International General Certificate of Secondary Education (IGCSE) Chemistry Practice Exam

In the process of galvanising, which metal is used to protect iron from rusting?

1. Copper

2. Aluminium

3. Zinc

4. Lead

The correct answer is: Zinc

In the process of galvanizing, zinc is used to protect iron from rusting. This method involves coating iron with a thin layer of zinc, which serves as a sacrificial anode. Zinc is more reactive than iron, meaning it will corrode first if exposed to moisture and oxygen. This reactivity effectively prevents corrosion of the underlying iron, thereby prolonging its life and maintaining its structural integrity. The protective mechanism relies on zinc's ability to oxidize preferentially. Even if the zinc layer is damaged, the exposed iron will still be safeguarded as long as there is surrounding zinc available to corrode in its place. This process is particularly useful in outdoor and marine environments where iron is susceptible to rust due to high moisture levels. Other metals such as copper, aluminium, and lead do not provide the same protective effect in galvanizing applications. Copper can form a patina that protects it but is not effective for iron. Aluminium has some resistance to corrosion but is not commonly used for galvanizing iron. Lead shows poor corrosion resistance in these contexts and is not practical for this purpose either. Thus, zinc remains the ideal choice for galvanizing iron against rust.