Why copper vessel gets covered with a green coating during rainy season?

Copper vessels develop a green coating, known as patina, due to a chemical reaction with moisture and oxygen in the air, particularly during the rainy season. This reaction forms copper carbonate and copper hydroxide, which give the vessel its characteristic green color. The presence of pollutants, such as sulfur compounds, can also accelerate this process. While the patina is often seen as undesirable, it actually protects the underlying copper from further corrosion.