Cathodic protection of a ship propeller shaft by impressed current anodes

This work studies the application of cathodic protection by potentiostatic polarization method with impressed current anodes for preventing corrosion phenomena on ship propeller shafts made of 17-4PH stainless steel, in seawater. Tests were carried out on a full scale propeller system (more than 3 m long) by using one or two activated titanium wires placed lengthwise in the interspace between the shaft and the stern tube. In order to simulate ship navigation and ship berthed in harbour, flowing (40 L/min) and stagnant seawater were respectively considered. Both technical solutions, consisting in the use of one or two titanium anodes, were able to protect the shaft. The results are compared with the data reported in previous works with different types and geometries of the anode.