Direct current (DC) is necessary for plating because by moving electrons from the anode to the cathode it causes the metal of the anode (which has lost electrons) to oxidize into metal ions dissolving into the plating solution ... and metal to grow onto the cathode because the excess electrons there get neutralized by pulling metal ions out of the solution and reducing them to metallic form.

Although batteries can be used as the DC source for small tests and science projects, significant plating requires more powerful DC power supplies. Platers tend to call their DC power supplies "rectifiers".