Aluminium-Zinc-Silicon alloy is a material candidate for low voltage sacrificial anode. Nevertheless, iron-rich intermetallic phase that formed in the interdendritic region can reduce its efficiency due to the self-corrosion phenomenon. Samarium addition is expected to modify the formation of iron-rich intermetallic phase. The alloying process was conducted with melting of aluminium and other additional element in mini electric resistance furnace. Furthermore, characterization of the alloys was performed using optical emission spectrometer, differential scanning calorimetry, optical metallography and scanning electron microscopy equipped with energy dispersive spectrometer. The result showed that samarium can refined the secondary dendrite arm spacing (SDAS) from 89.6 μm to 61.4 μm. Samarium also shifted the solidification temperature of the alloy which affected the size of SDAS and formation of Al2Si2Sm intermetallic phase. © Published under licence by IOP Publishing Ltd.