ti alloy

The anodizing process of titanium (Ti) implants and their alloys improves their corrosion resistance and life service by naturally increasing the thickness of the passive oxide layer formed on the surface. Among the parameters that affect the properties of the anodized layer, voltage is a significant one due to the kinetic and thermodynamic processes. In this paper, commercial pure titanium (cp-Ti) coupons with the dimensions of 20 ×10 × 1 mm3 were used as the anode in 1 M sulfuric acid solution at different voltages of 3, 6, and 9 V, current intensity of 3 A, electrolyte temperature of 60 °C, and duration time of 30 s. The phase composition analysis, morphology, and corrosion behavior of the anodized Ti were examined by Grazing‐Incidence X‐Ray Diffraction (GIXRD), Field‐Emission Scanning Electron Microscopy (FESEM), and electrochemical impedance, respectively, in Simulated Body Fluid (SBF) at 37 °C. The results confirmed the formation of titanium oxide coating with a hexagonal structure. A smoother surface was obtained upon increasing the voltage up to 6 V. However, the surface became rougher with further voltage increase up to 9 V. The highest charge transfer resistance (37354 and 58127 ohm.cm-2) was achieved at 6 V after 1 and 24 hours of immersion in the SBF solution, representing 84 % and 2440 % increase, respectively, compared to the cp-Ti sample. The double layer helps prevent the formation of localized corrosion sites, such as pitting and crevice corrosion, which can be particularly damaging to Ti alloy as an implant in the human body. Although rising the voltage from 3 to 6 V resulted in a more hydrophobic surface (as shown by an increase in the contact angle from 63.8° to 74.1°), further voltage increase up to 9 V made the surface more hydrophilic than before.

Electrochemical depositions of calcium phosphide layer on Ni-Ti alloy in concentrated simulated body flood (SBF×5) were carried out by cathodic electrodeposition. This layer was deposited on Ni-Ti alloy substrate under 10mA/cm2 current density for 2 hours at room temperature. Then, in order to investigate the bioactivity of the pre-calcified samples, they were put in SBF for 1 and 3 days at room temperature. The microstructure, chemical composition, and bioactivity of the coatings were evaluated using scanning electron microscopy(SEM), energy dispersive spectroscopy(EDS), X-ray diffraction(XRD) and Fourier transform infrared spectroscopy(FTIR) techniques. Results showed that the activation of the surface of the Ni-Ti alloy by electrochemical process can significantly enhance the biomimetic deposition during time. On the other hand, by increasing immersion time of pre-calcified samples in SBF from 1 to 3 days, the biomimetic coating uniformly covered the surface of the sample. The ratio of the Ca/P for the pre-calcified sample after immersion in SBF for 3 days was about 1.5 which is very close to the Ca/P ratio of stoichiometric hydroxyapatite.