Rusting is an example of a corrosion reaction involving iron coming in contact with oxygen. All metals corrode over time thanks to their reaction with oxygen.
Iron rusts when it comes in contact with oxygen or water, according to the Franklin Institute. Iron and oxygen combine to form iron oxide, or rust, using the chemical formula 4Fe + 3O2 = 2Fe2O3. Oxidation, or loss of electrons, occurs when oxygen molecules react with iron and remove electrons from the iron. The electrons lost from the iron travel through water. The presence of salt increases the rate in which the iron rusts because the salt increases the conductivity. This in turn allows electrons to travel through water more quickly.