The optimization of microbial influenced corrosion resistance of HVOF sprayed nanostructured WC-10Co-4Cr coatings by ultrasound-assisted sealing

In this study, high-velocity oxygen-fuel (HVOF) sprayed nanostructured WC-10Co-4Cr coatings were subjected to seawater with sulfate-reducing bacteria (SRB) for different time. The effect of ultrasound-assisted sealing with aluminum phosphate on the microstructural features and microbial influenced corrosion (MIC) behavior was evaluated using scanning electron microscopy (SEM), potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results showed that the ultrasound-assisted sealing promoted the infiltration of the sealant into as-sprayed coating, enhanced the resistance values of about one order of magnitude, and reduced the corrosion current density. During the whole immersion period, the MIC process of both unsealed and sealed coatings can be divided into two different stages, and the ultrasound-assisted sealing treatment significantly delayed the MIC process, suggesting that the ultrasound-assisted sealing with aluminum phosphate is an effective way for controlling the MIC of SRB on the WC-10Co-4Cr cermet coatings in marine environment.