ANODE SHAFT 3/4

Function and technical context

The shaft anode is a sacrificial element that is part of the boat's cathodic protection system, acting directly on the tail shaft to prevent galvanic corrosion that affects submerged metals. Being made of zinc or aluminum alloy depending on the version, this component corrodes in a controlled manner instead of the nobler metallic elements of the propulsion assembly - axle, propeller and horn -, significantly prolonging its useful life. Its correct installation is especially critical in salty or brackish waters, where electrochemical corrosion acts more aggressively. Without effective cathodic protection, the propulsion shaft can suffer pitting, loss of section and, in advanced cases, breakage or seizure inside the horn, with the operational and economic consequences that this implies.

When to replace this part?

The main indicator of exhaustion of a shaft anode is the loss of more than 50% of its mass: when the anode appears clearly reduced, deformed or with deep surface cracks, it must be replaced immediately. Inspection is recommended at least once a season, usually at the annual beaching, although in areas with high water conductivity or with electrical installations on board with stray currents it may be necessary to inspect it every six months. Replacing the anode preventively at each seasonal tune-up is the most cost-effective measure to avoid damage to the shaft or propeller, repairs that cost much more than that of this component.