Cadmium electroplating

Electroplating Cadmium is usually electroplated from a cyanide solution. Zinc is also deposited from cyanide electrolyte, but for some applications mildly acidic and alkaline non-cyanide electrolytes are increasingly being used. Typical cyanide-based electrolyte formulations for both metals taken from Specifications DTD 903 and 904 are given in Table 13.6. 

Hodes G, Manassen J, Neagu S,Cahen D, Mirovski Y (1982) Electroplated cadmium chalco-genide layers Characterization and use in photoelectrochemical solar ceUs. Thin Sohd FUms... 

Provision for electroplating cadmium from 0.1 MCdS04 onto platinum electrode dilute (2 percent) cadmium amalgam (1 mL) eye dropper constant-temperature baths set at 15, 25, and 35°C ice bath approximately 0.1 A/CdS04 solution (150 mL) ice (1 kg). 

Cadmium is used very little as the pure metal, but it does have important uses as a constituent of many alloys and in its various salt forms (for review, see Waalkes et al. 1991d Stoeppler 1991). The primary uses for the majority of cadmium include batteries, electroplating, stabilizers, and pigments. Cadmium is used as the negative electrode in rechargeable Cd-Ni batteries. Electroplated cadmium provides excellent protective properties... 

Cadmium is used industriadly as a protective coating for iron, steel, and copper by electroplating. Cadmium sulfide and sulfoselenide are used as pigments in plastics, enamels, and paint. It may also serve as an alloy with copper for coating telephone cables, trolley wires, and welding electrodes. The stearate is used as a stabilizer in plastics, and cadmium electrodes are found in alka-... 

Ion plating has often been used to coat very large structural parts with aluminum for corrosion protection as an alternative to electroplated cadmium. Ion-plated coatings can also be used for depositing adherent layers as a base for further deposition by other techniques such as electroplatingt and painting. 

Vacuum cadmium plating The vacuum deposition of cadmium on high strength steel to avoid hydrogen embrittlement of the steel, which can occur in electroplated cadmium. Also called Vac cad plating. 

Aqueous Electrodeposition. The theory of electro deposition is well known (see Electroplating). Of the numerous metals used in electro deposition, only 10 have been reduced to large-scale commercial practice. The most commonly plated metals are chromium, nickel, copper, zinc, rhodium, silver, cadmium, tin, and gold, followed by the less frequendy plated metals iron, cesium, platinum, and palladium, and the infrequendy plated metals indium, mthenium, and rhenium. Of these, only platinum, rhodium, iddium, and rhenium are refractory. 

Cadmium, cobalt, copper, and nickel sulfamates react with lower aHphatic aldehydes. These stable compositions are suitable for use ia electroplating solutions for deposition of the respective metal (see Electroplating). 

SAE 780 tin, silicon, and copper alloy, and SAE 770 using tin, copper, and nickel are aluminum alloys which have been widely used in medium- and heavy-duty diesels (6). With siUcon and cadmium incorporated for improved compatibiUty, both SAE 781 and 782 are used as an 0.5 mm to 3.0 mm overlay on a steel backing with a thin electroplated babbitt overlay. Traditional 6% tin—aluminum is also used as the SAE 780 alloy with an overlay. Eleven percent siUcon alloys are used for highly loaded diesel bearings in Europe. 

Cadmium acetate is a colorant for glass and textiles, a glaze for ceramics where it produces iridescent effects, a starting material for preparation of the cadmium haUdes, and is an alternative to the cyanide bath for cadmium electroplating. In 1991, cadmium acetate dihydrate sold for 59.50/kg in 2 kg lots of reagent-grade material. 

Electroplated Metals and Alloys. The metals electroplated on a commercial scale from specially formulated aqueous solutions iaclude cadmium, chromium, cobalt, copper, gold, iadium, iron, lead, nickel, platinum-group metals, silver, tin, and ziac. Although it is possible to electroplate some metals, such as aluminum, from nonaqueous solutions as well as some from molten salt baths, these processes appear to have achieved Httie commercial significance. 

Cadmium. In 1989, U.S. consumption of cadmium for coatings was 1474 t (7), compared to 1552 t in 1970, 2089 t in 1979, and 1230 t in 1985. Cadmium plating amounts to about 15% of total cadmium production (see Cadmiumand cadmium alloys). Of the cadmium being plated in 1989, 30% was for automotive parts, over 22% for electronics, and 18% for industrial fasteners. Because of cadmium s high and weU-pubHcized toxicity and very tight waste restrictions, there are considerable efforts to develop alternative materials, and the quantities of cadmium used in electroplating ate expected to decrease. The price of cadmium anodes in early 1993 was about l/kg. 

Concentrated, aqueous solutions of ZnCla dissolve starch, cellulose (and therefore cannot be filtered through paper ), and silk. Commercially ZnCla is one of the important compounds of zinc. It has applications in textile processing and, because when fused it readily dissolves other oxides, it is used in a number of metallurgical fluxes as well as in the manufacture of magnesia cements in dental fillings. Cadmium halides are used in the preparation of electroplating baths and in the production of pigments. 

BS 1706 Electroplated Coatings of Cadmium and Zinc on Iron and Steel... 

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