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Cathodic protection is one of the corrosion control techniques frequently used with satisfactory results to control corrosion in submerged and buried pipelines; however, when the corrosion phenomenon is generated microbiologically (MIC) by Sulfate-Reducing Bacteria (SRB), the efficiency of cathodic protection decreases significantly due to a series of factors among which the following can be mentioned: the fact that microbial corrosion may increase the kinetics of corrosion reactions, the current required to achieve the appropriate polarization of the material and the surface of the exposed area. In addition, bacteria may attack epoxy resin-based pipelines and ultimately, the extracellular polymeric membrane (EPS), which is produced by the bacteria, may increase the ohmic drop and produce the shielding of current lines. This research work focuses on a review of the NACE, ISO and BS cathodic protection standards, some experiences reported worldwide concerning the issue of cathodic protection when SRB are present, and the results of a research carried out by means of the installation of an impressed current cathodic protection pilot system (CPPS) in the field in order to estimate the polarized potential criteria that needs to be kept to achieve cathodic protection of submersed pipelines when SRB are present. The methodology consisted in installing first, corrosion coupons to 25 meters deep at a gas compression plant, and then the pilot system to evaluate pipelines both uncoated and coated with FBE (Fusion-bonded epoxy) and high density polyethylene so as to determine the efficiency of cathodic protection when SRB are present at different potentials being applied. With this study it was found out that within a three month period, MIC with 4x104 cel/cm2 took place, and that when keeping negative potentials of -1.150 mV vs Cu/CuSO4, no MIC damages due to SRB were observed.
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