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Old March 29, 2011, 07:26 PM   #1
snuffy
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What! copper brass?

WTH copper brass?
I can find more ways to screw up! What's happened to this load of brass in my HF sonic cleaner?





I was running some mildly corroded LC brass,(new,never fired), through to remove the water caused corrosion. I had already done 3 batches with no problems. Using the new Hornady one shot case clean solution.

What was different for this load was I had dropped a steel shoe horn into it to see if it would remove the rust. I forgot it was in there, dropped the 100 cases in and started it up.

Maybe somebody on here with chemical knowledge will tell me why the brass that was in close proximity to the steel shoe horn was discolored to a copper color. The steel was covered in a black powder, as were some of the copper colored brass. They have been through a 2 hour tumble in my vibratory cleaner with corn cob and nu finish/flitz polish.

I'm aware of the fact that brass that turns copper color is probably missing zinc, or the zinc has leeched out of the brass. Almost looks like electrolysis has taken place. But where did the electrical charge come from?

I won't try to load ANY of the brass involved because it may be weak, at least not until I find out what happened. Waddaya think?
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Old March 29, 2011, 08:19 PM   #2
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College Chemistry was a long time ago but......

Okay, after some deep memory searching and a little 'google' refreshing here goes.

You are correct that the brass (chemical formula Cu3Zn2) has lost zinc to the steel shoe horn (containing Carbon). That explains the discoloration in both your brass and your shoe horn. Without knowing the exact type of steel in the shoe horn (different steels have different carbon compositions) it is impossible to determine exactly what happened and in exactly what amounts.

I agree that I would NOT load these cases as the removal of the zinc has definitely softened the cases. In basic terms, your process has made carbon tubing out of your brass cases.
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Old March 29, 2011, 08:47 PM   #3
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I'd like to see a picture of the shoehorn too.
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Old March 29, 2011, 09:10 PM   #4
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Zinc + Iron is a bad combination. The Zinc gets eaten alive.


However, it's surprising that the reaction occurred so quickly.

What chemicals were you using?
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Old March 29, 2011, 09:16 PM   #5
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You essentially zinc plated the shoehorn using the brass as the anode (electron donor) and the showhorn as the cathode (electron recipient). The zine went from the brass over to the shoehorn. Because of the acidic environment, the zinc oxidized black.

I believe I would scrap the brass too.
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Old March 29, 2011, 10:29 PM   #6
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All the cases? I don't have a problem with loosing 100 cases, chalk it up to my lousy memory and ignorance. But the cases that are still brass looking should be okay---------right?

I might try a couple of the copper ones with low pressure lead boolit loads. And watch to see if they look like they're weak.

I'm ignorant as heck about chemistry, but I should have said galvanic reaction?

Lesson learned is to keep different metals out of a US cleaner with an acid bath!
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Old March 29, 2011, 10:37 PM   #7
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Most of thats brass though. But copper is really expensive, why use copper.
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Old March 29, 2011, 11:18 PM   #8
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it is probably good for 1 loading. Id give it a go, but im not as diligent as some. It may cause a bit more pressure on the bolt lugs from lateral expansion of the soft brass during firing, but it will have less a chance of separating. 1 is as far as id go however.
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Old March 29, 2011, 11:42 PM   #9
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I'm not a chemist or certified metallurgist, but I believe this type of reaction occurs as a micro-layer on the surface only. It wouldn't be able to penetrate deep within the alloy without destroying the structure itself, and is likely nothing more than a surface issue. If you polish the brass in a regular tumble medium, it will likely knock off the outer layer of copper to reveal the brass is fine right below the surface. I could be wrong, and maybe someone with a degree will chime in. But I'd say you're probably fine. Try a light load first, inspect, and go from there.

Usertag>> Brass is an alloy of copper and zinc. The iron consumed the zinc on the surface and left the copper behind--essentially making a copper washed brass.
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Old March 30, 2011, 12:05 AM   #10
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I put this on several other boards, it turns out to be a galvanic reaction. Actually it could be reproduced any time. 2 different metals in an acid bath and heat made it happen pretty fast. Zinc and steel are pretty close on the galvanic chart, but copper is way up. The heat caused it to happen faster.

