Evaluation of new marine coatings based on organometallic biocides supported on zeolites under real conditions for biofouling prevention

Abstract

An epoxy-based coating incorporating copper nanoparticle-modified zeolites and capsaicin as a biocide was evaluated. The system was exposed to marine conditions in Talcahuano Bay (Chile) for four months and characterized using atomic force microscopy (AFM), confocal microscopy, and electrochemical impedance spectroscopy (EIS). Antifouling efficacy was determined according to ASTM D3623-78a, with fouling resistance indices above 90 in formulations containing copper and capsaicin. Antimicrobial viability was confirmed through live/dead staining and confocal microscopy, showing 60 % of dead bacteria, whereas 15 % was observed in formulations without biocides. The average contact angle (ASTM D7334-08) was 70°, and the surface was not classified as hydrophobic. Surface roughness, measured by AFM, ranged between 95 and 295 nm. The coating's mechanical properties were evaluated using standardized tests: adhesion (ASTM D4541-22), with maximum tensile loads of approximately 1.5 MPa; flexibility (ASTM D522-17), with fracture lengths less than 22 mm; drawing (ASTM E643-15), with capsaicin formulations reaching 2.99 mm in cup height; and abrasion (ASTM D4060), with wear rates less than 0.3. Finally, the anticorrosive protection was confirmed by EIS, obtaining impedances of ∼105 Ω, supporting the system's effectiveness as a multifunctional antifouling and anticorrosive coating.