Influence of fluoride concentration and pH on corrosion behavior of Ti‐6Al‐4V and Ti‐23Ta alloys in artificial saliva

Abstract

Titanium alloys exhibit an excellent corrosion resistance in most aqueous media due to the formation of a stable oxide film and some of these alloys (particularly Ti‐6Al‐4V) were chosen for surgical and odontological implants for this resistance and their biocompatibility. Treatments with fluorides (F−) are known as the main method to prevent plaque formation and dental caries. Toothpastes, mouthwashes and prophylactic gels can contain from 200 to 20 000 ppm F− and can present neutral to acidic character, which can affect the corrosion behavior of titanium alloys devices present in the oral cavity. In this work, the behavior of Ti‐6Al‐4V and the new experimental Ti‐23Ta has been evaluated in artificial saliva of pH 2, 5 and 7 and different F− concentrations (0, 1000, 5000 and 10 000 ppm), through open‐circuit potential measurements, potentiodynamic polarization and electrochemical impedance spectroscopy. A defined correlation between pH and F− concentration settled the active or passive character of the materials. For both alloys, an active behavior was observed for pH 2 and 1000 to 10 000 ppm F− and for pH 5 and 5000 and 10 000 ppm F−. The passive behavior was observed for the other investigated conditions. The F− concentration increase and pH decrease reduced the corrosion resistance of the alloys and decreased the stability of their passive film. The corrosion behavior of both alloys was very similar, but the Ti‐23Ta alloy generally presented slightly higher corrosion resistance.

Simultaneous degradation by corrosion and wear of titanium in artificial saliva containing fluorides

“…This solution was chosen on one side since it is frequently used in previous research work [1,5,30,31], but also because it generates a similar electrochemical behavior of metallic materials as observed in human saliva [32]. NaF was added to the Fusayama's stock solution to reproduce F -concentrations found in the oral cavity.…”

Wear and Corrosion Interactions on Titanium in Oral Environment: Literature Review

“…Nevertheless, other formulations have also been reported as most appropriate for studying corrosion of dental materials [49]. Even though the extensive number of different artificial saliva formulations is found in the literature, Fusayama's solution has been largely used to study the corrosion of dental materials including titanium and its alloys [49,50,[54][55][56][57]. Concerning several parameters such as the use of artificial saliva, studies should be standardized in order to compare the results reported in the literature.…”

Tantalum effect on the corrosion behavior of titanium-tantalum alloys in an environment containing fluoride ions

“…The basis consists in evaluating materials behavior in electrolytes simulating body environment (SBF, physiological solution, Ringer solution, model saliva, etc.) [5,6]. These tests may be followed by a more strict evaluation modeling the boundary conditions of real exposure (increased environment aggressiveness in consequence of an inflammation, etc.).…”

“…These tests may be followed by a more strict evaluation modeling the boundary conditions of real exposure (increased environment aggressiveness in consequence of an inflammation, etc.). This may also include tests carried out in environments containing fluoride ions at pH values in the acidic region, which are used in the testing of dental alloys [6][7][8].…”

“…However, only a small attention has as yet been devoted to Ti-based alloys with tantalum. Robin et al [6] compared corrosion resistance of Ti23Ta and Ti6Al4V alloys in a model saliva environment with a fluoride ions content ranging from 0 to 10000 ppm, and with pH ranging from 2 to 7. Based on the measured impedance spectra and potentiodynamic dependences, the authors noted a slightly higher corrosion resistance of Ti-23Ta as compared with Ti6Al4V.…”