A steel sheet mainly suitable for strength members of automobiles or building materials, which has a tensile strength of 1,180 MPa or more, and which is excellent in delayed fracture resistance and primary rust prevention performance. The steel sheet includes a coating, placed on a surface of a cold-rolled steel sheet with a tensile strength of 1,180 MPa or more, containing one or more metalates selected from molybdates and tungstates and a P compound. The sum of the coating weights of the metalates in terms of Mo and W is 10 mg/m.sup.2 to 1,000 mg/m.sup.2 and is preferably 50 mg/m.sup.2 to 1,000 mg/m.sup.2. The coating weight of the P compound in terms of P is 10 mg/m.sup.2 to 1,000 mg/m.sup.2.

A steel sheet mainly suitable for strength members of automobiles or building materials, which has a tensile strength of 1,180 MPa or more, and which is excellent in delayed fracture resistance and primary rust prevention performance. The steel sheet includes a coating, placed on a surface of a cold-rolled steel sheet with a tensile strength of 1,180 MPa or more, containing one or more metalates selected from molybdates and tungstates and a P compound. The sum of the coating weights of the metalates in terms of Mo and W is 10 mg/m.sup.2 to 1,000 mg/m.sup.2 and is preferably 50 mg/m.sup.2 to 1,000 mg/m.sup.2. The coating weight of the P compound in terms of P is 10 mg/m.sup.2 to 1,000 mg/m.sup.2.

A composition for surface treatment capable of imparting to a steel sheet, plate corrosion resistance, corrosion resistance of processed parts, pit corrosion resistance, blackening resistance, pipe forming oil infiltration, and alkali resistance, and improving foreign-matter defects; and a steel sheet using the same. The composition for surface treatment of a steel sheet includes a trivalent chromium compound; and adhesiveness improving agent containing a silane compound; an acidity modifier including acids; a crosslinking agent containing a silicate compound; a vanadium-based pit corrosion-improving agent; a polymer resin; and a solvent.

This surface-treated steel includes surface-treated steel comprising: a steel sheet; a plated layer including zinc formed on the steel sheet; and a film formed on the plated layer, wherein the film has a thickness of 100 nm or more and 1000 nm or less, wherein the film includes: an amorphous phase A containing Si, C, O, P, Zn, and V, and one or two or more kinds selected from the group consisting of Ti, Zr, and Al as constituent elements, wherein Zn/Si, which is a peak intensity ratio between Zn and Si, is 1.0 or more, and V/P, which is a mass ratio between V and P, is 0.050 to 1.000 when analysis is performed by EDS; and an amorphous phase B containing Si, O, and Zn, wherein the amorphous phase B has a Zn/Si ratio of less than 1.0, the Zn/Si ratio is a peak intensity ratio between Zn and Si when analysis is performed by EDS, a Zn content of the amorphous phase A is 10 mass % or less, and in a cross section in a thickness direction, a percentage of a length of an interface between the plated layer and the amorphous phase B to a length of an interface between the plated layer and the film is 30% or more.

This battery unit is a battery unit including a battery pack that houses a battery cell, and a water-cooling medium flow path formed outside a bottom surface of the battery pack, in which the water-cooling medium flow path is made of a Zn-based plated steel sheet, an inorganic film or a resin film is formed as a chemical conversion coating film on a surface of the Zn-based plated steel sheet, and the inorganic film contains a Si-based component or a Zr-based component as a main component.

Provided is a solution composition for steel sheet surface treatment, comprising 30 wt % to 60 wt % of a trivalent chromium compound containing chromium phosphate (A) and chromium nitrate (B); 0.2 wt % to 0.4 wt % of a rust-inhibiting and corrosion-resisting agent; 0.1 wt % to 0.3 wt % of a molybdenum-based compound; 5 wt % to 10 wt % of a water-soluble cationic urethane resin; 0.5 wt % to 2.0 wt % of a silane coupling agent; and 27.3 wt % to 64.2 wt % of water, a zinc-based plated steel sheet surface-treated with the same, and a manufacturing method therefor, the zinc-based plated steel sheet surface-treated with the solution composition for steel sheet surface treatment containing trivalent chromium may have an excellent effect on corrosion resistance, blackening resistance, fingerprint resistance, oil resistance, and alkali resistance.

