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 Replies: 43 / Views: 12,453 |
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Pillar of the Community
United States
8517 Posts |
Wouldn't xrf testing be a definitive test ?
Oregon coin geek.....*** GO BEAVS ! ! ! ***
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Moderator
  United States
56855 Posts |
Quote:
Wouldn't xrf testing be a definitive test ? That needs to be answered by Roger.I am more confused now then before I sent it to Roger. I also read that it could be something called "copper wash"  John1  |
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Pillar of the Community
United States
3592 Posts |
What I'm wondering:
1. Is this a known error ?
2. What amount of copper defines this error ?
3. Can a metal detector realy tell the difference since copper content is normally 75% anyway ?
4. What is the name of this error ? It is already a copper/nickel alloy.
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Pillar of the Community
United States
1915 Posts |
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If nickel reading/tone then Mike D. is correct. What I am wondering is why there would be any reason to doubt Mike in the first place? I would think most would know that he is the absolute authority when it comes to error coins. |
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Pillar of the Community
United States
3640 Posts |
M.M.
#3 Yes it can. Some use XRF. Even only at 25 % nickel
it over powers the copper. Nickel is closer to gold than to copper MD signal wise as are some other alloys.
Seal
No reason to doubt Mike's opinion.
Like a stated, if it rings nickel then his
opinion is correct. Unless it does not ring nickel. I have a true black beauty.
It is an improper annealing process. Still rings nickel
though. Always a chance that stock was made from an improper
alloy mix but in this case I would not know unless the coin
was rung up/tested. I believe it is just a nickel period,
that was in the ground for a while or an improper annealing process.
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Bedrock of the Community
Australia
21788 Posts |
XRF would prove it OK.
Personally, I would't bother.
I have seen a very large number of 75/25 copper nickel coins developing this sort of rich copper patination.
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Moderator
Canada
10458 Posts |
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I doubt it's a case of a poorly mixed alloy. It's probably a case of improper annealing, which causes copper to segregate out and migrate to the surface. The improper annealing you speak of occurs at the ionic level, which would form a very thin layer on the surface. That is the beauty of the XRF, if the beam is powerful enough, it penetrates the surface. I have a quite powerful one, with an alloy software package. You cannot argue with the laws of physics, absolute authority or not. This coin is an alloy mixing error, comprising of more than 83% Cu... unless you have a better explanation... "Discovery follows discovery, each both raising and answering questions, each ending a long search, and each providing the new instruments for a new search." -- J. Robert OppenheimerContent of this post is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported License. See: http://creativecommons.org/licenses...0/deed.en_USMy eBay store
Edited by SPP-Ottawa
01/23/2013 8:13 pm
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Pillar of the Community
United States
1796 Posts |
XRF doesn't penetrate very far, only perhaps a few layers of molecules at best. This is why it often detects silver *plated* coins as silver.
The definitive test would be to cut it down the center with a hack saw or buff it in half with a grinder and see if it's some sort of patina by testing the core.
Edited by SteveCaruso
01/23/2013 8:33 pm
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Pillar of the Community
United States
1796 Posts |
As an example: I know of several compounds that can dissolve the nickel and leave the copper behind. If you XRF these nickel-leached coins, they will come back as a higher-copper alloy where the core is still 75-25 Cu-Ni.
