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Knowledge Bank

WIOPEDIA - The WIOTEC® electroplating encyclopaedia

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This is the term for the electrochemical decomposition of electrolytes by direct current. So-called "redox reactions" occur at the two electrodes immersed in the liquid phase, in which one reaction partner transfers electrons to another reaction partner.

Reduction takes place at the negative pole, the cathode.
At the positive pole, the anode, oxidation occurs.

Depending on the operating conditions of cations and the electrolyte composition, e.g.:
Cu2+ + 2e‾ Cu; 2H+ + 2e‾ H2), anions (CrO4 2- + 8H+ + 6e‾ Cr + 4 H2O) or neutral molecules (Cl2 + 2e‾ 2Cl‾).

Analogously, an electron donation occurs at the anode, e.g.:
Fe2+ Fe3+ + e‾; 2Cl‾ Cl2 + 2e‾; 2H2O O2 + 4H+ + 4e‾), whereby in the case of a soluble anode (such as the copper anode) during electrolytic copper refining, (Cu Cu2+ + 2e‾) the electrode material itself can also dissolve.
(Source: "Magazine for Surface Technology")

Under these conditions, insoluble anodes (e.g. made of graphite, platinum or stainless steel) are not attacked. To prevent the electrolytically formed products from mixing, it is advisable to separate the anode and cathode compartments by means of a diaphragm. If the externally applied DC voltage exceeds the decomposition voltage of the electrolyte, which depends on the respective redox potentials, electrolysis occurs.

If several reactions are possible, the normal potential often decides. During the electrolytic decomposition of an aqueous saline solution at the cathode, no metallic sodium is normally formed, with discharge of Na+ions), but the nobler hydrogen is formed.

Technically significant electrolysis processes are, for example:

production of metal coatings in electroplating
chlor-alkali electrolysis for the production of chlorine, hydrogen and alkaline solutions
various cleaning and frahling processes for metals such as copper, tin and aluminium.

Etching, pickling and polishing can also be carried out electrolytically.

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Auf den Geeren 9-11
59469 Ense-Höingen, Germany

WIOTEC® Arnsberg GmbH & Co. KG
Wagenbergstraße 55
59759 Arnsberg, Germany

+49 2938 97833-0
+49 2938 97833-20

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