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

Abstract

To obtain smooth TiO2 coatings 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 recognized biocompatibility and corrosion resistance. A required feature on surfaces in contact with blood is a low level of roughness (Ra ≤ 50 nm) that does 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 (0.1-4 M) as electrolyte and applying different voltages (from 20 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 caused by changes 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.

Effect of fluoride on the thickness, surface roughness and corrosion resistance of titanium anodic oxide films formed in a phosphate buffer solution at different applied potentials

“…According to Vera et al (2017), the characteristics required for oxide film in contact with blood is a level of roughness (Ra) lower than 50 nm, because it can avoid the promotion of blood clots. In our study, the coating roughness (Ra) were lower than 50 nm in the presence of the NaF in solution.…”

“…This naturally grown film is mainly amorphous and very thin, presenting a thickness generally in the scale of nanometers (Mazzarolo et al, 2012). According to Vera et al (2017), they also present a high density of defects in native oxide film, which can decrease their corrosion resistance, depending on the conditions and environment. These defects can be reduced by oxide film thickening using oxidation techniques such as anodization (Simka et al, 2011;Diamanti & Pedeferri, 2007;Liao et al, 2017).…”

“…Another important factor is the coating roughness. The promotion of blood clots, which can lead to thrombosis, can be avoided when the biocompatible metal has a low surface roughness (coating roughness) (Ra ≤ 50 nm) (Vera et al, 2017).…”

Oxidation Resistance and Modification Reaction Mechanism of Al Coating Sprayed on Pure Ti Substrate

“…Titanium and titanium alloys are widely used in the fields of aerospace, chemical production, and the like, due to their high specific strength, low density, and the superior corrosion resistance [1][2][3][4][5]. However, when the temperature is higher than 873 K, the life of the materials is seriously affected due to several factors [4]. ese include a decrease in the strength and decay of other mechanical properties, such as plasticity.…”

“…(a) Cross-sectional BSD image of Al coating after testing for 5 hours at 973 K, and (b) the expanded view of region I inFigure 3(a). XRD spectrum after removal of 500 μm thick surface layer 4. Advances in Materials Science and Engineering…”