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    STP1188

    The Characterization of the Coarsening of Dealloyed Layers by EIS and Its Correlation with Stress-Corrosion Cracking

    Published: 01 January 1993


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    Abstract

    The origin of the reversibility of the environmental embrittlement of an Ag-20 at. % gold alloy in 1 M HClO4 has been investigated. The structure of the porous gold layer formed on this alloy under potentiostatic polarization has been studied by electrochemical impedance spectroscopy (EIS). In the as-dealloyed state, a 50-μm layer has impedance behavior electrically equivalent to a layer containing 1011 cylindrical pores/cm2 (geometric area) each with a radius of 9 nm. Upon aging, the pores closest to the substrate coarsen first, destroying the ability of the layer to inject a brittle crack into the uncorroded substrate. This change in structure is observable as a change in the low-frequency portion of the impedance spectrum. The observed potential dependence of this coarsening indicates that it occurs due to surface diffusion of gold atoms.

    Keywords:

    dealloying, stress-corrosion cracking (SCC), porous electrodes, surface diffusion, coarsening, film-induced cleavage


    Author Information:

    Kelly, RG
    Research assistant professor, University of Virginia, Charlottesville, VA

    Young, AJ
    Research student and reader, Corrosion and Protection Centre, University of Manchester Institute of Science and Technology, Manchester,

    Newman, RC
    Research student and reader, Corrosion and Protection Centre, University of Manchester Institute of Science and Technology, Manchester,


    Committee/Subcommittee: G01.11

    DOI: 10.1520/STP18065S