This lesson explores the use of zinc in coinage, highlighting both its advantages as a cheap metal and its limitations due to corrosion. Two case studies will be examined: the 20-cent zinc coin issued by the French Vichy government in 1941 and the modern U.S. penny.
Objectives
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Understand why zinc was adopted for coinage in different historical contexts.
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Recognize the corrosion problems of pure zinc coins, known as “zinc disease.”
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Identify the composition of zinc-based coins through XRF spectroscopy.
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Compare wartime coinage with modern strategies for cost-effective minting.
Materials
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Vichy France 20-cent coin (1941)
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U.S. pennies (post-1982 zinc core)
Lesson Plan
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Introduce zinc as a low-cost but unstable material for coin production.
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Present the Vichy coin as an example of pure zinc coinage, and discuss its surface degradation.
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Examine the coin with XRF spectroscopy to confirm pure zinc composition.
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Compare with U.S. pennies, explaining the shift from copper to zinc cores after 1982.
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Demonstrate XRF spectra of coated and abraded pennies, highlighting differences in copper and zinc signals.
