Epoxy on Alu

[TiggerToo]

In another thread, I asked about what people do when they copper-coat the hull of a boat with an alu sail drive. A few said that, contrary to hear-say, coating the saildrive will not be a problem corrosion-wise because there is no conductivity between the copper and the alu.

This makes sense to me.

Does this mean that it is perfectly feasible to copper coat an aluminium hull of, say, an Ovni?

Just wondering...

 

[Tranona]

www.coppercoat.com will amswer your questions. Suitable for wood, GRP, steel, ferro and aluminium. So your dreams are intact, a Coppercoated Ovni it is.

 

[noelex]

There has to be electrical connection between the copper and the aluminium to cause a problem so it is feasible.

Saildrives would worry me far more than an aluminium hull as the aluminium used in sail drives is less resistant to corrosion and it is only a small piece of metal. The corrosion rate will be higher than on a larger aluminium hull.

However, I still don't think it is a good idea.

 

[RichardS]

CopperCoat is non-conducting because each particle of copper is surrounded by a dielectric resin so it's safe to coat metal. Getting it to stay coated is another issue and the metal surface needs a lot more careful preparation and priming than GRP.

Richard

 

[Tranona]

However, I still don't think it is a good idea.

Why don't you think it is a good idea when logic says that there is no connection between the copper in the resin and the aluminium and the manufacturers clearly recommend it?

 

[noelex]

Copper is very toxic to aluminium. The system relies on the resin and barrier coats isolate the aluminium from these copper flakes. A less harmful (to aluminium) antifouling compound is safer in my view.

 

[macd]

Copper is very toxic to aluminium. The system relies on the resin and barrier coats isolate the aluminium from these copper flakes. A less harmful (to aluminium) antifouling compound is safer in my view.

Flakes? Thought we were talking Coppercoat, not Kellogs

 

[lw395]

I've seen carbon fibre parts in contact with aluminium destroyed by the corrosion of the ali.
I would have thought the carbon was similarly insulated by epoxy....

 

[Tranona]

Copper is very toxic to aluminium. The system relies on the resin and barrier coats isolate the aluminium from these copper flakes. A less harmful (to aluminium) antifouling compound is safer in my view.

I think you misunderstand the way that Coppercoat is formulated. Pretty sure if the manufacturer of the coating did not have evidence that it is fine on aluminium hulls (and saildrives) they would not recommend it. Imagine the damages claims if it was not safe. No manufacturer that has been in business as long as they have would risk it.

Of course if you have evidence to the contrary then it would be interesting to see it.

 

[William_H]

I've seen carbon fibre parts in contact with aluminium destroyed by the corrosion of the ali.
I would have thought the carbon was similarly insulated by epoxy....

Yes if you put a multimeter on ohms scale on any bare piece of carbon fibre you get a relatively low resistance despite the fact that theoretically the carbon is encapsulated in the epoxy or any other resin. Aluminium must be insulated from carbon fibre especially if any electricalm potential is involved. No idea about coper coat however. But a multimeter would show fairly easily if there is conduction. olewill

 

[Daydream believer]

CopperCoat is non-conducting because each particle of copper is surrounded by a dielectric resin so it's safe to coat metal.

Richard

You may well be correct but i understood that for the coppercoat to work the surface layer of copper has to be exposed to the elements. Hence the need to lightly abrade the surface every couple of years to ensure copper is exposed. If that is the case then the copper is not 100% encapsulated --which you may be suggesting in the second part of your post

 

[RichardS]

You may well be correct but i understood that for the coppercoat to work the surface layer of copper has to be exposed to the elements. Hence the need to lightly abrade the surface every couple of years to ensure copper is exposed. If that is the case then the copper is not 100% encapsulated --which you may be suggesting in the second part of your post

The abrading thing is something of an urban myth. The resin used in Coppercoat is self-eroding which is why the coating "only" lasts 10 - 15 years. Abrading would only be needed if, for some reason, something water-resistant has coated the surface. Brushing the surface to remove slime on a little-used boat is worthwhile but only for cosmetic or speed reasons.

The copper surface is therefore exposed by the self-abrading but each sphere of copper is still laterally isolated from its neighbour.

Richard

 

[Daydream believer]

deleted

 

[Daydream believer]

The abrading thing is something of an urban myth. The resin used in Coppercoat is self-eroding which is why the coating "only" lasts 10 - 15 years. Abrading would only be needed if, for some reason, something water-resistant has coated the surface. Brushing the surface to remove slime on a little-used boat is worthwhile but only for cosmetic or speed reasons.

The copper surface is therefore exposed by the self-abrading but each sphere of copper is still laterally isolated from its neighbour.

