Insitu SVET studies on the current density distribution on dissolving of Mg, MgZn<sub>2</sub>, Mg<sub>2</sub>Si and Al<sub>4</sub>Cu<sub>2</sub>Mg<sub>8</sub>Si<sub>7</sub> surfaces in NaCl solutions
Alexander I. Ikeuba, Peter C. Okafor, Benedict I. Ita, Anthony I. Obike, F. E. Abeng, Uduak Essien, Abiola Bamigbola
Abstract
Purpose This paper aims to acquire the current density distribution on dissolving of Mg, MgZn 2 (η -phase), Mg 2 Si (ß-phase) and Al 4 Cu 2 Mg 8 Si 7 (Q-phase) surface in NaCl solutions. Design/methodology/approach MgZn 2 (η -phase), Mg 2 Si (ß-phase) and Al 4 Cu 2 Mg 8 Si 7 (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, MgZn 2 (η -phase), Mg 2 Si (ß-phase) and Al 4 Cu 2 Mg 8 Si 7 (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 MgZn 2 displayed localized anodic and cathodic sites while that of Al 4 Cu 2 Mg 8 Si 7 > Mg 2 Si 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 > Mg 2 Si > Al 4 Cu 2 Mg 8 Si 7 > MgZn 2 . SEM/EDX reveal that the highest mass loss recorded after the SVET test was manifested by Mg 2 Si followed by MgZn 2 then Al 4 Cu 2 Mg 8 Si 7 . 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.