Which post-weld treatment is commonly specified to restore corrosion resistance in stainless steel after GMAW?

• A. Polishing to a mirror finish restores corrosion resistance.
• B. Grinding alone restores corrosion resistance.
• C. Passivation is commonly specified to restore corrosion resistance after stainless steel welding.
• D. No post-weld treatment is ever required.

Answer: (C)

Welding stainless steel can damage the protective chromium oxide passive film that keeps the metal corrosion-resistant, especially in the heat-affected zone created by GMAW. Passivation uses an acid solution to remove surface iron and contaminants and to allow chromium to re-form its protective oxide layer, restoring the stainless steel’s corrosion resistance. Polishing or grinding may improve surface finish but doesn’t reliably reestablish the chemical passivity needed for corrosion resistance. Saying no post-weld treatment is required isn’t accurate because the welding process can compromise the protective film. Passivation is the commonly specified post-weld treatment to restore corrosion resistance.