A CP system turns the pipeline surface into:

The reason the correct answer is that a cathodic protection (CP) system turns the pipeline surface into a cathode is rooted in the fundamental principles of corrosion control. In cathodic protection, the goal is to prevent corrosion by ensuring that the metal surface of the pipeline becomes the cathode in an electrochemical cell.

In this arrangement, the cathode is the electrode where the reduction reaction occurs, which involves the gain of electrons. By making the pipeline a cathode, the CP system effectively minimizes the oxidation processes that lead to corrosion. Corrosion typically happens at the anode, where metal loses electrons and degrades. Therefore, by converting the pipeline surface into a cathode, the system directly counters the electrochemical conditions that facilitate corrosion.

This approach is a proactive measure because it mitigates the factors that contribute to corrosion, keeping the integrity of the pipeline intact over time. Without this understanding, it would be easy to confuse the roles of anodes and cathodes in the corrosion process, which is crucial for those engaged in pipeline maintenance and protection against corrosion.