Can acid washing and passivation of stainless steel restore its color? Can it also restore its corrosion resistance?
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Dear teachers, I have a question to ask: After welding stainless steel, its surface often turns purple or black. In the case of fillet welds, when the plate is relatively thin, dark marks become visible on the reverse side. Generally, pickling and passivation are considered as solutions for these issues. Pickling and passivation can restore the surface color of the weld bead to silver-white, but do they also help to restore the corrosion resistance that has been reduced due to the purple or black discoloration of the weld bead?
After welding, the weld bead turns purple and black; the alloy elements have been severely eroded. This undoubtedly affects the corrosion resistance of the stainless steel (of course, it’s impossible to determine the extent of this effect based on surface color alone). Acid pickling and passivation cannot restore its corrosion resistance.