General
- Pure silver has a
brilliant white metallic luster. It is a little bit harder than gold and
is very ductile and malleable. Pure silver has the highest electrical
and thermal conductivity of all metals, and possesses the lowest contact
resistance. Silver is stable in pure air and water, but tarnishes when
exposed to ozone, hydrogen sulfide, or air containing sulfur.
- Typically a
silver-plating specification will specify a matte, semi-bright, or
bright finish with or without a chromate post treatment to improve
tarnish resistance. Plating specifications also designate the base
coating to be applied under the silver plate. The thickness of coatings
can range from 1 micron for short-term shelf life and solderability, to
10 microns for thermo-compression bonding and die attachment, and up to
40 microns for severe wear resistance applications.
Process
- Silver plating
intended for engineering purposes is usually employed for solderable
surfaces, electrical contact characteristics, high electrical and
thermal conductivity, thermocompression bonding, wear resistance of
load-bearing surfaces, and spectral reflectivity.
-
In order
to locate the silver deposition on a selected area of the fabric, it is
necessary to make the fabric surface act as a catalyst. The activation
energy of the catalytic route is lower than the homogeneous reaction in
solution. A smooth deposition is obtained if the metal deposited by
autocatalysis acts as a catalyst. Based on the method of chemical
silver-plating for a nonmetal substrate, three main steps, namely
pre-treatment, the plating process and post-treatment were
employed.
Applications
-
Advantages
of Silver Electroplating: Superior Fatigue Resistance, Provides Dry
Lubricity, Corrosion Resistance, Thermal Conductivity, Electro Magnetic
Shielding, Offers Malleability, Reduces Friction, Facilitates Joining of
Materials, High Tensile Strength, High Ductility, Algaecidal –
Bactericidal – Antibacterial , Advantageous Alloying and, Wetting
Properties, Efficient Catalyst , Resists Oxidation.
-
The
plating thickness of some items, such as fuse caps, is less than one
micron although the silver then tarnishes more easily. Coatings of two
to seven microns are normal for heavy duty electrical equipment. Silver
plating is used in a wide variety of applications from Christmas Tree
ornaments to cutlery and hollowware.
-
The silver plated fabric has very effective shielding of
electromagnetic radiations, also in the frequency range of mobile
phones. The plated composite yarn after
deknitting can be used as very flexible and expandable wire for special,
low current applications. It also can be knit into any desired shape
since the plated metal layers endure the deknitting and knitting
process. By appropriate voltage supply a extremely flexible and
accurately controllable heated fabric sheet, or any other shape device
can be made by knitting weaving.
Market and Report
-
Today,
apart from London, the largest supplier of silver to India is China. As
the Indian market develops and a wider range of precious metal
investment products becomes available, there will be increased trading
opportunities within India and with the global market – which will
benefit from being backed by the quality assurance of the Good Delivery
List. Approximately 4,000 tonnes of silver are consumed annually in
India, the vast majority of which is used in the production of
ornamental items – jewellery, utensils and gift articles. Industrial
uses play a smaller part, accounting for about 300
tonnes.
-
Industrial
uses account for about 300 tonnes of consumption a year. The biggest
increase in industrial silver demand in India last year came from
pharmaceutical and chemical usages, which rose over 60 %, with much of
the growth due to silver nitrate production. In addition to its uses in
photography and medicine, silver nitrate is used to make mirrors,
indelible ink and silver plating.
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