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Old 20-03-2014, 18:23   #31
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Re: Cleaning Copper Cladding

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Originally Posted by Cheechako View Post
Good question; smooth copper or rough oxide? hmmm... not really sure. My guess is the oxide will hold it just as well if it's tight like most... but not sure if anybody knows. We all tend to sand our props and then the paint doesnt stick well... what if we just cleaned them only?
Now there's a thought I hadn't thought of (as my granddaddy used to say).

I'll simply acetone, prime and bottom-paint the oxidized cladding as is, and see how it holds up.

Thanks Cheechako.

Jacques
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Old 20-03-2014, 18:26   #32
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Re: Cleaning Copper Cladding

Almost any chemical that works on lime deposits will attack the copper. Have you considered new cladding? - might be easier & faster.

If you are determined to clean it you might try a Scotch-Bright disk in a right angle tool. We have these on bench grinders at the shop and they put a bright polish on copper & brass almost instantly.

On-line Product Catalog:Ā*Scotch-Briteā„¢ Metal Finishing Wheels

bench wheel:


angle pads:
https://www.google.com/search?q=3m+s...e+pad&tbm=shop
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Old 20-03-2014, 18:29   #33
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Re: Cleaning Copper Cladding

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Originally Posted by Neeltje View Post
Now there's a thought I hadn't thought of (as my granddaddy used to say).

I'll simply acetone, prime and bottom-paint the oxidized cladding as is, and see how it holds up.

Thanks Cheechako.

Jacques
Try brushing a patch of primer on it and let it sit a day, then see if it comes off easy or hard....
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Old 20-03-2014, 19:17   #34
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Re: Cleaning Copper Cladding

A few comments from another chemist. One problem with "painting" over the oxide is that most oxides are not well adhered to the substrate metal. Aluminum is the exception that I can think of. But an experiment wouldn't hurt, except for the time it would take. I mean, the oxide could flake off taking the primer with it.

With a thin cladding, I wouldn't use a concentrated solution of a strong acid. Don't trust labels, you might want to get the MSDS for any product you try; but they can be a little deceptive too. No muriatic (hydrochloric) nitric, or sulfuric acids. They could eat through the cladding before you could wash them off.

My suggestion would be to use vinegar with table salt. That's a fairly weak solution (5%) of acetic acid with sodium chloride. Honestly, I'm not sure what the salt adds to it but I've used that mix to clean off electrical cables before soldering or crimping. It's an old ham radio operator formula. Anyway, make a solution of cheap white vinegar with table salt. Make it about 1 tbs of salt per cup of vinegar. You could spray this on and spread it around and leave it for about a minute. That should clean the copper pretty well of oxide. Then neutralize it with a pretty concentrated solution of baking soda (sodium bicarbonate). Maybe a cup per half gallon or so. Baking soda is cheap. Rinse with water. For cleaning cables I usually follow with rubbing alcohol (isopropanol, 70%) to get all of the other crap off. But acetone would probably be better.

The disadvantage to this treatment is that in your case it will tend to dry out the wood, if it leaks through the copper cladding. That's probably not really horrible. If you use a bunch of baking soda solution and keep spraying it on you will certainly neutralize the acid. Rinse the hell out of it with a hose. Let it dry for a couple of days in hot sunshine to get any excess water out of the wood, in case it leaked through. Then prime and go for it.

One side remark. Barnacles (and other marine life) produce a hellacious glue to stick to surfaces. Chemists have been trying to duplicate this for many decades. I really don't know of any chemical treatment that you would want to use that would get that bioglue off.

Good luck and please keep us posted on what you try and what works.

Bill
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Old 20-03-2014, 19:34   #35
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A few comments from another chemist. One problem with "painting" over the oxide is that most oxides are not well adhered to the substrate metal. Aluminum is the exception that I can think of. But an experiment wouldn't hurt, except for the time it would take. I mean, the oxide could flake off taking the primer with it.

