Abstract: A coated steel sheet composed of a steel sheet and at least two types of coating layers formed thereon is provided with an electrodeposition painting having a superior appearance. The coated steel sheet has an arithmetic mean roughness Ra, which is defined by JIS B 0601-1994, of from about 0.7 to about 1.5 ?m and a peak per inch PPI of from about 180 to about 250.

Abstract: The tin-plated steel sheet includes a base steel sheet; a tin plating layer coating approximately more than 97.0% of the base steel sheet; and a chemical conversion coating having approximately 0.5 to 100 mg/m2 phosphorus and approximately 0.1 to 250 mg/m2 silicon formed on the tin plating layer and an unplated region corresponding to approximately less than 3.0%. The tin-plated steel sheet does not contain chromium which is harmful to the environment but has superior overcoat adhesion property, discoloration resistance, and rust resistance.

Abstract: A coated steel sheet composed of a steel sheet and at least two types of coating layers formed thereon is provided with an electrodeposition painting having a superior appearance. The coated steel sheet has an arithmetic mean roughness Ra, which is defined by JIS B 0601-1994, of from about 0.7 to about 1.5 &mgr;m and a peak per inch PPI of from about 180 to about 250.

Abstract: A surface treated tin-plated steel sheet which has an alloy layer formed on the surface of a steel sheet, a tin plating layer being formed on said alloy layer with a remaining exposed portion of the alloy layer having an area of 30% or more of that of the alloy layer and, formed on said tin plating layer and said exposed portion of the alloy layer, a coating film containing P and Si in an amount of 0.5 to 100 mg/m2 and 0.1 to 250 mg/m2, respectively; and a chemical treatment solution for use in preparing the steel sheet which comprises a phosphate ion, a tin ion and a silane coupling agent and has a pH of 1.5 to 5.5. The surface treated tin-plated steel sheet is free from chromium which causes problems from an environmental view point, and also is excellent in adhesion with a paint, corrosion resistance after being coated, rust resistance, and formability.

Abstract: A surface treated tin-plated steel sheet which has (1) an alloy layer formed on the surface of a steel sheet, (2) a tin plating layer being formed on said alloy layer with a remaining exposed portion of the alloy layer having an area of 30% or more of that of said alloy layer and, formed on said tin plating layer and said exposed portion of the alloy layer, (3) a coating film containing P and Si in an amount of 0.5 to 100 mg/m2 and 0.1 to 250 mg/m2, respectively: and a chemical treatment solution for use in preparing the steel sheet which comprises a phosphate ion, a tin ion and a silane coupling agent and has a pH of 1.5 to 5.5. The surface treated tin-plated steel sheet is free from chromium which causes problems from an environmental view point, and also is excellent in adhesion with a paint, corrosion resistance after being coated, rust resistance, and formability.

Abstract: The coated steel sheet includes a zinc phosphate coating containing Mg on a surface of a galvanized steel sheet, and an orthophosphoric acid ester-containing coating on a surface of the zinc phosphate coating. The coated steel sheet has no coating fall-off even during a chemical conversion treatment step of an automobile producing line and has excellent perforative corrosion resistance either with no-painting or after electrodeposition painting, chemical conversion treatability and press formability.

Abstract: The coated steel sheet is a zinc-based plated steel sheet which has a zinc phosphate-based coating containing magnesium thereon and a silicone resin coating containing a functional group which reacts with an organic substance on the surface of the zinc phosphate-based coating. The coated steel sheet has superior perforative corrosion resistance, paint adhesion, electrodesposition paintability, press formability, and weldability without using chromium and therefore is useful as an anti-corrosive steel sheet for automobile bodies.

Abstract: The tin-plated steel sheet includes a base steel sheet; a tin plating layer coating approximately more than 97.0% of the base steel sheet; and a chemical conversion coating having approximately 0.5 to 100 mg/m2 phosphorus and approximately 0.1 to 250 mg/m2 silicon formed on the tin plating layer and an unplated region corresponding to approximately less than 3.0%. The tin-plated steel sheet does not contain chromium which is harmful to the environment but has superior overcoat adhesion property, discoloration resistance, and rust resistance.

Abstract: A galvanized steel sheet includes a galvanized coating layer having a coating weight of from about 20 to about 60 g/m2 formed on at least one surface of the steel sheet, and a zinc phosphate coating layer having a coating weight of from about 0.5 to about 3.0 g/m2 formed on the galvanized coating layer. The zinc phosphate coating layer contains from about 0.5 to about 10.0 percent by weight of magnesium, from about 0.1 to about 2.0 percent by weight of nickel, and from about 0.5 to about 8.0 percent by weight of manganese. However, the manganese content and the nickel content satisfy the following relationship: [Ni]×7.6−10.9≦[Mn]≦[Ni]×11.4 wherein [Mn] represents the manganese content, in percent by weight, and [Ni] represents the nickel content, in percent by weight. This steel sheet exhibits superior perforative corrosion resistance.

