Microbiologically Influenced Corrosion (MIC) In Tanks

Microbial, bacterial or biological – Whatever you want to call it, it’s dangerous, destructive and just downright tough to deal with. While steel panel tanks make for incredibly strong structures, failing to properly maintain their interior surfaces invites a range of sneaky, ‘back door infections’ to find a way to ruin their integrity.

Water Tank Failure is detrimental to businesses on both commercial and industrial levels. Check out our blog article above for further insights on how to keep your storage units contaminant-free.

Although virtually impossible to completely stamp out, there is plenty we can do to minimise the risk of MIC attacks
Read more below about why we need to consider how MIC will impact future projects and how we can incorporate mitigation and observation strategies to reduce the threats of corrosion

What Is MIC?


Microbiologically Influenced Corrosion is basically a type of bacterial growth that ‘influences’ how corrosion will impact a steel surface. Commonly a fungal-type growth, microorganisms develop on steel surfaces increasing or worsening areas with either existing corrosion or that were about to experience corrosion issues.

Put simply, the bacteria amplifies the scale and impact of new and already-forming rust, obviously something you’d want to try and avoid at all costs as a commercial tank owner. Microbial bacteria will eat away at all steel tanks eventually regardless of the type or grade. Microbes are known to easily survive in drinking water, passing through distribution and piping systems to multiply and attach themselves to walls. Practically, the longer MIC activity is left, the more difficult it becomes to get rid of.

What Causes MIC?


MIC can be rather challenging to prevent and eliminate since it must be determined as either a root cause or an additional element aggravating the corrosion. This often requires extensive scientific assessment and testing which spells out big dollars and big headaches for those responsible for treatments.
MIC usually stems from biofilm sticking to piping systems within storage tanks. But let’s get technical for a moment to truly explain what’s happening inside your tanks causing MIC to form. Biological corrosion initiates when hydrogen sulphide gases from bacteria living in your tank are produced. These react with other elements inside the tank (air and moisture), to make highly corrosive sulfuric acid. A number of bacteria are known to cause this in stainless steels, carbon steels and alloys and are generated in soil and water stored between 10 and 50 degrees Celsius – making both indoor and outdoor liquid storage systems ideal conditions for MIC breeding grounds.
Microorganisms multiplying in potable water tanks and their piping can shut down an entire drinking water supply. Municipal tank storage provides more than enough nutrient sources for bacteria to rapidly multiple and easily render them offline.

Where Is MIC Found?


Nutrients present in water sources is primarily what MIC feeds and thrives off, but remember it’s merely a contributor to corrosion, not a type of corrosion itself. Sulphate reducing bacteria or SRB comes from sea water and is a stainless steel surface’s worst enemy.

MIC effectively reduces the overall material strength of a tank extremely quickly, attacking joints, seals, bolts and a variety of other components crucial to keeping steel tanks useable. MIC has been found among waters used for drinking, hydrotesting, cooling and fire suppression.

Tank bottoms are usually the most nutrient rich area for bacteria to live in as water and ‘food’ will always be present as long as the tank remains slightly filled with liquid. Bacteria found in piping releases a slime-like substance to protect itself from disinfection, paving the way for further and more successful microbial growth. 

Microorganisms can grow on metal constructions such as tanks and liquid storage systems that are frequently exposed to:

    • – Salt spray from being situated close to the ocean
    • – Any type of water
    • – Low water flow through horizontally-orientated pipes
    • – Oils and fuels
    • – Chemicals (Gas and Liquid Facilities)

Industries Commonly Experiencing MIC Attacks Australian industry sectors heavily reliant on liquid storage systems for their operations frequently have to try and find new ways to manage and deal with MIC situations.Not only are they hit with replacement and reinstallation costs, but the downtime suffered by sites when liquid storage systems go offline is simply another blow below the belt. Identifying and managing MIC attacks early can mean the difference between a thriving commercial environment and an unsalvageable one.

As you’ll discover below, microbiologically influenced corrosion doesn’t discriminate and can affect how water tanks and a range of other liquid containment systems are run and maintained. 

