Copper Alloy ERCuNi
UNS C71581 · GB HSCuNi
ERCuNi is a 90/10 copper-nickel filler wire (C71581) matched to Cu-Ni piping alloys in the AWS A5.7 family, chosen for seawater and brine welds that need corrosion and biofouling resistance.
Reference datasheet — ERCuNi is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the AW condition
ERCuNi tempers and conditions
ERCuNi is supplied in 3 conditions, soft to hard. AW is the default FabDigit quotes; the values on this page are for it.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
AW | Pick for higher deposition on thicker Cu-Ni pipe and plate; pulsed spray with argon or Ar-He keeps porosity down. | 215 | 395 | 30 | 92 HB | 4.5 % IACS |
AWDefault As-welded deposit | Default condition: undiluted all-weld-metal deposit properties used for procedure qualification and design. | 220 | 400 | 32 | 90 HB | 4.6 % IACS |
AW | Pick for root passes, thin-wall Cu-Ni tube and heat-exchanger work where the cleanest, lowest-oxygen deposit is needed. | 225 | 410 | 34 | 88 HB | 4.7 % IACS |
Supply forms, finishes and certifications
Ways ERCuNi is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
WIRE | As-supplied cold-drawn filler wire/rod | Supply form |
AW-OVERLAY | AW overlay | Surface finish |
What is ERCuNi?
ERCuNi is a 90/10 copper-nickel filler wire (C71581) matched to Cu-Ni piping alloys in the AWS A5.7 family, chosen for seawater and brine welds that need corrosion and biofouling resistance. As-welded properties are 400 MPa tensile, 220 MPa yield, 32% elongation and 90 HB, with service to 315 °C and a corrosion-resistance score of 74; supplied as GTAW cut rod, GMAW spool wire and overlay wire. Joints must be free of oil, sulfur and lead, and welds need wide grooves with low heat input. For non-seawater bronze repair, ERCuSn-A or ERCuAl-A2 are cheaper choices. ERCuNi has a density of 8.94 g/cm³ (0.323 lb/in³), heavier than 90% of copper alloy grades. It melts at 1,170°C (2,138 °F). ERCuNi has a yield strength of 220 MPa (31.9 ksi) and a tensile strength of 400 MPa (58 ksi) — weaker than 51% of copper alloy grades. Elongation at break is 32% and the elastic modulus is 152 GPa (22 Msi).
What is ERCuNi used for?
- seawater piping welds
- shipboard CuNi tubing
- offshore condenser tube repair
- desalination plant piping
Advantages
- Stiff — 152 GPa (22 Msi), better than 99% of copper alloy grades
- High service temperature — 315°C (599 °F), better than 92% of copper alloy grades
- Readily welded — 78/100, better than 91% of copper alloy grades
- Good corrosion resistance — 74/100, better than 88% of copper alloy grades
- Forms and bends easily — 75/100, better than 82% of copper alloy grades
Limitations
- Poor heat conductor — 28 W/m·K (16.2 BTU/hr·ft·°F), worse than 96% of copper alloy grades
- Low electrical conductivity — 4.6 % IACS, worse than 96% of copper alloy grades
- High embodied carbon — 6.2 kg CO₂/kg, worse than 93% of copper alloy grades
ERCuNi properties
Typical room-temperature values for ERCuNi-AW; bars are the position among copper alloy grades.
Physical3
ERCuNi has a density of 8.94 g/cm³ (0.323 lb/in³), heavier than 90% of copper alloy grades. It melts at 1,170°C (2,138 °F).
Mechanical14
ERCuNi has a yield strength of 220 MPa (31.9 ksi) and a tensile strength of 400 MPa (58 ksi) — weaker than 51% of copper alloy grades. Elongation at break is 32% and the elastic modulus is 152 GPa (22 Msi).
Thermal6
ERCuNi is rated for continuous service to 315°C (599 °F). It conducts heat at 28 W/m·K (16.2 BTU/hr·ft·°F), worse than 96% of copper alloy grades. Thermal expansion is 16.2 µm/m·K (9 µin/in·°F).
Electrical3
ERCuNi conducts electricity at 4.6 % IACS, worse than 96% of copper alloy grades.
Chemical & Environmental3
Corrosion resistance is very good (74/100), better than 88% of copper alloy grades.
Sustainability4
Producing a kilogram of ERCuNi takes about 78 MJ of energy and emits 6.2 kg of CO₂ — more than 90% of copper alloy grades. Typical recycled content is 25%.
