• DEF STAN 02-835
  • NES 835
  • DOD-C-24676
  • EB4223A
  • UNS C72420
View Data Tables For This Product

Hiduron 191 (UNS C72420)

Long Description

Hiduron® 191 is medium-strength precipitation hardened cupronickel alloy supplied in the hot worked condition. It contains about 14.5% nickel and 4.5% manganese strengthened by additions of aluminium and iron, which may be refined by controlled small amounts of chromium.

In many critical marine applications, for example on oil platforms and naval ships, the requirement for instant service following periods of inactivity favours the anti-fouling and corrosion resistance characteristics of cupronickel; but conventional cupronickels have the disadvantage of inherently low strength. A combination of reasonable strength with good corrosion resistance and impingement resistance is achieved with nickel aluminium bronze but the higher strength levels are only achieved at the expense of toughness with consequently limited resistance to shock.

Hiduron® 191 was developed to provide both the corrosion resistance and anti-fouling characteristics of conventional cupronickels but with superior tensile and toughness properties compared to aluminium bronzes. Its resistance to marine corrosion is comparable with that of conventional cupronickels, the combination of tensile strength and toughness is far superior to that available with aluminium bronzes and its properties are largely independent of section size. In addition, Hiduron® 191 has a relatively high modulus of elasticity of cupronickel compared with most other bronzes.

Hiduron® 191 has the inherent good resistance to bio-fouling of cupronickel whilst the additional elements in its composition not only improve mechanical properties but also increase resistance to localised corrosion and to impingement attack in seawater. It is virtually non-magnetic and possesses excellent sub-zero properties. Hiduron® 191 has good machineability, and good weldability and can also be forged, hot upset and thread rolled without difficulty. It meets the requirements of NACE MR 0175.

Hiduron 191


  • DEF STAN 02-835
  • NES 835
  • DOD-C-24676
  • EB4223A
  • UNS C72420
View Data Tables For This Product

Data Tables

Chemical Composition:


Mechanical Properties:

Bars up to and including 5”(125mm) diameter or sectionBars greater than 5” (125mm) diameter or section
0.2% Proof Stress430 N/mm262.4 ksi400 N/mm258 ksi
Tensile Strength725 N/mm2105.1 ksi710 N/mm2103 ksi
Elongation, 5.65√S018%18%
Hardness (Brinell)163 min.170-280
Impact Strength (Room Temp)40J min.40J min.


  1. Testing shall be carried out in accordance with ASTM A370 or EN ISO 6892-1 (tensile), EN ISO 6506-1 (hardness)
  2. Minimum properties quoted (tested at room temperature in a longitudinal direction)
  3. Testing performed on each melt of material per heat treatment batch

Physical Properties:

Density (Kg/m3)8500
Magnetic Permeability (20°C)<1.01
Young’s Modulus (kN/mm2)145
Modulus of Rigidity (kN/mm2)52
Electrical Conductivity, 20°C (mΩ / mm2)2.85 (17% of IACS)
Mean coefficient of thermal expansion, 20-300°C (m/m/degC)16.0 x 10-6
Specific Heat, 20°C (J/kg.K)435
Thermal conductivity, 20°C (W/m.K)16.3

Product Features

Key Features

Hiduron 191 features the following key features:

  • Excellent corrosion resistance in marine environments – superior to nickel aluminium bronzes and 22% chrome duplex stainless steels.
  • Superior strength, jet impingement resistance and general corrosion resistance compared to conventional copper nickels.
  • Greater strength and toughness than nickel aluminium bronzes – strength is comparable to 22% chrome duplex stainless steel.
  • No loss of impact strength down to -196°C.
  • Excellent anti-galling properties, particularly when operating against stainless steel.
  • Good anti-fouling properties.
  • Freedom from hydrogen embrittlement.
  • Low magnetic permeability.
  • Approved as a named alloy by the world’s most prestigious navies.
  • Galvanic compatibility with other copper alloys and stainless steel.


Hiduron 191 has the following applications: 

  • Naval and Defence applications such as fasteners for ships and submarines, control elements of submarines, pump shafts, mechanical seals, winch components, gears, hose couplings, weapons handling equipment, components in sonar devices, propeller shafts, and drive bushes.
  • Oil & Gas industry components. This includes subsea bolting, shafts for pumps & valves, valve spindles, hydraulic pistons and cylinders.
  • Process industry applications such as impellers, pump shafts, valve components, and process control equipment.
  • Subsea mining applications, such as hydraulic connectors, pistons and cylinders, and pressure couplings.
Datasheet CA Hiduron 191 Brochure Hiduron 191 Detailed product information (rev2)
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