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.

Cu-bearing high-entropy alloys (HEAs) have been proposed for use as structural materials in the marine environment due to their superior mechanical and antimicrobial properties. However, the Al, Cu-enriched precipitations in HEAs damage their corrosion resistance. In this study, we used ultrasonic shot peening (USSP) technology to solve this problem. USSP caused severe plastic deformation of the Al_0.3Cu_0.5CoCrFeNi HEA surface and dispersed the long-strip Al, Cu-enriched phases into scattered dots, which reduced the galvanic corrosion of the HEA and enhanced passive film formation. The Al, Cu-enriched scattered precipitations also increased the number of Cu²⁺ ion dissolution sites, leading to the improvement of the alloy’s antibacterial properties.

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.

In this study, a durable superhydrophobic antibacterial coating was developed by a facile spraying method. A mixture of bisphenol A diglycidyl ether (BADGE) and hydrophobic SiO₂ nanoparticles was sprayed on carbon steel to provide a superhydrophobic substrate. D-cysteine (D-cys) functionalized SiO₂/dopamine/silver nanoparticles with multilayer core-shell structure were then sprayed on superhydrophobic substrate to enhance antibacterial performance. The results of morphology observation and X-ray photoelectron spectroscopy (XPS) indicated the successful preparation of antibacterial nanoparticles and presented the hierarchical micro/nanostructures of coating surface. The as-prepared coating exhibited superhydrophobicity, with the water contact angle of ~153°. The coating was endowed with good mechanical durability, which maintained the water contact angle of ~150° after 180 cycles in tape-peel tests. The results of electrochemical impedance spectroscopy showed satisfactory corrosion resistance of this coating during 3 days of immersion in 3.5% NaCl solution. Furthermore, the coating showed excellent antibacterial performances against Escherichia coli and Pseudomonas aeruginosa, which benefited from the synergistic actions of low wettability of superhydrophobic surface, bactericidal behavior of Ag nanoparticles, and biofilm inhibition effect of D-cys.

In recent years, CoCrFeMnNi high-entropy alloy (HEA) has attracted considerable attention owing to its exceptional mechanical properties, thermal stability and corrosion resistance. Friction surfacing (FS), as a solid-state additive manufacturing technology that can avoid point defects such as pores, has great application potential in the fabrication of HEA coatings. However, relevant research has been extremely limited so far. In this article, a CoCrFeMnNi HEA coating was successfully fabricated on 304 stainless steel substrates via FS. The microstructure and corrosion behavior of as-cast HEA, solution-treated HEA and HEA coating prepared by FS were systematically analyzed. The results showed that the as-cast alloy exhibited severe dendritic segregation of Mn and Ni elements, with large-sized MnCr₂O₄-MnS composite inclusions widely distributed. Solution treatment could alleviate this segregation and partially suppress the corrosion rate. In contrast, the thermo-mechanical coupling imposed by FS eliminated the dendritic segregation and promoted compositional homogeneity. Moreover, FS effectively fragments the inclusions in the HEA, leaving only small-sized MnCr₂O₄ observable. These effects substantially reduced the defect density in the passive film on the FSed-coating surface, leading to a marked enhancement in corrosion resistance. The corrosion current density (i_corr) of the coating decreased from 0.55 μA/cm² in the as-cast state to 0.11 μA/cm², and the pitting potential increased from −120.3 mV to 125.7 mV.