Manufacturability8
ERCuNi's machinability is poor (28/100, worse than 78% of copper alloy grades); weldability very good (78/100); formability very good (75/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the copper alloy family
Yield strength against density for every copper alloy grade FabDigit runs. ERCuNi is highlighted; hover a dot for its name, or open the interactive family chart.
Working with ERCuNi
Is ERCuNi easy to machine?
Weld metal machines like 70/30 Cu-Ni — gummy, ~20 % of AISI 1212; use sharp positive-rake carbide, slow feeds and generous coolant.
Can ERCuNi be welded?
GTAW/GMAW with 100 % argon (or Ar-He) DCEN/DCEP; joints must be oil-, sulfur- and lead-free, use wide 70–80° grooves, stringer beads, low heat input and interpass ≤150 °C, no preheat or PWHT normally required.
Can ERCuNi be formed, bent or molded?
Supplied as cold-drawn spool or cut rod; the deposit itself is highly ductile and can be dressed or peened cold without cracking.
ERCuNi chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| NiCo counted as Ni | 29 – 32 | 30.5 |
| Fe | 0.4 – 0.75 | 0.55 |
| Tideoxidizer, controls porosity | 0.2 – 0.5 | 0.35 |
| Mn | ≤ 1 | 0.6 |
| Si | ≤ 0.25 | 0.1 |
| C | ≤ 0.05 | 0.02 |
| P | ≤ 0.02 | |
| S | ≤ 0.01 | |
| Pb | ≤ 0.02 | |
| Other, total | ≤ 0.5 | |
| Cu | balance |
What surface finishes work on ERCuNi?
Pickle or wire-brush (stainless brush) to remove weld oxide; not anodizable — leave bare for natural patina/biofouling resistance or apply antifouling-compatible coatings only where required.
Surface treatments FabDigit runs on copper alloy parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Equivalent designations
Standards and trade names that resolve to Copper Alloy ERCuNi in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- C71581
- GB (China)
- HSCuNi
How much does ERCuNi cost?
ERCuNi is a high-cost copper alloy ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
ERCuNi — frequently asked
What is ERCuNi used for?
ERCuNi is typically used for seawater piping welds, shipboard CuNi tubing, offshore condenser tube repair and desalination plant piping. In short: matched 90/10 Cu-Ni filler; seawater corrosion resistance; sensitive to joint contamination.
What is the yield strength of ERCuNi?
ERCuNi has a typical yield strength of 220 MPa (31.9 ksi) and a tensile strength of 400 MPa (58 ksi) — weaker than 51% of copper alloy grades. Strength varies by condition: see the 3 listed tempers.
Is ERCuNi easy to machine?
Not especially — machinability is rated poor (28/100, worse than 78% of copper alloy grades). Weld metal machines like 70/30 Cu-Ni — gummy, ~20 % of AISI 1212; use sharp positive-rake carbide, slow feeds and generous coolant.
Can ERCuNi be welded?
Yes — weldability is rated very good (78/100). GTAW/GMAW with 100 % argon (or Ar-He) DCEN/DCEP; joints must be oil-, sulfur- and lead-free, use wide 70–80° grooves, stringer beads, low heat input and interpass ≤150 °C, no preheat or PWHT normally required.
What surface finishes work on ERCuNi?
Pickle or wire-brush (stainless brush) to remove weld oxide; not anodizable — leave bare for natural patina/biofouling resistance or apply antifouling-compatible coatings only where required.
Can ERCuNi be formed, bent or molded?
Supplied as cold-drawn spool or cut rod; the deposit itself is highly ductile and can be dressed or peened cold without cracking.
What is the maximum service temperature of ERCuNi?
ERCuNi is rated for continuous use to about 315°C (599 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between ERCuNi-AW and ERCuNi AW-GTAW?
AW is the default condition — default condition: undiluted all-weld-metal deposit properties used for procedure qualification and design. AW-GTAW: pick for root passes, thin-wall Cu-Ni tube and heat-exchanger work where the cleanest, lowest-oxygen deposit is needed. Yield strength is 220 MPa in AW versus 225 MPa in AW-GTAW.
How much does ERCuNi cost?
ERCuNi is a high-cost copper alloy ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- AWS A5.7/A5.7M — Specification for Copper and Copper Alloy Bare Welding Rods and Electrodes — AWS (2011)
- ASME BPVC Section II Part C, SFA-5.7 — ASME (2023)
- UNS C71581 / C71500 alloy data — Copper Development Association (2023)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys — ASM International (1990)
- Copper-nickel filler metal datasheets (ERCuNi) — Various welding consumable producers (2023)
- Guide to the Welding of Copper-Nickel Alloys — Nickel Institute / CDA (2018)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.