CEOCOR COMMITTEE ON THE STUDY OF PIPE CORROSION AND PROTECTION SECTOR C MATERIALS
CRITERIA FOR THE SELECTION OF METALLIC PIPELINES COATINGS
GUIDELINES
May 2005 Edition
INTRODUCTION
These guidelines deal with coatings (internal and external) for non-alloyed or lowalloyed steel, stainless steel, copper and cast iron pipe coatings, in other words, the widely used metals for water and gas pipeline systems. Metal corrosion occurrences can be controlled by using two techniques, which are generally jointly used: the passive protection and the active protection or cathodic protection. The passive protection consists in an electrolytic separation between the metal and the pipeline environment, through applying appropriate coatings. The pipeline coating plays an important role in the anticorrosion protection system and its effectiveness is essential for the piping system durability. Due to the difficulty of their inspection, mainly for buried or immersed pipelines in deep waters, it is essential that the use of coatings provides the same durability properties as the one expected for the piping system (40 years or more). On buried or immersed, electrically continuous metallic pipelines (welded or shunted joints), cathodic protection is realized with an appropriate electric current circulation between an artificial anode and the pipeline, which constitutes the cathode of the system. When the direction and the applied current intensity assure a sufficient lowering of the electrochemical potential of the metal, the material is located in the immunity field at the metal-electrolyte interface, where corrosion phenomena reduce to industrially negligible values. Cathodic protection is usually applied on the external surfaces of buried or immersed non alloyed or low alloyed steel pipelines (welded joints or metallic connections); in special circumstances, it can also be applied at the internal surfaces of these pipelines. The cathodic protection of externally coated and buried stainless steel pipelines is only applied in particular cases. On buried cast iron pipes, due to the electrical discontinuity of the joints assembly, cathodic protection is only exceptionally applied. This technique no more applies for copper pipelines. In order to obtain an excellent durability of a pipeline, the selection of the coating, the application and its control after the application are fundamental. Therefore these guidelines, prepared by a group of European experts, are to be considered as a useful supplement to National, European and International standards, and a precious help for the designers and the end users. Easy to employ, it can be considered as an important working tool for all who may be interested.
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The chapters in the guideline cancel and replace the following former recommendations: Chapter 1: Criteria for the selection of steel pipes coatings, April 1992 Ed. Chapter 2: Criteria for the selection of non- and low alloy steel pipelines accessories coatings, March1994 Ed. Chapter 3: Criteria for the selection of pipelines external coatings of stainless steel tubes and accessories, May 1998 Ed. Chapter 4: Criteria for the selection of external coatings of copper pipe systems, April 2001 Ed. and March 2003 Ed. Chapter 5: Coating selection criteria for cast iron pipes, April 2001 Ed. and March 2003 Ed.
The members of the Working Groups who contributed to the elaboration of this document are: M. Arpaia, I E. Bini, I D. Copin, F E. Di Caprio, I G.P. Guidetti, I M. Langenfeld, F J. Mailliard, F G.C. Mei, I L. Rigosi, I M. Romagnoli, I, G. Rouleau, F H.E. Wolff, D
(chapter 1) (chapter 1) (chapters 1, 2, 3, 4, 5) (chapter 3) (chapters 1, 2, 4, 5) (chapter 5) (chapters 1, 2, 3) (chapter 4) (chapter 3) (chapters 1, 2, 3, 4, 5) (chapters 1, 2, 3) (chapter 1).
