Corrosion Resistance Characteristics And Applications Of Titanium And Titanium Alloys

1. Corrosion resistance of titanium

Titanium is a metal with strong passivation tendency, in air and oxidizing or neutral aqueous solution can quickly generate a layer of stable oxidizing protective film, even if the film is damaged for some reasons, but also can quickly and automatically recover. Therefore, titanium has excellent corrosion resistance in oxidizing and neutral media.

Because of titanium's great passivation properties, in many cases with dissimilar metals in contact, and does not accelerate corrosion, but may accelerate the corrosion of dissimilar metals. Such as in the low concentration of non-oxidizing acid, if the Pb, Sn, Cu or Monel alloy and titanium contact to form an electric couple, these materials corrosion accelerated, while titanium is not affected. And in hydrochloric acid, titanium and mild steel contact, due to the titanium surface produces newborn hydrogen, destroyed the titanium oxide film, not only caused by titanium hydrogen embrittlement, but also accelerate the corrosion of titanium, which may be due to the titanium of hydrogen has a high degree of activity caused by.
Iron content in titanium has an impact on the corrosion resistance of certain media, the reason for the increase in iron in addition to the raw material, often welding stained iron penetration into the weld channel, so that the weld channel in the localized iron content increases, when the corrosion has an uneven nature. The use of iron parts to support titanium equipment, iron staining on the iron titanium contact surface is almost inevitable in the iron stained area corrosion acceleration, especially in the presence of hydrogen. When mechanical damage occurs to the titanium oxide film on the stained surface, hydrogen penetrates into the metal, and depending on the temperature, pressure and other conditions, hydrogen diffusion occurs accordingly, which makes titanium produce varying degrees of hydrogen embrittlement. Therefore, titanium should be used at moderate temperatures and pressures and in hydrogen-containing systems to avoid surface iron contamination.

In general, titanium will not occur pore corrosion. Titanium also has corrosion fatigue stability.

Titanium crevice corrosion resistance is better, especially Ti-0.3Mo-0.8Ni and Ti-0.2Pd alloys, so Ti-0.3Mo-0.8Ni and Ti-0.2Pd alloys are widely used in the sealing surface materials of the container equipment to solve the problem of crevice corrosion of the sealing surface of the equipment.

2. Application of titanium

Due to the excellent corrosion resistance of titanium, titanium is widely used in petroleum, chemical, salt production, pharmaceutical, metallurgy, electronics, aviation, aerospace, marine and other related fields.

Titanium has excellent corrosion resistance for most salt solutions, such as titanium in chloride solution than high chromium-nickel steel corrosion resistance, and no pore corrosion phenomenon. However, the corrosion rate is higher in aluminum trichloride, which is related to the hydrolysis of aluminum trichloride to produce concentrated hydrochloric acid. Titanium also has good stability to hot sodium chlorite and various concentrations of hypochlorite. Therefore titanium is widely used in vacuum salt making and bleaching essence industries.

Titanium has good corrosion resistance to most alkali solutions. Titanium is stable in sodium hydroxide and potassium hydroxide solutions with concentrations less than 50%. If the alkali solution contains chloride ions or chlorides, its corrosion resistance even exceeds that of nickel and zirconium. However, the corrosion will increase in the case of increasing temperature and concentration. Nowadays, the chlor-alkali industry is a big field of domestic civil titanium application.

Titanium in the dry chlorine gas is not corrosion resistant, while there is a risk of fire, but in the wet chlorine gas has a high stability, more than zirconium, Hastelloy C and Monel alloy, and even in the saturated chlorine sulfuric acid, hydrochloric acid and chlorides and other media is also stable, so titanium is the sulfuric acid method of titanium dioxide production of key equipment materials.

Because of the corrosion resistance of titanium in hydrocarbons is very good, even in the presence of acid and chloride impurities are also very good. Therefore, titanium is also widely used in organic chemicals, such as PTA (fine terephthalic acid), PVA (vinylon) and so on.

Titanium has excellent corrosion resistance in seawater, so titanium is also widely used in offshore oil rigs, desalination and other marine fields.