Resources
What to ask for in an aluminium material certificate
Published 2026-09-15
Most purchase orders for extruded aluminium end with a line that says material certificate required, and most buyers never look at what arrives until something has already gone wrong. Then the document turns out to describe a cast of metal, not the bundle in the rack; or it carries a temper that was never tested on the extruded product; or the lot number on it matches nothing printed on anything in the delivery. None of that is fraud. It is what you get when nobody said, before the order, which document they actually wanted. This is the version of that conversation we would rather have up front.
A certificate is a record, not a promise
It is worth being precise about what the document is. A material certificate states that specified properties were measured, on a specified thing, by a specified party, on a date. It is evidence. It is not a warranty that every piece in the container shares those values, and it was never meant to be read that way.
That distinction is the whole reason the rest of this article exists. The question a buyer needs answered is not is 6063 a good alloy — it is does this bundle, in my rack, correspond to the document in my hand. Everything below is about closing that gap.
If you take one thing away: the useful certificate is the one whose identifiers appear on the material. A perfect test report that cannot be tied to a physical bundle proves that somebody, somewhere, made good metal.
Three different documents get called 'the certificate'
The first is the billet or cast certificate, issued by whoever melted and cast the metal. Its subject is a cast of aluminium, and its natural content is chemical composition. This is the document most often forwarded when a buyer asks for a certificate, and on its own it says nothing about the profile you bought.
The second is the extruder's own inspection report: what was checked on the finished product after pressing, ageing, cutting and finishing. Dimensional inspection and coating thickness testing are part of our standard quality control and the results are available on request — that report is about your parts, and it is the one most buyers actually mean.
The third is a third-party inspection report, produced by an inspector who is not the manufacturer. It costs money and time, and for most orders it is unnecessary. It exists for the cases where the specification, the end client, or a building authority requires that the party attesting is independent of the party selling. EN 10204 is the standard that names these document types — if your spec calls for a particular one, put that in the enquiry rather than assuming, because which document a supplier can issue is not the same question as whether the metal is good.
Composition and mechanical properties answer different questions
Chemical composition is a property of the cast. It is decided in the melt, it does not change when the metal goes through a press, and it traces back to the casthouse. This is what tells you whether you have 6063 or 6082 — the alloy limits themselves live in EN 573-3, and a composition result either falls inside them or it does not.
Mechanical properties are a property of the product, not the cast. Strength in an extruded profile comes from what happened at the press and in the ageing oven, so two profiles from the same cast, run on different presses or aged differently, are genuinely different material. EN 755-2 is the standard covering mechanical properties for extruded rod, bar, tube and profile.
The practical consequence is a single sentence you should be able to say about any certificate you are handed: this number was measured on the extruded product, or it was measured on the billet. If a document shows a temper designation but every measurement on it came from the casthouse, the temper on that page is a statement of intent, not a test result. That is the most common gap we see, and it is usually nobody's bad faith — it is simply the wrong document being forwarded.
Traceability always stops somewhere — find out where
Traceability is not a yes or no. It is a resolution: how finely the delivery is divided into lots that can each be tied back to a record. A whole shipment under one number, one number per cast, one per press run, one per bundle — these are four very different levels of protection, and all four are sometimes called traceable.
So ask the question in that form: what does the lot number on the bundle label refer to, and what will it let you retrieve later. If a customer finds a problem on one elevation two years from now, the level of traceability you agreed today decides whether the investigation covers three bundles or the entire order.
Then check the link physically. Marking on the bundle, the packing list and the certificate have to carry the same identifier, and the identifier has to survive the voyage on a label that is not a paper slip under the film. Reconciling those three at incoming inspection takes minutes; reconstructing them after the material has been cut takes weeks, and often cannot be done at all.
What the certificate does not cover, and what you have to ask for separately
Composition and mechanical properties say nothing about dimensions. Section tolerances, straightness and twist are a separate check against EN 12020 or against whatever you agreed instead — a material certificate has never been evidence that the profile fits the system it is going into.
It also says nothing about the finish. Anodic or coating thickness, adhesion, seal quality: these are surface results, produced on the finishing line, and they belong in their own report. Accepting a composition certificate as proof of finish quality is a substitution we see regularly, and it is the one that costs money later, because a finish problem usually appears long after the payment terms have closed.
Nor does it cover anything about form or workmanship on machined parts — cut length, hole position, burr, deburring, first-article approval. If your parts are machined after extrusion, the dimensional record you need is about the machining, and the extrusion certificate is not a substitute for it.
What to put in the enquiry, and when to push back
Ask for it before the order, not at delivery. A supplier who knows at quotation time that you require test results on the extruded product will plan the work and the paperwork together. Asked after the container has sailed, the same request turns into whatever documents happen to exist — and that is how the billet certificate ends up standing in for everything.
Name the subject and the party, not just the word certificate. Say whether you need results measured on the finished profile or composition from the cast, and whether the issuing party has to be independent of the seller. Two sentences in the enquiry remove almost all of the ambiguity described above.
Say that the lot identifier has to appear on the bundle label, the packing list and the certificate, in the same form. This single requirement does more for real traceability than any upgrade in document type, and it costs nothing.
And push back on two answers in particular. One is a composition report offered as proof of mechanical properties. The other is a certificate whose identifiers appear nowhere on the material. Neither is unusual, neither means you are dealing with a bad supplier — but both mean you do not yet have what you asked for. Send us your specification and what your end client requires in writing, and we will tell you which documents that actually needs before you place the order.
Related
Profiles in this guide