Electrochemical behavior of Ti and Ti6Al4V in aqueous solutions of citric acid containing halides

Abstract

This paper reports on an investigation of the electrochemical behavior of Ti grade 2 and Ti6Al4V alloy in aqueous citric acid solutions with pH 2.0 containing halide ions. Voltammetric studies of Ti and the alloy in citric acid, with and without chloride ions, indicate that the Ti and Ti alloy presented a passive behavior in the test solutions used. Pitting was observed at 3.0 and 2.5 V/SCE for Ti and Ti6Al4V, respectively, when bromide ions were added to the solution. In solutions containing fluoride ions, dissolution of the film occurred at potentials close to -1.0 V/SCE in both electrodes. The iodide ions oxidized on the passive oxide film at potentials close to 1.0 V/SCE. EIS results of the materials in citric acid solutions containing chloride ions revealed that the film's resistance increased as the applied potential rose from 0 to 1.0 V. In bromide-containing solutions, breakdown of the film was confirmed at potentials above 2.0 V/SCE in both electrodes. These results suggest film reformation for Ti and the alloy in solutions containing fluoride at potentials within the passive region.

On the Corrosion Behaviour of Low Modulus Titanium Alloys for Medical Implant Applications: A Review

“…Owing to their passive oxide layer, titanium-based alloys are resistant to some organic acids; for example, lactic acid and acetic acid. However, they can be corroded by some others such as citric acid [30,31]. Among halide anions, fluoride ions can more strongly cause dissolution of the passive oxide layer in titanium-based alloys [32].…”

Passivity Breakdown of Titanium in LiBr Solutions

“…Mott-Schottky analysis has proved that the behavior of the passive film on Ti against localized attacks in high LiBr concentrations is not directly related with its electronic properties. Figure 8 shows the experimental and simulated Nyquist diagrams for Ti in 0.1M, 0.5M, 3M and 11.42M LiBr solutions at 0.4 V. The experimental data have been fitted to the electrical equivalent circuit shown in Figure 9, commonly used to account for the bilayer structure of the passive film on Ti (porous outer layer and compact inner layer) [4,5,56] In all cases, Nyquist plots exhibit a typical passive state behavior characterized by semicircular shape and high impedance values, suggesting that a highly stable film is formed on all the electrodes [31][32][33][34].…”

Establishing the patterns in the formation of oxide films on the alloy Ti6Al4V in carbonic acid solutions

“…Valuable data on the effect of electrolysis conditions on the film structure are given, but there are no data about the formation dynamics. The effect of halide ions on the anodic behavior of titanium alloys in solutions of citric acid was studied in [16]. The alloys are prone to a transition to the passive state, but the features of oxide formation were not investigated.…”