Influence of alloyed Al on the microstructure and corrosion properties of extruded Mg–8Sn–1Zn alloys

•Influence of Al on the corrosion of extruded Mg–8Sn–1Zn alloys was investigated.•Alloyed Al in the ternary alloy resulted in the formation of AlFe or Al5Fe2 particles.•Alloys with 1–3 wt% Al exhibited very high corrosion rates in 0.6 M NaCl solution.•Al5Fe2 particles in the Al-containing alloys act as strong cathodic sites.

Microstructure and corrosion properties of extruded Mg–8Sn–1Zn alloys with varying Al contents were investigated. Microstructures of the extruded alloys mainly consisted of α-Mg grains and Mg2Sn particles in common. Addition of Al to the ternary alloy resulted in the formation of different types of Al–Fe-based intermetallic particles depending on Al contents. In 0.6 M NaCl solution, the extruded alloys with 1–3 wt% Al showed over 30 times higher corrosion rates than those containing less than 0.3 wt% Al; this discrepancy was attributed to the presence of Al5Fe2 particles acting as strong cathodic sites for H2 evolution during corrosion.