Abstract: A resin-coated Al—Zn alloy coated steel sheet is excellent in formability, resistance to chromium dissolution, corrosion resistance, alkali resistance, and paintability, and produced by the following method. That is, a silane coupling agent having amino group, chromium ion and at least one alcohol selected from the group consisting of trihydric alcohol and dihydric alcohol having the number of carbon of 2 to 3 are compounded into an acrylic polymer resin emulsion including carboxyl group and glycidyl group, and having an acid value of 10 to 60. A pH of the resultant mixture is adjusted within a range of 7 to 9 to obtain a chromate containing resin composition. The chromate containing resin composition is applied on an Al—Zn alloy coated steel sheet as a substrate, and then dried to obtain a resin film on the substrate. A compounding amount of the silane coupling agent is within a range of 0.5 to 3.0 wt % with respect to a resin solid component of the acrylic polymer resin emulsion.

Abstract: The protection against black and white rust on zinciferous surfaces by a conventional chromating treatment is improved by drying into place on the zinciferous surface before chromating a pre-treatment composition that contains hexavalent chromium ion plus one or more salts of nickel and cobalt, in an amount to produce an add-on of 0.5 to 100 mg/m.sup.2 of metal.

Abstract: An acidic substitutional plating bath for zinciferous surfaces, particularly zinciferous metal-plated steel sheet, with which sludge production and equipment corrosion are inhibited and which has an improved heavy metal ion deposition efficiency is provided by an aqueous composition that has a pH of 2 to 4.5 and that contains 1.5 to 40 g/L of at least one heavy metal ion selected from nickel, iron, and cobalt; 0.5 to 10 g/L of phosphate ions; 1 to 250 g/L of sulfate ion; and 1 to 20 g/L of organic acid.

Abstract: Drying into place a covering of an aqueous solution of nickel and/or cobaltous sulfate and/or phosphate salts on a zinc or zinc alloy surface improves at least one of the blackening resistance and corrosion resistance after subsequent chromating treatment and the corrosion resistance and paint adherence after subsequent chromating treatment and painting.

Abstract: Zinciferous surfaces, particularly those of galvanized steel, may be effectively protected against corrosion, either as treated or after painting, while remaining easy to weld, by contact with an aqueous solution containing chromium in both +6 and +3 valence states, phosphate, a tertiary alcohol or similar oxidation stable, water soluble organic compound as a wetting agent, and a silane coupling agent, followed by drying with a film from the solution still in place on the surface. A thin coating containing 10-200 mg/m.sup.2 of chromium is formed on the surface to provide a protective layer that is also an excellent base for paint.

Abstract: The resistance of chromated zinc surfaced steel objects, particularly plates and sheets, to extraction of hexavalent chromium by alkaline degreasing solutions used on the chromated objects, can be substantially increased by utilizing an aqueous acidic liquid chromating composition containing (A) about 9.6 to about 96 g/L, expressed as its stoichiometric equivalent as chromic acid, of total chromium; (B) about 2 to about 35 g/L of trivalent chromium ions; (C) about 1 to about 128 g/L of phosphate ions; and (D) about 0.3 to about 4 g/L of fluorozirconate ions, with the chromium ratio in the aqueous acidic liquid composition being about 0.41 to about 0.70, the chromic acid/fluorozirconate weight ratio being about 10 to about 40, and the PO.sub.4 /Cr.sup.+3 ratio being greater than about 0.03, greater than or equal to about {(9.2) (the chromium ratio)-4.0}, and less than or equal to about {(9.2) (the chromium ratio)-1.2}. . .

Abstract: The present invention relates to a process for surface treatment for cathodic electrodeposit coating of a zinc-plated or zinc alloy-plated steel sheet comprising coating and drying a protective coating material on said steel sheet chromate-treated beforehand, to form a protective film before subjecting the sheet to the cathodic electrodeposit coating, which comprises coating a protective coating material having as a principal constituent of film-forming organic component a block isocyanate-containing prepolymer containing in one and the same molecule respectively at least one blocked isocyanate group, hydroxyl group, and tertiary amono group and containing 10-100 parts by weight of silica sol relative to 100 parts by weight of said prepolymer, in an amount of 0.3 g-4 g/m.sup.2, and then heat-drying the same.

Abstract: An aqueous solution of a reducing agent is applied to a chromate coated metal surface to reduce the extent to which the chromate coating undergoes dissolution during a subsequent cleaning process.