Effects of Alloying Elements, Mo, Sn and Ge, on Repassivation Potential for Crevice Corrosion of 25Cr-6Ni Steel

Abstract

Effects of alloying elements, Mo, Sn and Ge, on the repassivation potential, E_R, and the initiation potential for crevice corrosion, V_crev, of 25Cr-6Ni duplex steel have been studied by using a nut/nut crevice in 0.5mol/l NaCl solution at 30°C. In this study, cyclic polarization curves to determine E_R were measured by using Tsujikawa et al method. Results obtained are summarized as follows: (1) Potential scan rates and holding time at potential to maximumn current had no influence on E_R values of 25Cr-6Ni steel in 0.5mol/l NaCl solution at 30°C. (2) The alloying of Mo, Sn and Ge, generally moved E_R toward noble potential direction. (3) E_R values of these steels generally coincide with each initiation potential for crevice corrosion, V_crev, except 3% Mo steel in reheated conditions and Sn bearing steels.