which anaodes do you use in fresh water and which in salt water?

Salt water= zinc or AL

Freshwater= Magnesium

what would you use for brackish (salt/fresh)?

one of each??

Direct from the West marine advisor. Enjoy.



Which anode is right for you?
Zinc or aluminum for salt water: If you are a saltwater boater, you should install zinc anodes to prevent galvanic corrosion on the engine and underwater parts of your boat. Look for aluminum anodes as a possible replacement because they last longer while providing the same level of protection as zinc.

Magnesium for fresh water: Since freshwater is much less conductive than saltwater, magnesium anodes are the best choice because they’re more active (less noble) than zinc or aluminum so they will protect your engine parts much more effectively. Caution: do not use magnesium anodes in any application other than a freshwater because they corrode rapidly, exposing your boat and engine to possible damage.

Aluminum for salt & brackish water: More active than zinc, aluminum anodes are a good compromise for a mix of fresh and saltwater, e.g. in the brackish water of river deltas. In brackish water zinc is too passive and magnesium corrodes too rapidly (because of the water’s salt content), leaving your boat without adequate protection.

great information thanks!!!

I cannot see how aluminum anodes would do much for you on a powerboat, unless you are just trying to protect the stainless parts, or you have a cathodic protection system. After all, we already have several hundred pounds of Al in the water more than willing to do that job

Painted drive AL vs bare anode aluminum would be my guess.

Strip the paint off your drive, then I assume you have 1 big anode.