Electrochemical Study on the Kinetic Properties of Fe 2+ /Fe, Ni 2+ /Ni, Cr 2+ /Cr and Cr 3+ /Cr 2+ in Molten MgCl 2 -KCl-NaCl Salts

Abstract

The fundamental kinetic parameters of corrosion product ions (Fe, Ni and Cr ions) are of significant importance to understand the corrosion mechanisms of the structural materials in the molten salts. In the present study, the fundamental data of Fe 2+ , Ni 2+ , Cr 2+ and Cr 3+ (diffusion coefficient D , exchange current density i 0 , charge transfer coefficient α , limiting current density i L and standard rate constant k 0 ) were measured at different concentrations (1.53 × 10 −6 −7.48 × 10 −4 mol cm −3 ) and temperatures (600 °C–800 °C). The values of D are independent of concentrations and follow Arrhenius law with temperature, which descend in the order of D C r 2 + > D F e 2 + > D C r 3 + > D N i 2 + , with values ranging from 0.94 × 10 −5 to 3.31 × 10 −5 cm 2 s −1 . Both i 0 and k 0 depend on the temperatures, which also follow Arrhenius law. The values of the estimated k 0 descend in the order of k C r 2 + 0 > k F e 2 + 0 > k N i 2 + 0 > k C r 3 + 0 , which range from 1.88 × 10 −5 to 9.06 × 10 −4 cm s −1 .