What dezincification-resistant brass is, what ISO 6509 does and does not decide, and how to write the requirement on an insert purchase order.
Short answer: DZR brass is brass built and tested to resist dezincification, the selective loss of zinc that leaves weak, porous copper behind. ISO 6509-1 is the test method for it, but the method sets no pass or fail limit. For an insert purchase order, name the grade, the test standard, the acceptance criterion and the destination market, and ask for a test report on finished parts.
Key Takeaways
- Dezincification removes zinc from brass and leaves a porous, copper-rich structure, so a part can look intact while its strength is gone.
- Copper-zinc alloys with more than 15% zinc are susceptible, which includes common forging brasses.
- ISO 6509-1 describes how to measure dezincification depth. Acceptance criteria sit in a separate document or in the rules of the market.
- “DZR” on a certificate is only a claim until a test report on the delivered parts backs it.
- DZR and lead-free are two separate questions, and an order has to answer both.
What is DZR brass?
DZR brass is a copper-zinc alloy made and processed so that it resists dezincification in water. The letters stand for dezincification resistant, and the property comes from the alloy, the processing and the verification together. Three points keep the term honest:
- A tested property: resistance is proven by test results on the finished part, not by a grade name alone.
- Not a lead statement: a DZR grade can still contain lead for machining, so it is not automatically lead-free.
- Not unlimited: DZR brass resists the attack in water the test represents, and your own water and operating conditions still matter.
Our comparison of CW617N and CW602N shows how the best-known European DZR grade differs from a general forging brass.
What is dezincification and what causes it?
Dezincification is the selective removal of zinc from brass, and it leaves a porous, copper-rich structure behind. AMPP, the Association for Materials Protection and Performance, states that copper-zinc alloys containing more than 15% zinc are susceptible. It appears in two forms:
| Type | What happens | Conditions AMPP links to it |
|---|---|---|
| Plug-type | Attack is localized and penetrates deep into the sidewalls of valves and fittings | Neutral or alkaline water that is high in salt, at or above room temperature |
| Uniform-layer | Zinc leaches from a broad area and wall thickness shrinks evenly | High oxygen and carbon dioxide, stagnant or slow-moving water, high chloride |
AMPP adds that slightly acid or alkaline water, low aeration, low flow rates, relatively high wall temperatures and permeable deposits favor the attack. The practical result for a buyer is that the same brass can last in one water supply and fail in another.
How does DZR brass resist dezincification?
DZR brass resists dezincification through its composition and its processing, and both have to be right. Supplier technical pages describe the same building blocks:
- Controlled zinc content: less zinc means less material to lose, but also changes strength and machining behavior.
- An inhibiting addition: small amounts of an element such as arsenic are added to slow zinc loss in the structure of the brass.
- Controlled processing: heat treatment after forging brings the structure into the condition the alloy needs to resist attack.
Because processing is part of the recipe, the same bar can pass or fail depending on what happens after forging. This is why a test on finished, heat-treated parts matters more than a certificate on raw bar. AMPP recommends that buyers require alloy designations or chemistry from manufacturers and not accept inexpensive yellow brasses without confirming they meet standard performance requirements.
What does ISO 6509 actually say?
ISO 6509-1 specifies a test method and nothing else: it does not decide whether a result is good enough. The EVS catalogue page for EN ISO 6509-1:2014 and the BSI Knowledge page describe it in the same terms:
- Scope: a method for determining the dezincification resistance of copper alloys with zinc, covering exposure to fresh or saline waters or drinking water.
- Material range: the method is intended for alloys with a zinc mass fraction above 15%.
- Result: the dezincification depth is calculated after the test.
- Criteria: BSI states that the standard describes only the test methodology and does not set out criteria for acceptability, and it refers readers to ISO 6509-2, which is titled “Assessment criteria”.
The consequence is simple: “tested to ISO 6509” is an incomplete statement. A purchase order has to say which criterion the depth is judged against, because the test alone gives a number and not a verdict.
Where do rules require dezincification resistance?
Requirements come from market rules and project specifications, not from the brass itself, so the destination decides. A WRc test code sheet hosted by WRAS shows how one market has handled it. The sheet (issued August 1998) covers these points:
- Which fittings: dezincification testing applies to wetted parts of brass fittings installed below ground or in an inaccessible position, and to certain safety valves and backflow devices.
- Which method: the sheet names BS EN ISO 6509 as the test method.
- Which criterion: it states that the fitting shall meet the acceptance criteria of AS 2345, Table 1.
