METHOD OF REGENERATING CHROMATE SOLUTIONS OF PASSIVATING Russian patent published in 2019 - IPC C23C22/86 C25D21/16 C25F7/02 C02F103/16 

FIELD: technological processes.

SUBSTANCE: invention relates to electrochemical regeneration of chromate solutions used for passivation of cadmium coatings. Method involves treatment of regenerated solution in anode chamber with anode from platinised metal of three-chamber electrolysis cell consisting of anode chamber separated from it by cation-exchange membrane of middle chamber and cathode chamber separated from middle chamber by anion-exchange membrane. Electrolysis is carried out in two stages, at the first stage, cathode is placed in cathode chamber containing solution of sulfuric acid 10–50 g/l, passing through electrolysis cell 25–80 Ah/l of electricity at cathode and anode current density of 1–10 A/dm², then, at second step, cathode is placed in middle chamber with sulfuric acid solution of 10–50 g/l and 0.8–4 A/l of electricity is passed at cathode and anode current density of 0.05–0.5 A/dm². After that, sodium carbonate is added to the solutions from the middle and cathode chambers to pH 9–10, then a mixture of cadmium and chromium hydroxides and carbonates is filtered and added to the solution treated in the anode chamber, and the cadmium metal precipitate is dissolved in the cadmium electrolyte.

EFFECT: invention provides regeneration of chromate cadmium passivation solutions, enables to eliminate losses of chromium and cadmium compounds and prevents formation of toxic wastes.

1 cl, 3 ex