Copper Coat on an Alu hull - yes or NO ?

[Uncle G]

I've built and owned 4 aluminium alloy yachts since 1982 to date.

Our latest one is due to go afloat this year and I have been looking at using Coppercoat on the bottom. The main reason for considering it being the increasing environmental restrictions regarding pressure washing and re-coating with conventional antifoul. 10 years of simply scrubbing with no re-application needed is very appealing.

I was concerned about using a 'copper paint' underwater but, after looking into it, I am now completely OK about that side of using Coppercoat on an alloy hull. Each grain of copper in the Coppercoat is surrounded by epoxy and so the coating is completely non-conductive and can't harm the alloy.

However, that is the problem from the antifouling side of it. If you simply apply all the layers of Coppercoat and leave it at that then it won't work at all since all the copper will be encapsulated. So you have to sand off some of what you've applied to expose the grains of copper. If you don't do it well enough you end up with patches that have no exposed copper - but if you do it too well then you risk going right through what you've just applied and maybe right through to the alloy.

Even if you do it perfectly some of the copper grains will be effectively cut in half and showing the maximum amount of copper (assuming that they are roughly spherical) but some of them will only just have a small sliver exposed and the rest will be the epoxy binder between each grain. Which may well explain why, as others have said, it's sometimes not very effective.

We've had great success with Seajet Emperor and will probably stay with it for the new boat:

https://www.seajetpaint.com/en/produ...et-034-emperor

Two coats of that have lasted us well for two years between haul-outs. Three at a push if we scrubbed regularly in the third year.

Dead easy to apply and no need to meticulously sand the whole underbody with various fine abrasives as would be needed with Coppercoat.

[motion30]

Many of the reports on copper coat are not great. I wouldn't waste the time or money unless you are a gambler. Just my humble opinion

[Jim Jones]

So the back story to this.....

The boat is going inland to a freshwater lake. Its a high Ph water at the lake so no one can tell me about antifoul and how it will/will not perform. Its a case of try it and see.

The boat yard where the boat WAS (now moved elsewhere due to predatory pricing and work practices) are the one who recommended it to me due to the location of where I am taking the boat. At that time I didn't know any better and took thier advice - because they are a big well established and well known boat yard where I am.

So I went ahead and ordered and paid for the copper coat. Its still sitting in UK at Copper Coat and waiting to be shipped.

However a few events happened along the way that has made it clear to me that this boat yard is not to be trusted. I was alongside the jetty at this boat yard for 3 months before I bailed. During that time a number of big "Oysters" came through for hauling out and basic service before they carried on with thier trip to the Caribbean/the Med etc. One of the Oysters, an Oyster 54 came in for a fresh anti foul. They wanted copper coat applied. Of course an Oyster is fiberglass, so all good. Being interested in copper coat I offered my help to mix the copper coat and to help to keep stirring it in the trys etc.

Whart I saw was mind boggling, at least to me. Remember this was on a not very old Oyster 54 - several million $ worth? This yard had non skilled/non trained guys helping to apply the copper coat to the Oyster hull. When the job was finished it was awful. It was very very patchy and streaky. One could clearly see the work of the different guys - some applying too light a coat, others applying a very heavy coat. I was appalled. For a boat of that magnitude having copper coat hand rolled on by guys who had never done it before, too me was a disgrace.

To my eyes the finished job was crap. I have watched a LOT of youtube videos on copper coat and I had not seen one that looked like this big Oyster now had on her. The yard wanted to get her back in the water before the owners returned.

Now this is one of the most expensive yards in the country where I am and they market themselves as the premier premium yacht service in this country. Prices are over the top crazy and yet the work is done by local guys. There is one expat at this yard who is a fitter and turner - so at least qualified in something. This guy knows his stuff but the workers under his command are all locals who are not qualified. Now some of these local workers are good. They may not be qualified by they know what they are doing and I would be happy to have them work on my hull.

However the other 3 or 4 guys they called in to help with this Oyster.......I was shocked to say the least. I will say again, .....what a crap job they did with the copper coat.

I have now moved to a yacht club and am finally up on the hard and I am engaging local trades people to do my work. Its 1/3 the price and these guys have long years of experience. Talking among some of the people here (which is an advantage of being at the Yacht club - many people with many years experience for advice) has revealed some doubt about copper coat on an Alu boat.

