Due to the excellent corrosion resistance of titanium materials, titanium materials are widely used in petroleum, chemical, salt, pharmaceutical, metallurgy, electronics, aviation, aerospace, marine and other related fields. Titanium has excellent corrosion resistance to most salt solutions, such as titanium in chloride solution than high chromium nickel steel corrosion resistance, no pitting phenomenon. However, the corrosion rate in aluminum trichloride is higher, which is related to the production of concentrated hydrochloric acid after the hydrolysis of aluminum trichloride. Titanium also has good stability to hot sodium chlorite and various concentrations of hypochlorite. Therefore, titanium materials are widely used in vacuum salt production and bleaching powder refining industries. Titanium has good corrosion resistance to most alkaline solutions. Titanium is relatively stable in sodium hydroxide and potassium hydroxide solutions with a concentration of less than 50%. If the alkaline solution contains chloride ions or chlorides, its corrosion resistance is even better than that of nickel and zirconium. However, corrosion increases with increasing temperature and concentration. Now the chlor-alkali industry is the largest field of domestic civil titanium application. Titanium is not resistant to corrosion in dry chlorine gas and has a fire hazard, but it has high stability in wet chlorine gas, surpassing zirconium, Hastelloy C and Monel alloys, and even in sulfuric acid, hydrochloric acid and sulfuric acid saturated with chlorine gas. It is also stable in chloride and other media, so titanium material is the preferred material for key equipment in the production of titanium dioxide by sulfuric acid method.
Due to the good corrosion resistance of titanium in hydrocarbons, it is also very good even in the presence of acid and chloride impurities. Therefore, titanium materials are also widely used in organic chemicals, such as PTA (purified terephthalic acid), PVA (vinylon) and so on. Titanium has excellent corrosion resistance in seawater, so titanium is also widely used in offshore oil drilling platforms, seawater desalination and other marine fields.
Corrosion resistance characteristics of titanium materials: Titanium is a metal with a strong tendency to passivation. It can quickly form a stable oxidative protective film in the air and in an oxidizing or neutral aqueous solution. Can quickly and automatically recover. Therefore, titanium has excellent corrosion resistance in oxidizing and neutral media. Due to the great passivation properties of titanium, in many cases it does not accelerate corrosion when in contact with dissimilar metals, but may accelerate the corrosion of dissimilar metals. For example, in low-concentration non-oxidizing acids, if Pb, Sn, Cu or Monel are contacted with titanium to form a galvanic couple, these materials will corrode faster, but titanium is not affected. In hydrochloric acid, when titanium is in contact with low carbon steel, new hydrogen is generated on the surface of titanium, which destroys the oxide film of titanium, which not only causes hydrogen embrittlement of titanium, but also accelerates the corrosion of titanium. This may be due to the high resistance of titanium to hydrogen. due to activity. The iron content in titanium has an impact on the corrosion resistance in some media. The reason for the increase in iron is that, in addition to the raw material, the iron contaminated during welding is often infiltrated into the weld bead, which increases the local iron content in the weld bead. Corrosion has a non-uniform nature. When using iron to support titanium equipment, iron contamination on the iron-titanium contact surface is almost unavoidable and corrosion accelerates in the iron-contaminated area, especially in the presence of hydrogen. When the titanium oxide film on the stained surface is mechanically damaged, hydrogen penetrates into the metal, and the hydrogen diffuses correspondingly according to conditions such as temperature and pressure, which makes the titanium produce different degrees of hydrogen embrittlement. Therefore, titanium is used in moderate temperature and moderate pressure and hydrogen-containing systems to avoid surface iron contamination. In general, pitting corrosion does not occur in titanium. Titanium also has corrosion fatigue stability. Titanium has good crevice corrosion resistance, especially Ti-0.3Mo-0.8Ni and Ti-0.2Pd alloys. Therefore, Ti-0.3Mo-0.8Ni and Ti-0.2Pd alloys are widely used as sealing surface materials for container equipment to solve the problem. The problem of crevice corrosion on the sealing surface of equipment.