Acknowledgments: I would like to thank my Working Group's colleagues for their precious help in the realization of these guidelines and my Sector C colleagues for their revision and critical comments during plenary meetings, chaired by B. Elzenga (first part of the document) and by S. Rigal (second part of the document). Special thanks go to D. Copin, G.P. Guidetti and M. Langenfeld for the final text revision; D.H. Deacon for the English translation of chapter 1 (a version of this chapter in Italian is also available); C. Triquet for the German and English translation of chapter 4; M. Langenfeld for the English and German translation of chapter 5; G. NOUAIL for the editorial setting and last checking, and up-dating some European standards or drafts indicated in the edition of March 2003. The Leader of Working Group "Coatings" M. Romagnoli
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CONTENTS AND SUBJECT INDEX OBJECTIVE.................................................................................................................................. 7 METALLIC PIPELINES DESIGN AND CONSTRUCTION............................................................. 8 CHAPTER 1 - CRITERIA FOR THE SELECTION OF COATINGS FOR NON AND LOW ALLOY STEEL PIPES................................................................................................................. 11 1.1 SCOPE .................................................................................................................... 11 1.2
REFERENCES ........................................................................................................ 11 International standards and draft standards ............................................................... 11 European standards and draft standards................................................................... 11 National European standards..................................................................................... 12 CEOCOR recommendations and bibliography........................................................... 14
1.3
TYPES OF COATINGS FOR NON AND LOW ALLOY STEEL PIPES ..................... 16 External coatings for underground pipes and those coming out of the ground ........... 16 External coatings for underwater pipes, whether or not in underwater excavation, or in tidal zone ............................................................................................................... 17 External coatings for pipes in the open ...................................................................... 18 External coatings for overhead pipes, in duct and in tunnel ....................................... 19 External temporary protection for pipes ..................................................................... 20 External coatings for hot or waste water pipes when passing through walls............... 20 Internal coatings for water pipes ................................................................................ 21 Internal anti-friction coating for gas pipes................................................................... 21 Internal coatings for vertical gas and oil pipes............................................................ 21 Internal coatings for hot and waste water pipes in buildings....................................... 22
1.2.1 1.2.2 1.2.3 1.2.4
1.3.1 1.3.2 1.3.3 1.3.4 1.3.5 1.3.6 1.3.7 1.3.8 1.3.9 1.3.10
1.4 COMPARATIVE CHARACTERISTICS OF COATINGS FOR NON AND LOW ALLOY STEEL PIPES............................................................................................................. 23 1.4.1 External coatings for underground, underwater, overhead pipes ............................... 23 1.4.1.1 Mechanical characteristics ........................................................................ 23 1.4.1.2 Physico-chemical characteristics............................................................... 23 1.4.1.3 Thermal characteristics ............................................................................. 27 1.4.2 Internal coatings for water pipes ................................................................................ 28 1.4.2.1 Mechanical characteristics ........................................................................ 28 1.4.2.2 Protection against corrosion ...................................................................... 29 1.4.2.3 Physico-chemical characteristics of thermosetting resins .......................... 29 1.4.2.4 Thermal characteristics ............................................................................. 29 1.5 1.5.1
1.5.2
COATINGS OF WELDED JOINTS FOR NON OR LOW ALLOY STEEL PIPES ...... 30 External coatings of welded joints for underground, underwater pipelines ................. 30 1.5.1.1 Anti-corrosive tapes................................................................................... 30 1.5.1.2 Shrink materials ........................................................................................ 30 1.5.1.3 Filling-in products...................................................................................... 31 Internal coatings of joints ........................................................................................... 31
1.6 Summary table of main types of external coatings for non and low alloy steel underground or underwater pipelines ...................................................................................... 32 1.7 Summary table of main types of internal coatings for non and low alloy steel pipelines ....................................................................................................................................
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CHAPTER 2 - CRITERIA FOR THE SELECTION OF COATINGS FOR ACCESSORIES ON NON AND LOW ALLOY STEEL PIPELINES............................................................................... 34 2.1 SCOPE .................................................................................................................... 34 2.2
TYPES OF ACCESSORIES .................................................................................... 34
2.3 TYPES OF COATINGS FOR ACCESSORIES ON NON ALLOY AND LOW ALLOY STEEL PIPELINES..................................................................................................... 34 2.3.1 Coatings for fittings on non and low alloy steel pipelines............................................ 34 2.3.1.1 External coatings for underground fittings and those coming out of the ground .................................................................................................................. 35 2.3.1.2 External coatings for underwater fittings, whether or not in underwater excavation, or in tidal zone .............................................................................................. 36 2.3.1.3 External coatings for fittings in the open.................................................... 37 2.3.1.4 External coatings for overhead fittings, in duct and in tunnel ..................... 38 2.3.1.5 External temporary protection for fittings ................................................... 39 2.3.1.6 External coatings for fittings on hot water or waste water when passing through walls .................................................................................................................. 39 2.3.1.7 Internal coatings for fittings on water pipelines .......................................... 40 2.3.1.8 Anti-friction internal coatings for fittings on gas pipelines........................... 40 2.3.1.9 Internal coatings for fittings on vertical gas and oil pipelines...................... 40 2.3.1.10 Internal coatings for fittings on hot water or waste water pipelines in buildings .................................................................................................................. 41 2.3.2