Richard

When my coppercoat failed the first question from the manufacturer was " did you abrade the copper coat?"
So if the manufacturer says it is necessary I would not call that a "myth"
Here is the extract from the application instructions
I was also told by the MD to do this every couple of years

"Treated boats will benefit from having the cured Co
ppercoat surface lightly burnished with fine “wet a
nd dry” paper or
sanding-pad prior to immersion – this will expose t
he copper powder and increase the immediate potency
of the anti-fouling.
This process is particularly beneficial in areas of
high fouling. (Tip – we recommend using 600 grade
paper, wet, or a
Scotchbrite sanding pad and lightly rubbing the sur
face in a fashion similar to applying polish to a c
ar bonnet.)

Note the part " expose the copper powder"

Last edited by Daydream believer; Today at 14:45.

 

[RichardS]

When my coppercoat failed the first question from the manufacturer was " did you abrade the copper coat?"
So if the manufacturer says it is necessary I would not call that a "myth"
Here is the extract from the application instructions
I was also told by the MD to do this every couple of years

"Treated boats will benefit from having the cured Co
ppercoat surface lightly burnished with fine “wet a
nd dry” paper or
sanding-pad prior to immersion – this will expose t
he copper powder and increase the immediate potency
of the anti-fouling.
This process is particularly beneficial in areas of
high fouling. (Tip – we recommend using 600 grade
paper, wet, or a
Scotchbrite sanding pad and lightly rubbing the sur
face in a fashion similar to applying polish to a c
ar bonnet.)

Note the part " expose the copper powder"

Last edited by Daydream believer; Today at 14:45.

It was the abrading every couple of years bit that I said was a myth.

The part about possibly abrading before first launch after coating is still valid as in areas of high fouling a considerable amount of fouling might have built up before the resin self-abrades to reveal the first surfaces of copper. Once the Coppercoat is active the company do not currently recommend further abrading unless something insoluble coats the copper and stops it working. It would be interesting to see what Ewan from Coppercoat says about the MD's advice to abrade every couple of years.

I don't know how long ago your experience was but perhaps they have changed the formula of the resin to make regular abrading unnecessary?

Richard

 

[Daydream believer]

It was the abrading every couple of years bit that I said was a myth.

The part about possibly abrading before first launch after coating is still valid as in areas of high fouling a considerable amount of fouling might have built up before the resin self-abrades to reveal the first surfaces of copper. Once the Coppercoat is active the company do not currently recommend further abrading unless something insoluble coats the copper and stops it working. It would be interesting to see what Ewan from Coppercoat says about the MD's advice to abrade every couple of years.

I don't know how long ago your experience was but perhaps they have changed the formula of the resin to make regular abrading unnecessary?

Richard

The point I really want to make is that the copper is not all encapsulated but exposed. It would not work if encapsulated. As time passes the coating to each grain has to " dissolve" to expose fresh copper. It is for this reason that I for one do not coat the areas near the saildrive ( only up to the seal) and around my rudder stock.

 

[Javelin]

I'd be very wary of adding anything else into the corrosion mix near an Ovni.
The speed some of the anodes go down is frightening whilst others are fine.
Even if you are using a quality galvanic isolator and can be sure of no locally generated leaks you can't say the same in some marinas.

Apart from all that we don't feel that copper coat works any better than the cheapest antifoul on the East coast rivers.
Believe me if we found it did work we'd be using it and pushing it.

 

[Tranona]

I'd be very wary of adding anything else into the corrosion mix near an Ovni.
The speed some of the anodes go down is frightening whilst others are fine.
Even if you are using a quality galvanic isolator and can be sure of no locally generated leaks you can't say the same in some marinas.

Apart from all that we don't feel that copper coat works any better than the cheapest antifoul on the East coast rivers.
Believe me if we found it did work we'd be using it and pushing it.

Can't see how it would have any effect on the erosion of anodes as there is no electrical path between the copper in the coppercoat and the aluminium hull.

Coppercoat is not necessarily better as an antifouling product than conventional paint. The advantage is that it does not need to be replaced regularly, just washed off. This can lead to huge savings. For me one lift and wash as year for £70 compared with full haul out, hire or buy a cradle, storage, cost of paint and 2 or 3 days of slog cleaning and painting each year. Worth the upfront cost if you have longish time horizons and an aversion to messy work (or paying somebody else to get messy).

 

[Daydream believer]

Coppercoat is not necessarily better as an antifouling product than conventional paint. The advantage is that it does not need to be replaced regularly, just washed off. This can lead to huge savings. For me one lift and wash as year for £70 compared with full haul out, hire or buy a cradle, storage, cost of paint and 2 or 3 days of slog cleaning and painting each year. Worth the upfront cost if you have longish time horizons and an aversion to messy work (or paying somebody else to get messy).

+1 for that comment