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

摘要

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 Al2O3 overlay on the top surface of sprayed YSZ coating. The corrosion behavior of the YSZ coatings with and without Al2O3 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 ZrO2 from a non-transformable tetragonal (t') phase to a monoclinic (m) phase emerged. In contrast, the surface morphology of the YSZ coating with Al2O3 overlay remained almost unchanged. No corrosion product or new phase was formed. These results proved that the Al2O3 overlay prepared by the MOD method can significantly improve the corrosion resistance of YSZ coating.