Copper Alloy Grades | Flange Material Reference

"Copper flange" on a requisition can mean any of a dozen alloys with very different properties. The groups below behave differently enough that substituting one for another is a design change, not a purchasing convenience.

Copper-nickels

The seawater alloys. Both grades carry a deliberate iron addition that makes the protective film erosion resistant. See copper-nickel flanges for the detail.

UNS	Common name	Nominal composition	Notes
`C70600`	90/10 copper-nickel	Cu bal, 10% Ni, 1.0 to 1.8% Fe, Mn	The default seawater piping alloy. Lower velocity ceiling than 70/30.
`C71500`	70/30 copper-nickel	Cu bal, 30% Ni, 0.4 to 1.0% Fe	Stronger, higher velocity and temperature. More sensitive to sulfides.
`C71640`	66/30/2/2 copper-nickel	Cu bal, 30% Ni, 2% Fe, 2% Mn	Higher iron and manganese for improved erosion resistance. Specialty.

Commercial coppers

Nearly pure copper. Excellent thermal and electrical conductivity, very good corrosion resistance in fresh water and many process fluids, low strength, and a low tolerance for flow velocity in salt water. These are process and utility materials, not seawater velocity materials.

UNS	Common name	Composition	Notes
`C10100`	Oxygen free electronic, OFE	99.99% Cu	Highest purity. Vacuum and electronics work.
`C10200`	Oxygen free, OFHC	99.95% Cu	No oxygen, so no hydrogen embrittlement risk when welded or brazed.
`C11000`	Electrolytic tough pitch, ETP	99.90% Cu, small O	The common commercial copper. The oxygen limits welding.
`C12200`	Phosphorus deoxidized, DHP	99.9% Cu, 0.02% P	The standard plumbing and refrigeration copper. Welds and brazes well.

Brasses

Copper and zinc. Cheap, easy to machine, and vulnerable to dezincification, where zinc leaches out and leaves porous copper behind. Tin additions and inhibitors reduce that, but do not eliminate it. Brasses also crack in ammonia.

UNS	Common name	Composition	Notes
`C46400`	Naval brass	Cu, 39% Zn, 1% Sn	Tin improves seawater resistance. Marine hardware and moderate duty.
`C36000`	Free cutting brass	Cu, 35% Zn, 3% Pb	Machines beautifully. Lead content restricted in potable water service.
`C68700`	Arsenical aluminum brass	Cu, 22% Zn, 2% Al, As	Condenser tube alloy. Arsenic inhibits dezincification.

Bronzes and aluminum bronzes

Harder and stronger than the coppers and copper-nickels. The aluminum bronzes in particular resist erosion and cavitation, which is why pump and valve bodies in seawater are so often cast in them.

UNS	Common name	Composition	Notes
`C83600`	Red brass, 85-5-5-5	85% Cu, 5% Sn, 5% Pb, 5% Zn	The classic cast bronze flange material behind ASME B16.24.
`C92200`	Navy M bronze	88% Cu, 6% Sn, 1.5% Pb, 4% Zn	Valve and fitting castings to naval requirements.
`C61400`	Aluminum bronze D	Cu, 7% Al, 2.5% Fe	Wrought. Plate and bar for erosion service flanges.
`C63000`	Nickel-aluminum bronze, wrought	Cu, 10% Al, 5% Ni, 3% Fe	High strength. Bar and forging stock.
`C95800`	Nickel-aluminum bronze, cast, NAB	Cu, 9% Al, 4% Ni, 4% Fe	The seawater casting alloy. Pumps, valves, propellers.

Nickel-copper

The reverse of a copper-nickel. Nickel is the base metal. Much stronger, much more expensive, and resistant to fluids that destroy copper alloys, notably hydrofluoric acid.

UNS	Common name	Composition	Notes
`N04400`	Monel 400	63% Ni, 30% Cu	Seawater, HF acid, high strength. Forgings per ASTM B564.
`N05500`	Monel K-500	63% Ni, 30% Cu, Al, Ti	Age hardenable. Shafts and fasteners more than flanges.

Selecting on price alone goes wrong here. These alloys are not interchangeable. Brass substituted for copper-nickel dezincifies. Copper-nickel substituted for aluminum bronze erodes in sandy water. Copper alloy substituted into ammonia service cracks. If a grade is being swapped for availability or cost, run it past the design authority.

Beyond copper

Texas Flange stocks and machines the full industrial materials list, not just copper alloys. Carbon steel in A105, A350 LF2, LF3, A694 and SA-516-70. Chrome alloys in A182 F1, F5, F9, F11, F22 and F91. Stainless in F304, F316, dual grades, and the H and L variants. Duplex in F51 and F53. Plus aluminum, Hastelloy, Inconel, Incoloy and titanium. There are grades no flange producer stocks, and we source and make those to requirement.

See the Texas Flange catalog for the full material range.

Common questions

What is dezincification and which alloys does it affect?

Zinc leaching selectively out of a brass, leaving a weak porous copper skeleton behind. It affects the brasses, so naval brass C46400 and the yellow brasses. Copper-nickels and the aluminum bronzes contain no meaningful zinc and are not susceptible.

When would I pick aluminum bronze over copper-nickel?

When the wear mode is mechanical rather than chemical. Aluminum bronze is harder and more erosion and cavitation resistant, so it belongs on pump internals, in lines carrying entrained sand, and where flow velocity is above what copper-nickel tolerates. Copper-nickel keeps the advantage on biofouling resistance.

Is Monel a copper alloy?

It is a nickel-copper alloy, about 63 percent nickel and 30 percent copper, so nickel is the base and copper is the alloying element. That is the reverse of a copper-nickel. Monel 400 is considerably stronger than either Cu-Ni grade and considerably more expensive.

Which grade is the cast bronze flange standard written around?

C83600, commonly called 85-5-5-5 or red brass, is the classic composition behind ASME B16.24 cast copper alloy flanges. It casts well and machines well, and it is fine for moderate water service. It is not a high velocity seawater alloy.

Not sure which grade the job needs?

Send the fluid, the velocity, the temperature and what the rest of the line is made of. That is usually enough for us to make the call with you.

Send the print, or send the size, class and grade. Texas Flange quotes quickly.

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