Microbially influenced corrosion: What is it, how does it impact business, and what do I need to know?

Published: 3-Apr-2024

Ali Aitchison from Eurofins discusses how microbially influenced corrosion can be a problem in the food sector

Corrosion is a word we’re all familiar with, but what does the process actually entail? It occurs when a material, such as a refined metal or alloy, degrades to a more chemically stable form.

One of the most well-known examples is rusting – the process whereby iron undergoes electrochemical oxidation and forms iron oxides. When microorganisms (bacteria, fungi, algae, etc) cause or promote the corrosion of a material, this is called Microbially Influenced Corrosion (MIC) or biocorrosion. 

Corrosion – and MIC in particular – is not limited to metallic materials, however. Other components, including ceramics and polymers, can be impacted by these chemical or electrochemical reactions.

Notably, MIC is prevalent in chemical engineering and biotech industries. But it’s not uncommon in other sectors too, including food and beverage manufacturing. 

This is article will cover everything you need to know about MIC, and why it can be problematic in the food sector. Plus, what are the ways in which businesses - irrespective of industry - can arm themselves against the threat of MIC: Microbially Influenced Corrosion is a process whereby microorganisms cause the corrosion of a product.

Corrosion – and MIC in particular – is not limited to metallic materials

Due to their metabolism, the microorganisms produce corrosive chemicals, such as hydrogen sulphide, ammonia, or acids. Where biofilms develop, persistent exposure to these chemicals (typically concentrated in one area) can result in pitting or crevice corrosion.

Once the corrosion starts, the pitted surface provides a greater harbourage and surface area for the microorganisms to adhere, allowing more biofilms to form, and so the degradation of the material intensifies. 

There’s a wide variety of ways in which MIC can – and does – impact business. It can compromise the safety of the working environment, reduce the lifespan of equipment, and add to maintenance costs. 

A process that many will be aware of is Sulphide Stress Cracking, where steel (and other metal alloys) reacts with hydrogen sulphide.

This is produced by sulphate-reducing bacteria under anaerobic conditions. The result? The metal becomes brittle, meaning the product or equipment is prone to fail: a costly consequence for companies. 

Microorganisms produce corrosive chemicals, such as hydrogen sulphide, ammonia, or acids

Within food and beverage manufacturing, biofilm formation can significantly impact the safety and hygiene of items, equipment and processes.

A corroded surface, for example, can prove more challenging to effectively clean, compared to one that is fully intact. There’s also an increased chance of physical contamination of food and beverage products from corroded equipment, posing additional risks to consumers.

So, how do we avoid it? First and foremost, having an awareness of MIC is vital so that regular monitoring of susceptible surfaces can be factored in and undertaken.

But there’s also a number of anti-corrosion, preventative measures that can be implemented, including: using antimicrobials to inhibit the growth of the microorganisms, applying protective surface layers to items, and (where present) immediately disrupting, and disposing of biofilms with physical and/or chemical action. 

A question regularly asked about this process is: if MIC has already taken place, is it too late? And while the answer very much depends on the specifics of each scenario, unfortunately once significant corrosion has occurred, the material is almost always no longer fit for purpose.

A process that many will be aware of is Sulphide Stress Cracking

If that’s the case, the only appropriate action is to replace (partially or entirely, depending on the damage), and to take steps to manage safety risks in the interim while replacements are arranged. 

At this point, it’s also incredibly useful to call in the experts. Not only can they help to mitigate the risks due to the corrosion caused, but they can review your processes, and provide solutions to reduce the risk of MIC reoccurring.

Plus, they can help you to decipher the rules and regulations within your respective industry that must be followed and abided by with regards to MIC. 

For example, where businesses have water systems on their premises (such as evaporative cooling towers, swimming pools and showers, or even simply taps and toilets), it’s important that they understand the consequences of MIC with regards to the effective control of Legionella, and the relevant Health and Safety legislation in the UK.

Materials which make up the structure of water systems can develop biofilms and become corroded providing harbourage for Legionella, increasing the risk of the bacteria’s presence in any aerosols which might be inhaled.

If MIC has already taken place, is it too late?

Moreover, the corrosion makes surfaces rough, porous, or brittle, which can make them more difficult to clean and treat. Due to this, companies must find appropriate solutions to ensure that the health risk from Legionella bacteria is safely controlled in water systems. 

Also, within a food processing environment, MIC can have an adverse effect on product quality and safety.

All Food Business Operators (FBOs) have a duty to meet the legal requirements that food is safe and wholesome, and of a nature, substance or quality that consumers expect.

To achieve this, companies are required to have a Food Safety Management System (FSMS) based on HACCP principles.

These management systems will inevitably include effective cleaning, ensuring food equipment is maintained and in good condition, and the active prevention of the contamination of foods - all processes that can be adversely impacted by MIC if it is not prevented. 

In food and beverage manufacturing, the consequences can also include contaminating food.

While legislation will be sector-specific, the priority for every business will always be safety. Affected materials can have significant consequences: for example, causing equipment failure, production delays, or risking the safety of both employees and other people in the local environment. 

In food and beverage manufacturing, the consequences can also include contaminating food.

If not dealt with appropriately, effectively and efficiently, the hazards created by MIC could pose potential harm to individuals including workers and consumers, which in turn could negatively impact brand reputation. Plus, depending on the severity of the issue, it could also result in hefty fines or even imprisonment. 

Due to this, it’s important to place sufficient time and resources into this arena, including appointing dedicated individuals who are responsible for keeping up-to-date and maintaining compliance.

Seeking external expert support will also help you to ensure you’re meeting legal requirements, and that safety is always upheld. 

In terms of food industry technical support, it can be the dream team

MIC is one of the topics that calls engineers and microbiologists across a multitude of sectors to work together to achieve collaborative success.

As a microbiologist, I always see these challenges as great opportunities to learn and connect, as well as a chance to impart some microbiological knowledge – information which can prove valuable for ensuring the safety and quality of services and products.

In terms of food industry technical support, it can be the dream team.

At Eurofins, we’re proud to be able to share some of this expert information with businesses across the UK to ensure they remain compliant and safe.

But we also conduct an array of services, dedicated to supporting companies with water systems and food safety management - such as a comprehensive review of the FBOs FSMS and their testing programmes.

All Food Business Operators (FBOs) have a duty to meet the legal requirements that food is safe and wholesome

Our extensive team of analysts can offer advice and guidance about what should be monitored, how to interpret the tests, and identify suitable actions to be taken in response to any adverse results.

As a true advocate for raising awareness about the importance of taking appropriate actions based on the results of regular testing, I’m passionate about continuing to educate individuals and businesses.

Eurofins’ experts provide consultancy, advice, and training across food safety, quality and authenticity topics – from sharing relevant resources or answering queries, through to hosting bespoke sessions to aid company-wide understanding and provide updates on the latest rules and regulations.”

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