Stainless Steel Passivation and Welding
Stainless steel, discovered in 1913, contains chromium that forms a thin chromium oxide layer on the surface, providing corrosion resistance. Passivation processes typically involve using nitric acid or citric acid to either create or facilitate the formation of this layer. Thorough cleaning is crucial to ensure contaminants, such as oils, spatter, or grease, do not interfere with the passivation process.
During stainless steel welding, heat input causes the material's color to change, indicating the formation of a heat affected zone. Depletion of chromium in this zone prevents the formation of the chromium oxide layer, requiring the removal of the oxidized layer to allow passivation to occur. Laser technology is now being used as a non-contact process to complement these methods and provide a cost-effective alternative.