The anode protects transmissions and propellers from galvanic corrosion (due to charges on the metal surface) caused by the induced currents generated by the movement of the boat and the water.
These currents cause corrosion that would attack the transmission, propellers, rudder and equipment that pass through the hull without the anodes.
The principle behind its operation is the same as that used for the corrosion protection of offshore drilling rigs, platforms and other high value constructions.
Cathodic protection is an electrochemical technique for safeguarding metal structures exposed to an electrolytic environment which can be aggressive towards the metal from corrosion. The material of choice for the sacrificial anode is zinc.
The sacrificial anode is destined to progressive wear over time; therefore, it is necessary to replace it periodically.
In this specific case, the sacrificial anode placed at the end of the propeller protects the propeller itself from galvanic corrosion.
The anode corrosion time is not the same for all boats and for all ports; but may vary on the same boat as boat conditions vary. It is therefore necessary to monitor the anodes of both the propeller and the boat even during the season.
If 50% of the anode is corroded, it must be replaced, in order to ensure its functioning, which is so important for equipment. The sacrificial anode must absolutely not be painted and when assembling make sure there is good contact between the surface of the anode and the one on which it is to be installed.