Influence of the microstructure on the corrosion behaviour of cast Mg-Al alloys

The influence of α-phase and β-phase (Mg17Al12) on corrosion of cast binary Mg-Al alloys was investigated by immersion testing in 5 wt.-% NaCl solution saturated with Mg(OH)2 and by measuring the corrosion potential Ecorr. The microstructure of the alloys regarding Al-content of α-phase and amount of β-phase was adjusted by solution heat treatments at various temperatures. Subsequently the continuity of β-phase (Cβ) was measured. With increasing Al-content in the α-phase, the impact of Cβ decreases. The results show that the Al-content of the α-phase is a very important factor to influence the corrosion resistance.