Corrosion characterisation of medical alloys modified by forming titanium nanotubes via anodic oxidation and annealing process

Three medical alloys Ti-6Al-4V, Ti-10Co and Ti-20Co were treated to form Ti nanotubes (TNTs) by anodic oxidation process. The average diameter of TNTs for Ti-6Al-4V and Ti-10Co alloys was 35 and 100 nm respectively. Owing to the alpha and beta phases of Ti-6Al-4V alloy, TNTs had different morphologies. Porous and dendrite structures were formed on the surface of Ti-20Co alloy. X-ray diffraction (XRD) patterns, optical micrograph images and scanning electron microscope images were used to analyse the produced structures. The XRD profiles of the treated Ti-6Al-4V alloys illustrate the amorphous, anatase and rutile structures of as anodised, annealed samples respectively. The TNTs over beta phase areas dissolved after anodic process from the surfaces of Ti-6Al-4V and Ti-10Co alloys. Rutile phase was the dominant phase in all XRD patterns of all annealed alloys at high temperatures. The effects of anodising process and annealing treatment on the corrosion parameters of the used alloy surfaces inside the simulated body fluid are studied. The annealing process enhanced the corrosion parameters for all samples due to the formation of a thick oxide layer.