An aerospace supplier rarely imports "metal." It imports a Grade 5 titanium bar to AMS 4928, a 4140 alloy steel billet for a precision-machined valve body, a Hastelloy C-276 forging for a hot section, or an Inconel 718 sheet that has to carry a mill certificate the prime is going to ask for on receiving inspection. The customs file has to reconcile to the material file. When it does not — when the invoice says "titanium bar" and the mill certificate says "Ti-6Al-4V ELI per AMS 4930" — the entry is technically clean but the program file is not, and that is the gap a CBP CF-28 (request for information) or a prime-customer audit will eventually find.
The Section 232 rate stack and where it lives in the HTS
Section 232 duties on steel and aluminum were imposed under Proclamation 9704 (steel, March 8, 2018) and Proclamation 9705 (aluminum, same date), with subsequent country exemptions, absolute quotas, and tariff-rate quotas issued through later proclamations. The headline rates remain 25% on covered steel and 10% on covered aluminum, applied through Chapter 99 subheadings 9903.80.xx (steel) and 9903.85.xx (aluminum). Country-of-melt-and-pour drives where the rate stack lands:
- South Korea, Brazil, Argentina — absolute or tariff-rate quotas in place of the 25% steel duty; entries inside quota use 9903.80.61/62/63, outside-quota entries are flatly inadmissible until the next quota period.
- EU, Japan, United Kingdom — tariff-rate quotas under separate proclamations (TRQs under 9903.80.65/.81/.83); in-quota duty-free, out-of-quota at 25%.
- Mexico melt-and-pour requirement — Proclamation 10783 (July 10, 2024) restored Section 232 duties on Mexico-origin steel articles that were not "melted and poured" in Mexico, the U.S., or Canada, and on aluminum articles containing primary aluminum smelted or cast in China, Russia, Belarus, or Iran. The country-of-melt-pour declaration is now an entry-line data element, not a paperwork curiosity.
- Section 232 exclusion process — Commerce/BIS exclusions are now product-specific and time-limited. An expired exclusion that has been used in broker tariff instructions for years is exactly the kind of finding a customs audit surfaces.
DFARS specialty metals, by clause name
For aerospace and defense suppliers, the specialty-metals constraint that touches the customs file is DFARS 252.225-7008 ("Restriction on Acquisition of Specialty Metals") and DFARS 252.225-7009 ("Restriction on Acquisition of Certain Articles Containing Specialty Metals"). Both flow down from Berry Amendment and 10 USC 4863 requirements and require that titanium, nickel-based alloys, specialty steels meeting the defined chemistries, and certain other alloys be melted or produced in a qualifying country. The customs entry does not establish DFARS compliance — counsel and the prime contract do — but the entry must not contradict it. If the mill certificate says melt in a non-qualifying country and the entry says the same, the program file is honest but ineligible; if the entry conceals it, the program file is worse.
A worked country-of-melt example
A precision machine shop imports 12 lots of Ti-6Al-4V round bar per year for a Tier-1 engine program. The mill certificates show melt and pour in Kazakhstan, hot-roll and pickle in Germany. The broker has been entering the bar under 8108.20.00 ("Titanium and articles thereof — Unwrought titanium; powders") which is wrong (unwrought vs wrought), at MFN 15% with no Section 232 because titanium is not covered by 232. The correct classification is 8108.90.30 ("Wrought titanium and articles — Other"), MFN 5.5%. The 9.5-point misclassification on $1.2M annual entries is $114,000 a year in overpaid duty — recoverable on entries inside the 300-day PSC window under 19 CFR 173.4, or the 180-day protest window under 19 USC 1514 if already liquidated. Separately, the DFARS 252.225-7009 file needs the Kazakhstan melt disclosed to the prime so they can apply the exception logic; customs does not police that, the contract does, but the entry should match.
Section 232, AD/CVD, and origin overlap
Section 232 is not the only customs risk on aerospace metal lanes. AD/CVD orders cover specific stainless steel, carbon steel plate, and aluminum extrusion categories from China, India, Korea, Vietnam, and others — the entry-line cash deposit can dwarf the Section 232 rate. Country-of-origin disputes arise when semi-finished goods cross more than one country (melt in country A, hot-roll in country B, machine in country C). 19 CFR 102 (rules of origin) and the substantial-transformation test from Bestfoods v. United States (CIT 2001) drive that analysis. Documentation gaps where the mill certificate, AS9100 records, and import declaration do not line up are the most common audit finding.
Broker instructions for aerospace materials
A broker instruction sheet for these lanes identifies material form (wrought/cast/forged/powder/sheet/tube), alloy family and specification (AMS, ASTM, EN), end-use program, manufacturer, country of melt-and-pour, substantial-transformation evidence where relevant, Chapter 99 subheading if any Section 232 applies, value basis, and any special duty treatment claimed. It also states what does not get filed without trade-ops escalation: any new mill not previously qualified, any country-of-melt change, any AS9100 nonconformance that touches origin, and any Section 232 exclusion approaching expiration.
