Investigations on corrosion proceeding path and EIS of Ni–ZrO 2 composite coating

Electrochemical impedance spectroscopy of Ni and Ni–ZrO₂ composite coatings was studied. 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 are the appropriate paths for corrosion to proceed. An equivalent circuit diagram based on blocked and partially corroded surface characterisations was proposed, and good agreement was observed between theoretical impedance spectra obtained on the basis of the equivalent circuit and spectra recorded during the measurements. Changes of microstructure and corrosion proceeding paths were recognised as the reasons for the higher corrosion resistance of Ni–ZrO₂ with respect to pure Ni.