Influence of Al2O3 overlay on corrosion resistance of plasma sprayed yttria-stabilized zirconia coating in NaCl-KCl molten salt

Abstract The pyrochemical reprocessing faces challenges in the selection of suitable materials for the fabrication of the container in electro-refining process. Yttria stabilized zirconia (YSZ) coating was considered as a promising material in this application, but the performance of YSZ coating in NaCl-KCl molten salt must be improved. In the present work, metal-organic decomposition (MOD) method was put forward to deposit an Al 2 O 3 overlay on the top surface of sprayed YSZ coating. The corrosion behavior of the YSZ coatings with and without Al 2 O 3 overlay in molten NaCl-KCl eutectic salt was investigated by immersion test. The results showed that the sprayed YSZ coating suffered severe corrosion and a NiO corrosion product formed on the coating surface. Meanwhile, a transformation of ZrO 2 from a non-transformable tetragonal ( t′ ) phase to a monoclinic ( m ) phase emerged. In contrast, the surface morphology of the YSZ coating with Al 2 O 3 overlay remained almost unchanged. No corrosion product or new phase was formed. These results proved that the Al 2 O 3 overlay prepared by the MOD method can significantly improve the corrosion resistance of YSZ coating.