Copper antifoul + mud = barnacles

[snowleopard]

Snow Leopard is on a half-tide mooring so spends half her time in soft mud. By the end of the season the area where the hull is in contact with the mud is covered in barnacles and when scrubbed the surface is black. Where only water touches it, the coating is green and weed-free.

I suspect the black is copper sulphide from H2S produced in the mud.

Has anyone come across this and found an answer?

The manufacturers say either re-coat with copper or put conventional antifoul over the top of it. As they say, I've had 7 years use so it's paid for itself but I fear that if I just put more of the same on I'd still have the problem and I'm reluctant to go back to annual repaints.

 

[RestlessL]

Same for Restless. She came out with a clean hull, but a 6 inch strip of barnacles on the inside of each keel. They came off with a pressure wash.

I also have a black surface, but this is mainly at the bottom of the keels. I had the same black surface the previous season with conventional anti-fouling.

I suspect that I am just getting a thin layer of mud sticking to the keels, which the barnacles manage to hold on to.

In any event, I have no regrets about the copercoat.

John

 

[Grajan]

Very common in East Coast Harbours (Scotland)
The sulphur gas coming from the mud changes the copper based antifouling and copper sulphide isn't an antifouling have had limited success with hard film teflon based antifoulings. currently not aware of any product that has not got some copper in it
The new "non stick" frightfully expensive A/F's might work
but wether it would still be there at the end of the season is a different matter!

 

[snowleopard]

Last year's YM report on one of the non-stick a/fs was discouraging to say the least.

Another factor is the friction as the keels sink into the mud which is gradually scouring the epoxy away.

 

[Malish]

If you can get it you might try some dilute nitric acid followed by a water rinse - the nitric should oxidise the copper sulphide to copper sulphate (which is water soluble). Try on a v small area first and be v careful - rubber gloves, eye protection, plastic apron & wellies

 

[VicS]

I agree with your findings about barnacles. My boat, which normally dries into deep mud, usually comes out completely covered with barnacles where it is in the mud. This year I have been on a different mooring with very little depth of mud. There were only a few along the bottoms of the keels.

Not sure about the suggestion to wash with dilute nitric acid. Will it oxidise the copper sulphide to copper sulphate when cold? It'll be cuprous sulphide I think as that is the stable sulphide. If there is any reaction with cold dilute nitric acid I would have thought cupric nitrate and elemental sulphur would be produced. Pretty academic anyway as it is hardly practical the haul the boat out and wash its bottom in nitric acid a couple of times during the season.

BTW I think the equation in the title should read

Copper antifoul + mud = N barnacles, where N is a very large number!

 

[wotayottie]

[ QUOTE ]
the nitric should oxidise the copper sulphide to copper sulphate (which is water soluble).[/quote}

Nitric acid will (surprise surprise) turn the sulphide into copper nitrate. That will be soluble and will wash away.

 

[amadeus]

Last year I used Micron Optima painted on top of the expired copperguard and had a 2 gallon bucketful of barnacles on the hull of my Parker 275 at the end of the summer. She sits in a mud berth and dries out on low water springs with the centreplate raised. This year I used Interspeed Ultra and neither my boat nor any of the rest of the Club boats on the Exe had a single barnacle. We reckon the river water was so fresh from the rain it killed them all! It seems the conditions decide how many little friends you attract not the type of antifoul!

 

[PCUK]

My Copperbot is over ten years old and still going strong after life in a mud berth.
An annual sand down of the black with an orbital sander takes care of the problem.
Use a respirator as although it's not pure poison like normal antifoul, it' still nasty.

 

[Leighb]

[ QUOTE ]
Last year I used Micron Optima painted on top of the expired copperguard and had a 2 gallon bucketful of barnacles on the hull of my Parker 275 at the end of the summer. She sits in a mud berth and dries out on low water springs with the centreplate raised.

[/ QUOTE ]

I am not surprised !! Optima is a very soft self polishing antifouling. When you scrub it ever so gently with a sponge you see quids worth of paint drifting off downstream /forums/images/graemlins/frown.gif
I used it for several seasons, and it was not bad, but shifted mooring to an area with stronger tidal stream, and it all eroded too fast. Last few races were a disaster that year.

Sitting in a mud berth I would imagine that it would only be a few weeks before you had precious little Optima left - hence the barnacle overcoat. As said above I changed to Seajet Shogun which has been excellent.