Corrosion is the process by which metals are gradually destroyed by substances such as moisture, acids, and salts in their surrounding environment. It occurs through chemical reactions that degrade the metal’s surface over time.

Copper develops a green coating, known as patina, while silver forms a black coating when corroded. These coatings are examples of corrosion and affect the appearance of the metals.

The process is commonly known as rusting of iron, wherein iron articles develop a reddish-brown powder on their surface when exposed to moisture and oxygen.

Oxidation-reduction reactions involve the simultaneous occurrence of oxidation and reduction processes. The term “redox” is derived from the words “reduction” and “oxidation,” reflecting this dual nature of the reactions.

In a redox reaction, one reactant undergoes oxidation (loses electrons or gains oxygen) while another reactant undergoes reduction (gains electrons or loses oxygen), simultaneously.