Short communication on role of different variables on atmospheric corrosion in marine environment-Effect of proximity to sea

Abstract

Among the variables influencing the extent of atmospheric corrosion of metals and alloys in marine corrosion of metals and alloys in marine conditions, salinity of the atmosphere plays an important role. Chloride particles are carried mechanically by the wind as fine water droplets and, therefore, the amount of chloride in air decreases with increasing distance from sea. As a result, corrosion of metals and alloys is also affected as one moves away from sea. Doyle and Goddard1-3 exposed aluminium wires wound on steel bolts for a period of 3 months at different distances from the sea at Durban, Port Elizabeth and East London and found that after a rapid fall within the first half-mile distance, the corrosivity of the atmosphere became more or less constant up to five miles. One interesting observation made by them at Durban was a slight increase in the corrosivity from the one-mile to the five-mile points though no reason could be attributed by them to this upward trend. Earlier studies4.5 carried out on atmospheric corrosion at different locations in India revealed that corrosion rate of mild steel at Digha was one of the highest in India and that there was a marked effect of proximity on corrosion rate4.6. A more systematic and detailed study was, therefore, undertaken to determine the factors influencing the atmospheric corrosion rate at Digha. The data obtained over a period of two years have been presented in this communication. (Shri D.K. Basu, Senior Laboratory Assistant; and Shri D.K. Khan, Senior Technical Assistant; National Metallurgical Laboratory)