Question

The cell formed in bent pipes is an example of

• A. Concentration Cell
• B. Composition Cell
• C. Stress Cell
• D. Electrolytic Cell

Hint:

Remember that non-uniformity is a major cause of corrosion.
- Difference in metal type \(\rightarrow\) Galvanic/Composition Cell.
- Difference in oxygen concentration \(\rightarrow\) Differential Aeration Cell.
- Difference in mechanical stress \(\rightarrow\) Stress Cell.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The question asks to identify the type of electrochemical corrosion cell formed in a bent metal pipe.

Step 2: Key Formula or Approach:
This question is about electrochemical corrosion. Corrosion often happens when different areas on a metal surface develop a potential difference, creating a tiny galvanic cell. The cell is named based on the cause of this potential difference.

Step 3: Detailed Explanation:
When a metal pipe is bent, it is subjected to non-uniform mechanical stress.
- The outer curve is under tensile stress (stretched).
- The inner curve is under compressive stress.
A region of a metal under higher stress is more energetically active and thus has a more negative electrode potential. This makes the highly stressed region (the bend) anodic, while the less stressed regions become cathodic.
This potential difference, arising from differences in mechanical stress across the metal surface, creates a galvanic cell known as a

Stress Cell. This leads to accelerated corrosion at the stressed areas.

Step 4: Final Answer:
The cell formed in bent pipes is an example of a Stress Cell.