Chemical Film (Chem. Film)
Chromate conversion coatings are commonly used on parts in the aircraft industry, electronic cabinet and components industry, where it is often called chem film, chemical film, or the well-known brand names of Iridite or Alodine. It is a widely used process to protect aluminum from corrosion and to assure good paint adhesion.
Chromate conversion coating of aluminum is a type of conversion coating applied to passivate aluminum alloys to slow the formation of white corrosion. The process uses various chromium compounds which may include hexavalent (Cr6) chromium or non-hexavalent (Cr3) chromium compounds. The industry has developed non-hexavalent / trivalent less toxic alternatives in order to comply with the Restriction of Hazardous Substances (RoHS) legislation.
It has additional value as a primer for subsequent organic coatings, as untreated metal, especially aluminum, is difficult to paint or glue. Chromated parts retain their electrical conductivity to varying degrees, depending on coating thickness. The process may be used to add color for decorative or identification purposes.
DIFCO has both Barrel and Rack processes for chromate conversion coatings and meets the requirements of Mil-C-5541 and most corporate specifications.