Scientists have unlocked the secret behind a 1,600-year-old iron pillar in Delhi that remarkably defies the typical traits of iron by not rusting.
The recent study demystifies the enigmatic qualities of the iron pillar through findings that credit ancient Indian metallurgy with its enduring nature, Indy 100 reported.
Located in the ruins of a world heritage-listed temple in Delhi, the iron pillar not only stands as a testament to ancient engineering but also poses a scientific conundrum due to its corrosion resistance. The pillar measures 7.3 meters in height and weighs about 6.5 tonnes, withstanding centuries of environmental exposure without any sign of rust.
Historical records suggest the pillar was moved across India and originally cast during the reign of King Chandragupta II Vikramaditya, around 375 to 415 AD. Its surface bears an inscription in Brahmi script, dedicating it to the Hindu god Vishnu on the hill known as Viṣṇupada.
This artifact sparked numerous theories regarding its composition and origin, including speculations about advanced ancient civilizations and extraterrestrial interventions. Moreover, medieval traveler Ibn Battista remarked on the column's mystery, describing it as composed of a blend he referred to as ‘Haft Jûsh’ or ‘seven metals’, thought to imbue it with its imperviousness.
The controversy and awe generated by the pillar's enduring nature have made it a subject of study for years. Modern science, however, has begun to peel back the layers of myth surrounding the pillar.
Researchers from the University of Delhi have recently published a study in Applied Surface Science Advances that resolves much of the mystery. It turns out, that the pillar’s resilience is due to sophisticated iron purification and smithing techniques employed by ancient Indian metallurgists.
These metallurgists refined the iron to an astonishing purity of 98%, then hammered it to incorporate phosphorus-rich slag particles. This process not only strengthened the material but also enabled the formation of a unique microstructural feature – a thin protective film over the iron that drastically slows corrosion.
The study details how phosphorus present in the iron as ferric phosphate (FePO4) is oxidized to phosphate, which then acts as a corrosion inhibitor by forming protective oxide films around the metal.
The findings illustrate how ancient Indian smiths manipulated iron in a way that has preserved the pillar through the ages. "The corrosion resistant property of the sample of Iron Pillar in Delhi was mainly due to the mode of its fabrication resulting in high slag inclusions dispersed in three dimensions around the metal," noted the study.
Further deepening the understanding, researchers commented, "The pillar, renowned for its craftsmanship, flawless surface, and resistance to corrosion behavior, demonstrates an indisputable record of ancient Indian metallurgical and engineering marvel." Their work not only highlights the technical expertise of ancient smiths but also corrects many misconceptions about the pillar’s mystical attributes.
Far from the fantastical claims of otherworldly origins, the pillar’s true story is one of human innovation and the mastery of materials. "This goes against everything we know about metal, which is notoriously susceptible to elements," remarked an anonymous researcher, marveling at the ancient technology.
The Delhi iron pillar stands as both a monument to Vishnu and a testament to ancient Indian metallurgy, showcasing remarkable preservation over centuries. It highlights the advanced skills of ancient craftsmen, dispelling theories of extraterrestrial involvement and reinforcing their legacy of scientific achievement. This pillar serves as a lasting reminder of human ingenuity and knowledge.
