Patent ID: 6235180
Filing Date: 2001-05-22
Classification: C25D,C25F

Abstract:
A method for forming phosphate film on steel wires comprising a descaling process and a phosphate film forming process,wherein no smut or sludge is generated during the descaling process or the phosphate film forming process,wherein the descaling process is an electrolytic pickling of steel wires using the steel wires as cathode and using acid other than phosphoric acid as an electrolyte, and the phosphate film forming process is an electrolytic process using the steel wires as cathode and using a forming solution of phosphate film as an electrolyte,wherein an electrolyte in the descaling process is selected from sulfuric acid, hydrochloric acid, nitric acid, hydrofluoric acid, hydrosilicofluoric acid and zircon hydrofluoric acid, and a temperature of the electrolyte is 90.degree. C. or lower and a current density of the steel wires is 1 A/dm.sup.2 to 100 A/dm.sup.2 in D.C. and an electrolytic time is 1 to 60 seconds, andwherein an electrolyte in the phosphate film forming process contains 2 to 60 g/liter of zinc ion, 2 to 80 g/liter of phosphoric acid ion and 3 to 100 g/liter of nitric acid ion, and a molar ratio of zinc ion to phosphoric acid ion is 0.9 to 1.5 and a molar ratio of nitric acid ion to phosphoric acid ion is 0.7 to 2.5, temperature of the electrolyte is 90.degree. C. or lower, the current density of the steel wires is 1 A/dm.sup.2 to 100 A/dm.sup.2 in D.C. and an electrolytic time is 1 to 30 seconds.