Is There An Undiscussed Problem With Coppercoat?

[RichardS]

I haven't posted this until now because, even after the following discussions, I went ahead and had my cat Coppercoated so I felt it was rather disingenuous to raise the matter when I had already voted with my wallet! I am also not 100% sure of the facts as you will see.

I have also touched on this before but this is the whole story and it seems appropriate now as several threads about Coppercoat are active as people make a decision for the new season.

When I arrived down at the boat in Croatia last October she was out of the water and being prepared. The Service Manager asked me if I wanted to change my mind and have conventional antifoul applied because there were some problems with Coppercoat. I asked what were problems and he replied that sometimes it doesn't work and showed me a new Amel which was being stripped of Coppercoat applied by the manufacturer and another monohull which was CC'd a few years ago and looked fine, both in the yard. I have talked about the Amel in a previous post.

I asked who had CC'd the monohull (owned by a Brit incidentally) and he replied that they had done it and it had been successful ..... but it was not a saildrive. So what I asked. He replied that there have been serious problems with underwater metalwork, and in particular, saildrives and their anodes, corroding away very quickly on CC'd boats as if caused by them sitting in stillish (non-tidal) water surrounded by copper ions.

I said that I had never heard about this but to carry on with the CC and I would keep a close eye on my saildrive anodes - I reckon that I could even change them in the water if really necessary as a haul in and out will cost me £500 a throw.

A few days later I was standing near the travel hoist and I saw a CC'd saildrive monohull being lifted out. I wandered over to chat to the guy whom I assumed was the owner. It turned out that he was the owner of the charter company and they had 20 boats. I looked at the bottom and said something like "The Coppercoat looks like it's working well" and he said "Yes, it certainly keeps the fouling under control but having my fleet CC'd was a mistake because of the rate at which they go through anodes now and the haul-out costs are killing me. And, if you don't change the anode frequently, the saildrive is destroyed in a few months"

I asked how many anode changes on the boat we were looking at. He replied that this would be its third set that season.

I was so gobsmacked at though of the the cost of three changes per season that I didn't ask all the questions I should have. I did ask whether they were CCing the saildrive or keel but he said that CC would not adhere to metal at all well so they did not and I could see that they were conventionally antifouled. I have not CC'd the saildrive either for the same reason.

I wish I had asked about shore power and galvanic isolators as that, to me, seems like as likely an explanation. However, these are professional boat people so they would, presumably, know all about that. I use solar rather than shore power over the winter and I also have a GI. I think that the charter boats use a lot more shore power than I do and I saw that they were connected even though we were now out of season although that might have been just during their closing maintenance period. I am hoping that this is the issue.

I am sorry that I don't have any ready answers here, other than to watch your saildrive anodes and ensure you have a working GI. Having said that, I am now Coppercoated and waiting to see the results this season. If I have to get a lift-out three times a year that will have been an extremely expensive mistake but, as things stand at this moment, I am glad I went ahead.

I must also add that I have found Ewan at AMC (Coppercoat) to be extremely helpful and an excellent representative of a good British company. I would not want anyone to be put off Coppercoat by the above as I cannot swear that what I have been told is the absolute truth. It might be that the charter boats were not AMC Coppercoat but a rival company as the term seems to be a general one now, like Hoover.

However, if this issue has ever been reported to or investigated by AMC, I would be as interested as everyone to know if shore power earth leakage is the most likely cause.

Richard

 

[vyv_cox]

It has been stated in these forums many times that in genuine Coppercoat the copper particles are isolated from each other by the resin. Apparently it is even possible to use the product on saildrives, as CC is galvanically inert.

 

[RichardS]

It has been stated in these forums many times that in genuine Coppercoat the copper particles are isolated from each other by the resin. Apparently it is even possible to use the product on saildrives, as CC is galvanically inert.

All true but I'm not sure of the relevance Vyv.

At a molecular / ionic level, copper is leaching into the sea from exposed copper surface in the Coppercoat resin so the isolation in the resin is not relevant, assuming that there is any truth in the Service Manager's theory.

CC may be galvanically inert but if the real reason for three anode changes per year is galvanic action through shore power, CC is not going to stop it.

AMC recommended that saildrives are not coated because of adherence issues. As you say, there is no galvanic reason why they should not be coated but what is the relevance to the issue being raised?

Richard

 

[vyv_cox]

I don't agree with the theory that the boat is surrounded by a cloud of copper ions that is somehow reacting galvanically with the zinc. For a galvanic cell to be created the two metals need to be in contact with each other and immersed in the electrolyte.

In addition to that, Coppercoat as I understand it does not give off clouds of copper. The surface layer is oxidised/corroded in a short time to copper oxide, which is inert and is the antifouling agent.

