Which of the following methods is NOT used for preventing iron from rusting?

Correct option is D

The correct answer is (d) Heating

Explanation:

Method to prevent Rusting:

• Chrome plating is a method where a thin layer of chromium is applied to the surface of iron or steel to protect it from rusting. Chromium is highly resistant to corrosion and provides a protective barrier.
• Painting: When iron is coated with paint, it prevents moisture and oxygen from reaching the surface, thereby reducing the chances of rust formation. This is a common method used for protecting metal surfaces.
• Galvanising is also used for preventing rusting. It is the process of coating iron or steel with a layer of zinc. Zinc acts as a protective barrier and also offers sacrificial protection by corroding in place of the iron when exposed to moisture and air.
• Oil Coating: A thin layer of oil or grease can be used to protect iron from moisture and oxygen.

A heating iron does not prevent rusting. When iron is heated and then exposed to air, it is more likely to rust as the surface can be oxidized more quickly. Therefore, heating is not a method for rust prevention.

Information Booster:

• Rusting: The corrosion of iron, forming iron oxide (Fe₂O₃), is primarily caused by the reaction of iron with oxygen in the presence of water.
• Process of Rusting: Iron reacts with oxygen and water to form iron(III) oxide, commonly known as rust.
• The chemical reaction is: $$4Fe + 3O_2 + 6H_2O \rightarrow 4Fe(OH)_3$$​​
• Rust (iron(III) oxide) gradually flakes off, exposing fresh metal to further corrosion.

Factors Affecting Rusting:

• Presence of salt (e.g., saltwater increases rusting).
• Temperature: Higher temperatures speed up the rusting process.