Mechanistic insights into Pseudomonas aeruginosa biofilm-driven passive film degradation of Ti-9Mn alloy in marine environment

The rapid expansion of marine infrastructure will lead to a strong demand for metallic materials with excellent bio-corrosion resistance and mechanical properties. Ti-9Mn alloy, long utilized as a hydrogen storage material, has recently been introduced to be applied in the marine environment. However, corrosion and passivity of Ti-9Mn alloy in a simulated marine environment have not been investigated. In this study, the impact of biofilm formed by the marine bacterium, P. aeruginosa , on the passivity of newly developed Ti-9Mn alloy was comprehensively investigated. Results revealed that P. aeruginosa readily adhered and formed biofilms on the surface of Ti-9Mn alloy, and the numbers of sessile cells after 14 and 21 d of incubation were 8.6 × 10 6 and 4.5 × 10 7 cfu/cm 2 , respectively. P. aeruginosa lowered the charge-transfer resistance and enhanced both the cathodic and anodic current density of Ti-9Mn alloy. The corrosion current density ( i corr ) in the biotic medium was approximately 3 times higher than that in the abiotic medium. P. aeruginosa biofilm increased the defects in the passive film on Ti-9Mn alloy manifested as high content of Ti 2 O 3 and TiO at various sputtering depths (0–240 nm).