51314-4066-On-Site Evaluation of Microbiologically Induced Corrosion and the Effects of Continuous Low Dosage Corrosion Inhibitor Application

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Product Number: 51314-4066-SG

ISBN: 4066 2014 CP

Author: Renato De Paula

Publication Date: 2014

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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). Frequently bacterial activity on pipelines and vessels is determined by extrapolation of microbial 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 production system in North America. For this a sessile monitoring device was installed at the suction header. Coupons and fluid samples were removed at 30 60 and 90 days after initiation of flow and tested for the following: 1- Microbiological Analysis through qPCR Prokaryotic Speciation ATP quantification and serial dilutions; 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. andThermovirga 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. Taken together our results demonstrate that a diligent sessile monitoring program is extremely important to understand and mitigate microbial pitting corrosion.