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Old 24-01-2023, 21:53   #1
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Copper Coat on an Alu hull - yes or NO ?

Hi all,

I have my alu boat on the hard doing some work to her.

I had the hull sand blasted yesterday and found extensive fairing areas on the bottom. Looking at that more closely today.

As part of the bottom treatment I was going to put copper coat on the bottom. I have spoken extensively with the Cooper Coat people and they have given me the schedule of hull prep for an Alu hull.

Basically, an epoxy barrier coat done 4 times min. They say an extra coat or 2 of epoxy barrier coat will not hurt - ie, build up the thickness of the epoxy to keep the copper away from the Alu hull. Probably looing for around at least a 20 mil thickness in the epoxy barrier coat.

I am sure there will be people here who might know something about this and am very interested in your thoughts on the matter.

Looking forward to reading your comments.
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Old 24-01-2023, 23:22   #2
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Re: Cooper Coat on an Alu hull - yes or NO ?

I'd be careful about it. If you ever get some cracks or damage on the bottom corrosion will start..

I'd also think about resale value. Many might be hesitant to buy an AL boat with a Coppercoat bottom.
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Old 25-01-2023, 02:01   #3
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Re: Cooper Coat on an Alu hull - yes or NO ?

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Originally Posted by Jim Jones View Post
Hi all,

I have my alu boat on the hard doing some work to her.

I had the hull sand blasted yesterday and found extensive fairing areas on the bottom. Looking at that more closely today.

As part of the bottom treatment I was going to put copper coat on the bottom. I have spoken extensively with the Cooper Coat people and they have given me the schedule of hull prep for an Alu hull.

Basically, an epoxy barrier coat done 4 times min. They say an extra coat or 2 of epoxy barrier coat will not hurt - ie, build up the thickness of the epoxy to keep the copper away from the Alu hull. Probably looing for around at least a 20 mil thickness in the epoxy barrier coat.

I am sure there will be people here who might know something about this and am very interested in your thoughts on the matter.

Looking forward to reading your comments.
A very bad idea. Imagine building up 5-6 layers of barrier coat just to be able to use an incompatible antifouling

Use an antifouling for aluminum boats. Make sure you have an isolation transformer for shore power and have a silver chloride reference cell aboard for regular checks (available from boatzincs.com). I have met aluminum boats that have a permanently installed system with alarm function.
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Old 25-01-2023, 05:33   #4
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Re: Cooper Coat on an Alu hull - yes or NO ?

It's not a totally unheard of approach - typically done by French sailors - to use copper bottom paint on an ali boat with a heavy barrier coat, but I still think it's just asking for trouble.

If you haven't had the pain of replacing hull plates yet, once you do, you'll move heaven and earth to prevent that from happening again.

We had really good luck with Seajet copper free. But you're still limited to max of two seasons. It's just the nature of the beast

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Old 25-01-2023, 06:49   #5
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Re: Cooper Coat on an Alu hull - yes or NO ?

As a retired Certified Marine Corrosion Tech, I ask ... are you a gambler ?
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Old 25-01-2023, 08:57   #6
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Re: Cooper Coat on an Alu hull - yes or NO ?

Just sayin'

https://www.yachtingmonthly.com/boat...o9lyh5ezI7PKEo
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Old 25-01-2023, 09:17   #7
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Re: Cooper Coat on an Alu hull - yes or NO ?

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Wow! Thats incredible growth for a boat thats always moving. Does that stuff contain barnacle growth hormones ?

I've always had doubts that encapsulated copper powder could be released fast enough to work.

Any theories ?
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Old 25-01-2023, 09:36   #8
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Re: Cooper Coat on an Alu hull - yes or NO ?

My theory is that copper particles encased in epoxy make for a poor anti fouling coating. My theory is that Coppercoat releases so little copper biocide that it cannot adequately retard growth in all but the lightest of fouling conditions.
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Old 25-01-2023, 09:36   #9
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Re: Cooper Coat on an Alu hull - yes or NO ?

Ok, I hear you all.

Going to look at a hard anti foul instead. International rep coming by tomorrow sometime. Spoke briefly on the phone and he says they have a combination of coatings that can go 5 years. I'd be interested to know more about that.

This is interesting....."I have met aluminium boats that have a permanently installed system with alarm function"
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Old 25-01-2023, 09:45   #10
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Re: Cooper Coat on an Alu hull - yes or NO ?

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Wow! Thats incredible growth for a boat thats always moving.
Barry, of "The Old Sea Dog" on YouTube has a 3>4 part series of his passage from Panama to FP.
I think he holds the record for the longest "passage", (he basically drifted).
Anyway, the growth "came out of nowhere", so to speak, and was ~2" thick by the time he got to FP.
It's a steel boat, and I don't know the paint he used.
Back to regular programming, I would not use any paint that contains copper anywhere on an aluminum boat.
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Old 25-01-2023, 10:20   #11
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Re: Cooper Coat on an Alu hull - yes or NO ?

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My theory is that copper particles encased in epoxy make for a poor anti fouling coating. My theory is that Coppercoat releases so little copper biocide that it cannot adequately retard growth in all but the lightest of fouling conditions.
I agree.
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Old 25-01-2023, 10:26   #12
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Re: Cooper Coat on an Alu hull - yes or NO ?

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Ok, I hear you all.

Going to look at a hard anti foul instead. International rep coming by tomorrow sometime. Spoke briefly on the phone and he says they have a combination of coatings that can go 5 years. I'd be interested to know more about that.

This is interesting....."I have met aluminium boats that have a permanently installed system with alarm function"
There are impressed current systems on the market. They do work but there are a number of "re-branders" of chinese stuff that may not be quite kosher.

Some brands advertise it them as cures for "electrolysis". Don't buy from anyone who uses that word, they clearly do not know what they are doing as "electrolysis" does not occur on boats.

https://www.boatcorrosion.com/about-corrosion.html
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Old 25-01-2023, 10:28   #13
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Re: Cooper Coat on an Alu hull - yes or NO ?

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Don't buy from anyone who uses that word, they clearly do not know what they are doing as "electrolysis" does not occur on boats.
I love it when you talk like that
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Old 25-01-2023, 12:02   #14
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Re: Cooper Coat on an Alu hull - yes or NO ?

Coppercoat works great on my GRP boat. But on an aluminium hull, I would stay away even from the slightest chance of negative impact on the hull.
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Old 25-01-2023, 12:30   #15
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Re: Cooper Coat on an Alu hull - yes or NO ?

I think the theory is ok but one scratch or defect in the barrier coat and its game on.

Sorry for thread drift but if not copper coat then what for aluminium.

Please post feedback from the Intl paint rep as always interested in all options available.

Soft ablative over hard I have heard talk of lately.

Trilux in SE Asia seems to attract barnacles which is a shame as we don't have that many choices

Going to try Choguku (parent company of Seajet) Marine Star A next. Doesn't have the "yacht" premium in the price.
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