Recently; the Al2O3-TiO2 ceramic coating has been considered as an effective solution for protecting steel against corrosion and wear; due to its high hardness; strong wear resistance and excellent durability. However; the inherent porosity might strongly affect its protective performance. This study revealed the effectiveness of sealing process for the plasma sprayed Al2O3-40TiO2 ceramic coating by using aluminum phosphate (APP) as sealant; with or without the presence of ultrasonication (20-40 kHz). To investigate the effect of APP permeability condition on microstructure and corrosionerosion resistance of the coating; various methods have been carried out; such as SEM/EDX analysis; potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The experimental data indicated that the APP permeability condition under ultrasonication at 30 kHz during 5 hours provided the highest values of corrosion protection and erosion resistance.