Nippon Steel Corporation

Kouichi Wada

Fumio Yamazaki

Yoshio Shindo

Katsushi Saito

Yuujirou Miyauchi

Kazumi Shibata

Katsushi Saitou

Hidehiro Tomio

A surface-blackened steel sheet is produced by electrolyzing a steel sheet at a cathode in an acidic aqueous solution containing Zn.sup.2+, at least one of Fe.sup.2+, Co.sup.2+ and Ni.sup.2+, a film-improving ion consisting of at least one member selected from the group consisting of Cr.sup.3+, Fe.sup.2+, Pb.sup.2+, In.sup.2+, Ag.sup.2+, Sn.sup.2+, Ti.sup.2+, Al.sup.3+, Cu.sup.2+, Mo.sup.6+, V.sup.3+, V.sup.6+, Mn.sup.2+, Mn.sup.4+, Mn.sup.6+, Bi.sup.2+, sulfite ion, thiosulfate ion, thiocyanate ion, sulfamate ion and sulfonate ion, an oxidizing ion and an organic hydroxy-compound as main components, thereby forming a black film on the steel sheet, followed by water washing, a chromate treatment, if required, and coating with a guard coat.

Process for producing a surface-blackened 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

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Chiba, Japan

Kouichi Wada