Pollution's Impact: Corrosion's Unseen Enemy

Atmospheric corrosion is the most common form of corrosion, and it occurs when materials are exposed to air and its pollutants. Air pollution has been shown to have a significant impact on corrosion, with airborne contaminants such as corrosive particulate matter (PM) accelerating the decay of materials. This process is particularly pronounced in industrial cities, where high concentrations of corrosive pollutants in the air can lead to increased corrosion of metals and their alloys. The effects of corrosion are wide-ranging, from the deterioration of natural and historic monuments to the increased risk of equipment failures. With an estimated annual cost of $2.2 trillion worldwide, corrosion has a significant impact on the economy, highlighting the importance of corrosion management and the use of environmentally friendly compounds to protect materials from degradation.

Pollutants such as carbon dioxide and nitrogen oxide corrode materials like carbon steel and copper

Carbon steel and copper are two of the most widely used engineering materials. They are used in a variety of applications, including marine, power plants, transportation, pipelines, and construction. Despite their popularity, both materials have limited corrosion resistance. Atmospheric corrosion is a significant concern for these materials, especially in the presence of pollutants such as carbon dioxide and nitrogen oxide.

Carbon dioxide (CO2) is a well-known contributor to corrosion, often referred to as acid corrosion or sweet corrosion. When CO2 dissolves in water, it forms carbonic acid (H2CO3), which reduces the pH of the fluid and leads to corrosion. This type of corrosion is uniform and results in metal loss. The presence of water is crucial for CO2 to cause corrosion, as dry CO2 itself does not corrode metals. The concentration of CO2 and the presence of water, temperature, pressure, and other factors influence the corrosion rate.

Copper, widely used in water supply systems, is also susceptible to corrosion by carbon dioxide. The corrosion rate of copper increases with the concentration of free carbon dioxide in the atmosphere. This is because CO2 provides water with H+ ions, which assist in the reduction of dissolved oxygen, initiating the oxidation of copper.

Nitrogen oxides, including nitrogen dioxide (NO2), also contribute to the atmospheric corrosion of metals such as steel, copper, and zinc. The detrimental effects of nitrogen oxides on these materials are not yet fully understood, but they can have a significant impact on their corrosion behaviour.

In addition to carbon dioxide and nitrogen oxides, other pollutants such as sulfur dioxide (SO2) and oxides of nitrogen can also accelerate the corrosion of carbon steel. The presence of these pollutants in the atmosphere can increase the corrosion rate, with SO2 having a more substantial effect.

To mitigate the effects of corrosion caused by pollutants, protective measures such as surface treatments, galvanization, and the use of high-efficiency air filters can be employed. Additionally, in the case of carbon steel, small additions of copper, chromium, nickel, and phosphorus can significantly reduce the corrosion rate in certain environments.

Sulphur dioxide, a product of power plants and vehicle emissions, is one of the biggest contributors to corrosion

Sulphur dioxide is a colourless, odorus gas that is soluble in water. It is a by-product of the combustion of fossil fuels, particularly coal, which contains sulphur. As such, power plants and vehicle emissions are significant contributors to the release of sulphur dioxide into the atmosphere.

Sulphur dioxide is a major air pollutant, particularly in urban and industrial areas. It is corrosive to metals and alloys, except for silver and gold. When sulphur dioxide combines with other pollutants and moisture, it forms corrosive layers on metals. This is because, in the presence of moisture, sulphur dioxide tends to form sulphuric acid. The oxidation of sulphur dioxide forms sulphate ions in the surface moisture layer, and this is considered the main corrosion-accelerating effect of the gas.

The corrosion caused by sulphur dioxide is particularly aggressive towards copper contacts used in electronic equipment. Sulphur dioxide emissions can also damage trees and plants by destroying foliage and inhibiting future growth.

A study exposed various metal samples to an industrial city environment for 12 months to determine the effect of airborne pollutants on the rate of corrosion. The study found that metals corroded at a much faster rate during the winter when pollution levels were at their highest. This increase in pollution was caused by higher emissions from power plants and heating plants, as well as vehicle emissions and heating furnaces. Sulphur dioxide was one of the most common pollutants that accelerated corrosion, along with carbon dioxide, dust, and humidity.

