Development and optimization of Zn–Ni–TiO₂ composite coating, assessment of its corrosion resistance and antimicrobial activity

Zn–Ni–TiO₂ composite coating was developed through response surface methodology. The current density and concentration of TiO₂ were optimized to obtain a minimum corrosion rate. The optimized condition obtained from the central composite design achieved a minimum experimental corrosion rate of 0.122 mm/year as a response for the Zn–Ni–TiO₂ composite coating with a current density of 2.91 A/dm² and concentration of TiO₂ 4.9 g/L. The potentiodynamic polarization and electrochemical impedance spectroscopic method was used to measure the corrosion resistance. The antimicrobial activity of the composite coating was assessed. Growth of Gram-negative and -positive microbes was observed on the polished mild steel. However, the composite coating exhibited resistance to Gram-negative microorganisms. Surface characterization was carried out using scanning electron microscopy (SEM) along with energy-dispersive X-ray spectroscopy depicting the presence of Zn, Ni, Ti, and O elements in the composite coating. Atomic force microscopy confirmed the surface roughness and heterogeneous distribution of crystal grain.