Shanghai, June 2025 — In today’s high-performance marine and industrial applications, the demand for durable, corrosion-resistant materials is stronger than ever. At the forefront of this movement are Copper Nickel (Cu-Ni) flanges, specifically the 90/10 C71500 raised face (RF) and 70/30 UNS C70600 welding neck flanges. Manufactured in accordance with ASTM B151 / ASME SB151 standards and available in Class 300 (300#) pressure ratings, these components are playing a vital role in modern infrastructure and offshore systems across the globe.
With excellent resistance to saltwater corrosion, biofouling, and high temperatures, Cu-Ni flanges are now being widely adopted in shipbuilding, offshore energy, desalination plants, and other critical sectors requiring high-integrity metal joining solutions.
What Makes Copper Nickel Alloys Ideal?
Copper Nickel alloys, known for their excellent corrosion resistance in seawater and brine environments, are available in two main grades:
C70600 (Cu-Ni 90/10): Comprising 90% copper and 10% nickel, this alloy is widely used in marine applications due to its excellent resistance to biofouling and moderate strength.
C71500 (Cu-Ni 70/30): With 70% copper and 30% nickel, this grade offers higher strength and superior resistance to erosion and impingement in high-velocity water conditions, making it ideal for more demanding offshore and industrial environments.
Both materials provide excellent thermal stability, weldability, and mechanical performance, making them especially suitable for high-pressure and corrosive fluid transport systems.
Flange Types Explained: RF and WN
The article focuses on two widely used flange types:
1. Raised Face (RF) Flange – C71500 Cu-Ni 70/30
Raised face flanges are engineered with a small raised area around the bore to concentrate pressure on the sealing area and ensure a tight seal with gaskets. These flanges are especially beneficial in critical piping systems, where leakage prevention is essential.
2. Welding Neck (WN) Flange – C70600 Cu-Ni 90/10
Weld neck flanges feature a long tapered hub, which allows for a smooth transfer of stress from flange to pipe. This design minimizes stress concentration and is ideal for high-pressure and high-temperature environments. In marine and offshore systems, these flanges are typically welded to Cu-Ni pipes, forming strong, corrosion-resistant joints.
Manufactured to Global Standards
To ensure reliability and safety, Cu-Ni flanges are produced in strict compliance with:
ASTM B151 / ASME SB151: Governs the manufacturing of copper-nickel pipes, flanges, and fittings, ensuring material composition, tensile strength, yield, and elongation meet exacting criteria.
ANSI B16.5: Covers dimensional and pressure class specifications.
ISO 9001, PED, and DNV approvals: Common certifications that ensure product traceability, quality assurance, and safety compliance for international markets.
These standards make Cu-Ni flanges a trusted choice for engineers and procurement specialists who demand both performance and consistency in mission-critical applications.
Key Applications and Advantages
The benefits of Cu-Ni 90/10 and 70/30 flanges extend across numerous sectors:
● Marine and Naval Systems
Cooling water, ballast systems, and fire mains depend on Cu-Ni for their corrosion resistance and ability to withstand marine growth.
The anti-biofouling properties reduce maintenance, increasing vessel uptime and reducing costs.
● Offshore Oil & Gas
Used in platform piping systems, seawater injection lines, and riser connections, where extreme pressure and salt exposure are prevalent.
Cu-Ni flanges maintain mechanical integrity in subsea and topside environments.
● Desalination Plants
With high chloride content and brine discharge challenges, Cu-Ni is ideal for intake and discharge piping, ensuring resistance to pitting and cracking.
● Power Generation
Especially in thermal and nuclear plants, Cu-Ni flanges are used in heat exchangers, condenser tubing, and cooling systems, where consistent thermal performance is key.
● Chemical Processing
Resistant to sulfur compounds, chlorides, and organic solvents, these flanges are used in highly corrosive environments where alloy steel would quickly degrade.
Manufacturing Capabilities in China
China has become one of the world’s most important producers of Cu-Ni pipe fittings and flanges, with top manufacturers offering:
CNC-machined flange dimensions from ½” to 24” or DN15 to DN600
Pressure classes including 150#, 300#, and 600#
Flange types such as WN, SO, BL, TH, LAP JOINT
Customized machining for special bores, face finishes, and bolt hole patterns
EN 10204 3.1/3.2 MTCs, ultrasonic testing, and NDT upon request
With short lead times, competitive pricing, and OEM branding services, Chinese flange factories are well-positioned to supply both standard and project-specific requirements.
Logistics and Global Demand
With rising global infrastructure investments and a push toward decarbonization, the need for reliable, corrosion-resistant flange systems is growing rapidly. Export destinations for Chinese Cu-Ni flanges include:
Middle East: For desalination and petrochemical projects in Saudi Arabia, UAE, and Oman.
Europe: For shipbuilding, offshore wind, and green energy development.
Southeast Asia & Africa: For port infrastructure, water systems, and marine transportation.
North America: As part of refinery upgrades and naval modernization.
Most suppliers offer FOB, CIF, and DDP delivery, along with global freight support and documentation.
Sustainable and Long-Lasting
Copper-nickel alloys align with modern sustainability goals:
100% recyclable with no performance degradation.
Reduced maintenance and longer lifecycle, lowering total ownership cost.
Lower fouling and corrosion, which improves energy efficiency in cooling systems.
By choosing Cu-Ni flanges, industries not only gain technical reliability but also contribute to a circular economy.
Conclusion: A Future Secured by Copper-Nickel Engineering
As the world’s industries modernize and expand in harsh, corrosive environments, Copper Nickel flanges—C71500 RF and C70600 WN—are proving indispensable. Their balance of strength, corrosion resistance, and long-term performance has made them essential in sectors where failure is not an option.
Backed by global standards, rising production capabilities, and sustainable benefits, these flanges are set to remain a cornerstone of high-integrity piping systems well into the future.