Brass Alloy Grades Decoded: CW617N vs CW511L vs CW602N — How to Read EN 12165 Material Certificates When Sourcing Valves

The short version

The letters and numbers stamped on a brass valve body — CW617N, CW511L, CW602N — tell you which European Standard alloy the part was made from. But they do *not*, by themselves, tell you whether the part will survive 10 years of aggressive water. That answer lives in the material certificate and in one crucial word: DZR (dezincification-resistant).

If you source valves and faucets from Chinese, Indian, or European mills alike, learning to read an EN 12165 certificate is one of the highest-leverage skills you can build. This article shows you what each grade means, how dezincification testing works, and the five lines of a certificate you should never skip.

The three grades at a glance

All three alloys below are leaded brass (copper + zinc + lead), supplied as wrought forging stock or bar per the EN 12164/EN 12165 family. The difference is in the recipe — and in what happens when the valve meets warm, soft, or chlorinated water.

| Property | CW617N | CW602N | CW511L |

|---|---|---|---|

| Common designation | CuZn40Pb2 | CuZn36Pb2As | CuZn36Pb2As-type, DZR bar/rod |

| Typical copper | ~57–59% | ~61.5–63.5% | ~61.5–63.5% |

| Lead (typical range) | ~1.6–2.5% | ~1.6–2.5% | controlled / low-lead specs (verify on certificate) |

| Micro-alloying | — | Arsenic ~0.02–0.15% | Arsenic ~0.02–0.15% |

| Dezincification resistant? | No (standard grade) | Yes (DZR) | Yes (DZR) |

| Typical use | Hot-forged bodies, general fittings, interior plumbing | Forged valve bodies & fittings for potable/aggressive water | Machined components and bodies where DZR + machinability are both required |

| UK legacy name | CZ122 | CZ132 | — |

CW617N is the workhorse of the brass fittings industry: it hot-forges beautifully, machines cleanly, and is cheap. It is perfectly adequate for many interior, low-risk applications. The catch: with ~40% zinc and no inhibitor, it can dezincify — zinc leaches out and leaves porous, weak copper that eventually cracks and weeps.

CW602N adds a small arsenic dose that inhibits dezincification, making it the classic DZR forging brass for potable water, warm climates, and aggressive supply water. If an Australian, UK, or Middle East spec sheet asks for "DZR brass to EN 12165," CW602N is usually what the forger casts.

CW511L sits in the same DZR family but is most often encountered as bar/rod stock supplied against EN 12164 (rod for free machining) for machined parts, with some supply chains specifying a tighter lead ceiling for drinking-water contact. Because CW numbers occasionally collide across national supply habits, treat the certificate — not the marketing sheet — as the source of truth.

Why DZR matters: the failure nobody photographs

Dezincification is slow, internal, and invisible until the valve body develops a pinhole or a hairline crack. It is accelerated by:

• Warm water (30–60 °C supply and recirculating systems)
• Soft, aggressive, or low-mineral water
• Chlorine and chloramine residuals
• Stagnation and intermittent flow (a real issue in markets with unreliable supply — see [our guide on low-pressure and intermittent water systems](03-valves-low-pressure-intermittent-supply.md))

The standard laboratory proof is the dezincification test (EN ISO 6509 family, and AS 2345 in Australia), where a polished sample is immersed in copper(II) chloride solution and the penetration depth is measured under a microscope. A DZR-alloy part should show minimal attack; a standard CW617N part in the same test can show deep, spongy penetration. The exact pass/fail criterion is defined by the product standard you are working to — confirm the acceptance value cited on your certificate.

How to read an EN 12165 material certificate

A real certificate (often an EN 10204 3.1 inspection document) contains far more than the alloy name. Focus on these five zones:

Standard and material designation. Confirm the standard — EN 12165 (wrought and unwrought forging stock) vs EN 12164 (rod for free machining) vs EN 1982 (castings, e.g. CC grades). A body that is *forged* should trace to forging stock; a body that is *cast* is a different alloy family entirely, and the certificate should say so.

Chemical composition — limits vs actual. The certificate lists the standard's permitted ranges and the melt's *actual* analysis. Check the copper, lead, and — for DZR grades — the arsenic figure. If the arsenic column is empty on a "CW602N" certificate, the material is not what the label claims.

Delivery condition and property class. Brass bar is supplied in defined tempers/property classes (e.g., R280, R340-style strength designations). For forged bodies, the critical requirement is usually adequate hot workability and sound forging — your supplier's process control matters as much as the raw bar.

Melt/lot number and traceability. The certificate links a specific melt to a specific production lot. Your valve cartons should carry a lot code that traces back to that certificate. No lot number, no traceability, no certificate.

Inspection and test results. For DZR material, demand the dezincification test result. Some certificates will also show hardness or tensile data. If the buyer's product standard requires it, the test report should reference the correct edition of the test method.

Red flags when a supplier hands you "the brass certificate"

• A generic alloy datasheet instead of a lot-specific 3.1 certificate. A datasheet is marketing; a 3.1 certificate is evidence.
• Certificates that never change. A real certificate carries melt numbers and dates. If every shipment has the "same" certificate, it is a fiction.
• "DZR" claims without a test result. DZR is demonstrated, not asserted.
• CW numbers used interchangeably. A supplier that calls CW617N "basically the same as DZR" does not understand the material — and should not be forging your potable-water valves.

Choosing grades by application

| Application | Recommended approach |

|---|---|

| Potable-water valves, DZR-specified tenders | CW602N (forged) or CW511L (machined) with verified arsenic + dezincification test |

| Interior fittings, mild supply water, cost-sensitive | CW617N is defensible — document the water chemistry assumption |

| Hot water recirculation / aggressive water | DZR grades only; consider lead-safe variants for drinking contact |

| Cast bodies (large manifolds) | Use casting alloys (EN 1982 CC grades) — do not accept "forging grade" certificates for castings |

Bottom line

The CW number is the *name* of the alloy, not the proof of its behaviour. When you source valves, you are really buying the certificate chain: melt analysis → dezincification test → lot traceability → finished body. A factory that can show you that chain — and explain it — is a factory that understands why brass fails, which is exactly the partner you want for markets with demanding water quality.

About Xindong. Zhejiang Xindong Sanitary Ware Co., Ltd. has forged and machined brass in Yuhuan, Zhejiang since 1999, supplying faucets, valves, and thermostatic shower kits to regulated markets. With 65+ patents, an in-house laboratory, and strict incoming-material control — including verification of EN 12164/12165 certificates and DZR test results — our team routinely supports buyers who need documented material traceability. Ask our engineers how we document alloy compliance for your project: [email protected].

*Note: EN 12164/EN 12165 standards and their grade tables are periodically revised. Verify current editions and composition limits with your mill, certifier, or standards body before finalising specifications.*