What is MIC? Microbiological Influenced Corrosion (MIC) Testing

What is MIC?

Microbial-induced corrosion (MIC) is the phenomenon of corrosive activity by microbial organisms such as bacteria, fungi, and algae. MIC is seen in virtually all industries; however, some industries have greater difficulty with MIC than others (i.e., Marine, Oil). This article focuses on the challenges of MIC and its associated biofilms within potable and non-potable water systems.

What Are the Consequences of MIC?

Physical Damage to the Water System

Costly and potentially irreversible damage can occur in a water system if MIC is not regulated. In 2018, it was estimated that the cost of MIC was ~$2.9 trillion, with major, individual cases running into the hundreds of millions in damages, fines, and settlements (1). Therefore, it is more cost-effective in performing preventative, routine maintenance on these systems than to only address MIC when damage has affected the system’s performance.

Increased Risk of Infection

MIC can have an impact beyond physical damage to a water system. Bacteria responsible for MIC can also be known pathogens to humans. Pseudomonas, for example, is well known for inducing corrosion and as an opportunistic pathogen in humans. MIC in the form of slime-producing bacteria can also create environments that are conducive for pathogens. While Legionella is not associated with inducing corrosion it does, however, thrive in biofilms that are created by slime-producing bacteria.

Difficulties In Addressing MIC

Even though MIC is a prevalent problem, the factors that lead to it are complex and poorly understood. Due to this, each system’s microbiome will be different and present its unique challenges. Still, there are groups of bacteria that tend to occupy this space more frequently than others. Listed below are a few common types of corrosion, and the bacteria that frequently induce it:
  • Iron Related Bacteria (IRB)
    •       Pseudomonas and Shewanella bacteria.
    •       Synergetic with SRB.
  • Sulfate Reducing Bacteria (SRB)
    •        Desulfovibro
    •        Synergetic with IRB.
  • Slime Forming Bacteria
    •        Pseudomonas, micrococcus, and various enteric bacteria.
As to why these groups of bacteria are prevalent in water systems, one possibility could be due to a synergetic effect when a combination of these bacteria is present in a water system. In a study by Lv et. al, it was found that there was a greater degree of corrosion in the presence of both IRB and SRB than just in the presence of one. This was due to the consumption of oxygen by the aerobic IRB, which created favorable conditions for the anaerobic SRB (2). Similarly, slime-producing bacteria produce a biofilm that can provide a protective and beneficial environment for other types of MIC-associated bacteria to proliferate.

What You Can Do to Protect Your Water System

Currently, it is impossible to have total MIC prevention in any industry. Instead, the industry standard is to regulate bacterial load and makeup to minimize MIC. This involves routine testing and cleaning of these water systems. Testing methodologies can range from simple phenotypic tests that address individual corrosion types to in-depth metagenomic testing, which analyzes the water system’s ecosystem. Both types of analyses are available through EST, click here to learn more. References
  1. Microbially influenced corrosion—Any progress? – ScienceDirect
  2. Mechanism of microbiologically influenced corrosion of X65 steel in seawater containing sulfate-reducing bacteria and iron-oxidizing bacteria – ScienceDirect

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