I would not assume that the owner of a yacht charter company knows the first thing about corrosion theory.

 

[BlueChip]

My Yanmar saildrive leg is copper coated, over epoxy base coat.
My sail drive anodes last 2 seasons and even then doesn't really need changing

 

[RichardS]

My Yanmar saildrive leg is copper coated, over epoxy base coat.
My sail drive anodes last 2 seasons and even then doesn't really need changing

That's encouraging BlueChip, although the Coppercoating, or not, of the saildrive is not at issue.

I guess that you are in a tidal area which might be a factor if there is any basis to this problem. Contrary to Vyv's belief, I suspect that copper ions will be present in the seawater around a Coppercoated boat and will tend to be in higher concentration where there is little or no tide or current. However, even at the highest theoretical concentrations, I seriously doubt that this would impact on the anodes but something is apparently causing premature anode depletion in my Croatian marina and, according to the people who live and work there, this affects the Coppercoated boats.

I suspect the problem is more likely to be the shorepower system and is effecting the charter boats in particular because they spend a lot of time on shorepower and perhaps don't have a GI, but that is also speculation.

My boat, prior to CCing had similar anode wear to yours. I will see what happens over the next season but, if there is a problem, and this thread elicits comments from others, forumites might be in a better position to make a balanced decision.

Richard

 

[pvb]

I suspect the problem is more likely to be the shorepower system and is effecting the charter boats in particular because they spend a lot of time on shorepower and perhaps don't have a GI, but that is also speculation.

If that's the case, isn't it rather unfair to Coppercoat to give this thread the title "Is There An Undiscussed Problem With Coppercoat?"

 

[RichardS]

If that's the case, isn't it rather unfair to Coppercoat to give this thread the title "Is There An Undiscussed Problem With Coppercoat?"

I've been as balanced as I can be in the post bearing in mind that I am reporting exactly what I have been told by two sources who have no reason, AFAIK, to be negative towards CC. In fact, I would suggest that I have been emphatically pro-Coppercoat.

I have to mention Coppercoat in the title and I have to mention that it is about a potential problem and I think it wise to mention that it is previously undiscussed as otherwise the title would be meaningless or forumites would expect it to be the usual coating-a saildrive-with-Coppercoat non-issue, although Vyv did refer to this unrelated matter anyway.

However, if anyone can suggest a better title with the number of characters available I would be happy to change it, if that is possible.

Richard

 

[neilf39]

I thought the saildrive should be completely isolated so there is no way you can set up a galvanic current as there was no circuit. Article in PBO in the latest issue about saildrive and anodes and isolation from engine/prop. I guess you could, if you got carried away and applied it so the coppercoat bridged the isolation, and the copper mixing was not done well enough, may be able to make the circuit that could do it. If you painted onto the anode mounting and had shore power then that could also accelerate it.

If it was to do with copper ions suspended in water then wouldn't you need to leach the equivalent of what's vanished from the anode. If copper came out like that then I can't see there being much copper left on the hull after a few months. I'd be very suspicious of the epoxy coating used if it could do that.

I should add that's me just supposing aloud and based on my elementary knowledge so nothing authoritative in what I say whatsoever.

 

[pvb]

You can't edit thread titles.

 

[oldvarnish]

To answer the OP - there is no aspect of CC which hasn't been discussed here, other than how it tastes on chips.

 

[Vara]

To answer the OP - there is no aspect of CC which hasn't been discussed here, other than how it tastes on chips.

Love it

In response to OP, my shaft drive boat has been copper coated, and I have seen no electrolytic corrosion and anode wear is unchanged.

 

[RichardS]

I thought the saildrive should be completely isolated so there is no way you can set up a galvanic current as there was no circuit. Article in PBO in the latest issue about saildrive and anodes and isolation from engine/prop. I guess you could, if you got carried away and applied it so the coppercoat bridged the isolation, and the copper mixing was not done well enough, may be able to make the circuit that could do it. If you painted onto the anode mounting and had shore power then that could also accelerate it.

If it was to do with copper ions suspended in water then wouldn't you need to leach the equivalent of what's vanished from the anode. If copper came out like that then I can't see there being much copper left on the hull after a few months. I'd be very suspicious of the epoxy coating used if it could do that.

I should add that's me just supposing aloud and based on my elementary knowledge so nothing authoritative in what I say whatsoever.

I agree with you that this cannot be anything to do with the Coppercoat forming a conducting layer. The saildrive anodes are mounted in front of the prop and therefore well separated from the hull. Saildrives are not usually CC'd and the ones in Croatia were not so there is no chance of forming a direct electrical connection.

