Some imports of derivative aluminum products would be subject to an additional 10 percent duty, while some derivative steel products would be slapped with a 25 percent tariff, he said. Argentina, Australia, Canada and Mexico were exempted from the additional aluminum tariffs. As for the steel tariffs, exemptions were allowed for Brazil, Argentina, Canada, Australia, Mexico and South Korea. While imports of aluminum and steel have declined since the Trump administration imposed levies, some derivative products “have significantly increased since the imposition of the tariffs and quotas,” according to Trump’s proclamation. Since the beginning of his administration, Trump has used tariffs — and the threat of them — to affect policy.