Abstract: The potentiodynamic scanning polarization, electrochemical impedance spectroscopy and surface analysis methods were employed to investigate the effect of pseudomonas on the corrosion behaviors of stee1 A3 in cladosporium solution. It was showed that the existence of pseudomonas affected the anodic process of steel A3 in cladosporium solution, free corrosion current (icorr) of steel A3 decreased when the two microorganisms coexisted in the culture. With exposure time increasing, from the 7th day, the impedance value of steel A3 in the mixed-colony system was greater than that in the cladosporium system, which indicated that pseudomonas had an inhibitory effect on the corrosion of steel A3. The results of SEMindicated that pitting corrosion occurred in both of the cladosporium and the pseudomonas-cladosporium mixed colony systems, but the pitting holes of steel A3 in the latter solution were smaller and shallower.

Key words: Mixed colonies, Microbiologically influenced corrosion, Aerobe, Pseudomonas, Cladosporium