What factors can cause CP system failure?

• A. Incorrect potentials are the only factor.
• B. Insufficient anode area, burial or isolation of the structure, incorrect potentials, insufficient current supply, and stray currents.
• C. Temperature changes alone.
• D. Coating defects.

Answer: (C)

In cathodic protection, the structure is kept at a negative potential to prevent corrosion, and failure occurs when the protective current can't meet the structure’s needs across its surface. The most complete set of factors includes having too small anode area (or degraded/anodes not supplying enough current), burial or isolation of the structure (which hinders current flow to all parts), incorrect protection potentials, insufficient current supply from the source, and stray currents that pull current away from the protected surface. These together can prevent achieving and maintaining the required protective conditions.

Temperature changes by themselves don’t drive CP failure, and coating defects, while they increase local current demand where damage exists, aren’t the sole cause of system-wide failure.