The hull is the foundation of every ship. As the most exposed ship system, the hull requires planned maintenance. The savings that can be achieved with timely maintenance have encouraged shipowners to perform ship maintenance in the most optimal way. The smooth hull encounters less resistance, resulting in higher ship speed and lower fuel consumption. The primary focus of the shipowner is to keep the hull smooth, as it reduces fuel consumption. Hull hydrodynamics are threatened by corrosion and fouling. Maintenance takes place mainly in a dry dock, and consists of elements of hull surface preparation, coating and cathodic protection. Preparation involves the removal of dirt, fouling and rust. When the surface is clean, coatings that protect the hull from the formation of new fouling and rust are applied. If the coating is damaged, the cathodic protection must prevent the occurrence of corrosion on the principle of sacrificial anodes or on the principle of protection by applied current.