Investigation on the corrosion properties of co- electrodeposited Ni-ZrO2 composite coating usig EIS

Corrosion behavior of Ni and Ni-ZrO2 composite coatings were studied using electrochemical impedance spectroscopy (EIS) technic. An equivalent circuit diagram based on blocked and partially corroded surface characterizations were proposed and a good agreement was observed between theoretical impedance spectra obtained on the basis of the equivalent circuit and spectra recorded during the measurements. The changes in the charge transfer resistance obtained from impedance measurements were comparable with the changes in polarization resistance obtained from potentiodynamic measurements and both of potentiodynamic and EIS tests showed that the corrosion resistance of NiZrO2 was higher than that of pure Ni. Investigation of corroded surfaces showed that the cluster boundaries in pure Ni and weak bonds between Ni matrix and ZrO2 particles in Ni-ZrO2 composite coating were the appropriate paths for corrosion to proceed. Changing of microstructure and corrosion proceeding paths were recognized as the reasons for higher corrosion resistance of Ni-ZrO2 with respect to pure Ni.