What is valve corrosion? The corrosion of valves is generally understood as the damage of valve metal materials under the action of chemical or electrochemical environment. Because the phenomenon of “corrosion” appears in the spontaneous interaction between metal and surrounding environment, how to separate metal from surrounding environment or how to use more non-metallic synthetic materials is the focus of anti-corrosion. The valve body (including the bonnet) accounts for most of the weight of the valve and is in frequent contact with the medium.
Therefore, the selection of the valve usually starts from the valve body material. There are two kinds of corrosion of valve body, chemical corrosion and electrochemical corrosion. Its corrosion rate depends on the temperature, pressure, chemical properties of the medium and the corrosion resistance of the valve body material. Corrosion rate can be divided into six grades: 1. Complete corrosion resistance: corrosion rate is lower than 0.001 mm / year; 2. Extreme corrosion resistance: corrosion rate is 0.001-0.01 mm / year; 3. Corrosion resistance: corrosion rate is 0.01-0.1 mm / year; 4. Corrosion resistance: corrosion rate is 0.1-1.0 mm / year; 5. Poor corrosion resistance: corrosion rate is 1.0-10 mm / year; 6. Non corrosion resistance: corrosion rate is greater than 10 mm / year. How to prevent valve corrosion?
The anti-corrosion of valve body mainly depends on the correct selection of materials. Although the anti-corrosion information is very rich, it is not easy to choose it properly, because the problem of corrosion is very complex. For example, sulfuric acid has great corrosiveness to steel when its concentration is low, and passivation film will be produced to steel when its concentration is high, which can prevent corrosion. Hydrogen only shows strong corrosiveness to steel under high temperature and pressure, and the corrosiveness is not good when chlorine is dry Large, and has a certain humidity when the corrosion performance is very strong, many materials can not be used. The difficulty in selecting valve body material lies in not only considering corrosion, but also considering pressure and temperature resistance, economic rationality and easy purchase. So we have to work hard. First, take lining measures, such as lead lining, aluminum lining, engineering plastics lining, natural rubber lining and various synthetic rubber lining. If the media conditions permit, this is a saving method. 2、 Thirdly, in the case of low pressure and temperature, the main material of fluorine lined valve can effectively prevent corrosion. 3、 In addition, the external surface of the valve is also subject to atmospheric corrosion. Generally, steel materials are protected by painting.