Epoxy coating is a commonly used anticorrosive coating on metal surfaces. Pseudomonas aeruginosa has been reported to be able to accelerate the corrosion of metal materials, but its effect on the corrosion resistance of epoxy coatings is rarely reported. In this work, the accelerated deterioration of epoxy coating on carbon steel caused by marine Pseudomonas aeruginosa was investigated. The immersion tests of epoxy coatings in the sterile and P. aeruginosa-inoculated culture media with 100%, 10%, and 0% nutrients were performed. When the nutrient concentration was reduced, the number of P. aeruginosa cells attached to the coating surface was improved, and the coatings suffered more degradation under starvation conditions. The results of electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements showed that the presence of P. aeruginosa promoted the degradation of epoxy coating, and the coating had lower low frequency impedance modulus and higher corrosion current density in the inoculated medium with starvation conditions. The results of Fourier transform infrared spectroscopy (FTIR) indicated that the peak intensities of C-O-C and C-O groups of coatings decreased as nutrient concentration dropped in the inoculated medium. It indicated that P. aeruginosa accelerated the degradation of epoxy coatings through destroying the C-O-C and C-O groups.

The microbiologically influenced corrosion of 201 stainless steel by Shewanella algae was investigated via modulating the concentration of fumarate (electron acceptor) in the medium and constructing mutant strains induced by ΔOmcA. The ICP-MS and electrochemical tests showed that the presence of S. algae enhanced the degradation of the passive film; the lack of an electron acceptor further aggravated the effect and mainly affected the early stage of MIC. The electrochemical tests and atomic force microscopy characterization revealed that the ability of ΔOmcA to transfer electrons to the passive film was significantly reduced in the absence of the c-type cytochrome OmcA related to EET progress, leading to the lower corrosion rate of the steel.