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MIC

What is MIC?

Microbiologically Influenced Corrosion (MIC) is a type of corrosion caused or accelerated by the presence and activities of microorganisms. These microorganisms, which can include bacteria, fungi, and algae, colonize surfaces in contact with water, soil, or other environments where moisture and nutrients are present. MIC is a significant concern in various industries, including oil and gas, marine, water treatment, and infrastructure, as it can lead to severe damage and structural failures if not properly managed.

For technical engineers, understanding MIC involves grasping its mechanisms, detection methods, and mitigation strategies:

  1. Mechanisms: MIC occurs through various mechanisms, including the production of corrosive metabolic byproducts by microorganisms and the alteration of the local environment, such as pH changes or oxygen depletion, which can promote corrosion. Some microorganisms can directly attack the protective coatings on metal surfaces, making them more susceptible to corrosion.

  2. Detection: Detecting MIC early is crucial for preventing extensive damage. Engineers utilize various techniques such as microbiological testing, electrochemical methods, and surface analysis to identify the presence of microorganisms and assess corrosion rates. Monitoring changes in corrosion potential, microbial populations, and corrosion product formation can provide insights into the extent of MIC.

  3. Mitigation: Mitigating MIC involves a combination of preventive measures and treatment strategies:

    • Material Selection: Choosing corrosion-resistant materials can reduce susceptibility to MIC. For instance, using stainless steel or corrosion-resistant alloys in environments prone to microbial colonization.

    • Biocide Treatment: Applying biocides can help control microbial growth and reduce the risk of MIC. However, careful consideration must be given to environmental impact and potential resistance development.

    • Cathodic Protection: Implementing cathodic protection systems can minimize the corrosion rate by polarizing metal surfaces, making them less susceptible to microbial attack.

    • Coatings and Linings: Applying protective coatings and linings can create a barrier between the metal substrate and corrosive microorganisms, inhibiting microbial attachment and corrosion initiation.

    • Monitoring and Maintenance: Regular inspection and monitoring of equipment and structures for signs of microbial activity and corrosion are essential. Implementing proactive maintenance practices can help identify and address issues before they escalate.

Overall, a comprehensive approach that integrates materials selection, preventive measures, and ongoing monitoring is essential for effectively managing MIC and minimizing its impact on infrastructure and equipment integrity. Collaboration between engineers, microbiologists, and corrosion specialists is often necessary to develop tailored solutions for specific applications and environments.

Five fundamental MIC mechanisms can be delineated:

  1. Direct Electrochemical Interaction:

    • Microorganisms engage directly in oxidation or reduction processes, particularly under anaerobic conditions, through electron transfer. This involves the direct exchange of electrons between the metal and the microorganism, facilitated by the microorganism’s metabolic activities. This form of MIC results in a rapid and localized corrosion process.

  2. Metal as a Breeding Ground:

    • Steel serves as a substrate for microorganism growth and metabolism. Microorganisms utilize components present in steel, such as hydrogen and iron, releasing them in the process. Enzymes produced by microorganisms catalyze the dissolution of steel, contributing to MIC.

  3. Indirect Corrosive Substance Production:

    • Microorganisms indirectly promote corrosion by generating corrosive residues during microbial processes. While corrosion may not be their primary objective, substances like acetate, hydrogen sulfide, and sulfuric acid emerge as byproducts, influencing corrosion.

  4. Stimulation of Chemical Corrosion:

    • Microorganisms can stimulate ongoing corrosion processes by extracting products from the natural reaction. This interference disrupts the equilibrium reached during corrosion. For instance, bacteria consuming hydrogen formed at the cathode lead to cathodic depolarization, preventing equilibrium and sustaining corrosion.

  5. Formation of Corrosive Environments through Biofilms:

    • Microorganisms create biofilms, slimy layers adhering to surfaces. Within these biofilms, microorganisms facilitate substance exchange and establish zones that stimulate specific reactions. This can lead to the creation of corrosive conditions in previously neutral areas, impacting the corrosion environment.

MIC Mechanisms

Microbiologically Influenced Corrosion (MIC) manifests as a corrosion phenomenon driven or expedited by the actions of microorganisms. This encompasses not only direct impacts but also the indirect facilitation and acceleration of chemical corrosion. Did you know that five fundamental MIC mechanisms can be delineated?

