Next Generation Can End Stock: Advancing Sustainability and Safety

The first all-aluminum, seamless, two-piece beverage can was rolled out in 1959 by Coors – a famous American brewing company. In the same year, the company instituted a recycling policy by paying customers one cent for each can they returned. Clearly, this indicates that from the beginning, the aluminum beverage can was born to become the most sustainable beverage packaging it is today.

Since its first appearance in the 1959, the aluminum beverage can has never stopped evolving and is now the single most important market for aluminum. This market growth is the result of continuous improvements and innovations over the last 60 years in aluminum alloys and coatings, in the design of can bodies and can ends, and in manufacturing and recycling processes. Thanks to these successive product and process optimizations, the aluminum beverage can is now considered the most efficient and sustainable packaging for beverages.   

Historically, developments have largely focused on lightweighting the can, reducing the amount of material needed, and improving the efficiency and productivity of manufacturing processes in order to optimize costs. More recently, rising consumer awareness of sustainability and policies aimed at protecting the environment and health are driving new product developments, especially in can end stock.

The 2-Piece Aluminum Beverage Can

Today, the aluminum beverage can body and the can end are made from two different aluminum alloys that are not separated during the recycling process of used beverage cans (UBC). The AA5182 alloy used for the can end has a higher purity i.e. a less recycling-friendly composition than the AA3104 alloy used for the can body. UBCs are therefore recycled back into AA3104 alloy to produce new can body stock with a high recycled content and low CO­2­­ footprint. In contrast, AA5182 can end stock is most often sourced from smelters rather than from recycling.

A New Alloy to Increase the Recycled Content of the Can End

Constellium is developing a new, more recycling-friendly alloy for the can end to replace the current AA5182 alloy. The new alloy chemistry enables a higher recycled content. The new alloy has also been designed to be able to incorporate of a large proportion of UBC resulting in an improved circularity. Compared to the unialloy concept, where the AA3104 softer material used for the can body is also used for the can end with a significant upgauge, only a very limited upgauge is needed with our solution, limiting cost and enabling an easier implementation in current can end manufacturing lines. 

For this development, Constellium has relied on its R&D center C‑TEC, located in Voreppe, France. The expertise of the team, metallurgical models, prototyping capabilities, and the can end manufacturing pilot-line available in C‑TEC have been instrumental for this development. The R&D project has been able to demonstrate the feasibility of the solution by directly providing shells and ends to the customers for performance evaluation. Following Constellium’s classical “lab to industrial scale” development approach, Constellium’s Muscle Shoals and Neuf-Brisach plants have then taken over to supply trial coils to customers for industrial trials on their lines. Constellium is now participating in a European-level standardization project with three other leading aluminum can sheet manufacturers to make this solution available to the entire market.

New Generations of Coatings for Safer Food Contact

The internal surface of food and beverage cans is generally covered with polymeric coatings to preserve food and protect metal substrate from corrosion. For beverage can end stock, coils are coated at flat-rolled aluminum producers before delivery to the canmakers. Constellium, together with the coatings suppliers and the canmakers, is engaged in following all new regulations and recommendations from the European Food Safety Authority (EFSA) and US Food and Drug Administration (FDA) to ensure food safety. For several years now, these regulations have been driving major changes in the types of coatings used in beverage cans, replacing legacy epoxy resins with new generations of coatings based on polyesters, acrylics or polyolefins. 

Any new coating candidate must pass through an extensive qualification procedure before industrialization for serial production. At Constellium, this qualification procedure begins at the C‑TEC R&D center. 

The new coating is first applied in the lab with a bar coater on small sheets of can end stock. A series of lab tests are then conducted on the coated sheets to assess baseline performance of the coating (e.g. color aspect, friction coefficient, adhesion to the metal surface before and after deformation…). 

If this first round is successful, coil coating trials on the C-TEC pilot line begin. During these pilot-line trials, the behavior of the coating during the application process is studied, and recommendations on process parameters are communicated to Constellium plants to prepare the first industrial-scale trial. Samples from the small coated coils are then tested again in the lab to check coating performance. 

In addition, a small coil can be transferred to the C‑TEC can end-making pilot line to validate that the new coating does not cause major issues during forming in the shell press or conversion press. After the press trials, finished ends are available for additional testing to check coating barrier properties and coating adhesion during opening.

Once the first phase of qualification at C-TEC is completed, the procedure continues in our plants, with the first industrial trials producing coils that will be tested by our customers for final validation before entering serial life production.

Relying on Constellium C-TEC pilot lines for initial testing of new coatings offers several advantages. It reduces the cost of the qualification trials because the quantity of coating and metal involved is minimized and production in our plants is not interrupted. It also helps de‑risk the first industrial trials, whether on coating lines in our plants or on can end manufacturing lines of our customers. 

A Bright Future for the Aluminum Beverage Can

Today, the beverage can industry is reaping the rewards of continuous innovation in design, manufacturing, and recycling of the aluminum beverage can. The adoption of cans by an ever-growing number of brands and products – not only beers, soft-drinks, and energy drinks but also water, wine, seltzers and canned cocktails – is a testament to the high technical and sustainability performance reached by the aluminum beverage can.

The worldwide push to recycle more, reduce plastic packaging, and cut down on carbon emissions all points toward an increased demand for aluminum cans for the years to come. 

At Constellium, as a world-leading supplier and recycler of aluminum can body stock and end/tab stock, we are working at increasing the percentage of recycled content in aluminum can sheet by developing new, more recycling-friendly alloys, improving our recycling processes, and investing in additional recycling capacity. We are also working with stakeholders to increase scrap collection rates.

Together with new generations of coatings that ensure ever-improving food preservation and safety, the continuous reduction of the carbon footprint of beverage cans suggests that a more sustainable future is possible with aluminum cans.