In-situ synthesis of functional silica nanoparticles for enhancement the corrosion resistance of TBCs

• Sol–gel is effective approach to seal the porous thermally sprayed ceramic coating.
• Silica sol–gel significantly improved the corrosion resistance of alumina coating.
• Silica particles in TBCs protect the base metal from corrosive gases and fluids.

Ultra high temperature ceramic coatings (UHTCs) have a potential use as thermal protection systems in rocket exhaust cones, insulating tiles for the space shuttle, and engine components. The porous ceramic coatings require a sealing strategy with ceramic nanoparticles to enhance the corrosion resistance and prevent the formation of thermally grown oxides (TGO) at the ceramic/metallic interface. In this context, we report a simple, yet highly versatile sol–gel process to seal the pores in alumina coating with silica nanoparticles. Tetraethylorthosilicate (TEOS) was used as sol–gel precursor. Polysilicate molecules are likely formed inside the coating pores during the sol–gel process. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests were performed to measure the corrosion resistance of alumina coatings before and after treatment with TEOS. A significant enhancement of the corrosion resistance of alumina coating was performed via post-treatment with sol–gel silica which perfectly sealed the open pores and voids in alumina coatings.