Which substance is used to prevent rusting of iron in galvanisation process?

Question

Accepted Answer

The correct answer to the question is Option 2: Zinc.

1. **Explanation for Option 2 (Zinc):**
   - Galvanization is a process used to protect iron or steel from rusting by coating it with a layer of zinc. Zinc is chosen for this process because it provides a protective barrier against moisture and oxygen, which are the primary causes of rust. Additionally, zinc acts as a sacrificial anode. This means that even if the zinc coating is scratched or damaged, the zinc will corrode preferentially to the iron, thereby protecting the underlying metal from rusting. This sacrificial protection is a key reason why zinc is used in galvanization.

2. **Explanation for why other options are incorrect:**

- **Option 1 (Aluminium):** While aluminum does form a protective oxide layer that prevents it from corroding, it is not typically used in the galvanization process for iron. Aluminum is used in other forms of corrosion protection, such as anodizing, but it does not provide the same sacrificial protection as zinc does for iron.

- **Option 3 (Copper):** Copper is not used in the galvanization process because it does not provide sacrificial protection to iron. In fact, copper can accelerate the corrosion of iron if they are in contact with each other in the presence of an electrolyte, due to galvanic corrosion. Therefore, copper is unsuitable for preventing rust on iron through galvanization.

- **Option 4 (Magnesium):** Although magnesium can act as a sacrificial anode, it is not used in the galvanization process for iron. Magnesium is more reactive than zinc and is used in other applications, such as in cathodic protection systems for pipelines and tanks. However, it is not practical for use in galvanization due to its high reactivity and cost.

In conclusion, zinc is the most suitable and widely used material for the galvanization process due to its ability to provide both a protective barrier and sacrificial protection to iron, making Option 2 the correct answer.