Enhanced corrosion resistance of Mg17Al12 compounds by Ce modification

Mg17Al12-xCe (x = 0, 0.1, 0.5, 1 wt%) intermetallic compounds have been prepared by vacuum induction melting, in order to enhance the corrosion resistance of Mg17Al12 compound by Ce modification. The results have showed that the Mg17Al12 compound compose of β-Mg17Al12 substrate and eutectic structure (α-Mg and β-Mg17Al12 phases) distributed continuously along grain boundaries under non-equilibrium solidification conditions. A high cathode to anode area ratio of the eutectic structure results in poor corrosion resistance of the Mg17Al12 compound. The eutectic structure distributed continuously along the grain boundaries can be interrupted and corrosion could not propagate along the grain boundaries in Mg17Al12 compound alloyed by 0.1 wt% Ce. Hence, the corrosion performance of Mg17Al12 compound has been improved by 0.1 wt% Ce. With the Ce content further increasing to 0.5 wt%, the corrosion resistance of the compounds could be effectively improved due to the formation of dense corrosion products film. Additionally, the complete suppression of eutectic structure effectively reduces electrochemical corrosion of compounds containing more than 0.5% Ce. On the contrary, due to the precipitation of more Al11Ce3 phase, the corrosion resistance of Mg17Al12–1Ce alloy is slightly deteriorated based on the galvanic corrosion mechanism.