Behavior of biocide-free foul control paints for ships' hulls in the immediate proximity of ICCP anodes

Impressed current cathodic protection systems are used in combination with organic coatings to prevent corrosion of hulls. The reaction species which are formed in the proximity of the anodes, like chlorinated compounds and acidity, can stress the antifouling paints of the protective coating system. A 3 x 3 matrix was defined to drive the tests aiming to investigate the behavior of novel biocide-free foul release (FR) and self-polishing (SP) paints under this kind of attack. The matrix was featured by different pH and free chlorine (free-Cl) values derived by a galvanostatic test performed at an anodic current density required for the protection of paints roughly at their mid age. Chemical/physical characterization was performed through visual analysis, thickness measurements, profilometry, contact angle measurements, and FTIR-ATR analysis. Both FR and SP paints underwent adhesive failure only in the harshest conditions, pH = 3/free-Cl 3-6 ppm, with unmodified chemistry of the polymers. Both paints exhibited no detachment in milder pH/free-Cl conditions, but thickness and contact angle reduction were observed. Finally, results were discussed inferring possible behaviors of the tested paints in real applications.