So I was thinking this all over when I went ahead and got the sand blasting of the hull done. The sand blasting guy called his Jotun tech rep about the barrier coat to be applied and we went through what we had done so far.


***** Jotun tech rep has just arrived here at the club to take a look at the hull*****

Will finish this later.

[Anders]

Originally Posted by motion30

Many of the reports on copper coat are not great. I wouldn't waste the time or money unless you are a gambler. Just my humble opinion

Most reports both on.ine and in real life are great. My next boat will be coppercoated.

[Jim Jones]

Ok so the Jotun rep has been and gone. He is going away to get the answers for me on what to apply from the Jotun range.

The International rep said he is coming today, so will see what transpires.

AFTER we had sand blasted the hull the Jotun rep told me we had blasted with the wrong material. He said if we used a steel slag then we have contaminated the alu hull with steel. This led me to diving onto the net and researching this. I found a forum dedicated to Alu boats and the guys there say under no circumstances should an Alu hull EVER have a copper based antifoul applied as its just asking for trouble down the road. I had an extensive read through of this Alu forum and these guys sound like they know what they are talking about - ie, Alu workboats in Alaska.

So from all this and what has been said here, I am going to give the copper coat a miss. I was hoping to find some positive word on coppercoat on Alu but most everyone says NO DONT DO IT. SO I am going to run with that general consensus.

Why introduce a nightmare problem that has to be dealt with down the road ? I will stick to the Jotun or International antifouls and just deal with the recoats in the years ahead - some how or another. Thinking about it, if its hard to deal with a new anti foul where the boat is going, how will I deal with corrosion issues caused by copper coat ?

I think the best way forward here given all the opinions that simply say dont do it, is DONT DO IT.

Remember that this advice to go this way came from a boat yard that in my opinion is suspect at best. All they are interested in really is gouging boat owners for every penny they can - never seen anything like it in my entire life.

Re the sand blast - it transpires that we used a platinum slag - it was reclaimed though and we should not have used the reclaimed. The reason we did that was because the sand blast people said that it is much softer once its been used once. Its 36 hours now since blasting and there is no rust appearing on the hull so it seems we are good. However I will follow up with a 350 bar pressure water wash to wash anything in the pores of the roughed up Alu, out. Then I am told to give it an acid wash with Alu cleaner then water pressure wash again then do a "sweep" blast using Garnet.

There are extensive areas of "fairing" on the hull which was a surprise to me. I didn't realise an Alu hull got "faired". However people here tell me it is normal.

I am planning to blast all the fairing off and re do it - some people here at the club say I am wasting time and money to do that, but I think its better to get it all off to see whats under there in case there is any corrosion etc and then re do it. But I guess that is another thread topic.

[Hasbeen]

I ran a fleet of tourist day trip boats on the Oz great barrier reef. We took delivery of a new 29 meter, 335 passenger alloy International Catamaran. It was powered by 2 16V92TA 1250 horse power GM diesels.


Each engine room had a sea chest built into the inside of the hull for gate valves to supply raw salt cooling water to these, & other requirements of the boat. These were built of 18mm thick alloy, & could only be accessed from out side..



In one hull the sea chest was pin holing from corrosion after only 7 months in the water. There were sacrificial zinc blocks in each sea chest. On inspection in dry dock to fix the corrosion we found some dill had installed bronze sea cocks in that side, rather than the stainless steel specified, & installed in the other engine room. The zinc blocks in that sea chest had totally disappeared, just the mounting bolts left.



I would never knowingly allow any yellow metal such as copper anywhere near an alloy hull after this experience.

[Dr.No]

Jim, I specifically recommend Petit Aluma Protect as the first primer against the bare aluminum. Then build up with additional epoxy primers. My plan has been to use a Petit Alumacoat SR or Petit HRT ECO as antifouling paint. I will reevaluate when there is a launch date, And will take a look at other options like the Seajet Emperor - which I had not previously heard of. Look at Boatcorrosion.com. You may want to use mil spec aluminum anodes instead of zinc. There ios a lot to relearn with an aluminum vessel. Cheers!

[double u]

...there was this french aluminium boat on the hard in Raiatea, French Polynesia, in 1990 with a thousand toothpicks poking through little holes in the hull. The owner had drilled through all corrosion-pits & was waiting to have welded them shut. Came from unsuitable antifouling

[Epicurean]

Originally Posted by Audeamus

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.

