Abstract: A surface-coated aluminum and zinc plated steel sheet in accordance with the present invention includes: a plated steel sheet; a composite coating film formed by applying an aqueous surface treatment agent on the plated steel sheet and drying the aqueous surface treatment agent. The aqueous surface treatment agent contains a water dispersible resin (A), a cobalt compound (B), and water, and has a pH within a range of 7.5 to 10. The composite coating film contains the water dispersible resin (A) and the cobalt compound (B). A percentage by mass of the water dispersible resin (A) in the composite coating film is 90% or more. A mass of the composite coating film per one surface of the plated steel sheet falls within a range of 0.5 to 3.5 g/m2.

Abstract: The present invention provides a hot-dipped steel 1 that demonstrates favorable corrosion resistance and formability, and has a favorable appearance of a plating layer. The hot-dipped steel of the present invention includes a steel substrate formed thereon with an aluminum-zinc alloy plating layer. The aluminum-zinc alloy plating layer contains Al, Zn, Si and Mg as constituent elements thereof and the Mg content is 0.1% to 10% by weight. The aluminum-zinc alloy plating layer contains 0.2% to 15% by volume of an Si—Mg phase, and the weight ratio of Mg in the Si—Mg phase to the total weight of Mg is 3% or more.

Abstract: A surface-coated aluminum and zinc plated steel sheet in accordance with the present invention includes: a plated steel sheet; a composite coating film formed by applying an aqueous surface treatment agent on the plated steel sheet and drying the aqueous surface treatment agent. The aqueous surface treatment agent contains a water dispersible resin (A), a cobalt compound (B), and water, and has a pH within a range of 7.5 to 10. The composite coating film contains the water dispersible resin (A) and the cobalt compound (B). A percentage by mass of the water dispersible resin (A) in the composite coating film is 90% or more. A mass of the composite coating film per one surface of the plated steel sheet falls within a range of 0.5 to 3.5 g/m2.

Abstract: The present invention provides a Zn—Al—Mg—Cr alloy-coated steel material with excellent corrosion resistance. A molten Zn—Al—Mg—Si—Cr alloy-coated steel material which is a steel material having a Zn—Al—Mg—Cr alloy coating layer and which has an interfacial alloy layer formed of coating layer components and Fe at the coating layer-steel material interface, wherein the interfacial alloy layer has a multilayer structure consisting of an Al—Fe-based alloy layer and an Al—Fe—Si-based alloy layer and furthermore, the Al—Fe—Si-based alloy layer contains Cr.

Abstract: The present invention provides a hot-dipped steel 1 that demonstrates favorable corrosion resistance and formability, and has a favorable appearance of a plating layer. The hot-dipped steel of the present invention includes a steel substrate formed thereon with an aluminum-zinc alloy plating layer. The aluminum-zinc alloy plating layer contains Al, Zn, Si and Mg as constituent elements thereof and the Mg content is 0.1% to 10% by weight. The aluminum-zinc alloy plating layer contains 0.2% to 15% by volume of an Si—Mg phase, and the weight ratio of Mg in the Si—Mg phase to the total weight of Mg is 3% or more.

Abstract: Disclosed is a high-strength Zn—Al coated steel wire for bridges with excellent corrosion resistance and fatigue properties, the Zn—Al coated steel wire includes: a steel wire; and a Zn—Al coating having a coating body layer and an Fe—Al alloy layer formed in an interface between a surface layer of the steel wire and the coating body layer, wherein a chemical composition of a core material of the steel wire includes, by mass %: C: 0.70% to 1.2%; Si: 0.01% to 2.5%; Mn: 0.01% to 0.9%; P: limited to 0.02% or less; S: limited to 0.02% or less; N: limited to 0.01% or less; and the balance including Fe and unavoidable impurities, wherein wire-drawn pearlite is most abundant microstructure among microstructures of the core material of the steel wire; wherein an average composition of the Zn—Al coating includes, by mass %, Al: 3.0 to 15.0%; and Fe: limited to 3.0% or less, and wherein the Fe—Al alloy layer has a thickness of 5 ?m or less.

Abstract: The present invention provides a Zn—Al—Mg—Cr alloy-coated steel material with excellent corrosion resistance. A molten Zn—Al—Mg—Si—Cr alloy-coated steel material which is a steel material having a Zn—Al—Mg—Cr alloy coating layer and which has an interfacial alloy layer formed of coating layer components and Fe at the coating layer-steel material interface, wherein the interfacial alloy layer has a multilayer structure consisting of an Al—Fe-based alloy layer and an Al—Fe—Si-based alloy layer and furthermore, the Al—Fe—Si-based alloy layer contains Cr.