Introduction

The successful performance of many every-day products, and many common materials and construction techniques, is dependent upon adequate adhesion between two or more constituents. Most engineers, however, have only the haziest of ideas about the whole concept of adhesion. For to know ‘how’ to prepare substrate surfaces for bonding does not necessarily require a knowledge of ‘why’ adhesive materials should stick to them. It is the intention of this chapter to connect theory with practice, to enable the reader to appreciate ‘why’ before discussing aspects of surface pretreatment pertinent to applications of adhesives in construction.

The strength of bonded assemblies depends not only on the cohesive strength of the adhesive, but also on the degree of adhesion to the bonding surface. One of the disadvantages of adhesive bonding as a method of fastening is that the surfaces need to be clean and, whatever their chemical nature, coherent if a satisfactory degree of contact, and therefore adhesion, is to be obtained. Frequently the adhesive itself is wrongly blamed for ‘not sticking’, but the general source of trouble lies with the surface pretreatment. The use of cold-cure epoxies generally necessitates the careful preparation of metallic adherends in particular, to ensure satisfactory long-term performance. Indeed, whatever the nature of the substrate, or the adhesive to be used with it, its pretreatment is probably the single most important aspect of the bonding operation.