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KMID : 0362220100370040355
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Journal of The Korean Research Society for Dental Materials
2010 Volume.37 No. 4 p.355 ~ p.366
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Electrochemical Study of Oxide Layers on Titanium Alloys for Dental Implants
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Heo Kweon-Bong
Choi Ki-Yeol
Lee Joong-Bae
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Abstract
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The characteristics of oxide layers formed on cp-Ti, Ti6Al4V ELI alloy, and Ti6Al7Nb alloy were studied. The basic corrosion resistance was estimated by static immersion test, and the passivation behavior was studied by several electrochemical techniques; open circuit potential vs. time measurement, potentiodynamic polarization, potentiostatic current vs. time measurement, and electrochemical impedance spectroscopy (EIS). The polarization resistance of oxide layer was calculated by fitting the EIS data to the equivalent circuit model. The strong passivation was observed for all three materials. Only negligible amounts of metals were dissolved during the static immersion test, and the passive currents less than a few tens of μA/cm2 were recorded over a wide range of anodic potential in the electrochemical test. The typical shape of fast passivation was seen in the open circuit potential vs. time curves. The EIS data for three materials was fitted to the equivalent circuit model R(QR). Ti6Al4V ELI alloy showed the highest passivation rate among three materials at the initial stage of oxidation. However, the passivation was deteriorated in the electrochemical oxidation condition and also in acid solution, probably due to the damage of oxide layer, then the polarization resistance rapidly decreased. On the other hand, the passivation of pure titanium was stabilized in the electrochemical oxidation condition by thickening of oxide layer. Ti6Al7Nb alloy showed the lowest passivation rate among three materials in all conditions.
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KEYWORD
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Titanium, Oxide layer, Corrosion, Passivation, Electrochemical impedance spectroscopy, Olarization resistance
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