CONICET | Buscador de Institutos y Recursos Humanos

Anodic oxidation of Titanium and Titanium alloys produce a TiO2coating with better mechanical properties and corrosion resistance thanthe substrate. In addition, this TiO2 coating is a film with biocompatibleproperties [1], [2].In the present report, we determined and analyzed the effects ofdifferent acid electrolytes on the color, thickness, morphology andcrystalline structure of the coating. The electrolytes used were sulfuricacid (H2SO4) 0.1M to 4M and phosphoric acid (H3PO4) 1M, and thesubstrates were plates of Ti-6Al-4V alloy; the oxidation voltages usedranged from 10V to 100V.The thicknesses of the films were determined by X-ray reflectometrywith synchrotron radiation (D12A-XRD1 beamline of the BrazilianSynchrotron Light Laboratory, LNLS). The morphology of the filmswas observed using optical and scanning electron microscopy andthe crystalline phases of the oxides formed were determined by theglancing incidence angle X-ray diffraction technique with a glancingangle of 1º.The oxide films produced different interference colors dependingon the type of electrolyte and the voltage for oxidation applied. For bothelectrolytes, the fi lm thickness increased with the voltage applied.The concentration of the electrolyte produced minor shifts in color,negligible enough to establish a relation between color and thicknessof the fi lm for each electrolyte as a way to have a quick method todetermine thickness.The fi lms produced at low voltages were homogeneous, with lowroughness and amorphous. At higher voltages, sparks discharges wereobserved and porous fi lms, with a degree of crystallinity, were produced.The voltage for spark discharge depended on the electrolyte.Using H2SO4 1M as electrolyte, the fi lms produced were compact,homogeneous and no crystalline phases of TiO2 were detected up to60V. From 70V to 80V, the fi lms were porous and crystalline with theanatase phase formed, and above 80V, the rutile phase was formed. Asthe concentration of electrolyte increased, the conductivity increasedand the homogeneous/amorphous to porous/crystalline transition wasproduced at lower voltages.In the case of the H3PO4 1M electrolyte, there were no sparkdischarges or crystalline phases up to a voltage of 100V, which was thehighest voltage used.

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