CODDLING America’s steel industry has long been a policy of presidents from both sides of the political aisle. Donald Trump, in that respect, is not unusual. Yet no recent predecessor has been as aggressive in wielding tariffs to that end. In his first term Mr Trump imposed a 25% levy on steel imports and 10% on aluminium, though he granted exemptions to some trading partners, including Brazil and South Korea. On March 12th the tariff wall is due to rise higher still. A new 25% levy on all imported steel and aluminium products, with no exclusions, will come into force, as well as a bonus 25% tariff on products coming from Canada, which the president announced on March 11th. The measures are not only unlikely to raise domestic production of the metals. They will also cause many American companies pain.