To improve the corrosion resistance of a welded stainless steel pipe used in piping before piping work.
A produced welded stainless steel pipe is dipped in the hydrofluoric acid-nitric acid mixture contg. an org. compd. comprising the S, O and P having a lone electron pair or N atom as the pickling promoter and pickled. One or ≥2 kinds selected from the org. compds. based on sulfide, thiazole, phenol and thiourea are added to the hydrofluoric acid-nitric acid mixture as the pickling promoter. The corrosion potential of the surface of the pickled welded stainless steel pipe is somewhat lowered, and the galvanic potential difference of the weld as an anode is decreased. Consequently, the cathodic reaction in microcell corrosion is suppressed, and the corrosion resistance of the weld is improved.
NISHIKAWA MITSUAKI
ADACHI TOSHIRO
NAGOSHI TOSHIRO
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