Silver Plated Jewellery
Silver plated costume jewellery has been around for well over a hundred years and became much
more prevalent from about the 1920's when improved manufacturing methods and efficiencies made it possible
to mass produce high quality costume jewellery, much of it silver plated.
Silver plated costume jewellery enabled the average person to wear what was made to look like
the much more expensive real thing. This has been a great thing for the jewellery industry and consumers
however the downside is that all too often silver plated jewellery is being passed off as Sterling Silver.
As much as the silver plated jewellery can look very impressive, item for item they certainly do
not have the same value.
To assist in assessing whether an item is plated or not it may be advantageous to read this
article Telling Sterling Silver
Apart from Silver Plated
The following article from Wikipedia details Plating in a general sense with some references to
gold and silver plating of jewellery
From Wikipedia, the free encyclopedia,Text is available under the Creative Commons Attribution-ShareAlike License
is a surface covering in which a metal
is deposited on a conductive
surface. Plating has been done for
hundreds of years; it is also critical for modern technology. Plating is used to decorate objects, for
corrosion inhibition, to improve solderability, to harden, to improve wearability, to reduce friction,
to improve paint adhesion, to alter conductivity, to improve IR reflectivity, for radiation shielding,
and for other purposes. Jewelry
typically uses plating to give a silver
finish. Thin-film deposition
has plated objects
as small as an atom,
plating finds uses in nanotechnology
There are several plating methods, and many variations. In one method, a solid surface is
covered with a metal sheet, and then heat and pressure are applied to fuse them (a version of this is
Sheffield plate). Other plating techniques include
vapor deposition under vacuum and sputter deposition. Recently, plating often
refers to using liquids. Metallizing refers to coating metal on non-metallic
Main article: Electroplating
In electroplating, an ionic metal is supplied with electrons to form a non-ionic coating on a substrate. A common system involves a chemical solution
with the ionic form of the metal, an anode (positively charged) which may consist of the metal
being plated (a soluble anode) or an insoluble anode (usually carbon, platinum, titanium, lead,
or steel), and finally, a cathode (negatively charged) where electrons are supplied to
produce a film of non-ionic metal.
Electroless plating, also known as chemical or auto-catalytic plating, is a non-galvanic plating method that involves several
simultaneous reactions in an aqueous solution, which occur without the use of
external electrical power. The reaction is accomplished when hydrogen is released by a reducing agent, normally
sodium hypophosphite (Note: the hydrogen leaves
as a hydride ion), and oxidized, thus producing a negative charge on the surface of the part. The most
common electroless plating method is electroless nickel plating, although
silver, gold and copper layers can also be applied in this manner, as in the technique of Angel gilding.
Main article: Gold plating
Gold plating is a method of depositing a thin layer of
gold on the surface of glass or metal, most often copper or silver.
Gold plating is often used in electronics, to provide a corrosion-resistant electrically conductive layer on
copper, typically in electrical connectors and printed circuit boards. With direct
gold-on-copper plating, the copper atoms have the tendency to diffuse through the gold layer, causing
tarnishing of its surface and formation of an oxide/sulfide layer. Therefore, a layer of a suitable
barrier metal, usually nickel, has to be deposited on
the copper substrate, forming a copper-nickel-gold sandwich.
Metals and glass may also be coated with gold for ornamental purposes, using a number of
different processes usually referred to as gilding.
Sapphires, Plastics, and Carbon fiber are some other materials that are able to be plated using
advance plating techniques. The substrates that can be used are almost limitless. 
- This section is about the method of adding a thin layer of silver to an object.
For applications in electronics, silver is sometimes used for plating copper, as its electrical resistance is lower (see Resistivity
of various materials); more so at higher frequencies due to the skin effect. Variable capacitors are considered of the highest
quality when they have silver-plated plates. Similarly, silver-plated, or even solid silver cables, are
prized in audiophile applications; however some experts consider
that in practice the plating is often poorly implemented, making the result inferior to similarly priced
Care should be used for parts exposed to high humidity environments. When the silver layer is porous or
contains cracks, the underlying copper undergoes rapid galvanic corrosion, flaking off the plating and
exposing the copper itself; a process known as red plague.
Silver plate has been used since the 18th century, especially in England, to provide a cheaper
version of household items that might otherwise be made of silver, including cutlery, vessels of various kinds, and candlesticks. The earliest
kind was Old Sheffield Plate, but in the 19th century new methods of production (including electroplating)
were introduced: see Sheffield Plate. Britannia metal is an alloy of tin, antimony and copper developed as a base metal for plating
Another method that can be used to apply a thin layer of silver to several objects, such as
glass, is to place Tollens' reagent in a glass, add
Glucose/Dextrose, and shake the bottle to promote the reaction.
- AgNO3 + KOH → AgOH + KNO3
- AgOH + 2 NH3 → [Ag(NH3)2]+ + [OH]– (Note: see
- [Ag(NH3)2]+ + [OH]– + aldehyde (usually glucose/dextrose) → Ag + 2
NH3 + H2O
Rhodium plating is occasionally used on white gold, silver
or copper and its alloys. A barrier layer of nickel is usually deposited on silver first, though in this
case it is not to prevent migration of silver through rhodium, but to prevent contamination of the rhodium
bath with silver and copper, which slightly dissolve in the sulfuric acid usually present in the bath
Main article: Chrome plating
Chrome plating is a finishing treatment using the electrolytic deposition of chromium. The most common form of chrome plating is the
thin, decorative bright chrome, which is typically a 10-µm layer over an underlying nickel plate. When plating on iron or steel, an underlying
plating of copper allows the nickel to adhere. The pores (tiny holes) in the nickel and chromium layers work
to alleviate stress caused by thermal expansion mismatch but also hurt the
corrosion resistance of the coating. Corrosion resistance relies on what is called the passivation layer, which is determined by the chemical
composition and processing, and is damaged by cracks and pores. In a special case, micropores can help
distribute the electrochemical potential that accelerates
galvanic corrosion between the layers of nickel
and chromium. Depending on the application, coatings of different thicknesses will require different
balances of the aforementioned properties. Thin, bright chrome imparts a mirror-like finish to items such as metal furniture frames
and automotive trim. Thicker deposits, up to 1000 µm, are called hard chrome and are used in
industrial equipment to reduce friction and wear.
