Pyrometallurgy: Roasting, Smelting, Refining & Electrowinning

Pyrometallurgy: Roasting, Smelting, Refining & Electrowinning

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Help identifying tin bronze anomaly in copper cent (1 reply)

4 weeks ago
Coins7112 4 weeks ago

Need assistance in identifying a cause of a tin bronze occurring in 1910/1911 Lincoln wheat cent. Flake like features on a small run of Lincoln wheat cents have been identified. SEM/EDX reading shows flakes reading higher than normal SN and ZN. Copper cent should contain 95% CU and 5% ZN,SN. Flake readings are 86% CU 11%SN and 2.5%Zn, within these flakes there are multiple areas containing 64% CU and 33% SN. This flake becomes tin bronze and resists tarnish. I am trying to understand how this can occur. Any help would be greatly appreciated.

4D8A2FD5 4212 4CE3 9535 05377161C3B5
DD88A89E 66CD 40A7 8EEC 5B296E5A1D54
F6043670 1496 475C B9C5 42080EA8F099
C1C7DD60 9C88 4788 900F 6BA07F5E935D
4 weeks ago
SmartDog 4 weeks ago

The most likely reason would be poor control during the smelting proces allowing for poor mixing in the cupela or a batch of material with the wrong percentages in the mix.

Another possibility would be leaving the coin(s) out near an ammonia source or fumes as ammonia is a lixivent for copper.


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