHAPTER*L-2 93 8627740 0003443 5Tb W evaporation followed by neutralization of the silicate alkalinity (either by post curing solutions or by acids derived from the atmosphere such as carbonic acid) to form silicic acid. This then reacts with zinc ions to form the three dimensional zincoxygen-silicon (zinc silicate) matrix. Further atmospheric neutralization of residual alkali with consequent tightening of the matrix will occur with aging2'. 2. Alkyl Silicates The alkyl silicates form their matrix by an analogous route (evaporation of solvent, and hydrolysis of the vehicle to silicic acid by atmospheric moisture with evolution of the pertinent alcohol)z2. The silicic acid forms a matrix with the zinc similar to that described abovez3. Again, hydrolysis continues for some time after initial curing. The chemical nature of fully cured zinc silicates is (theoretically, at least) identical, irrespective of the silicate used. 3. Single-package Single-pack inorganic primers of the polyol silicate type involving ester exchange or interester exchange reactions with alkyl, alkoxy and hydroxy alkoxy silicates to form mixed esters pursue the same basic chemistry to provide similar film matricesz4. Organic moieties remain within these films and subtract from their wholly inorganic nature. Other routes to single package inorganic zinc-rich primers include the use of amine-initiated hydrolysis of alkyl polysilicate~,~~~~~ and the use of alkali metal alkoxide catalysis of hydroxyl free alkyl silicatesz7. Single pack inorganic silicate vehicles are now generally available. Some are modifications of silanes. 4. Inorganic vs. Organic With inorganic primers the P.V.C. concepts must be modified. Also, zinc levels lower than those necessary for the organics are possible with little immediate loss of performance. Zinc levels of 70% of film weight can give acceptable performance, and even levels of 50% (such as SSPC-Paint 29) if enhanced by other conductive pigments. Some have reported that reduced zinc level products do not have as good a performance in the long term as do the 85% loaded primers's. As discussed in the chapter on zinc-rich paints, the inorganic films show better performance than most organics. Their films are strong, hard, and resistant to impact and abrasion. They are quite resistant to heat. The matrix of the in-
organic primer film is not subject to age-related deterioration as are organic primers. Weathering may actually improve its physical properties. Adhesion is of an exceptionally high order and has led to speculation on the formation of primary valency linkages with the substrate as well as the zinc. The mechanism of adhesion at this point is 13 unknown. Surface preparation requirements are exacting (particularly with the alkaline silicate systems), a commercial blast being the very minimum acceptable, and a white or near white blast with a typical surface profile of 1 to 2 mils being more usual and often mandatory. Alkyl silicates are rather more tolerant of poorly blasted substrates than the water-based type, probably reflecting their higher organic content and lower surface energies. Despite their incompatibility with poorly prepared surfaces, the inorganics may be considered safer coatings than the organics. Not only are the organics subject to encapsulation, but also they can mislead the applicator by adhering initially to poorly prepared substrates. But adhesion is not protection, which is possible only through intimate contact of iron and zinc (the more contact, the better the protection). Inorganics require such contact (through good surface preparation) not only for protection, which may be initially difficult to determine, but also for good initial adhesion, which is easy to determine. If an inorganic sticks,. it should protect. If an organic sticks, protection is still an open question. 5. Secondary Mechanisms If cathodic protection were the sole mechanism of zinc-rich primers, they would rapidly break down as zinc was consumed. In practice, this is not the case. As zinc corrodes, its corrosion products (depending upon the environment) tend to polarize the reaction, coating the zinc and bridging the voids within the film, thereby packing them so that the primer is sealed from the environment. The film is slowly transformed from a zinc-rich primer to a barrier primer, and, in this state, it is maintained until the zinc is again exposed by some abuse. The zinc will then corrode again and be healed with corrosion product (providing that the agents of physical or chemical abuse have been removed). These phenomena are primarily responsible for long term zinc-rich protection. Zinc-rich primers are normally applied at approximately 3 dry mils. Some compositions form good films at thicknesses up to 6 mils, while others may severely mud-crack at these high builds. The porosity of zinc-rich films (particularly the
inorganic) can lead to problems because of air occlusion on top coating. The resultant bubbling and pinholing of applied top coats may necessitate the use of mist coats, thinned finish coats or tie coats (such as the WP-1 wash Orimer, SSPC-Paint 27) before finish coat application28. Careful formulation of solvent system and pigmentation of the finish coat can mitigate this problem, and many manufacturers carefully tailor finish coats for bubble-free application over the zinc-rich SSPC-PS Guide 8 includes a list of such finish coats. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*L-2 93 W 8627940 0003444 432 6. Pre-Construction Primers Single component inorganic zinc-rich films make good pre-construction primers, protecting steel during storage and fabrication. In thin films, they allow easy cutting of steel and good weldability, particularly when modified with the conductive extender, di-iron ph~sphide~'.~~. After fabrication, preconstruction primers may be recoated with a suitable primer and top coat. Further considerations on zinc-rich primers are discussed in a separate chapter. V. INTERMEDIATE AND FINISH COATS FOR STEEL A total coating system cannot be considered without regard for its external interface. While the primer mitigates metallic corrosion, the finish coat must counteract malignancies specific to the environment in which the system must function. As finish coats are designed at low p.v.c./c.p.v.c. ratios, they are dense, highly dielectric, and are applied in film thicknesses as high as possible. They are much like barrier primers, and play no inconsiderable part in assisting the primer in its anti-corrosive function. Unlike barrier primers, which are designed to be recoated and thus protected from the environment, the finish coat must contend with the environment from which it must shield the lower elements of the total system. Oleoresinous, varnish-type finish coats had to be built up of successive coats to the required film thickness, because of drying time difficulties inherent in thick, oxidizing films. High-build thermoplastics and high solids thermosets have enabled high film builds to be applied in single coats. While thinner coats applied successively give better solvent release, fewer pinholes and voids, and better continuity throughout the film, high-build systems have economic advantages and careful formulation can minimize their shortcomings. Statistically, more coats increase the risk of intercoat failure, although adhesion at any coatinglcoating interface is usually better than at a coatinglmetallic interface, In any coating system, compatibility between coats is critical. Compatibility can prevent solvent attack on primer films by the finish coat, solvent induced bleeding of organic pigments from one coat to a subsequent coat, and other pitfalls. Less appreciated are effects of poorly matched viscoelastic properties, which may become obvious only after aging. Inflexible finishes applied over flexible primers can eventually lead to cracking on aging. Too flexible a finish coat can actually pull an inflexible primer from the substrate. Cohesive failures (cracking, checking,
etc.), and adhesive failures (flaking, popping, blistering) can have grave consequences in anti-corrosive coating systems. All elements of the coating system must be matched to one another and to the substrate. For instance, thin steel siding requires a more flexible system than one applied to structural members, as does aluminum with twice the coefficient of expansion of steel. Flexibility can be built into a system by P.V.C. adjustments, or by vehicle changes including blending, copolymerization, and plasticization. Primers are generally kept less flexible than succeeding coats. Finish coat selection is dictated by the environment, although there are considerations with regard to the primer and intermediate coat that may influence this. Environments vary widely, ranging from exposure to weather and UV (ultraviolet light), to chemical immersion, high temperatures, and physical abuse. They may be simple or complex involving intermittent immersion, chemical attack, large temperature differentials, and extreme abra sion. All elements of the environment must be considered and evaluated in terms of their relative importance to provide the best compromise system. The vehicle binder of the finish must bear the brunt of the environmental attack. Most design decisions should be based on the polymer chemistry of the vehicle involved. An empirical awareness of the effects of UV, moisture, oxygen, chemical attack, microbiological attack, high and low temperatures, abrasion and impact, etc. on individual finish coat polymers will often suffice, but in-depth experience and understanding of the effects of such phenomena on molecular structure may be essential when resin systems must be mixed or synthesized to attain the desired result s.
An in-depth discussion of the wide ranging characteristics of each polymer type is quite beyond the scope of this chapter and is presented in a separate chapter. Table 1 presents a summary of the properties of finish coat materials. The following is no more than a brief discussion of those polymers commonly used in maintenance finishes. A. LACQUERS: THERMOPLASTIC COATINGS A lacquer is simply a coating that forms its film by solvent evaporation alone. Vinyls are the most common lacquers used in anti-corrosive maintenance finishes. Solutions of high molecular weight, vinyl chloridelvinyl acetate copolymers or terpolymers with vinyl alcohol or maleic acid, are used. Vinyls are distinguished by excellent acid and alkali resistance (their backbone being exclusively carbonkarbon bonds), good abrasion resistance and, when pigmented, excellent exterior durability. Vinyl films are attacked by the solvents from which they were cast (ketones, esters, etc.), also by concentrated organic acid, and softened by aromatics. They have low water and oxy. gen transmission rates, and are suitable for water immersion service. Acrylic films have even better resistance to ultraviolet Ilght than the vinyls, and show long-term gloss and color retention as well as good weatherability in exterior environments. They are more suitable for polymer modification than the vinyls, and copolymers of both acrylates and methacrylates are possible. Acrylics are also copolymerized with styrene and vinyl toluene. The introduction of such aromatics may slightly upgrade the acid and alkali Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 14
SSPC CHAPTER+L*2 93 = 86279YO 0003445 379 a resistance of acrylics, although the UV resistance is decreased. Styrene is also copolymerized with butadiene. These lacquers form films with better chemical resistance than the acrylics (all carbon-carbon backbones with the advantage of aromaticity), but aromaticity and unsaturation in certain species of these copolymers give poorer UV resistance. Chlorinated rubber coatings have perhaps even lower moisture and oxygen transmission properties than the vinyls, and the absence of pendent ester groups provides better chemical resistance than the acrylics. Solvent resistance is not as good as the vinyls, but chlorinated rubber has better compatibility with other film formers than have the unmodified In any lacquer, care must be taken with selection of additives and modifiers (such as plasticizers) to suit the re quirements of the environment. Where high alkali resistance is required, hydrolizable plasticizers (phthalates, etc.) are best avoided. The inert chlorinated paraffins are widely used with thermoplastics. Tricresyl phosphate is often used with vinyl systems. Because of the finite viscosity limitations of high molecular weight thermoplastics, high-solids lacquers are not possible. By judicious formulation with slow to medium evaporating solvents and efficient thixotropes, however, high-build thermoplastics (vinyls, chlorinated rubbers) are quite possible and widely used. Numerous other thermoplastics which can be employed in maintenance systems are beyond the scope of this chapter, although reference to their chemical structure will give a good general guide. Further data and case histories may be obtained from the respective resin manu fact urers. All thermoplastics display a glass transition temperature (Tg), and will flow at high enough temperatures, becoming soft and tacky. Heat resistance may be somewhat limited, and at low enough temperatures, the coatings will become brittle with reduced physicals. B. LATEX Latex systems show every possibility of expanding in. to the maintenance painting area as technologies dgvelop. Unlike lacquers, latexes are dispersions (not solutions) of thermoplastic polymers in water. Molecular weights are not restricted by solution viscosities, and much higher solids of very high molecular weight polymers are possible. Film formation involves evaporation of water followed by coalescence of discreet particles of polymer (micelles)
dispersed in the water. Total coalescence has never been and systems give higher moisture and oxygen transmission rates than their lower molecular weight analogues cast from solution. Great strides are being made and their excellent durability and mechanical properties indicate a bright future for latex maintenance systems in moderate environments. The PACE program of SSPC has included the evaluation of many water-based systems. C. OXIDIZING SYSTEMS Oxidizing systems are thermosets which convert to three-dimensional polymeric networks by absorption of atmospheric oxygen. Such systems are based on fish and vegetable oils (esters of glycerol and vegetable oil, fatty acids) or modification of such materials with other species. Unmodified oils are rarely used now except in certain specialized primers. They are slow drying and suscep tible to alkalis, but have excellent low surface energies and are perhaps the best vehicles where surface preparation is poor. Alkyds are oxidizing systems, the polycondensation products of multi-functional polyols and di-functional acids which are generally oil modified to give a wide variety of vehicles. Alkyds may also be copolymerized with phenol, silicones, styrene, acrylics and other resins. Still the backbone of the coatings industry, alkyds have limited applications in heavy-duty maintenance. As with oils, the ester groups in the alkyd backbone are easily cleaved by alkalis. Chemical resistance is poor, .and they are not suitable for immersion service, cementitious substrates, or for use directly over zinc-rich primers. They lend themselves well to polymer modification and may be used with certain thermoplastics to provide increased gloss and adhesion. Alkyds make an excellent choice of vehicle in lightduty environments. Thirty percent silicone modification provides finish coats that have excellent ultraviolet light resistance and exceptionally good weathering properties. More alkali-resistant oxidizing vehicles are obtained with the phenolic varnishes and epoxy esters (epoxy resins esterified with oil fatty acids). Both vehicles have better chemical resistance than either the unmodified oil or the analogous alkyd, and, as phenolic or epoxy content of such resins increases, so does their chemical resistance. Unfortunately, as with all epoxies, epoxy esters yellow and chalk markedly during exterior exposures, and while deterioration is not progressive, chalking restricts usage on aesthetic grounds. Epoxy esters are hard, resistant to abrasion, and soluble in aromatic and even aliphatic hydrocarbons. Replacing the dibasic acid with a polyisocyanate, the alkyd becomes an oil-modified urethane or uralkyd. Ester linkages are replaced by urethane linkages, and chemical and physical properties are again upgraded. Like epoxy esters, uralkyds both yellow and chalk on exterior exposure, and are difficult to recoat. D. CHEMICALLY CURING THERMOSETS Oxidizing systems are a special case of thermosetting
vehicle, where the activator is supplied by the environment. In other cases, water from the air will cure the vehicle. In baking finishes (e.g. alkydlamino) both reactive oligomers are added to one can, but are selected so that Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 15
SSPC CHAPTER*L.Z 93 8627940 0003446 205 the reaction will only occur when the system is applied as a film and subjected to high temperatures (180-400°F depending on vehicle type). More commonly, maintenance painting systems are designed so that reactions occur at room temperature. Reactive vehicles are packaged separately and combined in the field just before application. Of these two-package systems, the two most important are epoxies and polyurethanes. The properties of both systems are related to the chemical constitution of the reactants. Epoxies are less complex than polyurethanes because of the more limited choice of reactants. Epoxies are available in molecular weights ranging from materials which are liquid at room temperature to high molecular weight materials which may themselves be used without crosslinking as lacquers. The epoxy resin is most commonly cured in the field with polyamines or polyamides. With a given epoxy, polyamines produce a tighter crosslinked film having greater chemical resistance, hardness, and cure response than the same resin cured with a polyamide. The polyamides give better flexibility, water resistance and exterior durability. As a molecular weight (distance between reactive Oxirane groups) of the epoxy resin increases, the cured material becomes more flexible, but poorer in solvent res istance. In general, epoxies show excellent adhesion, good chernical resistance, especially to alkalis, and good solvent resistance. Epoxies have less acid resistance than vinyls and chlorinated rubbers, but show good abrasion and impact resistance. Exterior durability is hampered only by a tendency to chalk and yellow, which is not progressive and does not affect resistance properties. Chalk resistant epoxies with good color retention are now availableJ5. Because of the variety of possible epoxy resins and curing agents, performance capabilities will vary widely from one product to the nextJs. With certain coal-tar pitches, epoxy systems give synergistically improved coatings, which, at 16-20dry mils or so, give good protection against moisture and oxygen transmission, chemical attack and physical abuse. They are ideal coatings for areas with restricted access after application. Polyurethane systems have an even wider variety of possible reactants. While polyisocyanates are generally limited to adducts of toluene diisocyanate or hexamethylene diisocyanates, polyols used in the formulation are exceptionally varied. Almost any resinous material having di- or poly-functionality based on a hydrogen donor will react with isocyanates, although -OH functionality is most widely used in coatings. The opportunities for molecular engineering with the urethane (and its associated groups, ureas, substituted ureas, allo-
phanates, biurets, etc.) are much greater than with other types of vehicles. Hydroxy-terminated polyesters and acrylics, epoxies and other polyethers, phenolics, polycaprolactams, cellulosics, and even alkyds are all possible hydrogen donors. The urethanes may range from hard, chemically resistant finishes, to soft rubbery finishes having good abrasion resistance. Toluene diisocyanate coatings give exceptional chemical and abrasion resistance, while hexamethylene diisocyanate systems have exceptional light and weather resistance, and despite high costs are finding ever increasing markets. Urethanes show better curing properties at low temperatures than do most epoxies, but specific properties will depend greatly upon the type of modifier selectedJ7. VI. PIGMENTS IN ANTICORROSIVE FINISH COATS Pigments for finish coats must also be chosen with care. Some common types are discussed in a separate chapter. Alkaline pigments (calcium carbonate, ultramarine blue, etc.) must not be used in acidic environments, and alkalis will attack alkali-sensitive pigments (chrome yellow, iron blue, etc.). Metallic pigments may be attacked at either extreme of pH, but, used in flake form in neutral environments, reduce the moisture and oxygen transmission. Aluminum and stainless steel flakes are also ideal for high temperature coatings. Other inert finishes may be employed with nickel titanate, chromium green oxide, titanium dioxide, iron oxide (brown) and a range of calcined pigments based on mixed inorganic oxides. If both the environment and the chemistry of the pigment are understood, design error can be avoided, and pigmentation can assist the polymer in providing the necessary protection against the environment. Thus, pigments may actually improve the ultraviolet resistance of the vehicle, its resistance to microbiological and biological agents such as marine foulants and mildew, and its physical properties. Inert extenders may be used to advantage in finish coats to adjust the p.v.c./c.p.v.c. ratios, at less cost than prime hiding pigments. Pyrogenic and ultrafine silicas may also be used as thixotropes and flatting agents. VII. CONCLUSION: The design of effective anticorrosive coatings for steel structures is a complex discipline that borrows extensively from both corrosion science and coatings technology. Unhappily, all too often there is too little communication between these parent technologies and fewer attempts by scientists and engineers of either practice to cross the interface and assess the same problem from the other s perspective. If we are to serve our respective disciplines to mutual benefit in our avowed war on corrosion, a more intensive effort to appreciate the problems involved on both sides of
the interface is required of us all -corrosion engineer and paint chemist alike. A desire to foster such effort has been the driving force behind the presentation of this chapter. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 16
SSPC CHAPTER*1-2 93 m 8627740 0003447 141 m TABLE 1 SOME PROPERTIES OF FINISH COAT MATERIALS FOR EXTERIOR EXPOSURE Oil Paints FFPFGFFFPPPF Oil Paints Alkyd-LongOil F F P F G F G F P P F F Alkyd-LongOil Alkyd-MediumOil F F F F F G G F P F F F ' Alkyd-MediumOil Alkyd-SM Oil GPFFFGGFPFFF' Alkyd-ShortOil Alkyrhstyrenated F G F F F F G F F P F P ' Alkyd Styrenated Alkyd-Siliconized F G F F E E E F P F F VG ' AlkyrhsiIiconized Alkyd-AminoComb. E G G G G G G G G G E G * Alkyd-AmimCmb. Silicone GFFFEEEGGFGE Silicone Siliconized Polyester E E E G E E E E G G E E ' Siliconized Pdyester Thermoplastic Acrylic F G F G E E E G G P F P ' Thermoplastic Acrylic ThermosettingAcrylic E G G G E E E G G E G G ' Thermocetting Acrylic Acrylic Latex P E F P E G E F F F F P Acrylic Latex Fluorocarton E E E E E E E E VG E E E * Fluorocarton Epoxy-Polyester E G G G E E G G F G E G Epoxy-Polyester Epoxy-Phenolic E F G G P P P E E E E G ' Epoxy-Phenolic Epoxy-Amine EFGGGPPGEEEF Epoxy-Amine Epoxy-Amide E G G G G P P G VG VG E F Epoxy-Amide Epoxy Ester GGFFFPPFFGGF' Epoxy Ester UrethaneOil Modified G G G F P P P F P F F F Urethane01Modified UrethaneMoistureCure G E E G F F P G G G G F UrethaneMoistureCure UrethaneAliphaticTwo Pack E E E G E E E E E E E G ' UrethaneAliphaticTwo Pack UrethanekomaticTwo Pack E E E G F F P E E E E F ' UrethaneAromaticTwo Pack Vinyl Lacquer G E G E E E E E E F E P ' Vinyl Lacquer ChlorinatedRubber G G G Ë G G G E E P E P Chlorinated Rubber Styrene Butadiene G G G G G G G E E P E P Styrene Butadiene Asphaltics PGFEG--G G F E P Asphaltics Coal Tar FGFEP--G G F E P Coal Tar Coal Tar-Epoxy G F E E F --V G E G E P Coal Tar-Epoxy Key: E = Excellent VG = Very Good G=Good F = Fair P = Poor BIOGRAPHY ACKNOWLEDGEMENT Clive H. Hare of Coating The author and editors gratefully acknowledge the active System Design, Inc. has been participation of the following in the review process for this Editor of the Mate rials Technolchapter: Ted Dowd, Jarry Drake, Dick Drisko, Arnold Eickhoff, ogy section of the Journal of ProHarlan Kline, Frank LaQue, Bob Martell, William Mathay, John tective Coatings an d Linings Montle, Chuck Munger, Bruno Perfetti, Percy Pierce, E. Praschan, since 1989. In his work as a conMelvin Sandler, Ron Skabo, William J. Wallace, Jr., and Harry sultant, after hav ing spent ten Wonders. years as chief chemist of Cadillac Paint Ei Varnish, Hare has developed anti-corrosive coatings and coatings specifications for many organizations, such as
raw materials suppliers, the military, NASA, and highway departments. Among his numerous publications are Units 26 and 27 of the original FSCT Series on Coatings Technology (Corrosion and the Preparation of Metals for Painting and Anti-Corrosive Barriers and Inhibitive Primers); "Specific Utility in the Design of Coatings Systems for Steel Bridges," JPCL, October 1984, for which he won SSPC's Annual Publication Award; and the recently issued book, The Painting of Steel Bridges, a synthesis of highway practice emanating from his work for the Transportation Research Board. He is an active member of the National Association of Corrosion Engineers (NACE). --`,,,,`-`-`,,`,,`,`,,`--17 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERaL.2 93 8627940 0003448 088 M REFERENCES 1. L.I., Shreir, Corrosion Vol. 2, p.15.26 Wiley, New York, 1963. 2. C.H. Hare, Anti-Corrosive Barrier and Inhibitive Primers Unit ?7 Federation Series on Coatings Technology, Federation of Societies for Coatings Technology, Phila., 1979. 3. C.H. Hare, Corrosion and the Preparation of Metals for Painting Unit 26 Federation Series on Coatings Technology, Federation of Societies for Coatings Technology, Phila., 1978. 4. K.W. Allen, Strength and Structures Aspects of Adhesion Vol 1, 14, University Press of London, 1965. 5. T.R. Bullet and A.T.S. Rudram, J.O.C.C.A. 11, 1959, 789. 6. J.E.O. Mayne, Official Digest, 24, 325, 127, 1952. 7. D.M. MacDonald, Official Digest 33, 432, 7, 1961. 8. Pittsburgh Society for Paint Technology, Official Digest 33, 436, 1427, 1961. 9. W.W. Kittelberger and A.C. Elm, Ind. Eng. Chem., 44, 326, 1952. 10. J.E.O. Mayne, Br. Corr. J., 5, 106, 197.0. 11. J.E.O. Mayne and D.J. Mills, J.O.C.C.A., 58, 155, 1975. 12. C.C. Maitland, Ph.D. Thesis U. of Cambridge, England, 1959. 13. B.W. Cherry and J.E.O. Mayne, Official Digest, 33, 435, 469, 1961. 14. G.W. Raothwell, J.O.C.C.A., 52, 219, 1969. 15.. B.W. Cherry and J.E.O. Mayne, Sec. Int. Congress on Metallic Corrosion (N.Y.) 680, 1966. 16. J.D. Keane, W. Wettach and C. Bosch, J.P.T., 41, 533, 372, 1969. 17. A.W. Peabody, Principles of Cathodic Protection, NACE Basic Corrosion Course National Association of Corrosion Engineers, Houston, 1974. 18. M.J. Stern of Electrochemical Soc., 105, 11, 638, 1958. 19. A.J. Eickhoff, Am. Paint Journal, July 16, 1973, p54. 20. M. Kowalik, N. Intorp and N. Lange, 7th Int. Cong. on Metallic Corrosion, Rio de Janeiro, Brazil, 1978. 21. C.G. Munger, Mat. Perf. 14, 5, 25, 1975. 22. T. Ginsberg, C.N. Merriam, L.M. Robeson, J.O.C.C.A., 59,315, 1976. 23. D.M. Berger, Modern Paint and Coatings, June 1975. 24. D.M. Berger, Metal Finishing, 27, 1979. 25. G.H. Law, W.M. McMahon, US. Pat. 3,615,730 and 3,653,930. 26. G.H. Law, W.M. McMahon, Dutch Pat., 6,900,749. 27. A. Oken, U.S. Pat. 3,660,119. 28. M. Tellor, Mat. Perf., 17, 9, 37, 1978. 29. K.B. Tator, Mat. Perf. 15, 3, 9, 1976. 30. D.M. Berger, Modern Paint and Coatings, October 1980. 31. F.A. Simko, Jr., V.P. Simpson, J.C.T., 48, 614, 61, 1976. 32. R. Cressey, Bath Iron Works, Private Communication. 33. D.M. Berger, Metal Finishing, April 1978. 34. C.H. Hare, J.P.T. 47, 605, 69, 1975. 35. R.G. Young, J.C.T., 49, September 1977. 36. D.M. Berger, PDCA, November 1976. 37. D.M. Berger, Modern Paint and Coatings, July 1981. 18 --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with
SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*2.0 73 8627740 0003447 TL4 September 1993(Editorial Changes) CHAPTER 2.0 SURFACE PREPARATION by H. William Hitzrot I. INTRODUCTION It is widely recognized that surface preparation is the most Important single factor in coating performance. As our knowledge of the relationship. between coating and metal substrate expands, so also does the need for improved and varied surface preparation techniques. This series of chapters represents the current state of the art and covers most aspects of industrial applications of mechanical surface preparation. Chapter 2.1 Centrifugal Blast Cleaning Chapter 2.2 Metallic Abrasives Chapter 2.3 Non-Metallic Abrasives Chapter 2.4 Abrasive Air Blast Cleaning Chapter 2.5 Water Blast Cleaning Chapter 2.6 Hand and Power Tool Cleaning Chapter 2.7 Field Surface Preparation Costs Chapter 2.8 Other Methods and Factors in Surface Preparation Chapter 2.9 Chemical Cleaning in the Field Pickling is described in a separate chapter. The chapters were authored by recognized authorities and cover not only the methods of surface preparation but also equipment, types of abrasive, surface preparation cost and some future alternatives. They provide up-to-date information on mechanical surface preparation with a ready reference and background for ChOOSinQ the proper technique for a given job. For those experienced in the field this material not only reviews techniques but offers possible solutions for some of the out of the ordinary surface preparation jobs as well. Each mechanical method is described in detail together with recommended applications and examples. Also included are types of equipment and anticipated performance criteria. Both metallic and non-metallic abrasives are discussed. The various abrasives available are described along with recommended applications for these abrasives.
Reference is made to a number of specialty abrasive products and their applications. Surface preparation costs are discussed as a separate section, providing the reader with one means of comparison among the various approaches to mechanical surface preparation. These chapters cover those methods of surface preparation requiring mechanical force as well as the related equipment, abrasive materials, and costs. Mechanical methods include hand and power tool cleaning, centrifugal wheel blasting, compressed air blasting, high-pressure water blasting and high-pressure blasting with a mixture of water and sand. II. DISCUSSION Mechanical surface preparation has been the traditional approach to preparing metal substrates for subse quent coating systems. Surface preparation methods vary from the most rudimentary hand scraper to laser beams. The broad spectrum of tools available suggests that surface preparation is in fact a complex process and therefore requires a good understanding of the mechanical surface preparation process and job parameters that dictate the process. As an aid in selecting the proper mechanical surface preparation process, the following brief discussion of job parameters and associated techniques is provided. A. LOCATION OF JOB Although often not considered, the location of a job is an important parameter in the selection of a surface preparation method. If the job is on a production line, then an automatic operation such as a centrifugal wheel machine should be considered. On the other hand, outside fabrication, maintenance or repair jobs generally call for portable hand and power tools and manual sand blasting. If the job is located in an area where soluble salts could be a surface contaminant, such as near the ocean or in an industrial atmosphere, then wet blast cleaning may be preferable. B. CONDITION OF SURFACE The surface preparation method selected will depend on the condition of the surface to be cleaned. For example, is it coated, rusted, painted, or coming directly from the mill? Scaled and rusted surfaces are best cleaned by any of the mechanical methods that employ an abrasive medium. Painted surfaces can be cleaned by hand or with power tools to remove loose paint. For more extensive cleaning of painted surfaces, an abrasive blast cleaning method can be used. Steel coming directly from the mill is usually cleaned by means of production line centrifugal wheel machines. C. DEGREE OF CLEANLINESS The required degree of cleanliness as defined by the SSPC Surface Preparation Specification is a determining factor in the method of cleaning. Hand tool and power tool specifications apply only where localized surface prepara-
Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 19
SSPC CHAPTERsZ-0 93 m 8b27940 0003450 736 m tion is required, as in the removal of loose paint, loose rust, or other localized surface defects. Blast cleaning specifications usually cover applications where the entire surface is to be prepared to a defined degree of cleanliness. D. PHYSICAL VERSUS CHEMICAL CLEAN LIN ESS. Studies by R. Allen and A. McKelvie2, confirmed by SSPC3, show that residual chemical contaminants may be a greater threat to a coating system than physical surface imperfections. According to these studies, ordinary abrasive blast cleaning techniques do not remove nonvisible contaminants such as salts from a rusted, contaminated surface. Methods such as high-pressure water blasting and high-pressure water-abrasive blast cleaning have proven more effective in removing such surface contaminants. A further discussion of water blasting is given in the subsection dealing with water blast cleaning. E. PROFILE The surface finish (or profile) resulting from surface preparation should be compatible with subsequent coating or finishing steps. If the final coating is two mils or less, the surface finish should be finer than if a heavy coating were required. Ideally, test panels prepared prior to the start of a job offer the best method for testing the adequacy of a chosen surface finish. A report is available from the SSPC on profile, its formation, its measurement, its control, and its effect on coating performance4. Most coating manufacturers recommend a degree of cleanliness and a minimum etch or profile for good coating adhesion. When .choosing a mechanical surface preparation method, one should take into consideration the compatibility of the subsequent coating. To aid in selecting the proper abrasive for a given surface profile or etch, Table I is provided as a guide. F. ENVIRONMENTAL CONSTRAINTS In recent years environmental constraints have played an ever larger role in the selection of surface preparation methods. To minimize dust, cheaper sands are being replaced by costlier and less abundant products such as boiler slags or copper slags. Also, enclosed rather than open blasting is being favored. If enclosed blast cleaning is necessary, consideration should be given to recyclable steel abrasives and automated centrifugal wheel blasting TABLE 1 Typical Profiles Produced by Some Commercial Abrasive Media Maximum Typical Profile Height, (mils) U.S. Sieve Average
Size Maximum Maximum Steel Abrasives Shot Shot Shot Shot Grit Grit Grit Grit
5-230 20 2.9 f 0.2 2.2 f 0.3 S-280 18 3.5 f 0.3 2.5 f 0.4 S-330 16 3.8 f 0.4 2.8 f 0.5 S-390 14 4.6 f 0.5 3.5 f 0.7 G-50 30 2.2 f 0.3 1.6 f 0.3 G-40 20 3.4 f 0.4 2.4 f 0.5 G-25 16 4.6 f 0.5 3.1 f 0.7 G-14 12 6.5 f 0.8 5.1 f 0.9
Mineral 81Slag Abrasives Heavy Mineral Sand Medium-Fine 3.5 f 0.4 2.6 f 0.4 Flint Shot Medium-Fine 3.5 f 0.4 2.7 f 0.4 Silica Sand Medium 4.0 f 0.5 2.9 f 0.4 Boiler Slag Medium 4.6 f 0.5 3.1 f 0.5 Boiler Slag Coarse 6.0 f 0.7 3.7 fi 0.7 Stau rol ite Medium-Fine 2.6 f 0.4 2.2 f 0.4 Copper Slag (Air-Cooled) Coarse 6.0 f .7 5.5 f .5 Copper Slag (Air-Cooled) Medium 4.5 f .5 4.0 f .5 Copper Slag (Air-Cooled) Medium-Fine 3.5 f .5 3.0 f .5 Copper Slag (Air-Cooled) Fine 2.5 f .5 2.0 f .5 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*2.0 73 8627740 0003453 672 machines. To minimize subsequent environmental prob-BIOGRAPHY lems, one should investiaatethe environmental imDact of a given surface preparation mechanism. This subject is ex-Bill Hitzrot is an activ e member of the Steel Structures plored in a separate chapter on other surface preparation Painting Council and c urrently methods. This chapter is also available for those who have chairman of the Abras ives Comdifficult or unique cleaning problems or ones that require mittee. pent 31 years with Bethlehem Steel, initially in the a novel approach. Research Department and then with a business unit developing and then manufacturing steel abrasives. Currently, Bill is Vice ACKNOWLEDGEMENTS President of Chesapeake The author and editors gratefully acknowledge the active Specialty Products, Inc ., a participation of the following in the review process for this manufacturer of st eel abrasives. chapter: William Chandler, Ted Dowd, Richard Drisko, M. He is actively involved in the abrasives industry. Lichtenstadter, A.W. Mallory, Marshall McGee and William Pearson. REFERENCES 1. J.R. Allen and C. Calabrese, Corrosion, pp. 331-338, Vol. 34, No. 10, Oct. 1978. 2. A.N. McKelvie, Evaluation of Various Cleaning Processes for Steel , Paint Research Association, Waldegrove Rd., Teddington Middlesex, TW11 8LD, England. 3. J.D. Keane, J.A. Bruno and R.E.F. Weaver, Surface Profile for Anti-Corrosion Paints , Steel Structures Painting Council, 1976. 4. Keane, et. al. 21 --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*Z=L 93 W 86279YO 0003Y52 509 W CHAPTER 2.1 MECHANICAL SURFACE PREPARATION CentrifugaI Blast Cleaning by A. W.Mallory Centrifugal blast cleaning relates, not only to clean- Among the most prominent applications of centrifugal ing structural steel, but to a wide range of applications blast cleaning is surf ace preparation of structural steel for that include etching, deburring, deflashing, texturing, shot painting. Centrifug al blast cleaning of structural steel peening, cleaning and descaling. It is typically used for machine parts, castings, forgings, steel mill rolls, steel plates and shapes, fabricated units, molded plastic and rubber parts, cut stone and acoustical ceiling tile. The list grows annually as new applications are discovered, as costs of other means become prohibitive, and as pressures increase from OSHA, environmentalists and ecologists. The art of air blasting began prior to the turn of the century, but centrifugal (airless) blast cleaning, since its introduction in 1932, has emerged as an efficient process for ever increasing types of applications. --`,,,,`-`-`,,`,,`,`,,`--FIGURE 1 FIGURE 2Centrifugal Blast Wheel; Development of Blast Pattern. Centrifu gal Blast Wheel; Abrasive Feed and Blast. Courtesy of Wheelabrator-Frye Inc. Courtesy of Pangborn. 22 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
RECOMMENDED BLAST PATTERN FOR TYPICAL continuous surface preparation and paintin g systems, FABRICATED BEAM including air blast enclosures for touch-up blasting. Centrifugal blast cleaning machines are used in most steel fabrication shops. Traditionally, the process has been limited to installa tions in fabricator shops. However, portable systems recently have been developed to provide on-site, dust-free cleaning of structures, such as storage tanks and ships, during construction as well as maintenance. Portable systems are economical and environmentally acceptable. Mobile (transportable) systems also have been developed for surface preparation prior to steel coating at construction sites. Major advantages of centrifugal blast cleaning, compared to airblast cleaning, are savings in time, labor, energy and abrasive consumption. A further advantage is automation of the cleaning operation, which provides superior, more uniform cleaning of steel and more acceptable environmental operating conditions. 30 -MINIMUM EFFECTIVE ANGLE OF IMPINGEMENT FIGURE 3 Typical Blast Pattern; Wide Flange or Fabricated Beam (4 Blast Wheels). Courtesy of Pangborn. dates back to the late 1940 s and, of steel for major construction projects, to the middle 1950 s. Since then, centrifugal blast systems have been developed for cleaning structural steel before and after fabrication, including massive fabrications of irregular shapes and complex construction. Machines are often integrated into in-line , @l WHEEL UNIT i ~2 CABINET ,Y,_, FIGURE 5 Airwash Separator System. Courtesy Wheelabrator-Frye, Inc. 5DUST I. PRINCIPLES OF OPERATION Centrifugal blast cleaning machines use motordriven, bladed wheels to hurl abrasive at the surface by centrifugal force. The abrasive used for structural steel
cleaning consists of tiny particles of alloy steel, generally ranging in size from 0.005 to 0.040 inches in diameter. These particles, unlike sand, resist fracturing despite repeated impacts at high velocity. Abrasive is fed to the center of the wheel and moved onto the inner end of the blades by an impeller. As abrasive particles move down 4 ABRASIVE CLEANING & RECYCLING the blade (Figure l), they are accelerated and h urled at high velocity at the surface. Centrifugal blast wheels are FIGURE 4 Blast Cleaning Machine. available in several sizes and may be equipped with driv e Courtesy of Wheelabrator-Frye, Inc. motors of up to 100 hp (horsepower) for high production Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 23
SSPC CHAPTER*Z.L 93 ab27940 0003454 3ôL DESCALING MACHINE ABRASIVE REMOVAL SECTION EXIT ROLL CONVEYOR DRAG CHAIN CONVEYOR DRAG CHAIN CONVEYOR FIGURE 6 Pre-Fabricating Descaiing and Painting System. Courtesy of Wheelabrator-Frye, In c. applications. Generally, motor sizes of 15 to 60 hp, with wheels ranging from 15 to 20 inches in diameter, are used for structural steel cleaning. Until recently, under average operating conditions, velocities of the abrasive from the airblast nozzle or the airless wheel were similar, about 14,000 feet per minute (fpm). For special applications the velocity can be decreased by reducing air pressure to the nozzle or cutting the rotational speed of centrifugal units. New develop ments in centrifugal blast units have increased abrasive velocities to 18,000 -19,000 fpm, with impressive cleaning results. Since work accomplished is based on the familiar formula -, where M = MV2 2 mass and V = velocity of the abrasive particles, it is easy to visualize the effect obtained when the velocity component (V) is increased. FIGURE 8 Pre-Fabrication Descaling System (4 Blast Wheels); Cleaning of Small Parts on Racks. Courtesy of Pangborn. Because blast cleaning*results depend on volume or mass (M) of abrasive particles impinged against the surface per unit of time, additional horsepower also can be used to increase the volume of abrasive being thrown and to inI i 4 FIGURE 7 Pre-Fabrication Descaling System Channels-Prior to and After Blast Cleaning. Courtesy of Wheelabrator-Frye, Inc. --`,,,,`-`-`,,`,,`,`,,`--ClAl&&*L * crease the blast cleaning rate. Centrifugal blast cleaning machines incorporate one or more wheel units, positioned so the abrasive blast will reach the entire surface. Generally, the abrasive from each Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 24
SSPC CHAPTERx2.1 93 8627940 0003455 218 ROOF SLOT FOR OVERHEAD CONVEYOR OR CRANE --`,,,,`-`-`,,`,,`,`,,`--__---Y ~-~FIGURE 9 Post-Fabrication Descaling System. wheel is thrown in a fan-like pattern (Figure 3) covering an area about 3-4 inches wide and 36 inches long. The number of wheels needed is determined by the size, complexity and shape of the surface. Cleaning can be accomplished in one loadinglunloading cycle or, in the case of structural steel surface preparation, in one pass through the machine. Rate and degree of cleaning will vary depending on the number of wheels used and the size, type and quantity of abrasive. The nature of the material to be cleaned and other variables also must be considered. Specifications for the machine selected should be based on analysis of present and future surface preparation requirements, in terms of work size and production volume. Although larger and smaller machines are available for particular needs, a typical structural steel blast cleaning machine generally has a combination of four to eight wheels (Figure 4). If each wheel unit is powered by a 30 hp motor, a four-wheel cleaning system has the capability to propel approximately 3,200 pounds of abrasive per minute. An airblast cleaning operation would require forty-four 318-inch diameter nozzles and a 3,000 hp air compressor to equal this abrasive capacity. Courtesy of Wheelabrator-Frye, Inc. Essential components of all centrifugal blast cleaning systems are blast wheels, blast enclosure, work conveyors, abrasive recovery and recycling system, and dust collector (Figure 4). The type and arrangement of components will differ greatly, depending on application of the system. It is essential to provide sufficient ventilation to ensure that air pressure within the blast enclosure is lower than the ambient pressure. That allows dust generated by the blast cleaning to be drawn into the dust collector and prevents it from escaping from the blast enclosure into adjacent work areas. Openings provided for conveying the work through the blast enclosure must be equipped with good seals to prevent flying abrasive and dust from escaping. Spent abrasive thrown by the blast wheels drops into hoppers beneath the blast chamber. There it is recovered and conveyed to an abrasive reclamation system, where contaminants are removed in an air-wash separator (Figure 5) and reclaimed abrasive is returned to a storage
hopper. From there it is again fed to the wheels. Dust is drawn from the machine into a dust collector, keeping adjacent areas clean and dust-free. 25 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*2*L 93 W 8b27940 000345b 154 W II. PRE-CONSTRUCTION (SHOP) CLEANING A. PRE-FABRICATION SYSTEMS Systems designed to clean plate and structural members prior to fabrication will generally include a loading conveyor, possibly equipped with a drag chain loading table; a centrifugal blast machine; and an exit conveyor, which also may include a drag chain table for clean steel storage. Depending on requirements of the individual fabricator, the system also may include a paint spray booth and a drying oven (Figure 6). Prefabrication systems normally are equipped with roll conveyors. Illustrations of channels before and after blast cleaning are shown in Figure 7. Parts, which because of size or shape cannot be passed through the machine onto the rolls, may be placed on racks or screens as shown in Figure 8. FIGURE 10 Post-Fabricating Descaling System (8 Blast Wheels). Rack Loading -Gantry Crane Conveyor. Courtesy of Wheelabrator-Frye, Inc. Aside from reduced cleaning time obtained with automated cleaning systems, there are several advantages of cleaning steel prior to fabrication. They include: 1. Inspection of cleaned steel for defects revealed by the blast. 2. More accurate layout for fabrication operations. 3. Faster steel cutting and burning. 4. Improved tool life (punches, shears, saws, etc.). 5. Improved weld quality. 6. ~ l ior ~ i ~ ~ ~ ~ reduction of blast cleaningafter fabrication. A thin-film primer can be applied in line with the blast machine to minimize rustina durina fabrication. Opera--`,,,,`-`-`,,`,,`,`,,`--FIGURE 11 Post-Fabricating Descaling System (8 Blast Wheels); Rack Loading; Drag Chain Work Car Conveyor. Courtesy of Wheelabrator-Frye, Inc. FIGURE 12 ~~ Post-Fabricating Descaling System (8 Blast Wheels); Roll Conveyor. Courtesy of Pangborn.
Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 26
SSPC CHAPTER*Z-L 93 m 8627940 0003457 090 = FIGURE 13A Post-Fabrication Descaling System (Roll Conveyor); Entry Conveyor-prior to blast cleaning. Courtesy of Wheelabrator-Frye, Inc. tions such as welding, burning and punching can be performed without removing primer. Minimal touch-up is required before applying the final prime coat. Depending on the type of primer, a drying oven may also be required. There are fast-drying primers available that do not require a post cure at elevated temperatures, and, in lieu of a drying oven, a flash-off tunnel at the paint booth exit may be required to exhaust volatile paint fumes. B. POST-FABRICATION SYSTEMS A post-fabrication cleaning system (Figure 9) can clean external surfaces of a wide variety of fabricated sections, including massive girders and trusses for highway, power plant and industrial building construction. Post-fabrication systems generally include: a work conveyor of one of the following configurations: bridge crane; gantry crane; work car; and roll conveyor. an eight-wheel cabinet to accommodate work to be blast cleaned and a selected conveyor system. optional movable wheels to eliminate work-piece turnover. optional air blast unit for touch-up. In post-fabrication blast cleaning systems the blast chamber design may have a slot in the roof for a monorail, bridge crane or gantry crane conveyors (Figure IO),since many fabricated members cannot easily be conveyed on roll conveyors or work cars. Also, the machine generally is FIGURE 138 Exit Conveyor-after blast cleaning. Courtesy of Wheelabrator-Frye, Inc. located where crane access is required for other operations. If most of the work involves bridge girders, a work car system may be necessary with an overhead crane. This work may be extremely long and often will have a camber or slight curve. A push-pull, drag chain arrangement with
variable speed drive provides power to work cars (Figure 11). FIGURE 14 Post-Fabrication Descaling System (8 Blast Wheels); adjustable wheels to accommodate deep girders. Courtesy of Wheelabrator-Frye, Inc. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 27
SSPC CHAPTER*Z.L 93 8627940 0003458 T27 = Ship Hull Bottom Cleaning System: Two Wheel Blast Head Units in Foreground. (Official U.S. Navy Photograph) Racks can be mounted on work cars for stacking and hooking of miscellaneous structural members. The racks can be pre-loaded so the shop can take maximum advantage of the cleaning time available. A roll conveyor is the most economical way of handling structural steel. Use of a roll conveyor system (Figure 12) with an eight-wheel vertical cleaning machine offers a fabricator economical handling and efficient cleaning. (lllustrations of fabricated girders before and after blast cleaning are shown in Figures 13A and 138.) A multi-bay structural shop can use this system with the direction of the blast cleaning system either perpendicular to or in-line with the work flow by using drag chain tables for efficient work transfer to and from the conveyor at both sides of the machine. Steel that will not roll directly on the conveyor because of shape, size, or the presence of gusset plates, etc., can be placed in baskets or on racks that will support work through the blast cleaning machine. The combination of overhead and roll conveyor systems offers maximum flexibility to the shop that is engaged primarily in fabrication of steel for industrial and building applications. Generally, in an eight-wheel vertical design machine, five-to-six-foot high fabrications can be cleaned in a single pass through the machine. Machine designs also are available with moveable wheels to reduce handling of larger fabrications. Rather than turn deeper girders over, all eight wheels can be positioned upward, allowing the girder to be passed back through the machine to clean the remaining surface. All eight wheels must be moved to obtain the same degree of cleaning as during the first pass. Adjustment of wheels is illustrated in Figure 14 (also refer to Figure 9). 28 Shii, Hull-Side Cleaning System (Two Wheel Unit; 48 inch Cleaning'width). (Official U.S. Navy Photograph). Courtesy of Wheelabrator-Frye, Inc. c. SYSTEMS APPROACH TO EQUIPMENT SELECTION To achieve maximum savings from a centrifugal blast cleaning and painting system, the fabricating shop arrangement should be reviewed. Special tion should be given to the following areas: Shop layout and capability
FIGURE 17 Ship Deck Cleaning System (Two Wheel Unit; 48 inch Cleaning Width). (Official U.S. Navy Photograph). Courtesy of Wheelabrator-Frye, Inc. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER+Z.L 93 m 8627940 0003459 963 m DUST AND FIGURE 18 Portable Blast Cleaning System (Operational Schematic). Courtesy of Wheelabrator-Frye, Inc. Present and projected scope of production Cleaning and painting requirements Pre-fabricating de-scaling system Post-fabricating de-scaling system Selection of the blast cleaning machine depends on the configuration of the steel fabricated, cleaning requirements and shop layout. Most shops fabricate structural steel in one bay and bridge girders in another. Some have built separate shops due to the variation in methods of fabrication. A pre-fabricating cleaning system generally is located between the steel storage yard and the punch and drill operations, whereas a post-fabricating cleaning system is usually located in the painting and shipping area. In either case, it may be advisable to relocate the layout and fabrication to achieve efficient work-flow through the shop. Location of the blast cleaning system also may pose a problem in older structural shops planned prior to the advent of centrifugal blast cleaning. A systems approach to the selection of the blast cleaning equipment and work handling components results in a highly efficient, low cost surface preparation operation. Fabricators may be tempted to select centrifugal blast cleaning machines with a large number of wheel units with high horsepower to obtain fast cleaning speeds while neglecting thorough evaluation of work handling and auxiliary systems. The result can be an inefficient capacity to handle production capability of the blast cleaning machine. Cleaning costs can be reduced markedly by matching the throughput capability of the cleaning machine with existing, modified, or new work handling and other related systems. For either type of system, pre-fabrication or postfabrication cleaning, the evaluation of components blast cleaning machine, number and arrangement of centrifugal blast wheels, conveyor and work-handling mechanisms -presents an array of system combinations too numerous to discuss in this chapter. It is emphasized that work requirements must be thoroughly examined, and subsequent selection of equipment be based on use of the total system concept to obtain maximum efficiency and economy. FIGURE 19 Portable Cleaning System -with Auxiliary Dust Collector.(Steel Surface Parking Deck).
111. ON-SITE (PORTABLE) CLEANING Traditionally, airless centrifugal blast process has taken the form of fixed place equipment, with work to be cleaned brought to the machine. Applying the centrifugal wheel process to cleaning structures in place meant the traditional approach had to be reversed, ¡.e., it became necessary to take the surface preparation process to the work with a portable blast cleaning device. Development of portable, centrifugal blast cleaning systems dates back to the early 1960 s, but commercial application of such units first became reality in 1974. Since then, several systems have been developed and used for a wide variety of applications. For structural steel cleaning, applications presently include ship decks, ship hull bottoms and sides, storage tank exteriors (top and shell) and the wet side of tank bottoms. Machines are used during construction and for maintenance painting operations. Although many applications can be envisioned for portable centrifugal blast cleaning systems, the real impetus in the development of such systems was initiated Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 29
SSPC CHAPTER*Z.L 73 8627740 00034b0 685 FIGURE 20 Portable Cleaning System; Ship Deck Cleaning. (Official U.S:Navy Photograph) in the early 1970 s, the result of increasing pressure from environmentalists and OSHA, and emphasis on the need for more environmentally acceptable and economical alternatives to traditional, open airblasting. Most notably, the United States Navy became increasingly aware of this need because open airblasting of ship hulls and decks in drydock created huge quantities of dust that settled around the vessel and caused costly maintenance problems on board the ship and all over the shipyard. It also posed a major health (air pollution) hazard which had to be eliminated. In 1974 and early 1975 portable systems custom designed to Navy specifications were put into production first at the Norfolk U.S.Navy Shipyard for cleaning hull sides (Figure 16) and hull bottoms (Figure 15), and then at Long Beach US. Navy Shipyard for cleaning hull sides. These systems now are used routinely in ship hull maintenance painting operations. Machines incorporate one or two blast wheels and clean a swath approximately 28 and 48 inches wide, respectively. Similar but less costly and less complex systems are being developed for application on commercial and military vessels. A mobile, self-propelled centrifugal blast cleaning machine (Figures 17 and 20) for removal of heavy, anti-skid coatings from aircraft carrier decks was first put into service at Long Beach, California, in 1975. Like the hull bottom and side cleaners, two blast wheels are used to clean a 48-inch path. Smaller and more maneuverable companion machines subsequently have been put into routine service. Smaller units employ a single blast wheel and clean a swath 20 inches wide. In principle, the portable machines use the basic components required for stationary installation, ¡.e., the blast wheel, abrasive recovery and re-circulation, system ventilation, dust removal and collection and a work conveyor (Figure 18). In many applications, where small amounts of dust are generated during blasting or where minor dust effluent from the ventilationlcollector system is permissible, blast cleaning units are completely self-contained except for power supply. For applications where great amounts of blast residues are generated andlor where effluent dust cannot be tolerated, the total system includes a supplementary, large capacity dust collector (Figure 19). Portable blast cleaning units, the type illustrated in Figure 19, are used for the on-site blast cleaning of storage tank tops (both floater and cone). Similar equipment is be-
ing developed to clean the inside bottoms of the tanks. Modified versions of the basic blast machine also make it possible to clean the external surface of the tank shell. Smaller units, essentially hand-held, are being developed for touch-up blast cleaning of small areas and cleaning weld seams on horizontal and vertical surfaces. Cleaning rates obtained with portable units are many times greater than those produced by.airblast. Touch-up cleaning by airblast (or various types of powered hand tools) is required around narrow peripheral areas and protuberances. Otherwise, the operation is environmentally clean and economical. Because it is essentially an automated process, it provides greater consistency and uniformity of cleaning than airblasting does. REFERENCES 1. B. Baldwin, Methods of Dust-Free Abrasive Blast Cleaning. Plant Engineering, pp. 116-125,Feb. 16, 1978. 2. P.J. Bennett, Current Occupational Safety, Health, and Pollution Codes and Their Effect on Surface Preparation. Paper No. 46, pp. 1-9, 1973. 3. T.R. Bullett, Preparation and Protective Painting of Structural Steel. Corrosion Prevention and Control, Vol. 18, pp. 8-12, 1971. 4. Centrifugal Wheel Blast Cleaning of Steel Plate, Shapes and Fabrications, NACE Publication 6G-174, Materials Performance, June, 1974. 5. B. Cromwall, L. Thureson and V. Victor, Centrifugal Blasting of Steel: Cleaning and Coldworking. Swedish Corrosion Institute Bulletin, No. 67, 1971. 6. Impact Finishing: Synthetic Abrasives Erode the Natural Markets. lnd. Materials, No. 121, pp. 19-21, 23, 25-27, 29, 31, Oct., 1977. 7. A.W. Mallory, Centrifugal Blasting for Surface Preparation, Society of Manufacturing Engineers, Technical Paper MR79-764, 1979. 8. A.W. Mallory, Centrifugal Blast Cleaning of Surfaces for Painting, Materials Performance, Vol. 16, No. 2, pp. 11-17, February, 1977. 9. National Association of Corrosion Engineers Committee T6-6-13, Cleanliness and Anchor Pattern Available Through Centrifugal Blast Cleaning of New Steel. Materials Protecfion, Vol. 15, No. 4, pp. 9-13, April, 1976. 10. F.A. Scrima and A.W. Malldry, Centrifugal Blasting for Surface Preparation, American Society for Materials, Conference Specialized Cleaning, Finishing and Coatings Processes, February, 1980. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 30
SSPC CHAPTERa2.1 73 8627740 0003461 511 ACKNOWLEDGEMENT The author and editors gratefully acknowledge the active participation of the following in the review process for this chapter: Jim Flaherty, Bill Hitzrot, Charlie Lewis, Joe Mazia, Marshall McGee, Bill Pearson, and Bill Wallace. BIOGRAPHY A. W. DUKE MALLORY The late A.W. Duke Mallory was a 1939 Aeronautical Engineering graduate of Tri-State College, Angola, Indiana. Duke held various positions in Design and Sales Engineering and Marketing in the Landing Gear and Nuclear Reactor Components groups of the Bendix Corporation. In 1963 he joined Douglas Aircraft where he held positions of Design Engineer and Systems Design Analyst in Hydraulics, Landing Gear and Controls Systems Eñgineering groups. In 1966 Duke joined the Materials Cleaning Systems Division, Wheelabrator-Frye Inc., as a Project Engineer. He later was appointed Manager of Technical Development, Marketing Department, and in 1974 assumed the additional position of Manager of Product Planning for the Division. Duke actively represented Wheelabrator-Frye in the Steel Structures Painting Council, working on advisory committee activities in steel surface preparation cleanliness and profile studies, and in similar activities of other industry associations, including the National Association of Corrosion Engineers and the American Society for Testing Materials. --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 31
CHAPTER 2.2 METALLIC ABRASIVES by Einar A. Borch This chapter discusses the physical properties of metallic blast-cleaning abrasives and describes their versatility in producing various required degrees of finish, profile and cleanliness on metal surfaces. Also reviewed are types of metallic abrasives and an analysis of the .. mechanics of blast cleaning with these abrasives. Purchasing abrasive that meets the prescribed chemical and physical specifications is only one prerequisite for achieving the required cleaning and finish. An equally important requirement is for the user to maintain and operate the blast-cleaning system to produce a properly balanced size distribution in the abrasive working mix. This, in turn, can assure effective, efficient cleaning and uniform finish. These factors should be considered in evaluating the performance of a metallic abrasive used to achieve a specified finish: Time required to achieve the specified finish Abrasive consumption rate and its costs Cost of wear, parts and maintenance of the blast-cleaning equipment, including the effect of down time for maintenance work. No one type, size, shape or hardness of metallic abrasive can fulfill all requirements of blast cleaning for all applications. Therefore, the user must be prepared to evaluate the above factors in selecting proper abrasive. Metallic abrasives are available in a wide variety of types, shapes, hardnesses and sizes. It is possible to select a metallic abrasive with the right combination of properties to meet specified finish requirements. I. TYPES OF METALLIC ABRASIVES Three general types of metallic abrasives -cast steel shot and grit, malleable iron shot and grit and chilled cast iron shot and grit -are available for surface preparation. (Cut-steel wire shot is a fourth type, but represents less than one percent of all metallic abrasives produced.) The choice of one type over another is a matter of matching size, shape and hardness with the surface finish required and evaluating relative consumption rates and cost. In addition to hardness, the rapidity with which grit rounds up depends upon the frequency that individual particles are recycled. With the airless blast equipment, the frequency of recycling is rapid. In air-blast, due to the ex-
32 tremely low abrasive flow rates in relation to total abrasive in the system, the grit rounding process takes much longer. II. METHOD OF MANUFACTURE Raw materials and alloys are melted and adjusted to meet required chemistry specifications for iron or steel. Molten metal of the required temperature is removed from the furnace and is channeled into streams, which then drop onto jets of water under pressure, atomizing the molten metal into random sizes of shot that fall into a water-filled quenching pit. Atomization may also be accomplished mechanically, or by air or gas jets. The cast shot is removed from the quenching pit and heat treated. It is then screened into sizes in accordance with Society of Automotive Engineers (SAE) specifications (Table 1). Grit is produced by crushing hardened shot in roll-type crushers or ball mills, after which it is screened into SAE sizes and heat treated, as required. 111. HISTORY OF METALLIC ABRASIVES Chilled iron shot was the first cast metallic abrasive developed, coming into use shortly after the turn of the century. It satisfied a vital need in the granite industry for an improved, faster-cutting medium to replace sand, which was being used for the gang-sawing and polishing of granite blocks. Chilled cast iron abrasive cut much faster than sand, and because it could be reclaimed and re-used, resulted in dramatic reductions of cost per square foot of sawed or polished surfaces. Chilled iron shot and grit subsequently replaced sand as the medium in many air-blast applications equipment. Its use grew rapidly because one ton of chilled iron abrasive did the work of 40-50tons of sand. Chilled iron abrasive, moreover, cleaned better and faster. In the mid-I930 s, two events had major impact on the growth of the metallic shot and grit industry: anti-silicosis laws were imposed that prohibited the use of sand for blast cleaning inside industrial plants; and the centrifugal
(airless) blast-cleaning method was developed. Centrifugal blast cleaning, using chilled cast iron shot and grit, eliminated the silicosis hazard of sand. It also provided faster, more effective, and more economical cleaning than with air-blast methods using non-metallic abrasives. The use of metallic abrasives expanded rapidly. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERa2.2 93 m 8627940 0003463 394 m TABLE 1 SAE SHOT & GRIT SIZE SPECIFICATIONS WITH SUGGESTED REMOVAL SIZES(') CAST SHOT SPECIFICATIONS FOR SHOT PEENING OR BLAST CLEANING Screen Opening Sizes and Screen Numbers with Maximum and Minimum Cumulative Perc entages Allowed on Corresponding Screens N BS Screen No. Standard mm Screen Size (in) S1320 5550 SIE Shot Number S460 1 S390 S330 S2ôO I S230 5170 (3) (4) 4 5 6 7 8 10 12 14 16 18 20 25 30 35 40 45 50 80 120 200 4.75 4.00 3.35 2.80 2.36 2.00 1.70 1.40 1.18 1.00 0.850 0.710 0.600 0.500 0.425
0.355 0.300 0.180 0.125 0.075 (0.187) (0.157) (0.132) (0.111) (0.0937) (0.0787) (0.0661) (0.0555) (0.0469) (0.0394) (0.0331) (0.0278) (0.0234) (O 0197) (0.0165) (0.0139) (0.01 17) (0.007) (0.0049) (0.0029) Jggestei for Cleaning Structurai --Ail Pass 5% max 85% rnin 96% min -------0.0138 ---Ail Pass 5% max 85% min 96% min -----00117 --All Pass 5% max 85% min
96% min -0.0117 ----All Pass 5% max 85% mir 96% mir ---O0082 0.0070 --All Pass 10% max --35% min 37% min --0.0059 ---------Ail Pass 10% max 80% min 90% min ------Ali Pass 10% max 80% min
90% min 0.0049 0.0029I CAST GRIT SPECIFICATIONS FOR BLAST CLEANING Screen Opening Sizes and Screen Numbers with Minimum Cumulative Percentages Allo wed on Corresponding Screens NBS Standard Screen CAE Grit Number 1 I I Screen mm Size NO. (in) G10 G12 G14 G16 016 025 G40 GSO GE0 G120 6200 (3) (4) 4 4.75 (0.187) ----------5 4.00 (0.157) ----------6 3.35 (0.132) ----------7 280 (0.111) AllPass ---------8 2.36 (0.0937) -All Pass -------10 2.00 (0.0787) 80% -Ail Pass -------12 1.70 (0.0661) 90% 80% -Ail Pass ------14 1.40 (0.0555) -90% 80% -All Pass -----16 18 20 25 30 35 40 45 -
1.18 (0.0469) --90% 75% All Pass ----1.00 (O 0394) ---85% 75% -Ail Pass ---0.850 (0.0331) ----------0.710 (0.0278) ----85% 70% -Ail Pass 0.600 (0.0234) ----------0.500 (0.0197) ----------0.425 (0.0165) -----80% 70% -All Pass -0.355 (0.0139) -----------
50 0.300 (0.0117) ------80% 65% All Pass 80 0.180 (0.007) ------7 5 % 65% -All Pass G325 ----All Pass 20%
--`,,,,`-`-`,,`,,`,`,,`--120 O 125 (0.0049) ------75% 60% ~ 200 0.075 (0.0029) ---------70% 55% 325 0.045 (0.0017) ----------65% Suggested Removal Sizes for 0.0232 0.0165 0.0165 0.0138 0.0117 0.0062 0.0059 0.0049 0.0029 Cleaning of structural Steed2) (1) Courtesy Society of Automotive Engineers (SAE J444a). (3) Corresponds to IS0 Recommendations. (4) This is coarsest size in common use for blast cleaning structurai steel for painting Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 33
SSPC CHAPTERU2.2 93 m 8627940 00034b4 220 Much longer useful life -as much as a 2:l advanwas discovered that the combination of mass and velocity tage for steel abrasive of 45 Rockwell C hardness. of the extremely hard, friable chilled cast iron resulted in two serious problems: fast abrasive breakdown and resul- A. COMMON USES OF METAL LIC tant high consumption cost, and extensive and costly wear ABRASIVES As the use of centrifugal blast cleaning increased, it on the blast-cleaning equipment. Metallic abrasives have several common uses: These problems were minimized by development of to- 1. Surface cleaning and prep aration of metal prodday s superior metallic abrasive -steel shot and grit. The ucts prior to coating a nd painting of the surface change came about, however, in stages over a period of (removal of mill scale, r ust, old paint and other years. contaminants, and generation of an anchor patFirst, chilled iron shot and grit was subjected to a nor- tern to enhance coatin gs adherence). malizing process. The resultant malleable iron abrasive 2. Surface cleaning of f errous and non-ferrous had hardness values about half that of chilled iron castings (removal of molding sand, and heat treat abrasive, with economic benefits: malleable iron abrasive scaIe). had up to double the life of chilled iron; and malleable iron 3. Surface cleanin g of forgings, weldments and steel very markedly reduced the wear on blast-cleaning equip mill products including s labs, billets, bars, plate, ment. sheet and strip, pipe and rolled structural shapes Malleable iron abrasives provided definite improve- (removal of mill scale, rust and other oxide accrement in the economics of blast-cleaning, but introduced tions). new problems. Graphitic carbon, ordinarily present in the 4. Surface cleaning of heat-treated metal products malleable iron abrasive, often caused carbon deposition (removal of oxide scale) . on the work or substrate being cleaned, creating problems 5. Surface preparation of fiberglass reinforced in subsequent processing. Also, the use of malleable iron plastic products for b onding. shot and grit, being of lower hardness than chilled iron, 6. Etching of hardened steel mill rolls. resulted in measurable reduction in cleaning rates and 7. Shot peening to impart residual compressive sometimes in the ability to produce specified surface stresses to improve fatigu e properties of metal finishes or anchor patterns. products, and to minimize intergranular and stress corrosion cracking of alloyed metal prodIV. CURRENT PRACTICE ucts. Recognition of those problems led to the development 8. Peen forming of aircraft
wings. of cast steel shot and grit. Today, approximately 85 per- 9. De-flashing of prec ision molded rubber products cent of all metallic abrasives are cast steel, which has and some molded plastic (polymeric) parts. these advantages over malleable iron: 10. Reduction of chemically bonded mold an d core Wider selection of hardness ranges, permitting the sand lumps for reclamation an d re-use of foundry user to tailor abrasive hardness to finish re-sand. quirements.
Elimination of the graphitic carbon deposition problem. TABLE 2 DESCRIPTION OF PROPERTIES HARDNESS ABRASIVES SHAPE SIZE SHOT GRIT Cast Steel Shot or Grit Full range of SAE May be specified: sizes (SAE J-444) commercially available cast steel abrasives have mid-range hardnesses of approximately 35 Rc, 45 Rc, 55 Rc, 65 Rc. Malleable Iron Shot or Grit Full range of SAE 1 range 1 range sizes (SAE J-444) (28 RC -40 RC) (28 RC -40 Rc) Chilled Cast Iron Shot or Grit Full range of SAE --`,,,,`-`-`,,`,,`,`,,`--1 range 1 range sizes (SAE J-444) (57 RC -68 Rc) (57 RC-68 Rc) 34 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERt2.2 93 m 8627740 O003465 Lb7 m B. ADVANTAGES Compared to sand or other non-metallic abrasives, metallic abrasives are used differently and have certain advantages: I. Longer useful life as compared to that of sand, ranging from 50 times greater for chilled iron to more than 200 times greater for tempered cast steel. 2. Greater impact for given size particles, resulting in much faster and better cleaning. (Metallic abrasives have a density of approximately 1-112 to 2-112 times that of sand or other non-metallic abrasives.) 3. Versatility and adaptability. Cast steel offers a wide range of options in size and hardness, in addition to the basic choice between round shot and sharp, angular grit. 4. Much greater visibility while blasting. (Dusting of non-metallic abrasives causes visibility problems and can create environmental hazards.) 5. Minimal embedment of abrasive particles. (Nonmetallic abrasives, because they are so brittle and friable, have a different type of embedment than metallics2.) C. CONSTRAINTS Basic constraints that must be recognized in the use of metallic abrasives as a substitute for non-metallic abrasives in airblast equipment are 1. The blast-cleaning operation must provide effective reclamation and recycling to realize the durability advantage of the metallic abrasive (abrasive leakage must be kept to the minimum by proper maintenance of the blast-cleaning system). 2. To achieve consistent production cleaning quality, and optimum operating costs, careful attention must be given procedures for maintaining a stabilized work mix, or operating mix, in the system. 3. Metallic abrasives must be protected in such a manner that they are not exposed to moisture or corrosive environments. 4. Overblast must be avoided to assure proper profile for long-range performance of high-performance coatings.2 D. CHEMICAL AND PHYSICAL PROPERTIES (TABLE 2) There are two generally accepted specifications for cast steel shot and grit: 1. Society of Automotive Engineers -SAE J-827; and 2. Steel Founders Society of America -SFSA 20-66. From the standpoint of chemistry and screening, either of the above is suitable for specifying steel shot and
grit to be used in metalworking applications. However, with respect to hardness, it must be noted that both of these specifications were developed primarily for blastcleaning iron and steel castings, where an anchor pattern is seldom critical on the finished casting. For many other applications, and because of more critical finish requirements, the cleaning of structural steel and other products often requires abrasives of greater or lesser hardness values than those specified by SAE J-827 and SFSA 20-66 (Rockwell C40-50). The cost-benefit trade-offs in a user s selection of high versus low hardness in metallic abrasives requires evaluation of the finish, desired speed of cleaning, abrasive durability and equipment wear. Only the user can make the proper choice based on fhe priority placed on each of these factors. The generally accepted specification for malleable iron abrasive is SFSA 21-68. The size and chemistry specification in SFSA 21-68 also applies to cast chilled iron. V. MECHANICS OF BLAST CLEANING WITH METALLIC ABRASIVES Abrasive blast cleaning is a battering or bombarding of the work surface by continuing impact of abrasive particles propelled by compressed air through a nozzle, or by centrifugal force from an airless blast wheel. For abrasive particles to affect a change in the work surface, the stress exerted by the individual shot or grit particle at the point of impact must exceed the strength of the work surface itself. Four factors determine that stress: Energy contained in the propelled abrasive particle. Area upon which that energy is expended, and the angle of impingement. Strength and hardness of the work being cleaned. Strength and hardness of the abrasive particle. Energy contained in a single particle of abrasive is generally related to the variables of particle mass and velocity, as illustrated by the equation for kinetic energy -MV2 2 (M = mass; V = velocity) When selecting new blast-cleaning equipment for a given application, a choice of velocity is available. Velocity is governed by air pressure in airblast systems, or by the combination of wheel-peripheral speed, wheel diameter
(inside and outside) and shape and length of the wheel blade in centrifugal (airless) blast cleaning. It is apparent from the above equation that change in velocity has the most significant effect on kinetic energy of the particle. However, with any given blast-cleaning equipment and under a given set of operating conditions, the factor of velocity can, for all practical purposes, be considered constant. Thus, for an abrasive of given hardCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 35
SSPC CHAPTER*2.2 93 m Bb2799O 0003466 OT3 TABLE 3 EFFECT OF ABRASIVE SIZE ON IMPACT ENERGY AND COVERAGE SA Approxima te Approximate Relative Effect Shot -~ Shot Pellets on Impact Energy Size (1) Per Pound (2) (Based on Weight) (3) S-390 65,000 110 S-330 110,000 60 s-280 210,000 40 S-230 360,000 20 S-I70 660,000 10 s-110 1,700,000 5 S-70 7,000,000 1 (1) Basic shot size designations. (2) Based on the mid-size pellet of the purchased abrasive. (3) The weight of a particle of S-70 shot is considered as the base of 1 the cube of the diameter. The data shown cannot be translated directly as kineti c energy. all other values are relative to that base, varying as --`,,,,`-`-`,,`,,`,`,,`--S-330(through 18-Mor 20-M) S.330 (through 20-Mor 40-M) (NOTE: Round particles are fractures that have been rounded back into spheres.) FIGURE 1 Fracture Failure (shot particles from work mix) Courtesy: Ervin Industries, Inc. 36 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*2-2 93 8b27940 O003467 T3T ness, the mass of the individual abrasive particle becomes the significant variable in the energy exerted at impact on the work surface. Since the mass (in steel shot) varies as the cube of the diameter, it can be recognized that even slight changes in abrasive particle size can cause a major change in impact energy delivered. This, in turn, can account for pronounced changes in the effectiveness of contaminant removal and in the finish or anchor pattern produced. In addition to the impact energy delivered to the work, another critical factor in blast-cleaning effectiveness is coverage (a measure of impact distribution on the work surface by the many pellets contained in the abrasive work mix). Table 3 illustrates the dramatic differences in both impact energy and coverage as particle size is changed. A general rule is that if there is a difference in diameter of 2:1, the relative impact energy is approximately 8:l and the relative coverage (pellets per pound) is approximately 13. As Table 3 reveals, a work mix using S-390 as the original size and retaining particles as small as new S-70 will have the coarsest mid-size pellets delivering approximately 110 times more impact energy than the smallest mid-size pellets. Achieving the specified cleanliness and anchor pattern requires close control of the factors of impact energy and the coverage on the work surface. Such control is attained by maintaining an effective balance of the size distribution in the work mix. The mode of delivery or system by which the abrasive is propelled determines the abrasive flow rate and coverage per unit of time, which, in turn, affects finish and cleaning rates. Abrasive flow rates of equipment to be purchased are predetermined by choice of airblast pressure and nozzle configuration in airblast equipment or by choice of wheel diameter and width, rotational speed, blade (vane) design and drive-motor horsepower in centri fugal (a irl ess) b Ias t -c Ieanin g eq u ipm en t. As noted in the chapter on abrasive air blast cleaning, a 1/4 in. airblast nozzle has abrasive flow rates of about eight pounds per minute, depending upon the air pressure level. A 112 in. nozzle would have a flow rate of about 34 pounds per minute. Centrifugal blast-cleaning equipment G-25 working mix (.0165") 40 mesh G-25 working mix (.0079") 80 mesh FIGURE 2 Evolution of the working mix using steel grit: While all particles in the working mix started as original size G-25 (upper left), they eventually rounded up and diminished in size under repeated impact, which imposes the two modes of abrasive failures. (approxi-
mately 1OX magnification) Courtesy: Ervin Industries, Inc. 37 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERx2.2 93 = 8627940 0003468 97b develops much higher flow rates, ranging from 165 pounds with a 10 hp motor to as high as 2800 pounds per minute with a 100 hp motor. As noted in the chapter on centrifugal cleaning, this equipment for structural steel descaling typically may have four 30 hp wheels, each throwing approximately 600 to 800 pounds per minute. The mechanics of blast cleaning -how metallic abrasives develop their tremendous cleaning power -can be appreciated by thinking in terms of one 30 hp wheel throwing from 600 to 800 times the numbers listed in Table 3 as pellets per pound for the various sizes at velocities usually in excess of 240 feet per second. Harnessing that cleaning power to best advantage depends on proper abrasive selection (type, size and hardness) and constant control over the developed work mix. VI. MECHANICS OF METALLIC ABRASIVE FA1 LU RE Forces that work to develop the cleaning capability of metallic abrasives also tend to reduce the size of the abrasive particle and to cause its eventual breakdown to dust. Two modes of abrasive breakdown are involved. The first and predominant mode is fracture failure, the inevitable result of an abrasive particle s repeated impact against the work being cleaned and against the wear parts of the blast equipment itself. Such repeated impact fatigues the abrasive until it fractures. Chilled iron grit (55-67Rc) and full-hard (untempered) steel grit (66.68%) fracture rapidly to sharp edged angular particles. Tempered steel shot and grit and malleable iron shot and grit also fracture, but much more slowly. Under continuing impact the broken particles tend to be forged back into smaller, near-round shape. The fracture and rounding process continues until individual particles are so small that they are pulled out of the system by the abrasive separator (exhaust) system (Figures 1 and 2). The second mode of abrasive failure is called flaking
(Figure 3).As the outer surface of the abrasive particle
is fatigued by repeated impact, microscopic flaking of the surface occurs and, as impact continues, those flakes pop off and are withdrawn through the separator system to the dust collector. Hardness aside, the relative rate of failure of the different types of abrasive varies in accordance with basic chemistry and microstructure. Iron abrasives, due prin-
cipally to extremely high content of carbon, phosphorus and sulfur, fracture and fail much more rapidly than steel abrasives. In the case of steel abrasives that meet SAE andlor SFSA specifications for chemistry, microstructure and physical characteristics, hardness and microstructure are the critical factors with regard to fracture and flaking failure. Generally speaking, the harder the abrasive, the faster its breakdown from fracture failure. The lower its hardness, the more the abrasive resists and delays fracture failure, and surface flaking of the abrasive becomes a contributing factor in its ultimate failure. However, frac70-X 700-X FIGURE 3 Flaking failure of shot particles from work mix Courtesy: Ervin Industries, Inc. --`,,,,`-`-`,,`,,`,`,,`--ture failure is the dominant factor in the reduction of abrasive particle size. Harder steel abrasives, especially grit, also cause greater wear on blast cleaning equipment. Every point of hardness higher than that needed to provide the required Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 38
SSPC CHAPTER*2.2 93 m 8b2794O 00034b9 802 m finish in the required time cycle contributes both to faster abrasive failure and more rapid deterioration of the blast equipment. (See Surface Profile for Anti-Corrosion Paints, Ref. 2.) From the standpoint of relative metallic abrasive consumption (considering products that meet their respective SAEISFSA specifications), the following guidelines exist: Chilled cast iron abrasives have a breakdown rate as much as one third greater than full hard (65 plus Rc) untempered steel grit. Malleable iron abrasives have a breakdown rate of 50% to 100% greater than steel abrasive in the 40-50 ßc hardness range. Steel grit breaks down slightly faster than steel shot of the same size and hardness range. However, the smaller the size grit involved, the greater the difference in breakdown compared to shot. Similarly, increasing the hardness of steel shot or grit in a given operation increases the breakdown rate. Obviously, however, the more rapid breakdown of a harder steel abrasive becomes academic if it has been determined that a lower hardness will not do the job. VII. ABRASIVE WORK MIX As fracture and flaking failure continue, individual abrasive particles become smaller and smaller until they eventually are pulled out of the system by the separator mechanism. New abrasive must be added at regular intervals at rates corresponding to loss of abrasive due to the attrition or breakdown rate andlor by losses of usable abrasive via the separator system or carry-out with the work pieces. The combination of new abrasive being added and the gradual attrition and withdrawal of abrasive added earlier results in a mixture of sizes commonly called the work mix or operating mix . Size distribution within the abrasive work mix is influenced by these factors: Type and quality of abrasive Original size Original shape Original hardness and density Velocity of thrown abrasive
Hardness of work being cleaned Angle of impingement Adjustment of air-wash separator abrasive size withdrawn from the system) (to control --`,,,,`-`-`,,`,,`,`,,`--Loss of usable abrasive due to carry-out with work pieces Manner in which abrasive additions are made. Figures 4,5, and 6 illustrate size distribution of typical shotlgrit work mixes. 280 230 170 110 330 S330Work-Mix Courtesy: Ervin Industries, Inc. FIGURE 4 S.330 work mix. Work mix should contain all of above sizes, and should be neithe r predominantly coarse nor predominantly fine. Coarse particles provide optimum impact energy; smaller particles provide optimum cover age. 39 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*2-2 93 8627940 0003470 524 G=25 G-40 Courtesy: Ervin Industries, Inc. FIGURE 5 G-25 work mix (centrifugal blast unit). A G-25 work mix may also contain materia l as fine as G-80. G-25 work mix should contain all of the above sizes and should be neither predominantly coarse nor predominantly fine. C oarse particles provide optimum impact energy; smaller particles provide optimum coverage. VIII. ABRASIVE WORK MIX VS. FINISH Control of the work mix size and maintaining a stabilized work mix are vital factors in maintaining a consistent production rate and a quality finish. Representative samples of the work mix, which actually does the cleaning and provides the finish (anchor pattern), should be subjected frequently to careful sieve analysis to be sure the work mix has its size distribution in balance, ¡.e., not predominantly coarse or fine. The larger pellets in the work mix impart the greatest impact energy per pellet, cracking or fragmenting heavy surface contaminant on the work being cleaned and imparting identations of maximum peak-to-valley values. Medium and smaller pellets in the work mix provide greater coverage for scouring and complete removal of cracked or fragmented surface contaminant. Because of the decreased impact energy of the smaller abrasive particles, the peak-to-valley value is decreased. Also, because of the smaller size, greater number of impacts occur on a given area of the work piece and greater peak population results. Figures 7 and 8 illustrate the effect of changing the size distribution in the work mix on both profile height and peak distribution. Those are based upon SSPC experimental work in both laboratory and plant. Also see Commentary on Surface Preparation in Volume 2 of the Steel Structures Painting Manual. Each abrasive type, size and shape has its own inherent impact life cycle, generally measured in pounds used per blasting hour. Theoretically, new abrasive should be added to the system every blasting hour in amounts equal to the rate of withdrawal, or loss, from the system. In practice, however, making additions once a shift, or every eight hours, is acceptable. A continuous automatic system of abrasive replenishment is the preferred and most reliable method of maintaining a uniform work mix in a production operation. Delay in making new abrasive additions tends to decrease the percentage of coarser sizes in the work-mix; the result will likely be poorer quality cleaning and reduction of anchor pattern depth. Conversely, adding a large
quantity of new abrasive at one time increases the percentage of coarser sizes, resulting in a coarsening of surface profile, and for a given through-put speed, insufficient coverage and poorer cleaning. Maintaining a uniform and stabilized operating-mix also requires the abrasive particles removed from the blast machine to be of uniform size. To realize the greatest economic benefits of using metallic abrasives, the particle Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*2.2 93 8627940 0003471 460 m Courtesy: Ervin Industries, Inc. --`,,,,`-`-`,,`,,`,`,,`--.0394 .0278 .O165 (18-M) (25-M) (40-M) (50-M) FIGURE 6 S-330/Gm18*work mix (from centrifugal blast unit). Work mix should contain all o f the above sizes, and should be neither predominantly coarse nor predominantly fine. Coarse particles provide optimum impact energy; s maller particles provide optimum coverage. 55-60 RC TYPICAL EFFECT OF ABRASIVE SIZE ON PROFILE HEIGHT TYPICAL EFFECTOF ABRASIVE SIZE ON PEAK COUNT Effect of 4 Degrees of Cleoning IS Summed Out Effect of 4 Degrees of Cleaning is Summed Out SHOT T GRIT SHOT t4 GRIT E 1 I-Std Deviation II I-Std Deviotion T n E 2 1 O0 E I -L Each Profile Measured Optically by Averaging 60 Moximum Eoch Profile Measured witha Surfacouiit and a Brush Surfindicalar Peak- to-Valley Heights Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS FIGURE 7 FIGURE 8 From Surface Profile for Anti-Corrosion Paints , by Keane, Bruno, Weaver, 1976. (Re f. 2) 41
SSPC CHAPTERa2.2 93 8b27940 0003472 3T7 size removed should be the smallest size that is effective X. ABRASIVE SELECTION in the cleaning operation. Suggested removal sizes are Degree of cleanliness and lor profile are the main shown in Table 1 for each of the basic SAE sizes of shot reasons for impact clea ning and must be given priority and grit. Control of removal size requires careful attention over all other fact ors in abrasive selection. Obviously, conto adjustment of the separator system and of the air flow sideration must be giv en to the surface condition prior to through the separator. blast cleaning and its relation to the desired finish. IX. DEGREE OF CLEANING Abrasive selection depends on whether the surface has a light oxide scale or is heavily pitted and rusted, or whether Figures 9 and 10 are typical scanning electron photo- removal of paint or other coating is involved. The desired micrographs, taken by the SSPCin its profile study. They finish after blast clea ning may include a combination of show a comparison of degrees of cleaning of four sizes of degree of cleanliness, degree of roughness and type of steel shot and three sizes of steel grit. VARIOUS SHOT BLASTED SURFACES * 1OOX 60 VIEW S 230 S280 S330 S390 NEAR-WH I COMMERCIAL (SP 6) . FIGURE 9 and density (NJ estimated visually from SEM From: Surface Profile for Anti-Corros ion Paints , by Keane, Bruno and Weaver, 1976. (Ref. 2) 42 Profile (h,J stereo micrographs. --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*2-2 93 8b27940 0003473 233 surface texture. Size, shape and hardness of the abrasive Changing the angularit y of the surface finish changes particles in the work mix are the dominant factors in deter- the light reflectiv ity of the surface. The grit or etched finish mining whether the desired finish will be attained. appears nearer the parent me tal in color. Hard grit parShot pellets tend to burnish the surface and may ticles, even when fractured, re tain irregular or random leave a burnished scale condition in the root of the surface shape and produce a surface etch with more angularity indentation. Irregular pellet shapes in a grit mix, on the than a softer grit, w hich rounds up. Higher grit hardness, other hand, tend to reduce the entrapped burnished scale however, leads to short er impact life cycles and increased condition and can affect the angularity of the surface pro- usage. It also affec ts abrasive size distribution in the file. machine work mix; a harder grit work mix contains a lower VARIOUS GRIT BLASTED SURFACES * 1OOX 60 VIEW GL25 GL40 . GL50 hnax -Approximately 4 mils WHITE (SP 5) NEAR-WHITE (SP 10) COMMERCIAL (SP 6) FIGURE 10 Profile (hmeX) and density (NJ estimated visually from SEM stereo micrographs. From: Surface --`,,,,`-`-`,,`,,`,`,,`--BRUSH-OFF (SP7) Profile for Anti-Corrosion .dints . bv Keane. Bruno and Weaver, 1976. (Ref. 2) Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 43
SSPC CHAPTER*2.2 93 8b27940 0003474 L7T percentage of the coarser sizes and a higher percentage of )(l. CONCLUSION smaller sizes. Under a given set of equipment operating conditions, when using shot, variables in the profile attained usually relate directly and only to the size distribution in the work mix. However, when using grit, variables in the profile relate to abrasive hardness, size distribution, and particle shape. Steel grit, tempered to under 65 Rockwell C, rounds up under repeated impact; thus, the grit work mix is a mixture of new, angular grit, partially rounded particles and fully rounded particles. It is obvious that with the use of such grit, frequent and regular addition of new abrasive is absolutely essential to maintaining a consistent mix of particle size and shape. REFERENCES 1. ASM 6705-J, Specialized Cleaning, Finishing, Coating Process . ASM International, Materials Park, OH 44073. 2. John D. Keane, Joseph A. Bruno, Jr., and Raymond E.F. Weaver, Surface Profile for Anti-Corrosion Paints , Steel Structures Painting Council Report, Oct. 25, 1976. 3. H.J. Plaster, Blast Cleaning and Allied Processes -Vols. I and II,Garden City Press Ltd., Letchworth, Hertfordshire, England SG6 1 JS. 4. C.A. Reams, Modern Blast Cleaning and Ventilation , Penton Publishing, Cleveland, OH, 1939. 5. William A. Rosenberger, Impact Cleaning , Penton Publishing, Cleveland, OH, 1939. 6. SAE J792a, Manual on Blast Cleaning . Handbook Supplement 124, Society of Automotive Engineers, 400 Cornmonwealth Drive, Warrendale, PA 15096, June, 1968. 7. SAE J827, Cast Steel Shot , Society of Automotive Engineers, June, 1962. 8. SAE J444a, Cast Shot and Grit Size Specifications for Peening and Cleaning , Society of Automotive Engineering, November 1976. 9. SFSA 20-66, Cast Steel Abrasives , Steel Founders Society of America, Cast Metals Federation Bldg., 455 State, Des Plaines, IL 60016, 1966. 10. SFSA 21-68, Malleable Iron Abrasives , Steel Founders Society of America, 1968. Modern metallic abrasives, used in currently available blast-cleaning equipment, provide effective and economical means of preparing steel surfaces for coating applications. Available in a wide range of types, shapes and hardnesses to meet varying application needs, they offer extended use-life and high impact per particle. Optimum results can be obtained through an understanding of theories relating to the mechanics of impact cleaning and abrasive failure. Careful selection of shot or grit to satisfy surface finish specifications, along
with a disciplined program for controlling a proper balance in the work mix will produce optimum results when blast cleaning with metallic abrasives. BIOGRAPHY Einar A. Borch has been in the metal abrasive industry for over 50 years, being active inthe various management phases of the business, manufacturing, marketing and research development. He is currently working as a consultant for Ervin Industries. He has been involved in committee work relating to development of metal abrasive specifications for various technical societies including the Society of Automotive Engineers, the Steel Founders Society of America, the American Foundrymen s Society, the Casting Industry Suppliers Association, and the Steel Structures Painting Council. He is a former director of the Casting Industry Suppliers Association, a past trustee of the Foundry Educational Foundation and a past president of the Foundry Equipment Manufacturer s Association. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 44
SSPC CHAPTERlt2.3 93 8627940 0003475 O06 September 1993 (Editorial Changes) CHAPTER 2.3 NON-METALLIC ABRASIVES by H. William Hitzrot Non-metallic abrasives used for blast cleaning may be classified as (1) naturally occurring, (2) by-product and (3) manufactured abrasives. This chapter deals with these types, their physical attributes and the choices among them. Physical data are summarized in Table 1. I. TYPES OF ABRASIVES A. NATURALLY OCCURRING ABRASIVES Naturally occurring sands and flint sand are probably the most commonly used abrasives. Sands are a readily available source of abrasive and have been used for the blast cleaning of steel since the inception of this technique. Sand particles (Figure 1) range from sharply angular to almost spherical, depending on the source. Silica sands are an effective abrasive for blast cleaning new steel and for maintenance cleaning in non-critical areas. Since sands are often dusty, with a high degree of breakdown, they are not desirable for critical blast cleaning. In recent years silica sands have been replaced by heavy mineral sands or other products that contain little or no free silica . Nonsilica sands may also be used for blast cleaning. These are generally termed heavy mineral sands and include magnetite, staurolite, olivene rutile -either by themselves or in various combinations. These sands are tough and dense but generally of finer particle size than silica sand, with median size in the 70 to 100 rather than 20 to 40 sieve size range more typical of silica sands. An example of a heavy mineral sand is shown in Figure 2. Heavy mineral sands are effective for blast cleaning new steel, but are generally not recommended for maintenance applications. Garnet (Figure 3) is a tough, angular abrasive suitable for specialty-type blast cleaning of steel parts and castings, ¡.e., cleaning in a closed system that permits recycling the abrasive. Available in a range of sizes, it can be recycled a number of times because of its toughness. The high cost of garnet restricts its use to specialty cleaning applications that require only small quantities of abrasive. Zircon is another tough, angular abrasive (Figure 4). Its fine size limits its use to specialty blasting for removal of fine scale, leaving a smooth, matte finish. Like garnet, it has higher density and greater hardness than silica sand
and is considerably more costly. Novaculite, a very pure, siliceous rock, is ground to fine sizes for specialty blast cleaning. It leaves a satin 45 luster finish and is most commonly used to clean precision tools and castings. B. BY-PRODUCT ABRASIVES This group constitutes the most rapidly growing source of abrasive materials for cleaning steel structures. The relative low cost, availability in bulk, and low (less than 1%) free silica content make by-product abrasives well suited for blast cleaning large steel structures, both for new construction and maintenance cleaning. Conservation of materials and environmental concerns have given further impetus to converting by-products into commercial abrasives. Chief among the by-product materials being used as abrasives are slags from two sources: metal smelting slags (Figures 5 and 6) and electric power generating (bottom ash) slags (Figure 7). Smelting and boiler slags are generally glassy, homogeneous mixtures of various oxides, which give them uniform physical properties important for abrasive applications. Slag abrasives have a sharply angular shape ideal for efficient blast cleaning of new, corroded, or painted steel surfaces. They are available in the full range of abrasive sizes -coarse (8 sieve) to fine (100 sieve). Not all slags can be used as abrasives. They need to be tough, have a bulk density of 80 to 100 Iblcu ft, and exhibit a minimum amount of breakdown on impact in order to be effective abrasives. Agricultural shell products such as --`,,,,`-`-`,,`,,`,`,,`--walnut shells
(Figure 8) and peach pits offer a specialty by-product abrasive. Tough but lightweight with a bulk density of 42-47 Iblcu ft, agricultural shells are excellent for removing paint, fine scale, and other surface contaminants without altering the metal substrate. These shell products are FIGURE 1 Silica Sand Abrasive (X8 -Magnification 8 diameters) Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*2.3 93 8627940 0003476 T42 available from 10 to 100 sieve. Corncobs (Figure 9) are another agricultural product used for specialty cleaning to remove surface contaminants, such as grease and dirt, without destroying or altering the paint or metal substrate. Corncobs are also available in a full range of sizes. C. MANUFACTURED ABRASIVES Non-metallic, manufactured abrasives are made from raw material feed stock and can be produced for specific abrasive properties, such as toughness, hardness, or shape. Some examples are silicon carbide (Figure lo), a tough angular abrasive for specialty etching; aluminum oxides (Figure 11) for blast cleaning materials such as stainless steel; and glass beads (Figure 12) for peening and cleaning small, delicate parts. FIGURE 2 Because they are produced for specialized cleaning Heavy Mineral Sand Abrasive X8 needs, manufactured abrasives are 10 to 15 times more costly than by-product slags and 30 to 40 times more expensive than sand. For this reason, manufactured abrasives are not recommended for bulk cleaning jobs where the abrasive cannot be recovered for reuse. The tough, durable nature of most manufactured abrasives makes them particularly adaptable to recycling as many as 20 times. Consequently, net cost can be comparable to that of the by-product abrasives. II. CHOOSING THE RIGHT ABRASIVE The variety of materials available make it necessary to know how to select the proper abrasive appropriate for a given job. An abrasive has four parameters that determine its performance: shape, hardness, density and size. It is important to know how each of these parameters affects surface preparation. FIGURE 3 Garnet Abrasive X8 A. SHAPE (ANGULAR VERSUS ROUND) Because of their scouring action, angular particles are best suited for removal of soft friable surface contaminants such as paint, rust, and dirt. Figure 13 illustrates the scouring action. Round particles are best suited for removal of brittle Contaminants like millscale. Round particles are also used to produce a peening action when little or no change in surface configuration is permitted. B. HARDNESS (HARD VERSUS SOFT) Hard or tough particles are best suited for blast cleaning jobs where the primary objective is to remove surface contaminants. Hard particles leave less residue on the surface, minimize dusting, and, if recycling is employed, (see last column, Table l), provide the best durability. Soft abrasives remove light contaminants without disturbing the metal substrate or, in some cases, the coating system. Soft abrasives, such as yvalnut shells FIGURE 4 Zircon Abrasive X8 and corncobs, are used for cleaning valves or turbine rotor blades and for removing grease from motors and dirt or
other deposits on paint films. They are also effective in 46 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*2.3 93 86279LIO 0003477 989 cleaning industrial plants prior to repainting. C. DENSITY (DENSE VERSUS LIGHT) Generally, the denser the particle the more effective it is as an abrasive. Since the kinetic energy of a particle is equal to the mass times the square of the velocity, increasing the mass increases the amount of work done by each particle. The converse is also true. D. SIZE (LARGE VERSUS SMALL) Particle size is often overlooked as a parameter affecting the performance of an abrasive. But marked improvement in cleaning can be realized by controlling the size distribution of particles making up an abrasive. Cleaning rate is determined by the number of particle impacts rate. The limiting factor is that particles must be coarse per unit of time. The more impacts, the faster the cleaning Copper Slag Abrasive x8 FIGURE 5 enough to remove the surface contaminants. The best abrasive medium is one composed of a range of sizes because coarse particles will remove the coarser contaminants while fine particles will scour out the residual fine, friable corrosion products or old paint. For recycled abrasives, it is extremely important that the range of particle sizes or operating mix be maintained by regular additions of new abrasives to replace fractured particles removed from the blast cleaning system. 111. MATCHING THE ABRASIVE TO THE JOB In addition to understanding the relation between these parameters and abrasive performance, it is equally important to be aware of the job conditions that influence the selection of an abrasive. A. TYPE OF SURFACE The abrasive selected to do the most efficient cleaning will depend on whether the surface is rusted, scaled, FIGURE 6 Nickel Slag Abrasive X8 painted or produced in a foundry. Rusted steel requires an angular abrasive to scour the corrosion product. Scaled steel requires dense, spherical particles to pop off the oxide scale. Painted surfaces require coarse, angular particles to bite into more resilient paint coatings. A foundry casting requires a hard, high density particle to remove fused sand and metal flashing. B.SURFACE FINISH REQUIRED The desired finish is a factor in selecting the abrasive. For instance, if the coating is to be removed without altering the substrate, a soft, angular particle, such as walnut shells, may be used. Glass beads are suitable for removing oxide films on rotor blades, plastic molds, and other intricate parts where no dimensional change can be tolerated. At the other end of the spectrum, if a deep etch in the metal substrate is required to enhance coating adhesion, a coarse, hard, and angular abrasive such as copper slag is recommended. FIGURE 7 coalFired, il^^ Bottom Ash slag X8
--`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 47
SSPC CHAPTER*2.3 73 8627740 0003478 815 = FIGURE 8 Walnut Shell Abrasive X8 C. COATING SYSTEM Most manufacturers recommend a minimum surface texture on the abrasive-cleaned surface for good coating adhesion. The coating system will therefore also influence the choice of abrasive for surface preparation. D. CLEANLINESS Not all abrasives provide the same surface cleanliness. An abrasive effective for a commercial blast (SSPC-SP6) may not be able to provide a near-white (SSPCSP 10) or white-metal (SSPC-SP 5)blast-cleaned surface. It is important to know whether an abrasive can meet the specified degree of cleanliness. E. ENVIRONMENTAL CONSTRAINTS Environmental requirements affect the choice of abrasive. The need to minimize dust or airborne free silica may require replacing cheaper sands with more costly FIGURE 9 Corncob Shell Abrasive X8 by-product slags or replacing open blasting with enclosed blasting. Enclosed blasting is commonly associated with reclamation of the abrasive, which must be a high quality, tough, durable material if it is to be recycled many times. Although the most commonly recycled abrasives are the steel abrasives, manufactured and naturally occurring abrasives that exhibit excellent durability should also be considered for recycling. The carbide and alumina abrasives and naturally occurring garnets and heavy mineral sands can be reused many times. If conditions such as job location make recycling impossible, copper slag is recommended because it produces the least dust. F. ABRASIVE EVALUATION TESTS Finally, among the criteria for selection of abrasives are certain key physical and chemical properties of the abrasives. FIGURE 10 FIGURE 11 Silicon Carbide Abrasive X8 Aluminum Oxide Abrasive X8 48 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*2*3 93 8627940 0003479 751 1. Size consist is the size distribution of abrasive particles and is best determined by sieve analysis, outlined in ASTM-D 451. A consistent range of abrasive particle sizes must be maintained to produce a consistent surface and cleaning rate. 2 Abrasive breakdown is a measure of a particle breakdown after impact. The greater the particle breakdown the poorer the cleaning rate. That is, if most of the particle energy is dissipated in particle breakdown, little energy is left for removal of surface contaminants. Most manufacturers list a breakdown value, and standard test procedures are being established by California and the federal government. A proposed test procedure is outlined in Table 2, and Figure 14 illustrates the test equipment. FIGURE 12 Glass Bead Abrasive X8 Direction of Travel Twisting due to offset center of Gouging at point of impact FIGURE 13 Impact of Angular Abrasive Particle on Steel Surface --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS FIGURE 14 Sponge abrasive used for sponge jetting -no magnification. 49
SSPC CHAPTER*2.3 93 8b27940 0003480 473 3. Dust generation is the amount of dust generated by an abrasive on impact. Excessive dust can create visibility problems during blasting and cause environmental problems at the job site. A measure of dust generation may be obtained during the abrasive breakdown test described in Table 2. 4. The pH values of an abrasive should be nearly neutral when the abrasive is mixed with water. Most suppliers note the pH on the technical data sheet accompanying the abrasive. The pH value is easily checked and should be routinely monitored. An abrasive with an acid pH would cause premature corrosion of steel and could cause coating failure. 5. The soluble chloride test is important, because chlorides in an abrasive will leave a chloride residue on the blasted substrate that could be detrimental to the substrate and subsequent coating systems. Most chemical laboratories can routinely analyze for soluble chlorides. If the abrasive source is near seawater, routine checking for soluble chlorides is a must. 6. Analysis for free silica is generally provided by the manufacturer. The level of free silica should comply with governmental regulations. 7. Trace toxic contaminants should be reviewed prior to use, and suppliers should provide a trace element analysis for potentially toxic substances. TABLE 1 PHYSICAL DATA ON NON-METALLIC ABRASIVES Free Degree --`,,,,`-`-`,,`,,`,`,,`--Hardness Specific Bulk Slllca of (Mohr Scale) Shape Gravlty Density Color wt Yo Dusting Reuse Ibslcuft Naturally Occurring Abrasives Sands Silica 5 rounded 2-3 1O0 white 90+ high poor Heavy Mineral 5-7 rounded 3-4 128 variable (5 med good Flint 6.5-7 angular 2-3 80 grey-white 90 + med good Garnet 7.8 angular 4 145 pink nil med good Zircon 7.5 cubic 4.5 184 white nil low good Novaculite 4 angular 2.5 1O0 white 90 + low good By-product Abrasives Slags Boiler 7 angular 2.8 80-90 black nil high poor Copper 8 angular 3.3 100-120 black nil low good Nickel 8 angular 2.7 84 green nil high poor Walnut shells 3 cubic 1.3 44 brown nil low poor Peach pits 3 cubic 1.3 44 brown nil low poor Manufactured Abrasives
Silicon carbide 9 angular 3.2 k 105 black nil low good Aluminum oxide 8 blocky 4.0 * 120 brown nil low good Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 50
SSPC CHAPTERt2.3 93 8b27940 0003483 30T = ACKNOWLEDGEMENT BIOGRAPHY The author and editors gratefully acknowledge the active A biographical sketch a nd photo of Bill Hitzrot appear at the participation of the following in the review process for this end of Chapter 2.0 . chapter: Harlan Kline, A.W. Mallory, Joe Mazia, R.N. McCorrnick and William Wallace. --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 51
September 1993 (Editorial Changes) CHAPTER 2.4 ABRASIVE AIR BLAST CLEANING by P.J. Bennett Abrasive air blast cleaning provides a method of surface preparation that is rapid, proven, and well established. An understanding of air blast cleaning with various abrasives is essential for a successful operation. Proper surface preparation by this method provides a foundation for the paint system, resulting in a clean surface, uniform etch, and a long, economical coating life. In abrasive air blast cleaning, surface preparation can be achieved on parts or weldments that are not uniform in size or shape. Uniform or flat pieces may, especially on new work, be cleaned more efficiently with mechanical cleaning machines. I. DESCRIPTION Air blast equipment contains and meters abrasive into a compressed air stream through conveying hoses and nozzles to the work piece. In effect, the part being cleaned is eroded away by a mass of abrasive particles until a firm, clean surface results. Abrasive blast cleaning with a compressed air source, air hose, abrasive blast machine, abrasive hose, and nozzle imparts a velocity to the abrasive particle that becomes a working force. Because of its effectiveness in cleaning metals, the process has been widely accepted to remove mill scale, rust, paint and other contaminants. Various abrasives are used in the process, but the most widely used abrasive is silica sand that has been processed for a blasting abrasive. Respiratory protection must be given to the operator and workers in the blast cleaning area because of .spent abrasive and the contamination being removed from the surface. Selection of the abrasive in this process becomes a major factor in cleaning speed, surface etch and coating adhesion. The trend is to a finer size of abrasive because of increased cleaning speed on new or lightly rusted steel; a coarser size of abrasive is used for more corroded steel or harderto-clean surfaces. Paint coating manufacturers have found a uniform etch with a cleaner surface much more effective for coating adhesion than an overly smooth surface of similar cleanliness. It is important to maintain a proper size of abrasive for air blast cleaning. II. TYPES OF AIR BLAST EQUIPMENT A. PRESSURE TYPE In a pressure-type abrasive blast system the abrasive machine is under the same pressure as the entire system,
¡.e., the compressor, air lines, abrasive blast machine, abrasive blast hose and nozzle. This cleaning method is the most productive of abrasive blast cleaning. The efficiency is largely dependent on actual nozzle pressure, which should be 90-100 psi range. The pressure blast machine, or pot , varies in size, but must be under pressure for an even flow of abrasives. Velocity of the abrasive in the pressure method is greater than the abrasive velocity found in suction equipment (Figures 1, 2, 3, 4). B. SUCTION BLAST EQUIPMENT This equipment utilizes the suction jet method of obtaining abrasive from the abrasive tank that is not under pressure. The jet of air blasts the abrasive against the surface after sucking abrasive from the container. Cleaning speed is approximately 113 slower than that of pressure blast cleaning with similar size air jets. Its use should be limited to touch-up or spot cleaning jobs, where high speed cleaning is not a factor (Figures 5 and 6). C. VACUUM BLAST EQUIPMENT In the vacuum blast cleaning method, air and abrasive are captured in a rubber-hooded enclosure. They are drawn by suction back to the blast unit where reusable abrasive is separated from blast-cleaned surface contaminants, recycled, and reused. This is considered a dust free abrasive blast cleaning because it shields the blast surface area from flying particles and dust. It will not disturb adjacent machinery and workmen. Cleaning speed is limited because the surface is not visible to the operator. There are two methods of vacuum blast cleaning. In the suction type the abrasive is siphoned from container to the blast head. The pressure type machine delivers sand under pressure through a blast hose to the surface. The pressure method provides greater production. The process is limited to the use of reusable abrasives, such as metallic, steel shot or steel grit, aluminum oxide or garnet. In some cases, where moisture is a problem due to high humidity, a mixture of steel grit and aluminum oxide or garnet is recommended because it keeps the metal abrasive from lumping or congealing due to moisture (Figure 7). Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 52
SSPC CHAPTER*2*4 73 8627740 0003483 182 = FIGURE 1 Pressure blast machine. Courtesy of Clemco Industries. 111. ESSENTIAL INGREDIENTS OF AIR BLAST EQUIPMENT To achieve efficient abrasive air blast cleaning, specific attention must be given to each component of the air blast equipment (Figure 8). Components are air SUPPlY, air hoSe and CoUPlings, abrasive blast machines, abrasive blast hose and couplings, nozzles, operator equipment, air-fed hoods and control valves, and oil and moisture separators. A manager of an abrasive air blast operation should have a check list of each component to ensure peak performance. Each component is discussed in detail. A. AIRSUPPLY Air supply provides energy for the entire operation and is responsible for maintaining pressure and volume. Volume requirement is determined by the orifice nozzle size. The nozzle size in Table 1 indicates air consumption in cfm (cubic feet per minute) at 100 psi (pounds per square inch) without abrasive going through the nozzle. When determining the compressor size the next larger size compressor available for the nozzle should be used. It is also wise to consider other air requirements from the compressor, such as for an air-fed hood (20 cfm) and airdriven ventilating equipment (approximately 120 cfm). A separate air source for air-fed hoods may be required, unless a carbon monoxide detector is installed in the air system. Insufficient air supply results in excess abrasive and slower cleaning rates. B. AIR HOSE AND COUPLINGS Recommended size of the air supply hose should be 3 or 4 times the nozzle orifice. On lines over 100 feet, four times should be the minimum size. Often, the size hose used requires a coupling installed on the inside diameter of the air hose, which further restricts air flow. The I.D. of the coupling should be considered along with hose size. Another problem is the size of the air compressor manifold valve. It is common for air compressor manufacturers to furnish compressors with 1-inch outlets and valves. These should be removed and replaced with 1% or 2 outlets to match the main air supply hose. c. ABRASIVE BLAST MACHINES The pressure machine is a non-fired pressure vessel, built to ASME code requirements for 125 psi working
pressures, sized to maintain an adequate volume of abrasive for the nozzle orifice. TABLE 1 AIR CONSUMPTION NOZZLE CFM REQUIRED ABRASIVE CONSUMPTION ORIFICE @ 100 PSI PER HOUR 311 6 60 CFM 260 Lbs. 1 I4 105 CFM 490 Lbs. 511 6 160 CFM 812 Lbs. 318 53 --`,,,,`-`-`,,`,,`,`,,`--232 CFM 1152 Lbs. 711 6 315 CFM 1584 Lbs. 112 412 CFM 2024 Lbs. 518 580 CFM 2518 Lbs. 314 840 CFM 3174 Lbc. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERx2-4 93 8627940 0003484 019 = Cover (Optional) ---Screen (Optional) -Coded Pressure I Sand Valve (Grit Valve not shown) FIGURE 2 Diagram of pressure blast machine. Courtesy of Clemco Industries. It should have a sloping bottom for free flow of abrasives and be constructed with an abrasive metering valve to provide the correct abrasive-to-air mixture. The pressure tank, with pressurizing and depressurizing valves, becomes an abrasive blast machine, pressure type. Figures 9-11 illustrate various size machines. Smaller machines are adaptable to small nozzles and to smaller inaccessible type work, whereas larger machines can accommodate multiple large nozzle outlets for large flat areas. Suction machines are little more than small, nonpressured containers with screens and a bottom outlet for abrasive flow to a suction blast nozzle. Hose distance is less than 25 feet where abrasive can be vacuumed to the blast nozzle. D. ABRASIVE BLAST HOSE AND COUPLINGS Recommended size of the blast hose is important to an air blast operation because of friction loss measured in pressure drop of conveying abrasive. The recommended size is three to four times the nozzle size, except near the nozzle end. There, a short hose of smaller diameter should be used for operators convenience and flexibility. Typical abrasive blast operations will be 100 ft. of 1i/d-inch sandblast hose and 10 ft. of 1-inch hose (called a tail line or whip hose) for a 3/,-inch orifice nozzle. Hose construction is normally %-inch thick rubber tube with carbon black compounding for the dissipation of static electricity generated by an abrasive flow through tube. Dissipating static electricity prevents build up and shock to operator. The tube is covered by 2-or 4-ply wrapping to provide strength for pressure requirements. Normal working pressure should not exceed 125 psi.
A wear-resistant cover is applied over the ply to protect it against premature wear. In some cases an additional static wire or two is wrapped spirally around the tube between the ply to ensure drain of static electricity. In areas of volatile liquids this type of hose should be used. Parts that are abrasive FIGURE 3 Two chamber continuous action pressure blast machine. Courtesy of Clemco Industries. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 54
SSPC CHAPTERw2.4 93 8627740 0003485 T55 POP-UPValve Seat Gasket -,../'e-FIGURE 4 Diagram of two chamber continuous action pressure blast machine. Courtesy of Clemco Industries. blast cleaned should be grounded to prevent a spark that could ignite flammable material. Proper grounding prevents the spark and ensures safe working conditions. Couplings used on blast hoses should always be exterior and should be fitted to the hose in a snug, tight condition. Small screws through the coupling into the cover ply tube completes sure fastening of the coupling to the hose. The advantage of exterior couplings is that they do not contribute to friction loss. Normal pressure drop of sandblast hose with 3/,-inch orifice nozzle is 5 psi per 50 ft. length. Therefore, it is important to use large hose as short as practical. A word of caution: too large an abrasive hose (1-inch) on small nozzles (y,,-inch) may result in uneven abrasive flow. E. NOZZLES There are many types of blast nozzles, but construction material used in liners of nozzles determines the life and cost. Liners are constructed of ceramic, cast iron, tungsten carbide and boron carbide. Ceramic and cast iron are short life nozzles. Carbide nozzles are long life. Average life of tungsten nozzles is 200 hours. Ceramic and cast iron are 2-4 hours. Boron carbide nozzles can maintain their size for 1500 hours if properly handled to prevent cracking of the brittle carbide material. During construction of these nozzles a soft metal (lead and aluminum) is used to absorb shock and protect the liner. It is common to put a small, 4-6 inch piece of rubber hose over these nozzles for added protection. A polyurethane cover is also used over liners, but they should be checked for threads wearing. Nozzle shapes provide great advantages to nozzle construction. Venturi style nozzles (large throat converging to the orifice and then diverging to the outlet) provide rapid speed of abrasive particles through the nozzle, increasing cleaning rate compared to a straight bore nozzle of the same length. Nozzles are a very important part of an air blast operation and should be inspected regularly for orifice size and wear. Worn out and cracked nozzles result in increased compressor wear, increased abrasive usage, and poor nozzle pattern (Figure 12).
F. CONTROL VALVES Pressure abrasive blast machines have an inlet, outlet or depressurizing and choke valve and an abrasive metering valve. The abrasive inlet on air blast machines is called an air operating and sealing valve, but is not common to all machines (Figure 2). Valves mentioned are all manual because of safety requirements, the need for fewer operating personnel and the use of pneumatic valves controlled by operation. Two FIGURE 5 Suction blast equipment. Courtesy of Clemco Industries. 55 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*2*4 93 m 8627990 000398b 991 m G. OIL AND MOISTURE SEPARATORS The large consumption of compressed air in an abrasive blast operation introduces the problem of moisture (especially in high humidity areas) and oil mists from the lubricating oils in compressors. This is especially true in portable compressors. To combat this, an adequately sized oillmoisture separator should be installed at the blast machine (the most distant point from the compressor) to eliminate 95% of the contaminants. Separators are usually of the cyclone type with expansion chambers and small micron filters. They require solvent cleaning to remove oil and routine replacement of filters. H. AIR SUPPLIED RESPIRATORSIHOODS The protective helmet for abrasive blast cleaning operations has several requirements to be effective. It must be Safe to user, furnishing respirable air to operator at a low noise level and protecting operator from rebounding abrasive particles; FIGURE 6 Suction blast cabinet. Courtesy of Clsmco Industries. of these manual valves, the inlet and outlet, can be replaced. When these valves are replaced, the air blast machine becomes an automatic, one-man operated machine, remote controlled by the blast operator. Further advantage is obtained when an abrasive hopper is placed above the blast machine. This method is well suited for recycled abrasives in abrasive blast rooms or enclosed systems (Figure 13). The choke valve is seldom used, except for removing clogged abrasive, paper or foreign particles that block flow of abrasives. The choke valve is closed momentarily to force all pressure through the machine, freeing a clogged line. This usually takes 10 seconds. The abrasive metering valve is the carburetor that provides proper abrasivelair mixture to the nozzle orifice. It is very important that this valve be in good condition. Once it is set, it does not require constant or continual change. FIGURE 7 Vacuum blast equipment. Courtesy of Pauli 81 Griffin Company. 56
Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*2-4 93 8627940 0003487 828 W Points to Check 1. Large Compressor 2. Large Air Hose and Couplings 3. Portable High Production Sandblast Machines 4. Large Size Sandblast Hose with External Couplings 5. Large Orifice Venturi Nozzle 6. Remote Control Valves 7. Moisture Separators 8. High Nozzle Air Pressure 9. Proper Sandblasting Abrasive 10. Safety Air Fed Helmet 11. Training of Operators FIGURE 8 Essential components of a successful sand blast operation. Courtesy of Clemco Industries. Able to provide clear vision to operator; In a confined or congested area only a ir-fed helmets Comfortable and not restrictive. should be used. They should have a charcoal fil ter with air There are several types of abrasive blast hoods, in- regulator to filter air sup ply. The filter to the helmet hose cluding air-fed and non-air-fed. The non-air-fed hood is should be a minimum of JS-inch I.D. and constructed to satisfactory for light duty, non-continuous exterior work. convey compressed bre athing air. Air-fed helmets should They should not be used in confined or congested areas. A have NIOSH approval. specifically designed NIOSH approved dust respirator must be worn under the hood. IV. AIR BLAST ABRASIVES Many abrasives are used in air blast operations. Each has specific uses and provides a specific etch and surface appearance. The coating usually has a specific adhesion requirement, and a selection of the proper abrasive is most important. Generally, an abrasive is classified according to the following characteristics: Size -Usually by U.S. Sieve Sizes (¡.e., 16 x 40 mesh) -(.0469 x ,0165 -1.19mm x .42mm). Shape -Irregular, round, sharp. Hardness -Usually by Moh s Hardness Scale of the present element. Color -Light or dark. Lighter abrasives reflect light and restrict visibility. Dark abrasives absorb light. Chemical Components -Abrasives should not contain undesirable components that would remain on surface being cleaned. Specific Gravity or Weight -Heavy abrasives clean faster and impact much better while lightweight abrasives are primarily used for polishing. pH of Abrasive -A neutral pH within the range of
7.0 i 1 is desirable. Salt water washed abrasives are not recommended. Availability and Cost -Selection of abrasives could result in a high cost of transportation to using area. Quite often, freight costs exceed abrasive cost. FIGURE 9 Abrasives fall into five general categories: Large (8 ton capacity) portable pressure blast machine. Metallic -Steel, iron shot or grit. Courtesy of Clemtex Ltd. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 57
SSPC CHAPTER*2.4 73 m 8627940 0003488 764 m TABLE 2 ABRASIVE CHART MAJOR SPECIFIC ABRASIVE -TYPE COMPONENT SHAPE HARDNESS GRAVITY Steel Shot Metallic Iron Round Hard*' 7.2 Steel Grit Metallic Iron Angular Hard' 7.6 Iron Grit Metallic Iron Angular Hard 7.4 Alum. Oxide Oxide Alumina Angular Hard 3.8 Silicon Carbide Oxide Silicon Carbide Angular Hard 3.8 Garnet Oxide Iron-Silica Irregular Hard 4.0 Slag-Coal Conglomerate Iron-Alum Silica Irregular Hard 2.8 Slag-Copper Conglomerate Iron-Alum Silica Irregular Very Hard 3.3 SlagNickel Conglomerate Iron-Alum Silica Irregular Hard 3.2 Flint Silica Silica Sharp Medium 2.7 Sand Silica Silica Irregular Medium 2.7 Limestone Oxide Caco2 Irregular Soft 2.4 Magnesium Silicate Mineral Silicate Round Medium 3.2 Staurolite Mineral Silicate Round Hard 4.5 Walnut Shell Vegetable Cellulosic Irregular Soft 1.3 Zirconium Mineral Silica Round Hard 4.5 Corn Cob Grit Vegetable Cellulosic Irregular Soft 1.2 Sodium Chemical Sodium Bicarbonate Irregular Soft 1 .o Glass Beads Oxide Silica Round Medium 2.7 Plastic Beads Organic Polymer Resin Round/lrregular SoftlMedium 1 .o 'Soft materials are < 4 on Moh's hardness scale; Medium4 5 6; Hard 2 6 ""Various Hardnesses Available Oxides -Natural or manufactured. Silicas -Sands, staurolite, zirconium, magnesium to increase life and rate of cl eaning. Generally, the hard silicate abrasives, 65 Rockwell C Hardness, are used for etching, Vegetable -Cellulose type, walnut shells, corn cob but they break down rapidly. The softer abrasives, 30-40 grits. Rockwell C, are used for easier cleaning jobs. The softer Slags or conglomerates, coal, nickel, copper grit will round-up after reuse. Ave rage hardness of metal Table 2 is a guide for abrasive selection. Metal etch- abrasives is 45-50 Rockwe ll C, which works satisfactorily ing will remove mill scale, rust and other contaminants as an air blast abrasive . from metal to produce a white metal surface condition with an etch (anchor pattern) on the surface. Light clean- V. EFFICIENCY OF AIR BLAST OPERATIONS ing removes only old paint and loose rust. It is generally As with any productio n job, efficiency results in good used for maintenance or repainting. production rates and lower unit costs. This is especially Tests for abrasives, derived by the NACE T-6G Com- true in abrasive air blast op erations where a small drop in mittee, using a certain volume of abrasive to blast clean a pressure rapidly inc reases consumption of abrasive and steel plate at a constant pressure and distance, determine decreases cleaning ra te. Figure 14 illustrates the irn-
the breakdown rate of the abrasive and the abrading or portance of good nozzle p ressure. In a blast test of two metal removal quality. minutes, differences in nozzle pressure were compared. At Although this test is lengthy, it provides accurate in- 60 psi the rate of clean ing is 112 the rate at 100 psi and formation on abrasives. Silica abrasives (sand) range from abrasive usage is mor e than double. This is especially imsoft to hard and poor to good for metal removal. portant on interior work (insid e of tanks) where abrasive Field tests of abrasives by a qualified engineer should must be removed prior to painting. Pressures in excess of consider 100 psi tire the operator, and little is gained working above Size -Approximately 16 x 40 mesh (U.S. Sieve) these pressures. (.0469" x .0165" x 1.19mm x .42mm).
Cleanliness -Fresh Water Washed. A. PROCEDURE Contamination -(clay, iron, salt, etc.) that would re- To correctly set up an ai r blast the following promain on surface cleaned. cedures should be followed. Assume the correct size of Metallic abrasives present different problems. These nozzle, hose, machine and c ompressor. abrasives are normally heat-treated to various hardnesses 58 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERr2.4 93 = 8627740 0003489 bTO Connect respirator and safety equipment and check for operation. Depressurize machine, add abrasives, start blast cleaning operation, adjust abrasive metering valve to allow proper flow of abrasive to nozzle. The correct abrasive flow will be a steady flow to nozzle. Uneven flow or surging indicates too much abrasive. On completion of blast cleaning, the blast machine should be emptied to prevent introduction of moisture into abrasive. Prior to painting the surface, dry air from nozzle without abrasive should be used to blow down the surface to remove spent abrasive dust. The surface is now ready to be coated. B. VARIABLES Abrasives vary in their hardness and size. The greatest variable is the operator. Some people can be trained to perform satisfactorily, while others find this work monotonous or otherwise unacceptable. It is best to ensure operator comfort and safety. As with all cleaning operations, differences in surface condition, type of steel, corrosion, etc., affect the rate of cleaning. On large cleaning jobs it is wise to mark off a FIGURE 10 Large stationary pressure blast machine. Courtesy of Clemtex Ltd. Start compressor after the oil and water has been checked and compressor has been located upwind of blast operation. Uncoil air and abrasive hoses and lay out in most direct line to machine and work. Locate abrasive blast machine as close to work as possible to minimize abrasive hose use. Connect air hose with safety connections and blow out hose. Connect blast machine to air supply hose ahci blow out machine for any abrasive that may have been left over from previous use. Check all control valves on machine for correct working order. Partially open the moisture trap drain valve to drain FIGURE 11 moisture. Install safety clips on abrasive hose. Portable bulk abrasive pressure blast machine. Test complete unit without abrasives. Courtesy of Clemtex Ltd.
Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 59
SSPC CHAPTERs2-4 93 8627940 0003490 312 given area and run a cleaning test to achieve a more ac- Vi. PRODUCTION RATES OF CLEANING curate cleaning rate. Table 3 illustrates open air blast cleaning rates and Special consideration should be given to interior blast abrasive consumption On newly fabricated steel using a cleaning. A wide variation in production rates exists on in- J/,-inch orifice no zzle and 100 psi to a SSPC-SP 10 nearterior cleaning, as much as 2:l (112 exterior cleaning rate), white condition. because of visibility problems, ventilating problems, and inaccessi bi Iity. These variables can be mi ni mized with good lighting, ventilation and good scaffolding techniques. ~~ TABLE 3 EXAMPLES OF CLEANING RATES WITH TYPICAL ABRASIVES ABRASIVE PRODUCT ION ABRASIVE CONSUMPTION RATE COMMENTS Silica Sand 16/40 2.6 Lbs./Sq. Ft. 4.75 Sq. Ft./Min. 1Y' Mil Etch Mesh Dusty 'Garnet 36 Grit *3.6 Lbs./Sq. Ft. 3.55 Sq. Ft./Min. 1% Mil Etch -Very little dust-reusable *Aluminum Oxide *3.1 Lbs./Sq. Ft. 4.58 Sq. Ft./Min. 1% Mil Etch -Very 36 Grit little dust-reusable *G-40 Steel Grit '5.5 Lbs./Sq. Ft. 3.06 Sq. Ft./Min. 2'/2 Mil Etch-NO Düst Grey Metal-Reusable Crushed Flint 3.6 Lbs./Sq. Ft. 2.69 Sq. Ft./Min. 3 Mils -Reusable 12/30 Mesh Staurolite 3.1 Lbs./Sq. Ft. 4.85sq. Ft./Min. Mil Etch 501100 Mesh Smooth Surface Coal Slag 3.2 Lbs./Sq. Ft. 3.83 Sq. Ft./Min. 2% Mil Etch 16/40 Mesh Reusable-Imbedding Copper Slag 3.1 Lbs./St. Ft. 4.36 Sq. Ft./Min. 2 Mil Etch 16/40 Mesh Reusable-Imbedding *These abrasives are normally reused. CONVENTIONAL STYLE NOZZLE B:---sf High impact in center but diminishing -11 towards edge of pattern. Large fringe area. Requires more passes than Venturi to cover surface. Force of air and abrasive on fringe not being utilized. f' tun &celerates and develops an outlet speeà twice that of a straight barrel nozzle. FIGURE 12 Nozzle styles. Courtesy of Clemtex Ltd. 60
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SSPC CHAPTER*2.4 93 8b27940 0003493 259 = A general comment on abrasive tests would include the following: Only open blast cleaning is represented. Fine abrasives clean faster than coarse abrasives. Fine abrasives produce less etch than coarse abrasives. Reuse of abrasives lowers cleaning costs. Some abrasives imbed in mild steel. Illustrated is recessed Flo-Flor with 3 recovery pans. While configurations of Flo-Flor systems will vary, the components of each system will be the same NOTE: Attention must be given to drainage around recovery system. Moisture entering the recovery area will cause serious malfunction. FIGURE 13 Abrasive recycle system for blast room. Courtesy of Clemco Industries. VII. TRAINING OF OPERATORS A well trained sandblast operator can be a great asset. There are training films and training literature available from equipment manufacturers. It is easy to plan a training session. Specific topics that should be covered are Purpose of cleaning and degree of cleanliness required for protective coating to achieve maximum economical life. Training and familiarization of actual working pieces of equipment used in air blast cleaning operat ion. Air Compressor -start, stop, pressure adjustment. Abrasive Blast Machine -start, stop, abrasive filling, abrasive mixture control, choking machine to relieve moisture and inspection of ASME code stamp. Operator Remote Controls -start, stop and emergency shut-down. Trouble-shooting of problems. 61 a.. _L-
FIGURE 14 Effect of nozzle pressure upon cleaning rate. Cleaning time is two minutes. Courtesy of Clemtex Ltd. Air and sandblast hose -required for different size nozzles. Proper coupling techniques. Nozzle -proper size and care of (Figure 15). Complete equipment -with air-fed helmet (Figure 16), filter and pressure regulation. Care, maintenance and assembly. Proper grounding -of all equipment. Abrasive -type and size. A. SAFETY REQUIREMENTS It is necessary to stress the safety aspects of air blast cleaning. At the work place everyone should be advised of health hazards of improper grounding, abrasive dust, contamination, spent abrasive removal and known hazards of working with high pressure equipment. Scaffolding is not included in this section, but should not be overlooked. Safe scaffolding is very important and can provide many benefits. Safety requirements should be in accordance with all applicable federal, state, and local rules and requirements. They should also be in accord with instructions of the paint manufacturer and of insurance underwriters. A checklist of necessary precautions would include but not necessarily be limited to the following: 1. Proper grounding techniques -With the use of anti-static abrasive blast hose, the static electricity cannot build up as it dissipates immediately; however, precautions should be used when working with volatile, flammable materials. An example is petroleum storage tanks or similar containers. Equipment and the piece that is abrasive blast cleaned should be grounded. Quite often, patches (or repairs) to the vessel, valves and gauges are insulated from the tank itself by gaskets or epoxy adhesives; therefore, it is very important that all items be grounded and checked for ground potential. These pieces, when abrasive blast cleaned, build up high static electricity potentials. In some extreme cases the nozzle and worker should be grounded to the part being abrasive blast cleaned. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
--`,,,,`-`-`,,`,,`,`,,`--FIGURE 15 Effect of nozzle size increases production rate from 96 to 180 to 252 cq. ft. pe r hr. Courtesy of Ciemtex Ltd. When weldments or small parts are being cleaned, it is not required to go into such detail when proper equipment and static dissipating abrasive hose are used. In the interest of safety, these conditions must be checked before blast cleaning. 2. Breathing air -With oil-lubricated air compressors, whether driven by electric or gasldiesel engines, a proper charcoal filter, particulate filter ora chemical cartridge filter should be used to sup ply breathable air to air-fed blast hoods. In some cases a separate air source should be used. The air supply should be monitored or sampled routinely with a carbon monoxide detector to ensure safe air supply. The air-supplied helmet should have NIOSH approval for use as a Type CE abrasive blast air-fed helmet. The instructions on its use should be carefully followed and a maintenance system installed. 3. Abrasive dust -Abrasive blast operations require an understanding of the principles of industrial hygiene and personal protective equipment. Abrasives, as provided for use in the abrasive blast industry, do not pose a hazard because they are not themselves respirable. However, when they are used in the blast cleaning process, they create a fine respirable dust. Inhalation of this dust may be harmful to the respiratory system. Therefore, it is imperative that the abrasive blast operator wear a National Institute for Occupational Safety and HealthIMine Safety and Health Administration (NIOSHIMSHA) approved type CE positive pressure air supplied blast hood. Other workers in the area should also be supplied with respirators. If no respiratory protective device is used, crystalline silica abrasives can cause silicosis after several years of constant exposure. Therefore, extreme caution should be used with these abrasives. Use of a low silica substitute (less than 1% free silica) should be considered. Although particles in excess of 10 microns are not readily breathable, the nuisance dust should be avoided with respirators designed to guard against this dust. Metal abrasives, copper slag and coal slag abrasives do not contain free silica; however, they do break down and cause a dust that should be avoided. ALL abrasives used in abrasive blast cleaning do break down and create a dust hazard. Work-
ers involved in blast cleaning operations should be provided with personal protective equipment. Water blast cleaning minimizes dust levels. (Refer to Chapter 2.5.) Compressed air cooled aftercoolers also serve this purpose. They cause the compressed air to expand, lowering the dewpoint and eliminating moisture in the blast cleaning system. By drying the air, the aftercooler reduces abrasive use and resulting dust considerably. (Refer to Section IIIG) 4. Contaminated Dust -This dust is often overlooked and can be more of a problem than abrasive dust. As abrasive and the contaminant dust combine, it is wise to ensure that respiratory and skin protection devices are adequate to protect workers from such contaminants as old lead paint, coal tar derivatives, and various metal oxide decay. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 62
In a majority of air blast operations this area of abrasive and contaminated dust is confined to a 200-foot radius from the nozzle. All workers in this area should wear respirators designed to provide safe, respirable air to required health standards. 5. Hazards of working with high pressure equipment -Any type of pressure equipment must be designed in accordance with ASME Code for working pressure requirements and so labeled. Excess pressures to overcome pressure drops on long hose lines should be avoided to maintain safe working conditions. Pressure vessels should be inspected annually. Personnel should be completely familiar with their use and operation. Pressure vessels (abrasive blast machines are non-fired pressure vessels) should be depressurized prior to inspection, filling of abrasive, and maintenance on controls. These vessels should not be transported under pressure. Although abrasive blast machines are provided with pressure gauges, they are not reliable because of fine, abrasive dust and harsh treatment received in this type of work. Therefore, the vessel should be fitted with a depressurizing valve (bleed-off valve) near the abrasive opening to discharge pressure prior to opening. Safety procedures are generally furnished with airblast equipment. Safe maintenance painting practices should include, but not be limited to SSPC-PA Guide 3 A Guide to Safety in Paint Application . ACKNOWLEDGEMENT The author and editors gratefully acknowledge the active participation of the following in the review process for this chapter: Wallace Cathcart. Howard Cheshier, Charles Fox, Charlie Lewis, A. W. Mallory, R. N. McCormick, Marshall McGee, William Pearson. Robert Roth and William Wallace. BIOGRAPHY P.J. BENNETT P.J. Bennett is a Registered Professional Engineer with 38 years experience in the fields of surface preparation and abrasive blast cleaning. He received a Bachelor of Science in Civil Engineering from Texas A&M in 1950. He is a member of a number of professional organizations. REFERENCES 1. B. Baldwin, Methods of Dust-Free Abrasive Blast Cleaning .
Plant Engineering, pps. 116-125, February 16, 1978. 2. P.J. Bennett, Surface Preparation Abrasives . Materials Protection, July 1964. 3. H.P. Bradley, Tanks Can be Sandblasted Safely . Petroleum Refiner, January 1961. 4. N.D. Cosdorph; Engineering Approach to Chemical Plant Coating , Corrosion, 1960. 5. Use of Abrasive Blast Equipment . Clemco Industries.: FIGURE 16 Air-fed helmet with filter. Courtesy of Clemco Industries. FIGURE 17 By eliminating moisture in the blast cleaning system, compressed air aftercoolers reduce abrasive use and dust levels. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 63
SSPC CHAPTERt2.5 93 m 8627940 0003494 TbB m September 1993 (Editorial Changes) CHAPTER 2.5 WATER BLAST CLEANING by P. J. Bennett Water blast cleaning (sometimes called hydroblasting) uses water at high pressure, 10,000 or more psi, and low volume, 2 to 15 gallons per minute, to prepare metal for painting. This process removes loose, flaky rust and mill scale. It has gained wide acceptance where dry abrasive blast cleaning dusts and contamination present a hazard to personnel and machinery. Water blast cleaning does not replace abrasive blast cleaning. Water alone cannot etch a metal surface. injection of dry abrasive at the nozzle achieves a surface etch. Many applications prior to painting are enhanced by this method with these major advantages: fast cleaning of soiled surfaces, a neutral surface for application of paint coatings, and low cost. It is important to exercise caution when using high pressure forces, taking care to protect personnel and equipment. I. DESCRIPTION AND USE Hydroblast cleaning takes a clean, filtered water supply into a power driven stainless steel pump and increases water pressure to as much as 10,000 psi. High pressure water is conveyed through hoses to a hand-held gun with a small diameter orifice nozzle (Figure 1). When abrasive is injected into the water stream, the process becomes much more effective. This method restricts dust and flying particles. When abrasive is used to expose bare metal, a secondary washing procedure must follow to remove spent slurry. This procedure includes a rust inhibitor, which must be compatible with the painting system. Hydroblast cleaning offers the greatest advantage in maintenance because of cleaning speed. With abrasive injection, it can be used to clean irregular shapes, back-toback angles, corroded valves, marine vessels with sea water corrosion and similar hard-to-clean surfaces. It has a wide range of applications, but does not solve all cleaning problems. It is not used to shop clean new weldments. Abrasive air blast cleaning can be used effectively and economically on new steel construction, where inorganic The process has been used by industry to clean heat exchangers, boilers, flaking tar, clogged piping, rubber molds, concrete surfaces and latency from fresh concrete prior to pour. It also is used in plant filter screens and con-
taminated floor areas. II. LOW PRESSURE TYPES Waterblast cleaning with water pressure. up to 2000 psi is low pressure cleaning (Figure 2). As water pressure increases, so does cleaning rate. Low pressure waterblast cleaning uses the same equipment as large units, ¡.e., engine, pump, hose and gun, but a smaller size and less water volume. The size of the cleaning job dictates the equipment required. Low pressure cleaning is referred to as Power Washing and should be recognized in that service requirement. Low pressure Power Washers are especially suited for removing oil and grease accumulations when water is added to a detergent inhibitor. The volume of water, in gallons per minute, at this pressure also influences the cleaning rate. The greater the volume, the greater the force or cleaning rate. 111. HIGH PRESSURE High water pressure cleaning is most widely used (Figure 3). It provides higher pressures and volumes for greater production cleaning rates. Pressures up to 10,000 psi and volumes to 10 gpm provide maximum cleaning rates and maximum endurance of the operators physical ability. Pressures up to 20,000 psi have been used. The most commonly used pressure for maintenance surface preparation is 3000 to 6000 psi at 8-10 gpm water volume. This pressure and volume provides an operator with a workable cleaning force and limits fatigue, resulting in greater overall performance. High pressures require safety provisions for sure, sound footing for operators. Ultra high pressure methods, which may use pressures above 40,000 psi, are more efficient but also more expensive. zinc primers are used as permanent primer. The hydroblast method is not preferred, due to rust forming between the *For further informatio n on water blasting, see Recomdrying period and coating application. mended Practices NACE RP-01-72: Surface Pr eparation of Steel by Water Blasting by L.L. Sline. 64 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*2=5 93 8627940 0003495 9T4 W FIGURE 1 Typical Water Blast Equipment with Sand Injection. Courtesy of Partek Corporation of Houston IV. EQUIPMENT Abrasive is injected into the system after water is pressured by means of a suction head to prevent pump The basic waterblast unit consists of an engine driven damage. It is usually inj ected at the blast gun before the pump, inlet water filter, pressure gauge, hydraulic hose nozzle. The high pressure jet induces abrasive from short of burst pressure 3 times working pressure, gun and distances (up to 25 feet) by vacuum. The preferred method nozzle combination. The water gun should be a fail-safe is to use a pressure abras ive blast machine to ensure even dump gun, to relieve pressure should the operator release and adequate flow for distances greater than 25 feet. the trigger. Nozzles are usually circular orifices for concentrated round spray and tapered for flat or fan spray. Long hose may be used (200 -300 feet) without loss of pressure. Air compressors are not required for hydroblasting. V. INTRODUCTION OF ABRASIVES Any type of abrasive commonly used with air blast cleaning can be used in waterblast cleaning. Sand is the most common abrasive. Injecting abrasive into water eliminates dust that normally accompanies dry use of friable abrasives. Use of expensive abrasives is limited because spent abrasive becomes wet and contaminated. In this condition it cannot be economically dried, screened and recycled. FIGURE 2 FIGURE 3 Low pressure water blast cleaning with sand injection. High pressure water blast cleaning with sand injection. Courtesy of Acme Cleaning Equipment Company Courtesy of Tri-Tan Corporation 65 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERr2.5 93 8b279LIO 000349b 830 TABLE 1 SOME WATERBLAST CLEANING RATES* Sq. Ft. Per Hour SURFACE Water Only -W 0-2000 PSI 3000 -6000PSI 10,000PSI CONDITION Sand Injection -SI @ 5 GPM 6-8 GPM 10GPM Easy to clean, dusty settlement, flaky flat W 150 350 500 surface, light oil or grease SI 200 450 650 Average rusty surface W 75 200 250 angles and piping SI 1O0 225 350 Heavily corroded surface W 20 75 125 rust scale, irregular shape SI 25 1O0 175 NOTE: Hydroblast surface comparable to SSPC-SP 6 condition. Abrasive cleaned surface comparable to SSPC-SP 10 condition. *These rates not necessarily achieved under different surface conditions. VI. PRODUCTION RATES The speed of cleaning is dependent on highest VIII. COST COMPARISON manageable working pressure and volume of water. Depend- Hydroblast cleaning cos t can be nearly the same as --`,,,,`-`-`,,`,,`,`,,`--ing on surface condition, hydroblasting compares favorably dry abrasive blast cl eaning. Equipment costs are approxiwith dry or wet sandblasting. Table 1 is a guide to cleaning mately the same and production is comparable. There is a rates, based on the author s experience. difference because of inhibitors and rins ing costs. VII. INHIBITORS Steel cleaned by waterblast or water pressure flashes rust upon drying unless an inhibitor is in the spray solution or applied immediately after blasting. Inhibitors are generally injected at the blast nozzle, similar to sand injection. Inhibitors are generally sodium andlor potassium dichromate or phosphate. They mix well with water and retard corrosion until suitable paint is applied. The solutions, upon drying, leave salts that can produce adhesion problems for protective coatings. Hydroblast equipment manufacturers market chemical solutions that are very effective in retarding rust. The prime consideration should be to determine if the protective coating is compatible with the inhibitor. After hydroblast cleaning, the surface must be rinsed of spent abrasives. It is necessary to use an inhibitor that
prevents rust formation after rinsing. Inhibitors can retard rust up to seven days. This is par- FIGURE 4 ticularly useful in tank work. The entire surface can be Gasoline driven trailer mount -showing optional hose reel. Courtesy of Tritan Corporation cleaned prior to painting. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 66
SSPC CHAPTER*2*5 93 8627940 0003477 777 The blast gun should have automatic control to release pressure when the operator releases the trigger. A dump valve on the gun serves this purpose. Everyone within 50 feet of the work area should be warned of hazards associated with hydroblast cleaning (including signs a,nd rope-Offs where necessary). No electrical power should be in the work area. ACKNOWLEDGEMENT The author and editors gratefully acknowledge the active participation of the following in the review process for this chapter: James Flaherty, A. W. Mallory, Joe Mazia, Marshall McGee, William Pearson, John Perchall and Bill Wallace. BIOGRAPHY A biographiwl sketch and photo of Jim Bennett appear at the end of Chapter 2.4. FIGURE 5 Steel blasted to white finish (SSPC-SP 5) at 10,000 psi. Courtesy of Partek Corporation In maintenance painting, where job specifications require only removal of all loose paint scale and flaky rust and a thoroughly washed surface, the hydroblast method is very economical, compared to hand or power tool cleaning. Hydroblast cleaning may also be preferred where there are restrictions on äry abrasive blast cleaning. IX. SAFETY PRECAUTIONS AND PROTECTIVE EQUIPMENT Hydroblast cleaning uses high pressures. Extreme caution should be exercised with the equipment. Instruction and training of operators about correct use and equipment operation is essential. Surfaces, other than metal, can be damaged with high pressure water and should be protected from effects of the high pressure water blast. The operator of a hydroblast unit must have sound, safe footing. Extra caution should be taken on rigid scaffolding. Swinging stages and bosun chairs are not normally recommended for use with hydroblasting. The operator should wear a rain suit, face shield, hearing protection and gloves. 67
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SSPC CHAPTER+Z.b 93 m ab27940 0003502 964 CHAPTER 2.6 HAND AND POWER TOOL CLEANING by Preston S.Hollister and R. Stanford Short I. HAND CLEANING Hand cleaning is one of the oldest processes for preparing surfaces prior to painting. Generally, it is used only when power operated equipment is not available, if the job is inaccessible to power tools or when the job is small. Tools needed include wire brushes, non-woven abrasive pads, scrapers, chisels, knives, chipping hammers, and, in some instances, conventional coated abrasives. Specially shaped scrapers or knives are sometimes necessary. In close areas tools must be shaped so they can enter areas to be cleaned. Further limitations are also found with hand tools when tight mill scale or rust must be removed. These can be cracked on impact and removed with scrapers, abrasive paper or non-woven abrasive pads, a very slow and impractical method except for small areas. There is danger that deep markings in the metal from impact tools will leave a burr on the metal surface that interferes with coating systems performance. Generally, both hand and power tool cleaning are employed for economical cleaning. Before hand cleaning, the surface should be examined to determine the contaminants to be removed. Work should follow the Steel Structures Painting Council Surface Preparation Specification No. 2 Hand Tool Cleaning . Solvent cleaning should precede hand cleaning when detrimental amounts of oil and grease or other soluble contaminants may be present. This procedure is specified in detail in SSPC-SP 1. A. HAND CLEANING TOOLS Dried or caked soil and other such contaminants are generally removed with loose mill scale and rust by scraping, brushing with non-woven abrasive pads, wire brushing and hand chipping. It is important that any surface contaminant, such as gobs of oil or grease, is not distributed over the entire surface through cleaning operations. Some tools used for hand cleaning are illustrated in Figure 1. Wire brushes may be of any practical shape and size. Two general types are the oblong with a long handle and the block type. Bristles are of spring wire. Brushes should be discarded when they are no longer effective because of lost or badly bent bristles. Non-woven abrasives are used
in simple pad form or applied to a backup holder with handle (Figure 2). They are conformable and can be cut to fit various applicators. Scrapers may be of any convenient design. Figure 3 shows practical scrapers used by maintenance crews. Scrapers should be made of tool steel, tempered and kept sharp to be effective. Some scrapers are made by sharpening the ends of 1-112to 2-inch wide flat files or rasps and fastening them to a handle. The handle may be up to 5 feet long to increase the area that can be reached. Other chipping and scraping tools made from old files or rasps have both ends sharpened. Several inches from one end, the file is bent at right angles. Hand-chipping hammers are advisable in maintenance work where rust scale has formed. A chipping hammer is about 4 to 6 inches long with two wedge-shaped faces at either end of the head, one face perpendicular to the line of the handle and the other at right angles to the first face. Typical tools are illustrated in Figure 3. Auxiliary equipment includes dust brushes, brooms, various sizes of putty knives and conventional painters scrapers, coated abrasives, and safety equipment such as goggles and dust respirators. B. PROCEDURES Hand-cleaning operations vary depending on the job. Rust scale forms in layers. It is removed first, usually by impact from hand chipping hammers, sledge hammers, etc. Where rust scale has progressed to the point where thickness of the metal has been diminished, extreme care in removing rust scale by impact prevents heavy sledges from puncturing the metal. Deep marking of the surface must be avoided. Burrs interfere with performance of the coating system. After rust scale, oil, grease and similar contaminants are removed, all loose and non-adherent rust, loose mill scale and loose or non-adherent paint are removed by a suitable combination of scraping and nonwoven abrasive or wire brushing. The cleaning method depends on the surface. Loose, voluminous rust is easily removed by scraping with thin, wide-blade scrapers and then wire or non-woven abrasive brushing. Tightly adherent rust is generally removed with a heavy scraper. Hand cleaning does not remove tight mill scale and all traces of rust. Complete removal is extremely expensive and noneconomical, except for extremely small areas. Rust, scale, oil, grease, etc., should be removed from the surface before cleaning. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 6%
SSPC CHAPTER*Z.b 93 m 8b27940 0003503 BTO W 111. IMPACT CLEANING TOOLS Impact cleaning tools are characterized by chipping and scaling hammers. With these tools, a chisel is struck by an internal piston and strikes the work surface. Chisels can be adapted for scraping and chipping. This type of tool is useful when heavy deposits of rust scale, mill scale, thick old paint, weld flux, slag and other brittle products must be removed from metal. Typical tools are shown in Figure 4. Chisels have different shapes and are made of various materials. A needle scaler is a scaling hammer with a bundle of steel needles housed and positioned forward of the striking piston. The piston strikes all needles simultaneously, propelling them individually against the work surface. This FIGURE 1 Tools used in hand cleaning operations. An oblong type of wire brush is shown to the right of goggles and gloves; wide blade hand scraper; hand chipping hammer; long-handled, wide blade scraper; hammer and chisel used for removing rust scale. Hand-cleaning painted surfaces removes all loose non-adherent paint in addition to any rust or scale. If paint is thick, edges of the old paint should be feathered to improve the quality of the paint job. After cleaning, the surface is brushed, swept, dusted and blown off with compressed air to remove all loose matter. II. POWER TOOL CLEANING PLINTERS RUST CHISEL PAINTERS' SCRAPER Use of portable power tools -pneumatic and electric -is common for cleaning operations. Through careful selection and use of the great variety of power tools and accessories, many cleaning operations can be accomplished rapidly and produce satisfactory surface conditions with reasonable labor costs and good paint life. Power tools used for surface cleaning fall into three basic families: requirements. --`,,,,`-`-`,,`,,`,`,,`--Impact cleaning tools FIGURE 3 Rotary cleaning tools Shop drawings of typical hand tools. Rotary impact cleaning tools Tools in each family have unique characteristics that type of tool adapts to irr egular surfaces. Needle scalers make them adaptable to different cleaning operations and are illustrated in Figu re 5. They are most effective on brittle and loose surface contaminants. Piston scalers are similar to scaling hammers, but the piston is also the chisel. This minimizes the axial dimen-
sion and permits use in operations with limited access. This type of tool is available in single and multiple piston types. Some makes can be mounted in groups for cleaning large surface areas. Cleaning surfaces with scaling and chipping hammers is comparatively slow. When considerable rust scale or heavy paint formation must be removed, it may be the best and most economical method. Impact cleaning tools are available with various handle and throttle styles. They should be selected for FIGURE 2 specific operations with consideration for operator safety, Non-woven abrasive pad attached to plastic backup holder. convenience and prefer ence. This minimizes fatigue and Courtesy of 3M Company. improves operator productivity. 69 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERa2.6 73 8b27740 0003504 737 FIGURE 4 A selection of various chipping hammers and the chisels they use. Courtesy of ARO Corporation. Great care must be exercised in using tools because of the tendency to excessively cut into the surface, removing sound metal and leaving sharp burrs where the paint will fail prematurely. The cutting action of sharp chisels is valuable for shaping sharp edges to a rounded or less sharp surface so paint does not pull away. It also removes imperfections from the surface. These tools may be used to remove tight mill scale and surface rusting, but they are not the most practical or economical tools because they gouge metal, which must be smoothed to do a thorough job. Tools must be sharp or they may drive rust and scale into the surface. IV. ROTARY CLEANING TOOLS Rotary power tools do most hand-cleaning jobs rapidly. Rotary power tools and the cleaning media that fit them are discussed. A. CLEANING MEDIA There are three basic types of cleaning media for rotary power tools: non-woven abrasives, wire brushes and coated abrasives. As subsequently described, these media can be used on two basic types of tools. FIGURE 5 Typical needle scalers. Courtesy of ARO Corporation. Non-woven abrasives and rotary wire brushes can be used to remove old paint, light mill scale, rust, weld flux, slag and dirt deposits. Wire brushes (Figure 6) can be composed of differently shaped and sized wire bristles. Bristles may be crimped or knotted. Non-woven abrasive products (Figure 7) can be composed of various grades of abrasive and densities. Wire brushes and non-woven abrasives come in cup and radial (wheel) form. Non-woven abrasives also are available in disc form. Selection of style and type of bristle or non-woven abrasive composition should be based on trials. Surface condition affects the efficiency of cleaning. Non-woven abrasives are particularly FIGURE 6 Types of brushes used with power tools. On the left is shown a wheel type of stiff wire brush; in the center and on the right are shown cup types of wire brushes of knotted construction; on the lower right is a wire brush with a crinkled wire construction. On the lower left is a wire brush used for cleaning corners, etc.; in use it is held in an adaptor illustrated in the lower center. advantageous in removing coatings because of lowered susceptibility to loading, as compared to coated
abrasives. Coated abrasives are used in several converted forms (Figure 8). Discs and flap wheels are used to remove loose mill scale, old paint, etc. similar to wire brush applications, but can remove base metal. Loading from old paints may make such applications uneconomical for discs. B. TOOLS Tools for the three above media are divided into two basic types: straight, or in-line machines (Figure 9), and vertical or right angle machines (Figures 10, 11). The straight or in-line machine style is used with radial wire brushes, coated abrasive flap wheels and nonwoven abrasive wheels. The vertical machine style is suited for cup wire brushes, coated abrasive discs, nonwoven abrasive discs, cup wheels and wheels. The type of machine varies with job conditions. It is advisable to have both types on hand and generally both are used on field jobs. Operator fatigue is an important factor in power tool cleaning. An operator s preference should be considered in selecting a machine. In some cases, where much overhead work is to be done, small lightweight machines may be used. Machines may be operated by pneumatic or elecCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 70
SSPC CHAPTERt2.b 73 8b27740 0003505 673 Non-woven abrasive wheels are recommended where base metal should not be removed but where wire brushes are not aggressive enough. Non-woven abrasive wheels wear at a controlled rate. Fresh working abrasive provides a constant rate of surface cleaning with minimal loading. Non-woven abrasive wheels are useful in removing light mill scale. In many applications, non-woven abrasives are a quicker and more effective alternative to wire brushes or coated abrasives. In power wire brushing it is possible to cut through some mill scale by using the toe of a very stiff brush and bearing down hard. It is impractical to remove tight mill scale by power wire brushing. Generally, removal of only loose mill scale and rust is required. Too high a speed must not be used with rotary wire brushes and the brush must not be kept on one spot for too long. Detrimental burnishing of the surface may occur. Under such circumstances the surface is smooth and develops a polished, glossy appearance that provides a poor anchor for paint. It is clear that doing too much surface work is detrimental. Rotary wire brushes are particularly notorious FIGURE 7 for spreading oil and grease over the surface. Oily or Non-woven abrasive products are available (from right to left) in greasy surface s must be cleaned with solvent before disc, wheel and cup wheel forms. power brushing. Coated abrasive and non-woven a brasive Courtesy of 3M Company. products are also vulnerable to oily or greasy surfaces. tric motors. Lightweight machines operated by high fre- Solvent cleaning, prior to power cleaning, is recomquency current are available. mended. The machine should be compatible with the size and Coated abrasives are particul arly useful for applicaspeed rating of the cleaning media and should produce tion where metal removal i s either desired or acceptable, enough power to perform the operation efficiently. Most such as weld grinding. T ight mill scale cannot be removed air powered machines contain governors to limit the free with such media, but lo ose scale can be. operating speed. Governors respond to tool load resulting from thrust applied to the work surface and supply more V. ROTARY IMPACT TOOLS air to the motor, increasing power output and maintaining Rotary impact tools op erate on the same basic princiits rated speed while under load. Electrically driven ple as other impact tools, through cutting or chipping machines operate at a fixed speed. action, but rotary tools use a centrifugal pr inciple where cutters or hammers are rotated at high speed and thrown against the surface. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from
IHS FIGURE 8 Coated abrasives disc (left) or coated abrasive flap wheels (right) are used for surface preparation. Courtesy of 3M Company. 71
SSPC CHAPTER*Z.h 93 8b27940 0003506 50T --`,,,,`-`-`,,`,,`,`,,`--failure due to insufficient paint coverage. If these tools are used to remove all mill scale and rust from the surface, it is very likely that the surface will be too rough for satisfactory painting unless a very thick coating, such as coldapplied mastic, is applied. VI. TOOL SAFETY Safety is a very important consideration when using tools. It includes proper use and maintenance of tools, and protection from air-borne contaminants. Prescribed safety practices are published by various FIGURE 11 A non-woven abrasive cup wheel in use on a vertical power tool. Courtesy of 3M Company. organizations, including the American National Standards Institute, the National Safety Council, the Occupational Safety and Health Administration and the Environmental Protection Agency. Some publications are referenced at the end of this section to help users identify them, and include recommended operating procedures. Safety practices include the following considerations. Tool users and other people in the area should wear eye FIGURE 10 protection to guard against flying particles. Different Three air-powered vertical or right-angle power tools. types and requirements ar e prescribed in ANSI Z 87.1. Ear Courtesy of ARO Corporation. protection should be considered when impact tools a re 72 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*Z-b 93 8627740 0003507 446 D FIGURE 12 Top left are four types of cutters or stars. Next is a heavy-duty rotary peening flap. Pictured below the row is a rotary hammer. Courtesy of Desco Manufacturing Co. used. Particular attention should be paid when using several tools simultaneously in close proximity. Hand tools should be properly selected for the purpose and properly maintained. Hammers should be properly heat-treated and striking faces maintained to eliminate mushrooming and flying fragments. Chisels must be maintained on the striking and cutting ends. All sharpedged tools deserve respect and proper consideration. Electrical tools should be run in dry environments. They should be grounded or double insulated. Power cords should be kept in good repair. Impact tools should be operated only when the chisel or scaling tool is in position and in contact with the workpiece. Tools should not be used if ejection of an accessory might endanger personnel. Rotary wire brushes should be run at or below manufacturer s rated maximum operating speed. Gloves and leather aprons are additional safeguards to avoid injury from loose wires. Recommended guards should always be used. Coated and non-woven abrasives should be run at or below manufacturer s rated maximum operating speed. Non-woven abrasive wheels should be operated in the proper direction of rotation. The wheel or disc should be put on the tool and tightened securely while the tool is disconnected from the power supply. Guards should be used. Protective clothing should be considered. Proper air pressure to pneumatic tools is important. Proper rpm should be checked with a tachometer on all tools before use. Rotary impact tools also should be operated at or below manufacturer s rated maximum operating speed. Proper guards should be used on such tools. When using Heavy Duty Roto Peen, it is important to have flaps loaded for direction of rotation as recommended. These media should be tightened securely and run only when contacting an appropriate work surface. Respirators should be used if contaminants in the breathing zone exceed applicable threshold limits. This is of particular importance when cleaning paints containing lead, chromate or coal tar products. Since the cleaning operations can produce sparks,
care must be exercised when cleaning in the area of combustibles and volatile vapors. When such conditions cannot be avoided, only special non-sparking tools should be used. For more complete information on the subject of safety, refer to the following: Standard for Safety of Portable Electric Tools , C33.49. American National Standards Institute, 1 1 West 42nd St., 13th Floor, New York, NY 10036-8002. (Also UL45, Underwriters Laboratory). Safety Requirements for the Design, Care, and Use of Power Driven Brushing Tools , 8165.1, American National Standards Institute. Standard for Occupational and Educational Eye and FIGURE 13 This electric tool (right) used a flap loading of heavy duty rcitary peening (left) to remove mill scale from carbon steel. Courtesy of 3M Company and Desco Manufacturing Company. 73 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*2*b 93 8627940 0003508 382 Face Protection , 287.1. American National Standards Institute. Accident Prevention Manual for Industrial Operations , seventh edition, National Safety Council, 1121 Spring Lake Drive, Itasca, IL 60143-3201. Also, various Occupational Safety and Health As2;ociation regulations may be applicable. Reguiations are available from the Occupational Safety and Health Admiriistration, U.S. Department of Labor, Washington, DC. ACKNOWLEDGEMENT The authors and editors gratefully acknowledge the active participation of the following in the review process for this chapter: Dick Anderson, Duane Bloemke, William Mathay, Duke Mallory, Ben Nieters, Bob Roth, and Bill Wallace. BIOGRAPHIES Preston Hollister graduated from the University of Illinois at Champaign-Urbana in Decernber, 1979 with a B.S. in chemical engineering. He worked as a technical service engineer with Minnesota Mining and Manufacturing Company, Building Service and Cleaning Products Division, where he specialized in non-woven abrasive products for industrial applications. He actively represented 3M not only in the SSPC but on ASTM s D33 committee on Protective Coating and Lining Work for PowerGeneration Facilities and the Utilities Nuclear Coatings Work Committee. R. Stanford Short retired as Manager of Engineering Standards and Services at the Aro Corporation, Bryan, Ohio. He received a B.S.M.E. from Michigan State College (University) in 1950 and had been associated with The Aro Corporation and the pneumatic tool industry from 1953 to 1983. Mr. Short was engaged in the design, research and development of air tools and systems for 17 years. He holds numerous Datents for air tool inventions, has conducted numerous seminars, and has had papers --`,,,,`-`-`,,`,,`,`,,`--published on various facets of pneumatic tools and their use. In addition to having served the Compressed Air and Gas Institute (CAGI) as its representative to the European Committee of
Manufacturers of Compressors, Vacuum Pumps and Pneumatic Tools (PNEUROP), he was chairman of the CAGI Pneumatic Tool Engineering and Safety Committees. Mr. Short was also a member of various committees of the American National Standards Institute, PNEUROP and the International Organization for Standardization. His professional affiliations have included membership in the American Society of Mechanical Engineers, the American Society for Testing and Materials, the American Society for Metals and the U.S. Metric Association. SUGGESTED READING V.M. Gin, 3M Brand Heavy Duty Roto Peen Flap Wheel Coating Removal System , BS&CP Division, St. Paul, MN, 1977. V.M. Gin, Mill Scale. Removal with 3M Brand Heavy Duty Roto Peen Flap Wheel , BS&CP Division, St. Paul, MN, 1976. P.S. Hollister, Surface Preparation Procedure for Repairs of Nuclear Grade Coatings on Steel and Concrete , BS&CP Division, St. Paul, MN, 1980. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 74
SSPC CHAPTERr2.7 93 m Bb279LlO 0003509 219 m September 1993 (Editorial Changes) CHAPTER 2.7 FIELD SURFACE PREPARATION COSTS bY Robert B. Roth The cost for surface preparation of carbon steel substrates varies with the degree of cleaning specified, the cleaning method and the efficiency of the organization performing the work. Designated surface preparation must be companioned with the selected protective coating systems, and the inherent, desired or designed performance. Direct costs include labor, taxes and insurances, materials, supervision, scaffolding, equipment and inspection. Indirect charges cover items such as engineering input, overhead, cost of capital, administration of the work, depreciation and cost of down time. The total cost is the sum of direct and indirect amounts. This chapter presents general guidelines for the individual who has to select cleaning methods, design specifications and establish budgets for painting and coating work. It also deals with the standards available and relative cost factors. I. DISCUSSION The individual concerned with surface preparation must research the assignment and select a degree of surface cleanliness and a coating system based on the criteria demanded by the type of service or exposures presented. Costs are escalating and warranties are essential. Unauthorized or capricious deviations can lead to failures; replacement or correction can be very expensive. To assure successful performance of the selected protective paint or coating system and to enjoy the guarantees available, recommendations of the paint or coating manufacturers must be followed. Specific circumstances may require variances, but variances must be authorized, in writing, by the manufacturer. Inspection and documentation are necessary for each phase of the job for the warranty to be valid. II. SURFACE PREPARATION There are nine formal surface preparation specifications as covered by SSPC specifications. Each specification is designed to define a degree of surface cleanliness and eliminate misunderstandings between vendor and purchaser. Cost of surface preparation should be based on workhours per square foot of surface area to be cleaned, based
on job records. The individual responsible for preparing the cost estimate or proposal for the work must recognize the type and degree of cleaning, type of cleaning equipment, steel configuration (plates, shapes, fabrications, etc.), sur75 face condition (mill scale, previous coating, degree of rust, and deleterious material), and accessibility (on shop floor, part of existing structure and adjacent hazards). 111. SSPC SPECIFICATIONS The following sections assume identical conditions of field work, supervision, crew experience, environment and new, mill scale-covered steel with light surface rusting. A. SSPC-SP 1 SOLVENT CLEANING For mildly contaminated steel substrates, an effective solvent cleaning at the rate of 500 square feet per workhour can be expected. Material use is approximately one gallon per hour. Use the cost of one gallon per hour, recognizing this quantity is conservative, to cover expendables, such as rags, mops, gloves, etc. B. SSPC-SP 2 HAND TOOL CLEANING It is reasonable to expect hand tool cleaning rates in the range of 250 to 300 square feet per work hour. Tool allowance costs at the equivalent rate of four units (scrapers or wire brushes, etc.) per person per day is adequate. C. SSPC-SP3 POWER TOOL CLEANING It is not reasonable to expect a worker to use conventional heavy, vibrating power tools or equipment continuously for an eight hour day. Experience shows that three to four productive hours per day can be expected. Power tools have other pitfalls: power wire brushes can polish or burnish the substrate; chipping hammers and power chisels can gouge the surface; and power sanders clean only the high areas leaving some areas untouched. It is reasonable to assume a cleaning rate of 100 square feet per hour in an eight hour shift or 400 square feet per person per day for power tool cleaning. It is also reasonable to expect a minimum of two items such as wire discs, cup brushes, sanding inserts, or chisels and varnox tip sets to be replaced per person per eight hour day. EXAMPLE: Assume 5000 square feet of steel plate, to be cleaned per SSPC SP 1,2 and 3. Experience indicates that 50% of surface requires solvent cleaning, 80% hand tool cleaning and 20% power tool cleaning due to some tight scale, etc. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*2-7 73 m 6627740 00035LO T30 m Your estimate would allow: SSPC-SP 1 Solvent Cleaning 5 person hours SSPC-SP 2 Hand Tool Cleaning 14-16 person hours SSPC-SP 3 Power Tool Cleaning 10 person hours Allow for expendables of port ion.
material in the same pro-
D. BLAST CLEANING (SSPC-SP 5,6,7, and 10) Most modern field practices use abrasive blast cleaning as a method of preparation, conforming to one of the above specifications. Sandblast cleaning can be the least expensive method of field surface preparation, especially if sophisticated equipment is used. When estimating for basic blast cleaning costs, consider three persons working an eight hour shift as a crew day . Two nozzles would be working leaving one person to handle hoses, move gear and to relieve occasionally the other nozzle operators. Table I presents cleaning rate data obtained by blast cleaning lightly rusted steel plate with a synthetic abrasive of medium hardness (30 to 40 mesh) using a #6 nozzle (J/ diameter) operating at a nozzle pressure of approximately 80 psi. These production rates allow for the stoppages and inefficiencies inherent in all such operations. Variables such as nozzle diameter, dead-man or automatic shut off and adjustments influence the rates on the guide chart , Table I. E. SSPC-SP 8 PICKLING Pickling employs large dip vats and large cranes or handling equipment and is a shop or fixed-facility operation. Costs are elusive, particularly since each shop employs a proprietary process and keeps divergent cost records involving equipment depreciation, discounted cash flow and related economic factors. In modern industry, pickling has been decreasing in volume practice. Expect lower cleaning rates when blast cleaning a pickled substrate. Depending on the pickling process used, field sandblasting rates can be reduced by as much as 50to 60 percent. TABLE 1 Cleaning Rate Data F. SSPC-SP 11 POWER TOOL CLEANING TO
BARE METAL This method uses power-tool driven abrasives to produce a bare metal surface. It is used when a roughened, clean, bare metal surface is required, but where abrasive blasting is not feasible or permissible. It differs from SSPC-SP 3, PowerTool Cleaning, in that SSPC-SP 3 requires only the removal of loosely adherent materials, while SSPC-SP 11 requires producing or retaining a surface profile. The equipment required for this method is relatively inexpensive, though slightly more expensive than traditional power tools. It is quite effective at removing paint, tight rust and mill scale from flat surfaces when used in conjunction with solvent cleaning. It is significantly less effective at removing these materials from irregular, hard-to-reach surfaces. The quality of the prepared surface for painting is suitable for most coating systems, with a minimum one mil surface profile. However, productivity is low. The technique generates more dust and debris than SSPC-SP 3. Dust levels can be reduced by using the tools inside a vacuum-equipped containment which surrounds only the tool. IV. WATERBLASTING Costs vary widely with conditions but a cleaning rate of approximately.3500 square feet per eight hour day (two be eliminated from the --`,,,,`-`-`,,`,,`,`,,`--person crew) using waterblast cleaning on lightly rusted steel plate can be expected. Abrasive blast cleaning of a surface that has already been hydrocleaned can be accomplished at a one-third greater production rate than that shown in Table I. Often the solvent cleaning step can specifications. V. COST REVIEW When making an estimate of surface preparation cost, consider these factors: 1. Labor (a) Rate classification
(b) Mechanics and Helpers (c) Field Supervision (d)Specialists (Riggers and equipment operating personnel and so forth) Average Cleaning Blast Cleaning Rate Per Three Specified Person Crew Day SSPC-SP SSPC-SP SSPC-SP SSPC-SP
7 Brush Off 5200sq. ft. 6 Commercial 2500 sq. ft. 10 Near White 1500 sq. ft. 5White Metal 1000 sq. ft.
Abrasive Used Per Relative Crew Day costs 7,000 Ibs. 1 8,000 Ibs. 2+ 12,500 Ibs. 3 /2 10,000 Ibs. 5+ Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERU2-7 93 8627940 0003511 977 2. Labor (a) Health, Pension, Welfare, Vacation, Fringes etc. (b)Travel pay, if applicable (c) Collect ive bargai ni ng addit ives 3. Labor Burden (a) Payroll Taxes (b)Payroll Insurances (c) Bonding Costs 4. Material (a) Abrasive Media (b)Solvents, thinners and diluents (c) Expendable supplies (d)Sales or Use Tax on the foregoing (e) Delivery costs on above 5. Equipment (a) Standard Blue Book or A.E.D. sources Rental (b) Fuels, Lubricants (c)Transportation and handling costs (d)Use taxes on above 6. Site of Shop (a) Permanent personnel -Project Organization Managing and Administrative (b) Site of Shop Plant (c) Storage or Warehousing 7. Overhead (Often expressed as a percentage of cost, items 1 through 6) 8. Profit (Often expressed as a percentage of cost plus overhead, items 1 through 7 above) An excellent aid in determining the cost of operating a blast cleaning crew in the field may be found in the current Estimating Guide of the PDCA (Painting and Decorating Contractors of America). --`,,,,`-`-`,,`,,`,`,,`--VI. SUMMARY A successful protective coating operation starts with proper surface preparation. Assuming personnel are trained, qualified and properly instructed, paint failures are usually the result of faulty surface preparation rather than deficiencies in the coating material. In following the cost projection guidelines presented, it is important to compensate for the specifics of each situation since no two assignments are ever exactly the same. Experience and good record keeping is necessary to enhance your estimating procedures. ACKNOWLEDGEMENT The author and editors gratefully acknowledge the active participation of the following in the review process for this chapter: Wally Cathcart, Jim Flaherty, Lowell Hartman, Joe Mazia, Jack Oechsle, William Pearson, Steve Pinney, Bill Wallace. BIOGRAPHY Robert B. Roth is Past President of Oliver B. Cannon and Son, Inc. Following graduation from Yale University, Mr. Roth
joined Oliver B. Cannon in 1948, advancing to Executive Vice President in 1956 and President in 1972, a position he held until his retirement in 1987. Mr. Roth was a member of the American Society of Civil Engineers, National Association of Corrosion Engineers, American Nuclear Society, the Utilities Nuclear Coatings Work Committee, and the American National Standards Institute Coatings committee. Mr. Roth is the author of the Painting Section in Plant Engineers Handbook and of numerous articles on protective coatings in professional journals. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 77
SSPC CHAPTERs2.8 93 m 86279YO 00035112 803 m September 1993 (Editorial Changes) CHAPTER 2.8 OTHER METHODS AND FACTORS IN SURFACE PREPARATION by Bernard R. Appleman and John D. Keane I. INTRODUCTION of silica sand abrasives may cause a debilitating lung Most painting and corrosion scientists consider sur- disorder known as silicosis . Silicosis is caused by face preparation to be the key factor in coating perform- breathing minute dust particles. OSHA is considering ance and protection. The more commonly used techniques establishing a standard f or worker exposure to silica and such as abrasive blasting, water blasting, hand and power other abrasive dusts, which could greatly restrict the type tool cleaning, chemical cleaning and pickling are covered and quantity of abrasi ves used for blast cleaning(*). in separate chapters. This chapter describes the many new The Environmental Prot ection Agency (EPA) has approaches to surface preparation of structural steel that established limits on the total permissible concentration have developed from the need to protect worker health and of suspended particula tes in air(3). Proposed revisions by the environment. Several of these proposed new tech- EPA would impose restrictio ns primarily on particulates niques also offer the prospect of improving the quality, with a diameter of less than 10 microns. safety or cost of many surface preparation operations. The dust produced from sa nd blasting is also objecOpen air sandblasting is being restricted in certain tionable because of visu al p ollution. Although no Federal locales because the paint and dust pollute the air and standards are in effect, many states and municipalities use water. In addition the Occupational Safety and Health Ad- the Ringelmann scale(4 ). This scale indicates the proporministration (OSHA) is concerned about protecting tion of light obscured by the particulates. A rating of 2 on workers against silicosis and other respiratory diseases. In the Ringelmann scal e, for example, corresponds to a
cleaning an existing structure, it may be necessary to reduction of 40% in visib ility. recover and dispose of old paint particles, particularly Environmental and occup ational health officials have those containing lead or chromium compounds. been very concerned about the compo sition of the old The selection of the method of surface preparation paint being removed from stru ctural steel, some of which depends on a variety of complex factors such as location contains toxic lead and chromium compounds. Sand blastand criticality of structure, availability of funds, existence ing of paint cont aining lead will frequently produce airand enforcement of regulations, and the experience and in- borne concentrations of lead greater than the maximum genuity of owner and contractor. permissible by the EPA. In addition, the paint particles are Several of the alternative methods are variations, im- deposited on roadways, wa terways, and adjacent ground. provements, and modifications on existing techniques, The extent to which these particles pose a health hazard such as water blasting or abrasive blasting. Others are has not been determined. The National Ambient Air Quality based on non-mechanical forces such as xenon lamps, Standard (NAAQS) for lead is 1.5 micrograms per cubic lasers, ultrasonic waves or plasma streams. Both of these meter (pglm ), averaged over a 90-day period(5). categories are covered in this chapter( ). This chapter also The Occupational Safe ty and Health Administration describes some of the specialized equipment and has established standards for ai r-borne concentrations of engineering approaches attempted by government agen- lead and chromium to protec t the worker in the There is little hard data available on the cies and industry to recover the abrasive dusts and paints. workpla~e(~>~). Other chapters describe the latest advances in blast clean- levels of these comp ounds to which a sand blaster would ing, power tool cleaning, and chemical cleaning. be exposed. Another potential problem associated with abrasive blasting of paint containing lead is the disposal of spent II. ENVIRONMENTAL AND HEALTH FACTORS abrasive. Lead is one of the toxic substanc es covered Environmental and health problems associated with by EPA s Resource Conservation a nd Recovery Act (RCRA) abrasive blast cleaning have been among the major factors regulations on solid w aste disposaW. The 1980 Federal in the search for new methods. In this section we will Regulations require the u se of the Toxicity Characteristic
describe briefly the specific hazards and the type of regula- Leaching Procedure (TCLP) to determine the concentration tion being considered. of leachable lead. If the concentration of lead is greate r than Health officials have expressed concern that the use 5 milligrams per liter, the material is classified as hazardous Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 78
SSPC CHAPTER*Z.B 73 m 8627740 0003533 74T m Area of --`,,,,`-`-`,,`,,`,`,,`--Concern Regulatory Agency Worker Health Federal: OSHA Worker Health Federal: OSHA Worker Health Federal: OSHA Worker Health Federal: OSHA Clean Air Federal: EPA Clean Air Federal: EPA Solid Waste Federal: EPA Clean Water EPA, States, Fish & Game, Coast Guard waste. A similar standard exists for hexavalent chromium. The used abrasives (often several hundred tons) would then require disposal in a more costly and often difficult to find toxic waste disposal site. Recent blast cleaning of some bridges in Massachusetts has resulted in lead concentrations of up to 60mg/liter(g). In summary, conventional sand blasting and other paint removal methods may produce the detrimental effects listed above (Table 1). Let us consider the prospects for alleviating the above conditions and satisfying the regulations. It is useful to divide the technology into those methods which alleviate the air pollution problem and those which alleviate the dust and paint fallout into water, roadways, etc. As will be discussed, the new techniques have had reasonable success in reducing the air pollution hazards associated with abrasive blasting. The problem of preventing dust and paint from being deposited into the ground and water is much more difficult and costly. 111. VARIATIONS ON WET AND WATER BLASTING The chapter on water blast cleaning describes the use of high-pressure water (up to 10,000 psi) to prepare metal for painting. Water-blasting alone, even at high pressure,
will not remove tight, intact paint and heavy rust buildup from structural steel at acceptable production rates. Wet blasting (the use of water along with abrasives), on the other hand, can provide highly satisfactory results for these. There are several different types of equipment and approaches available; the effectiveness and the cost depend strongly on the particular system selected. The main systems described include wet abrasive blasting, sand injection, and air-water-sand. A. CONVENTIONAL WET METHODS 1. Sand Blasting with Water This technique incorporates water into a conventional abrasive air blast unit. The sand is projected TABLE 1: MATERIALS REGULATED Material Regulated Silica (Respirable) Nuisance Dust (Respirable Fraction) Lead (Total) (Construction and General Industry) Chromium (Respirable) Lead (in air) Suspended Particulates Leachable Lead & Chromium Lead Residues ~~ Permitted Limits 100 pglm3 (8 hr. average) 5 mglm3 (8 hr. average) 50 pg/m3 (8 hr. average) 50 pglrn3 (8 hr. average) 1.5 pglm3 (90 day average) 150 pg/ms (24 hr. average) 5 mg/L zero discharge in some locales against the surface to be cleaned by means of compressed air as in dry sand blasting. A separate hose delivers the water to the nozzle. In the water curtain version, the water forms a ring around the sand nozzle. In this method sand and water emerge from separate orifices. There is little loss of abrasive velocity leaving the nozzle; cleaning rates are much the same as with dry blasting(ID).
2. Water Blasting with Sand Injection The abrasive is injected or aspirated into the water stream at the nozzle. It must necessarily be introduced after the water is pressurized to avoid pump damage. Figure 1 shows a typical abrasive injection unit. Many types of abrasives can be used in wet blast cleaning, the most widely used being sand. The type and size of abrasive is directly related to the rate of cleaning and the surface roughness. Particles too small or too large for the type of surface being cleaned can slow production. Systems have been developed wherein the operator may selectively blast with or without abrasive injection. In this way a surface can be cleaned of biofouling or other contaminants by water alone without disturbing the intact paint. Corroded areas, however, can be cleaned to white metal only by injecting the abrasive into the water stream. FIGURE 1 A typical sand injection blast unit. Courtesy of Partek Corporatlon Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 79
SSPC CHAPTER*2.8 93 8627940 0003534 686 = FIGURE 2 Typical marine use of the hydraulic equipment with sand injection. Courtesy of WOMA Corporation The overall performance of water blasting with or without abrasives depends on the abrasive, inhibitor, operational technique, surface condition and degree of cleani ng required. Several federal and state agencies have evaluated the performance of moderate to high pressure hydraulic cleaning systems. In one evaluation, most of the systems failed to meet the performance requirements because of being underpowered (operated at 500-1200 psi using conventional pumps) or because of inability to meter the sand without clogging. The most successful unit used pressures of about 2000 psi with two or more nozzles operated at the manifold( )(Figure 2). 3. Air-Water-Sand Some recently developed processes utilize a combination of air, sand, and water to provide a highly versatile and efficient means of preparing surfaces. A British version of the air-water-sand method includes a large volume of air (300 to 400 cubic feet per minute) into which one to two gallons of water per minute can be entrained with or without acorrosion inhibitor. Sand or other abrasives may be added at 200 to 400 pounds per hour, and the mixture is delivered through an open-ended, coneshaped, wide-mouthed nozzle (0.5 to 1 inch in diameter) at pressures which can be varied from 15 to 100 psi. In various trials the speed of cleaning has been estimated to be from 50 to 200 square feet per hour depending on the surface, with reported removal of single coats of paint leaving the primer coat intact at rates as high as 300to 450 square feet per hour. Each of the quantities -air, sand, and water -is independently adjustable so that the system can be used without sand at low pressure merely to wash down the A U.S. version involves a somewhat similar unit which operates at about 1000 pounds per square inch water pressure with sand injection. Unlike the English system, this one entails remote control via micro switches of a seven-ton dry blast pot by the operator at the nozzle rather than by verbal communications with an operator. Also, unlike the English method, it involves a considerable amount of sand, which sometimes has a tendency to stick to the work as a slurry. This slurry is then allowed to dry and is washed off with an
auxiliary nozzle at perhaps 1000 to 1500 square feet per h~ur(~~)(Figures 3a and 3b). 4. Sodium Bicarbonate Sodium bicarbonate blasting is one of a group of wet blasting and waterjetting systems that employ water-soluble abrasives. Like most wet blast systems, they produce less dust than dry blasting. Residue can be sent to a wastewater facility, rather than disposed of as hazardous waste, if paint chips, especially those containing lead, can be separated from the wastewater. The technique does not damage a substrate although it is very effective in scrubbing a surface. Sodium bicarbonate blasting has been shown to remove epoxies and urethanes, oil, grease and loose rust. It will not remove tight rust or mill scale, and does not impart a profile, so it is best suited for maintenance painting. Adhesion of various coatings after use of the system is still being evaluated. While sodium blast cleaning is more expensive than other methods, the decreased costs of waste disposal when paint chips are separated must also be taken into account. B. IMPORTANT FEATURES OF WATER AND WET BLASTING 1. Water Volume The volume of water varies considerably among the techniques discussed. The sand injection methods rely on water as the primary medium; typical flow rates are 5 to 15 gallons per minute (gpm). The water curtain entails only the small amount of water necessary to contain the dust. The air-watersand process typically uses 1-2 gpm. 2. Sand Volume The sand injection method uses considerably less sand than dry blasting or water curtain. The airwater-sand processes provide a greater degree of control of the abrasive and consume still smaller quantities of sand, with the British version using the least. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 80
SSPC CHAPTERUZ.8 93 m 8627940 0003535 512 m FIGURE 3 Cleaning underside of European bridge with air-water-sand unit. Coauthor observed separate sections which were cleaned to white metal (passing potassium ferrocyanide test) and others involving spot removal of individual coats. Courtesy of KUE, Ltd. 3. Water Nozzle Thrust Conventional high pressure and sand injection units develop pressures up to 10,000 psi and thrusts of 50 pounds, which can be a significant safety hazard, particularly when operated from a scaffold or other location of precarious footing. The sand injection unit may be operated at lower pressure (2000-3500 psi) for removing loose paint and rust. The water curtain and air-water-sand units normally operate at 1000-2000 psi, thereby considerably reducing the safety hazard. For these operations, the major safety consideration is pressure used to propel the sand, which is normally at about 1000 psi. The reduced nozzle thrust obta¡ ned with the ai r-water-sand un its also produces less operator fatigue. For several of the high pressure-high thrust units (both with and without abrasive) the operator could work only for one or two hours at a time. 4. Dust The dust created by dry blasting can be controlled through the use of either a water injected system or a water curtain. 5. Costs It is difficult to compare wet abrasive cleaning costs with other surface preparation methods. Equipment and labor costs, surface conditions, and production rates all vary and have not been well documented. Compared to hand tool cleaning, the higher equipment costs of wet abrasive blasting are more than compensated in lower labor rate costs per square foot, a cleaner surface, and higher production rates. The total cost of wet abrasive blasting is in almost all cases higher than dry sand blasting. Observed rates vary from 125 to 200% of the latter. For the air-water-sand approach, the equipment costs are high compared to other methods; economics dictates that its use be limited to large scale appl ¡cations.
81 Most of the examples reviewed have been directed at producing blast-cleaned surfaces (e.g. SSPC-SP 6 or SP 10). For situations in which it is necessary to remove only loose rust or paint, the use of high pressure water alone or low pressure with sand might well provide higher rates and superior surfaces than either dry blasting or conventional hand and power tool cleaning. 6. Flash Rustingllnhibitor Flash rusting can occur within minutes after blasting with water (Figure 4). To prevent oxidation or flash rusting, a suitable inhibitor is usually injected into the blast hose or applied after blasting. It is important to use a rust inhibitor with a strong enough solution to retard rust after the final rinsing of the contaminants and spent abrasives has been completed. Inhibitors include soluble chromates, phosphates, nitrates, and molybdates(i4). Certain inhibitors, when dry, leave salts that could produce adhesion problems for protective coatings. Therefore, the inhibitor must be compatible with the paint system to be applied. Inhibitors must also meet EPA requirements and be non-pollutants. It is often preferable to apply the inhibitor solution after water blast, thereby minimizing operator exposure, saving inhibitor, reducing problems of liquid pollution, and often running scant risk of excessive flash rust. The air drying feature of the airwater-sand method is highly beneficial in minimizing flash rusting. 7. Production Rate The production rate for achieving a specific surface condition (e.g. near-white metal blast, SSPC-SP 10) depends on the type of system chosen, the particular unit, the proficiency of the operators and the original condition of the surface. The air-water-sand units are the most sophisticated system concepts and would probably be most competitive with conventional dry sand blasting for a full-scale field operation. The sandFIGURE 4 Flash rusting of water-blasted steel rail. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*Z.B 93 m 8b27940 00035Lb 459 m injection method has been documented as producing from 50 to 125% of the cleaning rate of dry blasting; most users concede that dry blasting is faster than a comparably-sized wet blast cleaning technique. The water curtain method should have little effect on the production rate, although some ad hoc or home built modifications have displayed considerably reduced rates. Because of the lack of extensive field experience by the users and manufacturers, these techniques are expected to have a higher rate of malfunction and down time than conventional dry sand blast and high-pressure water units. C.NOVEL USES OF WATER 1. Controlled Cavitation Water Jetting Under certain conditions of rapid water flow, numerous low pressure cavities or bubbles are formed. The collapse (implosions) of these bubbles is accompanied by the release of large amounts of energy. The formation, transport, and collapse of the bubbles is known as cavitation(ls1. Cavitation is well known as a destructive phenomenon which results in metal loss on or near propellers, pumps, etc. From efforts at countering these effects, researchers developed the technology to control and direct the forces of cavitation. The technique has been successfully utilized in boiler tube cleaning, rock drilling, and in removing underwater fouling from ship The technique of controlled cavitation also offers the possibility of certain advantages for surface preparation of structural steel. For a given water pressure and flow rate, cavitation develops higher forces at the point of impact than conventional high pressure water blasting. Thus, it could provide greater efficiency and higher production rates where abrasive blasting is restricted. Cavitation blasting does not introduce any solid abrasive onto the substrate. The prospects for recovering the old paint or surface debris are therefore enhanced due to the much smaller volume of solids compared to conventional sand blasting or wet abrasive blasting discussed earlier. The energy and water requirements for controlled cavitation blasting are similar to those for conventional high pressure water blasting (Figure 5). The efficiency and productivity of cavitation jetting depend on the operating pressure and flow rate, design of nozzle, size of orifice, standoff distance and angle of impingement. The application of this technique to surface preparation is still
in the early development stage. Current research efforts focus on a number of different areas pertaining to surface preparation, as well as related areas such as steel cutting and concrete rehabilitation. A government-sponsored program is concentrating FIGURE 5 Controlled cavitation blasting of galvanized steel. Courtesy of SEACO, Incorporated on developing units which produce less than 50 pounds of operator thrust. As with conventional high-pressure water jetting, operator fatigue is a limiting factor. The goal is to provide hand-held devices for complex structures and inaccessible areas. Researchers anticipate that rates for producing a clean, paintable surface (¡.e. removing loose paint, dirt, and loose rust) will range from 50-200 square feet per hour. These are based on the use of current technology nozzles. Additional research is directed at advancing the technology to achieve the more difficult task of removing hard rust and intact paint, and producing a surface profile at rates approaching those above (Le. 100 sq. ft.lhr.). In addition to the hand-held units, efforts are planned to develop high production units which would include features such as multi-nozzle arrays and automatic translation and thrust support. A further objective of the sponsors is to devise a means for recovering the paint and rust removed from the surface using suction, vacuum or other auxiliary to the cavitation system. The U.S. Air Force is investigating the use of cavitation to remove paint from aluminum. The technique s ability to control the depth of erosion could allow removal of the top coat alone, leaving the primer intact and avoiding damage to the aluminum substrate. 2. Automated Water Blasting Highway officials from Texas have developed a water jet cleaning system which does not require an operator at the nozzle. The high pressure jet nozzle is attached to a rig clamped onto the bridge beam and remotely controlled by an operator on the Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 82
SSPC CHAPTER*Z.B 93 8b27940 0003537 395 M FIGURE 6 Automated robot high-pressure water jet blasting. Courtesy of Texas Department of Highways and Public Transportation ground (Figure 6). The operator can translate the nozzle along the beam and change the angle sideways and up-down to allow access to over 90% of the surface area. The developers are working to increase this percent and the unit s overall versatility. The unit offers several important advantages. The safety is greatly improved because the operator does not direct the nozzle or support the thrust. The thrust, which may be as high as 100 pounds, could cause the operator to lose his balance on a scaffold or to blast himself or a coworker. In addition, with a hand-held unit, the operator becomes greatly fatigued in a few hours, which severely limits his productivity. The automated device should produce a more uniformly cleaned surface and permit more precise calculations of rates and costs. Some of the problems experienced are lack of maneuverability, cost and time for maintaining equipment, and the need for modifications to allow use on different types of structures. 3. SteamISand Blast A technique which uses steam to propel the abrasive has been developed by the JapaneseW The use of steam instead of water results in a shorter drying time and a significant decrease in the amount of rust formation in comparison with other wet blast methods. However, three major obstacles seem .to preclude its widespread use at this time. First, Ithe cloud produced by the steam obscures the operator s view of the work. Secondly, steam, because of its high temperature and release of energy upon condensation, poses special safety problems. Third, in this era of energy consciousness, steamisand blasting is one of the most energy intensive methods of surface preparation. IV. OTHER ABRASIVES AND MATERIALS Conventional and new metallic and non-metallic abrasives are discussed in separate chapters. In this section we consider several novel types of abrasives that have been proposed because of some special feature. A. CARBON DIOXIDE PELLETS Preliminary work has indicated that it may be possible to use carbon dioxide pellets as a blast cleaning medium in those areas where clean-up of spent abrasive is a problemW No reports or accounts could be obtained, however, of successful use on structural steel under controlled conditions comparable with those in shop or ship-
building. At the various meetings sponsored by the SSPC to discuss new surface preparation methods, verbal reports were presented indicating a series of problems which appear to render this method impractical for structural steel applications: the pellets were not effective in removing mill scale; visibility problems were presented by fogging at the nozzle; pellet-forming equipment was reported to be prohibitively expensive and difficult to maintain; problems were foreseen in ventilation and condensation of water. Attempts to arrange a demonstration by the inventor were unsuccessful. B. HIGH VELOCITY ICE PARTICLES This approach has been reportede01 to be effective in removing fouling and paint from ships. The process is FIGURE 7 Xenon flash lamp for surface preparation. Courtesy of Maxwell Laboratories Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 83
SSPC CHAPTER*2*8 73 m 8627940 00035LB 221 m claimed to be more efficient than metallic shot in removing biofouling but less efficient in removing paint. It is probably impractical for use on new steel. Because of its pollution-free characteristics, the use of ice may eventually assume a larger role in cleaning, particularly in the refurbishing of hulls. C. ZINC SHOT BLASTING Zinc shot blasting (zincing) is a modification of the normal blast cleaning procedure in which metallic zinc particles are substituted for all or part of the shot, grit, or sand. The result is a thin discontinuous deposit of metallic zinc left on the nascent, freshly-cleaned steel surface du ring blast ingIz2). This deposit is only about 0.05 mils (1.3 microns) thick but is sufficient to prevent rusting during the days, weeks, or months required for fabrication and construction. Since zinc metal is sacrificial
to steel, the coating need not be
continuous in order to protect the steel completely. These islands of zinc are so thin that they do not affect cutting, welding, or painting. To date the method, originated by the SSPCI22A) has been proven in both laboratory and pilot plant, but not yet demonstrated on a full scale. The zinc deposit can be achieved through either a onestep or two-step operation, but the two-step process appears to be the more practical. It consists of blast cleaning with steel (or sand) particles, followed by a separate blasting with zinc particles (usually in the same equipment sequence). Alternatively, both the cleaning and the zinc deposition can be carried out together in a single stage operation. Both the one- and two-stage processes have been demonstrated by the SSPC and cooperators with both nozzles and centrifugal wheel blast cleaning equipment. Only a small portion of the zinc is transferred to the clean steel by each particle impact. The zinc particles are, of course, recycled just as the steel shot and grit are recycled. During the recycling, zinc dust fines are removed just as steel dust is removed in the shotlgrit blast cleaning operation. The zinc deposit has been shown by SSPC to be com-
patible with conventional coatings, and actually to lengthen their protective life. Preliminary cost estimates indicate substantial savings in materials, time and manpower compared with conventional pre-fabrication primers. Additional work, however, would be necessary to demonstrate whether or not the new process, or avariation thereof, is applicable to a production construction or painting operation. SSPC work has been reported in 1963-73 and subsequently. One variation of the SSPC process, reported in 1976 and developed in Denmarkcz31, is to the use of zinccoated abrasives. Another variation uses sand coated with zinc dust. One investigator has achieved protection up to four months with the two-stage zinc blasting process in which conventional blast cleaning is used to remove rust and mill scale followed by blasting with zinc powder(24). NASA approved a variation of the process in 1973(22c). D. OTHER ABRASIVES SSPC work indicates that although zinc is the most effective inhibitive substance to date which can be applied in blast cleaning equipment, it is not the only one. In early work a wide variety of other inhibitive materials were investigated but were found to be less desirable because of the complicated particle-coating process, handling difficulties, toxicity, safety, shorter protection period, or necessity of removal before coating. Recently, however, one process has been offered which uses zinc-coated abrasive and has been used in blast cleaning below water. Subsequent to publication of the SSPC work, a modification was investigated elsewhere using a stearic acid inhibitor which gave temporary protection but had to be removed from the surface before painting(25). Attempts have been made to combine inhibitive phosphating treatment with blast cleaning(26). Although the SSPC has explored several alternative inhibitive materials to be used in solid, liquid, or vapor form during blast cleaning, additional work would be necessary in order to determine whether or not any of these have promise. Common practice for cleaning previously painted process equipment near machinery in industrial plants has been to use vegetable grit such as corn cobs, walnut shells, cherry pits, etc. Flintstone is also used. E. BACTERIAL CLEANING The Japanese127) have been experimenting with biological methods of cleaning steel. Scale and rust stains are removed by dipping or spraying the article with a solution containing a bacterium (thiobacillus ferrooxidans WU66-B or thiobacillus thiooxidans WU-79-A) plus an inorganic salt (iron sulfate or ammonium sulfate) plus glucose. This process has been shown to be environmentally acceptable. It is felt that this method might be applicable for those FIGURE 8 Navy hull cleaner.
Courtesy of Wheelabrator-Frye, Inc. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS a4
SSPC CHAPTERa2-8 73 8627940 0003539 3bA cleaning conditions where citric acid is now being evaluated. However, much developmental work needs to be done to make biological cleaning competitive or practical, especially for large surfaces. F. EXPLOSIVES The detonation of an explosive charge has been used to project abrasive particles such as sand or metal powder onto the surface to be cleaned(*@. Although this method shows some potential for cleaning the interior of pipes or other confined areas, its impact on the blast cleaning trade will most likely remain insignificant. G. CRYOGENIC COATING REMOVAL A new technique uses liquid nitrogen (-196" C) for cryogenic removal of organic coatings. The stream of liquid nitrogen sprayed onto the substrate embrittles the coating; it is then easily removed with recyclable plastic pellets. Additional engineering efforts are under way to improve the versatility and portability of the equipment(21). V. THERMAL AND HIGH ENERGY METHODS A. LAMPS There are a number of techniques which do not use any water or abrasives; instead they rely on some form of radiation to remove paint and prepare steel for painting. One such technique, under investigation by several government agencies, involves high intensity xenon light sources (Figure 7). These produce temperatures of the order of 3000 F (1700" C)(29). A recently developed proprietary system, known as FLASHBLASTTM, has shown great promise for removing thin layers of paint from a surface(30). This system emits very intense, ultra-short pulses of light with sufficient energy to vaporize or chemically alter most non-metal substances. Due to the short duration of the pulses, the effect is restricted to a layer approximately 0.001 " in thickness, with little or no effect on the underlying material. A typical FLASHBLASTTM system consists of a power supply and control module and of one or more flashlamp heads from which the light pulses are emitted. The power supply provides intense electric discharges which are carried through flexible cables to the heads where they give rise to the emission of short, intense pulses of light from Xenon flashlamps. The weight of the flashlamp heads is only a few pounds, and the flexible cables can be as long as 100 feet, permitting work on fairly large surfaces or objects without moving the heavy power supply module. The flashlamp heads must be in near contact with the surfaces under treatment since the intensityof the light drops rapidly with increasing distance from the lamps. Applications which have been studied experimentally
so far include removing thin paint layers from metal and underlying paint layers. Because of the high degree of con--`,,,,`-`-`,,`,,`,`,,`--FIGURE 9 Vacuum blast unit. Courtesy of Pauli 81Griffin trol afforded, the technique can allow precise, select removal of outer layers of materials without disturbing the inner substrate or paint layer. Additional work is planned to develop and evaluate full-scale systems and to determine the practicality and production rate for field applications. 6. LASERS Preliminary tests have shown that scale or other adhering deposits can be removed, at least from small specimens, when they are subjected to thermal shock or chemical decomposition using a laser beam(31). When rusted steel was exposed to laser beams of several kilowatts, the hydrated oxides were changed to a dense, hard scale of magnetite (Fe,O,), which could then be removed. It may prove practicable to carry out such operations in a reducing atmosphere to produce a readily removable layer of metallic iron. Although already applied to sculpture restoration, laser cleaning is not believed likely to have an impact on the cleaning of structural steel in the foreseeable future because of requirements of energy input and equipment development. C. ULTRASONIC CLEANING Ultrasonic cleaning is in widespread use in speeding the solvent cleaning of small parts, etc. Although it has been proposed for cleaning of larger structural steel, no Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 85
SSPC CHAPTER*ZmB 93 = 8b27940 0003520 98T unit larger than about 75 gallons capacity has been reported(32). D. FLAME CLEANING The heat energy of a direct flame of heated gas has also been used for steel cleaning. Surface preparation specification, SSPC-SP 4-64, "Flame Cleaning of New Steel" described a process for dehydrating and removing of rust, loose mill scale, and some tight mill scale by passing a flame over the surface. The surface is theh wire brushed to remove all loose materials. (SP 4-64 has been dropped from the new edition of Volume 2.) This technique can be hazardous or detrimental when used on previously painted surfaces. In addition, because of poor cost effectiveness and limited use, the SSPC has dropped this specification. E. PLASMA -HOT GAS A combustion unit that uses a mixture of liquid propane and compressed air to produce a blast of hot gas has been used extensively to remove road markings'33). The high temperature, 3000" F (1700" C), is sufficient to vaporize many organic paint films or at least to char them to the point where the high-velocity air blast can blow the surface clean. Treatment of a paint film with the hot air blaster makes any remaining paint easier to remove by conventional sand blasting. Use of this unit in the surface preparation of previously painted steel structures is not widespread. However, it shows considerable promise in those situations where a heavy vinyl or thermoplastic coating is to be removed, since the abrasive has a tendency to bounce off rather than fracture a thick flexible coating. In preliminary field tests some problems were found with this Red lead primer is not completely removed by the hot air blaster and must be removed by FIGURE 10 Vacuum blasting of bridge beam. Courtesy of Massachusetts Pori Authority conventional sand blasting. The five-foot long handle, necessitated by the intense heat and fumes, limits its use in confined areas and contributes to operator fatigue. Clearly, the safety problems related to fire, noise, and ventilation must be considered. Although currently limited in its use on steel structures, this hot gas unit has the potential to solve specialized surface preparation problems. For example, the combined operation of first vaporizing or charring the old paint with the hot gas blaster followed by conventional sand blasting may, in some instances, prove beneficial. Field work must be done to test this approach.
VI. SPONGE JETTING Sponge jetting is a recent surface preparation technique which uses compressed air and pieces of polyurethane sponge. The sponges are effective in removing oil and grease from pumps and motors. They may be impregnated with abrasive for more aggressive cleaning. The impregnated sponges are effective in removing paint, tight rust and mill scale from both flat and irregularlhard to reach surfaces. The method can achieve SSPC-SP 5,6,7and 10when used in conjunction with solvent cleaning. The equipment is fairly expensive. Productivity is low -from 1/4 to 1/2that of open blast cleaning. However, the technique produces much less dust and debris than open blasting. Despite the apparent lack of dust, both containment and personal protective equipment for workers are required. VII. COLLECTING ABRASIVES AND PAINT RESIDUES A. ABRASIVE RECYCLING In order to eliminate water and ground contamination, it is sometimes necessary to recover the spent abrasives and paint residues. Several techniques have been developed based on recycling of the abrasives. The abrasives must be metallic shot or grit or a recyclable non-metallic such as alumina or garnet. It is also necessary to filter off the paint residues and degraded abrasive to maintain a constant abrasive particle size distribution. 1. Portable Automatic Centrifugal Blasting Centrifugal (airless) blast cleaning machines have assumed an ever increasing percentage of the steel fabricating blast cleaning requirements. They provide rapid, uniform, automatic cleaning and greatly reduce the need to dispose of spent abrasives. The equipment is cumbersome and expensive, but for shop application the technique is extremely cost effect ive. The technique has also been applied to field preparation. The suitability and effectiveness in the field depend on factors such as the size of the operation, the configuration and accessibility of the structure, and the necessity for collecting the
Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 86
SSPC CHAPTER*Z=B 73 8627740 0003523 83b H residues and abrasives. It has been most suitable for use on large accessible areas such as ship hulls and decks and storage tanks. Contractors for the US Navy have designed large, mobile cleaning heads which can clean a swath up to 48 inches wide(35). These are mounted on a boom connected to a large truck. Because of the 80 foot reach, this unit can clean most of the ship s hull from dockside (Figure 8). Additional photographs and examples are given in another chapter. The portable centrifugal units are extremely effective in eliminating the environmental hazards and in producing highly uniform blast-cleaned surfaces. The large units used by the Navy and industry have limited mobility and reach. They require large amounts of energy and support equipment. In return, they can often provide higher production rates, and reduced labor and abrasive costs in comFIGURE 11 parison to conventional air abrasive blasting. A Enclosed blasting cages and residue collection system. more complete discussion of the principles and ap- Courtesy of Massachusetts Por t Authority plications is given in the chapter Centrifugal and canvas housing that the blaste r worked in; it rolled on Blast Cleaning. wheels along the handrail. Flexible tubing at the bottom of 2. Portable Air Blasting with Vacuum Recovery the enclosure let the spent abrasi ve drop to a floating barge This technique has been widely used for pre-on the river erection surface preparation in fabricating shops Massachusetts Port Authority ( Massport) modified the and certain field facilities, particularly nuclear above arrangement in several ways(38). They provided plants. Its application to existing field structures is mechanical suction to ex haust the dust fumes from the limited by the capacity and reach of the recovery enclosure to improve visibilit y and air quality inside the system. Like the centrifugal cleaning units, the booth. The tubing was connected to a dumpster equipped portable recovery units have difficulty in cleaning with a venturi water scrubbe r to separate the fine particles irregular surf ace feat ures. and emit them as sludge. Massport also substituted metal There are several different types of vacuum sheathing for the enclosure sides to provide better wear recovery machines available. These include port- (Figure 11). able units with single-chamber collection tanks; Massport reported that the abov
e enclosure system portable units with automatic discharge tanks, and for the longitudinal girders and handrails captured 80 to 85 mobile truck units with single chamber collection percent of airborne dust and l ead paint particles in addition tanks. These machines differ in their degree of port- to virtually all the blast ing grit. The shroud has also been ability, labor and utility support required, hose used for paint spraying under high wind conditions. sizes and costs (Figure 9). A discussion of the relative merits of each as used for surface prepara- C. TARPAULINS AND OTHER DEV ICES tion of tanks is given in an SSPC report done for Various approaches have been u sed to collect and the Maritime Administration(? contain dust and paint. Several highway agencies h ave There are also available recovery units which used heavy tarpaulins to prevent t he dust from blowing or rely on suction to collect the abrasives(37). These drifting into populated or r ecreational areas. The success suction (alternately called siphon) units sometimes has been varied. For large s tructures the tarpaulins arehave difficulty recovering the heaviest abrasives. o ften torn down by strong winds, as they create a sail efTheir production rate is much less than the pump fect. However, the use of tarpa ulins does greatly facilitate actuated vacuum units described above. They are the collection of sand from road ways. used primarily for small areas or touch-up work In order to prevent old paint co ntaining lead from con(Figure 10). taminating waterways, the California Department of Transportation has stationed barges beneath the bridge. TarB. BLASTING CAGES paulins and plastic sheets are used to funnel the particles Another approach to containing dust and paint in- onto the barge. This technique has proven satisfactory in volves the useof movable enclosures around the blaster. In many instances; some of the problems are that a signifian early version, a California contractor built an enclosure cant amount of sand or paint particles may still be dropped that covered the handrail assembly and longitudinal in the water, the barge may sink or spill the residue, and girders. It consisted of a rigid frame around scaffolding the costs are apprecia ble. 87 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*Z.8 93 8627940 0003522 752 The Iowa Department of Transportation requires the use of covers or drapes to collect paint wastes if they contain lead. The provisions also require contractors to collect floating paint wastes. The scum that forms in the water must be contained by straw dams or flóating boom devices. The State does allow alternate approaches when recovering and collecting are not possible because of bridge location and VIII. SUMMARY In this chapter we have described a variety of methods which have had varying degrees of success. The future of many of these methods depends largely on the regulatory authorities. Almost all of the newer techniques are more costly and less productive than sandblasting. In locales where sandblasting will continue to be permitted, it will probably remain the most cost-effective way to clean structural steel. For situations in which the major problems are those of air contamination, e.g. dust or lead paint particles, the use of some form of wet-blasting technique appears to be the best choice at present. Several of these water methods are highly sophisticated and are able to reduce the airborne particulate levels by 80-90 percent. In certain locales, such as near sensitive machinery, in densely populated areas, or over sensitive waterways, it may be necessary to eliminate any particles from contaminating the environment. For these conditions, it would be necessary to use the less productive, most costly techniques such as vacuum blasting or closed cages. Even these, however, are not sufficiently developed to be applicable to most of the structural conditions encountered. To improve these techniques would require substantial commitment by users, equipment manufacturera, and contractors. Thus, it is essential that the regulatory agencies provide clear guidelines and policies for the standards governing air and water quality, worker health and safety, and other requirements. The overall regulatory picture, however, is likely to remain complex. Several of the federal standards are not yet finalized; others are being considered for revision. State
and local regulations vary enormously from one jurisdiction to another. California, for example, frequently imposes the earliest and most severe restrictions. There is a wide variation in the awareness and enforcement of existing federal and state regulations. It is therefore not likely that any set of uniformly applied regulations would be adopted in the foreseeable future. There are factors other than actual or anticipated regulations which influence the development of surface cleaning techniques. These include the cost and supply of abrasives, the efficiency and cleaning rate of new equipment, the availability and cost of power and water, improved worker safety and comfort, and the requirements of varied coating materials. Thus, there is a continuing need to develop and evaluate new procedures and techniques for surface preparation of steel. ACKNOWLEDGEMENT Much of the material in this report benefits from a survey --`,,,,`-`-`,,`,,`,`,,`--made by the SSPC for the US. Maritime Administration through the Avondale Shipyard. The authors and editors also gratefully acknowledge the active participation of the following in the review process for this chapter: Einar A. Borch, Theodore Dowd, Preston S. Hollister, A. W. Mallory, Joseph Mazia, Marshall McGee, William Pearson, William J. Wallace, Jr., and Raymond Weaver. BIOGRAPHY Portraits and biographical sketches of Dr. Appleman and Mr. Keane appear at the end of the Foreword. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 88
SSPC CHAPTER*Z.A 73 Ab27740 0003523 699 W REFERENCES 1. John D. Keane, Joseph A. Bruno, Jr., and Raymond E.F. Weaver, Survey of Existing and Promising New Methods of Surface Preparation . (Report prepared by Steel Structures Painting Council for US. Maritime administration through the Avondale Shipyard). 2. OSHA, Standard for Abrasive Blasting . See Proposed ANSI Standard A10.29, American National Standard Practice for Construction Abrasive Blasting October, 1980. 3. Environmental Protection Agency, Federal Register, Volume 36, Number 84, April 30, 1981, National Primary and Secondary Ambient Air Quality Standards and Revisions of November 25,1981, July 1, 1976, December 1,1976,October 5, 1978, February 8, 1979. 4. US. Department of Interior, Bureau of Mines Informational Circular 8333. Ringlemann Smoke Chart, May 1967. 5. Environmental Protection Agency, National Ambient Air Quality Standard for Lead . Title 40, CFR Section 50.12, Appendix G (sets limits of 1.5 micrograms of lead per cubic meter averaged over 90 days) 6. OSHA, Final Standard for Occupational Exposure to Lead . Federal Register Vol. 43, No. 220 (Section 1910.1025,Table 2-2,amended to limit exposure to lead to 50 micrograms per cubic meter averaged over 8 hours), November 14, 1978. 7. OSHA, Title 29 -Labor . (29CFR1910.1000, Sub-part Z, Table 2-2 sets ceiling of 100 micrograms of chromic acid and chromates per cubic meter.) 8. Resources Conservation and Recovery Act (1976), Federal Register, May 19, 1980, pages 33127-33132, and amendments. 9. L. Stevens, Massachusetts Department of Public Works and M. Tobey, Massachusetts Port Authority, Private Communications, 1981. 1o. A. Ticker, and S. Rodgers, Abatement of Pollution Caused by Abrasive Blasting: Status in Naval Shipyards . NSRDC Report No. 4549, 79 pps., 1975. lla. US. Coast Guard, (Code G-EOE), Washington DC, District; Fifth Coast Guard District, Miami, FL; and Seventh Coast Guard District, Portsmouth, VA; private communication. llb. Federal Highway Administration, Evaluation of Commercial Blast Cleaning Systems . Report N-FHWA TS 81-xxx, Federal Highway Administration, Washington, DC 20590. 12. KUE Engineering Ltd., KUE: System 9-18 ,Polymers, Paint and Colour Journal, (Great Britain), pp. 202, March 9, 1977. 13. Equipment Technology, Inc., 5620 New Peachtree Road, Chamblee, GA, Private Communication. 14. Steel Structures Painting Council, Volume 2 Systems and Specifications , 4516 Henry Street, Suite 301, Pittsburgh, PA 15213-3728, 1991 Printin 15. V.E. Johnson, Jr., R.E. fohl, and A.F. Conn, Tunneling, Fracturing, Drilling, and Mining with High Speed Water Jets Utilizing Cavitation Damage . First International Symposium on Jet Cutting Technology, Coventry, England, 1973, Paper
A3 and Supplement. 16. Federal Highway Administration Reports FHWA RD-82-001 and FHWA RD-82-002, Development of System for Controlled Cavitation Blasting for Surface Preparation of Structurai Steel . 17. T. Appling, Texas Department of Highways and Public Transportation, Private Communication, 1980. 18. M. Hosoda, N. Saiki, and J. Nakamura, Sand Blasting with High-pressure Steam . Japanese Patent 7533,121, Dai Nippon Tokyo Company, Ltd. 19. C. Fong, Pollution-Free Blasting . National Paint and Coatings Association 16th Annual Maine Coatings Conference, 7 pps. 1976. 20. C.J. Sandwith, and T. Briewick, High Velocity Ice Particles for Cleaning Ship Hulls -A Feasibility Study . 4th International Congress of Marine Corrosion and Fouling, May, 1976. 21. T.W. Burke, Air Products and Chemicals, Inc., Allentown, Pennsylvania, 18105, Private Communications, 1981. 22. J.D. Keane, Zinc Shot Blasting of Structural Steel . SSPC Report, April 1964. 22A. J.H. McAuliffe, Zinc Shot Blasting of Structural Steel . Scientific Australian, March 1964. 228. Anonymous, Shotblasted Zinc Primer Weatherproofs Steel Iron Age, August 1, 1963. 22c. US. Patent 3,754,976 Babecki-Haehner to NASA. 23. B. BenderChristensen, An Investigation of a Combined Blasting and Coating Technique: A Patented Process . Hemple Marine Paints, Copenhagen, Denmark, 1976. 24. J.E. Sandford, Zinc Coating Blasted on Steel . Iron Age, August 1, 197 3. 25. I. Geld, L. Deutsch, and F.J. D Oria, A Comparison of Inhibitive Abrasive Blasting Techniques . Materiais Perforrnance, August, 1968. 26. G. Wallis, Phosphatizing -A New Approach . Industrial Finishing and Surface Coatings, Vol. 27, No. 326, pps. 5-6, 1975. 27. S. Usami, and H. Kozu, Microbial Surface Treatment of Metals . Ger. Offen, 2,409,649 (September 19, 1974) and Japan Appl. 23,749 (March 1, 1973). 28. P. Barrillom, Preservation of Materials in the Marine Environment -Analysis of Replies to the inquiry on Methodsof Surface Preparation in Shipyards , 1964. 29. Anonymous, Bright Ideas -Xenon Lamp s Intense Flash Burns Off Steel Truss Rust . Engineering News Record, pp. 11, May 31, 1979. 30. Maxwell Laboratories, Inc., Surface Preparation by Flashblasting . Technical Literature, San Diego, CA. 31. J.W. Hill, M.J. Lee, and I.J. Spalding, Surface Treatments by Laser . Optics and Laser TechnÖlogy, Vol. 6, No. 6, pp. 267-268, 1974. 32. Branson Cleaning Equipment Company, Ultrasonic Cleaning and Vapor , Parrot Drive, Shelton, CT 06484, 1980. 33. Prismo Universal Corporation, Hot Compressed Air (HCA) Equipment, Parsippany, NJ 07054. 34. A. Beitelman, US. Army Construction Engineering and Research Laboratories, Champaign, IL, private communica-
tion. 35. F.A. Boyle, New Methods of Surface Preparation by the US. Navy . Paper presented 1978 Federal Highway Administration Research Review Conference, College Park, Maryland, October 3-5, 1978. 36. National Shipbuilding Research Program, Procedure Handbook: Surface Preparation and Painting of Tanks and Closed Areas, 1981, Cooperative cost shared efforts by Maritime Administration, Avondale Shipyards (J. Peart, R&D Program Manager) and Complete Abrasive Blasting Systems, Inc., (J. A. Geis, Project Manager). 37. B. Baldwin, Methods of Dust-Free Abrasive Blast Cleaning . Plant Engineering, pps. 116-125, February 15, 1978. 38. M. Tobey, Painting of Mystic River (Tobin) Bridge . Paper presented 1980 Federal Highway Administration Research Review Conference, December 10-1 1, 1980. 39. Iowa Department of Transportation, Special Provisions for Repainting Bridges (Environmental Protection) . SP-240, Ames, IA, March 27, 1979. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 89
SSPC CHAPTERa2.9 93 8b27740 0003524 525 CHAPTER 2.9 CHEMICAL CLEANING by Melvin H. Sandler and Samuel Spring The importance of surface preparation to the durability of any coating system has been emphasized throughout this manual. Without proper surface preparation the finest coating applied with the greatest of skill will fall short of its maximum performance or may even fail miserably. A coating can perform its function only so long as it remains intact and firmly bonded to the substrate. An adequately prepared surface not only provides a good anchor for the coating, but also ensures a surface free of corrosion products and contaminants that might shorten the life of the film by spreading along the coating substrate interface and destroying adhesion, or by actually breaking through the coating. Thus, the initial step in any finishing operation is cleaning the surface. This chapter describes chemical cleaning materials and methods. Other chapters of this manual cover mechanical surface cleaning. I. GENERAL CONSIDERATIONS While a perfect level of cleanliness may not always be possible to attain, especially under field conditions, every effort should be made to reach the maximum level of cleanliness under the specific operating conditions. During manufacture, fabrication, and service, surfaces become soiled. They pick up some foreign matter as corrosion products that must be removed before final finishes or refinishes can be applied. The removal of these contaminating substances is covered under the term cleaning . There are countless contaminants (soils) to be removed, but in general they may be categorized as: 1. Oily Soils Examples: hydraulic oil, lubricating oil, light oil, oil-based rust preventatives, etc. When present as thin films or small residues, and when very viscous in nature, these soils may be removed by alkaline cleaners. On more stubborn areas solvent cleaners may be needed because the longer a soil ages the more difficult it is to remove. 2. Semi-Solid Soils Examples: viscous oils, greases, heavy rust preventatives, etc. These soils are usually re-
moved with heavy duty alkaline cleaners or a combination of solvent followed by the alkaline cleaner. 3. Soils Containing Solids Examples: mud, carbonized oils, corrosion products. These soils are usually the most difficult to remove and may require a combination of solvent, alkaline pressure spray and scrubbing, and in the case of corrosion products, acid pickling. Aged or impacted soils are generally the most difficult. In the cleaning process both the soil and the residues of cleaners, which may subsequently contribute to further corrosion or adversely affect coating performance, must be removed. II. TYPES OF CHEMICAL CLEANERS A. SOLVENTS Petroleum solvents such as kerosene, VM & P naphtha, mineral spirits, or chlorinated solvents such as triclorethylene or l,l,l-trichloroethene are used to dissolve and remove soil. Petroleum solvents may be used in hand, soak, or spray cleaning and are efficient in removing oils and greases. Chlorinated solvents are generally used in vapor degreasing units but may also be used at ambient temperatures by immersion or spray. They are effective in removing heavy oils, greases, and waxes. Chlorinated solvents should be inhibited against hydrolysis to prevent the formation of hydrochloric acid that may occur in the presence of water. This acidity can etch the metal. The solvent cleaners offer the advantage of leaving the part dry after cleaning and eliminating the need for additional rinsing. Regulations restricting the use of organic solvents havelbecome so stringent in recent years as to discourage their use. Thus, for other than small area cleaning the most commonly used cleaners are water-based, either alkaline or acidic. B. ALKALI Alkaline cleaners are composed of highly alkaline salts such as sodium hydroxide, silicates, and carbonates along with surfactants, sequestering agents, inhibitors, wetting agents andlor soaps. They function by wetting, Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 90
SSPC CHAPTER*2.9 93 m ôb27740 0003525 461 FIGURE 1 Steam cleaning of large or assembled structures. The steam cleaner may be directly fired or use plant steam as in the above photograph. When the distance from the gun is small, the temperatures are close to 2OOOF so high melting soils can be removed more readily. At more normally used distances of the gun from the surface, the temperature may be 160° to 180'F but a larger area is covered. The cleaning operation is under considerable control by the operator in terms of the time of exposure of the soil to the detergent spray and the distance from the gun. emulsifying, dispersing and solubilizing the soils. They are generally used at elevated temperatures. C. ACIDS Acid cleaners are usually composed of fairly strong acids with small quantities of surfactants, water miscible solvents and organic wetting and emulsifying agents. Acid cleaners remove a soil by chemical attack and by dissolving the reaction products. They are used primarily to remove corrosion products. D. DETERGENTS Detergent cleaners are composed of buffering salts, sequestering agents, dispersants, inhibitors, wetting agents andlor soaps. They function by wetting, emulsifying, dispersing and solubilizing the soil. They are generally used at temperature ranging from 150°F (SSOC) to boiling. 111. CLEANING WARNING -In the use of any cleaning method, appropriate safety precautions must be taken to protect personnel from materials and conditions which may present fire hazards, cause skin irritation, or have toxic effect when 91 breathed in high vapor concentrations. There is no single method of cleanin that will roperly condition all surfaces prior to preservation. The choice of cleaning method will depend upon the type of structure as well as other factors. Parts cleaned after assembly or in the field can require quite different methods from parts processed in a factory. If parts being reconditioned are to be cleaned prior to repainting, paint and rust must be removed in addition to other soils. Moreover, large parts may require procedures that differ from small parts. However, the principles governing cleaning are similar. In general, cleaners are more effective at higher temperatures and at higher concentrations. It is desirable to have application under conditions of high turbulence or force to dislodge the soil loosened by the action of the chemicals. This is true both of organic- and water-based systems, but temperature is less important for organic solvents. However, temperatures and turbulence may be prohibited for organic solvents since this would generate toxic
fumes. When cleaning with the alkaline or acidic materials, regardless of the cleaning method used, every effort should be made to thoroughly rinse the surfaces, not only to minimize the amount of soil remaining, but also to remove residues of the cleaning materials that may adversely affect subsequent coating performance by providing electrolyte for the action of galvanic cells when moisture penetrates the paint film. Another consideration is the ionic content of the rinse water. In addition to the calcium, magnesium, iron, etc. associated with hard water, water in some parts of the country also contains salts such as sodium chloride and sodium sulfate that are potent electrolytes in the corrosion process. Cleaning procedures can be divided into those used in the manufacturing process (factories), and those used in the field for cleaning large, assembled units. This discussion will be limited to on-site cleaning of assembled or large structures. Table I lists U.S. government chemical cleaning specif ¡cations. A. SOLVENT WIPE Wiping with solvent followed by a second wipe with clear solvent or by removal of excess solvent with a clean cloth can be effective depending on the soil. Mineral spirits and stoddard solvent are relatively convenient and inexpensive to use. The quality of cleaning obtained depends largely upon the severity of the soiling and the expertise of the operator. Good, well supervised workers using clear solvent and clean wiping rags can do a reasonably good job. Some soils may require more effective solvents such as xylene or chlorinated solvents other than those mentioned above. Solvent cleaning is most effective for removal of oils and greases from limited areas of structures and for occasional cleaning prior to painting. Where the complete structure is to be cleaned, other methods are more practical. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERl(2.9 93 W 862'7940 0003526 3TB W TABLE 1 Some U.S. Government Specifications for Chemical Cleaning* SDecification No. P-c-111 MIL-STD 338 P-C-436 P-c-437 TT-C-490 MIL-(2-10578 MIL-C-11090 MI L-H-13528 MI L-C- 14460 MIL-C-22542 MI L-C-38334 MIL-C-43616 MIL-'2-461 56 MI L-C-81302 --`,,,,`-`-`,,`,,`,`,,`--MIL-C-87936 Title Carbon Removing Compound Cleaning and Treatment of Aluminum Parts Cleaning Compound, Alkali Cleaning Compound, High Pressure (Steam) Cleaner Cleaning & Pre treatment of Ferrous Surfaces for Organic Coatings Corrosion Removing and Metal Conditioning Compound
Cleaning Compound, Degreasing & Depreservi ng Solvent Acid, Hydrochloric, Inhibited, RustRemoving Corrosion Removing Compound Cleaning Compound, High Pressure Cleaner, Liquid Corrosion Removing Compound, Prepaint, for AircraftAluminum Surfaces Cleaning Compounds, Aircraft Surfaces Corrosion Removing Compound Cleaning Compound, Solvent Cleaning Compounds, Aircraft Surfaces Material Monoethanolamine Alkaline base Hot alkaline phosphate solutions Alkaline phosphate & non-phosphate Solvent, Alkaline, emulsion & phosphoric acid Phosphoric-acid base;
6 types Esters and organic salts Hydrochloric acid Sodium hydroxide base Optional Phosphoric acid Opt ional Sodium hydroxide base Trichlorotrifluorethane Optional; water dilutable Application Soak Immersion Immersion Immersion, spray or brush Immersion. spray or brush Soak, brush or spray Soak Electrolytic or immersion High pressure steam cleaning machines, coil
type Spray or wash Spray, brush or foam Immersion Spraying, flushing, vapor degreasing, ultrasonics Purpose For use in softening and removing carbon gum & other contaminants. Cleaning aluminum prior to painting. Hot soak tank cleaning of ferrous & non-ferrous materials. For use in steam cleaning machines for cleaning various ferrous & nonferrous surfaces. Cleaning methods are intended for cleaning, rust removing, descaling or surface etching Rust remover. For use in removing oils, greases, asphalt, tars & rust preventive compounds from metallic & painted surfaces. For use in removing heavy rust deposits from
steel surfaces. Rust removal from bare and painted iron and steel. Painted and unpainted aircraft surfaces. For removing corrosion from aircraft aluminum surfaces. Intended for cleaning painted and unpainted aircraft surface. At elevated temperatures, will remove rust, paint, scale, grease, dirt, asphalt & carbon. For use in cleaning space vehicle components, precision assem bl ¡es, oxygen assemblies & electronic equipment. Painted aircraft surfaces. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS *The following specifications have been removed from this table to reflect curre nt practice: MIL-C-25769, MIL-C-27251, MIL-C-81533, MIL-S-10561, MIL-T-7003 92
SSPC CHAPTERr2.9 93 D 8627940 0003527 234 D TABLE 2 -TYPES OF BRUSH MATERIAL USED IN CLEANING --`,,,,`-`-`,,`,,`,`,,`--(1) NATURAL FIBERS TAMPICO FIBER PATENT FIBER PAYMYRA FIBER PALMETTO FIBER (2) ANIMAL BRISTLES HORSEHAIR BOAR BRISTLE (3) PLASTIC BRISTLES NYLON ACRYLIC PLASTICS (4) WIRE BRUSHES CARBON STEEL BRASS STAINLESS STEEL i\ c.._ ._ Good durability and water resistance, soft to medium stiffness Select grade of tampico, stiffer and more durable than tampico Lower cost, stiffer, reasonably durable Very good durability and water resistance Soft to slightly stiff, good durability, fair water resistance. Excellent durability and very good water resistance, soft to slightly stiff Very good durability, wide selection, resistance to alkaline cleaners but not to solvent, excellent water resistance Excellent durability and resistance to chemicals
Very stiff, tends to rust, high cutting action, heat resistant Very stiff, durable Very stiff, durable, expensive, non-corroding B. STEAM CLEANING A high pressure jet of steam, with or without cleaning compound, is used to clean ferrous, non-ferrous and painted surfaces. Steam removes grease, oil, and dirt by a combination of detergent action, water, heat and impact. Alkali cleaners used in steam cleaning will attack aluminum and zinc alloys, unless specifically inhibited against such action. They should be used selectively over painted surfaces to assure no damage to the paint if removal is not desired. The equipment required is a pressure jet steam cleaner (Figures 1 and 2). A separate solution tank or drum may be required for preparation of the cleaning compound. One type of steam cleaner stores the concentrated cleaning solution and mixes it with water at a constant rate to produce a uniform cleaning solution through a heating unit in which it is partially vaporized and put under pressure. The hot solution and steam are forced through the nozzles onto the surfaces to be cleaned. The same equipment can FIGURE 2 be used for cleaning with dry steam or with cold water Functional perspective of an oil-fired steam cleaner. Courtesy Allied Kelite under high pressure. This type of steam cleaner may be Div. Richardson Corp. Chicago either portable or stationary. 93 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*2-7 73 W 8627740 0003528 170 a. Courtesy Oxford Chemicals Div. Consolidated Foods Corp. FIGURES 3A and 3B Portable units that can be hooked into plant hot or cold water line for convenient cleaning, for spraying high pressure detergent solution. f b. Courtesy Olympic Mfg. Co. Div. Consolidated Foods Corp. Another type of portable pressure jet steam cleaner, sometimes called a hydro steam unit, requires an outside steam source. The cleaning solution is mixed and stored in a container or tank that is not part of the steam cleaner. No water is mixed with the solution in the steam cleaner, so the solution is made up at a lower concentration than that used for the other type of cleaner. The solution and steam are mixed in the cleaner and discharged through the nozzle of a steam cleaning gun. The same equipment can be used for cleaning with dry steam. In the steam cleaning procedure a stream of steam, with or without cleaning compound, is directed under pressure through a cleaning gun or guns against the surface to be cleaned. The pressure should be adjusted so that the area can be cleaned without requiring repeated or prolonged spraying. The cleaning guns may be furnished with interchangeable nozzles. A round one is used for most cleaning. Flat nozzles are used for flat surfaces. Dry steam may be used as the final step to aid drying. The material and surface finish of the surfaces determines whether drying is necessary after steam cleaning. C.HIGH PRESSURE-HOT DETERGENT The machines (Figures 3A and 3B) used to provide these sprays utilize pumps that develop pressures of 500
to 1000 psi. Volumes of detergent solution will vary with the larger machines (Figure 4), delivering 3-5gallons per minute. The cleaning procedure is basically the same as in steam cleaning with the detergent spray directed under high pressure through a cleaning gun against the surface to be cleaned. As with solvent and steam cleaning, the skill of the operator determines in large part how effective the procedure will be. There is an inexpensive unit that uses water line pressure for dispensing the detergent. The detergent solution is metered into the water line before spraying. In order to obtain reasonably good cleaning, the detergent solution is used at considerably higher concentration, usually 1 to 2 ounces per gallon. D. FOAM CLEANING Foamed detergent solutions are popular for cleaning food processing plants and automotive equipment such as trucks (Figures 6 and 7). They are also used to acid clean the inside of towers under conditions in which the tower is actually filled with foam, obviating the necessity for filling it with liquid. The foam is normally used to cling to vertical surfaces long enough for detergency to take place. Sometimes a gel is sprayed onto the surfaces to achieve even longer contact time. In general the foam is neutral SD that a limited residue may not adversely affect paint if rinsing is not complete. In this process foam is generated by mixing a high foaming surfactant, often containing foam stabilizer and detergent builder, with water and compressed air. Variations in foam cleaning (Figures 5A, 58 and 5C)include (A) the small unit that has a tube to pick up foaming concentrate from a drum, (6) the unit that pumps diluted foaming Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 94
SSPC CHAPTER*2=9 93 8627940 0003529 O07 m agent and detergent from a drum and (C) a self-contained unit in which foaming agent and detergent concentrate is mixed with water and air prior to spraying. These units are quite mobile, enabling the operator to reach areas difficult to clean. E. BRUSH CLEANING Brushes and sponges are useful for cleaning. They can remove stubborn soils and spot clean highly soiled areas to complement other methods of cleaning. Fiber, wire or plastic brushes may be used depending upon the type of cleaning required. Table 2 lists the various types of brush materials. Sponges are also available in a variety of forms and compositions, including some with abrasive surfaces attached to one side. IV. HANDLING THE CLEAN SURFACE Cleaned surfaces should be further processed with a prepaint treatment or painted as soon as possible after cleaning to prevent rusting or recoiling from the atmosphere. FIGURE4 High pressure spray machines in which the hot detergent solution is made up in a reservoir rather than being injected into hot steam. This provides a more predictable concentration of detergent and permits the spraying of a high volume solution of known detergent concentration. Courtesy, Oxford Chemicals Div. Consolidated Foods Corp. ,AIR INLET z FOAM OUTLET --`,,,,`-`-`,,`,,`,`,,`--FIGURES 5A, 58 and 5C Cleaning by the use of foam. Foam is generated by mixing a high foaming surfactant, often containing foam stabilizer and detergent builder, with water and compressed air. Variations in foam cleaning units include (A) the small unit with a tube that picks up foaming concentrate from a drum, (B) the unit that pumps diluted foaming agent and detergent from a drum, and (C) a self-contained unit in which foaming agent and detergent concentrate are mixed with water and air prior to spraying.
Courtesy DEMA Engineering Co. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 95
SSPC CHAPTERt2.7 73 8627740 0003530 829 Use of portable foamer. FIGURE 6 Courtesy Oxford Chemical Division, Consolidated Foods Corp. V. CLEANING FACES PREVIOUSLY PAINTED SURIf the painted surface has not been broken, it may be possible to paint with little or no chemical cleaning. However, if the surface has been exposed for any period of time, it has undoubtedly accumulated some atmospheric contaminants, as well as corrosion that must be removed before repainting. Any of the chemicals and cleaning methods mentioned previously may be used. Care must be taken, however, to insure that the chemical and cleaning procedures used do not attack the sound paint. Portable Foamer. FIGURE 7 Courtesy Oxford Chemical Division, Consolidated Foods Corp. VI. DISPOSAL OF CHEMICAL WASTES Chemical cleaning materials should be disposed of without violating of local, state, or Federal pollution regulations. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 96
SSPC CHAPTER*2.9 93 8627940 0003533 765 ACKNOWLEDGEMENT BIOGRAPHY The authors and editors gratefully acknowledge the active participation of the following in the review process for this chapter: P.J. Bennett, J. Carroll, James Davis, Ted Dowd, Arnold Eickhoff, Aaron Greenberg, Mark Kuchner, Robert McCormick, C. Munger, William Pearson, William Wallace. BIOGRAPHY Melvin H. Sandler has been involved in research and development and technical services on chemical coatings, metal preparation prior to painting, and corrosion control for over 35 years. During his service as a chemist and Division Chief at the former U.S. Army Coating and Chemical Laboratory, Aberdeen Proving Ground, MD, he was responsible for the development of coatings for the preservation of Army material. Mr. Sandler is the author of more than 50 technical publications and 20 military specifications dealing with coatings and corrosion and has served as a consultant to government and industry. In 1976 he joined Lenmar, inc., an industrial finishes manufacturer, with responsibility for new product development and other coat i ngs con su It ing servi ces. Dr. Samuel Spring received his B.S. from City College of New York in 1936, his A.M. from Columbia University in 1938 and his Ph.D. from Temple University in 1952. He was an instructor at City College of New York from 1936-1939; a chemist at Frankford Arsenal from 1940-1947; a group leader at Pennwalt Corporation from 1947-1956: laboratorv director at Kelite Corporation, 1956-1963; technical director at Oxford Chemicals, 1963-1970; technical director at Chemtrust Industries 1970-1973 and technical director at Gibson Chemicals, Ltd. (Australia) 1973-1977. He has been President, Southeast Laboratories, Inc. and a consultant from 1977 until the present. REFERENCES S. Spring, Industrial Cleaning, Prism Press, 1974. S. Spring, Preparafion of Metais for Painting, Reinhold Publishing of --`,,,,`-`-`,,`,,`,`,,`---
Corporation. Departments of the US. Army, Navy, Air Force Technical Manual No. 5-618, NAVFAC MO 110, AFM 85-3, Paints and Protective Coatings , January 15, 1969. U.S. Air Force Technical Manual No. T.O. 1-1-1, Cleaning Aerospace Equipment , Change 9 -March 15, 1976. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 97
SSPC CHAPTERm3-L 93 = 8627940 0003532 hTL CHAPTER 3.1 SPECIAL PRE-PAINT TREATMENTS: PHOSPHATING by Samuel Spring Most paints will adhere reasonably well to clean steel, especially if the surface has been abraded and surface oxides removed. The pickling and etching action of acids also improves adhesion. Pickling removes oxides and etches by selective solution of the steel, producing a larger surface area for contact with the paint. A more sophisticated method of surface preparation is to apply a chemical deposit or coating, normally phosphate, that holds paint because it is compatible with paint components and often provides an extended or porous surface for retaining more paint. Phosphate coatings are transformations of metal surfaces into new surfaces having non-metallic, and nonconductive properties. They are widely used in the manufacture of metal products for four principal reasons: 1. To precondition surfaces to receive and retain paint, and to protect surfaces against under-paint corrosion; 2. To prepare surfaces for bonding with plastic coatings; 3. To precondition surface for metal forming operations, such as cold extrusion, and for breaking in friction-bearing surfaces, by providing a base for drawing compounds and lubricants; and 4. To improve corrosion resistance by providing a good base for waxes and rust-preventive oils. By far the most widespread use of phosphate coatings is to prolong the useful life of paint finishes. Phosphate coatings in commercial use are crystalline zinc phosphate and microcrystalline (sometimes called amorphous) iron phosphate. In addition, a coating forms from phosphoric acid treatment (occasionally modified by the addition of other chemicals to accelerate reaction with the steel). The types of phosphate cleaning of steel are outlined in Table 1. Crystalline zinc phosphate coatings, properly applied, provide the highest level of quality, especially in outdoor exposure or conditions where there is the possibility of breaking the paint film by mechanical action, as by impact, cutting or abrasion. They prevent or reduce the spread of corrosion from the exposed area. This is also true for good iron phosphate coatings. As a matter of fact, the most used method of evaluating the quality of these coatings is
to cut a line through the paint film to the metal below and 98 then expose the part or panel to an atmosphere of salt --`,,,,`-`-`,,`,,`,`,,`--spray, ¡.e., a fog of water droplets containing salt, after which the distance of corrosion from the scribe line is measured (ASTM-B 117). i. NATURE OF THE PHOSPHATE COATINGS The zinc phosphate coating is formed by crystallization onto the surface by chemical reaction, but is integral with the surface rather than deposited on the surface. The continuous structure consists of the steel substrate, a thin layer of adherent iron oxide, then a mixed oxide-phosphate (iron andlor zinc), and finally a crystalline zinc phosphate. There are no sharply defined interfaces between the layers. When paint is applied to this adherent surface, it is held almost as tightly as though it were in good contact with clean steel itself. In addition, the surface area in contact is greatly increased, and a high quality surface treatment is obtained. Thus, there is a substantial barrier to atmospheric moisture and considerable resistance to chipping, cracking, and underpaint corrosion; and often a heavier paint film can be held in position in a single coating. Small crystals of limited porosity in such coatings provide the best performance. Iron phosphate coatings have been referred to as non-crystalline conversion coatings, but microcrystalline would probably be more appropriate. The coating is a mixture of adherent iron oxide and iron phosphate with minor quantities of other components from the bath occluded in the crystals. It is considerably thinner than zinc phosphate and essentially non-porous. The thinner deposit allows more flexibility with paints that are intrinsically less flexible but more enduring. Treatment with phosphoric acid does not provide much coating, but sometimes good results are achieved with certain highly impervious and inert paint systems. Prolonged treatment with phosphoric acid removes oxides and sometimes provides a light etch that is beneficial to adhesion. Residues from phosphoric acid treatment are less detrimental than those from sulfuric or hydrochloric (muriatic) acids. Phosphate coatings function in the following ways: 1. They put the surface in a non-alkaline condition: alkaline residues undermine paint finishes and thus promote corrosion; Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*3-L 93 E 8627740 0003533 538 TABLE 1 TYPES OF PHOSPHATE CLEANING OF STEEL Spray 3 or 4 stage Non-crystalline phosphatelcleaning 5 or 6 stage Non-crystalline phosphate with separate cleaning 5 or 6 stage zinc DhosDhate Immersion Zinc phosphate Non-crystalI¡ne phosphate Alkali clean -preferably with acidic rinse Acid DiCkle Vapour degreaser Manual Wipe-on wipe-off phosphoric acid clean Steam clean and phosphate Solvent clean Mechanical Abrasion 2. They impose relative uniformity in surface texture and improved uniformity of post treatments such as paint; 3. They increase the surface area upon which the systems of attractive forces causing adhesion can act; 4. They create capillaries and micro-cavities to (a) provide mechanical interlocking of coatings with surfaces, and (b) to hold drawing compounds, retain break-in oils, and improve rust resistance; 5. They cushion metals against scoring and scratching; 6. They insulate metals against electrochemical corrosion; 7. They prevent reaction between the oils in paint and sensitive metals; and 8. They inhibit the spread of corrosion from a damaged area to a sound area adjoining it. Characteristics Simple and effective. Good quality. Consider for
steel appliances. Top quality. Expensive on low volume lines. Excel lent. Satisfactory for non-critical work. Minimum performance; cheap. Minimum performance on rusted steel Minimum performance; expensive but no drv-off. reau ired. Adequate performance if done carefully. Adequate to good performance if operated carefully. Minimum performance. Good to excellent performance if done properly. sive and for average performance not difficult to maintain. The type of equipment and procedure depends on the number of parts to be processed and the size and shape of the parts. A schematic of phosphate process operations is presented in Table 2 to assist in making such decisions. This schematic applies essentially to factory application in the manufacture of such items as cabinets, appliances, and automotive units, either as subassemblies or completely fabricated units. Components of other types of structures, however, are sometimes handled similarly, including those treated and primed in a factory, then assembled in the field. Field application of phosphate coatings is sometimes done by manually operated steam cleaning or by machines using hot solutions at high pressures (see section on cleaning). Table 3 lists U.S. government specifications for phosphating steel surfaces. II. SELECTION OF THE TYPE OF A. ZINC PHOSPHATING PHOSPHATING Cost is an important factor in selecting a phosphating system. Generally, iron phosphate systems are inexpenIn this method the steel is treated with a chemical solution prepared by diluting a proprietary concentrate to the 2 to 4% level. Immersion baths are more concentrated --`,,,,`-`-`,,`,,`,`,,`--99
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SSPC CHAPTER*3-L 93 8627740 0003534 474 TABLE 2 PHOSPHATE PROCESS OPERATIONS Size Large: (e.g., an assembled bus or large tank assembly) Manual Substantial: (e.g., automobiles or large cabinet assemblies) Very low output (1 unit per hour) Manual Low output (4 unitslhour) Manual -for low capital costs Conveyorized spray -only if high quality requirement justifies the high capital and running costs. Line speed 4 ftlmin minimum even if loading is very light. Single chamber -multi spray -intermediate costs and performance --`,,,,`-`-`,,`,,`,`,,`--Moderate to high output (over 12 unitslhour) Conveyorized spray Moderate (e.g. domestic dishwasher or small filing cabinet) Very low output (4 unitslhour or less) Manual -if high quality is a minor factor Immersion Moderate to high output (over 25 unitslhour) Conveyorized spray -line speed 3 ftlmin minimum Conveyorized immersion -for lower line speeds or for maximum quality on internal sections Small: (e.g., bench appliances, lawn mower housings) Very low output (10 unitslhour or less) Manual -if quality is a minor factor Immersion Low output (around 40 unitslhour) Immersion Moderate to high output (over 80 unitslhour) Conveyorized spray -line speed 3 ftlmin preferred but with careful design may go lower in some cases Tipping basket or conveyorized immersion -for maximum quality on internal sections than spray baths and are usually operated at higher with the formation of the co ating.
temperature, 150-170°F in comparison to 100 to 145°F for A considerable amount of ex pertise is required to set spray baths. To obtain good coatings an accelerator is up a good system, but onc e this is done, controls can be added as the system is applied. performed by operators trained for the job. The essential components of a phosphating bath are Mild carbon steel equipment i s usually adequate a zinc salt, a phosphate from partially neutralized although stainless steel hea ders, risers, and nozzles are phosphoric acid, nitric acid and an oxidant, usually preferred in spray systems. When spraying, ingenuity may sodium nitrite (accelerator), added in small quantities con- be required to posi tion the work so that the spray impinges tinuously or intermittently. Zinc phosphate is precipitated on all critical surf aces. in crystalline form on the metal as the acidity is reduced by Sludge formed duri ng the process consists primarily reaction with the steel, while hydrogen gas formed at the of ferric phosphate. P rovision is made to allow this sludge same time is oxidized by the nitrite to water. This last ac- to settle by having heat sources along the side of the tion avoids formation of a gas layer that would interfere tanks, and by having c onstricted areas in which sludge Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 1O0
SSPC CHAPTER*3-1 93 m 8b27940 0003535 300 m TABLE 3 Some Government Specifications on Phosphating Steel Surfaces Application Base for organic coatings. Paint base. corrosion protection Corrosion resistance for moving parts. Corrosion protection resistant to alkaline environments, and prevention of galling. --`,,,,`-`-`,,`,,`,`,,`--Epoxy -used with phenolic varnish US. Gov't. Spec. No. Title TYPe TT-C-490 Cleaning Methods and Phosphate Pretreatment of Ferrous Surfaces for Organic Coatings MI L-S-5002 Surface Treatments Phosphate and Inorganic Coatings for Metal Surfaces of Weapon Systems MIL-C-13924 Coating, Oxide, Oxide Black, for Ferrous Metals DOD-P-16232 Phosphate Coatings, Manganese Heavy Manganese and phosphate, Zinc Base (for Ferrous zinc Met a Is) phosphate MIL-C-46487 Cleaning: Preparation Iron and Organic Coating of phosphate Steel Cartridge Cases may settle. This will reduce re-dispersion as the bath is used. The zinc phosphate system is usually applied in a fivestage process as follows: 1. Clean -alkaline cleaner 2. Rinse 3. Zinc phosphate 4. Rinse 5. Passivating final rinse An intermediate stage may be interspersed between stages 2 and 3 for the purpose of improving the crystal size
of the zinc phosphate by use of a colloidal titanium salt. Cleaners containing titanium may also affect the grain refining function. There will be further discussion below of the final rinse, which applies both to zinc and iron phosphate. B. IRON PHOSPHATE PROCESSES Most iron phosphate coatings are produced by spray. In contrast with zinc phosphate, there are few processes which operate successfully using immersion. Generally a salt of phosphoric or pyrophosphoric acid is used at pH of 3 to 5.5 in conjunction with relatively small quantities of various activators. There are many types of activators used with these baths. "Activators" (a term used loosely here) may be, for example, sodium motybdate, tannic acid, organic nitro compounds, hydroxylamine, and metal ions such as magnesium, zinc, and manganese. Requirements Paint adhesion, sait spray Salt spray Oxalic acid spot test and salt spray -96 hr. min. Salt spray 1.5-48 hrs. Salt spray 24 hrs. Maintaining the acidity within specified pH ranges is crucial. Ordinarily, this is done by adding proprietary salts, but occasionally phosphoric acid is used in addition. Concentrations normally range from '12 O/O to 2%. Best results are obtained at 120 to 150°F under spray application. There is more variation in quality of end result with these systems than with zinc phosphate, due, in part, to the widespread custom of cleaning and phosphating in the same spray system. Often variations in performance are determined more by cleaning than phosphating. Better quality is usually achieved in the lines where cleaning is done prior to phosphating, but most work is processed by dual-purpose chemicals to achieve the objectives of cleaning and chemical conversion. Maintaining two stages of cleaninglphosphating yields superior quality, but this is not done frequently enough in industrial practice. When it is used, it is preferable to have the first spray stage at higher pH and the second at lower pH. More often, a three stage system is employed: (1)Cleaner-phosphater (2) Rinse (3) Passivating Rinse. C.OTHER TYPES OF PHOSPHATING 1. Low Temperature phosphating
There are now available many iron and zinc phosphate materials which may be applied by spray or immersion at, or close to, room temperature, 60"-120"F (16"-49OC). These materials make possible considerable savings in heating costs through reduced fuel use. The prinCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 101
SSPC CHAPTERJ3-II 93 8627740 O003536 247 cipal advantages of low temperature processing are: a. dollar savings -less fuel b. shorter start-up time -because of smaller temperature differential c. better working conditions d. less wear on equipment e. less sludge 2. Solvent Phosphating The more widely used phosphating processes, such as those which have been discussed up to this point, are water-based. There is also a system using trichloroethylene as the base for cleaning, phosphating, and subsequent finishing. This method involves three stages and requires special equipment: a.vapor degreasing in a boiling bath of trichloroethylene at 188 F; b.phosphating by either spray or dip in the organic acid phosphates; c. coating with an organic finish using trichloroethylene as the solvent. 111. FIELD PHOSPHATING Zinc phosphate and iron phosphate coatings of highest quality are normally applied in the factory to items such as automobiles, refrigerators, washing machines, cabinets, assembled units and also to components that are subsequently asembled. However, a reasonably good job, certainly one superior to no phosphate coating, can be achieved in the field by spraying a mildly acidic phosphate solution onto the metal surface. The same iron phosphate chemicals used in factories are often employed. This may be done with steam cleaning machines or machines originally designed to spray hot detergent solution for cleaning under field conditions. Some machines spray detergent solution from one section and phosphating solution from another. These are available in a variety of designs and are treated in the chapter on cleaning. A considerable problem with phosphating in the field is the questionable adequacy of rinsing away the residues from the sprayed solution and the difficulties in supplying a passivating final rinse of chromic acid or acid chromate salts. There is also the problem of disposal of run-off
chemicals. The section on cleaning pointed out that the presence of salts or electrolyte under a paint film can be very harmful in causing blistering and underpaint corrosion upon exposure to highly humid conditions. While this is true of residues from alkaline detergents or hard water salts, it is also true of the chemicals of phosphating solutions that have not reacted with the metal. When a final chromic acid rinse is used, residues from phosphating solutions are insolubilized, or the tiny fraction of the surface that has not reacted to form a tight adherent coating is passivated (¡.e. converted to an adherent oxide by the chromate). The awkwardness of supplying good rinsing or passivating rinses in the field is a severe limitation to obtaining high quality paint adhesion, especially resistance to underpaint corrosion. Quite frequently, this limitation is compensated for by the application of inhibitive or sacrificial primers or quite heavy films of paint to reduce permeability to moisture and water vapor. However, field phosphating by the procedures just described does provide a substantial improvement in coatings performance, Field phosphatizing has been successful with benefit to farm and construction machinery, and to a lesser extent with ships, tanks, bridges, and other structures. Another type of treatment, sometimes incorrectly referred to as phosphating involves treatment with phosphoric acid as contrasted with other mineral acids such as sulfuric or hydrochloric (muriatic) acids. This treatment may utilize hot concentrated phosphoric acid to remove mill scale or heavy rust or rather dilute phosphoric acid to modify light to heavy rust to improve paint performance. It may also be applied to reasonably clean and unrusted steel to form a light phosphate coating, or at least a surface receptive to paint. Most paints can tolerate mildly acidic residues better than alkaline residues from cleaners, or indeed the iron oxide of rusted steel which also has an alkaline reaction. Under ideal conditions there is just enough rust to react with the amount of phosphoric acid applied, so that the result is an almost neutral system. Of course, loose rust which flakes off cannot be improved very much by such treatments. There is also limited use of phosphates of zinc or other metals containing phosphoric acid with other ingredients, including thickeners (some being thixotropic agents) to reduce run-off. If done properly, this provides considerable improvement, especially if applied by brush, which enhances penetration and removal of loose rust. This type of treatment probably has been used to a greater extent in Europe than in the U.S. Naval jelly is a popular
American product. At any rate, pickling with phosphoric acid offers an iron surface with less tendency to rust and improved paint adhesion, and reduces paint failure under outdoor weather exposure. It is occasionally applied to abraded surfaces with good results, especially if there is some rusting due to a delay in painting after blasting. IV. PASSIVATING RINSES Occasionally, the importance of an appropriate final rinse is neglected. We have emphasized the detrimental effect of electrolytic residues that prompt galvanic corrosion. A final rinse containing chromic acid can minimize such corrosion. The chromate insolubilizes some of the heavy metal ions and oxidizes steel which was not properly coated. A passive state is obtained and soluble residues are then flushed away. One common difficulty with chromic acid rinses is Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 102
lack of adequate control of composition and concentration. The desired concentration is so low (e.g., 2 to 4 oz/lOO gal) that small amounts of contaminant can reduce too much of the chromate to the chromic condition. Excessive concentration, on the other hand, can result in blistering under highly humid conditions. The rinse sometimes is used after excessive contamination by electrolyte salts. Disposal regulations are another diffjculty: the amount of chromate that can be introduced into the effluent is extremely small, for practical purposes, almost nil. This has resulted in the use of nonchromated final rinses, often merely very dilute phosphoric acid or de-ionized water, which are of limited value. Some chromium-free rinses are almost as effective as the chromic acid type when used with zinc phosphate coatings. Some of these also contain ions which have limited acceptance in effluent. These can be adequate for some purposes but are less safe to use than the chromic acid rinse, and require very close control. The low concentration of chromium in the chromic acid rinse makes it feasible to treat this effluent without high cost. V. COMPARING IRON AND ZINC PHOSPHATE TREATMENTS Maher and Pradel point out that both the iron phosphate process and the zinc phosphate process have inherent advantages for particular applications. A clear economic advantage of the iron phosphate method is that it usually requires few processing stages, because cleaning and phosphating can generally be accomplished in one step. This means that the pre-cleaning and rinsing associated with other processes are not required. Another economic advantage of the iron phosphating process is that the special acid-proof equipment frequently associated with other processes is not required. Thus, the initial capital investment for the iron phosphate process is usually considerably lower. On the other hand, because of its crystalline structure and more absorptive characteristics, the zinc phosphate coating process generally permits the application of heavier paint finishes with potentially longer life expectancy. ACKNOWLEDGEMENT The author and editors gratefully acknowledge the active participation of the following in the review process for this chapter: Jim Bennett, James Davis, Ted Dowd, Larry Drake, Arnold Eickhoff, H. Kline, Mark Kuchner, Howard Lasser, M.F. Maher, Jim Maurer, Joe Mazia, Robert McCormick, Lou Nowacki, William Pearson. Melvin Sandler and William Wallace. BIOGRAPHY A biographical sketch and portrait of Dr. Spring may be found at the end of Chapter 2.9. REFERENCES 1. M.F. Maher and A.M. Pradel, Phosphate Coatings , Metal
finishing Guidebook, pp. 674-687, 1981. 2. Samuel Spring, Preparation of Metals for Painting, Reinhold Publishing Co., New York, 1965. 3. Samuel Spring and K. Woods, Phosphatizing with NonCrystalline Coatings , Metal finishing, Volume 78, No. 9, p. 31, 1980. 4. K. Woods and Samuel Spring, Selection of a Paint Pretreatment System , Mefal finishing, Volume 78, No. 6, p. 17, 1980. 5. K. Woods, and Samuel Spring, Zinc Phosphating , Metal finishing, Vol. 77, No. 3, p. 24 and No. 4, p. 56, 1979. 6. K. Woods and Samuel Spring, Chromating as a Prepaint Treatment System , Metal Finishing, Vol. 79, No. 6, 1981. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 103
SSPC CHAPTER*3.2 93 8627740 0003538 OLT CHAPTER 3.2 PICKLING STEEL SURFACES by D. W. Christofferson I. INTRODUCTION Pickling is the immersion of objects in dilute acids. Pickling in metal working industries is a process in which metals are immersed in acid solutions to remove oxides or scales. Many excellent references are available1-16. The primary reference is the second edition of the Steel Structures Painting Manual, Volume i on Chemical Surface Preparation by F.P. Spruance, Jr., then Chief, Research and Development Section, American Chemical Paint Company. Most of the basic technical data on pickling is valid and included in this chapter with appropriate changes. Steel Structures Painting Council Surface Preparation Specification No. 8 covers several pickling processes. Various acids used in commercial pickling are sulfuric, hydrochloric or muriatic, nitric, hydrofluoric, phosphoric and mixtures of these. In the United States, sulfuric acid, because of its low cost, high boiling point, availability and general suitability, is used extensively in pickling simple and low carbon steels. They represent the bulk of tonnage pickled. Increased use of reclamation and regeneration of acids has made hydrochloric acid pickling prominent for most low-carbon steels. Without acid regeneration and reclamation some batch plant operations are being curtailed due to the high cost of disposing of waste pickle liquors. Disposal problems result from environ men tal reg u Iat ions. Hydrochloric or muriatic acid alone or in combination with sulfuric, nitric and hydrofluoric acid is used to brighten stainless and some alloy steels. The use of hydrochloric acid with some grades of stainless steel, especially 300 and 400 series, can increase the susceptibility to pitting and stress corrosion cracking and must be used with caution. This chapter primarily concerns structural grade low carbon steels. Pickling is usually done by immersing work into pickle baths in tanks. The same principles apply if the pickle solution is sprayed or flowed over the work or if the work is pulled through baths of acid as in the continuous pickling of strip steel. Acids suitable for pickling should remove only scale from base metal, but a substantial amount may be wasted dissolving the metal itself. Waste can be prevented with suitable inhibitors.
For the rolling process steel is heated below the melting point, usually in open furnaces in which oxygen from the furnace atmosphere combines with hot metal to form oxides of iron and alloying elements. On cooling, these oxides set as a hard, brittle, adherent and usually black coating. This is designated by various names, such as oxide, magnetic oxide, scale, mill scale, roll scale, forging scale, annealing scale, etc. Scale is brittle, expands less than the iron from which it is formed and cracks on cooling. It is not uniform in composition. The lack of uniformity is the difference in the amount of oxygen in various parts of the scale film illustrated in Figure l. The outer layer is richest in oxygen. It may approximate the formula Fe,O,, containing about 30% oxygen by weight. Beneath the outer layer is a material generally constituting the bulk of the scale and nearly corresponding to the formula Fe,O,, with about 28% oxygen. Next to the metal the oxide may approximate the formula Feo, which contains about 22% oxygen. Beneath this may be a layer of mixed oxide and metal of still lower oxygen content. The outer layer of scale is almost insoluble in sulfuric acid but slightly soluble in muriatic acid. The under layer or layers are more soluble and the metal itself quite sohble. When pickling steel in sulfuric acid the diluted acid penetrates through cracks in the outer scale layer and dissolves some scale beneath and works through to the metal or the scale layers rich in metal and low in oxygeni6. These dissolve rapidly, evolving hydrogen between the scale and metal. It is this hydrogen evolution that is responsible for removal of scale that is blown off in flakes of varying size. If all the scale were blown off at one time and the metal immediately removed from the pickling solution, there would be little preventable acid attack on the metal and little need for an inhibitor. This, however, does not occur. Scale is removed from parts of the surface quickly. The uninhibited acid attacks and pits these exposed areas before scale is removed from other areas. Also, when pickling with acids, the mill scale may be removed sooner than rust, which often exists on some local areas. When muriatic acid is used, the action is much the same as that of sulfuric acid, except all the scales are more soluble and some can be dissolved as well as blown off by the hydrogen evolutioni6. Acids remove surface deposits other than mill scale.
Rust is most generally encountered. Rust is a hydrated oxide of iron. It is more soluble in sulfuric, muriatic and phosphoric acids than are mill scales; therefore, rust coatings are removed by being dissolved rather than being blown off. Rust, unlike scale, continues to develop cyclically and if it were not removed along with chemicals that caused it, Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 104
SSPC CHAPTERa3.2 93 8627740 0003539 T5b ,-fRACKS IN SCALE7 FIGURE 1 Mili scale is composed of several layers: A. Fe,O, B. Fe,O, C. Fe0 D. Fe0 + Fe. Courtesy of Amchem Products, Inc. it would continue to form indefinitely even under coatings of paint, oil, etc. Sand or shot blasting is more convenient for rust and scale removal from large assembled structures such as ship hulls, bridge plates, gas holders, etc., that are too large and often too thickly encrusted with pitted rust to be pickled. On smaller assemblies weldments are normally abrasive blasted or mechanically cleaned to remove welding scale prior to the pickling. II. PICKLING PROCESS The pickling process is divided into three steps: Cleaning and preparation of metal Pickling Treating the pickled metal. Cleaning, preparation and treating will be discussed briefly before considering pickling in more detail. Surface treatments and pre-treatments are more fully discussed in Chapter 3. A wide variation exists in successful procedures; only a few will be discussed. A. CLEANING AND PREPARATION OF METAL PRIOR TO PICKLING Cleaning removes from metal any material that would prevent pickling acid from contacting the surface and removing scale. The coating most frequently encountered is oil. Oils can be removed with oil solvents, most of which are volatile and leave a thin film. Solvents can be applied by any convenient means and wiped off with clean rags. The metal can be degreased by immersion in solvents or solvent vapors. The latter method leaves metal free of oil but not from particles or smut held on the surface by oil film. Alkali cleaning is relatively inexpensive and should be provided when cleaning prior to pickling. This is required more or less regularly to remove oils, greases, cutting or forming compounds, etc. Other contaminants that should be removed prior to pickling are heavy rust and paint, which, on new steel, mainly involves shop and mill marks. Heavy rust that might prolong pickling can be removed by scraping, wire brushing or abrasive blast cleaning. Paint and other types of marking can normally be removed mechanically or with solvents. B. TREATING PICKLED METAL
1. Cold Rinsing When metal is removed from the pickle bath, a thin film of pickling acid and salts, resulting from reaction of acid with metal, clings to it. The acid and salts, with the exception of some produced from phosphoric acid, actually stimulate rust formation and must be completely removed before they dry. An ample supply of clean water must be available for rinsing, which may be accomplished by any convenient means. Steel, wood, or concrete tanks provided with a skimming trough to take care of an ample overflow of water are generally used, although water can be applied liberally with a hose. Pickled work should be rinsed promptly, particularly if the acid is hot. If the film dries, it is difficult to rinse away residues that can cause trouble in many of the following operations. 2. Final (Hot) Rinsing -Neutralizing When pickling acid and iron salts are removed or diluted, metal must be suitably treated in preparation for operations that follow. Treatment prevents steel from rusting and prepares it for painting. Weak alkali solutions, such as '/ito ounce per gallon of sodium carbonate or trisodium phosphate, are used in a boiling rinse following a cold rinse, previously described. The alkaline surface does not rust rapidly, but it if is to be stored indefinitely or exposed to weather, it should be oiled. Alkali cleaning solutions are suitable for application of oil but are not suited for application of paint. Also, there are other treatments that can be used to prevent rusting. 3. Preparing Metal for Painting Most paints do not adhere well and blister in a humid atmosphere if applied to an alkaline or neutral surface. For best painting results the surface pH should be slightly acid. Best results occur when the surface has a pH between 3 and 5. There are exceptions when using special paints, such as inorganic zincs, which normally are applied to neutral surfaces. In pickling processes for inorganic zinc applications, no further treatment is normally used after the hot water rinse. For most paints, other than inorganic zincs, it is important that proper acid be used to produce the proper pH. Phosphoric or chromic acids, or mixtures, produce best results. Muriatic or sulfuric acids should not be used because their residues stimulate rust under paint. It is desirable to further clean and treat pickled and rinsed steel in a phosphoric acid solution prior to painting. Good results can be obtained by adding approximately 0.25% by weight of concentrated phosphoric acid to the hot rinse bath, con-
tained in a steel tank, and maintaining this rinse Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 105
SSPC CHAPTER*3.2 73 8627740 0003540 778 at a pH of 3 to 5 by addition of acid as small quantities are needed. The cleanliness of the boiling rinse is important, since it is here that a satisfactorily cleaned surface can be spoiled for painting. For best results the bath should be discarded daily and the tank cleaned before making a new bath. This is not practical for large scale structural pickling operations, and good painting results can be obtained by merely maintaining a water rinse temperature at 140°F (60°C) or higher and painting promptly while steel is warm and dry. 111. ACID PICKLING Sulfuric, muriatic, phosphoric, nitric and hydrofluoric acids are used for pickling ferrous metals. Sulfuric acid is used most extensively for structural steel, although hydrochloric and phosphoric acids are also used for structural and other steels. Typical sulfuric acid pickling for low carbon structural steels may not be suitable for some high strength constructional alloy and heattreated alloy steels. Some higher carbon and alloy steels burn in acid very easily, making surface smut more of a problem. One method to help solve this is to add rock salt to the sulfuric acid bath. Navy specifications call for the bath to contain 1.5% sodium chloride. Test work is in order before pickling special steels for which prior experience or test data is not available, since steel composition also affects the time required for picklinglB. Tanks constructed of mild steel plate or wood can be used for both cold and hot rinse, but ordinary steel, unlined, cannot be used to contain any of the acid solutions used in pickling. Wood tanks can be used temporarily to contain sulfuric, muriatic, hydrofluoric or phosphoric acids, but more permanent equipment, steel tanks lined with materials that resist the acids, should be used to contain them. Table I includes acids and lining materials that resist them and that should be used to construct steam coils for heating. A pickle tank suitably lined and constructed should be equipped with a large bottom drain for rapid emptying and easy cleaning, heating coils or other source of heat, water for diluting acid and for washing the empty tank, and provisions for introducing acid into the bath. Water should never be added to strong acids. Even when properly adding concentrated sulfuric acid to water,
enough heat generates to boil and blow the acid about. Workers should stay as far as possible from acid when it mixes with water in the pickle bath. In small installations steel chutes or pipes should be provided over or through which the acid is poured. In large installations the acid should be transferred through a steel or lead pipe from the storage or measuring tank to the pickle tank. It is advisable to have a tank for measuring the acid added to each pickle tank. For concentrated sulfuric acid the storage tank may be safely constructed of mild steel, since it is not attacked. However, other acids in concentrated form will attack mild steel. The acid storage tanks must use material or linings suitable for the acid involved. Pickle houses are usually filled with steam, and in spite of the ability of inhibitors to reduce acid fumes, some escapes into the air, It is desirable to provide adequate ventilation. Warm air and exhaust ducts located over or near the tanks are helpful in clearing the atmosphere of fumes and acid mists. Also, structural steel within an enclosed pickle house should be properly coated with an acid-resistant coating system. IV. OPERATION OF THE PICKLE BATH WITH ADDED DETAILS ON SULFURIC ACID A. ACID Concentrated sulfuric acid neither attacks steel nor removes scale. It must be diluted with water before it can be used. The rate of attack of sulfuric acid solutions at TABLE I Acids and lining materials that resist them Acid ResisStainless tant masonry Wood Lead Rubber Steel (Brick) Vemporary) Sulfuric X X ... X X Muriatic ... X ... X X Phosphoric X X X X X Hydrofluoric X X ... ... ... ... --`,,,,`-`-`,,`,,`,`,,`--... X Nitric X ... Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 106
SSPC CHAPTERa3.2 93 8627940 0003543 bo4 M . .PUURIG FIGURE 2 Rate of attack of sulfuric acid on mild steel. Courtesy of Arnchem Products, Inc. 120°F (49°C) on mild steel is illustrated in Figure 2. Even at a temperature of 120°F (49"C), concentrated acid does not attack steel. Not until it is diluted with an equal volume of water is there any appreciable action. The activity of acid increases with its strength until it reaches 40% concentration. With further increase in strength, the attack decreases rapidly. Sulfuric acid pickle baths are usually operated within the range of 2% to 15% by volume of 66"Baume sulfuric or its equivalent strength of other commercial grades of this acid, and not at higher strengths approaching that of maximum activity. The greater the viscosity of the bath, the higher the dragout losses. The waste of acid in the spent bath prevents efficient use of acid at high concentrations. Figure 3 shows the relationship between acid attack and strength of 20" Be muriatic acid. Muriatic acid is hydrogen chloride gas dissolved in water. The 20" Be commercial grade contains only about 31O/O hydrochloric acid by weight. Undiluted 20" Be muriatic acid attacks steel more rapidly than stronger solutions and, as in the case of sulfuric acid, the attack in operating ranges is proportional to the acid's strength. B. TEMPERATURE While the activity of the acid solution within the usual pickling range is proportional to its strength, the activity of a pickle bath is markedly affected by its temperature, as is shown in Figure 4 for sulfuric acid. C. IRON SALTS A fresh pickle bath at a fixed temperature continues to remove scale from steel at the same rate; however, pickle baths do not stay fresh. Small amounts of scale and large amounts of metal that dissolve in the acid form iron salts, such as iron sulfate (copperas), in solution. The presence of iron salts in the bath has a significant effect on pickling. As salts build up, removal of scale is delayed, making the bath act as though the amount of acid in it had been reduced. With sulfuric acid pickling the effect of varying
amounts of sulfate in the bath is shown in Figure 5. As a result of the retarding action of iron sulfate, or salts from other pickling acids, the pickle baths should be discarded before they become saturated. D. TIME Time is an important factor in scale removal. Some time is required for acid to penetrate the scale and blow it off, and even more time is needed to undermine "rolled-in scale" or scale embedded in pits. Enough time must be allowed to remove scale completely. E. AGITATION Baths of fixed characteristics pickle faster if agitated than if still. This is clear when it is realized that the acid in contact with any part of the surface picks up more and more iron salts, such as the sulfates with sulfuric acid pickling, and loses strength quickly, as shown in Figure 5. The faster fresh acid is brought to the surface and salt contaminated acid is dispersed throughout the solution away from the metal, the faster the pickling. Agitation also washes off scale particles loosened from metal to expose fresh areas to the acid's action. This same effect is accomplished by mechanical means as, for example, with brushes. Agitation in pickle baths may be produced mechanically by moving the work through the pickling solution, as in the continuous and semi-continuous pickling of coiled strip steel, or with a pickling machine of the type illustrated in Figure 6. Agitation may also be created by moving the solution past work that is stationary in the tank. The plunger pickler, in which the pickle bath is caused to surge up and down by a large plunger, washes over the surface, changes the solution rapidly and removes loose scale. The most common type of agitation is produced by the steam used to heat the pickle bath. This may either be discharged through holes in the lead pipe near the bottom of the tank or through an injector nozzle, causing violent Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 107
SSPC CHAPTER*3*2 93 W 8627940 0003542 540 usual method is to keep acid strength constant and to increase temperature to offset the slowing action of the ac-,.I RATE OF ATTACK OF HYDROCHLORIC / \ cumulating iron sulfate. ACID AT VARIOUS When a pickle bath has dissolved about 2% pounds of I ON MILD STEEL TEMPERATURE 120°FAHR iron sulfate per gallon, its scale removing property is appreciably reduced (Figure 5). It is at or near this point that most picklers discontinue adding acid, so that which 1 I 1 remains can be consumed as completely as possible in I . useful pickling and so a minimum amount is left to be i discarded. To offset weakening acid and accumulating ferrous sulfate, bath temperature is gradually raised, eventually to the boiling point, and the bath is used as long as it ---I oe i--I pickles in a reasonable time. It is then discarded. In this way acid strengths can be reduced markedly but continue to be used; thus, substantial savings in acid can be made. The literature further discusses the influence of these IL i I O factors. 40-c Y F. ANALYZING PICKLE BATHS 30--Acid strength cannot be determined by taste, a oe method used by picklers years ago or by hydrometer, the w > -I --'? - reading of which is affected by both the acid and iron salts 20 in solution. Methods regularly used in the laboratory can
be used to titrate pickle baths for both acid and iron. It is IO common in steel mills to install such apparatus near the 40 60 EQUIVALENT PERCENT OF 2C 4000i FIGURE 3 3600 RATE OF ATTACK OF SULPHURIC Rate of attack of hydrochloric or muriatic acid on mild steel. ACID 5% BY VOLUME 66.d ON Courtesy of Amchem Products, Inc. MILD STEEL AT VARIOUS TEMPERATURES II AI circulation of the bath through a nozzle usually located at one end of the pickle tub. Agitation can be further increased by injecting compressed air through appropriate fittings. Violent agitation and heat is provided by a submerged combustion heater, in which heat from burning gas is transmitted to the pickle baths through walls of a pipe-like combustion chamber located at the bottom of the pickle tank, and from which the products of combustion, along with compressed air, are discharged into the solution. From consideration of the effects of acid concentration, bath temperature, agitation, and the retarding action of iron salts, a reasonable method for operating the bath becomes apparent. For example, a fresh sulfuric acid bath contains no iron sulfate and can be operated at relatively low temperatures with an amount of acid ranging from 2 to 15% by volume, as may be necessary to complete the pickling in the time allotted. As iron sulfate accumulates and slows pickling, the action can be speeded either by increasing the strength or the temperature of the bath. Both methods are used; however, since increases in FIGURE 4 temperature in most installations require the use of more Effect of temperatureo nthe rate of attack of sulfuric acid --`,,,,`-`-`,,`,,`,`,,`--onmild steam, the agitation of the bath is also increased. The steel. Courtesy of Anchem Products, Inc. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERs3-2 93 m 8627940 0003543 487 Equipment required: 1 -5 ml. pipette 1 1 -1 ml. pipette 2 2 -25 ml. burettes 2 1 -5 ml. measuring cylinder 1 Reagents required: burette stand 250 ml. glass beakers stirring rods glass indicator bottle 1.0normal sodium hydroxide solution 0.1 normal potassium permanganate solution methyl orange -1 gm./liter of H,O c.p. sulfuric acid, concentrated G. DETERMINING PERCENTAGE OF ACID Measure a 5 ml. sample of the pickling solution with a 5 ml. pipette and transfer it to a clean 250 mI. beaker. Add about 100 ml (half a beaker) of clean, fresh tap or city water and 2 or 3 drops of indicator solution (methyl orange). Fill a burette exactly to the zero mark with 1.0 normal sodium hydroxide. Stir the test sample constantly with a stirring rod and slowly run in 1.0 normal sodium hydroxide until the red color has changed to yellow. Stop adding this titrating solution at the moment the color of the test sample becomes pure yellow. Record the reading taken on the graduated burette. This is the number of mls. of 1.0 normal sodium hydroxide used. 1. Calculation The number of mls. of 1.0 normal sodium hydroxide used, multiplied by the appropriate factors shown in Table 2 below, gives the desired quantity of 66"or 60" Be sulfuric acid or 20" or 18" Be muriatic acid. 2. Determining iron Content Measure a 1 ml. sample of the pickling solution Y a W CY BO a 2
W o K 290 IOOL II ~SULPHPITECONCE~TRCIO~ I;TWHICH BATHS ARE USUALLY DISCARDED Il 1 I S~LPHATECONCENTR'ATIONS A; WHICH ADDITIONS OFACID ARE USUALLY DISCONTINUE0 II pickle or measuring tanks and to have titrations made at regular intervals, usually by the pickle foreman, who sees to it that acid is added in measured and recorded quantities to maintain the proper strength. TABLE 2 ICOL TABLE Percent by Volume ................... Grams per 100ml. .................... Poundspergal ....................... Percent by Volume ................... Grams per 100ml ..................... Poundspergal ....................... 66O Be 60° Be Sulfuric SuIfuric 0.573 0.740 1 .O53 1.263 8.771 10.525 20° Be 18O Be Muriatic Muriatic 1.999 2.288 2.319 2.612 19.353 21.796 --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 1o9
SSPC CHAPTER*3.2 93 m 8b27940 0003544 313 with the 1 ml. pipette and transfer it to a clean 250 ml. beaker. Add about 100 mls. (half a beaker) of fresh, clean water. Measure 5 mls. of concentrated sulfuric by means of the 5 ml. measuring cylinder and pour it slowly with constant stirring into the beaker. Fill a burette exactly to the zero mark with 0.1 normal potassium permanganate. Stir the test sample continuously with a stirring rod and slowly run in the permanganate solution until the color changes to a faint pink, which persists at least fifteen seconds. Stop adding solution when pink is obtained. Record the reading taken on the graduated burette. This is the number of mls. of 0.1 normal potassium permanganate used. 3. Calculation The number of ml of 0.1 normal potassium permanganate used, multiplied by 0.0465, equals the pounds of iron (Fe) per gallon of pickling solution. Pounds of iron (Fe) per gallon, multiplied by 12, equals grams of iron (Fe) per 100 ml of pickling solution. 4. Records With facilities to analyze the bath, pickling can be efficient. Complete records are essential. A simple procedure for recording strength and temperature of the pickle bath, its iron content, when and how much acid is added, the number of tons pickled, etc., is to plot the data at regular intervals on a chart. These records show consumption of acid per ton. Other pertinent data can be calculated. The graph indicates whether the bath has been discarded with too much acid or before enough iron has been dissolved. Records like this show the effect of different pickling procedures over periods of time. Other records help in cost accounting or comparing one practice with another. An example is comparing the effect of an inhibitor throughout the life of a pickle bath. Data and calculation sheets provide for calculation of the necessary cost per ton, or preferably, per 1000 square feet. When this figure is compared for two or more pickling practices, advantages can be seen. V. INHIBITORS Analysis and record keeping of tonnage, acid consumption, etc. make it possible to prevent careless waste. Pickling in uninhibited acid is a wasteful process because to remove scale it is necessary that acid dissolve some of
the underlying metalt8. Uninhibited acid does not stop dissolving metal after scale comes off. The result is that parts of the steel are usually badly over-pickled before all scale is removed. This wastes good metal and acid. Waste of acid and metal is prevented by inhibiting pickling acids. The effects of suitable inhibitors have been tabulated and p~blished,~ as well as methods of use and advantages2. In a typical pickling operation, when one pound of iron is saved, about 2% pounds of 60 Be suifuric acid is also saved, and nearly 7 cubic feet less hydrogen is evolved. Saving 10or more pounds of metal per ton is common with a suitable inhibitor. A minimum amount of acid, ranging from 1% to 10% by volume, is discarded with each spent bath. The less frequently the bath is discarded or the greater the tonnage pickled before the bath must be discarded, the less acid is lost per ton pickled. Dissolving less metal means less smut develops. A part of this is due to carbon particles that are left loose on the surface when iron dissolves. Other ingredients in steel are similarly exposed and dissolved in the pickling acid and subsequently plated out as a discoloration on metal surfaces. The effect is minimized by use of a suitable inhibitor, which makes it possible to pickle alloy and simple steels in the same bath with less smutting. Where harmful smut is formed on a steel surface, it must be removed before any coating is applied. This is best accomplished by washing or rinsing. Brushing and solvent wiping or mechanical means of supplemental cleaning can be used as required. The susceptibility of steels of different analyses and heat treatments to acid attack varies. A practice suitable for pickling one lot of steel in an uninhibited bath might result in overpickling and ruining another. This condition is corrected by use of a suitable inhibitor that prevents overpickling under normal and even under abnormal conditions. FIGURE 6 Pickling machine in use for the pickling of mild steel. Acid tank is on the left, while the rinse tank is on the right. Courtesy of Arnchern Products, Inc. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 110
SSPC CHAPTERa3.2 93 8627940 0003545 25T A. EFFECT OF HYDROGEN ON THE METAL When metal dissolves in acid, a definite volume of hydrogen is produced. The hydrogen gas, when evolved, consists of single atoms, (nascent or atomic hydrogen) which quickly combine in groups of two to become molecular or atmospheric hydrogen . It is apparently atomic hydrogen, absorbed or dissolved in steel, that affects its flexibility and ductility. This is hydrogen embrittlement or acid embrittlement . Blisters on sheets or plate during pickling and galvanizing are from the same cause. How and why hydrogen is absorbed into the metal is theory; but it is absorbed, and many demonstrations prove that hydrogen passes quickly and entirely through sheet steel. It may be surprising that a seemingly innocuous gas can have harmful effects on dense, tough steel. The situation exists as proven by the rejections of galvanized and other sheets, the breaking of both sheets and wire in drawing, the excessive wear on dies, the embrittling and breakage of spring steels, etc. These flaws continue in spite of elaborate precautions taken in the steel mills to prevent them. Many years of experience with a wide variety of steel plate structures and laboratory tests indicates that commercial pickling of low carbon structural steel, in accordance with procedures set forth by SSPC-SP 8, does not present an embrittlement problem. Normal combinations of acid strengths, bath temperatures and times are not conducive to this type of problem. For stainless and other special steels, more consideration of brittleness and appropriate pickling procedures and inhibitor use is needed. B. EFFECT OF HYDROGEN IN THE PICKLE BATH Atomic hydrogen that does not enter steel combines to form molecular hydrogen outside the pickled surface to cause other objectionable effects. Bubbles of molecular hydrogen that form at the metal surfaceduring pickling are extremely light. They rise rapidly through a poorly inhibited bath. As they reach the surface, they break violently and throw a pickling spray acid contaminating the air with suffocating fumes that can affect the health of workers and rapidly corrode any metal work and masonry in the pickling room. To old picklers this bubbling indicated the bath was working and fumes were looked upon as a necessary evil. Inhibitors minimize acid fumes by reducing hydrogen that causes them. Foam-producing grades of inhibitors, in addition to eliminating acid spray, prevent the escape of steam and loss of heat from the bath s surface. While the almost complete absence of bubbles in an inhibitor-con-
trolled pickle bath led many old picklers to think the bath was not working as fast as it should, such a bath may actually pickle faster than one less inhibited. VI. PICKLING PROCEDURES A. SULFURIC ACID PICKLING Details of sulfuric acid pickling are covered in general discussions and further discussed under Sulfuric-Phosphoric Acid Pickling, a process utilizing sulfuric acid pickling for scale and rust removal and phosphoric acid solution for final treatment. Here is the brief procedure: Preclean metal as detailed in the general discussion on Cleaning and Preparation of the Metal Prior to Pickling. Pickling in a solution of sulfuric acid with sufficient inhibitor minimizes attack on the base metal. Common pickling solutions contain 5 to 10 per cent by weight sulfuric acid at a minimum solution temperature of 140°F (60°C). Rinse adequately in clean hot water above 140°F (60°C). B. PHOSPHORIC ACID PICKLING In some respects, pickling with phosphoric acid is preferable to sulfuric-acid pickling. The number of dipping and rinse tanks can be fewer than in a sulfuric acid pickling system, where rinsing must be more complete. Phosphoric acid is not as corrosive as sulfuric acid under normal conditions, so less expensive construction and less maintenance is required. There are no obnoxious or corrosive acid fumes objectionable to operating personnel. Inhibitors are recommended to prevent overpickling, though the need is not as great as with sulfuric acid pickling. Phosphoric acid pickling generally utilizes a solution of 10-50% phosphoric acid in water. Frequently, the process also includes chromates, solvents, or detergents to assist in removing mill scale, grease and oil. Phosphoric acid first dissolves rust and mill scale and then forms a coating of iron phosphate on the surface. Various commercial phosphate coating processes use a solution with a lower free acid content, capable of producing a much heavier phosphate coating. With these solutions prior pickling with sulfuric acid is usually required. In England and Europe, phosphoric acid pickling has been used for years in batch pickling operations for processing structural steel. A typical process involves a first bath of 10 to 20% by wt. phosphoric acid followed by a water rinse bath and finally a 1 to 2% phosphoric acid bath. One of the earlier established processes utilized approximately 10% phosphoric acid at 85 C. This was followed by immersion in a 2% phosphoric acid solution at 85°C. The intermediate water rinse bath was omitted. The simpler version of phosphoric acid pickling is to pickle steel in a 10 to 25% by wt. phosphoric acid solution at a temperature of about 180°F (82°C)and then rinse with heated fresh water above 140°F (60°C). Test work in-
dicates the procedure produces excellent results for paintCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 111
SSPC CHAPTER*3.2 73 = 8627940 0003546 196 ing. Painting results are generally poor if the water rinse is omitted and paint is applied directly to phosphate residues from the pickling. For instance, Ihn steel panels were precleaned of all oil and grease and then pickled by immersion in 185°F baths of 13% and 23.5% by wt. phosphoric acid. While still hot, the panels were coated by dipping in a proprietary zinc-dust phenolic primer. The dry film was approximately 2 mils. After drying for 9 days the panels were immersed in distilled water. General blistering was evident within 17 hours and was more extensive with the 23.5% phosphoric acid panels. In contrast, panels pickled through the same procedures, but with a water rinse after pickling, showed no blisters after 10 months. Similar contrasts were obtained with a red-lead alkyd primer in a humidity exposure. Shop and lab test results by Hudson & Waring found that pickling times using phosphoric are greater than with suIfuric acid 13. Phosphoric acid pickling has not been used as extensively as sulfuric because the acid is much more expensive, but there are now processes that make phosphoric acid pickling more cost-competitive with sulfuric acid pickling. One successful process depends on continuous purification and reclaiming of the phosphoric acid pickling solution by means of an ion exchange unit, which converts iron phosphate to phosphoric acid. The zeolite cation exchange resin is regenerated by sulfuric acid. Details are explained by Paulson and Gilwood7. C. IRON CONTROL IN PHOSPHORIC ACID BATHS Iron is dissolved in phosphoric acid baths during steel processing, and the iron build-up in the phosphoric acid bath can lead to slowing the pickling rate, or cause difficult rinsing. The latter is evidenced often by a brown discoloration of the surface when the work emerges from the water rinse following the phosphoric acid stage. Normally, when iron build-up in phosphoric acid baths is excessive, the phosphoric acid bath is either drained
and a new bath charged or the contaminated bath is overflowed and partially made fresh. The following factors determine the amount of iron that can be tolerated in a phosphoric acid bath: strength of the bath; type of scale, rust, etc., to be removed; time available for phosphoric acid treatment; type and cleanliness of rinsing available. Certain phosphoric acid pickling baths must be discarded when iron concentrations reach 0.3 pounds of iron per gallon, whereas others can be operated until the iron builds up to 1.0 pound per gallon, depending upon variables mentioned above. DETERMINATION OF IRON IN PHOSPHORIC ACID BATHS: Take 1 ml phosphoric acid bath sample measured accurately with pipette and add to 125 ml. Erlenmeyer flask. Add 1 ml of 50% C.P. sulfuric acid and about 25 ml of distilled water. Add 0.18 normal potassium permanganate from titration burette, with stirring, to solution in the 125 ml Erlenmeyer flask until the solution first turns a permanent pink color. Record number of ml of permanganate solution used. Calculation: Each ml of permanganate solution used is equivalent to 0.08 Ib./gal. iron in the phosphoric acid bath. If 3.0 ml were required to obtain the pink color then 3.0 x 0.08 Ib./gal. = 0.24 Ib./gal. iron in pickle bath. A titration requiring 12 ml of permanganate solution would equal an iron concentration of 1 Ib./gal. D. SULFURIC-PHOSPHORIC ACID PICKLING Originally called the Footner process in England and now used in this country for steel plate, it is an efficient, economical means of removing mill scale from steel5. It also provides a clean, dry surface with an iron phosphate coating that improves the bond between paint and steel. The process consists of immersing material in baths of sulfuric acid, rinse water, and phosphoric acid. Normally, a coat of priming paint is applied immediately after drying to all surfaces that require painting. Sulfuric-phosphoric acid pickling is particularly effective in removing mill scale from carbon steel plate, angles, channels, and other shapes produced by rolling. It is also used to provide a --`,,,,`-`-`,,`,,`,`,,`--clean surface for priming coats of paint on pipe.
