Definition - What does Atmospheric Air mean?
Atmospheric air is the air which is prevailing under atmospheric conditions. Atmospheric conditions are different for different locations and patterns of wind. Atmospheric air is corrosive in areas where corrosive pollutants are present or emitted.
Since atmospheric air compositions and its ability to cause corrosion are not same for different settings, the air from industrial settings is more corrosive than from other areas. Generally atmospheric corrosion is caused by the presence of corrosive pollutants (such as sulfur and carbon oxide) and moisture in the air.
Corrosionpedia explains Atmospheric Air
The main components of atmospheric air are nitrogen and oxygen. Both of them form 99.03% of clean, dry air. Other contents are water vapor and trace gases, which account for roughly 0.25% and 0.97% of the atmosphere by mass respectively. Among the trace gases, greenhouse gases are prominent. The corrosion ability of atmospheric air is primarily dependent on how much pollutant it contains. The pollutant contents are not uniform in different atmospheric settings.
Atmospheric air is more polluted in an industrial areas. Air from these areas contains high levels of sulfur compounds like sulfur dioxide (SO2), causing acid rain, and nitrogen oxides (NOx). When dew or fog are added to the acid rain, it causes an extremely wet, corrosive environment. The different types of chlorides also contained in atmospheric air are much more corrosive than the acid sulfates.
Atmospheric air in marine environments is laden with mist of fine particles of chloride salts. In extreme weather conditions, it forms a highly corrosive salt crust on the environment.
Atmospheric air in rural areas is generally harmless, and does not contain hazardous pollutants. When there is little or no rainfall, high relative humidity and occasional condensation occur. These conditions cause the production of a highly corrosive environment.
Atmospheric air in urban areas is similar to rural air. In these areas very little industrial activity is seen and pollution is mainly from automobiles and domestic fuel emissions.