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• Dental implant showed the scratches in the vertical direction made by machine. • Sandblasted surface showed the indented trace instead of mechanical scratch. • In surface by plasma electrolytic oxidation, the pore shape was different on implant parts. • Nanotubes were uniformly well-formed in the α-phase but not well in the β-phase. • The surface with pores showed low corrosion potential and high current density. In this study, the corrosion behaviors of macro/micro/nano-scale surface modifications of Ti-6Al-4V dental implant for bio-implants were investigated. For this purpose, macro/micro/nano-scale surface roughness was formed on the surface of Ti-6Al-4V alloy using plasma electrolytic oxidation (PEO), anodization, and sandblasting. Potentiodynamic and potentiostatic methods were used to investigate the corrosion behavior of the samples. The surface properties of the alloy were observed using field-emission scanning electron microscopy and X-ray diffractometry. The bulk sample exhibited scratches in the vertical direction created by the machine. The sandblasted sample showed an indented trace instead of a machined scratch. The PEO-treated sample showed different pore shapes in the screw valley, screw flank, and screw top. Nanotubes were uniformly formed in the α phase but not well formed in the β phase. In the case of nanotubes on sandblasting, the nanotubes were not well formed in the defect areas formed during the sandblasting process. In a corrosion test, the corrosion potential significantly increased with no surface treatment, whereas it significantly decreased when defects or pores were formed on the surface. The current density–time curves revealed that the sandblasted specimen showed the most unstable film behavior and in the case of the nanotube and nanotube-on-sandblasting specimens, the current density increased with time. [ABSTRACT FROM AUTHOR]

• Needle-like structure of Ti-40Nb-xZr alloys changed to equiaxed structure as Zr content increased. • Nanoindentation hardness and elastic modulus of Ti-alloys decreased as the Zr content increased. • Irregular pores were formed on the alloy surface as the applied voltage increased in the PEO process. • Surface roughness of the PEO-treated Ti-alloys increased as the applied voltage and Zr content increased. • Contact angle of the PEO-treated Ti-alloys decreased as the applied voltage and Zr content increased. In this study, the formation of micro-scale morphology on Ti-40Nb-xZr alloys was investigated under plasma electrolytic oxidation (PEO) treatment. By varying the Zr content to 0, 3, 7, and 15 wt.%, non-toxic, low-modulus alloys were prepared. PEO was then performed using a direct current power source with the sample as the anode and a carbon rod as the cathode in an electrolyte solution of 0.15 M calcium acetate monohydrate + 0.02 M calcium glycerophosphate. The applied voltage was varied from 180–380 V at a current density of 75 mA for 3 min. In the Ti-40Nb-xZr alloys, as the Zr content increased, the microstructure changed from a needle-like structure to an equiaxed structure, and the elastic modulus and hardness in nanoindentation tests decreased (from 120 to 67 GPa and 4.55 to 2.00 GPa, respectively). As the applied voltage increased during the PEO process, the pore size increased. The TiO 2 layer formed on the alloy surface contained Ca and P from the electrolyte. The surface roughness obtained from atomic force measurements was the lowest in the bulk samples (0.133 to 0.024 μm), and it gradually increased as the applied voltage increased and decreased as the Zr content increased. As the applied voltage increased, the contact angle decreased, whereas as the Zr content increased, the contact angle increased. [ABSTRACT FROM AUTHOR]

• Number of pores increased in the plasma electrolyte oxidation (PEO) as sr ions increased. • The pore size decreased in the PEO process as Sr concentration increased. • In the case of Si and Sr addition to electrolyte, corrosion potential was apparently increased. • Polarization resistances of PEO-treated Sr and Sr/Si specimens showed the higher compared to bulk. The purpose of this study is to investigate the electrochemical characteristics of Sr/Si-doped hydroxyapatite coating on the Ti-6Al-4V alloy surface via plasma electrolytic oxidation(PEO). Ti-6Al-4V alloy of extra low interstitial grade disk was used as the anode and the carbon rod was used as the cathode. PEO treatment was carried out using pulsed DC power at 280 V for 3 min. The electrolyte used for PEO was prepared by mixing Ca(CH 3 COO) 2 •H 2 O, C 3 H 7 NaCaO 6 P, Sr(CH 3 COO) 2 •0.5H 2 O, and Na 2 SiO 3 •9H 2 O. The potentiodynamic polarization test were performed by potentiostat in a 0.9% NaCl solution at 36.5 ± 1°C. Electrochemical impedance tests were carried out using potentiostat at the open circuit potential in a 0.9% NaCl solution at 36.5 ± 1°C. The PEO-treated surface and corrosion morphology were investigated by field mission scanning microscopy and energy dispersive X-ray spectroscopy. The number of pores increase and average size of the pores decreased as Sr increase, and area occupied by pore was decreased. In the case of Si and Sr addition to electrolyte, corrosion potential was apparently increased compared to specimen of Sr addition to electrolyte. Polarization resistances of PEO-treated Sr and Sr/Si specimens showed the higher than those of Bulk and CaP specimens from data of electrochemical impedance test. [ABSTRACT FROM AUTHOR]