Patent ID: 6168670
Filing Date: 2001-01-02
Classification: C23G

Abstract:
A method of pickling articles of copper or articles of copper with a metal less noble than copper, comprising the steps of: (a) treating said articles with an aqueous peroxosulfate pickling solution, thereby forming a used pickling solution, depleted in peroxosulfate, and containing dissolved copper or dissolved copper and metals less noble than copper, said used pickling solution further comprising: (1) at least one compound selected from the group which consists of alkali sulfates and ammonium sulfate and mixtures thereof in an amount of 50 to 350 g/l and; (2) at least one compound selected from the group which consists of zinc sulfate, copper sulfate and iron sulfate and mixtures thereof in an amount of 20 to 250 g/l; (b) cathodically reducing said used pickling solution with cathodic deposition of copper from said used pickling solution, thereby forming a reduced solution; (c) adding to said reduced solution a relatively high concentration of at least one additive promoting anodic peroxosulfate formation and selected from the group which consists of organic sulfur compounds, inorganic sulfur compounds, organic sulfur-free nitrogen compounds, inorganic sulfur-free nitrogen compounds and mixtures thereof; (d) anodically oxidizing said reduced solution to which said additive has been added to regenerate peroxosulfate from sulfate ion therein, thereby forming a regenerated peroxosulfate pickling solution, and recycling said regenerated pickling solution to step (a); (e) inhibiting a dissolution velocity of said metal less noble than copper during treatment of said articles in step (a) by adding to said pickling solution a compound selected from the group consisting of cyanides, cyanates, cyanamides, hexamethylenetetramine and urotropin in a concentration of 10.sup.-2 to 5.times.10.sup.-2 mol/l.; and (f) adding to the solution in step (a) at least one organic complex-forming substance.