The effects of corrosion caused by sulphur dioxide emissions can have a significant impact on infrastructure and equipment. This includes damage to steel-reinforced highways, electrical towers, parking structures, bridges, commercial airplanes, vehicle electronics, hard disks, computers, server rooms, and museum artefacts.

Air pollution causes corrosion, and the rise in pollution levels has led to a corresponding increase in corrosion

Air pollution is a significant cause of corrosion, and as air pollution levels have risen, so too has corrosion. Atmospheric corrosion is the degradation of materials exposed to air and its pollutants. This process of decay is accelerated by exposure to warm temperatures, acids, and salts. All natural and man-made materials are subject to decay, and air pollution can speed up this process.

Airborne contaminants such as corrosive particulate matter (PM) are created by chemical reactions between liquids and solids. These same liquids and solids, including salt and black carbon, can interact with the molecules within metals and accelerate their decay. Gaseous acidic contaminants, such as sulfur dioxide, play a major role in the corrosion of materials, either directly or as precursors of corrosive PM. Sulfur dioxide is one of the biggest contributors to corrosion and is particularly aggressive towards copper contacts used in electronic equipment. It is generated by power plants and vehicle emissions, which release harmful pollutants such as nitrogen oxides, particulate matter, and sulfur dioxide.

The effects of corrosion are wide-ranging and include damage to vehicles, household electronics, outdoor furniture, household tools, and even historical monuments. It can also cause significant deterioration to important infrastructure such as highways, electrical towers, parking structures, and bridges. The annual cost of corrosion worldwide is estimated to be $2.2 trillion, or 3 to 4% of the GDP of industrialized countries. This significant cost reflects a lack of understanding of the consequences of corrosion and the critical need to control it.

To prevent corrosion, there are several methods that can be employed. Surface treatments and galvanization can be used to protect metals from airborne pollutants. Additionally, investing in high-efficiency air filters can improve indoor air quality and eliminate harmful pollutants that contribute to corrosion.

Corrosion can be prevented by using surface treatments, galvanizing metal products, and investing in high-efficiency air filters

Corrosion is a natural process that occurs when metals react with their environment. This can be accelerated by exposure to warm temperatures, acids, and salts. Airborne contaminants, such as corrosive particulate matter (PM), are created by chemical reactions between liquids and solids, which can interact with metal molecules and speed up decay.

There are several ways to prevent corrosion caused by pollutants. Firstly, surface treatments can be applied to metals to protect them from airborne pollutants. This involves a series of operations, including cleansing, the removal of loose material, and physical and/or chemical modification of the surface. Correct surface preparation is vital to the success of any surface treatment. It ensures the coating properly adheres to the substrate material, increasing the durability of the adhesion bond.

Secondly, galvanizing metal products can make them more resistant to corrosion. This process involves coating steel or iron with a layer of zinc, which acts as a barrier between the metal and its environment. Zinc is a highly corrosion-resistant material and will corrode before the underlying steel does, even if the coating is scratched.

Lastly, investing in high-efficiency air filters can improve indoor air quality and eliminate harmful pollutants that contribute to corrosion. These filters can be used in conjunction with air-side economizers, which allow outdoor air to pass through filters and provide direct cooling, to further reduce the risk of corrosion.

Atmospheric corrosion is the most common form of corrosion, and it is accelerated by air pollution

Airborne contaminants, such as corrosive particulate matter (PM), are created through chemical reactions between liquids and solids. These same liquids and solids, including salt and black carbon, can interact with the molecules within metals, accelerating their decay. Gaseous acidic contaminants play a significant role in the corrosion of materials, either directly or as precursors of corrosive particulate matter.

The impact of air pollution on corrosion is evident in a study conducted in Oman, which revealed that copper and mild steel are highly susceptible to corrosion, while stainless steel, aluminum, and epoxy are more resistant. The results also showed that locations closer to the seacoast, such as the Airport and Sohar areas, had higher concentrations of chlorides, contributing to corrosion.

The effects of atmospheric corrosion are far-reaching, impacting natural and historic monuments, vehicles, household electronics, outdoor furniture, and even communication and data transfer facilities. The annual cost of corrosion worldwide is estimated at $2.2 trillion, highlighting the economic significance of addressing this issue.

To mitigate the effects of air pollution on corrosion, various methods can be employed, including surface treatments, galvanization of metal products, and the use of high-efficiency air filters to improve indoor air quality and eliminate harmful pollutants.

Frequently asked questions