Cathodic - Propeller Shaft Earthing System

If the ship has a system of cathodic protection, whether it is sacrificial anodes or an impressed current cathodic protection system, the shaft insulation will prevent the propeller and the boss from receiving protection. The electrical potential between shaft and hull can also cause a heavy current to flow in bearings when the oil film breaks down or is contaminated with seawater.This current can cause deep pitting of the bearing surface. Excessive wear on the shaft bearings can often be traced to this cause.Trouble can be avoided and cathodic protection extended to the propeller if the shaft is properly earthed with a shaft earthing system.