1、 WORLDWIDE ENGINEERING STANDARDS Material Specification SUPERCEDED GMW4205 Plating Multilayer Coating/Black Type Replaced by GMW16730 Copyright 2013 General Motors Company All Rights Reserved December 2013 Originating Department: North American Engineering Standards Page 1 of 5 1 Scope This specific
2、ation covers requirements for a corro-sion resistant black finish over an electrolytically deposited zinc-iron alloy, nickel alloy and/or zinc-nickel alloy substrate. 1.1 Material Description. This coating system shall be free of hexavalent chromate in final prod-uct per GMW3059 requirements. The pl
3、ating shall be called out on the part drawing per example shown in paragraph 7. 1.2 Typical Application. This coating is intended primarily for bulk processed small steel parts such as bolts, screws and nuts used on exterior and in-terior visible parts (cosmetic applications). This coating is especi
4、ally suitable for internal drive (cross recess, 6 lobed socket etc.) threaded fasteners and self drilling and tapping screws. 1.3 Remarks. Use of this coating system on threa-ded surface and/or bearing surface of joints could affect the torque-tension relationship. It is recom-mended that a torque-t
5、ension study of the fastener joint be performed before releasing this finish on any new application. 2 References Note: Only the latest approved standards are applicable unless otherwise specified. 2.1 External Standards/Specifications. ASTM D523 SAE.USCAR-1 ASTM F1470 SAE.USCAR-5 DIN 946 SAE.USCAR-
6、7 ISO 9227 SAE.USCAR-11 SAE J1960 VDA 621-415 2.2 GM Standards/Specifications. GM4260P GM9540P GM4465P GMW3001 GM9071P GMW3059 GM9501P 3 Requirements 3.1 Appearance. This finish shall provide uniform black color on coated parts. The finished part shall have a gloss of 4 or higher (20 degree gloss me
7、ter per ASTM D523). Note: Gloss level of the finished parts (when small) shall be measured on standard panel (steel, 75 x 200 mm) processed with the production parts. 3.2 Thickness. This finish shall not fill driver re-cess or threads nor interfere with normal fastener installation procedures. The f
8、inish shall withstand normal handling and storage conditions without damage (chipping, flaking or other) and must not stain or transfer to adjacent parts or operators hands. 3.2.1 The total coating system as received shall not adversely affect the drive system: Internal recess dimensions, hex size,
9、etc. or function of the fastener. 3.2.2 Typical zinc-iron (containing 0.4 1.0% Iron), nickel or zinc-nickel (containing 8- 15% nickel) al-loy layer shall be (5-20) m and topcoat layer shall be 25 m max. with a total thickness 45 m. Thickness shall be determined by microscope ex-amination of cross se
10、ctions taken perpendicular to significant surfaces. See GM4260P, Recommen-ded Practices for Measuring Thickness of Plated Deposits and Anodic Coatings. Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted with
11、out license from IHS-,-,-GM WORLDSIDE ENGINEERING STANDARDS GMW4205 Copyright 2013 General Motors Company All Rights Reserved December 2013 Page 2 of 4 3.2.3 In case of bolts and screws, plating thickness shall be determined at top of head at midpoint of largest continuous surface. In case of nuts,
12、deter-mine at midpoint of flats (wrenching facets). 3.2.3.1 The maximum thickness of coating which may be applied to threads on threaded products is limited by the basic thread size (tolerance h or H). After coating, parts must gage with appropriate basic size G0 thread gage. Threads may be pro-duce
13、d undersize/oversize (before coating) to ac-commodate the coating thickness, providing the finished product (after coating) meets all specified mechanical properties. Where mechanical proper-ties are not specified, undersizing/oversizing is subject to approval by pertinent engineer, and all undersiz
14、e/oversize shall be within permissible limits as agreed upon. 3.2.3.2 Recess Fill Test. Apply the coating to surrogate P/N 11516629 (4.2x 1.4x1.6 round large crown washer head screw with 1A cross recess) or equivalent in production environment (sample size, N= 10 min.). Perform recess tests before a
15、nd after plating to confirm that the recess dimensions are correct on the unplated fastener. Check the recess penetration depth, gage penetration depth and wobble degrees per the drawing requirements (P/N 11516629) to the following recess data on the coated parts: Recess Penetration Depth -2.31- 2.7
16、7 mm Gage Penetration Depth - -1.90- 2.36 mm Wobble Limit- 10 degrees max. Refer to GM Standard Parts specification C200 for penetration gaging and C201 for Wobble gaging instructions Note: The Recess Fill test is required for initial chemicals/ process approval and every PPAP submission of fastener
