GMNA GM4431M PDF

This specification covers the requirements for two grades of chromate finishes for zinc die castings - finishes which are generally colorless or pale yellow. It covers the protective characteristics of such coatings. Processing details and suitability for paint base are not covered. Only trivalent chromates may be used; hexavalent chromates are forbidden.

Material Description.

Material Identification.

Grade 168. Is applicable to a wide range of automotive (and related industry) castings. A supplemental sealer over the trivalent chromate may be required to achieve this performance level.

Grade 108. Is applicable primarily to parts which are tumble processed (as in revolving barrels), thus are susceptible to the development of white corrosion products as points of impact at somewhat earlier stages of test and/or service than parts which are racked and otherwise more carefully handled during processing and shipment.

In the absence of grade designation as a suffix to basic GM number, it shall be assumed that Grade 168 is required.

Typical Application. Functional components that do not have appearance requirements and are not exposed to severely corrosive environments.