Surface pretreatments for optimised adhesive bonding

Abstract In optimising both the initial strength and long-term durability of bonded joints, a ‘system’ approach must be taken, i.e. the substrate(s)/surface pretreatment(s)/adhesive/primer combination must be considered. In this system, the role of the pretreatment on each substrate is to create a functionalised, wettable surface which is free from the presence of weak boundary layers. A particular surface pretreatment might also confer other desirable properties such as microtexture or nanotexture and, in the case of metallic substrates, corrosion resistance. The importance of optimising surface pretreatment is highlighted by the fact that, when bonding some polymers, initial levels of adhesion can be increased by at least a factor of 10, compared to no treatment being used. In the case of metallics, the pretreatment can provide a significant increase in joint durability, thereby enabling bonded metallic structures to survive in harsh environmental conditions for many decades. Without optimised pretreatments, such performance would not be possible. This section provides an overview of the surface processing methods which might be considered for use on key engineering materials.