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.