Electrochemical Studies of the Corrosion of Pure Fe, Ni and Cr in Molten (Li,Na,K)F

Abstract

The corrosion of structural materials is a great challenge for the applications of a molten salt reactor using molten fluorides. In this paper, electrochemical behavior of pure Fe, Ni and Cr has been investigated in molten (Li,Na,K)F at 973 K by potentiodynamic polarization and electrochemical impedance spectroscopy. The experimental results indicated that three metals are all in active state at the corrosion potential, with an increase in the corrosion potential by the following order: Cr, Fe, Ni. The free corrosion current density of Ni is more than one order of magnitude lower than that of Fe and Cr. A Warburg impedance was observed in the impedance plots for the corrosion of Cr, but not for Ni and Fe. Ni is the most stable metal, then Fe and Cr, and the corrosion of Cr is controlled by the diffusion of oxidants in the melt.