Among various metal materials, titanium has good corrosion resistance in wet chlorine gas, sericin solution (except for high temperature and high concentration of ZnCL, AIClR, and CaCl), and chlorine-containing compounds (such as sericin, chlorite, hypochlorite, and perchlorate), and has been successfully applied in bleaching plants, electrolytic chlorine plants, and wastewater treatment plants. However, titanium materials will suffer crevice corrosion in high temperature and high concentration chloride solutions, especially when contacting with organic compound materials such as polytetrafluoroethylene, crevice corrosion is more serious. Titanium produces severe corrosion in dry silkworm gas and even causes fire and spontaneous combustion. The reaction of Ti and CI generates TiCL4, which is an exothermic reaction. As long as the water content in the medium is very low, the heat released can promote the combustion of titanium until dry chlorine or titanium is exhausted. If chlorine contains water, titanium tetrachloride will undergo a hydrolysis reaction to produce white titanium hydroxide. Titanium hydroxide is a stable solid compound, not a highly volatile liquid like titanium tetrachloride (boiling point 136 ℃). The boundary between "dry" and "wet" is related to environmental temperature and alloy composition. It is reported that the minimum water content for industrial pure titanium to maintain its passive state in silkworm gas at about 200 ℃ is about 1.5%; Under normal temperature, as long as the minimum water content is kept above 0.3%~0.4%, it will not ignite. Ti-Pd alloy and Ti-Ni-Mo alloy can maintain metal passivity at lower water content.
