Corrosivity and durability maps of India

THE ATMOSPHERIC corrosion behaviour of engineering materials such as mild steel, zinc, galvanized steel, and aluminium has been studied at 40 exposure stations in India, and corrosion data from the sites have been collected for over 11 years, from 1993-2004. The data collected from these sites have been analyzed and presented in the form of updated corrosion maps of India. In these maps, the annual corrosion rate for each particular material have been arranged in four ranges, which are colour coded. An interesting feature of the maps is that the corrosion is area-specific, and not region-specific. The durability factor is defined as the ratio between the corrosion rate of mild steel and that of a non-ferrous metal exposed at a particular location. The durability data have been analyzed and are presented as durability maps of India. The data clearly indicate that non-ferrous metals, such as galvanized steel, zinc, and aluminium, have better corrosion resistance than bare mild steel. However, the factors vary from area to area. These data were calculated from one-year exposure studies. If the durability and the cost factors are taken together, it can be clearly seen that aluminium has an appreciable cost-benefit ratio; at certain locations, galvanized steel may also prove to be a cost-effective material.