E. MATERIALS, SULFURIC ACID BATHS The initial concentration of sulfuric acid is 5% to 10% by weight. In the original Footner process the bath was FIGURE 7 Immersing steel plates in sulfuric acid pickling tank. 112 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERa3-2 93 8627940 0003547 O22 FIGURE 8 Pickling set up for sulfuric-phosphate pickling. Sulfuric acid tank is on the ri ght, rinse tank in the middle, and phosphate tank on the left. A pickled plate is being withdrawn from the sulfuric acid bath. maintained at about 140-149°F (60-65°C). Now a temperature in the range of 160 to 170°F (71-76°C) is common. Normal pickling times to remove all scale and rust is approximately 15 to 20 minutes, but varies with scale and thickness of plate. If bath conditions are the same, pickling time for heavy plate, such as 1 '' to 1?h", may be 30 to 40 minutes. Further additions of sulfuric acid should be made when pickling time increases appreciably. The bath should be discarded when accumulation of sediment and the concentration of iron in the solution interferes with pickling and causes the plate to come out dirty. This condition of the bath corresponds to a specific gravity of about 1.18-1.20 with an iron content of about 6%. After lifting from the acid bath, steel should be allowed to drain into the acid bath for 15 to 30 seconds before immersion in clear water rinse. F. CLEAR WATER RINSE The normal temperature is 140-149°F (60-65°C) but excellent results are obtained without heating. The plate and other work being treated should be dipped in this rinse before passing to the final bath. There should be a very small flow of water through the rinse bath to prevent total acidity, as determined by titration with phenolphthalein, from exceeding 0.1 gram of sulfuric acid per 100 mi. It is possible to determine the necessary flow of water after using the process a short time. G. DILUTE PHOSPHORIC ACID BATH In the original Footner Process this bath was maintained at a temperature of about 180°F (52"C), with plates immersed at least 3 to 5 minutes. The bath was originally charged and maintained at approximately 2% free phosphoric acid and 0.3-0.5% of iron. It is now common and important to maintain the high temperature and to charge the bath in the range of 1 to 1.5% free phosphoric acid and operate closer to the 1 YOconcentration by occasional additions of phosphoric acid. It is not necessary to hold immersion time to a minimum of three minutes. Successful results can be obtained with immersion of approximately one minute. Though results are successful within all mentioned ranges, the lower phosphoric concentration and shorter immersion tends to produce thinner and less porous phosphate coatings. This type of coating is an excellent base for most paints, even though the thicker phosphate film might be more rust inhibitive by itself. Either way, the film of iron phosphate prevents surface rusting in a sheltered exposure, such as a fabrication shop, for an extended period of time, even though primer is
normally applied while the steel is warm. To prepare this bath the necessary amount of iron in the form of steel drillings, steel wool, etc., should be dissolved in 8-10% phosphoric acid heated to 176°F (80°C) and then diluted with water to the required concentration. The dilute phosphoric acid bath may be used over a number of runs provided that the pickled material when taken from the bath is clean and free from loose deposits. H. METHODS The sulfuric-phosphoric pickling process can be summarized as follows: Immersing steel in hot sulfuric acid until the mill scale and rust are removed (Figure 7). Dipping steel in clear water to rinse off residual sulfates. immersing steel in hot phosphoric acid with small amounts of iron added. A coating of iron phosphate is deposited on the steel surface. After drying, painting with priming paint while the steel is warm and placing it in racks to dry. This eliminates any danger of the surface becoming moist or dirty before paint is applied and improves considerably coating adhesion. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 113
SSPC CHAPTER*3-2 73 W 8627740 0003548 Tb7 W Equipment for this pickling process is similar to that normally used in industrial acid pickling. Three baths, all of which can be steam heated, are required and their dimensions are determined by the size of plate to be pickled. Plants are now in operation where plate measuring approximately 8 feet by 40 feet are pickled without difficulty (Figure 8). Typical structures where steel is processed in this manner include oil and chemical storage tanks, floating roofs, water storage tanks, standpipes, elevated tanks, steel pipes, and other miscellaneous structures. The most successful lining material for sulfuric acid descaling baths and the dilute phosphoric acid baths is rubber, which is cheaper than lead in first cost and in certain instances gives longer service. A wood framework is fitted inside the baths to prevent mechanical damage to the lining. The waterwashing bath requires no lining. With a single installation of three baths, it is possible to pickle 500 tons of average tank plate per week. I. CONTROL The control necessary is simple and rapidly becomes routine. A full strength concentration of sulfuric acid in the descaling bath is not usually maintained in acid-pickling work, although there is no objection to the concentration being increased up to 10%. In fact, the higher concentration tends to produce a cleaner plate in less time, but careful time control may be required to prevent pitting. The iron content of the dilute phosphoric acid bath almost controls itself, since the bath makes up considerably from the live steam used for heating, and as the amount of iron going into the solution is small, the concentration never exceeds the maximum specified. The amount of sulfuric acid carried over into the dilute bath is, of course, small and need not be considered at all. Traces of sulfuric acid in this bath do not seem to affect the efficiency of the iron phosphate film on the pickled plate. Technical phosphoric acid can be used, which contains the usual small amounts of impurities. It is desirable to add a suitable inhibitor to the sulfuric acid bath to reduce the attack of the acid on good metal. J. PAINT PERFORMANCE EVALUATIONS PICKLED AND BLAST CLEANED SURFACES Pickling has been used for years as an alternate to blasting for certain exposures, including inside and outside surfaces of water storage tanks. Though field results have been very good, it is always worthwhile to verify them by tests. Many tests have been run. In one, involving 23 different water-immersion paint systems applied to 4 x 10 x panels of A283, Grade C steel, each system was applied to a panel prepared in commercial baths for the 3-bath Sulfuric-Phosphoric Acid Pickling Process. Also, each system was applied to panels prepared in a commercial shop by blasting with Ottawa Flintshot Silica Sand to SSPC-SP 10, Near-White. The panels were immersed in
November, 1966, and formal observations were last reported after 44 months, in July, 1970. All paint systems are not detailed other than to say they were various manufacturer s proprietary systems, as well as several of the standard systems from AWWAD102-64. These included vinyl, epoxy, chlorinated rubber, phenolic, asphalt and coal tar epoxy systems. Ratings were tabulated from the three exposure zones; ¡.e. the vapor zone above the high water level, the fluctuation zone and below the fluctuation zone or continuous immersion. The results, especially as related to surface preparation, were: 1. Above Fluctuation Zone All systems were rated the same on both pickled and blasted panels with 22 out of the 23 systems rated good. The one failed system primarly involved intercoat adhesion. 2. Fluctuation Zone The overall system results were not as good, but 20 of 23 systems showed essentially equal results over pickling and the SP-10 blasting. Of the three systems showing a difference related to surface preparation, two systems involved multiple coats of zinc-rich chlorinated rubber and the remaining one was an amine-epoxy. Only eight systems were rated good on both pickled and blasted panels while eight others suffered intercoat failures on both types of panels. One zinc dust-phenolic failed to metal over both surface preparations. The remaining three systems showed miscellaneous degrees of failure without notable difference in surface preparation. Results with paint systems were far more attributable to the coating system characteristics than to the pickling vs. blasting surface preparation. 3. Continuous Immersion Zone Only one amine-epoxy showed a better result over the blasted panel. Even the two zinc-rich chlorinated rubber systems with inferior results for pickling in the fluctuation zone showed equal and good results in the immersion zone. In this zone, 11 systems showed good results with eight others suffering intercoat failures. The remaining four systems had miscellaneous failure without significance to surface preparation. K. ELECTROLYTIC PICKLING Electrolytic pickling of iron and steel is used to avoid difficulties encountered in still pickling. The removal of rust is comparatively easy with still pickling methods, but removal of the black magnetic oxide of iron, Fe,O,, which is slowly soluble in sulfuric acid, is difficult without the use of electrolytic methods. Electrolytic pickling is usually much more rapid than
still pickling because of greater evolution of hydrogen during electrolytic pickling, which agitates the pickling solution, reduces scale, and tends to pry off scale from the surface of the steel. In acid consumption, however, there is Iittle difference between electrolytic pickling and inhibitedCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 114
SSPC CHAPTER*3.2 93 Ab27940 0003549 9T5 acid pickling. Absorption of hydrogen, which may lead to embrittlement, occurs in both electrolytic and still pickling. The effects of absorbed hydrogen can be removed by baking the work material for about one hour at 300°F or a shorter time at higher temperature. A number of processes are availableB but are not used for structural steel. VII. MISCELLANEOUS ACID PICKLING PROCESSES A. SULFURIC -SODIUM DICHROMATE/ PHOSPHORIC ACID This process is essentially set forth in SSPC-SP8, and even though some variation in concentration of various materials may be used, the main item of difference from the sulfuric-phosphoric process is the addition of sodium dichromate to the final passivating bath. The U.S.Navy has often required this process for shipyard steel. The sodium dichromate-phosphoric acid bath produces more complex surface deposits, believed to be chromium phosphate and chromite phosphite complexes, than does the phosphoric acid-iron phosphate solution. However, without attempting to judge the overall merits of the two types of surface films for the wide variety of paints and exposures involved, it can be said that the use of the sodium dichromate in the solution presents problems of operation and added cost. The sodium dichromate solution tends to give excess powdery deposits, especially if the temperature is allowed to be a little low. Also, with excess precipitation, it is necessary to drain, clean and refill the bath in a matter of days as compared to months for the more common sulfuric-phosphoric process. B. HYDROCHLORIC ACID PICKLING In accordance with SSPC-SP 8, hot or cold solutions of hydrochloric acid as well as sulfuric and phosphoric acid are used along with a heated water rinse. Hydrochloric acid pickling lines at steel mills were commonly used in the past, and such lines are thoroughly discussed in reference article^'^^'^. But more recently, several of these pickling processes have been closed due to E.P.A. restrictions. For pickling structural steel it is not certain how much hydrochloric acid pickling is being done, but there are installations in the US. and overseas where immersion bath processes are used, as well as spraying processes. One process involves from four to six hours immersion or one to two hours spraying of an inhibited solution of 28% minimum hydrochloric acid at ambient temperature. This is followed by an ambient water rinse by spray and a final neutralization by bathing in a 2% solution of phosphate soda at 53% minimum and ammonium phosphate at 10% minimum plus water and other additives. Another plant operation has involved pickling in 10 to 25% HCI at 120°F (49°C) for 30 minutes or less plus a heated water rinse and a final immersion in 1.5 to 2%
phosphoric acid at 175 to 180°F (80-82°C) for 5 minutes. Results are expected to be about the same as for the sulfuric-phosphoric process, especially if the phosphoric bath conditions are the same. C. PICKLING FOR INORGANIC ZINC PAINT AND GALVANIZING When pickling as surface preparation for inorganic zinc paint, it is common to use sulfuric acid pickling plus hot water rinsing, as per SSPC-SP 8. Most operations use an inhibited sulfuric acid bath of 5% to 6% by weight at 160" to 170°F (71-76°C). The minimum water rinse temperature of 140°F (60%) is a necessity to insure rapid drying of the plate. This is more important than when a third high temperature inhibitive bath is used. This type of pickling and priming is widely and successfully used on a variety of tanks, refinery vessels, and other miscellaneous structures, primarily for atmospheric exposure. Pickling also is used successfully to prepare the surface for coating systems to be used in immersion service. In one water immersion test, pickling and SSPC-SP 10 blasting were used on panels testing four inorganic zinc topcoat systems. After 44 months of immersion, there was no failure of the three different inorganic-zinc primers over pickled or blast cleaned surfaces. However, most systems suffered failure between the epoxy and vinyl top coats and the zinc primer. The recommendations and pickling processes used in surface preparation for painting are not normally directly applicable as surface preparation for hot-dip galvanizing and should not be specified for such. The galvanizing shop should be consulted for pickling or other surface preparation recommendations. Normally, pickling is accomplished in the galvanizer's shop. ACKNOWLEDGEMENT The author and editors gratefully acknowledge the active participation of the following in the review process for this chapter: Jim Bennett, Larry Drake, A.W. Mallory, Jim Maurer, C. Munger, William Pearson, G. Satterfield, William Wallace. BIOGRAPHY D.W. Christofferson was a continuous employee of Chicago Bridge & Iron after graduation with a Bachelor of Science Degree in Civil Engineering from the University of Wyoming in 1942. He has worked on all aspects of surface preparation and protective coatings used in the steel plate fabrication industry. Mr Christofferson IS a Registered Professional Engineer in the State of Illinois and
a NACE Accredited Corrosion Specialist. He is also a Certified Nuclear Safety Related Engineer Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 115
SSPC CHAPTERU3.2 93 8b27940 0003550 bL7 A member of the SSPC Research Committee since 1958, Mr. Christofferson has been active on various other technical committees such as AWWA D102, NFPA #22, NACE T-6 Committees, ANSI N101.2, ASTM D01.43, and ASTM D33. He is the author of a number of papers on corrosion, shop surface preparation and painting, and maintenance and painting of steel water storage tanks. REFERENCES 1. F.P. Spruance, Jr., Chemical Surface Preparation , Chapter Three, Steel Structures Painting Manual, Volume 1, 1963. 2. American Chemical Paint Company, Bulletin No. 13, Efficient Pickling with Rodine , September, 1952. 3. J.M. Camp, and C.B. Francis, The Making, Shaping and Treating of Steel, Sixth Edition. 4. G.G. Eldredge, and J.C. Warner, Inhibitors and Passivators , Corrosion Handbook, The Electrochemical Society, Inc., New York, New York. 5. H.B. Footner, A Modern Method of Pickling Steel, Fifth Report of the Corrosion Committee, Special Report No. 21, The Iron and Steel Institute, London, S.W.l. 6. Walter R. Meyer, The Electrolytic Pickling of Iron and Steel, Metals Handbook, 1948. 7. C.F. Paulson, and M.E. Gilwood, New Process Slashes Cost of Phosphoric Acid Pickling , American Chemical Paint Co. 8. John A. Gurklis, and L.D. McGraw, Pickling and Descaling Stainless Steels and High Temperature Alloys , Metal Progress, June 1963. 9. John M. Griffith, Chemical Cleaning Needn t Cause Corrosion , The Oil & Gas Journal, March 4, 1963. 10. Fred H. McCurdy, Jr. and Charles L. McGranahan, Recent Advances In Pickling Technique with Hydrochloric Acid Compound Iron & Steel Engineer, September 1965. 11. British Steel Corporation Report No. EX/9/73/47 Evaluation of Scalamil Descaling Solution , November 23, 1973. 12. Sulfuric Acid Batch Pickling Process Promises No Waste, No Pollution. Magazine of Metals Producing, August 1966. 13. R.M. Hudson, and C.J. Warning, Removing Hot-Mill Scale with Phosphoric Acid . Metal Finishing, November 1977. 14. Pickler s Pickle -Sulfuric or Hydrochloric , -Steel, June 20, 1966. 15. R.O. Bailey - Inhibited Pickling in Production Steel Processing, April 1954. 16. R.M. Hudson, and Cid. Warning, Factors Influencing The Pickling Rate of Hot-Rolled Low Carbon Steel in Sulfuric and Hydrochloric Acids , Metal Finishing, June 1980. --`,,,,`-`-`,,`,,`,`,,`--116 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*4.3 93 8627940 0003553 553 September 1993 (Editorial Changes) CHAPTER 4.1 PAINT MATERIALS Sidney 8. Levinson and Saul Spindel I. INTRODUCTION Knowledge of the many types of paints available to coat structural steel is useful in understanding the capabilities and limitations of these products. Such knowledge facilitates making the best choice for a coating system to meet painting requirements and service. There are reasons for the variety of paint systems offered that become apparent with insight into their basic composition. The information presented in this chapter helps explain which paint or paint system is best for the particular combination of conditions present or anticipated, ¡.e., the condition of the steel, painting conditions, coating properties desired, and the environment to be withstood by the applied finish, as well as the total cost for material and application. II. PAINT INGREDIENTS Paints are composed primarily of pigments dispersed in a film-former, or binder, which is either dissolved in solvent or emulsified in water to make paint fluid enough to apply by brush, roller or spray. After application of the paint in a relatively thin film, the solvent or water evaporates and the remaining film dries or cures to form a tough, adherent coating. If no pigment is used, the coating is clear as, for example, a varnish on wood surfaces. Coatings for use on structural steel are pigmented either with anticorrosive pigments to produce primers or with opaque, colored pigments to produce various colored topcoats. A. PIGMENTS Here is a list of several reasons for adding pigments. 1. Opaque pigments are added to enable the paint film to obscure the surface painted. These materials are available in various colors. 2. Metallic pigments are added to produce metallic finishes. Aluminum and zinc are by far the most common metallic pigments. 3. Anti-corrosive pigments are used in primers to prevent or inhibit steel corrosion. They may also be added to intermediate and even finish coats to enhance corrosion resistance. 4. Extender pigments, which are not opaque, are added to reduce gloss (to produce semigloss or flat finishes), to aid intercoat adhesion properties, to increase viscosity and to decrease cost. (See chapter on pigments.) B. METHOD OF CURE Paint binders vary in their method of curing or drying. Knowledge of various ways paint binders cure is helpful in
understanding comparisons among binders discussed in this chapter. 1. Oxidation Oxidation is a method of curing solvent-thinned paint film. Oxidation, or absorption of oxygen from the air followed by polymerization, is called air drying. Many alkyd resins, for example, dry by oxidation. 2. Solvent Evaporation The binder is dissolved in a mixtureof solvents. (See Solvents.) When applied, the solvent evaporates, leaving a dry film that does not undergo further change. However, the coating can generally be softened or dissolved with strong solvents or solvents similar to that in which it was dissolved originally. Coatings that dry by solvent evaporation are called lacquers. Vinyl or chlorinated rubber coatings are examples. Since drying depends only on solvent evaporation, lacquer coatings can be applied at relatively low temperatures. 3. Chemical Reaction The paint is supplied in two packages or two components: a base and a hardener. When mixed, the two react to form a final coating. Since the reaction continues whether the mixed paint is in the container or applied, the paint has a limited pot life (useful life), usually a working day or less. Epoxypolyamides are typical of this type of coating. On the other hand, since two-component paints do not rely on oxidation to cure, some formulations can be applied in relatively thick coats. 4. Coalescence Latex binders are made of synthetic colloidal latex polymer particles dispersed in water. Often called emulsions, they are actually colloidal dispersions or suspensions. When the paint is applied, latex particles begin to press together or coalesce, as the water evaporates. A coalescing solvent in the paint softens the particles and causes them to form a continuous film. Latex coatings tend to allow movement of water vapor through the coating, although after the film has coalesced they are essentially resistant to water. Consequently, latex paints can be used on Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 117
SSPC CHAPTERt4.1 93 m 8b27940 0003552 49T m damp (not wet) surfaces. On the other hand, latex pains will generally not coalesce well at temperatures under 50°F or at either very low or very high relative humidity. Instead, they will produce undesirable, d iscont in uous, non-adherent, nonresistant films. C.PAINT BINDERS The paint binder is the major ingredient in the paint and determines the major performance characteristics of the coating. The binder is the cement or adhesive that binds pigment and provides adhesion to the surface, ¡.e., steel or previous coat of paint. The more commonly used paint binders are discussed below. They are listed in alphabetical order. I. Alkyd Alkyd binders of coatings used on structural steel are vegetable oil-modified phthalate resins that air dry by oxidation. Alkyd finishes are of the general purpose type, are economical and available in a wide range of colors and gloss levels, from high gloss to flat finishes. They are relatively easy to apply and can, if necessary, be used on surfaces that have been only moderately cleaned, e.g., SSPC-SP 3. Alkyd finishes have excellent durability in rural environments, but are only fair in marine or corrosive environments. Typical specifications are SSPCPaints 101 and 104 as well as the SSPC-Painting Systems 2.00 and 2.05. 2. Epoxy Epoxy binders are available in three types: epoxy ester, epoxy lacquer resin and two component epoxy. 3. Epoxy Ester These are vegetable oil-modified epoxy resins. Consequently, they are similar to alkyds except they are more expensive and produce films that are harder and somewhat more alkali resistant. Generally, they have less gloss retention when exposed. Epoxy esters are sometimes used where slightly more alkali resistance than provided by alkyds is desired, but at a lower cost than twocomponent epoxies. 4. Epoxy Lacquer Very high molecular weight epoxies can be formulated as lacquer-type binders by solution in a mixture of strong solvents. (See Solvents.) They are sometimes used in organic zinc-rich primers
because they dry quickly at low temperatures and can be recoated with topcoats, such as two-component epoxy paints. The two-component epoxies contain strong solvents that will soften the primer slightly and improve intercoat adhesion. 5. Two-Component Epoxy Epoxy resins of this type cure by chemical reaction. 118 (See Chemical Reaction.) The epoxy is generally combined with either of two types of hardeners: polyamine or polyamide. Epoxy-polyamine blends are more resistant to chemicals and solvents and are often used for lining tanks. Epoxy-polyamides exhibit longer pot life, superior flexibility and durability, and have adequate chemical resistance under most conditions. Furthermore, they enable packaging of the epoxy and hardener in separate, equal size packages. Epoxy-polyamide paints are the most popular of all epoxy binders for use on structural steel. When exposed to weathering, they chalk quickly, but retain their excellent chemical resistance properties. SSPC-Paint 22 is a typical specif icat ion. 6. EpoxyCoal Tar Epoxy binders are often combined with coal tar where color is not important, since the color of the resultant coating is generally brown or black. Epoxycoal tar paints are almost as corrosion and chemical (not solvent) resistant as epoxy-polyamide paints, but are less expensive. They are often used on submerged surfaces where color is of no importance. Epoxy-coal tar finishes have high build, but tend to lose flexibility as they age, so substrates must be relatively rigid. Typical specifications are SSPC-Paint 16 and SSPC-Painting System 11.01. 7. Inorganic Inorganic binders are used with zinc dust in zinc-rich paint where galvanic protection of steel is desired. Common inorganic binders are silicates, either lithium, sodium, potassium, ethyl alkyl, or quaternary ammonium.* Zinc-rich paints contain a relative ly high concentration of zinc dust, 75% minimum by weight of total solids, which provides intimate contact between the steel and zinc dust when the coating cures. Inorganic (silicate) zinc-rich paints must be applied to blast-cleaned surfaces, at least SSPC-SP 6, to obtain proper adhesion. They are reviewed in depth by Munger in a separate chapter. (See Chapter 4.2) When properly used, they produce extremely hard, abrasion resistant films that are very
resistant to corrosive environments. SSPC-Paint 20 and SSPC-Painting Systems 12.00-12.01 deal with both organic and inorganic zinc rich. A typical specification for zinc-rich primer is SSPC-Paint 29. 8. Latex Latex paints are based on emulsions (actually colloidal dispersions) of very high molecular weight, such as acrylic, polyvinyl acetate, ethylene vinyl acetate, acrylonitrile or styrene butadiene and their copolymers. They are relatively easy to apply and dry by coalescence of the latex particles to form tough, durable coatings. Latex paints have little odor, are non-flammable, and generally meet air pollution Ethyl silicates are not true inorganics but are generally included in this group. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*4.L 93 m 86279YO 0003553 326 m regulations. They are economical and somewhat more durable than oil paints (see Oil Paints) in rural environments, exhibiting less chalking and much better color retention. Latex paints are relatively porous and allow moisture vapor through the film and thus can be used on damp (not wet) surfaces. On the other hand, latex paints will not coalesce properly when applied at temperatures below 50°F or at either very low or very high relative humidity and require careful surface preparation on chalked, glossy or dirty surfaces, since they do not contain solvents that will readily wet or soften these surfaces. SSPCPaints 23 and 24 and SSPC-Painting System 18.01 and 24 are concerned with latex paints. 9.Oil Vegetable oils (especially linseed oil) are the oldest paint binders with the longest history of performance. Oil-based paints dry by oxidation, but more slowly than other binders. They wet the surface better than any other binder discussed and therefore need less careful surface preparation. Oil-based paints are easy to apply and are adequate for rural environments. They are not recommended in corrosive environments. Typical specifications are SSPC-Paint 1 and the SSPC-Painting System 1.00 series. 10. Phenolic Phenolic resin binders are varnishes made by processing vegetable oils (usually linseed or tung, also known as chinawood) with phenolic resins. They make excellent aluminum-pigmented paints and have resistance in humid environments and to immersion in fresh water. On the other hand, phenolic coatings are relatively dark (except in aluminum paints), and they tend to darken further during exposure. Phenolic coatings are very hard and need care to ensure proper intercoat adhesion. Typical specifications are SSPC-Paint 5 and SSPC-Painting Systems Guide 3.00. 11. Rubber-Base There are two major commercial types of rubberbase binders: styrene or vinyl toluene copolymers and chlorinated rubber. Styrene-butadiene (SIB), vinyl toluene-butadiene (VTIB) and styrene-acrylate (SIA) are similar in characteristics. They are used in lacquers that dry rapidly by solvent evaporation to form coatings resistant to water and mild chemicals. Therefore, they can be used in humid and wet areas. Styrene-butadiene can be combined with silicone resins (see Silicone Resins) to produce heat resistant aluminum paints. The limited flexibility of these copolymers restricts their use on exposed structural steel.
12. Chlorinated Rubber Chlorinated rubber resins can be used in two ways: a. They can be plasticized to form fast drying lacquers, which are highly chemical (not solvent) resist an t. b. They can be combined with alkyd resins to speed drying of the alkyd resins and increase their chemical resistance and durability. Typical specifications are SSPC-Paints 17, 18, and 19 and SSPC-Painting Systems 15.00-15.01. 13. Silicone Silicone resins are available in two forms for use on structural steel: pure silicone resin and siliconemodified alkyd resins. a .Silicone Resin Pure silicone resins are expensive, but extremely durable, and resistant to high temperatures, especially when pigmented with aluminum. They can be added to styrenebutadiene resins or polyacrylates to reduce cost but are still very good heat-resistant aluminum paints. b. Silicone Alkyd Alkyd resins produced with some silicone resin result in silicone-modified alkyds, which have improved durability, especially in marine environments, as well as improved heat resistance. Typical specifications include SSPCPaint 21 and SSPC-Painting System 16.01. 14. Urethane Urethane or polyurethane binders are available in three types: a. Oil-Modified Urethane These also are called uralkyds, since they are similar to alkyds in processing, method of cure (oxidation) and use. However, they produce coatings that are harder and more resistant to abrasion than alkyds. Unfortunately, although uralkyds have excellent durability as clear finishes, pigmented uralkyd coatings are not durable enough to be used on exposed structural steel. b. Moisture-Cured Urethane These urethanes react uniquely with air moisture to cure. They produce the hardest, toughest coatings available in one package. Pigmentation is extremely difficult because of their moisture sensitivity, so they are used primarily as clear finishes. They can be pigmented, provided moisture-free materials are used and proper precautions are taken during manufacture and use. c. Two-Component Urethane Urethanes can also be reacted with products such as polyols, polyethers, polyesters or acrylics to produce extremely hard, resistant and durable coatings. These are binders of major interest for use as topcoats on structural steel exposed in marine or corrosive environments. d .Aromatic YS Aliphatic Urethane -Urethane polymers can be made from isocyanates, which
are either aromatic or aliphatic. Aliphatic urethanes are preferred for exterior use, despite their high cost, because of their outstanding Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 119
SSPC CHAPTER*4-L 93 8627940 0003554 262 durability, color and gloss retention. Pigmented aromatic urethanes are extremely hard, tough, and chemical resistant, but chalk rapidly when exposed to sunlight. SSPC-Painting System 17.00 is a guide to urethane painting systems. 15. Vinyl Vinyl binders are available in three types. a. PVB -Polyvinyl butyral resins are the binders used in wash primers. When combined with basic zinc chromate pigment and phosphoric acid, they improve adhesion of the paint system tremendously. This can be critical for some vinyl paint systems, which have excellent resistance and durability but may be sensitive to surface conditions with respect to adhesion. Wash primers are also used as metal treatments for galvanized steel and aluminum. b .Polyvinyl Chloride and Polyvinyl Acetate Vinyl chloride and vinyl acetate resins produce lacquers that dry rapidly by solvent evaporation to form extremely durable coatings for use in marine or corrosive environments. They generally are not brushed, due to rapid drying, but can be sprayed. They are low in solids, so multiple coats are usually necessary and surface preparation is critical (see polyvinyl butyral resins). One spray coat of vinyl may yield only one mil of dry film thickness. However, because vinyls release solvents so rapidly, as many as 4-6 coats may be applied in a 24-hour period. Vinyls are extremely resistant (except to strong solvents), durable in most environments and can also be used for lining tanks for water immersion service. Low-solids, high-polymer vinyls are covered in SSPC-Paints 8, 9, and 106, as well as in SSPC-Painting Systems 4.00 through 4.05. c. Vinyl-Alkyd-A compromise, which is effective for most environments, is to combine hydroxylmodified vinyl and alkyd resins. Surface preparation requirements are slightly less critical than for vinyl binders. Brush application can be easier, total solids are higher, and exterior durability is excellent. However, they are not recommended for highly corrosive environments. D. COMPARISON OF PAINT BINDERS Properties of the most popular binders for use on structural steel have been summarized in Tables 1-4 to facilitate comparison of their characteristics, outstanding properties and limitations. It must be kept in mind that these tables compare the binders used alone in top quality formulations. It is possible that blends or formulation modifications can change the characteristics and performance of any of the binders resulting in a different performance level than the generic binders. Where blends are used,
average the data given for each binder in the blend. Common binders described in the tables include alkyds; epoxy (epoxy-polyamide-two component); acrylic latex; linseed oil; phenolic varnish; chlorinated rubber; urethane (aliphatic two-component); and vinyl (polyvinyl chloridel acetate copolymer). Inorganic silicate binders are not included because these materials are used only in zinc-rich paints, as discussed in the chapter on that subject. E. SOLVENTS The third major ingredient in paints is the solvent. Paint binders are polymerized to accelerate drying or curing and to produce as tough acoating as possible. When pigment is added, the viscosity of the mixture is increased sharply to a point that would make the product incapable of application. Therefore, the major functions of solvents are to dissolve (or disperse, in the case of latex) the pigment/ binder and to make its viscosity low enough to enable application by brush, roller or spray. Solvents, with the exception of water, can also be chosen andlor blended to produce the desired rate of evaporation during application. For example, brush or roller applications require relatively slow solvent evaporation, while spraying is improved with fast solvent evaporation. Slower evaporating solvents improve applications and leveling during hot weather. Table 5 compares the major solvents used in paints and lacquers. Note that some of these solvents are also used for cleaning before painting, or cleanup after painting. This data is presented under the fol lowing head ings: Evaporation Time -Relative time to evaporate the same amount of solvent. The lower the number, the faster the evaporation rate. Flash -Flash Point in OF (Tag Closed Cup). TLV -Threshold Limit Values in parts per Million (ppm). This is an 8-hour day with no ill effects. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 120 --`,,,,`-`-`,,`,,`,`,,`---
SSPC CHAPTERx4.L 93 = 8b27940 0003555 lT9 TABLE 1 APPLICATION PROPERTIES Alkyd 2-Can Acrylic Linseed Chlorinated Aliphatic Aliphatic EPOXY Latex Oil Phenolic Rubber Urethane Vinyl or Solvents Aromatic Lacquer Water Aliphat ic Aromatic Aromatic Lacquer Lacquer*** Min. Surface Preparation* SP 3 SP 6 SP 6 SP 2 SP 6 SP 6 SP 6 Stability During Use EX F EX EX EX EX F EX Brushability G F EX VG G F G P Method of Cure Oxid. Chem. Coal. Oxid. Oxid. Evap. Chem. Evap. Speed of Cure 50 OF-90 OF* * G EX F EX EX EX 35OF-50OF* NR NR P G G G Film Build per Coat VG F G G VG G Use in Primers EX F EX G G G Use on Damp Surfaces G VG P P G G *SSPC Surface Preparation Specifications "Painting should not be done above 90°F or below 34°F 'Usually used in topcoats TABLE 2 APPEARANCE PROPERTIES 2-Can Acrylic Linseed Chlorinated Aliphatic Alkyd Epoxy Latex Oil Phenolic Rubber Urethane Use as Clear Finish (Varn ish) VG F P NR VG NR EX Use in Ready Mixed Aluminum Paint G F NR F EX F F Pale Color VG G EX G P VG EX Ability to Produce High Gloss EX EX F G EX VG EX TABLE 3 PERFORMANCE PROPERTIES 2-Can Acrylic Linseed Chlorinated Aliphatic Alkyd Epoxy Latex Oil Phenolic Rubber Urethane Hard ness G VG F P VG VG EX Adhesion G EX F VG G VG VG Flexi bi Iit y G G EX VG F VG VG
Resistance To A bras ion VG F P G VG EX VG Water EX F P EX EX VG EX Strong Solvents EX F P G P EX P Acid VG F P EX EX EX EX Alkali EX G P G EX VG EX Heat -200°F G F F G NR G NR Vinyl NR G EX F Vinyl G F EX --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 121
SSPC CHAPTER*LI-L 93 W 8b27940 0003556 035 Moisture Permeability Normal Exposure Marine Exposure Corrosive Exposure Color Retention Gloss Retention Chalk Resistance CODES EX -Excellent VG -Very Good G -Good F -Fair P -Poor NR -Not Recommended 111. TYPES OF PAINT 2-Can Alkyd EPOXY Mod Low VG VG F EX F EX G P G P G P SOLVENTS TABLE 4 DURABILITY Acrylic Linseed Chlorinated Aliphatic Latex Oil Phenolic Rubber Urethane Vinyl High Mod Low Low Low Low VG G VG EX EX EX F F G EX EX EX F NR G VG EX EX VG F P G EX VG EX P G G EX VG VG P G G EX VG ABBREVIATIONS Aliphatic -Mineral spirits Oxid. -Oxidative polymerization or oxidation Aromatic -Xylene, toluene, etc. Chem. -Chemical reaction (two component) Lacquer -Aromatic plus ketone, ester, or Coal. -Coalescence (latex) ether solvents (See Solvents) Evap. -Solvent evaporation (lacquer) Following are the most common types of paints used on structural steel.
A. METAL TREATMENT Wash primer is discussed under vinyl. It is sometimes considered a metal treatment (or etch primer) rather than a primer, since it is applied at very low film thickness (0.3-0.5 mils) and is used primarily over galvanized steel or to improve adhesion of paints, such as vinyls, which are sensitive to surface conditions and surface preparation. Use of this product is designated as SSPC-Paint 27. Metal treatments do not replace anti-corrosion primers. B. ANTI-CORROSION PRIMER Anti-corrosion primers prevent or inhibit corrosion or rusting of steel if moisture gets to the steel surfaces through missed spots, breaks or pinholes in the coating. To be effective, primers must be in direct contact with steel, except when used over wash primer, which contains an anti-corrosive pigment (basic zinc chromate).* Primers, with the exception of zinc-containing paints, are not formulated to be exposed to the environment, but require a topcoat for protection. Furthermore, they are rarely colored, other than the color produced by the anti-corrosive pigment. This may be grey, yellow, orange, white, red or shades thereof, depending on the pigment used. Zinc-rich primers are durable and can be used without a topcoat in normal environments where there is no danger of reaction with very acidic or very alkaline chemicals. In Min. -Minimum C. INTERMEDIATE COAT When a coat of paint is applied, it is likely there will be missed spots (holidays) and pinholes. Consequently, it is best to apply multiple coats. Since the primer and topcoat perform different functions, and both may have the above defects, it usually is best to apply three coats. Furthermore, for best results on exposed structural steel, the total minimum dry film thickness (dft) should be 5-6 mils. Three coats usually are needed to achieve the desired conventional total dry film thickness. The intermediate coat may be primer or topcoat. It should be tinted slightly so its color can be discerned both during application and topcoating. D. TOPCOAT The topcoat provides color and protects the primer from the environment so the primer can perform its function without being degraded. E. PAINTING SYSTEMS The paint system is the combination of surface preparation, primer, intermediate coat and topcoat. However, it may have more or less than 3 coats to achieve the desired thickness. For most painting systems, increased film thickness decreases permeability and improves performance and durability. In repainting, the painting system consists of surface preparation followed by application of the touch-up primer plus the topcoat (see SSPC-PA 4). Details of the painting system are described in Volume 2 of the SSPCManual.
*Chromate pigments are toxic substances. Follow all applicable health, safety and environmental requirements in rich primers. applying, handling or disposing of these materials. the latter exposure, they must be topcoated. SSPC-PS Guide 8 provides more information on choosing topcoats for zinc--`,,,,`-`-`,,`,,`,`,,`--122 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERm4.L 93 8627940 0003557 T7L TABLE 5 PAINT SOLVENTS Evap.* Flash TLV** Time (OF) (ppm) Aliphatic Hydrocarbons (Petroleum Solvents) VM&P Naphtha 20 50 300 Mineral Spirits 1O0 Aromatic Hydrocarbons (Stronger than Aliphatics) Toluol (Toluene) 20 45 1O0 Xylol (Xylene) 35 85 1O0 Esters (Lacquer Solvents) Ethyl Acetate 8 40 400 Isopropyl Acetate 10 50 250 Butyl Acetate-N 30 90 150 Amyl Acetate 50 1O0 1O0 Ketones (Lacquer Solvents) Acetone 4 5 750 Methyl Ethyl Ketone (MEK) 8 30 200 Methyl Isobutyl Ketone (MIBK) 20 65 50 Methyl Isoamyl Ketone (MIAK) 70 115 50 Diacetone alcohol 200 145 50 Glycol Ethers (in Lacquers and Latex)*** EGMEE 1O0 104 5 EGMEEA 66 124 5 EGMBE 500 141 25 Alcohols Ethyl Alcohol (Ethanol) 20 60 O00 Isopropyl Alcohol (Isopropanol) 25 65 400 Butyl Alcohol (Butanol) 70 105 50 Amyl Alcohol 1O0 115 1O0 Water 100 None Safe Nitroparaffin 2-Nitropropane 30 1O0 10 Chlorinated Solvents l,l,l-trichloroethane 5 None 350 Methylene chloride 2 None 50 Evaooration Time. Ether = 1 * *American Conference of Governmental Industrial Hygienists (1991) * * EGMEE -Ethylene glycol monoethyl ether EGMEEA -Ethylene glycol monoethyl ether acetate EGMBE -Ethylene glycol monobutyl ether REFERENCES
1. Paints and Protective Coatings, Army TM 5-618, NAVFAC MO-110, Air Force AFM 85-3, US. Government Printing Office, Washington, D.C. 1969. 2. A.G. Roberts, Organic Coatings, Properties, Selection and Use , Building Science Series 7, National Bureau of Standards, US. Department of Commerce, Washington, D.C. 3. A. Banov, Paints and Coatings Handbook, Structures Publishing Co., Farmington, Michigan. 1973. 4. Paint/Coatings Dictionary, Federation of Societies for Coating Technology, Blue Bell, PA 1978. 5. S.B. Levinson, Solvents, American Paint Journal, July 19, 1966. 6. Handbook of Organic Industrial Solvents, Technical Guide No. 6, American Mutual Insurance Alliance, (now Alliance of American Insurers), Schaumburg, IL. 7. TLVs Threshold Limit Values for Chemical Substances and Physical Agents in the Workroom Environment, American Conference of Governmental Industrial Hygienists, Cincinnati, OH. 1991. 8. Raw Material Index, National Paint and Coatings Association, Washington, D.C., 1979. 9. S.B. Levinson, Painting , Facilities and Plant Engineering Handbook, McGraw Hill Book Co., New York, N.Y. 10. Fire-Hazard Properties of Flammable Liquids, National Fire Protection Association, Boston, Mass. 11. Federation Series on Coating Technology, Federation of Societies for Coatings Technology, Blue Bell, PA. ACKNOWLEDGEMENT The authors and editors gratefully acknowledge the active participation of the following in the review process for this chapter: AI Beitelman, Alex Chasen, Lawrence E. Drake, Arnold Eickhoff, Dave Eskra, J. R. Garland, Dan Gelfer, Joseph F. Guobis, W. A. Haldeman, L. Hartman, Leondard Haynie, Joseph Mazia, Marshall McGee, John Montle, C. G. Munger, Dan Nemunaitis, John Perchall, W. Richter, Melvin Sandler, L. M. Sherman, V. J. Todd, Duane Werkman and Rufus F. Wint. Industrial Consulting Laboratories, AdcO Chemical Company, Garland Company, D.H. Litter Company, David Litter Laboratories and DIL Laboratories. His professional associations include: the Association of Consulting Chemists and Chemical Engineers, the Federation of Societies for Coatings Technology, the American Society for Testing and Materials, the American Chemical Society, the National Association of Corrosion Engineers, the Scientific Committee of the National Paint and Coatings Association, the Washington Paint Technical --`,,,,`-`-`,,`,,`,`,,`--123 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERa4.L 93 8627940 0003558 908 Group, the Commercial Development Association and Steel Structures Painting Council. He is a former president of the New York Society for Coatings Technology and received their highest award, the TaVaC. He was recently made an honorary member of ASTM Committee D1 (Paint and Related Coatings and Materials) and was elected its chairman. During these years he has held office as President of the New York Society for Coatings Technology, and as Chairman of Committee D-1(Paintings and Coatings) of the American Society for Testing and Materiais (ASTM) for three consecutive terms, the maximum allowed. At present, he is an honorary member of the New York Society for Coatings Technology, as well as both ASTM and its Committee D-1, and he is a 50-year member of the American Chemical Society, the Federation of Societies for Coatings Technology, and the National Paint and Coatings Association. BIOGRAPHY Saul Spindel, a graduate of Brooklyn College, has over 40 years of plant and laboratory experience in production, formulation, testing and customer service for the development and application of trade sales, maintenance, marine and in-plant industrial coatings. He is a certified Corrosion Specialist and a licensed Professional Engineer in corrosion. He has presented numerous talks and has authored a variety of articles on paint technology as well as hundreds of private reports. As president of DIL Laboratories, Spindel has been engaged in a variety of operations in the coatings industry involving testing, formulation, technical service, surveys, field inspection, legal assistance, expert testimony, preparation of specifications and manuals and laboratory personnel training. Spindel, who has served as chairman of the Corrosion Committee, the Technical Advisory Committee and the Planning Committee of the Federation of Societies for Coatings Technology, is also a member of a number of coatings and sealant organizations. He is especially active in the American Society for Testing and Materials, the National Paint and Coatings Organization and the New York Society for Coatings Technology, of which he is a past president. He has received the Award of Merit from ASTM, making him a Fellow of that organization. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 124
SSPC CHAPTER+4=2 93 m 8b27940 0003572 288 m CHAPTER 4.2 ZINGRICH PRIMERS by Charles G.Munger Since the invention of steel, it has been a primary structural material used for all critical structures in modern society. There are many reasons for this strength, workability, adaptability. It may be rolled, cast or welded into any conceivable shape and, when properly protected, will last for centuries. Bridges, ships, skyscrapers, towers, tanks, pipelines, railroads, automobiles, and offshore drilling equipment are examples of the multiple uses of steel which contribute to the well-being of humanity. The key words are properly protected . Without protection, steel structures tend to revert to their natural state of iron, ¡.e., iron oxide or rust. I. HISTORICAL From earliest time, keeping steel in its usable form was the goal of all who used it, and there have been thousands of materials used on steel surfaces in an effort to resist change from usable metal to its non-usable oxide. Of all of the materials tried for steel protection, zinc has been the most successful. The first record of its use dates back to 1840 when a French engineer, Sorel, patented a process for coating steel with zinc to prevent rusting. The simplest process to provide protection using zinc was dipping a piece of steel in molten zinc and providing a complete layer of zinc over the steel surface. This procedure gave birth to the galvanizing industry, which has been a growing one ever since. There are increasing references to zinc in coatings in the early 19OO s, and the use of zinc increased until, at the present time in the United States, 150 million tons of zinc are used annually. A large percentage of this is for protection of iron and steel either as galvanizing or in zinc-rich coatings. Most of this expansion has come since the 1920 s and ~O S,and it wasn t until the 1930 s that anyone gave a great deal of scientific thought to making a long-lasting, corrosionresistant coating from zinc dust. The movement started in two different places, and the concept of zinc-rich coating was as different in each place as the places were far apart. The English started with the idea of using zinc dust in organic vehicles to provide a zinc-rich coating while a completely different concept was started in Australia, where the inorganic zinc-rich materials were conceived. The idea of incorporating zinc dust into an organic vehicle coincided with the time that the more sophisticated synthetic resins became available. These more resistant materials were needed since zinc reacted readily with most of the
oleoresinous products that were used for coatings prior to this time. By using very resistant synthetic resins, such as chlorinated rubber, to start and incorporating high-loading of zinc into the vehicle, the organic zinc-rich products were born. They provided protection to steel surfaces that was not available by other coating means except through the galvanizing processes. Only very alkali-resistant resins could be used effectively for zinc-rich coatings, and as the epoxy resins entered the coatings field after World War Il, the expansion of zinc-rich coatings was rapid and continuous. In Australia, Victor Charles Nightingall, an engineer, spent several years studying ways a chemical compound could be made with high durability and long-lasting corrosion protection. His basic idea, which was unique, was that if he could make a coating that would closely simulate chemical characteristics of willemite or zinc silicate, he would be able to accomplish the goal. He studied the ore and came up with a mixture of zinc and sodium silicate which, when applied to clean steel surfaces and heated to 250°F or above, would form a hard, adherent, corrosionresistant coating. This was the state of the art up to 1950, even though millions of square feet of the zinc silicate coating had been applied on above-ground structures in Australia up to that time. All of it, however, was stoved or baked to bring about, as he states it, the rapid silication of sil ica-zi nc iron. The procedure used to coat steel in the late ~O S,using the zinc silicate, was to pickle steel free of all mill scale and all other contaminants. Following pickling, the steel surface was scrubbed with fiber brushes to remove the black pickling deposit and washed with dilute sodium hydroxide to remove sulfuric acid. Finally, it was rinsed with dilute phosphoric acid to prevent rust forming on the steel pipe before the coating could be applied. As soon as the surface was prepared, the coating was mixed by weighing about 10 pounds of sodium silicate and a small amount of sodium bicarbonate into a bucket. Twenty pounds of zinc dust and about three pounds of red lead followed. The whole mix was stirred vigorously with a stick. There was no premanufacturing of inorganic zinc coating at that time. It was made and used within a few minutes, since it was rather reactive and left for any period of time would solidify in the bucket. After mixing the coating, painters applied it to the steel surface with large 6 in. brushes. The coating was worked well into the surface to eliminate holidays and, surprisingly, a relatively even coat of zinc silicate was obtained. The aim was to apply approximately one ounce of zinc per square foot. This was determined by the amount of zinc used in the coating Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 125
SSPC CHAPTER*4-2 93 m 8627940 0003573 114 = and applied to the steel surface. The water-base coatings dried within a few minutes and then the coated steel was moved into either a large stoving area, where the temperature was brought up to 200-300°F or, if the coating was applied to the pipe exterior, the pipe was moved in front of large burners that blew flame, hot air and combustion products into the pipe at one end and out the other. As soon as steel was brought up to temperature, the coating was dry, very hard, and very metallic. ! The first well documented field test of this product was in 1942, on a section of steel pipe in the Woronora pipeline, which was part of the water system for the city of Sydney. The line ran above ground, close to the bay and a few feet from some large oyster beds. The pipe was inspected in 1950 and it was in perfect condition. It still exists. The Morgan Whyalla line, which is thefamous250-mile pipeline in inorganic zinc silicate history, was negotiated in 1941-42 and completed in 1944. The negotiations included a 20-year guarantee on coating performance. This was done with little more than the Woronora pipe section to go on. Victor Nightingall passed away in 1948, long before the guarantee was up, and before he could see the revolution in coating technology that his ideas created. His work was carried on by another engineer with the same drive and single-minded approach, M. G. McKenzie, whose leadership in the inorganic field helped create the worldwide use of zinc coatings. Woronora pipe and Morgan Whyalla pipeline were the beginning of an era for inorganic zinc coatings. Presently, the heat curing or stoving process has been used on some 3,000 miles of above-ground pipeline. The process is still being used in Australia today, and heat curing provides a very fast method of in-plant coating with water base inorganic zinc products. The result of McKenzie s convinction, that a zinc coating was a permanent one, was entirely borne out by the guarantee period, which passed in 1965. In 1970, the South Australia government duplicated the original Morgan Whyalla line, using the same exterior coating. A section of the original line at Whyalla was inspected firsthand in 1972. The pipe was in perfect condition and showed no evidence of rusting, chalking or any change from the long exposure to the atmosphere. This particular area was adjacent to Spencer Gulf and a steel plant. It had both a mild marine atmosphere and an industrial atmosphere to provide corrosive conditions. Even the field welds, which were touched up and allowed to dry, showed no corrosion. II. AMBIENT CURING It was recognized early that for this material to be entirely effective the stoving or baking step had to be eliminated. The early research set out to find a way that the coating could be formed without heat and yet obtain all of the excellent characteristics of the zinc silicate. Manyat-
tempts were made to cure the coating with various salt solutions. One attempt was to use a wash primer developed by the U.S. Navy and Union Carbide during the war, as both a cure for the zinc coatings and a primer for organic coatings to follow. Such an attempt was made on a very badly corroded naphtha tank at one of the refineries on the U.S. east coast. While not perfect, the coating did stand up and prevent corrosion for many years under a very difficult industrial atmosphere. Many attempts were made to use various salt solutions. These primarily were fairly concentrated water or alcohol solutions of magnesium chloride, zinc chloride, aluminum chloride, some soluble phosphates, etc. One manufacturer recommended washing with sea water. These trials had some basis in fact, as this over-simplified chemical diagram suggests. 2 Zn + 2NaCI + 3H,O -ZnOZnCI, + 2NaOH + 2H, The zinc oxy chloride, or basic zinc chloride, is practically insoluble. This compound, complexed with zinc hydroxide or zinc carbonate, which would surely be part of the reaction products, could provide sufficient insolubility to the silicate matrix to hold it until the zinc silicate reactions could take place. Actually, none of these procedures worked satisfactorily, except under very limited and control led conditions. Finally, it was determined that a solution of dibutylamine phosphate, applied after the zinc silicate coating had dried, insolubilized the zinc silicate coating enough so the resulting product had all of the good characteristics of the stoved inorganic zinc as originally conceived by Victor Nightingall. This was the post-cure inorganic zinc coating that started the revolution in coating steel structures in most areas of difficult corrosion, high humidity, and particularly in marine atmospheres. Hundreds of ships were coated with this material, along with offshore platforms, wellhead structures, onshore installations of all types including tanks, heater treaters, bridges, pipe racks, bulkheads, refineries, and chemical plants. Once the postcured inorganic zinc demonstrated the efficiency of this coating procedure, research was instituted by many U.S. companies. Many materials were tried, including sodium silicate, with many sodium oxide to silica ratios. Using sodium silicates with higher silica ratios helped eliminate white deposits that formed on the coating surface during cure. Potassium silicate provided a somewhat faster cure and eliminated much of the white deposit. Lithium silicate produced a faster cure and harder product. Lithium silicate was the base for one of the more successful commercial inorganic zinc silicate coatings. Quarternary ammonium silicate, while tried very early in the various research programs, was proven effective only in more recent formulations. Ammonium silicate systems are not as hard as some of the zinc silicates and do not possess the glasslike properties of alkaline metal silicates. Colloidal silica, silica colloids in solvent, and silica gels were all tried
alone and in combination with other silicates. Basic inorganic materials such as phosphates, titantates, borates, zinc oxychlorides, and similar materials were also formed Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 126
SSPC CHAPTERU4-2 93 m Ab27940 0003574 050 m into coatings with somewhat fewer properties. Some were with many materials list ed above. Acid-hydrolyzed ethyl also added to silicate vehicles in an effort to provide im-silicate combined wit h powdered zinc was one of the proved coating characteristics. earliest, and one of the first successful self-c uring zinc During this time many other inorganic materials were silicate products. The alka li hydrolysis product of the ethyl being tried, such as ethyl silicates, cellosolve silicates, silicate was used to produce effective zinc coatings. (See and similar organic silicates, alone and in combination Table 1 for some interes ting combinations of silicates ~~ TABLE I Typical Examples of Various Zinc-Rich Paint Formulations Type* Vehicle Pigment Weight Ratio pigmentvehicle IA Post-cured Water Based Inorganic Zinc-Rich Paints A 3.2 ratio sodium silicate; 22% 30,; Zinc dust + red lead 2.8 sodium dichromate B 3.2 ratio sodium silicate; 24% SO,; Zinc dust 3.2 potassium dichromate IB Self-cure potassium silicate A 2.9 ratio potassium silicate; 14% SiO,; Zinc dust 2.9 manganese dioxide; sodium dichromate B 2.4 ratio potassium silicate; 9.25% SiO,; Zinc dust 2.0 acrylic emulsion C 2.8 ratio potassium silicate; 18% SO,; Zinc dust + red lead 2.8 quaternary ammonium hydroxide; soluble amine; carbon black D 3.2 ratio potassium silicate; 15% 30,; Zinc dust 2.5 quaternary ammonium hydroxide; soluble amine; carbon black Self-cure Iithi um si Iicate Lithium-sodium silicate; 19% 90,; sodium Zinc dust + iron oxide 3.3 dichromate Self-cure silica sol Silica sol; 32% SiO,; soluble amine; Zinc dust + red lead 4 .1
potassium dichromate; carbon black Self cure-quaternary ammonium silicate A Quaternary ammonium silicate; 32% SiO, Zinc dust 2.5 B Quaternary ammonium silicate; sodium Zinc dust 2.5 silicate; 20% SiO, Solvent Based Inorganic Zinc-Rich Paints IC Self-cure A Partly hydrolyzed ethyl silicate; 10% SiO,; Zinc dust 2.2 clay fillers B Partly hydrolyzed ethyl silicate; 22% SiO, Zinc dust 3.4 C 127 --`,,,,`-`-`,,`,,`,`,,`--Basic hydrolyzed ethyl silicate; 15% SiO,; Zinc dust + iron oxide 2.4 clay fillers D Polyol-Alkyl Silicate; 20% SiO, Zinc dust 2.2 'As per SSPC-Paint 20 -Zinc-Rich Paint Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*Y-Z 73 m 8627740 0003575 T97 m some have proven to be most practical and successful.) Following development of self-curing ethyl silicate zinc coatings was a great amount of research to produce selfcuring coatings from all other silicate materials. Research has progressed to the point where there are a number of single package zinc silicate products on the market that are not only fully combined into a single package, but are self-curing, as well. A number of these have proven to be excellent products, particularly when overcoating with organic coatings is a requirement. Progress has been made in the last thirty years from the original product, which was made by mixing the individual ingredients just prior to application, to the point where the finished product in a single package may be used essentially like paint. These products have caused a coating revolution. Some, in a single coat, provide protection in severe atmospheres that is better than a galvanized surface. Others, when overcoated, increase the life of the organic topcoats several times. 111. MECHANISMS Inorganic zinc coatings, including those formed from sodium silicate, potassium silicate, lithium silicate, colloidal silica, the various organic silicates and even galvanizing, are reactive materials from the time they are applied. Inorganic zinc coatings, including galvanized metal, are in a state of constant change. This change depends on their exposure -marine, industrial or rural. It is a slow, continuing process until the zinc is practically consumed in protecting the steel it is applied to, or inactivated by an accumulation of zinc salts on the coating surface. Some of these typical zinc reactions are: Zn (metal) + H,O -Zn" + 2eThis is the normal corrosion reaction for zinc. Zn + 2H,O + -,Zn (OH), + H, Zn + H,O + CO, -,Zn CO, + H, 2 Zn + 2NaCI + 3H,O -,ZnOZnCI, + 2NaOH + 2H, Galvanized surfaces or pure zinc react with carbon dioxide and oxygen in air to form zinc carbonate or zinc oxide on the surface almost as soon as it comes out of the galvanizing bath. The original bright zinc surface, after a few days in weather, turns dull gray, and, at times, will accumulate a substantial quantity of white salts on the surface. The inorganic zinc coatings are somewhat more complex. They are composed of powdered metallic zinc mixed into a reactive silicate solution. The first reaction is the
concentration of silicate zinc mixture by evaporation of most of the solvent. The solvent can either be water, in the case of water-base products, or organic solvents, in the case of the organic silicates, leaving a non-reacted deposit of a silicate gel and zinc powder. Once initial drying has taken place, environmental reactions such as those described previously take over and chemical curing of the coating begins. At this point the coating may be hard and abrasion resistant, or somewhat soft with little abrasion resistance. In either state, it is uncured and may be sensitive to water. In every case, regardless of the environment, the original reactions of either the water-base or the organic base silicates are essentially the same. The initial reaction is for water and CO, from the air (H,O + CO,-H,CO,) to ionize some zinc on the surface of zinc particles. The slightly acidic water helps to hydrolyze organic silicates to silicic acid and to hydrate water soluble silicates to form silicic acid. The ionized zinc then reacts with silicic acid groups on the silicate molecules in the silicate gel structure. This insolubilizes the coating and provides its initial properties. At this time there is also some reaction of the silicate vehicle with the iron surface to form a chemical bond. Iron ions are formed reacting with the silicate vehicle at the iron surface in the same way that zinc does. Most coatings at this point are somewhat porous, largely because of the compacting quality of spherical zinc particles. This can be seen in scanning electron microscope photographs, and substantiated from a practical standpoint. In many cases where inorganic zinc coatings have been overcoated with organic coatings, within a short time after application bubbling of the organic coating takes place. This is due to penetration of organic solvents into the zinc coating creating a vapor pressure that causes bubbling of material applied over the zinc coating. Inorganic zinc coatings which are post-cured have much less porosity due to the immediate formation of zinc phosphate on and within the pores of the coating. This makes for a high density, relatively pore-free coating. Removal of the curing agent is necessary prior to topcoating. The reactions described are taking place during formation of the coating. From this point on, the reactions will be those that take place over a long period of time and ones characteristic of the environment in 'which zinc coatings are placed. Humidity and condensation of moisture on inorganic surfaces plus carbon dioxide continue to create a very mild acid condition that results in continued hydrolysis of the vehicle and ionization of zinc. Zinc ions diffuse deeper and deeper into the gel structure until there is a zinc silicate cement or matrix formed around each of the zinc particles binding the coating together and to the steel surface. This zinc silicate cement is hard, insoluble, durable, and rock-like in character (Figure 1).
Since zinc coating is porous, ionization of zinc on the surface of zinc particles can occur any place within the coating. In so doing, it provides electrons that protect the underlying steel from corrosion (Figure 4). If water and CO, are present, zinc hydroxide and zinc carbonate also are present. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 128
SSPC CHAPTER*4.2 93 8b27940 000357b 923 Coating Surface 2 inc Discontinuous Surface silicate a But Interface of Steel and Coating: Chemical Bond FIGURE 1 Inorganic zinc coating inc Particle Sand Blasted Surface Interface Between Cnatinn nnd _.a-Steel accounts for zinc silicate coatings gradually becoming harder, more dense, and more adherent. This process continues for many months and years, and with the formation of every zinc ion, electrons are released, which protect the iron substrate from corrosion. This is a very important react ion, since it increases the effectiveness, du rab¡ Iity and chemical resistance of the inorganic zinc coating with age. One very important characteristic of inorganic zinc coatings is the electrical conductivity of the matrix. Because of this, electrons formed by ionization of zinc at any point within the coating can migrate to the steel substrate and provide cathodic protection to any steel area that may be exposed. Particle-to-particle contact of the zinc pigment is not required for conductivity in inorganic zinc coatings, since it is in a conductive, organic, zinc-rich matrix. OH I -Si4 I P SC
r --% O Q t -di-oI OI :i-o-diOH - -N Zn kn I c N Witn excess Zn++ f.ion zinc dcst,silicate polymer continues to grow ad eventual :; saturates with zinc. These reaction products, zinc carbonate and zinc hydroxide, are more voluminous than the zinc silicate. They can form within the pores of the coating as well as on the surfaces. This fills the pores and seals the surface to create a very hard, abrasion-resistant metallic film. This Na 1 Na O/Si02 @ 1/3.0 Ratio -Na-O2 Na 9I YH Y Na-O-Si-O-Si-O-Si-OH dH h OH ++ I II on OH JH Na
+ Fe++ 1 ++ 7 TH PH + Pb -)Na-O-Si-O-Si-O-Si-OH ++ III + Zn tT? Fe Pb Zn I II O 00 I II Na-O-Si-O-Si-O-Si-OH I O (! I ¿H 1 Na Fe++ from Steel Substrate Pb++ from Red Lead Additive Zn from Zinc Dust Silicate polymer complexed with Iron, Lead and Zinc. Ammonium, Potassium and Lithium Silicate reactions substantially same as for sodium From Air ia and Water P Na-O-Si-+ H2C03 +OH-i-+ Na CO H 23 White deposit on coating surface removed by weather. Sodium in polymer removed by reaction with CO2 from air ++
Excess Zn carbonate Zn++ reacts with CO and H O to form insoluble zinc 2 2 + 20H + H2CO3+ZnCO3 (SSPC-Paint 20, Type IA or 16). 129 + 2H2Q FIGURE 2 Chemical Reactions within a Zinc Silicate Coating -Water Base --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*4.2 93 W 8627940 0003577 4bT W The chemistry of these inorganic coatings is very complex. The effectiveness of the end product depends on the skill of the formulator and his addition of minor ingredients that insolubilize the matrix around the zinc particles. It is believed that all of the truly inorganic zinc coatings ultimately have matrices composed of heavy metal silicates. The primary heavy metal is zinc derived from ions dissolved from zinc particles mixed into silicate solution, either water or solvent based. Minor quantities of many heavy metals may be reacted into the silicate matrix FIGURE 3 -lead, magnesium, aluminum, calcium, barium, iron, etc. Zinc reaction within a porous inorganic coating Immediate insolubility in water is the goal, with the conO0 acid II CH + HsO*-+Et-O-Si-O-Si-O-Et + Et OH 23 CH3CH2 Tetra Ethyl Silicate Some other organic silicates may be added to or substituted for ethyl silicate with similar II It It Ethyl Silicate Polymer I $ + H2O and CO from humid air 2 QH 0" ++ + Zn --`,,,,`-`-`,,`,,`,`,,`--end results. (Silicate Zinc Polymer. 1 OH in I
4PH HO-Si-O-Si-OH I1 OH , OH Final Ethyl Silicate Zinc Polymer similar to Sodium Silicate Zinc Polymer. FIGURE 4 N Chemical reactions within an ethyl silicate zinc coating. 130 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*4-2 93 = 8b2794O 0003578 7Tb tinued long-time reaction of zinc finalizing the insolubility. Figures 2 and 4 indicate the possible reactions that take place within the coating to form the insoluble matrix. No other common metal powders react to form an insoluble silicate polymer in the same way. Unsuccessful efforts have been made to use both metallic aluminum and mag nec iu m. IV. ORGANIC ZINC RICH Organic zinc-rich primers, in contrast to the inorganic zinc-rich products, involve very little chemistry in formation. These products are simple mixtures of zinc dust or metallic zinc pigment into the organic vehicle. Zinc is the primary pigment in these organic zinc-rich coatings, with very little addition of other pigmentation. There are two requirements essential for effective operation of organic zinc-rich coatings: 1. Zinc in the vehicle, in order to provide the cathodic protection required by zinc-rich coatings, must be in particle-to-particle contact or contain a conductive filler, such as iron phosphide, to make an electrically conductive path through the organic matrix. Without this particleto-particle contact, zinc in the coating essentially would be inert and surrounded by the organic vehicle, which would not allow the zinc to go into solution and provide the cathodic protection. 2. The second important consideration in organic zinc-rich primers is that the vehicle or carrier of zinc pigment be alkali resistant. This is important since zinc, particularly under chloride environments, reacts to form a strong alkali that would adversely effect any alkali-sensitive resin or binder. The primary organic resins used to make organic zinc-rich primers are chlorinated rubbers, phenoxy resins, or catalyzed epoxy resins. While there are a number of other materials that can be used, these are the principal ones applied to steel structures. V. SSPC CLASSIFICATION The specification for SSPC-Paint 20 includes the types of zinc-rich primers common at this time. There are two basic types, Type 1 -Inorganic zinc-rich; and, Type 2 -Organic zinc-rich. Description of the various zinc-rich paints available are outlined in the above specifications as follows: Type 1-A Inorganic post-curing vehicles, which are water soluble, include alkali metal silicates, phosphates and modifications thereof, which must be subsequently cured by application of heat or a solution of a curing compound. Type 1-A has a very broad area of application. It is a water-based material, and wherever water will evaporate from the coating, this product can be used. It may be applied under cool or warm and dry conditions. Because of
the post-curing agent it will form an effective coating under this wide span of atmospheric conditions. It is not effective in freezing conditions or in very high humidity when water will not evaporate from the system within a short period of time -a matter of a few minutes to one or two hours. After that length of time zinc tends to separate in the vehicle, making a poor coating with little resistance. It is also difficult to use where rain showers are frequent, since the coating must be cured with the curing solution before additional water contacts the coating. A rain shower on a Type 1-A coating prior to application of the curing agent will break up the silicate gel film -and the coating becomes useless. Post-cured inorganic zinc coatings are most effective when used alone, without topcoats, since removal of the curing agent residue is essential when topcoats are to be applied. Type 1-B Inorganic self-curing vehicles, which are water reducible, include water soluble alkali metal silicates, quaternary ammonium silicates, phosphates and modifications thereof. These coatings cure by crystallization after evaporation of water from the coating. Several water-based silicates are included in this category -and many are most effective when applied during warm, dry conditions. In this case, the water evaporates rapidly from the coating, leaving a hard metallic coating, which becomes insoluble to water in a short time. Then it continues to cure to full hardness and adhesion by the above chemical reactions. Some formations require more humidity for a complete cure than others. Again, these materials are not effective under cold, highly humid conditions, since water will not evaporate from the film within a reasonable period of time. Type 1.C Inorganic self-curing vehicles, which are solvent reducible, include titanates, organic silicates, and polymeric modifications of these silicates. These systems primarily are dependent on moisture in the atmosphere to complete hydrolysis, forming the polysilicate. This category covers many different formulations, most of which are based on an ethyl silicate vehicle. There are a number of other organic silicates used or combined with ethyl silicate to provide specific coating characteristics. Because of variation in properties and application characteristics this class of inorganic primer is used widely throughout industry as a base for high performance coatings. There are too many variations to outline the specific properties of each product in this chapter. Nevertheless, they all primarily follow the same chemical reactions shown previously (Figure 4) to form the final coating. The majority work best, application wise, under cool, reasonably humid conditions. Moisture from the air is required for a complete cure and many formulations will not cure well or completely under hot, dry conditions. Since they are solvent based materials, many are more subject to overspray under warm, windy conditions than water base products (1-6).
There are two specific types of solvent base inorganics (1-C) that are variations from the standard twopackage products. 131 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*4-2 93 W 862 7940 O003579 632 m The first is the single-package inorganic. This product combines the ingredients of the coating including zinc into a single package, ready for application directly from the container. The product characteristics are similar to the two-package material, as are the basic chemical reactions that forms the films. The main advantage of this product is simplicity in handling a single container that only requires stirring prior to use; one container to handle during transportation and storage; and one container for painters to work with on the job. Most single-package products are used in areas where topcoats are to be applied. The second is the modified inorganic zinc primer. Here the solvent base (IC)inorganic is modified by the addition of a compatible organic resin, usually a vinyl butyral, which is soluble in alcohol solvents. The product characteristics are a compromise between completely inorganic zinc coating and organic zinc-rich primers, with some of the good properties of each appearing in the modified product. Any deficiency would be due to the life of the organic resin incorporated into the system. Advantages claimed for this material are improved application properties, a smooth film, easy and rapid overcoating, adhesion to most clean steel surfaces and good repair properties for previously zinc primed and overcoated surfaces. This product usually is used where topcoats are to be applied. Type 2 organic vehicles include phenoxies, catalyzed epoxies, urethanes, chlorinated rubbers, styrenes, silicones, vinyls and other suitable resinous binders. The organic vehicles covered by this specification may be chemically cured or may dry by solvent evaporation. Under certain conditions heat may be used to facilitate or accelerate hardening. There is good reason for the number of different types of zinc-rich primers. The basic use of the material -as well as the conditions under which it is applied -dictates what types of formulations should be used. Type 2 primers can be applied under most conditions where an organic vehicle applies effectively; however, they also are subject to the basic problems inherent in organic vehicles, such as weathering, undercutting, release of adhesion from water absorpfion, blistering and so forth. One good use of organic-based zinc-rich coatings is as a repair primer for inorganic zinc primers and galvanized surfaces that have been topcoated and have been damaged during use. By using organic zinc-rich primer, the zinc base coating is maintained over the bare steel area while the organic vehicle is compatible with the organic topcoats, allowing it to be feathered out over the edge of the existing organic material. With the many different formulations of both inorganic and organic zinc-rich primers -some with high
zinc loadings and others with a minimum, some with additives and others without -some precautions should be taken in selecting a product. The best insurance is to use a material with an extensive background of good performance for similar use. Without this, it is suggested information be obtained on the total solids content, theoretical and practical coverage, percent of zinc in the dry film, type of binder and scope of duration of actual field applications or field tests of the several materials considered. If there are requirements for high-performance coating, the best is none too good. Since material cost is only a small part of the completed coating job, only the best material, not the cheapest, should be selected. The information above can be a good basis for comparing various zinc-rich coatings offered for a project. Each type of zinc-rich primer has specific areas of use where it is most effective. The above information allows the corrosion engineer and applicator to select material most effective for particular requirements. VI. PRE-CONSTRUCTION PRIMERS One additional type of zinc-rich primer should be mentioned: the preconstruction primer. It may be either 1-B or I-Ctype. It is formulated to be applied as a very thin material, approximately one mil in thickness, and is usually applied to steel prior to fabrication. In many shipyards the preconstruction primer is applied to all plate as it comes into the yard. There it goes through an automatic blast-cleaning operation followed immediately by application of inorganic preconstruction zinc-rich primer. These materials are applied under controlled conditions and have proven very effective in providing a corrosion-free surface during construction. They may be over-coated directly with organic topcoats or recoated with additional zinc-rich primers, depending on coating requirements. Steel with preconstruction primers applied must be capable of being cut with manual and automatic gas torches and welded by manual and automatic welding equipment, without any loss in cutting speed or weld strength. Recently, preconstruction primers have been formulated with an iron phosphide additive that improves the weldability and resulting weld. As much as 40% iron phosphide, based on total pigment content, has been added without apparent changes in the corrosion-resistant characteristics of the primer. VII. COMPARISON WITH GALVANIZING Zinc-rich primers have often been compared directly with galvanizing. There are many similarities; however, there are also many differences. Galvanizing can be considered an inorganic zinc primer and, in many ways, it will do the same things an inorganic zinc-rich coating will. Both galvanized and inorganic zinc coatings are chemically bonded. Galvanizing is an amalgamation or mutual absorption at the iron-zinc boundary, while the inorganic zinc matrix forms a chemical compound of iron and silica at the interface of
the coating and metal. Both types of coating provide protection to the steel surface by cathodic protection, so there are many similarities. The inorganic zinc-rich coating has, however, some basic differences: Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 132
SSPC CHAPTER*4.2 93 8627940 0003580 354
Zinc in the coating is not continuous. It is made up of zinc particles, surrounded by and reactive with an inert zinc silicate matrix. This matrix is very inert and, except for strong acids or alkalies, is inert to most environmental conditions where coatings would be used. Because of the formation of the coating by zinc particles in an inert matrix, the coating controls reactivity and conductivity. This has been proven by actual measurements where zinc was coupled with iron, and the inorganic zinc silicate coating was coupled with iron. The actual potential of the two coating materials was essentially equivalent. However, the current flow or amperage between the galvanized surface and iron was practically double the current flow between the inorganic zinc silicate coated panel and the steel panel. The zinc on the galvanized surface went into solution much more rapidly than the zinc held within the matrix of the inorganic silicate coating. As surprising as it may seem, many of the inorganic zinc silicate coatings end up much harder, and more abrasion resistant than the metallic zinc in galvanizing. These points generally indicate a longer life span for inorganic zinc silicate coatings, compared to galvanized steel. This has proven true in tests, and in certain full-scale exposures where the two materials were used side by side. Type II, the organic zinc-rich primer, should not be compared directly with galvanizing because of the organic nature of the binder. VIII. CHARACTERISTICS -INORGANIC (TYPE I) The outstanding characteristics of inorganic zinc-rich primers are: Cathodic protection is provided by inorganic zincrich coatings. The inorganic matrix is conductive and allows zinc to go into solution in a controlled manner, making it anodic to steel and able to cathodically protect any breaks that occur in the coating. Eventually, any minor holidays, pinholes, scratches or scars heal by formation of zinc reaction products, such as zinc hydroxide arid zinc carbonate. It is unaffected by weather, sunlight, ultraviolet radiation, rain, dew, bacteria, fungus or temperature. Since it is unaffected by weatheroriented factors, the coating does not chalk or change with time. The inorganic zinc film remains intact with essentially the same thickness, even after many years of exposure. The inorganic binder chemically reacts with the
underlying steel surface in a similar way to its reaction with the surface of the zinc particles. This reaction occurs at the interface between the steel and the coating, forming a permanent chemical bond. This is an important property, since it prevents the undercutting of coating by corrosion. With this bond, an inorganic zinc-rich primer can form a base coating that does not undercut or allow underfilm corrosion. This property cannot be overemphasized. The majority of organic coating failure under severe corrosion conditions is by underfilm corrosion, starting at small breaks in the coating. This property of the inorganic zinc base coat multiplies the effective life of an organic topcoat. This has been shown by test and field experience. One of the most important characteristics of inorganic zinc coatings is that they do not shrink while drying or curing, like organic coatings do. Once applied, the inorganic material follows the configuration of the surface. This is due to the method by which the film is formed and is a major advantage in overcoating rough, pitted, corroded surfaces or rough welds. Inorganic zinc materials are relatively unaffected by temperatures above the melting point of zinc. Used as a primer and topcoated with silicone base topcoats, the combination has provided protection even at temperatures of 1000°F. High speed production welding cannot be accomplished with a full thickness of zinc rich. Porous welds may result. Nevertheless, Battelle Memorial Institute and several foreign laboratories have confirmed that inorganic zinc coated steel may be welded without any reduction in strength of the steel joint. This is because the zinc silicate matrix reacts with the welding flux and prevents zinc occlusions in the weld. Inorganic zinc coatings are unaffected by organic solvents, even the very high strength ones, such as ketones, chlorinated hydrocarbons, aromatic hydrocarbons, etc. They are also unaffected by gasoline, diesel oil, lube oil, jet fuel and many similar refined products. This being the case, they may be used alone or in the connection with topcoats for continuous exposure to such chemicals. The very strong rock-like film and chemical adhesion of inorganic zinc coatings form a base with outstanding friction characteristics, and therefore may be used as a coating for faying surfaces (the friction interface between structural steel sections) on buildings, bridges, towers, tanks, etc. A comparison of the coefficient of friction for various surfaces highlights this outstanding property. The
higher the friction coefficient, the less the chance of joint slippage. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 133
SSPC CHAPTER*4.2 93 8627940 0003583 290 H Coefficient of Surface Conditions Friction Solvent-based inorganic coating 0.52 Rusted and wirebrushed surfaces 0.51 Post-cured inorganic zinc 0.48 Rusted surfaces 0.48 Water-based zinc coatings 0.47 Sandblasted surfaces 0.47 Mill scale surfaces 0.30 Galvanized surfaces 0.25 Rust-preventative paint 0.11 Red lead paint 0.06 Any coefficient of friction less than a sandblasted surface (.47) usually is not acceptable for steel construction. Inorganic zinc coatings are unaffected by gamma rays or neutron bombardment. These coatings have been exposed to atomic radiation up to and beyond 1 x 10IDR,without any change in properties. The basic surface formed by inorganic zinc coatings is very hard, metallic and abrasion resistant. This is an important property as a base coat, since even though the topcoat may be abraded away, the inorganic zinc base remains and prevents serious corrosion. This has proven extremely important on ship hulls above the water line where abrasion due to docking can cause severe coating damage. Compared to metallic zinc, the chemical resistance of inorganic zinc coatings is excellent. This has been proven in test and by use in industrial areas where acidic fumes or fallout have caused rapid galvanized failure. This is due to the inorganic matrix surrounding zinc particles. Inorganic base coats have excellent resistance to undercutting when overcoated with chemical resistant organic coatings and subject to very corrosive industrial atmospheres. IX. CHARACTERISTICS -ORGANIC (TYPE Il) The outstanding characteristic of organic zinc-rich primers is their compatibility with organic and steel surfaces. This is extremely important in coating repair and may be important during original construction, where many types of surfaces are involved and all require excellent corrosion protection. Organic zinc-rich coatings provide cathodic protection, providing the formulation maintains particle-to-particle zinc contact.
With an organic binder, the application of organic zinc-rich coatings covers a very wide range of application conditions. Organic binders may be very fast- or slowdrying and curing conditions can vary widely, depending on requirements of application. A binder in an organic zinc-rich primer may be chemical-resistant, depending on the binder and its use requirements. It is often claimed that the organic zinc-rich primers are less subject to critical surface preparation than inorganic zinc materials. This may be true for initial application, since they would be less subject to problems from organic contamination. On the other hand, eliminating the organic contamination factor, light rust coloration on the steel surface may be more easily tolerated by an inorganic zinc coating than by an organic based material. This is due to the possibility of the inorganic thoroughly wetting the oxide and reacting with it. Organic zinc-rich primers, depending on their formulation, are more compatible with oleoresinous topcoats than are inorganic zinc coatings. X. SOME LIMITATIONS Much has been discussed about application of zincrich products to steel surfaces. In many ways it is a controversial subject. However, much depends on the severity of the exposure and the type of metal (corroded, new, mill scale) to which the coating is applied. There have been many claims about advantages of organic zinc-rich from a surface preparation standpoint compared to inorganic zinc-rich. Many claims have been self-serving with little basis in fact. As with all high-performance coatings, the very best possible surface preparation should be used and, irrespective of the coating, the better the surface preparation, the better the coating performance will be. There are, however, differences in adhesion characteristics of organic and inorganic zinc-rich materials. The primary difference is in the ability of organic zinc-rich to be applied over some organic material, such as old coatings, paint or slight oil contamination. On the other hand, the inorganic zinc-rich materials will not tolerate organic materials and will immediately check, crack and chip off organic surfaces. Inorganic zinc coatings should never be applied over old paint. There are different adhesion characteristics among various inorganic zinc-rich products. There are some, such as lithium base materials, which require the best surface preparation and substantial surface profile to provide maximum adhesion. On the other hand, the original Australian formulation was applied over pickled surfaces, which were thoroughly clean but did not have the advantage of the surface profile of a blast-cleaned surface. Also, some Type l-B and C materials can be applied to pickled surfaces.
Type 1 materials cover the whole gamut of surface preparation and each has proven to work well over surfaces they are specifically adapted to. All work well over SSPC-SP 5 (White Metal Blast) and SSPC-SP 10 (Near White) types of surface preparation. For preparation less than this, that is, SSPC-SP 6 (Commercial Blast) or SSPCSP 8 (Pickled) surfaces, the manufacturer s literature should be consulted for each product and each type of surface. Organic zinc-rich primers also have specific limitations. As previously mentioned, organic-based materials will tolerate some organic material on the surface. Organic Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 134
SSPC CHAPTERm4.2 93 m 6627940 0003582 127 m zinc-rich coatings may be applied over SSPC-SP 6 (Commercial Blast) providing the application is to new steel or a non-corroded previously coated surface. Also, as previously noted, organic zinc-rich may be used for spot repair to provide a zinc-based coating directly over bare steel and yet provide a tie between the old and new organic coating. Organic zinc-rich primers are subject to the difficulties of any organic material applied directly over steel surfaces. This means they are subject to undercutting, blistering and similar adhesion problems not normally encountered with the inorganic zinc-rich primers. XI. CASE HISTORIES It is not intended that detailed application instructions and surface preparation methods be outlined here. This is well covered by most manufacturers literature for specific products and, in general, in Steel Structure Painting Council PS 12.00, Guide to Zinc-Rich Coating Systems and SSPC Paint System 12.01, One Coat Zinc-Rich Coating System . The uses of zinc-rich coatings are almost too numerous to detail: they cover almost any use of steel structure where high-performance coatings are required. These products have been applied to objects as small as nuts and bolts and to the interior and exterior of the largest ships in the world. They have been used in the waterworks industry, sewage industry, on pulp and paper plants, chemical plants, refineries, atomic energy facilities, geothermal energy plants, pipes, tanks, stacks and an infinite variety of other onshore steel surfaces. Offshore, or in the marine industry, zinc-rich materials are standard primer for all surfaces subject to severe seawater corrosion. Zinc-rich primer has been applied on floating equipment and stationary marine structures in tropical rivers in South America, barges in the fjords of Alaska, in Japan, Korea, Singapore, Western Australia, the East Coast of Australia, New Zealand and many areas in Europe and the Middle East. Many icebreakers in the U.S.S.R. are coated with inorganic zinc primers. These materials are a worldwide answer to severe marine coating problems. Some specific applications that indicate the versatility of zinc-rich products follow. A. EARLY TESTS Some of the earliest tests of inorganic zinc coatings in the U.S. (early 1950 s) were located on the 80-foot lot of the International Nickel Company s testing area at Kure Beach, North Carolina. Some of the original panels were there with the inorganic coating still fully protecting after 23 years. The first test panels were heat cured and of essentially the same composition as Australian material of the. same period. A second test set also exposed 23 years is one of the first trials of a non-baked or stoved inorganic coating. The 80-foot lot at Kure Beach is recognized as one of the most corrosive of the marine test areas. Twenty-three years under these conditions illustrates the
outstanding resistance that one coat of inorganic zinc provides. The SSPC Zinc-Rich Committee has also had panels under test at both the 80 and 800 lot since 1963 (18 years). B. FIRST FIELD TESTS Some early applications were in the marine field and the Gulf Coast, where its high temperatures and humidity provided a need for new protective coating. Applications were primarily in the oil industry, onshore and offshore. Well heads and Christmas trees were some of the first to receive the coating. These were pieces of equipment that were subject to severe corrosion and small enough to make good tests. Heater-treaters were field tested. These were somewhat larger in size and followed by other equipment on the offshore production platforms. C.PORTABLE OFFSHORE DRILLING RIGS One of the early applications was the first Mr. Gus. This was a large, portable offshore drilling platform responsible for many offshore wells in the Gulf of Mexico. A later and possibly more spectacular drilling structure was the Monopod installed at Cook Inlet, Alaska, where tides are very high and ice in the winter continually flows past and against the structure. This platform was coated with inorganic zinc from the mean low tide line up. The largest semi-submersible drilling rig in the world, the ODECO Ranger, was coated with inorganic Type l-C. It was recently built in Japan for use in the North Sea. D. PRODUCTION PLATFORMS Offshore petroleum production platforms are an area where corrosion protection is imperative. The corrosive conditions for such structures are most severe and many hundreds of stationary drilling and production structures have been coated with inorganic zinc, from highly humid tropical areas of Indonesia, Singapore and the Persian Gulf to the United States Gulf Coast and Mexico, extending into the Arctic areas of Alaska and the North Sea. The inorganic coatings applied alone, ¡.e., Type l-A or 1-B or overcoated Type l-C for additional protection and for safety coloration, are providing maximum protection for these essential pieces of equipment. E. BRIDGES Bridges, like offshore structures, are extremely vulnerable to corrosion, perhaps more so since many bridge structures are formed from structural steel shapes, with all of the corners, edges, crevices and surfaces defects that are inherent in such shapes. One of the earliest bridges of this type to be coated was a drawbridge across a tidal river in Florida. This bridge was coated in 1956, with the open grill work being the most difficult part of the structure to protect. It was well protected after 15 years by a single coat of Type l-A inorganic zinc coating. One of the new bridges in Australia is a very interesting structure. It is the Batman Bridge with a main span of 675 feet across the Whirlpool Reach on the Tamar
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SSPC CHAPTERaY.2 93 = 8627940 0003583 Ob3 = River in Tasmania. A massive 320 ft. high back-anchored cabled A-frame tower leans out at an angle of 20 degrees and supports a 3,000 ton clear span of 45 ft. long deck trusses. Each leg on the A-frame comprises eighteen, 15 ft. high sections, one 18 ft. section and a top section 23 ft. high. All tower sections, some weighing up to 32 tons each, were connected on the site by high tensile, friction grip bolts. The 3 mil inorganic coating Type l-A was applied to all steel surfaces on this bridge, and the faying surfaces of the individual members were provided the optimum coefficient of friction by use of an inorganic zinc coating. The bridge across Golden Gate in San Francisco is probably the world s most famous bridge. It is subject to as corrosive an environment as any existing bridge. There are only thirty days or so a year when the sky is clear and the temperature above 60°F. The bridge is exposed to extreme atmospheric conditions of the salt and fog. It is constantly wet and damp. The bridge is also designed to move. It sways as much as 24% feet and may rise and fall as much as twelve feet, due to winds and temperature changes. The inorganic zinc coating Type 1-B was first applied in 1962. It is not only protecting the metal of the bridge and providing safe passage for 80,000 cars a day across its 8,940 ft. span, but it is providing longer life for the reddish-orange topcoat, the historical color of this bridge. Since 1961 the SSPC has cooperated with the management in evaluating several series of coatings, not only 22 zinc-rich systems but also other generic types such as vinyls, epoxies, coal-tar epoxies, chlorinated rubbers, alkyds and urethanes. F. REFINERIES Cooling tower piping is a problem area in most refineries because of the heat and continual wetting and drying of the surface. It was one of the applications where inorganic zinc coatings first proved effective. Another refinery and chemical exposure difficult to maintain is pipe racks. There are hundreds of miles of pipe racks in the US., many that have been fully protected since erection with zinc-rich primers. G. INTERIOR TANKER TANKS There have been many and varied uses of inorganic zinc coatings in the marine field. One major use has been lining the interior of tanker tanks, primarily those transporting refined fuel. One of the oldest documented applications of inorganic zinc coatings is to the No. 1 center tank in the UTAH STANDARD. This was applied in 1954 to a previously heavily corroded tank surface. The tank was inspected in 1965, after 11 years, and with the exception of holidays or missed areas in the original application, there was no rust or loss of metal. It is still in service today, without repair, and is in very nearly original condi-
tion after more than 20 years of continuous use in refined oil products. One coat of inorganic zinc Type l-A over a previously heavily corroded surface has provided this protection. H. VERY LARGE CARGO CARRIERS (VLCC s) The six Universe class tankers, 320,000 tons each, are a good example of ships constructed in Japan protected both on the interior and exterior with inorganic zinc. These ships were first coated with an inorganic preconstruction Type l-B primer, and in the most critical areas, with a full.coat of inorganic zinc Type l-A. The total footage coated with inorganic zinc in these six vessels was over 18 million square feet. Almost 10 years of service shows no corrosion on the exterior, except at severely abraded areas. The new medium-size crude carriers built for Alaska crude transportation on the Pacific Coast are coated with Type l-C inorganic zinc primer. The touch-up and repair areas on the VLCC s were extensive. All spots where the final coatings had been applied were coated with Type 2 organic zinc-rich primers. They are epoxy-based and applied by either brush or air spray. Many Japanese and European shipyards use Type 2 zinc-rich primers for preconstruction primers. I. ATOMIC POWER PLANTS Inorganic zinc is unaffected by radioactivity or radiation. This being the case, inorganic zinc coatings Type l-C are used to protect steel in the containment shells at most nuclear power plants that have been or are being constructed. This is the structure containing the atomic reactor, subject to high levels of radiation. From hundreds of tests and years of actual exposures it is expected that the inorganic zinc will protect the containment vessels for their entire design life, 40 years. J. MORGAN-WHYALLA PIPE LINE No discussion of zinc-rich coatings is complete without mention of the earliest large application of any zinc-rich product in the world. This was Morgan-Whyalla Pipe Line, which was originally constructed between 1940 and 1945, to transport water 240 miles across South Australia. The pipe was coated with a very crude product in a crude manner. Nevertheless, a 1972 inspection by the author, after it had been in service for 30 years, found it in practically the same condition as when inspected in 1950. Little, if any, corrosion was evident anywhere except for isolated pinpoints of rust showing in some brush marks in the coating. A second line has now been installed with the same type of l-A coating, also stoved. During the 35 years the line has been in service, almost complete protection has been maintained in the face of sandstorms, grassfires, marine exposures, normal weathering, and almost every severe condition conceivable. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from
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SSPC CHAPTER*4-2 93 = 8627940 0003584 TTT Inorganic zinc coatings have come a long way since originally conceived by Victor Nightingall in Australia and the organic zinc-rich primers about the same time in England. Their use now can be expressed in acres rather than square feet, and they have proved effective in hundreds of areas of severe corrosion. Their continued use will provide longer life and less maintenance for both new and existing structures in the foreseeable future. ACKNOWLEDGEMENT The author and editors gratefully acknowledge the active participation of the following in the review process for this chapter: Alex Chasan, Dan Gelfer, Tom Ginsberg, Joseph Guobis, Dr. C. M. Hendry, Norbert B. Intorp, Sid Levinson, Walter McMahon, Igriatius Metil, Walt Pregmon, and David Sealander. BIOGRAPHY C.G. Munger -consultant in coatings and corrosion -has been engaged in corrosion control activities for more than fifty years. He pioneered in the development of plastic and synthetic resin materials for combating corrosion of steel and concrete surfaces, as well as inorganic coatings for marine and industrial structures. Previously, he was Vice President, International of Ameron, Monterey Park, California, and President of Ameron Corrosion Control Division. He has been affiliated with Ameron since 1935. Mr. Munger is Past President of the National Association of Corrosion Engineers, of which he has been a member for over forty years, and a member of the Los Angeles Section since its organization. He received the 1968 Frank Newman Speller Award during the NACE conference held in March 1969, one of the two highest awards presented annually by NACE for outstanding contributions to the science and technology of corrosion. He is a member of the Steel Structures Painting Council and received their John D. Keane Award of Merit in 1986. In 1993 he was elected as a NACE Fellow in recognition of distinguished contributions to the field of corrosion and its prevention. Mr. Munger is a Fellow of the American Institute of Chemists and a member of the American Chemical Society and the federation of Societies for Paint Technology. He is also a registered professional chemical engineer, as well as a Registered Corrosion Engineer in the State of California. He holds a BA in chemistry from Pomona College, Claremont, California, and did graduate research work for two years on resin formulation and polymerization at Claremont College. He is the author of the book Corrosion Protection by Protective Coatings and co-editor of the NACE Corrosion Engineers Reference Book. He has also authored over 100technical articles on coatings, corrosion, and corrosion control, and has received several patents on corrosion
control materials and methods. REFERENCES 1. Dean M. Berger, Current Technology Review -Zinc-Rich Coatings , Modern Paint and Coatings, June 1975. 2. D.M. Berger -Gilbert Associates, Inc., Zinc Rich Coatings Technology, Septem ber 1974. 3. Walter W. Cranmer, Modern Coatings for Tankership Compartments, Annual Tanker Conference, American Petroleum Institute, 1957. 4. J.F. Delahunt and N. Nakachi, Journalof Protective Coatings and Linings, Long-Term Economic Protection with one Coat of Inorganic Zinc-Rich, February 89, p. 48-53. 5. Daniel H. Gelfer, Rapid Topcoating of Inorganic Zinc-Rich Primers -A Case for Improved Productivity . Presented at N.A.C.E. Corrosion 80. 6. D. H. Gelfer, Comparison of Self-curing and Post-Cured Inorganic Zinc Coatings as Permanent Primers for Steel. Materials Protection, Vol. 3, No. 3, p. 54, March 1964. 7. Norbert B. Intorp. Enhanced Zinc-Rich Primers . Paper #114, N.A.C.E. Corrosion 80. 8. Zinc Silicate Coatings -40 Years Experience, Journal of Protective Coatings and Linings, March 85, p. 34-44. 9. R. Mallet, BritAssociation Advancement Science 10, 221-388, 1840. 10. Dr. Ignatius Metil, Recent Developments In Inorganic Zinc Coatings, Modern Paint & Coatings, December 1979. 11. C. G. Munger, Report of the Inspection of Di-Met Products Used in Australia, November 17, 1949 -December 20, 1949. Amercoat Corporation file. 12. C. G. Munger, Background Notes on Dimetcote No. 2, October 1950. Amercoat Corporation file. 13. C. G. Munger, Solvent Service Corrosion in Tanker Ships. lndustrial & Engineering Chemistry, July 1957. 14. C. G. Munger, Review of Zinc Dust Coatings -presented at Washington Paint Technical Group at annual symposium, Washington, D.C., May 12, 1964. 15. C. G. Munger. A Revolution in Industrial and Marine Coating, May 22, 1967, Seventh Annual Symposium, Washington Paint Technical Group. 16. C. G. Munger, Inorganic Zinc Coatings , published in the proceedings of II Simposio Sul-Americano de Corrosao Metalica, Rio de Janeiro, Brazil, 1971. 17. C. G. Munger, Marine Corrosion Prevention With Inorganic Coatings , May 1972. 18. C. G. Munger, Coatings for Nuclear Plants, N.A.C.E. Western Regional Conference, October, 1974. 19. C. G. Munger, Petroleum Industry Use of Zinc-Rich Coatings , National Zinc-Rich Coatings Conference, Zinc Institute. 1974. 20. C. G. Munger, Inorganic Zinc Coatings -Past, Present and Future. N.A.C.E. 1975, Toronto. 21. C. G. Munger, Dimetcoat #3 Story , Ameron- Publication, 1975. 22. C. G. Munger, Inorganic Zinc Coating Protection of Marine Structures , Fourth International Congress of Marine Corrosion & Fouling, Antibes, France, 1976. 23. C. G. Munger, Environment -Its Influenceon InorganicZinc Coatings , N.A.C.E., 1976.
24. C. G. Munger, Environmental Impact on Inorganic Zinc Coatings , A.C.S. Division of Environmental Chemistry, San Francisco, 1976. 25. Munse, Walter H., Static and Fatigue Tests of Bolted Connections Coated with Dimetcote, Report, March 10, 1961. 26. N.A.C.E. Tech. Committee T-6H, Hot Dip Galvanizing as a Protective Coating in Atmospheric Corrosion. 27. Organic and Inorganic Zinc Filled Coatings for Atmospheric Service. N.A.C.E. publication 68173. 28. D. I. Netting, H. H. Weldes, M. R. Derolf, Aqueous Quarternary Ammonium Silicate Vehicles for High Performance Zinc-Rich Primers and High Temperature Resistant Paints , International Marine Corrosion Conference, 1976. 29. New Jersey Zinc Company, Zinc Dust Metal Protective Coatings . 30. Victor Nightingall, Aust. Patent 113,946. 31. Victor Nightingall, U.S.Patent 2,462,763, February 22, 1949. 32. Victor Nightingall, British Patent 505,710, May, 1939. 33. Victor Nightingall, U.S. Patent 2,440,969, May, 1948. 34. Victor Nightingall, Di-Metalization for the Prevention of the Corrosion of Iron, Steel & Concrete. Melbourne, Australia, 1940. 35. H. E. Patee and R. E. Monroe. Battelle Memorial Institute, CoLumbus, Ohio, Research report on effect of Dimetcote Coatings on Weldability of Selected Steels , April 19, 1967. 36. Pourbaix, Marcel, Atlas of Electrochemical Equilibria in Aqueous Solutions , Chapter IV, Section 51.1, N.A.C.E., 1974. 37. E. G. Rochow, Chapter XV, Chemistry of Silica , Comprehensive Inorganic Chemistry, Pergamon Press. 38. A. H. Roebuck, Inorganic Zinc Coatings -Some Disadvantages & Remedies , N.A.C.E. Corrosion, 1980. 39. Steel Structures Painting Council, Topcoats for Zinc-rich Coatings, Journal of Protective Coatings and Linings, 1987. SSPC 87-06. 40. O.P. Velsboe, Organic Zinc Coatings , presented at the International Ship Painting and Corrosion Conference and Exhibition, May 1974. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 137
SSPC CHAPTER*4.3 93 = 8b27940 0003585 936 September 1993 (Editorial Changes) CHAPTER 4.3 CORROSION INHIBITIVE PIGMENTS AND HOW THEY FUNCTION bY Arnold J. Eickhoff Metal corrodes because of one or more environmental factors and gradually disappears or disintegrates through physical and chemical processes. Corrosion is essentially the formation of a more stable compound of metal. Most pure metals are unstable and tend to return to original form. Undoubtedly, corrosion plagued early Egyptians, Hebrews and Greeks. There is evidence that an iron tool was found inside the great pyramid of Khufu at Gizeh, dated about 3100 B.C. In the Book of Judges of the Old Testament, iron is mentioned in connection with construction of chariots. Homer s Iliad, written about 1200 B.C., also contains a reference to iron. A broken axle on a chariot in 2000 B.C. was as embarrassing as a corroded water tank in the twentieth century. An early reference to protecting iron or steel against corrosion is in the writings of Pliny the Elder , written about 1900 years ago. He describes how iron workers used bituminous materials for varnishing iron. White lead and fatty acid pitch also is mentioned for use as a protective coating. One method to prevent corrosion is to incorporate inhibitive pigments in the protective coating applied to metallic substrates. Their purpose is to impart corrosion inhibitive properties to the organic or inorganic binders or vehicle portions of the primer coatings. Many investigators consider only the pigment, and not the vehicle, when they attempt to evaluate a corrosion inhibitive pigment. I. SUGGESTED INHIBITIVE MECHANISMS reported in 1954 that water was noncorrosive after contact with paints prepared by grinding basic pigments in linseed oil. Immersion tests showed lead and calcium soaps of formic acid were corrosive. Lead and calcium soaps of azelaic and pelargonic acids were inhibitive. The corrosion of steel is retarded by several mechanisms: By anodic inhibitors such as red lead, zinc
yellow, strontium chromate, etc. By cathodic inhibitors or cathodic polarization By cathodic protection -e.g. zinc rich coatings. In this instance, the metal, in form of zinc dust in the paint film, is the anode and sacrificially corrodes to protect steel from rusting. By mechanical protection, ¡.e. by the use of thick (10 to 20 mils) relatively impervious films. These films have extremely low moisture vapor and oxygen transmission. Appleby and Mayne4 reported on the degradation products of four red lead paints formulated with linseed oil, oiticica oil, alkyd resin, and tung oil. The degradation products were identified by vapor phase chromatography. Mayne and Ramshaws showed azelaic acid was the principal degradation product of linseed oil fatty acids. Extending this to the other three vehicles (¡.e. linseed oil, alkyd resins, tung oil) suggests that their metal protective properties may be evaluated by their ability to form lead soaps of azelaic acid. Based on inhibitive properties, linseed oil was best, followed by oiticica oil and finally alkyd resin. Tung oil had the poorest inhibitive properties. The relative amounts of degradation products were 11.9 for linseed oil, 8.9 for oiticica oil, 3.5 for alkyd resin, and 1.1 for tung oil. Partial immersion tests of mild steel coupons confirmed the analyses of the aqueous extracts. To obtain optimum substrate protection the protective coatings system must be carefully evaluated considering many factors, such as environment; 0 physical chemistry of pigment-vehicle combination in different environments; 0 chemical reactions that may occur between pigment and the vehicle while paint is in the container before it is used; 0 electrochemical reactions that occur at the anodic and cathodic areas or interface between the dry paint film and the steel substrate; electrochemical reactions that take place when coated steel substrate is exposed to high humidity or condensed moisture (dew); electrochemical reactions that take place when the coated steel substrate is exposed to salt spray (fog) e.g. in a marine or chemical environment; and Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 138
SSPC CHAPTER*4-3 93 8627940 0003586 872
electrochemical reactions that take place when coated steel substrate is immersed in fresh water. Misleading information can be derived from salt spray (fog) or salt water immersion tests, when steel panels are coated with films that are not alkali resistant. U.R. Evans pointed out that sodium hydroxide can soften oil-modified films and lead to their disintegration and a type of film failure not encountered in a salt-free environment. Fancutt6 and Hudson tested 127 paint systems on steel immersed in sea water. They confirmed Evan's views. Mayne' reported that panels coated with polystyrene and immersed in sea water for 46 days showed rust nodules at the anodes and liquid filled blisters at the cathode areas. Liquid in these cathodic areas was 1.1 to 1.3 normal sodium hydroxide. Mayne expressed it in simple chemical equations: 4Fe" + 8CI- -+4FeCI, + 8e- (anodic reaction) The 8 electrons are consumed by reacting with water and oxygen to form sodium hydroxide viz: 8e-+ 20, + 8Na' + 4H20+8NaOH (cathodic reaction) When products at the anodic and cathodic areas combine in the presence of excess oxygen, the final product is rust or Fe,O,.H,O. 4FeCI, + 8NaOH + 0,-2Fe,O;H,O + 8NaCI + 2H20 With the indicated reformation of sodium chloride, and in the presence of moisture (water), the overall reaction is repeated. The above reactions8 describe the corrosion process if salt (sodium chloride) is present. If only oxygen and water are present (no corrosive salts) the electrochemical dorrosion of iron (formation of rust) is as follows: 4Fe "+4Fe++ + 8e- (anodic reaction) 20, + 4H,O + 8e-80H-(cathodic reaction) By combining these two reactions we obtain: 4Fe" + 20, + 4H2O-4Fe(OH), (yellow rust) In the presence of excess oxygen, red rust forms. 4Fe(OH), + 0,-+2Fe,O;H,O + 2H,O This reaction shows that water is a by-product of corrosion. Once corrosion has started, it is self perpetuating,
as long as oxygen can penetrate the paint film. Thus, low oxygen and moisture permeabilities are very important film properties -especially if a steel surface must depend only on mechanical or barrier protection. Paints prevent corrosion by various mechanisms: Mechanical protection or thick films; Chemical inhibition; and Galvanic or cathodic protection. Mechanical protection is simple: the paint film acts as a waterproof coating or an electrical insulator between the anodic and cathodic areas. If the surface to be protected is not completely covered with a film free of pores, corrosion may not only continue at the exposed sections of the steel, but also accelerate due to concentrated anodic attack. Paints specially prepared for application in strong acid and alkali environments provide effective mechanical protection. Usually these paints rely on thick films (10to 20 mils) and freedom from pinholes to protect the substrate. Chemical inhibitive films are useful because they are not as sensitive as the mechanical film to undercutting when small breaks or pores are present. Also, moisture permeability does not have to be as low to ensure useful film life. The pigments in inhibitive paints act as a source of a passivating agent. II. EFFECT OF PIGMENT VOLUME CONCENTRATION Pigment volume concentration (PVC) and critical pigment volume concentration (CPVC) of anticorrosive primers are very important. PVC is the ratio of pigment volume to the volume of nonvolatile material, ¡.e. pigment and binder present in the coating. It is usually expressed as a percentage. CPVC is that level of pigmentation in dry paint, where just sufficient binder is present to fill the voids between the pigment particles. CPVC is especially significant in flat paints. Various film properties are greatly affected by variations in PVC. Asbeck and Van Loo9 showed how formulating can affect the parameters of permeability, rusting and blistering. These authors showed there is a minimum of rusting and blistering when PVC is slightly less than CPVC. Eickhoff'O also demonstrated this with a series of epoxy-polyamide primers applied to cold rolled steel panels and exposed at tide range. The PVCs varied from 17.5% to 42.0%. The 42% PVC primers were very blister- and corrosion-resistant. The evaluation of an experimental anticorrosive pigment can be very misleading, even erroneous, if the primer formulator merely substitutes the experimental pigment for a pigment of proven performance on an equal volume basis.
PVC and CPVC are extremely important when formulating anticorrosive primers and subsequently interpreting their behavior in various environments. 111. LIFE EXPECTANCY OF A PAINT FILM How long will a paint film protect a steel substrate? A discussion of corrosion inhibitive pigments is not complete without mention of four important variables: Environment; Surface preparation; 0 Composition of the pigment and vehicle; and 0 Dry film thickness of the paint. The Protective Coatings Sub-Committee of the British Iron and Steel Research Association11 published some very interesting results. Steel specimens were primed with two coats of red lead-linseed oil and topcoated with two coats of iron oxide-linseed oil. The panels were exposed in an industrial atmosphere (Sheffield, England). Other studies of a similar nature have been reported by Liebman',. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 139
SSPC CHAPTER84.3 73 8627940 0003587 707 Effect of Surface Preparation on Paint Life Relative Surface Preparation Durability Sand blasted 10.3 years Pickled 9.6 years Intact Mill Scale 8.3 years Weathered & Hand Cleaned 2.3 years The effect of surface preparation on paint life, as shown above, is self-evident. IV. POLARIZATION Polarization has been described in technical literature for ears'^,'^,^^. In corrosion prevention its usage is becoming more common. Following is a very preliminary discussion of polarization. A more detailed discussion appears in references 16 and 17. Moisture or water makes iron or steel corrode. Hydrogen ions from the water or moisture corrode steel and one product is hydrogen gas. Hydrogen, as bubbles, collects on the cathodic areas of steel and acts as a blanket to reduce corrosion. This is called polarization. If it occurs on the cathode, it is called cathodic polarization. Practically all water or moisture has some dissolved oxygen. Oxygen combines with the covering of hydrogen; the covering is destroyed; more water is formed and polarization starts again. The result is that corrosion continues unabated. In this case oxygen in the air acts as a depolarizer. It is for this reason that water or moisture with a high oxygen concentration is more corrosive. V. CHEMICAL REACTIONS IN PAINTS A can of liquid paint is a chemical factory. This applies to the same paint when it is spread over an area in a thin film that changes from liquid to solid film. There are two reaction sites between the pigment and nonvolatile portion of the vehicle. A. SITE ONE: REACTIONS IN THE PAINT CAN What reactions occur between the pigment and the nonvolatile portion of the vehicle while paint is in the can? Regardless of the chemical reactions, they have an important bearing on liquid properties (viscosity, drying time, etc.) of paint in the can and the physical properties (hardness, flexibility, adhesion, weather resistance) of paint when it is spread over an area in a thin film and allowed to dry. During World War II everyone was in a hurry. Due to shortages of materials, someone developed a product calted "linseed replacement oil." The linseed oil was heatpolymerized. It was then blended with raw linseed oil and mineral spirits and used to replace raw linseed oil.
Sometimes Fed. Spec. TT-P-86, Type 1 red lead primer had excellent viscosity stability and sometimes it would gel in 24 hours. Sometimes if the gelled paint aged 7 to 15 days it would de-gel, revert to its original viscosity, and be suitable for use. After extensive laboratory studies18 it was learned that when the oil polymerizing temperature was 625 to 650°F (330-343"C), the red lead paint gelled. If the polymerizing temperature was 575 to 585"F (302-307 OC), package-stable red lead primers were easily obtained. The acid number of polymerized oil was not a controlling factor. The only conclusion was that the nature of the linseed oil polymer formed at the higher temperature was the offending factor. A study of the chemical reactions of a pigmentvehicle combination that occurs in a closed container is discussed by Eickhoff, et. al.''. It describes the effects of varying the true red lead (Pb,O,) content of the pigment, time, temperature, moisture, and solubility of the reaction products in the vehicle. The study concluded that red lead pigments containing 92% or more Pb30, do not react with alkyd resin vehicles to form lead phthalate. B. SITE TWO: REACTION IN THE FILM What reactions occur between pigment and the nonvolatile portion of the vehicle after paint is spread in a thin film? It is common knowledge that when a mixture of raw linseed oil and metallic driers is spread in a thin film and allowed to dry, a wide variety of organic acids are formed. These include formic, acetic, propionic, ketoxy, etc. It is easy to understand how basic pigments in oxidizing oilmodified, alkyd resins can readily affect dry film properties of paint. An example of paint film that becomes hard and brittle when aged is a zinc chromate primer, made according to Federal Specification TT-P-645. If a similar primer is made with the zinc chromate replaced by an equal volume of basic lead silicochromate, the dry paint film is tougher and more flexible than zinc chromate pigmented film. This is an example of a factor that should be considered when the formulator selects a pigment-vehicle combination for a given purpose. Other factors to consider include drying time, color retention, and chalk resistance. Metallic soaps formed in the dry paint film from different basic pigments impart different physical properties to the dry paint film. These physical properties influence hardness, toughness, flexibility, and adherence of paint to the steel substrate. O'Neill and Brettz0 studied reactions in paint films between the paint and the atmosphere, between the paint and the substrate, and between the medium (binder or vehicle) and the pigment.
They showed red lead and zinc oxide are appreciably reactive in the dry film; iron oxide and calcium carbonate very much less so; and anatase titanium dioxide showed Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 140
SSPC CHAPTER*4.3 93 W 8627940 0003588 b45 W no detectable reactivity. They also reported on the percent The initial reaction takes place in a water slurry of litharge metal in films of linseed oil dried on different metal and chromic acid. substrates. Lead, copper, cadmium and zinc substrates have an appreciable effect on the percent metal in the H20 various films. Iron was considerably less and aluminum 2Pb0 + CrO-PbO'PbCrO, none. If the percent metal in the dried linseed oil film was relatively high, the drying time was shortened. In a rotary kiln unreacted lead monoxide (PbO) reacts with the monobasic lead chromate to form tetrabasic lead VI. SOME COMMON INHIBITIVE PIGMENTS chromate. Characteristics of common inhibitive pigments are 3Pb0 + Pb0.PbCr0,+4Pb0.PbCr04d iscussed in alphabetical sequence (see Table 1.) Temperature is increased and the tetrabasic lead A. BARIUM METABORATE chromate reacts with silica to form monobasic lead Commerciallyz1, this pigment is known as modified chromate and tri-basic lead si licate. barium metaborate. The theoretical chemical formula is: BaB,O,. HzO. 4(4Pb0.PbCr04) + 3Si02+4(Pb0.PbCr0,) + 3(3Pb0. PbSiO,) Physical Properties Specific Gravity ................... .3.24-3.35 Color .......................... ... Orange Pounds per Solid Gallon .............27.5 Specific Gravity ....................4 .10 Refractive Inäex. .................. .1.55-1.60 Pounds per solid gallon .......... .. .34.1 Oil Absorption .................... .30 Oil Absorption .................... .10 to 18 Av. Particle Size. .................. .4.8 micrometres Color.. .......................... .White Specific Surface Area .............. .1.3 mz/cm3 Type of Inhibitor .................. .Anodic In 1874 Benedikt2* prepared barium metaborate (BaO.B,O,) by fusing sodium borate and barium chloride. Both active ingredients contribute to the corrosion inLevin and McMurdieZ3 reviewed these early studies and hibitive mechanism of basi
c lead silicochromate. These confirmed the findings of Benedikt. active ingredients are monobasic lead chroma te and gamThe modified barium metaboratez4 is prepared by ma tribasic lead silicate. Mecha nical mixtures of these coating barium metaborate with silica. According to two compounds plus silica ha ve some corrosion inhibitive Buckman, et. the corrosion inhibitive properties of properties, but they do not have as effective inhibitive modified barium metaborate are due to alkalinity and the properties as the produ ct made by calcination. Tribasic metaborate ion which passivates the anode in essentially lead silicate has defin ite anticorrosive properties when forthe same manner as the chromate ion. mulated with drying oils or oleoresinous ve hicles. When B. BASIC LEAD SILICO-CHROMATE*'* * formulated alone in an oleoresinous vehicle, the tribasic lead silicate pigment is very reactive and has a very brief This pigmentz5 is a chemical complex that results package stability. from mixing litharge, chromic acid and silica in a water It is not fully underst ood why the kiln-formed tribasic slurry2'. The filtered product is furnaced at about 600°C and lead silicate in com bination with monobasic lead ground to a size suitable for use in paints. The resultant chromate is a package -stable product in many paint product is a mixture of two chemical compounds - vehicles. It also is more effec tive as an anticorrosive pigmonobasic lead chromate and gamma tri-basic lead ment than either monobasic lead chromate or basic lead silicate -on a silica core. X-ray and chemical analyses silicate alone or a mech anical mixture of monobasic lead show basic lead silico-chromate pigment has the following chromate and tribasic lead silicate. typical composition: The kiln product, monobasic lead chromate-tribasic lead silicate, is stable with a wide variety of coating vehicles. This indicates the material is highly complexed. Gamma Tri-basic Lead Silicate ......... .25% Microscopic examination of the mill ed pigment reveals Monobasic Lead Chromate .............29% that practically all of the silica core surface is covered with Silica ............................... 46% a very thin coating of basic lead chr omate. _-This pigment has relatively low hiding power. For this reason small amounts of red iron oxide (5 to 10% by weight) are ideal for improving the hiding power. Low 141 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from
IHS
SSPC CHAPTERm4.3 93 D 8627940 0003589 581 W TABLE 1 TYPICAL PIGMENT COMPOSITIONS Ca0 P,O. B,O* sio. Calcium Dhosohosilicate 44.9 9.0 -41.O Calcium 44.9 -10.1 38.9 boro. 44.9 -10.1 38.9 silicates 43.5 -17.4 33.0 Calcium barium DhosDhosilicate 37.1 6.1 -39.8 Calcium strontium DhosDhosilicate 37.2 7.8 -39.7 Zinc DhOSDhOSiliCatB 46.5 8.9 -46.5 hiding power also facilitates use of this pigment in pastel primers and topcoats. A commercial grade of this pigment is described in ASTM Specification D-1648. C. BASIC BOROSILICATE AND BASIC PHOSPHOSILICATE COMPOSITE PIGMENTS These essentially white or colorless pigments'27) are silicate composites of basic phosphates of calcium, barium, magnesium, or zinc. Calcium phosphate, calcium borate and silicates are recognized corrosion inhibitors. Complexing these crystalline pigments and changing them to amorphous pigments improves their anticorrosive pro pert ¡es. These pigments function as anodic and cathodic depressants. However, the cathodic protection is the more pronounced. These pigments form metallic soaps with oil or oil-modified alkyds. The hydrolytic products resulting from the hydrolysis of the metallic soaps inhibit corrosion. Corrosion is inhibited by direct and indirect functionality, soap formation, acting on the barrier coat and function improvement in adhesion. Boron and phosphosilicate pigments include the calcium, zinc, barium, and strontium types. Most of them are relatively insoluble in water. Their specific gravities and tinting strengths are low. Because they are white or colorless, they permit a wide selection of tint and color.
D. LEAD SUBOXIDE** Lead suboxide is a gray amorphous pigment manufactured from agitated molten pig lead in an electric furnace. It is not a true chemical compound but a mixture of lead and lead oxide on a core of metallic lead. A typical composition is: Loss on Mean Part. Sp. Oil Ba0 lanition Size Microns Gravity Absorption -4.6 5 2.9 67.5 -5.6 7 2.6 34.7 -5.6 5 2.6 34.7 -5.6 7 2.6 32.0 13.2 3.8 5 2.96 54.5 -3.9 5 2.86 69 -4.6 7 2.6 55 The suggested mechanism of corrosion inhibition is SrO ZnO -----11.4 -10.2 --`,,,,`-`-`,,`,,`,`,,`--that of anodic passivation. Extracts of lead suboxide are depositedz8 on the anode and insulate the anodic areas from the cathodic areas, thus preventing under-film corrosion. Lead suboxide functions as an anticorrosive pigment by reacting with the oxidation products of the vehicle. For example, with linseed oils or oxidizing alkyds, lead soaps are formed in the presence of water or water vapor, hydrolyze, concentrate on the steel substrate and are adsorbed .on the metal surface. This results in anodic passivation. Mayne and RamshawZ9 discuss in detail the formation of lead soaps in paint films applied to Steel Surfaces. Even with the high metallic content of lead in the lead suboxide pigment, it does not function as a cathodic inhibitor similar to zinc dust. E. MOLYBDATE PIGMENTS This class of pigments is commercially available in two types of compounds. The molybdated zinc oxide pigment is used for oleoresinous-organic solvent types of anticorrosive primers. The basic calcium zinc molybdate is suggested for use in latex and other water-borne anticorrosive primers. X-ray diffraction indicate that a series of relatively pure pigments can be produced ranging from 1:l to 1O:l molar ratio of ZnO to MOO,. The molybdated zinc oxide pigment has the general formula (ZnO), (Moo,),, where y is greater than x. The basic calcium zinc molybdate is specifically for water-borne and latex metal protective primers3'. The molybdates inhibit corrosion by anodic passivation. The following is quoted from Sherwin Williams Bulletin No. 343, page 2:
The mode of passivation is believed to occur as follows: as iron corrodes in a solution containing chloride and sulfate, molybdate ions in competition with these ions adsorb on the surface and form a complex with divalent iron ions. This complex offers no protection. However, the Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 142
SSPC CHAPTERJV-3 93 8627940 0003590 2T3 W divalent iron is oxidized by dissolved oxygen to the ferric or trivalent state. Thus, the ferrousmolybdate complex on the surface of the metal is converted to a ferric molybdate which is insoluble in neutral or basic solutions. Eventually, all of the corroding surface is covered with a protective film of ferric molybdate and the corrosion ceases. Physical Properties Basic Zn Molybdate Basic CaZn Molybdate Color. ............... white white Sp.Gravity ........... 5.06 3.00 Wt. per Solid Gal. 42.1 Ibs. 25.0 Ibs. Oil Absorption ........ 14 18 Av. Particle Size ...... .1.35microns 2.5 microns Specific Resistance (Ohms) ............ 500 5000 ~.~ ~__ F. RED LEAD** Red lead probably has the longest history as an anticorrosive pigment. In 77 A.D. the ancient Roman writer pl in^^^ mentioned that a painter called Micias used red lead as a pigment about 320 B.C. Today, red lead is available in various33 grades, such as 85%,95% and 97% PbJO,. Other than small amounts of trace elements, the remainder is lead oxide or PbO. Pure red lead is the lead salt of ortho-plumbic acid (plumbus orthoplumbate). The structural formula is: Red lead is made by heating metallic lead in an excess of oxygen. heat 2PB + 0,-2Pb0 6Pb0 -heat 2Pb,0, Physical Properties Color ............................. Orange Specific Gravity ................... .8.9 Pounds per solid gallon .............74.1 Oil absorption (gl100g) ..............6 to 9 Av. particle size ....................lto 3 micrometres Type of Inhibitor ...................Anodic While red lead has the longest history of use as an anti-corrosive pigment, it also has the longest history of controversy regarding its corrosion inhibitive mechanism. Prolonged shows that the corrosion in-
hibitive powers of red lead are not because it is an alkaline pigment or because it acts solely as an oxidizing agent over anodic areas. As early as 1951 Mayne38 showed that water was non-corrosive after contact with linseed oil fatty acid soaps of lead, zinc, barium, etc. After some involved laboratory procedures Mayne39 concluded that in the presence of water and oxygen the lead soaps of the linseed oil fatty acids yield soluble inhibitive degradation products. Mayne40 also stated that the soaps of saturated acids such as palmitic and stearic do not render water non-corrosive. On the other hand, lead soaps of oleic, linoleic and linolenic degraded to yield rust inhibitive compounds. Mayne and Ramshaw41 showed that lead salts were more efficient inhibitors than fatty acid soaps of calcium or sodium. Optimum efficiency occurred when both the mono-basic and di-basic acids had a total chain length of 8 to 9 carbon atoms. They showed that azelaic acid was the principal degradation product of linseed oil fatty acids. More extensive work showed that oiticia oil and tung oil metallic soaps had poor rust inhibitive properties relative to linseed oil metallic soaps. In conclusion, the inhibitive action of red lead is complex. In addition to its oxidizing properties, red lead forms soaps in the dry film. These soaps undoubtedly enhance the mechanical properties of the film and in the presence of moisture, hydrolyze to release organic acids and soluble lead compounds. Mayne has shown that soaps can inhibit corrosion of steel. Mayne's studies in combination with studies by Hawke & indicate that inhibitive or passivation of steel under a red lead paint film can occur by three mechanisms, either singly or in combination, so that one supplements the other. 1. Anodic adsorption of organic acid molecules. A water extract of linseed fatty acids (no lead compound present) has a definite corrosion-inhibitive effect. 2. Anodic adsorption of soluble lead compounds. Under certain conditions, soluble lead compounds will inhibit corrosion. 3. Anodic precipitation by oxidation. In the presence of red lead, ferrous compounds are oxidized to ferric compounds and precipitated on the metal. None of the hypotheses fully explain all of the observations. A provocative survey of the action of metal protective paints was prepared by Elm43. G. STRONTIUM CHROMATE* Strontium ~hromate'~ is readily prepared by mixing a solution of strontium nitrate with sodium chromate. The result is a yellow pigment. Sr(NO,), + Na,CrO,+SrCrO, + 2NaN0,
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SSPC CHAPTER*4.3 93 8627940 0003573 L3T The residual sodium nitrate content should be kept below 0.8% in order to minimize blistering when it (SrCrO,) is part of the anticorrosive pigment. Many years ago strontium chromate was used for making artists colors. Organic pigments have now replaced it as a color pigment. As an anticorrosive pigment SrCrO, is used in coatings for the light metal alloys. Babcock and Reth~isch,~describe the use of SrCrO, in combination with aluminum pigment as an aluminum flake corrosioninhibitive coating. Strontium chromate can be purchased to meet ASTM-D 1649. Typical Properties Color ............................ .Yellow Strontium as SrO. ..................41.0% (minimum) Chromium as CrO,. .................41.0% (minimum) Chloride as CI .................... .0.1 /0 (maxi mum) Sulfate as SO, .................... .0.2% (maxi m u m) Sp. Gravity ....................... .3.67 to 3.77 Pounds per solid gallon .............30.6 to 31.4 Oil Absorption ..................... .33 Particle Size (microns) ............. .10to 15 Type of Inhibitor ...................Anodic H. TRIBASIC LEAD PHOSPHOSILICATE* * This is a corrosion-inhibitive white pigment described in US. Patent 3,080,248. It can be modified with chromic acid to make a light orange lead silicate-lead chromate
pigment. This material conforms to ASTM-D 2744. Physical Properties Color.. .......................... .White Specific Gravity ....................6.00 Pounds per Solid Gallon .............50.0 Oil Absorption .................... .12 to 16 Mean Particle Size. .................0.25 micron Typical Composition Lead oxide as PbO. .................83 to 87% Phosphorous Pentoxide .............4.5 to 5.25% Silica as SiO, ..................... .7.1 to 7.9% Water of Hydration .................1.5 to 2.5% I44 I. X0, -INHIBITORS This group of pigments is of scientific interest, but to date, they do not appear to have any practical application in coatings except as chromates, phosphates and molybdates. Cartledge46 studied the behavior of inorganic ions and molecules of the general formula X0,n-derived from the elements of the VI to VIII groups of the periodic table. The metals include salts or oxides of vanadium, niobium, chromium, molybdenum, tungsten, technetium, rhenium, ruthenium and osmium. Technetium was especially interesting. The atomic number is 43. It was the first of the previously unknown elements to be artificially prepared in 1937 by Perrier and Segle4 . Its radioactivity is so low that dilute solutions can be handled without special precautions. The nuclear properties of technitium make it useful in studying the mechanism of inhibition. The inhibition depends upon the maintenance of some minimum concentration of pertechnetate. In this case it was potassium pertechnetate (KTcO,).
Not all X0,n-1 type ions are inhibitors. The mechanism of inhibition becomes more complex due to differences in behavior of the SO, , CrO,=, PO,= and Mn0,- ions. It is well known that the sulfate ion accelerates corrosion. According to Pryor and the phosphate ion is an active inhibitor if oxygen is present. If inhibition by chromates is due to the unreduced ion, it is difficult to understand the great difference between the sulfate and chromate ions. Cartledge4g proposed the necessity of looking within the inhibitor particle for the property responsible for its unique action, and led to the hypothesis that a suitable degree of internal polarity might be the distinguishing feature of inhibitors of the XO, . type. J. ZINC CHROMATE, BASIC* Basic zinc chromate is also known as zinc tetroxy chromate. It is the most popular of the oxychromates. The assigned chemical formula is 4Zn(OH), Zn CrO,. Physical Properties Sp. Gravity ....................... .3.87 to 3.97 Color ............................ .Yellow Oil Absorption .................... .46 Pounds per Solid Gallon ............ .32.3 to 33.1 Type of Inhibitor ...................Anodic The water solubility is very low -on theorder of 0.02 g CrO, per liter. For comparison, the common potassium zinc yellow is about 1.1 g. CrO, per liter of water. The principal use for this basic pigment is in the production of a wash primer50 or etch primer. A popular wash primer formula is described in Steel Structures Painting Council Specification SSPC-Paint 27 and also in Military Spec. DOD-P-15328. These wash primers are two-compoCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*4.3 93 6627940 0003592 O76 m nent products and are mixed together just prior to use. Any wash primer that cannot be used within a maximum of eight hours after mixing with the acid diluent must be discarded. The chemistry of wash primers is more fully discussed by Rosenbloom5'. Whiting52 published an excellent history and review of the uses and types of wash primers. He believes they function in three ways: 1. by forming both an inorganic and organic film on a metal surface, 2. by preventing or retarding corrosion, and 3. by providing a base that improves the adhesion and integrity of subsequent protective coating systems. Wash primers can be reactive or non-reactive. The reactive type is a two-package product described in SSPCPaint 27. The non-reactive type is a one-package product. This one-package type does not adhere to metals as well as the two-package type. The essential components of wash primers are phosphoric acid, chromate pigment and a polyvinyl acetal resin -usually a vinyl butyral resin. Ei~khoff~~ studied many variations of the reactive or two-package wash primer. The overall performance of these variations was considerably less than the original two-package wash primer developed by Whiting52. If optimum results are required, the metal surfaces must be clean and free from dirt, grease, etc. If the metal is steel, mill scale and rust must be removed to produce a near-white to white metal surface. Some investigators say a small amount of rust is not objectionable. However, any visible rust will detract from wash primer performance especially if the painted steel object is continually submerged in either fresh or salt water. The thinnest coating that forms a continuous film is recommended -e.g. 0.5 mils. Films over 1.0 mil dry film thickness do not develop good adhesion or adequate toughness. Wash primer is especially effective when applied to galvanized steel or aluminum, but is not effective if applied over another primer. It must be applied directly over a metal substrate. K. ZINC DUST Almost a century and a half Davy, in England, reported that metallic zinc would sacrificially plrotect steel immersed in sea water. In 1916, GardneP promoted the use of zinc dust in primers. From the mid-1940s the development of zinc rich primers has progressed rapidly. There are two general types -the organic and inorganic binder types.
Gassing in the container can be a problem unless the paint manufacturer is careful in formulating. Many of the zinc rich paints are supplied in two containers and mixed for use at the time of application. Zinc rich paints are also supplied in one-package containers. Zinc dusts vary in particle size. Accordingly, formulators' ideas vary as to which particle size is preferable. Organic zinc rich paints depend on particle-to-particle Properties of Zinc Dust Color. ........................... .Gray Total Zinc (as Zn) .................. .97% Metallic Zinc (as Zn) ................94% Zinc Oxide ....................... .4 to 6% Type of Inhibitor ...................Cathodic electrical contact and also electrical contact with the steel substrate. The zinc in inorganic zinc coatings is held in a conductive medium so that particle-to-particle contact is not required. Zinc dust in zinc rich coatings acts as the anode and corrodes while protecting the iron or steel substrate. The development and use of zinc-rich primers is discussed by Charles Munger in a separate chapter. L. ZINC OXIDE Zinc oxide was known long before Cle~patra~~. It is a product of copper as well as zinc ore smelting. Zinc as an element was discovered by Paracelsus in 1520. In 1850the New Jersey Zinc Company produced zinc oxide from the metal, using a method which came to be known as the American process. Physical Properties Sp. Gravity ....................... .5.6 Weight per Solid Gallon ............ .46.7 Ibs. Color. ........................... .White Oil Absorption .................... .10 to 25 Commercial zinc oxide is available in either acicular
or nodular form. Normally, zinc oxide is not considered a corrosion inhibiting pigment. For many years zinc oxide has been used in combination with zinc yellow-alkyd primers to improve the film-forming properties of the zinc yellow. With the advent of water-borne (latex) metal protective primers, zinc oxide has shown some excellent metal protective properties. Mayne5' and Van Rooyen have reported on the passivating action of various metallic soaps of linseed fatty acids -including zinc. EvanP classifies zinc oxide as a cathodic inhibitor. While zinc oxide is used in many types of coatings, in this treatise only its use in metal protective coatings is discussed. M. ZINC POTASSIUM CHROMATE* Zinc potassium chromate or zinc yellow, in its crude form, was prepared in the early part of the 19th century. In 1829 Lampadi~s~~ suggested its use as a paint pigment. Zinc yellow as it is known today is a basic potassium zinc chromate with the assigned formula 4Zn0.K20.4Cr0,. 3H,O. Brizzolara60 et al pointed out that zinc yellow is a unique compound and varies slightly in composition. Commercial zinc yellows contain very small amounts of Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 145
SSPC CHAPTER*4.3 73 H Ab27740 0003573 TO2 sulphates and chlorides. See ASTM Specification D-478, Type 1 for a description of the low sulfate, low chloride type. Color ............................. Yellow Specific Gravity ................... .3.5 Weight per Solid Gallon .............29.2 Ibs. Oil absorption .................... .34 Type of Inhibitor ...................Anodic There is some difference of opinion whether or not this pigment is a true chemical compound. When mixed with water, the pigment undergoes partial decomposition and releases potassium chromate and potassium dichromate. This type of zinc chromate is not suitable for making wash primers or etch primers. With the development of fast drying vehicles, zinc chromate is used extensively in aircraft primers. Zinc yellow-alkyd primers have a tendency to become brittle with age, perhaps due to the common tendency of formulators to include some zinc oxide along with the zinc chromate. Like other pigments, the corrosion-inhibitive mechanism of zinc potassium chromate is not readily explained. The slightly soluble chromate ion is definitely a factor. Zinc yellow is not recommended for use in linseed oil vehicles because linseed oil films are not sufficiently water-resistant. The pigment is excellent for use in the water-resistant, oil-modified, synthetic resins. According to Jordan and Whitby3 chromates can inhibit corrosion by keeping the primary invisible oxide film in good repair. Chromates are essentially anodic inhibitors. Chromates also precipitate ferrous salts even in the absence of alkali to give a mixture of ferric and chromic oxides -a protective matrix which binds the pigment particles to the metal. Further theorizing is intere~ting~~ newly but designed aríd carefully conducted experiments are needed to more fully explain laboratory and field observations. N. ZINC PHOSPHATE Zinc phosphate is one of the more recent non-lead, non-chromate, corrosion inhibitive pigment developments. Early work done in England was reported by J.B. Harris~~-~~~ and his associates. One formula assigned for zinc phosphate is Zn3(P0,),2H,0. Color. ........................... .White
Oil absorption .................... .30 Specific Gravity ....................3.15 Wt. per solid gallon, Ibs. .............26.2 Particle shape ..................... Lamel la One of the producers of zinc phosphate cautions the formulator that salt spray and high humidity diminish outdoor performance. BarracloughB6 and Harrison propose that zinc phosphate protects steel by phosphate ion donation. Barraclough believes further supporting evidence for phosphate ion donation is shown by using the capacitance ce1I tec hnique6 . PantzerB8 promoted the idea that phosphate pigments build up protecting films in the anodic areas. His report gives a schematic diagram showing the reaction process for zinc phosphate. MayneB8 has established that, even though zinc phosphate has very low water solubility, aqueous extracts from zinc phosphate ground in linseed oil are inhibitive and behave similarly to an extract from zinc phosphatelinseed oil fatty acid soaps. Mayne also believes that during soap formation a small quantity of phosphoric acid is liberated and possibly improves the protective properties of paints containing this pigment. O. ZINC PHOSPHO OXIDE This is a relatively new, white anticorrosive pigment. According to Davidson70, it is an oxide of phosphorous acid and zinc -sometimes called a zinc phospho oxide complex. Physical Properties Color.. .......................... .White Sp. Gravity ....................... .4.06 Wt. per Solid Gallon ................33.8 Oil absorption .................... .40 to 60 Zinc Content (as Zn) ............... .61O/O
Av. Particle Size. ...................less than 1 micrometre According to Davids~n ~this pigment is a compound made from zinc as a cation and a phosphite anion. US. Patent 3,969,293 describes this complex as a basic zinc phosphite (XZnO.ZnHP0,) where X varies from 0.5 to 10. By using the proper proportions of zinc oxide, water, and phosphorous acid, tribasic zinc phosphite can be formed (3 ZnO .Zn HPO,). This pigment has low hiding power, enabling its use in pastel primers and topcoats. P. ZINC SALTS OF ORGANIC N ITROCOM POUN DS With the imposition of more and more environmental restrictions, the development of lead-free, chromate-free, anticorrosive pigments is important. Pantzer reported on a zinc organic nitrocompound (Sicorin). --`,,,,`-`-`,,`,,`,`,,`--146 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*4-3 73 8627740 0003594 949 Physical Properties Zinc Content ..................... .about 45% Organic components ...............a bo ut 50O/O Nature of the compound. ............powder Color ............................. colorless Resistance to temperature. ..........about 300°C (572 OF) Sp. Gravity ....................... .2.6 Pounds per Solid Gallon .............21.7 Oil Absorption .................... .35 to 40 Pant~er~~ Sicorin is electrochemical instates an hibitor and suggests its use in combination with zinc phosphate. VIL SUMMARY From the efforts of investigators to understand the secrets of corrosion inhibition, various schools of thought have developed their own theories and explanations. The coatings industry must maintain a certain practical attitude toward the results from these investigators. Of necessity it cannot ignore the effect of the binder, or resin, or oil that carries the pigment. A~pleby~~, Elm76, Clay and Ashworth and Evans79, Barraclough and HarrisonBo and MayneBi performed physicochemical tests that often included some type of organic or inorganic binder to form a protective coating that will protect our bridges, tanks, automobiles and the myriad of other items. In summary, Evans considers the chromate ion to act because of its oxidizing power. Uhligs2 ascribes the inhibitive mechanism to the effects associated with absorption of the unreduced ions. Pryor and Cohena3 ascribe the action of molybdate and tungstate ions as arising from film repair, even though the molybdate and tungstate ions are weaker oxidizing agents than the chromate ions. VIII. CONCLUSION Today, most industries are experiencing numerous and rapid changes, many of them influenced by concerns about pollution and toxicity. The list of scientific contributors has become long and varied. Maybe Shakespearea4 was peering into his crystal ball when he wrote, O for a Muse of fire that would ascend the brightest heaven of invention. There is magic about research. It is planned, calculating progress. When improperly planned it is extravagant and wasteful, but the one item more costly than
research is no research. Barnetta5 aptly stated the problem when he wrote Probably the weakest point in our knowledge of pigments is that we do not know how our pigments are formed, how many molecules combine to make initial units to precipitate from liquid or gas, or whether these continue to grow by addition of single molecules or by aggregation of the precipitated units. So what does the future hold concerning new pigments for anticorrosive paints? For one thing waterthinnable binders and pigments compatible with them will be large market factors. Much of our knowledge of the mechanism of anticorrosive pigments is based on studies of oleoresinous film formers. The water solubility or water dispersion of alkyds, epoxies, etc. creates a new class of film formers and as a result will require new studies to explain their pigment-vehicle anticorrosive mechanism. Equally important is the issue of pigment toxicity. Our knowledge of the corrosion inhibitive mechanism of nonlead, non-chromate pigments in aqueous media is extremely limited. The present non-lead or non-chromate pigments leave much to be desired. In the next five to ten years we will see the development of a whole new class of commercially available, anticorrosive compounds. These compounds now exist -it is just a question of some modifications in order to put them to use. J. Paul Hogan said, It s what you learn, after you think you know it all, that counts. *Chromate pigments are toxic substances that are closely regulated. Users are urged to follow all applicable health, safety and environmental requirements in applying, handling or disposing of these materials. *Based on their toxicity and the precautions required by law for their use and disposal, SSPC has proposed to withdraw all SSPC specifications for paints which use lead pigments. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 147
SSPC CHAPTER*4.3 93 m 8627940 0003595 BB5 = ACKNOWLEDGEMENT REFERENCES The author and editors gratefully acknowledge the active participation of the following in the review process for this chapter: AI Beitelman, Stephen G. Cantrell, Alex Chasan, Theodore Dowd, Raye Fraser, Carl Fuller, Tom Ginsberg, Leonard Haynie, A.R. House, W.G. Huckle, Sid Levinson, Charlie R. Lewis, Jr., Joe Mazia, Robert C. McClelland, Marshall McGee, Gordon D. McLeod, Ray McMaster, John Montle, Chuck Munger, John Perchall, Lother Sander, L.M. Sherman, V.P. Simpson, William Spangenberg, Armand Stolte, Hank Stoner, Verne J. Todd, William Wallace, Duane T. Werkman and Rufus Wint. BIOGRAPHY Arnold J. Eickhoff, who has retired, was a technical consultant in surface preparation and steel painting problems. He graduated from the University of Arizona with a B.S. in chemistry. He first became interested in protective coatings at the National Bureau of Standards in Washington, D.C. During World War II he was concerned with marine corrosion problems. After 26 years with NL Industries he became Head of the Pigments and Coatings Section at the Research Laboratory. Mr. Eickhoff was a consultant for the Steel Structures Painting Council and chairman of a committee to develop specifications for a latex metal primer and latex topcoat. He holds memberships in the American Society for Testing and Materials, the American Chemical Society, the Federation of Societies for Paint Technology, and the National Association of Corrosion Engineers. He is accredited by NACE as a Corrosion Specialist. 1. K.C. Bailey, The Elder Pliny s Chapters on Chemical Subjects, Edward Arnold, London, p. 61, 101; 1932. 2. J.E.O. Mayne, Corrosion Technology, pp. 286-290, Oct. 1954. 3. J.E.O. Mayne, and D. Van Rooyen, Journal of Applied Chem. 4, pp. 384-394, July 1954. 4. Appleby, A.J. and J.E.O. Mayne, Journal of Oil & Colour Chemists Assoc., pp. 59, 69, 1976. 5. J.E.O. Mayne, and E.H.J. Ramshaw, Applied Chemistry, Vol. 13, p. 553, 1963. 6. F. Fancutt, and J.C. Hudson, Journal of Iron and Steel lnstitute, p. 154, 1946. 7. J.E.O. Mayne, Journal of Oil and Colour Chemists Assoc., pp. 183-199, March 1957. 8. J.E.O. Mayne, The Mechanism of the Protection of Iror and Steel by Paint , Anticorrosion, pp. 3-8, Oct. 3, 1973. 9. Asbeck and Van Loo. Critical Pigment Volume Relation-
ships Industrial & Eng. Chem., Vol. 41, p. 1470, 1949. 10. Eickhoff, Unpublished information. 11. F. Fancutt, and J.C. Hudson, The Work of the Protective Coatings (Corrosion) Sub-Comm: British Iron & Steel Research Assoc. , Journal of Oil and Colour Chemists Assoc., Vol. 35, No. 396, Aug. 1962. 12. A.J. Liebman, Mechanical Surface Preparation See/ Structures Painting Council Manual, Vol. 1, p. 8, 1954. 13. J.O.M. Bockris, Modern Aspects of Electrochemistry Butterworth Scientific Publications, London, p. 180, 1954. 14. J.A.V. Butler, Trans. Faraday Soc., Vol. 19, pp. 729-734, 1924. 15. K.J. Vetter, Electrokinetics Academic Press, New York, 1967. 16. J.F. Bosich, Corrosion Prevention for Practicing Engineers Barnes and Noble Inc., New York, 1970. 17. Clive Hare. Corrosion and the Preparation of Metallic Surfaces of Painting. Federation of Soc. for CoatingTechnology, Unit 26, 1978. 18. Unpublished information. 19. A.J. Eickhoff, L.M. Kebrich, and J.G. Wills, Red Lead-Alkyd Resin Reactions. lnd. & Eng. Chemistry, Vol. 37, p. 399, April, 1945. 20. L.A. O Neill, and R.A. Brett. Chemical Reactions in Paint Films Journal of Oil & Colour Chemists Assoc., Vol. 52, pp. 1052-1 074, 1969. 21. S. Buckman, et al., figment Handbook, John Wiley and Sons, New York, Vol. 1, pp. 935-946. 22. R. Benedikt, On Some Salts of Boric Acid, Ber. Deut. Chem. Ges., Vol. 7, pp. 700-704, 1874. 23. E.M. Levin, and H.E. McMurdie, The System BaO.B,O, J. Am. Ceram. Society, Vol 32, No. 3, pp. 99-105, 1941. 24. US. Patents 3,033,700 and 3,060,049. 25. US. Pat. 2,668,122. 26. Eickhoff and Pitrot, Basic Lead Silicochromate Anticorrosive Pigment, Industrial 8. Eng. Chem., Vol. 51, p. 57A, August 1959. 27. W.C. Spangenberg. Private communication. 28. Harvey Bennett, Private communication. 29. Mayne and Ramshaw, Jour. Applied Chem., Vol. 13, p. 553, 1963. 30. US. Patent 3,677,783. A basic zinc molybdate. 31. US. Patent 3,353,979. 32. Pliny, Historia Naturalis, 34-54; 35, 20C AD 77. 33. A.J. Eickhoff, Anticorrosive Pigments, Chapter 4 of OrganicProtective Coatings by Von Fischer & Bobalek, Reinhold Pub. Corp. 34. Jordan & Whitby, Sixteenth Bulletin Res. Assn. of British Paint, Colour & Varnish Mfgrs., Teddington, England, 1936. 35. A.J. Eickhoff, ti W.E. Shaw, Principles of Protecting Metals with Organic Coatings . Corrosion, Oct. 1948. 36. W. Beck, Reaction Change of Red Lead Films Schweig. Arch. Angew. Wiss. Tech., Vol. 8, pp. 45-52, 1942. 37. H. Wagner, Korrosion & Metalschutz, Vol. 20, p. 221, 1944. 38. J.E.O. Mayne, J. Oil & Colour Chem. Assoc., Vol. 34, p. 473, 1951. 39. J.E.O. Mayne, The Mechanism of the Protection of Iron & Steel by Paint. Anti-Corrosion, pp. 3-8, Oct. 1973. 40. Ibid., pp. 3-8. 41. J.E.O. Mayne, and E.J. Ramshaw, Appi. Chem. Vol. 10, p. 419, 1960. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from
IHS 148
SSPC CHAPTER*4*3 93 = 8627940 000359b 711 = 42. D.L. Hawke, & W. Shaw, Unpublished observations. 43. A.C. Elm, Paint Oil ¿t Chem. Rev., pp. 16-32, 38, Aug. 19, 1948. 44. E. Lalor, Pigment Handbook, John Wiley and Sons, New York, Vol. 1, pp. 851-859. 45. US. Patent 2,701,772 (Feb. 1955). 46. G.H. Cartledge, The Pertechnetate Ion as an Inhibitor of the Corrosion of Iron and Steel. Corrosion, Vol. 11, pp. 335t-342t, August, 1955. 47. C. Perrier, & E.J. Segre, Chemistry Phys., Vol. 5, p. 712, 1937. 48. Pryor and Cohen, J. Electrochemical Soc., pp. 100, 203, 1953. 49. G.H. Cartledge, The Mechanism of the Inhibition of Corrosion by the Pertechnetate Ion , J. of Physical Chemistry, Vol. 59, p. 979, 1955. 50. US. Patent 2,525,107, Oct. 10, 1950. 51. Rosenbloom, Industrial 8, Eng. Chem., Vol. 45, p. 2561, Nov. 1953. 52. L.R. Whiting, Wash Primers, Magazine Corrosion, June, 1959. 53. A.J. Eickhoff, Unpublished information. 54. E. Davy, Communications to the Fifth Meeting of the British Association, p. 34, 1835. 55. H.A. Gardner, Anticorrosion Paints for Steel Hulls , Scientific Section Circular, No. 49. 56. Percy, Metallurgy, John Murray, London, p. 524, 1861. 57. Mayne and Van Rooyen, Jour. Applied Chemistry (London), Vol. 4, p. 384, July, 1954. 58. U.R. Evans, Metallic Corrosion, Passivity and Protection, Longmanc Green and Co., New York, p. 535, 1945. 59. Lampadius, W. Tech. Oekon, Chem., Einige Berner Pungen fur Farbenfabrikanten, Vol. 4, p. 443, 1829. 60. A.A. Brizzolara, et. al. Industrial and Eng. Chemistry, Vol. 29, p. 656, June 1937. 61. A.J. Eickhoff, Unpublished data. 62. M.P. Wood, Rustless Coatings for Iron & Steel , Trans. Am. Soc. Mech. Eng., 16, p. 671, 1895. 63. H.G. Cole, & H. Le Brocq, Journal Appl. Chem., Vol. 5, p. 149, 1955. 64. Burns & Schuh, Protective Coatings for Metals, New York, pp. 299-301, 1939. 65. J.B. Harrison, et al. J.O.C.C.A., Vol. 45, p. 571, 1962. 66. Barraclough et al. J.O.C.C.A., 341-355, April, 1965. 67. J.K. Gentles, J.O.C.C.A,, Vol. 46, p. 850, 1963. 68. R. Pantzer, Anti-Corrosion, pp. 3-7, June-July, 1975. 69. J.E.O. Mayne, Paints for the Protection of Steel: A Review of Research into Their Modes of Action British Corros. Jour., Vol. 5, p. 106, 1970. 70. S.L. Davidson, J. Oil and Colour Chem. Assoc., Vol. 58, 435-442, 1975. 71. R. Pantzer, Anticorrosion, pp. 3-7, June, July, 1975. 72. R. Pantzer, Deutsche Farben-Zeitschrift, p. 13, 1975. 73. J.E.O. Mayne, Current Views on How Paint Films Prevent Corrosion J. Oil and Colour Chem. Assoc., pp. 183-199, March, 1957. 74. J.E.O. Mayne, How Paints Prevent Corrosion , Corrosion Technology, pp. 286-290, Oct., 1954. 75. Appleby and Mayne, The Relative Protection Afforded by Red Lead Dispersed in Linseed Oil, Tung Oil, Oiticica and a Long Oil Alkyd Varnish , J. Oil and Col. Chem. Assoc., pp. 59,
69-71, 1976. 76. A.C. Elm, The Mechanism of Action of Metal Protective Paints Paint, Oil and Chemical Review, Aug. 19, 1948. 77. Clay and Cox Chromate and Phosphate Pigments in AntiCorrosive Primers , J. Oil and Colour Chem. Assoc., Vol. 56, pp. 13-16, 1973. 78. Ashworth and Proctor. The Role of Coatings in Corrosion Prevention -Future Trends, J. Oil and Colour Chem. Assoc., Vol. 56, pp. 478-490, 1973. 79. U.R. Evans, Metallic Corrosion, Passivity and Protection, Chapter X. 80. J. Barraclough and J.B. Harrison, New Leadless Anticorrosive Primer , Jour. Oil and CoIour Chem. Assoc., pp. 341-355, April, 1965. 81. J.E.O. Mayne, The Mechanism of the Protection of Iron and Steel by Paint , Anticorrosion, pp. 3-8, Oct., 1973. 82. H.H. Uhlig, Metal Inter-Interfaces , A Symposium, Am. Soc. Metals, pp. 312-335, 1951. 83. M. Pryor, and M. Cohen, Journal. Electrochem. Soc., Vol. 100, p. 203, 1953. 84. King Henry V., Prologue, Line 1. 85. C.E. Barnett, Industrial and Eng. Chemistry, Vol. 41, p. 272, Feb. 1949. --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 149
SSPC CHAPTER*5-L 93 8627940 0003597 658 CHAPTER 5.1 PAINT APPLICATION by Sidney 5. Levinson and Saul Spindel Paint is not a finished product until it has been applied to the substrate. Therefore, proper application of the paint is a critical part of the complete paint system. High performance paint systems are especially sensitive to misapplication and may fail drastically, even more so than conventional paint systems, which are much less sensitive to application variables. Therefore, it is imperative that instructions be followed explicitly, particularly when applying expensive and sensitive high performance paint systems. A detailed specification covering the general requirements of high performance paint application is given in SSPC-PA 1, Shop, Field and Maintenance Painting , as outlined in Table 1. Surroundings may prohibit use of spray application because of fire hazards or potential damage from overspray. Parking lots and open storage areas are common examples. Adjacent areas or objects not to be coated must be masked before spraying and the masking material must be removed afterwards. This takes time and, if extensive, may offset the advantages of the rapid area coverage of spraying operations. Weather conditions are very important for good results. Avoid painting below 45°F or above 95 F, if the relative humidity is above 8O%,during rainy weather, when wind velocity is above 15 miles per hour or if freezing will occur before the paint dries. If lacquer coatings, such as those based on vinyl or chlorinated rubber resins, are used, they may be applied at temperatures as low as 35°F. Brushing is ideal for small areas, edges or corners. Roller coating is most efficient on large, relatively flat surfaces. Spraying is most suitable for large areas but works just as well on irregular shapes such as bridge steelwork. The surface should be completely dry and between 45°F and 95°F before painting. However, damp (not wet) surfaces may be painted with some water-base or latex paints, and certain other systems as recommended by the coating manufacturer. Lacquer products, such as vinyls and chlorinated rubber, which dry rapidly, should be applied by spray. Brush or roller application may be extremely difficult, especially in warm weather or outdoors on breezy days. Each method of application has a different effect on dried coating. Brushing tends to leave brushmarks and 1o. 11.
Drying & Handling 12. Inspect ion Safety --`,,,,`-`-`,,`,,`,`,,`--rolling may cause stipple marks. Spraying, when done properly, gives the smoothest and most uniform paint film, TABLE 1 SUMMARY OF SSPC-PA i-Shop, Field & Maintenance Painting 1. Scope 2. Definition 3. Pre-application Procedure 3.1 Materials Handling & Use 3.2 Storage of Paint & Thinner 3.3 Surface Preparation 3.4 Pretreatments 3.5 Mixing & Thinning 4. Factors Affecting Application of Paint 4.1 Temperature 4.2 Moisture 4.3 Humidity 4.4 Cover 4.5Damage 4.6 Striping 4.7 Continuity 4.8 Thickness 4.9 Recoating 4.10 Tinting 4.1 1 Intercoat Adhesion 4.12 Contact Surfaces 5. Application Methods 5.1 General 5.2 Brush 5.3 Spray -General 5.4 Air Spray 5.5 Airless Spray 5.6 Hot Spray 5.7 Hot Airless Spray 5.8 Roller 6. Shop Painting (Types, Coats, Contact, Welding, Damage, etc.) 7. Field Painting (Cleaning, Touch-Up, Procedures, etc.) a. Maintenance Painting (Cleaning, Compatibility, Records, etc.) 9. Special Coatings 9.1 Conventional Types 9.2-9.6 Other Generic Types Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 150
SSPC CHAPTERUSOL 93 = 8627940 0003598 594 though sagging can occur if too heavy a coat is applied. The degree of training and experience of the personnel may influence the choice of method of application. Spraying requires the greatest degree of skill. Rolling is the easiest. I. PAINT PREPARATION Since paints are pigmented they can become nonuniform during storage. During long periods of storage, the pigment, which is more dense than the vehicle, tends to settle and sometimes cakes at the bottom of the container. The liquid component might separate and form a thin layer at the surface, or it could form a skin, especially in a partially full can. Mixing is required to make the paint homogeneous and uniform before use by stirring the vehicle, dispersing the settled supernatant liquid, and removing all skins, lumps and other large particles. The paint, if stored at cold or hot temperatures, should be brought to a moderate temperature for application. Two and three component paints must be carefully mixed just prior to use. HEAVY-DU~YELECTRICS Al R \ \ FIGURE 1 Drum Paint Agitator Courtesy of Quick Spray, Inc. The paint also may be tinted with some added color, such as for use as an intermediate coat. Paint should be stored at a moderate temperature. Rotate stock and use older material first. Also. reverse eFIGURE 2 Paint Shaker Courtesy of Red Devil - Union, Inc. containers at intervals to prevent settling. Check seals to be sure there is no leakage. Check dated products and replace outdated materials. A. MIXING A mechanical mixer is preferred because it is faster and produces a uniform mixture. If manual mixing is . necessary, don t use cans larger than two gallons.
If there is a skin on the surface of the paint, carefully remove before mixing to avoid the formation of lumps or gelled particles. Depending on the size of the container, mixers are available, from attachments for hand drills to large portable units, which can be used to mix 55-gallon drums of paint. Most of these attachments are propellers with the following typical dimensions: Shaft Length -11 to 36 Propeller diameter -2 to 8 Horsepower -Up to h H.P. These mixers may be powered by electric, air or portable drills. Multiple propellers, (two or more stacked on the shaft) are also used in larger containers, such as drums, to achieve uniform mixing (Figure 1). Some propellers are of expanding type so that they can be inserted through the bung opening of the drum. During mixing they open to a diameter of 8 inches. When mixing stops, the blades collapse allowing removal through the bung opening of the drum. Paint shakers can be used to remix containers of five gallons or less without opening the cans (Figure 2). They operate by an eccentric cam which shakes the can vigorously. Most paint distributors have these units. Avoid shaking partly full cans of latex paint. It can cause foaming. Avoid splashing. Speed should be set as low as possible to create moxement of the paint with only a slight vortex, or central depression, at the surface. A large vortex should be avoided, especially with latex paints, since this will result in drawing in air and foaming. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 151
SSPC CHAPTERxS-II 93 m 8b27940 0003599 420 m Discard all paint beyond that time. When one component is a powder, e.g., zinc, aluminum or bronze, be sure that the liquid component is completely uniform before proceeding. Follow manufacturer s instructions as to whether pigment is added to the liquid component or the liquid component is added to the pigment. Add very slowly while mixing continuously until the paint is smooth. Avoid the formation of lumps, which may cause clogging of spray equipment. B. THINNING Do not thin the paint unless recommended by the supplier or needed for spray application. If the paint is cold, do not add thinner to make application easier. Instead, bring the paint to 50-90 OF. When thinning the paint, first be sure that it is well mixed before adding the thinner. Then continue mixing until the paint is uniform in consistency. Be sure to use a thinner that is recommended for the product. Paint heaters can be used to reduce viscosity for spray application, thus avoiding the addition of thinners. Observe safety precautions. Do not apply warm paint to cold steel. Results are best if both are similar in temperature. C.TINTING Do not tint paint unless recommended by the supplier or tinting is necessary to change the color for an intermediate coat. If tinting is done, first premix the paint. Make sure the tinting color is compatible before adding. The type and maximum amount should be determined by the paint manufacturer. Mix mechanically and continue until the paint is uniform in color with no streaks on its surface. FIGURE 3 Rapid Paint Strainer Tinting colors may be recommended to achieve Courtesy of The DeVilbiss Co. desired topcoat colors. Follow the paint manufactu rer s directions explicitly since colorants may not be compatiFoam is extremely difficult to eliminate and will result in ble with all types o f coatings despite the designation bubbles or craters in the applied paint film. Universal . Do not use more than the maximum recomScrape the bottom and lower sides of the container to mended by the manufacturer . disperse all settled pigment. When mixed, the paint should WALL look uniform from top to bottom, showing no striations or color streaks on its surface. If manual mixing is necessary, pour some of the paint into another clean container. The balance of the paint can then be readily mixed, after which the removed paint can be poured back and mixed in. Follow the same precautions as in mechanical mixing with regard to the bottom and
sides of the container. When mixing two-component paints, check and remix each component individually. Then blend the two comFIGURE 4 ponents at low speed until the mixture is completely Typical Paint Brushes uniform in color. Often, the two components are supplied Courtesy of E 2 Painter Corporation in different colors so that a good mix can be readily determined. Do not mix more than a few gallons at a time since Try to use the same ba tch number of topcoat in any the exotherm caused by the mixture may be so high as to one area since there can be a slight color difference bemake the paint solidify in the can. Be sure to use the paint tween batches. If d ifferent batches are needed, combine within the pot life recommended by the manufacturer. batches as much as possible to avoid the possibility of Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 152
SSPC CHAPTER*S.L 93 m Ab27940 0003600 T72 m -LENGTH OUT STRIP OR FILLER FERRULE HANDLE FIGURE 5 Paint Brush Construction. Courtesy of American Brush Manufacturers Association color differences. Alternatively, if colors of the topcoat are found to be slightly diffferent from one batch to another, finish using one batch at the edge or corner so that batchto-batch color differences will not be as noticeable. D. STRAINING Paints should be strained after mixing if there is any evidence of skins, lumps, color particles or foreign materials. Straining is especially recommended if paint has been previously used and allowed to stand for any length of time or if the paint is going to be sprayed. Strain after completing all mixing, thinning, tinting or boxing. Strain through a fine sieve (80 mesh) or a commercial paint strainer (Figure 3). E. TEMPERATURE Temperature of paint may be excessively high or low depending on storage or shipping conditions. If so, warm or cool the paint to a temperature of 50-90 OF before mixing and use. II. APPLICATION METHODS There are five methods of paint application: brush, paint pads, roller, mitt and spray. The choice of method to be used depends on the type of coating being applied, adjacent areas that might be damaged by overspray and degree of skill of the personnel. Whatever method is used, tools should be of first quality and should be maintained in top condition. A. BRUSH APPLICATION Brush application requires the least amount of preparation before use and cleanup afterwards. Only the brush has to be cleaned. However, brushing is slower than other methods and should be used mainly for small areas and for cutting in corners or edges. Brushing is also useful to improve wetting of primers on difficult-to-paint surfaces. There are two general designs of brushes which may be used in painting steel: conventional and flat brush. The most common brush used on steel structures is the conventional wall brush, varying in width from 3
to
6 and with bristling varying in length from 4 to 7 . Small areas require narrower sash brushes, 2 to 3 wide. Irregular surfaces are best painted with oval brushes up to 2 in diameter (Figure 4). The brush is constructed by cementing the bristling ends in a setting compound then adding a handle. The setting compound and flat end of the handle are fastened together with a metal ferrule. Strips or fillers are inserted inside and at the bottom of the bristling. This forms a cavity that holds more of the paint and also reduces the total volume of bristling, making it easier to spread paint and reducing cost (Figure 5). Bristling is controlled in length so the longest bristles are in the center and their length is tapered toward the outer bristles. This makes painting easier. The flat brush is made up of short nylon or polyester filaments, 1 long, attached to a flat base, about 4 x 7 . This allows for wider contact with the surface being painted. A metal grip is attached to the other side of the base. This brush holds about twice as much paint as a conFIGURE 6 Industrial Paint Roller and Tray Courtesy of Arcco Paint Rollers, Inc. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 153
SSPC CHAPTER*S-L 93 8627940 0003601 907 M a FIGURE 7 Use ventional --`,,,,`-`-`,,`,,`,`,,`--of Roller Extension Poles on Water Tank Courtesy of the National Paint & Lacquer Association & E z Painter Corporation brush and applies paint more rapidly. It is especially effective in forcing paint into crevices and around projections. It also can be used with an extension pole. Flat brushes require roller tray, are ineffective inside angles, and are more difficult to clean. A flat brush also drips more, adding to clean-up problems. Two general types of bristling are used: natural bristles and synthetic filaments. Traditional paint brush bristles come from Chinese hogs. These produce excellent paint bristles since the ends of the bristles are flagged , or naturally split so they hold a considerable amount of paint. Unfortunately, hog bristles are very expensive and are not practical foi hot water-thinned paints. Other animal bristles, such as horsehair, have been used but generally are inferior to hog bristles. The oldest synthetic filament is nylon. Flagged ends are produced by artificially splitting the filament tips. Nylon is much more water-resistant than natural bristles and works better with water-thinned (latex) paints since nylon bristles do not soften excessively after prolonged use. Nylon loses stiffness in lacquer solvent and alcohol and should not be used with paints containing those solvents. Polyester filaments are widely available. They appear more water resistant than nylon and soften less after prolonged use. They also are less affected by lacquer solvents. FIGURE 8 Pipe Paint Roller Courtesy of E ZPainter Corp. Many brushes are made of blends of natural, nylon andior polyester to combine the application qualities of bristle, the wear resistance of nylon and the resistance of polyester to water and high humidity. It is important toase high quality brushes and keep them in top shape. Avoid brushes with horsehair or with
filaments that are not flagged. Conventional brushes should be tapered from side to center. The brush should feel solid with a good quantity of bristles and still be flexible. All bristles should be firmly set with no loose bristles. Dip the brush into the paint to about half the bristle length, then withdraw at the edge of the container in a partial wiping motion or shake to remove excess paint. Hold the (conventional) brush at an angle of about 75 to the work. Make several light strokes to transfer paint to the surface. Spread the paint evenly and uniformly. Do not press down on the brush. Pressing can create excessive brushmarks or cause wiping off some of the paint. Paint the adjacent area, completing the brush strokes into the edge of the previously painted area. This prevents excessive pileup of paint in the lapped areas, which can result in lap marks. Finally, cross-brush lightly to eliminate any sag or brush marks. Avoid poking the brush into corners and crevices. Instead, use the end of the brush and twist it slightly to get the bristles into hard-to-reach areas. Flat and oval brushes are used in a similar manner but are held so bristle ends directly face the work. 8.PAINT PADS Paint pads hold more paint and are faster than brushes. They are almost as versatile for covering small areas but require a tray and are more difficult to clean. Because of their relatively low cost, they can be discarded Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 154
SSPC CHAPTERx5.L 93 8627940 0003b02 845 --`,,,,`-`-`,,`,,`,`,,`--FIGURE 9 Pressure Paint Roller Courtesy of Thomas Industries after use. Their use on structural steel is limited. They consist of roller-type synthetic fabric attached to a foam backed flat pad about 4 x 7 in size. The fiber length is about 3/tsrr. A spring-loaded handle keeps the pad parallel to the work. The handle is threaded to accept extension poles. FIGURE 11 Paint Mitt in Use Courtesy of Bestt Roller, Inc. C.ROLLER APPLICATION Paint rollers are excellent for large flat areas and do not require the skill of spray application. They hold much more paint than a brush and are two to four times faster. They require the use of trays (or grids in large containers), are more difficult to clean and are not as effective in applying paint evenly and with good wetting on difficultto-wet surfaces, e.g., hand cleaned, rusted or pitted steel. Roller cleaning is not critical since they are economical enough to be discarded. Paint rollers consist of three major units: roller cover, roller handle and paint tray or grid. 1. Roller Covers Roller covers vary in diameter, length, type of fabric and fiber length (Table 2). Diameter: Roller cover diameters may be 1% or 2% . The 1 diameter is most common. Paint Mitts FIGURE 10 Length: This may vary from 1 to 18 . The 9 length is most common. A 2 x 9 roller will hold Courtesy of Bestt Roller, Inc. twice as much paint as a 1 Ir x 7 155
roller and a 2%
Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*5=1 93 W 8627940 0003603 781 TABLE 2 CHOICE OF ROLLER FABRIC AND NAP Type of Surface Smooth Rough Flat finish-oil or Polyester Polyester water-based -Y2n y2 -y4 r Paints containing Special stapled covers strong solvents Enamels and gloss Woven Lambskin paints %8 -Y2I 1k -y, ABCDEF -Air Valve G -Pattern Control H -Gun Body (or Handle) I-Fluid Packing Nut --`,,,,`-`-`,,`,,`,`,,`--FIGURE 13 Conventional air spraying with lh inch fluid hose and X inch air hose. Courtesy of DeVilbiss Company NEEDLE V4LYE SrEu ANNULAR R NG AROUND THE FLUID NOZZLE TIF (2i CONTAINMENTHOLES 1 I 0 0 WINGS:.HORNS OR.EARS. @ SIDE-PORT HOLES @ ANGULAR CONVERGINGnaEs FIGURE 14 Air spraying at oil refinery, with pressure pot, provides control in FIGURE 12 spraying small structural shapes. Construction of Air Spray Gun Courtesy of DeVilbiss Company Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 156
FIGURE 15 Air spray painting at electrical power plant. Courtesy of DeVilbiss Company x 18 roller will hold up to 4 times as much paint, as much as a quart if a long fiber fabric is used. Fabric: The most common fabrics are polyester, verel, nylon, mohair and lambskin. The choice of fabric and fiber length (nap) depend on the type of paint and the condition of surface, as shown in Table 2. CROSS SECTIONAL VIEW OF AIRLESS SPRAY TIP MATERIAL FLOW RAY UNDER HYDRAULIC j GLE PRESSURE (Controls Flow-Creates High Velocity from Pressure) FIGURE 16 Airless Spray Action Courtesy of the Aro Corporation Woven Fabrics (as opposed to knit) are available. They shed fewer lint particles, are designated all paints or Enamel on the label and are better than knit fabrics for gloss paints. Core: The core of the roller may be made of plastic impregnated fiber or wire mesh. Be sure the core is resistant when using epoxies, vinyls, urethanes and other materials that contain strong solvents. FIGURE 17 Airless Spray PumpAir Operated, Suction Hose Type Courtesy of Graco, Inc. Fiber Length (Nap) or Pile Height: The length of fiber in roller fabrics used on steel surfaces varies from IA to 3A . Longer fibers hold more paint, but do not give as smooth a finish. Therefore, they are used on rougher surfaces with faster drying paints. F FIGURE 18 Airless Spray Unit With Two Guns-Air Drive + Agitator Courtesy of Nordson Corporation Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 157
SSPC CHAPTER*S-L 73 FIGURE 19 Airless Spray Unit 2. Roller Handle --`,,,,`-`-`,,`,,`,`,,`--Dolly Mount, Air Drive Courtesy of Alemite Division of Stewart-Warner The handle is made of stiff wire (app. l/4 " in diam.), with a comfortable handle for holding the roller at one end and bent at the other end to form an offset right angle. The angle end has a spring wire or metal attachment to enable slipping the roller on and off, yet holding it firmly during use. The end of the handle is hollow and threaded so an extension pole may be used. Extension poles as long as 16 feet are available to avoid the use of ladders (Figure 7). 3. Paint Tray Paint rollers must be worked in when loaded with paint. The roller (on the handle) is partially inserted into the paint, then rolled on the ramp until uniformly coated. Most trays hold about '/2 gal. of paint. Some are large enough to hold several gallons (Figure 6). An alternative method is to use a large paint FIGURE 20 FIGURE 21 Airless Spray Unit -Suction Hose, Air Drive Courtesy o1 Binks Manufacturing Co. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 158
SSPC CHAPTER*S.L 93 m 8627940 bucket, e.g., a 5-gal. can with a roller grid, on which the roller is worked in. This allows the use of rollers on ladders and scaffolds. 4. Pipe Roller This special roller is made up of 2 to 5 narrow rollers on a spring spindle. They readily conform to contoured surfaces, such as piping. The size of the pipe determines the number of segments required. The threaded handle allows the use of extension poles (Figure 8). 1 s 3 For long hose lines 1. Pump Unit 2. Fluid Hose 3. Fluid Header (removed from pump) 4. Fluid Hose to guns 5. Air Hose from compressor For shorter, direct hose lines 1. Pump Unit 2. Fluid Hose to guns 3. Air Hose from compressor 1 For heavy and filled materials 1. Basic Pump Unit 2. Flow Control Valve 3. High Pressure Fluid Hose 4. Air Supply Hose FIGURE 22 Portable and Maintenance Painting Hook-ups O003606 490 m PUMP UNIT 1. Pump-to meet delivery and pressure needs 2. Regulatorto control pump operation 3. Fluid Outlet fittings for required hoak-up
4. Drum Lidfor mounting pump 5. Agitator-for continuous agitation of material 6. Liftconvenient, quick change of drums --`,,,,`-`-`,,`,,`,`,,`--FIGURE 23 Air Driven, Drum Mount, Airless Pump With Agitator Courtesy of DeVilbiss Company 5. Fence Roller Roller covers with extra long naps (1'1'4 ") enable rapid painting of wire fence from one side. The long nap surrounds the wire and coats it on both sides at once. 6. Pressure Roller Pressure rollers allow continuous painting by steadily supplying paint from a pressurized tank directly inside the roller. The roller cover is made of a perforated metal core that enables paint to pass from inside the roller. A valve controls pressure either on the roller handle or the tank (Figure 9). 7. Application Roller application requires a very different technique than that required for brushing. 8. Loading by Roller If a tray is used, fill it half full with the premixed paint. If a grid is used, place it into the can (usually 5 gals.) of paint, setting it at an angle from one side of the bottom of the can to the other side of the can at the top. Dip the roller cover into the paint until completely wet with paint. Then roll it up and back along the tray ramp or the grid until the paint is completely worked in. Before starting to paint, roll the first load out on scrap paper to eliminate any air bubbles trapped within the roller cover fibers. 9. Applying the Paint Place the loaded roller against the surface to be Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 159
SSPC CHAPTER*S.L 93 8b27940 O003607 327 D. PAINT MITTS A paint mitt is ideal for painting odd-shaped objects, such as pipes and railings, when spray painting is not feasible. It consists of a lambskin glove with or without a thumb. It is dipped in paint and applied to the surface (Figures 10 and 11). E. SPRAY APPLICATION The fastest way to paint large structural areas is by spray. Table 3 gives some idea of the relative efficiency of different methods of application: TABLE 3 TYPICAL AVERAGE AREA COATED PER DAY Method Square Feet Brush 650 Roller 1,200-2,600 Air Spray 2,000-6,000 Airless Spray 3,000-8,000 Spray equipment also is versatile as shown by the variety of equipment available: a. Air spray (conventional) b. Airless spray -Ambient and heated c. Heated spray -Air and airless FIGURE 24 d. Electrostatic spray -Air and airless Airless Spray Unit -Electric Drive Courtesy of Binks Manufacturing Co. e. Two-component application equipment painted and roll the paint out in the form of a V or W. Its size depends on the square area that eventually will be filled in around the V or W. A 7-inch roller, for example, will cover an area about 3 x 3 feet. Then roll out the paint to fill in the square area. Finish with light vertical strokes in the direction which produces the smoothest finish. It is not necessary to press hard on the roller. In fact, doing so will cause foaming and possible cratering by entrapping air. Moderate pressure is all that is required. Also, do not roll too rapidly, since doing so will cause the paint to spatter. A moderate rate of speed is best. Airless Spray Unit Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS--`,,,,`-`-`,,`,,`,`,,`--FIGURE 25 FIGURE 26 Gasoline Operated Electrostatic Airless Spray Unit -Dolly Mount, Air Drive, Heat ed Courtesy of H. G. Fischer & Co. Courtesy of Nordson Corporation
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SSPC CHAPTERx5.L 93 8627740 1. Air Spray The original method of spray application was by air atomization. A compressor supplies air under pressure via an air hose to a spray gun that atomizes the paint to produce a fine spray which is projected onto the surface. Paint is usually kept in pressurized containers. From there compressed air forces the paint to the gun via a fluid hose (Figure 12). Air atomization of the paint can result in considerable overspray. Consequently, not only must adjacent areas and objects be covered, but also paint losses may vary from 20% to 40% on structural steel. The painter must wear some protection to avoid breathing paint mist. 0003b08 263 D EFFECT OF TEMPERATURE ON A TYPICAL ENAMEL AND A TYPICAL LACQUER --`,,,,`-`-`,,`,,`,`,,`--I O FIGURE 28 Effect of Temperature -Paint Viscosity vs Temperature Courtesy of Nordson Corporation 2. Airless Spray Airless spray relies on hydraulic pressure rather than air atomization to produce the desired spray. An air compressor, electric motor or gas engine is used to operate a pump to produce pressures of FIGURE 27 FIGURE 29 Extension Spray Gun Air Driven, Heated, Airless Spray Unit with Compressor Courtesy of Nordson Corporation Courtesy of Nordson Corporation Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 161
SSPC CHAPTER*S=L 93 6627940 0003609 LTT 1,000to 6,000 psi. Paint is delivered to the spray gun at this pressure through a single hose. Within the gun, a single paint stream is divided into separate streams, which are forced through a very small orifice resulting in atomization of paint without the use of air. This recuits in more rapid coverage with less overspray (Figure 16). The following comparison (Table 4) demonstrates the differences between conventional and airless spray: Airless spray usually is faster, cleaner, more economical and easier to use than conventional air spray. The absence of atomizing air prevents potential contamination from oil or water in the compressed air, or from the cooling effect of atomization in humid atmospheres. Airless spray is for large areas and the airless gun has fewer adCONVENTIONAL AIR SPRAY ENERGY RMUIREO **; 9.3 H P / GP.M Mx) PARTS AIR i.1.1 HOT SPRAY HYDR&ULIC SPRAY COLD AIRLESS :NERGY REQUIRED IIHPIGPM VISCOSITY 22 @ 59~~ 70' . HOT AIRLESS 'NERGY REQUIRED .32 H.P. I G.P.M. FIGURE 31 Electrostatic Spray Units -Electric Drive Courtesy of Graco, Inc. TABLE 4 CONVENTIONAL VS AIRLESS SPRAY VISCOSITY 150 @ 70'mT * :* VISCOSITY 150 d 70"
''SF' 25 @ 150 22 @ 170' FIGURE 30 Comparison of Spray Methods Courtesy of Nordson Corporation Coverage, sq.ft/day Overspray, YO Portability Direct drive units Hoses Masking Penetration of corners & voids Thinning before spray Film build per coat Moisture (Compressor) Versatility Paint clogging problems Safety during cleaning Conventional Airless 4-8,000 6-10,000 20to 40 10 to 15 Fair Excel lent No Yes 2 Usually 1 Considerable Moderate Fair Good Usual Sometimes Lower Higher Possible None More Less Slight Possible Excellent Poor 162 --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERw5-1 73 = 8b279LiO 0003610 711 followed. of power sources: by compressed 3. Power Sources --`,,,,`-`-`,,`,,`,`,,`--FIGURE 32 Wraparound Effect of Electrostatic Spray Courtesy of Graco, Inc. justments than conventional spray guns. Different spray patterns may require a change in nozzles. Because of very high pressures, paint must be thoroughly screened to prevent clogging of the nozzles, and cleaning the equipment may be extremely hazardous unless proper precautions are Airless spray units are available in a wide variety a. Air Driven Units -The hydraulic unit is driven air using an air compressor FIGURE 33 Two-Component Spray Gun Internal Mix Courtesy of DeVilbiss Company FIGURE 34 Two-Head Spray Gun Courtesy of Binks Manufacturing Co similar to that used in conventional spraying (Figure 17-23). b. Hectric Driven Unit -The unit is selfcontained with its own explosion-proof electric motor. Sizes vary from small units weighing about 40 Ibs to large units, which handle two guns yet can be wheeled by one man up or down stairways (Figure 24). c. Gas Driven Unit -The spray unit is operated by a gasoline engine for use in the field (Figure 25). 4. Mounts Airless spray units vary in mounting or the method used to admit paint to be sprayed. a. Suction Unit -The spray unit is mounted on wheels, and paint is aspirated in a hose or pick-up tube that sucks paint from any container, including drums (Figures 21, 24, 28). b. Pail-Mounted Unit -The spray unit is mounted directly onto the paint container, e.g., a 5-gal. can or 55-gal. drum (Figures 18, 20). c. Dolly-Mounted Unit -The spray unit is mounted on a wheeled dolly which also supports the paint container. It is excellent for larger containers, e.g., 10, 20 or 30 gals (Figure 26). d. Immersion Tube Unit -The wheeled spray unit
has a rigid tube at the bottom. The unit is tilted so that the tube can be inserted into a 1-to 5-gal. can of paint. Some units are modified so a unit and a can of paint can be maneuvered together (Figure 24). e. Drum-Mounted Unit -Large units, which can Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 163
I CORRECT, I I STROKE PULL TRIGGER PULL TRIGGER STROKE HOLD GUN PERPENDICULAR TO SURFACE BEING SPRAYED \'l RIGHT e --r FIGURE 35 Correct Handling of Air Spray Gun Courtesy of Binks Manufacturing Co. handle up to 4 guns, are mounted on a 55-gal. drum of paint (Figure 23). f. Self-Contained Unit -The container is part of the spray unit the paint must be poured into before use (Figure 25). 5. Agitators Many pail- or drum-mounted units have built-in agitators that keep the paint uniformly mixed during the spraying (Figures 18, 23). Strainers Since paint cleanliness is critical in order to prevent clogging of nozzles, almost all airless spray units have built-in strainers. Extension Guns Airless spray extension or pole guns, up to 26 ft. long, are available to reduce the necessity of scaffolding or staging. Some have swivel heads to enable spray coating of inaccessible areas (Figure 27). Heated Spray Heating paint before spraying reduces viscosity (Figure 28).Thinning is reduced and paint solids are increased, enabling application of thicker coats. Caution must be observed because most solvent-thinned paints are flammable. Avoid applying heated paint on cold steel. Condensation at the interface may adversely affect adhesion. a. Equipment -Spray units which preheat paint to 12O0-2OO0Fare available. They are portable but tend to be cumbersome because of the added preheating unit (Figure 29). b. Advantages -Heated spray units have a number of advantages over unheated units: Faster application if viscosity is reduced Lower pressure required -under 1,OpOpsi Can spray at lower ambient temperatures but
avoid cold steel Less overspray and bounce back from corners 9 Less solvent fumes 9 Increased thickness per coat if solids are increased Faster dry Smoother finish (No pinholes) Improved paint adhesion possible except on cold steel Less power and air required INSiOE I U3!!! &1 'I \ Il FIGURE 36 Spraying Inside Corners Courtesy of DeVilbiss Company 9. Comparison of Spray Methods Figure 31 demonstrates the advantages of airless and heated spray. 10. Electrostatic Spray Portable electrostatic spray units are ideal for spraying odd-shaped metal objects like wire fence, angles, channels, cable and piping. These units produce a very high electrostatic charge, up to 60,000volts, which causes sprayed paint to coat all exposed conductive areas more uniformly, including edges and areas opposite the object (the wrap-around effect). Portable units use a transformer that can operate on 115 v (Figures 31, 32). The method has not yet been adapted for use on exteriors of large steel structures. It has a number of advantages and disadvantages vs. conventional spray equipment. Advantages include (a) complete coverage of odd shapes; (b) lowest paint loss of all spray methods; (c) less overspray; (d) very uniform finish. Its disadvantages include (a)vulnerable to wind; (b) equipment expensive; (c) formulation critical; (d) slower operation; (e) only thin coats can be applied; (f) possible shock hazard; (9) expensive servicing; and (h) as yet unsuitable for LARGE steel structures. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from
IHS 164
SSPC CHAPTER*5-3 93 = 8627940 0003632 794 -* Li 1 . 13 I &ofnew 15, r11-MANCHESTER -II9 INSTRUMENTS LTD ENOLAM , 21, 7 3 FIGURE 37 Wet Film Thickness Gage Courtesy of Gardner Laboratory, Inc. 11. Two Component Spray Guns These are special guns that enable the use of twocomponent coatings, which have very short pot Iives. THICKNESS FIGURE 38 Elcometer Dry Film Thickness Gage Courtesy of Gardner Laboratory, Inc. They are either made of two guns attached or a single gun with the two components mixed together while they are sprayed. In both types, separate hoses are used and no mixing takes place until the two spray streams merge just beyond the nozzle. This prevents reaction of the two components within the equipment (Figures 33, 34). 12. Spray Technique The procedure for spray painting varies slightly for each type of spray equipment and type of paint. The following description for conventional air spraying is essentially similar for all. FIGURE 39 Inspector Dry Film Thickness Gage Courtesy of Gardner Laboratory, Inc.
a. Paint Viscosity -Adjust paint viscosity only when necessary, and follow the manufacturer s instructions. Excessive thinning results in more overspray, sagging, insufficient film thickness, insufficient hiding and inadequate protection. b. Air Pressure -Always use the lowest air pressure that produces the desired finish. Excessive pressure will increase overspray. It may be necessary to increase pressure when paint is viscous or the hose is longer than normal. With conventional spray, turn off the atomizing air valve and adjust the paint valve at the pot to achieve a solid stream of paint about 24 inches from the gun. Gradually open the air valve to achieve the desired finish. c. Spray Pattern -Conventional spray guns enable an adjustment of the spray pattern by turning the air control valve. Turn it clockwise for a round pattern and counter clockwise for a fan pattern. With airless spray guns, the pattern can be adjusted by changing the tip or adjusting the Adjusta-Tip. d. Spraying Technique -To achieve desired coverage with a uniform coating with no sag, hold the gun at the following distance from the work: Conventional -6 to 8inches Airless -10 to 12 inches Holding the gun too close will cause sagging and irregularities in the film from spray pressure. If it is too far away, the result will be dusting . Some solvent will evaporate before paint reaches the surface creating virtually dry paint particles which cannot flow to the surface. The gun must be perpendicular to the surface at all times and should never be tilted. Tilting will cause one side of the pattern to be closer to the surface than the other side, causing non-uniform coating. Use a free-arm motion, pulling the trigger after beginning the stroke and release it just before the end of the stroke. Move in a straight line, parallel to the surface. Stop 1 to 2 inches from the edge. When spraying an outside corner, hold the gun facing the edge of the corner, then sweep along the corner to cover both sides. On inside corners, spray each side separately, sweeping along the corner. Apply the paint to all edges prior to painting the entire surface (Figures 35, 36). When painting a large area, start at the top corner and spray to the end of the top area, (except for the edge), then return, overlapping the first area just enough to form a uniform coating. With conventional spray this will be almost half of the first pattern, but with airless spray it will be slight. When spraying horizontal surfaces, start at one side of the near edge and spray to the other
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SSPC CHAPTER*S-L 73 6627740 0003b13 b20 W side of the near edge, then reverse direction work- ACKNOWLEDGEMENT ing away from the near edge. 111. FILMTHICKNESS To do the job correctly, it is necessary to apply each coating at the wet film thickness recommended by the paint manufacturer. A practice area is recommended. Measure the film thickness as the job progresses using a wet film thickness gage (Figure 37). When each coat has dried, use a dry film thickness gage to check the actual thickness of the number of coats applied versus the required thickness. This requirement is most important for the complete system (Figures 38 and 39). Also see chapter on inspection. IV. CLEANUP All paint application tools and equipment must be carefully cleaned. Dried paint in the equipment will ruin it. Remove as much paint as possible. With solvent paints, clean thoroughly with a compatible solvent. Use a detergent solution with latex paint. Clean two or three times with fresh solvent (or warm mild detergent solution), then wipe clean and dry. Well cleaned tools and equipment will last longer and always be in prime condition. Be sure to clean brushes down to the heel, since paint tends to dry in this less visible area. This can make the bristles shorter and less flexible. After washing, twirl to remove excess water and comb to straighten the bristles. Finally, wrap in paper or place in a brush keeper and lay flat until dry. Never allow a brush to rest on its bristles. This can cause permanent damage. If a roller is used, clean and wash the paint tray and partially fill it with solvent (or mild detergent in water for latex paints). Work the roller out on newspaper until most of the paint has been removed. Then work in the solvent (or detergent) and roll on the tray ramp until worked in. Again roll out on newspaper until all the solvent is removed. Repeat twice with clean solvent or detergent. Take care to discard the paper used to clean the roller because of potential fire hazard. Stand roller on one end until dry. Since some roller covers are relatively inexpensive, it may be more economical to discard them (keep the handle). Using a large container, wash the paint mitt used for solvent paints in three changes of solvent or warm mild detergent depending on the type of paint. The solventcleaned mitts should then be washed in mild detergent
solution. Rinse in clear warm water, then hang up to dry. Place clean solvent (or detergent solution) in pots and pass through hoses and spray guns. Be sure to remove the tip from airless spray guns and wash separately. Never immerse the gun in solvent because this can ruin the packing. Clean with three changes of solvent (or detergent). Then dry. When cleaning after spraying water-based paint, be sure to finish rinsing with a water miscible solvent, such as alcohol. Otherwise, some parts of the spray equipment may rust. Make sure that all hoses are flushed thoroughly. The authors and editors gratefully acknowledge the active participation of the following in the review process for this chapter: Earl G. Anderson, AI Beitelman, Alex Chasan, John B. Conomos, Lawrence Drake, Arnold J. Eickhoff, Raye A. Fraser, J. Roger Garland, Dan Gelfer, Tom Ginsberg, Russ Harmon, Leonard Haynie, Robert L. Hooker, R. Kramer, Jay Leanse, Joseph Mazia, Marshall McGee, John Montle, Clint Ryno, Melvin Sandler, L. M. Sherman, Henry Stoner, Verne J. Todd, Ted Tomlin, William J. Wallace, Duane T. Werkman, Virgil P. Williams, Rufus Wint, and Joseph E. Ziegeweid. REFERENCES 1. Paints and Protective Coatings, Army TM 5-618,Navfac MO-110,Air Force AFM 85-3, US. Government Printing Office, Washington, D.C. 2. S.B. Levinson, Painting , Facilities and Plant Engineering Handbook, McGraw Hill Book Co., N.Y., N.Y. 3. S.B. Levinson and S. Spindel, Recent Developments in Architectural and Maintenance Painting, Federation of Societies for Paint Technology, Blue Bell, PA. 4. R.H. Reynolds, N.W. Karr, K.Buss, PDCA Craftsman Manual and Textbook, Painting and Decorating Contractors of America, Fairfax, VA. 5. All About Painting Tools, American Brush Manufacturers Association, Philadelphia, PA. 6. Equipment Selection for the Painting Contractor, Binks Manufacturing Co., Franklin Park, 111. 7. Airless Spraying, Binks Manufacturing Co., Franklin Park, 111. 8. The ABC S of Spray Equipment, The DeVilbiss Co., Toledo, OH. 9. Spray Gun Motion Study, The DeVilbiss Co., Toledo, OH. 10. Spray Painting Guide Thomas Industries, Sheyboygan, Wisc. 11. Surface Preparation and Application Guide, Tnemec Co., Kansas City, MO. 12. Safety Precautions for Use of Airless Spray Equipment, Civil Engineering Laboratory, Naval Construction Battalion Center, Port Hueneme, CA. 13. W.F. Gross, Applications Manual for Paint and Protective Coatings, McGraw Hill Book CO., N.Y., N.Y. 14. C.R. Martinson and C.W. Sisler, Industrial Painting, the Engineered Approach, Reinhold Book Corp. 15. Contract and Plant Force Painting, Advantages and Disad-
vantages, Materials Protection, Vol. 7, No. 2, pp 39-42,Feb. 1968. 16. How ,to Pick a Paintbrush, Popular Mechanics booklet. 17. How to Use a Paintbrush, Popular Mechanics booklet. 18. How to Care for a Paintbrush, Popular Mechanics booklet. 19. Preserving Quality Paintbrushes, PDCA, July 1972,Painting and Decorating Contractors of America, Fairfax, VA. *Completely non-rusting spray equipment should be used with water-base paints to prevent rusting. Try to leave the solvent in the system when possible to avoid build-up of paint in the hose. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 166
SSPC CHAPTER+S=L 73 8627740 0003bL4 567 20. Paint Brush Buyers Guide, American Brush Manufacturers Association, Philadelphia, PA. 21. E.G. Anderson, Those Costly Paint Brushes, Caring for Your Investment, PDCA, Nov. 1975, Painting and Decorating Contractors of America, Fairfax, VA. 22. Roller, Kit, Paint, Federal Specification H-R-5506, General Services Administration, Washington, D.C. 23. Volume II, Steel Structures fainting Manual. 24. fainting and Decorating Encyclopedia, Homewood, 111. BIOGRAPHY For biographies of Sidney U.Levinson and Saul Spindel, see the chapter on Paint Materials. --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 167
SSPC CHAPTER+5.2 93 8627940 0003635 4T3 CHAPTER 5.2 SCAFFOLDING by Sidney B. Levinson and Saul Spindel Some type of support or extension must be used when painting operations are beyond normal reach. Often these operations can be accomplished with extension poles with paint rollers or extension spray guns. Extension devices are not feasible during surface preparation, nor are they effective much beyond 20 feet. Consequently, some type of support or rigging must be used. Although they provide access to otherwise unreachable areas and improve efficiency, their use also introduces hazards that must be recognized and prevented. I. TYPES OF SUPPORTS The two major types of supports are Ground supports: Supports or supporting systems that rest on the ground or roadway, e.g., on a bridge. Aerial supports: Rigging supported from above or attached to the steelwork. A. GROUND SUPPORTS The most common ground supports are ladders and scaffolding. However, portable and self-propelled systems are available. These may be much more efficient, depending on the job. 1. Ladders There are three types of ladders: step ladders, straight ladders and extension ladders. Ladders are made of wood, aluminum or fiberglass. Wood ladders are sturdy but heavy and subject to rot, especially if stored in damp areas. Aluminum ladders are lighter but electrically conductive and subject to corrosion. Therefore, aluminum ladders should never be used near sources of electricity, nor should they be stored or used in corrosive environments. Fiberglass ladders are light, safe from electric shock and resistant to corrosion. 2. Step Ladders These are made of two straight ladders hinged at the top so they are self-standing when opened and locked in place. Although higher ladders are available, no ladder higher than 12 ft, when opened, should be used. Stepladders are not as sturdy as straight ladders resting against a structural surface, and should be used only at relatively low heights. 3. Straight Ladders Straight ladders are available in lengths up to
about 24 feet. They are used when working at low to intermediate heights. Extension Ladders The most common type of extension ladder is made of two or three straight ladders connected so they can be adjusted in length from that of a single ladder to the combined length, less about 3 feet of each that overlap. They are available up to 48 ft in two sections and 60 ft in three sections. Special Ladders Ladder modifications are available to make these ladders more useful: a. Double Stepladder: The ladder has steps on both sides so that either side can be used. b. Combination Step-fxtension Ladder: The same ladder may be used either as a step or extension ladder. However, its height is limited to about 8 ft when used as a stepladder and 14 ft when used as an extension ladder. c. Trestle Ladder: A double stepladder has a center vertical section, which can be raised to support a horizontal plank or trestle. The maximum height available is about 20 ft. The use of a trestle ladder on each side of a plank provides a stable support. Ladder Accessories The following accessories make ladders more useful and safe: a. Ladder Jacks: These lightweight folding jacks hook onto the rungs of the ladder and support trestles or planks. b. Planks and Stages: Planks and stages, usually made of aluminum to decrease weight, rest on the jacks. They are available in size from 8 ft x 12 in. to 39 ft. x 28 in. c. Work Platform: A one-man platform can be attached to rungs of the ladder enabling work in comparative safety (Figure 1). d. Cable Hooks: These are attached to the end of the ladder and can be hooked onto a cable or any projection on the structure to improve ladder stability. e. Pole Straps: The top of the ladder can be rested against or strapped to a vertical pole, piping or beam. f. Pail Shelf: A working shelf can be hooked onto the ladder rungs. g. Ladder Shoes: All ladders should have special shoes attached to the legs to prevent slipping. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 168
SSPC CHAPTERr5.2 73 = 86277LiO 0003636 33T --`,,,,`-`-`,,`,,`,`,,`--Ladder Platform 7. Scaffolding Built-up or portable scaffolds are much safer than ladders. They also make work easier and faster. There are two major types: stationary scaffolds and portable scaffolds or lifts. 8. Stationary Scaffolds Scaffolds were formerly constructed of wood at the site. New types, based on use of metal tubular construction, are faster to erect, safer and more economical since scaffold units can be used again with no danger of splitting or waste. Scaffolds are usually constructed of specially designed aluminum, or high strength (electrically welded) galvanized steel tubing, connectors and accessories. They are easily assembled to almost any shape and height. They can be adjusted to create a horizontal work surface on a stairway but can be made narrow enough to be moved through a doorway. Ladders and stairways can also be constructed as part of the unit, eliminating the necessity of using portable ladders. 9. Stationary Scaffold Accessories The following accessories improve the usefulness and safety of these scaffolds. a. Decks: These may be made of plywood, aluminum or expanded metal. They can be hooked onto horizontal frame members to form the work floor and add to the rigidity of the scaffold. They are available in lengths up to 10 ft and widths of 24 in. or more (Figure 2). b. Outriggers: These are adjustable and attached to high scaffolds to increase stability by increasing base dimensions. c. Locking Casters: These make the scaffold a portable unit, if desired. They must be locked in place while painting. IO. Portable Support Systems With some jobs it is possible to use a selfcontained ground or roadway support system. If this can be done, the time saved can be considerable. There are two major types: boom lift and scissors lift. Either may be self-contained and propelled up Two Stow Scaffold with Casters Courtesy of Perry Mfg. Co. 169 Copyright The Society for Protective Coatings Provided by IHS under license with
SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*5-2 73 m 8b27740 O003637 276 m FIGURE 3 Hydraulic Boom Lift -Self Propelled Courtesy of JLG Industries to 3 mph for job-site mobility, or they may be mounted on a truck for mobility. a. Boom Lift: The one-or two-person boom lift, often called a cherry picker, is very fast and versatile. It is self-contained and can be driven or towed from job to job. Units are available that support up to 2,000 Ibs at heights up to 85 ft, and even greater loads at heights up to 45 ft. They work at almost any angle horizontally, and some work at angles well below and up to 75" above the level of the truck. The boom is usually lifted hydraulically, but some are articulated in two booms to avoid obstructions. Their major limitation is the work area, which usually is large enough for only two people. This is compensated for by manueverability (Figure 3). b. Scissors Lift: The lift is raised from the chassis either hydraulically or electrically. The work area is as big as 6 ft x 13 ft, larger than a boom lift. It can be moved only vertically, limiting its utility. Some units carry a load of up to 4,000 Ibs at up to 40 ft (Figure 4). 11. Power Source The vehicle carrying a boom lift or scissors lift may be operated by a variety of engines, depending on the type of work required. Gasoline, diesel fuel, propane or electrical units are available. Some scissors lifts are mounted on portable trucks that can be moved by other power sources. 12. Rigging Systems It is often necessary or expedient to support the work platform from above rather than below. This is especially true when the work is too high to be reached with ground supporting systems, e.g., above 80 feet. There are two major types: cable supported units and suspended scaffolds and st aging. a. Cable Supported Scaffolds: These scaffolds are suspended by one or two lifts which, in effect, ride up or down a cable suspended from above. The lift is operated by a worker riding the support and can be raised or lowered at will. FIGURE 4 Scissors Lift -Self Propelled Courtesy of Fulton Industries Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from
IHS 170
SSPC CHAPTER*5.2 73 m 8627740 O003638 LO2 W FIGURE 5 Bosun Chair-Air Drive Courtesy of Sky Climber b. Operation: Three methods of operation may be available: Manual: Hand manipulated ropes are used. Electric: Either 110 or 220 volt motors are used. Some units enable changing from one to the other, depending on current available at the site. Air Motor: The air may be obtained from the compressor used for blast cleaning or spraying (Figure 5). Some motors enable change of speed up to 30 FPM, depending on the load. There are some systems with no limit to the height of the cable since the cable of these units runs through the hoist assembly. c. Supports:The support used depends on the curvature of the surface to be painted. Three general types are used: Bosun s Chair: This chair holds one person and is used where only one person can operate. The worker has full control of the operation but has no room for any special equipment. Equipment must be tied to the chair (Figure 5). Single Point Stage: This support, also called a work cage, which also rides on a single cable, can be made small enough to allow only one person to stand or even small enough to pass through a 20 in. opening, e.g., in a tank. Addition of sections on each side widen the cage, enabling two men to work comfortably (Figures 6 and 7). Swinging Scaffold: This is also called a power scaffold. It is usually supported by two cables, one at each end, and can be as large as 39 ft x 28 in. (Figures 8 and 9). Extendible Scaffold: Some scaffolds can extend beyond 40 ft. Swinging Platform: The use of four cables, one at each corner, allows the use of large working platforms (Figure 10).
d. Suspended Scaffolds: Suspended scaffolds are often used beneath structures to be painted, e.g., a bridge or overpass. Supports with flat horizontal bars are attached to the bottom flanges of the overhead beams. Sometimes, wheels are attached to these supports to enable the scaffold to be moved along the beam without dismantling. The scaffold planks rest on and are attached to the horizontal bars of the supports (Figures 10 and 11). II. CHOICE OF SUPPORT OR RIGGING The choice of supports depends on a number of considerat ions: The construction steel to be painted, e.g., tank, building, bridge, overpass, cables, etc. Difficulty in getting to the work surface and moving --`,,,,`-`-`,,`,,`,`,,`--from one area to another. FIGURE 6 One Man Work Cage Under Bridge Cable Courtesy of Spider Staging Sales Co. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 171
SSPC CHAPTERx5.2 93 = 8627940 0003619 049 The height of a structure above flat ground or highway. The relative cost-effectiveness of the support. Often it is more economical to use mechanical devices instead of labor to install support systems. However, the initial and operating cost of some mobile equipment is very high and warranted only when it can be used extensively. 111. SAFETY Because support systems are dangerous, proper precautions are of the utmost importance, especially with mob¡ le equipment. Follow equipment manu fact urers instruction and comply with federal, state, and local safety codes. Also see safety references 1, 4, 5,6,8, and 9 at the end of this chapter including SSPC-PA Guide 3 Guide to Safety in Paint Application, Volume 2, Steel Structures Painting Manual. A. STATIONARY SUPPORTS The following precautions apply to scaffolds: 1. Use galvanized steel, high carbon steel or aluminum tubing of equal strength in diameters up to 2 in. 2. Inspect all sections before use. Reject any defective or rusty parts. 3. Place supporting members on firm, rigid, smooth FIGURE 7 One Man Work Cage on Water Tank Courtesy of Spider Staging Sales Co. FIGURE 8 Swinging Scaffold Courtesy of Spider Staging Sales Co. sills or underpinnings. The upright legs must be plumb and securely braced to prevent swaying. Use cross bracing as required by law. 4. Anchor scaffolds to the structure if possible. If independent of the structure, guy Scaffolds at intervals no more than 25 ft horizontally and 15 ft vertically. Use horizontal diagonal bracing at the bottom and every 25 ft in height. 5. Provide guard railings 42 in. high, regardless of height, on the full length and the ends of the scaffold along with mid-rails where required. They should be made of tubular fittings, not cable or rope. 6. Provide access ladders to all work areas. 7. Be sure that all planking is of correct grading and at least 18 in. wide. Make sure it is fastened in place and will support the load with no significant deflection. Add supports at the center of the plank, if necessary. Test by using twice the anticipated load.
8. Keep scaffolds as dry as possible and free of any material or equipment that will make them slippery or unsafe. 9. Do not climb on the braces. 10. When using scaffolds, never over-reach or stretch beyond the unit s limits. Move the unit to get to another location. 11. Avoid operations within 10 ft of a power line, unless it has been shut down. 12. Do not ride on movable scaffolding while the unit is in motion. 13. Casters on movable scaffolds should be at least 6 inches in diameter and must have breaks. Lock the casters when the scaffold is stationary. 14. Do not attempt to move the scaffold without sufficient help. B. PORTABLE SUPPORTS lifts: The following precautions apply to boom and scissor I. Allow only authorized and trained personnel to --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 172
7. Set jacks on a firm surface or use shorings on a soft surface. 8. Be sure there are no obstructions, personnel or equipment in the way before extending the boom or moving equipment. 9. Never use a boom as a crane. Do not exceed the --`,,,,`-`-`,,`,,`,`,,`--SSPC CHAPTER*5*2 93 8627940 0003620 860 = operate the equipment. 2. Never operate a malfunctioning machine. 3. Inspect the equipment completely before use. 4. Do not move the machine unless the lift is down and locked in position and all outriggers and jacks have been retracted. 5. Avoid tipping the machine when moving over grades. 6. Do not operate the lift until the machine is stable and any outriggers or jacks are fully extended until they are in contact with the ground. Chock the wheels. FIGURE 10 Swinging Platform Courtesy of Spider Staging Sales Co. rated capacity of the lift. 10. Never stretch or over-reach beyond the side of the boom or scissor lift. 11. Post a lookout when reversing direction or when the user s view (on a boom) is obstructed. 12. Always keep your attention on the direction of travel of a boom. 13. Maintain a distance of at least 10 ft from power lines. 14. Do not allow personnel to go underneath a raised lift. 15. Keep the platform deck clean and free of oil, mud or any slippery substance. 16. Use extreme caution when entering or leaving the platform. Use the gate and be sure the platform is no more than one foot from a secure structure. Do not walk or climb the boom or scissors to do so. 17. Do not attach any cable to the platform. 18. Do not use a ladder on the platform to reach a higher elevation. Keep both feet on the deck. 19. Shut off all power controls before making any adjustments on the equipment. 20. If towing a mobile, but not self-propelled lift, keep speed below 10 mph. Do not tow on highways. C.RIGGING The following precautions apply to cable-operated rigging: 1. Always read instructions before use. Be sure equipment is in good operating order. Stay below rated
capacity of the rig. 2. Stages, except when necessary to pass through a FIGURE 9 manhole, should be at least 27 in. wide. Swinging Scaffold on Bridge 3. Check cable before use. Apply twice the rated loa d, Courtesy of Spider Staging Sales Co. lift about 1 ft above ground. Note any slip page. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 173
SSPC CHAPTERb5.2 93 m 8b27940 0003621 7Tï m FIGURE 11 Suspended Scaffold under Highway Courtesy of Spider Staging Sales Co. 4. Equipment should have free-fall safety devices as D. SUSPENDEDSCAFFOLDS well as manual controls, in case of power failure. The machine should be worm-geared and powered folds: The following precautions apply to suspended scafin both directions. It must not move when the power is off. In addition to the normal brake, power 1. Inspect all equipment ca refully before use. driven units must have an emergency brake that 2. Working surface must be at lea st 27 in. wide. operates automatically when normal descent 3. Guard rails shall be placed on eit her side of the speed is exceeded. scaffold, at about 42 and 20 in. with 6 in. high toe 5. Guy or brace suspended scaffolds to prevent sway- boards at toe level along i ts entire length and either ing. end. 6. Suspended scaffolds should have a guard rail (app. 4. Wear a safety belt at a ll times when working on a 42 in. high), an intermediate and toe rail along the scaffold. It should be atta ched to a lanyard and entire length on both sides and at both ends. fall-prevention device that is att ached to a lifeline. 7. Wear a safety belt at all times when using rigging. 5. Do not over-reach the side of the guard rail. The belt should be attached to a lanyard and fallprevention device attached to a lifeline. ACKNOWLEDGEMENT 8. No more than two men should work on a stage or The authors and editors gratefully acknowledge the active scaffold designed for a working load of 500 Ibs, and participation of the follow ing in the review process for this no more than three men should work on a scaffold chapter: AI Beitelman, Richard C. Bower, Alex Chasan, Lowell designed for a 750 Ibs working load. 9. Don t over-reach or stretch beyond the rigging s sides. Hartman, Cletus Junk, Paul Knobloch, Robert C. Kramer, and Mark Patterson. 174 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS--`,,,,`-`-`,,`,,`,`,,`---
SSPC CHAPTER*5-2 73 = 8627740 0003622 633 Others contributing to this chapter are listed under the illustrations and in the Reference section. REFERENCES 1. Operation and Safety Handbook , JLG Industries Inc., McConnellsburg, PA. 2. Paints and Protective Coatings , Army TM5-618, NAVFAC MO-110, Air Force AFM 85-2, Government Printing Office, Washington. D.C. 3. S.E. Levinson and S. Spindel, Recent Developments in Architectural and Maintenance Paintings, Federation of Societies for Coatings Technology, Blue Bell, PA. 4. PDCA Craftsman Manual , Painting and Decorating Contractors of America, Fairfax, VA. 5. Safety Requirements for Suspended Power Scaffolds , Scaffolding i3 Shoring Institute, Cleveland, OH. 6. Scaffolding Safety Rules , Scaffolding, Shoring and Forming Institute, Cleveland, OH. 7. Spider Staging , Spider Staging Sales Co., Renton, Wash. 8. Safety Requirements for Scaffolding , American National Standards Institute, New York, N.Y. 9. SSPC-PA Guide 3 A Guide to Safety in Paint Application , SSPC Manual, Volume 2. BIOGRAPHY For biographies and photos of Sidney B.Levinson and Saul Spindel, see Chapter 4.1, Paint Materials . --`,,,,`-`-`,,`,,`,`,,`--175 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*5.3 93 m 8627940 O003623 57T W September 1993 (Revised) CHAPTER 5.3 SAFETY IN PAINT APPLICATION by Sidney B. Levinson and Saul Spindel I. INTRODUCTION Every painting job exposes personnel to conditions and situations that represent actual or potential danger to themselves and others in the immediate area. The products and equipment used always present a potential hazard. The nature of the environment, for example the inside of a tank, represents a hazard in itself, or the hazard may be caused by operator carelessness or lack of information. If supervisory personnel and workers are always aware of potential hazards, they minimize risks and improve morale and efficiency. This chapter describes in general terms some typical hazards painters are exposed to and precautions that can be taken to minimize risks. It is not intended to provide specific answers to specific questions of safety that arise on painting jobs. Detailed guidance is available from a qualified safety engineer or industrial hygienist, and from publications listed in the reference section at the end of this chapter. Each SSPC specification has a section on safety, and SSPC-PA Guide 3 presents a safety checklist. II. KINDS OF HAZARDS Painters are subject to many kinds of accidents: electric shock, falls, suffocation, explosion, falling objects, inhalation of solvent or other chemicals and fire. in addition to accidents, hazards to health can result from using toxic materials. Typical examples follow. A. SURFACE PREPARATION Equipment and materials used for surface preparation can be hazardous if used carelessly. 1. Blast Cleaning Without proper precautions the high pressures used in blast cleaning can cause injuries. The extremely high pressures associated with water blasting can cause serious injury if not treated with respect. Abrasive materials may cause harm at high or even moderate pressures, and continuous exposure to the dust may result in lung disease. 2. Steam Cleaning The high temperatures and pressures reached during steam cleaning can be very hazardous but are quite safe if handled properly. 3. Paint Removers
Paint removal compounds may contain toxic and dermatitic solvents or highly acid or alkaline compounds. Some also are very flammable. 4. Cleaning Solvents Cleaning solvents may be toxic if vapors are inhaled, may be dermatitic if allowed to remain on the skin, and may be flammable. B. PAINT APPLICATION 1. Paint Materials Most paint solvents, many pigments and some binders are toxic. Essentially, all solvent-thinned paints also are flammable. However, most paint materials are quite safe if used with proper precautions. 2. Spray Equipment Paint application is carried out rapidly with pressure spray equipment. Airless spray equipment uses pressures that can be as high as thousands of pounds per square inch. This equipment can be extremely hazardous if handled carelessly. 3. Support Equipment Ladders, scaffolding, staging, work platforms, lifts, bosun chairs, and other support equipment may be used to reach inaccessible areas. Improper use, inadequate Set-ups, and defective parts may lead to serious accidents. 4. Environment Painting conditions may be more hazardous than anticipated, especially with solvent-thinned paints. Solvents can accumulate to dangerous levels within an enclosed area. Other hazards are always present, such as support equipment and mechanical equipment in the work area. Local contaminants may also be present. C. DEGREE OF HAZARD Risks faced in any paint job vary considerably, depending on the job location and the materials and equipment required. Painting a bridge railing at street level presents a relatively minor hazard, but using an airless spray on a scaffold suspended 100feet in the air or preparCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 176
SSPC CHAPTER*5.3 73 8627940 0003624 406 ing the surface inside an enclosed area may present a much more serious hazard. It is important to be aware that hazards exist. Proper precautions must be taken to reduce the possibility of an accident or over-exposure to solvent vapors. D. PAINTING CREW There is an element of risk even with well trained workers. However, lack of training, inexperience or inadequate knowledge of hazards by any painter can result in a threat, not only to himself but to other workers in the painting area. No safeguard can guarantee safety where there is ignorance or carelessness. Thus, every worker must be made aware of all hazards and the proper precautions necessary. Short cuts should be avoided because time saved will very often be more than lost if one accident occurs. Safety schools are recommended. 111. SAFETY MEASURES A. GENERAL A continuous and enforced safety program is mandatory to provide protection against potential hazards. All personnel must be made aware of hazards and the precautions against them. Disregard of any safety measure increases the potential danger and the odds that an accident will occur or health will be impaired because of excessive exposure to an unsafe environment or situation. B. GENERAL HEALTH, SENSITIVITY AND ATTITUDE All personnel should be in good health and required to have a periodical physical checkup. Illness increases susceptibility to health hazards. Anyone sensitive to paint materials should avoid the use of cleaning solvents and paint removers and should use less irritating paints, ¡.e. the water-based types. Anyone sensitive to heights should not be allowed to work on elevated structures or equipment. Careless people should not be on painting crews. C. ENVIRONMENT The general environment and working conditions in any work area should be evaluated for hazards, and safety precautions should be taken before starting work. Before workers enter an area, they should be protected by whatever devices, procedures, or clothing are necessary to enable safe work in complete confidence. D. RESPIRATORY PROTECTION In hazardous areas workers must wear face masks or helmet respirators approved by the National Institute for Occupational Safety and HealthlMine Safety and Health Administration (NIOSHIMSHA). The degree of respiratory protection required depends upon the kind and concentra-
tion of contaminants that workers will be exposed to, as well as the duration of their exposure. To choose respiratory protection appropriate for a given contaminated environment, consult an industrial hygienist. Specifications for respirable air should be taken from FEDSPEC BE-A-1034. FIGURE 1 Abrasive Blasting Helmet Courtesy: SoGo-JOSafety Hood Co. Abrasive Blasting Helmet The helmet covers the head and shoulders. Ventilation is supplied by fresh air blowers so the worker is not exposed to abrasive media or dust. (See Figure 1.) Dust Respirator The face mask has removable cartridges that remove dust only. (See Figure 2.) Chemical Cartridge Respirator The face mask either contains removable cartridges or is connected to containers with activated carbon cartridges. The cartridges absorb solvent, chemical fumes and vapors. (See Figure 3.) Air Fed Helmet or Respirator This respirator is similar to but lighter than a blasting helmet because no protection against blast media under high pressure is needed. The respirator covers the head and shoulders and fresh air is pressure fed. It enables personnel to work in confined areas, such as tanks. (See Figure 4.) Air fed to the blasting helmets and air fed to respirators must be clean, dry and free of oil or carbon monoxide. A separate air supply should be used. Do not attach air respirators to the same supply of air as spray guns. Keep diesel engine exhaust at least 25 feet from compressor intake. Compressed breathing air should comply with FEDSPEC BB-A-1034. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 177
SSPC CHAPTERI5.3 93 8627740 0003625 342 FIGURE 2 Dust Respirator Courtesy: Mine Safety Appliances E. EYE PROTECTION Safety goggles should always be worn to reduce the possibility of dust, fumes, or water under pressure striking the eyes during surface preparation or paint application. Goggles are not necessary if a helmet is used. Safety goggles should fit well and allow adequate peripheral vision. F. PROTECTIVE CLOTHING Protective clothing should be worn whenever there is a chance of a hazard. Protective clothing includes: Coveralls -including fireproof clothing; Safety helmets (See Figure 3); Steel-toed safety shoes; Non-skidsoles when working in enclosed areas or where flammable vapors may be present; Acid-proof clothing when handling acid cleaning materials in enclosed area; Rubber gloves or plastic protection. Do not store protective clothing that is saturated with chemicals. It should be laundered or disposed of. G. BUDDY SYSTEM Never work alone in a hazardous area. At least two people should work in the same area, and one should be visible to the other at all times. This enables one to help the other in the event of trouble. FIGURE 3 Safety Helmet, Chemical Cartridge Respirator Courtesy: Mine Safety Appliances IV. HEALTH HAZARDS A. TOXIC MATERIALS Typical toxic materials are solvent vapors or dust from blast cleaning of spraying operations, which may enter the body by breathing, swallowing or even absorption through the skin. Symptoms of excessive ingestion or absorption include irritation of the nasal membrane, headache, dizziness, rapid heart beat, loss of appetite, nausea and fatigue. i.Solvenìs Most solvents are toxic to some degree, depending upon exposure. The degree of toxicity can be measured by the Threshold Limit Value (TLV), expressed as parts per million (ppm) of solvent to air, that an operator may be exposed to during an 8-hour working day with no ill effects. This varies
from a high of 1,000 for ethyl alcohol to a low of 50 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 178
= SSPC CHAPTER*5.3 93 W 8627940 0003626 289 FIGURE 4 Air Fed Respirator Courtesy: E.D. Bullard Co. for alcohol and as lowas for Orne glycol ethers. (See chapter entitled Paint Materials .) If permissible exposure limits, as determined by an industrial hygienist, are exceeded, then respiratory protection becomes necessary. 2. Pigments Some pigments are toxic. The most common contain lead, e.g., red lead, basic lead silico chromate, chrome yellow and chrome green. Precautions should be taken when applying or removing paints containing these pigments. 3. Binders A few binders are toxic to some degree if exposure is excessive. Typical of these are epoxies, amine hardeners, acrylics (not latex), polyurethanes and polyesters. Polyurethane paints that contain certain isocyanate compounds are strong sensitizers with very low permissible exposure limits. Once a person is sensitized and has an allergic he shouldnot be subject to further exposure to these vapors. 4. Additives .%?x? Paint additives, such as the organotin Or organomercurial comPounds used to fungicidal properties, are toxic if inhaled, absorbed through the skin, or ingested. B. DERMATITIC MATERIALS Dermatitic materials affect the skin. The skin becomes irritated and can become infected if left untreated. 1. Solvents Solvents have a tendency to dissolve and remove natural oils and fats from skin, leaving it dry, chapped and sensitive to infection. Aliphatic hydrocarbon solvents, such as mineral spirits, are not as irritating as stronger aromatic hydrocarbons or oxygenated solvents such as toluene, methyl ethyl ketone or especially methylene chloride, which is used in nonflammable paint removers.
2. Binders Some epoxy resins, amine hardeners, polyurethanes, solvent-thinned acrylics (not latex) and polyesters may also irritate the skin to some extent. 3. Other Chemicals The following chemicals are corrosive and must be handled with particular care. a. Paint removers and brush cleaners containing phenol. b.Acid and alkaline cleaners for surface treatment. c.The acid or catalyst component of wash primers . C.PREVENTION OF HEALTH HAZARDS The following precautions should minimize hazards. They describe a common approach to avoiding contact, * Use surface preparation techniques that minimize dust whenever possible. Consult the Material Safety Data Sheet provided by the manufacturer. Use the material in conformity with the manufacturer s directions. * Use ventilation, where possible, to keep exposures to airborne contaminants below the TLV. If this not possible, use respirators and other personal protective equipment recommended on the MSDS. Prohibit eating and smoking where ingestion of toxic materials is likely. Provide areas for washing before meals, and for showering and changing at the end of the shift. D. FIRST AID Keep a first aid kit available. It should be stocked with fresh materials. All personnel should be able to give emergency first aid. Any worker who becomes ill or is injured on the job should be examined by a doctor as soon as possible, regardless of the apparent seriousness of the injury. Some toxic materials do not take full effect for days. Report all Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 179
mishaps to the foreman or first aid station. OSHA material safety data sheets should be available for all materials used. V. GENERAL PRECAUTIONS A. SIGNS AND BARRIERS Use signs and barriers to isolate the work area and to warn against smoking, flames, etc. B. MANUFACTURER S INSTRUCTIONS Follow the manufacturer s specific instructions and precautions for the handling of his product or equipment. C. GOVERNMENT REGULATIONS Be sure that all safety requirements, equipment and supplies conform to all applicablefederal, state and local regulations. See Chapter 26.0 for more information on federal health and safety regulations. ACKNOWLEDGEMENT The authors and editors gratefully acknowledge the active participation of the following in the review process for this chapter: AI Beitelman, Alex Chasan, Lowell Hartman, Morris L. Hughes, Paul Knobloch, Ben Nieters and Preston Hollister. BIOGRAPHY Biographical sketches and portraits of the authors appear at the end of the chapter entitled Paint Materials . REFERENCES 1. Occupational Safety and Health (OSHA) Reference Manual , Painting and Decorating Contractors of America, Fairfax, VA. 2. PDCA Craftsman Manual , Painting and Decorating Contractors of America, Fairfax, VA. 3. Operation and Safety Handbook , JLG Industries, McConnellsburg, PA. 4. Safety Requirements for Suspended Power Scaffolds . Scaffolding, Shoring and Forming Institute, Cleveland, OH. 5. Scaffolding Safety Rules , Scaffolding, Shoring and Forming. Institute, Cleveland, OH. 6. Handbook of Organic Industrial Solvents , Technical Guide No. 6, American Mutual Insurance Alliance, Chicago, IL. 7. TLVs -Threshold Limit Values for Chemical Substances and Physical Agents in the Workroom Environment . American Conference of Governmental Hygienists, Cincinnati, OH, 1991. 8. Fire-Hazard Properties of Flammable Liquids , National Fire Protection Association, Quincy, MA. 9. How to Handle Flammable Liquids Safely , Justrite Manufacturing Co., Des Plaines, IL. 10. Safety Precautions for Use of Airless Spray Equipment , Civil Engineering Laboratory, Naval Construction Battalion Center, Port Hueneme, CA. 11. A Manual for Painter Safety , National Association of Corrosion Engineers, Houston, TX. 12. SSPC-PA Guide 3, A Guide to Safety in Paint Application Steel Structures Painting Manual, Vol. 2, 1991. Copyright The Society for Protective Coatings Provided by IHS under license with
SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*b.O 93 8627940 0003628 051 m September 1993(Revised) CHAPTER 6 INSPECTION bY Kenneth B. Tator and Kenneth A. Trimber An analysis of the reasons for premature coating failure -deterioration of a coating system resulting in rusting, pitting, chemical attack or other deterioration in most cases leads to a finding of either improper surface preparation or deficient coating application. While there may be potentially many other reasons for premature failure such as poorly written specifications, choice of the wrong coating or paint for a given environment, coating misinformation, or a service environment more severe than originally anticipated, it is estimated that approximately 75% to 80% of all premature coating failures are caused in whole or in part by deficient surface preparation andior coating appl ¡cat ion. It is said that a painter covers his mistakes. This is unquestionably true. Unfortunately, after the surface has been coated, it is exceedingly difficult to verify the adequacy of surface preparation -especially blast cleaning. Furthermore, without the use of appropriate instrumentation, it is impossible to determine coating thickness or, in many instances, even the number of coats applied. However, during the course of application, these items as well as many others that might affect the ultimate coating quality -can be readily witnessed and easily verified. Accordingly, formal coating inspection, following established guidelines or procedures, is mandatory on many large projects (such as nuclear power plants) and is often a requirement on smaller, critical applications such as tank lining coating work. Where the consequence of failure is expensive, the coated steel is inaccessible after erection or the magnitude of painting great, formal inspection can often be justified. It must be recognized that any inspection, even the most casual kind, is an expense. Even during the performance of the work, fundamental inspection requires time. Inspection, in its simplest form, occurs when a painter stops after a certain portion of his work is completed and examines it for adequacy. Has he missed any areas? Are there any runs or sags? Is the blast cleaning pattern uniform and the cleanliness adequate -or in the case of hand or power tool cleaning, are there any loose mill scale or rust deposits remaining? Formal inspection is more costly. Inspection procedures must be written, and the quality of work witnessed and documented on a periodic (often daily) basis. The inspector must have access to the work area, and be allowed sufficient time to complete his inspection work. Often this must be done at the expense of
continuing coating operations -and although other tasks can be done during the inspection period, the net result is that the more stringent the inspection requirements, the longer it takes to complete the coating work. The direct costs of inspection must be considered because the inspectors are specially hired, trained, and equipped with expensive instruments in order to verify the quality of the work. Accordingly, inspection is often considered as an insurance against the possibility of a highly expensive premature coating failure. The purpose of this chapter is to outline the inspections required to assure quality coating work. In addition, paint inspection equipment is described and summarized, including advantages and disadvantages, calibration and use. This chapter is presented in the chronological order of the inspection sequence beginning with pre-surface preparation inspections and continuing through final dry film thickness and holiday testing. Inspection of the paint itself is covered in the two separate chapters on quality control. I. THE FUNCTION OF THE COATING INSPECTOR Throughout this discussion the term inspector shall be used to indicate an individual or a group of individuals whose job it is to witness and document the coating work in a formal fashion. While informal inspection may be done by the painter, the painter s foremen, or other persons directly involved with the coating work, this type of inspection shall not be considered in the course of this discussion. The inspector s purpose is to ensure that the requirements of the coating specification are met. His function is analogous to that of a policeman: he enforces the rules (specification) without exception even if he deems them to be inadequate. The authorization to deviate from the specification is the responsibility of the judge, usually the specification writer, contract administrator, or engineer in charge of the job. The inspector certainly may venture his opinion and give recommendations to the engineer, but cannot unilaterally deviate from the specifications at the working level. Besides specification enforcement, a thorough coatings inspector provides a job documentation including a commentary on the type and adequacy of equipment at the jobsite, the rate of work progression, information regarding ambient conditions and controls, and
verification that the surface preparation, coating application, coating thickness and curing are as required. This is Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 181
SSPC CHAPTERUb.0 93 ab27940 0003b29 T98 supplemented with any other information he deems of consequence to the quality and progress of the work. The amount and type of inspection will vary according to the size of the project and the type of application contract. There are a number of types of contracts, but for simplicity two general categories, fixed price and costplus will be addressed. Inspection under a fixed price application contract may be oriented to ensure that the contractor does not cut corners in order to hurry the job. While an evaluation of the equipment, work procedures, and sequence, etc. is important, the equipment and methods by which the contractor accomplishes the job are essentially at his discretion, provided the requirements of the specifications are met. When performing inspection services for a costplus application contract, a knowledgeable inspector must be able to evaluate the contractor s equipment for adequacy and must be able to assess whether the rate of progress is reasonable. II. SAFETY CONSIDERATIONS Safety is paramount on any job. Coating inspectors should be aware of basic safety requirements. Although the inspector is not expected to be proficient in all safety codes and regulations, common sense should certainly prevail. If lighting, scaffolding, or equipment malfunctions present safety hazards, the appropriate safety personnel should be notified. Paint application inherently presents some dangers because the solvents used are flammable anù because many objects to be painted are relatively high or inaccessible. To paint these areas requires elaborate staging or the use of spiders or swing scaffolding for accessibility. The knowledgeable inspector will assure himself of the safety of these appurtenances before he becomes involved. Other safety concerns are addressed more specifically in SSPC-PA 3, A Guide to Safety in Paint Application and the chapter on Safety in this volume. 111. INSPECTION SEQUENCE Inspection often begins with a pre-job conference at which the ground rules are set. The inspector is responsi. ble for witnessing, verifying, inspecting, and documenting FIGURE 1 SLING PSYCHROMETER -used for measuring wet and dry bulb temperatures in order to establish relative humidity and dew point. The instrument is spun in the air to reach temperature stabilization. FIGURE 2 ELECTRIC PSYCHROMETER -utilizes a fan to draw air across thermometer bulbs, providing the wet and dry bulb temperature readings. the work at various inspection points. The following points
will be reviewed along with the appropriate instruments used for each. I. Pre-Surface Preparation Inspection 2. Measurement of Ambient Conditions 3. Evaluation of Compressor (Air Cleanliness} and Surface Preparation Equipment 4. Determination of Surface Preparation Cleanliness and Profile 5. Inspection of Application Equipment 6. Witnessing Coating Mixing 7. Inspecting Coating Application 8. Determination of Wet Film Thickness 9. Determination of Dry Film Thickness 10. Evaluating Cleanliness Between Coats 11. Pinhole and Holiday Testing 12. Adhesion Testing 13. Evaluating Cure IV. PREWRFACE PREPARATION INSPECTION Prior to the commencement of surface preparation or other coating activities, it may be necessary to inspect to determine if the work is ready to be prepared and painted. Heavy deposits of grease, soil, dust, dirt, cement splatter and other contaminants must be removed. Removal of such large oil and grease deposits prior to blast cleaning assures that they are not redeposited onto freshly cleaned surfaces. This removal is accomplished by following the steps outlined in SSPC-SP 1, Solvent Cleaning . This is particularly important when abrasive recycling, blast cleaning methods are used so that the abrasive itself does not become contaminated. Such contamination would be deposited onto any steel subsequently cleaned with the same abrasive. The specification may require that weld splatter be ground or otherwise removed and that sharp edges be rounded. Laminations in plate steel, if detected prior to blast cleaning, should be opened. If deep enough, they may require weld filling, and, if sufficient deterioration has occurred to the structure, replacement of some Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 182
SSPC CHAPTER*b.O 93 W 8627740 0003b30 70T FIGURE 3 DIGITAL HYGRO-THERMOMETER -gives instant readout of air temperature, relative humidity and dewpoint. structural members, fish plating or other repair may be necessary. Responsibility for such repair should be specified in procurement documents but is not ordinarily considered to be part of the coating contract. As a prelude to most painting operations, taping, masking and protection of adjoining surfaces not to be painted must be accomplished. NACE S Visual Comparator for Surface Finishing of Welds Prior to Coating, referenced by NACE RP O178, may be used for inspection. If the work involves maintenance painting, a determination of the percentage of rusting in an area will be helpful. It should be made in accordance with SSPC-Vis 2 Standard Methods of Evaluating Degree of Rusting on Painted Steel Surfaces . In addition, the coating type should be ascertained in order to assure compatibility with subsequently applied coats. Although there is no quick fool proof field method for determining the type of coating present on a structure, a chemical test series referenced by ASTM test method D 5043, based on work done by the US. Naval Civil Engineering Laboratory, is available for general field studies. Alternately, and perhaps best, is a test patch application of the new coating over the old, two weeks or more in advance of production painting. The test patch is then examined for adhesion, signs of wrinkling, lifting, or other evidence of incompatibility. A more conclusive approach is to send coating samples to laboratories for quick, inexpensive determination of generic type (by infrared spectroscopic analysis). 183 V. MEASUREMENT OF AMBIENT CONDITIONS While this is not specifically an inspection hold-point, it is implicit that surface preparation and coating work be done only under suitable ambient conditions of temperature, humidity, and dew point. For most catalyzed coatings, specific minimum temperatures must be met. Many zinc-rich coatings require certain minimum humidities as well. The inspector should be cognizant of weather forecasts, particularly if coating work is to be done outdoors. Other ambient conditions that might affect painting operations should be noted such as potential industrial or
chemical airborne contamination, water spray downwind from a cooling tower, leaking steam or chemical lines, and contamination from normal plant or adjacent operations. Often, a heater or dehumidifier is used to control ambient conditions for painting operations. Ideally, a heater should be indirect fired so it does not contaminate the surface with products of combustion. Ventilation, if required, should provide for sufficient air flow and adequate ventilation of all areas where work is being performed. Most solvents are heavier than air; thus, the dangers of explosion and flammability are greatest in low-lying areas. Control of airborne contaminants such as dust and abrasive must also be effective in order to prevent contamination. While much of the above is inspected visually with the acceptance criteria governed by safety requirements and common sense, the ambient conditions of air temperature, relative humidity, and dew point are determined using instrumentation. This includes psychrometers (Figures 1, 2, and 3) or instruments that give direct read-out recording of humidity (Figure 4) or dew point. Measurements with these instruments are taken before the work begins each day and periodically throughout the day. A suggested minimum frequency is every four hours, or sooner if weather conditions appear to be worsening. The psychrometer consists of two identical tube thermometers, one of which is covered with a wick or sock that FIGURE 4 RECORDING HYGROMETER -relative humidity and air temperature are recorded on strip charts to provide permanent daily or weekly records. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
FIGURE 5A FIGURE 5B U.S. WEATHER BUREAU TABLES -a book of tables for converting dry bulb and wet bulb temperatures to relative humidity and dew point. is saturated with water. The covered thermometer is called the "wet bulb" and the other is the "dry bulb". The dry bulb gives the ambient air temperature while the wet bulb temperature results from the latent heat loss of water evaporation from the wetted sock. The faster the rate of water evaporation, the lower the humidity and dew point. There are generally two types of psychrometers: the sling psychrometer, shown in Figure 1, and the fan or motor-driven psychrometer, shown in Figure 2. When using the sling psychrometer, the wet bulb sock is saturated with water, the instrument whirled rapidly for approximately 20 seconds, and a reading of the wet bulb quickly taken. The cycle is repeated (spinninglreading without additional wetting) until the wet bulb temperature FIGURE 6 SURFACE TEMPERATURE THERMOMETER -for establishing temperaturesof substrates during blast cleaning and painting. stabilizes. Stabilization occurs when three consecutive readings of the wet bulb remain the same. At this time both the dry and wet bulb temperatures are recorded. When using the fan-operated psychrometer, the wet bulb sock is saturated with water and the fan is started. Approximately two minutes are required for stabilization, and one need only observe the wet bulb thermometer and record both temperatures when the wet bulb temperature remains unchanged. FIGURE 7 DIGITAL THERMOMETER for direct readout of surface tempera ture. When the instruments are used in air temperatures less than 32 degrees Fahrenheit, the accuracy of the readings is questionable. The wet bulb thermometer will drop below the 32 degrees Fahrenheit temperature to a certain point (e.g. 27 degrees Fahrenheit) then "heat up" rapidly to the 32 degrees Fahrenheit freezing point. Quite often when using a sling psychrometer, this will take place during the whirling of the instrument; therefore, a wet bulb temperature of 32 degrees Fahrenheit may always be obtained. When using the motor-driven psychrometer, one can observe the wet bulb temperature drop below freezing, then rise rapidly to 32°F. However, the low value may still be incorrect. Thus if the temperature is below 32"F, the ambient conditions will have to be established by other means. This could be accomplished by obtaining the humidity on a direct read-out instrument using
sophisticated equipment or even inexpensive humidity indicators available for home use. The ambient temperature will still be obtained using a standard thermometer. These two values can then be used to determine the wet bulb and dew point temperatures by plotting out this information "in reverse" on the charts or tables described below. After the dry bulb and wet bulb temperatures are determined, a psychrometric chart or table is used to determine the relative humidity and dew point temperatures of the air. Charts require plotting the dry bulb and wet bulb temperatures on different lines and interpolating the relative humidity and dew point from their intersection. The US. Department of Commerce Weather Bureau Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 184
SSPC CHAPTER*b-O 93 8627940 0003632 582 Psychrometric Tables (Figure 5) consist of individual tables for relative humidity and dew point. To use the table, the wet bulb temperature is subtracted from the dry bulb temperature and the difference found along the top row of the table. The dry bulb temperature is found down the left column and the intersection of the two is either the humidity or the dew point, depending upon which table is used. Other tables, such as the U.S. Department of Commerce, NOAA-WSTA B-0-6E(5-72), Relative Humidity and Dew Point Tables , include the relative humidity and dew point on the same table. FIGURE 8 Nozzle Orifice Gage (right) measures nozzle orifice and indicates CFM of air required for the size. Hypodermic Needle Pressure Gage (left) measures air pressure at nozzle by inserting needle through sandblast hose. Dew Point is defined as the temperature at which moisture will condense. Dew point is important in coating work because moisture condensation on the surface will cause freshly blast cleaned steel to rust, or a thin, often invisible film of moisture trapped between coats may cause premature coating failure. Accordingly, the industry has established an arbitrary dew pointlsurface temperature safety factor. Final blast cleaning and coating application should not take place unless the surface temperature is at least five degrees Fahrenheit higher than the dew point. Although, theoretically, a surface temperature just infinitesimally above the dew point will not permit moisture condensation, the safety factor of five degrees Fahrenheit has been established to allow for possible instrument inaccuracies or different locations where readings are taken. Different field instruments are used for determining surface temperature. One of the most common is a surface temperature thermometer (Figure 6), which consists of a bimetallic sensing element that is shielded from drafts. The instrument includes two magnets on the sensing side for attachment to ferrous substrates. Two or three minutes are required for temperature stabilization of this instrument. Other field instruments for determining surface temperature are direct reading thermocouplelthermisters (Figure 7). These instruments have a sensing probe touched to the surface, resulting in a direct temperature FIGURE 9 SSPC VISUAL STANDARDS -Photographic reference standards for abrasive blast cleaned
steel. Color print standards illustrate four degrees of blast cleaning (SP7, SP6, SP10, SP5) over four rust grades of steel. readout. Only a few seconds are required for a temperature reading to st a bi Iize. With any of the instruments used for determining ambient conditions and surface temperatures, the readings should be taken at the actual locations of the work. For general readings, however, one should consider the coldest point on the structure because a surface temperatureldew point relationship problem will occur there first. Air and surface temperature considerations are also important to ensure that coatings are not applied outside of their temperature limitations -in areas too cool or too warm. Accordingly, readings for this purpose should be made at the coolest or warmest areas. Typical requirements for ambient painting conditions --`,,,,`-`-`,,`,,`,`,,`--are given in SSPC-PA 1. FIGURE 10 SURFACE PROFILE COMPARATOR -consists of a lighted magnifier and reference disc (shown) for visually comparing the anchor pattern of blast cleaned steel. Reference discs are available for sand, grit, or shot abrasives. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 185
SSPC CHAPTER*b.O 93 8627940 0003633 419 ment -the compressor should be appropriately sized and have a suitable volume to maintain the required air pressures. Equipment suppliers have charts and data available which are excellent aids for determining required sizes of compressors, air and abrasive lines, nozzles, and so forth. FIGURE 11 Keane-Tator Comparator in use to measure surface profile. Courtesy: KTA-Tator VI. EVALUATION OF SURFACE PREPARATION EQUIPMENT The air compressor and other equipment used for blastcleaning and any hand or power tools should be inspected. The inspector need not have an extensive technical background on the equipment, but should be familiar enough with it to determine its suitability. A brief summary is provided below, but more detailed information is available in the chapters on Surface Preparation in this FIGURE 13 volume and in the Commentary on Surface Preparation in DIAL SURFACE PROFILE GAGE -a depth micrometer that Volume 2. measures the depth oí valleys on the steel surface after blast cleaning. Courtesy: Elcometer, Inc. The compressed air used for blast cleaning, blowdown, and spray application should be checked for contaminants. Adequate moisture and oil traps should be used on all lines to assure that the air is sufficiently dry and oil-free so it does not interfere with the quality of the work. A simple test for determining air cleanliness requires holding a clean white piece of blotter paper approximately 18 inches from the air supply downstream of moisture and oil separators. The air is permitted to blow on the blotter paper for a few minutes followed by an inspection for signs of detrimental amounts of moisture or oil contamination on the blotter. Obviously, if there is no discoloration on the blotter, the quality of the air is excellent, while streams of moisture and oil running down the sheet indicate unsatisfactory air. Unfortunately, the point where good air becomes bad is difficult to determine. However, by use of the blotter paper (or a clean cloth, handkerchief, or paper), one can make his own judgments as to the air quality. A thorough FIGURE 12 TESTEX PRESS.O-FILM TAPE -used to make a precise reverse inspection of the surfa ce after blast cleaning for signs of replica of the surface profile, which is measured with a spring moisture or oil contamination should be made and these micrometer. results correlated with the results of the blotter test. In ad-
A. AIR COMPRESSORANDAIR CLEANLINESS dition, the proper functioning of in-line mo isture and oil traps can be evaluated on a comparative basis from the When an air compressor is used -for blast cleaning, results of the blotter test. For work requiring that absolutepower tool cleaning, or the operation of spraying equip- ly no moisture or oil b e permitted in the compressed air; Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 186
SSPC CHAPTER*b.O 93 = 8627940 0003634 355 C. ABRASIVE There is a great variety of abrasives available for blast cleaning. The size, type, and hardness of the abrasive have a significant impact on the surface profile and speed of cleaning. Steel shot and grit, because they can be recycled, are most commonly used for rotary wheel blast cleaning. Where permitted by law, sand is a very common abrasive for most field operations. Various slag abrasives, due to lesser hazards from silica, are also widely used, particularly in tanks, ship holds and other relatively confined areas. Sand and slag are disposable abrasives and should not be recycled, whereas most metallic abrasives, such as iron and steel shot and grit, aluminum oxide, and expensive abrasives such as glass beads can be recycled if fines, paint, rust and mill scale can be adequately separated from the abrasive stream. Metallic and nonmetallic abrasives are reviewed in detail in other chapters of this volume. It is most important that all abrasives be clean and free of moisture. Abrasives should be stored off the ground, protected from moisture and the elements. Only sand or slag that has been washed at the manufacturing and packaging plant should be used. The washing should be done using fresh water only; if brackish water is used, FIGURE 14 chloride contamination of the cleaned surface can result, ZAHN CUP -for measuring the viscosity of coatings prior to ap- with subsequent r ust bloom in humid environments. plication. Although there is no inspection apparatus for determining the cleanliness of the abrasive used, a visual oil-less compressors and sophisticated air drying equip- inspection must be made to assure that it is not damp or ment are available. contaminated. When abrasive recycling systems are used, a simple test for the presence of oil or grease contaminaB. BLAST CLEANING MACHINE tion should be made. Drop some of the abrasive (e.g. a teaspoon full) into a small vial of water (pill bottle size) and The blast cleaning machine mixes the abrasive with shake vigorously. Inspect the top of the water for a film of the air stream. The abrasive metering valve regulating the grease or oil which w ill be present if the abrasive is conflow of abrasive into the air stream is perhaps one of the taminated. Dirt and d ust in the abrasive can be assessed most overlooked but important considerations affecting in the same manner. Small abrasive fines will be held by the the the use
work rate. Generally, too much abrasive is injected into surface tension at meniscus, and a dirty abrasive will air stream, resulting in both decreased production and color the water or ca turbidity. However, water-soluble
increased abrasive costs. The machine should be contaminants such as salt will not be detected using this equipped for dead man capability so that it can be shut test. If water-soluble con taminants are present, a litmus down from the nozzle in the event the nozzle is dropped. It paper test of the wa ter in the vial will tell if they are acid or should also be equipped with moisture and oil separators, alkaline. If neutral, add a drop of 5% silver nitrate solution or external separators should be provided. Since the tank to the water. The form ation of a white precipitate will inof the blast cleaning machine is a pressure vessel, it dicate the presence of ch lorides. Alternatively, allow the should be constructed according to pressure vessel codes. water to evaporate and look for salt crystals. D. FORCED AIR AND ABRASIVE HOSES Sharp constrictions or bends in these lines should be eliminated, and they should be kept as short as possible to avoid friction and loss of pressure. For the same reason, internal couplings should be avoided. For safety purposes, the couplings should be wired together to assure secure closure, and the blast hoses should be equipped with FIGURE 15 static wire grounding. WET FILM THICKNESS GAGE -measures coating thickness during application by progressively deeper steps marked in mils. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 187
SSPC CHAPTERxb.0 93 8b27940 0003635 291 E. BLAST CLEANING NOZZLES AND NOZZLE PRESSURE A great variety of nozzle sizes, types, and lengths are available for cleaning purposes. The specific nozzle chosen will depend upon the specific cleaning job. Venturi type nozzles provide a higher abrasive velocity than straight barrel types of the same orifice size. In general, the longer the barrel, the larger the orifice and the faster the cleaning rate. Cracked nozzles and worn nozzles, even if not cracked, will reduce the rate of blast cleaning. As a rule of thumb, a nozzle that has been worn beyond 25% of its original inner diameter (I.D.) should not be used. A nozzle orifice gage (Figure 8) is available from equipment suppliers for determining the orifice size after use. The number etched on the nozzle housing indicates the size when new. Nozzles are designated in sixteenths of an inch. Therefore a Number 8 nozzle is equivalent to '12 inch. The amount of air pressure at the blast nozzle is a FIGURE 16 determining factor in cleaning rate production. The opINTERCHEMICAL WET FILM THICKNESS GAGE timum nozzle pressure is 90 to 100 psig. T he blasting air pressure should be determined at the nozzle rather than at the gage on the compressor because there will be pressure drops in the system due to hose length, bends, restrictions, blast pot, and moisture traps. Air pressure at the blast nozzle can be determined using a hypodermic needle air pressure gage (Figure 8). The needle of the gage is inserted through the blast hose as close to the nozzle as is practical. The direction of needle placement should be toward the nozzle. Pressure readings are taken with the nozzle in operation (abrasive flowing). At the same time, all other pneumatic equipment using the same compressor system must be in operation. FIGURE 17 F. ROTARY WHEEL BLAST CLEANING MIKROTEST MAGNETIC PULL-OFF DRY FILM THICKNESS EQUIPMENT GAGE -non-destructively measures the thickness of coatings applied to ferrous substrates. Many fabricating shops and painting sites are equipped with rotary wheel blastcleaning equipment in order to effectively prepare a surface for painting. The number of wheels directly affects the area that can be cleaned, and the type of structural shapes that can be cleaned. Adjustments can be made to direct the blast pattern from each wheel to the desired location in order to provide a uniform cleaning pattern. The rate of speed through the machine determines the degree of cleaning; the slower the material goes through the machine, the FIGURE 18 ELCOMETER 211 THICKNESS GAGE -operates on the same principle as the Mikrotest for non-destructive coating thickness FIGURE 19
measurements. ELEKTRO-PHYSIK PENTEST (Top) and ELCOMETER (bottom) PENCIL PULL-OFF GAGES. 188 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERWb-O 93 8627940 0003636 128 the abrasive used, the pattern and degree of prior rusting and numerous other factors unique to each project. As a result, jobsite standards are often developed to reach agreement. Sections of the structure (or test panels of a similar nature) are prepared and all parties involved ultimately select one of the panels or areas that is representative of the desired end result. A complete listing of available standards is provided in the Commentary on Surface Preparation included in Volume 2. FIGURE 20 COUNTERWEIGHT\ POSIPEN PENCIL PULL-OFF GAGE REFERENCEMARK greater the degree of cleaning. Details are given in the chapter on centrifugal blast cleaning in this volume. Complex structural shapes are particularly hard to clean using automated equipment. The interior of box girders, enclosed shapes, and shielded members can not be cleaned, unless cleaning is done prior to fabrication. In many instances, fabricators will employ handheld blast cleaning equipment in tandem with the automated equipment to reach the inaccessible areas. G.OTHER METHODS OF SURFACE PREPARATION Methods such as vacuum blast cleaning, water blasting with or without sand injection, wet blast cleaning, hand and power tool cleaning will not be discussed here. FIGURE 21 VII. DETERMINATION OF SURFACE PREPARATION CLEANLINESS AND PROFILE A. CLEANLINESS When a certain surface preparation method is specified, the intent is that it be employed over 100% of All surfaces should be inspected after surface the area, not just the readily ac cessible areas. preparation to assure compliance with the specification. Cleanliness after surfa ce preparation is also very imThe SSPC Surface Preparation Specifications describe the portant. Residual trace s of abrasive must be blown, swept, appearance of various types of surface preparation or vacuumed from the surface prior to prime coating. It is methods, percentage of the surface area to be cleaned, also important to ensure that dust is removed from the surtype of residues permitted to remain on the surface, and so face prior to painti ng, particularly the fine film of dustforth. It is important that this inspection be timely, in order like spent abras ive often held to the blast-cleaned surface to avoid any rusting of cleaned surfaces prior to priming. by static electricity
. Any scaffolding, staging or support The written definitions are supplemented by SSPC- steel above the area to be coa ted must be blown down and Vis-1-89, which photographically depict the surface appear- cleaned to prevent a brasive dropping onto the freshly ance of various grades of blast cleaning over four initial mill cleaned surface, or later contaminating the freshly primed scale and rust conditions of steel (Figure 9). The standards surface. Concurrent blast cleaning and painting should are visually compared with the prepared surface to determine not be permitted un less the blast cleaning is adequately the degree of cleanliness. Other visual standards for surface isolated to preven t contamination of the freshly painted cleanliness evaluation include the NACE coupons, and the surf ace. International Organization for Standardization (ISO) Stan-The surface profile sh ould also be measured or dards. Agreement on the desired appearance of a cleaned estimated. Note that the profile or roughness of a blastsurface using commercially available standards is often diffi- cleaned substrate is different than, but closely related to, cult to achieve because of shadows and hues caused by surface cleanliness. 189 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC c IAPTERxb.0 93 8b27940 0003b37 Ob4 D B. NSPECTING SUF FACES FOR SALT cor TAMIN AT1 ON An inspection of the surface may be required to determine if it is chemically clean, free of salt contamination. 1. Evaluating the Surface Two approaches are described. First, a review of existing conditions prior to or immediately after surface preparation can identify areas where contamination may be present. Second, one of several methods could be used to sample the surface after surface preparation so that the extent of salt contamination can be estimated. a. Review of Conditions-Existing conditions before surface preparation that would lead an inspector to suspect that salt contamination is present include: heavy rusting and pitting at locations where the coating film has broken down; heavy blistering of a lining, abuse of the structure by chemicals or salts, e.g., splash or spillage of chemicals and salts in an industrial plant. The use of deicing salt on a bridge is also likely to lead to salt contamination. Identifying areas of concern before surface preparation can help limit the need for subsequent sampling of the surface to those locations believed to be contam inated . A common indicator of salt contamination which occurs after the surface is prepared is rapid rerusting in the absence of condensing-moisture. Most often such flash rusting will be associated with pitted or previously rusted areas on the structure. In some cases, the rerusting is more uniformly distributed. This may indicate that the use of abrasives or the surface preparation process itself has imparted chemical contamination to a surface. A simple water extraction test, ASTM D 4940, can be used to help determine if an abrasive is contaminated. b. Sampling Techniques -Several techniques are available to acquire samples for analysis in order to determine if an abraded surface is chemically clean. All depend upon a surface extraction of soluble salts. In almost all instances a pure deionized water supply is used to extract the salts from the steel surface. Salt retrieval methods used to determine surface concentrations of salt on ferrous metals fall into three general classes: Swabbing or washing methods; Cell retrieval methods; and, Total Extraction Methods. The first two methods can be used in both laboratory and field settings, while total extraction methods, such as the use of boiling deionized water to extract salts from a steel sample, are generally only useful when performed in the laboratory and will not be discussed further.
1) Figure 22 shows the swabbing method. An area of corroded steel has been marked off after abrasive blast cleaning of the surface. The FIGURE 22 The swabbing method for obtaining samples to determine the extent of salt Contamination. surface can also be cleaned by scraping or chipping off heavily rusted scale and cleaning with abrasive embedded discs. Surgical grade cotton swabs moistened with deionized water are used to remove salts from a known area of the structure. The method requires that the operator wear surgical latex rubber gloves to prevent cross contamination of the surface or the retrieved sample by salts naturally present on the surface of the skin. As an alternative to swabbing, a washing technique may be used. This method typically involves rinsing a prepared area of steel of known dimensions with deionized water until no further increase in the run-off water is noted. All run-off water is collected and analyzed. FIGURE 23 Using a magnetically attached limpet cell to obtain a sample. 2) Figure 23 shows an extraction using a limpet cell . The cell itself is constructed of machined plexiglas plastic plate and includes a conductivity meter to permit immediate reading of fluid conductivity and a syringe to pump fluid into and out of cell. The cell shown adheres magnetically to the structure. 190 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*h.û 93 = 8627940 0003638 TTO FIGURE 24 Bresle cells can also be used for sampling. The cell surface area is known and a set volume of deionized water is flushed in and out of the cell space to wash the salts from the steel surface. After a short period of time, normally about one to two minutes, the water is withdrawn from the cell and stored for further analysis. Samples may also be collected using a Bresle cell. a small adhesive oatch which expands when filled with sample liquid. Figure 24 shows a Bresle cell. Distilled water is injected into the cell with a hypodermic needle. The liquid is then retrieved from the patch and tested. There are no published reports yet on the effectiveness of the cell. The cell can hold only about 5 ml of sample, less than can be obtained with some other methods. 2. Analyzing the Samples Water samples from either swabbing or cell extractions can be analyzed in one of two general ways. The samples can be assayed for conductivity, using a simple cell arrangement or an analysis to identify the presence of individual ions can be performed. Specific Ons Of greatest interest are chloride, sulfate or ferrous. Commercial test kits are available for full extraction and analysis of these species. For more information on these tests, see the bibliography at the end of this chapter for articles on this subject published in the Journal of Protective Coatings and Linings. 3. Interpreting the Results None of the methods described will retrieve all the salt present on a contaminated surface. The proportion retrieved varies from method to method. Factors that affect the amount of salt retrieved include the method of retrieval, the performance characteristics of each method and the conversion of retrieved salt levels to actual surface concentration estim ates. Based on retrieval studies conducted in the SSPC laboratories the following performance characteristics are suggested for each extraction met hod: a. Swabbing Method -Between 15 to 35% of all surface salts extracted; b. Rigid Limpet Cell Method -Between 45 to 60% of all surface salts extracted;
c. Bresle Method -Between 45 to 60% of all surface salts extracted. The interpretation of the results of analysis is the subject of much debate among coating professionals. Actual target levels depend upon the type of coating to be used, the service environment of the structure and other engineering factors, for example, the presence or absence of cathodic protection. Target levels should be set forth in the contract documents or governing specifications. A draft technical update covering salt recovery and identification methods is being developed by SSPC and other levels of chemical cleanliness are being defined in SSPC-NACE Joint Task Groups. The IS0 has also been developing standards for assessing and quantifying surface cleanliness. FIGURE 25 Inside of Mikrotest Gage with components corresponding with those in Figure 21. Courtesy: GilbertlCommonwealth c. PROFILE The profile anchor pattern or roughness is defined as the maximum average peak to valley depth (or height) càused by the impact of the abrasive onto the substrate. A White Metal Blast can have a 1, 2, 3,.or 4 mil profile; likewise, a Commercial Blast can have a 1, 2, 3, or 4 mil profile. Specifying a certain blast cleanliness says nothing --`,,,,`-`-`,,`,,`,`,,`--of the profile requirement. It must be addressed separate,__
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SSPC CHAPTER*h.O 93 W 8627940 O003639 937 Surface profile is important because it increases the surface area to which the coatings can adhere, and provides a mechanical anchor, resulting in good adhesion. As a general rule, thick coatings require a deeper surface profile than thin coatings. Profile determinations are generally made in the field or shop using one of three instruments: a surface profile comparator, a depth micrometer, or a replica tape. Magnetic measurements of surface profile have been attempted with little success. More sophisticated laboratory methods include a profilometer and a depth measuring microscope. SSPC has developed a standard method of measuring profile using a microscope. This is included in the SSPC Study Surface Profile for Anti-Corrosion Paints. While all methods are worthy of consideration, only the fieldlshop instruments will be discussed. The most common comparator is the Keane-Tator Surface Profile Comparator (Figures 10 and ll), which consists of a reference disc and a 5-power illuminated magnifier. The disc is held magnetically against the magnifier, year that the master disc was formed is only significant if it were to be replaced at a later date. The Clemtex Coupons are another type of profile reference standard similar to the comparator discs. They are stainless steel coupons individually blast cleaned and measured for profile depth. IS0 also provides a visual profile comparator. Another field instrument useful for determining average profile depths is a depth micrometer (Figure 13). The depth micrometer consists of a conical pin which projects out from a large flat base approximately the size of a nickel. The instrument is calibrated on a mirror or plate glass by turning the entire scale ring so that the zero through which test surface and disc segments can be viewed simultaneously. The reference disc has five separate leaves or segments, each of which is assigned a number representative of the profile depth of the particular leaf. Each disc is a high purity nickel electroformed copy of a master. The master disc was measured microscopically by the SSPC to establish the profile depth. The reference disc is compared with the surface through the 5-power magnifier. The leaf or leaves which most closely approximate the roughness of the surface are considered to be the profile of that surface. For example, the profile might be 2 mils, or perhaps from 2 to 3 mils if the surface roughness appears to lie between the 2 mil and 3 rnil leaves. There are three surface profile discs available. The
one to use for measurement depends upon the abrasive used. Different types of abrasives may result in a different profile appearance, although the depths might be identical. For example, shot is round when compared with the more angular grit. In order to achieve similar profile depths, the shot by virtue of its shape will generally result in greater lateral distances between peaks than will grit, resulting in a lower peak count per given area. The optical effect provides an illusion that the shot-blast-cleaned surface is deeper than the grit-blast-cleaned surface even when they are identical. Therefore, it is essential that the correct comparator disc be selected for the abrasive used. The designations for three discs available with the instrument are for sand, s; for metallic grit or slag, GE;and for steel shot, SH. The numbering system on each leaf consists of a number followed by a letter designation, then another number. The first number represents the profile depth of that leaf, the letter represents the abrasive used, and the final number represents the year that the master disc was formed. For example, 1S70 indicates that that leaf was prepared to a 1 rnil profile using sand as the abrasive and that the master disc was formed in 1970.The FIGURE 26 PLASTIC SHIMS -for calibrating dry film thickness gages. --`,,,,`-`-`,,`,,`,`,,`--FIGURE 27 NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY CERTIFIED COATING THICKNESS CALIBRATION STANDARDS for magnetic pull-off gage calibration. lines up with the pointer. Theoretically, when the instrument is firmly placed on the blast cleaned substrate, the base will rest on the tops of the peaks and the pin will project into a valley. By taking a number of readings, an average profile can be obtained. It is important to pick the Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 192
SSPC CHAPTER*bmO 93 86277110 O0036110 659 instrument up and place it down for each reading, rather than drag it across the profile; otherwise, the point will become blunted, yielding erroneous readings. Surface profile can also be determined by using replica tape (Figure 12). The Testex Press-O-Film Replica Tape consists of an emulsion film of microscopic bubbles attached to a uniform, 2 mil film of mylar. The tape is pressed onto the blast-cleaned surface, emulsion side down, and the mylar rubbed vigorously with a blunt instrument, such as a swizzle stick or burnishing tool. The peaks of the profile will break the bubbles and ultimately touch, but not alter, the thickness of the mylar, as the mylar is incompressible. The tape is removed and measured using a light-weight, spring-loaded micrometer, which provides a reading from the upper or outermost surface of the mylar to the high spots on the emulsion which were not totally crushed (corresponding with the valleys of the profile). The total micrometer reading is adjusted for the thickness of the mylar by substracting 2 mils from the results to provide a direct reading of the maximum average profile. The tape is available in coarse for profile measurements from 0.8 up to 2.0 mils and X-coarse for measurements from i.5 to 4.5 mils. The replica tape will allegedly retain the impression indefinitely, provided it is stored in a cool area with no pressure applied. Conceivably, replicas of profiles could be kept on file permanently for future reference. It is important that the inspector realize that each of the above methods has its drawbacks. For example, the comparator is subjective, and persons using it could be biased by the results of others. The peaks of the profile may be too close together to permit the projecting pin of the Surface Profile Gage (depth micrometer) to reach the valleys, or the surface might be irregular or wavy, holding the base of the instrument slightly above the plane of the profile, giving erroneously high readings. The replica tape cannot be used for profiles exceeding 4% mils, or if there is any dirt or dust contamination on the surface. Such contamination will be picked up and incorrectly read as additional profile depth by the micrometer. Finally, it is important to realize that there may not be exact correlation among each of the above methods because each takes in a different peak count or surface area for its measurement. Therefore, it is advisable that all parties concerned agree on the instrument that will be used to determine the surface profile and not deviate from it. Because of the controversy in agreement in surface profile measuring methods, equipment or technique, manufacturers will occasionally supply a profile reference coupon representative of the roughness necessary for their product or alternatively specify the use of a specific instrument. The SSPC has prepared a report on profile, its origin, measurement, control and effect on coating performance. It is entitled
Surface Profile for Anti-Corrosion Paints . Methods for measuring surface profile are given in ASTM D 4417 and NACE RP 0287. The technology of surface preparation is covered in a series of separate chapters in this volume. VIII. INSPECTION OF APPLICATION EQUIPMENT The inspector must also be familiar with the methods and equipment used for coatings application. A brief summary is presented here, but more detailed information is provided in the chapter on paint application of this volume and in Volume 2. -ADJUSTMENT EXTENSION REFERENCE COATING FERROUS SUBSTRATE FIGURE 28 Operating principle of Pencil Pull-Off Gage. A. SPRAY APPLICATION EQUIPMENT Spray equipment is classified as either conventional (air atomized) or airless. With air atomization equipment, the paint is fed through the fluid line at relatively low pressures, and compressed air is directed at the fluid stream through an air cap to atomize it. Adjustment of the fluid stream and air pressure enables the painter to adjust the spray pattern. Only the minimum pressures necessary to adequately atomize the paint should be used. The proper fluid cap and needle must be chosen, as well as a corresponding air cap size. Because the compressed air mixes with the coating, filters should be used to ensure a clean air supply. In airless spraying, very high hydraulic pressure (1000-3000 psi) is used to atomize the paint through a precision-ground spray tip, much in the same manner as water is dispersed into droplets when passing through a garden hose spray nozzle. In an airless spray gun, generally, variations in the spray pattern can be attained only by changing the spray tip (fluid orifice), although some adjustable tips are now available. Consequently, choice of the appropriate tip, as well as variation of fluid pressure can result in a wide range of spray patterns suitable for almost any application. The coating manufacturer s application instructions usually recommend the appropriate spray tips and caps for conventional and airless application of their material. This, however, is only a recommendation and under certain conditions, other tip or cap combinations may be more apCopyright The Society for Protective Coatings Provided by IHS under license with
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SSPC CHAPTERxb.0 93 8627940 0003643 595 propriate. Care should be taken when cleaning the tip or caps as the orifice can be easily damaged. FIGURE 29 ELCOMETER 345 -digital gage measures coating thickness on ferrous substrates. Similar model uses eddy current principle to measure coating over non-ferrous metal substrates. The predominant malfunction in spray guns is attributable to lack of cleanliness, both of the spray gun itself and of fluid lines. Paint chips or agglomerations and most blasting abrasive particles are of sufficient size to clog the small diameter orifices, resulting in gun stoppage or clogging. Additionally, cleanliness of mixing pots, spray pots, spray lines, spray guns or other application equipment is important and necessary for good paint application. Dirty equipment can cause new paint to become contaminated with old. Dislodged particles can clog the spray gun or even result in the deposition of incompatible traces of previously applied material in the new paint film. Cleanliness of all spray application equipment should be verified prior to, or no later than, the time of mixing of the paint. Otherwise, resulting clogged paint equipment may cause the loss of the coating material due to expired pot life or the presence of contamination. B. SPRAY POT The spray pot should be clean and in working order prior to use. Many types of paints, particularly zinc-rich primers, require the use of an agitated pot (one equipped with a stirring paddle) in order to keep the paint components in suspension. Air and fluid pressure gages FIGURE 30 POSITECTOR6000 -digital gage measures coating thickness on ferrous substrates. Similar model measures coating thickness over non-ferrous metal substrates using eddy current principle. should be available and functional on conventional spray pots. The pressure release valve should also be operative. The conventional pot should be equipped with diaphragm pressure regulators, making it possible to control both air and fluid pressure to the spray gun from the pot. IX. MIXING OF THE PAINT MATERIAL This is probably one of the most important operations, as improper mixing or thinning will affect the coating s ability to resist the environment. However, mixing is not always specified as an inspection hold point in painting operations. Regardless, there should be some means to assure that all components of a multicomponent paint system have been added, that mixing is thorough and proper and that any required induction times have been met. Leaking or damaged containers should not
be used, particularly with catalyzed paints as some of the components necessary for complete cure may have leaked out and proper proportioning may not be obtainable. Containers with illegible labels should not be used. Mixing should be done until the paint becomes smooth, homogeneous, and free of surface swirls or pigment lumps or agglomerations. Many paints settle out upon prolonged storage, so boxing of these paints is beneficial to ensure that all pigment settled on the bottom of the container is incorporated in the mixed paint. 194 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERxb.0 93 = 8b27940 0003b42 421 = When adding zinc dust to the vehicle of zinc-rich primers, it is a usual practice to sift the zinc dust through a screen into the liquid portion while mixing. This helps to reduce a major problem when spraying two-component zinc-rich primers; that is, gun clogging caused by pigment agglomerations that are not properly dispersed upon mixing. For such heavily pigmented coatings, it is also important that the spray pot agitator is keeping the pigment in suspension. Preferably, only complete kits of multi-component paints should be mixed. If this cannot be done, the manufacturer must be consulted to assure that partial mixing of their material is permitted. If so, it is imperative that the components be carefully measured. Thinners are often required and should be well mixed into the paint material. The type and amount of thinner should be in accordance with the coating manufacturer s FIGURE 32 QUANIX 2300 -digital gage measures coating thickness over non-ferrous metal surfaces. 1 through 5. The manufacturer can be consulted as to the orifice size to use for his material, and the time in seconds for the volume of properly thinned material held by the cup to pass through the orifice. For example, the manufacturer might stipulate that the material should be thinned such that it will pass through a No. 3Zahn Cup in 20-30seconds at a given liquid paint temperature. The clean cup is fully immersed in the coating material and withdrawn quickly. A timer is started at the precise moment that the top of the cup leaves the level of the liquid. The material will flow steadily through the orifice. When the solid stream breaks at the base of the cup, the timer is stopped instantly. It is important to hold the cup one or two inches above the surface of the liquid so that the cup will remain in the solvent atmosphere and FIGURE 31 QUANIX 2200 -digital gage measures coating thickness on away from all drafts. Th e amount of thinner is adjusted ferrous substrates. accordingly so that volume of paint held by the cup will flow through the orifice within the stipulated time range. Viscosity measurements of this type are of value for recommendations. The amount of thinner used should be quick field determinations of thinning and will reveal if recorded by the inspector, as any thinner reduces the significant changes in the viscosity occurred from pot to volume of solid contents of the mixed paint. pot of material. However, the paint applicator himself is Measurement of viscosity assures that proper thin- generally the best judge of p
roper thinning ratios to assure ning ratios are used and that the thinning has not been that he can apply a smoo th wet coat without runs or sags. changed significantly from pot to pot. A common viscosity Additionally, the visc osity qf some high build thixotropic cup (Zahn), as shown in Figure 14, is simply a small cup of coatings cannot be m easured with the Zahn Cup, but other known volume with a precisely sized orifice in the center. viscosimeters can be used. In this case, the manufacturer Generally five orifice sizes are available and are numbered should be contacted for a recommendation. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 195
SSPC CHAPTERxb-0 93 m 8b23940 O003643 368 m and other areas where atmospheric contamination is present. Often water washing between coats or application of the topcoat within a minimum time interval is necessary. Otherwise, contaminants often invisible to the unaided eye may be coated over, leading to premature coating failure. Deficient and excessive coating thicknesses in multicoat systems should be observed. In cases where a topcoat is applied over a generically similar (non-rust inhibitive) primer, deficient primer thickness can be built up by additional thickness of the topcoat. However, where the primer contains rust inhibitors or is a different generic type, an additional coat of the primer or previously applied coating must be used before the topcoat can be applied. Another common practice is to use coatings of a different color, or to tint each coat. This is an excellent aid to the applicator and inspector to assure that complete coverage is achieved. Upper thickness limits are also specified in some cases. When paint thickness exceeds the specified thickness, the excess should be removed by grinding, sanding or blast cleaning as appropriate. Removal is usually followed by reapplication of a thin coat to seal irregularities. Excessive or unsightly runs, sags, drips, streamers, and other film deficiencies should be brushed out during application or removed after drying. This again is done by grinding, sanding, or in extreme cases, blast cleaning. FIGURE 33 QUANIX 1500 -digital gage measures coating thickness over ferrous and non-ferrous metal substrates. X. COATING APPLICATION Besides surface preparation, the actual coating application is the most visible aspect of the coating work. After surface preparation, it is the most important aspect as well. It has been said that the best coating specification is no better than the man behind the spray gun . Accordingly, the coating inspector should be knowledgeable of the various application techniques. These are briefly reviewed below, but detailed information is available in the .. z. chapter on Paint Application of this volume and in Volume When spraying with conventional (air atomized) equipment, the spray gun should be held from six to eight inches from the surface and maintained perpendicular to the surface throughout the stroke. For airless application, the distance should be from 10to 14inches. At the end of each pass, the gun trigger should be released. Each spray pass should overlap the previous one by 50%, and where possible, a cross hatch technique should be used. This requires a duplicate series of passes at 90 to the first to ensure complete and uniform coverage.
In brush application, the brush should be dipped approximately two-thirds of its bristle length into the coating. The bristle tips should be brushed lightly against the side of the container to prevent dripping, maintaining as fully loaded a brush as possible. Brushing is more effective than spraying for working paint into depressed irregularities, pits or crevices. However, care should be taken to ensure that the coating is not brushed out too thin. Other application methods include rolling, using mitts or pads, dipping, electro-static spraying, powder coating (using fluidized bed or electro-static spray), and, increasingly, roller coating using automated facilities for flat sheets. Each has its own specific technique as described elsewhere in this volume. Besides ensuring proper application technique, additional care is necessary when inspecting coating work at fossil fuel power stations, chemical plants, coke plants, XI. WET FILM THICKNESS DETERMINATIONS Wet film thickness readings are used to aid the painter and inspector in determining how much material to apply in order to achieve the specified dry film thickness. Wet film thicknesses on steel and most other metallic substrates are considered guideline thicknesses, with the dry film thickness being the thickness of record. However, when coating concrete or non-metallic substrates, the wet film thickness is often the accepted value because dry film thickness can be determined only by destructive means. FIGURE 34 MINITEST 1OOF -digital gage measures coating thickness over ferrous metal substrates. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 196
FIGURE 35 MINITEST4000 -digital gage measures coating thickness over ferrous metal substrates. Similar model measures coating thickness over non-ferrous metal substrates. The wet film thickness gage is generally a standard notch configuration (Figure 15), although circular dial gages are also used (Figure 16). The notch type gage consists of two end points on the same plane with progressively deeper notched steps in between. Each step is designated by a number representing the distance in mils or microns between the step and the plane created by the two end points. The instrument is pressed firmly into the wet film perpendicular to the substrate and withdrawn. In every case, the two end points will be wetted by the coating material, and in addition some of the steps in between. The wet film thickness is considered as being between the last wetted step and the next adjacent higher dry one. For example, if the 3 step is wetted and the 4 step is dry, the wet film thickness is between 3and 4 mils. If none of the steps or all of the steps in between the end points are wetted, it is necessary to turn the gage to a different face, as the wet film thickness is outside of that particular range. When using this instrument, it is necessary to stay away from any surface irregularities that could distort the readings. If determinations are being made on curved surfaces, it is important that the gage be used along the length of the curve rather than across its width, as the curve itself could cause irregular wetting of the steps. The gauge must also be cleaned thoroughly after each use to 197 ensure the accuracy of the readings. The Interchemical thickness gage is a narrow wheel with two outer rings of the same size and an off-set inner ring. The instrument is rolled across the surface and withdrawn. The wet film thickness is that point where the coating no longer wets the inner ring. Wet film thickness gages are of value only if one knows how heavy a wet film to apply. The wet film thicknessldry film thickness ratio is based on the percent solids by volume of the specific material being applied. The old theory of doubling the desired dry film thickness to determine the wet film to be applied is only correct if the solids by volume of the coating material is 50%. The solids by volume of the coating material is information readily available from the manufacturer and is commonly included in their product data sheets. The basic formula is DRY FILM THICKNESS = WET FILM THICKNESS X yoSOLIDS BY VOLUME. A more workable variation of the formula showing the required wet film thickness for the desired dry film thickness is as follows:
WET FILM THICKNESS = DESIRED DRY FILM THICKNESS Yo SOLIDS BY VOLUME FIGURE 36 ELCOMETER 300 -digital gage measures coating thickness over ferrous metal substrates. Similar model measures coating thickness over non-ferrous metal substrates. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*b-O 93 8b27940 0003645 130 = FIGURE 37 TOOKE SCRATCH GAGE -for determiningdry film thickness by cutting a cross section through the film and viewing it under magnification. The above formula is accurate provided the solids by volume of the material is accurate. The percentage will change, however, if any thinner is added to the coating. When thinner is added, the total volume of the material is increased without any corresponding increase in the amount of solids. Therefore, the thinned material will result in a lower percentage of solids by volume. Thus, when comparing thinned versus unthinned material in order to achieve a comparable dry film thickness, a heavier wet film application of the thinned material will be required. The following formula, which incorporates the new solids by volume, should be used to determine the required wet film thickness when the material is thinned: DESIRED DRY FILM THICKNESS WFT = /o SOLIDS BY VOLUME (100% +
/o THINNER ADDED)
For example, assume a material contains 78% solids by and is to be applied in one coat to a dry film thickness of 8 mils. Without thinner added, the required wet film thickness is determined as follows: WFT = -= 10.25 mils 0.78 If the coating in the same example is thinned 20%, the new required wet film is calculated as follows: WFT = -8 - -= 12.3 mils 0.78 (0.65) 1.2 This, without thinning, 10.25 wet mils are required to obtain 8 mils dry. After thinning, however, the solids by volume drops from 78% to 65% and the required wet film thickness increases nearly 2 mils. Because the use of the wet film thickness gage is dependent on the solids by volume, and the solids by volume is considered as the in can percentage, it is essential that wet film thickness readings be taken as soon as a film is applied to the surface. Actually, during spray application, between the time the material leaves the gun and reaches the surface, some of the solvents will already haveevaporated, changing the percent of solids by
volume slightly. But for practical applications, this change is not too significant. However,the longer one waits before taking a reading, the less accurate that reading becomes. For highly pigmented coatings (such as zinc-rich), or very fast dry coatings, wet film thickness readings may be unreliable. XII. DRY FILM THICKNESS Dry film thickness readings on steel substrates are commonly taken using magnetic gages. For non-ferrous metallic substrates, eddy current equipment is used. Calibration of magnetic thickness gages should be done in accordance with SSPC-PA 2, SSPC Method for Measurement of Dry Paint Thickness with Magnetic Gages . Although the standard is written for magnetic gages, many of the principles of operation and calibration techniques apply to the eddy current instruments as well. Determination of the thickness of each coat in a multicoat system should be an inspection hold-point. When using magnetic gages to measure multi-coat systems, the average of the first coat must be determined prior to application of the second coat. Readings taken after the second coat is applied will obviously be the total thickness of the two coats combined, and the specific thickness of the second coat can only be determined by subtracting the average thickness obtained from the first coat reading. The second coat thickness cannot be determined precisely, however, because it is highly unlikely that specific readings taken on the second coat will be over an area of the first coat that is exactly the first coat average. Therefore, with magnetic gages it is nearly impossible to Specifically determine the thicknesses Of Coats applied after the and One must rely On averages onlyIt is often a good idea, where practical, to provide a means to indicate coating thickness in areas where it is either thin or thick, so appropriate repair can be done by the coating applicator. Possible methods are brush application of a light tinted coat of the same paint, compatible felt tip marking pens, chalk or other material that can be readily removed or graphic plotting and notation on charts and records. Thickness readings are taken to provide reasonable assurance that the specified or desired dry film thickness has been achieved. However, it is not possible to measure every square inch of the surface. SSPC-PA 2 states that when using magnetic gages, five separate spot measurements should be made over every 100 square feet in area. Each spot measurement consists of an average of Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 198
SSPC CHAPTER+b.O 93 m 8627940 0003646 O77 m FIGURE 38 Modified version of the TOOKE GAGE with all three cutting tips --`,,,,`-`-`,,`,,`,`,,`--mounted on the instrument body and three bulbs to improve lighting. three gage readings next to one another. The average of the five spot measurements must be within the specified thickness, while single spot measurements are permitted to be 80% of the specified thickness. The single gage readings, however, making up the spot measurement, can underrun by a greater amount. For example, a specification calls for 10 to 12 mils. The five spot measurements (each a cluster of three gage readings) are as follows: Spot 1 (10, 11, 12; average 11); Spot 2 (7, 8, 9; average 8); Spot 3 (12, 12, 12; average 12); Spot 4 (7, 12, 11; average 10); Spot 5 (12, 13, 11; average 12). This measured area would be acceptable because the average of the five spots is 10.6 mils and within specification. According to SSPC-PA 2, unless otherwise specified, the 8 mil spot measurement would be acceptable because no single spot measurement ... shall be less than 80% of the specified thickness (8 mils is exactly 8O%), and the 7 mil reading is acceptable because single gage readings .._may underrun by a greater amount . Dry film thickness instruments fall into four basic categories: magnetic pull-off, magnetic-constant pressure probe, eddy current-constant pressure probe, and destructive. Each of the four categories are addressed separately. A. MAGNETIC PULL-OFF The magnetic pull-off type gages include the Mikrotest (Figure 17), the Positest, the Elcometer 21 1 (Figure 18), and the Pencil Pull-Off (Figure 19 and 20) type gage. Basically, a Mikrotest, Positest, or Elcometer 21 1 Gage consists of a lever running through the center of a scale dial which houses a helical spring. The scale dial is located at the fulcrum point of the lever. One end of the spring is attached to the lever and the other end to the scale dial. One side of the lever contains a permanent magnet while the opposite end contains a counterbalance (Figures 21 and 25). To operate, the scale dial is turned clockwise and the magnet brought into direct contact with the metal substrate (through the coating or non-magnetic barrier). Then the scale ring is turned counterclockwise, increasing the spring tension, which applies a pulling force onto the magnet. Ultimately, the spring tension overcomes the attraction of the magnet to the substrate, lifting the magnet from the surface. The spring tension is calibrated so that the point where the magnet breaks contact with the surface can be equated to the distance of the magnet from the surface. This distance is read directly from the scale dial in mils (or microns). The calibrated spring tension is an inverse logarithmic relationship of the distance between
the magnet and the substrate (e.g. the greater the spring tension required to remove the magnet, the thinner the coating). Note that the thickness reading shown on the scale ring when the magnet breaks contact with the surface represents the gap between the magnet and the substrate. This gap is considered to be the coating thickness. However, it could also be comprised of voids, rust, embedded contaminates, etc. Therefore, one must include a thorough visual inspection during the work to ensure that the coating is applied over a clean surface and does not become contaminated during drying. The Mikrotest, Positest, and Elcometer 21 1 Gages should be calibrated, or at least calibration verified, prior to, during, and after each use to assure that they are measuring accurately. Calibration methods are described in SSPCPA 2, Measurement of Dry Film Thickness with Magnetic Gages, which defines the pull-off instruments as Type 1 gages. Calibration test blocks similar to those supplied by the National Institute of Standards and Technology (NIST), which are chrome and copper plated steel (Figure 27) must FIGURE 39 A hand-held spring loaded micrometer useful for measuring the thickness of coating chips. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 199
FIGURE 40 Pocket-sized30X microscope with integral light source useful for examining coatings. be used to verify the calibration of Type 1 Gages. The use of plastic shims is not permitted. It is essential that the instrument is calibrated in the desired thickness range of use. If a coating is being measured in the thickness range of two to four mils, one would not use a gage calibrated at 15 to 20 mils. Calibration using the National Institute of Standards and Technology (NIST) plates is accomplished by first adjusting the instrument to read the thickness stated on the calibration blocks in the desired range of use. Next, take a gage reading of the bare, uncoated substrate after blast cleaning (or other surface preparation). The instrument will generally read between one and two tenths of a mil up to 1mil or more over the bare steel. Therefore, any coating thickness readings taken must be corrected by this bare steel base reading in order to determine the coating thickness above the peaks of the profile. Adjust subsequent thickness readings by subtracting the magnetic base reading. For example, if the instrument is calibrated to a 4 mil NIST Standard, and a 1/z mil magnetic base reading on bare blast cleaned steel is found, a paint thickness reading of 3% mils indicates that the true thickness above the peaks is actually only 3 mils. If one chooses not to physically adjust the instruments as described above, it will be necessary to develop a calibration correction curve using the instrument scale as an arbitrary scale. For example, a five on the scale may be equivalent to three mils, a ten equivalent to seven mils, and so on. Another type of magnetic pull-off gage based on a similar principle is the pencil pull-off gage (Figures 19, 20 and 21). Basically, the instrument housing is similar to a large pencil with a magnet at one end. An extension spring is attached to the magnet and to the top of the instrument housing. The instrument is held perpendicular to the surface and the magnet brought into contact with the substrate. As the housing is lifted, the magnet remains attached to the substrate until the spring tension overcomes the attraction of the magnet, popping it from the surface. The tension on the spring required to lift the magnet is read from the scale in mils or microns (Figure 28). This instrument can not be adjusted, although calibration should be verified. In this case, however, a calibration correction curve is necessary if the instrument does not read correctly on the shims. The preferred method for verifying calibration is the use of calibration test blocks. The pencil-style gages provide a quick check of coating thickness, but considerable judgment is involved in determining the point at which the magnet breaks from the surface. There are some precautions necessary when using
any instrument that has a magnet. First, the magnet is exposed and therefore susceptible to attracting iron filings, steel shot or grit particles. The magnet must be cleaned of any contaminants during use, or the contaminant will incorrectly be read as coating thickness. This is extremely important in shop work where grinding is employed. The resulting iron filings often necessitate that the magnet and coating surface be cleaned before each thickness reading. If the instrument is used on a soft film, allowing the magnet to sink into the surface, a thinner coating thickness will be recorded. This is because the coating itself may be tacky, holding the magnet beyond the point where the spring should have lifted it from the surface, or FINISH COAT d1 I n ' ),1 / PRIMER COAT A' A FINISH COAT THICKNESS 8' B PRIMER COAT THICKNESS ~ FIGURE 41 Measurement principle of the Tooke Gage. the coating under the depression caused by the magnet actually will be thinner. In this case, place a plastic shim on top of the surface to prevent the magnet from deformCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 200
SSPC CHAPTER*b-0 93 8627940 0003648 94T 9 ing the coating and subtract the shim thickness from any subsequent readings. In addition, if there are any vibrations in the area of instrument use, they could cause the magnet to be popped from the surface prematurely, giving an erroneously high thickness reading. The instrument should not be used any closer than 1 inch to an edge of the surface. In addition, residual magnetism in the structure on which the coating is measured can have an adverse effect on the readings. The scale dial type instruments have an additional human error problem during use. It is easy to continue to turn the dial beyond the point that the magnet has lifted from the surface, giving an incorrect thickness reading. It is imperative that the dial be stopped as soon as the magnet lifts from the surface. Automatic versions of the Mikrotest have addressed this problem by incorporating a self winding mechanism which automatically retracts the thumb wheel. B. FIXED PROBE MAGNETIC FLUX GAGES The fixed probe or magnetic flux type gages are described in SSPC-PA 2 as Type 2 gages. They include the Elcometer 345 (Figure 29), Positector 6000 (Figure 30), Quanix 2200 (Figure 31), Quanix 1500 FE (Figure 33), Minitest 200F (Figure 34), Minitest 4000 (Figure 35), Elcometer 300 (Figure 36), and others. The Type 2 gages also must be verified for calibration prior to use. Calibration verification is accomplished using the non-magnetic shim method (described below) or the NIST calibration plates described previously. When calibrating using the plastic shim method, verify the shim thickness with a micrometer. Hold the shim firmly on the bare clean(ed) substrate and measure it with the thickness instrument. If the instrument does not read the shim thickness, adjust the gage according to the manufacturer s instructions. Some gages cannot be field calibrated. Check the calibration by using shims of lesser and greater thickness to determine the range of accuracy. The instrument is now ready for use for measuring thicknesses within that range over the same substrate and surface preparation. If a section of the bare substrate is unavailable, blast clean small steel test panels (e.g., lhtrx 4 x 6 ) to obtain the same or similar anchor pattern, protect them from corrosion using a dessicant, VPI Paper, or other suitable means, and use the panels for calibration. The instrument will correctly record the thickness of the coating material. Any effect of surface roughness is calibrated into the instrument because it was adjusted over the bare steel, thus eliminating the need for a magnetic base reading correction factor. The magnetic flux gages experience some of the same problems as the pull-off gages: 1) lower than actual thickness readings on soft or tacky films; 2) necessity of staying away from the edges during use; and 3)difficulty in keeping the magnet clean. In addition, because the instruments are based on flux principles, they are vulnerable to the effect of flux leakage from the instrument to nearby ferrous masses, causing the instrument to be ineffective.
