Electrochemical characterization and passivation behaviour of new beta-titanium alloys (Ti35Nb10Ta-xFe)

Passivation kinetics is a crucial factor in the electrochemical behavior of passive metals and alloys when subjected to operating conditions in real systems such as biomedical devices or aeronautical applications. The aim of this work is to describe the passivation behavior of new beta-titanium alloys (Ti35Nb10Ta-xFe with x = 1.5, 3 and 4.5 where numbers indicate the %wt in the alloying elements) obtained by powder metallurgy using different electrochemical techniques and existing theoretical models for oxide film growth (High Field Model, HFM, and Interface Models, IFM). Influence of Fe content in the alloy and prevailing electrochemical conditions (i.e. applied potential) on the kinetic parameters were analyzed. The oxide film growth can be described by a HFM approach considering that the film thickness is related to the current flowing through the system, thus constant values for passive film formation were considered. The electric field in the film and the thickness of the oxide layer were quantified. Iron content in the alloy does not significantly modifies the passive film properties of the obtained materials but decreases the passive film growth of the resulting alloy. The applied potential reduces the electric field in the oxide layer while increasing its thickness.