Nonferrous metals like copper don’t ‘rust’, however, they do eventually oxidize—or corrode. When copper reacts with air it produces copper carbonate, which is the greenish-blue color found on copper as it ages. Copper is easy to clean and it’s possible to protect copper by applying a clear lacquer. However, with decorative copper items, there are reasons you might not want to clear coat them. Learn about what causes copper to oxidize and how it can be prevented.