Why can iron remain protected from rusting for some time even if the zinc coating in galvanisation is scratched?
Answer and explanation
Correct answer: Zinc is more reactive than iron and oxidises preferentially
Zinc is more reactive than iron. Therefore, when a zinc coating is scratched, zinc oxidises in preference to iron and provides sacrificial protection. As a result, the exposed iron can remain protected from rusting for some time. In contrast, a broken paint coating does not provide sacrificial protection, so exposed iron may rust on contact with air and moisture.
Frequently asked questions
What is the correct answer to this question?
Zinc is more reactive than iron and oxidises preferentially
Why is this the correct answer?
Zinc is more reactive than iron. Therefore, when a zinc coating is scratched, zinc oxidises in preference to iron and provides sacrificial protection. As a result, the exposed iron can remain protected from rusting for some time. In contrast, a broken paint coating does not provide sacrificial protection, so exposed iron may rust on contact with air and moisture.
Which subject and chapter does this question cover?
This is a Class 10 Science question. Chapter: Chemical Substances – Nature and Behaviour. Topic: Chemical Reactions and Equations.
