GMW 15287

WORLDWIDE ENGINEERING STANDARDS

Test Procedure QRD

GMW15287

Filiform Corrosion Test Procedure for Painted Aluminum Wheels and Painted Aluminum Wheel Trim

1 Scope Note: Nothing in this standard applicable laws and regulations.

supersedes

Note: In the event of conflict between the English and domestic language, the English language shall take precedence. 1.1 Purpose. This test specification defines a procedure that was developed for generating and evaluating filiform corrosion on painted aluminum wheels and painted aluminum wheel trim. This test has been used to evaluate the effectiveness of process and material changes with respect to filiform corrosion on aluminum wheels or trim. This procedure has also been used to evaluate filiform corrosion on painted aluminum body panels and parts. Unless otherwise noted, the procedure for testing these parts is identical to that used for testing wheels. 1.2 Foreword. Not applicable. 1.3 Applicability. Not Applicability. Not applicable.

2 References

3.3.1 Control Samples. Control Samples. Control samples must be included in every test to assure that the test conditions are normal. See 4.3.2 for selection and validation of the control samples. Consult GMNA Materials Engineering for further guidance. 3.4 Test Time. Calendar time:

28 days

Test hours:

678 hours

Coordination hours:

1 hour

3.5 Test Required Information. Information. Not Not applicable. 3.6 Personnel/Skills. Not Personnel/Skills. Not applicable.

4 Procedure 4.1 Preparation. Not Preparation. Not applicable. 4.2 Conditions Conditions.. 4.2.1 Environmental Conditions. Not applicable. 4.2.2 Test Conditions. Deviations from the requirements of the procedure shall have been agreed upon. Such r equirements shall be specified on component drawings, test certificates, reports, etc.

Note: Only the latest approved standards are applicable unless otherwise specified.

4.3 Instructions.

2.1 External Standards/S Standards/Specification pecifications. s.

4.3.1.1 Check the humidity cabinet for the temperature, humidity, air flow and exhaust vent settings. Correct any discrepancies from predetermined levels.

ASTM D1193 D1193 2.2 GM Standards/Specifications. GMW14458 GMW14885

GMW15282

2.3 Additional References.

4.3.1 Filiform Test Procedure.



Temperature

60 ± 1°C



Humidity

85 ± 3% RH



Drawing DWO-4828

3 Resources Not applicable. 3.1 Facilities. Facilities. Not 3.2 Equipment. 3.2.1 Copper Accelerated Acetic Acid Salt Spray (CASS) cabinet per GMW14458. 3.2.2 Humidity cabinet per the requirements of 4.3.1. 3.3 Test Vehicle/T Vehicle/Test est Piece.

Air Flow 6 to 24 m/minute ft/minute) in the test area

(20 to 80

4.3.1.2 Control samples (reference 4.3.2) which have been evaluated over a period of time and have a known filiform growth rate must be tested with every batch of test samples to assure test consistency. 4.3.1.3 Mark the samples to be tested with the proper identification. Make sure that ID location will not affect test results. Preferably mark on back of sample.

© Copyright 2007 General Motors Corporation All Rights Reserved

May 2007

Originating Department: North American Engineering Standards

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GMW15287

GM WORLDWIDE ENGINEERING STANDARDS

4.3.1.4 Visually examine the painted surface and record any adverse conditions, such as sags, paint films porosity, scratches, etc. on the schematic drawing. Measure the paint film thickness over the area to be scribed and record this on the schematic drawing. The film thickness will vary depending on the particular paint system being measured. 4.3.1.5 Scribe the painted wheel to the base metal with carbide tip scribing tool per GMW15282. The scribe must be as close to perpendicular to the machine lines on the wheel as possible. A fixture is recommended (contact GMNA Materials for drawing DWO-4828, refer to Appendix A, Figure A1) in order to make a straight scribe line on the test sample. Check the scribe line, with multimeter, to assure electrical continuity from end to end. To do this, probes of the multimeter are first touched together to assure that the meter does read a completed electrical circuit. After the meter is checked, ground one of the probes to the sample, then run the other probe down the full length of the scribe. There must be electrical continuity down the full length of the scribe. If continuity is not continuous, a fresh scribe must be made. This maybe done on the same sample if there is at least 15 mm of separation from the old scribe. Continuous continuity will assure that the scribe exposes the base metal. Particular care must be taken to scribe through multiple layers of paint. 4.3.1.6 Place the scribed parts in the CASS cabinet such that the wheel and scribe are at an angle of approximately 45 degrees to the horizontal on a suitable non-metallic rack. 4.3.1.7 Expose the parts for 6 h ± 15 minutes in the CASS cabinet as described in GMW14458. The scribe must be fully exposed to the CASS fog settling on the part. The scribe should be at approximately 45 degrees to allow no puddles of the solution on the part. 4.3.1.8 Prepare a container, approximately 5 gallons (19 L) in size, with a constant overflow of deionized water that meets the latest issue of ASTM D1193 (Type IV). The DI water must enter the bottom of the container to promote flushing of any contamination out of the container with the overflowing water. Dip-rinse the parts in this container. The parts should be dipped in a vertical direction and then turned slowly 90 degrees, then back 90 degrees to the initial dip position. The parts are then removed in the same vertical direction. The total time for the dip-rinse procedure is 2 to 3 s. The objective is to remove only the excess CASS solution. After approximately 25 samples have been dipped, the water in the

