Corrosion Behavior of Electrochemical and Thermal Treated Titanium into Artificial Saliva: Effect of pH and Fluoride Concentration

This work compares the corrosion behavior in artificial saliva of oxide thin films grown on pure titanium, via electrochemical oxidation (EO) in sulphate bath at 1V and thermal treatment (TT) at 450°C, for durations between 20 min and 4 h. Surface characterizations were performed through morphological and microstructural analysis using scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction. Electrochemical behavior was conducted in Fusayama-Meyer solution (pH= 6.50 and T= 37°C) using linear polarization and electrochemical impedance spectroscopy, under varying pH and fluoride concentrations. The results demonstrated that a 3-hour duration treatment provided the optimal corrosion resistance for both EO and TT processes. Acidic and basic electrolytes both increased Icorr and decreased Rp, indicating degradation of the passive layer outside neutral conditions. Increasing fluoride concentrations significantly impaired the corrosion resistance. At 12,300 ppm F⁻, untreated Ti showed severe degradation, with the formation of a porous outer layer (Rf = 33 Ω.cm²) and a weakened inner barrier layer (Rct = 21 kΩ.cm²). In contrast, TT-treated surfaces remained highly protective with the highest resistances for both the outer and inner layers (Rf = 1610 KΩ.cm²; Rct = 1583 KΩ.cm²), significantly outperforming the EO film.