Effect of Cathodic Protection Potential and AC Interference on Cathodic Stripping Properties of Coatings

Through cathodic stripping test, the cathodic stripping distance of the newly-built FBE coating and the in-service 3PE coating samples under different cathodic protection potentials (applied potentials) and AC interference conditions was explored, and the coating performance under the coexistence of AC interference and cathodic protection was also explored. Through electrochemical impedance spectroscopy (EIS) test, the cathodic stripping process of the FBE coating was monitored. The results showed that when the AC interference of the newly-built FBE coating sample was 60-300 A/m², its influence on the cathodic delamination of the coating was small. The cathodic stripping distance of the newly-built FBE coating increased with the negative shift of the applied potential and the extension of time. For the 3PE coating in service for 15 years, when the applied potential was -1.2 V (CSE), cathodic disbondment occurred rapidly in the early stage of the test, and the growth rate of the peeling distance in the later period slowed down significantly, and there were typical protection zones shielding zones, and new peeling zones. The stripping area was related to the cathodic disbondment resistance of the underlying coating. In the normal cathodic protection potential range, when the protection potential shifted negatively, the cathodic stripping distance increased. When the cathodic protection potential was -0.85 - -1.0 V, as the AC interference intensity increased, the cathodic stripping distance increased. When the applied potential was -1.2 V, the impact of AC interference on cathodic stripping was small.