Coppercoat - galvanic reaction around anodes?!

[Babylon]

I wonder what's going on here?!

Boat was lifted a few days ago and - for the first time since she was Coppercoated in 2015 - some kind of galvanic reaction is apparent in the areas of the two main hull anodes, the big pill jobbie and the smaller one on the skeg.

The only thing I can think of to explain the difference between now and the previous seven years is that last winter I'd left the engine and domestic battery banks switched on by mistake, which, despite wind-gen charging, resulted in both banks discharging. I thought at the time this was to do with residual current in the circuits, but could this be related to the engine earth being bonded to the pill anode (however not the skeg one)?

Any ideas?

 

[Ammonite]

Happens a lot, mines the same, and the guy that does the copper coating in our yard sees it all the time. I suspect you are right about the bonding but I'd be keen to understand the process. Its not ideal but painting a square of Trilux around the anode gets round it.

Edit: brick cleaner will remove the build up. You'll probably experience the same thing if you have a keel cooler fitted. The (coppercoated) unbonded thru hulls don't experience this.

 

[tross]

This is can be a problem with copper coat - I have the same sort of issue with the sail leg and the aluminum rudder post on my Hanse 315b. I use a non-coppoer based antifloul to create a "fence" around them

 

[vyv_cox]

AMC state that Coppercoat does not react galvanically, as the individual grains of copper are surrounded by isolating epoxy. If it was galvanic the zinc would be attacked as it is more anodic(!).

It is not clear to me in the photos: is the Coppercoat lost or covered with marine growth?

 

[Babylon]

Thanks for that input Tross and Vyv.

I wasn't there when the boat was lifted and pressure-washed on Monday, so I don't know why those patches of growth weren't (our couldn't be) jetted off, but I'm almost totally sure they are hard growth over intact Coppercoat. I'll be back down for a couple of day's work next week, so will have a go with brick-cleaner and a scraper etc.

 

[Kelpie]

I have a similar thing happening around my anode. I'm puzzled about it. It seems like the CC just becomes ineffective there and hard growth builds up.
I scrub underneath the boat weekly, and have ruled out my previous theory that it was simply the slightly harder access around the anode that was causing this.

 

[Ammonite]

AMC state that Coppercoat does not react galvanically, as the individual grains of copper are surrounded by isolating epoxy. If it was galvanic the zinc would be attacked as it is more anodic(!).

It is not clear to me in the photos: is the Coppercoat lost or covered with marine growth?

On mine it's definitely marine growth over intact coppercoat around any exposed metal (anodes and keel cooler) attached to the bonding system. It's a shell type deposits that fizzes away to nothing when you douse it with brick cleaner.

Edit: it doesn't affect the area around the stainless rudder shaft though, just the anodes and keel cooler

 

[Whaup367]

I have a similar issue, picture below. The coppercoat seems compromised around the anode but I don't understand the mechanism that would cause this, given that the Copper particles are insulated by the epoxy substrate.
Boatyard suggested it could be an electrical issue in the boat (bad earthing?)... that doesn't seem to make sense to me.

Could it be localised reduction of the copper due to proximity to the aluminium anode, rather than connectivity?

 

[srm]

I had similar when I lifted out after ten years. A few years earlier the CC was covered with growth extending from a sintered bronze cooling plate for the fridge and a smaller patch around the zinc hull anode. However after ten years the CC had disappeared when cleaned off leaving a patch of the undercoat epoxy about 40 cm radius around the bronze fitting and a smaller patch around the anode. I had a few other small patches and blisters in the epoxy undercoat to touch up so re-coated the bare areas.

Lifted out again a couple of weeks ago after a further four years afloat and all coatings are still intact.

A not very bright surveyor (judging by his insurance survey of my boat) on seeing the patch at ten years dismissed it as electrolysis, but after correcting too many factual errors in his report I have zero faith in anything he said.

 

[Babylon]

Interesting to hear similar experiences. Amazing that there's no clear reason why!

After cleaning, if my CC is compromised (and maybe even if it isn't) I'll apply fresh CC to the effected areas. As I said earlier, I never had this in the previous seven years, so hopefully a fresh coat will keep it at bay for another seven.

