Write short note on following- Corrosion

Corrosion is a slow process in which metals are eaten up and gradually converted into its undesirable compounds of sulphides, carbonates, oxides etc, by the action of air, moisture present in atmosphere or by an acidic chemical on their surface. For example- Rusting of iron is a redox reaction in which reddish brown coating is formed on iron. Black coating on silver. Green coating on copper. It also weakens the iron or steel structures and objects such as railing, bridges, ships, etc. To prevent this, the processes like oiling, painting, galvanization can be opted. The following chemical reaction can be observed during corrosion- 4 Fe Iron + 3 O 2 Oxygen + 2 xH 2 O Water → 2 Fe 2 O 3 . xH 2 O Hydrated iron III oxide Rust

Those substances which are made by combining two or more metals or a metal and a non-metal and possessing the metallic character or desirable qualities of metals like hardness, lightness and strength is known as an alloy. They form homogeneous mixtures. They are more resistant to corrosion. For example- Steel, Brass, and, bronze. Brass is an alloy of two metals- copper and zinc. Steel or and stainless steel is an alloy of iron and carbon.

Corrosion is the damage caused to the metal by the chemical reaction of air, water and acids with the surface of the metal. Generally reactive metals corrode easily and non-reactive metals have good resistance to corrosion. For example, Copper reacts with moist carbon dioxide in the air and gets a green coat of copper carbonate.