Identifying Genuine Missing Copper Layer Cents
FlyingAl
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We had a fun chemistry lab today, and it got me thinking.
We took some cents and electroplated them in a solution of zinc and hydrochloric acid (the supplies for which could be bought rather cheaply).
The finished product was good, very good in fact. If I had taken more care and tried to get it perfect I think it would have ended up nearly unidentifiably plated to the naked eye. However, in my rush to get to my next class I neglected to weigh the cent after the plating to see how much weight was truly added.
Here's my question - if one took a low tolerance cent, electroplated it, and it remained within tolerance, how would that coin be identified? Is weight the only check on these coins?
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Comments
That’s awesome — sounds like you really got into that lab! From a chemistry student’s perspective, what you did with the zinc and hydrochloric acid solution was a perfect demonstration of electrochemical reduction. The zinc ions in solution were reduced at the surface of the copper-coated cent, forming a thin metallic zinc layer. Because this deposited layer is only a few microns thick, the added mass is incredibly small—usually just a few milligrams. That means your plated cent would almost certainly still fall within the U.S. Mint’s legal weight tolerance, making it undetectable by weight alone.
However, the chemistry changes more than just the mass. Electroplating modifies the surface properties of the coin. The zinc coating affects the way light reflects off the surface, changing the color and luster from the typical reddish tone of copper to a more silvery appearance. Even if the plating looked perfect to the naked eye, a microscope would reveal subtle texture changes because electrodeposition tends to smooth or fill the original metal’s tiny surface features.
If someone wanted to analyze the coin scientifically, there are several ways to detect the plating. An X-ray fluorescence (XRF) scan would show an outer layer rich in zinc and a diminished copper signal underneath. Even simple conductivity or density tests would hint that the surface composition doesn’t match the expected copper-zinc balance of a normal cent. These methods are quick, non-destructive, and commonly used in both metallurgy and coin authentication.
So, in short, your plated cent might pass for normal in everyday use, but chemistry gives it away instantly. The underlying electrochemical reactions and the surface composition tell the full story—and that’s what makes experiments like this so fun for chem students. You get to see real-world applications of redox chemistry while learning how small atomic-level changes can have visible, measurable effects.
(AI generated for FlyingAI)
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Very interesting. I wonder if the TPGs XRF each of the coins that come in for error attribution.
I'm assuming that a genuine unplated cent's surfaces would show flow lines or something similar from being struck, which presumably would not be present on a regular cent that had been zinc plated (?).
Original mint luster is the first thing I look for on unplated cents.
i like this answer. seeing all the plated counterfeits on ebay, one thing you can see is sometimes they shine but they never have luster
Thanks. Yeah cartwheel luster is the key. Plated cents “shine” like you say, while de-plated cents have a dull and rough appearance.