The US primary aluminum map is changing again. On July 1, 2026, Magnitude 7 Metals confirmed it will restart part of its idled smelter in Marston, Missouri, before the end of the year. The plant has sat dark since early 2024, when its power contract lapsed. The company credits one factor for the reversal: the 50% Section 232 aluminum tariff, which has pushed US aluminum prices high enough to make domestic smelting pay again.
For anyone buying aluminum die casting parts for the North American market, this is worth a close read. Restarts like this one shape the Midwest premium, and the Midwest premium shapes what US-based casters pay for metal.
What Was Announced
Magnitude 7 Metals will bring one of the three potlines at its Marston smelter, in New Madrid County, Missouri, back online before the end of 2026. One potline adds about 75,000 metric tons of primary aluminum per year. The full site carries a nameplate capacity of 263,000 tonnes, which made it the second-largest primary smelter in the US before it went idle. This is the company's second restart attempt at the site; the first followed the original 10% Section 232 tariff in 2018.
Why the Smelter Shut Down, and What Changed
Electricity is roughly 40% of the cost of making primary aluminum at Marston. When the plant's power agreement was not renewed in early 2024, the economics collapsed and the site was fully idled. Two things have moved since then. The Section 232 aluminum tariff doubled to 50% in June 2025, and the US Midwest duty-paid premium followed it upward, reaching a record of about $2,182 per tonne (near 99 cents per pound) in February 2026 after crossing 90 cents per pound for the first time in late 2025. At those levels, a US smelter earns the LME price plus a premium that now rivals half the metal's base value, and that spread is what makes the restart math work.
The Numbers at a Glance
| Item | Figure |
|---|---|
| Restart capacity (potline 1) | ~75,000 t/year |
| Marston nameplate capacity | 263,000 t/year |
| Section 232 aluminum tariff | 50% (since June 2025) |
| US Midwest premium record (Feb 2026) | ~$2,182/t (~99 c/lb) |
| Share of smelting cost from electricity | ~40% |
The American Primary Aluminum Association says this restart, together with other announced capacity moves, would lift US primary output by more than 20%. The trend is broader than one plant: Century Aluminum is advancing a greenfield smelter project in Oklahoma, the first new US smelter in decades, backed by supply agreements involving EGA and US Aluminum Company.
What This Means for Die Casting Buyers
Will the restart lower US aluminum prices? Not by much, and not soon. One potline is 75,000 tonnes against US imports that run into the millions of tonnes per year, so the structural shortage that supports the Midwest premium stays in place through at least 2027. US casters will keep paying tariff-inflated metal prices, and those costs flow straight into domestic part quotes, since alloy typically makes up a large share of a die cast part's price. We broke down that cost mechanism in our earlier report on aluminum price volatility.
Three practical points for 2026–2027 sourcing plans:
The US-offshore cost gap stays wide. A restart that trims the premium by a few cents per pound does not close a spread created by a 50% tariff on the metal itself. Offshore casting programs, where the caster buys alloy at regional non-US prices, keep their raw-material advantage on finished parts.
Watch the premium, not the announcements. Restart headlines moved sentiment in 2018 too, and that attempt did not hold. The Midwest premium quotes published weekly are the honest signal of whether new tonnes are actually reaching the market.
Secondary alloys respond differently. Die casting grades such as A380 and ADC12 are mostly scrap-based, so they track scrap spreads as much as primary prices. Higher domestic primary output tightens scrap demand at the margin, which can firm secondary alloy prices even as primary premiums ease. Cost planning for aluminum die casting projects should treat the two markets separately.
Sources
- CRU Aluminum Market Update — Magnitude 7 Metals Plans Partial Restart of New Madrid Smelter (July 2, 2026)
- Bloomberg — Aluminum Smelter Idled Since 2024 to Restart in US After Trump Tariffs (July 1, 2026)
- KFVS12 — Magnitude 7 Smelter in New Madrid County Could Open Before End of Year (July 2, 2026)
- S&P Global Commodity Insights — Aluminum US Midwest Premium Reaches 90 cents/lb for the First Time
- Oklahoma Department of Commerce — Oklahoma Aluminum Hub Agreement: US Aluminum Company, EGA, Century Aluminum
