How does rusting of iron occurs?
When an iron object is left in damp air for a considerable time, it gets covered with a reddish-brown flaky substance called rust. This is called rusting of iron.
It occurs in the presence of oxygen and water.
$$Iron(Fe) + Oxygen(O_2 ) + Water(H_2O) \rightarrow Rust(iron\ oxide \ Fe_2O_3)$$