Effects of exposing duration on corrosion performance in weld joint of Ni-Mo-Cr alloy in FLiNaK molten salt

Abstract

Effects of exposure duration on corrosion performance of Ni-Mo-Cr weld joint was investigated in present work. Two batches of FLiNaK molten salt was used for the corrosion test. The corrosion process was mainly controlled by selective dissolution of Cr. The corrosion rate was increased rapidly at short-term duration up to 400h and then slowed down to a plateau for long-term duration up to 3000h. The corrosion performance was exactly the same between the base zone and weld zone of the weld joint after long-term exposure. The corrosion rate was mostly promoted by impurities at early stage and essentially controlled by Cr diffusion from matrix to surface. Impurities of metal ions in salt substituted Cr and deposited on surface of weld joints. The corrosion was significantly mitigated in well purified FLiNaK salt.