|Nickel silver alloys (sometimes called German silver)
derive their name from their bright silvery appearance though they
actually contain no silver at all. They are alloys of copper, nickel and
zinc and they find many applications in housewares (such as cutlery) as
well as some industrial applications (such as component manufacture).
Nickel silver alloys contain 10-25% nickel and 17-40% zinc with the
remainder being copper. They are usually classified by their nickel
content with higher nickel contents producing a whiter, silvery colour.
Corrosion resistance increases with higher nickel
content and the resulting alloys are less vulnerable to stress corrosion
than some brass alloys. Strength also increases with nickel content but
the increased nickel has little effect on ductility.
For industrial applications there is limited advantage
in exceeding a nickel content of 18%, however for decorative
applications a higher nickel content will provide maximum resistance to
stain and tarnish.
The spring properties of the alloys are good and
remain so at elevated temperatures. This makes nickel silver well suited
to a number of specific applications where this is a requirement.
The electrical conductivity of nickel silver is much
less than that for copper.
Where a nickel silver alloy is to be machined, lead
can be added to the alloy (usually 1-2%) to improve results. However,
this will reduce the cold workability of the alloy
Nickel silver alloys find many applications where a decorative
appearance is required
e.g. housewares and giftware. They are also sometimes used as a metal
substrate for silver-plated (or electroplated) goods because even if the
silver plating wears off, the nickel silver underneath will still
provide an attractive appearance. Sometimes this material will be
referred to as EPNS (electroplated nickel silver).
In industrial applications, nickel silver alloys are
often used where a combination of good
strength and corrosion resistance is required. They also find
take advantage of the materialís springing properties. One such
application is in spring contacts for the telecommunication industry.
With lead added to the alloy, the improved
machinability makes it especially suitable for engraving.