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

Abstract

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 Fe30Cr25Mn5Mo20W10B5C3Si2 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).

Keywords

• corrosion resistance
• high velocity oxy fuel spraying
• iron-based amorphous metallic coating