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Choice of sacrificial anodes for aluminum boat

Which is the preferred anode to use on an aluminium boat below the waterline for use in salt water. Aluminium or Zinc anodes and why is this so.

Peter Mcmullan
Captain - Asker, Akershuus, Norway
2005

The purpose of sacrificial anodes is to corrode preferentially over more noble metals. Therefore, to work, the sacrificial anode has to be a DIFFERENT metal (and one lower on the corrosion scale) than the one being protected. So, the answer to your question is Zinc - a sacrificial aluminum anode would do little to nothing depending on alloying factors.

That being said, magnesium is even lower than zinc and may provide you with better protection since zinc and aluminum are quite close together (zinc however works great with other, higher, metals).

See letters 30607 and 5497 for more info.

Good luck!

Jim Gorsich
Compton, California, USA
2005

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