1、 WORLDWIDE ENGINEERING STANDARDS Material Specification GMW16929 Organic Clearcoats for Aluminum Trim Parts Copyright 2013 General Motors Company All Rights Reserved November 2013 Page 1 of 5 1 Scope 1.1 Material Description. This specification covers requirements for organic coatings (paints) used
2、to provide environmental protection for exterior aluminum applied parts. Coatings may be liquid or powder and may be applied over aluminum surfaces that are anodized (incompletely sealed) or chemically conversion coated. Any pretreatment or posttreatment must be free of Chrome VI. 1.2 Symbols. Not a
3、pplicable. 1.3 Typical Applications. This coating is used to improve the chemical resistance of formed aluminum trim parts (window moldings, roof rack rails, etc.) 1.4 Remarks. For general requirements regarding aluminum materials and for anodizing as a pretreatment, reference GMW14665 Appendix A, F
4、ETu. This organic coating specification is intended to parallel the requirements of GMW3005 Class 2, Type B, for exterior topcoats and GMW14669 for painted part performance. This coating may be used to meet the requirements of GMW14665 Class A2. Inorganic topcoat material for aluminum trim is covere
5、d in GMW16209. 2 References Note: Only the latest approved standards are applicable unless otherwise specified. 2.1 External Standards/Specifications. ISO 2808 ISO 2815 SAE J2527 2.2 GM Standards/Specifications. 9982075 GMW14124 GMW14701 GMW14873 GMW3005 GMW14665 GMW14729 GMW15359 GMW3059 GMW14669 G
6、MW14829 GMW15777 GMW3221 GMW14698 GMW14865 GMW16209 2.3 Additional References. TMC003 Material Safety Data Sheet guidance documents (available at ). 3 Requirements 3.1 Requirements on Test Specimens. Reference GMW3221 Code B for sample conditioning before tests. 3.2 Appearance. Painted parts shall c
7、onform to GMW15777 Zone A requirements. There shall be no visible orange peel, and at least minimum visual appearance master standard(s) must be met. 3.3 Coating Materials. 3.3.1 Chemical Fingerprint. The supplier must provide infrared data to document the fingerprint of the recommended formula. All
8、 materials subsequently supplied under this specification must correspond to the reference spectrum when compared under the same conditions. GM may conduct infrared spectrophotometry analysis of the material supplied to this specification. Analysis may also be performed on coating removed from repre
9、sentative samples that have film thickness and bake at target levels. The infrared spectra established for initial approval shall constitute a reference standard and shall be part of the submission package. Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot
10、 for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW16929 Copyright 2013 General Motors Company All Rights Reserved November 2013 Page 2 of 5 3.4 Coating Performance. Note: Items listed “for initial approval” are not required for regu
11、lar quality control tests once basic material approval is obtained. A summary of testing requirements is given in Table A1 for new approvals and for regular quality checks. 3.4.1 Corrosion Performance. Painted parts shall conform to all GMW14669 Type A1 requirements except as follows: 3.4.1.1 For in
12、itial approval, crosshatch adhesion evaluations shall be conducted on initial (fresh) sample materials and again after 240 h humidity. After approval, evaluate and then repeat the evaluation after 120 h humidity. 3.4.1.2 For initial approval, all four corrosion tests must be successfully completed (
13、GMW14669: salt spray, cyclic corrosion, cyclic climate, and filiform). For regular quality testing, only the salt spray and filiform tests are required. The GMW15359 white corrosion rating scale shall be used to assess performance where applicable. 3.4.1.3 Scratch Resistance. Perform scratch resista
14、nce according to GMW14698 in the as-received condition and after 144 h of salt spray. The spring tension at which the tip of the test rod just fails to penetrate the coating shall be recorded. A minimum spring tension of 4.00 N with no penetration is required. 3.4.1.4 Clearcoat Delamination. Whether
15、 or not associated with creepback corrosion, there shall be no evidence of clearcoat delamination from scribe, edge, or other area of test panels after corrosion exposures. 3.4.2 Automotive Environmental Cycling (GMW14124). There shall be no coating cracking or adhesion loss after 15 cycles of Cycle
16、 A plus 96 h of humidity (GMW14729). Adhesion (GMW14829) must be run after humidity. A maximum rating of 1 is allowed. 3.4.3 Determination of Scratch Resistance of Organic Coatings Simulation of Car Wash Installations (GMW14865). This test is for initial approval only and must be run on flat test pa