Into the brass recycle bag they all go! Chalk it up to my lousy memory and ignorance.

I took one of the copper colored ones, crushed it with a pliers. It collapsed with very little force.

RF, I tumbled all the cases for 2-3 hours in my vibratory tumbler with nu-finish and flitz. They are copper clear through.
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Old March 30, 2011, 12:12 AM   #11
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WOW!! It pulled all zinc out entirely?? That's one I might have to pass along to the swagging group! Just might be fun to turn all the .22 rimfire swagged jackets into nice shiny copper ones... I could think of a few other uses along those lines too... Now you went and got my head working--right as I was unwinding for bed, no less!
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Old March 30, 2011, 05:23 AM   #12
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I use citric acid to clean my brass all the time and found that it will plate the brass with a very thin layer of copper if the concentration is too high. (I've since backed off the cocentration.) I haven't had any problems with the plated brass, generally, it sizes, shoots and lasts just fine. In fact, most of it can generally be removed by chucking the drill and polishing with steel wool or just be resizing the brass.
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Old March 30, 2011, 06:16 AM   #13
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I still want to see a picture of the shoehorn.
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Old March 30, 2011, 09:49 AM   #14
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Quote:
I use citric acid to clean my brass all the time and found that it will plate the brass with a very thin layer of copper if the concentration is too high.
It is NOT platting the brass with copper, it is removing the zinc from the brass.
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Old March 30, 2011, 11:01 AM   #15
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Quote:
I still want to see a picture of the shoehorn.
I took some steel wool to it, the black stuff,(oxidized zinc), came right off, leaving a shiny steel finish. The rust was all gone. That shoe horn had been in my locker at work for many years to help get my work shoes on. When I cleaned out my locker, it came home with me, a good feeling to be retired!

I'll snap a pic later.

BUT I'll have to revise what I posted last night. I just took that case I crushed so easily, cut it with a tin snips. It's clearly only a surface coating of copper. Then I stuck another copper colored one in a lee spinner, spun it holding some steel wool against it. The copper came right off, it's a very thin film. No matter though, some of the zinc is gone, therefore some of the strength is also gone, so in the recycle bag it goes. That shows how little metal is removed in a tumbler, hardly any!



What's barely visible on the shoe horn is an impression of a logo of the shoe company my dad used to order shoes from via mail order. It says, Miller Jones Footwear Co. Seems I remember they sent a shoe horn with each pair of shoes he ordered.

It seems to have some copper on it, like it was the base coat for plating. It may have been chrome or nickel plated at one time.
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Old March 30, 2011, 11:34 AM   #16
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Congratulations!

It may be off topic, but, Snuffy, Congratulations on making it to retirement!
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Old March 30, 2011, 03:33 PM   #17
testuser
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Quote:
I use citric acid to clean my brass all the time and found that it will plate the brass with a very thin layer of copper if the concentration is too high.

It is NOT platting the brass with copper, it is removing the zinc from the brass.
Either way, it's a very, very small amount of material and has never impacted the life of my brass. Light buffing and it's yellow brass again, so whatever occurs is only happening in a layer so thin that it can generally be removed by steel wool. I just reduced the concentration a bit and the problem went away.

Last edited by testuser; March 30, 2011 at 03:41 PM.
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Old March 30, 2011, 03:56 PM   #18
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BUT I'll have to revise what I posted last night. I just took that case I crushed so easily, cut it with a tin snips. It's clearly only a surface coating of copper. Then I stuck another copper colored one in a lee spinner, spun it holding some steel wool against it. The copper came right off, it's a very thin film. No matter though, some of the zinc is gone, therefore some of the strength is also gone, so in the recycle bag it goes.
OK, that's more consistent with what I expected you'd find. All things considered, you'd loose the same amount of outer layer by tumbling off oxidation from a case. I would seriously consider not junking these cases just yet. With such a minute amount of removal from brand-new brass, there shouldn't be any issue at all with weakening.
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Old March 30, 2011, 06:58 PM   #19
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My thoughts.

