Next-Gen Testing for Aluminum Can Lids: Advanced EIS Techniques for Beverage Can Durability


Devdiscourse News DeskDevdiscourse News Desk | Updated: 31-05-2024 15:10 IST | Created: 31-05-2024 15:10 IST
Next-Gen Testing for Aluminum Can Lids: Advanced EIS Techniques for Beverage Can Durability
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A study from the School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, and Novelis Global Research and Technology Center, Kennesaw, addresses the long-term degradation of aluminum beverage can lids due to the high impact forces during fabrication and the corrosive nature of beverages. The research presents a novel can lid coating testing method using in-situ Electrochemical Impedance Spectroscopy (EIS) monitoring under real-world conditions with actual beverages.

Overview of the Beverage Can Industry

The beverage can industry, valued at 40 million dollars annually, produces over 370 billion cans each year. The introduction of polymer coatings on the inner surface of aluminum cans has significantly mitigated corrosion issues, although not entirely eliminating them. These coatings prevent the metal from imparting a metallic taste to beverages and reducing the corrosiveness of liquids like sodas. Despite advancements, the can lid, more susceptible to corrosion due to its fabrication process, necessitates a thorough assessment of coating efficacy.

Limitations of Traditional Pack Tests

Traditional testing methods, such as the pack test, involve storing cans for several months before analysis, making the process lengthy and labor-intensive. These limitations drive the need for faster and more efficient testing methods. Electrochemical methods, particularly EIS, offer a promising alternative. EIS measures the impedance of the coating, providing insights into its degradation over time. However, previous studies have mostly tested cans without lids and under ambient conditions, which do not accurately reflect real-world scenarios.

To address this, the researchers developed a custom-designed chamber that replicates the conditions inside a beverage can, including carbonation levels and internal pressures. This setup allows for continuous EIS monitoring of can lids under both stressed and non-stressed conditions. The experiments used different polymer coatings, such as lacquers and laminates, and various commercial beverages to assess their impact on the coating's degradation.

Efficiency of the New Testing Method

The study found that laminate coatings generally exhibited superior performance compared to lacquer coatings. Notably, sugary beverages seemed to contribute less to coating degradation, possibly due to a protective mechanism offered by the sugar content. The research demonstrated that this new testing method could effectively simulate multi-month pack tests in a significantly shorter time frame, providing quicker and more insightful assessments of can lid coatings.

The experimental setup involved testing up to 12 lids simultaneously in chambers that maintained specific temperatures and pressures. The EIS measurements tracked key parameters such as pore resistance, charge transfer resistance, coating capacitance, and double layer capacitance. These parameters provided a comprehensive view of the coating's integrity and its interaction with the beverage.

Enhanced Protection by Laminate Coatings

The results indicated that the degradation of coatings occurred primarily within the first 10-20 days, after which the rate of degradation slowed down. Elevated temperatures accelerated the degradation process, highlighting the importance of temperature control in these assessments. The study also compared the performance of different coatings and found that laminate coatings showed lower degradation, validating their superior protective properties.

Additionally, the research explored the impact of different beverages on coating performance. It was observed that sugary beverages resulted in higher pore and charge transfer resistance compared to diet-carbonated beverages, suggesting a potential protective effect of sugar. These findings underscore the importance of considering beverage composition in the assessment of can lid coatings.

Overall, this study presents a significant advancement in the assessment of aluminum beverage can lid coatings. By incorporating real-world conditions and using advanced electrochemical methods, the researchers have developed a robust and efficient testing platform. This method not only provides faster results but also offers valuable insights into the performance of different coatings and their interaction with various beverages. The potential for this method to replace traditional pack tests could lead to improved quality and longevity of aluminum beverage cans, benefiting both manufacturers and consumers.

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