|
A study of the mechanisms of interaction of 1,2-diaminoethane with aluminium surfaces covered with a native oxide film will be presented as a case example of the importance of understanding bonding mechanisms to control practical properties such as adhesion or corrosion performance. Di-amines are used both as hardeners in epoxy glues and corrosion inhibitors. When an epoxy adhesive is brought into contact with a metal, the formation of a region with finite volume and distinct properties (or a gradient of properties), called the interphase, is observed. It is generally admitted that the performance of adhesive bonds is strongly influenced by the properties of the interphase and extensive work has been devoted to understand its formation. In particular, specific interaction between the amine hardener and the metal surface, leading to dissolution of the oxidized metal surface by the amine hardener, has been proposed as the first step in the formation of the interphase. On the other hand protection of metal surfaces against corrosion by di-amines is often ascribed to adsorption of these molecules onto the oxidized metal surface which leads to blocking of the active sites and avoids dissolution of the metal into the electrolyte. A combined XPS, spectroelectrochemistry and atomic emission spectroscopy (ICP-OES) study of the interaction of 1,2-diaminoethane with oxidized aluminium surfaces will show that such a contradictory behaviour between protection by adsorption and dissolution can be ascribed to differences in the mechanisms of interaction of the amine molecule with the surface. |