Therefore, it is necessary to stay at least three inches away from any nearby iron or steel object, or the instruFIGURE 42 View through Tooke Gage Microscope. The interface of the coatinglsubstrate is one division to the left of .O6 on the scale. Coating thickness is measured from this point to the left ending at the black bench mark at -05. FIGURE 43 TINKER-RASOR LOW VOLTAGE WET SPONGE HOLIDAY DETEC. TOR -used for finding pinholes and holidays in non-conductive paint films up to 20 mils thick when applied to conductive substrates. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 201
SSPC CHAPTERab.0 93 M Bb27940 0003b49 BBb ment calibration must be readjusted in these specific areas. If used inside a tank or vessel, they should be calibrated inside the vessel to compensate for flux leakage. The probe of these instruments must also be kept perpendicular to the coated substrate during use; otherwise, incorrect readings will result. C. MICROPROCESSOR-CONTROLLED GAGES Computer chips are now commonly incorporated into dry film thickness gages. A hand-held microprocessor with digital thickness display is available with its physical operation similar to the magnetic flux gages above (Figure 36). D. EDDY CURRENT GAGES Eddy current instruments measure the thickness of non-conductive coatings on non-ferrous metal substrates. Included with this type of instrument are the Quanix 2300 (Figure 32) and Quanix 1500 (Figure 33). The probe of these instruments is energized by alternating current, inducing eddy currents in the metal. The eddy currents create opposing alternating magnetic fields within the metal, modifying the electrical characteristics of the probe coil. The extent of these changes is determined by the distance of the probe from the substrate and is shown on a meter as coating thickness. The eddy current instruments are calibrated using the plastic shim method. E. DESTRUCTIVE TEST INSTRUMENTS Destructive thickness testing includes the use of the Tooke Gage (two models are shown in Figures 37 and 38), Micrometers (Figure 39),or microscopes (Figure 40). The Tooke Gage consists of a 50X microscope that is used to look at slits in the coating made by precision cutting tips supplied with the instrument. The principle of the Tooke Gage is basic trigonometry. By making a cut through the coating at a known angle and viewing perpendicularly to that cut, the actual coating thickness can be determined by measuring the width of the cut from a scale in the eyepiece of the microscope. The instrument can be used for determining the thickness of underlying coats in multicoat systems and eliminates many of the drawbacks of the magnetic instruments caused by magnetic fields, proximity to edges, irregular surfaces, magnetic effect of the substrate, profile, and so forth. The instrument can be used on coating thicknesses up to 50 mils provided the coating is not too brittle or elastic for a smooth cut to be made. Cutting tips of different angles are available. They are designated as either lX, 2X, or 1OX. The tip used determines the thickness equivalent for each line in the microscope eyepiece. The number of lines corresponding with the coating is divided by the number of the tip used. Therefore, 1 line when using the 1X tip is equivalent to 111 or 1 mil; 1 line with the 2X tip is YZor .5mil, and 1 line with the 1OX tip is or .1 mil. Thus, if the coating cross-section covers 7 lines and the 2X tip is used, the thickness is or
3.5 mils (Figures 41 and 42). 202 Another means of destructively measuring the coating thickness is the use of either a depth micrometer or a standard micrometer. The depth micrometer can be used by removing a small section of the coating down to the substrate, permitting the base of the instrument to rest on the coating while the projecting pin is adjusted to the substrate. Alternatively, a sample of the coating can be removed from the substrate and the thickness measured using a standard micrometer. The coating chips could also be returned to a laboratory for microscopic thickness determinations. The Tooke gage could also be used for this purpose. When viewing the edge (cross section) of a disbonded chip, each division of the microscope is equivalent to 1.0 mil. XIII. CLEANLINESS BETWEEN COATS Where more than one coat is to be applied, a proper inspection hold point is the determination of the cleanliness of the surface immediately prior to application of the next coat. In addition to dirt and dust, quite often dry spray, or overspray, will cause a problem. All should be removed because the presence of these contaminants can result in reduced adhesion between coats and porosiFIGURE 44 USING A LOW VOLTAGE WET SPONGE DETECTOR -to locate discontinuities in non-conductive coatings applied to conductive metal substrates. Official U.S. Navy Photograph ty, rendering the coating less resistant to the effects of the environments. The surface should also be inspected for any adverse contamination from the environment (e.g. residue from chemical facilities, salt, etc.) Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*b*O 93 = 8627940 O003650 5T8 = XIV. PINHOLE AND HOLIDAY DETECTION After all the coats of paint have been applied, the inspector should verify that the appropriate clean-up is done, and that any abrasions, nicks, or scrapes are repaired as required. Often holiday, pinhole, or spark testing is used to find the nicks, scrapes, and pinholes in the coating film, particularly if the coating is intended for immersion service. Holiday testing may be required after application of either the next to last, or last coat of paint. Usually when such testing is specified, it is done before final cure of the coating has occurred so that any repair material applied will successfully bond to the underlying coat. Pinhole and holiday detectors are three general types: low voltage wet sponge (Figures 43,44 and 45), DC high voltage (Figures 46, 47 and 48), and AC electrostatic types. The low voltage wet sponge holiday detectors are used for finding discontinuities in non-conductive coatings applied to conductive metal bases. The low voltage detector is suitable for use on coatings up to 20 mils in thickness. The basic unit consists of the detector itself, a ground cable, and a sponge electrode. The around cable is firmly attached to the bare substrate and the sponge electrode is saturated with tap water. The electrode is moved across the entire surface, the water permitting a small current to flow through the pinholes down to the substrate. Once the current reaches the substrate, the circuit is completed to the detector unit and an audible signal can be heard indicating that a pinhole or discontinuity is present. When coatings are in the range of 10 to 20 mils, a non-sudsing wetting agent (such as Eastman Kodak Photo-FIO) may be added to the water to increase the wetting properties. If the coating system is found to be outside of the 20 mil thickness limits, high voltage holiday detection equipment should be used. High voltage detectors basically function on the same operating principle as the low voltage described above, except that a sponge is not used. The instrument consists of a testing unit capable of producing various voltage outputs, a ground cable, and an electrode made of conductive materials such as neoprene, brass, or steel. High voltage units are available up to 20,000 volts and more. High voltage detectors are used for non-conductive coatings applied to conductive substrates. The ground wire is firmly attached to a section of the bare substrate and the electrode is passed over the entire surface. A spark will jump from the electrode through the air gap down to the substrate at pinholes, holidays, or missed areas, simultaneously triggering audible andlor visual signaling
device in the unit. For exterior pipeline work, many times the ground wire of the holiday detector is permitted to drag across the earth provided the pipe itself is grounded to the earth. However, the preferred method of testing is to attach the ground wire directly to the substrate whenever possible. When using high voltage holiday detectors, it is important to use only the voltage level recommended by the coating manufacturer for the coating thickness. OtherFIGURE 45 K-D BIRD DOG LOW VOLTAGE WET SPONGE HOLIDAY DETECTOR -utilizes a wetted sponge and ground wire to find pinholes and holidays in dry paint films applied to conductive substrates. FIGURE 46 SPY HIGH VOLTAGE HOLIDAY DETECTOR -for uncovering flaws in thick film systems. Voltages are available up to 22,000 volts DC. A spark jumps from the electrode through the coating at deficient areas. wise, damage to good coating could occur. A rule of thumb is to apply 100-125 volts per mill of coating for thicknesses in excess of 20 mils. When testing conductive linings applied over steel substrates (¡.e. conductive rubber linings), the AC Tesla Coil type electrostatic testers are generally used. The AC tester has a variable voltage output (preferably, the voltage is indicated) but does not require the use of a ground wire. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*b=O 73 m 8b27740 0003b5L 434 m The unit constantly emits a corona which is blue in color, but when a break in the lining is passed over, a white spark will jump to the substrate at the holiday or imperfection. Note that surface contaminants or dampness may also cause a color change or spark; therefore, it is advisable to clean and retest questionable areas to confirm that a break in the lining is present. XV. FIELD ADHESION TESTING Occasionally, there is a need to test the adhesion of the coatings after application. There are different types of adhesion testing methods used from the simple penknife to more elaborate testing units. The use of a penknife generally requires a subjective evaluation of the coating adhesion based on some previous experience. Generally, one cuts through the coating and probes at it with the knife blade, trying to lift it from the surface to ascertain whether or not the adhesion is adequate. A modified version of this type of testing is the crosscut test. The cross-cut test consists of cutting an X , or a number of small squares or diamonds through the coating down to the substrate. Tape is rubbed vigorously onto the scribes and removed firmly and quickly. The cross-hatch pattern is evaluated according to the percentage of squares delaminated or remaining intact. The X and cross-cut tape adhesion tests are described in ASTM D-3359, Measuring Adhesion by Tape Test . There are also instruments available for testing the tensile adhesion strength of coatings. They apply a value to the adhesion strength in pounds per square inch, thus eliminating some of the subjectivity of the above tests. Instruments for tensile testing include the Elcometer, Patti (Pneumatic) and the Hate (Hydraulic) Adhesion Testers (Figure 49). The adhesion testers consist of the test unit itself and aluminum or stainless steel test stubs. The pull stubs are cemented to the coating surface using an adhesive. After the adhesive has cured, the piston or claw of the test instrument is placed over the pull stub. The test unit applies a pulling force on the pull stub, ultimately breaking it from the surface. The point of the break is read from the scale on the instrument in pounds per square inch. This method is described in.ASTM D4541. Not only is the numerical value of importance when using this instrument, but also the type of break. For example, there is a significant difference in the test results if one finds a clean break to the substrate or between coats, compared to finding a cohesive break within a coat. Many times one may experience a failure of the adhesive. If this occurs, it establishes that the coating tensile adhesion strength is at least as good as that pressure that broke the adhesive. It is generally recommended that the two-component type epoxy adhesives be used in preference to the single component fast drying cyano-acrylate types. When testing zinc-rich coatings, for example, it has been found that the
thin cyano-acrylates have a tendency to penetrate and bond thezinc particles together, resulting in a much higher tensile pull than should be expected. In other cases, the adhesive appears to soften and cause premature failure of the coating systems. XVI. EVALUATING CURE When a coating is to be used in immersion service, the FIGURE 47 TINKER-RASOR HIGH VOLTAGE HOLIDAY DETECTOR -used for non-conductive coatings applied to conductive substrates. FIGURE 48 D.E. STEARNS HIGH VOLTAGE HOLIDAY DETECTOR -used for non-conductive coatings applied to conductive substrates. applied coating film must be allowed to dry cure for a given length of time prior to being placed into service. This dry cure time is generally shown on the manufacturer s product information. Alternately, forced-heat curing may be used to reduce the time between curing and service. Determining the cure of coatings is generally difficult. ASTM D1640 outlines one method, but there are no universally reliable field tests for such purposes. Solvent rub tests can be used, as well as sandpaper tests. When most coatings are suitably cured, rubbing them with sandpaper will produce a fine dust. If the sandpaper gums up, depending upon the coating, it may not be cured properly. Certain phenol-containing coatings may discolor upon heating -and the cure of phenolic tank lining coatings is often determined by comparison of their color with color reference coupons supplied by the coating manufacturer. Because a coating is dry or hard does not necessarily mean it is cured. In fact, for most coatings, hardness is not synonymous with cure. The only coating types for which this is true are the solvent deposited Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 204
SSPC CHAPTER*6-0 73 m coatings such as the chlorinated rubbers and vinyls. Even then, residual retained solvents (and moisture in water emulsion coatings), under certain atmospheric conditions FIGURE 49 TENSILE ADHESION TESTERS -Pneumatic (back left), Elcometer (back right), and Hydraulic (front). Pull stubs positioned in front of each model. of temperature andlor humidity may take a long time to escape from the paint film. Final attainment of film properties will be acquired only upon satisfactory loss of these entrapped solvents. In some cases this evaporation process may take as long as two or three weeks or more. XVII. CONCLUSIONS There is a wide variety of inspection instruments available for use to assure the adequacy of the ambient conditions, surface preparation, wet and dry film thicknesses, and final coating continuity. The instruments all have advantages and disadvantages, but the overriding factor in their successful use is the knowledge and ability of the individual using them. It is important that the instruments be cared for, calibrated, and used properly. However, instrument inspection is only part of the total inspection process. It must be combined with a good, common sense visual inspection for detection of misses, skips, runs, sags, surface contaminants, overspray, dry spray, and any other defects objectionable for the service intended. Proper instruments, specific knowledge, common sense and good judgment are required for good coatings inspection. Finally, all results of any inspection should be thoroughly documented in writing to verify that the specified requirements have been met. Future maintenance or the removal and maintenance of a failed
coating system may be dependent on the factual reporting of every phase of the work. 8627940 0003652 370 W ACKNOWLEDGEMENT The authors and editors gratefully acknowledge William Corbett's update of this chapter. Both William Corbett and Steve Pinney provided photos. AI Beitelman, Robert Doyle, Arnold Eickhoff, Lewis Gleekman, Joseph Guobis, Ronald Hamm, John D. Keane, Jay Leanse, Charlie Lewis, Jr., M. Lichtenstadter, Marshall McGee, Stan Mroz, Melvin Sandler, L. M. Sherman, and William Wallace participated in the review process. BIOGRAPHIES Kenneth B. Tator is the President of KTA-Tator, Inc., a consulting engineering firm specializing in industrial protective coatings. A registeredprofessional engineer, Mr. Tator is the USA Delegate to the International Standardization Organization TC351SC12 Surface Preparation Committee. He is active in the National Association of Corrosion Engineers, the American Societv for Testina and Materials, the'society for Pãint Technology, and the Steel Structures Painting Council. Mr. Tator holds an MBA from Columbia University and a B.S. in Chemical Engineering from Lafayette College. He is the author of numerous publications and has presented technical papers at many association meetings and corporate seminars Kenneth A. Trimber is the Vice-president of KTA-Tator, Inc., a coatings consulting firm based in Pittsburgh, PA. He is also the Vice President of KTA Services, Inc. and the Manager of its KTA Environmental division. Mr. Trimber began his employment with KTA on a part-time basis in 1968, and became a full-time employee after his graduation from Indiana University of Pennsylvania in 1974. He is active in many technical societies involved with protective coatings and serves on the Steel Structures Painting Council (SSPC) Board of Governors. He is Chairman of the SSPC committees on Surface Preparation and Visual Standards, and is Vice Chairman of the Lead Paint Removal Committee. Mr. Trimber is also the Chairman of American Society for Testing and Material: Dl which deals with all paints and protective coat-
ings. He has authored numerous papers on coating evaluation, surface preparation, inspection, lead paint removal, and coating failure analysis. Mr. Trimber authored the Industrial Lead Painf Removal Handbook, which serves as the text for SSPC Lead Paint Removal Tutorials. He was the 1988 recipient of the SSPC Outstanding Publication Award for the development of a system for classifying the condition of bridge coatings, and was given the SSPC John D. Keane Award of Merit as the Protective Coatings Specialist of the 1980s. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 205
SSPC CHAPTERsb.0 73 = Bb277LiO 0003b53 207 = REFERENCES 1. William F. Gross, Applications Manual for Paint and Protecfive Coatings, McGraw-Hill Book Company, New York, NY, 1970. 2. Paul E. Weaver, Industrial Maintenance Painting, 3rd Edition, National Association of Corrosion Engineers, Houston, TX, 1967. 3. Blast-Off , Clemco Industries, San Francisco, CA, 1970. 4. Kenneth B. Tator, and Kenneth A. Trimber, Coating Inspection Instruments , Plant Engineering, Sept. 19 and Oct. 3, 1974. 5. K.A. Trimber, and C.A. McCartney, Importance of Coating Application Inspection and Instruments Available for Use , presented at NACE 14th Annual Liberty Bell Corrosion Course, Sept., 1976. 6. D.M. Berger, and S.E. Mroz, Instruments for Inspection of Coatings , Journal of Testing and Evaluation, Vol. 4, No. 1, pp. 28-39, Jan., 1976. 7. Kenneth B. Tator, and Kenneth A. Trimber: Coating (Paint) Inspection Instruments, Types, Uses, and Calibration , Paper Number 254, NACE Corrosion 80. 8. NACE Standard RP-01-78 Recommended Practice -Design, Fabricatiorl, and Surface Finish of Metal Tanks and Vessels to Be Lined for Chemical Immersion Service , December, 1977. 9. NACE Standard RP-02-74 Recommended Practice -HighVoltage Electrical Inspection of Pipeline Coatings Prior to Installation , August, 1974. 10. SSPC-PA 2 - Method for Measurement of Dry Paint Thickness With Magnetic Gages . 11. NACE - TPC Publication No. 2 -Coatings and Linings for Immersion Service , Chapters 2 and 4, Houston, TX. 12. John D. Keane, Joseph A. Bruno, Jr., and Raymond E.F. Weaver, Steel Structures Painting Council, Surface Profile for Anti-Corrosion Paints , Pittsburgh, PA, 1976. 13. Bernard R. Appleman. Painting Over Soluble Salts: A Perspective. Journal of Protective Coatings and Linings. October 1987, pp. 68-82. 14. Kenneth A. Trimber. Detection and Removal of Chemical Contaminants in Pulp and Paper Mills. Journalof Protective Coatings and Linings. November 1988, pp. 30-37. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS--`,,,,`-`-`,,`,,`,`,,`--206
SSPC CHAPTERa7-L 93 = 8b27940 0003654 I43 CHAPTER 7.1 QUALITY CONTROL OF PAINTS AS MANUFACTURED by John F. Montle and Mary Ann Stephens The purpos of quality control of paints -as manufactured -is to assure the paint manufacturer that materials supplied are acceptable to the consumer. Materials must be consistent from batch to batch and must have satisfactory appearance, stability, application characteristics and performance. To achieve these objectives, a quality control program must be designed that is significantly more comprehensive than merely evaluating the coating materials produced. The primary function of quality control for coating manufacturers is to assure overall quality and performance. Such a program encompasses significantly more than batch quality control testing for uniformity of material. The quality control group should have responsibility for all phases of manufacturing concerning quality. This includes raw materials, the manufacturing process and the finished coating materials through packaging, filling and shipping. The purpose of testing every batch manufactured is to assure reproducibility of various paint and coating materials. This is the basic purpose of quality control from a coatings manufacturer s standpoint. The quality control tests must be selected and run on every batch of coating materials produced to assure that a given batch is reasonably consistent with batches previously produced. The quality control laboratory is responsible for evaluating the material only in accordance to standards and specifications indicated by the coatings formulator. It is the responsibility of the coatings formulator to build quality into the formulation and develop quality control instructions through proper selection of significant quality control tests. These facets are essential if the materials manufactured are to be suitable for field use. Another factor that varies considerably, depending upon the type of market for a particular coating, is quality control of compliance with existing customer specifications. It is critical that those specific quality control tests be run. However, merely verifying that a coating meets existing specifications is not necessarily sufficient quality control testing. Testing for a given specification might indicate reproducibility as manufactured, but this may still be insufficient to ensure the suitability of a product. Frequently, additional quality control tests have to be designed by the coatings manufacturer to guarantee the product s suitability for use, in addition to tests designed
to meet specifications (see Appendix). Quality control tests are elected i provide consistency in manufactured products. Therefore, test values and ranges for satisfactory performance are not necessarily valid over the the entire shelf life of the coating material. Many test values change with age. For example, drifts in viscosity can occur, but are not necessarily indicative of any change in the product s suitability. Tests should be designed to maximize detection of errors in manufacturing andlor variations in raw materials. Examples of common ones are shown in the Appendix. Proper selection of quality control range values is as important as selection of the proper tests. While ranges should be as tight as necessary to guarantee reproducibility, they should be wide enough for practical purposes. While the assigning of original test values is based on previous experience and skill of the formulator, the test values should be continually monitored so the ranges are proper. Frequently, standard quality control tests, such as shown in the Appendix, are sufficient for many paints and coatings that are manufactured for general use. However, special tests are frequently designed for specialized products and critical raw materials that have unique enduse applications. It is advisable to use standard ASTM or Federal Test Methods whenever possible. However, standard tests that will measure those parameters critical to proper end-use of a specific coating material are not always available. Therefore, a significant amount of laboratory time and effort must be spent developing special quality control tests. I. CONSIDERATIONS IN CONTROLLING QUALITY A. QUALITY OF FORMULATIONIPRODUCT DEVELOPMENT 1. Consumer Needsfperformance Characteristics When a coating is formulated, the first step is to define the product characteristics, which are usually predetermined by its purpose. The purpose of a formulation can be as simple as providing a competitive product or as complex as providing the means to answer a need that has puzzled the market for decades. Understanding the use and purpose of a coating is the first probCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 207
SSPC CHAPTER*7.L 93 W 8b27940 0003b55 OBT W lem of a coatings engineer, since this is the beginning of the formula design. The criteria may be based on either the wet material (perhaps predefining application characteristics), or the dry material (involving a coating s reaction to its environment), or both (a sprayable coating that is highly abrasion-resistant). So, investigating and understanding the end-use and purpose of a coating is primary in designing it. 2. Response to Needs -ProducüSystem Effectiveness Once the performance characteristics are understood, the next phase in formulation development is to formulate and evaluate the coatings generated to meet these requirements. In some cases, the experimental phase consists only of several candidates; in other cases, hundreds of possibilities are tested. Optimizing the required criteria as well as associated factors such as ease of manufacture, cost, application properties, gloss, etc., are all considered. The final product must have all the required properties and satisfy the end-use requirements of the customer. As candidates are created, investigated and eliminated, tests should be continuous to verify conformance to wet and dry coating requirements. Coating materials may be subjected to simulated use testing, involving coating integrity under many environmental conditions, or under physical stress. Coatings may also be continuously analyzed for wet properties to meet specifications or demands for shelf stability or application properties. Consideration must also be given to the coatings system in which the coating will be used; whether it is intended as a primer, intermediate, or finish coat and how this affects other coatings that may be used with it. It is essential to devise and employ methods of simulating use and testing of coating material under many circumstances to ensure the material has met design purposes. 3. Design of Inspection/Conformance Criteria Satisfying performance characteristics completely is impossible unless the proposed design ensures repeated duplication of properties under normal circumstances. Beyond specifying instructions for combining ingredients, the formulator must specify the type and quality of raw materials, all pertinent facts concerning combination and incorporation of these raw materials along with intermediate and final test methods and tolerances. Instructions for labeling, handling and storing coating material must be determined,
and specified and detailed procedures given on use and application. In designing tests for new coatings, controls must be based on predictions rather than statistics, since many variables exist. Tests must be designed to test all variable properties that could affect usability or performance. Test results should make it obvious when the product is not meeting end-use requirements and should assure that upon completion, if stored, handled and used properly, the coating material performs as intended. E. QUALITY OF RAW MATERIALS 1. Selection for Suitability Selection of proper raw materials is essential in optimizing selected properties of the finished product. Selection is normally dictated by past experience with material, what properties it has imparted, the quality and consistency with which it has been received, the ease and safety of use, and cost. Selection of materials that the formulator has had no previous experience with is more difficult, but these can be screened in the design development phase. Other criteria in selecting component materials must include considerations of long-term availability, and delivery and quality of packaging to assure stability. Additional considerations, such as compatibility among various raw material components within a formulation, must also be taken into account. Alternate suppliers for key raw materials should be evaluated thoroughly to assure consistent, qual it y avai la bi I it y. 2. Establishing Acceptance Criteria When a raw material is suitable for use, its parameters must be defined to assure the material is of consistent quality. Only in this way can duplication of the original design be possible. It is necessary to determine which properties of the raw material are essential to the quality of the product. These properties must be definable and measurable so that the requirements can be communicated to the supplier prior to purchase. Decisions must be made on whether the properties are critical to the finished product and must be tested upon receipt, or spot-checked at random, and checked for appearance. It must be determined whether it is necessary to check the condition of the container to satisfactorily preserve the quality of the material. Communicating the criteria for acceptance to the suppliers of these raw materials helps assure that the material received meets specification standards. 3. Testing for Conformance Having established criteria and tolerances, it remains only to subject selected materials andlor
lots of materials to actual inspections. It is necessary to provide inspection personnel with required equipment, acceptance standards and test procedures, and instructions. Many times, the Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 208
SSPC CHAPTERW.~ 73 m 8627940 0003656 TL6 W test procedures are standards that the industry routinely uses to test the particular material. In other cases, tests are unique to the material or a simulation of the end-use of the material. This is the point at which a decision is made whether or not the raw material is fit to provide the required end properties of the coating product. This step is no more or less critical than the previous one defining the tolerances of this measure of acceptability. 4. Quality Data Analysis Analysis of quality data generated through raw material testing or experience is important to continuance of quality in the raw material and finished product. Coupled with analysis of finished goods test data, statistical analysis provides information necessary to adjust raw material specifications to improve the quality, properties or stability of the finished product. It provides objective data on the reliability of raw materials andlor suppliers and makes qualification or disqualification an easy task. It also simplifies selection of quality raw materials to be used in products yet to be developed. This data provides feedback and closes the loop between specifying and using. C. QUALITY OF MANUFACTURE 1. Equipment and Processes The ability of coating material to conform to finished specifications can be affected. by the method of manufacturing. Trial and error during product development normally provides the basis for equipment use and selection, but the formulation type usually eliminates certain methods of manufacture. Use of pilot plant facilities for large scale simulation tests is also helpful in selecting appropriate equipment for production. Optimum batch size must be determined during the first several batches produced, since the process can be more or less efficient depending on the volume. Once criteria are established, each batch must be checked to affirm that the grind, viscosity, color and other properties are within specification. As equipment technology improves, it is necessary to re-evaluate the manufacturing method for many standard products. Continuous improvement in manufacture helps increase the efficiency and may reduce the cost of a quality product. 2. People and Procedures Training of production workers is a key consideration in quality control. The ability of a worker to recognize when something is out of the ordinary
may prevent a batch from proceeding to the next quality control test point without corrections. Clear, non-ambiguous instructions to production personnel leave no room for erroneous interpretaitions. The input from quality control testing should be communicated to production workers as affirmation that the job is being done properly. Problems should be discussed with these people since they have firsthand experience on each batch. Many production units have an assigned technician to work with the formulator to determine the process equipment, check point testing, batch sequence of raw materials, and final acceptance criteria. In the case of resin manufacture, sequence of raw materials, time, and temperature controls must be monitored. It should not be overlooked that appropriate training can prevent many problems in quality. 3. Instruments and Controls Continuous monitori ng and in-process test ing must be planned and executed to assure that batch making is proceeding properly. Temperature monitoring can provide information on the rate or progress of a chemical reaction or be used as a guideline to judge the phase of the mixing process. Viscosity checks can monitor development of thixotropic agents throughout the batchmaking process. Periodic fineness of grind tests are essential in determining proper dispersion of pigments and fillers added in the process. In addition to demonstrating that a batch is progressing as planned, monitoring and inprocess testing may detect problems occurring in batch-making. If testing is done at critical points of the process, any problems discovered can be identified and remedied. In-process batch adjustments, dictated by test results, are a reliable method of assuring that the batch meets established quality criteria. Modifying a completed batch for conformance is far more difficult and frequently less successful than in-process adjustments. The reliability of measuring and test equipment is of utmost importance to quality. Proper use and care of scales and meters must be communicated and monitored as necessary. Regular checking and calibration of test equipment are necessary to guarantee reliable test results. D. QUALITY OF FINISHED PRODUCT i.In-Process Inspection and Adjustment In-process inspection points provide the opportunity to assess progress and quality of the coating material as it is being manufactured. If deviations are discovered at the critical points, modifications can be made and the batch making
can continue. It is possible to identify most critical points during the formulating stage. With experience, in-process tests can be added as reCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 209
SSPC CHAPTER*7.L 93 m 8b27940 0003b57 952 m quired to reduce failure, to meet final test requirements or reduce the necessity of making batch adjustments at inconvenient points. Some additions can be made only at certain points during the batch making; trying to achieve a fine grind of added pigment in a portion of the batch that has very low viscosity, for example, is impossible. Being cognizant of appropriate test points, parameters and tolerances simplifies the task of making successful in-process batch adj ustments. 2. Final InspectionIConformance to Specificqtions It should be evident that if quality is not built into product formulation, the selection of raw materials, and the manufacturing procedure and instructions, it is impossible to build it in at the inspection stage. The function of final inspection is for verification. Pertinent in-depth testing should be used to verify that the batch has been manufactured properly and according to procedures and meets specifications for the finished product. The most important properties to verify on almost every coating material are batch-yield, to verify that the volume produced conforms to the theoretical batch volume; batch weight per gallon, to verify that the material produced exhibits the same density as the theoretical calculation of the component ingredients; appearance, to verify that the batch has been mixed properly, and contains no contamination; fineness of grind, to verify that the ingredients have been adequately dispersed. Verifying these properties assures that formulation instructions have been followed with respect to type and quantity of raw materials added and mixing and grinding during the manufacturing phase. Further wet properties verification includes tests of the following types: viscosity, application properties, film build and sag tests, wet opacity, dry or cure time, usable pot life, percent solids, percent pigment, percent vehicle, and flash point. Additional wet properties tests may be run, depending upon the type of coating material and specifications. Dry properties verification frequently includes hiding power, gloss, hardness of film, and color, as well as additional inspection depending upon coating type and required specifications. Further testing frequently is performed as applicable to test the coating for end-use properties. 3. Testing Through Simulated Use Frequently, pertinent testing includes verification of end-use properties. Adhesion of the coating to a specified substrate or to another coating is important; flexibility of the coating in a particular application may be specified, or resistance to a cer-
tain type of abrasion may be required. Among other end-use tests are weathering in various environments, immersion in chemical solutions, resistance to ultraviolet light and other tests measuring the physical integrity of the coating. Normally, these types of tests are run during the final stages of the formulation design phase, and properties required are built into the formulation. Verifying conformance can be done on initial batches produced and then routinely tested on batches chosen at random. 4. Handling, Storing and Shipping How the product is handled after batch completion is an important consideration from a quality standpoint. Adequate packaging assures that the product is protected from contamination. Packaging must be specified so the product remains stable at specified temperatures. The shelf life of a product depends on how successfully it can be isolated from the environment and is ascertained by the actual storage history of the product. Normally, lower temperatures maximize the useful life. Temperature must be considered during shipping, which may be long enough to adversely affect shelf life. Environmental control assures that a quality product, once manufactured, can be maintained until used. E. QUALITY OF SERVICE 1. Opportunities for Improvement With each batch of coating material shipped, the coating manufacturer has an opportunity to test the effectiveness of the quality control system. Communication from the user is the most valuable information that a manufacturer can obtain to assess the success of quality control. The whole system, from inception based on end-use suitability, can be finally tested and critiqued by the user. All complaints must be investigated and the source of problems determined so that quality control measures can be investigated and, when required, adjusted. Efficient use of quality data provides knowledge necessary for a dynamic control system with potential for improvement with each problem. 2. Success of Recommended Application To close the loop of the quality control system, the success of each product in each application must be communicated to the engineer and formulator to be used as data for designing or improving products.
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SSPC CHAPTER*7-L 93 m 8627940 0003658 899 APPENDIX: TYPICAL QC TESTS* Numerous tests are used for evaluating and monitoring quality control of paints and coatings; the examples shown here are merely typical and illustrative and not intended to be inclusive. Federal Standard 141 A) Viscosity (consistency) Brookfield Viscosity Stormer Viscosity 4281 #4 Ford Cup 4282 Zahn Cups Gardner-Holdt Tubes 4271 B) Dispersion (grind) Hegman Gage C) Density (weight/gallon) Weight/Gallon Cup 41 84 Pycnometer 41 83 Westphal Balance 41 83 Hydrometer 41 83 D) Application Characteristics Levelling Brushing Properties 4321 Spraying Properties 4331 Dipping Properties 21 21 Reducibility & Dilution Stability Odor 4401 Hiding Power E) Film Characteristics Drying Time Gloss Color (Pigmented Coatings) F) Physical Characteristics of Film Flexibility (Elongation) -Mandrel 6222 -Conical Mandrel 6222 Hardness -Pencil -Sward Rocker -Indentation Hardness 621 2 -Durometer Abrasion Resistance -Falling Sand 61 91 -Tabor Abrasor Adhesion 6302
6303 ASTM D D D D D
2196 562 1200 1084 1545
D 1210 D D D D
1475 891 891 891
D 4400 D 823 D 1296 D 344, D 2805 D 1640 D 523 D 3134* D 522 D 522 D 3363 D 2134 D 1474 D 2240 D 968 D 1044 D 2197 --`,,,,`-`-`,,`,,`,`,,`--211 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER87.1 93 8627940 G) Appearance in Container General Condition Coarse Particles and Skins Skinning (partially opened container) Storage Stability (filled container) H) Compositional Volatile & Non-Volatile Content Pigment Content (centrifuge) Water Content -reflux I) Resistance (performance) Immersion Humidity Salt Spray (Fog) Accelerated Weathering (open arc) (Q.U.V.) 0003b59 725 W Federal Standard 141 ASTM 41 O1 3018 404 1 4022 4032 4052 601 1 6071 6061 61 51 61 52 D D D D
2090 185 154 1849
D 2369 D 2698 D 2247 B 117 D 822
*ASTM test similar, but not identical, to Federal Test Method. **Prepared by Ber nard M. Krarnper 53 Note: Test methods vary. All parties should agree upon the accuracy and precisio n required. ACKNOWLEDGEMENT The authors and editors gratefully acknowledge the active participation of the following in the review process for this chapter: Dr. Bernard Appelman, AI Beitelman, Leon Birnbaum, Alex Chasan, Thomas A. Cross, Theodore Dowd, Leonard Haynie, Robert Klepser, I. Metil, William Pearson, Walter Pregmon, Dale E. Radde, Melvin Sandler, Verne Todd and William J. Wallace. BIOGRAPHY John F. Montle is Vice President-Technology of the Carboline Company, responsible for new products development, testing and technical assistance. Upon graduation from Washington University of St. Louis in 1958 with a Bachelor of Science degree in chemical engineering, Mr. Montle joined Carboline Company, where he has been engaged in research & development work on protective coatings for 35 years. He is a member of the National Association of Corrosion Engineers (Chairman of Task Group T-6G), the Subcommittee on American National Standards Institute N101.2, American Society for Testing and Materials D33, the Federation of Societies for Paint Technology, and is on the Executive Committee and Board of Governors of the Steel Structures Painting Council. He has 40 publications and papers on zinc-rich coatings, nuclear power plants, formulation, scanning electron microscopy and film density. Mary Ann Warner currently serves as a Technical Service Engineer for Carboline Company. She acts as research analyst, specification writer and advisor between the development laboratory and end-users. Mrs. Warner graduated from the University of Missouri, St. Louis with a Bachelor of Science degree in mathematics and a strong background in chemistry. First joining Carboline Company in 1973, she has worked as a Laboratory Group Leader, Quality ControllQuality Assurance Manager and Quality Specialist. Following four years of field sales, she accepted her current position. REFERENCES 1.
Paint Testing Manual , (GardneríSward) S.T.P. 500. ASTM,
13th Edition, 1972. 2. Manual of Coating Work for Light-Water Nuclear Power Plants , ASTM, 1st Edition, 1979. 3. Phillip B. Crosby, Quality is Free, McGraw-Hill Book Co., 1979. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 212
SSPC CHAPTER*7-2 93 m 8627940 0003660 447 m CHAPTER 7.2 QUALITY ACCEPTANCE OF PAINTS AS RECEIVED BY THE USER by John R. O Leary and Garland W. Steele Testing received products, referred to as acceptance I. ACCEPTANCE SAMPLING testing, is the responsibility of the purchaser. The purpose is to determine that the quality of a manufactured product Obtaining unbiased sa mples is the most important meets specified requirements. Acceptance testing main- phase of the acceptance p rocedure. If samples are not an tains the integrity of procurement procedures when pur- unbiased portion of the batch, no amount of testing can chases are made on the basis of low bid. reliably indicate characteristics of pa int. Extreme care Specifications accompanying a paint purchase or re- during sampling must be exer cised. The sampler should be quest for bid should reference the purchaser s acceptance familiar with the produc t, have knowledge of the manuplan and should be discussed with the paint manufacturer. facturing process and be aware of the importance of The acceptance plan should include, but not necessarily sampling techniques. be limited to, the following: Sampling containers should be at least one pint, Labeling requirements -information that iden-preferably glass or metal, with an air-tight lid. Containers tifies the product, and other data such as manufac- must be clean, dry and nonre active with paint. The conturer s name, batch number, type of paint, grade tainer, when filled, should have no more than 6 percent air (spray, brush, rolled), amount and type of thinning space. solvents, percent total solids by volume (for use in Sample containers sent to t he laboratory should be wet film thickness calculations); packaged for shipment and fully identified. Ma nufacturer s inspection of finished product -acceptable and name, batch number and the date o f sampling should be unacceptable conditions of the paint at the time of written on or attached to th e container. Other information, sampling, such as settling, skins, etc; such as quality control test results, de stination, color, Sampling -the number of samples that will be date of manufacture, order numbers, etc., should be with taken, the location and method of sampling; the sample or sent separately, if re quested by the Testing -the frequency of tests, number to be con- purchaser. ducted, procedure and time to conduct test; Method of identifying tested and approved A. SAMPLING FROM STORAGE TANKS OR
materials; and VATS Action available to the manufacturer when test It is recommended that sampling b e done by a purresults indicate material does not meet acceptable chaser s representative during pouring. Safety or other limits. considerations may require sampling by an employee of It is not believed advisable to accept material with the manufacturer. In this c ase, sampling should be marginally failing test results. Acceptance of marginally witnessed by a purchas er s representative. failing material, even at a reduced price, could suggest During filling, samples of sufficient size should be that the property being measured is irrelevant; that the drawn from the first on e-third, the second one-third, and purchaser recognizes the specification requirement is un- the last one-third of the pour. These samples should be realistic; or that the limits have been set without regard to tested individuall y by the supplier to determine uniformity. variables (material, manufacturing, sampling and testing). If test results such as weight per gallon, viscosity, and Waiving specification limits, regardless of how small the fineness of grind fall within specification limits, it can be deficiency, encourages laxity in the manufacturer s quality a,ssumed the material has been properly mixed and samcontrol. pled. Quality control test results should be available to the Realistic specification limits can be established purchaser s representative. Afte r the manufacturer s tests without costly and time consuming experimental projects. are completed and the r esults are acceptable to the Specifications can allow tolerances acceptable to the purchaser, the three sampl es are divided to form duplicate manufacturer and purchaser. Specifying target values, or triplicate samples, one to be sent to the purchaser s rather than limits, and using the manufacturer s tolerance laboratories for analys is, one to be retained by the can sharply reduce failures without sacrificing quality. purchaser s representativ e, and one for the manufacturer. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 213
STEEL STRUCI'URES PAINTING COUNCIL APPLICATION RECOLID Pano1 No. Looation Exporure Projmt No. Araooiitod Temts Supervised by Suriaoe REDUCTION Matarialm Protreotment 1.t coot 2nd Coat 3rd Coat Pmint name Ssoond pari Thinner uaed Vol. .% of paint Vimoooity I I l I PAINTING DETAILS Dato Painted I I I I I I Method Uoed 1 I I I Air Tem~orature I I I I ~ Surfaoe Temperatura I I Eumidity Weathor Woifht per fd. Wmiiht Belor, Weilht Attar I I 7 I Paint Ured I 1 1 I I 1 I Film Thioknoormeao. Workin$ Proputiso Paokade Condition PROPERTIES Color I I I I FIGURE 1 Steel Structures Painting Council Paint Application Record. --`,,,,`-`-`,,`,,`,`,,`--If the supplier wishes acceptance testing conducted using a sampling tube or oth er suitable device. When this before paint is poured into cans or drums, samples should sampling procedure is used, the supplier must ensure that be obtained at the top third, middle third and bottom third, the paint remains u niform until it is canned or packaged. 214
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TEST NO. PROBLEM NO. PAINT NO. SUBSTRATE LOCATION COLOR PURPOSE OF XPOSED TEST REMOVE0 EXPOSURE N Z F W VFRT. 4 so I IO 3 6 9 12 i5 18 21 24 27 30 33 36 39 42 45 48 Si 54 57 60 8 6 4 2 O IO 6 9 i2 I5 18 21 24 27 30 33 36 39 42 45 48 51 54 57 60 8 6 4 2 O FIGURE 2 Front side of Federation of Societies for Coatings Technology single panel form. 'This form has been cancelled. No replacement is available. 215 FEDERATION OF SOCIETIES FOR COATINGS TECHNOLOGY 1315 WALNUT ST., PHILADELPHIA, PA 19107 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERm7-2 93 = Bb279q0 0003bb3 156 I Sf COAT 2 NO COPT 3RD COAT 4 TH COPT ~ --`,,,,`-`-`,,`,,`,`,,`--PREPPRPTION OF THE SURFACE----. I I I J PROTECTION OF THE BACK________ I l l I 1 I I I I I I i REMARKS: ~~~ FIGURE 3 Back side of Federation of Societies for Coatings Technology single panel form. AMERICAN SOCIETY FOR TESTING MATERIALS 1916 RACE ST, PHILADELPHIA, PA 19103 216 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERa7.2 93 8627940 0003664 O92 B. SAMPLING FROM CONTAINERS If containers are filled before the purchaser s representative arrives, or if sampling is done at destination, two containers from each individual batch are randomly selected. Because of the likelihood of settling upon standing, thorough and careful agitation by mechanical means andlor boxing is recommended before sampling. The exception is paint that is formulated to be nonsettling. To test the effectiveness of agitation, pour half of mixed material into an empty container of equal size and determine the weight per gallon for each half. If results do not deviate more than 0.5 percent, it may be assumed that the material is adequately mixed. Some paints, notably latex, tend to trap air bubbles when stirred vigorously. Entrapped air should be allowed to escape before weight per gallon is determined. To minimize the time needed for this, excessive agitation should be avoided. When agitation is not possible and the container size facilitates shipping, two unopened containers should be sent to the purchaser s laboratories for complete analysis. Paints that are not ready-mix and are multi-component should be sampled as agreed between the purchaser and manufacturer. II. ACCEPTANCE TESTING (LIQUID PAINT) Most methods are standardized by paint technologists and measure characteristics or physical properties of paint. Results of paint testing depend on test procedures; therefore, it is critical that standardized test procedures be used and agreed to by the manufacturer and purchaser. Test procedures listed in this section include physical, chemical and instrumental test methods. Paint testing is standardized by the National Paint and Coatings Association, The American Society For Testing and Materials, and The Federation of Societies for Coatings Technology. Those interested in testing the composition or properties of coatings should have the following references. Federal Standard 141, Paint, Varnish, Lacquer and Related Materials, Method for Testing; American Society For Testing Materials, Paints 6.01, 6.02 and 6.03, which contain tests for paints, pigments, resins and other raw materials; and Garner/Sward (STP 500) Paint Testing Manual, published by the American Society for Testing and Materials, an excellent source which contains many tests for physical, mechanical, chemical and appearance properties of paints and coatings. Federal Test Paint Property Method ASTM Preparation of Panels D 609 Preparation of Tin Panels D 609
Viscosity (KU) 4281 D 562 Weight Per Gallon 41 84 D 1475 Fineness of Grind D 1210 Water Content D 95 Coarse Particles and Skins 41O1 D 185 Drying Times: D 1640 Set To Touch D 1640 Dry For Recoating Dry Hard Pigment Content D 2371 Vehicle Content D 2371 Non-Volat ¡le Con tent 4041 D 2369 Adhesion D 3359 Brushing Properties 4321 Spraying Properties 4331 Exposure Tests of Paints on Metals 61 60 D 1014 Salt Spray Resistance 6061 B 117 Accelerated Weathering 6151 D 822 61 52 Leafing 4451 D 480 7233 Flexibility 6222 D 522 Paint tests should be done under controlled laboratory conditions. Standard procedures often specify temperature and relative humidity. Test conditions have a profound effect on some properties while on others they will have little or no effect. When it is not practical to test under controlled conditions, the exact test conditions should be recorded. In case of dispute or disagreement between laboratories, the test should be conducted under the ASTM standard conditions. 21 in distilled water. *Test methods vary. Ail parties should agree upon the accuracy & precision required. --`,,,,`-`-`,,`,,`,`,,`--7 Methods in the following tables are commonly used. Most test methods listed are quantitative in nature. Methods like gas chromatography and infrared spectroscopy also lend themselves to the qualitative finger print technique. Infrared Spectroscopy -Its Use In The Coating Industry, published by the Federal Society for Coating Technology, is an exceptional reference for infrared analysis. Many other instrumental methods are available for testing and identifying paints and constituents. Another excellent reference for a variety of methods is Part 10 of GardnerlSward, STP 500. TABLE 1 PHYSICAL TESTS* Recoatability -The paint film shall not be lifted by a succeeding specified coating. Compatibility -Manufacturer s recommended volume of
paint and thinner shall be mixed without curdling, livering, separating, or otherwise affecting the paint except to thin it. Storage Stability -No gas pressure shall build up after 30 days storage at 75OF (24OC) f 5OF (3OC). Water Resistance -The paint shall show no visual deterioration, other than discoloration after two days immersion Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER+7.2 93 8627940 0003665 T29 Paint Property Test Method TABLE 2 Zinc Oxide ASTM D 34 CHEMICAL TESTS Zinc Powder ASTM D 521 Paint Property Chemical Resistance Liquid Dryers Drying Oils Aluminum Aluminum Silicate Barium Sulfate Basic Carbonate of Lead Basic Lead Silico-Chromate Basic Sulfate of Lead Calcium Carbonate Calcium Sulfate Chrome Green Chrome Orange Chrome Yellow Chromium Oxide Green Clay Copper Copper Oxide Extenders in Colors Iron Blue Iron Oxide Leaded Zinc Oxide Lithopone Magnesium Carbonate Magnesium Silicate Mercuric Oxide Mica Molybdate Orange Para Red Red Lead Silica Strontium Chromate Titanium Oxide Toluidine Red UItramarine BI ue Water Soluble Salts White Lead Yellow Iron Oxide Test Method ASTM ASTM ASTM ASTM ASTM
D D D D D
1308 564 555 480 718
ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM ASTM
D D D D D D D D D D D D D D D D D D D D D D D D
34, D 715 1301 1844 1301 34 34 126 126 126 126 36, D 718 283 283 126 1135 768, D 50 34 34 34, D 717 34 284 716 126 970
ASTM D 49 ASTM D 34, D 719 ASTM D 1845 ASTM D 2701, D 1394 ASTM D 970 ASTM D 1135 ASTM D 2448, D 2455 ASTM D 1301 ASTM D 768 The following cancelled specifications have been removed from this table: D 50, D 135, D 767, D 2742, and MIL-L-14486. Zinc Sulfide ASTM D 34 Zinc Yellow ASTM D 444 TABLE 3 INSTRUMENT TESTS Paint Property Test Method Instrument Dry Opacity ASTM A 2805 Reflectometer Gloss ASTM D 523 Glossmeter Color ASTM D 2244 Colorimeter Vehicle Identif ication ASTM D 3168 Infrared Spectro phometer ASTM D 3271 Gas Chromatograph Solvent
Identification ASTM D 3271 Gas Chromatograph Vehicle Solids Identification ASTM D 2621 Infrared Spectro phometer The listed methods can be obtained from the following: Paint Testing Manual, GardnerSward, STP 500 American Society for Testing and Materials 1916 Race Street Philadelphia, Pennsylvania 19103-1 187 Federal Test Method Standard No. 141 Superintendent of Documents U.S. Government Printing Office Washington, D.C. 20402-9325 ASTM Standards American Society For Testing and Materials 1916 Race Street Philadelphia, Pennsylvania 19103-1 187 Standardization Documents Order Desk 700 Robbins Avenue Building 4, Section D Philadelphia, Pennsylvania 191 11-5094 21 8 --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERJ7-2 93 8627940 O003666 965 TEST NO. PROBLEM HO.-___COLOR INSPECTED BY LOCATION EXPOSURE W S E W VERT. 45. DATE PINEL OR PAINT NO. PROPERTIES REYARKS I FIGURE 4 Federationof Societies for Coatings Technology multi-panel Record form. FEDERATION OF SOCIETIES FOR COATINGS TECHNOLOGY 1315 WALNUT CT.. PHILADELPHIA, PA 19107 111. ACCEPTANCE TESTING: OUTDOOR conductive material should be used as a barrier between EXPOSURE TESTS ON PAINTED METAL the panel and rack. Racks should not project sha dows There are two types of outdoor exposure tests: service across test panels. Test panels should be placed on the tests, in which painted portions of structures are tested; rack so shadows are not cast from one panel to the next, and field tests, in which panels prepared in a laboratory rain water will not dr ip or flow from one to another and are exposed to an environment similar to conditions of a water will not splash f rom the ground onto the panels. service test. Each type has advantages and disadvanB. TEST PANELS tages. Field tests are more easily standardized and are the focus of this discussion. Panels may contain many of the same features as A useful guide for testing methods is in the American structures to be painted, but not in such a way as to Society for Testing and Materials D 1014, Standard Method obscure performance on flat or scribed surfaces. Mill of Conducting Exterior Exposure Tests of Paint on Steel. scale, sharp edges and corners, angles, crevices, welds This describes the metal used for panels, size of panels, and rivets are commonl y encountered in steel structures, panel conditioning, field positioning and monitoring of and some types of test p anels contain these features. panels, and evaluation procedures. Each panel should have an individual and perm anent coded identification mark stamped on the back. Panels A. RACKS can be fabricated by the testing organization or purchased Racks used to hold panels for field tests can be con- from a number of commercia l firms. structed of any sturdy material. If racks are metal, a nonCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 219
SSPC CHAPTER*7.2 93 = 8627940 0003bb7 8TL C.PANEL PREPARATION Panels can be initially conditioned by degreasing and rusting. Panel rusting should be to the same degree as the substrate and when possible, should be in an environment similar to that in which shop or field paint is exposed. When field paint is used in a marine environment, rusting by salt should be considered. If paint is intended primarily for maintenance, panel rusting before cleaning should be severe. If the paint is for new structures, slight rusting is appropriate. After rusting, panels are cleaned in a manner encountered in the shop or field by hand cleaning, power tool cleaning, blasting, steam or hot water jets to remove salt, or other acceptable means. Paint application should be similar to that encountered in the shop or field. Paint film is measured (SSPC-PA 2) after thorough curing and examined visually with a magnifying glass. The dry film thickness and minor flaws of each coat on each panel are recorded on a form, such as shown in Figure 1. Panels with paint flaws that might influence performance may be discarded or if of interest to the purchaser, may be included in the evaluation. A minimum of four panels are typically prepared for evaluation of each paint or paint system, one to be retained as a reference, three to be installed on the racks. Blast-cleaned panels need fewer replicates because of more consistent performance. D. FIELD EVALUATION Periodically, field evaluations of test panels are made. No less than two per year are recommended. The evaluation team can include people who have had experience in paint performance evaluations. Rusting, as per SSPC-Vis 2 (ASTM-D 610) is usually a primary criterion in evaluating paints for protection of structural steel using pictorial standards. Properties such as chalking, checking, cracking, rusting, blistering, and others that are deemed important to the evaluation team should be given ratings from 10, representing the initial condition (perfect), to zero, representing complete failure. Ratings for each property of each panels should be recorded on forms such as those shown in Figures 2, 3 and 4. The use of the forms in Figures 2 and 3 is described in ASTM-D 1150, which also contains the tabulation listed below of pictorial reference standards. ASTM-D 4214 -Chalking ASTM-D660 -Checking ASTM-D661 -Cracking ASTM-D 772 -Erosion ASTM-D672 -Flaking ASTM-D610 -Rusting (SSPC Vis 2)
ASTM-D 714 -Blistering Pictorial reference standards can also be found in the ExACKNOWLEDGEMENT The authors and editors gratefully acknowledge the active participation of the following in the review process for this chapter: AI Beitelman, Robert Brady, Paul Campbell, Richard Drisko, Parker Helms, Marshall McGee, I. Metil, William Pearson, Eugene Praschan, Melvin Sandler, John R. Saroyan and William WalIace. BIOGRAPHY The late John R. O Learywas Assistant Director of the Materials Control, Soil and Testing Division of the West Virginia Department of Highways. He was employed by the Department beginning in 1963 in the capacity of Head of the Coatings and Corrosion Section. He was a graduate of Western Illinois University with a BS in Education in Mathematics and Colorado School of Mines with a Geological Engineering degree. He was a registered professional Engineer in the State of Illinois and West Virginia and a member of the American Society for Testing and Materials and the National Association of Corrosion Engineers. BIOGRAPHY Garland W. Steele, P.E., President, Steel Engineering, Inc., has over 37 yearsexperience in highway engineering. He received his BA degree from West Virginia State College and is a registered professional engineer in the States of West Virginia and Virginia. He is a member of the American Society of Civil Engineers, the National Society of Professional Engineers, the American Society for Testing and Materials (ASTM), and theAmerican Concrete Institute. During his thirty years with the West Virginia Department of Transportation (1955-1 988), he served as a member and chairman of many technical sections in the American Association of State Highway and Transportation Officials and the Transportation Research Board. He is currently a member of the ASTM Board of Directors. His major field of interest is in construction, maintenance, and operation of transportation systems with special emphasis on quality. His many papers and publications involve a wide range of subjects including statistical research, statistical quality assurance, probability specifications, certification for materials acceptance, com-
puter applications, technicians certification programs, polymer modified concretes, data handling systems, and performancespecifications. posure Standards Manual, published by the Federation of Societies for Coatings Technology. --`,,,,`-`-`,,`,,`,`,,`--220 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERa7.2 93 m Ab27940 0003bb8 738 m REFERENCES 1. ASTM Standards, Parts 27, 28, and 29 American Society for Testing and Materials. 2. Federal Test Method Standard No. 141, Paint, Varnish, Lacquer & Related Materials: Methods of Inspection, Sampling and Testing . 3. Henry ,A. Gardner and G.G. Sward, Paint Testing Manual , ASTM STP 500, 13th Edition, 1972. 4. Quality Assurance Through Process Control and Acceptance Sampling , U.S. Department of Transportation, Federal Highway Administration, Washington, D.C., April 1964. 5. Statistical Quality Assurance Workshop Proceedings , US. Department of Transportation, Federal Highway Administration, 1968. 6. Testing of Paints , Oil and Colour Chemists Association Paint Technology Manuals (No. 5), London, England. --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 221
SSPC CHAPTER*B.O 73 8627940 O003667 b74 September 1993 (Revised) CHAPTER 8 COMPARATIVE PAINTING COSTS By G.H. Brevoort, S.J. Oechsle, M.R. She Since the purpose of protective coatings is primarily economic, no practical treatise on painting structural steel is complete without a discussion of comparative costs. The specifier must have access to basic information and procedures identifying candidate systems that are suitable in the specific environment, costing each, making a selection and justifying the choice. Because there is considerable literature on coatings cost evaluation, this chapter deals primarily with hypothetical practical examples of alternative costs. Assumptions regarding paint life are very conservative and apply mainly to severe environments. Values for interest rates, labor, materials, salaries, overhead, energy, etc. have been assumed to make illustration possible. In some examples the time-value of money is neglected with the tacit assumption that interest rate is currently balanced by inflation rate. Maintenance examples are based, whenever possible, on new but sound industry practice, such as repainting when SSPC-Vis 2 Rustgrade 7 or 8 is reached or when 10-15% repainting is required. Cost factors in surface preparation are reviewed in a separate chapter. Cost data represent the authors best estimate for 1992-93, and are intended only to illustrate methods of comparing alternatives. Prices and costs in specific areas should be secured from local paint suppliers and contractors. Subjects covered in this chapter include Elements of Field Painting Costs (She); Cost Factors in Coating Selection (Brevoort); and Types of Contracts (Oechsle). I. ELEMENTS OF FIELD PAINTING COSTS When selecting paint or a protective coating system, a study of comparative costs of the systems is usually made. Typical choices involve generic types of coating, number of coats, shop or field coating and surface preparation met hods. The cost of labor, equipment and material is constantly changing. A coating system considered too expensive today may become economically attractive if material costs rise faster than labor, or if a technological improvement reduces the required labor. The number of circumstances to consider are too great to list individually. Coating steel involves the condition of steel, geographic location, accessibility, size of the project, specifications and other factors.
One preferred method for evaluating and selecting a coating system is to secure a detailed analysis and cost estimate from an experienced coatings estimator such as a @Portionsof this text copyrighted 1993 by NACE International. All Rights Reserved by NACE; reprinted by permission. 222 painting contractor or applicator. In this manner, specifics of the particular job can be dealt with, and the estimate reflects all aspects that might otherwise be missed. The cost of each alternate should be considered on a total project rather than a per square foot basis for several reasons. First, the magnitude of the work can be recognized and reflected in the cost estimate. Secondly, certain aspects of the work are better evaluated on a whole project basis. Different surfaces probably have different costs per square foot (structural steel, tanks, piping, valves, etc.). Certain elements of the estimate such as productive labor operations (abrasive blasting, coating application, etc.) lend themselves to a square footage basis for production rates. Support operations and equipment generally are expressed in terms of productive labor requirements (e.g., one pot tender for every two productive workers during the abrasive blasting and priming operation). And finally, some operations are most appropriately expressed in terms of the total project, such as move-in and move-out, rigging, and similar operations. A. ELEMENTS OF COSTS 1. Labor Labor should be figured on a person-hour or person-day basis for the project based upon the operations performed. Typically, these include cleaning, abrasive blasting, application of each coat of paint, pot tending (for abrasive blasting), helping rigging, removing spent abrasive and supervising. Productive operations are calculated on the basis of labor production rates applied to each surface area classification involved. Classifications might include large structural shapes, small structural shapes, miscellaneous steel (handrails, ladders, etc.), piping, valves, equipment, vessels and so forth. Following is a description of typical labor support categories: a. Pot Tender -Assists abrasive blasting operators to adjust abrasive blasting pots, refill pots and frequently assists priming operations. The ratio of pot tenders to blasters depends on equipment involved and labor restrictions. A single tender should be able to handle at least two pots. When bulk abrasive is used, pot tending is much less time consuming; frequently, the crew foreman doubles as pot tender. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from
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SSPC CHAPTERU8.0 93 m 8b27940 O003670 396 m b. Abrasive Handlers -Handle spent abrasive, when required. Most frequently abrasive handlers are used to remove the abrasive from inside a vessel or from the immediate work area; sometimes, the abrasive must be hauled to a remote dump site. Abrasive removal is normally figured on a pounds per hour or tons per day basis. The rate is determined by the distance the abrasive has to be moved, the obstacles in the way, and the equipment. c. Helpers -Number varies with the requirements of the project. Helpers may be used to mix paints and assist in moving rigging; spray painters frequently take care of these operations when working on the ground but not when working off staging. The need and degree of use of helpers should be evaluated on a case by case basis. d. Riggers -Deployment, placement and removal of equipment enabling workers to gain access to surfaces to be cleaned and coated. This normally includes hanging suspension scaffolding and cages, erecting scaffolding, etc. The most efficient rigging method should be evaluated for each case; it is frequently dependent upon the operations to be performed (Le., abrasive blasting versus hand or power tool cleaning). e. Supervisors -Field supervision. This is normally figured based on the number of crew days and supervisors required. A single supervisor seldom has more than 8 to 10 workers. A working foreman may be employed on crews of up to about 6 persons. Once the person-hours for each labor operation are determined, the labor cost can be determined by multiplying the person-hours by the hourly rate for each classification of worker. The person-hour rate is the labor cost plus an overhead fee. Labor cost is the sum of wages, fringe benefits, travel pay and subsistence. Companies differ in how they handle fees on labor and the other components of the total system cost. One method is to apply only payroll taxes, insurance, small tools and expendables to the labor cost; labor cost is then accumulated with equipment and material cost and profit and overhead is applied to all of it as a group. Some firms consider payroll taxes and insurance as part of labor cost instead of fees, but the difference in methods is not significant for the purpose of comparison. There is normally a difference in wages paid to skilled and unskilled labor. Blasters and painters receive more than helpers. Many unions require premiums for wages on such items as abrasive blasting and spray painting, working with epoxies and other exotic materials, working more than fifty feet in the air and so forth. Supervision normally receives the highest hourly rate.
2. Equipment Equipment required for individual jobs varies with type of job, size and configuration of the structures, type of surface preparation, type of paint or coating, etc. Following is a description of typical operations and the equipment required. a. Abrasive Blasting and Priming -Compressed air for the abrasive blasting is determined by the nozzle size and other factors, figuring 350-450 CFM per nozzle for aiypical job. Blast pots, hoses, nozzles and helmets (with appropriate air lines and filters) need also to be figured. Spray equipment for priming would be figured as indicated below; since a large source of compressed air Wou Id al ready be avai IabIe, add it ional compressed air would not be needed for spraying primer after abrasive blasting. b. Conventional Spraying -Spray pots are figured as required; the larger pots can handle two spray guns. If compressed air is not otherwise available, a small compressor may be needed. c. Airless Spraying -Airless pumps are figured as required. Production sized units can normally handle two guns unless the material is highly viscous or other circumstances warrant. A power source (electrical or compressed air) needs to be used for the pump. d. General -All jobs need a pickup or larger trucks to haul workers, equipment, and materials. Additionally, the project may require rigging cages, lifts, scaffolds, or similar items. Offices, change rooms, storage rooms, sanitary facilities, etc., may also be required. The cost of equipment is figured on the number of days each piece of equipment is used at reasonable rental rate. Even if the firm owns all of the equipment, it should recognize and allow for recovering the investment in that equipment. Items costing at least several hundred dollars are normally considered rental equipment. Supplies associated with rental equipment are either allowed for in the rental rates or are themselves rental items. Included in this category are hoses, nozzles, guns, abrasive blasting helmets, fuel, and so forth. Local rental firms or published sources such as the Rental Rate Blue Book can be used to determine rental rates. Rental rates are normally based upon continuous charge during the possession of the equipment with 5-day, 40-hour weeks. The renter normally furnishes fuel and the operator. 3. Materials a. Abrasives -The cost is figured by applying a consumption rate to the number of abrasive blasting person-hours or person-days figured. For abrasives such as sand, slag, and many mineral Copyright The Society for Protective Coatings Provided by IHS under license with
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SSPC CHAPTER*B.O 73 H 8b27940 0003b71 222 D abrasives, one-quarter to one-half ton is used per hour. The higher consumption rates would be expected on large jobs with continuous operating bulk equipment. The cost of abrasives can vary so greatly that the cost of the entire coating system can more than double if changing from one of the lesser expensive when the abrasive is not recycled. Delivery costs of abrasive can also be a major cost factor in remote locations. When estimating costs, the abrasive supplier should be contacted for a price to avoid serious errors in the total system cost. b. Paint andlor Protective Coatings -The quantity of each paint or coating is determined by dividing the surface area to be covered with that material by the practical coverage. The practical coverage is the theoretical coverage less a loss factor, typically 20-30%.The quantity of solvents required for thinning and clean up should be figured, typically this is about 20-30% of the quantity figured for paint. The quantity of each material is multiplied by the cost per unit and taxes and freight charges added in, for the total paint cost. 4. Cost Summary The costs individually calculated for labor, equipment and materials are added together and a fee for overhead and profit applied to give a total system cost. When considering alternatives to be undertaken by the same firm, the amount of the fee for overhead and profit is not important to determine relative costs. On the other hand, if an owner is considering alternatives involving work by different vendors or himself and a vendor, differences in fees by the different organizations might be significant. B. AN EXAMPLE Consider cleaning and painting the exterior shell of a new 200 foot diameter x 48 foot high storage tank. The calculated square footage is 30,159. If the first alternate is a near white blast (SSPC-SP IO),3 dry mils of inorganic zinc and 5 dry mils of polyamide epoxy, the system cost could be estimated as follows: TABLE 1: Summary of Assumed Costs for Example of Storage Tank Coating NOTE: The following 1992-93 data and cost calculations are presented as examples only and are not intended for use on actual jobs. Costs vary by location, job, and time. Secure est imates locally on the specific job involved. *Assumed Labor Costs: Journeyman wage
Foreman wage Fringe benefits Assumed equipment costs (fueled): 750 CFM Compressor Four-nozzle blast pot with all hose, hoods, nozzles, etc. Airless spray rig with hose and 2 guns Spider Pickup truck Assumed abrasive cost: Assumed coatings cost: MIN* MAX USE $15.00/hour $22.50/hour $19.00/hour $17.50/hour $25.00/hour $21.00/hour $ 4.00íhour $ 7.50/hour $ 5.501hour $1 80.001day $100.00/day $ 35.001day $ 30.00lday $ 30.001day $60.00/ton delivered Inorganic zinc -$35/gallon -theoretical coverage 300 sq. ft./gal. @ 3 mils Polyamide epoxy -$18/gallon -theoretical coverage 160 sq. ft./gal. @ 5 mils Thinner for both -$8/gallon Assumed internal company costs Taxes and insurance 60% of wages Tax Social Security Federal Unemployment tax State Unemployment tax Liability Workers Compensation Overhead and profit 35% of total labor, equipment and material --`,,,,`-`-`,,`,,`,`,,`--224 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
Summary of Assumed Costs for Example of Storage Tank Coating (Cont'd) Assumed production rates: Blast @ 100 sq. ft./hr. 302 worker hours Prime @ 300 sq. ft./hr. 101 worker hours Finish @ 500 sq. ft./hr. 60 worker hours Rig (from experience) 16 worker hours Foreman (working) 1 :4 120 worker hours TOTAL --599 worker hours Pot tender and helper were not figured separately because with this small crew t he foreman could fulfill those functions. The labor cost would be as follows: Journeyman 479 @ $19 $9,101 Foreman 120 @ $21 $2,520 Fringes 599 @ $5.50 $3,295 Subtotal = $14,916 Taxes & Insurance @ 60% (Wages only) = $ 6,973 TOTAL LABOR = $21,889 After blasting and priming is completed, the large compressors could be exchange d for smaller compressors, but since the finch coating will be done in such a short period of time, t his is impractical. With a 5-person crew working 8-hour days, the job will be done in 15 working days: Therefore, th e equipment is: 750 CFM Compressors 2 units x 15 days @ $ 180 = $ 5,400 Blast pot 15 days @ $ 100 = $ 1,500 Airless spraying rig 2 units x 15 days @ $ 35 = $ 1,050 Spider 4 units x 15 days @ $ 30 = $ 1,800 Pickup truck 15 days @ $ 30 = $ 450 TOTAL EQUIPMENT = $10,200 Materials cost: Abrasive -Vz ton per worker hour 302 x '1'2 @ $60 = $ 9,060 Theoretical (25% loss) Practical Gallons Coating Zinc-rich EPOXY Coverage Coverage 300 225 160 120 Thinner -385 gallons x 20% Required 134 251 = 77 Price $35
$18 $8 cost $ 4,690 $ 4,518 $ 616 Total coatings Abrasive from above = = $ 9,824 $ 9,060 Subtotal Sales tax 5% = = $18,884 $ 944 TOTAL MATERIALS = $19,828 Price Summary Labor Material Equipment $21,889 $1 9,828 $1 0,200 Overhead & Profit @ 35% Subtotal $51,917 $18,171 TOTALCOST = $70,088 'Labor rates for the Northeast If the system were being compared to a system of commer- would be required for a brasive blasting equipment and less cial blast (SSPC-SP 6) and three 2.5 mil coats of alkyd, the abrasive would be u sed. The cost of the coating materials calculations could result in a price of, say, $40,000. The in the second alterna te is less also. second alternate would be less for the following reasons: The second alternate a t $40,000 is lower in initial cost; Abrasive blasting to a commercial blast is faster than but is it the most econom ical in the long run? Perhaps not. to a near white. Spraying alkyd is slightly easier and faster The analysis must be continued: What is the ultimate servper coat than either inorganic zinc or epoxy, plus the ice life of each alternat e (¡.e., how long before the system millage is lower per coat. The fact that this is a three-coat fails and has to b e blasted off)? What maintenance costs rather than a two-coat system would be substantially will be entailed during the service life and when will they be washed out by the increased production rates. Less time incurred? 225 Copyright The Society for Protective Coatings Provided by IHS under license with
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SSPC CHAPTER*B.O 93 8627940 0003673 OT5 This example leads into the other portions of this chapter which deal with identification of candidate paint systems, expected service life, and economic evaluation and justification. The analysis of coating alternatives begins with the determination of cost using either currently available, specifically applicable cost data or a detailed cost estimate. The maintenance cost and projected service life must also be considered, weighing the value of monetary expenditure over time. II. COST FACTORS IN COATING SELECTION Identifying and justifying acceptable paint and protective coating systems for a given environment is difficult, and often neglected. If the project is a new plant, specifications often cal¡ for hand (SSPC-SP2) or power-tool (SSPCSP 3) cleaning, a shop primer and one or two topcoats of alkyd applied at the jobsite. Sometimes an old specification from a previous job is simply pulled from the file, renamed, and used on the current job without consideration of whether or not it is acceptable in the new environment. Frequently, the coatings engineer is nonexclusive and has other areas of responsibility. Paint and coating selection cost estimates and justification for new construction or maintenance can be a confusing and difficult task for the nonexclusive coatings engineer. It need not be. The purpose of this cost guide is to help coating engineers understand basic cost elements, show how to calculate approximate applied costs and outline procedures for arriving at an intelligent coating selection based on fact with supportable detail. Use of the guide can help clarify coating selection and increase effectiveness. It must be emphasized that this cost guide is just that -A GUIDE. It is not intended as an infallible or absolute cost source. It is not meant for use in calculating actual job costs, nor as a tool for negotiating with contractors and fabricators. The cost guide gives the specifier a simplified means of calculating total applied costs based on current material, cleaning and application costs. The cost information has been supplied by representative US.applicators and paint suppliers. The base cost produced by the guide is for structural steel on the ground at the jobsite, with costs for jobsite touchup if shop priming is considered. Percentage factors also are included to convert base costs to in-place costs. The cost guide gives nonexclusive specifying engineers a method to help them identify candidate systems for a given environment. It establishes a pro-
cedure for calculating approximate applied costs and for estimating expected service life and cost per year for each proposed system. The use of the guide facilitates comparison, selection and justification of a suitable system. --`,,,,`-`-`,,`,,`,`,,`--A. PRELIMINARY COST ISSUES Some common questions, factors and influences that the specifying engineer will encounter are discussed on the following pages. Why Attempt Cost Calculations? We live in a world of costs, numbers and justification . Decisions on most matters and materials are made on the basis of cost savings and economics. To make good selections -and have them accepted by management -the specifying engineer must include a sound economic analysis. Why Paint At All? Unfortunately, without a protective coating, steel rusts and corrodes at varying rates depending on environment andlor climate. An alternative to painting is to specify thicker steel to compensate for corrosion loss. Assuming a twenty-year plant life, if the corrosion rate of the steel in a particular environment is above 2 mils per year, painting is less expensive than increasing steel thickness.(7) Aesthetics, too, are an important reason to paint. Any structure simply looks better painted. While some people discount painting for appearance, it is, in fact, an important consideration in most cases. Importance of Initial Painting Once a structure is in operation, it is sometimes impractical, if not impossible, to blast clean, spray or to get sufficient down time to do an adequate maintenance painting job. In most cases, the original painting is the only time in the life of the structure when the job can be done effectively and economically. Therefore, the initial coating selection is of critical importance. The alternative is costly andlor ineffective maintenance for the life of the structure. Design For Total Structure Life Whether for new construction or maintenance the coatings engineer should consider the total cost and number of paintings required for the design or total life of the structure. If the design life is three years, a coating system should be selected that will last only that long. However, if the design life is 20 years, a long-life system requiring a minimum
number of maintenance paintings make sense. See below, Required Life (Design Life) for more details. To be cost-effective the immediate painting must be evaluated from both a short-term, immediate economic viewpoint as well as the long-term, total-structure-life viewpoint. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 226
SSPC CHAPTERt8.0 93 8627940 O003674 T3L 5. Why Blast? Hand (SSPC-SP2) or power-tool (SSPC-SP 3) cleaning does not remove mill scale. In severe environments, mili scale pops off in one to three years and takes the coatings with it. Blast cleaning is the most practical and effective means of cleaning the surface. It removes mill scale and creates an anchor pattern, which is essential for good paint adhesion. While commonly considered more expensive than hand or power-tool cleaning, shop blasting can cost less, since it lengthens the service life and reduces the cost per year. 6. Field YS. Shop Blasting and Priming On new construction, shop blasting is considered to be about half the cost of field blasting. This means that where a minimum of 250 tons of steel is involved, shop blasting can be done for less than the cost of hand andlor power-tool cleaning in the field. See Table 5and 6 for direct comparisons. This assumes the fabricator has centrifugal wheel-bl ast ing equip m ent. More important than the cost, shop blasting and priming allows and justifies application of a suitable protective coating system at the one time in the life of the plant when the job can be done effectively and economically. Application is easier on the ground, spray loss is reduced and personal safety enhanced. Job-site conflicts, scheduling difficulties and comprised applications common on most construction projects are greatly reduced or eliminated. Selection of abrasion-resistant primers, such as inorganic zincs, plus use of wood dunnage for shipping, should be included to reduce in-transit damage and job-site touch up. 7. More Than One Coat In the Shop? Painting can be controlled better in the fabricator's shop than at the job-site. Theoretically, the entire system or primer and intermediate coat can be applied in the shop. When it is impractical to apply coatings in the field, such as an expansion of an operating facility in a highly corrosive environment, total shop application is desirable. Before the decision is made to apply totally or partially in the shop, it should be recognized that many steel fabricators have limited capability to hold steel for extended periods. Some shops are not enclosed or heated. Frequently, a maximum of only 24 hours can be tolerated by the fabricator for blasting, painting and loading. If applying totally or partially in the shop, be certain the steel fabricator selected can effective-
ly shop apply all coats. Make sure the coating system selected will dry and cure adequately within the period the fabricator can accept, and that the coating manufacturer is in agreement. On a practical basis, touch-up the final coat after all repairs and welding are completed. 8. Galvanizing YS. Zinc-Rich Coatings Galvanizing and zinc-rich coatings, with their galvanic action, have revolutionized steel protection. Galvanizing with 1% ounces of zinc per square foot is equivalent in thickness to 2.5 mils dry of a zinc-rich coating. From a protection standpoint, they are about the same. Galvanizing via a "bath" treatment is more easily applied to small parts, gratings, etc. However, facilities are not always close to the job, and vat size can be a limitation. Heat resistance is somewhat below the melting point of zinc (75OoF-399"C). Compared with galvanizing, zinc-rich coatings are more easily applied to existing structures in place. They tend to weather better in marine and coastal environments, and accept top coats more readily(5.e), They are less expensive on. large structural members, and inorganic zincs have heat resistance somewhat above the melting point of zinc (750°F-399"C). On a cost basis, the break point is approximately 275 ft.Vton. Galvanize if the area is greater; coat with zinc-rich if it is less. 9. Cost Per Square Foot YS. Per Ton or Total Job Basis It is impractical, and generally unnecessary, for the specifying engineer to attempt a take-off and total job estimate. For system comparison and selection, cost per square foot can be estimated through use of this cost guide in sufficient accuracy for an intelligent decision. To convert to typical painting cost per ton size, multiply cost per square foot by 250. For large structural members, use 100-250 ft.2/ton; for medium 200-300 fL2lton; for light structural, 300-400 ft.Vton; and trusses 350-500 ft.21ton. 10. Delay Topcoating? Many new construction projects run over budget, and it is not uncommon for construction managers to search for items that can be delayed until after start-up when maintenance dollars are used instead of capital dollars. US.tax classifies maintenance painting as a deductible expense; and, thus, a delay in topcoating could represent a
reduced cost. To the uninformed construction manager, topcoat application might appear to .be a good candidate for this. If top coating is selected for delaying, "midstream" after the specification has been written and priming has been accomplished, and if the primer does not protect adequately for the extended period or in the environment, a major problem can result. The specifying engineer must be Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 227
SSPC CHAPTERx8.0 93 m 8627790 0003b75 778 m aware of this possibility, and if it is likely to occur, select a coating system with a primer that resists the weather and environment for an extended period. The engineer should be sure to include immediate and adequate touch up of scars, bolts and decontamination of the primer prior to application of final coats so rusting and undercutting would not occur. 11. Do Prejudices Exist? Often the specifying engineer is confronted with preferences/prejudices by projectiplant personnel or client representatives concerning types of coatings or suppliers, ¡.e., inorganic zinc, epoxy, can only afford alkyds , can t afford or tolerate blast cleaning , etc. These prejudices may or may not represent acceptable systems or conditions. Include them in the analysis and make certain the recommended system is sound and its selection based on facts with supporting detail. 12. Maintenance Procedures See Typical Maintenance Painting Practices below: Typical Maintenance Painting Practices The sequences followed by users maintenance repaint (spot prime in maintenance painting vary widely. and full coat), and For come, the only criterion is, Does full repaint. it need painting? In reviewing the subject with a Life of the repainting steps will varynumber of painting contractors, the according to whether the ldeal/Opticonsensus is that most users gener- mum or Practical approach is ally follow these painting sequences: used. original painting, spot touch-up and repair, The following is an example of the approximate results. Approximate Cosi If Original Cost If Orig. Painting Operation Life in Field in ShoplField occurs I ideaUOptlmum Fkpalnting and Maintenance Sequence: Initial Painting Table I Touch-up Maint. Repaint 50% of I 75% of I 25% of Orig. 55% of Orig.
I
Life Original Cost Original Cost O year
40% of Orig. 70% of Orig. 8th year 121h year Full Repaint 100% of 1 115% of Orig. 150% of Orig. 18th year P Practlcal Repalntlng and Malntenance Sequence: Initial Painting P Life. Original Cost Original Cost O year Table 1 Touch-up Maint. Repaint 25% of P 40% of P 40% of Orig. 70% of Orig. 50% of Orig. 80% of Orig. 12th year 15th year Full ReDaint 100% of P 115% of Oria. 150% of Oria 19.8th vear 13. Economic Analysis and Justification This subject is sometimes misunderstood for paint and coating systems. Capital items require intricate analysis to identify full financial impact. Paint and coating systems are basically expense items without salvage value or depreciation considerations. Relatively few calculations are required to compare one system with another and to measure each system s true cost in comparable dollars reflecting the time value of money. For each system used or considered, simply list the timing, number, and cost of painting operations required to protect the structure for its projected life. This should include such items as original painting, touch-ups, touch up and full coats, and full repaintings. The cost of each painting operation should be calculated in three categories: 1) At current cost levels. 2) At net future value levels -current cost with inflation included. How much will it cost, in inflated dollars in the year scheduled? 3) At net present value levels -the present worth of the inflated cost (NFV) in monies today invested at current interest rates. For example, a current cost of $10 today inflates to $12.76 in five years, assuming 5 percent inflation; $12.76 is the NFV. The formula for calculating this is: NFV =Current cost x (1+i) (1) (i = inflation, n = years)
To calculate the NPV, or What the $12.76 is worth today invested at current interest rates for five years?, the following formula:
use
NPV = NFV x 1 or $7.92 (2) (1+i) $7.92 invested today at 10 percent for five years = $12.76. While interest and inflation rates are constantly changing, the decision on coating selection is usually based on current rates. By making these calculations for each system, the true cost and number of painting operations can be compared. I Steps for Calculating an Economic Analysis of a Coating System Using the current interest rate, a separate sheet for each), draw calculate and record the NPV(of a time line for the projected life the NFV) for all painting operof the structure. ations. For each system, mark on the For each candidate system (use For each system, total the sum time line when all painting oper- of the three categories (current ations will take place: original cost, NFV, and NPV). painting, touch-up, maintenance Compare these values, particurepainting, and full repainting. larly NPV, for a direct compariInsert their current costs. son of each system s true cost Using the current inflation rate, in monies today. calculate and record the NFVfor all painting operations. A system may be cheaper to install initially, but if it has a shorter life and requires frequent repaintings, its financial cost can be measured, and the impact on plant disruptions must be recognized. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 228
SSPC CHAPTER*B=O 73 m 8627740 0003676 804 W See the example of a present value analysis below. Example of Present Value Analysis Economic Anaiyas Wwksheel Total Psnbng Cost Per Sq Ft lor &her Plant Life Shree-CoaiEWXVPnmedHB EDOXV.CPB EiQhi-YearSVRem Lile ShapiField/Flsld Years O 5 10 15 20 25 ~ 30 t tt t 1 Prnmnp j ,Original Touchup Maintenance Full Repaint Touchupc~m) Painting Year 8 Repaint Year 12 Year 18 Year 26 B!!s caro 8 +$l71 y170 $1 22 12 61 IO70 t 897 cuimnlIS) NFVmils ) Furure~aiur)~U mu 16?8 m3 am , !adurn ) On new capital projects, coating costs are often capitalized, which will require considerations for depreciation, taxes, etc. These are not necessary for maintenance work. When required, however, the same present value analysis should be conducted to make the coating selection, and the analyses turned over to project management for further financial treatment. B. HOW TO USE THE COST GUIDE Before proceeding it is suggested that the reader review the tables and worksheets presented below. 1. Estimated Service Life (Table 3) How long will the coating system last? The answer depends on t.he particular user s approach to, and philosophy of, maintenance painting. Is protection alone important, or is appearance a consideration? Is painting looked at as a necessary evil, or is costeffective protection the approach? The guide supplies system life estimates for two maintenance approaches, ldeal/Optimum and Practical : (See Table 3) IdeallOptimum life is the time until initial breakdown (three to five percent) of the top-coats
occurs, before rusting begins, when first maintenance painting takes place. Practical life is the time until five to 10 percent breakdown occurs, active rusting of the substrate occurs, and Rust Grade 4 is present. Most users follow the Practical approach, thinking it is the cheaper or that they cannot afford or be bothered by painting sooner. A comparison of the two approaches, however, will nearly always show the ldeal/Optimum approach to be the more cost-effective method (Table 2). Simply stated, once aggressive rusting and coating breakdown occur, it is more costly to repair, and protection is reduced. (See Table 2 for comparisons.) 2. Field Painting Costs Regional US 1992 costs for cleaning and paint application at the site are included in Table 6. Note the factors at the bottom of the table to convert (1) to in-place costs depending on type of structure and surface, and (2) to per-ton costs. 3. Shop Painting Costs (See Table 5) For steel fabricators with automatic wheel-blasting equipment, Table 5 gives regional U.S. 1992 costs for cleaning and painting at the shop. Note that usually a minimum of 250 tons is required to obtain competitive costs. After 1992 these costs should be inflated by the inflation rate since 1992. 4. Paint and Coating Materials Costs (See Table 4) Current 1992 material costs for most commonly used generic types of coatings are included in this table. Typical dried film thickness (DFT) per SSPCPA 2 for each type are shown, as well as theoretical and practical costs. After 1992 inflate at current inflation rates since 1992. 5. Worksheet A Use this worksheet for all systems to be applied at the job-site. Note conversion factors at the bottom to convert costs (1) to a per-ton basis and (2) from structural steel on the ground to specific surfaces or structures in place. 6. Worksheet B Use this worksheet for all systems to be shop primed with touch up and top coating in the field. Note the same conversion rates at the bottom of the worksheet. 7. How to Make a Coatings Cost Analysis a. Step 1: What system(s) will work in the environment involved? Identify the specific environment and contaminants and begin with Table 3- Estimated Service Life . Review the system(s) that will work in the environment and examine their longevity. Select the ones that have the longest life, but include, for comparison and analysis, other systems that are popular or thought to be economical. Be
sure your analysis includes the effect of surface preparation on expected life. Include, if possible, a comparison of thensame generic system with different cleaning grades. If you are confronted with prejudices/preferences by projectlplant or client personnel, include their systems for economic comparison and analysis. b. Step 2: On new construction compare field painting vs. shop priming. As outlined before, if a minimum of 250 tons of steel is involved, shop blasting and priming is about half the cost of the same work at the site. The job is done more efficiently and many of the normal jobsite conflicts and compromises are eliminated. Shop application usually gives better results. For the candidate system(s) selected in Step 1, include in your analysis a comparison of each Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 229
system with both field and fabricator shop appli- d. Step 4: Calculate the longterm cost and numcations. ber of painting operations over the structure s life, c. Step 3: Prepare worksheets (A, B or both) on all by preparing a present value analysis for each cancandidate systems. didate system as outlined above. TABLE 2 Typical System Costs, Life, Cost Per Year, Long-Term Costs, and Number of Paintings Over a 35 Year Structure Life ldeal/Optimum Life TOTAL INSTALLED COST LONG-TERM COST Initial cost/ Total Cost surf. Installed Years Yearl No. @ Current System Prep. cost Life fi2 Ptgs. Cost Levels 2-coat HB surf. SP6 $2.14 8 $0.27 6 $ 8.04 tolerant epoxy 2-coat HB surf. SP2 1.76 6 $0.29 8 9.06 tolerant epoxy 2-coat HB surf. SP6 2.13 6 0.36 8 10.96 tol. epoxylure. l-coat HB surf. SP6 1.60 5 0.32 10 10.96 tolerant epoxy l-coat HB surf. SP2 1.23 3 0.41 16 13.23 tolerant epoxy Pract ¡cal I Life TOTAL INSTALLED COST LONG-TERM COST System surf. Prep. Initial Installed cost Years Life cost/ Yearl ft* No. Ptgs. Total Cost @ Current Cost Levels 2-coat Hl3 surf. tolerant epoxy
SP6 $2.14 12 $0.18 6 $ 9.32 2-coat H8 surf. tolerant epoxy SP2 1.76 9 0.20 7 9.66 2-coat HB surf. tol. epoxylure. SP6 2.13 9 0.24 7 1 1.71 l-coat HB surf. tolerant epoxy SP6 1.60 7.5 0.21 9 10.56 l-coat HB surf. tolerant epoxy SP2 1.23 4.5 0.27 14 12.76 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 230
SSPC CHAPTER*8.0 73 8627740 0003678 687 TABLE 3 Estimated Service Life(') (in Years, Before First Maintenance Painting) of Protective Coatings, Zinc-Rich Coatings, Galvanizing, and Zinc-Metallizing Sy stems 6.0 I 4 3 3 25NN3 25 N 8 5 3 P 6 45 45 375 N N 45 3.75 N 12 7.5 4.5 6.0 I 6 5 5 5NN5 45 N 10 7 5 P 9 75 N N 75 675 N 15 10.5 7.5 75 75 6.0 I 7 6 6 55 N N 6 5.5 N 11 8 6 P 10.5 9 9 825 N N 9 8 25 N 16.5 12 9 4.0 I 2 1 05 05 N N 05 05 05 4 2 1 P 3 15 075 075 N N 075 075 O75 6 3 1.5 4.0 I 3 2 1 1 NN1 1 1 7 4 2 P 4.5 3 15 15 N N 1.5 1.5 1.5 105 6 3 60 I 3 2 1 1 NNl 1 1 7 4 2 P 4.5 3 15 15 N N 15 15 15 105 6 3 6.0 I 4 3 I5 1.5 N N 1.5 1.5 t,5 9 6 3 P 6 4.5 2.25 2.25 N N 225 225 225 135 9 4.5 4.0 I 3 2 N N NNN N N 7 4 2 P 4.5 3 N N NNN N N 10.5 6 3 6.0 I 4 3 N N NNN N N 9 6 3 P 6 45 N N NNN N N 135 9 4.5 4.0 I 2 1 05 05 N N 0.5 05 05 4 2 1 P 3 15 075 0.75 N N O75 075 075 6 3 15 40 I 3 2 1 1 NNl 1 1 7 4 2 P 4.5 3 15 15 N N 15 i5 15 105 6 3 6,O I 3 2 1 1 NNl 1 1 7 4 2 P 4.5 3 15 15 N N 15 1.5 15 105 6 3 --`,,,,`-`-`,,`,,`,`,,`--6.0 I 4 3 $5 i5 N N 15 1.5 15 9 6 3 P 6 45 2.25 2.25 N N 225 225 225 135 9 45 6.0 I 4 3 3 2 NN3 2 3 8 5 3 P 6 45 45 3 "453 45 12 7.5 4.5 6.0 I 5 4 4 3 NN4 3 4 9 6 4 P 7.5 6 6 45NN6 45 6 135 9 6 7.5 I 5 4 3 3 NN3 3 3 9 6 4 P 7.5 6 4.5 45 N N 45 45 45 135 9 6 7.5 I 7 6 5 5 NN5 5 5 11 8 6 P 10.5 9 7.3 75 N N 75 75 75 155 12 9 5.0 I 4 3 3 2 NN3 2 3 8 5 3
P 6 45 45 3 N N 45 3 45 12 7.5 4.5 5.0 I 6 5 5 4 NN5 4 4 10 7 5 P 9 75 75 6 N N 75 6 6 15 10.5 7.5 10.0 I P 10.5 mo I 9 P 13.5
7 6 6 5 NN6 5 5 11 8 6 9 9 75NN9 75 75 165 12 9 8 8 7 N N 7 ~ 6 14 10 8 12 12 105 N N 12 105 9 21 15 12
8.0 I 5 4 4 5 NN4 5 3 11 7 4 P 7.5 6 6 75NN6 75 45 165 10.5 6 8.0 I 7 6 6 7 NN6 7 4 13 9 6 P 10.5 9 9 105 N N 9 105 6 195 13.5 9 12.0 I 9 8 7 8 NN7 8 5 15 11 8 P 13.5 12 1051 12 N N i05 12 75 225 16.5 12 12.0 I 11 10 9 10 NN9 10 6 17 13 10 P 16.5 15 135 15 N N 135 15 9 255 19.5 15 12.0 I 10 9 8 9 N N 9 ~ 7 16 12 9 P 15 135 12 i35 N N 12 13.5 105 24 18 13.5 12.0 I 12 11 10 21 N N 10 11 9 18 14 11 P 18 165 15 T65 N N 15 16.5 135 27 21 16.5 7.0 I 4 4 5 NN4 5 31063 P 6 s 7dNN6 73 4.5 15 9 45 7.O i B 5 8 7 NN6 4 51285 P 9 75 9 10.5 N N 9 10.5 7.5 18 12 7.5 10.0 I 11 9 6' 7' N N 6' 7' 10 19 13 9 P 16.5 13.5 9* 10.5' N N 9. 10.5' 15 285 195 135 10.0 1 12 10 6. TNN6'7'11 XI1410 300"' P 15 15 9' î0.5' N N 9' 10.5' 16.5 30 21 15 6.0 1 4 3 3 2 NN3 2 3 953 P 6 45 45 3 N N 4.5 3 4.5 13.5 75 4.5 6.0 I 6 5 5 4 NN5 4 61175 P 9 6 7,5 6 N N 75 6 9 16.5 10.5 75 6.0 I 7 6 6 5 546 5 71286 P 10.5 9 9 7.5 75 6 9 7.5 105 18 12 9 6.0 I 6 5 5 4 NN5 4 51175 P 9 7.5 75 6 "756 7.5 i65 10.5 7.5 6.0 I 7 6 6 5 NN6 5 61286 P 10.5 9 9 7.5 N N 9 7.5 9 18 12 9 35. 2 HBEpoxyPnmer/ 6 8.0 I 7 6 6 5 NN6 5 61286 HB EWXY P 10.5 9 9 7.5 N N 9 7.5 12 18 12 9 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from
IHS 231
SSPC CHAPTER*B-O 93 Bb2794O 0003679 513 = TABLE 3 (cont.) Estimated Service Life(') (in Years, Before First Maintenance Painting) of Protective Coatings, Zinc-Rich Coatings, Galvanizing, and Zinc-Metallizing Sy stems 36. 2 HB Epoxy Pmner/ 10 8.0 I 8 7 7 6 65 7 Hú Epoxy P 12 10.5 10.5 9 9 7.5 10.5 37. 3 Epoxy Primar/ 6 10.0 I 9 8 8 7 NN 8 7 10 HB Epoxvl P 13.5 12 12 10.5 N N 12 10.5 15 HB Epoxy 38. 3 Epoxy Primar/ 10 10.0 I 10 9 9 8 87 9 li3Epoxy/ P 15 13.5 13.5 12 12 10.5 135 Epoxy 39. 2 HB Epoxy Pnmerl 6 6.0 I 5 4 4 5 NN 4 -IC Urethane P 7.5 6 6 7.5 N N 6 75 4.5 15 40. 2 HB Epoxy her/ 10 6.0 I 6 5 5 6 NN 5 6 4 11 ~ayltcUrethane P 9 7.5 75 9 NN 7.5 9 4.5 16.5 1 41. 3 Epoxy PrimerlHB 6 8.0 I 7 6 6 7 NN 6 EpoxyiAcrylUre P 10.5 9 9 10.5 N N 9 42. 3 Epoxy Pnmer/HB 10 8.0 I 8 7 7 8 NN 7 8 6 13 Epoxy/Acryl Ure P 12 10.5 10.5 12 N N 105 43. 2 HB Epoxy Primed 6 6.0 I 6 5 5 5 NN 5 Polyester Ure P 9 7.5 75 75 NN 75 44. 2 HB Epoxy Primed 10 6.0 I 7 6 6 6 NN 8 6 7 12 Polyester Ure P 10.5 -9 9 9 NN 9 9 10.5 18 t 45. 3 Epoxy Pnmeri 6 8.0 I 8 7 7 7 NN 7 7 8 13 HB Epoxy/ P 12 10.5 10.5 10.5 N N 105 Polyester Ure 46. 3 Epoxy Primer/ 10 8.0 I 9 8 8 8 NN 8 HB Epoxy/ P 13.5 12 12 12 N N 12 Polyester Ure 47. 2 IOïíHB Epoxy 6 7.0 I 10 8# 4' 3' NN 4' P 15 I% 6' 4.5-N N 6' 48. 2 loz/HB Epoxy 10 7.0 I 11 9# 4' 3' 87 4' P 16.5 13.M 6' 4.5' 12 105 6. 49. 3 IOIRtB Epoxy/ 6 11.0 I 12 10% r 6' NN 7" 6' t2 HB Epoxy P 18 1M 10.5' 9' N N 1oJ" 50. 3 IOtliB Epoxy/ 10 11.0 I 13 1I# 7' 6' 10 9 7' P 19.5 16.M 10.5' 9* 15 13.5 10s 9. ta5 3' 2 IOutrB HB EpoxyAuyltc 6 7.0 I 10 e# 3' 4' NN51. Ursthane P 15 12# 7.5' 6' N N 4.5' 52. 2 IOUHBAcryltc 10 7.0 I 11 9# 3' 4^ NN 3. UfbNiaflE P 16.5 13.S 45' 6' N N 4.6* 53. 3 IOUHBAcryl Ure/ 6 11.0 I 12 1oW 6-7' NN H0Acrylic Ure P 18 15# 9' 10.5' NN 9" 54. 3 IOZñiBAcryl Ure/ 10 11.0 I 13 11# 6' 7' H3 Acrylic Ure P 19.5 16.W 9-10.5' N N 9' 55. 2 ûalvNB Epoxy PCKL 7.4 I i? 9# 4. 3' 8 7 P 16.5 13.H 6* 4.5' 12 105 6+ 4.5* 16.5 56. 3 GalviHB Epoxy/ PCKL 11.4 I 13 11x 7' 6'
6' N N 6' 44 3. 11 10 9 r 6' 13
1.40Epoxy P 19.5 16.M 105' 9' 15 135 10.5' 9. 19.5 57. 2 Zinc Metallizing/ 10 9.0 I 12 1W 4" 3' 9 8 4. 3' t2 HB Epoxy P 18 15# 6' 4.5' 135 12 6" 4.5' 18 58. 3 Zinc Melaliizingl 10 13.0 I 14 1% 6' 5' 11 10 6' 5' 14 HB Epoxy/ P 21 18# 9. 7.5". 16.5 15 9' 75' 21 HB Epoxy 59. 3 IOUHB Epoxy/ 6 9.0 I 12 lo# 6' 6" NN 6' 6' 12 Poiywter ufa P 18 15# 9' 9' NN 9' 9' 18 60. 3 IOUHB Epoxy/ 10 9.0 I 13 Il# 6' ô' NN 6' 6' 13 Polyester Ure P 19.5 16.S 9' 9' N N 9' 9" 18.5 61. 3 GahW poxyt PCKL 9.4 I 13 1It 6' 6' NN 6' 6' 12 Pdyestw Ure P 19.5 16.M 9' 9' NN 9* 9' $8 62. 3 IOUHB Epoxy/ 6 9.0 I 11 9# 6' 7' NN 6' T" 10 Acrykc Ure P 16.5 13.W 9. 10.5* N N 9' 10,5' 15 83. 3 IOUHBEpoxy/ 10 9.0 I 12 101t 6' 7' NN 7' 11 Aciyhc Ure P 18 1% rt" 10.5' N N 9. 64. 3 GahNB Epoxy/ PCKL 9.4 I 12 10# 6' 7' NN 6' Aaylk Ure P 18 15# 9' 10.5' NN 9. 6% 2 IOUWaterborne 6 6.0 I 9 7# 3" 3' NN 3' 3' Aeryltc P 13.5 10,5# 4.5' 4.5' N N 4.5' 4.5' 66û. 2 IWaterborne 10 6.0 I 10 Ba 3' 3' NN 3' 3' Actyl= P 15 12# 4.5' 4.5' NN 4 5" 4.5' 67. 2 Epoxy .TlncJ 6 7.0 I 9 7 5' 4" N N .Y 4' HB Epoxy P 13.5 1W 7.5' 6' N N 7 5' 6' 68. 2 Epoxy ZncJ 10 7.0 I 10 w1 5' 4' 87 5-4' HB Epoxy P 15 1% 7.5' ô' 12 10.5 7.5-6' 69. 3 EpoxyZinc/ 6 11.0 I 11 9# 8' 7' NN o 7 HB Epoxy/ P 15.5 13.# 12' t0.5 N N 12-16.5 th5 2885 t HB Epoxy 70. 3 EpoxyZinc/ 10 11.0 I 12 io# --`,,,,`-`-`,,`,,`,`,,`--8' 7' 89 ortssot Hû Epoxy/ P 16 1M 12' t0.5' 12 13.5 12' 10.5' f8 30 2 HB Epoxy 71. 2 Epoxy Zinc/ 6 7.0 I 9 7# 3* 4' NN 9 4. 8 15 i0 HúAcryls Ure P 13.5 10s 4.5' B' N N 45' 6' tS 22.5 15 1 __. 232 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERt8.0 73 86277YO O003680 235 TABLE 3 (cont.) Estimated Service Life") (in Years, Before First Maintenance Painting) of Protective Coatings, Zinc-Rich Coatings, Galvanizing, and Zinc-Metallizing Sy stems 72. 73. 2 3 Epoxy zw hytto Ure Epoxy mdHfl Acrylic Ure/ 10 6 70 11.0 I P I P 10 15 11 165 8n 12# 9# 13W 3' 45' 6. 9' 4' 6' 7" 105' N N N N N N N N 3. 4.5" fi* 9" 4* 6' 7" 10.5' 9 13.5 10 15
16 4 19 285 11 16.5 13 19.5 8# 12# 911 13.# 300"" 3OOm H3 Ac~~llc Ure 74. 75. 3 3 ww mdHfl Acrylic Ure/ MAcryiic Ure ww HB EwwI 10 6 110 90 I P I P 12 18 11 165 1M 15# 9# 13W 6' 9' 7' 105' 7' 10s 6" 9' N N N N N N N N 6. 9' 7' 10.5" 7
10.5' 6' 9' 11 16.5 11 16.5 21 31 5 19 28.5 15 22.5 13 19.5 10# 15# 9# 13.S 300" 300") 76. 3 Polyswertke iroxy aw 10 90 I P 12 18 1M 1% 7 105" 6' 9+ N N N N 7. 10.5' 6^ 9' 12 t8 20 30 14 21 tO# 15# 300q*i Ure 77 78. 3 3 Epoxy tirae/HB EpoxyiACryfic Ure 90 90 I
P I 10 15 11 8# 12# 9 # 6' 9. V Y 10s P N N N N N N 6" 9' 6. P 10.5' 7' 9 13.5 to 18 27 19 12 18 13 c 12x 9# 3M1""i 3OOw' Ure P 165 135# 9' 105-N N 9. 10.5' 15 28.5 19.5 13.W 79. 2 60 I 6 5 4 5 N N 4 5 N 10 7 5 140-160q~i 80. 2 H0 Vinyl Vinyl Pnmerl H3Vinyl 50 P I P 9 7 105 75 6 9 6 5 75 7.5
6 9 N 5 75 N 4 6 6 5 7.5 7.5 6 9 N N N 15 1116.5 105 8 12 75 6 9 140-16o"o' 81. 82' 83. 3 3 3 Vinyl Rimer/ H3vinyl/ HBVinylVinyl&mer/ HBvinyuH3Wnyl IOZRt6 Vlnyü 10 6 100 100 110 I P I P I 9 135 10 15 il 8 12 9 135 W 7 105 8
12 S 6 8 12 9 135 ' N N 7 10.5 N N N 6 9 N 7 10.5 8 12 5' 8 12 9 13.5 6' N N N N N 13 19.5 14 21 16 10 15 11 16.5 12 8 12 9 13.5 9# 140-15o"i 140-160" 140.160" 9' 7.5' 9' 165 13.SX 75'
H3vinyl P NN 24 18 13.S N S 6' 3 IOUHBWnyU 10 11.0 I 12 17 13 i# 140-160""' 5' 6' N 84. lo# 10 9 18 15# 7.5' 9' 15 135 7.5' 9' WB Vbyt P N 25.5 195 1% I 12 10 5"s 10 9 5" 5' N 17 GahrMB WnyV PCKL 11 4 13 1# 140-1W'i 85, 3 P 18 7.5' 79 15 135 7.5' 75'; N wVinyt 195 1# 25.5 is8 2 Coal Tar Epoxy 6 160 8 7 NN 8
7 8 13 10 8 200" 93. I 10 P 15 12 12 105 N N 12 10.5 I2 19.5 15 12 94. 2 CoalTarEpoxy 10 16.0 I 11 9 9 8 P 165 735 135 12 ga 1 InorgaokTKIc 6 30 P 13 li# N N 99, 1 IrmrganieZinc 10 30 P 15 t3# N N?m.f OrmnicZjnc Rich 6 30 P 5 4 # N N h1030P65#NN PCKL 34 P 13 11# N N 5 5.0 P 16 14# N N Notes: Life shown is for protection only, not cosmetic appearance. N-Not recommended. '-Assuming topcoats are intact. and zinc is not exposed. #-Assuming pH is within 5.5to 10 range. ~'i"ldeal1Optimum"life is defined as the time until the first maintenance painti ngttouch-up should occur, when three to five percent breakdown of the topcoats occur, before active rusting begins. Normal maintenance repainting cycles include: original painting ("I"iife), spot touch-up at end of "I"Me, spot prime and full coat after an additional 50 p ercent of "I"life. and a full system repaint after an additional 75 percent of '"I"system life. This can vary f15 percent, depending on local conditions and timing of inspectionirecogni tion of topcoat breakdown. i2Colors will darkeniyeliow, and loss of gloss will occur. ~3~Thermoplastic.Softens at 160°F. but protection remains. Will pick up dirt when softened. l']Grades of cleaning are geared to SSPC standards: SP-2 = hand wire-brushing; SP-3= power tool cleaning; SP-6 = commercial blast (S A-2 or NACE-3); and SP-10= near white blast (SA-2 112 or NACE-2). IWFT. Minimum Dried Film Thickness in mils. 1.0 mils = 25.4 pm. ")Maintenance Schedule/Approach. I = IdealIOptimum; P = Practical. PIA minimum SP-10 (SA4 112 or NACE-2) is required for immersion service. 11 9 9 8 9 14 11 9 200" 16.5 135 13.5 12 13 5 21 165 13.5
N N N N 19 26 16 6#W N N 20 27 17 NN N N 16 8 4 3# fEP0XY) N 14p1w (Vinyl B CR) 7# 6# N N I7 9 5 íEp0.WN 140-le@
Il# 740.1,wO' 12# 740-1.000° 250-300"
4# 250-300"
5 [Vinyl & CR) N N 20 27 17 12# 7400 N N 25 30 20 14 740" Definitions of Environments: SEACOAST MARINE = Within five miles of coasüsalt water and no industrial plants or fumes present. SEACOAST HEAVY INDUSTRIAL = Within five miles of coastisall water and in presenc e of heavy industrial plants with high levels of fumes and fallout. CAUSTIC = Caustic soda up to 50 percent concentration, with splash, spills, and fumes. ACID = Minerai acids at approximately 10 percent concentration, with splash, spi lls, and fumes. FRESH WATER = Immersion at ambient temperature. SALT WATERIBRINE = Immersion at ambient temperature. AMMONIA = Ammonia splash, spills, and fumes. CHLORINE = Chlorine splash, spills, and fumes. SOLVENTSIGASOLINE = Aromatic hydrocarbons, selected esters, gasoline. and alcoho l splash, spills. and fumes. MILD = Rural or residential with no industrial fumesffallout. MODERATE = Industrial plants present but no heavy contamination by industrial fu mes and fallout. SEVERE = Heavy industrial and chemical plant area with high levels of fumes and fallout. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 233
SSPC CHAPTER*8.0 93 Ab27940 0003b81 171 = TABLE 4 Typical Material Costs of Paints and Protective Coatings Approx. Cost per Sq. Ft. QTypical DFT Prpct. Coatlng Min. DFT Theor. sprayPtaet, BN8hf Rgll Acrylic, Waterborne Primer Acrylic, Waterborne Topcoat Alkyd Primer' Alkyd Gloss Topcoat' Alkyd Silicone Coal Tar Epoxy Standard* Coal Tar Epoxy C200" Chlorinated Rubber Primer 3.0 3.0 2.0 2.0 2.0 8.O 8.0 2.0 $0.070 0.083 0.036 0.040 0.076 0.104 O.lt5 0.075 $0.100 5.119 0.051 0.057 0.109 0.149 0.164 0.107 $0.078 0,092 0.040 0.044 0.084 0.116 0.128 0.083 ChJorinated Rubber HB Inte&/Top Chlorinated Rubber Topcoat Epoxy Primer' Epoxy HB Primer'
Epoxy HB IntermediateBopcoat* Epoxy Topcoat' Epoxy, Waterborne Epoxy, HB Surface Tolerant' Epoxy, Ester, Frimer Epoxy, Ester, Topcoat Latex Emulsion, Primer 4.O 1.5 2.0 4.0 4.O 2.o 3.O 5.0 1.5 2.o 2.o 0.166 0.062 0.037 0.080 0.080 0.042 0.095 0.104 0.029 0.055 0.051 0.237 0.089 0,053 0.114 0.114 5.060 u.i36 0.149 0.041 0.079 0.073 0.184 0.0e9 0.041 0.089 0.089 0.047 0.106 0.116 0.032 0.061 0.057 Latex Emulsion, Topcoat Universal Primer, 1-pack Urethane, Elastomeric Solvented 2.o 2.o 20.0 0.054 0.061 0.755 0.077
0.087 1 .O71 0.060 0.068 NA Urethane, Aromatic HB Primer' 5.0 0.155 0.214 0.167 Urethane, Aliphatic Acrylic" Urethane, Aliph. HB Acryl Inter/Top' 2.o 4.0 0.073 0.145 0.104 0.207 0.081 0.161 Urethane, Aliphatic Polyester' Urethane, Moisture-Cured Aluminum 2.o 2.5 0.091 0.076 0.130 0.109 0.101 0.084 Vinyl, Solution Primer"' Vinyl, Solution HB IntermedBop'" Vinyl, Solution Topcoat" Vinyl Ester zinc Rich, Inorganic' Zinc Rich, Organic Zinc Rich, Moiare-Cured Urethane 2.o 4.0 1.5 20.0 3.0 3.0 3.0 0.075 0.145 0.072 0.640 0.092 0.116 0.1ta 0.107 0.207 0.103 0.9f4 0.131 0.165 0.169 0.083 0.161 0.580 NA NA NA
NA 'Available in high-solids versions. Application costs and the cost per mil squar e foot are about the same as for the low-solids versions. '"Becoming available in high-solids versions. Application costs and the cost per mil square foot are about the same as for low-solids versions. Notes: Costs are approximate based on 1992 data secured from representative U.S. paint and coating suppliers. DFT = Dried film thickness in mils (I mil = 25.4 pm). Spray Practical = 30% loss. RoWBrush Practical = 10% loss. NA = Not applicable; must be applied by spray. TABLE 5 Shop Painting Costs per Sq. Ft. Including Labor, Equipment, and Related Costs (No Material Cost Included) For Typical mix of sizes and shapes Large structural 100 Medium structural 200 Light structural 400 Light trusses 500 Notes: Costs shown are approximate, based on 1992 data secured from representative US. steel fabricators. Steel plate cleaning costs are about 20 percent less than pri ces listed above for structural steel. Costs shown are for steel fabricators having centrifugal wheel blasting equipment. For steel fabricators without centrifugal wheel blasting equipment or for those using conventional air blasting, costs will approximate f ield blasting levels shown in Table 6. To convert to cost per ton see above. 234 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*B-O 93 D 8h27940 0003682 O08 TABLE 6 Field Painting Costs per Sq. Ft. Including Labor, Equipment, and Related Costs (No Material Costs Included) U.S.A. Fkrglons CleaningGrade East en^ Gulf West SF-2 SP-3 Hand Cleaning Power Tool Cleaning $0.47 0.63 $0.45 0.60 $0.55 0.65 $0.50 O.65 SP-11 Power Tool-Bare Steel I .o2 1.o2 1.o2 1 .o2 SP-7 Brush-Off Blast 0.52 0.50 0.50 0.60 SP-6 Commerciaf Blast 0.80 0.80 0.85 O.85 SP-1O Near White Blast 0.95 0.95 I .o0 1.o0 SP-5 White Metai Blast 1.20 1.15 1.20 1.20 Water Wash Prior to Surface Pteparation 0.22 0.25 0.25 0.20 Hi Press. Wa?er/Steam Chan prior to Surf. Prep. 0.33 0.35 0.35 0.35 Water Slurry Blast 1.20 120 1.25 1.30 Applicatkm One-Pack by BrusWRoHer 0.22 O 25 0.30 0.25 One-Pack by Spray o 18 0.20 O 25 0.18 TwOPack Epoxies, by Spray Zinc Rich Primers, by Spray TwoPack Urethanes, by Spray 0.27 O 33 0.33 0.25 0.30 0.30 0.30 0.35 0.35 0.25 O 30 o 30 Touch Up on the Ground' 0.18 O 16 0.16 0.15 *Assuming 10 percent of surface needing touch-up, calculate touch-up rate times total square footage of exposed steel. Notes: Costs shown are approximate, based on 1992 data secured from representative U.S. painting contractors.
Costs shown are for calculating the base price of new steel cleaned and painted on the ground at the job site. Follow instructions on Worksheet A, follow -, dtrecttons on Worksheets A and 6, using using the followingpercentage factors -: the faflowing percentage factors: Yultlply . Multiply Field */w Multiply For Labor by For Cost by For by Simple structures 40-11high > 125% Uaintenance. Typical mix of sites and Ltght rusting, pitting, and > 100% shapes 250 Elevated tanks, intricate > 15048 paint breakdown structures, or structures (SSPC * vis 1-e) Large structurai 1O0 >%-fi high (Europ Std. Re 5-6) (SNAME T&R 21, Figure 5) Medrum stfflctural 200 Ground tanks > 90% Heavy paint breakdown, r 120% severe rustrng and pitting Light structural 400 Piping: 1-2 in. i 1% (SSPCVIS. i-D) 4-6 in > 100% (Europ Std Re8) Light trusses 500 12 and 24 in > 95% (SNAMET8R 21, 48 in. > 90% Rgures 3 and 6) Extremegy heavy paint > 135% films above 20mils with extreme breakdown ad substantial pitting and rusting (SNAMET&R 21, Figure 7) Adherent Millscale > 100% (CSPC-VIS 1-A) Flaking/Rusting Millscale > 90% (SSPC ~ vis 1-8) --`,,,,`-`-`,,`,,`,`,,`--235 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*ô-O 93 8627940 0003bA3 T44 m Work Sheet A -All Surface Preparation and Painting in Field Project Name 8, Location oil Storage Tank, St. Louis New Construction ~ Maintenance X Material Cost Practical' (Table 4) Type DFT CostlSq. Ft. ~ ~ Primer Acrylic Waterborne ~-3 $ .1O0 Intermediate -$ Topcoat Acrylic Waterborne -3 $ ,119 Total New Construction Total DFT 6 $ 219 (1) Material Cost Labor, Equipment, and Related Costs SP BlastlClean (Table 6) $- (b/c) Prime Coat (Table 6) $ .20 Intermediate Coat (Table 6) $ Topcoat (Table 6) $ .20 Total Base Labor Total base labor or New Construction (2) New Construction Labor labor for steel with adherent millscale: $ 1.oc wlAdherent millscale New Const.-flaking/rusting millscale, multiply blastlclean cost by 90% and re-total labor costs. -or$ (blc) x 90% = $-. Re-totaled labor $ (3) Total New Construction Labor-Flk millscale Installed Cost: $1.00(2) or (3) x *Yo2 $ .go (4) Total Installed Labor and Equipment Recap-Total Installed Cost Material Costs (1) from above $ 219 Material Cost Labor and Equipment Costs (4) from above $-90 Labor & Equipment Total Installed System Cost per Square Foot $ 1.1 19 (5) Total Installed New Construction Cost3 Maintenance Painting: Multiply total installed cost (5) by percentage below'
Total Installed $1.119(5) x 120 0%' = $ -1.34 Maintenance Cost3 EnvironmentlLife (Table 3) moderate 7.5 Years life ~ Cost Per Square Foot Per Year3 $ ,179 (Cost + Life) *30 percent spray loss, 10 percent loss by brushlroller. IMainfenance: Light rust, pits, and paint breakdown, no change. Heavy paint breakdown, severe rusting and pitting, 120 percent total installed c ost. Extremely heavy paint films above 20 mils with extreme breakdown and substantial pitting and rusting, 135 percent total installed cost. 2For installed prices: simple structures less than 504 high, 125 percent of fiel d labor; elevated tanks, intricate structures, structures greater than 50-ft high, 150 percent field labor; ground tanks, 90 percent of fi eld labor. Piping: 1 to 2 in., 150 percent; 4 to 6 in., 100 percent; 12 and 24 in., 95 percent; 48-in., 90 percent; typical mix of sizes, 10 0 percent of field labor. TO convert to a typical ton mix of sizes and shapes cost, multiply by 250; for l arge structural, 1OOX; medium, 2OOX; light, 400X; light trusses, 500X. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 236
SSPC CHAPTER*B*O 93 8627940 0003684 980 Work Sheet B -Shop Blast and Prime, Topcoat(s) in Field Project Name & Location Material Cost Practical. (Table 4) Type Primer Zinc Rich -inorganic ~ Intermediate Epoxy Polyamide Topcoat Acrylic Polyurethane ~ Touchup (10% of shop-applied coatsprimer, primerlintermediate, etc.) Simple Span -Highway Bridge -Detroit, Michigan ~ DFT 3 ~- 4 2 CostlSq. Ft. $ -~,131 5 ,114 5 .1 04 5 .O13 5 362 (1) Total Material Cost 5 .33 Recap 5 .27 Field Labor $ .16 5 .16 $ .25 5 .25 $ $ 5 .30 $ .30 $ .71 $ 1.31 (2) Total Labor and Equipment Costs --`,,,,`-`-`,,`,,`,`,,`--5 .18 5 1.49 (3) Total Installed Labor and Equipment
5 36 Material Cost 5 -1.49 Labor & Equipment $ 1.85 Total Installed 16.5 Years life (to first maintenance) $ ,112 (cost -Life) Total DFT -~9 Labor, Equipment, and Related Costs SP 6Blast/Clean (Table 5 -shop) Prime Coat (Table 5 -shop) Primer Touchup (Table 6 -field) Intermediate Coat (Table 5 -shop; 6 -field) Intermediate touchup, if inter, shop applied (Table 6 -field) Topcoat (Table 6 -field) Subtotal, Field Labor Installed Costs: Multiply Field Labor and Equipment Costs only by O/O shown below' 5 .71 field labor x 25%= Recap-Total Installed Cost Material Costs (1) from above Labor and Equipment Costs (3) from above Total Installed System Cost per Square Foot2 EnvironmentlLife (Table 3) marine (deice salt) Cost Per Square Foot Per Year3 *30 percent spray loss, 10 percent loss by brush/roller. 'For installed prices: simple structures less than 50-ft high, + 25 percent of f ield labor; elevated tanks, intricate structures, structures greater than 50-ft high, +50 percent field labor; ground tanks, -10 percent of f ield labor. Piping: 1 to 2 in., +50 percent; 4 to 6 in., as is; 12 and 24 in., -5 percent; 48 in., -10 percent; typical mix of sizes, as is. 2To convert to a typical ton mix of sizes and shapes cost, multiply by 250; for large structural, 1OOX; medium, 200X; light, 400X; light trusses, 500X. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 237
SSPC CHAPTER*B-O 93 8627940 O003685 817 111. TYPES OF CONTRACTS, BIDS, AND PROPOSALS Considering current levels of inflation, never before has there been such a problem of outage costs (or downtime) as currently in the 1980 s. Because of this volatile and changing situation, many different contract and proposal forms are being used to reflect the inflationary and changing conditions and to give adequate protection to both client and contractor in business awards. Listed below are the main types of proposals and contracts currently being used with an explanation of each. To organize this subject, US. government terminology and definitions will be used with a relation to commercial practices where applicable. A. TYPES OF BIDS AND PROPOSALS 1. Request for Proposal (RFP) These are solicitations of written offers on negotiated requirements. This usually encompasses a written or verbal request to various firms to submit a written proposal for the job at hand. 2. Invitation for Bid (IFB) These are soliciting bids on formally advertised requirements. The resulting contract will always be a Fixed Price Contract. B. TYPES OF CONTRACTS After award, contracts generally fit into one of the following categories: 1. Firm Fixed Price Contract Provides for a price not subject to any adjustment by reason of cost experience of the contractor in performance of the contract. The IFB must have definite design or performance specifications that are not expected to change in the life of the contract. The owner and contractor must agree on fixed price at inception. 2. Fixed Price Contract Escalation Provides for the upward or downward revision of stated contract price upon occurrence of certain contingencies specifically defined in the contract. The IFB must have definite design or performance specifications. Used where market or labor conditions are expected to be unstable over an extended production period. Conditions are industry-wide and beyond contractor control. Contingencies must be specifically defined in the contract.
This form is used extensively in the construction industry -often with some modification. The industrial owner will often request a firm, not to exceed, figure or bid, a price with the escalation figured in. Most major construction firms are concerned about estimating construction labor costs two and three years hence. 3. Fixed Price With Redetermination Calls for the subsequent negotiated adjustment, in whole or in part, of the originally negotiated (base) price. Consistent with the particular form of price redetermination clause selected, contract price should be adjusted upward or downward, and retroactively or prospectively, or both. RFP can be negotiated to a realistic current price but not for later periods of performance. Retroactive After Completion: Fixed price cannot be negotiated initially; amount so small or time so short any other contract type is impracticable. This form of contract is often used in industry for special equipment or services and sometimes in the construction industry for special equipment or emergency services. 4. Fixed Price incentive Contract A fixed price contract providing for adjustment of total target profit and establishment of contract price by a formula based on the relationship which the final negotiated total cost bears to the total target cost. Where cost uncertainties exist and there is the possibility of cost reduction by giving contractor: (I) a degree of cost and responsibility, and (2) a positive profit incentive. This form of contract is used by industry, but will generally carry a penalty for poor performance as well as an incentive for good performance. 5. Cost and Cost Sharing Contracts A cost-reimbursement type contract under which the contractor receives no fee or a costreimbursement type contract under which the contractor receives no fee and is reimbursed for an agreed portion of its allowable costs. Normally development or research projects jointly sponsored by Government and contractor where contractor anticipates commercial benefit in lieu of fee under the contract. This form is not used by industry. As a rule, a supplier will contract at a reduced price to get a prototype installation in service. R 8, D is usually complete except for field test.
6. Cost Plus Fixed Fee Contract (CPFF) A cost-reimbursement type contract providing for payment of a fixed fee to the contractor. The fixed fee, once negotiated, does not vary with actual cost but may be adjusted as a result of any subsequent changes in the work or services Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 238
to be performed under the contract. Generally a research or other development effort when the task or job can be clearly defined, a definite goal or target expressed, and a specific end-product required. Negotiated estimate of costs; fee fixed initially except for change in the work or services required. A completelapprovedlcontractor accounting process is required. This is the least desirable type contract from the owner s point of view. There is the least responsibility for costs from the contractor s point of view. However, this contract form is becoming common in industry. This format can be improved, from the owner s standpoint, by fixing certain items of cost. The ability to fix any item will depend on the specific work to be accomplished. In some cases, material, equipment, mobilization, and demobilization lend themselves to this approach. 7. Cost Plus Fixed Fee and A ward Contract (CPF F A) A cost reimbursement type contract providing for payment of a fixed fee to the contractor plus an award fee. The fixed fee, once negotiated, does not vary with actual cost but may be adjusted as a result of any subsequent changes in the work or services to be performed under the contract. The award fee is determined monthly based on defined criteria established in the negotiating process. Typical criteria would be: Costs, Schedule and Quality. Award fee is based on performance and is an agreed percentage of fixed fee, based a rating on each criteria. Now being used in the Nuclear industry where the job or task can be only generally defined and the schedule is uncertain. Negotiated estimate of costs; fee fixed initially and award process agreed to, except for major change in the work or services required. A complete approved accounting process is required. This is a more desirable contract format than the CPFF. Generally, the qualified contractor will reduce his fixed fee anticipating that his performance will result in a substantial award. Cost reduction, meeting schedules and quality all gain under this system. 8. Cost Plus Incentive Fee Contract (CPlF) A cost-reimbursement contract with provisions for a fee which is adjusted by formula in accordance with the relationship which total allowable costs bear to target costs. Generally for development and test when incentive formula can provide positive incentive for
effective management. The formula should provide incentive effectiveness over variation in costs throughout the full range of reasonable foreseeable variation from target cost. This contract type is not normally used in industry. The contract must be sizeable in order to make overseeing the contract worthwhile. 9. Time and Material (T & M) and Labor Hour (L-H) Contracts Provides for purchase of property and services on the basis of direct labor hours at specified hourly rates (including direct and indirect labor, overhead and profit) and material (T & M); direct labor hours at specified hourly rates (including direct and indirect labor, overhead and profit) and no material (L-H). IO. Letter Contract A written preliminary contractual instrument authorizing immediate commencement of manufacture of material, or the performance of services including but not limited to preproduction planning and procurement of necessary materials. Situation requires immediate binding agreement so work can begin but time does not permit negotiation of a definitive contract. This concept or a variation thereof is often used in industry for emergency services. 11. Indefinite Delivery Contract A fixed price contract for delivery or orders or calls . Generally for single type parts or items where quantity and time may not be known. This form of contract is often used in industry. Can be set up as annual purchase or time purchase of any type other than labor or service which would fall under the T & M or L-H contract. 12. Two Step Formal Advertising The owner will request, in step one, technical proposals based on design and performance requirements, operational suitability and ease of maintenance, the need for special skills and facil it ¡es. The contractor responds and his technical proposal is evaluated. Acceptable proposers are asked to price their proposal only. Award is made to the low bidder. This is a unique procurement system. It pro vides added flexibility in awarding contracts that include important technical consideration. The owner has the freedom to weigh factors other
than price (Step one) and award to the lowest acceptable bidder (Step two). With present day increases in technical and performance requirements on many coating and lining contracts, it becomes critical that the Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 239
SSPC CHAPTER*B*O 93 W 8627940 0003b87 b9T W owner use every means to get the best application at the lowest price. The owner would normally set up a small group of personnel from Purchasing, Engineering and Maintenance or any combination that can best evaluate a technical proposal. The owner has a further advantage in that the contractor may submit more than one proposal. The owner can then take advantage of improvements in the state of the art or an entirely new approach to the specific problem. Keep in mind that the technical proposal becomes the statement of work under which the contractor must produce. It is difficult to complain about a statement of work or specification if the contractor prepared the document. It is extremely qualified group tracts. Table 7 uation. If only tract should be been priced.
important that a technically be established to evaluate concan be used as an aid in this evalone contractor is qualified, the connegotiated after his proposal has
If more than one contractor has submitted proposals, be certain that each has bid on identical conditions and types of proposals. It is suggested that an evaluation recap be created that becomes a permanent part purchasing record. This will protect the against future claims that the award was a biased manner.
sheet of the owner made in
IV. SUMMARY A knowledge and basic understanding of field and shop applied paint and coating costs is necessary to properly choose the painting system that provides maximum benefits for a given structure. The corrosiveness of the structure must be known. The expected plant life of structures should be known. At the one time in the life of a structure when a proper protsctive coating system can be selected, justified and applied, poor decisions are frequently made. Usual reasons are initial cost considerations or failure to use cost and service life data. This chapter presents elements of field painting costs, current cost data, an expected life table, cost worksheets, justification procedures and a definition of contract forms that can be used on actual jobs.
To protect clients and sub-contractors from inflation and changing conditions, understanding and use of special contract forms designed to deal fairly and predictably with these changes is highly recommended. The ability to effectively communicate with management in economically justifying a painting system requires a basic knowledge of cash flow, discounting practices and tax benefits by the corrosion engineer. ACKNOWLEDGEMENT Steve Dobrosielski provided cost updates for the revised chapter. M.R. Sline contributed to an earlier version. The authors and editors gratefully acknowledge the active participation of the following in the review process for the original version of this chapter: M. Batchelder, D.G. Beebe, J. Brock, J. Brown, Bill Chandler, D.W. Christofferson, D. Davis, J. Davis, Dick Drisko, Noel Duvic, P.J. Foehl, Raye Fraser, Tom Ginsberg, R.L. Goetz, Ron Hamm, Dale Harp, M.W. Howie, H.H. Jacobs, G.N. Kirby, C. Leavitt, M. Lichtenstadter, Jim Lisa, J. Macrae, A.W. Mallory, Marshall McGee, C.T. Main,J. Oeschle, C. Reed, D. Reese, M.W. Repasky, Jon Rodgers, G. Schirmer, L. Sherman, W. Stanford, T. Stein, Ken Tator, Verne Todd, F. Trotter, R. Vansant, and W. Wallace. BIOGRAPHY Gordon H. Brevoort is a 43-year veteran in the heavy duty paint and protective coatings industry. He is well known for his work in creating the Paint and Coatings Selection and Cost Guide which has been published biennially through NACE since CORROSION 79 and which he has computerized into SpecMate-1 and SM1 customizer for industrial plants and SpecMate-2 for bridges. For a number of years, Mr. Brevoort has been active in the National Association of Corrosion Engineers, and the Steel Structures Painting Council (SSPC), and has conducted Coatings Eco-
nomics Tutorials for SSPC at their annual meetings and at their industry Seminars. He received SSPC s 1988 COATINGS EDUCATION AWARD at that year s Annual Meeting. Mr. Brevoort has worked for a number of major suppliers to the Industrial Maintenance Protective Coatings and Rail Finishes Markets. Mr. Brevoort is president of Brevoort Consulting Associates, Inc., which he formed in 1985 and which offers a broad range of technical, marketing, and business management services to the paint and coatings industry. Professional Estimator. He has held chairmanships at various levels in National Association of Corrosion Engineers, the American Society for Testing and Materials, the American Society of Professional Estimators, and the International Maintenance Institute. (A picture and biography of Jack Oechsle are given at the end of the chapter on Thermal Spraying.) Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 240
SSPC CHAPTER*B=O 93 Bb27ïYO 0003böô 52b = REFERENCES 1. Abrasive Blasting Guide for Aged or Coated Steel Surfaces . T&R Bulletin 4-27. (New York, NY: The Society of Naval and Marine Engineers). 2. Bernard R. Appleman, Economics of Coatings . Journal of Protective Coatings and Linings, March 1985, pp. 26-33. 3. Wallace P. Cathcart, Warrants or Guarantees in the Rail Car Industry for Lining and Painting . Journal of Protective Coatings and Linings, July 1988, pp. 52-56. 4. European Scale of Degree of Rusting for Anti-Corrosive Paints. Photographic Material Supplied by The Corrosion Committee of The Royal Swedish Academy of Engineering, Stockholm, 1961. 5. Financial Compound Interest and Annuity Tables, Table 5, Fifth Edition, (New York, NY: Financial Publishing Co., 1970). 6. S. Frondistou-Yannas, Coating & Corrosion Costs of Highway Structural Steel , FWHA Report No. RD-79-121, March 1980. 7. Walter W. Kaminski and J.R. Allen, What is Inspection Worth? Journal of Protective Coatings and Linings, August 1984, pp. 30-35. 8. J.D. Keane, W. Wettach, W. Bosch, Minimum Paint Film Thickness for Economical Protection of Hot-Rolled Steel Against Corrosion . J. Coatings Tech., 44, No. 533, June 1960. 9. J.D. Keane, Evaluation of Coatings in Potable Water Tanks . Materials Protection, 7, No. 4, 1968. 1O. J.D. Keane, Protective Coatings for Highway Structural Steel . Steel Structures Painting Council/National Cooperative Highway Research Project Report 74, 1969. 11. C.G. Munger, Petroleum Industry Use of Zinc-Rich Coatings . The Zinc Institute National Zinc-Rich Coatings Conference, Chicago, Illinois, pp. 77-81, December 4, 1974. 12. R.I. Pamer, Corrosion Protection of Chemical Industry Facilities with Zinc Rich . The Zinc Institute National Zinc-Rich Coatings Conference, Chicago, Illinois, pp. 34-37, December 4, 1974. 13. A.H. Roebuck, et al, Economics of Zinc Coating Systems for Corrosion Protection . Journal of Protective Coatings and Linings, July 1984, pp. 20-25. 14. Standard Method of Evaluating Degrees of Rusting on Painted Surfaces SSPC-Vis 2-8 and ASTM D610-85 Steel Structures Painting Council, Pittsburgh, PA and ASTM, Philadelphia, PA. 15. Steel Structures Painting Council, Good Painting Practices, Volume 1, chapter 8 (Pittsburgh, PA SSPC). 16. R.K. Swandby, How to Analyze Costs of Painting a New Plant . Chemical Engineering, 62, May 28, 1962, p. 115. 17. J.J. Van der Veken, Cost-Effective Maintenance Via Quality Control . Journal of Protective Coatings and Linings, September 1985, pp. 40-45. 18. D.E. White, P.A. Johnson, P.M. Charlton, R-O-W Vegetation Control: The Never-Ending Process . Electrical World, August 1986, p. 41. SUGGESTED READING MATERIAL 1. Anonymous, Estimating Guide , Painting and Decorating Contractors of America. 12th Edition, 1980.
2. Anonymous, High Maintenance Costs Call for New Approach to Protective Paint Work , Construction News, March 16, 1978. 3. Anonymous, Rising Costs Favor Long Life Paints . Finishing Industries, August 1978. 4. Anonymous, The Painting and Decorating Contractor 1977 New Construction Profile and Estimating Guide . McGraw-Hill Information Systems Company, 1977. 5. Abel Banov, Maintaining With Urethanes . American Painting Contractor, February 1980. 6. Gordon H. Brevoort, and A.H. Roebuck, Costing Considerations For Maintenance and New Construction Coatings . Paper No. 335 at NACE Corrosionl92. 7. J.E. Haskins, Jr., Maintenance Painting Costs . Plant Engineering, February 1980. 8. John D. Keane, Protection of Structural Steel Work: Some US. Experience and Practice Corrosion in Civil Engineering, Proceedings of the Institution of Civil Engineers, pp. 31-57, February 21-22, 1979. 9. Brian Mills, Selling Management a Cost Effective Painting System , NACE Symposium on Protective Coatings, September 25, 1979. 1O. J.W. Perchall, Economical Coating Protection for Fabricated Steel & Plate . Canadian Structural Engineering Conference, 1978. 11. A.H. Roebuck and L.L. McCage, Coating Economics . Materials Performance, October 1976. 12. Bill Sisler, Industrial Painting Costs . American Painting Contractor, August 1979. 13. J. Weber, The Economics Significance of Corrosion and its Prevention , Engineer s Digest, September 1977. 14. P.E. Weaver, Industrial Maintenance Painting, NACE 1973. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 241
SSPC CHAPTERUS-O 93 = 8627740 0003bBS 4b2 CHAPTER 9 SHOP PAINTING OF STEEL IN FABRICATING PLANTS by W. J. Wallace.Jr.* *An update of the first edition chapter written by Jonathan Jones, former chief engineer for Bethlehem Steel, and Joseph Bigos, formerly Senior Fellow at Mellon Institute. I. INTRODUCTION The purposes of shop painting structural steel are to protect it from corrosion for a limited time until it is erected in its final location, and to provide a sound base for the complete paint system. Shop painting is the painting done by the fabricator at the place of fabrication and before shipment to the site of erection. Some fabricators go so far as to send the steel to shops that specialize only in blast cleaning and painting. The process includes the surface preparation, pre-treating, and application of paints; also, the supplying of all labor, material, and equipment, as well as the drying and protection of the painted surfaces. The three principal aspects of shop painting are (1) the preparation of the surfaces; (2)the choice of paint; and (3)the procurement, storage, mixing and application of the protective material. In recent years most of the paint specifications generated for shop painting have specifically listed the generic type of paint material to be used. The developments which have led to present general practice in structural and steel fabricating shops will be discussed in this section; specialized aspects will be covered more fully iri later sections. The first two of these items may vary greatly in costs; they are, however, only the first steps in the total protective system to be given the structure; therefore, the economic choice of one method or material as against another can be made only when the total system is studied and specified. It is not within the province of this chapter to debate the economic advantage of one total system as against others, although some factors that have a bearing in that direction are mentioned. Such economics can be calculated only when the life of the complete paint system is known; this life is dependent upon the use and environment of the structure, as well as upon the cleaning and painting in the shop.
To illustrate the foregoing: for a given structure a painting system may be adopted that involves a rriinimum first cost, anticipating that there will be considerable repair of weak spots over the first few years of service life, until a stabilized condition is reached. Or. for a similar structure, a different system may be adopted, which involves a considerably greater initial cost, anticipating that few if any repairs will be required until the lapse of years makes general repainting necessary. The choice between two such systems, or of some intermediate system, will be made partially on the basis of estimated annual cost over a long term, and partially, perhaps, upon other circumstances important to the owner of a particular structure. Such estimates of total annual costs are beyond the scope of this chapter. Also beyond the scope of this chapter is a detailed discussion of surface preparation or the technology of current alternative shop primers. These are covered in separate chapters. A. PREPARATION OF SURFACE The existing practices described below are fairly representative of structural steel fabricating plants. This country contains thousands of fabricators of structural steel, from small tovery large, and exceptions could doubtless be found to practically any statement that could be made about shop practice. An initial expression such as In general or For the most part should, therefore, be assumed to precede most of the statements that will be made. Structural steel as it leaves the hot-bed at the rolling mill is covered with layers of oxides of iron, necessarily formed while the hot steel is exposed to the atmosphere. This coating of mill scale varies from steel to steel, from product to product, and frequently over different portions of the same rolled piece. Assuming that the steel has been rolled on specific orders from fabricators, and not for storage at the mill, it will be promptly loaded and shipped, with this mill scale virtually intact; there may, however, be exceptions, as when mill scale is shaken loose in the process of straightening a beam or bar that acquired a curvature while cooling. Large portions of the mill scale, usually firmly attached to the steel, are difficult to dislodge, and if held intact under a reasonably good paint system in atmospheric exposure should be a source of added protection in mild non-corrosive environments. Other portions of the scaled surface, however, frequently are quite susceptible to atmospheric attack, because they are soon penetrated by water and air. With the ensuing formation of rust they are still further penetrated, and if this mill scale is not removed Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
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SSPC CHAPTER*S-O 93 m 8b27940 0003690 184 m it will be a source of trouble under even the most adequate of paint systems. Since the many steel shapes arrive at the fabricating shop from various mills and at various times, there may be a considerable waiting period in the shop receiving yard before the material enters the shop for fabrication. In the shop, the steel passes through a myriad of operations that crack and remove the mill scale. Consequently, by the time the members have been completely fabricated and are ready for painting, the surface of a single member may vary (and almost certainly the surfaces of the many members making up a structure will vary) from surfaces containing the original tightly rolled mill scale, to surfaces on which the mill scale is cracking or badly cracked, to surfaces where considerable rusting has already taken place. This variation of surfaces inevitably faces the fabricator when the work is ready to be cleaned and painted. In the past, some specifications had permitted steel to be shipped, erected and weathered before painting. Such practice has long been eliminated in favor of shop cleaning and painting; the resultant paint system has a longer life than it would have if it were painted over weathered steel from which all the rust was not removed. Many structures, particularly tier building frames, must be shipped without paint because they are to be encased in concrete after erection. The cleaning required at the shop is only a simple manual wire brushing to remove scale and corrosion products already evident; a slightly rusted condition at the time the concrete is poured around the steel is generally considered to be in no way detrimental. Many other structures, particularly the frames of manufacturing buildings, while not encased in concrete, will be permanently enclosed within walls and roofs, and kept dry and warm. They also can be given a rapid manual cleaning followed by an inexpensive shop coat of paint. It has become mandatory to blast clean and shop prime structural steel that is to be used in the construction of motels, hotels, and office buildings, etc., since the shop primed structural members are then coated with a fireproofing material prior to completion of the structure. It is generally conceded that the breakdown of a priming coat would be delayed over the longest period of time if, before painting, the steel were descaled, ¡.e., all scale whatsoever removed, which might be accomplished either by pickling the steel before fabrication, or by sand or grit blasting after fabrication. Pickling could be performed only prior to fabrication, as the pickling of a fabricated member would be impracticable on account of the sizes and shapes involved, and also might be a failure because of the entrapment of acid in the many interstices between component pieces. Furthermore, such pickling would lose much of its value
because of the rusting and contamination that would occur in subsequent fabricating operations before the paint could be applied. Thus, the prior pickling of the structural steel for bridges and buildings may be regarded as practically non-existent at present. Many steel fabricators use automatic centrifugalwheel blast cleaning equipment, while others use air blast. In each operation the blast cleaning medium (metallic shot, grit, or a combination) is recycled. These operations have reduced the cost of shop surface preparation considerably. Sand or grit blasting, like pickling, must be followed by prompt painting before the bright surface begins to rust. In the case of sand or grit blasting, however, in contrast to pickling, it is practical to perform the operation after the fabrication is complete. B. SELECTION OF PRIMING PAINT In the priming paint, the purposes of the pigment are: (1) to interfere chemically with or to inhibit the solution of iron and formation of rust in the presence of moisture and (2) to minimize the amount of moisture and oxygen penetrating the paint film to the substrate. The purposes of the vehicle are: (1) to bind the pigment in intimate contact with the steel surface and (2) to assist in excluding the invading moisture and oxygen. For many years, fabricators acted on the assumption that if they used exactly the paint that was called for by the owner s specification, and applied it conscientiously, responsibility for its behavior thereafter lay with the owner. But it is a fact that the fabricators are forced to share the responsibility for the performance of the asapplied primer. For many years, it was generally advertised and accepted that red lead (Pb,O,) and the more expensive lead chromate were the best possible inhibitors. It was also considered that linseed oil, either 100°/~raw or with some admixture of bodied oil, was the best possible vehicle to carry the red lead. The Federal Government specification for red lead in oil, therefore, was a popular specification for steel structures. Various proprietary brand name paints have appeared from time to time in competition and have been specified for various reasons; but none achieved a permanent status comparable to that of red lead in oil. In the original treatment of this chapter, one of the authors traces the development of Bethlehem Primer that was the forerunner of the current Federal Specification No. TT-P-86, Type II Red Lead Alkyd Paint . The increased use of blast cleaning has led to an increased use of proprietary primer paints. These primer paints, some of which are modifications of the red lead have good protective qualities and, in the interest of production, faster dry times. Since the good wetting quality of the long oils is not necessary with the blast cleaned
surfaces, the specification writers should be aware of the fabricator s shop facilities and specify primer paints that do not impede the production process by being very slow driers. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 243
SSPC CHAPTERx9.0 93 W 8627940 0003b9L 010 W C. APPLICATION OF SHOP PAINT General practice in a large number of steel fabricating plants may be exemplified by the following summary of practice. Detailed requirements are given in SSPC-PA 1, Shop, Field, and Maintenance Painting. The works drafting room prepares and sends to the shop a paint sheet that digests from the job specification whatever the shop staff must know about the specified cleaning, the type or brand of paint, the ordered quantity of paint and, if special, the requirements for application. The drafting room also prepares and sends to the purchase department a requisition for the purchase of paint, including specified type or brand, quantity, and required dates of delivery. On a large contract, monthly shipments may be requisitioned to ensure the use of fresh material. In recent years a large number of steel fabricators have employed paint specialists to handle painting problems. The paint specialist reviews all specifications, makes recommendations, issues painting instructions for shop and field painting, and in general assists the various operating departments in the paint application work. The constant updating of the product information sheets on the part of the paint manufacturers has virtually eliminated the need for in-house testing on the part of the fabricator. However, it is good practice to have some personnel trained in the art of rudimentary testing of paint materials, for instance for viscosity, flashpoint, dry time (8stages), solids content, and settling. Paint materials are stored in the paint house, and when deliveries are made, each is identified and marked for the contract on which it is to be used. This work is done by the paint house attendant, who reports and maintains records of all incoming and outgoing shipments. He also dispenses all materials to the painters; and before a painter can obtain any paint, he must state the contract on which he is working. This is an additional check to ensure that he is using the correct material. Record of the gallonage used by each painter on each contract is also made by the paint house attendant and forwarded to the office daily. As a preparatory painting step on the steel structures contracts where exposure will be lengthy and severe, all edges may be initially striped with the specified primer and allowed to dry. This eases the problem of pull-back that is apt to occur from edges and leaves a double coat in these vulnerable places. The paint for the prime coat is seldom thinned beyond the packaged condition, and then only on the specific instructions of the paint manufacturer. All drums should be mechanically agitated before the paint is issued and during application. The primer is applied by spray, except when the customer prefers another method of application. II. GENERAL
Paint is generally appliei in such a manner as to obtain a dry film thickness recommended by the paint manufacturer. Dry film thicknesses are measured using pull-off or fixed probe magnetic gages such as a Mikrotest or Elcometer. It is vital to remember that the magnetic gage should be calibrated on a piece of steel blast cleaned in exactly the same way as the steel to be painted. Continuous inspection is important. Every piece of painted steel should be inspected before it is moved from the painting skids. A final inspection should be made after loading to remove all marks and handling damage. Records of these inspections should be maintained for at least the guarantee period of the job contract. The most important factor in obtaining long paint life, with attendant protection of the steel, is proper preparation of the surface. Despite advertising to the contrary, there is no magic paint that will eliminate the necessity for a clean surface. Experience has proved that when steel is completely descaled and free of rust, oil, grease, and other contaminants, great variations in the composition of the paint are possible without seriously changing the degree of protection in atmospheric exposures. Paint life on such completely cleaned steel may vary from two to five times the paint life on poorly cleaned and rusted steel, depending of course, upon the paint system and the exposure. On the other hand, many recorded cases show that paint applied over clean, dry, tight mill scale has lasted as long as paint over sand blasted or pickled steel. Such sound mill scale is conceded to be a good base for painting if the exposure is not very severe. Lately, it has become a basic tenet of economic survival that the fabricator must have some recognized method of shop surface preparation, or lose the work to a competitor who can do shop surface preparation. There are a few instances in which the cost of full field work is justified, but even these instances require considerable deliberation before electing to do all cleaning and painting in the field. Unfortunately, there is no guarantee that paint applied over mill scale will give satisfactory performance. There is no method presently known that can determine the suitability of the remaining mill scale for painting. However, the mill scale that shows visible cracks after rolling or fabricating is almost sure to cause trouble later. Despite careful cleaning, a certain amount of the mill scale remaining will later loosen and carry away the applied paint. In mild atmospheric exposure, the amount of mill scale that loosens after proper cleaning and painting is slight. In severe exposures, such as chemical environments or water immersion, mill scale should be completely removed to guarantee against large scale lifting of the paint. As stated earlier, this problem is really one of eco. nomics; the owner of the structure must decide how far he
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SSPC CHAPTER*S*O 73 W 8627740 0003b92 T57 will go in paying for the increased cost of the best surface preparation. It is not enough to point out the increased life of the paint when applied over completely cleaned steel. Experience has also proved that it is economically feasible to clean by hand or by power wire brushes and paint over the remaining mill scale when the structure will be exposed to mild atmospheres. Much of the tonnage of the steel fabricated in this country today falls into this category. The extra years of protection afforded by better surface preparation may not always be justified. A paint system that protects the steel for fifteen years may not be economically sound when the structure must be repainted every ten years for the sake of appearance. In the final analysis, the owner must calculate the cost of painting in dollars per square foot of surface per year for the alternative paint systems that are suitable for use. Note that the problem is based on surface area since cleaning and painting costs depend directly upon the area to be cleaned, not the tons of steel. The fabricator who makes estimates and calculates such costs on the ton must be certain that his figures are truly representative because of the wide variation in square feet of surface per ton of steel. One cannot separate discussion of surface preparation from the priming paint. The two must be considered together in deciding the type and degree of surface preparation or the primer that will be used. When the primer is arbitrarily chosen, the surface preparation limitations are fixed. For example, when a fast drying, poor wetting primer is to be used, the surface preparation must include removal of mill scale, rust, grease, and oil. If the chosen primer is a slow drying paint containing oil and adequate rust inhibitive pigments and possesses good wetting ability, then hand cleaning may suffice. The degree of hand cleaning must be determined by the exposure and service expected of the shop coat. It is generally true that the shorter the drying time of a paint, the less effective is its power to wet the surface, although paints of equal drying time may differ greatly in their wetting ability. Wetting of the surface, in turn, has been found to be the most important factor in determining the protection afforded by properly pigmented rust inhibitive primers over the less well cleaned surfaces. Poor shop cleaning prior to painting leaves a surface with mill scale, rust, oil, grease, moisture, soil, and other contaminants; the amount retained varies with the original condition and the thoroughness of the cleaning. For such service, the properly pigmented primer must have strong wetting ability to penetrate through the film of oil, rust, etc. While mill scale itself is non-porous, fabricating operations crack mill scale and permit water and air to enter and begin rusting underneath the outer layer of the mill scale. A good wetting primer will penetrate these cracks as well as the underlying rust and will retard further corrosion and
subsequent mill scale lifting. It is the opinion of many qualified engineers and paint technologists that the vehicle of the primer applied over hand tool or power tool cleaned steel should consist of raw linseed oil, or one sufficiently rich in raw oil to provide the desired wetting. It is believed that such a vehicle (when used with proper pigments) is about as close to foolproof as any available for shop primers. Unfortunately, raw linseed oil has disadvantages in shop primers that almost outweigh its advantages. It attains its excellent wetting ability from its low surface tension; by remaining fluid for a long time, it develops good adhesion. For shop use, and in most cases in the field, driers must be added to permit drying and handling in a reasonable time. This cuts down the degree of wetting, but because of its wetting ability, the raw linseed oilcontaining paints still have the best wetting characteristics of the recommended shop primers. Even with the use of driers, raw linseed oil paints require 48 or more hours for drying. It is not uncommon to have such paints dry on the surface, but remain wet underneath for weeks. This is hazardous for steel workers who might skin off the surface and lose traction or slip. A second disadvantage of the use of such paints is the poor resistance of raw linseed oil to water or chemicals; this lack of resistance makes the paints particularly vulnerable when they are placed in service shortly after painting. Raw linseed oil paints are currently considered poor for underwater exposure. Before leaving this subject, a few remarks on pigments and other primers may be pertinent. Red lead has proved itself to be unsurpassed as a pigment for heavyduty primers. Formerly, it was felt that the pigment should be all red lead, and that as much red lead as possible should be crammed into a gallon of paint even though the paint was difficult to apply. The validity of these beliefs is open to argument in view of the facts that have developed in testing and evaluating of paints. The writer s opinion, based upon the results of many tests performed by a number of organizations, is that just as good a primer can be formulated by replacing a portion of the straight red lead pigment by other pigments, such as basic lead silicochromate pigments. Two primers have already been mentioned; both of these have a pigment composed of 75% red lead and 25% iron oxide. Test results indicate that they perform as well as 100% red lead pigments. Other test results indicate the red lead content can be decreased still further by adding other pigments. Addition of mica to the red lead and iron oxide does not seem to decrease the performance, and might improve it for some services. The addition of other pigments and extenders should not be considered a lowering of quality as long as sound formulation principles are adhered to. The iron oxide decreases one fault of pure red lead paints: their poor weathering resistance. If not covered by a top coat, red lead primers will carbonate on long exposure to air and
turn a gray-white; however, the performance does not appear to be adversely affected. Addition of the iron oxide decreases this tendency and permits touch-up or shop priming to be exposed to the weather for a long time without harm due to failure to recoat. Addition of mica or other suitable extenders decrease the permeability of the paint to water and oxygen. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 245
SSPC CHAPTER*S.O 93 m Bb279LiO 0003b93 993 m Other rust inhibitive pigments used extensively are zinc chromate, lead chromate, zinc oxide, and zinc dust. Zinc chromate and lead chromate are mixed with other pigments for primers. The usual red oxide shop primer can be greatly improved in its rust inhibiting ability by the substitution of about one-third of the normal pigment weight by zinc chromate. Zinc dust has great merit in a rust inhibitive primer when used with zinc oxide in a proportion of about 80 parts zinc dust to 20 partszinc oxide by weight. When used with raw linseed oil, this primer has good wetting ability but is also slow drying. For freshwater paints, the zinc dust-zinc oxide combination is among the best, particularly when the vehicle is a phenolic varnish and the steel is sandblasted. In recent years, vinyls, epoxies, inorganic zinc (one and two package), organic zinc, and chlorinated rubbers have been used as shop priming paints. In this same period of time environmental regulations havecomplicated the steel fabricating industry efforts to achieve better shop painting performance. For example, in many areas the traditional paints containing red lead, chromates, and large amounts of volatile organic compounds are no longer permissible. The specification writer should be aware of the laws and regulations governing paint, paint selection, and the areas in which the paint is to be applied and exposed. Before discussion of specific procedures is begun, it might be well to point out that proper application of paint is no less important than choice of the proper paint. In fact, a good paint poorly applied can be much worse than a poorer paint that is well applied. A. DESIGNING FOR BETTER PAINTING It is unfortunate, but true, that many structures are designed so that they cannot be adequately painted or properly maintained after erection. The designer should keep in mind the necessity of having weather-exposed surfaces accessible for cleaning and painting. Where it is impossible to provide accessibility, the member should be completely sealed by welding, riveting or caulking. Corrosion activity in a sealed interior will use up the available water and oxygen and then stifle itself. Therefore, it is not necessary to provide protective coating in such hermetically sealed enclosures. Gratings, decks and open flooring should be of a design that eliminates crevices and cracks such as occur when riveted, expanded grating is used. An example (Figure 1) of a clean cut, open design is shown here; however, even this grating may be difficult to paint. The use of galvanized or fiberglass reinforced gratings is increasing because of the difficulty in painting and maintaining steel grating. Collars for pipe hangers and similar projections cause difficulty because they collect water and rust the pipe; pitting may be severe in localized areas. It is difficult to
keep them painted or to seal the cracks because of expansion and contraction of the pipe. Lugs welded on the pipe, to which hangers are bolted, will remedy most of the difficulty. Corrosion that does occur attacks the hanger or the lug and does not weaken the pipe itself. Riveted or bolted joints should be placed so that they can be cleaned and painted. Too often, a line of rivets is placed so close to a corner that it is almost impossible to clean or properly paint one side of the rivets or joints. Sometimes the design does not permit sealing of joints by rivets and rusting spreads the joint apart. More recently, inorganic zinc primers are permitted on splice areas that will be connected by bolts or rivets in the shop and field. Pockets in fabricated members that can collect dirt should be eliminated; roller shapes should be positioned so that dirt and water are not retained. If it is necessary to have the open side of a channel facing upwards, weep holes should be cut into the web. Many times angles or channels are placed back to back, but are separated by a thin gusset plate or washers. This leaves a space that is extremely difficult to clean and paint. Furthermore, it traps soil and has a tendency to remain wet, accelerating corrosion. Channels or angles used for stiffeners should not be placed with the open angle against the steel and left open at the top and sealed at the bottom, since such a design permits water to accumulate. Such stiffeners should have a flat surface against the wall to be stiffened so that the crack may be sealed with paint, as is done in placing stiffeners on webs of plate girders. When the structure is exposed to salt spray or contamination, or acid, or alkali, in fact any strong electrolyte, it is particularly important that the designer eliminate pockets or corners that may trap contamination and water. Electrolytic action in such spots often causes sufficient loss in section to cause failure of the member. When the structure is exposed to periodic stresses, stress fatigue coupled with corrosion can cause early failure at stress values far below the design limitations. Corrosion at localized spots may set up stress raisers which can cause stress fatigue at the spot. FIGURE 1 Example of a clean cut design of grating to eliminate crevices that trap contaminants and accelerate corrosion. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 246
SSPC CHAPTER*S.O 93 m 8627940 O003694 82T m When a structure is exposed to severe attack, such as salt water or a chemical atmosphere, design engineers should specify complete scale removal. Mill scale in such environments becomes the cathode in local galvanic cells on the surface of the steel. The mill scale is protected by sacrificing bare steel (perhaps at cracks in the mill scale). Under this condition, the total amount of corrosion is usually the same as for descaled steel, but corrosion is concentrated at discontinuities in the mill scale. The result is pitting, sometimes severe enough to perforate the metal and cause a failure. When complete descaling is not feasible, adequate maintenance painting must be scheduled since extra thickness for corrosion allowance may not insure the structure against failure from localized corrosion. Noble metals such as copper, nickel, etc., should not be fastened with steel rivets or bolts since galvanic action will destroy the fastening while protecting the plates. On the other hand, noble metals can generally be used as rivets or bolts to fasten steel or iron. Here the galvanic attack on the iron is distributed over a large area and little, if any, harm is usually done. When dissimilar metals are to be in contact, the contacting surfaces should be insulated. Paint is usually satisfactory for this purpose. When steel is to be in contact with a porous material that may be wet (such as wood), the contact surface should be painted. In general, anodic areas (steel) should not be painted if the cathodic area (copper, brass, etc.) is unpainted when the galvanic couple is exposed to an electrolyte. Paint both, or else the cathode alone; otherwise, a break occurring in the painted anodic area may quickly lead to failure of the steel. Steel that is encased or fireproofed with lightweight concrete (aggregate) or other lightweight, porous, fire retardant material (vermiculite) should be painted with at least one coat of good quality rust inhibitive primer. When conditions are severe, or humidity is high, two or more coats of paint should be applied as the concrete may accelerate corrosion. When steel is enclosed in concrete of high density or low porosity, and when the concrete is at least two to three inches thick, painting is not necessary, since the concrete will protect the steel. Steel enclosed in masonry should be painted with at least one coat of rust inhibitive primeras leaks in flashings, condensation of water permeating the masonry, etc., may cause localized corrosion. Steel that is in partial contact with concrete is gen-
erally not painted. This creates an undesirable condition as water seeps into the crack between the steel and the concrete. Corrosion may then occur and a sufficient volume of rust may be built up to cause spalling of the concrete as in the corrosion of reinforcing bars in concrete highways. The only remedy known to the author is to chip or leave a groove in the concrete at the edge next to the steel and seal the crack with an alkali resistant caulking compound (such as bituminous cement). Steel should not be encased in concrete that contains cinders since the acidic condition will cause corrosion of the steel. Designing to eliminate crevices is of particular importance in underwater structures. Flat areas, such as tank roofs, should be designed to eliminate low spots which will collect and hold water. Other details requiring precaution in design are included in various chapters of this book, and particularly in Chapter 25. Frequently the consulting engineer, architect, or owner specifies a paint system that the fabricator, because of his previous experience, knows is inadequate for the job. The fabricator should have a competent person look over the specifications for each new job to decide whether he can honestly endorse the specified system. He should do this in his own interest since he may be held responsible in the event of a failure. Quite often he can have the specification changed to include a material that he feels confident will be better, or at least will not fail to perform satisfactorily. Sometimes through lack of knowledge, customers will specify a paint to be used over a type of surface prepara tion that is inadequate for the paint. Either the paint should be changed or surface preparation improved. Fabricators usually have a preference for a certain type of shop paint. When the customer does not specify the paint, the fabricator should consider the service and exposure of the structure and decide whether his usual shop cleaning and painting will be adequate for the job. Better cleaning and higher quality of paint may increase the cost estimate for the job; it is hard for the fabricator to quote on expensive cleaning and painting while his competitors quote on poorer work. Here, preliminary negotiations with the customers may make the customer realize that his specifications need to be changed so that better, even though more expensive, painting is called for. If this fails, the fabricator who wants to do the right thing must hope that customer s satisfaction or insurance against paint failure will offset his decreased profit on the job. Other design factors are covered in Chapter 25. B. THE CLEANING AND PAINTING SHOP Cleaning and painting costs can be kept to a minimum by efficient layout and planning of the cleaning and painting shop (or shops, since some fabricators find it advan-
tageous to separate these operations). Basic fundamentals of sound industrial engineering should be adhered to in establishing flow patterns for the work, eliminating crossover and backtrack as much as possible, and providing adequate facilities for efficient operation (Figures 2-8). A large portion of the painting costs in the fabricating shop are attributable to handling; the direct cost chargeable to crane time, etc., is easily recognized. Just as large, or larger, indirect costs are often occasioned by lost time waiting for cranes, handlers, and back tracking for touch up of damage done in handling. Operations should be set up so that handling or moving is kept to a minimum. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 247
SSPC CHAPTER*S*O 93 8627940 0003695 766 W Continuous production lines should be set up whenever possible; if the fabricated objects are more or less uniform, and not too large, a mechanized conveyor (overhead, track, etc.) should be used to expedite handling of the work. In general, mechanical equipment should be used to the maximum degree possible and manual labor kept to a minimum. There is a trend, especially in shops that fabricate small parts, to employ the automatic spray line in conjunction with electrostatic paint application. This innovation has been used to coat large diameter line pipe. When continuous production lines are impractical, semicontinuous lines might be feasible; such work can sometimes be handled efficiently on carts or trucks running on small track. Extremely large beams and girders can be set up on flat freight cars and run through a cleaning and painting shop that is built up on either side of the track. This process is not to be confused with the poor practice of loading fabricated steel on cars for shipment, then cleaning and painting just prior to the shipment. Whether the cleaning and painting shop is best housed in the same building with the fabricating opera tions is decided by the individual fabricator. Handling costs are generally lower if they are in the same building. However, the effect of the cleaning and painting operations on the remainder of the plant must be considered. If blast cleaning is done in the shop, separate rooms or cabinets are a must for efficient, safe operations. Even if only hand or power tool cleaning is done, the effect of the painting operations may warrant a separate building. Spray painting has been eliminated in some plants because of the complaints of other workers who object to the fumes, even when no overspray carries to their portion of the plant. To forestall such a contingency a spray booth, downdraft ventilation, or other positive measures are necessary. All fabricating shops should have adequate facilities for cleaning and painting under cover. In warm climates, where the temperature does not drop below 40°F (4"C), an FIGURE 2 Plate sand blasting in fabricating plant. Courtesy: Chicago Bridge and Iron open-sided shed is sufficient, but the roof should extend over the sides sufficiently far to prevent a driving rain from ruining the paint job. In such open sheds, there is a danger from high humidity in cool weather, or during rainstorms and fogs. In cold climates, the paint shop should be en-
closed and heated at least enough to keep the temperature above 40°F (4°C). If practical, the temperature should be kept up to 6570°F (18-21OC), for temperature and humidity have considerable effect on the quality of the paint job. Low temperature or high humidity slow the rate of drying; it is very possible that under such conditions the painted steel can be dried for the normal time and loaded for shipment before it has dried (or cured) sufficiently. The life of a paint is affected by the atmospheric conditions to which it is first exposed, particularly when it has not dried completely. Heating the paint shop and the paint in cold weather is desirable for several reasons. Cold weather makes the paint viscous and it will not flow properly; thus, it fails to wet the crevices and cracks in the steel surface and the adhesion is poorer. The cold paint is difficult to apply and painters will not want to brush properly; brush marks remain in the paint film and are weak points because of the thin film in the marks. Painters will thin the paint to compensate for its increased viscosity; the result is a dried film of paint that is thinner than normal, and consequently poorer protection. In cold weather, moisture condenses on the steel, even indoors, when the dew point of the air is reached. When the air is heated, the humidity is usually increased. Since the steel temperature lags behind the air temperature, it acts as a condenser and collects water on the surface. Water wets the surface of steel and causes rust; it is drawn into the cracks of the mill scale, under the edges of the mill scale, and into the rust. Even on scrupulously clean steel, a layer of water will be built up. Painting over this water, which is generally impossible to detect, locks in a potential corrosive medium. Rusting proceeds under the mill scale, and eventually the mill scale lifts and ruins the paint. Most cases of paint failure due to mill scale lifting occur on steel that was fabricated, cleaned, and painted during the winter.
Other facilities will be discussed under the various headings that follow. In summary, when setting up or changing the painting shop, use mechanical or automatic equipment as much as possible; keep handling to a minimum unless a completely mechanized handling system is feasible; provide adequate and protected space for cleaning, painting and drying. C.QUALIFICATIONS OF LABOR In many shops, cleaning and painting are considered jobs that require no skill, but a good job at minimum cost can be done only by trained men who are qualified for the work. The practice of random assignment, on a day-to-day basis, of manual labor for cleaning and painting should be eliminated. One reason for poor paint jobs is that some Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 248
SSPC CHAPTER*S*O 93 8627940 0003b7b bT2 workers are led to consider it just another job. Generally, however, the worker is basically proud of his skill and ability; given an even break he will try to do a job of which he is proud. He can be relied upon if he is educated to do good work and is provided the means to do it. Methods of training workers vary with the plants; most often, training is by on-the-job methods, or through apprenticeship when this is required by union rules. Some plants have set up training programs that cover considerable ground and a long period of time. In such cases, perhaps eight hours a week are devoted to instruction and discussion; the remainder of the time is spent in doing work, but the time for each type of job, or for each different phase of activity, is programmed. At the end of six months, or a year, the worker is promoted from apprentice, or helper, to painter if he passes a qualifying test. Because of the increased cost of labor, and the sophistication of the newer paint materials, most fabricating shops use automatic blast cleaning equipment and spray application of the paint. In those shops, and particularly in the field, where personnel are assigned the task of blaster-painter there is a lack of skill due to fatigue, especially when after spending most of the day blast cleaning, the person is now required to apply the paint. Spray painting is not a strictly mechanical operation; it requires more skill than brush or roller application, plus a technical knowledge of the equipment. In using the newer, fast drying paints, correct know-how in the application is positively essential for their success. In recent years the major manufacturers of paint spray equipment have sponsored week-long classes in the proper methods of equipment handling and spray painting techniques. In the final analysis, the man who applies the paint determines its performance. No matter how good the surface preparation or the paint, it is no better than the man who applies it; always remember, even the best paints will fail if not properly applied. The painter must be aware of the importance of his work and proud of its quality; if he is doing something against his will or for low pay it will be reflected in poorer paint performance. 111. SHOP CLEANING AND PRETREATING The cleaning of the surface has already been discussed in a general way; specific details are covered in the chapters on mechanical and chemical surface preparation. This section deals with specific operations in the fabricating shop. Fabricated steel ready for cleaning and painting consists of a varied assortment of surface conditions. New steel (steel that has been shipped from the rolling mill and has not weathered in the fabricator s yard) will usually consist of almost intact mill scale. Weathered steel will
vary from almost complete rust to almost intact mill scale, depending upon how long it is stored in the fabricator s yard, and whether it is stored under cover or not. The surface conditions of the usual rolled shape will vary; perhaps one face may be completely rusted, while others will have only patches of mill scale remaining. If the steel has been stored for a long time, rust scale may be present on a portion of the surface area. Oil will be present from handling, drilling, reaming, etc. Grease will be present from the machinery lubricants, crane drippings, etc. Carbonized residues from riveting and welding operations may be present. Chalk marks, perhaps drawing compounds, mill identification marks, piece numbers, etc., will be present. Water soluble cutting compounds, or emulsions are sometimes present. Salt is sometimes present on the surface. Mud and dirt are often present, as are hand prints. The methods of surface preparation generally used in the fabricating shops are as follows: 1. Nominal Cleaning 2. Solvent Cleaning 3. Hand Cleaning 4. Power Tool Cleaning 5. Blast Cleaning 6. Pickling All, except for the first, are covered by Steel Structures Painting Council Surface Preparation Specifications and Commentary and will not be repeated in this chapter. As a precautionary note, the reader should familiarize himself thoroughly with the SSPC Surface Preparation Specifications and then take a hard, realistic look at the physical capabilities of his workplace before committing himself to a method of surface preparation that would be impractical. Photographs of various methods of surface preparation are presented for the reader s familiarization. IV. SHOP PRIMING The basic requirements of shop primers have been FIGURE 3 Side view of centrifugal blast cleaning unit showing driving motor and wheel housing. Work is cleaned as it passes the wheel only. A fortyeight foot long cleaning chamber is provided, but most of this space is a tunnel which serves only to trap abrasives and act as a shelter. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 249
SSPC CHAPTERx7.0 73 8b27740 0003677 537 Illustration of a centrifugal wheel used for blast cleaning. Note the extensive repair work which has been necessary on the housing due to the wear from the abrasive. discussed; it was shown that the most severe test of a shop coat is long exposure without topcoats, such as on steel for a large structure. Since the dried film thickness of --`,,,,`-`-`,,`,,`,`,,`--cised that the second coat of paint is compatible with the first, since inter-coat peeling may result if adhesion is not good; also, the solvent in the second coat must not be powerful enough to lift the fresh primer. Another method is to shopcoat the steel in the normal manner and ship the steel to the job site. Before erection, the steel is given a second coat of paint. The prime coat should weather long enough to lift vulnerable mill scale. Spot cleaning and touch up of these areas is necessary before the second coat of paint is applied. Unfortunately, painting of the steel in the field before erection requires extra handling operations. But the extra cost for handling is offset by the timely on-site paint application. When the period of exposure before field painting is short, or when the surface preparation is of good quality, the burden thrust upon the shopcoat is eased, and considerable variation in the primer is possible. Here, zinc chromate primers show to advantage. Another alternative is the application of inorganic zinc, epoxy, vinyl, etc., as primers. However, caution must be exercised by the specifier when he contemplates the use of these materials as primer paints. They often require special surface preparation and application, and their suitability for specific environments must be considered. FIGURE 4 a good shop coat is only about two mils, it is not at all surprising to find considerable failure of the paint after long exposures. The type of exposure has much to do with the manner in which the shop coat survives the interim period before field painting. A heavy industrial atmosphere, marine atmosphere, high humidity, or chemical environment will cause much more damage to the shop coat than exposure in a rural atmosphere. When it is known that the exposure will be long and severe, several methods of circumventing probable failure of the shop coat are possible. In the first method, two coats of paint are applied in the shop. The first, or prime coat, must be allowed to dry thoroughly before the second coat is applied. This has the big disadvantage of tying up large amounts of the drying and painting facilities of the fabricator. Naturally, the fabricator will want to be paid, if production of his plant is slowed down. Moreover, he will not want to use this method because the real costs would
be enormous. The difficultv can be alleviated bv usina a - FIGURE 5 semi-quick drying paint as &,e second coat. Here, one can Exterior oí a nozzle bla st cleaning room showing two continuous type feed tanks in the foreground along with control equipment, take advantage Of synthetic type resins to Provide a more and oil and water seDa rators: abrasive recoverv eauioment is in I .. weather resistant outer coat of paint. Care must be exer- the background. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 250
SSPC CHAPTERa9.O 93 m 8627940 O003698 475 m FIGURE 6 Interior view of blast cleaning room shown in Figure 5. feed connection to operator s mask for fresh air supply tually blast cleaning. Solenoid control of blast stream is available but is not shown. Material passing through is carried on a continuous conveyor.
Note air when acby operator this room
A. RECOMMENDED SHOPCOAT PRIMERS There are a tremendous number of primers availáble for steel; the extravagant claims made for some of them are completely unsubstantiated in actual use. Others, while well formulated and of high quality, show little or no superiority over proven formulations when the primers are compared in controlled tests. Any primer that is sold on the basis that it eliminates preparation of the surface should be viewed with extreme caution. Before widespread use it should be tested in service to determine whether it will perform satisfactorily or meet the requirements of the fabricator and the customer. Reports of investigations of primers for structural steel shopcoats have been made by many investigators. The tables below list paints that have been used as primers for structural steel. They have been chosen as being representative of the types and classes of primers that have proved themselves in actual service. Due to limitations, easily understood, many good primers have been left out. Specifications for many of these paints are included in SSPC Volume 2, Systems & Specifications ; the others are easily procurable. The reader should not get the idea that because a primer is not included it is not good, or that proprietary products may not work as well. In fact, many of these paints could be improved if enough time and money were spent for that purpose. Also, many proprietary paints meet and often exceed these specifications. No primer has been found suitable for general use for all service. A minimum number of primers should be chosen for standard operations by each fabricator to be used on work for which no prime paint was specified. However, it is a rare case when contract specifications are written that allow the fabricator to choose the paint. Normally, the contract specifications call for generic types of paint to be shop applied. In a majority of cases brand names are mentioned, accompanied by an or-equal clause. A variety of paint materials, all of which can be used as primer paints, are presented in Table I.Also included for each paint is a description of the pigment, vehicle, and the minimum surface preparation required for each paint. Most of the paints shown in the table are very seldom specified. Several others have been banned from use by one or more federal agencies, and the use of many of these paints has been severely limited by standards of these same agencies. It is the responsibility of the owner and his agent to be aware of the regulations governing the use of certain
paints that could cause health and safety problems. In selecting primers for shop coats, the following points should be considered: (1) the corrosiveness of the exposure environment, (2) the length of time that the steel will be exposed, (3)the surface preparation that is acceptable or economical. Furthermore, the primers that are suitable must be selected upon the basis of the drying time available and the wetting ability required for the degree of cleaning contem plated. B. SHOP PRIMING PROCEDURES To obtain satisfactory performance of any paint, proper application is essential. Detailed specifications for proper application are found in Volume 2 of the manual; FIGURE 7 Pickling Set-up with three pickling tanks in the foreground. The furthest tank is a sulfuric acid pickling tank, the second is a water rinse, and the closest tank in the foreground is a phosphoric acid treatment tank. Concentrated sulfuric and phosphoric acid are stored in the iron tanks beneath the crane runway. Solvent cleaning of the steel takes place in the background prior to immersion in the sulfuric acid tank. Drying and painting racks and skids are shown in the foreground. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 251
SSPC CHAPTER*S*O 93 8627940 0003699 301 and general instructions for application are included in other chapters of this volume. It is also extremely important to consult the paint manufacturer on details regarding application of a particular paint. Details of application that are primarily of concern to the fabricator are covered in this section. i.Shop Control of Paint Properties Some control system should be set up to check the important properties of the paint. Procedures for such checks are covered in chapters on quality control. Probably the most important characteristics of paint that affect its application are viscosity, drying time, brushing properties, spraying properties, and (in some cases) dipping properties. Other characteristics, such as storage stability and hiding power, have an indirect but important effect on application. Even where no laboratory facilities are available to the fabricating plant, some person should be sufficiently trained to enable him to check the most essential of these properties. The necessary equipment is basically a viscosimeter (Zahn or similar type), a thermometer, a watch with a second hand, a scale for weighing, and some facility for drying weighed samples of paint when the percent of volatile matter is to be checked. While critical checks and tests should be conducted by competent laboratory personnel, the tests conducted by the shop personnel can guard against acceptance of a paint that is not in compliance with the specifications or the properties advertised by the manufacturer. Such crude checks will not reveal improper pigments, resins, or oils, or fraudulent substitutions with intent to deceive. On large jobs where considerable money is invested in the cleaning and painting, the services of a commercial testing laboratory should be utilized if the plant does not have an adequate laboratory. Weight per gallon can be checked by taking a filled one gallon or five gallon container and weighing it, then deducting the weight of the empty container. Small platform scales are usually available around the plant that will weigh to within one ounce in 25 pounds. Allowing an error of two ounces from the true weight in the weighing or over filling, the accuracy of such a method of determining the weight per gallon is 1/2 of one percent. This will readily show whether the paint meets the specification weight. When samples are taken from large containers, the withdrawal of a representative sample requires diligent precautions.
Viscosity can readily be checked by dipping a #2 Zahn viscosimeter in the paint, allowing the viscosimeter to remain in the mixed paint for approximately 20 seconds to achieve temperature equalization between the paint and the cup. Withdraw the viscosimeter and simultaneously start the stop watch. Time the flow of material through the cup and stop the time when the flow of coating interrupts the first time. The viscosity is compared to the previously measured or specified viscosity; since temperature affects viscosity, a chart of viscosity versus temperature should be prepared for each paint that will be used. This method of measuring viscosity works relatively well for usual shop paints, but should not be used without due precautions for thixotropic materials. Brushing, spraying, and dipping properties are easily determined by actual application to small panels; an experienced observer should make the test. Drying times are determined by exposing these panels in the shop or paint room. Here, the shop has an advantage over the labora tory because the determination is made under the conditions in which the paint will actually be applied. Since drying time is affected by temperature and humidity, the paint cannot always be blamed for improper drying; it may dry in the time specified when exposed to standard dry conditions (about 77" F or 25" C and 50% relative hum id it y). Paints are thinned with varying proportions of thinners; some paints have almost no thinner, others may run about 50% by volume of thinner. For example, when a paint that is 50 percent by volume thinner dries, only about half the volume of paint deposited on the steel as a wet film remains in the form of dried paint (assuming little evaporation takes place in the application). This means that four mils of wet film must be deposited when specifications for such a paint require two mils dried paint thickness. The same line of reasoning holds true for paints with more, or less, than 50 percent by volume thinner. The more thinner in the paint, the more wet film will
have to be deposited to achieve the specified dry film of paint. Most paint manufacturers produce paint ready for spray application without the need of additional thinning. The standard nowadays is airless spray application. Therefore, application methods other than airless spray may dictate that the paint be thinned. In any case, the manufacturer's recommendations regarding thinning should be adhered to very strictly. The fabricator is not interested in buying large quantities of thinner that will evaporate, causing health and fire hazards; therefore each paint should be formulated with only the necessary amount of thinner to keep the resin in solution and to maintain the proper viscosity for application. The volatile content of a paint can be checked quite simply; for precise work, a drying oven and analytical balance are essential. For a Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 252
SSPC CHAPTER*S*O 93 8627940 0003700 953 = TABLE 1 TYPICAL PRIMER PAINTS FOR STRUCTURAL STEEL MINIMUM PRIMER PIGMENT VEHICLE SURFACE PREPARATION SSPC Paint 9 100% Titanium Vinyl Blast Cleaning Dioxide SSPC Paint 11 40% Oxide Raw Linseed Oil Hand Cleaning 40% Zinc Yellow and Alkyd Varnish 20% Extenders (equal parts) SSPC Paint 13 60% Red or Brown Raw Linseed Oil Hand Cleaning Iron Oxide Tung Oil Ester 12% Red Lead Gum Varnish ' 3% Zinc Chromate Bodied Linseed Oil 25% Magnesium Silicate SSPC Paint 15 Red Iron. Oxide Alkyd Resin Solids Hand Cleaning Magnesium Silicate Mineral Spirit Thinner Inhibitive Pigment Driers SSPC Paint 16 52% Coal Tar Pitch Epoxy Polyamide SSPC-SP 6, "Commercial 48% Magnesium Silicate Blast Cleaning" SSPC Paint --`,,,,`-`-`,,`,,`,`,,`--17 35% Rust Inhibitive Chlorinated Rubber, Pigment suitably plasticized 12% Tinting Pigments and stabilized. 55% Extender Pigments SSPC Paint 20 Type I 87% Zinc Dust Inorganic Type II 93% Zinc Dust Organic SSPC Paint 22 Inhibitive Pigment Epoxy Polyamide SSPC-SP 6 SSPC Paint 23 Inhibitive Pigment Latex SSPC-SP 6 SSPC Paint 25 Zinc Oxide Linseed oil/ Hand Cleaning Red Iron Oxide Alkyd Magnesium Silicate Mica SSPC Paint 28 Not specified Water Borne Blast Cleaning EPOXY Preferred SSPC Paint 29 Minimum 50% Inorganic or Blast Cleaning zinc dust in dry Organic film
TT-P-641 80% Zinc Dust Raw Linseed Oil Hand Cleaning Type I 20% Zinc Oxide Oil TT-P-641 80% Zinc Dust Alkyd Varnish Blast Cleaning or Type II 20% Zinc Oxide Pickling TT-P-645 50% Zinc Yellow Alkyd Varnish Blast Cleaning or 14% Titanium Dioxide Pickling 17% Zinc Oxide 19% Extender TT-P-636 50% Iron Oxide Alkyd Varnish Hand Cleaning 10% Zinc Yellow 10% Zinc Oxide 30% Extender TT-P-31 60% Red or Brown Linseed Oil Hand Cleaning Iron Oxide (5 parts) 12% Zinc Oxide Spar Varnish 28% Extender (1 part) Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 253
SSPC CHAPTERtS-O 73 m 8627740 0003701 89T m TABLE 2 SOURCES OF INFORMATION PERTAINING TO CLEANING AND PAINTING HAZARDS National Safety Council 1121 Spring Lake Drive Itasca, IL 60143-3201 American National Standards Institute 11 West 42nd Street, 13th Floor New York, NY 10036-8002 National Fire Protection Association 1 Battery March Park, P.O. Box 9101 Quincy, MA 02269-91 O1 American Foundrymen's Society 505 State Street Des Plaines, IL 60016-8399 Chemical Manufacturers Association 2501 M Street, NW Washington, DC 20037-1 303 simple and fairly accurate check, less sensitive scales can be used. Photographic supply houses sell small inexpensive scales that can be used for fairly accurate work. About 5to 10 grams of paint are poured into a dried, weighed tray made of folded aluminum foil (about 4" x 4"; the lid of a quart can may be used, but the sensitivity of the procedure is reduced); it must be weighed quickly, since the solvent will start to evaporate immediately. If the paint forms skins in drying, a small piece of wire should be weighed with the tray and left in during drying; it is used to break up skins that may form. The sample of paint is dried at about 220" F (104" C) until the weight becomes constant. The loss in weight of the sample is used to calculate the percent of volatile in the original sample of paint by weight. This can be recalculated into volume percent, when the type of thinner is known. Paints which deviate significantly from specifications or known volatile content should be checked by a more accurate method before investigation of the reason for the discrepancy. Periodic checks should be made of paint from painters' buckets or spray pots. Viscosity checks will show whether paint has been excessively thinned or adequately mixed. It is best National Paint and Coatings Association
1500 Rhode Island Avenue, NW Washington, DC 20005-5597 Painting and Decorating Contractors of America 3913 Old Lee Highway, Suite 338 Fairfax, VA 22030 Canadian General Standards Board 222 Queen Street, Suite 1412 Ottawa, Ontario, K1A 1G6 U.S. Department of Labor Occupational Safety and Health Administration 200 Constitution Avenue, NW Washington, DC 20210 U.S. Department of the Interior Bureau of Mines 810 7th Street, NW Washington, DC 20241 to check both weight per gallon and viscosity since both improper thinning and mixing errors may compensate each other. Since the sample of paint will be small, a weight-per-gallon cup should be used. 2. Storage of Paint When a paint order is accepted, it should be stored until required. Fire insurance policies, government regulations, and manufacturer's instructions dictate that paint materials be stored in fireproof rooms at controlled temperatures. In addition, most jobs call for temperature control of the stored paint. The storage room should be kept locked and only qualified personnel should be authorized to remove paint or thinner. Upon receipt of a lot of paint, the job number of the paint should be marked on each container. If the paint is for general use, it should be marked accordingly. In any case, stock on hand should be used first. Containers of paint should be turned over about once each month to help keep the pigment from settling hard. On some jobs paints that have a limited shelf life are specified. The expiration date of these materials should be shown, and they should be used as soon as possible or returned to the manufacturer prior to expiration of the shelf life. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 254
SSPC CHAPTERrS.0 73 8627940 0003702 726 FIGURE 8 Section of paint storage room showing power driven mixers connected to built-in stirrers in drums of paint which are in use. Paints are drawn from spigots at the bottom of the drums when required. In the center of the photograph note pressure regulating equipment which is used to maintain an inert atmosphere of nitrogen above paints when they are being circulated throughout plant circulating system (which was not being used). Note electrical ground to paint drum shown on right. Mechanical equipment, on the left is available, for lifting heavy containers of paint. The storage area should be kept warm in cold weather to prevent the paint from freezing. 3. Mixing The paint room should be equipped with mechanical mixing equipment; all pumps or motors should be explosion-proof. It is essential that mixing be thorough. After mixing, the container should be checked for residual solid material remaining on the bottom of the container. This solid material should be broken free of the container, broken up as much as possible, and the entire contents of the container re-mixed until a complete homogeneity is attained. The process should be repeated as often as necessary to insure thorough mixing. The fabricator who uses drums of paint may order them with a built-in mixer, to which is connected a driving motor or a hand crank when the paint is to be mixed (See Figures 9 and 10). When large quantities of paint are being used, paint recirculating systems are available. The paint is mixed continuously and stored in the paint room. It is pumped through pipes to the various stations where it is used; it returns through another pipe to the original containers and is constantly recirculated so that it does not settle in the pipes. Control of the paint mixing and thinning rests in the hands of the paint room attendant. Such systems should be kept under an inert atmosphere, such as nitrogen. Where paint is to be supplied from drums for brush painting, it should be kept in continuous agitation and also under nitrogen while on demand. For this purpose, propellor-type mixers are inserted in the drum of paint; these units are driven by electric or air motors. The small plant that does not find it economical to go to mechanical mixing equipment should purchase paint in five gallon pails. The paint can then be stored and mixed when necessary. Small mechanical mixers and shakers are also available for
5-gallon units. 4. Thinning The thinning of paint must be done by qualified personnel under careful supervision. There is a feeling among some paint users that paint should be purchased and applied at the greatest coverage per gallon possible. This belief is encouraged by some paint salesmen who claim amazing square feet per gallon coverage for their paints. The reasoning is false and poor economy. Paint should be applied at a coverage or spreading rate that will ensure a dried film thickness capable of protecting the steel. When too much thinner is used, it may be impossible to obtain adequate thickness of dried paint. Paints will run and sag if the painter attempts to build up thick films with overly-thinned paints; in such a case the only remedy is to apply extra coats of paint. The thinner used must be compatible with the paint being used. If the wrong thinner is used, it may throw resin out of solution and ruin the paint. Most oil-base paints are thinned with mineral spirits or V.M. & P. naphtha. The directions of the paint manufacturer or the specification should be followed regarding thinning of the paint. Some of the newer paints with synthetic resins require thinners composed of aliphatics, aromatics, and ketones. These thinners should never be used to thin oil-base paints. It is possible to use aromatic thinners in oil-base paints; however, extreme caution should be exercised if this course of action is planned. Before paint is thinned for spraying, it should FIGURE 9 Air driven motor connected to built-in mixer in drum of paint. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 255
SSPC CHAPTER*S.O 93 m 86279VO 0003703 bb2 m FIGURE 10 Typical drum handling equipment; drum holder is handled easily by shop crane and drum may be tipped when desired to draw paint. Tongs in foreground are used for handling drums of paint by shop crane. be spray-applied in the as-received condition to determine the ease of application, flow, levelling characteristics, film build, running and sagging, and so forth. Modern spray equipment is capable of atomizing most paints, and it may be that no thinning will be necessary. The result is a greater film build per application. As long as the thickness of the paint deposit does not become excessive, thicker coats of paint are advantageous. In any event, the thickness of the dried paint film must be adequate and should be controlled. Thinning of paints for dipping operations is a specialized operation that requires individual recommendations. If dipping is to be done, the advice of a competent paint company or specialist should be solicited. Figure 11 illustrates a dipping operation used to ease application of paints to small, difficult to paint, fabricated assemblies. 5. Application Equipment In some cases the type of paint to be used will dictate the method of application. However, paint is usually applied by spray or brush. There is still considerable controversy regarding the merits of brush versus spray painting, although it is generally conceded that if application methods are correct, either method is suitable. Brushing of the prime coat of paint into the surface has a tendency to promote better wetting and adhesion; this is offset by the thinness of paint in the brush marks. Spraying, on the other hand, deposits a more uniform coat of paint than brushing, but it has a tendency to bridge over dirt and cracks, and to be blown away from corners. When a difference in performance has existed between spraying and brushing there is usually some unrecognized factor that has caused the discrepancy in performance. In cracks and crevices, around rivet heads, on sharp edges, in corners, and similar places, sprayed films are usually very thin, if not altogether missing. For example, it is not uncommon to find one side of sprayed rivets barely covered by paint. Here, brushing is a definite advantage, and a striping coat is recommended prior to spraying. When brushing and spraying result in equal thicknesses of dried paint over properly prepared steel, there is no difference in the durability of the applied primers.
Since spraying of paint is faster than brushing, the saving in cost of application makes its use advantageous; there may be factors which preclude its use, however, such as toxic hazard to personnel. Despite opinions to the contrary, when proper precautions are taken, the hazard from spray painting is negligible. Some modern spray paint systems are so efficient that it is not necessary for the operators to wear face masks. New developments in paint application by spray are making headway in fabricating plants. The use of paint recirculating systems has already been mentioned. Since so much thinner is wasted in the synthetic resin paints, particularly those that dry by solvent evaporation, some plants have FIGURE 11 Paint dipping setup. The tank of paint is raised by hydraulic jacks and then lowered, rather than dipping the work into the paint. Excess paint drips on the collecting trough on the left. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 256
SSPC CHAPTER*S*O 93 Ab27940 0003704 5Tï switched to hot spray application. Here, the amount of solvent is reduced to a minimum by heating the paint and spraying it hot; the paint dries faster and the build per coat is much greater (Figure 12). This is a particular advantage when it is difficult to get more than one mil of dried paint per coat using conventional means. Paint heaters may also be used for painting in cold weather. However, there is a danger factor involved. Caution must be exercised when applying hot paint over cold steel and vice-versa. A thin layer of condensation is formed, and usually becomes entrapped at the paint-steel interface. This is a cause of blushing (alkyds) and discoloration (vinyls). If this practice is used, the paint should be applied in thin films until the specified thickness is obtained. In a few plants, solvent recovery systems have been installed; the economy of this operation in the ordinary fabricating plant at this time is questionable. Developments in ventilating equipment have made a marked difference both in working conditions and in plant appearance. Modern methods of collecting overspray are to use either down-draft ventilation or spray arrestors. In down-draft ventilation, the spraying takes place over or near a grilled opening in the floor connected to a powerful exhaust system, while the overspray is sucked into the system and collected. The principle of operation is explained in Figure 13. The other general type of system utilizes a painting booth; air is drawn through the booth, picking up the overspray in the process. In both these methods, the air then passes through a water curtain or a iilter to catch the paint before passing through the exhaust fan. Paint may be reclaimed from the separators, but its re-use for structural steel priming is not recommended. FIGURE 12 Flow diagram through a paint circulating heater. New developments that have been introduced into the fabricating plants include automatic spraying of paint -used when the work is not varied; electrostatic spraying -in which the paint particles are charged with electricity and are attracted to the work, even around corners; electrostatic de-tearing -in which the tear drops that form on dipped articles are removed; application by flow or curtain coating -in which the paint is applied and allowed to drain off and is then collected in a sump and recirculated.
To speed up production and improve the performance of paint, some plants have installed drying ovens. Here, even paint on structural steel can be dried in several hours. When the paint requires a long drying time even at oven temperatures, the paint can be dried enough to permit its handling and stacking. Figure 14 illustrates such an oven. Even some brush painting has been mechanized; for instance in the use of a rotary cupshaped brush for spotting rivet heads prior to spraying. Fountain type paint brushes are available, in which paint is supplied through the brush handle from a pressure pot. 6. Application of the Paint The actual application of paint, whether by brush or spray, requires plain common sense and experience. It also requires patience on the part of the applicator, and more so on the part of management, so that this important part of shop work is not done sloppily. The surface must be cleaned of all dust, oil, or grease that may have been deposited after the cleaning operation. The critical points should be stripe painted by brush with the same paint as will be used for the prime coat. The critical points are rivets, welds, joints, cracks, corners, edges, interstices, and any other place where the paint has a tendency to break down first. At this time, or even earlier, small areas should be painted for transferring piece or identification marks. The paint should be the same as the priming paint; after it dries sufficiently, piece marks are transferred by (or checked by) an inspector or foreman. The striping paint should be allowed to dry, if possible, before the full prime coat is applied. If this is not practical, as much time as possible should be allowed for it to dry. It should at least set to touch. Drying time for the striping paint should not be so long as to cause rusting or deterioration of the remainder of the cleaned steel. The prime coat of paint is then applied according to the instructions in the chapter on paint application and the manufacturer's instructions. If it is sprayed, the operator should be careful of his technique. Fast drying synthetic paints may be ruined if the gun is swung in an arc, or if it is held too far from the surface and the paint is deposited "dry." If the gun is held too close, the paint may be too thick and run, sag, or curtain. Spray equipment manufacturers should be called upon to Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 257
SSPC CHAPTER*S*O 93 8b27940 0003705 435 = l I. 1. for training. --`,,,,`-`-`,,`,,`,`,,`--DOWN DRAFT SPRAY BOOTH FIGURE 13 Schematic diagram of a down draft spray booth. Courtesy: Binks Manufacturing Co. assist in instructing painters in spray techniques. Parenthetically, spray equipment manufacturers conduct schools to which operators can be sent The thickness of the wet film can be determined with a wet film paint thickness gage immediately after application. The competent and experienced painter will take two or three wet film thickness readings per piece of painted steel. He should also know how to read the gage. For example, the painter is using a material that has a nonvolatile content of 50 percent and the specification calls for a dry film thickness of 2.0 mils. By dividing 2.0 by 50 percent (2.0 -0.50) the painter will know that he needs a minimum wet film thickness of 4.0 mils to obtain the 2.0 mils dry film thickness. The painter should place the "teeth" of the gage against the painted surface perpendicular to the plane of the surface and, without smearing or sideways motion, withdraw the gage. If he sees that the tooth marked 4 is wet and the next highest number tooth is dry, then he reads the wet film as between 4 and 5 or 4 and 6 whichever is the next highest number. If 4 is not wet, the painter should be instructed to apply more paint. Dry film thicknesses should always be checked as soon as possible so that errors can be corrected prior to shipment of the painted steel. It is impossible to obtain accurate wet film thickness readings on zinc-filled paints. Therefore, the zinc-rich paints should be allowed to dry, measured, and repainted, if necessary, to obtain the specified dry fiIm thickness. The amount of paint lost by overspray may reach 40 or 50 percent. Because of this unknown quantity, estimates of dry paint thickness from paint consumed and area painted may be quite erroneous and are more likely to be in error on the dangerous side. If precautions are not taken, the thickness of the applied paint will vary between the easily reached and the less accessible surfaces. Great
care should be exercised to coat the bottom surfaces of flanges, etc., with the correct amount of paint. When the paint gun is held at an angle, there will be a difference in paint deposited per square inch across the cross section of the spray pattern. Areas that are difficult to reach by brush or spray should be examined with the aid of a mirror under strong light. The interiors of boxed members that are not accessible after fabrication should be completely painted before final assembly. In many cases, a spray gun can be used to reach difficult areas. Extension handles are available for lengthening the paint gun assembly in order to reach inaccessible areas. Often, a brush will be needed to coat edges, corners, or the blind side of rivets that cannot be reached by the spray pattern from the gun. Contact surfaces for riveted structures should not be painted, since the hot riveting operation will destroy the paint. Destruction of the paint is not serious as the rust inhibitive pigment Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS FIGURE 14 Oven for force drying painted steel.
SSPC CHAPTER*S.O 93 m 8627740 000370b 371 = will still be there, but the fumes that develop are hazardous to workmen. When structures are bolted together, the contact surfaces should be painted, except when high tensile strength bolts are used. Since these loose-fitting, bolted joints depend upon friction of the contact surfaces, no paint or other lubricant should be used between the faying surfaces. Recent studies by the AISC show that inorganic zinc paint is acceptable for use on these surfaces. However, the contract specifications will determine the course of action to be taken. Shop welds should be cleaned as thoroughly as possible before painting to remove weld slag and spatter. The use of anti-spatter compounds has been successful in eliminating most of the difficulty with weld spatter. However, when more than one pass per weld is necessary, or when welds meet, as in a corner, the first weld burns off the anti-spatter compound. It then becomes a matter of shop practice as to the removal of additional weld spatter, just so long as it is removed. Weld spatter can be removed by hand or pneumatic chipping action. However, recent advances in grinding tool design make it more profitable to remove weld spatter by grinding. When field welding is specified, the edge of the steel is usually left unpainted for at least four inches along the edge to be welded. In the field, this edge must be very thoroughly cleaned and painted after welding. This is a potential weak spot in fabricated steel, since the edges are usually badly rusted by the time fabrication is completed. An additional reason for painting, or at least the application of a temporary coating, is the fact that the weld metal is a different metal than the parts being joined, in effect a cathodic cell. This surface must be cleaned as well, if not better than the surfaces in the shop, and must receive the same coats of paint as were applied in the shop. Edges of the steel left unpainted for field welding or riveting may be protected temporarily by a thin coating of lacquer, varnish, or weld preparation paint, which will be burnt off by the heat when welding or riveting. Caution should be exercised when applying the weld-through zincfilled primers. These paints can and have caused major problems when they are subjected to x-ray and radiographic testing. Machined surfaces should be protected from rusting by an application of an approved rust preventive compound. These compounds can be
applied by brushing, daubing or spraying, and may be removed by mineral spirits in the field if necessary. Application is illustrated in Figure 16. After painting, the steel should be examined FIGURE 15 Painting and drying racks for fabricated plate. Notice contact sur. faces for field joints are left unpainted. by a competent, experienced inspector. He should require another application of paint over thin areas; runs or sags should be worked out by brush; a critical examination of rivet heads, welds, edges, etc., should be made to be sure they are adequately covered. Abraded or damaged areas should be touched up. 7. Handling, Drying, and Storing of Painted Steel Handling, drying, and storage of painted steel vary widely in the different shops.
Dry for handling
times quoted for paints are not significant because of the difference in opinion regarding how dry paint should be before it is handled. In some plants, steel is handled immediately after painting and placed in the storage area for drying. If this is done, the storage area must be warm and dry, and the steel should be touched up immediately where it has been scoured or abraded in handling. In other plants, the steel is allowed to remain in place after painting until it is dry, perhaps 24 or 36 hours. Actually, if it is a heavy duty primer, the paint is not really dry, but dry only on the surface. It can easily be skinned in handling. In any case, it is good practice to rack, stack, or otherwise place freshly painted steel so that there will be a flow of air over the painted surfaces. Preferably, the air should be warm, starting from the lowest point (floor) and moving. This process will remove solvent vapors, thus eliminating solvent washing of the paint btefore the film is dried. In general, the manufacturer s recommendations regarding dry time are the governing factor in most shop painting operations (Figures 16 and 17). Regardless of the exact procedure used to dry painted steel, the painted steel should be dried in a warm, dry atmosphere -preferably
under cover, since rain or freezing can damage the paint and necessitate its removal and repainting. The maximum allowable time should be permitted for drying; the harder the dry, the better the paint can withstand exposure to the elements. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 259
SSPC CHAPTERt9.O 93 86279gO 0003707 208 V. SUPERVISION AND INSPECTION The entire shop painting should be under the supervision of an individual on the staff who has sufficient authority to make changes in operating procedures, material, equipment, and suppliers despite controversy that might be heard from the shop. Fabricators have long been reputed to have an aversion to cleaning and painting steel. Their dislike of this necessity has been one barrier to more progress in this field. A. SUPERVISION The top level supervisor must have a working knowledge of paints, cleaning, painting, and corrosion in general. If his knowledge on these points is limited, he must know where to turn for sound advice and guidance. Most of all, he must have an open mind and must be willing to accept new methods that are technically sound. Unfortunately, a great number of the engineers, architects, and fabricators have little knowledge of painting; they rely on specifications that are outmoded, basically unsound, and even impossible to achieve. The writer has run across specifications in use today that were issued long before the first edition of this work was first published. In those days there was a general lack of technical expertise in all phases of steel painting. More amazing is that despite the advances made, architect-engineers still produce unworkable, incompetent and contradictory painting specifications. This lack of expertise may be due to an unwillingness to become current in the state of the art . Some of these specifications are filled with such outmoded clauses as all rust and millscale shall be removed by hand wirebrushing . Accepting a contract with unenforceable clauses is likely to cause expensive litigation over a costly paint failure. For his own protection, the fabricator should have competent supervision over the cleaning and painting, from original estimates for bids until the steel is shipped and erected. Supervision of actual operations in the shop should, of course, be in charge of qualified personnel. Here, the lack of knowledge concerning the causes and prevention FIGURE 16 Machined surfaces are usually coated with a rust-proofing compound of grease consistency. This type of coating is being applied to machined surfaces on the right, while in the center the unmachined areas are being painted with the specified shop primer. of poor paint performance is acute. Education and training are essential to instill in the minds of these personnel, and top management personnel as well, a proper attitude towards these operations. They, as well as the actual painters, should be aware of the reasoning behind each operat ion. B. INSPECTION Even when the customer inspects and passes on all
painting of his steel, the fabricator should provide his own inspection system. Acceptance by the customer s inspector does not relieve the fabricator of responsibility. The fabricator who knows his painting system is good must in turn educate the customer and his inspector. Many times customers are arbitrary in insisting on procedures that might be detrimental to performance of the paint. Details of inspection are reviewed in a separate chapter. The minimum inspection should cover the steel after cleaning and prior to painting and after painting. Inspection of the actual cleaning and painting operations is advantageous. No steel should be painted before it is inspected; the inspector may be the immediate supervisor on the job. The cleaned steel should be checked for: 1) Oil or grease remaining on the surface: rubbing a white tissue across the steel will indicate the amount of residue; see (9). 2) Dirt, soil, chalk marks, etc., that are visible to the eye. 3) Rust: the amount of rust remaining depends upon the method of cleaning. Rust stains will be evident on the surface unless the surface is blast cleaned to white metal or pickled. 4) Rust scale: no rust scale (flaky or stratified rust) should be left on the steel. 5) Mill scale: all mill scale should be tight and not removable if the inspector recleans the surface in the specified manner. (This is true of all these items.) 6) Residue from cleaning operation: the surface should be free of dirt, dust, or other residue from the cleaning operation 7) Steel blast cleaned to white metal should be free of any visible rust, mill scale, oil, grease, or any other contaminant. 8) Pickled steel should be free of rust, mill scale, pickling smut, harmful acid or alkali: the surface if tested with pH indicating paper should test at the same pH as the last rinse. 9) Solvent cleaned steel should be free of detrimental amounts of oil or grease residue. The amount tolerable will depend upon the wetting power of the paint to be used. If alkali or cleaning compounds are used, the surface should be neutral or at a pH of 7.5 or less. In no event should the pH of Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 260
SSPC CHAPTERIS.0 73 8b27940 0003708 144 the surface exceed that of the fresh, clean rinse water. Substrate temperatures should be checked and recorded. Some manufacturers have maximum and minimum temperature (substrate) limitations for application of their paint. Profile depth of the blast cleaned surface should be checked using acceptable instruments. In general, the inspector should be sure that the work has been done as well as possible and meets the intent as well as the wording of the specification. Particular care should be taken that no areas or spots have been missed. He should check the tools of the workmen to see that they are in proper condition, that brushes are effective, that dirty solvent is not being used. If in the opinion of the inspector the steel has been cleaned as specified, but is still in an improper condition for the paint and the expected service (for example the mill scale is badly cracked but not removable by hand cleaning), the owner should be advised. If pretreatments have been applied, another inspection should be made. If cold phosphate has been used, the surface should be dry and of a gray-white color. The powdery deposit must be light; if it is excessive, it must be removed by brushing. If any dark, sticky liquid (unreacted acid) remains, it must be washed from the surface. When wetting oils are used, the surface must be examined for dry areas that require further oil; excessive oil should be wiped from the surface; rust and scale loosened by the oil should be removed; the wetting oil should be allowed to set or dry for the specified time before painting. Wash primer should be checked for thickness; it should not exceed the specified thickness, even if the underlying steel shows through (this is normal). The wash primer should not be white in spots; when dry, it should be tested for adhesion to the steel by scraping it away with a knife. The age of the mixed wash primer should be carefully checked if it is the two-component type. Painted steel should be inspected for the following: (a) Dried paint film thickness: learn the correct manner of using the instruments; paint over mill scale and rust reads high if the instrument is zeroed on bare metal; this is also true over rough blast cleaned steel. (b) Dryness: check the condition of the paint to see that it has dried properly and in a reasonable time. (c) Completeness of coverage: no holidays; edges, rivets, and welds satisfactory. (d) Correct paint: was the right paint used? (e) Brush marks, runs,sags, etc., should be eliminated. (f) Wrinkling of dried paint indicates faulty paint or too thick an application.
(9)Adhesion of dried paint: It should be tested by knife, or by the method specified in the contract. (hlIdentificationmarks: are numbers correct and adequate? (i) Inaccessible surfaces: were they painted specified number of coats? (j) Orange peeling of paint: paint poor or improperly applied. (k) Elasticity of paint: does paint curl properly when undercut by a knife? If not, the paint may have frozen during drying, or paint may have deteriorated in storage prior to use. (i) Blisters, pores, crazing, cracking, etc.: paint or application improper. VI. SAFETY AND HEALTH The fabricator should comply with the safety regulations promulgated by the various government agencies. Information about protective devices, as well as flammability and toxicity data on paints and solvents can be obtained from the US. Bureau of Mines, and are reviewed in a separate chapter. The danger from toxic or fire hazards should be always in the minds of the supervisors as well as the workers. They are usually aware of the hazards from mechanical equipment, cranes, ladders, staging, etc.; but they do not realize the tremendous damage that may result from a small quantity of vaporized volatile solvent as an explosion hazard, nor do they appreciate the dangers to health inherent in fume and dust exposure. Lists of respiratory protective devices officially approved for most types of industrial exposures are available from the U.S. Bureau of Mines. Burning and riveting operations may create toxic hazards if paint is decomposed; in addition to volatilized toxic compounds such as lead, zinc, cadmium and chromates, acrolein may be formed from decomposition of the oils in the paint. The hazards in using chemical compounds such as acids and alkalies are generally known and precautions should be taken to protect personnel from all contact, including spray, mist, spillage or vapor. The Chemical Manufacturer s Association has published adequate methods for safe handling these. FIGURE 17 Painting and drying shop with tracks and carts for handling painted steel. The shop is heated in cold weather. When carts reach the far end of the shop, they are placed on the incline on the left and returned to the area in the foreground. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
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SSPC CHAPTERs9.O 93 m 8b279LlO 0003709 080 m A. SOURCES OF INFORMATION Safety considerations are discussed in a separate chapter. The protective clothing and equipment necessary for the various operations is listed in publications of the National Safety Council, the American National Standards Institute, the National Fire Protection Association and others. Insurance companies should be contacted for technical advice on safety measures if there is any question. The safety precautions necessary in cleaning operations are numerous; a highly recommended code for safe practice is Code of Recommended Good Practices for Metal Cleaning Sanitation issued by the American Foundrymen s Association. Authoritative and detailed references for safety precautions for the many hazards encountered in the cleaning and painting of steel are available from the sources listed in Table 2. ACKNOWLEDGMENT The author and editors gratefully acknowledge the active participation of the following in the review process for this chapter: T. Dowd, R.L. Doyle, James Flaherty, Raye Fraser, Lewis Gleekman, R.W. Hamm, Fred Lichtenstadter, A.W. Mallory, Robert McClelland, Marshall McGee, Joe Mazia, William Pearson, Verne J. Todd. --`,,,,`-`-`,,`,,`,`,,`--262 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*LOmO 93 Ab27940 0003710 BT2 W CHAPTER 10 PAINTING OF RAILROAD BRIDGES AND STRUCTURES by Raye A. Fraser Procedures and materials presented in this chaptgr where salts are present, in d esigns where water can colare guides only. Other methods and materials may be of lect or in chemical atmos pheres unless it is painted in the equal value. All known methods that have proved desirable same manner as convent ional steel.' Galvanized steel is are included. Details of cleaning and painting in the shop becoming more common and is the preferred treatment for are not included since they are covered in other chapters. new gratings, handrai ls and other small incidental items. In preparing this chapter current industry practices Improvements in surface pre paration, in treating were surveyed through a questionnaire circulated with the cleaned steel, in appl ying paint and paints themselves are cooperation of the American Railway Bridge and Building made periodically. Somet imes, a less expensive method Association (ARBBA) and Committee 15 of the American with a shorter life is more economical than an expensive Railway Engineering Association (AREA). Much of the technical information has been supplied from work by the Steel Structures Painting Council. Any reference to blast cleaning refers to conventional dry sand blast cleaning. I. GENERAL DISCUSSION FVater happed b! Jiructural mrmbers The cost of painting a structure can be estimated, but the cost of deferring painting is much more difficult to assess, particularly for railroad structures, though it is clear that a good painting program is less costly than frequent steel replacement. In every location there is slow rusting of unprotected ferrous metals representing loss of sound metal. Since a single railroad may have several Tvpcs of creoirrs thousand steel bridges, the situation cannot be allowed to get out of hand. But painting programs of many railroads have been restricted by a lack of funds in recent years, and Even Thin coating cooti ond Iiablc to 70% of those responding to the questionnaire indicated damogcmaintenance paintin g was not sufficient to protect the steel. Funds have been concentrated on a small number of structures in particularly corrosive environments. The frequency of repainting ranged from 5 to 40 years, with an average of 16.5 years. It is common to see railroad bridges entirely covered by rust.
Most of these structures are in an environment where Effect of surface contours the corrosion rate is slow. The menace of dripping salt brine from bunker refrigerator cars has passed into history. However, deep corrosion pits formed by dripping brine are still present and are sites for active corrosion. The main problems for most railroads are marine environments. One line of attack is to attempt to use a construction material that needs little or no corrosion protection. In new construction many structures are built from concrete, and others are a combination of steel and concrete with a PROBLEM SOLUTION weathering steel. ASTM Type A-242 is also being used FIGURE 1 alone in larger structures. Weathering steel is not suitable A few design featur es to be av~ided'~ 263 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER+LO.O 93 8b27940 00037LL 739 method with a long life. On the other hand, there is only A. NORMALLY DRY (RURAL ) -ZONE 1B false economy in using inexpensive short-lived paints when cleaning and application costs are the same. The majority of bridge engineers realize the solution to corrosion problems cannot be obtained with a magic paint that is cheap, has great coverage, is easily applied, requires no surface preparation and has a long life. There is a never-ending search for better paints, but the potential life of good paints is seldom reached because of improper surface preparation and application. The fault is not always that of the railroad, or painter, because adverse conditions may make it impossible to do a good job. Paints that do the best job possible under adverse conditions should be chosen. Of all corrosive atmospheres and environments to which railroad bridges and structures are subjected, the rural is the mildest, its severity depending upon climatic variations, particularly humidity. But even in a rural location, a structure may be subject to corrosive attack. For instance, one end of a long bridge may be exposed to a mild rural environment while the other end may be exposed to corrosive gases or mists from a chemical plant; or the steelwork of a bridge above the trackline may be exposed to a mild rural atmosphere while the floor system may be severely attacked by the spray of de-icing salt slush from a high-speed expressway passing underneath. TABLE 1 Survey of Environmental Zones for Railroad Bridges Location Zone 1A Zone 16 Normally Dry -Interior Normally Dry -Exterior (or rural) * 92.1 '/o Zone 2A Frequently Wet by Fresh Water (splash, condensation, immersion) -5.6% Zone 26 Zone 3 Frequently Wet by Salt Water (Marine or de-icing salts) Chemical Exposure } -2.3% Design is an important part in corrosion prevention. Narrow cracks and crevices that result in inaccessible surfaces, box members that allow only very limited access and sections that trap water are to be avoided. Some other undesirable features are shown in Figure 1. II. ZONES The first consideration in any paint job is to determine the environment in which the structure is exposed, keeping in mind that different parts of a single structure may be
subject to different environments. Standardized environmental zones (defined by the SSPC) are widely recognized as outlined in Chapter 1 of Volume 2 of the Steel Structures Painting Manual and in Table 1 below: The percentages in Table 1 are based upon the foregoing survey and show that the vast majority of railroad bridges are in Zone 1B. Figure 2 illustrates some of the many SSPC tests conducted on railroad bridges in a wide range of environments. Table 2 illustrates typical paint systems used in these environments. These are discussed in Section VII-D. One SSPC test in a rural environment is illustrated in Figure 2b. In a rural atmosphere, only natural elements of water and oxygen are subjecting the bridge to corrosion. Therefore, if oxygen and water cannot come into contact with the steel, little or no corrosion occurs. There is no paint or organic coating known that is completely impermeable to oxygen or water, but increasing the thickness of the coating provides added resistance to passage of water and oxygen through the coating to the steel. Gradually, outer coats of even the best paint system deteriorate and erode from exposure to sun and moisture, exposing underlying coats or primer. This is a natural process and indicates that steel has been protected to the limit of the paint system. The steel has not corroded and the structure is ready for repainting, which requires only minor cleaning, spot priming, and a new topcoat or two. If deterioration is permitted, the exposed primer rapidly fails and leaves steel unprotected. Rusting begins and failure of the remaining paint is greatly accelerated. Now the cost of suface preparation alone may be greater than the cost of Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 264
SSPC CHAPTER*LO=O 93 8627940 0003732 675 repainting, had the repainting been done before the onset of rusting. When rust appears in pinpoints on the surface or causes blisters under the surface, the paint has failed. Such a shortening of the paint life is probably caused by improper surface preparation, improper application, improper paint, or a combination. FIGURE 2a FIGURE 2d FIGURE 2b FIGURE 2e FIGURE 2c FIGURE 2f FIGURE 2 The SSPC has conducted a number of extensive paint tests on railroad bridges in the past. Examples of these shown above, include: (Figure 2a) test on Protecting Load-Bearing Surface of Steel Bridges on the Chic ago-Great Western; (Figure 2b) Painting of Steel Bridges for Mild Exposures on the Atchison, Topeka and Santa Fe Railroad System; (Figure 2c) Bridge Paints with Resistance to Salt Brine on the Missouri-Pacific Railroad; (Figure 2d) Paints over Hand-Cleaned Steel on the Sea board Cost Line Railroad; (Figure 2e) a series of tests of Oil-Base and Urethane Paints on the Bessemer and Lake Erie Railroad from 1965to the present time; (Figure 2f) Paint Systems over HandCleaned Steel. Other empirical paint evaluation tests were carried out with the cooperation of the Association of American Railroads on the bridges of the Southern, Great Northern and Penn Central Railways. 265 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*LO.O 93 8b27940 0003713 501 TABLE 2 TYPICAL RAILWAY BRIDGE PAINTING SYSTEMS' ZONE ENVIRONMENT 1A Interior. normally dry Steel used in dry railroad buildings. 1B Exterior, normally dry. Includes many railroad structures Surface Prep: Primers: Intermediate Coats: ToDcoats: 2A Frequently wet by fresh Paint Systems: water. Includes condensation, splash, spray or frequent immersion. Surface Prep: Primers: Topcoats: TYPICAL SYSTEMS" ALTERNATIVE SYSTEMS" SSPC-PS 18.01, Latex Paint System SSPC-Paint 15 (Type I), Steel Joist Shop Paint SSPC-PS 14.01, Steel Joist Paint System TT-P-664, Primer Coating. Alkyd, CorrosionInhibiting, Lead and Chromate Free, VOC Compliant CANICGSB i.40-M89, Primer, Structural Steel, Oil Alkyd Type Finish Coat Optional See SSPC-PS Guides 1.00 and 2.00 Also SSPC-PS 1.09 Oil Base Paint System or proven proprietary systems. Commercial Blast Clean (SSPC-SP 6) Surface Prep: Hand Clean (SSPC-CP 2)or Power Tool (SSPC-SP 3) SSPC-Paint 11, Alkyd-Linseed Oil Primer with Red Iron Oxide, Zinc Chromate Primers: TT-P-1757, Primer Coating, Zinc Chromate,
TT-P-t 757, Primer Coating, Zinc Chromate, Low-Moisture-Sensitivity Low-Moisture-Sensitivily SSPC-Paint 25, Red Iron Oxide, Zinc Oxide, CANICGSB -1.40 -M89. Primer. Structural Steel, Raw Linseed Oil and Alkyd Primer (Without Oil Alkyd Type Lead and Chromate Pigments) SSPC-Paint 101 (Type il), Aluminum Alkyd Paint Any of the above primers, tinted. SSPC-Paint 101 (Type I).Aluminum Alkyd Paint TT-P-38, Paint, Aluminum, Ready Mixed AASHTO M-69, Aluminum Paint CANICGSB-1.69-MB9, Paint, Aluminum SSPC-Paint 102, Black Alkyd Paint Surface Prep: Near White Blast Clean (SSPC-SP 10) SSPC-Paint 104, White or Tinted Alkyd Paint Primers: SSPC-PS 12.00, Guide to Zin c-Rich Coating TT-P-81, Paint, Oil: Ready-Mixed, Exterior, Systems Medium Shades MIL-P-38336, Primer Coating, Inorganic Zinc Dust AASHTO M-68, Black Paint for Bridges Pigmented, Self Curing AASHTO M-70, White and Tinted Ready Mixed Paint Topcoats: SSPC-PS 4.02-4.05. Vinyl Painting System CANICGSB -1.59-M89, Enamel, Exterior, Gloss, SSPC-PS Guide 15.00 Alkyd Type Chlorinated Rubber Painting Systems SSPC-PS 13.01 Epoxy Painting System Proven proprietary systems of either multicoat or single high-build coat type See SSPC Paint System Guides 4.00 (Vinyl), 12.00 (Zinc-Rich), 15.00 (Chlorinated Rubber), PS 11.01 (Coal Tar Epoxy). PS 13.01 (Epoxy). or proven proprietary systems. White Metal Blast Clean (SSPC-SP 5) or Surface Prep: White Metal Blast Clean (SS PC-SP 5) Near-White Blast Clean (SSPC-SP 10) SSPC-Paint 20 or Paint 29 (Type i-inorganic) Pretreatment: SSPC-Paint 27. Basic Zinc Chromate-Vinyl Zinc-Rich Primer Butyral Washcoat MIL-P-38336, Primer Coating, Inorganic, Zinc Dust Pigmented, Sell Curing, for Steel Surfaces Primers: MIL-P-24441, Paint, Epo xy-Polyamide, General AASHTO M300 Inorganic Zinc-Rich Primer Speciíication for 1 GP-171M and amendment, Coating. MIL-P-15930, Primer Coating, Shipboard, Inorganic Zinc Vinyl-Zinc Chromate (Formula No. 120) CANICGSB 1.122-M91 (Type I),Primer, Vinyl, The topcoat andlor a tie-coat shall be supplied Anti-Corrosive Organic Zinc-Rich by the same manufacturer as the Inorganic System Specifications Zinc Primer (Example: SSPC-Paint 20. Type Il-Organic) Proven proprietary systems Intermediates: SSPC-Paint 8,Aluminum Vinyl Paint
SSPC-Paint 9. White (or Colored) Vinyl Paint Topcoats: SSPC-Paint 8,Aluminum Vinyl Paint SSPC-Paint 9, White (or Colored) Vinyl Paint i-GP-182M, Paint, Vinyl, Exterior Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 266
SSPC CHAPTER*LO.O 93 8b279Li0 0003714 448 TABLE 2 (Continued) ZONE ENVIRONMENT TYPICAL SYSTEMS" ALTERNATIVE SYSTEMS" 28 Frequently wet by Paint Systems: See SSPC Paint Systems and Guides 12.00 Pain t Systems: See Alternatives to Zone 2A. salt water. Includes (Zinc-Rich), 4.00 (Vinyl), 15.00 (Chlorinated condensation, splash, Rubber), 13.00(Epoxy), PS 11.01 (Coal Tar spray or frequent Epoxy) or proven proprietary system. immersion Also see recommendations for Zone 2A. 3 Chemical Exposure Others as for Zone 2A. but the zinc base coatings must be used with caution when conditions are strongly acid or strongly alkaline. Topcoats required. (pH 5.5 or lower) Acidic -SSPC Paint System Guide 4.00 (Vinyl). (pH 5.5 to 10.5) -SSPC Paint System Guide 12.00 (Zinc-Rich) (pH 10.5 or above) Alkaline -SSPC-PS 11.01, Coal Tar Epoxy, SSPC Paint System Guide 13.00 (Epoxy) and 15.00 (Chlorinated Rubber). 'The following specifications have been removed from the revised table to reflec t current practice SSPC-Paint 1, SSPC-PS-1 04 -1 08,SSPC-PS 4 01, SSPC-PS 7 01, TT-P-66, TT-P-615, TT-P-636, MIL-P-15929, DOD-P-23236, AASHTO M-72, 1-GP-14, 1-GP-140, 1GP-166, 1-GP-167, CISCICPMA 1-73a "Ail coats of a paint system should be provided by the same supplier B. FREQUENTLY WET BY FRESH WATER ZONE 2A Water is the primary cause of corrosion. Without water, corrosion would normally stifle itself, even with a plentiful oxygen supply. Dangerous corrosion can occur under some circumstances in the absence of oxygen. Corrosion can occur when soluble matter dissolves in water, such as the electrolytes formed by the solution of salts or corrosive gases. In the absence of oxygen, the damage is usually caused by galvanic action of mill scale and steel, or rust and steel. Stray electric currents can do great damage in localized areas, causing complete failure of some steel work. With a plentiful supply of oxygen, water becomes very corrosive and the condition is accelerated by the presence of salt or corrosive gases. If the structure is completely immersed, cathodic protection used in conjunction with suitable coatings provides adequate protection in salt or fresh water. The steelwork in the splash zone above the water is the most difficult to protect as is witnessed by the severe corrosion that takes place in the region just above the waterline on pilings or groins. Here, the best practice may be enclosing the vulnerable portion of the steel in thick concrete. Problems encountered and possible solutions are discussed and summarized by La Que.2 The portion of piling driven into the earth below the
water does not corrode once available oxygen is used. Oxygen seldom can be replaced, so that portion of the piling presents no problem. The section of the piling in the mud is subject to corrosion because oxygen is usually present in decaying organic matter and because of its constant turmoil and replenishment. In the water region, the piling is also free to corrode, and the portion just above the water corrodes quickly. It is best to design steel structures to minimize the immersion. Other structures that are accessible for inspection, cleaning and painting can be protected at reasonable expense. C.FREQUENTLY WET WITH SALT WATER ZONE 2B The protection of steel structures in marine atmospheres and those exposed to de-icing salts presents severe conditions for railroad structures. High humidity and salt are the culprits. Sea water consists of about 3 percent sodium chloride in water, along with a number of other salts present in small quantities. Common sodium chloride, salt, is one of the worst inciters of corrosion when wet or in solution. Its electrolytic action causes rapid corrosion in localized sites of steel and protects other areas. The result is pitting of the steel, weakening the structure more than if the corrosion occurred uniformly over the entire structure. This electrolytic corrosion can easily perforate a steel member. Corrosion products create an alkaline condition under the paint, which chemically attacks oil- and alkydbased paints, and they soon disintegrate and wash away. The result is exposure of more steel, an increase in electrolytic action and more intensified paint deterioration. This is a cycle that, once started, is very difficult and expensive to stop. The electrolytic action cannot take place without moisture. High humidity drives water into the paint film and keeps it wet, permitting the flow of localized electric current to corrode the steel. No organic protective coating is impermeable to water. There is no protective coating that adequately protects steel if salt remains on the steel before it is painted. The problem is solved if no salt is allowed to come in direct contact with steel. Not all portions of a steel structure exposed to marine atmospheres are uniformly attacked. Exposure varies from complete immersion of steel piling, footings and groins in sea water, to the much less severe exposure of high structures to salt-laden wind, rain and mists. The severest attack is not on steel immersed in the salt water but on steel in the splash zone just above high --`,,,,`-`-`,,`,,`,`,,`--267 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from
IHS
SSPC CHAPTER*LO.O 93 m 8627940 0003735 384 m tide. Here, although steel is never completely immersed, it is always wet, making it difficult to paint, and there is plenty of oxygen to corrode it. This portion of a structure has a tendency to provide cathodic protection to the steel completely immersed in the sea water by sacrificing itself. An excellent discussion of this situation is given by H~mble.~ Escalante and Iverson studied the protection of steel pilings in sea ~ater.~ The right way to protect a structure exposed to marine atmosphere is to begin at the design stage. The steel should be blast cleaned and shop coated with a synthetic resin paint that has proved capable of standing up against marine atmospheres. If field coats are applied, any salt contamination must be removed from the surfaces by washing or steaming with salt-free water. Finish coats must be resistant to salty atmospheres. Maintenance painting of existing structures must include removal of salt contamination from painted or rusted surfaces along with the rust and scale. Hand cleaning is not adequate, but steam cleaning after thorough wire or power brushing is effective. The primers and finish coats must then be applied over salt-free surfaces. Another factor, not ordinarily encountered in fresh water, is the abrasive action of sand on piling. At the sand line, where the sand is moving because of wave action, any organic protective coating is quickly cut through and protection is very diffi~ult.~ D. CHEMICAL EXPOSURES -ZONE 3 Steel in chemical or industrial atmospheres corrodes much faster than in rural atmospheres. The life of any paint can be shortened by chemical attack of corrosive gases, mists and dusts found in industrial atmospheres, though the rate depends upon the kind of chemical or industrial atmosphere and climate. While it is possible for paint to have a shorter life in a rural atmosphere in Florida than in an industrial atmosphere in Pennsylvania, paint generally has a shorter life in an industrial atmosphere. Accelerated corrosion in industrial atmospheres is caused mainly by the presence of sulfur dioxide and trioxide. These gases, when dissolved in water, form acids; and the dew, rain or mist in industrial areas is actually a weak acid that acts as an electrolyte. Soluble gases and salts ionize and penetrate protective coatings along with oxygen and water. The result is accelerated corrosion caused by direct chemical attack of the steel and the electrolytic action set up. The paint film itself may be damaged by the active chemical nature of the contaminants.
The effects of corrosive industrial atmospheres are evidenced in the early failure of galvanized iron in such exposure. The life of galvanized roofing may be cut 50% to 75% by the failure of a zinc coating to form a protective layer of corrosion products as it does in rural or marine atmospheres. It is not surprising to find that galvanized roofing must be painted to obtain an economical life in industrial plants or in smoky atmospheres. Paint systems used in rural atmospheres may be inadequate in industrial atmospheres. E. BURIED STRUCTURES Buried structures are in the soil or are in contact with soil under conditions in which oxygen can be replaced. This exposure is very severe. Protection must be adequate for many years because of the expense in excavating to make structures available for repainting. This environment is discussed in the chapter on pipelines. All soils are not equally corrosive. Some soils are neutral, dry and well packed, and little corrosion occurs. Unfortunately, much of the steel along the railroads is subject to corrosive conditions when buried. Possibly the worst condition is encountered when the steel is buried in cinders. Cinders are acidic and, when wet, are very destructive to any coating. Even galvanized iron fails rapidly in this environment. Brine drippings and de-icing salts also soak into the soil and have the same corrosive effect. Other contributing factors are ladings and drippings from cars carrying high sulfur coal. Stray electric currents are encountered along railroad tracks, particularly along electrified systems. Direct current can cause great damage where it leaves the steel and enters the ground. To protect against stray currents (where the amount of steel corroded is directly proportional to the flow of direct current) steel must be insulated by a protective coating. Concrete permits flow of current, and disruption of the concrete is caused by the tremendous force exerted by the corrosion products on the surface of reinforcing steeL5 Even without stray current, spalling of concrete is caused by the rusting underneath the concrete when the concrete is too thin, improperly made or applied, or when water creeps in around the edge of the concrete and rusts the steel. Buried steel can be protected by application of thick coatings such as coal tar enamels or asphalts, but under very severe conditions steel is best protected by coating in conjunction with cathodic protection. If possible, steel should not be buried. Pipelines, conduits and other steelwork should be supported above the ground where it can be protected by conventional means. When steel is buried, as in culverts, the nature of the fill must be taken into account. Basic conditions should be maintained. Cinders should not be used as a backfill, but
limestone may be used as a fill around the buried steel or to support steel. Because fills are porous and act as a sponge to maintain wet conditions around the pipe, drainage provisions should be made. For a further discussion of the effect of burial on steel surfaces, see the chapter on protection of underground structures and pipelines. F. TIMBER AND TIE BEARING SURFACES Damage that occurs to steel when it is in contact with timbers and ties is usually aggravated by the fretting acCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 268
SSPC CHAPTER*LO-O 93 W 8627940 0003736 210 tion of timber moving when under load or impact. Even inspecting and painting, g reat care be devoted to the when no fretting action occurs, water is absorbed by the following: timber or drawn into the crack between the timber and the steel surface. Since those surfaces rarely dry out, conditions for accelerated corrosion are established. Overcoming fretting or galling action is difficult. It is almost impossible to anchor the ties sufficiently to prevent movement. An SSPC study6 indicated that very few coatings withstand the abuse suffered under the bearing surface (Figure 2a). The exceptions were metallizing and inorganic zinc coatings, both of which are able to withstand the fretting action for a considerable time. Some railroads have had success with mastic pads placed under the ties, but they must not absorb water. Good results are obtained by using soft coatings with a grease or heavy oil base that do not dry out. A coating used under the ties should have some inhibitive chemical present to retard corrosion. When the contact is not subjected to fretting action, protection is possible by more ordinary methods. 111. TYPES OF STRUCTURES Typical railroad structures that require painting are bridges, fuel oil tanks, sand tanks, steel pipe, transmission towers, smokestacks, trainsheds, track scales, radio towers, flood light towers, catenary poles or docks, coal docks, sanding stations, buildings, roofs and many other miscellaneous structures. A. BRIDGES The greatest tonnage of steel that requires protection is found in bridges of all sizes and types, including trestles, viaducts and highway overpasses. There are more than 94,000 steel bridges with an aggregate length of 1,800 miles that are being protected by railroads. Each bridge must be considered in relation to exposure, service, difficulty of repainting, traffic and the cost of protection. An idea of the magnitude and cost of painting bridges can be obtained from the experience of the Southern Railway.8 When painting a new bridge over the Cumberland River near Burnside, Kentucky in 1950, it required 19,000 gallons of paint, which, at ten pounds of solids per gallon, represents a load of 190,000 pounds. It took 30 men six months to paint the bridge, and a normal maintenance crew requires two years to repaint it. Bridges usually get the best protection of any railway structures because they are expensive and the investment must be protected. Cleaning and painting costs on bridges are so high that there is no point in using low-cost paints.
If structural failure of a bridge occurs, the damage done and liabilities incurred are often greater than for other structures. Bridges, therefore, should receive good corrosion protection and should be inspected at frequent intervals for possible damage because of corrosion. A committee report of the American Railway Bridge and Building Association (ARBBA) recommends that when 1. Girders: Tops of outstanding legs of inside bottom flange angles; the vertical legs of the same angles; inside of web plates and stiffner angles, particularly around the bottom of the outstanding angle where it bears on the flange angle. 2. Floor Beams: Tops, edges and undersides of top flange angles and cover plates; top sides of outstanding legs and vertical legs of bottom flange angles; webs and gusset plates outside the rails. 3. Stringers: Both sides of the outstanding legs of top and bottom flange angles and webs, particularly on the side nearest the rail. 4. Laterals: Outside of the rails along stringer connections and lateral plates to girders. 5. Decks: To facilitate maintenance and repair of the track, bridges are often of the solid floor, ballasted track type. Steel floor plates corrode and require protection or periodic expensive replacement. Dirty ballast remains wet and accelerates corrosion of floor plates. Waterproofing deck plates with asphalt membranes is successful. Unless stringent precautions are taken, deck coverings are not waterproof and the plates still corrode. Some railroads have had success by asphalt coating deck-plates and laying a slab of concrete over the asphalt before the ballast is applied. Drainage of accumulated water to keep ballast dry is of great benefit when the drains can be kept open. Maintenance men should see that drains provided for the purpose of keeping structures dry are kept open. 6. Superstructure: It is practical to specify a different method of protection for the portion of a bridge above the track line, where exposure is less severe. 7. Steel piling: Steel piling for bridges or trestles must be given adequate protection which cannot be as thin as ordinary paint films unless the surfaces will be available for repainting.
8. Tonnage and Area: Costs of bridges are almost always calculated on a per ton basis; therefore, most records of the railroads usually contain accurate figures of the tonnage. However, cleaning and painting costs are best based upon the square feet of surface area to be treated, and those figures are not available in most instances. Therefore, railroad personnel usually calculate painting costs on a per ton Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 269
SSPC CHAPTER*LO.O 93 W 8627940 0003717 157 = basis. This practice is satisfactory as long as the possible variance in the square foot of surface per ton of steel is considered. In the final economic analysis, cost per square foot is the governing factor. To facilitate estimating costs and keeping records, Table 3 is a guide to the surface areas requiring cleaning and painting on various types of railroad bridges: TABLE 3 Average Sq. Foot of Surface Type of Bridge Exposed Per Ton Rolled Beam 90-150 Plate Girder 80-1 10 Pony Truss 105-120 Deck Truss 115-125 Thru Warren Truss 105-1 20 (a) Riveted Joint 110-125 (b) Pin connected 160-190 Thru Curved Chord Truss 105-1 25 For accurate work the actual surface should be calculated from the surface of the component plates and shapes, making allowance for the surfaces in contact. ~ B. BUILDINGS Painting buildings made of masonry, plaster or wood are outside the scope of this chapter, but many steel buildings or component parts of buildings do require painting. Most require little special precaution because exposure is mild in the interior of most buildings. Interior paints do not require the durable qualities of those used on exterior surfaces; primers are less expensive than heavy-duty primers used on bridges and exteriors; surface preparation is less demanding; and repainting is done at longer intervals. When appearance is a factor, enamels give good results and long life. Exterior steelwork of buildings should be given durable protection. If the steelwork is enclosed in masonry, an inhibitive primer should be applied to protect steel from any condensation of moisture or leakage from faulty flashings or roofing. Steel completely enclosed with concrete does not require protection if the concrete is at least two inches thick. Most metal roofing on buildings is galvanized. Galvanized roofing in severe service fails at the laps. These laps should be protected when a new roof is laid by a good paint or a mastic coating. As soon as galvanized
roofing shows the first signs of rusting, it should be painted. Failure to do so results in greater cleaning costs and a shortened life of the coating applied. New galvanized roofing cannot be painted unless special paints are used. A separate chapter discusses painting galvanized surfaces. Flashings, downspouts, eaves and rain conductors may be galvanized iron and should be painted. Copper does not require painting except when the unsightly stains it causes on light coloured masonry or paints is considered detrimental. Aluminum flashing and downspouting is being used more and more. It should not require repainting; but if it is to be painted, wash primer (SSPC-Paint 30) should be used. C.OTHER STRUCTURES Towers of light angle or lattice construction present a large square footage of surface that is costly to clean and paint. These structures should be galvanized and painted before the galvanizing is lost. In painting signal standards and bridges, glossy paints should not be used since they reflect lights at night so that misinterpretation of signals is possible. 1. Tanks Interiors of fuel tanks do not require painting, except when oil or settled water is corrosive, or in the vapor space above the liquid level. Sometimes, the bottom and the lower side are protected, perhaps with coal tar enamel. The exterior of fuel oil tanks, storage bins, hoppers, etc., should be given the same protection as superstructures of bridges. Interiors of bins holding sand and similar material are difficult to protect because of the abrasive action of the contents. If their contents are not very corrosive, they can be given the same protection as the exterior, but frequent repainting may be necessary. If the contents are corrosive, a paint resistant to the corrosive material and to abrasion should be used. 2. Steel pipe Steel pipe or other steel to be buried requires special treatment such as hot-applied coal tar or asphalt coatings. For severe conditions galvanized culverts should be coated with an asphalt coating or coal tar enamel. Interiors of culverts should have a bituminous pavement to prevent wearing away of the protective coating when the flow of sand or gravel is severe. 3. Turntables Turntables and trackscales should be protected the same as bridges, when they are in a dry surrounding. If they are in damp pits, the paint system used must be resistant to high humidity.
4. Fences Fences are a costly item to repaint; they should be galvanized originally and repainted before rusting makes their repainting very costly. Long nap roller coaters are effective in lowering the cost of painting fences. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 270
SSPC CHAPTER*LO-O 73 I 1 I I 1 O 2 4 6 8 lo Nominal Thickness. Mils FIGURE 3 Average paint life YS. thickness (oil and alkyd paints). From an SSPC report.'O Regardless of the type of structure, paint or other protective coating should be chosen with regard to the type of exposure and the use of the structure. Specific recommendations are given later, but one point should be kept in mind. It is often better to sacrifice some protection by standardizing on a few paints. IV. SURFACES ENCOUNTERED The condition of a steel surface to be painted depends upon whether or not the structure is being painted for the first time. Field painting new structures entails three basic types of surfaces. A. SHOP-PRIMED In shop-primed steel for field painting, spot cleaning and touch-up priming are required. If shop painting is done well and the paint is of good quality, little touch-up is necessary. Rust that forms on scarred places is loose and easily removed. If extensive rusting and mill scale lifting has occurred, the shop coat has failed and the responsibility for the failure should be determined. The buyer cannot specify that only loose mill scale and loose rust be removed and then expect to get a perfect paint job. It is inevitable that some remaining mill scale loosens, depending upon the period of exposure of the prime coat. Even after application of the field coats, additional mill scale loosens in spots and lifts coats of paint. This is becoming less of a problem because most fabricators use a standard practice of rotary wheel blasting all steel. Soil may be found on steel resulting from dragging it through mud, storing it on the ground and subjecting it to other abuse. Oil drippings, grease, cement spatter, chalk marks and other foreign matter found on steel must be removed. Solvent and detergent cleaning are usually 8627740 00037LB O93 necessary to remove these materials, although scraping or --`,,,,`-`-`,,`,,`,`,,`--power tool abrasive cleaning is satisfactory when the soil is dried or caked. B. SHOP-FINISHED
This type of surface receives all its coats of paint in the shop. If damage in handling is slight, then field touchup of the coating system can be kept to a minimum. C. FIELD-PAINTED New steel that has not been shop-painted requires extensive cleaning. It is necessary that loose mill scale, rust and the foreign matter be removed. The amount of loose mill scale and rust depends upon the length and severity of the weathering. Since the steel was not shop-coated, it is assumed that the weathering is deliberate. Unless the period of weathering is very long or conditions very severe, there may always be some mill scale on the surface. This adherent mill scale is tenacious and difficult to remove, and it is not to be confused with the mill scale that has been under-cut and is easily removed. Unless this weathered steel is blast cleaned, the surface is poor for painting. Any cleaning method less effective than blast cleaning dooms the paint to a greatly shortened life. If steel is not blast cleaned, it is much better to paint over tight mill scale before it gets a chance to weather. A comprehensive analysis of the results of all paint tests available to the Steel Structures Painting Council indicates that painting over rust, even though the rust is thin and tight, results in shortened paint life. Rusting of bare steel, even before blast cleaning, has also been shown to reduce paint life in severe environments. Therefore, steel should be blast cleaned and painted before it has undergone any appreciable outdoor exposure. According to the questionnaire, 50% of the railroads responding specify shop priming with topcoating in the field; 25% specify the entire coating system to be shop-applied; and the remainder specify the entire coating system be applied in the field, presumably after erection. D. MAINTENANCE SURFACES Maintenance painting encounters all possible surface conditions. Large amounts of rust (beyond Rustgrade 7 of SSPC-Vis 2), indicate that painting has been deferred too long. The cost of cleaning, when there are large areas of rusty steel, may be as great as the total cost of painting with one coat of paint applied in time. When paint is well adhered and no rust has developed, a light brushing or solvent cleaning, followed by application of a single coat of paint, livens the old paint and provides additional protection. Rusted areas require thorough scraping, wire brushing or power tool cleaning followed by spot-priming with an inhibitive primer. If the areas are large, blast cleaning and prime painting on the same day are recommended. When the cost of scaffolding is high, it may be Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 271
cheaper to get several extra years of life out of the paint by allowing it to deteriorate further. The increased cost of cleaning and spot painting at frequent intervals may be less than the cost of scaffolding. When the paint must be completely removed, blast cleaning is recommended. Stainless steel and aluminum are encountered on occasion, and if painted, require pretreatment before painting; otherwise, paint does not adhere (see SSPC-Paint 27). The type of old coating is always a factor in maintenance painting. Compatibility of the new paint with the old is a prerequisite to satisfactory performance. Normally, no difficulty is encountered with most paints over old, weathered paints, but there may be a tendency for the new paint to lift the old coating, especially if the old coating has cracked or checked, or some paints may contain a solvent that acts as an efficient paint remover on the old paint. Usually, a small test should be made by applying a brushful of paint and observing its action on the old paint before painting on a full scale is begun. If the coating is a mastic type of coating, or grease, or non-drying oil, trouble occurs unless the new coating is of the same type. SSPC-PA Guide 4 is a guide to maintenance painting and SSPC-PA 1 is a specification for applying paint in shop, field, and maintenance situations. V. LABOR CONSIDERATIONS Increasing labor costs make higher productivity imperative. On railroads, where paint gangs have been eliminated, painting is being done by regular bridge and building crews that also do other maintenance work. This practice reduces painting skill. Field painting is being contracted in many instances. In this case, workers are usually experienced, but it is not unusual for contractors to recruit labor locally. Too often, both the contractor and his men are interested only in getting the painting completed as soon as possible and collecting fees. Consideration should be given to the integrity and reputation of the painting contractor rather than awarding contracts solely on the basis of the low bid. According to the questionnaire, 40% of painting is done by special paint crews, 25% by regular bridge crews, and 35% is contracted. There is great variance, and the percentages in each case ranged from O to 1OOoh for different railroads. There is a slight trend back to using special paint crews. Mechanized equipment, such as rotary power tools, abrasive pads, brushes, pneumatic chippers, and airless
spray paint outfits, has increased labor productivity. By reducing scaffolding costs large amounts of money may be saved. Increased production may be achieved by more effective work. VI. OTHER CURRENT RAILROAD PRACTICES Some aspects of mechanical and chemical surface preparation and paint application have special relevance to railroad practice. A. MAINTENANCE SURFACE PREPARATION Cleaning prior to painting has been the most troublesome process in proper railroad maintenance painting. The value of proper surface preparation cannot be overemphasized. There are numerous figures reported in the literature relating surface preparation to coating durability. One reportg issued by the Steel Structures Painting Council lists 37 references. One set of results from that report is averaged in Table 4. TABLE 4 Typical Effect of Surface Preparation on Paint Life* Millscale Rusty Exposure Blast Clean Wire Brush Wire Brush Semi-Rural 9.6 7.6 8.0 Marine 6.7 3.7 3.0 Results after 8 years exposure of two prime coats plus topcoat based on 25 widely different paint systems on 360 panels. (10 = Perfect) There is such a variety of surfaces, environments and materials that these figures should be taken only as a general indication, but all references agree on several points. The more thorough the surface preparation, the longer before repainting is required, regardless of the coating or exposure. More severe exposures (meaning usually more moist) require a better degree of surface preparation. Many coatings (¡.e., inorganic zincs) require a high degree of surface preparation to avoid disastrous failure. Methods of cleaning steel reported by the railroads in the field are as follows: 1. Hand cleaning using scrapers, wire brushes, chipping hammers, chisels and other impact tools (SSPC-SP2). 2. Power tool cleaning using electrically or pneumatically driven power tools such as rotary wire brushing machines, sanding machines, power chipping hammers,
scaling hammers, scalers and a variety of abrasive pads and grinding wheels. Radial or cup wire brushes are satisfactory for use. Scalers may be pistonless vibrating or rotary mechanical scalers. Rotary abrasive cleaning pads are available which are better than power wire brushes (SSPC-SP 3). Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 272
SSPC CHAPTERkLO-O 93 8627940 0003720 741 a 3. Blasf cleaning sand blasting, using compressed air and sand (SSPC-SP5, 10,6 or 7). (Field blast cleaning using crushed iron, grit or shot is uneconomical unless practically all of the grit can be recovered for reuse.) These methods of cleaning, which are considered mechanical, are, in some cases, preceded by chemical cleaning methods utilizing solvent cleaners or other chemical methods such as steam cleaning. Cleaning in maintenance painting or cieaning of weathered steel structures prior to priming may often be the most expensive of all the operations, and in turn, the major cost of cleaning is the labor required. The work is usually tiring and unpleasant; therefore, cleaning must be carefully supervised and inspected. Bridge ends usually are in the poorest condition. Accumulations of dirt, leaves, and other debris collect on cover plates, flanges, angles of braces and similar places, and must be removed. Particular attention should be paid to bridge seats, bridge pedestals, shoes, base and sole plates and expansion joints. Steel should be washed off with water, preferably under pressure. This wets the steel and delays painting, but in most cases the debris or soil is wet anyway and water has soaked into the paint. No painting should be done until the surface is dry. Often debris is blown off with compressed air aided by light scraping, but this usually does not leave a clean surface. When there is heavy rust scale, it should be knocked off with hammers, using chisels on the difficult spots. This scale is porous and acts like a sponge in holding water, resulting in faster corrosion. It cannot be protected by any type of coat ing. 4. Solvent Cleaning When grease or oil are present, they should be removed by solvents rather than by spreading the contaminants over a large area by the cleaning tools (SSPC-SP1). Power wire brushing, for example, spreads oil and grease over large areas causing poor adhesion of the paint. When the surface is contaminated with deicing salts, salt from the sea, bird excrement, or other corrosive agents, thorough washing with fresh water or steam cleaning is necessary. 5. Spot Cleaning In maintenance painting, the structure should be
repainted or spot painted as the first breaks in the paint occur and rust is just starting to form. At this stage, cleaning costs are minimized since spot cleaning using hand tools is usually adequate. If extensive areas of the bridge are rusty, hand cleaning is burdensome, tiring, and expensive; power tool cleaning will be more efficient; but blast cleaning is often required to obtain a satisfactory surface for repainting. If paint has deteriorated to the point where it must be completely removed, sand blasting is most economical. Removal of old paint by hand is time consuming and ineffective. Power tools are an improvement, but labor requirements are still excessive. It is a difficult task to remove tight, welladhered old paint and the necessity or advisability of removing such paint should be examined. When old paint is so thick that it tends to crack and scale, it should be removed. Blast cleaning is the best method to remove all rust, scale and old paint from steel surface. Loose mill scale and loose or non-adherent rust are easily removed, but the degree of removal of the more adherent rust and mill scale, as well as old paint, depends upon the thoroughness of the cleaning. Power tools remove much of the scale and rust, but they have a tendency to drive rust and scale into the surface. They do not remove rust from pits and may cut the steel surface leaving sharp ridges or peaks on the steel. These should not be allowed since the paint will fail quickly over such projections. 6. Choice Hard and fast rules do not apply in choosing a method of surface preparation. All methods give satisfactory results under certain conditions. The more severe the surface, the higher the quality of cleaning necessary. There are some restrictions placed on blast cleaning, but it is the preferred method of surface preparation. The experience and judgment of the engineer responsible for the condition of the structure are necessary for a satisfactory decision. The engineer s decision should be based on costs, practicality and the demands of the paint to be used as primer. Cleaning should comply with the provisions of the Steel Structures Painting Council s Surface Preparation Specifications; the particular specification used should be modified if necessary to meet local conditions. Regardless of the method used to prepare steel for repainting, it must be cleaned of residues of salt, leachings, alkali, acid or other chemical contaminants. Any protective coating applied over such corrosive agents is doomed to an early failure. It is not sufficient to remove such corrosive agents completely; strict precautions must
be taken to prevent recontamination of the surface before the primer is applied. Contamination between coats of paint or before the paint is dry is less detrimental, but should be avoided if possible. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 273
SSPC CHAPTER*LO.O 73 W 8627740 0003723 b88 B. PAINT APPLICATION SSPC-PA 1is a guide to Shop, Field Painting, and SSPC-PA Guide 4 is a Repainting with Oil Base and Alkyd helpful in the procedures involved
and Maintenance Guide to Maintenance Paints. These are in paint application.
1. When To Faint: While cleaning can be done in most weather, within limitations, weather affects paint application principally and therefore limits the season during which painting can be done. Painting should not be done outdoors in cold weather, and it is the usual practice to discontinue painting during winter in the northern parts of the continent. The lower temperature limit at which most paints can be applied is not definite; 40" to 50°F (4" to 10°C) is considered to be the lowest practical limit,' however, certain paints may require a minimum as high as 60°F (15.5%). Paint becomes thick in cold weather, and painters tend to use large quantities of thinner so it is easier to apply. The result is a thin coat. In addition, no paint should be subjected to freezing after application until it has dried. Moisture has worse effects on paint life than cool weather. The foreman or engineer responsible for the work has a difficult decision to make when rain is imminent. Many foremen keep protected parts of the bridge in reserve for rainy weather. The exposed portions are worked on first; the sheltered portions can be worked on during high winds or rain. Moisture harms paint when the relative humidity is above 85% and the condensation point has almost been reached. Painting should be stopped when the dew point is within 5"F(3"C) of the air temperature. A slight cooling, or a few degrees lower steel temperature, causes condensation that may be invisible but still detrimental to the coating life. Hot dry weather does not affect painting. Paint has a tendency to be less viscous, which causes a thinner film, runs or sags; but these problems can be overcome partially by not thinning the paint. No proof exists that it is detrimental to apply paint on hot steel at a temperature of 125°F (52°C) or over. Under such conditions, however, catalyzed coatings may have an excessively short pot life. The effect of weather is very important to successful application of paint, thus every supervisor should consult the weather forecasts before
scheduling work. 2. Painting: Paint failures occur primarily through improper cleaning; secondly, through improper application; and finally, through poorly chosen paint. FIGURE 4 Single spider cages in use in the painting of bridge. (Northern Pacific RR photo) Proper mixing of paint is essential. Many railroads purchase paint in five gallon pails. Hand mixing of paint in five-gallon pails is satisfactory, provided all settled pigment is put into suspension. Mechanical mixers give best and quickest results. If large drums of paint are used, careful supervision of the mixing is necessary, and mechanical mixers are essential to get a uniform mix. Sloppy workers pour off the top of the paint, getting too much vehicle and not enough pigment; when they get to the bottom of the drum, the paint is almost all pigment, so they add thinner. Maintenance personnel should realize that making the paint go farther is bad practice. Pigment of paint in buckets, spray pots or cans may settle during the application and should be stirred at intervals. Mechanical stirrers on spray paint pots are recommended, and they are essential if the pots are greater than five gallons in capacity. These mechanical mixers may be hand-operated, or driven by air motors. Constant mechanical mixing is required for certain paints, such as those with a high zinc metal content. Large drums of paint are easily fixed with airoperated stirrers. If electric stirrers are used, they should be explosion-proof. Pumps used to pump paint directly from the drum require auxiliary stirrers to keep the paint mixed. Actual paint application is normally by brush or spray. A controversy still exists about which gives better results. Both yield satisfactory results if properly done. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 274
SSPC CHAPTER*LO.O 93 M 8627740 0003722 514 M Conventional air spraying is two to three times faster than brushing, and the paint film tends to be more uniform. Spray paint has a tendency to bridge over tiny pits and cover surface dirt or oil on a poorly prepared surface. Regardless of the method, the surface should be dusted by brush or compressed air. Paint must be applied evenly so no skipped spots or holidays occur, and as uniformly as possible without running or sagging. A combination of brushing and spraying is almost always necessary on railroad bridges even when spraying has been selected as the best method. The interiors of boxed members are difficult to paint. Many railroads stencil the date of painting and the paints used on the structure. This information is of value to the inspector, but is a duplication of information that should be kept in the records of painting. Such records are of great value to the railroad if a complete breakdown of the costs is recorded along with the material used, cleaning, labor requirements and rates, type of surface and the life of the paint job. Only when such records are kept up to date does the railroad know the costs of painting and whether changes in methods are really economical. Application methods for asphalt-oil, bridge cement, greases, emulsions, hot-coatings, etc., will differ from those of conventional paints. C. CURRENT RAILROAD PAINTING SYSTEMS The questionnaire revealed a wide variety of coating materials are used on railroad structures. A large number of railroads select different coating systems for different environments. Some use their own specifications, and many have settled on certain proprietary products. The vast majority of coatings used are oil, oil-alkyd or alkyd based, apparently due to the versatility of these types of paints and their good performance in most environments. Several railroads use the same coating materials in all applications but vary the number of coats to suit the situation, for example adding a third coat in a corrosive environment rather than switching to a completely different system. Others are making limited use of epoxy, urethane and inorganic zinc coatings. One proprietary product used by several railroads for a number of years is of interest in that it can give sufficient film build in one coat for most environments (5 mils dry film). Compared to previous surveys there has been a marked decline in the use of red lead primers.
There is a general reluctance to use coatings that require special care or precautions unless absolutely necessary. Considering the conditions in the railroad industry under which paints are used, this is understandable. Generally, unskilled painters with too little technical training in sophisticated coatings are given responsibility to apply these paints. Some railroads have used grease or petrolatum materials for many years and feel they are giving good, low-cost service when properly maintained. Other companies feel they make bridge inspection difficult or unsafe (due to slipperiness), and allow underfilm rusting to proceed undetected. It is a fact that they are very difficult to remove from a surface, and once applied, the owner is almost forced to continue using this type of material. A considerable number of railroads use this type of product on load-bearing top flanges when ties are being lifted and time limitations make the application of conventional paints next to impossible. There is little use by the railroads of pretreatments before painting, such as penetrating or wetting oils of the drying type, phosphate treatments, or basic zinc chromate wash coat priming. The basic zinc chromate washcoat pretreatment known as wash primer (¡.e. SSPC-Paint 27) is applied like an extremely thin coat of paint. It is used over bare steel and forms an outstanding foundation for many paint systems. It can be used to prepare galvanized surfaces for painting, but the instructions must be followed very carefully. Wash primer permits many types of conventional paint to be used over galvanizing. It is also used to provide adhesion of paint to stainless steel and aluminum and may be required by some vinyl paint systems. Various chemical pretreatments using phosphoric acid or phosphates as the main ingredients are on the market. Often extravagant claims are made of their merit on steel that is covered with mill scale, but a number of tests have disproved such claims. In some cases their use is detrimental. They are effective when the steel is descaled but has an extremely light deposit of rust, a condition that is rare on railroad structures. D. LIFE EXPECTANCY OF PAINTS The life of any paint system is dependent on the surface preparation, paint application, climatic and atmospheric conditions and paint materials. There is an interest in determining the relative importance of each of these factors under controlled situations in full sized field tests. By holding one of these factors constant, and varying the others, comparative results can be determined. The effect of film thickness was discussed in a report in the June, 1969 Journal of Coatings Technology.10 Some of the results are summarized in Figure 3. The expected life of good paint systems exposed to
clean, rural atmospheres is easily 10 to 12 years. The possible variation is due to the condition of the steel before painting and to the paints used. In such mild atmospheres, linseed oil paints remain elastic and durable for long periods. In desert atmospheres, 15 years of life is common. The expected life of good paint systems exposed to industrial atmospheres is six to eight years, as an average. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 275
SSPC CHAPTERaLO-O 93 8627940 O003723 450 The life of paints exposed to marine atmospheres is variable and unpredictable because of the variance in local conditions. If a good paint job is obtained on clean, dry, uncontaminated steel, six to eight year's life should be obtained without difficulty in regions such as the Atlantic Coast. Under severe conditions, much shorter paint life occurs on portions of the structure. In the Gulf Coast area, 2% to 3 year's life for paint is common unless topcoated zinc-rich primers are used. In actual field service, the maximum life of the paint is seldom .realized due to failures that occur because of rusting under the paint, mainly because of inadequate surface preparation. When the full life of the paint is realized, failure will occur by a gradual weathering of the top coats resulting in a chalking condition of the paint. E. PAINTING EXPERIENCE AND COSTS Costs vary greatly. Each railroad has some idea of its own costs, but in most cases they should be developed more fully. Major points to be considered are costs of setting up at the job site; material costs including paint, cleaning equipment, compressed air, staging or scaffolding; and labor costs, which should be broken down into various functions, Set-up, surface preparation and coating application. With labor costs it is better to work in worker-hours rather than dollars. The actual costs can be converted to dollars per ton or dollars per square foot from workerhours when required. In each railroad, many structures are similar, so for quick reference costs could be kept on the basis of a plate girder span of X length or a truss span of Y length. Costs for other lengths or multiple spans can then be easily calculated. Another interesting figure to keep in the actual working hours per week or per job free of interruptions. Even with good background figures, there can be large variations due to the type of structure, location of the structure, condition of the surface, weather conditions, traffic patterns, etc. However, these variables are no excuse not to keep a careful record of all costs. On a typical job where the entire surface was given a near-white blast cleaning (SSPC-SP 10) the cost breakdown could be: Materials -20% (5-25);labor and equipment costs for cleaning and Set-up -60% (40-80);labor and equipment costs for two-coat application of paint -20% (10-40). (Figures in brackets are possible ranges due to the above variables.) Typical cost analyses of painting alternatives are given in a separate chapter. F. OTHER RESPONSES Questionnaire respondents indicated they were mainly interested in (1)longer paint life, (2) reducing costs of ap-
plication, (3) reducing number of coats, and (4) better surface preparation. These are ahead of five other possible answers to the question. All these factors obviously reduce costs. To discuss these in turn, longer paint life, as stated previously, depends first on a well prepared surface, and secondly on proper application of the paint. A very common failing is too thin an application; many times the life of the coating would be prolonged several fold if one more coat had been applied at a small additional cost. The life of the coating also can be prolonged by the choice of coating, particularly in the more corrosive environments. Reducing the costs of application can be achieved mainly by applying fewer coats. High-build coatings are becoming more common, and if the same dry film build can be obtained with two coats rather than three coats of a similar material, the savings are obvious. In some situations there may be savings in having faster drying paint, Almost certainly less expensive surface preparation means shorter coating life and results in no savings, The cleaning of new steel at the fabrication plant can be done at a much lower unit cost than in the field. However, if a particular specification for cleaning is used that differs from the shop practice, an extra cost per ton is charged. The perfect coating does not exist and probably never will. Be suspicious of materials for which the following claims are made: (1) requires minimum or no surface preparation, or (2) dries instantly, or (3) can be applied in most or all weather conditions, or (4) tolerates damp surfaces, or (5)will double or triple your coating life. Advances in coatings are being made, but great break-throughs are rare. When presented with a new coating material that has not been used before, you should, after careful consideration, field test if it appears promising. Do not be rushed into a quick evaluation. At least several years of study are required. The results of accelerated tests, such as salt fog or condensation cabinet exposures, are of interest but are sometimes misleading and cannot be relied on. The use of scaffolding and rigging is a specialized subject covered in another chapter. The cost of these items can be considerable, but devices that reduce labor costs generally prove economical. The use of small, air operated winches along with light timber frames fastened together with eye bolts permits easy hanging of scaffolding. Various types of aluminum staging are also available which combine light weight with strength (Figure 4). Special trucks are now available with hydraulically
powered, aerial booms that are used to reach overhead structures from roads or under structures from track. They can be purchased with maintenance bodies to store supplies and equipment. Heights as high as 30 to 40 feet may easily be reached without use of scaffolding. Such equipment is shown in Figures 5 and 6. VII. RECOMMENDATIONS FOR PAINTING OF RAILROAD BRIDGES AND STRUCTURES New structures should be designed with a thorough knowledge of the corrosiveness of the environment.'l The following condensed summary of good practices is recomCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 276
SSPC CHAPTER*LO.O 93 = 8627740 0003724 397 mended for the consideration of those responsible for the economical protection of railroad bridges and structures. A. STORAGE AND HANbLING OF PAINTS IN THE FIELD It is desirable to have a separate temperature controlled building to store and mix paint materials. Paints stored for a long time should have the position of the containers inverted often enough to prevent hard settling of the pigment. The shelf life or storage life of paints may vary with different products and should always be considered. Too long a storage period makes some paints unfit and makes proper mixing difficult. It could use up any savings from large volume purchases. To mix paints, a mechanical rotating machine equipped with paddles which can be inserted into the containers to agitate the contents thoroughly is very desirable. A broad paddle with a lifting motion up through the vehicle should be used. Paint should be thoroughly agitated. It is always advisable FIGURES 5 AND 6 to pour the paint from one container to another near the Special trucks with aer ial booms can reach overhead structures end of the agitation process. When aluminum paste pig- from roads or under struc tures from track. ment is used, the pigment should be placed in a container, and the vehicle added slowly as the mixing progresses. Paint generally should be mixed without the addition of thinners. In cold weather, a small amount of thinner may be permitted for spraying. Whether paint is furnished by the owner or by the contractor, it is desirable that paint for each day's use be mixed on the job at the beginning of the day. If the work is being done by contract, the owner's inspector should be present to observe the mixing technique, and to see that thinners are used only to the extent allowed by the specif ¡cat ions. Paints should be stored in the original metal shipping containers. The containers should be clearly marked to show the type and color, specification number, quantity, name of manufacturer, batch number, date of manufacture and any other information desired, such as special application instructions. B. SURFACE PREPARATION It is essential that a clean, dry surface be obtained for the paint. Blast cleaning is highly recommended for all surfaces. The three commonly accepted degrees of blast cleaning are defined and described in SSPC-SP 5, White Metal Blast Cleaning; SSPC-SP 6, Commercial Blast Cleaning; and SSPC-SP 10, Near-White Blast Cleaning. In most situations commercial blast cleaning will be sufficient, but there will be situations or coatings which will re- removed. If any f
ield welding was done, special care must quire near-white or white metal blast cleaning, normally be given in cleaning ar ound the welds. The weld area must Zones 2A, 28 and 3. Because of the construction opera- have all peaks and rough edges removed and all weld spattions involved in building of a new structure, especially ter removed. When too long a period elapses between field bridges, there are special cleaning problems. Cement or coats, dirt may need to be removed before the second field mortar may have dripped or spattered on the steel; oil from coat is applied. hydraulic jacks, reamers, or drills may have dripped on the Cleaning before pain ting should be done in accordsteel or painted surface; steel shavings and other con- ance with the applicable Surface Preparation Specificastruction debris may be present. All of these must be tions in Volume 2 of the S teel Structures Painting Manual. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 277
SSPC CHAPTER*LO-O 93 = 8627940 0003725 223 C. APPLICATION OF PAINTS TO STRUCTURES IN THE FIELD When painting is done by contract, it is common for the railroad owner to furnish paint to the contractor, especially when the railroad s own specification paint is used. The film thickness is critical and the use of a thickness gauge, such as the Elcometer, is essential. Normally, prime coats should be at least 2 mils thick; intermediate and top coats should total 1 to 4 mils in thickness. On new work, the field bolt heads should be spot painted as soon as possible, as should all scars, bruises, rust spots, and thin spots in the shop coat, in advance of application of the first field coat. The first field coat should be thoroughly dry before the second coat is applied. A test for this is to press the thumb firmly against the paint surface, then twist. If the paint skin does not slide, or come off, the paint is sufficiently dry to apply the second coat. One or two days are usually sufficient for this drying time. Oil paints may not dry enough in this time to pass such a severe test; they should be tested by pressing hard without twisting. To require too long a period between coats of paint may increase scaffolding costs. Here it must be remembered that too thick an application may slow down drying. However, the re-use of scaffolding without moving it is no reason to permit application of the second coat of paint before the first is dry. Generally, painting should proceed from the top down. From the standpoint of inspection, it is desirable to paint from the top to bottom, or from one end towards the other, without skipping around. When the bridge is being painted under traffic, the work must not interfere with the movement of trains. Care should be taken that lines and scaffolds do not get within prescribed clearance. In the case of movable bridges, which must be opened on demand by boat traffic, scaffolding must not be placed to interfere with movement of the bridge. In buildings, erection of new steel should be followed up by spot painting of skinned, bruised or thin areas, and bolt heads, etc. If the steel is to be fireproofed, spot painting of the shop coat is sufficient. Do not paint metal to be embedded in concrete. On exposed interior columns and beams, additional field coats are required of the type and color of the final coat. When the steel is encased or fireproofed with a thin or porous coating of concrete or light weight aggregate, an inhibitive primer should be used. If exposure conditions are severe, such as in salt water, at least two coats of high quality inhibitive paint should be used. When the concrete is two to three inches thick, dense, of good quality, and without acid consti-
tuents, priming is not generally considered necessary because of the protection afforded by the concrete. This is usually the case when steel is used in reinforced concrete; here, the bond necessary between the steel and concrete precludes the use of paint. D. PAINTING SYSTEMS Table 2 outlines paint systems as described in Volume 2 of the Steel Structures Painting Manual. The recommendations are based on the environment to which the structure or parts of the structure will be exposed. All primers included here are rust inhibiting and have been proved in service. Complete painting systems will be found in Volume 2 of the SSPC Manual. The paints in Table 2 are listed by specifications in current use; proprietary paints meeting or exceeding these specifications are available and can be used provided the user has had satisfactory experience with the seller. The TT numbers listed refer to Federal Specifications; the SSPC numbers refer to the Council s specifications; the MIL refer to U.S. Military specifications; the AASHTO refers to American Association of State Highway Official s specification. The GP numbers refer to Canadian Government Specifications Board. The CISC numbers refer to the Canadian Institute of Steel Construction. The intermediate and finish paints used depend largely upon the primer used. The methods of surface preparation and pretreatment affect the selection of the primer directly, but only indirectly affect the choice of topcoats. Care must be used when hard, quick drying topcoats like some of the short oil alkyds and phenolics are used over soft primers such as linseed oil; unless the oil primers are thoroughly dry, the topcoats may crack or wrinkle. When using unusual combinations, test patches should be applied and inspected. Any detrimental film irregularities should develop within 24 hours. E. INSPECTION Questionnaire responses indicated that many railroads do not specify coating thickness. The common procedure is to apply, for example, two coats of paint and assume all is well. This may be a relatively safe procedure
if well-known paints are used for many years. But even different batches of the same paint from the same supplier can vary considerably in film build properties. It is not at all difficult for an expectedly thin application to be applied and cut the protective life of the coating system in half. Film thickness gauges are not expensive and can be easily used by the supervisor or foreman on the job after a minimum of instruction. It is a very small price to pay to help ensure a satisfactory paint application. Equally important and more difficult to control is the quality of surface preparation. The life of the coating depends largely on the thoroughness of surface preparation. Interestingly, most railroads seem to control application by contractors more closely than when their own crews are involved. VIII. SAFETY All application should be carried out in accordance with federal, state and local requirements. They should also be in accord with the instructions of the paint Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 278
SSPC CHAPTERsLO-O 93 m 8b27940 000372b LbT m manufacturer and requirements of the insurance underwriters. Safety considerations should include, but not be limited to, those presented in SSPC-PA Guide 3, A Guide to Safety in Paint Application . Proper handling and storage of paint materials on the job should include safety considerations to avoid loss or damage, as well as to avoid hazards to workers. Hooks for scaffolds, as well as all blocks and falls, including ropes, should be examined every day or before use and replaced before they are in an unsafe condition. Cleaning materials should be properly used to prevent fires, and toxic fumes from them should be avoided. While wire brushing, chipping, or scraping, workers should be required to wear goggles to protect their eyes. With sandblast cleaning, proper helmets with a source of clean air must be provided for operators of blast guns. Scaffold ropes should be wrapped to prevent damage from blast cleaning. Gloves and protective clothing should be worn. It is always necessary to in a manner that does not movements over the bridge highway traffic under the
conduct painting operations cause danger to railroad train structures, or to river traffic or bridge.
