First: is chemical corrosion: surface pollution: attached to the surface of the workpiece oil, dust and acid, alkali, salt and other conditions into corrosion medium, and some components in the stainless steel chemical reaction, chemical corrosion and rust. Surface scratch: all kinds of scratch damage to the passivation film, so that the protection ability of stainless steel is reduced, easy to react with chemical media, chemical corrosion and rust. Cleaning: pickling passivation after cleaning is not clean resulting in residual liquid remaining, direct corrosion of stainless steel parts.
Second: is electrochemical corrosion: carbon steel pollution: and carbon steel contact caused by scratches and corrosive medium galvanic cells produced electrochemical corrosion. Cutting: cutting slag, spatter and other rusting material adhesion and corrosion medium to form galvanic cells and electrochemical decay. Baking school: the composition and metallographic structure of the flame heating area changes and is not uniform, and the galvanic cell formed with corrosive medium produces electrochemical corrosion. Welding: the physical and chemical defects in the welding area and the corrosive medium form galvanic cells to produce electrochemical corrosion. Material: chemical defects and surface physical defects of stainless steel are conducive to electrochemical corrosion by forming galvanic cells with corrosive media. Passivation: pickling passivation effect is not good resulting in stainless steel surface passivation film is not uniform or thin, easy to form electrochemical corrosion. Cleaning: the remaining pickling passivation residual liquid and stainless steel chemical corrosion products and stainless steel parts to form electrochemical corrosion.