February 1, 2026•14 min read
The 1,600-Year Corrosion Riddle: The Chemistry of the Delhi Iron Pillar
Standing more than seven metres tall in Delhi's Qutb Complex, the Gupta-era Iron Pillar has survived for over 1,600 years with remarkably little atmospheric corrosion. Modern metallurgical studies reveal that its unusual phosphorus-rich wrought iron, slag inclusions, forge-welded structure and protective phosphate and iron oxyhydroxide layers work together to slow rusting.
