Brass is an antibacterial and seawater-resistant metal alloy that’s easy to machine. This metal is mainly made up of copper and zinc, but it also has trace amounts of lead, iron, and other elements in it. In , the USA was the fourth largest exporter of brass in the world with a total export value of almost $22 billion. The largest was Chile ($40 billion), followed by Germany ($29 billion) and Japan ($24.7 billion).

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This article will discuss what brass is and the various types of brass, as well as their mechanical and chemical properties. Figure 1 below shows some brass bars:

What is Brass?

Brass is a workable, machinable, antibacterial, and anti-biofouling material. As briefly covered in our intro, brass is a metal alloy of copper and zinc that typically has a golden-yellow color but if the alloy has a lot of copper in it, it could sport a reddish hue. This type is called “red brass.” The exact quantities of copper and zinc (or other alloying elements) in the brass will determine its type and properties. Lead in brass will improve its corrosion resistance and machinability, and including iron will make it harder and easier to forge.

Types of Brass

There are many brass alloys and they differ in their elemental makeup. Here are some of the most commonly used ones.

1. Alloy 260 (Cartridge Brass): This has around 70% copper and 30% zinc with impurities. This alloy has excellent hot formability and is readily cold-worked.
2. Alloy 280 (Muntz Brass / Muntz Metal): This brass alloy contains approximately 60% copper and 40% zinc, as well as trace amounts of iron. A common application for Muntz metal was as a less expensive replacement for the copper sheeting formerly placed on boat hulls to prevent the growth of sea organisms such as barnacles on the hulls. 
3. Alloy C360 (Free Machining Brass): This brass alloy contains approximately 60% copper, 35.5% zinc, up to 3.7% lead, and trace quantities of iron. This alloy is one of the easiest materials of all the brasses to machine and is classified as having a 100% machinability rating. It’s commonly used for parts like gears and bushings.
4. Alloy 385 (Architectural Bronze): Despite being called bronze, 385 brass has around 59% copper, 42% zinc, and up to 3.5% lead in it. This mixture makes it more machinabile and formabile, which is why it’s popular in architecture for aluminum extrusions. 
5. Brass 464 Marine Grade (Naval Brass): This brass alloy contains approximately 59% copper, 40% percent zinc, and 1% tin, with a small amount of lead. The combination produces a metal with exceptional corrosion resistance to seawater. Applications can include the various fittings found on the deck of a boat.

Properties of Brass

Table 1 below lists the mechanical and elemental makeup of the more common brass alloys. Many of these alloys instant quote on Xometry’s platform as a manufacturing material option.

Brass Advantages

Brass has many advantages. In addition to being one of the easiest materials to machine (free-machining brass has an 100% machinability rating), it also has a low coefficient of friction (in layman’s terms, its surface is very smooth and slippery, which makes it great for parts that need to slide against each other without wearing down quickly). The copper content in brass can kill certain types of bacteria, making it the go-to for things for high-touch surfaces like door handles. It’s also used in marine industries thanks to its biofouling properties, meaning that algae and barnacles won’t grow on it.

How Strong is Brass?

Brass is quite strong and durable but the level of its strength depends on its composition and the type of heat treatment it has gone through. When naval brass is cold drawn and annealed, it gets a tensile strength of 580 MPa which is impressively as high as some steel grades. Brass that has been heat-treated is strong enough to be used for valve bodies that need to withstand high pressures.

Is Brass Safe to Use?

Yes, brass is safe to use for general engineering applications but is not recommended when coming into contact with acidic food (pH < 6). Brass is toxic to some microscopic organic life due to the negative effect of copper ions on various microscopic living organisms. Brass can also prompt an allergic reaction in persons with skin sensitivity. 

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Does Brass Violate REACH or RoHS?

Copper Alloys such as brass and bronze (which contain Lead) in their solid form and under normal conditions do not violate REACH (REACH is about inhaling, ingestion, or contact health hazards). Xometry would only ship final products and therefore do not present any hazards. The hazards are generated during welding, heating, and dust generation activities, such as machining.

The lead content in brass has a special exemption in RoHS (Exemption 6c) which allows brass to contain up to 4% lead by weight. Note that not all brass alloys qualify so it’s important to communicate RoHS or REACH requirements during the quoting phase of a project to ensure material compliance in manufacturing. You can learn about Xometry’s REACH/RoHS Declaration here.

Copper vs. Brass vs. Bronze

All three of these are commonly referred to as “red metals.” Brass and bronze contain copper as their main element. Brass contains zinc as the main secondary element, while bronze typically has tin. Bronze is especially resistant to corrosion from seawater whereas brass has excellent low-friction capabilities. Copper is great for electrical applications like wiring or busbars due to its high conductivity.

When you come into contact with antique brass, it can be difficult to tell whether they are solid brass, or simply plated with brass. Here are some simple ways to find out.

Using fridge magnets 

Brass is an alloy of zinc and copper which are neither magnetic. Hold a magnet close to the item, if it attracts, it's not brass.

Scratch test

Use a sharp tool to scratch the object. If you see a shiny gold scratch, it is likely to be solid brass. Be careful not to damage the object.

Weight test

Brass is a dense and heavy metal. You could easily tell it apart from the plated ones for items such as kitchen handles. If the item feels heavy, it is likely to be solid brass, if it is not, the handles are usually made of a cheaper zinc alloy. 

Sound test 

Brass will have a very clear and loud sound. Use a metal spoon and hit the brass to see if you could hear that sound. Combine this test with other tests for a more certain conclusion. 

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