Corrosion of titanium and titanium alloys

Full corrosion

Uniform corrosion occurs on the surface of titanium samples or workpiece, forming a layer of uniform thickness of corrosion products, tightly attached to the surface of titanium, generally will not expand inward with the extension of time, but there are exceptions. In many corrosive media, titanium corrodes as well or better than other metals with protective coatings, such as aluminum. The corrosion of titanium is usually electrolytic, so there is a certain relationship between corrosion and electrode potential and electric current. Anode and cathode polarization also have strong influence on corrosion mechanism and speed. The potential of titanium depends largely on the insulating properties of oxide film. Therefore, the properties of titanium oxide film play a decisive role in its corrosion resistance. All the factors that can improve the density, thickness and insulation performance of oxide film are conducive to the improvement of corrosion resistance. On the contrary, any factor that reduces the effective protection ability of oxide film, whether mechanical or chemical, will make the corrosion resistance of titanium sharply decreased.

Local corrosion

The corrosion of titanium is local in most conditions, and the degree of corrosion at one point is different from that at another point. Crevice corrosion, cavity corrosion, stress corrosion cracking and so on are all local corrosion. Gap corrosion occurs more often at the edge or the edge of the crevice and the gap near the accumulation, the gap is too small or too large will not occur. Cavitation corrosion is a kind of corrosion occurring in open holes, which is easy to occur in the presence of CI -, Br - and I - plasmas. Stress corrosion cracking is a kind of corrosion of workpiece or sample under the combined action of tensile stress and corrosive environment.

abrasion

The corrosion form of the sample or workpiece in the corrosive flowing medium is accelerated by the mechanical action of the fluid, because the fluid can take away part or all of the corrosion products, expose the new surface, and accelerate the corrosion.

Contact corrosion of dissimilar metals

Dissimilar metal contact corrosion is also known as galvanic corrosion. In the corrosive environment, two metals or structural parts with different potentials are placed. In the case of electrical short circuit, the metal with low potential will corrode.