Question

What is rusting? How is rusting prevented?

Answer 1

Rusting - The reaction of iron with oxygen and moisture in air resulting in the formation of reddish-brown coloured hydrated iron oxide(rust) is called rusting.

Chemical reaction -

$\underset{\mathrm{Iron}}{4\mathrm{Fe}\left(\mathrm{s}\right)}+\underset{\mathrm{Oxygen}}{3{\mathrm{O}}_2\left(\mathrm{g}\right)}+\underset{\mathrm{Water}}{{\mathrm{xH}}_2\mathrm{O}\left(\mathrm{l}\right)}\to \underset{\mathrm{Hydrated}\mathrm{ferric}\mathrm{oxide}\left(\mathrm{Rust}\right)}{2{\mathrm{Fe}}_2{\mathrm{O}}_3.{\mathrm{xH}}_2\mathrm{O}\left(\mathrm{s}\right)}$

Necessary conditions for rusting -

• Presence of oxygen(air).
• Presence of water.

Effects of rusting -

• It corrodes articles made of iron.
• It weakens the structure of buildings.
• It causes contamination.

Prevention of rusting -

• Painting - The articles made from iron are coated with a layer of paint to prevent their exposure to oxygen and moisture.
• Applying a thin layer of oil or grease - Machine parts are coated with grease to avoid contact with water and air and also lubricate the parts.
• Galvanization - The process of coating the articles of iron with a protective layer of zinc metal to prevent rusting is called galvanization.
• Chrome plating - The process of coating iron articles with chromium metal is called chrome plating.