Microstructural and Corrosion Studies by Immersion in 3.5% NaCl Solution on Aged Mg-9Al-1Zn-XCa Alloy

Abstract

The experimatal alloys were aged at different temperatures of 180°C, 200°C, 220°C, and 240º C with calcium addition levels of (X=0.5, 1, 1.5, 2%) on Mg-6Al-1Zn-XCa alloy were investigated in 3.5% NaCl solution. All the experimatal alloys were immersed in 3.5% NaCl solutions and the resulted surface were analyzed to study the corrosion behaviour and its surface topography by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersed spectroscopy (EDS) and X-ray diffraction (XRD) techniques. The result shows that corrosion attack occurred predominantly on ß phase and α phase exhibit relatively minor corrosion. In addition to that the increased aging temperature coarsens the intermetallic as well as α- Mg grains, which shows adverse effect to corrosion resistances and the best result were obtained at composition of 0.5wt.% Ca aged at 200°C.