Edited by SteveCaruso
01/23/2013 8:36 pm
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Moderator
Canada
10458 Posts |
Quote:
XRF doesn't penetrate very far, only perhaps a few layers of molecules at best. Actually, the beam can penetrate several microns. The instrument I use can easily detect the iron (steel) core in any Canadian multi-ply plated (i.e., plated with a thin layer of nickel, thick layer of copper and thick layer of nickel) coin. This is why archeologists like using this instrument, because it can penetrate through oxide, sulphate and other coatings. I can "see" right through any silver or gold plating, and have used this instrument to document counterfeits by doing so. Of course, you will pick up traces of the plating, from attenuation of the beam. Quote:
The definitive test would be to cut it down the center with a hack saw or buff it in half with a grinder and see if it's some sort of patina by testing the core. I fully intend to do that, and run a quantitative analysis traverse across the cut face with a SEM. Quote:
As an example: I know of several compounds that can dissolve the nickel and leave the copper behind. If you XRF these nickel-leached coins, they will come back as a higher-copper alloy where the core is still 75-25 Cu-Ni. The coins still weigh the same, how do you account for the loss of nickel, yet maintain mass balance? "Discovery follows discovery, each both raising and answering questions, each ending a long search, and each providing the new instruments for a new search." -- J. Robert OppenheimerContent of this post is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported License. See: http://creativecommons.org/licenses...0/deed.en_USMy eBay store
Edited by SPP-Ottawa
01/23/2013 10:09 pm
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Pillar of the Community
United States
1796 Posts |
Quote:
Actually, the beam can penetrate several microns. The instrument I use can easily detect the iron (steel) core in any Canadian multi-ply plated (i.e., plated with a thin layer of nickel, thick layer of copper and thick layer of nickel) coin. This is why archeologists like using this instrument, because it can penetrate through oxide, sulphate and other coatings. I can "see" right through any silver or gold plating, and have used this instrument to document counterfeits by doing so. Of course, you will pick up traces of the plating, from attenuation of the beam. Once again, depends on how thick the plating is. I have some counterfeits in the Uncatalogued Stacks of The Black Cabinet that had heavily-plated planchets. XRF says they're sterling silver (which is what flagged their previous owner to something fishy). The file marks on their edges (when their previous owner decided to check) say they're brass cores. :-) With counterfeits, it's always a matter of cat and mouse anyways. Quote:
I fully intend to do that, and run a quantitative analysis traverse across the cut face with a SEM. Thassa spirit! :-) Quote:
The coins still weigh the same, how do you account for the loss of nickel, yet maintain mass balance? The loss of nickel is only fractions of a fraction of a gram, much like if you were to copper plate it (which would add fractions of a fraction of a gram). Oxidize the surface a bit, and it's near a net zero. |
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Moderator
Canada
10458 Posts |
Quote:
I have some counterfeits in the Uncatalogued Stacks of The Black Cabinet that had heavily-plated planchets. XRF says they're sterling silver (which is what flagged their previous owner to something fishy). That is a function more dependent on the instrument itself, and not the analytical technique. How powerful was the beam on the instrument you used, and was the detector and instrument calibrated to handle analysis of alloy metals? I use an INNOV-X X-5000 Series Bench Top Instrument, with a 10 Watt X-ray tube, 50 keV, 200 μA (max) and a silicon drift detector. I have penetrated platings that I know were well in excess of 100 microns thick... Quote:
The loss of nickel is only fractions of a fraction of a gram, much like if you were to copper plate it (which would add fractions of a fraction of a gram). Oxidize the surface a bit, and it's near a net zero. See my earlier note, about being able to penetrate right through oxidized surfaces - I can provide published literature on the topic, if necessary. "Discovery follows discovery, each both raising and answering questions, each ending a long search, and each providing the new instruments for a new search." -- J. Robert OppenheimerContent of this post is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported License. See: http://creativecommons.org/licenses...0/deed.en_USMy eBay store
Edited by SPP-Ottawa
01/24/2013 10:03 am
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Pillar of the Community
United States
3640 Posts |
SPP-Ottawa
If a true black beauty nickel is known as
an annealing process error then why
does the color go all the way through the coin ?
Maybe the term then is incorrect on the beauty
and or it's cause.
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Pillar of the Community
United States
1796 Posts |
Quote:
That is a function more dependent on the instrument itself, and not the analytical technique. How powerful was the beam on the instrument you used, and was the detector and instrument calibrated to handle analysis of alloy metals? I use an INNOV-X X-5000 Series Bench Top Instrument, with a 10 Watt X-ray tube, 50 keV, 200 μA (max) and a silicon drift detector. I have penetrated platings that I know were well in excess of 100 microns thick... I wasn't the one who analyzed it, the previous owner was, so I'm honestly not sure what the specs on their equipment were. I'll see about asking them. Quote:
See my earlier note, about being able to penetrate right through oxidized surfaces - I can provide published literature on the topic, if necessary. Aye, but it's not just a case of oxidization. The oxidization would add back the weight removed from nickel-leaching. In any case, the only way to really proceed from here is to crack one of them open like an Oreo and find out. :-) |
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Moderator
Canada
10458 Posts |
Well, the logical solution is to test this hypothesis. I will take the next "brown" nickel I find that is in excess of 82% copper on my XRF, and then grind off one side until I am well into fresh metal. Then, I will test that freshly ground side and compare the results. That should resolve the issue whether this is surface annealing or a compositional error.
I guess I would pose the question in a reverse engineering fashion. Can anyone here 'create' a brown nickel, by taking a normal, dull grey 75% Copper 25% Nickel and leaching it to create a surface of more than 82% copper?
"Discovery follows discovery, each both raising and answering questions, each ending a long search, and each providing the new instruments for a new search." -- J. Robert OppenheimerContent of this post is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported License. See: http://creativecommons.org/licenses...0/deed.en_USMy eBay store
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Replies: 43 / Views: 12,453 |
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Posted 01/23/2013 10:43 am
