Corrosion behavior of magnesium and its alloy in NaCl solution

The electrochemical behavior of cast Mg, AZ91, and cast AZ91 in 0.1 M NaCl solution is investigated by measuring open-circuit potential (OCP), steady-state current-potential, and electrochemical impedance spectra (EIS). The similar electrochemical impedance behavior is found of three corrosion electrodes. There are two capacitances in high-and medium-frequency domains and one inductive loop or component in low-frequency domain. From equivalent circuit simulation, cast AZ91 has the worst corrosion resistance. The EIS results are in good agreement with those obtained by OCP and polarization curves. Based on the Cao theory, a simple corrosion mechanism is put forward, supplying a possible explanation for low-frequency inductive behavior for Mg and its alloy in NaCl solution at OCP. Published in Russian in Elektrokhimiya, 2007, Vol. 43, No. 7, pp. 878–885. The text was submitted by the authors in English.