Why USMCA Does Not Save You from Section 232 Steel Tariffs

It comes up in almost every Mexico sourcing conversation. A procurement manager learns that their supplier in Monterrey can ship steel parts to the US under USMCA. The regional value content is above 75%. The certificates are clean. They expect 0% duty.

Then the shipment arrives and the duty bill is 25%.

Section 232 steel tariffs apply to Canadian and Mexican goods. USMCA does not exempt them. Understanding exactly when you do get relief, and when you do not, is the difference between a correct landed cost model and one that is off by 25 percentage points.

What Section 232 Actually Is

Section 232 of the Trade Expansion Act of 1962 authorizes the President to impose tariffs on imports that threaten national security. Steel and aluminum were designated national security threats under Proclamation 9705 (steel, March 2018) and Proclamation 9704 (aluminum, March 2018).

These proclamations came from a different legal basis than IEEPA or Section 301. Congress granted this authority explicitly. That is why, unlike IEEPA tariffs, Section 232 survived the Supreme Court's February 2026 ruling.

Current rates: Section 232 steel (HTS Chapters 72, 73) at 25%, and Section 232 aluminum (HTS Chapter 76) at 10%. These apply to imports from virtually all countries, including Canada and Mexico.

The USMCA Misunderstanding

USMCA grants preferential tariff treatment on qualifying goods. For most product categories, a USMCA-origin good from Canada or Mexico enters the US at 0% instead of the MFN rate.

But Section 232 is not part of the USMCA tariff schedule. It is a separate national security measure that was carved out of the agreement. USMCA Article 32.10 explicitly preserves each party's right to take actions it considers necessary for national security. Section 232 operates under that carve-out.

What USMCA gives you on steel and aluminum is a reduced Section 232 rate, not elimination:

This is meaningful, but it is not zero. If your landed cost model assumed 0% on USMCA-origin steel, your margin calculations are wrong.

The One Real Exemption: Melt and Pour

There is a genuine Section 232 exemption for Canadian and Mexican steel, but it has nothing to do with USMCA qualification. It comes from Presidential Proclamation 9705, as amended.

Steel that was both melted AND poured in the United States, Canada, or Mexico is exempt from Section 232. This is the "melt and pour" standard.

What that means in practice: if your Mexican supplier's steel coil was produced in a mill in Monterrey or Hamilton (Ontario) or Pittsburgh, and you can document the melt and pour origin, that steel is Section 232 exempt.

What it does NOT mean: steel that was fabricated into parts in Mexico, but sourced from Chinese or Brazilian mills, is not exempt. Fabrication does not equal melt and pour. The exemption goes to the metallurgical origin of the steel itself, not the location of value-added manufacturing.

Documentation required for melt and pour exemption claims:

• Steel mill certificate identifying the melt facility
• Country of origin statement from the mill (not just the fabricator)
• If the steel passed through multiple processors, a chain-of-custody document tracing back to the producing mill

Customs brokers sometimes mislabel this as a USMCA certificate. It is not. A standard USMCA certificate covers RVC and tariff shift criteria. The melt and pour exemption requires mill-level origin documentation.

How the Duty Stack Actually Calculates

Take a practical example: a steel tube fitting (HTS 7307.92) manufactured in Mexico from Brazilian-origin steel billet.

Now the same fitting, made from Mexican-mill steel where melt and pour occurred in Mexico:

That is a 12.5 percentage point swing based entirely on which steel mill supplied the raw material. For a $1 million annual import volume, that is $125,000 in duties.

Aluminum Has Additional Complexity

For aluminum (Chapter 76), Section 232 works similarly, but there is an additional complication: some aluminum product categories have separate derivative tariff classifications that depend on the origin of the primary aluminum content.

Products with the material_determination_required flag in CBP's tariff schedule require a pre-classification interview to determine whether the product is "derivative" aluminum subject to Section 232 or a manufactured product that falls outside the direct scope. This is not something a standard tariff lookup tool handles automatically.

Triangle Trade Intelligence flags these products during the tariff lookup process. When you look up an aluminum product with a complex material composition, the tool returns a preflight question about material origin before calculating the Section 232 exposure. This prevents the common error of auto-applying (or auto-exempting) Section 232 on aluminum products without understanding the underlying material source.

Common Mistakes in Landed Cost Modeling

• Mistake 1: Applying USMCA = 0% total duty on all Mexico sourcing. The correct assumption is USMCA = 0% MFN base rate. Section 232 is separate and likely applies unless you have mill certificates.
• Mistake 2: Treating a USMCA certificate as a Section 232 exemption document. These are two different documents with two different legal bases.
• Mistake 3: Assuming all Canadian steel is melt-and-pour exempt. Canada qualifies for the exemption, but only if the steel was actually melted in Canada. Canadian distributors who import steel from other countries and re-sell do not trigger the exemption just by being Canadian.
• Mistake 4: Not accounting for Section 122 on non-USMCA steel. As of February 24, 2026, Section 122 (10% global tariff) is active. USMCA partners are exempt, but non-USMCA origin steel carries the additional 10%.

How to Verify Before You Commit

Before finalizing a Mexico or Canada sourcing contract that relies on steel or aluminum content:

• Ask your supplier for the steel mill certificate (the actual producing mill, not the fabricator)
• Run the HTS code through a tariff calculator that layers Section 232 correctly (not just MFN + USMCA)
• Confirm whether the product has a material_determination_required flag that requires additional review
• Model both scenarios (melt and pour exempt vs. not exempt) in your landed cost

The Tariff Calculator at Triangle Trade Intelligence handles this correctly. Enter your HTS code and country of origin, and the tool returns the full duty stack: MFN rate, USMCA rate, Section 232 with the USMCA 50% reduction applied, Section 122 exemption status, and whether material origin documentation is required.

The Bottom Line

USMCA is real and valuable. For most manufactured goods, USMCA origin means 0% MFN duty, Section 122 exemption, and a 50% reduction in any Section 232 exposure. That is a significant advantage over China-origin goods.

But for steel and aluminum, the full exemption only comes with melt and pour documentation. Without that documentation, you are looking at 12.5% on steel and 5% on aluminum even on perfectly qualifying USMCA goods.

Model it correctly. Your margins depend on it.