Anodizing

From GAWDAwiki

Anodizing is a method of artificially thickening the oxide film on an aluminum alloy by an electrolytic process. The component to be treated is made the anode in a tank of electrolyte, and on the passage of electric current, oxygen is produced which reacts with the metal surface to form a tightly adherent oxide coating. Dyes may be added to the electrolyte to produce color anodized surfaces. ^[1]

References

1. http://www.bocindustrial.co.uk/bocindustrial/technical/glossary/a.asp