GMW-4707-2002.pdf
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1、Material Specification Finish (Coating) GMW4707 Corrosion Protective Coating Zinc Plating/Organic 1 Scope This specification covers requirements for a non-oily corrosion protective coating consisting of zinc plate and subsequent aluminum rich topcoat. 1.1 Material Description. This coating system mu
2、st be free of hexavalent chromium, with no hexavalent chromium in final product per GMW3059 require- ments.The plating shall be called out on the part drawing per example shown in section 7. 1.2 Cross-Reference of Replaced Specifications. GMWGMW4707 Delta Motors GM do Brasil GM Holdens GMNAGM7113M I
3、SUZU ITDC SAAB 1.3 Symbol. Not applicable. 1.4 Typical Application. The coating is suitable for internally and externally threaded and nonthreaded ferrous parts where a high level of corrosion protec- tion is required. When applied over steel that is to be coupled with aluminum, the coating provides
4、 excep- tional galvanic protection. 1.5 Remarks.Use of this coating system on threaded surface and/or bearing surface of joints could effect the torque-tension relationship.It is recommended that a torque-tension study of the fastener joint be performed before releasing this finish on any new applic
5、ation. 2 References Note: Only the latest approved standards are appli- cable unless otherwise specified. 2.1 Normative. ASTM F1470DIN 946 ISO 9227SAE/USCAR-1 SAE/USCAR-5SAE/USCAR-7 SAE/USCAR-11 2.2 GM. GM4260PGM4265P GM9071PGM9501P GM9508PGMW3001 GMW3059 3 Requirements 3.1 Requirements on Delivery.
6、 3.1.1 Chemical Requirements. Not applicable. 3.1.2 Mechanical Requirements. Not applicable. 3.1.3 Physical Requirements. 3.1.3.1 Appearance.This coating shall have a uniform gray/green appearance and shall be free of tears, sags, and excess coating which affects appearance and performance. The coat
7、ing shall not be oily or tacky to the touch. 3.1.3.2 Thisfinishshallnotfilldriverrecessorthreads nor interfere with normal fastener installation proce- dures. The finish shall withstand normal handling and storage conditions without damage (chipping, flaking or other) and must not stain or transfer
8、to adjacent parts or operators hands. 3.1.3.3 The total coating system as received shall not adversely affect the drive system: internal recess di- mensions, hex size, etc. or function of the fastener. 3.1.3.4 Thickness. The zinc plate and passivation treatment thickness shall be minimum 6 m unless
9、otherwise specified. The total coating thickness shall be (12.20) m. 3.1.3.4.1 Thickness shall be determined by mi- croscopicexaminationofcrosssectionstaken perpendicular to significant surfaces. See GM4260P, Recommended Practices for Measuring Thickness of Plated Deposits and Anodic Coatings. 3.1.3
10、.4.2 In case of bolts and screws, plating thick- ness shall be determined at top of head at midpoint of largest continuous surface. In case of nuts, deter- mine at midpoint of flats (wrenching facets). Copyright 2002 General Motors Corporation All Rights Reserved Originating Department: North Americ
11、an Engineering Standards, Records and Documentation April 2002Page 1 of 3 GMW4707GM WORLDWIDE ENGINEERING STANDARDS 3.1.3.4.3 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 w
12、ith appropriate ba- sic size GO thread gage. Threads may be produced undersize/oversize (before coating) to accommodate the coating thickness, providing the finished product (after coating) meets all specified mechanical prop- erties. Where mechanical properties are not speci- fied, undersizing/over
13、sizing is subject to approval by pertinent engineer,and allundersize/oversizeshallbe within permissible limits as agreed upon. 3.1.3.5 Adhesion. Parts coated to this specification shall show no evidence of blistering or other appear- ance changes after exposure to humidity testing per GM4465P for 96
14、 h minimum. When tape tested per GM9071P, 10 minutes after removal from humidity there willbenomore than3.0 mmtotalpeelback (peel back adding both sides of scribed line) from the lines scribedinanXandnoother peelingin theareaunder the tape. This is not applicable to threaded fasteners. Note:This tes
15、t is applicable for initial approval, ap- plicator approval and PPAP submission parts. 3.1.3.6 Corrosion Resistance. Significant surfaces of parts exposed to neutral salt spray per ISO 9227 shall show no base metal corrosion after 480 h ex- posure.For this test externally threaded fasteners shall be
16、 power driveninto a tapped hole or nut or steel panel, simulatingproductionusage, removed, thenin- stalled finger tight or with a hand driver with proper drive bit into acrylic plastic or other inert panel, and exposed to salt spray at (15.30)?from the vertical to allow wetting. Fasteners shall not
17、drip onto other fas- teners during the test (SAE/USCAR-1). 3.1.3.6.1 For normal production, processes that are in statistical process control shall yield parts that are capable of meeting the salt spray requirments. 3.1.3.6.2 A periodic NSS test of the parts being pro- cessed on each line running th
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