Electrochemical impedance spectroscopy as a tool for investigating the quality and performance of coated food cans

Abstract

In the present work, electrochemical impedance spectroscopy (EIS) is explored as a tool for evaluating the quality of coatings on food cans. The properties of the coating-metal interface are evaluated using an equivalent electrical circuit representing intact and defect coating areas. The element corresponding to the charge transfer capacitance under pores, proportional to the wetted metal surface, is found to be the most useful element for quality evaluation. It is shown that with EIS, differences can be detected between new and filled cans from different suppliers, as well as between different product formulations. Three measurement techniques, i.e., initial state characterization, rapid dc aging, and long-term electrolyte aging, are applied to a series of petfood and beverage cans, and the results compared with the performance of the same cans after filling and storage. It is shown that all three measurement techniques give basic guidance as to the long-term performance of the filled cans. However, the electrolyte-aging test was found to give the best precision in the performance prediction.