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 Replies: 16 / Views: 3,576 |
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Pillar of the Community
United States
3330 Posts |
I am trying to calculate the Copper Plating Weight. I would be happy for someone to check my math!
8 micron thick Cu plating = .01mm
= 5.73 cubic mm of Cu in a cent
= .00573 cubic centimeter
Copper weighs 8.95g/cubic cm
~0.0513 g of Cu in the plating of a cent
Allow for edge = 0.0521 g of Cu in a cent (approximately)
Edited by Pete2226
06/26/2017 2:38 pm
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Moderator
 United States
56855 Posts |
That's tiny math  John1  |
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Pillar of the Community
United States
7512 Posts |
Pete, you did fine ,now I know who to send my math issues to  Edited by Chase007
06/26/2017 2:49 pm
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Moderator
United States
56855 Posts |
Here is the problem. A scale that goes down to 0.0000g cost a lot of money  . So for example,an unplated zinc cent. John1 |
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Pillar of the Community
 United States
3330 Posts |
Quote:
Here is the problem. A scale that goes down to 0.0000g cost a lot of money . So for example,an unplated zinc cent. I think this means, that since the weight of the copper plating is less than 1/2 of the tolerance for cent weight, the weight of a cent is irrelevant in trying to determine whether or not it is missing the plating. Edited by Pete2226
06/26/2017 4:53 pm
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Pillar of the Community
United States
3330 Posts |
Quote:
Pete, you did fine ,now I know who to send my math issues to Thank you - my undergraduate degree was in Mathematics, but it has been so long ago I have forgotten most of it! I knew Fourier and LaPlace Transformations at one time, but thankfully this involves only simple algebra! |
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Bedrock of the Community
Australia
21788 Posts |
To get a reliable weight of copper plating the thickness of the plating needs to be measured over several places on several newly struck coins.
Another way would be to ask the U.S. Mint, but don't hold your breath waiting for the answer.
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Rest in Peace
 United States
1380 Posts |
Wouldn't it be simpler to start with a weight of 2.5 grams total for a copper plated zinc cent, then take the official composition of 97.5% zinc, 2.5% copper and figure from there? All of that 2.5% copper is plating, so 2.5 grams times 2.5% equals 0.0625 grams of copper plating per cent.
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Pillar of the Community
United States
3463 Posts |
The Copper plating isn't always the same thickness, so there is no accurate way to weigh the difference between a plated and unplated cent.
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Pillar of the Community
United States
3330 Posts |
Quote:
All of that 2.5% copper is plating, so 2.5 grams times 2.5% equals 0.0625 grams of copper plating per cent. This is not true. The zinc planchet is Zinc Alloy 190 which contains some copper: ALLOY 190: COMPOSITION (% by Weight) Lead = 0.005 max; Iron = 0.010 max; Cadmium = 0.005 max; Copper = 0.7 to 0.9; Zinc = Balance. |
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Pillar of the Community
United States
3330 Posts |
Quote:
The Copper plating isn't always the same thickness, so there is no accurate way to weigh the difference between a plated and unplated cent. Can you cite the study which documents the variations of thickness of copper plating? I would be interested in learning the degree of variation. I do agree that there is no accurate way to measure, by weight, the difference between plated and unplated. I did not know that for certain until I calculated the weight of the plating and found it to be less than 1/2 the tolerance for the weight of the cent. I think that this is more the reason for not being able to tell the difference rather than any variations in the thickness of the plating. Such would be quite minor, I would guess, compared with the weight of the plating itself. |
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Pillar of the Community
United States
3330 Posts |
Quote:
To get a reliable weight of copper plating the thickness of the plating needs to be measured over several places on several newly struck coins.
Another way would be to ask the U.S. Mint, but don't hold your breath waiting for the answer. The answer I found comes from a study commissioned by the U.S. Mint: Concurrent Technologies Corporation, "Alternative Metals Study", Final Report, August 31, 2012 Contract Number: TM-HQ-11-C-0049 Submitted to the U.S. Mint, http://www.usmint.gov/about_the_min...12-08-31.pdf 8/12/2015. Accessed 8/12/2015. Edited by Pete2226
06/27/2017 08:34 am
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Pillar of the Community
United States
3330 Posts |
Here is what I have found (so far): Variation of thickness of copper plating can be a problem. However there are ways to address the problem: Quote:
"Actually, electroplating CAN deposit very uniformly and, barring other factors, Faraday's Law dictates that it will (at 100 percent efficiency, 96500 amp-seconds will always deposit one gram equivalent weight)
So if the current distribution is uniform, the plating thickness will be uniform. But to even out the thickness when geometry favors higher or lower current density to certain areas, three "mechanical" techniques are shielding (the use of plastic shields to block off the shortest path), thieving (the use of conductive wires as cathodes to steal some of the current away from high current areas, and auxiliary anodes (anode material in close proximity to the work in the areas which need more current)." https://www.finishing.com/3600-3799/3795.shtml Accessed 6/27/2017 |
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Bedrock of the Community
Australia
21788 Posts |
Do a complete destructive chemical analysis on 100 newly issued examples.
From a legal aspect not lawful, but from a practical aspect, quite OK, and the U.S. would ignore to prosecute.
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Bedrock of the Community
United States
17884 Posts |
The thickness on the struck coin would vary due to compression in some areas and stretching in others. but the thickness on the planchets should be fairly uniform, the tumbling action of the barrel plating ensures a pretty uniform layer. I did the same math years ago, both methods, and the answers are close enough together that I've just used a "rule of thumb" of a weight of .05 grams. It is close enough and it proves that weight is not a valid way to check for a non-plated cent.
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Pillar of the Community
United States
3330 Posts |
Conder101  |
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Replies: 16 / Views: 3,576 |
Posted 06/26/2017 2:49 pm
