Chem film is a chemical conversion coating primarily used to protect aluminum from corrosion. It is often referred to by its trademarked names Alodine®, Iridite® coating, or Yellow Iridite®.
In chem film coatings, also known as chromate conversion coating, the outer portion of the metal surface is chemically transformed into a protective layer. The coating of Alodine® is what leaves a base on the surface finish for organic coatings, provides aluminum corrosion protection, and can also protect against the loss of electrical conductivity.
Chromate conversion coatings are used for heat sinks, automotive wheels, and everyday aluminum hardware and components. In aerospace applications, chromate conversion coatings are used on aircraft hulls, including shock absorbers, side and torsion struts, landing gear, and flight control systems such as rudder systems and wing parts.