Electrolytic copper plating is the oldest process used in electroplating, dating back to 1830. The first copper coatings were obtained by separating copper from acidic copper sulfate solutions. 10 years later, a cyanide bath was also used for the first time. At KNK zamac, copper plating processes have been carried out since 1986, with the galvanic line gradually undergoing several complete reconstructions and copper plating first takes place in alkaline cyanide baths, which are indispensable as a base layer for zinc alloy plating, and then, if necessary, copper plating is carried out in acidic sulfate baths.
Electrolytic copper plating is a process carried out in electrolytic baths in which the product to be plated acts as the cathode, while the anode consists of cathodes in pure copper. Metal electrodes are placed in a solution of electrolyte, i.e. a substance that conducts electricity, and these copper electrodes are connected to a direct current source. Due to the potential difference on the electrodes, free positive ions migrate towards the cathode – the product. The galvanic bath is an aqueous solution of chemical compounds, which consists of salts of the metal being plated, as well as other organic and inorganic compounds that affect the conductivity of the solution and the quality of the resulting coatings.
The cyanide mediation bath consists of a complex cyanide solution Na3Cu(CN)4. Cyanide copper plating is essential for further plating processes. The role of cyanide copper plating is to create a base layer of copper that can be applied directly to zamak alloys of zinc, brass and iron with a typical thickness of 5-8 microns, the layer is semi-matt to glossy depending on the substrate without the possibility of providing the corrosion resistance of the zinc alloy.
It creates a high-gloss decorative copper surface with the ability to level the surface with a roughness of 1000 microns. Layers of 10-40 microns are applied as needed. It is also mostly used as a base for other layers such as brass, chrome, matt chrome, nickel, matt nickel and black nickel. If this copper layer is to be final, it must be passivated, e.g. by clear varnishing.
