Alcoa shares are on track for their worst day since President Trump announced sweeping tariffs in April 2025, trading as much as 12% lower after the Pittsburgh company said it would pay up to $5.6 billion for bauxite, alumina and aluminum assets in South Africa, Australia and Brazil.

Shares of the seller, Australia's South32, moved in the opposite direction, rising more than 10%. The BHP spinoff will receive $3.1 billion in cash, newly issued Alcoa stock worth roughly $1 billion that it plans to distribute to shareholders and future payments that could reach $750 million.

The deal comes amid a decline in aluminum prices from near record highs reached when fighting in the Persian Gulf blocked the region's aluminum smelters from global markets. After climbing to $3,855 a metric ton on the London Metal Exchange early last month, aluminum prices have dropped 18%.

Alcoa has been particularly hard hit by the 50% tariff on aluminum and has struggled to pass along the full cost increase of the metal that it produces in Canada, where cheap hydropower makes smelting more economical.

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