1、 WORLDWIDE ENGINEERING STANDARDS Test Procedure GMW15288 Scab Corrosion Creepback of Paint Systems on Metal Substrates Copyright 2013 General Motors Company All Rights Reserved July 2013 Page 1 of 3 1 Scope Note: Nothing in this standard supercedes applicable laws and regulations. Note: In the event
2、 of conflict between the English and domestic language, the English language shall take precedence. 1.1 Purpose. This test method outlines the procedure to be followed when evaluating scab corrosion resistance on painted metal substrates such as steel, zinc coated steel, and aluminum. Scab corrosion
3、 is the loss of paint adhesion and corrosion of the base metal which results in the distortion or upheaval of the paint film. 1.2 Foreword. Not applicable. 1.3 Applicability. Painted metal substrates such as steel, zinc coated steel, and aluminum. 2 References Note: Only the latest approved standard
4、s are applicable unless otherwise specified. 2.1 External Standards/Specifications. None 2.2 GM Standards/Specifications. GMW3286 GMW15282 3 Resources 3.1 Facilities. 3.1.1 Calibration. The test facilities and equipment shall be in good working order and shall have a valid calibration label. 3.1.2 A
5、lternatives. Alternative test facilities and equipment may also be used. However, all measuring variables as specified in this standard shall be determined correctly with respect to their physical definition. 3.2 Equipment. 3.2.1 Humidity Cabinet. The apparatus for the humid stage shall have the abi
6、lity to maintain the following environmental conditions: Temperature: 60 C 2 C Humidity: 85% 3% relative humidity (RH) 3.2.2 Thickness Measuring Device. Electrical film thickness measuring device. 3.2.3 Test Solution and Container. A plastic reservoir (open at the top) of 5% sodium chloride solution
7、 (per GMW3286) used for test sample immersion. 3.2.4 Test Panel/Parts Mounting Rack. Non-metallic racks for test samples. 3.2.5 Scribe Equipment. Refer to GMW15282 for equipment necessary. 3.3 Test Vehicle/Test Piece. Not applicable. Copyright General Motors Company Provided by IHS under license wit
8、h General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW15288 Copyright 2013 General Motors Company All Rights Reserved July 2013 Page 2 of 3 3.4 Test Time. Calendar time: 28 days Test hours: 672 hours Coordinat
9、ion hours: 1 to 2 hours 3.5 Test Required Information. Not applicable. 3.6 Personnel/Skills. Not applicable. 4 Procedure 4.1 Preparation. When this specification appears on an engineering drawing, actual parts coated with the representative paint system shall be used. Visually examine the painted su
10、rface and record any adverse conditions such as sags, solvent pops, or scratches. 4.1.1 Film Thickness. Measure paint film thickness in multiple locations with three measurements minimum on each part/panel and record the average film thickness in micrometers (m) for potential use in future analysis.
11、 4.1.2 Scribe Installation. Scribe the test panel/parts as specified in GMW15282. Length and number of scribes to be determined based on part size and test requestor. 4.1.3 Panel/Part Mounting. Place the test panel/parts with the scribed mark in horizontal position on a suitable nonmetallic rack. 4.
12、1.4 Test Duration. Expose the panels/parts for 20 cycles unless otherwise specified in the material specification. 4.2 Conditions. 4.2.1 Environmental Conditions. Not applicable. 4.2.2 Test Conditions. Deviations from the requirements of this standard shall have been agreed upon. Such requirements s
13、hall be specified on component drawings, test certificates, reports, etc. 4.3 Instructions. 4.3.1 Monday. 4.3.1.1 Hold the samples at 60 C 2 C for 1 h in air-circulating oven. 4.3.1.2 Transfer the samples to cold cabinet at a temperature of -25 C 2 C and hold for 30 minutes. 4.3.1.3 Transfer the sam
14、ples to 5% sodium chloride solution at ambient conditions, immersing for 15 minutes. 4.3.1.4 Take samples out of sodium chloride solution and hold at ambient conditions for 1 h, 15 minutes. 4.3.1.5 Transfer the samples to humidity cabinet; holding for 21 h (Monday only). 4.3.2 Tuesday through Friday
15、. 4.3.2.1 Transfer the samples to 5% sodium chloride solution at ambient conditions, immersing for 15 minutes. 4.3.2.2 Take samples out of sodium chloride solution and hold at ambient conditions for 1 h, 15 minutes. 4.3.2.3 Transfer the samples to humidity cabinet; hold for 22 h, 30 minutes 85% 3% R
16、H at 60 C 2 C. 4.3.3 Saturday and Sunday. 4.3.3.1 Samples shall remain in humidity cabinet over the weekend. Note: The exposure sequence described above from Monday to Monday constitutes five cycles. 4.3.4 Test Panel/Part Rinse. After completion of the last cycle, remove the test panels from the cab
17、inet and immediately rinse with warm water. 4.3.5 Test Panel/Part Examination. 4.3.6 Scribe Creepback Measurement. Unless otherwise stated on the specification or drawing, evaluate scribe line creepback by measuring the distance between the unaffected paint surfaces on each side of the scribe line.
18、The summation of the maximum left hand side creepback measurement and maximum right hand side creepback measurement is defined as the documented scribe creepback performance. This technique is referred to as zero to peak + zero to peak and is illustrated in GMW15282, Appendix C. Copyright General Mo
19、tors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW15288 Copyright 2013 General Motors Company All Rights Reserved July 2013 Page 3 of 3 5 Data 5.1 Calculations
20、. Scribe creepback measurement is illustrated in GMW15282, Appendix C. 5.2 Interpretation of Results. Acceptance criteria shall be specified on the engineering drawing or in the material specification. 5.3 Test Documentation. At a minimum, document maximum scribe creepback. In addition scribe creepb
21、ack measurements in standard increments along the scribe line may be taken in order to establish an individual sample average. An example of scribe creepback evaluation and example data documentation sheet is shown in GMW15282, Appendix D. In addition, visually examine the samples for failures such
22、as corrosion and loss of adhesion or blistering. Document results next to the creepback measurement. 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
23、of the user of this 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. RH Relative Humidity 8 Coding System This standard shall be refere
24、nced in other documents, drawings, etc., as follows: Test to GMW15288 9 Release and Revisions This standard was originated in April 2006. It was first approved by the Global Laboratory Corrosion Testing Harmonization Team in October 2006. It was first published in March 2007. Issue Publication Date
25、Description (Organization) 1 MAR 2007 Initial publication. 2 SEP 2008 4.3.1.5 changed 2 h to 21 h. (Global Laboratory Corrosion Testing Harmonization Team) 3 JUL 2013 Five year refresh of standard. Modified 4.1.1 (defined film thickness parameters and units); 4.3.1.3, 4.3.1.4, 4.3.2.1 and 4.3.2.2 (changed “room temperature” to “ambient conditions”). (Corrosion Subsystem Leadership Team) Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
