Structure and corrosion behavior of TiO₂ thin films deposited onto Mg-based alloy using magnetron sputtering and sol-gel

Recently, magnesium and its alloys have been investigated as potential candidates for orthopedic implants, due to their numerous beneficial mechanical properties. Nevertheless, magnesium is characterized by its poor corrosion resistance in chloride-rich environment, present in the human body. Unfortunately, this major disadvantage limits the biomedical applications of magnesium alloys. The corrosion rate of these materials can be decreased with the use of oxide films (e.g. ZnO, TiO₂, MgO). In the article, a comparison was conducted, with regard to the structure and corrosion behavior of TiO₂ films, with the thickness of about 300 nm, deposited onto MgCa4Zn1Gd1 alloy by magnetron sputtering and spin coating methods. The structure observations of the oxide films in scanning electron microscopy are also presented. The phase analysis using X-ray diffractometer and structure identification using the Raman spectrometer are also shown. Moreover, the paper also includes a discussion on the topography observations and roughness measurements in atomic force microscopy. The results of the potentiodynamic and immersion tests of corrosion resistance of TiO₂ films in Ringer's solution at 310.15 K are also presented. The analysis of investigation results shows that both of the studied films have an anatase structure. The surface of TiO₂ applied using the magnetron sputtering method is characterized by smaller and more uniform grains, compared to the film applied via spin coating. TiO₂ applied using the physical vapor deposition method has a slightly higher electrochemical corrosion resistance. The results of immersion tests have shown, that the alloy with TiO₂ film deposited by sol-gel is more resistant to corrosion.