Degradation of atmospheric plasma sprayed Gd4Al2O9 coating attacked by molten Na2SO4+V2O5 salt mixture at 700–950 °C

Abstract

In this work, investigation on degradation of the APS Gd4Al2O9 as a new coating against the 50 wt% Na2SO4+50 wt% V2O5 molten salt mixture at 700oC–950 °C for 2 h and 10 h has been conducted. Results indicate that the as-sprayed Gd4Al2O9 coating exhibited outstanding corrosion resistances. Factors related to higher Gd3+ cation ratio, Gd2O3 as a stronger basic oxide than Al2O3, Gd–O with larger chemical bond length and lower bond energy were responsible for a rapid formation of a continuous GdVO4 corrosion layer at any temperature level and corrosion duration. Amorphous phase with much reduced chemical bond strengths in the as-sprayed Gd4Al2O9 coating leading to a significantly reduced apparent porosity level but rather increased corrosion reaction speed played an important role in consuming and solidifying the molten salt mixture as fast as possible.