ANODE SHAFT 7/8

Function and technical context

Shaft anodes are sacrificial elements made of zinc or aluminum alloy that are installed directly on the boat's tail shaft to protect it from galvanic corrosion. They work within the cathodic protection system, acting as a negative electrode that corrodes in a controlled manner instead of the nobler metal of the axle, the drive shaft or the metal parts close to the propeller. Without correct cathodic protection, the stainless steel or bronze shaft is exposed to electrolysis caused by the potential difference between different metals submerged in water, which can lead to pitting, structural weakening and, in advanced cases, shaft breakage while sailing. The CMC-2 anode, with a shaft diameter of 7/8 inch, is designed to precisely fit shafts of that size, guaranteeing effective electrical contact and an adequate sacrificial surface for the navigation season.

When to replace this part?

The most obvious symptom that the shaft anode has reached the end of its useful life is a reduction in mass by more than 50%, at which point the active surface area is no longer sufficient to protect the shaft and adjacent components. In practice, the inspection should be carried out at least once a season, coinciding with the beaching or annual maintenance of the bottom, and it is recommended to replace it preventively every season or sooner if the vessel operates in waters with high electrical conductivity or ports with high eddy currents. Replacing the anode at the beginning of each season is the most economical measure to avoid costly damage to the shaft, impeller and horn seals.