Electrical equipment installed at industrial or commercial facilities could be exposed to both indoor and outdoor environment. Corrosive atmospheres are usually classified into four basic types, although most environments are mixed without any clear borderlines. These four types are indoor, rural, marine, and industrial. Atmospheric corrosion is accelerated by several environmental factors, such as elevated RH, high temperatures, presence of particulate matter and aerosols, and corrosive gases. The behavior of aerosol particles in outdoor atmospheres depends on their formation, movement, and capture. Oxidized forms of sulfur are generated as combustion products of sulfur-bearing fossil fuels such as coal, diesel fuel, gasoline, and natural gas. Bare aluminum is used in the electrical industry to manufacture busbars, transmission and distribution conductors. The usual corrosion behavior in the atmosphere involves pitting and roughening of the surface with a fairly large decrease in the corrosion rate.