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Corrosion behavior of Ti–Ta–Nb alloys in simulated physiological media
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Materials Letters 62 (2008) 1843 – 1845 www.elsevier.com/locate/matlet
Corrosion behavior of Ti–Ta–Nb alloys in simulated physiological media Ahmad Ivan Karayan a,b,c , Sang-Won Park b,c , Kwang-Min Lee a,⁎ a
c
Department of Materials Science and Engineering, Research Institute for Functional Surface Engineering, Chonnam National University, Gwangju 500-757, South Korea b Department of Prosthodontics, School of Dentistry, Chonnam National University, Gwangju 504-190, South Korea Dental Science Research Institute and BK21 Project, School of Dentistry, Chonnam National University, Gwangju 504-190, South Korea Received 8 April 2007; accepted 11 October 2007 Available online 17 October 2007
Abstract The purpose of this research was to study the corrosion behavior of Ti-8Ta-3Nb and Ti-10Ta-10Nb in simulated physiological media in comparison to that of CP Ti and Ti-6Al-4V. In the Ringer's solution, Ti-8Ta-3Nb exhibited a higher passive current density than CP Ti and the other Ti-based alloys. Increasing the alloying additions of Ta and Nb to Ti successfully suppressed the oxygen evolution, lowered the passive current density, and shifted the corrosion potential in the noble direction. While the current densities of CP Ti, Ti-6Al-4V, and Ti-8Ta-3Nb significantly increased at a potential N 1.0 VSSC, the current densities of Ti-10Ta-10Nb tended to remain constant. The deconvolution of the O 1s peaks for Ti-10Ta10Nb showed the peaks of O2−, OH− and H2O. However, Ti-8Ta-3Nb only showed the peaks of O2− and OH−. The superior property of the passive film on Ti-10Ta-10Nb, in comparison to that on Ti-8Ta-3Nb, was attributed to the presence of the hydrate group inside the passive film. © 2007 Elsevier B.V. All rights reserved. Keywords: Corrosion; Passive current density; Passive film; Titanium; Tantalum; Niobium
1. Introduction Ti and Ti-based alloys have been widely used as implant materials due to their good mechanical properties and corrosion resistance. The good corrosion resistance of Ti and its alloys is due to the presence of a protective and self-adherent oxide film, which is mainly composed of titanium dioxide (TiO2) [1–5]. Ti-6Al-4V is the Ti-based alloy the most frequently used as an implant material. However, some authors have reported that vanadium is toxic to the human body [6,7]. This concern has led to the development of vanadium-free titanium implant alloys with mechanical and corrosion properties similar to those of Ti-6Al-4V. Due to the detrimental effect of vanadium, Semlitsch [8] developed Ti-6Al-7Nb alloy as an alternative and found that the corrosion resistance of this alloy was second only to that of CP Ti. The present authors [9–11] proposed using Ti-8Ta-3Nb and Ti-10Ta-10Nb to replace Ti-6Al-4V in biomaterials. Unfortu-
⁎ Corresponding author. E-mail address: [email protected] (K.-M. Lee). 0167-577X/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2007.10.028
nately, no detailed information on the corrosion behavior of these alloys in Ringer's solution could be found in the literature. The objective of this research was to study the corrosion behavior of Ti-8Ta-3Nb and Ti-10Ta-10Nb in simulated physiological fluid in comparison to that of CP Ti and Ti-6Al-4V. 2. Experimental procedures The materials used in this experiment were CP Ti (purity 99.99%), Ti-6Al-4V (Ti 90.30%, Al 5.30%, V 4.30%, impurities 0.10% max), Ti-8Ta-3Nb (Ti 88.50%, Ta 8.50%, Nb 2.90%, impurities 0.10% max), and Ti-10Ta-10Nb (Ti 79.90%, Ta 10.10%, Nb 9.90%, impurities 0.10% max). The corrosion behavior of CP Ti and the Ti-based alloys was studied in Ringer's solution: 9.000 g/l NaCl, 0.240 g/l CaCl2, 0.430 g/l KCl, 0.200 g/l NaHCO3. The test solution was prepared from high purity 18 MΩ cm water. All of the specimens were sequentially polished with 220-, 600-, 1000-, 1500-, and 2000-grit silicon carbide (SiC) abrasive papers and then with 0.1-μm diamond paste. After polishing, the specimens were ultrasonically cleaned in acetone for 10 min
