| 摘要 |
PURPOSE: A Zn-Co-W alloy electroplated steel sheet the surface of which has superior whiteness and corrosion resistance, and on which double plating layers are formed is provided, and a preparation method of the Zn-Co-W alloy electroplated steel sheet having superior whiteness and corrosion resistance by controlling tungsten content of the plating layers is provided. CONSTITUTION: The Zn-Co-W alloy electroplated steel sheet comprises a lower plating layer comprising 0.1 to 3 wt.% of cobalt as metal cobalt plated on steel sheet, 0.1 to 2 wt.% of tungsten as metal tungsten plated on the steel sheet and a balance of zinc and having the minimum plating adhesion amount of 5 g/m¬2; and an upper plating layer comprising 0.1 to 3 wt.% of cobalt as metal cobalt plated on the lower plating layer, less than 0.08 wt.% of tungsten as metal tungsten plated on the lower plating layer and a balance of zinc and having a plating adhesion amount of 0.5 to 2 g/m¬2. The preparation method of the Zn-Co-W alloy plated steel sheet comprises a step of forming a lower plating layer on a base steel sheet by plating a plating solution on the steel sheet at the minimum plating current density of 20 A/dm¬2 so that 5 g/m¬2 of the minimum plating adhesion amount is maintained, wherein the plating solution has pH of 3 to 6 and comprises 0.1 to 4 g/L of tungsten selected from the group consisting of 60 to 200 g/L of zinc chloride, 0.1 to 6 g/L of cobalt chloride, sodium tungstate, ammonium tungstate and potassium tungstate, 0.5 to 10 g/L of citric acid selected from the group consisting of sodium citrate, ammonium citrate and potassium citrate, 30 to 400 g/L of at least one or more of electroplating additives selected from the group consisting of potassium chloride, ammonium chloride and sodium chloride and 0.1 to 2 ml/L of polyethylene glycol based additive having a molecular weight ranging from 100 to 2000; and a step of forming an upper plating layer by plating the plating solution on the lower plating layer at a plating current density of 15 A/dm¬2 or less so that 0.5 to 2 g/m¬2 of a plating adhesion amount is maintained.
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