In this study, we designed a thermal barrier coating (TBC) system—Yb2O3–Gd2O3–Y2O3 co-stabilized ZrO2 (YGYZ) coating—with a Lewis neutral B–SiO2 layer applied on its surface via a sol–gel-based glassification process and investigated its long-term corrosion resistance under corrosive environments. The corrosion behavior of the B–SiO2-covered YGYZ coating was assessed after 20, 40, 80, 160, and 320 h exposure to a hot corrosive environment of Na2SO4 + V2O5 at 1100 °C. Results indicated that the B–SiO2 layer effectively prevented the penetration of corrosive salts and formation of m-ZrO2 phase in the coating layer as well as generated vertical cracks that could release the residual stress. Therefore, it is concluded that depositing a Lewis neutral B-SiO2 layer on YGYZ coatings is highly beneficial for extending the lifetime of the TBCs.
