MICROSTRUCTURAL AND CORROSION STUDIES BY IMMERSION IN 3.5wt % NaCl ENVIRONMENT ON Mg-6Al-1Zn-XCa ALLOY WITH Ca ADDITION AND AGED AT DIFFERENT TEMPERATURES

The effect of aging at different temperatures of 180ºC, 200ºC, 220ºC, and 240º C with various level of calcium (X=0.5, 1, 1.5, 2%) addition on Mg-6Al-1Zn-XCa alloy were investigated in 3.5Wt.% NaCl solution. The specimen was subjected to immersion testing in 3.5Wt.% NaCl, 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 the 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.