Applications of electrodeposition from aqueous solvents

Many metals are made by electrodeposition. Several metals are prepared by electrolysis in molten salts (Section 7.6). A variety of plating processes have been developed for the metals deposited by electroplating. Quite different, usually aqueous, electrol54es are used. Each electrolyte has characteristic features and produces deposits with quite different properties. As an example, some electrolytes for the plating of copper will be described. Other important plating processes, e.g., zinc, nickel, tin, and lead, are described in detail in the literature.  

The deposition mechanism can be quite complex, e.g., chromium can be deposited from hexavalent chromic acid. In this case, a layer of chromium oxides of lower valence is formed on the metal surface. 

Electrodeposition of copper is one of the most important deposition processes in industry. Copper is already being refined by electrolysis. Copper plating is the main deposition process for the production of printed circuit boards. Plating processes for many applications are known with varying results for the characteristic properties of the deposits. Examples are 

Typical additives are polyethylene glycol, an organic sulfur compound, e.g., thiophene and a brightener, e.g., cresyl violet. 

Less copper sulfate (20-80 g dm CuS04-5H20) and more sulfuric acid are typical for this electrolyte, while the other conditions are similar. 

---