What CP-related coating issue can occur if a protective coating is misapplied, and what design considerations ensure compatibility?

• A. CP can cause coating edge disbondment if misapplied; ensure coating compatibility with CP design, proper pretreatment, and avoid CP settings that aggressively attack coating adhesions.
• B. CP has no interaction with coatings and does not affect adhesion.
• C. A proper coat always adheres better under CP regardless of pretreatment.
• D. Edge disbondment occurs only when coatings are applied improperly without CP.

Answer: (A)

When a protective coating is used with a cathodic protection system, the electrochemical environment can stress the coating at defects or edges. If the coating is misapplied or not compatible with the CP design, hydrogen evolution and moisture can build up at the coating–metal interface, especially near edges, causing the coating to detach from the substrate along those edges. This edge disbondment undermines the protective barrier and allows corrosion to start under the coating.

To prevent this, design the coating system to be CP-compatible: choose coatings that perform well under the expected cathodic potentials, ensure thorough pretreatment and surface preparation to maximize adhesion, and apply the coating correctly with proper curing and thickness. Also, avoid CP settings or operating conditions that aggressively attack coating adhesions, since overprotection can accelerate disbondment.