Effect of Surface Oxide Films on Degradation of Titanium

Abstract:

Thermal desorption spectroscopy (TDS) was applied to measure the hydrogen in titanium (Ti). Because fracture by hydrogen embrittlement for medical/dental devices of Ti and Ti alloys was reported, dependence of surface oxidation film on hydrogen absorption and desorption behaviors of cp-Ti was carried out. To form the surface oxide film (rutile), the Ti wire samples were annealed in an ambient air at 800oC for 2 hours. Half of the specimens were immersed in a mixed solution of NaF and H3PO4 (APF). The part of the specimens were removed the surface films by abrasion after the heat and the immersion in the APF solution. TDS analysis was applied to detect released ions/molecules during heating from room temperature to 1200oC in a high vacuum vessel for the TiH2 powders, the Ti samples with and without the above treatments. High ion intensity was detected for hydrogen (m/z = 2), and ion intensities of the other ions/molecules were almost the background level in measurements. The concentration of hydrogen in the samples related with heat and chemical process was determined quantitatively, and was not significantly increased by the annealing and the immersion in APF solution if the sample had the tough surface film. However, the sample, which had been removed the surface films before the immersion in APF, showed typical chemical degradation after the immersion in APF for 7 days, that is, high ion intensities of hydrogen, fluoride, water and hydroxyl ions were detected. It was concluded that the control of the surface oxide film on the medical/dental Ti devices is important in determining its longevity.