I've used both Chugoku paints, Marine Star and the other one (I forget which is which, now) on my Al Mumby both in the Andaman and crossing the Indian Ocean. Didn't last a year - either.
About Cu (Actually Cu2O) on Al - I have a paper I can send you:
"The Use of Copper-based Antifoulings on Aluminium Ship Hulls"
By
Frank William Bagley, Mehmet Atlar, Alasdair Charles
(Newcastle University, UK)
and
Colin Anderson
(American Chemet, USA)
The concluding line in the abstract is: "Copper leaching out of Cu2O based antifoulings had no affect on the corrosion of Marine-grade aluminium."

I personally never had any corrosion problems on my 11 y.o. boat. which was almost always antifouled with Cu2O.

[Leee]

Re copper coating on aluminum hulls:


I had to have it all sandblasted back to bare aluminum and start from scratch only a few months after a yard in Portimao, Portugal applied copper antifouling (with all sorts of assurances of method and past experience of course) to my hull. Prior to that, the hull coatings were in perfect condition. The shipyard in Sicily did a great job (well documented) of it and there have been no issues since but I certainly would not try that again.

[Mark Hall]

I have had copper coat on my aluminum schooner for ten years. Just replaced it (actually just added additional coats after patching up some weak areas. My hull is very well isolated but I have had no problems with corrosion that I know of. When I rebuilt the boat in 2011-12 I did have to correct corrosion issues, but they were from the failure of the interior barrier coat against concrete/lead ballast. My boat is in Mexican waters and I don't suppose it is superior antifouling, but it is a very hard surface and easy to clean. It was much better when in San Francisco.
Mark Hall
Del Viento

[Centreboard2017]

Absolutely not - we have an aluminium boat and use a non copper antifoul. See below from International Paint -

Antifouling paint used for aluminium should not contain cuprous oxide biocide as the high copper content can lead to corrosion problems unless the hull is expertly painted and protected using sophisticated impressed current protection systems.

[nmccubbin]

We have had an aluminum boat for 20 years, and have used various antifouling paints
Worst was Seahawk biotin
International disappointing
Best by far SeaJet 038

[kryg]

Originally Posted by Jim Jones

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.

I have an Aluminum 50' Sail boat, I was not happy with antifouling on offer only lasted a few weeks in the summer. For this reason, I did look into in to finding a solution some years ago. I found Steve Dashew used cooper antifouling. I'm not sure if it was Cooper coat or not, on His boat Wind Horse. You need to do some research on his method of application. If I recall, he used a heavy zinc primer as a sacrificial protectant for the bare hull, then applied cooper antifouling or copper coat?.

Having owned my boat for 35 years now, and still going strong. My limited experience advice is; in your case, the 2 of epoxy barrier coat would not help protect your hull unless you follow S. Dashew approached. You should do some more homework, reading his solution.
All the same, the world has moved on in Anti fouling. In my case I did two things, I use VIVID antifouling designed for Aluminum boats. And had ordered a custom build NZ ultrasonic transduces installed 18 months ago. (Store ones I found are hyped up but ineffective) I just had the boat slipped, today after 19 months, Today just relaunched it. Yes there was weed, but no hard shell but still on the prop, which my bay is known for. To be fair, the hull after 6- 8 months, my hull need scrapping (de weeding) every four months thereafter, but I got two seasons out of my system, instead of two weeks with frustrating shell growth taking hold as I experienced for years before.

This is not a yes or no answer you're seeking.

My advice is if you don't want to put your boat in harms way, you need to do some more independent of Cooper Coat supplier research before you jump into applying cooper coat just yet.

As a side, I stuck with my aluminum boat, as I would never again own a fiber glass sail boat again, full stop. Yes, it is worth getting antifouling solution solved to your satisfaction for your boat. For me owning Skoiern IV since 1987 in my experience Aluminum boat is the best compromise than other materials so you got that part right. Good luck.

[Jeff F]

I have an aluminum boat that was professionally finished in specialty epoxy underwater and Awlgrip elsewhere.

The builder put VC17 on the bottom. Fresh water only.

It scares me. I'd be very apprehensive leaving the boat in salt water.