Abstract
Ti-Nb-Zr alloys are interesting materials for implant applications due to the atoxic character of the Nb and Zr alloying elements and to their low elastic modulus when compared to CP-Ti. In this work, the corrosion behaviour of CP-Ti, Ti-5Nb-13Zr, Ti-13Nb-13Zr, and Ti-20Nb-13Zr alloys was investigated in Ringer’s solution of pH 2, 5, and 7.5 without fluorides and containing 1000 ppm F at 37°C, through open-circuit potential measurements, potentiodynamic polarization, and electrochemical impedance spectroscopy. The four materials showed a passive behavior in Ringer's solution without fluorides for pH ranging from 2 to 7.5 and in Ringer's solution of pH 5 and 7.5 containing 1000 ppm F but presented an active behavior in Ringer's solution of pH 2 containing fluorides. The corrosion resistance of all materials in Ringer's solution decreases with both decrease of pH and addition of fluorides. Ti-13Nb-13Zr alloy is a little more corrosion resistant than the Ti-5Nb-13Zr and Ti-20Nb-13Zr alloys and, in most conditions, the Ti-Nb-Zr alloys present higher corrosion resistance than CP-Ti.
Highlights
Pure Ti (CP-Ti) is widely used in restorative surgery as dental and orthopedic implants, due to its high corrosion resistance in physiological media and biocompatibility [1]
It was shown to be passive in simulated physiological solutions, such as Ringer’s solution [4, 10, 12, 16], Hank solutions [8, 13,14,15], artificial saliva [9], and phosphate-buffered saline solution (PBS) [5,6,7], but active in hydrochloric acid solutions [4]
The Open-circuit potential (OCP) shift in the noble direction, which indicates the formation and growth of passive films on all materials
Summary
Pure Ti (CP-Ti) is widely used in restorative surgery as dental and orthopedic implants, due to its high corrosion resistance in physiological media and biocompatibility [1]. Due to this difference in rigidity, there is a poor load sharing between the bone and the implant and bone resorption may occur These negative aspects of CPTi led to the development of more corrosion-resistant, more biocompatible, and more wear-resistant titanium alloys with better biomechanical compatibility. Among these materials, Ti-Nb-Zr ternary alloys are promising since they present a lower Young’s modulus (60– 90 GPa) when compared to CP-Ti. The Ti-13Nb-13Zr alloy was the most studied material of this family [4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20]. The Ti-22Nb-6Zr alloy was passive in 0.9% NaCl solution and more corrosion resistant than Ti-22Nb [22]
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