Corrosion behavior of ZnNiAl2O3 nanocomposite coatings obtained by electrodeposition from alkaline electrolytes

The aim of this work was to investigate the anti-corrosive properties of nanocomposite ZnNi coatings containing Al2O3 nanoparticles, prepared from alkaline commercial electrolytes (pH 13), (PERFORMA 280.5, COVENTYA S.A.S, France), by electrodeposition on carbon steel (OL37). The corrosion resistance of the coatings prepared with different concentrations of Al2O3 (5, 10, and 15g/L) was evaluated in 0.2g/L Na2SO4 solution (pH 5) by open circuit potential (OCP) measurements, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) techniques. The results of electrochemical measurements were corroborated with those obtained by using X-ray diffraction analysis. The obtained results show that the introduction of Al2O3 nanoparticles in the plating bath generally brings an increase in corrosion resistance of ZnNi layers and put in evidence the existence of an optimal Al2O3 concentration. Under the examined conditions, the optimal concentration determined from polarization measurements was proven to be 5g/L Al2O3. The highest value of the polarization resistance, Rp, obtained from impedance measurements corresponds also to ZnNi with 5g/L Al2O3, which is in agreement with the results obtained from polarization and XRD measurements.