Corrosion endangers metallic systems present in water treatment plants, manufacturing facilities, and process piping. It is a constant source of frustration for maintenance management professionals.
Corrosion endangers systems in water treatment plants, manufacturing facilities, and process piping.
The Chemistry Behind Corrosion
Corrosion is a naturally occurring electrochemical process that leads to the decay of metallic products. During the oxidation phase, iron atoms lose electrons and become positively charged iron ions. Concurrently, oxygen atoms gain electrons and react with water to form hydroxide ions. The positively charged iron ions and the hydroxide ions chemically react to form rust (Fe₂O₃·xH₂O).
As we can see, chemically, the only two materials required to corrode metallic products are water and oxygen. The presence of salts or acids can accelerate corrosion, but the threat of corrosion is constant. Industries such as oil & gas, water treatment, and manufacturing present ideal conditions for corrosion due to the harsh chemicals, high humidity, and systems immersed in water.
The importance of preventative corrosion management and effective corrosion repair is underscored by how expensive full replacement can be. For critical lines inhibited by corrosion, replacement would mean a plant-wide shutdown and hundreds of thousands of dollars in repair and lost revenue.
Types of Corrosion
There are multiple kinds of corrosion. Customers may be challenged by stress corrosion, crevice corrosion, or pitting corrosion.
Stress Corrosion Cracking
Stress corrosion cracking (SCC) is common in high-strength steel like carbon steel or stainless steel. It results from stress combined with a corrosive environment and is influenced by environmental factors like oxygen, pH level, temperature, and the presence of chlorides or nitrates.
SCC is common in high-pressure pipelines or pressure vessels because of the constant stress to which the systems are subjected. Buried steel pressurized pipelines facing corrosive underground environments or pressurized vessels in nuclear power plants are some systems that might be susceptible to this failure.
Crevice Corrosion
As the name implies, crevice corrosion occurs in cracks or crevices, usually where there is a difference in oxygen concentration. This type of corrosion is typical underneath washers, gaskets, or surface deposits.
Crevice corrosion is problematic for wastewater systems with complex geometries, flange connections of process piping, and cooling systems where stagnant water can accumulate.
Pitting Corrosion
Pitting is usually caused by microbially induced corrosion (MIC), forming low pH environments and sulfuric acids from sulfate-reducing bacteria. Pitting corrosion can be systemic and cause through-wall failure in localized spots.
Pitting corrosion can be pervasive in acidic or corrosive solutions like seawater. Seawater tanks, offshore rigs, and water runoff piping can be particularly prone.
Pitting is usually caused by microbially induced corrosion (MIC).
Effective Corrosion Management
Effective corrosion management requires implementing best practices for corrosion prevention and consistent inspection and monitoring, including proper coating selection.
Coatings are a key part of effective corrosion management.
There are many different types of coatings for preventing corrosion. Barrier coatings designed to prevent atmospheric corrosion include multi-coat zinc primer, epoxy base coat, and urethane top coat. For water immersion barrier coatings, epoxy, vinyl ester, or polyurea is preferred for robust barrier protection. Other coating types include sacrificial coatings. These coatings oxidize instead of the metal substrate.
For a chemical manufacturer in Texas, an acidic digester tank needed an effective corrosion management solution after a failed internal lining system. A new, chemically-resistant epoxy novolac coating was installed instead. Advanced FRP Systems recommended the system, catered to the acidic application.
This acidic digester tank used a customized, chemically-resistant epoxy novolac coating.
The best coating choice depends on the application and the environment. To learn more about selecting a coating, visit Our Coatings Page.
Consistent inspection and monitoring prevent unexpected failures.
Each asset should include expected service life and a management plan. The management plan includes short-term and long-term milestones and expected inspection frequency. In order to determine the inspection frequency of each asset, you will have to look at both a risk assessment of potential corrosion failure and the expected rate and probability of corrosion.
Frequent, strategic inspection plans extend asset life and reduce downtime. It also increases the chance of finding problems before it’s too late.
