Publications

The interfacial bonding properties of carboxylic polymers on a Zn substrate have been investigated. Poly(methyl vinyl ether-alt-maleic acid monobutyl ester) and cured propoxylated bisphenol A fumarate unsaturated polyester were applied on a set of differently treated Zn samples. The buried metal–polymer interface was studied by polymer removal and evaluation of the residue layers on Zn surfaces representing the metal–polymer interface region. Additionally, the interfacial bondings were mimicked by adsorption of the representative carboxylic monomers, i.e., succinic and myristic acids. The differently treated Zn surfaces were found to be capable of adsorption of the carboxyl functionality of the polymers, resulting in formation of carboxylates. A comparison of the interfacial bondings by the residue layers of the polymers with those formed due to the molecular adsorption showed comparable adsorption mechanisms. Additionally, it was found that the polymer–metal interfacial bonding density mainly depends on the Zn surface hydroxyl fraction, while Zn oxide semiconductor properties play an important role when a curing process occurs during the polymer interaction with Zn surfaces.

The purpose of this article is to re‐examine Theophilus' and Cellini's recipes, to understand what they were used for and to find out whether they could have been used for the Notre‐Dame shrine of Huy (Rheno‐Mosan art, 13th century). A historical sample (the statuette of St Jacques the Major of the Notre‐Dame shrine) was studied with X‐ray fluorescence (XRF) in order to determine the presence of iron at its surface. The preparation of model samples gave the opportunity to study Cellini's recipe better. These model samples were characterised with colorimetric analysis, scanning electron microscopy–energy dispersive X‐ray (SEM–EDX) analysis and AES. It is observed that applying Cellini's recipe results in a colour change, due to the presence of iron and oxygen at the surface of the samples. The presence of iron at the surface of both the model samples and the statuette of St Jacques is a good indication that the recipe may have been used on the statuettes of the Notre‐Dame shrine of the Collegiate of Huy. Moreover, it is shown that the iron is not influenced by the artificial ageing of the model samples. The possible use of Cellini's recipe for changing the colour of gilding is a very new point of view to consider middle‐age shrine. The practical implications for restoration are that it is important not to change the oxidation state of the iron and so the gilding colour. It is recommended to remove the black coating on the statuette's surface but without using techniques like, e.g. EDTA baths. Copyright © 2008 John Wiley & Sons, Ltd.

This research investigates the deposition mechanism of a hybrid Zr-aminosilane conversion coating as a replacement for the conventional pretreatment systems on a zinc substrate. The traditional Zr-based conversion treatment has been optimized by the addition of both Cu as an accelerator and aminosilane as an adhesion promotor. The deposition mechanism was unraveled using complementary surface analytical techniques such as XPS, FEG-AES, EDX, GDOES, and ToF-SIMS. The results showed the addition of aminosilane has resulted in the incorporation of N into the Zr oxide layer. This suggests that the influence of aminosilane is not only on the top surface, as an adhesion promoter, but also on the chemistry of the deposited layer. Additionally, the properties of this pretreatment on zinc is compared to Advanced High Strength Stainless Steel (AHSSS) as another automotive material. This was done in order to compare the behavior of active and passive substrates in the same conversion treatment. This comparison shows that zinc as an active material can show higher interaction with the conversion treatment which results in a ticker film formation.

Self-healing polymer coatings are a type of smart material aimed for advanced corrosion protection of metals. This paper presents the synthesis and characterization of two new UV-cure self-healing coatings based on acrylated polycaprolactone polyurethanes. On a macroscopic scale, the cured films all show outstanding mechanical properties, combining relatively high Young's modulus of up to 270 MPa with a strain at break above 350%. After thermal activation the strained films recover up to 97% of their original length. Optical and electron microscopy reveals the self-healing properties of these coatings on hot dip galvanized steel with scratches and microindentations. The temperature-induced closing of such defects restores the corrosion protection and barrier properties of the coating as shown by electrochemical impedance spectroscopy and scanning vibrating electrode technique. Therefore, such coatings are a complementary option for encapsulation-based autonomous corrosion protection systems.

