POSCO Holdings Inc.
Manufacturing method of surface-treated zinc-nickel alloy electroplated steel sheet having excellent corrosion resistivity and paintability

Abstract:

Provided is a manufacturing method of a surface-treated Zn--Ni alloy electroplated steel sheet, the method comprising the steps of: preparing a Zn--Ni alloy electroplated steel sheet including a steel sheet and a Zn--Ni alloy-plated layer with an Ni content of 5-20 wt % (S1); preparing an alkaline electrolyte solution in which 4-250 g/L of potassium hydroxide (KOH) or sodium hydroxide (NaOH) or both combined are added in distilled water (S2); and inside the alkaline electrolyte solution, placing the Zn--Ni alloy electroplated steel sheet as an anode and installing another metal sheet as a cathode, and applying 2-10 V of an alternating or direct current to conductor electrochemical etching such that a 3-point average value of the arithmetic average roughness (Ra) of the surface of the Zn--Ni alloy electroplated steel sheet reaches 200-400 nm, thereby producing a surface-treated electroplated steel sheet (S3).