Question

If a galvanized iron sheet is scratched and the iron surface is exposed to the atmosphere, the iron does not undergo corrosion. This is because:

• A. Zinc forms a protective oxide layer that covers the scratch.
• B. Iron has a higher reduction potential than zinc, making iron the cathode.
• C. Zinc has a lower oxidation potential than iron, acting as a sacrificial anode.
• D. Electrons flow from the iron to the zinc to prevent oxidation.

Hint:

Zinc is more easily oxidised than iron, so zinc is the sacrificial anode and iron acts as the cathode.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept
Galvanized iron is coated with zinc. When the coating is scratched, zinc and iron form a small electrochemical cell in the presence of moisture.

Step 2: Compare potentials
Zinc has a more negative reduction potential than iron (\(E^{0}_{\text{Zn}^{2+}/\text{Zn}}=-0.76\) V, \(E^{0}_{\text{Fe}^{2+}/\text{Fe}}=-0.44\) V). So iron has the higher reduction potential.

Step 3: Roles
Zinc is oxidised and acts as the anode, while iron becomes the cathode and is protected.
Option (B) states that iron has a higher reduction potential than zinc and is the cathode.

Final Answer:
Iron has a higher reduction potential than zinc, so iron acts as the cathode. \[ \boxed{\text{(B) }\text{Iron has a higher reduction potential than zinc, making iron the cathode.}} \]