Nisshin Steel Co., Ltd.

Nippon Paint Surf Chemicals Co., Ltd.

Nippon Steel Nisshin Co., Ltd.

Hirofumi Taketsu

Masaya Yamamoto

Masanori Matsuno

Tadashi Nakano

Shinya Furukawa

Koichiro Ueda

Atsuo Shimizu

Shigeyasu Morikawa

Keiji Izumi

Yukio Uchida

Mitsuo Asabuki

Yusuke Miura

Shuntaro Sudo

Yasumi Ariyoshi

Shintaro Nakamura

Kouichiro Ueda

A hot-dip Zn alloy plating layer is formed on a surface of a base steel sheet by immersing the base steel sheet in a hot-dip Zn alloy plating bath containing Al and Mg. An aqueous solution containing a polyatomic ion including Siand/or a polyatomic ion including Cris then contacted with a surface of the hot-dip Zn alloy plating layer. All of the aqueous solution coating the surface of the hot-dip Zn alloy plating layer is removed with a squeeze roller. The aqueous solution contains the polyatomic ion in a concentration of 0.01 g/L or more in terms of atom of Si and Cr. A surface temperature of the hot-dip Zn alloy plating layer when the aqueous solution is contacted with the surface of the hot-dip Zn alloy plating layer is 100&#xb0; C. or above and equal to or less than a solidifying point of the plating layer.

Method for producing hot-dip Zn alloy-plated steel sheet

A hot-dip Zn alloy plating layer is formed on a surface of a base steel sheet by immersing the base steel sheet in a hot-dip Zn alloy plating bath containing Al and Mg. An aqueous solution containing one of or two or more of polyatomic ions selected from the group consisting of a polyatomic ion including V, a polyatomic ion including Si, and a polyatomic ion including Cris then contacted with a surface of the hot-dip Zn alloy plating layer. The aqueous solution contains the polyatomic ion in a concentration of 0.01 g/L or more in terms of one of or two or more of atoms selected from the group consisting of V, Si, and Cr.

Provided is a method for obtaining a chemical conversion coating-treated zinc-aluminum-magnesium alloy-plated steel sheet having extremely excellent in corrosion resistance and adhesiveness to a resin coating film. The method is for treating the surface of a zinc-aluminum-magnesium alloy-plated steel sheet with a metal surface treatment agent, in which the metal surface treatment agent contains a compound (A) having a zirconyl ([Zr&#x2550;O]) structure, a vanadium compound (B), a titanium fluorocomplex compound (C), an organic phosphorus compound (Da) containing a phosphoric acid group and/or a phosphonic acid group, an inorganic phosphorus compound (Db), a specific aqueous acrylic resin (E), and an oxazoline group-containing polymer (F) as a curing agent, each in a predetermined amount, and the pH of the metal surface treatment agent is 3 to 6.

Method for treating surface of zinc-aluminum-magnesium alloy-plated steel sheet

A method of producing a hot-dip Zn alloy-plated steel sheet includes: dipping a base steel sheet in a hot-dip Zn alloy plating bath to form a hot-dip Zn alloy plating layer on a surface of the base steel sheet; and contacting an aqueous solution containing a water-soluble corrosion inhibitor with a surface of the hot-dip Zn alloy plating layer to cool the base steel sheet and the hot-dip Zn alloy plating layer having a raised temperature through formation of the hot-dip Zn alloy plating layer. A temperature of the surface of the hot-dip Zn alloy plating layer when the aqueous solution is to be contacted with the surface of the hot-dip Zn alloy plating layer is equal to or more than 100&#xb0; C. and equal to or less than a solidifying point of the plating layer. The aqueous solution containing the water-soluble corrosion inhibitor satisfies the Equation [{(Z&#x2212;Z)/Z}100&#x2265;20].

Method of producing hot-dip Zn alloy-plated steel sheet

The present disclosure relates to a chemically treated zinc-based plated steel sheet that is superior in weather resistance, water resistance, blackening resistance and film adhesion. A chemical conversion film having a thickness 0.5-10 &#x3bc;m is formed by coating and drying a chemical treatment solution on a surface of an aluminum-containing zinc-based alloy plated steel sheet. The chemical treatment solution contains a fluororesin containing 0.05-5% by weight of a hydrophilic functional group selected from the group consisting of a carboxyl group and a sulfonic acid group and 7-20% by weight of a fluorine atom, the fluororesin in which a number-average molecular weight is 1,000-2,000,000, and an oxoate, a fluoride, a hydroxide, an organic salt, a carbonate or a peroxygenated salt of a group 4A metal.

Chemical conversion coated plated steel sheet and method for producing same

A black-plated steel sheet has a Zn-plating layer containing molten Al and Mg, containing Al in the amount of 1.0-22.0 mass %, containing Mg in the amount of 1.3-10.0 mass %, and having a Zn black oxide distributed in a lamella pattern in the plating layer. The Zn black oxide is a Zn oxide derived from a ZnMg phase. The brightness of the surface of the Zn-plating layer containing the molten Al and Mg has an L* value of 60 or less.

Black-plated steel sheet

The present invention pertains to a method for producing a black-plated steel sheet capable of being blackened in a short amount of time, and exhibiting an excellent ability to maintain a black appearance after processing. As an original sheet, the sheet used is a Zn-plating steel sheet which contains molten Al and Mg and has a Zn-plating layer containing molten Al and Mg, containing Al in the amount of 1.0-22.0 mass %, inclusive, and containing Mg in the amount of 1.5-10.0 mass %, inclusive. The plating layer is blackened by causing the molten-plating steel sheet to contact water vapor inside a tightly sealed container. When doing so, the concentration of oxygen inside the tightly sealed container is 13% or less.

