Rusting of iron refers to the formation of rust, a mixture of iron oxides, on the surface of iron objects or structures. This rust is formed from a redox reaction between oxygen and iron in an environment containing water (such as air containing high levels of moisture). The rusting of iron is characterized by the formation of a layer of a red, flaky substance that easily crumbles into a powder.
Chemically, rust is hydrated ferric oxide (Fe2O3.nH2O)
Rust is hydrated iron (III) oxide (Fe2O3.xH2O). The rusting of iron is a chemical change because we cannot get back pure iron from rusted iron by reversing the conditions.