Performance of corrosion inhibitors used in underground petroleum product pipeline under microbial influenced corrosion risk

To combat internal corrosion of cross country petroleum product pipeline, injection of corrosion inhibitor is one of the acceptable methods.  NACE TM 0172 test method can be used to assess the efficacy of such inhibitors. This method simulates pipeline corrosivity situations in a petroleum product environment with addition of water using a rotational stirrer. This method predicts corrosivity in short duration, however, it does not address the effects of presence of MIC causing microbes on the pipeline internals.
The present study was designed to examine the Performance of corrosion inhibitors used in cross country petroleum product pipeline under MIC condition. In the study, the metallic coupons have been exposed to simulated corrosive environment of pipeline under dynamic condition in corrosion wheel test and corrosion rates have been measured by gravimetric method with presence of MIC causing microbial consortium.
It is observed that the corrosion inhibitors used in the study rendered acceptable performance at 4ppm, 6ppm & 8ppm dosage as per NACE TM 0172 and in corrosion wheel test. But in the presence of MIC causing microbes the corrosion protection efficacy of the corrosion inhibitor was significantly reduced.  The finding of the study adds a new dimension for selection of suitable pipeline corrosion inhibitor.