What is the ISO 6509 test?

ISO 6509 is the standard accelerated laboratory test for the dezincification resistance of brass. A polished cross-section specimen is exposed to a 1% copper(II) chloride solution at 75°C for 24 hours, then sectioned and examined under an optical microscope, and the depth of dezincification is measured in micrometres. ISO 6509-1 defines the test method; ISO 6509-2 covers the assessment criteria.

What is a passing result in the ISO 6509 test?

The test itself measures a depth; the pass threshold comes from ISO 6509-2, the product specification or the certification scheme applying it. In common practice for arsenical DZR brass such as CW602N, a maximum dezincification depth of 200 μm is the widely applied criterion, and silicon brasses such as CW724R typically show 100 μm or less. The applicable scheme or customer specification always governs.

Which brass alloys pass the ISO 6509 dezincification test?

Arsenic-inhibited CW602N (CuZn36Pb2As) and the silicon brasses CW724R and C69300 (CuZn21Si3P) are dezincification-resistant and pass the test. Standard free-machining and forging brasses — CW614N (CuZn39Pb3) and CW617N (CuZn40Pb2) — are not dezincification-resistant and fail in aggressive water conditions.

Does passing ISO 6509 mean a part is approved for drinking water?

No. ISO 6509 characterises a material property — resistance to dezincification. Drinking-water approval (WRAS, KIWA, DVGW, ACS or national positive lists) applies to the finished product and is held by whoever places that product on the market. A component supplier provides DZR material with an EN 10204 3.1 batch certificate as the evidence base; the end-product approval is the buyer's.

When should I specify DZR brass instead of standard brass?

Specify DZR (CW602N or a silicon brass) where the part sees water with dezincification risk: soft or low-mineral water, elevated chloride content, warm stagnant conditions, or markets that mandate DZR such as Australia, the Netherlands and parts of Scandinavia. In neutral hard water, standard CW614N and CW617N perform well and machine faster.

What does dezincification actually do to brass?

It selectively leaches zinc out of the alloy, leaving a porous, copper-rich but mechanically weak layer. Externally the part can look intact apart from reddish patches; internally the affected depth has lost its strength, which is why failures appear as leaks or sudden breakage at threads and thin walls.

Can Brassland supply parts with ISO 6509 test evidence?

Brassland machines DZR brass CW602N and lead-free silicon brass CW724R/C69300 to drawing, and every shipment carries an EN 10204 3.1 certificate with the batch analysis that documents the alloy. Where a customer programme requires ISO 6509 test reports for the material, this is agreed at the ordering stage together with the material supply chain.

Dezincification Resistance of Copper Alloys with Zinc

The ISO 6509 Test,
Explained Properly

24 hours in hot copper chloride decides whether a brass may call itself DZR. What the test does, what the depth numbers mean, and what passing does — and does not — entitle anyone to claim.

1% CuCl₂ · 75°C · 24 h CW602N & CW724R Pass Material Property — Not an Approval

01

The Short Answer

The test in one paragraph

02

What Dezincification Is

And why it ruins brass from inside

03

The Test, Step by Step

Method per ISO 6509-1

04

Alloys: Pass or Fail

CW602N, CW724R vs CW614N, CW617N

05

The Honest Boundary

Test result ≠ product approval

06

FAQ

7 common questions answered

The Test in One Paragraph

Hot copper chloride, then a microscope

A prepared specimen is exposed to a 1% copper(II) chloride solution (12.7 g/L CuCl₂·2H₂O) at 75°C for 24 hours; it is then cut, polished and examined under an optical microscope, and the depth of the dezincified layer is measured in micrometres.

Part 1 defines the method; Part 2 covers assessment. A low measured depth is what earns alloys such as CW602N and CW724R the label DZR — dezincification resistant.

Test Parameters

At a glance

Solution1% CuCl₂ (12.7 g/L dihydrate)

Temperature75°C

Duration24 hours

Measurementdepth in µm, optical microscopy

Method / criteriaPart 1 / Part 2

Cross-section

Field failures rarely announce themselves: the part weeps at a thread, or a fitting shears at a wall that had quietly lost its zinc. The full failure-mode picture — including meringue dezincification under deposits — is covered in our brass corrosion guide.

Method per ISO 6509-1

1

Prepare — specimen cut, embedded, surface metallographically polished.

