| The anti-corrosion of the valve body is mainly the correct selection of materials. Although there is a wealth of information on anti-corrosion, it is not easy to choose the right one, because the problem of corrosion is very complicated. For example, sulfuric acid is very corrosive to steel at low concentrations, and high concentrations of steel can cause steel The passivation film can prevent corrosion; hydrogen only shows strong corrosiveness to steel at high temperature and pressure. The corrosion performance is not great when chlorine is in a dry state, and the corrosion performance is strong when there is a certain humidity. Many materials cannot be used. . The difficulty in selecting the material of the valve body lies in the fact that not only the corrosion problem can be considered, but also the pressure and temperature resistance, whether it is economically reasonable, and whether it is easy to purchase and so on. So you have to be careful. |
Followed by lining measures, such as lead lining, aluminum lining, engineering plastics, natural rubber and various synthetic rubber. If the media conditions permit, this is a way to save.
Thirdly, when the pressure and temperature are not high, using non-metals as the main material of the valve can often prevent corrosion very effectively.
In addition, the outer surface of the valve body is also corroded by the atmosphere. Generally, steel materials are protected by painting.
Valve corrosion is generally understood as the damage to valve metal materials under the influence of chemical or electrochemical environment. As the "corrosion" phenomenon occurs in the spontaneous interaction of metal with the surrounding environment, how to isolate the metal from the surrounding environment or use more non-metallic synthetic materials is the focus of anti-corrosion.
The valve body (including the valve cover) occupies most of the weight of the valve and is in constant contact with the medium. Therefore, the choice of valve often starts from the material of the valve body.
There are two forms of valve body corrosion, namely chemical corrosion and electrochemical corrosion. Its corrosion rate is determined by the temperature, pressure, chemical properties of the medium and the corrosion resistance of the valve body material. The corrosion rate can be divided into six categories:
1. Complete corrosion resistance: the corrosion rate is lower than 0.001 mm / year;
2. Extremely corrosion-resistant: The corrosion rate is 0.001 to 0.01 mm / year;
3. Corrosion resistance: The corrosion rate is 0.01 to 0.1 mm / year;
4. Corrosion resistance: the corrosion rate is 0.1 to 1.0 mm / year;
5. Poor corrosion resistance: the corrosion rate is 1.0 to 10 mm / year;
6. Non-corrosion resistance: The corrosion rate is greater than 10 mm / year.