Abstract: A hot-dip Zn—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—Al alloy coated steel sheet are provided. The hot-dip Zn—Al alloy coated steel sheet includes a hot-dip Zn—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—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° C. at a cooling rate of 1° C. to 15° C./sec.

Abstract: 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/m2. 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.

Abstract: A hot-dip Zn—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—Al alloy coated steel sheet are provided. The hot-dip Zn—Al alloy coated steel sheet includes a hot-dip Zn—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—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° C. at a cooling rate of 1° C. to 15° C./sec.

Abstract: 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/m2. 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.

Abstract: A black colored steel sheet comprises a Zn—Ni-plated steel sheet having a blackening-treated layer and a coating film on the surface of the Zn—Ni-plated steel sheet. The blackening-treated layer has a thickness of 0.01 to 1.0 ?m. The Zn—Ni-plated steel sheet having a blackening-treated layer has an arithmetical mean roughness Ra of 0.7 to 2.0 ?m and the number of peaks per inch (PPI) of at least 180.