Chapter 18, Problem 38A

Interpretation Introduction

Interpretation: Cathodic protection which is applied to prevent oxidation of steel tanks and pipes needs to be explained.

Concept Introduction: Electrolysis is the breakdown of compound’s chemical bonds to create elemental substances. The method involves passing of electrical current through the electrolyte to be degraded at different voltage between two electrodes. The electrolytes consist of cations and anions.

Answer to Problem 38A

Cathodic protection is used to prevent corrosion of steel tanks and pipes. In this method to resist oxidation, magnesium metal is connected through a wire. Magnesium resists the iron from being oxidized.

Explanation of Solution

The method cathodic protection is used to protect steel in buried fuel tanks and pipelines. In this method, a metal like magnesium gives electrons more easily than iron. It is connected by a wire to the pipeline or tank that is to protect from oxidation. Magnesium is a good reducing agent than iron. Hence, electrons flow via the wire from magnesium to iron pipe. The electrons are supplied by the magnesium instead of iron and it keeps the iron from being oxidized. As oxidation of magnesium occurs, so, the magnesium dissolves, and must be regularly substituted.

Conclusion

In order to avoid corrosion in cathodic protection, all anodic positions on the metal surface are transferred to cathodic sites by providing electrical current.