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How to tell if aluminum is good quality before you buy it
The quality of flat-rolled aluminum is verified with four documents and tests: the lot's mill test report (chemistry and mechanical properties), thickness and flatness measurement on receipt, a bend or draw test on your own line, and a supplier audit. A supplier that does not provide the mill's original test report cannot guarantee the lot. Almexa provides a report per lot and receives customer audits. Source: Almexa quality practice, 2026.
"Their quality is bad" is a line heard in purchasing without anyone having measured anything. This guide turns the line into four checks any quality department can run.
1. The mill test report
Every lot of flat-rolled aluminum leaves the mill with a mill test report (certificate of analysis). Check:
- Alloy and standard: it should say 3105, not "3000 series".
- Chemistry: each element within the alloy's standard range.
- Mechanical properties: tensile strength, yield and elongation measured, not just "conforms".
- Temper: O, H14, H18.
- Lot and cast number: for claims and for origin traceability.
A distributor that hands you a report with no mill name or "per standard" without measured values cannot guarantee the lot. Ask for the original.
2. Measurement on receipt
With a micrometer and a tape, at five points across the width and three along the length:
| What to measure | What to expect | What it means if it fails |
|---|---|---|
| Thickness | Within agreed tolerance | Poorly controlled rolling; will stop your die |
| Width | Agreed slitting tolerance | Poor slitting |
| Flatness | No edge or center wave | Residual stress; waves in panels |
| Surface | No scratches, oxide or oil stains | Poor handling or annealing |
| Camber | Within standard for strips | Off-axis slitting |
3. A test on your line
No data sheet replaces a strip in your die or a circle in your press. Ask for a sample of the lot and make the part. If it cracks on the bend, the temper is wrong; if it tears in the draw with an irregular break, there are inclusions; if the paint lifts, pretreatment or curing failed. The defect tells you where it was born: alloy, temper, melting or process.
4. Supplier audit
Before approving, visit the plant or ask for the evidence:
- Certified quality system (ISO 9001; IATF 16949 in automotive; FSSC 22000 in food contact).
- In-house lab with spectrometer and tensile tester.
- Traceability from cast to coil.
- Who answers for a defective lot and in how many days.
A mill can show you the furnace where your lot was melted. An importer shows you an email.
What doesn't measure quality
Price, country of origin or the mill's brand say nothing about a specific lot. Two coils from the same mill can differ. That is why quality is verified lot by lot, with documents and a micrometer, and the supplier is judged by how it responds when one goes wrong.
What Almexa does
Every lot ships with a mill test report with values measured at the plant, the plant operates under ISO 9001, IATF 16949 and FSSC 22000, and receives customer audits by appointment. If a lot fails on your line, your line's sales executive and the plant lab review it with you; there is no third party in between.
Frequently asked questions
What is an aluminum mill test report?
A per-lot document issued by the mill with the alloy, the measured chemistry, the mechanical properties and the temper. It is the evidence of quality and of origin of the material.
How is aluminum temper verified?
With the strength and elongation on the mill test report, and in practice with a bend or hardness test: an O temper bends without cracking on tight radii; an H18 cracks.
Does Almexa provide samples for testing?
Yes, arranged with your line's sales executive by product and lot.
Leads Almexa Aluminio, Mexico's integrated flat-rolled aluminum mill. Writes about alloys, process, pricing and supply for industrial buyers in North America. LinkedIn