The interaction mechanism of titanium alloy TC4 between passive film and sulfate reducing bacteria biofilm in marine environment

In marine environment, the surface of titanium alloys typically forms a composite film consisting of passive film and biofilm, which affects the service performance. However, the interaction mechanism between passive film and biofilm is not well understood. In this study, the interaction between passive film and Sulfate Reducing Bacteria (SRB) biofilm on the surface of titanium alloy TC4 in marine environment is investigated by immersion in an artificial seawater-based culture medium with SRB. The SRB biofilm on the surface of titanium alloy TC4 is in a dynamic evolution, and gradually increases from 1.16 % at 1 day to 47.76 % at 7 days and decreases to 22.62 % at 14 days, which alters the contact process between the corrosive medium and titanium alloy TC4. On the other hand, the metabolic activities of SRB biofilm, through the depolarization of the cathode, promote the occurrence of the anodic reactions, which change the composition and structure of the passive film and promote the change of the relative content of TiO₂, thereby affecting the corrosion rate of titanium alloy TC4. These results provide a valuable reference for the biofouling and corrosion prevention strategy of titanium alloy TC4 in marine service.