What Is C71500 Copper Nickel
C71500, the 70/30 copper-nickel alloy, contains approximately 70 percent copper and 30 percent nickel with deliberate additions of iron and manganese. It retains the corrosion behavior of the 90/10 grade, C70600, but offers superior resistance to high-velocity seawater and erosion, and it can operate at higher temperatures. These characteristics make it the preferred material for critical marine hardware and high-stress heat exchange systems.
Chemical Composition
| Element | Content |
|---|---|
| Copper | Balance |
| Nickel | 29.0-32.0 percent |
| Iron | 0.5-1.0 percent |
| Manganese | 0.5-1.2 percent |
| Zinc | 0.3 percent max |
| Lead | 0.02 percent max |
Mechanical Properties
In the annealed condition, C71500 tube has a minimum tensile strength of 52 ksi and a minimum yield strength of 18 ksi at 0.2 percent offset. The higher nickel content raises strength well above the 90/10 grade while retaining good ductility, supporting bending, rolling, and expansion during tube installation.
Seawater Performance
C71500 forms a stable protective film in seawater that resists erosion, impingement attack, and biofouling. It performs better than C70600 in high-velocity and turbulent flow conditions, and its higher operating temperature ceiling ensures a long and reliable service life in condenser and cooler duty. The alloy also resists stress corrosion cracking in marine environments.
Applications
Power plant heat exchangers and steam condensers.
Steam coils and waste heat recovery equipment.
Chemical and petrochemical coolers.
Air coolers, oil coolers, hydrogen coolers, and generator coolers.
Offshore platforms, seawater piping, and desalination plants.
Governing Standards
C71500 is supplied under ASTM B111 for seamless condenser tubes, ASTM B171 for plate, ASTM B466 for seamless pipe, ASTM B151 for rod and bar, and the corresponding ASME SB specifications. Historical military specifications such as MIL-C-1726F and MIL-C-24679 also cover the alloy.
Frequently Asked Questions
Q: Is C71500 susceptible to stress corrosion cracking?
A: C71500 has excellent resistance to stress corrosion cracking in marine environments, a key reason for its use in seawater systems.
Q: What cleaning methods are recommended for C71500?
A: Mild non-abrasive cleaners and fresh water rinses are adequate for routine cleaning; diluted sulfamic or citric acid can remove scale with proper procedures.
Q: Can C71500 be used in contact with sulfuric acid?
A: No, C71500 is designed for neutral to alkaline saline environments and has poor resistance to oxidizing acids and ammonia.
Q: What product forms are available?
A: Seamless and welded tubes, pipes, sheets, plates, forgings, and castings.
Q: How does C71500 compare with C70600?
A: C71500 has higher nickel content, greater strength, and better resistance to high-velocity seawater erosion, while C70600 offers better formability and anti-fouling behavior at lower cost.
Q: What standards cover C71500?
A: ASTM B111, B171, B466, B151, and their ASME SB equivalents.
