Cathodic Protection Under a Simulated Coating Disbondment: Effect of Sulfate-Reducing Bacteria

In this study, the effect of cathodic protection and sulfate-reducing bacteria (SRB) on corrosion and potential distribution of pipeline steel under simulated coating disbondment was investigated. In this regard, a setup simulating a coating disbondment with a gap size of 3 mm was designed and made. Different levels of cathodic polarization were applied to the open mouth (OM) of the simulated coating disbondment. The OM was the only location open to the surrounding environment, where soil solution and cathodic current could penetrate under the coating disbondment. Results showed that potential and corrosion of the pipeline steel were not distributed uniformly under the simulated disbonded coating. Cathodic potential and pH decreased under the simulated coating disbondment by moving from the OM toward the end of disbondment. Differences in cathodic polarization levels in biotic (presence of SRB) and abiotic (absence of SRB) environments under the simulated coating disbondments were insignificant. Despite the insignificant differences in the level of cathodic polarization, corrosion of the pipeline steel under the simulated coating disbondment was more severe in the presence of SRB.