Corrosion behavior of WC-η coatings in molten zinc

The WC-based coating containing a Co-W-C phase was fabricated to prevent steel components from molten Zn corrosion in galvanizing industry. The corrosion extent of the coating was determined through quantitative analysis of Co dissolved in molten Zn. It was found that slight oxidation of η phase by interstitial oxygen diffusion facilitated Zn substitution for Co and hence corrosion of the coating. The penetration rate of Zn from the sides of coating was significantly higher than that from the top surface. The formation of WO3/CoWO4 over the coating dramatically suppressed the dissolution corrosion process but may cause cracking and material exfoliation.