COMPREHENSIVE TECHNICAL ANALYSIS AND DATASHEET OF UNS C70600 CUPRO-NICKEL 90/10 FASTENERS
UNS C70600, globally recognized as Cupro-Nickel 90/10 or Alloy 706, is a premier marine-grade copper alloy engineered specifically for relentless exposure to flowing seawater. Comprising approximately 90% Copper and 10% Nickel, this alloy is distinctively fortified with a crucial ~1.4% addition of Iron (Fe). This specific iron inclusion profoundly alters the alloy's surface chemistry, forming a highly tenacious, self-repairing protective oxide layer that shields the metal from high-velocity seawater erosion and impingement attacks.
Beyond its structural stability and excellent fabrication qualities, C70600 possesses inherent biocidal properties. The copper-rich matrix actively repels marine biofouling, preventing the attachment of barnacles, algae, and mollusks. This combination of anti-fouling capabilities, absolute immunity to chloride stress-corrosion cracking, and total lack of magnetic permeability makes Cupro-Nickel 90/10 fasteners the cornerstone of naval shipbuilding, offshore desalination piping, and coastal power generation cooling loops.
■ Product Overview & Specifications
| Material Classification | Copper-Nickel Alloy (90/10 CuNi) |
|---|---|
| UNS Designation | C70600 |
| Microstructure | Single-Phase Alpha Solid Solution |
| Magnetic State | Completely Non-Magnetic |
| Density | 8.94 g/cm³ (0.323 lb/in³) |
| Size Range | Metric: M4 to M48 | Imperial: 3/16" to 2" |
| Primary Attribute | Supreme Resistance to Marine Biofouling & Seawater Erosion |
■ Proprietary Datasheet Download (GATED)
UNS C70600 Cupro-Nickel 90/10 — Complete Technical Datasheet
Contains detailed maximum seawater velocity limits, galvanic compatibility charts for mating with Titanium or Super Duplex piping, and approved maritime welding parameters for C70600 studs.
⬇ DOWNLOAD DATASHEET■ MTC Integration Section
In high-stakes naval and offshore engineering, the precise balance of Iron and Nickel is critical. If the Iron content drops below 1.0%, the alloy's resistance to seawater erosion plummets. Ananka provides absolute metallurgical transparency mapping back to the primary mill.
- EN 10204 Type 3.1: Validates the mandatory 9.0–11.0% Nickel baseline, certifies the critical 1.0–1.8% Iron addition, and confirms the annealed or cold-worked temper limits of the finished fastener.
- EN 10204 Type 3.2: Routinely facilitated for critical naval shipyard contracts (NAVSEA) and offshore platform manifolds requiring DNV, ABS, or Lloyd's Register classification sign-offs.
■ Chemical Composition
The formulation of C70600 is elegantly specialized for the ocean. Nickel provides general structural stability and prevents pitting, while the specific inclusion of Iron (Fe) combined with trace Manganese (Mn) generates the impenetrable, self-healing oxide film necessary to survive fast-moving, turbulent seawater.
| Copper (Cu) | Nickel (Ni) | Iron (Fe) | Manganese (Mn) | Zinc (Zn) | Lead (Pb) |
|---|---|---|---|---|---|
| Balance (~88.6) | 9.0 – 11.0 | 1.0 – 1.8 | 1.0 Max | 1.0 Max | 0.05 Max |
■ Mechanical Properties
| Mechanical Property | Typical Limits (Half-Hard Temper) |
|---|---|
| Tensile Strength | 44,000 - 60,000 psi (300 - 415 MPa) |
| Yield Strength | 20,000 - 45,000 psi (140 - 310 MPa) |
| Elongation (in 2 inches) | 25% - 40% |
| Hardness (Rockwell B) | 65 - 80 HRB |
■ Equivalent Grades & Designations
| Standard / System | Designation |
|---|---|
| ASTM Specifications | ASTM B151 (Rod & Bar), ASTM F467 / F468 |
| Common Trade Names | 90/10 CuNi, Alloy 706, Copper-Nickel 10% |
| European Equivalent | EN CW352H / CuNi10Fe1Mn (DIN 2.0872) |
| Military / Marine Std | MIL-C-15726 (US Navy), DEF STAN 02-779 (UK) |
■ Applications & Industries
- Shipbuilding & Submarines: Critical structural bolting, seawater intake screens, and flange fasteners for fire-main piping networks onboard naval and commercial vessels.
- Desalination & Power Generation: Tube sheet bolting, condenser water boxes, and evaporator internal hardware handling hot, concentrated, fast-flowing brine.
- Offshore Oil & Gas: Subsea manifold fasteners, splash-zone hardware, and rig cooling loops where immunity to chloride stress cracking and biofouling is required.
■ Compatible Fastener Assemblies
| Mating Bolts/Studs | Internal Threads (Nuts) | Washers |
|---|---|---|
| C70600 CuNi Hex Bolts & Studs | C70600 Finished Hex Nuts | C70600 CuNi Flat Washers |
■ Torque & Installation Guidelines
C70600 is highly ductile and features a relatively low yield strength compared to alloy steels or Aluminum Bronzes. Overtorquing will rapidly stretch the bolt beyond its elastic limit. Thread galling is also a persistent risk in marine environments; premium marine-grade, nickel-compatible anti-seize must be utilized during joint assembly.
| Nominal Diameter | Threads Per Inch (UNC) | Max Target Torque (in-lbs) | Max Target Torque (ft-lbs) |
|---|---|---|---|
| 1/4" | 20 | 60 - 70 | ~ 5.5 |
| 3/8" | 16 | 180 - 200 | ~ 16 |
| 1/2" | 13 | 360 - 400 | ~ 32 |
| 3/4" | 10 | 1200 - 1400 | ~ 110 |
■ Frequently Asked Questions
1. Why add Iron to a Copper-Nickel alloy?
Pure Copper-Nickel is excellent at resisting stagnant saltwater, but when seawater flows rapidly through a pipe or around a bolt, the sheer mechanical force of the water tears the protective oxide layer away, leading to rapid "impingement" erosion. The addition of just 1.0% to 1.8% Iron radically strengthens that oxide layer, allowing the metal to withstand much higher water velocities without eroding.
2. How does C70600 (90/10) compare to C71500 (70/30) Cupro-Nickel?
C71500 (70/30) contains 30% Nickel, making it significantly stronger and capable of withstanding even higher seawater velocities than the 90/10 grade. However, 70/30 is considerably more expensive and harder to machine. For the vast majority of general marine piping, cooling loops, and submerged hull hardware, 90/10 (C70600) provides the optimal, cost-effective balance of corrosion resistance and biocidal performance.
3. Do Cupro-Nickel fasteners really prevent barnacle growth?
Yes. The high copper content in C70600 naturally releases microscopic copper ions into the immediate surrounding water. This local environment is highly toxic to marine microorganisms, larvae, and biofouling agents like barnacles or mussels. Using CuNi fasteners on underwater grates or pump housings ensures those components remain clear of marine growth, eliminating the need for constant mechanical scraping.
