Section 232 Enacted: 25% Steel and 10% Aluminum Tariffs — The Origin of Modern US Trade Policy

President Trump imposed 25% tariffs on steel imports and 10% tariffs on aluminum imports effective March 23, 2018 under Section 232 of the Trade Expansion Act of 1962, citing national security concerns over the decline of US domestic steel and aluminum production. Initial exemptions were provided for Canada, Mexico, the EU, Australia, Argentina, Brazil, and South Korea while bilateral negotiations were underway. This was the first major use of Section 232 authority in decades and established the national security tariff framework that has since been expanded to cover copper, automobiles, lumber, and semiconductors.

All US importers of steel mill products (HTS Chapters 72-73) and aluminum articles (HTS Chapter 76) from all countries not receiving initial exemptions. Downstream manufacturers — automotive, construction, packaging, appliances — faced higher input costs from day one. The US steel and aluminum industries welcomed the protection. This action initiated the modern era of broad executive tariff authority that defines US trade policy through 2026.

Section 232 Enacted: 25% Steel and 10% Aluminum Tariffs — The Origin of Modern US Trade Policy (effective 2018-03-23). President Trump imposed 25% tariffs on steel imports and 10% tariffs on aluminum imports effective March 23, 2018 under Section 232 of the Trade Expansion Act of 1962, citing national security concerns over the decline of US domestic steel and aluminum production. Section 232 of the Trade Expansion Act of 1962 authorizes the President to impose tariffs or quotas on imports when the Department of Commerce determines that the import levels threaten to impair national security. The statute provides broad executive authority and has been used extensively since 2018 to cover steel and aluminum, with subsequent expansions to copper, automobiles, lumber, and semiconductors. Section 232 tariffs are notably permanent in character — unlike Section 122, they carry no statutory expiration and can remain in effect indefinitely once imposed. Products covered by Section 232 are exempt from the Section 122 surcharge under the February 2026 proclamation, meaning importers of S232-covered goods do not face double-stacking of these two tariff authorities. However, S232 rates do stack on top of MFN base rates, and China-origin products that fall under Section 301 may face additional tariff layers on top of S232. The expansion of Section 232 to cover copper in March 2025 and semiconductors in January 2026 reflects a broader industrial policy strategy to protect domestic manufacturing capacity in strategic sectors. Importers of S232-covered products should verify the exact HTS classification of their goods and confirm whether any country-specific exemptions or quotas apply to their sourcing country.

Manufacturers and importers of S232-covered products should work with licensed customs brokers to verify HTS classifications and ensure correct duty application. Country-of-origin documentation is critical: the S232 tariffs apply to the country where the product was substantially transformed, not simply where it was last shipped from. Some S232-covered products have product-exclusion processes through the Department of Commerce; check current exclusion orders before assuming the full rate applies to your specific product.

• Section 232 Explainer
• Steel & Aluminum Guide
• US Tariff Timeline