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HomeOPINIONWhy doesn’t the Iron Pillar at Delhi rust despite heat, rain, or...

Why doesn’t the Iron Pillar at Delhi rust despite heat, rain, or dust?  

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Isn’t it strange that the Iron Pillar of Delhi at Mehrauli didn't rust or corrode despite being continuously exposed to heat, rain, humidity, air, and dust for nearly 1,600 years?

Most people must have heard of the famous Iron Pillar of Delhi at Mehrauli. However, perhaps none of them would have bothered to wonder why this pillar didn’t rust or corrode despite continuous exposure to the elements (heat, rain, humidity, open air, and dust etc.) for nearly 1,600 years?

Bodies of brand new cars, produced by the most modern technology of this age, develop rust on all those areas that are not protected by several layers of special car paint after just one rainy season and driving on muddy roads! Should not the fact of this pillar having valiantly weathered the ravages of everything that fell upon it for 1,600 years and still not rusting have amazed you and rattled your mind?

Most probably you have just not bothered to think about it. Reason is most Hindus have been brainwashed by the Nehruvian education system into ignoring the great scientific achievements of our ancestors, not to speak of taking any pride in the glorious heritage. Hardly any domestic tourist visits the place specifically for seeing this pillar and admiring the wonder. Most people go for seeing the so-called Qutb Minar and might just happen to glance at it in passing. What a pity!

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The Marvel That Is the Iron Pillar of Delhi

In a previous article, ‘Hindus Made the Best Steel and Swords in the World’, we saw that the steel produced by the Hindus was famous throughout the world even 2,350 years ago in recorded history and probably much before that! The Iron Pillar of Delhi is yet another living monument of the great progress that the Hindus had made in the field of metallurgy and chemistry, even as the rest of the world was centuries behind coming anywhere close to it.

This pillar is taller than 8 metres (7.21 metres above ground and 1.12 metres below ground with a diameter of 42.4 cm at the bottom and 30.1 cm at the top). It weighs more than six tons and was made by forge-welding iron blocks of appropriate sizes.

It is generally believed to have been built by the famous king of the Gupta dynasty, Chandragupta Vikramaditya / Chandragupta II who ruled during 375 to 415 AD. This is also confirmed by an inscription on the pillar which is dated 400-450 AD. This inscription of six lines in Sanskrit says that Raja Chandra erected this as the Dhwaj Stambh (flag pole) of Bhagwan Vishnu in Vishnupadgiri. This place Vishnupadgiri has been identified as the current Udaygiri near Sanchi in Madhya Pradesh.

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It is believed that when King Anangpal Tomar established Delhi in the 11th century, he got it moved here. Since then, it has defied all odds there. Even the barbarian invaders over the centuries could not harm it. In 1739, a last attempt was made when Nadir Shah ransacked Delhi and he also wanted to destroy it. They fired cannon balls at it but they could not break it and the pillar stood proudly as ever. Marks of the cannon balls hits can be seen on it even now.

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There Are Many Other Similar Marvels of Iron in the Country

Lest someone think that it was a one-off wonder, I must hasten to inform that this is not the only iron structure in the country that has resisted rust or corrosion of any other kind. There are other structures of the same property and this confirms that the great knowledge of chemistry and metallurgy that enabled the ancient Hindus to produce such iron was not accidental knowledge. How they acquired that knowledge, is lost in the mists of time. However, the very fact that people thousands of kilometres apart from each other had the same knowledge shows that the Hindus as a homogenous and solid religio-cultural nation exchanged knowledge widely and freely even if political unity amongst kings was lacking.  

Fragments of Iron pillar at Dhar near Indore in Madhya Pradesh

We have the Iron Pillar at Dhar near Indore. It was of a similar size, being nearly 13 metres tall and 7.3 tons in weight. Now it is found lying in three fragments, all without rust. It was built most probably by the legendary king famous as Raja Bhoj of the Parmar dynasty in mid-11th century, who was a great patron of scholars of all fields. It is believed that he himself was an expert in metallurgy and wrote a book on metallurgical processes and metal weapons, called Yuktikalpataru.

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We have similar pillar at the Mookambika Temple at Kodachadri Hill, Kollur in coastal Karanataka. The temple was built in the 8th century. Legend is that Adi Shankaracharya himself had installed the deity there.

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Then we have the world-famous gigantic Sun Temple at Konark, near Puri built in the 13th century. In this temple, 29 iron beams have resisted rust and corrosion despite being so close to the sea and its salty coastal air. The largest of them is nearly 11 metres long and has a cross section of 28×28 cm and weighs nearly 2.7 tons. Iron nails are used to connect stone pieces and they have also not rusted. In the 12th century Gundicha temple at Puri (also known as the Garden House of Jagannath), there are 232 iron beams, the longest of them being over 5 metres in length.  All of these iron structures have resisted rust and corrosion for centuries.

