Bismuth bronze is a lead-free bronze in which bismuth replaces the lead used in traditional bearing and plumbing bronzes, delivering nearly the same machinability and performance without the toxicity. It is primarily a copper-tin alloy with a small percentage of bismuth, and it offers high tensile strength, good thermal conductivity, good corrosion resistance, and excellent machinability. Those qualities, plus its compliance with lead-free drinking-water regulations, make it the modern choice for faucets, valves, pump components, pipe fittings, bearings, and small gears.
This guide covers what bismuth bronze is made of, why it behaves the way it does, the common alloy grades, and where it is used, so you can decide whether it fits your part. For broader material selection, see our full materials range, and for how it compares with its cousin, our guide to bronze vs brass.
What Is Bismuth Bronze?
Bismuth bronze is a copper-base alloy of copper, tin, and bismuth, sometimes with zinc and nickel. It was developed to duplicate the properties of leaded tin bronze without the lead. Bismuth sits next to lead on the periodic table and shares lead’s useful trait of improving machinability through lubricity, while being far less hazardous. As a result, bismuth bronze is marketed as the environmentally friendly replacement for leaded bronzes, and it is often specified specifically because of environmental regulation rather than cost, since leaded bronzes are usually cheaper.
Bismuth also has a low melting point of 271 °C, so adding it lowers the alloy’s melting temperature. That improves castability and lets foundries pour intricate shapes more easily than with many other bronzes.
Composition and Common Grades
The defining feature is that bismuth, not lead, provides the free-machining and bearing characteristics. A widely used grade, C89833 (a lead-free replacement for the older leaded alloy C836), is roughly 87% copper, 5% tin, 3% zinc, and 2% bismuth, with copper not less than 86%. It carries a machinability rating around 81 and a density near 0.317 lb/in³. Related grades include C89835 and C89844, the latter used for fittings and valves in potable water.
| Property | Typical bismuth bronze (e.g. C89833) |
| Base composition | ~87% Cu, 5% Sn, 3% Zn, 2% Bi |
| Machinability rating | ~81 (good) |
| Lead content | Lead-free |
| Joining | Excellent soldering, good brazing |
| Notable traits | Polishes and plates well, pressure-tight castings |
Key Properties
Bismuth bronze delivers most of what leaded tin bronze offers. It has high tensile strength and good thermal conductivity, sound corrosion resistance suited to water and many industrial environments, and good machinability thanks to bismuth’s lubricity. It produces pressure-tight, corrosion-resistant castings, and it takes polishing and plating well. It solders excellently and brazes well, which matters for plumbing assemblies.
Why It Matters: Lead-Free Compliance
The biggest driver of bismuth bronze adoption is drinking-water regulation. Since the US lead-free requirements took full effect in January 2014, plumbing components that contact potable water must meet strict limits on lead content. Grades like C89833 are compliant with the Federal Safe Drinking Water Act, the Reduction of Lead in Drinking Water Act, California AB1953, and Vermont Act 193, and are certified to NSF/ANSI/CAN 61. They are also recognized as acceptable under California Proposition 65. For any wetted component, this compliance is the reason engineers move from leaded bronze to bismuth bronze.
Common Applications
Because it combines machinability, corrosion resistance, and lead-free safety, bismuth bronze appears throughout fluid-handling and mechanical hardware:
• Faucets, valves, and valve bodies
• Pump components and water-pump impellers
• Pipe fittings and plumbing goods
• Water meters and housings
• Small gears, bushings, and bearings
• Fasteners
It has a long history beyond plumbing too, from telegraph wire in the nineteenth century to decorative castings, and bismuth bronze artifacts date back centuries.
We machine and finish copper alloys including bronze through our CNC turning and CNC machining services. If you have a bismuth bronze part to make, request a quote and we will advise on grade and machinability.
Frequently Asked Questions
What is bismuth bronze used for?
It is used mainly for plumbing and fluid-handling parts that must be lead-free, such as faucets, valves, pump components, pipe fittings, water meters, and impellers, as well as bearings, bushings, small gears, and fasteners.
Is bismuth bronze lead-free?
Yes. Bismuth replaces lead while providing similar machinability. Grades like C89833 meet US lead-free drinking-water regulations and are certified to NSF/ANSI/CAN 61, which is the main reason the alloy is chosen.
How does bismuth bronze compare to leaded bronze?
It offers comparable strength, corrosion resistance, and machinability without the toxic lead. It typically costs more than leaded bronze, so it is usually selected to meet environmental and drinking-water regulations.
Is bismuth bronze easy to machine?
Yes. Bismuth’s lubricity gives the alloy good machinability, with grades such as C89833 rated around 81, making it well suited to turned and machined fluid-handling components.