Passivation

A passivation process is used to make the chemically active surface of a metal passive, and therefore more resistant to corrosion. The formation of a chemically inert, or passive, oxide layer on the surface of the metal can be achieved by various methods, depending upon the metal itself. Pure aluminium will naturally form a protective aluminium oxide layer when it reacts with air which prevents further reactions occurring. Ferrous metals are generally passivated by using acid to form the protective oxide layer.