17、s with recess drive. 3.3 Adhesion. Parts coated to this specification shall show no evidence of blistering or other ap-pearance changes after exposure to humidity testing per GM4465P for 96 h. There shall be minimum 99.0% of coating (topcoat) retention after the tape adhesion test per GM9071P Method
18、 B. In case of threaded fasteners, steel test panels shall be processed with fasteners for the adhesion test. Note: This test is applicable for initial approval of chemicals/process, applicator approval and parts PPAP submission. 3.4 Weathering Characteristics. Parts coated to this specification sha
19、ll show no blistering, peeling, cracking, loss of adhesion, discoloration, or red rust after 1316.7 kJ/m2 in xenon arc per SAE J1960. After weathering test finished parts shall have a gloss level of 3 or higher (20 degree gloss meter, per ASTM D523). Note: The weathering test shall be required to ru
20、n for initial chemicals/ process approval only. 3.5 Corrosion Resistance. Significant surfaces of parts exposed to neutral salt spray per ISO 9227 shall show no white corrosion after 48 h exposure, 10% white corrosion products after 144 h, and no base metal corrosion after 480 h exposure. For this t
21、est externally threaded fasteners shall be power driven into a tapped hole or nut or steel panel, si-mulating production usage, removed, then installed finger tight or with a hand driver with proper drive bit into acrylic plastic or other inert panel, and ex-posed in salt spray at an angle of 15-30
22、degree from the vertical to allow wetting per SAE/USCAR-1. Fasteners shall not drip on other fasteners during the test. 3.5.1 Normal production processes that are in sta-tistical process control shall yield parts that are capable of meeting the salt spray requirements. 3.5.2 A periodic NSS test of t
23、he parts being pro-cessed on each line running this coating shall be conducted with sample size of three pieces mini-mum per line per shift. 3.5.3 Actual processing control checks to be made and recorded shall be based on chemical manufac-turers instruction. 3.5.4 Parts must be NSS tested to meet th
24、e corrosion resistance requirements on significant surfaces for initial approval of the finish, applicators and PPAP submissions. NSS test need not be completed prior to shipment of parts. 3.5.5 Significant surfaces for test evaluation of fas-teners shall be all exposed surfaces of the fastener when
25、 installed, including but are not limited to fas-tener heads, socket recess, sems washers and external surface of nuts. Fastener threads and point are excluded unless otherwise specified on the drawing. 3.5.6 Significant surfaces on parts other than threaded fasteners shall be all surfaces. Deep re-
26、cesses, such as blind holes and the interior of tubes, are excluded unless otherwise specified on the drawing. Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDSIDE ENG
27、INEERING STANDARDS GMW4205 Copyright 2013 General Motors Company All Rights Reserved December 2013 Page 3 of 4 3.6 Temperature Resistance. After heating the parts for 1 h at + 150C (part temperature) the cor-rosion resistance requirements as specified in pa-ragraph 3.5 shall still be met. This test
28、requirement is only for initial approval of the chemicals/ pro-cess. 3.7 Accelerated Corrosion Test. Part Number 11516629 or similar cross recessed head screws, coated with this finish in production environment shall be used as sample (sample size N= ten mi-nimum) for Accelerated corrosion test. The
29、 test screws shall be power driven and seated with pro-duction type tooling into 60/60 galvanized steel test panels that have been painted with standard GM pretreatment, primer, and white base coat/clear coat. The test screws shall be installed in a hori-zontal row seated minimum 25 mm apart. The sc
30、rew shall be tested for 40 test cycles (five pha-ses) per GM9540P, Accelerated Corrosion Test. After 24 test cycles (three phases), the screw heads shall exhibit no red rust and 30% max. white corrosion coverage. After 40 test cycles, the screw heads shall exhibit 10% max. red rust coverage and 50%
31、max. white corrosion coverage. Note that all visible surfaces of the seated screw heads inc-luding screw heads edges shall be included in the percent of corrosion coverage. Note: This test shall be run with initial approval of chemicals/process and applicator approvals. Appli-cators are required to
32、perform this test (GM9540P) on processed parts minimum of two times per year. Parts performance records shall be retained for minimum 3 years for potential review. At a PPAP submission of a part the latest test results (not older than 6 months) of GM9540P test of the appli-cator can be submitted for
33、 approval. The 9540P test shall be run at the frequency deemed appro-priate by the applicator, such that a confidence in passing GM9540P requirements is developed. The twice per year minimum frequency requirement must be met. 3.7.1 VDA 621-415 (Cyclic Corrosion Test). The coating to this specificati
