Question

Explain why, when a copper object remains in damp air for a considerable time, a green coating is formed on its surface. What is this process known as?

Answer 1

When a copper object remains in damp air for a long time, it reacts slowly with oxygen, carbon dioxide, and water vapour present in the air to form a green coating of basic copper carbonate (CuCO₃.Cu(OH)₂) on the outside of the object. This process is known as corrosion. Copper is very low in its reactivity; therefore, corrosion of copper also occurs slowly.