2

Expose — 1% CuCl₂ solution (12.7 g/L CuCl₂·2H₂O), 75°C, 24 hours.

3

Section — cross-section through the attacked face, ground and polished.

4

Measure — optical microscope; dezincification depth recorded in µm.

Where the pass mark comes from: the test yields a depth, not a verdict. The threshold is set by ISO 6509-2, the product standard or the certification scheme invoking the test — which is why the same measured depth can pass one specification and fail another. The commonly applied practical criterion for arsenical DZR brass is a maximum depth of 200 µm.

Why Accelerated?

A decade of soft water in a single day

Hot copper chloride drives the same selective zinc attack that aggressive service water produces over years. It ranks alloys by the mechanism that actually kills fittings — not by a proxy.

That is why DZR mandates in Australia, the Netherlands and Scandinavia are written around this test, and why serious water-fitting specifications cite it by number.

Alloy	Zn content	DZR mechanism	Typical ISO 6509 outcome	Use where
CW602N · CuZn36Pb2As	~36%	Arsenic inhibition	Resistant — ≤ 200 µm criterion	DZR water-contact components, soft-water markets
CW724R · CuZn21Si3P	~21%	Silicon kappa-phase, intrinsic	Resistant — typically ≤ 100 µm	Lead-free + DZR programmes
C69300 · CuZn21Si3P	~21%	Silicon kappa-phase, intrinsic	Resistant — typically ≤ 100 µm	US lead-free programmes (NSF/ANSI 372 lead criterion)
CW614N · CuZn39Pb3	~39%	None	Not resistant — fails in aggressive water	General machining; neutral hard water
CW617N · CuZn40Pb2	~40%	None	Not resistant — fails in aggressive water	Hot forging + machining; neutral hard water

Typical Maximum Depth by Alloy (µm)

Where DZR is mandated or prudent: soft or low-mineral supplies, elevated chlorides, warm stagnant lines — and markets such as Australia, the Netherlands and parts of Scandinavia that require DZR grades for water fittings. In neutral hard water, standard CW614N/CW617N remain the faster-machining, lower-cost choice. Grade-selection help: alloy guide.

The Honest Boundary

Two levels, two owners

Material level (this page): CW602N resists dezincification per ISO 6509; CW724R/C69300 meet the lead-content criterion referenced by NSF/ANSI 372. Both are properties of the alloy, evidenced per batch by an EN 10204 3.1 certificate.

Product level (the buyer's): WRAS, KIWA, DVGW, ACS and national positive lists approve the finished fitting or appliance — held by whoever places it on the market.

Brassland machines components — not finished valves — and does not cast. Material-level ISO 6509 evidence is agreed at ordering where a programme requires it.

DZR Parts, Machined to Drawing

CW602N and lead-free CW724R — cut to ±0.005 mm

CNC to Ø 150 mm, Swiss-type to ±0.005 mm (Ø 2–32 mm) — with the batch analysis on every shipment's 3.1 certificate documenting the alloy.

Request a Quote Corrosion Guide

Materials & Alloys

CW602N — CuZn36Pb2As · DZR CW724R — CuZn21Si3P · lead-free C69300 — US lead-free silicon brass CW614N — CuZn39Pb3 · machinability 100 CW617N — CuZn40Pb2 · forging brass Alloy selection guide All 20 datasheets →

Industries

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Applications

Plumbing components HVAC applications Industrial engineering Electrical brass Automotive applications Renewable energy All applications →

Products

Custom CNC parts to drawing Brass nuts — DIN 934 / ISO 4032 Screw plugs — DIN 906 / 908 / 910 Tube fittings — DIN 2353 / 3852 Threaded inserts for plastics Hex standoffs — M2.5–M8 All brass products →

Standards & Quality

EN 10204 — inspection certificates EN 12164 — rod for free machining EN 12165 — forging stock ISO 2768 — general tolerances Brass corrosion guide Compliance — RoHS · REACH · SVHC All standards guides →

DZR Programme?

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Quotation typically within 24 hours — alloy evidence agreed at ordering.

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Sources & scope. Test method per ISO 6509-1:2014 (Corrosion of metals and alloys — Determination of dezincification resistance of copper alloys with zinc — Part 1: Test method) and assessment per ISO 6509-2:2017, cross-checked against independent laboratory descriptions and Brassland's corrosion engineering guide. Provided as an engineering reference; the current official editions and the certification scheme applying the test govern.

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