Detailed safety precautions included with each surface preparation specification of the Steel Structures Painting Council, shown in Volume 2 of this Manual, should be observed. Safety recommendations of the National Safety Council for Bridge Painting should be followed to avoid such accidents as falls; injuries due to excessive heat or cold; poisoning; injuries due to oncoming traffic; eye injuries while chipping, scraping, brushing, and riveting; drowning; and electric shock from power cables. People who work on elevated structures should be experienced and not be subject to dizzy spells or heart ailments. Physical examination before hiring is recommended. When working on bridges over water, workers should wear life belts, or a man in a boat should patrol the water under the work area. In hot weather, shade is beneficial to the workers and increases worker output. Approved respirators are worn if spraying or removing lead paints; protective creams or ointments are used on the face, neck and hands; workers wash thoroughly before eating and after work. Attention is also drawn to the hazards of chromate in paints and to the hazards of leadbase paints. ACKNOWLEDGEMENT The first edition chapter on this subject was authored by Manley A. Roose, who was very helpful in the preparation of the present chapter. Data on current practices were obtained by means of two questionnaires circulated to Committee 15 of the American
Railway Engineering Association -D.S. Bechley, then Chairman. The author and editors gratefully acknowledge the active participation of the following in the review process for this chapter: Carl Bye, Thomas A. Cross, Robert Doyle, Jim Hutson, Raymond C. McMaster, Gatewood Norman, William Pearson, and William J. Wallace, Jr. REFERENCES 1. Weathering Steel Committee Report . American Railway Bridge and Building Association, Proceedings, p. 73, 1972. 2 F.L. La Que, Corrosion and Protection of Off-Shore Drilling Rigs . Corrosion, Vol. 6, No. 5, p. 152, 1950. 3. H.A. Humble, Cathodic Protection of Steel Piling in Sea Water . Corrosion, Vol. 5, No. 9, p. 292, 1949. 4. E. Escalante, and W.P. Iverson, The Protection of Steel by Non-Metallic Coatings in Sea Water , Materiais Përformance, October 1978. 5. Investigation of Electrolytic Corrosion of Steel in Concrete . AAR Committee Report to Electrical Section of Engineering Division, Corrosion, Vol. 3, No. 1, p. 37, 1947. 6. John D. Keane, Protecting Load-Bearing Surfaces of Steel Bridges . Steel Structures Painting Council Report, 1968. 7. L.S. Crave, Corrosion Problems of the Railroads . Digest of Discussions, Second Railroad Corrosion Conference, International Nickel Company, 1951. 8. L.S. Crave, Corrosion Problems of the Railroads . Corrosion, Vol. 8, No. 4, p. 149, 1952. 9. John D. Keane, Surface Preparation Versus Durability , Steel Structures Painting Council Report, 1966. 1o. John D. Keane, William Wettach, and Waouter Bosch, Minimum Paint Film Thickness for Economical Protection of Hot-Rolled Steel Against Corrosion . Journal of Coatings Technology, Vol. 31, No. 533, pp. 372-382, June 1969. 11. C.E. Webb, Better Bridges Require Less Maintenance , Railway Engineering and Maintenance, Vol. 32, p. 37, 1936. 12. John D. Keane, Railroad Bridge Paints With Resistance to Salt Brine , Steel Structures Painting Council Report, 1968. 13. John D. Keane, Painting Railroad Bridges for Mild Exposures . Steel Structures Painting Council Report, 1968. 14. John D. Keane, Golden Gate Bridge Paint Test , Steel Structures Painting Gouncil Report, December 2, 1976. 15. John D. Keane, Protector of Structural Steel Work -U.S. Practice . Corrosion in Civil Engineering, Institution of Civil Engineering, London, 1979. BIOGRAPHY Raye A. Fraser has a B.Sc. in Chemistry from Mount Allison University and has held a number of positions at the Technical Research Centre of Canadian National Railways. During this time, he has been involved in laboratory and field evaluations of coatings, and the writing of coatings specifications as well as the CNR Corrosion Protection
Manual for Steel Bridges and Structures. He is a past-President of the Montreal Society for Coatings Technology and a past-Chairman of the Protective Coatings Division of the Chemical Institute of Canada. For the past 20 years he has been active on a number of Steel Structures Painting Council Committees. 279 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERxLL-O 93 8b27940 0003727 OTb CHAPTER 11 PAINTING OF HIGHWAY BRIDGES AND STRUCTURES by R.R. Ramsey and 8.R. Appteman I. INTRODUCTION II. STRUCTURES AND CONDITIONS This chapter covers present practice in the painting of highway bridges and related highway structures. It em- A. TYPES OF STRUCTURES phasizes painting done in the field. Shop painting is Highway structures requiri ng painting for protection covered in a separate chapter. against corrosion are chiefly bridges. But, there are also This chapter brings together both general and special corrugated culverts which are usually galvanized, guardconsiderations for the painting of highway bridges. While rails and posts, light poles, truck scales, buildings, roadsome of the material here overlaps with material in other signs and miscellaneou s structures. The same principles chapters, the emphasis is given to the conditions and fac- apply to all structur es, but only bridges will be discussed tors that are unique to or especially important for highway in detail. bridges. The discussion is brief in topics that are covered Steel highway bridge s vary in span length from 20 feet elsewhere. In the text the reader is referred to the most to the present Golden Gate suspension span of 4200 feet. relevant chapters, although this chapter is meant to stand The types of steel hi ghway bridges include the following: by itself. Beam spans -simple, cantilever, continuous or comHighway bridges are painted for long-lasting corro- posite; always decked struct ures, span lengths to 120 feet sion protection of the structure and improvement of its ap- (Figure 1). pearance at the minimum cost. Girder spans -riveted or welded; simple, cantileve r Paint should function as an inhibitor and barrier to or continuous; usually deck ed structures, sometimes comprevent, as much as possible, the corrosive attack of the posite with deck; some times designed as box girders; span steel substrate by moisture, air and oxidizing chemicals. lengths to 375 feet (F igures 2 and 3). Primer coats therefore usually contain rust inhibitive Rigid frames -riveted or welded, single or multiple pigments or pigments such as zinc dust that reduces cor- spans; decked structure s; span lengths to 130 feet. rosion through cathodic protection. The topcoats or finish Truss spans -usually riveted; simple, cantilever or coats, on the other hand, provide barrier protection continuous; through (Figure 4) or decked (the latter through the use of polymers and pigments that protect whenever practicable); spa n lengths to 1800 feet. against moisture permeation and the constant attack of Arches -usually riveted;
single or multiple spans; weather. through or decked; span lengths to 1675 feet. Arches may The second purpose of painting highway structures is be trusses or girders. for appearance. Quite often the color of the top coat is Suspension bridges -spa ns up to 4200 feet (Figure chosen to harmonize with the adjacent topographic 5). features. In some localities a leaf green top coat blends Deck type structures, particularly the shorter spans of well with the surroundings, while in others a gray or beams, girders and rigid f rames, are more protected from aluminum coat may serve better. An important considera- the weather than the thr ough and overhead types. Truss tion for top coat selection is the ability to retain the types are more suscepti ble to painting difficulties than the original color and gloss. Certain pigments (e.g. yellows, beam and girder types, because the latter have large blues) are prone to fading. Urethane top coats usually pro- smooth surfaces, whi le trusses are broken down into vide excellent color and gloss retention. multitudinous corners, edges and small parts. A timber or Some bridges are being painted in two colors to fur- open steel deck gives rise to more corrosion below deck ther improve their appearance. For through structures, than does a solid concret e slab. An exception to this case where night visibility is of prime importance, the blending has been noted in hi gh humidity environments where, apof colors to comply with the surroundings might be a detri- parently, condensati on with poor drying conditions causes ment. On the other hand, the painting of bridge end posts more corrosion below s olid deck structures. In the case of and steel members of overpass piers with obstruction a truss bridge with concret e floor, the paint on portions of markings is an unsightly e3pedient but often necessary for the structure above t he floor is often in worse condition safety reasons. than on the floor system below the deck. Although timber Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 280
SSPC CHAPTER*LL*O 93 8b2794O 0003728 T32 FIGURE 1 Beam spans can be simple, cantilever, continuous, or composite, but are always decked structures. Oak Hill Road Bridge illustrates rolled beam simple span. Courtesy of Cal Trans floors on bridges are nearly obsolete, old bridges with with moderate sulfur dio xide and moderate humidity, while timber floors and new bridges with open grating floors others may suffer from hi gh humidity, high sulfur dioxide, show corrosive conditions below deck about equal to and salt. Frequently there i s a large variation in the environthose above the deck. Corrosion occurs on the top flanges ment within a very sma ll geographic area due to local efof floor members, and dirt falls through and accelerates fects. Sulfur dioxide l evels may vary substantially from one paint failure by collecting on lower surfaces. Severe cor- end of a structure to the other. The direction of sun and rosive conditions are generally found at the ends of bridge wind and the degree of sheltering strongly influence the spans, at pin bearings, shoes, and expansion devices ex- highly critical time of wetness of structural members. Detending across the bridge floor. Water frequently flows off icing salts will nor mally affect specific areas of the superat the ends of spans, where the accumulation of moisture structure, up to 12 or more feet above the roadway and and foreign matter gives rise to corrosion. These places re- various members of the substructure. The presence of quire special attention when the bridge is to be cleaned. crevices or leaking jo ints will create accelerated local corPeriodic removal of the accumulated foreign matter in rosion. Faulty drainage an d poor regular maintenance maintenance operations will minimize corrosion at these cleaning of expansion jo ints further aggravate this situalocations. tion. Steel piling to be driven into the ground is not general- Identifying the corros ion environment is important ly painted except where it is exposed. The type of protec- because the suitabili ty and durability of the coating are tion to be chosen depends upon the type of exposure. directly affected by the ty pe of environment. Thus, in some locales, a relatively inexpensive, easily applied oil-alkyd B. EXPOSURE ENVIRONMENTS may last 15 years, whereas in more severe locations, th at system may show signif icant deterioration in 2-3 years. The local environment of the metal on a structure substantially influences the rate of corrosion of the ex- The environment can be determined from the geposed steel and the deterioration of the protective coating. ography (proximity of seacoast, industry, cities) and Volume 2 of the SSPC Manual(15) lists and classifies ex- climate (acidity and qu
antity of rainfall, relative humidity, posure environments. For highway bridges the following pollution levels). Howeve r, the decision on painting nortypes of environments are considered most relevant. mally requires individual in spection of the structure to determine its actual condition. In particular, one must note Mild: Low pollution in the form of sulfurdioxide, low the performance of the coa ting system used previously relative humidity, absence of chemical fumes or and the pattern of corrosion in order to select the most accumulation of deicing salts, usually an in- suitable coating for repainting. terior (inland) location. Humid, Inferior: high humidity, low sulfur dioxide, C. SURFACE CONDITIONS ENCOUNTERED little deicing salt. The surface of a bridge consists of a multitude of miniIndustrial: high sulfur dioxide, moderate or high surfaces with different condit ions. Because of the large humidity. diversity in structure types and designs, there is an enorMarine: high salt content from proximity to sea-mous variability in the proporti ons of edges, corners, bolts, coast or from deicing salt, high humidity and protrusions, back-to-back angles, joints, and flat areas. moistu re. Because these areas are not likely to be coated and proThe above definitions are, by necessity, arbitrary. tected evenly and because of differences in environments, Many bridges will not fall distinctly into any of the the condition of the subst rate will vary considerably from categories. Some bridges may have intermediate climates surface to surface. 281 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
Typical surface conditions encountered on bridges older than five years are as follows: 1. Tight, intact paint with no rusting. 2.Tight, intact paint, with some signs of visible rust. 3. Finish coat worn down to primer. 4. Popping of mill scale down to bare metal where shop cleaning was inadequate. 5. Flaking, blistering, alligatoring paint. 6. Bare steel corroding, tight rust. 7. Heavy rusting and pitting; loose, flaky scale. 8. Contamination from oil, dirt, debris. For each structure, highway officials have a series of options to consider, ranging from leaving the surface completely untouched to complete blast cleaning and repainting. In between are the options of spot cleaning, touchup, and overcoating. The action taken and the type of coating system selected depend on the extent of occurrence of the surface conditions described. Other factors, described in a later section, also influence the decision. The condition of the structure is normally described in terms of the percentage of the surface showing some sort of failure such as rust, blistering, or delamination. However, because of the variety of surfaces and nonuniformity of failure from beam to beam, the ASTM standards are difficult to apply. Frequently, the condition is expressed as the overall percentage of the area exhibiting deterioration. Alternatively, a rating system of 1 to 10 or excellent-good-fairpoor may be used. For bridges having less than 1 or 2% rust, the usual choice is to spot clean and spot prime, followed by one or two full topcoats. It is important to ascertain whether the intact paint is still tightly adhering and "alive", (e.g. not too thick or brittle). For structures showing greater than 20-25% surface deterioration, it is usually more cost-effective to clean the entire structure (particularly if abrasive blast cleaning is available). In the intermediate range, the decision is more difficult and usually depends on local preference. SSPCPA Guide 4 presents a set of guidelines16. It should be pointed out that the above visual percentage rating assigned a structure by an inspector or engineer is not equivalent to the ASTM visual rust ratings per SSPC-Vis 2 or ASTM-D 610". The former is normally based on a percentage of the area requiring repainting while the latter is a numerical identification of the fractional area covered by rust or failed paint. --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS FIGURE 2 Continuous girder spans, Elkhorn Bridge, Sacramento River.
Courtesy of Cai Trans 282
SSPC CHAPTER+LL-O 93 8627940 0003730 by0 D. BRIDGE STATISTICS from inadequate maintenance. The cost of that neglect is The following data are presented to demonstrate the magnitude of the problem of Qrotecting highway bridges. According to the most recent by the Highway Administration, there are approximately 112,000 steel bridges in the United States. Over 4000 of these are structurally deficient; a large part of the deficiency arises hundreds of millions of dollars per year. An approximate breakdown of the steel bridges is shown below (Table 1) interms of the type and size of structure and the bridge environment. These data are taken from a 1980 Federal ~ i~ d~~ ih~ i ~~ t ~ ~ research report,. TABLE 1 Distribution of Steel Highway Bridges Bridge Type and Size Girder, d 60 feet Girder, < 60 feet Truss, Q 60 feet Truss, < 60 feet accessible Truss, < 60 feet inaccessible Total Exposure Environment Rural Industrial Marine Total 30,000 20,000 11,000 61,000 14,000 10,000 6,000 30,000 5,000 3,000 2,000 10,000 3,000 1,000 1,500 5,500 3,000 1,000 1,500 5,500 55,000 35,000 22,000 112,000 *Includes bridges on Federal Aid highway system; most county-maintained structur es are not included. 111. COATING SYSTEMS FOR FIELD APPLICATI0N Coating systems are the principal means for corrosion protection for over 99% of the steel bridges in the U.S. The coating system as used in this text consists of the surface preparation, paint application, and coating materials. (What the author calls coating system is synonymous with what the SSPC calls painting system ). Each of these three elements is important for achieving satisfac-
tory protection. Most coatings experts consider the surface preparation to be the single most important part of the coating system. For some zinc-rich, water-borne, or other high-technologycoatings, the application is almost equally critical. These two aspects normally account for 50 to 80% of the total cost of bridge painting. In this section are discussed the more common highway practices in preparation, application, and choice of coating systems. More comprehensive treatments are given in other chapters. A. SURFACE PREPARATION Surface contaminants such as rust, rust scale, chemicals, salts, dirt, loose paint, dust, oil, grease and moisture will cause poor bonding of a coating to the substrate. Good surface adhesion of the primer coat is essential to long service life. If inorganic zinc primers are used, good surfaceadhesion requires an anchor pattern on the steel surface produced by abrasive blast cleaning. Surface contaminants on steel surfaces act as collecting sites for moisture and soluble salts, and if not removed they will cause accelerated rusting and corrosion product to build up on the underlying surface. This contributes to the early failure of the paint system. The methods of surface preparation for the field painting of steel highway bridges depend upon the condition of the surfaces prior to painting. There are at least nine methods of surface preparation described by SSPC. The most important ones for highway steel are hand and power tool cleaning (SSPC-SP 2 and SSPC-SP 3), commercial (SSPC-SP6), brush-off (SSPC-SP7), and near-white (SSPCSP 10) blast cleaning. In the painting of bridge structures, the most costeffective method for preparing large surfaces and intricate configurations is abrasive blast cleaning. This includes jobs requiring extensive touch-up work on corroded joints and newly erected steel, and the complete repainting of an existing structure. For minor spot repair, hand or powertool cleaning may be more practical. In addition, when painting over existing sound paint, water blasting may be preferred to brush-off blast cleaning. Concern over the toxicity of silica sand and paint dusts have caused regulators to impose limitations on dry abrasive blasting in some areas. Alternative cleaning methods such as wet sand or grit blasting, water blasting, Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 283
SSPC CHAPTER*LL.O 73 = 8627740 0003731 527 FIGURE 3 Box girder type bridge. Bryte Bend Bridge. Courtesy of Cal Trans or vacuum blasting and containment of abrasives are currently being evaluated and are discussed in a separate chapter. Abrasive blast cleaning removes most contaminants from the surface and provides a surface profile (pattern of peaks and valleys). The surface profile provides increased surface area for improved adhesion of the primer coat. Usually, excellent adhesion will be obtained if the average depth of the blast profile is approximately onethird the thickness of the primer. For example, self-curing inorganic zinc primers applied at three to five mils dry film thickness require a surface profile between one and two mils. The dry film thickness of the primer coat must provide adequate coverage above the surface profile peaks. Profile height is determined primarily by the mesh size of the abrasive, typically ranging from about 0.5 mils for 60-120 mesh sand up to 3-4 mils for 12-30 mesh. Additional information on surface profile is available from SSPCz. Daily abrasive blasting operations should allow sufficient time for a thorough inspection of the work after all of the loose debris is air-blown free of the steel surface. Areas found deficient in surface preparation should be marked with chalk and then re-blasted or touched up by power tool cleaning. The entire area should then be airblown down again with high pressure dry air just prior to application of the primer coat. Inspection of the daily work should commence by 3 p.m. or earlier, depending on the weather and the time of year. Mirror devices and lights should be used to check inside box girders. Bearing shoe assemblies, gussett plates, angle braces, cross braces, lattice work, bolted connections, rivet heads, faying surfaces, and flange edges are all troublesome areas to blast clean (Figure 7). To obtain a good painting job the contractor must fully understand the requirements of the surface preparation specifications. Demonstrations of surface cleaning by abrasive blasting at the bridge site prior to job bidding have proved quite successful in showing the contractor what degree of cleaning is acfually expected. Color photographs of the surface preparation or retained panels may be taken at this time and then used by the inspector throughout the course of the job. It is almost a certainty that the surface preparation will not meet the requirements of the specification if the contractor does not provide the ap-
propriate scaffolds and equipment to make the work area safe and accessible (Figure 8). It is also extremely important that the inspectors be able and willing to climb anywhere on the structure where inspections are necessary. The cost of preparing bridge surfaces by abrasive blasting can vary significantly depending on the structure type, structure condition, and the grade of surface preparation specified. The type of dust containment required can also have a significant impact on costs. B. PAINT APPLICATION The fundamentals and equipment for paint application, discussed in a separate chapter, are entirely applicable to bridge painting. (See SSPC-PA 1.) However, bridge painting also presents certain unique problems and considerat ions. The choice between roller, brush, conventional spray, or airless spray depends on the type of paint, the size of the job, the conditions at the site, and the capabilities of the contractor. Brushing and rolling are suitable primarily on spans over residential areas and for small touchup jobs, to reduce overspray, or in some instances, to comply with union restrictions. Many of the newer, high-technology coatings, such as zinc-rich primers, vinyls, high-build coatings, epoxies, and high-build coatings require spray techniques. Airless spray technique allows the use of more viscous materials than conventional spray. For trusses, lattice-work, structures with excessive bolts, and for painíing in confined spaces, airless spray may deliver too much material per unit of time. It becomes impossible to avoid excessive paint build-up on these areas. For such applications, conventional air spray, which allows greater control of the rate of paint application, is preferred. Whichever type of spraying equipment is used, it is important to keep the paint in the spray pot continuously agitated in order to prevent pigment settling. The air supply lines of the spray painting equipment should be equipped with water separators to insure a moisture-free air supply at the spray gun. Tip size and fan selection are especially important for efficient operation. FIGURE 4 Skyway Bridge illustrating through truss and deck truss. Courtesy of Florida DOT Copyright The Society for Protective Coatings Provided by IHS under license with
SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 284
SSPC CHAPTER*LL.O 73 8627940 0003732 463 FIGURE 5 Golden Gate Suspension Bridge, San Francisco, California. The SSPC has cooperated with the Golden Gate Bridge Highway & Transportation District in conducting tests of alternate paint systems on this bridge over a period of many years. These include evaluation of more than 20 alternate zinc-rich systems as well as other generic types. Similar cooperative SSPC tests have been conducted on bridges throughout the country. Courtesy Golden Gate BH&T District In structural steel spray painting, the primer coat should be applied in multiple spray passes to achieve a full wet coat without sags, runs, or dry spray. The intermediate coats (contrasting tint) and finish coat should be applied in the same manner. Areas that are difficult to paint such as rivets, bolted connections, flange edges, etc. should receive extra spray passes to insure good coverage and film build. When oil-base paints are used, it is advisable to brush the first primer coat application on the hard-to-paint areas; these areas are frequently also the ones not thoroughly cleaned. Additional coats of paint may then be applied by spraying. The paint inspector should be familiar with the paint materials used and should have knowledge of the proper spraying techniques. The inspector should observe the spraying techniques of each painter and should know the number of spray passes that are necessary to build the required paint film thickness over a given area. For many coatings (particularly new synthetic polymers) excessive film buildup may be as detrimental as too little paint. For inorganic zinc-rich primers, too heavy an application can lead to mudcracking and to problems of topcoat adhesion, bubbling, and pinholing. With inorganic zinc-rich primers, special care is needed to insure a uniform wet coat application without incurring dry zinc overspray. Inorganic zinc dry spray can result if conditions are windy and the spray pass is not 285 close enough to the surface. The dry spray can cause adhesion problems, and should be removed prior to application of the intermediate coats or finish coat. Constant agitation and short hoses help application and maintain zinc suspension. When practical, painting should be done during warm dry weather. The lower range of temperature at which paint may be applied depends on the generic type of paint used. It is, however, frequently limited by specification to 40°F (4°C). Most catalyzed epoxies will not cure below 50°F (lO°C),whereas inorganic zincs and vinyls can often be ap-
plied at 32°F (OOC). Most types of paint thicken in cold weather, and the painters use thinners to facilitate application, resulting in a thin coat of paint, adhesion problems, and poor film integrity. As a general rule, the specifications and the manufacturer's recommendations should be followed exactly. When the relative humidity of the air is greater than 85%,there is a danger of condensation of moisture on the steel with consequent bad effects upon the paint, particularly in regard to surface adhesion and water entrapment. Painting is usually not recommended until the relative humidity drops below 85% and the wind velocity is less than 15 mph. Surface temperature of the steel should be at least 5°F (3°C) above the dew point. It is important to be aware of the cooling and heating characteristics of the steel being painted. The surface temperature of the shady side of a structural steel beam may be several degrees cooler than the sunny side. Small members cool and heat more rapidly than the large structural elements. Exteriors of sealed boxes may reach temperatures of 130°F (54°C). C.TYPES OF PAINTS USED A survey of forty State Highway Departments conducted in 1968 by the Steel Structures Painting Council showed that lead-containing oil base and oillalkyd base paint systems were the primary paint systems used to paint highway bridges and structures throughout the United States3. In 1979 these systems still ranked first in overall usage. However, since 1968, organic and inorganic zinc-rich coatings have gained significant support. Over twenty-five states now allow the limited use of zinc coating systems4. Florida, for example, has used inorganic zinc-rich FIGURE 6 Modern mobile sandblasting unit. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*LL-O 93 W 8627940 0003733 3TT m FIGURE 7 Difficult areas to blast clean. primers on 90% of the bridge painting jobs contracted since 19705. Many states specify inorganic zinc-rich primers for new construction while maintenance painting continues to be done with oil-based or alkyd paints. Some states have specifications covering organic zinc-rich primers for repair work as well as new construction. Vinyl topcoats are commonly specified over zinc-rich primers. Both the low-build type applied by conventional air or airless spray and the high-build type applied by airless spray are in use. State specifications commonly require that the vinyl topcoat be supplied by the manufac- , turer of the zinc-rich primer to avoid compatibility problems. A tie-coat or mist coat may be necessary for this purpose. Several states permit the use of all-vinyl coating systems. The first coat is normally the vinyl butyral wash primer (e.g. DOD-P-15328or SSPC-Paint 27, followed by two or more coats of vinyl paint. Concern over restrictions on solvent emissions has stimulated interest in water-borne coatings. Florida DOT has been evaluating leaded and non-leaded water-borne systems on structural steel since 1975. In 1978, three inland bridges over fresh water were painted with the most promising of these systems. California DOT (Caltrans) has done extensive testing of water-borne systems, including both latex primers and topcoats, while avoiding the use of lead compounds. A styreneacrylic latex primer and an aluminum-pigmented acrylic latex topcoat have been applied to over fifteen structuresg. Other coatings that have been used include the follow ing: Epoxy Esters Catalyzed Epoxy Catalyzed and MoistureCured Urethanes Aluminum-Filled Epoxy Mastic Chlorinated Rubber Modified Alkyds (Silicone) Coal Tar Epoxy Coatings with Lead and Chromate-free Vinyls Inhibit ive Pigments Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS--`,,,,`-`-`,,`,,`,`,,`--Oil-Alkyd Coating System
Surface Preparation: Hand or Power Tool Cleaning (SSPC-SP 2 or SSPC-SP 3; SP 6 sometimes used to enhance longevity of system) Primers: (1) AASHTO M-72*,** or TT-P-86 , Type III, OilAlkyd Paint containing red lead (2) AASHTO M-229* or Federal Specification TTP-615*,**, Oil-Alkyd Paint containing basic lead silico chromate (3) SSPC-Paints 1*, 2*, and 25 Topcoats: (1) Federal Specification TT-E-489, High Gloss Alkyd (2) SSPC-Paints 101, 102, 104, and 108, Alkyd Topcoats Organic Zinc/Vinyl Coating System Surface Preparation: Commercial Elast Cleaning (SSPC-SP6) Primer: SSPC-Paint 20 Type II or Paint 29 Type II Tie-Coat: Vinyl Butyral Wash Primer (DOD-P-l5328*, SSPC-Paint 27* Topcoat(s): Vinyl Paint, e.g. SSPC-Paint 9 *Contains lead or chromate * *Canceled FIGURE 8 Portable rolling scaffolding. Courtesy of Florida DOT 286
SSPC CHAPTER*LL-O 73 8627940 0003734 236 W Inorganic Zinc/Vinyl Coating System Surface Preparation: Near-White Blast Cleaning (SSPC-SP 10) Primer: Inorganic Zinc-Rich; AASHTO M-300, see also SSPC-Paint 20 Type I or 29 Type I Tiecoat: Vinyl Butyral Wash Primer (DOD-P-15328* or SSPC-Paint 27*) Topcoat(s): Vinyl Paint, e.g. SSPC-Paint 9 Note: Variations on the zinc-rich systems include elimination of the vinyl wash primer and use of high-build vinyl topcoat. Organic or Inorganic One-Coat Zinc-Rich System See SSPC-PS 12.00 and PS 12.01 based on SSPC-Paint 20 Zinc-Rich, or Paint 29 Vinyl Coating System Surface Preparation: Near-White Blast Cleaning (SSPC-SP 10) Primer: Vinyl Butyral Wash Primer (DOD-P-15328* or SSPC-Paint 27*) Intermediate Coat: Vinyl Paint (SSPC-Paint 9, 2 coats) Topcoat(s): Vinyl Paint (SSPC-Paint 9, 2 coats) Water-Borne Systems Surface Preparation: Commercial Blast Cleaning (SSPC-SP 6) PrimerTTopcoat: Latex. Corrosion-Resistant (acrylic), SSPC-PS 24 Table 2 below gives typical coating systems for field repainting for representative bridge conditions and environments. SSPC-PA 2, Measurement of Dry Paint Thickness with Magnetic Gages and SSPC-PA Guide 4, Guide to Maintenance Repainting with Oil Base or Alkyd Painting Systems 16 give guidelines for application. D. LIFE EXPECTANCY OF BRIDGE PAINTS Life expectancy for paint on highway bridges depends upon the following factors: type of bridge, surface preparation, application of the paint, quality of paint, suitability of paint system to bridge design, number of coats, and climatic or other field conditions. With these variables, bridge paint may last from one to fifteen or more years. A bridge in a severely corrosive location with a poor quality of paint applied to an unprepared, dirty or wet surface will no doubt suffer early failure. A bridge located in a dry, rural atmosphere with the best of paint properly applied to a well-prepared surface is expected to be protected for many years. Because maintenance cleaning and painting is expensive, the longest possible paint life is usually the most economical.
An existing bridge exhibits a variety of surface and paint conditions. Any quantitative estimation of life expectancy of a paint system depends on the definition of criteria for failure. Frequently, a paint system is said to have failed if the amount of surface area rusted or deteriorated exceeds a threshhold figure (typically 16%). However, the distribution of deteriorated areas is often more important than the overall percentage. A structure may have a few areas subject to severe corrosion conditions that indicate localized paint failure, with the remainder of the paint in very good condition. In such cases a small amount of touch-up painting may add several years to the overall life of the paint. On another structure, blisters and rust spots may be visible on most of the webs, edges, and stiffeners; this situation would require a complete repainting. A given bridge may be hand- or power-tool cleaned, spot primed, and given two finish coats of paint after a certain number of years. The same bridge may possibly be allowed to stand twice this length of time and then be completely blast cleaned and given a prime coat and two finish coats of paint. Unless the latter method shows a considerable saving in cost over the first method, it will not prove economical because of the loss of metal through corrosion and abrasive blasting. Furthermore, the former method gives a greatly improved appearance over the years. The first maintenance painting after construction may compensate for lack of mill scale removal in the first surface preparation. Succeeding paintings often last up to 100 percent longer. On some bridges repeated applications of paint over 40 or more years results in excessive paint buildups (>25mils). This can cause film failure and shortened paint life even over intact mill scale. Several major bridges (principally toll facilities) have permanent paint crews so that the bridge is being cleaned and painted continuously. Many highway bridges are painted regularly, possibly every five to eight years; others in rural locations may not be painted more often than every ten or twelve years when regular maintenance is stipulated. In some jurisdictions, tight budgets and negligence extend the repaint cycle to 20 years or more. While data on the life expectancy of bridge paints vary considerably, it may be assumed generally that for a threecoat oil-base system on a well prepared metal base, the life expectancy in semi-dry and rural regions is from seven to fifteen years; the life expectancy for the same structure in humid, industrial, or marine regions is three to seven years. Inorganic zinc-rich coating systems have a life expectancy of ten years or more in a marine or industrial environment Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 287
SSPC CHAPTERtLL.0 93 m 8627940 0003735 172 m TABLE 2 Typical Coating Systems for Repainting Bridges Bridge Condition Mostly sound, intact paint (oil, alkyd) Severe corrosion in joints, connections, etc; rest of steel mostly sound Extensive deterioration paint, corrosion Extensive deterioration; mostly flat, accessible Extensive deterioration; many details, lattice work, etc. Environment All Humid, Marine, Industrial Mild Humid, Marine, Industrial Humid, Industrial Suggested Coating System Oil-Alkyd: spot hand-tool clean (SSPC-SP 2); spot prime; 1 or 2 full topcoats Organic ZinclVinyl: spot power-tool clean (SSPC-SP 3); or spot blast (SSPC-SP 7) topcoats (may require special tie-coat between old paint and vinyl) OiI-AIkyd: f u II blast (SSPC-SP 6); 3-coat system or Water- Borne: fuII blast
(SSPC-SP6); 2 primer coats; 2 topcoats. Inorganic Zi nclVi ny I: fulI blast (SSPC-SP IO); 2 or 3 coat system or Inorganic ZinclCatalyzed Epoxy1 Aliphatic Urethane: NearWhite blast (SSPC-SP IO); 3-coat system (for severe corrosion areas) Organic ZinclVinyl: full blast (SSPC-SP6); 3 or 4-coat system --`,,,,`-`-`,,`,,`,`,,`--and fifteen years or more in a rural environment. Organic zinc-rich and other synthetic polymer coating systems (¡.e. vinyl, urethane, catalyzed epoxy, chlorinated rubber) are considered superior to oil and alkyd systems, but not as effective as a well-applied high quality inorganic zinc system. For all of these newer coating systems the performance is strongly dependent on the specific formulation or brand selected. The water-borne coating systems are still in an early stage of development with only short-term field data available. The results indicate that these coatings should not be specified for conditions of high humidity or even for moderate industrial or marine environments. In certain mild environments, water-borne systems have given up to four years of good service, but have not yet demonstrated equivalance to standard oil-alkyd systemsg. In general, the deck beam and girder bridges in dry locations may be expected to have a maximum paint life, except for rail sections on parapet walls and raised medians of steel grill work. The latter are particularly subject to damage by deicing salts. Through bridges in dry locations or deck bridges in damp locations may be expected to have a somewhat shorter life. Certain sections of the bridge (e.g. expansion bays, pier caps, beam ends) might require added protection in situations in which oil-alkyd maintenance systems are considered suitable for most of the steel. IV. ADDITIONAL FACTORS INFLUENCING COATING SELECTION AND PERFORMANCE A. INSPECTION AND QUALITY ASSURANCE Quality assurance is the total process by which the state insures that the workmanship and materials meet the requirements of the contract and specifications. The key to quality assurance of highway bridge painting is inspection. In all cases of field cleaning and painting of highway bridges, the structure should be thoroughly inspected and
repaired before any cleaning or painting is allowed. Bent parts should be straightened. Rivets and bolts should be Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 288
checked for tightness and replaced when necessary. Rail- Inspection is particula rly important when using zincings should be checked for alignment and strength of con- rich, water borne, and other high-technology coatings. nections. Drains, floor expansion devices, shoes and bear- These coatings are mu ch less forgiving of poor or imings should be cleaned and repaired. proper surface preparation and paint applic ation techAn important duty of the inspector is to see that the niques compared to the oil and alkyd paints they are steel surfaces to be painted are clean and dry. The inspec- replacing. tor must obtain samples of the paint. The paint should then be tested in the laboratory to make certain it meets the B. ECONOMICS OF BRIDGE MAINTENANCE specification. The inspector should retain certified copies PAINTING of test reports. Inspectors must see that the paint is prop- The subject of cost s for coatings, surface preparation, erly mixed and applied; of uniform thickness and ap- and application has been di scussed elsewhere in this pearance; without sags, runs, or pools of excess paint; and manual. It should no t be assumed, however, that the most that rivet and bolt heads, edges and corners are thoroughly cost-effective coati ng system will be chosen. As shown in covered with each coat of paint. a recent FHWA report, the budgets for maintenan ce paintThe inspector has a continuous responsibility during ing of highway bridges is c onsiderably below that which is the cleaning and painting processes. The cleaning must be needed . Because of the limited funds, it is difficult to closely and promptly checked to ascertain the quality of convince bridge officia ls or legislatures to invest in the work. This will prevent the expense and delay entailed coatings with higher initial cost, although they may prove in the replacement of scaffolding and equipment. The least costly over an extend ed period. equipment and materials used for abrasive blasting, hand- For most bridges, the repainting consists of spot and power-tool cleaning, and cleaning fluids should be cleaning and priming the rusty or failed areas, followed by checked against the specifications. The paint should one or two full topcoats. N ormally, the decision to repaint always be checked to make sure it has been received from is based on an inspecti on report or as part of a fixed the proper source approved for the job. maintenance cycle. Significant savings w ould be realized if The inspector must witness all facets of the job. His the repainting were done b efore the appearance of exfailure to discard poor materials or stop faulty work is --`,,,,`-`-`,,`,,`,`,,`--cessive rust or failed paint which must be removed. Timely
almost equivalent to giving the engineer s approval of such repainting would great ly reduce the labor costs of surface practices. The inspector must see that all debris is re- preparation and priming . Too often, structures are not moved from the site at the conclusion of the work, that painted until they displ ay major signs of failure and corroconcrete is not spattered with paint, or surroundings sion. defaced. Much helpful information on inspection is included in Volume 1. Last, but not least in importance, adequate C. SAFETY PRECAUTION S information for permanent records of the painting job must be kept. The best workmanship can be expected only when proper attention is given to the safety measures provided for the work force involved in the painting of steel. Safety precautions issued by the American National Standards Institute (ANSI) and the National Safety Council (NSC) should be practiced. Additional sources of information are available from SSPC-PA Guide 3, A Guide to Safety in Paint Application and the pamphlet Play It Safe and Healt hy O. 1. Pathological The cleaning and painting of structural steel involves certain health hazards of which the owner and applicator must be aware. Chipping, grinding, and wire brushing of steel give rise to flying particles of steel, scale, and dirt, which could cause eye trouble unless goggles are worn. Dust particles, particularly those arising from sandblasting, may, after prolonged exposure, result in silicosis, or other lung diseases. Workers who are habitually exposed should be required to wear cartridge respirators or forced air helmets. Similarly, fumes arising from certain paint removers containing carbon tetrachloride or methyl FIGURE 9 Checking dry paint film thickness. ethyl ketone, and from the paint solvents, ma y conCourtesy of Florida DOT stitute a health hazard. In such cases, and when paint 289 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERxLL.0 93 H 8627940 0003737 T45 W is sprayed, adequate respirators should be used. Work clothes should be laundered frequently. When cleaning or painting is being done on the inside of tower legs or other large steel members, either an adequate ventilation system should be installed or respirators supplied with clean air should be used. Workers should eat with clean hands and faces in a clean, well ventilated location. No type of gasoline, leaded or unleaded, should ever be used as a solvent for personal cleaning. 2. Acciüents Falls from ladders and scaffolds are a frequent source of injury to workers who are cleaning and painting bridges. The supervisor in charge of field work should continually warn his crew to use precautions to prevent such accidents. All scaffolds, fixtures, hangers, cables, and ropes should be inspected by the job foreman each day, or before each use. Any defective scaffold plank, cable, or rope should be discarded and replaced with new equipment. All standing or hanging scaffolds should be inspected daily for strains or weaknesses caused by wind sway. Engineers and contractors should be familiar with the Occupational Safety and Health Administration (OSHA) Regulations for Construction, Part 1926. 3. Ladders Ladders used for access to scaffolds or other parts of the bridge should be securely lashed in place or provided with hooks at the top end. Lattice work on beams should not be used for climbing; a permanent metal ladder or a securely lashed ladder should be used. Ladders should never be permitted to stand in the roadway unless protected by red warning flags with an attendant on the traffic side of the ladder. 4. Boatswain s Chairs If a boatswain s chair is used, the worker should be fastened into the seat with a safety strap. Boatswain s chair ropes and pulleys should be inspected daily by the foreman on the job and the person who is to use the equipment. The following precautions should be observed: An attendant (not the person in the chair) should always be assigned to handle the hoisting and lowering of the chair. The chair should be attached to the gantline, using either a double becket hitch or a bowline hitch. The sling, or safety strap, must be securely fastened. 5. Life Lines Life lines should be used where required in accordance with OSHA regulation. In some cases contract provisions state that ropes and cables not be placed
on, or drawn across, freshly painted beams. This makes it difficult to use lines in some cases. Where life lines are used very little slack should be allowed -not more than two or three feet, preferably less, although this is difficult to enforce. A long line will foul easily and be heavy for a person to drag. Injury is sure to result if the person should fall. Life belts with a D ring in the back should always be used in conjunction with life lines; a loop of rope around the person s body should not be employed. Special care is necessary in extremely cold or hot weather to make certain that life belts are used and are in good condition. In very cold weather, a person s hands become numb, which could result in loss of grip, while hot weather sometimes causes dizziness. 6. Life Nefs Another effective form of protection is the life net. It may be erected under either individual scaffolds or complete bays of the bridge. Where used, the net should be inspected and kept in good condition. 7. Fire Most bridge paints and volatile liquids used in conjunction with them are flammable and should be kept in closed containers away from fires. Paints and thinners should not be stored on bridge decks, even in trailers. Smoking should not be permitted inside of paint storage rooms or near these flammable materials. Rags used to wipe paint and oils should be kept in a metal container in the open air away from stored paint materials. Great care should be exercised when painting in closed spaces since explosions may occur if the vaporized flammable solvent reaches the explosive concentration range. D. REGULATIONS IN EFFECT Environmental, health, and safety regulations are becoming an important factor in the choice of coating systems for bridges. Replacements for lead and chromate pigments have shown reduced ability to protect against corrosioni1. In addition, the performance of these coatings is very sensitive to the specific paint formulation, unlike the conventional lead and chromate pigments, which have been effective in a wide variety of binders and compositions. Thus, for the lead and chromate-free paints, the quality assurance of the coatings will be more critical. All of the states are required to submit State Implementation Plans (SIP) to the Environmental Protection Agency (EPA)12, describing how they plan to meet the clean air standardsi3. The published EPA guidelines did not specifically require any State action to control bridge coatings. It is expected, therefore, that until EPA issues more definitive guidelines, control of organic solvents in paints will be regulated at the local level. The anticipated restriction of solvents from the
California Air Resources Board (CARE) has led the State s highway laboratory (Caltrans) to develop and evaluate water-borne coatingsi4. Although there have been advances, there are still some severe problems in field usage of water-borne coatings. The requirements for surface preparation and application are more critical than for oilbased solvent-borne paints. In addition, water-borne coatings have not yet demonstrated the ability to provide Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 2i90
SSPC CHAPTER*LL=O 93 8627740 0003738 781 long-term protection in humid, polluted, or salt environment~~. The practice of open-air sand blasting, recognized as the most efficient and effective way to prepare surfaces for maintenance, produces several undesirable effects, including silica particles, dust clouds, and deposition of lead-containing paints in the environment. Efforts have focused on alternative methods for preparing surfaces such as water blasting, wet abrasive blasting, containment devices, acid cleaning, and non-silica abrasives. It is virtually certain that the newer methods will add significantly to the cost of surface preparation of bridges. Overall, the regulations are expected to have the following impacts on highway painting practices. (1) Decreased level of performance due to replacement of lead and chromate pigments, elimination of organic solvent, and use of less effective and more costly surface preparation techniques. (2) Need for greater attention to quality of surface preparation, application, and inspection. (3) Increased costs of protecting bridges due to increased costs of surface preparation, insurance, safety, equipment, coating materials, and training. (4) More frequent repainting to maintain same level of performance. The above factors will require greater allocation of funds for bridge maintenance painting. However, maintenance painting activities are competing with other --`,,,,`-`-`,,`,,`,`,,`--maintenance and construction needs for increasingly scarce highway funds. The availability of the funds needed to assure protection of the nation's bridges is still uncertain. Shortages of these funds would result in a general deterioration of their condition and safety. ACKNOWLEDGEMENT Particular recognition is due to Tom Shelley of CALTRANS for his advice and contribution to this chapter. The authors and editors also gratefully acknowledge the active participation of the following in the review process: Duane Bloemke, Carl Bye, John Conomos, Raye Fraser, S.C. Frye, Clive Hare, Preston Hollister, Robert J. Martell, Doug Nash, Charles Ray, Gary Tinklenberg and William Wallace. BIOGRAPHY Richard R. Ramsey received a B.S. in Chemistry from Otterbein College in 1959. For the past 15 years he has been a Materials Research Chemist
for the Florida Department of Transportation. His primary research interest is in coating systems for structural steel. He has been a member of NACE for 10 years. A biographical sketch and portrait of Dr. Bernard R. Appleman appear at the end of Chapter 2.8. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 291
SSPC CHAPTERULL.0 93 9 8627940 0003739 818 9 REFERENCES 1. S. Frondistou-Yannas, Coating and Corrosion Costs of Highway Structural Steel . Report No. FHWA/RD-79/121, March 1980. 2. J.D. Keane, J.A. Bruno, and R.E.F. Weaver, Surface Profile for Anti-Corrosion Paints . Report No. FHWA-PA-71/14, 1976. 3. J.D. Keane, Protective Coatings for Highway Structural Steel . National Cooperative Highway Research Program (NCHRP). Reports 74 and 74B, 1969. 4. C.J. Ray, F.A. Rideout, and L.E. Henton, Coating Systems for Painting Old New Structural Steel . NCHRP Report on Study 4-14, 1982. Published by Transportation Research Board, Washington, DC 20415. 5. Florida Department of Transportation: Standard Specifications for Road and Bridge Construction, 1977, Sections 560-562 and 971. 6. R. Warness, Water-Based Coatings for Protection of Steel Structures . Report No. FHWA-CAITL-79/24, November 1979; Low Solvent Primer and Finish Coats for Use on Steel and Other Structures . California Department of Transportation Research Study D-3-69 (604186), 1980-1982. 7. American Association of State Highway and Transportation Officials, Standard Specifications for Transportation Materials and Methods for Sampling and Testing . Part I Specifications . July 1978, Washington, DC 20001. 8. California Department of Transportation: Standard Specifications (Paint, Primer, Zinc-Rich Organic Vehicle Type); and Standard Special Provisions (Water Based Paints), 1981. 9. J.A. Bruno, and J.D. Keane, Evaluation of Low-Solvent Maintenance Coatings for Highway Structural Steel . Report No. FHWAIRD-811019, December, 1981; Annotated Bibliography, Report No. FHWA/RD-81/091, December, 1981. 10. Play It Safe and Healthy . (1967-72, 79), International Brotherhood of Painters and Allied Trades, United Unions Building, 1750 New York Avenue, N.W., Washington, D.C. 11. B.A. Appleman, J.A. Bruno, and R.E.F. Weaver, Performance of Alternate Coatings in the Environment (PACE) Volume I . Steel Structures Painting Council, i989. 12. Policy Statement on Use of the Concept of Photochemical Reactivity of Organic Compounds in State Implementation Plans for Oxidant Control . Office of Air and Waste Management and Office of Research and Development, U.S.Environmental Protection Agency, Research Triangle Park, North Carolina, December 5, 1975. 13. Air Quality . Federal Register 42, No. 131, pp. 353146, 1977. Most States Ready to Enforce Air Pollution Regulations . Products Finishing, 44, No. 12, pp. 546, September, 1980. 14. State of California Air Resources Board. Model Rule for Architectural Coatings . July 7, 1977. See also American Paint Journal; December 8, 1980, ((pp. 7-8); August 17, 1981, (pp. 45-46): November 2, 1981 (pp. 7-8, 12). 15. Steel Structures Painting Manual, Volume 2 - Systems and SDecifications . John D. Keane, ed. Steel Structures Paintina Council, 1982. 16. SSPC-PA 4, Shop, Field and Maintenance Painting . Steel
Structures Paintina Council, 1982. 17. SSPC-VIS 2, Standard Method of Evaluating Degree of Rusting on Painted Steel Surfaces , Steel Structures Painting Council. 1976. --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 292
SSPC CHAPTER*LZmO 73 m 8b27940 0003740 53T m CHAPTER 12 PAINTING OF VESSELS FOR SALT WATER SERVICE by David T. Bloodgood I. INTRODUCTION drydocking a supertanker runs into hundreds of thousands --`,,,,`-`-`,,`,,`,`,,`--The transition of shipbuilding from wood to ferrous of dollars, not including th e revenue lost while the ship is materials subject to corrosive attack by the environ-out of service. Thus effect ive corrosion control and antiment made it necessary to provide suitable methods fouling measures during const ruction are of utmost imto protect these materials. Coating systems comprised portance to the ship owner loperator. Also, strong conof dense barrier coats or containing inhibitive pigments sideration should be gi ven to repairability of coatings and can effectively protect against corrosion. Finish coats coating systems. When a ship is being constructed, areas are applied to improve appearance and to protect primers to be coated are usuall y accessible, and sufficient time against external influences so they retain anticorrosive can be spent on prepara tion and application. While in drydock, however, conditions for work can be marginal. propert ¡es. This chapter describes present day practices for ap- When coating systems are se lected, therefore, the overall plication, coating materials and surface preparation for all cost effectiveness should be studied, including cost of surfaces on a ship subject to corrosion. New construction maintenance, repair, a nd out-of-service costs. will be discussed separately from maintenance and repair Surface preparation and coating application tradibecause modern construction procedures have made con- tionally are the last sche duled and least considered struction coating procedures quite different from those operations of constructi on. Coating during the modular in maintenance and repair. Protection problems vary stage of construction has pa rtially relieved some probamong ship types such as tankers, freighters, bulk carriers lems, but has create d others. Final coating is still dependand small work boats. Specialized problems often arise in ent on the work schedu les of other crafts involved, whether a particular service, but answers will usually be evident if it is new construct ion or maintenance and repair. As a
fundamental principles of marine corrosion and its preven- result, efficient pla nning and operation must be maintion through the use of coatings are understood and tained if costs are to be li mited. followed. A. THE PROBLEM This discussion is limited to commercial vessels. Naval vessels are considered a special case and are When a vessel is built, cons ideration is given to how covered in a separate chapter. Even though surface to protect metal surfaces aga inst the environment. preparation, coating materials and application are Coatings are the primary meth od to protect surfaces. The generally the same, service requirements for naval vessels type of coating appli ed, surface preparation and film are different from those of commercial operators. Navy thicknesses will, to a de gree, depend on expected service criteria for testing and approving coating materials and conditions, such as sal t water immersion, fouling, atsystems are often a guide for selection of items by the mospheric exposure, etc. Often, cargo tanks should be marine community, and Naval approvals of proprietary coated to protect the steel from corrosion and the cargo systems often lead to acceptance of the systems by com- from contamination. mercial operators. Destruction of a coating film and subsequent protection breakdown is caused by steel rusting beneath the coating. Rusting occurs because of a reaction of the steel II. GENERAL DISCUSSION substrate with water and oxygen that diffuse through the Coating applicators and equipment manufacturers film. must follow government regulations covering application In a rural environment, good protection can be oband use of coating materials. For instance, the effects of tained by minimizing diffusion with a highly impervious surface preparation on air and water pollution is of con- film that functions as a barrier coating. In more aggressive siderable concern. Rules and regulations to control pollu- marine environments t he rate of corrosion is greater, partly tion add costs and other burdens for the shipyards. due to the presence of solub le gases and salts. Those Coating systems that minimize maintenance and the gases and salts ionize and dif fuse through the film. Corrofrequency of drydocking are cost-effective. The cost of sion is accelerated by c hemical attack on steel and elecCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 293
SSPC CHAPTER*LZ.O 93 Ab27940 0003743 476 trolytic action. The need for a high performance coating system in these circumstances is paramount. The underwater area of a ship can be one of the most critical areas for protection. Because it can be observed only while the vessel is in drydock or through a perfunctory inspection by divers, coating systems and other methods of corrosion control, such as cathodic protection, become increasingly important. Hull roughness, which is caused by corrosion, breakdown of the coating system and fouling can cause a loss in speed. To compensate for speed loss an increase in power and fuel consumption is required. Never in the history of the maritime industry has vessel downtime been so expensive. Drydock charges range from $10,000 to $30,000 and more per day, depending on the vessel s size. This, plus costs for yard labor and materials to prepare a dirty and fouled hull for coating, tends to make ship owners delay the chore until the very last minute. Many owners wait until seasonal slowdown or the deadline for its classification survey to minimize lost income while the vessel is out of service. Balanced precariously against the high cost of maintaining a vessel is the even higher cost of delaying maintenance for too long. Most vessel operators know that between 10 and 20 percent more power is required to maintain speed because of fouling (underwater marine growth on the hull and propeller) or because of hull roughness caused by pitting from corrosion. The increased cost of petroleum fuels and their potential scarcity, the need for extra power to stay on schedule, or additional voyage time from running at reduced speed to conserve fuel can quickly exceed the cost of recoating. A VLCC (Very Large Crude Carrier) operating at a reduced speed of 13 knots can consume more than $700,000 in extra (wasted) fuel during a 30-month drydock cycle because of drag caused by fouling. A typical 250,000 deadweight ton (dwt) tanker, with its hull freshly coated and smooth, will run at 13 knots with an output of approximately 14,500 shaft horsepower (shp). A year later, 16,000 shp will be required; by the end of two years 20,000 shp is required, and by 30 months the required shp will have gone over 21,000 -an increase of almost 30 percent. Operated at full power to hold schedules, the same tanker will start running close to 17 knots, drop to 16 knots after one year, 15 knots after two years and finally, struggle along after 30 months at 14.5 knots -with its engines developing full shp. Drastic increases in fuel consumption require vessel operators either to shorten the drydock cycle or to resort to interim hull maintenance, such as underwater cleaning to reduce hull drag caused by fouling. In addition to the general difficulties presented by
ships operational schedules, marine coatings must have many specific resistances. Even though areas on ships differ greatly, the following conditions are among those that cause the most trouble: 1. Presence of salt water, an excellent electrolyte for the promotion of corrosion. 294 2. Alternate immersion, such as alternate exposure to the air, sunlight and salt water, causing premature failure of coating materials. 3. Abrasion damage from rubbing against piers, tugs, loading barges, or the bottom when operating in shallow waters, etc. 4. Fumes from stack gases and port environments. 5. Pollution of waters in harbors and docking areas that may attack coatings. 6. Air pollution caused by industrial smogs. 7. Wide range of temperature, humidity and other conditions during application and service. 8. Cargo splash and spillage. B. ECONOMICS The economics of painting ships in service is complicated by the uniqueness of the services they perform and their size. A ship is only serving its function when moving cargo from one point to another. Each day a vessel spends tied at a shipyard represents a financial loss to the owners. Depending on prevailing cargo rates and the ship size, this loss can total thousands of dollars a day. When calculating the cost of repairing corrosion damage, it is first necessary to multiply the extra days in dock by daily charges and losses. Losses due to corrosion are usually represented by work, such as renewing welds, replacing steel, renewing piping, repairing equipment, installing new gear, etc. Large sums of money involved in ship repairs make it apparent that controlling corrosion, can reduce costs. Any effective corrosion preventive measures that can be applied when the vessel is built, or installed at regular visits to a shipyard necessitated by regulatory bodies (such as American Bureau of Shipping s Survey Requirements), should prove economical. Section 45 Surveys after Construction of the Rules for Building and Classing Steel of the American Bureau of Shipping shows there are definite intervals during the life of a ship when it must undergo inspection for corrosion damage. Some special surveys normally take a ship out of service for several days. This is an opportune time to consider corrosion prevention. High dollar value for a ship s availability requires a ship owner to study the total economics of corrosion protection with performance requirements and cost of installation compared with dollar returns. For high grade coatings there is usually a higher grade surface preparation required, which normally translates into time. The optimum time for coatings and other corrosion preventive measures is during construction. All areas of the vessel are more accessible at that time (Figures 1 and 2). During construction, conditions are more suitable for
surface preparation and coating than at any other time during a ship s service life. Maintenance planning should begin during design and be incorporated into construction. At this time a vessel owner should establish a tentative hull preservation and maintenance program. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*L2.0 93 8b27940 0003742 302 = FIGURE 1 Unit Construction of Ship. Courtesy: Bethlehem Steel Corp. C. SURFACE PREPARATION The effective life of any coating system depends on the condition of the surface to which it is applied. The surface preparation required may vary depending on the severity of service to which it will be subjected and the type of coatings applied. In an environment with any degree of aggressiveness, the higher the degree of surface preparation the longer the expected coating life. Surface preparation is so important and diversified that it is examined in several chapters of this volume. Standards for surface preparation have been developed by several organizations. The most widely used, particularly in the marine industry, are the Steel Structures Painting Council (SSPC) Specifications, which describe requirements for surface preparation from hand cleaning to abrasive blasting. Abrasive blasting specifications have been supplemented by pictorial standards, such as the Swedish Standards. Other pictorial standards are found in a publication offered by the Society of Naval Architects and Marine Engineersc3). The National Association of Corrosion Engineers also has standards for abrasive blasted steel. Abrasive blasting is the primary method used by shipyards for surface preparation. Blasting results in the required degree of surface cleanliness and surface profile with the greatest economy on large areas. For small areas, power or hand tool cleaning is generally accepted and is the most economically feasible. In repair yards, high pressure water jetting is used for removing fouling and loose paint from underwater hulls and for cleaning heavily scaled surfaces. Environmental regulations have an impact on surface preparation. Open air blasting is being scrutinized because of dust and health hazards associated with abrasives containing free silica or similar material. Closed cycle blasting machines have been developed for cleaning hulls and decks. Water blasting is being utilized on a larger scale by repair yards, but problems with pollution arise because of regulations against foreign matter being dumped into the water. The cost of surface preparation is increasing rapidly, partly due to these restrictions and regulations. 1. Abrasive Blasting Automatic blasting is an airless blasting technique (Figure 3) using a rotating wheel to throw abrasives at a surface at a high speed with great
force. Abrasives normally used, steel shot andlor grit, are recycled. The initial cost of abrasives is high, but recycling reduces the quantity per square foot of blasted surface, which makes their use viable and economic. The efficiency and effectiveness of this type of blasting is well documented. It is used by most new construction yards for preparing plates and shapes prior to assembly. Mill scale, rust scale and rust are primary contaminants that must be removed. Most new construction yards using this method for initial cleaning of plates and shapes apply a primer immediately after blasting, usually a pre-construction or after-blasting primer. This maintains the condition of the blasted surface during fabrication of units prior to application of specified coating systems. Portable closed-cycle blasting machines for cleaning hulls and decks are available (Figures 4, 5 and 6). Their importance increases as regulations against use of open air blasting become more prevalent. Small parts can be cleaned very efficiently and economically in closed cycle blasting cabinets by one person. These cabinets are available in a variety of sizes and capacities. 2. Nozzle Type Blasting This method (Figure 7) utilizes air to impart kinetic energy to the abrasive particles and is the FIGURE 2 Unit Construction of Ships. Courtesy: Bethlehem Steel Corp. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 295
SSPC CHAPTERUL2.0 73 8627940 0003743 247 FIGURE 3 A Typical Pre-Fabrication Structural Steel Cleaning Machine. Courtesy: Wheelabrator-Frye Co. most common and widely used method of cleaning in shipyards. Because of the large surfaces to be cleaned, it is the fastest and most economical method for field cleaning. In new construction yards, initial coatings are applied in the modular stage. Except for yards that have large facilities for centrifugally blasting modular units, nozzle blast cleaning is used. Most of this is done in an enclosed area where conditions can be controlled (Figure 8). Buildings in a number of yards have installed recycling systems, using steel grit, which falls through grated floors and is reclaimed just as in the closed cycle blasting machines. Other yards use mineral abrasives for blasting in blast and paint facilities. There is normally no recycling of these abrasives; therefore, vacuum systems andlor manual disposal is required. What is a viable and cost effective method for one yard may not be for another because of capital outlay, space allocation, climatic conditions, etc. Nozzle blasting is used to meet surface preparation requirements in tanks and on ships requiring recoating in drydock and to make other shipyard repairs. 3. High Pressure Water Cleaning High pressure water cleaning has been extensively used as a cleaning method for existing paint systems to remove haunches (barnacle roots), weed growth, loose paint flakes etc. The pressure required for this work does not usually exceed 137.9 to 206.8 bar (2000 to 3000 Ib1in2). High pressure water cleaning can be used, however, to provide a white metal finish with pressure up to 689.5 bar (10,000Ib1in2).A suitable mechanism injects fine grit of 3001400 mesh to create a slurry. This system can also be used to dose the blasting water with suitable chemical inhibitors that passivates the cleaned steel surface until coating can commence or to feed in detergent to enhance chemical cleaning. High pressure water blasting minimizes health hazards, material costs and the need to
remove blasting media. One advantage is the complete removal of all residual salts from pitted Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 296
vantages over electric tools. Some of the advantages are: a. More power per pound; air-powered abrasive tools are lighter, smaller and easier to handle than electric tools; b. No overheating; c. Low maintenance requirements. Basic types of hand power tools used in the shipbuilding industry are abrasive wheels of various sizes and shapes, scalers and. chisels. For description of types, maintenance and use of hand tools, see the Steel Structures Painting Council Manual, Volume 1, and the Catalog of Existing Small Tools. for Surface Preparation and Support Equipment for Blasters and Painters , prepared under a research project sponsored by the National Shipbulding Research Program(8 . FIGURE4 Por.table Ship Deck Cleaning System. Official U.S. Navy Photograph steel. Failure to remove contaminants, such as chlorides and sulphates, is one of the main factors that cause premature breakdown of paint systems. Water blasting can be a relatively cheap and effective method for the removal of: --`,,,,`-`-`,,`,,`,`,,`--a. exhausted anti-fouling composition; b. loosely adherent paint, rust and marine fouling; c. included residual salts; d. calcareous deposits caused by cathodic protection. 4. Hand and Power Tool Cleaning To supplement abrasive blast cleaning for small areas and areas where abrasive cleaning cannot be used, hand and power tool cleaning are used. Power tool cleaning is the most widely used method in commercial shipyards. Most yards use air-powered abrasive tools because of certain adFIGURE 6 Portable Ship Hull-Side Cleaning System. Official U.S. Navy Photograph D. SURFACE TREATMENT There are times when surface treatments are used on steel and other metals. When steel is cleaned using water, such as in hydroblasting, wet abrasive blasting or chemical cleaning, it must be inhibited to prevent flash
rusting. Inhibitors are introduced at the time of cleaning or are an integral step in a sequence, such as in a chemical cleaning. Inhibitors must be compatible with the coating. Volume 1 of the Steel Structures Painting Manual provides FIGURE 5 Portable Ship Hull-Bottom Cleaning System. much information on chemical surface treatments. A Official U.S. Navy Photograph washcoat primer (Navy Formula 117, Military Specif icaCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 297
SSPC CHAPTER*L2-0 93 8627740 0003745 O11 W FIGURE 7 Abrasive Blasting Under Controlled Conditions. Courtesy: Bethlehem Steel Corp. tion, MIL-P-15328, although of diminished importance, is still used on aluminum and galvanized surfaces of ships as a bond coat for subsequent coatings. 111. COATING THE SHIP When ships were erected plate by plate, surface preparation and coating were done after erection. Now, plates and shapes are normally abrasive blasted prior to assembly of block sections, which are units that may weigh 200 tons or more. Part or all of the specified coating system are applied before erection except for butts and seams, which are left bare for welding. Coatings, in many cases, are applied under roof, permitting application over properly prepared surfaces with optimum temperature and humidity (Figure 9). Many large ships are built today in building basins (Figure 10). Because of the construction sequences the units are erected on permanent blocks. It is therefore necessary to apply a complete underwater system prior to placing the units on the erection blocks. This includes the anti-fouling paints. Many of these ships are not drydocked prior to delivery because of size; therefore, the complete anti-fouling system must be applied early in construction. The effectiveness of the modern anti-fouling coatings is not deterred by this long exposure to the atmosphere prior to being placed in the water. There is a severe galvanic corrosion burden on the anti-corrosive, particularly when copper-based anti-fouling paints are used. The anti-corrosive must be a good enough barrier to prevent attack on the steel by copper ions leaching out of the anti-fouling paint. Contact with steel, because of poor barrier coatings, can cause inactivation of the paint. Barrier coats must be highly impervious to water. An excellent discussion on inactivation of antifouling paints appears in Marine Fouling and Its Prevention 4 . Except in the presence of abnormal harbor pollution and chemical wastes, the rate of steel corrosion in sea water is approximately 75 to 150 microns per year. Anticorrosive coatings should be capable of protecting the steel of a ship s hull from attack by sea water and be inert to normal pollution. Abrasion resistance can be of considerable importance, depending on the type of ship, ports of call, etc. When deep ships serve port areas with insufficient water, the wearing away of bottom coating systems can result. Consideration must be given to ports of call, time spent in
port, time between drydocking and how these conditions will affect the underwater system. A. UNDERWATER HULL Underwater coatings, in addition to having antifouling capability, should have good corrosion resistance, provide adequate abrasion resistance and good service life. Ship bottom coating consists of an anti-corrosive coating and anti-fouling paint. When an underwater system fails prematurely, it is because of corrosion and the breakdown of the anti-corrosive barrier. 1. Coating Systems The most widely used underwater systems are conventional bottom systems, consisting of an aluminum barrier coat with a copper oxide toxic in a bituminous resin-rosin anti-fouling matrix. These systems are easy to apply and do not require stringent surface preparation. They are easily repaired and maintained. They are also the least expensive but provide acceptable quality. Life expectancies on initial application under good conditions should be about 18 to 24 months. Repairs and renewals should give 12 to 18 months between drydockings. Conventional systems are a softer film material than the high performance systems and erode faster. Therefore, service conditions and drydocking periods may dictate high performance systems, which have higher initial FIGURE 8 Unit In Building Being Prepared for Blasting and Coating. Courtesy: Bethlehem Steel Corp. 298 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS ~
SSPC CHAPTER*L2=0 73 H 8627740 000374b T58 FIGURE 9 Ship Construction in Building Basin. Courtesy: Bethlehem Steel Corp. cost but could be more cost effective. Systems specified for the majority of new construction, particularly tankers, LNG s and high speed ships, are chlorinated rubber, epoxy barrier coats with various resin anti-foulings and highbuild vinyl systems. These coatings provide highbuild (> 250 microns) and long life. To keep ships out of drydock for longer periods harder anti-foulings are used, which can be cleaned by scrubbing while still in the water (Figure 11). It is costly to take a vessel out of service, drydock it and refinish the bottom; and if this operation can be postponed or delayed, it can represent substantial savings. Once a bottom has been scrubbed, however, it must be closely monitored for recurrence of fouling, since scrubbing tends to reduce the effectiveness of the remaining anti-fouling coating. The selection of anti-fouling paint is governed more by the time a ship spends at piers than by the severity of fouling in the waters. It is rare to see an active tanker fouled because its turn around time is so short. Ships that spend much time in port, particularly in heavy fouling areas, should use a high-grade, anti-fouling paint. Copper toxics, such as cuprous oxide, are still the major anti-fouling ingredients used. Organo-metallics, such as organotin compounds, are used as toxics, by themselves and in combination with copper compounds. A combination system may give better overall protection from shell fouling and grass than only one ingredient. There are other methods of preventing fouling, such as through the use of polymer compounds with varying properties. These are being brought into the market and may, in the long run, offer great advantages by producing a smoother hull, through a self-polishing action over long periods. The potentials for fuel savings could be great. (For recommended underwater hull systems see Table I.) 2. Cathodic Protection Cathodic protection supplements the protection against corrosion provided by underwater coatings. Where coatings are damaged and bare steel is exposed, cathodic protection will alleviate
corrosion and avoid renewals due to corrosion. Properly designed and installed anode systems reduce steel waste to 30 percent or less of that experienced in unprotected structures in salt waterC5). Service histories also show that pitting is effectively arrested. The need for cathodic protection should be established through careful study of corrosion experience. For existing vessels, corrosion effects may be assessed by inspectors or repair superintendents. Newly built vessels, or those in design, may have an anode scheme as part of the corrosion-control program. For exterior hull protection, impressed current protection systems are frequently used on new construction. These systems, which require an external source of direct current and some means of regulating the current, can, with a minimum number of anodes, provide full underwater hull protection. Sacrificial anodes, such as zinc, magnesium or aluminum, can be used to give stern protection. There are a number of good publications on cathodic protections(5 . B.SHIPBOTTOM MAINTENANCE PAINTING Ships are seldom drydocked for painting alone. A glance at the American Bureau of Shipping s survey requirements *) suggests some work that may have to be done in drydock. The time can vary from a few hours on a rudder or sea chest to several weeks burning, welding and riveting to replace corroded or damaged plates. Shipowners traditionally had been more concerned FIGURE 10 Underwater Cleaning of Ships Hulls. Courtesy: Jotun-Baltimore Copper Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 299
SSPC CHAPTERxL2.0 93 8627940 0003747 994 ~ ~ ~~~~~ TABLE I TYPICAL SHIPBOTTOM PAINTING SYSTEMS Surface Prepa- Paint Designation, Number of Coats ration New and Film Thickness Bituminous. Aluminum . Pigmented Vinyl EPOXY Polyamide Chlorinated Rubber Coal Tar EPOXY Flakeglass Epoxy or Polyester Construction Abrasive Blast to SSPC-SP 10, NearWhite Abrasive Blast to SSPC-SP 10, NearWhite Abrasive Blast to SSPC-SP 10, NearWhite Abrasive Blast to SSPC-SP 10, NearWhite Abrasive Blast to SSPC-SP 10, NearWhite Abrasive Blast to SSPC-SP 10, NearWhite Anti-corrosive Aluminum Barrier coal -2 coats a175 Microns MDFT
Vinyl Barrier High Build 3 coats a200 Microns MDFl Epoxy Barrier 2 coats a200 Microns MDFT Chlorinated Rubber Barrier 3 coats @225 Microns MDFT Coat Tar Epoxy 2 coats @400 Microns MDFT Flakeglass Barrier 1 or 2 coats Q 625 Microns MDFT Anti-fouling Repainting Procedure Rosin Base, Cuprous Fresh Water wash, spot Oxide Toxic -2 coats @75 Microns MDFT Vinyl-Rosin Base 2 coats @IO0 Microns. Toxic usually Cuprous Oxide Vinyl Anti-fouling 2 coats a100 Microns Chlorinated Rubber anti-fouling 2 coats blast or power tool clean bad areas. Fresh Water wash, spot blast bad areas Fresh Water wash, spot blast bad areas, step back anti-fouling in way of repair. Fresh Water wash, spot blast bad areas.
a100 Microns MDFT Vinyl Anti-fouling -*Fresh Water wash, spot 2 coats blast bad areas, step a100 Microns back anti-fouling in way of repair. Vinyl or Fresh Water wash, spot Chlorinated blast bad areas, step Rubber AF -back anti-fouling in 2 coats a100 way of repair. Microns Application Equipment Spray recommended, may be rolled. Spray recommended, small areas can be rolled or brushed Epoxy-Airless Spray recommended-antifouling spray -small areas can be rolled. --`,,,,`-`-`,,`,,`,`,,`--Airless Spray recommended, small areas can be rolled. Airless Spray recommended for epoxy spray anti-fouling, small areas can be rolled. Spray recommended anti-fouling may be applied by roller. Prior to recoating, remove oil, grease, salts and other surface contaminants. * Twenty-five microns = 1 mil. with the structural integrity of the hull and the proper functioning of valves, propellers and rudders than the application of bottom paints. However, the increasing cost of fuel has made owners aware that modern coatings can make a significant contribution to fuel savings. Nevertheless, the coatings specialist sometimes encounters opposition or indifference at the shipyard. To combat this the following procedures are suggested. 1. General Agreement Upon receipt of notice from a shipowner that a vessel is due to drydock, the ship s painting history should be reviewed and a general understanding reached with the owner as to whether the boottop and topsides, as well as the
bottom, are to be painted. It is advisable to come to an agreement about the type of paint to be used and surface preparation required for successful paint performance. This is contingent on the ship s availability and the condition of the bottom. Arrangements are made for delivery of enough paint to cover all reasonable contingencies, and a qualified field representative is assigned to the job. The representative should be aware of the ship s recent painting history and what can be expected on inspection of the bottom. He should be fully advised of the shipowner s wishes and given alternate procedures if inspection reveals a different situation than originally contemplated. The owner should, in the meantime, negotiate with the shipyard and advise them of the work he wants done as well as broad painting plans. It is usually advisable to wait until the ship has been inspected before writing detailed painting specifications. 2. Inspection of the Ship The owner s port engineer, a yard paint supervisor, the yard s ship superintendent and a paint company representative make the inspection so they can agree on the work and the time required. 3. Specifications Members of the inspection party should confer to Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 300
SSPC CHAPTER*L2.0 93 m 8627740 0003748 820 m FIGURE 11 Condition of Underwater Hull After Service. ~ ~~ ~~ Courtesy: Bethlehem Steel Corp. write the surface preparation and painting procedures. The paint company, advised of the owner s instructions, outlines the surface preparation and painting schedule. A yard paint foreman, familiar with manpower and equipment availability, comments on whether the work outlined by the paint company is possible. The ship superintendent, the person ultimately responsible for completion of the work, presents plans for scheduling the paint program and all other work that may be affected by it, or that may affect the painting and surface preparation. If there are no complications and the paint program complies with instructions, the port engineer will usually ask the paint company representative to write specifications for 301 signature. Should future events, such as rain, threaten successful completion of the work, it is important that all concerned be advised so the best alternate procedure can be determined. Many ship repair jobs involve complicated and tight schedules. It is here that an experienced paint person is valuable. He knows how to expedite surface preparation and painting procedures without subjecting the ship to serious corrosion or fouling between now and the next scheduled drydocking. Good painting specifications depend on the owner s willingness to pay for good work and on the paint person s knowledge of products. The most important factors in successfully carrying out painting specifications are: An adequate number of trained and conscienCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*L2-0 93 8627940 0003749 767 TABLE 2 TYPICAL BOOTTOP & TOPSIDE PAINTING SYSTEMS Surface Prepa- Paint Designation, Number of coats ration New and Film Thickness Application Type of Paint Construction Primer Top Coats Repainting Procedure Equipment Chlorinated Abrasive Blast to "Inorganic Zinc Chlorinated Rubber Wash and remove contaminants. Airless spray preRubber SSPC-SP 10, "Near-Silicate -One Two Coats Q 125 Abrasive blast or power t ool ferred -air spray White Metal" Coat Q 62.5 Microns MDFT clean damaged or failed can be used also Microns MDFT areas. Touch up using same roller and brush system as applied during for small areas. Chlorinated Rubber Chlorinated Rubber construction, wllnhibitive Pig- Two Coats Q150 ment -One Coat Microns MDFT @50 Microns MDFT EPOXY Abrasive Blast to "Inorganic Zinc EPOXY-TWO Wash and remove contaminants. Airless or air Polyamide SSPC-SP10. "Near- Silicate -One Coats @ 125 Abrasive blast or power to ol spray preferred White Metal" Coat Q 50 Microns MDFT clean damaged or failed areas. roller or bru sh Microns MDFT Where overcoating epoxy can be used for roughen edges to accept new small areas. Epoxy Primer wl Epoxy -Two Coats epoxy. Touch up using same Inhibitive Primer Q 150 Microns system AC applied during One coat 50 MDFT construction. Microns MDFT Vinyl Abrasive Blast to "Inorganic Zinc Vinyl -Two Coats Wash and Remove contami nants. Airless spray pre(Including SSPC-SP 10, "Near- Silicate -One 6150 Microns MDFTAbrasive blast or p ower tool ferred. Air spray Vinyl White Metal" Coat Q62.5 or clean damaged or failed areas. can be used Acrylic) Micron MDFT' Vinyl Hi-Build One Touch up using same system as Brush may be used Coat a100 Microns applied during construction. for small areas. Vinyl Primer wl + One Coat Vinyl Inhibitive Pig- Acrylic Q50 ment -One Coat Microns MDFT Q 50 Microns Vinyl -Two MDFT" Coats Hi-Build Q 200 Microns MDFT For Topside Areas Wash and remove contaminants. Air spray preon ships wlfairly Abrasive blast or power to01 ferred. Brush fixed load lines clean damaged or failed areas. or roller may be alkyd topcoats can used. be used over a
zinc rich primer with a compatible tie coat. Two coats alkyd top coat @ 100 Microns MDFT OThe inorganic as primer is the preferred system. 'Tie coat may be required with some vinyl materials, "Wash primer should be used as initial coat with some vinyl materials. tous supervisors to cover all shifts. The yard wire brushes or disc grinder. (and the shipowner) should insist that the Good equipment also means providing g ood --`,,,,`-`-`,,`,,`,`,,`--manufacturer of a new type of paint have a light under the flat bottom of a ship on drydock. representative present until the yard painters Most important, it means providin g good staging are taught the proper methods of application. or other means of getting surface cleaners and Availability of good equipment for surface painters close to the work. preparation and painting. This includes spray- 4. The Painting Report ing equipment, roller coaters, brushes, abrasive Most shipowners and paint compa nies require blasting machines, power scaling tools, power representatives to write a report of the paint job. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 302
SSPC CHAPTER*L2-0 93 8627940 0003750 489 m Variations from specifications should be noted. Compromises are necessary, but it is important for the shipowner and the paint company to know whether subsequent failures were caused by improper cleaning or application, or by inadequate paint. C. LIGHT LOAD LINEIRAIL Most experts agree that alternate immersion is a more severe service for coatings than continuous immersion. The hull, from the light load or ballast lines to the rail areas, are subject to salt water (both immersion and spray), sunlight, ice, etc. They are also subject to abrasion from piers, tugs, lighters, etc. and pollutants, such as oil or chemicals floating on water. 1. Boottop The boottop, the area from the light or ballast line to the deep load line, is subject to conditions of alternate immersion on all ships. The deep load line to rail is subject to these conditions on cargo runs of tankers and freighters. Coating systems used on the hull are normally the same for both areas on these types of ships. The only difference is that some owners specify an overcoating of anti-fouling as a grass deterrent. Ships with more fixed load-lines, such as passenger ships, do not require high performance coatings for the topside. Table 2 presents some information on the type of systems generally used for the boottop and topside. Zinc-rich coatings, particularly inorganic zinc silicates, are the base coat for most systems. Use of a zinc primer can be very expeditious and economical. After block assemblies are completed and ready for coating, a coat of zinc-rich primer is applied. This provides an optimum corrosion protection during vessel erection. Zinc coatings, particularly inorganic zinc, have excellent abrasion resistance and minimum burnback from welding or burning.
Where damage occurs, the surface is repaired and a coat of zinc can easily be applied for repairs. After erection and touch-up, zinc can be overcoated with a specified topcoat. A drawback is that on weathering, salts will form on zinc coatings. This can diminish topcoat adhesion, since zinc coatings are porous and will absorb dirt and oil. Prudent care and planning should be followed to ensure removal of salts and contaminants prior to overcoating. 2. Hull Coating Maintenance The first question to be considered in maintenance painting is where it should be done, in drydock or while the ship is in water. A ship is not drydocked exclusively for boottop and freeboard painting; therefore, it is an item that is usually done during general scheduled maintenance or, for a passenger liner, during dress-up prior to a cruise. Where the job is done is usually determined by the time the ship is in drydock andlor the yard schedules. Organizing, planning, inspection and reporting will be similar to that for underwater hulls. D. STEEL DECKS A good weather deck coating system starts with SSPC-SP 10, near-white blast followed by a coat of inorganic zinc. This is the basis of the system. Except for attack by stack gases, certain cargo spillage and being slippery when wet, the inorganic zinc could be a good weather deck coating. Therefore, for non-skid purposes and protection against certain aggressive environments, zinc is overcoated with materials such as chlorinated rubber, vinyl or epoxy. The non-skid additive may be incorporated into the final coat. Decks subject to heavy-duty traffic such as fork trucks, wheeled vehicles, etc., require a heavy duty coating system. These coatings are applied over an inhibitive primer. The normal makeup of heavy duty decking materials is a nonskid additive incorporated into pigmented epoxy or urethane resin matrix. These coatings are normally applied to approximately 450 microns dry film thickness. Interior decks receive a number of different materials. Wet spaces, such as toilets, showers, laundries, lockers used to store cleaning gear, etc., normally have a monolithic decking such as terrazzo, latex mastic or, for passenger spaces, ceramic tile. The decks in galleys, which are also wet spaces, are normally quarry tile for nonskid and cleaning purposes.
A guide to various deck coverings and preparation is published by the Society of Naval Architects and Marine Engineers Technical and Research Bulletin 4-1lr7) and should be consulted. E. SUPERSTRUCTURE, MASTS, BOOMS, DECK MACHINERY, ETC. These areas in the past were maintained by the crew; however, with a reduced labor force and union and safety regulations, this is now less common. To keep a better looking ship, many owners require a high-grade coating system. This is initially established during construction. The surface is prepared to an SSPC-SP 10, near-white and in most cases a coat of inorganic zinc silicate is applied. Topcoats applied are those that have a history of long life, withstand salt atmosphere and industrial air pollution, and maintain good color. Failure in these areas usually occurs on sharp edges, rough welds and inaccessible places, such as behind pipes, conduits and hangers. Usually, failures appear more seriously corroded than they actually are, because a small pinpoint of actual rust Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 303
SSPC CHAPTER*12.0 93 Bb279LiO 0003751 31.5 will evolve into a large area of rust bleed. Even with a zinc silicate primer, these conditions will prevail, although the amount is dim in is hed. Materials most used as topcoats in new construction are high grade alkyds, silicone alkyds, chlorinated rubbers, epoxies, vinyls and vinyl acrylics. If inorganic zinc is the base coat, compatibility must be considered, and proper barrier coats and tie coats should be specified. For example, alkyds cannot be applied directly over zinc-rich coatings; therefore, a tie coat should be used. Many smaller craft built today and older ships constructed without inorganic zinc as the base coat require inhibitive primers to prevent or reduce corrosion. The standards in the past for the marine industry, for the areas under discussion, were red lead and zinc chromate. These are still used to a great extent, but safety, health and air pollution requirements are forcing a search for other inhibitive pigments. Studies are being conducted by coating manufacturers and pigment companies to find suitable replacements. Coating systems for all exterior areas may be found in the SNAME Technical and Research Bulletin 4-1518). F. INTERIORS 1. Living Areas Painting of living areas in modern vessels is generally minimal. The steel is primed for corrosion protection and cleanliness, but steel surfaces normally are covered with insulation and fireproof board faced with decorative veneers. Where painted steel surfaces are used, gloss materials are recommended for washability. 2. Machinery Spaces Machinery spaces above the bilge areas are primed with an inhibitive pigmented material such as an alkyd. This primer is topcoated with an alkyd gloss or semi-gloss enamel. Topcoats should have good oil and moderate heat resistance, and if white, they should be nonyellowing. Machinery is factory finished; or, if required for special color, a machinery enamel, usually an alkyd type, is applied over factory applied coatings. Surfaces above 125°F (52°C) normally are coated with a heat-resistant aluminum. Bilge areas and below deck plates, are subject to standing water, oil, steam, etc. Corrosion in these areas can be severe; therefore, a high performance coating system, such as an epoxy or inorganic zinc silicate, should be applied.
Ships built prior to the era of high performance coatings have been coated with red lead primers and phenolic type topcoats. These paints will have to be maintained, normally with hand cleaning and touch-up with primers plus top coats to damaged and failed areas. Surface preparation in bilges is very difficult because abrasive blasting cannot be used. Power tool cleaning is tedious and time consuming. Chemical cleaning and high-pressure water jetting can clean such surfaces more thoroughly and efficiently. Usually steel in older ships is corroded and pitted. Removal of old paint and scale along with grease, oil, etc. offers a fair substrate to apply a paint system. However, systems must be very forgiving to surface preparations. Some systems, such as epoxies, are being applied to surfaces prepared as above. The success has been mixed, but technology is improving. 3. Tanks Coating liquid cargo tanks is beyond the scope of this chapter. It is a very complex subject with many ramifications, dependent on the type and variety of cargoes carried, ballast, temperatures, and product purity requirements. The majority of today s tankage is taken up with petroleum products. These can be divided into categories such as clean cargoes (gasoline, jet fuels, solvents, kerosene, etc.) and dirty cargoes (bunkers, heavy fuel, crudes, asphalt, etc.). The basic premise for tank coating is that steel must be cleaned to at least SSPC-SP 10, Near-White Blast Cleaning . Some petroleum products are very aggressive and attack steel substrates and weak coatings rapidly. To protect steel or, where necessary, to protect cargoes from contamination, the integrity of the coating system must be good. To ensure success, the coating system must be appropriate for the service required; the surface preparation and cleaning must be as specified; and the application equipment, techniques and conditions under which the coating is applied must be as close to optimum as possible. Control of humidity and temperature (air and steel) is very important. Proper curing time of the coating, before being subjected to any service, should be considered. The coating systems most widely used for coating cargo tanks are: Epoxy Amine cured Ketimine cured Amine Adduct cured Polyamide
Inorganic Zinc Silicates Water Base Solvent Base Urethanes Urethane Modified Epoxies Phenolic Modified Epoxies Selection of a proper coating system is very important, and its resistance to cargoes should Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 304
SSPC CHAPTER*12.0 93 m 8627940 0003752 251 m be known. Selective coating systems that have performed to some criteria gives an experience factor. For example, coatings qualified under Military Specif icat ian MIL-P-23236 Paint Coating Systems, Steel Ship Tank, Fuel and Salt Water Ballast have met a test requirement. (a) Potable Wafer The coating system most widely used in potable water tanks is a two-coat application of a zinc dust paint. The vehicle is an alkyd-phenolic. Pertinent government specifications for this type of material is MIL-P-15145, Zinc Dust Pigmented Enamel, Fresh Water Tank Protective, Formula 102.A zinc-dust enamel applied over steel cleaned to SSPC-SPIO, Near-White Blast can be expected to give a minimum of two years life without repair. Longer life systems such as epoxies, epoxy phenolics, etc., are being specified, particularly on new construction. Care must be taken to apply and mix them properly to preclude any taste being imparted to the water. All coatings used for potable water service must be approved by the United States Public Health Service. (b) Ballast Tanks Ballasting with sea water is a very important part of a ship s operation. Tanks are used to maintain stability and seaworthiness during certain voyages. Some tanks are used exclusively for ballast and carry only sea water. Others may be cargolballast tanks that will carry cargo on one leg of a voyage and ballast on another. The time in ballast has some bearing on the coating system used. On new construction the most widely used coatings are epoxy tank coating systems applied at a minimum of 200 microns. Under certain conditions where a ship, such as a tanker, may not be in ballast more than 28 to 30 days consecutively and the same amount of time out of ballast, consideration can be given to an inorganic zinc silicate, water base, applied to 125 microns. In tanks where liquid cargoes as well as ballast are carried, the coating system should be inert to the cargo and the water. The combination of cargo and sea water will sometimes give different conditions than when service is for4iquid cargo or ballast exclusively. For older ships that have been in service for years and tank coatings have failed or were never
coated, preparation of the surface to a hearwhite is very expensive. Therefore, a coating that can be applied over rust or old paint is beneficial. There are a number of coating materials on the market that can be applied to a scale-free surface. High pressure water blasting can be used to remove all loose scale, old loose paint and salts. Non-oxidizing, lanolin base, oil-type or pigmented hydrocarbon resin materials can be applied to rusted surfaces. Such coating systems will not have the life expectancy of a properly applied epoxy or inorganic zinc system applied over a well prepared surface, but a cost effective study could show the economic feasibility of using such a system. Oil-type materials that contain inhibitors can be spray-applied for the initial application and when required can be renewed by the flotation process. (This is in development status and the method is still being evaluated.) (c) Peak Tanks Peak tanks in ships are in a confined area cluttered with internal structural members. Coatings are difficult to apply in these areas, and abrasive blasting is very hazardous. Ships built prior to the block construction era usually were coated with asphalt emulsion applied over hand cleaned steel. With the new construction methods, units that make up an area, such as a peak tank, are more accessible. Better surface preparation can be used and higher grade coating systems applied. Peaks are sometimes used for ballast on tankers and for other types of ships. Owners are specifying epoxy systems or inorganic zinc silicates. After erection, because of the configuration of these spaces, abrasive blasting to clean erection welds and damaged areas is not possible. Touch-up must be done over power tool cleaned surfaces. The life of the coating in these areas is less than that of a coating over an abrasive blasted surface, and failures occur more readily under these conditions. A coating system for these areas should be tolerant to a lesser degree of surface preparation. (d) Cargo Holds For general dry cargo spaces, requirements for corrosion control are not particularly stringent. An inhibitive primer applied over a surface cleaned to a good commercial blast (SSPC-SP 6) is sufficient. The primer is overcoated with a light colored enamel for light reflectance. Aluminum pigmented topcoats are preferable for these areas. Holds designed to carry coal, sulfur, phosphate rock, etc. but not ballast, frequently are not coated, at least not in the lower regions subject to heavy abrasion from discharging equip-
ment. If a coating is required, it should be a material with good acid andlor alkali resistance and good abrasion resistance. Epoxy type coatings lend themselves to these conditions. Coatings in upper areas of holds intended to carry grain make them easy to clean. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 305
SSPC CHAPTERaLZ-0 93 W 8627940 0003753 198 (e) Cofferdams and Voids Cofferdams during construction are usually coated twice with an inhibitive primer, such as zinc chromate. A corrosion conscious owner could apply a coat of inorganic zinc silicate or other zinc-rich coating. If applied properly, maintenance primer may never be needed. Voids may be divided into two categories, accessible and inaccessible. Accessible voids are treated the same as cofferdams. Inaccessible voids that are welded watertight and airtight, where boundaries are not exposed to sea or standing water, do not require any preservative treatment. Where inaccesible voids must be coated on the inside, it is done through special plugs by filling and draining. If these areas are accessible during construction, they may be coated by spray prior to closure. Miscellaneous spaces are normally coated like other areas required to perform the same service. IV. SAFETY PRECAUTIONS AND THE USE OF COLOR TO PROMOTE SAFETY Paint solvents present a fire and explosion hazard. A study of the flash points and explosion concentrations of various solvents 6) reveals that some are more dangerous than expected. The importance of scheduling hot work and painting ship exteriors for maximum safety has been discussed. It should be noted that the space under the bottom of a large vessel sitting in a closely fitting drydock is almost the equivalent of an interior space, particularly when there is no wind. The only safe way to apply paints with dangerous solvents in confined interiors is to supply enough air and exhaust to maintain the solvent concentration well below the lower explosive limit. In addition, all sources of sparks and flames must be eliminated. No other trades should be working in the area of the ship being painted. OSHA recommends the use of certain colors to promote safety. These should be adopted for shipboard use. Red ...............Fire Protection Equipment Orange ............Hazard-attention Yellow ............. Caution-Physical Hazards Green .............Safety- First Aid Blue ...............Caution Purple ............ .Radiation Hazards Piping systems are frequently painted with bands of these colors to assist in rapid identification of various systems aboard.
ACKNOWLEDGEMENT The author and editors gratefully acknowledge the active participation of the following in the review process for this Foster, John F. --`,,,,`-`-`,,`,,`,`,,`--chapter: Leon Birnbaum, T.A. Corboy, Hing Dear, Raymond P. Devoluy, Theodore Dowd, Richard Drisko, J.R. Montle, Benjamin Fultz; Dan Gelfer, D.W. Metzger, N.M. Miller, C. Munger, Walter Radut, and William Wallace. REFERENCES 1. Your Ship and Its Maintenance , J.C. Hempel Foundation, 1965. 2. Rules for Building and Classing Steel Vessels , American Bureau of Shipping, Surveys after Construction, Section 45. 3. Abrasive Blasting Guide for Aged or Coated Steel Surfaces , Society of Naval Architects and Marine Engineers, Technical Bulletin 4-9, 1969. 4. Marine Fouling and Its Prevention , US. Naval Institute, by Woods Hole Oceanographic Institution, November 1952. 5. Fundamentals of Cathodic Protection for Marine Service , Society of Naval Architects and Marine Engineers, Technical and Research Report R-21, 1976. 6. Table of Fire-Hazard Properties of Flammable Liquids, Gases and Volatile Solids , National Fire Codes, National Fire Protection Assn., Vol. 111, Boston, Massachusetts, 1977. 7. Marine Deck Covering Guide , Society of Naval Architects and Marine Engineers, Technical Research Bulletin 4-11, July 1969. 8. Coating Systems Guide for Exterior Surfaces of Steel Vessels , Society of Naval Architects and Marine Engineers, Technical Research Bulletin 4-15, 1978. 9. Catalog of Existing Small Tools for Surface Preparation and Support Equipment for Blasters and Painters , National Shipbuilding Research Program. U.S. Department of Commerce, Maritime Administration, May, 1977. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 306
SSPC CHAPTER*L3-0 93 = Ab27940 0003754 O24 CHAPTER 13 PAINTING OF STEEL VESSELS FOR FRESH WATER SERVICE by J. R.Foster Inland waterways of the United States have been important to the country s rapid social, industrial and technological growth. They were the first exploration routes and determined paths used by settlers, who chose sites for communities. They became the transportation and communication links of communities, so most of the present great centers of population, production and distribution owe their origins to these arteries. Today 38 states, with about 95% of the nation s population, have commercial transportation services provided by vessels operating on rivers, canals, bays, sounds or lakes; and 131 of the 158cities with populations of 100,000 or more are located on commercial navigation channels . The earliest commercial use made of the river system was hauling coal from Pennsylvania to the Ohio and Mississippi rivers in the late 1700s. The vessels were flatboats constructed of logs, borne by the current and guided by long tillers. Since they were without power to travel against the current, trips were one way only and boats were usually dismantled at their destinations and sold for lumber. Steam power made its appearance on the rivers in the early 19th century, and soon increased steel production prompted the use of boats and barges made from steel. Commercial channels now make up more than 25,000 miles of navigable inland waterways plus 1,800 miles on the Great Lakes. I. TYPES OF VESSELS Most freight on these water routes is carried on barges made from welded steel. They are large, floating boxes, unmanned and without self-propulsion, with drafts of 6 to 14 feet. Barges are moved in groups by towboats or tugs. The hopper barge, because of its single large cargo space, is adaptable to a wide variety of loads and finds the greatest use of the several kinds employed. It may vary from 175 to 290 feet in length, 26 to 50 feet in width, with capacities from 1,000 to 3,000 tons. A typical covered hopper barge is shown in Figure 1. Liquid cargo or tank barges range in the same dimensions with capacities of 300,000 to 900,000 gallons. They may be of single skin design, where the sheel of the barge is also the tank wall, or of double skin, with an inner shell forming the tank, as in Figure 2. They may also take the
form of hopper barges carrying independent cylindrical tanks, where they are used to carry liquids under pressure, or where pressure is used to discharge the cargo. The deck barge is a simple box hull with a heavy plated, wellsupported deck, and in some cases a cargo box enclosing most of the deck area to contain the load it normally carries. It is usually a little smaller than the hopper or tank barge, varying from 110 to 195 feet in length and 26 to 35 feet in width, with capacities from 350 to 1,200 tons. Other, more specialized barges include dredges, barges used for shipping liquefied natural gas, and tip-up timber carriers. Although each is classified as a towing vessel, the towboat and tugboat are vastly different, as is seen in Figures 3 and 4. The tug is smaller, has a shaped bottom contrasted to the towboat s almost flat bottom, and is, in effect, an ocean-going vessel most frequently used in harbors, intracoastal canals and the open sea. For this reason the painting of tugs is not covered in this chapter, which deals with fresh water vessels. There are approximately 1,800 companies in commercial operations on inland waterways. These firms operate more than 17,000 dry cargo barges with a total capacity in excess of 19 million tons, 3,400 tank barges with a total capacity of 7 million tons and 4,300 towboats and tugs with aggregate power in excess of 4.3 million horsepower . There has been no survey of the number of other vessels using inland waters, such as ferries and pleasure craft, but painting recommended here can apply to them. II. CORROSION OF VESSELS Literature does not disclose amounts of corrosive damage to steel vessels operating on inland waterways, but preventive efforts have been roughly inversely proportional to the quality of water where vessels operate. Quality has been affected by Industry growth and mining ventures in the vicinity. Poor waste disposal practices contributing corrosive substances to rivers cause accelerated deterioration of steel hulls. There was a period of 25years after World War IIwhen efforts to protect immersed surfaces were greatly increased and new and effective coatings were developed for this purpose. Realization of limitations of the environment to absorb continued, unrestricted industrial development led to concerted efforts to reverse the trend of water quality decline. Results have been notable2, particularly in Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 307
SSPC CHAPTER*L3-0 73 8627340 0003755 TbO = FIGURE 1 Covered hopper barge. Covers roll awav to exoose carao cornDanment. Courtesy of Dravo Corporation streams fed by drainage from coal mines. Reduced acidity has diminished emphasis on prevention of hull corrosion by coatings. Corrosion on ships in the strictly fresh water of the Great Lakes is minimal. Many operators apply coatings on hulls for cosmetic purposes. The most serious corrosion is in areas where coal, salt or other chemicals accumulate for long periods, retaining moisture, such as blind areas on large decks. Good coating procedures can prevent damage. New coating systems are being tested and finding use in protection of steel in inland water service. At least one company has met the problem of towboat hull corrosion by cladding the entire hull with stainless steel3. Many protective requirements for boats and barges in fresh water can be met by coatings used for ships in salt water. Refer to Chapter 12 for further recommendations. The cost of building river vessels has skyrocketed in the past 20 years. While most vessels are amortized for 20 years, their useful life is 25 to 35 years. During that period many receive new hull side plates and some bottom plates. The majority of damage is due to exterior corrosion, the most noticeable attack occurring at water line areas where variations in load, moisture and oxygen, and dissolved species in water accelerate metal loss. See Figure 5. Abrasion against concrete lock walls is a serious cause of paint removal and exposure of bare side metal to corrosive elements, just as scraping sand bars and submerged rocks or other objects damages bottom plates and raked or square ends. Many towboats on inland waterways are equipped with Kort nozzles, which are tube-like enclosures around the propellors, designed to increase propulsive efficiency (Figure 6). They cause propellors to behave like pumps, and a considerable quantity of sand, gravel and debris are driven through the nozzles, particularly when boats are in shallow water, causing serious abrasion to the leading edges and interior surfaces. There are many factors in surface condition and exposure to consider in planning a coating system for steel to be used in or adjacent to inland water immersion. Among the most critical factors is the need to remove
traces of mill scale, particularly from surfaces to be immersed. Although a tightly bonded intact layer of mill scale can protect a bare steel substrate, it is not possible to fabricate steel plates into hulls and other vessels without producing cracks and discontinuities in the scale layer. If this type of surface is painted and subsequently damaged by scraping or scratching through the paint film, moisture will reach the metal surface, and mill scale will separate from the substrate, carrying with it any covering coats of paint. Under immersion conditions this failure may occur even without mechanical damage because of the permeability of coatings. The likelihood of abrasion also is greater. Proper blast cleaning prior to application can eliminate this. Another cause of paint breakdown is improperly cleaned welds. The joining process leaves deposits of slag, flux, fume and spatter granules that must be removed before painting. Usually, hand or power scraping or brushing accomplishes the required degree of cleanliness, but the best effect is achieved by power grinding, which also smoothes ripples of the weld metal. Examples of poor and acceptable practice are indicated in Figures 7 and 8. Resistance to impact damage should be considered when selecting coatings for river transportation service. Not only are hulls subject to collisions with docks, locks and floating objects, but cargo compartments receive frequent encounters with cranes, clamshell buckets and other loading equipment. Flexibility and good adhesion minimize damage. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 308
SSPC CHAPTER*L3.0 93 8627940 0003756 îT7 m The variety of liquid cargos transported in tank barges requires Coatings to resist solvent and other chemical exposures. Tank lining is the subject of another chapter; coatings for tank exteriors, however, must stand up against frequent cargo spills and splashes. Interior surfaces of side compartments, rake and square ends and void spaces between inner and outer bottoms are areas usually subjected to high humidity. Also, splashes and spills from cargos may get to these locations, making them vulnerable to corrosive attack. Coatings must prevent perforation from the back side, which is less frequently observed. Superstructures of towboats and barges require the same attention as land-based steel structures, and probably receive more cleaning and scrubbing. Selected coatings must resist chemical and abrasive action and weathering. Surface preparation requirements are not stringent for these surfaces, but coating adhesion must be adequate. --`,,,,`-`-`,,`,,`,`,,`--FIGURE 3 Good design can prevent early corrosion of all types Typical tugboat at work in harbor. Generally smaller, with hull of structures. The best vessel design is economical over lines different from a towboat. an extended period and minimizes maintenance. Diligent Courtesy of Dravo Corpora tion efforts should be made to include design features such as automated blast cleani ng and application of preprovision for complete drainage of fluids, smooth junc- construction primers to flat sheets and formed members tions between adjoining members and elimination of prior to fabri~ation~,~. The use of airless spray equipment is crevices. Improved paint application can be included as now common, and experime nts are in progress with eleca significant contribution. Several builders provide trostatic spray methods'. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS FIGURE 2 Doubleskin tank barge. Courtesy of Dravo Corporation 309
SSPC CHAPTER*L3.0 73 m 8b27740 0003757 833 m FIGURE 4 Typical towboat operating in inland waterways. Courtesy of Dravo Corporation 111. RECOMMENDATIONS FOR CLEANING AND PAINTING A. SURFACE PREPARATION 1. New Work. Methods used to prepare steel surfaces for first painting range from simple hand cleaning to gritblasting to a white metal surface with no trace of mill scale or other surface contaminant. They have been standardized by a number of concerned agencies, and for a thorough description of the various grades the reader is referred to the following sources: a. Surface Preparation Specifications and Pretreatment Specifications of the Steel Structures Painting Council FIGURE 5 Side of barge hull, showing accelerated metal loss between water lines. Courtesy of Dravo Corporation b. Surface Preparation Standards and Recommended Practices of the National Association of Corrosion Engineers. c. Standards and Recommended Practices for Preparation of Surfaces for Painting of the American Society for Testing and Materials. d. Abrasive Blasting Guide for Aged or Coated Steel Surfaces, Technical Bulletin No. 4-9 Society of Naval Architects and Marine Engineers. Specifications of SSPC are most widely adopted because of clarity and range, which include visual standards in the form of color photographs, approved jointly by SSPC-SP10, and preferably a higher grade of preparation if Other visual standards are offered by NACE in the form of prepared steel surfaces embedded in clear plastic. In general, all surfaces to be immersed in water should receive at least a Near-White Blast , according to SSPC-SP10, and preferably a higher grade of preparation if economics of the paint system justify it. The same require ment applies to surfaces exposed to cargo spill and splash. Other surfaces, such as superstructures and interiors, may receive solvent cleaning, according to SSPC-SP 1, followed by hand or power tool cleaning, according to SSPC-SP 2 or SP 3. In shipyards, where abrasive blast cleaning facilities are available, the use of brush-off blasting as in SSPC-SP 7 may be better and more economical than hand or power tool cleaning. The importance of adequate traps in the air lines of blasting equipment cannot be over-emphasized. It prevents contamination of freshly prepared surfaces.
On surfaces prepared by blast cleaning paint performance is improved by wash primer directly over the blasted substrate. This material is most frequently based on a vinyl butyral resin with inhibitive pigments and Istypified by Military Specification DOD-P-15328 and SSPC-Paint 27. Its use is not justified if the surface has not been adequately prepared. Under proper conditions it improves adhesion of alkyd or phenolic coatings and vinyls. It is particularly useful as a pretreatment on galvanized or aluminum surfaces. Abrasive blast cleaning with a water solution followed by application of corrosion inhibitors can be beneficial in two ways6. It not only slows down rusting, but reduces the amount of dust common to blast cleaning operations. For the latter reason, its use may increase significantly in proportion to regulations governing air quality in industrial areas. 2. Repair Work. The method of surface preparation for repairs is dlctated by the condition of the coating system to be fixed. Extensive deterioration calls for abrasive blast cleaning as specified for new work. This may require prior treatment with solvents or steam cleaning to remove heavy deposits of oil or grease. In less severe cases, power brushes, grinders, hand scraping or wire brushing are sufficient. As in the case of new work, brush-off blast cleanCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 310
SSPC CHAPTER*L3*0 93 8627740 0003758 77T B. PAINTING i.Hull Exteriors. Because these areas are constantly immersed in waters of varying aggressiveness and quality, it is important to devote careful attention to their protection. The necessity of integrity of hull surface is very important. During industrial expansion following World War II, there was a marked degradation of water quality in many inland waterways because of discharges of industrial wastes and run-off from coal stripping operations. These pollutants caused severe acid condition in rivers, which was deleterious to steel hulls inthem. It became important for operators to provide special protection if vessels were to remain in service for a reasonable time. With the adoption of measures to improve water quality by reduction of discharges to navigable streams, a noticeable attenuation of corrosive conditions has occurred. This has led to some reduction in the quality of hull coatings for _- some barges. FIGURE 6 Some barge owners apply no coatings below the light Stern area of a typical towboat, showing Kort nozzles. load line. For years it h as been apparent from inspection of Courtesy of Dravo Corporation barge side and bottom plates that painting at regular intervals can significantly extend the life of side plates. The ing may be the most economical and should be considered if equipment is available. same tests indicate no great benefit in coating horizontal In maintenance, the painting effort should be to bottom surfaces since the coating is quickly removed by duplicate the original paint system or improve it. Generabrasion on sand bars. Many owners feel the cost of protecting the sides by coatings is no longer justified by the ally, the original system will be used, except that cleaning increased life. Man y barges are launched today withbefore priming may be limited to spot areas. Cle aned minimal coating protection on exterior hull.^!.^.^ areas should be feathered and built up to the level of old Towboat hulls are sti ll considered worthy of ultimate paint in respect to protective quality, as well as to thickness. Where rusted areas are small, cleaning is less protection. Modern painting finds inorganic zinc-rich arduous and a better degree of surface preparation is primers employed with a catalyzed epoxy or coal tar epoxy usually sought. topcoat to be rated highest in service life. Straight epoxy systems show good results and multiple-coat vinyl systems over a wash primer perform quite well. The labor saved from a reduction in the number of coats makes the
epoxy systems, and they are preferable when low ambient high-build vinyl coatings has reduced the advantage of epoxy systems and they are preferable when low ambient temperatures prevent satisfactory application of epoxies. 2. Stern and Propellor Areas. Because of abrasion of these areas by sand and debris stirred up by the propellors, particularly in shallow water, the stern and nozzle surfaces require special attention. Vinyl and epoxy coatings are adequate except on interior surfaces and leading edges of Kort nozzles. Many materials have been tried unsuccessfully, including rubber lining. Coatings given the best chance for reasonable service life include urethanes and glass-flake reinforced polyesters. One company has met this problem by lining nozzles with stainless steel. It worked well enough to lead to similar plating of the entire hull of two towboats. 3. Hull Interiors. These are not always seen, so the cosmetic aspect is not normally considered. On rakes and FIGURE 7 square ends common practice is to apply a single coat of Example of a weld not properly prepared for painting. The spatter arid ridges will lead to early paint failure. an alkyd or oleoresinous coating o ver a minimally Courtesy of Dravo Corp. prepared surface. In wing compartments and inner botCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 311
SSPC CHAPTER*L3.0 93 8627940 0003759 bob FIGURE 8 Good surface preparation of welded area shows elimination of ridges, crevices and spatter. Courtesy of Dravo Corp. toms the same practice can be followed, but more often the coating is a rust-preventive compound of greaselike consistency and formulated from waxes or cut-back petroleum products. Typical materials of this type are represented by US.Maritime Administration Specification 52-MA-602b and their use is described in SSPC-PS 8.01. Reasonable protection has been afforded in these areas by flotation-applied petroleum products of proprietary nature. Although performing satisfactorily as corrosion preventives, they are objectionable from an environmental viewpoint because of a tendency to be discharged into water along with any bilge water that may require disposal to eliminate unwanted ballast. 4. Decks and Exteriors of Cargo Boxes. Most common painting practice consists of alkyd or epoxy ester systems applied over a blast cleaned surface to a commercial finish (SSPC-SP 6).For many towboats and barges with cargos requiring resistance to chemical attack, nearwhite blast cleaning is common, followed by priming with zinc-rich primers, either organic or inorganic, and topcoating with epoxy finishes. Whatever system, a common feature is skid-resistant material on the decks in walkway areas. The non-skid feature may be incorporated in coating material or may consist of fine sand evenly sprinkled onto the first coat while it is still wet. It is then covered by a second coat to encapsulate sand particles. 5. Interior of Cargo Boxes. Coating selection for cargo box interiors is indicated to a large extent by the cargo. The abrasive nature of bulk and equipment used to load it generally preclude the use of high quality coatings. In sand and gravel service, inorganic zinc-rich coatings have shown excellent performance over abrasive blasted surfaces, either alone or as primers for alkyd top coats. Although the latter coatlng combination is usually avoided because of the risk of saponification of the alkyd resin, Figure 9 shows a cargo box with good protection after five years in sand and gravel service. In coal service the life of zinc-rich coatings is short, and therefore coatings are not used. In covered hopper barges interior surfaces and the underside of covers may be blast cleaned and coated with epoxy or vinyl systems to protect the steel and prevent contamination of cargo. The more common practice is hand or power tool cleaning followed by a single coat of low grade pigmented coating, for cosmetic purposes. 6. Superstructures. A towboat is not only very useful
and expensive, but is also a great attention getter from the passing public and an advertising asset for its owner. For these and other reasons the best surface preparation and coating are customary in their construction and upkeep. Abrasive blast cleaning to at least commercial grade is ordinary, as are zinc-rich primers, followed with topcoats of epoxy, epoxy ester or alkyd compositionB. Because of their outstanding weathering properties, acrylic and urethane compositions may soon be common in these applications. 7. Painting Guide. Table 1 is a condensed guide to systems recommended for the various surfaces. Selection of the appropriate system where several are named depends upon factors such as ambient temperature and available surface preparation. FIGURE 9 Sideof cargo box, showing satisfactory performanceof alkyd top Coat overzinc.rich primer after five years service. Courtesy: Dravo Corporation --`,,,,`-`-`,,`,,`,`,,`--312 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERm13.0 93 m 8b27940 00037b0 328 m Typical Painting Systems for Fresh Water Vessels Surface to be Painted Towboat and barge hull exteriors Towboat and barge decks and covers Towboat superstructures and interiors Coal and acid-carrying barge decks and hoppers Barge rake interiors Barge innerbottoms and wings Typical Systems I, II, v, VI I, 111, IV, v, VI I, 111, IV, v, VI, VII, VIII --`,,,,`-`-`,,`,,`,`,,`--Typical Coating SSPGPS 12 and 13** SSPGPS 12 and 11 * * SSPGPaint 1û4* SSPGPaint 8* SSPGPS 15 SSPGPaint 8* SSPGPS 13 SSPGPaint 104' * 52-MA602 v, VI, VII, VIII IX IX, x Typical Coating Systems for Fresh Water Vessels Systems I II 111 IV V VI VI1
VIII IX X * *Topcoat Surface Preparation SSPGSP SSPGSP SSPGSP SSPGSP SSPGSP SSPGSP SSPGSP SSPGSP SSPGSP SWEEP
10 10 10 10 10 10 10 6 2
Primer Inorganic zinc-rich Inorganic zinc-rich Zinc-rich org. or inorg. Zinc-rich org. or inorg. Wash Primer Chlorinated Rubber Wash Primer EPOXY Alkyd Rust Preventive Finish EPOXY Coal tarepoxy Epoxy ester Alkyd Vinyl Chlorinated Rubber Vinyl EPOXY Alkyd Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*l3.0 73 Bb27740 00037bl 2b4 ACKNOWLEDGEMENT BIOGRAPHY The author and editors gratefully acknowledge the active James R. Foster is reti red He participation of the following in the review process for this worked in the Prod uction Enchapter: T. A. Cross, Theodore Dowd, Dr. Richard W. Drisko, gineering department of the DraRandy Fulkerson, Dr. Howard G. Lasser, D. W. Metzger, C. G. vo Lime Company, whe re he was Munger, William Pearson, and William J. Wallace, Jr. involved in production and quality control of pollution control materials He was formerly Research Engineer, Dravo Research and REFERENCES Development Department. He had 1. Big Load Afloat , American Waterways Operators, Inc., more than 25 years experie nce in Washington, D.C. coatings evaluations and corrosion 2. ORSANCO Quality Monitor , Ohio River Valley Water Sanita- control. A Registered Professiontion Commission, Cincinnati, Ohio. al Engineer in the State of Penn3. Harry M. Herald, Private Communication. Hillman Barge and sylvania, he was ac tive in the Steel Structures Painting Council and the Construction Co., Brownsville, PA. American Society for Testing and Materials 4. Wayne LaGrange, Private Communication. Jeffboat, Inc., Jeffersonville, IN. 5. Nicholas Dashko, Private Communication. Dravo Corporation, Pittsburgh, PA. 6. Naval Ships Technical Manual, NAVSEA 0901-LP-190-0002, Chapter 9190, Preservation of Ships in Service , US. Government Printing Office, Washington, D.C. 7. Clayton Wilson, Private Communication. United States Steel Corporation, Ambridge, PA. 8. B.A. Rich, Private Communication. Valley Lime Co., Cincinnati, OH. 9. Edward L. Shearer, Private Communication. Hillman Barge and Construction Co., Brownsville, PA. 10. A.J. Liebman, The Painting of Steel Vessels for Fresh Water Service , in Steel Structures Painting Manual, 2nd ed., Volume 1, Chapter 12. Steel Structures Painting Council, Pittsburgh, PA. 11. Alan H. Edwards, Private Communication. Hillman Barge and Construction Co., Brownsville, PA. 12. Robert Kappler, Private Communication. Dravo-Mechling Corporation, Pittsburgh, PA. 13. Robert A. Labdon, Private Communication. Federal Barge Lines, Inc., St. Louis, MO. 14. Brent J. Lirette, Private Communication. Delta Shipyard, Houma, LA. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
31 4
SSPC CHAPTER*14.L 93 m 8627940 0003762 LTO m CHAPTER 14.1 PAINTING STEEL TANKS W.J. Wallace, Jr. This chapter presents information about painting interiors and exteriors of steel tanks. The discussion deals with selection of materials, inspection, and maintenance. The scope is limited to steel tanks for storage of water, oil, gasoline, and other commercial liquids; it does not consider the very specialized area of tank lining, which is taken up in another chapter. Surface preparation, safety and application techniques are also covered in separate chapters. I. SELECTION OF MATERIALS A. TANK INTERIORS The American Water Works Association (AWWA) standards list ten paint systems for tank interiors. They are 1) a three-coat system consisting of two aluminum phenolic paint coats over red-lead primed surfaces; 2) a four- or fivecoat vinyl paint system; 3) a zinc dust-zinc oxide, phenolicvehicle paint system; 4) a four-coat, singlesolution, highsolids vinyl paint system; 5) a cold-applied petroleum wax coating; 6) a hot-applied petroleum wax coating; 7) a metallic sprayed zinc coating; 8) a X,-inch, hot-applied coal tar enamel coating; 9) a cold-applied coal tar coating above the high water level only, and 10) a cold-applied tasteless and odorless tar-base paint. In addition, coal tar epoxies, catalyzed epoxies, alkyd-phenolics, three-coat high-build vinyl paints, epoxylester paints, and chlorinated rubber paints are also covered. While these paint systems can yield satisfactory results, problems may develop. For instance, coal tar epoxies have limited flexibility. When used as shop primers they cannot be topcoated later without additional surface preparation. If zinc-rich primers are not topcoated quickly after applications, negative effects can result. Phenolic vehicle paints, including zinc-oxide, zinc-dust phenolic, alkyd phenolic, and epoxy-phenolic materials will not accept a topcoat after they are exposed to the atmosphere for periods of 6-9 months. The paint surface becomes very hard, and hardness increases with time. Exposure to direct sunlight accelerates the hardening of the phenolic radical. Zinc-filled chlorinated rubber paints and zinc-filled epoxy paints can also degrade rapidly when exposed to sunlight, especially if condensation or high humidity becomes a factor. The non-filled chlorinated rubber paints can fail quickly if they are not topcoated and isolated from daylight within 60 days. shop primers, re-dissolving has been primed steel was stacked and subjected tion or high humidity. Coal tar primer
With water-base encountered when to rain, condensapaints, particularly
the primers for coal tar enamels, are subject to rapid degradation in outdoor exposure. Some of the exempt solvents are hydrophillic and if all of the solvent does not escape from the paint film, the solvent will absorb water back through the film and cause disbonding. The list of problems can be extensive. It is no wonder that the inexperienced paint specifier sometimes fails to make appropriate selections. Paint systems for tank interiors must conform with regulations issued by the Food and Drug Administration (FDA), the Environmental Protection Agency (EPA), the Na tional Public Health Service, the Occupational Safety and Healt h Administration (OSHA), and other reg u latory bod ies at all levels of government. Conforming to these regulations can be difficult. Regulations often serve crosspurposes or are inconsistent. For instance, there are regulations prohibiting the use of coal tar derivative coatings in a water tank, but none prohibiting the use of coal tar type coatings on the interior surfaces of pipes that transport water to and from the same tanks. Confusion in response to various regulatory bodies had had at least one beneficial side effect. The AWWA D102 Committee has formed a toxicological study group to work closely with EPA in the formulation of a test protocol. If the test protocol is satisfactory to both government and industry, the combined effort can then determine which paints or coatings other than catalyzed epoxies and vinyls are suitable for potable water service. Until government regulations change, the specifiers and fabricator-paint engineers who wish to avoid problems with regulatory bodies and litigation with consumers can write their painting specifications for the inside surfaces of potable water tanks as follows: Surface Preparation: SSPC-SP 10 NearWhite Metal Blast Cleaning or SSPC-SP 8 Pickling . Paint materials should be limited to VR-3 vinyl (4-coat system) to a total dry film thickness in the range 5-6 mils; a high-build vinyl (3-coat) to a total dry film thickness in the range 6-8 mils; or a catalyzed epoxy system (2-coat) either amineadduct or polyamide cured, to a total dry film thickness in the range 10-16 mils. All coats should be different in color to facilitate rudimentary inspection. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 315
SSPC CHAPTERUL4-L 93 8b27940 00037b3 037 FIGURE 1 Spray painting the exterior of a water storage tank. Courtesy Chicago Bridge and Iron On tankage to be used exclusively for fire protection, especially where the stored water is pumped through sprinkler heads, water cleanliness is of prime importance. Particulate matter entering the pipe can clog the sprinklerhead system. The inside surfaces of such tankage should receive the best possible degree of cleaning, careful removing of all blast cleaning media and coating with twocoat catalyzed epoxy or coal-tar epoxy, or a three coat high-build vinyl paint system. Fire protection water tanks should be inspected at least once a year, if for no other reason than to remove stagnant water. If the tank cannot be inspected frequently, or the stored water cannot be Turned-over on a regular basis, then a fungicide should be introduced into the paint to prevent algae growth. The use of a fungicide in paint must be predicated on the knowledge that the water for fire protection cannot ever enter into the drinking water supply. The same arguments regarding cleaning and painting should be assumed to be true for fuel oil tankage, where the fuel oil is pumped directly to the burners. Another sound argument for painting or lining oil-storage tanks is the fact that oils, even in the refined state, may contain free sulfur. This sulfur is corrosive and attacks steel. Be cautious about using zinc-rich paints on the inside surfaces of fire protection tanks and fuel oil tanks. If the water becomes stagnant, the zinc dissolves very quickly. If the fuel oil contains free sulfur, and most of them do, there is a formation of zinc-sulfide, and both the paint and the stored product can be ruined. The condensate water that forms in all oil tanks attacks the zinc paint and causes rapid dissolution of the paint. B. TANK EXTERIORS There are several paint systems for the exterior surfaces of tanks. The systems range from the simple threecoat alkyd to the sophisticated epoxy-urethane and all sorts of combinations in between. In general, most petroleum and solvent storage tanks are painted white (decals excluded) or very light pastel colors to provide heat reflectance. On water storage tanks, the color is typically chosen by committee, and usually the committee compromises on some shade of blue or green. The current version of AWWA D102 lists five paint
systems for exterior surfaces: 1) three-coat alkyd, 2) fourcoat alkyd, 3) two-coat alkyd with silicone alkyd finish coat, 4) three-coat vinyl and 5)an organic zinc-rich with chlorinated rubber alkyd topcoats. In all probability, the primer chosen for number 5 will be azinc-filled chlorinated rubber paint. Trouble can develop in this type of paint system if the topcoats are not applied immediately after priming. In addition to the systems shown in AWWA D102, there is a wide variety of proprietary paint systems, all of which have some merit and all of which have their limiting characteristics. For instance, a true silicone-alkyd paint contains approximately 33 percent silicone. This paint cannot be roll-coated without causing a serious bubbling problem. The problem can be overcome in several ways, such as overloading the paint with bubble-buster or reducing the amount of silicone to prevent the bubble formation. The best solution is the addition of the bubblebuster . Some studies have shown that a silicone-alkyd can be applied by roller when the silicone content is below 18 percent. Therefore, a specifier of silicone-alkyd should be aware of two things: 1) if the location will permit spray painting, and 2) if the silicone-alkyd is less than 33 percent silicone. As the silicone content becomes lower than 33 percent, gloss and color retention is also lowered, sometimes disproportionately. An ordinary three-coat alkyd paint system is superior to a silicone-alkyd system with a low silicone content. FIGURE 2 Tank depicting earth as seen from fllghts in space. Courtesy Chicago Bridge and Iron Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 316
SSPC CHAPTER*L4.L 93 öb279qû 00037b4 Ti3 FIGURE 3 Roller application of paint to tank exterior. Courtesy Chicago Bridge and Iron The specifier must use caution in choosing the proper paint system. Consider, for example, the urethanes. The most promising system on the market today is the epoxy-urethane paint system, that is, a prime coat of catalyzed epoxy paint, topcoated with a two-pack aliphatic-polyester urethane paint. There are other urethanes: single-pack (aromatic) vinyl-urethanes, epoxyurethanes, acrylic-urethanes, and so forth. Most of these combination urethanes do not have the gloss and color retention of the aliphatic-polyester urethanes. Therefore, it behooves the potential specifier to be able to ask questions in order to know what he is getting in a urethane. If doubt persists about a given paint material, help is available from AWWA, or some member of the SSPC Tank Painting Committee. The specifier should also be aware and beware of the or-equal clause. This clause is a two-edged sword that has caused much grief in the world of painting. For instance, it is all well and good to use the phrase generic or equal , providing, of course, that the specifier has listed a number of paint suppliers, all of whom manufacture an identical system, paint-for-paint. If only one of the manufacturers listed has a unique system, then, the specifier must 1)accept paint from a manufacturer NOTon his list, 2) accept an alternate but equal system, or 3) be prepared to accept total responsibility for what is in effect a closed specification. II. INSPECTION Regardless of the type of tank built, the type of service or the type of paint system, the as-painted interior surface that is in contact with the product and the surfaces that suffer exposure to condensate waters and vapors should be tested for continuity of the paint film before the painter leaves the site. The two most common methods are the wet-sponge test and the spark or jeep test. The wetsponge test, generally used on coating films up to 25 mils thick, is conducted using a low-voltage, hand-held apparatus that issues a warning sound (bell, beep, or horn) when the probe is passed over a holiday or void in the coating film. The probe is a sponge, saturated with a solution of 5 percent table salt (electrolyte) and 2 percent detergent (surfactant), in water. On tankage in nuclear sites, where the very thought of chloride ions in water causes mental spasms, the test solution is generally plain water adjusted to approximately 10 thousand ohmcentimeter resistivity. The spark or jeep test is used to detect holidays and areas of insufficient coating thickness on coating films thicker than 25 mils. The normal operating voltage is 1000 times the square root of the specified coating thickness. Failure is detected by formation of a
spark, accompanied by snapping or crackling sounds. Inspectors using holiday detection equipment should be aware that this equipment cannot be used on zinc filled paints, metallized surfaces and aluminum filled paints such as vinyl aluminum. The inspectors should also be aware that certain structural members that are not seal welded or caulked, such as the roof supports (rafters), bolted surfaces, box supports for roof columns and so forth, cannot be painted properly. As a result, a test of these members will indicate a failure of the paint system. Therefore, unless it is specifically stated that these FIGURE 4 Water tank designed creatively to suggest its function. Courtesy Chicago Bridge and Iron Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 317
SSPC CHAPTER*L4-L 93 W 8b27940 00037b-5 90T M voids be sealed prior to painting, it is recommended that they not be tested for holidays. The same reasoning applies to dry film thickness measurements. The dry film thickness should be measured in accordance with SSPC-PA 2 with a magnetic gauge that measures dry film thickness within an accuracy of 0.25 mil. As many dry film thickness measurements as feasible should be made so that there is approximately one measurement (three readings) for each 100 sq. ft. of surface painted. If an owner s representative is at the site, the dry film thickness measurements should be made while surfaces are accessible at locations selected by the owner s representative. Extensive rerigging after paint has dried so that dry film thickness measurements can be made is not required provided that a sufficient number of the locations tested meet or exceed the minimum dry film thickness specified. The inspector should also be aware that dry film thickness readings obtained on edges, fillets, welds and so forth may not be accurate because of differences in magnetic fields. Therefore, it is pointless to take these measurements. It is good, sound practice to inspect the paint applied to the water-bearing surfaces of a tank within the first year to 13 months after painting has been completed. In a majority of cases, 90 to 95 percent of all areas that can fail do fail in the first year of exposure. Moreover, the paint work is under guarantee for this period of time, and barring unforeseen complications, the remedial work can be accomplished at no cost to the owner. This is a policy adopted by the AWWA, and it is fair to both owner and contractor. The 13-month limit also gives the conscientious owner plenty of time to make arrangements for proper inspection of his tank, and the opportunity to start his maintenance painting program. 111. MAINTENANCE A maintenance painting program begins with a burning desire to preserve an already expensive installation, an absolute willingness to accomplish the task and the necessary funds to do the work. Water tanks in particular get painted many times during their service lives, and maintenance painting often represents more expenditure than the original paint work. Therefore, it behooves the owner or his representative to think seriously about some of the do s and don t s associated with maintenance painting. The most obvious do is to obtain the painting history on the subject tank. An accurate history reveals the tank age, the original paint system (generic), subsequent repairs and repaint work, and generic changes in the paint system. In short, the history contains most of the informa-
tion required to make an informed judgment about the proposed paint work. In the absence of a written history, the owner, his representative, or a competent inspection firm should remove cuts of paint from the tank in several locations. These cuts should remove the paint down to the metal. In this way, the inspector can determine, from the layers of paint, how many times the tank has been painted. Laboratory analysis of the paint cuts determines what paints have been used previously. Such an inspection, andlor careful analysis of the written history provides the owner several options prior to repainting. An owner should hire a third party, knowledgeable in paint work, to inspect the work and make recommendations; and the owner should follow these recommendations. Never keep repainting a tank, or anything else for that matter, without effectively removing deteriorated paint. The following is a true example of the kind of problems that can develop if one hurries into repainting a structure without considering its history. One rather large industrial firm owned an old 250,000 gallon elevated water tank that was painted on the exterior surfaces as follows: commercial blast cleaning followed by two coats of alkyd enamel (black). The tank was repainted with the same paint system twice in the next 10 years. During the next 30 years it was painted six times using the company colors. In 1978 the company was going to paint the tank again. Moreover, they rejected the advice of some very knowledgeable people that some sort of surface preparation work be performed on the paint. Two competent tank painting firms declined to bid the work. A first-hand inspection revealed stress cracks in the paint, large enough to reveal the black paint. But the tank was painted, and within three months large chunks of paint fell off the tank. Recently, this tank was blast-cleaned to white metal and painted with an epoxy-aliphatic urethane system on the exterior surface. It now has a properly restored paint system. FIGURE 5 Interior water tank paints were evaluated in a series of tests initiated in 1931 and carried out jointly in 1950 and again in 1958-59 by the SSPC, the Ambridge Water Authority and the Pittsburgh Des Moines Steel Company. The latter tests included 196 test areas (each 21 feet tall) involving chiefly phenolics, which failed and vinyls (per SSPC-PS 4.00) which, with touch-up, were still effective as described in Reference 4. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 318
SSPC CHAPTER*L4.L 73 = 8627740 0003766 846 = IV. SUMMARY Tank painting can be relatively simple, environmentally acceptable and still comply with government regulations and AWWA requirements. The interior surfaces of potable water tanks should be painted with two coats of catalyzed epoxy (polyamide or amine-adduct cured) to a dry film thickness in the range 10-16mils or a three-coat or four-coat (VR-3) vinyl paint system. The three-coat vinyl system affords the option of a thicker coating (7-8mils dry film) than does the VR-3 (four-coat) system. In both cases the final coat should be an SSPC-Paint 8 Aluminum Vinyl Paint to achieve an effective seal over the preceeding coats. The exterior surfaces are still painted as elected by the owner. However, the specifiers should be painfully aware that new OSHA regulations have virtually banned the use of the lead-bearing primers. The OSHA regulations have also placed the chromate pigments in jeopardy. Therefore, it is a wise specifier who determines, in writing of course, that a particular manufacturer s primer is leadfree and will NOTdisbond under severe condensation conditions. The same line of reasoning holds true for the topcoats. There are some totally lead-free primers that are proving satisfactory for the exterior surfaces of water tanks, and eventually, the applicators will catch-up with the technology. In any case, the major considerations in choosing exterior surface paints are location, (proximity to houses, etc.), time of year painting will be accomplished, and application characteristics of the paint (can it be rolled as well as sprayed). If, for instance, one is contemplating the purchase of a new tank, and it will be placed in an open area that will eventually be surrounded by buildings, then it is time to consider the long-lasting systems, such as epoxies, epoxy-urethanes or the highbuild vinyl enamels. If the tank is or will be placed in crowded conditions, pick a system that will afford the fewest problems in applications. Petroleum tankage should always be painted. White is an excellent choice for the exterior surfaces. The interior surfaces should be coated with epoxy or epoxy-phenolic materials or lined with a baking phenolic material . It is good to remember the following: steel is relatively inexpensive. In fact, the steel is the least expensive item on the job. If, then, the cost of design, fabrication, labor, and erection are the most expensive factors, why do we pay so little attention to protecting the basic item of the structure? The replacement costs are enormous. Again, if all of these beautiful steel structures are designed and built as a monument to man s ability to overcome nature, why do we become so penurious regarding the one thing, painting, that will protect our genius from the ravages of nature?
ACKNOWLEDGEMENT The previous chapter on this subject was written by the late J.O. Jackson. The authors and editors gratefully acknowledge the active participation of the following in the review process for this chapter: AI Beitelman, Duane Bloemke, Wallace Cathcart, William Chandler, R. Burt Chase, T.A. Cross, Ted Dowd, Richard Drisko, Ronald W. Hamm, Leonard Haynie, Harlan Kline, Iggy Metil, John Montle, C. Munger, Joe Richard, Harry A. Skilton, T. Wilhelm, Louis Zadra. REFERENCES 1. J.O. Jackson, Painting of Steel Tanks Steel Structures Painting Council, Volume 1, pp. 298-308, 1952. 2. Final Report of Ambridge Test of Paints for Water Tank Interiors , Pittsburgh-Des Moines Steel Company Technical Bulletin No. 3304, 1933. 3. Second Report of Inspection of Test of Steel Priming Paints and Methods of Surface Preparation After 584 Days Exposure, Pittsburgh-Des Moines Steel Company, May 4, 1941. 4. J.D. Keane, A 25-Year Evaluation of Coatings for Water Tank Interiors , Steel Structures Painting Council Report, December 1, 1975. 5. Painting and Repainting Steel Tanks, Standpipes, Reservoirs, and Elevated Tanks for Water Storage , American Water Works Association, Inc. February 11, 1964. --`,,,,`-`-`,,`,,`,`,,`--319 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*L4.2 93 8627940 00037b7 782 CHAPTER 14.2 THE LINING OF STEEL TANKS by Wallace P. Cathcart and Albert L. Hendricks I. INTRODUCTION This chapter describes accepted practices for selecting and applying protective coatings to the interior surfaces of steel tanks. These coatings used as linings protect tank interiors from corrosive andlor erosive products and often prevent contamination of the product by the steel substrate. The tank may be used for processing, transporting or storing chemical or food products. The requirements necessary to obtain economical service life with a coating as a lining include safety, designlfabrication, selection of coating materials, surface preparation, application techniques, curing, inspection and maintenance. For purposes of this chapter the discussion of a protective coating used as a lining is limited to materials applied in one or more coats by conventional air spray or airless spray methods to a total dry film thickness of no greater than 50 mils. This chapter does not include other application techniques such as flame spraying, sheet-applied linings, metallizing or hand lay-ups. The success of a coating system depends upon the design of the tank, intended use, coating selection, total dry film thickness of coating and application technique. These factors make it essential to seek advice from a competent supplier of coating materials and a knowledgeable, experienced applicator. II. SAFETY Assuring the safety of workers in tank lining is of utmost importance. Working in confined areas with dust and toxic andlor flammable materials can create hazardous conditions. Individuals working in these areas should be familiar with precautions necessary to prevent accidents . Regulatory bodies, such as OSHA, have guidelines that must be followed. In addition, training program should be established to educate all individuals who apply coatings to steel tanks. Use of a check list such as the following, prior to starting work, helps to establish conditions necessary for safety: Barricades Elect ri cal Hazards Explosion Proof Electrical Equipment Eye Protection Falling Objects
Fire Alarm Station Fire Extinguisher -Fire Blankets Flammability of Materials Used Ground Fault Interrupter Nearest Telephone Nearby Traffic, Cranes, Moving Objects Protect ive Clothing Respiratory Protection Safety Permits Safety Rescue Equipment Safety Showers Scaffolding Source of Breathing Quality Air Spark Proof Tools Static Equipment Grounded Toxic Materials Warning Tags and Signs Precautions in excess of standard industrial safety practices must be followed for the work performed inside tanks. For instance, all electrical power to work areas must pass through a ground fault interrupter. Clothing must be sufficiently thick to protect the skin from bombardment during abrasive blasting and to provide protection from the coating material during application. Foot wear for individuals applying the coating should have soft nail-free soles that resist solvents, prevent sparking and provide good traction. All workmen inside a tank should be equipped with forced, fresh air breathing apparatus when any blasting or spraying is being done (Figure 1).An alternate or standby source of breathing air must be available to provide a safe escape time in the event the primary source fails. Ventilation must remove blasting dust for visibility and provide sufficient air to maintain solvent vapor concentration below both the lower explosive and threshold limits. Because nearly ali solvent vapors are heavier than air, they tend to concentrate in low afeas so it is necessary to assure such areas are well ventilated. Detailed information pertaining to explosive and threshold limits can be obtained from various publi~ations.~~~ Eye protection should be mandatory for all workmen in the tank and in the area of the tank when they are handling abrasive or when abrasive blasting is in progress. All pressure equipment including blast pots must be constructed as specified by National Board Code and the ASME Code for Unfired Pressure Vessels. Safety relief valves should Oe tested daily and pressure tests should be conducted at least once and preferably twice a year. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 320
SSPC CHAPTER+14-2 93 = 8627940 0003768 619 D FIGURE 1 Safely equipped man spraying the inside of small food processing tank. Courtesy: Tank Lining Corp. 111. DESIGN AND FABRICATION TO RECEIVE LINING Whether a tank is being lined to prevent contamination of a product or to provide protection from corrosion, the coating must act as a barrier between the product and the steel tank. The coating must be essentially continuous to perform effectively. Long or meticulously detailed specifications for tank design are needed only for the most exacting conditions as when a highly corrosive environment is to be handled. More commonly though, coatings are used as linings to prevent iron or oxide contamination of the product and the specifying engineer should address himself to the difference. The essentials of good tank design, stated simply, are these: avoid or eliminate sharp edges, projections, crevices, acute angles and pits; design the tank so that all surfaces are visible and accessible to the workers preparing the surface and applying the coating. The surface tension of most liquid coatings tends to pull the film from the apex of any edge or projection and thus leave less film to protect the substrate. Arbitrarily, the industry has assumed a minimum of ya radius of a sharp edge, but more significantly, sharpness must be el imi nated. Consideration should be given to designing nozzles that extend into the tank for inbound flow to prevent high concentrations of solutions from running down the sides of the lining. In addition, the nozzle should have a large diameter and short length to facilitate coating application to the interior surfaces. When applying a coating by spray, excessive thicknesses tend to accumulate in areas where crevices, pits and acute angles exist. If such areas cannot be avoided in the design, they should be eliminated by fillet welding. The contour should be smooth enough for the lining material to be applied uniformly4 (Figure 2). IV. SELECTION OF MATERIAL Selecting the coating material for immersion service is one of the most difficult functions and requires the greatest degree of engineering skill and effort. Immersion service is usually thought of as immersed or submerged in a liquid. In this chapter that is the assumption; however, it must be realized that tanks, silos, railroad cars and hoppers are often lined to handle a dry
product such as grain, plastic pellets or salt. When lining for dry service, it is sometimes assumed that the absence of liquid eliminates the stringent requirements for coating application. But there are several factors that may counteract the apparent lack of liquid. In the case of plastic pellets, for instance, where the lining is used solely to protect the product, a chip or flake of the lining that may be of little concern in a liquid contamination environment could be of great economic concern if it managed to get into the rollers of a high speed film manufacturing plant. In another instance, hydroscopic properties of a product, such as sodium chloride, can result in severe corrosion in covered hopper cars after as little as three years. For dry service, caref u I, knowledgeable engineer¡ ng wi II sometimes allow deviations from recommendations for immersion; however, this is the exception rather than the rule. Among all the factors in coating selection, the three most critical are (1) resistance to the reagent or the product to be stored; (2) resistance to undercutting or underfilm attack at points of minor breaks, discontinuities or permeations that exist or develop; and (3)physical properties such as flexibility, adhesion and elongation that are FIGURE 2 Lining of baked phenolic over carbon and stainless steel for high pressure and temperature chemical separator. Courtesy: Tank Lining Corp. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 321
SSPC CHAPTERUL4-2 73 8627740 00037b9 555 satisfactory for the service for which the lining is intended. For instance, a thick brittle lining might work well in a fixed, rigid storage tank yet fail prematurely if used in a railroad tank car or a thin-walled storage silo. Lesser factors, but nevertheless sometimes important, are (4) resistance to water and oxygen passage; (5) resistance to abrasion; (6) resistance to aging; (7) application and curing characteristics such that a proper coating film is feasible in the specific vessel to be lined. As an example, the baking phenolic coatings that are final cured at 400°F. (204°C.) cannot easily be applied in extremely large tanks due to the difficulty in obtaining a uniform temperature. Final cure temperature is limited to the temperature resistance of the insulation on the vessels that have been permanently insulated. Also doubleskinned barges, as now designed, cannot be baked above approximately 300°F. (149°C.) because the inner tank expands and distorts or even splits the outer shell. When selecting the proper coating system, it is necessary to understand all of the conditions to which the lining will be subjected, such as product type, exposure time, temperature variations, temperature source, vapor area, pressure, cleaning procedures, agitation, wet and dry conditions, versatility, degree of abrasion or erosion, thermal shock, trace chemicals present and possible physical impact, either on the lining or the reverse side. Figure 3 shows a typical failure that occurred, in part, because all of these conditions were not taken into account. Gathering information on the variable in making a selection is simplified if identical field history exists. But even seemingly insignificant variations should be judged by an experienced person competent in understanding their significance. Some material suppliers and some application companies keep extensive records of successes and failures of each coating system used. This information is often available, but it must be used judiciously. If actual experience is not available, it is necessary to conduct either field or laboratory tests. Field testing in the actual environment is the most effective because it takes into consideration all of the variables that exist. Field testing is painstaking, time consuming and many times impractical; therefore, the tendency is to utilize accelerated laboratory testing. But it must be emphasized that evaluation by accelerated tests is a technique to be used with great caution as it will only reject bad selections and not prove good ones unless there is favorable correlation between the results and similar performances. In field testing, application of the test material to the actual substrate is preferred since it is then exposed completely to all the variables. If substrate testing is not feasible, it is then advisable to suspend or attach a coupon within the tank. Dissimilar metals should be insulated from the sample to prevent a galvanic differential between
the sample and the vessel itself. The difference in the temperature on a coating and the temperature of the outside tank wall may also be significant to its performance. When suspending a panel, however, the variable of * A *ha! *~ FIGURE 3 Failure of water tank lining from poor design, fabrication, material selection and application. Courtesy: D.M. Berger temperature differential is lost. Thus, the results must be carefully interpreted. Laboratory tests are normally conducted on steel coupons prepared under laboratory conditions by individuals well versed in the application of coatings to test samples. Coated coupons are exposed to the product intended for storage or transportation by submerging in a container or using an Atlas Test Ce1L5 The samples are normally observed at various intervals from 24 hours to one year or until failure occurs. The Atlas Test Cell consists of an open pipe to which test panels are bolted on each end to form a double end flange (Figure 4). The center piping has openings where heating elements, condensers, thermometers andlor agitators can be inserted. The body of the cell is constructed of glass, resistant alloy or coated steel. This test can simulate many of the conditions experienced in actual service, such as agitation, temperature differential across the surface and temperature sources from inside or out. In evaluating a protective coating for immersion the test should be conducted for a minimum of six months and ideally for one year. Any changes in the appearance of the coating should be recorded. Failure is normally indicated if blistering, severe softening, swelling or severe discoloration has been noted. With regard to softening and discoloration, the difference between severe and less severe or inconsequential requires considerable experience and indepth understanding of the expected performance of the lining. Likewise, failure of the panel is indicated if the liquid is affected by the exposure in any significant manner. Again, experience and understanding of expected performance is necessary to interpret what is significant. Following is an example of what can be significant. The liquid in a particular test has a pickup of two parts per million of iron. By comparing liquid volume to surface area, relating all to time and exposure in test as compared Copyright The Society for Protective Coatings Provided by IHS under license with
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SSPC CHAPTERt14.2 93 = 8627940 0003770 277 to anticipated time of exposure and use, the amount of iron pickup can be calculated and judgments made as to whether it is significant. In some circumstances, any measurable extractable or any color change of the product is deemed to be a coating failure. Normally, a slight color change in the coating, a slight weight loss or a slight weight gain are not considered failures. An important final determination of a test coupon, even though the coating appears to be unaffected, is to remove the coating from the steel and inspect for any signs of damaging permeation or under-film attack. Several different generic coating systems are used as protective barriers for vessels in immersion service. The resistance of each type varies with the individual formulation. Resistance tables can be obtained from coating manufacturers or organizations such as the National Association of Corrosion Engineers. These tables should be used with discretion since slight variations in formulations could decrease the resistance of a specific generic type. Interpretation of these charts is also important. Good alkali resistance does not mean the system is resistant to 73'/0 caustic soda but possibly resistant to pH slightly in excess of 7. Similarly, good solvent resistance does not normally mean the coating system has resistance to immersion in methylene chloride. The following is a brief description of the major generic types of coating materials presently used as linings: A. PHENOLIC A high-bake pure phenolic, unplasticized, based on a phenol formaldehyde resin, often referred to as a straight phenolic. Polymerization is accomplished by heat curing at metal temperatures ranging between 350" to 450°F. (177" to 242°C.). They are spray applied in a number of coats to a total dry film thickness ranging between 4-8 mils. The pigmentation used in formulations affects the end color, adhesion, permeability and spray characteristics. The chemical and physical properties of bake phenolic systems are excellent. They are unaffected by most solvents, including hydrocarbons, alcohols, ketones and chlorinated solvents. They are resistant to concentrated sulphuric acid but due to the limitation on total dry film thickness cannot be used in dilute acids where the corrosion rate on the underlying steel would be excessive. They exhibit poor resistance to alkalies, alkali salts and strong oxidants. This system normally meets all the requirements of the FDA and USDA for protecting substrates exposed to products intended for human consumption. Because of the limitation on film thickness, this system normally is not specified as a pin-hole free lining. B. PHENOLIC/EPOXY BAKING TYPE Formulations based on a phenol formaldehyde resin crosslinked with a Bisphenol A Epichlorohydrin.
Polymerization is accomplished by heat curing at metal temperatures of 350" to 450°F (177" to 242°C.). This type FIGURE 4 Test cell indicates failure as a result of adhesion loss. Courtesy: Gilbert Associates formulation is normally applied by spray in a number of coats to a total dry film thickness ranging between 4 and 8 mils. Pigmentation varies to enhance adhesion, permeability, spray characteristics and color. Chemical and physical properties.are excellent, although when compared to the unmodified or straight phenolic, the resistance to solvents and concentrated acids is lower. Some modifications can result in an increase in resistance to alkalies and strong oxidants. Due to the limitation on film thickness, this system should not be used in highly corrosive areas and is not pinhole free. Similar, but generally less resistant, formulations are available that, while still thermosetting, can be polymerized at lower temperatures. Optimum cure is obtained at approximately 200°F. (93°C.) metal temperature. Much of the disparity in resistance can be overcome by these material's ability to be applied at much heavier films, 8-12 mils. C.EPOXY Formulations based on Bisphenol A Epichlorohydrin resin utilizing either amines, amine adducts or polyamide curing agents for polymerization. Heat, while not always necessary to cure, does optimize resistance. This type of system can also be modified with phenol formaldehyde resins, coal tar or other resinous materials. It is possible to formulate systems with no volatile solvent, various solvent combinations or with water. Pigment is added to the formulation to obtain color, workability, adhesion or abrasion resistance. The resistance of this category varies substantially based on the formulation, but, generally, it will have excellent resistance to various chemicals that range in a pH from 4 to 12. The solvent resistance will be fair. Its exposure to severely corrosive environments will be limited due to normal film thicknesses ranging from 8 to 30 mils when applied by spray. Heavier films (not in the scope of this chapter) can be formulated containing flaking or fibrous fillers and applied by spray, trowel, or hand lay-up. D. POLYESTER-VINYL ESTER Formulations based on either a polyester or vinyl ester resin contain styrene or a similar monomer at a varying percentage up to 55 percent. The styrene monomer enters into the cross linking but also evaporates; therefore, it is difficult to determine coverage by normal Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 3283
SSPC CHAPTER*34-2 93 8627940 0003773 303 volumeisolids methods with either of these materials. H. PRECAUTIONS Polymerization is accomplished with peroxide type catalysts and promoters. Pot life can vary from 15 minutes to 8 hours, depending on the reactivity of the formulation. The pigmentation varies depending on the intended use and the manufacturer s preference. Formulations containing chopped glass, glass flake or inert oxide flake pigment are used for lining vessels. Film thickness varies with the formulation, but for immersion application from 30 to 60 mil films are applied by spray. Heavier films (not in the scope of this chapter) from 40 to 120 mils may be applied by trowel or hand lay-up. The chemical properties are defined as excellent with resistance to various acid and alkali environments. The solvent resistance is generally fair. A pinhole free film can be obtained with these systems. E. NEOPRENE Synthetic elastomers that may be dissolved in solvents or as a latex dispersed in water. Common curing agents are zinc or magnesium oxide. The solvent materials are spray applied in thicknesses of 20 or more mils and have excellent resistance to both alkalies and acids. The latex materials (like the styrene butadiene latex) are sprayed in thicknesses of 10-25 mils and are widely successful in strong alkali immersion (50 and 73% caustic soda) but not in acids. All neoprene are considered to be relatively poor in solvent environments. F. INORGANIC ZINC Formulations are based on either alkali or alkyl silicates with a varying percentage of zinc pigment. The alkali formulations are water based and the alkyl, solvent based. The amount of zinc loading will determine the degree of galvanic protection offered. This kind of system may be self-curing, or it may rely on moisture in the air, or it may be post-cured by application of an acid solution. Its chemical resistance is excellent in solvents and petroleum products that are relatively free of water and with a near neutral pH. It prevents corrosion of steel substrates by sacrificial or preferential action. Topcoating is therefore advantageous to prevent rapid deterioration of the zinc. Possible contamination of the stored product may result when zinc coatings alone are used for immersion service. G. VINYL Solutions consisting of vinyl chloridelvinyl acetate copolymers in ketonelaromatic solvents. Low volume solids normally necessitate the application of several coats to achieve recommended film thickness of 5-12 mils. Special high build formulations are available, but selection should be made with extreme caution since the pigmentation can provide a very porous film unsuitable for immersion service. Vinyls formerly were widely used in a multitude of chemical and food services, but now are
somewhat limited to water, fatty acids and salt solutions. They exhibit poor resistance to solvents. The phenomena of cold wall effect, that is, a driving, permeating force assisting ionic passage through the coating to the metal in the direction from a hot liquid to a cold wall, has been reported and is a significant adverse factor in the performance of some lining. Conversely, with a heated exterior wall, the heat comes from the exterior towards the contents and within reasonable extremes, the lining seems to be protected and the performance is improved in these areas.6 Coating materials used as linings tend to be the most sophisticated of the paint and coating formulations. With this often comes unusual sensitivities. Care should be taken to insure that coatings used as linings are well within the shelf life as defined by the material supplier. The storage or shelf life may be materially affected by elevations in temperature or by exposure to sunlight. Others, if once frozen, may not be suitable for usage. Storage under controlled temperatures and safe ventilation with scheduled package inverting as recommended by the supplier is essential for optimum shelf life. V. SURFACE PREPARATION Surface preparation is important in obtaining successful linings for tanks. It should provide a substrate that is free of contaminants, uniformly roughened and cleaned to a white metal, such as outlined in SSPC-SP 5. This type of surface can be created only by abrasive blasting. The industry has not established a guide for degree of profile, although certain manufacturers do specify depth of profile required for their systems. Observation indicates that with some coating systems in certain environments the depth of surface profile can significantly alter the results. Determination of the depth of profile in the field has been made by using visual comparators, by making microscopic measurements and by measuring depths imposed on a tape. However, the accuracy of this type of equipment has not been established. As environmental and health standards often prevent preparation of substrates by blasting with sand, evidence shows that a clean angular iron or steel grit of proper hardness can provide an excellent surface. Steel surfaces blasted with metallic grit do not have the classic white metal appearance, nor do they have the same light reflectant properties as steel blasted with sand because of the absence of sand residues. In selecting any abrasive, care must be taken to insure that it is clean and noncontaminating. After abrasive blasting, dust must be removed from surfaces and from the air. Once the dust has settled, the surface should be carefully brushed andlor blown down with moistureioil-free air, andlor vacuum cleaned. This is a critical step in surface preparation for coatings to be used as linings. Surface preparation of tanks that have previously been exposed to liquids requires special treatment. Prior
to blasting, it may be necessary to clean residues of previous contents with solvent, caustic, acid, detergent or Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 324
SSPC CHAPTER+L4.2 93 8627940 0003772 04T = steam. However, no one or combination of these cleanings is consistently successful. Many early failures have occurred even after the expensive but common procedure of abrasive blasting first, then one or more cleanings followed by another abrasive blast. The only consistently successful procedure is as follows: 1. Clean by an approved method to a visual cleanliness. 2. Prebake the vessel to a temperature of at least 25 F (14 Co) above the temperature that the tank will encounter either in curing the coating, as in a high bake coating, or the tank s highest operating temperature. The prebaking is most important in used tanks that are pitted or have been in a sulfide or salt environment. 3. Abrasive blast the vessel to the specified surface requirement. VI. APPLICATION TECHNIQUES The first coat must be applied as soon as possible after surface preparation to prevent rust blooming or oxidation of the substrate. To delay even a few hours could be detrimental unless the relative humidity and the temperature of both the air and metal can be carefully controlled. The first coat is normally applied by spray. If the material s wetting properties are poor or the surfaces are pitted, brushing should be considered. After the first coat has been applied, it is often a good practice to brush one or more coats on welds, edges or any area that is not ideally fabricated. The brushing of welds, called stripping, is done to insure better coverage and continuity. It should be accomplished with care to avoid excessive film build. Depending upon the coating material, it is often advisable to thin the coating to obtain better wetting characteristics. The humidity must be controlled inside the tank during application of the coating due to possible and often invisible surface condensation. A psychrometer is used to determine the relative humidity, and thermometers are used for determining air and surface temperatures. A spray painter must be properly trained to apply a coating. There are no hard and fast rules about the number of passes or the speed with which they should be applied; therefore, technique and experience are important. Applying a coating in a criss-cross pattern provides a more uniform coating thickness and improved film continuity.
Some coatings require that a first pass be applied as a fog or mist coat. This very thin but uniform film allows solvents to flash off quickly, and the coating will then hold or take subsequent and relatively heavier, slower passes. Well trained, experienced spray painters, with proper supervision can work out the best spraying procedure for any given material. The wet film thickness obtained can be measured with a wet film gauge. This should be considered an estimate measurement because the solvents in the coating evaporate during the spraying process. The type of solvent, method of application, and the environmental conditions during the application are all factors which determine the readings. Good air circulation is required to remove the solvents. Extreme cleanliness is required throughout the coating application. Clean, lint-free clothing should be worn. For safety reasons shoes should provide good traction but should have smooth soles to prevent tracking. If the conditions of traction allow, a wrapping of the shoes with polyethylene or other plastic film not affected by solvents in the coating can be advantageous. To prevent contaminating the surface, lint-free gloves should be worn during all phases of coating application. Application equipment must also be kept extremely clean. New hoses for each type coating are desired, but if not available, previously used hoses must be meticulously cleaned as residues of other products may have a severely detrimental effect, particularly on a catalyzed coating. A thorough cleaning should be done immediately after use of application equipment. Coating materials used as linings, as discussed in this chapter, are spray applied by either conventional air or airless spray (Figures 5 and 6). Air spray indicates that the coating comes in direct contact with air for atomization while airless spray utilizes high pressure through a small orifice with no direct air contact. Air spray allows the sprayer better control for thickness, particularly in confined areas andlor around intricate shapes in corners, etc. The major disadvantage of air spray is that in spite of all warnings, the air supply used for spraying may contain detrimental amounts of oil or water. Small amounts interjected in certain coating systems could result in a change of physical properties such as the development of pinholes, blistering, fish eyeing, blushing or poor adhesion. The.airless spray eliminates potential problems with contaminated air. In addition, overspray is appreciably reduced. But the high volume of output makes it difficult to handle in confined areas and around intricate shapes. Improper buildup of some materials can result in a porous or cheesy film due to entrapped solvents. Multiple-coat lining systems require thorough visual inspection of all surfaces between coats, sanding or scraping out rough areas or entrapped foreign materials and then repairing by brushing or additional spray applica-
tions. Additionally, inspection after the first coat is the time to pick up previhsly undetected fabrication or plate shortcomings. In most cases, these can be corrected by chipping or grinding and the first coat reapplied as a touchup. If additional welding is required or if the coating material is one in which the depth of anchor pattern is of real significance, then it becomes necessary to reblast those areas and reapply that first coat. Proper mixing of a coating system is important and the supplier s instructions should be carefully followed. His restrictions on material temperature, relative humidity, cleanliness of equipment, and proportion of activator are important and in some cases are critical . Add only ingredients supplied or specified by the supplier and adjust Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 325
SSPC CHAPTER*L4=2 93 8627940 0003773 T8b 9 FIGURE 5 Two-hundred-foot diameter, open top tank being lined via rolling scaffolding. Courtesy: Tank Lining Corp. with thinner as precisely as possible to the specified viscosity. VIL CURING AND BAKING Coating materials are commonly classified as air dry, force cured or baked. Force curing of even an air dry material does improve its performance characteristics to a degree, depending on the generic type. Force curing can appreciably increase adhesion, improve crosslinkage, insure that all solvents are removed and provide a more complete reaction. When the lined tank is to be exposed to environments such as potable water, food, food packaging materials or any other environment where odor or trace chemical pickup could be of concern, force curing normally is necessary to insure elimination of all solvents and products of polymerization. For all force intercoat drying, an indirect fired heater should be used whenever possible since coating systems may be sensitive to products of combustion. If the fuel is dirty or the fuel-air mixture is incorrect, an invisible film may be deposited on the surface that would affect the adhesion of the succeeding coats. The size of the tank and the equipment available dictates the type of heat source. For indirect heaters the common fuels are oil, steam, natural gas or propane. Curing of high bake coatings, where metal temperatures of 350°F to 450°F (177°C to 242°C) are necessary, usually requires the use of direct fired heaters. Common fuels are natural gas or propane. To attain these temperatures on large tanks the exteriors must be insulated, but present capability limits the size of tank to about 80 feet in diameter. Smaller shop-fabricated vessels are usually force cured andlor final baked in ovens. The prerequisite is an
even distribution of heat with reasonable temperature control. The source of heat can be electricity, gas, or oil, but again the products of combustion should be of primary concern. Ovens provide a more controlled environment and better heat distribution and are more economical for handling small components. Properly controlling the curing of high-bake systems prevents overcuring on intermediate bakes which would result in loss of adhesion, or undercuring of the final coat, which would result in poor chemical resistance. Overcuring on the final coat, short of charring, is not considered to be detrimental. There is no correlation between air temperature and metal temperature during the heating of a tank. The only concern for proper cure is the temperature of the lining. For practical purposes, the exterior metal temperature and the lining temperature are identical. It is most convenient, unless baking in an oven, to use the exterior metal temperature as a control by using recording or contact thermometers and heat indicating crayons. This measurement of surface temperature allows the operator to determine when minimum temperatures are obtained and where cold or hot spots exist, thus assuring uniform distribution of heat. With today s technology the operator does not have an overall temperature but merely a group of readings on which he must rely. Using this information an experienced operator can detect the hot or cold spots and provide for the control of air movement throughout the tank (Figure 7). FIGURE 6 Lining being spray applied in railroad tank car for shipment of clean chemical or food product. Courtesy: Tank Lining Corp. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 326
SSPC CHAPTERxL4-2 93 8627940 0003774 912 NACE Chapter 3 TPC Publication No. 2 states, The factors necessary to complete proper cure of linings are based primarily on knowledge and skills derived from experience. The factors include proper BTU capacity, proper design, method, type and degree of insulation required, ways and means of setting up ducting and curing time. Still, curing must be considered an art rather than a science and proficiency is found principally with those few organizations specializing in the application of tank lining materials as discussed in this rep~rt. ~ Throughout drying between coats, force curing andlor baking, substantial volumes of air should be directed to ventilate all areas. Inadequate ventilation can result in insufficient cure andlor a build up of solvent vapors until runs or solvent wash occurs. VIII. INSPECTION The common view of inspecting painting does not apply to the inspection of coating that are applied as linings. Adherence to this view can be detrimental to the performance of the lining and can greatly increase cost. For example, commonly the word inspection means inspecting by purchaser for acceptance of the workmanship. But while this is a perfectly acceptable technique when inspecting workmanship which can be defined by go or no-go testing, it is not acceptable testing for the application of coatings as linings. Ongoing inspection of linings provides assurances that every phase of surface preparation, application and curing are properly performed. Variations in any phase must be immediately recognized and corrective action taken or performance of the lining can be adversely affected, even though the lining may not fail any acceptance inspection test. The shortcoming of the lining industry is due partially to the limited number of instruments available for measuring the quality of coating work and the resultant over-attention to the few facets that can be measured. Instruments that are available must be calibrated and used properly to be of significant value. Any inspection requires a broad knowledge of the functions of coating work in order to evaluate the quality of work accomplished. Over-inspecting, like overspecifying, can add extra costs, which do not always provide added life to the coating system. Nevertheless, every single phase of the entire work must be inspected to be certain that all is as it was engineered to be, including design, fabrication, material, mixing, application and cure. The design and fabrication of a tank should be inspected to insure that the welds are continuous, the splatter removed, and the heavy ripple ground. Internals having sharp edges should be radiused as needed to allow for coating buildup on edges. Nozzles leading into the tank should be of a large enough diameter to allow surface
preparation and coating application. Following surface preparation, the surface should be inspected for contaminants such as grease, oil, dust or blasting abrasive. Visual laminates and defects on the steel are best detected at this time and corrected before the surface preparation is continued. Inspection for surface preparation to specification should be made keeping in mind that the actual surface preparation and its light reflectant quality varies appreciably with the abrasive used. The intensity and depth of anchor pattern can be rqeasured by a number of available instruments or by comparing to previously prepared laboratory panels. The accuracy of field instruments to measure anchor patterns has not been proven. Inspecting for coating application should be conducted by observing for runs, sags, foreign objects, craters, thickness, curing andlor drying between coats. The dry film thickness should be determined by using a non-destructive gauge, normally of the magnetic type. Variations in readings may be attributed to anchor profile, wall thickness or magnetic effects in an enclosure. An extra coat or additional thickness may diminish rather than enhance the quality of the lining. Even the most rigid tank moves appreciably as it is loaded or emptied and as it is heated or cooled. Stresses exist or develop in many of the materials used as linings; therefore, applying the coating to the minimum thicknesses required allows the film to maintain its adhesion and still have a low permeation rate so that it performs effectively in the environment. The extra coat syndrome so common in maintenance painting is a fallacy that creates many troubles inside a tank. Inspecting for discontinuities (holidays) is extremely important when the corrosion rate of the solution involved isextreme. When the lining is used solely for protecting from contamination, isolated pinholes are not detrimental to the lining, as when a bake phenolic system is immersed in con cent rated su If uric acid. Continuity testing is accomplished by utilizing either a high voltage or low voltage (wet sponge) tester. The wet sponge tester is effective with coating films up to approximately 20 mils. Discontinuities in heavier films can be located by a high-voltage detector. Little work has been done to determine what detrimental effects voltage has on lining films. Unfortunately, when coatings are used as linings in severely corrosive environments, it is imperative that every possible passageway be located and corrected. Until some other way is found, high voltage spark testers will be used, but they should be used judiciously. Voltages must be selected with consideration to the electrical resistance of the formulation and the total film thickness applied. Consideration also must be given to the speed the detector travels over the surface, the number of passes made over a surface and the minimum voltage required to
pass the air gap for a specific thickness. Throughout the inspection any instrument that is destructive to the integrity of the coating should not be used for testing. If it becomes necessary to use such an instrument, the damage must be repaired. Inspection for cure of most coatings is extremely difficult. Hardness tests and solvent softening tests must be used with considerable skill or either can be misleading. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 327
SSPC CHAPTER*L4*2 73 = 6627740 0003775 859 = ing or abrasive blasting to obtain roughness and then wiping with a solvent to remove the sanding particles. With the high bake and most thermosetting materials the overlap is kept to a minimum as the solvents will not wet the completely cured coating. X. CONCLUSIONS Coatings are used as linings for various types of applications such as food containers, hot water tanks, tank trucks, tank cars, storage silos, water treatment systems, large chemical storage tanks, and stacks. The success of a coating system depends greatly on proper design, material selection, and proper application. The versatility of carbon steel plus a coating as a lining gives it advantages over other steel alloys which are extremely costly. Time will advance the know-how, bring better quality assurance techniques, and improve coating formulations. Possibly, supersonic cleaning to replace abrasive blasting, electrostatic deposition to replace spraying and induction heating to replace hot air heating will reduce the time involved in lining a tank to a few hours and eliminate possible errors involved with application. FIGURE 7 Metal temperature at many different areas during curing and baking of linings can be reviewed and recorded simultaneously. Courtesy: Tank Lining Corp. For high bake coatings the degree of cure is well determined by the change in color as compared to control panels. IX. MAINTENANCE Maintenance is just as important for coating systems used in tanks as it is for exterior paint systems. But unfortunately, because the economics differ substantially, so do the maintenance programs. To obtain accessibility to the interior of a process tank, the process must be shut down, and the commodity must be transferred to another lined tank. For exterior paint systems it is practical and economical to inspect on some engineered schedule, such as each quarter or each year, and touch up as needed. Contrarily, lining systems, to be economical, must be designed to give maintenanyfree extended service life. A common rule of thumb is-aminimum of three years, but in most environments a minimum of five years is required and readily obtainable. The coating materials regularly used successfully as linings have long maintenance-free service lives. A typical, good grade, proprietary, high bake, thermosetting phenolic performs for five years in the most severe instances and ten years in many more.
When designing a lining system, consideration must be given to its ability to be touched up or repaired because of physical damage, design change in the tank, industrial accidents or shortcomings in application. Repair materials should be selected for their compatibility and adhesion with the original material, their adhesion to steel and their resistance to the environment. Because there is seldom any appearance requirement, there is little reason to use the same material as the original. The procedure for repairing a coating is normally identical to the procedure used in initial application. Where the repaired coating intersects the existing coating, it is normally recommended that the existing coating be feathered to accept the repaired coating. Feathering requires sandCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 328
SSPC CHAPTERr14-2 93 86279YO 0003776 795 = ACKNOWLEDGEMENT REFERENCES The authors and editors gratefully acknowledge the active participation of the following in the review process for this chapter: T.A. Cross, Richard Drisko, Noel Duvic, Dan Gelfer, Tom Ginsberg, Lewis Gleekman, Leonard Haynie, Harlan Kline, Howard Lasser, D.W. Metzger, John Montle, C. Munger, Bill Pearson, W.A. Severance, William Wallace. BIOGRAPHY Albert L. Hendricks is President of Wisconsin Protective Coating Corporation, Green Bay, Wisconsin, where he has been employed since 1958. His activities while employed at Wisconsin Protective Coatings have been directly related to coating work at various levels including manufacturing, testing, research, quality control, application and soecifvina. -r--, He häs been accredited as a Corrosion Specialist by the National Association of Corrosion Engineers (NACE), and is actively involved on various technical committees within NACE, the Steel Structures Painting Council, the American Society for Testing and Materials, the American Concrete Institute, and the American Water Works Association. He has been an officer at Section, Region and National levels within NACE. BIOGRAPHY Wallace P. Cathcart is Technical Counsel, Trinity Industries Inc. His technical efforts for more than forty years have been in the selection and application of coatings and linings for industries involved with storage and transportation. He co-founded and for 34 years was CEO of Tank Lining Corp. He is accredited as a Corrosion Specialist by the National Association of Corrosion Engineers and is a registered professional engineer in the state of California. He was awarded a certificate of recognition from Steel Structures Painting Council as Paint Manual author, author and editor of the JPCL and technical committee chairman. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from
IHS--`,,,,`-`-`,,`,,`,`,,`--329 1. Chapter 1 of TPC publication No. 2 of the National Association of Corrosion Engineers Coatings and Linings for Immersion Service has compiled detailed safety information for work inside tanks. 2. National Association of Mutual Casualty Company, 20 North Wacker Drive, Chicago, IL 60606. 3. The American Gas Association, 1515 Wilson Boulevard, Arlington, VA 22209. 4. NACE Standard RP-01-78 Design, Fabrication and Surface Finish of Metal Tanks and Vessels to be Lined for Chemical Immersion Service. 5. NACE TM-01-74 -Laboratory Methods for Evaluation of Protective Coatings Used as Lining Material in Immersion Service. 6. Bryan I. Zohn, Protective Lining Performance, Chemical Engineering Progress, Vol. 66, No. 8, August 1970. 7. See NACE TPC Publication No. 2, Coatings and Linings for Immersion Service.
SSPC CHAPTER*LS-O 93 8627940 0003777 b2L = CHAPTER 15 PAINTING HYDRAULIC STRUCTURES by J. i. Kiewit Steel in dams, hydroelectric plants and irrigation works is coated primarily to prevent corrosion and secondarily to improve appearance. The ideal of permanent preservation is rarely attained. Weathering and fresh water immersion exposures are less severe than many encountered in other industries, but hydraulic structures are built to last a century or more. Time takes its toll. Corrosion engineers must exercise skill in evaluating deteriorative elements in each coating exposure to make the best possible selections, and to accomplish each step in the process necessary to extract full service potential from the chosen coatings. The design of hydraulic structures is performed by several kinds of engineers and architects, some of whom are only peripherally knowledgeable about corrosion and coatings. Trained corrosion engineers can contribute vitally to design. For instance, an overview of the complete project may reveal the existence of bimetallic couples with nonferrous metals such as copper grounding mats or electrolytic corrosion currents in the soil, which could profoundly influence corrosion rates and coating performance. A corrosion engineer can recommend measures to eliminate or reduce corrosion, such as the selection of noncorrosive materials where economically feasible, and the installation of cathodic protection systems in conjunction with coatings for steel. Even though steel continues to be used widely, and protective coatings usually are the major means of protection and decoration, a corrosion engineer provides essential support to design engineers in the selection and use of materials. Before the coatings for new structures are selected, the ferrous metalwork should meet design specifications for painting. For instance, specifications may require that edges be rounded to minimize thinning of the coating and that welds be ground and weid spatter removed. Back-toback angles with space between them or intermittent weld should both be avoided. Other failures attributable to faulty design are discussed in a separate chapter. Planning the sequence of painting operations can preclude the difficulty of painting inaccessible areas or awkward scheduling situations, such as the excessive weathering of primed surfaces. While this review of coatings for hydraulic structures is
not exhaustive, it presents descriptions of materials and methods that time has proved effective. Present federal requirements and others certain to come from the EPA, FDA, and OSHA foreshadow
the emergence of new coating
materials and mandatory procedures. Unfortunately, answers have not yet surfaced in all potentially troublesome areas, such as a replacement for the critically vital sandblast cleaning method. However, the best guess is that industry will develop water-based and solvent-free coatings to resolve the solvent emission dilemma. It would not be surprising to find that new methods and materials do more things better than the old. The discussion mentions a few important coatings that are usually or always applied by shop processes. However, emphasis is placed on coatings applied in the field and by conventional methods to in-place, large and small piping, gates, cranes and diverse metalwork items. I. SELECTION OF COATINGS Before focusing on specific coatings for hydraulic structures, the overall objectives and a variety of factors affecting the coating selection should be considered: Related Factors Coating Requirements Design for painting Surface preparation Coordination with Specialist services construction activities Ambient conditions (temperMethod of specifying ature, moisture, ventilation, cost etc.) Safety requirements Latitude (tolerance to adverse conditions Objectives Item or Structure Protection Location of applicaAppearance tion (shoplfield) Dura bi Iit y Size Maintainability Surface configuration Accessi bility Possible handling and
traffic damage Some or all of the above may present problems in a given case, and problems easily resolved in new construction may become acute in maintenance painting. Coatings will be categorized in terms of the exposures for steel found in and around hydraulic structures, and recognition of the major deteriorative elements in these exposures becomes pertinent. A few of the more common ones are: Water Cavitation 9 Chemical attack (acids, Soil stresses and bases, organics) punctures Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 330
SSPC CHAPTER*L5-0 93 8b27940 0003778 568 Abrasion (debris in a Biodegradation water, windblown sand,
Weathering ice) a Corrosion currents Erosion (waterborne Temperature variations sand or gravel) a Freeze-thaw Impacts Vandalism The engineer must identify deteriorative elements in a particular situation and select a coating system proven resistant to all. The instances of coating failure from unanticipated causes underline the importance of carefully analyzing exposures. Coatings for hydraulic structures protect steel primarily by three mechanisms: Barrier The coating isolates the substrate from its environment, as if the surface to be protected were wrapped in a completely inert and impermeable plastic bag (e.g., coal-tar enamel). Inhibition The coating modifies the environment in contact with the substrate. Concrete and cement mortar produce a ph of 9-12, in which steel usually does not corrode in the absence of high chloride concentrations. Some paint pigments also tend to inhibit corrosion. Substitution The steel is coated with a metal having different corrosion resistance characteristics (e.g., zinc, which acts as a sacrificial anode in immersion exposures). Most of the coatings considered are of the barrier type, although the effectiveness of the barrier may vary considerably. Since World War II, the coatings industry has presented corrosion engineers with a bewildering array of coatings with enhanced capabilities. But rather than simplifying selection, this complicates it. In the absence of time or facilities for lengthy laboratory and field investigations, perhaps the best guide to selecting a coating is demonstrated performance under identical or closely similar service conditions. We cannot wait for 50-year performance to verify coating serviceability; however, the behavior of organic coatings in the Bureau of Reclamation s Shasta field test3 may be instructive. In this test, 70 percent of the organic coatings that were com-
pletely defect-free at five years were also defect-free at 15 years. Thus, some projection of coating serviceability can be made -cautiously, and with high regard for the comparability of exposure conditions. Thick coatings usually serve longer than thin ones. Similarly, hot-applied, baked or chemically set coatings generally outperform cold-applied, solvent-based type. Performance depends, in part, upon the degree of cure obtained and the relative chemical inertness and resistance of coatings to water permeation. In this context, shop painting offers advantages of superior facilities and better control of the more sophisticated baked, hot-applied and FIGURE 1 Shasta Dam, part of the Central Valley Project, California, il. plant, switchyar ds, and a visitors center. lustrates the many protective and decorative painting re. Courtesy U.S. Bureau o f Reclamation quirements of hydraulic structures. Visible are penstocks, power 331 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERULS.0 93 8627940 0003779 4T4 internal-set coatings. On the other hand, the large size of some equipment necessitates field painting, and durable yet practical coatings must be provided. A field coating with few rigid application limitations and great tolerance for unfavorable combinations of marginal surface preparation, temperature and humidity is much to be preferred over one that might last longer but seldom is applied correct ly. Cost is a major selection factor. Corrosion engineers are well aware that the per gallon price of paint materials is a poor criterion of coating economics. Cost should be based on the total applied cost divided by the expected service life. Clearly, the 50-to 100-year life of cement mortar or coal-tar enamel coatings produces a coatings bargain, particularly when the extraordinary costs of taking outages for maintenance of vital, revenue-producing structures are included. Space limitations and the vast number of coatings generated by the industry since World War II necessitate confining the discussion to the most common generic types of coatings. Coatings for which specifications are listed in Section V have performed well and are in wide use. Coating selection and practices of large organizations concerned with hydraulic structures are described in their manuals and reports (see references), which can serve as a source of additional information. A. UNDERWATER EXPOSURES Items fabricated of steel that are continuously submerged in normal operation include high-pressure gates; roller gates; valves, trashracks and interiors of water storage tanks; and pipe used for penstocks, outlets, conduits, siphons, pump discharge lines and water distribution lines. In addition to continuous immersion, coatings may be subject to erosion, abrasion, andlor cavitation. While protecting steel, coatings also prevent rust tuberculation that may sharply reduce the hydraulic efficiency of piping. Proven immersion coatings expected to provide service approximating the life of the structure are limited to cement mortar and coal-tar pitch or enamel. Other common coatings holding high promise and awaiting the validation of sufficient history include coaltar epoxy and fusion epoxy. These and others are grouped for the present in a second tier of materials expected to last over 20 years, provided they are maintained regularly. The role of rigorous surface preparation in the performance of organic immersion coatings can hardly be overemphasized. The tolerance of poorly cleaned metal varies somewhat (e.g. low tolerance by vinyls, better tolerance by coal-tar epoxies, fairly high tolerance
by coal-tar enamel), and a slight concession in the intensity can be allowed. Experience shows blast cleaning or the equivalent to be essential. Lesser methods, which do not remove all contaminants and roughen the surface, almost invariably lead to substantially reduced durability. Cement mortar alone tolerates truly superficial surface cleaning. 1. Cernent mortar Cement mortar is among the oldest and best pipe linings. Mortar reliably protects for over 50 years in water distribution systems by creating a corrosioninhibitive alkaline environment (pH-12) at the surface of the steel. The preponderance of linings, ranging from x6 to 3h inch (4.8 to 19.0 mm) in thickness, are plant-applied by the centrifugal casting* (spinning) process to piping ranging from 12 to about 60 inches (0.3 to 1.5 m) in diameter. Bends and other special shapes unsuitable for spinning are lined by handtroweling. An external coating can be applied concurrently as discussed in section B. An option to apply mortar linings to piping already in place assumes great importance when large-size pipe must be lined or an old line has corroded and requires replacement or abandonment. Piping as large as 21 feet (6.4 m) in diameter has been lined, although the lining of sizes over 14 feet (4.3 m) in diameter is uncommon. Of course, the lining thickness must be increased in proportion to the increasing pipe size. Further, an in-place lining plugs up and seals most small holes up to as much as 3/4 inch (19.0 mm), restoring the integrity of an old corroded line and restoring it to approximately its original carrying capacity. A major advantage of in-place motor lining lies in its tolerance to only superficial preparation. Old lines can be FIGURE 2 Soon after painting, rust (by knife) began draining from under a 'Centrifugal ca sting -a process in which the Coating radial gate member secured by intermittent welds. For best material is introduce d into rotating pipe and spreads to design, the inaccesible space should be sealed by a continuous weld or equivalent. a smooth, continuous lining of uniform thickness. Also Courtesy US. Bureau of Reclamation called spinning. 332 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*LS=O 93 8627740 O003780 LLb cleaned sufficiently by pulling scrapers through the piping. The alkalinity from water permeating the coating to the metal surface nullifies further corrosion. Plant-applied water linings usually crack if allowed to dry after curing. Most are hairline (less than 1/32 inch (0.08 mm)) and close upon rewetting and expansion of the lining. Alkalinity stifles corrosion even in open hairline cracks and, in some waters, the cracks heal (¡.e., build up a calcareous scale). Cement mortar linings depend on arch action to hold their position in piping, not on adhesion in the usual sense. Thus, the small shrinkage cracks or slight gaps between the lining and the metal usually are not a concern. Mortar linings afford good protection against erosion by sand and gravel-laden water, by virtue of their thickness. They generally resist water velocities up to 20 to 25 feet per second (6.1 to 7.6 mls). Although mortar exhibits considerable resistance to freeze-thaw action, gradual deterioration proceeds, and mortar lining above-ground piping, which will be exposed and empty during winters in cold climates, may not be advisa le. Mortar-lined piping so exposed is best kept ful of moving water or thoroughly dried during he winters. 2. Coal-tar coatings Coat-tar pitch as a principal constituent in coatings has long been prized by the coatings industry, primarily because of economics and its hydrophobic property. Suitably processed coal-tar products absorb little water and are virtually unaffected by long periods of water immersion. In this respect, they are generally considered to be superior to asphaltic compositions. They also are toxic to most organisms and discourage biological degradation. Thick, hot-applied versions of coal-tar coatings afford the longest service. OSHA, EPA and other regulatory agencies are currently evaluating the carcinogenic effects of coal-tar as it is applied and exposed in coatings. Obviously, this could lead to specific or effective proscription of one of the best coating constituents. It is hoped the evaluation is unhurried and realistic. 3. Coal-tarpitch Hot-applied coal-tar pitch, applied by dipping, has preserved submerged trashracks for nearly half a century on Bureau of Reclamation projects. The extensive equipment required for dipping justifies this excellent coating only for very large jobs, and it has been seldom used in recent years.
4. Coal-tar enamel Coal-tar enamel is especially appropriate for lining and coating steel pipe. Service records project a life of 50 years or more. It is commonly applied to straight individual sections by centrifugal casting (spinning), which can be readily controlled to provide a uniformly thick, 3/32 inch (2.4 mm), lining of glass-like smoothness. This characteristic is advantageous in achieving low friction losses with resultant economies in design and operation. The lining is most frequently applied in the pipe fabricator s plant, but a few independent applicators are organized to apply the lining by hand at the jobsite. Pipe lined by the plant process has ranged from 4 inches to more than 10 ft. (0.1 to 3.0 m) in diameter, and the cost of mechanically applied enamel, including blast cleaning, is moderate. By using mechanical couplings, individual sections may be lined for the full length, and no hand work is required. Coal-tar enamel with wraps can be applied to exterior pipe surfaces in the same plant operations, as discussed in section B. For larger diameter, mechanically lined pipe in which sections are joined by field welding, joint areas are lined after installation by hand daubing. Hand daubing must be used for irregular shapes not adaptable to spinning. For pipe under 27 inches FIGURE 3 Rigorous sandblasting removed hard, tight, rust scale (right of rivets) in 30-year old pipe. It also removed corrosion products from the bottom of pits preparatory to painting. Courtesy U.S. Bureau of Reclamation Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 333
SSPC CHAPTER*LS=O 93 m 8627940 0003783 O52 m FIGURE 4 --`,,,,`-`-`,,`,,`,`,,`--Glassy smooth surface of shop spun coal-tar enamel provides low hydraulic fricti on in water piping. Courtesy U.S. Bureau of Reclamation (0.69 m) in diameter, it is necessary to employ 5. Cold applied, coal-tar coatin gs mechanical couplings rather than welding because Coal-tar pitch also has been in corporated into a of the difficulty or impossibility of hand daubing variety of cold-applied, rela tively thin film coatings. joint areas or of performing maintenance. Very Some are solvent cutbacks modifie d with various large diameter pipe, over 15 ft. (4.6 m) in diameter, fillers and other constitu ents. In others, the coal tar may have to be lined in its entirety by hand daubing has been used as an extende r. Among the best and even though the cost is much higher than for lining most widely distributed of t hese is the coal-tar by spinning. epoxy paint. Coal-tar enamel should be selected only Such paints afford more than 20 years of servwithin its limitations. It is suitable for large, ice to metalwork in immersion exposures and are essentially cylindrical surfaces such as piping, easily brush- or spray-applied to piping and the but is very difficult to apply to complex shapes, irregular surfaces of bulkhead gates and trashsuch as bulkhead gates or items having beams or racks. Those suitable for potabl e water may be girders. Enamel linings in empty piping are some- used above as well as below th e minimum water what susceptible to cracking and spalling in cold surface of tanks, since they a re less susceptible weather, and to bond deterioration and a different than coal-tar enamel to crack ing under the suntype of cracking where the pipe exterior is exposed induced heat in the top and sides of the tank. to the sun in warm weather. It resists poorly the Because the combination of hea t and condensate erosive effect of sand and gravel in water, or the (essentially, distilled water ) in the upper part of the cavitation occasionally present in high-velocity above-ground tanks constitutes a severe exposure, flows. It also degrades rapidly by hardening and a coating proven in this servic e should be selected. cracking in direct sunlight. And, finally, enamel Coatings containing coal lar f requently are inmust be applied by specialists with suitable equip- compatible with other coatin gs. Attempts to apply ment and experience, backed up by knowledgeable other coatings over coal tar may encounter poor inspection. adhesion. In fact, one vinyl resin paint bonded
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SSPC CHAPTER*L5.0 93 8627940 0003782 T99 FIGURE 5 Coal-tar enamel applied by hand daubing in Shasta Dam penstock presents a distinctive pattern. The slightly greater roughness of daubed enamel is not considered significant in large piping. Courtesy U.S. Bureau of Reclamation poorly to a surface formerly coal-tar coated, even though that surface had been sandblasted thoroughly. In addition to affecting coating bond, the coal-tar oils may bleed through and disfigure the top coat. 6. Coa/-tar epoxy Coal-tar epoxy paint came into wide use in the 1960 s and serves as an example of the new breed of two-component immersion paints. Epoxy resins adhere well to several substrates and allow considerable latitude in the quality of surface preparation. Extending epoxy resin with economical, water-resistant coal tar produces a high-solids coating that has performed well for more than 15 years in piping and on bulkhead gates, trashracks and spiral cases. It may be brush-, roller-, or sprayapplied with or without a primer, and two coats provide a thickness of about 16 mils (0.4 mm). The chemical-setting mechanism imposes rigid requirements for thorough mixing and adherence to application and curing times and temperatures. Some prefer to apply coal-tar epoxy paints over epoxy- or zinc-pigmented primers for enhanced adhesion and durability. 7. Other epoxies Other epoxies contain no coal tar and may be obtained in any color. Many cure to a tile-like gloss, are easily cleaned and are approved for potable water tanks. A few are 100 percent solids, obviating problems with solvent-release regulations. Others can be applied underwater, although usually with considerable difficulty. A similar diversity of characteristics is represented among multicomponent paints composed of other synthetic resins or combinations thereof. 8. Solvent paints Solvent-release paints formulated with some of the same resins remain in wide use and high esteem for the simplicity of their handling, applications and established service records. For example, vinyl resin, phenolic and coal tar paints in various formulations have protected hydraulic equipment
for 20 years with proper maintenance. 9. Temporary protection When underwater protection is required for only a few years in mild exposures, simpler surface preparations and less expensive materials may suffice. Cold- and hot-dip-applied asphaltic coatings afford lower durability than the corresponding coal-tar coatings. Galvanizing metalwork, such as small slide gates, may be selected for high abrasion resistance and ease of recoating; however, while zinc has exhibited long life in some instances, it has succumbed quickly in more corrosive waters and its durability in immersion is not easily predictable. 1O. Other coatings Many excellent coatings, based on relatively new synthetic resins now in wide use, are establishing solid performance records in continuous immersion. Prominent among these are epoxies, vinyls, phenolics and urethanes and, for the time being, it appears the most durable of these is the multi-component type. To the extent of their suitability to water works structures, certain powder (fusion) coatings also offer great promise. Eventually, a few of these coatings will provide durability on the same order as cement mortar and coal-tar enamel. Two Bureau of Reclamation tests2 illustrate the progress industry has made in developing better immersion coatings. Twenty test linings were installed in the Unit 5 penstock at Shasta Dam in 1949. After 10 years, 32 percent of these remained in defect-free condition. Just 10 years later, 36 lining systems selected from the most promising materials then available were placed for testing in a siphon on the Collbran Project. Here, 70 percent survived 10-year exposure without defects; included were vinyls, epoxies, phenolics, neoprenes and coal tars, applied as solvent and catalyzed materials. Much longer exposure will be required to enable the selection of the best of the Collbran linings. B. UNDERGROUND EXPOSURE Buried steel in hydraulic structures usually comprises portions of penstocks and piping used in water irrigation and domestic water distribution systems. The importance of most buried structures and the difficulty of inspecting and maintaining them underline the value of quality and durability in the initial coating selections and of performing the applications correctly. The exposure demands maximum coating permanence. Requirements for the exCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 335
SSPC CHAPTER+LS.O 93 8627740 0003783 925 terior protection of such piping are essentially the same as for gas or oil piping. Pipe corrodes in soil as a result of deteriorative elements present in immersion exposures and the effects of soil stresses, punctures and bacteria. Water leaches chemicals from the coil and becomes very corrosive. Galvanic and electrolytic corrosion currents may dictate the dielectric properties of the coating. Consequently, a preliminary soil corrosivity survey is often conducted to reveal specific problems and possible need for cathodic protection. Coatings for buried metal usually are relatively thick films. If the coating is not inherently resistant to soil forces, sturdy wraps must also be provided. Cement mortar and coal-tar enamel are most commonly selected for buried piping, but a number of other materials offer attractive characteristics in some circumstances. 1. Cement mortar Cement mortar inherently resists most soil forces and requires no special wraps to prevent handling abrasion. Mortar containing sulfate-resistant cement is adequate for most high sulfate soil waters encountered in the United States. Wire-reinforced mortar usually is plant-applied to the exterior of piping up to 84 in. (2.13 m) in diameter, often in conjunction with mortar lining application. It can also be pneumatically applied to larger piping in the field or to irregularly shaped items. Unless strong electrolytic currents exist in the area, cathodic protection rarely is needed with mortar-coated lines, which are properly isolated electrically from other structures. 2. Coal-tar enamel and wraps Coal-tar enamel for exterior pipe surfaces is usuFIGURE6 Three experimental lining areas can be seen in siphon piping used for the Collbran test of pipe lining materials. Courtesy U.S. Bureau of Reclamation ally reinforced with an embedded fibrous glass mat, and an asbestos felt rock shield is bonded to the hot enamel. This coating is normally plantapplied to pipe in sizes up to about 10 feet (3.0 m) in diameter. An equivalent application can be performed in the field, but only with great difficulty
and by the most qualified personnel. When protected against handling damage during pipe installation and backfilling, the coating effectively and permanently isolates the steel from its soil environment and thus provides a high level of protection. The coating should be electrically tested for pinholes and impacted spots just prior to backfilling, particularly if cathodic protection will not be added. The highly dielectric enamel is especially compatible with cathodic protection. Since only the tiny bare metal areas in pinholes must be so protected, current demand is small, and a small cathodic protection installation often can protect great lengths of piping. 3. High Density Polyethylene The threat to continued availability of coal-tar enamel has spurred interest in other coatings. Among a variety of plastics that may be suitable is polyethylene; thick, tough, highly inert and dense. The Bureau of Reclamation permitted applications of such a coating to several sections of the 66 to 102 in. (1.68 to 2.59 m) diameter line piping on its Southern Nevada Water Project. The coating reportedly had been successfully in service for over 5 years on piping with diameters up to 42 in. (1.1 m) elsewhere in the United States, displaying low and steady cathodic protection current demand. Experience with Southern Nevada bore out this promise; current demand was significantly lower than for coal-tar enameled pipe. Plant application of the coating involved melting high density polyethylene beads at near 5OO0F for extrusion over a thin butyl adhesive on the rotating pipe. The wide spiral overlaps fused together to produce a continuous coating with a minimum thickness over 60 mils (1.5 mm). Under tension, the coating shrank back 2 to 4 in. (5 to 10 mm) from the pipe ends and stabilized within 30 days of yard storage. The coating displayed extreme resistance to handling and backfill damage during installation. In this first application to large diameter piping, a few problems developed. The coating tended to neck down and developed voids along high longitudinal welds, necessitating a filler application to the weld prior to coating. The coating also pulled away from the surface at cut-
outs for manholes, etc. These and the field joints were taped with butyl adhesive-polyethylene backing plastic tape. The 12 in. (0.3 m) wide tapes proved difficult to tighten properly by hand methods. While some plant and field refinements Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 336
SSPC CHAPTER*LS*O 93 = 8627940 0003784 861 of future high density polyethylene coatings may occur, virtually permanent protection of buried metal piping is expected. 4. Tapes Several tape coatings have performed well on buried piping. Hot-applied, double-wrapped, glassor fabric-reinforced coal-tar enamel tapes provide about the equivalent of a coal-tar enamel and wrap coating. Cold-applied polyethylene and polyvinyl chloride tapes 10 to 30 mils thick with pressuresensitive adhesives have been spirally wrapped on small diameter piping. Priming the surfaces enhances adhesion. A shield against scarring and puncturing the tape during backfilling often is essential. The industry appears to be developing heavier duty tape-coating systems with both high durability and resistance to soil and handling. 5. Fusion coatings Certain plant-applied fusion coatings exhibit tenacious adhesion and extraordinary toughness as well as the durable corrosion-preventive characteristics essential to soil burial conditions. Thorough surface preparation by blast cleaning is mandatory. Piping must be heated to a high temperature, perhaps 350°F (177°C) for coating. The powdered coating melts, fuses and reacts chemically as it contacts the surface. Smaller items, such as fittings for line piping, may be coated (internally and externally) in a fluidized bed of the powder. Powders can also be spray applied to preheated metal by hand and plant processes. 6. Unbonded sheet plastic Ductile and cast iron piping is now being protected solely by an unbonded sheet polyethylene wrap. It will not be surprising if some variation is developed for long-term protection of steel in the ground. 7. Joint Protection Joints present possibly the most difficult problem in providing external coating protection. The principle is that the joint coating must equal that on the rest of the piping, but irregular shapes and field conditions often frustrate this standard. For example, plastic tapes are suitable for field-welded joints and perhaps pipe couplings in small piping, but conform poorly over elbows, unions, tees, etc. Hot-applied, coal-tar enamel tape conforms well, but requires more time and care. Joints in mortarcoated pipe require field-placed mortar encasement complete with reinforcing wire mesh. Similarly, mechanical couplings in coal-tar enameled
piping may actually be encased by wrapping a diaper around the joint and pouring it full of enamel. The coating may even have to accommodate slight joint movement without rupturing. The variations are many, but full protection must result. C.ALTERNATING WATER AND AIR EXPOSURE Low-head gates, trashracks and other fabrications of steel used for controlling waterflow in spillways, checks, canal turnouts, etc., are subjected to combinations of immersion and atmospheric exposures. Portions of these items may be completely submerged, others exposed to continuous weathering and middle parts to a fluctuating water level. In some cases, structures may operate only during the irrigation season and be dry during the winter. Sand and gravel suspended in water erode coatings. Ice and floating timbers abrade them. In addition to protecting metal, coatings now are expected to clothe visible structures in attractive colors that harmonize with surroundings. In short, alternating exposure may be viewed as the most severe of all exposures, this being slightly mitigated by the accessibility of the metalwork for maintenance. Coatings for this alternating exposure must resist deteriorative effects of both immersion and weathering. Thus, the bituminous coatings that quickly embrittle, check, and degrade, and urethane, phenolic and epoxy paints that fade and chalk in direct sunlight do not perform well without weather-resistant topcoats. Tough, resilient paints best minimize damage from scrapes and impacts by floating debris. Obviously, blast cleaning is recommended for coatings in this exposure because they require the same high level of surface preparation as immersion coatings, if long service is to be realized. Also, many items in this exposure include edges, rivets, bolts, welds and junctions of metal parts. All of these are points of weakness in a paint coating, which should be reinforced by one or more edge coats. 1. Vinyl resin paints Paints based on formulations of vinyl resins have established solid records of service for more than 20 years on radial gates. (See Figures 1 through 4.) The several vinyl resins differ somewhat in properties so they can be compounded to exhibit varying degrees of hardness, toughness and impermeability to water. Some vinyl resins adhere to steel; others do not and may be used only in topcoats over adherent vinyl primers. Some vinyl systems include a special vinyl pretreatment called a wash primer, intended to improve adhesion and introduce a rust-inhibiting layer next to the steel. The solids content of most vinyl paints is low, usually necessitating application of at least four coats. Five to ten mil (0.13 to 0.25 mm) thick coatings are usually specified to ensure protec-
tion, the thicker coatings providing enhanced abrasion resistance. Pigmentation allows a wide range of color selection, including aluminum. 2. Galvanizing If small equipment items may easily be removed for Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 337
SSPC CHAPTERmLS.0 93 = 8627940 0003785 7T8 FIGURE 7 Sleevetype coupling in a coal-tar enamel coated pipeline has been completely coated with enamel. Workman is electrically inspecting the coating for pinholes, thus assuring coating continuity and joint protection equal to that on the shopapplied pipe coating. Courtesy U.S.Bureau of Reclamation maintenance during an off-irrigation season and appearance is secondary, galvanizing may be preferred. For example, galvanizing small turnout gates prevents the almost inevitable handling damage to paints incident to gate installation and operation. They can be removed and regalvanized at intervals, or, if the water proves aggressively corrosive, a more resistant coating such as vinyl resin paint can be applied. 3. Abrasion-Resistant Coatings Sometimes coating properties other than appearance and weathering resistance assume overriding importance. For example, the frames for moss collection screens are difficult to paint by conventional means, and these parts sustain severe abrasion. However, their small size permits application of thick, tough fusion epoxy by the fluidized bed process. In another example, the faces of eleven, 138 by 28 ft. (42.1 by 8.5 m) drum gates atop Grand Coulee Dam are scraped by metal seals, which have destroyed all coatings tried on the gates. Recently, a 25 mil (0.63 mm) thick, twocomponent urethane paint applied as a test on one gate survived two operating seasons in this severely abrasive exposure without significant damage. Direct sun, which affects most aromatic polyurethanes, does not reach the north facing Coulee gates, and more of them have been coated with the expectation that this vexing abrasion problem has been solved. D. ATMOSPHERIC EXPOSURE Protecting steel in a purely atmospheric environment against structurally critical corrosion ordinarily presents much simpler problems than encountered in exposures previously discussed. First, corrosion progresses much more slowly. Second, coating inspection and maintenance can usually be accomplished more readily on such accessible items, but this should not mean that atmospheric painting can be regarded lightly because high standards of appearance are demanded. Moreover, while properly maintained immersion coatings are expected to serve 20 years or more, few atmospheric paints exposed outdoors retain their highly attractive initial appearance much beyond 10 years. Cranes, exteriors of water and oil storage tanks and piping, handrails, substation electrical equipment, bridges, and exposed parts of pumps, turbines and gates are highly visible. They reflect the public image of their
owners and, therefore, invite frequent cosmetic treatments even though the surfaces may not corrode for much longer periods. The wide diversity of items to be painted in a multiplicity of colors imposes surprising demands on the corrosion engineer s time. 1. Outdoor Coatings Using the best cleaning methods for atmospheric coatings pays dividends in extended coating life. Blast cleaning should be considered in locations of intense airborne industrial contamination where metalwork is known to corrode rapidly. However, less rigorous methods that effectively remove all grease or other contaminants and loose matter from surfaces are more commonly and successfully used in rural environments. Rust-inhibitive primers with strong wetting properties tend to neutralize the effect of residual underfilm contaminants. (a.) Pigments -Aluminum-pigmented topcoats offer maximum durability because they protect the paint binder. Other pigmentations provide colors required for aesthetics. Paint pigments vary considerably in stability under weathering exposure. Bright blues and reds notoriously fade and chalk, while most tans, browns and grays hold up well. Further, different pigment combinations that yield the same paint color may weather quite differently. Durable colors and pigments can be selected to contribute years to the service of atmospheric coatings. (b). Vehicles -The oil and alkyd vehicles, long the staple bases of decorative topcoats, currently are being challenged successfully by a number of synthetic resins. Bonneville Power Administration (BPA) tests of topcoats for its electrical equipment revealed that silicone alkyd enamels retain color and gloss up to twice as long as alkyd-base materials, significantly reducing maintenance costs. Combinations including acrylic resins may be even more durable. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 338
SSPC CHAPTER*LS-O 93 oe 8627940 0003786 634 oe (c.) Water borne paints -Recognizing that the expected severe limitations on organic solvent emissions may virtually eliminate solvent-base paints, the industry has developed a few waterborne paint systems for metal. BPA formulated a stainless steel pigmented acrylic resin-based paint that outperformed all other paints tested at the severest seacoast BPA test site at Cape Blanco, Oregon. This material can act as the sole coating or as the primer for color-pigmented topcoats, either solvent or waterborne. Interestingly, this commercially available paint can be applied directly to some galvanized metal without pretreatments to insure adhesion. (d.) Zinc coatings -Galvanizing items of suitable size and shape affords long-term protection in most rural atmospheric exposures. The zinc coating is especially well adapted to steel, which receives extremely rough handling during assembly and is costly to paint after erection. The color and reflectivity of newly galvanized items are objectionable in some settings. In an effort to blend these items into surroundings, some users recently have treated galvanized steel with phosphoric acid-base dulling solutions, which may enhance protection and paintability of the zinc. Painting galvanized items permits a full range of color selection. Caution must be exercised, since obtaining coating adhesion to zinc presents special problems. Zinc-pigmented paints have undergone extensive development in recent years and now may be obtained in a wide variety of inorganic or organic vehicles. Those based on inorganic vehicles have demonstrated especially good resistance to atmospheric exposure when properly applied to blast-cleaned surfaces. Others serve as corrosionresistance primers. Where structural steel must be exposed outdoors for long periods after fabrication and before erection and final painting, mill-applied, weld-through, zinc-pigmented primers minimize the surface preparation necessary before field painting. Intercoat adhesion failure experienced with some zinc-pigmented primers prompts special care in selecting compatible topcoats. 2. Indoor Coatings Paints that need not resist severe weathering are selected primarily for aesthetic purposes. Gloss or semigloss finishes facilitate cleaning grease and dirt from machinery and promote good housekeeping. Suitable paints exist in a wide range of colors to produce any desired decor. Field painting of indoor metalwork can be performed with the same enamels as outdoor exoo-
sures or any of many synthetic-resin, single or multicomponent paints. Panelboards, enclosures and other equipment for control rooms are commonly furnished with attractive, highly cleanable finishes of various resins applied by plant processes. Further painting of such items not only is unneeded, but would be unwise, since the plantapplied finish often is superior to a field-applied coating. E. SPECIAL CONDITIONS While coatings for previously mentioned exposures afford protection to most surfaces of hydraulic works with only infrequent attention, similar exposures may include additional elements that may lead to rapid coating failure. Cavitation, erosion, abrasion and impacts are grouped together because all are forms of mechanical attack on the coating, even though the causes and mechanisms may be quite different. 1. Cavitation High water velocities, usually well over 45 ft./s (14 mls), occur frequently in localized areas of hydraulic equipment, often without adverse effects on coatings. When combined with surface irregularities (coating roughness, offsets in the surface, rapid changes in the direction of flow), negative pressures create vapor pockets. The collapse of minute vapor bubbles downstream from the surface irregularity rapidly destroys most coatings and often the substrate metal; this is called cavitation or cavitation erosion. No coating withstands severe cavitation. In this case, only weld repair with tough stainless steels or other special metals can extend the life of FIGURE 8 Dry film thickness of a coating on the stay vanes of a turbine spiral case is measured using a magnetic gage. Courtesy U.S. Bureau of Reclamation Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 339
SSPC CHAPTER*LS.O 93 = 8627740 0003787 570 an item such as a turbine runner. Tightly bonded, highly elastomeric coatings may resist mild to moderate cavitation for sufficient periods to justify their use. To do so, the special neoprene or urethane materials apparently must be applied to substantial thicknesses, on the order of 70 mils (1.8 mm). Thick, brittle coatings should be avoided since they cavitate readily and, once, cavitation starts, it tends to self-propagate, increasing in intensity downstream from the original site. The effectiveness of cavitation-resistant coatings can be proved quickly, within a year or less. Accordingly, small-area testing of coatings proposed for this service is highly recommended. 2. Erosion Erosion from sand- and gravel-laden waters in siphons and pump impellers is best resisted by elastomeric coatings, and lesser thicknesses suffice. Inadvertently, the Collbran site3 provided an excellent field erosion test of lining materials, since an unlined canal upstream fed sand and gravel into the water. Erosion wore through coal-tar enamel in 10 years, and a catalyzed phenolic paint fared only somewhat better. Only a six-coat, 30 mil (0.76 mm) liquid-applied neoprene lining remained unaffected. All other linings were gone or were showing significant damage within the 10-year period in the siphon invert. The field performance of these linings agreed with a laboratory erosion test of si mi lar I in ing~.~ In other locations, A in. (3.2 mm) thick, bonded sheet neoprene was performing well at 9 years in a large siphon subject to severe erosion where the bedload included even small- to medium-sized rocks. In addition, rigid coatings with pigments such as aluminum oxide or coatings in which hard sands have been embedded have proved fairly serviceable. Cement mortar linings provide long service partially by virtue of their great thickness. 3. Abrasion and impacts Thickness in excess of that required only for corrosion resistance helps in minimizing the effects of abrasion and impacts. Again, the coating properties of strong bond, toughness and resilience prolong the life of the coating. 4. Chemical attack Chemicals find only incidental use in and around hydraulic structures, although chlorine may be required in water treatment plants. Protection against chemical exposures is discussed elsewhere in this manual. Higher than normal concentrations of chemicals can shorten coating life and
permit premature corrosion. Distilled water is often used in short-term laboratory tests of coatings. Unusually pure water constitutes a sort of chemical exposure that may deteriorate some coatings. Mountain waters may attain purity such as to attack coatings that may perform well in lower elevations where water contains more solids. Condensing conditions occur frequently in hydraulic structures. For example, water condenses on interior surfaces of tanks above the waterline and on the exterior of waterbearing pumps and piping. The condensate is essentially distilled water. The coatings discussed earlier for immersion exposure generally resist pure water. However, equipment that sweats frequently in an otherwise atmospheric exposure should receive the same thorough surface preparation and coating selections for alternate atmospheric and underwater exposure. A few soil waters display unusual acid levels or sulfate contents, which may be deleterious to buried mortar coatings. Organic coatings or galvanizing that perform well in rural areas may permit early corrosion in industrial areas. Corrosion surveys or observations of existing structures detect such conditions so that appropriate surface preparation and coating selections can be made. No organic coating is invulnerable to attack by all organic materials, but relatively few such virulent exposures occur around hydraulic structures. Most enamels resist grease and oil lubricants on the exterior of machinery, and their gloss or semigloss finishes facilitate cleaning the equipment. Vinyl and epoxy paints are essentially immune to grease and oil and, in fact, are recommended for interiors of oil storage tanks, oil circuit breakers, and like items. II. QUALITY CONTROL OF COATINGS No attempt is made to suggest one best quality control procedure. This subject is covered in a separate chapter. However, an observed failure rate of about 20 percent among tested paints points to considerable variability in the level of manufacturers control measures and, hence, the need for the purchaser to utilize the best available quality control methods. The cost of testing and, indeed, the cost of the materials themselves represent only a small part of the total investment. If failure occurs prematurely as a result of poor materials, the cost of protection multiplies. In passing, it should be emphasized that a paint test can be no better than the sample. The sample should be taken from the actual material to be furnished, and the contents of the container must be thoroughly mixed to obtain truly representative material. All too often this seemingly obvious step is neglected and the test results are suspect or meaningless.
111. THE FIELD COATING OPERATION Correctly selecting a coating and assuring its quality are essential first steps in providing coating protection. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 340
SSPC CHAPTER*LS-O 93 m 8627940 0003788 407 m However, coating engineers express the view that faulty application is a more common cause of failure. Failure diagnosis seldom conclusively pinpoints the painting operation because evidence is gone and a good coating may be discredited undeservedly. Surface preparation often suffers from neglect in the field operation, yet many feel it contributes over half the durability of coating protection. However dirty, costly and tediously unpleasant, cleaning the surface is an integral part of painting. All obstacles must be removed to provide a sound base for the coating. Most field coatings are applied by a brush, roller,, andlor spray, with some variations imposed by the special requirements of particular materials. Painting hydraulic structures is industrial, not residential painting; equipment and rigging must be equal to the task. Acceptable painting conditions are required, and specifications andlor manufacturer s painting instructions should be followed. A. INSPECTION Inspection records are kept to assure that standards have been established for all phases of painting. Compliance will enhance the expected coating performance. Instruments can quantify many coating properties. A trained, experienced and somewhat hardnosed inspector, supported by solid specifications, can contribute immeasurably to the level of workmanship and the success of the application. Inspection focuses on a few key aspects of application: O Surface preparation -Inspection confirms that grease and weld spatter removal precedes the mechanical cleaning. When blast cleaning is specified, NACE Standard TM-01-70 provides a set of comparison panels that have been carefully blast cleaned to reflect both the broad recognized NACE and SSPC surface preparation stan--`,,,,`-`-`,,`,,`,`,,`--FIGURE 9 Near-white blast cleaning removes all contaminants prior to painting. Here a weld is properly cleaned, and blasting reveals significant pits not evident before removal of an old coating. Courtesy US. Bureau of Reclamation dards. Used as an inspection tool on the job, these plastic-encased panels preclude much controversy as to when sufficient cleaning effort has been expended. Photographic standards such as SSPCVis 1, Color Photographic Standards for Surface Preparation , serve the same purpose. These stan-
dards cover lesser levels of cleaning as well as sandblasting. Where specified, hand- or power-tool cleaning can be accepted when all contaminants and loose materials are removed. When painting begins, surfaces must not have rusted in the interim and must be free of residual dust, ice or condensate. Application of coating -Application should be observed for proper materials storage, the existence of acceptable ambient conditions, mixing and handling as instructed by the manufacturer, correct application techniques and conformance to good painting practice. The coating can be evaluated primarily on the basis of its properties. Gauges monitor the wet film thickness of the coating as it goes on. Dry film thickness may be measured nondestructively with any of several magnetic gauges (SSPC-PA 2); taking many measurements should confirm uniformity of workmanship. Destructive thickness gauges can be used to view a scribed groove in the coating, measuring thickness accurately in cases of doubt. Adhesion -Surface preparation and application procedures should be sufficient for adhesion. Unfortunately, adhesion tests are destructive and require repair; nonetheless, a few such tests in representative areas may be justified for critical coatings in severe exposures. Repairs are easy after coal-tar enamel bond tests, which should be made frequently during field applications. Adhesion testing procedures for coal-tar enamel are described in the AWWA Specification C203. Coating continuity -Pinholes, skips or voids in the film must be prevented. When at least two coats are applied, the frequency of discontinuities usually decreases to a tolerable level for most purposes and visual inspection for complete coverage of each coat suffices. However, continuity can be confirmed by electrical holiday detectors with voltages selected to match the coating type and thickness. Detectors range from the six volt wet sponge for thin films to the 10,000 volt dry detector for coal-tar enamel. Drying or curing -The final requirement is a complete cure before the coating goes into service. The inspector need only confirm, in most cases, that curing times and temperatures are as instructed, although specific tests exist for some coatings. Minimum inspection of field painting requires a few
simple tools, some training and common sense. In addiCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 341
SSPC CHAPTER*LSmO 93 8b27940 0003789 343 tion, the inspector is required to read pertinent topics and obtain a sense as to what constitutes good painting practice regarding many phases of the operation. It can confidently be anticipated that even minimum inspection will markedly enhance final results. B. SURFACE PREPARATION It is well known that some types of paint tolerate foreign matter on a steel surface better than others, and the degree of cleaning varies. The method that provides the most nearly perfect base for painting is not always practical. In addition to paint type, the size and shape of the object to be painted, its exposure, whether it is in a fixed position and whether it is to be painted in the shops or in the field are considerations. Other chapters in this volume deal in detail with surfac:e preparation, and Volume 2 contains widely used surfac:e preparation specifications. 1. Surface repair A first step in preparation of any surface for painting is correction of any metal deficiencies. It is desirable, though not always feasible, to round sharp edges and corners. Scabs and other metal defects incident to the steel rolling and fabrication operation should always be removed and the surface smoothed. Field welds usually require the most attention. The sharp projections on a weld should be ground down and weld spatter removed. 2. Grease removal It is best to remove any deposits of grease or oil before beginning mechanical cleaning. Blast cleaning is often thought to remove these contaminants, but this is not necessarily so. Prior removal is recommended. Oil can be removed by washing with a solvent. Mineral spirits, xylene and others are excellent for this purpose; however, benzene, gasoline and certain other solvents are unsafe. Cleaning solvent and rags must be replaced frequently; otherwise, solvent cleaning can actually spread the grease contamination over a wider area than it originally covered. If the abrasive in blast cleaning is to be reused, it must be oil free; steel
grit and shot require cleaning at intervals. Shaking the abrasive a few seconds in a small vial of water will determine the presence of oil. 3. Blast cleaning In addition to complete removal of all surface impurities, blast cleaning roughens the surface to provide keying for good bond. With some types of paint, blast cleaning is considered essential to proper adhesion, and their use becomes contingent on whether blast cleaning can be employed. Blast cleaning should be specified for coal-tar coatings, vinyls, phenolics, neoprene coatings, and in general, for all coatings (except cement mortar) to be in buried or immersion exposures. This method is usually faster, cheaper and more satisfactory than other methods for less crucial exposures. 4. Hand or power fool cleaning Power wire brushing, scraping, sanding and other hand methods are usually permitted only for steel exposed to the atmosphere. When done well, these methods are generally adequate for such exposures, and are normally less expensive and troublesome than blast cleaning. When circumstances dictate hand tool cleaning in spite of the need for blast cleaning, the service life of the coating may be extended somewhat by the careful application of the phosphatizing treatments which attack residual contaminants, leave a paintable deposit and may later retard underfilm reactions. --`,,,,`-`-`,,`,,`,`,,`--FIGURE 10 Electrostatic spray painting permits rapidly coating the complex shapes of a transformer, the paint even penetrating to coat interior rows of the cooling pipes at right in the picture. Courtesy U.S. Bureau of Reclamation 5. Dust removal Regardless of the cleaning method, dust or grit should be removed from the surface just before painting and painting should proceed before rust forms on the cleaned surface. If the atmosphere is dry, rusting of blast cleaned surfaces may not occur for days; but under humid conditions, rust can be evident within an hour or so. A freshly painted
surface should be protected from dust, and any dirt that collects between coats should be removed. C.APPLICATION OF COATINGS Before field coating proceeds, favorable conditions Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 342
SSPC CHAPTER*LS=O 93 8b279LlO 0003770 Ob5 FIGURE 11 Roller gate in Rock Island navigational dam is in near-perfect condition after 12 years service. Threecoat vinyl system per CW 09940 specifications was used. Courtesy U.C. Corps of Engineers and Gilbertlcommonwealth for the application must be guaranteed. Planning promotes satisfactory final results as well as minimizing delays and various misfortunes during the work. It may become important to establish positive control over ambient conditions. Application personnel should be acquainted with coating characteristics and specifications andlor manufacturers instructions pertaining to them. They should also be provided with essential rigging and clean, operable equipment. Such precautions set the stage for smooth field applications. Factors in paint application are covered in SSPC-PA 1 and SSPC-PA Guide 4. 1. Ambient application conditions -Specified minimum painting temperatures are often around 45OF (7°C)for conventional paints. Most chemically set paints require at least 5OoF (10%). While maximum temperatures sometimes do not appear in specifications, problems may be encountered above 95OF (35OC).The best paint working qualities and results are usually realized in the middle of this temperature range. High humidity not only threatens freshly prepared surfaces but may affect some paints adversely. Good ventilation protects the painters and hastens drying of most paints. Positive control of these ambient conditions presents difficult problems in cool, damp locations with adverse weather conditions. 2.Paint preparation -Prior to application, settled and stratified paints must be restored to their original uniformity. If pigments do not disperse on thorough mixing, as often happens with red lead primers, the material should be discarded. It is usually desirable to premix separately the liquid parts of multi-component paints before adding them together. Obviously, thorough mixing of the combined components is necessary to produce a uniform coating material, one that sets and cures completely and at the same rate over the entire surface. 3. Thinning -Few paints require thinning if applied at normal temperatures. The frequency of excessive thinning is remarkable, particularly since stretching the paint defeats the objective of building coating thickness to a specified level in a certain number of coats. When thinned, most current industrial paints require quite specific solvents and diluents or combinations thereof. The wrong thinners may produce strange effects -including unaccountably short coating life.
4. Application methods -Most paints for field application are applied by conventional brush, roller or spray methods. Contractors favor the high application rates and greater film build attainable by spraying for prime coats as well as succeeding coats. This point is debatable. It can be argued that brushing or rolling stirs any residual dust away from the surface and works the paint into better contact, thus promoting better coating bond, particularly if the paint has poor wetting properties. Some paints, such as vinyls, are difficult to brush. Observing that dust removal is erratic at best, however, the Bureau of Reclamation has long favored brushing of primers., Spraying is recommended for topcoats. In special cases, electrostatic spraying produces more complete, uniform and rapid coating of complex and poorly accessible shapes, such as closely packed piping systems, than does conventional spraying. The term good painting practice covers, among other things, accepted techniques for the various application methods, and proper time between coats and for full curing; other chapters examine these matters in detail. Field painting should result in the specified coverages, thicknesses and conformity to the special requirements of each type of paint. Attaining the correct minimum total dry film thickness is especially important for coatings to be in immersion exposures, and extra edge coats are highly recommended where the paint film thins out and fails early at high points of welds, over corners, and around rivets. D. APPLICATION OF SPECIFIC COATINGS 1. Applying cement mortar A comprehensive description appears in Federal and American Water Works Association specifications (AWWA C205and C602)for applying and handling mortar linings and coatings. Such linings are usually placed by specialized and skilled plant operators or field contractors. But some aspects of mortar inspection deserve comment. Some of the criteria for organic coatings already mentioned clearly do not apply to cement mortar. Mortar linCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 343
SSPC CHAPTERrL5-0 93 m Bb27940 0003793 TTL m ings are not bonded in the ordinary sense, and discontinuities in the form of narrow cracks are not cause for alarm. Thickness should be as specified, and proper curing is most essential to a sound coating. The curing procedures specified should be fully observed. The mortar, like concrete, develops its full strength and soundness by reaction with the mix water, and this process should not be interrupted. Water should be added during curing of plant-lined pipe and pipe sections sealed with sheet plastic covers. Water can be retained in inplace linings by blocking airflow through the piping, Maintaining moisture until the piping fills is beneficial in minimizing or preventing cracking of the lining. Steam curing most conveniently and reliably accomplishes the curing of both plantapplied linings and coatings. The coating ordinarily shows little or no cracking because shrinkage is uniformly distributed by the embedded reinforcement. However, transportation of plant-lined pipe sections usually results in drying shrinkage and numerous cracks in the lining. Upon rewetting, the lining expands. Cracks not significantly wider than lL2in. (0.8 mm) will usually close, and the corrosion-inhibitive alkalinity extends somewhat into narrow gaps in the lining. The crack widths for which repair should be considered vary with lining thickness and other factors, but probably begin at about '/,e inch (1.6 mm). Lining continuity at field joints is accomplished by filling the gap between pipe sections with mortar. For pipe too small for workmen to enter, the joint surfaces are "buttered" before the joint is made, and a prepositioned, pipe-size ball is drawn past the joint area to smooth the mortar. The exterior of the joint likewise is filled with mortar by grouting or encasement; this mortar must be reinforced so the protection at the joint area equals that on the rest of the piping. FIGURE 12 Debris pounds the roller dam gate. Vinyl coating system contains garnet to help withstand the abrasion. Courtesy U.S.Corps of Engineers GilberUCommonwealth 2. Applying coal-tar enamel AWWA C203 specifications provide ample instructions on the application of this material, the largest quantity of which is now plant-applied. Special shapes and pipes so large they must be lined or coated in place require field application, and the unusual features of such applications justify emphasizing some critical points. Following blast
cleaning, Type B primer should be spray applied at a uniform thickness of 0.5to 1.0 mils (0.013 to 0.025 mm) and protected against dust, water and oil fumes until enamel can be applied. To bond well, enamel must be at the correct temperature, about 450 to 500°F (232 to 260°C) when it contacts the primer. It should also have been heated and handled properly so as to retain good plasticity [penetration, ASTM Designation: 5-73 at 77 "F (25"C)I. Inspection procedures for enamel are somewhat special and assume critical importance in field work. The bond test described in the AWWA specifications establishes in one step whether the surface preparation, primer and enamel application have all been accomplished properly. Inspection for enamel bond, thickness, penetration and continuity are more fully described in Reference 1, which is recommended reading if such work is in prospect. 3. Applying vinyl resin paints Paints composed primarily of vinyl resins are characterized by low-solids content, high solvent volatility and setting or curing solely by solvent volatilization. Their relatively low surface wetting properties dictate a high level of surface preparation, not less than a near white blast, which ideally should not exceed a 2 mil (0.005mm) profile. For the same reason, brushing or rolling the first coat promotes vinyl coating bond. The rapid solvent loss during application requires some adjustment - .. of the ordinary brushing technique and also unusual care to ensure that, in the following coats, the spray gun is held close enough and normal to the surface so a wet coat always is deposited. Vinyl resin paint systems, both proprietary and those conforming to standard specifications, exhibit considerable differences. Some are composed entirely of vinyl resins that are adherent to steel. In others, only the primer is adherent, and therefore must precede the nonadherent topcoats that can easily be stripped off if applied directly to metal. Other variations include hardness, pigment loadings and dry times. In general, the minimum thickness for immersion exposures of vinyls should be about 5 mils (0.13 mm), and one system for abrasive exposures calls for 10-mil (0.25 mm) thickness. For effective protection from such thin films, the specified Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 344
SSPC CHAPTER*LS-O 93 m 8627940 0003792 938 m FIGURE 13 Cleaning and touching up a lock-gate in upper Mississippi River. Vinyl system is in excellent condition after 17 years service. Courtesy U.S. Corps of Engineers and GilbertlCommonwealth minimums must be met at all points on the surface. Multiple vinyl coats help to assure uniformity and minimize pinholes. Skillful spray techniques, including multipass cross spraying, should be exercised to attain the desired per-coat thickness, and to maximize uniformity. Although highly volatile solvents for vinyl paints rapidly produce a surface-dry condition, the last solvent leaves the film slowly. Thus, the specified cure time, usually 3to 10 days, depending on conditions and the particular vinyl systems, should elapse to allow developing an adequate cure before placing them in service. The minimums not withstanding, further curing enhances the resistance properties of film and clearly is desirable wherever possible. 4.Applying multicomponent, chemically set coatings This section focuses on the unusual application characteristics of coatings prepared by mixing two or more components that react chemically to produce setting and a final cure. The reactive resin types usually are epoxy or urethane, but these may be combined with nonreactive resins or extenders such as phenolics, vinyls, silicones or coal-tars. Solvents may or may not be present. Regardless of the resin, the chemical reaction involved imposes special constraints on the application process. Coal-tar epoxy paint, currently one of the most widely accepted materials, serves as an example. The components are furnished separately in the exact quantities necessary to produce the desired chemical reaction. Premixing the components separately may be desirable. Obviously, thorough mixing of the reactants is essential to producing a material that will set uniformly and fully when applied to steel. Once mixed, coal-tar epoxy paint must be applied within a limited time, about three hours at normal temperatures. Other multicomponent paints may have a longer or shorter pot life . Some may react so quickly as to require application by means of a mixing head spray gun. A few require an induction period before the application can begin. In any event, the manufacturer s instructions must be followed strictly. Application of coal-tar epoxy can be by brush,
roller or spray. Because the material is somewhat heavy-bodied, it is difficult to brush to uniform thickness, and brushing is limited to irregular surfaces. Prior to the first coat, vigorously brushcoating welds and rough surfaces is recommended to ensure complete coverage free of pinholes; the first general coat may then be applied over the wet brush coat. Medium sized areas are often rollercoated with spraying reserved for topcoats and larger areas. In any case, the application must be complete within the pot life of the material at the prevailing temperature. Some chemically set paints, when fully cured, produce a smooth, glazed surface so inert that another coat of the same paint does not bond well. Poor intercoat adhesion, widely experienced with coal tar epoxy paint, can be prevented by applying topcoats well before a full cure develops. Again, the manufacturer sets forth the necessary timing in literature on the particular paint. Paint and metal temperatures must be within specified limits during both the application and curing periods, otherwise incomplete or incorrect curing results. A temperature of 50°F (2OOC) frequently is mentioned as a minimum, but a midrange application temperature produces the best results, and a short cure at an elevated temperature may enhance the cure and durability of some materials. 5.Other coatings Many metal primer and topcoat paints have been successfully field applied for so long by conventional means that they require little comment. The water-borne coatings increasingly replacing some atmospheric coatings present no new problems except that they should not be exposed to freezing before they dry. 6. Applying temporary coatings Temporary protection may be required for machined surfaces during transport and storage. For this purpose a number of rust preventives are available to be applied by brushing, dipping or spraying. When the equipment is to go into service, they are removed with solvents. Since temporary rust preventives may contain greases and tars, they should not be used on surfaces eventually to be painted. Some rust preventives are available that will accept paint. Cast iron pipe, valves, fittings and some machinery may be received with a soft varnish or Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 345
SSPC CHAPTERtL5.0 93 D Ab27940 0003793 874 W tarry shop coating, which varies considerably in thickness. The tar may bleed persistently through paint applied over it, and the coating may not resist impacts or distortion normally. The temporary paint should be removed before any permanent paint system is applied. E. MAINTENANCE OF COATINGS Maintainability is a factor in the initial coating selection because all coatings require attention. The questions are: how much, how often, by what methods and at what direct and indirect costs? Occasionally, the total cost of maintenance in locations such as turbine units may include the loss of revenue during outages, making actua¡ painting costs become negligible. Thus, indirect costs may loom large, justifying coating that reduce maintenance to a minimum, even though at greater initial cost. cost. Knowing the condition of a coating obviously is the first step in maintaining it. Its history provides some idea as to how rapidly it is deteriorating. Adding to this, the type of paint, age and application data such as surface preparation enables more discriminating choices between total replacement and maintenance procedures. Inspection of a coating after a year s service is recommended. At this time gross deficiencies iii application usually become apparent and can be corrected. Thereafter, inspections should be scheduled at 2-to 5-year intervals for coatings exhibiting normal behavior, with more frequent inspections being given to problem areas. It is important to know what to look for and what interpretation to attach to what is seen, because the evaluation dictates the timing and types of maintenance painting. Chapter 23 on causes and prevention of paint failure explores this subject in detail. It suffices here to note that the condition of the steel is the primary concern. Corrosion, such as rapid pitting affecting the integrity of the metal, should prompt early attention to remedial action. Corrosion uniformly distributed over the surface, which actually consumes the same quantity of metal, may be tolerated somewhat longer. Coating repairs should be made before deterioration has progressed so far that costly, thorough surface preparation and complete repainting become necessary. Since deterioration in localized areas of a coating aged several years usually indicates weakening of the entire coating, it may be worthwhile to follow spot repairs with at least one overall coat. For example, touch up repair and
application of one or two topcoats are recommended after 10 years service for Bureau of Reclamation vinyl resin paint VR-3 in immersion exposures. If there is poor service, and reason to believe another type of paint andlor a better application could produce better results, it is often best to let repairs go and get all the benefit possible before the affected surfaces are completely repainted. The need for surface preparation appropriate to the coating and exposure are just as great for maintenance as for new work if the expected results are to be obtained; unfortunately, greater obstacles to good cleaning usually exist. Blast cleaning remains essential for full durability of replacement immersion coatings and is preferable for touch up. Where it is plainly not feasible for small areas, surfaces can be cleaned to base metal and somewhat roughened with tools such as the car body sander, or even by hand sanding. This cleaning may be augmented with a phosphoric acid, rust-inhibitive wash. Hand or power tool cleaning (SSPC-SP 2 and 3) will do for milder exposures; however, the adhesion of the remaining coating should be checked. Paint so poorly bonded that it might soon fail by lifting and flaking should be removed by scraping or other effective means. When an overall coat is to be applied to existing paint, any obstacle to adhesion must be removed. Dirt, scum and oil commonly deposit in tightly adherent films on immersed surfaces and must be scrubbed off. Weathering ordinarily results in chalk, a layer of pigment loosely held by the degraded binder. For best results, any appreciable chalk should be removed by abrasive scrubbing. Assuming that a good initial coating was satisfactorily applied, repainting the affected area with the original type of paint is usually best. This circumvents compatibility problems between paints. A different repair paint should be tested for compatibility. Adhesion deficiencies also may develop with the highly inert, chemically set paints, as noted in the discussion of coal-tar epoxy paint, whereby special measures would have to be taken to achieve an effective repair. IV. SPECIFICATIONS A. STANDARD SPECIFICATIONS Standard specifications are grouped according to the exposures commonly found in hydraulic structures. Generally, this listing does not repeat the applicable SSPC painting systems in Volume 2 of the manual. Before selecting any specification, the user should always obtain and read the full specifications to ensure correct use of the material and to select the proper type, class and grade, if any. UNDERGROUND EXPOSURES
Cement mortar shop American Water Works Assoapplied (lining and coating) ciation (AWWA) C205 Coal-tar enamel AWWA C203 (specify enamel Primer (Type 6) having 15-20 penetration at Enamel 77°F (25°C)) Fibrous glass mat Coal-tar saturated asbestos flat, K:aft paper Whitewash Pipe coating, thermoplastic AWWA C 210 resins or thermosetting epoxy Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 346
SSPC CHAPTER*LS-O 93 8627940 0003794 700 UNDERWATER EXPOSURE Cement mortar linings Shop applied AWWA C205 In place AWWA C602 Coal-tar enamel AWWA C203 (specify enamel having 15-20 penetration at 77OF (25OC)) High-Performance Low VOC Corps of Engineers, C200 Commercial Tar Epoxies (SSPC-Paint 16 and SSPC-Paint System 11.01) Pretreatment primer DOD-P-I 5328 (wash primer) Vinyl resin US Bureau of Reclamation VR-3 (4 coats to 6 mils) VR-6 (6 coats to 10 mils) Corps of Engineers, V766 and others High-Performance Low VOC Epoxies, Urethanes & Polyesters Coatings ALTERNATING WATER AND AIR EXPOSURE Vinyl resin As above High-Performance Epoxies, Urethanes, Low VOC Coatings & Polyesters (Weathering Topcoat where required) Aluminum paint Mixing varnish (phenolic) TT-V-119 Aluminum paste for the above A-A-341 AIR EXPOSURE Primer Coating, Alkyd, Corrosion TT-P-664 Inhibiting, Lead and Chromate Free, VOC Compliant Zinc dust chlorinated TT-P-I 046 rubber primer Zinc dust -zinc oxide primer TT-P-641, Type II Aluminum paint Mixing varnish (regular) TT-V-81 Mixing varnish (phenolic) TT-V-119 Aluminum paste for the above A-A-341 Ready mixed TT-P-38 Machinery enamels Alkyd (gloss) TT-E-489
Alkyd (semigloss) TT-E-529 Silicone alkyd (gloss) TT-R-I 593 Silicone alkyd (semigloss) TT-E-490 Acrylic emulsion paint TT-P-19 Acrylic emulsion coatings for steel Galvanizing ASTM Al23 SPECIAL COATINGS AND TREATMENT Rust preventive MIL-C-16173, Grades 1 and 2 Metal conditioner MIL-C-10578 FIGURE 14 Painting gate during winter. Vinyl coatings must be applied. Courtesy U.S. Army Corps of Engineers and GilbertlCommonwealth B. SPECIFYING COLOR Color serves purposes other than aesthetics, such as pipe coding; organizations (e.g., telephone, gas, oil and auto companies) often standardize distinctive combina tions of colors to represent themselves. Although they may select proprietary paints and colors at a particular time, these later may be discontinued, or the organizations may wish to enable several suppliers to bid on furnishing the paints. Whatever the reason, it is often desired to specify color with reasonable exactness according to a widely recognized system. Several systems exist, but none has attained universal acceptance. Federal Standard 595A offers a moderate choice of arbitrarily selected colors displayed by small chips in a loose-leaf book, and available as 3-by 5411. coupons. The colors are identified by 5-digit numbers, the first digit of which denotes flat, semigloss, or gloss luster. This standard is fairly well known in the paint industry, but usually is not used in product lines. The Munsell color system covers the full color range and precisely describes any desired color in terms of a numerical system representing hue, value and chroma. The smallest possible color differences distinguished by the Munsell system are so slight as to be almost undetectable to the naked eye. This enables specifying color precisely and establishing limits on the acceptability of color matches. Paint manufacturers are aware of the Munsell system, but find its cost and complexity to be limiting factors. V. SAFETY AND HEALTH The Occupational Safety and Health Administration (OSHA), the Environmental Protection Agency (EPA) and local regulators are involved in the control of materials to protect the environment and construction workers against known or suspected health threats. Regulations governing emissions, pollutants and toxic substances have already affected coating development, and more profound changes 347
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SSPC CHAPTER*LS.O 93 862791rO 0003795 b47 clearly are in prospect. The safety and health of painters have become a primary concern at this time as data accumulate showing the toxic effects from inhalation or skin contact with dusts or paint constituents. Limiting concentration values of solvents are being lowered, instrumental monitoring is being promoted and protective measure for personnel are being intensified. The rapid change in regulatory safety and health procedures precludes discussing specifics here. Many common paint marerials present little hazard if handled sensibly; on the other hand, it is possible to mishandle most with disastrous results. Ordinary care calls for ventilating properly, keeping open flames or sparks away from flammable materials, avoiding excessive inhalation of blast dust or any paint vapors and minimizing protonged skin contact with coating materials. Both workers and their supervisors should be alert for particular physical circumstances that hold the potential for a catastrophic event, such as painting in confined spaces. See Chapter on Safety in this volume and Guide to Safety SSPC-PA Guide 3 in Volume 2. Modern industrial painting tends to include more and more sophisticated protective coatings that present new hazards not readily apparent. The epoxy resins may be taken as a familiar example of such paints. The constituents of two-component epoxy paints often cause allergic reactions, such as itching and rashes. Some people are hypersensitive to these compounds and react promptly and violently. In other cases the effects are cumulative; repeated exposures without apparent effect may produce sudden hypersensitivity with serious consequences. Inhalation of the special solvents in industrial paints not only may cause immediate discomfort, but may damage organs of the body in ways not fully understood at this time. Prudence dictates caution in handling new materials. Paint manufacturers usually provide detailed hazard warnings with products. Accordingly, an important first step in the application of an unfamiliar coating is a careful reading of the manufacturer s literature and making provisions for protective clothing, respirators and so on as indicated. The instructions may include any special treatments to be used upon exposure to the material. For example, soap and water is recommended for removal of epoxy constituents; on the other hand, most organic solvents should not be used because they can carry the toxic chemicals deeper into the skin, thereby aggravating the situation. Ordinary construction hazards especially common to painting operations include the rigging and scaffolding necessary for access to awkward locations. The common sight of a painter seemingly engaged in acrobatics to
reach the work is evidence of an unsafe condition in need of correction. High work and steeply inclined piping often require anchored rigging and heavy staging. The strength and condition of welds, bolts, cables and ropes should be evaluated by a qualified inspector. Lifting machinery should be designed for fail-safe operation. Finally, on-the-job safety training has a place in field painting. Each worker can be his own best safety device if alerted to the hazards inherent in his occupation and the consequencbs of mishandled materials, unsafe equipment and faulty procedures. Ideally, a qualified safety engineer, experienced in painting operations, well versed in the prevailing regulations and the reasons therefore, would counsel the workers, the object being to enlist their support in assuring their own safety. ACKNOWLEDGEMENT The author and editors gratefully acknowledge the active participation of the following in the review process for this chapter: AI Beitelman, James Foster, John Perchall and William Wal lace. BIOGRAPHY Mr Jack Kiewit, who is retired, was the Head, Materials Science Section of the Applied Sciences Branch in the Division of Research, U S Bureau of Reclamation Engineering and Research Center in Denver, Colorado He graduated with a 6S in Chemical Engineering from the University of Nebraska, after which he joined the U.S Bureau of Reclamation in February 1950 as a chemical engineer in the Cement Unit He transferred in 1953 to the Paint Investigations Unit as a materials engineer, and a coatings specialist In 1975 he was selected as Head, Materials Science Section, responsible for Section research, quality, control, and technical assistance for a wide variety of engineering materials for water-works structures He is a registered professional engineer and corrosion specialist (National Association of Corrosion Engineers) and co-author with P S Lewis of the Third Edition Revision of U S Bureau of Reclamation Paint Manual REFERENCES 1. U.S. Bureau of Reclamation, Paint Manual . US. Government Printing Office, Washington, D.C. 20402, 3rd Edition, 1976. 2. Corps of Engineers Specification CW-09940, Painting: Hydraulic Structures and Appurtenant Works , January 1977. 3. J.L. Kiewit, Field Tests of Water Pipe Linings . U.S. Bureau of Reclamation Lab Report REC-ERC-72-1, January 1972.
4. H. Johns, Erosion Studies of Pipe Lining Materials -Fourth Progress Report . U.S. Bureau of Reclamation Lab Report ChE-97, June 1969. 5. US. Army Corps of Engineers, Paint Manual -New Construction and Maintenance . EM 110-2-3400, May 1967. 6. Steel Structures Painting Manual, Volume 2, Systems and Specifications , 1991. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 348
SSPC CHAPTERtL6.L 93 m 8b27940 0003776 583 m CHAPTER 16.1 COATINGS FOR PIPELINES AND OTHER UNDERGROUND STRUCTURES --`,,,,`-`-`,,`,,`,`,,`--by R.N. Sloan and A. W. Peabody This chapter on coatings covers the fundamentals for II. DESIRABLE CHARACTERISTI CS OF A selection, application, and performance of pipe coatings PIPE COATING used to prevent the deterioration of metals buried in earth or submerged in water. A. EFFECTIVE ELECTRICAL INSULATOR Regulations from Department of Transportation, Oc- Since soil corrosion is an el ectrochemical process, a cupational Safety and Health Act (OSHA), and Department pipe coating has to stop the current by isolating the strucof Environmental Resources (DER) have all had an impact ture from the environment. on the pipe coatings industry. The energy shortage and the emphasis on energy conservation, along with other governmental regulations, will continue to influence the selection B. EASE OF APPLICAT ION and use of pipe coatings. The coating material must be suitable and properly And yet a twenty-six year old statement by Norman applied to be effective. Many excellent pipe coatings rePeifer and Frank Costanzo is still the norm for corrosion quire exacting application procedures that are difficult to protection on underground structures: Effective coatings maintain. Consistent qua lity may be obtained with a complemented with cathodic protection have been most coating system that is leas t affected by variables. Coating successful in arresting and in preventing corrosion application specifications a nd good construction praclosses
.
tices combined with proper inspection contribute to the Asphalt and coal tar enamel coatings are the most quality of the finished coatin g system. widely used external pipe coatings.2 C. APPLICABLE TO PIPING WITH A MINIMUM I. PURPOSE OF PIPE COATING OF DEFECTS Pipe coating on underground structures isolates This characteristic correlates w
ith ease of applicametal from contact with surrounding environments. Since tion. No coating is perf ect, and that is why cathodic proa perfect coating cannot be assured, cathodic protection tection is required. Do not buy a pipe coating that has toois used in conjunction with the coating syst em to provide many holidays (voids in coating) even before it leaves the the first line of defense against corrosion. And since a mill. properly selected and applied coating should provide 99% of the protection required, it is of utmost importance to D. ADHESION TO PIPE SU RFACE know the advantages and disadvantages of available coatings. The right coating material properly used will Coating adhesion is impor tant to eliminate water make all other aspects of corrosion control relatively migration between the met al substrate and the pipe easy .3 coating. The coating adhesion assures permanence and The number of coating systems available necessi- ability to withstand handling d uring installation without tates careful analysis of the many desired properties for losing effectiveness. an effective pipe coating. The National Association of Corrosion Engineers clearly defines the specific qualities that E. RESIST DEVELOPME NT OF HOLIDAYS a pipe coating should possess in NACE Standard RP-01-69, Once the coating is bur ied, two areas that may Section 5:Coatings4 destroy or degrade coatings are soil stress and enCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 349
SSPC CHAPTERxLb-L 73 = 8627740 0003797 4LT vironmental contaminants. Soil stress, brought about in certain soils that are alternately wet and dry, creates tremendous forces that may split or cause thin areas. Adhesion, cohesion, and tensile strength are important properties to evaluate in order to minimize this problem. The coating s resistance to chemicals, hydrocarbons, and acidic or alkaline conditions has to be known in order to evaluate performance in known contaminated soils. F. HANDLING, STORAGE, AND INSTALLATION The ability of a coating to withstand damage is a function of its impact, abrasion, and ductile properties. Pipe coatings are subjected to a great deal of handling from application to backfill. While precautionary measures of proper handling, shipping, and stockpiling are recommended, coatings vary in their ability to resist damage. Outside storage requires resistance to ultraviolet rays and temperature changes. These properties must be evaluated to assure proper performance. G. CONSTANT ELECTRICAL RESISTIVITY Since corrosion is an electrochemical reaction, a coating with a high electrical resistance over the life of the system is important. The percentage of initial resistance drop is not as indicative of the pipe coating quality as the overall level of electrical resistivity. H. RESISTANT TO DISBONDING Since most pipelines are eventually cathodically protected, it is necessary for the coating to withstand cathodic disbondment. The amount of cathodic protection is directly proportional to the quality and integrity of the coating. Considering interference and stray current problems, this becomes a most important requirement. Cathodic protection does two things. First, it drives water through a coating that would ordinarily resist penetration. It also may produce hydrogen at the metal surface where current reaches it, and the hydrogen breaks the bond between the coating and metal surface. No coating is completely resistant to damage by cathodic protection, but it is very important to choose a coating that minimizes these effects. The ASTM G8 test for Cathodic Disbonding of Pipeline Coatings, commonly known as the salt crock test, measure a coating s resistance to damage by cathodic protection. An intentional holiday is placed in the coating and the sample is immersed in a 3% salt solution (1% Sodium Carbonate, 1% Sodium Sulfate, and 1% Sodium Chloride). Then, when a negative electrical potential is applied through the aqueous salt solution by an anode or rectifier, an electrical current flows through the solution to the bare metal surface. This test is run at ambient temperatures; the sample is maintained at a constant potential; and the current drain required to protect the sample is measured periodically. After 30 to 90 days the sample is removed and examined
for undercutting or any discontinuities. Discontinuities are identified by an accumulated calcite deposit around them. Relative resistance of the coating to cathodic protection is determined by the number of unintentional holidays, by the amount or increase in current, and by the amount of cathodic disbondment or undercutting that has occurred around the intentional holidays. The difference in reactions to this test by various coatings is sometimes vivid. In some cases, such a quantity of water is driven through the coating that the coating develops large water blisters around the sample. In other cases the cathodic disbondment around the intentional holiday is so great that the entire sample is disbonded from the surface. Some samples experience very frequent unintentional holidays, little water being driven through the coating, and almost no cathodic disbondment around the unintentional h~liday.~ I. EASE OF REPAIR Recognizing that some damage may occur and that the weld area must be field coated, compatible field materials are required to make repairs and complete the coating after welding. Manufacturers recommendations should be followed. Variables in conditions influence selection of materials. All nine of these characteristics (A-I) are important when evaluating the selection of a pipe coating. The following factors should also be considered when selecting a pipe coating? 1. Type of Soil or Backfill Soil conditions and backfill influence the coating system selected and thickness specified. USDA Soil Survey Manuals help determine soil types along the right-of-way. Soils are rated by their shrink-swell factor (soil stress). High shrink-swell soils can damage conventional coatings. Ideally, trenches should be free of projections and rocks, permitting the coating to bear on a smooth surface. When backfilling, rocks and debris should not strike the pipe coating. The following ASTM tests are recommended to measure resistance to penetration of the pipe coating if set on stcnes in the trench: ASTM D 785, Method of Test for Rockwell Hardness of Plastics and Electrical Insulating Materials, ASTM D 5, Method of Test for Penetration of Bituminous Materials, and ASTM D 2240, Method of Test for Indention Hardness of Rubber and Plastics by Means of a Durometer . The following ASTM tests are recommended to measure the resistance against damage by rock in back fill: ASTM G 13, Limestone Drop Test and ASTM G 19, Falling Weight Test . Soil stresses on pipe coatings may be evaluated by ASTM D 427, Method of Test for Shrinkage Fac-
tors of Soils . Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 350
SSPC CHAPTER*Lb.L 93 8627940 0003798 356 FIGURE 1 A good cleaning job coming out of the shot blast machine. Courtesy: Irish Pipe Coating Co., Inc. 2. Accessibility of Pipeline When a pipeline is inaccessible or in a marine environment, the best system should be selected with less emphasis on initial cost. Experience under similar conditions for at least five years or well-designed laboratory tests on new products are the best criteria for coating selection. 3. Operating Temperature of Piping Surface temperature and environmental conditions must be considered, because, once buried, a coating experiences a wet heat condition, which is more detrimental than dry heat and harms coating effectiveness. A modified disbondment test, ASTM G 8 Cathodic Disbonding of Pipeline Coatings , determines resistance to elevated temperatures. 4. Ambient Temperatures During Construction and Installation Temperatures during construction and installation are often more critical than operating temperatures. For instance, some thermoplastic systems such as mastics, tapes, or enamels may become brittle in freezing temperatures. (Polyethylene coating systems, however, have been field bent at -40 FI -40 OC). Above recommended operating temperatures, thermoplastic systems may cold flow. Extra care in handling, transport and storage is needed under extreme conditions. 5. Geographical and Physical Location Pipe source and coating plant location often determine the coating or are a cost factor in selection. Severe environments, such as river crossings, pipe inside casings, exceptionally corrosive soils, high soil stress areas and rocky conditions require special consideration. On large projects in remote areas, the economics may favor a railhead or field coating site. 6. Handling and Storage Handling, shipping and stockpiling are important in the selection process. Some coatings require special handling and padding. All require careful handling. Most underground coatings are not designed for above ground use and are affected by excessive above-ground storage. Coal tar asphalt
enamel and mastic coatings are protected from ultraviolet deterioration by whitewash or kraft paper. In polyethylene, the addition of 2.5 percent carbon black is the most satisfactory deterrent. Stock should be rotated, first-in, first-out, to minimize the potential problem. Long-term storage requirements could determine coating selection. 7. Costs Evaluation of pipe coating properties with the above considerations assists in selection. The most misunderstood factor is costs . In pipe coating economics the end has to justify the means. The added cost of coatings and cathodic protection has to pay for itself through reduced operating costs and longer life. True protection costs include not only initial costs of coating and cathodic protection but also installation, joint coatings and repairs . Field engineering and facilities to correct possible damage to other underground facilities may add costs, possibly outweighing initial costs of the pipe coating.* 111. DESCRIPTION OF COATING SYSTEMS A. ENAMELS Bituminous enamels are formulated from coal tar pitches or petroleum asphalts and have been widely used as protective coatings for over sixty-five years. Coal tar and asphalt enamels are available in summer or winter grades. These enamels are the corrosion coating, combined with glass andlor felt to obtain mechanical strength for handling. These materials should meet requirements of the National Association of Corrosion Engineers, National Association of Pipe Coating Applicators or The American Water Works Association. Enamel coatings have been the workhorse coatings of the industry and provide efficient, long-life corrosion protection. Bituminous enamel systems may be used within a temperature range of 30°F to 180°F (-1.1 C to 82°C). When temperatures fall below 40°F (4.4 C), precautions should be taken to prevent cracking and disbonding during field installation. Enamels are affected by ultraviolet rays and should be protected by kraft paper or whitewash. Enamels also are affected by hydrocarbons. A barrier coat Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 351
SSPC CHAPTER*Lb.L 93 8b27940 0003799 292 FIGURE 2 A 30-inch pipe, shot blast-cleaned, with the primer being sprayed on. Courtesy: Irish Pipe Coating Co., Inc. is recommended when contamination exists. This coating is available on all sizes of pipe. Recently, enamel use has declined for the following reasons:9~1a Reduced suppliers OSHA, EPA, and FDA environmental and health standards Increased acceptance of plastic coating Utilization of raw materials as a fuel. Pipe should be bare and free of mill coatings for the best surface preparation. Prior to blast cleaning, the pipe is heated to drive off surface moisture and loosen mill scale. Blast cleaning uses sand, steel shot, or grit or a combination for the desired profile and cleaned surface. Blasting operations remove all rust, scale and other impurities from the surface, exposing base metal over all, which presents a grayish matte appearance between Steel Structures Painting Council Standard SSPC-SP 6 and SSPC-SP10. This is equivalent to NACE Standard TM-01, Visual Standards, between NACE No. 3 and NACE No. 2 (Figure 1). FIGURE 3 Pipe going through the coating machine with a rabbit to keep the enamel off the bevels. The rabbit travels through the machine at the same speed as the pipe. The blast cleaned surface is primed (Figure 2), and when dry, coating and wrapping is performed by the hot application of a bituminous coating. The coating is pumped from the coating machine through a spreader, from which the coating flows in a flood coat onto the pipe surface. Be sure that the coating material is melted properly and brought to application temperature gradually. This is done in an agitated kettle. Agitation maintains uniform heat and prevents
mineral fillers (25 to 35 percent) from settling out. Settling fillers may develop hot spots, or carbon spots, on the kettle bottom. These small carbon spots break down and get into the coating and eventually cause jeeps or holidays in the line. Carbon spots are cathodic to the metal and cause pits. Thus, the melting operation and mechanical agitators --`,,,,`-`-`,,`,,`,`,,`--are of extreme importance. z FIGURE 4 A pipe being holiday-detected. Courtesy: Irish Pipe Coating Co., Inc. Asbestos felt has generally been used as the outer wrap, but with restrictions on asbestos as a carcinogen, it is being replaced by an asbestos free glass wrapper. The glass wrap must be properly encapsulated with enamel to prevent a wicking action of moisture from the environment to the steel. Mill wrapping with various specifications of bituminous coating materials is applied to a nominal 3/2 (.24 cm) thickness, followed by the glass or asbestos felt or combination. Multiple enamel coatings are often applied to build up thickness where greater protection is required (Figure 3). An electrical inspection of completed coatings is made in accordance with procedures established by NACE Standard RP-02, Recommended Practice for High Voltage Electrical inspection of Pipeline Coatings (Figure 4). For a more detailed treatment of this subject, the ANSI/ AWWA C203 American National Standard for Coal-Tar Protective Coatings is recommended (Figures 5 and 6). B. ASPHALT MASTIC Asphalt-Mastic pipe coating is a dense mixture of sand, crushed limestone, and fiber bound with a select, airCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 352
SSPC CHAPTER*Lb-L 93 m 8627940 0003800 834 m FIGURE 5 Thermal oxidizer for air pollution. Courtesy: Irish Pipe Coating Co., Inc. blown asphalt. These materials are proportioned to secure maximum density of approximately 132 pounds per cubic foot. This mastic material is available with various types of asphalt. Selection is based on operating temperature and climatic conditions to obtain maximum flexibility and operating characteristics. This coating is a thick, Y2 "to X" (1.27 cm to 1.6 cm), extruded mastic resulting in a seamless corrosion coating. Extruded asphalt mastic pipe coating has been in use for over fifty years. It is the thickest of the corrosion coatings and is cost effective for offshore installations. Its ability to dissipate heat while providing a relatively holiday-free coating has made it the most used pipe coating for pipe-type cable installation^.^^ Asphalt mastic systems may be designed for installation and use within an operating temperature range of 40°F to 190°F (4.4"C to 88°C). Precautions should be taken when handling in freezing temperatures. Whitewash protects it from ultraviolet rays, and this should be maintained when in storage. This system is not for aboveground or in hydrocarbon-contaminated soils. This coating is available on 4% "to 48"0.D. (11.4 cm to 122 cm) pipe. The application pr~cedure'~ is as follows. Prior to FIGURE 6 Pipe in storage at plant. Courtesy: Irish Pipe Coating Co., Inc. blast cleaning, the pipe is heated to drive off surface moisture and loosen mill scale. A combination of shot and grit removes all rust, scale and other impurities, exposing base metal, which presents a grayish matte appearance between Steel Structures Painting Council Standard SSPC-SP 6 and SSPC-SP 10 (NACE 2 -NACE 3). Pipe is then spray coated with an asphalt primer prior to extrusion of the hot mastic mix to the circumference of the pipe. The extrusion forms a seamless coating bonded to the pipe. Whitewash is applied to reflect the sun's rays and to facilitate stockpiling (Figure 7). An electrical inspection of the completed coating should be made in accordance with the procedures established by NACE Standard RP-02, Recommended Practice for "High Voltage Electrical Inspection of Pipeline Coatings". Holidays are patched and retested. Patching is relatively easy because the mastic is thermoplastic and can be heated and worked with a trowel to reseal.
FIGURE 7 Pipe exiting from extrusion process, forming a seamless coating. Whitewash is applied to reflect sun and facilitate stockpiling. Courtesy: Bredero Price Co. C. EXTRUDED PLASTICS -POLYETHYLENE AND POLYPROPYLENE Extruded plastic coatings have been available since 1956. Their growth and acceptance have been remarkable. Initial problems of stress cracking and shrinkage have been minimized by better quality and grade of high molecular weight polyethylene resins. There are two systems available in the United States. One is an extruded polyethylene sleeve, shrunk over a 10-mil asphalt mastic. The other is a dual extrusion where a butyl adhesive is extruded onto the blast-cleaned pipe followed by multiple fused layers of polyethylene (Figure 8). The latter utilizes multiple extruders in a proprietary method, which obtains maximum bond with minimum stress. The sleeve type is available on " through 24" O.D. (1.3 cm through 61 cm) pipe, while the dual extrusion is presently available on 2%" through 103" (6.35 cm through 262 cm) pipe. The operating temperature range for polyethylene systems is from -40°F to 180°F (-40°C to 82"C), and for polypropylene it is -5°F to 190°F (-21 "C to 88°C). Polyethylene systems have been successfully Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 353
SSPC CHAPTER*Lb.L 73 8627740 000380L 770 FIGURE 8 Dual side extrusion, butyl adhesive followed by polyethylene. Courtesy: Bredero Price Co. field bent (1.9
per pipe diameter length) at -40°F
( -40°C). Swelling may occur in hydrocarbon environments. Polyethylene has excellent dielectric strength. With proper selection of polyethylene resins and addition of 2%% carbon black, a dual extrusion system has withstood long-term above-ground storage and aboveground use. An electrical inspection in accordance with NACE Standard RP-02 is recommended practice for
High
Voltage Electrical Inspection of Pipeline Coatings . Application methods follow: Both methods preheat bare pipe prior to grit blast cleaning to a commercial (SSPC-SP 6) blast clean. With the sleeve type coating, the adhesive undercoating is applied by flood-coating the hot material over the pipe before it passes through an adjustable wiper ring that controls thickness. After mastic is applied, the pipe passes through the center of the crosshead die where plastic is extruded in a cone shape around the pipe. Immediately the plastic is water quenched to shrink it around the undercoating and pipe. Following electrical inspection, pipe ends are trimmed for cut back, and the coated pipe is stockpiled. In the dual extrusion system, the cleaned pipe is rotated at a calibrated rate. The first of two extruders applies a film of butyl adhesive of predetermined width and thickness, fusing the film to the rotating pipe in two layers. While the butyl is still molten, high molecular weight polyethylene is applied from the second extruder in multiple layers of a predetermined thickness, producing a bonded coating 50 to 100 mils thick. Water quenching, electrical inspection, and cut back is completed prior to stockpiIing. Polyethylene systems have been in use in Europe for approximately fifteen years with both crosshead and side extrusion methods. In addition to the butyl adhesive or asphalt mastic adhesive, some systems use polyethylene copolymer adhesive. This system requires high temperature (200°C -390°F) heating for application of the adhe~ive ~.For more detail on extruded plastic pipe coating systems, read Extruded Plastic Pipeline Coatings 16. D. FUSION-BONDED THERMOSETTING
POWDER RESINS Fusion bonded powder pipe coatings were introduced in 1959 and have been commercially available since 1961. These coatings are applied to preheated pipe surfaces 400°F to 500°F (204°C to 26OOC) with or without primers. On some resins post-curing is required. This coating is applied in a 12 to 25 mil thickness. The fusion-bonded powder coatings have good mechanical and physical properties and may be used above or below ground. On above-ground installations, to eliminate chalking and to maximize service life, topcoat with a urethane paint system. Of all the pipe coating systems, the fusion-bonded thermosetting resin systems are the most resistant to hydrocarbons, acids, and alkalies. Perhaps the main advantage of fusion-bonded powder pipe coatings is that because they cannot cover up apparent steel defects due to their lack of thickness, they permit excellent inspection of the steel surface before and after coating. The number of holidays that occur is a function of the surface condition and thickness of the coating. A steel surface profile study by John D. Keane, Dr. Joseph A Bruno, Jr. and Raymond E. F. Weaver17 of the Steel Structures Painting Council found the existence of abrasiveformed hackles of steel that protrude up to 6 mils from the surface. In SSPC three-dimensional photos, the hackle stands out in stark relief against its surroundings, but is barely visible in two dimensions. Increasing the thickness of the applied coating by fusion bonding should minimize this problem. These coatings are available in -43 (1.9cm-122cm) O. D. pipe. Thermal-bonded powder resins require great care to apply them properly. Prior to cleaning, pipe is heated to remove moisture and loosen mill scale. It is necessary to clean the surface to a near-white metal finish as defined in SSPC-SP 10 (NACE NO.2). The pipe is heated uniformly to the recommended application temperature (400 OF-500 OF1204 OC-260 C). Each material has its own requirements and tolerance level that must be strictly adhered to. If primer is required, there are minimum-maximum overcoat times. Powdered resin is applied by electrostatic deposition to a 12-25 mil thickness (Figure 9). Certain resins require post-heat treatment for proper cure. Inspection by a minimum of 100 volts per mil of thickness is recommended. Pipe requiring limited repair (to be agreed to between customer and applicator, perhaps one holiday per ten square feet) due to hackles, coating imperfections and other minor defects is repaired by a heat bondable polymeric hot melt patch stick. A 100% solids liquid epoxy repair material is recommended within 12 of each end of pipe. Manufacturers recommendations for field application of patching materials should be followed. For more detail on Fusion Bonded Thermosetting Powder Resins , read ANSIIAWWA Standard C215.
Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 354
SSPC CHAPTER*Lb=L 73 m 8627740 0003802 607 m FIGURE 9 Powdered epoxy resins, post-heating pipe following electrostatic deposition. Courtesy: Bredero Price Co. E. LIQUID EPOXY AND PHENOLICS There are many liquid systems available that cure by heat andlor chemical reaction; some are solvent types and others are 100% solids. Their use is mostly in larger diameter pipes where conventional systems may not be available or where they may offer better resistance to operating temperatures in the 200°F (93°C) range. Generally, epoxies have an amine or a polyamide curing agent and require a near-white blast cleaned surface SSPC-SP 10 (NACE 2). Coal tar epoxies have coal tar pitch added to the epoxy resin. A coal tar epoxy cured with a low molecular weight amine is especially resistant to an alkaline environment such as occurs on a cathodically protected structure. Some coal tar epoxies become brittle when exposed to sunlight.18 For a mill-applied system the pipe is placed on rotating rollers mounted on a tracked dolly that automatically feeds the pipe into a grit blasting machine. It is cleaned inside and out. Then it is transferred into a spray booth where the interior and exterior can be simultaneously coated with two separate spray coats to provide a dry film thickness of 12 mils, after which the coated pipe is subjected to hot air blowers for proper curing prior to inspection at 100 volts per mill9. F. MILL APPLIED TAPE COATING SYSTEMS Tape systems have been in use for over 30 years on pipelines. AWWA C209 Standard covers the manual application of cold-applied tape coatings for special sections, connections and fittings. The Steel Water Pipe Manufacturer Technical Advisory Committee Task Group #10 has a standard in the final draft form that covers the plant application of prefabricated cold-applied tape sisting of primer, corrosion preventive tape (inner layer), and a mechanical protective tape (outer layer). This system is available on 2 through 120 O.D. pipe and is recommended for temperatures up to 140°F (60°C). This temperature is a limitation imposed by AWWA, but there are tape systems presently available for temperatures up to 200°F (93°C). The primer s function is to provide a bonding medium between the pipe surface and the adhesive or sealant on the inner layer. The inner layer tape consists of a plastic backing and adhesive. This layer protects against corrosion, so it has to provide a high electrical resistivity and low moisture absorption and permeability, along with an effective bond to the primed steel. It is always a minimum
thickness of 15 mils, with the total system a minimum of 40 mils. The outer layer tape consists of a plastic film and an adhesive of the same types of materials used in the inner tape, or materials that are compatible with the inner layer tape. The purpose of the outer layer tape is to provide mechanical protection to the inner layer tape, and also to be resistant to the elements during outdoor storage. The outer layer tape is always a minimum of 25 mils. Pipe diameter, wall thickness, and construction conditions determine thickness of the system. Cold-applied, multi-layer tape systems are designed for plant coating operations and result in a uniform, reproducible, holiday-free coating over the entire length of any size pipe. The multiple layer system allows the coating thickness to be custom-designed to meet specific environmental conditions. These systems have been engineered to withstand normal handling, outdoor weathering, storage, and shipping. Bare pipe is heated prior to blast cleaning to remove moisture and loosen mill scale. Abrasive blast cleaning is used to obtain a NACE No. 3, Steel Structures Painting Council Specification SSPC-SP 6, commercial blast finish. A quick-drying primer is applied to the blast cleaned pipe surface at a coverage rate of approximately one gallon per eight squares of tape applied. The inner-wrap tape is applied over dry primer with proper mechanical equipment that applies the inner layer to the pipe under tension (10 Ibs. per inch of width minimum), resulting in a tight, wrinkle-free coating. The spiral overlap should be approximately one inch. The outer-wrap tape is simultaneously applied under tension (12-14 Ibs. per inch of width minimum) to obtain a tight, wrinklefree coating. The laps of the inner and outer wraps should not be on top of each other, but should be staggered. Holiday detection should follow with a minimum of 6,000 volts, conforming to NACE Standard RP-02-74. All holidays should be repaired. Coated pipe should be handled carefully to protect pipe and coating from damage. The weld seam of longseam welded pipe should not contact the adjacent pipe in pyramid stacking, and spiral welded pipe should be separated by coatings. stripping. For normal construction conditions, prefabricated Polyvinyl, polyethylene, and c oal tar tapes are widely cold-applied tapes are applied as a threelayer system con- used for joint coatin g protection or for odd shapes or 355 --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*Lb.L 93 m Bb279'40 0003803 543 m bends on mill-applied applications. The trend is to heavier butyl-mastic type adhesives for better adhesion and elimination of water migration at the overlap. When tapes are applied at a coating plant, padding, or rockshield must be provided to minimize shipping damage. Over the trench, field-applied tapes may be applied with tape wrapping machines. Coatings applied over the ditch are less susceptible to physical damage because of reduced handling, but they can be more affected by variations in ambient temperatures and h~midity'~. Together with inadequate surface preparation, these are the main disadvantages of a field-applied coating system. The important developments in plastic tapes have been an increase in their thickness, use of stronger resins, and improved adhesion by the use of new types of adhesives and primers.21 Mill-applied tapes capable of service temperatures to 210°F (99°C) are available. G. WAX COATINGS Wax coatings, in use for 48 years, are still used on a limited basis. Microcrystalline wax coatings are usually used with a plastic overwrap. Wax waterproofs the pipe and the wrapper protects the wax coating from contact with the soil and affords some mechanical protection. The most popular use of wax coating is the over-the-ditch application with a combination machine that cleans, coats, wraps, and lowers into the ditch in one operation. Because there are no objectionable or toxic fumes or smoke present, this system is more acceptable than some others. H. POLYURETHANE FOAM INSULATION Efficient pipeline insulation has become increasingly important as a means of operating hot and cold service pipelines. This is a system controlling heat transfer in above ground, below ground, and marine pipelines. While generally used with a corrosion coating, if the proper moisture vapor barrier is used over the urethane foam, effective corrosion protection is obtained. This is a plantapplied process where the carrier pipe is centered within the outer jacket, which contains and molds the foam as well as provides effective moisture vapor barrier. Metered quantities of foam components are rapidly introduced between the carrier pipe and the outer jacket. The foam is restrained by end caps and rises on a first-in basis forming a uniform composite unit. When properly jacketed, usually with polyethylene or coated steel, the system is moisture and corrosion-resistant, sufficiently strong to resist crushing, and flexible enough to permit allowable field bending22. I. CONCRETE Mortar lining and coating has the longest history of protecting steel or wrought iron from corrosion23. When
steel is encased in concrete, a protective iron oxide film forms. As long as the alkalinity is maintained and the concrete is impermeable to chlorides and oxygen, corrosion protection is obtained. See AWWA C205 for a detailed reference on concrete coatings. Today, concrete as corrosion coating is limited to internal lining. The external application is applied over a corrosion coating for armor protection and negative bouyancy in marine environments. A continuous reinforced concrete coating has proved to be the most effectively controlled method. Materials including water, sand, andlor heavy aggregate and cement are mixed in the application plant. The materials are conveyed by belt to the throwing heads where controlled-speed beltlbrushes throw the mixture onto the coated pipe surface. The rotating pipe is moved past the throwing heads to receive the specified thickness of concrete. Simultaneously, the galvanized wire reinforcement is applied with an overlap (Figure 10). To increase tensile strength and to improve impact resistance, additional layers of wire or steel fibers may be specified24. Welded wire cages are another alternate method of reinforcement. Other application methods include forming or molding of concrete in place or applying it to the pipe by means of a plastic film. IV. APPLI CATI0N SPECI FICATIONS Because of the multiplicity and complexity of coating systems, the user should refer to manufacturers' recommendations and applicable specifications from the National Association of Pipe Coating Applicators, American Water Works Association, Department of the Navy25.26, and FIGURE 10 Application of continuous reinforced concrete pipe coating for negative bouyancy and armor protection. --`,,,,`-`-`,,`,,`,`,,`--Courtesy: Bredero Price Co. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 356
SSPC CHAPTER*Lb=L 93 8627940 0003804 48T the National Association of Corrosion Engineers. The National Association of Corrosion Engineers Standard RP-02-75, Application of Organic Coatings to the External Surface of Steel Pipe for Underground Service, is a comprehensive standard prepared to assist users of all types of organic coatings in obtaining a satisfactory application of the selected coating system and is an excellent guideline in preparing a specification. This Recommended Practice, issued by NACE Group Committee T-10 on Underground Corrosion Control, was prepared by Task Group T-10D-8 of Unit Committee T-1OD on Protective Coating Systems. This Recommended Practice is included, in Appendix A as a general guideline to be used along with sources listed previously. A. SELECTION OF APPLICATOR A major cause of pipeline coating failure is improper application. A quality material poorly applied is of little value and the quality of a pipe coating is only as good as the quality of application. To assist in the evaluation of an applicator, the following points should be consideredz7: i.Experience Research and trial and error have gone into the development of every coating, with close cooperation between applicator, coating manufacturer, equipment manufacturer and customer. The transition from laboratory to production line is usually a costly experience, which should not be ignored. 2. Reputation This is an asset earned by consistent performance. Not only good quality work but also solving problems and correcting mistakes help to develop a reputation. 3. Reliability There are many variables in the application of coatings. A reliable work force, well maintained equipment and consistent quality performance are prerequisites for an applicator. 4. Conformance to Coating Manufacturer s Specifications The manu fact urer s establis hed minimum specifications for application of materials should be met. 5. Modern Automated Equipment Capital expenditure on automated application equipment is an important part of the success of plastic coatings. Elimination of human errors through automation and controls continues to be an important factor in improved pipe coatings.
6. Quality Control Conformance to specifications has to be checked regularly. Knowledge of applicator s quality control procedures on materials, application, and finished product is essential in the selection of an applicator. B. INSPECTION PROCEDURES Once the coating system and applicator are selected, an important part of a quality installation is good inspection. Inspection should begin with stockpile of bare pipe through coating operations, load out, coated pipe stockpile, field inspection, joint coating procedure and back fill of coated pipe. Knowledge of the coating system, plant facilities, quality control methods, shipping requirements, handling, joint coating, field conditions, field holiday detection and repair are requirements for proper installation(z8). Experience and common sense in interpretation of specifications and analysis of test results will contribute to obtaining the best possible coating results. C. COATINGS EVALUATION The best criterion for coating selection is twenty years without failure in ground. This method may be most expedient and least expensive if records show that the coatings performance has been satisfactory. However, because of increased demands on coatings performance and availability of new materials, alternate methods of coating evaluation are necessary. The American Society of Testing and Materials (ASTM), National Association of Corrosion Engineers (NACE), and the American Water Works Association (AWWA) have developed standard tests for this purpose. Eleven standard test methods are now available from ASTM, which were developed in conjunction with the American Gas Association. A summary of these test procedures follow^(^^): i.Physical and Mechanical Tests a. Abrasion Resistance of Pipeline Coatings, ASTM G 6 -An accelerated test that subjects coated pipe samples to a controlled rate of abrasion using a slurry of coarse aluminum oxide in water. The specimens are revolved in the abrasive medium until failure occurs. The failure point is detected by an electrical monitoring circuit. b. Bendability of Pipeline Coatings, ASTM G 10 A method to determine the effect of short-radius bends on small-diameter, coated pipe. A bending mandrel forms the pipe until the point of crazing, cracking, or other mechanical coating failure is reached. c. impact Resistance of Pipeline Coatings (Limestone Drop Test), ASTM G 13 -A method for estimating the effect of falling stones on a coating surface. After a pattern of systematic exposure to a charge of classified limestone aggregate, the coating specimen is electrically inspected for pinhole coating breaks. d. Impact Resistance of Pipeline Coatings (Falling Weight Test), ASTM G 14 -A method providing a
systematic means for measuring controlled impact damage on a coating surface. A statistical calculation is used to compute the mean impact strength at the point of coating failure. 357 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*Lb.L 93 = 8b27940 0003805 3Lb = e. Penetration Resistance of Pipeline Coatings, ASTM G 17 -A static loading test to determine the deformation-underload characteristics of pipe coatings. The test simulates concentrated point loading encountered in pipe stacking or in the inclusion of rocks and debris in trench backfill. 2. Electrical and Electrochemical lests a. Cathodic Disbonding of Pipeline Coatings, ASTM G 8 -An accelerated test for measuring the rate of coating damage and adhesion loss caused by the application of cathodic protection to holidays in coated pipe, useful for the initial screening of new materails. The method provides for both the visual and electrical monitoring of holiday propagation. b. Water Penetration into Pipeline Coatings, ASTM G 9-A method for measuring the rate and approximate depth of water absorption by a coating. The test uses differential capacitance and power factor measurements to monitor the degradation of coatings dielectric properties. c. Test for Joints, Fittings and Patches in Coated Pipelines, ASTM G 18 -An adaptation of the Water Penetration Test, ASTM G 9 to evaluate patch and joint performance. Capacitance and power factor measurements monitor water absorption into the patched areas. d. Disbonding Characteristics of Pipeline Coatings by Direct Soil Burial, ASTM G 19 -A field version of ASTM G 8, using soil as the electrolyte. Disbonding is measured over an 18-month test period. Results are more representative of operating conditions but subject to greater variability among specimens. 3. Chemical and Atmospheric Tests a. Effects of Outdoor Weathering on Pipeline Coatings, ASTM G 17 -A standard procedure for exposing coated pipe samples to local atmospheric conditions. The controlled exposure period permits subsequent evaluation for ultraviolet deterioration, disbondment, loss of impact resistance, or other pertinent characteristics. b. Chemical Resistance of Pipeline Coatings, ASTM G 20 -Provides a standard method for evaluating the deterioration of coating properties after exposure to chemical liquids and their vapors. The method includes a check of dimensional stability and coating bond loss at intentional holidays. The success of any test program is contingent on many variables, one of which is the objectivity of test personnel. Selection of production samples, adequate sampling and uniformity of test procedures and interpretation makes data comparisons more meaningful. D. SUMMARY It is not easy to select the best coating system to fit
any given environment or soil condition. Knowledge of operating and installation conditions is the beginning of the process. Steel source and job location may limit the coatings available to each project. Selection of a quality applicator is the most important consideration and frequently is the most neglected. Following coating and applicator selection, inspection at the coating mill and especially on the job site during construction will go far in assuring that a high quality pipe coating system has been installed. APPENDIX A: NACE RP-02-75 Application of Organic Coatings to the External Surface of Steel Pipe for Underground Service (Reprinted with permission) Section 1: General 1.1 The scope and purpose of this Recommended Practice are to set minimum acceptable requirements for the application of organic coating materials to pipelines for underground service. 1.2 The purpose of the coating is to prevent corrosion of steel pipe by isolation from the surrounding environment. 1.3 This Standard describes the practices common to the application of pipe coatings, care and handling of materials, surface preparation, field joints, inspection for defects, repair of coating defects, and the handling of coated pipe prior to and during installation. 1.4 Plant application and field application are considered separately, when necessary, to account for the capabilities of available plant and field equipment. 1.5 The selection of specific coating materials is left to the user s discretion and is therefore not considered. 1.6 Detailed instructions for applying a specific coating are not included since these are furnished by material suppliers. 1.7 Good technical judgment should determine the degree to which the minimum requirements should be exceeded in compensating for unusually severe environments, such as river crossings, rocky or exceptionally corrosive soils, and pipe inside casings. Section 2: Cafe and Handling of Materials 2.1 All pipe coating materials must be kept free from contamination or damage prior to and during application. Material with limited storage life should be examined for deterioration prior to use and discarded or exchanged for fresh material if the specified life is exceeded. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 358
SSPC CHAPTER*Lb*L 93 8627940 0003806 252 D 2.2 All cartons or containers should be plainly and permanently marked with the name of the manufacturer, product identification, and batch or lot numbers. 2.3 Primers 2.3.1 Primers are to be stored in tightly sealed containers and only that portion required for immediate use shall be drawn from containers. 2.3.2 Storage must be at temperatures within manufacturer s recommended range, and exposure to extreme temperatures should be avoided. 2.3.3 Primers are likely to be volatile and flammable and must be kept away from open flame or other sources of ignition. 2.3.4 Primers must be mixed thoroughly prior to use and agitated during use, if required, to prevent settling. 2.4 Hot Applied Enamels, Mastics and Waxes 2.4.1 Materials must be stored unopened in the original containers within temperature ranges specified by the manufacturer. 2.4.2 Hot-applied materials must be heated within the manufacturer s recommended temperature range to assure proper application. When required, the heating and agitation of hot-applied materials must be properly controlled to prevent settling of fillers, decomposition, excessive loss of light ends, and foaming. 2.4.3 Melting pots that have been used for other materials must be drained and cleaned before use. 2.4.4 Melt and transport hot-applied materials in a manner to prevent contamination by foreign materials. 2.5 Cold-Applied Mastics, Waxes, and Greases. 2.5.1 Materials must be stored in the original containers. Those containing volatile solvents must be stored in sealed containers at a temperature within the range recommended by the manufacturer. 2.5.2 Materials containing volatile and flammable solvents must be kept away from open flame or other sources or ignition. 2.6 Tapes and Wrappers 2.6.1 In this category are pre-formed tapes including heat applied, cold-primer applied, pressure sensitive tapes, and overwrapping or supporting materials, such as felt, fiberglass, and paper. 2.6.2 Tapes and wrappers should be stored as directed on the cartons, in a dry place, and should remain under cover until ready for use. 2.6.3 Tapes and wrappers should not be handled
with hooks or be thrown from trucks. Materiais showing evidences of damage or deterioration must not be used. 2.6.4 Prolonged exposure of tape to sunlight must be avoided. 2.7 Thin-Film Coatings 2.7.1 In this category are fusion-bonded powder coatings -either thermoset or thermoplastic, and liquid coatings, usually thermoset (with or without solvent) and catalyzed coatings, such as the coal tar epoxies. 2.7.2 Materials must be stored unopened in the original cartons or containers in adry place at temperatures within the range specified by the manufacturer, and should remain under cover until ready for use. 2.7.3 Materials containing volatile and flammable solvents must be stored in a selected area away from sources of ignition and identified as flammable. Only that portion required for immediate use should be drawn from containers, which should then be resealed. 2.7.4 Powdered coatings must be handled so as to exclude the introduction of foreign materials, solvents, or excessive moisture. 2.8 Plastic Sleeves 2.8.1 In this category are heat-shrinkable fieldapplied joint materials and mill-applied extruded sleeves which may or may not be extruded over mastic materials. 2.8.2 Materials must be stored unopened in the original cartons or containers in a dry place. Section 3: Surface Preparation 3.1 Surface Condition and Storage 3.1.1 Pipe must be purchased with instructions to omit all types of oil, lacquers, or varnish. 3.1.2 Identifying markings must be made with a material either removable or compatible with the coating to be used. 3.1.3 Primer applied at the pipe mill must be compatible with the final protective coating. 3.1.4 When pipe is temporarily protected in storage, a material compatible with the final coating must be used. 3.2 Over-the-Ditch 3.2.1 Prior to cleaning, foreign materials, weld slag and burrs, excessively high weld buttons, oil, grease, and moisture must be removed from the pipe. 3.2.2 The pipe must be machine or blast cleaned prior to coating application. Copyright The Society for Protective Coatings Provided by IHS under license with
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3.2.3 The cleaning machine must be properly centered on the pipe to insure uniform rotation of the cleaning head. Allcleaning tools must be properly tensioned against the pipe. 3.2.4 Machine crawlers or cleaning tools that will burr or scar the pipe must not be used. 3.2.5 Rust, mill scale, and dirt must be removed from the pipe. 3.2.6 When primers are used that must dry before coating is applied, all moisture, dust, and dirt must be removed from the primed pipe before coating. 3.2.7 Cradles for the coating machine must be of a type that will not make track marks or remove the primer. 3.3 Coating in the Plant 3.3.1 Unless otherwise recommended by the coating material manufacturer, as a minimum, the pipe must be grit or shot blast cleaned to SSPC-SP 6, NACE No. 3 Test Method entitled Visual Standard for Surfaces of New Steel Centrifugally Blast Cleaned with Steel Grit and Shot (Commercial Blast Cleaned Surface Finish). 3.3.2 Pipe must be dry and free of oil, grease, and blasting grit or shot. 3.3.3 If used, the primer must be applied to freshly cleaned surfaces within five minutes after cleaning. 3.3.4 For surface preparation of field joints and repair of coating defects, see Sections 4 and 5. Section 4: Field Joints 4.1 Coated pipe sections connected by welding andlor mechanical coupling by means of valves or other underground appurtenances will be considered field joints. Coating of field joints must be equal to or better than the coating on the pipeline. 4.2 Surface Preparation 4.2.1 In removing coatings to make tie-ins, care must be taken to avoid the disbonding of the adjacent coating. Edges of thick film coatings must be tapered and enough of the wrapper removed to ensure adhesion of the new coating to the existing coating. 4.2.2 Surfaces to be coated must be thoroughly cleaned with solvents to remove all oil and grease. All dust, dirt, rust, mill scale, loose shop coating, dead primer, welding slag, slivers, and burrs must be removed with wire brushes or scrapers. Nicking the bare pipe surface must not be permitied. 4.3 Materials 4.3.1 Where materials requiring primer are used, the primer may be hand applied in a uniform coat. Curing or drying time must be
in accordance with manufacturer s specifications. 4.3.2 Coating materials for field joints must be equal in quality to, and compatible with, coating on the pipeline. 4.3.3 Coating materials must be applied substantially free of voids, wrinkles, and air or gas entrapment. This may require the use of materials that will conform to the shape of irregular appurtenances, such as valves. 4.3.4 A new coating must overlap and adhere to existing material. The overlap must be sufficient to allow for shrinkage of both new and existing coatings. Section 5: Repair of Coating Defects 5.1 After the coating has been applied, inspection should follow. Any defects discovered should be repaired. 5.2 Procedure 5.2.1 A sufficient portion of the coating must be carefully removed from defective areas of pipe to ensure that the remaining coating is satisfactory and well bonded. Edges of the area should be tapered to increase the strength of the patch. 5.2.2 Foreign matter must be removed from the area to be repaired. 5.2.3 Primer applied to the area, if required, must be allowed to dry properly before the coating is applied. 5.2.4 The coating material used for patching must be such that proper adhesion will occur between the existing coating material and the patching material. Section 6: Handling Coated Pipe 6.1 Coated pipe should be handled in a manner to minimize damage. 6.2 Handling equipment 6.2.1 Equipment which is injurious to the coating must not be used. 6.2.2 Belt slings must be sufficiently wide and free of protruding rivets or bolts to prevent damage to the coating. 6.2.3 Skids and racks must be of sufficient width, or must be padded, to prevent the edges from cutting the coating and should be arranged to permit the coated pipe to bear on the full width of the skid. 6.3 Storage and Shipping 6.3.1 Coated pipe that is ta be stacked should be nested so that adjacent pipe lengths bear equally against each other throughout their coated lengths, or should be suffiCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from
IHS 360
SSPC CHAPTERxLb.1 93 W 8627940 0003808 025 W ciently padded. Excessively high stacking . -of coated pipe must be avoided. 6.3.2 Devices used to secure pipe during shipping must not cause damage to the coating, pipe, or pipe bevels. 6.4 Installation 6.4.1 Pipe which is not placed in the ditch immediately after coating should be supported on skids sufficiently wide andlor adequately padded to prevent damage of the coating. 6.4.2 Foreign objects which could damage the coating must be removed from the bottom of the ditch before the pipe is lowered into position. When rocks or other items cannot be removed, sufficient padding must be used to prevent coating damage. 6.4.3 When the coated pipe is lowered in the ditch, care must be exercised to prevent the pipe from swinging against or rubbing on the sides of the ditch. If coating damage occurs, it should be repaired according to Section 5. 6.4.4 When the ditch is backfilled, care must be exercised to prevent damage to the pipe from rocks, clods, and similar objects. Padding or shielding material may be necessary to prevent such damage. ACKNOWLEDGEMENT The authors and editors gratefully acknowledge the active participation of the following in the review process for this chapter: Leonard Choate, S.C. Frye, W. Kemp, Donald King, Dr. Howard Lasser, Henry R. Stoner, Rupe Strobel and William J. Wallace, Jr. BIOGRAPHY Richard N. Sloan, a graduate of Drexel University Evening College with a B.S. degree in Industrial Administration, is Vice President -Marketing ot Ameron Price, Fontana, California. He is an active member of NACE and AWWA Societies. Sloan has been employed by H.C. Price Company for twentyeight years after starting as a Clerk in 1952. He has held positions as Office Manager, Sales; Sales Manager; Assistant Re-
gional Manager; and Regional Manager at their Pennsylvania pipe coating plant prior to transfer to Bartlesville, Oklahoma, as Marketing Manager. BIOGRAPHY A W Peabody worked as a Consulting Engineer in Corrosion Control Until 1980, he was the Director of Corrosion Engineering for EBASCO Services, Inc in New York and Houston, where he was involved with assignments related to electric utilities, underground pipelines, industrial plants, and marine facilities For EBASCO he also served as Supervising Corrosion Engineer and Principal Corrosion Engineer He was a ;! member of the State DeDartment Cultural Exchange Delegation on Corrosion to the Soviet Union in 1962 and recipient of the Frank Newman Speller Award in Corrosion Engineering by the National Association of Corrosion Engineers in 1979. He was recipient of the Col. G. C. Cox Outstanding Award in 1979. He has published numerous articles on corrosion, and a book on pipeline corrosion control. Mr. Peabody graduated from the University of Maine in Electrical Engineering, and did graduate study at Brooklyn Polytechnic Institute. He is a registered professional engineer, and a Life Member of the National Association of Corrosion Engineers (NACE), and of the Institute of Electrical and Electronic Engineers. He was elected a fellow of NACE in 1993. REFERENCES 1. Norman Peifer and Frank Costanzo, Protection of Pipelines and Other Underground Structures . Steel Structures Painting Manual, Vol. 1, Chapter 3, pps. 323-349, 1954. 2. Industrial Writing, Inc., Coal Tar Enamel Leads in Pipeline Coatings . Pipeline Digest, p. 9, March 16, 1981. 3. A.W. Peabody, Coatings . Control of Pipeline Corrosion, Chapter 3, pps. 9-18, 1954. 4. National Association of Corrosion Engineers Standard, NACB RP-01-69, Recommended practice -Control of External Corrosion on Underground or Submerged Metallic Piping Systems . Sections 5.1.2.1 and 5.1.2.2, p. 5, 1969. 5. S. Boysen, Jr., Coating Fundamentals . NACE 19th Annual Appalachian Underground Corrosion Short Course, May 1974. 6. NACE RP-01, p. 5, 1969. 7. Jack T. Kiuchi, Plastics for the Protection of Underground Pipe . Purdue University 6th Annual Underground Corrosion Course, March 1, 1967. 8. O.W. Wade, and J.F. Gosse, A Study of Test Methods for External Coatings for Underground Pipelines . American Gas Association Distribution Conference, 1966. 9. Dean M. Berger, Selecting Coatings for Underground Steel Pipe . Plant Engineering, p. 105, September 30, 1976. 10. R.W. Horner, Extruded Plastics . NACE 18th Annual Appalachian Underground Corrosion Short Course, May, 1973. 11. Kiuchi, Plastics for the Protection of Underground Pipe.