There would have to be some mechanism whereby a copper ion / sodium chloride concentration swilling around the saildrive and zinc anode and perhaps interacting with the metal pontoon or other boats is somehow accelerating the normal erosion of the zinc, perhaps enhanced by earthing issues with the shorepower / other boats which are being amplified by the "unusual soup" around the metal components.

I have no idea whether there is any scope in any of that but is it not the case that many problems of this kind created by a particular set of circumstances are brought to light by a chance observation (or a chance posting on a forum - I can think of a subsequently very well documented example from circa 2009!

Richard

 

[tcm]

Good experiences here with CC on a cat, and yes, even on the sail drives. I used 2 coats of epoxy primer first, then the CC. Slow anode usage I(sort of half an anode a year...) before and after applying tho not often on shore power.

Oh, and CC actually tastes of nothing much, but is a bit gritty with or without chips ...

 

[RichardS]

To answer the OP - there is no aspect of CC which hasn't been discussed here, other than how it tastes on chips.

I'll take your word for it Paul but I have to say that I cannot recall reading any posts concerning vastly accelerated anode depletion arising from Coppercoating. I apologise if I have missed them.

Nothing to do with you Paul but just to emphasise, we are talking about saildrives here. However, any evidence of accelerated anode wear on shaft drive boats might be relevant if it exists.

Jesus - this is beginning to sound like some kind of conspiracy theory of mine but surely exchanging information in good faith is what this forum is for?

I have sat on this for 3 months now in the hope that someone else might raise the same issue. If, in a few weeks time, in finally transpires that there is an issue here, undiscussed or not, I will expect to be raised to the level of a Sailing Deity ..... minimum!

Richard

 

[vyv_cox]

or forumites would expect it to be the usual coating-a saildrive-with-Coppercoat non-issue, although Vyv did refer to this unrelated matter anyway.

Far from unrelated, there can be no better illustration of the galvanically inert nature of Coppercoat. Saildrives seem to corrode at the drop of a hat, even when anodes that may be slightly suspect are connected to them. A copper-based conventional antifouling would corrode them, whereas Coppercoat does not. How then can it be that CC corrodes anodes that are galvanically less noble than a saildrive leg?

 

[VicS]

Saildrives seem to corrode at the drop of a hat, ............ A copper-based conventional antifouling would corrode them,

not even sure that this is totally true. I notice Jotun say their Seaforce30 and Mare Nostrum antifouling ( maybe others as well but those are the two I checked on) can be used on aluminium, provided they are applied over a two part epoxy . Both are copper(I) oxide based,.


It would be interesting to immerse a piece of aluminium in seawater containing some added copper salt(s). I wish I still had access to lab facilities!

 

[RichardS]

Far from unrelated, there can be no better illustration of the galvanically inert nature of Coppercoat. Saildrives seem to corrode at the drop of a hat, even when anodes that may be slightly suspect are connected to them. A copper-based conventional antifouling would corrode them, whereas Coppercoat does not. How then can it be that CC corrodes anodes that are galvanically less noble than a saildrive leg?

"On immersion, seawater attacks the exposed pure copper powder, causing the formation of cuprous oxide. This highly effective anti-fouling agent deters growth until the surface degrades further to become cupric hydrochloride. This final copper form is highly unstable, and is washed away by the movement of the yacht, thereby removing any accumulating silt or slime. This automatically exposes a fresh copper-rich surface whereby the process starts again." Coppercoat Website

There is no doubt therefore that "highly unstable cupric hydroxide", whatever that is, is probably leaching into the water around the boat and breaking down into ...... what?

The fact that the copper has certain properties when it is bound within the resin might be irrelevant. If the boat is not moving and there is little water current, might the higher concentration of these ions be amplifying any shorepower earthing problems or enhancing normal anode depletion in some way. In both cases enhanced by the large surface area of aluminium sitting in the middle of all this.

These are just hypotheses. Hopefully we might have someone come along with some more empirical evidence. If there is none then I will be delighted since I have just spent £4,000 on this!

Richard

 

[Hydrozoan]

... Coppercoat as I understand it does not give off clouds of copper. The surface layer is oxidised/corroded in a short time to copper oxide, which is inert and is the antifouling agent. ...

Firstly, no copper compound which forms upon a copper surface is going to be ‘inert’. There will be some solubility, normally giving rise to enhanced copper in local solution (see below).

Secondly, I am not convinced that a copper oxide is the ultimate solid corrosion product on a copper surface immersed in seawater. I answered an old question by macd on this subject, on a recently resuscitated thread here: http://www.ybw.com/forums/showthread.php?263637-More-coppercoat.

This was macd’s orginal point:

‘According to Coppercoat's website:
"On immersion sea water attacks the exposed pure copper powder, causing the formation of cuprous oxide. This highly effective antifouling agent deters growth until the surface degrades further to become cupric hydrochloride. This final copper form is highly unstable, and is washed away by the movement of the yacht, thereby removing any accumulating silt or slime. This automatically reveals a fresh copper rich surface, whereby the process recommences."