Internal corrosion photo
Electrochemical icon

Direct Electrochemical Interaction

Microorganisms engage directly in oxidation or reduction processes, particularly under anaerobic conditions, through electron transfer. This involves the direct exchange of electrons between the metal and the microorganism, facilitated by the microorganism’s metabolic activities. This form of MIC results in a rapid and localized corrosion process.

Substance icon

Indirect Corrosive Substance Production

Microorganisms indirectly promote corrosion by generating corrosive residues during microbial processes. While corrosion may not be their primary objective, substances like acetate, hydrogen sulfide, and sulfuric acid emerge as byproducts, influencing corrosion.

Breeding ground icon

Metal as a Breeding Ground

Steel serves as a substrate for microorganism growth and metabolism. Microorganisms utilize components present in steel, such as hydrogen and iron, releasing them in the process. Enzymes produced by microorganisms catalyze the dissolution of steel, contributing to MIC.

Biofilm icon

Formation of Corrosive Environments through Biofilms

Microorganisms create biofilms, slimy layers adhering to surfaces. Within these biofilms, microorganisms facilitate substance exchange and establish zones that stimulate specific reactions. This can lead to the creation of corrosive conditions in previously neutral areas, impacting the corrosion environment.

Chemical icon

Stimulation of Chemical Corrosion

Microorganisms can stimulate ongoing corrosion processes by extracting products from the natural reaction. This interference disrupts the equilibrium reached during corrosion. For instance, bacteria consuming hydrogen formed at the cathode lead to cathodic depolarization, preventing equilibrium and sustaining corrosion.

External corrosion photo

Where can I find MIC?

Swab sampling material failure due to pitting
Sampling of pitting corrosion to measure the root cause and measure microbiology

Unlocking the Secret World of Microbial Corrosion: A Journey Through Industrial Environments

In the vast landscapes of industrial facilities and power plants, where cooling towers stand as sentinels of efficiency, a silent threat lurks beneath the surface – gel-like biofilms teeming with microorganisms. These unassuming structures, formed by the intricate dance of bacteria in cooling water, hold within them the potential for havoc.

Delve deeper, and you’ll encounter a microbial community where iron-oxidizing and acid-producing bacteria reign. Their clandestine activities lead to the sinister phenomenon known as Microbiologically Influenced Corrosion (MIC), quietly sabotaging equipment integrity and inviting failure. But the troubles don’t stop there; these biofilms provide a fertile ground for the growth of Legionella, compounding the challenges faced by industrial operators.

Venture into the realm of oil and gas pipelines, and you’ll find a battleground of microscopic proportions. Here, amidst the flow of resources, a multitude of microbial adversaries – acetogens, fermenters, and sulfate-reducing bacteria, to name a few – wage war against the integrity of pipelines. Their relentless assault, exemplified by the rapid formation of pit corrosion, accounts for a staggering 30% of equipment damage in the oil and gas industry.

Journeying to coastal structures, where the land meets the tumultuous embrace of the sea, we encounter another facet of microbial corrosion. Bacteria, unseen but omnipresent, adhere to metal surfaces with tenacity, initiating localized corrosion in the face of fluctuating seawater levels. In this battleground of elements, the relentless march of microbial agents threatens the stability of vital marine infrastructure.

Descend into the depths of the earth, where underground structures lie concealed from sight but not from the reach of microbial adversaries. Tanks and storage vessels, once thought secure, become battlegrounds where anaerobic bacteria thrive. Here, in the absence of oxygen, they produce corrosive hydrogen sulfide gas, accelerating chemical corrosion and contributing to material degradation and leakage problems. Microbiologically Influenced Corrosion (MIC) asserts its dominance, claiming at least 20% of the challenges faced in these subterranean environments.

In the intricate tapestry of industrial landscapes, microbial corrosion emerges as a formidable foe, challenging the resilience of infrastructure and the ingenuity of human innovation. Yet, armed with knowledge and vigilance, we navigate these unseen realms, striving to safeguard the foundations upon which our industries stand.

As we traverse the landscapes of industry, the specter of microbial corrosion extends its tendrils into diverse realms, reminding us of nature’s relentless influence on the engineered world.

In the bustling heart of industrial facilities, where the rhythm of production pulses ceaselessly, a hidden menace lurks within the confines of pulp and paper mills and food processing plants. Here, amidst the heat and abundance of nutrients, bacteria find a thriving haven. The combination of elevated temperatures and dissolved solids in process water sets the stage for a silent assault on metal surfaces. Pitting corrosion, the insidious consequence, strikes indiscriminately, eroding even the stout defenses of stainless steel.

