Abstract Magnesium alloy has a poor corrosion resistance, especially in marine environments. Based on first-principles calculations, a quantitative prediction on electrochemical polarization potential U α /current ( J tot ) for pure magnesium with chlorine or oxygen adsorption has been done in this work. FCC site for chloride and HCP site for oxygen are figured out by adsorption energy ( Δ E ads ) screening. The material parameters (crystal plane work function Φ (uvtw) , crystal plane surface en