What design practice helps ensure compatibility between coatings and CP in service?

• A. Ignore pretreatment; apply CP aggressively.
• B. Ensure coating compatibility with CP design, proper pretreatment, and avoid CP settings that aggressively attack coating adhesions.
• C. Use the same coating regardless of CP.
• D. Avoid any CP.

Answer: (B)

Coatings must be designed to work with the cathodic protection system; compatibility is built into the design. The coating material and its surface preparation should be selected with the CP scheme in mind so the potential distribution in service won't cause coating detachment or underfilm corrosion. Proper pretreatment ensures a strong bond to the substrate before electrical protection starts, which is essential when currents and hydrogen evolution can stress the interface. CP settings should be tuned to protect the metal without overprotecting, which can aggressively attack coating adhesions and lead to blistering or disbondment. When these elements are coordinated, the coating remains adherent and protective under service conditions. Ignoring pretreatment undermines adhesion; aggressive CP can damage coatings; using the same coating for all CP scenarios ignores compatibility; avoiding CP eliminates protection.