The Aviles and La Coruna plants were two of the least productive due to intrinsic structural problems such as inefficient technology and high fixed costs.
The US imposed the tariffs on Canada and Mexico in June. Although Canada and Mexico agreed a renewed continental trade deal last week, the measures remain.
Chinese aluminium exports are expected to surge in coming months and next year after Beijing boosted tax rebates as part of a package to soften the impact of a trade war with the United States.
