ADVANCED MATERIALS & PROCESSES | JULY/AUGUST 2025 24 KEY TAKEAWAYS • The use of alloy 5052 for U.S. aluminum highway signage is attributed to its early specification during the post WWII highway construction boom. • The presence of Cr and low tolerance for other impurities make it difficult to increase the recycled content and lower the carbon footprint of alloy 5052 road signage. • Chromium is a strategic metal and must be imported from Africa. Where possible it should be eliminated from the aluminum scrap recycling system. • Higher purity smelter metal is not required for road-sign applications and should be reserved for other more critical aluminum applications. • Substitution of alloy 5052 by existing 3xxx or 5xxx alloys can dramatically improve the carbon footprint (~95%) with no functional difference in performance. In Europe, higher recycled content alloys are in common use for road sign applications. • The Aluminum Association, in collaboration with producers and ASTM, could support the need to register new alloy products based on end use and carbon content, not just chemical composition or mechanical properties. While aluminum itself is not classified as a “strategic” material, we should point out that aerospace alloys, electrical conductors, and other critical applications require smelter grade aluminum of 99.7% or higher as a base. Smelter production in North America has dropped from 5.51 million metric tons in 2000 to less than 4 million metric tons in 2024[14]. For U.S. aluminum production taken separately, a recent Reuters article cited the current U.S. smelting capacity as 607,000 metric tons. From 2000 to 2024, the number of aluminum smelters in the United States shrank from 24 to just 4[15]. The use of primary aluminum in North America to produce 5052 alloy for road signs is not a necessary or wise use of scarce primary metal. As described below, recycling-based alloys can easily supply the market for highway signage without the need for any substantial quantity of primary metal. ALLOY SUBSTITUTIONS For many applications, 5052 alloy rolled products are sold through a distribution market where mills supply coils to companies that slit to width, cut blanks, or otherwise prepare the sheet for sale to end-use customers. Having standard alloys, tempers, tolerances, and surface finishes is critical for this market. Road-sign stock, fuel tanks, marine sheet, and plate are examples of products that are often sourced through distributors. On the other hand, mills may sell directly to OEMs, (Ford Motor Company, for example) who need large quantities of the same specification. Efforts by Alcan/Novelis to substitute alternative alloys for 5052 for more than twenty years have met with resistance to change[16]. The historic problem was that neither the customer nor government agency was interested in challenging an existing standard. Other issues arose from OEM specifications and drawings that would need to be changed. And who was going to pay for necessary testing and requalification? Customers exhibited little or no interest because they did not want to invest the time, resources, or incur the cost. The situation in Europe offers a logical option for alloy substitution in the highway sign market. In the EU, the use of 5052 for all applications is quite limited: about 30,000 metric tons/year out of a market for rolled products of more than 1 million metric tons[17]. Here it should be noted that 5052 never had a widespread application in Europe where the most common medium strength alloy is 5754 (see Table 1). Speira Aluminium, based in Germany, promotes their standard sign stock alloy as a “3% Mg alloy with a high recycled content[12].” Notably the composition range for 5754 alloy allows more generous limits for Fe, Mn, and Cr. Their promotional video notes that the demand for replacement of road signage in Germany alone is about 1.8 million signs per year[12]. OUTLOOK FOR THE FUTURE While there was little or no interest as recently as 2017, the economic and cultural emphasis for sustainable products is now getting much more traction in North America. We believe that there is a receptive audience within the customer base for a sustainability message. A second positive trend is the shift toward alloy 5754 to replace 5052 in the automotive market. This effort started in Europe and showed up in North American customer inquiries during the 2015 to 2020 time frame. The initial volumes were small and specific to North American aluminum distributors or parts manufacturers who were selling to European customers. By 2024, aluminum sheet suppliers saw a shift toward alloy 5754 for automotive parts that were historically 5052. Choosing the “right” alloy to replace 5052 for road signage is actually a non-issue. There is enough experience with alternative alloys such as 3104, 3105, or 5754 to be confident that the mechanical property levels of 5052-H38 can be easily met. With at least four major suppliers of product to the NA industry, there will likely be a range of alternative alloys to replace a volume of 100 to 150 million pounds of 5052. The flexibility for different suppliers to offer their own alloy options ensures that the use of scrap can be maximized to lower the carbon footprint of road sign stock. A pressing issue today in the effort to lower the carbon footprint of aluminum transportation infrastructure is one of communications. The customer base is dispersed among many companies supplying signage to many different federal, state, and municipal end users. Industry and material associations can assist in a focused effort with regulatory
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