Ferrite-based materials for anticorrosion: comparative study of ZnFe₂O₄, CuFe₂O₄, and SrFe₁₂O₁₉

Three chitosan ferrite nanoparticles-ZnFe₂O₄, CuFe₂O₄, and SrFe₁₂O₁₉-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 ZnFe₂O₄ and cuprospinel CuFe₂O₄. In contrast, SrFe₁₂O₁₉ exhibited coexistence of hexagonal M-type ferrite and rhombohedral α-Fe₂O₃, 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 ZnFe₂O₄-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.