Cathodic Protection Tester Practice Exam

According to the NACE Criteria for Underground Steel Pipe, what is the required negative potential?

1. -700 mV relative to a copper sulfate electrode

2. -800 mV relative to a copper sulfate electrode

3. -850 mV relative to a copper copper sulfate reference electrode

4. -900 mV relative to a copper sulfate electrode

The correct answer is: -850 mV relative to a copper copper sulfate reference electrode

The requirement for a negative potential of -850 mV relative to a copper/copper sulfate reference electrode is based on established standards for effectively protecting underground steel pipelines from corrosion. This specific voltage indicates that the pipeline is polarized adequately through cathodic protection, which minimizes the risk of corrosion. When a cathodic protection system is functioning correctly, a negative potential of -850 mV or more signifies that the pipeline is sufficiently protected. This level of potential helps to shift the electrochemical reactions at the surface of the steel, reducing the likelihood of corrosion by making the pipeline the cathode in the electrochemical cell. By meeting this criterion, operators can ensure that the integrity of the steel pipe is maintained over time, preventing leaks and failures that can arise from corrosion. Understanding this required potential is crucial for anyone involved in cathodic protection, as it helps to define the operational benchmarks for maintaining an effective corrosion control program.