scope:

This specification covers black oxide finishes applied over iron and steel parts and 300 series stainless steel parts for decorative or identification purposes. It offers little wear resistance, and the corrosion resistance of the base metal is not improved by the finish. Black oxide is not generally used for 400 series stainless steel and offers little protection when applied over 200 series stainless steel parts. Protective oils and waxes may be applied over black oxide to improve resistance to corrosion, in which case the improvement is proportionally equal to the quality of the oil/wax. Oil and/or wax coating shall be specified as a suffix to specification if required. Example: GM4347M, Oil.

Material Description. At present the suppliers of this specification provide coatings with hexavalent chromate and some without hexavalent chromate. All Chemical Suppliers/Applicators who are providing hexavalent chromate free coating shall submit to the GMNA Finish Committee the name of the chemicals currently used and a signed certificate that their coating system is free of hexavalent chromate, with no hexavalent chromate in the final product per GMW3059 requirements. GMW3034 will be used as a referee test.

Parts supplied to this specification shall be free of hexavalent chromate effective July 2005 or model year 2006 parts whichever is earlier.