Corrosion Behaviour of Uncoated and Ceramic Coated 9Cr-1Mo Steel in Molten LiCl-KCl-UCl3 Salt

9Cr-1Mo steel has been proposed as the container material for the electrorefining process of pyrochemical reprocessing of spent metallic fuels from the future sodium cooled fast breeder reactors. The electrorefining process was carried out using LiCl-KCl-UCl3 molten salt as the electrolyte at 500 A degrees C under argon atmosphere. To protect the electrorefining vessel, made of 9Cr-1Mo steel from the attack by the electrolyte, yttria stabilized zirconia (YSZ) ceramic coating was deposited on 9Cr-1Mo steel by thermal spray process. The corrosion behavior of 9Cr-1Mo steel with and without YSZ coating was evaluated in LiCl-KCl-UCl3 molten salt at 600 A degrees C under argon atmosphere for various durations (100, 250, 500 and 1000 h). The results revealed that with increase in exposure time, the weight loss of uncoated 9Cr-1Mo steel samples increased, while YSZ coated 9Cr-1Mo steel samples exhibited insignificant weight loss. SEM examination of exposed uncoated 9Cr-1Mo steel samples showed Cr depletion on the surface and formation of chromium based oxides as corrosion products. After the corrosion experiment, SEM/EDS and XRD analyses of both coated and uncoated samples showed the presence of Fe-Cr and UO2.