Influence of the Electrolyte Concentration on the Smooth TiO2 Anodic Coatings on Ti-6Al-4V

To obtain smooth coatings of TiO2 for building a new design of Ti-6Al-4V heart valve, the anodic oxidation technique in pre-spark conditions was evaluated. TiO2 coating is necessary for its recognize biocompatibility and corrosion resistance. A required feature on surfaces in contact with blood is a low level of roughness (Ra ≤ 50 nm) that not favor the formation of blood clots. The present paper compares the coatings obtained by anodic oxidation of the Ti-6Al-4V alloy using H2SO4 at different concentrations (0.1 M to 4 M) as electrolyte and applying different voltages (from 20 V to 70 V). Color and morphological analysis of coatings are performed using optical and scanning microscopy. The crystalline phases were analyzed by glancing X-ray diffraction. By varying the applied voltage different interference colors coatings were obtained. The differences in morphologies of the coatings, due to the change in concentration, are more evident at high voltages limiting the oxidation conditions for the desired application. Anatase phase was detected from 70 V for 1 M H2SO4. An increase in the concentration of H2SO4 decreases the voltage at which the transformation of amorphous to crystalline coatings occurs, i.e. with 4 M H2SO4 the anatase phase appears at 60 V.

Fabrication of Antibacterial Titanium Implant Using Anodic Oxidation Technique

In the present study, we demonstrated that antibacterial titanium can be simply fabricated by anodic oxidation technique, which involves connecting the Ti to the anode and then applying a direct current through the electrolyte. The substrate was soaked in 100−mM NH4NO3, 100−mM (NH4)2SO4, and (NH4)3PO4aqueous solutions, after which a constant current of 50 mA cm-2 was galvanostatically applied for 30 min. The substrate was thereafter annealed at 723 K in air for 5 h, in order to improve the crystallinity. The XRD pattern showed the layer comprised TiO2 with anatase and/or rutile type structures. All the anodized substrate could degrade methylene blue solution under ultraviolet (UV) and visible light illuminations. Antibacterial activities of the treated substrates were estimated using Escherichia coli (E.coli). The anodized Ti substrate showed sufficient antibacterial activity under weak UV light illumination with the intensity of 100 μW cm-2. In conclusion, anodic oxidation is expected as one of the promising surface treatments, in order to improve the safety of Ti devices in human use.