Question

Write two methods of preventing the rusting of iron?

Answer 1

Hint: The process of slowly eating away the metal due to moisture and air is called corrosion and the rusting of iron is an example of corrosion. Covering the metal with oil, grease, or paint can be one method to prevent the rusting of iron. Galvanization is a major process used to prevent corrosion.

Complete step by step answer:
The process of the slow deterioration of the metal due to the attack of the atmospheric gases on the surface of the metal resulting in the formation of compounds such as oxides, sulfides, carbonates, sulfates, etc is known as corrosion. One of the most common examples of corrosion is the rusting of iron. Hydrated ferric oxide $F{{e}_{2}}{{O}_{3}}.x{{H}_{2}}O$ is rust.
Prevention of corrosion is very important because enormous damage occurs to buildings, bridges, ships, and all other objects made of iron.

Some of the methods of preventing the rusting of iron are:
(i)- Barrier protection: The metal surface is coated with paint which keeps it out of contact with air, moisture, etc till the paint layer develops cracks. The rusting of iron can be prevented by applying a film of oil and grease on the surface of the iron tools and machinery since it keeps the iron surface out of contact with moisture, oxygen, and carbon dioxide. Non-corroding metals such as nickel, chromium, aluminium, etc are used to coat the surface of the iron.

(ii)- Sacrificial protection: Sacrificial protection means covering the iron surface with a layer of metal that is more active (electropositive) than iron and thus prevents the iron from losing electrons. The more active metal will convert itself into an ionic state by losing electrons in preference to the iron metal. With the passage of time, the more active metal will get consumed but so long as it is present there. It will protect the iron from rusting. It does not allow even the nearly exposed surface of iron to lose electrons. Zinc is the metal that is most often used for covering iron with more active metal. This process is called galvanization.

Note: The factors which promote corrosion are reactivity of the metals, presence of impurities, presence of air and moisture, strains in metals, and presence of electrolytes.