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A.I. Karayan et al. / Materials Letters 62 (2008) 1843–1845
Table 1 Corrosion parameters obtained from potentiodynamic polarization tests Samples
Corrosion potential (Ecorr), (VSSC)
Passive current density (ipass), (A/cm2)
CP Ti Ti-6Al-4V Ti-8Ta-3Nb Ti-10Ta-10Nb
− 0.43 − 0.37 − 0.49 − 0.34
5.29 × 10− 7 5.81 × 10− 7 8.94 × 10− 7 6.04 × 10− 7
to remove grease, and then rinsed with high purity 18 MΩ cm water. A three-electrode electrochemical cell was used as the polarization test cell, consisting of the studied specimen, the silver/silver chloride (SSC) electrode in saturated KCl employed as the reference electrode, and a platinum grid as the auxiliary electrode. Two types of polarization tests were performed on the specimens to investigate their corrosion and passivity behaviors: potentiodynamic polarization scans and potentiostatic tests. Prior to the polarization tests, the specimens were immersed in the Ringer's solutions for 1 h to reach a steady state open circuit potential (OCP). Nitrogen gas was purged into the solution for 1 h before immersion and during the polarization tests. A scan rate of 0.166 mV/s was used for the potentiodynamic polarization scans. In order to investigate the stability of the passive film, a potential of 0.5 VSSC was applied to the specimens during the potentiostatic tests. Five samples of each alloy were prepared for electrochemical measurements. The chemical compositions of the passive film formed on Ti8Ta-3Nb and Ti-10Ta-10Nb were studied using XPS after applying a potential of 0.5 VSSC, located in the passive region, for 25 min.
An extreme increase in the current density was observed for Ti-8Ta-3Nb at a potential N 1.0 VSSC. Previously published studies showing an increase in the current densities for CP Ti and Ti-6Al-4V were confirmed in this study [12,13]. The abrupt increase in the current densities observed at potentials more anodic than 1.0 VSSC is due to oxygen evolution. This increase in the current densities suggests that the passive film formed on the surface is less blocking in terms of the electrolytic conductivity, so that a higher current flow is allowed to oxidize the species in the electrolyte [13]. The potential plateau observed after an abrupt increase in current densities corresponds to the secondary passivation on the surface. Considering a higher value of current densities at this potential plateau, the passive films in this region might be less stable and less protective as compared to those observed at the first passivation region existing below the oxygen evolution region. Further studies are needed to evaluate the characteristics of passive films formed at the oxygen evolution region and the potential plateau. The optical microscopy images of the anodically polarized CP Ti and Ti-based alloys revealed the absence of any type of localized attack at potentials at which increased current densities were observed. Potentiostatic tests were carried out at the potential of 0.5 VSSC to evaluate the stability of the passive film formed on CP Ti, Ti-6Al-4V, Ti8Ta-3Nb and Ti-10Ta-10Nb during 25 min (Fig. 1b). We found that a higher current density was observed in Ti-8Ta-3Nb, which was the same tendency as observed in the potentiodynamic curve (Fig. 1a). Even though the value of the current density observed in the potentiostatic tests for each alloy is not exactly the same as that observed in the potentiodynamic scans
