Thermodynamic parameters of electrodeposition of Zn‐Co‐TiO₂ composite coatings

Zinc‐cobalt alloys have been electrodeposited from a sulphate bath. The effect of process variables, including temperature, time, concentration of cobalt sulfate and current density on the Zn‐Co deposition was investigated from kinetic and mechanistic viewpoints. Activation energies, enthalpies and entropies were determined according to Arrhenius and absolute rate theories. The codeposition mechanism of TiO₂ with cobalt‐zinc in the presence of benzyl triethanol ammonium exthoxylate (BTAE) has been studied. The optimum concentration of the additive was reported. The mechanism of incorporation of TiO₂ was suggested and confirmed in view of calculated free energy of adsorption of TiO₂. Corrosion resistance of Zn‐Co‐TiO₂ alloy was determined by a salt spray test under most of the plating conditions studied.