Effect of high-temperature furnace treatment on the microstructure and corrosion behavior of NiCrBSi flame-sprayed coatings

• Heat treatment significantly reduces area porosity in NiCrBSi coatings.
• Surface roughness decrease as a consequence of subsequent heat treatment.
• Heat treatment at 1080 °C eliminates the network of interconnected porosity.
• Subsequent heat treatment improves the corrosion resistance of NiCrBSi coating.
• Heat treatment reduces pitting initiation rate and improves the ability to repassivate.

The microstructure and corrosion properties of flame-sprayed and heat-treated NiCrBSi coating on low-carbon steel are analyzed using an optical microscope, SEM/EDS and cyclic polarization electrochemical tests. Heat treatment was performed at 930 °C, 1040 °C and 1080 °C for 10 and 20 min where densification of the coating occurred. Electrochemical corrosion tests in a 3.5 wt.% NaCl solution were performed on a low-carbon mild steel substrate, as-sprayed coating and on furnace treated coating partially melted and fused between solidus and liquidus points at 1080 °C to evaluate the influence of heat treatment on corrosion resistance.