Brass: Composition, Properties, and Alloys

Brass and bronze are often used interchangeably in everyday language, but they're technically two different materials. Brass is a copper-zinc alloy, bronze a copper-tin alloy. That distinction shows up quickly once you're sourcing turned parts, fittings, or fixtures in brass. The supplier will almost always ask for the exact alloy, material number, and underlying standard. Leave that open, and the order stalls, or you receive a material that doesn't meet the spec.

In brief: Brass is a copper-zinc alloy, usually 55 to 95 percent copper. Depending on the exact ratio and additions like lead, different alloys emerge with their own material numbers, such as CuZn37 or CuZn39Pb3. Each has different strength, machinability, and corrosion resistance. Brass is often confused with bronze, which is a copper-tin alloy instead.

What is brass made of?

Brass is fundamentally a copper-zinc alloy. The copper share typically ranges from about 55 to 95 percent depending on the grade, with zinc making up most of the remainder. These two metals form a solid-solution alloy whose properties shift noticeably with the mixing ratio. More copper makes the material softer and more ductile, more zinc increases strength and hardness.

Many alloys also contain a small amount of lead to improve machinability. The share is usually 1 to 3 percent, with special grades containing up to 3.5 percent. These variants are commonly called free-cutting brass, since they machine especially well on automatic lathes. Lead-free alloys are becoming more important due to statutory limits for drinking water installations, such as Germany's Trinkwasserverordnung and comparable regulations elsewhere. This applies particularly to parts in contact with drinking water.

In our sourcing projects across the Far East, we regularly see customers order "brass" without specifying the exact alloy. That almost always triggers a follow-up question from the supplier, or worse, a delivery that is technically brass but doesn't meet the required strength or machinability.

What properties does the material have?

The common alloys stand out for good machinability, solid corrosion resistance, and an attractive gold-like appearance useful for both technical and decorative applications. According to the Deutsches Kupferinstitut (German Copper Institute), the melting point of the wrought alloys named in this article (CuZn37, CuZn39Pb3, CuZn40Pb2, CuZn20Al2) sits between roughly 880 and 970 degrees Celsius. That's considerably lower than steel. Copper-rich special alloys such as gilding metal can run higher.

It conducts electricity and heat well, though not as well as pure copper. It resists fresh water and many chemicals. In ammonia-rich environments, though, it can suffer from stress corrosion cracking. Chloride-rich, salty water mainly promotes the dezincification described below. Buyers should weigh this point when selecting materials for coastal applications or chemical plants.

A further, practically relevant risk is dezincification. In aggressive water, certain standard alloys can preferentially lose their zinc content, leaving behind a porous, mechanically weakened copper structure. For fittings and valves in contact with drinking water, dezincification-resistant brass is therefore common (DZR, e.g. CuZn36Pb2As / CW602N). Arsenic is deliberately added as an inhibitor.

Source: Deutsches Kupferinstitut, Informationsdruck i.5 – Kupfer-Zink-Legierungen (Messing und Sondermessing), values for CuZn37 (CW508L), CuZn39Pb3 (CW614N), CuZn40Pb2 (CW617N), and CuZn20Al2 (CW702R).

What is the difference between brass and bronze?

The key difference is the alloying partner: brass is a copper-zinc alloy, while bronze is a copper-tin alloy. Both materials look similar and are frequently confused in everyday use, but they differ substantially on a technical level.

Bronze is generally harder and more wear-resistant, better suited to plain bearings or bells. Brass, by contrast, machines more easily and is therefore the more common choice for turned parts, fixtures, and fittings. For a material order, a description like "bronze-coloured" or "brass-coloured" isn't enough. Only the exact material designation matters.

What brass alloys and material numbers are there?

For sourcing, the exact material number matters most, since it fixes the composition and properties precisely and prevents misunderstandings between buyer and supplier. The most common alloys carry European-standard designations such as CuZn37 or CuZn39Pb3, where the number after "Zn" states the zinc content in percent. Alongside the CuZn designation, the shorter CW number is also common, such as CW614N. This abbreviation is frequently used in parallel with the chemical short name on drawings and specifications.