Industries most susceptible to MIC contamination include:

      • – Water Treatment and Storage
      • – Power Generation
      • – Underground Piping
      • – Waste Management
      • – Oil and Gas
      • – Marine and Aviation
      • – Heavy Industries

Regulatory concerns can be devastating to businesses in the event that a tank system fails and harms people, property or the environment. With above ground tanks being the main storage choice for a range of hazardous liquids (and large volumes of them), a disaster could just be moments away at any time.

The MIC Process – How It Starts?


Penetration rates recorded as a result of MIC are enough to make you seriously question whether it’s worth short-cutting on maintenance procedures for another year. In some cases, MIC has eaten through up to one-eighth of an inch of surface steel in just 1-4 months depending on the type!

          • 2. Non-flowing water promotes bacterial growth on metal surfaces a relatively short time following the initial uses of your tank.
          • 3. Attached microbes colonise and form deposits and create a ‘biofilm’.
          • The biofilm eventually grows and transforms into a ‘biomound’ or a thicker, reddish-brown deposit.
          • 4. Corrosion begins by formation of concentration cells or differential aeration
          • 5. Microbes find their way onto welds, joints and a range of sub-surface cavities and multiply using the nutritious conditions inside the tank.
          • 6. Without a proper cleaning and maintenance schedule, the ever-developing microorganisms proceed to accelerate surface and joint corrosion leading to inevitable leaks and structural damage.

Prevention Tactics for MIC


There is some good news amongst all this talk of corrosive damage, and it’s that there are measures you can take to combat problematic MIC in your tanks. The rate of microorganism activity ranges and fluctuates inside liquid containment systems depending on a number of factors including what it’s storing, its material composition and the environment where it’s located. 

Here’s what you should be doing to prevent the likelihood of your tanks being overrun by bacterial growth:

          • Ensure a regular cleaning and maintenance schedule is adhered to by industry-certified professionals
          • Adding corrosion inhibitors to the tank
          • Employing chemical treatment using biocides restricting bacterial growth.

Regularly draining the tank and replacing old, stagnant water sources where possible – bacteria just can’t get enough of that stale, humid environmen. 

Will Draining Rid Commercial Tanks of Microbes?

Complete water removal is often required with fire and potable water tanks in attempt to eliminate microbial activity. While it might be seemingly impossible to drain 100% of the water due to a tank’s configuration, it’s still one of the most effective bacteria reducing strategies you can apply. The biggest problem with liquid storage tanks is that they’re either:

            • Above ground and feature convex surfaces at the bottom encouraging water entrapment, or
            • o Underground tanks that can become unlevel over the long-term, with their orientation adjusting in association with soil movement.

How Long Does It Take For MIC To Form?

MIC consumes steel tanks in a termite-like manner and generally starts to occur just a few years after the tank’s first fill. What begins as a rather small issue, rapidly transforms tanks from useable to a state of disrepair and danger. A collapsed commercial water tank that’s been neglected can result in flooded facilities, electrical hazards and a whole range of irredeemable circumstances.

Raven Tanks offer Microbiologically Influence Corrosion inspections and oftentimes this is all it can take to recognise the issue and apply remedial treatment techniques for elimination. Today we’ve learnt that MIC is an accelerant to the rate of corrosion regarding commercial and industrial water tanks, among being a contributing factor of many corrosion issues across Australian industries. A significant percentage of liquid containment systems are compromised and completely lost due to microbiologically influenced corrosion and the key to avoiding such incidents is simply prevention. There have been multiple instances where an MIC attack could have been avoided through a relatively easy draining and drying process following testing. Ongoing efforts amongst industries will likely be required for quite some time before any solid solutions present themselves. It’s time for tank owners to tackle MIC with new prevention strategies, treatment options and through innovative maintenance techniques to help slow corrosion and prolong tank lifespans.

Contact the Raven Tanks team for an inspection and find out if any repair works or replacement components are necessary for your commercial or industrial water tanks.

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