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The chemical composition of alloys CuNi 90/10 and CuNi 70/30 have been optimised in order to maximize the behaviour of the metal under the most stringent conditions of seawater corrosion. Additionally, CuNi 90/10 and CuNi 70/30 meet all requirements of most international standards.
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| Corrosion Behaviour |
| CuNi 90/10 and CuNi 70/30 have an excellent behaviour when exposed to all forms of marine corrosion. This property is mainly due to the fact that the alloy prevents dissolution by forming a very strong protective surface film. |
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| CuNi 90/10 and CuNi 70/30 possible factors of corrosion |
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| Corrosive environment |
Probable Corrosive |
Behaviour in service |
| Clean sea water circulation at a velocity of up to 1 m/s |
Uniform or general |
0,0025 – 0,025 mm/an |
| Clean sea water circulation at a velocity of up to 3,5 m/s* : CuNi 90/10 and 4,5 m/s* : CuNi 70/30 |
Impact corrosion |
Satisfactory |
| Polluted sea water |
General corrosion and accelerated pitting corrosion |
Less resistance |
| Deposits accumulated at the surface |
Local attack |
Generally good |
| Corrosion + stress |
Stress corrosion |
Very resistant |
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| *The local speeds resulting from obstructions can be higher |
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| Physical Properties |
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| Typical values |
Units |
CuNi 90/10 |
CuNi 70/30 |
Density (20°C) |
Kg /m3 |
8900 |
8900 |
Electrical resistivity (20°C annealed) |
µΩ.cm |
19 |
34 |
Thermal conductivity ( 20° to 200°C) |
W/m.°K |
50 |
30 |
Coefficient of expansion ( 20° to 200°C) |
C x 10-6 |
17 |
16 |
Modulus of elasticity ( 20°C annealed) |
MPa |
126 000 |
126 000 |
Annealing temperature |
°C |
760 - 800 |
780 - 820 |
Melting interval |
°C |
1100 - 1150 |
1180 - 1240 |
Magnetic Permeability ( 20° annealed) |
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1.08 – 1.80 |
<1.05 |
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| Mechanical Properties |
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Typical values |
Units |
CuNi 90/10 |
CuNi 70/30 |
Tensile strength (UTS), (Rm) |
MPa |
≥ 310 |
≥ 350 |
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µΩ.cm |
19 |
34 |
Proof stress (YS 0,2), (Rp 0,2) |
MPa |
≥ 110 |
≥ 130 |
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ksi |
≥ 16 |
≥ 19 |
Elongation (E 5,65 √S) |
% |
≥ 35 |
≥ 30 |
Hardness (HB10 D2) |
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≥ 70 |
≥ 80 |
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