The influence of yttrium (Y) on the corrosion of Mg–Y binary alloys

Corrosion of Mg–Y alloys was studied using electrochemical evaluations, immersion tests and direct observations. There were two important effects. In 0.1 M NaCl, the corrosion rate increased with increasing Y content due to increasing amounts of the Y-containing intermetallic. In 0.1 M Na2SO4, the corrosion rate decreased with increasing Y content above 3%, attributed to a more protective surface film, despite the intermetallic. The corrosion rate evaluated by electrochemical impedance spectroscopy was somewhat smaller than that evaluated from H evolution as expected from the Mg corrosion mechanism. A mechanism is proposed for filiform corrosion. Direct in situ corrosion observations revealed that a predominant feature was hydrogen evolution from particular parts of the alloy surface.

Research highlights
► The Y-intermetallic can accelerate corrosion and Y can increase the protectiveness of the surface layer.
► In 0.1 M NaCl, the corrosion rate of Mg-Y alloys increased with increasing Y due to the Y intermetallic.
► In 0.1 M NaCl, there was filiform corrosion.
► In 0.1 M Na2SO4, the corrosion rate of Mg-Y alloys decreased with increasing Y in the range 3–7%Y.
► Hydrogen evolution was observed from particular parts of the alloy surface.