The anti-fouling system based on the electrolytic principle. It consists of copper and aluminium anodes which are fed with an impressed electrical current from a control panel. The anodes are usually mounted in pairs in the ship sea chest or strainer where they are in direct contact with the flow of water entering the seawater lines. In operation, the copper anode produces ions, which are transported by the seawater and carried into the pipework system. Although the concentration of copper in solution is extremely small – less than 2 parts per billion, it is sufficient to prevent marine life from settling and multiplying. At the same time, the slow dissolution of the aluminium anode produces ions which spread throughout the system and produce an anti-corrosive layer on the internal surfaces of pipes.