These silver coloured copper-nickel-zinc alloys containing 10-20% nickel (but no silver) can be regarded as special brasses. They polish to a fine silvery colour which accounts for their use over several centuries.
In most respects they show similar corrosion characteristics to the brasses but the higher nickel versions have superior tarnish resistance and resistance to stress corrosion cracking.
They are available in all forms and are used for tableware (silver-plated to give EPNS), telecommunication components, better quality keys, high quality fishing reels and rod fittings, food manufacturing equipment, jewellery, model making, tool brush anchor wire and pins, musical instruments, e.g. ‘silver bands’, flutes, test probes and contact springs.
None, nickel silvers are copper-nickel-zinc alloys which have an attractive colour when polished.
Electroplated nickel silver.
They can be polished to a silvery appearance.
Copper strip and wire may be produced with a combination of high elastic limit and good corrosion resistance, making them an ideal choice for springs. The main groups of alloys are:
- Phosphor bronze, typically CW451K (PB102) with a yield strength of about 500 N/mm2.
- Nickel silver, typically CW409J (NS106).This is silver coloured and has excellent tarnish resistance.
- Copper-beryllium CW100C (CB101). This alloy is used where very high yield strength is required (greater than 1000 N/mm2). These alloys are expensive and phosphor bronze will be adequate for most engineering applications.
A useful Specification is BS EN 1654:1998 (Copper and copper alloys. Strip for springs and connectors).