Copper Antifouling on a Painted Aluminum Hull?

[svpresent]

Good morning cruisers,

I'd like to know if there's anybody here with knowledge/experience using copper containing antifouling on a painted aluminum hull.

I'm looking for better protection against growth, aren't we all.
My alu hull is completely covered with a thick layer (>500 mu) of vinyl-epoxy. So, theoretically there is no direct electrical connection that enables a circuit.

But the operative word here is of course: theoretically.

Anybody had the guts to try this? Please let me know your findings.

Or if anybody knows why I should NEVER start experimenting this way, please enlighten me. Till now I only read and hear that it's not done. Mostly because International and the likes want to sell their copperthiocyanate?
I'd be very grateful for your time.

Regards,
Len,
S/v Present

[GordMay]

Greetings and welcome aboard the CF, Len.

According to Interlux, their “Trilex 33" is a TBT free antifouling for Aluminum, that does not contain cuprous oxide, but does contain copper thiocyanate (CHCuNS)*

* CHCuNS as a marine anti-fouling agent
Copper: 51.0 – 53.0%
Iron: 0.02% max.
Sodium: 0.1% max.
Water: 0.5% max.

All of which leaves me very confused.
Let us know anything you may learn offsite.

[svpresent]

Hi GordMay,

Thanks for the welcome. I joined somewhere last year but guess I never got round to post a message.

I would like to know if there is any experience here with the copper- or copperoxide-containing AF paint on a painted alu hull, not the copperthiocyanate.

I have tried Trilux33. For me, it doesn't do what it says on the tin/can.
I am in the Caribbean, and planning to cruise in the pacific, also around the equator so you can imagine what my hull looks like after a few months. To be honest, I would buy the highly effective TNT-containing stuff but you can't buy that anymore.

I learned so far that: (Please correct me when I learned something wrong) copperthiocyanate is "neutral" when we talk about the reaction between dissimilar metals like alu and copper because the copper has already reacted with the cyanide. Unfortunately this means that the anti fouling characteristics are flawed as well.

And yes, I will report here what I might find out on other forums.

Fair winds,
Len.
S/v Present

[GordMay]

Placing dissimilar metals in proximity to each other on a boat is a very, very bad idea. Applying a thick layer of primer, or barrier coat, between your aluminum hull and copper-based antifouling paint will provide protection from galvanic corrosion only so long as the paint systems remain absolutely un-compromised. For this reason, many experts endorse a non-copper-based antifouling on an aluminum hull; however, some feel that copper-based paint can be used if the barrier coat is maintained, and the yacht's crew inspects the bottom regularly for damage that exposes bare metal.

As I said earlier, I remain confounded on this subject, and will welcome any technical expertise.

Capt. Alan Hugenot tries to answer the question in this article: “Which paint system works best with aluminum?”
However, I don'r feel the article provides enough detail to inspire my confidence.
➥ Sea Magazine | Boating Community Forums, Boating News, Boat Tests, Latest Boating Gear, Tips&Tricks

Perhaps the members at aluminumalloyboats might have some specific expertise/experience:
➥ AluminumAlloyBoats.com

Good luck !!!

[Boracay]

Having thought very carefully about the causes of a small amount of electrolytic corrosion of Boracay (steel, 44) which peeled some of the paint from the hull I came to the conclusion that it was possible for the antifouling to have had a part in it.

There look to be a myriad of causes. Stray currents from the marina or other boats or even from within the boat itself, uneven paint, small defects in the paint, uneven protection - the list could go on forever.

The real problem is that once it starts it peels the paint from the hull which accelerates the process so that increasing amounts of paint peel off. I found I could go from a full set of anodes to nothing in months, maybe even weeks.

You have good paint now on an aluminium boat!!! If I were in your place I would move heaven and earth to keep it that way.

I have already had a diver go down once to give everything a clean and a report on hull, prop and mooring. I'll probably get one again before I haul.

