Microbiologically Influenced Corrosion (MIC)

Microbiologically Influenced Corrosion (MIC) is a type of corrosion caused or influenced by microorganisms such as bacteria, fungi, and algae. These microorganisms can thrive in moist environments and create localized corrosion on metal surfaces by producing corrosive byproducts that damage the metal.

MIC can occur in various industrial settings, including oil and gas pipelines, marine vessels, and water treatment systems. It can significantly damage metal structures and equipment, leading to costly repairs and downtime.

Preventing and managing MIC involves a combination of strategies, including regular monitoring and maintenance, using biocides and inhibitors, and selecting appropriate materials and coatings. Understanding the specific environmental conditions that promote MIC is also essential for effective prevention and management.

MIC can occur in various industries where metal structures or equipment are exposed to moist environments and in contact with microorganisms. Some of the industries that commonly experience MIC include:

• Oil and gas industry: MIC is a significant concern in the oil and gas industry, particularly in pipelines and production equipment that come into contact with corrosive fluids and microorganisms.
• Marine industry: MIC can occur in marine vessels, offshore platforms, and underwater structures that are exposed to saltwater, which creates an ideal environment for microorganisms to thrive.
• Water treatment industry: MIC can occur in water treatment systems, particularly in areas where water is stagnant, such as cooling towers, condenser tubes, and water distribution systems.
• Chemical industry: MIC can occur in chemical plants, where metal equipment is exposed to corrosive chemicals and microorganisms that can thrive in the presence of these chemicals.
• Food and beverage industry: MIC can occur in food and beverage processing equipment, mainly where food residues create a favorable environment for microorganisms to grow.

In summary, any industry that uses metal structures or equipment in a moist environment and where microorganisms can grow has the potential to experience MIC.

Some materials are more susceptible to Microbiologically Influenced Corrosion (MIC) than others. Generally, metals that are more reactive or have a higher potential difference in the galvanic series are more susceptible to MIC. The following are some of the materials that are more susceptible to MIC:

• Carbon Steel: Carbon steel is highly susceptible to MIC. Microorganisms can produce corrosive byproducts, such as hydrogen sulfide, that can cause pitting and crevice corrosion on carbon steel surfaces.
• Copper Alloys: Copper alloys, such as brass and bronze, are susceptible to MIC, especially in marine environments. In addition, some microorganisms can produce organic acids that erode copper alloys.
• Aluminum Alloys: Aluminum alloys are susceptible to MIC, particularly in marine environments. Microorganisms can produce organic acids that can corrode aluminum alloys.
• Nickel Alloys: Nickel alloys, such as Inconel and Monel, can be susceptible to MIC in specific environments. Some microorganisms can produce corrosive byproducts, such as sulfuric acid, that can cause pitting and crevice corrosion on nickel alloy surfaces.
• Zinc: Zinc is susceptible to MIC in specific environments, such as water treatment systems. Some microorganisms can produce corrosive byproducts, such as sulfuric acid, that can cause corrosion on zinc surfaces.

In summary, materials more susceptible to MIC include carbon steel, copper alloys, aluminum alloys, nickel alloys, and zinc. However, the susceptibility of materials to MIC can vary depending on the specific environmental conditions, the type of microorganisms present, and other factors that can promote corrosion.

Preventing microbiologically influenced corrosion (MIC) involves a combination of strategies, including:

• Regular monitoring and maintenance: Monitoring metal surfaces and equipment for signs of corrosion can help detect the early stages of MIC. Cleaning, coating, and protecting metal surfaces can prevent the growth of microorganisms that can cause corrosion.
• Use of biocides and inhibitors: Biocides and inhibitors can be used to control the growth of microorganisms and prevent them from causing corrosion. Biocides are chemical compounds that kill or control the growth of microorganisms. At the same time, inhibitors are chemicals that can slow down or prevent corrosion by forming a protective layer on the metal surface.
• Appropriate materials and coatings: Selecting proper materials and coatings resistant to corrosion and microorganism growth can help prevent MIC. Materials such as stainless steel and copper alloys are less susceptible to corrosion caused by microorganisms than other metals like carbon steel.
• Control of environmental conditions: Control of environmental conditions such as temperature, humidity, and pH can help prevent the growth of microorganisms and corrosion caused by them. For example, maintaining adequate chlorine levels in water treatment systems can prevent the development of microorganisms that can cause MIC.
• Proper design and operation: Proper design and operation of metal structures and equipment can help prevent the accumulation of stagnant water, promoting the growth of microorganisms and causing MIC.

Preventing MIC requires a multi-faceted approach that includes regular monitoring and maintenance, biocides and inhibitors, appropriate materials and coatings, control of environmental conditions, and proper design and operation.

