How are CP potentials interpreted for buried structures?

• A. Potential readings are ignored for buried structures.
• B. Measured potentials against a reference electrode are compared to standards to determine if protection is adequate.
• C. Only current measurements matter, not potentials.
• D. Surface color indicates protection level.

Answer: (B)

When evaluating cathodic protection on buried structures, you assess protection by measuring the metal’s potential in the soil and comparing it to standard criteria using a reference electrode. The reference electrode provides a stable baseline, so the measured potential tells you how negative (or positive) the structure is with respect to the soil environment. If the potential is sufficiently negative compared to the standard, the structure is considered adequately protected; if not, the protection may be under-applied and adjustments to the CP current or coating systems are needed. Overprotection can also be a concern if the potential goes too far negative, potentially causing issues like coating disbondment.

This is why the option describing readings against a reference electrode being compared to standards is the best choice. The other ideas—ignoring potentials, focusing only on current, or judging protection by surface color—don’t provide a reliable measure of corrosion risk for buried structures.