Priority audit table
| Material / part flow | Customs risk | Documentation packet |
|---|---|---|
| Titanium bar, billet, plate, or forgings | HTS form distinctions, origin evidence, Section 232 or specialty-metal review. | Mill certs, invoices, purchase orders, alloy/spec sheet. |
| Inconel / nickel-alloy inputs | Valuation and classification ambiguity between raw/semi-finished forms. | Material certs, engineering spec, supplier/manufacturer chain. |
| Bearings, valves, gears, precision assemblies | Part vs assembly classification and origin when components cross borders. | Drawings, BOM, end-use statement, assembly flow. |
| Optical glass, ceramics, sensor housings | Specialized headings and customer-program documentation demands. | Datasheets, program requirements, origin support. |
90-day audit plan for an aerospace precision shop
Days 1–10 — material lane map. List every mill, distributor, processor, heat-treat vendor, and machining house in the supply chain for the top five revenue programs. For each lane, capture country of melt-and-pour, country of hot/cold work, and country of last substantial transformation. Most aerospace shops discover at this step that the "country of origin" field in the broker filing has been copied from the supplier invoice rather than derived from the mill certificate.
Days 10–30 — material-family classification rebuild. Group recurring entries into titanium (Chapter 81), nickel alloy / Inconel / Hastelloy (Chapter 75/72), specialty steel (Chapter 72), bearings (8482), valves (8481), and finished assemblies (Chapter 88 for aircraft parts). For each group rebuild the HTS, flag any 9903.80.xx (steel) or 9903.85.xx (aluminum) coverage, and screen for AD/CVD orders by case number.
Days 30–60 — refund and DFARS reconciliation. For overpaid duty inside the 300-day PSC window (19 CFR 173.4) or the 180-day protest window (19 USC 1514), file in batches grouped by program and supplier. In parallel, reconcile mill certs against the AS9100 receiving file and the DFARS 252.225-7008/7009 program file; any country-of-melt mismatch between customs entry and program file becomes a counsel-routed item, not a broker fix.
Days 60–90 — forward controls. Rewrite broker tariff instructions per material family. Add a quarterly country-of-melt refresh requirement on every active mill. Build a finance flag so that resourcing a Ti-6Al-4V or Inconel lane triggers a customs review before the PO is released — the duty delta on a quota-out-of-window steel grade or a mis-melted DFARS specialty metal exceeds the price delta of switching suppliers in almost every case we have seen.
Evidence packet for specialty metals imports
The packet keeps invoice, packing list, material certification, mill certificate, supplier country, processing country, country-of-melt-and-pour declaration, HTS candidate, Chapter 99 subheading, Section 232 review notes (including any current exclusion), AD/CVD screen with case numbers, AS9100 receiving records, and the relevant DFARS 252.225-7008/7009 program-flow-down language all in one bundle keyed to the entry number. The goal is not to turn a broker into an aerospace lawyer. The goal is to make sure that when CBP or the prime asks a question, the customs facts and the material facts answer it the same way.
Official sources to keep open
- CBP Section 232 trade remedies (steel + aluminum)
- Proclamation 9704 — 25% steel duty (Mar 2018)
- Proclamation 9705 — 10% aluminum duty (Mar 2018)
- Proclamation 10783 — 2024 Mexico melt-and-pour requirement
- DFARS 252.225-7008 — Restriction on Acquisition of Specialty Metals
- DFARS 252.225-7009 — Articles Containing Specialty Metals
- 19 CFR Part 102 — Country of origin (substantial transformation)
Need a customs-side review for this import stack?
Greenwich Mercantile can review the recurring entries, supplier lanes, HTS candidates, origin records, and broker instructions before the next shipment gets filed.
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FAQ
Do aerospace manufacturers need a specialized customs broker?
They need either a specialized broker or a trade-ops layer that understands aerospace material files. Routine clearance alone is not enough when HTS, origin, material certificates, and prime-customer flow-downs must line up.
Does Greenwich give DFARS or export-control legal advice?
No. Greenwich handles customs-side classification, origin, valuation, broker coordination, and documentation organization. Government-contract and export-control legal conclusions should stay with counsel.
What is the quickest aerospace import audit?
Review the top recurring metal and precision-assembly imports by value, then compare invoice descriptions, HTS classifications, material certificates, country-of-origin records, and broker filing instructions.
This guide reflects publicly available U.S. import and trade-compliance information as of May 2026. It is not legal, tax, or export-control advice. Importers should verify current requirements with CBP, USTR, BIS, Treasury/IRS, DHS, or qualified counsel before filing entries or making regulated claims.