Anodizing is an electrochemical corrosion protection process commonly in use since the 1930s. Several metals are capable of being anodized including aluminum, magnesium, titanium, and tantalum. Anodized aluminum is used in many applications due to its low cost, aesthetic qualities and ideal mechanical properties.
Unlike most protective coatings, anodizing permanently changes the outer structure of the metal. When aluminum is exposed to air it naturally develops a thin aluminum oxide film that seals the aluminum from further oxidation. The anodizing process makes the oxidized surface much thicker, up to several thousandths of an inch thick. The hardness of the anodized aluminum oxide coating rivals that of a diamond, enhancing the abrasion resistance of the aluminum. The added depth of the oxide layer improves the corrosion resistance of the aluminum, while making cleaning of the surface easier. The porous nature of particular types of anodizing makes it possible to dye the aluminum a variety of colors, making it more attractive.