Accelerated corrosion of 2304 duplex stainless steel by marine Pseudomonas aeruginosa biofilm

Microbiologically influenced corrosion (MIC) in the marine environment is a serious threat to the service life of marine materials. MIC pitting corrosion rate is usually much faster than the general corrosion process. The 2304 duplex stainless steel (DSS) is an excellent alternative to 316L SS in marine applications, while its MIC behavior is barely known. In this work, surface analysis and electrochemical techniques were used to study the corrosion behavior of 2304 DSS caused by the ubiquitous marine aerobe Pseudomonas aeruginosa. Compared with the abiotic control, the largest pit depth showed that the P. aeruginosa biofilm greatly accelerated the pitting corrosion (11.0 μm vs. 4.8 μm for the abiotic control). The presence of P. aeruginosa biofilm oxidized the passive film of 2304 DSS from Cr2O3 to CrO3, which was a water-soluble compound, resulting in the decrease of the relative Cr content and destruction of the passive film. The linear polarization resistance (LPR), electrochemical frequency modulation (EFM), electrochemical impedance spectroscopy (EIS) and polarization curve analyses all demonstrated that 2304 DSS was susceptible to MIC.