KIT ANODOS DISCO POPA 135X35mm (ZN)

Function and technical context

The zinc (ZN) stern disc anode kit is the galvanic protection set specifically designed to be installed on the stern disc of the transmission, acting as a controlled sacrifice against the electrolytic corrosion suffered by the submerged metal parts of the boat. Its function is to attract galvanic corrosion to the anode itself, thus protecting critical components such as the tail shaft, propeller, transmission housing and the aft disc itself. It works within the external or semi-inlet propulsion system, being especially relevant in salt or brackish water environments, where the electrochemical activity between different metals is more aggressive. Without adequate anodic protection, corrosion directly attacks the structural parts of the transmission, generating pitting, loss of material and, in advanced cases, mechanical failures that can leave the boat without steering. The disc format with dimensions 135x35 mm guarantees a sufficient sacrificial surface for a full season of use under normal conditions.

When to replace this part?

Zinc anodes should be inspected at least at the beginning and end of each nautical season, and replaced when they have lost between 30 and 50% of their mass, since below that threshold they no longer offer effective protection. The most obvious symptoms that the anode is exhausted are the appearance of pits or orange rust spots on the stern disc, shaft or propeller, indicating that corrosion is already acting on the base metal. It is recommended to replace the complete kit preventively at each annual grounding: it is a minimal investment compared to the cost of repairing or replacing a transmission damaged by galvanic corrosion.