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Old 09-11-2014, 12:09 AM   #1
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electrolysis, or total lack of, after 4 years

Recently pulled my boat for a bottom job after 4 years. Bottom paint was ok. Had a few barnacles, plenty of slime (mostly fresh water/mississippi river). Added 4 gallons of ablative after pressure washing. BTW, mixed 50/50 black and "clown" blue for the nicest navy blue color you could want. The most interesting thing was that my zinks were still in decent, useable condition. No evidence of corrosion on any running gear or fitting. Props were perfect. Shafts were perfect. I left the old zinks on the shafts and added new ones. The rudder zinks were fine. I have a large plate zink that is attatched electrically to the tuna tower by a flat copper strap for lightning dissapation, it was fine. I have to contribute this to my boat being totally "unbonded" by me. I have been relentless in removing all the bonding crap, and I'm paranoid about battery chargers. So far this is the least amount of electrical activity I've seen on a boat thats been in the water this long.
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Old 09-11-2014, 05:56 AM   #2
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Zincs dont work much in fresh water. So they stay new.

There are other protection methods , magnesium .
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Old 09-11-2014, 08:20 AM   #3
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True, freshwater makes a difference. I was just amazed at the complete absence of any kind of electrical activity.
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Old 09-14-2014, 07:18 AM   #4
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I have to replace anodes every 2 years using magnesium in fresh water. On previous boat in fresh water never replaced anodes in 13 years that I know of probably more, I suspect they were zink.
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Old 09-14-2014, 08:25 AM   #5
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I will change to magnesium next haulout.
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Old 09-14-2014, 08:27 AM   #6
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Should you put both zinc and magnesium if you planning on being in both salt and fresh? I have zinc and after two years no problem when hauled out. A few barnacles on the shaft , in fresh water.
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Old 09-14-2014, 08:33 AM   #7
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Greetings,
Mr. k. "A few barnacles on the shaft , in fresh water.". Hmm...no barnacles in fresh water as far as I know...but good question. CAN one put both zinc and mag' anodes on at once. Can't remember my electrochemistry.
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Old 09-14-2014, 08:47 AM   #8
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I like Kulas44, I am in Louisiana about 8 miles from the Gulf. I would think with a strong and long south wind we could have a little salt water blow in.
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Old 09-14-2014, 09:09 AM   #9
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It's more a matter of the electricity in the water where the boat is docked. As for material magnesium is better in fresh water.
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Old 09-14-2014, 10:59 AM   #10
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Just picked up this nice explanation about zinc in fresh water off this morning's T&T digest, courtesy of "Sean":

"Can someone please explain why zinc anodes are not recommended for fresh
water."

Yes. In fresh water, the electrolyte is much weaker and the activity
level of the zinc does not support enough sloughing of the material. In
very short order, the zinc will become coated with an impermeable layer
of zinc hydroxide (the way zinc naturally oxidizes in the presence of
water, unrelated to galvanic action). Once this layer is in place, the
galvanic action will stop entirely, and the zinc essentially becomes
passive -- it provides no anodic protection whatsoever. Whatever else
on the boat is then the next least noble metal, such as an aluminum
part, then becomes the anode for the whole boat.

... The idea is to protect the prop, not to make the anode go away.

If the anode does not "go away" then it's not protecting anything.
That's how it works.
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Old 09-14-2014, 02:35 PM   #11
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Quote:
Originally Posted by kulas44 View Post
True, freshwater makes a difference. I was just amazed at the complete absence of any kind of electrical activity.
It doesn't mean an absence of electrical activity. It means zinc anodes do not work in freshwater.
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Old 09-14-2014, 02:37 PM   #12
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Quote:
Originally Posted by kartracer View Post
Should you put both zinc and magnesium if you planning on being in both salt and fresh?
No. Do not mix anode materials. You know, unless you like galvanic corrosion.

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Old 09-14-2014, 02:47 PM   #13
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This thread and the info it provides is very timely. I'm hauling my boat next week and I'm going to replace my zincs, paint the bottom and straighten a prop that we used to test the water depth....("OUCH").

I do have a couple of questions. 1. Where's a place to buy zincs where they don't think they're made of solid gold? 2. When the zincs become coated with the Zinc Hydroxide and lose their effectiveness, is it possible to grind that layer off and continue to use the zincs?

I'm in fresh water and the zincs look like new except for that layer that has developed.

Thanks,

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Quote:
Originally Posted by caltexflanc View Post
Just picked up this nice explanation about zinc in fresh water off this morning's T&T digest, courtesy of "Sean":

"Can someone please explain why zinc anodes are not recommended for fresh
water."

Yes. In fresh water, the electrolyte is much weaker and the activity
level of the zinc does not support enough sloughing of the material. In
very short order, the zinc will become coated with an impermeable layer
of zinc hydroxide (the way zinc naturally oxidizes in the presence of
water, unrelated to galvanic action). Once this layer is in place, the
galvanic action will stop entirely, and the zinc essentially becomes
passive -- it provides no anodic protection whatsoever. Whatever else
on the boat is then the next least noble metal, such as an aluminum
part, then becomes the anode for the whole boat.

... The idea is to protect the prop, not to make the anode go away.

If the anode does not "go away" then it's not protecting anything.
That's how it works.
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Old 09-14-2014, 03:21 PM   #14
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My boat has spent a little time in salt water, probably got the barnacles then. Even given the fresh water the boat lives in it shows no electrolysis at all. In the marinas I normally inhabit I will see some indication but not this time. If the zinks were in fact not working at all (possible) I would expect to see some indications at least on the props.
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Old 09-14-2014, 04:16 PM   #15
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Regarding the cost of zinc, zinc mines are being exhausted and no new major deposits have been in found in years while demand for zinc is rising. Get used to higher zinc prices.

Later,
Dan
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Old 09-14-2014, 04:44 PM   #16
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Switch to aluminum anodes. They're cheaper.
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Old 09-15-2014, 06:10 AM   #17
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use zincs made by a US company , not Chinese recycled scrap.
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Old 09-16-2014, 11:10 AM   #18
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I've had great success with www.boatzincs.com

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Old 09-16-2014, 12:41 PM   #19
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Kulas44 When you say you unbonded everything does this also deal with grounding? You have to be careful for your boat and others boats and people in the water(fresh water in particular) that your boat while it is not losing zincs does not become a danger.
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Old 09-16-2014, 01:45 PM   #20
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Quote:
Originally Posted by kulas44 View Post
... I have to contribute this to my boat being totally "unbonded" by me. I have been relentless in removing all the bonding crap, and I'm paranoid about battery chargers. So far this is the least amount of electrical activity I've seen on a boat thats been in the water this long.
If you unplug a table lamp, the light bulb will last a long time too because it does no work.

What is it about battery chargers that makes you paranoid?

What do you consider 'bonding crap'? The bonding straps are there to protect your boat's metal components. Why did you 'unbond' your boat?

Have you consulted a marine expert who advised this is the proper approach to making your zincs last longer? I'm not being sarcastic here, but seriously want to learn why you consider this the right thing to do to protect your boat from electrolysis.

Thanks
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