Role of Sn in corrosion and passive behavior of extruded Mg-5 wt%Sn alloy

• Corrosion behavior of extruded Mg and Mg5Sn (in wt%) alloy was investigated.
• During an immersion test, corrosion rate of the Mg was much faster than the Mg5Sn.
• Cathodic reaction was inhibited in the Mg5Sn alloy in comparison with the Mg.
• Metallic Sn was enriched at the film-metal interface during the immersion test.

Corrosion behavior of extruded Mg and Mg5Sn (in wt%) alloy was investigated, and a passivated surface of the Mg5Sn was examined. Immersion test in a 0.6 M NaCl solution revealed that corrosion of the Mg was significantly faster than the Mg5Sn alloy, and vigorous H2 evolution was accompanied with the severe corrosion of Mg. Polarization tests confirmed that cathodic reaction was inhibited in the Mg5Sn alloy. It was considered that the decreased H2 evolution of the Mg5Sn alloy was attributed to the formation of Sn-accumulated layer between the passive film and matrix, which was examined by an XPS analysis.