Impedance characterization of the electrochemical environment under a polymer film artificially delaminated

Knowledge of the electrical conductivity of the zone under a delaminated paint film is one necessary input parameter for the simulation of electrochemically driven underpaint corrosion. In this work, a microelectrode array system has been developed, tested, and applied to measure the spatial distribution of resistivity in the delaminated zone along the metal/polymer interface. The experimental device consists of a linear array of six 100 μm diameter stainless steel microelectrodes (100 μm in diameter) embedded in a steel substrate. A polymer coating was applied and an artificial “delaminated zone” was created using the laser-induced decohesion technique. The electrochemical impedance was measured between the first uncovered electrode and the electrodes at progressively increasing distances in the artificial delaminated zone. A steady decrease in the impedance with time can be observed, probably due to the continued ingress of electrolyte and a variation of the gap width.