A method for evaluating commercially applied organic coatings must consider the observed distribution of coating performance for a given population. A sample of cans was examined using electrochemical impedance spectroscopy (EIS). The low-frequency impedance (the impedance between 0.01 Hz and 1 Hz) measured during the first month of exposure was analyzed statistically and used to evaluate performance of three coating populations. To verify EIS results, comparison was made to an 8-week analysis of aluminum concentration in solution and to visual observations at 8 months. Statistical analysis of EIS data and visual observations agreed well. Coating performance was related to chemistry and cure schedule.

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NACE International
1997
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