Slurry erosion-corrosion resistance and microbial corrosion electrochemical characteristics of HVOF sprayed WC-10Co-4Cr coating for offshore hydraulic machinery

The slurry erosion-corrosion and microbial corrosion electrochemical behavior of high-velocity oxygen-fuel (HVOF) sprayed WC-10Co-4Cr cermet coatings and the reference stainless steel 1Cr18Ni9Ti were both investigated. The slurry erosion-corrosion test was performed in a rotating disk rig facility with circulating system using distilled water and 3.5 wt% NaCl slurries. The microbial influenced corrosion behavior in the presence of SRB was evaluated by electrochemical measurement. The results showed that WC-10Co-4Cr coating exhibited higher slurry erosion-corrosion resistance compared to the stainless steel 1Cr18Ni9Ti in both distilled water and 3.5 wt% NaCl slurries. The evolution of the slurry erosion mechanism of the coatings with the augment of NaCl concentration was cracks and microchipping in distilled water slurry, and a combination of detachment of binder phase, microchipping and fragments in 3.5 wt% NaCl slurry. Potentiodynamic polarization and electrochemical impendence spectroscopy (EIS) results showed that the WC-10Co-4Cr coating had a comparable microbial influenced corrosion resistance in seawater with SRB as compared to the stainless steel 1Cr18Ni9Ti.