Why iron pillar is not rusted?

Iron pillar usually rusts as iron reacts with water and oxygen to form hydrated iron (III) oxide, which forms rust.

Iron + Water + Oxygen -------> Hydrated Iron (III) Oxide

Fe  + H2O + O2    → Fe2O3·H2O

In Delhi, the Iron pillar of Qutub Minar does not rust as it is passively protected with 98% Wrought Iron. A high concentration of phosphorus (around 1%, which is higher than 0.05% in today's iron) and the absence of sulfur or magnesium in the iron are responsible for the protection of iron from rusting.
A thin film of misawitea (formed due to the presence of phosphorus in iron), a compound of iron, oxygen, and hydrogen, slowed down the rusting of the iron pillar.


Simply Easy Learning

Updated on: 15-Mar-2023


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