Dissecting Anticorrosion and Antimicrobial Potency of an Ag Nanoparticle/NbC Nanocomposite Coating in a Marine Environment Containing Sulfate-Reducing Bacteria

To mitigate the microbiologically influenced corrosion of metallic components serving in marine environments, an innovative Ag nanoparticle (AgNP)/NbC nanocomposite coating was synthesized using a double glow discharge plasma method. The coating was composed of Ag nanoparticles together with NbC nanocrystals embedded in an amorphous carbon (a-C) matrix. The incorporation of Ag into the NbC coating played a significant role in determining both the grain size and crystallographic texture of the NbC phase, as well as the bonding state of the carbon species and the surface morphology of the coating. Following immersion in sulfate reducing bacteria (SRB)-inoculated artificial seawater, the planktonic SRB cell count for the AgNPs/NbC nanocomposite coating was found to be two and three orders of magnitude lower than those of the Ag-free NbC coating and bare Ti-6Al-4V, respectively. The electrochemical corrosion behavior of the AgNPs/NbC nanocomposite coating was evaluated and compared to the Ag-free NbC coating and bare Ti-6Al-4V in SRB-inoculated artificial seawater by using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The semiconducting properties of the oxide film grown on the nanocomposite coating were drawn from Mott-Schottky analysis. The results showed that Ag additions improved the microbiologically influenced corrosion (MIC) resistance of the NbC coating and led to the transformation of the electronic structure of the oxide film from an n-type semiconductor to a p-n heterojunction structure.