Jfe Steel Corporation

Jfe Galvanizing & Coating Co., Ltd.

Rie Umebayashi

Susumu Satoh

Satoru Ando

Akira Matsuzaki

Susumu Sato

Kazuhisa Okai

Shigeru Takano

Akihiko Furuta

Etsuo Hamada

Hideo Ogishi

Hideo Koumura

Yoshito Furuya

A hot-dip Zn&#x2014;Al alloy coated steel sheet exhibiting a beautiful coating appearance with metallic luster, in which no spangle or very fine spangles are formed, and having excellent blackening resistance and a method for manufacturing the hot-dip Zn&#x2014;Al alloy coated steel sheet are provided. The hot-dip Zn&#x2014;Al alloy coated steel sheet includes a hot-dip Zn&#x2014;Al alloy coating layer containing 1.0 to 10 percent by mass of Al, 0.2 to 1.0 percent by mass of Mg, 0.005 to 0.1 percent by mass of Ni, and the balance being Zn and incidental impurities on at least one surface of a steel sheet. The manufacturing method includes the steps of dipping the steel sheet into a hot-dip Zn&#x2014;Al alloy coating bath and pulling up and cooling the steel sheet, wherein the steel sheet pulled up from the coating bath is cooled to 250&#xb0; C. at a cooling rate of 1&#xb0; C. to 15&#xb0; C./sec.

Hot-dip Zn&#x2014;Al alloy coated steel sheet and producing method therefor

An aqueous surface-treatment liquid is a treatment liquid containing a water-soluble zirconium compound, water-dispersive particulate silica, a silane coupling agent, a vanadic acid compound, a phosphoric acid compound, a nickel compound, and an acrylic resin emulsion in particular proportions. A surface-treated galvanized steel sheet produced using the treatment liquid is a galvanized steel sheet having a surface-treatment coating on a surface thereof, and the coating contains a zirconium compound, particulate silica, a silane-coupling-agent-derived component, a vanadic acid compound, a phosphoric acid compound, a nickel compound, and an acrylic resin in particular proportions. The amount of coating on a zirconium basis is 10 to 200 mg/m. This surface-treated galvanized steel sheet is chromate-free and has superior flat-portion corrosion resistance, blackening resistance, and appearance and corrosion resistance after press forming.

Surface-treated galvanized steel sheet with superior flat-portion corrosion resistance, blackening resistance, and appearance and corrosion resistance after press forming and aqueous surface-treatment liquid for galvanized steel sheet

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Tokyo, Japan

Rie Umebayashi