SURFACE CHARACTERIZATION OF COMMERCIALLY PURE TITANIUM AND TITANIUM ALLOY AFTER MECHANICAL STRESSES AND FLUORIDE APPLICATION

Objectives: To characterize topographically and chemically, the surface of commercially pure titanium (CpTi) and titanium aluminum vanadium (Ti-6Al-4V) alloy after mechanical stresses, fluoride application and their combined effect.
Methods: CpTi and Ti-6Al-4V alloy cylinders 6mm in diameter and 8 mm in length were used in this study. The specimens were grouped according to the treatment applied into 5 experimental groups; group I included the as-received cylinders; group II included specimens that were im­mersed in artificial saliva for 28 days; in group III, specimens were subjected to 50,000 cycles of 100N axial loading under compression while immersed in artificial saliva; group IV included speci­mens that were immersed in artificial saliva containing 1500 ppm sodium fluoride for 28 days and in group V, specimens were subjected to 50,000 cycles of 100N axial loading under compression while immersed in artificial saliva containing 1500 ppm sodium fluoride. Surface topography was evaluated using atomic force microscope (AFM), scanning electron microscope (SEM) and chemi­cal changes were assessed using Energy-Dispersive X-ray Spectroscopy (EDX).
Results: AFM results showed increased mean roughness (Ra) of both CpTi and Ti-6Al-4V alloy after exposure to fluoride as well as combination of mechanical stresses and fluoride. SEM evaluation showed alteration in surface topography of both groups showing deposits, cracks and concavities. EDX analysis for both groups revealed the presence of Ca, P, Na and F together with Ti for CpTi or Ti, Al, V for titanium alloy suggesting the formation of sodium and fluoride complexes with titanium, in addition to Ca/P deposits.
Conclusions: Fluoride application as well as combination of mechanical stresses and fluoride application can induce surface chemical and topographical changes which may have an impact on corrosion behavior of CpTi and Ti-6Al-4V alloy