engleski

Cathodic Delamination Tests During the Initial Stage of Coating Cure in Seawater Performed under Various Polarization Regimes

Cathodic delamination tests have been performed on steel plates protected by 100% solids, solvent free, epoxy coating intended for immersion service. To mimic the situations in which cathodic protection is on during the coating application or out of service until the coating application job is done, two types of experiments were conducted. Firstly, the plates were subjected to cathodic polarization potentials of -1.0, -1.1 and -1.4 VAg/AgCl starting immediately after coating application and continued for 30 days. Secondly, the experiments were done on identically prepared plates, at potentials of -1.4, to -1.0 VAg/AgCl, after 7, 21 and 28 days of immersion without polarization. All the tests were done on samples with and without the artificial coating defect. Cell voltage and current were recorded as a function of time. The results of the long term experiments show that the optimum potential that did not cause any coating delamination and that yielded the lowest current consumption due to the most favourable conditions for the formation of protective calcerous deposits is -1.1 VAg/AgCl. IR drop contributions of seawater, coating and calcerous deposit were assessed by off-potential measurements, with reference electrode tip located at different sites with respect to the coating damage.

cathodic protection ; epoxy coating ; cathodic delaminating

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