Photothermal eradication of biofilms and microbiologically influenced corrosion on stainless steel using FeCoNiTiCu high-entropy alloy nanoparticles

Microbiologically influenced corrosion (MIC) is a persistent threat to stainless steel assets in marine environments, where biofilms accelerate localized corrosion damage. This work reports FeCoNiTiCu x high–entropy alloy nanoparticles (HEA-NPs) as a photothermal antibacterial synergistic platform that simultaneously clears biofilms and mitigates MIC. At practical loadings (400 μg mL −1 to 600 μg mL −1 ), the nanoparticles suppress planktonic cells and remove ≥99% of mature biofilms under simulated illumination (1 kW m −2 , 30 min) in marine 2216E medium. Electrochemical tests in a Pseudomonas aeruginosa –2216E system showed that i corr decreased from ∼180 nA cm −2 (bacterial control) to 5 nA cm −2 with Cu 1.0 HEA-NPs, and further to 3 nA cm −2 under illumination, corresponding to inhibition efficiencies of ∼98% and ∼99%. Confocal microscopy confirmed that Cu 1.0 reduced maximum pit depth from 4.7 μm (bacterial) to 1.6 μm, substantially approaching the sterile-control level of corrosion resistance. XPS depth profiling revealed that the passive film remained intact, as the antibacterial capability of the HEA-NPs prevented biofilm-induced damage. These results confirm that the mitigation of MIC is achieved through the antibacterial and biofilm-removal capabilities of the HEA-NPs, which prevent the biofilm from attacking the passive film, thereby preserving the metal's inherent corrosion resistance.