Improving anti-corrosion properties AZ31 Mg alloy corrosion behavior in a simulated body fluid using plasma electrolytic oxidation coating containing hydroxyapatite nanoparticles

Orthopaedic implants often make use of magnesium and its alloys. These alloys are more mechanically compatible with bone tissue than other alloys, such as titanium, cobalt, and nickel, but a loss of implant mechanical strength can occur due to their low corrosion resistance. The plasma electrolytic oxidation (PEO) method was used to modify the surface of AZ31 magnesium alloy in this study. The effects of varying concentrations of hydroxyapatite (HA) nanoparticles (1, 3, and 5 g/l) on the morphology and corrosion characteristics of coatings were examined using phosphate-based electrolytes. The elemental composition was determined using Energy dispersive spectroscopy (EDS), elemental map analysis (MAP) and phase X-ray diffraction analysis (XRD). Field emission-SEM was employed to investigate the surface morphology and cross-section of the coatings. The corrosion characteristics of all samples were evaluated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) in Ringer’s solution. The sample with 3 g/l HA showed the best anti-corrosion performance, as it had the smallest average pore size (8.7 µm), the thickest coating (22.5 µm) and the lowest corrosion current density (0.034 µA/cm2) among all the samples tested.