sacrificial anodes

Choose material according to cruising area

Zinc works reliably in saltwater but quickly loses its effectiveness in brackish water. Aluminum anodes cover a broader spectrum and are a good choice in most cruising areas. In freshwater, magnesium is the only alloy that remains electrochemically active enough – zinc and aluminum do virtually nothing there. If you cruise in varying waters, aluminum offers the most flexibility.

Check shape and dimensions precisely

Anodes are not universal. The hole spacing, bore diameter, and external dimensions must match your drive or shaft system; otherwise, the anode will not sit firmly on the metal surface – and an air gap will render the protection useless. Therefore, always check the manufacturer's specifications for your unit and, if in doubt, measure the old anode before ordering.

When to replace?

Rule of thumb: If an anode is worn down by about half, it should be replaced – if you wait until the off-season, it may be used up beforehand. Anodes that have been painted over with antifouling no longer protect; the product electrically insulates the surface. When installing, sand the contact surface bare to ensure proper electrical connection.

Typical pitfall: Mixed metals

If stainless steel, bronze, and aluminum lie next to each other in the water on the ship, a galvanic element with varying potential differences is created. A single anode in the wrong place is then not enough. Consider which components are in the water and place the anodes specifically near them.