Silvering
Under Silver refers to all industrial processes that produce a coating of silver on solid objects. When silvering of glass is also called mirror coating.
Generally
A silver is only useful on largely inelastic materials, because otherwise the compound dissolves in places and the silver layer permanently peels everywhere.
Metals and alloys such as nickel silver (which is a nickel-copper -zinc alloy, which appears to be silver), copper, brass, zinc, tin, lead, iron, steel, and nickel, as well as nonmetallic materials such as glass or plastics for the silver suitable.
Special properties of silver coatings:
- The excellent electrical conductivity is important for contacts, wires and waveguides in electrical engineering
- Decorative appearance of art, jewelry or utilitarian objects, such as cutlery
- Silver has a very good reflectivity. Therefore, it is used in the production of mirrors and reflectors used.
- Corrosion protection in the chemical industry
The layer thicknesses of silver coatings are very different depending on the application. While electronic parts often enough one to a few microns, are locally deposited up to 120 microns in cutlery.
The common name cutlery at 90 or 100 differs from the thickness specified in microns and refers to the amount of precipitation metal in grams. It is taken as a basis, that 90 g, and 100 g of silver deposited on an area of 24 dm ². Typically, this area is given by 12 of cutlery, forks and spoons 12, with layer thicknesses of approximately 34 to 37 microns at 90 and 45 microns arise in 100 silver plating. The first indication of the overall strength of the silver plating is often followed by a second number, which is directly related to the corresponding piece of cutlery. However, only a dozen of the same items of cutlery is taken as a basis, which means that Tablespoon are hallmarked usually with. A common hallmark of cake on a fork indicates, therefore, that 18 grams of silver were needed to twelve cake forks to silver with the same layer thickness as the main cutlery.
Vapor deposition
The deposition of a silver reference as thermal evaporation is the simplest coating technology. The silver is heated (for example, a so-called " vapor deposition boats " tungsten ), or an induction heater ( roughly in an oven ) using heat-resistant ceramic crucibles at temperatures in the vicinity of the boiling point by means of a resistance heater. It evaporates, spreads gas in the oven or in the vacuum chamber (depending on equipment used ) and condenses on the cooler substrate opposite. The silver vapor where it forms a thin layer. The layer thickness depends on the duration of vapor deposition.
Galvanic silver
In the galvanic plating, the articles are immersed ( after pretreatment ) in a silver and electrolytes by the application of an electric potential is deposited on the surface of a silver coating from. To further improve the surface properties is often followed by a subsequent treatment. Little known is that of sterling quality manufactured goods often a galvanic coating of fine silver get to hide Lötfugen and unify color differences. The silver plating is one of the oldest applications of electroplating. On July 24, 1838, on 25 March 1840, the first patents were filed this in England by Messrs. Elkington GR and H. Elkington under the patent number 8447. Starting in 1842, there was a connection and license agreement with Charles Christofle & Co, Paris. Only since the 1870s, the galvanizing widespread even in the German producers of silver cutlery.
Electroless silver plating
For electroless silver plating to use hot baths containing cyanide with silver nitrate ( " brewing process " ) or aqueous solutions of silver nitrate, ammonia, hydrazine sulfate and sodium hydroxide. For silvering non-metallic objects (mirrors, Christmas ball ) must be specially treated surface. For plastics, first a copper layer has to be applied.
Feuerversilbern
The Feuerversilberung counts similar to the fire-gilding to the historical processes that are no longer used because of toxic elements mercury or lead.