MEASURES TO PREVENT STRESS CORROSION CRACKING OF ALUMINUM CANS FOR CARBONATED BEVERAGES

Common containers for carbonated beverages are PET bottles and aluminum cans. These different materials are chosen based on marketing and convenience reasons. While the shelf life of carbonated beverages packed in PET bottles is affected by the CO2 permeation through the polymer matrix, aluminum cans allow the gas retention and guarantee a higher quality during storage. Indeed, the shelf life of canned carbonated beverages is commonly >= 1 year. While the longer commercial life is an advantage from a commercial point of view, it increases the probability of occurrence of failure due to corrosion. Stress Corrosion Cracking (SCC) occurring from the outside of the can would prejudice the integrity of the container, provoke the product loss and, what is probably worst, could determine a chain-effect on other adjacent cans if the product is spilled from the damaged can. Normally, aluminum cans are internally lacquered for protecting the metal from corrosion by the food components. Chlorine from the conditioning water bath and storage environmental moisture determines the onset of SSC, while temperature and internal gas pressure speed up the failure of cans. This study aimed at evaluating the potential of a supplementary outer enamel for preventing stress corrosion cracking, and proved that this measure, which does not imply significant process changes or supplementary costs, could effectively reduce the risk of product loss, with consequent need for damaged products withdraw and disposal, and prejudice for the image of the producer.