Electrophoretic deposition and characterization of CS/nanoHAp/AgNPs composite coatings on titanium from ethanol-based suspensions

Titanium implants possess bioinert surfaces that limit osseointegration and are prone to bacterial colonization, necessitating functional coatings. This study investigated the electrophoretic deposition (EPD) of composite coatings composed of chitosan (CS), nanohydroxyapatite (nanoHAp), and silver nanoparticles (AgNPs) on grade 2 titanium using an ethanol-acetic acid suspension. The influence of deposition parameters (10-30 V; 3-5 min) on coating microstructure, adhesion, corrosion resistance, wettability, bioactivity, and silver release was systematically examined. The coatings reached a maximum thickness of ~ 7 μm at 30 V/5 min, while the most uniform and adherent coating (class 1, EN ISO 2409) was obtained at 10 V/3 min. Increasing voltage and time produced rougher (Sa up to 1.3 μm) and more porous surfaces, but decreased adhesion. Corrosion resistance improved with coating thickness, with open circuit potentials shifting positively up to + 0.15 V versus the reference electrode. Wettability tests revealed hydrophilic behavior with contact angles of ~ 80°. Bioactivity in simulated body fluid was confirmed by calcium phosphate precipitation on all coated samples, particularly thicker ones. Silver ion release was controlled by deposition parameters, ranging from 0.9 mg/L (10 V/3 min) to 1.8 mg/L (30 V/5 min) after 7 days, indicating a balance between antibacterial functionality and coating integrity. These results demonstrate that ethanol-based EPD can fabricate bioactive, corrosion-resistant CS/nanoHAp/AgNPs coatings with tunable properties. Optimized coatings show potential for biomedical applications, particularly in reducing implant-associated infections while supporting bone integration.