U.S. Copper Market After Tariffs – Imports Collapse, Inventories Surge, Arbitrage Premium Vanishes

On August 1, 2025, the United States imposed a 50% tariff on imported semi-finished copper products. In the months leading up to this policy, U.S. traders rushed to stockpile refined copper, driving record-high import volumes. Between March and June, weekly imports of refined copper averaged around 44,000 tonnes—almost triple the ~15,000 tonnes per week seen a year earlier—bringing in an extra ~400,000 tonnes, equivalent to seven months of normal import demand. As expectations of the tariff solidified in late July, imports fell sharply. By August, semi-finished imports had virtually dried up, while only limited inflows of tariff-exempt refined cathode continued.

Inventories in the U.S. ballooned to unprecedented levels. By the end of August, COMEX warehouse stocks reached ~247,000 tonnes, an all-time high and even greater than total LME warehouse copper globally (~156,000 tonnes). In the short term, the U.S. is “copper-saturated”: the import window is closed, and the market is entering a destocking phase expected to last 4–5 months.

Price spreads swung wildly. In early July, markets assumed refined copper would be tariffed, causing COMEX copper to soar. On July 29, the COMEX-LME spread widened to more than $2,700 per tonne, triggering massive arbitrage flows into the U.S. But when the White House confirmed cathodes were exempt, the arbitrage collapsed. Within 48 hours, the spread crashed from $2,700/t to just $30/t. By mid-August, U.S. prices had normalized back to typical transport parity levels, effectively shutting the import window.

Overall, the U.S. copper market in August–September shifted to a pattern of collapsing imports, record-high inventories, and normalized spreads, moving from panic buying to forced destocking.