ANODE SHAFT 2-1/4

Function and technical context

The shaft anode is a sacrificial element that acts within the boat's cathodic protection system, mounted directly on the tail shaft to protect it against galvanic corrosion produced by the action of salt or brackish water. Being made from a zinc alloy with a higher negative electrochemical potential than stainless steel or shaft bronze, it attracts galvanic current and corrodes in place of the shaft, thus preserving the structural integrity of this critical drivetrain component. Without this protection, the propulsion shaft can suffer pitting, sectional weakening and, in severe cases, premature fracture, which would compromise the seaworthiness of the vessel and require a high-cost repair at the dock. The CMC-9A model is sized for 2-1/4 inch diameter shafts, adapting to the corresponding standard section to ensure effective electrical contact and secure attachment.

When to replace this part?

Shaft anodes must be inspected at least once a season and replaced when they have lost around 50% of their mass, since below that volume their protective capacity decreases considerably and the shaft is exposed to galvanic corrosion. Obvious symptoms of a depleted anode include the appearance of orange pits or stains on the surface of the stainless steel shaft or discoloration changes on bronze shafts, signs that electrolysis is acting directly on the structural metal. It is recommended to renew the anode preventively at each annual beaching, especially in mooring areas with high electrical conductivity or presence of parasitic currents, to avoid irreversible damage to the shaft that would require its complete replacement.

Compatibility table