12. K.Channing Verbech, Protective Coatings . New England Gas Association, June 19, 1969. 13. R.N. Sloan, Present Trends in Coatings to Protect Pipe Type Cable in the Utilities Industry . Materiais Performance, 18, NO. 7. PPS. 27-30, July, 1979. 14. R.N. Sloan, Asphalt Mastic Coatings . NACE 15th Annual Appalachian Underground Corrosion Short Course, 1970. 15. N. Schmitz-Pranghe, Mannesmann s Approach to Extruded PE Mill Coating . Pipe Line Industry, p. 40, March, 1976. 16. R.N. Sloan, Extruded Plastic Pipeline Coatings . NACE Southeast Regional Engineering Conference, October 21-24, 1979. 17. John D. Keane, Joseph A. Bruno, Jr., and Raymond E.F. Weaver, Surface Profile for Anti-Corrosion Paints . Steel Structures Painting Council Report, 165 pps., October 25, 1976. 18. Richard W. Drisko, Introduction to Protective Coatings . Western States Corrosion Seminar, California State Polytechnic University, Session No. 6, Paper No. 7, May 6-7-8, 1980. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 361
SSPC CHAPTERtL6.L 93 = 8627940 0003809 TbL 19. Linden Stuart, Modern Pipe Coating Techniques and Equipment in the Mill and Field . NACE Corrosionl78, Paper No. 65, 1978. 20. Emil Senkowski, Materials Specifications and Evaluation . NACE 15th Annual Liberty Bell Corrosion Course, 1977. 21. Peifer and Costanzo, pp. 323-349. 22. Prilo-K Bredero, Polyurethane Foam Insulation Bulletin . Mfg. Literature, Bredero-Price, Inc. 23. John G. Hendrickson, Internal and External Concrete Coatings for Corrosion Control . NACE 15th Annual Appalachian Underground Corrosion Short Course, p. 358, 1970. 24. Anonymous, Steel Fibers Toughen Coating for Offshore Pipelines . Pipeline and Gas Journal, Staff Report, May 1975. 25. Naval Facilities Engineering Command, NAVFAC Specification TS-15057, Coal Tar Coating Systems for Steel Surfaces , April, 1974. 26. Naval Facilities Engineering Command, NAVFAC Specification TS-09809, Protection of Buried Steel Piping and Steel Bulkhead Tie Rods , September, 1975. 27. Verbech, Protective Coatings . 28. Wade and Gosse, A Study of Test Methods for External Coatings for Underground Pipelines . 29. Emil Senkowski, Standard Laboratory Tests for Pipeline Coatings . Materials Performance, Vol. 18, No.8, pps. 23-28, August, 1979. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS--`,,,,`-`-`,,`,,`,`,,`--362
SSPC CHAPTER*Lb=2 93 m 8627940 00038LO 783 m CHAPTER 16.2 CATHODIC PROTECTION by A.W. Peabody I. INTRODUCTION Since Volume 1 of the SSPC Manual was first published, general knowledge of cathodic protection and its practical application have increased greatly. Its importance can be seen in the federal regulation that all new construction for hazardous pipelines must include the use of effective coatings and cathodic protection. Because a comprehensive discussion of cathodic protection would be voluminous, this chapter presents only a general introductory account. Other sources provide more specific treatment',*. II. HOW CATHODIC PROTECTION COMPLEMENTS A COATING Coatings used on pipelines and other underground structures frequently need to protect very large areas of underground metal, especially with major cross-country pipelines. For instance, only 10 miles (16.09 km) of 48" (1219.2 mm) diameter steel pipeline has an exterior surface area of approximately 15.2 acres (6.2 hectares). Such large areas, when coated and buried, cannot remain permanently free of all pinholes, developed defects, or outside damage. Even though the coating may, initially, be free of holes in the film, pipe movement with temperature variations, soil stresses, and damage from outside sources (such as excavation work on other projects) will ultimately expose bare metal to the corrosive effect of the surrounding environment (soil or water). The amount of metal exposed will be determined by the quality of the coating used and the severityof the hazards working to damage the coating. Even though 99.9999% of the surface area might remain fully and effectively protected by the coating, the remaining 0.0001 YOcould be a problem. On the 10 miles of 48" pipe mentioned earlier, this represents some 0.6635 square feet of exposed metal. Serious damage could occur on this much exposed surface if corrosive effects are not controlled. To put the 0.6635 square feet in better perspective, it represents in the order of 50 one-half-inch diameter holes in the coating for each mile of the 48" diameter pipe. A lot can happen at these locations. Although the coating-cathod ic-protection combination is used widely on pipeline exterior surfaces, this working team can also be used on the interior surfaces of pipelines carrying electrically conductive materials such as water or other conductive solutions. Although there
may be unique design considerations when planning a cathodic protection system for pipeline interiors, such a system can work very effectively. Cathodic protection current must be able to reach all of the pipeline's exposed metal. If, for example, a coating material is not bonded to the pipe surface, it may permit water to reach the metallic pipe surface under the disbonded coating around coating holidays. Where the disbonded coating has a high electrical resistance, cathodic protection current cannot flow through it to reach the pipe surface, and active corrosion may result. While cathodic protection current can enter the space between the disbonded coating and pipe surface, the thin water film there may prevent the protection current from penetrating in sufficient quantity for adequate protection. If the space between a disbonded coating and pipe surface remains dry, there will normally not be a corrosion problem. If water does enter the space, however, an electrically insulating coating acts as an "electrical shield" preventing the effective cathodic protection of the pipe at that location. Electrical potential measurements may indicate that the pipe is cathodically protected in accord with an accepted criterion at the disbonded area, whereas it may, in fact, be corroding. The pipeline operator will normally find that a top grade coating will give the best practicable corrosion control for his metallic pipe when it is complemented by a cathodic protection system which has been properly designed, installed and maintained. 111. RELATION BETWEEN COATING CHARACTERISTICS AND CATHODIC PROTECTION The characteristics of a coatings system determine the requirements for cathodic protection. If a coating on a buried or submerged pipeline forms a high electrical resistance barrier between the pipe and surrounding earth or water, the electric current needed to provide cathodic protection will be less than with a coating barrier having a lower effective electrical resistance, and lower current requirements for cathodic protection mean a lower investment for the cathodic protection system. The designer and operator of the cathodic protection system for a coated pipeline are concerned with three maCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 363
SSPC CHAPTER*16.2 93 8627740 0003811 bLT jor coating characteristics: 1) Effective coating resistance; 2) Bond between coating and protected structure as discussed in the preceding section; 3) Coating stability. Of these three, coating stability is perhaps the most important. A stable coating has effective resistance and bond for a long period of time. A coating with a high effective resistance will be chosen for pipeline application. This effective resistance per average square foot depends upon the basic resistivity of the coating material itself, the coating thickness, number and size of holidays in the coatings, deleterious effect of the environment on the coating, the resistivity of the conducting environment in which the pipeline is buried or submerged, and the bond between pipe surface and coating. If effective resistance is unstable, the electric current needed for cathodic protection may double every few years, causing increased costs for installation of new cathodic protection facilities, maintenance, and energy. Resistance almost always declines as additional coating defects are generated through environmental effects. While the cathodic protection engineers are able to measure the effective resistance of a coating on a pipeline, this measurement can be misleading if the pipe has been installed in dry earth and not given time enough for the backfill to settle and for moisture to permeate all existing coating pinholes and holidays. Measurements made under these conditions will normally indicate a higher effective resistance (possibly much higher) than what actually exists. Thus, experience is required to judge the validity of coating resistance measurements and to use them for calculating the design of cathodic protection systems. There is a great difference between the resistance of a perfect pipeline coating and one with even just a very few small pinholes. To illustrate: the resistance across a 3/32 (2.38mm) thick completely pinhole-free coal tar enamel coating having a volume resistivity of 1013 ohmcentimeters on a ten-mile (16.09km) length of 36 (914.4 mm) diameter pipeline in a 1000 ohm-cm environment would be approximately 5148.2ohms. This is equivalent to an effective coating resistance of 2.56 x lo9 ohms per average square foot. However, if there were just one (1.59mm) diameter pinhole filled with the 1000ohm-cm environment, the resistance across the 3/32 (2.38 mm) length of the pinhole would be 12,026ohms. This resistance in parallel with the 5148.2-Ohmcoating resistance
would be approximately 3605ohms, which is equivalent to an apparent coating resistance on the ten-mile (16.09km) section of 1.79x lo8ohms per average square foot -a 30% reduction from the perfect coating condition. Under practical conditions, the chances are that there would be many more than one pinhole in a ten-mile pipeline section. Assuming there were fifty pinholes of the size stated in the example, the parallel resistance across the fifty pinholes would be 240.52 ohms. This figure, in turn, in parallel with the 5148.2-ohmcoating resistance would give a net resistance across the ten-mile (16.09km) length of 229.8ohms which is equivalent to an apparent coating resistance on the ten-mile (16.09km) section of 114.3x lo8ohms per average square foot. Although this is still a high resistance figure (and indicates a very low electrical energy requirement for cathodic protection), it nevertheless represents a 95.5 reduction from the perfect coating condition. Coating bond also effects resistance particularly adjacent to any pinholes or holidays in the in-place coating. Any lifting of the coating because of disbondment at such openings in the coating increases the amount of pipe metal exposed to the surrounding environment, reduces the effective coating resistance, increases the electrical current requirements for cathodic protection and introduces the possibility of under-film corrosion that is electrically shielded from the beneficial effects of cathodic protection. It doesn t take much disbondment to double the area of exposed metal at the usual small coating defect. For example, doubling the exposed metal area at the base of a (6.35mm) diameter hole in a pipe coating involves a disbondment lifting of only approximately 52 mils (1.32 mm) from the edges of the hole. Disbonding effects can be far worse than this. IV. BASIC THEORY OF CATHODIC PROTECTION To understand how cathodic protection works, it is necessary to understand corrosion. On a pipeline, corrosion causes a flow of direct current between the elements of a corrosion cell on the pipeline or between the pipeline and some external entity which may be affecting the pipeline. Fig. 1 illustrates this. As shown by the figure, areas where corrosion is occurring are called anodic , which means that they are discharging corrosion current to a conductive electrolytic environment, earth or water. When direct current leaves the surface of pipe metal to enter such an electrolytic environment, it takes the metal with it, and the pipe suffers corrosive deterioration. On the Anodic Areas (Pipe Corrosion Current (Represented by Arrows)
Flows &the Surrounding Earth or Wuter the Anodic Areas on he Pipeline and Removes Metal at These 1ocations. FIGURE 1 Typical Components of Pipeline Corrosion Cell. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 364
SSPC CHAPTER*Lb-2 73 8627740 0003832 556 (Ueturn-Flow AnodicCurrent Through Previously~~ Pipeline to Source Areas of Direct Current Source of Diract Current LAuxiliar Ground Connection (ü8Udy 7 ermcd Ground Bed ) FIGURE 2 Basic Concept of Cathodic Protection. other hand, when direct current flows from a surrounding electrolytic environment onto the pipe surface at cathodic areas, there is no corrosive damage. If there were a way to convert all anodic areas on a buried or submerged pipe surface to corrosion-free cathodic areas, corrosive damage would be eliminated. This is exactly what is accomplished with a properly designed, installed and maintained cathodic protection system. Basically, this is done by using some external source of direct current to neutralize and counteract the natural corrosion currents discharging from anodic areas. Figure 2 illustrates the concept of cathodic protection. The figure shows a ground connection established separate from the pipeline. A source of direct current metallically connected between the pipe and ground connection forces the ground connection to discharge current. The system is designed to regulate the amount of current discharged (cathodic protection current) so that it eliminates the flow of corrosion cell current from anodic areas by converting them to cathodic areas. A net flow is established from the conductive environment onto the previously anodic areas. Because the cathodic protection system ground connection (also known as
ground bed or
anode bed ) is
discharging current to do its job, it is subject to corrosion. Thus, a ca!hodic protection system, although it renders a protected structure surface free of corrosion, does not eliminate corrosion -it transfers the corrosive effect from critical operating structures such as pipelines
to known locations (the ground connections) where replacements may be made periodically (10 to 15 years or more) without making it necessary to take the protected operating pipeline out of service. V. CRITERIA USED FOR EVALUATING CATHODIC PROTECTION Criteria have been developed to determine that a structure has been made completely cathodic, or in other words that it is fully protected from corrosion. These criteria are set forth in National Association of Corrosion Engineers (NACE) Standard RP-01-69 (use latest revision) titled, Recommended Practice -Control of External Corrosion on Underground or Submerged Metallic Piping Systems. These criteria are also contained in Section I, Corrosion, of Part 192 (Transportation of Natural and Other Gas by Pipeline: Minimum Federal Safety Standards), Title 49 of the Code of Federal Regulations, which was prepared following the passage by the Congress of the Natural Gas Pipeline Safety Act of 1968. Probably the most used criterion is the one based on a simple measurement of the electrical potential between the pipeline and adjacent earth or water. The wording of this criterion is as quoted below from the NACE Standard RP-01-69: A positive indicator for steel and cast iron structures is A negative (cathodic) voltage of at least 0.85 volt as measured between the structure surface and a saturated copper-copper sulphate reference electrode contacting the electrolyte. Determination of this voltage is to be made with the protective current applied. This is all based on the fact that when a pipeline is under cathodic protection, direct current flows from the conducting environment onto the pipeline as shown by Figure 3. This current flow through the environment and coating resistance forces the pipeline to assume a negative electrical polarity with respect to the environment. The question, then, is just how negative the pipe should be to serve as an indication that full protection has been attained. The value of -0.85 volt is used for steel pipe as measured using a standard copper-copper sulphate reference electrode to contact the environment. If other types of reference electrodes are used, the values will be different. Figure 4 illustrates how the protective potential is measured. The reference electrode (used to assure stable and repeatable readings) is normally placed on the earth surface directly above the pipeline as shown. This position Arrows Designate Cathodic Protection Current Fiow Onto
the Pipeline +I + FIGURE 3 Current Flow Pattern at Cathodically Protected Pipe. 365 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*Lb-2 93 8b27940 0003833 492 Electrical Direct Current Vohneter With Test Station /W9h internal Resistance ___) Buried Coated Pipeline FIGURE 4 Measurement of Pipeline Protective Potential. --`,,,,`-`-`,,`,,`,`,,`--tends to be a neutral zone where there is the least net concentration of cathodic protection current flow between the electrode and the pipe surface. When working with submerged pipelines, suitable submersion electrodes may be lowered to a position just above the pipeline. Potentials on steel pipe which are less negative than -0.85 volt to copper-copper sulphate electrode indicate less than full cathodic protection. On the other hand, potentials more negative than -0.85 volt to copper-copper sulphate electrode indicate wasted energy -since once corrosion is stopped at -0.85 volt, there is no real need to carry more negative potentials at a given point as far as corrosion control at that point is concerned. In actual practice, however, it is usually necessary to maintain more negative potentials at drainage points of cathodic protection current along a pipeline in order to maintain the minimum of -0.85volt at locations remote from the drainage points. This is primarily a result of attenuation -voltage drops caused by cathodic protection current on the pipeline flowing through the longitudinal resistance of the pipeline steel in order to return to the drainage point. In this respect, large diameter coated lines are much easier to protect cathodically than are small diameter coated pipes because the larger cross sectional steel area in a large pipe means lower longitudinal electrical resistance with resulting lower attenuation. Where there are more negative than necessary cathodic protection potentials on coated pipelines, gaseous hydrogen is generated at coating defects in the steel surface. Hydrogen bubbles may cause mechanical lifting of paint around defects, increasing the current requirements for cathodic protection. This effect is most likely to occur in environments of low resistance. Avoiding coating damage by excessive cathodic protection is best accomplished by avoiding over-protection in the first place although coatings that are resistant but not immune to this effect can be selected. Normally, cathodic protection design engineers will strive to keep the polarization potential on their protected pipeline below the hydrogen over-voltage potential, which is the point at which free hydrogen starts to evolve. The polarization potential is the potential measured be-
tween the pipe and adjacent earth immediately (within a fraction of a second) after cathodic protection current flow to the pipe is interrupted. The reading must be taken very quickly because the polarization potential decays very rapidly at first. Although its rate depends upon environmental conditions, free hydrogen evolution on steel pipe can be looked for when the polarization potential approaches a value in the order of -1.2 volt as measured to a copper-copper sulphate reference electrode. Other accepted criteria for steel (and cast iron) structures which may be used are given below based on the NACE Standard RP-01-69 and are supplemented by explanatory notes as appropriate. 1) A minimum negative (cathodic) voltage shift of at least 300 millivolts, produced by the application of protective current. (Notes: The voltage shift Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 366
SSPC CHAPTERr16.2 93 8627940 0003814 329 W is from cathodic protection current ON to the value read immediately -within a fraction of a second -after turning the cathodic protection current OFF. Does not apply to all structures; not applicable to structures in contact with dissimilar metals. Used where -0.85 volt to copper-copper sulphate electrode not readily attained. Not always feasible to simultaneously interrupt all cathodic protection current sources on a protected section of pipeline.) 2) A minimum negative (cathodic) polarization voltage shift of 100 millivolts measured between the structure surface and a saturated coppercopper sulfate reference electrode contacting the electrolyte. (Notes: This is a measurement of the cathodic protection-OFF decay in the polarization potential. This decay must be to a point at least 100 millivolts less negative than the polarization potential measured immediately -within a fraction of a second -after first turning the cathodic protection current OFF. Full decay may take excessively long on some pipelines. Not always feasible to simultaneously interrupt all cathodic protection current sources on a protected section of pipeline.) 3) A structure-to-electrolyte voltage at least as negative (cathodic) as that originally established at the beginning of the Tafel segment of the E-Log-I curve. (Notes: The E-Log-I curve is developed, using specific techniques, by applying increasing increments of cathodic protection current to an initially unprotected pipeline and measuring the pi pel ine-to-reference electrode potential at each value of applied current. These potentials are plotted against the logarithm of applied current. Typically, starting from the minimum applied current value, the plot will appear as initial and final straight line portions connected by a curved section or break. It is the indicated pipeline-to-reference electrode potential at the begining of the final straight line portion that is used as the criterion of protection. Effective, but a slow procedure.) 4) A net protective current from the electrolyte into the structure surface as measured by an earth current technique applied at predetermined current discharge (anodic) points of the structure. (Notes: Simplest evidence of compliance is a definite indication that reference electrodes placed on each side of the pipeline opposite the previously anodic spot are electrically positive with respect to a reference electrode placed directly above the pipeline at the previouslyanodic spot. This indicates that direct current is
flowing onto the pipeline from the environment on each side.) While the criteria discussed above are the accepted working tools used by pipeline corrosion engineers to evaluate the effectiveness of their cathodic protection systems, the ultimate criterion is whether or not the development of pipeline corrosion leaks has been effectively stopped. VI. TYPES OF CATHODIC PROTECTION There are two general types of cathodic protection systems widely used on pipeline facilities. These are: galvanic anode systems that generate their own electrical energy for protection and impressed current systems that require energy from an outside source. These two systems are discussed below. A. CATHODIC PROTECTION WITH GALVANIC ANODES A particularly troublesome source of corrosion damage can be the dissimilar metal corrosion cell. If, for example, copper and steel are in electrical contact with each other and both are in contact with a corrosive (low resistivity) earth or water, the steel is anodic and corrodes faster than is the case if the copper is not present. The copper in the case cited, being cathodic, shows little or no attack. But the negative effect of dissimilar metal corrosion cells can be reversed if the
right
with the steel pipe. The right metal
material is in contact is higher than steel in
the electromotive series of metals and, as a result, anodic while the steel in the dissimilar metal corrosion cell becomes cathodic and is thereby protected from corrosion. Materials used for galvanic anodes include zinc, magnesium and (in certain applications) aluminum. The material is usually cast into various commercial shapes (called
anodes ) with lead wires attached. Particularly for
anodes to be buried in earth, they are commonly pur-
chased with a package
of a compatible chemical
backfill surrounding the anode. This permits more uniform performance and better anode efficiency. Galvanic anodes generate their own current through galvanic action
or battery action
when they are in
electrical contact with the pipe metal. This permits a simple construction method which is illustrated in its simplest form by Figure 5. The two dissimilar metals of the anode and the pipe, when electrically connected with a wire as shown, constitute a simple battery causing current to flow from the anode through the earth to the pipe and back to the anode through the interconnecting wire. Anodes may be installed individually or in groups. Their size, material, intervals between installations along a pipeline, and other details are designed by the corrosion engineer. Design determinants include pipe material and physical size, type and condition of the coating, resistivity of the earth or water surrounding the pipe, presence of stray earth currents from other sources, available construction sites, weather, and other similar factors. Although galvanic anodes can control pipeline corroCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 367
SSPC CHAPTER*Lb.2 93 8b27940 00038L5 265 8rade1 I Porous Container (Pa kage) ContoiningChemical Backfill FIGURE 5 Cathodic Protection Using Galvanic Anodes. sion, they are themselves corroded and consumed in the process of supplying the necessary cathodic protection current to the pipeline. The cathodic protection system designer takes this into account by providing enough anode material to give a reasonable operating life. The following figures are practical allowances of galvanic anode material required for one ampere of current flow for one year. TABLE 1 GALVANIC ANODE MATERIAL ALLOWANCE PER AMP-YEAR Anode Material Zinc Magnesium Aluminum (in sea water) Weight of Anode Material, in Pounds 30.8 20.6 8.5 Using figures such as these (which are based on typical efficiencies and replacement of anodes after they are 85% consumed), the designer can, by straight proportion, determine the minimum amount of anode material for any given amount of average current discharge and for any given planned installation life. B. CATHODIC PROTECTION WITH IMPRESSED CURRENT Although galvanic anodes are a simple and reliable source of cathodic protection current and are almost foolproof, they are limited in their application. The prime limitations are (1) the fixed low driving voltage between the
pipe metal and the galv?nic anode metal being used this is the battery voltage between anode and pipe and (2) the large amounts of galvanic anode metal needed for reasonable life in high current applications. While neither of these limitations is insurmountable, the use of galvanic anode installations in high resistivity environments (where the low driving voltage becomes a problem) for high current output at a given location may not be economical. An impressed current system can overcome the limitations described above. In this system direct current from an outside power source is impressed between the pipe metal and a ground connection (or ground bed ) making electrical contact with the earth or water surrounding the pipe. This is illustrated in simplified form by Fig. 6. Of the several possible sources of direct current shown on the figure, that most frequently used is the a-c to d-c rectifier which converts a-c power from commercial power lines to d-c power of the desired voltage and current rating for a specific application. Rectifier units are typically furnished with adjustable d-c output voltage and current giving the corrosion engineer substantial flexibility in the design of his cathodic protection systems. When commercial power is not available where impressed current installations are needed, one of the other d-c power sources shown on Fig. 6 may be selected. These units likewise have the advantages of flexibility in d-c output voltage and current. These alternate power sources can be briefly described as: 1. Engine generators Internal combustion engines or turbines (usually fueled from the protected pipeline) powering a d-c generator of appropriate size or an a-c alternate feeding a conventional a-c to d-c rectifier. 2. Thermal-electric generators Generators directly converting heat (from DiDeline-fueled flame) to d-c electricitv. II 3. Solar-powered generators Using sunlight in a direct conversion process for generation of d-c electricity. Requires storage batteries to provide steady current output through dim and dark periods. 4. Wind-powered Windmills drive are required to through periods 5. Fuel cells
generators d-c generators. Storage batteries provide steady output current of little or no wind.
Devices which depend on the combining of gaseous fuel materials to produce d-c electricity. Flame is not involved. The ground connection, or ground bed, discharges current to earth and therefore corrodes just as galvanic anodes do. But an impressed current system can use relatively inert materials for ground bed anodes. Because these materials corrode at very low rates compared to the corrosion rates of galvanic anode materials, it is possible to design long-life, high current-output ground beds with Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 368
SSPC CHAPTERaLb.2 93 8b279'iO 00038Lb LTL B reasonable quantities of ground bed materials. Materials used include the following: a) Graphite (carbon) b) High-silicon cast iron c) Magnetite (iron oxide -Fe,O,) d) Platinized metals e) Steel Of these, the first three are consumed at rates ranging from a fraction of a pound to around two pounds per ampere per year depending on material used, current discharge density, and the nature of the environment. Platinized metals are used in special applications where the cost is justified. Platinum corrodes at an extremely low rate. For ground bed use, it is normally plated in a thin layer on a substrate such as titanium or columbium. Because these materials resist the discharge of current once the platinum plating is consumed, the substrate material is not severed by local corrosion. Steel corrodes at a rate of about 20 pounds per ampere per year but can be useful in some applications because it generates less gas at the anode surface than the other materials. Where a backfill can be used around the impressed current anodes, carbonaceous materials (coal coke, calcined petroleum coke, crushed man-made graphite, or natural graphite flakes) can extend anode life even further. Much of the anode current is carried to the backfill through direct contact. Actual material consumption, then, tends to be concentrated in the outer layers of the carbonaceous backfill where the discharge to surrounding earth occurs. I. I. (Coated Pipeline Source of Direct Current Power Such as: A-C to D-C Rectifiers Engine -Generators Thermul-Electric Gencrators Solar -Powered Generators Wind -Powered Generators .Fuel Cells
Materials Circles Represent FIGURE 6 Basic Impressed Current Cathodic Protection System. --`,,,,`-`-`,,`,,`,`,,`--Ground Bed Anodes. VII. DATA REQUIREMENTS PRIOR TO DESIGNING CATHODIC PROTECTION SYSTEMS Before designing a cathodic protection system, the corrosion engineer will need the following information: 1) Data on the pipe itself in the pipeline section to be protected. This would include length, diameter, wall thickness, resistivity or metal analysis, and type of joint (if other than welding). 2) Data on the pipeline protective coating. Includes type, thickness, application specifications and conditions, and (particularly) the effective in-place coating resistance after backfill stabilization. 3) Data on weight coating for applications where used over a protective coating. Type and thickness of the weight coating should be known as well as the nature of metal reinforcement in the weight coating and how it is installed. 4) Expected pipeline operating life. 5) If the pipeline is already equipped with electrical test stations for evaluating cathodic protection and, if so, details on the number, type and location of all existing test stations. 6) Details of cased crossing installations: size of casing, whether or not casing is coated and (if so) with what material, how casing is insulated from carrier pipe, how casing ends are sealed, and details of vent pipe or pipes (if any). 7) Information on all other pipelines which cross or I. Current Eorth From Ground Bed to Pipeline Ground Connection (or "Ground Bed'') Throuqh Which Current is forced
Various Designs and Possi &le. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 369
SSPC CHAPTER*Lb=Z 73 m 8b27740 0003837 038 m are closely parallel to the pipeline section to be protected. Data needed includes exact location, ownership, bare or coated, whether or not cathodically protected, and availability of test points. 8) Current required for cathodic protection. This may be estimated using data from items 1 and 2, but is preferably determined using field current requirement tests. 9) Availability of commercial electric power for impressed current cathodic protection installations. 10) Evaluation of suitability of other impressed current power sources if commercial power is not available. 11) General data on soil resistivity distribution along the pipeline section -high, low and average figures. 12) Data on stray current activity. Can natural telluric currents of serious magnitude be expected or are there man-made sources of stray current (d-c transit systems, d-c mining operations, d-c welding operations, cathodic protection installations on adjacent systems, or other such sources) that must be compensated for in the overall cathodic protection system design? Specific data is needed on the magnitude and time duration (where cyclic effects exist) of the stray current interference. 13) Decision on type of system to be used -galvanic anode or impressed current cathodic protection. 14) Detailed soil resistivity data at locations selected for installation of cathodic protection facilities. 15) Pipeline route features which may affect the construction of a cathodic protection system -difficult terrain, weather problems, access restricted by land owners, possible crop damage, etc. VIII. FACTORS INVOLVED IN THE DESIGN OF CATHODIC PROTECTION SYSTEMS This section reviews design considerations for the two general types of cathodic protection system. It is not intended, however, to be a guide to detailed design procedures. Those wishing to pursue the matter further are referred to more detailed texts in the Reference section of this chapter. A. DESIGNS USING GALVANIC ANODES The following affect the design of a galvanic anode system expected to develop a predetermined protective current output to a buried structure.
1. Driving Voltage As has been discussed earlier in Section F, galvanic anodes generate their own electrical voltage through battery action when electrically connected to a cathodic metal in a pipe or other structure. These voltages are quite low. The driving voltage between, for example, a structure at a protected potential of -0.90 volt to coppercopper sulphate electrode and the usual galvanic anode materials would be approximately: 0.15 volt for aluminum (in a sea water environment) 0.20 volt for zinc 0.65 to 0.90 volt for magnesium (depending on alloy) These voltages will be higher or lower with changes in the protective potential obtained on the structure at the anode installation site. Knowledge about the driving voltage of a given anode material and about the amount of current required for protecting a structure, will determine requirements for the electrical circuit resistance needed for the proper amount of current flow. 2. Soil Resistivity The resistance to earth of a galvanic anode is proportional to the electrical resistivity of the surrounding earth or water. If the resistivity is very high, the anode resistance will likewise be high. With a fixed low driving voltage as discussed above, the current output may be too low to be of practical value unless unusually long anode life is desired or only a limited amount of pipe is to be protected. These considerations illustrate why detailed knowledge of the resistivity at a proposed galvanic anode installation is essential if it is being designed to produce a specific value of current output under design conditions. 3. Life Galvanic anode life is proportional to the amount of anode material available at a given current output. When the designer has established the desired installation life (say 15 years) at a specific protective current output, he can calculate the amount of anode material needed to attain that life. To do this, he needs to know (1) the theoretical maximum ampere hour content per pound of the specific anode material to be used, (2) the anode efficiency which determines the ampere hours per pound available for useful output (some anode material is used up in selfcorrosion; there is a wide variation in efficiency depending on material used and design conditions), and (3) the point at which replacement will be necessary, such as when 85% of the anode material has been used up. 4. Circuit Resistance
The principal elements of the circuit resistance are (1) the effective resistance to earth of the coated pipe or structure at the point where the galvanic anode installation is to be made, (2) the resistance of wires interconnecting the galvanic anodes used and connecting the anode instailation to the pipe or structure, and (3) the resistance to earth of the galvanic anodes themselves. Of Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 370
SSPC CHAPTER*Lb=2 93 8627940 00038L8 T74 these, item (1)is not controllable but can be determined by electrical measurements in the field. Items (2) and (3) are controllable and subject to design. Knowing the soil resistivity at the galvanic anode site and the physical dimensions of the anodes being used, the resistance to earth of various numbers of anodes connected in parallel can be determined using design curves or procedures set forth in other source material. The designer can select the appropriate number and size of anodes to create the desired circuit. There are definite limits to the amount of current that can be obtained from a galvanic anode location. If, for example, the resistance to earth of a coated pipe or structure was found to be 5 ohms at a given installation site, the maximum current which could be obtained using galvanic anodes (assuming a driving potential of 0.9 volt) would be less than 180 milliamps no matter how low the soil resistivity or how many anodes are used. It is quite probable, however, that this much current would not be needed to gain an adequate level of protect ion. 5. Anode Shape A long, slender anode permits a lower resistance to earth in a given environment resistivity than does a short thick anode shape. This fact can be used to advantage when designing anode installations for placement in high soil resistivity locations. 6. Stray Current Effects Stray current effects (see Section J) on a pipe or structure must be evaluated to determine if pipeto-earth potentials vary so much (as a result of the stray current effects) that adequate protective potentials cannot be maintained using galvanic anodes. This is normally done with recording instruments which permit a permanent record of all variations occurring during the observation period. 7. Meteorological Data The effect of weather can be significant. For example, if galvanic anodes are installed in soils subject to extreme dryness during parts of the year, the circuit resistance will go up as the soil dries, and anode current output may drop below the minimum necessary to maintain cathodic protection on the pipe or other structure. Or another example: if anodes are installed in an area where the earth surrounding the anodes will freeze during the winter season, the high resistivity of the frozen earth can likewise cause anode current
output to drop to ineffective levels. 8. Hot Spot Protection Galvanic anodes are widely used for protecting small actively corroding areas, particularly on pipelines. Such areas often require only small amounts of cathodic protection current. These requirements are met easily and economically with galvanic anodes. 8.DESIGNS USING IMPRESSED CURRENT The following paragraphs describe some of the fac tors that must be considered when designing an impressed current cathodic protection installation, 1. Current Required for Protection Determining the amount of current needed for cathodic protection at a given location will help the corrosion engineer choose either an impressed current installation or a galvanic anode installation. Unless considerations such as stray current effects dictate otherwise, galvanic anode installations tend to be the most economical for small current requirements up to an ampere or two for anode installations in soil. This should be taken as a generalization only and final decisions made only after a complete consideration of all factors. 2. Commercial Power Availability Information must be obtained on the location of commercial low voltage power lines in the areas where impressed current cathodic protection installations are contemplated. The easy availability of commercial power permits use of the reliable a-c to d-c rectifier as the source of cathodic protection current. 3. Alternate Current Sources If commercial power is not available, consideration has to be given to the relative practicality and cost of alternate current sources such as enginealternator-rectifier units, direct thermal-electric generators, fuel cells, solar-electric units, and wind-powered generators. 4. Current Source Rating One of the significant advantages of impressed current systems is the freedom to select (particularly when using rectifiers as the current source) a very wide range of direct current and voltage output capacity. This makes it possible to accommodate large or small installations as well as low resistivity or high resistivity ground bed installation sites. The design consideration is to select a current source with an output rating consistent with the requirements of the specific in-
stallation site -and normally including some reserve capacity for possible future increased cathodic protection requirements. The amount of reserve capacity to allow is a matter of engineering judgment based on knowledge of the system to be protected. In general, however, the percentage allowance on a newly coated and buried pipeline or other metallic structure would be Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 371
SSPC CHAPTER*Lb.Z 93 8b279LiO 0003819 900 substantially greater than on an older longstabilized system. 5. Soil Resistivity Having detailed data on soil resistivity makes it possible to design a ground bed with the proper resistance. When considered with the remainder of the circuit resistance external to the current source, the ground bed resistance should form a reasonable match with the rating of the impressed current source to be used. 6. Power Requirement Where a-c to d-c rectifiers fed by commercial power lines are used, the power requirement is not necessarily a controlling factor. For the larger installations, however, it becomes increasingly important to use rectifiers with the highest practicable efficiency can reduce power costs. This may involve using three-phase rectifiers rather than single-phase units, preparing the overall design so that the rectifier used will be operating at the peak of its efficiency curve, and using filters in the rectifier output circuit. On the other hand, small rectifier installations may not require enough a-c power to come up to the minimum monthly bill at certain locaon a volve --`,,,,`-`-`,,`,,`,`,,`--tions. In this event, highly efficient equipment will not reduce costs. Where commercial power lines are not available to supply rectifiers, the selection of an alternate current source can be affected by the amount of output power required. For the larger power needs, engine-alternator-rectifier units may be the best choice, while the use of thermal, solar and wind generators or fuel cells will usually be restricted to smaller direct current output requirements. The actual selection should be based study of economics, maintenance needs, reliability, and other factors. 7. Maintenance Maintenance requirements for impressed current systems can be costly. Impressed current installations must be inspected at prescribed maximum intervals on federally regulated pipelines. Does this create a physical hardship at some locations? How about the operating reliability of the direct current power source selected; is it apt to require frequent visits by a repair team or to inexpensive component replacement? Depending on the specific application, such questions may have a direct bearing on the type of im-
pressed current selected or may result in the use of a galvanic anode system that can be more expensive to install but more economical over the life of the installation. 8. Life The desired life of an impressed current installation will be a prime factor considered when designing the ground bed to be used with the impressed current system. More anode and backfill materials are usually needed for the longer-lived installations. 9. Stray Current Variations caused by stray current in pipe- or structure-to-earth potentials may result in the loss of full cathodic protection from an impressed current system. Where higher variations are involved, creating problems, automatic potential-controlled or automatic constant-current rectifiers may be used. These are more expensive than the conventional, manually controlled units but have much greater compensating capabilities. In more severe instances of stray current effect, specific stray current compensating measures (such as reverse current switches in drainage bonds, for example) may be needed in addition to the cathodic protection system. 1o. Variable Circuit Resistance If it is known that an impressed current source will be forcing current into a variable circuit resistance caused by variations in weather, automatic potential-controlled or constantcurrent rectifiers may be considered as a means of maintaining a reasonably constant level of cathodic protection on protected structures. IX. CONSTRUCTION PRACTICES FOR CATHODIC PROTECTION SYSTEMS Assuming that a cathodic protection installation has been properly designed for a given environment, practices followed during construction of the system can have a considerable effect on its long-term performance. A. IMPRESSED CURRENT SYSTEMS Probably the most susceptible to damage and the most difficult to repair is the underground (or underwater) ground bed assembly connected to the positive terminal of an impressed current source. Being positive to earth, current will discharge through any imperfection in cable insulation or in field-installed insulation on cable splices. This will cause corrosion and failure of the cable system. Good construction practice calls for great care in handling all ground bed system cable (anode leads and header cable) to avoid damage to the cable insulation. One hundred percent inspection is essential to locate and repair in-
sulating, inspecting, and repairing (if necessary) field splices between anode leads and the header cable or in the header cable itself. necessary) field splices between anode leads and the header cable or in the header cable itself. When installing separate anodes and carbonaceous backfill, particularly in vertical holes, care must be taken to compact the backfill around the anode to entirely fill the space between the anode and the sides of the hole. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 372
SSPC CHAPTER*Lb-2 93 W 8627940 0003820 622 W Likewise, where packaged anodes are used (anode and carbonaceous backfill prepacked in a sheet steel canister), care must be taken to entirely fill the space between canister and sides of the hole with compacted backfill earth. Voids can cause an increase in anode-to-earth resistance and thereby reduce anode life. Another area of concern is the connection between a steel pipeline, or other structure, and the copper cable returning current to the impressed current power source. The connection is a copper-steel dissimilar metal corrosion cell that can result in corrosion of the steel if not properly waterproofed and insulated. An inadequate waterproofing job under a layer of tape or coating material may permit water to reach the copper-steel junction (activating the corrosion cell) while the overlying insulating tape or coating will act as an electrical shield preventing cathodic protection current from reaching the corroding steel. The impressed current power sources must be installed in accord with good construction practices for electrical equipment. Any applicable codes must be observed. The equipment must be installed so that it will be accessible for maintenance and periodic tests. The installation should be planned to protect it from natural hazards such as high water, for example, which could put the installation out of commisison. B. GALVANIC ANODE SYSTEMS For most installations in earth, galvanic anodes are obtained in packaged form so that the anode and its special chemical backfill material can be installed as a single unit. When installing such anodes in augered holes, particularly, it is important that they be so backfilled that no voids are left around or under the anode package. If voids exist (and after the anode package container deteriorates), the chemical backfill can fall away from the anode and cause an increase in anode resistance, drop of anode output current, and loss of anode operating efficienCY. As was the case with impressed current systems, the connection between a steel structure and the copper wire from a galvanic anode (or group of anodes) needs to be carefully waterproofed and insulated. This is to eliminate problems with a steel-copper dissimilar metal corrosion cell at the structure surface. X. STRAY CURRENTS The term stray current is an all-inclusive expression used to cover a variety of situations that result in the presence of direct current flowing in the earth. Where, such current is free to enter an underground steel structure (particularly pipelines), follow it for a distance, and then discharge to earth in order to continue its journey, corrosion can occur at the point of current discharge. In severe cases, the corrosion rate can be catastrophic.
Knowledge of any stray current conditions affecting a pipeline or other steel structure is essential for the designer of a cathodic protection system, especially because the effects of stray current can be worse than the normal corrosion caused by contact with the environment. Where stray current exists, additional cathodic protection or special and sometimes rather sophisticated countermeasures may be needed. If stray currents exist and are not properly taken into account, they can at least partially nullify the beneficial effects of a cathodic protection system designed to protect a steel pipeline or other structure against the corrosive effect of the environment. A. STEADY-STATE MAN-MADE STRAY CURRENT The most prevalent sources of this type of stray current are cathodic protection systems on structures other than the one which the corrosion engineer is trying to protect. This can be a particular problem, for example, on pipelines in areas where they are closely paralleled by other systems or where cathodic protection impressed current power sources on lines of other ownership ( foreign lines) are close to the pipeline at points of crossing. The problem (normally termed interference ) is usually confined to relatively small areas which are fixed as to location and can be readily identified by field test. B. CONTINUOUSLY VARIABLE MAN-MADE STRAY CURRENT Current sources contributing to this stray current category include direct-current-powered electric railway systems (surface and subsurface), mining operations using d-c power, electric welding facilities, etc. A corrosion engineer can usually identify this type of stray current by taking recordings of any stray current effect on his steel structure. Typically, there will be continuous (and often extreme) variations in the recorded effect over a 24-hour period or more. Where the source is man-made, however, there will normally be a pattern characterized (if the source is an electric railway) by more intense stray current activity during hours of peak railway usage. If the source is industrially-oriented (such as mining or welding operations), the thing to look for on the recording is a reduction in the stray current activity at work shift changes or periods of no work. Man-made stray current of this type, can cause major corrosion problems if not kept under close control at all times. C. NON-MAN-MADE STRAY CURRENTS The earth s magnetic field is subject to variation from effects such as sunspot activity. As the intensity of the magnetic field increases and decreases, direct current, in effect, is generated. When such current, often referred to as telluric current , gets onto underground pipelines, it can create corrosion problems.
The effects of telluric current on underground pipelines are typically without any consistent pattern. The Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 373
SSPC CHAPTERxLb-2 93 8627740 0003821 569 areas of current pick-up and discharge from a pipeline tend to change continually. The direction of current flow also reverses its direction. Except in unusual situations, the effective amount of current flow seldom renders normal cathodic protection systems ineffective. Unusual situations, however, can occur; and this possibility needs to be evaluated when planning cathodic protection systems on major structures. During periods of magnetic storms, variations in pipeline protective potentials can make it difficult to properly evaluate the level of cathodic protection on pipelines. Short-term magnetic forecasts (1to 3 days in advance) can be obtained by contacting the Space Environment Service Center (SESC) duty forecaster by telephone at (303) 499-1000, Ext. 3171, (Boulder, Colorado) from 7 a.m. to 12 p.m. MST seven days a week. Additionally, after-the-fact indices of magnetic activity (based on data at Fredericksburg, Virginia) are published in the National Association of Corrosion Engineers (NACE) publication, Materials Performance. D.CORRECTIVE MEASURES Steady-state, man-made stray current can normally be handled by (1)placing cable bonds between the structures involved so that the stray current will harmlessly discharge through the metallic path rather than discharge to earth with resulting corrosion, by (2) installing galvanic anodes at established points of discharge, or by (3) coating bare pipe (or upgrading the coating on older poorly coated pipe) to reduce the amount of interference current interchange to the point that normal cathodic protection will handle it. If, however, there are situations where one operator s pipeline passes close to an impressed current cathodic protection ground bed on another operator s system, the interfering stray current may be of such magnitude that none of the corrective measures cited above can be applied economically. Adequate correction may then require deactivating or moving the installation causing the stray current. Where interference stray current conditions exist between adjacent structures (primarily pipelines), they are best solved by cooperative tests made by corrosion engineering representatives of the two operators so that mutually acceptable corrective procedures can be worked out. In the underground pipelining industry, there is a network of electrolysis committees which are industry-
sponsored groups of people dealing with corrosion that help to recognize and solve problems of stray current interference in their designated area. A list of electrolysis committees currently active can be obtained by writing to NACE, P.O. Box 21830, Houston, Texas 77218. In areas where continuously variable, man-made stray current is a problem, developing corrective measures can be difficult and involved. Where intense and damaging current discharge exists, sophisticated field tests are required to locate points of maximum current discharge and to determine the source of the stray current where it is not obvious. The basic corrective measure is to install, where possible, a heavy copper drainage cable to the d-c power supply causing the problem. Where there are periods of time when current flow is such a bond reverses (with resulting increased corrosion of the structure being protected) automatic equipment or devices are necessary to block the reverse current flow. In instances where drainage cables to the d-c source are impracticable, use of rectifierpowered, current drainage installations may be utilized with automatic potential-controlled or automatic constantcurrent rectifiers to maintain the structure at a reasonably constant level of protective potential as the stray current effect varies. In still other instances, it may be possible to cooperatively arrange for bonds to structures or pipelines of other ownership which pass more closely to the power source and are bonded thereto. Stray currents of magnetic origin (telluric currents) are normally not considered to be serious enough to warrant special action if the affected pipeline or other structure has an adequate cathodic protection system. But in some instances telluric current can discharge in a limited area for enough of the time and to such a degree that it can be a matter of serious concern. When this is the case, forced drainage installation (using automatic rectifier
equipment) can be used to remove the current during periods of telluric current activity. XI. PIPELINE SYSTEMS IN PERMAFROST Increasing activity in arctic environments warrants comments specific to cathodic protection for pipelines and other steel structures located in these environments. Small steel structures, other than pipelines, that are completely buried in permafrost (permanently frozen earth), and are themselves below freezing temperature, will normally have such a low rate of corrosion that cathodic protection may not be required. If, however, such structures are partly in permafrost and partly in thawed earth (permanently or seasonally), that part in thawed earth will be subject to corrosion and may require cathodic protection to supplement protective coatings. The pipeline industry has to deal with two distinct conditions in an arctic environment. These consist of cold and hot lines. Cold lines (such as pipes carrying gas chilled to below the freezing point) will be solidly frozen into permafrost. Hot lines (such as pipes transporting hot crude oil) develop zones of thawed earth surrounding the pipe. The corrosion problems on cold lines in permafrost can be expected at non-frozen inclusions in the permafrost. Non-frozen inclusions can exist under deeper rivers or lakes, can be a result of geothermal heat from below the permafrost, or can be interspersed between islands of permafrost on the southern edges of arctic permafrost areas. At any rate, the non-frozen inclusions tend to be anodic to the pipe that is solidly frozen in. Where the inclusions are small, the effect is that of small-anode-largecathode that can be expected to result in rapid corrosion Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 374 ~-~
SSPC CHAPTERULb-2 93 Ab27940 0003822 4T5 in the small anodic areas, Warm pipelines, on the other hand, have a corrosion control problem throughout their buried length. The severity of the problem will be a function of the corrosivity of the thawed earth mass surrounding the pipe. The elevated temperature, which may be well in excess of 100°F (38°C) also increases the severity of the problem. Cold pipelines may be protected by a combination of coatings and cathodic protection. Current requirements are very low for coated pipe solidly frozen into the permafrost. The necessary current can be forced into the earth from remote ground beds installed in the permafrost. At any non-frozen inclusions, however, the current requirements for protection may be so high that it is difficult or impractical to force enough current to flow through the high resistivity permafrost to these locations from remote cathodic protection installations. In these instances, galvanic anode material may be used. Additionally, if telluric currents are present (and they tend to be a problem on arctic lines), current may tend to discharge to earth at the relatively low pipeline-to-earth resistance at non-frozen inclusions; with galvanic anodes at each non-frozen inclusion, the brunt of the corrosive effect of the discharging current will be borne by the anodes. Warm pipelines in permafrost are also protected with a combination of coatings and cathodic protection. The cathodic protection application, however, is quite different
from that used on cold pipelines. With a continuous warm thaw bulb along the entire buried length, current needed for cathodic protection may be higher per unit area than comparably sized ambient temperature lines (with similar quality coating) in the temperate zones. It may be a problem getting sufficient current to flow from remote cathodic protection installations through the high resistance permafrost to the pipeline and attain uniform protection along the line. An approach that has worked well consists of installing continuous strip zinc anodes along the entire length of buried line as illustrated by Fig. 8. This same type of protection can be utilized through non-frozen inclusions on cold pipeline in permafrost. Zinc is used because of its optimum anode potential and high operating efficiency, both of which are favorable to the longest practicable life. Bare strip zinc anode material has been used where it can be placed in the pipe trench bottom (during construction) so that it will have the least subsequent oxygen availability. The continuous strip anode protection system results in uniform protective potentials along the pipeline. Additionally, it serves to accommodate the major part of
telluric stray current discharge wherever it tends to occur along the line. XII. OPERATION AND MAINTENANCE OF CATHODIC PROTECTION SYSTEMS The major cause of problems with cathodic protection systems is failure to exercise suitable practices of operation and maintenance. Because it can t be heard, seen, felt or smelled once it is installed, a cathodic protection system is often forgotten. But, as with any electrodynamic system, a cathodic protection installation has to be operated and maintained effectively if it is to provide corrosion control. A. GALVANIC ANODE SYSTEMS Operating practices for cathodic protection installations using galvanic anodes should include, as a minimum, the following: 1. Annual measurement of structure-to-reference electrode potentials to determine whether or not full cathodic protection is being maintained. 2. Annual measurement of galvanic anode current output to permit an annually updated forecast of anode life. If the potential measurements of item 1 indicate loss of protection, the reason for such loss should be ascertained promptly. Typical reasons could be: 1. Contacts with other structures resulting in overloading the cathodic protection system. These could be failure of insulating devices or inadvertent electrical bypassing or could be direct underground metallic contact between the protected structure and foreign structures. 2. Breakage of underground wiring connecting the galvanic anodes to the protected structure as a result of construction activity or other reasons. 3. Increase in current requirements for full protection of the protected structure as a result of coating damage on the structure from construction activity, gradual and normal deterioration of the coating with time, additions to the structure itself resulting in an increased total surface area to be protected, increases in stray current activity, and other similar reasons. Depletion of galvanic anode material (end of their useful life). Good maintenance practice calls for prompt correction of deficiencies found as a result of annual inspections. Prompt action is necessary since corrosion is a function of time. If loss of protection is allowed to exist for long periods, unnecessary corrosion failure may be experienced. This means that the full advantage of the initial expenditure for the cathodic protection system is not being realized. B. IMPRESSED CURRENT SYSTEMS
Operating practices for impressed current cathodic protection installations should include, as a minimum, the following: 1. Scheduled inspections of the d-c power source at nominal intervals of two months or less. Includes verifying that the installation is operating properly, logging operating data, and determining if there has been a change from past inspections Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 375
SSPC CHAPTER*Lb*2 93 8627740 0003823 331 which could indicate possible problems with level of protection. 2. Annual measurement of structure-to-reference electrode potentials to determine protection level. 3. Inspection at nominal monthly intervals where impressed current equipment is used for stray current control of a critical nature. If the potential measurements of item 2 reveal that full protection has been lost, the reason(s) for such loss should be determined at once. Typical reasons include the following: 1. Contacts with other structures as listed under galvanic anodes. 2. Breakage of underground wiring (at test points, crossbonds, etc.) as a result of construction activity or other reasons. Underground wiring associated with impressed current ground beds is subject to corrosion damage as described in Section t. Such damage, when it results in cable failure prior to the end of ground bed life, will normally be apparent from data logged during periodic power source inspections. 3. Increase in current requirements as discussed under galvanic anodes. The --`,,,,`-`-`,,`,,`,`,,`--4. Reduction in current output of the impressed current power source. This can be either problems in the power source itself or increased ground bed resistance as the ground bed anodes approach the end of their design life (apart from ground bed cable breaks which are repairable). principles of good maintenance practice as described for galvanic anode installations apply to impressed current installations as well. ACKNOWLEDGEMENT The author and editors gratefully acknowledge the active participation of the following in the review process for this chapter: Vic Chaker, John F. Fitzgerald, E.G. Haney, L. Liszczynsky, Bill Mitchell, David C. Pearce, R.N. Sloan, L.P. Sudrabin, Bill Wallace, E.N. Steinmann. BIOGRAPHY A portrait and biographical sketch of A.W. Peabody appears following the chapter entitled Coating of Pipelines and Other Underground Structures . REFERENCES 1. NACE Standard RP-01-69 (latest revision), Recommended Practice -Control of External Corrosion on Underground or Submerged Metallic Piping Systems National Association of
Corrosion Engineers, P.O. Box 218340, Houston, Texas 77218. 2. A.W. Peabody, Control of Pipeline Corrosion, National Association of Corrosion Engineers, Publication No. 5101 1. 3.Designing Impressed Current Cathodic Protection Systems with Durco Anodes. The Duriron Company, Inc., P.O. Box 8820, Dayton, OH 45401-8820. 4. J.E. Wright, Practical Corrosion Control Methods for Gas Utility Piping, National Association of Corrosion Engineers, Publication No. 51012. 5. A.W. Peabody, Corrosion Aspects of Arctic Pipelines, Materials Protection, May, 1979, pp. 27-32. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 376
CHAPTER 17 PAINTING OF INDUSTRIAL PLANTS by William F. Chandler The subject Painting Industrial Plants can be mind boggling. Take the number of substrates, add the multiplicity of operating exposures, stir in the problem of choosing among the various available types of protective coatings -and the complexity is clear. But engineering sense can be made out of this complex subject. The following series of chapters illustrates how the level of efficiency can be raised in the choice and use of protective coatings on steel in typical plants in industries such as waste treatment, coke, petroleum, chemicals, paper, food and power. I. A CALL FOR EXCELLENCE Business managers are finding it ever more difficult to sustain adequate net profits. Likewise, deciding to commit funds for new production capacity is an ever more speculative undertaking. What is the relationship between these problems and painting steel in industrial plants? Exactly this: there is no room for excuses or half-way measures. Only by combined professional efforts, strong specifications, carefully chosen coatings systems, precise surface preparation and application, rigid inspection and good communications can managements contain year-toyear painting costs. II. PLANNING THE COATINGS PROGRAM Management can win the cost control battle by properly planning and administering coating programs for new construction and maintenance. The ultimate goal is that maintenance will include removing surface dirt and adding an occasional touch-up and single finish coat to maintain film thickness and appearance. In addition to setting up details of surface and exposure identification, types of coatings, specifications, costs, and records, a properly planned program establishes minimum standards for surface preparation, application, film thickness and appearance for each type of surface and coating system. It requires all estimators, applicators, supervisors, and inspectors to meet minimum standards. A. CHOICE OF MATERIALS The objective in choosing materials is simply to find for each type of substrate and exposure the paint coatings system that is most efficient in terms of dollars per square foot per year. While the objective is simple, accomplishing the objective is difficult. Coating material costs rarely run
above 20% and usually average only 10-15O/0 of the total coatings job cost. Yet, after all the money is spent for engineering, specifying, surface preparation, application, inspection and clean-up, it is the integrity of a few mils of the protective coating that determines the service life of the structure. Choice of the proper coating for each major surface and exposure is critical to efficiency. It follows that coating materials cannot be chosen on a per gallon or a mil foot per gallon cost basis. Only by developing the applied cost for desired mil thickness and factoring in service life expectancy can a sound judgment be made. There are three ways to choose materials. 1. Going it alone Some large, sophisticated, multi-plant, industrial companies have the inclination and facilities to plan the coatings program completely and run evaluations of available coatings within their own organization. 2. Reliance on an independent consultant Some companies retain a competent, independent consultant and rely on the consultant to supplement its own coatings program or to develop the entire program, including choice of materials. 3. Reliance on coatings supplier@). Other users find it practical to rely more and more on their coatings supplier(s) in choosing painting systems. Leading coatings manufacturers often carry on active research for development of better materials and protective coatings systems. B. CHOICE OF COATINGS SUPPLIERS Choice of coatings suppliers is of prime importance and should be made only after careful search on the basis of reputation for quality, service, and integrity; demonstrated technical proficiency; and capability, availability, and desire to assist management and its specifying engineers. Assistance is required in detailing specifications; interpreting specifications to bidding fabricators, contractors, or in-house crews; training inspectors and cooperating at fabricating shops and jobsites in pre-job conferences and in setting up standards. When management does a good job in choosing its coating supplier(s), it relies on the supplier(s) in an onstaff, on-call relationship to assist in selecting materials Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 377
and solving problems. Often, the client on a new construction project instructs his design engineer to work with a preselected coating material supplier. Most engineers appreciate that such instruction expedites and smooths out the work. C. GOOD SPECIFICATIONS The bid package for contract painting on new construction or maintenance is a vital communications link. Information shall include the following: Clear identification of surfaces to be painted a Access, storage of materials and services available Possible complications with other trades or operating plant conditions Surface preparation clearly referenced to recognized standards Materials -brand name, type, number of coats Maximum and minimum allowable wet and dry film thickness of each coat Required color differential between coats a Application methods and tools Inspection and approval of surface preparation, application and finished appearance -when, by whom, how, and with what tools a Safety Clean up a Communications D. PRE-JOB CONFERENCE Anticipating problems and solving them before they start is good for all concerned. The pre-job conference prevents aggravation and is a sign of good management. It is highly recommended for inclusion in the specification. The project manager or engineer in charge should call a pre-job conference of interested parties including representatives of owner, specifying engineer, general contractor, painting contractor andlor steel fabricator, material supplier and inspector. The purpose of the conference is to establish clear communications, interpret specifications, agree on inspection and arrange for job standards. E. JOB STANDARD In addition to the pre-job conference, the following or a similar statement regarding job standards is excellent insurance against misunderstandings, controversy or requests for extras: before starting any work, the painting contractor, at the direction of the project manager and under supervision of a technical representative of the material supplier, will apply the specified materials on sample test surfaces to establish the minimum acceptable standard of quality for the project.
F. THE BOTTOM LINE It may not always be the best procedure to insist on a coating system known to project lowest costs per square foot per year. Certainly, a project designed for limited life span could properly be specified with a cost saving Coatings system. In nearly all cases, management should insist on the most efficient coatings systems for new construction. The slightly higher initial costs are returned in long-term dividends through reduced maintenance charges and minimal disruption of plant operation. Rarely is there justification for using a system other than the most costeffective for maintenance. ACKNOWLEDGEMENT The author and editors gratefully acknowledge the active participation of the following in the review process for this chapter: T.A. Cross, S. Frye, Dan Gelfer, R. Klepser, Marshall McGee, John Montle, Dan Nemunaitis, William Pearson, Warren Stanford, William Wallace, Tom Wilhelm. BIOGRAPHY The late William F. Chandler was a consultant and former president of Porter Paint Company. Mr Chandler held a B.A. from Washington and Lee University and an L.L.B. from the University of Louisville. He was a charter member of the Kanawha Coatings Society, a National Association of Corrosion Engineers CorporateRepresentative, and a member of its Publications Committee. He also lectured on protectivecoatings for the University of Wisconsin. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 378
SSPC CHAPTER*27-2 93 8b27940 000382b 040 CHAPTER 17.1 WASTE TREATMENT PLANTS by Thomas P. Delany Since the signing of the Clean Waters Act in 1966 and the classification of most of America s waterways according to the type of effluent that can be discharged into them, there has been a tremendous increase in construction of new water pollution control plants and in upgrading and enlarging existing plants. At the same time, the country has been undergoing an environmental and ecological revolution. The community is more aware of treatment plants and has made demands regarding the plants appearance and function. Consequently, water treatment and water pollution control plants have changed rapidly and radically in design. Modern treatment plants can be beautifully designed and efficiently run. Between the influent and effluent channels, extremely complex physical, biological and chemical processes are conducted. They create some of the most severe conditions encountered by any mechanical equipment. Thus, these plants have needs for corrosion protection rarely found in other types of construction. The ever-increasing role of complex chemicals in industry and the regulation of their discharge, together with household detergents and municipal biological wastes, have created new problems for water pollution control plant designers. Coatings that were accepted for many years to protect submerged surfaces in water pollution control plants are outmoded because of increasingly harsh sewage. During these years, coal tar epoxy coatings have come of age because of their high degree of chemical resistance. Recently, because of advantages in function, application and esthetics, the colored high build epoxies have found favor in submerged applications and are replacing coal tar epoxies in many instances. Large, complex treatment plants take from two to four years to build and can treat anywhere from one million to 100 million gallons or more of wastewater per day. The equipment and steel fabrications required can come from dozens of manufacturers and fabricators from various parts of the country. They often sit around at the construction site for months before being used. I. SPECIFICATION Putting together a good protective coating job in large and complex water treatment and water pollution control plants is not easy. It certainly is not a one-man operation. A good protective coating requires teamwork. The
engineer, applicator, coatings manufacturer and inspector must cooperate. Working together, they can produce maximum benefits, long term protection, pleasing appearance 379 and easy maintenance. The corrosion engineer or specification writer carries a great deal of the responsibility. He must prepare specifications that include coating system, number of coats, film thickness, surface preparation, application and inspection procedures. The engineer often relies heavily on the cooperation of coatings suppliers with many years of experience in protective coatings. Whether for new construction or maintenance painting, a good protective coating system begins with a prop erly written, well conceived painting specification. A complete paint specification covers every phase of the project. It helps assure uniform bidding, effective job timing and compatibility of shop- and field-applied coatings. It spells out to fabricators, equipment manufacturers and the painting contractor the surface preparation, number and types of coatings, dry film thickness of systems and application requirements. In determining dry film thickness for a coating system, the corrosion engineers must consider: Service requirements and environmental conditions Type of surface to be coated Type of coating system being used Volume solids content of the coating Number of coats Surface preparation Method of application Economics Physical Limitations II. SELECTION OF THE COATING SYSTEM In selecting the proper coating system for a water pollution control plant, the project engineer has three prime objectives: Long term protection Pleasing appearance Ease of maintenance during operation The type of coating system selected should be dictated by service requirements and environmental conditions of the unit, the substrate to be protected and economics. In this application, economics means longterm economy. The high performance coating systems require sophisticated and expensive surface preparation and are often the most expensive; however, they represent the best value because they withstand severe service requirements, provide long-term protection and create considerably longer repaint cycles.
Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
The best time to prepare and coat submerged service areas is during construction. When taken down for service at a later date, which can be extremely difficult and costly, painting conditions are almost never as favorable as during construction. This is particularly true of interiors of concrete process tanks. Recently, coating specifications have been simplified by greater use of high performance coatings. Engineers are trying to make specifications simple by using as few coating systems and thinners as possible. Fewer product classes simplify inspection and application and minimize compatibility problems. There have even been a few suggestions that an entire facility be coated with high build epoxy on both submerged and non-submerged areas. This might be carrying simplification to extremes and slightly limits good color selection and long-term appearance because of early chalking and loss of gloss of epoxy coatings from sunlight exposure. 111. SUBMERGED EXPOSURE There has been a growing use of colored, high build epoxy coatings on submerged steel and concrete surfaces. They are frequently used in process tanks in place of the coal tar epoxy coatings. The colored high build epoxy coatings offer functional and esthetic advantages. Esthetic advantages are obvious. Coal tar epoxy is a black coating while high build epoxy is available in a range of colors. Light greens and tans are most popular for immersion. It is more pleasing to see a treatment plant with its large screw pumps, grit chambers, clarifiers, aeration tanks, chlorine detention tanks and other large process tanks coated with attractive and durable pastel colors instead of a drab black coating. Courtesy International Paint Company, InCa FIGURE 1 Bio-disc filter. Primed with high-build epoxy, topcoated with tan epoxy gloss finish. Steel surface preparation SSPC-SP 10, Near White Blast. Functionally, high build epoxy coatings offer certain advantages regarding recoat limitations and intercoat adhesion, when compared with coal tar epoxy coatings. Coal tar epoxy coatings, when cured, are very slick and solvent-resistant; consequently, they have intercoat adhesion problems. Most coating manufacturers place a recoat limitation of 24 to 72 hours, depending on the formulation. Top coats of coal tar epoxy applied after that time cannot
be expected to yield optimum intercoat adhesion. Many engineers specify that coal tar epoxy be top coated within 48 hours. If this time is exceeded, all surfaces must be sweepblasted to provide
tooth before top coating.
Because of the complexity and size of today s plants, the recoat limitation presents serious problems. It also eliminates the use of coal tar epoxy as a shop coating and dictates using a catalyzed epoxy inhibitive primer as the shop primer with top coats applied later in the field. More recently, high build, high solids coal tar epoxy coatings have been offered that can build films of 15 to 20 mils dry in a single coat. This one coat high build potential would certainly eliminate the intercoat adhesion and recoat limitations of multi-coat coal tar epoxy systems. High build epoxy coatings, because of their pigmented matte finish, generally do not present the intercoat adhesion problems and time limitations for recoating. They can be used as shop primers or as fully shop-applied systems since they are easily repaired and recoated. Often a thin, two mil dry film thickness coat of high build epoxy is applied in the shop to abrasive blasted steel. The same coating can then be applied as two additional five mil coats at the job site during construction. The time lapse between shop primer and field coats could be several months or even years with no serious intercoat adhesion problem. Another esthetic drawback of coal tar epoxy coatings is that they blush when applied or cured during periods of high humidity or if a condensate forms on the coated steel during curing. This leaves a streaky, mucky brown appearance that is not pleasing to the engineer or client, even though this blushing has no harmful effect on the coating system. Coal tar epoxy coatings lose gloss and can become dull in prolonged sunlight. It is not unusual for coated steel and equipment to be sitting at the job site for many months before being put into service. Many high build epoxy coatings have the necessary approvals for use in potable water and are a major lining system for water storage tanks. This facilitates selection of coatings for a water treatment plant since the coating system can be identical to the wastewater plant. The role of coal tar epoxy, despite its limitations, continues to be very important in waste treatment plants.
These coatings are excellent for applying .. . -to the backfill, below grade surfaces of process tanks and buildings. Coal tar epoxy coatings perform an important service in protecting concrete pipeline and manholes from the OXidation of hydrogen sulfide, which takes place mainly or exclusively above the water line. A two coat, 16 mil dry film Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 380
SSPC CHAPTER*17=1 93 8627940 0003828 913 m Courtesy International Paint Co., Inc. FIGURE 2 Bio-sorption unit. Exterior tank shell coated with three-coat acrylic emulsion s ystem --`,,,,`-`-`,,`,,`,`,,`--in tan finish. Stairs, handrails and bridge over tank coated with light green epoxy system. Interior immersion area painted with two c oats of coal tar epoxy. thickness, coal tar epoxy system should be specified for system in these applica tions offers the water and concrete pipe carrying raw waste to the treatment plant. chemical resistance req uired for the service conditions Polyvinyl chloride sheet linings have also been used exten- and at the same time gives the esthetic benefits of good sively and successfully to protect concrete pipe carrying gloss and color retent ion. raw sewage. The vinyl sheet liner is mechanically built into the pipe when the pipe is constructed. V. SUNLIGHT AND WEATHER EXPOSURE The selection of coatings for outside exposure is IV. NON-SUBMERGED -SEVERE EXPOSURE similar to selection in a normal industrial e nvironment exCatalyzed epoxy enamels are used extensively for cept for sewer gas. This is usu ally an esthetic problem moist atmosphere, non-submerged service conditions on since the sewer gas, hydro gen sulfide, can discolor steel surfaces, machinery and equipment in indoor areas. coatings, particularly those containing lead. Although the Wherever wastewater surfaces are exposed, moisture con- concentration of gas is not sufficient to affect coating indenses on cool steel surfaces and unites with gases to tegrity, lead-free coatin gs should be specified and used in create highly corrosive conditions. These conditions are this service environmen t. Items to be painted under this frequent in wet wells, grit and screen chambers, chemical service condition incl ude exterior plant structures, piping, mixing rooms, pump stations and dry wells. The enamel valves, ramps, doors, sash , handrails, motors, fences and epoxy coatings are used because of the high gloss finish other similar structure s. and broad color selection rather than the high build epoxy. The coatings system generally used for outside exHigh builds can certainly be used in this service area, par- posure is the alkyd . The same vinyl coatings used in nonticularly if a satin sheen appearance is preferred and if submerged severe condi tions could also be used if the insimplification of the specifications by fewer product lines tent is to use as fe w products as possible. But alkyd is desired. Epoxy coatings should not be used in exterior systems usually offer much broader color selection than moist atmosphere, non-submerged, severe service condi- do vinyls and have fewer problems of compatibility with tions because they lose gloss rapidly and chalk early. The shop primers and othe
r coatings. In addition, the alkyd chalking is non-progressive and film integrity is good; the coating offers simpl er application properties to the conproblem is essentially an esthetic one. tractor. Vinyls, because they dry quickl y, cannot generally For this service area, the vinyl coating systems per- be applied by brush or rol ler. form well on exterior applications. In many cases bridges, The newer acrylic emu lsion coatings make an excatwalks, handrails and other steel equipment over cellent choice for this servi ce in place of the alkyd system clarifiers and aeration tanks are painted with a vinyl or over alkyd shopcoats. The acrylic emulsions offer better system in a color that matches the high build epoxy used color and gloss retenti on than the alkyds, although their on the submerged surfaces. The top sides of fixed and initial gloss is not so hi gh as that of the alkyd system. The floating digester covers and floating gas holders can also newer acrylic emulsio n coatings meet all air emission be painted with a colored vinyl coating system. The vinyl regulations and presen t no discoloration problems. These Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 381
SSPC CHAPTER*L7*L 73 86279qO 0003827 85T Courtesy International Paint Co., Inc. FIGURE 3 Auger screw pumps coated with two coats light blue high build epoxy system, i0 mils dry film thickness over SSPC-SP 10 NearWhite Metal Blast. coatings can, however, present weather-related application problems. If applied below 50°F they do not coalesce properly and film integrity is weakened. This can be a serious shortcoming in new construction because painting cannot always be carried out under ideal conditions. VI. INSIDE DRY EXPOSURE This service condition includes laboratories, workshops, pump rooms, blower rooms, control rooms and similar facilities. Items painted include walls, ceilings, concrete floors, doors, frames, sash, control boxes, pumps, motors, handrails, piping, etc. The main reason for painting is generally for appearance and improved housekeeping. Hydrogen sulfide gas should not normally be present, but the possibility exists for minimal amounts that might cause discoloration in some coatings, so lead free coatings should be selected. The alkyd coating systems are generally used on metal surfaces and on piping and equipment to provide color coding. The above-grade walls, which are often concrete block, are filled with a latex block filler and often topcoated with a two coat catalyzed epoxy enamel to simulate an inexpensive tile-like finish. Ceilings are generally painted with two coats of a latex flat white. For sewage plant service, exterior latex coatings are preferred to the interior type because of the lower pigment volume and higher binder content. There is a trend to use many of the emulsion type coatings for inside dry areas, particularly the new acrylic emulsions on walls. The acrylic emulsion coatings are single-package, tough, attractive coatings that become hard and serviceable. Since acrylic emulsions are waterthinned, there are no strong solvent odors to irritate the other trades working near the painting operations. Since they contain no solvent, they present no problems regarding environmental regulations for air emissions. They dry quickly, permitting more than one coat to be applied in a day and minimizing movement of staging and rigging. They are very easy to use for both new construction and maintenance painting. These attractive and convenient semi-gloss and gloss acrylic coatings are replacing chlorinated rubber and epoxy coatings as wall coatings in buildings where surfaces stay dry most of the time and the service condition is
normal industrial exposure. Today s modern waste treatment plants are generally weil ventilated and heated, so there are many more areas where acrylic emulsion coating systems can be used. Below-grade, poured concrete walls and ceilings are usually painted with latex emulsion flats, either vinyl acetate, vinyl acrylic or straight acrylic emulsions. Two coats of the same product are generally sufficient. Concrete floors are another area of concern for painting inside the buildings in a water pollution control plant. They are generally painted for appearance and plant housekeeping, which is complicated by substantial abrasion and abuse in addition to spills of chemicals and water. The catalyzed epoxy enamels perform best because of their toughness, abrasion resistance and resistance to water and chemicals. A three coat system is usually applied with the first coat thinned at least 25% to increase penetration and promote adhesion. A non-skid additive is frequently added to the last coat to minimize slipping, particularly when the floor is wet. Care should be taken to properly prepare the concrete floor either by acid etching or sweepblasting. Some water pollution control plants may have equipment with hot surfaces to be painted while in operation. It is important to know precisely the metal temperature involved. Heat resistant coatings require a good surface preparation, at least an SSPC-SP 6 Commercial Blast and preferably an SSPC-SP 10 Near White Blast for the higher temperatures. There is a great variety of heat resistant coatings available and each manufacturer has his own approach regarding temperature ranges. Instructions should be followed carefully. Generally, a silicone Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 382
SSPC CHAPTER*L7.L 73 8627740 0003830 571 FIGURE 4 In the foreground coated steel shows typical coal tar epoxy blush. Concrete chan nels coated with two coats of coal tar epoxy. Handrails and bridges have epoxy gloss finish. Courtesy: Ervin Industries, Inc. alkyd can be used for temperatures in the range of 300" to a wastewater plant wi ll, in a similar exposure, give good 5OO0F, and straight silicone aluminum should be used in service in a water treat ment plant. The reverse may not the 800" to 1000°F range. Inorganic zincs have been used always be true because ce rtain gases, acid, oils, greases successfully up to 900°F. and soaps are present in the wastewater plant exposure that are not normally found in water treatment plants. SERVICE CONDITION TABLES Following is a comparison of service conditions in water and waste treatment Although water and wastewater plants are alike in coating systems are subjected. Also included in summary many ways, they are quite different in their effect on a fOrm are appropriate co ating systems, coating system. The wastewater plant is generally far thickness, surface Prepara tion and major equipment more difficult to protect with a coating system. Generally tanks to which we mig ht expect to apply speaking, any coating system that will give good service in Coatings. plants to which protective System film or Protective --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 383
SSPC CHAPTER*L7.L 93 D 86279YO 0003831 Y08 TABLE 1:Typical Submerged Senrice Conditions SERVICE CONDITIONS 1. Submerged Exposure Water Plant Wastewater Plant a Water Yes Yes b. Dissolved Oxygen Yes Occasionally (at water level) c. Hydrogen Sulfide present No Small amount in raw sewage d. Carbon Dioxide present Not generally Usually e. Oils, greases & soaps No Yes f. Floating matter No Yes g. Chlorine Yes Yes h. Alum present Yes No STEEL Surface Preparation: Minimum SSPC-SP 10 Near White Blast Coating System & Dry Film Thickness High Build Epoxy (color) 2 coats 10 mils total Coal Tar Epoxy 2 coats 16 mils total High Build Coal Tar Epoxy 1 coat 16 mils total CONCRETE Surface Preparation: Sweepblast preferred, usually only stiff brushed Coating System & Dry Film Thickness High Build Epoxy (color) 2 coats 10 mils total First coat thinned 25% Coal Tar Epoxy 2 coats 14-16 mils total First coat thinned 25% Oils, greases and soaps in wastewater coat the sur- system be applied to a given level above and below the face below the waterline, preventing easy passage of oxy- waterline, usually abo ut two feet, while others coat the engen and acids, and offer some protection toconcrete. Most tire wall and floor su rfaces of concrete process tanks. destruction of concrete and damage to coating systems in Examples of equipment a nd structures most frequentprocess tanks is at the waterline. It is here that the coating ly coated in this service condition are screw pumps; grit system is subject to damaging cyclic effects: hotlcold, chambers; screens; sluic e gates; weirs; baffles; clarifiers; weffdry, freezelthaw and sunlight, in addition to the settling tanks; digesters; underside of digester covers; abrasive effects of floating matter, all of which contribute aeration tanks; chl orine detention tanks; aerating, scrapto the destruction of the concrete and the coating system. ing, and mixing equip ment in process tanks; and trickling Thus, some engineers specify a protective coating fi Iters. TABLE 2 Typical Moist Atmosphere Conditions 2 Moist Atmosphere Exposures Water Plant Wastewater Plant a Moisture and Oxygen present Yes Yes b. Hydrogen Sulfide present No Yes c. Carbon Dioxide present Not Often Yes d. Sulfur Dioxide present Not Often Not Often
e. Carbonic Acid present Not Often Yes f. Sulfur Acids present Not Often Yes g. Cyclic changes (hot to cold, etc.) Yes Yes h. Alum present Yes No STEEL Surface Preparation: SSPC-SP 6 Commercial Blast Coating System & Dry Film Thickness Epoxy Primer & Epoxy Enamel 3 coats 6 mils total Epoxy Primer & High Build Epoxy 2 coats 6 mils total Vinyl Primer & Vinyl Finishes 3 coats 56 mils total Chlorinated Rubber Primer & Chlorinated Rubber Finishes 3 coats 56 mils total For exterior exposures, a vinyl system would be preferred to an epoxy system sin ce epoxies chalk early and lose gloss on sunlight exposure. 384 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*L7-L 93 8627740 0003832 344 TABLE 2: Typical Moist Atmosphere Conditions (continued) This is non-submerged severe exposure and unites with gases to create highly cor rosive conditions. represents the most difficult service conditions for Also included in this servi ce condition is all equipment coatings in a wastewater or water treatment plant. These subject to moisture, ch emicals and condensation, parconditions prevail in wet wells, enclosed grit chambers, ticularly on below-grad e surfaces that are constantly wet. screen chambers, equipment inside buildings, manholes, This also includes ferrou s metals in the vicinity of or adjaexterior of closed steel tanks or wherever wastewater sur- cent to chlorine deli very, storage and evaporation faces are exposed in an enclosed area. Moisture con- facilities. Also included h ere are exterior surfaces such as denses on cool steel surfaces, including pumps, motors, catwalks, bridges, handr ails and equipment over process handrails, etc. as well as masonry surfaces. The moisture tanks and the top side of digester roof covers. TABLE 3 Typical Weather Expures 3. Outside Sunlight 81 Weather Exposure Water Plant Wastewater Plant a Actinic light & radiant heat Yes Yes b. Hydrogen Sulfide present No Yes, sufficient to discolor certain coatings. c. Sulfur Dioxide present Sometimes enough Sometimes enough to discolor to discolor. certain coatings. d. Carbon Dioxide present Small amount Yes e. Salt Air (seacoats) Occasionally Occasionally f. Abrasion from blown sand Yes Yes g. Cyclic physical changes Yes Yes STEEL Surface Preparation: SSPC-SP 6 Commercial Blast, SSPC-SP 3 Power Tool Clea n, SSPC-SP 2 Hand Tool Clean Coating Systems i3 Dry Film Thickness Steel: Alkyds, acrylic emulsions, chlorinated rubber, 5-6 mils, 3 coat systems Polyurethanes for maximum gloss & color retention, 5-6 mils, 3-coat systems Concrete: Vinyls, latex emulsions, chlorinated rubber, 5-6 mils, 3-coat systems This service condition is similar to the normal industrial cient to affect coati ng integrity. environment of the area except for the presence of sewer Areas to be coated in t his service condition are expumps, --`,,,,`-`-`,,`,,`,`,,`--gas. This is usually an esthetic problem since the sewer terior plant structures , piping, valves, motors, gas can discolor some coatings, particularly those con- doors, sash, handrails, ramps and fences. taining lead. The concentration of sewer gas is not suffi-
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A Inside Dry Atmosphere Exposure a Moisture b. Oxygen c. Hydrogen Sulfide present d. Sulfur Dioxide present STEEL CONCRETE FLOORS CONCRETE, MASONRY --`,,,,`-`-`,,`,,`,`,,`--SSPC CHAPTER*L7-L 93 m 8b27940 0003833 280 TABLE 4 Inside Exposures Water Plant Wastewater Plant Very little Very little Yes Yes No Often enough to discolor certain coatings. Very little Very little Surface Preparation: SSPC-SP 6 Commercial Blast; SSPC-SP 3 Power Tool Clean, SSP C-SP 2 Hand Tool Clean, SSPC-SP 1 Solvent Clean. Coating System & Dry Film Thickness Alkyds, acrylic emulsions, dry film thickness 4-5 mils, 3-coat system Surface Preparation: Acid etch with 15-20°/0solution of muriatic acid to produce texture of fine sandpaper or sweep sandblast. Coating System & Dry Film Thickness Epoxy enamels, dry film thickness 5-6 mils, 3-coat system Chlorinated rubber coatings, 5-6 mils, 3-coat system Walls & Ceilings Coating System & Dry Film Thickness Latex emulsions, epoxies, chlorinated rubber, dry film thickness 3-4 mils, 2-coat system Latex block filler added for block or porous surfaces WOOD Oil, alkyds, latex emulsions, two finish coats over wood primer. Included in this service condition are offices, painting here is appearance and plant housekeeping. laboratories, workshops, storerooms, pump rooms, blower Hydrogen sulfide gas sho uld not normally be present here; rooms and control rooms. Surfaces include pumps, however, the possibility does e xist for minimal amounts motors, control boxes, handrails, doors, frames, sash, that might cause discolor ation in some coatings, so care walls, ceilings and concrete floors. The main reason for should be used in selec ting lead-free coatings. VII. SURFACE PREPARATION regarding the degree of surface preparation to be The performance of every paint job is dependent on specified, the engineer or sp ecification writer must con-
the condition of the substrate. When making a decision sider the nature and cond itions of the surface to be coated, the type of coating system that is to be applied, the environment, service conditions, economics, physical limitations and other facts. Some coatings have greater bonding or surface wetting properties than others and are more tolerant of minimal surface cleanliness. The engineer must know the limits of rust, oil and soil that the coating system tolerates. Generally speaking, high performance coatings used in the most severe conditions, submersion or moist atmosphere and chemically corrosive environments, require the most careful and thorough surface preparation. The best surface preparation for steel is removal of all rust, mill scale and surface contaminants. This is most efFIGURE 5 fectively accomplished by abrasive blasting either in the Floating digester roof cover coated with Vinyl System for gloss field or shop wi th centrifugal blast equipment. Abrasive and color retention. Underside coated with two coat, high build blast cleaned su rfaces should be coated the same day as epoxy. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERWLL 93 m 8627740 0003834 117 over the interior submerged surfaces of concrete process tanks with nothing more than a stiff brooming of the concrete surfaces. Concrete floors must be especially well prepared because of the abrasion involved. Sweep abrasive blasting is a good preparation on concrete floors; however, it is often impractical in a treatment plant because the project is fairly well along the way before the floors are painted. The accompanying abrasive grit or sand cannot be tolerated where equipment or instrumentation may be in place. Consequently, the preparation often used for concrete floors is an acid etch. First coats in multi-coat systems applied over concrete, particularly concrete that has not been acid-etched or sweepblasted, should be thinned at least 25% with the appropriate thinner to penetrate and promote adhesion. B. GALVANIZED SURFACES Oil or alkyd coatings applied directly to zinc can allow moisture and oxygen to reach the metal surfaces. Moisture combines with zinc to form normal corrosion products such as zinc oxides and zinc carbonates. These salts can react with oils or fatty acids in the paint binder to form a chemical soap film that destroys the paint bond. Non-oilbearing coatings should be used on galvanized surfaces. Courtesy International Paint Company, Inc. Properly formulated high build epoxie s adhere well as do FIGURE 6 oil-free acrylic latex metal primers. Zinc dust-zinc oxide Two coat, light blue high build epoxy system on steel centerpiece primers serve well under oil or alkyd top coats. The vinyl and submerged steel in clarifier. Two-coat, high build epoxy wash primers also p erform well as a pretreatment on system in same color on sidewalls of concrete tank. Vinyl system applied to bridge and handrails for improved gloss and color galvanized steel to promote adhesion. Galvanized surretention. faces must be free of all oil, dirt, grease and other foreign matter before coating. The painting of galvanized surfaces blasted. Properly cleaned steel provides an excellent is discussed in detail els ewhere in this volume. painting surface and also provides the base for superior, long lasting protection. C. ALUMINUM Abrasive blasting is generally specified according to All surfaces must be free of all oil, dirt, grease the standards established by the Steel Structures Painting and other foreign mat ter. After cleaning, painting may Council and is covered in detail in other sections of this be carried out with t he coating system that is appropriate volume. for the service condition to which the aluminum will be exposed. Vinyl wash primers and acrylic latex metal
A. CONCRETE primers make excellent primers for aluminum surfaces. Concrete should be permitted to age at least 28 days D. WOOD SURFACESunder good conditions prior to applying a coating system. Paintable curing compounds may be used to permit Wood surfaces are not very comm on in water and coating in seven days. To prepare masonry and concrete wastewater treatment plan ts, but they should be for painting, the same caution should be exercised for the thoroughly cleaned an d free of all oil, grease, dirt and complete removal of all surface contaminants. Sweep other foreign matter. All crac ks, nail holes and other surabrasive blasting is the most effective method of surface face defects should be properly filled and sanded to a preparation. There should be no evidence of laitance on smooth finish. All sandi ng dust must be wiped away the concrete surfaces before coating, and all soft or loose- before painting. ly bound surfaces should be cleaned down to a hard Canvas insulation covering sh ould be cleaned free of substrate, preferably by abrasive blasting. dirt, dust and other foreign matter, then primed with two Catalyzed epoxy and coal tar epoxy coatings provide coats of a high solids latex primer-sealer. excellent adhesion to concrete surfaces; vinyl and chlorinated rubber coatings are also used. In construction VIII. APPLICATION of water and wastewater treatment plants, it is not uncom- Coatings must be appl ied in accordance with the mon to apply a high build epoxy or coal tar epoxy system engineer s detailed speci fications and the approved conCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 387
SSPC CHAPTERmL7.L 93 = 8627940 0003835 053 tractor s submittals that become part of the project specifications when accepted by the engineer. In addition, coatings should be applied in strict accordance with the paint manufacturer s recommendations and should be subject to inspection at all times by representatives of the owner, engineer andlor manufacturer. Deviations from specifications or manufacturer s recommendations can be considered and approved or rejected at the pre-job conference among the engineer, general contractor, coating supplier and painting contractor. In the absence of such recommendations, SSPC-PA 1, Shop, Field and Maintenance Painting , may be followed in storage, handling, and application. Careful and proper application is necessary to obtain the specified protection. Protection of the properly prepared surface is dependent upon film thickness; the minimum dry film thickness specified for service areas must be achieved. Films must be of uniform thickness without low spots, pinholes or holidays. Particular attention must be paid to edges and angles to be certain that these vulnerable areas are adequately coated. The contractor s equipment, brushes, rollers, ladders and other equipment must be in good, clean, workable condition. Compressors and spray equipment must be in good condition with proper moisture traps, regulators and gages in place. Spray application is generally preferred and required for the high build coatings to attain high film build properties in the number of coats specified. However, high build epoxy coatings are being successfully applied in heavy films with long nap rollers and in many instances provide adequate protection on the concrete surfaces. To attain the specified film build, without excessive sags, most materials should be applied by the double-pass, crossspray method. The second pass should be at right angles to the first. Excessive atomization can cause a dry spray condition, as can failure to hold the spray gun perpendicular to the surface or holding the spray gun too far from the surface. Films formed with excessive dry spray may be permeable to corrosive agents and provide inadequate protection. A spray technique can be developed at the inception of the coating job by taking wet film readings immediately after application and calculating the resulting dry film thickness from the volume solids of the coating. In this way, the applicator can determine the technique that best produces the wet film required to attain the specified dry film thickness. On ferrous metal surfaces, the dry film thickness can be measured with a magnetic film thickness gage. However, by using the wet to dry technique, the applicator can minimize surprises in the form of low film thickness that would require additional coats. On concrete
surfaces, knowing the wet-to-dry ratio and the maximum spreading rates allows the applicator to control and attain specified film build. Recommendations for drying times must be followed. Some coatings require the application of succeeding coats within a maximum time interval to develop proper intercoat adhesion, for example, the coal tar epoxy discussed earlier. Temperature and humidity limitations must be followed. Many catalyzed coatings do not cure properly below 50°F (10°C) or above 85% relative humidity. Water reducible coatings also have temperature limitations; usually a minimum of 50°F (10°C) is specified. Coatings should not be applied when temperature is below the dew point. With the exception of very fast dry coatings, such as vinyls, coatings should not be applied if a 20 F (11 Co) drop in temperature is anticipated within four to six hours after painting. Painting in confined spaces having inadequate ventilation such as a tank interior or below ground chambers can have an adverse effect on both safety of the workers and film formation and integrity of the coating. Solvent fumes are heavier than air and collect at the bottom of a tank. A solvent vapor layer retards curing of the coating. Solvents trapped in the coating can seriously affect the usefulness of the coating by causing pinholing and blisters which create avenues for water and other corrosives to reach the substrate. Fumes must be removed, either by blowing through bottom openings or exhausting through the top by means of air ducts extending to the bottom. The safety aspect is a most important consideration of the applica tion procedures. Appropriate measures should be taken to prevent the confinement of explosive solvent vapor-air mixtures. Explosion-proof lights and nonsparking tools and equipment should be used to provide added safety. OSHA Material Safety Data Sheets are available from coating suppliers. The information should be kept on file at the job site first aid section or in the paint superintendent s office.6 Tank painting is discussed in greater detail in another chapter of this volume. IX. INSPECTION Inspection is the means by which the corrosion or project engineer reinforces instructions detailed in the specif ¡cations. Thorough and adequate inspection of a treatment plant should be an ongoing process -and the inspector should be representing the design engineer and the owner. The owner or engineer should have a competent inspector on the job. Some engineering firms have their own inspection crews or specialists. The engineer should require the general contractor to arrange a pre-job conference involving the engineer, painting contractor, coating supplier and general contractor. At this meeting, the involved parties can go over the specifications and definitions to make certain everyone
understands what is expected. Inspection is discussed in greater detail in another section of this volume. X. CONCLUSION For the modern treatment plant to be adequately and properly protected and decorated with a protective coating system, provisions must be made for a well written paintCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 388
SSPC CHAPTER*L7-L 93 8627940 O003836 T7T ing specification defining the proper coating system applied expertly over a thoroughly cleaned and prepared surface that receives regular and careful inspection. This requires the cooperative efforts of all parties: owner, engineer, general contractor, coatings supplier and equipment manufacturer. ACKNOWLEDGEMENT The author and editors gratefully acknowledge the active participation of the following in the review process for this chapter: Wally Cathcart, Bill Chandler, S. Frye, Dan Gelfer, Howard Lasser, Marshall McGee, I. Metil, Chuck Munger, J. O Connor, W.S. Rosenthal, Henry Stoner, Bill Wallace, Tom Wilhelm. BIOGRAPHY Thomas Delany retired from the Valspar Corporation in 1993 after twenty years of service, most recently as Industry Manager for both the water and waste industry and the power industry. Mr. Delany had been active in the coatings industry for 46 years in sales, technical service, sales training and sales management. Mr. Delany is a graduate of the Wharton School of the Universitv of Pennsvlvania. He is a m6mber of the Steel Structures Painting Council, the National Association of Corrosion Engineers, American Water Works Association, and the Water Environment Federation. REFERENCES 1. Steel Structures Painting Manual, Volume 2, Systems and Specifications , John D. Keane ed. Steel Structures Painting Council, 4516 Henry Street, Suite 301, Pittsburgh, PA 15213-3728, 1991. 2. Surface Preparation Specifications. Steel Structures Painting Council, 4516 Henry Street, Suite 301, Pittsburgh, PA 15213-3728, 1991. 3. M.A. Vivona, and T.P. Delany, A Simplified Guide for Selecting and Using Protective Coatings in Wastewater Treatment Facilities , Presente% at the New England Water Pollution Control Association Meeting, October 24, 1979 (Portland, ME). 4. M.A. Vivona and T.P. Delany, Selection and Use of Protective Coatings in Water and Wastewater Treatment Facilities, Wafer and Sewage Works, June, 1980. 5. M.A. Vivona and T.P. Delany, The Role of Protective Coatings in Water Treatmbnt Plants and Storage Tanks , Presented at the New York Section of the American Water Works Association Meeting, April 23, 1980 (Binghamton, NY). 6. D.M. Berger, Liquid Applied Linings for Steel Tanks ,
Chemical Engineering, Dec. 22, 1975 and Jan. 19, 1976. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 389
SSPC CHAPTERxL7-2 93 8b27940 0003837 926 m CHAPTER 17.2 PAINTING OF COKE AND STEEL PLANTS bY Arthur R. Thompson and S.C.Frye Protection and preservation of buildings, equipment and machinery is a major responsibility of the steel industry. Maintenance painting includes not only anticorrosion painting of building exteriors, outdoor equipment and machinery, but also interiors, equipment, machinery and, in some cases, even concrete. Proper interior palnting has a beneficial effect on employees. Good housekeeping and better lighting are apparent in a newly painted building interior. With the current emphasis on safety, good housekeeping and improved lighting, improvements like clearly marked passageways, neat parts storage and extensive safety color use have gone a long way toward improving the appearance of steel plants. Maintenance painting has greatly contributed to this aspect of good management. To control costs, it is necessary to use appropriate coating systems applied in accordance with the manufacturer s instructions. Experienced painters, using proper painting and safety equipment, are expected to perform the coating work. Good inspection and adequate records should be maintained. One important cost control measure is to recoat before the old coating must be completely removed and primer replaced as per SSPC-PA Guide 4. This minimizes costs by permitting a single coat of paint to be applied over existing cleaned paint. I. SURFACE PREPARATION For steel subject to severe corrosion where maximum paint life is desired, abrasive blasting, according to SSPCSP 10, Near White Blast Cleaning, is the minimum cleaning required. In mildly corrosive areas, steel surfaces can be prepared according to SSPC-SP 3, Power Tool Cleaning. Better paint system service life results if abrasive blast cleaning to minimum SSPC-SP 6, Commercial Blast Cleaning, is specified. In noncorrosive or dry interior areas, steel surfaces can be prepared in accordance with SSPC-SP 3, PowerTool Cleaning. II. PAINTS and the vehicleare the two main tuents of most paint compositions.
A. PRIMER PAINTS The pigment should be rust inhibitive and can be zincrich, basic lead silico chromate, zinc chromate, iron oxide, zinc dust, borates, phosphides or phosphates or aluminum complexes. Such pigments have a sacrificial, inhibiting or passivating effect on steel surfaces so rusting is retarded. For power-tool-cleaned surfaces, SSPC-SP 3, the paint vehicle should be able to wet the steel surface for maximum penetration. After drying, the vehicle should be relatively impermeable to moisture and compatible with the finish paint. Long oil alkyd, certain vinyl copolymers and certain catalyzed epoxy vehicles provide good results over power-tool-cleaned surfaces. Primers specified in Volume 2, Systems & Specifications of the SSPC Painting Manual, have been used successfully. They are the result of extensive testing; however, many proprietary formulations have also been evaluated and may provide equal or superior performance. Careful choice must be made to select the appropriate primer. SSPC-Paint 11 (zinc chromate primer) has been used for both initial and maintenance priming with good results. Be aware of limitations of the vehicle in the plant surroundings when selecting a primer. Relative resistance of some vehicles is shown in Table 1. Priming galvanized steel can be difficult. One system is to reprime degreased zinc-coated steel with a vinyl butyral wash primer conforming to DOD-P-15328 and then apply an appropriate coating. This eliminates premature peeling and failure of paints on galvanized surfaces. Other systems are described in the section on roofs. In non-acid corrosive areas, where a corrosionresistant topcoat is required, inorganic zinc-rich coatings conforming to SSPC-PS Guide 12.00 are recommended. Abrasive blast cleaning to minimum SSPC-SP 10 is required. B. FINISH PAINTS Finish paints should provide good appearance, impermeability to moisture, primer protection, and recoatabiIity. Federal Specification TT-E-489 and SSPC specifications for alkyd finish paints, including aluminum paint, should be the minimum quality for alkyd, general weathering finish paints. They can be used only in mildly corrosive areas. In severely corrosive areas, epoxy polyamide, epoxy Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 390
SSPC CHAPTER*L7.2 93 8b27940 0003838 862 Table 1 ResistanceTo Environment Vehicle Weathering Salt Water Acid Caustic Solvent Long Oil Alkyd Excellent Fair Good Poor Fair Fair Epoxy Ester Very Good Good Good Fair Fair Good Vinyl Copolymer Very Good Excel lent Very Good Excellent Excel lent Fair Catalyzed Epoxy Excellent (Chalks) Excellent Excellent Very Good Excellent Excel lent Inorganic Silicate Excellent Excellent Very Good Very Good Excellent Excel lent (Use topcoat) inch and heavier films can be built. Coal tar mastics are usually applled at dry film thicknesses of 0.04 inch to 0.1 inch, and usually are not effectlve In heavier films. Heavier coal tar mastics have a tendency to crack or alligator when exposed to direct sunlight. In such cases, the coal tar mastic should be coated with a coal tar emulsion. Blast cleaning should be the method of surface preparation for application of mastics. If blasting is not feasible, another method of surface preparation can be used, but the coating performance may be inferior. It is common to apply primer before application of asphalt mastics. A fast-dry primer can be used if the surface is blasted. The primer should be dry before applying asphalt mastic. Coal tar mastics soften and destroy the bond of conventional primers to the steel surface, so primers are not used under coal tar mastics. There are, however, coal tar primers available if a primer is necessary. 111. EXTERIOR PAINTING In exterior painting, the general aim is to repaint FIGURE 1 Good surface preparation, application and coatings contribute to before the coat ing has completely failed. (See SSPC-PA 4 the appearance and the life of blast furnaces. Guide to Maintenance Repainting .) W ith little primer touch-up and a complete coat of finish paint, costs can be amine, epoxy polyester, vinyl and aliphatic acrylic minimized and the out-of-ser vice time of outside equipurethane coatings over an inorganic zinc-rich primer or ment can be minimal. their generic primer are recommended. Inorganic zinc-rich primers should not be used in an acid exposure without A. BLAST FURNACES topcoati ng. Repainting before the coating fails is difficult for Black, aluminum and iron oxide red finish paints are blast furnaces, since they cannot be painted while in the major exterior colors used in steel plants, but are by no operation. Paintin
g can be done only when the blast furmeans the only ones. Many mills use more stable and nace ls down for relining, w hlch may occur between four colorful pigmented paints on exteriors and interiors. and six years after the pr evious reline (Figure 1).After such C. MASTICS a service period, complete abrasive blast cleaning is usually necessary. The blast furnace stack, top, uptake, stove Bituminous coatings such as coal tar and asphalt bodies, gas mains, skip hoist a nd dust catcher are coated mastics have traditionally proved effective in protecting with two coats of sili cone acrylic. Temperatures of the steel against severe corrosion. Protection is afforded by stove tops and downcom er can exceed 400°F (204°C). thickness and inertness to corrosive attack. Asphalt They should have the surfac es prepared to SSPC-SP 6, mastics are applied at a minimum dry film thickness of 118 Commercial Blast Clean ing , be primed with an inorganic Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 391
SSPC CHAPTER+L7*2 93 W Ab27940 0003839 7T9 vironmental conditions. However, these areas are still aggressively corrosive. Primers, if left exposed, and finish paints used without primer in non-corrosive areas of steel plants will still fail prematurely. The service life of such paints is often measured in months rather than years. While black is the most common color in coke oven plants, there are areas where another color is better. Colors must be chemically resistant and vehicles such as phenolics, chlorinated rubber, urethanes and epoxies both air dry and chemically-cured types -provide good protect ion. Coal tar epoxy is being used on new types of quenching stations because of its moisture resistance. --`,,,,`-`-`,,`,,`,`,,`--FIGURE 3 Precoated corrugated siding shown on a coke battery pre-heat tower. FIGURE 2 Hot stacks require high temperature coatings carefully applied in accordance with the manufacturer s instructions. zinc-rich primer and finished with a heat resistant silicone coating system. Alternatively, after commercial blast cleaning, all high temperature surfaces are coated with silicone-zinc dust primers of an appropriate temperature range. Steel surfaces with operating temperatures between 200°F (93°C) and 450°F (232°C)are finish coated with modified siliconebased coatings. Steel surfaces with operating temperatures above 450°Fare coated with heat resistant, siliconealuminum coatings. B. COKE OVEN PLANTS Problems in maintenance painting of coke oven plant buildings, equipment and machinery have lessened because of the installation of apparatus to improve en392 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*L?.2 93 W 8627740 0003840 410 W C.HOTSTACKS Hot stacks present an interesting painting problem. Stacks can be divided into two classes: those with stack temperatures from 450°F (232°C) to 900°F (482°C) and those with stack temperatures below 450°F (232°C). Temperatures refer to exterior steel surfaces and not to gases inside the stacks (Figure 2). Stacks should be cleaned and painted when out of service. Surface preparation should be abrasive blast cleaning, in accordance with the coating manufacturer s recommendations. Two coats of heat resistant paint are usually applied. One coat can be applied to low temperature stacks, if recommended by the manufacturer. If a top coat is desired with inorganic zinc-rich coatings, it can generally be applied the day following application of the primer. Stacks with temperatures below 450°F (232°C) may be painted with heat resistant oleo-resinous or silicone paints, or with inorganic zinc-rich coatings. Two coats of aluminum-pigmented silicone resin give excellent protection at stack temperatures between 450°F (232 OC) and 900OF (482OC). Premature coating failure of hot stacks should be investigated before repainting. Vibration and stress in stacks are major causes of premature coating failures. Poor surface preparation and failure to follow manufacturer s application directions also cause failures. D. ROOFS Corrugated, galvanized steel sheets are a common type of roofing. Critical areas of the roofing are laps where moisture collects, causing more corrosion than on the rest of the sheet. This problem can be corrected by coating lap areas with zinc dustlzinc oxide (TT-P-641, Type li) paint before joining, by applying a butyl tape at the joint or by applying a fillet bead of sealant meeting Federal Spec TTS-1543. Other procedures for painting roofs are to use proprietary self-priming aluminum-pigmented epoxy mastic coatings or asphalt-base, fibrated roof coatings (non-as bestos). If painting galvanized sheeting the usual primer is zinc dustlzinc oxide or vinyl butyral wash primer. Prepainted sheets now supplant field painting because pre painted sheets are often less costly and provide a higher quality finish paint. Coatings used on pre-painted galvanized sheets include: inorganically pigmented 70% polyvinylidene fluoride; chromate-bearing epoxy prime coat finish-coated with urethane; epoxy primer finishcoated with silicone-polyester; and epoxy primer finishcoated with vinyl plastisol.
On older buildings, built-up roofs with layers of tar paper coated with coal tar are common. After careful examination for blisters, water pockets and paper tears, which must be repaired, the roof can be recoated by spraying or mopping. Use the same coating as the original, since coal tar and asphalt are not compatible. Coal tar FIGURE 4 The attractive appearance of this major mill motor is evidence of the meticulous maintenance that it receives. andlor asphalt-modified polyurethane elastomeric coatings have been used for recoating weathered, built-up roofing. Stainless steel and 12% chromium steel sheets have also been used for roofing and siding on mill buildings. Practically no maintenance Is required, and generally they are not painted if used in mildly corrosive areas. However, if stainless steel sheets are installed in highly corrosive areas, such as those involving hlgh chloride or sulphate concentrations, painting extends service life. E. SIDING Galvanized corrugated steel sheets have long been used as siding. Precoated corrugated galvanized steel coils, protected with high quality coatings, are now being used extensively for siding. F. OUTSIDE EQUIPMENT The coating and surface preparation for painting outside equipment, such as tanks, towers, condensers, coolers, piping, etc., may depend on the time allowed for outside service and the environment. Alkyd resin paints with hand tool cleaning are often used in non-corrosive areas. In corrosive areas, the type of coating systems used in coke oven plants should be specified. IV. INTERIOR PAINTING Appearance is the primary reason for indoor painting, although corrosion protection can be a factor. Colors should be visible and distinguished from each other and the background. Ease of cleaning is a factor in choosing the type of coating. Standard safety colors must be used where applicable. Light colors, such as aluminum, light green, light gray and tan, are widely used in contrast to black, dark brown, and dark gray used in the past. Re-painting should be done before the old finish fails. Surface preparation is recommended by solvent cleaning or a mild detergent wash using a non-Ionic detergent followed by a water rinse. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 393
SSPC CHAPTER*37=2 93 m 8627940 0003893 357 m A. INTERIOR OF BUILDINGS Old mill buildings were usually constructed of brick, masonry or protected metal siding, usually black. When using colors other than black, the siding must be sealed, usually with an aluminum paint such as SSPC-Paint No. 101. Aluminum pigment in a shellac vehicle is also good. An aluminum pigmented paint can be the finish coat or the base for a color coat. Galvanized sheet steel should be primed with zinc dustlzinc oxide or a vinyl butyral primer, prior to applying a color coat. Brick, masonry and block walls are collectors of dirt and dust and should be washed before painting. They can be primed with a sealer and finish-coated; or they can be coated with a high build modified epoxy or an acrylic coating, which allows some vapor transmission. Concrete floors, where being attacked, must be cleaned and neutralized to pH 7-8 and washed before painting. Ifthe attack is chemical, the floor should be leveled or smoothed and painted with a material that withstands the chemical attack and traffic. Wooden buildings are not common in steel plants. However, old mill buildings may have wood roof decking, which may have been painted with standard paints for noncorrosive conditions. There is a problem of fire protection for wood areas. The use of intumescent fire-retardant paints has increased materially because of this problem. B. MACHINERY AND EQUIPMENT Machinery and equipment like rolling mills, motors, machine tools, cranes, crane hooks, etc., are handled like buildlng interiors. Practically all machinery and equipment is primed prior to installation; cleaning and application of a finish paint is all that is needed. Cleaning is usually by wire brushing (SSPC-SP 2) with some spot priming. For re painting, good cleaning by solvent washing or steam cleaning is necessary before applying finish paint. If chemical resistance is needed, reprime with universal primer then apply epoxy or urethane top coats (Figures 4 and 5). Functional painting to distinguish moving parts of the machines must be clearly delineated. Standard safety colors are required. V. TANKS There is a wide variety of tanks in steel plants. Some are in non-corrosive service where contents would not seriously impair the finish coat. The finish can be an alkyd synthetic resin paint, an acrylic latex or many others of the
desired color. Surface preparation requires a light wire brushing, a solvent or water wash. There are tanks and towers in very corrosive service containing acids or other corrosive materials. These tanks are usually lined with highly resistant linings that have a relatively long service life. Prior to lining, white metal blast cleaning, in accordance with SSPC-SP 5, is required. Chemical-resistant coatings applied to the exterior of tanks may be epoxy-phenolic, polyester, vinyl, chemically cured epoxies or coal tar epoxies, depending upon the chemical exposure. When repainting is necessary, surface preparation is important. Solvent cleaning and water rinsing must be thorough to be sure all contaminants are removed from the old surface. Abrasive blast cleaning should be done to the degree necessary under the prevailing circumstances. A. SAFETY COLORS The use of safety color paints is a requirement in maintenance painting and is a part of plant safety programs. Where hazards exist, the American National Standards Institute safety colors must be applied. Pipelines must be at least circumferentially striped to denote the material being carried. Care must be taken to prevent abuse of the use of safety colors. It is advisable that the plant Safety Department be involved in the selection and the application of safety colors. VI. RECORDS Written records are the best way to collect information on paint system performance. Records should include: what was painted date of painting surface preparation quantity, type of paint and manufacturer application equipment FIGURE 5 Visibility is the most important function of the coating system on this yellow coil carrier. 394 --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER+L7.2 93 8627940 0003842 273 W ACKNOWLEDGEMENT This chapter is a complete update of that by S. C. Frye which appeared in the first edition of this volume. The authors and editors gratefully acknowledge the active participation of the following in the review process for this chapter: William F. Chandler, Seymour K. Coburn, R. Dashner, W. E.Kemp, James R. Lopata, Bruno Perfetti, H. R. Stoner, William R. Wright, and William J. Wallace, Jr. REFERENCE Anonymous, Heat-Resistant Coatings Help Huge Mill Extend Periods Between Shutdowns, Plant Services, page 51, July 1981. BIOGRAPHY Arthur R. Thompson was a project engineer for the Inland Steel Company. He obtained his BSIM and MSIM from Purdue University and worked with the Inland Steel Company starting in 1964. He was in the Industrial Engineering group from 1964-1 973 and in EngineeringStandards and Specifications as a project engineer beginning in 1973. Seymour C. Frye was a representativeto the SSPC starting in 1952 and is a former Vice Chairman of the Research Cornmittee. He is a Chemical Engineering graduate of Drexel University and was employed by E.I. du Pont de Nemours & Co., inc. Paint Division for 16 years, last serving as laboratory supervisor on paints, enamels and varnishes. He joined Bethlehem Steel Corporation in 1946 as a research engineer specializing in the specification and use of paints both in the plants and on structures built by Bethlehem Steel Corporation. He was promoted to Staff Engineer, Research Department, and later to Manager of the Organic Coatings and Corrosion Section at Bethlehem. He has developed specifications for Bethlehem and for the SSPC. He has been a member of the American Iron and Steel Insti-
tute, American Society for Testing and Materiais and the American Water Works Association; Chairman of the subcommittee on, and former Director of, the Steel Water Pipe Manufacture? Technical Advisory Committee of the AWWA; director of the National Association of Corrosion Engineers; and an accredited corrosion specialist. Mr. Frye has presented papers on the cleaning and painting of structural steel to many organizations and published papers in the American Paint Journal, Transactions of the American Society of Civil Engineers, Materials and Corrosion Prevention, Factory, and the Journal of the American Water Works Association. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 395 --`,,,,`-`-`,,`,,`,`,,`---
SSPC CHAPTER*L7-3 93 8627940 0003843 12T m CHAPTER 17.3 PETROLEUM REFINERY COATINGS by W.E. Stanford I. INTRODUCTION sibilities for maintenance coating to people already overburdened or unqualified, emphasis on coatings and corroProtective coatings are one of the primary means of sion protection is reduced. Low priority given to coating controlling corrosion in refinery exposures. For this work can result in a serie s of rushed projects, poorreason, costs for maintenance painting can account for as specifications, poor vendor selection, improper surface much as 15-25 percent of the maintenance budget. Ade- preparation, hasty choice of materials, and, of course, quate interest return is expected for every dollar invested eventual higher cost s. in painting. Production outages should also be reduced and life expectancy of key process equipment extended. IV. COATING SCHEDULES Important by-products include improved appearance and A coating program for the maintenance of refineries better morale and community relations. Refinery painting, which includes process equipment, should begin with an audit. The audit should include storage tanks, piping, etc., presents a broad spectrum of verification of existi ng and new coating records and an upexposures that involves a variety of physical and chemical to-date appraisal of coating conditions in all areas of the conditions. Because of this, coating procedures and refinery. It is also importa nt to note causes of coating materials selection change from area to area. Although all failure. With this da ta, assessment of coating material reareas cannot be covered in this chapter, some of the most quirements, scheduled timing costs, manning, and equipcommon ones will be discussed to aid the refinery ment can be determined for the maintenance coating proengineers in creating an effective maintenance program. gram. This audit and pla nning of refinery coating can be handled effectively through inspection departments within II. HISTORY OF REFINERY COATING the refinery. In dayto-day activity, appraisal o f progress in coating application and general conditions of existing The evolution of coating technology in the past 20 coatings can be recorded for reference in program planyears has resulted in more efficient materials performance ning. than was previously obtained from oil-base aluminum and other similar coating formulations. With earlier coating V. TECHNOLOGY
materials, painting was an annual occurrence. Today, Careful consideration must be given to normal and coating systems that will perform for up to 25 years are not upset operating condi tions before coating materials are uncommon. A typical high performance system is organic selected for a specific r efinery painting job. The data or inorganic zinc-rich primer with suitable topcoats. Th e should reflect temperat ures (high and low), cycling, total dry film thickness of such high performance systems chemical exposures and mechanical conditions the should be 8-10 mils in atmospheric exposure. These coating will be subjected to. Also consider whether the systems can be applied on new construction and are vir- equipment is indoors or outdoors and its geographical tually maintenance free for the expected life of the equip- location. The coatin g engineer must also know how the ment. Economics and investment return can be improved equipment will be used in the refining process. For examsignificantly with properly administered maintenance ple, tanks are used to stor e finished volatile products. In coating programs. order to decrease product loss from vaporization, storage tanks are often painted white to reflect solar heat and 111. PERSONNEL decrease vapor pressures. Individuals in charge of maintenance coating must Coating requirements often enc ountered in refineries work effectively with the entire organization. The coating (from a technical and operational point of view) are resisengineer is called upon to be organizer, manager, corro- tance to chemicals (inc luding crude oils), permeability, sion engineer, record keeper, performance analyst, and tolerance of temperature extremes, abrasion and impact, budget salesman, with a knowledge of materials composi- resistance, flexibility, and weather resistance. Other proption, selection, application methods, and equipment. erties, such as heat emissi vity and solar heat reflectance, Administration of good maintenance programs is ahould be considered where insula ting qualities or heat paramount to success and overall performance of transfer is important. With this background as a guide, coatings. However, when management delegates respon- desired coating properties can be established. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 396
SSPC CHAPTER*L7=3 93 D 8b27940 0003894 Obb m A. RESISTANCE (CHEMICALS AND CRUDE OIL) Petrochemicals produced in refineries deteriorate coating films if proper materials are not selected. Crude oil, for instance, can cause extensive corrosion damage, especially when water separates from oil onto the bottom of storage tanks. High concentrations of hydrogen sulfide in crude oil also result in corrosion damage. For these problems, applications of inorganic zinc-rich primers with epoxy polyamide topcoats, coal tar epoxies and polyesters have performed satisfactorily. These coating systems are effective on exposures that can range from fumes, splash, and spillage to total immersion. B. PERMEABILITY The rate at which water or solvents penetrate dry coating film varies greatly among generic types of coatings, seriously affecting service life of some systems in operations where moisture condenses on equipment during heating and cooling cycles and permeability through the coat ing increases. Si mi larly, the permeabi Iity rate increases in humid weather. Some coatings used to control these conditions are aliphatic urethanes and ïnorganic zinc-rich primers with epoxy polyamide or vinyl topcoats at a dry film thickness of 6-8 mils. C. TEMPERATURE High and low temperature resistance is often required in refinery coating. Temperature may be ambient or steel skin temperatures of process equipment. In atmospheric temperatures the range can be from -40°C (-40°F) in northern climates to 54°C (130°F) in southern climates. The process temperatures will range from -4O"ClF to a high of 648°C (1200°F). Temperatures as low as -40°C will be found in refrigeration systems and on boiler breaching as high as (648°C) in the typical limits of the refinery. Coating materials selected for this broad temperature range include epoxy, modified epoxy, phenolics, modified phenolics, acrylics, silicone acrylics, urethanes, inorganic zincs, silicones, and heat inducting, glass-fil led inorganics. To obtain accurate steel surface temperatures, the skin temperature of equipment surfaces should be measured, since it can be higher or lower than operating temperatures. Significant energy savings can result if the proper coatings are selected. D. ABRASION AND IMPACT In a refinery coated surfaces can be damaged by airborne abrasives such as sand, coke dusts, andlor products containing particulate matter. In daily maintenance operations and during refinery turnaround, coated equipment is bumped together when new piping or vessels are installed. During maintenance repair, heavy wrenches and tools are often dropped on coated surfaces. Another source of damage is steel cables and slings that are used to hoist
coated parts into place. Because of these conditions, coatings must have properties that will resist abrasion and impact. The coating selected should be a fast-cure that will form a hard film within several hours. For these applications, self-cure, ethyl silicate based, inorganic zinc-rich primers and other similar fast cure primers are used. In some areas, where pH ranges are between 6.0-9.0, the primer is not topcoated. Where top-coating is necessary, epoxies, vinyls, acrylics, urethanes and other fast-dry coatings are used to coat equipment after installation. E. FLEXIBILITY Wind, temperature or process pressures can cause materials to flex. For example, in large floating roof storage tanks, roof sections can flex as much as 10 inches under high wind velocity. In process operation, the heating and cooling of thin shell vessels produces flexing as well as contraction and expansion. Materials that will meet flex requirements are, generically, epoxies (flexible), vinyls, urethanes, neoprene, and other similar materials. Each parameter should be investigated before a coating system is selected. F. WEATHERABILITY Weather resistance of coating materials varies widely. Close to the Equator, coatings must withstand intense solar radiation. Close to the Arctic Circle, coatings must withstand intense cold. In hot, humid and cold climates, vinyls, epoxies, acrylics, alkyds, urethanes, chlorinated rubber, and similar generic types are good candidate materials. G. HEAT EMISSIVITY As the need to conserve energy increases, emissivity becomes important. Coating materials can be used to decrease or increase heat transfer to save energy. Consider compression areas where gases are passed through piping to storage under pressure. In this case, compression requirements can be decreased if process equipment temperatures are decreased using solar-reflective materials. In other applications, heat can be absorbed to assist in raising the temperature of a tank's contents for pumping, such as with some crude oils. Where reflectance of solar energy is required to conserve volatile finished products, white coatings can be used advantageously. Heatllight reflection of black is near O, aluminum and medium gray 40-50, and white above 80. H. COMPOSITION To select coating materials that will provide the performance expected, the material's generic composition must be known. The binder, pigments, fillers, emulsifiers, and other additives contribute to film properties and subsequently to film performance. When referring to materials on coating specifications, Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from
IHS 397
SSPC CHAPTER*Lï.3 93 8b27940 0003845 TTZ the exact name of the generic materials coating formulation should be given. It is not good practice to specify by broad generic names alone, such as epoxy , because of the considerable difference among epoxy coatings. The performance of epoxy polyamide and epoxy amine can vary widely. There are areas where they should or should not be used. For example, when the application of an uncured coating is subject to condensation or high relative humidity, an epoxy amine may not cure properly. The amine catalyst can be leached out of the coating by moisture and thus not be available to react with epoxy resins. Epoxy polyamide should be used in such cases because cure will continue even though moisture is present, although cure may be at a slower rate. Other materials, such as self-cure inorganic zincs and moisture-cured urethanes, can be used under moist conditions. Paint and coating materials are manufactured by a batch process. Components in a formulation can vary. To assure consistent quality and composition, coating materials should be fingerprinted , using infrared methods described in ASTM Reference Paint Testing Manual . These methods require little time but are very effective in monitoring quality of materials. Other methods, such as pyrolytic gas chromatography and mass spectroscopy are useful in identifying components of dry films or liquid samples. In critical projects requiring large quantities of coating materials, samples from each production lot should be tested. Lots should be scanned by infrared to establish and ensure consistent material composition. For coating applications in refineries, the generic materials most frequently used are alkyds, acrylic latex, coal tar epoxy, epoxy, epoxy phenolic, chlorosulfonated polyethylene, inorganic zinc-rich primers, mastics, organic zinc-rich primers, polyester, silicones, silicone acrylics, urethanes, vinyls, and vinyl latex. I. REGULATIONS Federal, state and local regulations control abrasive and solvent materials used to clean or coat equipment surfaces. The regulations that apply include those written by the National Fire Prevention Agency (NFPA), Occupational Safety Health Administration (OSHA), Environmental Protection Agency (EPA), Department of Defense Fuel Containers List (DOD), California Air Resources Board (CARB), Texas Air Control Board (TACB) Regulation 1, Philadelphia Regulation V, and similar local controls. In coating internal storage tanks for military fuels, the coating material should be approved and included on the DOD list. If zinc or other extraneous liner material is found in jet fuels, the product will not be purchased by the government or by some domestic customers. Other regdations are directed to controlling solvent, dust and emissions of other materials into the environ-
ment where they are hazardous. The limits and federal regulations can be obtained from the Federal Register. State and local regulations can be obtained from respective government offices. These documents reference regulation details. They will not be reviewed here because of their complexity. VI. SPECIFICATIONS To assure satisfactory coating performance, clear, accurate specifications for coating application should be written. A coating manual prepared by the combined efforts of research engineering and inspection departments would make the job of writing specifications easier. The manual will include information on surface preparation, coating materials, areas to be painted, exposures, and special applications. In Appendix A is a typical form used by refinery management to initiate bids on work and pro. vide a definitive coating specification. Other similar forms are used for coating stationary and on-stream process equipment. Whatever system is used, all specifications should clearly establish the following items as they relate to scope and objectives: Type and grade of surface preparation, abrasives, and anchor pattern. Generic type of primer and finish coats. Wet and dry film thicknesses of primer and finish coats. Number of primer and finish coats. Equipment to be used for applying materials ~ (airless gun, spray gun parts such as nozzle, hoses, etc.). Safety precautions to be observed. Weather limitations such as high relative humidity, rain, cold temperatures, etc. Inspection, type of tests to be performed, by whom, and results to be expected; instruments required. The manufacturer s coating instructions, noted and referenced. Spot repair procedures. When specifications are complete, they are used to obtain contractor bids on the coating application. During negotiations of the contract, any changes or additions to the specifications should be agreed upon. From this point
until the job is completed, the specifications should be closely followed to achieve optimum coating performance. VII. LABORATORY TESTING An effective program for materials research and new product evaluation should be maintained to update technology and coating performance in refinery maintenance. Research projects provide guidance in selecting materials and improving coating service performance. The data provides a basis for projecting economic costs and service life expectancy, and ultimately, for making decisions on coating system investment. At the same time, materials that are not adaptable to refinery conditions are screened, eliminating early and costly maintenance coating repairs and replacement. Laboratory screening tests should employ a series of viable tests using simulated refinery conditions and ASTM procedures. This approach can project what might be exCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 398
SSPC CHAPTER*L7*3 93 8627940 0003846 939 pected in service environments. Test parameters for physical and chemical exposure must be accurately established before testing can proceed. These parameters should include skin temperatures of equipment, surface irregularities, chemical concentrations, adjacent process effluent, contamination drift, weather conditions, thermal shock or cyclic conditions and other pertinent history available from engineering and operations. With this background, screening tests can proceed. Tests most often used are a) Abrasion -ASTM C-190 b) Cathodic Disbonding -ASTM G8-69T c) Drying Time -ASTM D-1640 d) Exterior Exposure (Coastal & Inland) -ASTM D-1014 e) Flexibility -ASTM D-6222 f) Synthetic Seawater Spray (4%) -ASTM B-117 g) Fresh Aerated Water Immersion -ASTM D-879 h) Synthetic Seawater Immersion Aerated ASTM D-870 i) Solvent Resistance -ASTM 0-2792 j) Temperature Resistance -ASTM D-2488 k) Weatherometer -ASTM D-822 I) Heat Emissivity -ASTM E-307-68T m) Permeation -ASTM D-1653 To substantiate laboratory data, as much in-service data as possible should be obtained. D-ocumanted evidence, such as case histories of materials in similar refinery conditions, should be considered. To reduce the risk of making errors in the application of paint to test panels in the laboratory, arrangements should be made with the manufacturer to provide first-coated test panels. Usually, the coating manufacturer will supply coated
panels andlor wet samples. Other manufacturers should be excluded from test information. After the first series of screen tests, some in-house panels should be coated to establish material workability, ease of clean up, drying times, hiding power, and other data. If some of the tests are suspect, panels can be prepared for retesting. Of current interest are rapid laboratory instrument test methods and procedures using the scanning electron microscope (SEM), pyrolytic gas chromotography (PGC), infrared spectrophotometry (IR), emission spectroscopy (ES), and ultraviolet spectroscopy (UV). Methods and procedures for these tests are available from ASTM Reference Paint Testing Manual , STP-500, Thirteenth Edition, and other sources. These procedures can be used to determine coating film generic composition, mechanisms of film deterioration, coating composition comparison with similar products, and to control quality by infrared fingerprinting coating materials. In laboratory tests of maintenance coating systems, scribing is used to determine how effectively a coating will protect metal after it has been abraded, chipped and exposed. A scribe inch wide is cut in an X shape across the coated test panel to a depth sufficient to expose the metal substrate. Edges of the coating along the scribe should not be damaged when the scribe is cut, or poor test agreement will result. To accomplish this a panel scriber equipped with a metal saw is used. With this equipment scribes are uniformly and easily cut to the desired depth (Figure 1). FIGURE 1 Panel Scriber Courtesy Gulf Oil VIII. FIELD TESTING Once initial screen tests are complete, field evaluation will substantiate laboratory results. This phase will generate in-service data to assist management when making investment decisions on coating systems. Personnel making the field tests also have an opportunity to evaluate film forming, handling, and drying characteristics. Field test applications on exterior and interior tank surfaces yield beneficial data that can be effectively used to determine expected performance of a coating system. To evaluate coating materials for ess vessels, test racks are used. hold about 10 to 12 (size 3 x 5 two mild steel Corrosion coupons. port rods used to construct racks
internal use on procRacks are designed to x IL ) coated panels and Metal frames and supare made of Monel or 316
stainless steel. When racks are assembled, support rods are insulated from the frame with Teflon tubing; each panel is separated from the other by one-half inch Teflon spacers. Metal corrosion coupons are accurately tarred to measure corrosion loss in the vessel. From field test data suitable materials and necessity for coating can be established (Figure 2). At the refinery, test records are usually developed by the Inspection Department. At regular intervals a report of test items is compiled. This background and data is then filed for future reference. IX. SURFACE PREPARATION In all refinery coating applications, proper grade of surface preparation is vital in obtaining satisfactory coating performance. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 399
SSPC CHAPTER*L7-3 93 D 8627940 0003847 875 FIGURE 2 Typical Test Rack Assembly For Internal Vessel Testing Steel Structures Painting Council Surface Preparation Specifications and Photographic Standards (SSPCVis 1) are used to establish conditions and degree of coating deterioration. With these procedures, we can identify specific surface preparation requirements. Other conditions that should be observed for surface preparation are General Cleaning All surfaces must be free of condensation or moisture prior to surface preparation or coating. Steel Where millscale is present, shop blasting and pickling and blasting are effective and practical. When required, on-site blasting is preferred to hand cleaning. On-site pickling is unsatisfactory due to problems with handling acid solutions and safety. In field blasting, the first coat of paint should be applied the same day that steel is blasted to prevent rust from forming on the blasted surfaces (free of chromates or other toxicants). Dry Blast Cleaning Abasives used in blasting should be selected from materials of mesh size to produce the anchor pattern required for the coating to be applied. Abrasives may be sand, steel shot, grit and others that will not contaminate the etched surfaces. Coordina tion Operations of sandblasting and painting should be coordinated to avoid embedding sand or other debris in tacky or wet paint films. Lack of coordination can cause coating problems, particularly when internally coating tanks where dust from blasting can accumulate on surfaces to be coated. Hand Cleaning When hand or mechanical cleaning (SSPC-SP 2) is used to remove weathered miliscale and other contamination, the proper primer should be selected. The primer should have good wetting and slow drying properties and should be followed by compatible topcoats. Galvan king
New galvanized surfaces should be cleaned by oil dissolving solvents, detergents, brush blasting or chemicals before coating to avert disbonding and poor intercoat adhesion. Galvanized surfaces should be permitted to weather for several months to improve paintability. Where neither approach is possible, special primers can obtain proper bonding of the topcoat. Vinyls, epoxies, latex base coatings and wash primers are widely used on galvanized surfaces. Copper Copper and its alloys are not coated since they form their own protective oxide film. However, should coating be necessary, copper should be allowed to weather until dark oxides appear or roughening of the surface develops. The primer used should be conventional alkyd or oleoresinous materials. Where coating is not possible and discoloration of copper is objectionable, the use of lead coated copper should be considered. Aluminum Aluminum can be cleaned and etched by using a solution of water containing about lo/dwt. caustic or by brush blasting (SSPC-SP 7). Effective proprietary solutions are also available for preparing aluminum to receive coatings. Surfaces should be coated with zinc chromate-base primer or other lead-free materials. If lead is present, it will promote pitting of an aluminum surface. Wood Before painting, wood surfaces should be tested with a moisture meter to be certain the wood is dry. Where new wood is finish coated with water dispersed latex systems, the test should also be made, since primers are usually oil base. Previously painted wood can often be painted, even though some moisture is present, if water soluble latex coatings are used and priming is not required. Masonry New plaster, concrete, and brick should be allowed to cure before coatings containing solvent are applied. When new water soluble coatings are used, complete cure is not essential. It is advisable to acid etch concrete with a muriatic acid solution 10 to 20% by FIGURE 3 Typical Refinery Tank Farm Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 400
SSPC CHAPTER*L7.3 93 8627940 0003848 701 =6 FIGURE 4 The Storage Tanks in Background are Large Floater Roof Type. In the Foreground are Typical Roof Birdbaths That Fill With Water. volume. The surface should then be neutralized with ammonium carbonate, washed with clear water and allowed to dry. In refinery coating, costs for surface preparation will vary widely on the U.S. labor market. For example in 1981 typical costs of white metal blast ranged from $0.60/sq. ft. in Gulf coast states to $1.2O/sq. ft. in northern states. Surface preparation costs normally represent much of the cost for coating. Removal of oil, grease, and residue from tank bottoms will be necessary before surface preparation can proceed in many refinery applications. On the exterior, this can be accomplished by using solvent (SSPC-SP l), detergents, caustic cleaning, and brush blasting (SSPC-SP 7). Interior removal is more difficult. For example, removal of sludge collected on the bottom of a crude oil tank is a big problem, particularly when the tank is a large floating roof (250 m bblslcap). The sludge is usually a heavily caked or viscous residue, difficult to shovel and expensive to remove using other cleaning methods. The most effective approach is to pump residue using a vacuum tank truck, then haul it to a disposal area. Remaining wax or dirt-filled residue can then be broken manually into chunks and removed by shovelling. If the tank structure permits, a section of the shell can be removed so that a front end loader can remove the residue. To remove residual oil on steel FIGURE 5 Naphtha Feedstock Storage Tank of Riveted Construction. Note Seepage at Seams. surfaces, detergents and steam generators are effective. Final clean-up of bottoms can be accomplished using mops and rubber squeegees to remove water and other residue from low areas. Surfaces should be allowed to drv can be used. When oil is present, the oil will fluoresce under the black light. When no fluorescence is noted, oil has been effectively removed. FIGURE 6
Naphtha Feedstock Storage Tank in Figure 5 After Seams Were Sealed With Flexible Epoxy. In recent years, hydroblasting has been used to clean exterior storage tanks and other equipment in areas where airborne dusts are not permitted by regulation or where equipment cannot be exposed to dust. When hydroblast is used, the water should be inhibited to prevent surface rusting. X. COATING APPLICATION Coating materials are often applied in refinery operations by qualified contractors in the area. Contractors handle all provisions related to materials, personnel and equipment. Large jobs, such as exterior storage tank coating, are usually let out for bids. At the refinery, maintenance painting crews are also employed for special coating applications on process equipment and smaller projects. Application equipment commonly used at the refinery are paint spray guns (airless and conventional), rollers (with proper roller composition), brushes, and specialized guns. The type of equipment to be used for application is given in coating manufacturer s instructions. Specialized spray equipment with intermix spray caps and fiberglass choppers are sometimes used to apply fiberglass reinforced coatings on storage tank bottoms and shells. They are also used to apply some type of fireproofing using Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 401
SSPC CHAPTERxL7-3 93 FIGURE 7 View of Refinery Stocks and Areas Where High Temperature Coatings are Required. fiberglass filler. Where heavy monolithic materials are used, the gunnite process is also implemented. If certain factors are overlooked, a good application will not be achieved. Follow these guidelines to ensure a good coating. 1. The primer must be compatible with the surface preparation and topcoat. Primers such as inorganic zinc-rich will not perform well over wire brushcleaned surfaces and cannot be topcoated with alkyd or other oleoresinous materials, since saponification of the topcoat will result. 2. All coatings should be applied in strict accordance with manufacturers instructions, observing minimum application temperatures, catalyst type and addition rates, thinners and amounts allowed. 3. Internal tank bottom coatings and buried pipeline coatings should be checked for defects in the coating using a suitable holiday detector. The holiday detector specified in AWWA Specification C-203 is satisfactory. Voltages should never exceed the dielectric strength of the coating film, or damage of the film will occur. The greatest amount of steel surface to be coated in refineries is contained in steel storage tanks. These tanks range in capacity from 1to 250,000 bbls. Figures 3 through 9 are typical refinery tank farms and battery limits exposures. FIGURE 8 Spheres and Storage Tanks Painted White to Reduce Recompression Required and Vapor Loss. When storage tanks or other refinery equipment are coated, two general areas should be considered. They are (1) new equipment, and (2) maintenance coating repair on existing structures. The most effective and economical approach on new storage tanks and process equipment is to shop blast and prime coat at the mill. This provides protection for steel tank plate while in outdoor yard storage prior to construction. When storage tanks are erected, weld seams can be blasted and primed, and damaged areas can be spot primed with portable equipment. Process equipment is usually coated by the manufacturer where it is fabricated. With minor touch-up, coatings retain their appearance and protective qualities. The second approach to new storage tank painting is to acid pickle the steel at the mill to remove millscale. The tank is then field constructed, blasted, and coated by contractors. This can be more expensive and time consuming
tRan mill coating and can cause delays on process equipment in short turnaround schedules. Weather and atmospheric conditions can present difficulties when work is done outdoors. For these reasons, shop coating is preferred over field application, particularly when large surfaces are involved. FIGURE 9 Color Coding Used to Identify Refinery Chemical Storage Tanks. When deciding whether to repair or replace existing coating, consider economics, coating compatibility with existing films, surface preparation of existing coating film and the type of spot repair needed. As a guide to appraisal of coated surfaces, reference is made to SSPC (Pictorial Standard Vis 2.) to establish what course of action is required. NACE Standard TM-01-70 is also an excellent guide to follow. The criteria for recoating is the percentage of coated area that is unprotected, such as the exterior of a storage tank. When the unprotected area is 75% or greater, the coating should be replaced. If the unprotected area is below 75%, attempts to repair the existing coating should be considered, unless the failures at lower percentages are widely dispersed, in which case full replacement may be more economical than sandblasting and priming Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*L7.3 93 H 8627940 0003850 3bT the entire area. When internal linings are involved, conditions that exist for specific equipment must be determined. When corrosion rates are low, repair intervals may be extended. When corrosion rates are high and equipment failure is imminent and critical, repairs should be made as soon as possible to avoid pitting damage and production loss. To maintain the coating, regular inspections should be performed and the entire coated surface tested with a holiday detector, properly adjusted. Defects should be marked with chalk and repaired by established repair procedures. Coating process equipment on-stream has been increasingly used in refinery operations. To accomplish this, detailed procedures relating to safety and protection of sensitive equipment components have been developed (See Appendix B). In this approach, production interruptions are avoided and better corrosion protection is obtained. Tables 1 and 2 summarize surface preparations and coating systems suggested for refinery application. XI. INSPECTION In refinery coating operations, competent inspections can yield big dividends. Adequate inspection averts production losses and improves materials performance and operational efficiency. The three most critical periods for inspection on coating application work are: 1. When quality of surface preparation is critical, particularly when immersion conditions require a white metal blast (SSPC-SP 5). 2. When coating materials are sprayed, particularly when work starts, so that standards of work expected from the spray gun operator are clearly establ ished. 3. When final tests on coating films are conducted, and when repair of holidays is made. As work progresses, the inspector should record application data and comment daily. These records can serve as valuable future references. The inspector should have test instruments available and in good working order. Instruments should include a pocket knife, wet film paint thickness gauge, dry film thickness gauge, high and low voltage holiday detectors (portable), magnifying glass with light source and a portable vapor-proof spotlight. With these it is possible to perform nearly all the initially required tests. The inspection must determine proper cure time on a coating material. Following are some tests used to determine cures.
a) A coin is used to strike the surface of inorganic zinc-rich primers. If no zinc metal is removed from the surface, cure is adequate to topcoat. b) Most coating systems attain a definite hardness when cure is complete. To determine cure, prepare a standard with the coating system on a 6 12 x i/g
x
mild steel panel to specified thickness. Cure
for the specified time and temperature. Test the hardness of the system with a portable hardness tester (Rockwell C or other). Obtain the average hardness from 10 readings until maximum hardness is indicated. The average hardness can be used as an index number to determine when final cure of the film is reached. c) A quick test for cure is to briskly rub the coating with a clean, white cloth dampened with solvent. If the coating is not softened and does not rub off, the cure is complete. XII. SAFETY To avoid accidents, all safety regulations must be strictly observed and should be included in coating specifications. Before coating materials are mixed and sprayed, cleaner and solvent composition should be established. From this data proper safety equipment selection (air masks, etc.) can be made. When coating the inside of tanks and other confined spaces, atmosphere should be tested with gas and explosive meters to determine if toxic or explosive concentrations from process vapors exist. As work progresses, intermittent gas tests should be performed to ensure that ventilation is adequate to keep solvent vapor at concentrations below explosive or hazardous limits. The reference entitled Threshold Limit Values (TLV) of Airborne Contaminants for 1982 (revised annually) for Chemical Substances and Physical Agents in the Workroom Environment can be used to determine hazardous limits. This document can be obtained from the American Conference of Governmental Industrial Hygienists. During application of coatings reinforced with polyester fiber that require peroxide catalysts, fires may occur, unless materials are handled carefully. It is important to dispose of old containers properly in specified areas. To avoid fires from catalyst oxidation or spon-
taneous combustion, used containers with residual aluminums and other pigment should not be emptied in the vicinity of the storage tank farm. A checklist of some safety concerns is given in SSPC-PA Guide 3, A Guide to Safety in Paint Application , and in a separate chapter in this volume. XIII. ECONOMICS In refinery coating operations, economics and investment returns should be considered for costs involved in a project. This is a complex task for some operations, but fortunately, for refinery coating cost comparisons, it is a straightforward procedure. The one often used by the Refinery Engineering Economics Section for coating systems is Discounted Cash Flow . This can be effectively applied when making performance cost comparison between extended service life and nominal life protective coating systems. However, when determining investment Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 403
SSPC CHAPTER*37-3 93 ab27940 0003853 2Tb W CRUDES HIGH IN H,S CRUDES LOW IN H,S FLOATING ROOF TANKS CONE ROOF TANKS SURFACE PREP COATING SURFACE PREP COATING INSIDE BOTTOM Sandblast to (AND UP 15'Á Near White, Epoxy 16s ON SHELL) SSPC SP-10 mils rnin. I ~~ Sandblast to I 1 Coat of Same as for Floatinq White Metal I Zinc-Rich White Metal, I Zinc-Rich SSPC SP-5 Inorganic Roof Tanks SSPC SP-5 Inorganic INSIDE SHELL I @ 3-5 mils; -_---_----or --No Coatinq (UPPER RINGS) 1 Plus 4 mils Sandblast to I Coal Tar- I I Catalyst-Near White, 1 Epoxy.@ 16B I , Cured Epoxy SSPC SP-1 o I mils min. I ~ INSIDE SHELL (MIDDLE AND No Coating No Coating No Coating No Coating LOWER RINGS) INSIDE ROOF No Coating C No Coating No Coating Sandblast to 1 Coat of Sandblast to ' 1 Coat of OUTSIDE ROOF White Metal, I Zinc-Rich Same as Exterior White Metal, I Zinc-Rich Same as Exterior SSPC SP-5 Inorganic Tank Shell SSPC SP-5 1 Inorganic Tank Shell 1 @ 3-5 mils @ 3-5 mils A -This recommendation is for new tanks. For repairing old bottoms, glass-reinfo rced polyester and epoxy coatings are recommended. E -To be applied in number of coats to achieve this dry film thickness, but in n o case should this be less than two coats. Coating to then be checked with a Holiday Detector, normally at 1000to 2000volts depending on coating manufacturer's recommendation. C -For corrosion protection, it is advisable to apply same coating system as on upper rings. From a practical standpoint, however, it is often not economically possible to coat the underside of the roof because of structural supports, etc.
Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 404
SSPC CHAPTER*L7=3 93 m 8627940 0003852 132 m Table 2 REFINERY PAINTING SYSTEMS SCHEDULE FOR STEEL SURFACES RE CO MM EN DE D SCHEME SURFACE SURFACE PR EPAR AT ION PRIMER FINISH COMMENTS I Buried Piping Buried Structures, other than piping Docks (Above Water) & Mooring Buoys Docks (Below Water) & Sheet Piling, Before Driving I Fence Fabric, Chain Link (Un insulated ) Exchangers, Vessels, Heaters, Stacks, Above Ground Piping, Etc ---__--To 200°F In relatively noncorrosive areas In seacoast or corrosive areas Insulated Surfaces Under Insulation if Metal Skin Operating Temperature will be under 256 F Prepainted Items (Compressors, Pumps, Motors, Etc.) Structural Steel In relatively noncorrosive areas
In seacoast or corrosive areas Sandblast (NearWhite) Sandblast (Near-White) Sand blast (Near-White) ( Near-Wh itel Sandblast (Commercial) Sandblast (White Metal) Coal Tar Primer + 2 Coats Hot Coal Tar Enamel with 1 Glass & 1 Felt Wrap & Finish Coat of White Wash (see AWWA Spec C-203) Coal Tar-Epoxy (16 mils min.)* Catalyst-Cured Epoxy (8 mils min.)* Galvanize or Aluminum Coat If black coating is acceptable, the alternate is lower cost and just as effective. ~~ In addition to the coating, cathodic protection should be considered for maximum protect ion. (11 With some items galvanizing may be considered instead of coating. (2) Compatibility of topcoat with zinc-rich primer must be determined before application. _-~_____--(1I These are not perfect materials but are probably the best available recommendations for hot surfaces. (2) The zinc-rich inorganics do
a good job of corrosion protection but some coating suppliers may be able to furnish a suitable silicone topcoat, where color is important. 1 or 2 Coats Inorganic Zinc-Rich (2-1/2 mils min.) ___-_ ---__ 1 or 2 Coats Epoxy (2-1 12 mils min.) -----_ --1 or 2 Coats Heat Resistant Topcoats (normally modified silicone) 1 Coat Zinc-Rich inorganic (3-5mils) 1 Coat Heat-Resistant Primer __ ----_Sandblast (White Metal) Sandblast (White Metal) Sandblast (Commercial1 2 Coats Straight Silicone; Inorganic Zinc-Rich, Zinc-Dust Gray preferred, aluminum is acceptable. (Paint must be cured at 400"F within two weeks of application 1. ~~ Coat Tar-Epoxy (8mils min.) Number of coats depending on hiding required. If galvanized or shop-coated with zinc-rich inorganic, clean and blast welds and touch-up
with compatible zinc-rich coating after erection in field. None normally required Sandblast Hot Dip Galvanize (Commercial) (2-1 /2 mils min.) or mill pickle plus I brush-off blast in field _----_--------Galvanize Note: Film thicknesses shown are to be measured dry. Color of finish coat to be selected by owner. All coatings to be applied strictly in accordance with manufacturer's recommenda tions. "To be applied in number of coats required to achieve this film thickness, but i n no case less than 2 coats. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 405
SSPC CHAPTERxL7.3 73 m 8627740 0003853 079 m Table 2 (Cont'dI REFINERY PAINTING SYSTEMS SCHEDULE FOR STEEL SURFACES RECOMMENDED SCHEME SURFACE Walkways, Handrails, Ladders, Line Supports, Nuts, Bolts, and Miscellaneous Hardware ~ Tanks, Interior Clean Petroleum Products (Finished Products) --_ ----Brine or Waste Water -_-----Clean Water, or Condensate -_----Crude, Bottom & Up 18" on Shell Crude, Lower & Middle Shell Plates, and Roof -- - ----. Crude, Top Ring (Floating Roof Only) Tanks, Exterior Above Grade, Shell & Cone Roof -_ In relatively non-corrosive areas --------. In seacoast or corrosive areas
----_---Below Grade Shell SURF ACE PREPARATION Sandblast (White Metal) Sandblast ( Near-White 1 Sandblast (White Metall Sandblast (Near-White) Sandblast ícommerciaiì or Mill Pickle __-_-Sandblast (White Metal) Sandblast (Commercial1 Sandblast (White Metal) Sandblast (Near-White) Sandblast (Near-White) Sandblast PRIMER FINISH On entire interior, 1 Coat Zinc-Rich Inorganic (3-5 mils) plus Topcoat Bottom and up 15" on Shell with Catalyst Cured Epoxy (8 mils min.)"
______-_____ --Coal Tar-Epoxy (16 mils min.)* __________ -----Catalyst-Cured Epoxy-Phenolic (1 2 mils min.)" -__-___-___---Coal Tar-Epoxy (16 mils min.)' Catalyst-Cured Epoxy (8mils min.)" 1 or 2 Coats Rust Inhibiting Alkyd Primer (2-1/2 mils min.) 1 Coat Zinc-Rich inorganic (3-5mils) 1 or 2 Coats Alkyd Finish (2-1/2mils min.) 1 or 2 Coats: Hi-Build Vinyl or Catalyst-Cured Epoxy Amine (4 mils min. 1 Coat Inorganic Zinc-Rich (3-5miis) ---__ -_-------Coal Tar-Epoxy (16 mils min.)* Apply cathodic protection COMMENTS It is recommended that micarta blocks (or similarly effective materials) be cemented and sealed under pipeline where they rest on supports. (11 Even if tank is not to be coated, it is recommended that steel be sandblasted or pickled to remove millscale. This is a good protection against pitting. (2)All coating formulations should appear on Department of Defense Acceptable List. -
If for any reason slight discoloration of brine is objectionable, follow recommendations for clean water tanks. -----_ ----If potable water, coating should be FDA approved. -_----_--~ Use alternate only if crude not sour. --_ ------For light products,a chalking white finish is preferred to minimize evaporation losses. Where pickup of dirt in the atmosphere is a problem on light colored finish, overcoating with a soil retardant solution should be considered. For alternate, if postcured zinc-rich inorganic is used, make certain curing agent is removed before topcoating. ______---In addition to coating, cathodic protection should also be considered for max¡mum protection. Set tanks on sand, pulverized
limestone, or concrete pad slightly above grade where possible. Note: Film thicknesses shown are to be measured dry. Color of finish coat to be selected by owner. All coatings to be applied strictly in accordance with manufacturer's recommenda tion. "To be applied in number of coats required to achieve this film thickness, but i n no case should this be less than 2 coats. --`,,,,`-`-`,,`,,`,`,,`--406 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
Table 2 (Contd) REFINERY PAINTING SYSTEMS SCHEDULE FOR STEEL SURFACES OTHER THAN RECOMMENDED SCHEME SURFACE Aluminum Concrete, Interior Walls Tanks, Brine & Waste Water Copper ~ Galvanized Plastered Walls, Offices, Halls, etc. Washrooms, etc. Wood, General Outside Walls Insulation Coverings, Canvas __L -__-_ Firetard Bit u men Mastics Urethane Foam SURFACE PREPARATION None Normally Required Clean Clean allow to dry Clean & Dry
PRIMER 1 or 2 Coats White Latex Block Filler (Until Voids are fiIled) 1 or 2 Coats White Latex Block Filler (Until Voids are filled) Coal Tar-Epoxy (16 FINISH ~ 1 or 2 Coats 2-Package Polyester, or Catalystcured Epoxy (an alkyd, vinyl latex, or acrylic latex may be substituted where washability is not important) --------. 1 or 2 Coats 2-Package Polyester (an alkyd, Ext. Vinyl Latex, or Ext. Acrylic Latex may be substituted. --_ ---2 Coats Catalyst-Cured Urethane COMMENTS Do Not Use Lead Base Primers on Aluminum Number of Coats depends on hiding required. For previously painted walls, check with block filler manufacturer on possibility of adhesion problems. (1) Preferred System cannot be applied over conventional alkyd or Oleoresinous Paints. (2) Consideration should also be given to tile, other flooring
materials, and to tinted concrete. Sandblasting or acid-etching may be required. -----`,,,,`-`-`,,`,,`,`,,`--______(1 With Catalyst-cured Epoxy, wall sealer may or may not be required, depending on manufacturer. (2) Topcoat should be mildewresistant for humid areas. Topcoats should be mildew resistant for humid areas. Elastomeric Coating most usef u I. None Normally Required No Coating Normally Required for Several Years Clean 2 or 3 Coats Latex (Acrylic or Vinyl) Clean 1 Coat Emulsion-Type 2 Coats, 2-Package Prime-Sealer Polyester or Catalystcured epoxy Clean & Dry 1 Coat Wood Primer 2 Coats AI kyd or Oleoresinous _ Clean 81 Dry 1 Coat Wood Primer 2 Coats Latex House Paint for Latex Sanded, Clean & Dry I 3 Coats Urethane Floor Varnish Clean 2 Coats Emulsion-type FireRetardant Insulation Sealer _-----i----------------Clean & Dry---1 or 2 Coats Fire-Retardant Paint Not Normally Required unless color is important In accordance with Foam Manufacturers Recommendations Note: Film thicknesses shown are to be measured dry. Color of finish coat to be selected by owner. All coatings to be applied strictly in accordance with manufacturer's recommenda tions. *To be applied in number of coats required to achieve this film thickness, but i
n no case should this be less than 2 coats. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 407
SSPC CHAPTER*Li.3 93 8627740 0003855 941 m return, there are shortcomings related to dollar value and time. For example, on extended service life coating systems, it may be as long as four years from the time of initial application before savings or returns are realized. Even the poorest coating system will last four years, and progressively less as severity of exposure increases, before repair or replacement is necessary. Therefore, the higher cost justification for extended service-life coating systems must be based on performance derived in excess of four years after the initial application. To make a simplified comparison of any two coating systems, the following items are required; a) In the year of capital expenditure, the cost for initial application, which includes surface preparation, materials, labor, etc., for coating system X and Y; b) Cost for touchup at third year X and Y; c) After five years the cost to recoat X and touchup Y; d) Cost for touchup at seven years for X and for applying cosmetic coat to Y; e) After ten years the cost to repaint X and touchup Y; f) Cost for touchup at 12 years for X and Y. By determining the difference (X -Y) between these costs, the savings possible will be indicated for a period of 12 years. With this data, calculations for discounted cash flow can proceed. When this method is applied by the economics engineers, if the sum including the initial investment is O or greater, the project will have the desired return on investment. If the sum is negative, the decision to use the coating system should be negative.* Details relating to discounted cash flow require lengthy definition. Typical economic comparisons of alternative painting systems are given in a separate chapter. With continued changes in the national and international economy, each investment in materials should be closely scrutinized before decisions are made. XIV. SUMMARY Topics discussed in this chapter are believed to be primary elements that are part of all successful refinery coating programs. When proper coating materials and systems are selected and properly applied, corrosion in refineries is controlled. The guide to effective refinery maintenance programs should include the following items: a) Selecting qualified personnel to supervise work. b) Establishing coating schedules based on an
accurate refinery coating audit. c) Initiating cooperative programs for testing between laboratory and field exposures, with a good exchange of data between personnel. d) Preparing coating specifications that clearly specify proper surface preparation grade, materials selection, and application procedures. e) Inspecting and testing coating application, safety provisions and regulation conformance. f) Evaluating economics to establish viability of coating invest ment. g) Planning a maintenance coating program that assures quality coating application on every project. When these provisions are followed, corrosion protection is increased and overall annual costs for maintenance can be reduced. In addition, longer equipment service life and fewer production interruptions will be achieved. The trend in refinery coatings is to use the higher performance systems on long term projects (15 years and up) due to better return on investments and reduced maintenance costs. The need for the old standard coating systems and materials will continue for projects where service life up to 10-12 years is expected. 'Another way to look at it; any combination of paint system, surface condition, and environmental condition creates a repaint cycle that yields a minimum average annual painting cost. Determining and using this cycle will result in minimizing painting costs versus protection. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*13*3 93 m 8627940 000385b 888 m APPENDIX A SURFACE PREPARATION AND PAINTING RECOMMENDATIONS To Zone Area WO No. WO Date Tank Dia. Ht. Area: Roof-Shell-Grounded Surface Preparation 1 Completely sandblast to white metal 2 Spot sandblast to commercial grade 3 Completely sandblast to commercial grade 4 Completely scatter sandblast (brush blast) 5 Tool clean CODE DESIGNATION Coatings Coat Material Application Thinner Cleaner Name Cat. No. Method Sq. Ft. /Gal. Wet Mils Name Cat. No. Pt./ Gal. Name Cat. No. RECOMMENDATIONS Surf ace -Coating Preparation First Coat Second Coat Third Coat Fourth Coat ~Exterior Spot Complete Spot Complete Spot Complete Spot Complete Entire Tank Roof Roof Accessories Roof Stairway Shell Stairway Stair Runners Stair Tread (Btm) Stair Tread (Top) Stair Railings Platform Platform (Top) Platform (Btm) Shell MW Covers Foam Lines Service Lines Interior Roof & Rafters Shell Bottom Corrosion Control Section 1. Paint Tank No. and date on shell with nL. BY 3. 409
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SSPC CHAPTER*L7-3 93 W 8627940 0003857 714 = APPENDIX B B. Tanks in this category may be sandblasted and painted. The products of the tanks may be at any GENERAL SAFETY PROCEDURE level during that time. They may be pumped out of, PREPARING AND PAINTING EXTERIOR OF but shall not be pumped into, during actual p reparTANKS CONTAINING PRODUCTS ing or painting operations. C.The roof on both cone roof and floating roof tanks I. GENERAL in this category, as well as the shell, may be sandA. This procedure covers the preparation for painting blasted. and the painting of the exterior of refinery storage D. When floating roof tanks are gas tested to detertanks while they contain products. mine if they belong in this category, tests s hall be made at the following places on the roof: inside the B. The following items apply to all tanks which are to pontoon hatches, behind t he shield covering the be prepared or painted while they contain prod- seal, in the open sleeves which hold the adjustable ucts. In addition to these, further specific items for legs, at the lower slots of the slotted gauge pipe, different categories of tanks appear later. and around the roof hatches. 1. The Inspection Engineering Department shall inspect all tanks prior to any preparing or painting 111. TANKS WITH VAPOR SPACE I N EXoperations. It will be their responsibility to PLOSIVE RANGE decide when tanks containing products may be safely prepared for painting from the standpoint A. For the purpose of this proc edure, tanks containing vapors which test between 50 percent of the of tank condition. This would include conditions such as leaks, pper explosive the roof, etc. be considered
weak spots in the metal, holes in lower explosive limit and the u limit Results of the inspection shall be as defined in Section IV shall to be
reported to the department in charge of the in the explosive range. tank. B. Cone roof tanks must not be sandblasted, hand cleaned, or painted while they remain in the ex2. A hot work permit issued by the department in plosive range category. If the vapor space is encharge of the tank shall be required before startriched by being blanketed with inert or flammable ing the preparing and painting operations. The gas to raise it above the upper explosive limit as permit must be renewed at the beginning of
each day. defined in Section IV, a tank may then be handled under the procedures outlined in Section IV. 3. An explosibility gas test shall be required at the (Blanketing can be by either inert or flammable beginning of each work day. Tests for toxic gas for the following reasons: It has been found gases shall be made where appropriate, as rethat introducing a stream of inert gas into an exquested by the department in charge of the plosive vapor space above a flammable liquid tank. will not have the effect of reducing the vapor 4. The planner responsible for the tank to be space test to a smaller percentage of the lower prepared or painted shall request the Fire Pro- explosive limit. On the contrary , it has the eftection Section to provide a minimum of one fect, by reducing the oxygen content , of even30-pound dry chemical extinguisher at the tank tually making the vapor space tes t above the upsite and to inspect the tank to see that foam per explosive limit. The same test result is obchambers and fire screens on conservation tained when a flammable gas is added t o the equipment are in good order. The department in vapor space. Therefore, either an inert or a flamcharge of the tank shall not issue the hot work mable gas, when added in suffici ent quantities, permit until those things have been done. will change an explosive vapor space i nto one 5. Painting operations mentioned in this pamphlet that is too rich to burn.) may be by any method (brush, spray, etc.). C. Floating roof tanks which test in the explosive 6. Hand cleaning operations mentioned in this range category shall be handled un der the same pamphlet refer to hand tools only, and not hand- procedures as outlined in Secti on IV-C. (See test held power tools. locations specified for floating roofs in Section IID.) II. TANKS WITH VAPOR SPACE BELOW EXPLOSIVE LIMIT IV. TANKS WITH VAPOR SPACE ABOVE UPPER EXPLOSIVE LIMIT A. For the purpose of this procedure, tanks containing vapors which test between zero and 50 per cent A. For the purpose of this pr ocedure, a tank shall be of the lower explosive limit shall be considered considered in this category whe n an explosimeter below the explosive limit. test of a vapor space sample, when mixed with an
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SSPC CHAPTERUL7.3 93 H 8627940 0003858 650 equal amount of fresh air, indicates the mixture to be above the upper explosive limit. B. Cone roof tanks which test in this category shall be handled as follows: 1. Sandblasting shall be done only on the shell. The roof shall be hand cleaned. 2. Tanks should be filled to the point where the vapor space is reduced to a minimum. They must not be pumped into or out of during any cleaning or painting operations. 3. Gas tests shall be made around the gauge hatch, roof manholes, and conservation equipment to check for escaping explosive or toxic gases. If the gauge hatch or manholes leak gas, they shall be sealed with masking tape or similar material. If the conservation equipment shows escaping gas, exhaust ducts at least eight feet high shall be placed over it so as to carry the gas vapors away from the work area. 4.A grounding and bonding system shall be required when sandblasting tanks in this category to avoid the accumulation of a static charge and possible sparking. The bonding system shall include: (1) grounding of the tank to the ground, (2) bonding of the hose, and (3) groundingof the sandblasting equipment to the ground. The total grounding system shall not have more than 5 ohms resistance. The required hot work permit shall be countersigned the first day of work by the maintenance foreman as well as by the operations foreman to indicate that the grounding and bonding system has been installed. C. Floating roof tanks which test in this category shall be handled as follows: 1. Sandblasting of the roof or the inside of the shell shall not be done. 2. Sandblasting and painting may be done on the outside of the shell. The same grounding and bonding system shall be required for the sandblasting as outlined in Section IV.B.4. In addition, a check shall be made to be sure that the bonding from the roof to the are 3. Hand cleaning and painting may be done on the roof and the inside of the shell as long as frequent gas tests of the immediate work area show it to be free of gas. 4. There should be no movement of products while these tanks are being prepared and painted. The roof may be kept at any level. However, it must be afloat, and not resting on its legs. D. Spheres, spheroids, and LPG storage tanks shall be hand cleaned only, and not sandblasted, while in service. They must not be pumped into or out of during the cleaning or painting operations.
In special cases it may be impractical to conform to the above procedures. In those cases, minor deviations may be agreed upon by the Operating and Maintenance Departments and the Accident Prevention Division as long as the safety of personnel and equipment is not affected. Such deviations, however, are not to be considered permanent modifications of the outlined procedures. ACKNOWLEDGEMENT The author and editors gratefully acknowledge the active participation of the following in the review process for this chapter: Emil Bereczky, William Chandler, T.A. Cross, D. Koenecke, Marshall McGee, R.L. Merritt, William Milek, John Montle, C. Munger, David Neill, J. Peters, L.M. Sherman, Rick Sline, William Wallace. In addition special thanks goes to the Communications Processes Department of Carnegie-Mellon University. BIOGRAPHY W.E. Stanford, who has retired, served as a representative of the American Petroleum Institute lo the Steel Structures Painting Council Prior to his retirement he was a Sr Project Chemist in the Technology and Materials Department of Gulf Science and Technology Company, Pittsburgh, PA. He graduated from Kansas State College with a B.S in chemistry and attended the same school for graduate work. He has also attended other universities for SDecialized trainina in other materialsoriented fields. He provided technical assictake and counsel to strategy centers throughout Gulf Oil Corporation on corrosion control and protective coating materials. He was active in several professional societies and in corrosion control activities. --`,,,,`-`-`,,`,,`,`,,`--411 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERa17.4 93 m 8627940 0003859 597 9 CHAPTER 17.4 PAINTING CHEMICAL PLANTS by J. Roy Alien and David M. Metzger I. INTRODUCTION Chemical plant exposures represent a highly varied, and in most cases, demanding technical challenge to the design and application of effective protective coating systems. These exposures are characterized by a generally high level of chemical activity in the immediate environment and potential corrosivity to metal (carbon steel) substrates. Properly selected coating systems for use in chemical plants should minimize metal loss by protecting substrates from attack by an environment that may contain, for example, any of the following: Mineral acids Organic acids Alkalis Corrosive salts Solvents Gases Weather The wide variety of exposures, often combined within the same processing area or plant, necessitates proper selection of painting practices and systems. Such conditions have spurred the development of many specialized chemically resistant coatings, formulated for use in systems at general total dry film thicknesses of 7 mils (175pm) or greater. The recommended chemical plant painting concept involves a systems approach that combines the elements of material selection, surface preparation, application and inspection to produce the desired level of protection for structural steel and equipment in a corrosive environment. Following is a synopsis of current guidelines and practices recommended for painting metal surfaces in chemical plants. The systems and elements described should be regarded in the context of atmospheric exposure and resistance to chemical splashes, spills, and fumes only. Excluded from this discussion are linings or coatings intended for immersion service. They are covered elsewhere in Volume I. II. ECONOMICS OF PAINTING
Economic evaluation of maintenance practices, candidate coating systems and alternate materials of construction are key ingredients in the cost analysis of maintenance finishing. Further, reliable input is needed on coating performance, expected life of project, level of protection and appearance expected, and initial and continuing costs. The initial cost of painting alone should not be the overriding factor in the analysis of economic considerations. Rather, it is evaiuated in the context of continuing repair costs estimated to maintain a desired level of protection and appearance for a stated period of time at a minimum cost per sq. ft. per year (Figure 1). The key to sound long-term economics consists of adequate original painting followed by a continuing maintenance program. For example, painted steel surfaces in chemical plants should be inspected immediately and between 6 and 12 months after painting. At that time touchup repairs should be made to correct damage or defects in the original job. Establishing priorities and scheduling is very important. Touchup and repair or repainting at the right time, before excessive failure occurs, can provide substantial savings. Maintenance of painted steel surfaces should be executed before coating failure reaches the point where cleaning and priming more than twenty percent of the surface area would be required (Figure 2). Another rule-ofthumb is to re-paint before Rust Grade No. 8 of SSPC-Vis 2 is reached as outlined in SSPC-PA Guide 4. Not all painted surfaces in poor condition requiring complete cleaning, priming, and finishing should receive
top priority. Delaying some of these does not significantly increase the cost of repainting. A portion of the maintenance painting budget should be allocated for repair and maintenance of painted surface with less extensive failure. The objective is to maintain adequate protection and appearance at minimum average annual cost. 111. SURFACE PREPARATION While coating systems must meet certain requirements in the performance evaluation formula, surface preparation, representing a significant part of total coating system cost, is considered by many to be the single most important factor influencing performance. Since it is often in this area that applicators will attempt to save time and cost, surface preparation deserves close attention. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 412
SSPC CHAPTERxL7.4 93 m 8b27940 0003860 209 m --A-SSPC,SP2,ALKD,6 MILS A-16.5 c/sq.ft./yr, IB 14.5 c/sq.ft./yr. IÍ---BSSPC,SP6,ALK D(6MILS 3 *.*.. C-SSPC,SP-6, INORGANIC ZINC/ EPOXY(8 MILS J-CUMULAT --`,,,,`-`-`,,`,,`,`,,`--1VE I c 10.5$/sq.ft./yr. ................ 10.5 $/sq.ft./yr. COST 2 $/sQ.FT. 1-0 4 L - - Ir 0 ........................ 0 Id-td I -0 Non-metallic abrasive blast cleaning is considered In maintenance painting, wher e painting previously the best field surface preparation. There are situations in painted surfaces is
involved, careful consideration should which it is not practical, permissible, or economically ac-be given to deciding whether full or spot blasting should ceptable. However, from a costlperformance point of view, be specified. Factors influencing this judgment include it is more often justifiable to devise a means for making the extent and distrib ution of paint failure, previous surblasting feasible in chemical plants than for applications face preparation, typ e and condition of paint, and comin less severe environments. Chemical-resistant coatings patibility of a newly s pecified coating with the existing depend on adequate surface preparation to optimize their one. If paint failure i s as high as 50to 60percent of the sursystem performance properties. face, and especially if the steel has not been pr eviously How a surface is prepared depends on several fac-blast cleaned, full blasting is advisable. tors, among which are compatibility with the environment, Where paint failure is less than 50 percent of the surthe coating system to be used and, of course, economic face and the existing coa ting is sound and tight over considerations. There is a variety of methods and equip-previously blast cleaned steel, spot blasting is recomment available for surface preparation. Dry abrasive blast-mended. Except in cas es of highly corrosive-exposure, ing, wet blasting, water blasting, steam blasting, and high temperature or immer sion, blasting to a commercial power water cleaning are the most efficient methods. standard (SSPC-SP6)is the r ecommended surface preparaCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 413
SSPC CHAPTERxL7-4 73 FIGURE 2 Maintenance is being executed before coating failure on these tanks reaches the point which would require cleaning and priming of more than 20% of the total painted surface. tion for atmospheric exposures. Adequate and properly adjusted blasting equipment is necessary for efficient cleaning. Frequent blasting errors, which are detrimental to efficiency, include inadequate air pressure or volume at the nozzle and excessive abrasive flow rates. Another important factor is the abrasive used (type, particle size and shape). It should be clean, hard and of a particle size that will produce 1-2 mil (25-50pm) surface profile on the steel surface. If heavy, tight rust or thick paint is to be removed, a coarserabrasive with angular particles is suggested. When regulations or operating conditions prevent abrasive blast dust from being released into the atmosphere, wet blasting or high pressure water containing a pressureinjected abrasive should be considered. To limit flash rusting, inhibitors are available for addition to the water stream or to the surface after cleaning, but this treatment must be compatible with the primer to be used. When water-abrasive blasting is used as the only cleaning method, the rust inhibitor is promptly applied to the freshly blasted surface after cleaning. This cuts down consumption of the chemical inhibitor and improves its effectiveness. When surface or environmental factors prevent abrasive blasting, hand or power tool cleaning is often recommended. While these methods are sometimes necessary, experience has shown that they are not as effective as methods that create a higher level of surface cleanliness. For example, when hand or power cleaning is used, coating performance over chemically corroded steel is greatly reduced (Figure 3). These methods are adequately covered in SSPC specifications. Excessive power wire brushing can produce burnishing -a common mistake which, if left uncorrected, is detrimental to paint performance. Steam and pressure water cleaning, usually with the addition of cleaners or chemicals, are effective when surfaces are contaminated with alkali, acid, dirt or paint chalk. Acid cleaners, such as phosphoric acid, neutralizes alkaline contaminated surfaces. Detergents or alkaline cleaner additions neutralize acid contaminated surfaces. Steam and pressure water methods are frequently used in conjunction with other methods of surface preparation. These methods, with the addition of selected clean-
ers, effectively remove dirt, oil, grease, and paint chalk from metal surfaces. When cleaners or chemicals are added to the steam or water, the metal surface must be thoroughly rinsed with clean water to ensure proper adhesion. The effect of residual surface contaminants on the life expectancy of coating systems has been demonstrated.
Trace amounts of sulfur and chlorine compounds
remaining on the surface of chemically-exposed steel, even after stringent surface cleaning and abrasive blasting, can measurably degrade the performance of organic coatings. The use of these cleaners prior to hand or blastcleaning, frequently necessitated by the relatively high level of surface contamination, differentiates chemical from general industrial plant painting (Figure 4). IV. SELECTION OF CHEMICAL-RESISTANT COATING SYSTEMS Resistance to a variety of types and concentrations of chemical exposure and good overall durability are primary considerations in selection of a coating system for chemical plant service. Because they have a proven track record in chemical environments, several generic types of high performance coatings are being used in chemical plant maintenance and new construction painting: Chlorinated Rubbers Epoxies Polyurethanes Silicones (high temperature only, not highly corrosion resistant). Vinyls Zinc-rich (as primer) Combinations of these generic classifications are possible when primer and topcoat are incorporated into a system. The system choice depends on the type@) of chemical resistance desired, the relative importance of appearance and the quality of surface preparation needed before priming. Since conventional alkyds and most water-borne coatings are not as effective as those listed above in harsh chemical environments, they will not be discussed here for chemical plant application. However, they have been generally acceptable for use in the peripheral areas of chemical plants, such as tank farms, where severe
chemical exposure is not usually encountered. Future development of water-borne technology is expected to provide coatings that will more fully meet the demands of chemical plant exposures while providing environmentally acceptable levels of solvent emissions. Paint systems designed for chemical environments are generally applied at heavier total film thicknesses than those intended for milder exposures. Typically, for moderate to severe chemical exposure, a dry film thickness of 7.0 mils (175pm) or greater is required to counteract the efCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 414
SSPC CHAPTERsL7-4 93 8627940 O003862 081 = TABLE I RESISTANCE CHART Max. Cure Oxidizing Temp. Generic TvDe Mechanism Acid Acid Alkali Salt Solvent Weather (dry heat) Chlorinated Rubber solvent evap. VG VG G VG P G 150°F Epoxy (polyamide) chem. crosslinking E G E E VG G 250°F Polyurethane (aIipathic) chem. crosslinking VG G VG E VG E 250°F Silicone (Alum.) solventlheat P P F G F G 1000°F Vinyl solvent evap. E E VG E P VG 15OOF Zinc Rich Inorganic hydrolysis E' E* E* E E E 75OOF" Organic chem. crosslinking VG* VG* VG* VG VG VG 3OO0F'* Rating Scale: (E) Excellent -no effect, best selection where performance and appearance retent ion are desired. (VG) Very Good -no effect on performance, very little appearance degradation. little effect on performance, some appearance degradation. performance and appearance affected by exposure. not suitable, coating attacked. 'Results indicate zinc rich coating performance when topcoated. Use of these coa tings untopcoated in chemical environfects of the environments and the substrate roughness characteristics (blast profile). These systems generally include a primer, an intermediate and a topcoat, or a primer and a high-build topcoat to achieve desired film thickness, in Table 1 the relative strengths and weaknesses (resistance) of some generic classes of coating are indicated for various chemical exposures (including weather and temperature). The cure mechanism operative for each of these classifications is also shown. Generally, the type of exposure and surface characteristics govern selection of the primer and topcoat system. Component compatibility of a multicoat system is essential to achieve adequate performance. Compatibility can usually be assured by using the same generic types of coatings throughout the system. For example, the use of a polyamide epoxy enamel over a polyamide epoxy primer constitutes a compatible system, provided exposure criteria are met by the system. Under certain conditions, however, it is not practical to adhere to this guideline. For example, when painting hand-cleaned steel prior to exposure in a chemical environment, use of an alkyd primer may be warranted with characteristics providing good wetFIGURE 3 ting of the adhering rust and mill scale. Chemical The coating on the hand-cleaned and painted portion of this pipe (above weld) totally failed after two years of service in a chemical resistance Of the can then be achieved by
Diant. The coatina on the lower oortion which was sandblasted using a compatible intermediate and topcoat. Sufficient prior to being painted did not fa¡¡. drying time must be allowed between each coat. (G) Good (F) Fair (P) Poor ments is not recommended. **Limited by topcoat in the system. --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 415
SSPC CHAPTERaL7.4 93 8627940 0003863 TLB = FIGURE 4 The upper portions of the two panels were abrasive blast cleaned to white metal prior to 24 hours of outdoor exposure. Panel on the right was steel corroded in a chemical plant. Rusting was rapid and extensive on the corroded panel due to the presence of residual chemicals after blasting. Little rusting occurred on the new steel (on left). An effective guideline for primer selection for chemical environment is: if the steel surface to be painted (in a moderate-to-severe chemical environment) can be abrasive blast cleaned to SSPC-SP 6 commercial blast or better, the highest level of system performance can be obtained by using inorganic zinc-rich primers. While these primers must be topcoated when subject to chemical environments, their ability to be topcoated with a wide range of chemical-resistant finishes (e.g., epoxies, polyurethanes, vinyls, etc.) and the level of protection that they afford steel substrates make them sound economic choices. The galvanic protection that zinc-rich primers provide is generally not matched by organic coating alternatives and thus pays dividends in the extension of coating system life and reduction in the frequency and degree of re-priming and re-painting. Normally, thorough cleaning and application of chemical-resistant topcoats may be all that is required for system maintenance (Figures 5A and 5B). In maintenance applications, if the old coating system is not completely removed, compatibility with the previous paint system may be a deciding factor in system selection. In this situation, it may be necessary to use a special barrier coat to prevent lifting of the original film. Lifting can pose a problem when recoating alkyds or some chemical-resistant coatings, which dry by solvent evaporation. If the original topcoat is unknown, or if lifting is suspected, primers and new topcoats used for spot repair should first be patch-tested to ensure that lifting or attack of the old coating will not occur (See SSPC-PA Guide 4). One key to effective corrosion control through the use of high performance coating systems in harsh chemical environments is simplicity -keep the number of selected systems, adequate for the job, to a minimum. This reduces chances of failure due to confusion and misuse of systems or system components. Because the requirements for coating chemical plants are demanding, a specialist or reputable coatings supplier should be consulted prior to maintenance painting. Cooperation and consultation with a coatings manufacturer will help assure selection of an optimum system. An important element in selection of coating systems for corrosive environments is experience, which can be gained only over relatively long periods of time. Testing of proposed or candidate coating systems with anticipated
surface preparation on tests panels provides an important source of this experience. When panels are exposed to environmental conditions on test racks located at chemical plant sites, the results of controlled tests can be excellent real-time indicators of coating system performance. When panels are prepared, as in the accompanying photographs, performance can be objectively compared on flat surfaces, edges, and damaged (scribed) areas. This testing overcomes the limitations of laboratory evaluations as the ultimate test for prediction of field performance. V. APPLICATION The method of application affects the quality and FIGURE 5 New steel sandblasted, primed with inorganic zinc and finished (right) was sandb lasted and finished with an alkyd paint system. with a polyamide epoxy topcoat. No failure at scribe (rusting) Failure noted aft er six years chemical plant exposure. after six years chemical plant exposure (left). The new steel panel 416 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*L7=4 73 8627740 0003864 954 FIGURE 6 Roller application to this storage tank is the method of choice when circumstances dictate against overspray. economics of painting. Therefore, its selection should be based on the type, nature, and size of the surface to be painted; the application characteristics of the coating(s); and the location of the item or structure to be painted. Brush, roll, and spray are the most commonly used methods of application. Spraying usually results in lowest costs and highest application rates. Unless otherwise indicated, the general order of application preference is spray, roll, brush. Application rates usually decrease in this order. Higher production rates are possible with airless spray when compared to conventional air atomization spray. Spray application normally provides better film build on round edges than brushing. Regardless of which method is selected, film build on sharp edges requires great care and often additional coats. For proper spray application, the spray equipment must have adequate controls, be large enough for the job and capable of spraying the coating material. Information is available from reputable manufacturers of coating materials and spray equipment and from the chapter on paint application in this volume. Spraying should be done by qualified people who will execute proper spray technique to meet the specifications. When it is not possible to spray, a roller should be the second choice, especially for large surface areas. While application by spray or roller is preferred, brushing is often necessary as a complementary method. It serves well for cut-in, trim, and touch-up (Figure 6). Specifications for protective painting in chemical plants should clearly define the required film thickness and accepted methods of measurement. Adequate film thickness is necessary for hiding and protection. The application must provide desired film thickness, uniformity, and continuity. To this end, each coat in a paint system should be a different color than the preceding coat thickness less than the critical minimum, which varies depending on the type of coating and exposure, results in a drastic reduction in the protective life of a coating system. SSPC-PA 2 is a specification for measurement of dry film thickness. Careful inspection must be exercised throughout the application toensure that all specifications are met. FIGURE 7 Surface preparation (abrasive blasting) and painting of subassemblies on-site prior to installation reduces initial painting costs, improves quality of application and results in improved
system performance. --`,,,,`-`-`,,`,,`,`,,`--417 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERaL7-4 93 8627940 0003865 890 Environmental conditions, such as atmospheric temperature, substrate temperature, humidity, wind, precipitation, and chemical contamination, can have a significant effect on performance of a coating system. The desirable atmospheric temperature range for coating application is 60 to 90°F. Unless specifically formulated, coatings should not be applied when the atmospheric temperature is below 40°F (50°F for epoxy) or above 100°F. Temperatures below 45OF may retard curing or drying. High temperatures will accelerate both. Substrate temperatures above 100°F may also cause rapid solvent release from some coatings and result in bubbling and pinholing. Substrate temperature does not have much of an effect on spray application of slow drying materials. Relative humidity, substrate characteristics, and ambient temperatures all affect the application. To avoid condensation, most protective coatings should not be applied to steel unless the surface temperature is, and remains, at least 5 OF above the dew point. When materials containing solvents with high evaporation rates are sprayed, the material and surface temperatures may be reduced considerably. For example, if the temperature drops below the dew point, moisture condensation will occur on the surface and in the coating, affecting adhesion and subsequent film integrity. Relative humidity also affects drying and curing times of coatings. High humidity generally slows drying time for coatings that cure by air oxidation. High humidity accelerates, and a certain level may be required, curing certain types of polyurethanes and inorganic zinc coatings. Information on the effects of temperature and humidity and combinations thereof on drying and curing should be obtained from the coatings manufacturer. Coatings should not be applied outdoors when high winds can (a) carry dust, dirt, etc., which become embedded in the coating causing pinholes and poor appearance; (b) interefere with spray painting; (c) carry overspray to areas where it is not tolerable; or (d) cause dry overspray. Coatings should not be applied outdoors during precipitation or when it is imminent. In chemical atmospheres, the coating system should be completed within the shortest possible time, consistent with proper drying and curing of each coat, to avoid chemical contamination between coats. If contamination occurs, it should be removed, usually by washing with detergent and water followed by thorough rinsing. One means of specifying paint application in accordance with good practice is to cite SCPC-PA 1, Shop, Field and Maintenance Painting.
VI. NEW CONSTRUCTION PAINTING The easiest and best time for painting steel is at construction. Efforts to minimize capitalized costs and project budgets frequently compromise the quality of original coating systems. The quality of original painting has a lasting influence on performance and cost of subsequent maintenance painting, as well as on the life of the facility. As much cleaning, priming, and coating as practical should be done before installation. Cleaning, priming and sometimes applying the intermediate coat at the fabricator s shop or at the site before erection is sound practice. This practice is economical and provides the best application conditions. Proper care in handling during shipping and erection results in little touchup before the final coats are applied (Figure 7). Design has a significant influence on cost and performance. Protective coatings should be included as one factor in design considerations. Features such as back-toback angles, skip welds and inaccessible areas should be avoided. Vents and overflow arrangements should be located to minimize the effect on coated surfaces. It is difficult to obtain off-the-shelf items such as pumps and motors with chemical-resistant coating systems. Special coatings for these items are prohibitively expensive, and obtaining them unpainted may also be expensive. For critical exposures, it may be necessary to blast clean and paint these items. A compromise is to obtain the manufacturer s coating system with the best surface preparation offered and coat it with a compatible chemicalresistant finish or a barrier (tie) coat prior to topcoating. PROTECTION 1 U FIGURE 8 Unlike the chicken and the egg , proper protection provided by --`,,,,`-`-`,,`,,`,`,,`--painting has a definite beginning and end. All elements must work together to achieve this fragile balance. Failure of any one of these four elements results in a loss of corrosion protection. VII. SUMMARY The importance of specifying and using the proper paint system cannot be overemphasized. While initial expenditures for properly engineered, high performance coating systems may seem high, this investment pays off in considerably reduced long-term maintenance costs. Once the best decision has been made on selection of Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from
IHS 418
SSPC CHAPTER*L7-4 93 m 8627940 0003866 727 m the coating system, clearly detailed specifications are required to communicate and execute that decision. Painting system sDecifications. such as those of the SSPC. I -~ should indicate all of the following: Coating description, including product numbers or specificat ions; Surface preparation description; Special mixing andlor application instructions, application conditions; Minimum (maximum) dry film thickness per coat; Minimum (maximum) dry film thickness of total system. To be effective, detailed specifications should be supported by thorough inspection to ensure that ali elements of the coating system specification are followed. Many coating systems, properly selected and painstakingly specified, have prematurely failed because inadequate inspection permitted improper application (Figure 8). Specification and inspection should take safety into account. Worker protection during rigging, surface preparation, paint application and clean-up are paramount Any special precautions to be observed in operating or processing areas should be included in the specifications or should be a topic of discussion before placement of the painting contract. Painting a chernical J plant should always be considered from a Systems standpoint. Attention to all elements of the system provides the best opportunity for economical and effective long-term protection of steel. ACKNOWLEDGEMENT The authors and editors gratefully acknowledge the active participation of the following in the review process for this . chapter: Darre1 Campbell, T. ArCross, Randy Fuikerson, Marshall
McGee, John Montle, C.Munger, William Pearson and William Wallace. BIOGRAPHIES J. R. Allen has retired from E.I. du Pont de Nemours and Co., Inc. He served as a member of the Research Committee of the Steel Structure Painting Council. He graduated from the Georgia Institute of Technology in 1943 with a B.S. in Ceramic Engineering. After service in the US. Army, he joined the staff at the Engineering Research Laboratoryof du Pont and Co., Inc., where he was engaged in research and development of nonmetallic materials of construc :tion for chemical plants and eauiDment. From 1975 until his retirement, he worked with the Engineering Service Division as an engineering materials consultant, specializing in protective coatings and thermal insulation. David w. Metzger is a member of the SSPC Research Committee, He received his B.S. degree in Business Managet-f~entfrom Lehigh University in 1968. He joined DuPont that same year in the company,s Finishes Division of the Automotive Products Department. Since that time, he has held various technical sales and marketing positions, including Senior Product Specialist with Maintenance Finishes Sales. REFERENCES C. Calabrese and J. R. Allen, Surface Characterization of Atmospherically Corroded and Blast Cleaned Steel . Corrosion Vol. 34, No.10, October, 1978. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 419
SSPC CHAPTERrL7.5 93 8627940 0003867 663 m CHAPTER 17.5 PAINTING PULP AND PAPER MILLS by C.Edwin Wilkins and William F. Chandler This chapter provides the engineering and maintenance departments of pulp and paper mills with coating systems effective for construction and maintenance. Substantial monetary and productivity rewards are derived from a good coatings program. The coatings material and technology are available. The problem is how to combine available materials and technology into working protective coatings programs that provide corrosion protection, safety and appearance at the lowest cost. The results of ineffective programs are lower productivity and morale together with higher maintenance and replacement costs. I. SCOPE This chapter deals primarily with protection of mild steel, galvanized steel and other metallic and non-metallic substrates exposed to the corrosive environment of pulp and paper mills. For mills exposed to additional corrosive elements produced by neighboring plants, good protection can usually be attained by minor upward adjustments in system film thickness or by wider use of bleach area systems. Special attention is directed to the concept and implementation of the protective coatings program as it relates to construction and to maintenance. New facilities and additions are covered under New Construction. Work by plant painting crews and by outside painting contractors is covered under Maintenance. II. THE PROTECTIVE COATINGS PROGRAM A. MANAGEMENT SUPPORT NEEDED To be effective, the program for construction and maintenance needs to be professionally conceived and administered. It certainly needs management s support and interest. B. PROTECTIVE COATINGS COMMITTEE
While there are several ways of developing a sound protective coatings program, one choice is to assign authority and responsibility for the program to a Protective Coatings Committee headed by a qualified coatings engineer and made up of selected personnel from Engineering and Maintenance Departments. While the primary concern of this Committee will be maintenance coatings work, it can assist design engineers by providing information based on operating experience with protective --`,,,,`-`-`,,`,,`,`,,`--coatings. Following are some of the functions and responsibilities of the Protective Coatings Committee. 1. Corrosion Survey The purpose of the survey is to identify the surfaces to be coated, taking into consideration the following: Location Chemical nature of the environment Operating temperatures Practical surface preparation methods and materials Condition of existing coatings and their generic ~ composition (for maintenance painting) Safety requirements Physical factors involved such as abrasion resistance. 2. Selection of Coatings Systems Choice of exact coatings systems, including surface preparation, number of coats, film thickness, etc. for each substrate and exposure should be worked out through cooperation of the Committee with one or two selected coatings manufacturers or with the help of an independent coatings consultant. Also consider: Length of service Ease of maintenance Compatibility of selected coatings with any existing coatings (for maintenance painting) Conformance with applicable environmental regulations Special appearance requirements, e.g., color stability, chalk resistance. 3. Color Selection Here again, close cooperation with the coatings supplier is recommended for selection of colors. When selecting colors full consideration should be given to OSHAIANSI safety requirements and corporate color standards.
4. Specifications A vital connecting link between concept and finished work is the coatings specification. There are four basic types of specifications: new construction shop painting (see Appendix A), new construction field painting, contract maintenance Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 420
SSPC CHAPTER*L7-5 93 8627940 00038b8 5TT painting and maintenance painting by in-house crews. Each of these specifications vary somewhat in content, but should cover all or most of the following: Identification and location of project Scope of work -surfaces to be painted Services available, storage facilities, utilities, etc. Definitions Schedule of work Shipping instructions Work by others Specified systems and coating materials Surface preparation -Excellent surface preparation procedures are outlined by S.S.P.C. and should be referenced. The life of a coatings system is directly related to the degree of surface preparation. Application Pre-job conference and job standards -See Chapter XVII Introduction Inspection parameters, equipment and responsibility Special conditions 5. Inspection and Spot Repair There is no better way to insure cost efficiency of a coatings program than by instituting and maintaining a rigid program of inspection and spot repair. No matter how well a coatings job has been engineered and applied, its performance cannot be taken for granted. A systematic program of inspection and spot repair within six months of completion and every 18-24 months thereafter is good insurance. Very aggressive environments, such as bleach areas, may need inspections every 6 months. 6. Approval Final approval and acceptance of the coatings work is the responsibility of the Protective Coatings Committee or its representative. 7. Cost Estimates for Budgets Making realistic estimates of coating maintenance costs projected for the coming year is a proper responsibility of the Committee. 8. Cooperation with Design Engineers Based on close working experience with coatings performance in existing plants, the Committee can assist its own in-house engineering department or the contract design group by recommending coatings specifications for new construction.
9. Reports and Records Systematic reporting and recording of worker hours, materials, and unit costs for all coatings work in each area is of continuing help in planning and controlling costs of future work. 421 111. NEW CONSTRUCTION A. STRUCTURAL AND MISCELLANEOUS STEEL 1. The Case for Surface Preparation and MultiCoating in the Fabricator Shop Surface preparation of structural and most miscellaneous steel by efficient centrifugal blasting equipment and application of primer in fabricating shops earned early acceptance for new construction of pulp and paper mills. More recently, the benefits of adding a second, and in some cases, a third coat in the shop have been recognized. Per ton costs of multi-coating in the shop are substantially lower than in the field. Time and money are saved in surface preparation, application and inspection. Problems of intercoat contamination are practically eliminated, which is especially important for additions to operating plants. Cost differences bet ween b Iasting, priming and coating in the shop versus blasting and priming in the shop and finishing in the field can be readily established by taking alternate bids on each. 2. Advantages of Cleaning and Coating in the Fabricator Shop Advantages in the shop are as follows: a. Blasting is more uniform and less costly. b. There is less chance of contamination before priming or topcoating. c. Primer application is easier, more uniform and less costly. d. Intermediateltopcoat application is easier, more uniform and less costly. e. Inspection of surface preparation and coatings application is easier and more effective. f. No areas are inaccessible for painting. 3. Advantages at the Job Site a. Less painting to be done. b. Less conflict with other trades. c. Lower painting costs. d. Lower inspection costs. e. Higher probability of a more durable, longerlasting coatings system. 4. Multi-Coat Coatings Systems for Application in Fabricator Shop (Figure 1) Coatings systems that have been successfully
adapted for multi-coat work on structural and miscellaneous steel in fabricating shops include: Epoxy Zinc RichlHigh-Build Epoxy Inorganic Zinc RichlHigh-Build Epoxy In hi bi t ive EpoxylHig h-Build Epoxy Gloss seal coats of epoxy, vinyl or aliphatic polyurethane are often selected as a third coat for use in more aggressive environments, such as Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
bleach plants. Gloss epoxy seal coats can be applied in the fabricator shop. Vinyl seal coats are normally applied at the job site because of sensitivity to abrasion damage. FIGURE 1 Multi-coating in the fabrication shop. lhe conveyor at left brings the steel from the centrifugal blaster. Then the steel is loaded onto bucks by overhead crane. Courtesy Linc York B. SPECIFIC STRUCTURES (See Table ifor typical painting systems used on specific structures) 1. Field Erected Tanks Field erected tank sections should be blasted and exterior sides primed. When fabricating and coating tank sections in a shop, a weldable preconstruction primer should be applied. When tanks have been erected, bare steel exteriors and welds can be blasted and primed prior to application of a finish system. Interior steel tank surfaces are to be specifically treated after erection, depending upon use (Figure 2). 2. Steel Gratings Steel gratings are difficult to blast clean and costly to paint. Most new construction utilizes galvanized steel gratings, which can be degreased and acid etched prior to applying the selected coatings system. Gratings are best painted prior to erection. FRP grating is also finding use in the industry. No painting is required. 3. Handrails Aluminum or galvanized handrails are often used in new construction. Aluminum handrails are usually not painted. Galvanized handrails should be degreased and then acid etched or sweep blasted prior to coating. Some mills defer painting on new galvanized. 4. Concrete slab roof over wet end of machine For all surfaces except top surface, which gets roof coating, remove laitance by brush blasting or by acid etching (followed by a rinse); apply 4 mils D.F.T. of a high build, non-gloss epoxy. The above can be done most efficiently prior to erecting the slabs. If two coats are used, the 422 first coat is to be thinned for better penetration. Slab rebar should be galvanized or coated with an
inhibitive epoxy primer. 5. Salt Cake Silo (exterior) a. Shell -Use normal system for the environment, but add an extra gloss coat to bring the total D.F.T. to 10 mils. b. Flat Roof -Use inhibitive epoxy primer and topcoat with 16 mils D.F.T. of coal tar epoxy. Special attention should be given to welds, edges, bolts and other sharp surfaces. 6. Conveyors Back-to-back angle braces, skip welds and difficult-to-reach areas are hard to protect. Backto-back angle braces should be sealed. Open welds should be caulked. Three coats, including a zinc rich primer, should be used to develop adequate thickness. lt is advisable to have idler arms galvanized. 7. Chip Blow Line A white or light colored finish coat reduces pipe and air temperature. 8. Storage Tanks for Hot Liquor, Etc. (exterior) When expensive insulation is not justified, a corkfilled asphalt mastic may be used. This should be applied over SSPC-SP 6 blasted steel and primed with 2 mils D.F.T. of an inhibitive epoxy primer to minimize underfilm corrosion. The flat roof of the tank should receive one coat of coal tar epoxy at 12-16 mils D.F.T. Handrails and ladders should also receive 12-16 mils D.F.T. of coal tar epoxy. It is good practice to blast and prime the entire tank and then apply the finish coats. 9. Concrete Pipe and Pits Carrying Effluent to Clarifier, Etc. Severe corrosion andior erosion can be controlled by applying 18-20 mils D.F.T. of coal tar epoxy. The concrete must be sweep blasted and a coal tar epoxy primer applied prior to application of the coal tar epoxy topcoat. 1o. Steel Stacks -Maximum Operating Temperature of 7OOOF All surfaces must be sandblasted to SSPC-SP 5. Apply 1.5-3.0 mils D.F.T. of an inorganic zinc rich coating. An unmodified heat cured silicone aluminum finish may be applied, if desired, at 1.5 mils D.F.T. C. NEW EQUIPMENT The protective coatings system applied on original equipment may not be suitable for service in aggressive environments. When ordering equipment for critical or severely exposed areas, it is good to request a description of the coatings system the manufacturer intends to supply. If this system is not adequate for the projected service, request a cost estimate for special finishing to conform
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SSPC CHAPTER*17*5 73 W 8627740 0003870 158 W TABLE I TYPICAL PAINTING SYSTEMS FOR PULP & PAPER MILLS GENERAL PLANT AREA Wood Preparation Digester Area Liquor Evaporators 81 Waste Handling & Washing IL Preparation & Bleach Plant & Recovery Process Water Treatm ent SURFACE TO BE COATED Chipping Screening Storage Pulp Storage Boilers Plant Plant Steel or Iron Submit Details 3.2or Structural Steel 3.1 (1) 1.2 1.1 3.3 1.1 1.1 1.1 Convevor Steel 3.1II1 1.2 3.2or Carbon Steel Pipe 3.1 (1) 1.2 1.1 3.3 1.1 1.1 1.1 Steel Tanks (Lining) 36 34 11 or 11 (Hot) Steel Tanks (Outside) 1.2 3 5 (3) 1 4 (Cold) 11 Stacks, Ducts, Breechings, Kiln When specification detail furnished -Inorganic Z inc with Silicone Topcoat Optional will be used if painting required. Handrails B Gratings (7) 1.4 1.4 1.4 1.4 1.4 1.4 1.4 Pipe Hangers: Brackets 3.1 (I) 1.2 1.1 1.4 1.1 1.1 1.1 Steel Doors, Windows, Frames 1.2 1.2 1.2 1.2 1.2 1.1 1.2 Machinery; Equipment B Motors 1.2 1.2 1.2 1.2 1.1 1.2 Paper Machine -Large Process Equipment 1.2 1.2 3.3 1.2(A) 1.1 1.2 Wood Surfaces 2.2 Masonry Surfaces Exterior Concrete Block 4.1 4.1 4.1 Interior Concrete Block 4.2IAì 4.2 IA) 4.2 Exterior Concrete (Dry) Interior Concrete (Dry) Concrete Basin Concrete (Weti 5.3 5.2 3.4 Concrete Floors (Wet-Chemical) 5.3 5.3 5.3 5.3 5.3 Brick, Plaster, Stucco
3.4 3.4 3.4 3.4 3.4 3.4 3.4 Pump & Equipment Bases (Wet) Stock Preparation 1.1 1.1 1.1 1.4 1.1 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS--`,,,,`-`-`,,`,,`,`,,`--Shops, Warehouse PAPER MACHINE BUILDING & Maintenance Finish Goods -Control Rooms Administration Areas Roll Finishing Stores Change Houses Office Areas Power Plant Steel or Iron 2.1 or 1.1 1.1 1.1 (2) 1.1 (2) 2.3 1.1 Structural Steel 1.1 1.1 1.2 Conveyor Steel 2.1 or 1 .I 1.1 1.1 2.3 1.1 Carbon Steel Pipe Steel Tanks (Lining) 3.6 Steei Tanks (Outside) Stacks, Ducts, Breechings. Kiln 1.4 1.4 1.4 1.4 1.4 1.4 Handrails B Gratinas 2.1or 6.1.1 1.1 1.1 1.1 2.3 1.3 Pipe Hangers, Brackets 423
SSPC CHAPTER*L7=5 8b2ïîYO 0003871 ow m TABLE 1 (Continued) TYPICAL PAINTING SYSTEMS FOR PULP & PAPER MILLS GENERAL PLANT AREA Shops, Warehouse PAPER MACHINE BUILDING 8 Maintenance Finish Goods -Control Rooms Administration Areas Stock Preparation Roll Finishing Stores Change Houses Ollice Areas Power P lant 2.1 or 1.1 1.1 1.1 1.1 1.1 2.3 1.3 Steel Doors, Windows, Frames 2.1 or 1.1 1.1 1.1 1.1 1.1 2.3 1.3 Machinery; Equipment & Motors 1.1 1.1 1.1 1.1 Paper Machine -Large Process Equipment 6.2.2 2.2 2.2 2.2 Floors 6.7.1 (4) Wood Surfaces Masonrv Surfaces 6.4.1 4.1 4.1 4.1 4.1 Specify Specify Exterior Concrete Block ~ ~~ 641 42 42 41 42 when detail is when detail is interior Concrete Block 42 available from available from Exterior Concrete (Dry) 4.2 architect. architect. Interior Concrete (Dry) 5.2 5.2 Concrete (Wet) 5.3 5.3 (6) 5.3 Concrete Floors (Wet-Chemical) 5.1 5.1 Brick, Plaster, Stucco 3.4 5.3 Pump & Equipment Bases (Wet) STEEL System 3.3 (A) CONCRETE System 1.1 1 CI.Vinyl Primer 1 ct. High Build Vinyl Coat System 5.1 1 ct. Epoxy-Polyamide Zinc Rich 1 ct. Vinyl Seal Coat 2 cts. Acrylic Latex Mason ry Coating 1 ct. Epoxy-Polyamide High Build System 3.4 System 5.2 System 1.1 (A) 2 cts. Coal Tar Epoxy Coaling 2 cts. Chlorinated Rubber High Buil d 1 CI.Inorganic Zinc Rich 1 ci. Epoxy-Polyamide High Build System 3.5 System 5.3 Syrtm 1.2 1 ct. Epoxy-Polyamide Zinc Rich 1 ct. Bituminous 1 CI.Epoxy-Polyamide Clear 1 CI.Epoxy-Polyamide Clear 1 ct. Epoxy-Polyamide Primer 2 cts. Epoxy-Polyamide Finish System 3.6 System 5.3 (A) System 1.2 (A) 1 ct. Epoxy-Polyamide Tank Lining Primer 1 ct. Epoxy-Polyamide Tank Lining 1 ct. Epoxy-Polyamine Concrete Sealer 1 cl. Epoxy-Polyamine Surfacer
1ct. Epoxy-Polyamide Primer 1 ct. Epoxy-Polyamide Tank Lining (Opt.) 1 ct. Epoxy -Polyamine Finish (opt.) 1 ci. Epoxy-Polyamide High Build 1 ct. Epoxy-Polyamide Gloss System 6.1 System 1.3 WOOD White or Yellow Traffic Marking Paint 1ct. EpoxyEster Primer System 6.2.1 System 7.1 2 cts. Epoxy-Ester Finish System 1.4 1ct. Alkyd Primer 2 cts. Alkyd Enamel 1 cl. Epoxy-Polyamide Clear 2 cts. Moisture Cure Polyurethane Varnish 1 ct. Epoxy.Polyamide Primer 1 ct. EpoxyPolyamide Semi-Gloss 1 cl. Aliphatic Urethane Gloss System 2.2 1ct. Alkyd Undercoat 2 CIS.Epoxy Ester Enamel FOOTNOTES System 3.1 1 CI.Epoxy-Polyamide Zinc Rich 1 CI.Epoxy-Polyamide High Build 1 CI.Epoxy-Polyamide Finish System 6.2.3 1ct. Alkyd Primer 1 ct. Acrylic Latex Exterior Paint (I) Epoxy-Polyamide Finish for easy repair of damage. (2) Structural steel may be separated by job lot for mild areas -Interior only. System 3.1 (A) MASONRY (3) Insulation coating depending on re 1 CI.Inorganic Zinc Rich quirements based on heat, location, 1 cl. Epoxy-Polyamide High Build 1 CI.Epoxy-Polyamide Finish System 4.1 1ct. Acrylic Latex Concrete Filler and color specification. (4) Sand between coats. System 3.2 1 ci. Inorganic Zinc Rich 1 ct. Wash Primer or Tie Coat 1 ct. High Build Vinyl 2 cts. Acrylic Latex Masonry Coating System 4.2 1 ct. Acrylic Latex Concrete Filler 2 CIS.Epoxy Ester Enamel (5) Where equipment is primed with epoxy primer omit Universal Primer from system. (6) Apply under Paper Machine to permit cleaning and waste removal. System 3.3 1 CI.Universal Primer 1 ct. High Build Vinyl Coat 1 ct. Vinyl Seal Coat System 4.2 (A) 1 ct. Epoxy-Ester Cementitious Filler 1ct. Epoxy TiieLike Coating 1 ct. Epoxy TileLike Coating
(7) If galvanized. substitute acid etch for primer. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*17*5 93 8627940 0003872 T20 with your system. If this cost is too high, as it may w.ell be, the only alternative is to have the equipment delivered and then finished according to your own system. IV. MAINTENANCE PAINTING PROGRAM While protection needs are essentially the same for construction and maintenance, some variances in specifications and procedures are necessary. A. VARIANCES 1. Surface Preparation It is often difficult to isolate selected areas so sandblasting can be done without danger to personnel or equipment. Yet there is no adequate substitute for sandblasting. Even so, blasting is seldom used inside machine buildings. In some cases, areas andlor equipment can be sectioned off with polyethylene so steel can be blasted. In others, the compromise of hand-tool cleaning with power wire brush, disk sander, needle gun or other similar equipment can suffice. Careful use of power wire brushes and needle guns may be the most effective surface preparation short of sand blasting. 2. Drying the cleaned steel is essential but can be difficult Heat lamps andlor hot air blowers can be useful. Do not use oil-fired heaters. 3. Protection of edges is extremely important Pulp and paper mills are ever more relying on epoxy zinc rich primers, intermediates and finish coats because of their superior edge build, corrosion resistance and fast recoat characteristics. Even with the best available materials, painters need to pay special attention to application on edges, welds and irregular shapes. An additional brush applied coat of the finish coat improves edge protection. 4. lntercoat contamination Salt cake and other fallout can cause premature paint failures. To combat this, maintenance coating systems for pulp and paper mills should perform well when applied almost wet-on-wet. Some evaporation of solvent is necessary before the succeeding coat is applied. Complete drying should not be a requirement except in special cases. The heavier the rate of salt cake fallout , the sooner the entire system should be applied. This consideration is important when planning and scheduling work. In selecting specific coatings materials, credit should be given to those demonstrating superior film and
edge build characteristics and fast recoatability. B. MAINTENANCE BY PLANT PERSONNEL Suggestions for increasing effectiveness of the protective coatings program: 1. Awareness From top management to the newest painter, everyone must feel that the coatings program is important to the operation and profitability of the mill. Management s skill in organizing and motivating a competent plant painting crew pays substantial dividends in efficiency. 2. Training A training program should be established for everyone involved, covering instructions on coatings, rigging, equipment, application and inspection. Training programs should be set up by the Committee with cooperation from the technical departments of coatings and equipment suppliers or by a consultant. The training sessions should include lecture, discussion and onthe-job demonstrations. All persons involved should understand what is expected of them, and why their work is important and be challenged to develop a sense of accomplishment, professional competency and pride in the finished work. 3. Specifications Should be well defined, measureable and enforced. 4. Personnel Capable and motivated planners, supervisors, and inspectors should be designated by and report to the Maintenance Coatings Committee. They should spend substantial time where the work is being done and require that the work meets specifications. 5. Records An effective system should be created for recording the work done and detailing the area, workerhours, materials, equipment and the application conditions. 6. Inspection A systematic program of inspection and spot repair should be instituted and maintained by the Protective Coatings Committee. V. MAINTENANCE BY OUTSIDE CONTRACTOR The Protective Coatings Committee is responsible for coordinating work with outside contractors. Many mills rely on outside contractors for jobs requiring critical rigging and for tight schedule work during shutdowns. The follow-
ing areas should be considered: i.Planning Carefully implement the work with good specificaCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 425
SSPC CHAPTER*L7.5 93 8b27940 0003873 967 FIGURE 2 Coatings for structural and miscellaneous steel. Usually struc- can be blasted a nd coated more successfully after erection. tural steel can be coated successfully and at lower cost (all coats) Courtesy of Linc York in the fabricator s shop. Tanks -insulated and non-insulated tions, time and safety requirements and a descrip- the owner, and the contractor should work tion of possible conflicts with plant operating re- together in a cooperative, p rofessional relationquirements. ship for the best possible finished jobs. 2. Screening 8. Conclusion Screen and invite no more than three or four At the conclusion of all major jobs by plant or qualified contractors to bid based on their record contract personnel a program of inspection and for integrity, professional competence, reliability spot repair will serve as a strong preventive and financial stability. maintenance measure. 3. Bids Arrange for pre-bid meetings (preferably with one VI. SUMMARY bidder at a time) so all bidders can ask questions. Rewards for conceiving, impl ementing and adArrange to have necessary drawings available. A ministering an effective and pro fessional protective representative of the Committee, the coatings coatings program are substantial i n terms of yearly costs supplier and contractor should inspect areas to and production continuity. Colla teral benefits include imbe coated. Bidders should be made aware of the proved working conditions, employ ee safety, morale and owner s concern for the work and the owner s in- enhanced public image. The stakes a re high. Affirmative spection plans. management action is recommended. 4. Testing If blasting is a major requirement, encourage bid- APPENDIX: ders to test blast a representative area to establish the rate of production possible and TYPICAL COATING REQUIREMENTS FOR understand owner s interpretation of specifica-STRUCTURAL AND MISCELLANEOUS STEEL COATED AT FABRICATOR SHOP* tions. 5. Quality Scope At start-up of work, a job standard for quality ac- These requirements detail th e surface preparation, ceptance should be set, with a representative of coating, and handling of struct ural and miscellaneous the owner and of the materials supplier present. steel in the fabricator shop. T hese specifications cover (See chapter on Job Standards.) service at operating temperatures up to 200°F. Als o includ-
6. Selection ed are details on inspection, transfer of coated steel and Some owners select and supply coatings on the touch-up and repair in the field. premise that by doing so they are more likely to get the specified coatings thicknesses. 7. Cooperation Alternatively, application may be based upon SSPC-PA 1 Shop, The Protective Coatings Committee, representing Field and Maintenance Painting . Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 426
SSPC CHAPTER*L7.5 73 8b27740 0003874 8T3 FIGURE 3 Transfer and handling of coated steel. The proper use of dunnage helps minimize damage to coatings in transit. Intent It is the intent of this specification to prescribe first-class workmanship in all phases of coatings work. The following important details shall be considered as a part of the specif ¡cat ions: The use of cutting oils shall be such that a minimum of oil is deposited on the steel so as to minimize solvent cleaning. All contact surfaces connected by bolts shall be blasted and primed before being shop-bolted. Faying surfaces should be primed but not topcoated. Most inorganic zinc rich coatings are suitable for use on faying surfaces. Where mild steel bolting (not cadium-plated or galvanized) is used in the shop, the boltheads and nuts shall be blasted and coated. The cleaning of abrasive before reuse shall be such that the blasted steel is free of smudge. All back-to-back angles shall be blasted and primed before assembly or designed out if possible. Weld spatter shall be removed before priming. Slivers and laminations shall be ground smooth before priming. All sharp, rough, or burred edges shall be ground round. All abrasive shall be removed before priming. No bleed through materials shall be used for ID markings. Bucks shall be cleaned of foreign paintslcoatings so as to avoid contamination of the coating system. Paint hoses shall be cleaned of dried paint to avoid loose paint falling into wet coatings. Special care shall be used by painters to assure proper thickness on flanges -inside and out. If identification tags are welded to the steel, the weld shall be continuous to avoid corrosion underneath the tags. Dunnage shall be used carefully to minimize damage to coatings in loadinglshippinglunloading. Use of nylon slings will minimize coatings damage. At the jobsite the steel shall be unloaded so as to minimize coating damage. In stacking the steel at the jobsite, ample dunnage shall be used. Again, nylon slings will minimize coatings damage. Surface Preparation All surfaces shall be blasted so as to meet the SSPC-SP 6 Commercial standard or better.
All blasted steel shall be coated within 10 hours of blasting and before there is visible rusting. Coatings Observe minimum and maximum limits for Dry Film Thickness (DFT). Five readings out of 50, at least 6 inches apart, on one piece of steel will be the basis of requiring an additional coat (if below minimum) or reblasting and recoating (if above maximum).* All areas where the primer thickness is below 2.0 mils or above 5 mils shall be corrected. All areas where the two-coat system is below 5 mils or above 12 mils shall be corrected. Surface temperature of steel to be coated shall be 50°F minimum and at least 5°F above wet bulb air temperature reading. Coatings can be applied by airless or conventional spray equipment. System No. 1 Average DFT Mils* Primer -Epoxy Zinc Rich 2.5 Topcoat -High Build Epoxy -5.0 7.5 System No. 2 Primer -Inorganic Zinc Rich 2.5 Topcoat -High Build Epoxy -5.0 7.5 System No. 3 Primer -Inhibitive Epoxy PoIyam ide 2.5 Topcoat -High Build Epoxy 5.0 7.5 Primer: DFT Mils Minimum DFT 2.0 Maximum DFT 5.0 Full System -2 Coats: Minimum DFT 6.5 Maximum DFT 12.0 Allow the primer to cure prior to application of second coat until it remains intact using the following test. Press thumb onto coating using 10 pounds of pressure and rotate 45 .If primer is not damaged, proceed with topcoating. Allow coatings system to dry prior to handling until there is no damage to substrate when applying moderate cutting pressure with the thumbnail. *Alternate -Specify SSPC-PA 2 Measurement of Dry Paint Thickness with Magnetic Gages . **Thickness in accordance with manufacturer s recommendations. Many recommendations, including those of SSPC, for example, specify 3.0 f 0.5 mils for zinc-rich primers. Measure according to SSPC-PA 2 unless otherwise specified. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 427
SSPC CHAPTER*L7.5 93 = 8627940 0003875 73T BIOGRAPHY Inspection Adequate inspection of surface preparation and coatings application should be provided during the job. Full-time inspection isdesirable, but with intermittent work schedules, this is not always possible. Full-time inspection is needed at the job start and until work is progressing smoothly, then as required to assure specifications are being met. Transfer of Coated Steel (Figure 3) Handling, shipping and unloading procedures, if not properly executed, can seriously reduce the effectiveness of even the best high performance coating systems. Coated members must be handled with care to avoid damaging the coating system -particularly the edges. Field Touch-Up of Coatings Damaged in Loadinglirection All areas damaged to bare metal shall be prepared in accordance with SSPC-SP3. Spot prime all cleaned areas with Epoxy Zinc-Rich Primer to 2% mils DFT. Dry to thumb-shear hardness. Apply High Build Epoxy intermediate coat to primed areas: 7 mils DFT (primer + intermediate coat). Dry to thumb-shear hardness. Apply Gloss Epoxy Topcoat if specified, to total DFT of 9 mils, (2 mils DFT of topcoat). System DFT Mils Minimum 8.5 Maximum 12.0 Once steel has been erected, damage from handling and welding should be repaired as soon as possible. The sooner the damaged areas are corrected, the less surface preparation will be required. Field touch-up and repair procedure should be part of overall specification along with a clear definition of exactly whose responsibility it is to perform the touch-up and repair. ACKNOWLEDGEMENT Special assistance in the preparation of this chapter was provided by Linc A. York. The authors and editors gratefully acknowledge the active participation of the following in the review process for this chapter: Jim Baker, Noel Duvic, Randy Fulkerson, Lewis Gleekman, Marshall McGee, John Montle, John Perchall, Dave Roberson, L.M. Sherman, Bill Wallace, J.N. White. C. Edwin Wilkins has a B.S. in
Chemistry from the University of North Carolina, Chapel Hill. Until his retirement, his entire business career (42 years) was concerned with high-performance coatings, the first 14 years as a laboratory chemist. He has performed technical service in most of the United States, also in South America, Europe, and Near and Far East. For 27 years he was involved in protective coatings salesíservice with Mobil Chemical. After 1972 he served as Technical Sales Representative with Porter Coatings, Division of Porter Paint Co. He was a long-time member of the Technical Association of the Pulp & PaperIndustry, the N ational Association of Corrosion Engineers, the American Chemical Society and active on many committees. William F. Chandler -A biographical sketch and portrait of William F. Chandler can be found at the end of Chapter 17.0. REFERENCES Paul E. Weaver, Industrial Maintenance Painting: National Association of Corrosion Engineers, Houston, Texas. 1976 NACE Standard RP-01-78. Design, Fabrication, and Finish of Metal Tanks and Vessels, 1977 L. W. Gleekman, Preparation, Application, and Inspection (P-A-1) for Coatings Systems, Pulp and Paper Industry Corrosion Problems: NACE, 1974 Martinson and Sisler, industrial Painting -The Engineering Approach, Reinhold Publishing Company, 1961 Economics of Chemical Plant Maintenance Painting, NACE Publication 6D461. National Association of Corrosion Engineers, P.O. Box 218340, Houston, TX 77218-8340. Industrial Maintenance Painting Program,
NACE Publication
6D160. Contract and Plant Force Painting: Advantages and Disadvantages, NACE Publication 6D168. Industrial Painter Education, NACE Publication 6D361. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 428
SSPC CHAPTERkL7.b 93 8627940 O003876 b7b = CHAPTER 17.6 PAINTING FOOD PLANTS by Steven L. Schmidt Food processing plants are primarily concerned with converting, producing, packaging and preserving edible foods. There are hundreds of types of food processing plants -beverage, brewing, distilling, canning, dairy, beef and poultry packing, bakeries, flour mills, grain storage and many others. This discussion, therefore, concerns painting food processing plants from a condition and environment standpoint rather than from the standpoint of specific products and processes. New construction and maintenance painting are included as well as coatings selection, surface preparation, application, inspection and touch-up and repair. Coatings must be resistant to physical, bacterial and chemical exposures including varying levels of moisture, condensation, steam, mold growth, organic wastes, cleaning solutions and abrasion. Floors, walls and machinery are subject to chemical and moisture attack and usually abrasion. Many areas are wet and warm while others are cold and damp. Some may cycle from hot to cold causing condensation and also exerting physical stress on protective coatings and their underlying substrates. Exterior surfaces are subject to the hazards of the weather as well as the destructive effects of ultra-violet light on protective coatings. One of the most common problems in food processing plants is the growth of mold, mildew and other fungi. These air-borne spores multiply and feed on food particles, attaching themselves to a surface. They usually spread and can actually digest coatings with a free oil nature. Therefore, alkyd and epoxy ester coatings for use in food plants should contain effective and approved fungicides and bactericides. Ideally, a food plant coating would be USDAIFDA approved, hard, tough, impervious to water vapor, resistant to a wide variety of acids and alkalis, and prohibit the growth of mold, fungi and mildew. It would be a self-priming, highbuild, high-gloss finish that could be brushed, rolled or sprayed in a variety of temoeratures over steel, concrete, block, aluminum, galvanized metal and any other number of substrates. It would withstand high temperature, caustic rinses and be available in hundreds of decorator colors while possessing unlimited gloss and color retention when exposed to ultra-violet light. Of course, no such miracle coating exists. A coatings
specification for a new food processing plant may call for six or more different generic types of coatings and several types within each generic classification. There is no place for lead, mercury or any other toxic pigmentation in food plant coatings. The subject of USDA, FDA and other regulations will be dealt with in some detail later. With the conditions prevalent in most food processing plants, only the best high performance coatings stand any chance of long-term survival and resultant per-squarefoot-per-year cost efficiency. Since coatings material costs are usually less than one-fourth of the total painting cost, it is essential to go first class . The design or maintenance engineer who approaches protection and sanitary maintenance with cost cutting in mind does so at the risk of classical penny wise, pound foolish results. I. NEW CONSTRUCTION A. DESIGN CONSIDERATIONS FOR NEW PLANTS A universally accepted objective of food plant design is to assure economical, sanitary maintenance. The ideal food processing facility would be constructed completely of corrosion-resistant materials with a minimum of cracks, edges, corners and inaccessible areas. Plant sanitation could be easily performed with no adverse effects on the appearance of structural integrity of the facility. This plant does not exist because it would be prohibitively expensive and time-consuming to build. But many things can be done with common materials of construction to design plants that are easy and economical to maintain. Some of these are Design the plant to accommodate the process and afford ease of access for maintenance and cleaning; Avoid edges and crevices and design for smooth, pin-hole free surfaces in all process areas; Provide ample drains with sloped floors to permit rapid removal of wastes and wash water; . Avoid bar joist and deck construction in process areas; Avoid materials that have poor moisture A separate treatment of painting food plants, written by Harry Howard and emphasizing flow charts of process areas, is available through SSPC. 429 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from
IHS
SSPC CHAPTER*L7.6 93 W 8627940 0003877 502 W FIGURE 1 Processing room with high moisture content in the air is coated with a water-based epoxy system. Courtesy of Carboline Company resistance (drywall, plaster, plywood, etc.) in process areas; Enclose structural steel when possible; Use high-quality, chemical, abrasion and moisture resistant protective coatings for all steel and concrete in process areas; and Comply with FDA, USDA, OSHA, state and local regulations. Proper design and use of high-performance coatings go a long way toward producing the ideal plant -one that is functionally efficient and easy to maintain. There is only one time to achieve this condition: when the plant is constructed. This requires extensive study and careful selection of construction materials. These in turn must be woven into the design with an eye towards corrosion control, sanitation and plant maintenance. These steps should lead to the generation of tight, well-written specifications. The work must follow specifications under tight inspection before the new plant is accepted by the owner. With such a conscientiously designed and built facility, the maintenance engineer stands an excellent chance of controlling maintenance costs. Unfortunately, not enough projects go this way from start to finish. B. SPECIFICATION FOR STRUCTURAL STEEL Whether steel is shop or field painted, or both, a detailed specification is necessary to insure maximum performance of the coatings system. 1. Shop Painting Specifications for shop painting must detail surface preparation, coating and handling of the steel. Inspection, transfer and field touch-up should also be explained in detail. The following items should be included in the specification for shop painting: a.The use of cutting oils should be kept to a minimum and grease and oils removed from steel before blasting. b. All contact surfaces connected by bolts should be blasted and primed before being shop bolted. Faying surfaces should be primed with zinc-rich primer but not topcoated. Where steel bolting is used in the shop, the boltheads and nuts should be blasted.
c. All abrasives should be kept clean. d. Back-to-back angles should be designed out or at least blasted and primed prior to assembly. e. Weld spatter should be removed before priming. f. Slivers and laminations should be ground smooth before priming. g.All sharp, rough or burred edges should be ground smooth before blasting. h. All abrasives must be removed before priming. i. Painting bucks and paint hoses must be kept clean to minimize contamination. j. Welded identification tags should be continuously welded to avoid corrosion underneath the tags. k. All blasted steel should be primed within 10 hours of blasting and before there is visible rusting. I. Dunnage should be used carefully to minimize damage to coatings in loading, shipping and unloading. Use of non-metallic slings will minimize damage to coatings. m.At the job site, the steel should be unloaded carefully to minimize damage. The steel should be stacked off the ground, and ample dunnage should be used. n. Primers and topcoats should be applied in strict accordance with manufacturer s instructions. If the job calls for a second coat in the shop, application details should be spelled out. These include mixing, application and temperature parameters. The specifier should provide a table for film thickness, time intervals between coats and all inspection procedures and handling times. A job standard should be established prior to beginning to identify minimum acceptable standards for surface preparation, application, film build and final appearance. 2. Field Topcoating A separate specification is required for field topcoating work that takes place after erection of the steel. Careful inspection of the steel is necessary to determine surfaces requiring touch-up painting. Washing may be required to remove dirt and contamination. Power tool cleaning (SSPC-SP 3) Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 430
SSPC CHAPTER*Lï-b 93 m 8627940 0003878 449 m FIGURE 2 The walls in this cold meat storage room are held at 45-48OFyear round. Resurfacing with a water-based epoxy system is now a routine matter every four years or more, whereas previously the room was repainted every two years. Courtesy of Carboline Company followed by touch-up with polyamide epoxy rustinhibitive primer and finish coat works well. The polyamide epoxy primer is compatible with epoxy, urethane and acrylic finish coats. C. COATING SYSTEMS BY SUBSTRATES 1. Structural Steel -Interior Process Areas a. Zinc-Rich Primers -In most cases the logical choice for protection of structural steel is a zincrich primer with appropriate topcoat(s). This may be achieved in several ways: Method One: Shop prime, Field topcoat Method Two: Field prime, Field topcoat Method Three: Shop prime, Shop topcoat, Field touch-up The price depends upon many factors such as job location, shop location, amount of fabrication and size of plant. If Method Three is chosen, the primer and top coat are applied in the fabrication shop; the coated steel is shipped to the job site and erected, and bolts and damaged areas touched up. Method Three saves 10-40% over Method Two and makes sense even if a third coat is to be field applied. If only two coats are specified, Method One is less expensive and a better method. It is also better because uniform appearance of the finish coat is assured. With the three-coat systems, Method Three should be specified with the third coat field applied after proper touch-up has been completed. Considerable cost savings and higher quality work results. Care must be exercised in selecting two-coat shop systems because not all coatings manufacturers can supply them. Often two coats do not provide adequate protection. b. Top Coats -In addition to the polyamide and polyamine epoxy finish coats, several other generic types work well in food processing plants.
Aliphatic urethane, like polyamine epoxy, provides extra toughness and chemical resistance for aggressive areas and is usually of very high gloss. It does not yellow like the epoxy coatings and has better caustic resistance than epoxy polyester. Acrylic-epoxy is recommended in place of the solvent-based polyamide epoxy where a waterreducible, low-odor coating is needed. It performs in a manner equivalent to solvent-based polyamide epoxy once fully cured. This topcoat is not suited for humid areas. Gloss epoxy polyester coatings (catalyzed, twocomponent and not to be confused with epoxy ester) may be selected if a white finish is needed. Unlike epoxies, it does not yellow with age. Do not use in areas where caustic is present because it has poor caustic resistance. All of the above finish coats require a minimum of 50°F (10°C) to achieve cure except the aliphatic urethane which may be applied at temperatures down to 35°F (2°C). 2. Galvanized Metal Decking Metal decking can be very difficult to coat successfully. a. Factory finishing -The first recommendation is to specify the metal decking to be galvanized and factory finished with baked-on coating suited to the service area. This requires careful handling during transportation and erection. Any damage can be spot primed and touched up. 6. Field finishing -The galvanized decking should be specified to be phosphatized (preetched) or wash-prime treated by the fabricator. After erection it should be thoroughly cleaned and finished with 4.0-6.0 D.F.T. semi-gloss polyamide epoxy (Appendix B, #D). 3. Structural Steel -Exterior Gloss epoxy finish coats are not recommended for structural steel exposed to the weather, due to chalking. They require acrylic emulsion or aliphatic urethane finish coats to insure gloss and color retention. The preferred system is SSPC-SP 6 (Commercial Blast Cleaning) followed by a system of zinc-rich epoxy primer and high-build polyamide epoxy intermediate coat applied in the fabrication shop. After erection of the steel, touch-up of damaged areas and bolts can be performed with zinc-rich epoxy primer or rustinhibitive polyamide epoxy primer. The third coat Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 431
FIGURE 3 New structural steel in cool, damp storage area to be enclosed; epoxy zinc-rich primer over SSPC-SP 6,
Commercial Blast Clean-
ing ; coated at the fabrication shop and touched up in the field; no topcoat to be applied. Courtesy of Porter Coatings of aliphatic urethane can then be applied. This system (Appendix B, #A) provides maximum chemical and abrasion resistance and long-term gloss and color retention. The alternate system is SSPC-SP6 (Commercial Blast Cleaning) followed by application of an inorganic zinc-rich primer in the fabrication shop. Bolts and damaged areas are touched up with zinc-rich epoxy or rustinhibitive polyamide epoxy primer. Once touch-up has been completed, the steel should be finished with two coats of acrylic emulsion. 4. Concrete Ceilings Properly prepared and coated concrete ceilings are economical to maintain and to sanitize. Careful surface preparation is essential. Curing compounds, form-release agents and surface hardeners can be removed by brush sandblasting. Where dust is a problem, a water ring adjustment or wet blasting is recommended followed by a thorough rinsing to remove any blasting mud . Filling holes is important. Holes of diameter or more should be grouted. Smaller holes should be filled with water resistant cementitious filler. Ceilings in aggressive areas should be finished with 8-10 mils D.F.T. of gloss epoxy (Appendix B, #G).An alternate system for less aggressive service can be one or two coats of high build polyamide epoxy semi-gloss (Appendix B, #D). Two coats are needed to insure gloss uniformity. 5. Concrete Floors and Toppings a. Concrete Floors -No other areas in a food processing facility present more challenges to protective coatings than do concrete floors. There are few areas in food processing plants where concrete floors survive unprotected. Concrete is
readily attacked by acids, strong alkalis, nitrates, chlorides, sulfates, phosphates, sugars and some fats and oils. The best time to insure protection is at the time of construction and before the plant is in operation. Dealing with contaminated floors will also be addressed. New concrete should age a minimum of 28 days and have a maximum moisture content of 8-10%. It is important to install vapor barriers under ground level concrete floors to prevent adhesion problems due to hydrostatic pressures. Concrete floor surface preparation includes brush blasting, centrifugal blasting and power tool cleaning. As with ceiling panels, this may be accomplished by wet or dry methods. If wet blasting is performed, !horough rinsing with fresh water is necessary to remove blasting mud . Two other commonly used methods are scarifying and shot blasting. Both achieve the same results with no dust or water. Scarifiers remove up to inch of concrete surface with rotating sharp knives in a self-contained unit resembling a plant sweeper. Portable shot-blasters designed for flat steel surfaces also work well on concrete. The steel shot is centrifugally hurled against the floor and blasted with no dust. While units have vacuum attachments to pick up loose concrete dust, it is good practice to follow with a thorough vacuuming using an industrial sweeper. Scarifying, shot blasting and sandblasting remove laitance, curing compounds and surface hardeners. For best results and long-term savings, one of these should be specified and used on new construction floors. b. Floor Toppings -For toughest process areas in food plants, an 8-15 mil paint system is not enough protection. At the base of machinery where constant spills occur, on floors that stay wet with organic acids, and in areas where forklifts drag, drop and push large steel pots, the floors need maximum protection. In these very rough service areas, heavily aggregated, trowel-applied Y4 inch floor toppings provide the best protection. These are usually 100% solids epoxy or polyester materials that are so heavily loaded with inert aggregate that they require mixing in rotating drum mixers. They are usually classified two ways -food and chemical grade. Food grade toppings are USDA approved and able to take most process area conditions. Chemical grade floors are expensive and designed for areas where concentrated batch chemical spills take place, such as concentrated acids and alkalies. They are also designed to withstand steam impingement, while food-grade toppings soften under the same circumstances.
6. Concrete Walls -Block, Poured, Precast Walls are usually constructed from concrete block, concrete poured in place or tilt-up panels. New food plants should not have plaster, drywall, stucco or wood walls in process areas. Ceramic Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 432
SSPC CHAPTER*L7-b 93 8627740 0003880 OT7 tile is often specified, but the mortar joints eventually erode from washing and chemical attack and support growth of mold and mildew. Glazed ceramic tile walls cost 4-6 times more per square foot than walls using the best coatings available. a. Concrete Block Walls must have expansion joints to prevent cracking where the block meets structural steel, lintels and corners. Without block fillers, coatings flow into pores and a rough finish with pinholes results. The only surface preparation requirements for concrete block is that it be clean and dry. Concrete block is steam cured during manufacture and has no laitance. The block may be slightly dampened prior to application of water-based cementitious block filler, but should not be dampened for any solvent-based material. The preferred system of 8.0 mils D.F.T. polyamine epoxy over the flush-fill block filing system combines maximum chemical resistance and washability with maximum epoxy attractiveness. Polyester should be avoided because of its poor resistance to caustics. b. Poured and Precast Concrete Walls -They should be treated like concrete ceiling panels. Surface preparation should be wet or dry sandblasting. Under no circumstances is acid washing an acceptable method of surface preparation. For heavy process areas, the dry film thickness of the system should be at least 8.0 mils. Any damaged areas must be repaired following evaluation. The proper use of a wet film thickness gauge during application can be helpful to ensure proper dry film thickness. 7. Equipment Structural steel, ceilings, floors and walls of a food plant are often well protected, while machinery and equipment are not. Protective coatings applied on original equipment may not be suitable for service in aggressive environments. When ordering equipment for critical or severely exposed areas, request a detailed description of coatings the manufacturer supplies. If this system is not adequate, request a cost estimate for special finishing to conform with your selected system. If this cost is exorbitant, the alternative is to have the equipment delivered and finished at the job site, according to your own selected system. If field welding is to be done during installation, it is best to specify that it be primed at the manufacturer's shop and field topcoated after welding. Damaged areas have to be cleaned,
prepared and coated. The rust-inhibitive polyamide epoxy primer works well as a touch-up primer. If the equipment manufacturer cannot blast, the specification should call for degreasing and solvent cleaning (SSPC-SP 1) followed by hand or power tool cleaning (SSPC-SP 2 and SSPC-SP 3) and treatment with a phosphoric-acid-based metal pretreatment. 8. Piping Ideally, carbon steel piping should be blasted to SSPC-SP 6 Commercial Blast and have 2.0-3.0 mils zinc-rich primer applied before reaching the job site. This insures that no unprotected and inaccessible areas are formed when the pipe is welded. Once these steps are taken, the pipe should be cleaned, and damaged areas touched up before topcoating. Use the same topcoat options over the zinc-rich primer as listed for structural steel. If piping is inside the plant, gloss epoxy finish coats work well. Outside, however, the aliphatic urethane works best over 3.0-5.0 mils polyamide epoxy because it holds its gloss and color. Epoxies are a poor choice for exterior exposure due to their chalking in the presence of u It raviolet Iig ht . Operating temperatures of pipes must be identified so that the coating system can be specified. Following are temperature tolerances of various systems for pipes. Below 225°F - Epoxy primer and aliphatic urethane finish coat (Appendix B, #X). 225"F-3OO0F- Silicone-acrylic or silicone-alkyd nish coat (Appendix B, #W). 300°F Plus -Inorganic zinc-rich primer untopcoated or silicone-based highheat coating (Appendix B, #W). If the temperature of the piping is above 225"F, the surface preparation should be blast cleaned. All piping operating at less than 250°F to be insulated can be coated with an alkyd red oxide primer. Pipes operating above 250°F to be insulated require no coating. 9. Tank Exteriors Exteriors of carbon steel tanks should be blasted and primed at the shop and finish-coated at the job site. If the tank is inside the plant, blast the ex-
terior to SSPC-SP 6 and apply a zinc-rich primer at 2.0-3.0 mils D.F.T., followed by 3.0-5.0 mils of polyamide epoxy or vinyl. Finish the job with a suitable gloss finish coat of either polyamide epoxy, vinyl, polyamine epoxy or aliphatic urethane depending upon conditions (Appendix B, #A). If the tank is outside and exposed to sunlight, use the system above with the aliphatic urethane finish coat. If there is no strong chemical environment, a system of SSPC-SP 6 Commercial Blast, Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 433
SSPC CHAPTER*37.6 93 = 8627940 0003883
33
FIGURE 4 Structural steel in wet processing areas. Epoxy zinc-rich primer and high-build epoxy intermediate coat applied in the fabricator shop. Gloss epoxy finish applied after erection. Courtesy of Porter Coatings 2.0-3.0 mils inorganic zinc-rich primer and two coats of vinyl or gloss acrylic emulsion finish coat works well (Appendix B, #C). 1o. Tank Linings a. Dry Food Linings, such as grain hoppers or flour bins, should have a USDA and FDA approved system for food contact surfaces. Steel should be blasted and coated with two coats polyamide epoxy or polyamine epoxy in an FDA approved formulation. Total D.F.T. should be 10.0 mils minimum. For dry food lining, concrete tanks and silos, a three-coat system with 12.0 mils D.F.T. minimum is recommended over a brush-sandblasted surface. The extra coat is necessary to compensate for the sealing action of the first coat. b. Linings For Liquid Foodstuffs require highly specialized materials and application. This subject is covered in the chapter on steel tank lining. Since potable water is a foodstuff and may be a direct food additive, use the same systems as specified for dry food. The lining must be FDA approved and should be acceptable under current EPA guidelines. The coatings supplier should be able to certify FDA compliance and have acceptability letters from the EPA and approval letters from the State Health Departments. No coal-tar based coatings or coating containing heavy metals or toxic materials are acceptable for potable water service. Most rustinhibitors fall into this latter category. Since the dependence is on a barrier coat in potable water service, internal coatings systems in all steel tanks should be checked for pinholes with a suitable holiday detector. 11. Painting Non-Ferrous Surfaces a. Copper -Copper to be painted should be sanded and a coat of polyamide epoxy applied at 3.0-5.0mils. Do not use a rust-inhibitive primer, since the inhibitor may react with copper. Use a topcoat product. Finish with a thin coat of gloss epoxy or aliphatic urethane.
b. Aluminum -is only difficult to coat if the layer of aluminum oxide is not removed. This is accomplished by acid etching after detergent and solvent cleaning. Once dry, apply a coat of polyamide epoxy at 3.0-5.0mils dft and finish with gloss epoxy or aliphatic urethane. If aluminum is outside and is in a nonaggressive area, two coats of acrylic emulsion works well after the proper surface preparation, as outlined above. c. Galvanized Steel -If there is no chemical environment, galvanized metal should not need coating, except for color. But there are very few areas in food processing facilities that are normal environments. Surface preparation is the key to successfully painting galvanized steel. Solvent and detergent cleaning removes all greases, oils, dirt, emulsions and waxes. The metal must be etched with a proper etching compound. Vinegar washes and other household remedies do not work. Etching can be eliminated by ordering pre-etched galvanize, but the solvent and detergent cleaning must still be performed. For details, see the chapter on painting of galvanized steel. D. THE MAINTENANCE PAINTING PROGRAM It is much easier to apply first class coating systems when a plant is under construction than after it becomes operational. Once a plant is built, operational maintenance painting becomes a continuing and expensive problem. A well conceived maintenance painting program is worthy of management attention and pays for itself through savings and reduced downtime. The maintenance engineer, with professional help from a qualified coatings supplier, can work out practical specifications for preparing and coating various surfaces. Good specifications detail surface preparation, exact coatings, number of coats, film thickness, application and inspection procedures. Outside painting contractors and plant maintenance crews appreciate management s recognition of their contributions to successful plant operation. Cooperative scheduling ensures that maintenance coating can be done without interfering with plant operations. 1. Selecting Maintenance Coatings Use coatings recommended in the New Construction section of this chapter. Tie-coats of alkyd Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 434
SSPC CHAPTERbL7.b 93 8627940 0003882 97T primer or polyamide epoxy should be used on old and new coatings. Zinc-rich primers should be used on steel surfaces whenever possible. Aliphatic urethane fihish coats work best in process areas. Thermoplastic coatings, such as acrylic, alkyd, vinyl and chlorinated rubber, should be avoided in process areas. Alkyd and acrylic finishes do not have the necessary chemical resistance and do not stand up to washing and sanitation rinses. They also develop mold and mildew unless specifically formulated with fungicides and bactericides. They may blister in very wet environments, characteristic of many food processing plants. Vinyl and chlorinated rubber have good acid and alkali resistances, but are not without problems. Both require meticulously clean surfaces to avoid adhesion problems. Both have low volume solids, which means large amounts of strong solvents are liberated when these products are used. Chlorinated rubber is dissolved by some animal fats and vegetable oils. Neither vinyl nor chlorinated rubber washes particularly well because of poor abrasion resistance. Their use must be carefully studied to avoid serious difficulties. Vinyls are used as linings for fresh water tanks and as exterior surfaces. 2. Maintenance Surface Preparation The key to successful maintenance painting in food processing plants is surface preparation. Nearly all surfaces in operating plants are contaminated by raw materials and finished product. These include grain dust, greases, oils, sugars, salts, mild acids, caustics, condensation and any number of other compounds. These contaminants must be removed before coating. Removal may involve any combination of degreasing, steam cleaning, solvent washing, water blasting, abrasive blast cleaning or power tool cleaning. The fundamental goals of surface prepara tion in this setting are complete removal of contaminants, increase in surface area for mechanical bond and removal of all coatings that are not performing properly. If carbon steel has mill scale remaining it should be blasted to a Commercial Blast (SSPCSP 6). This may require extensive effort to protect machinery and equipment, but can usually be accomplished by skilled applicators. The extra cost of plastic wrapping and ventilation is inevitably recouped by the long-term savings in corrosion control costs. Concrete surfaces that still contain laitance should be blasted or acid-etched. Contaminated surfaces must be cleaned prior to any wet or dry
blast operation. Wherever possible, blast cleaning should be specified. Dust and contamination can be controlled by wet blasting, vacuum blasting, centrifugal shot blasting or scarifying techniques. Whole areas can be secured by using plastic barriers. Power-tool cleaning and other marginal surface preparation techniques are labor-intensive and therefore costly. Additionally, the service life of maintenance coatings depend on the effectiveness of the surface preparation. New power tool devices are promising in dust control, cost and quality of surface. 3. Application Film thickness of the coating system is a key factor in the success of maintenance (See SSPC-PA 2). All prominent points, such as bolt heads, sharp edges and welds should receive an extra coat of primer or topcoat with either brush or spray. When a roller is used, two coats are usually required to achieve the specified edge film thickness. Temperatures during curing can be particularly troublesome in food processing plants. Epoxy, epoxy zinc-rich and epoxy polyester coatings do not cure below 50°F (10°C). The curing process of all coatings is directly related to temperature and relative humidity. Some coatings dry at lower temperatures, but do not perform as well as if fully cured at higher temperatures. Whenever possible, process areas should be warmed to 70°F and dried to 50% relative humidity. Painting of damp surfaces is not recommended. There are some alkyd-type products that adhere marginally to damp surfaces and form a dried film, but maintenance painting of this type is a temporary measure. See SSPC-PA 1 for paint application requirements and checklist. 4. Inspection Periodic inspections minimize maintenance painting costs. When problems are diagnosed, underfilm corrosion can be checked before it becomes serious. Any plant maintenance program that calls for annual inspection and painting during a short maintenance shutdown is less than effective. Constant vigilance and ongoing maintenance assure the lowest cost per square foot per year. Proper inspection should be carried out during each step of maintenance painting. Surface preparation should be checked to make sure greases, oils and dirt have been removed. Where blasting is specified, conformance to industry specifications should be assured before applica-
tion. The inspector should check equipment for cleanliness and condition. Oil and moisture separators, tip sizes, fluid filters and other Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 435
SSPC CHAPTER*L7-6 93 m 8627940 0003883 806 FIGURE 5 Piping and Equipment. Rust inhibitive polyamide epoxy primer with aliphatic urethane finish coat. Courtesy of Porter Coatings necessary items should be verified. During application, wet film thickness measurements should be made and visual checks done for sags, runs, curtains and other application problems. After application full inspection should be performed on all coated surfaces. This should include dry film thickness measurements and checks for adhesion and final appearance. A conscientious and well structured maintenance painting program saves dollars. It also results in a cleaner, safer, more pleasant and efficient processing plant. E. USDAIFDA REGULATIONS FOR PROTECTIVE COATINGS Two government agencies are concerned with protective coatings used in food processing plants: the U.S. Department of Agriculture (USDA) and the U.S. Food and Drug Administration (FDA). 1. USDA The USDA is required by law to maintain safe and sanitary conditions in federally inspected meat and poultry plants. The specific laws are the Federal Meat Inspection Act as amended by the Wholesome Meat Act of 1967 and the Poultry Products Inspection Act as amended by the Wholesome Products Act of 1968. These statutes are enforced by the Animal and Plant Health Inspection Service of the USDA through the Meat and Poultry Inspection Program (MPIP). In meat and poultry plants, all coatings must 436 be approved by the USDA. There are two types of approvals: one for coatings applied to direct food contact surfaces and one for what is termed incidental food contact surfaces . This refers to all areas of a plant where the foodstuff is not in direct contact with the protective coating and includes ceilings, walls, floors and all other fixtures and equipment. The coatings manufacturer must follow a
detailed procedure to receive USDA approval for a coating product. The company must supply a dry sample, formula and product label to the Compounds Evaluation Unit of the USDA. After evaluation and approval, the manufacturer receives an approval letter. These are separate letters for direct contact and incidental contact services. Important: If the manufacturer changes the formulation, product name, or product label, all approvals are lost and the coating must be resubmitted for evaluation and approval. 2. FDA The FDA is responsible for maintaining safe and sanitary conditions in all food processing plants, other than those covered by the Meat and Poultry Inspection Program. The FDA does not approve coatings, but has guidelines for acceptability of protective coatings on food and drug contact surfaces. It is the responsibility of the coatings manufacturer to certify that the coating product is acceptable under FDA guidelines for this service. The manufacturer must do two things: formulate the coating entirely of materials listed as acceptable under FDA Title 21, Paragraph 175.300; and run specific extractability tests as detailed in Paragraph 175.300. If a coating passes the extractability tests, the manufacturer may certify its acceptability for application to direct food contact surfaces. This certification letter is the equivalent of a USDA approval letter for the same service. 3. Simplified Interpretation a. Meat and Poultry Plants -must have USDA approval on all coatings in process areas. Any direct food contact requires the second level of USDA approval. Coating manufacturers must provide copies of letters to the user upon request. b. Other Food Processing Plants -should have USDA approved materials on all surfaces in all process areas and must have FDA approvable coatings on any direct food contact surfaces. Coating manufacturers must provide USDA approval letters and FDA certifications to the user upon request. USDA contact surfaces approval is not a substitute for FDA compliance in these plants. --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*L7.6 93 8627740 0003884 742 APPENDIX A TYPICAL PROTECTIVE COATINGS SYSTEMS FOR FOOD PROCESSING PLANTS SURFACE PREFERRED SURFACE ALTERNATE SURFACE TO BE COATED EXPOSURE SYSTEM* PREP SYSTEM PREP COMMENTS Structural & Interior A SSPC-SP 6 B SSPC-SP 6 With System A the first two coats Misc. Steel may be shop-applied followed by touch-up and application of third coat in the field after erection. With System E, epoxy zinc-rich primer only to be applied in the shop. Structural & Exterior A SSPC-SP 6 C SSPC-SP 6 Primer in System C may be shop- or Misc. Steel field-applied. If shop-applied, touch-up of damaged areas should be done with epoxy zinc-rich or rust-inhibitive polyamide epoxy prior to top-coating with acrylic emulsion. Piping Interiori A SSPC-SP 6 B SSPC-SP 6 Piping should be blasted and primed Exterior in shop. All pipe varnish must be (UP to removed prior to coating. 225°F) (107°C) Piping Interiori N SSPC-SP 6 Exterior 225 "-300 "F (107 "-149 OC) Piping Interior/ P SSPC-SP 10 None Exterior 300 "-700 "F (149"-371 "C) Ceilings-Interior D Detergent z Galvanized & Wash Phosphatized Steel Ceilings-Steel Interior E SSPC-SP 7 F SSPC-SP 10 Pre-coated not and Galvanized SSPC-SP 3 Ceilings-Poured Interior G SSPC-SP 7 H SSPC-SP 7 Ceilings may be dry- or wet-bla sted. or Precast If wet-blasted, ceilings must be
Concrete thoroughly dry before application of System H. Walls-Interior I Paint only H Paint System I will have best overall Concrete Block or clean, dry only clean, appearance and washability. System J J surfaces dry should be selected if stain resistance surfaces is primary consideration. Walls-Poured Interior G SSPC-SP 7 H SSPC-SP 7 Walls may be dry or wet blasted. or Precast or Concrete J Floors-Poured Interior-K SSPC-SP 7 None -This exposure is characterized by Concrete Very aggressive or splash and spillage of chemicals, Areas Scarify constant wetness or overflow of prodor uct. Severe abrasion also dictates the Shot Blast use of a heavy monolithic system. Under no circumstances should acid etching be substituted as a surface preparation method. Floors-Poured Interior-L SSPC-SP 7 M SSPC-SP 7 System M will provide clean finis h or for dust control and will not yellow Scarify with age. or Acid Etch Concrete Normal to or semi-severe Scarify areas or Shot Blast "See Appendix B for paints used in each system --`,,,,`-`-`,,`,,`,`,,`--437 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*L7*6 93 8627940 0003885 b89 APPENDIX A (Continued) PREFERRED ALTERNATE SUR FACE SYSTEM SURFACE SYSTEM SURFACE TO BE COATED EXPOSURE (from Appendix 6) PREP (from Appendix B) PREP COMMENTS Pre-primed & Interior F SSPC-SP 1 None -*This includes door frames, handrails, Pre-coated and switch boxes, electric boxes, etc. Surfaces SSPC-SP 3 Tank Linings- Interior-Dry O SSPC-SP 5 None -NOTE: Linings for liquid foodstuffs Steel Foodstuffs or require highly specialized materials Potable water and application. This subject is covered in a separate chapter. Tank Linings- Interior-Dry R SSPC-SP 7 None Third coat is necessary on concrete Concrete foodstuffs or to insure pinhole-free finish. potable and process water ~~ ~ Non-Ferrous Interior S Sand to D Sand to Do not use rust-inhibitive primer Metals <225"F remove remove direct to copper. Copper (107°C) oxides oxides Non-Ferrous Exterior S Sand to T Sand to Metals <225"F remove remove Copper (107"C) oxides oxides Non-Ferrous Interior S SSPC-SP 1 D SSPC-SP 1 Metals and and Aluminum acid etch acid etch or or brush blast brush blast Non-Ferrous Exterior S SSPC-SP 1 U SSPC-SP 1 Metals and and Aluminum acid etch acid etch or or brush blast brush blast Non-Ferrous Interior S SSPC-SP 1 D SSPC-SP 1 Metais and and Galvanized Steel acid etch acid etch Non-Ferrous Exterior S SSPC-SP 1 U SSPC-SP 1 Metals and and Galvanized Steel acid etch wash prime or
acid etch Plaster, Stucco Interior V Acid etch D Acid etch Epoxy coatings systems should n ot and Brick not be applied to conventional limeputty plaster Plaster, Stucco Exterior U Acid etch None and Brick High Temp. Interior & P SSPC-SP 5 W SSPC-SP 5 Steel Surfaces Exterior 300"-800"F New Equipment interior & A SSPC-SP 6 SSPC-SP 1 (Carbon Steel Exterior and Surfaces) SSPC-SP 3 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 438
SSPC CHAPTER*17.b 93 Ab27940 O003886 515 APPENDIX B DESCRIPTION OF TYPICAL SYSTEMS SYSTEM Dry Film Thickness (Mils) A. 1 ct. Epoxy or Inorganic Zinc-Rich Primer 1 ct. High-Build Polyamide Epoxy 1 ct. Aliphatic Urethane B. 1 ct. Epoxy or Inorganic Zinc-Rich Primer 1 ct. Semi-Gloss High-Build Epoxy-Polyamide C. 1 ct. Inorganic Zinc-Rich 2 cts. Acrylic Emulsion D. 1 ct. Semi-Gloss High-Build Epoxy-Polyamide E. 1 ct. Rust-Inhibitive Polyamide Epoxy Primer 1 ct. Semi-Gloss High-Build Epoxy-Polyamide F. 1 ct. Universal* Alkyd Primer or Epoxy Primer 1 ct. Gloss Polyamide Epoxy Finish G. 1 ct. Cementitious Acrylic Block Filler 1 ct. High-Build Epoxy-Polyamide 1 ct. Epoxy-Polyamine H. 1 ct. 1 ct. I. 1 ct. 1 ct. High-Build Epoxy-Polyamide Epoxy-pol yamine Cementitious Acrylic Block Filler Epoxy-Polyamine J. 1 ct. Cementitious Acrylic Block Filler 1 ct. Semi-Gloss High-Build Epoxy-Polyamide 1 ct. Aliphatic Urethane K. 1 ct. 100% Solids Epoxy Floor Sealer 1 ct. @ ,!,-Ih Monolithic Epoxy-Aggregate Floor System 1 ct. Epoxy-Polyamine (Optional color coat) L. 1 ct. High-Build Epoxy-Polyamide 1 ct. Epoxy-Polyamine (Non-Skid Additive Optional) M. 1 ct. Clear Polyamide Epoxy 1 ct. Clear Aliphatic Urethane 2.5-3.0 3.0-5.0 1.5-2.5 7.0-10.5 2.5-3.0 4.0-6.0 6.5-9.0 2.5-3.0 1.5-2.5 1.5-2.5
5.5-8.0 4.0-6.0 4.0-6.0 2.0-2.5 4.0-6.0 6.0-8.5 2.0-3.0 2.0-3.0 4.0-6.0 to fill 3.0-4.0 6.0-7.0 9.0-11.0 4.0-5.0 6.0-8.0 10.0- 13.0 to fill 8.0-9.0 8.0-9.0 to fill 4.0-6.0 2.0-2.5 6.0-8.5 6.0-8.0 125.0-250.0 6.0-8.0 137.0-266.0 4.0-6.0 6.0-7.0 10.0-13.0 1.5-2.5 2.0-2.5 3.5-5.0 --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS *Capable of being recoated with strong solvent or epoxy urethane 439
SSPC CHAPTERmL7.b 93 m 8627940 0003887 451 m APPENDIX B (Continued) SYSTEM N. 1 ct. Inorganic Zinc-Rich Primer 2 cts. Silicone-Acrylic Finish O. 1 ct. Alkyd Zinc-DustIZinc-Oxide Primer 1 ct. Silicone Alkyd Finish P. 1 ct. Inorganic Zinc-Rich Primer Q. 2 cts. Epoxy-Polyamide or Epoxy-Polyamine (Must be USDAIFDA Approved product for direct contact with dry foodstuffs or potable water) Alternate: 3-coat vinyl system per AWWA specs. R. 3 cts. Epoxy-Polyamide or Epoxy-Polyamine (Must be USDAIFDA Approved product for direct contact with dry foodstuffs or pot ab Ie water) S. 1 ct. High-Build Epoxy Polyamide I ct. Aliphatic Urethane T. 2 cts. FungusIMildew Resistant Alkyd Gloss Finish U. 2 cts. Acrylic Emulsion v. 1 ct. Epoxy-Polyamide 1 ct. Epoxy-Polyamine W. 1 ct. Silicone-Alkyd Aluminum Finish X. 1 ct. Rust-Inhibitive Polyamide Epoxy Primer 1 ct. Aliphatic Urethane Y. 1 ct. High-Build Rust-Inhibitive Polyamide Epoxy PrimerlFinish Z. 1 ct. Wash Prime Mil P 15328 2 ct. Acrylic Emulsion Dry Film Thickness (Mils) 2.0-3.0 1.5-2.0 1.5-2.0 5.0-7.0 2.0-3.0 1.5-2.0 3.5-5.0 2.0-3.0 2.0-3.0 5.0-7.0 5.0-7.0 10.0-14.0 4.0-6.0 4.0-6.0 4.0-6.0 12.0-18.0
4.0-6.0 2.0-2.5 6.0-8.5 1.5-2.5 1.5-2.5 3.0-5.0 2.0-2.5 2.0-2.5 4.0-5.0 2.0-3.0 5.0-6.0 7.0-9.0 1.5-2.5 1.5-2.5 2.0-3.0 1.5-2.5 3.5-5.5 5.0-6.0 5.0-6.0 0.3-0.7 3.0-5.0 --`,,,,`-`-`,,`,,`,`,,`--440 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERUL7.b 93 8627940 0003888 398 W ACKNOWLEDGEMENT BIOGRAPHY The author and editors gratefully acknowledge the active Steve L. Schmidt is Vic e participation of the following in the review process for this President Marketin g for Courchapter: A.R. House, John Montle, Dan Nemunaitis, Dave Roh- taulds Heavy Duty Co atings, son, Bill Wallace, Tom Wilhelm. Louisville, KY. His eighteen-year career has included experience in all facets of protective coatings. He founded Porter International in 1989 and is the author of numerous articles on protective coatings technology. He is an active member of the National Association of Corrosion Enqineers and has served on the Executive Committee of the Board of Governors of the Steel Structures Painting Council. --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 441
SSPC CHAPTER*L7.7 93 8627940 0003889 224 CHAPTER 17.7 POWER GENERATION FACILITIES bY Ronald R. Skabo This chapter deals specifically with painting power generation facilities. While such facilities do not present any major differences in the basic approach to good painting, and while a properly engineered coating system can be developed for a power generation facility just as it can for a chemical plant or petroleum refinery, each facility has special conditions, environments or regulatory restraints that will affect the selection of coatings systems( ). For the most part, power generation facilities, historically, were not located in aggressive environments. Thus, painting systems were often selected on the basis of the lowest initial cost. While high performance was not a major consideration, there were some exceptions, most notably, power plants located in sea coast environments, where higher quality coatings were justified because of humid, salt-water environments. Several major developments in power generation have resulted in significant changes in painting attitudes, and more importantly, in requirements for paint performance. Nuclear power generating facilities probably had the greatest impact on painting practices. Because of special requirements for paint performance mandated by government agencies, the quality of surface preparation, application, paint and inspection has been raised to a level never before required in the power generation industry (Figure 1). In fossil fuel plants, particularly coal-fired, the enforcement of air quality standards has forced installation of flue gas desulfurization (FGD) systems at many facilities. These systems have created chemical plants in each power station resulting in aggressive, corrosive environments that tax the best protection system. Other factors that have resulted in painting changes include increased maintenance cost and aesthetic awareness. In addition to protection required for structural steel, there is a need for lining systems that can adequately protect ferrous substrates in a totally immersed environment. These typically include hydraulic structures, various storage tanks, and some process vessels. As is the case in most industrial plants, painting is required in power plants for protection against corrosion, for reasons of safety, or for aesthetics, but not always in that order of preference.
I. SPECIFIC PLANT REQUIREMENTS There are severalmethods for generating electrical power. The greatest percentage of megawatts generated 442 in the United States comes from fossil and nuclear fueled plants. They also represent the most demanding painting and the greatest challenge to the owner. Equipment and structures requiring painting are common to both types of generating facilities, but there are special circumstances in each type of plant that deserve attention. Nuclear power plants have more regulatory restraints imposed which affect all facets of critical coating work. A. NUCLEAR POWER PLANTS For nonradiation areas of nuclear power plants, painting requirements generally are the same as for fossil plants or other industrial complexes. However, in radiation areas, a new set of criteria is imposed. It includes the ability to be decontaminated and the ability to withstand conditions postulated for a Design Basis Accident (DBA) or Loss of Coolant Accident (LOCA) (Figure 2). There are several ANSI and ASTM standards that pertain to coatings in nuclear plants (ANSI N5.12(* , N101.2@), N101.4í4), and D4082, D4256, D4227, D4228, D4537). Refer to Part 45 of the ASTM Nuclear Standards for present and future standards pertaining to nuclear plant coatings. Courtesy Klaas Brothers, Inc. and GilbertlCommonwealth FIGURE 1 Installing the nuclear reactor at Hanford Station. The interior of the containment vessel is coated with a special nuclear grade coating. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*L7=7 93 m 86279i.10 0003890 TLtb Courtesy GilbertlCommonwealth FIGURE 2 Three Mile Island Nuclear Power Plan!, Middletown, PA. Uni! 1 is on right. Uni! 2 in operation (prior to accident). Paint performance is of particular concern in areas where failure could jeopardize plant safety. ANSI Standard N5.12 defines the most critical areas as Coating Service Level I pertaining to those coating systems, applied to structures, systems, and components, which are essential to the prevention of, or the mitigation of the consequences of, postulated accidents that could cause undue risk to the health and safetyof the public. Of major concern are the consequences of failure on the safe shutdown of the plant, mainly within the primary containment structure. Less critical areas exist in Service Level Il, which applies to those coating systems which are essential to the attainment of the intended normal operating performance. The United States Nuclear Regulatory Commission (NRC) exerts control over nuclear power plants pertaining to public health and safety. Included are painting requirements.* The previously mentioned ANSI Standards and more recent ASTM Standards detail critical items pertaining to painting nuclear power plants. The nuclear power generating industry requires strict performance criteria for coatings: extensive testing, quality assurance and quality control programs for manufacturers, applicators and inspectors. The resistance of paint to longterm radiation exposure and decontamination procedures becomes the first concern. Corrosion resistance (other than from decontamination chemicals) and aesthetics are less important. Code of Federal Regulations, Title 10, Chapter 1, Energy, Office of the Federal Register, National Archives and Record Service, General Services Administration. Obtainable from the Superintendent of Documents, Washington D.C., Part 50, Licensing of Production Utilization Facilities (10 CFR 50). The potential for radioactive contamination associated with nuclear plants requires concrete surfaces to be painted with materials similar to those used on steel substrates. One of the most critical aspects of selecting coatings for Coating Service Level I is determining which system meets the criteria. Probably the most significant tests that systems must pass include 1) the DBA, 2) exposure to radiation, and 3) ability to be decontaminated. The DBA test involves exposure to a temperature/ pressureltime environment, plus certain spray solutions such as sodium borate, sodium thiosulfate, sodium hydroxide, andlor boric acid. Depending upon the nuclear
reactor design, the temperaturelpressureltime sequence can vary, with temperatures often exceeding 300°F and pressures approaching 70 psi. In addition, the coating must withstand anticipated radiation levels and then be able to be decontaminated to acceptable levels. The severity of these tests limits the generic types of coatings that can pass and places a greater than normal emphasis on the total coating system including surface preparation, application, and inspection. Coatings that meet these criteria for steel surfaces are inorganic zincs (Figure 3), epoxies, or modified epoxies. As with any critical application, there can be no compromise in the quality of surface preparation and workmanship (Figure 4). B. FOSSIL POWER PLANTS For many years, a great number of fossil fuel power plants were fired with gas or oil. These are relatively clean fuels that do not Create Serious atmospheric COrrOSiOn problems or place Special demands on paint performance. Even with coal fuel, there was little effect on paint reCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 443
Courtesy Mobil Chemical and GiIbertlCommonweaIth FIGURE 3 Inorganic zinc coating applied to liner plate prior to assembly of nuclear reactor building at Calvert Cliffs Nuclear Plant. quirements since coal was generally high quality and low sulfur. In recent years the use of high sulfur coals and restraints of local, state and federal agencies against discharging pollutants into the atmosphere have created a whole new ball game for painting in fossil fuel power plants. The need for FGD systems on many coal-fired power plants has created a very significant chemical plant operation on the end of these plants. The major impact has been on various lining materials that are required in vessels, absorbers and ductwork, which often contain very aggressive environments (Figure 5). Exterior exposures around these FGD systems often expose coated surfaces to highly alkaline environments due to the nature of the neutralization chemicals used (lime, limestone). Another problem created by plants burning high sulfur coal is the highly acidic condition encountered around the wet coal. Surface drainage from a pile of high sulfur coal can have a pH value of 2 or less. This acidic condition must be recognized when engineering a coating system. CourtesyAmeron and Gi,bertlCommonwealth FIGURE 4 Spraypointing of contoured panel as a part of nuclear qualifica. tion of painters. C. COMMON PAINT PROBLEMS Some areas in nuclear and fossil power plants have painting requirements that are common with each other. Some areas are innocuous, not requiring paint to provide protection against corrosion but to fill aesthetic needs. Examples are the turbine-generator area and control rooms. One of the more aggressive environments common to both generating facilities is the water treatment area. Demineralization units require acid and caustic for regeneration, creating a potential for chemical exposure to spillage areas and adjoining painted surfaces. Further discussion on painting water treatment facilities appears later in this chapter. Special precautions must be taken if successful cervice life is to be achieved with most lining systems in immersion service. There cannot be a successful service life
if frequent inspection and maintenance are not performed. The more aggressive the environment, the more frequent the inspection. Few systems can be placed in immersion service without some failure occurring in the first year of service. A systematic program of inspection and repair can achieve a good service life. Frequent wash down is recommended where chemical spillage occurs. II. SURFACE PREPARATION With few exceptions, prior to the existence of nuclear plants and FGD systems, the power generating industry was not prone to specify high quality surface preparation. Such an attitude was acceptable since high quality coating systems were not often specified. But now, a higher degree of sophistication has developed in the engineered approach to good painting practice because of the need for higher performance coating systems to satisfy requirements for nuclear service, to withstand the rigors of FGD systems, to reduce maintenance costs and to provide better plant appearance. Accepted standards for surface preparation have been developed by the Steel Structures Painting Council B) (SSPC). These are the final word on how a substrate should be prepared. For immersion service, white metal blast cleaning (SSPC-SP 5) is much preferred. Surfaces that are condensing and running wet (¡.e. inside of chimneys downstream of FGD systems) should be considered as immersion service. Such an environment can be more aggressive to coating systems than conventional immersion service because of the higher rate of moisture vapor transmission. There are few situations or coating systems that compromise the requirement for a white metal surface for immersion service, but the compromise would only down-grade to SSPC-SP 10, near-white blast cleaning. In less critical areas of nuclear and fossil plants, coating systems are being built from the substrate up, requiring good quality surface preparation for most surfaces. Because of the increased availability of centrifugal wheel blasting equipment, either in steel fabrication or paint shops, much of the major structural steel and equipCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 444
SSPC CHAPTER*L7.7 93 8b27940 0003892 819 ment is being cleaned and primed in the shop. In most cases commercial blast cleaning (SSPC-SP 6) is usually specified. TABLE 1 FOSSIL FUEL PLANTS Although there are exceptions, the use of hand tool or power tool cleaning (SSPC-SP 2 and SSPC-SP 3) is usually limited to touch-up, repair, or small items. Seldom are these methods specified for major equipment items and structural steel. With many developments in abrasive blast equipment and techniques, plus the greater desire to obtain high performance coating systems, there is an ever increasing use of higher quality surface preparation throughout most power generation facilities. 111. TYPES OF PAINT It is difficult to state which coating systems are typical for the power industry. However, with the emphasis on high performance coating systems, including improvement in surface preparation and a more engineered approach, the quality of coatings has reached a new high. Their performance is gauged by durability in severe chemical exposure (FGD systems); resistance to radiation, chemicals and heat (nuclear plants); and overall aesthetics. These performance parameters, and other regulatory restraints make it uneconomical to address the problem of paint selection casually. It is necessary to consider carefully all aspects of the painting requirements and to specify the appropriate coating for each plant section. Courtesy: GilbertiCommonwealth FIGURE 5 Corrosion failure inside 1000 ft. flue gas stack of desulfurization unit after 1% years service. Over 1700 holes were found in the polyester lining and the stack itself due to acid attack. After reapplication of a fluoroelastorner, the unit is still in operation after four years. Coal Handling: Commercial blast clean (SSPC-SP 6); inorganic zinc primer with epoxy topcoat, or a total epoxy system (primer and topcoat). Structural Steel: Commercial blast clean (SSPC-SP 6); inorganic zinc primer with topcoats of either epoxy, polyurethane, chlorinated rubber, or acrylic latex for exteriors; silicone alkyd on interior, but usually with alkyd primer. Hydraulic Interior surfaces of circulating water lines, Structures: condenser waterboxes, and water treatment equipment are often protected with phenolic, epoxy or coal-tar epoxy systems, flake glass polyesters, or sheet rubber. White-metal blast cleaning (SSPC-SP 5) is
generally specified, although near-white metal blast cleaning (SSPC-SP 10) is often used. High Temperature Commercial blast clean (SSPC-SP 6) or betSurfaces: ter; use an all-silicone system or an inorganic zinc alone or topcoated with a silicone. Mechanical Commercial blast clean (SSPC-SP 6); alEquipment: kyd primer and topcoat with alkyd enamel. FGD Systems Commercial blast clean (SSPC-SP 6); epoxy (Exterior): topcoat over inorganic zinc or use a total epoxy system. Inhibitive pigments in alkyd primers plus alkyd topcoats are used. Some units are insulated. FGD Systems White metal blast clean (SSPC-SP 5); condi(Interior) (Stacks, tions and designs vary greatly; reinforced Duct Work, Venturi polyesters, fluoroelastomers, reinforced Area): epoxies, rubber, foam glass block, and cementitious materials have all experienced varied success. Water Treatment Commercial blast clean (SSPC-SP 6); use an (Exterior exposure): inorganic zinc primer and topcoats of vinyl or chlorinated rubber. Potable Water: White metal blast clean (SSPC-SP 5); use coating systems suitable for potable water such as epoxy or vinyl, per American Water Works Association specifications. 445 --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
A. PRIMERS Economics are an important factor in daily operations. Time is money. This also applies to painting, par- TABLE 2 ticularly in fabrication shops. With large quantities of steel NUCLEAR POWER PLA NTS being shop primed, shop production must not be obstructed by long delays waiting for primers to dry. There is a need for fast-dry primers. Care must be taken when specifying primers if the majority of priming work is done in the shop. Fast dry primers are available in most generic types including alkyds (modified), epoxies, vinyls and inorganic zincs. Because of their fast dry properties, these products usually require a cleaner surface than slow drying penetrating primers. Another consideration created by construction practices is the result of extensive on-site storage of shopprimed equipment and structural steel. Construction time for most power plants, particularly nuclear, is 8 to 10 years, with frequent delays being common. Most construction primers were not intended to withstand long-term outdoor storage without a top-coat. Frequently, shop-primed structures require total re-prime by the time they are ready for top-coating because of their exposure to the elements. A partial answer to this problem is found in zinc-rich primers, particularly inorganic zincs. As discussed in the chapter on zinc-rich paints, inorganic zincs have excellent resistance to most outdoor weathering environments, but are not problem-free. Since zinc is a very reactive metal and is amphoteric (corroded by both acid and alkaline environments), it can be attacked if the construction site storage area is subjected to acid or alkaline fall-out from any up-wind facilities. Coal dust, a fact of life around fossil plants, can be detrimental to inorganic zincs, either by their galvanic relationship (carbon versus zinc) or the acidic conditions of some high sulfur coals. There have been problems with storage of inorganic zinc primed structures due to inadvertent contact with uncoated steel (again a galvanic corrosion problem). Corrosion occurs by the formation of zinc salts from puddling water on the primed surfaces. B. FINISH COATS Application of the finish coat(s) is typically done after erection of major steel components, even though many innovative techniques have been proposed and used, ¡.e. finish paint before erection. The variety of generic systems and specific requirements for each plant makes it impossible to say that there are specific systems unique to the power generating industry. The variety of generic types is a help to the engineer who can tailor the paint system to meet each specific requirement of his plant. In many plants, aesthetics plays a major role, requiring that painted surfaces maintain a new look (color and gloss retention). A number of products can meet this criterion including alkyd enamels, acrylic latexes, acrylics
and polyurethanes. At this time, polyurethanes represent the newest development in industrial painting. They provide excellent color and gloss retention and give good corGeneral: Criteria for selecting these systems include identification of specific surface and substrate condition. Coatings criteria include temperature, humidity, radiation level, decontaminability and chemical resistance. Level 1 coatings tests involve resistance to fire, radiation, design basis accident and unusual environmental conditions. Suppression White metal blast clean (SSPC-SP 5); use inChambers: organic zinc primers (without topcoats), epoxy or modified phenolic primers and topcoats, or metallized aluminum, with epoxy or epoxy-phenolic topcoats. Steel White metal or near-white metal blast clean Containment: (SSPC-SP5 or SSPC-SP IO)with inorganic zinc primer topcoated with an epoxy or epoxy-phenolic, inorganic zinc primer (untopcoated), or prime and topcoat with an epoxy or epoxy-modified phenolic. Concrete Walls Epoxy surfacers and topcoats to meet ANSI and Floors Standards. Structural Steel: Generally the same as fossil plants. (Outside of Containment) Building Siding: Same as fossil plants. Hydraulic Generally same as fossil plants. Structures: Mechanical Same as fossil plants if outside of containEquipment: ment. Water Treatment Same as fossil plants. rosion resistance. Acrylic-modified polyurethanes and various water based epoxy coatings are also being used. In nuclear applications, inorganic zincs, modified phenolics and epoxy based materials have an edge over other generic types. Rigorous conditions imposed by DBA test criteria have shown that these materials generally perform best. There are many generic paints that have worked in power generating facilities. As in other applications, the proper choice must be determined from many factors (cost, environment, application, service life). A great
amount of work has been done by SSPC, NACE(5), ASTM, and other technical organizations to acquire knowledge of paint technology and optimize material selection. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 446
SSPC CHAPTER*17-7 93 = 8b27940 0003894 691 W IV. TYPICAL COATING SYSTEMS Tables 1 and 2 list coating systems that have worked well for the specified application. They indicate no preference but list typical systems. The final choice must be made by the coatings engineer, who must tailor the selection to meet his specific requirements. ACKNOWLEDGEMENT The author and editors gratefully acknowledge the active participation of the following in the review process for this chapter: Duane Bloemke, J. Byers, Harlan Kline, M. Masciale, Marshall McGee, John Montle, Bill Pearson. T. Rudaitis, M. Shook, Bill Wallace, Frank Windler. worked in the petroleum industry, heavy chemical production, engineeringkonstruction, and consulting engineering. He is a registered professional engineer in several states, and a National Association of Corrosion Engineers (NACE) certified Corrosion Specialist. He holds memberships in the Steel Structures Painting Council, NACE, the American Society for Testing & Materials, the
American Water Works Association and serves on several technical committees in each organization. REFERENCES 1. American Society for Testing and Materials, Manual of Coating Work for Light-Water Nuclear Power Plant Primary Containment and Other Safety-Related Facilities . ASTM, 1916 Race St., Philadelphia, PA 19103-1 187, 1979. 2. American National Standard Institute, ANSI N512, Protective Coatings (Paints) for the Nuclear Industry . ANSI, 11 West 42nd St., 13th Floor, New York, NY 10036-8002, 1974. 3. American National Standard Institute, ANSI N1 01.2, Protective Coatings (Paints) for Light-Water Nuclear Reactor Containment Facilities . ANSI, 11 West 42nd St., 13th Floor, New York, NY 10036-8002, 1972. 4. American National Standard Institute, ANSI N1 01.4, Quality Assurance for Protective Coatings Applied to Nuclear Facilities . ANSI, 1430 Broadway, New York, N.Y. 10018, 1972. 5. National Association of Corrosion Engineers, Publications 6D170, Causes and Prevention of Coatings Failures . National Association of Corrosion Engineers, P.O. Box 21 8340, Houston, TX. --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 447
SSPC CHAPTER*LB*O 93 8b27940 0003895 528 CHAPTER 18 GOVERNMENT PAINTING PRACTICES by Richard W. Drisko and Howard G. lasser The federal government is the largest purchaser of paints and painting services in the United States, spending hundreds of millions of dollars annually. Thus, in 1977, the General Services Administration (GSA) spent about $58 million for 3400 paint items for stocking and subsequent distribution to federal agencies. About 60% of government painting is done under contract and about 40% (mostly maintenance) by in-house personnel. The trend is to increase the amount done under contract. Contractorfurnished paint may be specification or proprietary and is purchased directly from a supplier. Thousands of federal governmental activities, some very large and some quite small, each with its own organizational structure, require painting services on a periodic or continuous basis. In order for all these activities to procure quality materials and services in the most economical and efficient manner, a common set of published procedures, standards and specifications is prepared. Although they may seem unnecessarily numerous and complicated, they were prepared to meet the many government requirements and still be fair for suppliers. A new procurement policy, the Federal Acquisition Regulation (FAR), is being prepared for use by Federal Executive Agencies. It will provide a uniform regulation covering procurement and testing of paints. This chapter provides basic information about operational procedures of the federal government and advises state and local governments and private industry of available specifications and standards. The federal Freedom of Information Act makes all federal information, except that with a security classification, available to the public. In 1921, a standardization section was formed at the National Bureau of Standards to establish requirements and a format for procurement specifications. This section became the nucleus of the Office of Standards and Quality Control in the GSA, which now generates federal specifications and standards. The GSA has responsibility for all federal standardization documents, except those describing items specifically for military use. The first military standard concerned the design of a rifle with interchangeable parts invented by Eli Whitney. From this the military standardization program developed into the Defense Supply Center located in Alexandria, VA. The reponsibility for preparing procurement pro-
cedures for paints and coatings was assigned to GSA( ) to provide uniformity. If paint and coating materials are pro448 cured for stocking and storage by the federal government, GSA has responsibility for inspection and testing; if individual agencies procure such materials for their own use, then they have the inspection and testing responsibility(*). Published specifications, standards and qualified products lists are available from a single source, the Navy Publications and Forms CenteP). In general, when specifications and standards are used to provide a service to the federal government, commodity documents become secondary references, and documents dealing with government contracts are used as the primary reference~ ~.~). I. MATERIALS SPECIFICATIONS AND STANDARDS There are about 320 federal and 240 military specifications for paint and coating materials. These specifications are of two general types -those associated with compositional and those associated with performance requirements. The latter may have a qualified products list (QPL) of approved suppliers for approved formulations(E). Qualification may require both laboratory and exposure testing for conformance to specification requirements. The fact that a product has been examined, tested and placed upon a QPL by the preparer of the specification signifies only that at the time of inspection and test the manufacturer could make a product that met all specification requirements. It in no way relieves the supplier from the obligation to deliver items meeting all requirements. There is a mandate from Congress to make greater use of commercial standards because of availability and cost considerations. These standards are described as rules, conditions, or requirements established by commercial standards-setting bodies concerning definition of terms; classification of components; specification of materials, performance, or operations; delineation of procedures; or measurement of quantity and quality in describing materials, products, systems, services, or practices (7 . There are standard pr~cedures(~~~~~) for preparation, updating and cancellation of federal and military specifications as the need arises. The user is responsible for preparing a specification. The Materials and Mechanics Research Center, which lists all projects in the Federal Standardization Class 8010 for the Department of Defense, establishes projects for each user requesting a project nurnber lol. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERxL8.0 93 8b27940 0003896 464 Titles of specifications for paint materials use one key noun (e.g., coating, paint, enamel, compound, etc.) followed by descriptive adjectives (e.g., textured, vinyl, anticorrosive, etc.). The federal code system for specifications for paint and coating materials usually starts with TT-, followed by the first letter of the type of material (e.g., E for enamel, P for paint, C for coating, etc.) and a number. A letter, starting with A, is added after the number as modifications are made. Thus, TT-E-489F Enamel, Alkyd, Gloss (For Exterior and Interior Surfaces) is the code and title of the sixth revision of a specification for a commonly used enamel. Specifications for similar materials are sometimes grouped together. Thus, TT-P-300 to TT-P-500 are reserved for pigments. (Many of the pigment specifications that previously fell in this category have been replaced by ASTM specifications.) in addition to specifications, there are federal tests (Federal Test Method Standard No. 141) and a few federal standards (e.g., Federal Standard No. 595Colors) that are available from the Specification Distribution Branch of the GSA(ll). A listing of all such specifications and a Federal Supply Classification listing can be found in the Index of Federal Specifications and Standards, available on a subscription from the Superintendent of Documents. Single copies of specifications for bidding can be obtained free from any GSA Business Service Center located in different cities. Military specifications are distinct from other federal specifications. They are generally written with the prefix MIL- or DOD- (Department of Defense), followed by a code letter designating the type of product and a number assigned to each product. Federal and military specifications are being updated in metrics. When complete, the MIL- is changed to DOD-. MIL-P-15328C Primer (Wash) Pretreatment was changed to DOD-P-15328D. Navy coatings for ships frequently have formula and specification numbers. MIL-P-24441 includes formulas 150 through 156. A few JAN (Joint Army-Navy) specifications, forerunners of the MIL specifications, are still used. Military Specifications, Standards, and Qualified Products Lists can be obtained from the Naval Publications and Forms Center. There are a few specifications that have been issued by other federal agencies. These agencies include the Maritime Administration, the Bureau of Reclamation, Corps of Engineers and U.S. Postal Service. Many of these specifications have been changed to federal or military specifications. Specifications of such groups as the Steel Structures Painting Council and American Association of State Highway and Transportation Officials find occasional use by federal agencies. Other procurement documents include purchase descriptions, type specifications, guide specifications and
Military and Federal Construction Guide Specifications. Purchase descriptions cover items for a single procurement. Type and guide specifications provide information covering a description of services required for construction or maintenance of structures such as bridges, storage tanks and buildings. They are frequently used in the preparation of contracts. Several compilations or summaries of documents are available. A Guide to U.S. Government Paint Specifications is available from the National Paint and Coatings Association. This contains abstracts of most government documents with essential data on paint products and raw material ingredients for quick reference (but not for bidding use) by paint technologists, formulators, buyers, sellers and writers of specifications. It is updated about every three months. Visual Search MicroFilm (VSMF) is provided by Information Handling Services. It provides not only microfilms of all federal and military specifications, standards and QPLs, but also federal supply schedules, including GSA catalogs and federal construction specifications, standards and regulations for use on microfilm readers and printers. Microfilms of new and modified specifications ( Hot Specs ) are distributed every 15 days. The Department of Defense Index of Specifications and Standards (DODISS) is published annually with cumulative bi-monthly supplements for each part (Part I Alphabetical Listing; Part II -Numerical Listing). It is available at a subscription rate from the US. Government Printing Office. An additional charge is required for foreign mailing. The Federal Supply Classification Listing (a cumulative listing of documents alphabetically within their FSC classes) is also available from the U.S. Government Printing Office at a subscription rate with an additional charge for foreign mailing. II. PAINT SELECTION, PROCUREMENT, AND TEST1NG Many agencies prepare general guides for the selection and use of paints and coatings. One of the best known is the Tri-Service Manual, Paints and Protective Coatings (I*). Another is the National Bureau of Standards, Organic Coatings -Properties, Selection and Use [131,available from the U.S. Government Printing Office. More specific instructions are also available. Of special interest because of excellent technical contents are Naval Ships Technical Manual, Chapter 631 (formerly 9190), Preservation of Ships in Service (Paints and Cathodic Protection) [14 , General Specifications Section 631, Guide for Painting Ships Under C~nstr~~tion ~~~~; and U.S. Coast Guard Manual, Coatings and Color Manua1 (I6). The previously mentioned specifications also
provide much detailed information on painting specific structures and provide guidance useful in preparing contracts. Federal Specification No. 595 Colors presents a collection of standard colors used by the federal government for a variety of materials, including coatings. These standard colors, identified by 5-digit numbers and defined by colormetric data, can be used to select and procure a coating with the desired color. The standard also includes Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 449
SSPC CHAPTER*LB.O 93 m 8627940 0003897 3T0 m %-by-I-inch chips for desk use and 3-by-5-inch chips available in sets of 496 or as individual chips for inspection use. Kelly and Judd"') of the National Bureau of Standards describe a method or language of designating colors in simple, easily understood but accurately defined leveIs. GSA purchases and stocks commonly used specification paints in large volume so that it can supply these paints to agencies at a low price. Paints stocked by GSA are analyzed for conformance to specification and checked annually at one of its regional laboratories. Use is made of the Class 8010 listing of the Federal Supply Classification. Agencies usually have the authority to purchase small volumes of paint from local suppliers. Although GSA-supplied paints are tested for conformance to specification, a purchaser may have a paint tested if there is reason to believe it has deficiencies. When specification paints are purchased by a contractor for use at 'a government agency, the agency may accept an affidavit from the supplier that the paint conforms to specification or have the paint analyzed by the supplier, a government laboratory or a private laboratory. When government specifications list physical or chemical requirements for paint, they reference or describe the methods of testing. Referenced methods are usually those of Federal Test Method Standard No. 141 or the ASTM). The trend is to use ASTM rather than federal standards. When the desired test is so unique that it has not been published in either of these sources, the method must then be written in full in the specification. 111. SURFACE PREPARATION AND PAINT APPLICATION AND INSPECTION Surface preparation standards used in government contracts for painting steel surfaces are generally those of the Steel Structures Painting Council118). The pictorial surface preparation standards prepared by the Swedish IVA Corrosion Committee and jointly approved by SSPC, ASTM and the Swedish Standards Association are occasionally used in the field. Standards of the National Association of Corrosion Engineers and Society of Naval Architects and Marine Engineers are less often used. The equipment and methods for achieving these standard conditions are described in the Tri-Services Manual~lzl, National Bureau of Standards Building Science Series 7113), type specifications, and special instructions, such as Chapter 631 of Naval Ships Technical Manual(14)'. The US. Department of Interior has published a paint manual describing the application and use of high performance systems for large hydraulic str~~t~re~~~~~.publications and the These specification itself provide general instructions for the
mixing, thinning, coverage, and application of specification coatings. Suppliers of proprietary coatings provide product data sheets on their coatings. Inspection of government painting contracts is usually conducted by trained government inspectors. These inspectors check for level of surface preparation, general apTABLE 1 ADDRESSES OF REFERENCED ORGANIZATIONS American Society for Testing and Materials 1916 Race Street Philadelphia, PA 19103-1 187 General Services Administration Federal Supply Service Environmental 8, Engineering and Commodity Management Center Environmental, Engineering Policy Division (FCRE) Washington, DC 20406-0001 General Services Administration Specifications Unit Branch L'Enfant Plaza Washington, DC 20407 GSAIFSS Paints & Chemicals Commodity Center Engineering Division (9FTE-1 O) GSA Center Auburn, WA 98001 Information Handling Services 15 Inverness Way East Englewood, CO 801 12 National Association of Corrosion Engineers P.O. Box 218340 Houston, TX 77218-8340 National Paint and Coatings Association 1500 Rhode Island Avenue, NW Washington, DC 20005-5597 Society of Naval Architects and Marine Engineers 601 Pavonia Avenue Suite 400 Jersey City, NJ 07306 Standardization Documents Order Desk 700 Robbins Avenue, Building #4, Section D Philadelphia, PA 191 11-5094
Steel Structures Painting Council 4516 Henry Street Suite 301 Pittsburgh, PA 15213-3728 Superintendent of Documents U.S. Government Printing Office Washington, DC 20402-9325 U.S. Dept. of the Interior Bureau of Reclamation Box 25007 Denver, CO 80225 --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 450
SSPC CHAPTER*LB.O 93 8627940 0003898 237 pearance of canned paints, adequate workmanship during application, required wet andlor dry film thickness, complete curing, acceptable appearance of applied paint, and absence of holidays and other defects. They also check to determine that all health, safety, and environmental restrictions are met in full. The federal government has a unique system for the procurement of painting materials and services. It was designed to obtain such materials and services that meet satisfactory standards at minimum costs. It is only from a thorough understanding of this system by government and private industry that a satisfactory relationship between them can be reached. ACKNOWLEDGEMENT The authors and editors gratefully acknowledge the active participation of the following in the review process for this chapter: AI Beitelman, Leon Birnbaum, Dave Bloodgood, R. Brady, Paul Campbell, A. Chasan, T. Corboy, T.A. Cross, Hing Dear, Ted Dowd, J. Foster, Harlan Kline, Melvin Sandler, and Bill Wallace. The chapter was also presented to the following for advance review: B. Appleman, Duane Bloemke, R. Brown, Jack Kiewit, and Bill Pearson. BIOGRAPHY Richard W. Drisko has BS, MS, and PhD degrees from Stanford University. He has been employed at the Navy s Civil Engineering Laboratory since 1950 and is currently the Director of the Materials Science Division. His special area of expertise is protective coatings. He is a member of various committees of the SSPC. He is also involved in the development of their inspection manual. He has belonged to several technical societies such as the American Chemical Society, the National Association of Corrosion Engineers, and the Federation of Societies for Coatings Technology, serving in organizational offices and on technical committees, chairing symposia and presenting papers, and authoring articles in scientific journals. He has also served in offices of civic, health, and professional organizations and is a registered professional engineer (corrosion) in the State of California. BIOGRAPHY Howard G. Lasser has BS, ChE, and D.Eng. degrees from Lehigh University, Columbia
University, and Darmstadt Polytechnic Institute, respectively. He has worked for different organizations in the federal government for about 30 years and industry for 12 years specializing in application and uses of coatings. Currently he is a chemical engineer with Materials Research Consultants. He has authored about 500 technical articles and specifications and has received six patents. He is a member of numerous professional and honorary societies including Sigma Xi and Tau Beta Pi and is a registered professional engineer in the District of Columbia and the states of California and Virginia. REFEREN CES 1. Selling to the Military , Sup. Doc. Stock No. 008-000-00226-6, Superintendent of Documents. 2. An Introduction to the Defense Supply Agency , Public Affairs Office, Cameron Station, Alexandria, VA 22314. 3. A Guide for Private Industry , Department of Defense Single Stock Point for Standards and Specifications. 4NDNPFC-412013 (Ref. 1-75), Plate No. 17023, Navy Publications and Form Center. 4. How to Obtain Consideration for Architect-Engineer Contracts with Department of Defense , Office of Assistant Secretary of Defense (I&L). Sup. Doc. No. 008-007-02778-6, Superintendent of Documents, June 1976. 5. Selling to Navy Prime Contractors NAVMAT P-1030. Chief of Naval Material, Navy Publications and Forms Center, July 1976. 6. F-M, Standardization Policies, Procedures, and Instruction , Defense Standardization Manual 4120. Superintendent of Documents, Jan. 1972. 7. Executive Office of the President, Office of Management and Budget letter to the Heads of Executive Departments and Establishments, Nov. 30, 1976. 8. Outline of Forms and Instructions for the Preparation of Specimens and Associated Documents , MIL-STD-961. Navy Publications and Forms Center, Sep. 22, 1975. 9. Outline of Forms and Instructions for the Preparation Standards and Military Handbooks , MIL-STO-962. Navy Publications and Forms Center, Sep. 22, 1975. 10. Standardization Directory 1 July 1977 , SD-1, Navy Publications and Forms Center (updated quarterly). 11. Paint, Varnish, Lacquer, and Related Materials; Methods for Testing of , Federal Test Method Standard No. 141, Feb. 1, 1979 with later change notices, Navy Publications and Forms Center. 12. Paints and Protective Coatings; Army TM 5-618, NAVFAC MO-110, and Air Force AFM 85-3; Superintendent of Documents. 13. A.G. Roberts, Organic Coatings Properties, Selection and Use . National Bureau of Standards Building Science Series 7, Feb 1978, Superintendent of Documents. 14. Preservation of Ships in Service (Paints and Cathodic Protection) , Chapter 631 (Formerly 9190). Naval Ship Systems
Command (1979). US. Government Printing Office. 15. General Specifications for Ships of the United States Navy, Section 631, Department of Navy, 1978, Superintendent of Documents. 16. Coatings and Color Manual CG 263, Department of Transportation, U.S.Coast Guard, with Amendments 1 and 2, July 1973, Superintendent of Documents. 17. K.L. Kelly and D.B. Judd, Color -Universal Language and Dictionary of Names . National Bureau of Standards, (Dec 1976). Superintendent of Documents. 18. John D. Keane, Systems & Specifications . Steel Structures Painting Manual, Volume 2, 1982. 19. Paint Manual , U.S. Dept. of Interior, Bureau of Reclamation, 1976. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 451
SSPC CHAPTER*LSmO 93 8627940 0003899 173 CHAPTER 19 TRAINING PROGRAMS FOR PAINTING by Jay/. Leanse I. INTRODUCTION Training programs are used by many companies that want employees to become efficient and productive, particularly where technical advances require improvement in knowledge and skills. In the coatings industry the use of high performance protective coatings, the critical need for effective surface preparation and paint application, and the development of sophisticated equipment make it necessary to have ongoing training programs for workers. There are increasing numbers of government regulations affecting the entire coatings industry. To comply, manufacturers must develop new materials. Trends away from low-solids systems have developed new technologies including coatings with at least 70% solids, two-part catalyzed systems, emulsions and latices, water-soluble and colloidal dispersions, powders, and radiation-cured systems.(V New systems require the development of different equipment and application methods. Regulations are felt in the paint shop in new procedures and techniques. Changes in materials and equipment make the old ways of painting unsatisfactory. New ways must be learned. Procedures associated with development of the latest materials and equipment must be communicated to those responsible for the work. Training provides an ideal forum for transmission of information. Training programs also make good economic sense. Most companies cannot afford to have their employees learn jobs by trial and error. For example, changes in resin formulations are taking place in the coatings industry to accommodate other new technologies and regulations. Resin systems will be made of more constituents and of higher priced raw materials. One anticipated result of the changes in resin systems is that in ten years the average price of a chemical coating is expected to be three to five times present levels. Higher prices makes it increasingly expensive to waste materials.
