MICROBIOLOGICALLY INFLUENCED CORROSION

Microbiologically influenced corrosion, also called MIC, is an extremely fast form of local corrosion caused by micro-organisms. MIC is a known phenomenon in various industries where metal has been (at least temporarily) in contact with non-sterile water.

MIC regularly occurs in the maritime and offshore environment as a result of the combination of seawater and the active role of micro-organisms in the sea.

MIC diagnosis
Determining biocorrosion is about collecting the correct data. MIC results from a complex number of interactions between microorganisms, the environment and the material. A diagnosis must be carefully documented on a “case-by-case” basis using:

  • MIC-related material “failure” analysis
  • Chemical analysis
  • Microbiological analysis

The chance of an incorrect interpretation is greater if one of the above analysis is not included. At ENDURES we combine all available tools to conduct such an extensive (comprehensive) investigation.

Visual and microscopic “failure” examination
A physical relationship between the damaged material and microorganisms is the key to correct MIC determination. In some cases, damage to the surface of the material may indicate MIC. So this can be an important indicator during the research process.

The ENDURES laboratory has several microscopes including stereo, fluorescent and “scanning electron” microscopes.

Micro-bacterial growth-based detection methods
In many circumstances, “growth-based methods” are a good indicator of potential corrosive microbial activity. Our laboratory is fully equipped with everything necessary to reproduce the growth of MIC-related organisms. Examples of this are:

SFB – slime-forming bacteria
APB – acid-producing bacteria
IO / IRB – iron oxidizing and reducing bacteria
SOB – sulfur – oxidizing bacteria
SRB – sulfate – reducing bacteria
MnO – manganese – oxidizing bacteria
…and various other MIC related microbial groups such as nitrate reducing bacteria.

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Molecular Research Methods for Microbially Affected Corrosion 

In addition to traditional techniques based on culture methods, ENDURES also has advanced molecular techniques for analysis and diagnosis of MIC. Molecular techniques have the great advantage that they can also be used for microorganisms that cannot be cultured.

For analyzes at the DNA level, we use quantitative polymerase chain reaction technology (qPCR). This enables us to determine and quantify the corrosive activity for various corrosion-relevant micro-organisms. Through cooperation with our partners, we also have access to the latest technology of Next Generation Sequencing (NGS), which in addition to a broader and more specific insight into the MIC population and its activity.

The main advantages of molecular techniques are:

Speed: Hours instead of days with breeding methods;
A-selective: All organisms are included in the analysis. There is no selection pressure on organisms that cannot be cultivated or are outcompeted by other organisms;
Very useful for organisms that can or want to grow (only) under extreme conditions (high / low temperature; high pressure) and are often not cultivable.

Fight against MIC
As soon as it has been established with reasonable certainty that the corrosion problem is related to micro-organisms, ENDURES can advise on the best options for control:

  • Advice on the use and testing of antimicrobials
  • Use of inhibitors
  • Advice on the design and protective measures for the entire installation.
  • If desired, the sensitivity of relevant organisms isolated from the problem situation to specific antimicrobial agents can be investigated.

Our recommendations naturally take into account the feasibility in the specific situations of our customers.

With a chosen control method for the MIC problem, ENDURES can help you monitor the effectiveness of the treatment, for example with advice on measuring relevant parameters in the installation and by applying corrosion coupons with which the course of the process can be followed and analyzed.

MIC under extreme conditions
As a result of climate change and increasingly scarce raw materials, the (maritime) industry has started to develop more activities in the arctic regions and in the deep sea in recent years. Technology and materials for this must be able to withstand the (extreme) exposure conditions in environments with (very) low temperatures, high pressures and sometimes aggressive chemicals. Microorganisms occur under all kinds of extreme conditions and have a very high adaptability; there is therefore a chance that, for example, MIC may also be an important factor, or precisely under such circumstances. ENDURES can conduct targeted research into the susceptibility of materials to corrosion under such circumstances and on that basis give advice on correct material specifications and resistance of materials.

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