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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corrosion damage with the presence of microbes at some point in the corrosion process. 2 TM0212-2012 states that three conditions need to be met to validate MIC as the cause of internal corrosion: • Assuming there is no known or suspected contamination from outside sources, the first condition is a demon- stration of increased levels of specific types of viable microorganisms (bacte- ria, Archaea, or fungi) associated with the corrosion, as compared to samples taken outside of the corroded area. • The second condition is the identifi- cation of chemical indicators in the corroded area that support the microbi- ological evidence (e.g., elevated levels of sulfide or sulfur in pit deposits for SRB, or organic acids for APB). • The third condition is the identification of biotic factors as the primary contrib- utor to the corrosion damage. The nature of the corrosion damage to the pipeline system should be consis- tent with the nature of the identified microorganism(s) and their byproducts or physical influence on corrosion cell formation. For example, if viable APB or methanogens are concentrated at the corro- sion damage relative to the environment, and evidence of their metabolic activity (organic acids) is determined to be associ- ated with the corrosion, the nature of the corrosion damage should be consistent with these observations (e.g., accelerated corrosion damage or pitting beneath the biofilms). This is an important step in a diagnosis of MIC because it is often difficult to discern between the relative contribu- tions of various biotic and abiotic factors that affect localized corrosion. To properly diagnose MIC, investiga- tions should comprise a combination of chemical, metallurgical, and microbiological analyses. TM0212-2012 presents informa- tion on sample collection, testing methods, corrosion/microbiology monitoring, and how to relate the results to MIC. Sampling Sampling programs generally collect information on operating conditions, Internal corrosion of a pipeline caused by MIC. A micrograph shows Desulfovibrio vulgaris, a species of SRB that reduce sulfate to hydrogen sulfide (H 2 S). FEATURE ARTICLE 28 DECEMBER 2014 MATERIALS PERFORMANCE NACE INTERNATIONAL: VOL. 53, NO. 12

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