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Corrosion protection application of titanium alloy in power industry

Titanium has good stability in hot water containing chloride, sulfide and other corrosive substances, so it has been widely used in thermal power plants as heat exchanger cooling pipe. After replacing the cu-ni alloy tube with thin-walled titanium tube, the service life is greatly increased, and the maintenance time is greatly reduced, and the economic effect is very significant.

Titanium and titanium alloys have good corrosion resistance and are also used in steel chimney lining. In the domestic zhangzhou houshi power plant of fujian province, the seawater desulfurization system without GGH and bypass is adopted.

Industrial pure titanium is a kind of thermally unstable metal. If Ti2 + can be formed by dissolution, the standard electrode potential at the time of titanium ionization is -1.63 V, so titanium is easily dissolved in water and releases hydrogen. However, in many corrosive media, titanium has very strong corrosion resistance, which is due to its great passivability. Its passivity exceeds that of cobalt, nickel and stainless steel. It is very corrosion resistant in many active media, especially for oxidation media and medium containing chlorine and chloride, corrosion resistance is the best, but titanium in sulfuric acid, hydrochloric acid stability is poor. In order to solve the problem that the corrosion resistance of conventional titanium and titanium alloy to reducing medium such as sulfuric acid and hydrochloric acid is not strong, adding molybdenum element (10% 32%) in titanium alloy can greatly improve the corrosion resistance of titanium alloy to reducing medium. The higher the content of molybdenum, the better the corrosion resistance, but the more difficult melting and processing. It is mainly manifested in the strengthening of the alloy, which affects the application of the alloy to some extent. The corrosion resistance of ti-mo alloy is shown in table 2.Ti-mo alloy is more suitable as steel chimney anticorrosive material than pure titanium. Ti-molybdenum alloy of ti-20mo and above grade can meet the requirements, and because titanium alloy has strong resistance to chloride corrosion, it is especially suitable for power plants that adopt seawater desulfurization.

Thin - walled titanium tubes are used for condensers in binhai power station. Before the 1960s, aluminum brass or B30 copper tubes were used. With the increasing pollution of sea water, the service life was significantly reduced. As early as in the 1960s, the United Kingdom has been using all-titanium condenser, and in the 1970s, Japan introduced the condenser with thin wall (0.3-0.5mm) welded titanium tube, which greatly reduced the cost. By 1987, 30 percent of industrialized countries had titanium condensers. Due to the high requirements for safe operation and reliability of nuclear power plants, special attention is paid to the use of titanium condensers, most of which adopt thin-wall welded titanium tube and seamless titanium tube. China began to test domestic titanium tubes in the late 1970s.Since 1983, 18 titanium condensers have been used in 9 power plants, such as zhejiang taizhou power plant, Shanghai jinshan thermal power plant and zhejiang zhenhai power plant.
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