ANODE SHAFT 1-1/8`` ALUMINUM

Function and technical context

Shaft anodes are cathodic protection elements designed to be mounted directly on the boat's drive shaft, acting as sacrificial metal that corrodes preferentially compared to higher value metal parts such as the shaft, propeller or hub. This aluminum anode for a 1-1/8" (28.575 mm) shaft is installed in the shaft line, between the hull and the propeller, protecting the underwater transmission assembly against galvanic corrosion caused by the difference in electrochemical potential between the different submerged metals. The aluminum composition makes it especially effective in salt and brackish waters, offering active and continuous protection while the boat remains in the water. Without adequate anodic protection, the shaft can suffer pitting, accelerated corrosion and material loss that compromises the structural integrity of the transmission and can lead to costly axle or horn replacements.

When to replace this part?

The clearest symptom that a shaft anode has exhausted its useful life is the visible reduction in its mass: when the anode has lost approximately 50% of its volume, it must be replaced immediately, since below that threshold the cathodic protection is insufficient. It is recommended to check the condition of the anodes at each beaching or, at least, once per nautical season; In areas with high electrical conductivity of water or with intense mooring activity in ports with eddy currents, inspection should be more frequent. Replacing the anode preventively at the beginning of each season is the most common practice among professional marine mechanics, since the cost of the anode is minimal compared to repairing or replacing a corroded shaft.