Alternating Current (AC) Impedance Testing of Coated Traycans

Abstract

Abstract : This is the final report on Cortest Columbus Technologies' program entitled 'AC Impedance Testing of Coated Traycans', performed under Contract DAAK60-90-1301. The overall objective of the program was to evaluate the relative resistance of several candidate coatings prior to retorting to a solution containing NaC1 and citric acid (simulating saline, acidic food product) at ambient temperature. An additional objective of the program was to perform an initial assessment of the applicability of the AC impedance technique as a quality assurance technique for traycan coatings. The performance of the coatings was evaluated by means of an Electrochemical Impedance Spectroscopy (EIS) technique, also referred to as AC impedance. The EIS technique was found to be a sensitive technique for measuring coating degradation on the traycans. Of the coatings analyzed, the VMC coating, in general was found to be the best performer, followed closely by DMS and VMS. The control coating as found to be the poorest coating, of the coatings analyzed. No measureable effect of forming the corners of traycans on coating performance was found in the study. The EIS technique is promising for quality control but further research is needed to optimize the analysis time and simplify the test technique.