Have you ever wondered how to fix the dreaded zinc rot on pennies? You may have found a small stain or spot on your coin. This stain or spot is a result of corrosion. It may look like a fingerprint or it may be stripes. Whatever the case, corrosion is a permanent process that will ruin your coins. To get rid of this dreaded stain, you need to first understand how the corrosion process takes place.
Copper and zinc corrode from each other. The two metals react with oxygen and sulphur in the air. The result is a brown rust-like substance called copper oxide. You can use a mild acid to dissolve the copper oxides, releasing water and hydrogen gas. If you don’t have any of those available, you can use phosphoric acid instead. Just make sure to keep the acid away from the coin.
A recent study exposed post-1982 pennies to hydrochloric acid and found that they corroded more rapidly than pre-1982 pennies. This corrosion process was not as visible in pre-1982 pennies or silver-colored coins. Nonetheless, all coins were dulled and lost their luster after more than two days in the acid. These results have led to concerns about the health effects of exposure to hydrochloric acid.
The corrosive action of zinc rot on pennies is a natural process that happens to all metals. But some metals are more prone to oxidation than others. While some metals such as copper corrodes due to oxygen and rain, other metals, such as aluminum, can oxidize without iron. And rust is the result of this oxidation process. So how do you prevent the rot from happening on your pennies?
Chemical cleaning is also another effective way to remove zinc oxidation from your pennies and nickels. Copper soap paste or Vitrolin copper soap is a good choice for cleaning zinc coins. These two methods are usually more thorough and more effective. For stubborn cases, you can also use sulfuric acid (H2SO4). Just be sure to dilute the acid with water and apply it in a fine stream. When the zinc rot has been removed, you should now be ready to use a protective museum wax.
In 1982, the composition of pennies changed. Previously, pennies were 95 percent copper and five percent zinc. But as copper became more expensive, the composition changed. Today, pennies are made of a zinc core with a thin layer of copper. This changes the way a penny corrodes. In 1982, a group of scientists at the University of Michigan studied the radiographic appearance of corroded zinc coins. The researchers found that the corrosion was caused by a small amount of atmospheric acid.