Metal passivation is the oxidative transformation of the metal's surface into an inert state that strongly inhibits corrosion.
The passivation of a metal provides corrosion resistance from the environment. This is achieved by the deposition of a material for protection of the substrate. Some materials are self-passivating and others require coatings known as micro-coatings. When exposed to air, many metals naturally form a hard, relatively inert (passive) surface. For the latter, a thin protective coating is applied, usually in the form of metal oxide to provide a corrosion barrier.
Oxidizing chemistries are most often used in the metal finishing industry to supplement the natural properties of many metals. This can be either a chemical reaction or an electrochemical process. In most cases the corrosion resistance of the material to its environment is enhanced.