Probing the dealloying critical potential - Morphological characterization and steady-state current behavior
A Dursun, DB Pugh, SG Corcoran
article (Uluslararası, Hakemli) | Yazar(lar): A Dursun, DB Pugh, SG Corcoran | Yıl: 2005 | Dergi/Kurum: JOURNAL OF THE ELECTROCHEMICAL SOCIETY | İndeks: WOS.SCI | DOI: 10.1149/1.1848351 — Özet: One of the important characteristics of dealloying systems is the location of the critical potential which marks the transitio
One of the important characteristics of dealloying systems is the location of the critical potential which marks the transition from a "passivated" alloy surface to the sustained formation of a bicontinuous porous structure. A steady-state method for accurately determining the dealloying critical potential is compared with the more traditional approach of extrapolation from anodic polarization data. Misinterpretation in the literature of short-term potential-hold data is discussed in light of these results. The dealloying critical potentials for Ag0.80Au0.20, Ag0.75Au0.25, and Ag0.70Au0.30 were 0.80, 0.94, and 1.01 V (normal hydrogen electrode), respectively. The polarization data is shown to overestimate these values by 100 mV. Morphological investigations confirm the presence of porosity for a potential hold only 10 mV above the critical potential. For alloys with compositions between 70-80 atom % Ag, the critical potential increased by 20 mV per atom % decrease in the Ag composition. Long-term current fluctuations were observed during the potential hold experiments that suggest the presence of a surface corrosion instability occurring over 1-5% of the total surface area. (C) 2005 The Electrochemical Society. All rights reserved.