The mystery of the 1,600-year-old stainless steel exposed iron pillar

Delhi Iron Pillar is one of the famous ancient monuments of India. Delhi is an iron pillar cast in the 5th century, erected by King Kumara Gupta I of the Gupta dynasty, who ruled north India in the period 320-540.

This column was originally part of the Muttra temple, with the Garuda idol on top. However, after this Hindu temple was destroyed by Qutb-ud-din Aybak to build the Qutub Minar and the Quwwat-ul-Islam mosque, it was the only remaining part.

The strange thing is that despite being exposed to the sun and rain outdoors for thousands of years, Delhi's iron columns show almost no signs of rust. For decades, metal scientists and engineers from around the world have proposed a series of theories about the properties of this unusual wonder.

Decoding the mystery of the thousand-year-old stainless iron pillar

It has a height of 7.2 m from the ground and a total weight of about 10 tons. Several hundred years ago it was moved to its current location. It has gone through more than 1,600 years of exposure to rain and sun but has not rusted at all. The inscriptions left on its body show that people built it to praise the Hindu god and King Chandra - a mysterious king who is still a puzzle to historians.

Legend has it that this iron pillar was cast to commemorate King Chamdaro.

But what surprises people is that the iron column has been standing in the open for more than 1,600 years, having gone through countless rains and winds until today, still not seeing a single rust stain.

Meanwhile, iron is a metal that easily rusts after a few decades, not to mention more than a thousand years.

Until now, Earth people have not found an effective method to prevent rust from iron objects. Although in theory, pure iron does not rust, pure iron is difficult to refine and the price is extremely high. Furthermore, some scientists have analyzed the composition of the iron column, discovering that it contains many impurities rather than pure iron. And in theory, iron columns rust more easily than regular iron.

If it is assumed that the ancient Indians soon mastered the technique of smelting stainless iron and this technique was lost, why did they not smelt other stainless iron items? Moreover, in the iron making books of ancient Indians, there is not a single line of record mentioning this issue.

That iron pillar stands alone, seemingly challenging humanity's intelligence and discovery. The sky is also a symbol of ancient Indian civilization.

Outdated technology creates extraordinary miracles

But finally, experts from the Indian Institute of Technology IIT have decoded the mystery of the longevity of the Delhi iron pillar. Observing through a microscopic microscope, they discovered an extremely thin layer of "coat" covering the entire surface of this pillar.

Taking samples for research, the composition of that shell was determined to be a compound of iron, oxygen and hydrogen. It is this compound that prevents the iron metal of the column from coming into contact with the air. Thanks to that, the chemical corrosion reaction cannot occur, making the iron column immortal.

Radioactive isotope analysis also showed that this protective layer began to form about three years after the iron pillars were made, meaning their lifespan is equivalent to the lifespan of the pillar. During more than a millennium, they continued to thicken year by year at a very slow rate. After 1,600 years, this crust has only reached a thickness of about 1/20 of a millimeter.

The ancient writing is still as sharp as if it had just been engraved, even though thousands of years have passed.

But how does this iron pillar have such a precious protective covering? The announcement of a research group has surprised scientists around the world: It was the outdated metallurgical technology of the fourth century that accidentally created this compound. Dr. Balasubramanian - head of the research team, said his team found an unusually high level of phosphorus in iron samples collected from this pillar.

The phosphorus ratio analyzed was more than 1%, much higher than the phosphorus ratio in today's modern irons, which is less than 0.05%. It is this high phosphorus content that acts as a catalyst, promoting the reactions that create the above protective substance.

This was an unintentional achievement, stemming from the very rudimentary metallurgical techniques of that time. Ancient Indians mixed coal with iron ore to shorten smelting time. With this method, the phosphorus contained in iron ore cannot be completely separated and remains in the finished iron.

Meanwhile, with modern iron smelting technology using blast furnaces, the phosphorus content can be reduced to very low levels. It is the purity created by modern technology that makes modern iron unable to have the same longevity as Delhi steel columns.

The findings of these scientists were further reinforced when people found a number of weapons such as swords, arrows, knives... in India that were of the same age as the Delhi steel pillars and were almost identical to them. Rusty. This confirms that it was the outdated metallurgical techniques of early times that created surprisingly precious masterpieces for future generations, making them last forever. The veil of mystery has been lifted for a long time by scientists.