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Historic Preservation - Technical Procedures

Spectitle:

Nickel Silver: Characteristics, Uses And Problems

Procedure code:

0501017S

Source:

20Th Century Building Materials (Ed. Tom Jester, Nps)

Division:

Metals

Section:

Metal Materials

Last Modified:

02/24/2012

Details:

Nickel Silver: Characteristics, Uses And Problems



NICKEL SILVER: CHARACTERISTICS, USES AND PROBLEMS


This standard includes general information on the characteristics
and common uses of nickel silver and identifies typical problems
associated with this material along with common causes of its
deterioration.  For guidance on cleaning nickel silver, see 05010-
02-P.


INTRODUCTION

Characteristics of nickel silver:

-    A copper-nickel-zinc alloy that contains no silver.

-    Contains 50-80 percent copper, 5-30 percent nickel and 10-35
    percent zinc; it may also contain small percentages of lead,
    tin and manganese.

-    Higher amounts of copper make the nickel silver metal more
    ductile and more resistant to corrosion.

-    Higher amounts of zinc slightly improves corrosion resistance,
    lowers the melting point, raises its strength and hardness,
    but decreases its ductility.

-    Has many of the same characteristics as brass and bronze.

-    Has existed for over 2000 years.

-    May be wrought, cast, rolled, stamped, forged, drawn, extruded
    and machined.

-    Silvery-white in color.

-    Takes a high polish.

-    Extremely hard.

-    Abrasion-resistant.

-    Malleable.

-    Ductile.

-    Nonmagnetic.

-    Highly resistant to environmental corrosion.

-    Suitable for soldering and welding, depending on the presence
    of lead.

-    Develops a protective oxide, or patina when exposed to oxygen;
    the patina is brownish-green when exposed for long periods of
    time.

-    Called copper-nickel or false copper in the late 1600s due to
    the reddish color of the ore, but lacking the ductility and
    malleability of copper.

-    Discovery that the silver ore contained nickel occurred in the
    mid 1700s; established as a new elemental metal by Aksel
    Frederik Cronstedt.

-    A German version called new silver was marketed in the 1800s.

-    Called German Silver in England up until World War I; called
    nickel silver after that time.


TYPICAL USES

Typical historical uses for nickel silver include:

-    Nickel alloys commonly used for coins and ornamental objects.

-    Tableware and plated objects.

-    In the 1840s, nickel superseded copper as the material of
    choice for silver plating; nickel was harder, stronger and
    more durable than copper.

-    Electroplating became the most fundamental application of
    nickel silver in the early 1900s; some uses included costume
    jewelry, keys, soda fountain and bar equipment, cigarette
    cases, automobile radiators and hub caps.

-    Used for more decorative and structural elements in the 1920s,
    such as decorative panels, doors, grilles, railings, plumbing
    fixtures, plaques, trim and divider strips in terrazzo floors.

-    Popular for door knobs, handrails and pushplates because of
    its abrasion-resistance.

-    Use of nickel silver declined in the 1950s.

-    After World War II, stainless steel and aluminum replaced the
    use of nickel silver due to their low production cost.

-    Most buildings containing nickel silver were constructed in
    the 1920s and 1930s.

Typical current uses for nickel silver include:

-    Industrial and electrical purposes.

-    Cast and wrought forms of the metal are occasionally found in
    building designs.

-    Manufactured today only in silver white or white with a yellow
    tint; shades of pale yellow, green, pink and blue can also be
    produced by varying the nickel content; custom orders can also
    be made to match an older nickel alloy finish if necessary.


NATURAL OR INHERENT PROBLEMS

-    Corrosion: The zinc content of Nickel Silver makes the alloy
    metal sensitive to acid and sulfur pollutants and will tarnish
    in their presence.

-    Stress Corrosion Cracking: Tensile strength combined with
    exposure to a corrosive environment; factors affecting this
    type of deterioration include temperature, metal composition
    and metal structure.

-    Sensitive to chromic and nitric acids, due to its high copper
    content; copper is very sensitive to these acids.


VANDALISM OR HUMAN-INDUCED PROBLEMS

-    Scratches and dents.

-    Susceptible to mechanical deterioration such as fatigue, but
    not creep.

                         END OF SECTION