Effects of Cu on Corrosion Resistance of Duplex Stainless Steel with Lower Ni and Mo Contents

摘要

Corrosion resistance of duplex stainless steels containing 4 percent Ni-23 percent Cr-0.3 percent Mo-0.2 percent N and 0 to 2 percent Cu was investigated in aqueous chloride solutions. The addition of Cu showed no effect on the pitting potential, while it improved the crevice corrosion potential and the repassivation potential. The Cu alloying was effective on suppressing the pitting corrosion in boiling 25 percent NaCl solution with phosphoric acid, but was not effective in that with dichromate. The Cu addition was effective on improving the resistance to depassivation in acidic environments, while it increased the passive current density and the critical passivating current density.