The traditional solution used for industrial hard chrome plating is made up of about 250 g/L of
CrO3 and about 2.5 g/L of SO4–. In solution, the chrome exists as chromic
acid, known as hexavalent chromium. A high current is used, in
part to stabilize a thin layer of chromium(+2) at the surface of the plated work. Acid chrome has poor
throwing power, fine details or holes are further away and receive less current resulting in poor
Zinc coatings prevent oxidation of the protected metal by forming a barrier and
by acting as a sacrificial anode if this barrier is damaged. Zinc oxide is a fine white dust that (in contrast to
iron oxide) does not cause a breakdown of the substrate's
surface integrity as it is formed. Indeed the zinc oxide, if undisturbed, can act as a barrier to further
oxidation, in a way similar to the protection afforded to aluminum and stainless steels by their oxide layers. The majority of hardware parts are zinc plated,
rather than cadmium plated.
The tin-plating process is used extensively to protect both
ferrous and nonferrous surfaces. Tin is a useful metal for the
food processing industry since it is non-toxic,
ductile and corrosion resistant. The excellent ductility of tin allows a tin coated base metal sheet to
be formed into a variety of shapes without damage to the surface tin layer. It provides sacrificial
protection for copper, nickel and other non-ferrous metals, but not for steel.
Tin is also widely used in the electronics industry because of its ability to protect
the base metal from oxidation thus preserving its solderability. In electronic applications, 3% to 7%
lead may be added to improve solderability and to prevent the
growth of metallic "whiskers" in compression stressed deposits, which would otherwise cause electrical
shorting. However, RoHS (Restriction of Hazardous Substances) regulations enacted
beginning in 2006 require that no lead be added intentionally and that the maximum percentage not exceed 1%.
Some exemptions have been issued to RoHS requirements in critical electronics applications due to failures
which are known to have occurred as a result of tin whisker formation.
In some cases, it is desirable to co-deposit two or more metals resulting in an electroplated alloy deposit.
Depending on the alloy system, an electroplated alloy may be solid solution strengthened or
precipitation hardened by heat treatment to improve the plating's physical and
chemical properties. Nickel-Cobalt is a common electroplated alloy.
Metal matrix composite plating can be
manufactured when a substrate is plated in a bath containing a suspension of ceramic particles. Careful
selection of the size and composition of the particles can fine-tune the deposit for wear resistance, high
temperature performance, or mechanical strength. Tungsten carbide, silicon carbide, chromium carbide, and aluminum oxide (alumina) are
commonly used in composite electroplating.
Cadmium plating is under scrutiny because of the environmental toxicity of the cadmium metal.
However, cadmium plating is still widely used in some applications such as aerospace fasteners and it
remains in military and aviation specs however it is being phased out due to its toxicity.
Cadmium plating (or "cad plating") offers a long list of technical advantages such as excellent corrosion
resistance even at relatively low thickness and in salt atmospheres, softness and malleability, freedom from sticky and/or bulky
corrosion products, galvanic compatibility with aluminum, freedom from stick-slip thus allowing reliable torquing of plated threads, can be dyed to many colors and
clear, has good lubricity and solderability, and works well either as a final finish or as a paint
If environmental concerns matter, in most aspects cadmium plating can be directly replaced with gold plating
as it shares most of the material properties, but gold is more expensive and cannot serve as a paint base.
The chemical reaction for nickel plating is:
At cathode: Ni → Ni2+ + 2e–
At anode: H2PO2 + H2O → H2PO3 + 2 H+
Compared to cadmium plating, nickel plating offers a shinier and harder finish, but lower corrosion
resistance, lubricity, and malleability, resulting in a tendency to
crack or flake if the piece is further processed.
Electroless nickel plating
Electroless nickel plating, also known as enickel and NiP, offers many advantages: uniform
layer thickness over most complicated surfaces, direct plating of ferrous metals (steel), superior wear and
corrosion resistance to electroplated nickel or chrome. Much of the chrome plating done in aerospace industry
can be replaced with electroless nickel plating, again environmental costs, costs of hexavalent chromium waste
disposal and notorious tendency of uneven current distribution favor electroless nickel plating.
Electroless nickel plating is self-catalyzing process, the resultant nickel layer is NiP compound, with
7–11% phosphorus content. Properties of the resultant layer hardness and wear resistance are greatly altered
with bath composition and deposition temperature, which should be regulated with 1 °C precision, typically at
During bath circulation, any particles in it will become also nickel plated, this effect is used to
advantage in processes which deposit plating with particles like silicon carbide (SiC) or polytetrafluoroethylene (PTFE). While
superior compared to many other plating processes, it is expensive because the process is complex. Moreover,
the process is lengthy even for thin layers. When only corrosion resistance or surface treatment is of
concern, very strict bath composition and temperature control is not required and the process is used for
plating many tons in one bath at once.
Electroless nickel plating layers are known to provide extreme surface adhesion when plated properly.
Electroless nickel plating is non-magnetic and amorphous. Electroless nickel plating layers are not easily
solderable, nor do they seize with other metals or another electroless nickel plated workpiece under pressure.
This effect benefits electroless nickel plated screws made out of malleable materials like titanium. Electrical
resistance is higher compared to pure metal plating.