A Study Corrosion Properties by Magnetron Sputtered Nanocrystalline Al2o3 Thin Films

Titanium (Ti-6Al-4V) alloys had been mostly used for medical applications due to its good mechanical and chemical properties. This alloy tendency to emanate toxic aluminium (Al) and vanadium (V) due to their low corrosion resistance in body conditions. In this work, radiofrequency magnetron sputtering was used to prepare the Al2O3 thin films at different temperatures (400, 500, and 600oC) to increase the biocompatibility of Ti-6Al-4V alloy. The structure of the Al2O3 films was determined by the X-Ray diffraction (XRD) technique. The phases of Al2O3 thin films observed after heat treatment and its intensity phases increase at 600oC. The effect of depositing temperature on the microstructural morphologies of the thin films was studied by Field Emission Scanning Electron Microscope (FESEM). The particle size of the sputtered Al2O3 films ranged from 200 nm to 400 nm and was strongly influenced by annealing temperatures, the morphology of the films deposited before and after annealing has a characteristic agglomeration of particles. Potentiodynamic polarization analysis of the Al2O3 films confirms the inverse relationship between polarization resistance and corrosion current. The biocorrosion measurements for Al2O3 films deposited on the Ti-6Al-4V substrate in 3.5% NaCl solution have also been obtained. Clear improvement in the corrosion resistance was observed rather than for untreated, especially for thermally annealed (600oC) Al2O3 /Ti-6Al-4V samples. The corrosion rate was 0.356 mm/y for the uncoated sample, while 0.055 mm/y for Al2O3/Ti-6Al-4V in samples after annealing at 600oC. The average corrosion potential calculated was -0.117 V. The results confirmed that coated alloys with 600 degrees C thermally treated exhibited a better electrochemical behaviour compare with uncoated and non-thermally treated alloys possibly due to the better cohesion degree of the coatings.