Anodising is an electrolytic process used to produce thick oxide coatings, usually on aluminum and its alloys. In this process, the components to be treated are made an anode in a dilute acid solution. Oxidation occurs at the component surface, resulting in the formation of a coherent oxide film that is very adherent to the underlying metal substrate. The oxide layer formed is typically 5 to 30 µm in thickness. Anodising provides a protective coating on the metal surface, improves surface resistance to wear and corrosion resistance, and gives aluminum metal a good resistivity towards corrosion, high durability, and high strength.

Applications of anodising include:

• Providing a protective coating on the metal surface
• Forming a black film on steel, which is used as decorative articles
• Giving several color coatings on zinc
• Anodising on silver jewelry
• Increasing the thickness of the natural oxide layer on the surface of metal parts