What should be done when corrosion occurs on the polished stainless steel pipes

When corrosion occurs on the polished stainless steel pipe, the following treatment measures can be taken according to the severity of the corrosion and specific circumstances:

Minor corrosion

Mechanical grinding: For cases where there are only minor corrosion spots on the surface, fine sandpaper or grinding cloth can be used to gently grind the corrosion area, removing the corrosion layer and exposing the fresh metal surface. During the grinding process, attention should be paid to uniform force to avoid generating new scratches. After grinding, clean it with a clean cloth.

Chemical cleaning: Special stainless steel cleaning agents can be used for treatment. Dilute the cleaning agent to an appropriate concentration, then use the soaking or wiping method to allow it to fully contact the corrosion area, and remove the corrosion products through chemical reactions. For example, for stainless steel cleaning agents containing nitric acid and hydrofluoric acid, the nitric acid concentration is generally 5% - 10%, and the hydrofluoric acid concentration is 0.5% - 1.5%. The soaking time should be controlled at 10 - 30 minutes. After cleaning, thoroughly rinse with clean water to prevent cleaning agent residue from causing further corrosion.

Moderate corrosion

Re-pitting treatment: After cleaning the corrosion area, re-pitting treatment is required to restore the passivation film on the surface of the stainless steel pipe. The stainless steel pipe can be immersed in a passivation solution containing potassium dichromate or nitric acid, for example, using a 5% - 10% nitric acid solution, and soaking for 15 - 30 minutes at room temperature. Then, remove it, rinse with clean water and dry, to enhance the corrosion resistance of the stainless steel pipe.

Electrolytic polishing repair: If the area of the corrosion is large, electrolytic polishing can be considered for repair. By adjusting the appropriate electrolyte composition and electrolysis parameters, such as using a phosphoric-acid - sulfuric acid type electrolyte, control the temperature at 40 - 60℃, current density 15 - 30A/dm², and perform electrolytic polishing on the stainless steel pipe to remove the corrosion layer and make the surface reach a smooth and flat state, while forming a good passivation film.

Severe corrosion

Local replacement: When the corrosion degree of the stainless steel pipe is relatively severe, such as large areas of perforation or deep corrosion causing a significant reduction in the pipe wall thickness, consider replacing the severely corroded local area. First, cut off the corrosion area, and then select a suitable stainless steel pipe section for welding connection. When welding, pay attention to using appropriate welding processes and parameters to avoid new corrosion problems caused by welding heat influence.

Overall scrapping: If the corrosion range of the stainless steel pipe is extensive and the degree is severe, and cannot be restored to its usage performance and corrosion resistance through local treatment or repair, consider scrapping the entire pipe to avoid safety accidents or other adverse consequences caused by using a stainless steel pipe with severe corrosion problems.