Titanium is a kind of very reactive metals, the equilibrium potential is very low, the thermodynamic corrosion tend to be large in the medium.But in fact, titanium in many medium is stable, such as titanium in oxidizing, neutral and weak reducing medium is corrosion resistant.This is because has a great affinity, titanium and oxygen in the air or oxygen medium, and generate a dense layer of titanium surface oxidation film, strong adhesion, large inertia, protect the titanium substrate from corrosion.Even if due to mechanical wear and tear will soon heal or to regenerate.It shows that the titanium is a strong passivation tendency of metal.Medium temperature under 315 ℃ titanium oxide film has always been to maintain this feature. Including TA0, pure titanium TA1, TA2, TA3, etc.