With the rapid development of the economy, especially the acceleration of technological transformation and upgrading in the chemical industry, the application of special metal materials is more and more extensive. Petroleum, chemical and other related industries also put forward higher anti-corrosion requirements for the materials of production equipment, which led to the development of related research institutes and processing enterprises.
Titanium is a metal with the strong passivating tendency. In the air and oxidizing or neutral aqueous solutions, a stable protective oxide film can be formed rapidly and automatically, even if the film is damaged for some reasons. Therefore, titanium has excellent corrosion resistance in the oxidizing and neutral medium.
Because of titanium’s huge passivating performance, it is possible to accelerate the corrosion of heterogeneous metals rather than accelerating the corrosion in many cases. In low concentrations of non-oxidizing acids, when Pb, Sn, Cu or monel alloy contact with titanium to form an electrical pair, the corrosion of these materials will accelerate, while titanium will not be affected. When titanium is in contact with low carbon steel in hydrochloric acid, the titanium surface produces new hydrogen that destroys the titanium oxide film, which not only causes the hydrogen embrittlement of titanium but also accelerates the corrosion of titanium.
The iron content in titanium affects the corrosion resistance of some media, and the increase of iron is often due to the iron infiltration of the stained weld bead during welding, which increases the iron content in part of the weld bead, so the corrosion has an uneven nature at this time. It is almost inevitable that iron contamination on the titanium contact surface will accelerate in the iron contamination area, especially in the presence of hydrogen. When the titanium oxide film on the stained surface causes mechanical damage, hydrogen seeps into the metal. According to temperature, pressure and other conditions, hydrogen diffuses accordingly, which makes titanium produce different degrees of hydrogen embrittlement. Therefore, titanium should avoid surface iron contamination when used in medium temperature and pressure and hydrogen bearing systems.
Due to its excellent corrosion resistance, titanium is widely used in petroleum, chemical, salt, pharmaceutical, metallurgy, electronics, aerospace, Marine and other related fields.
Titanium has excellent corrosion resistance to most salt solutions. For example, titanium is more resistant to corrosion than high-cr-nickel steel in chloride solution, and there is no hole corrosion. However, titanium has a higher corrosion rate in aluminum trichloride, which is related to the formation of concentrated hydrochloric acid by the hydrolysis of aluminum trichloride. Titanium has good stability to hot sodium chlorite and various concentrations of hypochlorite, so titanium is widely used in vacuum salt making and bleaching powder industry.
Titanium is not resistant to corrosion in dry chlorine gas and is even at risk of catching fire. Titanium is highly stable in moist chlorine, exceeding zirconium, harshard C, and monel, and even in saturated chlorine-containing sulfuric acid, hydrochloric acid and chloride, so titanium is the first choice for the key equipment of titanium dioxide production by the sulfuric acid method. Titanium materials have excellent corrosion resistance in seawater, so titanium materials are also widely used in offshore oil drilling platforms, seawater desalination, and other Marine fields.