And yeas, I now dangle a couple of old electrodes over the side with the wire connected to the hull.

[SabreKai]

A fellow docked at our club last summer with a beautiful steel sloop, which had copper bottom paint on it. I specifically asked him about it, turned out he was an engineer who had spent years in industrial settings, and he had absolutely no qualms about coating his hull with epoxy primer and then putting on copper paint. According to him, he's been doing it that way for over 10 years if I remember correctly. As mentioned above if the primer is intact the copper and steel are never in contact.

So how often do you put your hull against a piling or scuff up the bottom?


Sabre
84 days n a wake up.

[David M]

Copper has been painted over steel ships forever. Aluminum though is is more reactive than is steel. Therefore copper affects aluminum much more than it affects steel.

I run an aluminum boat for a living and I would never take the risk of effectively turning my hull into a battery by applying copper paint. Its just not worth the risk, even with multiple layers of an epoxy barrier coat. All it would take is one hit from a log or something to scrape enough of the epoxy coat off the hull to reveal bare aluminum.

I too use Trilux 33 and it is garbage compared to copper based paint. Unfortunately there is nothing better for aluminum hulls. I am always looking but have found nothing yet. I just have to haul once a year but with an aluminum hull its probably good to haul once a year anyways because of how quickly aluminum can corrode.

Reactivity series

[fastcat435]

Hallo Len
It is no problem to put a copper based anti fouling on to an aluminium hull ,
you need a good cover of an epoxy primer . since all the copper particles are not touching
you will not get a problem of corrosion between dissimilar metals, we import and supply coppercoat in the Netherlands and have many aluminium and steel boats protected by copper based anti fouling since 5 years with any problems.

Does COPPERCOAT cause any problems with regards to electrolytic/galvanic action?

No. With the resin carrier insulating each copper sphere, the final coating is inert and non-conductive. A current can not pass through COPPERCOAT and this coating does not cause or promote electrolysis or cathodic decay. Consequently COPPERCOAT can be safely applied to metal structures such as iron keels and steel or aluminium craft (after the application of an appropriate epoxy primer). The property of electrical non-conduction in metallic powders including copper was first discovered in 1890 by Eduard Branley and is known as the "Branley Effect". Sacrificial anodes should be fitted in the usual manner.

Gideon

[swagman]

Hi,
I can understand how the barrier paint works but we once had an aluminium race boat and someone dropped a coin below which clearly had a copper content. I found it lodged above a stringer and laying against the bare plate hull. It has corroded a coin sized dip maybe 2 mm into the aluminium plate. Had we not found it I am sure we would have eventually seen a perfectly circular leak!
So IMHO best plan would be to find another paint rather than take the gamble.
Cheers
JOHN

[GordMay]

Originally Posted by fastcat435

... Does COPPERCOAT cause any problems with regards to electrolytic/galvanic action?

No. With the resin carrier insulating each copper sphere, the final coating is inert and non-conductive. A current can not pass through COPPERCOAT and this coating does not cause or promote electrolysis or cathodic decay. Consequently COPPERCOAT can be safely applied to metal structures such as iron keels and steel or aluminium craft (after the application of an appropriate epoxy primer). The property of electrical non-conduction in metallic powders including copper was first discovered in 1890 by Eduard Branley and is known as the "Branley Effect". Sacrificial anodes should be fitted in the usual manner.
Gideon

TECHNO-BULL !!!

CopperCoat may be non-conductive and inert, and safe & effective for use on Aluminum - or it may NOT be - but it’s safety certainly cannot be explained by the so-called “Branly Effect”.

In quoting the Aquarius Marine Coatings FAQ*, Gideon (& they) are misinterpreting the “coherer effect" (discovered by Edouard Branly).

* “Does Coppercoat cause any problems with regards to electrolytic/galvanic action?
➥ Coppercoat - multi-season antifouling. 10 years protection hard wearing copper filled epoxy resin copper antifoul antifouling.