Waste is not the only consideration with higher-priced coatings. Painting a 50-foot freight car requiring an average of 29 gallons of paint cost $350 in 1977, including stenciling and labor.@) A decade from now the cost of the paint alone will be at least $500 -four times more than the $130 spent for the paint in 1977. Programs aimed at demonstrating correct procedures and techniques help to better use expensive materials and reduce costly mistakes caused by uninformed employees. Another way to use training is to target and eliminate specific or recurrent problems. If, for instance, delivery dates are constantly missed or certain coatings consistently present application problems or failures, a company should take measures to correct the problems. Once identified, paint defects, which result in costly and timeconsuming work, can be eliminated. Thorough instruction in airless equipment, for example, may be all that is necessary to reduce operator problems associated with high pressure spray equipment. Training can be regarded as a motivation tool or as a productivity initiator . People generally want to do quality work. But all workers must understand why things are done in a recommended way. If workers know why coatings must be applied in a particular way, they take greater pride and satisfaction in the work, and the owner gets desired results. II. STEPS FOR SUCCESSFUL TRAINING Application procedures must be followed correctly to produce high quality coatings. For this reason, emphasis on motivation is an integral part of any training program. Workers must have a sense of pride and of the importance of their work. Without that feeling even the most dedicated worker can lose interest. For training to be effective, the company must be receptive to change. Management must understand the need and objectives of training and support it. Training will not attain its potential if employees are not allowed to practice what they have learned. Acceptance must come from everyone -from upper management to supervisors and co-workers. In a study of problems that exist between learning and changes in behavior on the job, Katz@) says that once a worker recognizes a need to improve, and wants to learn how, other conditions must exist in the work environment. Primarily, it must be a permissive climate where new knowledge and skills can be used. A company not hostile to change can reap the benefits of an employee s training experience. Once the need for training is recognized, the next step is to determine the areas of need. Specific problems must be pinpointed. This task is more difficult than it first appears. Copyright The Society for Protective Coatings Provided by IHS under license with
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SSPC CHAPTER*LS.O 93 8627940 0003900 715 A. IDENTIFY TRAINING NEEDS A systematic approach helps determine the training needs of a company. For example, a trainer wishing to develop materials for painters and blasters must know specifically what those workers should learn. The question asked by the trainer, precisely what do the operators need to know to do the best possible job?
is commonly
answered, they must know everything about cleaning the surface and the equipment.
This may be true, but the
answer is too general to be of any value. The identification of specific tasks required of the operators must follow so that appropriate and useful materials can be developed. Trainers have developed a number of approaches to determine training needs. They include performance reviews, records, patterned interviews and surveys. One systematic approach includes four relatively simple techniques.WThe first of these is an individual performance appraisal. Once a person or group s performance has been evaluated, training can be developed in areas that specifically need improvement. A supervisor or worker should be able to isolate the problem. A second approach is to conduct a more general survey. A list can be given to supervisors asking them to rank the degree of need for different areas. Results can determine the content of the training program. A third method is to pre-test trainees to find what they already know. In training first-line supervisors, for example, their field experience is a sound training basis. Simply build on and reinforce knowledge that already exists. If skills are going to be taught, a perform-
ance teat should be designed; if knowledge or attitudes are to be taught, a written test is appropriate. The fourth approach is to seek help from an advisory committee of key people in the company. The committee helps to determine training needs and later to implement the program once designed. The trainer should be able to present the committee with materials for consideration, rather than asking broad and general questions. The purpose of the committee is to advise from different viewpoints within the company. This kind of committee is valuable when asking for reactions to information previously collected or for recommendations on how to proceed with training. The four approaches provide a basis for a training program. However, determination of needs alone does not assure a successful program. Once needs are identified, a logical step is to determine whether the problems can be solved by training, or whether procedural changes would be more effective. Training objectives should be outlined. B. WHOM TO TRAIN Once objectives are determined, a training program can be designed and trainees selected. A program could be designed for the entire paint department, with special emphasis for different job categories. For example, firstline supervisors can be trained for management duties while painters receive training in airless spray equipment, application of inorganic zinc or in safety and health procedures. Who is trained depends on the previously determined needs. There is a great difference in training for skills development and management responsibilities. Training related to painting procedures can also be designed for employees in other departments. If an objective is to design clearer specifications, then spec writers should receive training, perhaps in conjunction with the foremen in the paint shop. Other personnel who may be trained in the paint shop are QA and QC managers, field inspectors or supervisors and program managers. An effective level for training is with new employees. At this point basic skills instruction can be taught, especially if the employees are new to the field and unfamiliar with elementary painting procedures. This is also a good time to introduce company policy to employees, no matter what their status. Employees already with the company can also be trained. If an objective is to introduce new and better equipment and techniques to painters, employees must be brought up-to-date on changes. Training can be used as a motivational tool, especially when an employee has potential and desire to move up. Up and down the career ladder, all employees can
benefit from training, but only if the program is designed to meet specific needs. It cannot be over-emphasized that problem areas must be carefully determined and analyzed to set objectives and decide which employees will benefit most from a training program. C.TRAINING METHODS Once a company decides whom to train and what to teach, several training methods can be chosen. It is important to remember that training adults is different from formal schooling. Training should be compatible with the way adults learn. Trainers have identified certain patterns of adult learning that are important when preparing training programs. The following rules suggested by John Randall apply to every type of learning, whether it is acquiring skills, facts or changing attitudes.( ) Adults must want to learn; they must have some sort of an incentive, such as job advancement or a raise in salary. Adults learn only if they feel a need and can see the immediate benefits, such as learning a technique that makes a job easier. Learning and retention rates are highest among adults if they have active involvement in the learning process, such as immediate practice and continued use. This is especially true when learning new and unfamiliar skills. Adults build new learning on their previously acquired knowledge and experience. This is both an asset and liability in terms of training. If knowledge interpreted in terms of past experience does not fit well with previous experience, it is likely to be rejected. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 453
SSPC CHAPTERtL9.0 93 m 8b27940 000390L b5L m An informal environment is best. Even in classroom sessions adults should be treated as adults, not chi Idren. Adults learn better if information is presented in several ways. The instructor should make strong impressions on the five senses, particularly seeing and hearing. The more senses involved, the greater the learning. The shotgun technique of using lectures, visual aids and group discussions appeals to the wide range of individuals. Adults want guidance, not grades. They want to know how to measure their own progress without fear of failure or humiliation. In selecting a training method, advantages and disadvantages of each kind should be considered. Probably the most questionable training is in selftaught programs. The success of these programs depends on the student, who must have enough discipline and interest to read materials, absorb information and use what has been learned. Self-teaching programs present material in only one way and do not include practice, discussion, guidance and feedback. This method is more suitable as a guide rather than a teaching instrument. Ideally, on-the-job training is best. Since people are not perfect, they will make mistakes and acquire bad habits on the job. When one person passes knowledge to another, the bad is picked up with the good. This is especially true in the buddy system . Even the most exemplary worker, one who makes very few mistakes, may not be able to explain the how s and why s of the job. In addition, an experienced worker may have developed a unique method or style of doing a job that works well for him but not for an inexperienced co-worker. Experience and practice for a new employee in on-thejob training is valuable and can be effective when combined with formalized training in a classroom. This training can be implemented either by company staff or by outside trainers. D. WHO TRAINS The use of staff members is a cost savings to a company implementing a training course. For example, a paint
shop foreman may be chosen to develop training materials for painters because of experience in the field. The foreman is familiar with the company policies, procedures and objectives, as well as methods used. Trainees may know the foreman and there is no need to establish credibility. There are some drawbacks. First, he may have no experience in developing training materials and courses. An excellent foreman may be a terrible instructor. Second, his responsibilities as a trainer are an addition to his regular work. The training program is therefore not a top priority and the extra work may cause resentment. if the paint foreman is unfamiliar with designing and implementing training courses, the company can send him to a public course. In many cases, materials used in these courses can be brought back and adapted to the training needs of a company. Outside courses offered by experts may be more costly than in-house training but offer advantages. Primarily, the courses are given by specialists who are also established trainers. In this situation people from different companies share and interact and receive feedback from trainers. A public course brings together trainees from different companies that have similar jobs. In many courses there are opportunities for small work groups where trainees discuss and solve problems. They may also be assigned certain tasks, such as writing a specification. By interacting with workers from other companies a trainee must not only rely on his knowledge and skills, but can pick up valuable information from others. Training specialists can also design courses customized to a particular company. All the advantages of having in-house training can be realized along with the extra benefit of working with experts who have training experience. There may be a cost-savings because the company can hold the course on-site and train a large number of employees at once without additional costs of transportation.
E. EVALUATION OF TRAINING After implementing a training program a company will want to know if it was worth the time and expense. Trainers are continually trying different techniques of measuring changes in human behavior.(4) One way to evaluate a training program is to measure it in terms of onthe-job results. A successful program will meet the objectives set out in the beginning. Does the program address specific areas of need determined by the company? If workers are applying knowledge and skills, are on-the-job improvements visible? Have the costs been reduced or production increased? In addition to observing workers, trainees can be asked if they felt it was effective. Trainees reactions and evaluations may provide valuable insights for future programs. Unexpected benefits can also arise, for instance, improved morale, a greater sense of identification with a company and a decrease in organizational tensions. One study indicated that from the supervisor s viewpoint, what they learned was a secondary benefit of training.(3) Researchers found the primary benefit was that trainees had an opportunity to share and discuss problems with others in similar fields. The fact that the company had involved them in a training program showed their problems were a concern of management. Being included in the program also instilled a sense of importance among a group of workers who found themselves easily frustrated by their jobs. All of these factors contributed to a decrease in personnel tensions. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 454
SSPC CHAPTER*Lï.O 93 8627940 0003902 598 Even the most successful training program should not be considered a cure-all for a company s problems. Nevertheless, a properly-implemented program, designed for specific needs, provides a more effective workforce and contributes to the company s ultimate protective coating objectives. By implementing a training program a company can fill its ranks with efficient employees who will increase productivity. Educated employees are likely to be more efficient workers than those who have received no training. With greater efficiency among employees, productivity is increased and costs are reduced. Trained workers do a job right the first time and thus eliminate work and cost overruns. ACKNOWLEDGEMENT The author and editors gratefully acknowledge the active participation of the following in the review process for this chapter: Robert F. Bra dy, Jr., Alexander S. Chasan, Dr. Richard Drisko, Robert Klepser, R. McClelland, Marshall McGee, E. Praschan, L.M. Sherman, and William J. Wallace, Jr. --`,,,,`-`-`,,`,,`,`,,`--BIOGRAPHY Jay I. Leanse is Chairman of the Procos Group of Companies, manufacturers and distributors of paints, coatings and color. In addition, he is President of the Institute of Applied Technology, a technical and training organization concerned with painting and coating practices and productivity. REFERENCES 1. John D. Keane and Joseph A. Bruno, Jr., Evaluation of LowSolvent Maintenance Coatings for Highway Structural Steel, Steel Structures Painting Council, October 1981. 2. Anonymous, Working on the Railroad, Modern Painfs and Coatings, October 1978. 3. James A. Belasco, and Harrison Trice, Unanticipated Returns of Training, Training-and Development Journal, July 1969. 4. Ronald J. Burke, A Plea for Systematic Evaluation of Train. ing, Training and Development Journal, August 1969. 5. Robert Katz, Human Relations Skills Can Be Sharpened, Harvard Business Review, July-August 1956. 6. Donald L. Kirkpatrick, Determining Training Needs: Four Simple and Effective Approaches, reprint from Training and Development Journal, 1975. 7.John Randall, You and Effective Training: Part 2 -The Lear-
ning Process, Training and Development Journal, June 1978. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 455
SSPC CHAPTER*20-0 33 8b27940 0003903 424 CHAPTER 20 THERMAL SPRAYED COATINGS by S.J. Oechsie and J.N. Childs, Jr. Thermal spraying, formerly called metal spraying, or metallizing, is an effective type of protective coating, either by itself or in combination with organic coatings. In practice, the two most common metals applied by the technique are zinc and aluminum. Thermal spraying is the only practical method of applying metallic coatings to large fabrications, often in the field. The metallic sprayed surfaces are excellent bases for accepting sealers andlor applying top coats that bond strongly to the metal coating. Metallic coatings with or without topcoats often offer unique properties to help solve some corrosion problems that organic coating systems alone cannot provide, particularly in galvanic protection or abrasion resistance. This discussion provides familiarity with thermal spraying, and covers the types of thermal spraying equipment, principles of operation, hazards involved, characteristics of sprayed metal, nature of protective functions, the extremely important subject of surface preparation and the use of sealers and topcoats. The American Welding Society through its C-2 subcommittee on thermal spraying is an up-to-date source on all aspects of the subject and publishes a wide variety of information. In particular, its publication, "Corrosion Tests on Flame-Sprayed Coated Steel -19 Year Report", is a valuable practical report on the results one can expect from actual tests in a wide variety of industrial and marine atmospheres. The large subjects of thermal spraying for repair of mechanical parts and for obtaining desired surfaces in the manufacture of new equipment and engines are not discussed in this article. I. TYPES OF EQUIPMENT The thermal spraying process consists of melting the metal or ceramic and then spraying it onto a prepared surface by means of compressed gas, which aids in the division of the molten particles and the projection from the vicinity of the melting onto the surface. One tool commonly used is a hand-held gun with an air motor that draws the metal in wire form through knurled feed rolls into an oxygen-fuel gas flame where the wire is melted. The molten metal is then projected onto the prepared surface by the products of combustion augmented by an air blast.
The metal wire, (usually zinc or aluminum) is ordinarily or Jlis" (3.2mm or 4.8 mm) diameter. Such a gun is capable under ideal conditions of spraying zinc at a rate of 60 pounds per hour (27 kglhr) or aluminum at the rate of 17 pounds per hour (7.7 kglhr). This is equivalent to 1000 sq. ft. of zinc coating per hour 1 mil thick (93 sq. ml25p) or 1250 sq. ft. of aluminum coating per hour 1 mil thick (116 sq. mi25p). Because of field conditions, such as erecting scaffolding, changing wire, moving, etc., these rates are rarely practical and actual rates are more likely to be 60-65% of these amounts. Such wire guns typically weight three to five pounds (1.4-2.25kg) are used in much the same manner as paint spray guns and can be readily handled at the end of a considerable length of oxygen, fuel and air hoses, often in excess of 200 ft. (60 meters). The hoses and feed wire make the handling of the gun a little more difficult than would be suggested by the light weight of the gun alone. Another type of thermal spray gun is the plasma spray gun. In this process the metal is introduced into the plasma arc cavity in powder form in a gas stream and projected onto the prepared surface by the force of the plasma jet. The gun is light, like the oxygen-fuel gas gun described above, but attached to it are two fairly stiff electric leads and the powder feed hose, all of which tend to decrease maneuverability. The metal-sprayed deposit rate is about the same as with the oxy-fuel gas equipment. The plasma spray equipment requires a special power source, and the lead distance from this source is appreciably less than the case of the oxy-fuel gas equipment. Some oxy-fuel gas thermal spraying equipment uses powder as a source of coating material. As in the plasma arc equipment, the powder is introduced in a gas stream (usually air) into the combustion area. The oxy-fuel gas powder equipment is of interest because it can be used for the thermal spraying of certain organic materials such as powdered thiokol or polyethylene. Another type of thermal spraying equipment is the electric arc gun. In this equipment the tips of two wires are brought together so they arc continuously in the presence of an air jet. The molten metal is conveyed to the prepared surface by the air jet. This equipment is bulkier and somewhat heavier than any of the equipment described above and with six leads (two power cables, two wire feeds, one air hose, and one electric control cable) is more awkward to handle. On the other hand, the deposit rate is considerably higher, by a factor of two to three. The deposit is usually slightly less dense than in the case of the oxy-fuel gas equipment. The requirement that the power supply be relatively Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 456
SSPC CHAPTER*20.0 93 = 8627940 0003904 360 close to the gun tends to limit maneuverability, particularly sprayed coatings a re formed helps in understanding these when scaffolding is involved. characteristics. As the molten particles are torn away from the wire tip, they assume a roughly spherical shape that is II. OPERATIONAL PRACTICE maintained in transit. Upon striking the surface, the p arMost field work in thermal spraying is performed with oxy-fuel gas, wire fed equipment. The discussion that follows will describe the practical hook-up and operation of such equipment. Much of the discussion also applies to use of plasma, powder, or electrical arc equipment. Oxygen and fuel gas (usually acetylene or propane, particularly the latter if the hoses are long and safety considerations keep acetylene bottles from certain areas) are connected through two stage regulators to the gun. For best operation, flowmeters should be used. Flowmeters (usually tapered glass calibrated tubes) permit accurate volumes and ratios of gases to be obtained independent of inaccurate regulators or hose friction. Excess oxygen results in coatings containing considerable oxides accompanied by low spraying speeds and poor atomization. The compressed air should be as free of excessive oil and moisture as is practical, and some kind of filter should always be used. A pressure regulator just for the gun itself is important in producing a good and consistent quality coating. Areas to be sprayed should be marked off, and the required amount of wire for each area should be weighed carefully and placed on a wire reel stand. Once the gun is ignited, the wire speed is adjusted to obtain proper atomization and deposit, usually by adjusting a regulator. In order to minimize fatigue on the operator, he normally does an area about 18 inches square (.46 m sq.) completely before proceeding to another area. The gun should be held at 6 to 10 inches (15 cm. to 25 cm.) from the surface and as nearly perpendicular to the surface as possible. Straight uniform passes should be made, overlapping somewhat on each pass. After the square is covered, the operation should be repeated -this time with the passes at right angles to the previous passes. The thickness of the deposited coating can be checked with a magnetic thickness gage. After a little practice, an operator will learn about how fast he must move to put down a given coating thickness per pass (usually 2 to 3 mils or 0.05 to 0.08 mm). Inspection of a fairly large area (approximately 100 sq. ft. or 9.3 sq. m.) should be made with a magnetic thickness gage soon after it is finished. This will permit additional metal to be deposited in areas before the surface has a chance to become damp or otherwise contaminated.
l. CHARACTERIST CS OF SPRAYED METAL Certain characteristics are common to all sprayed metal deposits, and a knowledge of the manner in which ticles flatten into irregular-shaped discs and at the same time flow into the pores and irregularities of the surface. Part of the attachment is due to mechanical interlock, and part of it is due to the chemical affinity of the sprayed metal for the prepared surface. The measurements of bond strength between the coating and the base are not fully verifiable; but indications are that it varies from a few pounds to about three thousand pounds per square inch, depending on the type of surface preparation, the kind of coating metal, and the method of measurement. As the coating is built up, a thin oxide film is formed on the particles as they accumulate on the surface. Total oxide in the coating runs from 0.5% to 3.0%,depending on the coating metal and the spray technique. Because of oxide inclusion and the incomplete filling of pores, the specific gravity of the coating is 85% to 95% of that of the parent wire. As the molten particles flatten and are quenched against the surface, the contraction of freezing and normal thermal contraction produce a tendency to shrink . This tendency varies with different metals, and is important in deciding the type of surface preparation needed, since the shrink imposes a stress on the bond to the base. Thick coatings require a more thorough blast preparation (¡.e., coarser abrasive, higher pressure) than thin coatings, since the stresses developed are cumulative. Zinc and aluminum are the only metals widely used in preventing corrosion of steel structures. Some of the physical properties of sprayed deposits of these metals are given below. The practical thickness of a sprayed aluminum coating is in the range of 0.002 inches to 0.010 inches (0.05 mm to 0.25 mm) applied over a minimum surface profile of 0.002 inches (0.05 mm) at the lower coating thickness range and over a minimum roughness etch of 0.0045 inches (0.11 mm) at the 0.010 inch (0.25 mm) coating thickness range. Sprayed zinc, with its greater ductility, can be practically applied over a much larger thickness range, ,003 inches (0.08 mm) to 0.025 inches (0.64 rnm) or more, over a minimum surface profile of 0.001 inches (0.03 mm) at the lower coating thickness range and over a surface profile etch of 0.003 inches (0.08 mm) at the 0.010 inch (0.25 mm) or more coating thickness range. Bond strengths of three thousand pounds per square inch are achievable, and with plasma or electric arc equipment can be considerably higher. The most important practical element in obtaining good bond strength is surface preparation. The appearance of the metal sprayed
surface is similar to that of medium grit sandpaper. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 457
SSPC CHAPTER*20.0 93 8627940 0003905 2T7 TABLE 1 PROPERTIES OF SPRAYED METAL DEPOSITS Tensile Strength* Sprayed Metal (PSI) kgkm2 Aluminum 19,500 (1371) Zinc 13,000 ( 914) Spec. Gravity Shrink (Yo of Hardness (infin.) Orig. Wire) (Rockwell) 0.007 94.1 H 72 0.01o 89.0 H 46 *These figures will vary with the method of measurement and are intended as a gu ide only. IV. NATURE OF PROTECTION There are three basic methods of protecting steel against corrosion. The first and most common method is the exclusion of the environment from the metal, by means of painting, plating or dipping, metallizing, vitreous enameling, cladding, or sheet lining. The second is based on reducing the aggressiveness of the reagent which reaches the surface. This may be done with inhibitive pigments in paints or by inhibitors added to the reagent, as in a re-circulating water system. The third is by cathodic protection. The protection provided by sprayed metal systems employs to some extent all three of these principles. These principles will be discussed in the order given above. Exclusion of the environment may be accomplished in some cases by using sprayed metal with no sealer. As sprayed, the coatings are slightly porous and will transmit moisture more readily than even a very poor paint system. However, in some environments the pores are soon filled with salts formed within the coating itself, and thus the coating becomes relatively impermeable. Since it is not always easy to determine the effects of the environment, sprayed metal coatings are frequently given a sealing treatment. Inhibitive pigments used in paint systems for steel structures may be added to the prime coat, and may also be a part of the body or top coats. Generally, such pigments as zinc chromate are slightly soluble and their use is limited to the prime coat. When sealers or paints are used with sprayed metal, a prime application containing an inhibitor is generally useful and often essential. Such coatings passivate the surface and have some compatibility with moisture, in addition to their inhibitive properties. It should be noted here that primers are not needed to promote bonding of body or finish coats to the sprayed metal;
the texture of sprayed metal is such that peeling of paint coats is not encountered unless there is a rather violent reaction under the paint film. Cathodic protection provided by sprayed zinc or aluminum coatings is not subject to many of the limitations inherent in the usual cathodic protection systems. Sprayed coatings of these metals protect electrochemically in atmospheric exposures as well as underground or immersed in water. When steel is exposed, as by mechanical damage, the adjacent sprayed metal will confer electrolytic protection over considerable areas in some environments. Aluminum coatings are usually slightly cathodic to steel when freshly sprayed, due to the oxide film surrounding the particles that make up the coating. As the coating weathers, the potential reverses and the coating becomes anodic. This reversal requires only a few minutes or hours in salt water but may require several weeks in atmospheric exposures. As a result, unsealed sprayed aluminum when exposed in a humid atmosphere will often show a light red oxide staining on the surface after a few days. An examination of the aluminumlsteel interface will disclose no visible rusting of the base, and the bond to the base is not measurably impaired. But since stained surfaces are unsightly, a sealer is generally used on sprayed aluminum for atmospheric exposures. Sometimes the fresh, aluminum sprayed surface is treated with an anodizing solution to . make the surface almost immediately anodic. Cathodic sprayed metal coatings such as bronze, monel, stainless steel, etc., are seldom used as protective coatings on structural steel because their cathodic nature stimulates attack of the base steel when steel is exposed to alkaline solutions with a pH of 11 or more. V. SURFACE PREPARATION FOR METALLIZING In order to bond properly, sprayed metal coatings require a thoroughly cleaned and roughened base. For most corrosion preventive work, only abrasive blasting can produce suitable surface characteristics. Cleanliness is important regardless of the type and thickness of the coating metal. Fingerprints or other traces of moisture or contamination may result in practically no bond. Slight rust discoloration, such as may appear on blasted surfaces after a few hours, does not necessarily impair the bond Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 458
SSPC CHAPTER*20-0 93 8627940 0003906 133 seriously, but the presence of rust indicates a strong probability that some adsorbed moisture will seriously affect the bond. Oil or moisture originating in the air used for the blast operation can cause trouble. Thus, additional oil or moisture separators are often required or specified in the compressed air lines. Occasionally, even the humidity of the air in contact with the area to be sprayed must be controlled. Dehumidifiers with large volumes, for instance, can be used inside closed vessels and ships. Thick sprayed metal coatings require a rougher surface than thin coatings, and aluminum requires a rougher surface than zinc of equal thickness. With any given abrasive, roughness may be increased somewhat by increasing the air pressure. As a rule, however, the required roughness is obtained by selection of the proper abrasive. Several types of abrasive, so long as they are angular and sharp, may be used for the blast cleaning operation. On inside work where the abrasive can be reclaimed, angular chilled iron grit or aluminum oxide is generally used. This material may be reused from ten to one hundred times if kept free from contamination and excessive fines. The most commonly used material for inside work is angular chilled iron grit, size numbers SAE G-18and G-40. The size depends on degree of roughness and bond strength required. Suction feed, force feed, and centrifugal blast machines are used. Adequate ventilation or respiratory protection and eye and ear protection must be provided for the operator. VI. COMBINATION SYSTEMS At first consideration it would seem unnecessary, redundant, and overly expensive to treat a zinc or aluminum sprayed coating with a sealer or to apply a paint, but there are many advantages to doing so and present practice is to employ such treatment in almost all cases. A. ADVANTAGES OF SEALERS Among the advantages of combination coatings are: Providing both barrier and cathodic protection against corrosion; Providing superior adhesion for painting as compared to most metal surfaces; Permitting the wide variety of color finishes that are available in paints; Reducing tendencies of the sprayed metals to retain dirt and dust; and Offsetting the relatively high cost of sprayed
metal by using a thinner sprayed coating and a proper sealer. B. DISADVANTAGES OF SEALERS Disadvantages of sprayed metal as a paint base are: It usually requires more paint to cover a given area because of the rough and porous nature of the sprayed metal. It requires even more paint if the final surface is to be relatively smooth for easy cleaning. Because not every organic sealer or top coat is compatible with the sprayed metal, considerable care must be exercised in selecting a formulation. C.REQUIREMENTS FOR SEALERS The principal requirements of paints or sealers to be used with sprayed metal are as follows: 1. They must be resistant to the environment. However, paints that might fail by crazing or loss of adhesion on other surfaces can sometimes be used because of the better anchor available over sprayed metal. 2. Coatings must be chemically compatible with the sprayed metal. Some formulations that perform well on steel fail rapidly on zinc or aluminum. For example, short oil phenolic varnishes generally fail rapidly when applied to sprayed zinc and exposed to a wet environment. Vinyl copolymers applied directly to zinc, without a wash primer, sometimes blister in a short time. Films formed from tung or linseed oils or alkyds may become slightly acidic under some conditions and may disbond when used in paints applied to aluminum. Bituminous paints or enamels should be used with caution over zinc, but have stood up well on aluminum in some cases. 3. Coatings must have good penetrating ability. Heavy, viscous paints applied directly to the sprayed metal may do more harm than good. Such paints allow moisture to enter unfilled pores in the sprayed metal and to cause blistering. Heavily pigmented paints should be avoided except as topcoats after the pores are filled with one or more coats of sparingly pigmented paint. The fact that organic materials must be compatible with the sprayed metal cannot be emphasized too strongly. There are far too many examples of failures because one application firm applied the metallized coating and a second applied a paint coating on top of it that should not have been used. It would have been far better to leave the metallic coatings bare and uniformly corroded than to cause spot failures and localized corrosion. A wash primer, preferably of the polyvinyl butyral type containing not over 4% by weight of phosphoric acid in the mixed material, should be used with coating systems that will be exposed to wet environments. It should also be
used, regardless of environment, if there is any chance that the sprayed metal has absorbed any moisture prior to the painting operation. If the wash primer is omitted, blistering is almost certain under the above conditions. A suitable wash primer is US. Military Specification DODP-15328; application is covered by Steel Structures PaintCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 459
SSPC CHAPTERx20.0 93 8627940 0003907 07T W ing Council Specification SSPC-Paint 27, Chromate-Vinyl Butyral Wash Primer .
Basic Zinc
Sealers or top-coats based on vinyl co-polymers or vinyl-alkyds have given excellent results with sprayed aluminum. Formulations of this type perform well with sprayed zinc, but in the case of zinc the wash primer should be used. Generally, phenolic base paints or varnishes should not be used over sprayed zinc, and the use of straight oil base paints is not recommended. As a rule, the pigments used in paints are not a critical factor, particularly in the newer vehicles, which provide films having low permeability. However, red lead pigments have not been satisfactory in paints used over sprayed zinc, and some failure of red lead pigment paints applied to sprayed aluminum have been reported. Pigments such as zinc, zinc oxide, aluminum powder or flake, titanium oxide, or white lead have all been used in paints that performed well over both zinc and aluminum. VII. EXPERIMENTAL RESULTS A program sponsored by the American Welding Society subcommittee on Thermal Spraying studied the actual results of more than four thousand test panels exposed to various environments at eight different test sites for nineteen years. The results of this program have been published in Corrosion Tests of Flame-Sprayed Coated Steel 19-Year Report , AWS-C2-14-74, Miami, Florida. Exposures include total and half tide immersion in sea water, as well as rural, seacoast and industrial atmospheres. (See Appendix A.)The report lists the results in eight general areas as follows: (See Appendix A of this chapter for the conclusions as they appear in the 19-Year Report.) 1. Aluminum-sprayed coatings 2. Unsealed zinc-sprayed coatings 3. Severe marine atmospheres 4. Thincoats of aluminum coatings 5. Damaged aluminum coatings 6. Effects of surface preparation 7. Flame sprayed coatings 8. Chlorinated rubber For those who have followed these tests through the six-year and nine-year reports, the most striking results were: Many of the metallic coatings look as though they will continue to succeed for another nineteen years. The aluminum sprayed panels survived the exposure better than the zinc sprayed ones. The thickness of the sprayed aluminum does not appear to be a major factor in protection. The corrosion protection afforded by sprayed zinc and aluminum coatings does not depend
on the surface preparation (other than a clean, dry, abrasive blasted surface preparation). The use of a steel flash-bond coat is not essential. VIII. RECOMMENDATIONS AND COSTS The principal choices in connection with a specific application are whether to use zinc or aluminum as the coating material and whether or not to use a sealerltop coat. The characteristics and special evaluations of these choices may be summed up in the following paragraphs: A. ZINC Zinc wire with a minimum purity of 99.9% is used. A coating 0.003inches (0.08 mm) thick provides one and onehalf ounces per square foot of surface (460 glsq. m.) and compares in weight with the average galvanized coating. However, the user is not limited to this thickness, but may apply coatings up to 0.020 inches (0.5 mm) thick. Zinc applied by hot-dipped galvanizing has a life roughly in proportion to its thickness. The same is generally true of heavy coatings of sprayed zinc and of light coatings if properly sealed. Unless sealed, thin coats of sprayed zinc 0.001 inches to 0.003 inches (0.025 mm to 0.076 mm) may corrode quickly because of electrolysis which occurs at the voids. Under conditions that result in the formation of dense, relatively insoluble salts in the pores of the zinc, sealing may not be necessary. Such a condition would exist in well aerated fresh water having a pH value of 8 to 9. Zinc is at its best in the pH range of 7 to 10, but under some conditions it may show good resistance in slightly acidic environments. On outside structures having areas not readily accessible, zinc probably has an advantage over aluminum because of the greater electrolytic protection it affords. In a sense, sprayed zinc coatings can often be considered as a form of cathodic protection. Sprayed zinc used on underground or immersed surfaces will confer a measure of protection to other parts of the structure that are bare. While there may be some superficial rusting at adjacent areas, heavy attack and pitting is often prevented in the same way that zinc slabs on a ship hull prevent serious pitting at breaks in the paint. The coating will, of course, sacrifice to the extent that it protects bare steel areas, and if the ratio of bare area to coated area is large, the coating cannot be expected to last very long. Highly reactive wash prime treatments containing over 4% by weight of acids, which may be suitable for hotdipped zinc, should not be used prior to applying sealers or top-coats. Straight oil bases, alkyd-oil bases, and short oil of 100% phenolic bases are not generally satisfactory. Recommendations of recognized contract shops should be taken with regard to the proper sealers, usually special vinyls. Chlorinated rubbers are not recommended. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 460
SSPC CHAPTER*20.0 73 m 8627740 0003908 Tob m TABLE 2 TYPICAL THERMAL SPRAYED SYSTEMS EXPOSURE SPRAYED METAL THICKNESS SEALING OR PAINTING Rural Atmospheres Aluminum 0.004 epoxy.
0.1 mm Sealed with 1 coat of clear vinyl or
Rural Atmospheres Zinc 0.003 0.076 mm Painted with 2 coats aluminum vinyl or 1 coat of anti-corrosive vinyl with colored vinyl or vinyl alkyd top coat. Industrial Atmospheres Mild (light) Aluminum 0.004 0.1 mm Sealed with 1 coat of clear vinyl or epoxy. Severe (heavy) Aluminum 0.006 0.15 mm Painted with 2 coats of aluminum vinyl or colored alternate as above. Marine Atmospheres Mild (light,no salt spray) Zinc 0.006 0.15 mm Wash primer and aluminum vinyl optional. Severe (heavy with spray) Zinc 0.012 0.3 mm Wash primer and aluminum vinyl optional. Severe (heavy with spray) Aluminum 0.006 0.15 mm Wash primer and aluminum vinyl. High Humidity Atmosphere Zinc 0.004 0.1 mm Painted with 3 coats of aluminum vinyl. Fresh Water Immersion Below 120°F. (49°C.) Zinc 0.010 0.25 mm No subsequent treatment. pH above 6.57.5 Salt Water Immersion Zinc 0.012 0.3 mm Wash primer and aluminum vinyl op tional. Salt Water Immersion Aluminum 0.006 High Temperature Aluminum 0.006 paint.
0.15 mm Wash primer and aluminum vinyl.
0.15 mm Two coats aluminum silicone
B. ALUMINUM C. TYPICAL METAL SPRAYED SYSTEMS The results of the AWSC2.14-74 19-Year Report have Thickness of sprayed metal co atings is determined by done much to do away with any hesitation regarding use of the severity of the ex posure and by the required life of the sprayed aluminum as a protective coating. coating system. Obviously, it would be wasteful to apply a Aluminum has many advantages over zinc for certain protective system that would be expected to last twenty classes of work. It has better resistance to slightly acid en- years to a struct ure that will be obsolete in five or ten vironments, and has been used in contaminated waters years. Furthermore, on stru ctures where periodic repainthaving a pH value as low as 3.0. It has better resistance ing will be done to ma
intain good appearance, thin than zinc to sea water, brine, or salt atmospheres. It has sprayed metal coating s will serve as well as heavier and much better resistance to industrial atmospheres than more expensive coatings. does zinc, whether used as sprayed, or as a paint base. Table 2 shows thicknesse s and supplementary treatWhen only a small part of a submerged structure is to ments commonly recommended for the various types of be coated, aluminum should be used instead of zinc. The exposure. When the term s ealed is used, it indicates a potential difference between aluminum and steel is low single application of cle ar sealer such as vinyl lacquer or enough so that aluminum will not sacrifice rapidly, except clear phenolic varnis h. The term painted indicates a in extreme cases. Zinc, on the other hand, will dissipate treatment that not onl y fills the pores but also forms a film rapidly under such conditions. on the surface, with materials such as vinyls, vi nyl alkyds, The same factors in selecting sealing or top-coats ap- or suitable enamels. Thes e recommendations are useful plicable to zinc are generally applicable to aluminum. as a general guide. Howev er, each job should be conSelection of chlorinated rubber is not recommended. A sidered as an individual p roblem, with special factors to be coating 0.004 inches thick (0.1 mm thick) provides one considered before specify ing the coating system to be used. ounce per square foot of surface (305 glsq. m.). Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 461
SSPC CHAPTERr20.0 93 8b27940 0003909 9Y2 TABLE 3 TYPICAL METAL SPRAYING DATA* The following numbers are from tables contained in a typical equipment handbook and represent the theoretical performance of new equipment under optimum conditions. Use with discretion. Consumption Per Hour Coverage Wire Size Weight Oxygen Acetylene Per Hour" Inches mrn Pounds kg cu.ft. CU. rn. cu.lt. CU. rn. sq.lt. sq. rn. Aluminum 716 4.76 17.6 8.0 80 2.27 39 1.12 250 23 Aluminum 'is 3.17 10.7 4.86 78 2.21 38 1.1 157 15 Zinc %6 4.76 61.0 27.7 84 2.38 41 1.16 247 23 Zinc 'i, 3.17 40.7 18.5 81 2.29 40 1.13 160 15 --`,,,,`-`-`,,`,,`,`,,`--'Theoretical data based upon 100% capacity and no lost time. "Any applied zinc coating 0.005" thick (5 mils or 0.127 mm) requires the sprayin g of approximately 0.25 Ibs. (4.0 oz.) of zinc per square foot (1223 g1sq.m.). An aluminum coating 0.005" thick (5 mils or ,127 mm) requires the spraying of ap proximately 0.07 Ibs. (1.12 oz.) of aluminum per sq. ft. (342 g/sq.m. for ,127 mm thickness). These are average deposition ef ficiencies for normal metallizing operations but do not allow for edge or other unusual losses. A more typical comparison table used by an experienced contractor might be as fo llows: INORGANIC Field Performance: 'h" AL. 7,s " AL. ZN Xe" ZN ZINC One hour gun operation 100 sq.ft./hr. 150 sq.ft./hr. 100 sq.ft./hr. 150 sq.ft./h r. 350 sq.ft./hr. with good clear open (9.359 sq.m./hr.) (13.9 sq.m./hr (9.31 sq.m./hr (32.5 sq.m. /hr (32.5 sq.m./hr) space, no scaffolding, 5 mils thick 5 mils thick 5 mils thick 5 mils thick 4 mil s thick no time out for measure- (.127 mm) (.127 mm) (.127 mm) (.127 mm) (.1mm) ment, operator change, 7# AL. 10.W AL. 25# ZN 38# ZN breaks, etc. Cannot (3.2 kg) (4.8 kg) (11.4 kg) (17.3 kg) be maintained for ZINC RICH
eight hours. 350 sq.ft./hr. (32.5 sq.m./hr.) 2% mils thick (.O64 mm) Inspection of all operations must be thorough for A small area, approximately I/ z inch x $/Z inch (12 mm good results; failures that have occurred have been traced x 12 mm) can be marke d by a chisel and the sprayed to improper procedures. The blast cleaned surface should coating lifted off with a knife to give a rough indication of be inspected to determine that the surface profile is suffi- bond strength and t hickness. ciently rough and that adequate cleaning has been done. The damage done by such a bond test is readily Blast abrasives should be checked for sharpness, repaired by reblasting and reco ating. cleanliness, and proper size; proper air pressure and clean air are essential. D. COSTS There are several instruments available for the nondestructive measuring of the thickness of applied sprayed Blasting costs, subjec t to a great deal of variation, are metal over a steel substrate. Most of them respond to the discussed elsewhere in this manual. It should be noted magnetic reluctance of the gap caused by the non-ferrous that the blasting requi rements for thermal spraying work film. are high, and fall in the category classified as "White Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 462
SSPC CHAPTER*20*0 93 8627940 0003910 664 Metal Blast Cleaning,
SSPC-SP 5.
Thermal spraying costs are also subject to considerable variation. Accessibility of the work is one of the largest variables, but it should be noted that any scaffolding suitable for blast cleaning will also be suitable for thermal spraying. Transporting personnel and equipment and setting up equipment constitute a small percentage of total cost when large areas are involved, but it may greatly increase the cost per square foot on jobs involving small areas or remote locations. The configuration of the work introduces another variable: edge loss on bridge trusses or light steel towers may be considerable, while on a ship hull or water tank they are negligible. Each job must be treated as an individual problem of cost. The variables must be evaluated and added to the total. Information necessary to compute basic costs and consumptions for the actual thermal spraying operation are given in Table 3, which is based on a wire-type thermal spraying gun of the latest design. E. HAZARDS Metallizing with zinc or aluminum may be carried out safely if certain basic facts are recognized. Fire and explosion hazards are normally associated with gas fuel systems. Safety considerations often require that propane be used in preference to acetylene. Zinc dust and fumes irritate the eyes and will cause nausea and zinc chills if breathed to excess. For this reason, a force-feed mask is generally used unless very good ventilation is provided, and even on outside work a force-feed mask may be required. The minimum requirement for outside work is a nose respirator. It has been reported that finely divided aluminum dust has been used to inhibit silicosis. However, a force-feed mask must always be worn when working in closed vessels, since some carbon monoxide may be present. It has been reported that the thermite reaction can result if rusted steel is coated with aluminum and struck sharply. Although the spraying of lead and cadmium is not covered in this chapter, it should be stressed that these metals are extremely toxic, and special precautions must be taken if they are to be used. Metal dust that is allowed to accumulate is a potential explosive hazard. All finely divided metals will ignite under the right conditions. When spraying in a closed space as in a tank, the concentration of dust in the air will not ordinarily approach the explosive limit, but due precaution must be taken to protect against unforeseen contingencies. It is particularly dangerous to allow large quan-
tities of dust to accumulate, and then to blow out with an air hose. The hazards involved in sandblasting and in the use of organic coatings have been covered elsewhere in this manual; metallizing safety measures are covered in another specification of the AWS2. REFERENCES 1. American Welding Society, C2.2, Recommended Practices for Metallizing; Part 1B -Application of Aluminum and Zinc for Protection of Iron and Steel , 1967. 2. American Welding Society, C2.1, Recommended Safe Practices for Thermal Spraying , 1973. 3. American Welding Society, C2.14, Corrosion Tests of FlameSprayed Coated Steel, 19-Year Report , 1974. 4. American Welding Society, Corrosion Tests of FlameSprayed Coated Steel, 12-year Report , 1967. 5. American Welding Society, Corrosion Tests of FlameSprayed Coated Steel, 6-Year Report , 1961. 6. H.S. Inghram, and A.P. Shephard, flame Spray Hand Book, Metco, inc., Westbury, NY, 1964. 7. American Welding Society, PR. Preprints of Papers Presented at the Eighth International Thermal Spraying Conference , 1976. 8. J.A. Catheral, Measurements of Bond Strength of FlameSprayed Deposits , Metal Construcfion, January 1972. 9. R.D. Greene, Metallizing Developments Utilizing Stabilized Methyacetylene Propadiene , Welding Journal, Vol. 45, No. 12, pp. 992-998, 1966. 10. W.E. Ballard, Metal Spraying and the Flame Deposition of Ceramics and Plastics, 4th ed., London, 1963. 11. W.E. Stanton, Contraction Stresses in Sprayed Metal Deposits , Second International Metal Spray Conference, Birmingham, AL, 1958. Appendix A -Eight Conclusions as They Appear in 79-Year Report 1. Aluminum-sprayed coatings 0.003 in. to 0.006 in. (0.08 mm to 0.15 mm) thick, both sealed and unsealed, gave complete base metal protection from corrosion in sea water and also in severe marine and industrial atmospheres. 2. Unsealed zinc sprayed coatings required 0.012 in. (0.30 mm) minimum thickness for complete protection in sea water for 19 years. In severe marine and industrial atmospheres, 0.009 in. (0.23 mm) of unsealed zinc or 0.003 in. to 0.006 in. (0.08 mm to 0.15 mm) of sealed zinc are needed for 19year protection. 3. In severe marine atmospheres, the application of one coat of wash primer plus one or two coats of aluminum vinyl enhanced the appearance and extended the life of zinc coatings at least 100°/~. With aluminum, the sealing system primarily enhanced appearance, because both systems showed no base metal rust after 19 years. 4. Thin coats of aluminum perform better because they have less tendency to develop pits and
blisters and therefore extended life is expected. Vinyl also seems to perform better because it must penetrate to the base metal. 5. Where aluminum coatings showed damage such as chips or scrapes, corrosion did not progress, suggesting the occurrence of galvanic protection. 6. The corrosion protection afforded by zinc and aluminum coatings is not affected by the method of surface preparation used for this test. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 463
SSPC CHAPTERlc20.0 93 8b27940 Specifically, a steel flash-bond coat is not essen? tial. For large parts, or where coating thickness will exceed 0.006 in. (0.15 mm), a coarse abrasive is recommended. 7. The use of flame-sprayed aluminum and zinc coatings is recommended as a means to extend the life of such iron and steel structures as bridges, highway or street light poles, marine piers or pilings, ship hulls, storage tanks, industrial structures, etc. Corrosion is thereby combatted, and the natural resources needed in the manufacture of iron and steel are conserved. 8. Chlorinated rubber is an unsatisfactory seal coat for both aluminum and zinc thermal sprayed coatings. ACKNOWLEDGEMENT The authors and editors gratefully acknowledge the active palrticipation of the following in the review process for this chapter: Roy Bishop, H. Campbell, Pam Claassen, B. Cook, F.W. Gartner, E. Horvick, K. Karsten, Frank Longo, Frank Porter, H.W. Raths, William Wallace. BIOGRAPHY Prior to his retirement, John N. Childs, Jr. served as Chairman of the Board of Metalweld, Inc. He had also held the positions of Vice President -Engineering, Treasurer, and of Manager, Industrial Maintenance Division. Before his employment with Metalweld, Mr. Childs was employed as an engineer at the Massachusetts Institute of Technology, where he received his B.S. in Electrical Engineering, and served as Engineer and Project Engineer at the Naval Research Laboratory in Boston. Mr. Childs professional activities have included membership in the American Welding Society, the American Institute of Electrical Engineers, the American Society of Mechanical Engineers, and the National Association of Corrosion Engineers. He is a Registered Professional Engineer in the states of Pennsylvania and California. 0003911 5T0 BIOGRAPHY S. John Oechsle, Jr. has been a Senior Associate with S.G. Pinney &Associates since 1988. In prior years he was President of Metalweld, Inc. and President
of Surface Protection Engineering Consultants, Inc. He is a consultant to the SSPC and a retired member of the Metco System Contractors Association (President 1957). He has been active in the National Association of Corrosion Engineers (NACE) as Chairman of 19 committees and task groups; the American Welding Society; the Young President s Organization; the Air Force Association; the American Society for Testing and Materials; and, the Utilities Nuclear Coating Work Committee (Vice-chairman 1972 to 1983). He is a registered professional engineer, NACE Corrosion Specialist, and a Registered Nuclear Coating Engineer. He has broad and responsible pioneering experience in ship painting, metallizing, FRP pipe and lining, rubber lining, and painting of nuclear power facilities in the United States, Japan and Taiwan. He has delivered 61 lectures and addresses on painting technology, and is the author of 11 technical papers. He received the Citation of Recognition for Outstanding Contributions to NACE in 1975. --`,,,,`-`-`,,`,,`,`,,`--464 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*ZL=O 93 W 8627940 0003912 437 W CHAPTER 21 HOT DIP GALVANIZING by Ernest W. Horvich I. ABSTRACT Hot dip galvanizing is a simple, but versatile process used to coat steel or iron in all shapes and forms with zinc. The process is applied to finished articles and also to semi-fabricated materials -sheet, strip, wire and tube. Galvanizing after fabrication has the advantage of completely sealing edges, rivets and welds, so that there are no uncovered parts where rusting can start and penetrate recesses. Complete protection is given to what would be corrosion sites with other coating systems. The process is applicable to fabrication of geometrical shapes ranging from nuts and bolts to large tanks and structural members. With existing molten metal vessels 52 feet long and larger, structural members 90 feet long can be handled by double dipping. Since double dipping has occasionally been misused or misinterpreted, an explanation of this practice is covered in the text. The ability to coat large pieces and to bolt or weld prefabricated sections after galvanizing allows almost any structure to be galvanized. Complex shapes and open vessels can be zinc coated inside and out in one operation. While wire, tubing and strip can be hot dip galvanized, the emphasis in this chapter is on geometric shapes, such as structurals. The fundamental steps in the galvanizing process are: Soil and grease removal: hot alkaline or solvent cleaner is usually used to remove oil, grease, shop oil, and soluble paints. This will not, however, remove such things as epoxy, vinyl, asphalt, or welding slag. These soils must be removed by grit blasting, sand blasting or other mechanical cleaning not normally the responsibility of the galvanizer. Scale removal: accomplished by acid pickling or abrasive blasting. Fluxing and hot dipping: the hot dip galvanizing process consists after cleaning of fluxing the surface of an iron or steel article and immersing the articles in molten zinc. There the base metal and zinc react to produce several intermetallic compounds that usually form distinct layers on the iron or steel. When the reaction subsides after proper length of time, the article is withdrawn from the molten bath. As it emerges, it carries with it a layer of unreacted zinc that quickly freezes to cover the iron-zinc alloy
layers with a bright lustrous metallic coating. The material so processed has enough zinc on it as a surface film to give the desired coating for protection from corrosion. The amount of pickling of the material to be galvanized, proper regulation of the zinc kettle temperature, fluxing of the surface of the molten zinc and the position of the material as it is lowered into thszinc all are important factors. Each of these factors affects the quality of the coating produced. Galvanizers have no time tables regulating the amount of pickling or the time that the material must be immersed in the molten zinc to insure proper alloying. The process of commercial galvanizing is a skill. Few pieces of structural steel being galvanized are the same size, shape or even of the same type material; therefore, the quality of the galvanizing depends on the skill of the craftsman performing the process. Once the steel has been properly prepared, the development of a galvanized coating is generally predictable for a given set of steel and operating conditions. II. INTRODUCTION Many methods have been employed to fight the expensive corrosion of steel. These include painting, cladding with a relatively thick layer of metal less susceptible to rust and developing special steel alloys to withstand highly corrosive conditions. One of the most widely used methods for protecting steel is to coat it with a relatively thin layer of some other metal. Among the common metals used for this purpose are zinc, lead, tin, copper, nickel, chromium and aluminum. Because of its special advantages, zinc is used for protective coatings far more than any other metal. The principal reasons for its use are that it has inherent corrosion resistance; it is easy to apply (relatively low melting point, 787°F); it is relatively inexpensive and readily available; it has a hard, smooth surface which is comparatively resistant to abrasion; and it is highly amenable to continuous processing. Zinc is one of the most versatile materials available
for coating other metals. It can be applied as a metal by hot dip galvanizing, flake galvanizing, electrodeposition, thermal spraying or metallizing, mechanical or peen plating, sherardizing or cementation, brush scratching or rubbing, plasma arc spraying, shot blasting, vacuum metallizing and non-vacuum vapor condensation deposition. Zinc dust can also be used as a pigment in protective paints. Each of these methods of applying zinc coatings Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 465
SSPC CHAPTERUZ3.O 93 = 8627940 0003933 373 = has its specific reason for being and in certain applications is to be preferred. While there is always at least one process applicable to any particular set of circumstances, the processes are complementary rather than competitive, so that rarely are more than two to be seriously considered as the best choice for a particular job. Economic aspects are important factors in making the decision. Where there is little difference in cost, consideration should be given to the serviceability required. Factors such as size, shape and complexity have to be taken into account in choosing the most suitable process for a particular application. In hot dip galvanizing, thoroughly cleaned steel or iron is immersed in molten zinc and withdrawn to provide a smooth, even coating that frequently has a crystalline, spangled appearance. The galvanized coating is applied by various means: hand-dipping of fabricated items of irregular shapes, either singly, e.g. for items such as structural beams, or in baskets for coating nails, bolts and similar products; intermittent or semi-continuous mechanical dipping of pipe; and a highly automated dipping that enables steel strip and wire to be galvanized by passing continuously through molten zinc. Coatings produced by the third method are quite uniform in thickness and are very ductile. In the hot dip galvanizing operation the steel is first cleaned of all foreign material before immersion in thezinc bath. This is generally accomplished by removing grease, oil and other foreign contaminants either by alkaline or solvent degreasing and thorough rinsing, then by acid pickling or blast cleaning and fluxing which further cleans and activates the surface. One type of continuous galvanizing surface preparation is effected by gas pickling in an atmosphere which reduces and eliminates the oxide film generally found on exposed steel. The steel is then immersed in the molten zinc which readily wets the clean surface of the base metal and fuses with it to form the coating. The thickness of the coating is largely determined by the temperature of the bath, time of immersion, fluidity of the bath, the rate of withdrawal from the bath, and the thickness and weight of the article. On withdrawal from the bath, coating thickness of strip sheet, wire and pipe is further controlled by mechanical means. This text, however, will concen?rate on hot dip galvanizing after fabrication. The process is very versatile and has been used to protect articles ranging in size from very srnail to very large. This size range, together with the ability to bolt (friction grip or conventional using galvanized bolts) or weld prefabricated sections after galvanizing, enables almost any structure to be galvanized. Of particular interest to the process industries is the fact that tubes, open vessels and
complicated shapes can be galvanized inside and out in one operation. All types of plain carbon and some low alloy as well as iron and steel wood, monel metal or --`,,,,`-`-`,,`,,`,`,,`--steels can be galvanized, castings. 111. SURFACE PREPARATION While a clean surface is necessary for the successful application of any coating to a base metal, it is especially so for applying a zinc coating by hot dip galvanizing to steel. Because the molten zinc fuses with the base metal to form a metallurgical bond with it, the steel surfaces must be practically surgically clean to allow the reaction to take place completely. The molten zinc cannot bond to the steel if anything foreign is present. Surface preparation, in general, requires a number of steps. Cleaning is necessary to remove dirt or grime accumulated during shipping, storage or manufacture. Removal of paint or similarly adherent materials requires other means to be discussed later. Degreasing with an organic solvent or hot alkali solution removes oils or similar organic materials. A. PICKLING Since pickling is considered fully in another chapter of this Manual, only those aspects pertinent to hot dip galvanizing will be mentioned here. While the previous surface preparation procedures aim toward complete removal of dirt, grime, grease and other contact contaminants, scale has to be removed by pickling or blasting. For pickling, suitably diluted sulfuric or hydrochloric acid is used. The time required for pickling will depend upon the surface condition and nature of the steel and the thickness of the scale. Usually 10to 15 minutes of immersion is sufficient. Immersion time should be as short as possible to minimize hydrogen absorption and undesirable attack on the work surface. Inhibitors are recommended to minimize attack on the metal. They lower acid consumption, reduce hydrogen absorption, decrease acid fuming and help prevent burned work. In addition, they improve general working conditions around the pickle tank.
If an effective inhibitor is used, no harm results from leaving the material for a prolonged period in the pickling acid. If no inhibitor is used, hydrogen evolved when the iron dissolves in the acid is liable to be absorbed by the steel and may cause embrittlement or give rise to a blistered coating when the material is dipped in the molten zinc bath. Hydrofluoric acid is required to properly prepare surfaces contaminated with silica from sand molds or welding rods. Scale removal must be complete to obtain high quality zinc coatings. Scale, if not removed, will result in uncoated or roughly coated areas. Although scale removal is mandatory, overpickling will yield abnormally heavy zinc coating and occasionally poor adhesion of the galvanized coating. Small articles are pickled in baskets or crates of other suitable acid-resistant material. Sheets are held in acid-resisting frames and are Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 466
SSPC CHAPTER*ZLmO 93 8b27940 0003934 20T often agitated mechanically, while pipes are raised and molten zinc. Spowers, a notable galvanizing authority, lowered at an angle inclined to the horizontal to ensure recommends a flux solut ion of zinc ammonium chloride of adequate movement of the acid through them. composition ZnC12*3NH,CI. Proprietar y fluxes consist of zinc ammonium chloride with the addition of a wetting B. WASHING agent. Except when the pickling acid (hydrochloric acid) The solutions may be made up f rom the ammonium serves also as a flux, an undesirable practice, the work and zinc salts in corre ct proportion and wetting agents. must be thoroughly washed after pickling. The first rinse is Flux baths contain 20-30% by weight of the salts, and are best done in warm water because the iron salts dissolve normally operated at tem peratures around 50°F (10OC), more easily. But a warm rinse must be kept slightly acid though they may be left cold. (pH 3-4) to prevent hydrolysis of the ferric salts formed by Pickling leaves a f ilm of dissolved iron salts on the atmospheric oxidation; in the absence of acid, ferric surface of the iron or ste el. Whether or not these are hydroxide would be deposited on the steel. The warm, washed off the surface depe nds on which galvanizing slightly acid rinse needs to be followed by a second dip in techniques is used. cold running water to complete the removal of iron salts. It There are a number of different processes. These inis suggested that only cold water should be used for rins- clude the so-called O ld Dry Process, in which the salts ing, and that the quantity should be kept small, again to from a hydrochloric ac id pickle are dried on the work and reduce hydrolysis. act as a flux, the Wet Process, where work is usually taken directly from the rising tank to the galvanizing bath that C. BLAST CLEANING has a blanket of molten flux floating on the zinc, and the Dry Process, in which the pickled work is rinsed, immersed Grit, shot or sand blasting are not commonly in a tank of flux and then dried. I t coats the works with a employed as methods of surface preparation for hot dip thin layer of salt that p rotects the steel from air until it is galvanizing. Acid pickling is less expensive and more prac- galvanized. Generall y this is required for complex parts. tical; where it can be employed, it is generally used. In the Pickling plus flux assures the fabricator that the entire surpast, blasting was confined mainly to cleaning of ferrous face of the work is co vered with a fresh layer of flux castings or heavily rusted articles. It is especially ap-leading to a better and more consistent finish. Work that plicable to ferrous castings, since their complex and ir- has been pickled and d ried should be galvanized without regular surfaces require excessive pickling time which can delay as the flux coa
ting picks up moisture from the air result in uneven, heavy galvanized coatings. Also, castings and also tends to ox idize. do not respond to the conventional chemical cleaning The fresher and more fluid the flux, the greater is its process employed by most galvanizers, primarily because effectiveness and the mo re readily is it dispelled from the of burned-on sand from the casting operation. surface of the steel. Because of l ocal chilling action before Blast cleaning precludes hydrogen embrittlement, a it enters the bath, the steel invariably carries with it some condition that can result from acid pickling. Its peening ac- salt. Time must be allowed for the steel to reach the tion has a tendency to minimize or eliminate stresses that temperature of the ba th and for the article to be held in the might be induced by severe cold work during fabrication. zinc bath until bubblin g subsides and a preliminary inspecUnlike acid pickling, it removes only surface contamina- tion has shown a contin uous coating of zinc has formed. tion and does not attack the steel. Very thick galvanized coatings can be obtained by E. DRYING deliberately roughing the surface of work by blast cleaning. Also, it eliminates some problems of disposing of acid After fluxing and dr aining, the work is dried in a low waste. temperature oven. In the case of plates, spacers are sometimes used to improve drying. Heat can be supplied conveniently by passing the flue gases from the galvanizD. FLUXING ing bath through separate compartments forming the After thorough washing, the work is dipped in a flux sides of the oven. Products of combustion containing solution. Fluxing is mandatory to dissolve any oxide film sulphur must not enter the oven or come in contact with that has formed on the steel after pickling and galvanizing, the work before dip ping. The temperature of the oven and to absorb any remaining impurities on the metal sur- should not exceed 300°F ( 149"C), since the flux may face, all to ensure that clean steel or iron contacts the decompose if it is hea ted too strongly in drying. Iron salts molten zinc. It also acts as a preheating and drying can also be formed during d rying by interaction between medium to permit wet material to be immersed into the the flux and the metal sur face, thus, the drying galvanizing bath with a minimum of spattering. Reducing temperature and time sho uld not exceed what is oxidation of the molten zinc surface greatly lowers zinc necessary to produce a degree of dryness that avoids ash formation, minimizing bath degradation. Proper flux- splashing during the su bsequent galvanizing dip. In an ing reduces the cost of galvanizing as well as heat loss. oven with a sufficient ly high draught, rapid drying can be The flux, of course, facilitates wetting of the steel by the done at 212°F (100°C).
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SSPC CHAPTER*2L.O 93 M Ab27940 0003935 L4b = IV. DIPPING PROCEDURES A. START-UP OF A NEW KETTLE Slab zinc should be stacked vertically on edge in the pot to insure the best contact of the zinc slabs with the kettle walls. Additional rows of vertically stacked zinc should also be set on edge, from kettle walls toward the center. Some space should be left, usually near the center of the kettle, for thermal expansion and moisture release. This vacant space may be filled with water to insure fairly uniform heating of the entire contents of the kettle up to 212°F (l0O C).To avoid overheating, the temperature should be raised very slowly until melting starts. As the zinc slabs melt and the pool of liquid zinc increases, the rate of heating may be increased gradually. Once galvanized baths have been started up, they are usually maintained hot throughout their operating life because solidification of the zinc in the bath may cause warping and fracture of the bath walls. The design should allow the pot to be changed without difficulty when a new one is required. For wet galvanizing, a fresh fluid blanket of flux should cover the end of the kettle where the material being dipped enters the zinc. Zinc ammonium chloride or ammonium chloride flux is used and maintained in an active condition by the frequent addition of small portions of fresh flux. Accumulation of heavy, pasty flux immediately above the molten zinc should be removed frequently. Items are Withdrawn at the opposite end of the galvanizing kettle through a clean zinc surface. The work is immersed in the galvanizing bath with tongs or by the aid of suitable overhead tackle, or automatically. When large parts are being galvanized, they should be pre-heated before dipping. Parts should be immersed only until they reach the temperature of the bath. Flux patches can be avoided by withdrawing the finished work through a portion of the bath surface from which the flux and oxide coating has been skimmed back. When immersed in the galvanizing bath, iron and steel are immediately wetted by the zinc and react to form ironzinc layers. At normal galvanizing temperatures of 835855°F(446-457%), the rate of reaction is very rapid at first with a boiling-off action. The main thickness of coating forms during this initial period. Subsequently, reaction slows down and the coating thickness does not increase greatly if the article is immersed in the bath for a much longer time. The normal period of immersion is a minute or two, but longer for work that is particularly heavy or requires draining from internal spaces. Galvanizing proceeds until a normal coating develops. As the work is removed from the bath, some molten zinc is taken out on top of the alloy layers, the whole coating being metallurgically bonded to the base metal. Thus, the galvanized product has a coating made up
of two major parts: the zinc-iron alloy layer, which is the portion that forms in the kettle and is influenced by the steel chemistry, immersion time, and galvanizing bath temperature, and a covering of bath metal which gives the galvanized product its characteristic bright, shiny appearance. If the coating consists of zinc-iron reaction products only, it has a matte gray finish. The free zinc portion of the coating varies in thickness and in the percentage of total coating weight, depending upon the speed of the withdrawal and the wiping practice, if any. There is no real line of demarcation between the steel and the zinc, but a gradual transition through a series of iron-zinc alloys that provides a metallurgical bond. B. SIZE OF KETTLE The capacity of the kettle should exceed what is necessary to accommodate the material being handled: the articles have to be heated to the temperature of the zinc during immersion, and unless the bath has sufficient heat content and ample heating surface areas, high rates of heating which shorten the life of the pot are required. A formula for estimating the permissible throughput of a galvanizing bath is that the weight of steel galvanized per hour should not exceed one-twentieth of the weight of zinc in the bath. If this formula is adhered to, rapid temperature fluctuations can be avoided. The real limiting factor is, however, the temperature of the bath wall. Zinc melts at 787°F (419°C) and in the molten state attacks all ferrous metals, the rate of attack depending primarily upon the temperature and becoming rapid about 878°F (479°C). The galvanizing bath should, therefore, be run at the lowest possible temperature and hot spots must be avoided. Hot spots can be prevented if the bath is very uniformly heated, and temperature carefully controlled. C.WITHDRAWAL RATE Rate of withdrawal from the spelter also influences formation of spots. Steel strip of known spotting tendencies was galvanized under identical immersion time and temperature. Samples withdrawn rapidly revealed considerably less spotting because zinc did not drain so rapidly from the surface, resulting in a heavier coating which froze before it had opportunity to diffuse into the base metal to form a spot. Slow withdrawal was accompanied by deposition of 1.012 ounces of zinc per square foot with bad spotting compared to 1.258 ounces per square foot for
rapid withdrawal with little spotting. The rate of withdrawal controls the thickness of the coating between quite wide limits; the faster the rate, the heavier the coating. Thus, for control of thickness and elimination of waste, a multi-speed, power driven hoist is advisable for most large work. Five feet per minute has proved a convenient and satisfactory withdrawal rate for many types of larger work. In addition to the speed of withdrawal, the free zinc portion of the coating will be influenced by the temperature of the bath. For a given withdrawal speed, the amount of free zinc that mechanically attaches itself to Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*ZL.O 93 W 8627940 00039Lb 082 W the existing work will decrease as the temperature increases. This is due to a slight change in the fluidity of the zinc and also to the improved drainage that results from the higher temperature metal. When the coating is completed, the submerged parts are moved to the flux-free area of the kettle, which should be cleaned of oxide with a skimmer. Then the work should be withdrawn with a slow, steady pull. The work is held over the bath for a short time and allowed to drain. Shaking the piece will facilitate draining. At this time, parts should be inspected for uncoated spots, which usually appear black. If such spots appear, they may be eliminated by dusting the spot area with a pinch of sal ammoniac ( ,CI) and reimmersing in the bath. D. DROSSING Galvanizing baths should be freed from dross at weekly or somewhat longer intervals. The bath should be allowed to stand for three hours before drossing to allow the dross to settle, at a temperature sufficiently low to minimize the quantity of iron actually dissolved in the zinc. E. TUBE GALVANIZING Unfabricated tubes generally used for electrical conduits are usually galvanized by the manufacturer who has a galvanizing plant designed for semi-automatic handling. The protective coating forms on the inside as well as on the outside of the tube. Normal practice is to smooth and then to blow steam under pressure through the inside of the tube to remove molten zinc and leave a smooth bore. Consequently, the coatings on unfabricated tube are usually thinner than those on tubular fabrications. F. PIPE ASSEMBLIES While the surface must be thoroughly cleaned to produce the galvanized coating, pipe commonly presents two special cleaning problems. The mill coating (varnish, iacquer and similar materials) applied by the manufacturer is normally removable at the galvanizing plant at extra cost. However, because some formulations, both foreign and domestic, are extremely difficult to remove with common cleaning solutions, blasting may be required. Removing this mill coat at the galvanizing plant can be avoided by ordering uncoated pipe from the supplier. Welding millcoated pipe burns and carbonizes the varnish in the surrounding heated areas. This soot requires blasting or other mechanical removal. The burned coating could be
removed when blasting to remove weld flux, but if welding has been done with an uncoated rod, any blasting or other hand cleaning is expensive and highly impractical. Most pipe is galvanized by the steel producer. Such pipe is used as electrical conduit. G. CENTRIFUGING Centrifuging or spinning is a common practice used to control the thickness of the free zinc portion of galvanked coatings. It works effectively on small parts such as nuts and bolts that are galvanized in a wire mesh basket or perforated cage. After removal from the galvanizing bath, this basket is immediately placed in a low speed centrifuge to get rid of excess zinc on screw threads and other areas and to prevent the articles from sticking together. High centrifuging speeds are not required. Small thick parts, castings or forgings, are usually quenched in water to make the coating set quickly. Slow delivery to the centrifuge spinner or low to medium spin speeds require heating the spinner. Labor savings are possible using a spinner as it eliminates hand wiping or hand shaking. A spinner generally assures more consistent coating thickness and conserves zinc. Limited production, high production and automatic centrifuges are available. H. DOUBLE-DIP PROCESS MISUNDERSTOOD Double-dipping in the galvanizing trade is not dipping a product in the molten bath, withdrawing and reimmersing it in the bath. Double-dipping means immersing onehalf of a structural in molten zinc, withdrawing, and then dipping the other half in the bath. Thus, an item 85-90 feet or even larger can be galvanized. Should the length be such that the center portion would not be galvanized, that area can be zinc coated by thermal spraying. I. EMBRITTLEMENT To prevent embrittlement during galvanizing, all malleable castings should be heated to 1,200 to 1,500 F (649-816°C) and water quenched. The holding time and the temperature of the quench water are not important. J. APPEARANCE OF ZINC COATINGS Varying with different types of steel, the rate of alloy-
ing is determined by composition of the base material. With some compositions of the steel base, the rapid reaction between zinc and steel produces coatings consisting entirely of (or almost entirely) zinc-iron compound. These may be gray, with matte surface, and are usually thicker with ordinary steel compositions. This condition may be planned, as with pole line hardware using higher silicon steels to secure unusually heavy coatings, or it may be the unexpected result of the use of certain low-alloy, high strength steels for their increased elastic strength. Where undesirable appearance or reduced adhesion of the coating accompanies such excessive growth, the galvanizer may be able to modify his operations to relieve, in part, this condition. Some of these fast growing coatings consist of an intimate mixture of zinc-iron compound with zinc of the composition of the bath, and as such are two phase materials with potential difference of several tenths of a volt between the constituents. This may adversely affect corrosion resistance in wet exposure, and is usually accompanied by reduced adhesion of the coating. Such structures are termed diffuse alloy. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 469
SSPC CHAPTERxZL-O 93 m 8627940 0003917 TL9 m K. COATING THICKNESS Coating thickness depends on the composition and physical condition of the steel being treated and on a number of factors within the control of the galvanizer. For example, heavier coatings tend to be deposited on rough surface and coarsegrained steel, and, at the same time, the total thickness of the alloy layers tends to be slightly greater at corners than at hollows. The coating weight is controlled by the growth of the iron-zinc alloy layer. Articles galvanized after fabrication generally have coating weights of at least two ounces per square foot of surface or the equivalent thickness of about 3.4 mils. The usual range is from 3.5 to 5.0 mils. Normally, about half the coating thickness is iron-zinc alloy and half is practically pure zinc. When very long life is required, extra thick galvanized coating can provide it. Prior grit blasting of mild steels will enable the coating thickness to be increased by up to 50-1O0Oh wit ho ut c hang in g the g a Iva n izi n g tech n iq u es. Coatings to five mils may be produced on reactive siliconcontaining steel (e.g. silicon-killed ). These thick coatings are very protective but will tend to be a dull, dark grey because the alloy layers extend to the outer surface. The galvanizer should be consulted if coatings thicker than those normally given in ASTM and other standards are required. With steels of unknown compositions or those having less than the optimum surfaces required for good galvanizing, constant monitoring should take place to check on the coating thickness applied to ensure that zinc is not being utilized uneconomically. Unfortunately, it is not possible or practical to check the composition of each piece of steel processed. L. MEASUREMENT OF COATING THICKNESS Regular measurements of coating thickness by the weight, strip weight method or by microsectioning are time consuming and destructive, while the copper sulphate (Preece) test is suitable only for checking the thinnest area of a coating. Magnetic gages provide simple and convenient non-destructive means of testing coating thickness. They measure either the magnetic attraction between a magnet and the base metal (e.g. the Tinsley Pencil Gage) or the reluctance of a magnetic flux path passing through the coating and the base metal (e.g. the Elcometer). ASTM Standard E376 describes recommended practice for using these instruments. In converting coating weight to coating thickness, one ounce per square foot of surface is equivalent to a thickness of ,0017 inch. V. DESIGN CONSIDERATIONS FOR GALVANIZING The quality of a zinc coating is determined to a major
degree by the design of the steel or iron to be protected. Because poor design can reduce the effectiveness of a coating, the protective system should be regarded as an integral part of products made from steel and iron and should be considered at the design stage. It is not too difficult to protect a smooth, flat surface to which a coating can be applied in a continuous film of proper thickness. But the coating problem becomes more difficult when the structure has a variety of angles, corners, welds, rivets and edges. In these areas film thickness and adhesion are often inadequate, making them susceptible to corrosion. Minor modifications in design to eliminate areas that would be difficult to coat adequately can substantially reduce maintenance costs throughout the life of the structure. A. LIAISON Considering that design, fabrication and zinc coating are the three important areas in the production of a galvanized product, close liaison must be maintained among designer, fabricator, and galvanizer before the product is manufactured and arrives at the galvanizing shop. This three-way consultation can eliminate many galvanizing problems before they arise. Subjects worthy of joint decision-making are steel selection, combinations of materials or surface, welding procedure, cold forming, size and shape, venting and draining, pipe assemblies, minimizing distortion, overlapping surfaces, castings and moving parts. The galvanizer can explain how design and manufacture influences the quality of galvanizing. To derive maximum benefit from his services, it may be helpful to consult him frequently and become familiar with the requirements of the galvanizing process. B. DESIGN FEATURES THAT AFFECT THE LIFE OF A ZINC COATING Ideally, materials should be designed so that the corrosive attack never has a chance to get a foothold and begin its destructive work. All features that trap or hold moisture and atmospheric grime should be avoided because they remain damp long after the rest of the structure has dried. Nooks, crannies, and horizontal ledges should therefore be avoided, and for the same reason butt welds are
preferred to lap joints. Where such features are essential, they should be designed so that water runs off them and is not retained on the surface. Also, rounded corners are preferable to sharp ones, both on exterior and inside surfaces. Poor assembly techniques and designs that include blind pockets and cavities will prevent the galvanizer from applying a complete coating. Moving parts such as handles or hinges should be galvanized separately and assembled after galvanizing to prevent freezing. C. MATERIAL AND SURFACE COMBINATIONS Galvanizing becomes complex when assemblies of different materials andlor structures must be coated. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 470
SSPC CHAPTER*ZL.O 93 8b27940 000391i8 955 When galvanizing structural steel, miscellaneous cavities turns to steam when he ated in the hot dip metals (steel and iron), or other work such as pipe or cor- galvanizing process and can result in an explosion of the rugated sheets, special requirements are introduced into member, endangering per sonnel. In service, processing liqthe design. ASTM 385 outlines precautions to be taken. uors will penetrate into the cavities, probably remain there Plain carbon and some low alloy steels, iron, and steel and lead to rapid attack of the metal. For tube assemblies, castings can be galvanized. Soldered components cannot internally open-mitred jo ints should be used at all time to be galvanized, and before brazed and welded assemblies avoid sealed sections. are designed, the galvanizer should be consulted. Pickling times vary with different ferrous materials (also for old and F. TANKS new steel). Thus, a fabrication consisting of various Tanks to be galvanized mus t be designed to produce materials should be avoided because uneven pickling af- uniform coatings of corr ect thickness, especially on the infects the uniformity and appearance of the coating. side surface. To be effectiv e, the design must enable careful handling. D. OVERLAPPING SURFACES There should be at least four openings 1 to 2 in When contacting surface such as back angles and diameter in each tank, preferabl y two on one lengthwise channels cannot be avoided, all edges should be com- centerline on the shell and the other two on opposite pletely sealed by welding, since the viscosity of the zinc diameters to these, a s close to the heads as is practical. It prevents it from entering any space less than y32n. is also desirable to have an opening in each head. There are further problems with tightly overlapping The opening must be placed s o that the flux on the surfaces. Pickling liquids that are trapped will volatilize to part can float to the surface of the bath. It must also presteam when immersed in the galvanizing bath. The blow- vent air pockets that will keep pickle solution from coming out of this steam can prevent zinc from adhering to pletely cleaning the insi de areas. the area adjacent to such a lap. If there is any retained Vessels must be filled with pickling and cleaning solupickle liquor, it will weep out and can then damage the tions and emptied severa l times prior to galvanizing. The galvanized coating while in service. cost of handling is determined by the size of the openings. Pickling salts can be retained in these tight areas due To prevent bare spots, s ide openings must be provided for to the impossibility of adequate rinsing. The galvanized gas from pickling to es cape. All openings inside the tank coatings may be of good quality in the adjacent area, but must be flush. humidity encountered weeks or even months later may wet In the submersion of a t ank or fabricated product in
these acid salts and cause unsightly rust staining to run molten zinc at approxi mately 850 F (454 OC), the proper out on top of the galvanized coating. design allows for fast and complete fillin g of the tank with Oils and greases trapped between tightly contacting zinc through a bottom openin g while gas and moisture can surfaces will not be effectively removed by the cleaning be freely liberated fro m a top opening. solutions. They will partially volatilize at the galvanizing In the removal of t he tank, vessel or structure from the temperature and prevent a satisfactory zinc coating in the bath, the zinc should flow from the bottom opening rapidly, immediate area of the lap joint. Contacting joint surface draining out excess zi nc while air is freely admitted should be thoroughly cleaned before fabrication and then through the top opening . completely sealed by welding. If the area of an overlap is large, there should be G. TUBULAR STRUCTURES AND CO LUMNS vented holes through one or both sides into the lapped Pipe assemblies present t he same problems as tanks aieatopreventanymoisturethat gets in through a pin hole and closed vessels. They must be designed to permit free in the weld from building up explosive pressure. This vent- flow of molten zinc and the exoulsion of all air and ing becomes more and more important as the area is larger moisture. They must no t contain unvented sealed secor as the steel is thinner. tions. Molten zinc must enter all sections. Drainage holes E. CLOSED SECTIONS, FILLING, VENTING must be placed in the pipe so that molten z inc can flow in- AND DRAINING to all areas and on all surfaces. If these holes a re not large The design of products which are to be galvanized enough, the withdrawal speed w ill be greatly reduced, should provide for proper drainage of all sections. Hollow resulting in lowered quality of the galvanizing. Frames articles must fill rapidly with molten zinc. The gases must fabricated from chan nels and gussets on fabricated colescape and the zinc drain completely in order to give a con- umns should have cr opped corners to allow the free flow of tinuous and uniform coating. metal. For the safety of personnel, internal pressures produced by the combination of heat, air and moisture must H. VENTS FOR PIPE STRUCT URES be allowed to vent to the atmosphere. With internal vent holes, drainage of zinc occurs Sealed cavities or those having small openings through the bottom of the vertica l member. This gives the should always be avoided. Moisture trapped in such optimum galvanizing results. 471
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Grit blasting the entire assembly minimizes these differences in pickling requirements and results in a heavier galvanized coating that gives a longer life at higher initial cost. Different techniques for pickling (solution concentrations, temperatures, immersion time) and galvanizing (both temperatures, immersion time) are required for excessively rusted surfaces; pitted surfaces; machined surfaces; cast iron (especially with sand inclusions); cast steel; malleable iron; hot rolled steel; cold rolled steel; and steels containing more than normal carbon, phosphorus, manganese and silicon. For acceptable quality, the galvanizer must be notified of any steel compositions other than low carbon steel . Combinations of steel, such as low carbon (0.15% max.), medium carbon (0.15-0.30%), high carbon (0.30-0.5%), high strength low-alloy, and high silicon will result in different coating thicknesses and surface appearance. While this is not necessarily detrimental to certain applications, the designer and fabricator must consider it and consult their galvanizer in the planning stages. With external vent holes, draining zinc flows over the surface of the pipe and results in a generally rougher coating. All sections of pipe must be vented to allow complete circulation of molten zinc through every area of the fabrication. VI. WELDING PROCEDURE AND WELDING FLUX REMOVAL Very important points to the galvanizer are cleanliness of the weld area after welding and the metallic composition of the weld itself. Several welding processes have been found to be most satisfactory for galvanizing. Since welding flux residues are chemically inert in normal pickling solutions, they will not be removed by standard cleaning techniques and must be chipped away or otherwise mechanically removed by grit or sand blasting, wire brushing, or power abrasive wheel cleaning. This flux removal is normally the responsibility of the fabricator, or by mutual agreement, by the galvanizer. It is, therefore, good to choose a welding technique which will nearly slag itself or which produces no slag at all. Galvanized items can be joined by bolting (including friction grip connections), welding, riveting and adhesives; but where welding has taken place after galvanizing, the actual weld must be protected by the application of a fresh zinc layer. VII. STEEL SELECTION The galvanized coating has as its basis the reaction between clean steel and molten zinc. This reaction results in the formation of a series of zinc-iron alloy layers that are covered by a layer of zinc as the steel is withdrawn from the galvanizing bat h.
Most hot rolled steels respond to the galvanizing process in a predictable manner, ¡.e., the zinc-iron alloy portion of the coating will represent 50 to 70 percent of the total coating thickness. However, certain combinations of elements may result in a coating that is all or mostlyzinc-iron alloy. While a description of the mechanism that causes the alloy type coating is complex, the description of the coating characteristics is not. Even in cases where a steel is selected for considerations other than galvanizing, and the chemistry of the elements (C, Mn, P and Si) exceeds the previously mentioned limits, it usually can be galvanized satisfactorily. The grade of steel selected should be qualified with the galvanizer so that he can determine what special galvanizing processing is required. Every attempt should be made to see that steel to be galvanized is specified accordingly. A. MOST Hot dip variety bon and
STEELS CAN BE GALVANIZED galvanized coatings are applied to a wide of ferrous metals, ranging from cast iron to low caralloy steels.
Most of the known methods may be used to produce steel that is to be galvanized. The selection depends on the physical requirements of the end product and the limits of the processing equipment at the mills. Following is a general classification of open hearth steels commonly used on galvanizing orders: RIMMED STEEL 1. Regular low carbon rimmed 2. Extra-low carbon rimmed SEMI-KILLED STEEL 1. Partially killed with silicon 2. Partially killed with aluminum FULLY-KILLED STEEL 1. Fully killed with aluminum as chief deoxidizer 2. Fully killed with silicon as chief deoxidizer CAPPED STEELS 1. Mechanically capped 2. Silicon capped or killed in the top B. SELECTING THE BASIS METAL The composition of the base metal is varied where necessary to obtain certain desired characteristics in the zinc coat. With regard to carbon content of the base metal, the form of the carbon is as important for galvanizing considerations as is the amount of carbon. (High carbon steels are not generally considered suitable for galvanizing.) In malleable cast iron it exists as temper carbon; in cast iron in the form of graphite flakes; in steels, both low and high carbon mainly in the form of ironlcarbon compound Fe&. The effect that carbon content has on iron cannot be generalized, but must be seen in terms of each individual
case. Roughly speaking, however, the higher the carbon content, the greater the zinc-iron reaction. Copper is frequently added to steel in quantities over 0.2 percent to improve corrosion resistance, and occasionally ingot iron sheets made from highly refined iron are used as the base metal for the same reason. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 472
SSPC CHAPTER+ZL.O 93 = 8b23740 0003720 503 C. INFLUENCE OF STEEL ON GALVANIZING Galvanizing is much more tolerant of defects in the base metal than most other coating processes. The absence of defects ensures a better quality coating, particularly where appearance is important. Excessively rusted or pitted steel may require longer pickling time than steel that is not rusted, and the resultant rough surface may pick up a substantially heavier zinc coating. Blast cleaning before pickling will help to equalize differences in surface finishes. Steel chemistry has pronounced effects on various aspects of galvanizing, for example, the effect of galvanizing time on coating microstructure. This is clearly depicted in the difference in the metallurgical bond and zinc coating thickness obtained from unkilled (rimmed) and siliconkilled steels. Steels containing carbon below 0.25%, phosphorus below 0.05%, and manganese below 1.35%, either individually or in combination, will normally develop a typical galvanized coating when conventional galvanizing techniques are used, providing the silicon is .05% or less. In general, steels containing greater than 0.25% carbon, 1.35% manganese, or 0.06% or more silicon, such as might be found in structural steels, are highly reactive and will develop excessive coating weights under normal galvanizing conditions. However, there are controls available to the galvanizer to assist in minimizing coating weight. Phosphorus and silicon affect the alloying rate more than most other steel constituents. An increase in silicon content from 0.06 to 0.20 percent will triple the rate of alloying. Fabricators and consumers should be aware that a gray or matte (non-harmful) appearance may occur with silicon content in excess of .O6%. Welding wire containing a high percentage of silicon will tend to produce a poor galvanizing job. Some welding wire materials may also tend to be reactive in the pickling acid. Welding flux residues and slags must be removed. VIII. TYPE OF ZINC A number of grades of commercial zinc are available for use as a coating metal. They may vary considerably in composition, but the grade commonly used in the galvanizing industry is designated as Prime Western , although any of the grades could be used. The content of impurities in the coating bath can be controlled within definite limits for most contaminants or alloying elements with the exception of iron. As steel passes through thezinc bath, some iron goes in solution in the zinc. However, the maximum solubility of iron in zinc is soon reached, and the excess precipitates as an intermetallic alloy of iron and zinc. Minute crystals of this alloy are held in suspension in the molten zinc and eventually aggregate into larger particles which settle to the bottom of the pot as dross. This process takes place during the life of the bath so that the precipitation occurring in
the molten zinc tends to establish an equilibrium, and keeps the liquid phase at a constant iron content. It is necessary to remove dross from the pot at regular weekly intervals to prevent it from interfering with the normal coating operation. The ASTM Standard Specification for galvanized products simply states that the zinc used for the coating shall conform to Specification ASTM B06, for zinc metal (slab zinc) and shall be at least equal to the grade designated as Prime Western
. Latest issue of the galvanized coating
specification deletes the section on Impurities - the aluminum content of the bath during actual galvanizing operations shall not exceed 0.01 percent . Prime Western, the grade commonly used for hot dip galvanizing, requires maximum percent content of 1.4 lead, 0.05 iron and 0.02 cadmium. ASTM BO6 states in a footnote that aluminum in Prime Western Zinc shall not exceed 0.05%. The effect of elements that are either found in or may have been added to the coating bath vary considerably. The impurities found in slab zinc must be known to the galvanizer if he is to achieve all the desired economies, as well as the best quality coating. A. IRON The influence of any minor elements in the galvanizing bath on the galvanized product is of primary interest to galvanizers. The first element to be considered is iron, since reaction between iron and zinc is the basis for hot dip galvanizing. As the work passes through the galvanizing bath, molten zinc reacts with the steel to form zinc-iron alloys on the steel. These alloys constitute a true metallurgical bond between the steel being processed and the zinc in the kettle. Although the galvanizing process depends upon the reaction of iron and zinc, iron has a very low solubility limit in molten zinc. At about 850°F (454 C), the solubility limit is 0.034% iron. The presence of iron in the bath cannot be avoided in practice, but it can become undesirable when enough of it is in suspension as dross to be carried mechanically into the coating. In abnormal quantity, it may form undesirable projections or irregular patches of crystalline particles in the coating. B. LEAD While some consider lead -in the amounts that are soluble in zinc -as having no influence on the physical properties or life of galvanized coatings, it is commonly felt that its presence improves the coating. A certain percent of it is necessary for the production of spangles. lt should be noted, however, that lead concentrations that are too high may adversely affect adhesion between free zinc and zinc alloy layers if the parts are exposed to elevated temperatures.
The specifications for Prime Western Zinc sets a maximum limit for lead content at 1.4%; typical lead contents are 1.0-1.3%. The solubility of lead in zinc is governed by the temperature of the bath. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 473
SSPC CHAPTER*ZL-O 93 m 8627940 0003923 44T W Research has shown that additions of lead up to about one percent do not change the viscosity of the molten zinc. However, that level of lead in the bath reduces the surface tension by more than 40% -compared to pure zinc. This reduction in surface tension tends to help the drainage of the bath metal from the work as it exits from the galvanizing bath and probably accounts for the improved drainage reported by many galvanizers using lead-saturated baths. A layer of molten lead about 2 to 4 deep is kept in the bottom of the bath to facilitate the removal of hard zinc (dross), which floats on the lead layer. The solubility of the lead in molten zinc is about 1YO,so unless the zinc added to the bath contains this amount of the metal, deliberate additions of it must be made so that the lead layer is maintained. C. ALUMINUM Aluminum is not normally found in the zinc metal; rather, it must be added to the galvanized bath. The presence of aluminum in galvanizing baths has a number of well-defined effects. By forming a thin impervious film of aluminum oxide on the surface of the metal, aluminum retards the growth of the heavy zinc-oxide films that may interfere with the smooth flow of zinc over the surface of the work, and gives the bath the appearance of greater fluidity. The normal concentration of aluminum is about 0.005%, and because it is preferentially oxidized, small regular additions to the bath are necessary to maintain constant level. Small amounts of aluminum brightness, tightness and coatings. Small additions drainage of zinc from the ing bath.
markedly increase the uniformity of galvanized of aluminum also improve the work as it exits from the galvaniz-
The effect of aluminum is to decrease the thickness of the alloy layer between the base metal and the zinc coating, by retarding the reaction between the molten zinc and the ferrous metal surface. D. CADMIUM Cadmium is a common impurity in zinc ore and frequently is found in remelted varieties. It does not have a detrimental effect upon the galvanized bath or the galvanized coating. It might be present at a level of up to 0.1Yo in commercially available Prime Western Zinc. Cadmium significantly reduces the oxidation rate of molten zinc, promotes coalescence of iron compounds, which minimizes floating dross, and has a beneficial effect on the flux blanket. When used alone it contributes fluidity to the bath. Its effects are influenced by the presence of small amounts of other elements. With antimony it gives a
medium to large frosty spangle. E. COPPER The typical copper content of Prime Western Zinc used in galvanizing is almost always less than 0.5%. However, copper is soluble in zinc up to about 2% at the galvanizing temperature. A high copper content (.4% Cu) in the galvanizing bath can lead to some structural change in the basic galvanized coating and to rapid erosion of galvanizing kettles. However, the copper concentration required is much greater than that usually encountered in the galvanizing bath, unless some exogenous copper is introduced into the bath, e.g. from using the brightener alloy of high copper content. Copper, in concentrations of less than 0.2% by weight, does not affect zinc coatings. In greater amounts, copper increases the thickness and the speed of formation of the brittle alloy layer, and can cause a spotting reddish scum on the bath. When exposed to acid environments, the galvanized coating will turn black. F. MAGNESIUM Magnesium, in concentrations of about 0.05% by weight, is reported to improve corrosion resistance. Magnesium also has a tendency to promote the formation of zinc ash on the surface of the bath. G. TIN AND ANTIMONY Both tin and antimony have been used to influence the spangle or crystalized appearance. Additions of up to 1O/O of tin increase the solidification range of the coating and give rise to bigger zinc crystals. Both additions are said to decrease the ductility of the coating and may result in staining. The effects of tin, like those of other agents, are modified by the bath temperature, cooling rate, thickness of the base metal and the concentration of the agent in the bath. Antimony may be used as a brightener to improve spangle appearance. About 0.1YOby weight is considered maximum, as larger quantities could embrittle the coatings or cause staining as the antimony oxidizes. IX. PROCESS VARIABLES A. INFLUENCE OF TEMPERATURES After steel that has been dipped reaches the bath temperature, since the flux further reduces the surface tension and enables wetting to occur very rapidly, fusion takes place at a rapid rate. The molten zinc bath should be maintained at the lowest temperature consistent with the free drainage of zinc from the work during withdrawal. Low temperatures help reduce dross and ash as well as increase kettle life. Generally speaking, all work to be processed can be satisfactorily galvanized when the zinc bath is maintained between 800°F (425°C) and 860°F (460°C). Very little
galvanizing work is done below 820°F. It should be noted that the zinc alloy layers grow faster at the higher temperat ures. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 474
SSPC CHAPTER*2L*O 93 8627940 0003922 386 = B. INFLUENCES OF TIME 2. Roughness The development of the galvanized coating is a function of the time in the zinc bath. Steel should be submerged as rapidly as possible and in line with safety practices for the operator s safety. The total immersion time will depend on the size and composition of the part. The surface of the work must reach the melting point of the zinc before galvanizing can begin. Once the steel has reached the galvanizing temperature, the reaction between the molten zinc and steel proceeds very rapidly; with additional time, the growth rate is much reduced. C. INFLUENCE OF SURFACE PREPARATION Surface contamination is a prime consideration. It is the fabricator s responsibility to see that all compounds are free from welding slag, anti-spatter compounds, paint and varnish, oil and excessive rust. Normal pickling will not remove these contaminants, and an extra cost will be incurred if the galvanizer has to clean the article before pickling. All overlapping surfaces must be particularly clean before fabrication, since any oils and greases will volatilize during galvanizing and prevent the zinc from sealing open edges. Careful preparation throughout cleaning, pickling, rinsing and prefluxing assures that the work about to be dipped will react freely with the molten zinc to provide a continuous and tightly adherent coating. Various pickling operations develop different steel surface roughness, coating structures and weights when galvanized. D. DEFECTS Occasionally, defects in the galvanized coating mar the appearance of the coating and may affect the coating performance. In some cases, the causes of a particular defect can be determined from the surface appearance of the galvanized product. They may be due to the steel quality, inadequate processing of it prior to coating operation, faulty galvanizing practice or other factors. By using the correct technique for specific products the galvanizer can determine the quality of the coating. 1. Adhesion Problems Galvanized coating adhesion problems are encountered occasionally, but adhesion of the zinc coating should not be a problem unless a reactive steel is galvanized, in which case the characteristically thick, gray and somewhat brittle coating may be encountered. Under these conditions, some loss of adhesion may be expected; bare spots should be touched up with zinc-rich paint or metallizing. Loss of adhesion on nonreactive steels probably indicates poor surface preparation, and the work would probably be rejected on the basis of bare spots. The coating
must adhere well enough to withstand subsequent handling, fabrication and final application. Surface roughness of the galvanized coating is due to several factors. One of the causes is excessive or uneven growth of the alloy layers arising from the composition or surface condition of the steel, which are factors outside the control of the galvanizer. Features of the galvanizing process which can also give rise to general roughness are over-pickling, excessive immersion in the bath or excessive bath temperature. The surface uniformity of the coating is controlled primarily by the drainage of the zinc as the work leaves the galvanizing bath. A lumpy and uneven coating results when the rate of withdrawal is too fast or the bath temperature too low to allow surplus zinc to run back into the bath. Runs may also occur because of delayed drainage from bolt holes, folds, seams and other pockets where zinc collects. A similar effect may result where articles are withdrawn in contact with each other. Often, however, the condition is due to high silicon content of the steel. Another cause of rough areas on galvanized surfaces is the presence of dross inclusion in the coating manifested as protrusion or nodules. In applications where the rough finish is aesthetically unacceptable or would interfere with the intended use of product, it is rarely possible for the galvanizer to effect any improvement; steel composition and surface condition should be more closely specified. 3. Peeling Peeling results from detachment at the inter-face of the zinc layer and the contacting zinc-iron alloy layer. It occurs where the product has slowly cooled after removal from the galvanizing bath and subsequently heated to temperatures below the melting point of zinc. Typical examples are bundled tubing or thick structurals that have been stacked on top of each other soon after removal from the galvanizing bath. Examination shows that, even where the coating seemed to be unaffected, there is an almost continuous break in the coating at the bath metallzinc-iron alloy interface. The same type of defect occurs when a galvanized coating is subjected to elevated temperatures. The free zinc layer peels from the zinc-iron layer leaving a total alloy coating. Peeling can be minimized by quenching material immediately after galvanizing. Hot galvanized products should not be stacked on top of one another immediately after removal from the
galvanizing bath. 4. Rust Stains Rust stains on the coating generally arise from contact with or drainage from rusty steel surCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 475
SSPC CHAPTERa2L.O 93 8627940 0003923 212 faces. The galvanized coating remains intact under the stain and will fully protect the base steel. Rust staining can also be caused by seepage of entrapped pickling acid from seams and joints; this will cause damage to the coating and requires modification in design. Early staining can also sometimes occur if the coating consists entirely of zinc-iron alloy and arises from the iron in the coating itself. It should not be confused with rusting of the base steel. It is not harmful to the corrosion resistance of the coating since exposure trials have shown that the corrosion resistance of the alloy is similar to that of the zinc itself. 5. Pimples Pimples are caused by inclusions of dross in the coating. These may arise from iron salts carried over on the work from the pickling tank which are unable to escape from the surface of the coating. Contamination may also arise from agitation of the dross layer at the bottom of the bath. Dross has a rate of corrosion similar to zinc, and its presence as finely dispersed pimples is often objectionable. However, major dross inclusions are normally grounds for rejections as they tend to embrittle the coating. 6. Bare Spots Because of the sacrificial action of the zinc, localized flaws are usually self-healing and have little effect on the coating life. Where considered necessary such spots may be patched using one of the repair methods available for restoring damaged galvanizing. Gross uncoated areas, however, should be rejected unhesitatingly. Some of the causes of bare spots in galvanized steel are described below. a. Under-Preparation. Remnants of paint, oil, grease, scale, or rust are perhaps the most common cause of uncoated spots. Such residues are not wetted by the molten zinc and, therefore, deter the normal coating reactions. It cannot be overstressed that thorough preparation of the steel is the foundation of good galvanizing practice and calls for the utmost care and diligence in its execution. b. Welding Slag. Slag deposits from arc welding are resistant to normal pickling acids and must be completely removed before the work enters the galvanizing process. Grit or sand blasting is strongly recommended for this purpose and is preferable to the less reliable method of hand chipping and wire brushing. This cleaning is usually done by the fabricator. c. Rolling Defects in Steel. These defects may be
broadly classified as discontinuities in the steel that have been closed and elongated during rolling but have not welded. Examples are lamina tions, laps and folds, and non-metallic impurities rolled into the metal surfaces. Defects of the first type are sometimes detected before or after pickling, but sometimes may not become apparent until opened by the heat of the galvanizing bath. In the case of rolled-in impurities, conventional methods for surface cleaning are generally ineffective. Minor flaws in the steel may be removed by local grinding, but little reclamation is possible where the steel surface is seriously defective. d. Articles in Contact. The importance of allowing the zinc free access to all parts of the surface and preventing articles entering and passing through the galvanizing bath cycle while in tight contact with each other is self-evident and requires no elaboration. 7. Blisters Blisters are occasionally encountered in galvanized surfaces. They vary in size from minute projections to large defects. Small fine blisters sometimes are barely discernible to the eye. Blisters are known to be caused by discontinuities in the basis steel traceable to the presence of non-metallic inclusions, laminations, piped steel , imperfectly welded blowholes, seams or other faults. The nascent hydrogen liberated by the reaction of the acid on the steel in pickling diffuses readily through the steel and is absorbed in these voids or inclusions. Upon subsequent heating in the galvanizing operation, the substantial increase in volume of the hydrogen gas exerts pressure great enough to raise the steel surface at points of discontinuity. Properly made rimmed steels have a heavy skin and are relatively free from the surface blowholes that are a direct cause of seams, and the occurrence of the defect is largely confined to semi-killed and killed steels. If the blister is in the free zinc layer, which it usually is, it can be eliminated by regalvanized without stripping. The free zinc layer is melted by the galvanizing bath, allowing the gas to escape, thereby eliminating the blisters. Similar blisters can occur on malleable iron castings caused by moisture or flux entrapped by the irregular surface profile. 8. Gray Coatings Gray coatings appear in small localized areas or as a complete dull gray surface, with no spangle at all usually, but on occasion in very small
spangles. This appearance is commonly caused by diffusion of iron to form the zinc-iron alloy phase at the surface of the coating. It first develops as a localized dull patch or lace-work pattern on an otherwise normal surface but may extend over the entire surface. Gray coatings Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 476
SSPC CHAPTER*ZL.O 93 m 8627940 0003924 159 m generally occur as a result of the combination of steel chemistry and galvanizing conditions. While there are numerous factors related to the formation of gray coatings, the major ones are attributable to a defective steel base. For instance, the steel base may be an over-oxidized steel base, usually accompanied by an excess of inclusions and porosity. An over-pickled steel base results in excessive amounts of absorbed hydrogen and a porous surface, both of which interfere with the normal crystallization of the zinc. Over-pickling also may cause embrittlement. The composition of the steel base can affect the formation of gray coatings. The silicon content is especially important, and gray coatings result with increasing severity as the silicon content is raised from 0.05 percent to 0.20 percent. Some other conditions that favor the formation of iron-zinc alloys will result in gray coatings, for instance, decreasing the rate of cooling by artificial means, as in the manufacture of dull coat coatings or the effect of heavier gauges in cooling from the coating temperature. Another factor is the degree of roughness of the surface as it provides more or less surface for the alloying action to progress. Gray coating can sometimes be minimized by controlling immersion time, galvanizing temperature, and quenching time. For example, galvanizing a delineator post for five minutes at 850°F and air cooling resulted in a gray coating. Reducing the galvanizing time to 2% minutes at 850°F and water quenching produced a coating that displays the typical shiny galvanized coating appearance. Water quenching is important in reducing the frequency of dull gray coatings because it restricts the alloy layer growth and results in the presence of a free zinc layer on the surface of the coating. However, this is a cosmetic defect only; the corrosion protection afforded by a gray coating is comparable to that of bright shiny coatings. Gray coatings can be eliminated by specifying the steel composition to preclude silicon-killed and semikilled steel, if possible. Otherwise, the material should be galvanized at low temperatures for short times and then water quenched as quickly as possible after withdrawal from the galvanized. bath. Since these coatings are often thicker than the normalbright coatings, they will give a longer life. It is rarely possible for the galvanizer to minimize this effect when it is due to the composi-
tion of the steel. 9. Distortion Because galvanizing takes place at the low end of the stress-relieving temperature range, some stress relief takes place and distort.ion or warping 477 may result in non-symmetrical stressed pieces. Precautions shall be taken to avoid distortion or warpage of members during galvanizing. The procedures suggested in ASTM-A 384 Recommended Practice for Safeguarding Against Warpage and Distortion During Hot-Dip Galvanizing of Steel Assemblies should be observed. Material failing to meet the required criteria for straightness and length should be rejected. 10. Strength and Ductility Normally, no significant changes occur in the mechanical properties of construction steel due to galvanizing. In applications which require heavy cold working of steels that are susceptible to strain or age hardening, stress relieving may be needed before galvanizing (or any other process involving a similar heating cycle) to ensure adequate ductility in the product. 11. Lumps and Runs in utilitarian applications lumps and runs caused by uneven drainage are not harmful to the life of the coating. Fabrications with drainage spikes of such a size that they can be knocked off, exposing bare steel, require remedial action, either repair or reject ion. 12. Fluxing Defects Serious corrosion of galvanized coatings is invariably caused by the inclusion of flux, especially when it has lost its fluidity due to loss of most of its ammonia content, or to oxidation. It will then become too viscous to flow out freely from tiny crevices on the metal surface or the pockets in the irregularly growing alloy layer. 13. Residues A number of reaction products or residuals stem from the hot dip galvanizing process. These are dross, ash, and flux skimmings. While their forma tion cannot be totally-eliminated, it can be minimized by exercise of controls and care in practice. Dross is a pasty solid comprised of zinciron alloy and much adhering zinc. It is denser than zinc and sinks to the bottom of the kettle. While zinc-iron alloys contain 6-12% iron, dross removed from the bottom of the galvanizing bath analyzes at about 97% zinc and 3% iron.
X. AFTER-TREATMENTS After galvanizing, the work may be quenched in water or cooled in air, Small parts, such as nuts, bolts, and washers that are galvanized in baskets in a batch are usually centrifuged to remoye excess zinc before it freezes. No after-treatment is essential, but components are often quenched to allow handling and to limit further growth of the alloy layers that have a dark gray appearance. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERa2L.O 93 = 862 7940 0003925 O95 a Where work is likely to be stored or transported under bad conditions of ventilation, a simple chromating treatment may be used to prevent wet storage stain (white rust). Such treatments are usually not suitable as a pretreatment for painting. A. TREATMENT FOR WET STORAGE STAIN Wet storage stain is the name given to the bulky white or grey deposit that may form on the surface of closely stacked, freshly galvanized articles that become damp under poorly ventilated conditions during storage or transit. In extreme cases, the protective value of the coating may be seriously impaired, but the attack is often light despite its appearance. This porous deposit is not protective and must be removed even if the attack is superficial as the essential protective patina of tightly adherent corrosion products will not form in these areas. Light deposits can be removed by brushing with a stiff bristle brush. Heavier deposits can be removed with a5 per cent solution of sodium or potassium dichromate with the addition of 0.1 per cent by volume of concentrated sulphuric acid. This solution is applied by brush or spray and left for about half a minute before thorough rinsing and drying. After removal of these heavier deposits, a check should be made on the coating thickness. B. MARKING FOR IDENTIFICATION Units to be galvanized must be free from marking paint such as might be used for addresses, shipping instructions, and job numbers. For temporary identification use water soluble paint or detachable metal labels. For permanent identification to be legible after galvanizing use large heavily punched or embossed marks. XI. OTHER METHODS OF GALVANIZING While this chapter is mainly on products hot dip galvanized after fabrication, it is pertinent to mention two other zinc coating fields. These are continuous line galvanizing of steel strip and wire, and electrogalvanizing of steel strip and wire. Strip continuous galvanizing is by far the largest market in that, in an average year, about 7 million tons of steel are zinc coated. A. CONTINUOUS HOT DIP GALVANIZING Several designs of continuous hot-dip galvanizing lines are in commercial use. In the simplest arrangement, a continuous strip of box-annealed and temper-rolled steel is passed from an uncoiler through a long acid pickling tank into a galvanizing pot. A more elaborate design utilizes the so-called dryfluxing practice. In this modification, a thin film of flux in aqueous solution is applied to the strip after it leaves the cleaner, and the strip then passes through a drying furnace into the zinc pot.
Another line is characterized by a continuous anneal during which the strip is exposed to a complex gas containing hydrogen chloride. A fourth type of line includes controlled oxidizing and reducing steps prior to coating. The cold-reduced strip passes from the uncoilers through an open-flame oxidizing furnace, which also serves as a flame degreaser, into a reducing furnace where it is annealed or normalized, and the oxide film formed in the first furnace is reduced by hydrogen gas. A fifth type of line, which may or may not use alkaline cleaning or acid pickling, anneals the steel in a gas-fired, direct-flame-impingement reducing furnace and cools it in a closed compartment containing a reducing atmosphere from which the steel enters the zinc bath. In other installations, strip material is alkaline cleaned, rinsed and dried, bright annealed, cooled to slightly above pot temperature, and introduced into the coating bath while still protected by the furnace atmosp here. B. ELECTROGALVANIZING In electrogalvanizing, steel strip or wire is fed continuously through suitable entry equipment, a series of washes and rinses, and a plating bath. The pure zinc coating deposited is highly ductile. Because of its excellent adhesion, electrogalvanized steel strip and wire have good working properties, and the coating remains intact after severe deformation. 1. Strip and Sheet Electrogalvanized steel is produced in strip coils or sheets. Most products have a coating weight in the range of 0.06 to slightly less than 0.2 oz. per sq. ft. (0.00005 to 0.00017 in. thick on each side). A small amount carries considerably less -about 0.025 oz. per sq. ft. (0.000021 in. on each side). Electrogalvanized sheets are produced in various tempers suitable for simple bending or forming, for curving, and for rolling into cylinders without fluting. Spot welding is easily accomplished provided care is taken. Electrogalvanized steel is easily prepared to receive decorative finishes. Much of it is produced with a phosphate treatment or an organic coating. The phosphate treatment provides adequate tooth for a good bond with organic finishing materials. Organic coatings applied over electrozinc so treated maintain good adhesion in adverse conditions such as sudden changes in temperature and high humidity. Phosphatized electrogalvanized steel is used for parts subject to atmospheric corrosion or salt spray, and for parts that are to be lacquered or printed. Phosphate treatment increases corrosion
resistance to a marked degree, particularly in atmospheres with a high sulfur content. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 478
SSPC CHAPTER*ZL=O 93 D 2. Applications Electrogalvanized sheet is used for manufacturing water cooler housings and exterior panels on ranges, freezers, dryers, washers, air conditioners and other major appliances. It is used for deepdrawn parts for kitchen cabinets, refrigerators and allied products instead of plain cold-rolled sheet because zinc holds better in the dies and cuts down greatly on breakage. Bakery equipment and other merchandizing display cases, stud systems for steel building construction, acoustic ceiling members, and television masts are also made of electrogalvanized steel. ASTM Standard Specification A525 for Steel Sheet, Zinc Coated (Galvanized) by the Hot Dip Process is the master specification for galvanized sheet. It spells out the general requirements, whereas other specifications go into specifics more clearly. It lists the different kinds of surface finishes available as well as supplementary finishes to further retard corrosion such as oiling and chemical treatments. The latter includes the various chromate conversion coatings or modifications thereof that are used for white rust control. ASTM Standard Specification A591 for Steel Sheet, Cold Rolled, Electrolytic Zinc Coated is the document covering the parameters of electrogalvanized steel. XII. ADVANTAGES AND LIMITATIONS An important advantage of the hot-dip galvanizing process is that unless zinc is removed by mechanical devices (a practice confined to the specialized galvanizing of sheet, strip, wire and tube), the work is bound to be thoroughly covered and to carry a thick coating, usually weighing from 1.8 to 2.2 oz. of zinc per square ft. of surface. All edges, rivets, seams and welds are thus sealed by the hot-dip process. Furthermore, it will often be the most economical process where large amounts of steel have to be treated. Galvanizing can be specified to good advantage on many construction projects. The architect and specification writer should be selective in their use of galvanizing, just as they are selective in the use of other materials. Technical and economic requirements must dictate the choice of materials. XIII. CONCLUSION Hot dip galvanizing methods and practices have improved considerably. The technical aspects of galvanizing have .been emphasized. It is hoped that the design engineer will benefit as well as the corrosion engineer from this discussion. Zinc coated steel is the dominant
method used for economical long-term protection of steel structures. = 8627940 0003926 T21 Appendix Specifications for Galvanized Coatings Pertinent ASTM specifications concerned with zinc and some technical practices are: A 53 Standard Specification for Pipe, Steel, Black and Hot Dipped, Zinc Coated Welded and Seamless A 90 Methods of Test for Weight of Coating on ZincCoated (Galvanized) Iron or Steel Articles A 11 1 Spec. for Zinc-Coated (Galvanized) Iron Telephone and Telegraph Line Wire A 112 Spec. for Zinc-Coated (Galvanized) Steel Tie Wires A 116 Spec. for Zinc-Coated (Galvanized) Iron or Steel Farm-Field and Railroad Right-of-way Wire Fencing A 120 Spec. for Black and Hot Dipped Zinc-Coated (Galvanized) Welded and Seamless Steel Pipe for Ordinary Uses A 121 Spec. for Zinc-Coated (Galvanized) Steel Barbed Wire A 123 Spec. for Zinc (Hot Galvanized) Coatings on Products Fabricated from Rolled, Pressed, and Forged Steel Shapes, Plates, Bars, and Strip A 143 Rec. Practice for Safeguarding Against Embrittlement of Hot Dip Galvanized Structural Steel Products and Procedure for Detecting Embrittlement A 153 Spec. for Zinc Coating (Hot-Dip) on Iron and Steel Hardware A 385 Standard Practice for Providing High-Quality Zinc Coatings (Hot-Dip) A 591 Standard Specification for Steel Sheet, Electrolytic Zinc-Coated for Light Coatings Mass Applications A 641 Spec. for Zinc-Coated (Galvanized) Carbon Steel Wire A 642 Spec. for Steel Sheet, Zinc-Coated (Galvanized) by the Hot Dip Process, Drawing Quality, Special Killed A 767 Standard Specification for Zinc-Coated (Galvanized) Steel Bars for Concrete Reinforcement A 780 Standard Practice for Repair of Damaged and Uncoated Areas of Hot-Dip Galvanized Coatings
B6 Spec. for Zinc Metal (Slab Zinc) B 454 Spec. for Mechanically Deposited Coatings of Cadmium and Zinc on Ferrous Metals B 487 Measurement of Metal and Oxide Coating Thicknesses by Microscopical Examination of a Cross Section B 498 Spec. for Zinc-Coated (Galvanized) Steel Core Wire for Aluminum Conductors, Steel Reinforced (ACSR) B 499 Measurement of Coating Thicknesses by the Magnetic Method: Nonmagnetic Coatings on Magnetic Basis Metals B 504 Measurement of Thickness of Metallic Coatings by the Coulometric Method B 555 Guidelines for Measurement of Electrodeposited Metallic Coating Thicknesses by the Dropping Test B 571 Test for Adhesion of Metallic Coatings Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 479
B 695 Standard Specification for Electrodeposited Coatings of Zinc on Iron and Steel E 376 Rec. Practice for Measuring Coating Thickness by Magnetic-Field or Eddy-Current (Electromagnetic) Test Methods B 633 Spec. for Electrodeposited coatings of zinc or steel (see 6454) A 591 ASTM Standard Specification for Steel Sheet, Cold Rolled, Electrolytic Zinc Coated. ACKNOWLEDGEMENT The authors and editors gratefully acknowledge the active participation of the following in the review process for this chapter: Willard Lantz, Howard Lasser, Marshall McGee, John Montle, Jack Oechsle, Walter Pregmon, Walter Radut, Melvin Sandler, and William Wallace, Jr. REFERENCES 1. Specifying Galvanized Steel For Construction Projects . The Construction Specifier, October 1973. 2. U.S. Steel Corporation, The Making, Shaping and Treating of Steel, 1971. 3. Faults in Hot Dip Galvanizing , Max Planck Institute Booklet, 1975. 4. American Society for Testing and Materials, Annual Book of Standards, 1980. 5. Fabricating Continuous Galvanized Steel , Steel Processing and Conversion, June 1958. 6. Zinc -Science and Technology of the Metal, Its Alloys and Compounds , C.H. Mathewson, Ed. American Chemical Society Monograph Series No. 142 (1959). 7. Inspection Manual for Hot Dip Galvanized PrÓducts, Zinc InstitutelAmerican Hot Dip Galvanizers Association, 1979. 8. The Design and Fabrication of Galvanized Products, Zinc InstituteiAmerican Hot Dip Galvanizers Association, 1979. 9. The Galvanizing Manual, St. Joe Minerals Corporation, 1974. BIOGRAPHY Ernest W. Horvick has worked for the Zinc Institute, Weirton Steel Company, Bell Aircraft and Minneapolis Honeywell, in technical, supervisory and marketing capacities. He is a member of ACS, the American Society for Metals, the Society of Die Casting Engineers, the American Society for Testing and Materials, the National Association of Corrosion Engineers and is a Society of Manufacturing Engineers Certified Manufacturing Engineer in the field of Inorganic Coatings. --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 480
SSPC CHAPTER*22.0 93 W 8627740 0003728 8T4 W CHAPTER 22 PAINTING OF GALVANIZED STEEL by Richard W. Drisko, Ph.0. I. INTRODUCTION Hot-dipped galvanizing of steel is achieved by immersing cleaned steel in a bath of molten zinc. The zinc is metallurgically bonded to the steel to form a tight metallic layer that provides both barrier and cathodic protection. Cathodic protection comes into play wherever there are imperfections in the zinc protective film. The length of protection provided to steel structures is related both to exposure environment and to the thickness of the zinc, which is sometimes expressed in ounces per square inch. Mils increasingly are also being used to describe the thickness of the zinc film. Electrodeposition of zinc usually results in much thinner films of zinc than does hot-dipping, so that the latter is usually preferred for long-term protection. Although galvanizing itself may provide many years of protection to steel structures, coating will extend the period of protection as well as provide other desirable features. This chapter addresses the benefits of coating galvanized steel and how best to achieve them. For more information on galvanizing, see chapter 21. II. REASONS FOR COATING GALVANIZING There are basically three reasons for coating galvanized steel structures: extended corrosion protection, color cod- FIGURE 1 Galvanizing may be painted to extend corrosion protection. Early ing and appearance. corrosion of galvanized steel in tropical environment, cause d by A. EXTENDING CORROSION PROTECTION water drainage problems. Although galvanizing may protect steel for 30-40 or more required for cathodic p rotection on buried or immersed strucyears in moderate environments, this period of protection tures. The cathodic pr otection provided by galvanizing, or may be much less in severe environments. Being ampho- an external cathodic prote ction system protect organic coatteric (attacked by both acid and alkali), zinc is especially sus-ings from under cutting at holidays and other imperfections ceptible to attack in acidic and alkaline environments. that arise in the paint film with time. Properly selected and applied coatings can significantly ex- B. APPEARANCE tend the life of galvanized coatings on steel surfaces in a Hot-dipped galvanizi ng of steel results in a metallic fin-
range of environments. ish that may not be pleasing to some people for some appl iThere is some evidence that galvanizing and coating cations. They may desire a f inish to produce a more pleasing with an organic finish have a synergistic effect in protecting steel, ¡.e., the total time of protection is greater than the sum appearance. of the times normally provided by the zinc and the organic coatings. This additional protection is said to be similar to C. SAFETY MARKING/ COLOR CODING the combined effects of cathodic protection and organic coat- Galvanizing may al so be coated when regulations reings on buried or immersed steel structures. quire safety coding. For instance, OSHA regulations require Organic coatings physical hazards from galvanizing der this system,
reduce the rate of zinc consumption that workers be alerted to using a safety just as they reduce the amount of current color code system. Un the color red signi-
Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 481
SSPC CHAPTER*22=0 93 m Ab27940 0003929 730 m circumstance which could cause a worker to trip or fall, to be caught in between two surfaces or to strike against something. Aviation regulations also require some color coding. Tall galvanized structures such as antennas may constitute a hazard to aircraft unless treated by a system that provides a quick visual identification by pilots. 111. BACKGROUND Historically, there have been problems obtaining good performances from organic coatings on galvanized steel. These have usually been related to improper cleaning of the galvanizing or improper selection of the organic primer. A. PROBLEMS RESULTING FROM IMPROPER CLEANING Necessary cleaning of galvanizing for coating includes removal of all surface contaminants that would adversely affect primer adhesion. After the hot dipping of steel, the galvanized finish is sometimes coated with a thin film of oil or given a hexavalent chromate treatment to protect it from formation of white rust (zinc corrosion products) during exterior storage. Galvanizing is susceptible to accelerated crevice corrosion during exterior storage, if water gets between sheets or other components. FIGURE 4 Rustingof steel through galvanizing. Zinc was badly corroded due to exterior storage of siding. Oil and chromate protective treatments will prevent good adhesion of primers, so these materials must be removed prior to priming. The oil is easily removed by solvent cleaning (SSPC-SP 1). The hexavalent chromate treatment is more difficult to remove, and so its use should be prohibited if the FIGURE 3 Galvanizing may be painted for the purpose of color coding haz- galvanizing is t o be painted with an organic coating. ASTM ards, for instance aviation hazards. D 2092 Appendix X2 describes how the chroma te can be identified using 1,5-diphenylcarbohydrazidesolution and refies danger , and is required for danger signs and for safety moved by weathering f or 6 months, abrading the surfaces cans containing flammable liquids. Red also signifies stop , by sanding, or brush-o ff abrasive blast cleaning (SSPC-SP7). and is required for emergency stop bars, buttons or switches on hazardous machines. The color yellow signifies caution and is used to signal a structure, piece of equipment or other
Galvanizing may be painted when the appearance of a structure is a consideration. --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 482
SSPC CHAPTER*22-0 93 8627940 0003930 452 5. PROBLEMS RESULTING FROM IMPROPER SELECTION OF ORGANIC PRIMER 1. Alkyd Coatings Alkyd coatings using such primers as TT-P-641 were once used by direct application to galvanized steel surfaces, with limited success. Galvanizing always has a film of alkaline zinc corrosion products on its surface. This alkalinity saponifies (hydrolyzes) alkyd or other oil-containing primer binders and may cause disbonding of the total coating system after only 6 months. Treatment of galvanized surfaces with an acidic wash primer (e.g., SSPC-Paint 27 or MILP-15238) increased the adhesion of alkyd primers and the performances of alkyd systems, but performances were still significantly poorer than those of other generic systems. 2. Cement Coatings Cement coatings have been used on galvanizing, but they are too rigid to expand and contract with the metal. Also, they have saponification problems, if drying oils are incorporated into their formulations. 3. Vinyl, Acrylic and Chlorinated Rubber Lacquers Vinyl, acrylic, and chlorinated rubber lacquers have been successfully used over wash primed galvanizing but will not be discussed further here, because they cannot successfully be formulated as low-VOC coatings (coatings with low solvent content required in locations with poor air quality.) 4. Bituminous (Coal Tar and Asphalt) Bituminous (coal tar and asphalt) and coal tar epoxy formulations are not recommended for exterior service, because they become embrittled by the sun s ultraviolet light. 5. Home Remedies A number of home remedies have also been used in the past to promote adhesion of the primer to galvanizing. These include washing with vinegar or a solution of copper sulfate to produce surface texture. Neither was advantageous. Surface treatments for galvanizing prior to coating are not recommended, because they are not necessary with the recommended coating systems and thus comprise an unnecessary expense. Also, if not properly done this procedure may be detrimental. IV. HOW AND WHEN TO CLEAN AND COAT GALVANIZED STEEL A. CLEANING
1. Solvent Cleaning New galvanizing is easily prepared for coating by solvent cleaning (SSPC-SP 1) to remove any grease or oil or washing with a mild detergent solution to remove any dirt or other loose surface contaminant. Either the solvent or the steam cleaning alternatives of SSPC-SPI should be used. Do not use the alkali alternative, since it may damage the galvanizing. 2. Abrasive Blasting and Waterblasting There is some concern in cleaning weathered galvanizing or galvanizing which has localized rusting that abrasive blast cleaning may remove significant amounts of the zinc. It has been shown, however, that only very slight amounts are removed by waterblasting or brush-off abrasive blasting (SSPC-SP 7). Localized rusting may have been initiated during improper exterior storage. 3. Weathering Another approach to obtaining improved primer adhesion and coating performance is to allow the galvanizing to weather for six months before painting. Although the surface roughness may contribute to better primer adhesion, surface contaminants on weathered galvanizing may adversely affect the coating performance. Thus, deliberate weathering of galvanizing prior to coating is not recommended. 4. Shop YS. Field Cleaning It is preferable to clean and coat new galvanized steel ina shop before erection of a structure. When this method is used, there is no problem with adhesion of the recommended coating systems to new galvanizing, and the cleaning and application will be much more effective in a controlled environment. Field cleaning and application is especially difficult on tall structures. B. COATING 1. Spraying Application of coating systems is best accomplished by spraying. This is another reason to coat galvanizing in a shop environment, where overspray will not drift to some undesired surface. 2. By Brush Application of coatings by brush is normally preferred in the field, where spraying may be a problem. It can result in fairly uniform dry film thickness. 3. By Roller Application of coatings by roller may be very effective on flat surfaces. It is less effective on surfaces that are not flat and usually results in greater film thickness variations than does brush application.
4. By Mitt Application using a synthetic wool mitt is often done on tall structures but is not recommended. It always results in a great variation in coating thickness and is usually messy. 5. Striping Prior to application of the primer coat, it is recommended that all galvanized steel edges, corners, Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 483
SSPC CHAPTER*22.0 93 8627940 0003933 399 = crevices and other surfaces that are hard to paint receive an extra coat of paint, a procedure known as striping . These hard-to-paint surfaces usually receive only thin films of paint by conventional methods of coating application and thus only limited protection from corrosion. V. RECOMMENDED COATING SYSTEMS FOR NEW EXTERIOR GALVANIZING A. GENERIC COATING SYSTEMS Two generic coating systems are recommended for galvanizing, an epoxy system (with an aliphatic urethane finish for exterior service) and an acrylic latex system. FIGURE 5 Test racks used to evaluate the performance 1. Relative Merits Examples --`,,,,`-`-`,,`,,`,`,,`--of particular coatings. The epoxy systems will provide long-term performance, while the acrylic latex system will provide a cheaper, easier-to-apply system with a wider range of colors and glosses at a slight reduction in service life. Both systems are readily available in VOClimited and lead- and chromate-free formulations. of appropriate government and SSPC specifications are included. The recommendations are based on extensive long-term exposure testing of the Naval Civil Engineering Laboratory at Florida and Bermuda. 2. Application With the epoxy and epoxy urethane systems, it is best to apply the topcoat on the day after application of the primer. If a delay of more than 7 days occurs before topcoating, apply a thin film (1-2 mils wet film thickness) of the primer and allow it to cure for 4 hours before applying a full coat of the finish. This will result in good adhesion of the finish coat. B. SPECIFICATIONS 1. New exterior galvanizing a. Epoxy polyurethane -1) Apply one primer coat of epoxy polyamide (e.g., MIL-P-24441, Formula 150) to give 3 mils dry film thickness. 2) Apply one finish coat of aliphatic urethane (e.g., MIL-C-85285) to give a minimum of 5 mils total dry film thickness. 6.Acrylic latex -Use SSPC-PS 24. Apply 2-3 coats of the system to give 5-7 mils DFT. 2. New interior galvanizing Apply two coats of epoxy polyamide (e.g., MILP-24441, Formulas 150 and 152) to give a minimum
of 6 mils total dry film thickness. VI. RECOMMENDED COATING SYSTEMS FOR MAINTENANCE PAINTING Maintenance painting may be required to correct fading, discoloration or limited intercoat peeling, or when the existing orange and/or white painted bands on tall structures fail to meet the requirements of the color chart of the FAA Advisory Circular 70/7460-lG. A. PROCEDURE 1. Surface Preparation The only surface preparation required for cosmetic repairs is removal of paint chalk andlor other loose surface contaminants by washing or scrubbing with a bristle brush. The weathered coating exteriors will have sufficient texture to permit good adhesion of finish coats. The damaged coating should be scrubbed with a bristle brush to remove all loose coating material and clean any exposed galvanizing. The sound coating adjacent to cleaned damaged areas should be feather-edged by light sanding to permit tight bonding of repaired areas onto existing sound coating. 2. Compatibility Maintenance painting to correct coating defects, other than cosmetic, requires use of repair materials that are compatible with the existing deteriorated coating. Generally, this means use of the same system already on the tower. Where the existing systems are no longer permitted (e.g., vinyl and chlorinated rubber systems in geographical areas with VOC limitations), another compatible system must be used. If the generic type of the existing finish coat is not known, a solvent-solubility test should be done. To do this, soak a portion of cloth or a cottontipped swab stick in methyl ethyl ketone or acetone, rub it against the existing finish, and visibly check whether it has picked up the finish. The finish is classified as solvent soluble if paint is picked up, and as solvent insoluble if not. B. SPECIFICATIONS Alkyd and epoxy systems are also included for coating damaged areas where rusted steel but no galvanizing is present. 1. Maintenance Painting of Galvanized Steel with No Rusted Steel Galvanized steel with damaged coatings but no more than a few pinpoint areas of rusted steel Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from
IHS 484
SSPC CHAPTERr22.0 93 8627940 0003932 225 should be painted by System A or B, depending upon the type of existing coating to be repaired. a. Repair System A -If the existing finish is known to be oil, alkyd, latex, vinyl or chlorinated rubber or was found to be solvent soluble , apply two coats of quality acrylic latex coating (e.g., TT-P-2784 or SSPC-PS 24) each at 1 1/2 mils dry film thickness. b. Repair System B -If the existing finish is known to be urethane or epoxy or was found to be solvent insoluble : (1) Apply a thin film (1-2 mils wet film thickness) of epoxy polyamide primer (e.g., MIL-P-24441, Formula 150) to the repair area and allow it to cure for 4 hours before applying a full coat of this primer at 3 mils dry film thickness. (2) For exterior service, apply a finish coat of aliphatic urethane (e.g., MIL-C-85285) at 2 mils dry film thickness. (3) For interior service, apply a second coat of epoxy polyamide (e.g., MIL-P-24441, Formula 152) at 3 mils dry film thickness. (4) High-build zinc dust tower paint can be used for repair of galvanized utility towers. (Stainless steel flake can be added to increase the life expectancy in corrosive or coastal environments). Apply a single coat of 8-10 mils DFT. For these repair systems, overlap the repair area 1 inch onto the surrounding sound coating. If the color match of the repair area to the existing coating is adequate, topcoating of undamaged areas will be unnecessary. 2. Maintenance Painting for Appearance (Cosmetic Defects) Apply two coats of a quality acrylic latex finish (e.g., TT-P-2784 or SSPC-PS 24) to completely hide the existing paint. 3. Maintenance Painting of Galvanized Steel with Rusted Steel If the coating deterioration and the zinc corrosion have occurred to the extent that significant areas of rusted steel but no galvanizing are exposed, spot repair of the surface is more complicated. The rusted steel must first be hand tool-cleaned (SSPC-SP 2) or power tool-cleaned (SSPC-SP 3 or 11) to remove rust and loose paint. The preferred method of cleaning is SSPC-SP 11. Power Tool Cleaning to Bare Metal , because it not only removes all visible rust but also produces a roughened surface. Powered needle guns and grinders with flexible wheels and disks can be used to produce the SP 11 surface. Cleaned steel should be primed the same day before flash-rusting occurs. If flash rusting occurs before priming, the steel
must be recleaned. a. Existing Solvent-Soluble Coating -If the existing finish coat is known to be oil, alkyd, latex, vinyl, or chlorinated rubber or was found to be solvent-soluble : (1) Apply two coats of alkyd primer (e.g., TT-P-645) to the cleaned steel each at 2 mils dry film thickness. (2)Apply two coats of alkyd or silicone alkyd (e.g., TT-E-489 or MIL-P-24635) finish over the primer each at 2 mils dry film thickness. b. Solvent-lnsoluble Coating -If the existing finish coat is known to be urethane or epoxy or if it was found to be solvent insoluble (1) Apply a thin film (1-2 mils wet film thickness) of epoxy polyamide primer (e.g., MIL-P-24441, Formula 150) to the repair area and allow it to cure for 4 hours before applying two coats of this primer each at 3 mils dry film thickness. (2) For exterior service, apply a finish coat of aliphatic urethane (MIL-C-85285) at 2 mils dry film thic kness. (3) For interior service, apply a finish coat of epoxy polyamide (e.g., MIL-P-24441, Formula 152). 4. Total Coating Replacement When coating deterioration occurs extensively on galvanizing that is still in good condition, it will probably be necessary to remove the remaining coating and recoat as recommended for new galvanizing. Brush off blast cleaning (SSPC-SP 7) or high pressure water jetting (10,000 psi or greater) are suitable methods for removing the existing deteriorated paint. ACKNOWLEDGEMENT The authors and editors gratefully acknowledge the active participation of Donald H. Wetzel in the review process for thic chapter. Pictures were provided by: Dr. Drisko, Donald H. Wetzel and Keeler and Long. Ernest V. Horwick wrote an earlier chapter. BIOGRAPHY A portrait and biographical sketch of Richard W. Drisko appear at the end of the chapter on Government Painting Procedures. REFERENCES 1. American Galvanizing Association and Zinc Institute. Painting Galvanized Structural Steel. 1986. 2. American Galvanizing Association. Zinc Coatings. 1988. 3. American Galvanizing Association. Touch-up Material forGalvanized Steel. 1979. 4. R. W. Drisko, D. R. Polly, and L. K. Schwab. Salt Spray Evaluation of Coated Galvanized Steel . Journal of Protective Coatings and Linings, February 1985, pp. 30-39. 5. M.F. Lichenstadter, Lloyd Smith, Dean M. Berger, Gary Satterfield. Problem Solving Forum: How Is Galvanized Steel Painted? Journal of Protective Coatings and Linings, September 1986, pp. 19-24. 6. D. John Long. The Painting of Galvanized Transmission Towers and Substation Structures . Journal of Protective Coatings and Linings, November 1987, pp. 32-41.
7. D. John Long, Bruce Delventhal, W.D. Dickinson, Jr. Problem Solving Forum: Most Occupational Safety and Health Administration (OSHA) Safety Colors Contain Lead Color Pigments. Does the Lead Content Constitute a Hazard in Application or Removal of These Coatings? Are Suitable Alternatives Available? Journal of Protective Coatings and Linings, December 1992, pp. 9-1 1. 8. Jan F.H. Eijnsbergen. Duplex Systems . (To be available, 1994). Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 485
CHAPTER 23 CAUSES AND PREVENTION OF PAINT FAILURE by Charles G.Munger Coatings or pair s are the prin ipal materials of corrosion protection for all steel structures. This is true almost without regard to the use of the structure, whether it be a bridge, ship, chemical plant, tank farm, refinery, high rise office building or underground pipe line. Every exposure of a coating is different, even though it may be used for the same purpose at different locations. Bridges in Florida are exposed to vastly different conditions than bridges in the northern part of the United States or Canada, and a tank farm in California is exposed to conditions quite different from one on the Gulf Coast. As coatings are the primary protection for all of these vastly different exposures, it is understandable that failure of coated surfaces is inherent and that time to failure is the critical dimension in this phenomenon. Failure can occur for a number of reasons: 1. Improper selection of the coating for the service. Too often, a coating designed for steel surfaces may be extended out over a concrete or wood surface from the steel structure with rapid failure occurring on the non-metallic surface. Also, a coating which might be excellent on the exterior of a storage tank may be a complete failure on a chemical reaction vessel. Proper selection of a coating for any specific purpose is extremely important. 2. The coating may fail from causes inherent to that specific coating. Such failure could be chalking, checking or alligatoring. 3. Adhesion-related failures are most numerous and can be catastrophic. Such failures are blistering, flaking and peeling. 4. Failure can occur from the surface to be protected (the substrate). The coating may be incompatible with the surface; there may be a chemical reaction between the surface and the coating; or the density or smoothness of the surface may cause the coating to have poor adhesion. 5. The coating may fail from exterior forces such as chemical exposure, abrasion or severe weathering. 6. The coating may fail because of poor or inadequate surface preparation or application. Here, surface contamination, poor surface profile, inadequate thickness control, pinholes, overspray, improper drying, lack of cure or holidays can cause rapid failure.
7. The design of the structure itself is often a cause for severe failure. Sharp edges, crevices, skip welds, back-to-back angles all are focal points for failure. All paints, and particularly many of the more advanced coatings, are complex chemical mixtures that must react in place on the surface over which they are applied. Paints and coatings contain a number of interacting ingredients: resins, plasticizers, curing agents, pigments, extenders, catalysts, fungicides and solvents. These are applied to the surface as a very thin film, a few micrometers or thousandths of an inch in thickness. The solvents must evaporate properly. The non-volatile portion of the liquid coating must deposit in a continuous even film over the surface. It must adhere to and possibly react with the surface. It also may react with internal curing agents, with oxygen from the air or with water from the air in order to become an insoluble, relatively inert film of low permeability which has good appearance. This thin film must then withstand rain, wind, the sun s rays, humidity, cold, heat, oxidation, physical abuse, chemicals, biodegradation and other forces. With all of the variables involved in the formation and use of paints or coatings, it is obvious that there can be many causes for coating failures. The common causes for paint or coating failure which are listed above will be taken up individually. I. SELECTION OF THE COATING SYSTEM The primary requirement of a coating system is that it shall resist deterioration by the environment in which the coating is to serve as a protection for a substrate. Since no one coating, or type of coating, is resistant to all environments (atmospheric, aqueous, or chemical), many types of coatings have been developed for service under special conditions and for application by various methods. Selection of a paint from among these many types can be made intelligently only on the basis of the following factors: the known performance of coatings in similar applications, the known chemical composition and physical properties of the paints, and the results of exposures of Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 486
SSPC CHAPTER*23.0 93 öb27940 000393Li OTB FIGURE 1 Note chalking of primer on deck. the coatings under consideration to test environments simulating the conditions of use. Of these factors, the best basis for critical judgment of the relative suitability of a paint system is previous experience with the performance of that coating. Nevertheless, actual first-hand observations of the serviceability of a coating can be misleading if the new environment in which the paint is to serve is dissimilar or if the composition of the paint has been modified. Knowledge of the chemical and physical properties of a coating (e.g., acid and alkali resistance, heat resistance, abrasion resistance, etc.) is a selection aid but should not be the sole basis for final selection. If the durability of a coating has not been proved in field tests or by service in commercial uses, the paint should be evaluated by accelerated tests. However, it must be emphasized that evaluation by accelerated tests should be used cautiously and then only for comparison purposes. The results of such tests must not be valued too highly unless there is correlation between their results and the observed performance of the paint in actual use. Unfortunately, correlation between the results of accelerated tests and performance during service is usually not available. A source of information by which to select a coating is the manufacturer of the paint or the supplier of materials for paints. Yet, such information can be incomplete or misleading if a precise description of the conditions to be met is not given to the persons whose advice is sought or if the basis on which their recommendations are made is not disclosed to the potential user of the coating. Selection of paint on the basis of price only or on the unsubstantiated opinion of a salesman can prove to be extremely costly. Mixing of paint systems is often practiced by persons with limited knowledge of coatings, usually as a matter of expediency. This can result only in costly failures. The compatibility of one coat with another is extremely important to the satisfactory service life of a paint. Generic types of coatings should generally not be mixed unless recommended by the manufacturer, nor should the products of one manufacturer be mixed with that of another. Only the manufacturer can know the true compatibility characteristics of the paint system which he has developed and is recommending. Selecting parts of paint systems from different manufacturers or from different generic types without basic knowledge of the products is almost a guarantee of failure.
II. COATING FAILURES WHICH ARE INHERENT WITHIN THE COATING ITSELF (FORMULATION RELATED) There are many failures of coatings due to the basic formulation, the resins used, the pigments or the many other ingredients used in coatings. The relation of the inherent coating failures to coating classes should be considered: ¡.e., those based on organic materials and those based on inorganic vehicles. A. ORGANIC COATINGS, FORMULATIONRELATED FAILURES i.Chalking With chalking, the organic binder in the coating tends to gradually disintegrate on the surface releasing the pigments and allowing them to remain on the surface as powder or chalk. This is strictly a surface phenomenon. While in some cases it can result in rapid reduction in coating thickness, it is generally a relatively slow process and one which does not result in catastrophic failure or severe corrosion to the substrate. Chalking, or powdering, is primarily caused by the action of the actinic rays of the sun on the organic binder. Permanently shaded areas seldom chalk. Humidity and oxygen from the air also play a part in this phenomenon. The resins which make up the binder are the key to the chalking rate. As an example, many epoxy coatings have a strong tendency to chalk. Properly formulated, they chalk minimally; however, there have been epoxy formulations that chalk at a sufficient rate so that a coating of eight or ten mils thickness can be reduced to the point where the primer is visible in a one-year period. On the other hand, acrylic, silicone, and polyurethane resins are only slightly affected by the sun s rays, and a coating system formulated from these may remain in a chalk-free condition for several years. Pigments also play a very important part in the chalking reaction. Some pigments, such as anatase titanium dioxide, chalk very readily and rapidly, while most rutile titanium dioxide pigments are very resistant to chalking. Many pigments tend to catalyze the chalking reaction. Some black pigments will chalk after a short period of time, while others will remain for years Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 487
SSPC CHAPTERr23.0 93 m 8627940 0003935 T34 m with little surface effect. Iron blue pigments tend to bronze as the first step in their chalking process. The influence of pigments on chalking is not all bad inasmuch as they tend to reduce chalking by shielding the resin from the sun s rays. Aluminum pigmentation is an excellent example of this type of shielding. The shingle effect of the leafing aluminum flake pigment prevents the sun s rays from penetrating to the coating vehicle. Almost any coating vehicle is more resistant to chalking when formulated with leafing aluminum pigment. The use of the newer resins, such as the acrylics and aliphatic polyurethanes, combined with chalking resistant pigments and the use of coating additives, such as ultra-violet absorbers, has resulted in paints and coatings which remain free of any surface change or change in gloss over a period of several years. The chalking reaction has been one used by a number of manufacturers to produce coatings with self-cleaning properties. When chalking is properly regulated through the prudent selection of the coating binder and the pigments, the chalking reaction can be controlled to the point where the surface erodes slowly, but at a sufficient rate to keep the surface free from any grime or dirt which might otherwise accumulate from the atmosphere. In these cases, the reduction in thickness is uniform and relatively constant so that sufficient coating remains to fully protect the surface over a number of years. Chalking may result in some color change and a reduction in gloss of the coating, and such factors must be considered in selecting a product. Of all the types of coating failure which can occur, chalking can be considered preferable to the rest. A clean, chalked surface, which is free from other types of failure or corrosion, is considered a satisfactory surface over which to apply additional coats of paint for maintenance. 2. Erosion Erosion is a type of failure caused by the wearing away of the coating down to the base surface or to the primer. This wearing away of the surface may be related to the above chalking mechanism. On the other hand, it may often be aggravated by the surface being exposed to heavy rainfall, hail, high winds or a combination of high winds and rain. Sand erosion of the coating caused by high winds and sand, such as encountered in beach
areas or in the deserts of the west, cannot be considered in this same category since such erosion may be catastrophic from one storm. Erosion is often seen in brushed coatings where the high ridges of brush marks are exposed because of the greater erosion of the raised area. Erosion of this type can best be prevented by the selection of a chalk resistant coating as described above and one which tends to flow out to a very smooth film. ASTM-D 662 describes degree of erosion of exterior paints. ASTM-D 821, describes degree of abrasion and erosion. ASTM-D 913 describes degee of chipping of traffic paint. 3. Checking Checking is an age-related failure of a coating. It is characterized by uneven and generally nonlinear, non-continuous breaks in the coating. These breaks are primarily a surface phenomenon and do not penetrate the full depth of the coating. Checking can be characterized as visible if the checks can be seen with the naked eye, or microscopic if they can be seen only under low magnification. There can be several causes of checking. It is generally a formulation problem which results in surface stresses in the coating. It can occur when solvents evaporate very rapidly from the surface and cause the surface to shrink more rapidly than the body of the coating. It can be caused by resins which oxidize on the surface or by certain pigments which apparently catalyze the checking reaction on the surface. Essentially, it is a stress set up in the surface which causes the small checks to appear while the body of the coating IS not subject to the same reaction. Wetting and drying, heating, cooling and sunlight exposure may all contribute to the checking of a coating. While initially the checks in a coating do not FIGURE 2 Badly eroded paint. (Federation of Societies For Coatings Technology Photo) Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 488
SSPC CHAPTER*23.0 93 m 8627940 000393b 970 pene.trate, if the coating is left without maintenance, the coating will eventually break down by further checking in the same area until the checks become cracks and the underlying surface is exposed. Checking is prevented primarily in the selection of the coating. A coating formulated with weather resistant resins should be selected, with pigments that do not contribute to checking and with reinforcing pigments that aid the coating in resisting surface stresses. ASTM Standard D-660-44, reapproved 1976, provides a standard method for the evaluation of the degree of checking in exterior paints. 4. Cracking Cracking is also an age-related failure caused by similar conditions to those described under checking . It contrasts with checking in that it is not a surface phenomenon but one where breaks in the coating penetrate to the underlying surface. This makes it a much more damaging type of failure than checking, since corrosion can rapidly take place at the breaks in the coating. It may occur in an irregular pattern where the coating stresses are rather uniform. It may be linear, following brush marks or even some spray patterns, or it may occur in a curved pattern with the cracks meeting and intersecting in a rather typical form. A surface such as wood that rapidly expands and contracts can contribute to cracking. Excessive thickness of coatings can also cause cracking because of increased stresses on drying or curing. Cracking is a formulation defect which can be overcome by the use of proper weather resistant resins and pigments plus the addition of two additional ingredients that help materially to reduce the interior stresses within the coating. One of these is reinforcing pigments. Such pigments are fibrous or acicular and act very much like chopped glass fibers in reinforced plastics. They definitely add physical strength to the coating film. The second is a permanent plasticizer or soft, compatible resin that increases the elasticity of the coating. Increased reinforcing and elasticity both reduce the physical stresses caused by weathering, heating and cooling or wetting and drying. Coatings made from oxidizing materials, such as oils or alkyd resins, or internal curing resins such as epoxies, are often susceptible to this type of failure since they continue to cure, become more brittle and shrink with time. Fully polymerized materials, such as vinyls, acrylics and chlorinated rubbers, when properly formulated, are less susceptible to cracking since
they continue to cure, become more brittle and shrink with time. FIGURE 3 Checking magnified ten times. (Federation of Coatings Technology Photo) Societies for --`,,,,`-`-`,,`,,`,`,,`--ASTM Standard D 661 provides a method for the evaluation of the degree of cracking in exterior paints. 5. AIligatoring Alligatoring can be considered a macro-checking failure and is caused by internal stresses set up within and on the surface of the coating. The stresses cause the surface of the coating to shrink much more rapidly and to a much greater extent than the body of the coating. The strong surface stresses, because of the shrinkage, tend to create very large checks in the surface that do not penetrate to the substrate. These can be caused by rapid polymerization of the resin on the surface, rapid oxidation of the surface of the coating or a very rapid release of solvents or volatile plasticizers from the surface. As an example, some air drying or chemically cured coatings, when applied over a cold surface and then heated on the coated surface to speed the drying, often alligator. Such a reaction may be found on coating the interior of tanks or tank cars. This is caused by shrinkage of the surface while the body of the coating, because of the cold metal, does not change at the same rate as the coating surface. Basically, it is a physical phenomenon whereby the coating surface hardens and shrinks at a much faster rate than the body of the coating itself. It may also be caused by the application of a very strong, tough, hard top coat over a softer, more resilient primer. In this case, the undercoat flows and moves as the top coat tends to shrink. It is almost a rule of thumb that a hard, tough top coat should never be applied over a soft undercoat. Asphalt and coal tar coatings are often subject to this phenomenon. The surface hardens due Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 489
SSPC CHAPTERx23-0 73 m 8b27740 0003737 807 m more rubbery one. 6. Mud-Cracking Mud-cracking can be considered a macrocracking phenomenon where the breaks in the coating usually go down to the substrate. In this way, it is a much more dangerous failure than alligatoring. It can cause immediate corrosion and result in the chipping and flaking of the coating from the surface. It is not a common failure of organic coatings that are properly formulated for weather exposure. It may occur where coatings are very highly filled and where they are applied to a surface that dries the coating extremely rapidly. Mud-cracking is often a phenomenon of base coatings and improperly cured in- water --`,,,,`-`-`,,`,,`,`,,`--organic zinc-rich primers. Because most water base coating materials are emulsions or dispersions, very rapid drying prevents the resin parFIGURE 5 Alligatoring ticles from coalescing into a continuous film. By contrast, where the resins are dissolved in a solvent, a true solution exists and the resin is in a continuous phase as the solvent evaporates. Mudcracking can be prevented by proper formulation to prevent the too rapid drying of water base coatings and by the use of reinforcing pigments. Mud-cracking can also be prevented by satisfactory drying conditions, by application of the coatings in thinner films and by elimination of sags or puddles where rapid drying could cause this type of failure. Ethyl silicate zinc-rich primers will mud-crack if applied too thick (over 6 mils). This generally is caused by the lack of moisture (too low humidity). Thus, a heavy film would not allow moisture to penetrate and properly cure the zincrich primer. FIGURE 4 FIGURE 6 Cracking due to overthicknessof coating. Mud-Cracking 490 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERU23-0 93 Ab27940 0003938 743 FIGURE 7 Mildew on painted surface. Microscopic examination is often necessary to determine the difference between mildew and dirt. (Federation of Societies for Coatings Technology Photo) 7. Wrinkling Wrinkling is the formation of furrows and ridges in the surface of a paint system. It occurs when the surface of the paint film expands more rapidly during drying than does the body of the paint. It is proportional to the thickness of the surface layer that dries more rapidly than the body of the paint film and to the difference between the drying rates and the expansion of the surface layer and the main body of the paint. Wrinkling results from a formulation failure and is most common with oil base paints or alkyds containing driers that increase the rate of drying. Driers serve two general purposes: to dry the surface of the paint, and to dry the body of the paint film; that is, surface driers and body driers, respectively. Cobalt compounds are a common type of surface drier; zinc and lead compounds are classified as body driers. Ordinarilv. Daints are formulated so that the ,, . drying process proceeds at the same rate on the Failure of inorganic zinc-rich by pinpoint rusting. surface and in the body. However, when a paint contains an excess of surface driers, the surface of the paint will swell by absorption of oxygen and will wrinkle. Such a reaction depends on air temperature, surface temperature and coating thickness. Excessive thickness aggravates the wrinkling process, since the body of the paint cannot cure sufficiently to resist the change in volume of the paint surface. The temperature of cure can influence the rate of wrinkling. Paints that cure without wrinkling, at normal temperatures, may wrinkle if curing is accelerated by baking. Also, if the amounts of surface driers and body driers are balanced for curing at a given temperature, a paint may wrinkle at a higher temperature, because the increase in the temperature tends to cure the surface more rapidly than the body of the paint. To prevent wrinkling, make certain that airoxidized or air-reacting coatings are properly formulated for the conditions under which the
coating will be applied. Where wrinkling of a coating appears to be a problem, the coating should be applied in a thin, even film with no areas of excessive thickness such as runs or puddles. 8.. Microorganism Failure Both bacteria and fungi can cause coating failure. They primarily attack biodegradable coatings where the fungus or bacterium derive their energy from the materials making up the coating. Oil type coatings, alkyds, polyamide epoxies and coatings using biodegradable plasticizers are most often affected. On the other hand, coatings made from vinyl chloride acetate resins or chlorinated rubber coatings using non-biodegradable plasticizers have excellent resistance to biological attack. One example of the comparative resistance of two similar coatings is in their exposure to sewage conditions. A polyamide epoxy may rapidly disintegrate due to bacteria or fungi attack under severe sewage conditions. On the other hand, a polyamine epoxy can remain unaffected under the same exposure. A fungus attack often occurs on the north or shady side of a structure under damp, humid conditions. A coating under these conditions turns grey or green, with black splotchy areas over the surface. In these areas, a 10-power glass reveals fungus growths acting on and within the coating. Prevention of such attack is primarily by formulation of the coating. Fungus attack is reduced or completely FIGURE 8 coatings, such 491 --`,,,,`-`-`,,`,,`,`,,`--eliminated in oil type coatings by the addition of zinc oxide, fungicides, bactericides or a combination of the three to the formulation. In non-oil type as pure epoxies, vinyls or Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
COATING FAILURE 1. Chalking 2. Erosion 3. Checking 4. Cracking 5. Alligatoring 6. Mud-Cracking 7. Wrinkling 8. Microorganism 9. Discoloration TABLE 1 A SUMMARY OF FORMULATION-RELATED FAILURES FAILURE APPEARANCE CAUSE OF FAILURE Organic Coating Failure Surface soft and powdery. Easily removed by wiping surface. Similar to chalking. Surface removed on high spots and brush marks to base coating or primer. Surface phenomena -uneven, small, non-continuous fissures in coating which do not penetrate to the substrate. Small breaks in coating to substrate. May be linear, crosshatched, or curved. Cracks may or may not be continuous. Very large macro-checking, generally cross-hatched pattern. Large macro-cracking. Coating may curl at cracks and lose adhesion. Furrows and ridges in coating surface. May be linear or random pattern. Wrinkle may be fine or quite large. Softening or slime reaction of coating. Blotchy brown or black spots on coating surface causing
poor dirty appearance. Yellowing, greying or darkening of coating. Surface disintegration by actinic rays of sun on the organic resin binder; improper pigmentation. Chalking mechanism with coating surface removed by weathering and abrasion. Surface stresses caused by shrinkage due to weathering and continued coating polymerization and oxidation. Stress set up in coating due to continued polymerization and oxidation -improper pigmentation, or improper coating system. Internal stresses where surface shrinks more rapidly than body of coating. Hard top coat applied over soft undercoat. Rapid drying of highly filled coatings, especially water based materials (water emulsion paints) Surface reaction where surface of coating expands more rapidly during drying than does the body of the film. The biodegradation of the coating by bacteria or fungi¡. The coating is used as a source of nourishment. Resin or pigment color change due to weather or chemical action. REMEDY Select coatings formulated with radiation resistant resins (acrylics) and noncatalytic, high hiding pigments. Select a tough chalk resistant coating with a good flow out to a smooth film. Select coating formulated with weather resistant
resins and inert reinforcing pigments in addition to non-catalytic colored pigments. Select coating formulated from non-reactive weather resistant resins, reinforcing pigments and non-reactive colored pigments. The primer must be compatible with intermediate and finish coats. Apply thin coats and thoroughly dry before adding additional coats. Never apply hard top coats (epoxy) over soft undercoats (asphalt). Use coatings with strong adhesion. Apply coatings under proper drying conditions and prevent sags, puddles or areas of excess thickness. Choose coatings with even, thorough drying characteristics. Apply evenly, avoid excessive thickness. Use oil paints which contain permanent fungicides or bactericides. Non-oil coatings should use non- biodegradable modifiers. Select coating formulated with both color stable resins and pigments. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 492
SSPC CHAPTERU23-0 93 8627940 O003940 3TL TABLE 1 (Continued) COATING FAILURE FAILURE APPEARANCE CAUSE OF FAILURE REMEDY Inorganic Coating Failure 1. Checking Usually fine visible or micro- The zinc pigment to binder ratio Form ulation should include scopic checks. Do not penetrate is high -rapid drying conditions reinforcing pig ments. to the substrate. cause surface checking. Apply coating as thin as recommended. Second coat, if necessary. Apply under favorable drying conditions. 2. Mud-Cracking Fine to fairly large segments Application of coating too heavy. Apply coating at no more (Yi ") flaking from surface. Rapid drying conditions. than recommended thickness . Apply under favorable drying conditions. 3. Chemical Pinpoint rusting progressing Acid or alkali reaction on both Apply r esistant topcoats from limited to continuous silicate binder and on metallic zinc. over inorganic zinc rusting. coatings. 4. Pinpoint Rusting Pinpoint spots of corrosion Uneven coating thickness -thin T his is normal failure progressing from a few per square coated areas show first failure. pattern for i norganic foot to almost continuous. zinc coatings. Apply maintenance coat at first sign of pinpoint failure. 5. Pitting in Seawater Strong anodes (rust tubercles) Reaction of chemicals with Top coat the inorganic --`,,,,`-`-`,,`,,`,`,,`--form in breaks in coating. surface of inorganic zinc or galvan- zinc with a stro ngly izing, causing it to become inert and adherent resistant thus a massive cathode. coating system. TABLE 2 MOISTURE VAPOR TRANSMISSION RATES OF CHARACTERISTIC COATING TYPES Test Permeance Thickness Gramsll00 sq. in./ Coating Type Perms' Mils 24 Hours Epoxy polyamide 0.16 8.10 .17 Amine catalyzed epoxy 0.19 7.5 .30
Vinyl Chlorideacetate 0.31 5.5 .a3 Vinyl acrylic 0.54 5.10 .a3 Alkyd (short oil) 2.4 5.10 3.7 'Perms = grains of moisturell hr./sq.ft./P (in. of Hg) Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 493
SSPC CHAPTER*23-0 93 m 8b27940 0003941 238 m chlorinated rubbers, plasticizers or modifiers should be nonbiodegradable. ASTM-D-3274 describes degree of surface disfigurement by fungal growth or soil and dirt accumulation. 9. Discolora tion Because appearance may be as much a function of a coating as its corrosion resistance, coatings that change color after application and become unsightly can be considered to have failed. This type of failure is, of course, one based on formulation and arises from a number of causes. Many of the resins used to formulate coatings contain unsaturated photosensitive groups which, on exposure to sunlight, cause darkening, yellowing or other discoloration of the vehicle. Vinyl chloride-acetate coatings, as an example, if used as clear coatings will turn dark brown or even black within a few weeks of exposure to sunlight. Some epoxy resins tend to yellow as do some of the more resistant polyurethane resins. Proper pigmentation to shade the basic resin from sunlight is one of the prime methods of preventing discoloration. Often, however, pigmentation is not sufficient. Coatings subject to strong sunlight and weather conditions should preferably be formulated with silicones, acrylics or aliphatic polyurethanes in order to reduce any possible color change to a minimum. Many pigments can also cause color change in a coating. Some orange pigments are color reactive and darken. Certain yellow pigments tend to grey and whiten. Lead pigments are particularly susceptible to attack in sulfide atmospheres and turn dark or even black. Iron blue pigments tend to bronze or turn brown. Obviously, these pigments should not be used in formulations where the appearance of the coating is important and where it is exposed to severe weat her conditions. 10. Sulfide Discoloration This is the staining of the film by hydrogen sulfide. Hydrogen sulfide attacks paints containing lead or mercury turning them gray or black in patches or streaks. Exposure of copper base antifouling paints not only turns them black but can inactivate the copper causing them to foul rapidly. This often occurs in contaminated water. This blackening may be distinguished from mold growth by treatment with dilute hydrochloric acid; disappearance of the blackening indicates
the presence of sulfide. When repainting or painting in hydrogen sulfide areas, use paints that do not contain mercury, lead or copper pigments or lead driers. If emulsion paints are used for repainting, it would be necessary to remove any undercoats which contain lead or mercury. B. INORGANIC COATINGS, FORMULATIONRELATED FAILURES Inorganic zinc coatings also have some inherent failures because they are made primarily from silicate vehicles and metallic zinc. 1. Checking Inorganic zinc coatings are particularly subject to checking if the formulation or the application are not proper. These coatings are highly filled with powdered metallic zinc and other pigments. The ratio of the pigment to a relatively low viscosity binder is high, and under these conditions, rapid drying can cause the surface checking of the coating. Many formulations contain fibrous pigments to help prevent checking as well as special solvents and silicate binders to aid in controlling the drying rate. The tendency to check can also be improved or prevented by proper application. The coating should be applied as thinly as is practical, with a second pass if necessary to reach the recommended thickness. As rapid drying increases the tendency to check, application should be under controlled temperature conditions or under less severe drying conditions, ¡.e., applying it under cover, or when in the open, in the early morning or late afternoon. The application conditions established by the manufacturer should be closely followed. Since checking is a surface phenomena and does not extend through the coating, it is much less of a problem with inorganic zinc coatings than with organic coatings. As long as the adhesion of the inorganic zinc is unimpaired, the fine checks will gradually fill with zinc reaction products, and the effectiveness of the coating will be maintained. Evaluation of checking is covered by ASTM-D 660. 2. Mud-Cracking Mud-cracking, because the breaks extend through the coating to the substrate, is a more serious problem than checking. Adhesion is often impaired with the coating flaking from the surface. Mud-cracking is primarily a problem of excessive thickness where the thickness exceeds the manufacturer s recommendations. It is found, for the most part, in runs or puddles or where heavy
overlapping occurs. The reason for this type of failure is similar to the reason for checking. The volume of the pigmentation is high compared to the volume of the vehicle in the dried film. Where applied in excessive thickness, the volatile ingredients in water base zinc-rich coatings evaporate rapidly Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 494
SSPC CHAPTER*23*0 93 86279YO 0003942 174 with shrinkage taking place throughout the coating before any chemical reaction can occur. Such areas will eventually pull themselves away from the surface and chip or flake. To eliminate or prevent this problem, apply the coatings in relatively thin films (not over the maximum thickness recommended by the manufacturer). Heavy coats (over 6.0 mils) tend to mud-crack. For ethyl silicate zinc-rich primers, mud-cracking is caused by lack of moisture needed to cure the coating beneath the surface of the film. 3. Chemical Resistance Obviously, coatings containing zinc, organic zinc coatings, inorganic zinc coatings or galvanizing should not be used alone or without top coats in a strongly acidic atmosphere. Because of the zinc in the coating, acid attack is rapid and the coating would be subject to failure. Under these conditions, galvanizing would tend to fail faster than the inorganic zinc coatings, inasmuch as the zinc in the inorganic coating is partially protected by the silicate matrix. Strong alkali will tend to react with the silicate vehicle as well as with the zinc at pH values above 10. 4. Pinpoint Rusting Zinc coatings, either galvanized, inorganic zinc or organic zinc, normally fail at the end of their useful life by pinpoint rusting. This occurs primarily in areas that are thinner than the remainder of the coating, starting with an isolated pinpoint of rust showing here and there in these thin spots. As time goes by, the pinpoints will become closer together, and finally, at the time of full failure, the spots of pinpoint rust will be almost continuous and general over the entire surface. Such failure usually occurs after many years of service, even under marine atmospheric conditions. While this type of failure can be expected, it can also be prevented by proper maintenance and repair of the thin areas that first show failure. ASTM Standard D 610 provides a method of evaluating rusting. A maintenance coat of inorganic zinc may be applied over itself or over galvanizing at the time of the first indication of failure. Light abrasion of the surface by hand sanding or brush blast is necessary for proper adhesion of the maintenance coat. 5. Pitting in Seawater Inorganic zinc coatings or galvanizing immersed
in seawater may pit after exposure of from 12 to 24 months. This phenomenon occurs because of the reaction of some of the salts in the seawater with the surface of the zinc to such an extent that the surface becomes insoluble and no longer provides zinc ions to protect the steel surface from corrosion. Normally, zinc coatings provide cathodic protection to the steel surface; however, CIS the chemical reaction from seawater takes place on the surface of the zinc, the surface becomes inert, although it is still conductive. 1Jnder these conditions, since zinc ions are no longer available, the zinc coating becomes cathodic and the holiday or break becomes an anode. When this happens, pitting will take place where breaks occur or where there are sharp edges, abrasion or holidays. Pitting can be prevented with a compatible and proper organic coating system over the zinc, wherever it is exposed to seawater immersion. II I. ADHES1ON-RELATED FA1LURES 1. Blistering Blistering is one of the most common forms of adhesion related coating failure, particularly where the coating is immersed in water, seawater or other liquids. It can also occur in areas of high humidity where there is continuing or intermittent condensation on the surface. Blistering is caused by gases or liquids within or under the coating that exert pressures stronger than both the adhesion and the internal cohesion of the coating. This allows the coating to stretch and to form the hemispherical blister. The blister will generally increase in size until the tensile strength of the coating is greater than the internal pressure. If the pressure is greater than the tensile strength, the blister will break. This is often the case where a brittle coating with little extensibility is involved. After the blister breaks, frequently the substrate will be readily attacked, causing rust. F STEEL b FIGURE 9 Osmosis --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 495
There are several forces that contribute to the formation of the liquid or gas underneath or within the coating. In addition to strength of adhesion the key to most blistering is the moisturevapor transmission rate of the coating. Each coating formulation has its own characteristic moisture-vapor transmission (MVT) rate, the rate at which molecular water passes through the inter-molecular spaces in the coating. Any area of poor adhesion will tend to accumulate moisture or moisture-vapor at the interface between the coating and the substrate. Moisture-vapor in this area creates a vapor pressure that causes blisters to form. Generally, coatings with the lowest MVT rate (the greatest resistance to the passage of molecular water through the coating) will have the least tendency to blister. Table 2 lists some typical MVT rates for several of the common coating types. It must be stressed again that these rates are for specific coating formulations and do not necessarily indicate a positive relationship between coating types. Permeation is influenced by film thickness, coating pigmentation and means of application. As blistering is an adhesion-related failure, there is a general rule of thumb that applies: a coating with excellent adhesion, even with high MVT, will have a low tendency to blister. At this point, it should be stated that there is no correlation between the moisture absorption of a coating and the moisture-vapor transmission rate. Moisture absorption is the amount of molecular water which is held within the molecular structure of the coating. There are some coating materials which may have a rather high moisture absorption but which do not have a high moisture-vapor transmission rate. The converse is also true There is one synthetic resin material which has zero water absorption, yet has an extremely high MVT rate. This being the case, moisture absorption is not necessarily a good measure of the blistering tendency of a coating.
Osmosis also contributes strongly to the transmission of water or moisture through a coating. Osmosis occurs when moisture vapor passes through a semi-permeable membrane from the water solution having the lesser concentration to the one with a higher concentration of dissolved solids. As an example, if a coating were applied in a marine atmosphere to a piece of steel having a salt deposit on the surface, and if after the coating were applied and dry the steel were subject to immersion, moisture would be forced through the coating from the water on the outside of the coating to the salt crystalson the underside of the coating. The salt crystals would absorb a small amount of moisture in the beginning, creating a solution with a high concentration of salt. Osmotic pressure is created by the moisture vapor which has passed through the coating from the more dilute side to the more concentrated . side of the membrane. The pressure built up on the underside of the coating may be quite high (several ounceslsq. in.). Moisture vapor being forced by the osmotic process through a coating with poor adhesion can cause blisters to form. But coating may have adhesion stronger than the osmotic pressure that develops and thus will not blister. Osmosis can also cause blistering if water soluble materials are incorporated into the coating itself. Oftentimes, primers contain inhibitive pigments having a degree of water solubility, for instance, zinc yellow or zinc chromate. This pigment is an excellent inhibitor of corrosion; on the other hand, if a primer made with zinc chromate is top coated and immersed, blistering will often result. In this case, because of the solubility of the chromate, osmosis conditions are set up within the coating itself forcing water to the area where the soluble chromate is located. Coatings formulated with such soluble pigments should not be used for immersion purposes. Table 3 lists several chromates that have been used or are presently being used in coatings. The ones with the lowest solubility are preferable from the standpoint of resistance to osmosis and blistering. Another blister forming process is that of electroendosmosis. In this process moisture vapor or molecular water is forced through the coating by an electrical current in the direction of the electrical pole with the same charge as the coating. Most coatings are negatively charged, and if the underlying metal
surface is cathodic, or has a source of negative electrons, moisture is then drawn through the coating towards the negative pole. Under these conditions, if there are areas of poor adhesion, blisters form readily. Incidentally, this process has caused coatings on structures subject to excessive cathodic protection to blister away from the surface. Cathodic potentials in excess of 1.0 volt cause many coatings to blister and lose adheCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 496
SSPC CHAPTER*23-0 93 8627940 0003944 T47 the paint before the solvent is removed. After rnost of the solvent has evaporated, the baking TABLE 3 temperature can be increased to cure the paint SOLUBILITY OF CHROMATE PIGMENTS completely. Blistering can be caused also by hydrogen Grams of CrO, in absorbed in the surface of the steel during pickSolution in 1000 CC. ling, that is, during the process of removing rust Pigment Water at Equilibrium 25OC and mill scale before the surface is coated. I f, Calcium Chromate 17.0 after the coating has been applied, the temperature of the coated object is raised, this hydrogen Zinc Yellow 1.I will leave the metal; and, if the rate of hydrogen Strontium Chromate 0.6 evolution is more rapid than the rate of diffusion Basic Zinc Chromate 0.02 of the gas through the paint, pressure areas will be formed at the metal-paint interface. When the Barium Chromate 0.001 pressure of the gas under the coating exceeds the Lead Chromate 0.00005 force of adhesion between the two surfaces, the paint will be lifted off the metal in blisters. After pickling steel plate or shapes, hydrogen can be sion. Coated pipelines in wet soil conditions have eliminated by heating the ste el prior to applying often shown this type of failure. the coating. Preferably the coating should be apBlistering most often results from poor sur- plied while the steel is still warm . face preparation or applying a coating over a dirty, There is a strong tendency for some coating greasy, moist or contaminated surface. Such a materials to blister on cast iron. Cast iron is much surface is the cause; osmosis or electroendos- more porous than steel and contai ns gases that mosis is the process that makes it take place. expand, particularly when heated. Coatings apA coating can also blister when it is used as a plied even to clean, sand blaste d cast iron, when it lining and is subject toa warm water solution, with is cold, often blister as th e temperature increases. the steel substrate being considerably cooler than If the cast iron is heated su
fficiently to release the the liquid (for example, an uninsulated tank con- gases and the coating is appli ed to the cast iron taining liquid at a higher temperature than the while it is still warm, blisteri ng will not occur. outside air). In this case, the moisture passes Chemical exposure often causes b listering through the film, and because the steel surface is and loss of adhesion of coati ngs, particularly cooler than the vapor, it condenses underneath where a coating may be subject to volatile acids the coating causing blistering. such as acetic acid, hydrochloric acid or nitric Another cause of blistering is entrapped acid. These volatile materials can pene trate the solvents. These are solvents that remain in the coating and react with the under lying metal surcoating for some period of time, usually by solu- face. With moisture vapor alwa ys present, a tion in the coating resin. If the temperature of the strong acid solution is for med that not only has a coating system is raised and the rate of diffusion strong osmotic pressure, but also is strongly reactive with the metal surface, creating hydrogen of the solvent vapor through the film is slower than the rate of formation of the vapor, then blistering will take place. Many coatings that dry rapidly on the surface ELECTRO-ENDOSMOSIS are subject to this type of blistering, particularly where applied in the sun or on a heated surface. When the pressure exerted by the solvent vapor CATHODIC AREA OF MOISTURE PENETRATION ANODIC CATHODIC AREABLISTERS FORMING becomes greater than the adhesion of the paint, TOWARD NEGATIVE CHARGE AREA IN T HIS AREA blisters will be formed and will increase in size until equilibrium between the pressure and the strength of the film is established. If the pressure becomes greater than the cohesive strength of the film, the blisters will break. Blistering due to entrapped solvents is common when baked finishes are used. It can be . ? avoided if the coating is prebaked at a STEEL temperature high enough to drive out all the sol-FIGURE 10 vent but not high enough to cure the surface of Electroendosmosis 497 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERW3.0 93 8627940 0003945 983 BLISTERINQ DUE TO THBRMAL GRADIENT FIGURE 11 Theirmal Gradient Across Coating gas. Acetic acid is a good solvent for many coating materials, but its presence increases the probability of blistering. Blistering conditions can best be prevented by using a coating with very strong adhesion characteristics and a low moisture-vapor transmission rate and applying the coating over a perfectly clean surface. The best surface is perfectly clean and white-metal blasted (SSPC-SP 5). It has been proven by many tests and hundreds of actual coating applications that (with all exposure conditions being equal) proper surface preparation can reduce blistering to a minimum or completely prevent it. ASTM Standard D 714 provides a good method of describing the degree of blistering of paints. 2. Peeling Peeling is a coating failure usually caused by a coating having a tensile stength greater than its bond strength to the surfaces. This was a common early-day cause of vinyl coating failure. It has been overcome by vinyl primers now having superior bond strength when they are applied to clean -preferably abrasive blasted -surfaces. Any coating will peel or pull from the surface if it has less adhesion to the substrate than it has tensile strength, or if it reacts adversely with the substrate over a period of time, thus substantially reducing the adhesion. 3. Flaking and Scaling These two types of failure are adhesion-related. Flaking is a term describing a condition where small pieces of coating detach themselves from the surface of the substrate. Its edges are generally raised up from the surface and the small pieces can be rather easily removed, leaving the bare substrate. Flaking is quite common on wooden surfaces and tends to occur after oil paints have oxidized for a period Of years. It is a common sight on fences and old wooden buildings. Flaking also occurs on metal surfaces, particularly those which have been galvanized. Alkyds or oil type paints applied to galvanized surfaces eventually age and oxidize to the point where the film shrinks suffi-
ciently to pull itself away from the surface. There can also be an interfacial chemical reaction, creating a zinc soap between the organic coating and the zinc substrate, which causes loss of adhesion and flaking. Scaling is similar to flaking, except that the pieces that break away from the surface are much larger. This is a common type of failure on coated, galvanized surfaces. Pieces of coating several inches in diameter may crack due to aging stresses, curl and come off in large flakes. Scaling can also occur where a new coat is applied over a very old, well oxidized coating. The adhesion between the two surfaces, where surface preparation is poor, is low and the top coating on aging will tend to curl and to scale. The prevention of flaking and scaling is primarily one of surface preparation. Clean surFIGURE 12 Blistering Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 498
SSPC CHAPTERr23-0 93 8627740 000394b 8LT faces, with a good anchor pattern, combined with a coating that has strong adhesion and good aging characteristics will prevent this problem. ASTM Standard D 772-47 (reapproved 1975) is a standard method for the evaluation of the degree of flaking and scaling of exterior paints. 4. Intercoat Delamination This is the failure of one coat to adhere to an underlying coat, whether applied as one coat following the other or where the top coat is applied as a maintenance coating after some period of time. The cause is generally within the coating itself. Air-reactive coatings, either those that require oxygen or moisture for cure, or coatings that react internally by the action of catalysts or reactive resins are subject to this type of failure. Compatibility of one type of coating to another is essential. In the case of air-reactive coatings, either by the absorption of oxygen or water, the surface becomes rapidly insoluble and dense. In the case of internally reactive coatings, the entire coating becomes insoluble and dense. In both cases, the coatings are insoluble in the original solvents in the liquid coating. Solventless coatings are also subject to intercoat delamination. The second coat should be applied over the first after the initial set of the first coating, but before that coating has been completely cured either by internal or exterior forces. The temperature of application is also critical. Since the curing reactions are temperature-dependent, the higher the temperature, the more rapidly the second coat should be applied over the first. Manufacturer s instructions should be closely toiiowed where internally or exFIGURE 13 Peeling FIGURE 14 Flaking ternally cured coatings are used. Polyurethanes, epoxies, coal tar epoxies and oxidizing coatings are subject to this type of failure. Where catalyzed epoxy is applied at low temperatures, an exudate may remain on the surface causing incompatibility with subsequent topcoats. Coal tar epoxy coatings have special problems of intercoat delamination. In addition to the normal internal curing of the coating, external forces also create intercoat delamination. Even
though the curing of the coating has not progressed to the point of insolubility, if the coating is subject to condensation, rain, or moisture prior to the application of the second coat, intercoat delamination is probable. Also, if the coal tar epoxy coating is applied in the sunlight, even though the coating has not reacted to the point of insolubility, intercoat delamination may occur due to the heat and actinic rays of the sun, causing the surface to cure beyond the point where good adhesion between the two coats can result. Whenever any of the above phenomena occur and the second coat is applied over an insoluble coat, there is a positive interface between the coats. When water or moisture penetrates to the interface, any apparent adhesion between the two coats is lost, causing delamination to occur. Lacquer-type coatings, such as vinyls, acrylics or chlorinated rubbers are not as subject to this type of failure as are the reactive type coatings. Lacquer-type coatings are permanently soluble in their own solvents, thus allowing the second coat to dissolve into the first coating, reducing the chance of any interface forming between the two coats. An additional major cause of intercoat delamination is the contamination of the first coat before the application of the second. Moisture, dust, fumes, chemical fall-out, oil and Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 499
= SSPC CHAPTER*23.0 93 8627940 0003947 75b -I\. Scaling 5. acrylics, if Undercutting --`,,,,`-`-`,,`,,`,`,,`--FIGURE 15 grease all can cause this result. The method of prevention is obvious: prevent the contamination from reaching the coating during application. Where this is impossible, particularly when applying coatings to structures or tanks subject to fallout from adjacent plants or adjacent operations, very fast drying lacquer coatings, vinyls or applicable from a corrosion standpoint, should be used. The second coat should be applied as rapidly as possible following the first to provide good results. Undercutting is another type of adhesion failure that involves the gradual penetration of corrosion underneath the coating from a break or pinhole in the film or from unprotected edges. Undercutting often occurs when a coating has been applied over mill scale. Moisture and oxygen penetrate the coating and react with the scale causing it to lose adhesion and thus form progressive corrosion beneath the coating. The application of coatings over a very smooth, dense surface where adhesion is critical also creates a condition inviting this type of failure. Most of these undercutting failures can be substantially reduced by proper surface preparation prior to the application of the coating and the use of a coating with strong adhesion characteristics. One of the preferred methods of preventing undercutting on steel surfaces is the application of an inorganic zinc coating as a permanent primer before the organic coating is applied. The inorganic binder reacts chemically with the steel, providing very tight adhesion and preventing the undercutting which is characteristic of most organic paints or coatings. This coating system has been successful on hundreds of millions of square feet of surface exposed to extreme marine or industrial conditions.'
IV. FAILURE DUE TO THE SUBSTRATE The substrate is not often considered as being a major factor in the failure of protective coatings, but it is extremely important. The common surfaces that need to be considered are steel, aluminum, zinc, copper, concrete and wood. Each of these have a very different effect on the coating. One coating may be very effective over one surface and completely ineffective over another. An example of this is the coating of steel surfaces for exposure to sodium hypochlorite. Even though the coating applied may be completely pinhole free, because of the breakdown reaction of the sodium hypochlorite on aging into nascent oxygen and sodium chloride, coatings applied over a steel surface generally last only a very short period of time. Nascent oxygen will penetrate the coating and react with the surface underneath the coating. Tuberclës are formed which break the coating, allowing corrosion to proceed very rapidly. On the other hand, if the same coating were applied over concrete, long life could be expected because the concrete itself is unaffected by the nascent oxygen. While this is rather an extreme example, it nevertheless demonstrates the importance of the substrate to the life of the coating. Steel may be the best and the easiest surface over which to apply a coating. It is a very dense, and essentially non-porous material; therefore, a coating can be applied over it as a continuous film with relative ease. While the steel surface is reactive, it is less so than many other surfaces over which coatings are applied, and most coatings or paints adhere reasonably well over a clean dry steel substrate. Coating compatibility with the steel is not as critical as it can be with other materials. FIGURE 16 Intercoat Delamination To assure consistently good coating life, abrasive 500 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*23.0 93 8627940 0003948 b92 l FIGURE 17 Undercutting blasting of steel is recommended to remove all contamination and oxidation and to increase the surface area for maximum coating adhesion. SSPC-Vis 2 provides a standard for evaluating the degree of rusting on painted steel surfaces. This standard is also available as ASTM-D 610. Concrete, on the other hand, is a chemically active, non-uniform, porous surface filled with water and air pockets, thus making a surface that is very difficult to paint properly with a continuous coating. In addition to a very variable surface, it is sensitive to moisture, and when the moisture is confined under a coating, a pH of up to 13 may be encountered. Only a very inert, highly alkaliresistant and penetrating coating can be expected to perform satisfactorily. As can be seen in Figure 19 the problems of coating a concrete substrate to obtain a failure-free coating are primarily physical. The surface is variable with the most consistent concrete being a hard, steel-troweled surface (sidewalk finish). This surface is preferred for coating. However, because it is often glazed due to the troweling action, the glaze must be removed by acid etching (1 part commercial hydrochloric acid and 5 parts water followed by a clean water wash) or a light brush blast for consistent coating adhesion. A poured concrete surface as shown in Figure 19 is the most difficult of all surfaces over which to apply a consistent, uniform, pore-free coating. All surface imperfections, air pockets and pinholes must be eliminated. The surface must receive a coat of cement plaster, hard troweled as described above, or a resinous concrete surfacer must be applied which will fill all the concrete surface imperfections, have some penetration into the concrete for maximum adhesion and provide a
smooth, pore-free base for the subsequent coatings. Both of the above methods are applicable for the best coating service under difficult conditions. Where concrete or stucco surfaces are coated for decoration only, such surface treatments may not be required. Aluminum generally has a dense, smooth surface with a tight aluminum oxide coating on the surface. While this surface is relatively stable, it can cause adhesion problems for some coatings. Where there are breaks, particularly under alkaline conditions, undercutting and even perforation of the metal may occur. Copper provides a dense surface with a copper oxide film over it. Many coatings fail to obtain proper adhesion to this surface. In many ways, it is similar to aluminum, although it is not as reactive a surface so that coating failure is not as prevalent. The failure of many effective coatings is caused by these types of smooth, dense surfaces. A light dust blasting with used sand or very fine sand and low pressure air will break up the surface, increase the surface area and allow adhesion that cannot be obtained by any other means on either of these two types of surfaces. Zinc is a more reactive metal than aluminum, which is the reason for its use as a galvanic coating. Galvanizing and inorganic zinc coatings have proven to have a very long life in many atmospheres. In spite of this, under certain marine or highly humid conditions, when used as a base coat, zinc may react under the top coat producing a voluminous white corrosion product. This causes coating failure by white salts of zinc corrosion that completely undercut the coating and lift it from the surface. There are also coatings that react with the various alkaline zinc hydroxides to form zinc soaps. These are oil paints or alkyd coatings and are not recommended for direct application over galvanizing or inorganic zinc. Top coats for zinc surfaces should be inert, thoroughly compatible with zinc, have high adhesion and a low MVT rate. UNDERCUTTING OF AN ORGANIC COATING BY RUST QR CORROSION FIGURE 18 Undercutting 501 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from
IHS
SSPC CHAPTER*23-0 93 W 8627940 00039Vq 529 W TABLE 4 SUMMARY OF ADHESION-RELATED FAILURES COATING FAILURE FAILURE APPEARANCE CAUSE OF FAILURE REMEDY 1. Blistering Minute to large (1"+) Blistered coatings have adhesion Select a co ating with very hemispherical bubbles in coating problems due to poor surface prepara- strong ad hesion characcontaining gas or liquid. May tion, internal soluble materials or teristics and a low moisture. range from 1 per square foot to poor wetting of substrate. Osmosis, vapor transf er rate. Apply several hundred per square foot. electroendosmosis, gases absorbed in- to a clea n, abrasive blasted See ASTM Std D 714-56 (revised to the metal surface or solvent en- surface with care. 74). trapment cause blisters to form. 2. Peeling Coating may be smooth and lying Adherence is less than the tensile Se lect a coating as outlined on surface or it may be hanging strength of the coating. When broken under blist ering. in shreds. Little or no adhesion the coating can easily be pulled from is evident. the surface leaving the original surface of the substrate. Coating may react with substrate and lose adhesion. Coating usually flexible. 3. Flaking or scaling Small ('A,") to large (1"+) Coating usually brittle with i nternal Select a coating as outlined pieces of coating, curling at the shrinkage characteristics in addition under bl istering. For edges -easily removed from the to marginal adhesion. Oil type galvanizing use a primer surface leaving bare substrate. coatings may scale or flake from a compatible wi th zinc. galvanized surface. 4. Intercoat The top coat does not adhere to The top coat is not compatible with Select coatings with good delamination the undercoat. It may lie on the undercoat; the surface of the comp atibility and adhesion surface, blister, flake or peel. undercoat may be contaminated; between coats. M ake the undercoat may be over-cured to certain undercoat is clean complete insolubility. before application of the second coat. Do not expose coal tar epoxy coatings to water or excessive sunlight before overcoating. 5. --`,,,,`-`-`,,`,,`,`,,`--Undercutting Corrosion tends to build up Poor adhesion due to surface contami- S
elect a coating with under coating, at breaks, edges or nation, a very smooth surface or lack very hi gh adhesion. Apply holidays; corrosion is progres- of compatibility with the surface. over a clean, abrasive sive under the coating. blasted surface. Using inorganic zinc coatings as a first coat reduces undercutting. Certain vinyls, epoxies and chlorinated rubbers work well. rather porous, soft s ummer grain. This is very Zinc also has a smooth surface; however, once it is oxi- characteristic of woods such as Oregon pine, cedar, ash dized by exposure to the atmosphere for a period of and many other open-grained woods. Maple, birch and several weeks or months, the smooth surface tends to woods which are very dense are somewhat less of a probdisappear, providing much better adhesion. If a new lem, although both types of surface, ¡.e., summer and galvanized surface must be coated, it should be lightly winter grain, are presen t. These grains tend to expand and dust blasted, as indicated for the aluminum or copper sur- contract at a differe nt rate due to varying humidity and faces, or it should be chemically treated with a zinc sur- temperature, and any coating which is applied over these face treatment (commercially available) prior to coating. surfaces and which wil l not expand and contract with Wood has its own inherent characteristics which them, will tend to fail rather q uickly along the grain boundcause coating failures. It is very moisture sensitive and aries (Figure 20). will swell during times of high humidity and shrink when Any coating which is ap plied over a surface must be conditions are dry. This dimensional change can take thoroughly compatible with that surface, must have strong place on a daily cycle, in addition to climatic changes permanent adhesion to it and must not chemically react which occur over longer periods. Wood has two types of with it. Unless the coati ng has these capabilities, failure is surfaces: that provided by very dense winter grain and the inevitable. 502 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*23-0 93 m 8627940 0003950 240 m penetrate the coating, causing early failure in the previously corroded area. There are two methods that can be used to improve this situation. 1) After the original blasting, react the surface with a dilute phosphoric acid solution (5%), allow it to dry, and then re-blast the surface. This procedure produces a reaction that allows the minute amounts of corrosion product to be removed on the second blasting. 2)The second procedure, where an inorganic zinc coating can be used as a permanent primer, is a very satisfactory one. The inorganic zinc coating tends to react with the minute FIGURE 19 amount of corrosion product on the surface, eliminating Poured Concrete Surface its corrosive tendency, and at the same time to react wi th the steel surface to provide a very strong chemical bond. The failure of a coating over a used surface is much Following the application a nd cure of the inorganic zinc, more probable than when applied over a perfectly new, the required top coating c an then be applied. original surface. This has been proven many times. As an example, tanks in the west Texas oil fields, where sulfides are a problem, have been repaired by the use of new steel sheets. The entire surface of the tank was then sand blasted to white metal and the coating applied with equal care over the new and the old surface. In a matter of just a few months, the coating applied over the old surface failed, while it was still completely effective over the new steel. This same phenomenon occurs aboard ship where corrosion has taken place on steel plates. It occurs in chemical tanks and on the exterior of structural steel bridges. This problem occurs to the greatest extent on steel surfaces and in areas where severe corrosion conditions exist. The previous use of the steel must be taken in- FIGURE21 to consideration in order for the coating to be effective. Adhesion Retention -s and blasted vs. cold rolled steel. Panel #69, sand blasted, and panel #73,cold rolled steel, both exposed The problem is the retention of very minute quantities of to water for the same period, demonstrate the benefit of physical corrosion product in the rough corroded areas of the steel, adhesion. and when the contamination is not completely removed, they continue to react with the moisture vapor which can Do not underestimate th e problems involved with used steel surfaces. Untold failures of coating have occurred because this problem of prior use was not recognized. Used aluminum and zinc surfaces are less of a problem. However, care should be taken whenever a surface has been subjected to serious corrosion.
Wood and concrete are definitely affected by previous use. Both can absorb and retain soluble or reactive materials, which if not removed prior to the application of the coating, will cause blistering, lack of adhesion and coating failure. The density or smoothness of a surface over which a coating is applied is extremely important. As an example, cold rolled steel is much more difficult to coat than hot rolled steel with the mill scale removed. Cold rolled steel has an extremely dense, smooth surface, and it has proven in the laboratory many times that a coating applied over such a surface compared to a coating applied over a sand blasted, cold rolled surface will fail much faster when both are subject to the same conditions. The problem, of FIGURE 20 course, is that the very dense, smooth surface does not Paint failing on wood grain. allow the same quality of adhesion of the coating a s does Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 503
SSPC CHAPTERa23.0 93 8627940 0003953 187 TABLE 5 SUMMARY OF SUBSTRATE-RELATED FAILURES COATING FA1 LU RE FA1 LURE APPEARANCE 1. On Previously Blistering, rust, tubercles, loss Used Steel of adhesion in areas where steel was previously exposed to corrosive conditions. 2. On Galvanized or White zinc corrosion product formMetallic Zinc ing under the coating or actually Surfaces breaking through the coating. 3. On Aluminum White corrosion product causing pinpoint failure in coating loss of adhesion because of very smooth surface. Possible blistering. 4. OnCopper Greygreen corrosion product, loss of adhesion, blistering. 5. On Wood Checking and cracking of coating. Flaking from hard winter grain. Blistering of dense coatings with a low MVT rate due to absorption and evaporation of moisture from the wood. 6. On Concrete Blistering of coating. Formation of calcium salts under coating, forcing coating from the surface. Loss of adhesion and peeling. CAUSE OF FAILURE REMEDY Retention of minute amounts of corro- Wash blast surface with sion product or contaminant on water or dilute phosphoric the steel surface, even though acid solution and reblast. blasted to white metal. Apply an anticorrosive primer with strong adhesion. Where applicable, an inorganic zinc primer may react with the minute surface corrosion after first blasting and provide a base coat. Formation of zinc salts (oxide, sul- Brush blast zinc surface or fide, oxychloride, zinc soap), treat with commercial zinc underneath coating. treatment. Apply a non-oil base, inert strongly adherent primer. The very smooth aluminum oxide sur- Very lightly dust blast the face. No physical adhesion. aluminum surface, or where applicable, treat with commercial aluminum treatment.
Apply a primer with known compatibility and strong adhesion to aluminum surface Very smooth copper oxide surface. Brush blast copper surface No physical adhesion. or etch with commercial copper treatment. Apply a primer with known high adhesion to copper. Expansion and contraction of wood Start with a clean, newly due to varying temperature and sanded wood surface. Apply humidity. Differential expansion low molecular weight, highly of the grain. Very hard penetrating paint, preferdense winter grain combined with ably oil base, with suffisoft porous grain, causing cient elasticity to expand a variation in coating adhesion. and contract with the wood surface. Paint should have relatively high moisture porosity to allow wood to breathe. The chemical reactivity and moisture The concrete should be clean content of concrete. Its non- and the surface dry. It may homogeneous, very porous structure. be acid etched or lightly Pinholes, water and air pockets in blasted to obtain proper poured concete surfaces. surface condition. Use a low molecular weight, highly penetrating primer with strong alkali resistance (liquid epoxy). Primer should be heavy body and thixotropic to fill imperfections in concrete surface. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 504
SSPC CHAPTER*23.0 93 = 86279YO 0003952 013 the one that has been roughened and that allows mechanical adhesion in addition to normal wetting of the surface. Cleanliness of the surface is vitally important, of course, to the life of any coating. It is a rule of thumb that any coating applied over a perfectly clean surface will last longer and be more effective than the same coating applied over a lesser surface. This applies to metals, concrete and wood to the same degree. It also applies to the repair and maintenance of coatings as well as to original coating installations. V. APPLICATION-RELATED FA1 LURES Application-related failures are undoubtedly the cause of the majority of difficulties encountered with protective coatings or paints of all types. Paints and coatings are failure-oriented, particularly on large structures, bridges, off-shore platforms, ships, nuclear energy plants and similar structures, for a number of reasons. The painting or coating operation is the last item of work on most large projects. The contractor, the owner and the engineers are pushing to have the job completed. Many times their completion deadline may be passed, which puts pressure on to complete the coating job as rapidly as possible. This get the job done fast philosophy is a source of many coating failures. There is also a natural tendency on the part of people to overlook and resist the proper cleanliness and the proper surface preparation that is needed for an effective coating job. There are untold examples of this where chewing tobacco, cigarettes, small rocks, mud, steel shot and similar trash have been carefully coated over. Most of the defects that occur in applied coatings are not related to the coating manufacturer, a poor formulation or the selection of a wrong material, but are peoplerelated. This is caused by lack of knowledge, lack of training and lack of understanding of the consquences of a poorly applied coating. Other contributing factors are a lack of proper coating application specifications and a !ack of proper inspection. Care in writing the application specifications, proper training of applicators, care in the application itself, and care in the inspection of the finished coating are essential for a proper coating application and for an effective coating result. 1. Mixing Paint, as supplied by the manufacturer for a specific use, is usually ready for application by brushing or by spraying when received by the ap-
plicator. Such paint will have been formulated to have more than sufficient durability in the environment where it is to be used, and no change should be made in the composition or in the adjustment of the consistency of the liquid coating unless specified by the manufacturer. For proper application, a paint must be a homogeneous mixture, as it was when manufactured. In the mixed state, the consistency of the formulation is uniform and the pigments are evenly dispersed. During prolonged warehouse storage, pigments tend to settle to the bottom of containers. Also, the surface of some paints may be covered with a tough skin. It is essential that a paint be carefully remixed before application is attempted. All settled pigment must be redispersed and any surface skin must be removed. Failure to effect such complete mixing can cause early failure of the paint system. 2. Thinning As previously stated, the consistency of a paint or coating is usually correct as it is received from the manufacturer. Most manufacturers attempt to provide the liquid coating at the proper consistency in order to prevent failures related to thinning. There is no universal thinner for the wide range of sophisticated coatings that are necessary today. Improper thinning can cause many different types of failure. As an example, mineral spirits can be tolerated by liquid vinyl coatings in certain amounts; however, if added excessively to a vinyl coating poor adhesion will result. Improper thinning of an epoxy coating can increase the viscosity rather than reduce it. An alcohol type solvent for a polyurethane could cause immediate jelling. While thinners are an essential part of any coating, they are incorporated in the manufacture for proper application, proper leveling on the surface and proper drying. It is occasionally necessary to decrease the viscosity of a paint by the addition of thinners. Such adjustment of the consistency should be made only as directed or advised by the manufacturer, by means of the proper specified thinners and at ratios specifically recommended. Substitution of other thinners for the specified ones should not be undertaken without consultation with the suppliers; for none of the many thinners available are generally adaptable for all paint formulations. Thinners should be added slowly and with
constant stirring. Adding a large amount all at once may result in local overdilution and may cause curdling of the paint or flocculation of the pigment. This precipitation may appear to stir in, but that portion of the mix that has curdled or flocxlated is never restored to its original condition, zausing early failure. 3. Atmospheric Conditions Painters normally determine the time of applica1tion, which can contribute to the success or failure of the coating, depending on the condition >f the atmosphere. Certainly, it is a poor decision :o apply a coating before an approaching rain jquall, and yet this is often done. Painters have Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 505
SSPC CHAPTER*23.0 93 m 8b27940 0003953 T5T m also been observed wiping condensed moisture from the surface of the steel structure and then applying the coating. Inorganic zinc coatings have been applied to steel surfaces which were sufficiently cold to freeze the water from the liquid coating, making the coating useless. Water base coatings do not evaporate properly when the humidity is too high or the temperature too low, and the coating will not form properly under these conditions. The condition of the atmosphere while the paint is being applied and cured can contribute to its success or failure. Paint should be applied during relatively dry conditions. The relative humidity should be 80% or less with the dew point at least 3 Co(5 F") less than the ambient metal or surface temperature. When the metal temperature is above 38°C (IOOOF), precautions must be taken to make certain that the paint or coating does not dry too rapidly. Organic coatings tend to overspray or surface dry and blister. Inorganic zinc coatings may form a powdery soft film that does not harden properly. Temperature is critical for the cure of many coatings, particularly epoxies and coal tar epoxies. Because they are internally reactive, unless the temperature is proper, they will not cure to a satisfactory coating. Such materials should not be applied at temperatures less than 25°C (60°F) except on recommendation by the manufacturer. It is wise not to paint if the ambient temperature is below5"C(40"F),orlessthan3C0(5 F")abovethe dew point. Application should be restricted to those hours when the temperature is sufficiently high to offset the possibility of condensation of moisture during application and the drying period. 4. Coating Thickness A coating is a relatively thin film or barrier separating two reactive materials: the atmosphere on one side and the substrate on the other side. This barrier must have an even thickness over the entire surface to be protected; otherwise, there will be areas prone to early failure because they are too thin to separate properly the two reactive elements. Thickness, therefore, is extremely important. Each coating should have optimum thickness, depending upon the surface over which it is applied and the atmosphere in which it is to operate. This optimum thickness can be determined only by actual experiment or by consulting the manufacturer of the coating. While too thin a coating can cause early failure, an excessively thick coating can also
cause early failure. This is particularly true of inorganic zinc coatings. Where they are applied too thickly, they tend to mud-crack. Internally reactive coatings, such as epoxies and polyurethanes, tend to crack and disbond due to internal stresses within the coating because of shrinkage during the curing reaction. Many such coatings have literally pulled themselves off the surface due to excess thickness. Any painter or coating applicator should understand the problems arising from either too thin a coating or one which is considerably over the optimum thickness for proper use. It must also be recognized from a practical standpoint that the coating applicator cannot apply a completely uniform coating, particularly to complicated structures. Coating specifications often give a minimum thickness, such as "the coating shall be applied in two coats to a minimum of 10 mils". Such a specification does not recognize the excess thickness that may result. A proper specification should recognize the practical aspects of application and provide the applicator with a range of thickness which, if followed, will provide the proper average coating thickness for the use involved. The thickness of a coating can be measured during the application process by a wet film thickness gage. While this is not a positive instrument, it does indicate what the thickness of the coating will be after it has dried. A number of instruments provide the thickness of the coating after it has dried. Such an instrument is an essential part of the equipment of any paint foreman or inspector who is doing a proper job. 5. Overspray Overspray is a major cause of pinpoint rusting of steel surfaces. Many modern, high-performance coatings have a tendency to overspray unless properly applied. These include coating types such as solvent-based inorganic zincs, organic zincs, solvent-dry vinyls, chlorinated rubbers, acrylics, heavy-bodied epoxies, and other similar formulations. Overspray is the adherence of semidried coating particles to the surface to be coated. The dust or coating particle dries partially in the air between the spray gun and the surface, and does not then flow together with or join other particles to form a continuous coating. There are bare or very thin areas between these discrete coating particles. These bare areas act the same as pinholes, and pinpoint rusting results. Because overspray is the result of incorrect spray technique or improper adjustment of spray equipment, it can occur in any coat from the primer to the final top coat. It may be caused by
the spray gun being held too far away from the surface to be coated, being held at a long angle to the surface rather than perpendicularly, or having been adjusted with too little material pressure Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 506
SSPC CHAPTER*23.0 73 8627740 0003754 996 W and too much air pressure. With airless equipment, overspray can be caused by too small a gun tip or one with too wide a spray pattern. Airless equipment is preferred for application of a material with a tendency to overspray because there is no air atomization involved. The proper technique to prevent overspray requires optimum spray gun adjustment for both air and liquid volume and the application of an even, wet coat over the surface, with each pass of the coating being overlapped 50 percent. This method ensures that any minor dry particles at the edge of the fan are incorporated into a wet coating surface. Existing overspray on a surface being coated must be removed or pinhole failure will almost surely occur. At best, an unsightly coating application will result. The dry, adherent particles should be wiped, scraped or sanded from the surface before a proper wet coat is applied, or, if pinholing of the coat applied over existing overspray has already taken place, the overspray area should be given a wet brush coat to work the coating into the existing porous overspray area. 6. Pinholes Pinholing is a common type of application failure. It may result from several causes. The formulation of the coating itself can cause pinholes, primarily because of improper solvent balance when solvents evaporate too rapidly at one stage of the drying process. Another, more common cause is improper application, usually during spraying. The spray gun may be held too close to the surface with excessive atomization pressure, or excessive material pressure may be combined with low atomization pressure. A third cause of pinholes may be the surface itself. Concrete may already contain innumerable bugholes that must be filled if an impervious coating is to be obtained. Pictorial descriptions of bugholes in concrete are found in the ASTM Manual of Coating Work for Light Water Nuclear Power Plant Primary Containment and Other Safety-Related Faci Iit ¡es. One cause of pinholing is the top coating of inorganic zinc primers with organic top coats. During a period shortly after the inorganic zinc coating has been applied, it remains a porous film and solvents from the organic top coats can easily penetrate into the inorganic coating. When the top coat is applied in the sun or under warm con-
ditions, the penetrated solvent evaporates rapidly causing vapor pressure within the inorganic zinc and under the organic top coat. This vapor pressure may create small blisters or bubbles which, when they break, cause pinholes to form. Top coats with slow drying characteristics or with high solids and a low solvent content help to alleviate this condition. Pinholes are an immediate problem. Once they occur, they will persist no matter how many subsequent coats are applied. As one coat is sprayed over another, or over pinholes in the substrate, the existing pinholes will act as a reservoir for solvent vapor from the following coat. The vapor pressure in the pinholes will then cause a bubble in the following coat that will eventually break, leaving a passage to the original pinhole and the underlying surface. Mechanical force is necessary to fill the pinholes with liquid coating. This filling is accomplished by brushing a coat into the pinholed area. Several passes over the same area may be required to fill all pinholes. Pinholing occurs most readily in lacquers and solvent-dry coatings. Extra care should be taken during application of these coatings to prevent pinholes from forming. 7. Spatter Coating Spatter coating is caused during the spraying process where the liquid coating particles hit the surface, but the number of particles is insufficient to form a complete and continuous wet coat. This is often caused where a painter does not sufficiently overlap each pass of the spray gun, or where he tends to flick the spray gun at a long angle to the surface at the end of his spray pass. Oftentimes, particularly under poor lighting conditions, the surface may look as though it is completely coated. On the other hand, once the coating has been exposed for a short period of time, particularly on steel, general pinpoint rusting will occur over the area where the spatter coating exists. These pinpoints of rust will take place wherever there is an opening between the droplets of the coating. While it doesn t seem like this type of coating failure should be common, it is one which is quite prevalent on many steel structures. The answer to this, like many other application related failures, is care during the application process, making certain that each pass of the spray gun is overlapped at 50% with the coating going on as a wet film, making sure that the spray gun is held perpendicular to the surface and that
the gun is not flicked at an angle at the end of the spray pass. Cross spraying is also a method of application which helps to provide an even, uniform coating. 8. Holidays A painter s holiday is any place on a structure the painter has missed. This can be behind angles, around rivets, longitudinal areas on pipe, or any Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 507
SSPC CHAPTER*23=0 93 = 8627940 0003955 822 area where the coating has failed to be applied. Spatter coating is related to holidays in that, as previously indicated, some areas of the coating appear finished, even though the coating is not continuous in that area. Holidays can be overcome only by care on the part of the painter during the application. 9. Ciatering Cratering in a coating can be a most difficult application problem. Most cratering is encountered during the application of slow drying or baked coatings, such as pure phenolics, epoxy phenolics, pure epoxies, polyurethanes, etc. The internal cure coatings appear more susceptible to this phenomena than faster drying coatings such as vinyls and chlorinated rubbers. Cratering can be caused by several different conditions. (a) One of the most common causes is oil in the blasting or atomizing air. Here the condition will be general and caused by minute droplets of the incompatible oil on the surface or incorporated into the liquid coating during application. (b) Minute particles of dust or contamination from the atmosphere may cause pinholes. They can fall on the surface either before or during the application and may come from steam blow off, dust or soot from boiler stacks, fall out from paper mills, fertilizer plants or other similar operations. Fallout from jet aircraft around airports may cause problems. (c) Some cratering has been found which is due to the various protective skin creams used by workmen during the surface preparation or other sources during application of the coating. Silicone creams are particularly difficult. Cratering in these instances is usually localized and due to contamination of the surface by those materials. Most silicone resins are incompatible with other coating vehicles thereby causina craters to occur. Cratering can be defined as the formation of small bowl shaped depressions at a point of contamination on the surface. The craters are caused by the surface tension of the coating being greater than the surface tension of the contaminant. A repelling of the coating away from a point due to a difference in static charge between a particle at the point and the coating itself will cause a crater. At times, the coating itself may be the cause of the difficulty, having sufficient surface tension so that heavy areas of the coating will
tend to pull together. Irrespective of the cause, failure of the coating can be expected in the low areas of these craters, usually in the form of pinpoint rusting starting at that point. Once the cratering has occurred, it Is difficult to overcome inasmuch as a second coat applied over the same area may again crater in the same spot. The procedure suggested in these cases is to physically roughen the cratered area by hand sanding or other means, and then apply the coating over the area by brush, working the coating into the cratered areas in order to physically coat the bottoms of the craters and make sure that the coating thoroughly wets the surface. Where this is not practical or it does not prevent the cratering, the coating must be removed and the surface reprepared, making sure that the cause of cratering is eliminated before applying the repair coating. 10. Bleeding This is the transfer of a soluble colored pigment or vehicle in a dried film to a subsequently applied topcoat. It may also be the discoloration caused by the diffusion of soluble ingredients in the substrate. To correct this situation, coat the film containing the bleeding ingredient with two coats of a sealer in which the bleeder is insoluble. An aluminum or emulsion finish over asphalt vehicles or solvent type primers over wood substrates are examples. For areas of serious corrosion any sealing material must be selected with care to make sure of compatibility and proper adhesion. 11. Blushing This is the hazing or whitening of a finish as the result of absorption and retention of moisture formed on the film during or immediately after spraying. It is normally restricted to lacquers. Correction of this problem is not always possible without reducing humidity; however, recoating using a mist coat of retarder or a slower evaporating reducing thinner may help. Correct air pressure at the gun is important. Avoid using higher air pressure than needed as this will cause rapid evaporation and thereby increase moisture condensation. 12. Lifting This usually occurs when the solvents in a topcoat attack and swell the previously applied film resulting in distortion, blisters or the formation of a wrinkled finish. It may also be caused by wax on the surface, use of incorrect thinner, poor dry of undercoats or poor adhesion of old film.
To correct, remove finish from affected areas and refinish. Make sure surface is clean and dry. Allow longer drying time before recoating the undercoat. Make sure the solvent in the topcoat is compatible with the previous coat or undercoat before recoating. 13. Orange Peel This is a bumpy pattern inherent in nearly all Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 508
SSPC CHAPTER*23.0 93 8627940 0003956 769 sprayed films, caused by either the spray pattern or the drying characteristics of the finish. It is an appearance problem and should not cause coating fail Ure. If the degree of orange peel is objectionable, then improvement in flow can be obtained from better spraying technique, application of a good wet film, or addition of a small amount of slower solvents. COATING FAILURE 1. Improper Mixing of Coating 2. Improper Thinning of Coating 3. Poor Atmospheric Conditions for Coating Application 4. 5. 6. Pinholes Improper Coating Thickness Overspray --`,,,,`-`-`,,`,,`,`,,`--14. Runs or Sags Runs are downward movements of a paint film resulting when excess material continues to flow after the surrounding surface has set. Sags are downward movements of a paint film between the times of application and setting resulting in a curtain appearance. Both of these problems may be caused by the use of too much wet paint. Coating failure can ocTABLE 6 SUMMARY OF APPLICATION-RELATED FAILURES FAILURE APPEARANCE Thin coating -non-uniform pigment distribution. May be areas of poor adhesion, uneven color, checking or cracking. Poor adhesion, pigment float or flooding (uneven color). Separation of pigment and vehicle after application -pinholing,
blushing (coating turning white after application). Poor adhesion and blistering from humid, damp conditions. Overspray -powdery coating where drying is too rapid. Soft uncured film. Areas of pinpoint corrosion between areas of solid coating where coating is thin. Checking, cracking, flaking where coating is overly thick. Very rough coating surface. May appear like sand in the coating. Some dry coating, like dust, on the surface. Small, visible holes in the coating (YS2 ). Holes generally appear in concentrations with a random distribution. CAUSE OF FAILURE Most common cause is improper pigment-vehicle ratio, where settled pigment remains in the bottom of the can. Thinner incompatible with resins or pigments. Improper drying change in surface tension. Thinner evaporation too rapid, causing moisture to condense on liquid coating. Condensation of moisture on the surface prior to application. Lack of proper cure due to too low or too high temperature during application. Thin areas, spatter coating, holidays. Runs, puddles, excessive number of spray passes in areas where coating is difficult. Improper spraying technique. Uneven spray passes with gun too far from the surface. Spray pressure too low, atomizing air pressure too high. Lacquer type coating most subject to overspray. Improper spray technique. Spray gun too close to the surface with air bubbles being forced into the coating. Spray pot pressure too high
with atomizing air pressure too low. Pinholes may exist in the substrate (concrete). REMEDY Thoroughly mix the liquid coating (preferably by mechanical means) to an even, smooth, homogeneous liquid with no color variation. Continue mixing as necessary during use. Use only manufacturer s recommended thinners, add slowly with thorough mixing. Apply coatings at relative humidity of 80% or below and at least 3 Co(5 F ) above the dew point. Apply paint and coatings at 5°C (40°F) or above except for internally reactive materials which should be 25°C (60°F) or above. Careful application -even spray passes with each pass overlapped 50%. Use cross spray technique. Apply coating with care and with even wet spray passes overlapped 50%. Use wire screen and sandpaper to obtain smooth surface before topcoating. Apply coating with care with spray gun at the optimum distance from the surface. Make sure spray gun is properly adjusted. If pinholes already exist, apply coating by brush, working it into the surface. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 509
SSPC CHAPTER*23=0 93 8627940 0003957 bT5 TABLE 6 (Continued) COATING FAILURE FAILURE APPEARANCE CAUSE OF FAILURE REMEDY Area of thin coating, usually at Discrete coating droplets which are Apply coati ng with care. end of spray pass or around a not continuous over the surface. Use even, wet spr ay with complex section of structure. Inconsistent spray passes not over- each pass over lapped 50%. Small spots of coating which are lapped 50%. Spray gun flipped at Use cross spra y technique. noncontinuous over substrate. end of spray pass. Catalyst cured In poor light, may seem contin- coatings most subject to spatter. uous. Bare areas of the surface which Poor, inconsistent application. Lack Apply coati ng in a careful, were uncoated by the painter. of care. consistent manner, making Most often in difficult areas certain that no areas to coat. remain uncoated. Bug eyes, fish eyes or craters Improper solvent mixture, oil in Once cratering o ccurs, sand randomly dispersed over coated atomizing air, surface contamina. or roughen crat er area. area, May be more prevalent in tion, particulate fall-out during Apply another c oat by brush, in thicker sections. application, high surface tension, working coating into cra tsilicone contamination. ered area. Make sure contaminant is removed. Staining of top coats. Soluble resins or pigments in under- Seal with coating in coat. which bleeding ingredient is insoluble. Haziness or whitening of film. Condensation of moisture on coating Wait for impr oved due to rapid dripping of solvents. humidity conditions. Reduce atomizing air pressure to a minimum. 12. Lifting Wrinkling, swelling or blistering Attack or swelling of film by solv ents Remove old coating and of film. in top coat. recoat. 13. Orange Peel Overall bumpy pattern. Surface Spraying technique, drying charApply a wet spray coat. is smooth but irregular. acteristics of the film. Add a slower solvent. 14. Runs or Sags Coating running in droplets down Excessive application. Apply t hinner coats. vertical surface causing curtain Check surface temperature. effect. May be too cold for proper drying. 8. Holidays 9. Cratering 7. Spatter Coat 10. Bleeding 11. Blushing
cur because of thin coating above the sag or run. Following are a number of typi cal areas, primarily on Reduce material according to label direc- steel structures, where coating proble ms are much more tions, apply thinner coat if rolled or brushed on. prevalent than on plain surfa ces. Regulate fluid adjustment on the spray gun to cut 1. Edges down flow of material. Make sure temperature of Edges are always a problem on st ructures using surface and coating are at acceptable level. steel shapes, where the number of l ineal feet of If runs or sags are objectionable, the surface edge compared to the ptain surfac e is large. The should be removed with solvent or sanded smooth edges of sheared plate are one o f the worst areas and refinished. because they are very sharp. The rounded edges of steel shapes, such as on I-beams, H-beams and VI. DESIGN-RELATED FAILURE angles are less of a problem; however, almost inMany coating failures occur because of the design of variably where failure occu rs on a steel shape, it the structure. Unfortunately, most structures are not will be on the edge first. designed with the painting or coating process in mind. One cause is that many of the more This being the case, many failures are due not to the sophisticated coatings, su ch as vinyls, epoxies or coating or its application, but merely to difficult problems polyurethanes, have a high surface tension and of application created by the design. Where there are also tend to shrink during curing. A high surface design problems that make a structure difficult to coat tension of the coating t ends to pull the coating adequately, proper selection of the coating and careful away from an edge, in ma ny cases leaving an exand proper application can overcome many of the inherent tremely thin coating at that point. This being the problems created by the design. case, failure is inherent along the edge. On Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 51O
SSPC CHAPTERa23.0 93 H 8627940 0003958 532 = I-beams, angles and similar shapes, the applicator more often than not sprays on the plain surface while the edge is at a tangent to the spray and only becomes spatter coated, even though it may look well covered. Horizontal surfaces on structural shapes (I-beams, H-beams, etc.) tend to accumulate dust, dirt and chemical fumes that flow toward an edge when any condensation or precipitation occurs. As a result, a relatively strong chemical deposit forms and remains on the edge. Such a situation makes the edge even more susceptible to coating faiIu re. There should be a direct application of the coating to edges prior to applying an overall coat to the structure. Edges should be double coated with each individual coat. This procedure will help to maintain a full coating thickness in these areas. Deep square corners These areas are on the interior of angles and on the interior angle of H-beams, I-beams and very often on built-up, complicated steel sections. There are two problems. The first is that these ' areas will accumulate dirt and dust, and even though the surface is well prepared by abrasive blasting, dust seems to accumulate in these areas to a greater degree than on the plain surfaces. It is also more difficult to remove. When a coating is applied over dust or dirt in these areas, shrinkage and oftentimes actual cracking of the coating occurs, creating an area for immediate failure. Second, even though the surface is thoroughly clean and free from dust, these areas more often than not receive a heavy coat because of the application of the coat to the flat areas with the spray overlapping into the corner. This can create the coating thickness on the interior corner which is greater than recommended for the flat surface. During curing and when shrinkage occurs, the coating may tend to pull itself away from the interior corner, creating a very thin film or a void underneath the coating. Although the coating may look continuous, if it is exposed to serious corrosive conditions or immersion, failure occurs by moisture penetration into this area. The ultimate cracking and breaking of the film occurs at this point.
To overcome this design difficulty, apply thin, multiple coats to the deep corner, allowing each coat to dry before a second coat. Discontinuous areas These areas are located around rivets, boltheads, threads and similar areas. The cause of failure is similar to that of sharp edges and corners. Careful appl ¡cat ion can el imi nate discontinu ities in these areas. A brush coat should be applied on all sides and edges of the discontinuous area prior to applying the overall spray coat. A brush coat is preferable to spray for the initial application as the physical action of brushing forces the coating into crevices and other small openings where the spray coat will not reach. 4. Welds There are literally millions of lineal feet of welds in many structures. Relatively smooth machine welds create few problems. Even so, there can be undercuts along edges that should be watched. Hand welds, in particular, require more care than plain surfaces. These welds are much rougher than machine welds and may have deep undercuts and holes along the edges, with weld spatter on adjacent surfaces and, in some cases, very rough, sharp protrusions. All of these are focal points for corrosion and for coating failure. Weld spatter, small balls of metal, are spattered away from the weld proper during the welding process. They are always focal points for failure. Many times they are lightly adherent and provide not only protrusions, but undercuts as well. Weld spatter must be removed from the surface for a proper coating job. These are not always removed by sand blasting. Once the surface is prepared, however, it is the recommended procedure to brush coat a weld, working the coating into all of the rough areas before applying the overall coat to the plain surface. This aids materially in preventing premature failure at that point. Where welds are treated in this manner, oftentimes the plain surface of a coating will fail before the area of the weld. 5. Skip welding Overlapping plates and roof plates are often skip welded. The reinforcing ring around the top of a tank may be skip welded. Angles and similar shapes are skip welded where a continuous weld is not necessary for ultimate strength. From a coating standpoint, wherever serious corrosive conditions exist, skip welds are an invitation to coating failure and very inadequate surfaces for
proper coating even in mild environments. Water and moisture accumulate between the plain surfaces of the plates. The skip weld does not keep out the moisture. It is almost impossible to apply a coating to the crevice between the skipwelds and to obtain a satisfactory corrosion resistant coating at that point. The only practical answer is complete welding of all the seams to insure proper coating life in corrosive areas and to maintain good appearance without rust stains even under milder conditions. Caulking may even be necessary in some cases. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 511
SSPC CHAPTERx23.0 73 8627740 0003959 478 TABLE 7 SUMMARY OF DESIGN-RELATED FAILURE 5. Skip Welding 6. Back to Back Angles 7. Storage Tank Roofs -Interior 8. Pipe Structures ~ ~~ ~ ~ FAILURE APPEARANCE CAUSE OF FAILURE REMEDY Corrosion linear with the edge and coating being undercut away from edge. A void or blister under the coating at interior corners. Corrosion failure on edges of threads, bolt heads, rivets. Coating failure along welds, particularly hand welds; coating undercutting starting at weld. Discontinuous welds with skips from 6 to several feet between welds. Corrosion between overlapping metal undercuts coating. Corrosion between back to back angles undercutting coating. Umbrella type roof -center pole and rafters. Coating failure between roof and rafter and between lapped roof plates. Coating failure at welds or longitudinal with pipe. Surface tension of coating pulling liquid coating away from edge. Precoat edges prior to coating flat surface. Overlap coating on flat surface over edge. Spray directly at an edge to build thicknesses. Apply coating in thin, multiple coats, thoroughly drying or curing between coats. Many small surfaces to cover with a Brush coat surfaces prior high ratio of sharp edges and cor- to full coating. Overlap ners to plain area. Surface tension brush coat with each coat. of coating pulls coating away from Multiple thin coats are points and edges. better than one thick one. Welding flux in undercuts along weld. Remove all blue scale or Rough weld surface. Soap remaining soap solution. Grind rough from pressure testing of welds. welds smooth. Blast weld Blue scale (similar to mill scale) at least 2 -3 on each remaining on weld. side. Apply first coat by brush, working it into all rough weld areas.
Continuously weld all overlaps before applying coating in any corrosive environment. Excessive thickness, causing coating to shrink on curing. Impossible to apply coating in crevice between metal surfaces. Impossible to apply coating in crevice between roof plates and between angles. fill crevice with heavy, Use T bar or pipe for construction. As a stopgap, resinous caulking and overcoat with a compatible coating. Impossible to apply coating in cre- Butt weld or double weld vice between roof plates and between roof plates. Precoat roof plates and rafters. rafters and underside of roof. Rough welds between pipe sections See No. 4, Welds . Apply (see No. 4, Welds ). Lack of coating carefully, assuring sufficient overlap during coating 50% overlap on all passes. application. Most application linear with pipe. ~~ COATING FAILURE Edges Interior Corners Discontinuous Areas 4. Welds 6. Back to back angles angles is difficult to clean and impossible to coat Many steel buildings have trusses, lattice work, properly. Where such designs ex ist and where corand similar areas constructed from angles which rosion dictates, the only practi cal answer is to fill are placed back to back. In some instances, the all of the void spaces between t he angles with a anglés are precoated by galvanizing or with in- plastic mastic or caulking compoun d and then aporganic zinc. However, in any severely corrosive ply a compatible coating over i t. This, at best, is a environment, even this procedure is prone to stop-gap measure and is no substitu te for the use failure and extremely difficult to protect properly of T shapes or pipe for struct ures where corby the use of coatings. The area between the rosive conditions exist. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 512
SSPC CHAPTER*23.0 93 862 79400003960 L9T 7. Storage tanks Many storage tanks are constructed with cone or umbrella type roofs where there is usually a center pole with I-beam rafters extending out to the edge of the tank. In addition to the many corners, edges, welds, bolts and rivets, there are two particularly difficult areas from the standpoint of the interior coating of such tanks. The first is the steel between the 1-beam rafter and the steel roof plate. Here the steel plate is merely laid on the rafter, and unless the coating is applied to the underside of the plate and the topside of the rafter prior to installation, this area will fail even under mild conditions. If the coating is to be applied after construction, it is necessary to raise the roof by wedges and prepare the surface to coat in the best manner possible. This area is particularly vulnerable due to moisture condensation. The second area is the crevice between the lapped roof plates. Generally, the roof plates are welded on the exterior with the lap on the interior. In this reservoir for corrosive solutions failure takes place rapidly. A coating cannot prevent corrosion with this type of construction. Where a coating is required on the interior of such a tank, roof plates should be butt welded or should be welded on each side of the lap so that a continuous coating is possible. 8. Pipe structures Much of the construction of off-shore platforms is done with pipe to minimize coating failure and corrosion. Pipe provides a plain surface with no sharp corners or edges subject to early failure. It would seem, therefore, that pipe would be an ideal type of surface to coat. There can be problems, however, primarily ones of ap plication. If failure occurs, other than at a joint, it is usually longitudinal with the pipe. This is caused by insufficient overlapping of the spray passes during the coating process. In coating pipe, it is essential that each spray be overlapped at least 50%. With large pipe, this means that there are numerous passes required in order to obtain a hol iday-free coating. In addition to areas where pipe is used as the principal construction member, there may be hundreds of miles of pipe used in a single industrial plant, all of which require coating. Here, in addition to the cylindrical structure, there are pipe flanges, valves, threaded joints, bolts, pipe
hangers and pipe racks. These areas have all of the focal points for corrosion which have been previously discussed, and wherever corrosion is a factor, care must be taken to make sure that all of the difficult areas are fully coated. Much pipe used for new construction comes with a factory applied temporary coating. This must be removed by abrasive blasting for proper coating adhesion and performance. Care in the surface preparation and care in the application of the coating are the only answers to a satisfactory coating job. VIL FAILURE BY EXTERIOR FORCES In almost all coating failures exterior forces are involved, since the environment in which the coating operates is the primary cause of failure. If there were no exterior corrosive environment, then no coating failure could occur, even though there were coating imperfections. In this section, however, ordinary atmospheric conditions are not considered, since it is taken for granted that coatings must withstand most exterior conditions, including marine conditions. 1. Chemical failure Chemicals are the most obvious exterior force that can cause the failure of coatings, since the chemical industry, considered in its broadest scope, is one of the largest, if not the largest, industry where severe coating failures can occur. There are literally thousands of different chemicals to which a coating may be exposed and, this being the case, it is understandable that there are also hundreds of specialty coatings that have been developed to resist attack by these chemicals. The attack may be by simple solution of the coating, reacting with the coating to render it useless, or chemicals may actually penetrate the coating and cause corrosion to the steel underneath. Attack by volatile acids, such as hydrochloric and nitric, often cause the latter failure. The caustic chlorine industry and the rayon industry can cause coating failures both by actual coating attack and by penetration and under-film corrosion. The interior and exterior of tank cars, specialty tankers and storage tanks in terminals are all areas where chemical attack of coating is common. There is no universal solution to the problem. Each condition must be considered on its own. The proper coating must be selected. The best surface preparation must be used and a defectfree application obtained. An improper coating selection or improper application of the right coating can be disastrous.
2. Erosion and abrasion These are exterior forces that can cause coating failure. One example is erosion by sand and wave action of coatings applied to steel piling on beaches. Sand erosion by wind is another example. Other examples are the abrasion on the interior of Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 513
SSPC CHAPTERx23.0 93 = 8627940 000396l 026 = hopper cars, interior abrasion in pipe lines due to determined that inorganic zi nc silicate coatings particulate matter in the liquid, or abrasion on have adequate friction resistan ce and can be floors by wheeled traffic. The, moving and han- used as a coating between the co ntact surfaces in dling of many fertilizers can cause both abrasion riveted and bolted joints. The use of the inorganic failure and chemical failure of the coating. In such zinc coating as a base coat ing within and outside cases, specialty coatings must be selected to of the joint provides an excellent corrosion resisresist the abrasion and erosion as well as the nor- tant answer for coating bolt ed or riveted strucmal corrosion which might be expected should tures. the coating wear through. When there is liquid penetration at such 3. Faying surfaces joints, crevice corrosion can occur due to the oxyCoating failures can occur where joints in steel gen concentration cell effect, especially if disstructures are formed by riveting or by the use of similar metals make the steel surface cathodic to the bolt of high-strength steel. TABLE 8 SUMMARY OF FAILURE BY EXTERIOR FORCES COATING FA1 LU RE FA1 LU RE APPEARANCE CAUSE OF FAILURE REMEDY 1. Chemical Solution of coating, undercutting, Unsuitable coating selection. Poo r Proper selection of coating underfilm corrosion. coating application. for the service is a prime requisite. This must be followed by the best surface preparation possible and a defect-free application. Coating worn away, leaving sub- Wear by wheeled vehicles, impact, Specialty coat ing must be strate subject to corrosion. wind or liquid born abrasives. selected to resist s pecific abrasion. Coating must have strong adhesion in addition to wear resistance. (Polyurethane coatings are most abrasion resistant.) Coating failure and corrosion Crevice between contacting steel sur- Prior to joi ning metal$urin joint. faces joined by rivets or high strength faces, sand blast and apply bolts. an inorganic zinc coating to joint area and beyond. When the two surfaces are joined, a corrosion-free joint will result. VIII. SUMMARY
high strength bolts. Such joints are common on bridges and in many open steel work plants such Coating failures may be caused b y the coating foras refineries and chemical plants. If there is a mulation or the materials from which it is made; by the crevice at the joint, the coating applied to the sur- basic characteristics of t he surface coated; by improper face can fail at that point, allowing access to surface preparation; by the desi gn of the structure coated; moisture or chemicals, with resulting corrosion. or by poor coating application procedures. Coating Most coatings are unsuitable for use within the failures can be prevented only b y using the proper material joint itself as they do not provide the proper coef- for the job, and by care in the application to achieve comficient of friction to maintain the joint in a static plete, uninterrupted coati ng coverages irrespective of the condition. Even galvanized surfaces do not have built-in problems of the design and materials of construcsufficient coefficient of friction to provide a prop- tion. On any coating job, the following procedures are er joint. recommended to assure coating success. In the past, most joints have been made on a 1. Analyze the exposure and the str ucture, and steel to steel basis in order to obtain the proper specify the material which wi ll properly meet the friction resistance. Recently, however, it has been conditions. Do not compromis e on price or qual2. Erosion and A brasion 3. Faying surfaces --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 514
SSPC CHAPTER*23-0 93 8627940 0003962 T62 ity. The material is the least costly item of a coating application. 2. Use a detailed specification covering the method of surface preparation and the application of the coating. A general specification is not adequate. 3. Make a detailed inspection of the surface preparation and the application procedures to assure conformity with the specification in numbers 1 and 2 above. Irrespective of the structure or the corrosive conditions, a strong specification and good follow-up inspection are the two most important keys to a successful and failurefree coating job. ACKNOWLEDGEMENT The author and editors gratefully acknowledge the active participation of the following in the review process for this chapter: AI Beitelman, Wallace P. Cathcart, Thomas A. Cross, Theodore Dowd, J. Roger Garland, Dan Gelfer, Lewis Gleekman, H.W. Hitzrot, Joe Mazia, Marshall McGee, I. Metil, John Montle, William Pearson, E.A. Praschan,.Melvin Sandler, William Wallace. A portrait and biographical sketch of Charles G. Munger can be found at the end of Chapter 4.2. REFERENCES 1. G.W. Segreu, Causes & Prevention of Paint Failure , Steel Structures Painting Manual, Volume 1, Good Painting Practice, Chapter 18, 1954. 2. Paint and Protective Coatings, Chapter 5, U.S.Government Publication, Department of Defense, Army -TM5-618, NAVFAC MO-110, Air Force -AFM-85-3, 1969. 3. C.G. Munger, Causes of Coating Failure , paper presented at NACE South East Regional Meeting, November 1975. 4. C.G. Munger, Coating Failures , Plant Engineering, 1974. 5. C.G. Munger, Protective Coating Failures; Coating Formulation & Selection (Part l), Plant Engineering, April 15, 1976; Substrate Material & Condition (Part 2), Plant Engineering, April 29,1976; Coating Application Procedures (Part 3), Plant Engineering, May 13, 1976. 6. C.G. Munger Repairing Protective Coatings: Evaluating Coating Condition (Part l),Plant Engineering, November 11, 1976; Procedures for Metallic Substrates (Part 2), Plant Engineering, December 23, 1976; Procedures for NonMetallic Substrates (Part 3), Plant Engineering, January 20, 1977; Effects of Coating Types (Part 4); Plant Engineering, February 17, 1977. 7. C.G. Munger, influence of Environment on inorganic Zinc Coatings , Materials Performance, March 1977. 8. C.G. Munger, Sulfides -Their Effect on Coatings & Substrates , Materials Performance, March 1977. 9. C.G. Munger, Coating of Contaminated Ferrous Surfaces , 1979 Coating Symposium, Niagara Falls, NY, 1979.
10. C.G. Munger, Practical Aspects of Coating Repair , Materials Performance, February 1980. 11. Causes and Prevention of Coating Failures , NACE Report 6D170. 12. Corrosion Control -Principles and Methods , Ameron Publication. --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 51 5
SSPC CHAPTER*24*0 93 Ab27940 00039b3 9T9 September 1993 (Revised) CHAPTER 24 PAINTING NAVY SHIPS by Stephen D. Rodgers, Richard W. Drisko, and John Tock I. INTRODUCTION The operational readiness of a modern, technologically sophisticated fleet is of paramount importance to the defense of our nation. Marine coatings comprise a key element in the maintenance program required to achieve and retain this readiness. The United States Navy is committed to providing this protection in the most reliable and cost effective manner available. This is being achieved through an active research program to develop (1)new formula-type coatings which can be purchased competitively and (2) performance-type specifications for which manufacturers can qualify products. Most of the coatings used on Navy ships are of the high performance type that require surface preparation and application by experienced personnel. Those coatings used by ship forces for everyday maintenance (e.g., alkyds) are more tolerant of applicator skill. The effectiveness of the coatings in the Navy s ship corrosion control program is reflected in the present drydocking cycles of five to seven years. Coated surfaces on Navy ships are subjected, as shown in Figure 1, to a variety of destructive conditions (e.g., a salt laden, high humidity atmosphere; total seawater immersion; and acidic exhaust gases) with temperatures ranging from those of the tropics to those of the Arctic. They must be resistant to physical damage from such forces as cavitation, drag (friction), impact with waves and mooring structures, and abrasion by chains. Each coating system must adhere tightly to the particular substrate (ferrous and nonferrous metals, wood, plastics, and elastometers) to which it is applied, and it must resist deterioration from a variety of chemicals (e.g., distilled, potable, and salt water; hydrocarbon fuels and lubricants; and sanitary wastes). In addition, antifouling coatings must prevent the attachment and growth of marine organisms on immersed surfaces. These organisms increase frictional drag, which results in loss of speed and maneuverability and increased fuel consumption. Fouling may also promote localized corrosion, damage to coatings, reduced buoyancy, and inoperable equipment. Thus, ships of the Navy require a combination of versatile and specialized coatings to meet many different requirements to keep them operational. Many of these coatings may also prove to be as cost effective on commercial ships II. BACKGROUND Coating materials and techniques utilized by the Navy have generally changed in much the same manner as
those of the commercial sector. Prior to World War II,most of the maintenance painting was done by sailors using chipping hammers and other hand tools to clean steel surfaces and brushes to apply drying oil (e.g., alkyd) paints. Since that time both cleaning and application techniques and coating materials have improved greatly. All shipyard and maintenance depot painting is done by civilian (civil service or contractor) personnel who clean steel surfaces to a near white blast (SSPC-SP 10) with automated equipment wherever possible to reduce emission of particulates, and apply coatings with modern spray equipment. The everyday maintenance painting is still accomplished by less experienced ship personnel. In the last forty years, paints used on Navy ships have changed from the drying oil (alkyd) formulations, such as Navy Formula I(1944),of the early forties to vinyls, such as Navy Formula 119, of the early fifties to epoxies, such as MIL-P-23236 (1962) and MIL-P-24441 (1972), currently in use today. The drying oil paints were relatively easy to apply since they did not require a high level of surface preparation, but they had limited resistance to marine service. The vinyl paints were much more durable, but they required a higher level of surface preparation and more coats to achieve a desired thickness. The epoxies have proved to be more cost effective in that, even though they still require a relatively high level of surface preparation and should be applied at temperatures above 35OF, they provide a very durable barrier in fewer coats. Prior to World War II, Navy ships were coated with paints produced in Navy factories according to Navy specifications. Today, the Navy obtains from commercial suppliers a mixture of Navy formula (Military Specification), Federal Specification, and qualified commercial products. Table 1 identifies the paint formulations most commonly used on Navy ships along with their specifications and uses. The current procurement procedures permit the maximum cost effectiveness while taking advantage of the latest coatings technology of private industry and research and development of coatings with Navy-unique purposes (Le., coatings for camouflage, as on those of the Navy. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS--`,,,,`-`-`,,`,,`,`,,`--submarines, and extreme durability). 516
SSPC CHAPTER*24.0 93 8b27940 0003964 835 Antennas and Superstructures o Acidic Exhaust Fumes o Extreme Temperatures -IzL -o Intense Sunlight o Thermal Shock 6 r-, ---__ ___~-==æ .-_ Wind Driven Saltwater and Spray ~ Deck Areas ____ / o Mechanical Abrasion iLines, Chains, etc) ~ ~ t-4-c:,=--9 I o Fuel/Chemical Spills -_ 7. -. o Humidity o Heat/Fire o Cooking Fumes Soiling o Abrasion 1 Ballast, and Cargo Tanks -z2_r$So o Hydrocarbon Fuels WATER o Distilled, Potable, and Salt Waters FUEL CARGO CARGO 0 Corrosive and Sensitive Cargoes W BALLAST -.__-\/Y o JChlorination System ~. I Underwater Hu I I o Marine Fouling o Seawater Immersion o Abrasion
o Galvanic Corrosion o Cavitation FIGURE 1 Environments that are destructive to chipboard coatings. --`,,,,`-`-`,,`,,`,`,,`--517 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*24-0 93 m 8627940 0003965 771 = TABLE 1* * IDENTIFICATION OF COATINGS USED ON SHIPS NAVY FORMULA -84 and 84D 111 121 124 125 126 129 150-1 56 --`,,,,`-`-`,,`,,`,`,,`--SPECIFICATION TT-S-711 formerly MIL-V-I 174 TT-V-119 now used TT-P-6456 MIL-E-15090 MIL-P-15931 DOD-E-24607 DOD-E-24607 DOD-E-24607 formerly MIL-P-16189; MIL-P-15931 now used MI L-P-2444 1 MIL-C-11796
MIL-R-15058 MIL-C- 1 6 1 73 MIL-D-23003 DOD-P-23236 DOD-P-24380 MIL-D-24483124667 DOD-P-24555 DOD-P-24596 TYPE' oil stain oleoresinous phenolic varnish alkyd-zinc molybdate al kyd/powder vinyl-cuprous oxide chlorinated alkyd chlorinated alkyd chlorinated alkyd vinyllcuprous oxide epoxy polyamide (different colors) petrolatum epoxy polyamide epoxy chlorinated rubber epoxy si lico ne-al u m i n um USE wood interiors spar varnish anticorrosive primer for steel and aluminum enamel for equipment antifouling (red) nonflaming (white) nonflaming (green) nonflaming (gray) antifouIing (black) general use on metals
corrosion-preventive compound coating outboard shafting corrosion preventing compound nonslip deck covering fuel and ballast tanks anchor chain nonslip deck coating high temperature fire protective coating compound Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 51 8
SSPC CHAPTER*24-0 73 8627740 0003766 608 TABLE 1 (Continued) IDENTIFICATION OF COATINGS USED ON SHIPS NAVY FORMULA --`,,,,`-`-`,,`,,`,`,,`--SPECIFICATION TYPE* USE - MIL-P-24647 -antifouling systems MIL-(2-46081 intumescent insulating coating - TT-P-28 silicone-aluminum high temperatures - TT-V-51 asphalt varnish anchors and chain MIL-E-24635 silicone-al kyd exterior semi-gloss enamel 'MIL-P-indicates military specification (being replaced by DOD-P-) DOD-P- indicates Department of Defense specification TT-P- or TT-E- indicates Federal specification 'The following specifications have been removed from the table to reflect curren t practice: TT-C-542, TT-E-489, TT-E-490, TT-L-26, TT-LdO, TT-P-320, TT-P-595, MIL-C-17504, MIL-E-17970, MIL-E-17971, MIL-L-19537, MIL-P-15929, MIL-P-15930, MIL-P-19451, MIL-P-19452, MI L-P-19453, MIL-P-22298, MIL-P-22299, MIL-P-22750, MIL-P-23377, DOD-E-699, DOD-E-1821 O, DOD -P-15328, DOD-P-17545, DOD-P-23236, Class 2-4, DOD-P-24588 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 519
SSPC CHAPTER*24*0 93 D 8627940 00039b7 544 M 111. CURRENT PRACTICES ing all governmental regulations are specified for painti ng Painting during acquisition of ships is covered by the operations. general specification requirements that are included in A. SURFACE PREPARATION contracts for the building of a ship. While they reflect the latest painting technology at the time the contract is Currently recommended met hods of preparing difwritten, they may not reflect the latest technology at the ferent ship surfaces for coating are listed in Table 2. Steel --`,,,,`-`-`,,`,,`,`,,`--time of delivery of the ship seven to ten years later. Modifi- surfaces are much more prevalent on Navy ships than cation of contracts to reflect changing technology has other materials, with alu minum representing a large proven to be difficult and costly. portion of superstructures. A near-white blas t finish is Maintenance painting of ships in service is covered in suitable for all the coat ings used on steel surfaces. Of the great detail in Navy Ships Technical Manual, Chapter 631. many different types o f coatings used on ships, inorganic This document provides information on surface preparation, zinc primers are the least tolerant of a lower level of thickness of paint films, coatings to be used, and applica- cleaning: It should be noted that even in shipyards and tion procedures. Touching-up by currently recommended maintenance depots, mechan ical cleaning is occasionally pra~tices~~~ used on small touch-up areas or those areas difficult to is emphasized. Strict safety precautions meetreach with blast cleaning. TABLE 2 RECOMMENDED METHODS OF SURFACE PREPARATION OF VARIOUS SUBSTRATES FOR COATING SUBSTRATE RECOMMENDED METHOD OF SURFACE PREPARATION Steel Abrasive blast cleaning to near-white finish (SSPC-SP 10) for touch-up and full scale repainting at shipyards and maintenance depots. Hand or power (preferably) tool cleaning with wire brushes, chipping hammers, grinders, sanders, needle guns, etc., for maintenance by ship forces. Galvanized steel Solvent cleaning (degreasing) new surfaces followed by applicat ion of one Coat of Formula 150.
Aluminum 80 grit Garnet or Aluminum Oxide at 65 psi blast pressure. Wood Scraping to remove loose coating and sanding or planing with hand or power equipment. Plastic Solvent cleaning and light sanding. B. COATING APPLICATION use, as shown in Tables 3 and 4. In addition, their use in potable water tanks was approved by the The Navy is currently changing its recommended Navy Bureau of Medicine and Surge ry. method of coating application from an atomized spray to airless spray techniques. It is also experimenting with multicomponent airless spray equipment. Ship forces generally use brush or roller techniques since they require less skilled personnel. C. TYPES OF COATINGS 1. Steel Surfaces The great versatility of formulas 150-156 of MILP-24441 accounts for their widespread shipboard 520 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*24*0 73 Ab27940 0003968 480 The approved inorganic zinc primers are providing ex- Because of the high fire r isk associated with cellent corrosion control on exterior surfaces above the boot- storage of flamma ble and explosive materials, nontopping (see Table 3). The cathodic protection provided by flaming, highly chlor inated alkyd paints (Formulas these primers has not been long lasting in continuous im- 124,125 and 126) are u sed on interior overheads and mersion service, even when topcoated, because of topcoat bulkheads (see Table 4) . Recent tests by the Navy's damage during service. As indicated in Table 3, Formula 150 David Taylor R&D Cen ter have shown that these (epoxy) can be used as a barrier coat between these primers paints can be rated as noncombustible (when testand the silicone alkyd finish coat (MIL-E-24635). This is re- ed by ASTM E-162) at a dry film thickness of 20 mils, quired because of an incompatibility between zinc-rich coat- equivalent to 1O co ats. The new performance-type ings and drying oil paints.' A new performance-type specification DOD-C-24596 co vers fire-resistant coatspecification for zinc-rich primers for shipboard use, DOD- ings for many substr ates and uses. P-24648, was approved in 1985. In the interior wet spaces (see Table 4), the Formulas 121 (red) and 129 (black) are cuprous oxide- epoxy (Formula 150) system is required because of containing antifouling paints which have received extensive its greater resistan ce to water and soiling. Thus, it use. Their effectiveness, however, is usually limited to two has performed much better than alkyds. years, depending upon the type of service. New ablative cuprous oxide antifouling paints for 5 to 7 years service are described by MIL-SPEC-MIL-P-24647. TABLE 3 COATING SYSTEMS FOR EXTERIOR STEEL SHIP AREA COATINGS IN SYSTEM AND NUMBER OF COATS Hull from keel to *Formula 150 (1); Formula 151 (1); Formula 154 (1) or Formula 153 (1); Formula 121 (2) start of boottopping *NAVSEA** -approved commercial epoxy; Formula 121 (2) MIL-P-24647(5 -7 year system) Hull boottopping area *Formula 150 (1); Formula 161 (1); Formula 154 (1); Formula 129 (2) * NAVSEA-approved commercial epoxy; Formula 129 (2) MIL-P-24647(5 -7 year system) Near vertical *Formula 150; Formula 151;MIL-E-24635 surface above boottopping NAVSEA-approved commercial inorganic zinc primer (1); Formula 150 (1 ); MIL-E-24635 Horizontal surfaces and waterways *NAVSEA-approved commercial inorganic primer (1); Formula 150 (1); Formula 151 o r MI L-E-24635
Formula 150 (1); MIL-D-24483or MIL-D-23003, Type II nonslip coating *Preferred or most used systems "'Naval Sea Systems Command --`,,,,`-`-`,,`,,`,`,,`--52 1 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERm24.0 73 W 8627740 00037b7 317 W In the early 1970s, the Navy began using flame- corrosive. Initially used only o n components that sprayed aluminum to protect the faying surfaces could be removed for metallizing ashore, it now between aluminum superstructures and steel finds occasional use on deck and bulk head areas hulls. In 1978, this technique was extended to and on the special items listed i n Table 5." As with areas that were difficult to reach or extremely TABLE 4 COATING SYSTEMS FOR INTERIOR STEEL SHIP AREA COATINGS IN SYSTEM AND NUMBER OF COATS Overheads and Bulkheadsa Formula84(1); Formula 124(1) or Formula 125 (1) or Form ula 126 (2)' Bulkheads in wet spacesb Formula 150 (1); Formula 152 Decksa NAVSEAd approved deck coatingse Bilges and machinery NAVSEA-approved commercial system under DOD-P-23236, Class 1 rooms Formula 150 (1); Formula 151 (1); Formula 156 (1) Saltwater tanks NAVSEA-approved commercial system under DOD-P-23236,Class 1 Formula 150 (1); Formula 151 (1); Formula 152 (1) Potable water tanks NAVSEA-approved commercial epoxy system Formula 150 (1); Formula 156 (1); Formula 152 (1) Gasoline and jet fuel NAVSEA-approved commercial system under DOD-P-23236,Class 1 tanks Formula 150 (1); Formula 151 (1); Formula 152 (1) Sanitary tanks Formula 150 (1); Formula 156 (1); Formula 151 (1); Formula 152 (1 ) MIL-P-21006flotation type rust-retarding compounds Fire stop bulkheads MIL-C-46081intumescent coating aOn dry, living (habitable) spaces, such as sleeping, messing, recreation, and p assageway areas. 'Sculleries, washrooms, showers, etc. 'Formula 124 can be tinted with DOD-C-22325colorants to other colors. 522 Inaccessible voids
dNaval Sea Systems Command. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS--`,,,,`-`-`,,`,,`,`,,`---
SSPC CHAPTERU24.0 93 8627940 0003970 039 TABLE 5 ITEMS REC EIVI N G FLAME-SPRAYED ALU MI N UM M ETALL IZIN G MILITARY STANDARD 2138 AREA OF USE SPECIFIED ITEMS METALLIZED Topside Exterior Use Deck hardware and machinery; tiedowns; steam riser valves a nd piping; exhaust stacks and covers; fire station hardware; lighting fixtures; masts; and booms. Topside Interior Use Equipment foundations; deck areas; coaming around doors and scuttles; heads, and sculleries. Propulsion Plant Steam valves, reducers, stops, strainers, and piping; bottom bl ow valves and Machinery and piping; pump and machinery foundations; boiler skirts; electri cal and mechanical casings; diesel headers and exhaust system components; hangers; brackets; and supports. zinc-rich coatings, flame-sprayed aluminum is 2. Galvanized Steel topcoated with organic coatings. Flame-sprayed Galvanized steel ship surfaces ex cept for bilges and aluminum is also being introduced to replace the ballast tanks are painted with one coat of Formula 84 silicone-aluminum heat-resisting coatings (TT-P-28 or 150followed by 1or 2coats of the appropriate topand DOO-P-24555) currently specified for heated coat. In bilges and ballast tank s, one coat of Formula ferrous sheet metal piping, fittings, and valves that 150,one coat of Formula 15 1, and one coat of Formula have a very limited service life (about one year). 156 are applied. Table 6 lists coatings recommended for such services. TABLE 6 COATINGS FOR MACHINERY AND PIPING SURFACE COATINGS IN SYSTEM AND NUMBER OF COATS Ferrous sheet metal Formula 84 (1); Formula 111 (1) (exterior or interior; heated) Formula 84 (1); Approved coating to match surroundings (2) Ferrous sheet metal TT-P-28 (1) (exterior or interior; heated) DOD-P-24555(1) Ferrous machinery TT-P-28 (exterior; heated) DOD-P-24555(2)
Machinery gage boards Formula 84 (1); Formula 111 (2) (including gages and clocks) Piping, valves, and Formula 84 (1); Approved finish coat (2) fitti ngsa aFinish is to match surroundings or color coded for content identification. If insulated, insulation is coated to match surroundings. 523 --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*24-0 93 m 8627940 0003973 T75 m TABLE 7 COATING SYSTEMS FOR ALUMINUM SURFACES SHIP AREAS COATING IN SYSTEM AND NUMBER OF COATS Boottopping and hull NAVSEA-approved commercial system with noncopper antifoulin g coating Exterior topside Formula 150 (1); Formula 151 (1); MIL-E-24635 (2)a Habitability areas Formula 84 or 84D (1); Formula 124 (2) Wet spacesb Formula 150 (1); Formula 152 (2) Bilges and seawater Formula 150 (1); Formula 151 (1); Formula 152 (1) ballast and fuel tanksc aFor decks, MIL-E-24635gray deck or MIL-D-23003,Type IIor MIL-D-24483nonslip coatings are substituted for TT-E-490. bSculleries, washrooms, showers, etc. On fuel tanks, the bottom and walls up to 6 in. are coated. 3. Aluminum before applying adesired finish or antifouling paint of The coating systems used on aluminum alloy ship Table 3. Exterior reinforced pla stic laminate is surfaces are listed in Table 7. In March 1974, the repaired and recoated as desc ribed in MIL-R-19907. Naval Ship Engineering Center issued a pocket- Interior reinforced plastic lamin ate receives two coats size manual ( Ship Hull Structure Maintenance and of Formula 124. Repair ) to provide additional practical information 6. Miscellaneous items on topside coating. It includes specific recom-For more information on types of coatings, consult mendations related to aluminum super-structures, Naval Ships Technical Manual, C hapter 631. such as dissimilar metal problems, surface preparation, aluminum flame spray techniques, coating D. SAFETY PRACTICES materials, sealants, and application methods. Metal The Navy safety procedures r eflect the latest commercontaining paints should not be used on aluminum. cial practices in the protecti on of the health of workers 4. Wood and the physical integrity of the structures being coated. Wood that is to be varnished is first filled with a The health aspects are overs een by the Navy s Bureau of filler (paste). Exterior painted wood is treated as Medicine and Surgery, and th e structural aspects by the shown in Table 8. Interior wood is either covered ship operational organization and the facilities command. with one coat of approved aluminum paint and two The controlling documents are a ll cited and discussed in Naval coats of approved finish paint to match the sur- ShipsTechnical Manual, Chapter
631 (Preservation of Ships roundings or stained with commercially available stain in Service). and coated with three coats of Formula 80 varnish. IV. TRENDS 5. Plastic Changes in painting practices for Navy ships will Plastic surfaces to be painted are treated with be directed toward more durable, longer lasting sysFormula 150. Additional primer coats are not required tems that will require les s maintenance and permit Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 524
SSPC CHAPTER*24-0 93 W 8627740 0003972 901 W TABLE 8 COATING SYSTEMS FOR EXTERIOR WOOD SHIP AREA COATINGS IN SYSTEM AND NUMBER OF COATS Hull from keel to start of boottopping Formula 150 (1); Formula 121 (2) Boottopping area Formula 150 (1); Formula 129 (2) or MIL-P-24647system for 5-7 year life. Vertical surfaces above boottopping Approved aluminum painta (l), MIL-E-24635(2) Horizontal surfaces Approved aluminum painta (2); Formula 20 (2) waterways Masts and spars Approved aluminum painta (2); Formula 20 (2) aPrepared by mixing 2 Ib. of TT-P-320,Type II,Class 2 aluminum paste into 1 gal. of Formula 80 varnish. longer periods between dry docking . Greatly improved V. SUMMARY fouling -control (5 years or more) with safe materials is The severe environment al forces encountered by Navy sought through such systems as renewable (self-polishing) ships require tough, d urable, and often specialized coatand controlled-release antifouling paints. Antifouling ings. The presently used systems described in this chapter rubber, plastics and greases will also be considered for have provided satisfact ory protection in a cost effective selected surfaces. Smooth hull coatings that also perform manner. Improved paint ing materials and procedures are other necessary requirements may impart a microsmooth sur- sought, however, to c ontrol spiraling maintenance costs, face texture with minimum drag. permit improved operational capabilities, and co nform to The Navy paints of the future must meet all environ- governmental regulations re lated to health, safety and mental, health, and safety requirements of federal and environmental concerns. T he research and development local governments. Currently, the State of California is required to meet these and future needs will berestricting the use of volatile organic compounds (VOC) in challenging. marine coatings, and other states will follow this action. Work is now being done by coating suppliers and the Navy to develop water borne and high solids marine coatings that meet these and other anticipated restrictions.
The Navy Environmental Health Center has recommendedlo other materials or procedures be substituted for lead or chromium pigments in metal primers for corrosion control. While substitute pigments are available,li their long-term effectiveness in marine primers has yet to be established. However, current navy policy is to restrict lead and chromate content to 0.005°/o. Environmental restrictions have already been placed on abrasive blasting and chemical cleaning procedures of ship surfaces for painting. New, acceptable cleaning procedures must be developed, and the primer materials applied must be compatible with these surfaces. 525 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS--`,,,,`-`-`,,`,,`,`,,`---
TABLE 9 COATINGS FOR MISCELLANEOUS ITEMS ITEM Anchor chain, anchor and securing chains Antenna insulator fittings Bilge keels (Internal surfaces) Catapult launching valves and exhaust tees; lagging on Exterior canvas and life floats (rafts) Fire plugs and foam discharge valves Furniture and joiner doors Helmets Inaccessible surfaces (galvanized and nonferrous) Inaccessible surfaces (ungalvanized steel) Messenger buoys Propellers (composition or corrosion-resistant) Rings buoys Rudders and skegs (internal surfaces) Shafting, in board Shafting, outboard Shaft tube (internal) Smoke pipes Sonar domes: Rubber Plastic and HY80 steel Stainless steel Structure behind insulation Ventilation ducts and trunks (ungalvanized steel)
Turntable pits (LSTs) COATING SYSTEM AND NUMBER OF COATS TT-V-51 MI L-P-24380 Formula 150 (2) MIL-C-16173, Grade 1 rust preventive DOD-P-23236, epoxy coating TT-P-595 gray canvas, preservative Formula 150 (1); MIL-E-24635 color to match; Formula 40 (1) As specified in MIL-F-90; MIL-E-24635 (haze grey) Unpainted 1 coat inorganic zinc or MIL-C-11796, Class 1 or A, or 2 coats Formula 150 Formula 150 (2); TT-E-490 international Orange (2) or MIL-E-24635 Clean and polish bright Orange plastic compound (3) MIL-C-l6173D, Grade 1 or 3 rust preventive Formula 150; Formula 151 (1) MIL-R-15058 or resin-glass cloth coating and antifouling Formula 150 (1); Formula 151; Formula 152 TT-P-28 (2) M IL-P-24647 NAVSEA-approved epoxy or MIL-P-24441 system for hulls (see Table 2); Formula Formula Formula Formula
121 150 150 150
(2) or unpainted (1); Formula 151 (1) (1); 151 (1); 152 (1) or
inorganic zinc; Formula 150 (mist coat); 151 (1); 152 (1) or DOD CTD 2138 526 DOD-P-23236 (2 or 3 coats) --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERk24.0 93 W 8627940 0003974 784 = ACKNOWLEDGEMENT RE FER ENC ES The authors and editors gratefully acknowledge the active participation of the following in the review process for this chapter: Leon Birnbaum, David Bloodgood, Theodore Dowd, Ben Fultz, Dan Gelfer, Jack Hickey, Edward Hobaica, Hing Dear, AI Hohman, Howard Milam, Neil M. Miller, Hugh E. Peck, Walt Radut, Alfred E. Smith, William Wallace. BIOGRAPHY Stephen D. Rodgers has been employed in the paint field for 35 years. Mr. Rodgers specializes in protective finishes and the related surface preparation technology for the marine industry. Mr. Rodgers' experience includes 22 years in paint RDT&E with the Navy, 7 years as the Head of the Corrosion control Branch of the Naval Sea Systems Command, with responsibilities for corrosion mitigation by design, cathodic protection and protective finishes. As a Senior engineer, Mr. Rodgers has provided consulting engineering services in private industry for 5 years. Mr. Rodgers is a registered professional Corrosion Engineer in the State of California and a Nuclear Safety Related Coating Engineer (National Board of Registration for Nuclear Safety Related Coating Engineers and Specialists). Mr. Rodgers has 8 patents and 45 publications. John J. Tock has been employed by the U. S. Navy since 1971, initially working at the Naval Ship Engineering Center. He is currently employed as the Senior Materials Engineer of the Corrosion Control Division of the Materials Engineering Group, Naval Sea Systems Command, Washington, DC. Mr. Tock has a Bachelor's degree in Zoology from the Pennsylvania State University (1965) and a Bachelor's degree in Chemical Engineering from the University of Florida (1971). He is and has been primarily responsible for the corrosion control of Navy ships through the application of protective coatings. Mr. Tock specifies coating systems for shipboard applications based on expected performance and environmental compliance. He is responsible for writing and updating material specifications, qualifying and approving materials, writing Naval Technical Manuals and developing ship specifications for coating systems. Mr. Tock has been involved in efforts to develop and evaluate water based paints, fire resistant coatings, anticorrosive primers and intumescent fire protective coatings. A portrait and biographical sketch of Richard W. Drisko appear at the end of the chapter on Government Painting Procedures. 1. Naval Ship Systems Command. NAVSHIPS Technical Manual, Chapter 631. Preservation of Ships in Service (Paints and Cathodic Protection). Washington, January 1970.
Washington, January 1970. 2. C.G. Munger, Practical Aspects of Coating Repair, Materials Performance, vol. 19, no. 2, pp. 46-52, February 1980. 3. Civil Engineering Laboratory. Techdata Sheet 80-06: Repair of Exterior Protective Coatings. Port Hueneme, CA, July 1980. 4. Civil Engineering Laboratory. Techdata Sheet 79-04: Surface Preparation for Coatings. Port Hueneme, CA, April 1979. 5. Civil Engineering Laboratory. Techdata Sheet 77-09R: Coating Interiors of Steel Potable Water Tanks. Port Hueneme, CA, July 1979. 6. Naval Ship Systems Command. NAVSHIPS Notice 9190: Navy Polyamide-Epoxy Systems for Interior and Exterior Ship Surfaces. Naval Ship Systems Command, Washington, June 1972. 7. Civil Engineering Laboratory. Techdata Sheet 77-19: Incompatibility of Paints. Port Hueneme, CA, November 1977. 8. H.H. Vanderbilt and R.A. Sulit. Thermal Spray Technology Research, Development, Test, and Evaluation and Service Applications in the US. Navy, Tri-Service Conference on Corrosion. US. Air Force Academy, Colorado, November 1980. 9. H.S. Preiser and S.D. Rodgers. "Coatings -the Promise and Challenge for Enhanced Naval Performance," chapter in Corrosion Control by Coatings, H. Leidherser, Jr. (editor). Princeton, NJ, Science Press, 1979. 10. Navy Environmental Health Center letter 41AIJRB:crh 6260.1G serial 9-130 of May 14, 1979. 11. J.D. Keane, J.A. Bruno and R.E.F. Weaver. Performance of Alternative Coatings in the Environment (PACE), Steel Structures Painting Journal. Pittsburgh, PA, August 20, 1979. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 527
SSPC CHAPTER*25.0 93 W 8627940 0003975 bLO = CHAPTER 25 DESIGN OF CORROSION-SAFE STRUCTURES by V. Roger Pludek I. INTRODUCTION The rising cost of labor and energy and the scarcity of raw materials make conservation a necessity today, particularly with regard to steel structures that cannot easily be dismantled and replaced. When they suffer unchecked corrosion, steel structures fail, and their failure has a profound influence on the economic and social welfare of all people. As more and more corrosive effluent is being emitted, and the corrosiveness of atmosphere, soil and natural waters increases, the negative effect on steel structures is compounded. The effects of poor design can seldom, if ever, be corrected by coatings. Preventive control, beginning with design, offers the best answer to the difficult problem of corrosion. A majority of service failures caused by corrosion would not occur if proper precautions were taken at the design stage. All designers, engineers and technical workers engaged in a construction project must work together to create an integrated corrosion control system." II. REQUIREMENT OF CORROSION EXPERTISE There is a great deal of knowledge about corrosion that is not being translated duly into practice. Much better effort to improve communication and cooperation between individual specialists, in management, purchasing, designing, production, and installation should be made. Rather than learning by trial and error, an exceedingly expensive process, the designer and all other workers in design should be aware of the best sources of advice about corrosion control. Scientists, engineers, technologists, technical and managerial workers must be educated about corrosion and its control to conserve materials and prevent failures due to environmental or bad design inf luences. 111. MATERIALS Among the most fundamental design activities, the appreciation and evaluation of materials of construction take the lead. Only thus can unnecessary work be avoided and serious mistakes prevented. 'A full account of Mr. Pludek's corrosion control work exists in his book, Design and Corrosion Control, Macmillan, 1977. Another excellent account of the subject is given in National Association of Corrosion Engineers Standard RP-01-78.
All materials of construction and preservation must be appreciated and evaluated, not only individually but also en masse, in complete units or components. Not only the structural steel is considered, but also the necessary weld metal, fasteners, plastics, separation materials, sealants, coatings, etc., all together in their rational relationship. Good design must create a unified, reliable and safe functional complex. The main purpose of such materials association is to fulfill its prime requirement of functional utility and also the requirements of safety and survival stability. It is not possible to separate the functional appreciation of materials from its corrosion engineering counterpart. Even high quality materials can become casualties as a result of poor design and poor corrosion control. In general, the prime requirement of integrated corrosion control is to provide a parallel system of appreciation, evaluation, and selection of materials, both for their functional suitability and for their ability to sustain this positive function for the required length of time at an economic cost. Requirements for structural material include the following: 1. Select materials for their functional suitability and ability to maintain their function safely for an economical period of time at a reasonable cost. 2. Specify accurately and test on delivery for conformance with specif ¡cations. 3. Select more corrosion-resistant materials for more critical structural members or where relatively high fabrication costs are involved. 4. Compromise where necessary; trade-off mechanical advantages for corrosion protection. 5. Do not specify more expensive materials than absolutely necessary, except for long-term economy or preservation of the safety of personnel or product. 6. Do not mix short-life materials with long-life materials in sub-assemblies that cannot be repaired. 7. Evaluate for suitability not only the structural members but also their basic treatments (chromate passivation, galvanizing, etc.). 8. Do not use flammable materials in critical places. 9. Do not use materials producing corrosive or toxic fumes for steel structures subject to fire hazard. 10. Select metals of construction in accordance with a comprehensive selection list that takes into account both Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 528
SSPC CHAPTER*25-0 93 8b27940 0003776 557 function and corrosion controls. Metals should be selected on the basis of their physical properties, design limitations, fabrication character, and economic utility. In each of these areas function and corrosion control must be considered. IV. COMPATIBILITY A. INTRODUCTION Some designers don t appreciate the total structure as one complete whole with its inherent design character, which transcends its material and elemental boundaries. This badly conceived inter-relation among the materials within the structure can ruin even the best design. All intermaterial parameters must be properly appreciated and evaluated before any final design decision is taken. This evaluation must take into account problems caused by direct contact between dissimilar metals or induced by changes of polarity, by transfer of electrolysis through a medium, by transport of metallic particles in the environment, by stray currents or by any other adverse effect arising from the proximity of incompatible materials. B. DISSIMILAR METALS 1. Faying surfaces of dissimilar metals should be designed for effective separation. Separation materials of suitable shape, thickness, consistency and mode of application should be used (gaskets, butyl tape, sealant, etc.). 2. Insulation must be sufficiently thick and cover sufficient area of bimetallic joints to prevent conductive medium from by-passing it and reaching the faying surfaces of the connection. 3. Crevices between structural metals and plastics may support an increased rate of corrosion (crevice and chemical attack). Test their compatibility. 4. Input of large cathodic areas of metal with small anodic areas must be prevented in design of structures exposed to corrosive environments. 5. Key structural units, especially if these are smaller than adjoining units, should be made in more noble metals (Figure 1). 6. Less noble structural members in bimetallic structures should be made larger or in a thicker metal form MONEL -I to allow for corrosion waste and sacrificial protection of cathodic members. 7. Design must provide for an easy replacement of anodic structural units. 8. Laminar composites may be used in marine environments for bimetal composite structures: noble metal clads, sacrificial metal clads, corrosion barriers, complex
multilayers (Figure 2). Y-I i z m U SEA WATER FIGURE 2 9. Clad metals can be used as transition joints in structures. 10. Edges of clad metals in corrosive environments must be well protected (Figure 3). SEALANT OR LEADS FIGURE 3 11. Proper structural design must conduct moisture away from bimetallic joints. 12. Dissimilar metals connected in a couple must not be embedded in any porous environment or material without effective protection (insulation, concrete, soil, etc.). 13. Structures embedded in porous environments and in proximity of other structures having dissimilar metals will suffer galvanic corrosion unless adequately protected. 14. The designer must specify against the use of backfill containing rough, coarse carbon cinders and ashes around buried structures. Burying structures in old household and industrial dumping grounds must be discouraged. 15. If a dielectric separation is not possible, fasteners must be coated with anti-corrosive primer and their exposed ends encapsulated. 16. An application of moisture-proof coating or --`,,,,`-`-`,,`,,`,`,,`--organic sealant over a bimetallic connection should be considered a measure of lesser effectiveness. 529 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS FIGURE 1
SSPC CHAPTER+25=0 93 6b27940 0003977 493 C.COATINGS, FILMS AND TREATMENTS 1. The component parts of a bimetallic joint should be cleaned, pretreated and primed prior to assembly in she1 t ered conditions. 2. Relative proportion of discontinuities in the protective coating of a bimetallic joint between its anodic and cathodic element affects its corrosivity. 3. Painting does not provide dielectric separation against galvanic corrosion. 4. A metallic coating used on the bimetallic connection overall must be less noble than either of the metals used in the connection (Figure 4). - ANODIC CATHODIC CORRODES ZINC ALUMINUM CAOMIUM TIN CHROMIUM NICKEL LEAD COPPER METALS STAINLESS STEEL SILVER FIGURE 4 5. Coatings containing metals or their active compounds must not be applied on top of coatings containing zinc or aluminum on structures to be submerged in sea water. 6. The designer must consider the possibility of a change of polarity of metallic coatings on bimetallic connections under any probable environmental conditions. 7. Partially cured or under-cured organic materials and coatings can be a source of corrosion. 8. At temperatures above 150°F (66°C) the possibility of emission of hydrochloric acid should be considered for certain vinyl paints. 9. Zinc- or cadmium-plated components should not be used in heated compartments containing phenolics, varnishes, unstable insulating materials or encapsulants. 10. Galvanized fasteners should not be used on stainless steel structures at high temperatures. D. STRAY CURRENTS 1. Avoid passage of electric current between structures and environment as described in the chapter on cathodic protection (HVDC, other DC and AC stray currents; electric traction, welding plants, power undertakings and cathodic protection stray currents). 2. Insulating couplings can be used to separate metallic components for control of stray currents. 3. In a conductive environment however, surface films can negate the effect of an increase in the length of the insulating couplings, and result in external current jump. 4. Avoid critical leakage of stray current by increas-
ing the earth contact resistance of structures, insulating structures from earth, applying insulating coatings or placing structures in conduits. 5. Protecting structures with a cathodic protection system can be effective (see chapter on that subject). V. GEOMETRY With appropriate geometry in the design of a structure, the designer can do much to control corrosion. 1. Structural design is an integral part of a structural member and its function. 2. Structural design geometry should be simple, sleek and streamlined. 3. Design forms should assist in preventing geometry-dependent corrosion (crevice, impingement, galvanic, electrolysis, etc.). 4. The designer should select shapes, forms or their combinations whose fabrication, jointing and treatment does not worsen the corrosion hazard. 5. The design geometry must support all or most of the selective corrosion preventive measures (initially and within lifetime). 6. Corrosion-prone areas must be accessible. 7. Size and shape of structural members must conform to the method and technique of the selected protection (e.g. for galvanizing by single, double dipping; progressive galvanizing). 8. Prevent entrapment of liquids and absorbent solids within the structural assembly. Provide adequate drainage (Figure 5). I ENTRAPMEUT COTITS. WELD DRAIN HOLE BETTER BEST BAD BETTER BEST FIGURE 5 9. Good design of the geometry of structures should aid in preventing condensation and accumulation of corrosive media in joints and other spaces. 10. The designer must avoid laps and crevices in structural design, if possible. If these are unavoidable, the laps must face downwards on exposed surfaces and all such connections must be well sealed (Figures 6 and 7). Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 530
RAIN \ \ \\ [SHEET METAL /+ SPOT WELD Iu BAD FIGURE 6 FILLET SIDE SEALING COMPOUND A FIGURE 7 11. Steel reinforcement must be embedded in sufficient thickness of concrete to suit the severity of environment. Minimum thickness of concrete for mild conditions is inch (1.3 cm); for corrosive conditions, 2 inches (5 cm); and for hydraulic structures, 2-3 inches (5-8 cm). Reinforcing steel can be bare, clean metal; coated metal where shallower embedment is indicated; powder epoxy coated where concrete is exposed to sea water or road salt; or even combined metal coating and powder epoxy coating in concrete exposed to exceptionally severe environments. 12. The designer should not use back-to-back angles that are bolted or intermittently welded (Figure 8). BAD BETTER BEST FIGURE 8 13. The designer must avoid designing structural forms that contain horizontal runs of welding, especially if these are not accessible for cleaning, grinding or blasting. VI. GEOMETRY FOR COATING 1. Structural surfaces to be joined must be accessible for easy cleaning, coating and maintenance (Figure 9). BACK OF FLANGE POOR BETTER FIGURE 9 2. The design layout of structures must offer easy initial preservation and repainting (Figure IO). K PIPES rPIPES7 ACCESS HOLE BAD BETTER
FIGURE 10 3. Structural steel for galvanizing must be designed without extremes in weight and cross-section. It must be reinforced and braced, if necessary, for prevention of warpage and distortion (Figure 11). BRACING NNEL FIGURE 11 4. Joined structural members prepared for galvanizing must be fully enclosed by sound, poreless and continuous welds (does not apply to open ends of hollow section members). 5. The geometry of structural steel for metal spray deposition must permit efficient blast cleaning overall as well as complete coverage of surface with the spraydeposited metal. 6. Complex structural shapes diminish the effectiveness of paint applied over them. Protruding fasteners should be avoided. Corners should be well rounded to aid efficiency of the painting films (Figures 12 and 13). Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 531
SSPC CHAPTER*25.0 93 = 8b27940 0003979 2bb AVOID PREFERRED damage, corrosion fatigue and fretting corrosion, due to the mode of their attack on the mechanical strength of structural metals, justify separate attention. --@-1-1 The insidious attack of these four types of corrosion occurs largely inside of the structural metals or on the hidden interfaces, and therefore it cannot be detected in time I to obviate the failure by a suitable remedy. It remains thus in the hands of the combined design team to prevent or delay the risk of the crisis by their able preventive work. Generally speaking, none of the metals or alloys used in construction can be excluded from these hazards. Among the most susceptible alloys are those normally selected for today s highly stress-loaded and critical applications. A cooperative and parallel appreciation of function and corrosion is a sound policy. A. MECHANICAL DESIGN REQUIREMENTS Sound design is based on the comprehensive consideration of materials, stress levels, environments, service conditions variations and the reliable design life of the structure. 1. The designer must avoid specifying materials susceptible to stress corrosion cracking or corrosion fatigue for highly loaded and critical structures in a hazardous environment -present or expected, of local or FIGURE 12 distant origin. AVOID PREFERRED 2. Hydrogen embrittlement must be avoided during cleaning, welding, treatment, cathodic protection and operat ion. 3. Irregularities of surface on structural members (notches, grooves, screw threads, changes of section, etc.) weaken their load bearing capacity. 4. Intermittent wetting and drying of the critical structural members should be prevented. 5. Good structural design must provide for exact assembly of individual structural members without undue stressing; joining without misalignment is in the interest of good corrosion control. 6. In structures subject to stress loading, simple welded joints should be preferred to lap welding, spot welding, riveting or bolting. 7. Incomplete or intermittent welds must be avoided in stressed structures (Figure 14). AVOID PREFERRED FIGURE 13
VIL MECHANICS sion. Thus, all Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS--`,,,,`-`-`,,`,,`,`,,`--Mechanical integrity of any structural metal can be reduced or terminated by any of the known types of corrorelevant types of corrosion should be carefully considered in the design and appropriate protective measures taken. Stress corrosion cracking, hydrogen FIGURE 14 532
SSPC CHAPTER*25-0 93 86279LIO 0003980 T88 B. SURFACE TREATMENT REQUIREMENTS 1. The designer must specify a uniform, and in critical areas, the top grade cleaning of surfaces. Ali surface layers contaminated in storage, fabrication, and heat treatment must be cleaned. 2. High strength steels should be cleaned preferably by blast cleaning methods. 3. Formation of stress raisers through careless fabrication methods (deep surface finish marks) must be prevented. 4. To improve on the fatigue strength of structural steel, specify shot peening to create compressive residual stresses. 5. The designer must not specify surface finishes that may produce tensile stresses in the structural materials or cause hydrogen embrittiement. 6. Conversion coatings may occasionally help in reducing the probability of the initiation of the stress corrosion cracking. 7. An increase of the coefficient of friction in structural joints can reduce the probablity of fretting corrosion. 8. Only those coatings approved by the American Institute of Steel Construction (zinc-rich, etc.) should be used in high-strength frictional bolted joints. 9. Application of any efficient and compatible painting system should assist in reducing the chance of an initiation of stress corrosion cracking or corrosion fatigue. 10. Coating structural surfaces with organic coatings after metallizing improves the resistance to stress corrosion cracking and the fatigue strength. 11. Coating structures with metallic and organic coatings where a possibility of hydrogen embrittlement arises can be recommended only under the condition that the structures are not made in high strength steel, that they are not under stress loading and that the coating does not contain reactive zinc or corrosive chemicals. 12. Wide radii bends for structural steel to be galvanized reduce the local stress concentration. 13. Welds must be stress relieved before galvanizing. VIII. SURFACE CONFIGURATION Corrosion usually originates at the surface. There are inherent characteristics of surfaces that may significantly change or complement the conclusions arising from the considerations of the geometry. Among the moot points in appreciation of the surfaces are the optimal configuration of these surfaces, their cleanliness, preparation, texture and their electrical and electrochemical stability in the given and expected environmental conditions. A. SURFACE DESIGN REQUIREMENTS 1. The surfaces should be simple, compact, smooth, well shaped, optimally positioned and angled. The surfaces should not be rough or devised for entrapment and retention of corrosive substances. The surfaces should
render full support to corrosion protection whether this is intrinsic to the design proper or extraneous. 2. Rounded contours and corners provide the best continuity of surface (Figure 15). FIGURE 15 3. Multiform or random combination of surface planes complicates the corrosion control of structures (Figure 16). FIGURE 16 4. Critical surfaces of structures must be visible and accessi ble. 5. Well-designed structures should show overall continuity of profile flow as well as detail continuity of surfaces. The detail can be improved by reduction of crevices, grooves, faying surfaces and by improvement of their drainability. Further, it can be improved by complete sealing of surface discontinuities. 6. The unity of multishape surfaces of structural members can be improved by overall sealing or tape wrapping. (Note: The metal must be coated with inhibitive paint prior to sealing.) --`,,,,`-`-`,,`,,`,`,,`--533 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERm2-5-0 93 m 8b1279400003981 914 m 7. No part of a metal surface (painted or unpainted) within the structural entity can be allowed to have an adverse corrosion effect on other surfaces of the design conglomerate. All surfaces must be electrically stable in the given medium under all possible environmental conditions. 8. Electrical stability is to be supported by beneficial sizing of compatible metal surfaces within the structural assembly and by efficient surface coating of both anodic and cathodic surfaces. 9. Excessive roughness of structural metal surfaces should be leveled out by grinding down protrusions and filling in hollows with fillers. 10. Haphazard application of insulation or surface coverings can cause adverse corrosive conditions (chemical effect, thermal or electrochemical imbalance). 11. The designer should provide for reduction of surface damage of materials in storage, fabrication or erection. 12. The relative position of individual structural members and their shape must not be the cause of a significant corrosion within the structure. 13. Structural welds must be technically sound, welllaid and clean. Flux, metal spatter, welding residue, burrs and other weld defects must be removed prior to overall surface cleaning (Figure 17). ROUGH FDI ATTSD / SURFACE BAD BETTER BEST FIGURE 17 14. The surfaces of structural steel for pickling should provide homogenous continuity (no crevices, ledges, recesses, etc.). 15. Crevices in structural steel for galvanizing shouJd be completely enclosed by sound and complete welding. B. SURFACE PREPARATION 1. Exposed surfaces should be protected in storage, fabrication, assembly and in use by temporary or permanent protective measures. 2. The texture of surface not only influences the mechanical efficiency of structures, but it has also an effect on the results obtained from the corrosion control. This applies whether the structures remain bare or a coating is applied. 3. A smooth surface finish avoids sharp irregularities that are potential source of fatigue cracks and corrosion. 4. The designer should evaluate which texture of surface provides the best base for the protection and specify this in the design. He should stipulate whether the structural material should remain raw as is, untreated as fabricated, or whether it should be blast cleaned, roughened, anodized, passivated, metallized, surfaced, sealed, prefabrication-treated or painted. The texture of the
substrate and the coating finish are relevant. 5. Surface conditions must be reconciled with surface treatments to follow and their application techniques. 6. Oil, grease, salt deposits and organic or inorganic contaminants must be removed before the specified surface cleaning. 7. Only the anodic cleaning of high-strength, lowalloy structural steel is permitted. Cathodic cleaning supports corrosion. 8. Flame cleaning of new structural steel does not remove mill scale. 9. The preferred method of cleaning structural metals is abrasive blasting. The blasting profile should fit the thickness, consistency, smoothness and adhesion of the specified coating. IX. PROTECTION A. COATINGS Protective coatings alone can not maintain a poorly designed structure in a usable state. The true function of protection is to retain and improve the effectiveness of those anti-corrosion properties that have been built into the design of the structure itself. These intrinsic corrosioncontrol attributes of the designed structures and the extrinsic corrosion protection are complementary to each other. Their use will depend largely on their economic advantages and engineering value. The corrosion protection should be made up to suit the whole structural entity. Piecemeal protection of in dividual structural members, sub-assemblies or units is shortsighted and illogical. For the best protection, the geometry of the structures, location and relative position of the critical parts of the structures, the degree of application difficulties, and the reciprocal effectiveness of the protective measures must be reconciled. The new, sophisticated, protective measures must not be incorporated into the design haphazardly. The design of the structures must suit their use. The less the surfaces are accessible, the better must be their protection. The designer must not be rigid in his attitude toward protection. Heshould specify only the necessary, safe and economically feasible methods of protection. He should give preference to methods and techniques that can be utilized by skilled personnel under controlled conditions. Local climatic conditions on the production site and subsequent ports of call, including the erection site, will have a considerable influence on the eventual selection of the protective measures. Difficulties in obtaining skilled labor could critically affect the reliability and safety of the adopted protective measures. It is usually preferable, therefore, to select materials, methods or techniques that will give the best possible results and that can be readily secured in the operational locality of the structures. Basically, the corrosion protection of structures con-
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SSPC CHAPTER*25.0 93 = 8627740 0003982 850 sists of the protective measures that provide the separation of surfaces from the environments, those that provide cathodic protection or anodic polarization and those that cater to the adjustment of the environment. The available methods can be used singly, individually, or they can be combined to suit the requirements. Usually, the sum of two or more protective measures can provide a much better degree of protection than the straight total of their individual effects. B. PROTECTION DESIGN REQUIREMENTS 1. The separation of materials from environments is provided by application of metallic coatings, by painting, by coating with plastics, ceramics or glass, by lining, sealing, enveloping, insulating, wrapping with tapes and by applying temporary protectives (oils, greases, removable plastics, etc.). Each involves a change of the surface composition and in most cases a change in dimension and weight of the structural element. 2. The most effective separation of surface requires an exclusion of air and moisture or other corrosive media from the protected substrate. 3. To accomplish this, the designer may call for various forms of protective systems. 4. Metal coating processes can be classified as anodic and cathodic. The anodic coatings protect the metals (steels, etc.) even if they are porous or damaged. The cathodic coatings protect the substrate by their superior resistance to corrosive environment; once damaged these will accelerate the corrosion of the substrate. The anodic metallic coatings are mostly used for protection of structures. 5. Preconstruction primers must be considered in structural engineering as an important and integral part of the whole preservation system. Their effectiveness must be maintained during the whole production and erection program. 6. The main purpose of a sealer or topcoat is to extend the utility and life of the anti-corrosive compositions (primers, metallic coatings, etc.) in an efficient state for an economic period of time. 7. A good seale: provides good adhesion to the anticorrosive primer (with or without a tie coat); low permeability to the prevalent corrosive media; high film thickness; good chemical resistance; good abrasion resistance; and good climatic resistance. 8. Protective coatings should be used only if they are more economical than corrosion-resistant materials. 9. Structural materials protected by coatings must be stored, handled, and maintained with due attention to the maintenance of the coating integrity. Prevention of physical damage, contamination and deterioration should be duly planned in design. 10. The designer must review, before deciding on the coating system and its individual components, all problems and limitations of individual applicators, the climatic
and working conditions on the sites of application, the properties of material components of the system in relation to procedures and schedules, suitability of application methods for the structural geometry selected, the choice of techniques allowing the maximum use of money-saving practices, reduction of complexity in reducing the number of materials and color schemes and, lastly, the expected maintenance. 11. The designer must plan and specify coating of the faying surfaces of structures prior to the mating. 12. The complete painting of surfaces that become inaccessible on assembly must be specified in the drawings to be completed prior to the assembly. 13. Cutting and welding of coated structural members must be minimized. 14. To obtain best results from protective coatings the designer must provide optimum geometry for cleaning, application, inspection and maintenance; optimum knowledge of materials and methods of protection; reputable and approved contractors and applicators; optimum and thorough inspection methods; and earliest repair of local breakdowns. 15. The designer must appreciate, when deciding on cathodic protection of structures, the compatibility of cathodic and coating protection. 16. The corrosion of structures can be considerably reduced by a suitable change of environment by one or several of the following methods: ventilation, dehumidification, air conditioning, cleansing, filtration, separation, reduction of acid strength, reduction of the peak metal temperature and the use of inhibitors in surrounding media. 17. The change of environment by ventilation must satisfy the habitability requirements, control the corrosiveness of atmosphere, direct and distribute air flows, prevent the access of corrosives to vital structures, reduce condensation on vital surfaces, keep relative humidity below 6O%, and accelerate the drying of surfaces. 18. The designer must avoid using insulation, materials, sealants, etc. that contain soluble salts or acids or emit corrosive vapors causing the corrosion of structural materials. X. MAINTAINABILITY A. INTRODUCTION Structures may fail as a result of catastrophic failures of individual structural components or by a progressive degradation and deterioration of performance. Each of these failures can be attributed to factors of mechanics and corrosion. The structures must be so designed that their maintenance can be undertaken as a regular and economically feasible activity. B. DESIGN REQUIREMENTS FOR MAINTAI NABILITY 1. The designed structures must be open to observaCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from
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SSPC CHAPTER*25=0 93 8627940 0003983 797 tion and inspection for reliability and safety. 2. As far as possible all corrosion-control precautions must be repeatable and reparable . 3. The designer should evaluate whether it is more economical to replace the whole structure or its components instead of repetitive maintenance. 4. The design of structures must be based on the optimal length of corrosion prevention. 5. A planned maintenance program must not interfere with the utility of the structure. 6. The design of structures must provide for the safety of all maintenance personnel while performing their various tasks. 7. Critical members of the structures and those subject to accelerated corrosion must not be located in inaccessible places. 8. Structural materials and their protective systems should be selected to provide an economic period of anticorrosion resistance. 9. Accessibility for maintenance of structures is necessary (Figure 18). STRUCTURE i BAD FIGURE 18 10. Obstructions to the maintenance of structures should be avoided. 11. The designer must provide sufficient access space behind any auxiliary structures or equipment standing in the way of the main structures or he should, if possible, incorporate such elements into the main structures. 12. Where blast cleaning of structures in situ will be required, all precautions must be taken in design to protect other structures and equipment from damage by abrasives or dust and from ingress of abrasive particles into vital frictional spaces. 13. The local and general geometry of the structures must be designed for repetitive cleaning and preservation. Where this is not possible, such areas should be fully enclosed and airtight. XI. ECONOMICS A. INTRODUCTION Corrosion causes loss of capital assets and business profits. Corrosion control, therefore, can justify itself in economic terms, as well as in terms of safety, health and pollution control. But the most advanced and sophisticated corrosion control parameters and technology may not be the most economical way of obtaining economy and reliability of the structure.
