Study of the surface state of nickel electrode during polarization in an alkaline medium by electrochemical impedance spectroscopy method

• V.E. Kasatkin, L.P. Kornienko, A.I. Shcherbakov, I.G. Korosteleva, I.V. Kasatkina and V.N. Dorofeeva

A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Leninsky pr. 31, 119071 Moscow, Russian Federation

Abstract: The state of nickel electrode surface in a weakly alkaline medium was investigated by the Electrochemical Impedance Spectroscopy method (EIS). This system was chosen as a model where nickel has sufficient stability, which makes it possible to minimize the probability of a significant change in the electrode properties in the course of a single measurement of the impedance spectrum and to carry out studies in a wide range of potentials. The impedance spectra obtained under the conditions of potentiostatic and galvanostatic polarization turned out to be similar in both modes. An equivalent electrical circuit of the processes occurring in an oxide–hydroxide film and at its boundaries with a metal and a solution is proposed, which adequately and with good accuracy describes these processes and allows to evaluate the properties the electrical circuit elements. The regularities of the effect of experimental conditions on the parameters of the equivalent circuit elements are discussed. At potentials not exceeding +400…+500 mV, two characteristic semicircles are observed on the Nyquist diagram. In the region of higher anodic polarization, the shape of the low-frequency semicircle is deformed, taking the form of a pseudo inductive loop, characteristic for the active dissolution of the electrode metal. It was found that the high-frequency region of the impedance spectrum is practically independent of the electrode potential and is associated with the presence of an oxide–hydroxide layer on the nickel surface. The possibility to distinguish the processes of Faraday oxidation of nickel at the metal–film interface and the ionic charge transfer at the film–solution interface is revealed. Capacitive and resistive parameters of the studied processes are calculated.

Keywords: nickel, alkaline, pitting corrosion, electrochemical impedance spectroscopy method

Int. J. Corros. Scale Inhib., 2020, 9, no. 4, 1516-1529 PDF (358 K)
doi: 10.17675/2305-6894-2020-9-4-21

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