Which one of the following is a wrong statement about cast iron

Options

A. It is also called pig iron
B. It contains about `4.5%` carbon
C. It is corrosion resistant
D. It contracts on cooling

Answer

To determine which statement about cast iron is incorrect, let's analyze each of the provided statements step by step.

### Step 1: Identify the Statements
1. Cast iron is also called pig iron.
2. Cast iron contains about 4 to 4.5% carbon.
3. Cast iron is corrosion-resistant.
4. Cast iron contracts on cooling.

### Step 2: Evaluate Each Statement
1. **Cast iron is also called pig iron.**
- This statement is **correct**. Cast iron is often referred to as pig iron, especially in its raw form.

2. **Cast iron contains about 4 to 4.5% carbon.**
- This statement is **correct**. Cast iron typically contains a carbon content ranging from 2% to 4%, with 4% being common.

3. **Cast iron is corrosion-resistant.**
- This statement is **correct**. Cast iron has good corrosion resistance due to the presence of graphite, which forms a protective layer.

4. **Cast iron contracts on cooling.**
- This statement is **incorrect**. Generally, cast iron expands when it solidifies and then contracts upon cooling. However, it does not contract significantly compared to other metals, and the statement implies it remains the same, which is misleading.

### Conclusion
The incorrect statement about cast iron is: **"Cast iron contracts on cooling."**