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July 3, 2024 •EAPA Newsletters
Have you ever experienced a water cut due to a burst pipe and found out that the failure was due to corrosion? Frustrating isn’t it; to not being able to bathe after a long day at work, right? Then, you will be wondering what engineers have been doing to safeguard our nation’s assets. Corrosion is a naturally occurring phenomenon commonly defined as the deterioration of a substance (usually a metal) or its properties because of a reaction with its environment.1 Like other natural hazards, such as earthquakes or severe weather disturbances, corrosion can cause dangerous and expensive damage to everything from vehicles, home appliances, and water and wastewater systems to pipelines, bridges, and public buildings.
The science of corrosion prevention and control is highly complex, exacerbated by the fact that corrosion takes many different forms and is affected by numerous external factors. Corrosion professionals must understand the effects of environmental conditions, such as geological contributions, water tables, and dissolved minerals. In addition, various materials, the type of product to be processed, handled, or transported; the required structural lifetime have distinguished roles in the corrosion process. Third-party external factors such as stray current from rail systems and high voltage transmission lines can also contribute to the corrosion phenomena, just by physically being in close proximity to the metallic asset for example buried pipeline.
Below are some examples of major worldwide incidences that were attributed to corrosion:
- Genoa, Italy Bridge Collapse
In August of 2018, a bridge collapsed in Italy, resulting in the death of 43 people. The bridge was only 51 years old and was frequently used by local citizens. The steel cables supporting the bridge failed due to damage from corrosion.2
- Sinking of the Erika
In December of 1999, a Maltese tanker broke in two while traveling near the coast of Brittany, France. Nearly 19,800 tons of oil were spilled. There were multiple parts of the ship that had failed due to corrosion, and the final straw that broke it apart was severe weather.3
- Fall of Railway Traffic Lights
In November 2014, a train traveling through England struck the railway traffic lights that had fallen near an intersection. The post holding the lights fell due to corrosion at its base and was then struck by an oncoming train. Corrosion ate through the pole, causing it to fall and ultimately resulting in the entire track being blocked.4
- Bhopal, India Incident
In December of 1984, one of the world's largest industrial disasters occurred, resulting in the death of nearly 8,000 people. Corrosion caused toxic gas (phosgene, monomethyl amine (MMA), methyl isocyanate (MIC) and the pesticide carbaryl, known as Sevin) from a pesticide plant to leak into the atmosphere. The final death toll was estimated to be between 15,000 and 20,000.5
From the examples listed, one can see very clearly that corrosion has a massive impact on people’s health, safety, asset integrity and the environment as well as an impact on the economy due to the direct and indirect costs incurred.
Hot, Humid Climate
Malaysia, located close to the equator, has a hot and humid climate with rainfall experienced throughout the year. Rain and humidity are crucial elemental factors in the process of developing corrosion, thus, requiring effective corrosion control materials, design, and maintenance. Malaysia also has long coastlines and industries which are set up by the coast or even offshore such as maritime facilities, oil and gas facilities, and power plants. Proximity to water, especially salt water, causes numerous corrosion concerns and ongoing work to protect and extend the lifetime of assets located there. The unique geography and climate conditions of Malaysia require corrosion professionals and companies to be trained and diligent in their efforts to protect people, assets, and the environment
Whereas in other areas, corrosion will still occur because of the four basic elements that cause corrosion, hence a holistic approach in terms of corrosion management plays a major part in the protection of submerged or buried metallic assets. Local corrosion management team who are passionate about safeguarding our nations’ assets and familiar with our environment and technical specifications, consisting of competent and internationally-certified cross-disciplinary members of home-grown local professionals.
Corrosion Control
Steps and processes taken are crucial in combating the corrosion menace. International standards and best practices with regard to corrosion shall be adopted, and then integrated to develop corrosion management strategies which are relevant in the Malaysian context.
