Soda cans consist mainly of 3004 aluminum alloy (1.0%-1.5% manganese, 1.0%-1.5% magnesium), whose tensile and yield strengths are as much as 285-400MPa and ≥200MPa respectively. Cold rolling process causes the can wall thickness to fall to 0.097mm±0.003mm, hence reducing the weight of regular 330ml cans to 9.8 grams. 42% lighter than it used to be in the 1990s. Ball Corporation’s “Ultra-Thin wall technology” utilizes H19 hardened processing to maintain the axial pressure capability of the tank at 90psi (approximately 620kPa), reduce the thickness of the tank bottom from 0.45mm to 0.28mm, reduce the aluminum used in a single tank by 19%, and save more than 250,000 tons of aluminum per year worldwide. According to the International Aluminum Association (IAI), 3004 alloy’s break elongation (≥8%) and corrosion resistance (3,000 hours of salt spray test without corrosion) are the reasons it is the best choice to provide lightness with toughness.
In the lid part, 5182 aluminum alloy (magnesium 4.0%-5.0%) is widely used because of its high hardness (Vickers hardness ≥110HV), its tensile strength ≥380MPa, can withstand the local stress peak when the lid is opened (about 150MPa), and the thickness is controlled at 0.21mm, 17% thinner than the traditional 5052 alloy. Crown Holdings’ Deep Stamping technology uses multi-step die drawing technology to increase the Blank Diameter/Punch Diameter ratio of 5182 aluminum caps from 2.0 to 2.5, increasing production efficiency by 30% and producing 120,000 can caps per hour on a single line of production. Breakage rate is less than 0.005%. For example, after being put into practice at the European bottling plant of Coca-Cola, the weight of the lid went down from 1.2 grams to 0.9 grams, saving more than $18 million annually in logistics costs.
In recycling, the strength properties of recycled 3004 alloy (with 85% recovered aluminum) reduce by just 3%-5%, while the production cost is 23% lower compared to virgin aluminum. Novelis’s closed-loop recycling technology reduces the tank recycling cycle to 60 days, whereas the carbon footprint of recycled aluminum (0.8 tCO2e/t) is a mere 5.7% of primary aluminum (14 tCO2e/t). European Union’s “Packaging Materials Recycling Act” has a regulation for the percentage of recycled aluminum content in cans of beverage to be ≥50%, which has resulted in making businesses optimize the alloy ratio – increasing 0.1% copper element to offset the loss of strength of the recycled aluminum in an attempt to decrease the rate of fluctuation of the tank’s compressive strength from ±5% to ±1.2%.
In practical application, the “ultra-light tank” released in 2023 by Pepsi utilizes 3004-RSS aluminum alloy with silicon content of 0.3% and again reduces the tank wall thickness to 0.085mm, reduces the weight to 8.5 grams, increases anti-corrosion capacity by 40% by employing nano coating technology with 0.05μm thickness, and reduces cost by 15% for inner coating. Japan Daiwa tank’s “dynamic sealing technology” generates micron-level oxide layer (2-5μm thickness) on the surface of 5182 aluminum cap, which increases the sealing strength to 45N/15mm and decreases the gas leakage rate from 0.03% to 0.001%. According to McKinsey, beverage can production lines constructed with the optimized aluminum reduce energy and carbon emissions by 18% and 27%, respectively, as well as meeting the high standards of the FDA Food Contact Materials Standard (CFR 21) and the EU’s EN 602 regulation.
Future innovations include Ardagh Group’s “nanocrystal aluminum alloy” (grain size ≤50nm), which test results show is capable of 600MPa tensile strength and tank wall thickness can be decreased further to 0.065mm, but mass production cost is now 42% higher than conventional 3004 alloy. Alcoa’s “self-healing coating technology,” which uses microcapsules that release anti-corrosion ingredients, can extend tank life to 10 years and will change the technical standard for type of aluminum in soda cans when it is launched in 2030.