The Iron Pillar – “Rust Proof”!

If you are ever in Delhi and you have a few hours to do some sightseeing, even if you do not see anything else, do not miss seeing the iron pillar of Delhi. This pillar has been a curiosity for archaeologists, metallurgists & historians from the world over. In fact there are those who even believe it was forged by alien technology.

The iron pillar is located in the courtyard of the Qutub Minar complex in Delhi. So what makes this iron pillar so amazing?? The height of the pillar is 23 ft 8 in of which 3 ft 8 in is below the ground. The pillar’s lower diameter is 16 inches and this tapers to 12 inches at the top giving it a bell pattern. It weighs over 6 tons and is made up of 98% pure wrought iron. It is estimated to be 1600 years old and despite being exposed to the rains, winds and temperature fluctuations it has not rusted.

According to historians the pillar was erected by Chandragupta Vikramaditya ( 375 AD – 414 AD )of the Gupta dynasty. It served as a sun dial at Vishnupadagiri in Madhya Pradesh which was a center for astronomical studies. The pillar has an Sanskrit inscription in Brahmi script which states that it was erected in honour of Lord Vishnu and it also praises the valour & qualities of a king referred to as Chandra identified by historians to be Chandragupta Vikramaditya. It was moved to Delhi about a 1000 years ago.

In a report published in the journal Current Science, R. Balasubramaniam of the IIT Kanpur explained how the pillar's resistance to corrosion is due to a passive protective film at the iron-rust interface. 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-stages formation of that protective passive film.

There was a popular belief no doubt bolstered by Indian movies that it was considered good luck or your wishes would be granted if you could stand with your back to the pillar and make your hands meet behind it. A fence erected around the pillar in 1997, protects it from damage that might be caused by visitors.

While we’d like to credit the lack of corrosion of the pillar to metallurgical techniques or even alien technology, in fact the pillar is naturally rust-proofed by the accidental formation of a ‘passive protective film’

As they say “Truth is stranger than fiction”.