Atmospheric corrosion of 18 years study

Abstract

The enormous loss caused due to corrosion of metal is a great economic concern of each and every country to-day. In India, premature failure of machinery, equipment, structural breakdown, explosion due to leakage of inflammable gases or liquid from corroded pipelines, contamination of products/water, etc. lead to losses around Rs 8000 crores/annum ($2800 million). The National Metallurgical laboratory and other Govt. organizations have been active in the study of atmospheric corrosion since their inception. They have carried out extensive research on different aspects of corrosion, including atmospheric corrosion of metals, alloys and coated panels in both industrial and marine atmospheres. In view of the importance of corrosion in coastal regions, and the acute corrosion problem being faced by India's growing navy and her sea going vessels, installations in sea, etc.. Marine Research Stations have been established at Digha. A mass of data has been collected on corrosion rates of ferrous and non-ferrous metals and alloys, using modem technique;. Atmospheric pollution, relative humidity, state of exposure and composition of material has been found to have great influence on corrosion rate. Comparative corrosion rate plotted against time of exposure have shown decreasing corrosion in the order of low alloy steel and mild steel, On prolonged exposure, the tow alloy steel shows lower corrosion rate. Cu, Ni, and Cr contribute in decreasing the corrosion rate of steel. Some selective coatings are very effective in both marine and industrial atmospheres. Meteorological and pollution data were collected and co-related with the corrosion rates. Based on the atmospheric data, Corrosion Map of India has been published. Under the collaborative project with NRIM, Japan and TISCO, some of Japanese and TISCO steels were exposed at both Industrial and Marine atmospheres. The data and the methodologies adopted are discussed in detail in this talk.