Anodizing is an electrolytic process for producing controlled aluminum oxide films on aluminum. Oxide forms naturally on untreated aluminum, but the anodizing process produces a coating which is uniform, much harder, and more dense than natural oxidation. Aluminium oxide also possesses excellent thermal and electrical insulating qualities.

Hard coat or hard anodizing (Type III) is similar to standard anodizing, (Type II) in as much as it also creates a film of aluminum oxide on the part.

All chromate conversion coatings use chromic acid in the form of its soluble salts. During the process, a thin, gel-like film is produced on the aluminum surface.