One of the fundamental characteristics of aluminium is that when exposed to air, it will immediately form a natural oxide layer. This natural oxide layer is, however, very thin; approximately one hundredth of a micron and therefore of limited long term appeal.
Anodising is an electrolytic process which artificially increases the film thickness to approximately 20 micron. In anodising, more accurately termed anodic oxidation, the component is made the anode in a dilute acid solution and the oxygen liberated at the anode by the passage of an electric current, results in the formation of the oxide film as an integral part of the metal.
This thicker oxide layer allows aluminium to be used in a wide variety of applications.
The anodic film is stable and hard, resulting in much improved corrosion and abrasion resistance. The film is both transparent and porous, giving the opportunity to use the visual appearance of the natural metallic finish or to process further in a range of colours.
A good quality anodic finish is perfectly capable of having a life expectancy in excess of 40 years.