Gold Plating

Gold Plating 

the process of applying layers of gold (from tenths of a micron to two or three microns thick; up to 20–25 μm in certain critical circumstances) to the surfaces of articles, designs, and architectural structures.

The so-called sheet method of gold plating was used in ancient Egypt. It involved sticking from one to three layers of the finest petals of gold onto the prepared surface of an article. The method was used widely in Kievan Rus’ beginning with the tenth and 11th centuries A.D. By the 19th century the iron or copper cupolas of churches and the roofs and spires of palaces were gilded by this method. The lifetime of such sheet gold coverings was about 50 years. Later, the firing method came into use. Here, a dough-like paste consisting of an amalgam of gold (a compound of gold and mercury) was applied to a surface. When the article (made of porcelain or metal) was heated, the mercury vaporized and a compact gold covering remained. Such coverings last 100 to 150 years. The galvanic method has been used since the middle of the 19th century. Here, the gold is precipitated onto the surface from a solution of dicyanoaurate KAu(CN)₂. Such a covering is very stable chemically, possesses high thermal and electrical conductivity, and is used not only in jewelry and watch-making, but also in the electronics industry—mainly to cover the electrical contacts of electronic computers. The galvanic method is used not only for gold plating but also for coatings made of compounds of gold with silver, antimony, nickel, cobalt, copper, and other elements. Such coatings approximately double the hardness of a surface and are a good means of protecting surfaces against corrosion.

V. I. LAINER