Abstract
Three chitosan ferrite nanoparticles-ZnFe(2)O(4), CuFe(2)O(4), and SrFe(12)O(19)-were synthesized via an ultrasound-assisted PEG route, yielding phase-pure products with controlled morphologies. Structural and compositional analyses confirmed phase purity, tailored morphology, and mesoporosity across systems for cubic spinel ZnFe(2)O(4) and cuprospinel CuFe(2)O(4). In contrast, SrFe(12)O(19) exhibited coexistence of hexagonal M-type ferrite and rhombohedral α-Fe(2)O(3), indicating a multiphase nature. These nanoparticles were incorporated into chitosan-ferrite nanocomposites and evaluated as corrosion inhibitors for carbon steel in 1.0 M HCl via potentiodynamic polarization (PDP), electrochemical frequency modulation (EFM), and electrochemical impedance spectroscopy (EIS). All of the techniques revealed concentration-dependent inhibition, with ZnFe(2)O(4)-based composites consistently demonstrating the highest efficiencies (up to 98.73% by PDP, 94.35% by EFM, and 97.38% by EIS). The inhibition mechanism was identified as mixed-type, primarily affecting the cathodic reaction, supported by causality factors and impedance parameters such as increased R (ct) and decreased C (dl). Adsorption modeling showed strong monolayer behavior with spontaneous composite-metal surface interaction, validated by Langmuir fitting and values (∼-28 kJ mol(-1)). These results highlight the performance of ultrasound-engineered ferrite nanocomposites in forming protective films and reducing acid-induced corrosion, underscoring their application potential in advanced coating systems.