Formulations of chitosan/TiO2/ZnO ternary nanocomposites-based alkyd nanopaint for marine anti-biofouling application

Marine biofouling is a significant challenge for the performance and durability of marine vessels and structures. This study focuses on developing a chitosan/TiO₂/ZnO nanocomposite-based alkyd nanocoating to mitigate biofouling. Chitosan was effectively extracted from shrimp shell, pristine ZnO and TiO₂ nanoparticles were synthesized to form binary and ternary nanocomposites. The resultant materials were characterized using various analytical techniques. UV–Visible spectroscopy confirmed that the ternary nanocomposites exhibited a shift in the absorption edge at the interface between pristine TiO₂ and ZnO. X-ray diffraction and High-Resolution Transmission Electron Microscope confirmed wurtzite ZnO as hexagonal nano rods and anatase-phase TiO₂ with a spherical morphology. Raman and X-ray photoelectron spectroscopy confirmed the presence of pristine TiO₂ and ZnO nanoparticles in the composites. The chitosan/TiO₂/ZnO composite materials were evaluated at a concentration of 50 μg/mL and demonstrated enhanced antibacterial and antibiofilm activities. In addition, alkyd resin-based nanopaints were formulated by incorporating these nanocomposites and coated onto mild steel coupons. The residue weight of TiO₂ and ZnO (32.49 % in 760 °C) in the formulation was confirmed by thermogravimetric analysis. The water contact angle measurement indicated a hydrophobicity of 90.17° for the ternary composite. Mesocosm experiments and field exposure trials showed a notable reduction in microfouling and macrofouling on surfaces coated with chitosan/TiO₂/ZnO paint. Notably, the barnacle attachment count on coupons submerged in seawater for 45 days showed 10 % adherence on the chitosan/TiO₂/ZnO paint. The results of the field immersion study indicate that this nanopaint exhibits significant potential as an effective material for marine antifouling applications.