PURPOSE: To develop a double layer galvanized steel sheet excellent in press workability and corrosion resistance, on the surface of a steel sheet, a forming a Zn-based substrate plated layer and a silica-contg. Zn-based composite plated layer thereon.
CONSTITUTION: On the surface of a steel sheet such as a cold rolled steel sheet, a hot rolled steel sheet or the like, a galvanized layer or a galvannealed layer is formed by 10 to 80g/m2 coating weight. The surface is furthermore plated with Zn or a Zn alloy contg. anion-type or cation-type fine colloidal silica having 10 to 100nm grain size in the ratio of 3 to 20wt.% by the ratio of 2 to 15g/m2 coating weight to form a composite plated layer. The double layer galvanized steel sheet free from a powdering phenomenon and a build-up phenomenon at the time of press forming and furthermore excellent in corrosion resistance can be obtd.
KOMORI TSUTOMU
MORITO NOBUYUKI
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