Flexi Says: Rust is a result of chemical reaction where iron gets oxidized in presence of oxygen and moisture to form iron oxide. The chemical reaction for rusting is: 4Fe + 3O2 → 2Fe2O3. Iron is first oxidized to iron(II) ions by oxygen. In the second step, the iron(II) ions are further oxidized and combine with water and oxygen gas to produce a hydrated form of iron(III) oxide known as rust. Rusting is one of many example of corrosion. Corrosion is the deterioration of metals by redox processes. Corrosion causes enormous amounts of damage to buildings, bridges, ships, cars, and other objects.