Microstructure and corrosion resistance of Fe-based amorphous coating prepared by detonation spray

The Fe-based amorphous coatings were successfully prepared on the surface of Q235 carbon steel by detonation spraying process under different oxygen-fuel ratio (2.5, 2.0 and 1.7), and the resultant coatings were named as coating A, B and C. The macro-structure and corrosion behaviors of the coating were investigated in detail by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in 3.5 wt% NaCl solution. It was found that the corrosion resistance is correlated with the microstructure, phase component, and porosity of Fe-based amorphous coating. The morphology of the microdomains showed that coating B was highest dense and had no obvious defects, and the thickness, porosity was about 220 ± 10 μm, and 0.5% respectively. The electrochemical tests showed that Fe-based amorphous coating has effective protection for Q235 carbon steel in 3.5 wt% NaCl solution, and coating B has the highest corrosion potential (−283 mV vs −501 mV for coating A, −336 mV for coating C), and lowest corrosion current density (5.14 μA cm−2 vs 17.54 μA cm−2 for coating A, 9.71 μA cm−2 for coating C), and the highest the |Z| value (103.7 vs 103.1 for coating A, 103.4 for coating C), which indicates that coating B has superior corrosion resistance. Besides, as the oxygen-fuel ratio changes from 2.5 to 1.7, the corrosion mechanism of the coating changes from inner corrosion to galvanic corrosion. •Fe-based amorphous coatings were prepared by detonation spray.•The oxygen-fuel ratio controls the microstructure and phase composition.•At high oxygen-fuel ratio of 2.5, the defects cause inner corrosion.•At low oxygen-fuel ratio of 1.7, the galvanic corrosion dominates.