Analysis of new methods for the determination of the cathodic disbonding behaviour of hull coatings

The work proposed here is devoted to the evaluation of cathodic protection effects on some commercial coatings prepared with an artificial holiday drilled in the centre of each testing panel. A new method for the determination of the cathodic disbonding behaviour of hull coatings was determined; it draws inspiration from the following standards: BS EN 10289, UNI EN and NACE TG-470. The main parameters are: synthetic sea water, replaced once a week, Pt anode, room temperature, applied potential = -1500 mV vs SCE, duration time = 13 weeks. In the cathodic side, brucite grew in areas of the thinner coatings far away from the site where the artificial defect was produced, witnessing intense coating damage. This phenomenon induces the increase of cathodic current request to maintain the fixed potential and the related anodic processes. In the anodic side, a pH drop, below 6, in times shorter than that planned for the solution renewal, was evidenced, inversely correlated to the current enhancement. The possibility of slowing down the acidification rate was examined, in presence and absence of anode isolation.