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O: Oberflächenphysik

O 46: Grenzfläche fest-flüssig

O 46.1: Vortrag

Freitag, 12. März 2004, 11:15–11:30, H45

In-situ Electrochemical Corrosion studied with Synchrotron Radiation — •Frank Uwe Renner^1,2, Andreas Stierle², Helmut Dosch², and Jörg Zegenhagen¹ — ¹ESRF, BP 220, 38043 Grenoble Cedex, France — ²Max-Planck-Institut für Metallforschung, 70569 Stuttgart, Germany

In our humid atmosphere, most corrosion processes are electrochemical in nature, driven by contact potentials, e.g., forming between dissimilar metals. For the basic understanding of corrosion and similar technical processes, in-situ structural methods capable of atomic resolution, such as scanning probe or hard X-ray techniques are necessary. Binary metal alloys serve as model systems for more complicated technically used metal alloys. We used in-situ methods, like X-ray diffraction and anomalous X-ray scattering and ex-situ AFM, to study Cu₃Au(111) single crystal surfaces in 0.1M H₂SO₄ electrolyte as a function of electrode potential. During the initial electrochemical corrosion Cu atoms are dissolved and a passivating layer is formed. The experiments show the formation of an epitaxial ultra-thin Cu_xAu_1−x(111) phase on the surface at a potential where Cu dissolution starts. At higher potentials thicker and still epitaxial Au islands are emerging on the surface. The applied potential range is although always well below the so-called critical potential, where the passivation breaks down and massive Cu dissolution starts. AFM images reveal a surface that is densely packed with Au islands of a homogeneous size distribution. Only with longer timescales a more porous morphology of the surface evolves.