Minerals and Metals in Ancient India v1.c27.s3.t1.6

v1.c27.s3.t1.6

Ghosh (1963) has extended Hadfield’s (1912) idea that ancient wrought irons being purer are more corrosion-resistant, but this view is not accepted by many modern scholars who attach greater importance to the environmental factors. Wranglén (1970: 767-69) favours the environmental theory and yet strikes a reconciliatory note by commenting that while the environmental factor may cause the variation of the corrosion-rate of similar samples by a factor of 100, there could be tenfold variation in the corrosion rates of different kinds of ferrous materials kept in the same environment. He also cites Evans (1955, 1957, 1960 and 1968) explaining the apparent rustlessness of some of the ancient iron samples in environmental terms. In the ancient eras, the environments were much less polluted with acidic oxides (CO₂ and SO₂), there being more ammonia from the biological waste-products contributing a passivating effect on the samples. “The initial conditions of exposure often determine the life of a metal in the atmosphere, and under favourable conditions, a protective layer of corrosion products is formed that protects the metal when the atmosphere becomes more polluted”.