A process for producing a zinc-iron alloy plated steel sheet having good plating adhesion, surface roughness and surface appearance

摘要

The present invention relates to a chloride-based zinc-iron alloy plating bath comprising zinc chloride and iron chloride and one or more kinds of supporting electrolytes such as potassium chloride, calcium chloride, sodium chloride and ammonium chloride, And an aromatic acid are added to improve the adhesion of the plating layer and to obtain a plating layer having a good surface roughness and surface appearance (whiteness and gloss). The water concentration of the zinc ion of zinc chloride is 0.5-2.5 moles (H (OCH _{2) 2) based} on a water concentration of 0.1-0.5 mol / liter, a water concentration of chloride ion of 4.0-9.0 mol / liter, an iron ion ratio of 0.05-0.3: 1, CH ₂ ) nOH is in the range of 10-20 and 20-30, and the mixing ratio thereof is in the range of 1: 2-1: 5 by weight, and the concentration of the mixed polyethylene glycol is 5-15% To the aqueous solution were added an aromatic acid and methoxypoly Ethylene glycol and the solution is 2-10% of the number in the range 10 to 40 of polymerization degree of N _{(CH 3 (OCH 2 CH 2} ) nOH), polyethylene glycol and methoxy polyethylene glycol sum to maintain 8-22% An organic solvent additive having an aromatic acid content of 0.1-1.0% based on the weight of the mixed solution is added at a concentration of 0.2-8.0 ml / L, and the pH of the plating solution is adjusted to 1.0-6.0 using a zinc chloride-iron alloy electroplating solution. 70 ° C, a current density of 20-200 A / dm ^2, and a relative flow rate of the plating solution and the cathode of 0.5-2.5 m / sec.