Silver plate

Electroplating. Most silver-plating baths employ alkaline solutions of silver cyanide. The silver cyanide complexes that are obtained in a very low concentration of free silver ion in solution produce a much firmer deposit of silver during electroplating than solutions that contain higher concentrations. An excess of cyanide beyond that needed to form the Ag(CN)2 complex is employed to control the concentration. The silver is added to the solution either directly as silver cyanide or by oxidation of a silver-rod electrode. Plating baths frequently contain 40—140 g/L of silver cyanide... 

Electrodes. AH of the finished silver electrodes have certain common characteristics the grids or substrates used in the electrodes are exclusively made of silver, although in some particular cases silver-plated copper is used. Material can be in the form of expanded silver sheet, silver wire mesh, or perforated silver sheet. In any case, the intent is to provide electronic contact of the external circuit of the battery or cell and the active material of the positive plate. Silver is necessary to avoid any possible oxidation at this junction and the increased resistance that would result. 

Potassium cyanide is primarily used for fine silver plating but is also used for dyes and specialty products (see Electroplating). Electrolytic refining of platinum is carried out in fused potassium cyanide baths, in which a separation from silver is effected. Potassium cyanide is also a component of the electrolyte for the analytical separation of gold, silver, and copper from platinum. It is used with sodium cyanide for nitriding steel and also in mixtures for metal coloring by chemical or electrolytic processes. 

Silver-plating bath compositions are somewhat variable a typical composition contains 36 g silver cyanide, 60 g potassium cyanide, 45 g potassium carbonate, and 1000 mL distilled water. A pure silver anode is required (179). 

Most electroless silver appHcations are for silvering glass or metallizing record masters. Mirror production is the principal usage for electroless silver. The glass support is cleaned, catalyzed using a two-step catalyst, and coated on one side with an opaque silver film (46). Silver-plated nylon cloth is used as a bacteriostatic wound dressing. A tiny current appHed to the cloth causes slow silver dissolution. The silver acts as a bactericide (47). 

A phenomenon known as silver migration has limited the use of silver plating in miniature circuit boards under a positive d-c potential within a damp environment silver can migrate across insulation. On drying, silver is found in the insulation or media creating a leakage path. Silver plating is forbidden in many military specifications for circuit boards. 

The main incoming mate coniacts are generally made ot copper or brass and are cither hotted or damped on die vertical bus. Since tlic bus is generally of aluminium. Ihe coniacts may form a bimelaltic join wilh Ihe busbars and cause corrosion and pilling of ibe melal. This may result in a failure of the joinl in due course. To mininii/e rnelal oxidation and bimetallic corrosion, the conlacls must be silver plated. 

In a draw-out MCC all current-carrying components should be periodically checked for their silver-plating, proper contact area, spring pressure and tightness of joints (this procedure can follow the manufacturer s maintenance schedule) or at least during the six-monthly or yearly maintenance check ups of the busbars and the busbar joints as noted above. The contacts or their springs may be replaced when the contacts are worn out or... 

Tarnishing (blackening) of contaels is a common eharaelerislie of silver-plated eontaels. It is the formation of silver oxide film which is a good conductor of heat and electricity is not a cause for concern. 

A) 1 For busbars and busbar connections of aluminium or copper 2 For busbars and busbar connections of aluminium or copper silver plated or equivalent 3 Terminals for external insulated cables 50 65 70 90 105 110... 

Bus conductor with plain connection joints Bus conductor with silver plated or welded contact surfaces... 

Pure uninhibited tetrafluoroethylene can polymerise with violence, even at temperatures initially below that of room temperature. There is little published information concerning details of commercial polymerisation. In one patent example a silver-plated reactor was quarter-filled with a solution consisting of 0.2 parts ammonium persulphate, 1.5 parts borax and 100 parts water, and with a pH of 9.2. The reactor was closed and evacuated, and 30 parts of monomer... 

L. J. M. Daguerre s photographic process (silver plate sensitized by exposure to iodine vapour)... 

Silber-plattierung, /. silver plating, -probe, /. test for silver, silver assay, -protein, n. Pharm.) silver protein. 

Versicherungsschein, m. insurance policy bond, vcrsickem, v.i. ooze away, seep away, percolate. Verslckening, /. seepage, percolation, versiegeln, v.t. seal, seal up. versiegen, v.i. dry up, be exhausted, versllbcm, v.t. silver, silver-plate. 

Versllberung, /. silvering, silver plating. Versilberungsbad, n. silver bath, versinken, v.i. sink. 

Nickel-plated copper/silver-plated copper... 

Copper/silver-plated copper Solder-dipped copp>er/tin-plated aluminium Copper/tin-plated copper Copper/solder-dipped copper Copper/reflowed tinned copper Silver-plated copper/tin-plated copper Silver-plated copper/solder-dipped copper Gold-plated copper/tin-plated copper Aluminium/tin-plated aluminium (zincate process)... 

Aluminium/brass Aluminium/copper Tin-plated aluminium/copper Aluminium/nickel-plated copper Aluminium/nickel-plated brass Aluminium/silver-plated copper Tin-plated aluminium/silver-plated copper Aluminium/gold-plated copper Tin-plated aluminium/gold-plated copper... 

Copper and silver tarnish readily in sulphide atmospheres, and copper in contact with sulphur-vulcanised rubber will sometimes react with the sulphur, devulcanising it in the process. The growth of conducting sulphide whiskers on silver is noteworthy as these whiskers may give rise to short circuits across silver-plated contacts. Ammonia has little effect on most metals, but traces will tarnish many copper alloys and cause stress-corrosion cracking of certain stressed brasses. 

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