Lewis Acid/Lewis Base Effects in Corrosion and Polymer Adhesion at Aluminum Surfaces

Lewis acid/Lewis base (electron acceptor/electron donor) interactions are important in the breakdown of oxide films on aluminum by chloride ions and in the adhesion of organic polymers onto oxide-covered aluminum surfaces. This paper considers the pitting of aluminum by (a Lewis base) in terms of the acid-base nature of the oxide film. Topics addressed are the adsorption of on oxide films on aluminum, the effect of pH on the pitting potential of aluminum, and the pitting potential of various pure metals or surface-modified aluminum. Lewis acid/Lewis base interactions are also important in the adhesion of polymers to oxide-covered metal surfaces, as shown by experimental adhesion tests. The adhesion strength of a basic polymer poly(methyl methacrylate) was greatest on the most acidic oxide films. The adhesion strength of an acidic polymer (a commercially available pressure-sensitive adhesive) was the greatest on the most basic oxide films.