GMNA GM7111M PDF

This specification covers the basic requirements for a corrosion protective coating process consisting of zinc phosphate treatment, a zinc rich epoxy resin coating, and an aluminum tint organic top coating. The coating may be applied by dipping or spraying. Part configuration dictates the application process. Internally threaded parts (nut) shall be coated in a canting centrifuge. Parts without internal threads can be coated by other processes.

Note: Any additional approved source of this finish shall have canting centrifuge application equipment.

Material Description. The coating system is free of hexavalent chromate, with no hexavalent chromate in final product per GMW3059 requirements. GMW3034 will be used as a referee test. This coating process does not generate hydrogen, however, pretreatment processes i.e. acid pickling could cause hydrogen absorption. Nonelectrolytically applied zinc rich coating has high permeability, which allows effusion of hydrogen during curing that might have been absorbed during acid pickling.

Typical Application. The coating is suitable for bolts, clips, and other ferrous parts where above normal levels of corrosion protection and freedom from hydrogen embrittlement are required.

This finish is not recommended for 360 degree Nylon Patch Nuts.

Use of this finish on threaded surface and/or bearing surface of joints could affect the torquetension relationship. It is recommended that a torque- tension study of the fastener joint should be preformed before releasing this finish on a new application.