One of the main difficulties present in the materials manufacturing is the selection of substances that generate less polluting residues as well as effective in the synthesis process. In this study, we obtained TiO2 through electrochemical anodizing, using an acid easy to neutralize (hydrochloric acid), ethylene glycol and distilled water. The results showed the presence of nanostructures over the anodized surface observed by Scanning Electron Microscopy, with anatase and rutile phases, identified with Raman Spectroscopy. The presence of a nanostructured material on the surface of titanium, improved the value of Vickers Micro-hardness from 240 HV to 400 HV. It was possible to obtain a reduction of the friction coefficient from 0.8 to 0.2 as minimum value. The presence of a nanostructured layer of TiO2, with a mixture of anatase and rutile, markedly improved the mechanical properties of the titanium sheet.

Electrochemical anodizing is one of the processes that due to its practicality, versatility, and excellent results has been used for decades for the oxidation of any metallic surface and the formation of nanostructures. In the present work was anodized commercially pure titanium using a solution based on hydrochloric acid, ethylene glycol, and deionized water. Varying the voltage from 21 to 24 volts was observed the formation of tube-shaped nanostructures in the anodized samples like a characteristic growth due to the use of HCl in the solution. Using Raman spectroscopy were identified the vibrational modes corresponding to the anatase phase. Using Vickers Microhardness and Nanoindentation it was demonstrated that the mechanical behavior was favored in the sample obtained with 24 Volts and growth time of 60 minutes. Finally, the TiO2 layers obtained improved the friction coefficient value of the titanium sheet, reducing its value from 0.8 to 0.4.

Currently, there are different synthesis techniques to obtain new materials, however, one of the most used is electrochemical anodizing, which, by means of oxide-reduction reactions, allows modifying the surface of a metal, thus generating an oxide layer that protects the material in such a way that it improves its hardness values. In this research work, an electrochemical anodizing process was carried out on titanium grade 2, using HCl in aqueous solution with a concentration of 0.15 M and with voltage variation of 10V, 11V, 12V, 13V, and 14V as electrolyte. Subsequently, an annealing process was carried out at 550°C for 4h to obtain a crystalline titanium oxide coating. For the analysis of the oxide layer obtained, Vickers hardness tests were carried out with an applied load of 50g. The presence of a titanium oxide layer improved the hardness values ​​from 2.07 GPa to 4.12 GPa.

It was possible to obtain TiO2 doped with K and Cr by electrochemical anodizing technique. An unexplored synthesis route was considered where the electrolyte used for the anodization was HCl and K2Cr2O7 as the precursor of the incorporated metals. Subsequently, the heat treatment temperatures of 400, 500, 600, 600, 700 and 800 °C were varied in order to observe the morphological, structural and hardness changes of the obtained films. The presence of nanotubes was observed on the anodized surface and the samples were annealed at 400, 500 and 600 °C, and grain formation for the samples were annealed at 700 and 800 °C. The presence of K and Cr in the TiO2 structure, together with the temperature changes, favored the transformation of anatase to rutile, which gave a hardness improvement of up to 4.8 times more compared to that of titanium without any treatment.

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