Copper-zinc alloys containing more than 15% zinc are subject to dezincification. I read somewhere that cartridge brass is approximately 70% copper and 30% zinc. In dezincification, the zinc, as the anode, is leached from the surface, leaving the copper behind. Among possible electrolytes we would consider the following:
1. If the solution were acidic, pH lower than 7.0, then dezincification can occur. I’m not familiar with your solution, so I don’t know on this one.
2. Chlorinated water
3. Water with high carbon dioxide (not likely) or high oxygen content (does your liquid splash around enough to absorb oxygen?)
4. “Aggressive” water, i.e., water with high electrical conductivity. Perhaps the rusty shoe horn significantly changed the conductivity of the water.
Selective removal of zinc with results in a weak porous surface, but I wouldn’t know if there would have been sufficient time or mechanical agitation for “micro” cavitation to occur. It would be interesting to examine the damaged cases under magnification. I suspect the surfaces would be rough when compared to the other brass. Heat and high fluid velocity will increase corrosion rates.
Another unpleasant thought is the brass could have been affected by prior corrosive action, but we’ll set that one aside since the other brass appears ok. It appears ok, doesn’t it?
The dezincification process is basically chemical corrosion. We now add to the mix electrochemical corrosion in which two conditions are necessary – an electrical potential difference of metal surfaces which are immersed in an electrolyte. If zinc were leached out of the brass then we would expect deposition of zinc on the shoe horn because pure zinc is more active than steel or nickel. Of interest is the fact that steel is more active (anodic) than brass, so I might would have expected deposits of steel on the brass, but it appears this didn’t occur. Instead there appears to be traces of copper on the shoe horn. According to my galvanic chart, nickel along with certain types of stainless and chrome can be passive or active; however, I’ll vote for them being passive in your case since copper was plated onto the shoe horn.
If the proceeding boring analysis is close to being right, it would mean not only did you lose zinc, but you lost copper too. Bummer! When you spin and shine, you would be removing the “loose” copper from the outer part of the brass. I’d be tempted to weight 50 and compare to 50 good ones.
Proceed with caution.
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Old March 30, 2011, 07:02 PM   #20
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In reference to the above tumbling statement, have we ever determined if material is actually removed by tumbling?
Don't mean to rabbit trail.
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Old March 31, 2011, 01:01 PM   #21
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Quote:
I just reduced the concentration a bit and the problem went away.
Removing a layer of copper form brass that has had the zinc removed is hardly "reducing the concentration."

The inside of the case is likely about the same, so you have reduced the brass thickness by twice the thickness of the copper you removed.

Removing brass from cases intended for ~65,000 PSI is not the best idea.
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Old March 31, 2011, 06:44 PM   #22
testuser
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Quote:
Removing a layer of copper from brass that has had the zinc removed is hardly "reducing the concentration."
I think you misunderstood.

"I just reduced the concentration a bit and the problem went away. "

More simply put...

- High concentration of the citric acid solution caused this to happen to me.

- Reducing the concentration prevented this from happening again.

- The concentration was lowered and now it does not occur.

- Impacted brass was monitored and is not brittle, does not stretch excessively, that is, nothing out of the ordinary at all.

If there were spots inside the case, then that didn't end up being relevant. Still, he'll have to make his own assessment on his own brass. I only have to go some photos on the internet. I wanted to relay some information about a simliar incident.

In my case, everything was fine. Cleaning brass with a mild acid is safe, so long as the concentration isn't too high, and has been recommended in the past by the NRA and practiced by large arsenals.
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Old April 1, 2011, 12:13 PM   #23
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Even sulfuric acid has been used to clean cases.

It needs to be diluted enough and washed away fast enough to not eat at the zinc.

If the cases come out copper colored you removed some zinc.

Lower acid strength or less time with acid on them, or just use a tumbler with some mild abrasive (like jeweler's rouge).
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Old April 1, 2011, 12:42 PM   #24
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I would still use those cases. If I were counting my number of times reloaded and planned to retire them at 5 or 6 because they were hot loads, I might bump the counter.
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