Metal oxide medium after treatment, the corrosion rate than the original untreated significantly decreased the phenomenon known as the metal passivation. The passivation mechanism can mainly be explained by the thin film theory, that passivation is due to the role of metal and oxidizing medium, the role of the metal surface to generate a very thin, dense, good coverage, can be firmly attached to the metal Passivation film on the surface. This film exists as an independent phase, usually a compound of oxygen and metal. It plays a role of the metal and the corrosive medium completely separated to prevent the metal and the direct contact with the corrosive medium, so that the basic dissolution of the metal to form a passive state to achieve the effect of preventing corrosion
Passivation is the last process step in chemical cleaning and is a crucial step toward the protection of materials. Such as the boiler pickling, water rinse, rinse, the metal surface is very clean, very activated, it is vulnerable to corrosion, it must be immediately passivated to clean the metal surface to generate a protective film to reduce corrosion.