The two names get used as if they were a colour choice, but they are two different alloy families with different alloying elements and different failure modes. Pick the wrong one and the part either machines badly and costs more than it should, or dezincifies in service and comes back as a corrosion claim.
What is the difference between brass and bronze?
Brass is copper alloyed mainly with zinc; bronze is copper alloyed mainly with tin (with modern bronzes also using aluminium, silicon, manganese or phosphorus). Brass is cheaper because zinc is cheap, machines faster, takes a better polish and is the default for fittings, threads, terminals and decorative parts. Bronze is stronger and tougher, resists wear and seawater better, and is chosen for bearings, bushings, marine hardware, pump parts and anything that has to slide or survive salt. Both are non-magnetic. The practical decision usually comes down to three questions: does the part see seawater or chloride, does it slide against something, and does it need to be machined at the lowest cost.
What is actually in each alloy
- Brass - copper plus 5–45% zinc. Free-cutting brass (C36000) adds lead for machinability; naval brass adds tin and a little arsenic to resist dezincification; cartridge brass (C26000) is the deep-drawing grade.
- Bronze - copper plus tin (classic, C93200 bearing bronze), or copper plus aluminium (aluminium bronze, C95400), or copper plus phosphorus (phosphor bronze, C51000 for springs and contacts).
- Nickel silver and cupronickel - separate families again; the second family is what marine and coinage work uses when chloride resistance has to be high.
- What they share - both are non-magnetic, both conduct heat and electricity well (copper more than either alloy), and both are easy to braze and solder.
Side by side
| Property | Brass (CuZn) | Bronze (CuSn / CuAl) |
|---|---|---|
| Main alloying element | Zinc | Tin, aluminium, silicon or phosphorus |
| Colour | Yellow to golden, bright polish | Reddish brown to golden, more muted |
| Machinability | Excellent - free-cutting grades are the reference for machinability | Good, but generally below free-cutting brass |
| Strength and wear | Moderate; work-hardens quickly | Higher; better under load and sliding contact |
| Seawater / chloride | Dezincification risk unless a naval or DZR grade is specified | Good to excellent, especially aluminium bronze |
| Cost | Lower - zinc is the cheaper addition | Higher - tin and aluminium bronze cost more |
| Typical parts | Fittings, threads, terminals, valves, decorative trim | Bearings, bushings, worm wheels, pump and marine parts |
| Magnetic | No | No |
The failure mode that decides most arguments: dezincification
In warm, chloride-bearing water, ordinary brass can lose zinc selectively and turn into a porous copper sponge - the part keeps its shape while losing its strength, and it fails without warning. That is why seawater service calls for a naval brass, a DZR (dezincification-resistant) grade, or a move to bronze or cupronickel. If the drawing says only "brass" and the part goes into a marine or hot-water environment, the specification is the problem, not the material.
How the choice changes the machining route
- Free-cutting brass - runs fast on a lathe with a clean chip and a bright finish; the cheapest route for turned fittings and threaded parts.
- Bronze - tougher, so speeds drop and tool wear rises. In exchange the part resists galling and sliding wear, which is exactly what a bearing needs.
- Lead-free brass - required for potable water in a growing number of markets. It machines differently and machines slower; a drawing written before the rule change may need a cost revision.
- Deep drawing - cartridge brass and copper draw well; bronze is not a drawing material for the parts we make.
Key point
Choose brass for machinability, threads, terminals and cost; choose bronze for sliding wear, load and chloride service. If a brass part must live in seawater or hot chlorinated water, upgrade to a naval or DZR brass or move to bronze - and put the grade code on the drawing rather than the word "brass".
Frequently asked questions
Is brass or bronze stronger?
Bronze is generally stronger and tougher, and it holds up better under sliding contact. Brass is strong enough for most fittings and threads, and it is far easier and cheaper to machine.
Is bronze magnetic?
No. Bronze is diamagnetic, like copper and brass, so a magnet will not attract it in any practical test.
Which one is better for seawater?
Bronze, particularly aluminium bronze or a cupronickel, is the safer choice. Ordinary brass can dezincify in warm chloride water unless a naval or DZR grade is specified.
Can brass and bronze be used in the same assembly?
Yes, but the pair should be checked for galvanic effects against whatever else is in contact, and both should be stated by grade rather than by family name.