Corrosion And Protection Of Valve Body

Valve housing includes valve body, valve cover, etc., which occupies most of the weight of the valve and is in constant contact with the medium. Therefore, the selection of valves is often based on the material of the valve housing.

There are two forms of corrosion of the shell, namely chemical corrosion and electrochemical corrosion. Its corrosion rate depends on the temperature, pressure, chemical properties of the medium and the corrosion resistance of the shell material. Corrosion rate points

a. Completely resistant to corrosion-corrosion rate <0.001mm/year; b. Extremely resistant to corrosion-corrosion rate of 0.001~0.01mm/year; c. Corrosion resistance-corrosion rate of 0.01 ~ 0.1mm/year; d. Still corrosion resistant

The corrosion rate is 0.1~1.0mm/year; e. The corrosion resistance is poor and the corrosion rate is 1.0~10mm/year; f. The corrosion rate is not resistant to the corrosion rate> 10mm/year.

The anti-corrosion of the shell is mainly based on the correct selection of materials. Although there are many anti-corrosion materials, it is not easy to choose the right one, because the problem of corrosion is very complicated. For example, the concentration of sulfuric acid is low.

It is very corrosive to steel when the concentration is high, and when the concentration is high, it will produce a passivation film on the steel, which can prevent corrosion; hydrogen only shows strong corrosiveness to steel under high temperature and high pressure; it corrodes when ammonia gas is in a dry state

The performance is not great, and the corrosion performance is very strong when there is a certain humidity, and many materials cannot be used. The difficulty in selecting the shell material is that it cannot only consider the corrosion problem, but also must consider the pressure and temperature resistance.

Ability, whether it is economically reasonable, whether it is easy to buy, etc., so you must be careful.

The second is to take lining measures, such as lining lead, lining aluminum, lining engineering plastics, lining natural rubber and various synthetic rubbers. If the media conditions permit, this is an economical method.

Thirdly, when the pressure and temperature are not high, using non-metal as the valve body material can often effectively prevent corrosion. In addition, the outer surface of the shell is also corroded by the atmosphere, generally steel materials

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