In the joining of metals there is a growing use of the family of advanced methods for solid state bonding, which includes friction welding and diffusion bonding. With these joining techniques a new range of quality and inspection problems are encountered. These problems, in particular for diffusion bonds, have become well known and there are the requirements for inspection techniques which can be used to give data to correlate with the bond’s mechanical strength. Various studies [1,2,3] have considered the destructive examination of bonds and categorised these in terms of characteristics seen in an examination of micrographic sections. A range of ultrasonic studies have also been undertaken [4,5,6], however conventional C-scan techniques have yet to be shown to provide the required reliable bond characterisation.