Surface contamination: attached to the surface of the oil, dust and acid, alkali, salt and other conditions into a corrosive medium, and some of the stainless steel parts of the chemical reaction, resulting in chemical corrosion and rust.
Surface scratches: a variety of scratches on the destruction of the passive film, so that the protection of stainless steel reduced, easy to react with the chemical medium, resulting in chemical corrosion and rust.
Cleaning: pickling passivation after cleaning is not clean caused by residual liquid retention, direct corrosion of stainless steel pieces
Carbon steel pollution: contact with carbon steel caused by the scratches and corrosive media to form the original battery and electrochemical corrosion.
Cutting: cutting residue, splash and other easy to rust the attachment of the material and the formation of the original battery corrosion and electrochemical corrosion.
Baking school: the composition of the flame heating area and microstructure changes and not uniform, and corrosive media to form the original battery and electrochemical corrosion.
Welding: the physical defects in the welding area (undercut, pores, cracks, not fused, not welded, etc.) and chemical defects (coarse grain, grain boundary poor chromium, segregation, etc.) and corrosive media to form the original battery and electrochemical corrosion The
Material: stainless steel chemical defects (uneven composition, S, P impurities, etc.) and surface physical defects (loose, trachoma, cracks, etc.) is conducive to the formation of the original medium with corrosive media and electrochemical corrosion.
Passivation: pickling passivation effect is not good caused by stainless steel surface passivation film is uneven or thin, easy to form electrochemical corrosion.
Cleaning: The remaining pickling passivation residue and stainless steel produce chemical corrosion of the product with stainless steel to form electrochemical corrosion.
In short, thin wall stainless steel tube
due to its special microstructure and surface passivation film, making it in general difficult to react with the media and corrosion, but not under any conditions can not be corroded. In the presence of corrosive media and incentives (such as scratches, splashes, slag, etc.), stainless steel can also be corroded with chemical and electrochemical reactions with corrosive media, and the corrosion rate is very fast under certain conditions Corrosion phenomena, especially pitting and crevice corrosion. The corrosion mechanism of stainless steel is mainly electrochemical corrosion.