34、on shall be exposed per VDA 621-415 Cyclic Corrosion test method. After 3 test cycles of VDA 621-415, the significat areas shall exhibit no red rust and 10% max. white corro-sion coverage. After 6 test cycles, the significant areas shall exhibit no red rust. Note. VDA 621-415 Cyclic Corrosion test c
35、ould be used by GME as an alternate test method to GM9540P test. 3.8 Aluminum Galvanic Corrosion Test. The test fasteners (sample size N=10 minimum) coated with this finish in production environment shall be power driven and seated with production type tooling into an aluminum test panel (AA 6061 gr
36、ade, 4 mm min. thick). The test fasteners shall be installed in a horizontal row seated minimum 25 mm.apart. The fasteners shall be tested for 40 test cycles (5 pha-ses) per GM9540P, Accelerated Corrosion test. The test fasteners shall be removed after 40 test cycles and the pit depth in aluminum te
37、st panel shall be measured for each test fastener. The lar-gest pit depth shall not be more than 5% of test panel thickness for each fastener. Note: This test is required to be run for the initial approval of chemicals/process of the finish. 3.9 Gasoline Resistance. For initial approval of new mater
38、ials, coated parts shall be soaked for 200 2 s in gasoline as described in GM9501P. After removal of the parts, they shall be allowed to air dry before visual examination. There shall be no color change, wrinkling, or any other change in the coating appearance. 3.10 Relief of Hydrogen Embrittlement.
39、 All parts heat treated or highly cold worked to a specified core hardness HRC 32 or greater or surface hard-ness HRC 35 or greater, that are processed through a hydrogen generating process, shall be processed by the finish applicator per SAE/USCAR-5 and tested for de-embrittlement per SAE/USCAR-7.
40、The sample size for the SAE/USCAR-7 test shall be per ASTM F1470. 3.10.1 When supplementary treatment is specified for a part that requires baking after plating, the supplementary treatment shall be applied after the baking operation. 3.10.2 Hardened parts which have been tempered at +175C shall be
41、heated to +150C and held 8 h, or longer, if necessary. 3.11 Torque-Tension Test. Metric threaded faste-ners M6 and larger shall be subject to torque-tension monitoring through the use of surrogate M10x1.5 test bolts. Ten surrogate bolts shall be processed with the production parts. A minimum of 10 b
42、olts per finish line per shift shall be monitored per SAE/USCAR-11, except tightening speed shall be 30 3 min-1 (RPM). The six (6) sigma torque range values shall be within the listed range (see Table 1). The test results shall be maintained on file to be submitted when required. Note: Engineering d
43、rawings for surrogate faste-ners for Torque-tension test are available from Global Engineering Documents/IHS. 3.12 Coefficient of Friction. The coefficient of friction of threaded fasteners shall be 0.13 0.03 (six sigma values) when tested per DIN 946 with the following exceptions: Copyright General
44、 Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDSIDE ENGINEERING STANDARDS GMW4205 Copyright 2013 General Motors Company All Rights Reserved December 2013 Page 4 of 4 Test samples (exc
45、luding driven fasteners) shall be thoroughly cleaned with an appropriate flu-id/chemical to remove any grease/oil/wax/other contaminants. Test clamping force shall be calculated as 75% of proof load. Note: Both Torque-Tension and Coefficient of Fric-tion tests are required only for the initial appro
46、val of the chemicals/process. Suppliers/Applicators can run either Torque-Tension Test or Coefficient of Friction Test for quality control. Table 1: Torque Range Values Thread Size Surrogate Bolt Part Number Test Nut Part Number Test Washer Part Number Torque in Nm SAE/USCAR 11 Tension in kN M10 x 1
47、.5 11516105 11516090 11502644 48 8 28.3 4 Manufacturing Process Not applicable. 5 Rules and Regulations 5.1 All materials supplied to this specification must comply with the requirements of GMW3001, Rules and Regulations for Material Specifications. 5.2 All materials supplied to this specification m
48、ust comply with the requirements of GMW3059, Re-stricted and Reportable Substances for Parts. 6 Approved Sources Engineering qualifications of an approved source is required for this specification. Only sources listed in the GM Materials File (i.e., MATSPC) under this specification number have been
49、qualified by eng-ineering as meeting the requirements of this speci-fication. For other GM locations, the responsible engineer-ing group should be contacted to obtain the approved source in that individual country. 7 Coding System This material specification shall be referenced in other documents, drawings, VTS, CTS, etc. as fol-lows: Material per GMW4205 8 Release and Revisions This standard was originated in January 2000. It was first approved in July 2001. It wa
