Bharat Ek Khoj – Ancient Vigyan
The Rust-Resistant Iron Pillar
The Iron Pillar at Mehrauli in Delhi standing tall for the past 1600 years has attracted the attention of archaeologists and material scientists across the world because of its high resistance to corrosion. The base of the Pillar rests on a grid of iron bars soldered and is estimated to weigh more than 5,000 kilograms. The 23 feet 8 inches high Pillar made of 98 per cent wrought iron stands testimony to the high level of skill achieved by the ancient Indian metallurgists in the extraction and processing of iron.
According to researchers, the corrosion resistance results from an even layer of crystalline iron hydrogen phosphate film that serves to protect the Iron Pillar from corrosion. The presence of second-phase particles (slag and unreduced iron oxides) in the microstructure of the iron, that of high amounts of phosphorus in the metal, and the alternate wetting and drying existing under atmospheric conditions are the three main factors in the three-stage formation of that protective passive film.
-Dr Shobha Tawade
Team, ScienceNow Digital
