METHOD OF CLEANING CHROMIUM PLATING ELECTROLYTES Russian patent published in 2013 - IPC C25D21/18 C23C22/86 

FIELD: chemistry.

SUBSTANCE: method involves electrolysis in several steps in a continuous mode in electrolysis cells with cation-exchange and anion-exchange membranes with lead anodes and stainless steel cathodes. The electrolyte is first diluted to content of chromium anhydride of 20-40 g/l, trivalent chromium ions of 0.5-5.0 g/l, iron ions of 0.4-2.0 g/l and sulphate of 0.2-0.8 g/l. The cleaning process is carried out first in the anode chamber of a two-chamber electrolysis cell with a cation-exchange membrane with 5-10 A·h of electricity passing through the solution and rate of circulation of the solution of 1 l/h, then successively in middle chambers of four three-chamber electrolysis cells with cation-exchange and anion-exchange membranes with 30-60, 15-30, 15-30 and 8-15 A·h of electricity passing through the solution, respectively, and then in reverse sequence in anode chambers of the same four electrolysis cells. Iron ions removed from the cleaned electrolyte are accumulated in the catholyte which contains 2-50 g/l sulphuric acid and 5-75 g/l iron ions and circulating through cathode chambers of one two-chamber electrolysis cell and four three-chamber electrolysis cells, and are deposited in form of a metal on cathodes in these electrolysis cells.

EFFECT: preventing loss of chromium during the cleaning process and high efficiency of said process by preventing reverse diffusion of chromic acid.

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