Molten Salt Corrosion Resistance of Yttria Stabilized Zirconia Coating with Silicon Carbide Interlayer on High Density Graphite

The high temperature corrosion behaviour of yttria stabilized zirconia (YSZ) coated high density graphite (HDG) with and without SiC interlayer was evaluated in LiCl-KCl molten salt at 600 A degrees C. The YSZ coated HDG samples without interlayer were tested for 50, 250, 1000 and 2000 h and the YSZ coated HDG samples with SiC interlayer were studied for 50, 500, 2000 and 3500 h durations. Characterisation of the corrosion tested samples revealed no delamination or failure of the YSZ coating in both the cases, and insignificant weight gain was observed in all the tested samples in the molten salt. The lamellar morphology of the plasma spray coating was intact even after exposure to molten salt for long duration, implying no corrosion attack of the coating and HDG in the molten salt. SEM cross-section examination confirmed neither coating degradation, nor penetration of molten salt into the HDG substrate. X-ray diffraction and Laser Raman spectroscopic analyses ascertained that no phase change occurred in YSZ after the long exposure in molten salt. Present study confirmed the phase stability and durability of YSZ coating in providing corrosion resistance and protection to HDG for high-temperature molten salt applications.