ZINC BAR 35x400

Function and technical context

The 35x400 mm zinc bar is a sacrificial anode designed for the cathodic protection of the tail shaft of vessels, acting as a galvanic element that corrodes preferentially against the noble metals of the assembly (propeller, horn, stainless steel shaft). Its function within the propulsion system is to absorb the electrolytic corrosion generated by the potential difference between different metals in contact with salt or brackish water, thus preventing galvanic corrosion from damaging high-cost structural components. Without this active protection, the drive shaft, horn and brass fittings would be exposed to accelerated deterioration that would compromise both the mechanical integrity of the transmission and the tightness of the shaft line. Zinc is the material of choice in salty marine environments due to its ideal electrochemical potential for protection against stainless steel and copper alloys.

When to replace this part?

Zinc anodes must be inspected at least at the beginning and end of each navigation season, and replaced when they have lost approximately 50% of their mass, since below that threshold their protective capacity decreases significantly and the metals of the axis are left unprotected. Symptoms of a depleted or missing anode include superficial pitting in the stainless steel shaft, erosion in the brass horn, and, in advanced cases, unusual looseness or vibration in the shaft line. The professional recommendation is to renew the zinc bar preventively at each annual beaching: the cost of an anode is minimal compared to machining or replacing an axle damaged by galvanic corrosion.

Compatibility