Why Delhi's 1,600-Year-Old Iron Pillar Has Barely Rusted: The Science Explained

Anyone who has lived through a monsoon has seen what rain can do to iron. A gate starts turning orange. A railing begins to flake. A tool left outside gathers a rough reddish coat. Iron and rust usually go together.  That is what makes one pillar inside Delhi’s Qutub Complex so fascinating. For nearly 1,600 years, the Iron Pillar has stood in the open, facing rain, heat, humidity and pollution. By ordinary logic, it should have corroded much more by now. Yet the 7.2-metre-tall, six-tonne monument remains remarkably intact. For visitors, it may look like a simple old pillar. For scientists, ...