Cr7C3-based cermet coating deposited on stainless steel by electrospark process: structural characteristics and corrosion behavior

The electrospark deposition (ESD) technique has been successfully applied to deposit at room temperature a cermet layer of Cr7C3 carbide bound with 20 wt.% Cr on a AISI 304 stainless steel substrate. It has been possible to obtain a fully dense, uniform and strong adherent coating layer of 10–30-μm thickness. The corrosion properties of this coating system have been evaluated in HCl electrolyte by conventional anodic polarization tests and impedance measurements. The results indicate an exceptional resistance of the coating to both general and localized corrosion attack. Some surface stress relief microcracks formed during the ESD deposit cycles do not impair the corrosion resistance of the coating even after long time immersion in HCl.