| 摘要 |
PURPOSE:To obtain a composite plated steel sheet having superior corrosion resistance, workability, adhesion to paint and weldability by depositing specified amounts of Co, Cr and Al in a zinc layer formed on a steel sheet by galvanization. CONSTITUTION:To an acidic galvanizing bath are added 0.3-60g/l (expressed in terms of metallic Co) one or more kinds of water soluble Co<2+> compounds, 0.2-2.5g/l (expressed in terms of metallic Cr) one or more kinds of water soluble Cr<3+> compounds and 0.5-20g/l (expressed in terms of alumina) boehmite- base alumina sol. A steel sheet is galvanized in the resulting bath to form a zinc layer contg. 0.1-10wt% Co, 0.05-5wt% Cr and 0.05X8wt% Al on the steel sheet.
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