ANODE SHAFT 3-1/2

Function and technical context

This shaft anode acts as a sacrificial element in the boat's shaft line cathodic protection system, being installed directly on the tail shaft to protect it against galvanic corrosion caused by prolonged immersion in salt or brackish water. Its function is to degrade in a controlled manner before the structural metal components of the propulsion assembly - shaft, propeller, horn and rudder -, thus avoiding electrolytic corrosion that could compromise the mechanical integrity of the entire transmission. Without adequate cathodic protection, the propulsion shaft can suffer pitting, material loss and, in severe cases, breakage or structural failure while sailing. The CMX-15 anode is sized for 3-1/2 inch diameter shafts, being a specific solution for vessels with larger shaft lines.

When to replace this shaft anode?

Shaft anodes must be inspected at least at the beginning and end of each sailing season: when the anode has lost approximately 50% of its mass or presents irregular and advanced erosion, it must be replaced immediately, since below that threshold its protective capacity drops drastically. An unmistakable symptom of insufficient cathodic protection is the appearance of pitting or discoloration on the stainless steel shaft or bronze propeller. It is recommended to replace the CMX-15 anode preventively at each annual grounding: the cost of an anode is minimal compared to the cost of repairing or replacing a propulsion shaft damaged by galvanic corrosion.