Electrodeposition


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electrodeposition

[i¦lek·trō‚dep·ə′zish·ən]
(metallurgy)
Electrolytic process in which a metal is deposited at the cathode from a solution of its ions; includes electroplating and electroforming. Also known as electrolytic deposition.

Electrodeposition

 

(also electrolytic deposition), the deposition of a metal or an alloy at a cathode during the electrolysis of a solution or melt of the respective salt.

Crystal growth during electrodeposition has much in common with crystallization from a vapor or a solution. The factor that governs supersaturation in electrodeposition is the overvoltage that occurs at an electrode during an electrochemical reaction. Depending on the magnitude of the overvoltage, crystal growth may occur by means of spiral growth on screw dislocations, the formation and growth of two-dimensional crystal nuclei, or—at high enough overvoltages—the formation of three-dimensional nuclei. The formation and growth of two-dimensional nuclei are typical of dislocationless crystals; the formation of three-dimensional nuclei is the normal process of crystal growth.

The possibility of varying the cathodic overvoltage over a wide range makes it possible to obtain metallic layers that have markedly different properties. Thus, depending on the formation conditions for deposits, the dislocation density in a deposit may range from 106 to 1012 cm–2. Consequently, such properties as conductivity, hardness, and ductility may also be varied. High dislocation densities have been found in deposits of, for example, copper, nickel, iron, chromium, platinum, and silver.

The adsorption of surfactants and the incorporation of impurities have an especially strong effect on the structure of the metallic deposits obtained by electrodeposition.

Electrodeposition is the basis of electrometallurgy, the refining of metals, and electroplating technology.

IU. M. POLUKAROV

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