3. Results and discussion 3.1. Corrosion test The corrosion parameters obtained from the potentiodynamic polarization scans are displayed in Table 1. We found that the values of corrosion parameters among CP Ti, Ti-6Al-4V, Ti-8Ta-3Nb, and Ti-10Ta-10Nb were not significantly different. Ti-10Ta-10Nb exhibited a corrosion potential, Ecorr, of −0.34 VSSC, which was slightly more noble than the corrosion potentials observed at Ti-6Al-4V, CP Ti, and Ti-8Ta-3Nb with the values of −0.37, −043, and −0.49 VSSC, respectively. The highest passive current density, ipass, of 8.94 ×10− 7 A/cm2 was observed at Ti-8Ta-3Nb. Fig. 1(a) shows the potentiodynamic polarization curves of CP Ti, Ti6Al-4V, Ti-8Ta-3Nb, and Ti-10Ta-10Nb in Ringer's solution at a pH of 7.4 and temperature of 37 ± 1 °C. All of the specimens were spontaneously passive upon anodic polarization. The passive current density of Ti-8Ta-3Nb was found to be approximately 8.94 × 10− 7 A/cm2, which was slightly higher than that of the other Ti-based alloys and CP Ti. The highest passive current density for Ti-8Ta-3Nb, shown in Fig. 1(a) and (b), suggests that the alloying additions of 8% Ta and 3% Nb to Ti cannot significantly decrease the passive current density. On the other hand, the alloying additions of 10% Ta and 10% Nb to Ti result in the lowering of the passive current density (6.04 × 10− 7 A/cm2), which indicates the formation of a more protective passive film. Unlike CP Ti, Ti-6Al-4V, and Ti-8Ta-3Nb, no significant increase in the current density was observed for Ti-10Ta-10Nb at potentials more anodic than 1.0 VSSC.
Fig. 1. (a) Potentiodynamic and (b) potentiostatic curves for CP Ti, Ti-6Al 4V, Ti-8Ta-3Nb, and Ti-10Ta-10Nb in ringer's solution at the temperature of 37 ± 1 °C.
A.I. Karayan et al. / Materials Letters 62 (2008) 1843–1845
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10Nb, whereas only the peaks of O2− and OH− were found in the case of Ti-8Ta-3Nb. The hydroxyl group is an effective species to form the hydroxylated metallic ion by capturing the metal ions which are released from the surface. It is known that the hydroxylated metallic ion, MOH, contributes to repair film integrity. The hydrate group can increase the resistance of this film to the attack of chloride ions. The presence of a high ratio of hydroxyl/hydrate inside the oxide film suggests a highly protective quality of hydrated metal hydroxylated oxide in an amorphous oxide film [14].
4. Conclusions We found that Ti-10Ta-10Nb and Ti-8Ta-3Nb showed outstanding resistance to corrosion. Ti-8Ta-3Nb, however, has a lower corrosion resistance than CP Ti, Ti-6Al-4V, and Ti-10Ta10Nb, as characterized by its high passive current density. The improved corrosion resistance of Ti-10Ta-10Nb compared to Ti8Ta-3Nb was attributable to the increase in the Ta and Nb contents. Increasing the alloying additions of Ta and Nb to Ti successfully suppressed the oxygen evolution, lowered the passive current density, and shifted the corrosion potential in the noble direction. The superior properties of the passive film on Ti-10Ta-10Nb, in comparison to that on Ti-8Ta-3Nb, was attributed to the presence of the hydrate group inside the passive film. References Fig. 2. Deconvolution of the O 1s signal for: (a) Ti-8Ta-3Nb and (b) Ti-10Ta10Nb after potentiostatic tests in Ringer's solution at 0.5 VSSC for 25 min.
