Aluminum Beverage Can Lid Testing Method Under Real Conditions with EIS Online Monitoring

The coatings on aluminum beverage can lid interiors can be prone to long-term degradation due to the high impact forces during fabrication and the corrosive nature of beverages. Multi-month tests are required to assess their resistance to this degradation. The purpose of this work is to introduce an accelerated can lid testing method with online Electrochemical Impedance Spectroscopy (EIS) monitoring under real conditions and with real beverages that can imitate the lengthy pack tests typically employed. Twelve reactors were constructed and incorporated in a testing setup, EIS spectra were collected and analyzed using equivalent circuit models. The effect of test duration, pressure, temperature, and beverage on the degradation of the lids were investigated. The results showed that both temperature and pressure accelerate degradation. In addition, 10-day accelerated tests with EIS online monitoring were compared to 10-day and 6-month pack tests. Metal Exposure and aluminum concentration from the pack tests were correlated with the pore resistance, the charge transfer resistance, and the double layer capacitance of the lids extracted from the EIS spectra. The developed method has the potential to mimic the multi-month pack tests and offers a quicker, more insightful, and less laborious alternative for the lid degradation assessment. Ultimately, this method could help in improving the longevity and quality of aluminum beverage cans.