A 1,600-year-old iron pillar in Delhi has barely rusted — a metallurgical puzzle solved only recently.
The Delhi Iron Pillar (Gupta era, c. 400 CE), ~6m and ~6 tonnes of wrought iron, stands almost rust-free in the open air.
— Delhi Iron Pillar (Gupta era, c. 400 CE); IIT-Kanpur study, 2003
Corrosion science — passivation by protective surface films.
A genuine, defensible parallel.
The pillar is real, genuinely old, and genuinely rust-resistant — and the explanation is good science, not magic. In 2003, IIT Kanpur metallurgists showed the iron's unusually high phosphorus content (from the ancient charcoal smelting process) formed a thin protective layer of 'misawite' (an iron hydrogen phosphate hydrate) over centuries, which passivates the surface.
The honest notes: it isn't 'stainless steel' (it's phosphorus-rich wrought iron), Delhi's dry climate helps, and parts below ground have corroded more. But the craftsmanship — forge-welding tonnes of low-slag iron and inadvertently engineering corrosion resistance — is a legitimate ancient metallurgical triumph.