ANODE SHAFT 7/8`` ALUMINUM

Function and technical context

Shaft anodes are cathodic protection elements designed to be electrochemically sacrificed in place of vital metal parts of the vessel. This aluminum anode for 7/8 inch shaft acts as a galvanic barrier in the propulsion system, protecting the tail shaft, horn and adjacent components from electrolytic corrosion caused by contact between dissimilar metals in a conductive medium such as salt or brackish water. The aluminum alloy used in its manufacture makes it the appropriate choice for marine and brackish waters, offering a protective performance superior to zinc in these environments and superior to magnesium in waters with a certain salinity. If this component is not replaced in time, galvanic corrosion directly attacks the propulsion shaft, which can cause pitting, loss of metal section and, in advanced cases, structural failure of the shaft or damage to the stuffing box and the stern tube bearing.

When to replace this part?

The main indicator that a shaft anode needs to be replaced is its mass reduction: when it has consumed approximately 50% of its volume or presents an irregular surface with severe erosion, it no longer offers sufficient protection and must be replaced immediately. The inspection is recommended at least once per nautical season, coinciding with the annual beaching, although in areas with high electrolyte activity or stray currents a mid-season inspection may be necessary. Replacing the anode preventively, without waiting for its total consumption, is the most economical measure to avoid costly damage to the propulsion shaft or the helmet horn.