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October 17, 2008, 10:12 PM | #1 |
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Join Date: October 4, 2006
Location: California
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Copper-colored patches on brass...
Got 45 pieces of old 270 Winchester brass. They were heavily tarnished. After 2 hours in my tumbler with walnut media, all the black tarnish turned a reddish copper color.
The reddish copper color can be taken off with 0000 steel wool, although some discoloration remains in its place. Not a metallurgist, so I don't know the extent of this stuff. Is it corrosion, or just a cosmetic defect? Want to avoid shooting weak brass. I'm real close to throwing these out...what do you guys think? Sorry, don't have access to a camera right now.
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October 18, 2008, 12:35 AM | #2 |
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Pitch 'em. The red colour is the copper coming out of the alloy. Midway wants $16.49 per 50 for Winchester brass. $167.99 per 100.
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October 18, 2008, 09:37 AM | #3 |
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Thank you, sir. With their low replacement cost, it's not too painful to toss them...certainly less painful than if they rupture.
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October 18, 2008, 02:08 PM | #4 |
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And the correct answer is
Cartridge brass is 70% copper and 30% zinc. The zinc leeches from the brass at a rapid rate, either with basic compounds like ammonia or from the formation af small electrovoltaic cells where the case is in contact with something and water. The longer the contact, the more that is leeched. A small reduction in the % zinc will cause the brass to be brittle and can cause catastrophic rupture of the case.- - - The reddish color is the copper that remains in the brass after zinc has been removed.
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