Edouard Branly’s “coherer effect" occurs when an oxidized metallic powder undergoes an electrical transition from an insulating to a conductive state, when an electromagnetic wave is emitted in its vicinity. Exactly the opposite of what we'd wish, in this application.

See:

“Understanding the Branly Effect” ~ by Charles Hirlimann

“At the end of the nineteenth century Édouard Branly discovered that the electrical resistance of a granular metallic conductor could drop by several orders of magnitude when excited by the electromagnetic field emitted by an electrical spark ...”

➥ http://arxiv.org/ftp/cond-mat/papers/0703/0703495.pdf

“Turbulent Electrical Transport in Copper Powders”
by E. Falcon, B. Castaing and C. Laroche

“Compressed copper powder has a very large electrical resistance (1MOhm), due to the oxide layer on grains (100 μm). We observe that its voltage-current U-I characteristics are nonlinear, and undergo an instability, from an insulating to a conductive state at relatively small applied voltages ...”

➥ http://www.msc.univ-paris7.fr/~falcon/europhyslett03/EurophysLett04.pdf

[neelie]

A question regarding Copper Coat.

For it to work as an anti foul, surely there must be some naked copper granules exposed to the seawater.

If the bottom paint gets damaged, by scraping on a reef or whatever, then the electrolyte will have access to both metals.

Resulting in corrosion.

Or have I missed something?

[svpresent]

Neelie. In my efforts to try and understand fully what is happening when copper and alu are both bare and submerged in saltwater-electrolyte I read and heard several times that the mere submersion has still no effect.
The both metals have to be connected by physical contact in order to obtain a circuit. I understood that the surrounding with saltwater is not providing a circuit that allows for current to flow both from copper to alu and from alu to copper. Compare this with the experiment with two bars, one copper and one alu in a container with salt water. There will be no ciurrent until you connect the two bars with a conductor.

This is the reason why Gideon can say Coppercoat is safe. For me the only doubt comes from the total integrity the barrier coat should have. If there is a unnoticeble crack, what will happen?

[fastcat435]

Hallo Len wij hebben over de laatste 5 jaar meer dan 40 aluminium en stalen schepen in Nederland voorzien van Coppercoat en tot op heden geen enkel probleem
wel altijd voorzien van een goede dekkende epoxy primer laag

hartelijke groet

Gideon

[swagman]

Guys,

People have differing views on most things and it seems we've got opposing views on this question also and the guy asking the question is possibly just as confused as I am about the tecnho arguments posed by both sides.

All I know is our aluminium racer also had an aluminium hollow keel, into which lead was cast, and then that lead itself encased in epoxy bog to supposedly keep it insulated from the aluminium keel to stop any reaction. Now how could that go wrong?

Not sure. But it did.

That was 20 years ago.

I personally doubt the boat is still floating as each year we'd find pin holes corroded in that keel casing - presumably caused by the proximity of the lead and the salt water.

Seriously, do not take the risk. Go find an alternate antifouling.

More aluminium production boats built now days than ever before - why not use what they use?

Good luck
JOHN

[David M]

Originally Posted by svpresent

Neelie. In my efforts to try and understand fully what is happening when copper and alu are both bare and submerged in saltwater-electrolyte I read and heard several times that the mere submersion has still no effect.
The both metals have to be connected by physical contact in order to obtain a circuit. I understood that the surrounding with saltwater is not providing a circuit that allows for current to flow both from copper to alu and from alu to copper. Compare this with the experiment with two bars, one copper and one alu in a container with salt water. There will be no ciurrent until you connect the two bars with a conductor.

This is the reason why Gideon can say Coppercoat is safe. For me the only doubt comes from the total integrity the barrier coat should have. If there is a unnoticeble crack, what will happen?

Almost ,
The salt water acts as the electrolyte (the medium used for the movement of ions). Its the same thing as the electrolyte (sulfuric acid in this case) found in a lead-acid battery.