Atmospheric corrosivity Survey of India

atmospheric corrosion accounts for many failures in terms of cost and tonnage. The aggressiveness of an atmospheric environment can be assessed by measuring the limatic and pollution factors, or by determining the corrosion rates of exposed metals and coatings. Corrosivity of the atmosphere in a particular area is important in the selection of materials and suitable protective coatings. A corrosion map is useful, as it gives a general or broad indication of the corrosivity of the atmosphere in different locations in the country. It has been customary to classify environments as rural, urban, industrial, marine, or combinations of these. Rural environments generally are the least corrosive and normally do not contain chemical pollutants, but do contain organic and inorganic particulates. The urban environment is similar to the rural ty. *p e, in that there is little industrial activicy. Industrial atmospheres are associated with heavy industrial manufacturing fa-I cilities and can contain concentrations of I sulfur dioxide (SO,), chlorides, phosphates, and nitrates. Fine wind-swept chloride particles deposited on surfaces characterize the marine atmosphere