conducted at the same applied potential, the trend in the current density is the same. 3.2. Chemical compositions of passive film determined by XPS The deconvolution of the O 1s peaks for Ti-8ta-3Nb and Ti-10Ta10Nb is shown in Fig. 2. While Ti-10Ta-10Nb (Fig. 2(b)) showed the peaks of O2−, OH− and H2O, Ti-8Ta-3Nb (Fig. 2(a)) only showed the peaks of O2− and OH−. Yu and Scully [12] reported that the modification of TiO2 by Nb2O5 led to the improvement of its resistance to pitting. As regards the deconvolution of the O 1s peaks for the titanium-tantalum-niobium alloys tested in this study, peaks for O2−, OH−, and H2O were found in the spectra corresponding to the inside of the passive film of Ti-10Ta-
[1] R.W. Schutz, L.R. Covington, Corrosion 37 (1981) 585. [2] K.A. De Souza, A. Robin, Mater. Corros. 55 (2004) 853. [3] Y. Oshida, R. Sachdeva, S. Miyazaki, J. Mater. Sci., Mater. Med. 3 (1992) 306. [4] Y. Oshida, R. Sachdeva, S. Miyazaki, Biomed. Mater. Eng. 2 (1992) 51. [5] C. Kuphasuk, Y. Oshida, C.J. Andres, S.T. Hovijitra, M.T. Barco, D.T. Brown, J. Prosthet. Dent. 85 (2001) 195. [6] T.J.B. Simons, Nature 281 (1979) 337. [7] K.L. Wapner, Clin. Orthop. 271 (1991) 12. [8] M. Semlitsch, Clin. Mater. 2 (1987) 1. [9] D.J. Lee, K.M. Lee, K.K. Kee, H.K. Cho, J. Kor. Acad. Dent. Tech. 26 (2004) 97. [10] D.J. Lee, K.K. Lee, B.S. Park, K.M. Lee, S.W. Park, Kor. J. Mater. Res. 16 (2006) 277. [11] D.J. Lee, K.K. Lee, K.M. Lee, S.W. Park, J. Kor. Inst. Surf. Eng. 39 (2006) 43. [12] S.Y. Yu, J.R. Scully, Corrosion 53 (1997) 965. [13] E. Alkhateeb, S. Virtanen, J. Biomed. Mater. Res. 75A (2005) 934. [14] C.C. Shih, C.M. Shih, K.Y. Chou, S.J. Lin, Y.Y. Su, J. Electrochem. Soc. 153 (2006) 403.
Materials Letters 62 (2008) 1843 – 1845 www.elsevier.com/locate/matlet
Corrosion behavior of Ti–Ta–Nb alloys in simulated physiological media Ahmad Ivan Karayan a,b,c , Sang-Won Park b,c , Kwang-Min Lee a,⁎ a
c
Department of Materials Science and Engineering, Research Institute for Functional Surface Engineering, Chonnam National University, Gwangju 500-757, South Korea b Department of Prosthodontics, School of Dentistry, Chonnam National University, Gwangju 504-190, South Korea Dental Science Research Institute and BK21 Project, School of Dentistry, Chonnam National University, Gwangju 504-190, South Korea Received 8 April 2007; accepted 11 October 2007 Available online 17 October 2007
Abstract The purpose of this research was to study the corrosion behavior of Ti-8Ta-3Nb and Ti-10Ta-10Nb in simulated physiological media in comparison to that of CP Ti and Ti-6Al-4V. In the Ringer's solution, Ti-8Ta-3Nb exhibited a higher passive current density than CP Ti and the other Ti-based alloys. Increasing the alloying additions of Ta and Nb to Ti successfully suppressed the oxygen evolution, lowered the passive current density, and shifted the corrosion potential in the noble direction. While the current densities of CP Ti, Ti-6Al-4V, and Ti-8Ta-3Nb significantly increased at a potential N 1.0 VSSC, the current densities of Ti-10Ta-10Nb tended to remain constant. The deconvolution of the O 1s peaks for Ti-10Ta10Nb showed the peaks of O2−, OH− and H2O. However, Ti-8Ta-3Nb only showed the peaks of O2− and OH−. The superior property of the passive film on Ti-10Ta-10Nb, in comparison to that on Ti-8Ta-3Nb, was attributed to the presence of the hydrate group inside the passive film. © 2007 Elsevier B.V. All rights reserved. Keywords: Corrosion; Passive current density; Passive film; Titanium; Tantalum; Niobium
