PURPOSE: To efficiently replenish Cr3+ ions, etc., while managing the concn. of sulfuric acid by dissolving and circulating Zn and chromic acid by using the sulfuric acid obtd. by taking out a part of a plating liquid and dialyzing this liquid at the time of executing plating by using an insoluble anode and an acidic soln. of sulfuric acid.
CONSTITUTION: A part of the acidic plating liquid of the sulfuric acid contg. the Zn2+ ions and the Cr3+ ions is taken out of a plating cell 1 through a circulation tank 2 into a dialysis cell 3. The sulfuric acid is dialyzed via an ion exchange membrane 8 of this dialysis cell 3 and is concentrated 4. The concentrated sulfuric acid 11 is then introduced into a mixing tank 5, where metal Zn 6 and chromic acid 7 are charged to prepare an electrolyte contg. the Zn2+ ions and the Cr3+ ions. This electrolyte is then returned to a cell 1, where plating is executed by impressing DC current between the insoluble anode and the base material.
MOCHIZUKI KAZUO
NAKAMARU HIROKI
MORITO NOBUYUKI
