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: 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: 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: 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 porcelain enameled steel sheet comprises an aluminum/zinc alloy-plated steel sheet and a porcelain enamel coating layer as the upper most layer of the steel sheet, wherein an interstitial layer having good adhesion to the plating layer and the enamel coating layer is sandwiched between these two layers. The intermediate layer is preferably a member selected from the group consisting of: (1) the surface layer on the aluminum/zinc alloy-plating layer, whose aluminum content is not less than 96% by weight; (2) the surface layer on the aluminum-zinc alloy-plating layer, which comprises aluminum, nickel and not more than 1% by weight of zinc; (3) a coating layer comprising at least one member selected from the group consisting of Ni, Co, Mo, Mn, Ni--P, Ni--Co--P and Co--P; (4) a chromate layer; and (5) a coating layer comprising at least one member selected from the group consisting of zinc phosphate, manganese phosphate and aluminum phosphate.

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: An organic composite coated steel sheet having excellent chromate dissolution resistance, wet adhesion, and corrosion resistance before and after working. The steel sheet comprises a chromate-silica film on at least one face of a zinc or zinc base alloy plated steel sheet, the silica-added chromate film having about 5 to 500 mg/m.sup.2 in terms of metal Cr content and being formed from a chromate solution containing about 25 to 70 wt % of Cr.sup.+6 based upon total Cr content. A resin coating film is adhered to the chromate-silica film and is formed from an aqueous paint. The aqueous paint includes an aqueous anionic resin and/or an aqueous nonionic resin, a reducing agent, and a water-dispersed silica. The resin coating film is deposited in a dry weight amount of about 0.1 to 3 g/m.sup.2.

Abstract: The improved organic composite coated steel plate includes a zinc or zinc alloy plated steel plate as a substrate that has on its surface a chromate film the Cr.sup.6+ content of which is no more than 70% of the total Cr content and which is deposited in an amount of 5-500 mg/m.sup.2 in terms of metallic chromium, the chromate film being overlaid with a resin layer that is deposited in an amount of 0.1-3 g/m.sup.2 on a dry weight basis and which is formed primarily of water-dispersed silica and one organic resin member as selected from the group consisting of an anionic aqueous resin, a nonionic aqueous resin and an anionic aqueous urethane resin. This steel plate is adapted for not contaminating the environment of the earth in the process of its manufacture.

Abstract: There is provided an ultra-thin and high strength three-piece can-making plated steel sheet which is excellent in weldability and flange forming processibility containing C .ltoreq. about 0.004 wt %, Si.ltoreq. about 0.03 wt %, Mn: about 0.05-0.6 wt %, P.ltoreq. about 0.02 wt %, S.ltoreq. about 0.02 wt %, N.ltoreq. about 0.01 wt % Al: about 0.005-0.1 wt %, Nb: about 0.001-0.1 wt % and the balance of inevitable impurities. The steel sheet has a maximum recrystallization grain size of 30 .mu.m or less and a ratio of area of 50% or more which is occupied by recrystallization grains of about 5-25 .mu.m.

Abstract: A raw plated steel sheet for can comprises recrystallized particles containing approximately C<0,004%, Si<0.03%, Mn:0.05-0.6%, P<0.02%, S<0.02%, N<0.01%, Al:0.005-0.1%, Nb:0,001-0.1%, B:0.0001-0.005% in weight. The maximum diameter of a particle is less than about 30 .mu.m, and an area ratio of particles ranging about 5-25 .mu.m being more than about 50%. Such a steel sheet has excellent processing characteristics and good uniformity in product quality.

Abstract: A surface-treated steel strip adapted for electric resistance welding is 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, wherein the electrolytic chromate treatment is carried out in a bath which contains an amount of a chromate compound to give 10 to 100 g/l of CrO.sub.3 and has a weight ratio of H.sub.2 SO.sub.4 /CrO.sub.3 in the range between 3/1000 and 1/100.