Effects of Mn Addition on Corrosion Resistance of Mg-5Al Magnesium Alloy

The effects of Mn content on microstructure and corrosion behavior in NaCl solution of as-cast Mg-5Al alloy have been studied.The results show that with the addition of Mn,Al8Mn5 phase forms preferentially and the grain is refined obviously,meanwhile,the continuous or semi-continuous net-like β-Mg17Al12 phase is converted into discontinuous or dispersed one and the amount of β-Mg17Al12 phase reduce.With increase addition of Mn,the corrosion rate and corrosion current of the alloys are reduced whereas the film and charge resistance are improved,indicating that the corrosion resistance of the alloys is improved remarkably.The alloy with 0.5% Mn has the best corrosion resistance,and the corrosion rate is only 1.08mg·cm-2·d-1,which is decreased 72% compared with the alloy without Mn addition.