Method for producing black-plated steel sheet, and method for producing molded article of black-plated steel sheet

The present invention pertains to a method for producing a black-plated steel sheet capable of being blackened in a short amount of time, and exhibiting an excellent ability to maintain a black appearance after processing. As an original sheet, the sheet used is a Zn-plating steel sheet which contains molten Al and Mg and has a Zn-plating layer containing molten Al and Mg, containing Al in the amount of 0.1-22.0 mass %, inclusive, and containing Mg in the amount of 0.1-1.5 mass %, inclusive. The plating layer is blackened by causing the molten-plating steel sheet to contact water vapor inside a tightly sealed container. When doing so, the concentration of oxygen inside the tightly sealed container is 13% or less.

Disclosed is a chemical conversion coated Al-plated steel sheet which has excellent weather resistance, water resistance and coating film adhesion. Specifically, a chemical conversion coating liquid is applied over and dried on the surface of an Al alloy-plated steel sheet, thereby forming a chemical conversion coating film that has a film thickness of 0.5-10 &#x3bc;m. The chemical conversion coating liquid contains: a fluorine-containing olefin resin, which contains 7-20% by mass of F atoms and 0.05-5% by mass of hydrophilic functional groups that are selected from among a carboxyl group, a sulfonic acid group and salts of carboxyl group and sulfonic acid group and has a number average molecular weight within the range of 1,000-2,000,000; and an oxygen acid salt, fluoride, hydroxide, organic acid salt, carbonate or peroxygenated salt of a group 4A metal.

A chemically processed steel sheet comprises a steel base coated with an Al&#x2014;Si alloy plating layer, whose Si content is preferably adjusted to 5&#x2013;13 mass % as a whole and to 7&#x2013;80 mass % at a surface, and a converted layer generated on the surface of the plating layer. The converted layer contains both soluble and scarcely-soluble compounds. The soluble compound, such as a manganese oxide or hydroxide, or a valve metal fluoride, is once dissolved into water in an atmosphere and then re-precipitated as scarcely-soluble compounds at defective parts of the converted layer. The scarcely-soluble compounds act as a barrier for corrosion prevention of a base steel. Due to the re-precipitation, i.e., self-repairing faculty, excellent corrosion resistance of the converted layer is still maintained even after defects are introduced therein during plastic deformation of the steel sheet.

Chemically processed steel sheet excellent in corrosion resistance

An Al-coated steel sheet is improved in anti-scratching property during press-working and corrosion-resistance to a stored fuel by direct formation of an alkali-soluble resin film on an Al-coated steel sheet. An alkali-soluble resin, which can be dissolved in an alkali liquid of pH 9.0 or higher, is preferably urethane or acrylic resin with an acid value of 40-90 having a carboxyl group in its molecule. Alkali metal may be substituted for 1-50% hydrogen atom of the carboxyl group. A powdery synthetic resin at a ratio of 1-25 mass % and/or powdery silica at a ratio of 1-30 mass % may be dispersed in the resin film. The resin film is preferably of 0.2-5.0 &#x3bc;m in thickness. After the Al-coated steel sheet is painted with the resin, it is shaped to upper and lower halves of a fuel tank and washed with an alkali to dissolve off the resin film. The upper and lower halves are welded together and coated with a paint at their external surfaces to fabricate a fuel tank.

Fuel tank made from aluminum coated steel sheet

A chemically processed steel sheet comprising a steel base coated with an Al&mdash;Si alloy plating layer, whose Si content is preferably adjusted to approximately 5-13 mass % as a whole and to approximately 7-80 mass % at a surface, and a converted layer generated on the surface of the plating layer. The converted layer contains both soluble and scarcely-soluble compounds. The soluble compound such as a manganese oxide or hydroxide or a valve metal fluoride is once dissolved to water in an atmosphere and then re-precipitated as scarcely-soluble compounds at defective parts of the converted layer. The scarcely-soluble compounds act as a barrier for corrosion-prevention of a base steel. Due to the re-precipitation, that is self-repairing faculty, excellent corrosion resistance of the converted layer is still maintained even after defects are introduced therein during plastic deformation of the steel sheet.

A new processed steel sheet comprising of a steel base coated with a Zn or its alloy plating layer and a converted layer, which contains both of at least an insoluble or scarcely-soluble metal compound and at least a soluble metal compound. The insoluble or scarcely-soluble compound may be one or more of valve metal oxides or hydroxides, and the soluble compound may be one or more of valve metal fluorides. The converted layer may be also composed of one or more of complex compounds of Mn and Ti. The insoluble or scarcely-soluble compound acts as a barrier for insulation of a steel base from an atmosphere, while the soluble compound exhibits a self-repairing faculty to repair defective parts of the converted layer. Due to the converted layer, the processed steel sheet is remarkably improved in corrosion resistance, without the presence of chromium compounds which would put harmful influences on the environment.

Chemically processed steel sheet improved in corrosion resistance

In a chromating solution comprising a water-soluble chromium compound and a reducing agent and in which hexavalent chromium ions produced by dissolution of the water-soluble chromium compound have been partly reduced with the reducing agent to trivalent chromium ions, an oxycarboxylic acid compound is used as the reducing agent. This chromating solution causes neither gelation nor sedimentation of the solution even when hexavalent chromium ions are reduced to trivalent chromium ions at a reduction percentage of more than 50%. The chromating solution and a chromate film formed on a steel sheet may also contain an organic resin, phosphoric acid or a phosphoric acid compound, or a silica sol.

Growing community of inventors

Sakai, Japan

Hirofumi Taketsu