Coatings for taps on non and low alloy steel pipelines ............................................... 42 2.3.2.1 External coatings for underground taps..................................................... 42 2.3.2.2 External coatings for taps in the open ....................................................... 42 2.3.2.3 Internal coatings for taps........................................................................... 43
2.3.3
Coatings for regulation instruments on non and low alloy steel pipelines ................... 43 2.3.3.1 External coatings for regulation instruments.............................................. 43 2.3.3.2 Internal coatings for regulation instruments............................................... 43
2.3.4
Protection for mechanical joints on non and low alloy steel pipelines......................... 44 2.3.4.1 Temporary protection or primer for flanges and opposite-flanges.............. 44 2.3.4.2 External coatings for bolts and nuts........................................................... 44
CHAPTER 3 - CRITERIA FOR THE SELECTION OF EXTERNAL COATINGS ON STAINLESS STEEL PIPELINES................................................................................................. 45 3.1 SCOPE .................................................................................................................... 45 3.2
REFERENCES ........................................................................................................ 45 European standard .................................................................................................... 45 CEOCOR bibliography............................................................................................... 45
3.3
STAINLESS STELL GRADES ................................................................................. 46
3.2.1 3.2.2
3.4 EXTERNAL COATINGS APPLICATION ON STAINLESS STEEL PIPES AND ACCESSORIES ...................................................................................................................... 46 3.5 3.5.1 3.5.2
TYPES OF COATINGS FOR STAINLESS STEEL PIPES ....................................... 47 External coatings for underground pipes and those coming out of the ground ........... 47 External coatings for underwater pipes, whether or not in underwater excavation, or in tidal zone ............................................................................................................... 47
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3.6 TYPES OF EXTERNAL COATINGS FOR ACCESSORIES ON STAINLESS STEEL PIPELINES ................................................................................................................. 48 3.6.1 External coatings for taps .......................................................................................... 48 3.6.2 External coatings for underground taps and those coming out of the ground, for underwater taps, whether or not in underwater excavation, or in tidal zone ............... 48 3.7 EXTERNAL COATINGS FOR WELDED JOINTS OF UNDERGROUND OR UNDERWATER STAINLESS STEEL PIPELINES................................................................... 48
CHAPTER 4 - CRITERIA FOR THE SELECTION OF EXTERNAL COATINGS FOR COPPER PIPELINES ................................................................................................................................. 49 4.1 SCOPE .................................................................................................................... 49 4.2
REFERENCES ........................................................................................................ 49 International and European standards and draft standards........................................ 49 CEOCOR bibliography............................................................................................... 49
4.3
COPPER PIPELINES DESIGN AND SERVICE....................................................... 50
4.4
TYPES OF EXTERNAL COATINGS FOR COPPER PIPES AND FITTINGS........... 50
4.5
EXTERNAL COATINGS OF WELDED JOINTS FOR COPPER PIPELINES ........... 51
4.2.1 4.2.2
4.6 COMPARATIVE CHARACTERISTICS FOR EXTERNAL COATINGS OF COPPER PIPELINES.............................................................................................................. 52
CHAPTER 5 - CRITERIA FOR THE SELECTION OF CAST IRON PIPELINES COATINGS ...... 54 5.1 SCOPE .................................................................................................................... 54 5.2
REFERENCES ........................................................................................................ 54 Standards and draft standards, CEOCOR recommendations .................................... 54 Regulatory documents ............................................................................................... 55 Bibliography............................................................................................................... 56
5.3
TYPES OF COATINGS FOR CAST IRON PIPELINES............................................ 57 External coatings for underground, underwater or aboveground pipes ...................... 59 Internal coatings of pipes ........................................................................................... 59 Coatings for fittings and accessories.......................................................................... 59
5.2.1 5.2.2 5.2.3
5.3.1 5.3.2 5.3.3
5.4 MAIN CHARACTERISTICS FOR STANDARD COATING OF CAST IRON PIPELINES ................................................................................................................................. 5.4.1 External zinc coating.................................................................................................. 61 5.4.2 Internal cement mortar lining...................................................................................... 61 5.5
COMPARISON BETWEEN DIFFERENT COATING TYPES ................................... 62 Comparison of external coatings for buried cast iron pipes ........................................ 63 Comparison of internal coatings for cast iron pipes.................................................... 64
5.6
ANNEXES ............................................................................................................... 65 Protection mechanism of the external zinc coating .................................................... 65 Protection mechanism of the internal cement mortar lining ........................................ 67
5.5.1 5.5.2
5.6.1 5.6.2
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OBJECTIVE This guideline is intended for an usage by metallic pipelines users, designers or piping operators, to allow the selection of the correct coatings (type of use, cost, ease of application, ease of use) for pipes, fittings and accessories to afford protection against mechanical and/or corrosive action : • from external sources (soil, atmosphere, water..) • from the transported fluid (water, gas…).
