04 October 2011

GOLD usage and application in various fields other than jewellery

Gold's great virtues of malleability, ductility, reflectivity, resistance to corrosion and unparalleled ability as a thermal and electrical conductor mean it is used in a wide variety of industrial applications consuming close to 300 tonnes annually.
The prime use is in electronics. Our age of high technology finds it indispensable in everything from pocket calculators to computers, washing machines to television and missiles to spacecraft. The rocket engines of American space shuttles are lined with gold- brazing alloys to reflect heat, and the lunar modules of the Apollo programme that put men on the moon were shrouded with gold foil acting as a radiation shield. More commonly, the humble touch telephone in your home typically contains 33 gold-plated contacts. The plating of such contacts in switches, relays and connectors is the major application of gold in electronics. Contacts are electroplated with a very thin film of gold using gold potassium cyanide (GPC), often called plating salts. This touch of gold on a contact ensures rapid dissipation of heat and guarantees freedom from oxidation or tarnishing at extreme low or high temperature, thus providing an atomically clean met- al surface with an electrical con- tact resistance close to zero. Not surprisingly "nothing is as good as gold" to provide total reliability, whether out in space or in the home.
The production of plating salts accounts for 70% of the more than 150 tonnes of gold used annually in electronics. Althoughnew technology has enabled plating thickness to be pared down to less than one-thousandth of a millimetre of gold. Gold consumption has been maintained because of the myriad new electronic applications.
Gold's other main role in electronics is in semiconductor devices, where fine gold wire or strip is used to connect parts such as transistors and integrated circuits, and in printed circuit boards to link components. Again, the need for reliable connections makes gold indispensable. This bonding wire is one of the most specialised uses of gold; it is highly refined to 999.99 purity and the wire has a typical diameter of one-hundredth of a millimetre.
Japan is the major fabricator of electronics products in the western world, accounting for over 45% of gold consumption, followed by the United States with nearly 30%. The United Kingdom and Germany are the only other significant contributors at about 6 and 7% respectively although South Korea is growing. Dental gold is the second important sector. Gold has been used in dentistry for almost 3000 years. The Etruscans in the 7th century BC used gold wire to fix substitute teeth when their own were lost. In the 16th century an early dental textbook recommended gold leaf for filling cavities.
Gold's malleability and resistance to corrosion render it eminently suitable for dental use, al- though its softness means that it must be alloyed to retard wear. The most common companion metals are platinum, silver and copper. A typical alloy may contain anywhere from 620-900 fine gold depending on the precise end-use. In recent years the price of gold has resulted in a trend towards cheaper alloys with as little as 30% gold and towards palladium-based alloys which contain scarcely 2% gold. Gold alloys have also suffered competition from new techniques such as ceramic dental crowns. In addition, social security payments for gold dental work have come under tighter scrutiny; reductions in such insurance payments make gold use more price sensitive. These factors initially contributed to a sharp fall in gold use by the dental sector,
from 64 tonnes in 1980 to 48 tonnes by 1987. However, there has since been a recovery because of its non-allergic properties; demand has revived to 60 tonnes annually.
Japan is the leading dental gold fabricator, accounting for roughly 28% of the market, followed by Germany and the United States. There is significant unrecorded use, however, in Asia and Latin America where it is not unknown for dentists to melt down gold coin to make their own alloy. Other applications for gold include decorative plating of costume jewellery, watchcases, pens and pencils, spectacle frames and bathroom fittings. Gold-based points are used for decoration of china and glass. Demand for gold from this sector is around 90 tonnes per year. The gold is used in various forms, such as rolled gold and gold fill, although both of these are under competition from new techniques. On the other hand, the use of gold electroplating in watchcases and similar products is increasing.
Visually, the most spectacular use of decorative gold is gold leaf which has been used for centuries to adorn the domes or ceilings of public buildings, because its resistance to corrosion means it will outlast paint by many years. Gold's ability to reflect heat in summer and help retain it in winter has also led to the use of glass coated with a thin film of gold in several modern buildings, especially in North America; one ounce of gold covers typically one thousand square feet of glass. This reflective glass can cut cooling and heating costs by 40%. The major consumption of decorative gold is in the United States and Japan. All told, the industrial uses of gold provide a very steady element in gold demand, requiring more than the equivalent of all Australian gold production annually.
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