Chromate conversion is a type of conversion coating that is applied to passivate aluminium, zinc, copper, silver, cadmium, magnesium, tin and their alloys to slow down corrosion. This process use different deadly chromium compounds which may consist of hexavalent chromium. Now the industry is developing less toxic alternative so as to comply with substance restriction legislation. One choice is trivalent chromate conversion that is not as effective but it is less environmentally damaging. It is also usually used on aluminium alloy parts in aircraft industry where it is frequently called chemical film.

This has an added value as a primer for following organic coatings, as raw metal, particularly aluminium, is so difficult to paint or glue. The chromated parts keep their electrical conductivity to changeable degrees, depending upon the coating thickness. This process can be used to add color for enhancing or identification purpose. Chromate coatings are very soft and gelatinous when applied first but hardens and becomes hydrophobic as they grow old. Curing process can be accelerated by heating it to 70°C, but very high temperatures would gradually damage the coating over time