High Temperature Corrosion Studies in Molten Salt Using Salt Purification and Alloy Coating

Abstract

Molten salt FLiNaK (LiF–NaF–KF: 29–12–59 wt%) is a promising candidate as high temperature coolant for next generation nuclear reactor. Major technical challenge in implementation is the selection of structural material which can withstand corrosive nature of FLiNaK. Purification of FLiNaK salt was carried out by preheating and vacuum drying to remove moisture content. Moisture removed by preheating and vacuum drying was found as 28.81 wt% and 45.62 wt%, respectively. The corrosion resistance was found to increase by 51% due to salt purification. The effect of coating on the corrosion characteristics of different high temperature alloys in molten FLiNaK was also investigated. Ni coating acts as a protective barrier against the dissolution of Cr content of alloys into molten salts. Corrosion of various alloys such as Hastelloy-B, Inconel-625 and Hastelloy-X was studied in molten FLiNaK salt in static condition at 650°C in graphite crucibles for 60 hours under inert atmosphere. The surface morphology of the alloy samples was analysed by Scanning Electron Microscopy. Corrosion rate of Ni (10% P) coated Hastelloy-B was reduced in comparison with non-coated Hastelloy-B by 24%. The rate of corrosion was significantly reduced due to moisture removal and Ni coating.