What is rust? How is it formed?

• Rust is an iron oxide, a usually reddish-brown oxide formed by the reaction of iron and oxygen.

• The nature of rust changes with time, reflecting the slow rates of the reactions of solids.

• The iron reacts with Moisture present in air and oxygen from the air to form hydrated iron(III) oxide, which we see as rust.

• Here is the word equation for the reaction

• Iron + water + oxygen → hydrated iron(III) oxide.

         Fe  + H2O  + O2    → Fe2O3·nH2O