Question

Which one of the following is essential in corrosion of iron metal?
1. Oxygen only
2. Oxygen and moisture
3. Hydrogen only
4. Hydrogen and moisture
5. None of the above/More than one of the above

Answer 1

Correct Answer - Option 2 : Oxygen and moisture

The correct answer is Oxygen and Moisture.

• The reaction of iron and oxygen forms an iron oxide which is a reddish-brown oxide. This is called Rust or corrosion of iron metal.
• This reaction happens only in presence of oxygen and moisture.
• The presence of impurities like Moisture, Acid, salt, Temperature, Presence of acid etc. is some factors that affect corrosion.
• Here the chemical reaction of Rust:-
  • Fe²⁺ + 3O₂ → 2Fe₂O₃
  • Fe₂O₃ + xH₂O → Fe₂O₃. xH₂O (rust)
• It can be protected using the following methods-

1. Electroplating
2. Cathodic Protection
3. Galvanization
4. Painting and Greasing
5. Using corrosion inhibitor

• Different Types of corrosion are-

1. General Corrosion- overall attack on surface without distinguishing anodic and cathodic areas.
2. Galvanic Corrosion- When two metals are connected to an electrode, here anodic material will corrode.
3. Pitting Corrosion- is the localized corrosion of a metal surface confined to a point or small area, that takes the form of cavities.
4. Crevice Corrosion- takes place in confined liquid-filled slots.
5. Intergranular Corrosion- occurs between grain boundaries inside a metal.
6. Selective corrosion- occurs when alloying elements are not uniformly distributed.
7. Cavitation Corrosion- occurs where vapour bubbles are formed due to low pressure.