Study of oxide layers on metals and alloys by cyclic local voltammetry

The paper deals with the possibilities of local electrochemical analysis (LEA) in the investigation of anode properties and predicting corrosion behavior of metals and galvanic alloys. Our aim is to study changes in the surface composition in the process of anodic dissolution, determine the phase composition and quality of passive films on the surface of metals and alloys and control oxide nanofilm resistivity. We show the possibility of using the hybrid LEA method that combines cyclic local voltammetry and abrasive voltammetry to investigate the kinetics of oxide layer growth, determine their thickness, phase composition and resistivity. Analysis of one polarization curve makes it possible to monitor the process of oxide film formation on the metal surface (anode part) and estimate its phase composition and resistivity (cathode part). We propose a novel way of calculating the resistivity of the oxide film and an equation that describes its growth. The results of theoretical calculations are confirmed by the experimental data obtained in the course of analyzing the polarization of tin, lead and their alloys in an aqueous alkaline solution. The dependence of the oxide film thickness on the time of film growth is exponential.

ACTIVITY AND ACTIVITY COEFFICIENTS OF DISSOLVING PHASE OF HETEROGENEOUS ALLOY UNDER CONDITIONS OF LOCAL VOLTAMPEROMETRY

The new expressions for the activity coefficients of dissolving phase and for calibration curves i=f(С) are presented as the result of development of previous studies of an anode dissolution process of heterogeneous alloys at the conditions of local voltammetry.