Two-electrode electrochemical impedance spectroscopy at polymer/oxide interfaces

This work presents an interfacial two-electrode electrochemical impedance analysis of the ingress of water and the resulting formation of an interfacial electrolyte layer at the adhesive film/oxide interface. For this approach, interdigitated oxide-covered aluminium electrodes were deposited on glass substrates by physical vapour deposition and coated with a free-standing epoxy adhesive film. The obtained results were compared to the impedance analysis of the adhesive film using a three-electrode setup. Based on this approach, the influence of short-chain adhesive promoters such as 3-aminopropylphosphonic acid (APPA) and (3-aminopropyl)triethoxysilane (APTES) on the wet-adhesion of the adhesive could be investigated. The surface chemistry was analysed via polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) and X-ray photoelectron spectroscopy (XPS). The results indicate that the interfacial disbonding process caused by water ingress can be monitored using the two-electrode setup. Moreover, the effect of molecular adhesion promoters on the wet-adhesion of adhesives can be studied based on this approach. Possible applications include atmospheric corrosion monitoring or biosensing. • Two-electrode EIS setup enables direct analysis of polymer/oxide interfaces. • Monitoring of water ingress and disbonding in real-time via impedance. • Adhesion promoters APPA and APTES increase interfacial impedance in epoxy/Al system.