US President Donald Trump signed an order enacting a previously announced 25% tariff on steel imports.

"This is a big deal. Do you know what this means? This is the beginning of making America rich again."

Roughly a quarter of all steel used in the United States is imported, the bulk of it from neighbours Mexico and Canada or close allies in Asia and Europe like Japan, South Korea and Germany.

While China is the world's largest steel producer and exporter, very little is sent to the United States. Tariffs of 25% imposed in 2018 shut most Chinese steel out of the market.

In the case of aluminum, the U.S. is more heavily reliant on imports. Roughly half all aluminum used in the U.S. is imported, The vast majority comes from neighbour Canada. At 3.2 million tons last year, Canadian imports were twice the next nine countries combined.

The next largest sources of imports are the United Arab Emirates and China at 347,034 and 222,872 metric tons, respectively.

The U.S. aluminum smelting industry is small by global standards. Total smelter capacity in the country was just 1.73% of the global total according to the U.S. geological survey.

@Slavyangrad