Effect of Electrolyte Chemistry on the Structural, Morphological and Corrosion Characteristics of Titania Films Developed on Ti-6Al-4V Implant Material by Plasma Electrolytic Oxidation
The present work is aimed at the optimisation of an electrolyte system for the development of an oxide layer on Ti-6Al-4V implant material by plasma electrolytic oxidation (PEO) process, to improve its corrosion resistance under 4.5 pH osteoclast bioresorption and 7.4 pH simulated body fluid physiological conditions. All the PEO experiments were conducted for 12 min in constant current mode by a DC power supply unit with 7 different electrolyte systems consisting of methodically varied concentrations of tri-sodium ortho phosphate (Na3PO4.12H2O), sodium meta silicate (Na2SiO3.9H2O) and potassium hydroxide (KOH). The phase composition of the fabricated oxide coatings was analyzed by X-ray diffraction (XRD) technique. The morphology and thickness of the coatings were determined by scanning electron microscopy (SEM) and the corrosion characteristics were assessed by potentiodynamic polarization and electrochemical impedance spectroscopic techniques. The XRD results demonstrated that the oxide coatings mainly consisted of anatase and rutile phases with different proportions. While the average surface pore size was in the range of 3 to 6 µm, the thickness of the coating varied from 5 to 20 µm. A significant improvement in the corrosion resistance and an added capacitive nature was observed for the PEO treated Ti-6Al-4V implant material compared to that of the untreated. The variation in the proportions of anatase and rutile phases, the surface pore size distribution, the thickness of the coating and the corrosion characteristics of the developed coatings were correlated with the composition and concentration of the electrolyte system. Of the seven different electrolyte systems employed in the present study, the one consisting of 10 g Na3PO4.12H2O, 2 g Na2SiO3.9H2O and 2 g of KOH was established to be an optimized electrolyte system for developing oxide coatings on Ti-6Al-4V to minimise corrosion and thereby reduce the metal ion release under physiological conditions.
Eyup Sabri Kayali, Gultekin Goller and Ipek Akin
K. Venkateswarlu et al., "Effect of Electrolyte Chemistry on the Structural, Morphological and Corrosion Characteristics of Titania Films Developed on Ti-6Al-4V Implant Material by Plasma Electrolytic Oxidation", Key Engineering Materials, Vols. 493-494, pp. 436-441, 2012