Effects of surface treatments of AA 2024-T3 aluminum sheet on bonding to epoxy-based film adhesive

Abstract

Abstract Four different surface treatments were performed on aluminum sheets that were then bonded with an epoxy-based film adhesive in an autoclave to achieve good adhesion. Specimens were examined to determine the microstructure of the porous oxide layer on the aluminum sheet surface and its effects on the bonding performance. Based on the failure modes of the bonded surfaces, the peeling strength, and an analysis of the microstructure of the porous oxide layer, this study showed that chromic anodizing the aluminum sheet had the best bonding performance, whereas sulfuric and hard anodizing exhibited the worst bonding performance. Hot etching exhibited a bonding performance somewhere between that of chromic anodizing and that of sulfuric anodizing. The chromic anodizing surface treatment can produce more pores on the oxide layer of aluminum sheet surface, which can enlarge the bonding areas and consequently enhance its bonding performance.