Provided is a solution composition for steel sheet surface treatment, comprising 30 wt % to 60 wt % of a trivalent chromium compound containing chromium phosphate (A) and chromium nitrate (B); 0.2 wt % to 0.4 wt % of a rust-inhibiting and corrosion-resisting agent; 0.1 wt % to 0.3 wt % of a molybdenum-based compound; 5 wt % to 10 wt % of a water-soluble cationic urethane resin; 0.5 wt % to 2.0 wt % of a silane coupling agent; and 27.3 wt % to 64.2 wt % of water, a zinc-based plated steel sheet surface-treated with the same, and a manufacturing method therefor, the zinc-based plated steel sheet surface-treated with the solution composition for steel sheet surface treatment containing trivalent chromium may have an excellent effect on corrosion resistance, blackening resistance, fingerprint resistance, oil resistance, and alkali resistance.

Provided is a surface-treating solution composition, a zinc-based plated steel sheet surface-treated using the same, and a method for producing the same, wherein the surface-treatment solution composition includes: 10 wt % to 20 wt % of a trivalent chromium compound containing chromium phosphate (A) and chromium nitrate (B), the content ratio thereof, A/(A+B), satisfying 0.3 to 0.6; 20 wt % to 40 wt % of a silane-based sol-gel resin in which three types of silane compounds are crosslinked; 0.2 wt % to 0.4 wt % of a rust-inhibiting and corrosion-resistant agent; 0.1 wt % to 0.3 wt % of a molybdenum-based compound; 5 wt % to 10 wt % of a water-soluble cationic urethane resin; 0.5 wt % to 2.0 wt % of a silane coupling agent; 0.5 wt % to 2.0 wt % of an Al compound; and 25.3 wt % to 63.7 wt % of water. The zinc-based plated steel sheet surface-treated with the surface-treatment solution composition containing trivalent chromium has an excellent effect on corrosion resistance, blackening resistance, fingerprint resistance, piping oil infiltration, and alkali resistance.

Provided is a surface-treating solution composition, a zinc-based plated steel sheet surface-treated using the same, and a method for producing the same, wherein the surface-treatment solution composition includes: 10 wt % to 20 wt % of a trivalent chromium compound containing chromium phosphate (A) and chromium nitrate (B), the content ratio thereof, A/(A+B), satisfying 0.3 to 0.6; 20 wt % to 40 wt % of a silane-based sol-gel resin in which three types of silane compounds are crosslinked; 0.2 wt % to 0.4 wt % of a rust-inhibiting and corrosion-resistant agent; 0.1 wt % to 0.3 wt % of a molybdenum-based compound; 5 wt % to 10 wt % of a water-soluble cationic urethane resin; 0.5 wt % to 2.0 wt % of a silane coupling agent; 0.5 wt % to 2.0 wt % of an Al compound; and 25.3 wt % to 63.7 wt % of water. The zinc-based plated steel sheet surface-treated with the surface-treatment solution composition containing trivalent chromium has an excellent effect on corrosion resistance, blackening resistance, fingerprint resistance, piping oil infiltration, and alkali resistance.

Disclosed herein is a composition comprising a first lanthanide series metal, wherein the composition has a pH of less than 2.0 and is substantially free of peroxide. Also disclosed herein is a composition comprising a first lanthanide series metal and at least one of a second lanthanide series metal, copper, an inorganic phosphate compound, an organophosphate compound, and an organophosphonate compound; wherein the composition is substantially free of peroxide. Also disclosed herein are systems and methods of treating a metal substrate. Also disclosed are substrates treated with the systems and methods.