17、nels. After 200 test strokes, there shall be no more than a 20% change in gloss value (examples: an initial gloss reading of 80 shall not be reduced to lower than 64, and an initial gloss reading of 20 shall not be reduced to lower than 16). In order to effectively measure this gloss change, it may
18、be helpful (or necessary) to evaluate the clearcoat as applied to a black E-coated (electrocoated) standard panel. Coating tested may also compare favorably to a control sample consisting either of bare, sealed, anodized aluminum or of an approved body basecoat/clearcoat (BC/CC) system. Final accept
19、ability judgment is to be made by GM Engineering. 3.4.4 Resistance of Coatings to Chemical Etching and Distortion (GMW14701). For initial approval, there must be no objectionable surface changes after exposure to all environmental materials listed. 3.4.5 Environmental Damage Resistance. This is an o
20、ptional test for initial approval. Compare with controls in Jacksonville, Florida. This 14-week test is performed on a yearly basis beginning in May and ending in September for clearcoat evaluation only. Control sample(s) are to be an approved body basecoat (black)/clearcoat system. Etch resistance
21、is classified by a Jacksonville rating from 1 to 10, with 1 being the best. Performance must be noted and must be comparable to the control. 3.4.6 Weathering for Initial Approval. Accelerated weathering tests (Xenon) are used as an aid in predicting long-term durability performance (outdoor weatheri
22、ng). All tests must be conducted with control samples painted with an approved body BC/CC system. Outdoor exposure performance takes precedence over accelerated exposure performance in the event of disagreement. 3.4.6.1 Accelerated Weathering (Xenon Exposure; SAE J2527). Exposure is according to SAE
23、 J2527 plus 96 h humidity and tape adhesion. Total test exposure is to be 3500 kJ, with a minimum of 75% gloss retention (unpolished) (or 80% polished) and no cracking. Inspect test materials per GM Engineering agreement, throughout the test. Rate panels for gloss and Distinctness of Image (DOI) ret
24、ention, cracking, color change, and yellowing. Evaluate polish back (hand polish only) if gloss retention is below minimum specification, using polish compound 9982075. 3.4.6.2 Outdoor Weathering of Automotive Exterior Materials (GMW14873). Requirements for these aluminum clearcoats parallel the req
25、uirements for GMW3005 Class 2, Type B. Additional panel testing is done after each yearly exposure interval. Coatings must have a minimum of 24 months exposure on the exact system and five years on the prototype system prior to production release. Five south black box exposure is to be followed. A m
26、inimum of two samples per exposure duration must be tested (one for appearance and one for further testing). Total five-year test duration and yearly sample performance criteria are given in GMW3005. Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for Re
27、saleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW16929 Copyright 2013 General Motors Company All Rights Reserved November 2013 Page 3 of 5 3.4.7 Buchholz Hardness (ISO 2815). Applied coating shall have a minimum hardness value of 77. If t
28、his value cannot be obtained, the responsible GM Engineer must be contacted. This test only applies to coatings that are at least 15 m thick. 3.5 Preparation of Test Panels. 3.5.1 Paint Application. All test materials must be sprayed/dipped/etc., at the target application viscosity, voltage, flow ra
29、te, etc., as typical for the particular technology. 3.5.2 Film Thickness. Thickness is to be measured per ISO 2808. Specific film build targets and upper/lower limits are established by initial screening. These will vary by technology. 3.6 Target Bake Definition. Coating bake window must be defined
30、for minimum and maximum time and temperature (reference GMW3005 Target Bake definition). 3.7 Paint Repairs and Reprocessing. If repairing or reprocessing of painted parts is to be allowed, conduct reprocess studies as defined in GMW3005. 4 Manufacturing Process Not applicable. 5 Rules and Regulation
31、s 5.1 Legal Regulations. All materials must satisfy applicable laws, rules, regulations and recommendations valid in the country of usage. 5.2 Language. In the event of conflict between the English and domestic language, the English language shall take precedence. 5.3 Inspection and Rejection. Sampl
