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

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 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.