Understanding Microbiologically Influenced Corrosion: How Microbes Affect Steel Pipes

Microbiologically Influenced Corrosion (MIC) is an often-overlooked phenomenon that can lead to significant issues in various industries, particularly where steel pipes are prevalent. As we delve into this topic, we will explore how microorganisms, including bacteria and fungi, interact with metal surfaces, causing corrosion that can compromise the integrity of infrastructure. Understanding the mechanisms behind MIC is crucial for anyone involved in maintenance and engineering, as it not only affects the lifespan of pipes but also poses potential safety hazards.

What Causes Microbiologically Influenced Corrosion?

MIC occurs when microbial communities form biofilms on the surfaces of steel pipes. These biofilms create localized environments that accelerate corrosion processes. Unlike uniform corrosion, MIC typically results in pitting or crevice corrosion, which are more insidious and difficult to detect.

The microorganisms responsible for MIC are often classified into several groups based on their metabolic activity, including:

• Sulfur-Reducing Bacteria (SRB): These bacteria reduce sulfate to hydrogen sulfide, creating an acidic environment that promotes the formation of iron sulfide deposits, accelerating corrosion.
• Iron-Oxidizing Bacteria (IOB): These bacteria facilitate the oxidation of ferrous ions, leading to the formation of rust-like deposits on pipe surfaces.
• Acid-Producing Bacteria (APB): These bacteria generate organic acids that lower the pH, contributing to the dissolution of protective oxide layers on metal surfaces.
• Fungi and Other Microorganisms: Fungal species can also play a role by producing organic acids or physically disrupting protective layers.

The Impact of MIC on Steel Pipes

The consequences of MIC can be severe, leading to costly repairs, operational downtime, and safety hazards. The most common effects include:

1. Pitting and Localized Corrosion: MIC often results in small, highly localized corrosion sites that can penetrate pipe walls.
2. Reduced Structural Integrity: Over time, MIC weakens the pipe material, making it more susceptible to leaks and ruptures.
3. Operational Failures: Blockages caused by biofilm and corrosion products can restrict flow and reduce system efficiency.
4. Health and Environmental Hazards: Leaks in water or chemical pipelines caused by MIC can lead to contamination and environmental damage.

Detection and Monitoring Techniques

Early detection of MIC is essential to minimize damage and extend the life of steel pipes. Common detection methods include:

• Visual Inspections: Identifying visible signs of pitting, discoloration, or biofilm formation.
• Ultrasonic Testing (UT): Measuring wall thickness to detect thinning caused by corrosion.
• Electrochemical Methods: Monitoring corrosion rates through techniques like linear polarization resistance (LPR).
• Microbial Analysis: Sampling and identifying microbial populations present in the system.

Prevention and Mitigation Strategies

Effective strategies to prevent and mitigate MIC include:

1. Material Selection: Using corrosion-resistant materials or coatings to protect pipe surfaces.
2. Chemical Treatments: Applying biocides to control microbial growth and corrosion inhibitors to reduce metal dissolution.
3. Regular Cleaning: Removing biofilms and corrosion products through mechanical or chemical cleaning.
4. Environmental Control: Reducing moisture and nutrient availability to inhibit microbial colonization.
5. Cathodic Protection: Installing systems to protect steel from corrosion by making it the cathode of an electrochemical cell.

Leveraging Nitrogen Systems to Combat MIC

One innovative solution for preventing MIC in fire protection systems involves the use of nitrogen generators, such as the NITROGEN-PAC™ system from United Fire Systems. By introducing high-purity nitrogen into dry and pre-action fire sprinkler systems, the NITROGEN-PAC™ system effectively reduces oxygen levels, thereby minimizing the conditions that promote microbial growth and corrosion. This approach not only extends the lifespan of steel pipes but also reduces maintenance costs and enhances the reliability of critical infrastructure.

Conclusion

Understanding and addressing MIC is essential for maintaining the longevity and safety of steel piping systems. By recognizing the role of microbes in corrosion processes and implementing proactive monitoring and prevention measures, industries can significantly reduce the risks and costs associated with this form of corrosion.

Written By:

Ashley Villa

Marketing Manager

avilla@ufpco.com