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Microstructure and corrosion behaviour of a Mg-9Al alloy with minor alloying

additions (Mn, Y, Nd, Ca and Sn) are evaluated. All of the additions form Al-rich

intermetallics with varying amounts of Fe, while Ca and Sn are also incorporated

into the eutectic β-phase (β-Mg17Al12). Special attention is given to the surface

potential values of the microconstituents, which are related to the formation of

microgalvanic couples. Scanning Kelvin Probe Force Microscopy (SKPFM)

measurements revealed that all the alloying elements, except Sn, reduced the potential

difference between the secondary phases and the matrix, which is the main reason

for the improvement of the corrosion resistance of Mn-, Y- and Nd-modified alloys.

The beneficial effect of Ca is additionally related to the microstructure refinement

and an increased area fraction of the β-phase.
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