Abstract: This invention relates to a composition for the brightening and/or passivating of stainless steel after pickling. The invention is based on the discovery that the presence of organic compounds containing multiple hydroxyl groups with at least 3, but not more than 8 carbon atoms as a further ingredient of passivating and brightening solution significantly increases the desmutting performance of pickled stainless steel surfaces. The compositions of the invention are especially useful for the passivating and brightening of stainless steel grades being alloyed with sulfur. The invention thus further encompasses a passivating and brightening process for pickled stainless steel surfaces wherein the stainless steel is alloyed with at least 0.10 at.-% of sulfur.

Abstract: The present invention relates to the use of an alkaline, aqueous coating composition for coating of zinc or zinc alloy coated steel substrates, comprising one or more alkaline sulfates, and one or more alkaline carbonates, wherein the pH of the composition ranges from 9-12. The present invention also defines a method for the non-reactive coating of zinc or zinc alloy coated steel substrates by use of said compositions and further relates to the application of said method as a surrogate for pre-phosphating of zinc or zinc alloy coated steel substrates in industrial applications.

Abstract: The present invention relates to the use of an alkaline, aqueous coating composition for coating of zinc or zinc alloy coated steel substrates, comprising one or more alkaline sulfates, and one or more alkaline carbonates, wherein the pH of the composition ranges from 9-12. The present invention also defines a method for the non-reactive coating of zinc or zinc alloy coated steel substrates by use of said compositions and further relates to the application of said method as a surrogate for pre-phosphating of zinc or zinc alloy coated steel substrates in industrial applications.

Abstract: The present invention relates to an acidic aqueous solution suitable for the pickling of stainless steel grades that comprises accelerators based on water soluble inorganic compounds comprising at least one nitrogen atom in an oxidation state in the range of ?2 to ??. The present invention further encompasses a process for the pickling of stainless steel that makes use of a pickling solution comprising the above-mentioned accelerators.

Abstract: This invention relates to a composition for the brightening and/or passivating of stainless steel after pickling. The invention is based on the discovery that the presence of organic compounds containing multiple hydroxyl groups with at least 3, but not more than 8 carbon atoms as a further ingredient of passivating and brightening solution significantly increases the desmutting performance of pickled stainless steel surfaces. The compositions of the invention are especially useful for the passivating and brightening of stainless steel grades being alloyed with sulfur. The invention thus further encompasses a passivating and brightening process for pickled stainless steel surfaces wherein the stainless steel is alloyed with at least 0.10 at.-% of sulfur.

Abstract: The present invention relates to an acidic aqueous solution suitable for the pickling of stainless steel grades that comprises accelerators based on water soluble inorganic compounds comprising at least one nitrogen atom in an oxidation state in the range of ?2 to ??. The present invention further encompasses a process for the pickling of stainless steel that makes use of a pickling solution comprising the above-mentioned accelerators.

Abstract: The use of complex fluoride ions of elements of groups 4, 13, or 14 of the periodic table of the chemical elements (preferably selected from complex fluoride ions of the elements B, Si, Ti, and Zr) in concentrations from 30 t 500 millimoles per liter in process solutions for pickling steel or for bleaching and/or passivating pickled surfaces of stainless steel; a process solution for pickling steel or bleaching and/or passivating pickled surfaces of stainless steel comprising: a) one or more strong acids, b) one or more oxidizing agents in the bleaching/passisvating process, c) complex fluoride ions of elements of groups 4, 13 or 14 of the periodic table of the chemical elements in concentrations from 50 to 500 mmoles per liter; replenisher or concentrate containing a combination of active substances thereof; a process for pickling steel or for brightening and/or passivating of pickled surfaces of stainless steel, wherein the surfaces are brought into contact with such a process solution.

Abstract: A process for pickling martensitic or ferritic stainless steel, preferably in the form of wires, tubes or rods, wherein the stainless steel is placed in contact with a pickling solution which has a temperature in the range 15 to 29° C. and contains 50 to 120 g/l of free sulfuric acid, 5 to 40 g/l of free HF and 5 to 40 g/l of Fe(III) ions. Such pickling may be incorporated into a sequential process, wherein the stainless steel is a) subjected to a treatment during which the oxidic coating is applied, preferably sand-blasting or metal-blasting, treatment with a molten salt or treatment with an aqueous permanganate/alkali metal hydroxide solution, b) pickled in accordance with the aforedescribed process, and c) post-treated with a passivating solution.

