A cathodic protection system uses galvanic anodes, an impressed current system, or a combination of both. The cathodic protection system should provide sufficient and well-distributed currents to the ship hull steel surfaces so that the surfaces can be polarised to the potential within the limits given by the protection criteria (refer to this chapter, Sect. 2.3) over the design life (refer to this chapter, Sect. 2.2). The potential should be as uniform as possible over the entire submerged surface. This objective may only be approached by adequate distribution of the protective current over the structure during its normal service conditions. Special considerations should be given for areas such as water intakes, thrusters, and sea chests.