Certains des effets de la corrosion comprennent une détérioration importante des monuments naturels et historiques. La pollution de l’air entraîne la corrosion et elle prend de l’ampleur dans le monde entier.
L'une des conséquences de la pollution atmosphérique dont on parle rarement est l'effet de la corrosion sur les matériaux synthétiques à travers le monde. Les niveaux de corrosion ont augmenté en conséquence avec l’intensification de la pollution atmosphérique dans les pays industrialisés. Comment se forme la corrosion ? Quels en sont les effets sur l’environnement et la santé ? Comment la prévenir ?
Selon EonCoat, la corrosion est le processus de dégradation d'un matériau provoqué par une réaction chimique avec son environnement. La corrosion du métal se produit lorsqu'une surface exposée entre en contact avec un gaz ou un liquide, et lorsque le processus est accéléré par l'exposition à la température chaude, aux acides et aux sels.
La corrosion, processus chimique, survient donc quand le métal rencontre l'oxygène et l'humidité. Ce contact le transforme en une "batterie" électrochimique. Une zone du métal devient l'anode, perdant des électrons et s'oxydant, tandis que la cathode reste intacte. La perte d'électrons à l'anode forme de l'oxyde métallique, ou rouille. L'eau et l'oxygène dans l'air favorisent ce processus, la pollution et les variations de température peuvent l'amplifier, accélérant ainsi la corrosion. La raison en est que les contaminants aéroportés tels que les matières particulaires naissent suite à des réactions chimiques entre liquides et solides. Ces mêmes liquides et solides, notamment le sel et le carbone noir, peuvent interagir avec les molécules contenues dans les métaux et accélérer la désintégration.
Bien que le mot « corrosion » soit utilisé pour décrire la désintégration des métaux, tous les matériaux naturels et synthétiques sont sujets à la dégradation.
What Is Corrosion?
Corrosion is the process of decay on a material caused by a chemical reaction with its environment. Corrosion of metal occurs when an exposed surface comes in contact with a gas or liquid, and the process is accelerated by exposure to warm temperature, acids, and salts.
Although the word ‘corrosion’ is used to describe the decay of metals, all natural and man-made materials are subject to decay, and the level of pollutants in the air can speed up this process.
The reason is that airborne contaminant such as corrosive particulate matter (PM) are created because of the 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 decay. Additionally, gaseous acidic contaminants have a major role in corrosion of materials, either directly or indirectly as precursors of corrosive particulate matter (PM).
In fact, sulfur dioxide that is generated by power plant and vehicle emissions is one of the biggest contributors to corrosion. Sulfur dioxide is particularly aggressive towards copper contacts used in electronic equipment.
High levels of sulfur dioxide can also damage trees and plants by destroying foliage and inhibiting future growth. A recent analysis from Greenpeace also states that high levels of sulfur dioxide result in disastrous air pollution and premature deaths as well. (1)
In other words, sulfur dioxide doesn’t just help degrade metal and other materials; it also results in disastrous air pollution has some harmful health effects. The U.S. Environmental Protection Agency (EPA) has found that short-term exposure to sulfur dioxide can worsen asthma symptoms and make breathing difficult. (2)
Atmospheric Corrosion Study Sheds More Light
A recent atmospheric corrosion study has helped to shed more light about how airborne pollutants directly affect metals in an industrial city environment.
Researchers began with the thesis that atmospheric corrosion of metals and their alloys is very common in the industrial city environment due to the high concentration of corrosive pollutants in the air. (3)
In other words, researchers theorized that air pollution in a major city would accelerate the corrosion process and help degrade metals faster than if the pollution was at a lower level.
To test this theory, researchers exposed various metal samples to an industrial city environment for 12 months to determine the effect of airborne particulates on the rate of corrosion. They chose an area within the test city that had a high level of pollutants.
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 generated by nearby power plants and heating plants, as well as from vehicle emissions and heating furnaces that were in wide use due to the cold weather.
The most common pollutants that accelerated corrosion were sulfur dioxide, carbon dioxide, dust and humidity.
Additional contaminant resulting in high levels of corrosions include hydrogen sulfide generated by waste facilities, geothermal activity or anaerobic digestion of organic waste; nitrogen dioxide from traffic and combustion processes, hydrochloric acid, chlorine, acetic acid (the vinegar molecule) and process chemicals released to the environment.
Corrosion Hazards for Electronic Equipment
Corrosion induced equipment failure has been a fact since the mechanical telephone switch centres in the beginning of the 19th century.
The extensive use of computers and electronic equipment in today’s society together with increasing pollution, especially in large cities and in industrial locations put even higher demands on finding solutions to lower the risk of failure.
Currently, communication and data transfer facilities are of great importance. One way to reduce the cost for cooling is to use “free cooling” or “air-side economizers” which refers to systems that allow outdoor air to by filters pass into the room to provide direct cooling when outdoor temperature and humidity permits. Download our White paper on Corrosion Hazards for Electronic Equipment here.
Les fortes concentrations de dioxyde de soufre peuvent nuire aux arbres et aux plantes en détruisant leur feuillage et en entravant leur croissance. Une étude récente de Greenpeace (classement des points chauds de la pollution atmosphérique mondiale par le SO2) indique également que de fortes concentrations en dioxyde de soufre peut fortement polluer l'air et entraîner des morts prématurées.
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