In our experience, it's worth specifying not just the material number in the technical specification, but also the underlying standard, such as EN 12164 for free-cutting brass. Where relevant, a material certificate is worth adding too. That way, the delivered batch can be checked unambiguously against the order, especially with suppliers in newer sourcing markets.

Where is the material used in industry?

It turns up wherever good machinability, corrosion resistance, and an attractive finish are needed, for example in plumbing fittings, valves, connectors, furniture fixtures, and musical instruments. In mechanical engineering, matching parts also commonly serve as bearing elements or connectors where steel is unsuitable due to weight or corrosion concerns.

For importers sourcing such parts from the Far East, it's also attractive because it machines well on CNC equipment. That makes even complex geometries economical to produce at volume. A more expensive stainless steel solution isn't always necessary. Buyers looking for new supply sources can find an overview of relevant regions in our article on procurement markets.

The material is also popular for short runs and prototypes, since geometry changes are noticeably faster and cheaper to implement than with hardened steel. In the plumbing sector, many standards and approvals now require lead-free or dezincification-resistant alloys exclusively for drinking water installations. Buyers should clarify this point during supplier selection to avoid approval issues later on.

What should buyers watch for when sourcing these parts?

Anyone sourcing such parts internationally should contractually fix the material number. It's also worth fixing the origin of the alloying components, the required surface treatment, and, where relevant, a material certificate. For parts in contact with drinking water, lead-free or dezincification-resistant alloys and the corresponding approval deserve particular attention.

An incoming goods inspection with material verification protects against a wrong or substandard alloy slipping unnoticed into production. We describe how such a check works in practice in our article on incoming goods inspection. For tightly toleranced turned parts, it's also worth checking the applicable general tolerances so dimensional variation is planned for realistically from the start.

Availability matters too. Standard alloys such as CuZn39Pb3 are usually available from stock in common dimensions at short notice. Lead-free or dezincification-resistant special alloys, by contrast, are often made to order and carry correspondingly longer lead times. Clarifying this point with the supplier early avoids delays further down the project.

Frequently asked questions about brass

Is brass waterproof?

Yes, the material is generally resistant to fresh water and suitable for use in damp environments. For sustained contact with salt water or ammonia-containing media, though, a specifically corrosion-resistant alloy should be chosen instead, such as Admiralty brass or a dezincification-resistant DZR grade.

What is the melting temperature of brass?

Depending on the alloy, the melting point of common wrought alloys sits between roughly 880 and 970 degrees Celsius, meaning the material can be processed at considerably lower temperatures than steel.

Is brass magnetic?

No, due to its copper-zinc composition the material is not magnetic. That makes it a simple way to distinguish it from magnetic materials like steel during sorting or quality checks.

Conclusion: The right alloy protects quality and cost in sourcing

Brass is a versatile material whose properties depend heavily on the exact copper-zinc ratio and additions such as lead or arsenic. Anyone sourcing these parts should specify not just "brass" but the exact material number, standard, and, where needed, a material certificate. That avoids misunderstandings with the supplier and ensures the delivered parts meet requirements.

As process specialists, we at Line Up support our clients from the material selection stage onward, matching alloy, machinability, and inspection requirements to the specific part. 👉 Book a free consultation and we'll help you find the right alloy for your next project.

Sources:

• Deutsches Kupferinstitut / kupfer.de: Copper-zinc alloys (brass)

• Deutsches Kupferinstitut: Informationsdruck i.5 – Kupfer-Zink-Legierungen (Messing und Sondermessing), PDF (German-language technical reference)

• Materialarchiv.ch: Brass CuZn39Pb3 (German-language technical reference)

• DIN Media: DIN EN 12164 – Copper and copper alloys, rod for free machining purposes