OBERFLAECHENBEHANDELTES SCHWARZES STAHLBLECH UND VERFAHREN ZUR HERSTELLUNG DESSELBEN.

摘要

A colored zinc composite-plated steel sheet which comprises a steel sheet or a plated steel sheet, a colored composite-plating film comprising zinc and an oxide of a coloring metal such as nickel, cobalt, iron, chromium, tin or copper and provided on the steel sheet at a coverage of 0.1-5 g/m<2> and a transparent guard coat having a thickness of 3 mu m or less provided on the film is obtained by carrying out electrolysis in an acidic aqueous solution containing zinc ions, coloring metal ions and nitrate ions, nitrite ions, perchlorate ions, chlorate ions and/or condensed phosphate ions and having a pH of 1-4 using the steel sheet or plated steel sheet as a cathode at a current density of 5-100 A/dm<2> and a current quantity of 20-200 coulomb/dm<2>.