The Corrosion Resistance Mechanism of Fe-Based Amorphous Coatings Synthesised by Detonation Gun Spraying

To improve the corrosion resistance of Q235 carbon steel in 3.5 wt.% NaCl solution, an Fe-based amorphous coating was deposited on the surface of Q235 carbon steel by detonation gun (D-gun) spraying method. It was found that the coating showed a typical amorphous phase with hardness of about 850 Hv. The morphology of the microdomains showed that the coating was dense, contained no visible defects, and its porosity was about 0.7%. The micro-regional element analysis indicates the formation of Cr7C3 during the spraying process. Compared with Q235 carbon steel, electrochemical tests show that the coating has higher pitting corrosion potential (- 296 versus - 914 mV for Q235 carbon steel), and lower corrosion current density (1.7 versus 24.6 mu A/cm(2) for Q235 carbon steel), and larger polarisation resistance (11,306.8 versus 1,821.1 omega cm(2) for Q235 carbon steel), indicating that the coating is more resistant to corrosion. XPS analysis shows that the coating forms a passivation film, rich in Cr and Mo, in the 3.5 wt.% NaCl solution. It exhibits excellent corrosion resistance, and limits the severity of corrosion, of carbon steel.