1. Introduction Ti and Ti-based alloys have been widely used as implant materials due to their good mechanical properties and corrosion resistance. The good corrosion resistance of Ti and its alloys is due to the presence of a protective and self-adherent oxide film, which is mainly composed of titanium dioxide (TiO2) [1–5]. Ti-6Al-4V is the Ti-based alloy the most frequently used as an implant material. However, some authors have reported that vanadium is toxic to the human body [6,7]. This concern has led to the development of vanadium-free titanium implant alloys with mechanical and corrosion properties similar to those of Ti-6Al-4V. Due to the detrimental effect of vanadium, Semlitsch [8] developed Ti-6Al-7Nb alloy as an alternative and found that the corrosion resistance of this alloy was second only to that of CP Ti. The present authors [9–11] proposed using Ti-8Ta-3Nb and Ti-10Ta-10Nb to replace Ti-6Al-4V in biomaterials. Unfortu-
⁎ Corresponding author. E-mail address: [email protected] (K.-M. Lee). 0167-577X/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2007.10.028
nately, no detailed information on the corrosion behavior of these alloys in Ringer's solution could be found in the literature. The objective of this research was to study the corrosion behavior of Ti-8Ta-3Nb and Ti-10Ta-10Nb in simulated physiological fluid in comparison to that of CP Ti and Ti-6Al-4V. 2. Experimental procedures The materials used in this experiment were CP Ti (purity 99.99%), Ti-6Al-4V (Ti 90.30%, Al 5.30%, V 4.30%, impurities 0.10% max), Ti-8Ta-3Nb (Ti 88.50%, Ta 8.50%, Nb 2.90%, impurities 0.10% max), and Ti-10Ta-10Nb (Ti 79.90%, Ta 10.10%, Nb 9.90%, impurities 0.10% max). The corrosion behavior of CP Ti and the Ti-based alloys was studied in Ringer's solution: 9.000 g/l NaCl, 0.240 g/l CaCl2, 0.430 g/l KCl, 0.200 g/l NaHCO3. The test solution was prepared from high purity 18 MΩ cm water. All of the specimens were sequentially polished with 220-, 600-, 1000-, 1500-, and 2000-grit silicon carbide (SiC) abrasive papers and then with 0.1-μm diamond paste. After polishing, the specimens were ultrasonically cleaned in acetone for 10 min
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Table 1 Corrosion parameters obtained from potentiodynamic polarization tests Samples
Corrosion potential (Ecorr), (VSSC)
Passive current density (ipass), (A/cm2)
CP Ti Ti-6Al-4V Ti-8Ta-3Nb Ti-10Ta-10Nb
− 0.43 − 0.37 − 0.49 − 0.34
5.29 × 10− 7 5.81 × 10− 7 8.94 × 10− 7 6.04 × 10− 7
to remove grease, and then rinsed with high purity 18 MΩ cm water. A three-electrode electrochemical cell was used as the polarization test cell, consisting of the studied specimen, the silver/silver chloride (SSC) electrode in saturated KCl employed as the reference electrode, and a platinum grid as the auxiliary electrode. Two types of polarization tests were performed on the specimens to investigate their corrosion and passivity behaviors: potentiodynamic polarization scans and potentiostatic tests. Prior to the polarization tests, the specimens were immersed in the Ringer's solutions for 1 h to reach a steady state open circuit potential (OCP). Nitrogen gas was purged into the solution for 1 h before immersion and during the polarization tests. A scan rate of 0.166 mV/s was used for the potentiodynamic polarization scans. In order to investigate the stability of the passive film, a potential of 0.5 VSSC was applied to the specimens during the potentiostatic tests. Five samples of each alloy were prepared for electrochemical measurements. The chemical compositions of the passive film formed on Ti8Ta-3Nb and Ti-10Ta-10Nb were studied using XPS after applying a potential of 0.5 VSSC, located in the passive region, for 25 min.
