Investigation On Corrosion Behavior Of Ultrafine-grained CP-Ti Processed By ECAP At Room Temperature

Commercial pure titanium (CP-Ti) becomes the most promising biomedical metalmaterials as a result of excellent biocompatibility, mechanical compatibility, corrosionresistance and non-magnetic, but due to lower strength and bad wear resistance, puretitanium as body implants is limited. The microstructure refinement process is aneffective way to improve mechanical properties of CP-Ti. In this paper, theultrafine-grains CP-Ti was prepared by the advanced technology of Equal ChannelAngular Pressing (ECAP). It studied corrosion behavior of the ultrafine-grained CP-Tiprocessed by ECAP in simulated body fluid, and the effect of chloride ion concentrationand fluorine ion concentration by electrochemical testing methods such as polarizationcurves, Electrochemical Impedance Spectroscopy (EIS) and Mott-Schottky curves, andcombining X-ray photoelectron spectroscopy (XPS) and other methods. The mainresearch results are as follows:(1) The corrosion resistance of the ultrafine-grained CP-Ti processed by ECAPwas higher than that of CP-Ti, but the improvement of corrosion resistance done notincrease with increasing of pressing pass, the corrosion resistance of2passes was thebest, when more than the pass, the corrosion current density showed a rising trend, thecorrosion resistance decreased.(2) The electrochemical experiment of the ultrafine-grained CP-Ti processed byECAP in simulated body fluid showed that the corrosion resistance of pure titanium wasclosely related with the passive film which formed on surface. The passive film hadn-type semiconducting properties. The main component of the passive film was TiO2, at the same time contained a small amount of TiO. ECAP deformation resulted in changeof microstructure and stress, that made the resistance of the passive film increase, thedefect reduce, thereby improving the corrosion resistance. The ultrafine-grainedmicrostructure obtained by ECAP made passive film thicken, resistance increase, thecorrosion resistance increased.(3) Chloride ion in NaCl solution significantly affected the corrosion resistance ofthe corrosion resistance of the ultrafine-grained CP-Ti processed by ECAP, with thechloride ion concentration increased, the corrosion resistance of the specimendecreased.(4) The ultrafine-grained CP-Ti processed by ECAP had a certain resistance insimulated saliva of low fluorine ion concentration. when the fluoride ion concentrationin simulated saliva reached0.5%, the resistance value of the surface oxide film of thespecimen was significantly decreased, its corrosion resistance decreased.