A steel sheet for can making and methods for manufacturing the same. The steel sheet includes, in order from a steel sheet side, an iron-nickel diffusion layer, a metallic chromium layer, and a chromium oxide layer. The iron-nickel diffusion layer has a nickel coating weight of 50 mg/m.sup.2 to 500 mg/m.sup.2 per surface of the steel sheet and a thickness of 0.060 ?m to 0.500 ?m per surface of the steel sheet. The metallic chromium layer includes a flat-like metallic chromium sublayer and a granular metallic chromium sublayer placed on a surface of the flat-like metallic chromium sublayer. The total chromium coating weight of both sublayers per surface of the steel sheet is 60 mg/m.sup.2 to 200 mg/m.sup.2. The chromium oxide layer has a chromium coating weight 3 mg/m.sup.2 to 10 mg/m.sup.2 per surface of the steel sheet in terms of metallic chromium.

The invention relates to a method and system for treating flue gases comprising generating a superimposed DC time-varying pulsed wave by superimposing a direct current on a low frequency time-varying pulsating electromagnetic wave signal, providing a treatment medium comprising water, using the superimposed DC pulsed wave to treat the treatment water medium, negatively charging the treated treatment water medium, and passing the negatively charged treated treatment water medium into a chamber containing flue gas such that the negatively charged treated treatment water affects the gas components of the flue gas and converts the gas components respectively to one or more of sulphates, nitrogen, oxygen, bicarbonates, carbonates and carbon, which can then be removed with used treatment water or exhaust gases. In particular, the invention relates to methods and systems for applying a superimposed time-varying frequency electromagnetic wave comprising both AC and DC components in a pulsating manner to enable the removal of pollutant gases from flue gases.

The invention relates to a method and system for treating flue gases comprising generating a superimposed DC time-varying pulsed wave by superimposing a direct current on a low frequency time-varying pulsating electromagnetic wave signal, providing a treatment medium comprising water, using the superimposed DC pulsed wave to treat the treatment water medium, negatively charging the treated treatment water medium, and passing the negatively charged treated treatment water medium into a chamber containing flue gas such that the negatively charged treated treatment water affects the gas components of the flue gas and converts the gas components respectively to one or more of sulphates, nitrogen, oxygen, bicarbonates, carbonates and carbon, which can then be removed with used treatment water or exhaust gases. In particular, the invention relates to methods and systems for applying a superimposed time-varying frequency electromagnetic wave comprising both AC and DC components in a pulsating manner to enable the removal of pollutant gases from flue gases.

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.

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.

An electroplating bath is configured to precipitate a black trivalent chromium layer onto an object to be plated. The electroplating bath includes a nanodiamond and a thiocyanate ion as color enhancers.

There is provided a steel sheet for cans including, on a surface of a steel sheet, a chromium metal layer and a hydrated chromium oxide layer stacked in this order from the steel sheet side. The chromium metal layer has a coating weight of 50 to 200 mg/m.sup.2, and the hydrated chromium oxide layer has a coating weight of 3 to 30 mg/m.sup.2 in terms of chromium amount. The chromium metal layer includes a base portion of flat plate shape and granular protrusions provided on the base portion. At least 20% of the granular protrusions has a circularity C of 0.85 or less. The circularity C is expressed by C=4?A/U.sup.2, when the outer perimeter of a projection image of a granular protrusion is represented by U, and the area thereof is represented by A.

There is provided a steel sheet for cans including, on a surface of a steel sheet, a chromium metal layer and a hydrated chromium oxide layer stacked in this order from the steel sheet side. The chromium metal layer has a coating weight of 50 to 200 mg/m.sup.2, and the hydrated chromium oxide layer has a coating weight of 3 to 30 mg/m.sup.2 in terms of chromium amount. The chromium metal layer includes a base portion of flat plate shape and granular protrusions provided on the base portion. At least 20% of the granular protrusions has a circularity C of 0.85 or less. The circularity C is expressed by C=4?A/U.sup.2, when the outer perimeter of a projection image of a granular protrusion is represented by U, and the area thereof is represented by A.

[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.