This paper summarizes the corrosion of lower titanium in various forms, hoping to be helpful to you:
1. Crevice corrosion
In the cracks or defects of metal components, local corrosion phenomenon is caused by electrolyte stagnation, which forms an electrochemical cell. In neutral and acidic solutions, the probability of contact corrosion in the cracks of
titanium alloy is much higher than that of alkaline solution. Contact corrosion does not occur in the whole gap surface, but eventually leads to local perforation and failure.
2. Pitting phenomenon
Titanium has no pitting phenomenon in most salt solutions, which mostly occurs in non-aqueous solutions and boiling solutions of high concentration chlorides. In the solution, halogen ions corrode the passivated film on the surface of titanium, and then pitting occurs when they diffuse into the titanium, and the pitting aperture is less than its depth. Some organic medium and titanium alloy in the halogen solution pitting phenomenon, titanium alloy in the halogen solution pitting generally occurs in a high concentration of high temperature environment, in addition, the pitting in sulfide and chloride requires specific conditions and limited.
3, hydrogen embrittlement
Hydrogen embrittlement (HE), also known as hydrogen-induced cracking or hydrogen damage, is one of the reasons for early damage failure of titanium alloy. The passivation film on the surface of titanium and its titanium alloy has high strength, and the sensitivity of hydrogen embrittlement increases with the increase of strength, so the passivation film is very sensitive to hydrogen embrittlement.
4. Contact corrosion
The passivation oxidation film on the surface of titanium can promote the positive electric displacement potential of titanium and improve the corrosion resistance of titanium to acid and water media. Due to the high potential on the surface of titanium alloy, it is bound to lead to the formation of electrochemical circuits with other metals in contact with the resulting 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. A modified layer is usually formed on the surface of the matrix by anodization to prevent contact corrosion.