B. ECONOMIC DESIGN REQUIREMENTS Clear and comprehensive specifications are imperative for an accurate economic evaluation; accurate description of the job; instructions in exact technical terms or references to standards; production and application methods accurately described (including tools and auxiliary equipment); corrosion-control systems and their conditions of applications accurately stipulated; safety requirements stated; and materials and product movements, housekeeping, workmanship, weather limitations, production flow, assembly, decontamination and ventilation procedures, inspection procedures, etc., comprehensively descri bed. The designer s task is to obtain the desired degree of corrosion control at the lowest cost. The designer must appreciate if a timely replacement of the deteriorated structural material is more beneficial than high-cost corrosion control precautions. The service life of structural materials is based on wasteage limits in a given environment, critical strength of structural materials, renewal periods of materials in particular locations, distribution of materials among structural members or groupings, material repairs of structures and possible benefits of corrosion. In painting jobs the cost of paint itself is a small part of the total compared with the cost of labor (approximately 8O%), scaffolding, plant, ventilation, drying, lighting and cleaning. The cost of structural steel is closely associated with its weight. The cost of fabrication, transport, erection, maintenance and corrosion control increases with the increase of the weight of steel in the structure. Optimum corrosion control leads to a reduction in the weight and cost of structures. This will also reduce the cost of maintenance painting. Simplifying and standardizing structural assemblies also reduces the cost of maintenance. Permanent structures designed for a service life exceeding five years should be protected with the best available coating system, possibly combined with other types of protection. XII. PLAN OF ACTION A. INTRODUCTION The designer must create a plan for corrosion control. The plan of action is the expression of functional corrosion control and investment know-how of the cooperative team and must be written in a language understood by all of them. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 536
SSPC CHAPTER*25=0 93 8b2794O 0003984 623 9 B. REQUIREMENTS A properly designed structure must serve its purpose with an acceptable degree of efficiency. It should last only as long as it is to the advantage of the proprietor or user, and it should be as cheap as possible. It does not need to last forever. Corrosion of the structures must not limit their life to a significantly short period; it must not vitally interrupt their inherent utility; and it must not endanger the life and health of the users. Reasonable precautions should be taken in the plan, but an overdesign should be avoided. Considering the shortages of raw materials facing the world, the recoverable and recycleable materials of the structures should be preserved from total destruction. The constantly changing causes of corrosion from new techniques and new chemicals or processes has to exert a significant influence on the concept of corrosion control planning. Given the shortage of materials and energy, designing obsolescence into any structure by increasing its corrosion potential, by selecting corrosion-prone materials and treating them with negligent protective coating systems, is a serious error. Well-balanced design, integrated function, corrosion control and reasonable cost are sound policies. ACKNOWLEDGEMENT The author and editors gratefully acknowledge the active participation of the following in the review process for this chapter. Frank LaQue, R. Martell, W. Mathay, I.Metil, C. Munger, Melvin Sandler, Eugene Praschan, Melvin Sandler. BIOGRAPHY V.R. Pludek, prior to his retirement, was a corrosion control consultant and proprietor of CORROSION DESIGN CONTROL . He worked on diversified corrosion engineering projects in the U.K., Europe, the Americas, Asia, Africa and Australia for 35 years. He has lectured at the University of Calgary and the Southern Alberta Institute of Technology. Following an undergraduate degree in Europe, he took post graduate studies in the U.K., Canada, and the U.S.A. He is a Fellow of the Institution of Corrosion Science and Technology, London, U.K., and a Corrosion Specialist in the National Association of Corrosion Engineers. He is a member of the American Society for Metals and the Sea Horse Institute, and a
past member of the Canadian Forces Corrosion Prevention Committee, the Canadian Institute of Mining and Metallurgy, and the Electrochemical Society. He has been a corrosion consultant in numerous countries, dealing with corro5,ion control for ships, shipyards, harbors, nuclear energy facilities, food plants, and oil industries. He has several inventions related to corrosion prevention in stacks, aerials, and ship shafts. His many published works include an EnglishlCzech bilingual technical dictionary (1942), and a book on Design and Corrosion Control (1977). --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 537
SSPC CHAPTER*Zb.O 93 8b279qO 0003985 5bT CHAPTER 26.0 SAFETY AND HEALTH IN THE PROTECTIVE COATINGS INDUSTRY by Daniel P. Adley, D.Brian Shuttleworth, Scott Ecoff, Sidney Levinson * and Saul S pindel* I. INTRODUCTION In 1991, 6.3 million U.S. workers became ill or were injured on the job. The total includes both minor discomfort and serious injury. Roughly 8 people in every 100 were affected. Of course, some industries are more dangerous than others. In the painting and paperhanging industry, (no breakdown for painting only is available), the rate was somewhat higher than average -9.9 per hundred, while the injury rate for ship building and repairing was 44.1. By contrast, the rate in the financial industry was only 2.3 per hundred. Workers in the painting industry have to be alert to the possibility of falling from scaffolds, being struck by material falling from above, becoming caught or being electrocuted by the machinery their jobs require. They also need to be aware of occupational illnesses that may result from coating and coating removal operations. Exposure to lead pigments and silica in abrasives can cause serious and even fatal illness. Various solvents affect the nervous system and are known or possible carcinogens. About 2,800 workers were killed on the job in 1991, or 4.3 per 100,000 full-time workers. According to the Bureau of Labor Statistics, although fatalities are not available for the painting industry alone, the incidence is not much higher than this national average. These figures suggest that it is in the best interest of everyone engaged in the painting and coating trades, employers, employees, managers and suppliers, to take health and safety issues quite seriously. A. COST BENEFITS FROM SAFETY Of course no company wants to see workers hurt or killed, but there are also external incentives to safety, particularly the costs of such incidents. Lost worktime decreases worker productivity and lowers morale. Many facility owners and general contractors are prequalifying contractors based on their safety record, and companies cannot afford to present the image of safety being anything but a top priority. Workers compensation and health care costs are becoming more of a drain on all businesses, particularly small companies, and any costs that can be avoided will benefit
Authors of Chapter 5.3, Safety in Paint Application, from the second edition of Volume 1, portions of which have been incorporated into the current chapter. these firms. An effective safety program may help reduce these costs. While the workers compensation system has traditionally precluded a worker suing an employer for workplace injury, various exceptions have been granted by the courts, and more can be expected to follow. For instance, because several different entities are often involved in a paintingjob, an injured worker employed by a contractor may bring suit against a third party such as the specifier. B. ROLE OF OSHA, NIOSH, AND OTHER ORGANIZATIONS AND SAFETY PROFESSIONALS In 1970, Congress passed the Occupational Safety and Health Act, which created the Occupational Safety and Health Administration, a division of the Department of Labor. OSHA is responsible for developing and enforcing mandatory job safety and health standards. OSHA receives assistance from NIOSH, a complementary agency established under the Act as a branch of the Department of Health and Human Services. NIOSH conducts research on safety and health issues, and provides technical assistance to OSHA. Safety and health organizations such as the American Industrial Hygiene Association, the American Conference of Governmental Industrial Hygienists, the American Society of Safety Engineers and the National Safety Council provide information to help managers with many other responsibilities, as well as the health and safety professional, stay abreast of developments in this rapidly changing field. Professional organizations for the painting and coating trades, such as the Steel Structures Painting Council, the International Brotherhood of Painters and Allied Trades, the National Paint and Coatings Association and the Painting and Decorating Contractors of America, can provide information specific to the industry. C. WHY OWNERS AND SPECIFIERS NEED TO BE AWARE OF SAFETY AND HEALTH Owners and specifiers have a stake in ensuring that contractors they employ have the capability to comply with health and safety regulations. Many painting specifications require the successful bidder to comply with all applicable safety regulations during the performance of a contract. In order to comply, a contractor must know what materials employees Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 538
SSPC CHAPTER*26.0 93 8627740 0003986 4Tb may be exposed to and what federal, state and local regulations require. The contractor must also be familiar with various approaches to compliance, including engineering, work practice and administrative controls, air and personnel monitoring and the proper use of personal protective equipment. A contractor who does not have the expertise to keep abreast of safety regulations and to comply with them may be subject to regulatory fines and civil and criminal liability. The owner who hires such a contractor runs the risk of being included in legal actions against the contractor. For instance, according to OSHA guidance to inspectors, when one employer is not meeting requirements to inform employees of workplace chemical hazards at a multi-employer work site, the other employers may be cited also. Contractors who do not make health and safety a priority often suffer reduced productivity and lower worker morale. The owner may also be affected by unnecessary work stoppages and slow downs, and unfavorable publicity as a result of a serious accident or pattern of occupational injury and illness at its work site. Contracting firms who value their employees and practice safety on each job every day will reap many benefits not only for themselves but for the owners that hire them. Good safety performance reduces lost work hours, which in turn reduces the contractor s insurance costs while increasing productivity. A contractor with lower insurance costs can do the job at less cost to the owner. Everybody wins. D. RESPONSIBILITIES OF EMPLOYERS, EMPLOYEES AND INSPECTORS, CONSULTANTS AND ENGINEERS Conscientious painting contractors have written safety programs based on all safety standards applicable to the industry, and make every effort to routinely train their employees to comply with the written program. Many progressive firms have active safety committees which include management and worker representatives and continuously refine the safety program and refer suggestions for improvement to upper management. A truly professional contractor evaluates the hazards of each job undertaken before any equipment is brought on site, and develops a plan to control the hazards expected during each phase of the job. For example, the project manager may hold a pre-job safety meeting with workers and supervisors, and follow up with weekly tool box meetings with workers to ensure that expected hazards are being controlled and unexpected hazards are recognized as they develop. Daily routine job site safety inspections by the person responsible for safety and health are also advisable. Workers who consistently violate safety regulations should be suspended, and in some cases terminated.
Owners and specifiers can reduce the odds of contractor safety violations by pre-qualifying contractors before they allow them to submit a bid. OSHA s recent regulation on process safety management (PSM) requires owners in the chemical process industry to evaluate the safety record of contractors before they are hired. Although other sections of the industry are not required to do this, it is a good way for them to protect themselves. Examples of indicators to measure a firm s safety performance include the contractor s worker s compensation experience modification rate (EMR), total cases and lost workday incident rates and serious and willful OSHA citations. In addition to pre-qualifying contractors, owners and specifiers should routinely outline in their specifications the safety responsibilities of the contractor and enforce the safety and health section of the specification just as stringently as the quality assurance sections. Owners can also require the low bidder to submit a site specific safety and health plan which the owner must approve before awarding a contract. II. HAZARDOUS OPERATIONS IN THE PROTECTIVE COATINGS INDUSTRY A. MATERIALS 1. Fire Hazards and Explosions a. Causes -Most solvent-thinned paints and paint solvents are highly flammable and extremely dangerous when they, or especially their vapors, are exposed to open flames, sparks or very high temperatures. The results may be fire or explosion, if in a confined area, unless proper precautions are taken. A certified industrial hygienist or certified safety professional should be consulted for advice about safe working conditions, particularly in confined spaces. FIGURE 1 Paint vapors can be flammable if adequate ventilation is not provided. b. Flammability of Paints -Many solvent-thinned paints are flammable and precautions need to be taken when handling these types of coating systems. Two examples of solvent-thinned paints include: (1) Two-Component Paints -Two-component paints should never be mixed in large quantities, generally no more than five gallons at a time. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 539
SSPC CHAPTER+Zb.O 93 8627740 0003987 332 They usually create heat because they react immediately upon mixing. The larger the volume mixed, the higher the temperature. The temperature may become high enough to create a hazard. (2) Oil Paints and Specialty Coatings -Waste or wiping rags soaked with paints based on linseed oil may catch fire spontaneously if left lying around, especially during warm weather. Spillage of peroxide catalysts used in polyester laminates and other similar chemicals can cause combustion. c. Flammability of Solvents and Thinners -Most paint solvents and the solvents used in solventthinned paints are volatile and will flash in the presence of a flame or electric spark. Usually, the faster the solvent evaporates -the lower its flash point. Therefore, solvent-thinned brushing or rolling paints, which dry relatively slowly, will contain solvents with a flash point of about 105OFor somewhat higher. A solvent-thinned spray paint that requires fast evaporating solvents may contain solvents that flash as low as 3OOF. A spray gun, which applies a pint to many quarts of paint per minute under high pressure, will produce a greater volume of solvent vapor than brushes or rolled paint. Therefore, all spray equipment must be grounded to prevent accidental ignition by static electricity. This includes containers. Painters should bond their empty bucket to the bulk drum while filling it and the drum should be properly grounded. Pure solvent vapors are heavier than air and tend to move along the ground when in confined areas. Thus, all flames near the area must be extinguished. Solvent vapors must be mechanically exhausted from all enclosed areas with the ventilation designed for efficient air flow. Explosion proof lights must be used. All electric motors should be turned off. d. Preventionof Fires -The following precautions will help prevent the possibility of fires: (1) Store solvents in Underwriter s Laboratory (UL) listed containers. (2) Prohibit smoking anywhere solvent-thinned paint is stored, mixed or used. Allow no other sources of ignition such as electric coffee pots, hot plates, or other such appliances in the area. (3) Provide adequate ventilation in all working areas to prevent a build-up of explosive concentrations of solvent vapor. Properly calibrated direct reading detection instruments should be used to monitor confined areas or closed spaces to be sure vapor concentrations are maintained below explosive limits. (4) Do not use metal ladders in confined areas
or within 10 feet of exposed electric wiring. (5) Use non-sparking tools to clean metal surfaces where fire hazards are present. (6) Extinguish all sources of flame in the area. Turn off all gas valves and open all electrical switches if working in confined areas or near electrical equipment. (7) Be sure that all equipment, motors and lights in the area are grounded and consider using only explosion proof lighting. (8) Keep fire extinguishers nearby. Be sure that they are of the proper type, as follows: Class A -Paper, wood, rubbish, where water is effective; Class B -Burning liquids, where smothering action is required; Class C -Electrical equipment, where the extinguishing agent must be non-conductive. (9) Keep pails of sand or similar absorbent materials near dispensing pumps and spigots to absorb any spills. Replace all leaking containers. (10)Clean up before, during and immediately after painting operations. Wet down sweepings, rags and waste with water and store in closed metal containers. Dispose of daily. (11) Always clean up paint or solvent spills immediately. 2. Health Hazards a. Causes -A variety of paint ingredients or chemicals may be harmful to the human body. For instance, some chemicals may cause irritation, sensitization, central nervous system effects, or systemic effects. Most people can withstand chemical exposures for short periods of time at low doses; however, some people are immediately sensitive to some ingredients and almost everyone will be affected to a degree if exposed for a cuff icient period of time. Continued exposure may cause the body to become sensitized so that subsequent contact may result in an aggravated reaction, especially for anyone with a chronic illness. b. Types and Components of Paints -The term paint is commonly used to identify a range of products including conventional paints, varnishes, enamels, and lacquers. Conventional paint is an inorganic pigment dispersed in a vehicle consisting of a binder and solvent, with selected fillers and additives. Varnish is a nonpigmented product based on oil and resin in a solvent that dries first by the evaporation of the solvent and then by the oxidation and polymerization of the resin binder. A pigmented varnish is called an enamel. Lacquers are coatings that are commonly based on a cellulose ester in a solvent that dries by evaporation leaving a film that can be redissolved in the original solvent. (1) Alkyd Paints -employ metal soaps of organic acids to catalyze the oxidation of the drying oil component. Because lead soaps are commonly used, lead is a potential hazard in any drying-
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SSPC CHAPTER*Zb.O 93 = 8b27940 0003988 279 oil-type paint (alkyd, epoxy ester, oleoresin, and urethane-oil). Lead used as an oxidation catalyst may comprise 0.5 to 1.0 percent of the paint solids by weight. (See also discussion of lead under pigments.) (2) Liquid Epoxy Resins and Curing Agents -are primarily used in solvent-borne and waterborne two-component epoxy paints. These liquid resins are modified by the addition of reactive diluents (glycidyl ethers). These reactive diluents are themselves irritants to the skin, the eyes, and the respiratory tract. (3) Aliphatic and Aromatic Polyamines, Polyamine Adducts and Polyamides -are used as curing agents in two component epoxy coating systems. The aliphatic amines are potent irritants and sensitizers; the aromatic amines are somewhat less potent. The polyamide resins are relatively harmless. Acid anhydrides and formaldehyde resins are used as cross-linking agents in powder coatings and baking enamels. The acid anhydrides are irritants and sensitizers. Formaldehyde is a strong irritant and is also considered a human carcinogen. (4) Epoxy Resins -are commonly reacted with fatty acids to produce epoxy esters. Because coatings produced with these resins contain no unreacted epoxy groups, no hazard exists. (5) Urethane Resins -organic isocyanates are the principal hazard associated with urethane coatings. Isocyanates can cause severe irritation to the conjunctiva, and respiratory distress. They react with various protein functional groups and should be capable of forming antigens. A typical response to isocyanate inhalation, either as a vapor or an aerosol, is the manifestation of an asthma-like syndrome, characterized by a feeling of chest constriction and difficult breathing, sometimes accompanied by a dry, irritant cough. A small percentage of the population may become sensitized to isocyanates, whereupon the above symptoms are produced on exposure to even low airborne concentrations. The toxicity can be minimized by avoiding use of smaller molecular weight species. c. Hazards of Solvents and Thinners -Most solvents are toxic to some degree, depending upon exposures. Solvents may enter or affect the body in three ways. The most frequent way solvents affect the body is by skin contact. When a solvent is allowed to contact the skin, even for a short period of time, it will start to damage the skin or cause dermatitis. Dermatitis is reddening and swelling of the skin. The second route of entry of solvents into the body is by breathing, or inhalation. Once solvents are inhaled, the vapors can pass
from the lungs directly to the blood. The solvent may irritate the respiratory tract and/or cause adverse health effects to other body systems by being transferred via the blood stream. The third route of entry of solvents into the body is by ingestion. Ingestion of solvents may affect the gastrointestinal tract as well as other body organs. The following precautions should be used while working with toxic solvents: (1) Properly label, seal and store all toxic solvents when not in use. (2) Adequately ventilate all areas where solvents are used or stored. (3) Wear the proper respirator and eye protection. (4) If a solvent gets splashed into the eye, immediately flush the eye with water for a minimum of fifteen minutes and seek medical attention. (5) Wear the appropriate gloves and clothing when handling solvents. (6) Practice good personal hygiene after handling any solvents. (7) Consult the Material Safety Data Sheet (MSDS) to determine the toxicity of the material that is in use, and the specified protective equipment needed when using the material. (8) If permissible exposure limits are exceeded, as determined through air monitoring conducted by an industrial hygienist, then engineering control and respiratory protection becomes necessary. d. Prevention of Health Hazards -The following precautions should help reduce potential hazards. They describe a common sense approach to avoiding contact: (1) Identify and seal all toxic and dermatitic materials when not in use. (2) Adequately ventilate all painting areas. Provide general exhaust ventilation in the form of blowerdfans supplying fresh outside air to the work area where necessary and use National Institute for Occupational Safety and HealthlMine Safety and Health Administration approved respiratory protection equipment if the vapors cause irritation or intoxication. When surface preparation involves removal of old paint films, take care to minimize dusting, to protect workers from the dust and to properly dispose of coating residues, in accordance with applicable state and federal regulations. (3) Wear goggles and the proper respirator when spray painting or performing any operation where an abnormal amount of vapor or dust is formed. (4) Wear appropriate gloves and clothing when handling dermatitic materials. Change and clean work clothing daily. (5) Avoid touching any part of the body when handling dermatitic materials. Wash hands, face and
arms thoroughly before eating and at the end of 541 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERs2b.O 93 8627740 0003989 105 e. Hazards of Pigments and Other Additives (1) Heavy Metal Pigments -Pigments are another paint component that may be toxic to the human body. The most common contain lead, chromium, and oxides of iron, titanium, and zinc. Precautions such as ventilation, respirators, hygiene facilities, and personal protective clothing should be implemented when applying or removing paints containing these pigments. The substitution of hazardous pigments with nonhazardous pigments is the best method of controlling future occupational health hazards. The removal of paints containing heavy metal pigments without control measures greatly increases an employee s chances of developing a heavy metal poisoning. Airborne pigments such as lead may enter the body by inhalation and ingestion. Exposure to lead may affect each person differently. Even before symptoms appear, lead may cause unseen injury to the body. During early stages of lead poisoning, mild symptoms may be overlooked as everyday medical complaints, including: loss of appetite, trouble sleeping, irritability, fatigue, headache, joint and muscle aches, metallic taste, decreased sex drive, lack of concentration and moodiness. Brief intense exposure or prolonged overexposure may result in severe damage to the bloodforming, nervous, kidney and reproductive systems. Some noticeable medical problems include: stomach pains, wrist or foot drop, high FIGURE 2 blood pressure, nausea, anemia, constipation or Eye and respiratory protection are needed for spray painting. diarrhea, tremors, convulsions or seizures. (2) and the der
Silica -Silica (both crystalline and amorphous) the silicates clay, diatomaceous earth, mica, day. Try to shower at or near the jobsite. and talc are widely used as exten pigments.
Change clothing before leaving. Toxicants can With the exception of clay, all ha ve been demon--`,,,,`-`-`,,`,,`,`,,`--be transferred easily. strated to produce fibrosis of the lung. A prelimi(6) Paint removers containing solvents are often nary study of the health hazard s in the painting toxic. They should be used only with ventilation trades suggested that mixed dust pneumoconicontrols and/or respiratory protection. osis is common among painters. While exte nder pigments are used in substantial quantities in some paint formulations, these materials may be at least partially locked up by encapsulation in the resinous binder.
(3) Organic pigments -The chronic hazards posed by these materials are largely unknown. Many of the pigments are based on dyestuffs: the dyestuff is combined with an inorganic compound to produce an insoluble pigment. The dyestuffs have been studied more extensively than the pigments, and several have been implicated as cancer risks. In paint the biological availability of these materials is probably limited by the insolubility of the pigments and their partial encapsulation in the paint resin matrix. Fat andlor water soluble dyes are used in some wood stains, inTable 1. Health Effects of Lead creasing the potential hazard. 542 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERmZb-0 93 8627940 0003990 927 (4) Activators and Catalysts -Activators and catalysts found in some coatings, such as mercury compounds, can be very harmful if proper protective clothing and respiratory protection is not used. f. Hazards ofSurface Preparation Materials (1) Dusts and Abrasive Fines -Blast cleaning can turn paint, rust and substrate surfaces into a dust cloud consisting of many airborne particles, some too small for the naked eye to see. Whether or not any of the airborne dust particles are a potential health hazard depends on the size of the dust particles, the toxicity of the materials in the dust, and the amount of dust breathed into the lungs. To determine the toxicity of the dust refer to the MSDS for the abrasive in use, and identify the chemical makeup of the coating being removed and the substrate or object being cleaned. To control workers exposures to potentially toxic dust, a well designed ventilation system should be installed. Respirators and proper protective equipment should also be used to ensure adequate protection. Abrasive fines used to remove paint coatings that contain lead, cadmium, chromates, zinc or nickel should be treated as hazardous unless testing can prove otherwise. In addition, abrasives may contain small amounts of toxic heavy metals such as lead, copper, arsenic, cadmium and beryllium. Respiratory devices and protective clothing should be worn when working with abrasive fines. Of particular concern is the presence of silica (quartz) in sands and other mineral abrasives. (See below.) (2) Silica and Silicosis -Chronic or acute shortterm exposure to silica dust can cause a debilitating disease known as silicosis. Air-supplied respirators, operated in accordance with OSHA respiratory standard 1910.134, can protect blasters from this hazard. However, because of poor maintenance of respiratory equipment and poor hygiene, many workers have been exposed to and injured by excessive levels of silica. NIOSH recommended as early as 1974that abrasive blasting be restricted to abrasive with a maximum of 1 percent silica content. In a recently issued Hazard Alert, NIOSH described specific health hazards from silica, and cited several case histories where blast cleaners had died from this condition. NIOSH also identified inadequate engineering controls, inadequate respiratory protection, and failure to conduct adequate medical surveillance programs as contributing to the development of silicosis. NIOSH recommends a series of measures, including substitution of alternative abrasives, air monitoring, use of con-
tainment structures, personal hygiene, protective clothing, respiratory protection, medical monitoring, posting of warning signs, and worker training. The Texas Department of Health also issued an advisory on the hazards of using silica abrasives to the oil and gas pipe coating industry. Both documents strongly recommend observing OSHA s PEL of 100 pg/m3 based on an 8-hour time-weighted average. (3) Chemical Strippers -Chemical strippers are used to soften the existing coating for removal by scraping andlor flushing. Chemical strippers eliminate airborne hazards but proper protective clothing such as coveralls, gloves and glasses should be worn to prevent skin and eye irritation. Caustic compounds in some chemical strippers can cause burns if not immediately washed off the skin and can cause eyes, nose and throat irritation upon inhalation. Solvent-based strippers are also available. Health hazards may vary from irritation and central nervous system depression possible with substances such as xylene to the possibility of human carcinogenicity, as with methylene chloride. Chemical strippers containing solvents may require use of respiratory protective devices. (4)Acids and Alkalis -Acids and alkalis commonly found in wash primers and chemical strippers (e.g., sodium hydroxide and phosphoric acid) are highly corrosive, and appropriate measures should be instituted concerning storage, handling, waste disposal, ventilation, personal protection and first aid. (5)Chemical Spills -Clean up spills immediately and wash immediately if skin comes into contact with a hazardous substance. If a solventlchemical gets splashed into the eye, immediately flush the eye with water for a minimum of fifteen minutes and seek medical attention. Wear the appropriate gloves and clothing when handling spills. Practice good personal hygiene after handling any spills. Consult the Material Safety Data Sheet (MSDS) to determine the toxicity of the material that is in use, and the specific protective equipment needed when using the material. Store and dispose of all oily or solvent wetted rags in metal containers with a tightly sealed lid. Respiratory protection should be worn if the spill creates a hazardous atmosphere, or the MSDS indicates it is necessary. (6) Materials Removed From Surfaces -A prejob analysis of the surface materials should be conducted to determine whether the coating contains hazardous materials. If the coating contains potentially hazardous constituents then respiratory and protective clothing should be worn when working with the removed material.
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SSPC CHAPTERs26.0 93 m 8627940 0003991 863 m B. PAINT APPLICATION i.General Paint products are used widely in industry to provide a surface coating for protection against corrosion, for appearance, as electrical insulation, and for a number of special purposes. The hazards associated with the industrial application of these products will be discussed in this section. Common methods of application include airless spray, conventional spray (air atomizing) and electrostatic spray. FIGURE 3 Airless spray systems exert considerable force and can cause serious injury if not handled carefully. 2. Airless Spray Because airless spray systems operate at high pressure, give special attention to safety during operation. A tip guard and trigger lock must be on all airless spray-guns. Fluid sprayed from the gun is propelled with sufficient force to penetrate skin and cause serious damage. In the event of injection, special treatment by a physician is required. The attending physician should be advised of the material s ingredients (an MSDS would be helpful) and of the nature of the injection (high pressure). The entire system is pressurized so that hose ruptures or leaks at fittings can result in dangerous high pressure spray. Some important safety practices to help avoid these hazards include the following: a. Never point the gun at anyone. b. Do not make adjustments to the equipment setup, such as changing nozzles or fittings, without first shutting off the pump and releasing the system press u re. c. Always make sure the fluid hose is in good condition before spraying; kinks or abrasion can develop into a rupture. Store hose in a dry area. d. Do not use standard hardware on an airless system; only high pressure fittings can be used. High pressure hose is required for fluid flow. The hose must never be bent or kinked in less than a four inch radius. e. Airless spray equipment must be grounded to prevent static sparking. If extension cords are used, make sure that they have a ground wire and that the ground is connected. f. Do not spray solvent through the nozzle tip because this can build up static electricity and cause explosion or fire. Take the tip off before spraying
solvent through the system. g. Secure blast hose at a point no more than 10 ft. from the operator. h. Conduct hydrostatic tests at least once, preferably twice a year. Check all valves, including safety valves, daily. 3. Air Atomization Method The air atomization spray gun is widely used because of its versatility, its low cost, and because it creates a high quality finish. In this method, compressed air provides the energy to atomize the finish. The atomization is produced by an air nozzle. Two types of nozzles are used: external mix and internal mix nozzles. In the external mix nozzle, the coating and the compressed air exit from separate orifices and are mixed outside the nozzle. The air jet atomizes and shapes the spray fan. Internal mix nozzles combine the compressed air and finishing materials in a chamber inside the nozzle. The atomized mixture is shaped by the geometry of the chamber opening. Regardless of which paint method is used, most industrial spray paint operations require exhaust ventilation, the use of air supplied respirators, protective clothing, and adequate washing facilities. 4. Electrostatic Spray In electrostatic spraying, an electrical charge is applied to the atomized coating particles, either by the creation of an ionized zone within the spray cone area, or by imparting a charge to the fluid stream prior to its release from the spray gun head. The charged, atomized paint particles are attracted to the conductive object being finished by the electrostatic potential between the paint and the object. The level of exposure to the paint is determined by the overspray and rebound that occurs during spraying. Effective ventilation controls, protective clothing and respiratory protection should be worn while using this painting method. All electrostatic equipment must be properly grounded. 5. Compressor Pumps When using a compressor never overload it. Place the compressor in an open and level area. Place the compressor in a remote location because it requires a good supply of clean, fresh air in order Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 544
SSPC CHAPTERW2b.O 93 8b27940 0003992 7TT H to properly operate. The compressor should also be grounded before being started. It should have reasonable time to warm up before building up pressure in the receiving tank. Never tamper with preset safety valves. Gauges should be kept clean and visible at all times. Workers need to see the gauges to tell whether all air pressure has been released before disconnecting any couplings or opening any lids. The gauges are also used to ensure that the compressor is operating safely. Do not add fuel to a gasoline powered compressor when it is hot or running. The fuel can easily ignite, causing a fire or explosion. All re-fueling of the compressor should be done in the morning before start-up. The compressor should be kept tuned-up and out of confined spaces. If compressors are used to supply breathing air for respirators they must be equipped with a carbon monoxide monitor and filter systems capable of providing Grade D air. FIGURE 4 Specialized protective equipment is required for abrasive blasting. C. SURFACE PREPARATION Without proper precautions the high pressures used in blast cleaning can cause injuries. Injection of water beneath the skin should be treated as seriously as any other chemical injection. In addition, abrasive material may cause harm at high or even moderate pressures, and continuous exposure to the dust may result in lung disease. 1. Abrasive Blasting --`,,,,`-`-`,,`,,`,`,,`--Protective equipment is essential to protect the abrasive blaster and fellow workers from the hazards of the job. At a minimum, a continuous flow re,spirator with helmet and wide angle, clear vision lens must be used by abrasive blasters. The helmet must fit completely over the head and neck to the shoulders. The helmet should be equipped with a constant supply of clean air (Grade D or better) of not less than six cubic feet per minute. The air-line should be equipped with air-purifying filters, pressure regulator gauge, relief valve, air-flow control valve and a NIOSH/MSHA approved blasting respirator. The abrasive blaster should also be equipped with appropriate work gloves, coveralls and other appropriate clothing.
The blaster must use a dead-man control valve on the blasting nozzle which cuts off the air and abrasive stream when the pressure on the control is released. The hoses for the blasting equipment must be equipped with a static dissipating tube or be lined with carbon black. This prevents shock from static electricity build-up. The shock from static electricity could cause the operator to fall if working from elevated surfaces. Before starting any abrasive blasting operation, thoroughly examine the condition of hoses, hose fittings, couplings and unions. Any of the above showing wear must be replaced to prevent sudden parting and whipping under pressure. 2. Hand and Power Tools Common hand tools used for hand tool cleaning are sandpaper, non-woven abrasive pads, wire brushes, chipping hammers, scrapers, hammers and chisels. Prolonged use of chipping hammers and chisels may cause trauma to the hands, wrists, and elbows. Use of shock absorbing gloves andlor wrist supports or ergonomically designed tools might be advisable. Common power tools are pneumatically driven hammers or rotary hammers, needle guns, roto peens, rotary grinders, sanders or wire brushing tools. It is important to have a proper equipment setup when using power tools. Follow the manufacturer s instructions for the tool being used. Power tools can be dangerous and safety precautions must be taken when operating them. Protective equipment must be worn. In addition to a hard hat, eye protection, and work gloves should be worn. Power tool cleaning may be very noisy. Therefore it is very important to use adequate hearing protection. Respiratory protection and coveralls are advisable whenever hand or power tools are used to remove paint, but are required for removal of lead based paints. If electrically driven (rather than air-powered) tools are used, they must be adequately grounded or double insulated, and used in a dry atmosphere Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 545
SSPC CHAPTER*26-0 93 8627940 0003993 636 to avoid the possibility of shock. Ground Fault Cir- emissions generated during surface cleaning. cuit Interrupters (GFCI) should be used with all elec- Means for fire protection and proper ventilation tric cords and tools. should also be provided during welding, cutting or In confined spaces and other areas where there heating. may be a danger of explosion, power tool cleaning should not be conducted because of the possibility of sparking. The operator must be certain that the tools in use are checked and safe. Make sure that the abrasive media is attached securely and tightened. Tools should not be operated above maximum operating speed. Tools should not be run unless in contact with the work surface. Manufacturer s directions should always be strictly followed. 3. Water Jetting Although water itself is relatively safe, the extremely high pressure often used for water jetting can be hazardous. Prior to starting any water jetting operation, employees should examine the condition of the hoses, hose fittings, couplings and unions. Any equipment showing wear should be replaced to prevent sudden parting and whipping under pressure. Water jetting hoses should be secured to the staging at the working level leaving only enough free hose so the hose weight can be properly and safely handled by the blaster. Any electrical equipment in the area of operations that presents a hazard to the operator should be de-energized, shielded or otherwise made safe. Operators should wear appropriate waterproof clothing, head, eye and hearing protection during all water jetting operations. When water jetting operations are conducted in confined spaces, the blaster should be in constant communication with the stand-by person. Employees should take precautions to protect the water blasting equipment from freezing in cold weather and signs should be posted to advise others in the area when water blasting operations are being performed. As always, injection of water beneath the skin should be treated as seriously as any other chemical, and a physician should be consulted. For more information on safe practices for water jetting, see The Water Jet Technology Association s booklet Recommended Practices for the Use of Manually Operated High Pressure Water Jetting Equipment. 4. Welding, Cutting or Heating All welding, cutting or heating on surfaces with preservative coatings should be performed accord-
ing to OSHA standard 29 CFR 1926.354,Welding, Cutting and Heating in Way of Preservative Coatings. Before welding, cutting or heating, the potential toxicity and flammability of preservatives should be evaluated. All surfaces covered with toxic coatings require the use of protective clothing and a respirator that is capable of filtering out the 546 5. Pressure Pots Sandblast pots and related blast machinery should be built to standards set by the American Society of Mechanical Engineers (ASME) or National Board Code. Pots not meeting these requirements must not be used. The ASME code means that everything has been done to make the vessel as safe as possible. The code prohibits any field welding on blast mach in es. Blast pressures should stay within the manufacturer s blast machine ratings. High blast pressures increase wear and tear on blast machines, and increase operator fatigue. Unless otherwise specified, maximum working pressure of blast machines and related components must not exceed national board approved 125 psis (8.5 BAR). Pot tenders and others working near abrasive blasting operations may need to be equipped with respirators, gloves, hard hats and safety glasses. Most abrasive blasting operations produce noise levels in excess of 90 decibels so hearing protection devices (ear plugs or earmuffs) should also be worn. Never force the lid off the sandblast pot. If the lid is difficult to open, stop and check the air pressure. The pot must be depressurized before opening the pot lid, or before any changes to hose couplings, or repairs of any kind are allowed. A blast machine should never be moved while it contains abrasives. Abrasive blasting machines which will be towed on a highway should be equipped with properly operating brakes, taillights, fenders and side reflectors. D. ACCESS AND RIGGING The proper use of scaffolds is discussed in chapter 5.2. The following precautions should be observed when using other access methods. 1. Ladders Use the following procedures in storing, setting up and using ladders: a. Use safety shoes on all ladders. b. Store ladders off the ground in a warm, dry area protected from the weather.
c. Protect wood ladders with a clear finish so defects are visible. d. Inspect ladders daily during use. Keep clean and free of oil or grease. e. Do not use ladders that are longer than can be carried and erected by two men. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*Zb*O 93 = 8b27940 0003994 572 = f. Do not use a stepladder over 12 ft. high. It should be fully opened with a locking device. Do not stand on the top step. One man should hold the ladder if the other is more than 8 ft. high. g. Avoid placing ladders in front of doorways, unless the door is blocked. h. Only one worker should work on a ladder at a time. i Do not use a ladder as a horizontal scaffold member. j. if the ladder is used to reach unusually high levels, its top must be at least three feet above the point of support and tied off FIGURE 5 Failure to use proper access equipment can lead to falls, a com-. mon source of injury in coating operations. 2. Fail Hazards Falls from heights are a significant hazard faced by painters and blasters in day-to-day work. Because falls are a routine hazard, there is a tendency not always to take the precautions necessary when working from elevated work surfaces. But when working from heights, safety can not be taken for granted. The hazards of high work subject employees to possible injury and death, and an employer to possible OSHA citations and fines. 547 a. Guardrails -The primary means for protecting workers from hazards of falls from heights is the use of a standard railing consisting of top rail, intermediate rail, and toeboard. Guardrails and toeboards should be installed on all open sides and ends of platforms to give maximum protection. The OSHA standard pertaining to this protection is 29 CFR 1926.500(d), which refers specifically to work on floors, platforms and runways. Other OSHA standards that discuss the use of guardrails are 1926.451, pertaining to scaffold arrangements, and 1926.550(g), pertaining to suspended personnel platforms. b. Safety Belts, Lines and Lanyards -Guardrails and toeboards cannot be used in all fall hazard situations. When guardrails are neither practical nor feasible, use a secondary means of fall protection. One such means is a lifeline system. Lifelines can be 2 basic types: 1) a catenary or horizontal lifeline between two fixed anchorages, independent of the work surface, to which a lanyard is secured, or 2) a dropline or personal lifeline system. The dropline or personal lifeline system is a rope system, used with some type of approved safety belt
or harness. This is worn around the waist and attached to a lanyard or rope grabbing device that is securely fastened to an anchorage point. The rope grabbing device should be attached to a lifeline of 3/4 inch manilla rope or equivalent, which in turn should be secured to an anchorage point capable of supporting 5,000 pounds. When used and maintained properly, these systems can be a key factor in preventing injury and death from falls. While federal regulations still allow use of safety belts, use of full body harnesses is advisable. c. Safety Nets -Sometimes safety belts, personal lifeline systems, guardrails, or other conventional protective equipment may be impractical or not feasible for the work method. In these situations, personnel safety nets can be installed under and around the work area. Personnel safety nets are typically used in bridge work and long-term structural projects where workers are exposed to significant fall hazards. OSHA requires the use of safety nets when work places are more than 25 ft. (7.6 m) above the ground or water surface and conventional protective equipment (personal lifelines, guardrails) is deemed impractical. Personnel safety nets must be manufactured and tested in accordance with all pertaining ANSI standards and OSHA standard 29 CFR 1926.105 requirements. Personnel safety nets should bear a label displaying the manufacturer s name, date of manufacture, and proof of load testing. Every net should also carry a serial number so that records can be kept of details such as repairs, inspections, and load test results. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERW6.0 93 ô627940 0003995 409 m 3. Confined Spaces OSHA s Permit-Required Confined Space Standard 1910.146,defines a confined space as a space that is large enough and so configured that an employee can bodily enter and perform assigned work; and has limited or restricted means for entry or exit (e.g., tanks, vessels, silos, storage bins, hoppers, vaults and pits are spaces that may have limited means of entry); and is not designed for continuous occupancy . The confined space standard states the minimal requirements for safe entry, continuous work in and exit from tanks and other confined spaces. A confined space program should include training in: a. the duties of a standby person; b. use of ventilating equipment; c. isolation of systems; d. atmospheric testing; e. confined space entry limits; and f. the use/purpose of an entry permit. ill. OSHA STANDARDS A. OVERVIEW OF OSHA 1. Authority In 1970,Congress passed the Occupational Safety and Health Act, which created the Occupational Safety and Health Administration, a division of the Department of Labor. OSHA is responsible for developing and enforcing mandatory job safety and health standards. The agency also conducts research, training and record keeping related to health and safety issues. Some states have been approved to administer their own state OSHA programs. 2. General Dufy Clause Although OSHA has developed a number of industry -and substance-specific standards, the general duty clause of the Occupational Safety and Health Act takes a very broad view of worker health and safety. It requires employers to furnish to their workers employment and a place of employment which are free from recognized hazards that are causing or likely to cause death or serious physical harm . OSHA can use this clause to cite an employer when conditions it believes to be unsafe do not violate specific OSHA regulations. 3. Regulatory Process Some OSHA standards have been mandated by Congress. They may also be initiated by the agency in response to petitions from other parties including the National Institute for Occupational Safety and Health (NIOSH), state and local govern-
ments, groups that develop voluntary industrial standards or labor representatives. Once the need for a new standard has been identified, OSHA Advisory Committees, which include representatives of management, labor and state agencies, develop recommendations. In the very early stages of the process, OSHA may request additional information needed for the development of a standard by publishing an Advance Notice of Proposed Rulemaking in the Federal Register, a daily record of federal business. When a first draft of the proposed regulations has been completed, a Notice of Proposed Rulemaking must appear in the Federal Register. Interested parties must then have at least 30 days to comment on the way proposed regulations will impact them. Following this comment period, the final regulations are published in the Federal Register, and incorporated into the Code of Federal Regulations, a permanent record of government regulations organized by subject. (See Appendix for more details on sources of information.) Those who feel they will be adversely affected by a standard may request a judicial review. Employers that cannot meet the standard, or believe an exception should be made in their case because their facilities or methods are at least as effective , can request a temporary or permanent variance. When new or particularly hazardous conditions warrant, OSHA may develop emergency standards, which take effect immediately. Once these standards have been published in the Federal Register, they are also subject to comment and review before they are published as permanent standards. 4. Enforcement and Interpretation Every establishment covered by the Act is subject to inspection by OSHA compliance safety and health officers. Inspections are generally conducted without advance notice, though OSHA is required to obtain a warrant if an employer does not consent. OSHA gives highest priority to workplaces: a. where there is imminent danger of death or serious physical harm; b. where fatal accidents, or those that hospitalized more than five employees have occurred; c. when employees complain of alleged violations and request an inspection; d. when specific industries, occupations, or materials are associated with high rates of illness or injury. If OSHA discovers violations during an inspection, the employer will receive a citation, which details the violation, includes information about penalties and a schedule for compliance. Penalties may depend on the seriousness of the violation,
knowledge of the violation, and a show of cooperation, or good faith. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 548
Type of Violation Criteria for Type of Violation Possible Penalty Other than Serious Violation Probably would not cause death or serious physical harm Penalty is discretionary and may range from $50-$7,000 for each violation, depending on a show of good faith Serious Violation Substantial probability of death or serious physical harm. Employer knows or should have known about the violation Penalty is mandatory and ranges to $7,000 for each violation Willful Violation Employer knows about the hazard or violation, and makes no reasonable effort to correct it Penalties range from $5,000to $70,000 for each violation Willful Violation Resulting in Death Fines of up to $25,000 for an individual and $500,000 for a corporation -possible six month jail term Repeat Violation Upon reinspection, a substantially similar violation is found Up to $70,000 for each violation Failure to Correct Violation A violation for a final citation has not been corrected by the prescribed abatement date Up to $70,000 for each day past the abatement date the violation continues Table 2. Possible fines for OSHA violations. Serious penalties are also possible for repeat recognition for those who accept the challenge. The violations and failure to correct previous violations. Star, Merit and Demonstra tion Programs are cooperEmployers may want to schedule an informal meet- ative programs, and participant s are volunteers. ing with OSHA s area director, who is authorized to These firms also receive limit ed exemptions from inenter into settlement agreements that revise cita- spect ion. tions and penalties. Local OSHA offices can also provide publicaThe employer may also contest both a citation tions, speakers, audiovisual mater ials and techniand associated penalties within 15 days. The writ- cal advice. OSHA provides fun ds to nonprofit ten Notice of Contest will be evaluated by the Oc- organizations to conduct work place training and cupational Safety and Health Review Commission. education. A number of private f irms and universiUnfavorable decisions can be appealed at this lev- ties also offer OSHA complian ce training. ei and to the U.S.Court of Appeals. Painting contractors are considered part of the B. COMPONENTS OF AN OSHA COMPLIA NCE construction industry for OSHA record keeping pur- PROGRAM poses. These businesses are most frequently cited Company Safety & Health Progra ms should be designed for failure to comply with the Hazard Communica- to be used in conjunction with
the current copy of the OSHA tion Standard. They are also frequently cited for lack Construction Industry Sta ndards, 29 CFR 1926, and the of accident prevention and training programs, not General Industry Standards, 29 CFR 1910. OSHA states in having or not using safety equipment such as side 29 CFR 1926.20 General Safety a nd Health Provisions , rails on ladders, railings on scaffolds, and hard hats. It shall be the responsib ility of the employer to initiate and Contractors also commonly forget to post a required maintain such programs as ma y be necessary to comply with poster informing employees of their rights and obli- this part (part refers to al l of 29 CFR 1926). gations under the Occupational Safety and Health The purpose of an OSHA Complian ce Program is to esAct. tablish and maintain policies, programs, and procedures that 5. Consultation Assistance are necessary to comply with all applicable OSHA stan dards, OSHA provides a Consultation Service that can help and to establish and maintain an effective program to preemployers evaluate and improve their compliance. vent accidents, injuries and il lnesses. The service was developed with small employers in The components of an OSHA Comp liance Program mind. Although the program is funded by OSHA, it should include: is entirely voluntary. No penalties are issued, and 1. Policy statement establis hing goals and commitment OSHA enforcement compliance officers do not see of management and the means for communicating the results. these to all employees. State officials or university staff often operate 2. Delegation of responsibilit ies for implementing the the Consultation Service. They may point out weaknesses in an employer s health and safety program program. and provide the training and technical assistance 3. Methods for identifying haz ards and hazardous acneeded to resolve any problems. Firms that partici- tivities and for controlling them. pate in the program receive a limited one-year ex- 4. Commitment to ongoing trai ning and education of emption from OSHA inspection. all supervisors and employees on all aspects of jo b OSHA s Voluntary Protection Programs en- safety and health.
courage employers to take their health and safety 5. Proper reporting and record keeping, and investiprograms beyond the letter of the law -and provide gation of all accidents, inju ries and illnesses. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 549
SSPC CHAPTER*26*0 93 = 8627940 0003997 281 6. Methods and procedures for complying with specific OSHA standards. 7. Periodic review of the program with revisions made as necessary. C. ORGANIZATION AND HIERARCHY OF OSHA STANDARDS The OSHA General Industry Standards 29 CFR 1910 contains several standards applicable to the protective coatings industry. When a construction industry standard 29 CFR 1926 is not applicable or is non-existent, the General Industry Standard (29 CFR 1910) Protective Coatings may be enforced. Some common aspects of the protective coatings industry and their related General Industry standards include: 1. Abrasive Blasting -No specific standard applies to blasting in the field but many aspects of blasting operations fall under other applicable standards. FIGURE 6 Workers may be required to wear hearing protection under OSHA s Occupational Noise Exposure Standard. 2. Noise/Hearing Conservation -Noise protection should be provided and a Hearing Conservation Program should be in place and be in compliance with OSHA standard 29 CFR 191 0.95, Occupational Noise Exposure. 3. Respiratory Protection -The selection, issue, use, inspection, cleaning, storage and repair of respirators should comply with the OSHA Respiratory Protection Standard, 29 CFR 1926.103 and 1910.134. See section IIIF for more information on choosing respirators. 4. Confined Spaces -Practices and procedures used to protect employees from the hazards of entry into permit required confined spaces should comply with OSHA Standard, 1910.146, Permit-Required Confined Spaces. D. CONSTRUCTION INDUSTRY STANDARD RELATING TO INDUSTRIAL PROTECTIVE COATING OPERATIONS The Construction Industry Standards, 29 CFR 1926 contain many standards that apply to industrial protective coating operations. Some of the common standards that apply to the construction industry include: 1. Hand Tools and Power and Pneumatic Tools All hand, power and pneumatic tools should be equipped, inspected, guarded, used and maintained according to the manufacturer s specifications and limitations and OSHA standards 29 CFR 1926.300-305, Tools -Hand and Power.
2. Compressed Air -There is no existing OSHA standard for compressed air. However, there are standards set by the American Society of Mechanical Engineers (ASME). 3.Electrical -All electrical systems and equipment should be designed and installed according to OSHA standards 29 CFR 1926.402-408, Installation Safety Requirements, and the most current edition of NFPA 70, National Electric Code. All employees performing work on electrical equipment or systems should comply with the work practices in OSHA standards 29 CFR 1926.41 6-417, Safety-Related Work Practices. 4. ye and Face -Eye and face protection should be provided when machines or operations present potential eye or face injury from physical and chemical hazards as required by OSHA Standard 29 CFR 1926.102, Eye and Face Protection. Eye and face protection equipment required by OSHA should meet the requirements specified in American National Standards Institute 287.1, Practice for Occupational and Educational Eye and Face Protection. 5. Fire Protection/Flammable, Combustible Liquids -Fire protection should be developed for all company activities according to OSHA standard 29 CFR 1926.150, Fire Protection. This should include providing, maintaining, inspecting, and testing fire suppression systems and portable fire extinguishers, as required by this OSHA standard. The fire prevention requirements, specified in OSHA standard 29 CFR 1926.151, Fire Prevention, should be implemented for all jobs. FIGURE 7 In order to test the level of air contaminants, a vacuum pump on the worker s belt is used to pull air through a specialized filter placed in the worker s breathing zone. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 550
SSPC CHAPTERa2b.O 93 m The storage, handling, use and fire protection requirements for flammable and combustible liquids and their containers should be in compliance with OSHA standard 29 CFR 1926.1 52, Flammable and Combustible Liquids. 6. Exposure to Gases, Vapors, Dusts, Mists and Fumes -Exposure of employees to inhalation, ingestion, skin absorption, or contact with any material or substance at a concentration above the permissible exposure limit (PEL) specified in OSHA standard 29 CFR 1926.55, Gases, Vapors, Fumes, Dusts and Mists is prohibited. Generally, OSHA requires employers to minimize employee exposure to air contaminants as far as possible through the use of engineering controls such as enclosure or confinement of an operation, ventilation, or substitution of less toxic 8627940 0003998 118 m The design, construction, load-bearing capabilities, platform guarding, and use of all scaffolding must comply with OSHA standard, 29 CFR 1926.451, Scaffolding. 9. Personal Protective Equipment a. Head Protection -Hard hats must be used where there is a possible danger of head injury from impact, or from falling objects, or from electrical shock and burns as required by OSHA standard 29 CFR 1926.100, Head Protection. Helmets and hardhats for the protection of employees against impact and penetration of falling and flying objects should meet the specifications contained in American National Standards Institute, 289.1, Safety Requirements for Industrial Head Protection. Helmets for the head protection of employees Task-Related Triggers and Required Protective Measures Workers engaged in the tasks listed must be protected as specified before air mo nitoring results are back and throughout the task unless monitoring results show that lower levels of protection are sufficient (29 CfR 7926.62fd)). Presumed Exposures for Specific Tasks Specific Tasks Protective Measures (A complefe list of options for respiratory protection appears in the Interim Final
Rule's Table on Respiratory Protection, 1926.62(f).) *manual demolition *manual scraping *manual sanding *heat gun applications *general clean-up -power tool cleaning with dust collection systems -spray painting *any other task where employer has reason to believe task could exceed PEL /protective clothing & equipment /change areas /hand washing facilities /training /initial medical surveillance: blood sampling and analysis /respirators with protection factor of 10, such as a half mask airpurifying respirator with highefficiency filters or operated in demand (negative pressure) mode 'power tool cleaning without dust collection systems *clean-up of dry expendable abrasives *movement and removal of abrasive blasting enclosures *use of lead-containing mortar *lead burning 'rivet busting /protective clothing & equipment /change areas /hand washing facilities i/training vinitial medical surveillance: blood sampling and analysis /respirators with protection factor from 25-50, such as a powered airpurifying respirator with loose fitting helmet or hood and high efficiency filters, or full facepiece air-purifying respirator with high efficiency filters >2,500 pg/m3 *abrasive blasting *welding, cutting, and torch burning /protective clothing & equipment /change areas /hand washing facilities
/training /initial medical surveillance: blood sampling and analysis /respirators with a protection factor of above 50, such as a full facepiece supplied-air respirator operated in positive pressure mode (assigned a protection factor of 2,000 in new rule) Table 3. Task-Related Triggers Under the Construction Industry Lead Standard. Table Courtesy of the Journal of Protective Coatings and Linings. materials. Only when acceptable levels of exposure cannot be achieved through these approaches (as is often the case in coating operations) may employers use respiratory protective devices to comply with these standards. 7. Housekeeping -During the work day, work areas, passageways and stairs in and around buildings or other structures must be kept clear of debris according to OSHA Standard 1926.25, Housekeeping. 8. Ladders and Scaffolding -Stairways and ladders must be designed, constructed and used according to the manufacturers' specifications and limitations and OSHA standards CFR 1926.450 through 29 CFR 1926.460. Job-made ladders must conform to the design and construction specifications of these OSHA standards. exposed to high voltage electrical shock and burns should meet the specifications contained in American National Standards Institute 289. b. Foot Protection -Where the potential for serious foot injury exists, safety-toe footwear for employees should be required and meet the requirements specified in American National Standard for Personnel Protection -Protective Footwear, 241. c. Body Protection -Employees working with chemicals or materials that can cause damage to the skin or that can be absorbed should be provided appropriate protective clothing. d. Respiratory Protection -The selection, issue, use, inspection, cleaning, storage and repair of respirators must comply with the OSHA RespiratoCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 551
ry Protection Standard, 29 CFR 1926.103 and Air-purifying respirators remove par ticulates from 191O. 134. See section III F for more information on the air in the worker s breat hing zone by filtering it choosing respirators. prior to the worker inhaling it. Supplied-air respirators supply breathing air from outside the work enE. STANDARDS FOR LEAD AND LEAD REMOVAL vironment. The Construction Industry Lead Standard, 1926.62, provides the practices and procedures for protecting employees exposed to lead on the job. All construction work excluded from coverage in the General Industry Standard for Lead by 29 CFR 1910.1025(a)(2) is covered by this standard. Construction work is defined as work for construction, alteration and/or repair, including painting and decorating. Lead paint removal and maintenance activities would be covered by the CFR 1926.62 Lead Standard. All other non-construction work is covered by the General Industry Standard 1910.1025. Protective measures required under the Construction Industry Lead Standard are shown in Table 3. F. CHOOSING RESPIRATORY PROTECTION DEVICES 1. Need for Respirators in Coating and Surface Preparation It is likely that workers will be required to wear some type of respiratory protection during most coating and surface preparation operations, particularly when removing lead paint using techniques such as powered hand tools and vacuum blasting, due to the very low levels of exposure required to trigger mandatory use (50,~g/mJ). In a containment structure in which abrasive blasting is occurring, workers will always be required to wear respiratory protective equipment, even if a well designed ventilation system is being used. It is also likely that most support personnel may be required to wear respirators in order to meet the permissible exposure limit. FIGURE 8 Air purifying respirators filter contaminants from the air workers breathe. 2. Types of Respirators In general there are two basic types of respirators. a. Air-Purifying Respirators -Air-purifying equipment has the advantage of being lighter and less restrictive, as well as more economical than supplied air respirators. b. Supplied Air Respirators -Supplied air respirators may have several advantages for coating work. They protect workers from simultaneous exposure to multiple contaminants, which is not uncommon in coating operations. High dust levels associated with many surface preparation techniques may quickly overload the filtering systems on which airpurifying respirators are based. And air-purifying
equipment may not be adequate to protect workers from high lead levels associated with containment systems. 3. Protection Factors Various groups have established protection factors for respirators, including NIOSH, OSHA, ANSI, and others. In fact, there is quite a controversy over the level of protection afforded by different categories of respirators. FIGURE 9 Supplied air respirators deliver breathing air from outside the work environment. In general, protection factor describes a degree of protection a given respirator will provide, versus some airborne concentration of contaminant outside the respirator. For instance, for the half-mask respirator equipped with HEPA filtration cartridge, a protection factor of 10is assigned for lead. This means that the respirator can be worn in an atmosphere up to 10 times the PEL, and still protect the worker so that the concentration of lead inside the mask is below the PEL. Assuming a PEL of 50p gím3, this respirator can then be safely worn when airborne concentrations are up to 500~g/mJ. Similarly, a proCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 552
SSPC CHAPTERU2b-0 93 8627990 0009000 474 tection factor of 50 is assigned for full-face respirators. Powered air-purifying respirators (PAPR) highlight a variation on assigned protection factors. For lead, NIOSH has taken a very conservative posture and established a protection factor of only 50 for PAPR s, while OSHA and others have established protection factors of up to 1000. Similar problems occur when looking at the standard respirator for blasting, the abrasive blasting hood. NIOSH s current position is to assign a protection factor of only 25, when OSHA may allow up to 1000 if proper airflows to each hood are maintained. One example of the discrepancy and variation that exists in evaluating protection factors is the fact that OSHA has proposed, in a draft chapter from their technical manual, higher protection factors for powered air-purifying respirator (PAPR s) that maintain higher flow rates to the facepiece. If the PAPR device delivers more than 6 ftYmin to the facepiece, the higher protection factor of 500 may be used. OSHA has proposed a similar approach for the blast hood. A protection factor of 1000 may be assumed for a respirator which provides a minimum flow through a tight-fitting hood designed to maintain a positive pressure under sustained heavy work. However NIOSH, which has the responsibility of establishing protection factors, hac not recognized this position and it is currently not clearwhich numbers OSHA might enforce in the Construction Industry. 5. Breathing Air Requirements With any of the supplied-air respirators, including abrasive blast hoods, it is essential that Grade D breathing air reach the respirator. ANSI Standards Z 86.1ICompressed Gas Association commodity specificationG-7.1 for Grade D air,requires normal oxygen levels, no more than 5 mg/m3 condensed hydrocarbon contamination, no more than 20 ppm carbon no pronounced odor, and a maximum of 1000 ppm carbon dioxide. controls must be installed on compressors to achieve and verify with these requirements,or specially built, dedicated breathing air compressors must be used. he control/filter systems of existing lubricated compressors must be equipped with a constant monitor or a for carbon alarm with frequent measurement of in-linecarbon monoxide, addition, periodic samples from the air stream should be drawn, bottled, and sent to a laboratory to verify that each parameter of Grade
D breathing air has been met. IV. IMPLEMENTATION OF SAFETY AND HEALTH PROBLEMS A. ESTABLISHING WORKER SAFETY AND HEALTH PROGRAMS 553 The first step in establishing a worker safety and health program should be to determine the program s purpose. The program s purpose is to establish and maintain policies, programs, and procedures that are necessary to comply with all applicable OSHA standards, and to implement and maintain an effective program to prevent accidents, injuries, and illnesses. The second step in establishing a worker safety and health program is to identify the program components. These components were discussed earlier in the Development of an OSHA Program section. The third step is to dedicate the time to sit down with all company managers and supervisors to review the program and set specified goals for implementing its requirements. Have managers and supervisors do the same for all the employees. Encourage participation. Be honest and sincere. Continually ask for feedback and ways for improving the program. Let everyone know they will be consistently held accountable for fulfilling their responsibilities under the program. Enforce the program by holding everyone accountable for their responsib es. Let good pertormers know that they are doing a good job. At the same time, do not let poor or mediocre performance go unnoticed. Monitor and maintain records relating to accidents, injuries, illnesses, medical examinations, training, fit testing, and exposure monitoring for the life of the company. Analyze the firm s total worker s compensation costs over the years. Compare accident rates and evaluate changes in employees attitudes and work quality. Seek assistance from employees to get feedback on the success of the program. B. OWNER EVALUATION AND MONITORING OFCONTRACTOR PROGRAMS A representative of each facility owner should evaluate and monitor all contractor health and safety and OSHA complianCe programs. These programs should be submitted and approvedlmonitored by a qualified individual, such as a Certified safety professional (CSP) or certified industrial hygienist (CIH). The program evaluations should be completed before any work begins. Monitoring of the programs should be conducted through job site visits and review of daily work logs. The OSHA Standard 1910.1 19 Process Safety Management of Highly Hazardous Chemicals contains the specific requirements, and responsibilities for owners and contractors safety and health programs. This standard states that the owner is responsible for obtaining and evaluating infor-
mation regarding the contract employer s safety performance and programs. A good example of a safety program that each contractor in the coatings industry should have is the OSHA 1910.146 Permit -Required Confined Spaces standard. Under this standard, the contractor must develop a written permit space entry program that complies with the requirements of the standard. This program must be reviewed by the owner to verify that the contractor s safety procedures and practices developed under the standard are adequate and are being followed. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*26.0 93 M 8627940 0004003 300 Maintaining a site injury and illness log, OSHA Injury and Illness Records Form 200, is another method employers must use to track work activities involving contract employees working on or adjacent to covered processes. Injury and illness logs of both the employer s employees and contract employees allow an employer to have full knowledge of process injury and illness experience. This log will also contain information which will be of use to those auditing process safety management compliance and those involved in incident investigations. It is very important for owners to write OSHA compliance requirements into their contracts and specifications. This will help ensure that the contractors are complying with the applicable OSHA standards. V. SOURCES OF INFORMATION ON HEALTH AND SAFETY A. ORGANIZATIONS American Industrial Hygiene Association (AIHA) 2700 Prosperity Avenue Suite 250 Fairfax, VA 22031 -431 9 (703) 849-8888 American Society of Safety Engineers 1800 East Oakton Des Plaines, IL 60018-2187 (708) 692-41 21 International Brotherhood of Painters and Allied Trades 1750 New York Avenue, N.W., 8th Floor Washington, DC 20006 (202) 637-0700 National Safety Council 1121 Spring Lake Drive Itasca, IL 60143-3201 (708) 284-1 121 National Paint and Coatings Association 1500 Rhode Island Avenue, N.W. Washington, DC 20005-5597 (202) 462-6272 NIOSH Publications Dissemination National Institute for Occupational Safety and Health Robert A. Taft Laboratories 4676 Columbia Parkway Cincinnati, OH 45226
(513) 533-8287 Painting and Decorating Contractors of America (PDCA) 3913 Old Lee Highway Suite 33-8 Fairfax, VA 22030 (703) 359-0826 Steel Structures Painting Council (SSPC) 4516 Henry Street Suite 301 Pittsburgh, PA 15213-3728 (412) 687-1 1 13 554 ., ~ The Water Jet Technology Association P.O. Box 1365 ,Golden, CO 80402 B. SELECTED HEALTH AND SAFETY REGULATIONS Existing Occupational Safety and Health Administration (OSHA) regulations which apply to coatings operations can be found in three volumes of the Code of Federal Regulations (CFR): 29 CFR Part 1900-1910 (1901.1 to 1910.999) 1903 Inspections, Citations and Proposed Penalties 1904 Recording and Reporting Occupational Injuries and Illnesses 1905 Rules of Practice for Variances, Limitations, Tolerances and Exemptions 1910.132-140 Personal Protective Equipment 191 0.1 55-1 65 Fire Protection 29 CFR Part 1910.1000 to End 1910.1000 Air Contaminants 191O. 1025 Lead 1910.1200 Hazard Communication 29 CFR Part 1926 (Construction Regulations) 1926.57 Ventilation 1926.62 Construction Industry Lead Standard 1926.102 Eye and Face Protection 1926.1 52 Flammable and Combustible Liquids 1926.354 Welding, Cutting and Heating in Way of Preservative Coatings 1926.803 Compressed Air
ACKNOWLEDGEMENT The authors and editors gratefully acknowledge the active participation of the following in the review process for this chapter: Rex Bison and Daniel O. Chute. Richard Grunberg provided a number of pictures for this chapter. BIOGRAPHY D. Brian Shuttleworth received a B.S. in Occupational Health and Safety Management from Slippery Rock University of Pennsylvania. He works as an Industrial Hygiene Associate with SE Technologies, Inc. and KTA Environmental. Mr. Shuttleworth is also experienced in research and planning for stringent quality assurancelquality control programs. Scott D. Ecoff received a B.S. in Industrial Safety Management from Indiana University of Pennsylvania and an M.S. in Inductrial Hygiene from Central Missouri State University. Mr. Ecoff is the Principal Industrial Hygienist and Technical Director of Safety & Industrial Hygiene Services for SE Technologies, Inc., and a Senior Consultant to KTA Environmental. His responsibilities include providing consultation to clients in the recognition, evaluation and control of occupational health hazards. Mr. Ecoff is a Certified Industrial Hygienist, and is also an active member of the American Industrial Hygiene Association and the Steel Structures Painting Council. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*26.0 93 8627940 0004002 247 Daniel P. Adley received a B.A. in Chemistry from St. Vincent College in 1977 and an M.S. in Industrial Hygiene from the University of Pittsburgh in 1984. Mr. Adley has 16 years of experience in providing broad based safety and health consulting to a diversified cross-section of American industry. He has worked for SE Technologies, Inc. as the Manager of the Safety, Occupational & Environmental Health Department for the past four years. He is also very involved in lead-based paint management, working as a Principal Consultant to KTA Environmental. Mr Adley is a Certified Safety Professional and a Certified Industrial Hygienist. He is Chairman of the SSPC Group C.5 Committee on Environmental, Safety and Health Compliance. Portraits and biographical sketches of Sidney Levinson and Saul Spindel can be found at the end of Chapter 4.1 SUGGESTED READING MATERIAL 1. Dan Adley, Scott Ecoff, and Larry Balint. Personal Protective Equipment For Maintenance Painting Operations. Journal of Protective Coatings and Linings, April 1992, pp. 46-54. 2. American Conference of Governmental Industrial Hygienists. Industrial Ventilation: A Manual of Recommended Practice. 3. H.R. Bleile and S.D. Rodgers. Specification Criteria for Abrasive Blasting Media. Surface Preparation: The State of the Art, SSPC, 1985, pp. 89 -123. 4. Jerry Burbank. Industrial Hygiene in Lead Abatement: A Contractor s Perspective. Lead Paint Removal: Meeting the Challenge, SSPC, 1991, pp. 168-172. 5. Daniel O. Chute. Protecting Workers from Lead: A Review of Regulations and Practices. Lead Paint Removal: Meeting the Challenge, SSPC, 1991, pp. 186-195. 6. Daniel O. Chute. Update on OSHA Lead in Construction Standard. Maintaining Structures with Coatings, SSPC, 1991, pp. 133-136. 7. F.E. Clayton and G.D. Clayton. Patty s Industrial Hygiene and Toxicology, third edition, Vol. 2A-2C. New York: Wiley & Sons, 1981. 8. Mark R. Cullen, K.F. Maurer, and Irene Kurylo Smith. Controlling Lead Poisoning on Bridge Sites. Industrial Lead Paint Abatement: Approaches, Alternatives, and Advances, SSPC, 1993, PP. 63-65. 9. R. DeReamer. Modern Safety and Health Technology. New York: John Wiley & Sons, 1980. 1O. Barbara DeWoody. Solvent Hazards and Controls. Journal of Protective Coatings and Linings, April 1993, pp. 75-78. 11. Scott Ecoff. Air-Borne Health Hazards Associated With Abrasive Blasting. Journal of Protective Coatings and Linings, May 1993, pp. 85-87. 12. Scott Ecoff. Basic Principles of Fall Protection From Elevations. Journal of Protective Coatings and Linings, November 1992, Pp. 77-80. 13. Scott Ecoff. Setting Up an Air-Line Respirator System for Abrasive Blasting Operations. Journal of Protective Coatings and Linings, January 1993, pp. 69-72.
14. Epidemiology Division, Texas Department of Health. Silicosis In Oil and Gas Pipe Coating. January 1992. 15. Federal Register. OSHA s Lead Exposure in Construction, Interim Final Rule. Volume 58, 2590, (May 4, 1993). 16. Kent Foster. Monitoring of Lead Levels Outside Contained Areas During Blasting Operation. Achieving Quality in Coating Work, SSPC, 1992, pp. 202-203. 17. Harold E. Hower. The Dilemma of Removing Lead-Based Paint. Journalof Protective Coatings and Linings, January 1988, pp. 30-37. 18. Journal of Protective Coatings and Linings. NIOSH Requests Assistance in Preventing Silicosis and Deaths from Sandblasting. April 1993, pp. 21-37. 19. Mark A. Katchen. Solvent Syndrome. Maintaining Structures with Coatings, SSPC, 1991, pp. 63-67. 20. Karen A. Kapsanis. OSHA s New Rule on Lead: Changing the Practice and Price of Lead Paint Removal. Journal of Protective Coatings and Linings, July 1993, pp. 46-51. 21. Philip J. Landrigan. Exposure to Lead from the Mystic River Bridge: The Dilemma of Deleading. New England Journal of Medicine, March 1982, Vol. 306, p. 676. 22. Richard J. Lewis, Sr., ed. Sax s Dangerous Properties of Industrial Materials, eighth edition. New York: Van Nostrand Reinhold, 1992. 23. John M. Lunardini. Lead Paint Removal: Specification Through Job Completion. Maintaining Structures with Coatings, SSPC, 1991, pp. 140-155. 24. Robert Manware. Lead in Construction. Industrial Lead Paint Removal: Compliance and Worker Safety, SSPC, 1992, pp. 57-58. 25. H. Everett Myer. Safe Use of HDI Polyisocyanate-Containing Pol yu ret h ane Coati ngs. Maintaining Structures with Coatings, SSPC, 1991, pp. 68-74. 26. H. Everett Myer. Some Plain Talk About Polyurethane Coatings: Definitions, Safe Application, and the Future Direction of Industry Safety Needs. Journal of Protective Coatings and Linings, January 1991, pp. 52-56. 27. National Institute for Occupational Safety and Health. Construction Bibliography, 1990. 28. National Safety Council. Accident Prevention Manual for Industrial Operations, 1978 edition, pp. 27-28. 29. Occupational Safety and Health Administration. AllAbout OSHA. OSHA 2056. 30. Occupational Safety and Health Administration. Consultation Services for the Employer. OSHA 3047. 31. Occupational Safety and Health Administration. OSHA Handbook for Small Businesses. OSHA 2209. 32. Occupational Safety and Health Administration. OSHA Publications and Audiovisual Programs. OSHA 201 9. 33. Occupational Safety and Health Administration. Personal Protective Equipment. OSHA 3077. 34. P. Orbaek. Effects of Long-Term Exposure to Solvents in the Paint Industry. Scandinavian Journal of Work and Environmental Health, 1985, #11, Supplement 2. pp. 1-28. 35. Frank J. Pokrywka. Controlling Hazards in Confined Space Work. Journal of Protective Coatings and Linings, August 1993, pp. 81-84. 36. Frank J. Pokrywka. Personal Hygiene and Skin Protection for Coating Applicators. Journal of Protective Coatings and iinings, December 1992, pp. 63-65.
37. Jeffrey D. Propst. Working Safely with Electrical Equipment. Journal of Protective Coatings and Linings, February 1993, pp. 91 -94. 38. John F. Rekus. Employees Have a Right to Know. Journal of Protective Coatings and Linings, April 1989, pp. 42-47. 39. John F. Rekus. The Occupational Lead Hazard. Lead Paint Removal, SSPC, 1988, pp. 1-13. 40. John F. Rekus. Eliminating Confined Space Accidents in the Coating and Lining Industry. Journal of Protective Coatings and Linings, April 1990. pp. 46-53. 41. Steven P. Roetter. Responsibility for Worker Safety on Lead Paint Removal Projects. I Industrial Lead Paint Removal: Compliance and Worker Safety, SSPC, 1992, pp. 14-18. 42. Gwen Russell. Personal Monitoring to Evaluate and Control Employee Exposure to Lead on Abrasive Blasting Projects. Industrial Lead Paint Removal: Compliance and Worker Safety, SSPC, 1992, pp. 53-56. 43. Randy L. Sadler and Frank J. Pokrywka. Safe Storage and Use of Flammable and Combustible Liquids. Journal of Protective Coatings and Linings, March 1993, pp. 71-76. 44. The Steel Structures Painting Council. SSPC Qualification Procedure No. 2(1), SSPC QP-2 (I), Standard Procedure for Evaluating the Qualifications of Painting Contractors to Remove Hazardous Paint 1992. 45. The Water Jet Technology Association. Recommended Practices for The Use of Manually Operated HighPressure Water Jetting Equipment. 1985. 46. Sheri L. Woodruff. Providing Safe Respiratory Protection in the Protective Coatings Industry, Journal of protective Coatings and Linings, August 1988, pp. 54-59. --`,,,,`-`-`,,`,,`,`,,`--555 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
CHAPTER 27.0 ENVIRONMENTAL REGULATIONS AFFECTING PROTECTIVE COATINGS by Bernard R. Appleman INTRODUCTION (Chapter 27.0) A. Operations that Affect the Environment B. How the Environment is Affected C. Regulatory Agencies D. Overview of Federal Acts and Regulations AIR QUALITY REGULATIONS (Chapter 27.1) A. General/Overview of Activities and Regulations B. Ozone & VOC C. Air Quality for Lead D. Air Quality for Particulates E. State & Local Regulation of Air Quality WASTE HANDLING AND DISPOSAL (Chapter 27.2) A. Definitions B. Classifying Wastes C. Responsibilities for Hazardous Waste D.Sampling & Testing E. Treatment & Disposal of Hazardous Waste F. State Regulation of Hazardous and Non-Hazardous Waste OTHER REGULATIONS AFFECTING PROTECTIVE COATINGS (Chapter 27.3) I. WATER QUALITY A. Federal Clean Water Act B. Reportable Quantities for Hazardous Substances C.Water Quality Standards D. National Pollutant Discharge Elimination System E. Potable Water in Storage Tanks II. HAZARDOUS MATERIALS A. Toxic Substances Control Act B. CERCLA & Superfund C. Right To Know -SARA Title III III. REGULATING STORAGE VESSELS A. Secondary Containment B. Underground Storage Tanks IV. MISC EL LAN EO U S REGU LATI ON S A. Regulating Coatings For Food & Beverage Facilities B. Soil Quality Regulations C. Regulating Antifouling Coatings APPENDICES Appendix A: Hotlines and Other Phone Numbers
Appendix B: Professional & Trade Organizations Appendix C: Selected Environmental Regulations INTRODUCTION A. OPERATIONS THAT AFFECT THE ENVIRONMENT Coating and lining activities have a significant effect on the environment. Some examples of these activities and their specific effects on the environment are as follows: 1. Abrasive Blast Cleaning In this process, hard, small abrasive particles strike the steel or other substrate at high velocities, fragmenting the abrasive particle and eroding the substrate. Significant quantities of dust from the abrasive and the surface debris are thus made airborne and can contribute to air pollution. This dust itself is recognized as a fugitive emission that is FIGURE 1 Dust from abrasive blasting operation. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 556
SSPC CHAPTER*27.0 73 M 8627740 0004004 OIT often regulated. In addition, specific species may be released, such as lead dust, other heavy metals, silica, or asbestos, which are separately controlled by environmental agencies. 2. Paint Application In the process of spraying (and other means of application), a substantial portion of the liquid coating does not reach the substrate but is lost due to overspray. In addition, most coatings have appreciable quantities of volatile organic compounds (solvents) that can contribute to smog formation. 3. Waste Production Both coating removal and coating application generate waste products, which must be properly disposed of. In many instances, the waste may be classified as hazardous by EPA or state environmental agencies because of the heavy metal (e.g., lead) content of the residue, or the solvents of unused paint or thinner. 4. Product Storage The storage of certain products (e.g., hazardous waste, petroleum compounds) is regulated by EPA because of the potential ecological damage that could result from a spill or leak from storage vessels. 5. Leaching of Coatings Under certain circumstances, toxic or otherwise undesirable components of applied coating films may leach into the environment. Examples include coatings used for lining of potable water storage tanks, coatings used in food and beverage plants, and antifouling coatings. Leaching occurs because many of these ingredients are water-soluble or flake or erode into the environment. B. HOW THE ENVIRONMENT IS AFFECTED The above activities collectively can affect almost all the major environmental receptors (¡.e., air, soil, groundwater, surface water, potable water). The environmental regulatory structure (as exemplified by the US EPA) is specifically organized according to the aspects of the environment affected, not by the industry activity producing the environmental impact. The EPA s authority to issue and enforce environmental regulations is based on the environmental statutes or laws passed by the US Congress. Major environmental regulations are listed in the References section. Almost all of these statutes and the resulting regulations have some applications to the protective coating industry. The ones which have had the greatest impact are the Clean Air Act, the Resource Conservation and Recovery Act, and the Toxic Substance Control Act.
Also as a result of the historical development of the regulations, there often exists within the environmental agencies (both at Federal and State levels) separation of activities according to the specific aspect of the environment (e.g., air or soil). The legislators and the heads of the environmental agencies have not established sufficient policies or procedures for coordinating the various divisions within the agency. Consequently, the protective coatings and related industries affected by these regulations must deal with these regulations individually, responding to and complying with each specific requirement. If there are inconsistent or conflicting requirements between one or more environmental regulations (even from the same agency), the industry may need to bring this to the attention of appropriate officials. This is not to say, however, that government agencies, be they federal, state, or local, cannot collaborate on enforcement as well as regulatory development. In one of the more dramatic instances of inter-agency cooperation, the Texas Air Control Board (TACB) developed a stringent regulation for containing lead-based paint debris during removal operations on water storage tanks. The TAC6 was responding in part to an incident in which citizens of Cedar Park, TX complained to the Texas Health Department about air-borne dust from an open blasting operation on a water tank. In the process of investigating the complaint, public health officials found lead-based paint chips contaminating the soil of the entire neighborhood, and the chips were traced to the open blasting operations. Not only did two agencies work together on this complaint, but the air quality regulation subsequently developed by the TACB had the effect of protecting the ground as well as the air. C. REGULATORY AGENCIES The Environmental Protection Agency is the federal agency responsible for developing and enforcing environmental regulations. Congress intended that protection be a joint Federal-state responsibility. Most of the statutes provide for states to implement and enforce the regulations. In some instances states must meet certain requirements to be delegated authority (e.g., hazardous waste regulation under RCRA). Individual states may have their own environmental agencies, variously known as the Department of Environmental Protection, Department of Environmental Resources, Department of Natural Resources or state EPA. Other state or local agencies that may be involved are health agencies and fish and game commissions. State environmental regulations must be at least as stringent as federal regulations, but they may be more stringent. In some cases, county or municipality requirements may be stricter than state or federal regulations. The following discussion focuses primarily on federal requirements. State and local authorities should also be consulted. D. OVERVIEW OF FEDERAL ACTS
AND REGULATIONS Congress responds to concerns about environmental problems by passing laws which outline a general response to a problem and direct the Environmental Protection Agency to develop regulations. The citations at the end of this chapter are for the authorizing legislation (Acts of Congress). The Federal regulations developed by EPA in response to Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 557
SSPC CHAPTER*27.0 93 8627940 0004005 T56 these Acts are published in the Code of Federal Regulations (CFR). They are described in Chapters 27.1, 27.2, 27.3 and listed in Appendix C. 1. Air Pollution Control Regulations a. Clean Air Act -The original Clean Air Act (CAA), passed in 1970, focused on several specific pollutants: sulfur dioxide, carbon monoxide, nitrogen dioxide, particulates, ozone and lead.2 Air quality goals known as National Ambient Air Quality Standards (NAAQS) were developed for these pollutants. Despite considerable progress, many regions of the country did not meet the standards within the prescribed deadlines. The original act also required that the EPA develop standards for toxic substances in the air, known as National Emission Standards for Hazardous Air Pollutants (NESHAPS), but because the NESHAPS system required the agency to prove the risk of the materials, only a few standards were developed. b. Clean Air Act Amendments -The Clean Air Act Amendments of 1990 (CAAA) require areas that are not in compliance with existing requirements for ozone, carbon monoxide and particulates to come into compliance, and provide a schedule for compliance.3 The Amendments also require control of air toxics, approximately 190 specific substances emitted by specific kinds of facilities. Many of the solvents that make up paint will be affected by both of these sections of the Clean Air Act Amendments. The new regulations will also affect much smaller sources than previous regulations. Air pollution control regulations can be found in 40 CFR 50-99.* 2. Water Quality Regulations a. Clean Water Act -The Federal Water Pollution Control Act of 1972 was the first legislation to take a national approach to meeting the goal of fishable, swimmable waterways.4 Secondary treatment of biodegradable materials such as domestic sewage was an important goal of early Clean Water legislation. Limits were also set for a relatively small number of common industrial pollutants. In 1977, the Clean Water Act (CWA) was passed. It extended deadlines for some of the requirements of the 1972 Act. Amendments passed in 1987 expanded the number of regulated pollutants to include 129 specific toxic pollutants.S Requirements are enforced through a permit system. Facilities must have a permit to discharge materials to waterways. There are some exceptions for facilities discharging to public wastewater treatment facilities. b. Safe Drinking Water Act -The Safe Drinking
Water Act (SDWA) was passed in 1974.6 It authorized the EPA to limit the amounts of various substances in drinking water. It was amended in 1986. NOTE: Citations include sections reserved for future regulations The amendments accelerated EPA s regulation of toxic contaminants, banned future use of lead pipe and solder in public water systems, mandated better protection of groundwater resources, and limited underground injection of waste. Drinking water regulations require that drinking water contain no more than the Maximum Contaminant Levels (MCL) for any particular substance. Drinking water standards are sometimes used to establish criteria for acceptable levels of hazardous material at waste sites. Regulations on Water Pollution Control and Safe Drinking Water Act are found in 40 CFR 100-149. Other Clean Water Act regulations are found in 40 CFR 400-699. 3. Hazardous Waste Regulations a. Resource Conservation and Recovery Act -The Resource Conservation and Recovery Act (RCRA), passed in 1976, was intended to provide cradle to grave management of hazardous wastes. Generators were required to evaluate all wastes generated; to identify those that were hazardous; and to properly store, transport and dispose of those that were determined to be hazardous waste. There were also stringent requirements to document proper handling of these wastes. RCRA regulations initially applied only to businesses that generated fairly large quantities of hazardous waste, more than 1000 kg (2,200 pounds or about five and a half full barrels) a month. The Hazardous and Solid Waste Amendments of 1984 extended similar requirements to businesses generating smaller quantities of waste, more than 100 kg (220 pounds or about half a barrel) a month.8 However, generators of small quantities of waste, less than 100 kg (about 220 Ibs) per month, do not have to meet all the requirements that larger generators do. Regulations on treatment, storage and disposal of hazardous waste are found in 40 CFR 260-280. b. Comprehensive Environmental Response, Compensation and Liability Act -The Comprehensive Environmental Response, Compensation and Liability Act (CERCLA), passed in 1980, authorized the EPA to respond to hazardous spills and clean up abandoned waste sites.9 The businesses that had generated the wastes were to pay the costs of cleanup, and the Act outlined procedures for recovering costs from these businesses. It also created a fund to pay for clean-up of abandoned hazardous waste sites,
known as Superfund The waste sites became known as Superfund sites. c. The Superfund Amendments and Reauthorization Act -The Superfund Amendments and Reauthorization Act (SARA), passed in 1986, reauthorized, refunded and refocused hazardous waste site clean up.10 It also created a new set of requirements Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 558
SSPC CHAPTER*27*0 93 8627940 0004006 772 included as SARA Title III,the Emergency Planning and Community Right-to-Know Act (EPCRA). Title III required state- and community-level emergency planning. It also required industries to report quantities of hazardous substances released into air or water or stored on site to these local agencies and to the federal government. SARA and CERCLA regulations are found in 40 CFR 300-399. d. Underground Storage Tanks -Regulations for underground storage tanks (USTs) were required by the Hazardous and Solid Waste Amendments of 1984.8 Many industrial storage tanks are covered by regulations requiring registration, improved design, leak detection, proper installation and closure. Regulations for tanks containing hazardous waste are more stringent. UST regulations are found in 40 CFR 280-299. 4. Hazardous Substances Regulations a. The Toxic Substances Control Act -The Toxic Substances Control Act (TSCA), passed in 1976, gives EPA the authority to approve newly developed or newly imported chemicals.ll In addition, the EPA has the authority to limit or ban use of specific chemicals which the agency determines pose an unacceptable risk to human health or the environment. These provisions have been used by the EPA to regulate asbestos and polychlorinated biphenyls. They are likely to be used to limit use of lead in industrial paints in the future. Toxic Substances Control Act (TSCA) regulations are found in 40 CFR 700-799. b. The Federal Insecticide, Fungicide and Rodenficide Act -Regulation of pesticides dates from the beginning of this century, but originally focused on effectiveness of pesticides. Amendments to existing laws in 1972 focused on health and environmental effects and came to be known as the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA).l* The regulations apply to a broad range of substances used to control unwanted organisms including insects, rodents, plants and microorganisms such as mildew. Additives to control microorganisms are common in paint. Pesticide regulations require that manufacturers register pesticides with the EPA. Labels that outline safe uses and practices are required and must be submitted as part of the registration process. EPA must weigh any health or environmental effects of a product against its benefits. It may ban or restrict the use of a product for which the risks outweigh the benefits.
Federal Insecticide, Fungicide and Rodenticide Act regulations are found in 40 CFR 150-189. 5.HUD Guidelines The Department of Housing and Urban Development has developed the only available guidelines on lead-based paint removal, entitled Hazard Identification and Abatement in Public and Indian Housing .13 The work was a joint effort of several federal agencies responsible for health and safety and the health effects of hazardous substances in the environment. Unfortunately, the guidelines were written with residential and domestic paint removal in mind. It is often difficult to apply them directly to industrial paint removal. The guidelines include information on identifying the level of lead in paint; when that level consti--`,,,,`-`-`,,`,,`,`,,`--tutes a hazard; acceptable methods of abatement; reducing dust levels; housekeeping; inspection; equipment used to protect workers from exposure to lead; and containment. 6. Soil There are no federal regulations regarding permissible levels for contaminants or hazardous material in soil relevant to protective coatings. The potential impact of soil contamination is discussed in Chapter 27.3. REFERENCES 1. Water Tower Project Shut Down for Lead Contamination: Citation and Lawsuits Follow, Journal of Protective Coatings and Linings (JPCL),October, 1990, pp. 97-99. Texas Reviews Comments on Blasting Rule for Water Tanks , JPCi, July, 1991, p. 31. 2. Clean Air Act, Public Law 91-604, December 31, 1970. 3. Clean Air Act Amendments of 1990, Public Law 101-549, November 15, 1990; and Public Law 102-187, September 4, 1991. 4. Federal Water Pollution Control Act, Public Law 92-500, October 18,1971, and Clean Water Act of 1977, Public Law 95-217, December 28, 1977. 5. Clean Water Act of 1987, Public Law 100-202, December 22, 1987. 6. Safe Drinking Water Act (Title XIV of the Public Health Service Act, Public Law 93-523, December 16, 1974).
7. Resource Conservation Act, Public Law 94-580, October 21, 1976. 8. Hazardous and Solid Waste Amendments, Public Law 98-616, November 9, 1984. 9. Comprehensive Environmental Response, Compensation, and Liability Act, Public Law 96-510, 1980. 1O. Superfund Amendments and Reauthorization Act of 1986. Public Law 99-499, October 17, 1986. 11. Toxic Substances Control Act, Public Law 94-469. October 11, 1976. 12. Federal Insecticide, Fungicide, and Rodenticide Act, Public Law 92-51 6, October 21, 1982. 13. Lead-Based Paint: Interim Guidelines for Hazard Identification and Abatement in Public and Indian Housing, September 1990, rev. May 1991. Washington, DC: Office of Public and Indian Housing, May 1991. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 559
SSPC CHAPTERa27.L 93 8627940 0004007 829 m CHAPTER 27.1 AIR QUALITY REGULATIONS by Bernard R. Appleman and Karen A. Kapsanis A. GENERAL OVERVIEW OF ACTIVITIES using maximum available control technology AND REGULATIONS (MACT). MACT is defined in part as the maximum degree of reduction in emissions of the hazardous 1. NAAQS air pollutants ... i4 A new source (¡.e., a new emitThe US Congress passed the Clean Air Act in 1970 ting facility) must achieve red uctions equivalent to to protect and enhance the quality of the nation s the best-performing similar sou rce. Existing sources air resources.* As a result of this act, EPA es- (the majority of facilities) ar e required under MACT tablished the National Ambient Air Quality to achieve the average reduction atta ined by the Standards (NAAQS), intended to promote the pub- best 12percent of similar source s (based on there lic health and welfare. Six primary pollutants were being a minimum of 30 such s ources). These stanidentified, for which EPA was to develop criteria, al- dards are thus based on t echnology rather than on lowing for an adequate margin of safety to protect health, as was earlier the ca se. the public health. These six pollutants are as follows: The facilities initially required to abide by MACT Lead are stationary sources emitting more than ten tons Ozone 19 megagrams (Mg)] per year of any single HAP or Particulate matter (10 microns or less) 25 tons (23Mg) per year total. Thus, a f acility apSulfur dioxide plying coatings containing 2 Ibs/gal (240g/L) of xyNitrogen dioxide lene would be limited to 20,000gallons (76,000 L) Carbon monoxide per year. Of most interest to the protective coatings in- According to a National Paint an d Coatings Asdustry are those for ozone, lead, and particulates. sociation analysis, EPA plan s to set MACT regulaNAAQS apply only to measured ambient levels (¡.e., tions in 1994 for marine coatin gs, wood furniture, dust or vapors that remain suspended). Air emis- and aerospace.14 The major sour ces generally must sions that deposit particles on the ground or adja- comply within 3years after t he effective date. Overcent properties are covered by CERCLA regulations all, MACT must be in place by the year 2000for all discussed in Chapter 27.3.9 source categories.
In 1990,Congress amended the Clean Air The CAAA also addresses the need to contr ol Act.3 The Clean Air Act Amendments (CAAA) are HAPS from area sources. These are sources that summarized in part B of this section. are too small to be regulated as major sou rces (¡.e., 2. HAPS less than 10 tons [9Mg] per year of a single HAP As part of the CAAA, Congress specifically added or 25 tons [23Mg] per year tota l HAPS) but which approximately 190additional Hazardous Air Pollut- collectively emit a substantia l volume of HAPS. ants (abbreviated as HAPS) to the list of sub- A second phase of HAPS implementa tion enstances that required control. This list included tails potential imposition of health-based standards. many of the common solvents used in paints, such Within 8 years after MACT stand ards are issued, as xylene, toluene, and methyl ethyl ketone (see Ta- EPA must issue additional re sidual risk standards ble l).Previously, under the National Emission if the períormance-based standards are determined Standards for Hazardous Air Pollutants program, to be inadequate.14 EPA had been charged with regulating HAPS. How- It is important for the industry to coordinate the ever, there was no significant progress because of control of HAPS under MACT wi th the control of the requirement to apply health-based standards VOCs under other provisions of t he CAAA, e.g., and because of the lack of specific targets. Control Technique Guidelines or Nat ional Rules. The CAAA selected specific HAPS (with provi- Recent activities to establish a co mbined HAPNOC sions for adding and deleting substances) and es- control strategy for the shipb uilding industry (marine tablished a new approach for controlling HAPS. The coatings) are summarized in S ection B.6. 190 substances listed will be subject to controls Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 560
SSPC CHAPTERU27-L 93 6627940 0004008 765 Table 1 HAZARDOUS AIRPOLLUTANTS USED IN PROTECTIVE COATINGS APPLICATIONS Chromium Compounds Epichlorohydrin (Chloro-2,3-epoxypropane) Ethylene Glycol Formaldehyde Glycol Ethers Hydrochloric Acid Isophorone Lead Compounds Methyl Chloroform (1,1,1,-Trichloroethane) Methyl Ethyl Ketone (2-Butanone) Methyl Isobutyl Ketone (Hexone) Methylene Chloride (Dichloromethane) Styrene Toluene Triethylamine Xylenes (m,o,p or mixed) B. OZONE AND VOC 1. Regulating Ozone Ozone, a reactive form of molecular oxygen, is a major component of smog. The detrimental effects of ozone occur when it is found in the lower atmosphere (troposphere), where humans and plant life exist. Here it affects human respiratory function at high ambient levels and can also damage plant life. In the upper atmosphere (stratosphere), however, ozone has a beneficial effect on human health, helping to absorb solar radiation that could otherwise reach the earth and increase the risk of skin cancer and other diseases. The coatings industry is involved in aspects of the ozone problem. First, ozone is produced by the reaction of compounds (VOCs) and nitrogen oxide. the organic solvents in coatings are
both ground level volatile organic Almost all classified as
VOCs, and hence are subject to regulation by EPA in the effort to control ground-level ozone. Second, in an effort to protect the stratospheric ozone from depletion, EPA and other agencies have restricted use of certain halogenated compounds that interact with and deplete the ozone. These compounds include degreasing solvents and some solvents used for dissolving resins and coatings. In the early 1970s, EPA established 0.12 ppm as the maximum concentration of ozone consistent with human health. To be in compliance, a district or region must not exceed this level for more than one hour per year over a three year period. Districts that meet this criterion are designated as attainment areas ; those that do not are non-attainment. Ozone is not a direct by-product of a painting operation, but, as indicated above, it is produced when VOCs react with nitrogen oxide under the influence of ultraviolet radiation. Therefore, regulating coating operations by requiring that the immediate vicinity of a coating application meet the 0.12 ppm ozone standard would not achieve air quality objectives. Rather, because they are the precursors of ozone and are much more readily manageable, EPA and other regulatory agencies have elected to control the amount of VOCs in paint. 2. PA Regulation of VOCs EPA defines VOCs as a group of chemicals that react in the atmosphere with nitrogen oxides in the presence of heat and sunlight to form ozone. Not included are methane and other compounds determined by EPA to have negligible photochemical reactivity. Many solvents used in paints contain VOCs. VOCs can be controlled in several manners. One approach (which has been used by EPA for certain industries) is to limit the total quantity of VOCs that can be emitted from a given facility for a unit of time (e.g., one ton of VOC per year). The second approach is to limit the amount or proportion of VOC permitted in a coating formulation. This method has also been widely employed by EPA and state agencies. This is the most common method, and will be discussed in greater detail below. A third approach is to control the transfer efficiency of the coating application. This approach reduces the amount of coating material that evaporates, rather than landing on the substrate. This is probably the least used of the three approaches described. EPA has classified VOC sources into two broad categories: mobile sources and stationary sources. Mobile sources include cars, trucks, and other vehicles. The VOCs produced by mobile sources are not relevant for the protective coatings industry.
Fabricating shops that coat steel are included among the stationary sources listed by EPA. There are numerous other stationary sources which use other types of coatings being regulated for VOC such as furniture, aerospace, and automotive. These are outside the scope of this chapter. Until the passage of the 1990 Clean Air Act Amendments, EPA was not mandated to regulate VOCs from coating operations. Rather, it was charged with preparing guidance documents, called Control Technique Guidelines (CTG) which states and localities could use as a basis for regulating VOC emissions from various shop coating operations. The CTG for industrial shop coating operations is discussed under item 4, VOC from Shop-Applied Coatings, below. 3. Clean Air Act Amendments of 7990 The CAAA set forth an ambitious program for reducing air pollution throughout the U.S.3They were developed in part, according to one author, because despite the success of the 1977 CAA in reducing emissions from individual sources, ambient air pollution was still a major health and environmental problem in urban areas. While individual source emissions were down, the number of polluting Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 561
sources such as automobiles had increased dramat- Typically, these rules are bas ed on a Control ically since 1977.15 Technique Guideline (CTG) issued in 1978 by the The EPA has identified four primary goals in EPA as a guidance document for ozon e nonimplementing the 1990 CAAA:16 attainment areas (¡.e., that have been designated to bring all cities into health standards at- as exceeding the national ambient air quality stantainment; dard for ozone).17 In the existing EPA CTG for surto cut air toxic emissions by 75%; face coating of miscellaneous metal parts and to reduce sulfur dioxide emissions by 10 mil- products, coatings are classified as follows, with lion tons; and their recommended VOC limitations, based on Ibs to phase out all chlorofluorocarbons by 1995. of VOC per gal. (911) of coating l ess water, and the The 11 titles that make up the CAAA create a definitions generally used to descr ibe the coatings. framework for achieving these goals. As the sum- a. Air-dried coatings: 3.5 Ibsl gal. (420 g/I) -dried mary given below of the 11 titles indicates, hazard- by the use of air or forced warm air at temperatures ous airborne emissions from coatings are but one up to 194OF (90OC); target of the CAAA. b. Clear coatings: 4.3 Ibslgal. (520 g/I) -unpig4. VOC from Shop-Applied Coatings mented or transparent coating, lacking color a nd The oldest type of VOC rule is the miscellaneous opacity; metal parts and products rule, which applies to coat-c. Extreme performance coat ings: 3.5 Ibslgal. (420 ing operations in fabricating and painting shops and gll) -designed for harsh ex posure or extreme enother stationary facilities. Rules of this type can be vironmental conditions; found in force statewide or locally in approximately d. All other coatings: 3.0 Ibslgal. (360 911) -any 33 states. other type of coating. Many states have established limits for the total amount of VOC that can be emitted from a facility in a non-attainment area in a year, a month, a day, or an hour. The most common limits are for total emissions per year. There is a great spread among states with levels ranging from 2.5 tons (2.3 Mg) to 100 tons (91 Mg) per year. Often a state will impose a lower limit (e.g., 10 tons, or 9.1 Mg) per year in urban areas with a relatively high ozone level, and less stringent levels (e.g., 100 tons, or 91 Mg) per year in other areas. This principle has been followed by the EPA under the Clean Air Act Amendments. The Agency has established major sources (¡.e., facilities subject to special requirements) for emission controls and reduction based on the clasFIGURE 2 sifications of ozone non-attainment areas shown below.
Table 2 CLASSIFICATION OF OZONE NON-ATTAINMENT AREAS Definition of Designation Ozone (ppm) Major Source Marginal 0.121 to 0.138 100 Tons (90 Mg)/year Moderate 0.138 to 0.160 100 Tons (90 Mg)/year Serious 0.160 to 0.180 50 Tons (45 Mg)lyear Severe 0.180 to 0.280 25 Tons (22.5 Mg)/year Extreme >0.280 10 Tons (9.1 Mg)/year Applying coating in the fabricating shop, --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 562
SSPC CHAPTERU27.1 93 m Title I - Provisions for Attainment and Maintenance of National Ambient Air Quality Standards reaffirms EPA s original commitment to reduce levels of six types of air pollutants: ozone, carbon monoxide, particulate matter (PM-101, lead, nitrogen dioxide, and sulfur dioxide. Title I sets specific timetables for states to reduce emissions of these pollutants. In addition, going beyond the classification scheme of the earlier Clean Air Act, the 1990 CAAA further classifies areas originally described as non-attainment for ozone into the categories of marginal, moderate, serious, severe, or extreme. (Table 2) Of the titles that affect coatings, Titte I is the most relevant, because as noted earlier, most of the organic solvents used in coatings are volatile organic compounds (VOCs) and, as such, contribute to the formation of ozone. (See section B of this Chapter, Ozone and VOC ). Title I affects coatings in two ways. It calls for a federal national rule to restrict VOC emissions from coatings applied to stationary structures such as bridges, industrial facilities, and storage tanks. It also calls for a review of existing federal guidance documents and issuance of several new guidance documents for the states to use to develop rules for controlling VOC emissions from coatings operations at fixed coating facilities. These include fabricating shops, auto body shops, and other sites where coating application is a dailyor at least regular operation. Title II -Mobile Sources. Title IIauthorizes EPA to set and revise emission standards for cars, light trucks, urban buses, and non-road vehicles such as locomotives. It also sets requirements for the use of clean fuels, reformulated gasoline, and oxyfuels; bans leaded gasoline in motor vehicles after 1995; and authorizes EPA to regulate refueling operations. Title III -Hazardous Air Pollutants (HAPS). Title Ill takes a broad approach to regulating toxic air pollutants. These pollutants are air-borne substances that may be hazardous to human health or the environment but that are not specifically regulated elsewhere in the CAAA. Listed in Title 111 are approximately 190 substances, many of which are solvents and other VOCs commonly used in coatings or coating operations. HAPS are regulated by restricting emissions from fixed site sources. Controls required are based on the amount of real or potential emissions from the source. Painting shops, dry cleaners, and chemical processing plants are among the fixed sources affected by Title III. As pointed out in a 1993 article on the CAAA, a VOC in a coating can be regulated under Title I and Title III if the VOC is also a HAP. S In a shop painting operation, for instance, the
VOC emission will be regulated by the state while the HAP emission will be regulated by a federal rule. TitleIV -Acid Deposition Control. Title IV is devoted to restricting sulfur dioxide and nitrogen oxide emissions from coal-burning electric utility plants to prevent what is known as acid rain. Acid rain occurs when sulfur dioxide and nitrogen emissions are transformed in the atmosphere and fall to the earth in rain, fog, and snow. 16 Acid rain can harm the natural environment as well as buildings. It ISalso suspected to be hazardous to human health. Title V-Permits. Title V calls for states to develop operating permits for major sources covered under Title l and for sources covered in other titles, including Title 111. The permitting program provides a way of tracking sources and their emissions. Shop painting ties are among the sources typically required to for operating permits, Title VI -Stratospheric Ozone Protection. Title provides measures for preventing the depletion of t stratospheric ozone layer, which is actually beneficial or good ozone. As described insection B of this chapter, Ozone and VOC, stratospheric ozone absorbs cosmic radiation before it reaches the earth. The radiation ISlinked to the risk of skin cancer. Some solvents used in degreasing operations or in coatings can contribute to stratospheric ozone depletion. Hence, such materials are also under the domain of Title VI. (See discussion under 8.8 Compliance with VOC Rules. ) Title Vfl -Enforcement. Title VI1 significantly strengthens the EPA s authority to enforce the CAM. The Title authorizes EPA to impose criminal as well as civil sanctions against violators. Title Vlfl -Miscellaneous Provisions. Title VIII addresses the control of air pollution on the Outer Continental Shelf (sources within 25 miles of shore); on the
US-Mexico border; and in international border areas (areas in the US that are subject to emissions originating outside the US). Title IX -Clean Air Research. Title IX calls for research on topics such as monitoring and modeling methods, health effects associated with air pollutants, the effects of air pollution on the ecosystem, modeis for predicting accidental releases, pollution prevention, acid precipitation, and clean alternative fueling. iitle X -Disadvantaged Business Concerns. Title X requires EPA to make at least 10 percent of federal funds for CAAA research available to disadvantaged business concerns, which are defined as those that are at least 51 percent owned and controlled by black americans, Hispanic Americans, Native Americans, Asian Americans, women, or disabled Americans. Title XI -Clean Air Employment Transition Assistance. Title XI amends the Job Training Partnership Act to include assistance to workers adversely affected by compliance with the CAAA. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 563
SSPC CHAPTER*Z?.L 93 H 8b2?940 00040LL 25T H Typical levels for daily emissions are 15 Ibs (6.8 kg) with a range of 5-100 among the various states. Also, many states have adopted a maximum level of 3 Ibs (1.4 kg) per hour. An application shop would have to install add-on controls to capture emissions in excess of these levels. 5.VOCs from Architectural and Industrial Maintenance (AIM) Coatings Rule Architectural coatings are generally defined as coatings applied to stationary structures and their appurtenances, to mobile homes, or to curbs. Several states have architectural coating rules that include specific VOC restrictions on coatings sold for use in field painting of bridges and industrial structures such as water tanks and plant facilities. As of January 1991, such rules were found in parts of Arizona, California, New Jersey, New York, and Texas.18 The CAAA will have a major impact on industrial maintenance-type coatings operations throughout the US. The Amendments call for an architectural coatings rule (including industrial maintenance) to be promulgated by EPA. According to EPA, such a rule is expected to be in place as early as 1996. Unlike EPA CTGs, which are intended for guidance on regulation development in ozone nonattainment areas, EPA rules, including the anticipated architectural coatings rule, are expected to be promulgated nationwide in ozone attainment areas as well as non-attainment areas. States and regions may establish and promulgate rules more stringent than the rule EPA eventually proposes, but no less stringent regulations will be allowed. Development of the national rule began in 1992 through a process called Regulatory Negotiation or Reg-Neg. lg Representatives of EPA, the paint industry, environmental groups, labor, other regulators and other affected parties met to discuss, draft, debate, and decide on how and at what levels VOCs will be regulated in AIM Coatings. In late summer 1993, the Reg-Neg committee had reached tentative agreement on a two-phase approach to achieve a 45 percent VOC reduction by 2003. In the first phase, a Table of Standards would be established. This table would set maximum VOC content for 30-40 categories of AIM coatings, which would need to be met by 1996. For industrial maintenance coatings, the expected maximum VOC level is between 340 and 380 gA(2.8 and 3.2 Ibslgal). The second phase would require coating manufacturers to achieve overall VOC reductions of 35 percent and 45 percent by 2000 and 2003, respectively, compared to 1990 emission levels. EPA planned to publish the proposed rule in the federal Register in early 1994.
6. Control of VOC s From Marine Coating Operations Under the CAAA, EPA was specifically directed by Congress to develop a Control Technique Guideline (CTG) to reduce emission of VOCs and PM-10 from shipbuilding and ship repair operations. EPA s aim was to develop limits for VOCs concurrently with those for HAPS. This was based on the assumption that many shipyards were major sources, for which HAPS regulations were required by November 15, 2000. In 1992, EPA surveyed shipbuilders and coating manufacturers to determine the current status of regulations and technology.20 Regulations affecting marine coating operations were in effect in California (several districts), Connecticut, Maine, Louisiana, Virginia, Washington, and Wisconsin. The most comprehensive regulations were those from California and Louisiana, which had specific rules for shipbuilding operations. From the survey, EPA, working with shipyard representatives, classified marine coatings into 12 specialty and 2 general categories. Four coating types (epoxy, alkyd, inorganic zinc and anti-fouling coatings) comprise 90% of the total coatings used for shipbuilding activities. Epoxy alone represented 60% of the volume for the shipyards surveyed. The survey also identified xylene, toluene, and MEK as the three most commonly used HAPS. Others were MIBK, hexane, ethyl benzene, and glycol ethers. In trying to develop a rule to encompass both HAPS and VOCs, EPA must combine the requirements for these two distinct rules. As discussed in Section A, HAPS require control using Maximum Available Control Technology (MACT). Regulation of VOC under the CTG as prescribed in the CAAA requires conformance with Best Available Control Measures (BACM). A detailed description of these terms is beyond the scope of this chapter. Some examples of approaches to meeting these requirements are suggested below, based on proposals by EPA. An example of Best Available Control Measure (BACM) would be to adapt the most stringent current VOC control regulations for marine coatings (Le., those in effect in California). For the HAPS, MACT is the average of the best 12% of the control technology. This 12% could be based on individual coatings or on individual shipyards. For example, EPA has characterized epoxy coatings based on their use and VOC levels. The MACT would be the average of the 12% of epoxy coatings having the lowest VOC requirements. This level is about 135 g/L (1.1 Iblgal), compared to the overall average for epoxies of 350 g/L (2.9 Ibs/gal). Alternately, the MACT could be computed based on the average VOC level for the 12% of the shipyards hav-
ing the lowest average VOC emissions. The regulation was still under development as of Fall 1993.20 EPA s basic concern is that reducing the VOCs does not increase the level of HAPS content in the Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 564
SSPC CHAPTERx27.L 93 Ab27940 0004032 396 coating. Most coatings contain a combination of HAPS solvents and non-HAPS solvents. The concern of the shipbuilders, the coating manufacturers, and others in the marine coating industry is that the resulting regulation not result in a significant loss in performance or increase in cost. 7. State Approaches to Regulating VOCs As of 1993,not all states took the same approach to regulating VOC emissions from paints. For instance, states such as Oregon, North Carolina, and Maryland regulate emissions from shop painting operations in ozone non-attainment areas only. Others, such as Pennsylvania and Ohio, regulate VOC emissions from shop painting operations throughout the state, imposing stricter requirements on operations in ozone non-attainment areas. By the same token, only a few states or air quality districts regulate VOC emissions from coatings applied in the field, and of those that do, VOC limits vary. Hence, New York restricts VOC emissions from industrial maintenance coatings to 3.8 Ibslgal (450 g/I) whereas California s South Coast Air Quality Management District (SCAQMD) caps them at 3.5 Ibs/gal (420 911). Until there is a national rule, states can also continue to differ in their principles of regulation. Air quality districts in California and states like New York and New Jersey regulate AIM Coatings primarily by function, such as concrete curing compounds, industrial maintenance primers, and traffic coatings. Texas, in contrast, regulates many AIM coatings by generic type, such as alkyd varnishes, epoxies, exterior alkyds, nitrocellulose lacquers, and urethanes. 8. Compliance with VOC Rules a. Reducing VOC in Coatings VOC regulations affect painting operations from formulation through application, performance, and service life. The principal approach for decreasing VOC emissions is by using coatings with reduced levels of VOC. This is accomplished by higher solids coatings, solvent-free (¡.e., 100percent solids) coatings, or waterborne coatings. Some of these new formulations may require special application equipment or specially trained applicators. The coatings industry has committed tens of millions of dollars of resources to develop, evaluate, and produce VOC-compliant coatings. Many technical articles, seminars, and product announcements address this issue, which has come to dominate the technology. Coatings chemists have thus been forced to find substitutes for solvent-borne coatings with high
VOC levels, and these substitutes have in some cases affected application properties -viscosity, for instance. Consequently, applicators have had to adjust to new equipment, methods and restrictions for applying high solids, high viscosity coatings and water-borne materials. Performance properties of coatings have also been at issue because of the need to formulate materials with lower VOC levels. With products being introduced quickly for long-term service, there is a very limited performance history for many products and thus little field data for lower VOC materials relative to the amount of data for older, solvent-borne coatings. Hence, specifiers have had to select products without strong evidence for or against a product. Instead, they have had to rely on accelerated test data and on abbreviated field trials or manufacturers claims. Users have found in some instances that the lower VOC products do not offer the chemical or weathering resistance or gloss retention of their solvent-borne counterparts. In other instances, however, the lower VOC products have performed as well as or better than their solvent-borne counterparts. A larger body of historical field data is needed to minimize problems with selection of low VOC products for regulatory compliance. A new SSPC Guide has been drafted which provides recommended procedures for qualifying and selecting VOC-compliant coating systems and for preparing specifications.21 b. Alternate Approaches for Compliance A second approach for compliance with VOC regulations is use of pollution abatement equipment that captures emissions. This approach is suited almost exclusively to shop painting operations, because abatement equipment typically is not portable. Even for fixed-site facilities such as steel fabrication and rail car paint application shops, the capital costs for this equipment are often extremely high. A third means of reducing VOC emissions is improving the efficiency of the application process. Using conventional air spray systems, much of the coating may not reach the intended surface, but instead be lost to the atmosphere because of wind, irregular surfaces, or poor applicator skill. Equipment such as electrostatic spray or high volume lowpressure spray can significantly increase the transfer efficiency. In addition, better training of applicators could also reduce the amount of paint and VOC lost during application. A fourth approach is the use of nonphotochemically reactive solvents, which are exempt from the VOC regulation. Exempt solvents that have been used are l,l,l, -trichloroethane and
methylene chloride which are good solvents for certain alkyd and other resins. There are several disadvantages to using these solvents. One is the possibility of adverse health effects, as both are listed as HAPS according to the 1990CAAA. The second Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 565
is that both solvents must be disposed of as hazardous waste. In addition, there is a strong international effort to ban the use of chlorofluorocarbons in coatings because they contribute to destruction of the ozone in the upper atmosphere (stratosphere). The solvent 1,l ,l-trichloroethane is listed as a Class I substance, ¡.e., as among the most ozone-depleting substances. Starting in May where 1993, any coating containing this material must carry a warning label stating that the product contains a substance which harms public health and the enVOC Wo = = VOC content in g/L of coating less water and exempt solvent Weight percent of organic volatiles (V, -W,) vironment by destroying stratospheric ozone. In ad- W, dition, production must be phased down by the year V, 2000 to 20% of its 1990 levels.14 D, D, 9. Methods of Measuring VOC VOCs are defined as the mass of volatile per volume of liquid (less water and exempt solvents). The most widely.used method for measuring VOC content is EPA Method 24, which is described in 40 CFR 60, Appendix A.Z2 The procedure for determining VOC content is also described in ASTM D 3960-91.23 There are some subtle differences between the EPA method and the ASTM method which are discussed below. The procedure consists of the following steps: Determine the percent volatiles by weight in the coating. Determine the density of the coating. Determine the water content (percent by weight) of the coating, and Compute the VOC. The standard equations are given below. --`,,,,`-`-`,,`,,`,`,,`--Equation 1 is for a solvent-borne coating that does not contain water or exempt solvent, and Equation 2 for a coating containing both solvents and water (but no exempt solvents). There have been several concerns or problems with using the EPA and ASTM test methods. These
are summarized below. Table 3 = = = =
Weight percent of water Volume percent of water (Ww)(Dc/Dw) Density of coating glL at 25°C Density of water, g/L at 25OC (0.997 x 103)
a. Baking of Multi-Component Air-Dried Coatings. Originally, the EPA and ASTM methods determined the volatiles using ASTM D 2369, which requires heating a sample at 1 10°C for one hour.24 One problem that arose was that the multi-component coatings were not fully cured before being baked. As a consequence, some of the unreacted low molecular weight species were volatilized and measured as VOCs although under air-drying conditions they would become part of the film (Le., non-volatile). There was also concern that at 110°C, some film additives, such as plasticizers, might also become volatilized, which would give artificially high readings of the VOC content. In 1992, EPA and ASTM agreed to allow the test specimens to stand at room temperatures for up to 24 hours to allow the coatings to cure prior to baking.25 b. Low-Solids, Water-Borne Coatings. Several coating manufacturers have pointed out that EPA Method 24 is not well suited to measuring the VOC content of low-solids waterborne coatings. This can be understood by examining Equation 2 for a lowsolids water-borne coating. Both the numerator and the denominator become very small, as the ratio of D,/D, approaches 1 and the W, (weight percent of water) approaches 100.There are inherent inaccuracies in dividing one very small number by another very small number. EPA has agreed to ANALYSIS OF VOC EMISSIONS Component Density Volume (W Weight (%o) Water 1.o 240 cc (24) 240 g (27.3) Solvent 0.75 300 cc (30) 225 g (25.6) Resin 0.9 460 cc (46) 414 g (47.1) Coating 0.88 100.00 (100) 879 (100.0) Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 566
SSPC CHAPTER*27=1 93 m 8627940 0004014 Th9 m review a proposed revision of the method for this type of coating. c. Non-Linearityof VOC Levels. Because of the way VOC is defined (¡.e., a s mass of volatiles divided by volume of coating less water), the VOC content does not provide a linear measure of the difference in VOC emitted from different coatings. As noted in ASTM D 3960, thus, a coating with VOC content of 3 Ibs of VOC per gallon ...would release about 85% less VOC than a coating with 6 Ibs of VOC per gallon of coating. 23 d. Inability to Compute Actual VOC Emitted. Because the volume of the water is subtracted from the volume of the paint, it is often difficult to compute the actual amount of VOC emitted for a gallon of paint. Consider the following hypothetical example of a coating with 240 cc of water, 300 cc of organic solvent, and 460 cc of resin to constitute 1 liter of coating (1000 cc). Using assumed densities of 1.0 for water, 0.75 for the solvent and 0.9 for the resin we can compute a VOC content of 296 g/L according to Equation 2. (Table 3) However, from an emissions inventory viewpoint, each liter of coating that is applied (e.g., at an application shop) emits 225 grams (300 cc). This situation can be confusing and can require several calculations to accurately compute total VOC emissions. e. Alternate Definitions of VOC. At least one state (Texas) has established a definition of VOC which is based on mass of volatiles emitted per volume of solid (¡.e., grams of VOC per liter of solids).26 This definition has the advantage of providing a linear relationship between the VOC content and the VOC emitted. A significant problem with this, however, is that the numbers required in Texas would be different from the numbers required in the other states because of the difference in definition. Another problem is that there is no established means of measuring fhe volume solids directly. Instead, the Texas Air Control Board has established a procedure to calculate its version of VOC from the EPA version. This calculation requires assumptions of densities for the solvents and has added to the confusion. Table 4 OZONE NONATTAINMENT AREAS IN 1990 Extreme Attainment Date 1 1 /15/201O Los Angeles -South Coast Air Basin, CA
Severe Attainment Date 11/15/2007 C hicago-Gary-Lake County , I L-l N Houston-Galveston-Brazoria, TX Milwaukee-Racine, WI New York-N New Jersey-Long Is, NY-NJ-CT Southeast Desert Modified AQMA, CA Severe Attainment Date 1 1 /1512005 Baltimore, MD Philadelphia-Wilm-Trent, PA-NJ-DE-MD San Diego, CA Ventura County, CA Serious Attainment Date 11/I 5/2000 Atlanta, GA Baton Rouge, LA Beaumont-Port Arthur, TX Boston-Lawrence-Worcester (E.MA), MA-NH EI Paso, TX Greater Connecticut Muskegon, MI Portsmouth-Dover-Rochester, NH Providence (All RI), RI Sacramento Metro, CA San Joaquin Valley, CA Sheboygan, WI Springfield (Western MA), MA Washington, DC-MD-VA Moderate Attainment Date 11/15/96 Atlantic City, NJ Charleston, WV Charlotte-Gastonia, NC Cincinnati-Hamilton, OH-KY Cleveland-Akron-Lorain, OH Dallas-Fort Worth, TX Dayton-Springfield, OH Detroit-Ann Arbor, MI Grand Rapids, MI Greensboro-Winston Salem-High Point, NC Huntington-Ashland, WV-KY Kewaunee County, WI Knox & Lincoln Counties, ME Lewiston-Auburn, ME Louisville, KY-IN Manitowoc County, WI Miami-Fort Lauderdale-W. Palm Beach, FL
Monterey Bay, CA Nashville, TN Parkersburg, WV Phoenix, AZ Pittsburgh-Beaver Valley, PA Portland, ME Raleigh-Durham, NC Reading, PA Richmond-Petersburg, VA 567 --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*27.1 93 8627940 0004015 9T5 TABLE 4 (continued) Salt Lake City, UT San Francisco-Bay Area, CA Santa Barbara-Santa Maria-Lompoc, CA St. Louis, MO-IL Toledo, OH Marginal Attainment Date 11 Il 5I1992 Albany-Schenectady-Troy, NY Allentown-Bethlehem-Easton,PA-NJ Altoona, PA Birmingham, AL Buffalo-Niagara Falls, NY Canton, OH Cherokee County, SC Columbus, OH Door County, WI Edmonson County, KY Erie, PA Essex County (Whiteface Mtn), NY Evansville, IN Greenbrier County, WV Hancock & Waldo Counties, ME Harrisburg-Lebanon-Carlisle, PA Indianapolis, IN Jefferson County, NY Jersey County, IL Sussex County, DE Johnstown, PA Kent and Queen Anne s Counties, MD Knoxville, TN Lake Charles, LA Lancaster, PA Lexington-Fayette, KY Reno, NV Scranton-Wilkes-Barre, PA Seattle-Tacoma, WA Smyth County, VA (White Top, Mtn) South Bend-Elkhart, IN Tampa-St. Petersburg-Clearwater, FL Walworth County, WI York, PA Youngstown-Warren-Sharon,OH-PA C. AIR QUALITY FOR LEAD 1.General Lead has been known to be toxic to humans for thousands of years. One of the major routes of exposure to humans is through inhalation of lead dust particles. In the 1970s EPA established the NAAQS level of 1.5 micrograms (pg) of leadlm3 averaged over 90 days.27 This regulation was intended for continuous operations that produced lead dust, such as battery or pigment manufacturing or lead
smelters. The 90-day provision allows for some variations in the daily emission levels as long as the 90-day average meets the criterion. This regulation affects the coatings industry because of the lead dust generated during removal of lead-containing coatings from bridges, water towers, and other industrial structures. The blast cleaning or power tool cleaning of lead paint can produce extremely high levels of lead dust in the workplace.Z* The EPA standard, however, is intended to protect the public health, not that of the employees, who are covered by the Occupational Safety and Health Administration. Thus, the air is typically monitored at the property limits (Le., immediately outside the location of the structure or facility from which the coating is being removed.) 2. Air Monitoring for Lead Ambient air monitoring for lead is performed relatively infrequently on most industrial projects. One reason is that on many projects, the abrasive blasting or removal operation is of short duration, or occurs sporadically, rather than constantly. Also, the vast majority of regulatory agencies have not enforced these regulations or notified the facility owners or contractors that paint removal operations were considered in the jurisdiction of these regulations. A few agencies, such as Allegheny County (Pennsylvania), have established specific limits for the level of lead dust, based on a 24-hour average rather than the 90-day limits established by EPA.29 Currently, under Title X of the 1992 Housing and Community Development Act, the US EPA is considering developing national guidelines on the need and procedures for monitoring ambient lead.30 3. Monitoring Procedures When removing lead or other hazardous materials, measurements for airborne lead and other hazardous elements can be made by instrument monitoring in accordance with EPA criteria. Levels of lead in air are regulated by both the EPA and OSHA. (For more information on health and safety issues associated with lead, see chapter 26.) Monitors are placed at appropriate locations based on wind direction and proximity to homes, playgrounds, businesses, bodies of water, etc. The following descriptions of methods for measuring ambient lead are derived from SSPC Guide 61, Guide for Containing Debris Generated During Paint Removal Operations, (March 1992).3l a. Method 07: PA Criteria for Lead-High volume air samplers equipped for the collection of total suspended particulate (TSP) are used. The CFR does not give specific procedures for number or placement of air monitors because of the irregular con-
figuration of water towers, bridges, and other structures. Thus, the placement of monitors must be determined on a site-specific basis, taking into account wind direction, and proximity to homes, playgrounds, businesses, bodies of water, etc. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 568
SSPC CHAPTER*27.L 93 = 8b27940 00040Lb 831 b. Modification for Under 90 Days -Because paint removal operations are not normally conducted continuously over a 90 day period, it may be appropriate to establish a daily criterion for monitoring. Note that the suggested modification of the procedure shown below may not be acceptable to state or local environmental officials. The appropriate officials should be contacted prior to its implementation. For example, if a project lasted only 30 days, the Daily Allowance would be 4.5 pglm3 based on the formula shown in Equation 3 below. The calculation provides an allowance criterion for a 24-hour period. In order to convert this value to an allowance corresponding to the hours worked, use Equation 4 shown below. DA = x 1.5 pglm3 (3) ~ PD where DA = Daily Allowance (pg/m3) PD = Number of preparation days anticipated in a 90 day period ADA = DA x 24 (4) ~ H where ADA = Adjusted Daily Allowance (pg/m3) H = Hours worked in 24 hours In the above example, if lead dust were produced for 8 hours (H = 8), the adjusted daily allowance would be 13.5 pglm3 (4.5 pg/m3 x 3) c. Method 03: OSHA Criteria for Lead -In this approach, air quality measurements for lead are determined in accordance with NIOSH Method 7082 using personal monitors outside of the containment areas.32 PEL lead limits are 50 pglm3 per OSHA General Industry Standard 29 CFR 1910.1025 and Construction Industry Standard 29 CFR 1926.62 (see chapter 26).33 34 Additional details on monitoring air quality for lead are given in the industrial Lead Paint Removal Handbook.35
D. AIR QUALITY FOR PARTICULATES 1. General Particulate matter is defined as any finely divided solid or liquid material. For airborne materials, this definition includes particles with a diameter of 100 microns or less. (The criteria for particulates should not be confused with the more specific criteria for PM-1O particulates, given below.) Other terms often used are air contaminant, fugitive emission, dust, and opacity. Air contaminant means any substance (e.g., particulate, gas, fumes, smoke) other than water vapor that is released or emitted into the atmosphere. A fugitive emission is particulate matter that is not collected by a catcher system (e.g., stack) and is released into the atmosphere at the point of generation. Dust is defined as fine-grained particles light enough to be suspended in the air. From the previous discussion, it is evident that there are numerous sources of air contaminants (fugitive emissions) arising from coating operations. These include dust and particulates from abrasive blasting, solvent fumes from paint applications, paint or grease removal, or any activity that disturbs solid debris. All of these would be classed as fugitive emissions because they are not discharged intentionally into the atmosphere by a stack, but rather escape from the area of operation. Fugitive emissions are generally considered undesirable and potentially harmful to humans and the environment. 2. PM-70 Emission Standards Under the National Ambient Air Quality Standard (NAAQS), in addition to the species identified earlier (ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide, lead, and HAPS), EPA regulates any particulates having a mean diameter of 10 microns or less. These are referred to as PM-10 and are too small to be seen with the naked eye. The smallest particle that one can see is about 50 microns in diameter (e.g., dust particles in a ray of sunshine). These very small particles (regulated under PM-10) are able to penetrate the body s filtering mechanism and enter into and damage the lungs. Under 40 CFR 50.6, EPA has established the following criteria for PM-10 emissions:36 a. Level not to exceed 150 pglm3 averaged over a 24-hour period. (NOTE: This level may not be exceeded more than once per year). b. Level not to exceed 50 pg/m3 (annual arithmetic mean). As with the regulations for lead, these were not designed with coating application or removal projects in mind. The ambient air quality standards for particulates were based on controlling the over-
all air quality for relatively large air quality districts, not for small point source emissions. There is relatively little information regarding the extent to which these criteria are exceeded in paint removal jobs. However, it is considered unlikely that the daily average (150 pglm3) will be exceeded outside of the work area except for extremely dusty operations. Numerous states and localities have estabCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS I569
SSPC CHAPTER+27.L 93 8b27940 00040L7 778 D lished their own regulations, criteria, and in some (e.g., property line). Possi ble frequencies include: cases permitting requirements for particulates and (1) Level O Emissions -No vis ible emission. Note: fugitive emissions. This level may not be achievable during abrasive blasting. (2) Level 1 Emissions -Random emissions of a cumulative duration of no more than 1% of the work day (e.g., five minutes in an eight-hour work day). (3) Level 2 Emissions -Random emissions of a cumulative duration of no more than 5% of the work day (e.g., 24 minutes in an eight hour work day). (4) Level 3 Emissions -Random emissions of a cumulative duration of no more than 10% of the work day (e.g., 48 minutes in an eight hour work day). (5) Level 4 Emissions -Emissions are unrestricted and may occur at any time. 6. Method A-2 -Opacity is the degree of obscuring of light. It is often measured on a scale of 0-100, based on the percent of light that fails to penetrate a plume (e.g., of smoke). Zero percent represents zero obscuring, and 100% represents complete obscuring of the light. Opacity measurements are made by trained, certified observers. A scale from 0% to 100%, in 5% increments, is used. Measurements are typically made at 15 second intervals for given periods of time (e.g., 30 minutes). The acceptance criteria must be established by the specifier. For example, a criterion might restrict the opacity to no more than 20% for any three-minute period in 60 minutes. Local regulations may provide guidance as to the level of opacity that should be required. Monitoring should be conducted prior to beginning the work, as appropriate, in order to establish background levels. c. Method B: Ambient Air Monitoring for PM-10 High volume air samplers equipped with PM-10 heads are used to assess the total amount of parFIGURE 3 ticulate matter ten microns (0.39 mils) or less in size Ambient air monitor for PM-10 particulates. that escape the contained work area. The number of monitors to be used is based on wind direction and proximity to homes, playgrounds, businesses, 3. Methods for Assessing Particulate Emissions bodies of water, Methods for quantifying the amount of dust and If acceptable to air quality debris escaping the work area are derived from authorities, the pg/m3 over a 24 SSPC Guide 6i.(37) Method A (visual assessment) hour period may 50 pglm3 over an provides immediate feedback on the emissions eight hour period, sions occur from
etc. local and state EPA level of 150 be modified to 4 provided no emis
created, while Method B (ambient air monitoring us- the worksite during the rema ining 16 hours. Again, ing high volume samplers) requires two to three monitoring should be conducted f or a few days pridays to receive results. Users must contact the ap- or to beginning the work (fo r eight hours to 24 hours propriate state and local authorities to ascertain per day, as appropriate) in o rder to establish backwhich of the methods are accepted for monitoring ground levels. emissions and to establish the appropriate acceptance criteria. 4. Determining the Need for Air Monitoring on Paint a. Method A-1: Visible Emission Duration -Obser-Removal Projects vations of visible emissions from the work area pro- As noted earlier, existing ambient air quality stanvide immediate feedback on the performance of the dards are not being imposed ro utinely on paint containment system. Visible emissions are permit- removal projects. As noted, th e thrust of such stanted at given frequencies or durations provided they dards is for the continuous monitoring of large areas do not extend beyond an established boundary line (e.g., entire cities) as compa red with individual shortCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 570
SSPC CHAPTER*27-1 93 = 8627940 0004018 604 = term projects. However, monitoring is being specified on some paint removal projects. Monitoring might be initiated when there is a belief that emissions from a short term paint removal project (particularly lead) could have an effect on the overall air quality in a region. Monitoring may also be imposed when the lead paint removal site is in a residential area, or next to schools, hospitals, playgrounds, and other areas of public access to better assure public health and welfare. For work already underway, complaints over visible emissions or questions as to the seriousness of emissions could be investigated using monitors. Prior litigation over emissions may also trigger monitoring on future projects. For example, monitoring has been required in Allegheny County, Pennsylvania, since 1987for most abrasive blast cleaning projects greater than 10,000 square feet (900m2) in area as a result of earlier litigation over silica contamination.29 From the above, it is obvious that the decision regarding whether to monitor a given project is not clear cut. However, if there is a potential for public exposure to the dust, such monitoring will provide a high degree of assurance that emissions are within acceptable limits. Without the monitoring, such judgments are strictly subjective. However, for work within the confines of a plant, where it can be established that dust and debris will not carry across the property line into a community, such monitoring will provide little benefit. If ambient air monitoring is specified, the costs of the project will increase. The cost will extend beyond the price of the monitoring and analysis as monitoring will usually necessitate tighter and more stringent controls over the containment. 5. Duration of Testing and Placemenf of Monitors 40CFR 58.13, Operating Schedule, identifies the frequency of monitoring required (e.g., daily, every other day, etc.). This section is intended for longterm continuous (permanent) monitoring at sites across the nation in order to establish air quality data. As a result, it provides no guidance on the duration of monitoring for short-term projects such as lead paint removal. Approaches in the industry include: Continual monitoring throughout the entire project; Monitoring during the initial week or two of the project; and Monitoring only when complaints are received.
Regardless of the approach selected, background levels for the jobsite must be established. The approach used for monitor placement in Allegheny County, Pennsylvania has been reported by Sadar and Pate1.37 A great deal of judgment is required for the selection of placement sites. Additional detail on air particulate monitoring is given in the Industrial Lead Paint Removal Handbook.35 E. STATE AND LOCAL REGULATION OF AIR QUALITY A number of state and local air quality agencies have enacted regulations to control air contamination by paint removal activities. These were summarized in a special JPCL report on Coating Regulations. 18 In addition to the imposition of NAAQS, control of emissions has been regulated by requiring permits (e.g., for abrasive blast cleaning), by general language restricting excessive or objectionable visible emissions, or by limiting the opacity of a dust plume. Agencies that require permits for blast cleaning include Allegheny County (Pittsburgh) Pennsylvania, the City of St. Louis, and the City of Cleveland, Ohio. Among the agencies that have instituted some control of opacity are Allegheny County, Pennsylvania, (20%),Washington County, Nevada (40%), Maricopa County (Phoenix) Arizona (20%),Wayne County (Detroit) Michigan (20%); State of Virginia (20% for short periods and 60% for any period); and the State of California (400/0). ~The State of California, the U.S. Navy, several DOTS and various private facility owners also restrict the type of abrasive. California requires that abrasives be certified in a biennial program in which abrasives are evaluated for their dusting and breakdown characteristics 8. The U.S. Navy specification for abrasives for shipyards includes limitations on heavy metal content and fine (dust-producing) particles.3* Some agencies have also regulated the airborne level of silica abrasive. These include several cities in Massachusetts; Wayne County, Michigan; and Allegheny County, Pennsylvania.18 Silica hazards to workers are discussed in Chapter 26 on Safety and Health. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 571 /
SSPC CHAPTER*27.L 93 8b27940 00040L9 540 m REFERENCES References 1-13 are listed at the end of Chapter 27.0. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. The Clean Air Act and The Paint and Coatinas Industrv. Issue Analysis by National Paint & Coatings Association, Washington, DC, 1992. Stanley Santire, 1990 Federal Clean Air Act Amendments: An Overview, JPCL, September 1993, pp. 46-50. a. Implementation Strategy for the Clean Air Act Amendments of 1990, Update 1992. Publication 400-A-92-004. Washington, DC: US. EPA, July 1992. b. The Clean Air Act Amendments of 1990: A Guide for Small Business, U.S. EPA, Office of Air and Radiation Publication 450-K-92-001. Washington, DC: US. EPA, September 1992. U.S. EPA. Control of Volatile Organic Emissions from Existing Stationary Sources, Volume VI: Surface Coating of Miscellaneous Metal Patts and Products. June 1978 EPA-450-12-78-015, NTIS PB-286-157. Update: Regulations on Coating Operations for Heavy-Duty Industrial Maintenance Painting, JPCL, February 1991, pp. 55-1 16. Negotiating Committee Agrees on VOC Limits: EPA to Draft Proposal, JPCL, October 1993. Summary of BACMIMACT Options, Shipbuilding and Ship Repair NESHAPICTG, U.S. EPA, Office of Air Quality Planning and Standards, May 25, 1993. SSPC Guide lox, Guide to Specifying and Testing Coatings Based on Volatile Organic Content, Draft #4, July 1993. Determination of Volatile Matter Content, Water Content, Den-
sity, Volume Solids and Waste Solids of Surface Coatings, 40 CFR Part 60, Appendix A, Method 24. ASTM D 3690 -Standard Practice for Determining Volatile Organic Compound (VOC) Content of Paints and Related Coatings., American Society for Testing and Materials. Philadelphia: 1991. ASTM D 2369 -Standard Test Method for Volatile Content of Coatings. American Society for Testing and Materials. Philadelphia: 1990. EPA Revises VOC Test Method, JPCL, September 1992, pp. 78-79. VOCs: Texas Extends AIM Rules; Revises Shop Rules, JPCL, August 1992, pp. 41-43. 40 CFR 50.12, National Primary and Secondary Ambient Air Quality Standards for Lead . Preventing Lead Poisoning In Construction, DHHS Publication 91-1 16, National Institute of Occupational Safety & Health (1991), JPCL, January 1992, pp. 40-54. K.A. Trimber, G. Manown, and L. Lambert, Air and Soil Monitoring During Elast Cleaning Operations, Lead Paint Removal from Industrial Structures, SSPC 89-02. Pittsburgh, SSPC, 1989. pp. 20-25. Housing and Community Development Act of 1992, Title X, Residential Lead-Eased Paint Hazard Reduction Act of 1992, 102nd U.S. Congress, October 5, 1992. Guide for Containing Debris Generated During Paint Removal Operations, SSPC Guide 61 (CON), SSPC 92-07. Pittsburgh: SSPC, March 1992. NIOSH Method 7082, Lead, National Institute of Occupational Safety ¿? Health. 29 CFR 1910.1025, Lead, (3, Permissible Exposure Limits (PEL) . 29 CFR 1926.62, Lead, 3, Permissible Exposure Limits (PEL) . K. A. Trimber, Industrial Lead Paint Removal Handbook, second edition. SSPC 93-02. Pittsburgh: SSPC, 1993. 40 CFR 50.6, National Primary and Secondary Ambient Air Quality Standards for Particulate Matter . A. J. Sadar and H. L. Patel, Air Monitoring Guidance for Abrasive Blasting Operations, JPCL, December 1987, pp. 31 -32, 68, 70. Abrasive Blasting Media, Ship Hull Blast Cleaning, MIL-A-2262A (SH), February 6, 1987. Washington: Naval Sea Systems Command. 1987. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 572
SSPC CHAPTER*27.2 93 86279qO OOOLI020 262 CHAPTER 27.2 WASTE HANDLING AND DISPOSAL by Bernard R. Appleman A. DEFINITIONS Waste is generally defined as any material which is discarded and not intended for some other productive use. EPA defines solid waste as any garbage, refuse, sludge, or semisolid. The definition also includes liquid wastes which are not otherwise regulated under the Federal Water Pollution Control Act. A waste is considered hazardous if it poses a substantial present or potential hazard to human health or the environment. A more formal definition of a hazardous waste is given below. Hazardous waste is a subset of hazardous substances. Materials may be defined as hazardous based on characteristics such as toxicity, corrosivity, ignitability (¡.e., flash point) and reactivity (e.g., explosion hazard). Also included as hazardous wastes are materials contributing to water pollution, hazardous air pollutants, or other substances defined as such by federal agencies. Thus, in identifying requirements for handling and treating wastes and other materials, it is necessary to know the agency or agencies having jurisdiction over the particular substances. The Federal EPA has jurisdiction over handling and disposing of hazardous and solid waste. In 1976 Congress enacted the Resource Conservation & Recovery Act (RCRA)7 which was amended in 1984 by the Hazardous and Solid Waste Amendments (HSWA).8 RCRA and HSWA are designed to track and regulate hazardous waste from manufacture to final disposal. Another federal regulation, the Comprehensive Environmental Response Compensation and Liability Act (CERCLA)g, also known as the Superfund , was enacted in 1980. CERCLA is intended to control cleanup and designate liability for abandoned, undercontrolled, or inactive waste sites, and to deal with hazardous waste releases in an emergency. CERCLA is discussed in Chapter 27.3. Congress main goal under RCRA is to reduce or eliminate the generation of hazardous waste and ensure that wastes generated are treated, stored, and disposed of so as to minimize present and future threats to human health and the environment. RCRA regulations include subtitles A through J. Subtitle C deals with handling, disposal, and treatment of hazardous wastes. (Subtitle D addresses state or regional solid waste.) Another subtitle of interest is Subtitle I, which covers regulations of underground storage tanks. The remaining subtitles deal with general administrative provisions of the Act.
RCRA regulations are published in the Code of Federal Regulations, Title 40, Parts 261-281. Sections of the hazardous waste regulations of most relevance to the protective coatings industry are as follows: Part 261 Identification and Listing of Hazardous Waste Part 262 Standards Applicable to Generators of Hazardous Waste Part 268 Land Disposal Restrictions Other portions which are of some interest include: Part 263 Standards Applicable to Transporters of Hazardous Waste Parts 264-265 Standards for Owners and Operators of Hazardous Waste Treatment, Storage, and Disposal Facilities See Appendix C (Chapter 27.3) for an outline of other relevant sections of 40 CFR. B. CLASSIFYING WASTE The provisions of Subtitle C apply to materials defined as hazardous waste. There are two means by which a waste can be classified as hazardous: it may be specifically included on any one of four lists of hazardous wastes, or it may have one of the characteristics which define hazardous wastes. Therefore, there are two types of hazardous waste: listed waste and characteristic waste. 1. Listed Wastes EPA has identified over 400 substances that are considered hazardous. These include spent paint solvents, such as xylene, acetone, ethyl acetate, and methyl isobutyl ketone, spent halogenated solvents (e.g., methylene chloride, l ,I ,l-trichloroethane and carbon tetrachloride), cyanide and compounds, toxic organics, and sludges from various manufacturing and treatment processes. Each of these has been assigned a specific EPA hazardous waste number (e.g., F003 for xylene). 2. Characteristic Wastes These are substances which are defined as hazardous based on one or more of the following four characteristics: ignitability corrosivity Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 573
SSPC CHAPTER*27-2 93 m 8627940 0004021 1T9 m
reactivity toxicity a. lgnitability-An ignitable waste is a liquid having a flash point of less than 60% (140°) using a designated ASTM method. This includes waste from solvent-borne paint and degreasing compounds and other solvents not covered as listed wastes. See 3(c) in this section for the definition of the minimum quantity of paint in a container designated as a hazardous waste. 6. Corrosivify -This category includes materials that have low or high pH (less than 2 or greater than 12.5) or are excessively corrosive to steel. These include rust removers, and acid or alkaline cleaning fluids (e.g., certain chemical strippers). c. Reactivity-This characteristic applies to materials that are unstable or undergo rapid or violent chemical reactions with water or other materials. Examples are cyanide, plating waste, waste bleaches, and other oxidizers. d. Toxicity -These are wastes which, when subjected to an extraction procedure using an acid, are found to contain high concentrations of heavy metals or pesticides that could be released into ground water. This is the characteristic by which lead paint residues may be classified as hazardous waste, and the RCRA provision having the greatest impact on the protective coatings industry. Other metals that may cause the waste to be classified as toxic include chromium, barium, cadmium and mercury. The test method for determining if a waste is hazardous is the Toxicity Characteristic Leaching Procedure (TCLP) (EPA Method 131 l).39The abrasive, paint, or other waste is broken up into small pieces and agitated in an acid for 24 hours. If the amount of lead or other metal which leaches (dissolves) into the acid is greater than or equal to the threshold value, the debris is considered hazardous. A waste from which 5 mg/l of lead or more leaches is considered a hazardous waste.40 Such a waste is described as a characteristic waste , and more specifically, a toxic waste. Table 5 below gives the threshold limits for the other metals. Each metal is assigned a specific waste code. The D series is designated for characteristic wastes (e.g., lead is D008). Table 5 CHARACTERISTIC LEVELS FOR TOXIC METALS40 Code DO04 DO05 DO06 DO07
Metal Threshold Concentration Arsenic 5.0 milligrams per liter (ppm) Barium 100.0 milligrams per liter (ppm) Cadmium 1.O milligrams per liter (ppm) Chromium 5.0 milligrams per liter (ppm)
DO08 Lead 5.0 milligrams per liter (ppm) DOO9 Mercury 0.2 milligrams per liter (ppm) DO1O Selenium 1.O milligrams per liter (ppm) DO1 1 Silver 5.0 milligrams per liter (ppm) 3. Other Considerations for Waste Classification a. Acutely Hazardous Waste -EPA has established special requirements for small quantities of waste considered extremely hazardous. These include certain pesticides and dioxin-containing wastes. These are not commonly generated in the protective coating industry, but do require special treatment and reporting. b. Recycled or Reused Hazardous Waste -A waste that is classified as hazardous according to the above criteria, but which is to be reused or recycled in some beneficial fashion, is not subject to the requirements of Subtitle C (See 40 CFR Part 260, Appendix I, Figure 3 for special provisions for certain hazardous wastes which are intended to be legitimately and beneficially used, re-used, recycled, or reclaimed.) c. Residues of Hazardous Waste in an Empty Container (40 CfR 267.7) -Definitions of an empty container are as follows: (1) All wastes have been removed using commonly employed procedures for emptying the container. (2) No more than 1 inch (25 mm) of residue remains on the bottom of the container. (3) No more than 3% by weight of the capacity of the container remains in containers of a capacity of 110 gal. (418 L) or less. (4) No more than 0.3% of the weight of the total capacity remains in containers of a capacity of greater than 110 gal. (418 L). An empty container as defined above would not be subject to RCRA rules. If the container contained more than this amount of solvent-thinned paint, there is a strong likelihood that the waste would require treatment as hazardous waste. Some disposal facilities may have more stringent criteria for a container to be considered empty. d. Disposal of Scrap Metal -Scrap metal, even if coated with lead paint, is considered a recyclable material and not subject to the requirements of Subtitle C. For this exemption to apply, the scrap metal must be reused by a steel mill or ferrous foundry as part of the raw materials for the process. If the scrap metal is simply to be discarded, then it would need to be handled and treated as a potentially hazardous waste and be tested by TCLP. C. RESPONSIBILITIESFOR HAZARDOUS WASTE 1. Major Parties Under RCRA, EPA was directed to establish a program designed to control the management of hazardous waste from its generation to its ultimate disposal (¡.e., from cradle to grave ). EPA has
assigned responsibility for three key groups: Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 574
SSPC CHAPTERx27.2 93 8b27940 0004022 035 the generator of the waste; shipper (transporter) of the waste; and the treatment, storage and disposal (TSD) facility. The protective coatings industry is generally not primarily involved in transporting, treating, or disposing of hazardous waste, although these activities may be an incidental part of the work done by a painting contractor or a facility owner. The major role of owners and contractors is that of generator. FIGURE 4 Clean-up of polluted waste site. A generator is defined by EPA as any person whose act or process produces hazardous waste. A facility owner is the primary generator of the hazardous waste produced by removing coatings from structures. This is true even though a contractor may be the party that actually physically removes the paint (e.g., by abrasive blast cleaning). In some states, the contractor has been designated as Co-generator, indicating a shared responsibility. However, this designation does not relieve the facility owner from full responsibility for ensuring that all operations (¡.e., generation [by removal], transportation and disposal) and the other activities described below are performed in accordance with RCRA rules. The disposal of waste paints or thinners determined to be hazardous may sometimes be the responsibility of the contractor who purchased them. If the coatings have been used in shop application (e.g., rail car or steel fabricating shop) the shop facility is the waste generator. A transporter is defined as the person engaged in the offsite transportation of hazardous waste. Accordingly, transporting the waste within a site (¡.e., relocating to a special storage area from the generation area) does not fall within 40 CFR Part 263, and may be performed by the generator without any additional permit. Treatment and disposal of hazardous waste are most commonly performed by specially licensed facilities located off the premises of the waste generation site. (NOTE: Only licensed transporters may be involved in shipping hazardous waste). Under some circumstances the waste generator may deliberately or inadvertently treat the hazardous waste. It is important to understand what types of treatments or processes are regulated and what the permitting or reporting requirements are. The responsibilities and regulations affecting
generators, transporters, and TSD facilities are described below. 2. Responsibility of Generators Generators are classified based on the amounts of hazardous waste generated. These are as follows: + Large quantity generator -Generates greater than or equal to 1,000 kg (2,200 Ib) per month, or accumulates more than 6,000 kg (13,200 Ibs) at the site at any one time. + Small quantity generator -Generates between 100kg and 1,000 kg (220-2,200 Ibs) per month and accumulates less than 6,000 kg. + Conditionally exempt small quantity generator -Generates less than 100 kg (220 Ib) per month. A large quantity generator must comply with all the requirements listed below. There are some minor differences in the requirements for a small quantity generator.35 A conditionally exempt small quantity generator does not need to follow the reporting requirements, but still must assure that the waste is properly tested and disposed of. The following activities are the responsibility of the generator: a. Identification of Waste (40 CfR 262.11). -This regulation requires that the generator determine if the waste is hazardous. This is accomplished by applying knowledge of the hazardous characteristics of the material in light of the process used, or through laboratory testing. If a project is consistently producing material with a similar composition and consistency, the generator can utilize documented process and test data as evidence of the material characteristics. For paint removal projects, the variability is such that the authoritative sampling is not appropriate, and representative samples must be taken for different waste streams and tested in a laboratory. Laboratory testing is intended to simulate the type of long-term leaching that could occur in sanitary landfills. In the case of lead paint debris, if the leaching meets or exceeds the allowable levels described above, the debris is considered to be hazardous due to toxicity. b. EPA Identification Number (40 CFR 262.12)-The generator must obtain a number to treat or store hazardous waste, or dispose of, transport, or offer it for transportation. This number is o btained from the state or local EPA office. Different types of EPA Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 575
SSPC CHAPTER*27.2 93 8627940 0004023 T7L identification numbers are available. The owner should determine the type needed. The different types are: (1) Regular -Permanent ID numbers are intended for facilities that will generate a hazardous waste on a long term, constant basis. Owners may desire to obtain a permit for all of their facilities where lead-containing debris will be generated under one ID number. (2) Site Specific ID numbers are intended for facilities that will generate a hazardous waste once. Owners may desire to identify each site, such as individual water towers, bridges, tank farms, etc., and have a unique ID number for each one. (3) ProvisionalID numbers are intended for unforeseen circumstances where a large amount (greater than 1,000 kg [2,200 Ibs]) of hazardous waste is generated. An example would be clean-up of soil from an accidental spill of diesel fuel. The owner may delegate obtaining Site Specific and Provisional EPA ID numbers to the contractor. c. Notification and Certification (40CFR 268.7and 40 CFR 268.9)-Notification and certification must be provided by the generator for each shipment of debris. The specific wording is found in the regulations, and it varies according to whether the restricted waste tests hazardous, non-hazardous, or has been treated to render it non-hazardous. Information required can range from an identification of the treatment standards that should be used for the debris, to certifications of personal knowledge of the waste, treatment process, and test results. False certification can result in a fine and/or imprisonment. d. Manifesting the Waste (40 CFR Part 262.20 through 262.23)-The generator must complete a hazardous waste manifest that accompanies each shipment. The manifest includes a description of the waste, the name of the facility permitted to handle the waste, and an alternate facility. The generator signs the manifest as does each transporter and the final disposal facility. The completed manifest must be returned to the generator within a designated number of days (45 days for large quantity generators and 60 days for small quantity generators). If the manifest is not received, the manifest and debris must be tracked and located. The manifest assures that the waste is properly handled from the collection of the debris to its final disposal. The manifest must be obtained from the state where the waste is being disposed of, if that state requires its use. If the disposal state does not supply the manifest, the form from the state where the waste is generat-
ed should be used. If neither state requires a specific manifest, a standard form can be used. e. Packaging and Labeling Requirements (40CFR 262.30through 262.33)-The waste must be packaged in accordance with the requirements of the 40 CFR 262 sections identified above, as well as Department of Transportation Regulations presented in 49 CFR 173, 178, and 179, with labeling accomplished in accordance with 49 CFR 172.(401) Essentially, these parts require that the packaging be capable of preventing leakage of the waste during normal transportation conditions as well as upset conditions (e.g. the container falls out of a truck). The rules also require the use of labels, marking, or placards to identify the characteristics or dangers associated with transporting the waste. f. Container Enclosure Requirements (40CFR 265) -The requirements vary for the large and small quantity generator, but both essentially require the use of leak-proof drums or bins with secure lids or covers for containing the material, with the storage site locked and located on well-drained ground. The containers must be inspected for corrosion and leaking. g. Contingency Plan and Training (40CFR 265 and 40 CFR 262.34)-These sections require that the personnel involved with the handling of hazardous waste be trained to respond effectively to emergencies. Paint removal crews must be trained. Basic safety information must be available, including hazard labels on containers, the date that the accumulation begins, the name and telephone number of a site employee who is the emergency coordinator, telephone number of fire department, location of fire extinguisher, and other similar contingency items. h. Waste Analysis Plans for On-Site Treatment (40 CFR 268.7)-If the generator decides to treat the waste on-site to render it non-hazardous, a written waste analysis plan must be filed with the EPA regional administrator a minimum of 30 days prior to the treatment activity. i.Waste Accumulation Time (40 CFR 262.34) There are restrictions on the length of time that the waste may accumulate on-site. The large quantity generator may accumulate hazardous waste on-site for 90 days or less without a permit from the EPA. An extension of up to 30 days may be granted due to unforseen, temporary, or uncontrollable circumstances. The small quantity generator may accumulate waste on-site for 180 days with a possible exemption permitting up to 270 days. If these time limits are exceeded, the generator may be considered an operator of a storage facility, and subject to very extensive requirements. i. Recordkeeping and Reporting (40CFR 262.40 through 262.44)-The signed manifests and associated documentation must be maintained for at least three years. For generators who treat the waste on-site, the recordkeeping requirements can be more elaborate.
Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 576
SSPC CHAPTER*27.2 93 8h27940 0004024 908 3. Responsibilitiesof Transporters and TSDF (Treatment, Storage and Disposai Facilities) a. Transportation-Waste containers can be transported on-site to temporary holding areas by the generator without special hauling permits. However, for off-site transportation, the requirements of 40 CFR 263, Standards Applicable to Transporters of Hazardous Waste, apply.41 b. Treatment, Storage and Disposal -Treatment, storage, and disposal are defined as follows under 40 CFR 260.10, Definitions. (1) Treatment -Any method, technique, or process, including neutralization, designed to change the physical, chemical, or biological character or composition of any hazardous waste so as to neutralize such waste, or so as to recover energy or material resources from the waste, or so as to render such waste nonhazardous, or less hazardous; safer to transport, store, or dispose of; or amenable for recovery, amenable for storage, or reduced in volume. (2) Storage -The holding of hazardous waste for a temporary period, at the end of which the hazardous waste is treated, disposed of, or stored elsewhere. (3) Disposal-The discharge, deposit, injection, dumping, spilling, leaking, or placing of any solid waste or hazardous waste into or on any land or water so that such solid waste or hazardous waste or any constituent thereof may enter the environment or be emitted into the air, or discharged into any waters, including ground waters. The TSDF is the last phase in the cradle-tograve concept of handling hazardous waste. The facility must return the signed manifest to the generator and comply with requirements for the ultimate disposition of the waste. The extensive requirements for these facilities are described in 40 CFR Parts 264 and 265.4* Details of generators , transporters and TSDFs responsibilities and specific application to hazardous lead paint are given in the Industrial Lead Paint Removal Handbook. 35 D. SAMPLING AND TESTING As noted above, it is the generator s responsibility to determine if the waste is hazardous. For listed wastes, such as xylene and other solvents, there is no need for testing. The waste is hazardous by definition. For waste paints, the determining factor for ignitability is the flash point. This may be obtained from the manufacturer; alternatively, an outside testing laboratory or an in-house testing facility could easily determine it using the ASTM method prescribed. For solvent-borne paints, it may be prudent to assume that the waste is hazardous and handle and treat it accordingly. Determining the pH of acid or alkali cleaners or chemical strip-
pers can be readily accomplished in the field using standard pH paper. The manufacturer s material safety data sheets (MSDS) will identify the characteristics of the material, including the pH and any toxic components. Unless the material has been diluted, mixed, or otherwise altered, one should assume that the most hazardous properties of the material are also true of the waste. For solid paint waste or abrasive residue suspected of containing lead or other heavy metals, a laboratory test is normally required to determine the leachate concentration of the metals. The collection and sampling of the waste to be tested must be performed according to EPA procedures. For example, the sampling must be taken from a homogeneous mix, using random sampling techniques. Typically, a minimum of four samples is required to demonstrate that a sample is non-hazardous (e.g., less than 5 mg/l for lead.) If the generator is willing to handle and dispose of the material as a hazardous waste, it is not necessary to test for the presence of lead or other heavy metals. However, at least one sample is recommended for historical records and to guide the disposal facility in the appropriate treatment procedu res. Samples required for the TCLP test normally must be about 100 g (1/4 Ib), placed in labeled containers. Testing should be done by a qualified lab experienced in TCLP testing. The test itself normally takes about 24 hours. Additional information on sampling procedures is contained in references 42-44. E. TREATMENT AND DISPOSAL OF HAZARDOUS WASTE If a waste that has been collected and tested is determinedto be hazardous, the generator must arrange for some type of treatment to render the waste non-hazardous. This requirement is based on the 1990 Land Disposal Restrictions ( Land Ban ) (40 CFR 268). This regulation prohibits the land disposal of any hazardous waste. Typical treatments for lead containing wastes are summarized below. Treatment is not required if the material is to be recycled or reused for beneficial purposes. As noted above, such materials are not classified as hazardous waste and are not subject to these RCRA requirements. For hazardous waste, treatment can be performed onor off-site. On-site treatment is permitted by EPA under very special circumstances as described below. Off-site treatment services are offered by a number of firms that specialize in this type of technology. 1. Off-Site Treatment of Hazardous Wastes a. Treatment Methods -One particularly common treatment method is the use of lime or portland cement. Lime stabilizes lead-containing debris by pH control. Addition of lime is effective at a level of about 10-15 percent by weight. Lead compounds are amphoteric, meaning they are soluble in acidic and alkaline solutions. Adding too much lime will
raise the pH and may result in a leachable lead concentration above 5 mgll. Laboratory testing is needCopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 577
SSPC CHAPTER*27.2 93 = 8b27940 0004025 BYY ed to determine the proper amount of lime to add. licensed hazardous waste haule rs can be obtained EPA Method 132045 is designed to simulate the from the appropriate state agency. long-term effect of leaching of landfills by ground water. It consists of successive leaching tests similar to TCLP on a waste sample. There are no known available results of this test being run on the limestabilized, lead-bearing waste.de Stabilizing lead with portland cement can be performed either as a dry addition or with water to make concrete. Adding portland cement at a level of 10 percent by weight or higher typically results in very low leachable lead concentrations, usually 0.05 to 0.1 mgil. Concretes can be made using a waterícement ratio of 0.5. A representative mixture design to form blocks is 300 pounds (136 kg) of debris, 94 pounds (43 kg or one sack) of cement, and 7.5 gallons (28 I)of water. Wastes stabilized in this manner have been evaluated for long term stability by EPA Method 1320 and show no increase in leachable lead concentration for ten (10) cycles.47 Fine-grained wastes such as dust from dust collectors or the fines from steel recycling units have been successfully stabilized with portland cement. However, more water must be added tothe mixture for these wastes. The above mixture design is not appropriate for fines. Laboratory tests must be performed to determine an adequate amount of water. Fines from dust collectors may be classified as a hazardous waste unless in-process treatment was performed. Once treated and found to be below the regulatory limit, EPA regulations permit the material to be disposed of in a Subtitle C (hazardous) or Subtitle D (nonhazardous) landfill. However, states may have additional requirements for testing and manifesting the waste. Waste thinners and paints are typically incinerated, because once the solvent is burned, the explosion or fire hazard has been eliminated. Acids and bases can be readily treated by neutralizing with other bases or acids respectively. b. Disposal Procedure -The generator normally does not treat the waste. It is necessary to select a treatment and disposal facility. There are numerous hazardous waste treatment facilities available in the United States. The state or regional EPA office can provide assistance in identifying these. The generator must inform the treatment facility of the quantity and hazardous nature of the waste, so the
facility can treat it prior to disposal. It is the generator s responsibility to assure that the disposal facility is permitted and reputable. It is also necessary to select a hazardous waste hauler. Hauling of the waste from the temporary storage site to the treatment, storage, or disposal (TSD) facility must be performed by a transporter having an EPA identification number. A list of 2. On-Site Treatment of Hazardous Waste Generators can treat the waste on-site in 90-day holding containers or tanks, if approved by the state or regional EPA office. A waste analysis plan must be submitted prior to treatment. The waste must be treated within the 90-day holding period allowed for waste accumulation. Once the waste has been treated and is determined to be non-hazardous (e.g., leachable lead level below 5 mgíl as measured by TCLP), it can be disposed of at a Subtitle C or Subtitle D landfill. 3. Pretreatment of Blast Abrasives There are several kinds of materials that, when added to abrasives prior to blasting lead containing paint, will result in a non-hazardous waste being generated. Examples are steel grit and a proprietary cementitious-type material. These additives chemically react with the lead during the TCLP digestion procedure and will reduce the solubility below the threshold limit of 5 mg/l. a. Steel Grit -A Federal Highway Administration (FHWA) studyde has shown that adding 3-6% by weight of G-80 steel grit to conventional expendable abrasives has reduced the leachable level of lead from over 50 mgíl to less than 1-2 mg/l. The same study, and other field histories, have indicated that the stabilization of lead may not be permanent, because over time the lead solubility could increase as the steel grit oxidizes. Thus, this treatment, while satisfying the letter of the RCRA law, could lead to leaching of lead into the environment, after the waste has been landfilled. Leaching, in turn, could cause significant problems for the generator. A potential solution to this problem is to further treat the grit-stabilized lead waste with one of the cementitious materials described above. In this case, however, the recordkeeping would be simplified because the waste is not hazardous and the requirements for holding containers and the waste analysis plan are not in effect. b. Proprietary Additives -Proprietary additives are typically incorporated at 15-18% of the weight of the conventional abrasive (e.g., coal slag, copper slag, silica sand). One such addition has been found to effectively reduce the leachable lead content to approximately 0.1 mgll, well below the threshold level.47 This stabilization method, as identified by the manufacturer, involves pH control and encapsulation. Unlike waste containing steel grit additives,
waste containing this proprietary material shows no increase in leachable content after running multiple leaching procedures. Because this material is blasted onto the surface along with the abrasive, it should be manufactured or treated to reduce dusting and to avoid leaving a soluble deposit on the Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 578
SSPC CHAPTERa27.2 93 8b27940 000402b 780 W steel to be subsequently painted. NOTE: The above discussion is derived from a proposed revision of SSPC Guide 7.48 F. STATE REGULATION OF HAZARDOUS AND NON-HAZARDOUS WASTE RCRA also provides for state regulation of the hazardous waste operations. States meeting certain EPA regulations may assume responsibility for hazardous waste control. States also have the authority to establish more stringent requirements. However, if state laws are less stringent than federal, states will not be given this authority. In 1989, approximately 45 states had received such authority from EPA. Authority is not absolute and requires participation by regional EPA offices. Almost every state has enacted regulations regarding production, storage, transport, treatment, or disposal of hazardous substances or waste. RCRA encourages states to assume some of the federal responsibilities for operating their own waste programs. In general, state laws and standards are required to be equivalent to or more stringent than federal requirements. There are some variations from state to state, and certain states have enacted more stringent hazardous waste requirements. For example, California has established limits for leachable content of heavy metals (Soluble Threshold Limit Concentration [STLC]), and for total heavy metal concentration (Total Threshold Limit Concentration [TTLC]).49 California, under Title 22, has also added several metals that are not on the EPA hazardous waste list, most notably zinc and zinc compounds. Thus, if zinc exceeds 250 mg/l in the STLC leach test or 5,000 mglkg under TTLC (total concentration), it is classified as a hazardous waste, so that disposal of spent zinc-rich paint may require testing to determine if waste is hazardous in California. Michigan also includes zinc as a metal that may be classified as hazardous.50 States are also responsible for the disposal of nonhazardous waste, which is not included under RCRA. Nonhazardous wastes are often classified as municipal and special, industrial, or residual wastes. Municipal wastes can be disposed of in a municipal landfill, along with household garbage. Non-municipal wastes often require special handling and paperwork. For example, Illinois EPA requires that any waste from abrasive blasting or other lead removal projects be tested and manifested, even if it is below the 5 mg/l threshold level for hazardous waste.51 For this industrial waste, licensed haulers must be utilized. Pennsylvania also has special regulations for residual wastes, which again require special handling and recordkeeping.52 In these instances, the cost of disposing of non-hazardous waste may approach that of hazardous waste, because ultimately the same standards are being applied. In states where there are no special requirements for non-hazardous wastes, costs for
disposal are significantly lower than for disposal of hazardous waste (e.g., on the order of $100 per ton rather than $400 per ton). In the future, more states are expected to establish special regulations for non-hazardous waste. In many cases, the landfill operators are reluctant to accept wastes that although non-hazardous by the TCLP, may still present a risk because they contain lead or other hazardous constituents. REFERENCES References 1-13 are listed at the end of Chapter 27.0. References 14-38 are listed at the end of Chapter 27.1. 39 40 CFR 261, Appendix II,Method 131 1, tic Leaching Procedure.
Toxicity Characteris-
40. 40 CFR 261.24, Table 1, Maximum Concentration of Contaminants for the Toxicity Characteristic. 41. 49 CFR 172-179, U.S. Dept. of Transportation Regulationc on Transporting Waste. 42. G. Tinklenberg and L. M. Smith, The Criticiality of Sampling and Quality Control for Hazardous Waste Testing, JPCL, April 1990, pp. 36-44. 43. Guide for the Disposal of Lead-Contaminated Surface Preparation Debris, SSPC Guide 71 (DIS), SSPC 92-07. Pittsburgh: SSPC, March, 1992. 44. Sampling for Lead Analysis, G. Tinklenberg, SSPC Lead Paint Bulletin, Summer 1993. 45. EPA Method 1320, published in EPA SW-846, Testing Method for Evaluating Solid Wastes: PhysicallChemical Methods, third ed. Washington, DC, Government Printing Office, November i986. 46. FHWA Contract DTFH61-89-C-00102 with S.G. Pinney & Associates, 1989. Removal, Containment & Disposal of Lead Paint From Highway Bridges. Preliminary results submitted for publication in SSPC Tutorial on Industrial Lead Paint Removal, by Principal Investigator L. M. Smith. 47. L. M. Smith, Pre-and Post-Blast Additives for Stabilizing Lead Waste, unpublished presentation, SSPC 6th Annual Conference on Lead Paint Removal & Abatement, March 15-17,1993. 48. Appendix D, Proposed Revision to SSPC Guide 7, Guide for the Disposal of Lead-Contaminated Surface Preparation Debris, August 1993. 49 California Administrative Code, Title 22, Section 66261.24. 50 The Effect of Zinc-Rich Coatings on the Environment, prepared by the SSPC Zinc-Rich Task Force, JPCL, July 1992, p. 45-53. 51 Illinois Issues Fact Sheet on Disposal of Lead-Based Waste, JPCL, March 1992, p. 45. 52. Guidelines for Disposal of Residual and Household Waste, Pennsylvania Dept. of Environmental Resources, 1992. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 579
SSPC CHAPTER*27-3 93 m 8627940 0004027 617 m CHAPTER 27.3 OTHER REGULATIONS AFFECTING PROTECTIVE COATINGS by Bernard R. Appleman and Monica Madaus I. WATER QUALITY A. FEDERAL CLEAN WATER ACT The 1972 Federal Water Pollution Control Act (FWPCA)4 and subsequent amendments in 1977 and 19875 established the current framework for water quality controls. The goal of this legislation is to minimize pollutant discharge into navigable waters (lakes, streams, oceans) and achieve water that is suitable for human recreation and aquatic organisms. The two basic approaches utilized are: Controlling the concentrations of toxics in the water; Controlling discharge of toxics into the water at the point of discharge. Both of these approaches are incorporated into the FWPCA, commonly referred to as the "Clean Water Act." As with other environmental statutes, the Clean Water Act is a far-reaching, comprehensive, multi-faceted federal/state program. Several of the provisions of the Clean Water Act potentially impact protective coatings activities, including the following: Reportable quantitiesforhazardoussubstances (40 CFR 117). Discharge permits under the National Pollutant Discharge EliminationSystem (NPDES) (40 CFR 122). . Water Quality Standards (40 CFR 131). National Drinking Water Standards (40 CFR 141). Table 6 FEDERAL AMBIENT WATER QUALITY CRITERIA FOR SELECTED METALS53 Freshwater Aquatic Life (pgll) 1 hr.' 4 day 1 hr." Cad m ium 3.9' 1.1** 4.3 Chromium (Vi) 16 11 1100 Copper Lead 18** 83* * 12 3.2** 2.9
140 AluminumMercury 750 2.4 87 0.012 2.1 Zinc 120" 110** 95 'These levels may be exceeded only once every three years. **This level is based on a water hardness of 100 g Caco3. Allowable level is inc reased as hardness increases. 580 B. REPORTABLE QUANTITIES FOR HAZARDOUS SUBSTANCES Approximately 300 chemicals have been designated by EPA as potential hazards when dissolved in water. Any discharge exceeding the reportable quantity is in violation of the Clean Water Act and must be reported. The list includes only a few materials commonly used in protective coating activities, such as toluene, xylene, and sodium nitrite (a wet blast inhibitor). Certain lead compounds are on the list, but not the type that have been used in painting of industrial structures. However, when the material being discharged is a waste product, the activity would be subject not only to FWCPA, but also to CERCLA (discussed under Part IIB of this chapter). Reportable quantities for lead or lead compounds and other toxic metals such as chromate are covered in that section. C. WATER QUALITY STANDARDS EPA has established National Ambient Water Quality Standards for a variety of materials including lead, chromium, copper and cadmium, These place limits on the maximum concentration of material at a given site for a one-hour period (acute) or over a four-day period (chronic). Standards 4 day Saltwater Aquatic Life (pgll) 9.3 50 5.6 0.025 86 --`,,,,`-`-`,,`,,`,`,,`--are set for human consumption (ground or drinking water) and for aquatic life. 1. Water Standards for Aquatic Life The ambient water quality standards for toxic metals address fresh water and salt water conditions. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*27.3 93 W 8b27940 0004028 553 = In fresh water for several metals the acute and ganisms to suspended or dissolve d substances chronic levels are based on hardness. Some exam- resulting from new paint materi als and paint and ples are given in Table 6. abrasive debris. In two studies (described below), there was evidence of toxic effect from some sur2. Drinking Water Standards face cleaning compounds used to pre-wash a bridge EPA has also established standards for maximum and from lead and other paint ing redients. The levcontent of metals and other constituents in drink- el of concentrations used in these studies exceeding water. Some of the criteria are listed below. ed levels measured in field an alyses. Table 7 A California Dept. of Transportation study inFEDERAL DRINKING WATER STANDARDS vestigated the effects of bridge painting opera tions FOR SELECTED METALS4 on fathead minnows, rainbow trout, and other speCadmium Chromium (Vi) Copper Lead Zinc 10 pgll 10 pgll 50 pgll 15 pgll 5000 pgll cie~.~~The results indicate that lead pigmented paints and zinc-rich paints may cause toxicity. Biocides from waterborne paints and cleaning detergents tested were highly toxic. A set of guidelines was developed to assist highway officials in deterThere is a direct relationship between the lev- mining and mitigating the impact of bridge painting el for drinking water and the level for certain heavy projects on the aquatic en vironment. Blasting abrametals under the Toxicity Characteristic Leaching sives range in toxicity from s omewhat toxic to inProcedure (TCLP). EPA assumes that water leached nocuous. from a landfill will be diluted by a factor of 100 be-The Dept. of Fisheries and Oceans of Vancoufore it can penetrate into drinking water sources. For ver, British Columbia, ha s also issued guidelines for example, chromium-containing waste cannot be the protection of fish and fish hab itats during bridge land-disposed unless the leachable chromium con- maintenance.57 These are based on a series of tests tent is less than 5000 pg/l(5 mg/l) which is 100 times on the effects of abrasiv es, paints, and surface the drinking water standard of 50 g/I. The drinking cleaning agents on rainbow t rout and other species. water standard for lead has recently been reduced The degree of toxicity depende d on the specific from 50 pg/l to 15 pg/l. The TCLP level for lead paint formulation, with some ch emical species found however, is still at 5 mgll. It is anticipated that with- to have lethal effects and long-term damage. The
in the next few years, the criteria for lead as a guidelines provide procedures and strategies, inhazardous waste will also be reduced from 5 mg/l cluding regular meetings among the affected parto 1.5 mgll. ties, scheduling to avoid spawning seasons, pre-testing of cleaning agents, greater control of degreasing, use of pressurized water jetting without abrasives, and containment. Even if federal water quality standards are not exceeded, it is prudent to avoid contaminating any bodies of water with paint or abrasive materials or waste. A number of states have more stringent regulations than EPA. For example, North Carolina Division of Environmental Management has an action level of 50 pg/l for zinc in fresh water.58 In addition, visible evidence of inadequate containment of debris from a structure (e.g., paint chips and residues floating on surface) can result in local FIGURE 5 Contamination of water from blasting debris. complaints. At the least such actions will generate bad publicity for the facility owner and the contractor. Citations for violating local nuisance ordinances, 3. Impact of Paint Removal on Aquatic Life Smith55 has reviewed a number of studies on the fines, and delays or shutdowns are also likely to occur. effect of lead paint removal and other painting activities on aquatic life. These studies present no evidence that such activities have resulted in any long-term or immediate violation of the Clean Water D. NATIONAL POLLUTANT DISCHARGE ELIMIN ATION SYSTEM Act. 1. Point Source Discharge and Permits A few researchers have conducted bioassays Because of the potential for damage t o human and of fish to determine the sensitivity of various or- aquatic life, EPA seeks to r egulate discharge of Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 581
SSPC CHAPTERm27.3 93 = 8b27940 0004029 49T industrial and other wastes into streams, lakes, and oceans. The Clean Water Act requires that states and the Federal Government establish a permit system to limit the discharge of effluent. This is the National Pollutant Discharge Elimination System (NPDES)permit system. NPDES permits are required for all point sources of discharge of effluent. A point source is normally an industrial or municipal discharge which is designed to emit effluent into a water body. Thus it covers operations at manufacturing plants, fabrication shops, mills, and shipyards. An example of a non-point source would be municipal or agricultural runoff. These are not covered under the NPDES permit system. Discharges from painting of bridges or other structures over or near water are not point sources, because there is normally not an intent to discharge into the body of water. However, these discharges may be treated as described below. FIGURE 6 Another case --`,,,,`-`-`,,`,,`,`,,`--of water contamination. 2. Storm Water Discharge In 1990, EPA started requiring industrial facilities and municipalities to acquire permits for storm water discharge and municipal storm water systems.59 An exception is that permits are not required for publicly owned treatment works facilities. Industries affected include waste treatment facilities, metal scrap reclaimers, and construction activities affecting five or more acres. Also affected would be paper mills, chemical plants, primary metals industries, and fabricators of structural metal. Paint and surface debris from a painting or paint removal activity which is not properly contained and collected could be considered an unpermitted discharge. Such discharge may be limited by state or federal regulation of water quality standards or other state or local ordinances. 3. State and Local Ordinances EPA has given states much of the responsibility to enforce the Clean Water Act and eliminate discharge into water bodies. Some states may issue ordinances regarding floating objects or debris, scum, oil or other materials, frequently described as nuisance ordinances. A report by the National Cooperative Highway Research Program60 has identified several states with nuisance and discharge regulations, including examples of permitting and reporting requirements.
E. POTABLE WATER IN STORAGE TANKS The Safe Drinking Water Act (SDWA) of 19746 charged EPA with the responsibility for issuing guidance to states on additives to drinking water. The EPA program, which included a list of approved coatings for potable water tank interiors, expired in April 1990. In its place, NSF International (Formerly National Sanitation Foundation) established voluntary standards in conjunction with the American Water Works Association, the Conference of State, Health, and Environmental Managers (COSHEM), and the Association of State Drinking Water Administrators (ASDWA)61. The goal was to develop third-party standards for evaluating the health effects of additives to drinking water. The principal standard of interest is ANSIINSF Standard 61, Drinking Water System Components Health Effects which deals with indirect additives that may contaminate drinking water. It was approved by NSF and ANSI in 1989. Section 5 (Protective Barrier Materials) of ANSIINSF 61 includes requirements for submittal and testing of coatings intended for use in potable water systems. The testing is designed to measure the quantity of heavy metals and organics leached from cured film applied to a glass substrate. The maximum allowable levels (MALs) of these contaminants is set at 10% of the maximum contaminant level (MCL) from EPA s Primary Drinking Water Standards, or by an alternate procedure outlined in Standard 61. The standard also evaluates the ability of coatings to support microbial growth. As part of the submittal, coating manufacturers must furnish composition data and product data sheets, including use and application instructions. An important variable, which affects the solubility of a leachate, is the ratio of the surface to volume of the vessel. This ratio increases as tank size decreases. Thus, the standard includes a normalization factor for MALs to account for this variation. Coatings meeting the criteria of this health-based standard will be certified by NSF. A large majority of the states contacted in a 1990 survey indicated their intention to adopt the NSF standards.62 The NSF has also established a program to evaluate coatings against this standard. Other thirdparty organizations may also serve as certifying bodies. The coatings submitted for testing are classified based on the temperature of the intended service and the size of the tank. Examples of coatings that have met the requirements of ANSIINSF 61 are shown below.63 Water tanks greater than 500 gallons (1,900 L) (cold) -epoxy: Water tanks greater than 1,000 gallons (3,800 L) (cold) -epoxy, vinyl, polyurethane; Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 582
SSPC CHAPTER*27.3 93 8b27940 0004030 LOI Water tanks greater than 1,000 gallons (3,800 L) (tested at 18OOF (82OC)) -phenolic epoxy; Water tanks greater than 50,000 gallons (190,000 L) (cold) -epoxy; Four-inch(100 mm) pipe and greater (cold) -asphaltic coating; Six-inch (150 mm) pipe and greater (cold) -polyurethane; and Repair materials -epoxy filter. Information on specific test requirements and a list of approved systems can be obtained from NSF International. As noted, ANSIINSF61 is a health-based standard and does not address performance aspects such as durability, resistance to undercutting, and application tolerance. These properties must be ascertained by the specifier or owner, as is done for other immersion-type linings. In addition, this standard does not evaluate taste or odor. II. HAZARDOUS MATERIALS A. TOXIC SUBSTANCES CONTROL ACT The Toxic Substances Control Act (TSCA), passed in 1976, was intended to cover uses and exposures to toxic chemicals not covered specifically under other environmental or health and safety regulations. Substances which are covered by other regulations, such as pesticides, are not covered by TSCA. TSCA is often thought of as a set of regulations that primarily affect paint formulators, and several sections are important to this segment of the industry. However, other sections of the act can soon be expected to affect the kinds of paint end users can use. 1. Provisions Which Will Affect End-users EPA intends to use TSCA to respond to broad concerns about exposure to lead, as it has in the past to regulate asbestos and PCB s. It is in the process of conducting a comprehensive review of lead under the act and is considering a variety of steps up to and including a ban or severe restrictions on the use of lead pigments in industrial paint. A variety of possible approaches were outlined in an Advance Notice of Proposed Rulemaking published in the Federal Register on May 13, 1991. Other options would include economic incentives for reductions in the use of lead. 2. Provisions Primarily Affecting Formulators The act authorized EPA to obtain and evaluate information on the health and environmental effects of chemicals. If EPA concludes that particular substances pose an unreasonable risk, it also has the authority to restrict, or even ban, use and manufacturing of the material. A manufacturer is required to notify the EPA
before manufacturing, using or importing a new chemical. This section of TSCA primarily affects coatings developers. A chemical may be considered new if it does not appear on the TSCA Inventory, a list of chemicals published by EPA. Formulators must file a Premanufacture Notice (PMN) for such a chemical unless they qualify for exemptions such as the one available for chemicals used only for research and development. Reviews may also be expedited for chemicals made or imported in quantities of less than 2200 pounds (1,000 kilograms) per year. The PMN should contain information on the chemical identity, how it is going to be used, the volume to be produced, by-products, the number of people likely to be exposed through manufacturing, and the intended means of disposing of it. The EPA normally has 90 days to review the information and to evaluate the risks of the chemical usually using existing chemical literature and comparison to similar chemicals. A notice of the review must appear in the Federal Register. In some cases, the EPA may extend the review and request additional information. The agency has authority to temporarily or permanently ban materials under review, but generally prefers to develop consent agreements under which the manufacturer agrees to restrictions on the use of the chemical. Restrictions may involve the amount of a material used, the way it is used, or personal protective equipment required for those exposed to it. By issuing a significant new use rule (SNUR), the EPA can extend the restrictions in such an agreement to other companies interested in manufacturing, using or importing the substance. The EPA can also use TSCA to require manufacturers to test chemical substances that are already in use, if insufficient information is available and the substances pose an unreasonable risk or are used in sufficiently large quantities to make exposure or release particularly significant. There are also several requirements for recordkeeping and reporting. For instance, chemical manufacturers, processors and distributors are required to keep records of health or environmental effects such as those reported by employees or consumers. They are also required to report any study or event which suggests that a particular chemical poses a substantial risk to the EPA within 15 working days. A description of the steps required by a manufacturer in producing a new material is provided in Reference 64. B. CERCLAANDSUPERFUND The Comprehensive Environmental Response, Com-
pensation, and Liability Act (CERCLA), issued in 1980, is intended to prevent and correct spills and releases of hazardous substances and wastes.9 It is also known as Superfund , because the act establishes a fund to clean up Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 583
SSPC CHAPTER*27.3 73 8627740 0004031 O48 = hazardous waste sites. The act was extended in 1986 under the Superfund Amendment and Reauthorization Act (SARA), which clarified provisions of CERCLA and increased the funds for clean-up.10 CERCLA authorizes EPA to force responsible parties to remove and remediate any release of hazardous substances into the environment. The definitions of these terms, given below, provide EPA with very broad power. 1. Definitions a. Hazardous Substance -Hazardous substances are defined by reference to substances listed or designated under other statutes. These include listed or hazardous wastes under RCRA (40 CFR 261), hazardous substances (Section 311) and toxic pollutants (Section 307) under the Clean Water Act, hazardous air pollutants (Section 112) of the Clean Air Act, hazardous chemicals (Section 7) of TSCA, in addition to substances listed under Section 102 of CERCLA. b. Release -A release is defined as a discharge or spill of any amount of the hazardous substances identified above. Thus there is no minimum quantity below which a facility owner is exempt. Under CERCLA, EPA also requires that any release at or above a designated quantity (the reportable quantity) be reported to the National Response Center. For example, for lead compounds, the reportable quantity is 10 Ibs (4.5 kg) of hazardous lead waste released within a 24 hour period. Amounts less than the reportable quantity need not be reported but are --`,,,,`-`-`,,`,,`,`,,`--still sufficient to establish liability. c. Threat of Release -Even if a release does not occur, a party can be held liable for remedial costs based on a substantial threat of release. Examples include lead lying on the ground, badly corroded chemical storage tanks, or abandoned drums. d. Environment-The environment is defined broadly to include surface water, ground water, drinking water supplies, land surfaces, subsurface strata, and ambient air. 2. Violations Triggering CERCLA Actions Examples of leaks and spills that have triggered CERCLA actions are as follows:68 a. Depositingof hazardous lead waste onto ground adjacent to paint removal operations on bridges and tanks. b. Leaks from tanks containing solvents and other chemicals. (NOTE: Petroleum products are specifically exempt from CERCLA.) c. Leaching of metal (e.g., lead) from a hazardous waste landfill. (NOTE: If the material has passed the TCLP and been properly buried, there is no longer
any liability under RCRA. CERCLA liability, however, extends indefinitely.) CERCLA violations can be brought to EPA s attention by reports submitted to EPA from the National Response Center, by investigations or inspections conducted by state and local officials, or by citizen complaint. Hazardous Substance Lead (as hazardous waste) Hydrochloric Acid Methyl Ethyl Ketone Methylene Chloride Sodium Hydroxide Sodium Nitrite Toluene 1,1,1,-Trichloroethane Trichloroethylene Xylene Zinc Metal Table 8 SELECTED LIST OF HAZARDOUS SUBSTANCES AND REPORTABLE QUANTITIES (40 CFR 302.4, Appendix A) Reportable Quantity 10 Ibs (4.5 kg) 5,000 Ibc (2,270 kg) 5,000 Ibs (2,270 kg) 1,000 Ibs (454 kg) 1,000 Ibs (454 kg) 10 Ibs (4.5 kg) 1,000 Ibs (454 kg) 1,000 Ibs (454 kg) 100 Ibs (45 kg) 1,000 Ibs (454 kg) 1,000 Ibs (454 kg) Comments Report if 2 5 mg/l per TCLP Used for etching concrete Paint solvent
Paint stripper Paint stripper, neutralizing agent Wet blast inhibitor Paint solvent VOC-exempt paint solvent Degreasing solvent Paint solvent Zinc-rich paints, galvanizing *The spill must be reported if this amount of waste is spilled in a 24-hour peri od. 584 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERm27.3 93 8627940 0004032 T84 As noted, the major purpose of the regulation is to provide the organizational structure and procedures for preparing for and responding to discharges of oil and releases of hazardous substances, pollutants, and contaminants. 3. Other Requirements of CERCLA Regulations The regulations provide details on the following procedures: Setting priorities for cleanup; Identifying remedial actions; Identifying responsible parties; Determining liability for cleanup costs; Enforcement and inspection of cleanup: and Record kee pi ng . 4. Superfund Portions of the clean-up are to be paid for from a national fund, Superfund , created by taxes on petroleum and the chemical industry, environmental taxes on corporations and general revenues. Overall, the Superfund program as administered by EPA has made little progress in achieving the intended cleanups. Over 50% of the several billion dollars that make up the fund have gone to administrative and legal fees. Examples of some hazardous substances and reportable quantities are given in Table 8. C. SARA Title III ( Right-To-Know ) The use of industrial chemicals is also affected by reporting regulations developed under the Emergency Planning and Community Right to Know Act (EPCRA). EPCRA was included in the legislation that reauthorized the Superfund program in 1986, known as the Superfund Amendments and Reauthorization Act (SARA), also known as SARA Title 111. 0 The legislation established requirements for federal, state and local governments and industry regarding emergency planning and community right-to-know reporting on hazardous and toxic chemicals. 1. Planning and Response Sections 301-303 of SARA Title IIIrequire state and local governments to develop or designate emergency planning and response commissions. Another provision requires companies to determine whether any chemical found on a list of over 300 extremely hazardous substances (40 CFR 355) was present at their facility at any one time in an amount exceeding the Threshold Planning Quantity (TPQ), a quantity that triggers regulation. The threshold planning quantity is 10,000 pounds (4540 kgs) for many extremely hazardous substances that do not have their own TPQ. However, it may be 500 pounds
(227 kgs) for some, particularly powdered solids, and as low as 10 pounds (4.5 kgs) for the most hazardous. Companies that determine that they have had more than the TPQ on-site must notify authorities and appoint a facility coordinator who will participate in local emergency planning. Comparing quantities of pure substances to the TPQ is relatively straightforward, but requires accurate recordkeeping. However, a mixture is assumed to present the same health hazards as any of the components that comprise one percent (by weight or volume) or greater of the mixture. Therefore, the quantity of a material on site must be multiplied by the percent of any extremely hazardous substance present in the material, and the resulting figure must be compared to the TPQ. This means that components that make up a small quantity of a material may exceed the TPQ if a facility uses a large enough quantity of the mixture, or the component is considered particularly hazardous.69 2. Emergency Notification To comply with section 304 of SARA Title III, companies must determine whether they produce, use or store a hazardous substance that is included on 1) the list of extremely hazardous substances (40 CFR 355) or 2) the list of substances subject to emergency notification requirements, found under CERCLA (40 CFR 302.4)70. A company that does produce, use or store such a substance is covered by section 304. It must notify the National Response Center, and the state and local emergency planning committees if it spills or otherwise accidentally releases more than the reportable quantity of any such substance that may result in exposure outside the company site. This does not include releases such as permitted discharges to water or emissions to air. The notification should include: a. the chemical name; b. an indication of whether the substance is extremely hazardous; c. an estimate of the quantity released into the environment; d. the time and duration of the release; e. known or anticipated acute or chronic health effects; f. proper precautions; and g. name and phone number of a contact person. A written emergency notice should include any more recent information including response actions and any need for medical attention for those exposed. 3. Material Safety Data Sheet Sections 31 1-312 of SARA Title III may apply to any company that must prepare or maintain a material
safety data sheet (MSDS) for any of the materials it uses, stores or manufactures. An MSDS is required for any material that is a physical or health hazard, including materials that can catch fire; are suspected of causing cancer: can cause central nervous system effects; or can irritate skin, eyes or Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 585
SSPC CHAPTER127.3 93 Ab27940 0004033 9LO the respiratory system. The regulations therefore term manufacturing also applies to a toxic apply to a very broad range of chemicals including chemical that is produced coi ncidentally during the solvents, paints and most other materials commonly manufacture, processing, use or disposal of another used in the coatings industry. This section may ap- chemical or mixture of chemi cals, including a toxic ply to many firms that produce or apply coatings. chemical that is a by-product or an impurity. Once again, regulations apply only to materi- The term processing applies to the p repaals that exceed the TPQ. The TPQ is 10,000 pounds ration of a toxic chemical, af ter its manufacture, for (4540 kgs) for any material that does not have its distribution in commerce, whe ther in the same form own substance-specific TPQ and 500 pounds (227 or physical state, or a different form or physical kgs) for extremely hazardous substances that do not state, than that in which it was received by the perhave their own TPQ. Hazardous components of mix- son preparing such a substance. Process also aptures must again be taken into account in calculat- plies to the processing of a toxic chemical contained ing TPQs and the amount of a chemical on-site. in a mixture or trade name produc t. In addition, the Carcinogenic compounds that make up 0.1 percent term processing applies to toxic chemicals a faciliof a mixture or greater must also be included for this ty adds to an article. sect ion. The term otherwise use includes any use of Those to whom section 31 1 and 312 apply must a toxic chemical that is not cover ed by the terms annually develop a list of all chemicals present in manufacture or process . This inc ludes use of quantities exceeding the TPQ. The information must a toxic chemical contained in a mixture or trade be provided by March 1 to the State Emergency name product. Relabeling or redist ributing a conResponse Commission, the local Emergency Plan- tainer of a toxic chemical where no repackaging of ning Committee and the local fire department. A the toxic chemical occurs does n ot constitute use form known as the Tier I form is used. Alternative- or processing of the toxic c hemical. ly, the company may submit the MSDS for each of Generally, the manufacturing and processing these materials. The company must also notify categories will apply to formulato rs and the otherthese groups of the average daily amount on site, wise used category will apply to applicators. the maximum amount on site on any day during the However, if a company coats a p roduct that it sells year, and the locations of these chemicals. Addition- (shop-applied coatings), c oating application would al information contained on a Tier II form may be then be considered processing.
requested. In determining whether they manufacture, 4. Toxic Chemical Release Forms process or store more than the TPQ of any chemiCompanies with more than 10 employees must de- cal, employers must again conside r the components termine if section 313 applies to them. They must of mixtures. Similar to sectio ns 31 1-312, compofirst determine whether they manufacture, process nents that make up 1 percent of a mixture, or comor otherwise use any material on the list of chemi- ponents that are carcinogens and make up 0.1 cals found in that section. Many materials commonly percent of a mixture must be considered. used in coating operations are found on the list, in- Under the regulations, sup pliers are required cluding solvents such as methanol, n-butyl alcohol, to inform their customers of the identities and conmethyl ethyl ketone, 2-nitropropane, toluene and xy- centrations of the material s that make up their lene, and pigments such as lead chromate, red lead, products. zinc dust, zinc chromate, titanium dioxide, and nick- To meet the requirements o f 313, companies el titanate. Some paint additives and resin compo- that exceed the TPQ must annu ally report routine nents are also found on the list, including melamine, emissions of each such che mical, including releases dibutyl phthalate, diethanolamine, ethyl acrylate, for- into water, air or soil during the preceding year. Filmaldehyde, vinyl chloride, methyl methacrylate and ing these reports can be a co mplicated process that toluene-2,3-diisocyanate. may require the help of an engineer or other perCompanies must next determine if their use of son with appropriate training. these materials exceeds the TPQ. The TPQ for A company that has determined that the promaterials that a company manufactures or visions of 313 apply to one or more of i ts materials processes is 25,000 pounds (1 1,360 Kg). The TPQ should draw a process flow diagr am to determine for a material that is eaves the system.
otherwise used is 10,000 each point at which the material l
pounds (4,540 Kg). For many coating operations, the primary release Obviously, the distinction between manufactur- is the evaporation of solvents an d other materials ing or processing and otherwise using is important. in a coating as it is applie d. However, material colAccording to the regulatory definition, a firm is con- lected by vapor control s ystems, discharged to
sidered to be manufacturing sposed of must
a material if it wastewater facilities or otherwise di
produces, prepares, imports or compounds it. The also be considered. 586 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERr27.3 93 = 8627940 0004034 857 After identifying all sources of chemical releases, the quantity released must be determined for each chemical that exceeds the TPQ. A number of approaches and formulas can be used to do this, including direct measurement, mass balance formulas and engineering calculations. Overspray releases are often the most important factor in estimating releases from coating operations, and published estimates are available for some types of spraying methods and surfaces. However, sitespecific calculations may be required. Current SARA 313 thresholds require only larger coating operations to report. These businesses often have greater resources and specialized personnel, and are better able to comply with 313 requirements. Proposals to lower TPQs would result in smaller operations, perhaps those using as little as 500 gallons (1,900 L) of paint, also being required to report under 313. EPA estimates, which are often low, show that reporting would mean 34 hours of additional work for small businesses. Using in-house personnel is estimated by EPA to cost $40 an hour; however, small businesses may not have the expertise to estimate releases and may need to hire consultants at considerably higher rates. 111. REGULATING STORAGE VESSELS A. SECONDARY CONTAINMENT 1. Affect on Coating Suppliers and Contractors Federal regulations require that some tanks be supplied with secondary containment, structures capable of preventing material stored in a tank from migrating to soil, groundwater or surface water. Other considerations such as CERCLA and civil liability associated with a spill prompt companies to invest in such systems.9 The need for secondary containment systems provides a business opportunity for coatings suppliers and contractors. Concrete is the material most often used for secondary containment structures. Coatings are an integral part of such designs because they increase the impermeability and chemical resistance of concrete and prevent cracking. 2. Regulatory Requirements a. Applicable Regulations -Tanks used to store and treat hazardous wastes are subject to 40 CFR Part 264 of Subpart J of the Standards for Owners and Operators of Hazardous Waste Treatment, Storage and Disposal Facilities (part of RCRA). The title of this section is somewhat misleading. The requirements apply both to treatment, storage and disposal facilities and to large quantity generators (those who generate more than 1,000 kg (2,200 Ib) of hazardous waste a month and store the material for more than 90 days on site). Tanks con-
taining hazardous waste must be equipped with secondary containment structures. An exemption is provided for hazardous waste that contains no free liquids and is stored inside a building with an impermeable floor. In order to prevent migration, a secondary containment system must be capable of containing spills and leaks, and must be equipped with a leak detection system to alert owners and operators to such an event. A containment system must also be made of or lined with materials compatible with the waste stored in the system. The system must include an appropriate foundation or base and be sloped or designed in such a way as to permit draining and removal of liquids.6566 The Oil Pollution Act of 199067 required EPA to study the need for similar regulations applicable to above ground tanks used to store petroleum products. b. Acceptable Containment Structures -Containment may be provided by an external liner, vault, a double walled tank, or an equivalent device. External liners and vaults must be capable of containing 100 percent of the capacity of the largest tank within their boundary. They must also prevent rain from entering the secondary containment system unless the containment system has the capacity to hold the extra liquid. (1) External liner systems must surround the tank completely and cover any surrounding soil likely to come in contact with leaked or spilled waste. (2) Vault systems must include water stops which are capable of resisting the waste in all joints, and must be coated with a wastecompatible lining that will prevent the waste from permeating the concrete. They must also be able to prevent the formation of and ignition of vapors within the vault. (3) Double walled tanks must be designed so that the outer tank completely surrounds the inner tank, preventing any releases and protecting the exterior of the inner tank from corrosion. Materials that could cause the tank or ancillary equipment or the containment system to rupture, leak or fail may not be placed in the tank. Owners and operators must use appropriate measures to prevent spills and overflows and must visually inspect visible portions of the tank and review data from monitoring and leak detection equipment at least once each operating day. 3. Coating Choices for Secondary Containment Systems
A secondary containment system must be able to survive contact with the substance in the tank until Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 587
SSPC CHAPTER*27.3 93 = 8627940 0004035 793 D a leak or spill can be removed. Since leaks and spills should be infrequent and a detection system is often required, secondary containment components are usually only exposed to the material for a short period of time. When a tank is used to store an extremely toxic or dangerous material, the secondary containment system should be more durable, and more expensive than it would be for a less hazardous material. Choice is complicated by the fact that a coating may need to be capable of resisting several different materials. Types of coatings commonly used to protect secondary containment systems include the following: a. Thin Films -Thin films (10 mils [0.25 mm]) of unreinforced spray-applied coatings are adequate for containment of less hazardous materials, and are less expensive than other approaches. However, some may not withstand long periods of chemical exposure. Epoxies, vinyls, chlorinated rubber, and urethanes are commonly used in this way. b. Flake and Fiber-filled Coatings -Flake and fiberfilled coatings typically result in films of 40 to 80 mils (1 to 2 rnm). They cost more than thin film coatings. Some may provide a longer period of containment. t FIGURE 7 Installing an underground storage tank. c. Reinforced Thick-film Systems -Reinforced thickfilm systems can be used to create films of more than 80 mils (2 mm). Glass cloth or synthetic fibers are chosen on the basis of their resistance to a particular chemical. These systems can be effective in preventing some cracks, and should be designed to withstand exposure to the most aggressive chemicals, for up to 72 hours. A resinous topcoat improves their chemical resistance. Coats of reinforced paint with one layer of reinforcement may be less expensive but also less chemical resistant than those with multiple layers. B. UNDERGROUND STORAGE TANKS 1. Introduction Certain underground storage tanks are regulated because they may leak and pose a threat to the environment and human health. Coatings and lining systems are among the accepted means of preventing leaks in underground storage tanks (USTs) and complying with federal and state regulations. There are several million underground storage tanks in the USA, containing petroleum or hazardous chemicals. The tank system consists of the tank itself and associated piping. A tank system
is considered underground if at least 10% of the volume is below grade level. The vast majority of underground storage tanks (in particular those installed before 1980) were constructed of bare carbon steel. As a result of differential aeration of soils, aggressive soil conditions, pH variation, and the presence of water and other corrosive materials inside the tank, there is the possibility of severe corrosion of both the interior and exterior of tanks and piping. As a result of corrosion as well as piping and mechanical failures and installation mistakes, many thousands of USTs are leaking. Leaks may also result from spills and overfills during filling, emptying, or operation of the tanking system. Leaking underground storage tanks can contaminate groundwater, which is a major source of drinking water for US populations. EPA estimates that as many as a quarter of all the tank systems in the US are leaking.71 2. 7984Federal Regulations In 1984, Congress included requirements for technical standards and corrective action requirements for owners and operators of underground storage tanks, when passing the legislation that led to the RCRA regulations discussed under chapter 27.2. The underground storage tank regulations (40 CFR Part 280) are intended to achieve the following goals: a. Prevent leaks and spills; b. Identify and correct problems; and Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 588
SSPC CHAPTER*27*3 73 8627740 000403b b2T D c. Ensure that owners and operators are able to pay for spill prevention and correction. The regulations apply only to USTs storing petroleum or hazardous chemicals. Some tanks are specifically excluded from the regulations including certain residential motor fuel and heating oil tanks and pits. Responsibility for complying with the regulations falls on the owners and operators of the tanks. The specific requirements depend on the date of installation of the tank. 3. New Petroleum USTs New USTs, those installed after December 1988, must meet the following requirements: a. Be properly installed -by qualified installers following industrial codes such as those established by Steel Tank Institute, American Petroleum Institute, National Leak Prevention Association, Petroleum Equipment Institute, National Association of Corrosion Engineers, and other organizations. b. Be equipped and used to prevent spills and overflow -through proper filling procedures, catchment basins, and alarms. c. Detect leaks. d. Protect the tank from corrosion -Among the methods to ensure proper corrosion protection for new tanks are the following: 1) Use of a corrosion resistant coating together with cathodic protection; 2) Construction of non-corrosive material (e.g., FRP); 3) Installation of bonded, secure system liner (note: the liner is not acceptable for piping); Special instructions are given for tanks depending on the size and age and for piping (depending on whether it is pressure or suction type). These cover topics such as monitoring of vapors from soil, monitoring liquid in groundwater, automatic tank gauging and automatic shutoff and tightness tests. 4. Existing Petroleum USTs For tanks built before December 1988, EPA has set deadlines for establishing corrosion protection, incorporating filling devices to prevent spills and overfill as well as leak detection systems. For corrosion protection, the following options are available for upgrading tanks: a. Install an interior lining. The lining must be inspected within 10 years after installation and every 5 years thereafter. (40 CFR 280.3 gives require-
ments for the inspection). b. Install cathodic protection systems. The tank must be internally inspected to ensure that it is free of corrosion holes by various methods described in 40 CFR 280.21. NACE RP02-85, may be used to verify proper inspection and operation of a cathodic protection c. Use both an internal lining and cathodic protection. d. Use a thick liner bonded to the exterior of the tank. This requires excavations around the tank and is not often feasible for existing tanks. Metal piping must be upgraded using a cathodic protection system. Upgrading of corrosion protection systems for all tanks and piping must be completed by December 1998. All new and existing tanks must also have leak detection installed by December 1993. The regulations also provide instructions on how to correct problems caused by leaking, how to permanently or temporarily close (take out of service) a tank system, and how to meet the extensive record keeping and reporting requirements. 5. Underground Chemical Tanks Underground storage tanks containing hazardous chemicals are also regulated under 40 CFR Title I (part 280). Hazardous chemicals are those that are listed in CERCLA (40 CFR 302.4, Table 1). CERCLA is discussed in Section II of this chapter. Hazardous wastes are excluded from this section of the regulation because they are covered under other provisions of RCRA. a. Corrosion Protection -These underground chemical storage tanks are subject to many of the same regulations as petroleum tanks. All chemical USTs installed prior to December 1988 must be upgraded by December 1998. Aswith petroleum tanks, the corrosion protection can consist of installation of a liner, a cathodic protection system, or a combination. The tank must also be provided with devices that prevent spills, overfills, and detect leaks. New tanks (those installed after December 1988) must meet the same requirements as the new petroleum USTs (¡.e., properly installed, spill and overfill protection, protection from corrosion, and equipped with leak detection). b. Secondary Containment -In addition, new tanks containing hazardous materials must be provided with secondary containment. The primary containment is the tank or pipe wall itself. Secondary containment systems are designed to prevent hazardous materials from entering the environment if there is a leak or break in the primary system. (See discussion under Part A of this section.) There are three types of secondary containment used for underground tanks and piping:
(1) Double-walled systems in which one tank is placed inside another, or one pipe inside another; (2) Concrete vaults which surround tank and piping systems and isolate this from the ground; Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 589
SSPC CHAPTER*27.3 93 Ab27940 0009037 5bb m (3) Chemical resistant liners placed around the epoxy, glass-flake-filled polyes ter and fiberunderground storage tank to isolate it from the reinforced polyesters. ground. c. Cathodic Protection -This consists of applying In addition to the above, the chemical USTs an external electric current to forc e the steel to bemust have a leak detection system that can detect have as a cathode. An electric al circuit resulting in a leak in the interstitial space between primary corrosion and loss of metal occur s only at the anode, and secondary containment. where the metal gives up electrons. Two types of These requirements for secondary containment cathodic protection have been devel oped: sacrifiof underground chemical storage tanks are essen- cial anodes and impressed curre nt. Sacrificial tially the same as the requirements for secondary anodes are metals such as zinc or magnesium, containment of storage tanks containing hazardous which are consumed (sacrificed ) while the steel rewaste. Additional discussion on the design of secon- mains intact. Impressed cur rent cathodic protection dary containment and the performance and chemical sends a continuous stream of D C electrical current resistance properties of liners and concrete struc- through the steel. The curre nt ensures that the steel tures are discussed in section HIA of this chapter. cannot discharge current (¡.e. , form ferrous ions) into the environment. Cathodic protection is also an in6. Corrosion Protection of Underground Storage tegral part of the STI-P3 system described Tanks d. External Coating Plus Sacrificial Anodes -For new The basic means of preventing corrosion are as tanks, a combination of a dielect ric coating and follows: sacrificial anodes has proven to be extremely effecAn external coating system applied to the ex- tive over the last 30 years. The S teel Tank Institute terior of the tank; has developed an industry standard known as STIA lining system applied to interior of tank; P3, which combines dielectric coati ng, sacrificial Cathodic protection applied to the exterior of anodes, and electrical The dielec tric the tank; and coating (e.g., typically coal tar epoxy, polyurethane, FRP construction. or FRP) serves as the first line of defense, with a a. External coating system -A coating system is complete covering of the externa l surface of the designed to isolate the steel of the tank from corro- tank. The galvanic anodes provide protection from sive soil conditions, thereby preventing the corro- nicks and scratches in the c oating, which are often sion cell from being completed. A significant amount produced during transportat ion and installation or of testing, research, and evaluation has been con- settling. Anodes are construc ted of zinc or magnesi-
ducted on underground coatings. Among the most um. The third component of the sy stem is to preimportant properties are adhesion, impact vent stray currents from entering the tank via the resistance, and impermeability. Among the most piping system or at other potenti al areas of metalwidely used coating systems are asphalt cutbacks, to-metal contact. STI also has established a quality coal tar epoxy, polyurethane coating systems, and assurance system for the testi ng of the coatings, the FRP coatings. Several of these systems have been fabrication of the tanks, and i nstallation, to help asapproved by the Steel Tank Institute under their sure long-term protection. STI-P3 ~ystern.~3 e, Fiberglass Reinforced Plastic Construction -FRP Application of a coating to a new steel tank can is a composite consisting of a chemically reacted be accomplished under factory shop conditions, resin impregnated with glass fibe rs. The resin syswhich allows much greater control of the quality of tem when reacted and cured, forms a strong, relathe surface preparation, application, and environ- tively impermeable barrier to moisture, while the mental conditions. Applying an external coating to fibers impart tensile strengt h. This results in a high upgrade an existing tank requires excavating strength-to-weight ratio for these light materials, and around the tank and back filling after application of provides an optimum combin ation of corrosion the coating. resistance and strength. FRP, like other construcb. Internal Lining System -To upgrade an existing tion and corrosion protection materials, must be tank, the lining can also be applied to the interior carefully selected, tested, designed, and installed of the tank. The API has issued recommended prac- to ensure proper performance a nd compliance with tice RP1631, Interior Lining of Underground design criteria. Storage Tanks, which describes the various steps More detailed discussions of cor rosion protecin preparing the tank and applying the lining, includ- tion alternatives and mat erials are given in various ing qualification of applicators and testing of lin- publications available from STI, NACE, and SSPC. ings.74 A number of coating systems have been (See Appendix for addresses.) used for lining of petroleum tanks, including epoxy polyamide, epoxy phenolic, epoxy amine, coal tar 7.State Regulation of Undergrou nd Storage Tanks The underground storage tank program, like many 590 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from
IHS
SSPC CHAPTER*27.3 93 8627940 0004038 4T2 federal laws, is delegated to the states. Many states perature and sterilization conditions required. The have adopted existing federal regulations for up- FDA does not approve coatings, but sets the guidegrading USTs or installing new USTs. Several states lines as described above. It is the manufacturer s have adopted or proposed to adopt their own regu- responsibility to ensure that the raw materials and lations, which may be more stringent than the fed- test results comply with the federal regulations. An eral regulations. For example, some states, such as appropriate statement by a m anufacturer would be Connecticut, limit the number of times that a tank that the coating will meet th e requirements of CFR lining can be used to extend the life expectancy of 175.300 (FDA) for use in con tact with specific fooda tank. Other states (e.g., Massachusetts and stuffs. The phrase approved by FDA s not valid. Maine) require double walls in all new tanks. Several 2. USDAstates require that all new tanks (including petrole- The U.S. Dept. of Agriculture, through its Fo od Safeum as well as chemical storage tanks) be provided ty & Inspection Service Divisi on (FSIS), is responwith secondary containment. Certain states also re- sible for inspecting and app roving coatings used in quire that installers be certified (e.9. Florida, Arkan- incidental contact area s at food and poultry sas, and California.) plants.76 77 These areas include warehouses, nonTwo standards, the Uniform Fire Code (UFC) process areas, and upper walls and ce ilings of 79 and National Fire Protection Association (NFPA) process areas where direct co ntact with food is not 30, are frequently cited in state UST regulations. normally expected. However, t hese areas may reThe standards outline safety parameters for tank lin- quire resistance to spills of food and to variousing procedures. UFC 79 does not permit repairs to sanitiz ing operations. USTs; NFPA 30 allows USTs to be repaired and The USDA determines the suitability of coatlined. Refer to the February 1991 Journalof Protec- ings based on a review of th e formulation, MSDS, tive Coatings and Linings for a recent update on and results of product testing supplied by the state UST requirements. * manufacturer. In addition, manufacturers may also be asked to supply a sample of the cured coating to verify that it will form a hard, intact film. IV. MISCELLANEOUS REGULATIONS If the Department s criteria are met, USDA will A. REGULATING COATINGS FOR FOOD & issue a letter to the manufacturer indicating that the coating that has been submitted is approved for use BEVERAGE FACILITIES on incid
i
ental surfaces of meat and poultry plants. The Federal Government regulates coatings intended These letters are furnished t o the owners and operafor surfaces at food and beverage plants, to assure that sani- tors of plants, w ho are ultimately responsible for tary conditions are maintained. The food and beverage in- complying with the USD A as well as FDA regudustry consists of production, processing, and distribution lations. facilities for fruits and vegetables, grain, meat and poultry, soft drinks, beer and other alcoholic beverages, and phar- B. SOIL QUALITY REGUL ATIONS maceuticals (because the end products are consumed). Fed- Soil can become contam inated with dust, paint, and eral agencies having jurisdiction are the Food and Drug abrasive debris. One of the primary concerns is lead conAdministration (FDA) and the US Department of Agriculture tamination of soils, b ecause of the potential health effect on (US DA). children in nearby communities. As of 1993, EPA had not 1. FDA issued a regulation on lead in soil. It is anticipated, however, The FDA regulates coatings that come into direct that as part of the EPA s mandate under Title X of the 1992 contact with food and beverages under 21 CFR 175, Housing and Community Developm ent Act, EPA will issue Parts 300-390. These include coatings applied to guidelines or regulations on ac ceptable levels of lead in soi1.30 floors, walls and counters, as well as containers and These regulations may also require remediation or other vessels. The FDA limits ingredients to those that are treatment for soil exceedi ng a defined level of lead. listed in the CFRs or that are generally recognized Because of extensive use of leaded gasoline and leadas safe for food. In addition, the cured film must containing traffic marking an d bridge coatings, much of the meet limits for the maximum amount of extractable soil in the US contains measur able amounts of lead. The gematerial. According to Boyer76, there are no limita- ometric mean in the US is 1 6 mglkg (ppm), but in urban or tions on solvents, and a wide range of organic industrial areas or along roadway s, concentrations often exbinders is permitted. There are, however, limitations ceed 100 mglkg.78 In 1989, EPA adopted an interim guideon the color of pigment allowed. line for cleanup of soil at Superfund sites of 500-1000 mglkg, The extraction tests are based on the food with the lower end of the range being considered more aptypes (e.g., acid, non-acid, dairy products, bever- propriate for residential ar eas and the upper end for use in ages, bakery products, and dry solids) and the tem- industrial settings.79 591 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*27-3 93 8627940 0004039 339 A review of guidelines and soil clean-up levels for lead in several states indicates a range from approximately 100-1000 mg/kg, with most values in the range between 250 and 500 mgikg.78 C.REGULATION OF ANTIFOULING COATINGS 1. Use Antifouling paints are used to discourage colonies of sessile marine organisms such as barnacles, mollusks, sponges and algae from building up on the bottoms of ships. Fouling increases the weight of ships, reducing speed and increasing fuel consumption. It also interferes with the operation of moving parts. Antifouling coatings are also being used to prevent zebra mussels from fouling fresh water intakes on power stations. Power stations have reported condenser tube blockage in unheated intakes.81 Protective coatings have been evaluated as alternatives to chlorination or water filtration and other chemical and physical treatment. 2. Organotin Antifouling Paint Act Until 1988, copper and organotins (such as tributyl tin) were the compounds most commonly used to prevent fouling of underwater hulls of ocean-going ships. Both types kill target organisms by releasing small quantities of materials toxic to them. Concern about effects of organotin compounds on non-target organisms such as oysters and crabs led to passage of the Organotin Antifouling Paint Control Act in 1988.80 The act limited releases of tin from such coatings to 4 pg/cmn/day. The legislation also required each state to set up a plan to certify applicators of these coatings. Organotin coatings are now seldom used except on aluminum boats, where copper (for which there is no release rate) cannot be used. Some states, for instance New York, also regulate such materials under their water quality regulations. 3. FIFRA Biocides like copper and organotin compounds are considered pesticides and must also be registered under the Federal Insecticide, Fungicide and Rodenticide Act.12 According to some paint manufacturers, meeting all the requirements for registering a new biocide is so prohibitively expensive ($2-5million) as to effectively preclude any uses of new materials. 4. Foulant Release Coatings Some ship and power plant operators have begun to use silicone, siloxanes and fluorinated resins because these materials do not need to be registered under FIFRA. They are not considered pesticides because they do not kill sessile organisms, but make
it difficult for them to attach to the painted surface.81 REFERENCES References 1-13 are listed at the end of Chapter 27.0. References 14-38 are listed at the end of Chapter 27.1. References 39-52 are listed at the end of Chapter 27.2. 53. FederalRegister. Volume 50, 30784 (July 29, 1985). Water Quality Criteria; Availability of Documents. 52 FR 621 43 (Zinc), Appendix A -Summary of Water Quality Criteria for Zinc. 54. Criteria and Standards Division, Office of Drinking Water, Environmental Protection Agency, Washington DC 20460. 55. Water Quality, Progress Report prepared by L. M. Smith for FHWA Contract DTFH61-89-C-00102. 1989. 56. H. Hunt and J. Gidley, The Toxicities of Selected Bridge Painting Materials and Guidelines for Bridge Painting Projects, Report FHWA/CA/TL/90/08, California Dept. of Transportation, September 1990. 57. Canadian Fisheries Dept. issues Guidelines on Protecting Aquatic Life During Bridge Painting. JPCL, January 1992, pp. 32-34. 58. G. Thorpe, Water Quality Impact: Environmental Viewpoint, Lead Paint Removal from Steel Structures, SSPC 86-01, 1988, pp. 50-54. 59. Car Department Officers Association Protective Coatings Committee. PA Update Paper: Overview of the Stormwater Permit Program. September 21, 1992. 60. M. K. Snyder and D. Benderski. National Cooperative Highway Research Program, Report 265. Removal of Lead-Based Bridge Paints. Washington DC: Transportation Research Board, December. 1983. 61. M. Bauer, Changing Regulations on Coatings for Contact with Potable Water, JfCL, December 1988, pp. 27-33 and 89-90. 62. Majority of States Plan to Adopt NSF Standards for Potable Water Contact, JPCL, October 1990, pp. 39-40 and 97-99. 63. Environmental Health & Safety Regulations, Unit 7 from SSPC 5-Day course on Specifying and Managing Protective Coating Projects. SSPC, May 1993. 64. G. Rauscher, Compliance with TSCA for Product Development, JfCL, May 1990, pp. 68-72. 65. P. R. Nau and B. S. Fultz. Coatings and Linings for Secondary Chemical Containment in Power Plants, JPCL, October 1990, pp. 42-49. 66. K. A. Kapsanis, Coating Concrete: A Review of Regulations, Technical Activities, and Resources, JPCL, August 1991, pp. 58-65. 67. Oil Pollution Act: Public Law 101-380, August 18, 1990. 68. EnvironmentalLaw Handbook, 12th Edition. Rockville, MD, Government Institutes, Inc., 1993. 69. U.S. EPA. Title 111 Fact Sheet: Emergency Planning and Community Right-To-Know. April 1988. 70. Guide to Pollution Prevention: The Fabricated Metal Products lndustry, Report EPA/65/7/90/006. Washington, DC, US. EPA, 1990. 71. U.S. EPA, Office of Underground Storage Tanks, Musts for Usts. July 1990, EPA/530/ UST-88/008. 72. Control of General Corrosion on Metallic Buried, Partially Buried, or Submerged Liquid Storage Systems, NACE RP02-85. Houston, NACE International, 1985. 73. R. C. Cronau, Protecting Underground Storage Tanks, JPCL, August 1988, pp. 48-49. 74. Interior Lining of Underground Storage Tanks, API RP 1631, 2nd ed. Washington DC, American Petroleum Institute, December, 1987.
75. Sti-P3 Single Wall Steel Underground Tanks: The Iron-Clad Storage Solution, Publication 3500M20. Northbrook, IL: Steel Tank Institute, 1987. 76. C. Boyer, Protective Coatings for Food and Beverage Plants: Regulatory and Formulating Issues. JPCL, July 1990, pp. 36-39. 77. D. Finch, Coating Selection for Food and Beverage Facilities: Regulatory Compliance and Corrosion Protection, JPCL, September 1992, pp. 62-72. 78. P. K. LaGoy and W. Wilder, Evaluation of the Potential for Environmental Exposure to Lead Released from Paint Containing Zinc Dust, JPCL, March 1993, pp. 24-36. 79. Interim Guidance on Establishing Soil Lead Cleanup Levels at Superfund Sites, Directorate 9355.4-02, EPA Office of Solid Waste & Environmental Response, September 7, 1989. 80. Organotin Antifouling Paint Control Act, Public Law 100-333, June 16, 1988. 81. E.G. Leitch and F.Z. Puzzuoli, Evaluation of Coatings to Control Zebra Mussel Colonization: Preliminary Results, 1990-1991 , JPCL, Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS July 1992, pp. 28-38. 592
SSPC CHAPTERu27-3 93 m 8b27940 0004040 O50 m APPENDIX A HOTLINES AND OTHER PHONE NUMBERS Clean Air Act Computer Bulletin Board (919) 541-5742 Emergency Planning and Community Right to Know (EPCRA) Information Hotline (703) 412-9877 (800) 535-0202 Emission Measurement Technical Information Center (CAAA) (91 9) 541 -1 060 Environmental Test Methods (SW 846 Manual) (703) 821-4789 EPA Control Technology Center (CAAA) (91 9) 541 -0800 FIFRA/General Pesticide Information (800) 858-7378 National Air Toxics Information Clearinghouse (919) 541-0850 National Lead Information Center (800) LEADFYI (532-3394) National Response Center (800) 424-8802 RCRAKERCLA Hotline (703) 305-5938 (800) 424-9346 Safe Drinking Water (800) 426-4791 Small Business Ombudsman Clearing houselHotline (800) 368-5888 (703) 305-5938 Solid Waste Assistance Program (800) 677-9424 Spill Prevention Control and Countermeasures (e.g., aboveground storage tanks) (202) 260-2342 Toxic Substances Control Act (TSCA) Information Source (202) 554-1 404 PUBLICATIONS US. EPA Public Information Center (PIC) (202) 260-7751 U.S. EPA National Center for Environmental Publications and Information (NCEPI) (513) 569-7980 US. EPA Center for Environmental Research In for matio n (CER I) (513) 569-7562 National Technical Information Service (NTIS) (703) 487-4650 EPA -FEDERAL ADMINISTRATIVE OFFICES Chemical Emergency Preparedness and Prevention Office (202) 260-8600 Office of Emergency and Remedial Response (OERR) (Superfund) (202) 260-2180 Office of Ground Water and Drinking Water (202) 260-5543 Office of Solid Waste and Emergency Response (OSWER) (202) 260-4267 Office of Underground Storage Tanks (OUST) (703) 308-8850 Office of Waste Programs Enforcement (OWPE) (202) 260-4814 APPENDIX B PROFESSIONAL AND TRADE ORGANIZATIONS Air and Waste Management Association
P.O. Box 2861 Pittsburgh, PA 15230 (412) 232-3444 American Petroleum Institute 1220 L Street, N.W. Washington, DC 20005 (202) 682-8000 American Water Works Association 6666 W. Quincy Ave. Denver, CO 80235 (303) 794-771 1 NACE International P.O. Box 218340 Houston, TX 77218-8340 (713) 492-0535 National Association of Environmental Professionals 5165 MacArthur Blvd., NW Washington DC 20016-3315 (202) 966-1500 National Fire Protection Association 1 Batterymarch Park P.O. Box 9109 Quincy, MA 02269 (617) 770-3000 National Lead Abatement Council 105 Campus Drive University Square Princeton, NJ 08543-7006 (604) 520-1414 National Leak Prevention Association P.O. Box 1643 Boise, ID 83701 (208) 389-2074 (208) 389-2074 National Paint & Coatings Association 1500 Rhode Island Ave, NW Washington, DC 20005 (202) 462-6272 NSF International 150140 Plymouth Road P.O. Box 1468 Ann Arbor, MI 48113 (313) 769-801 O Painting & Decorating Contractors of America 3913 Old Lee Highway, Suite 338 Fairfax, VA 22030 (703) 359-0826 Petroleum Equipment Institute
Box 2380 Tulsa, OK 74101 (918) 494-9696 Society of Environmental Toxicology and Chemistry --`,,,,`-`-`,,`,,`,`,,`--1010 North 12th Ave. Pensacola, FL 32501-33,07 (904) 469-1500 Steel Structures Painting Council 4516 Henry Street, Suite 301 Pittsburgh, PA 15213-3728 (412) 687-1113 Steel Tank Institute 570 Oakwood Road Lake Zurich, IL 60047 (708) 438-TANK (8265) Water Environment Federation 601 Wythe St. Alexandria, VA 22314 (703) 684-2400 APPENDIX C SELECTED ENVIRONMENTAL REGULATIONS FROM TITLE 40 OF THE CODE OF FEDERAL REGULATIONS. PROTECTION OF THE ENVIRONMENT* 40 CFR 50-99 Air Pollution Control Regulations 50 National Primary and Secondary Ambient Air Quality Standards 51 Requirements for Preparation, Adoption and Submission of Implementation Plans 53 Ambient Air Monitoring Reference and Equivalent Methods 60 Standards of Performance for New Stationary Sources 61 National Emission Standards for Hazardous Air Pollutants 66 Assessment and Collection of Noncompliance Penalties by EPA Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 593
SSPC CHAPTER*27*3 93 8627940 0004041 T97 81 40 CFR 100-1 49 112 116 117 122-1 25 136 1 41 -1 49 40 CFR 150-189 152 155 156 40 CFR 240-299 260 261 262 263 265 266 267 268 280 40 CFR 300-399 300 302 355 Designation of Areas for Air Quality Planning Purposes Clean Water ActlSafe Drinking Water Act Regulations Oil Pollution Prevention Hazardous Substances Under Federal Water Pollution Control Act Determination of Reportable Quantities for Hazardous Substances National Pollution Discharge Elimination System Permits Test Procedures for the Analysis of Pollutants Drinking Water Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) Regulations Pesticide Registration and Classification Procedures Registration Standards Labeling Requirements for Pesticides and Devices Solid and Hazardous Waste Programs General Guidelines for Hazardous Waste Management
Identifying Hazardous Waste Hazardous Waste Generators Hazardous Waste Transporters Owners and Operators of Hazardous Waste Facilities Standards for Management of Specific Hazardous Wastes and Facilities Interim Standards for Owners and Operators of New Hazardous Waste Land Disposal Facilities Land Disposal Restrictions Underground Storage Tank (UST) Regulations Superfund, Emergency Planning, and Community Right-to-Know Programs National Oil and Hazardous Substances Pollution Contingency Plan Designation, Reportable Quantities, and Notification Emergency Planning and Notification 370 Hazardous Chemical Reporting 372 Toxic Chemical Release Inventory Reporting, Community Right-to-Know 40 CFR 400-699 Clean Water Act (CWA) Regulations 40 CFR 700-799 Toxic Substances Control Act (TSCA) Regulations 71O Inventory Reporting Requirements 720 Premanufacture Notice 72 1 Significant New Use of Chemical Substances 723 Premanufacture Notice Exemptions 'Citations include some sections reserved for future regulations. ACKNOWLEDGEMENT The authors and editors gratefully acknowledge the active participation of the following in the review of this chapter: Kenneth Trimber, Mike Bauer, and John Montle. BIOGRAPHY A portrait and biographical sketch of Bernard R. Appleman appears at the end of the Foreword. BIOGRAPHY Karen Ann Kapsanis is the editor of the Journal of Protective Coatings and Linings (JPCL). Since joining the staff of JPCL in 1988, she has written extensively on environmental regulations that affect industrial maintenance painting operations. BIOGRAPHY Monica Madaus has worked as a technical writerleditor for a num-
ber of environmental and health and safetyfirms. She worked as a technical editor and regulatory assistant for the Center for Hazardous Materials Research where she assisted with a newsletter and a technical and regulatory hotline. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 594
SSPC CHAPTER*27.3 93 8627940 0004042 923 Appendix APPENDIX A: ABBREVIATIONS DOC -Department of Commerce DOD -Department of Defense The abbreviations and acronyms listed below include those used in this manual along with a few others that may help to clarify paint technology and regulatory language. AAQS -Ambient Air Quality Standards AASHTO -American Association of State Highway and Transportation Officials ACGIH -American Conference of Governmental Industrial Higienists AIHC -American Industrial Health Council AIM -Architectural and Industrial Maintenance (Coating) ANSI -American National Standards Institute (formerly ASA) APCA -Air Pollution Control Association (now AWMA) APCD -Air Pollution Control Districts AQCR -Air Quality Control Regions AQMD -Air Quality Management District ARBBA -American Railway Bridge and Building Association AREA -American Railway Engineering Association ASA -American Standards Association (now ANSI) ASTM -American Society for Testing and Materials AWS -American Welding Society AWMA -Air and Waste Management Association (formerly APCA) AWWA -American Water Works Association BACT -Best Available Control Technology BAT -Best Available Technology BATRA -Best Available Technology Reasonably Available BCT -Best Conventional Technology C -Degrees Centigrade CAA -Clean Air Act CAAA -Clean Air Act Amendments (1990) CERCLA -Comprehensive Environmental Response, Compensation and Liability Act CFM -Cubic Feet Per Minute CFR -Code of Federal Regulations CMA -Chemical Manufacturers Association COE -Corps of Engineers (US. Army) COH -Coefficient of Haze CPSC -Consumer Product Safety Commission CPVC -Critical Pigment Volume Concentration CTG -Control Technique Guidelines DBA -Design Basis Accident DEP -Department of Environmental Protection (States) DER -Department of Environmental Resources (States)
DFT -Dry Film Thickness DODIS -Department of Defense Index of Specifications DOE -Department of Energy DOL -Department of Labor DOT -Department of Transportation EP -Extraction Procedure EPA -Environmental Protection Agency EPCRA -Emergency Planning and Community Right-toKnow Act F -Degrees Fahrenheit FAR -Federal Acquisition Regulation FDA -Food and Drug Administration FGD -Fuel Gas Desulfurization Systems FHWA -Federal Highway Administration FIFRA -Fedral Insecticide, Fungicide and Rodenticide Act --`,,,,`-`-`,,`,,`,`,,`--FSCT -Federation of Societies for Coatings Technology FTC -Federal Trade Commission GFCI -Ground Fault Circuit Interrupter GSA -General Services Administration HEW -Department of Health, Education, and Welfare HRB -Highway Research Board IS0 -International Organization for Standardization JAN -Joint Army-Navy LAER -Lowest Achievable Emission Rate LEL -Lower Explosive Limit LC -Lethal Concentration LD -Lethal Dose LOCA -Loss of Coolant Accident LOSOLVE -Evaluation of Low-Solvent Maintenance Coatings for Highway Structural Steel LQG -Large Quantity Generator MAC -Maximum Allowable Concentration MARAD -Maritime Administration MEK -Methyl Ethyl Ketone MFFT -Minimum Film Forming Temperature
MPIP -Meat and Poultry Inspection Program mil -0.001 inches MSDS -Material Safety Data Sheet MSHA -Mine Safety and Health Administration MVT -Moisture-Vapor Transmission Rate NAAQS -National Ambient Air Quality Standards NACE -National Association of Corrosion Engineers NAD -Non-Aqueous Dispersion NAS -National Academy of Sciences NCHRP -National Cooperative Highway Research Program Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 595
SSPC CHAPTER*27-3 93 W 8627940 0004043 8bT W NESHAP -National Emission Standards for Hazardous Air Pollutants NFPA -National Fire Protection Association NIOSH -National Institute for Occupational Safety and Health NPCA -National Paint and Coatings Association NRC -Nuclear Regulatory Commission NSPS -New Source Performance Standards NVM -Non-Volatile Matter OSHA -Occupational Safety and Health Administration PACE -Performance of Alternative Coatings in the Environment PCB -Polychlorinated Biphenyls PDCA -Painting and Decorating Contractors of America PEL -Permissible Exposure Level PMN -Premanufacture Notice PRA -Paint Research Association PSD -Prevention of Significant Deterioration psi -Pounds Per Square Inch PVC -Pigment Volume Concentration QPL -Qualified Products List RACT -Reasonably Available Control Technology RCRA -Resources Conservation and Recovery Act CAE -Society of Automotive Engineers SEM -Scanning Electron Microscope SFSA -Steel Founders Society of America SIP -State Implementation Plan SNAME -Society of Naval Architects and Marine Engineers SNUR -Significant New Use Rule
SQG -Small Quantity Generator SSPC -Steel Structures Painting Council TACB -Texas Air Control Board TCLP -Toxicity Characteristic Leaching Procedure Tg -Glass Transition Temperature TLV -Threshold Limit Value TRB -Transportation Research Board TSCA -Toxic Substances Control Act TPQ -Threshold Planing Quantity TWA -Time Weighted Average UEL -Upper Explosive Limit UK -United Kingdom USDA -United States Department of Agriculture UST -Underground Storage Tank VLCC -Very Large Crude Carrier VOC -Volatile Organic Compounds VSMF -Visual Search Microfilm WFT -Wet Film Thickness 596 APPENDIX B: DEFINITIONS These definitions deal with some of the more specialized terms used in this manual. SSPC reports and manuals, the various regulations, ASTM methods and standards, and the open literature are sources for many of these definitions. Other sources include the PaintKoating Dictionary published by the Federation of Societies for Coatings Technology (FSCT) and Chapter 40 of the Code of Federal Regulations. Some definitions have been modified, when appropriate, to more fully reflect their common usage in coatings technology or regulation terminology (air pollution, toxic substances and health and safety) relating to the corrosion protection of structural steel. ABATEMENT -The reduction in degree or intensity of pollution. ABOVEGROUND STORAGE TANK -A device meeting the definition of tank that is situated in such a way that the entire surface area of the tank is completely above the plane of the adjacent surrounding surface and the entire surface area of the tank (including the tank bottom) is able to be visually inspected. ABRASION RESISTANCE -The ability of a coating to resist being worn away and to maintain its original appearance and structure when subjected to rubbing, scraping, or wear.
ABRASIVE -A fine graded (sized) granular or spherical material which is used in a blast cleaning process for structural steel. ABRASIVE BREAKDOWN -A measure of particle breakdown after impact. ACCELERATED AGING -Any set of conditions used in an attempt to produce in a short time the results obtained under normal conditions of aging. In accelerated aging tests, the usual factors considered are heat, light, or oxygen, either separately or combined. ACCELERATED TESTING -A set of conditions intended to simulate those encountered in practice, but which have been accentuated artificially in an attempt to provide useful performance results in shorter periods of time. Coatings do not necessarily behave under such tests exactly as they will under actual conditions, but many coatings which give good performance under these tests have possibilities which are worthy of further considerations and experiments. ACCELERATED WEATHERING -Tests designed to simulate, but at the same time to intensify and accelerate, the destructive action of natural outdoor weathering on coating films. The tests involve exposure to artificially produced components of natural weather, e.g., light, heat, cold, water vapor, rain, ionic solutions, etc., which are arranged and repeated in a specific cycle. There is no universally accepted test, and different investigators have found widely different cycles to be useful. ACCEPTANCE TESTING -The purchaser s testing of received products to determine that the quality of manufactured products meets specified requirements. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*27.3 73 8627740 0004044 7Tb ACRYLIC LATEX -Aqueous dispersion, thermoplastic or thermosetting, of polymers or copolymers of acrylic acid, methacrylic acid, esters of these acids, or acrylonitrile. ACRYLIC RESIN -A synthetic resin made from derivatives of acrylic acid. ACTINIC LIGHT -Light that effects chemical changes in a coating. ACTIVE INGREDIENT -Ingredient that has the capability by itself, when used as directed at proper dilution, to function as a pesticide, or an ingredient that has the ability to elicit or enhance a pesticide effect in a second compound whose pesticidal activity is substantially increased due to the introduction of the first. Compounds which merely enhance or prolong the activity of an active ingredient are not considered active ingredients themselves. ACUTELY HAZARDOUS WASTE -Wastes considered extremely hazardous, including certain pesticides and dioxincontaining wastes. These are not commonly generated in the protective coating industry, but do require special treatment and reporting. ACUTE TOXICITY -Any poisonous effect produced within a short period of time following exposure, usually up to 24 to 96 hours, resulting in severe biological harm and often death. ADDITIVE -Any substance added in small quantities to another substance, usually to improve properties. ADHESION -State in which two surfaces are held together by interfacial forces which may consist of valence forces or interlocking action, or both. ADSORPTION -Concentration of a substance at surface or interface of another substance. ADVANCE NOTICE OF PROPOSED RULEMAKING -Used by a regulatory agency to solicit information that can be used to develop a first draft of a new regulation. Published in the Federal Register. AERIAL SUPPORTS -Rigging supported from above or attached to the steel. AGING -Storage of paints, varnishes, etc. (under defined conditions of temperature, relative humidity, etc.) in suitable containers, or as dry films of these materials, for the purpose of subsequent tests.
AIR CONTAMINANT-Any substance of either man-made or natural origin in the ambient air, such as particulates (dust, fly ash, smoke, etc.), mists (other than water), fumes (gases), etc. AIR EMISSIONS -The release or discharge of pollutants into the ambient air. AIRLESS SPRAYING -Process of atomization of paint by forcing it through an orifice at high pressure. This effect is often aided by the flashing (vaporization) of the solvents, especially if the paint has been previously heated. AIR POLLUTANT -Dust, fumes, mist, smoke, and other particulate matter, vapor, gas, or odorous substances. AIR POLLUTANT, HAZARDOUS -Materials discharged into the atmosphere that have a proven relationship to increased human death rates, to increased serious irreversible illnesses, or to increased incapacitating reversible illnesses. AIR POLLUTION -The presence in the outdoor atmosphere of any dust, fumes, mist, smoke, other particulate matter, vapor, gas, odorous substances, or a combination thereof, in sufficient quantities and of such characteristics and duration as to be, or likely to be, injurious to health or welfare, animal or plant life, or property, or as to interfere with the enjoyment of life or property. AIR POLLUTION REGULATIONS -Legal constraints on pollutant emissions, production processes, or control systems. AIR-PURIFYING RESPIRATOR -Protects the wearer by preventing the entrance of airborne particulates such as dust, mist, metal fumes and smoke. Cannot protect the wearer from materials such as poisonous gases, because these materials can pass through the filter. AIR QUALITY CONTROL REGIONS (AQCR) -Geographical units of the country, sometimes involving several states, as required by U.S. law, reflecting common air pollution problems, for purposes of reaching national standards. The state implementation plans must provide for achievement of NAAQS in every AQCR. AIR QUALITY CRITERIA -The level of pollution and lengths of exposure above which may occur adverse effects on health and welfare. AIR QUALITY STANDARDS -The level of pollutants prescribed by law or regulation that cannot be exceeded during a specified time in a defined area. ALIPHATIC SOLVENTS -Hydrocarbon solvents compounded primarily of paraffinic and cycloparaffinic (naphthenic) hydrocarbon compounds. Aromatic hydrocarbon content
may range from less than 1% to about 35%. ALKYD RESINS -Synthetic resins formed by the condensation of polyhydric alcohols with polybasic acids. They may be regarded as complex esters. The most common polyhydric alcohol used is glycerol, and the most common polybasic acid is phthalic anhydride. Modified alkyds are those in which the polybasic acid is substituted in part by a monobasic acid, of which the vegetable oil fatty acids are typical. ALLERGIC RESPONSE -The first exposure causes no evident effect, but sensitizes the subject. After about two weeks, an identical exposure of the subject can result in a severe asthmatic response or skin eruption. ALLIGATORING-A type of crazing or surface cracking of a definite pattern, as indicated by name. The effect is often the result of weather aging of a coating. ALTERNATE IMMERSION (WATER) -An exposure in which a surface is in frequent, perhaps fairly long, immersion in either fresh or salt water alternated with exposure to the atmosphere above the water. ALUMINUM PAINT -Coating consisting of a mixture of metallic aluminum pigment in powder or paste form dispersed in a suitable vehicle. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 597
SSPC CHAPTERa27.3 93 m 8627940 0004045 632 m ALUMINUM PASTE -Metallic aluminum flake pigment in paste form, consisting of aluminum, solvent, and various additives. The metallic aluminum pigment can be in the form of very small, coated leaves or amorphous powder, known under the respective designations of leafing and nonleafing. AMBIENT AIR QUALITY -Average atmospheric purity, as distinguished from discharge measurements taken at the source of pollution. The general amount of pollution present in a broad area. AMBIENT AIR QUALITY STANDARD (AAQS) -A federally promulgated maximum level of an air pollutant that can exist in the ambient air without producing adverse effects to humans or to the public welfare. AMERICAN CONFERENCE OF GOVERNMENTAL INDUSTRIAL HYGIENISTS (ACGIH) -An organization of health and safety professionals employed by governmental agencies or educational institutions. Known particularly for developing threshold limit values. AMPHOTERIC -Exhibiting both basic and acidic characteristics. ANCHOR PATTERN -See PROFILE. ANTI-CORROSION PAINT OR COMPOSITION-Coating used for preventing the corrosion of metals and, more particularly, specially formulated to prevent the rusting of iron and steel. ANTI-FOULING PAINT -Paint used to prevent the growth of barnacles and other organisms on ships bottom usually containing substances poisonous to organisms. ANTI-LIVERING AGENT -Additive used to prevent the livering of a coating. ANTI-SAG AGENT -Additive used to control sagging of a coating. ANTI-SETTLING AGENT -Substance incorporated into a pigmented paint to retard settling and to maintain uniform consistency during storage or painting operations. These additives normally function by altering the rheological properties of the paint. ANTI-SKINNING AGENT -Any material added to a coating to prevent or retard the processes of oxidation or polymerization which results in the formation of an insoluble skin on the surface of the coating in a container. ANTI-WRINKLING AGENT -Material added to surface coating compositions to prevent the formation of wrinkles in films during drying.
APPLICATION -Process by which surface coating compositions are transferred to a variety of surfaces, such as: brushing; spraying (cold or hot); dipping (simple immersion); roller coating; flushing; and spreading. ARCHITECTURAL AND INDUSTRIAL MAINTENANCE (AIM) COATINGS -Architectural coatings are coatings applied to stationary structures and their appurtenances, to mobile homes, or to curbs. The Clean Air Act Amendments call for an architectural coatings rule (including industrial maintenance) to be promulgated by EPA which will have a major impact on industrial maintenance-type coating operations throughout the US. The rule will be promulgated nationwide in ozone attainment areas as well as non-attainment areas. ARCHITECTURAL COATING -Coating intended for on-site application to interior or exterior surfaces of residential, commercial, institutional, or industrial buildings -as opposed to factory applied (industrial) coatings. They are protective and decorative finishes applied at ambient temperatures. AROMATIC SOLVENTS -Hydrocarbon solvents comprised wholly or primarily of aromatic hydrocarbon compounds. Aromatic solvents containing less than 80% aromatic compounds are frequently designated as partial aromatic solvents. ARTIFICIAL WEATHERING -See ACCELERATED WEATH ER1 NG . ASPHALT MASTIC -A dense mixture of sand, crushed limestone and fiber bound with a select air-blown asphalt. ATMOSPHERE -The air surrounding the earth. Also called troposphere. ATTAINMENT AREA -An area which meets National Ambient Air Quality Standards for a particular pollutant such as ozone, lead and four other common pollutants. See NONATTA1 N M ENT AREA. BACKGROUND LEVEL -With respect to air pollution, the amounts of pollutants present in the ambient air due to natural sources. BACTERIAL CLEANING -Removal of scale and rust by spraying or dipping the steel into a solution containing a bacterium, an inorganic salt and glucose. BAKING FINISH -A paint or varnish that requires baking at temperatures above 150OFfor the development of desired properties. BARIUM METABORATE -White crystalline pigment prepared by precipitation from aqueous solution. Used in paint as an anti-corrosion pigment.
BARRIER COAT -Coating used to isolate a paint system from the surface to which it is applied in order to prevent chemical or physical interaction between them, e.g., to prevent the paint solvent attacking the underlying surface or to prevent bleeding into the new paint system. BASIC LEAD SILICO CHROMATE -Calcined basic lead chromate -basic lead silicate complex on a silica core, used as a corrosion-inhibitive pigment. BASIC ZINC CHROMATE -Yellow pigment used primarily for its corrosion-inhibiting properties. BEST AVAILABLE CONTROL TECHNOLOGY -An emission limitation based upon the maximum degree of reduction for each pollutant subject to regulation which would be emitted from any major stationary source or major modification thereof. In no event is the application of best available control technology to result in emissions of any pollutant which would exceed the emissions allowed by any applicable standard. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 598
SSPC CHAPTER*27.3 93 8627940 0004046 579 BINDER -Nonvolatile portion of the liquid vehicle of a coating. It binds or cements the pigment particles together and the paint film as a whole to the material to which it is applied. The amount of binder needed to completely wet a pigment is determined primarily by the particle size, shape, chemical composition, and density of the pigment; and the particle size, degree of polymerization and wetting properties of the binder. See also VEHICLE. BIOSPHERE-The portion of Earth and its atmosphere that can support life. BITUMINOUS COATING -Asphalt or tar compound used to provide a protective finish. BLAST CLEANING -Cleaning and roughening of a surface (particularly steel) by the use of metallic or nonmetallic grit or metal shot (usually steel), which is projected against a surface by compressed air, centrifugal force, or water. BLASTING CAGE -A movable enclosure around the blaster that contains dust and paint. BLEEDING -The diffusion of colorants through a coating from a previously painted substrate. BLISTERING -Formation of dome-shaped projections in paints or varnish films resulting from local loss of adhesion and lifting of the film from an underlying paint film (intercoat blistering) or the base substrate. BLUSHING-A film defect that appears as a milky opalescence as the film dries. BODY -Apparent consistency or viscosity of a paint as assessed subjectively. A practical term widely used to give a qualitative picture of consistency. For Newtonian liquids, body is the same as viscosity. BOSUN S CHAIR -A rigging system for a single individual that allows access to heights. BOTTOM-DRYING -Drying of a film from the bottom towards the top of the film. BOXING -Pouring paint from one container to another several times to ensure proper mixing. BRITISH STANDARDS INSTITUTION -A national organization which establishes and publishes standard specifica-
tions and codes of practice. BRUSHING -Application of a coating by means of a brush. BRUSH-OFF BLAST -Lowest blast cleaning standard. This standard is defined in Steel Structures Painting Council Surface Preparation Specification No. 7, Brush-off Blast Cleaning (SSPC-SP 7). BUBBLE BUSTER -Compound used to reduce the formation of bubbles in a coating. BUBBLE ONCEPT -Method Of implementing air pollution regulations where a giant bubble is imagined to be placed over a manufacturing plant. At the top of this bubble is a single Opening through which all the plant s pollutants escape. Under this approach, the only pollution measurement would be taken at the top of this bubble. Therefore manufacturers can control pollution from individual sources within their plants as they see fit, provided the air escaping from the top of the imaginary bubble meets the standards. See also OFFSETS. BUBBLING-Film defect, temporary or permanent, in which bubbles of air or solvent vapor, or both, are present in the applied film. BUILD -Real or apparent thickness, fullness, or depth of a dried film. CALCAREOUS DEPOSITS -Deposits containing calcium or calcium compounds. CATALYTIC CURING -Mechanism by which a coating is cross-linked by the action of a catalyst as opposed to oxidation, etc. Examples of such systems are two-part epoxies and polyurethanes. CATHODIC PROTECTION -A technique to reduce the corrosion rate of a metal surface by making it a cathode of an electrochemical cell. CAVITATION -The formation and rapid collapse within a liquid of cavities or bubbles that contain vapor or gas or both. CAVITATION EROSION -Progressive loss of original material from solid surface due to continuing exposure to cavitation. CEMENT PAINT -Paint supplied in dry powder form, based essentially on Portland cement, to which pigments are sometimes added for decorative purposes. This dry powder paint is mixed with water immediately before use. CENTRAL NERVOUS SYSTEM EFFECTS -Symptoms in-
volving the brain and spinal chord, affecting sensory impulses, thought and motor control. CENTRIFUGAL BLAST CLEANING -Use of motor-driven, bladed wheels to hurl abrasive at a surface by centrifugal force. CHALKING-Formation of a friable powder on the surface of a paint film caused by the disintegration of the binding medium due to disruptive factors during weathering. The chalking of a paint film can be considerably affected by the choice and concentration of the pigment. It can also be affected by the choice of binding medium. CHARACTERISTIC WASTES -A waste that does not appear on the four lists of wastes specifically designated as hazardous in 40 CFR 260, but which is considered hazardous because it has one or more of the following characteristics: CORROSIVITY, IGNITABILITY, REACTIVITY, TOXICITY. CHECKING -That phenomenon manifested in paint films by slight breaks in the film that do not penetrate to the underlying surface. The break should be called a crack if the underlying surface is visible. Where precision is necessary in evaluatinga paint film, checking may be described as ble (as seen by the eye) or as microscopic (as observed under a magnification of 10 diameters), (See also CRACKING). Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 599
SSPC CHAPTER*27.3 93 8627940 0004047 405 = CHEMICAL CONVERSION COATING -A treatment, either chemical or electrochemical, of the metal surface to convert it to another chemical form which provides an insulating barrier of exceedingly low solubility between the metal and its environment, but which is an integral pari of the metallic substrate. It provides greater corrosion resistance to the metal and increased adhesion of coatings applied to the metal. Examples are phosphate coatings on steel. CHEMICAL ENVIRONMENT -An exposure in which strong concentrations of highly corrosive gases, fumes or chemicals, either in solution or as solids or liquids, contact the surface. The severity may vary tremendously from mild concentrations in yard areas to direct immersion in the chemical. CHIPPING RESISTANCE -The ability of a coating or layers of coatings to resist total or partial removal, usually in small pieces, resulting from impact by hard objects or from wear during service. CHLORINATED HYDROCARBONS -Powerful solvents that include such members as chloroform, carbon tetrachloride, ethylene dichloride, methylene chloride, tetrachlorethane, trichlorethylene, etc. Generally, they are toxic and their use is now restricted in some countries. Their main applications include nonflammable paint removers, cleaning solutions, and special finishes where presence of residual solvent in the film is a disadvantage. CHLORINATED RUBBER -Resin formed by the reaction of rubber with chlorine. Unlike rubber, the resulting product is readily soluble and yields solutions of low viscosity. It is sold as white powder, fibers, or as blocks. Commercial products generally contain about 65% chlorine. It has good chemical resistance properties. It tends to cobweb when sprayed. Mostly chlorinated polymers are now used, ¡.e., i-butene, polyethylene, etc. CHRONIC -Long-lasting or frequently recurring. CHRONIC TOXICITY -The property of a substance or mixture of substances to cause adverse effects in an organism upon repeated or continuous exposure over a period of at least one-half the lifetime of that organism. CITATION -A written notice to a firm that OSHA believes health and safety standards have been violated on their premises. Will include a deadline for abatement. May include a proposed penalty. CLEAN AIR ACT (CAA) -The first legislation, passed in 1970, to set federal standards for air quality, including the NATIONAL AMBIENT AIR QUALITY STANDARDS. CLEAN AIR ACT AMENDMENTS (CAAA) -Legislation passed in 1990,which will affect much smaller sources than
previous air pollution control regulations. Paints and coatings operations will be affected by the Amendments because the solvents that make up many paints and coatings are one focus of several important sections. CLEAN AIR STANDARDS -The set of enforceable rules, regulations, standards, limitations, orders, controls, prohibitions, etc., which are contained in, issued under, or adopted pursuant to the Clean Air Act and amendments. CLEAN WATER ACT -Federal law intended to regulate discharges to water in order to meet water quality goals. CLEVELAND CONDENSING HUMIDITY CABINET -An accelerated weathering apparatus which operates on a condensation type of water exposure at elevated temperature. CLIMATE CABINET -Any enclosure used to simulate selected climatic conditions. COALESCENCE -The formation of a film of resinous or polymeric material when water evaporates from an emulsion or latex system, permitting contact and fusion of adjacent latex particles. Action of the joining of particles into a film as the volatile evaporates. COALESCENT (or COALESCING AGENT) -Solvent with a high boiling point which, when added to a coating, aids in film formation via temporary plasticization (softening) of the vehicle. COAL TAR EPOXY COATING -Coating in which binder or vehicle is a combination of coal tar with epoxy resin. COAL TAR URETHANE COATING -Coating in which binder or vehicle is a combination of coal tar with a polyurethane resin. COAT -Paint, varnish or lacquer applied to a surface in a single application (one layer) to form an evenly distributed film when dry. COATING-Generic term for paints, lacquer, enamels, etc. A liquid, liquifiable or mastic composition that has been converted to a solid protective, decorative, or functional adherent film after application as a thin layer. COATING SYSTEM -A number of coats separately applied in a predetermined order at suitable intervals to allow for drying or curing. COBWEBBING -Production of fine filaments instead of the normal atomized particles when some coatings are sprayed. CODE OF FEDERAL REGULATIONS -Yearly summary of Federal Regulations. Organized by subject. COEFFICIENT OF HAZE (COH) -A measurement of visibility interference in the atmosphere. CO-GENERATOR -One of two or more parties who meet the definition, and incur the responsibilities, of a hazardous waste generator.
COLD-ROLLED STEEL -Low-carbon, cold-reduced sheet steel. COLD WALL EFFECT -In tank linings, a driving, permeating force assisting ionic passage through a coating to a metal in the direction from a hot liquid to a cold wall. COLLOIDAL STATE -Particular state in which any substance may exist under the proper conditions, determined by fineness of particle subdivision. The colloidal state is defined by a more or less well-marked ultra-microscopic zone in the scale of subdivision, the lower extreme of the zone approaching molecular dimensions, and the upper end gradually passing over into molecular aggregates (suspensions) visible under the ordinary microscope. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 600
SSPC CHAPTERt27.3 93 8627940 0004048 341 COMBUSTIBLE LIQUID -Any liquid having a flashpoint of 10OOF (37.8OC) or higher, but below 200°F (93.3OC). COMMERCIAL BLAST -Moderate grade of blast cleaning. This standard is defined in Steel Structures Painting Council Surface Preparation Specification No. 6, Commercial Blast Cleaning (SSPC-SP 6). COMPLIANCE -Compliance with the clean air or water standards. Also, compliance with a schedule or plan ordered or approved by a court, the Environmental Protection Agency, or an air or water pollution control agency. COMPLIANCE DATE -The date upon which a source is required to meet applicable pollution control requirements. COMPREHENSIVE ENVIRONMENTAL RESPONSE, COMPENSATION AND LIABILITY ACT (CERCLA) -Legislation passed in 1980 which authorized EPA to respond to hazardous spills and clean up abandoned waste sites. It also created a fund to pay for clean up of abandoned hazardous waste sites, known as SUPERFUND. CONDENSATION EXPOSURE -An exposure where the surface is almost continuously exposed to saturated air, accompanied by very frequent or continuous condensation. CONFINED SPACE -An area which may be hazardous because a limited number of openings could make escape difficult in an emergency, and because ventilation may be inadequate to support life. The space may also present unknown hazards such as toxic or caustic chemicals. CONSENSUS STANDARD -A standard developed according to a consensus agreement or general opinion among representatives of various interested or affected organizations and individuals. CONTINGENCY PLAN -A document setting out an organized, planned, and coordinated course of action to be followed in case of a fire, explosion, or release of hazardous waste or hazardous waste constituents which could threaten human health or the environment. CONTINUOUS PHASE -The medium or continuum in which the dispersed phase is contained. CONTROLLED CAVITATION WATER JETTING -A technique of cleaning based upon the principle of cavitation. CONTROL STRATEGY -A combination of measures designed to achieve the aggregate reduction of emissions necessary for attainment and maintenance of a national standard. This is a necessary part of approvable state implementation plans.
CONVERSION COATINGS -A treatment, either chemical or electrochemical, of a metal surface to convert it to another chemical form to provide improved adhesion and corrosion resistance. CORROSION -The deterioration of metal by chemical or electrochemical reaction resulting from exposure to weathering, moisture, chemicals, or other agents in the environment in which it is placed. CORROSION-INHIBITIVE PIGMENT -A pigment that when made into a paint has the property of minimizing corrosion of the substrate to which it is applied. CORROSIVITY -A characteristic exhibited by a solid waste which is aqueous and is shown to have a pH of less than or equal to 2 or greater than or equal to 12.5 using standard tests. Also, a liquid which corrodes steel at a rate greater than 6.35 mm (0.250 inches) per year under standard test conditions. COUPLING AGENT -Solvent that will cause two immiscible liquids to mix. Also called COSOLVENT. COVERAGE -Ambiguous term that is used in some instances to refer to hiding power and in others to mean spreading rate . The more precise terms are preferred. See also SPREADING RATE and HIDING POWER. CRACKING -Generally, the splitting of a dry paint film, usually as a result of aging. The following terms are used to denote the nature and extent of this defect: HAIR CRACKING = Fine cracks that do not penetrate the top coat; they occur erratically and at random. CHECKING = Fine cracks that do not penetrate the topcoat and are distributed over the surface, giving the semblance of a small pattern. CRACKING = Specifically, a breakdown in which the cracks penetrate at least one coat and which may be expected to result ultimately in complete failure. CRAZING = Resembling checking, but the cracks are deeper and broader. CROCODILING or ALLIGATORING = A drastic type of crazing, producing a pattern resembling the hide of a crocodile. The use of a minimum magnification of i0 diameters is recommended in cases where it is difficult to differentiate between cracking and checking. CRATERING -The formation of small bowl-shaped depressions in a paint film. CRAWLING -Defect in which a wet paint film recedes from small areas of the surface, leaving them uncoated. CRAZING -A network of checks or cracks appearing on a coated surface. (See also CRACKING.) CREVICE CORROSION -Corrosion that occurs within or adjacent to a crevice formed by contact with another piece of the same or another metal or with a nonmetallic material. When this occurs, the intensity of attack is usually more se-
vere than on surrounding areas of the same surface. CRITERIA -As used in the Clean Air Act, information on adverse effects of air pollutants on human health or the environment at various concentrations. CRITICAL PIGMENT VOLUME CONCENTRATION (CPVC) -That level of pigmentation, pigment volume concentration (PVC) value in the dry paint, where just sufficient binder is present to fill the voids between the pigment particles. Below this level, a sharp break occurs in film properties such as corrosion resistance, etc. Different requirements for each product would dictate different PVC and CPVC ratios. --`,,,,`-`-`,,`,,`,`,,`--601 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*27.3 93 8627940 0004049 288 = CROCODILING -See CRACKING CRYOGENIC COATING REMOVAL -A new technique using liquid nitrogen at 196OC to remove organic coatings. A stream of liquid nitrogen embrittles the coating, which can then be removed with recyclable plastic pellets. CURE -To change the properties of a polymer system into a final, more stable, usable condition by the use of heat, radiation, or reaction with chemical additives. CURING AGENT -Additive that promotes the curing of a coating film. CURTAIN COATING -A coating that is applied and allowed to drain off. The excess is collected in a sump and recirculated. DEFLOCCULANT-An additive that prevents pigments in suspension from coalescing to form flocs. DEFOAMERS -Additives used to reduce or eliminate foam formed in a coating or coating constituent. DELAMINATION -Failure of a coating to adhere to the previous coating. DEMONSTRATION -The initial exhibition of a new technological process or practice or a significantly new combination or use of technologies, processes or practices, subsequent to the development stage, for the purpose of proving technological feasibility and cost effectiveness. DEPARTMENT OF ENVIRONMENTAL PROTECTION (DEP) DEPARTMENT OF ENVIRONMENTAL RESOURCES (DER) -Common names for state agencies charged with protection of the environment. DEPOSIT CORROSION -Localized corrosion under or around a deposit or collection of material on a metal surface. See also CREVICE CORROSION. DESCALING -Removal of mill scale or caked rust from steel by chemical or mechanical means. DEW POINT -The temperature at which moisture will condense. DILUENT -A volatile liquid which, while not a solvent for the nonvolatile constituents of a coating, may yet be used in conjunction with the true solvent, without causing precipitation. See also REACTIVE DILUENT. DIP COATING -The process in which a substrate is immersed in a solution (or dispersion) containing the coating
material and withdrawn. DIRECT COSTS -Such costs as labor, taxes, insurance, materials, scaffolding, equipment and inspection. DIRECT READING GAS DETECTOR -An instrument which directly records information about its surroundings, as opposed to one which does so inferentially. DISBONDING-Failure of a coating to adhere to a substrate to which it has been applied. DISCHARGE PERMIT -Authorization, license, or equivalent control document issued by the EPA or approved state to implement the requirements of water quality regulations. 602 DISCOLORATION-Change in the color of a coating after application, normally caused by exposure to sunlight. DISPERSANT-Additive that increases the stability of a suspension of powders (pigments) in a liquid medium. DISPERSED PHASE -That phase in an emulsion or suspension that is broken down into droplets or discrete particles and dispersed throughout the other continuous phase. Also called DISCONTINUOUS PHASE. DISPERSION-Process of dispersing a dry powder (or pigments) in a liquid medium in such a way that the individual particles of the powder become separated from one another and are reasonably evenly distributed throughout the entire liquid medium. DISPOSAL -The discharge, deposit, injection, dumping, spilling, leaking, or placing of any hazardous waste into or on any land or water so that such hazardous waste or any constituent thereof may enter the environment or be emitted into the air or discharged into any waters, including ground waters. DISPOSAL FACILITY -A facility or part of a facility at which hazardous waste is intentionally placed into or on any land or water, and at which the waste will remain after closure. DOUBLE-DIP GALVANIZING -Immersion of one-half of a structure at a time in a molten zinc bath when the structure is too large to be immersed in one dipping. DRIER -A composition that accelerates the drying of oil, paint or varnish. Driers are usually metallic compositions and are available in both solid and liquid forms. DROSSING-Removal of refuse and impurities from a galvanizing bath. DRYING-Process by which coatings change from the liquid
to the solid state, due to evaporation of the solvent, physicochemical reactions of the binding medium, or a combination of these causes. DRYING TIME -Time required for an applied film of coating to reach the desired stage of cure, hardness, or nontackiness. DRY INTERIOR ENVIRONMENT -Dry, relatively noncorrosive interiors of either buildings, plants, or void spaces. DRY SPRAY -Overspray or bounceback. Also sand-like finish due to spray particles being dried before reaching the surface. DRY-THROUGH-Film is considered dry-through when no loosening, detachment, wrinkling, or other distortion of the film occurs when the thumb is borne downward while simultaneously turning the thumb through an angle of 90° in the plane of the film. The arm of the operator is kept in a straight line from the wrist to the shoulder and maximum pressure is exerted by the arm. DRY-TO-HANDLE TIME -Time interval between application and ability to handle without damage. DRY-TO-RECOAT TIME -Time interval between the application of the coating and its ability to receive the next coat satisfactorily. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*27-3 73 m 8627740 0004050 TTT m DRY-TO-TOUCH TIME -Interval between application and tack-free condition. DURABILITY -Degree to which paints and paint materials withstand the destructive effect of the conditions to which they are subjected. DUST -Fine grain particles light enough to be suspended in air. EFFLUENT GUIDELINES -Any limit established as part of a permit issued by a state or the EPA, or any pretreatment required before discharging wastewater to a public wastewater treatment facility. ELECTRIC ARC GUN -A type of thermal spraying equipment, in which two wires are continuously in the presence of an air jet. While less maneuverable than the oxy-fuel gas gun, the deposit rate is two to three times higher. ELECTRODEPOSITION -Method of paint application in which an electrically conductive article to be coated is made one of the electrodes in a tank of water-thinned paint. The other electrode is generally a metal. The two electrodes are connected to a source of electrical power, the polarity of the article to be coated being of the opposite sign to that of the particles in the liquid paint in the tank. The charged particles move towards the articles under the influence of the electric field, and when they give up their charge at the electrode (article), they are deposited and ultimately form a continuous film of paint. ELECTROGALVANIZING-Steel wire or strip fed continuously through a series of washes and rinses and a plating bath. Electrogalvanized steel has good working properties; zinc applied in this manner has excellent adhesion. ELECTROSTATIC DETEARING -Removal of tear drops that form on dipped objects. ELECTROSTATIC SPRAY COATING -A solvent-borne, water-borne, or powder coating that uses the attractive force between materials of opposite electrical charge to form a uniform film coverage on the coated surface. ELECTROSTATIC SPRAYING -Methods of application spraying in which an electrostatic potential is created between the article to be coated and the atomized paint particles. The charged particles of paint are attracted to the article being painted and are there deposited and discharged. The electrostatic potential is used in some processes to aid the
atomization of the paint. EMERGENCY PLANNING AND COMMUNITY RIGHT-TOKNOW ACT (EPCRA) -Legislation passed as part of the Superfund Amendments and Reauthorization Act of 1986. Also referred to as SARA Title III.Regulations developed under EPCRA establish a list of extremely hazardous substances and threshold planning quantities that trigger reporting and emergency planning requirements. They are intended to facilitate the development and implementation of state and local emergency response plans. EMERGENCY TEMPORARY STANDARDS grave danger to workers, OSHA emergency standards that take main in effect until replaced
-In cases of is authorized to publish effect immediately and reby a permanent standard.
EMISSION -Discharges into the air by a pollution source, as distinguished from effluents, which are discharged into water. EMISSION LIMITATIONS -Requirements established by EPA or state or local government which limit the quantity, rate or concentration of emissions of air pollutants on a continuous basis, including any requirements which limit the level of opacity, prescribe equipment, set fuel specifications or prescribe operation or maintenance procedures for a source to assume continuous emission reduction. EMISSION STANDARD -The maximum amount of a pollutant that is permitted to be discharged from a single polluting source. EMULSIFICATION-The process of dispersing one liquid in another (the liquids being mutually insoluble or sparingly soluble in each other). When water is one of the liquids, two types of emulsions are possible: oil-in-water (water is the continuous state), and water-in-oil. The term oil describes any organic liquid sparingly soluble in water. EMULSIFIER -Substance that intimately mixes, modifies the surface tension of colloidal droplets, and disperses dissimilar materials ordinarily immiscible, such as oil and water, to produce a stable emulsion. The emulsifier has the double task of promoting the emulsification and of stabilizing the finished product. EMULSION -Two-phase liquid system in which small droplets of one liquid (the internal phase) are immiscible in and dispersed uniformly throughout a second continuous liquid phase (the external phase). EMULSION PAINT -A paint, the vehicle of which is an emulsion of binder in water. The binder may be oil, oleoresinous varnish, resin or other emulsifiable binder. Not to be confused with a latex paint, in which the vehicle is a latex.
END-USER -This term normally refers to the applicator of the coating. For example the structure owner and his crew, painting contractor, etc. See also USER. ENGINEERING CONTROL METHODS -Methods of preventing worker exposure to air contaminants without the use of personal protective equipment, including enclosure, confinement, general and local ventilation, and substitution of less toxic materials. ENVIRONMENT-Water, air, land, and all plants, animals, and man living therein, and the interrelationships which exist among them. ENVIRONMENTAL PROTECTION AGENCY (EPA) -An independent agency of the federal government formed in 1970 and responsible for pollution abatement and control programs, including programs in air and water pollution control, water supply and radiation protection, solid and toxic waste management, pesticides control, and noise abatement. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 603
SSPC CHAPTER*27.3 73 8627740 OOOL)O51 936 EPOXY -Group having the Oxirane structure. EPOXY ESTERS -An epoxy resin partially esterified with fatty acids, rosin, etc.; single package epoxy. EPOXY RESIN -Cross-linking resins based on the reactivity of the epoxide group. One common type is the resin made from epichlorhydrin and bisphenol A. Aliphatic polyols such as glycerol may be used instead of the aromatic bisphenol A or bisphenol F. EQUIVALENT METHOD -Any method of sampling and analyzing for an air pollutant which has been demonstrated to the EPA to have a consistent and quantitatively known relationship to the reference method. EROSION -Phenomenon manifested in paint films by the wearing away of the finish to expose the substrate or undercoat. The degree of failure is dependent on the amount of substrate or undercoat visible. Erosion occurs as the result of chalking or by the abrasive action of wind-borne particles of grit. EXEMPT SOLVENT -Any solvent that has not been declared photochemically reactive by any of several regulatory agencies, most notably, the Los Angeles Air Pollution Control District. EXPLOSIVE LIMIT -The upper and lower ends of the explosive range, the proportions of combustible vapor and air necessaryto produce an explosion. See UPPER EXPLOSIVE LIMIT and LOWER EXPLOSIVE LIMIT. EXPOSURE RACK -Term given to a frame on which test panels are exposed for durability tests. EXPOSURE TESTS -Tests conducted to evaluate the durability of a coating or film. They include exposure to ultraviolet light, moisture, cold, heat, salt water, mildew, etc. They can be generated either naturally or artificially. EXTENDERS-A specific group of achromatic pigments of low refractive index (between 1.45 and 1.70) incorporated into a vehicle system whose refractive index is in a range of 1.5 to 1.6. They are used to reduce cost, achieve durability, alter appearance, control rheology, and influence other properties. EXTREMELY HAZARDOUS SUBSTANCE -Any substance listed in the appendices to 40 CFR 355, regulations developed under the requirements of Emergency Planning and Community Right-to-Know regulations. FADEOMETER -An apparatus for determining the resistance of resins and other materials to fading. It accelerates the fading by subjecting the article to high-intensity ultraviolet wavelengths similar to those found in sunlight.
FADING -Subjective term used to describe the lightening of the color of a pigmented paint following exposure to the effects of light, heat, time, temperature, chemicals, etc. The observed fading may result from deterioration of the pigment, from deterioration of the vehicle, or from a decrease in gloss. A separation of the vehicle from the pigment particle in the interior of the film, with the subsequent introduction of microvoids that scatter light, may also be interpreted visually as fading. FAST SOLVENT -Solvent that evaporates rapidly under atmospheric conditions. FAYING SURFACE -Contacting surfaces where joints in steel structures are formed by riveting or by the use of high strength bolts. FEATHER EDGING -Reducing the thickness of the edge of a dry paint film, e.g., the edge of a damaged area, prior to repainting. FEATHERING -Operation of tapering off the edges of a coat of paint by laying off with a comparatively dry brush. FEDERAL INSECTICIDE, FUNGICIDE AND RODENTICIDE ACT (FIFRA) -Federal act regulating the use of pesticides. Requires that manufacturers register pesticides with the EPA. Labels which outline safe uses and practices are required and must be submitted as part of the registration process. EPA must weigh any health or environmental effects of a product against its benefits. It may ban or restrict use of those for which the risks outweigh the benefits. FEDERAL REGISTER -Daily chronological record of new federal regulations and other federal business. FIELD COAT -The coat or coats applied at the site of erection or fabrication. FIELD PAINTING -Surface preparation and painting operation of structural steel or other materials conducted at the project site. FILIFORM CORROSION -A type of corrosion that occurs under coatings on metal substrates characterized by a definite thread-like structure and directional growth. FILM INTEGRITY -Continuity of a coating free of defects. FILM THICKNESS -Thickness of any applied film, wet or dry. FILM THICKNESS GAGE -Device for measuring film thickness; instruments for measuring either wet or dry films are available. FINGER PRINT TECHNIQUE -Using analytic techniques to determine the composition of a coating.
