The Effect of Bath pH and Temperature on the Corrosion Behavior of Co-Electrodeposited Ni-Cu/Cr2O3 Nanocomposite Coatings

Abstract

The aim of this work was to assess the influence of pH and temperature of bath plating on the performance of Ni-Cu/Cr2O3 nanocomposite coatings in a corrosive environment. For this purpose, Ni-Cu/Cr2O3 nanocomposite coatings were successfully carried out on the carbon steel by co-electrodeposition method from an aqueous composing of H2O, NiSO4, NiCl, CuSO4, Na3C6H5O7, and H3BO3 with and without 6 g/L Cr2O3 nanoparticles. The microstructure of samples was studied by x-ray diffraction and scanning electron microscopy, and corrosion behavior of the coatings was assessed by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in the 3.5% NaCl solution. It was observed that by increasing the bath pH from 3 to 7 the corrosion current density (icorr) determined by Tafel extrapolation method was changed from 7.4 to 12.5 µA/cm2 and that polarization resistance (RP) obtained from EIS measurements was decreased from 850 to 452 Ω·cm2. The values of icorr and RP were changed from 11.2 µA/cm2 and 514 Ω·cm2 to 6.1 µA/cm2 and 1265 Ω·cm2, respectively, as the bath temperature was varied from 25 to 45 °C. Compared to the Ni-Cu nanocrystalline coating, the value of Rp showed more than 324% improvement when co-electrodeposition of Ni, Cu, and Cr2O3 was carried out at a temperature of 45 °C and pH value of 4.5.