| 摘要 |
PURPOSE:To manufacture a surface-treated steel sheet for vessel excellent in weldability, corrosion resistance, and painting property, by applying pickling treatment and Ni plating to the surface of a steel sheet at a time under specific conditions and by successively subjecting the above sheet to Sn plating, to melting treatment by heating, and then to coating with chromate film layer of a specific quantity. CONSTITUTION:A cold-rolled steel sheet is electrolytically degreased and then subjected, at a time, to pickling treatment and Ni plating treatment of 2-30mg/m<2> per side by means of cathodic treatment in 2-50A/dm<2> current density at a temp. between ordinary temp. and 60 deg.C in a pickling solution prepared by adding Ni<2+> ions to 0.1-10% sulfuric acid by 1.0-3.0g/l. Subsequently, the above sheet is subjected, in succession, to Sn plating in 300-2,000mg/m<2> coating weight, to melting treatment by heating (reflowing treatment), and then to chromate treatment under the conditions of >=about 5A/dm<2> current density, a temp. between ordinary temp. and about 95 deg.C, and about 0.5-20sec electrolysis time by using a chromating bath of CrO3-SO4<2-> type, etc., containing CrO3 at a rate of >=about 10g/l, so that a chromate coating layer in a coating weight of 1-50mg/m<2> expressed in terms of the quantity of chromium can be formed. |