FINGERNAIL TEST -Gouging a dried film with fingernail to make a subjective, qualitative estimate of the relative hardness and toughness. FINISH COAT -Final coat in a painting system. FIRST COAT -First coating applied in any painting schedule; in some cases, it could be the sealing coat; in others, the priming coat. FISH EYES -Paint defect that manifests itself by the crawling of wet paint into a recognized pattern resembling small dimples or fish eyes. FLAKING -The detachment of pieces of the paint film itself either from its substrate or from paint previously applied. Flaking (scaling) is generally preceded by cracking, checking or blistering and is the result of loss of adhesion usually due to stress-strain factors. FLAME CLEANING -Impingement of an intensely hot flame to the surface of structural steel resulting in the removal of mill scale and the dehydration of any remaining rust, leaving the surface in a condition suitable for wire brushing 604 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERx27-3 93 8627940 0004052 872 W followed by the immediate application of paint. This method has now fallen into disuse. The procedure is defined in Steel Structures Painting Council Surface Preparation Specification No. 4, Flame Cleaning of New Steel (SSPC-SP 4), which has now been discontinued. FLAME SPRAY -Any process whereby a material is brought to its melting point and sprayed onto a surface to produce a coating. The process includes metallizing, thermospray, and plasma flame. FLASH POINT -The lowest temperature of a liquid at which it gives off sufficient vapor to form an ignitable mixture with the air near the surface of the liquid or within the vessel used. FLASH RUSTING -Rusting that occurs on metal within minutes after exposure to moisture. FLATTING AGENTS -Material added to a coating to reduce the gloss of the dried film. FLEXIBILITY -Degree to which a coating after drying is able to conform to movement or deformation of its supporting surface, without cracking or flaking. FLOCCULATION -The formation of clusters of pigment particles in a fluid medium which may occur after dispersion has been effected. The condition is usually reversible and the particle clusters can be broken up by the application of relatively weak mechanical forces or by a change in the physical forces at the interface between the liquid and the solid dispersed particles. Flocculation is often visible as a Jack Frost pattern in a flowout of a dispersion; microscopically, it appears as a lacework or reticulum of loosely clustered particles. It results in more rapid settling although it is usually soft, shows loss of color strength and poor dispersion. Surface-active agents are often useful in reducing the extent of flocculation and hence the yield value. FLOW COATING -Process of applying paint in which the paint is poured or is allowed to flow over the object to be painted, the excess, if any, being allowed to drain off. FLUIDIZED BED COATING -Method of applying a coating in which a heated or electrostatically charged article is immersed or passed over a fluidized bed of powdered coating (the coating material adhering to the hot metal), then heated in an oven to provide a smooth continuous film. The bed of powdered resin may be fluidized by vibration or compressed air. FREE LIQUID -Material which readily separates from the
solid portion of a waste at ambient temperature and pressure. FREE SILICA -Silica generally present in small amounts in natural deposits of clay-like minerals and diatomaceous earth and usually considered to be a contaminant. FUGITIVE EMISSION -Particulate matter that is not collected by a capture system and is released to the atmosphere at the point of generation. FULL COAT -Application of a coating at a specified film thickness designed to achieve a desired effect. FUNGICIDE -Paint additive that discourages the growth of fungi. FUSION COATINGS -A powder coating that melts, fuses, and reacts chemically as it contacts a heated surface. GALVANIC CELL -Cell consisting of dissimilar metals or alloys in contact with the same body of an electrolytic solution such as seawater. Upon electrically connecting the dissimilar metals, a current flows as the result of accelerated corrosion of the more active of the dissimilar metals or alloys. GALVANIC PROTECTION -Reduction or elimination of corrosion of a metal achieved by making current flow to it from a solution by connecting it to the negative pole of some source of current. The source of the protective current for steel would be a sacrificial metal, such as zinc, magnesium, or aluminum. GALVANIZING -Application of a coating of zinc to steel by a variety of methods. GELLING -Any process whereby paint or varnish thickens to jelly-like consistency. Also see LIVERING. GENERAL DUTY CLAUSE -A clause in the Occupational Safety and Health Act which requires employers to furnish to their workers employment and a place of employment which are free from recognized hazards that are causing or likely to cause death or serious physical harm . OSHA can use this clause to cite an employer when conditions it believes to be unsafe do not violate specific OSHA regulations. GENERATOR -(Hazardous waste regulations) Any person, by site, whose act or process produces hazardous waste identified or listed in Part 261 of the hazardous waste regulations, or whose act causes a hazardous waste to become subject to regulation. GLASS TRANSITION TEMPERATURE (Tg) -The temperature range (relatively small for most polymers) within which an amorphous polymer changes from a rubbery or viscous state to a glass-like or brittle state.
GREASE PAINT -Nondrying and nonoxidizing coating for void spaces in ships. GRIT BLASTING -Abrasive cleaning of a surface by blasting with angular chilled iron grit, aluminum oxide, or any crushed or irregular abrasive. The grit is projected onto the surface either mechanically or by means of compressed air. GROUND -A conducting connection, whether intentional or accidental, between an electrical circuit or equipment and the earth, or some conducting body, such as a water pipe or ground rod that serves as the earth. GROUND BED (anode bed) -Cathodic protection system ground connection. GROUND FAULT CIRCUIT INTERRUPTERS (GFCI) -A device whose function is to interrupt the electric circuit to the load when a fault current to ground exceeds some predetermined value that is less than that required to operate the overcurrent protective device of the supply current. GROUND SUPPORTS -Supports or scaffolding that rest on the ground or roadway. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 605
SSPC CHAPTER*27=3 93 8623940 0004053 309 GUIDE COAT -Coat similar to the finish or color coat but of a different color to assure good coverage. HACKLES-Thin, needle-like or sliver-like protrusions (ranging from 3 to 6 mils) found on steel plates that have been blasted with steel or grit. HALOGENATED SOLVENTS -Solvents containing halogens (usually chlorine) having improved solvency and reduced flammability compared with the hydrocarbons from which they are derived. Some of these are highly toxic, and precautions must be taken to avoid inhalation of their vapors. HAND CLEANING -Surface preparation using hand tools such as wire brushes, scrapers, and chipping hammers. HARDENER -Additive (cross-linking agent, resin or other modifier) used to promote or control the hardening or curing reaction of a coating or resin system. HARDNESS -Ability of a coating film, as distinct from its substrate, to resist cutting, indentation or penetration by a hard object. HAZARD-The likelihood that injury will result when a substance or object is used in a particular quantity or manner. Note that, properly speaking, there are no hazardous substances or objects, only hazardous ways of using them. HAZARD COMMUNICATION STANDARD -OSHA regulation (CFR 1910.1200) that requires employers to take specific steps to inform workers of the hazards of materials used in the workplace. Among others, requires employers to obtain Material Safety Data Sheets. HAZARDOUS AIR POLLUTANTS (HAPS) -Approximately 190substances specifically listed in the Clean Air Act Amendments that may be hazardous to human health or the environment, but that are not specifically regulated elsewhere in the CAAA. HAZARDOUS AND SOLID WASTE AMENDMENTS (HSWA) -Amendments to RCRA which directed EPA to establish new requirements, bringing small quantity generators into the hazardous waste regulatory system. HAZARDOUS SUBSTANCE -A substance which, by reason of being explosive, flammable, poisonous, corrosive, oxidizing, or otherwise harmful, is likely to cause death or injury when misused. HAZARDOUS WASTE -A solid waste subject to RCRA regulations because it is specifically listed as one of the wastes to which such regulations apply, or because it exhibits the characteristics which define a hazardous waste. See CHARACTERISTIC WASTE, LISTED WASTE, and SOLID WASTE. HAZARDOUS WASTE NUMBER -A number assigned by EPA to each listed and characteristic hazardous waste.
These numbers must be included on paperwork such as a hazardous waste manifest. HEAD PROTECTION -Helmets meeting ANSI Z89.1 protect workers heads from impact and penetration from fall- under Department of Tra nsportation regulations, as determined by standard tests. IMMERSION SERVICE -Use in water or other liquid. --`,,,,`-`-`,,`,,`,`,,`--ing and flying objects. HEARING CONSERVATION PROGRAM -An employee hearing conservation program requires monitoring, employee notification, audiometric testing, protective equipment, training and recordkeeping. HEAVY INDUSTRIAL ENVIRONMENT -See CHEMICAL ENVIRONMENT. HIDING POWER -The ability of a paint or paint material to hide or obscure a surface to which it has been uniformly applied. HIGH-BUILD COATING -Coatings that are applied in thicknesses (minimum 5 mils) greater than those normally associated with paint films and thinner than those normally applied with a trowel. HIGH-SOLIDS COATINGS -Generally, a coating that contains at least 70% solids by volume. The term higher solids is more appropriate for coatings which have a higher percentage of solids than previous (conventional) formulations but still contain less than 70% solids by volume. HOLIDAY DETECTORS -Instruments utilizing electric current (low voltage, high voltage or ac electrostatic) to detect nicks, scrapes or pinholes in a coating film. HOLIDAYS -Application defect whereby small areas are left uncoated. HOT SPRAYING -Spraying of hot lacquers or paints, the viscosities of which have been reduced to spraying consistency by means of heat instead of by the addition of volatile solvents. By such a process it is possible to apply materials with higher solid contents. HOT SPECS -New and modified federal specifications issued every 15 days on microfilm. HOT-ROLLED STEEL -Steel that is hot reduced (formed and shaped while hot). HOTMELT COATINGS -Solventless coatings that liquify readily on heating, are applied to the surface in molten con-
ditions, and are allowed to cool on the substrate. HYDROBLASTING-Cleaning with high-pressure water jet. HYDROSTATIC TESTS -Used to measure the strength and leak-resistance of any hollow piece of equipment by internal pressure exerted by a test liquid. HYGROSCOPICITY-The capacity of a compound or substance to absorb water. IDENTIFICATION NUMBER -Number assigned by the EPA to each generator, transporter and treatment, storage and disposal facility. These facilities are required to submit an application for such a number. IGNITABILITY -A characteristic exhibited by a solid waste (excluding some alcohol solutions) that is a liquid which has a flash point less than 6OoC (14OOF) when standard tests are used, or one which is not a liquid but is a fire hazard when exposed to friction, moisture, or through spontaneous chemical changes. Also a compressed gas considered ignitable Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 606
SSPC CHAPTER*27.3 73 8627740 0004054 b45 IMPACT RESISTANCE -Ability of a coating to resist a sudden blow; ability to resist deformation from impact. INDIRECT COSTS -Such costs as engineering fees, overhead, cost of capital, and depreciation. INDUSTRIAL ENVIRONMENT -Atmospheric exposures that include urban communities, manufacturing centers, and industrial plants (but would not include heavy industrial environments such as coke plants, which fall under chemical environments). The atmosphere contains a considerable amount of gas containing sulfur and industrial fumes that increase the rate of corrosion and adversely affect the paint life. INDUSTRIAL FINISHES OR COATINGS -Coatings applied to factory-made articles (before or after fabrication), usually with the help of special techniques for applying and drying as opposed to trade sales paints. INDUSTRIAL MAINTENANCE PAINTS -High performance coatings formulated for resistance to heavy abrasion, water immersion, chemicals, corrosion, temperature, electrical current or solvents. INERT PIGMENT -A pigment that remains relatively inactive or chemically unchanged in paints under stated conditions. The term has little significance unless the conditions are stated. This term is also used to describe extender pigments. INHIBITIVE PIGMENT -Pigment that assists in the prevention of corrosion or some other undesirable effect. INHIBITOR -General term for compounds or materials that slow down or stop an undesired chemical change such as corrosion, oxidation or polymerization, drying, skinning, mildew growth, etc. INORGANIC COATINGS -Coatings based on silicates or phosphates and usually used pigmented with metallic zinc. Also see CEMENT PAINT and ZINC-RICH PRIMER. INSPECTOR -An individual or group of individuals whose job it is to witness and document the coating work in a formal fashion. INTERNAL PHASE -In an emulsion, the discontinuous phase. For example, in an oil-in-water emulsion, the oil is the internal phase. JEEP TEST -High voltage holiday detection test.
JOB STANDARD -The minimum acceptable standard of quality for a coatings project established prior to beginning the work. KORT NOZZLES -Tube-like enclosures around a propeller. LACQUER -Coating composition that is based on synthetic thermoplastic film-forming material dissolved in organic solvent and that dries primarily by solvent evaporation. Typical lacquers include coatings based on vinyl resins, acrylic resins, chlorinated rubber resins, etc. LAITANCE -A milky white deposit on new concrete. LAND DISPOSAL -Placement in or on the land, including but not limited to, placement in a landfill, surface impoundment, waste pile, injection well, land treatment facility, salt dome formation, salt bed formation, underground mine or cave, or placement in a concrete vault or bunker intended for disposal purposes. LAND DISPOSAL RESTRICTIONS -Section of hazardous waste regulations which identifies hazardous wastes that are restricted from land disposal and defines those limited circumstances under which an otherwise prohibited waste may continue to be land disposed. LANYARD -A rope, suitable for supporting one person. One end is fastened to a safety belt or harness and the other end is secured to a substantial object or a safety line. LARGE QUANTITY GENERATOR (LQG) -A business which generates more than 1,000 kg (2,200 pounds or about 300 gallons) of hazardous waste or more than 1 kg of acutely hazardous waste in any calendar month. Must comply with all applicable hazardous waste management rules. LATEX -Stable dispersion of a polymeric substance in an essentially aqueous medium. After polymerization a latex is a solid dispersed in water and therefore, technically speaking, it is not an emulsion. However, latex and emulsion are often used synonymously in the paint industry. The particle sizes range from 0.1 to 0.7 microns and form a mixture which is milky in appearance. LATEX PAINT -A paint containing a stable aqueous dispersion of synthetic resin, produced by emulsion polymerization, as the principal constituent of the binder. Modifying resins may also be present. LEAD -A heavy metal that may be hazardous to health if breathed or swallowed and for which national ambient air quality standards have been promulgated. LEAD POISONING -A disease resulting from exposure to relatively low levels of lead over a long period of time or very high levels over a short period of time. Can result in a wide
variety of symptoms, particularly nervous system effects. LEAFING -Action involving the floating and slight overlapping of certain metallic and other pigment particles in the form of laminar flakes on the surface of a coating. Leafing occurs when such pigments are mixed with a suitable vehicle and applied as a coating. LEAK DETECTION SYSTEM -System capable of detecting the failure of either the primary or secondary containment structure, or the presence of the product or hazardous waste the structure contains, or other accumulated liquid, in the secondary containment structure LETHAL DOSE 50% (LD50) -A method for expressing quantitatively acute toxicity. An LD50 value is the dosage that is likely to kill 50% of a group of animals identical with those tested. Small differences between the LD50s of two chemicals do not indicate important differences in hazard. Note that large LD50 values represent low toxicities while small LD50 values represent great toxicities. LEVELING -The measure of the ability of a coating to flow out after application so as to obliterate any surface irregularities such as brush marks, orange peel, peaks, or craters which have been produced by the mechanical process of application. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 607
SSPC CHAPTER*27.3 93 = 8627740 OOOLI055 581 = LIFELINE-A rope, suitable for supporting one person, to which a lanyard or safety belt (or harness) is attached. LIFTING -Softening and raising or wrinkling of a previous coat by the application of an additional coating, often caused by the solvents. LIMESTONE DROP TEST -A method for estimating the effect of falling stone on a coated surface on pipelines. LINSEED OIL -Drying oil from seeds of the flax plant. This best known and most widely used oil in the paint industry is characterized by its relatively short drying time. LISTED WASTES -Any of the more than 400 specific wastes that appear on any one of the four lists of hazardous wastes contained in RCRA regulations. LIVERING -The progressive, irreversible increase in consistency of a pigment-vehicle combination. Livering in the majority of cases arises from a chemical reaction of the vehicle with the solid dispersed materials, but it may also result from polymerization of the vehicle. The irreversible character of the changes in the livered material distinguishes it from thixotropic build-up, which is reversible. LOCAL CORROSION CELL -An electrochemical cell created on a metal surface because of a difference in potential between adjacent areas on that surface. LONG OIL ALKYD -An alkyd resin containing more than 60% of oil as a modifying agent. LONG OIL VARNISH -An oleoresinous varnish, other than alkyd, containing more than 25 gal of oil per 100 Ib of resin. A long oil varnish is usually slower drying, tougher and more elastic than a short oil varnish. LOW-SOLVENT COATINGS -Generally coatings which contain a reduced amount of volatile organic compounds (VOC) in the paint as applied. LOWER EXPLOSIVE LIMIT (LEL) -Low limit of flammability or explosibility of a gas or vapor at ordinary ambient temperatures expressed in percent of the gas vapor in air by volume. MAINTENANCE PAINTS -Coatings used to maintain manufacturing plants, offices, stores and other commercial structures, hospitals and nursing homes, schools and universities, government and public buildings, and both building and nonbuilding requirements in such areas as public utilities, railroads, roads, and highways; and including industri-
al paint, other than the original coating, the primary function of which is protection. Residential maintenance is excluded. MAJOR STATIONARY SOURCE -One which emits or could emit 1O0tons per year or more of a pollutant subject to regulations. MANIFEST -The shipping document originated and signed by the generator in accordance with hazardous waste regulations. MANMADE AIR POLLUTION -Air pollution that results directly or indirectly from human activities. compound a toxic chemical. The term manufacture also applies to a toxic chemical that is produced coincidentally during the manufacture, processing, use or disposal of another chemical or mixture of chemicals, including a toxic chemical that is separated from that other chemical or mixture of chemicals as a byproduct, and a toxic chemical that remains in that other chemical or mixture of chemicals as an impurity. MARINE COATINGS -Paints and varnishes specifically formulated to withstand water immersion or exposure to marine atmosphere. MARINE ENVIRONMENT -An atmospheric exposure that is frequently wetted by salt mist, but which is not in direct contact with salt spray or splashing waves. This environment contains a high concentration of chlorides. MASTICS -Adhesive composition. MATERIAL SAFETY DATA SHEET -Printed information concerning a hazardous chemical which must be provided by manufacturers and made available to all employees. It must include such information as the identity and chemical composition of the material, physical and chemical characteristics and hazards, health hazards, route of entry and permissible exposure limits. MAXIMUM ALLOWABLE LEVELS -Voluntary standards for levels of contaminants in drinking water established by NSF International in conjunction with the American Water Works Association, the Conference of State, Health, and Environmental Managers (COSHEM), and the Association of State Drinking Water Administrators (ASDWA). Generally equivalent to 10% of the maximum contaminant level (MCL) from EPA s Primary Drinking Water Standards issued under the Safe Drinking Water Act. Intended as third-party standards for evaluating the health effects of additives to drinking water. MAXIMUM CONTAMINANT LEVELS (MCLs) -The maximum permissible level of a contaminant in water which is delivered to the free flowing outlet of the ultimate user of a
public water system, except in the case of turbidity where the maximum permissible level is measured at the point of entry to the distribution system. Contaminants added to the water under circumstances controlled by the user, except those resulting from corrosion of piping and plumbing caused by water quality, are excluded from this definition. MEDIUM OIL VARNISH -Varnish of medium oil content, usually containing from 18to 25 gal of oil per 100 Ib of resin. METAL SPRAYING -Application of a spray coat of metal (usually zinc or aluminum) onto a prepared surface (usually shot blasted mild steel). The metal to be sprayed is rendered molten by passing it, in wire or powder form, through a flame pistol that projects the semimolten metal onto the surface by means of a jet of compressed air. METALLIZING -Applying a thin coating of metal to a metallic or non-metallic surface. See FLAME SPRAY. MANUFACTURE(Emergency Planning and Community Right-to-Know regulations) To produce, prepare, import or 608 --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*27=3 93 = 8627940 000405b 4LB MICELLE-Colloidal particle composed of many aggregated small molecules having a layered structure. MICROEMULSIONS-Transparent solutions of water and oil, that are thermodynamically stable and which spontaneously form when the components are brought in contact. MILDEW RESISTANCE -The ability of a coating to resist fungus growth that can cause discoloration and ultimate decomposition of a coating s binding medium. MILL SCALE -The heavy oxide layer formed during hot fabrication or heat treatment of metals. MINIMUM FILM-FORMING TEMPERATURE (MFFT) -The temperature below which the effective coalescence of emulsion particles cannot occur. MIST COAT -Very thin sprayed coat. MIXTURE-(Emergency Planning and Community Right to Know regulations) Any combination of two or more chemicals, if the combination is not, in whole or in part, the result of a chemical reaction. MOISTURE VAPOR TRANSMISSION RATE -Rate of movement of moisture vapor through a membrane. MUDCRACKING -Paint film defect characterized by a broken network of cracks in the film. NATIONAL AMBIENT AIR QUALITY STANDARDS (NAAQS) -Standards for national air quality developed by the EPA under the Clean Air Act for six primary pollutants including lead, ozone, particulate matter, sulfur dioxide, nitrogen dioxide and carbon monoxide. Intended to promote the public health and welfare. NATIONAL DRINKING WATER STANDARD -Sets a maximum content of metals and other constituents in drinking water. NATIONAL EMISSION STANDARD FOR HAZARDOUS AIR POLLUTANTS (NESHAP) -Standards for toxic substances in the air the EPA was required to develop under the Clean Air Act prior to the 1990amendments. Because they required the agency to prove the risk of the materials, relatively few were developed. NATIONAL INSTITUTE FOR OCCUPATIONAL SAFETY AND HEALTH (NIOSH) -A federal agency that assists the Occupational Safety and Health Administration, primarily through research. NIOSH develops industrial exposure limits for substances and tests and certifies respiratory devices and air sampling equipment. NATIONAL POLLUTANT DISCHARGE ELIMINATION SYS-
TEM (NPDES) -The national program for issuing, modifying, and enforcing permits and other water discharge requirements. NEAR-WHITE BLAST -Blast cleaning to a degree of cleanliness slightly less than white metal. This standard is defined in the Steel Structures Painting Council Surface Preparation Specification No. 10, Near-White Blast Cleaning
(SSPC-
SP 10). NEOPRENE -A synthetic rubber polymer derived from 2-chloro-l , 3-butdiene. NEW SOURCE PERFORMANCE STANDARDS -Requirements pertaining to any stationary source, the construction or modification of which is commenced after the publication in the Federal Register of proposed national emission ctandards for hazardous air pollutants which will be applicable to such source. NONAQUEOUS DISPERSION (NAD) -The solvent analog of a latex; the polymer is dispersed in a volatile organic liquid which is not a solvent for the polymer. Nonaqueous dispersions have a much higher solids content than conventional high molecular weight solvent coatings. Like lattices, the viscosity is independent of the molecular weight. NON-ATTAINMENT AREA -An area which does not meet National Ambient Air Quality Standards for a particular pollutant such ozone, lead and four other common pollutants, as shown by monitored data or calculated by air quality modeling (or other methods determined to be reliable). Nonattainment areas must make progress toward compliance under a schedule developed as part of the Clean Air Act Amendments. NONDEGRADATION CLAUSE -A legal provision stipulating that the present air quality of an area must not be lowered. The provision is meant to protect those areas whose air quality is already better than federal standards require. NON-METALLIC ABRASIVES -Naturally occurring, byproduct, and manufactured abrasives used for blast cleaning. NON-POINT SOURCE -A source of water pollutants which is not an industrial or municipal discharge from a discernible, confined and discrete conveyance, such as a pipe, ditch, or channel which is designed to emit effluent into a water body. See POINT SOURCE. An example of a non-point source would be municipal or agricultural runoff. Discharges from painting of bridges or other structures over or near water are non-point sources, because there is normally not an intent to discharge into the body of water.
NONVOLATILE MATTER -Ingredients of a coating composition that, after drying, are left behind on the material to which they have been applied, and that constitute the dry film. The term also applies to coatings components such as varnishes, resins, solvents, thinners and diluents, driers and additives, etc. Also called SOLIDS and TOTAL SOLIDS. NONVOLATILE VEHICLE -The liquid portion of a paint excepting its volatile thinner and water. NOTICE OFPROPOSED RULEMAKING -Anouncement of a federal agency s plans to propose, amend or revoke a regulation, published in the Federal Register. The public must have an opportunity to comment before a final rule is pubIished. OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION (OSHA) -Federal agency responsible for administration and enforcement of the Occupational Health and Safety Act. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 609
SSPC CHAPTERt27.3 93 8627940 0004057 354 OFFSETS -An air pollution control policy that treats an entire region as if it is in a gigantic bubble. The EPA insists only that the over-all clean air standards be achieved within the bubble without specifying the precise means. See BUBBLE CONCEPT. OIL LENGTH -Ratio of oil to resin in a medium. For an oleoresinous varnish, the oil length may be expressed in terms of parts by weight of oil to one part by weight of resin or, in American practice, in terms of U.S.A. gallons of oil per 100 Ib. of resin. Thus, a 25 gallon varnish would mean, in American usage, a varnish composed of 25 USA gallons of oil to 100 Ib of resin. For an alkyd resin, the oil length is expressed as the percentage of oil by weight in the resin. OIL PAINT -A paint that contains drying oil, oil varnish, or oil-modified resin as the basic vehicle ingredient. The common (but technically incorrect) definition is any paint soluble in organic solvents. OLEORESINOUS VEHICLE -A vehicle prepared by the addition of a resin to a drying oil. These two components may or may not be further processed to obtain specified properties. Alkyd resins are sometimes, but not generally, included in this category. OLIGOMER -A polymer composed of molecules containing only two, three or a few units, or mers. ONE-COMPARTMENT COATING -Cross-linking systems which can be stored in a single compartment, as opposed to a two-cornpartment coating. OPACITY -The degree of obscuration of light. Often expressed as the fraction (percent) of a beam of light that fails to penetrate the smoke or dust plume. OPERATING PERMIT -(AIR) Authorization to discharge air pollutants. The permitting program provides a way of tracking sources and their emissions. Shop painting facilities are among the sources typically required to apply for operating permits. Under the Clean Air Act Amendments, states must develop operating permit programs which can be expected to include facilities which have not needed a permit in the past. ORANGE REEL -Surface condition of a coating, resembling the texture of an orange skin. ORGANIC SOLVENTS -Organic materials, including diluents and thinners, that are liquids at standard conditions and that are used as dissolvers, viscosity reducers, or cleaning agents. ORGANOSOL -Combination of dispersion resins and plasticizer, dispersed in a mixture of volatile organic solvents, that contain both polar and nonpolar solvents.
OSHA INJURY AND ILLNESS RECORD -A log and summary of all recordable occupational injuries and illnesses that each employer must keep. Summaries must be posted ann ual Iy. OSHA LOG 200 -See OSHA INJURY AND ILLNESS RECORD. OTHERWISE USE or USE -(Emergency Planning and Community Right-to-Know regulations) Any use of a toxic chemical that is not covered by the terms MANUFACTURE or PROCESS. Includes use of a toxic chemical contained in a mixture or trade name product. Relabeling or redistributing a container of a toxic chemical where no repackaging of the toxic chemical occurs does not constitute use or processing of the toxic chemical. OVERSPRAY -In spray painting, the spray material that does not adhere to the object being sprayed. OXIDANT -A substance containing oxygen that reacts with chemicals in air to produce a new substance; primary source of photochemical smog. OXY-FUEL GAS GUN -Introduces a powder into a gas stream (usually air). Used for thermal spraying of organic materials such as powdered thiokol or polyethylene. OZONE -A pungent, colorless, toxic gas that contributes to photochemical smog. The national air quality standard for photochemical oxidants has been changed to an ozone standard. PACKAGE STABILITY -The ability of a liquid, such as paint or varnish, to retain its original quality after prolonged storage. PAINT -Any pigmented liquid, liquefiable, or mastic composition designed for application to a substrate in a thin layer that is converted to an opaque solid film after application. Used for protection, decoration or identification, or to serve some functional purpose. PAINTING SYSTEM -See COATING SYSTEM. PARTICULATES -Fine liquid or solid particles such as dust, smoke, mist, fumes, or smog, found in the air or emissions. PASSIVATION -Act of making inert or unreactive. PEELING -Spontaneous removal, in ribbons or sheets, of a paint, varnish or lacquer film from a surface due to loss
of adhesion. PEENING-Use of metallic shot to impart residual compressive stresses to improve fatigue properties of metal products, and to minimize intergranular and stress corrosion cracking of alloyed metal products. PERFORMANCE STANDARD -The EPA limit on emissions from an individual source within a specific source category. A source category is designated when the EPA determines that sources within the category contribute significantly to air pollution. PERMISSIBLE EXPOSURE LIMITS -An employee s exposure to an air contaminant regulated under 29 CFR I91O. 1O0and 1926.55 may not exceed this value. Often expressed as a time weighted average. PESTICIDE -Any substance, or mixture of substances intended for preventing, destroying, repelling or mitigating any pest, or intended for use as a plant regulator, defoliant, or desiccant. Some articles treated with preservatives, for instance treated wood, are exempted. Also does not apply to products that are intended to exclude pests only by 610 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*27.3 93 8b27940 0004058 290 m providing a physical barrier against pest access and which contain no toxicants. PESTICIDE REGISTRATION -Approval gained by submitting an application to the EPA in order to legally distribute or sell a new pesticide product. A pesticide is considered new if it is not contained as an active ingredient in any other pesticide product registered under FIFRA at the time the application for registration is filed. PETROLATUM -Purified unctuous mixture of semi-solid hydrocarbons derived from petroleum. PHENOLIC RESIN -Resin made by the condensation of phenols and aldehydes. PHENOXY RESIN -A high molecular weight, thermoplastic polyether resin based on bisphenol A and epichorohydrin having bisphenol A terminal groups. PHOSPHATING-Pretreatment of steel and certain other metal surfaces by chemical solutions containing metal phosphates and phosphoric acid as the main ingredients, to form a thin, inert, adherent, corrosion-inhibiting phosphate layer which serves as a good base for subsequent paint coats. PHOTOCHEMICALLY REACTIVE ORGANIC MATERIAL Any organic material that will react with oxygen, excited oxygen, ozone or other free radicals generated by the action of sunlight on components in the atmosphere, giving rise to secondary contaminants and reaction intermediates in the atmosphere which can have detrimental effects. PHOTOCHEMICAL OXIDANTS -Air pollutants formed by the action of sunlight on oxides of nitrogen and hydrocarbons. PHOTOCHEMICAL SMOG -Air pollution caused by not one pollutant but by chemical reactions of various pollutants emitted from different sources. PHOTOCHEMICALLY REACTIVE SOLVENT -Any solvent with an aggregate of more than 20% of its total volume composed of the chemical compounds classified below or that exceeds any of the following individual percentage composition limitations, referred to the total volume of solvent: (a) A combination of hydrocarbons, alcohols, -aldehydes, esters, ether or ketones having an olefinic or cycloolefinic type of unsaturation: 5%. (b) A combination of aromatic compounds with eight or more carbon atoms to the molecule except ethylbenzene: 8%. (c) A combination of ethylbenzene, ketones having branched hydrocarbon structures, trichloroethylene or toluene: 20%. (As defined by Rule 66, q.v.) PICKLING -Treatment for the removal of rust and mill scale from steel by immersion in an acid solution containing an
inhibitor. Pickling should be followed by thorough washing and drying before painting. This process is further defined in Steel Structures Painting Council Surface Preparation Specification No.8, Pickling (SSPC-SP 8). PIGMENT -Finely ground, natural or synthetic, inorganic or organic, insoluble dispersed particles (powder) that, when dispersed in a liquid vehicle to make paint, may provide in addition to color many of the essential properties of a paint: opacity, hardness, durability, and corrosion resistance. The term is used to include extenders as well as white or colored pigments. The distinction between powders which are pigments and those which are dyes is generally made on the basis of solubility, pigments being insoluble and dispersed in the material and dyes being soluble or in solution as used. PIGMENT VOLUME CONCENTRATION (PVC) -Ratio of the volume of pigment to the volume of total nonvolatile material (¡.e., pigment and binder) present in a coating. The figure is usually expressed as a percentage. PINHOLE -Film defect characterized by small pore-like flaws in a coating which extend entirely through the applied film and have the general appearance of pin pricks when viewed by reflecting light. The term is rather generally applied to holes caused by solvent bubbling, moisture, other volatile products, or the presence of extraneous particles in the applied film. PITTING-Formation of holes or pits in the surface of a metal by corrosion. PLASMA GUN -Introduces metal into the plasma arc cavity in powder form in a gas stream and projects onto the steel surface by a plasma jet. PLASTICIZER -A substance added to paint, varnish, or lacquer to impart flexibility. PM-10-Particulates having a mean diameter of 10 microns or less, as measured by a designated reference method, or by an equivalent method. POINT SOURCE -Any discernible, confined and discrete conveyance, including but not limited to any pipe, ditch, channel, tunnel, conduit, well, discrete fissure, container, rolling stock, concentrated animal feeding operation, or vessel or other floating craft, from which pollutants are or may be discharged. POISON-A layman s word for a material of great toxicity. In most states, a statutory poison is a material that will endanger the life of an adult when swallowed inthe amount of 60 grains (3600 milligrams). POLARIZATION-Occurs when bubbles of hydrogen col-
lect on the cathodic areas of steel when immersed in water. The hydrogen acts as a barrier to reduce corrosion, but oxygen in the air acts as a depolarizer, thus allowing corrosion to proceed. POLLUTANT, PRIMARY -A pollutant emitted directly from a polluting source. POLLUTANT, SECONDARY -A pollutant formed in the atmosphere by chemical changes taking place between primary pollutants and sometimes other substances present in the air. POLYAMIDE RESINS -Condensation resins of an amine and an acid, the repeated structural unit in the chain being of the amide type. POLYMER -Molecules which consist of one or more structural units repeated any number of times. POPPING -Eruptions in a film of paint or varnish after it has become partially set so that craters remain in the film. POST-CURE -Heat or radiation treatment, or both, to which a cured coating is subjected to enhance the level of one or more properties. 611 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*27-3 93 8b27940 0004059 127 m POT LIFE -The length of time a paint material is useful after its original package is opened, or after catalysts or other ingredients are added. POT TENDER -Person who assists abrasive blasting operators to adjust and refill abrasive blasting pots. POWDER COATING -A 100°/o solids coating applied as a dry powder and subsequently formed into a film with heat. POWER TOOL CLEANING -Use of pneumatic and electric portable power tools to prepare a substrate for coating. POWER WASHERS -Low pressure water blast cleaning equipment. PREFABRICATION PRIMER -Quick-drying material applied as a thin film to a metal surface after cleaning, e.g., by a blast cleaning process, to give protection for the period before and during fabrication. Prefabrication primers should not interfere seriously with conventional welding or cutting operations or give off toxic fumes during such operations. PREMANUFACTURE NOTICE -A notice to the EPA required under the Toxic Substances Control Act. Companies must notify the EPA that they intend to begin manufacturing, using or importing a chemical not already listed on a toxic substances inventory that the agency maintains. PRETREATMENT-Usually restricted to mean the chemical treatment of unpainted metal surfaces before painting. Sometimes a wash primer is called a pretreatment. PREVENTION OF SIGNIFICANT DETERIORATION (PSD) -The policy incorporated into the Clean Air Act that limits increases in clean air areas even though ambient air quality standards are being met. The policy is based on the premise that air of better quality than the ambient air quality standards is a valuable resource that should be protected. PRIMER -First complete coat of paint of a painting system applied to a surface. Such paints are designed to provide adequate adhesion to new surfaces and are formulated to meet the special requirements of the surfaces. The type of primer varies with the surface, its condition, and the total painting system to be used. Primers for steel work contain special anti-corrosive pigments such as red lead, zinc chromate, zinc powder, etc. PROCESS -(Emergency Planning and Community Rightto-Know regulations) The preparation of a toxic chemical, after its manufacture, for distribution in commerce : 1) In the same form or physical state as, or in a different form or physical state from, that in which it was received by the person so preparing such a substance, or 2) as part of an article containing the toxic chemical. Process also applies to the
processing of a toxic chemical contained in a mixture or trade name product. PROFILE-Surface contour of a blast cleaned or substrate surface, viewed from the edge. (Cross-section of the surface). PROFILE COMPARATOR -An instrument used to determine surface profile by comparing the surface with reference discs of various profile depths. PROFILE DEPTH -Average distance between top of peaks and bottom of valleys on the surface of a coating. PROTECTION FACTOR -A measure of the degree of protection provided to the wearer by a respirator. PSYCHROMETER-A test instrument that is used to determine humidity and dew point. QUALIFIED PRODUCTS LIST -A list of coating systems that have been approved by the user for the protection of structural steel. These coatings have passed such tests as the qualifying agency believes necessary to demonstrate satisfactory performance. QUALITY CONTROL -The system whereby a manufacturer ensures that materials, methods, workmanship, and the final product meet the requirements of a given standard. REACTIVE DILUENT -A viscosity reducer for coatings that has low volatility and will become a permanent part of the coating through chemical reaction, usually under ambient conditions. It is used in high solids coatings to reduce the loss of organic solvents into the atmosphere. REACTIVE PIGMENTS -Those pigments that react with the vehicle, as in the formation of zinc and lead soaps with drying oils, and pigments such as red lead which react with acids formed at metal surface to prevent rust. REACTIVITY -A characteristic exhibited by a solid waste which can be shown by standard tests to do any of the following: readily undergo violent change without detonating, react violently with water, form potentially explosive mixtures with water, generate dangerous quantities of toxic materials when mixed with water or other materials, or one that is capable of detonation or is a forbidden explosive under Department of Transportation regulations. REASONABLY AVAILABLE CONTROL TECHNOLOGY (RACT) -The lowest emission limit that a particular source is capable of meeting by the application of control technology that is reasonably available considering technological and economic feasibility. RECORDABLE OCCUPATIONAL INJURIES OR ILLNESSES -Those which result in: I) fatalities, regardless of the time between the injury and death, or the length of the illness; or, 2) lost workday cases, or other than fatalities, that result in lost workdays; or 3) Nonfatal cases without lost workdays which result in transfer to another job or termina-
tion of employment, or require medical treatment (other than first aid) or involve: loss of consciousness or restriction of work or motion. This category also includes any diagnosed occupational illnesses which are reported to the employer but are not classified as fatalities or lost workday cases. RED LEAD -Bright red to orange-red tetroxide; excellent opacity with good properties as a primary constituent of anticorrosive primer for iron and steel. REDUCERS -Solvents or thinners added to a coating, varnish, resin, latex or emulsion for the purpose of lowering its viscosity andlor nonvolatile content. REFERENCE METHOD -Any method of sampling and analyzing for an air pollutant as specified by the regulations. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 6'i 2
SSPC CHAPTER*2?.3 93 W ab27940 0004060 949 REGULATORY NEGOTIATION (Reg-Neg) -A variant on the regulatory development process in which representatives of EPA, industry, trade associations, environmental groups, labor, other regulators and other affected parties have input into environmental regulations that are being developed. EPA is engaging in regulatory negotiation in developing regulations on VOCs in ARCHITECTURAL AND INDUSTRIAL MAINTENANCE (AIM) coatings. RELEASE -Any spilling, leaking, pumping, pouring, emitting, emptying, discharging, injecting, escaping, leaching, dumping, or disposing into the environment (including the abandonment or discarding of barrels, containers, and other closed receptacles) of any hazardous chemical. REPLICA TAPE -A specially constructed tape used to measure surface profile. The tape is pressed against the surface, after which the impression created by the profile is measured with a micrometer. REPORTABLE QUANTITY -For any CERCLA hazardous substance, which appears in Table 302.4 of 40 CFR Part 302, the reportable quantity that appears in the table. For any other substance, the reportable quantity is one pound. RESIN -General term applied to a wide variety of more or less transparent and fusible products, which may be natural or synthetic. They may vary widely in color. Higher molecular weight synthetic resins are presently more generally referred to as polymers. In a broad sense, the term is used to designate any polymer that is a basic material for coatings and plastics. RESIN EMULSION PAINT -A water paint consisting of a water emulsion of an oil-modified alkyd or other resin that when dry leaves a tough film of resin. RESIN, NATURAL -A solid organic substance, originating in the secretion of certain plants or insects, that is thermoplastic, flammable, and nonconductive of electricity, breaks with a conchoidal fracture (when hard), and dissolves in certain specific organic solvents, but not water. RESIN, SYNTHETIC -Originally, a member of a group of synthetic substances that resemble and share some of the properties of natural resins, but now used for materials which bear little resemblance to natural resins. The term is generally understood to mean a member of the heterogeneous group of compounds produced from simpler compounds by condensation and/or polymerization. Chemically modified natural polymers are not considered to be synthetic resins. RESOURCE CONSERVATION AND RECOVERY ACT (RCRA) -Federal legislation that directed the EPA to develop and implement a system of regulation for the treatment, storage, transportation and disposal of hazardous waste.
RESPIRATORY PROTECTION -Devices worn when engineering controls are inadequate to prevent overexposure by inhalation to airborne contaminants. REUSED -See USED. RULE 66 -Los Angeles Air Pollution Control District rule that restricts the amount of photochemically reactive smogcausing solvent vapors which can be evaporated into the atmosphere. Photochemically reactive hydrocarbons and oxidants react with nitric oxide in the presence of ultraviolet radiation to form smog, causing eye irritation and other deleterious effects. RURAL ENVIRONMENT -An atmospheric exposure that Is virtually unpolluted by smoke and sulphur gases, and which is sufficiently inland to be unaffected by salt contamination or the high humidity of coastal areas. RUST -The reddish, brittle coating formed on iron or ferrous metals resulting from exposure to humid atmosphere or chemical attack. RUST GRADE SCALE -In evaluating ing, the linear, numerical rust function of the area of rust so ing have the greatest effect on (SSPC-Vis 2; ASTM-D 610).
the resistance to rustgrade scale is an exponential that slight amounts of first rustlowering the rust grade.
SACRIFICIAL PROTECTION -The use of a metallic coating, such as zinc-rich paint, to protect steel. Inthe presence of an electrolyte, such as salt water, a galvanic cell is set up and the metallic coating corrodes instead of the steel. SAFE DRINKING WATER ACT -Legislation passed in 1974 which gave the EPA responsibility for issuing guidance to states on additives to drinking water. SAFETY -A reasonable certainty that injury will not result when a substance or object is used in a particular quantity and manner. Note that properly speaking, there are no safe materials or objects, only safe ways of using them. Note also that safety is not absolute, it is only relative, analogous to the beyond a reasonable doubt of the legal profession. SAFETY BELT -A device worn around the waist which, by reason of its attachment to a lanyard and lifeline or a structure, will prevent a worker from falling. SAGGING -Downward movement of a paint film between the times of application and setting, resulting in an uneven coating having a thick lower edge. The resulting sag is usually restricted to a local area of a vertical surface and may have the characteristic appearance of a draped curtain. SALT SPRAY TEST -Test applied to metal finishes to determine their anti-corrosive properties, involving the spray-
ing of common salt (sodium chloride) solution on the surface of a coated steel panel. SAND BLAST -Use of sand, flint or similar non-metallic abrasive propelled by an air blast, on metal, masonry, concrete, etc., to remove dirt, rust, or paint. SAPONIFICATION-Alkaline hydrolysis of fats whereby a soap is formed. SARA TITLE Ili -See EMERGENCY PLANNING AND COM M U N ITY RIGHT-TO-KNOW ACT. SCALING -A condition whereby pieces of a coating detach themselves from the surface of the substrate. SCARIFYING -A method of preparing concrete surfaces for coating. Scarifiers are sharp rotating knives in a selfcontained unit resembling a plant sweeper. SECONDARY CONTAINMENT -Structures capable of preventing product or waste stored in a tank from migrating to soil, groundwater or surface water. Such structures are Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 613
SSPC CHAPTERt27.3 93 8627940 00040bL 845 = required for some tanks containing hazardous waste, but there are a variety of other incentives to use them. Containment may be provided by an external liner, vault, a double walled tank, or an equivalent device. A leak detection system is required for secondary containment systems for some tanks containing hazardous waste. SELF-CURING-Undergoing cure (cross-linking) without the application of heat. SELF-PRIMING -Use of same coating for primer and for subsequent coats. It may be thinned differently for the various coats. SENSITIZATION-A condition in which a chemical causes an allergic reaction after repeated exposure in a significant number of people. SERVICE LIFE -See USEFUL LIFE SETTING UP -Conversion of a liquid paint during storage to a gel-like or pseudosolid condition. The process is usually reversible by agitation and thinning but may be permanent when chemically reactive pigments or highly polymerized media are involved. The thickening which occurs when paint stands in an open can. The increasing viscosity of a paint film. SETTLING -The sinking of pigments, extenders or other solid matter in a paint standing in a container, with a consequent accumulation on the bottom of the can. SET-TO-TOUCH TIME -The time required for the coating to reach a point where the adhesion to an external object is less than the internal cohesion of the film. SHOP COAT -One or more coats applied in a shop or plant prior to shipment to the site of erection or fabrication, where the field or finishing coat is applied. SHORT OIL ALKYD -An alkyd resin containing less than 40% oil in solids. SHORT OIL VARNISH -A varnish containing little oil in comparison with the amount of resin present, less than 15 gal oil per 100 Ib (1.25 liters per kg) resin. SHOT BLASTING -Blasting with round iron shot, round steel shot, or any material that retains its spherical shape
for cleaning purposes. SIGNIFICANT DETERIORATION -Pollution from a new source in a previously clean area, that is an increase in air pollution in an area meeting a national ambient air quality standard beyond the allowable increments established by the Congress or EPA. SILICA -An extremely common mineral that is found in a number of forms. Sand is predominantly silica and chronic or acute exposure to the silica dust generated by sand blasting can cause a debilitating disease known as silicosis. Silicates are also the predominant component of clay, diatomaceous earth, mica, and talc, which are widely used as extender pigments. With the exception of clay, all have been demonstrated to produce fibrosis of the lung. SILICATE PAINTS -Water paints based on sodium, potassium, or lithium silicate. Used in zinc-rich paints. They are characterized by their nonflammability. Care must be exercised in the selection of pigments used with the silicate because of its alkalinity. SILICONE-One of a class of compounds comprising polymerizable, high-temperature-resistant resins, lubricant greases, and oils, organic solvent-soluble water repellants, surface tension modifiers for organic solvents, etc. SILICOSIS-A pulmonary disease caused by prolonged inhalation of silica dust. SKIN -Film formed over a vehicle or liquid coating during storage. SLOW SOLVENT -Solvent with a slow evaporation rate. SMALL QUANTITY GENERATOR (SQG) -A generator who generates between 100 and 1000 kilograms (between 220 and 2,200 pounds or about 300 gallons) of hazardous waste and no more than 1 kg of acutely hazardous waste in a calendar month. Most hazardous waste regulations apply to these generators. SMOG -The irritating haze resulting from the sun s effect on certain pollutants in the air, notably those from automobile exhaust and petrochemical processes. Also a mixture of fog and smoke. SOIL CORROSION -An electrochemical process that can
be prevented by isolating a steel structure from the soil and by cathodic protection. SOLIDS -Nonvolatile matter in a coating composition, ¡.e., the ingredients of a coating composition that, after drying, are left behind and constitute the dry film. Also called N ONVO LATI LE MATTE R. SOLIDS BY VOLUME -The volume of the nonvolatile portion of a composition divided by the total volume, expressed as a percent. SOLID WASTE -Any material not exempted under hazardous waste regulations (including solids, liquids and contained gas) which is discarded. SOLVENT -Liquid, usually volatile, that is used in the manufacture of paint to dissolve or disperse the film-forming constituents, and that evaporates during drying and therefore does not become a part of the dried film. Solvents are used to control the consistency and character of the finish and to regulate application properties. SOLVENTLESS COATING -A 1000/0solids coating. SPARK TEST -Method of detecting holidays on metallic substrates by means of a spark test tool. SPATTER COATING -An incomplete or not continuously wet coating caused by a faulty spray painting application. SPRAYING -Method of application in which the coating material is broken up into fine mist that is directed onto the surface to be coated. This atomization process is usually, but not necessarily, effected by a compressed air jet. SPREADING RATE -The area covered by a unit volume of coating material. Frequently expressed as square feet per gallon. STANDARD -A reference point or a practice established by general agreement. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 614
SSPC CHAPTER*27-3 93 8627 340 0004062 711 D STANDARD, PRIMARY -A national ambient air quality standard promulgated under the Clean Air Act. The primary standard establishes ambient concentrations of pollutants that could have an adverse impact on human health. STANDARD, SECONDARY -A national ambient air quality standard promulgated under the Clean Air Act. The secondary standard establishes ambient concentrations of pollutants that could have an adverse effect on the public welfare (other than human health). STATE IMPLEMENTATION PLAN (SIP) -The plan, including the most recent revision thereof, which has been approved or promulgated by the EPA as required under the Clean Air Act. Intended to identify methods of controlling designated air pollutants which meet the requirements of the act. STATIONARY SOURCE -Any building, structure, facility, or installation which emits or may emit any air pollutant subject to regulation under the Clean Air Act or amendments. STORAGE -Holding of hazardous waste for a temporary period, at the end of which the hazardous waste is treated, disposed of, or stored elsewhere. STORAGE STABILITY -General composite material s resistance to any change, a closed container, over a period of separation, formation of lumps, hard stantial changes in viscosity or pH, are examples of undesirable changes.
property of a generally when kept in time. Color and liquid pigment settling, subdevelopment of odor, etc.,
STORM WATER -Surface water run-off resulting from precipitation. In 1990, EPA started requiring industrial facilities and municipalities to acquire permits for storm water discharge and municipal storm water systems. Paint and surface debris from a painting or paint removal activity which is not properly contained and collected, could be considered an unpermitted discharge. Such discharge may be limited by state or federal regulations, water quality standards or other state or local ordinances. STRAY CURRENT -Direct current flowing in the earth and capable of causing corrosion damage. STRONTIUM CHROMATE -A bright yellow pigment of a type similar to lead chromate except that it is not blackened by hydrogen sulfide. It is used in corrosion-resistant primers. SUBACUTE TOXICITY -The property of a substance or mixture of substances to cause adverse effects in an organism upon repeated or continuous exposure within less than the lifetime of that organism.
SUBSTRATE -Any surface to which a coating is applied. SUPERFUND -See COMPREHENSIVE ENVIRONMENTAL RESPONSE, COMPENSATION AND LIABILITY ACT SUPPLIED-AIR RESPIRATORS -A respiratory protection device that incorporates a supply or a means of generating respirable air or oxygen. SURFACE DRYING -The premature drying of the surface of a liquid coating film, so that the under portion is retarded in drying. SURFACE PREPARATION -Any method of treating a surface in preparation for coating. Swedish standards (identical to SSPC-Vis 1) include photographic depictions of the surface appearance of hand and power tool cleaning and various grades of blast cleaning over four initial mill scale and rust conditions of steel. SURFACTANTS -Contracted from surface-active agents, these are additives which reduce surface tension and may form micelles and thereby improve wetting (wetting agents); help disperse pigments (See DISPERSANTS); inhibit foam (See DEFOAMERS); or emulsify (See EMULSIFIER). Conventionally, they are classified as to their charge: anionic (negative), cationic (positive), nonionic (no charge), or amphoteric (both positive or negative). SUSPENDING AGENT -A material used in a paint to improve its resistance to the settling of pigments. TACK-FREE -Freedom from tack of a coating after suitable drying time. In some cases, coatings are tack-free after application; tack may not develop until a little later. TANK -Stationary device designed to contain an accumulation of product, hazardous waste or other material which is constructed primarily of non-earthen materials such as wood, concrete, steel or plastic which provides structural support. TEST FENCE -An apparatus consisting of a fence strategically located in a part of the country for specific weather conditions (temperature, humidity, corrosivity, etc.) and facing a specific direction and angle. It contains a series of exposure racks on which test panels are exposed. TEST METHOD -A definitive, standardized set of instructions for the identification, measurement, or evaluation of one or more qualities, characteristics, or properties of a material. THERMAL SPRAYING -A process whereby a material is brought to its melting point and sprayed onto a surface to produce a coating. THERMOPLASTIC -Capable of being repeatedly softened by heat and hardened by cooling. THERMOSET -A material that will undergo or has under-
gone a chemical reaction by the action of heat, catalysts, ultraviolet light, etc., leading to a relatively infusible state. THINNER -The portion of a paint, varnish, lacquer, or related product that volatilizes during the drying process. Any volatile liquid used for reducing the viscosity of coating compositions or components; may consist of a simple solvent, a diluent, or a mixture of solvents and diluents. THIXOTROPIC PAINT -Paint that, while free-flowing and easy to manipulate under a brush, sets to a gel within a short time when it is allowed to remain at rest. Because of these qualities a thixotropic paint is less likely to drip from a brush than other types and can be applied in rather thicker films without running or sagging. THRESHOLD LIMIT VALUES -A figure developed by the American Conference of Governmental Industrial Hygienists which is intended to represent the level of airborne contaminants that will cause no adverse effects, even after prolonged exposure. A concentration of air-borne material that experts agree can be inhaled for a working lifetime by 615 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*27.3 93 Bb2794O 00040b3 658 almost all workers without any injury. The few workers who exposure periods betw een acute and chronic. Toxic effects will be affected will develop their symptoms so slowly that may be reversible or irreversible. With a Reversible effect, periodic medical examination can be expected to detect them soon after exposure ceases, the affected human returns comwhile the effects are still reversible. While Permissible Ex- pletely to his for mer state. There is no residue of effect whatposure Limits are legally binding limits, required by OSHA, soever. An Irreversi ble effect is a permanent change in an TLV s are recommended limits. affected human. His next exposure is more likely to have a THRESHOLD PLANNING QUANTITY (TPQ) -Quantities serious effect, because his respon se starts at a higher base of substances used in industry which trigger emergency plan- line. ning and reporting requirements. A lower TPQ reflects a sub- TOXICOLOGY (HUMAN) -The body of knowledge of the stance that is considered more hazardous. Applicable adverse effects upon humans of excessive exposure to TPQs for specific substances are found in several sections chemicals. of the regulations developed under the Emergency Planning TOXIC POLLUTANTS -Thos e pollutants that, after disand Community Right to Know Act. TPQ s are also given for charge and upon contact with any organism, either directly substances which are covered by the act, but for which there from the environmen t or indirectly by ingestion through food is no substance-specific TPQ. chains, will cause death, disease, behavioral abno rmalities, THROUGH-DRYING-Uniform drying throughout the film cancer, genetic mutations, phy siological malfunctions or as opposed to bottom-drying or top-drying. physical deformities in such organism s or their offspring. TIE COAT -Intermediate coat used to bond different types TOXIC SUBSTANCES CONTRO L ACT (TSCA) -Federal of paint coats. Coating used to improve the adhesion of suc- legislation that le d to the development of regulations that conceeding coatings. trol the manufacture, handling and use of toxic materials. TIME WEIGHTED AVERAGE -The average level of air- TRADE SALES PAINTS -Coatings ap plied on-site at amborne contaminants to which an employee is exposed. bient conditions by the cons umer using application methods Generally, the average is calculated for an 8-hour work shift. such as brushing or roller coating. TOEBOARD -A barrier secured along the sides and ends TRANSITION PRIMER -Coating compatible with primer of a platform, to prevent material or a person from falling from and also with f inish coat that is not compatible with the it. primer. See TIE COAT. TOOTH -Anchoring profile of a substrate that enhances TRANSPORTATION -Movement o f hazardous waste by
adhesion of a coating created mechanically or by the use air, rail, highway or w ater. of solvents. TRANSPORTER -Person engaged in the off-site transporTOP COAT -The coating intended to be the last coat ap- tation of hazardous waste by air, rail or highway. plied in a coating system; usually applied over a primer, un- TREATMENT-Any meth od, technique, or process, includdercoaters, or surfacers. ing neutralization, designed to change the physical, c hemiTOP-DRYING -Drying of a film on the top only. cal or biological character or com position of any hazardous TOUCH-UP PAINTING -Application of paint on small areas waste so as to neutralize such waste, or so as to recover of painted surfaces to repair mars, scratches, and small areas energy or materia l resources from the waste, or so as to where the coating has deteriorated, in order to restore the render such waste no n-hazardous, or less hazardous; safer coating to an unbroken condition. to transport, store or dispose of; or amenable for recovery, TOXICITY -Characteristic of a solid waste which is shown amenable for storage, o r reduced in volume. to contain specified contaminants, including lead and chro- TWO-COMPARTMENT COAT ING -Cross-linking systems mium, at a concentration equal to or greater than the regula- that must be store d in separate containers before use. Othertory level, using a standard test method known as the Toxicity wise they would r eact and form a useless gel. Characteristic Leaching Procedure. TWO-COMPONENT GUN -Spray gun having two separ ate TOXICITY CHARACTERISTIC LEACHING PROCEDURE fluid sources leading to the spray he ad. (TCLP) -A standard test used to determine if a solid waste UNDERCURE -A conditio n or degree of cure that is less is considered a hazardous waste by virtue of its toxicity. It than optimum, ¡.e., when insufficient time or temperature has is intended to simulate the leaching of toxic constituents that been allowed for adequate cure; may be evidenced by tackwould take place in a landfill. iness or inferior physical properties. TOXICITY (HUMAN) -The capacity of a substance to in- UNDERCUTTING-The gradual pe netration and spread of jure by chemical means. All substances are toxic. They differ corrosion beneath a coating from a break or pinhole in the in degree of toxicity and in the nature of injury they may film or from unprotec ted edges. cause. Toxicity is called ACUTE when the adverse effect is UNDERGROUND EXPOSURE -Buried surfaces in direct the result of swallowing a substance once, having it on the contact with the soi l. skin for a few hours, or breathing it for up to a work shift. UPPER EXPLOSIVE LI MIT (UEL) -Upper limit of flamma-
Toxicity is called CHRONIC when the adverse effect is the bility or explosivenes s of a gas or vapor at ordinary ambient result of swallowing, contact or breathing almost daily for a temperatures expre ssed in percent of the gas vapor in air year or longer. The word SUBACUTE is used for effects of by volume. 616 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*27*3 93 8627940 00040b4 594 W URETHANE COATINGS -Coating vehicles containing a polyisocyanate monomer reacted in such a manner as to yield polymers containing any ratio, proportion or combination of urethane linkages, active isocyanate groups or polyisocyanate monomer. The reaction products may contain excess isocyanate groups available for further reaction at the time of application or may contain essentially no free isocyanate as supplied. USEFUL LIFE -The length of time a coating is expected to remain in service. Also called SERVICE LIFE. USER -In the coatings industry, the user is normally the person who either applies the coating or who owns the structure to which the coating is applied. See END-USER. UNDERGROUND STORAGE TANKS (UST) -Any one or combination of tanks (including underground pipes connected thereto) that is used to contain an accumulation of regulated substances, and the volume of which is 10 percent or more beneath the surface of the ground. Any tank not specifically exempted under 40 CFR 280. VARIANCE -Permission granted by the federal Occupational Safety and Health Administration or state occupational safety and health agency to remain outside compliance with written requirements of health and safety standards. Employers may request a variance if they cannot fully comply with a standard or it they can prove their facilities or methods of operation provide employee protection at least as effective as that required by OSHA. VARNISH -A liquid composition that is converted to a transparent solid film after application as a thin layer. VEHICLE -The liquid portion of paint, in which the pigment is dispersed; it is composed of binder and thinner. VERMICULITE -Lightweight, porous, fire-retardant material. VINYL COATING -One in which the major portion of binder is of the vinyl resin family. Vinyl resins include polyvinyl acetate, polyvinyl chloride, copolymers of these, the acrylic and methacrylic resins, the polystyrene resins, etc. VOLATILE -The easily evaporated components of any coating composition in contrast to the nonvolatile components. VOLATILE ORGANIC COMPOUND (VOC) -Any organic compound which participates in atmospheric photo-chemical reactions or that is measured by approved methods. WASH PRIMER -Priming paint usually supplied as oneor two-water component systems. The paint contains carefully balanced proportions of an inhibiting chromate pigment,
phosphoric acid, and a synthetic resin binder mixed in an alcohol solvent. On clean, light alloy or ferrous surfaces, and on many nonferrous surfaces, such paints give excellent adhesion, partly to chemical reaction with the substrate, and give a corrosion-inhibiting film which is a good basis for the application of subsequent coats of paint. Although these materials are referred to as primers, the films that they produce are so thin that it is more correct to consider them as etching solutions and to follow them with an ordinary primer if maximum protection is required. WASTE ANALYSIS PLAN -Required for on-site treatment of hazardous waste. A written waste analysis plan must be filed with the EPA regional administrator a minimum of 30 days prior to the treatment activity. WATER BLASTING -Blast cleaning of metal using highvelocity water. WATER-BORNE COATINGS -Latex paints and paints containing water soluble binders. Paint, the vehicle of which is a water emulsion, water dispersion, or ingredients that react chemically with water. Also called water-based coatings and WATE R-RE D UCIBLE COAT INGS. WATER-DISPERSIBLE COATING -Those organic coatings which normally are solvent-based, but by adjusting the chemistry can be dispersed in water. WATER IMMERSION -An exposure in which the surface is in direct contact with fresh or salt water. WATER PAINT -A paint, the vehicle of which is a water emulsion, water dispersion, or ingredients that react chemically with water. WATER QUALITY STANDARDS -Provisions of state or federal law which consist of a designated use or uses for the waters of the United States and water quality criteria for such waters based upon such uses. Water quality standards are to protect the public health or welfare, enhance the quality of water and serve the purposes of the Act. WATER-REDUCIBLE COATINGS -Water soluble types of lattices or emulsions. Coatings which can be diluted (reduced) with water, water-cosolvent mixtures and sometimes with alkali (alkali-soluble resins). WATER-SOLUBLE RESINS -In most cases, amines andlor cosolvents are required to solubilize these carboxylcontaining resins. The preferred term is alkali-soluble resin. These systems are generally dispersions of micelles rather than true solutions. The particles are in the size range of 0.01 to 0.1 microns which produce a clear mixture in the absence of added pigment. WATER-THINNED COATINGS -Those coatings which are water-based and use water for thinning. WEATHERING -Behavior of paint films when exposed to
natural weather or accelerated weathering equipment, characterized by changes in color, texture, strength, chemical composition, or other properties. Natural outdoor weathering tests are normally carried out at selected exposure sites, on painted panels, generally exposed either vertically or at 45 degrees facing south in the northern hemisphere. WEATHER-OMETER -An apparatus in which specimen materials can be subjected to artificial and accelerated weathering tests which simulate natural weathering, by the use of controlled cycles of ultraviolet radiation, light, water, and heat. Electric arcs, water spray and heating elements are used to simulate the natural conditions of sun, rain, and temperature changes. WET FILM THICKNESS -Thickness of the liquid coating film immediately after application. Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 617
WET-ON-WET COATING -Technique of painting whereby further coats are applied before the previous coats have dried, and the composite film then dries as a whole. The process requires specially formulated paints. WET SPONGE TESTER -A low voltage holiday detection device. WET STORAGE STAIN -White corrosion products (zinc hydroxide or zinc oxide) on zinc coated articles. WETTING -The ability of a vehicle to spread uniformly and rapidly over the surface of pigment particles. A vehicle with good wetting properties assists in the grinding or dispersion of pigments and the ability to wet the surface to which the finish coating is applied. WHITE BLAST -Blast cleaning to white metal. This standard is defined in Steel Structures Painting Council Surface Preparation Specification No. 5, White Metal Blast Cleaning (SSPC-SP 5). WHITE RUST -White corrosion products (zinc hydroxide and zinc oxide) on zinc coated surfaces. WIRE BRUSH -Cleaning a surface with a wire brush including both hand wire brushing (SSPC-SP 2) and power wire brushing (SSPC-SP 3). WORK MIX -A mixture of sizes of abrasive comprised of newly added WRAP AROUND charge upon all exposed
abrasive and fractured or flaked, used abrasive. EFFECT -The effect of an electrostatic a sprayed coating, so that the coating covers conductive areas, including edges.
WRINKLING -A distortion in a paint film appearing as ripples. ZINC CHROMATE -Bright yellow pigment comprised substantially of zinc chromate. It is used in anti-corrosive paints and primers for steel. ZINC DUST -Finely divided zinc metal used as a pigment in protective paints for iron and steel. ZINC OXIDE -A fine, white pigment used in paint for mildew resistance and film reinforcing properties. Although not commonly considered an anti-corrosive pigment, it does add anti-corrosive properties to steel primers. ZINC-RICH PRIMER -Anti-corrosive primer for iron and steel incorporating zinc dust in a concentration sufficient to give electrical conductivity in the dried film, thus enabling
the zinc metal to corrode preferentially to the substrate, ¡.e., to give galvanic protection. ZINC SHOT BLASTING (Zincing) -A modification of the normal blast cleaning procedure in which metallic zinc particles are substituted for all or part of the shot, grit, or sand. ZINC SILICATE PRIMER -Inorganic zinc-rich primers that contain a silicate binder. --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 618
SSPC CHAPTER*27.3 93 ô627940 0004066 367 m APPENDIX C A90 Standard Test Method for Weight of STANDARDS AND SPECIFICATIONS Coating on Zinc-Coated (Galvanized) REFERENCED IN VOLUME 1 Iron or Steel Articles All1 Standard Specification for Zinc-Coated American Association of State Highway and Transportation Officials (AASHTO) AASHTO M-68 AASHTO M-69 AASHTO M-70 AASHTO M-72 AASHTO M-229 AASHTO M-300 (discontinued per Interim Specifications -Materials) Standard Specification for Black Paint for Bridges or Timber Structures Standard Specification for Aluminum Paint (discontinued per Interim Specifications -Materials) Standard Specification for White and Tinted Ready-Mix Oil Base Paint (discontinued per Interim Specifications -Materials) Standard Specification for Red Lead Ready-Mixed Paint Standard Specification for Basic Lead Silico Chromate, Ready-Mixed Primer Interim Specification for Inorganic ZincRich Primer American National Standards Institute (ANSI) ANSI B 165.1 ANSI N5.12 ANSI N1 01.2 ANSI N1 01.4 ANSI 241 ANSI 287.1 Safety Requirements for the Design, Care and Use of Power Tools, and Power-Driven Brushing Tools (obsolete) Protective Coatings (Paints) for the Nuclear Industry
(obsolete) Protective Coatings (Paints) for Light Water Nuclear Reactor Containment Facilities (obsolete) Quality Assurance for Protective Coatings Applied to Nuclear Facilities Personnel Protection -Protective Footwear Practice for Occupational and Educational Eye and Face Protection American Petroleum Institute API RP 1631 Interior Lining of Underground Storage Tanks American Society for Testing and Materials (ASTM) ASTM Parts 27, 28,29 ASTM Part 45 A53 Now Paints, Volumes 6.01, 6.02 and 6.03 Now Nuclear Energy (i),Volume 12.01 and Nuclear Energy II, Volume 12.02 Standard Specification for Pipe, Steel, Black and Hot-Dipped, Zinc-Coated Welded and Seamless 619 A112 A116 Al 20 A121 Al 23 Al 43 Al 53 A242 A384 A385 A5251A525M A591 A641 IA641 M A642 A767 A780
B6 B117 8454 (Galvanized) Iron Telephone and Telegraph Line Wire (canceled) Standard Specification for Zinc-Coated (Galvanized) Steel Tie Wires Standard Specification for Zinc-Coated (Galvanized) Steel Woven Wire Fencing (canceled) Standard Specification for Black and Hot Dipped Zinc-Coated (Galvanized) Welded and Seamless Steel Pipe for Ordinary Uses (replaced by A53) Standard Specification for Zinc-Coated (Galvanized) Steel Barbed Wire Standard Specification for Zinc (Hot-Dip Galvanized) Coatings on Iron and Steel Products Standard Practice for Safeguarding Against Embrittlement of Hot-Dip Galvanized Structural Steel Products and Procedure for Detecting Embrittlement Standard Specification for Zinc Coating (Hot-Dip) on Iron and Steel Hardware (AASHTO M-232) Standard Specification for High Strength Low-Alloy Structural Steel Standard Practice for Safeguarding Against Warpage and Distortion During Hot-Dip Galvanizing of Steel Assem blies Standard Practice for Providing HighQuality Zinc Coatings (Hot-Dip) Standard Specification for General Requirements for Steel Sheet, Zinc-Coated (Galvanized) By the Hot-Dip Process Standard Specification for Steel Sheet, Electrolytic Zinc-Coated, for Light Coating Mass Applications Standard Specification for Zinc-Coated (Galvanized) Carbon Steel Wire Standard Specification for Steel Sheet, Zinc Coated (Galvanized) by the Hot-Dip Process, Drawing Quality, Special Killed Standard Specification for Zinc-Coated (Galvanized) Steel Bars for Concrete Reinforcement Standard Practice for Repair of Damaged and Uncoated Areas of HotDip Galvanized Coatings Standard Specification for Zinc Standard Test Method of Salt Spray (Fog) Testing (canceled) Specification for Mechanically Deposited Coatings of Cadmium and Zinc on Ferrous Metals (replaced by
8695 and B 696) Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS ~
SSPC CHAPTER*27=3 73 8b27740 00040b7 2T3 8487 B498 6499 6504 8555 8571 8633 8695 8696 c190 D5 D14 D34 D36 D49 050 D95 D126 D135 Standard Test Method for Measurement of Metal and Oxide Coating Thickness by Microscopical Examination of a Cross Section Standard Specification for Zinc-Coated (Galvanized) Steel Core Wire for Aluminum Conductors, Steel Reinforced (ACSR) Standard Test Method for Measurement of Coating Thicknesses by the Magnetic Method: Nonmagnetic Coatings on Magnetic Basis Metals Standard Test Method for Measurement of Thickness of Metallic Coatings by the Coulometric Method
Standard Guide for Measurement of Electrodeposited Metallic Coating Thicknesses by the Dropping Test Standard Test Methods for Adhesion of Metallic Coatings Standard Specification for Electrodeposited Coatings of Zinc on tron and Steel Standard Specification for Coatings of Zinc Mechanically Deposited on Iron and Steel Standard Specification for Coatings of Cadmium Mechanically Deposited (canceled) Standard Test Method for Tensile Strength of Hydraulic Cement Mortars Standard Test Method for Penetration of Bituminous Materials (canceled) Specification for RubberLined Wire Hose for Public and Private Fire Departments (use 0296) Standard Guide for Chemical Analysis of White Pigments Standard Test Method for Softening Point of Bitumen (Ring-And-Ball Apparatus) Standard Methods of Chemical Analysis of Red Lead Standard Test Methods for Chemical Analysis of Yellow, Orange, Red and Brown Pigments Containing Iron and Manganese Standard Test Method for Water in Petroleum Products and Bituminous Materials by Distillation Standard Test Methods for Analysis of Yellow, Orange, and Green Pigments Containing Lead Chromate and Chromium Oxide Green (canceled) Specification for Asphalt Cement 120-150 Penetration for Use in Asphalt Macadam Products D154 D185 D283 0284 D296 0344 D427 D444 D451 D478 D480
D521 0522 D523 0555 D562 D564 D609 D61O D660 D661 D662 D6951D695M D714 071 5 Standard Guide for Testing Varnishes Standard Test Methods for Coarse Particles in Pigments, Pastes and Paints Standard Test Methods for Chemical Analysis of Cuprous Oxide and Copper Pigments Standard Test Methods for Chemical Analysis of Mercuric Oxide Pigment (canceled) Specification for RubberLined Fire Hose with Woven Jacket Standard Test Method for Relative Hiding Power of Paints by the Visual Evaluation of Brushouts Standard Test Method for Shrinkage Factors of Soils Standard Test Methods for Chemical Analysis of Zinc Yellow Pigment (Zinc Chromate Yellow) Standard Test Method for Sieve Analysis of Granular Mineral Surfacing for Asphalt Roofing Products Standard Specification for Zinc Yellow (Zinc Chromate) Pigments Standard Test Methods for Sampling and Testing of Flaked Aluminum Powders and Pastes Standard Test Methods for Chemical Analysis of Zinc Dust (Metallic Zinc Powder) Standard Test Methods for Mandrel Bend Test of Attached Organic Coatings Standard Test Method for Specular Gloss
Standard Guide for Testing Drying Oils Standard Test Methods for Consistency of Paints Using the Stormer Viscometer Standard Test Methods for Liquid Paint Driers Standard Practice for Preparation of Cold-Rolled Steel Panels for Testing Paint, Varnish, Conversion Coatings, and Related Coating Products Standard Test Method for Evaluating Degree of Rusting on Painted Steel Surfaces (SSPC-Vis-2) Standard Test Method for Evaluating Degree of Checking of Exterior Paints Standard Test Method for Evaluating Degree of Cracking of Exterior Paints Standard Test Method for Evaluating Degree of Erosion of Exterior Paints Standard Test Method for Compressive Properties of Rigid Plastics Standard Test Method for Evaluating Degree of Blistering of Paints Standard Test Methods for Analysis of Barium Sulfate Pigment Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 620
SSPC CHAPTER*27-3 93 W D716 Standard Test Methods for Evaluating Mica Pigment D717 Standard Test Methods for Analysis of Magnesium Silicate Pigment D718 Standard Test Methods for Analysis of Aluminum Silicate Pigment D719 Standard Test Methods for Analysis of Diatomaceous Silica Pigment D767 (canceled) Specifications for Venetian Red D768 Standard Specification for Yellow Iron Oxide Hydrated D772 Standard Test Method for Evaluating Degree of Flaking (Scaling) of Exterior Paints D785 Standard Test Method for Rockwell Hardness of Plastics and Electrical Insulating Materials (canceled) Method of Evaluating Degree of Abrasion, Erosion or a Combination of Both in Road Service Tesis of Traffic Paint D822 Standard Practice for Conducting Tests on Paint and Related Coatings and Materials Using Filtered Open-Flame Carbon-Arc Light and Water Exposure Apparatus D823 Standard Practices for Producing Films of Uniform Thickness of Paint, Varnish and Related Products on Test Panels 0870 Standard Practice for Testing Water Resistance of Coatings Using Water Immersion D879 (canceled) Specifications for Communication and Signal Pin-Type Lime-Glass Insulators Standard Test Methods for Specific Gravity, Apparent, of Liquid Industrial Chemicals D913 Standard Test Method for Evaluating Degree of Resistance to Wear of Traffic Paint D968 Standard Test Methods for Abrasion Resistance of Organic Coatings by Falling Abrasive D970 Standard Test Methods for Para Red and Toluidine Red Pigments
01014 Standard Test Method for Conducting Exterior Exposure Tests of Paints on Steel D1044 Standard Test Method for Resistance of Transparent Plastics to Surface Abrasion D1084 Standard Test Methods for Viscosity of Ad hesives D1135 Analysis of Blue Pigments 8627940 0004068 D1150 D1200 D121O D1296 D1301 D1308 D1394 D1474 D1475 D1545 D1640 D1648 D1649 D1653 D1737 D1844 D1845 D1849 D2090 02092 D2134 D2196 Standard Test Methods for Chemical D2197 D2200 Visual 621 --`,,,,`-`-`,,`,,`,`,,`--L3T = (canceled) Standard Single- and MultiPanel Forms for Recording Results of Exposure Tests of Paints Standard Test Method for Viscosity by
Ford Viscosity Cup Standard Test Method for Fineness of Dispersion of Pigment Vehicle Systems Standard Test Method for Odor of Volatile Solvents and Diluents Standard Test Methods for Chemical Analysis of White Lead Pigments Standard Test Method for Effect of Household Chemicals on Clear and Pigmented Organic Finishes Standard Test Methods for Chemical Analysis of White Titanium Pigments Standard Test Methods for Indentation Hardness of Organic Coatings Standard Test Method for Density of Paint, Varnish, Lacquer, and Related Products Standard Test Method for Viscosity of Transparent Liquids by Bubble Time Method Standard Test Methods for Drying, Curing or Film Formation of Organic Coatings at Room Temperature Standard Specification for Basic Lead Silico Chromate Pigment Standard Specification for Strontium Chromate Pigment Standard Test Methods for Water Vapor Transmission of Organic Coating Films (canceled) Method of Test for Elongation of Attached Organic Coatings with Cylindrical Mandrel Apparatus (replaced by 0522) Standard Test Methods for Chemical Analysis of Basic Lead Silicochromate Standard Test Methods for Chemical Analysis of Strontium Chromate Pigment Standard Test Method for Package Stability of Paint Standard Test Method for Clarity and Cleanness of Paint and Ink Liquids Standard Practice for Preparation of Zinc-Coated Steel Surfaces for Painting (canceled) Test Method forSofteningof Organic Coatings by Plastic Compositions Standard Test Methods for Rheological Propert ies of Non-Newtonian Materials by Rotational (Brookfield) Viscometer Standard Test Method for Adhesion of Organic Coatings by Scrape Adhesion Standard for Abrasive Blast Cleaned Steel (SSPC-Vis 1) Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*27-3 93 8627940 0004069 O76 Standard Test Method for Rubber Property -Durometer Hardness Standard Test Method for Calculation of Color Differences from Instrumentally Measured Color Coordinates Standard Practice for Testing Water Resistance of Coatings in lOOO/o Relative Humidity Standard Test Method for Volatile Content of Coatings Standard Test Method for Pigment Content of Solvent-Reducible Paints Standard Test Method for WaterSoluble Salts in Pigments by Measuring the Specific Resistance of the Leachate of the Pigment Standard Test Method for Identification of Carboxylic Acids in Alkyd Resins Standard Practice for Description and Identification of Soils (Visual-Manual Procedu re) Standard Test Method for Infrared Identification of Vehicle Solids from SolventReducible Paints D2698 --`,,,,`-`-`,,`,,`,`,,`--Standard Test Method for Determination of the Pigment Content of SolventReducible Paints by High-speed Centrifuging D2742 (canceled) Method for Chemical Analysis of Tribasic Lead Phospho Silicate D2744 (canceled) Specification for Tribasic Phospho Silicate D2792 Standard Test Method for Solvent and Fuel Resistance of Traffic Paint D2801 (canceled) Test Method for Leveling Characteristics of Paint by the Draw Down Method (replaced by 4400) 02805 Standard Test Method for Hiding Power of Paints by Reflectometry D3134 Standard Practice for Establishing Color and Gloss Tolerances 03168 Standard Practice for Qualitative Identification of Polymers in Emulsion 03271 Standard Practice for Direct Injection of Solvent-Reducible Paints into a Gas
D2240 02244 D2247 02369 D2371 D2448 02455 D2488 D2621 D3843 D3911 D3912 D3960 D4082 D4227 D4228 D4256 04400 D4417 D4537 D4541 D4940 D5043 D6222 El 62 E307 E308 Standard Practice for Quality Assurance for Protective Coatings Applied to
Nuclear Facilities Standard Test Method for Evaluating Coatings Used in Light-Water Nuclear Power Plants at Simulated Design Basis Accident (DEA) Conditions Standard Test Method for Chemical Resistance of Coatings Used in LightWater Nuclear Power Plants Standard Practice for Determining Volatile Organic Compound (VOC) Content of Paints and Related Coatings Standard Test Method for Effects of Gamma Radiation on Coatings for Use in Light-Water Nuclear Power Plants Standard Practice for Qualification of Journeyman Painters for Application of Coatings to Concrete Surfaces of Safety-Related Areas in Nuclear Facilities Standard Practice for Qualification of Journeyman Painters for Application of Coatings to Steel Surfaces of SafetyRelated Areas in Nuclear Facilities Standard Test Method for Determination of the Decontaminability of Coatings Used in Light-Water Nuclear Power Plants Standard Test Method for Sag Resistance of Paints Using a Multinotch Applicator Field Measurement of Surface Profile of Blast Cleaned Steel, Test Methods for Standard Guide for Establishing Procedures to Qualify and Certify Inspection Personnel for Coating Work in Nuclear Facilities Standard Test Method for Pull-off Strength of Coatings Using Portable Adhesion Testers Standard Test Method for Condumetric Analysis of Water Soluble Ionic Contamination of Blasting Abrasives Standard Test Methods for Field Identification of Coatings (canceled) Methods of Testing Automotive Airbrake and Vacuum Brake Hose (Flexibility) Standard Test Method for Surface Flammability of Materials Using a Radiant Heat Energy Source Standard Test Method for Normal Spectral Emittance at Elevated Temperatures Standard Test Method for Computing the Colors of Objects by Using the CIE System 03274
03359 D3363 D3842 Chromatograph for Solvent Analysis Standard Test Method for Evaluating Degree of Surface Disfigurement of Paint Films by Microbial (Fungal or Algal) Growth or Soil and Dirt Accumulation Standard Test Methods for Measuring Adhesion by Tape Test Standard Test Method for Film Hardness by Pencil Test Standard Guide for Selection of Test Methods for Coatings for Use in LightWater Nuclear Power Plants Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 622
SSPC CHAPTER*27*3 93 Ab27940 0004070 898 = Bureau of Reclamation M-54 VR-3 Vinyl Resin Paint M-55 VR-6 Vinyl Resin Paint California Department of Transportation E376 Standard Practice for Measuring Coating Thickness by Magnetic-Field or Eddy-Current (Electromagnetic) Test Methods G6 Standard Test Method for Abrasion Resistance of Pipeline Coatings G8 Standard Test Methods for Cathodic Disbonding of Pipeline Coatings G9 Standard Test Method for Water Penetration into Pipeline Coatings G1O Standard Test Method for Specific Bendability of Pipeline Coatings G11 Standard Test Method for Effects of Outdoor Weathering on Pipeline Coatings G13 Standard Test Method for Impact Resistance of Pipeline Coatings (Limestone Drop Test) G14 Standard Test Method for Impact Resistance of Pipeline Coatings (Falling Weight Test) G17 Standard Test Method for Penetration Resistance of Pipeline Coatings (Blunt Rod) G18 Standard Test Method for Joints, Fittings and Patches in Coated Pipelines G19 Standard Test Method for Disbonding Characteristics of Pipeline Coating by Direct Soil Burial G20 Standard Test Method for Chemical Resistance of Pipeline Coatings G53 Standard Practice for Operating Lightand Water-Exposure Apparatus (Fluorescent UV- Condensation Type) for Exposure of Nonmetallic Materials American Water Works Association (AWWA) AWWA C203 Coal-Tar Protective Coatings and Linings for Steel Water Pipelines -Enamel and Tape Hot-Applied AWWA C205 Cement-Mortar Protective Lining and Coating for Steel Water Pipe AWWA C206 Field Welding of Steel Water Pipe AWWA C209 Cold-Applied Tape Coatings for the Exterior of Special Sections, Connections and Fittings for Steel Water Pipelines ANSIIAWWA Extruded Polyolefin Coatings for the ExC215 terior of Steel Water Pipelines AWWA C602 Cement-Mortar Lining of Water Pipelines
AWWA D102 (withdrawn) Painting Steel Water(CALTRANS) Paint 721 -80-62 Paint PWB-72 Paint Paint Paint Paint Paint
PWB-83 PWB-86 PWB-88 PWB-89 PWB-142
Paint PWB-143 Paint PWB-145 Paint PWB-146 (deleted for most purposes) Phenoxy or Catalyzed Epoxy Zinc-Rich Primer Paint Water Borne, Replaced by PWB-142 Green Finish Paint -Water Borne White Tintable Finish Paint, (Revised) Replaced by PWB-145 Replaced by PW B-146 Red Primer Paint -Water Borne, Chromate Free Pink Primer Paint -Water Borne, Chromate Free Red Primer -Water Borne, Formula PWB-145 Pink Primer Paint -Water Borne -Formula PWB-146 Canadian General Standards Board (CGSB) --`,,,,`-`-`,,`,,`,`,,`--1 -GP-14 1 -GP-40 CANICGSB 1.40-M89 1-GP-59 CANICGSB 1.59-M89 1 -GP-69 CANICGSB1.69-M89 1 -GP-122 CANICGSB 1.122-M91 1 -GP-140 CAN ICGSB 1.140-M89 1 -GP-166 1 -GP-l66M 1 -GP-167
1 -GP-171 1 -GP-171 M and amendment 1 -GP-182 1 -GP-l82M (Withdrawn) Primer, Red Leadin Oil NOW: CANKGSB -1.40-M89 Primer, Structural Steel, Oil Alkyd Type, NOW: CANKGSB -1.59-M89 Enamel, Exterior, Gloss, Alkyd Type NOW: CANKGSB -1.69-M89 Paint, Aluminum NOW: CANKGSB -1.122-M91 Primer, Vinyl, Anti-Corrosive NOW: CAN KGSB -1.140-M89 Primer, Red Lead, Iron Oxide, Oil Alkyd Type NOW: 1-GP-166M Primer, Basic Lead Silico Chromate, Oil Alkyd Enamel, Exterior, Basic Lead Silico Chromate, Alkyd Type Now: 1-GP-171M and amendment Coating, Inorganic Zinc NOW: 1-GP-182M Vinyl, Exterior Paint, Storage Tanks (being Revised) Canadian Institute of Steel Construction (CISC) American Welding Society (AWS) CISCKPMA Quick-Drying One-Coat Paint for Use AWS C2.14 Corrosion Test of Flame-Sprayed Coat- 1 -73a with Structural Steel ed Steel Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 623
SSPC CHAPTERa27-3 73 8627740 000407L 724 = Code of Federal Regulations (CFR) Federal Specifications and Commercial Item Nuclear Regulatory Commission Descriptions 10 CFR 0-50 Nuclear Regulatory Commission Regu- FED-CTD-141 lations Food and Drug Administration (FDA) FED-STD-595 21 CFR 175 Indirect Food Additives: Adhesives and A-A-341 Components of Coatings BB-A-1034 Occupational Safety and Health Administration (OSHA) L-(2-530 P-c-111 29 CFR Part Safety and Health Regulations for P-C-4361900-1910 General Industry (1 901.1 to P-c-437191 0.999) 29 CFR Part SS-P-385 1910.1 O00 to End 29 CFR 1926 Safety and Health Regulations for TT-C-490 Construction Environmental Protection Agency (EPA)* TT-C-542 40 CFR 50-99 Air Pollution Control Regulations 40 CFR Clean WaterActlSafe Drinking WaterAct TT-E-489 100-1 49 Regulations 40 CFR Federal Insecticide, Fungicide and TT-E-490 150-1 89 Rodenticide Act (FIFRA) Regulations 40 CFR Resource Conservation and Recovery 260-280 Act (RCRA) Regulations TT-E-529 40 CFR Underground Storage Tank (UST) 280-299 (RCRA) Regulations TT-E-1593 40 CFR Superfund Amendments and Reauthori300-399 zation Act (SARA)/Comprehensive En- TT-L-26 vironmental Compensation and Liability Act (CERCLA) Regulations TT-L-50 40 CFR Clean Water Act (CWA) Regulations 400-699 40 CFR Toxic Substances Control Act (TSCA) TT-P-19 700-799 Regulations TT-P-28 Department of Transportation 49 CFR 172 Hazardous Materials Table, Special TT-P-3 1 Provisions, Hazardous Materials Communications, Emergency Response and TT-P-38
Training Requirements TT-P-8 1 49 CFR 173 Shippers -General Requirements for Shipments and Packagings TT-P-86 49 CFR 178 Specifications for Packagings TT-P-320 49 CFR 179 Specifications for Tank Cars TT-P-595 Compressed Gas Association TT-P-615 G-7.1 Commodity Specification for Air TT-P-636 (U.S. Army) Corps of Engineers c200 Coal Tar Epoxy (Black) Paint TT-P-641 V766 Vinyl-Type White (or Gray) Paint "Including reserved sections 624 Paint, Varnish, Lacquer and Related Materials; Methods of Inspection, Sampling and Testing Colors: (For) Ready-Mixed Paints Pigment, Aluminum, Powder and Paste Compressed Breathing Air Coating, Pipe, Thermoplastic Resin Carbon Removing Compound Cleaning Compound, Alkali, Boiling Vat (Soak) or Hydrosteam Cleaning Compound, High Pressure (Steam) Cleaner (canceled) Pipe, Steel, (Cement-Mortar Lining and Reinforced Cement-Mortar Coating) Cleaning Methods for Ferrous Surfaces and Pretreatments for Organic Coatings Coatin g , PoIy u ret ha ne, OiI-F r ee , Moisture Curing Enamel, Alkyd, Gloss, Low VOC Content Enamel, Silicone Alkyd Copolymer, Semigloss (For Exterior and Interior Non-Residential Use) Enamel, Alkyd, Semigloss, Low VOC Content Enamel, Silicone Alkyd Copolymer, Gloss, (For Exterior and Interior Use) Lacquer (Brushing, Clear and Pigmented For Exterior and Interior Use) Lacquer, Nitrocellulose, Acrylic and Acrylic-Butyrate, Aerosol (in Pressurized Dispensers) Paint, Latex (Acrylic Emulsion, Exterior Wood and Masonry) Paint, Aluminum, Heat Resisting (1200 Deg. F)
Paint, Oil: Iron-Oxide, Ready-Mixed, Red and Brown Paint, Aluminum (Ready-Mixed) Paint, Oil, Alkyd, Ready Mixed, Exterior, Medium Shades Paint, Red-Lead-Base, Ready-Mixed, (canceled) Pigments, Aluminum: Powder and Paste, for Paint (use A-A-341) Preservative Coating, Canvas (canceled) Primer Coating: Basic Lead Silico Chromate, Ready-Mixed (canceled) Primer Coating, Alkyd, Wood and Ferrous Metal (use TT-P-664 and MIL-P-53030) Primer Coating, Zinc Dust-Zinc Oxide (For Galvanized Surfaces) Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERx27.3 73 8627940 0004098 9-77oe TT-P-645 TT-P-664 TT-P-1046 TT-P-1757 TT-P-2784 TT-S-711 TT-S-1543 TT-V-51 TT-V-81 TT-V-119 Primer, Paint Zinc-Molybdate, Alkyd Type (revised to replace zinc chromate with zinc molybdate) Primer Coating, Alkyd, CorrosionInhibiting, Lead and Chromate Free, VOC-Compliant Primer Coating: Zinc Dust, Chlorinated Rubber, (For Steel and Galvanized Surfaces) Primer Coating, Zinc Chromate, LowMoisture-Sensit ivity Enamel (Acrylic Emulsion, Exterior Gloss and Semigloss) Stain; Oil Type, Wood, Interior Sealing Compound: Silicone Rubber Base (For Caulking, Sealing and Glazing in Buildings and Other Structures) Varnish: Asphalt Varnish: Mixing, for Aluminum Paint Varnish, Spar, Phenolic-Resin (US.) Maritime Administration 52-MA-602 (canceled) Compounds: Rust Preventive (U.S.) Military Specifications DOD-C-24596 MIL-C-24667 MIL-C-38334 MIL-C-43616 MIL-C-46081 MIL-C-46156 MIL-C-46168
MIL-C-46487 MIL-C-81302 MIL-C-85285 MIL-C-87936 MIL-D-23003 MIL-D-24483 MIL-D-24667 DOD-E-699 MIL-E-15090 MIL-E-15145 MIL-E-17970 MIL-E-17971 DOD-E-1821O DOD-E-24607 MIL-E-24635 MIL-F-902 MIL-H-13528 MIL-L-14486 Coating Compounds, Nonflaming, FireProtective (Metric) Coating System, Non-Skid, For Roll or Spray Application (Metric) Corrosion Removing Compound, Prepaint, For Aircraft Aluminum Surfaces Cleaning Compounds, Aircraft Surface Coating Compound, Thermal Insulating (Intumescent) Corrosion Removing Compound, Sodium Hydroxide Base, For Immersion Ap-
plication Coating, Aliphatic Polyurethane, Chemical Agent Resistant Cleaning, Preparation and Organic Coating of Steel Cartridge Cases Cleaning Compound, Solvent, Trichlorotrifluoroethane Coating: Polyurethane, High-Solids Cleaning Compounds, Aircraft Exterior Su rfaces, Water Di1 u table Deck Covering Compound, Nonslip, Rollable (Reinstated) Deck Covering, Spray-On, Nonslip Coating System, Non-Skid, For Roll or Spray Application (Metric) (canceled) Enamel, Exterior, Deck, Gray (Formula No. 20) (Metric) (use DODE-24635 and FED-STD-595) Enamel, Equipment, Light-Gray (Formula No. 111) (canceled) Enamel, Zinc Dust Pigmented, Fresh Water Tank Protective, Formula No. 102 (canceled) Enamel, Nonflaming (Dry), Chlorinated Alkyd Resin, Soft White, Semigloss, Formula No. 124/58 (use DOD-E-24607) (canceled) Enamel, Nonflaming (Dry), Chlorinated Alkyd Resin, Pastel Green, Semigloss, Formula No. 7 26/58 (use DOD-E-24607) (canceled) Enamel, Interior, Deck, Red (Formula No. 23) (Metric) (use MILE-24635 and FED-STD-595) Enamel, Interior, Nonflaming (Dry), Chlorinated Alkyd Resin, Semigloss (Metric) Enamel, Silicone Alkyd Copolymer (Metric) Furniture, Shipboard, Aluminum; General Specification For Hydrochloric Acid, Inhibited, RustRemoving (canceled) Lacquer, Vinyl Resin, SemiGloss (use MIL-C-46168) M IL-STD-33 8 MIL-STD-2138 MIL-A-8625 MIL-C-10578 MIL-C-11 O90 MIL-C-11796 MIL-C-13924 MIL-C-14460
MIL-C-16173 MI L-C-1750 4 MIL-(2-19537 MIL-C-19565 DOD-C-22325 MIL-C-22542 MIL-C-22750 Cleaning and Treatment of Aluminum Parts Prior to Painting Metal Sprayed Coating System for Corrosion Protection Aboard Naval Ships Anodic Coatings, For Aluminum and Aluminum Alloys Corrosion Removing and Metal Conditioning Compound (Phosphoric Acid Base) Cleaning Compound, Degreasing and Depreserving Solvent Corrosion Preventive Compound, Petrolatum, Hot Application Coating, Oxide, Black, for Ferrous Metals Corrosion Removing Compound, Sodium Hydroxide Base, For Electrolytic or Immersion Application Corrosion Preventive Compound, Solvent Cutback, Cold-Application Coating Compound, Acrylic, Clear Lacquer: Acrylic-Nitrocellulose Gloss (For Aircraft Use) Coating Compounds, Thermal Insulation, Fire- and Water-Resistant, VaporBarrier Colors, Tinting, For Interior Nonflaming (Dry) Paints (Metric) Cleaning Compound, High Pressure Cleaner, Liquid Coating, Epoxy, VOC-Compliant Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 625
SSPC CHAPTERa27-3 73 m 8627740 0004079 803 m MIL-L-19537 MIL-P-15147 DOD-P-15328 MIL-P-15929 MIL-P-15930 MIL-P-15931 MIL-P-1618 9 DOD-P-16232 DOD-P-17545 MIL-P-19451 MIL-P-19452 MIL-P-19453 MIL-P-22298 MIL-P-22299 MIL-P-23236 MIL-P-23377 MIL-P-24380 MIL-P-24441 MIL-P-24441/41 DOD-P-24555 DOD-P-24588 Lacquer: Acrylic-Nitrocellulose Gloss (For Aircraft Use) (canceled) Primer and Enamel, Coal Tar (use SSPC-PS 10.01 or AWWA C203) Primer (Wash), Pretreatment (Formula No. 117 for Metals) (Metric) (Equivalent to SSPC-Paint 27) (canceled) Primer Coating, Shipboard, Vinyl-Red lead (Formula No. 11 9) (use MIL-P-15930 or MIL-P-24441) Primer Coating, Shipboard, Vinyl-Zinc Chromate (Formula No.120) Paint, Antifouling, Vinyl (Formulas No. 121, 121A, 129 and 129A) (canceled) Paint, Antifouling, Vinyl, Black (Formula No. 129/63) (use MIL-P-15937) Phosphate Coatings, Heavy, Manganese or Zinc Base (For Ferrous Metals)
(canceled) Primer Coating, Alkyd-Red lead Type Formula No. 116 and No. 116D (Metric) (use TT-P-645) (canceled) Paint, Antifouling, Cold Plastic, Shipbottom Navy Formula No. 105 (canceled) Paint, Antifouling, Hot Plastic, Shipbottom Navy Formula No. 15HPN (canceled) Primer Coating, Shipbottom Paint, Anticorrosive Type I(use MILP-24441, MIL-P-24442) (canceled) Paint, Black, Polyisobutylene (Formula No. 133) (use DOD-P-24631) (canceled) Paint, Antifouling, Polyisobutylene (Formula No. 134) (use DOD-P-24 63 1) Paint Coating Systems, Fuel and Salt Water Ballast (Metric) Primer Coatings: Epoxy, Chemical and Solvent Resistant Paint, Anchor Chain, Solvent Type, Gloss Black (Metric) Paint, Epoxy-Polyamide, General Specification For (canceled) Paint, Epoxy-Polyamide, Black Nonabrasive Nonslip, Formula 163 Type IV (use MIL-C-24667) Paint, Aluminum, Heat-Resisting (650 C) Low Emissivity (0.40 or Less) (Metric) (Reinstated) (canceled) Paint, Antifouling, Vinyl, DOD-P-24648 iJllL-P-28577 MIL-P-28578 MIL-P-38336 MIL-P-53030 MIL-R-15058 MIL-R-19907 MIL-R-21006 MIL-S-5002 MIL-V-1174 Enamel, Silicone and Alkyd Copolymer (Metric) Primer, Water-Borne, Acrylic or Modified Acrylic, For Metal Surfaces Paint, Water-Borne, Acrylic or Modified Acrylic, Semigloss, for Metal Surfaces Primer Coating, Inorganic, Zinc Dust Pigmented, Self Curing, for Steel Surfaces Primer Coating, Epoxy, Water Reducible, Lead and Chromate Free (canceled) Rubber, Shaft Covering Materials (For Marine Propeller) Repair Kit, Glass Reinforced Plastic Laminate
(canceled) Rust Retarding Compound, Flotation Type, Ballast Tank Protective Surface Treatments and Inorganic Coatings for Metal Surfaces of Weapons Systems (canceled) Varnish, Spar, Water Resisting (Formula No. 80) (use TT-V-119) National Association of Corrosion Engineers (NACE) NACE RP0169 NACE RPO178 NACE NACE NACE NACE NACE NACE
RP0274 RP0275 RP0285 RP0287 TMO 70 TMO 75
Control of External Corrosion on Underground or Submerged Metallic Piping Systems Fabrication Details, Surface Finish Requirements, and Proper Design Considerations for Tanks and Vessels to Be Lined for Immersion Service High Voltage Electrical Inspection of Pipeline Coatings Prior to Installation Application of Organic Coatings to the External Surface of Steel Pipe for Underground Service Control of External Corrosion on Metallic, Buried or Submerged Liquid Storage Systems Field Measurement of Surface Profile of Abrasive Blast Cleaned Steel Surfaces Using a Replica Tape Visual Comparator for Surfaces of New Steel Airblast Cleaned with Sand Abrasive Visual Standard for Surfaces of New Steel Centrifugally Blast Cleaned with Steel Grit and Shot Camouflage (Formula No. 170, 171, 172, NSF International 173) (Metric) (use DOD-P-24647) ANSIINSF 61 Drinking Water System Components DOD-P-24631 Paints, Camouflage For Submarines, General Specification For (Metric) --`,,,,`-`-`,,`,,`,`,,`--Health Effects DOD-P-24647 Paint System, Anticorrosive and Antifouling, Ship Hull
Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 626
SSPC CHAPTER*27-3 93 ô627940 0004LOO 355 m Society of Automotive Engineers (SAE) SA J 444 Cast Shot and Grit Size Specifications for Peening and Cleazing, Recommended Practice SA J 827 Cast Steel Shot, Recommended Practice Steel Founders Society of America (SFSA) SFSA 20-66 Cast Steel Abrasives SFSA 21-68 Malleable Iron Abrasives Steel Structures Painting Council (SSPC) Surface Preparation Commentary Solvent Cleaning Hand Tool Cleaning Power Tool Cleaning (cancelled) Flame Cleaning of New Steel White Metal Blast Cleaning Commercial Blast Cleaning Brush-off Blast Cleaning Pic kling Near-White Blast Cleaning Power Tool Cleaning to Bare Metal Guide for Selecting Oil Base Painting Systems Guide for Containing Debris Generated During Painting Operations Three-Coat Oil-Alkyd (Lead- and Chromate-Free) Painting System for Galvanized or Non-Galvanized Steel (With Zinc Dust-Zinc Oxide Linseed Oil Primer) Three-Coat Oil Base Zinc Oxide Painting System (Without Lead or Chromate Pigment) Guide for Selecting Alkyd Painting Syst e ms Three-Coat Alkyd Painting System with Red Lead Iron Oxide Primer (For Weather Exposure) Three-Coat Alkyd Painting System for Unrusted Galvanized Steel (For Weather Exposure) Guide for Selecting Phenolic Painting Systems Guide for Selecting Vinyl Painting Systems Four-Coat Vinyl Painting System (For Fresh Water, Chemical, and Corrosive Atmosp heres) Four-Coat White or Colored Vinyl Painting System (For Fresh Water, Chemical and Corrosive Atmospheres) Black (or Dark Red) Coal Tar EpoxyPolyamide
Guide for Selecting Zinc-Rich Painting Systems SSPC-SP SSPC-SP SSPC-SP SSPC-SP SSPC-SP SSPC-SP SSPC-SP SSPC-SP SSPC-SP SSPC-SP SSPC-SP SSPC-PS Guide 1
COM 1 2 3 4 5 6 7 8 10 11 .O0
SSPC Guide 61 SSPC-PS 1 .O4 SSPC-PS 1.09 SSPC-PS Guide 2.00 SSPC-PS 2.03" SSPC-PS 2.05 SSPC-PS Guide 3.00 SSPC-PS Guide 4.00 SSPC-PS 4.02 SSPC-PS 4.04' SSPC-PS 11 .o1 SSPC-PS Guide 12.00 SSPC-PS 12.01 SSPC-PS 13.01 SSPC-PS 14.01 SSPC-PS Guide 15.00 SSPC-PS 15.01 SSPC-PS
16.01 + SSPC-PS Guide 17.00 SSPC-PS 18.01 SSPC-PS 24.00 SSPC-Paint 1 ' SSPC-Paint 2' SSPC-Paint 5 SSPC-Paint 8 SSPC-Paint 9 SSPC-Paint 11 ' SSPC-Paint 16 SSPC-Paint 17 SSPC-Paint 18 SSPC-Paint 19 SSPC-Paint 20 SSPC-Paint 21 SSPC-Paint 22 SSPC-Paint 23 SSPC-Paint 24 SSPC-Paint 27* SSPC-Paint SSPC-Paint SSPC-Paint SSPC-Paint SSPC-Paint
1O1 102 104 106 108
SSPC-PA 1 SSPC-PA 2 SSPC-PA Guide 3 SSPC-PA Guide 4 SSPC-Guide to
Vis 1-89 SSPC-Guide to vis 2 One-Coat Zinc-Rich Painting System Epoxy-Polyamide Painting System Steel Joist Shop Painting System Guide for Selecting Chlorinated Rubber Painting Systems Chlorinated Rubber Painting System (For Salt Water Immersion) Silicone Alkyd Painting System for New Steel Guide for Selecting Urethane Painting Systems Three-Coat Latex Painting System Latex Painting System for Industrial and Marine Atmospheres, Performance-8ased Red Lead and Raw Linseed Oil Primer Red Lead, Iron Oxide, Raw Linseed Oil & Alkyd Primer Zinc Dust, Zinc Oxide & Phenolic Varnish Aluminum Vinyl Paint White (or Colored) Vinyl Paint Red Iron Oxide Zinc Chromate, Raw Linseed Oil & Alkyd Paint Coal Tar Epoxy-Polyamide Black (or --`,,,,`-`-`,,`,,`,`,,`--Dark Red) Paint Chlorinated Rubber Inhibitive Primer Chlorinated Rubber Intermediate Coat Paint Chlorinated Rubber Topcoat Paint Zinc-Rich Primers (Type I-Inorganic & Type II-Organic) White or Colored Silicone Alkyd Paint Epoxy-Polyamide Paints (Primers, Intermediate & Topcoat) Latex Primer for Steel Surfaces Latex Semi-Gloss Exterior Topcoat Basic Zinc Chromate-Vinyl Butyral Wash Primer Aluminum Alkyd Paint Black Alkyd Paint White or Tinted Alkyd Paint Black Vinyl Paint High-Build Thixotropic Leafing Aluminum Paint Shop, Field & Maintenance Painting Measurement of Dry Paint Thickness with Magnetic Gages A Guide to Safety in Paint Application
Guide to Maintenance Repainting with Oil Base or Alkyd Painting System Visual Standard for Abrasive Blast Cleaned Steel Standard Method of Evaluating Degree of Rusting on Painted Steel Surfaces Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 627
SSPC CHAPTERx27-3 93 8627940 0004101 291 Steel Tank Institute STI-P3 Standard for Dual Wall Underground . . Steel Storage Tanks Underwriters Laboratory UL 45 Standard for Safety of Portable Electric Tools These painting systems and paints use chromate pigments, toxic substances that are closely regulated. Users are urged to follow all health, safety and environmental requirements in applying, handling or disposing of these materials +These painting systems and paints use lead pigments. It has become evident over the last several years that the hazards and precautions associated with leaded paints outweigh their merits. Leaded paint poses a health hazard both to those who apply it and those who remove it. Containment and disposal requirements add significantly to the cost of using leaded paint. SSPC has proposed to withdraw all SSPC specifications for leaded paint. Under this proposal, all specifications for paints that contain lead would be withdrawn. Paints containing lead would also be deleted from SSPC Paint Systems, Guides and Commentaries. If a system offers no non-lead alternatives for a particular use, the system itself would be withdrawn. --`,,,,`-`-`,,`,,`,`,,`--Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*27.3 93 8627940 0004102 128 W 5 3A O> W K 3 t-U K W nH W IE EEEEr r t-uz W -I a W U 4 O O4 n c o Cu x al Y W U 3 ta U
W (z I W ICopyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 629 --`,,,,`-`-`,,`,,`,`,,`---
. SSPC CHAPTERx27.3 öb279LìO 0004L03 Ob4 Index A Abrasion. exposure environments ............340 ............ .51 3.515 .................308 Abrasion resistance ......... .129. 134. 298. 303 . 338. 357. 397 Abrasive air blast cleaning ............. .29 5.296 equipment..................... .248. 250-251 Abrasive blasting. hazards ..................545 Abrasive blast cleaning ...............5 abrasive dusting ................... abrasive flow ...................... abrasive recycling ............ abrasive selection ........................ 52 abrasives .................. .57.58. 83-84. 187 air consumption .......................... 53 air supply .......................... .53. 186 air supply hose .......................... 53 air-fed helmets ...................... .62. 63 anchor patiern ........................... 58 blast couplings ....................... .5 4.55 blast hwds ........................... 56-57 blast hoses ........................... 54-55 blast nozzles ............................ 60 breathing air ............................ 62 choke valves ............................ 56 chromium paints. hazards .............. .7 8.79 compressor size ......................... 53 contaminated dust ........................ 62 control valves ........................ .55.56 conventional nozzle ....................... 60 ...................... 52 efficiency ............................. 58.59 etching ................................. 58 fabricating plants ........................ 243 field painting ....................54.55. 6162 grounding ..................... .54.55.61-62 hazards ....................... .62+ . 7879 helmet ............................ .i7 7.178 hose construction ........................ 54 hoses ................................. 187 lead paints. hazards ................... .7 8-79
metering valves ...................54.56, 187 moisture separato ........... .56. 186 new steel ...... ................ 64 nozzle materials .......................... 55 nozzle orifice size ....................55, i88 nozzle size ........... .............53 oil separators ....................... .56. 186 .............6163 paint residue recovery ................ .78. 87 portable enclosures ....................... 87 pressure pot ........ .............53 procedure .......... ........... 58.59 production rates .... .......... 60. 76 profile ............. .............58 regulations ............................. 283 respirators .............................. 56 safety requirements .......... 6163 silicosis ................................. 78 static electricity ...................... .54.61 steam propelled .......................... 83 variables ............................. 5960 venturi nozzles .................. water curtain ..................... Abrasive feed. centrifug cleaning ........... ............ 22 Abrasive flow ......... ............55 Abrasive handlers. field painting ............. 223 Abrasive injection. water blast cleaning ....... ............... 64 Abrasive cleaning Abrasive cleaning
recovery. centrifugal blast ............................. 23. 25 velocities. centrifugal blast ................................ 24
Abrasive volume. centrifugal blast ......................... 24 ........................ 297 Abrasives. abrasive blast cleaning .........57.58. 83.64 .187 .................... 189 ......................... 57
.....22 2.236 hardness ............................. 57-58 inspection .............. .........187 metallic .............. metallic. anchor pattern . metallic. breakdown ....................3 8.39 metallic. cast steel ...... metallic. characteristics .................... 58 metallic. chemical properties ...............35 metallic. chilled cast iron .............. .32. 34 metallic. common uses . . metallic. consumption rate metallic. cost of wear ..................... 32 metallic. coverage ............... metallic. cut steel wire ........... metallic. de.flashing. ...................... 34 metallic. degree of cleaning ................ 42 metallic. effect of hardness................. 35 metallic. failure ....................... .38.39 metallic. flaking failures ...................38 metallic. flow rates ....................... 37 metallic. fracture failures ...............36. 38 metallic. hardness ........ ..........38 metallic. history .......... metallic. impact energy .................37. 40 metallic. impact life cycle ........ metallic. iron grit ............... metallic. malleable iron ................ .32. 34 metallic. metallic. metallic. metallic. metallic. metallic. metallic. metallic. metallic. metallic. metallic. metallic. metallic. metallic. metallic. metallic. metallic.
microstructure .................... 38 operating mix ..................39-41 physical properties ..........32.34-35 production rates ..................60 profile .......... selection ........ shot peening ..................... 34 size distribution ................ 3941 size specifications size versus coverag size versus impact energy ..........36 steel grit ................. .58.60. 86 steel shot ................... .58.86 surface cleaning .................. 34 surface etching ................... 34 velocity ......................... 35 versus non-metallic
metallic. work mix . . . .32. 37-41. 43-44 metallic. work mix re nt ............40 metallic. zinc shot ........................ 84 non-metallic .................. .45.51. 58. 296 nonmetallic. aluminum oxides ..........46. 48. 52.58.60. 86 non-metallic. angular ...................... 49 nonmetallic.angular versus round ..........46
non-metallic. non.metallic. non.metal1ic. non.metallic.
boiler slags .45. 47 breakdown ...........49 breakdown ...........51 breakdown
non.metallic. by-product ............ .4546. 50 non.metallic. carbon dioxide pellets ..................... .... 83 non.metallic. characteristics ................ 58 non.metallic. chemical propenies .........48. 50 non-metallic. cherry pits ...................84 non.metallic. coal slag ............. .58. 60. 62 non.metallic. consumption rates .............60 non.metallic. copper slags .... .47. 48. 58. 60. 62 non.metallic. corncobs .......... non.metallic. degree of cleaning . non.metallic. dense versus light . . nonmetallic. density ............ non.metallic. dusting ...................... 50 non.metallic. environmental constraints ............................ 48 evaluation tests ....... -51 flint .................. 60 foundry castings ..............47 free silica .................48. 50 garnets ........... .454 6. 48. 52 . glass beads hard versus SOA...............46 hardness heavy mineral .................. 4546. 48 nonrmetallic. ice particles .............. .E3.84 non.metallic. non.metallic. non.metallic. non.metallic. non.metallic. non.metallic. non.metallic. non.metallic. non.metallic. sands non.metallic. non.metallic. non.meta1lic. non.metallic.
non.metallic. non.rnetal1ic. non.metallic. non.metallic. non.metallic. non.metallic. non.metallic. non.metallic. non.metallic. non.metallic. non.metallic. non.metallic. non.metallic. non.metallic. non.metaliic. non.metallic. non.metallic. non.metallic. non.metal1ic. impact ...................... 49 large versus small ............. 47 limestone .................... 58 magnetite .................... 45 magnesium silicate ............58 manufactured ...........45-46. 50 metal smelting slags ...........45 millscale surfaces .............47 naturally occurring ........ .45. 50 nickel slags .............. .47. 58 novaculite .................... 45 painted surfaces ..............47 peach pits ............ pH values ............. physical properties ...... plastic pellets ................. 85 production rates ..............60 profile .................... 47-48 recycling ..................... 48 rusted surfaces ....... .47 sands ....................... 45 selection ..................46-48 shape .... ............46 non.metallic. non.metallic. non.metallic. non.metallic. non.metallic. non.metallic.
sieve analy silica sands ........... .45. 52. 60 silicon carbide ......... .46. 48 .58 size ............. 4647 size slag
nonmetallic. soluble chloride ...............50 nonmetallic. staurolite ...
non.metallic. surface finish .................47 non.metallic. toxic contaminants ............50 non.meta1lic. walnut shells ....... .4M. 58. 84 non.metallic. zinccoated ................... 84 non.metallic. zircon .................... 45-46 non.metallic. zirconium .................... 58 pH ................... ...........57 recycling ............. ....... .61. 86 shape ............. .........57.58 specific gravity ....................... .57.58 water blast cleaning ...................... 65 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTER*27.3 93 Ab27940 0004104 TTO Acceptance tests. paints ............... .21 3.221 cleanliness. blotter test pri mers ............... Accessibility. pipeline painting ...............351 spray painting ....... prime rs. formulation .... Access and rigging, hazards ............... 546 Air-powered tools .............. ........... 297 Antifouling coatings ............. .6.298.299. 592 falls................................... 547 Air-wash separator. cenlri Federal Insecticide. Fungicide and guardrails. ............................. 547 blast cleaning ....... ......23.25 Rodenticide Act ....................... 592 ladders ................................ 546 Air-water-sand blast cleaning ..... .........79.81 foulant release coatings ..................592 lines and lanyards ....................... 547 Airless spray. application produc tion Organotin Antifouling Paint Act ............592 safety belts ............................ 547 rates ............................ ...... 160 regulation .............................. 592 safety nets ............................. 547 compa!ison with air spray ........ .........162 zebra mussels .......................... 592 Accessories, ladders ....................... 168 equipmenl.............. Appeara nce in container. paints. tests ........212 scaffolding ............................. 169 field painting ............ Appear ance properties, binders ..............121 Accidents, painting bridges .................290 gun ........................... ........ 157 Appearance. painting ...................... 280 Acid cleaners, solvent cleaning ...............91 paint application ............ ... .157. 159-1 60. Application characteristics, Acid concentration, effect on 194. 196 paints, tests ........................ pickling rate ....................... .10 7-108 safety ......................... .... 176. 544 Application equipment, paints ........... Acid embrittlement, pickling .................11 1 spray technique ............. ............ 165 Application properties. binders . . Acrylic emulsion, paints .................38 1-382 Alcohols. solvents .......... ............... 123 qualify control .......................... 252 Acrylic epoxy, paints ....................... 431 Application-related paint fail ures ......... .50 5-51 0 Additives, toxic materials ................... 179 Application technique .air sp ray ..............164 Adhesion failures ...................... .14, 66 adducts and polyamides . ...... ....541 inside corners .......................... 164 causes ................................. 11 inspection.......................... .... 196 Adhesion failures ............... .14, 66. 495-500 urethane binders ........ ... ..ll 9-120 Application, paint ..................... .15 0-1 67 Adhesion, chemically bonded. ...... Applicator. evaluation ..................... . 357
cross-cut test .................. surface preparation ...................... 105 Apprenticeship training of painters ...........249 effect of rust inhibitors ................ .66. 81 Alkali silicate. zinc-rich pr imers .............12-13 Approval. painting programs ................ 421 effect of surface contaminants .............. 10 Alkyd. binders ............... .118. 121-122 .138 Architectural and Industrial paint to metal ............................ i0 paints ..................... .15. 381-382. 416 Maintenance Coatings .................... 564 penknife test ........................... 204 vehicles ......................... ...... 338 Clean Air Act ...................... .558. 560 physical ................................ 10 Alkyd paints. health hazards ...... ...... .54 0-541 National Ambient Air Quality testing ............................ 204, 341 Alkyl silicates. zinc-rich primers .......... .13. 127 Standards .......... .558,560. 562.568.571 zinc-rich primers ................. .13. 133-135 Alligatoring. failures ........ ........... .489-490 Arch span bridges ......................... 280 Adjustable wheels. Centrifugal Aluminum oxides. non-metallic Aromatic. hydrocarb on solvents ..............123 blast cleaning ........................... 27 abrasives .............. .46. 48. 52. 58. 60.86 urethane binders ................... .11 9-120 Administration. painting programs ............396 Aluminum-related failures .... ............... 501 Asphalt enamel, paints ..................... 351 Aerial supports, bosun's chairs .............. 171 Aluminum. coatings. thermal s pray .......457-458. Asphalt mastic, extruded ................... 353 rigging........................ .168, 170-171 460-461. 463 paints .............. .............. .35 2-353 safety............................. .17 3-1 74 flake pigments .................. ........ 144 ASTM-D 1640 ............................ 205 scaffolding......................... .17 1-174 ladders ......................... ....... 168 Atlas Test Cell ....................... .32 2-323 work cage .......................... 171-172 painting ...................... .14 5, 434. 524 Atmospheric weathering, paints, After-blast primers .................... .29 5-296 pigments .................... ...... 1 17. 338 tests .................................. 358 Agitation. effect on pickling rate ......... .10 7-108 surface preparation ..... .............387. 400 Atmospheric exposure environments ..... .338-339, Air and Waste Management Association. Ambient conditions measurements. 381-382, 385 address .............................. 592 inspection .......................... 183-185 Atmospheric exposure environments, Air consumption versus nozzle Ambient curing. zinc-rich paints ................. ................ 347 size, blast cleaning ....................... 53 primers ........................ ... .12 6-127 Automatic spray .......................... 257 Air consumption, abrasive blast American Bureau of Shipping Azelaic acid ....... ...................... 138 cleaning ................................ 53 survey requirements ...............
. .294. 299 Air fed respirators, respiratory American Conference of Governmental protection ......................... .17 7-178 Industrial Hygienists ........... ......123, 538 Air powered machines, rotary American National Standards cleaning tools ........................ .7 1-72 Institute ...................... .......... 72 Air pressure. adjustment, spray American Petroleum Back to back angles. coating failures ......... 512 technique .............................. 165 Institute. address ................ ........ 592 Bacterial cleaning. surface Air quality American Railway Bridge and preparation .......................... . 84.85 lead....................... 560, 562,56 8-569 Building Association ............. ... .263. 269 Bacterial.exposure environments ............429 ozone and volatile organic compounds ......561 American Railway Engineering Ball ast tanks. ships. painting ................ 305 particulates. ................560.562, 569-571 Association...................... ....... 263 Barges. fresh water service .................307 Air quality monitoring. ................. .56 8-571 American Society for Testing paint residue recovery ..................... 87 duration of testing and placement and Materials ........................... 216 ..............309,31 1-312 of monitors ........................... 571 address ............................ ... 450 gments ...............141 lead .................................. 568 American Society of Safety Engineers ........ 554 Barrier. coatings ............................ 4 need. for paint removal .............. -570-571 American Water Works Association ...........315 paints .................. .lo-11,280. 298, 331 particulates ........................ .57 0-571 address ........................ ....... 592 paints, choice of vehicle ................... 11 Air quality regulations ..................56 0-572 Ammonium silicates. zinc-rich primers ................................. 10 Clean Air Act.. .................... .558,560 primers .......................... . .12 6-127 protection, zinc-rich primers ................ 13 Clean Air Act Amendments ........558. 560-565 Analysis. pickling baths ......... ... .108-110. 112 thermal spray coatings ...................458 federal ........................ .558, 560-572 Anatase titanium dioxide. pigment s ...........140 Barriers, safety ........................... 180 hazardous air pollutants ......558, 560-562, 564 Anchor pattern. abrasive blast Basic lead silico-chromate lead .............. .558, 560-561, 568-569, 571 cleaning ....................... ........ 58 pigments...................... .140-141.245 National Ambient Air Quality measurements ..................189. 192-193 Batelle Memorial Institute ................... 133 Standards ........... .558, 560. 562, 568-569 metallic abrasives ............... .. .37.40-41 Baths. immersion. phosphating ..............100 ozone and VOCS ................ .558.561-567 Angle of impingement. centrifugal s
pray. phosphating ...................... 100 particulates .................... .558, 569-570 blast cleaning ................. .......... 23 Beam span, bridges ....................... 280 state and local .................. Angular versus round, non-metallic Bendabilit y, paints, tests .................... 357 Air spray, application production rates ........ 160 abrasives ................. ............. 46 Bids................................. 238-240 application technique .................16 4-165 Angular. non-metallic abrasives ...............49 invitation for ............................ 238 comparison with airless spray .............162 Angular profiles ................ .. maintenance painting .................... 426 . equipment., ....................156-162. 194 Animal bristles. brushes ........ ............. 93 Bilge areas. ships. painting .................304 field painting ........................... 223 Anodic areas. corrosion ......... .........5. 365 Binders ............................. .118-120 gun ................................... 156 Anodic inhibitors. pigments ........ ...6.138. 146 acrylic latex ........................ .12 1-122 paint application ............... .156-157.160. Anodic passivation ............. ........... 142 aliphatic urethane ............. 194.196 adsorption ............................. 143 alkyd ..................... . 1 Ai: supply couplings, abrasive blast precipitation ............. appearance prop erties ........ cleaning ................................ 53 Anodic reactions. corro application properties .................... 121 Air supply hose, abrasive blast cleaning ........53 Anlicorrosion, paints . cata lyzed epoxy ......................... 391 Air supply, abrasive blast cleaning ....... .53, 188 pigments................... 117,122. 138-1 49 chlorinated rubber ...............119, 121-122 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERx27.3 93 I8627940 0004L05 937 m coal tar epoxy .......................... 1 18 comparisons............................ 120 curing methods ..................... .ll7.118 dermatitic materials ...................... 181 durability .................. epoxy ................................ 118 epoxy ester ...... ...........118, 391 epoxy lacquer .......................... 11 8 epoxy polyamide ........................ 118 epoxy polyamine ........................ 118 inorganic .............. inorganic silicate ........ 146, 245 long oil alkyd .......................... 391 oil-based ............................... 119 oiticica oil .............................. 117 paints ................................. 117 performance properties ...................121 phenolic ................ .119, 121-122 polyurethane ........................... 119 primer, purpose of ....................... 243 polyvinyl butyral ......................... 243 safety ................................. 176 silicone ................................ 119 sjlicone alkyd ........................... 119 styrene-based .......................... 1 19 thermoplastic .......... thermosetting .......... ............ 11 toxic materials ......... ...........179 tung~il................................ 138 two-component epoxy ........... .ll8, 121-122 urethane............................... 119 vinyl .............................. .12 0-122 vinyl acetate ............................ 120 vinyl butyral ............................ 145 vinyl chloride ........................... 120 vinyl copolymer ......................... 391 vinyl-alkyd ............................. 120 water-borne ............................ 147 zinc-rich primers ........................ 131 Bins, painting ............................ 270 Bituminous enamels, paints .................351 Black light test, surface contaminants .........401 Blast cleaning ............................ 273 abrasive air ...................52.63.295-296 abrasive air, equipment ...........248, 250-251 abrasive characteristics ................ .57.58
abrasives, inspection ..................... 187 centrifugal ........................ .22.32.34 closedcycle ............................ 295 dust-free................................ 52 equipment. abrasive air ................ .5 2-63 equipment. centrifugal ............... .24 9.250 equipment, inspection ................186189 equipment. pressure type .........52.55, 57, 59 equipment. suction type .................52.56 equipment, vacuum recovery ......52.56.85-87 field versus shop ........................ 227 inspection.............................. 188 interiors ............................... -60 mechanics. metallic abrasives ........35, 37-38 metallic abrasives ................ .3244, 295 non-metallic abrasives ............. .4551. 296 nozzle size, abrasive consumption ...........53 nozzle size versus air consumption ..........53 regulations ............................. 291 respiratory protection ..................... 52 room .................................. 251 safety ............................. 176.545 selection of metallic abrasives ......38.39. 4243 selection of non-metallic abrasives ... shop versus field .......... versus pickling, paint life ... water ................... water, high pressure .................29 5-297 Blast couplings. abrasive blast cleaning .....54-55 Blast enclosures, centrifugal blast cleaning ............................ .23, 25 Blast furnaces, painting ....... Blast hoods, abrasive blast cleaning ........56-57 Blast hoses, abrasive blast cleaning ........54-55 Blast nozzles, abrasive blast cleaning ..........60 Blast pattern .centrifugal blast cleaning............................. .22-23 Blast wheel. centrifugal blast cleaning ......................... .22.23. 25 Bleeding.failures .......................... 508 Blistering. causes .............. .io.12. 102.103. 105.112. 139 failures ........................... .49 5.498 osmotic ........................... 12 Blotter test. air supply. cleanliness ...........186 Blushing, coal tar epoxy paints ......... .380. 383 Blushing. failures ......................... 508 Boiler slags. nonmetallic abrasives ........45. 47 Boom lift. ground supports ..............16 9.170 Booths. painting .......................... 257 Boottops. painting cyst ...............302
ships. painting ..... ............... 303 Borosilicate pigments . ....... .142 Bosun's chairs. aerial supports ...... .171 painting bridges. ................ .290 Breakdown rates, non-metallic abrasives ............................... 51 Breakdown test. nonmetallic abrasives ........51 Breakdown. abrasives. test for rate ............58 metallic abrasives ..................... .3 8.39 non-metallic abrasives ..................... 49 Breathing air. abrasive blast cleaning .......... 62 Bridge crews. painting. railroad .............. 272 Bridges. arch span ....................... -280 beam span ............................. 280 costs. surface preparation ................ 284 decks ............................. 269. 280 design features ......................... 263 designs for corrosion prevention ...........264 exposure environment. railroad ............264 exposure environments. highway ...... .281. 283 field painting ........................... 283 floor beams ............................ 269 girder ................................. 269 ..................280 ............... 280-292 inspection, highway ............. .281. 288-289 inspection. railroad ...................... 269 laterals ............................... -269 life expectancy. paints. highway ....... .28 7.288 maintenance painting, highway ....... .281.282. 287-288 open deck ....... ............... 280 paint application. highway ................ 284 painting costs. railroad ............269 painting. accidents .. .............. 290 painting. painting. painting. painting.
fire hazards .................... 290 health hazards .............. .28 9.290 ladders ........................ 290 life lines ....................... 290
....290 painting. regulations ..................... 290 painting systems. highway ............ .28 4.288 pre-painting surface conditions, highway........................... .28 1-282 railroad. painting .................... .26 3.279 rigid span .......................
solid deck ....................... statistics. highway ....................... 283 stringers ............................... 269 superstructures ......................... 269 surface preparation ................. .28 3.284 suspension span ........................ 280 through and overhead .................... 280 tonnage and surface area .............26 9.270 truss span ............................. 280 zinc-rich primers .................... .13 5.136 British Iron and Steel Research Association............................. 139 Brush versus spray. paint application ............................. 256 Brush. paint application ............150. 152-1 54, 196.256, 274.275. 284.343 Brushes. animal bristles ..................... 93 application production rates ...............160 Chinese hog .............. .......154 cleanup ............................... 166 horsehair .............................. 154 natural fibers ............................ 93 nylon .............................. 153-154 paint. construction .................. ,153.1 54 paint. conventional .................. .15 3.154 painl, flat ...... ........... .15 3.154 paint. oval ..... ........... .15 3.1 54 paint. sash ............................. i53 paint, wall ......................... .i5 3.154 plastic bristles ............... polyester .......................... .15 3.154 solvent cleaning .......................... 95 wire .................................... 93 wire. hand tool cleaning ................ .68.69 wire. rotary cleaning tools .............. .7 0.71 Buddy system. safety ........ Budgets.painting programs ... Bureau of Reclamation. address ............. 450 specifications ........................... 449 Buried structures .......................... 268 Burn-resistant paints ....................... 303 Burnished. profiles ... ................. 43 Burnishing.power tool cleaning ............... 71 Burrs. hand tool cleaning .................... 68 power tool cleaning ....................... 70 By-product. non-metallic abrasives ...... .4546.50 C
Cable supported scaffolding ............ .17 0.171 Calcium barium phosphosilicate. pigments .............................. 142 Calcium borosilicate. pigments .............. 142 Calcium carbonate. pigments ................ 140 Calcium phosphosilicate. pigments ........... 142 Calcium strontium phosphosilicate . pigments .............................. 142 Calcium zinc molybdate. pigments ........... 142 Calibration, dry film thickness gages ............................. 199-201 Calibration standards. dry film thickness gages .................... .19 9.201 California Air Resources Board ............. 290 California Department of Transportation ...................... .87. 286 Carbon dioxide pellets. non-metallic abrasives ............................... 83 Cargo boxes. barges. painting ............... 312 Cargo carriers. zinc-rich primers ............. 136 Cargo holds. ships. painting ................. 305 Cargo tanks. ships. painting .........293. 304-305 Case hiclories. materials selection ........... 399 zinc-rich primers .................... .13 5.136 Cast steel abrasives .................... .32. 34 Catalysts. safety .......................... 179 Cathode. effect of location upon corrosion ................................ 5 Cathodic areas. corrosion ................5. 365 Cathodic disbonding. paints. tests ............ 358 pipelines ............................... 350 Cathodic inhibitors. pigments ........... .138. 145 Cathodic pigments .......................... 6 Cathodic polarization ...................... 140 Cathodic protection ............267.268. 280. 355 basic theory ....................... .364-365 coatings with .................... .7.363-364 construction of system ............... -372-373 current flow ........................ .36 6-367 design of system ................... .36 9.372 electrical potential ...................36 5.367 evaluating effectiveness ..... galvanic anodes ...........7. 367.368. 370-371.
373.375 hydrogen evolution ...................... 366 impressed current .................7.11. 299. 368.369. 371 .373. 375-376 pigments ........................... 138-139 pipelines .................. .349.350, 365376 pipelines in permafrost .............. sacrificial anodes .................. shipbottoms ...................... stray currents ...................... .37 3.374 system maintenance ................ .37 5-376 system operation ................... .37 5.376 thermal spray coatings ................... 458 throwing power ............ .........7 zinc-rich primers .......6. 13. 129. 131, 133-134 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 632
SSPC CHAPTER*27=3 93 E 8627940 0004106 873 = Cathodic reaction .......................... 10 Cathodic reactions. corrosion of steel ................................ 3-4 Cavitation erosion. exposure environments ...................... .33 9.340 Cellosolve silicates. zinc-rich primers ................................ i27 Cement mortar. application ............. .34 3.344 linings ........................ .332.333. 336 Centrifugal blast cleaning ..............22.32. 34 abrasive feed ............................ 22 abrasive recovery .................... .23. 25 abrasive velocities ........................ 24 abrasive volume ......................... 24 abrasives ............................... 23 adjustable wheels ....................... -27 advantages ............................. 23 air-wash separator .................... .23. 25 angle of impingement ..................... 23 blast enclosure ...................... .23. 25 blast patiern ......................... .2 2.23 blast wheel ....................... .22.23. 25 degree of cleaning ....................... 25 dust collector ........................ .23. 25 equipmenl..................... .188. 249-250 equipment selection ................... .2 8.29 gantrycrane............................. 26 hand-held systems ....................... 30 in-line systems ....................... .2 3.24 inspection.............................. 188 machines. operation ................... .2 3.25 pipelines............................... 351 portable systems ............ .23. 28.30. 86-87 post-fabrication system ................ .2 5.28 pre-fabrication systems ............. .24. 26-27 rate of cleaning .......................... 25 roll conveyors ........................ -26-27 self-propelled systems ..................... 30 ship deck systems ........................ 28 ship hull systems ......................... 84 ship side systems ........................ 28 shipbottom systems ....................... 28 ships .................................. 295 shop cleaning ........................ .2 6.28 wheel travel ............................. 25 work car ............................ -25.26 work handling ................. 23, 25. 27-29 Chalking. failures ..................... .48 7-488 Characteristics. thermal spray coatings ............................... 457 Checking. failures ................ .488-489. 494 Chemical analysis. paint tests .............. 21 7
Chemical bonding. adhesion .................10 zinciich primers ................... .128. i33 Chemical cleaning. government specifications ............................ 92 surface preparation ................... .9 0.97 Chemical coatings. phosphating ...........98.103 Chemical curing. paints ............. .15.16. 117 Chemical exposure environments. failures Chemical Chemical Chemical Chemical
................................ 513 exposures ....................... 268 inhibition ........................ 139 plant .painting ................41 2-419 plants. exposure
environments ........................... 412 Chemical properties .metallic abrasives ........35 non-metallic abrasives .................48. 50 Chemical reactions. paints ..................140 pigment-vehicle combinations .............. 140 pigments .............................. 138 zinc-rich primers .................126. 128-130 Chemical resistance. failures ................ 495 paints. tests ............................ 358 zinc-rich primers ........................ 134 Chemical resistant paints ...................397 Chemical separator. lining .................. 321 Chemical versus physical cleanliness .......... 20 Chemical, exposure environments .......BO.429 Cherty pits, non-metallic abrasives ............84 Chilled cast iron abrasives ................32.34 Chinese hog brushes ... Chip blow line. painting .................... 422 Chipper. rotary. rotary impact cleaning tools ............................ 72 Chipping hammers, hand tool cleaning ......6849 impact cleaning tools .... 69-70 Chisels .................. ...297 imDact cleanina tools .... .6 9.70 Chloiides. soluble .non-metallic abrasives ......50 Chlorides. surface contaminants ..........1O. 297 Chlorinated rubber. binders ........ .119, 121.122 paint application ........................ 150 paints ........................ .15. 315. 392. 415.483 Chlorinated solvents ....................... 123 solvent cleaning ...................... .90-91 Choke valves. abrasive blast
cleaning ................................ 56 Chromate-free acid rinses. ....................... 103 nts .................... 147 Chromates. pigments .......... .ll. 144-145. 246 pigments. solubilities ..................... 497 rust inhibitors ............................ 81 Chromic acid rinses. phosphating ........ 10 2-103 Chromic acid. pickling ..................... 105 Chromium paints. hazards. abrasive blast cleaning ........................ .7 8-79 Chromium. regulated materials ........... .il. 79 Circular nozzles. water blast cleaning .......... 65 Citric acid cleaning. surface preparation.............................. 85 Clean Air Act Amendments ......... .558. 560-568 architectural and industrial maintenance coatings rule ........................... 564 hazardous air pollutants ...558. 560-562. 564-565 maximum available control technology ..560. 564 summary ........................... 562-563 Cleaners. acid. solvent cleaning .............. 91 alkali. solvent cleaning ................. -90-91 detergent. solvent cleaning ................. 91 safety ................................. 179 Cleaning shop. fabricating plants ........ .24 7-248 Cleaning. field welds ....................... 259 shop welds ............................. 259 steel to be enclosed in concrete ........... 243 welds.......................... 308. 311-312 Cleanliness. abrasives .................... 189 between coats ...................... 202-203 paint application equipment ............... 194 surface preparation ...................... 189 Cleanup. brushes ......................... 166 mitts .................................. 166 paint application equipment ...............166 rollers ................................. 166 spray equipment ........................ 166 water-borne paint application .............. 166 Clean Water Act .......................... 558 Clemtex Coupons. profile measurements ......192
Closedcycle blast cleaning ................. 295 Coal slag. non-metallic abrasives ......... .60. 62 Coal tar enamel. paints ............... .315. 351 Coal tar ewxv .... binders .................... 118 paints ................. .16. 315-316. 334.335. 355.379.381. 383. 387.392 paints.blushing .................... .380, 383 Coal tar. linings ..................... .333. 336 paints ............................ .33 3.335 paints. application ....................... 344 paints. environmental constraints ........... 333 tapes ................................. 355 Coalescence .............................. 15 Coalescing paints ...................... 117-1 18 Coated abrasives. rotary cleaning tools ......7 0-71 Coated abrasives. safety. power tool cleaning ............................ 73 Coating operations. effects on the environment abrasive blast cleaning ................... 556 impad on acquatic life .... paint application ......... product storage ......................... 557 waste production ........................ 557 Coating system. with cathodic protection ................ Coating systems. design ..... Coatings. aluminum, thermal spray .......457-458. barrier.... cathodic pr concrete .. .......... designs for corrosion prevention ....... .52 8.537 extruded .......................... .35 3.354 fusion-bonded ...................... .35 4.355 hot dip galvanizing .................. .46 5.480 iron phosphate ........ .98.99, 101.103 .112-114 mechanism of corrosion prevention ........... 3 metallizing ........................ .45 6-464 osmotic effects ........................... 4 phosphating ........................ 98-103 pipeline, desirable characteristics ...................... .34 9.351 powder ................... .335, 337, 354-355 protection mechanisms ................ .i0.18 suppliers, painting programs .......... .37 7.378 tape ........................... 337, 355-356
thermal spray ...................... .45 6-464 thermosetting ........................... 354 water absorption ........................ -4 wax ................................... 356 zinc phosphate ...................... .9 8.103 zinc silicate ........................... 125 zinc, hot-dip galvanized .............. .465.480 zinc, thermal spray ................. .457-458, 460-461, 463 Code of Federal Regulations ........... .548, 558 Coefficient of friction, zinc-rich primers ........................... .13 3.134 Cofferdams, ships, painting ................. 306 Cohesion failures .......................... 14 causes ................................. t1 Coke oven plants, painting ............. .39 0.395 paints ................................. 390 surface preparation ...................... 390 Cold weather, painting .................... 248 Colloidal silica, zinc-rich primers ................................ 126 Colloidal dispersions ....................... 118 Color selection, painting programs ........... 420 Color, specifications ....................... 347 Colors, abrasives ......................... 57 safety ................ 306, 393.394, 420, 481 Comparators, profile measurements .......... 192 Compatibility between coats of paint ........... 14 Compatibility, maintenance painting ..... .272. 416 Composition specifications .................. 448 Composition abrasives............................. 57-58 millscale .............................. 105 paints, tests ........................... 212 pigments .............................. 142 Comprehensive Environmental Response, Compensation and Liability Act...................... 559,580, 563-585 environment ............................ 564 hazardous substance ................ 580.584 National Response Center ................ 585 release ................................ 584 reportable quantities ............ .580, 584-585 Superfund ............................. 558 threat of release ........................ 584 violations .............................. 584
Compressed air cooled aftercoolers ........... 62 Compressed air standard .OSHA............. 550 Compressor size, abrasive blast cleaning ................................ 53 Concrete encased steel. painting ........247, 278 Concrete pipe, painting .................... 422 Concrete-related failures .............. .501, 503 Concrete, coatings ........................ 356 painting .................. .394, 422, 432-433 surface preparation ................. 387, 432 Conductive extenders, zinc-rich primers...................... .12.14, 131-132 Conductor, electrical ......................... 4 electrolytic ...................... .4,363-365 Configuration.designs for corrosion prevention ................. .53 3.534 Confined spaces standard, OSHA ............550 Construction industry standard .OSHA.... .55 0-551 Consultation assistance, OSHA ..............549 Consumption rates, metallic abrasives ............................... 60 non-metallic abrasives ..................... 60 Contact surfaces, painting .....:.........25 8-259 Containers.sampling paints from ....... .213, 216 Contaminants.abrasives ...................189 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 633
SSPC CHAPTER*27=3 8627940 0004107 70T surface. chlorides ....................... 297 surface. effect on adhesion ............... 10 surface. sulfates ............... ...297 Contaminated steel. painting ....... ...273 Contamination . intercoat. maintenance painting ............................... 425 Continuous hot dip galvanizing ... .....478 Contractors maintenance painting ................ .42 5-426 painting. railroad ........................ 272 Contracts ........................... .23 8-240 cost and cost sharing .................... 238 cost plus fixed fee .............. cost plus fixed fee and award ..... cost plus incentive fee ............ 239 cost plus. inspection . . ...... fixed price. escalation .............. fixed price. firm ................... fixed price. inspection .................... 182 fixed price. with incentive .................238 fixed price. with redetermination . . indefinite delivery ....................... 239 labor hour .................... letter ......................... Control valves. abrasive blast cleaning.............................. 55-56 Controlled cavitation cleaning ................82 operator fatigue .......................... 82 production rates .......................... 82 profile .................................. 82 Conveyors. painting . . ................ 422 Copper-related failures ..................... 501 Copper slags. non-metallic abrasives ...... .47-48. 60. 62 Copper. painting .......... surface preparation ...... Corncobs. non-metallic abrasives ......... .46. 48. Corner-related failures . . ............ 511 Corners. inside. applicatio Corps of Engineers. specifications ...........449 Corrosion of steel. anodic reactions ........... 3-4 cathodic reactions ....................... 3-4
mechanisms .............................. 3 millscale formation ........................ 3 pitting ................................... 6 rust formation .................. theory ......................... Corrosion prevention. designs for ......... 246-247 29-430. 528-537 designs for. bridges ...... ......... 264 Corrosion survey. painting pr Corrosion. anodic areas ................. .5. 365 at discontinuities in a paint film ............................. 5-6 cathodic areas ....................... .5. 365 cells .................................. 3. 5 direct current ...................268. 363-365 effect of cathode location ................... 5 effect of dissimilar metals .................247 effect of film thickness . effect of millscale ..... effect of noble metals .................... 247 effect of polarization upon ..................5 effect of resistance upon .................. 5-6 effect of steel composition ..................7 effect of stray electrical currents ............................... 7 effect of surface contaminants ..............10 electrochemical ...................... .3. 349 electrochemical reactions .............. .4. 139 electrolytic ........................ .246. 267 fresh water service ...................... 310 galvanic ............................ .4. 6-7 ........................... 4 ....................... 3-4. 6 prevention. designs for ...............330. 418 prevention. function of coatings ..............3 protection. painting ...................... 280 reinforcing steel ......................... 268 stray electric currents .................... 268 Corrugated siding. painting ................. 392 Cost accounting. pickling ................... 110 Cost and cost sharing contract ..............238 Cost Cost Cost Cost
effectiveness. ships. painting ...........293 of wear. metallic abrasives ............. 32 plus contracts. inspection .............. 182 plus fixed fee and award
contract ............................... 239 Cost plus fixed fee contract . . 238-239 Cost plus incentive fee contract .............. 239 Costs. abrasive blast cleaning ................ 76
abrasives ............................... 57 estimating procedures. surface preparation ........................ .7 6-77 field painting ...................... .222-226, 229. 235 field painting . equipment .................. 223 field painting example calculation .................. field painting . labor ........... field painting. malerials ....... field painting. work sheet ...... field surface preparation ............... .7 5-77 fouling. Very Large Crude Carriers .............................. 294 hand tool cleaning ........................ 75 hydroblasting ............................ 76 inspection .............................. 181 paint materials ..................... .231-234 painting ...................... .229, painting, breakdown ................ painting. comparative ................ painting. discounted cash flow ........ .403. 408 painting. highway bridges .................289 painting. railroad bridges ................. 269 painting. total structure life ................226 pickling ................................. 76 pipeline painting ........................ 351 power too1 cleaning ....................... 75 review. surface preparation ............. .75-77 shop painting ...................... .229. 234 solvent cleaning .......................... 75 surface preparation ............... .75-77. 401 surface preparation. bridges ............... 284 thermal spray ...................... .46 2-463 water blast cleaning .................66-67. 76 wet abrasive blast cleaning ................ 81 Coverage versus size. metallic abrasives ................... Coverage. metallic abrasives ..............37. 40 Covered hopper barges. fresh water service ...................... .307-308 Covers. roller ........................ .155-156 Cracking. failures .................... .489. 492 Cratering. failures ......................... 508 Crevices. designs for corrosion prevention ............................. 529 Critical pigment volume concentration .................... .11-12. 139 Cross-cut test. adhesion .................... 204 Crude oil-resistant paints ...................397 Cryogenic coating removal,
surface preparation ....................... 85 Cure of coating. evaluation ....... solvent rub test ............... Curing agents. health hazards ............... 541 Curing. binders ...................... .11 7-1 18 inspection ............................. 341 paints. oxidation . . zinc-rich primers . Current flow. cathodic protection .........36 6-367 Currents. stray electrical. effect upon corrosion ...................... 7 Cut steel wire abrasives ..................... 32 Cutter bundles. rotary impact cleaning tools ........................ .7 2-73 Damp surfaces. paint application .............150 Dams. painting ....................... .330.348 De.flashing. metallic abrasives ................ 34 Decks. bridges ....................... .26 9.280 Decks. painting ......................... 312 Defects. hot dip galvanizing ............ .47 5-477 Defense Supply Center ..................... 448 Degree of cleaning. centrifugal blast cleaning ........................... 25 effect on surface preparation ............. t 9-20 metallic abrasives ........................ 42 non-metallic abrasives ..................... 48 Dense versus light. non-metallic abrasives ............................... 47 Density, measurements, paints. tests .................................. 211 non-metallic abrasives ........ .4 6-47 Department of Agricultur S .........591 Department of Defense Index of Specifications ........................ 449 Department of Defense, specifications ........................... 449 Department of Housing and Urban Development Guidelines ......... .559. 591-592 Depth micrometers. profile measurements ...................... 192-193 Dermatitic materials, binders ............ 179. 542
safety ................................. 179 solvents ............................... 179 Design Basis Accident, tests ................ 442 Design features . bridges ................... 263 Design. coating systems .................... .to considerations, hot dip galvanizing ...................... .47 0-472 for corrosion prevention ......... .246-247, 330. 418, 421, 429-430 for corrosion prevention. bridges .............................. 264 for corrosion prevention, coatings ...... .53 4-536 for corrosion prevention. dissimilar metals ...................... 529 for corrosion prevention, economics ........536 for corrosion prevention. geometry ..... .53 1-532 for corrosion prevention. insulation .........529 for corrosion prevention, joints ............. 246 for corrosion prevention, maintainability .................... .53 5-536 for corrosion prevention, materials ..... .52 8-530 for corrosion prevention, mechanical ... .53 2-533 for corrosion prevention. pipe hangers ......................... 246 for corrosion prevention, steel grating for corrosion for corrosion for corrosion
.......................... 246 prevention, stiffeners prevention, surfaces . prevention .
tank interiors .............. for corrosion prevention, vessels Design-related paint failures ...... Design. for better painting .............. .24 6-247 for corrosion prevention .............. .24 6-247 for corrosion prevention, bridges .............................. 264 joints. for corrosion prevention .............246 pipe hangers, for corrosion prevention ............................ 246 steel grating, for corrosion ........................ 246 rosion prevention ..........246
Detergent cleaners, solvent cleaning ...........91 Detergent cleaning, foamed detergent solution. ..................... 94-95 high pressure-hot ..................... .9 4-95 Dew point, measurements .............. .t84-186 measurements. psychrometer ..........18 4-186 Di-iron phosphide .............. .1 2. 14 . 131-132 Dial surface profile gage ................... 186 Dichromates, rust inhibitors .................-66 Digital thermometer ....................... 184 Dipping operations, thinnin paints ............... ..........256 Dipping procedure. hot dip galvanizing ........................ .46 8-470 Direct costs, surface preparation ..............75 Direct currents. corrosion .......... .268. 383-365 Disadvantages, sealers ..................... 459 Discoloration, failures ...................... 494 Discontinuities in a paint film. corrosion ............ 5-6 Discontinuity-related failures ................511 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERk27.3 93 8627940 0004108 646 m Discounted cash flow. painting costs ............................. 403. 408 Dispersion. measurements. paints. tests ....... 211 Dispersions ............................... 15 colloidal ............................... 118 Dissimilar metals, design for corrosion prevention ................. .52 9-530 eflect on corrosion ...................... 247 Documentation, inspection ..................181 surface preparation ....................... 75 DOD-P-15328 ....................... DOD-P-16232 ............................ 101 Drilling rigs. zinc-rich primers ................ 135 Drum handling equipment .................. 256 Drum paint agitator, mixing equipment ............................. 151 Dry bulb temperature measurements ..................... .183-184 Dry film thickness . gages .............. .19 8-201 gages, calibration .................... 199-201 gages, eddy current ..................... 202 gages, Elcometer 300 ............... .197. 201 gages, Elcometer 345 ............... .194. 201 gages. Elcometer Minitest 100 F ........................... 196, 201 4000 ............................ 197, 201 gages, Electro-Physik Pentest .............................. 188 gages. magnetic .................... .19 9-201 gages, magnetic, pull-off ..............19 9-201 gages, micrometer .................. .19 9-202 gages. microprocessor ...................202 gages, Mikrofest ............... .188, 192. 201 gages. Minitest ................. .196-197. 201 gages, Positector 6000 .............. .194, 201 gages, Ouanix 1500 FE ............. .196. 201 2200 ............................ 195. 201 2300 ............................ 195. 201 gages, Tooke ................... 198-199, 201
measurements ................. .165. 198-202, 244, 258, 318. 339 paint application ........................ 343 Drydocking, ships. painting ................. 293 Drying ovens ......................... 257-258 Drying times, primers. versus wetting ability ........................... 245 quality control .......................... 252 Drying, cleaned steel. maintenance painting ............................... 425 painted steel ...................... .259. 261 Dump guns. water blast cleaning .............65 Dump valves, water blast cleaning ............ 67 Durability, binders ......................... 122 Dust collector, centrifugal blast cleaning ............................. 23, 25 Dust-free blast cleaning ..................... 52 Dust removal. surface preparation ............ 342 Dust respirators, respiratory protection ... .17 7-178 Dust, contaminated, abrasive blast cleaning ................................ 62 Dusting, non-metallic abrasives ............... 50 E Ear protection. power tool cleaning ...... Economics. designs for corrosion prevention ............................. 536 painting programs .............. .403. 408. 412 ship painting ........................... 294 Eddy current. dry film thickness gages ............................. 198. 202 Edge-relaled failures .................. .510.51 1 Edge protection. maintenance painting ............................... 425 Edge striping ........................ Elcometer 300 . dry film thicknessgages ......................... 197 Elcometer. dry film thickness gages ......... Elcometer Pencil Pull-oif. dry film thickness gages ......... Electric arc gun. thermal spray .......... .45 6-457 Electric psychrometer ............
Electrical conductivity . zinc-rich primers .......129 Electrical conductor ......................... 4 Electrical potential. cathodic proteclion ........................ .36 5.367 Electrical standard. OSHA ..................550 Electrical tools. safety. power tool cleaning ............................ 73 Electrically driven machines. rotary cleaning tools ............................ 7t Electrochemical corrosion ............... .3. 349 Electrochemical inhibitors. ................. -147 Electrochemical reactions . corrosion ........4. 139 Electrochemical reactions. pigments ..... .13 8-139 Electrochemical tests. paints ................358 Electrogalvanizing .................... .47 8-479 Electrolytic conductor ................. .36 3-365 Electrolytic corrosion ................. .246. 267 Electrolytic pickling ................... .114. 115 Electrostatic spray ............... .257. 354 .355 equipment ......................... .i6 2-164 paint application ................... .160. 343 Electrostatic holiday detection instruments ........................ .203-204 Emission spectroscopy . paint tests ...........399 Emissivity. paints ......................... 397 Enamels. catalyzed epoxy .................. 381 painting systems ........................ 351 paints ............................ .35 1-352 Enforcement. OSHA ....................... 549 Environment-related paint failures ....... .51 3-514 Environmental constraints ................ .20-21 coal tar paints .......................... 333 non-metallic abrasives ..................... 48 painting ....................... .330. 347-348 painting navy ships ...................... 525 paints ................................. 382 phosphating ............................ 103 pickling ......................... .104. 115 pigments .............................. 147 solvent cleaning ..................... .90. 96 surface preparation ................ .30. 78-79. 88. 324 tank painting ...................... .315. 319 Environmental impact. surface preparation .............................. 21 Environmental Protection Agency ..... .72. 78. 81. 290. 315. 556-593 Environmental reactions. zinc-rich primers ................................ 128
Environmental regulations ......... .79. 246. 295. 556-594 air quality regulations ........... .558. 560-572 antifouling coatings ...................... 592 Clean Air Act ...................... .558. 560 Clean Air Act Amendments ....... .558. 560-568 Clean Water Act .................558. 580-582 Comprehensive Environmental Response. Compensation and Liability AC1............... .558. 580.583-585. 589 federal acts and regulations .......... .55 7-559 hazardous material regulations .... .559. 583-587 hazardous waste regulations ...... .558. 573-579 miscellaneous ....................... 591 -592 overview ........................... 556-559 pesticides ......................... .559. 592 regulatory agencies ...................... 557 regulatory structure ...................... 557 Resource Conservation and Recovery Act ................ .558.573-578 Safe Drinking Water Act .................. 558 soilquality ......................... 559. 591 sources of information ................59 2-593 storage vessels ..................... .58 7-591 Superfund Amendments and Reauthorization Act ........ .558-559. 585-587 Toxic Substances Control Act .........559. 583 waste handling and disposal regulations ............... .57 3-579 water pollution control regulations ..558. 580-583 Environmental zones ....................... 268 Environmental zones. painting systems ........................... .26 4-267 zone 10 ............................... 264 zone 2A ........................... zone 28 ............................ 267-268 zone 3 ................................ 268 Environments. resistance to. paints ..... .391. 415 Epoxy ester. binders ..................Il¿?. 391 Epoxy lacquer. binders ..................... ii8 Epoxy polyamide. binders .................. 118 paints ............. .1 6. 355. 398. 415416. 433 Epoxy polyamine. binders .................. 118 paints .......................... 16. 355 398
Epoxy polyester. paints .................... 431 Epoxy. binders .......................... 118 binders. two-component .............. .12 1-122 catalyzed. binders ....................... 391 catalyzed. enamels ...................... 381 catalyzed. paints ................... .382. 387 high-build. paints ............... .379-381. 387 linings ................................. 323 paints..................... .15. 284 . 315-317. 335. 392. 432 Epoxy resins. health hazards ................ 541 Equipment. air spray .............. .160-162. 194 airless spray ................... .160-164. 194 blast cleaning .......................... 188 blast cleaning. abrasive air ............. .52-63 blast cleaning. inspection ............ .i88-189 electrostatic spray .................. .16 2-164 field painting. costs ...................... 223 heated spray ........................... 164 new. painting ...................... .422. 425 paint application ................... .25 7. 401 painting ............................... 394 pickling ........................ 1 1 O. 112-114 steam cleaning ................... 93-94. 102 thermal spray ..................... .456. 462 two-component paint application ........................... 160 two-component spray gun ........... .163. 165 water blast cleaning ................... .6 5-66 Erosion. exposure environments ............ 340 failures ....................... .488. 513-514 Esters. solvents ........................... 123 Etch. surface preparation .................... 20 water blast cleaning ...................... 64 Etching. abrasive blast cleaning .............. 58 metallic abrasives .................. Ethyl silicates. zinc-rich primers .......... 127-128 Evaluations new paint materials ..................... 276 paint field tests ........................ -219 paint service tests ....................... 219 panel paint records ............. .215. 218-219
Evaporation times. solvents ............ .120. 123 Explosive-propelled surface preparation .............................. 85 Exposure environments. abrasion ............ 340 atmospheric ........... .338-339. 381-382 . 385 bacterial ............................... 429 buried structures ........................ 268 cavitation erosion ................... .33 9-340 chemical ...................... 268.340.429 chemical plants ......................... 412 erosion ................................ 340 frequently wet. fresh water ....... .267. 337-338 frequently wet. salt water. .............26 7-268 highway bridges ................... .281. 283 humid interior .......................... 281 hydrogen sulfide .................... .38 1-382 industrial ......................... .268. 281 interiors. dry ................... .382-383. 386 marine........................ .267-268. 281 mild .................................. 281 moist atmospheres ................. .381. 384 navy ships ............................. 517 normally dry (rural) ...................... 264 railroad bridges ......................... 264 splash zones ........................... 267 submerged .................... .380-381. 384 underground ................... .268. 335-337 underwater ......................... 332-335 Exposure to gases. vapors. dusts and mists standard. OSHA ...................551 Extender pigments ........................ 117 Extension ladders ......................... 168 Exterior areas. ships. painting ...........30 3-304 Exterior structural steel . painting ............................ 431432 Extruded asphalt mastic .................... 353 Extruded coatings .................... .35 3-39 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERr27.3 93 I8627940 OOOYLO9 582 Extruded polyethylene . ............. .35 3.354 peeling ........................ .... .49 8-499 Field welding. surface Extruded polypropylene ............. .35 3.354 pinholes ........................ ....... 507 preparation after ........................ 277 Eye protection. goggles ............ .178, 549 pinpoint rusting .... ._......... ...... Field welds. cleaning and hand tool cleaning.. .................. 72 pipe structures ..................... ..... 513 painting .............................. 259 power tool cleaning . .................. 72 runs and sags ...................... . 509-510 Filiform corrosion. causes .......... safety ............ ................. 178 scaling .............................. . 498 Film characteristics. paints . shop primers ........................... 250 .............................. 211 spatter coating .......................... 507 on. latexes ..................... . 15 steel-related ................... .500-501, 503 Film properties. paints. tests . ............... 211 storage tanks ........................... 513 Film thickness ................... ......... 278 sulfide discoloration. ..................... 494 calculations from volume Fabric. roller covers ... ... .15 6.1 57 thickness-related ..................... ... 506 Solids ........................... .19 7.1 98 Fabricated steel. surface thinning-related ......................... 505 dry. me asurements ..............165. 198.202. conditions.............................. 249 undercutting ....................13 9, 500-501 244. 258 .318. 339 Fabricating plants. cleaning underfilm corrosion, causes ............... 102 eff ect on paint life ....................... 271 shop ................ water tank lining ........................ 322 effect on p aint performance ................ 11 drum handling equipment ................. 256 weather-related................... .. .50 5.506 effect upon corrosion .................... -5-6 efficient layout .......................... 247 weld-related ................... ......... 511 finish coats .............................. 14 inspection records ....................... 244 wood-related .................... ... .50 2.503 measurements. effect of paint application .........244. 251.252. 254-259 wrinkling ..................... .......... 491 profile ............................... 200 paint. house ............................ 244 zinc-related ..................... ... .50 1.502 paint application ................ .166. 196-202 paint records ........................... 244 Faying surfaces, designs for wet. measurements .................... .165. painting costs .......................... 247 corrosion prevention ............. ........ 529 196-198. 258 painting in ......................... .24 2.262 zinc-rich primers .............. ........... 13 painting inspection ...................... 260 painting ......... Fingerprinting . paints ...................... 398 painting shop ...................... .24 7.248 zinc-rich primers . . Finish coat s. film thickness .................. 14 painting supervision ..................... 260 Federal Acquisition R ........448 selection of .......................... .1 4.16 production lines ......................... 248 Federal Highway Administration .. ...... .283, 289 selection of pigments ..................... 16 quality control ..................... .252. 254 Federal Register ............... ........... 548 vehicles. properlies of ..................... 17 safety.......... ........ -261.262 Federal specifications 448-449 Finished produ
ct. paints. quality selection of primer ....................... 243 Federal Specifications and contr ol ............................. 207-210 surface preparation ............. .242.243, 249 Standards, Index of ............ .......... 449 quality acceptance ....................... 213 training of painters ...................... 249 Federal Standard No 595 Fire ... .............................. 539-540 training of workers....................... 248 Colors........................... ...... 449 extinguishers ........................... 540 Fabricators, pre-job review Federal Supply Classification ................ 450 p revention ............................. 540 of specifications......................... 247 Federal Supply Classification Fir e hazards. painting bridges ............... 290 Factory application. phosphating .............. 99 Listing...................... ........... 449 Fire protection tanks. painting ............... 316 Failures, abrasion .................... .51 3.514 Federal Test Method Standard F ireproofed steel. painting ......... .243. 247. 278 adhesion ............................ 14. 66 No 141 ............................ .... 449 First aid. safety ........................... 180 adhesion. causes ......................... i1 Federation of Societies for Fish o il. paints ............................. 15 alligatoring ....................... .48 9-490 Coatings Technology ............. ........ 216 Fixed price contract aluminum-related ........................ 501 Fence rollers .................... ......... 159 escalation............................. 238 at intermittent welds ..................... 332 Fence painting ................. .......... 270 firm ................................... 238 back to back angles ..................... 512 Ferric molybdate, pigments ....... .......... 143 with incentive ........................... 238 bleeding ............................... 508 Fiberglass, ladders ............... ......... 168 with redetermination ..................... 238 blistering ...................... .139. 495-4913 Field application, phosphating ........... .99, 102 inspection.............................. 182 blistering, causes .... .lo. 12. 102.103. 105. 112 Field bolt heads, paint Flaki ng failures .......................... 499 blushing ............................... 508 application ....................... ...... 278 metallic abrasives ........................ 38 chalking............................ 487488 Field coating, paint application ... ........... 342 Flame cleaning surface checking ...................... .48&189, 494 Field history, materials selection ............-322 preparation.............................. 86 chemical exposure environments .......... -513 Field painting .................. ..... .250, 278 Flash points. solvents ................. 120. 123 chemical resistance ...................... 495 abrasive blasting ............... ........ 223 Flash rusting .............................. 81 cohesion................................ i4 abrasive handlers .................. ..... 223 Flashblast. surface preparation ... cohesion, causes ......................... il abrasives......................... .. 223-224 Flat brushes. paint .................... .15 3.154 concrete-related.................... .501, 503 ......................... 223 Fle xibility. paints ....................... 14. 397 copper-related .......................... 501 airless spray .................... ....... 223 Flexible flaps. rotary impact corner-related........................... 511 bridges .................. cleanin g tools ............... .7 2.73 cracking .......................... .489. 494 costs .................... Flint. non-metalli .................45. cratering ............................... 508 costs, equipment ................. ...... -223 58. 60 discoloration............................ 494 costs, example calculation .......
..... .22 4.226 Floor beams. bridges ...................... 269 discontinuity-related...................... 511 costs, labor ................... ..... .222.223 Florida Department of edge.related ........................ .51 0-51 1 costs, materials .............. ...... .22 3-224 Transportation .......................... 286 erosion ....................... .W.513-514 costs, work sheet ................... .23 6-237 Flow coating ............................. 257 faying surfaces ......................... 514 helpers .......................... ...... 223 Flow rates. metallic abrasives ................37 filiform corrosion, causes ..................i2 new steel ...................... ........ 271 Flue gas stack. painting .................... 445 flaking ................................. 498 paint application ................ ........ 223 Foamed detergent cleaning. ........................ 507-508 paints ................................. 224 so lvent cleaning ...................... .94.95 intercoat delamination ................49 9.500 pot tender ..................... ........ 222 Food and Beverages. coating contact lifting.................................. 508 riggers ........ .......... 223 .. ........591 metallic abrasives ..................36. 38-39 ..................271 microorganism-related.................... 491 shop primed steel ................ ....... 271 millscale lifting .......................... 248 solvents ...................... ......... 224 Food processing plants. mixingrelated .......................... 505 supervisors........................ ..... 223 painting ............................ 429441 ................ 490, 494 Field surface preparation, costs ........... .7 5-77 p ainting systems ..................... 437440 ................ 508509 Field tests, materials regulations ..................... ........ 436 ................ 506507 selection ..................... .322, 331, 399 Footner p rocess. pickling .............. .11 2.1 13 .................... 276 paint evaluations ........................ 219 Forms. p aint application .................... 214 paints, adhesion-related panel preparation ....................... 220 panel pai nt records ............. .215. 218-219 paints.application-related ............. 505-510 panel racks ................... ......... 219 Formulation. anticorrosion paints, causes ....... performance evaluations .................. 220 primers .. ....... 274. 486515 test panels ............................. 219 paints. quality contro l ................ .207.208 paints. design-related .. Field topcoating, specifications .............. 430 pr actices. primers ..... .........245246 paints, environment-rela Field versus shop, blast paints, formulation-related ............. 487495 cleaning ...................... .... .227, 421 paints. prevention .......... ..486-515 Field versus shop, paint paints, substraterelated ..... ..500-505 application ............... Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
= SSPC CHAPTER*27-3 93 Bb27940 0004110 2T4 painting systems ........................ 445 Ground fault circuit interrupters ..............546 metallic abrasives ...................... 38 Fouling. effect on ship General Services Administration ........ .44 8.450 metal lic abrasives. effect of .............. 35 operating costs ......................... 294 address .......................... ..... 450 non-metallic abrasives ..................... 46 foundry castings. non-metallic Geography. pipeline painting ............... 351 Hazardous materials. regulation ......559. 583-587 abrasives ............................... 47 Geometry. designs for corrosion Com prehensive Environmental Response. Fracture failures. metallic prevention ......................... .53 0.532 Compe nsation and abrasives ............................ 36. 38 Girder span. bridges ............. ......... 280 Liability Act .......... 558-559.580. 583-585 Free silica. non-metallic Girlars. bridges ......................... 269 Emergen cy Planning and Community abrasives ............................ 48. 50 Glass beads. non-metallic Right to Know Act ..........558.559. 585-587 Frequently wet exposure abrasives ........................ .46-47. 58 Federal In secticide. Fungicide and environments.paints ..................... 347 Glass transition temperature ..... ............ 15 Rodenticide Act .................. .559. 592 Frequently wet exposure. fresh Glycol ethers .solvents ..................... 123 SARA Title 111 .............. 558.559. 585-587 water ................................. 267 Goggfes. eye protection ............ ....... i78 Superfund Amendments and Reauthorization salt water ......................... .26 7.268 Golden Gate Bridge. zinc-rich Act ...................... 558.559. 585-587 Fresh water service. abrasion ............... 308 primers ...................... ......... 136 Toxic Substances Control Act ........ .559. 583 barges ................................ 307 Government painting practices ...... .... .44 8-451 Hazardous waste ................. .558. 573-579 corrosion .............................. 310 Government regulations ....... .290 -291. 293. 349 acutely hazardous waste ................. 574 corrosion of vessels ................. .30 7.309 safety ........................ .182. 538-555 characteristic wastes ................ .57 3.574 covered hopper barges .............. .30 7.308 Government specifications ....... ...... .44 8-451 classifying wastes .................. .57 3.574 hopper barges ......................... 307 chemical cleaning .................. ..... 92 contingency plan and training ............576 new work .............................. 310 phosphating ........................ ... 101 empty containers ...................... .5 7.4 old work ............................... 310 solvent cleaning .................. ........ 92 generators ................... .573. 575-576 painting. ships and vessels ........... .30 7.314 Gratings. steel. painting .... .............. 422 identification number ............... .57 5.576 tank barges ........................ 307.309 Grease paints ..................... ...... 275 land disposal restrictions ............ 573. 577 towboats ...................... .307. 310-31 1 Grease removal. surface listed wa stes ......................... 573 types of vessels ......................... 307 preparation ..................... ........ 342 manifests .............................. 576 Fresh water vessels .maintenance Grit. metallic. size on-site treatment ........ ............ 578
painting ............................... 311 specifications .................... ........ 33 packaging and labeling ..................576 painting ........................... .31 1.313 Ground supports. boom liít ........ ..... 169-170 pretreatment of blast abrasives ...........578 painting systems ....................... 313 ladders ........................... 168-169 recycled or reused ...................... 574 pretreatments........................... 310 portable .......................... . 169-170 responsibilities for ................. .57 4.577 surface preparation ................. .31 0.31 1 scaffolding.................... .... .16 8-1 69 sampling and testing ..................... 577 wash primers ........................... 310 scissors lift ..................... ... .i69-170 scrap metal ............................ 574 Fresh water. frequently wet Grounding. abrasive blast state regulations ........ ................ 579 exposure ....................... 267. 337-338 cleaning ....................... 5 4-55. 61-62 toxicity characteristic leaching Fuel oil tanks. painting ..................... 316 Guide to US Government proced ure .................. 574. 577-579 Fusion coatings ...................... .335. 337 Paint Specifications .......... .......... 449 transportation ...................... .57 6.578 Fusion-bonded coatings ............... .35 4.355 treatment. storage and disposal facilities .................... .573. 575. 577 waste analysis plan ................. 576. 578 waste accumulation time ................ 576 Hazards ............................ 539-548 Hammers. chipping. hand tool abrasive blast cleaning. Gages. dry film thickness ............. .16 5.166 cleaning...................... ....... 68-69 chromium paints .................... 78-79 wet film thickness ................... .16 5.166 chipping. impact cleaning abras ive blast cleaning. Galvanic anodes. cathodic tools .............................. .69.70 lead paint s ........................ .7 8.79 protection....................... .7. 367.368, rotary. rotary impact abrasive bl ast cleaning ...... .62. 64. 78.79 .545 370.371, 373. 375 cleaning tools ...................... .7 2.73 access and riggi ng ..................... 546 Galvanic corrosion ...................... .4. 6-7 scaling. impact cleaning tools ........... .69.70 air atomization method .................. 544 Galvanic couple ........................... 6.7 Hand and power tools. hazards .. ........... 545 airless spray .......................... 544 Galvanic primers ...................... .1O. 331 OSHA standard ................. ....... 550 compressor pumps ...................... 544 Galvanic protection ........................ 118 Hand tool cleaning ............ ......... .68.74. confined spaces ......................... 550 Galvanized decking. painting ............... -431 272, 283, 297 degree of ...... ........................ 176 Galvanized roofing ........................ 268 burrs........................... ........ 68 electrostatic spray ...................... 544 Galvanized roofing, painting ........... .270. 393 chipping hammer ............. ........ .68.69 fire hazards ........................ .53 9.540 Galvanized sieel .......................... 263 costs .......................... ......... 75 hand and power tools ................... 545 chemical treatments ..................... 483 eye protection ................... ........ 72 health hazards .................... .54 0.541 maintenance painting .................... 485 hand tools. safety ............... ......... 73 ladders ................................ 546 ..........122. 145, 339, 394. 434, loose rust ............................... 68 linseed oil primers ...................... 245 481.485, 523 non-woven abrasives ................... 68-69 paint application ...
................. .54 4.545 painting systems .................... .48 1-485 painted surfaces ............... .......... 69 painting .............................. 254 painting. problems ................... 482483 procedures ....................... .... 68.69 painting bridges .................... 289-290 painting. synergism ...................... 481 production rates ................ .......... 75 pressure pots .......................... 546 painting, tests .......................... 484 respirators ..................... ......... 73 pressure vessels ...................... 62.63 reasons for painting .................... -481 safety........................... ..... 72-74 solvents ............................... 306 repair systems .......................... 485 safety equipment ................. ..... 68.69 sources of information .............. .254. 554 surface preparation ..... .387, 400, 434. 482484 scrapers ...................... ...... .68.69 spray application ............... .256. 544-545 wash primer ............................ 483 solvent cleaning .................. ........ 68 surface preparation .......... .78. 254. 545-546 weathering ............................. 483 surface preparation ............... .. .105, 342 thermal spray .......................... 463 Galvanizing ..............125, 128. 335. 337-339 tight mill scale .............. ............. 68 water jetting ............................ 546 compared with zinc-rich tight rust ................................ 68 welding. cutting and heating ............... 546 primers ......................... .13 2.133 IOOIS............................... .. 68-69 wet abrasive blast cleaning ............... 81 hot dip, coatings. ................... .465-480 versus water blast cleaning .... ............ 67 worker awareness ....................... 177 pickling for ............................. 115 wire brushes .................... ..... .68.69 Health hazards ....................... .54 0.541 specifications ........................... 479 Hand tools, safety. hand tool ali phatic and aromatic polyamines. versus zinc-rich primers .................. 227 cleaning ....................... ......... 73 polyamine adducts and polyamides .......541 Gantry crane, centrifugal blast Hand-held systems. centrifugal alkyd paints .... ........................ 540 cleaning ................................ 26 blast cleaning .................... ....... 30 causes ................................ 540 Garnets. non-metallic abrasives ........... .4546, Handles. rollers ............ ............... 158 curing agents. .......................... 540 48.52, 58, 60. 86 Handling cleaned surfaces ................... 95 epoxy resins ........................... 541 Gas chromatography. paint tests ............216. Handling painted steel ........ ........ .259, 261 heavy metal pigments .................... 542 398-399 Handling painted pipeline ...................351 isocyanates ........... ................. 541 ........................... 145 Handrails, painting ........................ 422 liquid epoxy resins ...................... 541 Gels, phosphating ......................... 102 Hard versus soft. non-metallic m aterials removed from surfaces ........... 543 General duty clause, OSHA ................. 548 abrasives ...................... ......... 46 of types and components of paints ......... 540 General industry standard, OSHA ............550 Hardness. abrasives ............ ........ .5 7.58 organic pigments ........................ 542 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
637
SSPC CHAPTER*27-3 93 I6627940 0004LLL 130 pigments and other additives .............. 542 silica .............................. 542. 543 solvents and thinners .................... 541 surface preparation materials .......... .78. 543 urethane resins .........541 Heat curing zinc-ri ................ 126 Heat.resistant paints .................. .382.383. 393, 433 Heated spray. equipment ...................164 paint application ........................ 160 Heaters, paint ............................ 257 Heavy mineral sands. non-metallic abrasives ........................ .4546. 48 Helmets. air.fed. abrasive blast cleaning ..............62-63 Helpers, field painting ...................... 223 Hematite .................................. 3 High pressure hot detergent. solvent cleaning ...................... 94-95 High pressure, water blast cleaning .............................. 64-65 High voltage. holiday detection . instruments ........................ .20 3.205 High-build lacquers ......................... 15 High-build paints .................. 1 High-solids lacquers ................ High-solids paints .......................... 11 Highway bridges. exposure environments ........................... 283 inspection ..................... .281. 288-289 maintenance painting ............... .281.282. 287-288 paint application ............. painting costs ............... painting systems .............. statistics ............................... 283 ......... 280292 History. metallic abrasives ............... .32. 34 History.zinc-rich primers ..... .12 5.126 Holidays. detection ........................ 341
detection inspection ......... .203.204. 317. 327 detection. pipelines ............. .352.353. 355 failures ................... electrostatic .................. high voltage ................. K-D Bird Dog., ............... low voltage .................. spy ....................... Tinker-Rasor ............... Hoods. blast. abrasive blast cleaning .............................. 56-57 Hopper barges. fresh water service ................................ 307 Horsehair, brushes ........................ 154 Hose construction. abrasive blast cleaning ................................. Hoses. abrasive blast cleaning ..... . . 187 Hot dip galvanizing, coatings ............................ 465480 continuous ............................. 478 defects ...................... design considerations ............... .47 0-472 dipping procedure ................... 468470 process variables ................... .474-477 steel selection .............. surface preparation ......... treatments .................. type of zinc ................ welding procedures ...................... 472 Hot spray. paint application ................. 257 Hot stacks. painting ................... .39 2-393 Housekeeping standard. OSHA .............. 551 Hulls. exteriors painting .................... 311 interiors. painting ................... .31 1-312 ships. painting .......................... 303 Humid interior exposures ...................281 Humidity. paint application .................. 343 Hydraulic structures. maintenance painting ............................... 346 ............330-348 ...........330-340 ...... .6667, 79-83 ............. 76 production rates .... .............76 Hydrochloric acid. pickling ......... .104.109. 115 Hydrofluoric acid. pickling ..................106 Hydrogen embrittlemen!. pickling ............11 1 Hydrogen evolution. cathodic
protection .............................. 366 pickling ................................ 104 Hydrogen sulfide. exposure environment ....................... .38 1-382 Hygrometer. recording ..................... 185 Ice particles. non-metallic abrasives ............................. 83-84 Immersion process. phosphating ..... Impact cleaning tools. chipping needle scaler ....... power tool cleaning . Impact energy versus size. metallic abrasives ........................ 36 Impact energy. metallic abrasives ......... .37. 40 Impact life cycle. metallic abrasives ............. ......... 40 Impact-resistant paints ..................... 397 tests .................................. 357 Impact tools. safety. power tool cleaning ............................ 73 Impact. non-metallic abrasives ................49 Impressed current. cathodic protection ............... .7. 11. 299. 368.369. 371.373. 375-376 Injury and Illness .......................... 553 log ................................... 553 statistics. painting industry ................538 In-line machines. rotary cleaning tools ....................... .70. 72 In-line systems. centrifugal blast cleaning ........................ .2 3.24 Inaccessible surfaces. paint application ............................. 258 Indefinite delivery contract ..................239 Index of Federal Specifications and Standards .......................... 449 Indirect costs. surface preparafion .............................. 75
Industrial exposures ...................268. 281 Industrial plants. painting .37 7.378 Information Handling Services. ......................... 450 tests .............................. .39 8.399 Inhibitive mechanisms. pigments ........ .138.139. 142.144. 146 Inhibitive pigments ................. .11. 138-149 passivation ........................ .6. 10-1 1 Inhibitive primers ....................... .1 0.12 Inhibitive soaps ........................... 143 Inhibitors. chemical ........................ 139 electrochemical .. .147 paints ................................. 280 pickling .............................. .104. 110.111. 115 Inorganic silicate. binders ................... 391 Inorganic. binders ......................... 118 zinc-rich. painting system zinc-rich primers ....... 383. 392-393. 415-416. 444 zinc-rich primers. characteristics 135134 zinc-rich primers. pickling for ..............115 zinc-rich primers. single component ......................... .1 3-14 zinc-rich primers. surface pH .............. 105 zinc-rich primers. versus organic ...................... .13. 134-135 Inspection ....................... .181.205. 388 abrasives .............................. 187 adhesion testing .................204.205. 341 after painting ..... ................ 261 after pretreatments ................ 261 after surface preparation ..... . .26 0.261 air supply .................. ......186 ambient conditions
measurements.................... .18 3.1 85 anchor pattern measurements .185, 186, 192-193 and spot repair. maintenance painting ............. and spot repair, painting programs . . ................ 421 application tec blast cleaning .......... blast cleaning abrasives . . blast cleaning equipment ............. .i8 6.1 88 bridges. railroad ......................... 269 bridges. visual rusting .................... 282 cleanliness between coats .............20 2.203 cost plus contracts ...................... 182 crosscut adhesion test ...................204 cure of coating ..................... .20 4.205 curing ................................. 341 dew point measurements ............. .i8 3.186 digital thermometer ...................... 184 direct costs ............................ 182 dry bulb temperatura measurements.................... .18 4.1 85 dry film thickness measurements ............... .198.202, 318 fixed price contracts ..................... 182 formal ................................. 181 highway bridges ................ .281. 288-289 holiday detection ................... .203.204. 317. 327. 341 hypodermic needle pressure gage ................................ 185 informal ............................... 181 inspector s purpose ...................... 181 job documentation ....................... 181 maintenance painting ............... .403. 425. 435436 maintenance painting. ships . ........300 mixing ................................. 195 nozzle orifice gage ...................... 185 paint application ...............193-1 96. 261. 285. 327. 341. 357 painting ........................... .28 8.289 painting programs .................. .403. 418 penknife adhesion test ...................204 percentage of rusting .................... 183 pocket microscope ...................... 200
post-surface preparation ..............18 9.193 practices, railroads ...................... 278 pre-surface preparation ...............18 2.188 profile measurements ........... .189. 192-193 records. fabricating plants .... relative humidity measurements ships for corrosion damage ...............294 shop painting ...................... .26 0.261 soluble salts ....................... .19 0.191 solvent rub test .......................... 204 spray painting equipment .................194 surface preparation ......... .75. 188189. 284. 28a2~9.327, 341 surface temperature measurements .........185 surface temperature thermometer .......................... 185 tank coatings ...................... .31 7.318 tank linings ............................ 327 temperature measurements ............... 185 thinning ............................... 195 viscosity measurements ............. .187. 195 visual surface preparation wet bulb temperatur measurements.................... .184 .185 wet film thickness .................... 196-198 Instrumental analysis. paint tests ....217 Insulation.designs for corrosion prevention ....533 polyurethane foam ............... 356 Interchemical, wet film thickness gages ......................... 197 Intercoat delamination. failures ........... 499-500 Interior areas. dry, exposure ........ .382.383. 386 environments .................. .382.38 3. 386 painting ............................ 393-394 ships. painting .......................... 304 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 638
SSPC CHAPTER*27=3 93 m 8627940 0004LL2 077 m Interior blast cleaning .......................60 Interior decks. ships. painting ...............303 Interior process areas. painting ..............431 Interior structural steel. painting .............431 Intermediate coats. paints .......... ........112 selection of., ........................ .l 4.16 Invitation for bids .........................238 Iowa Department of Transportation ............87 Iron grit metallic abrasives ...................58 Iron oxide pigments .......................140 Iron oxide-linseed oil. paints ......... ........139 Iron phosphate coatings ............... .11 2.114 Iron salts. effect on pickling rate .....107.109, 112 Irrigation works. painting ........... .....33 0.348 Isocyanates. health hazards .................541 Job standards maintenance painting ............................... 426 painting programs ....................... 378 surface preparation ...................... 189 Joint Army.Navy, specifications ..............449 Joints, designs for corrosion prevention ..................... 246 K-0 Bird Dog. holiday detection. instruments .................... 203 Keane-Tator surface profile comparator .................... .185.186, 192 Ketones. solvents ......................... 123 Kort nozzles ......................... 308.311 L Labeling requirements. quality acceptance............................. 213 Labor hour contract ....................... 239 Labor, costs. field painting ...... .22 2.223 Laboratory. paints. quality screening. materials selection .. .39 8.399 testing. materials selection ....... .322.323. 331 Lacquers ......................... .14.15.117 ........................... 15
paint application .................. Ladders ............... accessories .......... ............168 paints ......... Layout. fabricating plants Lead air quality regulations ..558.560-562.56869.571 Lead and lead removal. OSHA standards ....551 hazardous waste regulations .......574. 577-578 monitoring..................... .56&569. 571 Lead chromate. pigments ...................141 Lead paints. hazards. abrasive blast cleaning .7879 Lead silicate. pigments ..................... 141 Lead soaps .......................... 138. 142 Lead suboxide. pigments ...................142 Lead. regulated materials .................... 79 abrasives ............... Limestone non-metallic abrasives ............................... 58 Limitations, water blast cleaning ..............64 Limitations, zinc-rich primers ............ .13 4.135 Linings. cement mortar .............332.333. 336 chemical separator .... coal tar .............. dry foodstuff tanks ....... epoxy ............... food processing tank ... liquid foodstuff tanks ... neoprene ............ phenolic ............................... 323 phenolidepoxy .......................... 323 polyester .......................... .32 3-324 polyethylene ....................... .32 6.337 polyvinyl chloride ........................ 381 railroad tank car ...... ............326 steel tanks ........... steel tanks. materials selection .... ....... .321 -324 tanks. curing ... ........ . .32 6.327 tanks, inspection ........................ 327 tanks. maintenance painting ...............328
tanks. paint application ........ tanks, surface preparation ............ .32 4.325 vinyl ........................ vinyl ester ................... water tanks. failures ........... zinc-rich primers .............. Linseed oil. binders ...... 138, 146, 245 Linseed oil and red lead primers ............. 243 Liquid epoxy resins. health hazards ............541 Lithium silicates. zinc-rich primers ........................... .12 6-127 Living areas. ships. painting ................304 Long oil alkyd, binders ..................... 391 Loss of Coolant Accident. tests ........ Low carbon steel pickling ............. Low permeability. paints .................... 397 Low pressure. water blast cleaning................. Low temperature, phosphating Low voltage. holiday detection. instruments .............. Low-alloy steel ............................ 7.8 Machined surfaces. painting ............ .25 9.260 Machinery areas. ships. painting .............304 Machinery.painting .............. .394. 433. 436 Magnetic. dry film thickness gages ............................. 198-202 fixed probe .......... .......20 1.202 pull-off .............. ...... .19 9.201 Magnetite.................................. 3 non-metallic abrasives ........ .......45 Maintainability. designs for corrosion prevention ................. .53 5.536 Maintenance painting. bids .................426 compatibility ............................ 416 criteria for recoating ..................... 402 descriptions ................. ......122 drying cleaned steel ..................... 425 edge protection ......................... 425 tresh water vessels ...................... 311 highway bridges .............281.282. 387-288 hydraulic structures ...................... 346 inspection .............182. 403. 425. 435436 inspection and spot repair ................426
inspection. ships ..... ......300 intercoat contamination ...................425 job standards ........................... 426 management awareness ..................425 materials selection ...............426, 434435 outside contractor .................... 425-426 paint application ... .435 paint compatibility . . .272 painting history ....... ............318 personnel ............ ............425 planning ............. .........42 5-426 plant personnel ......................... 425 procedures ............................. 228 procedures, ships ....................30 0-302 programs ..................... .402403. 412. 425426, 434436 railroad ........................... .27 1-272 records ................................ 425 reports, ships ...................... .30 2-303 specifications, ships ........... surface preparation ... .413414, 425, 435 tanks ........ .................... 318 versus initiai painting ........ Management awareness, maintenance painting ............................... 425 Manual process. phosphating ................99 Manufactured. non-metallic abrasives ........................ .45-46, 50 Manufacturer s instructions safety ... .180 Manufacturing methods. metallic abrasives .....32 Manufacturing, paints, quality control ..... .20 7-212 Manufacturing, process. paints quality control ......... Marine exposures ........ Maritime Administration specifications .........449 Material Safety Data Sheet .................541 Materials selection. case histories ............399 field history ............................ 322 field testing ................... .322, 331, 399 laboratory screening ................. .39 8-399 laboratory testing ................322-323,331 lining steel tanks ....................32 1-324 maintenance painting ............ .426, 434435
new product evaluation ...............39 8-399 painting programs .......... .377-380, 396-398, 414-416, 418, 420 painting, hydraulic structures .......... .33 0-340 Materials. designs for corrosion prevention ......................... .52 8-529 Materials, field painting, costs .......... .22 3-224 McKenzie. M . G........................... 126 Mechanical, design for corrosion prevention ................. .53 2-533 protection. pigments ................. .13 8-139 surface preparation .......... Metal smelting slags, non-metallic abrasives ............................... 45 Metallic abrasives ............. .32-44,52,58. 62 Metallic pigments ................... Metallic soaps ...................... Metallic versus non-metallic abrasives .........35 Metallizing ............................... 315 coatings ..................456-464 Metals. dis ct on wrrosion ............... noble, effect on corrosion .... Metering valves, abrasive blast c Microorganism-related failures ...............491 Microprocessor, dry film thickness gages ......202 Microscope, pocket size .................... 200 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 639
SSPC cHApTER1c27.3 93 8627940 0004LL3 TO3 Microstructure. metallic abrasives ............. 38 Mikrotest. dry film thickness gages .. .188. 199.200 MIL-C-10578 .............................. 92 MIL-C-11090 ........ .......... 92 MIL-'2-13924 ........ MIL-C-14460 .............................. 92 MIL-C-25769 .............................. 92 MIL-C-27251 .............................. 92 MILC-38334 .............................. 92 MIL443616 .............................. 92 MILC-46156 .............................. 92 MlLC-46487 ............................. 101 MILC-81302 .............................. 92 MILC-81533 .............................. 92 MIL-H-15328 .............................. 92 M IL-S-10561 .............. MIL-S-5002 ............... MIL-T-7003 ............................... 92 Mild exposures ........................... 281 Military specifications ................... 448449 Millscale. composition ...................... 105 effect on corrosion ................... .6. 247 effect on paint life ....................... 244 effect on paint performance ........... -242.243 formation ....................... .3, 104, 242 lifting .................................. 250 lifting, cause of paint failures .............. 248 removal ........................... -242-243 removal. non-metallic abrasives ............. 47 removal, pickling . ......... 104 tight. power tool CI Minitest. dry film thickness gages ........196. 201 Mitts, cleanup ............................ 166 paint application ............... .153. 155. 160 Mixing. equipment, drum paint agitator ........151 equipment, paint shaker .................. 151 inspection.............................. 195 latex paints ........................ .15 1.152 manual paint application ............. .15 1.152 mechanical. paint application .............. 151 paint application ............... .151.196, 343 paints ........................ 255,274, 277 related. failures ......................... 505 two-component paints ........... .151.152, 195 zinc-rich primers ........................ 195 Moist atmospheres. exposure environments ...................... .381, 384 Moisture separators, abrasive blast cleaning ...................... .56. 186 Moisture vapor transmission rates, paints ................ Moisturecuring, urethane binders
Molybdated zinc oxide. pigments ............ -142 Molybdates, pigments ................ .142, 144 rust inhibitors ............................ 81 Morgan Whyalla pipeline. zinc-rich primers 126. 136 Mudcracking, failures ................ .490, 494 Multicoat systems. shop painting ......... 421422 Muriatic acid. pickling ..............104-109, 115 NACE RP-0275 ...................... .35 8-361 Nap. roller covers ......................... 156 National Ambient Air Quality Standards ..... .78. 558.560. 562. 568.569, 571 National Association of Corrosion Engineers. address ..................450. 592 National Association of Environmental Professionals. address ...................592 National Bureau of Standards ...............448 National Fire Protection Association. address . .593 National Institute for Occupational Safety and Health. ................................ 548 address ............................... 554 National Lead Abatement Council. address ....593 National Leak Prevention Association. address .593 National Paint and Coatings Association ......449 address ....................... 450.554. 593 National Public Health Service ............... 315 National Safety Council .................72. 279 address ................................ 554 National Shipbuilding Research Program ...... 297 Natural fiber brushes ........................ 93 Naturally occurring non-metallic abrasives ............................ 45, 50 Naval Architects and Marine Engineers, address ............................... 450 Naval jelly ............................... 102 Naval vessels, painting ..................... 293 Navy safety procedures ................ .52 4-525 Navy ships, exposure environments .......... 517 painting ........................... .51 6-527 paints ........................ .520-524, 526 surface preparation ...................... 520 Needle scaler, impact cleaning tools ........... 69 Neoprene linings .......................... 324 New construction, painting programs ........ .418, 421425, 429434 New product evaluation, materials selection .......................... .39 8-399 New steel, field painting . . New structures, painting . . surface preparation ...................... 277 New work, fresh water service ...............310 Nickel slags, non-metallic abrasives ........... 47 Nightingall, Victor .................125-126, 137 Nitrates, rust inhibitors ..................81 Nitric acid, pickling ... ............. 104, 106 Nitroparaffin, solvents ...................... 123 Noble metals, effect on ' .......247 Non-metallic abrasives . .45-51, 58
Non-metallic versus met ........ 35 Non-silica sands, non-metallic abrasives ........ 45 Non-skid, paints .......................... 303 Non-woven abrasives, hand tool cleaning ....6 8-69 rotary cleaning tools ................... .7 0-72 safety, power tool cleaning ................. 73 Notch type, wet film thickness gages .........197 Novaculite non-metallic abrasives ............ 45 Nozzles, circular, water blast cleaning ......... 65 conventional, abrasive blast cleaning ........ 60 hypodermic needle pressure gage ......185, 188 inspection, abrasive blast cleaning ..... .18 6-189 Kort .............................. 308, 311 materials, abrasive blast cleaning . . orifice gage ............................ 185 orifice size, abrasive blast cleaning . orifice size, gage ........................ 189 pressure, abrasive blast cleaning ...... .61, 190 shapes, abrasive blast cleaning ............. 55 sizes, abrasive consumption, blast cleaning ...53 size versus air consumption, blast cleaning ...53 tapered, water blast cleaning ............... 81 thrust, wet abrasive blast cleaning ...........81 venturi, abrasive blast cleaning ......... .55,60 NSF International, address .................. 593 Nuclear power plants, painting ...........442447 painting systems ........................ 446 zinc-rich primers ........................ 136 Nylon brushes ....................... .15 3-154 O Organic pigments. health hazards ....... .54 2.543 Occupational Safety and Health Administration ......... .72. 78. 306. 315 authority ............................. 548 compliance program ........... consultation assistance ......... enforcement .......................... 549 general duty clause .................... 548 regulatory process ..................... 548 Ohm's Law ................................ 5 Oil-alkyd. painting system ...................286 Oil-based binders ......................... 119 Oil-modified urethane binders ...............119 Oil separators, abrasive blast cleaning .....56. 187 ollution Act of 1990.................... 587 ca oil. binders. ....................... 138 Old work. fresh water service ...............310 Olivene rutile, non-metallic abrasives ..........45 On-the-job training of painters ...............249 Opaque pigments ......................... 11 7 Open deck . bridges ....................... 280 Operating mix . metallic abrasives .......... .3 9.41 non-metallic abrasives ..................... 47 Operatior rJf centrifugal blast cleaning machines .................... .2 3.25 Operation procedures, pickling .............. 106
Operator fatigue. controlled mitation cleaning . . 82 plasma-hot gas cleaning ................... 86 water blast cleaning ..................... -83 Operators. abrasive blast cleaning ............ 59 Or-equal clause, specifications .............. 317 Orange peel, failures .................. .508.509 Organic zinc-rich primers .......... .12. 118, 125. 131.132, 415 zinc-rich primers, characteristics ........... 134 zinc-rich primers, versus inorganic ...13, 134-135 zinc.rich. painting system ............ .28 6.287 Orifice size, nozzles ........................ 55 OSHA standards ..................... .550.551 advance notice of proposed rulemaking .....548 applicable to abrasive blasting .............550 comment period ............. 548 compressed air ............. 550 confined spaces ......................... 550 construction industry ................ .55 0.551 electrical ......... ..............550 exposure to gases, vapors, dusts, mists and fumes ...................... 551 eye and face protection ................. -550 general industry ......................... 550 hand and power tools .................... 550 ladders and scaffolding ................... 551 lead and lead removal ...................551 noiselhearing conservation ................550 notice of proposed rulemaking ............. 548 organization and hierarchy ................ 550 personal protective equipment process safety management . . respiratory protection ...... .%O, 551-553 Osmotic blistering ..... Osmotic effects, coatings ..................... 4 Oval brushes ........................ .15 3.154 Overspray.failures .................... .506.507 Oxidation curing. paints ................ .15. 117 Oxygen-fuel gas gun. thermal spray .......456457 Ozone and volatile organic compounds ... .56 1.567 architectural and industrial maintenance coatings rule .......................... 564 non-attainment areas . .561, 565565, 567 relationship ............................ 561 P-C-111 .................................. 92 P-C-436 .................................. 92 PC437 .................................. 92 Pads. paint application ................ .15 3.155 Paint application .......... .150-167. 274-275. 325 adhesion testing ........................ 204 air spray., .............156-157. 160, 194. 196 airless spray .......... .157. 159.160 . 194. 196 application equipment ............. automatic spray .................. brush ................ .150.152.154 . 196. 256. 274-275. 284. 343 brush versus spray ...................... 256
cement mortar ..................... .343-344 chlorinated rubber ....................... 150 cleanliness between coats ............ .20 2.203 ...............344 contact surfaces .................... .25 8.259 cure of coating ... ............ .2O4 .205 damp surfaces .......................... 150 dry film thick .................258. 343 drying ovens ................. 257-258 drying painte .................. 259-261 effect of surroundings .................... 150 effect of weather ........ .... .15O. 274 electrostatic spray ....... .160.257. 343 equipment ........................ .257. 401 equipment. cleanliness ...................194 equipment. cleanup .... ....166 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 640
SSPC CHAPTER*27*3 93 8b27940 0004080 737 evaluation of applicator ................... 357 fabricating plants ........................ 244 faying surfaces ................ field bolt heads ................ field coating ............................ 342 field painting ....................... .22 2.226 field structures .......................... 278 field versus shop ........................ 227 film thickness .............. .166, 196-202. 278 flow coating ............................ 257 forms ................................. 214 handling painted steel .............. .259, 261 heated spray ........................... 160 highway bridges ........................ 284 hotspray .............................. 257 humidity ............................... 343 in fabricating plants ................. .25 1-259 inaccessible surfaces .................... 258 inspection .................193.205, 261. 285, 327, 341, 357 lacquer paints .......................... 150 maintenance painting .................... 435 manual mixing ..................... .I51.152 mechanical mixing ....................... 151 mitts ..................... 153, 155,160.483 mixing........... .151, 195, 255, 274, 277, 343 overspray loss .......................... 258 pads .............................. 153-155 paint heaters ........................... 257 paint recirculating systems ................ 255 painting booths ......................... 257 painting programs .......... .401.403, 416-418. 426-428 pipelines .......................... .35 2-361 power plants ........................... 446 pre-job conference ....................... 388 primers ........................... .25 7-258 production rates ......................... 160 railroad ........................... .27 4.275 records............................ 214, 275 roller................. .150, 153.160. 284. 417 rust preventives .................... .345.346 safety..................... .17 6.1 80,278-279 shop painting ...................... .42 6-428 shop versus field ........................ 421 solvent recovery ........................ 257 spray ................ .150, 152-1 53, 156-1 65, 194, 196, 249, 256-258, 274.275.
284.285. 343 spray pot .............................. 194 spray technique .................... .16 4.165 spreading rates ......................... 255 SSPC-PA 1 ............................ 150 storage ....................... .254.255, 277 storing painted steel .................259, 261 strainers .......................... .152-153 striping ........................... .25 6-257 tanks.................................. 402 temperature ...................... .153, 343 thinning .......... .152, 195, 255-256, 277. 343 tinting ............................ .i51.152 .......................... 151 two-component equipment ................160 twocomponent paints .................... 345 ventilation equipment .................... 257 vinyl ......................... .150.344-345 volume solids ..................... .19 2. 198 waste treatment plants ............... .38 7.388 water-borne paints ................. .150. 345 wet film thickness ....................... 258 zinc-rich primers ......................... 12 Paint application, hazards .............. .54 4-545 air atomization method ................... 544 airless spray ........................... 544 compressor pumps .................. .544445 electrostatic spray ....................... 544 Paint crews. railroad bridges ................ 272 Paint dusts, toxicity ........................ 283 Paint heaters, ............................ 257 Paint house, fabricating plants ............... 244 Paint life, effect of film thickness .........Il, 271 effect of millscale ....................... 244 effect of rusting environment ..............416 effect of surface pH ..................... 105 effect of surface preparation ......140, 244.245. 272, 415 effect of surface preparation. tests ......... 114 pickling versus blast cleaning .............. I14 rural exposures ..................... .26 4-265 variables affecting ....................... 139 Paint materials. safety ..................... 176 Paint records. fabricating plants ............. 244 Paint removers. safety ..................... 176 Paint residues. recovery ..................... 86
Paint shaker, mixing equipment .............. 151 Paint specialists .......................... 244 Paint trays ............................... 158 Paint viscosity, adjustment, spray technique ......................... 165 Painted surfaces. hand tool cleaning ..........69 non-metallic abrasives ..................... 47 solvent cleaning .......................... 96 Painters. qualification tests ............ .249, 444 Painting and Decorating Contractors of America ......................... .77, 554 Painting equipment, pre-fabrication ............24 Painting systems, descriptions ............... 122 Painting. aluminum .............. .145, 434, 524 appearance ............................ 280 ballast tanks. ships ...................... 305 barges......................... 309,31 1-312 bilge areas, ships ....................... 304 bins................................... 270 blast furnaces ...................... .39 1.392 booths ................................ 257 boottops, ships ......................... 303 bridge crews. railroad ......... bridges. accidents ....................... 290 bridges. bosun's chairs ...................290 bridges. fire hazards ..................... 290 bridges, health hazards .............. .28 9-290 bridges, ladders ......................... 290 bridges, life lines ........................ 290 bridges, life nets ........................ 290 bridges. regulations ...................... 290 cargo boxes. barges ..................... 312 cargo holds, ships ....................... 305 cargo tanks. ships .............. .293. 304-305 chemical plants ..................... .41 2-419 chip blow line ........................... 422 cofferdams, ships ....................... 306 coke oven plants ................... .39 0.395 cold weather ........................... 248 concrete .................. .394, 422, 432433 concrete encased steel .............. .247, 278 concrete pipe ........................... 422
contact surfaces ..................... 25&259 contractor. railroad ...................... 272 copper ................................ 434 corrosion protection ...................... 280 corrugated siding ........................ 392 cost effectiveness. ships. ................. 293 costs ............................. 245. 413 costs, breakdown ........................ 276 costs, comparative .................. .22 2-241 costs, fabricating plants .................. 247 costs, highway bridges ................... 289 costs, railroad bridges .................... 269 costs, total structure life .................. 226 conveyors.............................. 422 crude oil tanks .......................... 404 dams .............................. 330-348 decks ................................. 312 drydocking. ships ....................... 293 during construction, ships ................. 294 economics. ships ........................ 294 environmental constraints ........ .330. 347-348 exterior areas. ships ................. .30 3.304 exterior structural steel ............... 431432 faying surfaces ..................... .25 8.259 fences................................. 270 field erected tanks ....................... 422 field welds ............................. 259 fire protection tanks ..................... 316 fireproofed steel ................... .243, 247 flue gas stack .......................... 445 food processing plants ................ 429441 fossil fuel power plants .............. .442.447 fresh water vessels ................. .31 1.313 fuel oil tanks ........................... 316 galvanized decking ...................... 431 galvanized roofing ....................... 393 galvanized steel ........... .122,145.339. 394. 434.481.485. 523-524 government practices .................448-451 handrails .............................. 422 hazards ............................... 254 highway bridges and structures ........28 0-292 history determination ..................... 318 hot liquor tanks ......................... 422 hot stacks ......................... .39 2.393 hull exteriors ........................... 311 hull interiors ....................... .31 1.312 hulls. ships ............................. 303 hydraulic structures ................. .330.348 hydraulic structures. materials selection ........................ .330-340 infabricating plants ................. .24 2-262 industrial plants .................... .377 -378 initial versus maintenance ........... .22 6-228 inspection ..................... .261. 288-289 interior areas ....................... .39 3-394
interior areas. ships ...................... 304 interior decks. ships ..................... 303 interior process areas .................... 431 interior structural steel ................... 431 irrigation works ..................... .33 0.348 living areas. ships ....................... 304 machined surfaces ................. .25 9.260 machinery ......................... 433. 436 machinery and equipment ................ 394 machinery areas. ships ................... 304 masonry ............................... 394 masonry encased steel ................... 247 navy ships .................... .293. 516-527 navy ships. environmental constraints .......525 new equipment .................... .422. 425 new structures .......................... 271 nuclear power plants ................ .44 2.447 peak tanks. ships ....................... 305 penstocks.............................. 335 petroleum refinery .................. .39 6.41 1 petroleum tanks ......................... 319 pickling plants .......................... 106 pipelines .......................... .34 9-362 pipelines. regulations .................... 349 piping................ .270, 330.348. 433. 436 plastic................................. 524 potable water tanks ............ .315. 319. 380 potable water tanks. ships ................ 305 power plants ....................... .44 2-447 preferences ............................ 228 prejudices.............................. 228 process equipment ...................... 402 programs. administration .................396 programs. approval ..................... 421 programs. budgets ...................... 421 programs. coatings suppliers .......... .37 7.378 programs. color selection ................. 420 programs. corrosion survey ............... 420 programs. economics ........... .403. 408. 412 programs. inspection ............... .403. 418 programs. inspection and spot repair .......421 programs. job standards .................. 378 programs. maintenance .............. .42 5-426 programs. maintenance painting ...... .402-403. 412.434-436 programs. materials selection .... .377. 379-380. 396.398. 414-416. 418. 420 programs. new construction ...... .418. 421.425. programs. paint application .......... .401403. 41 6-41 8. 426428 programs. planning ................. .37 7.378 programs. pre-job conference .............. 378 programs. recommendation form ...........409 programs. records ....................... 421 programs. safety ................... .403, 409 programs. specifications ......... .378-379. 398.
417-421.430 programs. surface preparation ........ .399.401. 412-414. 418 pulp and paper mills ................ .42 0-428 railroad bridges and structures ........ .26 3.279 reasons for ............................. 226 records............................ 275. 394 roofing. galvanized ...................... 270 roofs .................................. 393 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 641
SSPC CHAPTERx27.3 93 = 8b279YO OOOYOBL b73 safety ............................. 289, 348 bituminous enamels ............... ...... 351 safety, ships ........306 burn resistant ........................... 303 salt cake silo ........................... 422 catalyzed epoxy ................. ...382, 387 salt contaminated steel .............. .268. 273 cement ........................ ........ 483 shipbottoms ........................ 29E-299 chemical curing ..................1 5. 16. 117 ships and vessels, fresh chemical reactions ....................... 140 water service. .................... .30 7-314 chemical resistant ............... .... ships and v water service ... .29 3-306 chlorinated rubber ...... .15. 315. 392. shop welds ................... 259 mal tar ....................... .270. 333-335 shop, fabric ............... 247-248 coal tar enamel .................... .315. 351 siding ................................ 393 coal tar epoxy .......16. 315.316. 3 34-335. 355. spray equipment ........................ 284 379381. 383. 387. 392. 485 steel enclosed in concrete ................270 coalescing ...................... .... 1 17-1 18 steel gratings ........................... 422 coke oven plants ................ ........ 390 steel piling ........................ .269, 281 compatibility between steel plants ........................ .39 0-395 compatibility with rust steel stacks ............................ 422 compatibility. mainten ........272 steel tanks ........................ .31 5-319 crude oil resistant ... ........3 97 steel to be fireproofed .......... steel to be permanently enclosed drying............................. 259, 261 stern and propeller areas ....... emissivity .............................. 397 superstructures ......................... 312 enamels .......................... . 351-352 systems, boottops .. environmental constraints ................. 382 systems, costs ................. .229-230,234 epoxy..................... .15. 28 4. 315-317. systems. enamels 335. 392 432, 485 epoxy ester ............................ 484 systems. food processing plants ........43740 epoxy polyamide ........I6. 355. 3 98. 415416. systems, fossil fuel power plants ........... 445 433. 488 systems, fresh water vessels .............. 313 epoxy polyamine ............16. 355. 398. 484 systems. galvanized steel epoxy polyester ......................... 431 systems, highway bridges ............ .284 -288 evaluation of new materials .... ...........276 systems, inorganic zinc-rich ............... 287 evaluations. field tests ...... .............. 219 systems, nuclear power plants ............. 446 evaluations. service tests systems, oil-alkyd ....................... 286 failures ...............
systems. organic zinc-rich .... failures. causes .................... .48 6.515 systems, petroleum refinery ... field painting ........................... 224 systems. pipelines .................. .35 1-356 fingerprinting ................. .......... 398 systems, power plants ................ 445446 failures. prevention ............. ..... .48 6.515 systems, pulp and paper mills ..........423424 fish oil ........................ ......... 15 systems, railroad bridges ..............26 6-267 flexibility.................... ....... .I4. 397 systems, railroads ..................275, 278 frequently wet exposure environmen ts ......347 systems, service life ................. .22 8-233 grease ....................... ......... 275 systems, shipbottoms .................... 300 heat resistant .............. .382 .383. 393. 433 systems, topsides ....................... 302 high-build...................... . 11. 276. 284 systems, vinyl .......................... 287 high-build epoxy. ............... .379-381.387 systems, water-borne .... high-Solids.............................. 11 tank barges ............ impact resistant ............... tank exteriors ...............316-317, ingredients ................... 433434 tank interiors .................. .315-316,318 ...................280 tank interiors, safety ..................... 320 ....................... 122 tank interiors, safety check list ............. 320 oil ..................... 13 9 tanks...................... 270, 394, 400402 ................. .14-15. 117 tests, railroad bridges .................... 265 ....15. 117.118. 382. 485 timber bearing surfaces ....... ..26 8-269 lead-free ........................... ... 381 towboats ...................... .309, 31 1-31 2 life expectancy ............ 275 -276 towers ................................ 270 life expectancy. highway bridges ... ....28 7.288 trackscales ....................... low permeability ......................... 3 97 training programs .................. materials. costs ................ .229-230. 234 ........................ 270 mixing ........................ 255.274. 277 ctures ...............349-362 moisture vapor transmission rates ..........493 underwater areas. ships .................. 294 navy ships ...................... .... 516-527 voids, ships ............................ 306 non-skid .................... . . 303 waste treatment plants ................37 9-389 oil base .................... . .483 water treatment plants ............... .37 9-389 oxidation curing .............. . 5. 117 weather decks, ships .................... 303 panel evaluation records ........ .215. 218-219 welds ................................. 308 petrolatum ........ ...............2 75
wood ............................. 394, 524 Paints, abrasion resistant ..... .298. 303. 338. 397 pigments .................. ............ 117 acceptance tests .................... 215221 pot-life .......................... ...... 117 acrylic ................................. 483 product information sheets ....... .........244 acrylic emulsion .................... .38 1-382 quality acceptance. users ...... ...... .21 3-221 acrylic epoxy ........................... 431 quality control .................. ........ 340 acrylics ................................. 14 quality control tests ............ ..... .20 7-212 adhesion to metal ................ quality control. manufacturing ......... .20 7-212 aliphatic urethane .............. .415, 431, 433 red lead-linseed oil .......... ............ 139 alkyd ................. .15. 381-382. 416, 483 residue recovery, abrasive blast cleaning . .78. 87 anticorrosion ................ .IO-18,298, 331 residue recovery. barges ........ ..........87 anti-fouling ...................... .6. 298-299 residue recovery. tarpaulins ... ....... 87 application equipment .................... 256 asphalt ...................... sampling. from containers ... sampling. from tanks ....... sampling. quality acceptance barrier ................. .10-11, 280, 298, 331 binders ........................... .I17-120 silicone aluminum ................. . .393. 415 bituminous................ solvents ...................... .117. 120. 123 spreading rates ......................... 255 standardized tests ............... 216 steel plants ............................ 390 storage ....................... .254.255. 277 synthetic polymer ....................... 288 temperature resistant .................... 397 tests, chemical analysis ..................217 tests. gas chromatography ................218 tests. infrared spectroscopy ..... tests. instrumental analysis ...... tests. physical properties ........ tests. qualitative ......................... 218 thermoplastic ...... ............ .I4.15 thickness. effect on life ...................271 thinning....................... .255.256. 277 thinning for dipping ...................... 256 topcoats ............................... 122 two-component ..................... .16. 117 underground exposure environments ........346 underwater exposure environments ......... 347 uralkyd ................................. 15
urethane.......... .16. 31 7.335. 338. 354. 392 vegetable oil ............................ 15 vinyl ..................... .14. 284. 286. 315. 335.337. 381. 386-387. 483 viscosity. effect of temperature .............161 water-borne ....... .28 6. 288. 315. 339. 381-382 water-borne epoxy ................... 430431 weatherability........................... 397 zinc dust-zinc oxide ...................... 485 zinc-rich primers .................... .43 1-432 Panel preparation. field tests ................220 Panel racks. field tests ..................... 219 Panel tests. scriber ........................ 399 Particle-teparticle contact. zinc-rich primers. ...........129. 131. 134. 145 Particulates .............. .79.558, 560. 569-570 air quality regulations ....... .558. 560. 569-570 methods for assessing particulate emissions .570 PM-1O emission standards ............ .56 9-570 Passivating rinses, phosphating ......... .IO2-103 Passivation, anodic ........................ 142 anodic. adsorption ....................... 143 anodic. precipitation ............. corrosion....................... inhibitive pigments .................. .6. 10-1 1 mechanisms............................ 143 pigments ............................. .4. 6 Peach pits, non-metallic abrasives ............45 Peak count. profile ....................... 41-43 Peak distribution. profile ..................... 40 Peak tanks ships. painting ...........305 Peak.to.valley. profile..... ..........4041 Peeling. failures ....................... 498499 Penetration resistance. paints. tests ..........358 Penknife test. adhesion .................... 204 Penstocks. painting ........................ 335 Performance. evaluations. field tests paints. tests .................. properties. binders ...................... 121 specifications ........................... 448 Personal protective equipment. OSHA standards .............. 551 head protection ......................... 551 foot protection .......................... 551 respiratory protection . . Personnel. maintenance pa
Pertechnetate. pigments .................... 144 Petrolatum paints ......................... 275 Petroleum Equipment Institute. address .......593 Petroleum refinery. .............396. 411 painting systems . ............. .405.407 ................. 398 Petroleum solvents. solvent cleaning ..........90 Petroleum tanks. painting ................... 319 pH of abrasives ...................... non-metallic ....................... pH of surface. effect on paint life ............105 for inorganic zinc-rich primer .............. 105 Phenolic. bin ................119.12 1.122 linings... ....................... 323 paints .................... .15. 315. 335. 392 Phenolic. epoxy. linings .................... 323 Phosphate pigments ....................... 144 Phosphates, rust inhibitors ............... .66. 81 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 642
SSPC CHAPTERm27.3 73 W 8627940 O004082 50T Phosphating .......................... .9 8.103 welded assemblies .............. ........ 105 chromate-free rinses ..................... 103 Pigment volume concentration .... .... .11.12. 139 chromic acid rinses ..................IO2.103 Pigment-vehicle combinations. comparison of zinc and iron phosphate ......103 chemical reactions ............. .......... 140 environmental constraints ................. 103 Pigments factory application ........................ 99 aluminum........................ . .117. 338 field application ..................... .99, 102 aluminum flake ................ ......... 144 gels................................... i02 anatase titanium dioxide ........... ....... 140 government specifications ................. 101 anodic ......................... ......... 6 immersion baths ........................ 100 anodic inhibitors ................. .. .138. 146 immersion process ....................... 99 anti-corrosion ............... 1 17 . 122. 138-1 49 low temperature .................... .IO1-102 barium metaborate ................ ...... 141 manual process .......................... 99 basic lead silicochromate ......... 140.141, 245 passivating rinses ................... .IO2-103 borosilicate.................... ......... 142 pretreatment ............................ 7.8 calcium barium phosphosilicate ... ......... 142 process operations ...................... 100 calcium borosilicate ............. ......... 142 selection of process ...................... 99 calcium carbonate ............... ........ 140 solvent ................................ 102 calcium phosphosilicate ........... ....... 142 spray baths ............................ 100 calcium strontium phosphosilicate . .........142 spray process ........................... 99 calcium zinc molybdate ............ ....... 142 Phosphoric acid .......................... 145 cathodic ........................ ......... 6 pickling ............... .104-106.111.113. 115 cathodic inhibitors ........ pretreatment ........................... 275 cathodic protection ........ treatments ......................... .98, 102 chemical reactions ............... ........ 138 Phosphosilicate, pigments .................. 142 chromate-free.................. ......... 147 Physical adhesion .......................... 10 chromates..................... . 144.145, 246 Physical properties. metallic abrasives ...32, 34-35 chromates. solubilities ...
................. 497 non-metallic abrasives ................. .48-51 electrochemical reactions ...... ...... .I38-139 paint tests ..................... .211.212, 218 environmental constraints ...... ...........147 Physical tests, paints ...................... 358 extender ..................... .......... 117 Physical versus chemical cleanliness ..........20 ferric molybdate ............. ............ 143 Pickling ............................. .IO4-116 inhibitive............. 11, 138149 acid embrittlement ....................... 111 inhibitive mechanisms .... 42.144 . 146 baths, analysis ................. .I08.I IO, 112 inhibitive, passivation ....... ..........6,10-1i baths, liner materials ..................... 114 iron oxide .................... .......... 140 baths. quality control .............108.110, 112 lamellar ...................... .......... 11 chromic acid ........................... 105 lead chromate ..................... ..... 141 clear water rinses ....................... 113 lead silicate ................... ......... 141 cold rinses ............................. 105 lead suboxide .................... ...... 142 cost accounting ......................... 110 lead-free......................... ...... 147 costs................................... 76 mechanical protection .............. . .I3 8.139 electrolytic.......................... 114-115 metallic......................... ....... 117 environmental constraints .............104,115 molybdated zinc oxide ........... ........ 142 equipment..................... .110, 112-114 molybdates ........................ .I4 2.144 fabricating plants ........................ 243 opaque ......................... ....... II7 Footner process ..................... 112-1 13 paints .......................... ....... 117 for galvanizing .......................... 115 passivation...................... ...... .4, 6 for inorganic zinc-rich primers ............. 115 pertechnetate................. .......... 144 heat treated steels ....................... 106 phosphates ..................... ....... I44 high strength steels. ..................... 106 phosphosilicate ................ ......... 142 hot rinses .............................. 105 primer. purpose of ............... ........ 243 hydrochloric acid ............... .104-109. 115 red lead .................. .138 . 140. 143. 245 hydrofluoric acid ........................ 106 safety........................ .1 76, 179, 542 hydrogen embrittlement .................. 111 selection of, for finish coats ...
............. 16 hydrogen evolution ...................... 104 sciorin........................... ...... 147 inhibitors.................. .104. 110.111. 115 sodium chromate ................ ........ 143 low carbon steel ........................ 104 strontium chromate ............... .. .I4 3-144 millscale removal ........................ 104 strontium nitrate ............... ..... .I4 3.144 muriatic acid ................... .IO4.1 09, 115 technetium .................... ......... 144 neutralizing rinses ....................... 105 toxic materials ................ ..... .I7 8.179 nitric acid., ....................... .104, 106 tribasic lead phosphosilicate .. .............144 operation procedures .................... 106 typical compositions ............. ........ 142 operation records ....................... 110 zinc.............................. ..... 117 phosphoric acid ........ .104-106,111-113, 115 zinc chromate ................. . 140.144. 146 plants, painting ......................... 106 zinc dust ....................... ... 145. 246 plants, ventilation ....................... 106 zinc oxide ................... post-treating of metal .................... 105 zinc phosphate .............. pre-cleaning of metal .................... 105 zinc phospho oxide .............. ........ 146 procedures............................. i13 zinc phosphosilicate ............... ...... 142 quality control .......................... 114 zinc potassium chromate ......... ..... 145-146 rate, effect of acid concentration ........10 7.108 zinc salts ................. ......... .I4 6-147 rate, effect of agitation............... .IO7.108 zinc yellow .................. ........... 145 rate, effect of iron salts ...........107-109,112 Pigments and other additives, health hazards ..542 rate, effect of temperature............ .IO7.108 chromium....................... ....... 542 rust removal ............................ 104 lead ............................. ..... 542 smut, causes ........................... 110 titanium .......................... ..... 542 smut, removal .......................... 11O zinc............................... .... 542 sodium dichromate ...................... 115 Piling. steel. painting ........... ...... .269. 281 special steels ........................... 11 1 Pinholes, failures ............. ............. 507 stainless steels .................... .104,111 Pinpoint rusting. failures ...... .............. 495 sulfuric acid ................... .104-113, 115 Pipe hangers. designs for sulfuric-phosphoric acid .............. .I12.113 corrosion prevention .......... .......... 246 tanks.................................. 251 Pipe rollers ....................... .. .154. 159 tanks, construction ................. .106, 114 Pipe structures failures ....... .............. 513 tanks, lining ........ .... .106,114 Pipeline, coatings, desirable versus blast cleaning. paint life ............ 114 characteristics..............
........ .34 9-351 cathodic disbonding ..................... 350 cathodic protection ...... .349-350.363. 364-376 cathodic protection in permafrost .......37 4.375 holiday detection ............... .352.353. 355 paint application .................... .352.361 painting ........................... .34 9.362 painting systems ................... .351, 356 painting. accessibility .................... 351 painting. costs .......................... 351 painting. geography ...................... 351 painting. handling ....................... 351 painting. soil conditions ..................350 painting. storage ........................ 351 painting. temperatures. ambient ............ 351 painting. temperatures. operating ...........351 regulations ............................. 349 surface preparation ................. .35 1.356 zinc-rich primers ................... .126. 136 Pipes, painting .......... .270. 330.348. 433. 436 Piston scaler, impact cleaning tools ...........69 Pitting. corrosion of steel ..................... 6 failures ................................ 495 Planning. maintenance painting ......... .42 5-426 painting programs ................... 377-378 Plant personnel. maintenance painting ........425 Plasma spray gun, thermal spray .........456.457 Plasma-hot gas cleaning, operator fatigue ................................. 86 surface preparation ....................... 86 Plastic bristles. brushes ..................... 93 Plastic pellets. non-metallic abrasives .......... 85 Plastic. painting ........................... 524 Pneumatic tools safety. power tool cleaning .....73 Polarization. cathodic ..................... 140 effect upon corrosion . Polyester, brushes ...... linings ............................. 323-324 Polyethylene. extruded .................35 3.354 linings ............................. 336-337 ........................... 355 tic. paints .................. 288 Polypropylene. extruded ............... .35 3.354 Polyurethane. binders ...................... 119
Polyvinyl butyral. binders ................... 120 Polyvinyl chloride. linings ................... 381 Polyvinyltapes ........................... 355 Porosity. zinc-rich primers ............. .128.130 Portable enclosures. abrasive blast cleaning ....87 Portable ground supports .............. .I6 9.170 Portable supports. safety ............... .I7 2.173 Portable systems. centrifugal blast cleaning.................... .23. 28.30. 86-87 Positector 6000.dry film thickness gage ..194. 201 Post.curing. zinc-rich primers ... Post-fabrication system. centrifug blast cleaning .............. Post-surface preparation. inspect Post-treating of metal pickling . . Pot tender. field painting ................... 222 Pot.life. paints ............................ 117 two-component paints .................... 152 Potable water tanks, painting .......... .315, 319 ships. painting .......................... 305 Potassium silicates. zin primers......I2 6-127 Powder coatings ..... ....335. 337. 354-355 Power plants. paint application ..............446 painting............................ 442447 painting systems .................... .445-446 surface preparation ................. .444-445 Power tool cleaning ............ .68.74. 272. 283 abrasive wheels ......................... 297 air-powered tools ........................ 297 burnishing .............................. 71 burrs................................... 70 chisels ................................ 297 coated abrasives. safety ................... 73 costs................................... 75 ear protection ............................ 72 electrical tools. safety ..................... 73 eye protection ........................... 72 impact cleaning tools .................. .6 9.70 impact tools. safety ....................... 73 non-woven abrasives. safety ................ 73 pneumatictools. safety .................... 73 production rates .......................... 75 respirators .............................. 73 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS
SSPC CHAPTERx27.3 73 W 8627740 0004083 44b W rotary cleaning tools ......... .6 9.70 rotary impact cleaning tools ........... .6 9.73 rotary impact tools, safety ................ 73 rotary wire brushes. safety .............. 73 roto peen. safety ...................... 73 safety ................ . . 72-74 scalers .......................... 297 solvent cleaning .......................... 71 tight mill scale ....................... 71 versus water blast cleaning .............67 Pre-cleaning of metal. pickling .............105 Pre-construction primers ..............14. 295 zinc-rich ............................. 132 Pre-fabrication cleaning. advantages ......... 26 Pre-fabrication painting equipment ............24 Pre-fabrication primers ............ .26-27. 84 Pre-fabrication systems, centrifugal blast cleaning ......................... 24-27 Pre-job conference. inspection ...............182 paint application ...................... 388 painting programs .................... 378 Pre-paint treatments, phosphating ........ .9 8-103 Pre-surface preparation, inspection ...... .18 2-183 Pressure gage, hypodermic needle ...... .185. 188 Pressure pot, abrasive blast cleaning ..........53 hazards ............................... 546 Pressure rollers .......................... 159 Pressure type blast cleaning equipment ................. .52-55. 57. 59 Pressure vessels, hazards ................ .6 2-63 Pretreatments ........................... 275 fresh water vessels ..................... 310 inspection ............................ 261 phosphating ........................ 7-8 phosphoric acid ...................... 275 wash primers ........................... 261 wetting oils ............................. 261 Prevention. health hazards ..................179 paint failures ...................... .48 6-515 Primer. selection of, fabricating plants .......243 Primers, after-blast ....................... 295 anti-corrosion ........................... 122 barrier ................................ 10 criteria for selection ...................251 drying time versus wetting ability ...........245
formulation practices ................ .245. 246 galvanic ............................ 10. 331 hazards .............................. 245 inhibitive ........................... .1 0-12 latex ........................... .142, 145 linseed oil ............................ 245 paint application ................... .25 7-258 pigment. purpose of ..................... 243 pre-construction ..................... .14. 295 pre-fabrication .................... .26-27, 84 red lead ............................... 245 red lead. linseed oil .................... 243 selection. effect of surface preparation ......245 shop ............................. 249-251 shop, typical ............................ 253 testing ................................ 251 vehicle. purpose of ...................... 243 wash .................... .120, 122, 144-145. 261. 275, 297. 387 water-borne .......................... 142 zinc-rich ............. .6, 10, 42. 122. 125-137. 145. 284-285. 315-316. 339 Procedure, abrasive blast cleaning ......... .6 8-69 hand tool cleaning .................... .6 8-69 maintenance painting .................... 228 pickling ............................... 113 Process Process Process Product
equipment, painting ................402 operations, phosphating .............100 variables. hot dip galvanizing .... .47 4-477 development. paints. quality
control ............................. 207-208 Product information sheets. paints ...........244 Production lines. fabricating plants ...........248 Production platforms, zinc-rich primers ........135 Production rates, abrasive blast cleaning .......................... 60, 76 air spray application ..................... 160 airless spray application .................. 160 brush application ........................ 160 controlled cavitation cleaning ............... 82 hand tool cleaning ........................ 75 hydroblasting . . . . . . . . . .76 metallic abrasives ................60 non-metallic abrasives ................. 60 paint application ..................... 160 power tool cleaning ..................... 75 roller application .............. 160 solvent cleaning ....................... 75 surface preparation ................7 5-77 water blast cleaning ................... 66 wet abrasive blast cleaning .............E1-82
Profile ............... .....285 abrasive blast cleaning ...............58 angularity .......................... 43 burnish ................................ 43 controlled cavitation cleaning ...............82 effect on film thickness measurements .... 200 height ............................. 40-41 measurements ......... .i85-187. 192-193, 324 measurements, Clemtex Coupons .......... 192 measurements, comparators ..............192 measurements, depth micrometers ..... .19 2-193 measurements, dial surface profile gage .... 186 measurements, Keane-Tator comparator ..................i85-1 86, 192 measurements, Testex Press-O-Film Tape ............................ 186, 193 measurements, replica tape .......... .186, 193 metallic abrasives ................. .37, 40-44 non-metallic abrasives ................ .4 7-48 peak count ........................... 41-43 peak distribution ......................... 40 peak-to-valley ........................ .4 0-41 requirement, effect on surface preparation ....20 surface preparation ............. .20, 189, 192 water blast cleaning .................... 64 Proposals .......................... 238-240 request for ............................ 238 Protective clothing, safety ..................178 Protective equipment, water blast cleaning ......67 Psychrometer, dew point measurements . . 182-185 electric ........................ .i8 2-185 relative humidity measurements .......183-185 sling ............................... 182, 183 Psychrometric tables ...................... 184 Pulp and paper mills . painting ......... .420, 428 painting systems ................ .42 3-434 Qualification tests. painters ...............444 Qualified products list ..................... 448 Qualifying test. painters .................... 249 Quality acceptance. finished product ..........213 labeling requirements .................... 213 paints, sampling ................ .213.214. 216 paints. users ............. .213.221, 398 specifications ....................... 213 testing procedures ..................... 213 Quality assurance .................... .28 8-289 Quality control. application properties .........252 drying times ......................... 252 fabricating plants .................. 252. 254 paints ............................ 340 paints, finished product ........ .207, 209-210 paints, formulation ................. .20 7.208
paints. laboratory ........................ 207 paints. manufacturing .................207.21 2 paints. manufacturing process .........207. 209 paints. product development ........ .207-208 paints, raw materials ........... .20 7.209 pickling ............................... 114 pickling baths ...................108-110. 112 tests. paints ....................... .207.212 thinning ............................... 252 viscosity .............................. 252 volatile content .................... .252. 254 weight per gallon ...................... 252 Railroads. bridges. inspection 269 inspection practices 278 maintenance painting 271-272 paint application ................... .27 4.275 painting systems ............ 275, 278 painting systems. bridges ......... .26 6.267 painting. bridges and structures ....... .26 3.279 tank cars. lining ......................... 326 Rate of cleaning. centrifugal blast cleaning .....25 Rate of consumption. metallic abrasives ........32 Raw materials. paints. quality control .... .20 7-209 Reaction cathodic ......................... 10 Recirculating systems. paint application ....... 255 Recoating criteria. maintenance painting ......402 Recommendation form. painting program ......409 Recording hygrometer ..................... 183 Records. inspection. fabricating plants ........244 maintenance painting .................... 425 paint application ........................ 214 paint. fabricating plants ...................244 painting .......................... .275. 394 painting programs ..................... 421 panel paint evaluations .......... .215. 218-219 pickling operations ...................... 110 Recovery. paint residues .................... 86 Recycling. abrasives ........................ 86 non-metallic abrasives ..................... 48 Red lead. pigments .......... .138. 140. 143. 245 Red lead-linseed oil. paints .................139 primers ................................ 243 Refineries. zinc-rich primers ................. 136 Regulated materials. chromium ...............79 silica ................................... 79 surface preparation ...................... 79 suspended particulates .................... 79 Regulations .............................. 251 abrasive blast cleaning .............. .283. 556 blast cleaning ..................... .291. 556 environmental ............. .246. 295. 556-593 food processing plants ................436 government .................... .290.291. 293
health & safety ..................... .53 8.555 painting bridges ......................... 290 petroleum refinery painting ................398 pipeline painting ........................ 349 surface preparation ...............79. 88. 291 tank interior paints ..................... 315 US Department of Agriculture ........ .436. 591 US Food and Drug Administration ..... .436. 591 Regulatory agencies ....................... 557 federal ............................ 548. 557 state .................................. 557 local ............................... 582 Reinforcing steel. corrosion .................268 Relative humidity. measurements ........ .18 3.185 measurements. psychrometer ......... .I8 2.1 84 Remote controlled. water blast cleaning .... .82.83 Replica tape. profile measurements ..... .186. 193 Reportable quantities. hazardous substance spills ......................... 580 Reports. maintenance painting. ships .... .30 2-303 Request for proposals ..................... 238 Requirements. sealers ..................... 459 Resistance. effect upon corrosion ............5.6 Resource Conservation and Recovery Act ........................ 78. 558. 573-579 Respiratory protection ................. .551-553 abrasive blast cleaning .............56.57. 177 air-purifying respirators ................532 blast cleaning ........................... 52 breathing air standards ................... 553 choosing ........................... 551-553 for lead removal ........................ 551 hand tool cleaning ........................ 73 need for ........................... 551-552 OSHA standard ................... 551 power tool cleaning ...................... 73 protection factors ........................ 552 supplied air respirators .............. .177. 552 types .................................. 552 Responsibilities. health and safety ........... 539 employers ............................. 539 employees ............................. 539 engineers .............................. 539 inspectors .............................. 539 Riggers. field painting ..................... 223
Rigging. aerial supports ......... .168. 170-171 choice of ......................... .17 1.172 safety ...................... .17 3.1 74 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 644
SSPC CHAPTERs27.3 73 8627740 0004084 382 Right angle machines. rotary cleaning tools ...............70. 72 Rigid span. bridges ...................... 280 Rinse water. ionic content. solvent cleaning ........................ 91 Rinses. chromate-free. phosphating ..........103 chromic acid. phosphating .......... .10 2-103 clear water. pickling ................113 cold. pickling ................105 hot pickling ........................... 105 neutralizing. pickling ..................... 105 passivating. phosphating ............ 10 2-1 03 Roll conveyors. centrifugal blast cleaning ......................... 26-27 Roller. paint application ................284. 417 Rollers. application production rates ..........160 cleanup ........................... 166 covers ........................... 155-157 fabric covers .................... .15 6-157 fence .............................. 159 handles ............................ 158 napcovers ........................ 156 paint application .............. .150. 153-160 pipe .............................. 154. 159 pressure ............................. 159 Rolling scaffolding ........................ 326 Roofing. galvanized .................. .268. 270 Roofs. painting ......................... 393 Rotary cleaning tools. air powered machines ....................7 1-72 coated abrasives ..................... .7 0-71 electrically driven machines ................71 in-line machines ..................... .70. 72 non-woven abrasives ................. .7 0-72 power tool cleaning ................-69-70 right angle machines ................ .70. 72 wire brushes ........................ .7 0-71 Rotary impact cleaning tools. cutter bundles ...................... .7 2-73 flexible flaps ....................... .7 2-73 power tool cleaning .............. .69. 71-73 rotary chipper ......................... 72 rotary hammers ...................... .7 2-73 roto peen ........................ .7 2-73
Rotary impact tools. safety. power tool cleaning ....................... 73 Rotary wire brushes. safety. power tool cleaning ........................... 73 Roto peen. rotary impact cleaning tools ................................ 72-73 safety. power tool cleaning ................ 73 Round versus angular. non-metallic abrasives ...46 Runs and sags. failures ................ .50 9-510 Rural exposures. paint performance ...... .26 4-265 Rust inhibitors .......................... 297 chromates ............................. 81 compatibility with paints .......... .64. 66. 81 dichromates ............................. 66 effect on adhesion ................. .66. 81 molybdate ............................. 81 nitrates ................................. 81 phosphates ......................... 66. 81 water blast cleaning .............. .64. 66. 296 wet abrasive blast cleaning ................81 Rust preventives. application ........... .34 5-346 Rust. composition of ......................... 3 formation of ............................. 3 loose hand tool cleaning .................. 68 removal. pickling ................... .104-116 tight. hand tool cleaning ...................68 Rusted surfaces. non-metallic abrasives ........47 Rusting environment. effect on paint life .......416 Rusting. percentage of. inspection .........183 visual inspection. bridges ............ 282 S Sacrificial anodes. cathodic protection ........299 Safe Drinking Water Act ......... .558. 581-583 drinking water standards ......... .581.583 maximum allowable levels .............582 maximum contaminant levels ........ .558. 582 Safety ......................... .53 8.539 incentives ............................ 538 sources of information ... .....554 Safety and health programs establishing ........................... 553 owner evaluation ..............553 Safety. professional organizations ............538
Safety ................... .17 6-1 80. 538-555 abrasive blast cleaning ......... .61-63. 545 airless spray ................. .176, 544 binders ............................. 176 blast cleaning .................... .176. 545 buddy system ......................... 178 catalysts ................179, 541. 543 check list. painting tank interiors ....... 320 cleaners .......................... 179. 543 colors ..................... .306. 393-394. 420 degree of hazard ...................176 dermatitic materials ...............179, 541 equipment. hand tool cleaning ... .68-69. 545-546 eye protection ..................... .178. 550 fabricating plants .................... 261 -262 first aid ............................ 179 government regulations ....... .180, 538-555 hand tool cleaning ............ .72-74, 545-546 health hazards ............. .178-179, 540-544 manufacturer s instructions ................180 paint application .... .176-180. 278-279. 544-545 paint materials ............... .176. 539-544 paint removers ................ .176. 543 painting .................. 289. 348. 544-545 painting programs .................. .403, 419 painting tank interiors ................... 320 pigments .................... .176. 542-543 portable supports ................. .17 2-1 73 power tool cleaning ........ .72-74. 545-546 procedures. navy ................ .52 4-525 protective clothing ................. .178. 551 respiratory protection ........... .177, 551 -553 rigging .............. .173-174. 176. 546-548 scaffolding ............. .172. 174. 176. 546 ships. painting ........................ 306 shop painting ................. .26 1-262 signs ................................. 180 solvent cleaning .................... .91, 176 solvents ....... .176. 178. 179. 539-541, 543 stationary supports ...................... 172 steam cleaning ........................ 176 surface preparation ..............176, 545-546 tank painting ...................... .410, 41 1 toxic materials ................ .178. 540-543 water blast cleaning .............. .64. 67. 546 Sags and runs. failures .............. .509-510 Salt cake silo. painting ..................... 422 Salt contaminated steel. painting ....... .268, 273 Salt water service. painting, ships and vessels ........................ 293-306 tugboats ............................... 309
Salt water. frequently wet exposure ...... .26 7-268 Sampling procedures, quality acceptance .................... 213, 214, 216 Sand injection. water blast cleaning ... .65. 79-80 Sand volume, wet abrasive blast cleaning .....80 Sands, non-metallic abrasives ...............45 Sash brushes ............................ 153 Scaffolding ....................... .16 8-175 accessories .......................... 169 aerial supports .............11 1-174 cable supported ..................17 0-171 choice of ......................... 171-172 safety ......................... .17 2-174 Scalers ................................ 297 Scaling hammers, impact cleaning tools .... .6 9-70 Scaling. failures ...................... .49 8-500 Scanning electron microscopy. paint tests .....399 Scissors lift. ground supports .......... .16 9-170 Scrapers. hand tool cleaning ........... .6 8-69 Scriber. panel tests ....................... 399 Sealers. advantages ...................... 459 disadvantages ...................... 459 requirements ........................ 459 thermal spray coatings ..............458-460 Secondary containment ............... .58 7-590 acceptable containment structures . .587. 589-590 choice of coatings ................. .587-588 flake and fiber-filled coatings ......... .588. 590 Oil Pollution Act of 1990 ...............587 regulations ..................... .587-588 reinforced thick-film coating systems ........588 thin film coatings ........................ 588 use of coatings ......................... 587 Selection of abrasive, air blast cleaning ........52 Selection. centrifugal blast cleaning equipment ........................... .2 8-29 Selection. phosphating process ............... 99 Self-curing. zinc-rich primers .... .127.128. 131-132 Self-propelled systems, centrifugal blast cleaning ........................... 30 Service life. painting systems ...... .22 9.233 Service tests. paint evaluations ..............219 Shape, abrasives ....................... .5 7.58 non-metallic abrasives ..................... 46 Sharp edges. rounding ..................... 182 Shasta Dam ............................. 331 Ship deck systems . centrifugal blast cleaning . . 28 Ship hull systems. centrifugal blast cleaning ....84 Ship side systems, centrifugal blast cleaning ....28 Shipbottom systems, centrifugal blast cleaning . . 28 Shipbottoms. cathodic protection ............ 299
painting systems .................... .29 8.300 Ships, ballast tanks. painting ...............305 bilge areas, painting ..................... 304 bootops. painting ........................ 303 cargo holds. painting ..................... 305 cargo tanks. painting .......... .293. 304-305 cofferdams. painting .................... 306 construction. painting .................... 294 cost effectiveness. painting ............... 293 drydocking, painting ..................... 293 economics. painting ..................... 294 exterior areas. painting .............. .30 3.304 fresh water service. painting ..........307314 hulls. painting ......................... 303 inspection for corrosion damage ...........294 interior areas. painting .................. -304 interior decks, painting ...................303 living areas, painting ..................... 304 machinery areas, painting ...............304 maintenance painting ................299, 303 navy. painting ...................... .51 6-527 peak tanks. painting ..................... 305 potable water tanks, painting ..............305 safety painting ......................... 306 salt water service. painting .......... .29 3-306 surface preparation .................... 295 underwater areas. painting ................294 voids, painting .......................... 306 weather decks, painting ..................303 Shop cleaning ............................ 249 centrifugal blast cleaning ...............26-28 Shop finished steel. field painting .......... 271 Shop painting ....................... .24 2.262 advantages ......................... 421-422 costs ............................. 229. 234 inspection ......................... 260-261 multi-coat systems ............... .42 1.422 paint application ....................42 6.428 safety ............................ .26 1.262 specifications .......................... 420 supervision ............................. 260 surface preparation ................. .42 6.428 Shop pretreating .......................... 249 Shop primed steel field painting ............. 271 Shop primers .................. .249.251. 253 failures ............................. 250 life expectancy .......................... 250 Shop versus field. blast cleaning ........ .227, 421 Shop versus field. paint application ..... .227, 421
Shop welds, cleaning and painting ...........259 Shot. peening, metallic abrasives .............34 Shot metallic, size specifications ..............33 Sicorin. pigments ......................... 147 Siding. painting ........................... 393 Sieve analysis. non-metallic abrasives ......... 49 Signs, safety ............................. 180 Silica, health hazards ............. .283. 542. 543 Silica sands, non-metallic abrasives .... .45. 52. 60 Silica sol, zinc-rich primers ................. 127 Silica. regulated materials ...................79 Silicates. zinc-rich primers .................. 128 Silicon carbide, non-metallic abrasives .. .46. 48. 58 Silicone acrylic. paints ............... .391. 433 Silicone alkyd. binders ..................... 119 paints ....................... 316. 383. 485 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 645
vehicles ............................... 338 Silicone aluminum. paints ............. .393. 415 Silicone binders ........................... 119 Silicosis. hazards .......................... 32 abrasive blast cleaning .................... 78 Single component. non-metallic abrasives ..................... 49 Size specifications. metallic abrasives .......... 33 Size versus coverage. metallic abrasives .......36 Size versus impact energy. metallic abrasives ...36 Size. abrasives ............................ 57 non-metallic abrasives .................. 46-47 Slags, boiler, non-metallic abrasives .... .45. 4748 coal. non-metallic abrasives ............ .60, 62 copper. non-metallic abrasives metal smelting. non-metallic abrasives .......45 mineral. non-metallic abrasives ............. 58 nickel, non-metallic abrasives ............... 47 Sling psychrometer ................... .182. 184 Soaps. inhibitive .......................... 143 lead ............................. .138. 142 .................... 140 ngineers.......... .32, 35 Society of Environmental Toxicology and Chemistry. address ...................... 593 Society of Naval Architects and Marine Engineers. address ...................... 303 Sodium chromate. pigments .. Sodium dichromate, pickling . Sodium silicates. zinc-rich primers ....... .12 6-127 Soil conditions. pipeline painting .............350 Soil. regulations Housing and Community Development Act ...559 Soils. oily. solvent cleaning .................. 90 semi-solid. solvent cleaning ................ 90 solid containing . solvent cleaning ........... 90 Solid deck bridges ........................ 280 Solubilities. chromate pigments .............. 497 Solvent cleaning ....................68. 71. 273 acid cleaners ............................ 91 alkali cleaners .... ............. .9 0.91 brushes ......... ................. 95 chlorinated solvents ............. .9 0-91 choice of methods ........................ 91 costs ................................... 75 detergent cleaners ........................ 91 environmental constraints .............. .90. 96 foamed detergent cleaning ............. .94-95 government specifications .................. 92 high pressure-hot detergent ............. .9 4-95 materials ............................ .9 0.97 methods ............................ .90.97 mineral spirits ........................... 91 oily soils ................................ 90 painted surfaces ......................... 96 petroleum solvents ....................... 90 production rates .......................... 75
rinse water. ionic content .................. 91 safety ............................. .91. 176 semi-solid soils .......................... 90 solvent wiping ........................... 91 sponges ................................ 95 steam cleaning .................... .91, 93-94 stoddard solvent ......................... 91 surface contaminants ..................... 90 surface preparation ........... .90-97. 105. 401 waste disposal ........................... 96 xylene .................................. 91 Solvent phosphating ....................... 102 Solvent recovery. paint application ........... 257 Solvent resistance. zinc-rich primers .......... 133 Solvent wiping. solvent cleaning .............. 91 Solvent-reducible zinc-rich primers ....... .13 1-132 Solvents. alcohols ......................... 123 aliphatic hydrocarbons ................... 123 aromatic hydrocarbons ...................123 chlorinated ............................. 123 comparisons ...................... .120. 123 dermatitic materials ...................... 179 esters ................................. 123 evaporation times .................. .120. 123 field painting ........................... 224 flash points ....................... .120. 123 glycol ethers ........................... 123 ketones................................ 123 nitroparaffin ............................ 123 paints ............... . .117. 120. 123 threshold limit values . . ...... .120. 123 water ................................. 123 Solvents and thinners ................. .53 9-541 fire hazards ........................ .53 9-540 health hazards .......................... 541 precautions ........... .176. 178-179. 306. 541 Southern Railway ......................... 269 Spatter coating. failures .................... 507 Specific gravity, abrasives ................ .57-58 Specifications. Bureau of Reclamation ........ 449 chemical cleaning ........................ 92 color .................................. 347 composition ............................ 448 Corps of Engineers ...................... 449 Department of Defense ................... 449 Department of Defense. Index of ........... 449 federal ............................. 448-449 field topcoating ......................... 430 galvanizing ............................ 479 government ........................ .44 8-451 Guide to U S Government Paint ........... 449 Joint Army-Navy ........................ 449 maintenance painting .................... 425 maintenance painting. ships .......... .30 0-301 Maritime Administration .................. 449 military ............................ .44 8-449 or-equal clause ......................... 317 painting programs .............. .378.379. 398.
417-421. 430 performance............................ 448 pre-job review of. by fabricators ............ 247 quality acceptance ....................... 213 shop painting ........................... 430 size, metallic abrasives .................... 33 solvent cleaning .......................... 92 Spills. hazardous substances ....... .558.584-585 reportable quantities ............ .580. 584-585 Splash zone exposures .................... 267 Sponges. solvent cleaning ................... 95 Spot cleaning. maintenance painting ..........273 Spray. application. hazards .................256 automatic .............................. 257 electrostatic ................... .257. 354-355 equipment. air ...................... .15 6.157 equipment. airless .................. .15 7.159 equipment. cleanup ...................... 166 equipment. hook-ups ..................... 159 gun. air ................................ 156 gun. airless ............................ 157 paint application ....... .150, 152.153, 156-165. 194. 249, 258-258. 274-275. 284-285. 343 painting. air supply ...................... 284 painting equipment ...................... 284 painting equipment. inspection ....... .193. 195 pattern adjustment, spray technique ........ 165 pot. paint application. .................... 194 process. phosphating ..................... 99 technique. air pressure adjustment .........165 technique. air spray ...................... 165 technique. airless spray .................. 165 technique. paint application ........... .16 4.165 technique. paint viscosity adjustment ....... 165 technique. spray pattern adjustment ........ 165 versus brush. paint application .............256 Spreading rates. paints .................... 255 Spy. holiday detection. instruments ........... 204 SSPC-PA 1 ............ .150. 185. 343. 388. 418 SSPC-PA 2 ................. .198, 199. 201. 417 SSPC-PA 3 ......................... .176, 182 SSPC-PA 4 ..................... .343, 391. 416 SSPC-Paint 5 ............................ 119 SSPC-Paint 8 ............................ 120 SSPC-Paint 9 ....................... SSPC-Paint 1 i ..................... SSPC-Paint 13 ..................... SSPC-Paint 16 ... .............. 118. 253 SSPC-Paint 17 ...................... .119. 253 SSPC-Paint 18 ........................... 119 SSPC-Paint 19 ........................... 1 19 SSPC-Paint 20 .................. .118. 129. 253 SSPC-Paint 21 ....................... 119. 253 SSPC-Paint 22 ....................... 118. 253 SSPC-Paint 23 ....................... 119. 253
SSPC-Paint 24. .......................... 119 SSPC-Paint 25 ........................... 253 SSPC-Paint 27 .................. .122. 144. 272 SSPC-Paint 28 ........................... 253 SSPC-Paint 29 ....... ............118. 253 SSPC-Paint 101 .......................... 118 SSPC-Paint 104 .......................... 118 SSPC-Paint 106 .......................... 120 SSPC-PS 1 .00 ............................ 119 SSPC-PS 2.00 ........................... 118 SSPC-PS 2.05 ............................ 118 SSPC-PS 3.00. .......................... -119 SSPC-PS 4.00. ........................... 120 SSPC-PS 11 .O1 ........................... 118 SSPC-PS 12.00 ...................... 1 18. 135 SSPC-PS 12.01 ...................... 1 18. 135 SSPC-PS 13.01 ........................... 118 SSPC-PS 15.00. .......................... 119 SSPC-PS 16.01 ........................... 119 SSPC-PS 17.00 ........................... 120 SSPC-PS 18.01 ........................... 119 SSPC-PS 24.00 ........................... 119 SSPC-SP 1 ...................... .75. 184. 273 SSPC-SP 2 ...................... .75. 272. 283 SSPC-SP 3 ...................... .75. 272. 283 SSPC-SP 5 .......................... .75. 273 SSPC-SP 6 ...................... .75. 273. 283 SSPC-SP 7 ...................... .75. 273. 283 SSPC-SP 8 ............................... 75 SSPC-SP 10 ..................... .75. 273. 283 SSPC-SP 11 .............................. 75 SSPC-Vis 1 .............................. 189 SSPC-Vis 2 .............................. 183 Stacks. steel. painting ..................... 422 Standardization Documents Order Desk ..... p. 218 State Highway Departments. survey .......... 285 State Implementation Plans ................. 290 Static electricity. abrasive blast cleaning ............................. 54. 61 Stationary scaffolding ...................... 169 Stationary supports. safety .................. 172 Staurolite. non-metallic abrasives ......... .45. 60 Steam cleaning. equipment .......... .93-94. 102 safety ................................. 176 solvent cleaning ................... .91. 93-94 Steam propelled. abrasive blast cleaning .......83 Steel encased in concrete. cleaning .......... 243 painting .......................... 247. 270 Steel Founders Society of America ...........35 Steel grating. designs for corrosion prevention ..................... 246 Steel grit. metallic abrasives .......... .58. 60. 86 Steel plants. painting .................. 390-395 paints ................................. 390 surface preparation ...................... 390 Steel related failures ................. .500.503 Steel selection. hot dip galvanizing ....... 472473 Steel shot. metallic abrasives ............ .58. 86 Steel Structures Painting Council. address ........................... 450. 593
Steel Tank Institute, address ................ 593 Steel. composition. effect upon corrosion ........ 7 galvanized ............................. 263 low-alloy ............................... 7-8 new. abrasive blast cleaning ............... 64 permanently enclosed painting .............243 plate. laminations ................... .18 2-183 surface preparation ...................... 400 theory of corrosion .... weathering ........................ .7-8. 263 Steels. heat treated. pickling ............... 106 high strength pickling ............ 106 special, pickling ......................... 111 stainless. pickling .................. .104. 11 1 Stepladders ............................. 168 Stern and propeller areas. painting ...........311 Stiffeners. designs for corrosion prevention ....246 Stoddard solvent. solvent cleaning ............ 91 Storage. paints .................. .254-255. 277 pipeline painting ........................ 351 Storage vessels. regulation ............. .58 7-591 hazardous waste ............... .587-588. 590 petroleum products ................. .584. 589 regulations. underground storage tanks ........................ 559. 588-591 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 646
SSPC CHAPTERa27.3 93 8627940 000408b 155 secondary containment ....... .587.588. 589-590 Storing. painted steel ................. .259. 261 Strainers. paint application ............. .I52.153 Stray currents. cathodic protection ....... .37 3.374 Stray electric currents. corrosion ............. 263 effect upon corrosion ...................... 7 ....................... 246 Stress raisers ............................ 246 Stringers. bridges ......................... 269 Striping coat ............................. 256 edges ................................ 244 paint application ........................ 257 Strontium chromate pigments ........... .I4 3-144 Strontium nitrate pigments .............. 143-144 Structures designs for corrosion prevention ....... highway. painting ......... railroad. painting .......... Styrene-based binders ..................... 119 Submerged exposure environments ...380-381.384 Substrate-related paint failures ...........500405 Suction type blast cleaning equipment ...52, 54-56 Sulfates surface contaminants ........... .lo.297 Sulfide discoloration. failures ................494 Sulfuric acid pickling ......104.106.108-111. 115 Sulfuric-phosphoric acid. pickling ....... .112. 113 and Reauthorization ........ .558-559.585-587 tion ..................585 National Response Center ..............585 planning and response ................. 585 section 301-303....................... 585 section 304........................... 585 section 31 1-31 2 ................... .58 5-586 section 313........................... 586 threshold planning quantity ......... .58 5.587 toxic chemical release inventory ..... .586.587 Superintendent of Documents. address .......450 Superstructures. bridges ................... 269 painting ............................... 312 Supervision. shop painting .................. 260 Supervisors field painting ................... 223
Surface area and tonnage bridges ....... .26 9-270 Surface conditions. effect on surface preparation ....................... 19 fabricated steel ................ pre.painting. highway bridges .... black light test ................. chlorides .......................... .lo.297 effect on adhesion ........................ 10 effect on corrosion ....................... 10 oily soils ................................ 90 semi-solid soils .......................... 90 solvent cleaning .......................... 90 sulfates .................. Surface finish. non-metallic abra surface preparation ....................... 20 Surface preparation abrasive air blast cleaning ............ .29 5-296 abrasive blast cleaning ........52.63. 105, 243. 283.342. 417 abrasives ............3244, 45.51. 86.295-296 air-water-sand blast cleaning .............79-81 alkali cleaners .................. aluminum...................... bacterial cleaning ..................... .84-85 blast cleaning ........ .2241. 52-63. 79.83, 273 blast cleaning. regulations ................291 bridges ............................ 283-284 centrifugal blast cleaning ........... .22.31. 295 chemical cleaning ...................... 9097 chemical cleanliness ...................... 20 choice of methods ................ .19.21. 273 citric acid cleaning ....................... 85 cleanliness ............................. 189 closed-cycle blast cleaning ................ 295 coke oven plants ........................ 390 concrete......... ............ 387. 432 copper .......... ................ 400 costs ............ .......75-77. 81. 401 costs. estimating procedures .............7 6-77 costs review . cryogenic coating removal .................85 direct costs ............................. 75 documentation ........................... 75 dust removal ........................... 342 effect of degree of cleaning ............. .l9.20 effect of job location ...................... 19 effect of profile requirements ...............20 effect of surface condition .................19 effect on paint life .......140, 244.245. 272, 415 effect on paint life tests .................. I i4 effect on primer selection ................. 245 environmental constraints . . 20-21, 30, 78-79, 88 environmental impact ..................... 21 explosive propelled ....................... 85
fabricating plants ............... .242-243. 249 field welding ............................ 277 flame cleaning ........................... 86 flash rusting ............................. 81 Flashblast............................... 85 fresh water vessels ................. .31 0-31 1 galvanized steel ........ .387, 400, 434, 483-484 grease removal ......................... 342 hand tool cleaning ............... .68-74. 105, 272.283. 297, 342 handling cleaned surfaces ................. 95 .............466-467 ................. 75 inspection ..........75. 188.193, 260-261. 284, 288-289. 327, 341 laser cleaning ........................... 85 maintenance painting ........413-414, 425, 435 masonry ............................... 400 mechanical .......................... .2 2-31 metallic abrasives ...... ......... .3 2-44 navyships ............................. 520 new approaches ...................... .7 8-79 new structures .......................... 277 non-metallic abras' ................45-51 painting programs ..399401, 412-414. 418 ...............9 8-103 physical cleanliness. ...................... 20 pickling ........................... .10 4-116 pickling. fabricating plants ................243 plasma-hot gas cleaning ................... 86 power plants ....................... .444445 power tool cleaning ....... .68.74, 272, 283. 297 production rates ...................... .7 5-77 profile ........................ .20. 192. 284 regulations ...... .79.88, 291. 543-546. 569-571 rust inhibitors ............................ 81 safety............................. .17 6-1 80 ships.................................. 295 shop cleaning ........................... 26 shop painting ....................... 426428 solvent cleaning ......... .90-97.105. 273. 401 spot cleaning ........................... 273 steel .................................. 400 steel plants ............................ 390 ....................... 342 ....................... 324 thermal cleaning ......................... 85 thermal spray coatings ............... .45 8-459
ultrasonic cleaning .................... .8 5.86 visual comparator .................. .185, 192 visual standards ........... ........ 189 warranties .............................. 75 waste treatment plants ............... .38 6-387 water blast cleaning ..... .64.67, 79-83, 295-297 water treatment plants ................38 6-387 wet abrasive blast cleaning ............. .7 9.83 wood ............................. 387, 400 xenon flash lamps ..................... 83, 85 zinc shot blasting ........................ 84 zinc-rich primers .................13, 134, 135 Surface preparation, hazards .... .78, 254, 543-546 abrasive blasting ........................ 545 acids and alkalis ........................ 543 caustics ............................... 543 chemical strippers ....................... 543 dust and abrasive fines ................... 543 hand and power tools .................... 545 pressure pots ........................... 546 precautions ........................ .17 6-180 silica.................................. 543 water jeíting ............................ 546 welding. cutting and heating ........... Surface repairs. surface preparation ..........342 Surface temperature, measurements ..........185 thermometer ................ Surface treatment, rust inhibitors . . Surface treatments. effect on painted steel ......8 Surfaces. designs for corrosion prevention ......................... .53 3-534 Sulfuric acid, pickling ..........105. 107. 112-1 13 Surroundings. effect on paint application ......150 Survey. State Highway Departments ..........285 Suspended particulates. regulated materials ....79 Suspension span bridges ...................280 Synergism. painting galvanized steel ..... .481-482 Synthetic polymer. paints ...................288 Systems. thermal spray .................... 461 T Tank barges. fresh water service ........307. 309 painting............................... 309 Tank painting, environmental constraints ......315 Tankers, zinc-rich primers .................. 136 Tanks, coatings inspection .............. 317-318 crude oil, painting ... ............. 404 dry foodstuff, lining . . exteriors, painting ........... .316-317,433434 field erected, painting .................... 422
fire protection, painting ...................316 food processing. lining ...................321 fuel oil. painting ......................... 316 hot liquor. painting ...................... 422 interiors, design for corrosion prevention ....321 interiors, painting ............... .315-316.318 interiors painting. regulations .............. 315 interiors. painting, safety .................. 320 interiors, painting. safety check list .........320 lining. curing ........................ 326-327 lining, inspection ........................ 327 lining, maintenance painting ...............328 lining, paint application ............... 325327 lining, surface preparation ............ .32 4-325 liquid foodstuff. lining .................... 434 maintenance painting ....... paint application ........................ 402 painting ...................270, 394, 400-402 painting, environmental constraints .........319 ...................... 319 ...................... 251 n ............... .106, 114 pickling, lining ..................... .106,114 potable water. painting .......... .315, 319, 380 safety. painting .................... .410, 411 sampling paints from ................ .21 3-214 steel, lining ........................ .32 0-329 steel, lining, materials selection ....... .32 1-324 steel, painting ...................... .31 5-319 storage. failures ......................... 513 water, lining failures ..................... 322 g...............318 ................337 cleaning ......... 65 Tapes, coal tar ........................... 355 coatings............................ 355-356 polyethylene............................ 355 polyvinyl ............................... 355 Tarpaulins, paint residue recovery ........ Technetium. pigments ..................... 144 Temperature resistance, zinc-rich primers .....133 Temperature-resistant paints ................397 Temperature effect on paint viscosity ......... 161 ambient, pipeline painting .................351 effect on pickling rate ............... .IO7-108 measurements ..................... .183-185 operating. pipeline painting ...............351 paint application ................... .153, 343
Test panels. field tests ..................... 219 Testex Pressa-Film Tape, profile measurements..................... .186. 193 Testing procedures, quality acceptance ....... 213 Testing, primers .......................... 251 Tests, abrasive breakdown rates .............. 58 abrasives ............................... 61 breakdown non-metallic abrasives ........... 51 Design Basis Accident .................. -442 effect of surface preparation on paint life ....114 evaluation of non-metallic abrasives .......48-51 evaluation, zinc-rich primers .......... .13 5-136 field. for abrasives ........................ 58 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 647
SSPC CHAPTERs27.3 93 8627940 0004087 091 field. zinc-rich primers .................... 135 Loss of Coolant Accident ............... 442 painting. galvanized steel ......... .48 1.485 painting. railroad bridges ..............265 paints. abrasion resistance ................357 paints. acceptance .................. .21 3.221 paints. appearance in container ........... 212 paints. application characteristics .......211 paints. atmospheric weathering ............358 paints. bendability ....................... 357 paints. cathodic disbonding ...............358 paints. chemical analysis ...............217 paints. chemical resistance ...............358 paints. composition ...................212 paints. density measurements .............211 paints. dispersion measurements ...........211 paints. electrochemical ...................358 paints. emission spectroscopy ............399 paints. film characteristics ................211 paints. film properties ..................211 paints. gas chromatography ...... .218. 398-399 paints. impact resistance ................. 357 paints. infrared spectroscopy ..... .218. 398-399 paints. instrumental analysis ..............218 paints. mass spectroscopy ................398 paints. penetration resistance ..............358 paints. performance ............... .21 1-212 paints. physical ......................... 358 paints. physical properties ............ .2t 1-21 2 paints. qualitative .............. .211-212. 218 paints. quality control ................ 207-212 paints. scanning electron microscopy .......399 paints. standardized ..................... 216 paints. ultraviolet spectroscopy ...........399 paints. viscosity measurements ........... 21 1 surface treatment on painted steel ......... 8 Thermal cleaning. surface preparation .........85 Thermal spray. aluminum coatings ...... .457-458. 460-461. 463 coatings ............................ 456-464 coatings. barrier ........................ 458 coatings. cathodic protection ...........458 coatings. characteristics ..................457 coatings. properties ...................... 458 coatings. sealers ................... .45 8-460 coatings. surface preparation ......... .45 8-459 costs .............................. 462-463 electric arc gun ................. .45 6-457 equipment ...................... 456. 462 hazards ............................... 463 oxygen-fuel gas gun ................. .45 6-457 plasma spray gun ....................45 6-457 systems .............................. 461 zinc Coatings ................ .457-461. 463 Thermite reaction ......................... 463
Thermoplastic binders ...................... 11 paints ............................... 14-15 Thermosetting binders ...................... 11 coatings .............................. 354 paints ............................... 15-16 Thickness-related failures .................506 Thickness. effect on paint life ...............271 Thinner. effect of additions on volume solids .......................... 198 Thinning-related failures .................... 505 Thinning. inspection ...................... 195 paint application .............. .152. 195. 343 paints ........................ .255-256. 277 paints. for dipping ....................... 256 quality control .................... 252 Thixotropic paints. viscosity measurements .......................... 195 Threshold limit values. solvents ......... .120. 123 Through and overhead bridges .............280 Throwing power. cathodic protection ............7 Tie-coats. zinc-rich primers .................. 13 Timber bearing surfaces. painting ....... .26 8-269 Time and materials contract .................239 Time of wetness .......................... 281 Tinker-Rasor. holiday detection. instruments ........................ .20 3-204 Tinting. paint application ............... .15 1-152 Tonnage and surface area. bridges ...... .26 9-270 Tooke. dry film thickness gages ................... .t98-199. 201-202 Tools. hand tool cleaning ............... .68-69 Topcoating. zinc-rich primers ....... .1 3. 115. 122. 128. 131-132. 134. 303. 339 Topcoats. paints .......................... 122 Topsides. painting systems .................302 Towboats. fresh water service ..... .307. 310-31 1 painting ....................... .309. 311-312 Towers. painting .......................... 270 Toxic contaminants. non-metallic abrasives .....50 Toxic materials. additives .................. 179 binders ............................... 179 pigments ............................. 179 safety ................................. 179 solvents ........................... 178-179 Toxic Substances Control Act .......... .559. 583
lead pigments in industrial paints ..........583 premanufacture notice ...................583 provisions affecting end users .............583 provisions affecting formulators ............583 significant new use rule .................. 583 Toxicity Characteristic Leaching Procedure ............. .78. 574. 577-579. 581 Toxicity. paint dusts ...................... 283 silica sand ............................. 283 Trackscales. painting ...................... 270 Training of painters. apprenticeship .......... 249 fabricating plants ........................ 249 on-the-job .............................. 249 Training of workers. fabricating plants ........ 248 Training programs. evaluation of program ........................ .45 4-455 identifying needs ........................ 453 maintenance painting .................... 425 painting ......................... .45 2-455 steps .............................. 452-455 trainee selection ........................ 453 training methods .................... .45 3-454 training staff ............................ 454 Training. operators . abrasive blast cleaning ........................ .6 1-63 water blast cleaning ...................... 67 Training. paint application .................. 151 Treatments. hot dip galvanizing ......... .47 7-478 phosphoric acid ..................... .98. 102 Tribasic lead phosphosilicate. pigments ....... 144 Truss span. bridges ..................... 280 TT-C-490 ........................... 92. 101 TT-P-641 ................................ 393 Tugboats. salt water service ...............309 Tung oil. binders .......................... 138 Turntables. painting ....................... 270 Two step formal advertising contract ..... .23 9-240 Two-component epoxy. binders .............. 118 Two-component paint application equipment ...160 paints ............................. .16. 117 paints. application ....................... 345 paints. mixing .................. .151-152. 195 paints. pot-life ......................... 152 spray gun ..................... ..16 3.165 urethane .............................. 119
U US Department of Agriculture regulations ........................ .436. 591 US Food and Drug Administration. regulations ........................ .436, 591 Ultrasonic cleaning. surface preparation .....E5-86 Ultraviolet spectroscopy. paint tests .......... 399 Undercutting. causes ...................... 139 failures ............................... 500 Underfilm corrosion. causes ................. 102 Underground structures .................... 268 painting ........................... .34 9-362 Underground. exposure environments .... .33 5-337 exposure environments. paints ............ 346 Underground storage tanks ........ .559, 587-591 corrosion protection ................. .589-590 existing petroleum underground storage tanks ......................... 589 federal regulations .............. .559. 587-590 new petroleum undergound storage tanks ...589 secondary containment .............. .587-589 state regulations ................... .59 0-591 underground chemical tanks .......... .589-590 Underwater areas. ships. painting ............294 Underwater exposure environments ...... .33 2-335 paints ................................. 347 United States Public Health Service ..........305 Uralkyd paints ............................. 15 Urethane. aliphatic. paints ......... .415. 431. 433 binders ................................ 119 binders. aliphatic .................. .11 9.122 binders. aromatic .................. .ll 9.120 binders. moisture-curing .................. 119 binders. oil modified ..................... 119 Urethane foam, insulation ..................356 Urethane, paints ..... .16, 317, 335, 338. 354. 392 Urethane resins, health hazards ............. 541 Urethane. two-component ................... 119 Users. paints. quality acceptance .... 213.221. 398 Vacuum recovery blast cleaning equipment .................... .52. 56. 85-87 Valves. choke. abrasive blast cleaning .........56 control. abrasive blast cleaning ........... 55.56 dump. water blast cleaning ................. 67 metering. abrasive blast cleaning .... .54.56. 187
Vegetable oil paints ........................ 15 Vehicles. alkyd ........................... 338 barrier paints. choice ..................... 11 primer. purpose of ....................... 243 properties of ............................ 17 silicone alkyd ........................... 338 Velocity. metallic abrasives .................. 35 Ventilation equipment. paint application .......257 Ventilation. inspection ...................... 183 pickling plants ......................... 106 Venturi nozzles. abrasive blast cleaning .... .55. 60 Very Large Crude Carriers. fouling cost .......294 Vessels. corrosion. effect of water quality ...... 307 corrosion. fresh water service ......... .30 7.309 designs for corrosion prevention ........... 309 fresh water service. painting .......... .30 7.314 salt water service. painting ........... .29 3.306 types. fresh water service .................307 Vinyl acetate binders ...................... 145 Vinyl chloride binders ...................... 120 Vinyl copolymer binders .................... 391 Vinyl. binders ........................ .12 0.122 ester. linings ...................... .32 3.324 linings ................................. 324 paint application ................ .150.344-345 painting system ......................... 287 paints ........... .14. 284. 286. 315. 335. 337. 381. 386-387. 483-485 Vinyl.alkyd. binders ........................ 120 Viscosity. measurements. paints. tests ........ 211 measurements. thixotropic paints ........... 195 measurements. Zahn cup ............ .187. 195 quality control ......................... 252 Visual standards. surface preparation ......... 189 Voids. ships. painting ...................... 306 Volatile content. quality control ......... .252. 254 Volatile Organic Compounds compliance with regulations .......... .56 5.566 from shop applied coatings ..............562 from marine coating operations ............564 low-voc coatings ........................ 565 measuring .......................... 566-567 state approaches to regulations ............ 565 Volume solids. effect of added thinner ........ 198
Volume solids. for film thickness calculations ........................ .19 7.198 paint application ........................ 197 Wall brushes. paint ................... .15 3.154 Walnut shells. non-metallic abrasives ..................... .45.48 . 58. 84 Warranties surface preparation ............... 75 Wash primers ............. .120. 122. 144-145 261 275. 297. 387 ~ fresh water vessels ..................... 310 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 648
SSPC CHAPTERs27.3 93 8627940 0004096 OT4 W galvanized steel ......................... 483 Waste disposal. solvent cleaning .............. 96 Waste handling and disposai regulations .................... .558.575579 hazardous waste ............... .558. 575579 non-hazardous waste .................... 579 Waste treatment plants. paint application . .38 7.388 painting ........................... .37 9.389 surface preparation ................. .38 6.387 Water absorption, coatings .................... 4 Water blast cleaning .............. .64-67. 79-83 abrasive injection. ........................ 64 abrasives ............................... 65 controlled cavitation ...................... 82 costs ............................. 66-67. 76 dump guns .............................. 65 dump valves ............................ 67 equipment ........................... .6 5-66 etch ................................... 64 high pressure ................ .64.65. 295-297 limitations............................... 64 low pressure ......................... .6 4.65 maintenance painting ..................... 67 nozzles. circular ......................... 65 nozzles. tapered ......................... 65 operator fatigue .......................... 83 operator training ......................... 67 production rates .......................... 66 profile .................................. 64 protective equipment ...................... 67 remote controlled ..................... .82-83 rust inhibitors ................... .64. 66. 296 safety .......................... .64. 67. 546 sand injection ........................... 65 scaffolding ............................... 67 versus hand tool cleaning .................. 67 versus power tool cleaning ................. 67 with sand injection .................... .7 9.80 Water curtain. abrasive blast cleaning ... .79. 81-82 Water Environment Federation. address .......593 Water Jet Technology Association. The. address ............................... 554 Water jetting. hazards ...................... 546 Water quality regulations ................... 558
drinking water standards ............. .580.583 Federal Clean Water Act ................. 558 maximum allowable levels ................ 582 maximum contaminant levels .............. 558 National Ambient Water Quality Standards ....................... .58 0-581 National Pollutant Discharge Elimination System ................ .58 0-582 permits ............................ 581-582 point source discharge ............... .58 1-582 potable water in storage tanks ........ .58 2-583 Safe Drinking Water Act ......... .558. 581-583 state and local ordinances ................ 582 storm water discharge .................... 582 Water tanks maintenance painting ........... 318 Water treatment plants. paint application .. .38 7.388 painting ........................... .37 9.389 surface preparation ................. .38 6.387 Water volume. wet abrasive blast cleaning ...... 80 Water. fresh. frequently wet exposure ......... 267 ships and vessels. painting ........... .30 7-314 Water. salt. frequently wet exposure ..... .26 7-268 ships and vessels. painting ........... .29 3-306 Water solvents ........................... 123 Water-borne epoxy paints .............. .43 0.431 Water-borne binders ....................... 147 Water.borne. paint application. cleanup .......166 painting system ......................... 287 paints ............ .286. 288. 315. 339. 381-382 paints. application ................... 150. 345 primers ................................ 142 Water-reducible zinc-rich primers ............. 131 Wax coatings ............................. 356 Wear. metallic abrasives .................... 38 Weather decks. ships. painting .............. 303 Weather-related failures ................ .505-506 Weather. effect on paint application ..... .150. 274 Weatherability. paints ...................... 397 Weathering steel ..................... .7-8. 263 Weathering. galvanized steel ............ 482-483 Weathering, zinc-rich primers ............... 133 Weight per gallon quality control .............252 Weld-related failures ....................... 511 Welded assemblies. pickling ................ 105 Welding. cutting and heating. hazards ........546 Welding procedure. hot dip galvanizing ....... 472 Welding. zinc-rich primers .................. 133
Welds. cleaning ...................... .31 1-312 cleaning and painting ............... .259. 308 improperly prepared ..................... 311 intermittent. coating failures ............... 332 properly prepared ....................... 312 spatter removal ......................... 182 Wet abrasive blast cleaning .............. .7 9-83 costs ................................... 81 hazards ................................ 81 nozzle thrust ............................ 81 production rates ...................... 81-82 sand volume ............................ 80 water volume ............................ 80 Wet bulb temperature. measurements .... .18 4-185 Wet film thickness. gages ...... .187.188. 196-198 gages. interchemical ................ .190. 197 gages. notch type ...................... 197 measurements ............. .165. 196-198. 258 Wetness time .................... Wetting ability. primers. versus drying time ............................. 245 Wetting oils. pretreatments .................. 261 Wheel travel. centrifugal blast cleaning ......... 25 Willemite ................................ 125 Wire brushes .............................. 93 hand tool cleaning .................... .6 8.69 rotary cleaning tools ................... .7 0.71 Wood ladders ............................ 168 Wood-related failures .................. .502-503 Wood. painting ...................... .394. 524 surface preparation ................. .387. 400 Work cage. aerial supports ............. .17 1.172 Work car. centrifugal blast cleaning ........ .25-26 Work handling. centrifugal blast cleaning .................. .23. 25. 27-29 Work mix. metallic abrasives ..... .32. 3741. 4344 replenishment. metallic abrasives ........... 40 Woronora pipeline, zinc-rich primers .......... 126 Wrinkling. failures ......................... 491 X Xenon flash lamps. surface preparation .... .83. 85 Xylene. solvent cleaning ..................... 91 Z Zahn cup. viscosity measurements .......187. 195
Zinc chromate. pigments .......... .140. 144. 146 Zinc dust. pigments .................. .145. 246 Zinc oxide. American process ............... 145 pigments ..................... .140. 145. 246 Zinc phosphate. coatings ............... .9 8.103 pigments .............................. 146 Zinc phospho oxide. pigments ............... 146 Zinc phosphosilicate. pigments .............. 142 Zinc potassium chromate. pigments ...... .14 5.146 Zinc-related failures ................... 501 -503 Zinc salts. pigments ................... .14 6-147 Zinc shot blasting. surface preparation .........84 Zinc silicate. coatings ...................... 125 Zinc yellow. pigments ...................... 145 Zinc. coatings. hot dip galvanized ....... .46 5-480 coatings. thermal spray .. .457458. 460-461. 463 Zinc. pigments ............................ 11 7 Zinc. type. hot dip galvanizing ............ 473474 Zinc-coated. non-metallic abrasives ............ 84 Zinc-dust-zinc oxide. paints ................. 485 Zinc-rich primers ........ .6. 10. 12. 122. 125.137. 145. 284-285. 315-316. 339. 431-433 abrasion resistance ................. .129. 134 adhesion ....................... .13. 133-1 35 alkali silicates ........................ .1 2.13 alkyl silicates ....................... .13. 127 ambient curing ..................... .126-127 ammonium silicates ................. .12 6-127 application of ............................ 12 barrier protection ......................... 13 binders ................................ 131 bridges ........................... .i35.136 cargo carriers .......................... 136 case histories ....................... 135-136 cathodic protection .... .6, 13, 129. 131. 133-134 cellosolve silicates ....................... 127 chemical bonding ................... .12 8-133 chemical reactions ........... chemical resistance ........... coefficient of friction ................. .13 3.134 colloidal silica .......................... 126 compared with galvanizing ........... .13 2.133 conductive extenders .......... .12.14, 131-132 curing ............................ .i2 6-131 drilling rigs ............................. 135 electrical conductivity .................... 129 environmental reactions .................. 128 ethyl silicates ...................... .12 7.128 evaluation tests ..................... .13 5.136 faying surfaces ..................... .13 3.134 field tests ..... ...............135 film thickness . . ................13 formulation ............. ... .12. 127
Golden Gate Bridge ..................... 136 heat curing ............................ 126 history ............................ .12 5.126 inorganic ............... .12-13, 118, 125-132, 383, 392.393, 415-416, 444 inorganic versus organic .......... .13, 134-135 inorganic, characteristics ........... inorganic. pickling for ............. inorganic, single component ........ inorganic, surface pH .................... 105 limitations ......................... .13 4-135 linings ................................. 324 lithium silicates ..................... .12 6.127 mist coats for ............................ 13 mixing ................................. 195 nuclear power plants ..................... 136 organic ............ .12. 118, 125, 131-132. 415 organic characteristics ................... 134 particle-to-particle contact ....12 9. 131, 134. 145 pipelines. Morgan Whyalla ........... .126, 136 pipelines, Woronora ..................... 126 porosity ........................... 128. 130 post-curing ................... .126, 127, 131 potassium silicates .................. .12 6-127 pre-construction primers .................. 132 production platforms ..................... 135 refineries .............................. 136 self-curing ................. .127.128, 131-132 silica sol ............................... 127 silicates ............................... 128 single component .................. .128. 132 sodium silicates .................... .12 6.127 solvent resistance ....................... 133 ................ 131 -132 ............ .13, 134-135 tankers ................................ 136 temperature resistance ................... 133 tie-coats for ............................. 13 topcoating ................. .i3. 115. 122, 128 131.132. 134, 303, 339 Type 1-A ................................ 131 Type 1-B ................................ 131 Type 1-C ............................. 131-132 Type 2 .................................. 132 versus galvanizing ....................... 227 water-reducible ......................... 131 weathering ............................. 133 welding ................................ 133 Zinc.rich, inorganic, painting system ..........287 Zinc.rich, organic, painting system ........286287 Zircon, non-metallic abrasives ........
Zones, environmental ...................... 268 chemical exposure ...................... 268 frequently wet, fresh water ................ 267 frequently wet, salt water ............. .26 7-268 normally dry (rural) ...................... 264 painting systems .................... 266-267 zone 1 B .............................. 264 zone 2A ................................ 267 zone 2B ............................ 267-268 zone 3 ................................ 268 Copyright The Society for Protective Coatings Provided by IHS under license with SSPCNot for ResaleNo reproduction or networking permitted without license from IHS 649
