Stainless steel gear pump causes corrosion

1 chemical corrosion 2.1.1 Surface contamination: Oil, dust, acid, alkali, salt, etc. attached to the surface of the workpiece are converted into corrosive media under certain conditions, and chemically react with certain components in the stainless steel to cause chemical corrosion and rust. 2.1.2 Surface scratch: The damage of the passivation film caused by various scratches, so that the protection ability of stainless steel is reduced, and it is easy to react with chemical medium, causing chemical corrosion and rust. 2.1.3 Cleaning: After pickling and passivation, the cleaning is not clean and the residual liquid remains, directly corroding stainless steel parts (chemical corrosion). 2 electrochemical corrosion 2.2.1 Carbon steel pollution: Scratches and corrosive media caused by contact with carbon steel parts form galvanic cells and cause electrochemical corrosion. 2.2.2 Cutting: The adhesion and corrosion of rust-prone substances such as cutting slag and splashing form a primary battery to produce electrochemical corrosion. 2.2.3 Roasting: The composition of the flame heating zone changes and the metallographic structure is uneven, and the primary battery is formed with the corrosive medium to cause electrochemical corrosion. 2.2.4 Welding: physical defects (biting, stomata, cracks, unfused, incomplete penetration, etc.) and chemical defects (grain coarse, grain boundary chrome, segregation, etc.) and corrosive medium forming the primary battery Electrochemical corrosion. 2.2.5 Material: Chemical defects in stainless steel (uneven components, S, P impurities, etc.) and physical defects on the surface (loose, blisters, cracks, etc.) are conducive to electrochemical corrosion caused by the formation of galvanic cells with corrosive media. 2.2.6 Passivation: The passivation effect of pickling is not good, resulting in uneven or thin passivation film on stainless steel surface, which is easy to form electrochemical corrosion. 2.2.7 Cleaning: The acid-washed passivation residue and the chemically corroded product of stainless steel form electrochemical corrosion with stainless steel parts. 3 Stress concentration is easy to cause stress corrosion In short, the stainless steel gear pump is difficult in general due to its special metallographic structure and surface passivation film. It is corroded by chemical reaction with the medium, but it cannot be corroded under any conditions. In the presence of corrosive media and incentives (such as scratches, splashes, slag, etc.), stainless steel gear pumps can also be corroded by slow chemical and electrochemical reactions with corrosive media, and the corrosion rate is quite fast under certain conditions. Corrosion occurs, especially pitting and crevice corrosion. The corrosion mechanism of stainless steel parts is mainly electrochemical corrosion. Therefore, all effective measures should be taken during the processing of stainless steel gear pump products to avoid rust conditions and incentives. In fact, many rust conditions and incentives (such as scratches, splashes, slags, etc.) have a significant adverse effect on the appearance quality of the product, and should and must be overcome.

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