The coating film-forming composition includes an aromatic compound having an amino group and an aromatic ring in one molecule, and thio compound (sulfur oxoacids having a pKa of 1.9 or less and salts thereof are excluded). pH of the coating film-forming composition is 4 to 10. The thio compound is preferably one that ionized to form anions in a solution, and thiosulfate and thiocyanate are especially preferable. By bringing the coating film-forming composition into contact with the surface of a metal member, a coating film is formed on the surface of the metal member, so that a surface-treated metal member can be obtained.

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.

Provided is a surface treated steel sheet for a fuel tank, the surface treated steel sheet including: a Zn plated layer or a ZnNi alloy plated layer which is formed on at least a surface of the steel sheet to be an inner surface of the fuel tank; and a chromate-free chemical conversion coating layer containing a water-and-oil repellent, the chromate-free chemical conversion coating layer being placed over the Zn plated layer or the ZnNi alloy plated layer on the surface to be the inner surface of the fuel tank. A water contact angle on a surface of the chromate-free chemical conversion coating layer is more than or equal to 70 degrees and an n-hexadecane contact angle on the surface of the chromate-free chemical conversion coating layer is more than or equal to 30 degrees and less than or equal to 70 degrees.

Provided is a surface treated steel sheet for a fuel tank, the surface treated steel sheet including: a Zn plated layer or a ZnNi alloy plated layer which is formed on at least a surface of the steel sheet to be an inner surface of the fuel tank; and a chromate-free chemical conversion coating layer containing a water-and-oil repellent, the chromate-free chemical conversion coating layer being placed over the Zn plated layer or the ZnNi alloy plated layer on the surface to be the inner surface of the fuel tank. A water contact angle on a surface of the chromate-free chemical conversion coating layer is more than or equal to 70 degrees and an n-hexadecane contact angle on the surface of the chromate-free chemical conversion coating layer is more than or equal to 30 degrees and less than or equal to 70 degrees.

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.

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.