Effect of alloyed Ca on the microstructure and corrosion properties of extruded AZ61 Mg alloy

Microstructure and corrosion properties of extruded AZ61 Mg alloys with varying Ca contents were investigated. Microstructure of the extruded AZ61 alloy consisted of α-Mg grains and Al8Mn5 particles. Alloying with 0.1-0.5 wt% Ca to the AZ61 alloy resulted in the additional presence of (Mg,Al)2Ca particles in the extruded microstructure. In 0.6 M NaCl solution at 25 °C, the extruded AZ61 alloys with 0.1-0.5 wt% Ca showed corrosion rates over 2 times faster than that of the AZ61 alloy without Ca addition. Such deteriorated corrosion resistance due to Ca addition is discussed in terms of passivation and microgalvanic corrosion.