Valeria Di Castro

Copper protection by self-assembled monolayers of aromatic thiols in alkaline solutions

Copper corrosion in alkaline solutions is inhibited by the formation of self-assembled monolayers of aromatic thiols, made of either benzenethiol or 2-naphthalenethiol or 4-acetamidothiophenol. Electrochemical experiments, based on voltammetry and impedance spectroscopy, point out the much lower reactivity of copper surfaces towards oxidation, when covered by compact adlayers of the above molecules bonded through the S atom. The peculiar shape and peak position in the voltammetric reduction of residual oxides grown on modified metal surfaces suggest that they are due to Cu(I) suboxides, probably grown on reactive metal defects. XPS experiments have confirmed that the aromatic adlayers are still covering most of the Cu surface even after 1 h immersion in 0.5 M NaOH. The main changes in Auger and XP spectra indicate the formation of much less Cu(2)O in the protected samples than in the corresponding bare Cu aged in NaOH. From the experimental data the presence of defective copper oxides on modified Cu has been deduced.

Growth of 2-mercaptobenzoxazole on Cu(1 0 0) surface: chemisorbed and physisorbed phases

We present a high-resolution UV photoelectron spectroscopy study of 2-mercaptobenzoxazole (MBO) adsorbed on clean Cu(1 0 0), by sublimation in controlled ultra-high-vacuum conditions, at room temperature and at 100 K. The photoemission data show the formation of an MBO layer chemically interacting with the copper substrate. Saturation coverage is achieved at room temperature with the chemisorbed phase, while a physisorbed multilayer is formed at low temperatures on top of the chemisorbed interfacial layer. 2002 Elsevier Science B.V. All rights reserved.

Study of the behavior of protective metal surfaces in the presence of gas by x-ray photoelectron spectroscopy

Abstract Photoelectron spectroscopic studies were made of the surface reactions which can occur on surfaces used for the protective covering of metals. The surfaces of particles of cadmium, zinc, CdO and ZnO, generated by condensation and collected on filters, and kept in contact with SO2 (in various concentrations) for different times, were analysed. The different behaviour of the particles of the metals and of the respective oxides with the formation of new products was shown; and by degassing, the variations in the amount of gas (sulphur dioxide and trioxide) adsorbed physically were shown. In the light of the results the efficiency of the protection of metals was considered.