Page 24 - CFCM May-June 2021_Neat

PLATING AND ANODIZING: PRECIOUS METALS PLATING

PLATING WITH

PRECIOUS METALS

recious metals occupy a special niche in plating. Methods of sell at far higher prices. However, these prices have historically been
applying gold and silver to various substrates date back mil- extremely volatile, so that developing markets for it is difficult.
Plennia, while plating with zinc or chromium dates back less The term ‘troy’ is of uncertain origin, possibly deriving from the
than a couple of centuries. French trading city of Troyes in medieval times, but it has been
Because several precious metals have excellent electroconduc- consistently used across Europe and the US since the 1800s.
tive properties, they have been increasingly in demand for the past There is no exact substitute for gold in industrial processes. It is
50 years. For example, any passenger vehicle on the road today has chemically inert and non-corrosive, being unaffected by most acids
between seven and a dozen small computers on board that use gold. and also most alkalis, and it is highly reflective.
The cellphone in anyone’s pocket probably has some gold among Because it is soft and ductile, like silver, gold has long been prized
its connections and other components. And, given the importance in for jewelry and for decoration on artworks. Silver, valued for similar
the past year of medical ventilators, it’s interesting to note that they reasons, melts at 962 deg. C, while gold’s melting point is 1,065 deg. C.
also use it for their control systems, along with the other advanced These thermal properties have put the metals in increasing
medical technology in any modern hospital. demand for on-board automotive computers in recent years. As
Gold isn’t the only precious metal used for plating and finishing, available under-the-hood space has declined, so ambient tempera-
of course, but it is one of the most prevalent. Silver and, in some tures in engine compartments have increased, making more
cases, platinum are used, as are less well-known metals such as pal- thermally resilient connectors and microchips essential.
ladium. Gold and silver can be alloyed without difficulty. Of all the metals deemed ‘previous,’ silver, which in April 2021
Palladium, however currently costs more than twice the price was selling for US$25, is the least expensive. Given its price, gold has
of platinum, and more than 50 percent more than the price of always been used solely in areas, and at specified thicknesses, as an
gold, which throughout this year has traded above US$1,700 application actually requires. Most plating of gold and its alloys is
per troy ounce. done using solutions containing gold as a soluble cyanide complex.
Rhodium, used in catalytic converters and for some types of Because of the sheer basic cost of working with these useful
jewelry, and generally considered to be the rarest metal on earth, can metals, suppliers have taken care to foster applications where
24 CANADIAN FINISHING & COATINGS MANUFACTURING MAY/JUNE 2021