Great inefficiencies may result if the entire CP system is not designed with the power supply in mind. Any reliable external source of DC current will suffice - the pipe doesn't care about the power source. Scrap iron is sometimes used as an anode simply because it is available. Non-uniform consumption, high rate of consumption, and discoloration of surrounding structures are distinct disadvantages. Graphite anodes are one of the most commonly used anodes for impressed current systems.
Most common applications are to protect underground structures.
Graphite anodes are suitable for deep, shallow vertical, or horizontal ground beds with carbonaceous backfill. High Silicon Cast Iron anodes are widely used in underground applications in both shallow and deep groundbeds. Specially formulated high silicon cast iron anodes are also used in seawater. Platinized Titanium anodes take advantage of the low consumption rate and high current density. Voltages in excess of 10 Volts will result in severe pitting of the titanium core causing premature failure.