Hydrogen Permeation Study with Palladium in a Sulfate-Reducing Bacteria Culture Available to Purchase

This study was undertaken to evaluate cathodic depolarization as the action mechanism triggered by sulfate-reducing bacterias (SRBs) in Microbiologically Induced Corrosion (MIC), using an inert substrate such as a 1-mm thick Palladium (Pd) strip with and without cathodic polarization, a H° permeation cell type by Devanathan and Stachurski, and the bacteria Desulfovibrio desulfuricans ssp. desulfuricans. The permeation tests were run using a de-aerated sterile culture medium inoculated with 10% D. desulfuricans at 10⁸ cell/ml. Bacterial growth was evaluated by the serial dilution technique and Scanning Electron Microscopy (SEM) was used to analyze the characteristics of the biofilm formed on the Pd strip. Results indicated bacterial growth in the order of 40x10⁹ CFU/ml at 24 hours in both polarization and non-polarization tests. This shows that these bacteria develop similarly, whether or not they are on a polarized surface as a source of H°, generating H₂S as a product of sulfate-dissimilating activity. It was also determined that, without cathodic polarization, there were no conditions for reduction and permeation of the H⁺ generated by H₂S dissociation. When cathodic polarization was applied, an increase was observed in the permeation current, which was associated with the maximum enzymatic activity phase of the bacteria.