Evaluation of Corrosion Resistance of Multi-Layered Ti/Glass-Ceramic Interfaces by Electrochemical Impedance Spectroscopy

Abstract

Practical applications of metal/ceramic joints can be found in the biomedical field regarding the encapsulation of implantable telemetric devices, the fabrication of crowns and bridges for dental restoration, or in the production of drug delivery systems, biomedical sensors and electrodes. Most of metal/ceramic joints are produced by the active metal brazing technique, which originates a multi-layered interface which should be able of accommodating the abrupt electronic, crystallographic, chemical, mechanical and thermo-mechanical discontinuity that characterize these systems. Additionally, when considering biomedical applications, corrosion resistance becomes of prime importance. In this work, the corrosion resistance of Ti/glass-ceramic interfaces obtained by active metal brazing was evaluated by electrochemical impedance spectroscopy (EIS) tests. The electrochemical behaviour of the interface was monitored, as a function of time, in a simulated physiological solution at room temperature. In order to evaluate the contribution of each layer and galvanic interactions between them, to the degradation mechanism of the interface, individual samples, representative of reaction layers present at the interface, were fabricated and electrochemically tested. Results show that the corrosion behaviour, of the whole interface was strongly influenced by the chemical composition of its constitutive layers. Thus, layers containing high contents of both titanium and silver showed a polarisation resistance increase with the immersion time, as a result of the formation of a thermodynamically stable passive film. On the other hand, the copper rich layer, appears to be the main responsible for the interface degradation. In fact, for high immersion times, an instable passive film is formed and, as a consequence, large amounts of copper are released. Galvanic interactions between the copper and the silver rich layers where also identified.

Effect of Gold Nano Dots in Microwave Brazing: A Novel Approach to Join Ti6Al4V to MACOR^®

“…High levels of hardness observed (1500HV) near the glass-ceramic interface [11] was attributed to the formation of intermetallics between titanium and SiO2 of glass-ceramic. The corrosion test of the MACOR ® to Ti joint was performed by some researchers [12,13] and it was observed that an AgCl layer was formed due to reaction with the braze alloy which acts as a passive film to prevent the degradation of joint. Liu et al [14] successfully brazed SiO2 glass ceramic and Ti6Al4V alloy with the help of Ti active metal braze alloy.…”

Effects of TiO2Addition on the Electrochemical Performance of the Overlay Welded High-manganese Steel Cladding

“…In this equivalent model, Rs is the solution resistance; Rp stands for the resistance of the sample in the solution, and CPE1 counts for the constant phase element corresponding to the capacitance of the corrosion pits. As the most important characteristic of all the EIS value, the polarization resistance Rp represent the resistant ability to against the corrosion [12,13]. Table 5 shows all the values of equivalent circuit elements of the cladding samples in 3.5% NaCl solution.…”