The aluminum used on cans for beverages to avert corrosion is primarily 3004 and 3104 aluminum alloy, selected because of its high corrosion resistance, strength, and light weight. The alloys contain approximately 1% manganese and 1% magnesium, which give them higher oxidation resistance and mechanical toughness. According to industry reports, over 75% of beverage cans worldwide are made from these alloys because they are resistant to acidic beverages such as soda, beer, and energy drinks, which have a pH level between 2.5 and 4.0. The choice of what type of aluminum is used in beverage cans is critical in preventing chemical reactions between the metal and the liquid inside.
Aluminum has a natural oxide coating that initially shields the metal from corrosion but demands additional coatings when long-term storage of a drink is required. There is a film of epoxy or polymer placed internally in the can to prevent contact between acidic drinks and the metallic surface. Lacking such a layer, reactions would lead to metal leaching, flavor alteration, and structural weakening of the can. A study by the Journal of Food Science demonstrated that polymer-coated drink cans extended shelf life by up to 12 months and reduced metal ion contamination.
The aluminum beverage can wall is roughly 0.097 mm thick, thinner than the hair on a human head, but must be able to withstand both the internal pressure of carbonation and the outside world. Carbonated beverages apply an internal pressure of up to 90 psi (pounds per square inch) to the can, nearly three times more pressure than in a car tire. Aluminum would quickly disintegrate without corrosion-resistant alloys to prevent it under those circumstances.
Corrosion resistance is just as vital to efficiency in recycling. Unlike plastics, whose degradation is boosted with every recycling cycle, aluminum maintains 100% of its original property even after several cycles of recycling. The Aluminum Association states that nearly 75% of all the aluminum ever produced is still in use today, primarily due to its anti-corrosive properties and recyclability. It is therefore the material of choice for beverage packaging over plastics and glass, which experience much higher levels of degradation.
Major drink companies such as Coca-Cola and PepsiCo rely on superior-quality corrosion-resistant aluminum alloys in order to ensure their product remains safe, fresh, and long-lasting during shipment and storage. In 2021, Coca-Cola made an announcement to use 50% recycled aluminum on cans by the year 2030, citing how important material efficiency and sustainability were.
Metallurgist and materials scientist Henry Bessemer used to say, “The efficiency of a material is not just in its strength, but in its ability to resist deterioration over time.” This has direct relevance to the use of 3004 and 3104 aluminum alloys, which are long-term corrosion-resistant without compromising cost-effectiveness and environmental friendliness. Choosing the aluminum material used for soft drink cans keeps today’s drink containers light, safe, and resistant to chemical degradation, thus making aluminum the packaging industry norm for longevity.