CORROSION BEHAVIOR OF DIE-CAST Mg-9Al MAGNESIUM ALLOY WITH RE ADDITION

The corrosion behavior of die-cast Mg-9Al magnesium alloy with RE addition (AR091) has been evaluated by general corrosion measurements and electrochemical methods in 3.5% NaCl solution saturated with Mg(OH)2.The experimental results were compared with those of commercial magnesium alloy ZM5 and AZ91D.AR091 magnesium alloy has better corrosion resistance than ZM5 and AZ91D alloy.The microstructure of AR091,ZM5 and AZ91D were examined by Electron Probe Microanalysis (EPMA) and Energy Dispersion Spectroscopy (EDS).The AR091 magnesium alloy showed microstructure characterized by α-phase solid solution,surrounded by less β-phase and more needle-like RE-containing phase.The excellent corrosion resistance of the AR091 alloy could be explained by the fact that the precipitated RE-containing phases are less cathodic.Moreover,the corrosion product film formed on the AR091 alloy surface was more protective.