Corrosion of the body, mainly the correct choice of materials. Although the anti-corrosion information is very rich, but it is still not easy to choose the right thing, because the problem of corrosion is very complex, such as sulfuric acid in the low concentration of steel is very corrosive, high concentration, then the steel production Passivation film, can be anti-corrosion; hydrogen only shows high corrosion resistance to steel under high temperature and pressure, chlorine corrosion performance is not large in dry state, and a certain humidity, the corrosion performance is strong, many materials can not be used . The difficulty of choosing the valve body material lies in that it can not only consider the corrosion problem, but also must consider the ability of pressure and temperature resistance, economically reasonable and easy to purchase and other factors. So you must be careful. Followed by the lining measures, such as lead-lined, lined with aluminum, lining engineering plastics, lined with natural rubber and various synthetic rubber. This is a saving method if the media conditions permit. Third, in the pressure, the temperature is not high, the valve body with non-metallic materials, often very effective control of corrosion. In addition, the outer surface of the valve body is also subject to atmospheric corrosion, the general steel materials are to paint to protect. Valve corrosion, usually understood as the valve metal material under the chemical or electrochemical environment suffered damage. Since "corrosion" occurs in the spontaneous interaction between metal and the surrounding environment, how to separate the metal from the surrounding environment or use more non-metallic synthetic materials is the key point of anti-corrosion. Valve body (including valve cover), accounting for most of the weight of the valve, but also in regular contact with the medium, so the choice of valve, often starting from the valve body material. Valve body corrosion no more than two forms, namely chemical corrosion and electrochemical corrosion. Its corrosion rate depends on the medium temperature, pressure, chemical properties and corrosion resistance of the valve body material. Corrosion rate can be divided into six grades: 1, Corrosion resistance: Corrosion rate lower than 0.001 mm / year; 2, Corrosion resistance: corrosion rate of 0.001 to 0.01 mm / year; 3, Corrosion: corrosion rate of 0.01 to 0.1 mm / Year; 4, still corrosion: corrosion rate of 0.1 to 1.0 mm / year; 5, poor corrosion resistance: corrosion rate of 1.0 to 10 mm / year; 6, corrosion resistance: corrosion rate greater than 10 mm / year.
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