Ok, I checked archives back to 2000 and no one had asked or answered anything about zincs made from aluminum. I was in Boater's World today and they had very few "traditional" zincs and a lot of aluminum zincs that were advertised as lasting 50% longer. What's up with this? I'm also curious HOW many of you utilize "galvanic isolators" on your boats that stay plugged into shore power with chargers, refers, and/or A/C running?
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There ain'n no such thing 
If they are made out of aluminum they are called aluminums. If made out of zinc call em zincs :>)
If they are made out of aluminum they are called aluminums. If made out of zinc call em zincs :>)
Anodes
A Galvanic Anode is a Sacrificial system, that utilizes the Potential Difference (reactivity) between metals, to provide passive protection for the more Noble (Cathodic) metal. The gradual “Erosion”* of the sacrificial Anode is a desirable sign that this is occurring. Hence, a “longer life” is NOT usually a particularly desirable feature of an Anode (/w rare exceptions). * Anode corrosion should appear to be a general erosion, and not localized “pitting”. Aluminum Alloy (**AlZnIn - Alum, Zinc, Indium, etc) Anodes have a potential of between -0.7 to -0.9 V, whereas “Zinc” Anodes exhibit a potential of about -1.0 V., providing a greater reactivity vs the Noble metals (SS Shaft, etc) we are protecting. ** Aluminum has been found to be stable due to the formation of a thin protective oxide, which has a high electrical resistance and thus renders “pure” aluminum useless as a sacrificial anode. Magnesium has the highest potential (-1.6 V) of any common Anode material, but should only be utilized by Experts. Different types of anodes (zinc and aluminum) should never be mixed. Further references: http://www.cruisersforum.com/showthread.php?s=&threadid=2469 http://boatpoint.ninemsn.com.au/portal/alias__boatpointau/tabID__200856/ArticleID__119752/Default.aspx http
A Galvanic Anode is a Sacrificial system, that utilizes the Potential Difference (reactivity) between metals, to provide passive protection for the more Noble (Cathodic) metal. The gradual “Erosion”* of the sacrificial Anode is a desirable sign that this is occurring. Hence, a “longer life” is NOT usually a particularly desirable feature of an Anode (/w rare exceptions). * Anode corrosion should appear to be a general erosion, and not localized “pitting”. Aluminum Alloy (**AlZnIn - Alum, Zinc, Indium, etc) Anodes have a potential of between -0.7 to -0.9 V, whereas “Zinc” Anodes exhibit a potential of about -1.0 V., providing a greater reactivity vs the Noble metals (SS Shaft, etc) we are protecting. ** Aluminum has been found to be stable due to the formation of a thin protective oxide, which has a high electrical resistance and thus renders “pure” aluminum useless as a sacrificial anode. Magnesium has the highest potential (-1.6 V) of any common Anode material, but should only be utilized by Experts. Different types of anodes (zinc and aluminum) should never be mixed. Further references: http://www.cruisersforum.com/showthread.php?s=&threadid=2469 http://boatpoint.ninemsn.com.au/portal/alias__boatpointau/tabID__200856/ArticleID__119752/Default.aspx http
Galvanic Isolators
I will be utilizing galvanic isolators on my new 393, but that's not for the same purpose as using zinc's. The isolators protect me from other boats in the marina that are gounding challanged, when I am on shore power. I plan to add a zinc fish connected to my shrouds (that is bonded to my boats ground, hopefully that will increase the life of the zinc on my shaft
I will be utilizing galvanic isolators on my new 393, but that's not for the same purpose as using zinc's. The isolators protect me from other boats in the marina that are gounding challanged, when I am on shore power. I plan to add a zinc fish connected to my shrouds (that is bonded to my boats ground, hopefully that will increase the life of the zinc on my shaft
Its not natural
for your zincs to erode away too fast. When that happens, you need to start looking for the problem. And it is probably not your boat causing the problem, but it could be.
for your zincs to erode away too fast. When that happens, you need to start looking for the problem. And it is probably not your boat causing the problem, but it could be.
Zinc Fish??
I have a Beneteau 331 and the little zinc on the prop nut only lasts about 2 months. Seems like it should last longer, although it is quite small. I am curious about the Zinc Fish. I have seen them and thought about using one. I thought that I would have to somehow attach it to the shaft. Can I attach it to the shrouds and get the same protection? Any advice would be appreciated. Thanks, Liam.
I have a Beneteau 331 and the little zinc on the prop nut only lasts about 2 months. Seems like it should last longer, although it is quite small. I am curious about the Zinc Fish. I have seen them and thought about using one. I thought that I would have to somehow attach it to the shaft. Can I attach it to the shrouds and get the same protection? Any advice would be appreciated. Thanks, Liam.
The zinc guppie will work just fine, depending on....
I usually dive our boat twice a year to check zinc and add new zinc if needed. When I don't have the time to dive it, I connect a zinc guppie to the boat. Depending on if your shrouds are connected, you may be able to connect the guppie cable to it. Just follow your shrouds and see where it goes. The consequences of not taking care of your boat can get pretty bad. A diver friend of mine who does underwater work for a number of boats and marinas showed me a shaft from a neglected boat. Here is a picture. You can see where the shaft goes through the cutlass bearing and where the zinc was mounted.
I usually dive our boat twice a year to check zinc and add new zinc if needed. When I don't have the time to dive it, I connect a zinc guppie to the boat. Depending on if your shrouds are connected, you may be able to connect the guppie cable to it. Just follow your shrouds and see where it goes. The consequences of not taking care of your boat can get pretty bad. A diver friend of mine who does underwater work for a number of boats and marinas showed me a shaft from a neglected boat. Here is a picture. You can see where the shaft goes through the cutlass bearing and where the zinc was mounted.
A real close up of the shaft
This really shows what will happen to your boat and other underwater metal parts. So, make sure you use the right zinc, and don't skimp.
This really shows what will happen to your boat and other underwater metal parts. So, make sure you use the right zinc, and don't skimp.
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