Corrosion resistance mechanisms of detonation sprayed Fe-based amorphous coating on AZ31B magnesium alloy

The microstructure and corrosion mechanisms of the detonation sprayed Fe-based amorphous coating on AZ31B magnesium alloy substrate were studied in detail by potentiodynamic polarization tests in 3.5 wt.% NaCl solution. The results show that the coating presents a typical amorphous structure, a fairly low porosity of less than 1%. Benefit from these structural advantages, the corrosion current density and impedance modulus are about 1/20 and 70 times that of AZ31B, respectively, which shows excellent corrosion resistance and protection. This distinguished corrosion resistance is mainly attributed to its unique disordered structure, uniform chemical composition, and the formation of uniform passive film on the surface, which hinders the invasion of chloride ions and prevents the further occurrence of corrosion. In addition, the ultra-high density of detonation sprayed coating also further hinders the penetration of corrosive media such as chloride ions, and provides a good corrosion protection for AZ31B.