Metal-adhesive interface, formation

The surface preparation must enable and promote the formation of bonds across the adherend/primer-adhesive interface. These bonds may be chemical (covalent, acid-base, van der Waals, hydrogen, etc.), physical (mechanical interlocking), diffusional (not likely with adhesive bonding to metals), or some combination of these (Chapters 7-9). 

The ability to modify the metal-ceramic interface in nanocomposites by the formation of intergranular films holds exciting prospects. From a thermodynamic point of view, the existence of a film at equilibrium indicates a lower interface energy than an interface without a film. This indicates the potential to increase the adhesion of interfaces, although experimental investigations are required to fully evaluate this effect. However, the promotion of particle occlusion due to the presence of the films has been shown,28 and this means that a new method to modify and control the microstructural evolution of nanocomposites is available, as discussed in the next section. 

Two principle mechanisms that are discussed as possible corrosion protection mechanisms on mild steel are discussed in short. ICPs may induce the formation of a passive oxide [206]. The ICP will be reduced as a consequence of passivation and will be reoxidized by oxygen reduction. Consequently, the ICP may promote the cathodic oxygen reduction on the polymer surface rather than at the metal-polymer interface. On the basis of the good corrosion results gained by the combination of a molecular adhesion promoter and the subsequent electrodeposition of the polymethylthiophene film Rammelt and coworkers [207] concluded that the essential aspect of the corrosion protection by ICPs could be the local separation of iron oxidation and oxygen reduction. This would eliminate the local pH increase at the metal surface and subsequent cathodic disbondment. 

Particularly, the formation of new chemical bonds at a metal-polymer interface has recently gained a lot of attention, thanks to development of surface analytical tools. In this connection, photoemission spectroscopies (XPS, UPS) have been extensively used. The adhesion is related to bond formation between the metal atom and the functional groups at the polymer surface. The presence of oxygen containing groups is found to lead to the formation of metal-oxygen-polymer complexes and to increase the adhesion. ... 

The outer portions of the underside of the metal trace become bronze colored. As the bond formation interaction progresses across the entire metal strip, a uniform bronze hue is achieved. In region B the metal/polymer adhesion is developed completely and no deleterious effects are observed. During this stage, adhesion at the metal lymer interface is predominately due to oxygen-aided chemical bonding between copper and polyetherimide l A Finally, in region C, overoxidation or thermal destruction of the chemical portion of the... 

Find et al. [25] developed a nickel-based catalyst for methane steam reforming. As material for the microstructured plates, AluchromY steel, which is an FeCrAl alloy, was applied. This alloy forms a thin layer of alumina on its surface, which is less than 1 tm thick. This layer was used as an adhesion interface for the catalyst, a method which is also used in automotive exhaust systems based on metallic monoliths. Its formation was achieved by thermal treatment of microstructured plates for 4h at 1000 °C. The catalyst itself was based on a nickel spinel (NiAl204), which stabUizes the catalyst structure. The sol-gel technique was then used to coat the plates with the catalyst slurry. Good catalyst adhesion was proven by mechanical stress and thermal shock tests. Catalyst testing was performed in packed beds at a S/C ratio of 3 and reaction temperatures between 527 and 750 °C. The feed was composed of 12.5 vol.% methane and 37.5 vol.% steam balance argon. At a reaction temperature of 700°C and 32 h space velocity, conversion dose to the thermodynamic equilibrium could be achieved. During 96 h of operation the catalyst showed no detectable deactivation, which was not the case for a commercial nickel catalyst serving as a base for comparison. 

Clustering of water at the metal-polymer interface and the subsequent formation of an electrochemical double layer can occur only if the adhesion between metal and coating is weaker than the bond between metal and water or pol5mier and water. For a proper evaluation, however, a distinction must be made between wet adhesion and osmotic blistering. 

A marked increase in aluminum Ep values towards anodic potentials was observed in the presence of marcescens, even in the sterile medium, suggesting the metal surface may experience some protective action by these bacteria. Local acidification enhanced by adhesion processes taking place at the metal/mycelia interface accounts for some of the specific effects of resinae in the corrosion process of aluminum alloys in fuel/water systems (Salvarezza et al., 1979). The acidification also has been reported in the literature as a differential effect between two Pseudomonas spp. in relation to aluminium corrosion. Acidity can prevent repasivation and may hinder the formation of a protective oxide film. Therefore, under acidic conditions, pitting of the metal by chloride anions occurs at more cathodic potentials than in neutral solution (Salvarezza et al., 1983). 

Abstract Proper treatment of an adherend surface is one of the most important factors in assuring high initial strength and extended durability of high-performance adhesive joints. There are several requirements for a good surface preparation (1) The surface must be cleaned of any contamination or loosely bound material that would interfere with the adhesive bond. (2) The adhesive or primer must wet the adherend surface. (3) The surface preparation must enable and promote the formation of chemical and/or physical bonds across the adherend/ primer-adhesive interface. (4) The interface/interphase must be stable under the service conditions for the lifetime of the bonded structure. (5) The surface formed by the treatment must be reproducible. In this chapter, high-performance surface treatments for several metals and other materials are discussed. Surface treatments of aluminum and other metals are used to illustrate how proper surface preparations meet these requirements. 

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