Which of the following metals can be used for the cathodic protection of Fe?

Mg

The correct answer is option 3. Mg

Cathodic protection is a technique used to control the corrosion of a metal surface by making it the cathode of an electrochemical cell. In the case of protecting iron (Fe), it is typically made the cathode to prevent its corrosion.

Among the options provided:

1. Mn (Manganese): Manganese is not commonly used for cathodic protection. While it can have some alloying effects on steel to improve its properties, it is not typically used as an anode or cathode in cathodic protection systems.

2. Li (Lithium): Lithium is not commonly used for cathodic protection. It is highly reactive and not practical for use in cathodic protection systems.

3. Mg (Magnesium): Magnesium is commonly used for cathodic protection. It is often used as a sacrificial anode in cathodic protection systems, where it corrodes preferentially to the protected metal (such as iron), thereby providing protection to the iron structure.

4. F (Fluorine): Fluorine is not a metal and is not used for cathodic protection.

The metal that can be used for the cathodic protection of iron (Fe) is:Mg (Magnesium)