Corrosion resistance of titanium–silver alloys in an artificial saliva containing fluoride ions

Abstract

Dental gels and rinses for caries prophylactic contain fluoride at concentrations ranging from 0.1 to 1%. In addition, many types of fluoride-releasing materials have been used in dental applications. The purpose of the study was to investigate the addition effect of fluoride into artificial saliva on the corrosion resistance of pure titanium and titanium–silver alloys. Titanium and titanium–silver alloys were arc melted, homogenized at 950°C for 72 h, hot rolled, and solution heat treated and quenched. In order to investigate the effect of the fluoride ions on the corrosion resistance, potentiodynamic polarization testing, potentiostatic testing, and open-circuit potential measurements were performed in plain artificial saliva and 0.1 and 1% NaF-added artificial saliva. The passive current densities of titanium and titanium–silver alloys increased with increasing fluoride-ion concentration. Ti2.0Ag and Ti3.0Ag exhibited a low current density relatively and showed a stable behavior compared to titanium. The open-circuit potential of titanium decreased and current density at 250 mV (SCE) potentiostatic testing reacted sensitively with increasing fluoride concentration. On the other hand, the open-circuit potential of titanium–silver alloys with a high silver content (3.0–4.0 at %) reacted less sensitively to the fluoride-ion concentration. Among titanium–silver alloys, Ti3.0Ag alloy had a higher resistance against the attack of fluoride ions and showed a more stable open-circuit potential and current density than titanium in the fluoride-containing solution. It is concluded that they are electrochemically stable and maintained good corrosion resistance in fluoride-containing artificial saliva.