The first step in effective corrosion control, is to have a thorough knowledge of the various forms of corrosion, its related mechanisms, how to detect them, and how and why they occur.8 There are as many as ten (10) primary forms of corrosion, but it is rare that a corroding structure or component will suffer from only one type. The combination of metals used in a system and the wide range of environments encountered often cause more than one type of corrosion. Even an alloy, such as stainless steel, that all-rounder alloy often touted as corrosion-resistant material, can be impaired by corrosion when its properties are not well understood and are utilized in inappropriate conditions or applications.
All forms of corrosion, except for some types of high-temperature corrosion, occur through the action of the electrochemical cell. The four elements that are common to all corrosion cells are an anode where oxidation and metal loss occur, a cathode where reduction and protective effects occur, and metallic and electrolytic paths between the anode and cathode through which electronic and ionic current flows. Potential difference is the main cause of corrosion and may be the result of differences between the characteristics of dissimilar metals, surface conditions, and the environment, including chemical concentrations. Ever wondered why the stainless-steel kitchen tap coupled with a brass coupler that you have installed is rusting away? Now you know.
Specific Mechanisms
There are specific mechanisms that cause each type of attack, different ways of measuring and predicting them, and various methods that can be used to control corrosion in each of its forms. A mind map illustrating the 10 primary forms of corrosion can be found in the following figure.
Mind map of the 10 primary forms of corrosion
There are many different methods of corrosion prevention and control. In general, the approach to control most corrosion is to understand the corrosion mechanism involved and remove one or more of the elements of the corrosion cell. For example, by electrically separating the anode and cathode from each other or from the electrolytic environment by reducing the driving potential, risk to corrosion is very much reduced. The most used corrosion control methods include materials selection and design using corrosion-resistant alloys, plastics, and polymers; organic and metallic protective coatings; cathodic protection (CP); and corrosion inhibitors. All these methods are appropriate for controlling corrosion in certain situations and not for others. They often are used together to solve a particular corrosion problem (for example, protective coatings and CP are a common and effective combination). Around the globe, corrosion professionals have the training and experience to identify which methods are appropriate depending on the issues faced in the various locations and elements.
Corrosion-Resistant Materials
Is it a myth or fact that stainless steel is the most corrosion-resistant material that is commonly seen being installed even as handrails, house gates, or even vessels? The answer is that it all depends on the application and operating condition of the material. There is no material 100% resistant to all corrosive situations, but materials selection is critical to preventing many types of failures. When selecting a material, the required characteristics are to be defined in advance. If no material has every characteristic that a specific project requires, a corrosion control system will be required, or the service conditions must be adjusted to meet the characteristics of the candidate material. Factors that influence materials selection are corrosion resistance in the environment, availability of design and test data, mechanical properties, cost, availability, maintainability, compatibility with other system components, life expectancy, reliability, and appearance. Appropriate system design also is highly important for effective corrosion control. Design includes the consideration of many factors, such as materials selection, process and construction parameters, geometry for drainage, avoidance, or electrical separation of dissimilar metals, avoiding or sealing of crevices, corrosion allowance, operating lifetime, and maintenance and inspection requirements.
Putting a barrier between a corrosive environment and the material to be protected is a fundamental method of corrosion control. Imagine this as wrapping the metallic structure tightly to ensure no other contaminants being able to reach the metallic structure. There are many organic and metallic coating systems to choose from, and they are available in various combinations. Coating system selection is like materials selection in that many factors need to be considered, including types of exposure, operating conditions, substrate, ambient conditions during application, environmental regulations, cost, application during operation or shutdown, time constraints, new construction or maintenance, shop or field application, and design/fabrication considerations. Common coating application methods include brush or roller, spray, and dipping. In addition to proper coating selection and application methods, substrate preparation is critical to the success of the coating. The majority of coating failures are caused either completely or partially by faulty surface preparation,2 such as leaving contaminants on the surface or having an inadequate anchor (sand blast) pattern. For example, using the most expensive, most advanced coating formulation would not guarantee the structure from not corroding, if the fundamental criteria are not met.
