Formulation
Cyanide Alkaline Electrolyte for Copper Plating

In the mineral skeleton of an alkaline copper-plating electrolyte, the soluble copper in the mother phase is in the monovalent state (Cu⁺). The formulation involves dissolving copper cyanide powder (CuCN) in an excess of potassium cyanide (KCN), in the presence of a slight excess of potassium hydrogen carbonate (KHCO₃) and potash (KOH), which provide the alkalinity required for the mixture's chemical stability. Potassium-based products are more expensive than their sodium-based counterparts, but they feature better solubility as well as lower kinematic viscosity and higher ionic conductivity, properties that notably extend the average life of a bath (solubility of KHCO₃) and facilitate rinsing of parts.

The passivity of iron in an alkaline environment means that this treatment can be applied to steel parts in bulk, by the fastener or continuously, provided...