Differences Between Copper, Brass, and Bronze

Introduction

We often call copper, brass, and bronze red metals. Although they are very similar in color, they are very different in composition, properties, and applications. Understanding the differences between copper, brass, and bronze is essential for choosing the right material for your project. This article will compare the properties of these three metals from multiple dimensions and explore how these properties affect their applications, in order to provide valuable reference and suggestions for your project material selection.

Difference Between Copper, Brass and Bronze

Appearance

Although copper, brass and bronze are all “red metals”, their different compositions give them different metallic appearances.

Natural pure copper shows a reddish-brown hue with a metallic sheen.

Brass shows a bright and golden appearance, similar to gold. As an alloy of copper and zinc, the color of brass is affected by its chemical composition. When the copper content of brass is high, the color of brass tends to be more like the reddish brown of pure copper; when the zinc content is high, the color of brass tends to be more like a bright golden yellow;

Bronze has an overall dark gold color.

Common Grades and Chemical Composition

Copper

Copper is one of the few pure metals that can be found in nature. The following are some common types of pure copper.

Oxygen-Free Copper

Oxygen-free copper is referred to as OFC. It refers to a type of electrolytically refined pure copper. The oxygen content of these pure coppers is less than 0.001%, which is almost zero.

Oxygen-Free Electronic (OFE) Copper

This type of pure copper has a copper content of 99.99% and an oxygen content of 0.0005%. This pure copper is processed in a strictly controlled oxygen-free environment.

Electrolytic Tough Pitch (ETP) Copper

This type of pure copper is mainly produced through the electrolytic smelting process. This is the most common pure copper used in electrical applications. The copper purity is 99.9% and the oxygen content is 0.02% to 0.04%.

Deoxidized High Phosphorus (DHP) Copper

DHP copper is made by adding phosphorus to deoxidize the copper to form pure copper with excellent corrosion resistance. This pure copper is often used in applications that require high electrical conductivity and good corrosion resistance, such as cable conductors, transformers, contactors, etc. in the power industry.

Tellurium Copper

Tellurium Copper is a copper alloy with a trace amount of tellurium added to pure copper. Tellurium is added to copper to improve the material’s processing properties. Tellurium copper is ideal for making a variety of cutting tools.

Beryllium Copper

Beryllium Copper is a copper alloy with 0.5–3% beryllium added to pure copper. Beryllium can significantly increase the material’s strength and hardness. Beryllium copper is used to make precision gears, bearings, and other wear-resistant parts.

Pure Copper and Copper Alloy Grades and Chemical Composition Chart

Brass

Brass is an alloy of copper and zinc, with the copper content being the larger. Copper accounts for about two-thirds of the total, while zinc accounts for about one-third. Additional elements such as arsenic, lead, phosphorus, aluminum, manganese and silicon can be added to improve the performance of copper-zinc alloys. Common brass alloy types are as follows:

Admiralty Brass

Admiralty brass is a copper-zinc alloy with a copper content of about 70%, a zinc content of about 29%, and an addition of 1% tin. The tin element makes admiralty brass more corrosion-resistant in marine-related applications. Common grades of admiralty brass are mainly distinguished by the content of arsenic, antimony and phosphorus. Admiralty brass is usually made into sheet and tube products and can be used to manufacture condenser tubes, evaporator and heat exchanger tubes, distiller tubes and still tubes.

Naval Brass

Naval brass is composed of about 59% copper, 40% zinc and 1% tin, as well as a small amount of lead. Compared with the admiralty brass, the naval brass has a lower copper content and a higher zinc content. The tin in the naval brass composition can inhibit zinc-leaching. Naval brass is widely used in the manufacture of marine hardware.

Yellow Brass and Red Brass

Yellow brass is a copper-zinc alloy with a high zinc content. The copper content is about 60% to 70%, and the zinc content is about 30% to 40%. The composition of red brass is characterized by a high copper content, generally 85%, and 15% zinc content. Red brass is often compared with yellow brass. Because of the high copper content, red brass will show a reddish color and have high corrosion resistance. It is used in the manufacture of metal products in seawater or chemical contact environments; while yellow brass has a high zinc content, which will show a golden appearance and has good processing performance. It can be used to manufacture decorative parts, door handles, lamps, accessories, etc.

