Question

Define rusting. How can it be prevented?

Answer 1

Rusting-

• It is processed when iron comes in contact with oxygen and moisture present in the air.
• $4\mathrm{Fe}\left(\mathrm{Iron}\right)+3{\mathrm{O}}_2\left(\mathrm{oxygen}\right)\stackrel{\mathrm{x}{\mathrm{H}}_2\mathrm{O}}{\to }2{\mathrm{Fe}}_2{\mathrm{O}}_3.{\mathrm{xH}}_2\mathrm{O}\left(\mathrm{Rust}\right)$
• It is of reddish-brown colour.
• ${\mathrm{xH}}_2\mathrm{O}$ indicates the presence of water molecules.

Rusting can be prevented in the following ways:-

• Applying oil or grease-
  • Moisture and oxygen cannot come into direct contact with the iron article by applying oil or grease.
• Applying paint-
  • Moisture and oxygen cannot come into direct contact with the iron article by applying paint.
• Galvanisation-
  • Iron is coated with zinc as zinc is more reactive.
• Tinning-
  • Iron is coated with Tin, so oxygen and moisture cannot come in contact with iron.
• Electroplating-
  • In this process, iron is coated with less reactive metal like chromium.
• Alloying-
  • By mixing iron with other metal or non-metal, it changes its property of rusting.