C22000 is best known by its traditional name, commercial bronze. The name is a piece of metallurgical history rather than an accurate description, because the alloy is a brass: approximately 90% copper and 10% zinc. It is supplied as sheet, strip, rod, wire and seamless tube, and polished tube is widely used where both corrosion resistance and appearance matter.
Naming and Basic Definition
The copper-zinc alloys are divided conventionally into two groups. Alloys with high copper content and a reddish colour are called bronzes in older literature even though their alloying element is zinc, while those with more zinc and a yellow colour are called brasses. C22000 sits at the boundary at 90% copper and is therefore named commercial bronze, although its structure and working behaviour are those of a low-zinc brass. The Chinese designation for the same 90/10 composition is H90, listed in GB/T 5231.
Chemical Composition and Physical Properties
| Element | Specified content |
|---|---|
| Copper | 89-91% |
| Zinc | Balance |
| Lead | 0.05% max |
| Iron | 0.05% max |
| Other elements, total | 0.10% max |
| Property | Value |
|---|---|
| Density | 8.80-8.86 g/cm³ |
| Melting range | approximately 950-980 deg C |
| Electrical conductivity | 35-40% IACS in the annealed condition |
| Thermal conductivity | approximately 120-140 W/(m·K) at 20 deg C |
| Colour | Golden yellow |
The main product specifications are ASTM B36/B36M for sheet, strip, plate and rolled bar, ASTM B134/B134M for wire and ASTM B135/B135M for seamless brass tube. European rod and bar, profile and wire products are ordered to EN 12163, EN 12164 and EN 12167, and Japanese rod and bar to JIS H3250.
Mechanical Properties by Temper
| Condition | Tensile strength | Yield strength | Elongation | Hardness |
|---|---|---|---|---|
| Annealed | 200-270 MPa | 60-100 MPa | 35-50% | HV 45-65 |
| Cold worked H02 | 300-370 MPa | 250-300 MPa | 15-25% | HV 70-90 |
| Cold worked H04 | 380-450 MPa | 340-400 MPa | 5-15% | HV 100-120 |
Product Forms and Typical Dimensions
| Form | Thickness or diameter | Width or wall | Notes |
|---|---|---|---|
| Sheet and strip | 0.2-6.0 mm | 50-500 mm | Length cut to order |
| Rod and bar | 3-50 mm diameter | - | Round, square and hexagonal |
| Wire | 0.3-12 mm | - | Bare or as drawn |
| Seamless tube | 1-15 mm wall | 10-150 mm outside diameter | Straight lengths or coils |
Performance in Service and Its Limits
C22000 has good resistance to atmospheric corrosion, fresh water and mildly aggressive chemical environments, and it is unaffected by the rural and urban atmospheres that attack plain steel. Its low-zinc structure also makes it more resistant to stress-corrosion cracking than the higher-zinc brasses used for machined fittings.
Its limits matter just as much. Commercial bronze is not a marine alloy: prolonged immersion in seawater or exposure to salt spray causes dezincification and general corrosion, and protective coating or a different alloy is required for such service. Ammonia and ammonium compounds attack copper alloys and can cause stress-corrosion cracking, so the material should not be used where such compounds are present, and cold-formed parts should be stress relieved before installation in aggressive environments.
Processing and Finishing Guidance
Cold forming: the alloy stamps, bends, spins and draws well in the annealed condition, with minimal tool wear, which is why it is a standard material for decorative and functional pressings.
Annealing: soft annealing is carried out in the 400-550 deg C range to restore ductility after cold working, followed by a suitable cooling practice to avoid embrittlement.
Machining: free-cutting behaviour is limited because lead is restricted to 0.05% max. Use sharp tooling, positive rake angles and an effective lubricant to control galling and built-up edge.
Welding and brazing: TIG and resistance welding can be used on thin sections, and brazing and soldering are straightforward. Excessive heat input should be avoided to prevent grain growth and loss of the polished surface condition.
Surface finishing: for decorative work, parts are polished, brushed or lacquered. A clear lacquer preserves the golden colour where the part is handled frequently or exposed to polluted atmospheres.
Applications
Typical uses include decorative and architectural trim, door furniture and handrails, roofing and cladding details, polished tube for plumbing fittings, valve components and decorative fixtures, low-current electrical connectors, terminal blocks and switch parts, stamped fasteners, bushings and general industrial hardware. Its combination of formability, colour and moderate strength keeps it in demand wherever appearance and function have to be delivered together.
FAQ
Q: Is C22000 a bronze or a brass?
Despite the traditional name commercial bronze, the alloy is a brass containing approximately 90% copper and 10% zinc. The name survives from an older classification based on colour rather than on alloying element.
Q: Can C22000 be used in seawater?
No. It has only limited resistance to seawater and salt spray and can dezincify in prolonged marine exposure. A copper-nickel alloy or an appropriate protective coating is required for such service.
Q: How does C22000 compare with C21000?
C21000 contains about 94-96% copper. The higher copper content gives slightly better corrosion resistance, while C22000 reduces cost and raises strength modestly at 89-91% copper.
Q: Is C22000 recyclable?
Yes. Copper-zinc alloys are fully recyclable and are collected and remelted as a standard industrial practice, which supports sustainability targets in construction and electrical applications.
Q: What is the Chinese equivalent of C22000?
The Chinese designation for the 90/10 copper-zinc composition is H90, listed together with its composition and impurity limits in GB/T 5231.
Q: How is polished seamless tube produced?
Seamless tube is produced from cast and extruded hollows, then cold drawn or pilger rolled to size, annealed and finally polished or bright annealed to give the smooth, uniform surface required for exposed plumbing and decorative applications.
