High Strength and Conductance Copper Nickel Silicon Alloy

Colisbro is a high copper alloy with minimal additions of silicon and nickel, which combine to improve the hardness, strength and wear resistance of the material, while retaining many of the physical benefits of copper itself. Colisbro is stocked by Columbia Metals in the completely heat treated condition so that the mechanical strength levels are maximized. These are developed by combining heat treatment and cold working with the ageing process or heat treatment, forming a nickel silicide precipitate that results in metal matrix hardening. Thus Colisbro has a higher strength when compared to many low alloy steels and stainless steels. It also has a yield strength that is 90% of the ultimate tensile strength, while retaining a good level of ductility.

The completely age-hardened Colisbro offers an excellent wear resistance, a high hardness level, excellent bearing properties and anti-friction properties particularly under high loading against hardened steels. The increased copper content of the alloy ensures that it maintains an attractive electrical and thermal conductivity value. Colisbro provides excellent fabrication properties and is machined readily especially in the heat treated condition where close machining tolerances can be held. Forming is possible either cold or hot but both the processes are performed better in the solution treated condition with any age hardening treatment being applied to the finished component. It can also be brazed, welded and soldered by traditional MIG and TIG methods as well as being resistance weldable.

Key Features

The key features of Colisbro are:

  • High corrosion resistance surpassing many copper alloys with complete freedom from stress corrosion
  • Outstanding cryogenic properties and a very low magnetic permeability
  • Complete freedom from hydrogen embrittlement
  • Spark resistant
  • Increased hardness and strength
  • Excellent wear resistance and bearing properties
  • Excellent thermal and electrical conductivities when compared to most non-ferrous alloys

Composition (%)

The composition of Colisbro is provided in the table below

Element Percentage
Nickel, Ni 1.6 to 2.2
Silicon, Si 0.4 to 0.8
Copper, Cu Remaining

Mechanical Properties (Specification Minima)

The mechanical properties of Colisbro are:

  ≤30mm dia 30< dia ≤50mm 50< dia ≤90mm
Ultimate Tensile Strength (N/mm2) 640 600 550
0.2% Proof Strength (N/mm2) 590 510 430
Elongation (%) 10 10 10
Hardness (HB) 180 165 155

Typical Physical Properties (as delivered)

The physical properties of Colisbro are:

Density (g/cm3) 8.87
Melting Range (°C) 1040 - 1060
Thermal conductivity (20°C - W/m°K) 160
Coeff. Thermal Exp. (0-400°C - m/m°K x 10-6) 16.0
Electrical Conductivity (I.A.C.S.) 35
Magnetic Permeability


Colisbro has high corrosion resistance in a number of industrial and marine applications and is superior to a number of other copper-based alloys and copper itself. With an increased corrosion resistance in sea and fresh water, it offers a high resistance to wet sulphurous atmospheres and a freedom from stress corrosion and hydrogen embrittlement.

The applications of Colisbro alloy are:

  • Automotive: valve guides, valve seats, gears, rocker and little end bushes etc. for internal combustion engines requiring extreme performance.
  • Electrical: current-carrying electrical components such as slip rings, squirrel cages, springs, rotary switch contacts, contact blades, short-circuit rings, heavy duty switchgear.
  • Offshore and marine: Fasteners, valves, choke stems, down-hole tooling, cryogenic storage tanks, pump bodies.
  • Other: Non-magnetic instrument components, spark-resistant safety tooling.


Colisbro is a precipitation hardening copper nickel silicon that provides an excellent blend of mechanical and physical attributes unrivalled by several grades of copper alloy. The combination of corrosion resistance, high strength, high electrical and thermal conductivity, spark resistance, high wear resistance and good cryogenic properties has enabled Colisbro to find a place in almost every engineering field, from electrical to mechanical and automotive to marine.

This information has been sourced, reviewed and adapted from materials provided by Columbia Metals.

For more information on this source, please visit Columbia Metals.


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