Abstract
The ability to properly monitor microbial growth and corrosion rates on-site is a critical step towards the development of a successful mitigation strategy to control microbiologically influenced corrosion (MIC). Commonly, bacterial activity on pipelines and vessels is determined by extrapolation of microbial loads detection in the planktonic phase. This often leads to misleading decisions around chemical treatments. To establish a correlation between microbial activity on metal surfaces and the corrosion process, an on-site evaluation was implemented in a produced water system in North America. For this, a sessile monitoring device was installed at the suction header. Coupons were removed at 30, 60, and 90 days after initiation of flow and tested for the following: 1- Microbiological Analysis through qPCR and Prokaryotic Speciation; 2 – Corrosion Analysis using white light interferometry for scanning electron microscopy (SEM) for determination of pit number, depth, and morphology. Our results indicated the presence of a number of organisms (Thermacetogenium phaeum, Desulfomicrobium baculatum, Desulfovibrio sp., and Thermovirga lienii) known to be involved in the MIC process. The presence of these microorganisms on the surface of the coupons showed a clear correlation with the corrosion rates and pit morphology. Interestingly, the corrosion process was dramatically increased only when the sessile bacterial activity reached a specific threshold. Additionally, a low dosage continuous treatment with a corrosion inhibitor, aiming to control solid deposition, showed little impact on biofilm formation and the associated MIC process and confirmed that corrosion inhibitors are not adequate to prevent MIC. Taken together, our results demonstrate that a diligent sessile bacteria monitoring program is extremely important to understand and prevent microbial pitting corrosion.
