Nippon Steel Corporation

Yoshio Shindo

Katsushi Saito

Fumio Yamazaki

Yujiro Miyauchi

Toshimichi Murata

Motoo Kabeya

Kouichi Wada

Teppei Tamura

Hidejirou Asano

Hidehiro Tomio

Koichi Wada

Mitsumasa Nagahisa

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 method for producing a steel sheet electroplated with a Zn-series alloy or Zn-series composite material, comprising, using an identical plating liquid, forming an initial electroplated layer in an amount essentially smaller than a subsequent main plating layer: relieving an electrodeposition strain in the initial electroplated layer after or during the formation thereof, and forming the main plating layer on the initial electroplated layer essentially free of the electrodeposition strain, thereby improving a plating adherence of the electroplated layer of Zn-series alloy or Zn-series composite material.

Method for producing a Zn-series electroplated steel sheet

In the electroplated steel sheets for automobile use, the chipping resistance, water-resistant adhesion, unpainted corrosion resistance, post-painted corrosion resistance, and resistance to secular exposure are improved by superimposing a chemical conversion layer between electroplated layers of zinc and iron, nickel, cobalt, or alloys thereof.

Surface treated steel material particularly electroplated steel sheet

Hot-dip galvanized steel sheet, wherein said coating layer is characterized by being highly resistant to flaking either in a high-temperature humid atmosphere or in long-term indoor aging. The coating comprises 0.1 to less than 0.2 wt % Al, 0.1-0.5 wt % Sb, the remainder being Zn and unavoidable impurities, the total of the unavoidable impurities other than Fe, namely Pb, Cd and Sn being less than 0.02 wt %, the ratio of Sb/Pb being 10-250, and the Al present in the coating layer being in the form of an Al-Sb eutectic.

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Kimitsu, Japan

Yoshio Shindo