Bronze: Definition, Composition, Properties, and Applications

Bronze isn’t all foam and no beer—it’s just as useful as it is pretty. You’ve surely seen it in the form of door handles, medals, and ornaments (you may even have some of these in your home), but those are certainly not all it’s good for. Engine parts, tools, and pumps are made from bronze, too (okay, and some other fun things like ship’s bells, fountains, and propellers). Read on to learn more about it, and how you can use it for your own manufacturing needs.

What is Bronze?

Bronze is a reddish-brown metal alloy in the “red metal” family made up of 88% copper, and 12% tin. It’s malleable (but harder than copper) so it’s easy to manufacture into different products and has low metal-to-metal friction. It also forms a natural protective layer (patina) on its surface that keeps it corrosion-resistant. Depending on what properties are needed, it’s sometimes mixed with other elements like phosphorus, silicone, or zinc. It’s made using the bronze casting process where it’s melted and mixed with whatever other elements needed, poured it into molds, and allowed to cool and harden. Here’s a cool object (if we do say so ourselves) we 3D printed with bronze:

What Is the History of Bronze?

Bronze has a remarkable history that spans well over six millennia. Archaeologists have found artifacts crafted around 4500 BCE. However, the use of bronze only became common in the 2nd millennium BCE and onward. The Bronze Age dawned in regions like Greece and China before 3000 BCE, while Britain didn’t embrace it until 1900 BCE. Bronze's exceptional hardness and durability revolutionized toolmaking, weapon crafting, and agriculture. Bronze Age civilizations, including Sumer, Babylonia, and Ancient Greece, thrived through trade and cultural exchanges. The Shang and Zhou Dynasties in China, running from 1600-256 BCE, saw bronze used for chariots, weapons, and vessels. However, by around 1300 BCE, iron became accessible. The Iron Age, which ran from roughly 1200-550 BCE, was fueled by that metal’s superior properties. Iron was easier to come by and also easier to process into a usable metal grade. This marked the decline of the Bronze Age.

Despite its diminished role in tools and weapons, bronze was still valued for statues and ornaments. It has also been used in modern times for 3rd-place sports medals. The tradition originated during the 1904 Summer Olympics in St. Louis, Missouri. Before this, silver medals were awarded to winners, while bronze medals were given to the runners-up. Today, bronze still has a wide variety of applications and can be found in items like springs, bushings, car gearboxes, hammers, ship propellers, musical instruments, and more. 

What Is the Other Term for Bronze?

There is no other term for bronze specifically. However, it does fall under the category of “copper alloy” or “copper-based alloy.” Bronze itself is a specific type of copper alloy, consisting primarily of copper and tin, but the broader term covers combinations of copper with other metals like aluminum, manganese, zinc, or phosphorus. Another example of a copper alloy is brass, consisting primarily of copper and zinc. 

Is Bronze Metal the Same as Copper?

No, bronze is not the same as copper. Bronze is an alloy that contains copper as part of its composition. 

What Is Bronze Made Of?

Bronze is made of copper and tin. Tin usually makes up around 12% of the total, with the remaining 88% being copper. The specific proportions vary based on use and manufacturer. It’s also possible for other elements to be included in the alloy mix. These elements include, but are not limited to: arsenic, aluminum, manganese, silicon, and phosphorus, which are added to alter certain properties. Different elements give the metal different levels of ductility, hardness, flexibility, and other properties. Some common bronze alloys include: aluminum bronze, leaded bronze, phosphorus bronze, silicon bronze, and manganese bronze.  

How Are Bronzes Made?

Bronze is typically made through a process called bronze casting, which involves melting and combining copper and tin in specific proportions. Once these two metals are melted, the mix is poured into a mold where it is left to cool and solidify into objects such as sculptures, medals, instruments, tools, and more. Bronze casting methods include lost wax casting, sand casting, and ceramic shell casting. 

What Are the Characteristics of Bronze?

Some of the common characteristics of bronze include:

1. Reddish-brown metallic color
2. Hard 
3. High ductility, but it becomes brittle under extreme forces
4. Good surface finish 
5. Excellent thermal and electrical conductivity 
6. Good corrosion resistance 
7. Good fatigue resistance
8. Low metal-to-metal friction 
9. High Melting point (950°C)
10. Non-sparking and non-magnetic properties 

What Is the Color of Bronze?

Bronze has a metallic brown color with a reddish hue. That is why it falls under the category of “red metals.” 

What Does Bronze Look Like?

The appearance of bronze can vary depending on factors such as its composition, age, and exposure to environmental conditions. Freshly cast bronze has a metallic brown color.

