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.