Once aluminium metal is exposed to air it will immediately combine with the oxygen in the air inorder to form aluminium oxide, an inert shielding layer. In nature this deposit of oxide is only millionths of an inch deep. Aluminium anodizing is a well known method of thickening the coating of aluminium oxide to provide greater protection. It is a restricted oxidation of the surface achieved by immersion in an electrolyte (usually will be dilute sulphuric acid).

Production of the Anodised Aluminium Coatings:

In the process, metal is used as an anode and a very low voltage, high amperage, direct current is then passed through the metal. A stiff, inert oxide film initially forms on the surface and is followed by a less dense oxide layer in which there are capillary pores. These capillary pores allow oxidation to proceed further. Unlike painting and plating that are coatings added on to the bottom metal, anodic coatings develop downward into the parent metal and form an integral part of the metal itself. These coatings cannot lift, flake or peel.