Bronze vs. Brass: What Are the Differences?

Brass and bronze are both classified as copper alloys or copper-based alloys. Brass consists of a mixture of copper and zinc, whereas bronze is a mixture of copper and tin. Both these alloys can be combined with other elements in small amounts to alter the properties of these metals. This includes elements such as aluminum, phosphorus, and silicon.

This article compares brass vs. bronze in terms of color, applications, costs, properties, and more. 

What Is Bronze?

Bronze is a copper alloy that consists of a mix of copper and tin (around 12%). Other elements like phosphorus, silicon, zinc, arsenic, manganese, and aluminum can also feature in its composition in small amounts to add different properties. Bronze exhibits good corrosion resistance, has low metal-to-metal friction, and is quite ductile.

However, bronze can be prone to oxidation which can lead to the formation of a greenish-blue patina. Oxidation can also lead to a darkish brown appearance over time. 

What Are the Advantages and Disadvantages of Using Bronze

The advantages of bronze include:

1. Compared to brass, bronze offers higher corrosion resistance (including against seawater corrosion). 
2. Hard and quite durable (harder than both copper and iron).
3. Has better electrical and thermal conductivity compared to most, but not all metals.
4. Has a better resistance against fatigue compared to most steels.

Despite its advantages, bronze also has some disadvantages like:

1. Due to its hardness, bronze is harder to work with compared to brass and pure copper.
2. Has limited resistance to ferric compounds, ammonia, and cyanides.
3. Oxidizes more easily than copper.
4. Is typically more expensive than brass. 

What Is Brass?

Similar to bronze, brass also falls under the category of copper alloys, but its composition contains copper and zinc instead of copper and tin. Other metals, such as aluminum, iron, silicon, and manganese can also be mixed with copper and zinc to get different properties and color variations of the alloy. For example, a high zinc percentage will give more strength and ductility, while manganese will lead to better corrosion resistance. Lead is often added in small percentages to further improve the workability of brass. The color of brass changes based on its zinc and copper content. The typical color for brass is a yellowish-gold hue, as seen in Figure 3:

However, a higher zinc content leads to a more silvery color, while more copper gives a reddish tone. 

Advantages and Disadvantages of Brass

Some of the advantages of brass include:

1. Better workability, machinability, and malleability compared to bronze. 
2. Has antibacterial properties. 
3. Distinctive gold-like appearance, which makes it aesthetically pleasing. 

Some disadvantages associated with brass include:

1. Susceptible to stress cracking when exposed to ammonia. 
2. Prone to tarnishing. 
3. Slightly lower melting point than bronze. 

Bronze and Brass: How They Are Made

The processes for making bronze and brass involve melting and combining two or more metals in specific proportions. For traditional bronze, the typical composition includes about 88% copper and around 12% tin, whereas for brass the copper concentration will range between 55–95% copper and 5-45% zinc. Once these metals are melted and properly mixed they are cast into molds to shape them into the intended shape or design. They are then left to cool and solidify. 

Properties Comparison of Bronze and Brass

Table 1 below shows a comparison between some of the properties of bronze and brass: 

Applications of Bronze and Brass

Some of the common applications of brass and bronze include the following:

1. Musical Instruments: Brass is very malleable and has good acoustic properties. This is why it is used to make such a wide range of brass instruments, including the French horn, saxophone, harmonica, tuba, cornet, trumpet, tenor horn, and euphonium. Bronze on the other hand, although also used for musical instruments, is used to make bells (crafted from bell metal) and cymbals. Phosphor bronze can also be used to make guitar and piano strings.  
2. Decorative Items, Coins, Sculptures, and Statues: Brass with its gold-like appearance is commonly used to make statues, jewelry, coins, and decorative items. Bronze sculptures and architectural finishes are also common. Architectural bronze typically preserves the natural color and finish of raw bronze, whereas outdoor sculptures or ornaments typically go for the patination of bronze, involving a greenish or green-blue hue on the surface of the bronze item. 
3. Machine Parts: Brass is commonly used in low-friction applications like gears, bearings, locks, doorknobs, and valves. It is also commonly used in both plumbing and electrical applications. Bronze, on the other hand, is commonly used for bearings, bushings, springs, and similar fittings. Phosphor bronze, a type of bronze alloy, is particularly common in precision-grade springs and bearings. Before stainless steel, bronze was also very common in ship fittings due to its toughness and saltwater corrosion resistance. Bronze is, however, still used for submerged bearings and ship propellers.    

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