Zinc. A silver gray metal that in pure state rapidly corrodes. While not a satisfactory metal in such state for striking coins and medals, zinc is widely used as an alloy, particularly with copper to form bronze and brass. While copper is the alloy's greater percentage, zinc ranges from one to 33 percent of bronze and brass alloys.Both coins and medals have been struck in pure zinc; it was a wartime alloy in the first and second World Wars when bronze for low value coins were greatly used for war armaments. Pure zinc coins do not work harden and are struck with less pressure. But, pure zinc items form white rust, a corrosion of a white powdery surface (zinc oxide) which forms form heat and exposure to moist air or water.In 1982 the United States converted from a bronze alloy for the cent coin denomination to a zinc base, copper coated composition (from 5% zinc prior to 1981 to 9x% zinc after). Collectors call this a zinc core alloy. The clad alloy required new technologies for its fabrication to its coining.The U.S. Mint obtains ready-to-strike blanks from contract suppliers: Alltrist Zinc Products (formerly Ball Corporation), Greeneville, Tennessee, and LaSalle Rolling Mills Inc., LaSalle, Illinois. In 1996 these same firms received the contract to furnish copper coated zinc blanks to the Royal Mint for Canadian cent coinage.For all other denominations, the U.S. Mint receives the strip only and continues to do the blanking within the Mint. This did eliminate at all United States mints, however, the need for a melt shop to formulate all coinage alloys.Zinc was used for coins in China, 1402-24 and 1660-1720.
excerpted with permission from
An Encyclopedia of Coin and Medal Technology
For Artists, Makers, Collectors and Curators
COMPILED AND WRITTEN BY D. WAYNE JOHNSON
Roger W. Burdette, Editor