Like most other metals, copper corrodes when left out in the elements. The greenish layer that forms is alternately called the patina or verdigris. ... When copper is exposed to air , the metal reacts with moisture(H2O) and atmospheric gases to form a mixture of copper carbonate and copper hydroxide

Galvanization or galvanizing is the process of applying a protective zinc coating to steel or iron, to prevent rusting. The most common method is hot-dip galvanizing, in which the parts are submerged in a bath of molten zinc