An extreme increase in the current density was observed for Ti-8Ta-3Nb at a potential N 1.0 VSSC. Previously published studies showing an increase in the current densities for CP Ti and Ti-6Al-4V were confirmed in this study [12,13]. The abrupt increase in the current densities observed at potentials more anodic than 1.0 VSSC is due to oxygen evolution. This increase in the current densities suggests that the passive film formed on the surface is less blocking in terms of the electrolytic conductivity, so that a higher current flow is allowed to oxidize the species in the electrolyte [13]. The potential plateau observed after an abrupt increase in current densities corresponds to the secondary passivation on the surface. Considering a higher value of current densities at this potential plateau, the passive films in this region might be less stable and less protective as compared to those observed at the first passivation region existing below the oxygen evolution region. Further studies are needed to evaluate the characteristics of passive films formed at the oxygen evolution region and the potential plateau. The optical microscopy images of the anodically polarized CP Ti and Ti-based alloys revealed the absence of any type of localized attack at potentials at which increased current densities were observed. Potentiostatic tests were carried out at the potential of 0.5 VSSC to evaluate the stability of the passive film formed on CP Ti, Ti-6Al-4V, Ti8Ta-3Nb and Ti-10Ta-10Nb during 25 min (Fig. 1b). We found that a higher current density was observed in Ti-8Ta-3Nb, which was the same tendency as observed in the potentiodynamic curve (Fig. 1a). Even though the value of the current density observed in the potentiostatic tests for each alloy is not exactly the same as that observed in the potentiodynamic scans
3. Results and discussion 3.1. Corrosion test The corrosion parameters obtained from the potentiodynamic polarization scans are displayed in Table 1. We found that the values of corrosion parameters among CP Ti, Ti-6Al-4V, Ti-8Ta-3Nb, and Ti-10Ta-10Nb were not significantly different. Ti-10Ta-10Nb exhibited a corrosion potential, Ecorr, of −0.34 VSSC, which was slightly more noble than the corrosion potentials observed at Ti-6Al-4V, CP Ti, and Ti-8Ta-3Nb with the values of −0.37, −043, and −0.49 VSSC, respectively. The highest passive current density, ipass, of 8.94 ×10− 7 A/cm2 was observed at Ti-8Ta-3Nb. Fig. 1(a) shows the potentiodynamic polarization curves of CP Ti, Ti6Al-4V, Ti-8Ta-3Nb, and Ti-10Ta-10Nb in Ringer's solution at a pH of 7.4 and temperature of 37 ± 1 °C. All of the specimens were spontaneously passive upon anodic polarization. The passive current density of Ti-8Ta-3Nb was found to be approximately 8.94 × 10− 7 A/cm2, which was slightly higher than that of the other Ti-based alloys and CP Ti. The highest passive current density for Ti-8Ta-3Nb, shown in Fig. 1(a) and (b), suggests that the alloying additions of 8% Ta and 3% Nb to Ti cannot significantly decrease the passive current density. On the other hand, the alloying additions of 10% Ta and 10% Nb to Ti result in the lowering of the passive current density (6.04 × 10− 7 A/cm2), which indicates the formation of a more protective passive film. Unlike CP Ti, Ti-6Al-4V, and Ti-8Ta-3Nb, no significant increase in the current density was observed for Ti-10Ta-10Nb at potentials more anodic than 1.0 VSSC.
Fig. 1. (a) Potentiodynamic and (b) potentiostatic curves for CP Ti, Ti-6Al 4V, Ti-8Ta-3Nb, and Ti-10Ta-10Nb in ringer's solution at the temperature of 37 ± 1 °C.
