Influence of Al-Mn master alloys on microstructures and electrochemical properties of Mg-Al-Pb-Mn alloys
(School of Materials Science and Engineering, Central South University, Changsha 410083, China)
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.
Key words: Al-Mn; master alloy; Mg-Al-Pb-Mn; hydrogen evolution; corrosion; seawater activated batteries