Morphological studies of a composite coating comprising anatase TiO₂, CeO₂ and HAp on magnesium alloy AZ31B using the plasma electrolytic oxidation method for orthopaedic implants

Abstract This research study focused on coating AZ31B magnesium alloy using plasma electrolytic oxidation with time durations of 4 min, 6 min, and 8 min in electrolytes containing sodium metasilicate and sodium hydroxide. The electrolytes were further enriched with different concentrations of cerium dioxide, anatase titanium dioxide and hydroxyapatite at a current density of 60 mA cm −2 and a frequency of 1,000 Hz. X-ray diffraction, field emission scanning electron microscopy and atomic force microscopy were employed to analyse the phase formation, microstructure, and surface roughness of the coatings. The results indicated the occurrence of micro-discharges during the plasma electrolytic oxidation process, resulting in highly porous and rough surfaces. The contact angle measurements for the uncoated substrate were found to be 144.74° (±2.08), whereas the coated substrates exhibited contact angles of 107.92° (±2.16), 95.88° (±2.06) and 66.05° (±2.09) for the respective coating durations. This study also explores how a coating comprising Ca 5 (PO 4 ) 3 /anatase titanium dioxide and hydroxyapatite affects the corrosion properties of AZ31B magnesium alloy when immersed in a simulated body fluid solution.