 

[trialframe]

It seems very common & I've never fully understood why. Ring of trilux seems to work well though.

 

[Babylon]

Just out of interest, are those skin-fittings electrically bonded to the engine earth?

 

[Sandy]

Perhaps somebody should get the nice people at Coppercoat to look at this thread as there is a body of evidence showing something is happening. I have always found them to be very helpful.

 

[geem]

I contacted them about it several years ago and they said it was calcium growth. I an not convinced and we still get it happening

 

[Babylon]

They're not wrong - it certainly looks like calcium - but the question is why it sometimes happens, and always, it seems, around anodes?

Don't get me wrong, I'm not knocking Coppercoat, it's a great product and I've been delighted with it for the last eight years: no hauling, scraping and painting. The current haul-out (for insurance survey) is only my third since 2015, the previous one was 2020 (standing rig replacement), etc. Otherwise it's just been dry-out on a wall, pressure wash, polish and grease prop, then float off. So, aside from the saving in elbow-grease and paint tins, it's already saved me a whole ton of money in yard costs.

 

[Fr J Hackett]

Does this help

Fitting Anodes To Copper-sheathed And Copper-clad Boats

 

[Babylon]

That's certainly very interesting!

I think the essential thing is to more properly isolate the anode from the copper-impregnated epoxy that surrounds it, i.e. make it less 'adjacent'.

This should be relatively easy with the massive and long-lasting pill anode on the hull, for which I can fashion a slightly thicker plastic barrier (the old blue foam one in my photo at top is probably now quite degraded).

But the skeg anode is maybe more of a problem? Here the CC is applied over the square steel plate on which the small rectangular anode is bolted (I assume the yard put a neat epoxy barrier over the bare metal before applying the CC).

I'll be able to work it all out once I've cleaned it all up - and I'd certainly prefer to avoid having to also apply Jotron or other AF paint as a ring-fence, as this would defeat the object of not having to paint.

 

[RobbieW]

That's certainly very interesting!

I think the essential thing is to more properly isolate the anode from the copper-impregnated epoxy that surrounds it, i.e. make it less 'adjacent'.

This should be relatively easy with the massive and long-lasting pill anode on the hull, for which I can fashion a slightly thicker plastic barrier (the old blue foam one in my photo at top is probably now quite degraded).

But the skeg anode is maybe more of a problem? Here the CC is applied over the square steel plate on which the small rectangular anode is bolted (I assume the yard put a neat epoxy barrier over the bare metal before applying the CC).

I'll be able to work it all out once I've cleaned it all up - and I'd certainly prefer to avoid having to also apply Jotron or other AF paint as a ring-fence, as this would defeat the object of not having to paint.

Just using a thicker pad wouldnt do it for the main anode I dont think. The anode is electrically connected to the bolts which have a flange on the outside of the hull which would connect with the coating. I see the same phenomenon on my current copper coated boat and saw something similar on my V28 which had copper in the gelcoat.

 

[Rappey]

A friends boat has the same problem around his bronze through hulls, except one which is isolated from all the others.

 

[Tranona]

That's certainly very interesting!

I think the essential thing is to more properly isolate the anode from the copper-impregnated epoxy that surrounds it, i.e. make it less 'adjacent'.

This should be relatively easy with the massive and long-lasting pill anode on the hull, for which I can fashion a slightly thicker plastic barrier (the old blue foam one in my photo at top is probably now quite degraded).

But the skeg anode is maybe more of a problem? Here the CC is applied over the square steel plate on which the small rectangular anode is bolted (I assume the yard put a neat epoxy barrier over the bare metal before applying the CC).

I'll be able to work it all out once I've cleaned it all up - and I'd certainly prefer to avoid having to also apply Jotron or other AF paint as a ring-fence, as this would defeat the object of not having to paint.

Looking at your photos raises the question as to why you need anodes at all. You don't say how the hull anode is connected and what it is protecting, nor how long it has been on. The skeg one is one the heel fitting but that may all be the same material, probably all 316. Presumably you have a feathering propeller with its own anode. How long does that one last?