The reasons of corrosion of stainless steel surface

- Nov 09, 2018 -

-Chemical corrosion

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 parts to cause chemical corrosion and rust.  

2, surface scratch: all kinds of scratches on the passivation film damage, so that the stainless steel protection ability is reduced, easy to react with chemical media, resulting in chemical corrosion and rust.  

3. Cleaning: After washing and passivation, the cleaning is not clean and the residual liquid remains, directly corroding stainless steel parts (chemical corrosion).

-Electrochemical corrosion 

1. Carbon steel pollution: Scratches and corrosive media caused by contact with carbon steel parts form galvanic cells and cause electrochemical corrosion.

2, cutting: slag, splashing and other rust-prone substances attached to the corrosive medium to form the primary battery and produce electrochemical corrosion.

3. Roasting school: The composition of the flame heating zone changes and the metallographic structure changes unevenly, and the primary battery is formed with the corrosive medium to cause electrochemical corrosion.

4, welding: physical defects in the welding area (biting, pores, cracks, unfused, not welded, etc.) and chemical defects (grain coarse, grain boundary chromium, segregation, etc.) and corrosive medium to form the primary battery to generate electricity Chemical corrosion.

5, material: stainless steel chemical defects (inhomogeneous components, S, P impurities, etc.) and surface physical defects (loose, sand holes, cracks, etc.) are conducive to the formation of galvanic cells with corrosive media and electrochemical corrosion.

 

 


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