Once aluminum metal is exposed to air, it will immediately combine with oxygen in the air to form aluminum oxide, an inert protective layer. In nature, this oxide deposit is only one millionth of an inch deep. Aluminum anodizing is a well known method of thickening the aluminum oxide coating to provide greater protection. It is a restricted oxidation of the surface achieved by immersion in an electrolyte (it will generally be dilute sulfuric acid). Production of anodized aluminum coatings: In the process, the metal is used as the anode and then a very low voltage, high amperage direct current is passed through the metal. A rigid and 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 continue. Unlike paint and plating which are coatings that are added to the lower metal, anodic coatings develop downward on the parent metal and form an integral part of the metal itse...
Once aluminum metal is exposed to air, it will immediately combine with oxygen in the air to form aluminum oxide, an inert protective layer. In nature, this oxide deposit is only one millionth of an inch deep. Aluminum anodizing is a well known method of thickening the aluminum oxide coating to provide greater protection. It is a restricted oxidation of the surface achieved by immersion in an electrolyte (it will generally be dilute sulfuric acid). Production of anodized aluminum coatings: In the process, the metal is used as the anode and then a very low voltage, high amperage direct current is passed through the metal. A rigid and 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 continue. Unlike paint and plating which are coatings that are added to the lower metal, anodic coatings develop downward on the parent metal and form an integral part of the metal itse...