| 摘要 |
PURPOSE: A galvanized steel sheet having excellent corrosion resistance is provided which can be coated at low current density, and in which magnesium in coating layer is not lost, and a manufacturing method of the galvanized steel sheet having excellent corrosion resistance is provided. CONSTITUTION: The surface treated steel sheet having excellent corrosion resistance is characterized in that magnesium coating layer and galvanized layer are formed on strip in multiple-layer, the outermost layer is galvanized layer having the minimum weight of 2 g/m¬2 or more, and the total coating layer has weight of 5 g/m¬2 or more, wherein the magnesium coating layer is magnesium oxide, magnesium hydroxide or a mixture thereof, wherein magnesium coating weight in one magnesium coating layer has 0.01 to 0.7 g/m¬2 of metal Mg, wherein the magnesium coating layer and galvanized layer are alternately formed on the strip in multiple-layer, and the outermost layer is galvanized layer, wherein a zinc phosphate based chemical conversion treated film is formed on the surface treated steel sheet, or a modified zinc phosphate based chemical conversion treated film to which one or more elements selected from Fe, Ni, Mn, Co, Cu, Mg and Mo are added is formed on the zinc phosphate based chemical conversion treated film in a coating weight of 0.1 to 3 g/m¬2, and wherein the galvanized layer is formed on the magnesium coating layer by galvanizing a magnesium coated steel sheet in galvanizing solution having pH 4 or more.
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