Guides / Compliance
Which Material Certificate Your Brass Part Actually Needs
September 21, 2026
Ask for a certificate and you will get one. Ask for the wrong one and you pay for controls you do not need, or you receive a document that does not prove what you assumed it proved.
EN 10204 defines four types. Only two of them matter for most brass work.
The four types
Type 2.1, declaration of compliance. The supplier states that the material complies with the order. No test results. Just a statement.
Type 2.2, test report. The supplier states compliance and includes test results, but those results come from non-specific inspection. The numbers are from the production run or from routine testing, not necessarily from your material.
Type 3.1, inspection certificate. Test results from specific inspection on the material actually supplied, validated by the manufacturer’s own authorised inspection representative, who must be independent of the production department.
Type 3.2, inspection certificate. As 3.1, plus a countersignature from either your own inspector or an independent inspection body named in the order.
Which you actually need
For machined brass parts, the honest answer for most buyers is 3.1.
It is the point where the document stops being a statement and starts being evidence. It reports real numbers on the material you received, validated by somebody who does not report to the person who made it.
2.2 is enough when the material is uncontroversial and the part is not regulated. General industrial hardware, brackets, non-critical fittings.
3.1 is right when you need to prove composition later: potable water parts, electrical parts with a lead limit, anything where a customer or regulator may ask.
3.2 is for pressure equipment, some rail and nuclear work, and situations where a third party inspection regime already exists. If you are unsure whether you need 3.2, you almost certainly do not.
What a 3.1 actually proves
This is where expectations most often break.
It proves: the chemical composition and the mechanical properties of the bar stock that your parts were machined from, with real numbers on the real material.
It does not prove:
- That the finished part meets any product standard. NSF/ANSI 61 certification, for example, is a separate exercise entirely. See NSF/ANSI 61 and 372 for brass fittings.
- That the dimensions are right. That is an inspection report, a different document.
- That the parts in the box came from that bar, unless the shop operates traceability that links them.
That last point is the one worth pressing on. A mill certificate photocopied and stapled to a delivery note proves nothing about the parts in the box. What makes it meaningful is the shop’s internal trail: this bar batch, cut on this date, produced these part lot numbers.
Ask how the shop does that. A shop with a real system will answer immediately. A shop without one will talk about the certificate instead.
Special tests worth naming separately
A standard 3.1 reports composition and mechanical properties. It does not automatically include everything you might need.
ISO 6509 dezincification test. If your part is going into hot water or a marine environment and the alloy is a DZR grade, ask for the ISO 6509 result explicitly. See dezincification resistant brass.
Lead content to NSF/ANSI 372. A standard composition analysis gives you lead percentage. Whether that satisfies the weighted average calculation for your assembly is your arithmetic, not the mill’s.
RoHS or REACH declaration. These are supplier declarations about regulatory status, not mill test results. Ask for them as separate documents. See RoHS exemption 6(c) and leaded brass.
Stress corrosion testing to ASTM B154 or ISO 6957 on finished parts. This is a part test, not a material test, and it is destructive on the samples used. See season cracking in brass parts.
Per lot or per first article
This is a real cost decision and it is worth making deliberately.
With the first article only. Cheap. Appropriate when you are qualifying a part and the material is not the risk you are managing.
With every lot. Expensive, because it forces material segregation through the whole process. The shop has to keep bar batches separate, record which parts came from which, and hold that trail through machining, finishing and packing.
If your customer or your regulator requires per lot certification, you need it and it is worth the money. If nobody has actually asked for it, you may be paying for a control that protects nothing.
What to write on the drawing or the order
Material certificate EN 10204 type 3.1 required.
Report chemical composition and mechanical properties.
Include ISO 6509 dezincification result.
Certificate required with first article only.
Lot traceability to bar batch to be maintained
and recorded.
Five lines that answer every question a shop would otherwise have to guess at. The last line is the one that turns the certificate from paper into evidence.
One practical note on lead-free
Lead-free brass stock is thinner on the ground than C360, so a shop may source from different mills for different lots. That is normal and it makes per lot certification more, not less, meaningful, and it makes naming a single alloy on the drawing more restrictive than naming the requirement. See leaded and lead-free brass compared.
Need certificates with your brass parts? Send the drawing and set the compliance field. Tell us in the description whether you need them per lot or on the first article, because it changes which shops can quote sensibly.
Frequently asked questions
What is the difference between 3.1 and 3.2?
A 3.1 certificate reports actual test results on the material supplied, validated by the manufacturer's own inspection department, which has to be independent of production. A 3.2 adds a second signature from either your own inspector or an independent body named in the order. In practice 3.1 covers the overwhelming majority of brass work, and 3.2 belongs to pressure equipment and regulated industries.
Does a 3.1 certificate prove my finished part is compliant?
It proves the composition of the bar the part was cut from. It says nothing about the machining, the dimensions or whether the finished part meets a product standard such as NSF/ANSI 61. Traceability from that certificate to your specific lot of parts is a separate control that the shop has to operate, and you should ask whether they do.
Can a machine shop issue a 3.1 certificate?
The mill issues the 3.1 for the bar. A machine shop passes it through and adds its own conformity document linking that certificate to your lot number. Some shops call their own document a 3.1, which is loose usage. What matters is that you get the mill certificate plus a traceable link to your parts.
Why does a certificate per lot cost more than one with the first article?
Because it forces material segregation. A shop that certifies every lot has to keep each bar batch separate, record which parts came from which bar, and hold that trail through machining, finishing and packing. That is a real operational cost. If you only need it on the first article, say so and do not pay for the rest.
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