Abstract: The invention provides a material coated with an organic film which exhibits excellent corrosion resistance and lacquer adhesion. The invention includes an electroconductive substrate coated with an electrolytically polymerized coating film containing chromium. Particularly, a zinc-type plated steel sheet coated with an electrolytically polymerized coating film containing chromium in accordance with the invention is well suited for application in vehicle bodies. The invention further provides a method of making a material coated with an organic film which involves forming organic coating material containing chromium on an electroconductive substrate acting as an electrode by electrolytically polymerizing an organic monomer in an electrolyte solution containing chromium. The method provides a monolithic composite structure comprising chromium compounds and an organic coating film, and avoid the problems associated with passivation after chromium plating of steel.

Abstract: A Zn or part-Zn plated steel sheet has an MgO coating free of metallic Mg thereon which increases corrosion resistance and plating adherence. The MgO coating is formed by coating according to the sol-gel method or by dipping or treating by cathodic electrolysis a Zn or part-Zn plated steel sheet in a molten salt bath mainly containing a magnesium salt.

Abstract: An organic film-coated plated steel sheet is disclosed which includes a base steel sheet, a zinc-base plated layer disposed thereon, and an organic film layer formed by cathodic polymerization of one or more monomers and superposed as an outermost layer on the zinc-base plated layer. The steel is excellent in corrosion resistance, weldability, electrodeposition paintability or paint adhesion and, thus, is suitable as a rust-proof steel sheet particularly for use in automobile bodies. Also disclosed is a process for producing that steel with less production equipment and reduced cost.

Abstract: The present invention relates to an electrolytic zinc-nickel alloy plating solution, which comprises a plating solution containing zinc chloride, nickel chloride, and potassium chloride; polyethylene glycol having a molecular weight of 400-800 as a nonionic surfactant in an amount of 0.01-1.0 gram/liter; and at least one compound selected from the group consisting of nicotinic acid, urea, thiourea, nicotinamide, thioglycolic acid and sodium thiosulfate as a compound having a lone pair of electrons in an amount of 0.001-1.0 gram/liter. When the plating solution of the present invention is used, needle-shaped stain is not caused on a plated surface and the edge of a plated steel sheet need not be trimmed because a less amount of burning is caused thereto.

Abstract: A process for the manufacture of tinplates comprising electroplating a substrate in a fused-chloride tin plating bath at a temperature of about 150.degree. to 350.degree. C., a current density of about 100 to 500 A/dm.sup.2 in an atmosphere of a non-oxidizing gas. This process may be converted to a process for the manufacture of reflow type tinplates by only changing the bath temperature, and vice versa. For the manufacture of no-reflow type tinplates, the bath is kept at 150.degree. to 232.degree. C., while for the manufacture of reflow type tinplates, the bath is kept at 233.degree. to 350.degree. C. In these cases, the bath includes SnCl.sub.2 and at least one member selected from the group consisting of KCl, NaCl, LiCl and AlCl.sub.3, and may preferably be operated while flowing the bath at a flow rate of about 0.1 m/sec higher.

Abstract: A plated steel sheet is produced by an electroplating in a plating bath of about 350.degree. to 500.degree. C. containing a chloride of Zn, a chloride of Mg and one, two or more of chlorides of Na, K and Li, with a plating current density ranging between about 20 and 350 A/dm.sup.2.The Zn-Mg alloy plated steel sheet superior both in plating adhesion and corrosion resistance has a plating layer formed on at least one surface thereof in an amount of about 10 to 60 g/m.sup.2, and by electroplating in a bath of a fused salts, the plating layer containing about 1 to 35 wt % of Mg, about 0.5 to 25 wt % of mean value of Fe and the balance substantially Zn and incidental inclusions. The Fe content in the plating layer has such a gradient that its concentration is greatest at the interface between the plating layer and the steel sheet and progressively decreases towards the surface of the plating layer opposite to the steel sheet where the Fe content is substantially zero.

Abstract: Surface-treated steel strips suitable for electric resistance welding are prepared by forming a first layer of iron-nickel alloy on a steel strip, said first layer having a weight ratio of Ni/(Fe+Ni) in the range between 0.02 and 0.50 and a thickness of 10 to 5,000 angstroms, forming a second layer of tin or iron-tin-nickel alloy on said first layer by tin plating to a coating weight of 0.1 to 1 g/m.sup.2 of tin and optionally, causing the tin to reflow, and forming a third layer on said second layer by effecting an electrolytic chromate treatment, said third layer consisting essentially of metallic chromium and hydrated chromium oxide in a total amount of 5 to 20 mg/m.sup.2 calculated as elemental chromium. More preferably, the electrolytic chromate treatment is controlled such that at least 2 mg/m.sup.2 of metallic chromium is present in the third layer.

Abstract: Surface-treated steel strips suitable for electric resistance welding are prepared by forming a first layer of iron-nickel alloy on a steel strip, this first layer having a weight ratio of Ni/(Fe+Ni) in the range between 0.02 and 0.50 and a thickness of 10 to 5,000 angstroms, forming a second layer of tin or iron-tin-nickel alloy on the first layer by tin plating to a coating weight of 0.1 to 1 g/m.sup.2 of tin and optionally, causing the tin to reflow. A third layer is formed on the second layer by effecting an electrolytic chromate treatment, this third layer consisting essentially of metallic chromium and hydrated chromium oxide in a total amount of 5 to 20 mg/m.sup.2 calculated as elemental chromium. Preferably, the electrolytic chromate treatment is controlled so that at least 2 mg/m.sup.2 of metallic chromium is present in the third layer.