Deterioration of marine antifouling coatings fragments and their possible environmental significance

Marine antifouling coatings (AFC) are widely applied to ship submerged surfaces to prevent biofouling, but the release of coating fragments, as biocide-containing microplastics into the environment, remains underexplored. This study investigates the behavior of fragments from three different self-polishing antifouling coatings (SPC #1, SPC #2, and SPC #3) under three simulated environmental conditions: (1) swirling (i.e., mechanical agitation) brackish water with full-spectrum LED light, (2) swirling brackish water in the dark, and (3) static brackish water in the dark. Results showed that both photodegradation and mechanical agitation significantly accelerated the breakdown of coating fragments and enhanced toxic metal leaching. FTIR spectra revealed characteristic broadening of O–H and C=O bands, consistent with hydrolysis and oxidation of the polymer matrix. Cu and Zn concentrations in water continued to rise, likely due to disintegration and exposure of fresh surfaces. These findings highlight the role of light and hydrodynamic conditions in driving the transformation and release of contaminants from AFC material released from ship surfaces.