Titanium is a very active metal with low equilibrium potential and high thermodynamic corrosion tendency in media. But in fact titanium in many media is very stable, such as titanium in oxidation, neutral and weak reducing media is corrosion resistant. This is because titanium and oxygen have a very large affinity, in the air or oxygen-containing medium, titanium surface generates a layer of dense, strong adhesion, inert oxide film, protect the titanium matrix from corrosion. They heal or regenerate quickly even due to mechanical wear. This indicates that titanium is a metal with a strong tendency to passivate. The oxide film of titanium always keeps this property when the temperature of the medium is below 315℃.