Chem Film Offers Long Term Protection from Corrosion on Aluminum

Chem Film is a type of coating that chemically alters the surface of an aluminum part so that it resists corrosion while it maintains electrical conductivity. A coating of chem film on aluminum is ultra-thin, and adds virtually no bulk to the part’s dimensions. It also improves adhesion and acts as an undercoat and preparation for primer and paint.

It’s known by many other names including chromate conversion coating (CCC), chromate pretreatment, yellow iridite, alodine, and alochrome. One term you may hear used interchangeably that is notably different is anodize, another way of treating and coating aluminum to prevent corrosion, but is used for cosmetic purposes. It’s a way of protecting, strengthening, and coloring aluminum through a controlled corrosive process.

Chem Film treated aluminum is often used in parts for the aerospace industry and the military. As a base coat for military vehicles and equipment, aircraft parts, and naval vessels chem film on aluminum protects against corrosion from saltwater, humidity, and other harsh or abrasive conditions. The electronics industry also benefits from the protective and conductive properties used with component housing and electromagnetic assemblies.

The most widely used military/DoD standard, MIL-DTL-5541F defines chromate conversion coating type II as one that does not use toxic or dangerous hexavalent chromium. Under this type classification are two classes that pertain to the level of corrosion protection. Class 1A provides the highest level of protection against corrosion and general wear, while class 3 is a thinner coating that provides less protection from corrosion but maintains higher electrical conductivity.

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