Chromate conversion coating is a type of
conversion coating used to
passivate steel,
aluminum,
zinc,
cadmium,
copper,
silver,
magnesium, and
tin alloys. It is primarily used as a
corrosion inhibitor,
primer, decorative finish, or to retain
electrical conductivity. The process is named after the
chromate found in
chromic acid, also known as
hexavalent chromium, the chemical most widely used in the immersion bath process whereby the coating is applied. However, hexavalent chromium is toxic, thus, highly regulated, so new, non-hexavalent chromium-based processes are becoming more readily available at a commercial level. One alternative contains trivalent chromium. The
RoHS (Restriction of Hazardous Substances) Directive is commonly referred to regarding elimination of hexavalent chromium.