Venturing beyond the confines of steel and concrete, we encounter the formidable adversary of microbial corrosion in unexpected places. In the sturdy edifices of bridges and buildings, and the labyrinthine networks of sewer pipelines, concrete stands as a bulwark against the elements. Yet, even here, microbial agents find purchase, insidiously undermining structural integrity. Through the production of acidic compounds, both organic and inorganic, these unseen assailants corrode reinforcing steel and degrade concrete components, casting a shadow over the very foundations of our built environment.

Turning our gaze seaward, we confront the challenges posed by offshore wind farms, where the relentless assault of environmental conditions meets the intricate dance of microbial life. Despite the shelter provided by wind turbine monopiles, the forces of corrosion remain undeterred. High salinity, oxygen-rich waters, and a multitude of microbial species converge to pose a threat that defies conventional wisdom. Within the closed compartments of these towering structures, the insidious whispers of chemical corrosion and Microbiologically Influenced Corrosion (MIC) echo, reminding us of the vulnerability inherent in our quest for renewable energy.

In the grand tapestry of industry and infrastructure, the phenomenon of microbial corrosion weaves its intricate patterns, challenging our resilience and demanding our vigilance. Yet, armed with knowledge and foresight, we navigate these unseen realms, striving to fortify the foundations upon which our future prosperity rests.

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Multiple lines of evidence

Diagnosing microbiologically influenced corrosion (MIC) through multiple lines of evidence is crucial for several reasons:

  1. Accuracy: MIC is often subtle and can mimic other forms of corrosion or damage. By utilizing multiple diagnostic techniques, such as microbial analysis, corrosion rate measurements, and examination of corrosion products, it becomes possible to cross-reference findings and increase the accuracy of diagnosis. This ensures that the true cause of corrosion is identified, leading to more effective mitigation strategies.

  2. Comprehensive Understanding: MIC is a complex phenomenon influenced by various factors, including environmental conditions, microbial communities, and material properties. By employing multiple lines of evidence, researchers can gain a more comprehensive understanding of the corrosion process. This includes identifying the specific microorganisms involved, understanding their metabolic activities, and assessing the extent of corrosion damage. Such insights are invaluable for developing targeted prevention and mitigation measures.

  3. Early Detection: Detecting MIC at an early stage is essential for preventing extensive damage to infrastructure and minimizing repair costs. By combining different diagnostic approaches, it becomes possible to detect subtle signs of MIC before significant corrosion occurs. For example, microbial analysis can identify the presence of corrosive microorganisms in biofilms, while corrosion rate measurements can indicate the severity of corrosion damage. Early detection allows for timely intervention and the implementation of proactive corrosion management strategies.

  4. Validation of Findings: Utilizing multiple lines of evidence allows for the validation of diagnostic findings through cross-referencing and corroboration. For example, if microbial analysis identifies corrosive microorganisms in a biofilm, this finding can be supported by corrosion rate measurements indicating accelerated corrosion in the same location. Validation enhances the reliability of diagnostic results and increases confidence in subsequent decision-making processes.

  5. Holistic Approach: MIC is influenced by a combination of biological, chemical, and physical factors. By adopting a holistic approach to diagnosis, incorporating microbial, chemical, and corrosion-related analyses, researchers can gain a more comprehensive understanding of the corrosion process. This enables the development of integrated mitigation strategies that address all aspects of MIC, from microbial control to corrosion inhibition.

In conclusion, diagnosing microbiologically influenced corrosion through multiple lines of evidence is essential for accurately identifying the underlying causes, gaining a comprehensive understanding of the corrosion process, detecting corrosion at an early stage, validating findings, and developing holistic mitigation strategies. By combining microbial, chemical, and corrosion-related analyses, researchers can effectively combat MIC and safeguard critical infrastructure against its damaging effects.

Chemical environment

Electron donors and acceptor combinations. . pH, salt concentrations, nutrient presence. Abiotic influences.

Operating conditions

Pressure, temperature, solids, inhibiting conditions, dead legs, behaviour of water. Mitigating effects (biocide).

MIC Diagnose

Materials & Corrosion products

Susceptibility of materials and surface area to MIC. Conductive or isolating corrosion products.

Microbiology

Presence and activity of relevant microorganisms. Community behaviour, competition for energy and nutrients(diversity, abundance and activity)