Microbial corrosion of Ni–Cu alloys by Aeromonas eucrenophila bacterium

The corrosion behavior of Ni–Cu alloy in Nutrient Broth medium (peptone from meat 5.0 g, meat extract (N source) 3.0 g, and sodium chloride 6.0 g in 1 L) and in the presence of Aeromonas eucrenophila, isolated from water treatment system, has been studied using electrochemical techniques. Results showed that the polarization curves exhibiting a cathodic shift of the corrosion potential confirmed the increase in the corrosion rates. According to EIS data lower QCPE value for 5 h indicates surface inhomogeneity resulting from surface metal roughening, which is the likely cause of the enhanced dissolution of the metal also observed in SEM micrographs. In addition, the pH values of the medium did not change throughout the experiment; however, after immersion the pH value decreased to acidic value and caused corrosion.

► Ni–Cu alloys are used as structural materials and pipelines due to corrosion resistance. ► Aeromonas eucrenophila attached on alloy surface and produced biofilm. ► The microbial corrosion was determined by the OCP, QCM, polarization curves and EIS. ► OCP decreased and the polarization curves exhibited a cathodic shift. ► Acidic groups in EPS increased Ni–Cu alloy corrosion by lowering the interfacial pH.