Anod, Johnson/Evinrude aluminium

Navalloy® anods from Performancemetals

Q. What anodes should I use in freshwater?

A. Where possible Navalloy™ (aluminum/zinc/indium alloy) anodes are recommended over zinc. Zinc anodes can become inactive after only a few months due to the build up of an insulating film of zinc hydroxide. Aluminum anodes will remain active. Don't take our word for it though, ABYC (American Boat and Yacht Council), who set the standards for the industry, clarified their recommendations on anode materials in the Standards and Technical Information Reports for Small Craft (July 2008-2009):

As you can see, the only anode type that is recommended for all water types is aluminum (Navalloy).

This chart summarizes the anode choices based on type of boat and water type:

The aluminum alloy used in Navalloy anodes is very different from normal aluminum. It includes about 5% zinc and a trace of Indium, which prevents the build up of an oxide layer.

Aluminum anode alloy provides more protection and lasts longer than zinc. It will continue to work in freshwater and is safe for use in salt water. Aluminum is the only anode that is safe for all applications.

Better Protection

Navalloy® has a higher protection voltage than zinc.

This particularly important when protecting aluminum components, like an outboard motor, which is an "active" metal.

Longer Life

Navalloy® lasts up to 30-50% longer than zinc.

Works in Fresh, Brackish and Salt

Zinc anodes can form a coating in freshwater after a few months, which will stop them from working. Navalloy® anodes will stay active.

Alloy meets ABYC (American Boat and Yacht Council) requirements for use in all types of water. (E-2 - Cathodic Protection Technical Standards, July 2008)

Reactivates after Exposure to Air

Navalloy® works immediately on re-immersion whereas zinc forms a non-porous layer which does not work unless rigorously cleaned.

Environmentally Friendly

Navalloy® does not pollute - zinc is a toxic metal and pollutes the water. Navalloy® contains only about 5% zinc. Zinc anodes are 99.9% zinc. Environmental agencies have determined that zinc sacrificial anodes are a major cause of pollution in marinas and in some cases zinc anodes are being banned (Maryland).

Navalloy® anodes are made to the military specification MIL-DTL-24779B(SH) and contains approximately 95% aluminuum, 5% zinc, 0.02% indium and less than 0.3% of other trace elements. The alloy is cadmium free.

(Text & pictures from performancemetals.com)