scope:

These specifications cover basic requirements for electroplated parts of the copper-nickel-chromium type as used on steel, zinc die cast, copper based alloys, and plastic components, and wrought, die-cast or forged aluminum and aluminum alloys, excluding wheels.

GM4372M and GM4374M are intended for exterior parts and provide 2 levels of corrosion protection. GM4374M provides corrosion protection for severe service conditions that include likely damage from denting, scratching and abrasive were in addition to corrosive environments such as encountered by automotive bumpers and related components. This specification differs from GM4372M in that it requires a longer corrosion (CASS) exposure, GM4372m provides corrosion protection for corrosive environments which receive little additional mechanical abuse, Both specifications require the use of discontinuous chromium plate in addition to a multiple layer nickel system.

GM4373M is intended for interior applications. It does not require the use of discontinuous chromium or multiple layer nickel systems.

When specifying chromium plating on aluminum, a coating must be applied to all of the non-significant surfaces which do not receive a full complement of plate and are exposed to severe corrosive environments. Aluminized wax or other corrosion protective coatings are recommended.