The Estimation of Corrosion Behavior of NiTi and NiTiNb Alloys Using Dynamic Electrochemical Impedance Spectroscopy

Linear anodic potentiodynamic polarization and dynamic electrochemical impedance spectroscopic (DEIS) measurements were carried out for NiTi and NiTiNb alloys in physiological 0.9 wt% NaCl solution in order to assess their corrosion resistance. DEIS measurements were performed from open circuit potential to dissolution potential. It was shown that the impedance measurements in potentiodynamic conditions allow simultaneous investigation of changes in passive layer structure. The impedance spectra of various potential regions were fitted and also discussed. The surface morphology of the alloys after linear anodic polarization test was studied using scanning electron microscopy (SEM) technique

Multiscale electrochemical investigation of the corrosion resistance of various alloys used in dental prostheses

The electrochemical behaviour of Ag-Pd (Paliag), Ni-Cr (Heraenium NA), and Co-Cr (Heraenium CE) alloys used in dental prosthetics construction of crowns and bridges was studied in 0.9% NaCl solution at 25 ºC. The localized electrochemical characteristics related to corrosion resistance and eventual breakdown of the protecting oxide layers were investigated by scanning electrochemical microscopy (SECM), whereas potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques were employed to establish oxide stability. When the corrosion resistance of the alloys was evaluated by means of the corrosion current value determined around their corresponding open circuit potential in 0.9% NaCl solution, good protection can be expected resulting from their spontaneous passivation (low current densities in the order of tenths of μA cm-2). The polarization resistance of all the samples increased with immersion time, in the sequence Ag-Pd < Heraenium NA < Heraenium CE. Yet, increased electrochemical activity was detected with SECM when the alloys were polarized at +0.40 VSCE, a value that may be eventually experienced in the human body. Though a passivation mechanism was still operating in the chromium-containing alloys, oxide dissolution and precipitation of corrosion products occurred on Ag-Pd instea