Cartridge Brass

Cartridge brass is mainly composed of about 70% copper (Cu) and 30% zinc (Zn). This copper-zinc alloy is widely used in the manufacture of cartridge cases, hence the name.

Free-Cutting Brass

Free-Cutting brass has a copper content of about 60% and a zinc content of about 35%. Free-cutting brass has 2.5%-3.0% lead added to it. When cutting, the lead particles act like a lubricant, making the chips break more cleanly and easier to discharge, hence the name free-cutting brass.

Architectural Brass

Architectural brass has a copper content of 60% and a zinc content of 30-40%. By adding lead and iron, the processing performance and strength of the brass alloy can be improved, and its high zinc content makes it appear golden in appearance, with a high degree of aesthetics, which is very suitable for some architectural exterior structures.

Clock Brass

Clock brass contains about 60% copper and 30% to 40% zinc, supplemented by trace amounts of lead and iron. Lead and iron improve the strength, durability and machinability of the copper-zinc alloy, so clock brass can be used to manufacture precision parts, such as watch parts.

Brass Alloy Grades and Chemical Composition Chart

Bronze

Bronze is an alloy of copper and tin, with a tin content of 12% to 12.5%. Other metal elements can be added, including aluminum, manganese, nickel, zinc, non-metals such as phosphorus, or metalloids such as arsenic or silicon. These additional elements can improve the material properties of copper-tin alloys.

Aluminum Bronze

Aluminum bronze is a bronze with aluminum as the main alloying element, with an aluminum content of about 4% to 11%. Aluminum bronze also has other elements such as iron, nickel, and manganese. Aluminum bronze is known for its strength and corrosion resistance, so aluminum bronze is mainly used to manufacture sliding bearings and landing gear components on aircraft, valve components, engine components (especially ocean-going ships), underwater fasteners for ships, and ship propellers.

Phosphor Bronze

Phosphor bronze is an alloy of phosphorus and copper. The tin content is about 0.5% to 11%, and the phosphorus content is 0.01% to 0.35%. Tin can improve the corrosion resistance and strength of phosphor bronze, while phosphorus can improve the wear resistance and stiffness of bronze. The cutting properties of phosphor bronze can be improved by adding 0.5% to 3% lead. Phosphor bronze can be used to make springs, bolts, bushings, bearings, etc.

Tin Bronze

The main alloying element of tin bronze is tin, which can reach 12% and above, and there are trace amounts of lead. Tin bronze has excellent castability and high corrosion resistance, so it can be used to make gears, bushings, bearings, pump impellers, etc.

High-Leaded Tin Bronze Alloys

This tin bronze alloy has a high lead content of about 7% to 30%. The high content of lead makes this type of tin bronze have excellent thermal conductivity and easy cutting. Tin bronze alloys have a slow failure mechanism that can temporarily prevent wear and seizure. The working principle of the slow failure mechanism is that the lead seeps out of the alloy and smears on the surface of the journal. Therefore, this tin bronze alloy is widely used in bearings and bushings.

Silicon Bronze

The main elemental component of silicon bronze is silicon, which has a content of 2.5% to 6%. Strictly speaking, this copper alloy can be called either red silicon brass or red silicon bronze, depending on the zinc and tin content. When the zinc content is higher and the tin content is lower, the copper alloy behaves more like brass; when the tin content is higher and the zinc content is lower, the performance is closer to bronze. The silicon element makes this copper silicon alloy more corrosion resistant in marine applications, and also has higher strength and hardness.

Manganese Bronze

Manganese bronze is a high-strength bronze alloy in which the alloying elements such as manganese, aluminum and tin effectively increase the strength and corrosion resistance of the bronze alloy. Manganese bronze has a tensile strength of up to 110,000 PSI. It is suitable for applications that require wear resistance and load-bearing strength.

