How Can an Aluminum Anode Protect an Aluminum Boat?
All too often we get the question, “How can an aluminum Anode protect an aluminum boat (or outdrive)?” In particular, there is the worry that they will not be suitable for salt water.
Navalloy (aluminum) anodes are not like regular aluminum. They are made from a special alloy with indium. It’s a bit like comparing regular steel with stainless steel – they are very different alloys with very different properties. In this case the Navalloy is like the regular steel and regular aluminum is like the stainless. Navalloy does not form an oxide coating. Regular aluminum does, and it’s this oxide coating that protects the aluminum from corrosion.
Aluminum anodes have many more benefits. For one thing they will work in any kind of water, from fresh to salt. Don’t take our word for it but ABYC’s who have carried out extensive testing and come up with recommendations in their technical standards:
Zinc is OK in salt water, but in fresh or even brackish water it stops working. It coats over and insulates itself. Magnesium is only OK in fresh water and can be dangerous in salt or brackish water due to over-protection.
Aluminum anodes also work slightly better than zinc for example, working at a lower voltage.
This is especially important when protecting aluminum hulls or outboards etc. The extra driving potential provides much better protection. That’s the reason all the major outboard and outdrive manufacturers have switched to aluminum anodes as standard. That and the fact that they work in any water type.
Aluminum anodes are also much better for the environment with lower zinc content.
They are usually less expensive as well!
And as for: “Will they work in salt water” and the answer is “Yes! Absolutely!” Most outboard manufacturers have switched to aluminum. The Navy is switching and pipelines and oil rigs universally use aluminum anodes in the ocean.
Performance Metals is the leading US manufacturer of aluminum anodes made to the military specification MIL-DTL-24779.