cleaning copper coat with acid?

[Ric]

My hull is treated with coppercoat which has worked well for many years. However, the last few years those hard calcium wormy things have started to attach to it (what are they?). Last year I blasted most of them off with a pressure washer, then lightly sanded with a disc-sander with P120 discs to get rid of the more resistant bits. But this year the little blighters have come back worse, so maybe sanding was not such a good idea.

So I am thinking this year of maybe trying to dissolve them with acid - maybe get come HCL and mix it up with wall-paper paste and brush it on?

Anybody tried it?

 

[emandvee44]

I use muriatic acid neat (i think it is supplied 28% strength) to clean calceous deposits such as barnacles and calceous wormy things from the prop., bow thruster blades, sail drive leg. It is hydrochloric acid, called "acido muriatico" over here.
Very fast results!
Beware of the fumes and wear protective stuff, for eyes and hands.
M.

 

[RichardS]

My hull is treated with coppercoat which has worked well for many years. However, the last few years those hard calcium wormy things have started to attach to it (what are they?). Last year I blasted most of them off with a pressure washer, then lightly sanded with a disc-sander with P120 discs to get rid of the more resistant bits. But this year the little blighters have come back worse, so maybe sanding was not such a good idea.

So I am thinking this year of maybe trying to dissolve them with acid - maybe get come HCL and mix it up with wall-paper paste and brush it on?

Anybody tried it?

That's very worrying because I get a horrendous build up of worm casts despite abrading every year. I have contacted Coppercoat and they say that the abrading with Scotchbrite is not vigorous enough and that I need to machine sand with 100 grit down to bare copper .... so that's what I'll be doing in a couple of weeks.

I've tried neat hydrochloric acid but with limited success because it runs off too quickly and the run off is bright green so it looks as if it is taking the copper with it more than the worm casts. If you can get it to stay on it might work better but perhaps don't use it too concentrated.

Richard

 

[dslittle]

I've tried neat hydrochloric acid but with limited success because it runs off too quickly and the run off is bright green so it looks as if it is taking the copper with it more than the worm casts. If you can get it to stay on it might work better but perhaps don't use it too concentrated.
Richard

I’ve used Kilrock Gel (https://www.kilrock.co.uk) with good results. As a gel it’s ’sticky’ and it does seem to dissolve the nasties on my prop shaft quite well. Might be worth a go. No connection etc it just worked for me...

 

[macd]

the last few years those hard calcium wormy things have started to attach to it (what are they?).

They're "tube-worms", which isn't at all specific since it includes many distinct species. To quote Wiki, "A tube worm is any worm-like sessile invertebrate that anchors its tail to an underwater surface and secretes around its body a mineral tube, into which it can withdraw its entire body."

Whatever type they might be, Coppercoat seems particularly susceptible to them, albeit in the relatively few places where they seem epidemic. We had a deep-pile carpet of the damn things after three weeks in Thessalonika. Nowhere else has been remotely as bad. Being regularly under way seems the best preventative.

If you're a capable swimmer, they're removed from Coppercoat relatively easily with a Bahco-type scraper whilst snorkelling. Works up a terrific thirst

 

[geem]

They're "tube-worms", which isn't at all specific since it includes many distinct species. To quote Wiki, "A tube worm is any worm-like sessile invertebrate that anchors its tail to an underwater surface and secretes around its body a mineral tube, into which it can withdraw its entire body."

Whatever type they might be, Coppercoat seems particularly susceptible to them, albeit in the relatively few places where they seem epidemic. We had a deep-pile carpet of the damn things after three weeks in Thessalonika. Nowhere else has been remotely as bad. Being regularly under way seems the best preventative.

If you're a capable swimmer, they're removed from Coppercoat relatively easily with a Bahco-type scraper whilst snorkelling. Works up a terrific thirst

We put together a low pressure hookah for cleaning the bottom of the boat. Since we are 7’2” draft cleaning the keel with a snorkel is a real chore.
The whole system only runs at approx 17psi compared to 145psi on regular dive gear. We have an aquarium compressor, 100ft of air breathing hose and a special low pressure regulator. The compressor plugs in to the boat 12v or 24v system and away you go. Uses very little power although the motor is supposed to be 120w it doesn't seem to use any thing like that much power. It works really well and takes up little space compared to dive tanks etc. All the bits came off Ebay.

 

[Peter]

Good idea and worth a try. do you have the detail of the bits, especially the regulator

Thanks

 

[ElizabethBrown22]

hey richard,
Thats true. Yesterday, I tried the same thing. what is the proportion to mix it well?

 

[geem]

Good idea and worth a try. do you have the detail of the bits, especially the regulator

Thanks

Peter,
The hose should be air breathing hose. We have about 100ft and its perfect for us. 10mm inside diameter. They sell it on Ebay for air fed masks when you are paint spraying toxic paint.
The second stage regulator should be set to 17psi. Its very low. They are normally set at 145psi. If you have a spare second stage a dive shop should be able to change the springs to give the desired low pressure setting. Alternatively you can buy one direct from the States from 1936margarita. Thats the Ebay seller name. Product number was 173443549042.

The compressor we purchased is 24v because our boat is 24v. It is made by a company called Resun. Ours moves 115l/m and has a 120w motor. They do a 12v version which is MPQ-906.
Happy scrubbing

 

[RichardS]

hey richard,
Thats true. Yesterday, I tried the same thing. what is the proportion to mix it well?

