Which of the following is NOT a typical factor causing CP system failure?

• A. Insufficient anode area.
• B. Burial or isolation of the structure.
• C. Coating the structure with extra protective coating.
• D. Incorrect potentials.

Answer: (C)

In cathodic protection, failure typically happens when the system can’t deliver or sustain enough protective current at the right potential. If the anode area is insufficient, there isn’t enough current to bring the entire structure to the protective, negative potential. If the structure is buried or isolated from the surrounding soil, the electrical circuit is broken and current can’t reach the metal. If the potentials are incorrect, the structure may not reach the protective level or could be overprotected, both of which leave the metal vulnerable or cause other issues. Adding extra protective coating, on the other hand, is generally beneficial—it reduces the metal’s exposure and the current demand on the CP system. It’s not a typical cause of CP system failure, though coating defects or disbondment can introduce separate problems.