(i) When metals come in contact with air and water then rusting takes place. In iron, rusting is a process in which iron is oxidised into ferric oxide (Fe₂O₃).

(ii) The presence of impurities in the iron like water vapours, acids, salts and carbon dioxide also responsible for rusting.

(iii) Iron does not rust in pure water which is free from dissolved salts.

(iv) Metals like chromium, zinc and magnesium prevent rusting. So zinc is used to galvanise the iron to prevent rusting of iron.