Acoustic characterization of powder coating adhesion

Modern powder spraying techniques now offer the possibility of modifying the surface of an engineering component. One important and often overriding factor is the degree of adhesion between the coating and its substrate. We have deployed a novel method of monitoring the tensile failure of the powder coating-substrate interface using the reflection of ultrasonic signals from the interface. These changes may be related to the strain of the coating under loading as well as the initiation and propagation of interfacial delamination or damage. The sensitivity of the acoustic method makes it an ideal way to monitor stress relaxation or creep processes as well as the impact of loading and unloading the sample. In this paper, we describe how the method was applied to the pure tensile mode testing of the powder spray coating's adhesive bonding strength.