Question

59. What is meant by the rusting of iron? State two conditions necessary for the rusting of iron to occur. Explain the methods of preventing rusting of iron.

Answer 1

Definition:

• When an iron object is kept open for a considerable time, it gets covered with a red-brown flaky substance called rust.
• This is called rusting of iron. It is a form of corrosion.

Iron + Oxygen + Water → Hydrated Iron Oxide
(Fe) (O₂) (H₂O) (Fe₂O₃.xH₂O)

Conditions necessary for rusting:
Two conditions are necessary for the rusting of Iron to take place:

1. Presence of Oxygen (of air)
2. Presence of water or water vapour.

Methods of preventing rusting of Iron:

• By painting
  • When a coat of paint is applied to the surface of an iron object, the air and moisture cannot come in contact with the Iron object, and hence, rusting doesn't take place.
• By applying grease or oil
  • On applying grease or oil to the surface of an Iron object, rusting is prevented.
• By galvanization
  • The process of depositing a thin layer of Zinc metal on iron objects is called galvanization.
  • The Iron pipes used in our homes to carry water are also galvanized to prevent rusting.
• By chrome-plating
  • Chromium metal is resistant to the action of air and moisture.
  • When a layer of Chromium is deposited on an Iron object, then the Iron object is protected from rusting.
• By alloying Iron to make stainless steel
  • When Iron is mixed with Carbon, Chromium, and Nickel, stainless steel is formed.
  • Rusting doesn't occur as cooking utensils, knives, scissors, and surgical instruments are made up of alloys.