Magnesium and its alloys are promising materials for temporary biomedical implants due to their properties that resemble bone tissue; however, low corrosion resistance hinders their clinical application. Surface engineering, particularly through oxide ceramic layers, offers a viable solution to enhance wear and corrosion resistance, thereby improving biocompatibility. Plasma electrolytic oxidation (PEO) was applied to modify pure magnesium samples using sodium silicate electrolytes with different types and concentrations of phosphates. Multiple characterization techniques were used for surface analyses, including SEM, EDS, contact angle measurements, and profilometry. The results delineate the influence of electrolyte composition and applied voltage on coating thickness, pore size, and elemental incorporation. The PEO coatings exhibited porous structures with diverse pore sizes, influenced by the electrolyte composition and voltage. Morphological analysis revealed a scaffold-like surface structure with spherical and irregularly shaped pores. Elemental analysis confirmed the uniform incorporation of Si and P into the coatings. Anionic interaction played a significant role in forming the oxide layer, which is crucial for potential biomedical application. The study highlights the varied thickness levels and quality of PEO coatings, influenced by electrolyte composition and applied voltage. Coatings from a C4 electrolyte showed higher P and Si contents and the C4 electrolyte at 250 V demonstrated favourable characteristics, positioning them as promising candidates for biomedical applications on biodegradable magnesium alloys.