[en] Plasma electrolytic oxidation (PEO) films on AZ31 magnesium alloys were prepared in alkaline silicate electrolytes (base electrolyte) with the addition of different volume concentrations of CH_3OH, which was used to adjust the thickness of the vapor sheath. The compositions, morphologies, and thicknesses of ceramic layers formed with different CH_3OH concentrations were determined via X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), and scanning electron microscopy (SEM). Corrosion behavior of the oxide films was evaluated in 3.5 wt.% NaCl solution using potentiodynamic polarization tests. PEO coatings mainly comprised Mg, MgO, and Mg_2SiO_4. The addition of CH_3OH in base electrolytes affected the thickness, pores diameter, and Mg_2SiO_4 content in the films. The films formed in the electrolyte containing 12% CH_3OH exhibited the highest thickness. The coatings formed in the electrolyte containing different concentrations of CH_3OH exhibited similar corrosion resistance. The energy consumption of PEO markedly decreased upon the addition of CH_3OH to the electrolytes. The result is helpful for energy saving in the PEO process. (paper)