Titanium alloy is an alloy made up of titanium and other elements. Titanium alloy is an ideal structural material for aerospace engineering (34.85, -0.28, -0.80%).In the actual production environment, different types of corrosion will occur, mainly including the following:
1. Crack corrosionBr
In cracks or defects of metal components, local corrosion is caused by electrolyte stagnation forming electrochemical cells. In neutral and acidic solutions, the probability of contact corrosion in gaps of titanium alloys is much higher than that in alkaline solutions. Contact corrosion does not occur in the whole gap surface, but ultimately leads to local perforation failure.
2. Pitting phenomenonBr
Titanium has no pitting phenomenon in most salt solutions, and it mostly occurs in non-aqueous solution and boiling highly concentrated chloride solution. Halogen-ions in the solution corrode the passivation film on the surface of titanium, and spread to the inside of titanium and pitting occurs, the pitting aperture is less than its depth. Some organic media can also pitting with titanium alloy in halogen solution. Pitting of titanium alloy in halogen solution generally occurs in the environment of high concentration and high temperature. In addition, pitting of sulfur and chloride requires specific and limited conditions.
3, hydrogen embrittlement
Hydrogen embrittlement (HE), also known as hydrogen-induced cracking or hydrogen damage, is one of the early damage and failure reasons of titanium alloy. The passivation film on the surface of titanium and its titanium alloy has a high strength, and the sensitivity of hydrogen embrittlement increases with the strength, so the hydrogen embrittlement of the passivation film is very sensitive.
4. Contact corrosionBr
The passivation oxide film on titanium surface promotes the positive potential of titanium electric displacement and improves the corrosion resistance of titanium materials to acid and water media. Due to the high potential on the surface of titanium alloy, it is inevitable to form electrochemical circuit with other metals in contact and cause contact corrosion. Titanium alloy is easy in the following two types of contact corrosion medium: the first is the tap water, salt solution and sea water, atmosphere, HNO3, acetic acid, etc., the solution of the stability of the Cd, zinc, Al electrode potential is more negative than Ti, anode corrosion rate in 6 ~ 60 times the second category is - H2SO4, HCl, Ti in the solution, may be in a passive state, may also in the activated state, the actual contact corrosion in the process of common corrosion for the first kind of solution. Anodization is usually used to form a modified layer on the surface of the substrate to prevent contact corrosion.