With a thin cladding, I wouldn't use a concentrated solution of a strong acid. Don't trust labels, you might want to get the MSDS for any product you try; but they can be a little deceptive too. No muriatic (hydrochloric) nitric, or sulfuric acids. They could eat through the cladding before you could wash them off.

My suggestion would be to use vinegar with table salt. That's a fairly weak solution (5%) of acetic acid with sodium chloride. Honestly, I'm not sure what the salt adds to it but I've used that mix to clean off electrical cables before soldering or crimping. It's an old ham radio operator formula. Anyway, make a solution of cheap white vinegar with table salt. Make it about 1 tbs of salt per cup of vinegar. You could spray this on and spread it around and leave it for about a minute. That should clean the copper pretty well of oxide. Then neutralize it with a pretty concentrated solution of baking soda (sodium bicarbonate). Maybe a cup per half gallon or so. Baking soda is cheap. Rinse with water. For cleaning cables I usually follow with rubbing alcohol (isopropanol, 70%) to get all of the other crap off. But acetone would probably be better.

The disadvantage to this treatment is that in your case it will tend to dry out the wood, if it leaks through the copper cladding. That's probably not really horrible. If you use a bunch of baking soda solution and keep spraying it on you will certainly neutralize the acid. Rinse the hell out of it with a hose. Let it dry for a couple of days in hot sunshine to get any excess water out of the wood, in case it leaked through. Then prime and go for it.

One side remark. Barnacles (and other marine life) produce a hellacious glue to stick to surfaces. Chemists have been trying to duplicate this for many decades. I really don't know of any chemical treatment that you would want to use that would get that bioglue off.

Good luck and please keep us posted on what you try and what works.

Bill
I am not a chemist, or even that formally educated, but...a have a hard time discerning how mixing an acid with salt is going to accomplish anything except neutralize the acid. Perhaps you could educate me on that.
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Old 20-03-2014, 20:13   #36
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Re: Cleaning Copper Cladding

Tantalus,

I think what happens is that the salt is included as a gentle abrasive, but I await the information of those more knowledgeable than I. The salt would eventually break down in the vinegar like it would do in salad dressing, but I don't know what the chemistry of that would be.



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Old 20-03-2014, 20:24   #37
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Re: Cleaning Copper Cladding

I wouldnt put anything on there like acid as it might wick into the wood beneath. The first thing wicked in will be the last you can get out. Either just take a vibrator sander and brighten it up or leave it. Most copper I've seen with red oxide on it... like but part of the surface. Is this the case with yours? Tight and cant be scraped off without scraping material off?
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Old 20-03-2014, 20:31   #38
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Re: Cleaning Copper Cladding

Neutralising the acid (in due course, and in crevices) might be another benefit of adding salt, in cases where you don't want the acid to go on working indefinitely.

This was an trick used by old-school metal workers after hardening tricky parts in alloy steel, to remove the inevitable scale, in the days before controlled atmosphere furnaces (eg by gunsmiths, making intricate trigger componentry).

The salt does not immediately dissolve in the vinegar, but eventually it does, presumably helping the attack to self-limit, rather than carrying on into the parent metal.
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Old 21-03-2014, 06:05   #39
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Re: Cleaning Copper Cladding

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I wouldnt put anything on there like acid as it might wick into the wood beneath. The first thing wicked in will be the last you can get out. Either just take a vibrator sander and brighten it up or leave it. Most copper I've seen with red oxide on it... like but part of the surface. Is this the case with yours? Tight and cant be scraped off without scraping material off?
The copper has turned grey (vert de gris) and looks more like pewter than anything else. 8 months after the initial (haul-out) pressure washing, I was able to scrape off what was left of the growth with a putty knife, but each barnacle left a 1 or 2 micron deep etching in the surface.

As mentioned before, the cladding isn't completely watertight, and I'm afraid that whatever chemical treatment I might use could seep in and continue it's dirty deed where I couldn't rinse it off.

Hence, my decision to do it "dry". I'll do a couple of test spots (with and without sanding) to see if the primer holds, and I'll get back to you with the results.

