Electrochemical corrosion behaviour of HVOF sprayed iron-based amorphous metallic coatings on AISI 316 stainless steel in an NaCl solution

New thermally sprayed amorphous metallic coatings have been developed recently that may provide a viable coating option for fluid handling equipment such as propellers, impellers and pumps. They possess the inherent risk of flow-dependent erosion-corrosion problems. In this investigation, iron based (Fe) amorphous coatings were deposited on AISI 316 stainless steel substrate by the high velocity oxy-fuel (HVOF) spraying process, and the coating microstructure was characterised using an optical microscope and scanning electron microscopy. The Fe-based amorphous coating consisted of an amorphous phase, an absence of dislocations, a nanocrystalline phase, less porosity and high hardness. The corrosion behaviour of the substrate and Fe-based amorphous coatings were evaluated by means of electrochemical tests in 3.5 wt.% NaCl solution. Three kinds of electrochemical tests were employed to identify the corrosion resistance of the coating and substrate. The results showed that the Fe Cr Mn Mo Si amorphous metallic coating had a superior corrosion resistance than 316 stainless steel. It was attributed to the amorphous structure and the presence of the corrosion resistant element chromium (Cr).