Microbiology Beyond the Laboratory: How Microorganisms Influence Corrosion
16 Sep 2026
Four Key Lessons from EUROMIC’s MIC & Marine Corrosion Industry Training
Microbiology Awareness Day is a reminder that microbiology extends far beyond healthcare. From protecting public health to preserving critical infrastructure, microorganisms influence far more than we often realise.
Following the MIC & Marine Corrosion Industry Training Course delivered by EUROMIC, we wanted to share four practical takeaways. These highlight the vital role microbiology plays in understanding corrosion, supporting investigations, and developing effective mitigation and management strategies.
Key Takeaway 1: MIC is More Complex Than Just the Presence of bacteria
Microbiologically Influenced Corrosion (MIC) is the corrosion of metal or other material due to the presence and/or activity of microorganisms. However, simply detecting microorganisms is not enough evidence that MIC is occurring.
Microorganisms are found almost everywhere, including in industrial water systems, pipelines, tanks, marine environments, and offshore infrastructure. The important question is therefore not, “Are microorganisms present?” but rather, “Has their presence or activities influenced the corrosion process?”
For MIC to occur, three factors must be present:
- Microorganisms such as SRB, IOB and others living within a biofilm
- A growth medium, such as seawater, produced water or other environments that support microbial activity by providing free metabolites such as sulphate or readily available carbon sources.
- Metal or other material providing microorganisms a place to attach to and for corrosion to occur.
MIC is not a single corrosion mechanism. Microbial communities can influence several electrochemical processes through biofilm formation, the production of corrosive metabolites, changes to the local chemical environment, under-deposit conditions, or the direct and indirect transfer of electrons.
Key Takeaway 2: Corrosion Threats Must Be Managed Through Coordinated Control Activities
MIC is a corrosion threat that can increase the likelihood of asset damage or failure. The resulting risk depends on both the probability of an event occurring and its potential consequences.
Managing that risk requires more than applying a biocide or corrosion inhibitor. It requires a structured programme of corrosion control activities, supported by an effective corrosion management system. This consists of threat assessment, prevention and mitigation, and monitoring and evaluation.
A corrosion threat assessment should consider all corrosion mechanisms that may reasonably be present, including both biotic and abiotic mechanisms. It should bring together chemical and microbiological data, operational information, process conditions, inspection findings, maintenance records, and results from corrosion monitoring devices such as coupons and probes.
Prevention and mitigation aim to reduce the likelihood and severity of corrosion. They should be considered from the design and installation stages of systems and not acted upon in a reactive matter when it may already be too late. These steps can include material selection, coatings and linings, system design, mechanical cleaning, and chemical treatment.
To ensure that the prevention and mitigation activities are working, monitoring and evaluation is crucial. This allows trends to be created and any changes to be closely monitored with timely actions put in place if needed.
Key Takeaway 3: Multiple Lines of Evidence Build a Stronger MIC Diagnosis
Effective MIC monitoring and diagnosis consists of multiple lines of evidence (MLOE). No single test can definitively diagnose MIC as it is more complex than microbiological data alone.
MLOE brings together evidence from four main areas:
- Microbiology - Investigate the abundance, activity, diversity, and potential functions of microorganisms.
- Chemical – Helps establish whether environmental conditions support microbial activity or alternative corrosion mechanisms.
- Materials and Corrosion products - Provide important evidence about possible mechanisms. However, corrosion products should always be interpreted carefully as compounds may have biological or abiotic origins and must be interpreted alongside other findings.
- Physical and operating conditions - Explain how factors such as design, flow, temperature, pressure, water wetting, deposits, cleaning and operating history may have contributed to corrosion at a particular location.
These lines of evidence become most useful when their relationships are considered. Chemical data contrasted with microbiological data, chemical conditions with corrosion evidence. Spatial comparisons between corroded and uncorroded areas can be particularly valuable as corrosion morphology alone is also not sufficient to diagnose MIC. A pit, deposit, or apparent tunnelling pattern may be consistent with MIC, but it is not proof of microbial involvement. Similar features can be produced by abiotic corrosion mechanisms.
Key Takeaway 4: Planning Is Key When It Comes to Sampling
Even the most advanced laboratory methods cannot compensate for a poorly selected, contaminated, unrepresentative, or incorrectly preserved sample.
Accurate diagnosis depends on appropriate sample collection, handling, preservation, and transport. Effective sampling begins long before arriving at the sampling point. The available information should be reviewed, including site plans, previous test results, operating history, and relevant environmental conditions. This then helps define the questions the sampling program needs to answer and determine which lines of evidence can be obtained.
Consider which environmental parameters can be measured on site, such as pH, salinity, dissolved oxygen, and redox potential, using handheld sensors or suitable field test kits. Understanding the system being sampled is also important. By consulting the relevant standards, identifying appropriate sampling and control locations, and agreeing the required sample types, preservation methods, and analyses with the receiving laboratory, a suitable plan can be in place before arrival at the site.
The sample type matters. Liquid samples are often convenient, but they primarily represent planktonic microorganisms suspended in the bulk fluid. MIC is commonly associated with sessile microorganisms living in biofilms, deposits, corrosion products, or other surface-associated material. Therefore, where practicable, a range of samples both planktonic and sessile should be taken to better understand the microbial communities in play.
Good sampling also requires sterile equipment, appropriate personal protective equipment (PPE) and careful labelling. Photographs, detailed field notes, and clear documentation of orientation and flow direction of sampled pipes all help build into the ideal sampling regime. Importantly samples should, where applicable, not be “One and done”. For example, a swab from a pipeline failure should be taken from the site of the failure, adjacent to the failure and from a non-corroded section. As all this data will feed into a better and more accurate diagnosis of the issue.
For more information on sampling, read our blog, “Monitoring Microorganisms in the Oilfield”.
Interested in learning more?
Training events like this demonstrate the importance of collaboration between academia and industry to improve MIC management and asset integrity. If you weren't able to attend the course, Intertek's Commercial Microbiology team also delivers a two-day Oilfield Microbiology course, covering the fundamentals of oilfield microbiology, MIC, monitoring techniques, data interpretation and mitigation strategies for industrial applications.
