What of the following represents process of passivation ?

Options

A. Coating the metal surface by point
B. Coating the metal surface with another metal
C. Connecting the metal with more easily oxidizable agent.
D. Treating the metal with a strong oxidizing agent.

Answer

To determine which process represents passivation, we need to understand the concept of passivation in the context of electrochemistry.

### Step-by-Step Solution:

1. **Define Passivation**:
- Passivation is the process of making a metal less reactive by forming a protective layer on its surface. This layer is typically an oxide that prevents further corrosion.

2. **Identify the Role of Oxidizing Agents**:
- Oxidizing agents, such as nitric acid (HNO3) and citric acid, are used in the passivation process. They help in oxidizing the surface of the metal, leading to the formation of a protective oxide layer.

3. **Consider the Example of Stainless Steel**:
- In the case of stainless steel, passivation is achieved by treating it with oxidizing agents. This treatment removes impurities and enhances the formation of a thin, protective oxide layer that makes the steel resistant to corrosion.

4. **Select the Correct Process**:
- Among the options provided, the process that involves "treating the metal with a strong oxidizing agent" is representative of passivation. This is because the oxidizing agent facilitates the formation of the protective oxide layer.

### Conclusion:
The correct answer to the question is: **4. Treating the metal with a strong oxidizing agent.**

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