Abstract: The use of complex fluoride ions of elements of groups 4, 13, or 14 of the periodic table of the chemical elements (preferably selected from complex fluoride ions of the elements B, Si, Ti, and Zr) in concentrations from 30 t 500 millimoles per liter in process solutions for pickling steel or for bleaching and/or passivating pickled surfaces of stainless steel; a process solution for pickling steel or bleaching and/or passivating pickled surfaces of stainless steel comprising: a) one or more strong acids, b) one or more oxidizing agents in the bleaching/passisvating process, c) complex fluoride ions of elements of groups 4, 13 or 14 of the periodic table of the chemical elements in concentrations from 50 to 500 mmoles per liter; replenisher or concentrate containing a combination of active substances thereof; a process for pickling steel or for brightening and/or passivating of pickled surfaces of stainless steel, wherein the surfaces are brought into contact with such a process solution.

Abstract: A process for pickling martensitic or ferritic stainless steel, preferably in the form of wires, tubes or rods, wherein the stainless steel is placed in contact with a pickling solution which has a temperature in the range 15 to 29° C. and contains 50 to 120 g/l of free sulfuric acid, 5 to 40 g/l of free HF and 5 to 40 g/l of Fe(III) ions. Such pickling may be incorporated into a sequential process, wherein the stainless steel is a) subjected to a treatment during which the oxidic coating is applied, preferably sand-blasting or metal-blasting, treatment with a molten salt or treatment with an aqueous permanganate/alkali metal hydroxide solution, b) pickled in accordance with the aforedescribed process, and c) post-treated with a passivating solution.

Abstract: Desludging device for a portion of the total volume of a liquid that contains suspended solids and/or can form sludge, arranged in a tank for the total volume of the liquid in such a way that at least a part of said desludging device including its floor is immersed in the total volume, wherein said desludging device has an inlet opening located above said floor through which a portion of the liquid can enter the desludging device, as well as a discharge device beginning above said floor, in the form of an exit pipe, a channel, an overflow weir or at least an opening in the wall, through which the liquid can be removed from the desludging device, and wherein said floor of the desludging device has at least one outlet opening through which sludge that has settled in said desludging device can be returned to the total volume of the liquid or passed to another settling device for concentrating the sludge. Preferably the settled sludge is recycled to the total volume through a Venturi-type nozzle.

Abstract: A process for electrolytic pickling of stainless steel of the ferritic, martensitic, austenitic and duplex series as well as superaustenitic and superferritic steels, nickel or Ni/Cr-based super alloys, and titanium and its alloys is provided. The process utilizes an electrolytic pickling solution containing H2SO4 in a concentration of from 20 to 140 g/l and Fe3+ ions in a concentration of from 15 to 80 g/l, the Fe2+ ions being present a quantity corresponding to a Fe3+/Fe2+ ratio of >1 and preferably >3.

Abstract: Stainless steel pickling process in which a pickling solution containing HF and Fe3+ ions as essential components is used, and wherein the oxidation to Fe3+ of the Fe2+ formed during the process in order to maintain the Fe3+ concentration to the predetermined value, is electrolytically carried out by submitting the pickling solution as it is to an oxidation process in an electrolytic cell equipped with anode made of inalterable materials chosen among graphite, granular coal, lead and with cathodes made of stainless steel, graphite or other unalterable materials, said cell working with an applied tension between 1 and 8 V and with an anodic current density between 0.4 and 15 A/dm2.

Abstract: Process for stainless steel pickling consisting in placing the material to be treated in a bath kept at a temperature ranging from 30.degree. C. to 70.degree. C. and containing:a) HClb) Fe.sup.3+c) HFd) emulsifiers, wetting agents, polishing agents, acid attack inhibitors;the bath being fed continuously with:an air flow equal to at least 3 m.sup.3 /h per m.sup.3 bath min. and an oxidizer quantity adjusted to the bath redox potential to be kept at 250 mV min.

Abstract: Process for stainless steel pickling consisting in placing the material to be treated in a bath kept at a temperature ranging from 30.degree. C. to 70.degree. C. and containing:a) H.sub.2 SO.sub.4b) Fe.sup.3+c) HFd) emulsifiers, wetting agents, polishing agents, acid attack inhibitors;the bath being kept under agitation with:an air flow and continuously fed with a quantity of oxidizing agent adjusted to the bath redox potential to be kept at 250 mV min.