Dhar pillar

During the Gupta Dynasty (320—480 A.D.) the production of iron in India achieved a remarkable degree of sophistication as attested by the Dhar Pillar, a seven-tonne, one-piece iron column made in the fourth century A.D. This implies that the production of metallic iron from the ores was a well-established process, and the people involved at that time were aware of the reverse reaction involving the oxidation of iron to produce the oxide (the familiar rusting of iron). 

R. Balasubramanium, A.V. Ramesh Kumar, Corrosion Resistance of the Dhar Iron Pillar, Corrosion Science, 45, 2451-2465, 2003. 

Several large masses of iron are to be seen in India made many centuries ago by welding together small blooms, obtained by the direct process and weighing several pounds each. That such huge masses could be constructed is a remarkable tribute to the skill of the early Indian metallurgists. The most famous of these are the Delhi Pillar, the Dhar PillarJ and the iron beams from the Black... 

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