Unfortunately, I've no idea. I was using the HCL at 19% as it came out of the bottle so you probably need to try diluting it with 75% water to see what happens but it depends what you are starting with .... that's if you can find a way to get it to stick on the vertical surfaces.

Richard

 

[macd]

As Richard suggested, you first need to know what strength of HCL you're starting with. HCl sold in supermarkets (often in red bottles or with red labels) is usually in the range of around 7 to 15% concentrated. This is certainly strong enough to clean calcareous growth from propellers, although it may require repeated treatment. HCl sold for swimming pool treatment may be 33%. In any case, the concentration should be clear from the container.

Note that in normal conditions HCl cannot exist at greater than 38% concentration, so pool acid is very strong (and tells you as much by its noxious fumes, which are particularly hazardous to respiratory tract tissues).

 

[Ric]

My post was not so much about efficacy of removing the tube worms - but whether it might be better at reactivating the copper coat. I usually abrade them off, leaving nice copper colour, but I now wonder whether that is not the best way to keep the copper active?

This year I'm going to try mixing up a vicious mixture of HCL, citric acid powder, oxalic acid crystals, and wall paper paste and plastering it over the copper coat, and see what happens. Hopefully it might take off all the tube works and also have some nice chemical reaction that keeps them away..

 

[sailaboutvic]

We put together a low pressure hookah for cleaning the bottom of the boat. Since we are 7’2” draft cleaning the keel with a snorkel is a real chore.
The whole system only runs at approx 17psi compared to 145psi on regular dive gear. We have an aquarium compressor, 100ft of air breathing hose and a special low pressure regulator. The compressor plugs in to the boat 12v or 24v system and away you go. Uses very little power although the motor is supposed to be 120w it doesn't seem to use any thing like that much power. It works really well and takes up little space compared to dive tanks etc. All the bits came off Ebay.

We had a hookup for some years now (10) although we brought our as a kit , it's paid for it self ten time over and more .

 

[Yngmar]

My post was not so much about efficacy of removing the tube worms - but whether it might be better at reactivating the copper coat. I usually abrade them off, leaving nice copper colour, but I now wonder whether that is not the best way to keep the copper active?

This year I'm going to try mixing up a vicious mixture of HCL, citric acid powder, oxalic acid crystals, and wall paper paste and plastering it over the copper coat, and see what happens. Hopefully it might take off all the tube works and also have some nice chemical reaction that keeps them away..

The acid will destroy the tube worm shells just fine, they're made of calcium, so it's much like descaling your kettle, where 15-20% hydrochloric acid does a very fast job (just did that the other day).

I'm no chemist, so I might get the details wrong here and my understanding is incomplete, but I think the basics are like this: Coppercoat is copper particles glued to the hull with resin, then sanded so they stick out. When it activates in the water and turns green, it turns into a copper oxide, which is the actual anti-fouling agent. Copper oxides dissolve in hydrochloric acid!

So by applying hydrochloric acid to the hull, you are disabling the Coppercoat. This may even work for a bit, as often fresh copper particles are exposed when the old are washed away, but eventually you will have to sand it down to expose more as there will only resin be left on the surface. So the acid treatment is quite counterproductive, at least with hydrochloric acid - other acids (citric? acetic?) may be able to remove the calcium remains without dissolving the copper oxides.

We usually scrape in the water and the hard plastic edge of a €1.50 scrubbing brush knocks any tube worm nests off pretty well, without damaging the Coppercoat like a metal scraper would. Something like that should work pretty well out of the water too.

 

[vyv_cox]

I agree wholeheartedly with Yngmar. Copper is not much of an antifouling medium, Coppercoat turns green after a period of immersion, I believe due to the formation of a copper oxy-chloride compound. It is this that is the antifouling agent. Acid will remove this and the whole process must then start again. Naturally, this consumes the copper.

We winter ashore and by spring time the tube worm shell can be brushed off. Even in the water a stiff brush will deal with most of it.

 

[Hydrozoan]

The acid will destroy the tube worm shells just fine, they're made of calcium, so it's much like descaling your kettle, where 15-20% hydrochloric acid does a very fast job (just did that the other day).

I'm no chemist, so I might get the details wrong here and my understanding is incomplete, but I think the basics are like this: Coppercoat is copper particles glued to the hull with resin, then sanded so they stick out. When it activates in the water and turns green, it turns into a copper oxide, which is the actual anti-fouling agent. Copper oxides dissolve in hydrochloric acid!

So by applying hydrochloric acid to the hull, you are disabling the Coppercoat. This may even work for a bit, as often fresh copper particles are exposed when the old are washed away, but eventually you will have to sand it down to expose more as there will only resin be left on the surface. So the acid treatment is quite counterproductive, at least with hydrochloric acid - other acids (citric? acetic?) may be able to remove the calcium remains without dissolving the copper oxides.

We usually scrape in the water and the hard plastic edge of a €1.50 scrubbing brush knocks any tube worm nests off pretty well, without damaging the Coppercoat like a metal scraper would. Something like that should work pretty well out of the water too.

Whilst the acidic ‘strength’ of acetic or citric acids would be less than that of a mineral acid, the acetate and citrate ions complex metals such as calcium and thus help bring them into solution - that is why they can be effective descalers. But they also, in the same way, complex copper (and copper for chemical reasons forms very strong complexes) so they would tend to dissolve copper solids as well as the calcium carbonate of the tubeworm shells. Any acid washing would simply tend to dissolve away accessible and active copper at the surface.