SLOTOLOY ZN "Generation VX": Alkaline zinc-nickel electrolytes for the future


Schlötter presents "Generation VX".  Schlötter’s new alkaline Zi-Ni electrolytes SLOTOLOY ZN 80 VX (rack process) and SLOTOLOY ZN 210 VX (barrel process) both feature a significantly reduced formation of cyanides and lower consumption of organic additives. 

The formation of cyanide when operating an alkaline zinc-nickel electrolyte is a well-known problem in electroplating. The organic additives used in alkaline Zi-Ni processes usually contain amines, which are incrementally oxidised into cyanides (CN-) at the insoluble anode. These cyanides and the nickel ions (Ni2+) in the electrolyte solution are transferred into a stable tetracyanonickelate complex. As a result, the complexed nickel is not available for the deposition on the cathode, which results in a reduced current efficiency and lower nickel content in the alloy. Consequently, the demand for nickel in the electrolyte increases, leading to more drag-outs and higher running costs. The effluent treatment of cyanide charged rinsed water is also significantly more complex.


In the field of electroplating, different approaches have already been developed in order to inhibt the cyanide formation in alkaline zinc-nickel electrolytes. This includes the application of selective membranes separating the anode compartment from the cathode compartment. The membrane technology requires high investment costs, additionally, the conversions of older plant installation is often not possible due to lack of spave. auszustatten.Therefore, Schlötter’s R&D team chose a different way and put the focus on the anodes themselves. The basic idea was to inhibit the formation of cyanide by the choice of the anode material. The developers tested numerous materials and finally achieved promising results with a new anode, distributed under the name Special Anode VX 1, so that they applied for a patent in February 2017.



Anti-ageing for alkaline zinc-nickel

Both SLOTOLOY ZN 80 VX (rack process) and SLOTOLOY ZN 210 VX (barrel process) are operated with special anodes (Special Anode VX 1). Field tests, substituting the convential nickel-plated insoluble anodes for special anodes VX 1 showed a positive result, which was already indicated by the colour of the electrolyte. The electrolyte changed from a brownish discolouration to a clear violet colour, showing visually that the the process contained less organic brekadown products. The cyanide content in the electrolyte was significantly reduced. With new SLOTOLOY ZN VX processes, many undesirable breakdown products can be avoided and a consistently higher current efficiency can be achieved. Existing installations of SLOTOLOY ZN 80 and SLOTOLOY ZN 210 can easily be converted to the new processes. To benefit from the VX-technology, users only have to exchange the anodes and the brightener. Capital expenditure is low: the new anodes roughly cost the same amount as regular nickel-plated steel anodes. 

The first installations on-site have been under operation for more than one year and have proved to provide excellent robustness and efficiency. 


Nominated for the award »THE SURFACE«

This new development also impressed the jurors from Fraunhofer IPA in Stuttgart who nominated Schlötter for their surface technology award »THE SURFACE«. Schlötter reached the finals and was presented with a certificate. The surface engineering award »THE SURFACE« has been presented by Fraunhofer IPA in Stuttgart since 2012 to innovative applications or technologies from the various sectors of surface engineering.