Metal finishing Q&As since 1989

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How to determine the composition of a coin

Hi, my name is Katia and I'm in 10th grade. I need to find a way to prove what metals are used in the fabrication of Canadian 1 cent, 2007 pennies with a science experiment. I found that these pennies are made of 94% steel, 1.5% nickel and that it is recovered with a layer of copper. HELP QUICK!

Katia K.
Student - Montreal, Quebec, Canada
November 5, 2008

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It is possible to determine the metals used in the core of a coin, even when it is coated with another metal, by techniques like "x-ray fluorescence" and "beta backscatter". You probably don't have access to those tools, but may want to research those terms for your report. To a lesser degree of exactness, it can be possible to determine materials of construction with a magnet (only certain metals are magnetic), and from their weight (search for "Archimedes Eureka"), and simply their color (copper is, uh, copper colored while steel is grey-white).

I don't think that at your grade level you will be able to "prove" the composition of the coin, but you should be able to offer some circumstantial evidence via magnetism, density, color, bending without breaking, getting the surface to corrode to a green color, getting the inside core to rust after you've cut the coin open, etc. Other readers may have more or better suggestions. Good luck.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
November 6, 2008