Effect of chromium addition on the corrosion behavior of WC Cermet coatings in strong acid environment

Abstract

Corrosion and corrosion-wear studies on WC cermet coatings were performed in a strong acid (5 wt.% H2SO4) solution. Four different coating compositions such as WC-Co, WC-Ni, WC-Co-Cr, and WC-CrC-Ni were used. An immersion test and an electrochemical test results showed galvanic corrosion ocurred between WC particle/binder metal in the coating layers and general corrosion of metallic binder for the WC-Co and WC-Ni coatings. Due to formation of beneficial chromium oxide on the coating surface, the best corrosion resistant and corrosion-wear properties were observed in the WC-Co-Cr coating. For the WC-CrC-Ni coating, the corrosion resistance depended on small inter-connected cracks in the coating layer.