Minerals and Metals in Ancient India v1.c27.s2.t2.36

v1.c27.s2.t2.36

Lahiri *et al.* (1963) found a corrosion loss of 5 μm/year after exposure of a small smaple from the Delhi iron pillar for 3-1/2 years at Jamshedpur. The rate is more than that of a copper-containing, slow-rusting steel kept at Delhi and of a normal carbon steel (of the composition of the Delhi iron pillar) exposed in Sweden. (Wranglén, 1970: 766) When a protective film is formed, its thickness increases according to the parabolic law: y² = K.t; with y = 5µm for one year, Wranglén calculated that for 1600 years, y = 200 µm which is in excellent agreement with the measurements by Bardgett et al. (1963).