What Century Aluminum Company told the SEC could break it.

Century Aluminum has extreme single-customer concentration: it derived approximately 54.0% of consolidated sales from Glencore in 2025 (59.1% in 2024 and 73.8% in 2023), and states it has historically derived substantially all of its primary-aluminum net sales from a small number of customers. Glencore — which is also a related party and significant shareholder — purchases aluminum from Century's U.S. smelters at LME-plus-Midwest-premium pricing. The loss of, or a change in the business or financial condition of, Glencore would be severely damaging. Glencore is captured as an edge; the aggregate dependence registers here as a high-severity concentration risk.

“For the years ended December 31, 2025, 2024 and 2023 we derived approximately 54.0 % , 59.1 % and 73.8 % of our consolidated sales from Glencore, respectively.”

As a primary aluminum producer, Century's revenue is fundamentally a function of the London Metal Exchange (LME) aluminum price plus regional premiums — it sells its output (notably to Glencore) at LME-based prices and runs LME forward financial sales contracts (a 48,400-tonne open position at year-end 2025) to fix forward prices. Margins are squeezed between volatile LME output prices and large, partly externally-sourced input costs (alumina, carbon products, and power for the electricity-intensive smelting process). A sustained decline in LME aluminum prices — or a spike in power/input costs — directly compresses profitability and can force capacity curtailments (as occurred at Mt. Holly). The dominant commodity-price exposure for the company.

“As of December 31, 2025, we had an open position of 48,400 tonnes related to LME forward financial sales contracts to fix the forward LME aluminum price.”

Century's economics are unusually policy-dependent — favorably so for now, but with reversal risk. The U.S. Section 232 aluminum tariff (10% in March 2018, now a 50% tariff on certain primary aluminum imports) protects domestic producers like Century from imports and has prompted it to return Mt. Holly to full capacity; its Iceland output gains EU-market access duty-free as part of the EEA while non-EEA competitors face EU tariffs. It also benefits from the IRA Section 45X production tax credit (10% of eligible production costs). Because much of its competitive advantage and margin support rests on these tariff and tax-credit regimes, any rollback — removal/reduction of the aluminum tariffs, loss of duty-free access, or repeal of 45X — would materially erode its position. A two-sided trade/industrial-policy dependence.

“the U.S. currently imposes a 50% tariff on certain primary aluminum imports into the United States.”

Smelting requires a steady supply of petroleum coke, pitch, carbon anodes, cathodes, alloys, caustic soda, natural gas and heavy fuel oil. For several of these — specifically coke, pitch and cathodes — Century has no internal production and relies on a limited number of suppliers for all of its requirements, with many supply agreements being short-term or expiring in the next few years and no assurance they can be renewed on favorable terms. A disruption, price spike, or non-renewal at a sole/limited-source coke, pitch, or cathode supplier could halt or raise the cost of aluminum production. Suppliers are unnamed, so this registers as a sole-source/limited-supplier risk for critical carbon inputs.

“For some of these production inputs, such as coke, pitch and cathodes, we do not have any internal production and rely on a limited number of suppliers for all of our requirements.”