Simultaneously improving mechanical and anti-corrosion properties of extruded Mg-Al dilute alloy via trace Er addition

•Trace Er addition improves mechanical and anti-corrosion properties simultaneously.•Much less noble Al8Mn4Er formed by Er addition decreases galvanic corrosion tendency.•Al8Mn4Er can effectively capture Fe and inhibit Fe-caused corrosion.•Trace Er promotes the formation of a more passivation and dense corrosion film.