Application of impedance imaging to evaluation of organic coating degradation at a local scale

M Szociński,K Schaefer,K Darowicki

doi:10.1007/s11998-012-9458-y

Abstract

A new approach for evaluating the local electrical properties of organic coatings has been proposed. It was performed with contact mode atomic force microscopy (AFM). A current response signal was measured when a single-frequency voltage perturbation was applied between AFM tip and coated metal. Suitability of the proposed technique has been presented on the representative acrylic coating degraded by two different factors—UV radiation and electrolyte exposure. It was possible to disclose the early stages of the coating deterioration, to spatially localize defective regions, and to observe distinctly different modes of the coating degradation as a result of exposure to various degradation factors.

Highlights

Performance of a protective organic coating depends on the performance of its weakest component
Taylor and Moongkhamklang utilized fluorescence microscopy to address the issue that has not been solved by the local electrochemical methods: whether the transport of water and ions occurs via discrete or regional heterogeneities within an epoxy coating or whether these species enter as a uniform front.[1,2]
The effect of relative humidity on moisture-enhanced photolysis of acrylic-melamine coatings was investigated by Nguyen et al using Fourier transform infrared spectroscopy (FTIR) and yielding complex and structure-specific degradation due to inherently heterogeneous microstructure of the coating.[3]

Summary

Introduction

Performance of a protective organic coating depends on the performance of its weakest component. Electrochemical impedance spectroscopy (EIS) is a popular tool in the field of organic coatings.[12,13,14,15,16,17,18] the investigated region typically engulfs the area of a few centimeters[2] and the results are significantly averaged and provide no or little information about local characteristics of the protective film.

Results

Conclusion