The chemical conversion treatment liquid according to the present invention, which is cobalt-free and is capable of forming a chemical conversion film having excellent corrosion resistance, contains a water-soluble trivalent chromium-containing substance, a water-soluble titanium-containing substance, and a water-soluble lactic acid-containing substance as essential components and may optionally contain a component at least a part of which is any of a water-soluble glycolic acid-containing substance and a water-soluble ineffective organic acid-containing substance. The water-soluble ineffective organic acid-containing substance is a water-soluble organic acid-containing substance based on an ineffective organic acid that is an organic acid other than lactic acid and other than glycolic acid. When the chemical conversion treatment liquid does not contain the water-soluble glycolic acid-containing substance and does not contain the water-soluble ineffective organic acid-containing substance, a titanium-equivalent molar concentration CTi of the water-soluble titanium-containing substance, a chromium-equivalent molar concentration CCr of the water-soluble trivalent chromium-containing substance, and a lactic acid-equivalent molar concentration CLc of the water-soluble lactic acid-containing substance satisfy the following Expressions (1) to (3):
CTi/CCr0.5(1);
CLc/(CTi+CCr)0.40(2); and
CLc/CTi2.6(3).

Provided is a zinc-based plated steel sheet having a post-treated coating filmed thereon including: a steel sheet; a zinc plated layer formed on the steel sheet; and a post-treated coating formed on the plated layer, wherein the atomic ratio (O/M) of oxygen (O) to metals (M) contained in the post-treated coating is greater than 2 and less than 20, and a method for post-treating a zinc-based plated steel sheet. According to this, the zinc-based plated steel sheet having the post-treated coating formed thereon has the effects excellent in lubricity, weldability, adhesiveness, film-removing property and paintability. As the method of post-treating a zinc-based plated steel sheet of the present invention employs a simple coating method irrespective of the kind of plating layer, the process is simple and economical and the process operation cost is low.

A metal sheet is provided. The metal sheet includes a substrate having two faces, each face hot dip coated with a metal coating of zinc, aluminum and magnesium. The metal coatings include between 0.1 and 20 wt % of aluminum and 0.1 and 10 wt % of magnesium. Layers of magnesium oxide or magnesium hydroxide are formed on outer surfaces of the metal coatings. The layers are altered by applying an acid solution on the outer surfaces of the metal coatings or by applying mechanical forces using a roller leveler, a brushing device, or a shot-blasting device on the outer surfaces of the metal coatings. The metal sheet also includes a layer of oil deposited directly on the outer surfaces of the metal coatings.

A metal sheet is provided. The metal sheet includes a substrate having two faces, each face hot dip coated with a metal coating of zinc, aluminum and magnesium. The metal coatings include between 0.1 and 20 wt % of aluminum and 0.1 and 10 wt % of magnesium. Layers of magnesium oxide or magnesium hydroxide are formed on outer surfaces of the metal coatings. The layers are altered by applying an acid solution on the outer surfaces of the metal coatings or by applying mechanical forces using a roller leveler, a brushing device, or a shot-blasting device on the outer surfaces of the metal coatings. The metal sheet also includes a layer of oil deposited directly on the outer surfaces of the metal coatings.

A sheet includes a steel substrate; a coating covering at least one face of the steel substrate, the coating comprising zinc, magnesium and aluminum; and a zinc hydroxysulfate/zinc sulfate-based temporary protection layer applied over the coating, the temporary protection layer having a sulfur content greater than or equal to 0.5 mg/m.sup.2 and less than or equal to 30 mg/m.sup.2.

A sheet includes a steel substrate; a coating covering at least one face of the steel substrate, the coating comprising zinc, magnesium and aluminum; and a zinc hydroxysulfate/zinc sulfate-based temporary protection layer applied over the coating, the temporary protection layer having a sulfur content greater than or equal to 0.5 mg/m.sup.2 and less than or equal to 30 mg/m.sup.2.

The invention relates to a method for producing a silane-modified silicate. In order to obtain optimal corrosion protection properties, a silane compound according to the invention is at least partially hydrolyzed and/or condensed in the presence of a silicate compound at a pH value greater than or equal to 8 and then a pH value less than or equal to 7 is set by adding acid. The invention further relates to an aqueous acidic passivation composition for metal substrate coated with the passivation composition.

The invention relates to a method for producing a silane-modified silicate. In order to obtain optimal corrosion protection properties, a silane compound according to the invention is at least partially hydrolyzed and/or condensed in the presence of a silicate compound at a pH value greater than or equal to 8 and then a pH value less than or equal to 7 is set by adding acid. The invention further relates to an aqueous acidic passivation composition for metal substrate coated with the passivation composition.

A steel substrate is provided, coated on at least one of its faces with a metallic coating based on zinc or its alloys wherein the metallic coating is itself coated with a zincsulphate-based layer including at least one of the compounds selected from among zincsulphate monohydrate, zincsulphate tetrahydrate and zincsulphate heptahydrate, wherein the zincsulphate-based layer has neither zinc hydroxysulphate nor free water molecules nor free hydroxyl groups, the surface density of sulphur in the zincsulphate-based layer being greater than or equal to 0.5 mg/m.sup.2. A corresponding treatment method is also provided.

A steel substrate is provided, coated on at least one of its faces with a metallic coating based on zinc or its alloys wherein the metallic coating is itself coated with a zincsulphate-based layer including at least one of the compounds selected from among zincsulphate monohydrate, zincsulphate tetrahydrate and zincsulphate heptahydrate, wherein the zincsulphate-based layer has neither zinc hydroxysulphate nor free water molecules nor free hydroxyl groups, the surface density of sulphur in the zincsulphate-based layer being greater than or equal to 0.5 mg/m.sup.2. A corresponding treatment method is also provided.