## 3 Results and Discussion
The table presents surface roughness parameters (Ra and Rq) and surface hardness (HR15N) for different treatments including mechanical polishing, hydrofluoric acid (HF) etching, sandblasting with different grit sizes (Zr), sandblasting followed by HF etching, and shot peening (Zr SP) with various parameters followed by HF etching. Values are presented as mean \(\pm\) standard deviation. and nanocrystalline phases. The progressive increase in spectral intensity and complexity from the original polished surface to the composite-treated samples correlates with the degree of surface modification. The absence of sharp, well-defined peaks in all treated samples suggests that the formed oxide layers are primarily amorphous or highly defective structures, a characteristic that may contribute to enhanced bioactivity. The combined treatment of shot peening and HF corrosion appears most effective in altering the surface chemical composition and structure. This synergistic effect may arise from the mechanical activation of the surface by shot peening, followed by controlled chemical etching, resulting in a unique surface oxide layer configuration. These results reveal the significant impact of different surface treatment methods on the oxide layer structure of Ti-64 surfaces. HF corrosion treatment promotes oxide layer formation, while shot peening may enhance subsequent oxidation processes by increasing surface activity. The combination of shot peening and HF corrosion demonstrates a notable synergistic effect, producing richer surface features than single treatments alone. From a biomedical application perspective, the complex oxide layer structure produced by this composite treatment may provide a more favorable microenvironment for cell adhesion and growth. The coexistence of anatase and rutile phases could contribute to enhancing the material's bioactivity. Future research should focus on correlating these surface structural changes with biological responses, including cell adhesion, proliferation, and differentiation. Before discussing the effects of different electrolytes on the electrochemical corrosion of Ti-64 surfaces, it is essential to compare the differences and advantages/disadvantages of immersion corrosion and electrochemical corrosion methods on material surface structures. Immersion corrosion is a relatively simple and traditional surface treatment method. It primarily relies on chemical reactions, with corrosion rates typically slower and more challenging to control precisely. Immersion corrosion usually produces relatively uniform surface morphologies but may struggle to form complex porous structures. Moreover, prolonged immersion can potentially lead to a decline in bulk material properties. However, the advantages of immersion corrosion lie in its simplicity of operation, lower cost, and suitability for large-scale processing. In contrast, electrochemical corrosion offers more precise process control. By adjusting current density, potential, and time, the depth and morphology of corrosion can be accurately controlled. Electrochemical corrosion can produce more complex and diverse surface structures, such as highly ordered nanotube  
Figure 6: Raman spectra of Ti-6 Al-4V surfaces at (**a**) short wavenumber range (250–700 cm\({}^{-1}\)) and (**b**) longer wavenumber range (1000–2000 cm\({}^{-1}\)) under various treatment conditions. arrays or porous structures, in a shorter time [26; 47; 69; 64; 67]. Furthermore, the oxide layers generated during electrochemical corrosion are typically denser and more uniform, contributing to improved corrosion resistance of the material. Another advantage of electrochemical corrosion is that it can be performed at room temperature, reducing potential material property degradation associated with high-temperature treatments. However, electrochemical corrosion equipment is relatively complex, and challenges may exist when processing large-area samples.