Influence of Tantalum Addition on the Corrosion Passivation of Titanium-Zirconium Alloy in Simulated Body Fluid

Abstract

Ti-15%Zr alloy and Ti-15%Zr-2%Ta alloy were fabricated to be used in biomedical applications. The corrosion of these two alloys after being immersed in simulated body fluid for 1 h and 72 h was investigated. Different electrochemical methods, including polarization, impedance, and chronoamperometric current with time at 400 mV were employed. Also, the surface morphology and the compositions of its formed film were reported by the use of scanning electron microscope and energy dispersive X-ray. Based on the collected results, the presence of 2%Ta in the Ti-Zr alloy passivated its corrosion by minimizing its corrosion rate. The polarization curves revealed that adding Ta within the alloy increases the corrosion resistance as was confirmed by the impedance spectroscopy and current time data. The change of current versus time proved that the addition of Ta reduces the absolute current even at high anodic potential, 400 mV. The results of both electrochemical and spectroscopic methods indicated that pitting corrosion does not occur for both Ti-Zr and Ti-Zr-Ta alloys, even after their immersion in SBF solutions for 72 h.

The Influence of the Tantalum Content on the Main Properties of the TixTa9Nb8Zr2Ag Alloy

“…Also, it can be observed that the addition of Ta moves the corrosion potential toward more electronegative values, a fact reported by other authors [31]. Regarding the corrosion rates in the NaCl environment with increased aggressiveness and due to the temperature of 37.5 • C, they increase as the tantalum content in the alloy increases but remain at lower values than those reported by [31] for the alloys commonly used in orthopedic surgery, Ti6Al4V. Thus, SK Yen [32] reported corrosion current densities greater than 45.93 µA cm −2 in a 0.6 M NaCl solution at room temperature, while the A 20 alloy with the smallest modulus of elasticity showed i cor = 1.1 µA cm −2 at a temperature of 37.5 • C. The superior corrosion behavior of these alloys can also be attributed to the beneficial influence of silver, explained in the literature also by catalyzing the oxygen reduction reaction and favoring passivation [33].…”

“…Regarding the electrochemical parameters extracted from the Tafel curves (Figure 7) systematized in Table 2, it is observed that after 168 h of immersion in the 3% NaCl solution, the equilibrium potentials of all the alloys are much more electropositive than the corrosion potentials, which means that the alloys are spontaneously in a state of passivity. Also, it can be observed that the addition of Ta moves the corrosion potential toward more electronegative values, a fact reported by other authors [31]. Regarding the corrosion rates in the NaCl environment with increased aggressiveness and due to the temperature of 37.5 • C, they increase as the tantalum content in the alloy increases but remain at lower values than those reported by [31] for the alloys commonly used in orthopedic surgery, Ti6Al4V.…”

Corrosion Passivation in Simulated Body Fluid of Ti-Zr-Ta-xSn Alloys as Biomedical Materials

“…In addition, all sintered alloys showed lower backward current values obtained when the potential was reversed from 400 mV to negative values. This proves that pitting corrosion does not occur under these circumstances [ 39 , 41 ].…”

“…Figure 1 and Figure 2 show that applying potential in a very negative orientation causes the current in the cathode to decrease due to the reduction of oxygen. Several studies [ 38 , 39 , 40 , 41 ] have shown that metals and alloys in a neutral solution such as a simulated body fluid undergo cathodic reduction of oxygen. 2H 2 O + O 2 + 4e − = 4OH − …”

“…Chronoamperometric current with time (CCt) measurements have been utilized to report the corrosion of various metallic structures at a fixed anodic potential value [ 38 , 39 , 41 ]. Figure 3 represents the CCt curves for (1) Ti-Zr-Ta-4Sn, (2) Ti-Zr-Ta-6Sn, and (3) Ti-Zr-Ta- 8Sn that were obtained at 400 mV after one hour in the SBF solution, while Figure 4 displays the CCt curves that were obtained at the same value of potential for the same alloys after exposure for 72 h. These figures show increases in the initial current that resulted from the dissolution of the oxide from the surface; this oxide must have formed either in the air before the measurement or during immersion in the SBF solution.…”