Shop rudder anodes at West Marine.

A problem that boat owners must protect their boats against is galvanic corrosion. For those unfamiliar with this phenomenon, it is a type of corrosion that occurs when two different metals are in contact with each other in an electrolyte, such as saltwater. The metal that is more active in the galvanic series will corrode preferentially to the metal that is less active. This can cause damage to the more active metal, which might be a propeller shaft, shaft strut, propeller or other parts such as outdrive lower units and transom-mount trim tabs. To protect against galvanic corrosion, sacrificial anodes must be installed.

What are rudder anodes?

One type of anode that West Marine offers are rudder anodes, which are also called rudder button anodes or clamshell anodes. These round, disc-shaped anodes are typically bolted on to metal rudders, shaft struts and on to transom trim tabs to protect these parts against galvanic corrosion.

Installation and Changing of Rudder Anodes

When installing rudder anodes, make sure to install the anodes on to clean metal surfaces to ensure that a good electrical contact is made. Anodes should never be painted. Over time, anodes will begin to waste away. To ensure continued protection, anodes should be changed when 50 percent or less of their material remains.

Rudder Anode Sizes, Materials and Brands

Rudder anodes are offered in diameters that range from less than 2" up to over 6". They are also offered zinc, aluminum and magnesium materials. For the best protection, you need to select anodes made of the material that works best in the type of water where you use your boat; zinc for saltwater, aluminum for salt- or brackish-water and magnesium for freshwater. Brands of anodes that West Marine offers include Sierra, Martyr and Sea Shield.