Exchange Current Densities and Charge-Transfer Coefficients of Chromium and Iron Dissolution in Molten LiF-NaF-KF Eutectic

The exchange current density (i(0)) and charge-transfer coefficient (alpha) for Cr2+/Cr-0 and Fe2+/Fe-0 couples are studied in molten LiF-NaF-KF eutectic. These two parameters are important for understanding the metal dissolution kinetics and development of corrosion model for applications using LiF-NaF-KF eutectic as coolant or electrolyte. The values are obtained by the optimized fitting of the polarization curves, the Tafel method, and the linear polarization method. The values of i0 of Fe2+/Fe-0 couple are about 1 order of magnitude larger than that of Cr2+/Cr-0 couple. The exchange current density increases with temperature and obeys the Arrhenius law. The activation energy for the exchange current density is evaluated to be 91 +/- 19 kJ/mol for Cr2+/Cr-0, and 93 +/- 6 kJ/mol for Fe2+/Fe-0 in the temperature ranging from 600 degrees C to 750 degrees C. The charge-transfer coefficient of Cr2+/Cr-0 couple slightly decreases with the temperature, while the a of Fe2+/Fe-0 couple shows little temperature dependence. (c) 2017 The Electrochemical Society. All rights reserved.