Understanding Microbially Influenced Corrosion (MIC)
Microbially influenced corrosion (MIC) is a type of corrosion caused by certain microorganisms that can accelerate metal degradation. MIC is a significant concern in industries such as oil and gas, water treatment, and power generation, where corrosion can lead to equipment failure, costly maintenance, and safety hazards. Unlike general corrosion, MIC is driven by microbial activity, which often goes undetected until severe damage occurs.
The Two Mechanisms of MIC
There are two primary mechanisms by which MIC occur:
- Chemical MIC (CMIC): This is an indirect process where microbes produce corrosive byproducts like hydrogen sulfide (H₂S), which react with metal surfaces, leading to accelerated corrosion.
- Electrical MIC (EMIC): Certain microbes cause direct electron transfer, extracting electrons directly from metal surfaces, resulting in localized pitting and rapid degradation.
What are MIC Biomarkers?
MIC biomarkers are genetic indicators of microbial species linked to direct corrosion. These biomarkers allow for early detection of corrosive microorganisms before visible damage occurs. By identifying specific microbial genes associated with MIC, industries can take preventative action to reduce corrosion risks, improve maintenance strategies, and extend the lifespan of assets.
Recent high-impact research published by ExxonMobil Upstream Research Company identified two EMIC related biomarkers, micC and micH, which can be targeted by qPCR to aid in MIC monitoring and MIC threat assessments.
- micC codes for a membrane-bound c-type cytochrome involved in extracellular electron transfer in certain species of sulfate-reducing bacteria. This enables direct interaction with metal surfaces, making it a strong indicator of MIC thread.
- micH codes for an [NiFe] hydrogenase enzyme by methanogenic species. This enzyme can accelerate corrosion by catalyzing the reduction of H+, leading to oxidation of iron on metal surfaces, significantly increasing MIC risk.
Due to the aggressive corrosion rates associated with direct MIC mechanisms, the detection of either micC or micH provides critical insight into the MIC thread level at a given site.
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