Influences of metallurgical factors on the corrosion behaviour of extruded binary Mg–Sn alloys

The corrosion behaviour of extruded Mg–(2–8 wt%)Sn alloys was investigated in aqueous chloride solutions, and the influences of the volume fraction of Mg 2 Sn intermetallics, solutionised Sn, and area fraction of grain boundaries on the corrosion behaviour were discussed. The Sn addition to α-Mg increased the solutionised Sn content in the matrix, increased the volume fraction of Mg 2 Sn intermetallics to 7.3%, and changed the grain size distribution. Regarding the corrosion behaviour, the Sn addition up to 8 wt% increased the overall dissolution rate of the alloys, although it promoted the passivity, which resulted from the increased H 2 evolution rate and increased numbers of initiation sites for pitting corrosion. The overall corrosion behaviour primarily depended on the amount of Mg 2 Sn intermetallics, which promoted passivity and notably increased the H 2 evolution rate, and functioned as pitting corrosion initiation sites. As the area fraction of grain boundaries increased, the H 2 evolution rate was also accelerated. In contrast, the solutionised Sn decreased the H 2 evolution rate.