ANODE SHAFT 35 MM.

Function and technical context

The shaft anode is the central element of the cathodic protection system on vessels with shaft drives, and acts as an electrochemical sacrifice to protect the submerged metal parts—tail shaft, propeller, and horn—against galvanic corrosion. It is mounted directly on the drive shaft with a diameter of 35 mm, hugging the piece using a fixing system that guarantees permanent electrical contact with the metal to be protected. Without this component, galvanic corrosion silently and irreversibly attacks the stainless steel or bronze of the shaft, potentially causing vibrations, looseness in the horn and, in advanced cases, the complete unusability of the propulsion line. Its correct sizing – in this case for 35 mm axles – is essential so that the active zinc surface is sufficient and the protection is effective throughout the season.

When to replace this part?

The clearest symptom that the shaft anode has exhausted its useful life is visible mass loss: when the zinc has reduced its volume by 50% to 75% compared to the new state, it must be replaced immediately, as the residual protection is insufficient. As a general rule of preventive maintenance, the shaft anodes are checked and replaced at least once a season, or sooner if the boat remains in the water for a long time or navigates in areas with high electrolyte activity. Changing the CMX-35 anode when taking the boat out of the water during seasonal stranding is the most recommended practice to avoid costly damage to the shaft and propeller that would require repairs at the strand outside the usual periods.