Cathodic and anodic protection are forms of corrosion control which leverage electrochemical techniques, some even call these corrosion control methods as magic as it is not able to be seen by the naked eye! Cathodic protection (CP) is an electrochemical technique used on such facilities as pipelines, underground storage tanks, and offshore structures that makes the structure protected by a cathode relative to an external anode that discharges a protective current to all exposed surfaces. The source of the protective current may be an active (impressed current) or passive (sacrificial) system of galvanic anodes (utilizing magnesium, aluminium, or zinc). CP is widely used in several environments, including water and soil. It often is used in combination with protective coatings that reduce the exposed surface area to receive a protective current. An example of this being used hand-in-hand is seen on a vessel. The photo below shows how this method is applied. On the other hand, anodic protection has more limited, but important, applications in chemical environments. It is achieved by maintaining an active-passive metal or alloy in the passive region by an externally applied anodic current.
Corrosion inhibitors are substances that, when added to an environment to decrease the rate of attack on the asset. Inhibitors are commonly added in small amounts to acids, cooling waters, steam, and other fluids, either continuously or intermittently. They generally control corrosion by forming thin films that modify the environment at the metal surface. Some retard corrosion by adsorption to form a thin, invisible film of only a few molecules thick. Others form bulky precipitates that coat the metal and protect it from attack. A third mechanism consists of causing the metal to corrode in such a way that a combination of adsorption and corrosion products forms a passive layer.
Holistic Approach
What have the various stakeholders done to safeguard our nation’s assets and ensure the safety of our people, environment, and other assets? Is corrosion taken seriously by all? Or is it just being noted, and asset corrosion surveys being performed, just to satisfy regulations with minimal action to improve corrosion protection? A holistic approach to corrosion management, along with an undisputable level of integrity and technical knowledge is crucial in ensuring public safety and sustainability. The key here is to prevent any unwanted leaks or catastrophic asset damage that could be detrimental to society and the environment from occurring and increase the longevity of assets. With good corrosion management practices, various stakeholders such as in the situation of cross-country pipelines which share the same right of way (ROW) in certain areas, or even high voltage transmission lines or railways running on electricity within close proximity can understand the impact of one’s asset to the other, allowing for better corrosion mitigation plans to take effect, ensuring all assets are well maintained.
Society in Malaysia and globally will continue to face critical challenges in corrosion prevention and control, where aging equipment and infrastructure, new product formulations, environmental requirements, and strict budgets require corrosion control programmes that are designed by highly skilled professionals for specific situations. The fields of corrosion science and engineering are of utmost importance to develop the experience and tools necessary to successfully reduce incidences, problems, and expenses caused by corrosion. By following appropriate strategies and obtaining sufficient resources for corrosion programs, the best engineering practices can be achieved. The payoff includes increased public safety, reliable performance, maximized asset life, environmental protection, and more cost-effective operations in the long run. Policy makers, stakeholders, and most importantly authorities should work hand in hand towards creating awareness of corrosion and its proper mitigation methods to prolong asset life and ensure adherence to ESG.
REFERENCES
- Corrosion Basics—An Introduction, L.S. Van Delinder, ed. (Houston, TX: NACE, 1984).
- Corrosion, Faulty Concrete Suspected in Genoa, Italy Bridge Collapse, Global Resilience Institute at Northeastern University (2018)
- Environmental Catastrophe: Sinking of the Erika, Corrosion Doctors
- Rail Report Finds Corrosion Caused Signal Post to Fall Onto Lines Near Newbury," BBC (2015)
- Bhopal disaster: Causes, Effects, Facts, & History, Britannica (2024)
- R. Bickham, “Effects of Simulated Marine Environments on Steel in Concrete,” materialsperformance.com (2021).
- F. Byron, “Corrosion Impact of Offshore Platforms, Structures, and Vessels,” materialsperformance.com (2020).
- NACE International Basic Corrosion Course Handbook (Houston, TX: NACE, 2000).
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