'Zinc' Analysis II
I am diverging too far from the original questions here, so starting a new (old subject I am sure..) page.
When we bought her, Knot Salted had only one large zinc plate anode on the transom to which all water contacting metal on the boat including seacocks, through hulls, Struts, rudders, engines and trannys were bonded. Not much erosion of the plate over 6 or more seasons including some with the PO, and no obvious erosion of any components visible. She has always been in fresh water.
We have had a few new neighbors at the dock, but no changes over the last two seasons. Last year I went to magnesium anodes, replacing the transom zinc, and adding mags to trim tabs and prop shafts. Rudders are bonded to the transom anode, and no mags were added to them directly.
My reasoning for the swap and additions was reading about zinc being of little real protection in fresh water, magnesium being a better choice, and wanting more coverage - just in-case of a change at the marina.
After one season, all the mag anodes are really chewed up. -I mean they will bite you if you grab them. The bulk of each of them is still present. At the end of this season, I will need to replace all for sure. Of course Mag is much more reactive, but it is still very surprising.
Have I created electrolysis? All mag anodes are mounted on directly bonded parts, except for the new prop shafts mags.
All anodes are Magnesium. No Zinc. Maybe this is my new normal?