Multiscale Electrochemical Investigation of the Corrosion Resistance of Various Alloys Used in Dental Prostheses

Abstract

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 instead.

Electrochemical characteristics of bioresorbable binary MgCa alloys in Ringer's solution: Revealing the impact of local pH distributions during in-vitro dissolution

“…With the development of the scanning microelectrochemical microscope (SECM), in vitro studies of the dissolution and passivation reactions of biomaterials can be performed with high spatial 4 and chemical resolution [41][42][43][44][45]. The basic operation principle of the technique consists in the transformation of a redox-active species to another redox state at a microelectrode tip while scanning a surface in close proximity.…”

Corrosion Behavior of Nickel–Titanium Continuous-Casted Alloys

“…The potential corrosion values for the investigated alloys were negative. Keeping in mind that positive potentials in the oral cavity could in some cases correspond to a polarization value of 300-400 mV [24], it is evident that NiTi as cast showed unsatisfactory results. The anodic curve for NiTi as cast showed practically only active anodic dissolution.…”

“…The increase in the polar-ization resistance indicates that the corrosion current density decreased. Moreover, if R p changes over time, that indicates some surface processes, usually oxide film formation [24]. The diagram given in Figure 4 represents linear polarization measurements (LPRs) after stabilization of the corrosion potentials of the investigated samples for 2 h. Based on the obtained values, it was demonstrated that NiTicc has a three-times-higher corrosion polarization resistance in comparison with the NiTi as-cast alloy.…”

“…The increase in the polarization resistance indicates that the corrosion current density decreased. Moreover, if Rp changes over time, that indicates some surface processes, usually oxide film formation [24]. Figure 5 shows the dependence of the polarization resistance over time.…”