Potentiodynamic Polarization of Pure Metals and Alloys in Molten LiF-NaF-KF (FLiNaK) Using the K/K+ Dynamic Reference Electrode

Abstract

The potentiodynamic polarization method using the K/K+ dynamic reference electrode was used to understand the corrosion behavior of Ni, Fe, Cr, the Ni-20Cr binary alloy, and 316L stainless steel in molten 46.5LiF-11.5NaF-42KF (FLiNaK, composition in mol %) salt at 700 °C. Exposure of the materials without an applied potential revealed that Ni and Fe were stable in FLiNaK, but Cr was dissolved rapidly. The apparent redox potentials of each material with respect to the K/K+ redox couple are compared to gain insight into how the applied potential relates to the dominant corrosion mechanism for each alloy. The polarized pure metals experienced uniform surface recession while corrosion in the alloys resulted in preferential elemental dissolution depending on the applied potential with respect to the K/K+ reference reaction.