Exposed to the oxygen, aluminium combines with oxygen to form a protective surface film which prevents further oxidation of the aluminium. Unlike steel or iron alloys, aluminium will not continue to oxidize once this protective layer is formed. This natural oxide is extremely thin and loosely stuck to the aluminium surface. Anodising is a process that thickens the layer of natural oxide on the surface of the metal. This produces a clear film of aluminium oxide on the aluminium’s surface. This provides better corrosion resistance and improved wear resistance. Anodising also creates better adhesion for paint primers.
Anodic films are generally much stronger than most types of paint and metal plating, but also more brittle. This means they are less susceptible to wear and tear but more likely to break under stress. Anodized aluminium can be nearly as hard as diamond under the right anodizing process. Many modern buildings use anodized aluminium in places where the metal framework is exposed to the elements.
Anodized aluminium is also a popular material for making high-end cookware such as frying pans and pots. Heat is distributed evenly across anodized aluminium, and the process of anodizing provides a naturally protective finish. Special dyes can also be used to colour the anodized aluminium for decorative uses like the special finishes that you can have on your iPod. Because of its strength and durability, anodized aluminium is also used in a number of other applications. Many of the satellites circling the Earth are protected from space debris by layers of anodized aluminium. The automobile industry relies heavily on anodized aluminium for trims and protective housings for exposed parts. Furniture designers often use anodized aluminium as the framework for outdoor pieces as well as the base metal for other items. Modern home appliances and computer systems sometimes use anodized aluminium as protective case.