Abstract
Highly creep resistant magnesium alloys containing Sc, rare earths (Gd, Ce, Nd, Y) and manganese exhibit a considerably higher corrosion resistance than high purity magnesium. This is attributed to the beneficial effect of rare earth elements on the stability of the protective surface layer, presumably magnesium hydride MgH2, deposited on the surface as a corrosion product. Ternary MgSc15Mn1 and quaternary MgSc6Ce4Mn1 behave differently. This is due to the high Sc content and its distribution (segregation and undissolved particles). The presence of intermetallic phases (Mg-rare earth) has no detrimental effect on the corrosion resistance, but the Mg12Ce phase can contribute to the high corrosion rate in alloys with a high Sc content.