Common Causes of Stainless Steel Parts Rust

Common Causes of Stainless Steel Parts Rust
1. Chemical corrosion
1) Surface contamination: oil, dust, acid, alkali, salt, etc. attached to the surface of the workpiece are transformed into corrosive media under certain conditions, and chemically react with certain components in the stainless steel parts, resulting in chemical corrosion and rust.
2) Surface scratches: Various scratches damage the passivation film, which reduces the protective ability of stainless steel, and is easy to react with chemical media, resulting in chemical corrosion and rust.
3) Cleaning: After pickling and passivation, the remaining liquid will remain and the stainless steel will be directly corroded (chemical corrosion) if the cleaning is not clean.
2. Electrochemical corrosion
1) Carbon steel pollution: Scratches and corrosive media caused by contact with carbon steel parts form galvanic cells and produce electrochemical corrosion.
2) Cutting: The adhesion of rust-prone substances such as cutting slag, splash and corrosive medium forms a galvanic cell and produces electrochemical corrosion.
3) Baking: The composition and metallographic structure of the flame heating zone change unevenly, and form a galvanic cell with the corrosive medium to cause electrochemical corrosion.
4) Welding: physical defects (undercuts, pores, cracks, lack of fusion, insufficient penetration, etc.) and chemical defects (large grains, chromium depletion at grain boundaries, segregation, etc.) in the welding area and corrosive media form galvanic cells to generate electricity Chemical corrosion.
5) Material: The chemical defects (uneven composition, S, P impurities, etc.) and surface physical defects (looseness, blisters, cracks, etc.) of the stainless steel material are conducive to the formation of galvanic corrosion with corrosive media.
6) Passivation: poor pickling and passivation results in uneven or thin passivation film on the surface of stainless steel, which is prone to electrochemical corrosion.
7) Cleaning: The remaining acid pickling passivation residue and the chemical corrosion products of stainless steel and stainless steel parts form electrochemical corrosion.
Surface treatment
1. Cleaning and polishing: If there is damage, it should be polished, especially scratches and splashes caused by contact with carbon steel parts, and damage caused by cutting slag must be carefully and thoroughly cleaned and polished.
2. Mechanical polishing: Use appropriate polishing tools for polishing, requiring uniform treatment, and avoid over-polishing and re-scratching.
3. Degreasing and dust removal: Before pickling and passivation of stainless steel parts, oil, oxide scale, dust and other debris must be removed according to the process.
4. Water sandblasting treatment: According to different treatment requirements, choose different micro glass beads, different process parameters, and avoid overspray.
5. Pickling passivation: The pickling passivation of stainless steel parts must be passivated in strict accordance with the process requirements.
6. Washing and drying: After pickling and passivation, neutralization, washing and drying should be carried out in strict accordance with the process to completely remove the residual acid.
7. Protection: After the surface treatment of stainless steel parts is completed, protection should be done to avoid secondary pollution from touching by personnel, oil, dust and other sundries.
8. Avoid reprocessing: After finishing the surface treatment of stainless steel parts, avoid reprocessing the parts or products
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