Ben Lee has this item over at Three Sheets Northwest:
We’re often asked by boaters about products they can use to reduce their environmental impact while enjoying their boat and the beautiful waters of Puget Sound. The three major responses are: cleaning supplies, non-copper bottom paint and aluminum/magnesium anodes. Let’s talk today about anodes.
What are anodes? They’re sacrificial lumps of metal attached to the bottom of your boat to prevent the wasting of the good metals of your boat (hull, shaft, propeller, etc) through galvanic corrosion. Basically, the anode corrodes before the boat does, saving you costly repairs and headaches. Anodes are a good thing. Heard of zincs? Zincs are anodes. But anodes don’t necessarily have to be zinc.