Fish type anodes
- Thread starter Kordie
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Some notes to consider: Remember that the ohm meter outputs a current in order that it measure resistance. This current is a smidge above the kinda normal currents that ya get in electrolysis.. I am talking normal electrolysis, not extreme cases.. so if you measure (with a good meter) very low ohms between say a shroud and the propeller shaft, you are OK with connecting the fish to a shroud.. BUT you have to KNOW that you have low/no resistance.. consider how tiny a wire has to be to carry a few milliamperes .. I am not saying that it is OK in all cases to connect your fish to a shroud.. I am saying that if you know the currents and resistances, you can do it and be OK.. This bank of knowledge must include a reference cell survey..
My impression about the thread has been, well ... I think simplistic. At the risk of questions about my credentials -- I admit that I'm not an electrical engineer. But I have a reasonable amount of basic chemistry and math and physics that I try to apply common-sense best I can. So maybe not a phd from MIT (or even an apprentice degree from the local junior college), but I do tend to understand a lot of basic concepts.
About six months ago, after getting the initial information while I was at the Strictly Sail show in Oakland CA, I spent quite a bit of time digging through lots of articles before I adopted my current sacrificial anode arrangement.
I don't understand why boat owners are so reluctant to become aware of Al alloy anodes and their potential advantages. On the post #2 of this thread (mine) I have included some links. Click on the links that are within it. And the subsequent links. And also do your own research about Al alloy anodes.
My shaft-collar zinc is still traditional zinc material and that is what I will maintain because it's lasting longer in conjunction with an Al alloy anode fish zinc (albeit that is bonded much better to the shaft than just putting a clip on the shrouds). I really believe that the Al fish anode is shedding protective electrons more readily than the zinc collar anode.
Going forward for me it is: Zinc on the shaft/prop. And Al alloy anode for a fish that is bonded in a way that is just as good as being bonded to the shaft in the water.
About six months ago, after getting the initial information while I was at the Strictly Sail show in Oakland CA, I spent quite a bit of time digging through lots of articles before I adopted my current sacrificial anode arrangement.
I don't understand why boat owners are so reluctant to become aware of Al alloy anodes and their potential advantages. On the post #2 of this thread (mine) I have included some links. Click on the links that are within it. And the subsequent links. And also do your own research about Al alloy anodes.
My shaft-collar zinc is still traditional zinc material and that is what I will maintain because it's lasting longer in conjunction with an Al alloy anode fish zinc (albeit that is bonded much better to the shaft than just putting a clip on the shrouds). I really believe that the Al fish anode is shedding protective electrons more readily than the zinc collar anode.
Going forward for me it is: Zinc on the shaft/prop. And Al alloy anode for a fish that is bonded in a way that is just as good as being bonded to the shaft in the water.
Maybe. But you would also be extending the life of your zinc shaft anode if the fish anode were also simply zinc.
Now that is the harder question. And when I researched, I couldn't come to a clear conclusion. But I did find lots of references that just putting on more "zinc" doesn't necessarily retard the over-all sacrifice rate. Over-zinc'ing can be a problem as well. And I would think that certainly if the fish zinc isn't bonded very-well to the shaft by a shaft brush or at least a thick wire to the engine block and the bonding wires are maintained for clean contact (I am doing all three), then the shaft zinc will sacrifice not much different than if no fish was hanging at all. That is why I am doing Al alloy anode material for the fish which has a higher sacrifice potential than zinc. I also think that just a fish, but without a shaft anode, is pushing the envelope for protection. Better than nothing, but not a safe substitute.
My understanding is that as far as the straight physics go; one anode lasts X long. Two anodes lasts 2X long. Bearing in mind that yes, it is possible to over-zinc.
Where does it go?
Since this whole sacrificial zinc anode thing is basically an electroplating process, the zinc has to be deposited on the negative side of the electrical charge couple. atoms of zinc leave the anode and get get deposited on the cathode. So why aren't we seeing something in the water getting all shiny and bright with a beautiful coating of zinc? where is all this zinc going?
Regarding using the battery for a zinc fish connection, seems like a really big fat battery cable bolted to the engine would be a very low resistance path to the shaft compared to just about any other connection on the boat other than directly attaching it to the shaft (as noted a brush type connection required for safety sake) or bolting it directly to the engine itself. I don't use these fish and scuba dive to change my zinc as required but it still seems if you want to use one this would be one of the easier ways to get a good connection to the shaft assuming the shaft isn't isolated?
Since this whole sacrificial zinc anode thing is basically an electroplating process, the zinc has to be deposited on the negative side of the electrical charge couple. atoms of zinc leave the anode and get get deposited on the cathode. So why aren't we seeing something in the water getting all shiny and bright with a beautiful coating of zinc? where is all this zinc going?
Regarding using the battery for a zinc fish connection, seems like a really big fat battery cable bolted to the engine would be a very low resistance path to the shaft compared to just about any other connection on the boat other than directly attaching it to the shaft (as noted a brush type connection required for safety sake) or bolting it directly to the engine itself. I don't use these fish and scuba dive to change my zinc as required but it still seems if you want to use one this would be one of the easier ways to get a good connection to the shaft assuming the shaft isn't isolated?
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