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Different Types of Corrosion
- Recognition, Mechanisms & Prevention

Microbiologically Influenced Corrosion (MIC)

Recognition of Microbiologically Influenced Corrosion (MIC)


microbiologically influenced corrosion,microbial corrosion,biological corrosionWhat is Microbiologically Influenced Corrosion (MIC)? Microbiologically Influenced Corrosion refers to corrosion affected by the presence or activity, or both, of microorganisms. In the corrosion literature, other non-standard terms used by some authors include microbial corrosion, bacterial corrosion, and biological corrosion.

 

There are about a dozen of bacteria known to cause microbiologically influenced corrosion of carbon steels, stainless steels, aluminum alloys and copper alloys in waters and soils with pH 4~9 and temperature 10oC~50oC.

 

These bacteria can be broadly classified as aerobic (requires oxygen to become active) or anaerobic (oxygen is toxic to the bacteria). Sulphate reducing bacteria (SRB) is anaerobic and is responsible for most instances of accelerated corrosion damages to ships and offshore steel structures. Iron and manganese oxidizing bacteria are aerobic and are frequently associated with accelerated pitting attacks on stainless steels at welds.

 

Many industries are affected by Microbiologically influenced corrosion (MIC):

  • Chemical processing industries: stainless steel tanks, pipelines and flanged joints, particularly in welded areas after hydrotesting with natural river or well waters.

  • Nuclear power generation: carbon and stainless steel piping and tanks; copper-nickel, stainless, brass and aluminum bronze cooling water pipes and tubes, especially during construction, hydrotest, and outage periods.

  • Onshore and offshore oil and gas industries: mothballed and waterflood systems; oil and gas handling systems, particularly in those environments soured by sulfate reducing bacteria (SRB)-produced sulfides

  • Underground pipeline industry: water-saturated clay-type soils of near-neutral pH with decaying organic matter and a source of SRB.

  • Water treatment industry: heat exchangers and piping

  • Sewage handling and treatment industry: concrete and reinforced concrete structures

  • Highway maintenance industry: culvert piping

  • Aviation industry: aluminum integral wing tanks and fuel storage tanks

  • Metal working industry: increased wear from breakdown of machining oils and emulsions

  • Marine and shipping industry: accelerated damage to ships and barges

Positive identification of microbiologically influenced corrosion requires chemical, biological and metallurgical analysis of the waters, soils and the metal samples.

 

Mechanisms of Microbiologically Influenced Corrosion (MIC)


What causes Microbiologically Influenced Corrosion (MIC)? Microbiologically influenced corrosion is caused by specific genera of bacteria which feed on nutrients and other elements found in waters and soils. Sea water is a primary source of sulphate reducing bacteria (SRB). The biological activities modify the local chemistry (acid-producing) and render it more corrosive to the metals. For example, iron-oxidizing bacteria can perforate a 5mm thick 316 stainless steel tank in just over a month!

 

Prevention of Microbiologically Influenced Corrosion (MIC)


How to prevent Microbiologically Influenced Corrosion (MIC)? Microbiologically influenced corrosion, or microbial corrosion or biological corrosion can be prevented through a number of methods:

  • Regular mechanical cleaning if possible

  • Chemical treatment with biocides to control the population of bacteria

  • Complete drainage and dry-storage

Modeling and Prediction of Microbiologically Influenced Corrosion

PipelineCompass®: Pipeline Corrosion Modeling, Prediction, Assessment & Solutions

PipelineCompass is not just for prediction of external corrosion and internal corrosion of underground pipelines, it also allows you to optimize cathodic protection design and operation, and to assess the level of CP protection from CP survey data. Corrosion predictions from PipelineCompass include: the corrosivity of soil, the maximum corrosion depth, the corrosion rate, effectiveness of cathodic protection, the remaining life of the pipeline, the major mode of failure, the probability of high pH SCC, the probability of near-neutral pH SCC, susceptibility to cathodic delamination of coatings due to overprotection by CP, possibility of Microbiologically Influenced Corrosion (MIC) at localized sites, stray current corrosion and AC corrosion. In the screen shot below, PipelineCompass predicts that MIC will occur at a rate of over 1 mm/y to the pipeline.

 

For more details on Microbiologically Influenced Corrosion (MIC)


Where can I learn more about Microbiologically Influenced Corrosion (MIC)? More details on microbiologically influenced corrosion or biological corrosion are included in the following corrosion short courses which you can take as in-house training courses, course-on-demand, online courses or distance learning courses:

Microbiologically Influenced Corrosion (MIC): -Recognition, Mitigation and Prevention (5 days)

Corrosion and Its Prevention (5-day module)
Corrosion, Metallurgy, Failure Analysis and Prevention (5 days)

Marine Corrosion, Causes and Prevention (2 days)

Accelerated low water corrosion (ALWC) - Mechanisms, Mitigation and Prevention (1 day)
Materials Selection and Corrosion (5 days)
Stainless Steels and Alloys: Why They Resist Corrosion and How They Fail (2 days)

Corrosion in Fire Protection Systems (FPS): - Detection, Mitigation and Prevention (1 day)

If you require corrosion expert witness or corrosion consulting service on microbiologically influenced corrosion, our NACE certified Corrosion Specialist is able to help. Contact us for a quote.


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