Résumé : The effect of marine B. vietnamensis, isolated from East Sea, China, on the corrosion behavior of SAF 2507 duplex stainless steel (DSS) was studied. A flat plate bioreactor was used to simulate the marine environment. And the environmental parameters such as temperature, pH, flow rate and oxygen content were controlled in bioreactor which operated aerobically for 30 days with either inoculated or sterile artificial seawater. Electrochemical studies demonstrated a noticeable decrease in open circuit potential and an increase in current density in solutions containing B. vietnamensis compared to the sterile artificial seawater which confirmed the enhancement of corrosion rate of 2507 DSS in the presence of bacterium. FESEM images showed the presence of porous and heterogeneous biofilm and oxide layer on the 2507 DSS surface in the presence of bacterium. The heterogeneity of biofilm and different thicknesses of biofilm made the oxygen concentration cells on the 2507 DSS surface and induced localized corrosion at longer exposure times. The biofilm composition also identified by FTIR.