Cleaning Copper Cladding

[Neeltje]

Hi folks,

I've got a solid oak barn door rudder whose lower section (bwl) is clad with a thin sheet of bare copper that I just scraped a 2-inch thick coat of barnacles off of.

As you can see below, the copper cladding is totally oxidized (vert de gris), and since I don't have enough grease left in my elbows to hand sand it, I was thinking of using some sort of etching compound to clean it before the epoxy primer and antifouling go on.

So far, I've found etching compounds for just about every metal under the sun except copper, and all of those warn against using their product on high copper content alloys.

I was thinking of trying the vinegar & ammonia concoction my grandmother used on her pots and pans, but since I never saw her use it on her iron kettles, I'm afraid it might eat the rudder's iron hinges off...

Any suggestions would be greatly appreciated. Thank you for your support,

Jacques

[Jim Cate]

Jacques, I can't help you with the alchemy, but would like to comment that your picture should be made a "sticky" here on CF... to be shown every time that someone comes up saying that copper sheathing is good antifouling!

What a mess! good luck with finding a good prep technique.

Jim

[Tingum]

Sno-bowl toilet cleaner will do the job.

[Neeltje]

Originally Posted by Jim Cate

Jacques, I can't help you with the alchemy, but would like to comment that your picture should be made a "sticky" here on CF... to be shown every time that someone comes up saying that copper sheathing is good antifouling!

What a mess! good luck with finding a good prep technique.

Jim

Yeah, it was always said that copper was by essence antibacterial. Now I know better than to confuse "antibacterial" with "antifouling".

Like my granddaddy used to say, "You live and learn, or you die trying"....

Jacques

[Neeltje]

Originally Posted by Tingum

Sno-bowl toilet cleaner will do the job.

Tingum,

You're not kidding, right? Cause I was about this far away from trying Drano as a last resort.

Jacques

[marujo.sortudo]

I would just give it a light sanding, prime it as your antifoul recommends for bronze fittings and the like and paint it. Epoxy seems like a solution in search of a problem here.

[pjazz]

Bonjour Jacques,

Now that you have scraped the solids off, I would try pressure washing first. I'm talking about a gas powered unit generating real high pressure (at least 3000 PSI). If that doesn't work, you could take a random orbital sander to it and experiment with different disk grits till you find the right one.

Bonne chance!

[DefinitelyMe]

I don't have much experience with copper cladding but i am a chemist. Vinegar will do no damage whatsoever to the iron and will help to clean up the copper. The reason your grandmother didn't use it on her iron kettle is that it wouldn't have done much! However, it will take a very long time indeed and a lot of scrubbing as it is a very, very weak acid. I don't see any reason not to use something much stronger provided you don't leave it on for too long. Something like the marykate product 'on&off', which is a strong combination of hydrochloric, phosphoric and oxalic acids. A cheaper alternative would be a solution of hydrochloric acid from a hardware store (probably sold under the old name of 'muriatic acid'). I would just brush it on, leave it for about 30 seconds and then wash it off. Perhaps dilute it 1:1 with water first. Mechanics often use a solution like this to clean the capillary tubes of a heat-exchanger, which are made of copper. At any rate, do a test patch first. It will fizz as it comes into contact with the barnacles and eat them away quite rapidly. I think you will find it will work fine, though it may leave the surface of the copper slightly more porous than it was previously and i'm not sure therefore whether it will have a negative impact on future fouling........... perhaps giving it a sand afterward to smooth it out will negate this potential.

I'd try a test patch and give it a sand after the acid treatment to smooth it out a bit. See how it looks and decide whether you're happy with it. Regarding the iron hinges, it will have the added bonus of removing the rust. Just treat them afterward with something like ospho (which is a phosphoric acid primer for iron. It changes rust (iron oxide) into iron phosphate) followed by an epoxy coating like 2000e to keep future moisture out.

Good luck!

[DefinitelyMe]

Oh, and drano wouldn't have done much. Drain cleaner is a strong base (the opposite of an acid). Since barnacles are made mostly from calcium carbonate, which is also basic, you would have been quite disappointed with the results methinks!

[Bluemansailor]

Am in the process of cleaning all my bronze portals, make a paste of vinegar and salt- apply, let it sit, wash off - that got rid of the majority of the heavy discoloring and grime and then I used a great bronze paste to bring it up to look like new.

[Neeltje]

Thanks All,

Lots of food for thought here. My concern at this point is not so much the copper, but the wood behind it. The cladding isn't airtight by any means, and since all potential chemical treatments will require rinsing before painting, I'm afraid that the runoff might seep in behind the plates and damage the oak.

Hence my decision to simply sand the cladding, acetone it, prime it and paint it.

Since the tendons in both my elbows are toast and don't allow me to do this kind of work for more than 15 minutes at a stretch without crying, it might take a little longer, but what the hey, I'll be crying a lot more when I start on the 500 sq.ft. of bright work that follows.

Before you tell me that I should have taken up Badminton instead of Boating, be advised that playing ambidextrous Badminton is how I trashed my elbows in the first place.

[senormechanico]

Muriatic acid would work, but there goes the wood at the same time.
That stuff eats anything organic pretty quickly.

[SVTatia]

Originally Posted by Neeltje

...Before you tell me that I should have taken up Badminton instead of Boating, be advised that playing ambidextrous Badminton is how I trashed my elbows in the first place.

Hey Neeltje, but you still have the option of crocheting...

[perchance]

Steel wool and elbow grease works.

[Neeltje]

senormechanico: Yes, I found that out the hard way when restoring an old Morgan many moons ago.

SVTatia: Bad advice. Crocheting is harder on your elbows than most anything else you can do with your hands aside from knitting.

perchance: I've got enough Stainless Steel Wool on hand to scrub the Queen Mary from top to bottom. What's lacking is the elbow grease to go with it.

Jacques