Amorphous aluminum oxide (alumina, Al2O3) forms in a layer 2-3 nm thick when bare aluminum is exposed to oxygen.
Aluminium anodizing is an electrochemical process in which an oxide (anodic) layer is chemically built on the surface of the metal. This oxide layer acts as an insulator and can be dyed in a wide variety of colors. Anodizing provides surface corrosion protection along with an excellent substrate for decorative finishes.
Anodizing is a process for producing decorative and protective films on articles made from aluminium and its alloys. It is essentially a process where a thick film of aluminium oxide is built up on the surface of the aluminium through the use of a direct current electrical supply.
Anodizing is an electrochemical process that converts the metal surface into a decorative, durable, corrosion-resistant, anodic oxide finish. Aluminium is ideally suited to anodizing, although other nonferrous metals, such as magnesium and titanium, also can be anodized.
While anodizing aluminium allows the metal to keep its natural appearance, the pores in the protective oxide layer also help to provide a better surface for the adhesion of paints and glues.
Anodized aluminium parts are commonly found in aircraft and architectural components, as well as consumer goods such as appliances (refrigerators, microwaves, and barbecues), sporting goods (baseball bats, golf carts, and fishing equipment) and electronics (televisions, smartphones, and computers).