Cadmium coatings electroplating

There has been some renewed interest in the use of tin-zinc alloy electroplate as a substitute for cadmium coatings on steel . It has been pointed out that tin-zinc coatings produce less loose corrosion product than zinc during full outdoor exposure... 

Since the 1960s, the use of cadmium for electroplating has dropped significantly due to environmental concerns. Discarded electroplated steel puts cadmium into the environment. Alternative coating methods are usually used now. 

Industrial uses of cadmium include electroplating and the manufacture of batteries, metal coatings, and alloys. Cadmium is also used as a pigment in paints and plastics. Some fertilizers also contain cadmium. 

International Standards Organization (1981). ISO 4520, Chromate conversion coatings on electroplated zinc and cadmium coatings, 2 pp. 

A separator was not required for this kind of battery. Average coulombic and energy efficiencies were up to 96% and 86%, respectively [57]. Over 1,000 cycles were achieved in a small laboratory cell. Zinc deposition from an alkaline zincate solution has been also investigated [58], and results show that zinc deposition on the cadmium substrate is better than other materials, for example, Cu, Pb. On the cadmium-coating electrode, electroplating behavior was simple and facilitated the discharge of zinc. 

Aluminium coatings electroplated from ionic liquids are considered as an alternative candidate to replace cadmium ones. The present studies are aimed at obtaining dense aluminium coatings adherent to the substrate with a definite thickness and mechanical properties. 

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. 

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

The technique may be said to combine the advantages of vacuum evaporation and sputtering, so that excellent qualities of adhesion are obtained without a limitation of maximum thickness of the coating—while at the same time the rate of deposition can be comparatively high. Many metals, alloys, and compounds may be deposited, on both metallic and non-metallic articles. However, its use at present is mainly for functional and protective applications, particularly where high resistance to corrosion is required. Thus, as examples, aluminium may be deposited on various types of steel and on titanium for uses in the aerospace and defence industries—and can be regarded as a less hazardous replacement for cadmium electroplating. 

The aluminizing process is a clean operation and the final products (Fig. 23), i. e., aluminum-coated metals, pose no environmental threat. We know today that aluminum can to a large extent replace cadmium as a corrosion-protective coating for work pieces [176]. Since cadmium is applied extensively in automobiles, aviation, on- and offshore industries, aluminum coating, i.e. both the aluminum electroplating process and the resulting coated pieces play an important role in environmental protection. The properties of the electrolytically produced aluminum layers on work pieces for aviation and space technology have been tested [183]. 

At one time, the most important use of cadmium was in the electroplating of steel. Electroplating is a process by which a thin layer of one metal is deposited on the surface of a second metal. An electric current is passed through a solution containing the coating metal. The metal is electrically deposited on the second metal. A thin layer of cadmium protects steel from corrosion (msting). 

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