Oxide film

From GAWDAwiki

Oxide film is a chemical compound that contains oxygen, which forms a thin layer on the surface of metals when exposed to air. Oxide film should be removed before welding.^[1]

Thin film of oxide formed on the surface of some metals as soon as they are exposed to the air. This oxide film makes the metal much more resistant to chemical attack. The considerable lack of reactivity of aluminum to most reagents arises from such a film.

The thickness of the oxide film can be increased by anodizing the aluminum.^[2]

References

1. http://www.toolingu.com/definition-650240-12124-zirconiated-tungsten-electrode.html
2. http://encyclopedia.farlex.com/oxide+film