Air-formed and anodized barrier-type aluminum oxides were studied in neutral borate electrolyte as a preliminary investigation into the possibility of using this environment for nondestructive evaluation of aluminum/polymer laminates. Polarization scans on air-formed oxides determined a potential range where the faradaic current was minimized and samples appeared unaffected after several days of exposure. X-ray photoelectron spectroscopy determined that borate exposure, under the prescribed testing conditions, does not permanently change the oxide thickness, and that borate ions are not incorporated into the oxide film. Analysis of the electrochemical impedance spectra of air-formed oxides and different thicknesses of anodized barrier-type oxide films established that the impedance response for all thicknesses could be described by a single-circuit model whose components correspond to a parallel-plate dielectric-filled capacitor.

The electrochemical impedance response of crevice geometries in aluminum/polymer structures is modeled using transmission line circuitry in an approach similar to porous electrode impedance analysis. The equivalent circuit model proposed for edge-exposcd rectangular defects in aluminum/polymer bonds allows the impedance response of a defect to be calculated as a function of defect dimensions, solution resistivity, and exposed planar surface area. Experimcnta] verification of the model is providcd by analysis of the electrochemical impedance spectra of aluminum laminates constructed with known defect dimensions. ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 169.230.243.252 Downloaded on 2015-03-30 to IP

Electrochemical impedance spectroscopy (EIS) is investigated as a potentially nondestructive method to evaluate the dimensions of edge-exposed rectangular disbondments in adhesively bonded aluminum structures. Calculations based on equivalent circuit modeling and experiments conducted on controlled laminate geometries demonstrate that changes in defect parameters such as the depth, width, and thickness have specific quantitatively predictable effects on the impedance spectrum of a defective sample. While the relationships between these effects can be complex, the results indicate that the impedance response of the defective sample can characterize changes in defect geometry. This study extends the theory developed for single defect impedance characterization to multiple defects and investigates the theoretical and experimental capabilities of EIS in the evaluation of multiple defects.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 193.0.65.67 Downloaded on 2015-06-20 to IP