Corrosion behavior of Ti and TI6Al4V in citrate buffers containing fluoride ions

Abstract

The effect of fluoride ions concentration on the electrochemical behavior of Ti grade 2 and Ti6Al4V in citrate buffers was studied. Open circuit potential (OCP) measurements and voltammetric studies of the samples in the fluoride containing citrate buffers revealed a dissolution process when the pH falls below 5.0 and the NaF content is higher than 0.01 M. However, in citrate pH 7.6 the materials showed a passive behavior even in 0.1 M NaF. Some micrographs of Ti grade 2 obtained after longer immersion times in citrate pH 5.0 with 0.01 M NaF showed a surface attack. EIS (Electrochemical Impedance Sprectroscopy) data obtained at the OCP revealed that the film resistance decreases when the immersion time is increased in pH 5.0 containing 0.1 M NaF. In the citrate pH 7.6 the EIS data indicated a two-layer model of an oxide film consisting of a more compact inner layer and a porous outer layer. On the other hand, the EIS results in citrate pH 4.0 change significantly when the fluoride ions concentration increases from 0.01 to 0.05 M. The electrochemical data revealed that the corrosion behavior of Ti grade 2 and Ti6Al4V in the citrate buffers depends on the pH, the fluoride content and the exposure time.

Influence of Hafnium Addition on the Microstructure, Microhardness and Corrosion Resistance of Ti20Ta20Nb20(ZrMo)20−xHfx (where x = 0, 5, 10, 15 and 20 at.%) High Entropy Alloys

“…In Figure 6 a, one can observe only a one-time constant which indicates the presence of a self-passive oxide layer on the tested HEAs. Additionally, the wide plateau in the frequency range of 0.01–1000 Hz visible in the Bode diagram proves the passive protection of the tested alloys [ 37 ].…”

Influence of Molybdenum on the Microstructure, Mechanical Properties and Corrosion Resistance of Ti20Ta20Nb20(ZrHf)20−xMox (Where: x = 0, 5, 10, 15, 20) High Entropy Alloys

“…The Bode diagrams displaying the φ in a function of the logarithm of the measuring frequency revealed a plateau in the range of medium frequencies, which indicates the passive protection of the studied electrodes ( Figure 6 b). Moreover, one time constant, visible on Bode diagrams, is characteristic of titanium and its alloys with a thin layer of self-passive oxide [ 64 ]. In any case, one can observe the deviation of the maximum values of φ from the ideal value of −90°.…”

The Influence of ZnO Oxide Layer on the Physicochemical Behavior of Ti6Al4V Titanium Alloy

“…However, interference with the human body environment disturbs its existing state of balance and thus triggers defense reactions, such as decreased pH of body solution and increased temperature. In some reports, in order to simulate relevant clinical scenarios, the pH of the solution was decreased by the addition of fluoride ions [ 32 , 33 ]. However, there is no clear information about the influence of chloride ions on the corrosive behavior of titanium alloys.…”