A method for electrolytically passivating an outermost chromium or chromium alloy layer to increase corrosion resistance thereof, including steps of (i) providing a substrate comprising said outermost chromium or chromium alloy layer, (ii) providing or manufacturing an aqueous, acidic passivation solution comprising trivalent chromium ions, phosphate ions, one or more organic acid residue anion, (iii) contacting the substrate with the passivation solution and passing an electrical current between the substrate as a cathode and an anode in the passivation solution such that a passivation layer is deposited onto the outermost layer,
wherein
the trivalent chromium ions are obtained by chemically reducing hexavalent chromium in presence of phosphoric acid and at least one reducing agent,
with the proviso that during or after the chemical reducing the one or more than one organic acid residue anion is present for the first time in the passivation solution.

To produce a chromium-containing multilayer coating on an object, alternate layers of nickel phosphorus alloy and trivalent chromium are deposited on the object until a desired thickness of coating has been reached. The coated object is then subjected to one or more heat treatments to improve the mechanical and physical properties of the coating and to produce multiphase layers comprising layers containing crystalline Ni and crystalline Ni.sub.3P and layers containing crystalline Cr.

[Problem] There is provided a colored stainless-steel product having excellent viewing-angle color tone discrimination and excellent corrosion resistance, in which a chemical coloration technique having sophisticated industrial color tone is used.

[Solution] The product is a chemically-colored stainless-steel product having an uneven surface formed by a grinding treatment, wherein the 60-degree specular gloss [Gs (60 degrees)] of the uneven surface is 5 to 50. The grinding treatment is performed by a single sandblasting treatment or a combination of the sandblasting treatment and an electrolytic polishing treatment. The sandblasting treatment is performed with a projection material configured from inorganic particles having a Mohs' hardness of at least six. A manufacturing method includes a sandblasting treatment step, an electrolytic polishing treatment step, a coloration treatment step for dipping stainless steel in a coloration treatment solution including a mixed solution of a chromic acid and a sulfuric acid to generate a colored film thereon, and a curing treatment step for dipping the coloration-treated stainless steel in a curing treatment solution including a mixed solution of a chromic acid and a phosphoric acid to cure the colored film.

[Problem] There is provided a colored stainless-steel product having excellent viewing-angle color tone discrimination and excellent corrosion resistance, in which a chemical coloration technique having sophisticated industrial color tone is used.

[Solution] The product is a chemically-colored stainless-steel product having an uneven surface formed by a grinding treatment, wherein the 60-degree specular gloss [Gs (60 degrees)] of the uneven surface is 5 to 50. The grinding treatment is performed by a single sandblasting treatment or a combination of the sandblasting treatment and an electrolytic polishing treatment. The sandblasting treatment is performed with a projection material configured from inorganic particles having a Mohs' hardness of at least six. A manufacturing method includes a sandblasting treatment step, an electrolytic polishing treatment step, a coloration treatment step for dipping stainless steel in a coloration treatment solution including a mixed solution of a chromic acid and a sulfuric acid to generate a colored film thereon, and a curing treatment step for dipping the coloration-treated stainless steel in a curing treatment solution including a mixed solution of a chromic acid and a phosphoric acid to cure the colored film.

The present disclosure generally relates to a sealed metal laminate structure comprising: a metal layer having a first surface and an opposite second surface; a first enamel layer laminated on the first surface of the metal layer, except at an exposed metal protrusion at a perimeter edge of the sealed metal laminate structure; a second enamel layer laminated on the second surface of the metal layer, except at the exposed metal protrusion at the perimeter edge of the sealed laminate structure; and a phosphate sealer deposited on the exposed metal protrusion of the sealed metal laminate structure. The present disclosure also relates to a metal laminate structure without a phosphate sealer. In addition, systems and methods for treating workpieces, including metal laminate structures, are discussed.

The present disclosure generally relates to a sealed metal laminate structure comprising: a metal layer having a first surface and an opposite second surface; a first enamel layer laminated on the first surface of the metal layer, except at an exposed metal protrusion at a perimeter edge of the sealed metal laminate structure; a second enamel layer laminated on the second surface of the metal layer, except at the exposed metal protrusion at the perimeter edge of the sealed laminate structure; and a phosphate sealer deposited on the exposed metal protrusion of the sealed metal laminate structure. The present disclosure also relates to a metal laminate structure without a phosphate sealer. In addition, systems and methods for treating workpieces, including metal laminate structures, are discussed.

The present invention provides a surface treated metal material for burn-in test socket wherein contact resistance between the contact of the socket and other metal materials being inserted is excellently suppressed when used for the contact for burn-in test socket.

The surface treated metal material for burn-in test socket, comprising a base material, a lower layer being constituted with one or two or more selected from the constituent element group A, the constituent element group A consisting of Ni, Cr, Mn, Fe, Co and Cu, an intermediate layer formed on the lower layer, the intermediate layer being constituted with one or two or more selected from the constituent element group A and one or two selected from a constituent element group B, the constituent element group B consisting of Sn and In, and an upper layer formed on the intermediate layer, the upper layer being constituted with one or two selected from the constituent element group B and one or two or more selected from a constituent element group C, the constituent element group C consisting of Ag, Au, Pt, Pd, Ru, Rh, Os and Ir, wherein the thickness of the lower layer is 0.05 m or more and less than 5.00 m, the thickness of the intermediate layer is 0.01 m or more and less than 0.40 m, and the thickness of the upper layer is 0.02 m or more and less than 1.00 m.

Provided is a chemical treatment steel sheet including a steel sheet; a composite coated layer which is formed on at least one surface of the steel sheet, and contains 2 to 200 mg/m.sup.2 of Ni in terms of an amount of metal Ni and 0.1 to 10 g/m.sup.2 of Sn in terms of an amount of metal Sn, and in which an island-shaped Sn coated layer is formed on an FeNiSn alloy layer; and a chemical treatment layer that is formed on the composite coated layer, and contains a 0.01 to 0.1 mg/m.sup.2 of Zr compounds in terms of an amount of metal Zr and 0.01 to 5 mg/m.sup.2 of phosphate compounds in terms of an amount of P.

Provided is a chemical treatment steel sheet including a steel sheet; a composite coated layer which is formed on at least one surface of the steel sheet, and contains 2 to 200 mg/m.sup.2 of Ni in terms of an amount of metal Ni and 0.1 to 10 g/m.sup.2 of Sn in terms of an amount of metal Sn, and in which an island-shaped Sn coated layer is formed on an FeNiSn alloy layer; and a chemical treatment layer that is formed on the composite coated layer, and contains a 0.01 to 0.1 mg/m.sup.2 of Zr compounds in terms of an amount of metal Zr and 0.01 to 5 mg/m.sup.2 of phosphate compounds in terms of an amount of P.

Disclosed is a surface anti-corrosion treatment method for stainless steel. The method comprises the following steps: (1) performing chemical de-oiling and alkaline corrosion treatments on the surface of stainless steel by using a sodium hydroxide solution and a solution containing an alkaline corrosion active agent, and then washing with water; (2) performing, by using an oxidation solution, an oxidation treatment on the surface of the stainless steel treated in step (1), and then washing with water; (3) using the surface of the stainless steel treated in step (2) as a cathode and soaking same in an electrolyte for electrolysis, and then washing with water; and (4) placing the surface of the stainless steel treated in step (3) at a temperature of 50 C.-60 C. under a humidity of 60%-70%, and performing a hardening treatment. Also disclosed are the use of the treatment method in the treatment of a stainless steel part and a stainless steel part obtained after the treatment by means of the treatment method.