container shall be dumped prior to proceeding with the sample rinsing procedure. 4.3.1.9 Place the parts directly into humidity cabinet, at a 45 degrees angle, f or 672 h (4 weeks). 4.3.1.10 To determine if design features are susceptible to filiform corrosion, unscribed and unrinsed samples should be exposed. This procedure, which is used for part (design) validation as opposed to system (coating) validation, will identify filiform prone locations such as uncovered edges and areas with inadequate paint film thickness. Any corrosion from design features must be addressed. 4.3.2 Validation of Control Samples. 4.3.2.1 A wheel with significant bright machined spoke area shall be obtained in quantity. Spokes from one whole wheel and half of two other wheels from the same batch shall be tested to validate variations around the wheel and from wheel to wheel. Once the candidate wheel has been validated as an appropriate control sample, the remainder of the wheels shall be utilized in subsequent testing. Control sample wheels and sections shall be stored in a controlled environment to avoid degradation of the parts. 4.3.2.2 The initial control sample data (from the control sample validation process described in 4.3.2.1) shall be plotted to create a control chart (with upper and lower control limits). Control samples shall subsequently be tested with each new sample group, and the control chart shall be updated upon conclusion of the testing. Unacceptable variation in control sample performance (i.e. outside the established control limits) , shall disqualify the control sample and all test parts in the sample group. 4.3.2.3 When the supply of the control samples is depleted, new control samples shall be obtained and validated in parallel with the previous reference standards. 4.3.2.4 When testing non-wheel related parts, standard painted aluminum test panels may be used in place of, or included with, standard wheel sections as reference standards.

5 Data 5.1 Calculations. 5.1.1 Filiform Length Measurements. 5.1.1.1 Measure the linear filiform corrosion growth once a week and record. Samples must not be kept out of the humidity chamber for more than 15 minutes per measurement. The cabinet should not


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GMW15287

be opened more than once per shift and not longer than 15 minutes.

magnitude and focus that will allow the filiform length to be independently audited.

5.1.1.2 Linear filiform corrosion measurements must be taken perpendicular to the scribe and not the angle from the scribe that the filiform corrosion may have grown. Measurements must be taken from the edge of the scribe to avoid including the scribe. Record the data with two significant figures.

5.3.4 Additional data requirements (i.e. area and distribution measurements) shall be agreed upon by the customer and the test analyst.

5.1.1.3 Measure the longest filament, in mm, from either side of the scribe (refer to Appendix A, Figure A2 for example measurement) and record as maximum filiform length. (Refer to Appendix A). 5.1.2 Area Measurements. If requested by the customer, measure the filiform damaged area (refer to Appendix A, Figure A3 for example data sheet). Contact GMNA Materials Engineering for guidance. 5.2 Interpretation of Results. 5.2.1 Acceptance Criteria. Acceptance criteria shall be specified on the engineering drawing and/or in the material specification (refer to GMW14885). 5.3 Test Documentation. 5.3.1 Report the maximum filiform length for each sample. 5.3.2 Update the control chart referenced in 4.3.2.2 with the maximum filiform length for each control sample. 5.3.3 Photograph the test parts and control samples within 96 h to document the filiform lengths at the end of test. (Filiform will continue to grow at room temperature). Any sample data not documented by photography or actual area and length measurements shall be considered invalid. Each photograph shall include sample identification and a scale. They must be of a

6 Safety This standard may involve hazardous materials, operations, and equipment. This standard does not propose to address all the safety problems associated with its use. It is the responsibility of the user of the standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

7 Notes 7.1 Glossary. Not applicable. 7.2 Acronyms, Abbreviations, and Symbols. ASTM

American Society for Testing and Material Standards

CASS

Copper Accelerated Acetic Acid Salt Spray

8 Coding System This standard shall be referenced documents, drawings, etc., as follows:

in

other

Test to GMW15287

9 Release and Revisions 9.1 Release. This standard originated in April 2006, replacing GM9682P. It was first approved by the Global Laboratory Corrosion Testing Harmonization Team in December 2006. It was first published in May 2007.


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Appendix A

Figure A1: Example Scribe Fixture


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GMW15287

Appendix A - Continued

Figure A2: Example Filiform Measurement


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Appendix A - Continued

F Max

Figure A3: Example Data Sheet


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