Mystery of Delhi's Iron Pillar unraveled

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Mystery of Delhi's Iron Pillar unraveled

 

Press Trust Of India

Thursday, July 18, 2002

 

New Delhi, July 18: Experts at the Indian Instituteof Technology have resolved the mystery behind the 1,600-year-old iron pillar in Delhi, which has never corroded despite the capital's harsh weather.

 

Metallurgists at Kanpur IIT have discovered that a thin layer of "misawite", a compound of iron, oxygen and hydrogen, has protected the cast iron pillar from rust.

 

The protective film took form within three years after erection of the pillar and has been growing ever so slowly since then. After 1,600 years, the film has grown just one-twentieth of a millimeter thick, according to R. Balasubramaniam of the IIT.

 

In a report published in the journal Current Science Balasubramanian says, the protective film was formed catalytically by the presence of high amounts of phosphorous in the iron—as much as one per cent against less than 0.05 per cent in today's iron.

 

The high phosphorous content is a result of the unique iron-making process practiced by ancient Indians, who reduced iron ore into steel in one step by mixing it with charcoal.

 

Modern blast furnaces, on the other hand, use limestone in place of charcoal yielding molten slag and pig iron that is later converted into steel. In the modern process most phosphorous is carried away by the slag.

 

The pillar—over seven metres high and weighing more than six tonnes—was erected by Kumara Gupta of Gupta dynasty that ruled northern India in AD 320-540.

 

Stating that the pillar is "a living testimony to the skill of metallurgists of ancient India", Balasubramaniam said the "kinetic scheme" that his group developed for predicting growth of the protective film may be useful for modeling long-term corrosion behaviour of containers for nuclear storage applications.

 

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And this today:

 

More research needed on Delhi Iron Pillar: experts:

 

[india News]: New Delhi, March 13 2005

 

The Delhi Iron Pillar, which has withstood corrosion for over 1,600 years, continues to attract the attention of archaeologists and scientists who want to undertake a systematic study to unfold the secret behind its strength.

 

A panel of scientists from across the country has recommended that the Government allow research on the pillar, a symbol of Indian metallurgical excellence, to ascertain its age, as well as for conservation of its underground part and the passive film that has preserved it through the ages.

 

"The Archaeological Survey of India has agreed to allow the use of well-established non-invasive techniques to ascertain as to when was the pillar built and its material aspects. But the efficacy of the techniques should be established by testing other ancient iron objects such as Iron Pillar at Dhar and Iron Beams at Konark," Director, Indira Gandhi Centre for Atomic Research, Dr Baldev Raj, who was a member of the panel that made the recommendations, said.

 

The panel had gathered here to review the status of scientific research on the pillar and make recommendations to the Government to initiate systematic scientific studies to gain more information about it.

 

Earlier studies, beginning in 1961, have thrown some light on the composition and the microstructure of the "rustless wonder", but difference versions exist on the scientific dating of the pillar, Professor R Balasubramaniam, a scientist at IIT Kanpur who has conducted extensive research on the pillar, said. PTI