Yet according to Wiki, cuprous oxide is red, sometimes yellow. So what's the green? (Evidently cuprous chloride (CuCl or Cu2Cl2) is green; cupric chloride, yellowish to brown; couldn't find any references to cupric hydrochloride.)

I've noticed that Coppercoat usually becomes a dull, dirty green, but occasionally have seen it much brighter and paler, almost an emerald green.

Any chemists out there?’

This was my (Hydrozoan’s) response:

‘Reading this resuscitated thread, with which I was not previously familiar, has prompted me to try to address your puzzlement.

Cuprite, the mineral form of cuprous oxide, is indeed red. I am not certain what compound is described by the term ‘cupric hydrochloride’; only a few chemical sites refer to it, but one of them gives the formula ClCuH+₂ which surprises me as a positive charge would not apply to a solid compound, but to an ion. It’s odd: perhaps it refers to cupric chloride (CuCl₂ (s)), which is green. (BTW, I use (s) to indicate a solid – not absolutely necessary here, but a widespread convention in aquatic chemistry to distinguish solid phases from dissolved complexes having the same formula.)

But as the name and formula are not chemically clear, I won’t pursue that further - especially as several other copper corrosion products are, I think, more likely to be ultimately stable under seawater conditions, and are also green. These are:

A basic copper carbonate: Cu₂CO₃(OH)₂ (s), Malachite in mineral form, which is the typical patina on bronze statuary exposed to weathering (aka verdigris, although that is also applied to a copper acetate).

A basic copper chloride: Cu₂Cl(OH)₃ (s), Paratacamite in mineral form (also Atacamite, Botallackite and Clinoatacamite).

I have not done a detailed literature search, and many relevant papers would be behind paywalls, but an abstract here http://www.sciencedirect.com/science/article/pii/S0010938X04001350 of the paper by L. Núñez et alia, ‘Corrosion of copper in seawater and its aerosols in a tropical island’, Corrosion Science, 47(2), 461-484) reports that Paratacamite was found to be the main copper patina ‘... formed under complete immersion, on the line of water and in the splash zone’.

So, my suspicion is that the green colour is a basic cupric chloride, although a basic copper carbonate (Malachite) might be another possibility (the phase diagram in Figure 4 here http://cool.conservation-us.org/jaic/articles/jaic31-03-007_2.html shows the Paratacamite/Malachite boundary occurs at around the typical pH of seawater).

I am sorry that this is rather a late response, but hope you and others may find it interesting and/or helpful nonetheless.’


With regard to the present thread, I emphasize that I wish only to:

1. Correct the notion that any corrosion layer on copper in contact with seawater will be completely ‘inert’. The laws of chemistry and physics mean that, unless the background concentration of dissolved copper is higher than the solubility of the copper corrosion product, there will be an enhanced dissolved copper concentration in the immediate vicinity of a layer of corrosion product on the surface of a copper particle.

2. Point out that the ultimate solid corrosion product is likely IMO to be not cupric oxide but a basic cupric carbonate - a hydroxy carbonate, if you prefer - like Cu₂CO₃(OH)₂ (s) (in mineral form, Malachite) or, and probably more likely, a basic copper chloride - a hydroxy chloride, if you prefer - like Cu₂Cl(OH)₃ (s) (in mineral form, Paratacamite). (It is also possible that either a basic chloride or a basic carbonate might form, under different conditions.)

Since writing my reply to macd’s original query, it has occurred to me that the Coppercoat site’s ‘cupric hydrochloride’ might in fact mean a ‘copper hydroxy chloride’ like Cu₂Cl(OH)₃ (s). But this may not be the case, and as the name ‘cupric hydrochloride’ is chemically unclear, I think it would be helpful to use modern chemical nomenclature in discussing what substances are likely to be involved.

 

[duncan99210]

No idea what esoteric copper salts may or not be forming round my boat but what I do know is that the Coppercoat has been on it for the past fourteen years. My Saildrive anode lasts two or three seasons, mainly dependent on going through the hassle of adapting it to the rope cutter. As others have said, there is no electrical connection between the hull and the Saildrive, so the anode only has to protect the Saildrive, a fairly small area of painted metal hence the slow use rate.

I can only think that the chap who's boat you saw in Croatia was not maintaining the electrical isolation between engine and Saildrive, hence the speed that his anodes were being used. I can see no mechanism whereby the Coppercoat could be involved in the reaction at all.

Forgot to mention, we're Med based, so little or no water movement to wash away any copper salts that might or might not be hanging round.