Effect of moisture on corrosion of Ni-based alloys in molten alkali fluoride FLiNaK salt environments

We investigated the corrosion characteristics on several selected alloys at 600 and 700 °C in FLiNaK molten salts with different moisture contents. Hastelloys-N and Hastelloys-B3 exhibited better corrosion resistances, while Haynes 263 showed the poorest corrosion resistance. The mass loss of the tested alloys is primarily determined by the purity of FLiNaK salts; however, the effect of temperature becomes more important on the mass loss of the tested alloys in the non-purified FLiNaK salts. When the residual moisture is present in the FLiNaK salts, the mass losses of the tested alloys varied linearly with original Cr content plus one-third of Mo content. The results of structural characterization revealed that the tested alloys in the FLiNaK salts with higher moisture content would aggravate intergranular corrosion and pitting.

► High-temperature corrosion behaviors of Ni-based alloys in molten FLiNaK salts.
► Effect of different residual moistures of FLiNaK salts on corrosion behaviors.
► Mass loss of tested alloys is primarily determined by the purity of FLiNaK salts.
► Original Mo content of alloys affects mass losses in moisture-containing salts.
► Higher moisture content in salts aggravates intergranular corrosion and pitting.