The generation of compact plasma electrolytic oxidation (PEO) coatings with outstanding corrosion resistance is essential for the widespread application of Mg alloys. In the present investigation, PEO ceramic coatings formed at different silicate concentration and oxidation time on AZ31 Mg alloy were studied, and the resultant surface structures of the oxide films were observed using scanning electron microscopy (SEM) and atomic force microscopy (AFM) analysis. X-ray photoelectron spectroscopy and thin film-X-ray diffraction analysis of ceramic coatings showed that the surface coating is mainly composed of Mg2SiO4, and MgO with different amount based on oxidation time. Further, the potentiodynamic polarization and electrochemical impedance spectroscopic (EIS) measurements were used to characterize corrosion behavior of PEO coated substrates in 3.5% NaCl solution. The results revealed that PEO coatings processed with 0.2 M silicate showed better performance due to its dense and compact coating with fewer structural imperfections in comparison to others.