Effect of Marine Bacillus Subtilis on Cavitation Erosion Resistance of HVOF-Sprayed WC-10Co-4Cr Coating in Artificial Seawater

This study examined the influence of Bacillus subtilis adhesion on the corrosion and cavitation erosion resistance of high-velocity oxy-fuel (HVOF) sprayed WC-10Co-4Cr coatings. The polished HVOF-sprayed WC-10Co-4Cr coatings were divided into two groups: one immersed in artificial seawater (ASW) and the other immersed in ASW containing Bacillus subtilis (BASW). Following an immersion period of 42 days, chromium oxide was detected on the ASW-immersed coating according to x-ray diffraction, while the BASW-immersed coating showed no signs of oxidation or corrosion. Electrochemical testing indicated compromised corrosion resistance in both the coatings. Nonetheless, the corrosion resistance of the BASW-immersed coating was much better than the ASW-immersed coating, suggesting that the Bacillus subtilis biofilm protected the coating surface from the corrosive substances in ASW, such as chloride ions and oxygen. Cavitation erosion testing revealed that prior immersion in ASW accelerated the erosion process, while the BASW-immersed coating displayed better resistance to cavitation erosion due to the inhibited corrosion attained by the Bacillus subtilis biofilm.