Thanks again for all your help,

Jacques
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Old 21-03-2014, 07:15   #40
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Re: Cleaning Copper Cladding

I don't have any idea what the table salt (NaCl) adds to the mix. (I'm a little embarrassed to admit) It's a "formula" that was told to me a few years ago by a Ham operator, for cleaning copper cables and it has worked for me. Frankly, from a chemical perspective I don't think it adds a thing.

Jacques, Regarding seepage into the wood. I doubt if the mild treatment would do anything that salt water wouldn't do. Try taking a piece of pine (less resistant than the oak) and put some vinegar on it and leave it for a week. Also, if you only leave the vinegar on for a minute or two and follow it with a serious neutralization with baking soda, it should all get neutralized, even the vinegar that seeps in.

But, it's an interesting problem in any case!

Bill
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Old 21-03-2014, 08:45   #41
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Re: Cleaning Copper Cladding

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I don't have any idea what the table salt (NaCl) adds to the mix. (I'm a little embarrassed to admit) It's a "formula" that was told to me a few years ago by a Ham operator, for cleaning copper cables and it has worked for me. Frankly, from a chemical perspective I don't think it adds a thing.

Jacques, Regarding seepage into the wood. I doubt if the mild treatment would do anything that salt water wouldn't do. Try taking a piece of pine (less resistant than the oak) and put some vinegar on it and leave it for a week. Also, if you only leave the vinegar on for a minute or two and follow it with a serious neutralization with baking soda, it should all get neutralized, even the vinegar that seeps in.

But, it's an interesting problem in any case!

Bill
Actually, I don't see why the p/o clad the rudder in the first place, unless it was intended to mask some pretty serious misery.

Also, since it was recently pointed out to me that since the tip of the rudder is lower than the skeg, there's a chance it might jump off its hinges when grounding.

I was therefore thinking of prolonging my shipwright's disease and building a new one, but out of teak just like the leeboard skids in the picture. They're below the waterline, bare as a baby's bottom, and they don't seem to want to rot or attract any kind of growth.
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Old 21-03-2014, 11:00   #42
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The purpose of copper cladding is to keep worms from eating the wood. Not sure if it's already been suggested but a wire(brush) wheel that you put in a drill will make short work of it. You can get fine medium or coarse. I would start with fine and if that doesn't work get coarser. The reason Lee boards are so clean is that the`re only in the water when you're sailing
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Old 21-03-2014, 11:51   #43
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Re: Cleaning Copper Cladding

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The purpose of copper cladding is to keep worms from eating the wood. Not sure if it's already been suggested but a wire(brush) wheel that you put in a drill will make short work of it. You can get fine medium or coarse. I would start with fine and if that doesn't work get coarser. The reason Lee boards are so clean is that the`re only in the water when you're sailing
Believe it or not, in the time you posted this, I went back to the boat yard where Neeltje sits and was told of a ship's carpenter who'd clad the entire bottom of his old wooden sailboat for just the same reason.

I'd already admired his boat anchored in Saint Augustine's southern most mooring field, but what I didn't know was that he works out of the Marine Supply Center I patronize on a regular basis, so I'm leaving to pick his brains as we speak.

BTW, if my leeboards look so "clean", it's probably due, in part, to the fact that they just got the same 12 coats of varnish that the rudder did.

Jacques
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Old 21-03-2014, 12:48   #44
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Re: Cleaning Copper Cladding

Jacques: <<The copper has turned grey (vert de gris)>>

Thanks for that ! I'd never considered the colour implication of the final word of "vert de gris" !

Bill_E: it makes sense to me to add an agent providing a *delayed* neutralising effect in the case of copper wire, where whatever you apply is going to inevitably wick its way along the strand(s) to a place from where it cannot be flushed.

Or ... are you implying (by refraining from endorsing the idea) that sodium chloride will not have any neutralising effect on acetic acid?
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Old 21-03-2014, 12:53   #45
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Re: Cleaning Copper Cladding

Doing archeological dives on ship wrecks from the late 1700's etc., often one of the only things left is sections of the copper sheeting. so apparently it lasts a long time in salt water.
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