In this thesis the concept of cathodic protection as an effective method of corrosion prevention primarily on ships but also on infrastructures is explained. Corrosion is a significant problem that leads to damage of materials and loss of functionality of structures. To prevent corrosion, cathode protection provides an effective way to preserve and extend the service life of the material. The thesis explains in detail the concept of corrosion and its mechanisms, as well as the potential consequences that corrosion can have on materials. Then the theory and principles of cathode protection, i.e., the type of cathode protection, are analysed with an emphasis on the use of impressed current cathodic protection. In addition, the current protection sacrificial anode cathodic protection will also be discussed. For impressed current cathodic protection, a feeder-control unit will also be described, which through its electrodes, control unit, and three phase half-controlled rectifier gives the output the appropriate protection in the form of current. At the end, it will be shown a case study of an Indonesian warship type KCR 40 that suffered damage, not installing properly, and not properly used impressed current cathodic protection.