Chemical Secrets of the Iron That Does Not Rust

In modern parlance, the Iron Pillar of Delhi is made of wrought iron as are other structures. Now what is wrought iron? Two forms of iron are obtained by smelting. One is cast iron and the other is wrought iron. Smelting is the process of applying heat and a chemical reducing agent to an ore to get the base metal from it. Cast iron is an alloy of iron that contains 2 to 4 per cent carbon, along with varying amounts of silicon and manganese and traces of impurities. Producing cast iron is cheaper than producing wrought iron, but it is more brittle and inferior in tensile strength. Wrought iron, on the other hand, is a ductile, fibrous variety that is produced from a semi-fused mass of relatively pure iron globules partially surrounded by slag. It usually contains less than 0.1 per cent carbon and 1 or 2 per cent slag. Slag, a by-product of smelting, is mainly a mixture of metal oxides and silicon dioxide.

Over the years, scientists have unearthed the chemical composition of our Iron Pillars. The conclusive finding is that of G. Wranglen in his 1970 research paper ‘The rustless iron pillar at Delhi’ in the journal Corrosion Science. His detailed chemical analysis found that the Iron Pillar at Delhi has 99.395% pure iron besides 0.25% phosphorous, 0.15% carbon, 0.005% sulphur, 0.05% silicon, 0.02% nitrogen, 0.05% manganese, 0.03% copper and 0.05% nickel. Iron structures at other places have almost similar compositions.

How this composition resists rust and corrosion has been the subject of fascinating research by many scientists. A very convincing explanation has been furnished by R. Balasubramaniam of the Department of Materials and Metallurgical Engineering, IIT, Kanpur in his 2000 research paper ‘On the corrosion resistance of the Delhi iron pillar’ in the journal Corrosion Science. Though the full explanation would be beyond most readers, I would simplify it.

We must first understand how rust forms. Rust is formed when a complex of oxides and hydroxides of iron are formed as a result of reaction with air and water. Rust forms on the surface of iron and is soft, porous and crumbly. It flakes off as more and more rust forms and eventually the iron crumbles away.

If you look up the article on ‘Rust’ in Wikipedia, you would find a highly illustrative photograph of heavy rust on the links of a chain near the Golden Gate Bridge in San Francisco; due to exposure to moisture and salt spray, causing surface breakdown, cracking, and flaking of the metal. You then compare it with the photo of the Iron Pillar at Delhi and your jaws would drop as the Golden Gate Bridge was completed in 1937, by which time the science of metallurgy was highly developed. 

Balasubramaniam found that the secret of corrosion resistance of our iron lies in the presence of phosphorous with iron. Corrosion is resisted because a protective passive layer is formed on the external surface of the structure as a result of chemical reactions with air and water that would, in the normal course, cause rusting. However, due to the presence of phosphorous in the given amount, a very thin film of crystalline Iron Hydrogen Phosphate Hydrate forms at the interface of metal and metal oxide and over it Ferric Oxyhydroxide and magnetite in non-crystalline (that is, amorphous) form. The crystalline Iron Hydrogen Phosphate Hydrate has extremely low porosity, which helps in corrosion resistance. 

The theory has been confirmed by analysing a similarly rust and corrosion-resistant piece of iron from the same period. This was obtained from an iron clamp that was removed from one of the stone blocks in the ruined Gupta temple at Eran, Madhya Pradesh.

Never Cease to Wonder and Lament

Now you must wonder at several things. First, how did they get iron of that high purity in the first place? Iron of such purity is not naturally available in our mines nor was it ever available. This means that it was refined by some process. That knowledge, by itself, is astounding. Second, how did they figure out that the thing critical to rust and corrosion resistance is phosphorous and that too in a certain percentage besides extremely low levels of sulphur and manganese? Third, how did they forge-weld pillars of such gigantic sizes and were still able to erect them without any mishap.

In all fairness, there is no reason to even suspect that the knowledge was obtained accidentally. Considering that we had made great progress in many other fields, it stands to reason that the knowledge was indeed the result of centuries old great tradition of brilliant scientists (that is, rishis, acharyas and scholars) devoting their entire lives in serious scientific research in their universities, gurukuls and hermitages.

Also Read: Hindus made the best steel and swords in the world

It rends my heart that generations of Indians who studied in schools and colleges after independence have been denied the knowledge of such wonders just because one man, Nehru in his twisted notions of modernity, hated the Hindu heritage. Back in 1881, even a British economic geologist V. Ball had felt obliged to conclude, “It is not many years since the production of such a pillar would have been an impossibility in the largest foundries of the world, and even now there are comparatively few places where a similar mass of metal could be turned out.” The greatness that an intellectually honest Englishman conceded so candidly, Nehru refused to even acknowledge. What ought to have been invariably taught in schools and colleges and made the topic of research in universities was sought to be side-lined to obscurity. 

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Dr N C Asthana IPS (Retd)
Dr N C Asthana IPS (Retd)
Dr. N. C. Asthana, IPS (Retd) is a former DGP of Kerala and ADG BSF/CRPF. Of the 56 books that he has authored, 20 are on terrorism, counter-terrorism, defense, strategic studies, military science, and internal security, etc. They have been reviewed at very high levels in the world and are regularly cited for authority in the research works at some of the most prestigious professional institutions of the world such as the US Army Command & General Staff College and Frunze Military Academy, Russia. The views expressed are his own.


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