Insitu SVET studies on the current density distribution on dissolving of Mg, MgZn₂, Mg₂Si and Al₄Cu₂Mg₈Si₇ surfaces in NaCl solutions

Abstract

Purpose

This paper aims to acquire the current density distribution on dissolving of Mg, MgZn₂ (η -phase), Mg₂Si (ß-phase) and Al₄Cu₂Mg₈Si₇ (Q-phase) surface in NaCl solutions.

Design/methodology/approach

MgZn₂ (η -phase), Mg₂Si (ß-phase) and Al₄Cu₂Mg₈Si₇ (Q-phase) are important intermetallic compounds found in aluminum alloys. Insitu scanning vibrating electrode technique (SVET) was used to acquire the current density distribution on dissolving of Mg, MgZn₂ (η -phase), Mg₂Si (ß-phase) and Al₄Cu₂Mg₈Si₇ (Q-phase) surface in NaCl solutions scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDX) was used to characterize the corroded surface.

Findings

SVET maps reveal that these compounds display characteristic dissolution features. Mg and MgZn₂ displayed localized anodic and cathodic sites while that of Al₄Cu₂Mg₈Si₇ > Mg₂Si displayed a diffused distribution of anodic and cathodic sites. The magnitude of the integrated anodic current densities on the compounds was noted to decrease with the progress of time, and the order of the magnitude of the current density with respect to the compounds is Mg > Mg₂Si > Al₄Cu₂Mg₈Si₇ > MgZn₂. SEM/EDX reveal that the highest mass loss recorded after the SVET test was manifested by Mg₂Si followed by MgZn₂ then Al₄Cu₂Mg₈Si₇.

Originality/value

Auxiliary information on the current density distribution on the corroding sample surface at the microscopic scale has been provided by SVET thereby taking care of certain limitations of traditional corrosion monitoring techniques such as gravimetric, hydrogen evolution and electrochemical measurements.

Citation

Ikeuba, A.I., Okafor, P.C., Ita, B., Obike, A.I., Abeng, F.E., Essien, U. and Bamigbola, A. (2022), "Insitu SVET studies on the current density distribution on dissolving of Mg, MgZn₂, Mg₂Si and Al₄Cu₂Mg₈Si₇ surfaces in NaCl solutions", Anti-Corrosion Methods and Materials, Vol. 69 No. 1, pp. 104-110. https://doi.org/10.1108/ACMM-07-2021-2518