Additional Resources
View additional resources for corrosion management from Advanced FRP, applicable for many different types of industries and end users.
Coating for Corrosion Resistance
Corrosion endangers metallic systems present in water treatment plants, manufacturing facilities, and process piping. It is a constant source of frustration for maintenance management professionals.
The Chemistry Behind Corrosion
Corrosion is a naturally occurring electrochemical process that leads to the decay of metallic products. During the oxidation phase, iron atoms lose electrons and become positively charged iron ions. Concurrently, oxygen atoms gain electrons and react with water to form hydroxide ions. The positively charged iron ions and the hydroxide ions chemically react to form rust (Fe₂O₃·xH₂O).
As we can see, chemically, the only two materials required to corrode metallic products are water and oxygen. The presence of salts or acids can accelerate corrosion, but the threat of corrosion is constant. Industries such as oil & gas, water treatment, and manufacturing present ideal conditions for corrosion due to the harsh chemicals, high humidity, and systems immersed in water.
The importance of preventative corrosion management and effective corrosion repair is underscored by how expensive full replacement can be. For critical lines inhibited by corrosion, replacement would mean a plant-wide shutdown and hundreds of thousands of dollars in repair and lost revenue.
Types of Corrosion
There are multiple kinds of corrosion. Customers may be challenged by stress corrosion, crevice corrosion, or pitting corrosion.
Stress Corrosion Cracking
Stress corrosion cracking (SCC) is common in high-strength steel like carbon steel or stainless steel. It results from stress combined with a corrosive environment and is influenced by environmental factors like oxygen, pH level, temperature, and the presence of chlorides or nitrates.
SCC is common in high-pressure pipelines or pressure vessels because of the constant stress to which the systems are subjected. Buried steel pressurized pipelines facing corrosive underground environments or pressurized vessels in nuclear power plants are some systems that might be susceptible to this failure.
Crevice Corrosion
As the name implies, crevice corrosion occurs in cracks or crevices, usually where there is a difference in oxygen concentration. This type of corrosion is typical underneath washers, gaskets, or surface deposits.
Crevice corrosion is problematic for wastewater systems with complex geometries, flange connections of process piping, and cooling systems where stagnant water can accumulate.
Pitting Corrosion
Pitting is usually caused by microbially induced corrosion (MIC), forming low pH environments and sulfuric acids from sulfate-reducing bacteria. Pitting corrosion can be systemic and cause through-wall failure in localized spots.
Pitting corrosion can be pervasive in acidic or corrosive solutions like seawater. Seawater tanks, offshore rigs, and water runoff piping can be particularly prone.
Effective Corrosion Management
Effective corrosion management requires implementing best practices for corrosion prevention and consistent inspection and monitoring, including proper coating selection.
Coatings are a key part of effective corrosion management.
There are many different types of coatings for preventing corrosion. Barrier coatings designed to prevent atmospheric corrosion include multi-coat zinc primer, epoxy base coat, and urethane top coat. For water immersion barrier coatings, epoxy, vinyl ester, or polyurea is preferred for robust barrier protection. Other coating types include sacrificial coatings. These coatings oxidize instead of the metal substrate.
For a chemical manufacturer in Texas, an acidic digester tank needed an effective corrosion management solution after a failed internal lining system. A new, chemically-resistant epoxy novolac coating was installed instead. Advanced FRP Systems recommended the system, catered to the acidic application.
The best coating choice depends on the application and the environment. To learn more about selecting a coating, visit Our Coatings Page.
Consistent inspection and monitoring prevent unexpected failures.
Each asset should include expected service life and a management plan. The management plan includes short-term and long-term milestones and expected inspection frequency. In order to determine the inspection frequency of each asset, you will have to look at both a risk assessment of potential corrosion failure and the expected rate and probability of corrosion.
Frequent, strategic inspection plans extend asset life and reduce downtime. It also increases the chance of finding problems before it’s too late.
Additional Resources
View additional resources for corrosion management from Advanced FRP, applicable for many different types of industries and end users.
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