Spray Rinses and Air Knives

These devices are grouped because of their similarity in application. When mounted on the lip of a process tank, a pipe directing a flow of either water or air at work pieces through appropriate nozzles can reduce the amount of solution carried over the subsequent process steps. Especially when applied to work pieces being removed from a plating solution, this can make it possible to keep solution in the process tank, 

Beginning with this option, process modification requires not only capital and downtime, but also floor space. This can be a significant barrier in many plating operations, and therefore this option is most easily implemented in new facilities or where substantial reconstruction of process lines is taking place. The concept is to use a non-flowing rinse, or empty tank, to capture process solution for eventual return to the process tank, with or without further separation or concentration. It has seen wide application with nickel and chrome plating, and seems to function quite well. Some concerns have arisen, however. 

The most important problem is that of contamination of process solutions. Just to take one example, that of nickel, sodium and calcium concentrations have been shown to increase when dragout is returned to the process solution, likely sources being the water used for rinsing. These contaminants interfere with the plating process. Organics, chlorides, and heavy metals, from sources including the process solution itself and the work being processed, can also accumulate and pose problems. And finally, nickel metal can rise to undesirable concentrations because of the difference in anode and cathode efficiencies. While these problems may take years to manifest themselves in a low-volume operation, eventually treatment and purification is required.[20] 

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