Publications

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In this work corrosion products present on Vietnamese archaeological bronzes from the Dông Sôn period are investigated using several complementary surface analysis techniques. An image with the accompanying depth profile of the different elements within the corrosion layer (Cu, Pb, Sn, O, Si, Al, Cl) was obtained by means of scanning electron microscopy—energy dispersive X‐ray analysis (SEM‐EDX). Raman spectroscopy revealed the presence of azurite, atacamite, and lead white in the corrosion layers. From X‐ray photoelectron spectroscopy (XPS) it is found that lead and tin are present as oxides, the chemical state of copper could not be determined univocally: copper is present as pure Cu or as copper oxide. On the basis of the SEM‐EDX measurements the samples are sorted according to a classification proposed by Robbiola et al . in literature. Copyright © 2008 John Wiley & Sons, Ltd.

The electrolyte film thickness condensation and evaporation is an important parameter for complexity of atmospheric corrosion. Atmospheric corrosion rate of zinc at the west coast of Singapore was measured for one year using an electrical resistance monitoring system. The analysis of the data reveals that significant corrosion rates only occur at specific hours on dry days. The beginning of this period corresponds to falling temperature and rising relative humidity resulting in the formation of a film of moisture on the zinc surface and the end corresponds to a point that this film dries as the temperature increases. This finding allowed the drying rate of the moisture film to be estimated for input into a moving boundary simulation model of the galvanic corrosion in scratched and zinc coating samples. The simulation results showed that the maximum corrosion rate occurs at electrolyte thickness of about 8 μm. Moreover, the simulation suggested that cut-edge is a more harmful defect than scratch, which was confirmed by the appearance of iron corrosion products on atmospheric exposed cut-edge samples whereas scratched samples were not corroded after one week of exposure. Finally, moving boundary simulation allowed to predict the changes to the geometry of the corroding electrodes.

Thin silane films with the incorporation of nano-dispersed CeO2 particles have been deposited by dip-coating over aluminium substrates. The silane molecule under investigation is bis-1,2-(triethoxysilyl)ethane (BTSE), which has been used as a water-based solution in order to fulfill the industry need for reducing the impact on human health and environment. The influence of the nano-oxides on the silane was first analyzed in the solution by means of 29Si NMR, which showed that the ageing and stability of BTSE are not affected by the presence of CeO2 nanoparticles in the silane matrix. The chemical interactions between CeO2 nanoparticles and the BTSE in the cured coating were investigated by XPS, and the results pointed to the possible formation of a bond between Ce and Si. Field emission scanning electron microscopy (FE-SEM), field emission Auger electron spectroscopy (FE-AES) and focused ion beam coupled with transmission electron microscope (FIB–TEM) were used to investigate the film structure and surface morphology. A major challenge in the formation of thin layers with the incorporation of nano-oxides is to avoid the formation of particles agglomeration, which affects the film uniformity and might create preferential paths for corrosion attack. This issue has been overcome and the resulting films appear uniform and homogeneous, with the nanoparticles well embedded in the silane matrix and always covered by a thin silane layer. Electrochemical impedance spectroscopy (EIS) measurements have been performed on the samples and the results show how the barrier properties of the thin silane films are improved by the addition of CeO2 nano-dispersed particles.

Organic coatings are often required for the protection of metals against environmental degradation. Despite their extensive use, only limited information is available on the initial stages of adsorption and formation of protective films, especially at the molecular and atomic levels. As a model system for coating formation, this study investigates the adsorption of glycerol molecules on the single-crystalline Cu(111) surface. A combined electrochemical and scanning tunneling microscopy study in NaOH aqueous solution enabled following the adsorption process in detail, providing molecular information on the glycerol film structure. A potential-driven adsorption of glycerol was observed, suppressing the adsorption of hydroxyl molecules and copper oxidation. The adsorbed species assembled in a nearest neighbor arrangement fitting a (√3 × √3) R30° hexagonal structure with respect to the Cu(111) lattice. This experimentally observed configuration was confirmed by density functional theory (DFT) calculations. DFT modeling indicates that a mixed adsorption mode involving the two primary alcohol groups adsorbed at different z-positions relative to the surface is the most favorable. This mixed configuration enabled the formation of an extended network of hydrogen bonds that aids in stabilization of the glycerol film. This implies that interactions between glycerol molecules have a non-negligible effect on the growth process of such an organic film, allowing the formation of organic layers in the absence of strong interfacial interactions.

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This study investigates the effect of different alkaline, acidic and thermal pre-conditioning treatments applied to different Al alloy surfaces. The obtained results are compared to the characteristics of Zr-based conversion coatings that were subsequently generated on top of these substrates. Focus is laid on typical elemental distributions on the sample surfaces, in particular on the amount of precipitated functional additives such as Cu species that are present in the substrate matrix as well as in the conversion bath solutions. To this aim, Field Emission Auger Electron spectra, depth profiles and surface maps with superior local resolution were acquired and compared to scanning electron microscopy images of the sample. The results show how de-alloying processes, which occur at and around intermetallic particles in the Al matrix during typical industrial alkaline or acidic cleaning procedures, provide a significant source of crystallization cores for any following coating processes. This is in particular due for Cu-species, as the resulting local Cu structures on the surface strongly affect the film formation and compositions of state-of-the-art Zr-based films. The findings are highly relevant for industrial treatments of aluminium surfaces, especially for those that undergo corrosion protection and painting process steps prior to usage.

Within the group of self-healing materials, research on self-healing coatings has been performed for about 15 years either only on polymeric materials or on corrosion inhibitors. This chapter is begins with a discussion of the most relevant publications in both fields including important analysis and coating application techniques. In the second part we present the results achieved so far in combining these two fields into more effective and robust coating systems.

This work aims at the elucidation of the interfacial interactions established between an epoxy-amine coating and hot-dip galvanized (HDG) steel. The influence of the Zr-based conversion treatment of the substrate and the use of the Cu(II) additive on interfacial bonding is studied. To this purpose, an amine-functionalized molecule – diethylenetriamine (DETA) – is adsorbed. The complex multi-metal oxide surface of the Cu-modified Zr-based converted substrate is decomposed in derivative (simpler) systems. The resulting DETA-adsorbed model and multi-metal surfaces are investigated by X-ray photo-electron spectroscopy (XPS), and by examination of the N 1s peak, the interfacial bond density is determined. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is performed to discriminate between the different metal oxide contributions present on the substrate surface. Preferential adsorption of the DETA molecule on the zinc atoms is found on converted substrates. The interfacial bonding with the Cu cationic sites introduced by the copper additive is proven.

No abstract is provided for this article.

No abstract is provided for this article.