<p>The research investigates corrosion resistance and the chemical–structural characteristics of coatings produced by plasma electrolytic oxidation (PEO) on AZ31B magnesium alloy. The primary objective was to enhance the corrosion resistance of magnesium alloys, a significant limitation in harsh environments. The PEO process was performed using a trapezoidal voltage waveform (up to 400&#xa0;V) in an electrolyte containing Na₂SiO₃ and NaOH, forming coatings composed mainly of MgO and Mg₂SiO₄. The effects of current density (10 to 20 A/dm²), pulse frequency (50 to 100&#xa0;Hz), and duration (30 to 60&#xa0;minutes) on coating properties were analyzed. During the study, coating porosity was also determined to assess surface uniformity. Analyses using electrochemical impedance spectroscopy (EIS), grazing incidence X-ray diffraction (GIXD), and energy-dispersive X-ray spectroscopy (EDS) showed that Mg₂SiO₄ enhances chemical and mechanical stability, while MgO limits corrosive agent penetration. Coatings formed at 15 A/dm² and 75&#xa0;Hz exhibited the highest corrosion resistance, as confirmed by their high total polarization resistance (<i>R</i>_tot). A strong correlation was found between oxygen and silicon content and corrosion resistance. The results emphasize the importance of optimizing PEO parameters to obtain uniform, low-porosity, and highly corrosion-resistant coatings on magnesium alloys.</p>