In order to study the effect of RE on anti-corrosion mechanism, high Mg content Zn-Al-Mg and Zn-Al-Mg-RE (where RE is Rare Earth) alloy coatings were produced on low carbon steel substrates by using cored wires and arc spraying. The electrochemical impedance spectroscopy (EIS) was used to determine the anti-corrosion mechanism of the two coatings in 5% NaCl solution. The composition and structure of corrosion products on the coatings surface have been investigated after corrosion tests by X-ray diffractometer (XRD). The results show that, Zn-Al-Mg-RE coating has superior corrosion resistance compared to Zn-Al-Mg coating due to the formation of more compact and uniform corrosion products. The self-sealing effect of the Zn-Al-Mg-RE coatings, especially for longer immersion times is extremely good. The role of the RE elements appears to be associated with the self-sealing process and the refinement of the coating microstructure.