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Old 30-12-2013, 00:55   #16
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Re: Zinc Anode Troubles

Thanks again folks ... I certainly appreciate all of your responses, suggestions and ideas. We're still trying to actually identify where the zincs connect with anything ... it's frustrating. Planning on checking out their outside location with an underwater video camera (it's cold in Puget Sound!) ... and then rummaging through the bilge, engine compartment, and rudder compartment to try and identify how the system all fits together. It's driving me crazy ... seems like it should be such a simple thing. I have noticed that all of the thru-hulls are "supposed" to be bonded ... the wire is present throughout ... but a few of the wires have been disconnected, and quite a few of the connections that are still present appear to have been painted over ... does not please me. Looks like we might be starting at square one.
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Old 30-12-2013, 06:43   #17
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Re: Zinc Anode Troubles

Quote:
Originally Posted by ambloplites View Post
Thanks again folks ... I certainly appreciate all of your responses, suggestions and ideas. We're still trying to actually identify where the zincs connect with anything ... it's frustrating. Planning on checking out their outside location with an underwater video camera (it's cold in Puget Sound!) ... and then rummaging through the bilge, engine compartment, and rudder compartment to try and identify how the system all fits together. It's driving me crazy ... seems like it should be such a simple thing. I have noticed that all of the thru-hulls are "supposed" to be bonded ... the wire is present throughout ... but a few of the wires have been disconnected, and quite a few of the connections that are still present appear to have been painted over ... does not please me. Looks like we might be starting at square one.
greetings folks for the new year.. With respect, most of you do not understand what ZINC/ALUMINIUM Anodes are or even for... So hear the first lesson of the year free as always... The World earth, has a Negative charge very small in pressure but unlimited in volume. Everything else not directly and electrically connected to it, therefor has some Positive charge. Nature will always and continually try and neutralise this difference and in the process will destroy that positive charge containing material...This is called ELECTROLYSIS and is the reason batteries work, metals corrode and your brightwork goes dull. It cannot be prevented but can be controlled. Zinc will produce a difference of about 0.5 Volt Negative compared to Earth. Not very much, but sufficient to overcome most of the effect of the earth charge. If this Voltage is applied to other metalwork within the same environment, it will substantialy reduce the neutralising effect of the earth. However Nature does not give up, and will still attack the Zinc first, thats why they are sacrificial...
Second point, to work at all, all other metalwork on the vessel in or out of the water must be properly electrically connected together and then connected to the anode or anodes. Water is more conductive than Air so it makes sense to put the anode in the water... If it does not have a common connection it wont work in your favour.
Third and very important, your electrical system should be isolated from the earth system. Ensure that there is a proper two wire system not a common earth return... If you are using a marina or shore supply, this must also be isolated from the ships earth. Invariably I have found a shore supply battery charger earthed to the ships earth, instead of to a seperate and dedicated shore supply earth. Do NOT Connect the Ships Earth to the Shore Supply Earth under any circumstances... I have seen a new gin palace yacht, lose most of both its large propellers in less than six months from doing just that, and it had never left its berth....Finally The number of the anodes is relative to the amount of protection required, the weight according to the time expected before next change. both factors should have been determined at the last inspection. As a very rough guide on a steel hull, one anode will protect an area of about 20 sq meters with the anode at its center...
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Old 30-12-2013, 13:20   #18
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Re: Zinc Anode Troubles

Three posts and the guy is in here calling everybody else ignorant. Funny, considering that he is misusing the very term his longwinded and elipses-laden post is based upon.

Here are some issues I have with the above post:

1.- "Electrolysis" is a commonly misused term amongst the boating community and is not a form of corrosion. It refers to a different process altogether. "Electrolytic corrosion" is the proper term for what is also known as stray current corrosion. This is caused when electrical current from an external source, often the boat's battery or the shorepower system, attacks underwater metals.

2.- Galvanic corrosion is not even mentioned by this guy. Two dissimilar metals in electrical contact with each other while immersed in an electrolyte (such as seawater) will cause the least noble of the two to corrode.

There are other types of corrosion found in boats as well but these are the two most frequently seen and anodes (be they zinc, aluminium or magnesium) are they way to protect underwater metal parts from them. I find nothing in this thread that would indicate that the users posting in it don't understand this.
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Old 30-12-2013, 13:47   #19
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Re: Zinc Anode Troubles

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. With respect, most of you do not understand what ZINC/ALUMINIUM Anodes are or even for...
wow, I didn't even read the rest

you go right onto the ignore list
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Old 02-01-2014, 04:06   #20
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Re: Zinc Anode Troubles

[QUOTE=fstbttms;1427122]Three posts and the guy is in here calling everybody else ignorant. Funny, considering that he is misusing the very term his longwinded and elipses-laden post is based upon.

Here are some issues I have with the above post:

1.- "Electrolysis" is a commonly misused term amongst the boating community and is not a form of corrosion. It refers to a different process altogether. "Electrolytic corrosion" is the proper term for what is also known as stray current corrosion. This is caused when electrical current from an external source, often the boat's battery or the shorepower system, attacks underwater metals.

2.- Galvanic corrosion is not even mentioned by this guy. Two dissimilar metals in electrical contact with each other while immersed in an electrolyte (such as seawater) will cause the least noble of the two to corrode.

