Influence of sealing treatment on the corrosion resistance of Fe-based amorphous coatings in HCl solution

Fe-based amorphous coatings prepared by high-velocity air fuel spray process on 304 stainless steel substrates were sealed with aluminum phosphate sealant. The morphology and microstructure of the gas-atomized powders, as-sprayed coating, and sealed coating were characterized by X-ray diffraction and scanning electron microscopy. The corrosion behavior of the coatings in HCl solution was examined using potentiodynamic polarization and electrochemical impedance spectroscopy. Results show that the aluminum phosphate sealant can penetrate into the coating and fill the microcracks. The corrosion resistance of the coatings is considerably enhanced after sealing treatment because the aluminum phosphate sealant prevents the penetration of corrosive solution. The corrosion resistance of sealed coatings decreases with the increase in HCl solution concentration. This work demonstrates that aluminum phosphate sealing is an effective method for filling the microcracks and improving the corrosion resistance of Fe-based amorphous coatings in HCl solution.