Common Causes of 304 Stainless Steel Pipe Corrosion
1 Chemical corrosion
1.1 Surface contamination: attached to the surface of the oil, dust and acid, alkali, salt and other under certain conditions into the corrosive medium, react chemically with some elements of stainless steel pipe, chemical corrosion and rust.
1.2 Surface scratches: various scratch destruction of the passive film, reduced ability to make stainless steel protection, prone to chemical reaction medium, chemical corrosion and rust.
1.3 Cleaning: Cleaning is not clean after pickling passivation resulting residue retention, direct corrosion of stainless steel (chemical etching).
2 Electrochemical Corrosion
2.2.1 Carbon pollution: in contact with the corrosive medium scratches caused by carbon steel with a galvanic cell to produce electrochemical corrosion.
2.2.2 Cutting: cutting slag, spatter and so easy to produce electrochemical corrosion rust and corrosion medium adhesion material form the original cells.
2.2.3 Roasted school: Ingredients flame heating zone to produce electrochemical corrosion and microstructure changes and uneven, and corrosive media, a galvanic cell.
2.2.4 Welding: physical defects (undercuts, pores, cracks, lack of fusion, incomplete penetration, etc.) and chemical defects in the weld zone (coarse grains, the grain boundary chromium depletion, segregation, etc.) and corrosive media, a galvanic cell generated electrochemical corrosion.
2.2.5 Material: stainless steel chemical defects (uneven composition, S, P impurities, etc.) and physical surface defects (loose, sand holes, cracks, etc.) in favor of a galvanic cell with the corrosive medium to produce electrochemical corrosion.
2.2.6 Passivation: stainless steel pickling passivation effect caused by bad or uneven surface passivation film is thin, easy to the formation of electrochemical corrosion.
2.2.7 Cleaning: product and stainless steel parts remaining residue with a stainless steel pickling passivation chemical corrosion formation of electrochemical corrosion.
2.3 stress concentration is liable to cause stress corrosion In short, due to its special stainless steel microstructure and surface passivation film, making it generally more difficult to react chemically with the medium is corrosive, but not not to be under any conditions corrosion. In corrosive media and incentives (such as scratches, splashes, cutting slag, etc.) the presence of stainless steel and corrosion can occur to produce medium slow chemical corrosion and electrochemical reactions, but under certain conditions the corrosion rate is quite fast corrosion phenomenon, especially pitting and crevice corrosion. Corrosion mechanism of stainless steel mainly electrochemical corrosion.
Therefore, industrial stainless steel pipe products should take all effective measures in the course of processing operations, to avoid corrosion conditions and incentives to produce. In fact, many corrosion conditions and incentives (such as scratches, splashes, cutting slag, etc.) also have a significant adverse effect on the appearance of product quality, and should also to be overcome.