- What is exempt: brass with less than 15% zinc, CZ132 grade brass, gunmetal and bronze are listed as outside the test.
This document is more than 25 years old and was written for the byelaws of its time, so use it as an example of structure, not as current law. Confirm today’s rules with WRAS or your importer. Our guide to WRAS versus NSF certification covers how the UK, EU and US routes differ.
Do brass inserts in plastic fittings need DZR?
Brass inserts need DZR when the destination rules, the specifier or the local water chemistry call for it, and not by default. An insert sits permanently in the waterway of a plastic fitting, so it is exposed to the water for its whole life. Three questions settle it:
- What does the market require? Some importers and project specifiers write DZR into every tender for their region.
- What is the water like? Soft water, high chloride, stagnant sections and warm service all raise the risk, as the AMPP conditions show.
- What else must the grade satisfy? Lead limits are separate. Read whether CW617N is lead-free before you combine the two requirements.
Stainless steel inserts avoid zinc loss entirely, because stainless steel contains no zinc. Our stainless steel versus brass insert guide helps with that decision.
What should the purchase order say about DZR?
The purchase order should state the grade, the standard, the criterion, the sample and the market, so that a DZR claim becomes something you can check. The table gives the minimum wording.
| Item | What to write | Why it matters |
|---|---|---|
| Grade | Alloy designation, for example CW602N, and not “DZR brass” alone | Makes the chemistry checkable |
| Test method | ISO 6509-1 on the delivered part | Fixes how the result is measured |
| Acceptance criterion | The named document, such as ISO 6509-2 or the standard your market uses | Turns a depth value into pass or fail |
| Test sample | Finished, heat-treated parts from the production lot, not raw bar | Processing is part of the property |
| Report | Test report tied to part number and production lot | Links the claim to what was shipped |
| Market and service | Destination country, cold or hot water, buried or exposed | Decides whether DZR and which criterion apply |
| Lead requirement | State separately from DZR | The two properties are independent |
Put these lines in the same package as the drawing, thread callout and knurl description. Our guide to writing a brass insert RFQ shows the full package.
How does Fenilo handle brass grades?
Fenilo’s standard brass for inserts and valve parts is hot-forged CW617N, also known as HPb59-1. Other material grades are discussed per project once the destination market and test requirements are clear. The controls around the material are these:
- Incoming inspection: all brass material is inspected before it enters production.
- Hot forging in house: forging, sandblasting, CNC machining, assembly and inspection run in one plant in Yuhuan, Zhejiang.
- Five-stage quality control: incoming inspection, in-process dimensional checks, pressure and leak testing for valve products, finished-product inspection and continuous improvement from production data and customer feedback.
- Samples: available for assembly testing and quality evaluation.
If your market requires dezincification resistance, send the requirement with your drawing so the grade and the test can be agreed before sampling. Our brass insert fittings page lists the inserts we make.
Need brass inserts with a material requirement?
Send your drawing, the destination market and the material requirement, including any dezincification or lead rules. We will review them and discuss the grade, samples and testing before quoting. Inserts are hot forged and CNC machined in our own plant in Yuhuan, Zhejiang, with five-stage quality control.
Send your requirementsFAQ
What does DZR mean in brass?
DZR in brass means dezincification resistant, which describes a brass made and processed to resist the selective loss of zinc in water. The property is confirmed by testing the finished part, not by the name alone.
What does ISO 6509 test?
ISO 6509-1 tests the dezincification resistance of copper alloys with zinc by exposing a sample and calculating the dezincification depth. It is a test method only, and the acceptance criteria are described separately, for example in ISO 6509-2.
Is DZR brass lead-free?
DZR brass is not automatically lead-free, because dezincification resistance and lead content are separate properties. A grade can resist dezincification and still contain lead for machining, so state each requirement on its own line.
Which brass is susceptible to dezincification?
Copper-zinc alloys containing more than 15% zinc are susceptible to dezincification, according to AMPP. Many common forging and machining brasses fall in that range, which is why grade and testing matter for water fittings.
Does Fenilo supply DZR brass inserts?
Fenilo’s standard brass for inserts is hot-forged CW617N (HPb59-1), and other material grades can be discussed per project. Send your destination market and test requirements with the drawing so the grade can be agreed before sampling.
Bottom line: treat “DZR” as a test result and not as a label. Write the grade, ISO 6509-1, the acceptance criterion and the destination market on the purchase order, and ask for a report on the parts you receive.