Effect of Li2O and LiOH on the Corrosion Behavior of Fe, Co, Ni, and 29NK Alloy in the FLiNaK Melt

Abstract—The search for candidate structural materials resistant to contact with molten FLiNaK is a challenging fundamental and applied problem. To study the mechanisms of corrosive interaction between multicomponent metallic materials and halide melts in detail and to guide the search for resistant structural materials, it is advisable to compare the quantitative characteristics of corrosion of an alloy and its constituent individual metals. The aim of this work is to investigate the corrosion behavior of individual metals, namely, Fe, Ni, and Co, and a 29NK alloy (51.14–54.5 Fe, 28.5–29.5 Ni, 17–18 Co) in the FLiNaK melt with the addition of oxygen-containing compounds ranging from 0 to 2 wt % (lithium oxide and hydroxide). Corrosion tests are performed at 500°C for 24 h in an inert argon gas atmosphere with a water content below 0.1 ppm and an oxygen content below 10 ppm. The corrosion potentials of Fe, Co, Ni, and 29NK alloy are measured relative to a platinum quasi-reference electrode. The corrosion resistance of the materials in the FLiNaK melt containing oxygen-containing additives increases in the following order: Fe → 29NK alloy → Ni → Co.