the double and progress of faradaic processes at the biofilm/substrate interface as represented by Ydl and Rct parameters, respectively. The 'Rs' represents the solution resistance and depends on the ionic conductivity of the S1, S2, and S3 media. The systems inoculated with bacterial strains showed a large Rbf and Rct values compared to the values obtained in the controlled medium (S1) (Table ). The relatively small Rbf and Rct values of SS304 in the S1 medium compared to S2 and S3 media corresponded to the aggressiveness MSM medium. However, in the presence of bacterial strains, the larger values of Rct were attributed to the formation of biofilm that hindered the approach of electrolyte to the biofilm/substrate interface. In other words, this behavior is related to the barrier characteristics of the biofilm and restricted the transport of ionic species to the interface as evident from the relatively large values of Rbf. Approximately 1.5 times larger Rbf and ~2 times lower Ybf of Bacillus subtilis strain compared to the Pseudomonas aeruginosa strain was associated with the intrinsic behavior of the biofilm. The Tafel polarization curves of the SS304 samples were also obtained in S1, S2 and S3 media as shown in Figure . These polarization curves were extrapolated to obtain Tafel slopes (βa, βc), corrosion current (icorr) and corrosion potential (Ecorr) as given in Table . The icorr values of SS304 samples are related to the corrosion rate as calculated by using Faradays' law. The microscopic features of the SS304 sample surface exposed to S2 and S3 media at 37 C after 14 days of incubation as shown in Figure . The biofilms were fixed on the surface by immersing in 3% glutaraldehyde. The SEM images showed the presence of rod-shaped bacteria encapsulated in EPS matrix and a formed thick and adherent biofilm of PA-ZK strains (Figure ). In the case of BS-S1X strain, threads like a 3D network of biofilm were formed on the surface of the SS304 sample as shown in Figure . The biofilms were removed by immersing the exposed samples in 1 M HNO3 solution. Compared to the as-prepared SS304 sample (ground surface up to 1200 grit size), appreciable surface dissolution was observed after exposure to S1 as shown in Figures and. Also, after cleaning, the samples exposed to S2 presented a relatively smooth surface compared to the sample exposed to the S3 systems, which experience pitting as shown in Figures and.