Influence of Al–Mn master alloys on microstructures and electrochemical properties of Mg–Al–Pb–Mn alloys

Abstract

Mg–Al–Pb alloy is one of the newly developed materials for the seawater activated batteries. As-cast Mg–6Al–5Pb and Mg–6Al–5Pb–0.5Mn alloys with different additions of Al–15%Mn (mass fraction), Al–30%Mn and Al–50%Mn master alloys were prepared by melting and casting. Their microstructures were observed by optical microscopy and scanning electron microscopy. The electrochemical properties, hydrogen evolution and mass loss of Mg–6Al–5Pb–0.5Mn alloys were studied. The results show that Mg–6Al–5Pb–0.5Mn alloy added with Al–50%Mn master alloy provides more negative corrosion average potential (−1.66 V), smaller corrosion current density (7 μm/cm2) and lower free corrosion rate (0.51 mg·cm−2·h−1) than other alloys. This is probably attributed to the presence of Al11Mn4 phase, which facilitates the self-peeling of corrosion products and enlarges the electrochemical reaction area as well as enhances the electrochemical activity.