Comparing transport properties of coatings using high throughput methods

A high throughput experimental procedure and analysis method based on electrochemical impedance spectroscopy (EIS) was developed to evaluate barrier coatings. This procedure is designed to generate parameters for bulk coating simulations, as a combinatorial method to rank coatings, and a means of understanding percolation within coating materials. The ability to examine large numbers of samples allows comparison of the variation in coating quality. The procedure begins with a single frequency measurement of the impedances as water is added to the cell. The EIS response is based on water intrusion into the coating. The second stage is a standard EIS spectrum taken after the coating has been exposed to water for an extended period of time and the coating has achieved saturation. Analysis of the time evolution of the single frequency data is accomplished with a computer code written to regress the single frequency impedance to estimate such parameters as saturation volume fraction of water, diffusion coefficient (and any anomalous behavior related to electrolyte transport), and relative dielectric coefficient. The potentiostatic frequency spectrum measures the bulk property of resistivity and pore resistance.