32、es of components or materials released to a GM material specification shall be tested for conformity with the requirements of this material specification and approved by the responsible Engineering department prior to commencement of delivery of bulk supplies. A new approval must be received for any
33、 changes, e.g., properties, manufacturing process, location of manufacture, etc. If not otherwise agreed, all testing and documentation normally required for initial release must be completed. It is the responsibility of the supplier to inform the customer in a timely manner, without solicitation, a
34、nd to include documentation of all modifications of materials and/or processes and to apply for a new release. If not otherwise agreed, all release tests shall be repeated and documented by the supplier prior to commencement of delivery of non-conforming bulk supplies. In individual cases, a shorter
35、 test can be agreed to between the responsible Engineering department and the supplier. 5.4 Material Safety Data Sheets/Safety Data Sheets (MSDS/SDS). For new product submissions, or when a change in chemical composition of an existing product has occurred, a complete copy of the Material Safety Dat
36、a Sheet/Safety Data Sheet must be submitted in compliance with the Globally Harmonized System of Classification and Labeling of Chemicals (GHS) requirements or other country-specific MSDS/SDS requirements. In addition, product MSDS/SDS submissions must be in compliance with specific country General
37、Motors TMC003 Material Safety Data Sheet/Safety Data Sheet guidance documents where available. 5.5 All materials supplied to this standard must comply with the requirements of GMW3059, Restricted and Reportable Substances for Parts. 6 Approved Sources Materials supplied to this specification must be
38、 approved by General Motors. A list of approved materials can be found in MATSPC. This GM Material File is provided to third parties to reduce redundant testing of materials. If approved material already listed is used, the part supplier can use GM Material File reference for Production Part Approva
39、l Process (PPAP) material approval. If the decision is made to use a not yet approved material, contact GM Regional Materials Engineering for details on the approval process. The material approval process must be completed prior to PPAP start date of the part supplied to General Motors. Copyright Ge
40、neral Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW16929 Copyright 2013 General Motors Company All Rights Reserved November 2013 Page 4 of 5 7 Notes 7.1
41、 Glossary. MATSPC: Global repository of GM approved materials for corresponding GM Engineering Standards. 7.2 Acronyms, Abbreviations, and Symbols. BC Basecoat CC Clearcoat DOI Distinctness of Image E-coated Electrocoated GHS Globally Harmonized System of Classification and Labeling of Chemicals GSS
42、LT Global Subsystem Leadership Team ISO International Organization for Standardization MSDS Material Safety Data Sheet N Newton (force) PPAP Production Part Approval Process SAE SAE International SDS Safety Data Sheet 8 Coding System This standard shall be referenced in other documents, drawings, et
43、c., as follows: Material per GMW16929 9 Release and Revisions This standard was originated in February 2013. It was first approved by the Finishes and Coatings Global Subsystem Leadership Team (GSSLT) in November 2013. It was first published in November 2013. Issue Publication Date Description (Orga
44、nization) 1 NOV 2013 Initial publication. Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW16929 Copyright 2013 General Motors Company All
45、 Rights Reserved November 2013 Page 5 of 5 Appendix A Table A1: Summary of Test Requirements Section/Paragraph Tests for New Material Approval 3.3.1 Chemical Fingerprint 3.4.1 Corrosion Performance 3.4.1.1 Crosshatch Adhesion - Initial (fresh) - After 240 h Humidity 3.4.1.2 Corrosion Tests - Salt Sp
46、ray - Cyclic Corrosion - Cyclic Climate - Filiform 3.4.1.3 Scratch Resistance 3.4.1.4 Clearcoat Delamination 3.4.2 Automotive Environmental Cycling 3.4.3 Delamination of Scratch Resistance of Organic Coatings Simulation of Car Wash Installations 3.4.4 Resistance of Coatings to Chemical Etching and D
47、istortion 3.4.5 Environmental Damage Resistance 3.4.6 Weathering for Initial Approval 3.4.6.1 Accelerated Weathering (Xenon Exposure) 3.4.6.2 Outdoor Weathering of Automotive Exterior Materials 3.4.7 Buchholz Hardness Tests for Regular Quality Monitoring 3.4.1.1 Crosshatch Adhesion - Initial - After 120 h Humidity 3.4.1.2 Corrosion - Salt Spray - Filiform 3.5.2 Film Thickness Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
