(Invited) Relating Paint Structure to Electrochemical Impedance Spectroscopy

Recent advances in the area of computed tomography (CT) for materials such as paint systems has provided a better understanding of the internal structures of different components that constitute a complicated material like a typical protective paint coating. Recent studies have shown differences in the density of the polymer component and the formation of clustering among inorganic particles. In the case of leachable inhibitors, the dissolution of the clusters dictates the kinetics of release of the inhibitor as well as leaving behind a cluster void through which many species can migrate. In some instances these cluster voids have fractal dimensions well below three. In the current paper the authors use EIS to follow the change in impedance of a pipeline coating during strain including in immersion conditions. This coating consists of a number of inorganic components in an epoxy binder. The same samples have been examined using CT to follow the development of changes in the coating, with a particular focus on the evolution of void space, with respect to the mechanical strain applied to the coating. The EIS data show dispersion effects under conditions, such as environmental exposure, and applied mechanical strain, for which the CT may provide some explanation.