Step-polarization impedance spectroscopy of implant alloys in physiologic solutions

Abstract

A novel test method is presented whereby the polarization behavior and impedance characteristics of an electrochemical interface can be determined simultaneously from potential-step current transient responses. In this test, small incremental steps in potential are applied to an electrochemical interface and the current transient response is collected digitally. Then, the data are subjected to a numerical Laplace transform technique to obtain the frequency-dependent admittance (reciprocal impedance) of the interface. From this analysis, several interesting and relevant parameters, including the high- and low-frequency resistances, interfacial capacitance, and polarization behavior, can be obtained. The mathematical basis for this technique is presented and the methodology is applied to three implant alloys (titanium, Co-Cr-Mo, and platinum). Electrochemical tests were performed in 0.9% NaCl at room temperature. Starting at an initial negative potential, the samples were stepped in 50-mV increments every 10 or 100 s up to a maximum potential and then reversed back to the starting potential. The impedances were calculated and used to evaluate the behavior. From these tests, one can determine the potential dependence of the oxide film thickness as well as the changes in the underlying electrochemical state of the interfaces with potential. This technique is inexpensive and easily applied to any electrochemical system, and yields significantly more electrochemical information than either anodic polarization or electrochemical impedance spectroscopy alone.

Electrochemical and corrosion behaviors of sputtered TiNi shape memory films

“…However, it was found that the series resistance varied with potential to some extent [31]. On the contrary, the polarization resistance showed little dependence on potential, which is contrary to the expected behavior [27].…”

The effect of scanning electrochemical potential on the short‐term impedance of commercially pure titanium in simulated biological conditions

“…In fact, the oxide layer is highly dynamic. It has been shown that the oxide structure, chemistry, and interfacial electrochemical impedance are modified with immersion in electrolyte solutions, [1][2][3][4][5][6] with electrical polarization, [7][8][9][10][11] and with interaction among biological species such as osteoblast-like cells, [12][13][14] fibroblasts, 15,16 and inflammatory products. [17][18][19][20][21][22][23][24] Fully characterizing the properties of the oxide film present on titanium implants over a spectrum of clinically relevant conditions will provide a detailed map of the properties contributing to biocompatibility.…”

EIS characterization of a Ti-dental implant in artificial saliva media: dissolution process of the oxide barrier

“…Corrosion processes that occur at implant surfaces, the role of oxide films in the corrosion process, alloy biocompatibility and the electrochemical response of these biomaterials to mechanical and electrical transients are all important factors in the behavior and success of implants [14].…”

“…However, Al enrichment of the aphase was found to be detrimental to the passivity and corrosion resistance of Ti. Gilbert [14] studied the polarization behavior and EIS response of the electrochemical interface of various materials (Ti, Pt and CoCrMo) in 0.9% NaCl. From these studies the potential dependence of the oxide film thickness and the changes in the underlying electrochemical state of the interface with potential were demonstrated.…”