PRODUCTION OF ELECTROLYTICALLY CHROMATED GALVANIZED STEEL SHEET EXCELLENT IN RESISTANCE TO CORROSION, FINGERPRINTING AND CHROMIUM ELUTION AND IN STABILIZED PRODUCTIVITY AND TO PROVIDE ELECTROLYTIC CHROMATING BATH USED IN THAT CASE

摘要

PURPOSE: To propose a method for producing an electrolytically chromated galvanized steel sheet excellent in resistance to corrosion, fingerprinting and chromium elution and in stabilized productivity and to provide an electrolytic chromating bath used in that case. ;CONSTITUTION: A zinc or galvanized steel sheet with at least one side glavanized is used as a cathode and electrolytically chromated in an electrolytic chromating bath contg. hexavalent chromium ion, trivalent chromium ion, bivalent Co ion, silica sol, phosphate ion and sulfate ion, with the trivalent chromium ion concn. in the bath/total chromium concn. regulated to 0.1 and the silica concn. in the bath/trivalent chromium ion concn. to 70 and kept at pH2.5-3.8 and 30-70°C bath temp. to form an electrolytic chromate film on the zinc or galvanized layer.;COPYRIGHT: (C)1996,JPO