Nippon Steel Corporation

Toshimichi Murata

Yujiro Miyauchi

Yoshio Shindo

Katsushi Saito

Yoshio Shindou

Fumio Yamazaki

Katushi Saito

Takashi Shimazu

Disclosed are a black surface-treated steel sheet, which comprises a steel sheet or plated steel sheet and a electrodeposited composite plating coating formed in a deposition amount of 0.1 to 5 g/m.sup.2 on the surface of the steel sheet or plated steel sheet, the plating coating containing metallic zinc or Zn--Ni alloy and oxides or hydrous oxides and sulfur compound, and a process for the preparation of a black surface-treated steel sheet, which comprises carrying out the electrolysis in an acidic aqueous solution containing Zn.sup.2+ and, as the main components, at least one member selected from the group consisting of Fe.sup.2+, Co.sup.2+ and Ni.sup.2+, and oxidative ion, and a thio compound, by electrolysis a steel sheet or plated steel sheet as the cathode, and water-washing and drying the treated steel sheet.

Black surface-treated steel sheet

Disclosed are a black surface-treated steel sheet, which comprises a steel sheet or plated steel sheet and a electrodeposited composite plating coating formed in a deposition amount of 0.1 to 5 g/m.sup.2 on the surface of the steel sheet or plated steel sheet, the plating coating containing metalic Zinc or Zn-Ni alloy and oxides or hydrous oxides and sulfur compound, and a process for the preparation of a black surface-treated steel sheet, which comprises carrying out the electrolysis in an acidic aqueous solution containing Zn.sup.2+ and, as the main components, at least one member selected from the group consisting of Fe.sup.2+, Co.sup.2+ and Ni.sup.2+, an oxidative ion, and a thio compound, by electrolysis a steel sheet or plated steel sheet as the cathode, and water-washing and drying the treated steel sheet.

Process for the preparation of a black surface-treated steel sheet

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.sup.2 and a transparent guard coat of 3 .mu.m or less thick provided on the film is obtained by carrying out electrolysis in an acidic aqueous solution containing zinc ion, a coloring metal ion and nitrate ion, nitrite ion, perchlorate ion, chlorate ion, condensed phosphate ion 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.sup.2 and a current quantity of 20-200 coulomb/dm.sup.2.

Method of making a black surface treated steel sheet

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Kimitsu, Japan

Toshimichi Murata