This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
Both metal and copper oxidize when exposed to oxygen and this is a natural process. Copper that is exposed to the outside environment is more likely to turn green and that is why copper vases and decorative pieces in gardens are often green.
Remove the cleaned penny from the liquid and let it sit for an hour. The residue that is on the copper surface promotes a reaction between the copper and the oxygen in the air. The resulting blue-green copper oxide is a tarnish that forms called patina. These are copper minerals that are observed in nature.Green patina forms when a shiny copper penny is removed from the salt/vinegar solution.e can take the solution that we have been cleaning the copper pennies and coat a nickel nail with copper metal. The reaction is: Check with the Table of Activity of Metals 1  : Reaction 3 is observed because nickel is higher up on the activity series of metal than copper.