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Does tarnish affect copper's strength?

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Does tarnish affect copper's strength?

Unread postAuthor: LikimysCrotchus5 » Mon Feb 23, 2009 9:32 pm

Title pretty much says it all.

It is winter over here and some of my copper chamber and barrel have begun to oxidize, tarnish. So i was just wondering is it hinders the strength of my chamber. Also, what would be a good way to get rid of it? Polish or sanding i presume?
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Unread postAuthor: dudeman508 » Mon Feb 23, 2009 9:40 pm

I would think that sanding it would decrease the burst preasure, but it wouldnt be enought to make a difference.
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Unread postAuthor: sputnick » Mon Feb 23, 2009 10:18 pm

I just use steel wool, and the copper would have to be EXTREMELY rusted and left in the rain for a very long time to affect the actual pipe.

Usually the tarnish encounter is so thin a few strokes with fine steel wool will get it to a shine again.

Nothing to worry about :)
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Unread postAuthor: LikimysCrotchus5 » Mon Feb 23, 2009 11:53 pm

Thanks, just curious. I knew it really wouldnt hinder its performance, but its better to be sure than not. I wonder how much would need to be tarnished in order for its strength to be diminished.

Hm...
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Unread postAuthor: Velocity » Tue Feb 24, 2009 12:00 am

If you can remove it with steel wool, its most likely insignificant. Like another poster said, it would need to be deliberately abused for an extended period of time to be weakened significantly for spudgun activities.
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Unread postAuthor: Davidvaini » Tue Feb 24, 2009 12:05 am

There are a couple good ways to get rid of the tarnish.

CLR is a very good cleaner that really works against calcium lime and rust. It cleans old coins really well.


There is also this powder stuff that when mixed with a little water becomes a paste. It is called CAMEO its copper, brass and porclean cleaner.

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I have used the CAMEO stuff on the copper pipes for my bathroom and it got rid of all the green yucky crap instantly. It then started to polish the pipe quite nicely getting rid of everything else that was left.
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Unread postAuthor: daxspudder » Tue Feb 24, 2009 2:43 am

unlike iron, when copper oxidizes (creating verdigris vice rust) it degrades the metal almost immeasurably, even thick verdigris ("ver-d'i-gree") has almost no effect on the metal it "grows" on(as long as it is copper carbonate...from air, not copper chlorate... from sea water)... so other than making it look bad it shouldnt hurt... there are however exceptions... like if it appears to be coming out of solder points... insufficient cleaning before applying flux can cause premature erosion of welds and create minor cracks in which verdigris can increase and even be caused by a reaction with excessive flux left behind...
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Re: Does tarnish affect copper's strength?

Unread postAuthor: Ragnarok » Tue Feb 24, 2009 4:32 am

LikimysCrotchus5 wrote:So i was just wondering is it hinders the strength of my chamber.

No. Copper tarnish is a layer only molecules thick, and it's a protective tarnish - that is, in forming, it protects the lower layers from tarnishing the same.

Where rust can go the whole way through the thickness of steel, copper tarnish is only on the very surface, not enough to affect it.

Personally, I'd just leave it - tarnish is not the prettiest thing in the world, but cleaning it is a lot of extra maintenance that doesn't need doing.
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Unread postAuthor: ralphd » Tue Feb 24, 2009 7:52 am

If you want nice and shinny copper then go to Graingers and buy "COIL Brite" coil cleaner. It an acid based foaming coil cleaner used in the HVAC industry. Make sure you don't get it in any cuts, it really hurts.
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Unread postAuthor: mark.f » Tue Feb 24, 2009 10:57 am

You guys are forgetting the fact that after you clean and polish it, it will just tarnish again in a matter of days, depending on the type of climate you live in (I live in Louisiana, so it's a matter of 2-3 days).

If you don't like it, clean it and then coat the chamber in some sort of protective varnish or clear-coat.
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Unread postAuthor: jimmy101 » Tue Feb 24, 2009 11:47 am

Another excellent cleaner, and the fastest and simplest, is Muriatic Acid (Hydrochloric Acid), which is available at most hardware stores.

20% HCl (what's in the jug you buy) will remove copper tarnish almost instantly without any scrubbing. Solder for copper pipe contains acid, the HCl does the same thing the flux in the solder does, it dissolves copper oxides. The HCL will remove the oxide coat but it won't polish the metal like sanding will.

You must thoroughly rinse the acid off. The acid will eat holes in your fingers, clothes etc. so be careful with it. The used acid can be flushed down a sink with large amounts of water.

Like markfh11q said, the copper will re-oxidize unless it is coated with something like a suitable laquer or a thin coat of oil.

I wouldn't use steel wool. Steel wool tends to leave fragments of iron behind that will rust within hours. The prefered abrasive for cleaning copper is fine wet-dry sand paper. You can use it dry, or better yet, use water as the lubricant. Sand paper is how plumbers clean pipe before soldering, I've never heard of a plumber using steel wool.
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Unread postAuthor: john bunsenburner » Tue Feb 24, 2009 12:23 pm

It is important to wash the acid of well though as it will form copper chloride which will weaken the chamber. I suggest leavign it be...
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Unread postAuthor: daxspudder » Tue Feb 24, 2009 2:31 pm

um HCL will produce copper chloride, the damaging verdigris(<<<means rust, but on copper not iron) rather than copper oxide, the tarnish... or course washing it off will not cause copper chloride, but the copper will tarnish as water help oxidize copper... use copper wool.... like steel wool but made from copper sheep instead
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Unread postAuthor: Davidvaini » Tue Feb 24, 2009 3:24 pm

if you use that cameo you dont even need sand paper or anything to polish it...

after you are done, just apply some sort of clear coat and you are good to go.
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Unread postAuthor: Big-E » Tue Feb 24, 2009 3:42 pm

Hi guys, new user here. Just thought this was a good opportunity to provide some input.

The more you polish any metal, the more it wears away at the material, especially with softer metals. Not a problem if you will only use a launcher for a few years, but if you want to use it in say, 30 years from now, it may weaken the tubing a bit. you would be best off letting the copper develop a natural patina (the brown patina looks great on copper, imo)

some people go through all kinds of trickery to force copper to look weathered. The oxidization is what makes copper roofing and the Statue of Liberty last so long.

If you do prefer the polished look, use as mild a method as possible to clean the copper. I would suggest electrolysis or some brasso (or any cleaner used to clean copper cookware and fixtures) and a soft cloth.

Oh, BTW, the clear coat idea will not work! I've tried it. You do end up with a most interesting glossy-looking dark jade green patina though! most clear coat is still porus, and it lets some trace moisture and air through. This is why the above described look comes on. Now if you primed, painted the tubing copper, and cleared it, then it will stay shiny. You could try a laquer-based clearcoat, it may work, trouble is, most clearcoat is made to be used with a base coat. Some clearcoats are designed to be used on bare metal however. Try an auto parts store, and buy clear engine paint if you want to go this route. No guarantees, though, because I never tried it on copper personally, but it's your best bet if you want to clearcoat it.

To keep the oxidization away, polish your copper, and apply Renaissance Wax (Museum Replicas sells it) it used to keep replica swords and armor from oxidizing when in storage. it should work on copper too, and would mean more time between polishings.
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