Electrochemical corrosion behavior of WC-Co and WC-Ni cemented carbides: Effect of chloride and sulfate ions

In this work, the influence of chloride and sulfate ions on the corrosion behavior of WC-Co and WC-Ni cemented carbides is investigated using open circuit potential monitoring, potentiodynamic polarization, electrochemical impedance spectroscopy, and surface analytical techniques. Results reveal that the corrosion resistance of WC-Co cemented carbide is significantly compromised in the presence of chloride ions, with more negative corrosion potentials and higher corrosion current densities compared to the alloy in presence of sulfate ions. In contrast, due to its lower corrosion sensitivity, WC-Ni cemented carbide exhibits only slight dissolution behavior in both media, especially in the less aggressive sulfate-containing environment, where it demonstrates an outstanding corrosion resistance. WC-Ni cemented carbide also displays higher polarization charge transfer resistance than WC-Co counterparts. This is primarily attributed to the stable passivation layer of the WC-Ni hardmetal surface, which slows the charge transfer at the interface, impeding the oxidative reaction processes and effectively preventing corrosion. This different corrosion response is supported by small-scale hardness changes observed in WC-Co and WC-Ni cemented carbides, after corrosive immersion of both materials, especially in chloride-containing environments.