## 3 Results and Discussion
Considering the advantages of electrochemical corrosion in surface modification, this study chose this method to investigate the effects of different electrolytes on Ti-64 surface morphology. Figure 7 shows SEM images of surfaces after electrochemical corrosion in four different electrolytes. Electrochemical corrosion in a 0.5 M HF electrolyte (Figure 7a) produced a highly porous surface structure with an irregular honeycomb-like morphology. Pore sizes ranged from the submicron to the micron scale. This structure likely originates from the selective dissolution of the TiO\({}_{2}\) protective layer by F\({}^{-}\) ions, forming [TiF\({}_{6}\)]\({}^{2-}\) complexes [75]. Such a porous structure is expected to increase surface area, potentially enhancing cell adhesion capability and osseointegration. In contrast, treatment with a 0.5 M H\({}_{2}\)SO\({}_{4}\) electrolyte (Figure 7b) resulted in a relatively smooth surface with only minor shallow pits and fine indentations. This morphology may be due to the uniform corrosion action of sulfate ions on the titanium surface, albeit with relatively weak corrosive power. While this surface may contribute to improved corrosion resistance, it might not be as conducive to cell adhesion as the HF treatment. The 0.5 M NaF electrolyte treatment (Figure 7c) showed almost no significant morphological changes, presenting a highly uniform and smooth surface. This may be due to the formation of a stable fluoride film during the electrolysis process, preventing further corrosion [75]. Although this surface may exhibit good corrosion resistance, it might not be favorable for cell adhesion and growth. Treatment with a 0.5 M HNO\({}_{3}\) electrolyte (Figure 7d) produced a unique surface morphology characterized by scattered circular pores. These pores varied in size, with diameters ranging from approximately 0.5 to 2 \(\upmu\)m. This structure may result from the strong oxidizing action of nitrate ions, leading to localized rapid dissolution. Such surface morphology might provide cell attachment sites while maintaining a certain degree of surface integrity. Comparing the results of the four electrolyte treatments, we can observe that the choice of electrolyte significantly influences the final surface morphology. The highly porous structure produced by the HF treatment may be most conducive to cell adhesion and osseointegration, while H\({}_{2}\)SO\({}_{4}\) and HNO\({}_{3}\) treatments achieve a balance between surface modification and maintaining material integrity. Although NaF treatment may enhance corrosion resistance, it might not be favorable for biological applications. These findings provide important guidance for Ti-6 Al-4V surface modification. Appropriate electrolytes can be selected to tailor surface characteristics according to different application requirements. For instance, HF treatment might be chosen for implants requiring rapid osseointegration, while NaF or H\({}_{2}\)SO\({}_{4}\) treatments might be considered for applications requiring long-term corrosion resistance. Future research should further explore the effects of these different surface morphologies on cell behavior, protein adsorption, and long-term implant performance. Additionally, studies combining multiple electrolytes or sequential treatments could potentially yield surfaces with optimized properties for specific biomedical applications. The interplay between surface topography, chemical composition, and biological response warrants in-depth investigation to develop next-generation implant surfaces with enhanced functionality and biocompatibility. Figure 8 presents the Raman spectra of the Ti-64 alloy after electrochemical corrosion in four different electrolytes (0.5 M HNO\({}_{3}\), 0.5 M NaF, 0.5 M H\({}_{2}\)SO\({}_{4}\), and 0.5 M HF). These spectra cover two critical wavenumber ranges, namely, 250-700 cm\({}^{-1}\) and 1000-2000 cm\({}^{-1}\), providing information for understanding the structural characteristics and evolution of the surface oxide layer.