Pickling is a process in which metals are soaked in strong acidic solutions to remove the impurities on the metal or to produce an artificial tarnishing on the metals. Metals like silver, bronze which are in oxidised form may be converted from compound forms to simple forms with the help of pickling. The solutions onto which the metals are soaked are either hydrochloric acid or sulphuric acid. These are brought to high temperatures so that the metals soaked leaves behind the oxide layer on the surface of the solution.