Experience has shown that varies depending on the atmospheric corrosion due to geographical. For illustration, it is recommended that the region is divided into four categories, namely : rural, urban, industrial and coastal areas. Village is basically pollution - free area. Low population density in the area, only non - polluting industries. Residential, commercial and light industrial area of the city is typical, lightly polluted in the area, such as traffic pollution. Air pollution caused by industrial zone for heavy industry area. Pollution may be due to the formation of fuel gases, such as sulfur and nitrogen oxides, or chemical or other gas processing plants release. Suspended tour of particles in the air, like steel or iron oxide deposit of dust produced in the production process also makes the corrosion increased.