Titanium coil is also a kind of titanium equipment, the general titanium coil is not prone to corrosion, but in a specific use environment, will not produce such a situation.
Titanium material in some inappropriate environment or in use conditions, but also produce some corrosion phenomenon. Next, xiaobian according to their own experience for you to explain in detail what the corrosion phenomenon of titanium equipment is.
1, gap corrosion
In the gap or disadvantage of metal components, due to the electrochemical cell formed by electrolyte stagnation, local corrosion phenomenon is caused. In neutral and acidic solution, the probability of touch corrosion in titanium alloy gap is much higher than that in alkaline solution. Touch corrosion does not occur in the whole gap surface, but eventually leads to local perforation damage.
2, pitting phenomenon
Titanium has no pitting phenomenon in most salt solutions, but mostly occurs in non-aqueous solution and exultant high-concentration chloride solution. The halogen ions in the solution corrode the passivation film on the surface of titanium, and spread to the inside of titanium, resulting in pitting, and the pitting aperture is less than its depth. Some organic media will also occur pitting phenomenon with titanium alloy in halogen solution, titanium alloy pitting in halogen solution generally occurs in high concentration and high temperature environment, in addition, in sulfide and chloride pitting needs 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 the early damage failure of titanium alloy. When it comes to the passivation film on the surface of titanium and its titanium alloy, it has high strength. The sensitivity of hydrogen embrittlement is added with the increase of strength, so the hydrogen embrittlement of passivation film is very sensitive.
4, touch corrosion
The passivated oxide film on the surface of titanium promotes the positive potential of titanium electric displacement and improves the corrosion resistance of titanium material to acid and water medium. Due to the high potential of titanium alloy surface, it is bound to form an electrochemical circuit with other metals it touches, resulting in touch corrosion. Titanium alloy is easy to touch corrosion in the following two types of media: The first type is tap water, salt solution, sea water, atmosphere, HNO3, acetic acid, etc. The stable electrode potential of the solution Cd, Zn, Al is more negative than Ti, and the anodic corrosion rate increases by 6-60 times. The second type is H2SO4, HCl, etc. Ti may be in the passivation state or activation state in these solutions. The first kind of solution corrosion is common in practical touch corrosion process. Anodizing treatment is generally used to form a modified layer on the surface of the matrix to prevent touch corrosion.
