Microbiologically Influenced Corrosion (MIC) may be a factor in 15?30A of failures due to corrosion in all industries. Chemical treatments for mitigating and controlling MIC processes represent significant cost and environmental liability. Because regulatory pressure on the use of toxic biocides is increasing, more environmentally acceptable control measures must be developed, To that end, laboratory experimental test-loops (TLs) were used to test more environmentally acceptable treatment chemicals. Produced waters from natural gas production and storage fields were recirculated through TLs under anaerobic conditions. Carbon steel coupons exposed to TL fluids were quickly colonized by microorganisms. Coupons continuously exposed to a quaternary amine (QA) in TL fluids had very low surface colonization and lower corrosion rates than did control coupons. The biocidal effect of QA in TL fluids appeared to be minimal. Coupons dipped in QA solutions and then exposed to control TL fluids also showed lower colonization and corrosion rates than did control coupons. These results suggest that QA may prevent MIC by mechanisms other than killing bacteria and that treatments preventing surface colonization may persist longer than most biocides.
Microbiologically Influenced Corrosion (MIC) is a significant problem in water systems associated with cooling and fire protection in buildings, as well as in the gas, oil, refining, electric power, nuclear, chemical, and water transportation industries. For example, in the natural gas industry, it has been estimated that up to 30% of the pipeline failures due to corrosion involve MIC. The current approaches for mitigating MIC in gas and oil production involve the use of biocides. Using biocide to treat MIC in these systems can be quite expensive because its effectiveness is highly variable from one environment to another; therefore, treatment dosages tend to be conservative. The use of biocides has improved because better test and treatment methods have been developed, the use of biocide has been minimized through targeted treatment, and incompatibilities of biocides with other chemicals have been identified. Even with these improvements, chemical costs are still high, and certain operating conditions (such as well production shut-ins) can frequently cause MIC problems to go uncontrolled for extended periods. As many of these chemical treatments come under increasing regulatory scrutiny and represent potential liabilities to various industries, environmentally acceptable treatments are needed.
Quaternary amines (QAs) and other organic film-forming inhibitors have been used for many years as corrosion inhibitors for such applications as acid pickling solutions, cutting oils, oil- and gas-producing pipelines, boilers, and heat exchangers. Much has been written and studied regarding the mechanism of action for these film-forming inhibitors in their prevention of both general and localized corrosion. Previous work has shown that QA used alone at reasonable and affordable treatment concentrations are generally not as effective as biocides in controlling microorganisms attached to metal surfaces and in bulk fluids, but QA increased the effectiveness of other biocides (such as glutaraldehyde) when added to them in small concentrations, Recent field tests at a natural gas storage field known to have MIC indicated that QAs were successful in protecting test coupons from microbial colonization and corrosion, yet the bulk fluids remained high in viable bacteria. 16 This result prompted further laboratory investigations to evaluate the mechanism of action for QA to prevent MIC processes in gas storage and production facilities. Our work indicate