Bronze Alloy Grades and Chemical Composition

Hardness

Of the three materials, brass has the highest hardness under normal circumstances. Brass is an alloy of copper and zinc, and zinc can increase the strength and hardness of the material. The higher the zinc content of brass, the greater its hardness and the more it can withstand higher mechanical loads and friction. Brass is suitable for manufacturing precision gears, valves, hardware parts, electronic connectors and other occasions that require good wear resistance and mechanical strength. The hardness of conventional bronze is lower than that of brass. However, by adding some alloying elements, the hardness of bronze can be effectively improved. Phosphor bronze, silicon bronze, aluminum bronze, etc. all have a higher hardness than brass. At the same time, bronze has high corrosion resistance and is widely used in marine-related applications such as offshore facilities, ships, propellers, etc. For marine applications, bronze is a solution that can take into account both hardness and corrosion resistance. Copper has the lowest hardness, and hardness is not its main advantage. But when we choose materials, we must also remember that the harder the material, the more brittle it is.

Strength

When we talk about the strength of a material, we usually refer to its tensile strength and yield strength. Bronze has the highest tensile strength and yield strength of the three materials, which makes it particularly suitable for applications that require high strength, high wear resistance and good load-bearing capacity, such as gears and worm gears, bearings and plain bearing sleeves, marine propellers, etc. Brass is weaker than bronze, so it is mainly used in some light-loaded mechanical parts or some parts that are not subjected to high stress, such as valve fittings, nuts and bolts, etc. Copper has the lowest strength of the three metals and is not suitable for applications that have high requirements for the material’s pressure bearing capacity.

Melting Point and Hot Formability

Generally speaking, in the hot forming process, the lower the melting point of the material, the lower the heating temperature required, the lower the processing energy consumption, and therefore it is easier to form. The following table shows the melting point ranges of the three materials for reference only. The melting point of pure copper is 1084°C, the melting point range of brass is 900°C to 1025°C, and the melting point range of bronze is 600°C to 913°C. Among them, copper has the highest melting point, so its hot forming performance consumption is larger. The melting point of brass is lower than that of copper, so it has better hot forming performance. The melting point of bronze is lower than that of brass, and it exhibits excellent hot forming performance.

Corrosion Resistance and Durability

The main components of pure copper, brass, and bronze are copper elements. When copper elements come into contact with oxygen, they react with oxygen to form a dense copper oxide (CuO) or cuprous oxide (Cu₂O) film. This oxide film has a protective effect and can prevent the metal body from further oxidation and corrosion.

Bronze alloys such as tin bronze, aluminum bronze, and manganese bronze contain tin, aluminum, and manganese elements, which react with oxygen to form an oxide film to prevent the material from being corroded and can also resist the corrosion of sulfides and chlorides. Therefore, compared with copper and brass, bronze is more suitable for applications exposed to natural environments or in marine environments.

The main components of general brass alloys are copper and zinc. Although zinc improves the plasticity of brass materials, zinc itself is highly corrosive. If used in seawater or an environment with chlorides, zinc acts as an anode in seawater for oxidation, releasing electrons and forming zinc ions. Zinc ions react with other components in seawater (such as chlorides, sulfides, etc.) to form zinc salts or other corrosion products. These corrosion products may form localized corrosion pits or cracks on the metal surface, further accelerating the corrosion of the metal.

Therefore, bronze has the best corrosion resistance and is the strongest and most durable of the three materials. Pure copper has slightly weaker corrosion resistance than bronze. Brass has the worst corrosion resistance and is prone to cracking in some marine applications.

Thermal Conductivity

In electronic equipment and applications such as radiators and heat exchangers, thermal conductivity is a very important consideration when selecting materials. Thermal conductivity determines the ability of a material to conduct heat. Among them, copper has the highest thermal conductivity, so we often see that many heat exchangers use copper fin tubes, and we can see pure copper heat dissipation modules on some notebook motherboards. The thermal conductivity of brass is lower than that of pure copper, but it has good mechanical properties and is suitable for applications that require both durability and medium thermal conductivity. Bronze has the lowest thermal conductivity and is not a good choice for such thermal conduction applications.

Electrical Conductivity

In the fields of power transmission, electronic components, and wires and cables, electrical conductivity is a key factor to consider when selecting materials. Based on the following two tables, pure copper has a very high electrical conductivity, second only to silver, and is the most ideal electrical conductor. Its excellent electrical conductivity makes pure copper used in cables, wires, and electronic equipment. The electrical conductivity of brass is between that of pure copper and bronze. Brass is suitable for applications with medium electrical conductivity requirements; bronze is suitable for electrical applications that do not require high electrical conductivity, but also have requirements for corrosion resistance, wear resistance, and mechanical strength of the material.