Over time, as the bronze oxidizes, it develops a patina that alters its appearance. The patina typically starts as a shiny golden brown, then transitions to various shades of brown. Eventually, it may develop into a greenish tint. The greenish hue is often associated with copper carbonate, a compound formed through the oxidation process.

This patina is a natural and protective layer that forms on the surface of the bronze, providing some resistance against further corrosion.

What Are the Different Types of Bronze?

There are so many different bronze alloy types (around 50, give or take) that if we were to go through all of them, we’d be here all day. We wrote an article about nine of them, and for ease of reference, we’ll list the five most common types used in manufacturing below, with the amounts of the other elements (in addition to copper) they contain.

What Are the Properties of Bronze?

In the following two sections, we’ll break down both the physical and chemical properties of bronze, helping you understand the metal a little better.

What Are the Physical Properties of Bronze?

The physical properties of bronze are outlined in Table 1:

What Are the Chemical Properties of Bronze?

The chemical properties of bronze are given in Table 2:

1. Tools

Bronze was being made into tools and weapons from as early as the Bronze Age (only around 5,000 years ago). Our ancestors were obviously onto something because it’s still being used today to make the same things, including hammers, wrenches, chisels, blades, gears, and bearings.

2. Architecture

Architects particularly love bronze as it’s a snazzy addition to any building, offering decorative flair, as well as strength and durability. It’s made into door or window frames, cabinet handles, or trims. Bronze used for architectural purposes is often more natural in color, but if it’s used outside (sculptures or ornaments) it’s usually patinized.

3. Coins

Back in ancient times, bronze was one of the two main metals for coins, alongside copper. Modern coins, though, have replaced them with metals like copper-plated steel, zinc, and nickel, mainly for pricing reasons.

4. Instruments

Cymbals, bells, gongs, and a host of other musical instruments can be made from bronze. They’re cast in a very interesting formulation called “bell metal.” Other types of bronze like phosphor bronze are sometimes used to make acoustic guitar and piano strings, too.

5. Bells

Bronze can produce a strong and clear tone, hence it’s used to make bells. Like with musical instruments, bells are made from the same “bell metal” which is basically made from 80% copper and 20% tin—a balance that creates very nice sounds and resonance by absorbing energy.

6. Bearings

Bronze, in a formulation called “bearing bronze” which is strong and hard, is great for making things like springs, bearings, and bushings, especially when it comes to car transmissions and small electric motors. These types of bearings are usually shock-, impact-, wear-, and corrosion-resistant, and used in sectors like food processing, injection molding, and automotive equipment.

7. Medals

Most of us will have first heard of bronze at an early age thanks to the “bronze medal” won in sporting events and other competitions. Before the 1904 Summer Olympics in St. Louis, MO, silver medals were given to winners, and bronze was awarded to the runners-up. Then gold entered the scene and our beloved bronze got relegated to third place.

8. Bronze Casting

Bronze casting is a traditional metalworking process with a rich history that spans civilizations. Molten bronze is poured into a carefully crafted mold to create objects and sculptures. Bronze casting has historically served to manufacture tools, weapons, sculptures, bells, and much more. 

What Are the Advantages of Bronze?

Bronze has the following advantages:

1. It’s much harder than pure copper or iron
2. It has better corrosion resistance, heat and electrical conductivity, and fatigue-resistance than most steels
3. It’s easier to cast than copper because it’s more fusible
4. It has low metal-to-metal friction
5. It’s both versatile and durable
6. It has a good surface finish

What Are the Disadvantages of Bronze?

Some of the disadvantages of bronze include:

1. Its hardness might make it more difficult to work with
2. It tends to oxidize more easily than copper does
3. It’s often more expensive than steel, brass, or copper
4. Its kryptonite is ferric compounds, ammonia, and cyanides—sulfur and chlorine can actually cause it to deteriorate in humid environments
5. As odd as it sounds, bronze can get sick. Bronze Disease (yes, this is a real thing) makes small, rough, pale green spots suddenly appear on its surface when oxygen and chloride react in water. Left unchecked, it could be totally destroyed.

What Is the Difference Between Bronze and Brass?

Xometry customers often ask us about the difference between these two metals when they need a nice-looking metal for their manufacturing needs. It mainly comes down to their composition and properties. Both are copper alloys and corrosion resistant, but bronze can make itself a protective patina, whereas brass will tarnish over time. Brass is made of copper, zinc, and other elements that contribute to its color, which can be bright gold, copper, or silver. It’s more malleable than bronze, which means you don’t have to worry about it breaking when hammered or rolled (within reason, of course).

To learn more, see our full guide on Bronze vs. Brass.

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