METALLIC PIPELINES DESIGN AND CONSTRUCTION In order to obtain the expected durability it is necessary to work out previously, while designing and realizing the work, the most suitable precaution against metallic pipelines corrosion. The main factors to consider as regards the coatings follow. External coating The external coating must be chosen in the light of the hereafter reported factors: • characteristics of the pipes; • geographical and physical location; • environment of the pipe; • accessibility of the structure; • proximity to other structures; • operating temperature; • ambient temperature and mechanical stresses during the application of the coating, transport, storage, installation and hydraulic testing; • durability of the structure and cost of maintenance; • any system of active protection; • economic conditions. The following specific factors are to be considered: Underground pipes: • nature of the ground: mechanical, physico-chemical and biological characteristics; • mechanical stresses transmitted by the ground: dynamic and static loads and stresses from backfilling, penetration of roots; • possible formation of electrochemical cells, presence of stray currents from d.c. or traction current installation, proximity of cathodic protection installation or cathodically protected structure, proximity of HV power transmission lines; Underwater pipes, whether or not in underwater excavation: • type of water: fresh, salt; • mechanical stresses: shallow or at great depth, special laying condition or particular situation;
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Overhead pipes: • type of atmosphere: rural, mountainous, urban, marine, industrial; • situation: overhead, in gallery, in tunnel, ventilated or not, humid atmosphere or not, etc.; • mechanical stresses during installation; Pipes coming out of the ground, or within the tidal range: • nature of the ground, water and atmosphere; • mechanical stresses; Hot water or waste water pipes, when passing through walls: • type of wall construction and others additional materials. The table next page shows a summary of the stresses and test methods concerning the behaviour of the coating for underground pipes.
Internal coating The coating must be chosen in relation to: • the type of fluid to be carried: water, gas, oil, etc.; • the characteristics of the fluid: chemical, physical, bacteriological composition; • operating temperature and pressure; • operating mode: temporary working or not, partially filled pipes or not, etc. As regards the mentioned fluids, account must be taken above all of: • water: tendency or not to form a protective metal oxide-calcium deposit; • gas: dehydration-, desulphurization-, etc, treatments: presence of residual water, carbon dioxide, hydrogen sulphide and other sulphur-containing components and solid impurities; • oil: presence or not of salt water, carbon dioxide, hydrogen sulphide, etc.
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Summary table of the stresses and tests concerning the behaviour of the coating for underground pipes Transport, storage and handling
Installation
Hydrostatic tests
Operation
↓
↓
↓
↓
Stresses from ambient environment Physico-chemical
Impacts (handling) Stresses involved
Creep and penetration Friction
- nature of the environment - chemical pollution - etc
Bending Shocks (backfilling)
Deformation of the pipe
Biological - micro-organisms - etc
Mechanical Climatic alteration
- soils stresses - etc
Presence of cathodic protection - Water migration - Electro endosmosis - Detachment
Thermal - operating temperatures - etc
↓
↓
Characteristics required
Resistance to penetration under load
Chemical stability of the coating
↓
↓
Chemical composition of the coating
Impacts strength Abrasion resistance
↓
Flexibility
Flexibility
Resistance to elongation
Impacts strength
Surface adhesion Crack resistance
Porosity, permeability Biological stability Adhesion to the steel, cohesion
Adherence to the steel Chemical resistance to alkalis
Cracking behaviour Resistance to elongation Thermal stability
Low permeability to ionic substances
Behaviour in extreme temperatures and cycles
Note: Stresses experienced by a coating and their transposition into typical test methods to evaluate the behaviour of the coating.
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