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An optical modeling procedure is developed to predict and model the colour of electro-coloured anodized aluminium that has been modified in pore structure for the generation of interference colours. The relation between the multi-layered, nano-sized oxide microstructure and the colour is experimentally determined and translated into an optical model that is able to predict the colour as a function of microstructural variations. The optical modeling procedure is highly sensitive to changes on the nano-scale (porosity, percentage of metal deposition, presence of barrier regrowth…), and has high potential as a predictive tool to relate the microstructure of a surface to the final colour characteristics of the metal, and as such to the used electrolytic processing conditions.

Medieval chemical coloration revealed by XANES measurements on the silver gilded statuettes from the Holy Lady Shrine, 13^th century. It is from the Holy Lady collegiate church in Huy, Belgium.

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In order to increase the sustainability of metals, a more detailed understanding of the corrosion phenomenon is of crucial importance. In current literature, corrosion is often considered as a purely chemical interaction with nearly exclusive dependence on compositional effects, whilst ignoring the microstructural features of the metal surface. In the present work, results are presented which illustrate both the role of grain orientation and grain boundaries in the corrosion process. To evaluate the grain orientation dependent electrochemical behavior, polycrystalline Cu, was brought into contact with a corrosive electrolyte. Subsequently, the attack was evaluated by measuring the surface with both Atomic Force Microscopy (AFM) and Electron Backscatter Diffraction (EBSD). It was demonstrated that the grain orientation itself did not significantly influence the corrosion kinetics, but, alternatively, that the orientation of the neighboring grains seemed to play a decisive role in the grain dissolution rate. To increase understanding on the role of grain boundaries, a method was developed based on the electrochemical (galvanic) displacement of gold, which is deposited from an aqueous solution on a pure copper substrate. This technique demonstrated its sensitivity to the grain boundary characteristics as far less gold was deposited on special boundaries, such as coincidence site lattice boundaries, as compared to the random high angle grain boundaries.

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Sodium silicate solutions, also known as ‘water‐glass’, are used for a wide variety of applications. In particular, they are commonly used in pre‐treatments of aluminum alloys as cleaners and corrosion inhibitors. Silicate films are known to be promising for corrosion protection and to confer high hydrophilicity. One of the main issues in the study of the formation of silicate films on metal oxides is the complexity of the anionic speciation in aqueous solution. In this work, the mechanism of sodium silicate interaction with porous anodic alumina and its dependence on the solution characteristics is studied by means of Fourier transformed infrared spectroscopy (FTIR). Grazing angle‐FTIR and attenuated total reflection‐FTIR are used in order to monitor the chemical changes occurring with time on the surface upon silicate adsorption. The effect of the SiO 2 /Na 2 O molar ratio and the temperature is studied. The role of rinsing is investigated when the alumina surface is washed in water after the silicate treatment. A chemical description of the phenomena occurring during silicate treatment is given. Copyright © 2013 John Wiley & Sons, Ltd.

Electrochemical impedance spectroscopy (EIS) is a very popular technique to investigate the corrosion behavior of metals and alloys in electrolytes. To interpret the EIS data, an equivalent electrical circuit (EEC) is built and the corrosion behavior can be explained on the basis of the values obtained for each element of the EEC after fitting the impedance data. Hence, the reliability of the interpretation greatly depends on the selection of the EEC for the impedance modeling. In this work, odd random phase electrochemical impedance spectroscopy (ORP-EIS) is used to investigate the corrosion behavior of Zn, Zn-Al and Zn-Al-Mg hot dip coated steel wires in 0.1 M NaCl. ORP-EIS uses a multisine excitation signal to obtain the impedance response of the electrochemical system. It is faster than conventional EIS as well as provides accurate information about linearity, stationarity and noise distortions of the system during the measurement. This is used to optimize the experimental conditions and to evaluate the correctness of the data modeling. The corrosion behavior of the metallic coated steel wires is quantified by EIS modeling. The validity of the proposed EEC is assessed based on the physical phenomena as well as the statistical evaluation of the modeling results.