Zinc Anode Replacement

Zinc anode replacement is the routine renewal of sacrificial anodes that protect a boat’s underwater metals from galvanic corrosion. Zinc (or aluminum in brackish water, magnesium in fresh) is less noble than the bronze, steel, or stainless it protects, so it corrodes preferentially under cathodic protection while the propeller, shaft, rudder, and through-hulls stay intact. Anodes are bolted to the shaft, hull, trim tabs, and engine, and are replaced when about half wasted, typically each haul-out or annually. A wasted or painted-over anode leaves the protected metal exposed to rapid pitting.