ANODE SHAFT 25MM ZINC

Function and technical context

The shaft anode is the key element of the cathodic protection system in shaft-driven vessels: its mission is to electrochemically sacrifice itself to protect the propulsion shaft, propeller and other submerged metals from galvanic corrosion. Made of zinc, this CMX-25 anode is specifically designed for 25 mm diameter shafts and acts as a sacrificial electrode as it is a more electronegative metal than stainless steel or bronze. Without active and well-maintained cathodic protection, the propeller shaft can suffer accelerated corrosion that compromises the structural integrity of the transmission and stern tube sealing, with the consequent risk of water entry into the hull or loss of maneuverability.

When to replace this shaft anode?

Zinc anodes should be inspected at least once a season—coinciding with the annual beaching—and replaced when they have lost approximately 50% of their mass, have a badly eroded, irregular surface, or visible cracks appear. A depleted anode no longer protects the shaft, evidenced by superficial pitting on the metal of the shaft or galvanic corrosion marks around the propeller hub. The professional recommendation is to preventively change the CMX-25 anode at each annual grounding: the cost of a new anode is minimal compared to machining or replacing a corroded shaft.

Compatibility table