The modern beverage can is a complex piece of engineering, designed to be lightweight, durable, and capable of withstanding the internal pressure of carbonated drinks. This container is constructed from specialized metal alloys and advanced polymer coatings. The distinct materials and components work together to protect the contents and ensure consumer safety.
The Primary Material: Aluminum and Steel
The vast majority of soda cans are made from aluminum, favored for its lightweight nature and superior malleability, which allows manufacturers to form the can body through a process called drawing and ironing. The aluminum alloy typically used for the can body is from the 3000 series (such as alloy 3004 or 3104), fortified with small amounts of manganese and magnesium to enhance strength and formability. This finished can body uses two-piece construction, meaning the body and the bottom are formed from a single, seamless piece of metal, which is highly effective for holding carbonation pressure.
While aluminum dominates the beverage industry, steel is still used, particularly in some parts of Europe and Asia, and for certain non-carbonated drinks. Steel cans are commonly made from tinplate, a thin sheet of steel coated with a layer of tin for corrosion resistance. These steel containers often use three-piece construction, where a flat sheet is rolled and welded into a cylinder, and separate ends are seamed onto the top and bottom. The choice between the two materials often depends on regional preferences, cost, and the specific requirements of the beverage.
The Engineered Components: Can Ends and Tabs
The top section, known as the can end or lid, is a separate, highly engineered component that must be sealed to the can body after filling. This part is typically made from a different aluminum alloy than the body, often from the 5000 series (such as alloy 5182). This alloy contains a higher percentage of magnesium, making it harder and stronger than the body material. This strength enables it to withstand the stresses of the sealing process and the internal pressure of a carbonated drink.
The pull tab, the mechanism for opening the can, is also made from an aluminum alloy, sometimes a slightly different composition like alloy 5052, and is attached to the end with a rivet. The tab works by leveraging a precisely scored line in the lid, an area of intentionally reduced thickness designed to break cleanly under the force applied by the consumer. This stay-on tab design prevents the tab from being fully detached and has become the standard for reducing litter.
The Inner Layer: Protective Linings
A non-metal layer is applied to the can’s interior to prevent the contents from reacting with the metal, which is necessary for safety and flavor preservation. Acidic beverages, like most sodas, would quickly corrode bare aluminum or steel, causing the metal to degrade and imparting an undesirable metallic taste to the drink. This protective lining acts as a barrier, ensuring the drink’s flavor profile remains consistent.
Historically, this lining was an epoxy resin that contained Bisphenol A (BPA), which provided a durable barrier against corrosion. In response to consumer concerns, the industry has significantly shifted away from BPA-based linings toward alternative polymer coatings. Current non-BPA internal coatings, referred to as BPANI (Bisphenol A non-intent), include materials like acrylics, polyesters, and new generations of BPA-free epoxy-like polymers. These modern linings are spray-coated onto the can interior and cured at high temperatures to form a thin, seamless film.
Why These Materials Are Chosen
The selection of aluminum and steel is driven by performance, economics, and environmental factors. Both metals offer superior barrier properties, necessary to contain carbon dioxide and keep the beverage fresh. The dome-shaped bottom, along with the high strength-to-weight ratio of the alloys, allows the thin-walled container to handle internal pressures exceeding 90 pounds per square inch, which is stronger than a typical car tire.
Aluminum’s light weight is a major economic advantage, as using less material reduces manufacturing and transportation costs, including fuel consumption. Furthermore, both aluminum and steel are highly valued for their sustainability profile, as they can be recycled infinitely without any loss of quality. The efficient recycling process uses up to 95% less energy than producing new metal, making the beverage can an environmentally efficient packaging choice.