Inspecting for Microbiologically Influenced Corrosion (MIC) involves several methods, including:

• Visual inspection: Visual inspection is the simplest and most common method for detecting MIC. It involves looking for signs of corrosion on metal surfaces, such as pitting, discoloration, and cracking.
• Microbiological testing: Microbiological testing involves collecting samples of metal surfaces and equipment and analyzing them for the presence of microorganisms that can cause MIC. Techniques such as DNA analysis, microscopy, and culturing can be used to identify and quantify microorganisms.
• Chemical analysis: Chemical analysis involves testing the chemical composition of metal surfaces and equipment for the presence of corrosive byproducts produced by microorganisms. Techniques such as Fourier transform infrared spectroscopy (FTIR) and gas chromatography-mass spectrometry (GC-MS) can detect and quantify these byproducts.
• Electrochemical testing: Electrochemical testing involves measuring the corrosion rate of metal surfaces and equipment using techniques such as electrochemical impedance spectroscopy (EIS) and polarization resistance (PR). Changes in the corrosion rate can indicate the presence of MIC.

Inspecting for MIC requires a combination of methods, including visual inspection, microbiological testing, chemical analysis, and electrochemical testing. The choice of method depends on the type of metal surface or equipment being inspected, the severity of corrosion, and the suspected cause of corrosion.

Standards for MIC

The American Petroleum Institute (API) has developed several standards related to Microbiologically Influenced Corrosion (MIC) in the oil and gas industry. Some of the API standards that apply to MIC are:

• API RP 571 - Damage Mechanisms Affecting Fixed Equipment in the Refining Industry: This standard provides an overview of various damage mechanisms, including MIC, that can affect fixed equipment in the refining industry. It covers the identification, inspection, and mitigation of MIC in oil and gas production, refining, and distribution facilities.
• API RP 939-C - Guidelines for Avoiding Sulfidation (Sulfidic) Corrosion Failures in Oil Refineries: This standard provides guidelines for preventing sulfidation corrosion, a type of corrosion that microorganisms can influence. The standard covers identifying sulfidation corrosion mechanisms, inspection and monitoring techniques, and mitigation strategies.
• API RP 14E - Recommended Practice for Design and Installation of Offshore Production Platform Piping Systems: This standard provides guidelines for the design and installation of offshore production platform piping systems, including the prevention of corrosion, including MIC. It covers material selection, coating and cathodic protection, and inspection and maintenance techniques.
• API RP 2A-WSD - Recommended Practice for Planning, Designing, and Constructing Fixed Offshore Platforms - Working Stress Design: This standard provides guidelines for the planning, designing, and constructing of fixed offshore platforms, including the prevention of MIC. It covers selecting materials and coatings, inspection and monitoring techniques, and mitigation strategies.
• API has developed several standards that cover the prevention, identification, and mitigation of MIC in the oil and gas industry. These standards provide guidelines and best practices for designing, constructing, and maintaining equipment and structures to prevent corrosion caused by microorganisms.

The National Association of Corrosion Engineers (NACE) has developed several standards related to Microbiologically Influenced Corrosion (MIC) in various industries. Some of the NACE standards that apply to MIC are:

• NACE Standard TM0194-2014 - Laboratory Methods for Evaluating the Resistance of Metallic Materials to MIC: This standard provides guidelines for laboratory methods to evaluate the susceptibility of metallic materials to MIC. The standard covers the preparation of test specimens, inoculation techniques, and test methods for assessing the resistance of materials to MIC.
• NACE Standard RP0775-2005 - High-Performance Coatings for Steel Pipelines for Corrosion Control: This standard provides guidelines for selecting and applying high-performance coatings to steel pipelines to prevent MIC. The standard covers coating selection, surface preparation, application procedures, and inspection and testing methods.
• NACE Standard SP0104-2014 - Standard Practice for Preparing Steel Surfaces for Coating: This standard provides guidelines for preparing steel surfaces before applying coatings to prevent corrosion, including MIC. The standard covers surface cleaning, surface preparation, and coating application procedures.
• NACE Standard RP0169-2017 - Control of External Corrosion on Underground or Submerged Metallic Piping Systems: This standard provides guidelines for the design, installation, and maintenance of underground or submerged metallic piping systems to prevent external corrosion, including MIC. The standard covers coating and cathodic protection, monitoring and testing methods, and maintenance and repair procedures.
• NACE has developed several standards that cover the prevention, identification, and mitigation of MIC in various industries, including oil and gas, water treatment, and chemical industries. These standards provide guidelines for material selection, coating, and cathodic protection, inspection and testing methods, and maintenance and repair procedures to prevent corrosion caused by microorganisms.