Modification of a Ti-Mo alloy surface via plasma electrolytic oxidation in a solution containing calcium and phosphorus

Investigations into the surface modification of a Ti-15Mo alloy via plasma electrolytic oxidation are reported. The oxidation process was conducted in a solution containing Ca(H₂PO₂)₂, H ₃PO₄, or (HCOO)₂Ca. Anodisation was performed at voltages in the range of 100-400 V. The morphology of the sample surface did not change during alloy oxidation at lower voltages. Higher voltages led to the incorporation of calcium and phosphorus or of calcium only into the formed oxide layer and to significant modification of the surface morphology. Based on the SEM and EDX analysis results, a set of samples was selected for further investigations. To study the surface of the Ti-Mo alloy after anodic oxidation, we used scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), thin-layer X-ray diffraction (TL-XRD), and X-ray photoelectron spectroscopy (XPS). The electrochemical characteristics of the modified alloy in Ringer's solution were determined. Anodisation results in a considerable increase in the corrosion resistance of the Ti-15Mo alloy.