Materials Performance

DEC 2014

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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M FEATURE ARTICLE Diagnosing Microbiologically Infuenced Corrosion in a Pipeline NACE Standard TM0212-2012 Focuses on Detecting, Testing, and Evaluating MIC on Internal Pipeline Surfaces Microorganisms—they have been around for billions of years and can live in incred- ibly difficult environments and under extremely severe conditions. They utilize exceptionally diverse food sources and some of the byproducts produced by their metabolisms can be damaging to metals. When the presence of microorganisms plays a role in the corrosion of a material, it is known as microbiologically influenced corrosion (MIC). Activities of bacteria, Archaea, and fungi in colonies that create biofilms on surfaces of materials, or in local environments that directly contact materials, can result in MIC; and most metals, as well as some nonmetals, can be affected by this type of corrosion. According to NACE standard TM0212- 2012, 1 which focuses on detecting, testing, and evaluating MIC on internal pipeline surfaces, MIC typically takes place in the presence of a conglomer- ate of microbes comprised of multiple types of microorganisms. Depending on the environment, these microbes may include metal-oxidizing bacteria, sulfate- reducing bacteria (SRB), acid-producing bacteria (APB), metal-reducing bacteria (MRB), and methanogens. The presence of micro organisms may create conditions that foster corrosion initiation, or their metabolic reactions may maintain condi- tions that promote continued corrosion. MIC does not produce visually unique corrosion morphology. Instead, MIC often results in pitting, crevice, and underde- posit corrosion, as well as dealloying. One of the most profound challenges that corrosion professionals face when trying to identify MIC is making a connec- tion between the microorganisms present in a system and the corrosion experienced by that system, says NACE International member Richard B. Eckert, senior princi- pal engineer—corrosion management, Materials Advisory Services, with DNV GL—North America Oil & Gas. In the oil and gas industry, microorganisms can be found in nearly every oil and gas produc- tion environment, especially pipelines. They inhabit the bulk fluids that flow through oil and gas pipelines, and also form biofilms on the internal surfaces of pipelines. Eckert, who serves as chair Kathy Riggs Larsen, Associate Editor of NACE Task Group (TG) 254, which published TM0212-2012, comments that the presence of microorganisms doesn't necessarily mean they are the cause of localized corrosion. In any environment, he says, there are usually multiple factors that contribute to corrosion, and different corrosion mechanisms, including MIC, can result in the same corrosion morphol- ogy. This is why it's crucial to verify there is a clear relationship between the biofilm and corrosion, he explains. For example, corrosion could be caused by an abiotic reaction fueled by the presence of water and oxygen that doesn't involve micro- organisms at all, even though they are present. There are several objectives for determining the characteristics of a micro- biological presence where corrosion is found. These include establishing a connec- tion between microbiological activities and corrosion reactions and corrosion products in a particular environment; identifying specific microbes that support the corrosion mechanism seen in that environment; and associating the corrosion reactions/ 26 DECEMBER 2014 MATERIALS PERFORMANCE NACE INTERNATIONAL: VOL. 53, NO. 12

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