Retarding the Pseudomonas aeruginosa corrosion of aluminum via chloride-assisted biofilm-thickening

Pseudomonas aeruginosa (P. aeruginosa), a marine electroactive microorganism, causes metal corrosion primarily via phenazine-mediated electron transfer, but its synergy with chloride ions is poorly understood. Chloride ions are well known to be aggressive which accelerate corrosion and trigger localized corrosion of metal. They also influence the metabolic behavior of bacteria. Here, we correlated microbial adhesion and metabolic activity with microscopic aluminum corrosion across varying biofilm coverage areas using focused ion beam-scanning electron microscope (FIB-SEM) and aberration-corrected transmission electron microscopy (TEM). Results show the corrosion rate increased nonlinearly as NaCl increased from 0 to 5 g/L. Chloride ions at a specific concentration (1 g/L NaCl) enhanced biofilm formation and triggered P. aeruginosa dormancy. The biofilm acted as a physical barrier, inhibiting corrosion and protecting the aluminum surface. This reveals the critical role of chloride ions in modulating microbial corrosion via biofilm and bacterial activity, providing novel insights into microbiologically influenced corrosion (MIC) mechanisms.