Abstract: In a method for surface treatment of stainless steel, the thermally produced layers of oxide are contacted with a composition effective to dissolve iron ions out of the layers of oxide.

Abstract: The present invention relates to a process for improving the heat and corrosion resistance of stainless steel by means of a novel passivation process. This process comprises a chemical treatment with an aqueous solution comprising a complexing agent combination of at least one oxidant, a subsequent rinsing and a subsequent treatment at elevated temperature in an oxygen-containing atmosphere. The stainless steel surfaces obtained according to the invention have a homogeneous passive layer having increased chemical resistance and resistance to thermal discoloration.

Abstract: In a method for surface treatment of stainless steel, the thermally produced layers of oxide are contacted with a composition effective to dissolve iron ions out of the layers of oxide.

Abstract: The present invention relates to a method of electrochemical polishing of surfaces of cobalt or cobalt alloys. It employs an electrolyte comprising glycolic acid and at least one alkane-sulfonic acid with an alkyl residue that has 1 to 3 carbon atoms. This electrolyte is also one aspect of the present invention. In one embodiment, at least one alkane-sulfonic acid comprises methane-sulfonic acid. The electrolyte and the method using this electrolyte are suitable in particular for surfaces of cobalt or cobalt alloys, including cobalt-chromium alloys such as stellite.

Abstract: The present invention relates to a process for improving the heat and corrosion resistance of stainless steel by means of a novel passivation process. This process comprises a chemical treatment with an aqueous solution comprising a complexing agent combination of at least one oxidant, a subsequent rinsing and a subsequent treatment at elevated temperature in an oxygen-containing atmosphere. The stainless steel surfaces obtained according to the invention have a homogeneous passive layer having increased chemical resistance and resistance to thermal discoloration.

Abstract: The present invention describes a cost-saving and environmentally conserving process for the electrochemical polishing of steel, in particular of low-alloy steels. The workpieces are rinsed after electropolishing in an arid phosphoric acid-sulfuric acid-bath in a first rinsing step with a phosphoric acid-containing solution, whereby a chemical attack on the freshly polished surfaces is avoided without the use of environmentally harmful and unhealthy inhibitors such as chromates. By recycling of the acids and the rinsing solution, these acids and solutions can be regenerated, whereby the process can be designed effluent-free.

Abstract: The present invention relates to a method of electrochemical polishing of surfaces of cobalt or cobalt alloys. It employs an electrolyte comprising glycolic acid and at least one alkane-sulfonic acid with an alkyl residue that has 1 to 3 carbon atoms. This electrolyte is also one aspect of the present invention. In one embodiment, at least one alkane-sulfonic acid comprises methane-sulfonic acid. The electrolyte and the method using this electrolyte are suitable in particular for surfaces of cobalt or cobalt alloys, including cobalt-chromium alloys such as stellite.

Abstract: The present invention relates to a method of electrochemical polishing of surfaces of titanium or titanium-containing alloys, such as Nitinol. An electrolyte is used that comprises methanesulfonic acid and one or more alkanediphosphonic acids. These alkanediphosphonic acids can optionally be substituted with hydroxy and/or amino groups. A further aspect of the present invention relates to the use of said electrolyte for the electropolishing of titanium or titanium-containing alloys.

Abstract: The present invention relates to a method for the electropolishing of surfaces of metals and metal alloys. Said method is characterized in particular in that it can be applied to a wide range of metals. Thus, it is suitable for the electropolishing of metal surfaces comprising iron, tungsten, magnesium, aluminum or an alloy of these metals. The electrolyte used in the method comprises methanesulfonic acid and at least one alcoholic compound selected from aliphatic diols of general formula CnH2n(OH)2 with n=2-6 and alicyclic alcohols of general formula CmH2m-1OH with m=5-8.

Abstract: The present invention relates to a method for the electrochemical polishing of surfaces of metals and metal alloys, in particular surfaces of niobium, niobium alloys, tantalum and tantalum alloys. It uses an electrolyte that comprises methanesulfonic acid and ammonium bifluoride, and which is also an object of the present invention. Said electrolyte makes it possible to electropolish niobium-containing and/or tantalum-containing workpieces efficiently, with high quality and in a manner that is harmless both for the workpiece and for humans and the environment.

Abstract: The present invention relates to the use of a mixture of urea and one or more alkane-diphosphonic acids, optionally substituted with one or more hydroxyl or amino groups, or salts thereof for the stabilization of an acidic, metal- and peroxide-containing polishing solution. The invention also relates to peroxide-containing solutions that are suitable for the stabilization of acidic, metal- and peroxide-containing polishing baths, and acidic, peroxide-containing polishing solutions that contain the stabilizer mixture according to the invention. A method of chemical polishing of metal surfaces using the stabilizer according to the invention is also described.

Abstract: The invention relates to a process for the demetallization of highly acidic baths based on phosphoric acid and sulphuric acid, and also to a process for the electropolishing of stainless-steel surfaces, in which a regeneration of, in particular, spent electrolyte compositions for electropolishing can be achieved by separate electrolytic reduction of Fe(III) to Fe(II) and subsequent removal of precipitates.

Abstract: It is provided in an electrochemical polishing and pickling method and apparatus for treating metal surfaces that an electrolyte stream (18) entering a casing (12) is divided into an anodic partial stream (20) and a cathodic partial stream (22). The anodic partial stream (20) flows past a dielectric wall (32) as well as the surface (10') to be polished or pickled, while the cathodic partial stream does not reach the surface (10') to be polished but instead is recycled directly into an electrolyte reservoir (30) after having passed the cathodes (24).

Abstract: An apparatus and a method serving for electrochemically polishing and/or pickling the inner surfaces (16) of pipes (10) provide for a polishing head (12) to be moved through the pipe. The polishing head (12) comprises a dielectric outer wall which defines a narrow working gap (28) together with the inner pipe surface (16) to be cleaned, the electrolyte flowing through said gap. This permits electrochemical polishing of high quality of the inside surface of the pipe with little consumption of electrolyte. The electrolyte stream may be divided into cathodic and anodic partial streams (30 and 32, respectively).

Abstract: The electrolyte according to the invention for electrochemically polishing articles made of steel, stainless steel, nickel alloys, aluminum, and aluminum alloys, and containing phosphoric acid and sulfuric acid comprises an addition of a chelating agent on the basis of phosphonic acids and, if desired, a stabilizer for the latter.