June 2025 – Shanghai, China — As global demand for corrosion-resistant, high-performance materials rises across marine, offshore, and industrial sectors, Copper-Nickel (Cu-Ni) flanges are increasingly becoming the material of choice for engineers, procurement managers, and EPC contractors worldwide. At the forefront are the C71500 (70/30) Raised Face (RF) flanges and C70600 (90/10) Welding Neck (WN) flanges, which comply with ASTM B151 / ASME SB151 and offer pressure ratings up to Class 300 (300#).
These flanges are not just a reliable component in piping systems — they represent the fusion of metallurgical engineering, long-term performance, and global standardization in mission-critical environments.
What Are Copper-Nickel Flanges?
Copper-Nickel alloys combine copper's excellent thermal and electrical conductivity with nickel's superior corrosion resistance. In the marine and chemical industries, where exposure to seawater, chlorides, and high-pressure systems is common, Cu-Ni alloys ensure low maintenance, extended lifespan, and resistance to pitting and stress corrosion.
The two main alloys used in flange manufacturing are:
C70600 (90/10 Cu-Ni): Composed of 90% copper and 10% nickel, this alloy offers outstanding resistance to seawater corrosion and is widely used in heat exchangers, seawater piping, and condenser tubing.
C71500 (70/30 Cu-Ni): With 70% copper and 30% nickel, this grade provides enhanced strength and resistance to high-velocity seawater, erosion, and industrial chemicals, making it ideal for offshore and power generation applications.
Flange Designs: RF and WN Explained
● C71500 Raised Face (RF) Flanges
Raised Face (RF) flanges are designed with a small raised area around the bore. This raised surface concentrates pressure on the gasket, resulting in improved sealing performance. C71500 RF flanges are used in high-pressure and temperature-sensitive systems where tight sealing is critical, such as marine main pipelines and chemical discharge outlets.
● C70600 Welding Neck (WN) Flanges
Welding Neck (WN) flanges are characterized by their long tapered hub and smooth transition from flange thickness to pipe wall thickness. This design reduces stress concentration and makes them ideal for high-pressure or cyclic loading environments. C70600 WN flanges are typically butt-welded to Cu-Ni pipes, forming a solid, leak-proof connection widely used in offshore and desalination applications.
Compliance with Global Standards
To ensure performance, safety, and compatibility, these flanges are manufactured in accordance with international standards, including:
ASTM B151 / ASME SB151 – Specifications covering seamless copper-nickel pipe, flanges, and fittings.
ANSI B16.5 – Standard covering pipe flanges and flanged fittings for sizes up to 24 inches.
ISO 9001:2015, PED, DNV, and Lloyd’s certifications – Common accreditations held by manufacturers for global supply and quality assurance.
These standards guarantee that flanges meet strict requirements for chemical composition, mechanical properties, and dimensional accuracy.
Industrial Applications Across Key Sectors
The use of Cu-Ni flanges spans numerous industries:
● Marine Engineering & Shipbuilding
Cu-Ni flanges are ideal for ballast systems, cooling water lines, bilge systems, and fire mains. Their inherent resistance to biofouling minimizes maintenance and ensures uninterrupted service over long operational periods.
● Desalination and Water Treatment
In high-salinity environments, Cu-Ni flanges outperform stainless steel by resisting pitting and chloride-induced cracking. They are essential in intake and brine discharge piping and high-pressure evaporators.
● Offshore Oil & Gas
70/30 Cu-Ni WN flanges are used in seawater injection lines, riser piping, and platform utility systems, where harsh conditions demand reliable corrosion resistance and mechanical strength.
● Power Generation
Thermal and nuclear power plants utilize Cu-Ni 90/10 components for condenser and heat exchanger systems, ensuring thermal conductivity, corrosion resistance, and ease of maintenance.
● Chemical & Petrochemical Industries
C71500 RF flanges are applied in systems handling sulfuric acid, organic solvents, and hydrocarbons, providing resistance to complex corrosion mechanisms without sacrificing weldability or structural strength.
Precision Manufacturing & Customization
Top-tier manufacturers, especially in China and India, offer a wide range of options, including:
Size Range: DN15 to DN600 (½” to 24”)
Pressure Rating: Class 150, 300, 600
Face Type: RF (Raised Face), FF (Flat Face), RTJ (Ring Type Joint)
Surface Finish: Serrated finish, mirror-polished, machined
Custom Drilling Patterns, special bore tolerances, and OEM engraving
Additionally, most suppliers provide EN 10204 3.1 / 3.2 MTCs, hydrostatic testing, PMI testing, and third-party inspections upon request.
Growing Demand and Market Outlook
The market for Copper-Nickel flanges is witnessing strong growth driven by:
Global naval fleet expansions
Green energy and desalination projects
Offshore platform retrofits
Infrastructure modernization across emerging economies
With increasing emphasis on sustainability and operational efficiency, Cu-Ni flanges are favored for their recyclability, low total lifecycle cost, and long service life.
China, particularly cities like Wenzhou and Cangzhou, remains a major global exporter, supplying to shipyards, EPC firms, and MRO companies in over 80 countries.
Sustainability and Future Developments
Cu-Ni flanges support long-term sustainability goals through:
100% recyclability with no material degradation
Reduced fouling and clogging, leading to lower pumping costs
Fewer replacements and repairs, which minimizes waste
The future of Cu-Ni technology lies in automated production, blockchain-enabled traceability, and hybrid alloy development, allowing even more durable and intelligent piping systems.
Conclusion: A Strategic Investment in Durability and Reliability
Whether used in the hull of a naval vessel, the heart of a power plant, or the core of a chemical process, Copper-Nickel flanges—particularly the C71500 RF and C70600 WN models—are integral to ensuring operational safety, durability, and performance.
With proven material properties, international certifications, and extensive application success, these flanges represent not only a product but a strategic engineering solution trusted by industries worldwide.
As global industries continue to confront environmental challenges, rising costs, and evolving performance expectations, Cu-Ni flanges will remain at the center of sustainable, high-integrity infrastructure for decades to come.