There are other types of corrosion found in boats as well but these are the two most frequently seen and anodes (be they zinc, aluminium or magnesium) are they way to protect underwater metal parts from them. I find nothing in this thread that would indicate that the users posting in it don't understand this.[/QUOTE ]
I understand the purpose of this forum to be a free exchange of ideas and information. Not a tally of brownie points for the most entries. Firstly I have only been teaching Physics for the last fifty years or so, I dont know everything and am always ready to learn more .However what ever you personally may call a particular electrical process, I suggest you look up the correct scientific term and meaning of ELECTROLYSIS before you criticise. Secondly, you dont appear to be able to understand what you are reading. All your critical remarks are fully covered in my article. Thirdly and most importantly, IF THE CONTRIBUTORS knew the answer to the subject they would not need to ask... If all you are looking for is jokes and one liners, maybe you would be better confining yourself to the Marina Bar... Only a little knowledge can seriously harm your professional Reputation if you have one.
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Old 02-01-2014, 09:03   #21
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Re: Zinc Anode Troubles

Conversely, you might find you get a better reception if you don't call people idiots when you first walk into the room.
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Old 03-01-2014, 04:05   #22
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Re: Zinc Anode Troubles

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Originally Posted by h the boat View Post
Second point, to work at all, all other metalwork on the vessel in or out of the water must be properly electrically connected together and then connected to the anode or anodes. Water is more conductive than Air so it makes sense to put the anode in the water... If it does not have a common connection it wont work in your favour.
Anyone following this thread would be well advised to take this advice with a pinch of salt. I do not have the through hull fitting electrically connected to the boats earth system and am not about to either, they are bronze and are quite happy on their own. The only connected items are the p bracket and the rudder stock.

Quote:
Originally Posted by h the boat View Post
Third and very important, your electrical system should be isolated from the earth system. Ensure that there is a proper two wire system not a common earth return... If you are using a marina or shore supply, this must also be isolated from the ships earth. Invariably I have found a shore supply battery charger earthed to the ships earth, instead of to a seperate and dedicated shore supply earth. Do NOT Connect the Ships Earth to the Shore Supply Earth under any circumstances... I have seen a new gin palace yacht, lose most of both its large propellers in less than six months from doing just that, and it had never left its berth.....
This is what a Galvanic isolator is used for.

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Old 03-01-2014, 04:11   #23
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Re: Zinc Anode Troubles

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Thanks again folks ... I certainly appreciate all of your responses, suggestions and ideas. We're still trying to actually identify where the zincs connect with anything ... it's frustrating. Planning on checking out their outside location with an underwater video camera (it's cold in Puget Sound!) ... .
Buy this, it's not cheap but it is a bible:

http://www.amazon.co.uk/Boatowners-M...8747446&sr=1-1
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Old 16-01-2014, 16:42   #24
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Re: Zinc Anode Troubles

Pete - bought it ... reading it ... sleeping with it under my pillow.

So, my zincs are attached to either side of the lower keel, just in front of the rudder, and just below the lower rudder bracket:

Click image for larger version

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I cannot for the life of me understand how that protects anything, as it is not in physical contact with anything but the keel. Unless ... the keel is encapsulated iron, and the engine mounts are embedded into it?? Or am I completely missing how zincs function??

If I'm thinking right, the prop is an alloy of copper with zinc (some kind of brass) ... the prop shaft is stainless steel ... because they're both in seawater, zinc from the prop is going to "electrically leach" (for lack of more technical terms) out of the prop making it weak and useless. Unless there is a sacrificial zinc physically touching the shaft/prop system? The sacrificial zinc can't just be "close by" ... correct?

And this is what my prop looks like (hope the pics come through, they're not showing in my preview):
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Old 16-01-2014, 16:51   #25
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Re: Zinc Anode Troubles

A quick note to help clarify the prop pictures ... unfortunately I was not present at the haul out and survey. The surveyor said that when tapping on the prop blades they make a dull thud sound, instead of a nice metallic "ting". Based on that, and spots of what appear to be coppery color, he believes that the prop is being de-zincified. However, to me, it looks like someone (I did not do it!) was turning the boat and ran the prop into rocks ... thus the chewed, ripped, and bent aspect of at least two of the blades. And it seems odd to me that both blades that can be seen have been basically destroyed in exactly the same configuration ... as though the prop had been turning while it chewed into something really hard?

I'm going crazy on this whole thing.
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Old 16-01-2014, 16:54   #26
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Re: Zinc Anode Troubles

Anodes must be in direct electrical contact with the part they are meant to protect. If they are not, they are not protecting. Also, the shorter the electrical path between anode and protected part, the more effective the protection.

BTW- while I'm sure your surveyor is correct, dezincification typically leaves bronze looking pink.
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Old 16-01-2014, 16:59   #27
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Re: Zinc Anode Troubles

fstbttms - that's what I thought ... thanks for helping me from going completely nuts.
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Old 16-01-2014, 17:07   #28
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Re: Zinc Anode Troubles

That problem is damage but you may have dezincification as well. I noticed that there is not much room for a collar anode in front of the prop. You might try pouring a zinc anode over the prop nuts. That is a common practice when you don't have enough room for collar anode. You could also use a shaft brush on the inside that is electrically connected to that anode that is in the picture.
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Old 16-01-2014, 17:11   #29
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Re: Zinc Anode Troubles

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Buy this, it's not cheap but it is a bible:

http://www.amazon.co.uk/Boatowners-M...8747446&sr=1-1
It's a good reference book ...
Only $33.55 in US ... Boatowner's Mechanical and Electrical Manual: How to Maintain, Repair, and Improve Your Boat's Essential Systems: Nigel Calder: 9780071432382: Amazon.com: Books
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Old 16-01-2014, 17:20   #30
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Re: Zinc Anode Troubles

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That problem is damage but you may have dezincification as well.
Looks like mechanical damage, perhaps by something softer than rocky bottom if metal was already weakened by GC.

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You could also use a shaft brush on the inside that is electrically connected to that anode that is in the picture.
I wonder if that anode is connected to ANY of boat's metals?
Can you x-ray that part of the boat ...
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