During single-nickel-salt Electrolytic Coloring, a closed rinsing process is designed to reduce the consumption of nickel sulfate in the coloring solution and to prevent contamination.

The process flow is as follows:
The coloring solution from the single-nickel-salt Electrolytic Coloring tank is circulated through an RO unit. Through the principle of reverse osmosis, nickel sulfate and boric acid in the coloring solution are separated and returned to the main coloring tank.
The permeate (RO water) enters the final rinsing tank, where it is used to control and maintain the nickel-sulfate concentration in the rinse tank.