The purpose of the Impressed Current Antifouling system is to prevent blockages in seawater cooling system caused by various forms of marine growth, primarily barnacles and mussels.

Blockages are expensive and time consuming to remove, particularly when whole sections of pipework need to be cleaned or replaced.

There is also the risk that seawater valves and other important items of equipment are affected jeopardizing the operational capability and safety of the vessel.

Even partial blockages can have serious consequences, making engines run at abnormally high temperatures and significantly increasing fuel usage. This has a direct bearing on the cost of vessel operation and profitability.

System Operation

The system is based on the electrolytic principle and usually consists of pairs of copper and aluminum anodes which are mounted in sea chests or strainers and wired to a control panel.

In operation, the copper anode produces ions which are carried by the flow of seawater, creating an environment in which barnacles and mussels will not settle or multiply. By introducing copper ions in very small concentrations, around 2 ppb, the Impressed Current Anti Fouling system interrupts the settlement sequence. The action of the copper ions is assisted by aluminum hydroxide created by aluminum anodes which flocculate the released copper ions. This highly gelatinous copper-aluminum hydroxide floc is carried throughout the system and tends to spread out into the slow moving areas closer to the pipe surfaces where marine larvae are most likely to settle.

As a result, marine growth larvae do not settle, instead passing direct to discharge. At the same time, a copper-aluminum film is built up on the internal surfaces of pipes to suppress corrosion.

In this way, the system has a dual action protecting seawater pipework against bio-fouling and corrosion.