Titanium alloy common form of corrosion

In the actual production environment, there will be different types of corrosion, there are the following categories:

1, crevice corrosion

In metal components gap or defect, due to the electrolyte stagnation of electrochemical cells caused by local corrosion phenomenon, in neutral and acidic solution, titanium alloy gap corrosion probability is much greater than the alkaline solution, contact corrosion does not occur In the entire gap surface, but eventually lead to local perforation damage.

2, pitting phenomenon

Titanium in most salt solution without pitting phenomenon, which occurred in non-aqueous solution and the boiling of high concentration of chloride solution, the solution of halogen ions on the titanium surface of the passive film corrosion, and titanium diffusion to the pitting occurs Pitting aperture less than its depth. Some organic media is also pitting corrosion with a titanium alloy in a halogen solution. Pitting of a titanium alloy in a halogen solution generally occurs at a high concentration and high temperature. In addition, pitting corrosion in the sulfide and chloride needs to be specific the conditions and limited.

3, hydrogen embrittlement

Hydrogen embrittlement (HE), also known as hydrogen-induced cracking or hydrogen damage, is one of the causes of early destroy failure of titanium alloy. The passivation film on the surface of titanium and its titanium alloy has superior strength. Sensitivity of hydrogen embrittlement increases with the strength Increase, so passivation film hydrogen embrittlement is very sensitive.

4, contact corrosion

Passivation of titanium oxide film to promote the potential shift to the positive potential of titanium, titanium and improve the acid resistance of water medium corrosion. Due to the higher potential of the titanium alloy surface. It is bound to cause contact with other metal formed electrochemical loop and cause contact corrosion. Titanium alloys are prone to contact corrosion in the following two types of media: the first category is tap water, salt solution, seawater, air, HNO3, acetic acid and the like. The stable electrode potentials of Cd, Zn and Al in this solution are more negative than Ti, The rate of increase of 6 to 60 times the second category is H2SO4, HCl, Ti in these solutions, may be in the passivation state, may also be in the activated state, the actual contact with the corrosion process is common for the first type of solution corrosion. Anodizing is usually employed to form a modified layer on the surface of the substrate, hindering the contact corrosion.