* Conductivity ratings are expressed as a relative measurement to copper. A 100% rating does not indicate no resistance.

Machinability and Weldability

Pure Copper

Pure copper has low hardness and strength, which makes it very plastic and ductile when processed. It can withstand large deformation during cold processing without breaking easily, so it is suitable for various cold processing such as drawing, stamping, extrusion, etc. Pure copper has good cutting performance, low cutting force required during processing, less tool wear, but care should be taken to avoid sticking. Due to its low strength, pure copper performs poorly in applications with high strength requirements, but performs well in most applications with low strength requirements.

In terms of heat treatment, pure copper has good thermal stability and can restore its high plasticity after annealing, making it suitable for hot processing. The welding performance is also very good, and common welding methods (such as arc welding and gas welding) can be well applied to pure copper.

Bronze

Bronze is an alloy formed by copper and tin (or other elements, such as aluminum, manganese, etc.), which usually has high strength and hardness. Due to its high hardness, bronze has relatively poor machinability, especially when cutting, which requires stronger cutting force and high-quality tools, which easily leads to tool wear. Bronze has poor plasticity, especially bronze with a high tin content, which is prone to cracking or breaking during cold working, so hot working is usually required to improve its plasticity.

Bronze has poor welding performance, especially high-tin bronze. The melting point of tin (231.93°C / 449.47°F) is lower than that of copper (1084 °C / 1983 °F). During welding, local overheating of the alloy may cause rapid dissolution of tin, forming relatively weak areas, thereby increasing the risk of cracks.

Brass

Brass is an alloy of copper and zinc, which has higher strength than pure copper while maintaining good plasticity. Brass has moderate hardness and strength, making its processing performance between pure copper and bronze. Brass has good cutting performance. Compared with bronze, it has less cutting force and is not easy to stick to the knife. It is suitable for high-speed cutting and precision machining. It has good plasticity and is suitable for cold working, especially for manufacturing thin-walled parts and precision parts.

In terms of heat treatment, brass has good thermal stability, and its plasticity and processing properties can be improved by annealing. Brass has good welding performance, common welding processes can be effectively applied, and cracks or loose joints are not easy to appear during welding. Brass has better wear resistance than pure copper, but not as good as bronze, and is suitable for general mechanical and construction applications, such as pipes, decorative parts and mechanical parts.

Therefore, in terms of the processing performance of the material, pure copper has the best processing performance, followed by brass, and bronze has poor processing performance.

Weight

Weight is a direct factor to distinguish copper, bronze and brass. Copper has the largest weight, with a unit volume weight of 8960kg/㎥. On the other hand, bronze is 8800kg/㎥ and brass is 8720kg/㎥. Therefore, copper is heavier than bronze and brass is the lightest.

Cost

In general, the price of materials is affected by many factors, such as specific alloy composition, processing technology, etc. But pure copper is usually the most expensive of the three metals. First, the copper content of pure copper is much higher than that of bronze and brass. Secondly, the production of pure copper is carried out in an oxygen-free environment, and the production cost is high. In terms of composition, bronze is mainly an alloy of copper and tin, and other alloying elements (such as aluminum, manganese, etc.) are added, while brass is mainly an alloy of copper and zinc. The cost of tin is generally higher than that of zinc, so the cost of bronze is higher than that of brass.

Therefore, in terms of cost, pure copper is higher than bronze, and brass has the lowest cost.

A Simplified Comparison Table of Copper, Brass and Bronze

In the above section, we have compared the advantages and disadvantages of copper, bronze, and brass in detail from multiple dimensions and their applications. The following is a simple table for you to quickly compare the three materials.

Choose HYT for Copper and Copper Alloy Solution

It is always very difficult to select materials based on a variety of factors according to the project. With many years of project experience and industry experience, HYT’s technical team can provide you with a more suitable material solution for your project based on your project description, and give you a satisfactory quotation. Please contact us for more information about copper, brass and bronze products.