Abstract
The protective properties of passive layers are of great importance for the understanding of the mechanisms of corrosion protection of metals. Surface analytical methods have been applied to get informations about their structure and composition. An electrochemical specimen preparation and transfer to the ultra high vacuum (UHV) within a closed system helps to minimize the occurance of changes during exposure to the lab atmosphere. X-Ray Photoelectron-Spectroscopy (XPS) has been applied to get quantitative information about the thickness and structure of these thin surface layers The relevant parameters or layer formation have been varied, such as time and potential, or tne composition of the metal and electrolyte. Not only the passive layer formation but also the change of its composition with the potential i.e. the chemical reactions of these films may be studied. Usually multilayer structures are found with the higher valent species and hydroxides at the outer part of the layer and the oxides and lower valent components at the inner part. ISS sputter profiles provide a detailed quantitative information of the cation composition with a monolayer depth resolution. UPS studies yield work functions and threshold energies and related electronic properties of these semiconducting surface oxides. The data are interpreted in close relation to the electrochemical findings. Results for pure metals as Fe, Ni, Cr, Cu and binary alloys as Fe/Cr and Fe/Ni are presented.
