UV-induced Hydrophilicity of Anodized Titanium Oxide at Low Current/Voltage

Objectives: To investigate an influence of UV on the hydrophilicity of oxide film on Ti-6Al-4V alloy prepared by anodization. Methods: 1×8×60 mm Ti-6Al-4V alloy plates were anodized to create oxide layer by two methods (galvanostatic and potentiostatic) in two kinds of electrolytes, 1M H₃PO₄ and 1M NaOH. Under galvanostatic anodization, low current densites ranged from 0.5-2 A/cm² were applied. While potentiostatic anodization, 0.5-6 voltages were applied for 5 minutes. After anodization, all specimens were subjected to 2 mW of 360 nm UVA radiation for 2 hours with one hour interval. Contact angle, characteristics and crystal structures of oxide layer were then observed. Results: The anodized oxide film prepared by both methods showed a significantly decreased contact angle and an increased surface roughness before UV irradiation, regardless of electrolyte usage. After 2-hour UV activation, only the anodized film formed with galvanostatic method in 1M H₃PO₄ at 1 A/cm² could lead to decrease in contact angle while the same result was not found on the anodized film formed in 1M NaOH at 1.75 A/cm². However, the contact angle of anodized film prepared by potentiostatic method was not changed after UV irradiation for 2 hours, regardless of types of electrolyte. With XRD analysis, Ti₂O₃, TiO₂ and TiO were found on anodized oxide film prepared with galvanostatic method in electrolyte of H₃PO₄. Whereas, only Ti₂O₃ and TiO₂ were found on titanium anodized in electrolyte of NaOH. Conclusion: It was implied that the anodized oxide film on Ti-6Al-4V alloy showed less contact angle comparing to non-anodized oxide film and UV activation could improve hydrophilicity by showing lower contact angle.