Abstract
Applications of low energy electron diffraction (LEED), Auger electron spectroscopy (AES), and electron energy loss spectroscopy (EELS) in the study of corrosion processes and corrosion inhibitor films are described. Studies in our laboratories of surface phemomena related to the depassivation, electrodissolution and corrosion of Fe-Ni-Cr alloys and the formation of polymer films on well- defined electrode surfaces will be presented to illustrate techniques and applications.
For example, exposure of clean Fe-Cr-Ni(111) and Fe-Cr-Ni(111) to aqueous electrolytes forms an amorphous, hydrated film on these surfaces. LEED patterns were only apparent after the oxide films had been annealed at 800°C. Interestingly, a hexagonal arrangement of chromium and oxide ions was obseved on either plane after this pretreatment sequence. The oxide-filmed (111) plane demonstrated greater stability towards attack by HC1. The annealed oxide film on the (100) plane was found to contain considerably less Cr than the corresponding film on the (111) plane. These observations point to a structural dependence of the passivity of 304 stainless steal. EELS and AES have been used to study the adsorption of monometric thiophene derivatives on Pt(111), dimers of some of these derivatives, and polymer films arising from oxidation of adsorbed 3-methylthiophene (3-MT) and from electrogeneration in solutions of 3-MT. In most cases studied thus far it has been found that the thiophene moiety was oriented nearly vertically with respect to the electrode surface and that polymerization occurred at the alpha- positions of the thiophene ring (adjacent to the sulfur atom in the ring).
