ANODE SHAFT 120 mm.

Function and technical context

The shaft anode is a cathodic protection element that is installed directly on the boat's propulsion shaft, acting as a sacrificial metal to preserve both the shaft and the other submerged metal components—propeller, horn, rudder—against galvanic corrosion. Its operating principle is based on the fact that zinc (or equivalent alloy) preferentially corrodes when in contact with salt or brackish water, consuming itself instead of allowing corrosion to attack the noble parts of the transmission system. With a diameter of 120 mm, this CMC-120 reference anode is sized for propulsion shafts of that caliber, guaranteeing effective electrical contact and sufficient sacrificial mass to cover a complete navigation season. Without proper cathodic protection, the shaft can suffer pitting, loss of section and structural weakening that compromises the integrity of the entire transmission system.

When to replace this part?

The clearest sign that the shaft anode needs to be replaced is if it has consumed between 50% and 60% of its mass: at that point it can no longer offer effective protection for the rest of the season. Visually, a very reduced anode, with irregular edges and a highly eroded surface, or on the contrary one that hardly shows wear on a boat that has been in the water for months, respectively indicate a lack of protection or an electrical continuity problem that also requires attention. Annual inspection and replacement coinciding with the seasonal tune-up is the recommended standard practice; Taking preventive action on this low-cost component prevents damage to the shaft and propeller that entails considerably more expensive repairs at the dock.