Selection of stainless steel plates in atmospheric environment

Media environments where comprehensive corrosion occurs are common, such as atmosphere, water, acid and salt media. In these environments, stainless steel plates generally do not suffer from local corrosion, and there are corresponding requirements for the selection of stainless steel plates. This article mainly talks about the selection of stainless steel in atmospheric environment.

According to the humidity level of the atmosphere, it is usually divided into dry atmosphere, tidal atmosphere and humid atmosphere. Their corrosiveness to stainless steel plates will increase as the humidity in the atmosphere increases. In order to resist atmospheric corrosion, the material selection of stainless steel plates is usually in the order of Cr13, Cr17, and 18-8. Up to 18-8 type Cr-Ni austenitic stainless steel can be used to meet the corrosion resistance requirements.

According to the environment in which stainless steel plates are located, the atmosphere can also be divided into rural atmosphere, industrial atmosphere and marine atmosphere.

The rural atmosphere is usually relatively clean except for moisture, so the corrosion resistance of stainless steel does not need to be too strong. Often, Cr13 and Cr17 steel can meet the requirements.

In addition to moisture, the industrial atmosphere often contains SO2, H2S, NH3, NO2, CO2, Cl2 and other gas impurities and suspended dust particles, and some gas impurities are easily soluble in water, falling or adsorbed to the surface of stainless steel, and then When dissolved in water, highly corrosive substances such as C1- and H2SO4 can be generated; some suspended particles and dust, some become corrosive after being dissolved in water, and some fall on the surface of stainless steel to form Gaps accelerate corrosion of stainless steel. Therefore, in an industrial atmospheric environment, if it is indoors, when choosing stainless steel plates, Cr13 and Cr17 stainless steel should still be considered; but outdoors, Cr17 steel is the lowest grade available.

The ocean atmosphere is not only humid but also contains a lot of sea salt particles such as NaCl, so chloride ion corrosion is particularly prominent. In this corrosive environment, Cr13 and Cr17 stainless steel will form a rust film on the surface after short-term use. However, the main danger is that they are very prone to pitting corrosion, especially in offshore and offshore areas. Although 18-8 type Cr-Ni stainless steel will rust in the harsh marine atmosphere, the rust layer is usually very thin and can be easily removed.