A.I. Karayan et al. / Materials Letters 62 (2008) 1843–1845
1845
10Nb, whereas only the peaks of O2− and OH− were found in the case of Ti-8Ta-3Nb. The hydroxyl group is an effective species to form the hydroxylated metallic ion by capturing the metal ions which are released from the surface. It is known that the hydroxylated metallic ion, MOH, contributes to repair film integrity. The hydrate group can increase the resistance of this film to the attack of chloride ions. The presence of a high ratio of hydroxyl/hydrate inside the oxide film suggests a highly protective quality of hydrated metal hydroxylated oxide in an amorphous oxide film [14].
4. Conclusions We found that Ti-10Ta-10Nb and Ti-8Ta-3Nb showed outstanding resistance to corrosion. Ti-8Ta-3Nb, however, has a lower corrosion resistance than CP Ti, Ti-6Al-4V, and Ti-10Ta10Nb, as characterized by its high passive current density. The improved corrosion resistance of Ti-10Ta-10Nb compared to Ti8Ta-3Nb was attributable to the increase in the Ta and Nb contents. Increasing the alloying additions of Ta and Nb to Ti successfully suppressed the oxygen evolution, lowered the passive current density, and shifted the corrosion potential in the noble direction. The superior properties of the passive film on Ti-10Ta-10Nb, in comparison to that on Ti-8Ta-3Nb, was attributed to the presence of the hydrate group inside the passive film. References Fig. 2. Deconvolution of the O 1s signal for: (a) Ti-8Ta-3Nb and (b) Ti-10Ta10Nb after potentiostatic tests in Ringer's solution at 0.5 VSSC for 25 min.
conducted at the same applied potential, the trend in the current density is the same. 3.2. Chemical compositions of passive film determined by XPS The deconvolution of the O 1s peaks for Ti-8ta-3Nb and Ti-10Ta10Nb is shown in Fig. 2. While Ti-10Ta-10Nb (Fig. 2(b)) showed the peaks of O2−, OH− and H2O, Ti-8Ta-3Nb (Fig. 2(a)) only showed the peaks of O2− and OH−. Yu and Scully [12] reported that the modification of TiO2 by Nb2O5 led to the improvement of its resistance to pitting. As regards the deconvolution of the O 1s peaks for the titanium-tantalum-niobium alloys tested in this study, peaks for O2−, OH−, and H2O were found in the spectra corresponding to the inside of the passive film of Ti-10Ta-
[1] R.W. Schutz, L.R. Covington, Corrosion 37 (1981) 585. [2] K.A. De Souza, A. Robin, Mater. Corros. 55 (2004) 853. [3] Y. Oshida, R. Sachdeva, S. Miyazaki, J. Mater. Sci., Mater. Med. 3 (1992) 306. [4] Y. Oshida, R. Sachdeva, S. Miyazaki, Biomed. Mater. Eng. 2 (1992) 51. [5] C. Kuphasuk, Y. Oshida, C.J. Andres, S.T. Hovijitra, M.T. Barco, D.T. Brown, J. Prosthet. Dent. 85 (2001) 195. [6] T.J.B. Simons, Nature 281 (1979) 337. [7] K.L. Wapner, Clin. Orthop. 271 (1991) 12. [8] M. Semlitsch, Clin. Mater. 2 (1987) 1. [9] D.J. Lee, K.M. Lee, K.K. Kee, H.K. Cho, J. Kor. Acad. Dent. Tech. 26 (2004) 97. [10] D.J. Lee, K.K. Lee, B.S. Park, K.M. Lee, S.W. Park, Kor. J. Mater. Res. 16 (2006) 277. [11] D.J. Lee, K.K. Lee, K.M. Lee, S.W. Park, J. Kor. Inst. Surf. Eng. 39 (2006) 43. [12] S.Y. Yu, J.R. Scully, Corrosion 53 (1997) 965. [13] E. Alkhateeb, S. Virtanen, J. Biomed. Mater. Res. 75A (2005) 934. [14] C.C. Shih, C.M. Shih, K.Y. Chou, S.J. Lin, Y.Y. Su, J. Electrochem. Soc. 153 (2006) 403.