Electrolytic medium and method for electrochemical polishing of metal workpieces using the electrolyte medium - Patent Application 20070122997

Abstract

The present invention relates to an electrolyte medium for electrochemically polishing a metal workpiece, the electrolyte medium containing, on the one hand, a plurality of solid granular particles and, on the other hand, a liquid electrolyte. According to the present invention, the liquid electrolyte has an emulsion containing a continuous phase of at least one conductive hydrophilic liquid and, emulsified therein, a dispersed phase, the dispersed phase containing at least one hydrophobic liquid that is immiscible with and has a lower electrical conductivity than the conductive hydrophilic liquid. The present invention also relates to a method for electrochemically polishing a metal workpiece, in which an electrolyte medium of the above type is placed in a container and conductively connected to a cathode, a metal workpiece is conductively connected to an anode and immersed in the electrolyte medium within the container, and a voltage is applied to both electrodes to move the workpiece relative to the plurality of solid granular particles of the electrolyte medium.

Description

[Technical Field]

[0001] The present invention relates to an electrolyte medium for electrochemical polishing of a metal workpiece, the electrolyte medium containing a plurality of solid granular particles and a liquid electrolyte. The present invention also relates to a method for electrochemical polishing of a metal workpiece, in which the electrolyte medium is placed in a container and conductively connected to a cathode, a metal workpiece is conductively connected to an anode and immersed in the electrolyte medium in the container, and a voltage is applied to both electrodes to move the workpiece relative to the plurality of solid granular particles in the electrolyte medium.

[0002] For the surface treatment of workpieces, a method known as drag finishing is known, in which the workpiece is immersed in a bed of solid abrasive or polishing particles arranged in a container and moved relative to the bed of granules. Drag finishing machines are typically used, which are special types of barrel finishing machines in which the workpiece to be processed is removably fixed, for example, alone or in one or more clamping devices of the machine's workpiece holder, so that it is polished or ground as a result of its relative movement relative to the bed of granules. Such drag finishing machines often have a roughly plate-shaped rotor driven by a motor via appropriate gears, to which multiple workpiece holders are fixed directly or indirectly, for example, via multiple lifting devices. This is typically done eccentrically with respect to the axis of rotation of the rotor of the drag finishing machine. As this part of the drag finishing machine, the so-called plate, rotates, the workpiece holders attached to it follow a curved path. In this case, the workpiece held by the clamping device of the workpiece holder is immersed in a container filled with a bed of granular particles, often with the addition of a liquid processing medium such as water, a surfactant, etc., and the surface finishing in the form of a barrel polishing process is performed by the relative movement of the workpiece with respect to the granular material. Such drag finishing machines are known, for example, from US Pat. Nos. 5,629,995, ...

[0003] Alternatively, or in addition, the container containing the granule particles can be moved relative to a workpiece that is also moving, e.g., rotating at least about its own axis, or a stationary workpiece, e.g., about its own axis and / or along a circular orbital curve, e.g., If only the container is moved and the workpiece itself does not undergo any translational motion, this is also called "dip grinding" or "dip polishing" as a special form of drag finishing, and in such machines the workpiece holder that holds the workpiece during surface processing is substantially stationary, and is also called a dip finishing machine.

[0004] These granule particles can be of fundamentally different nature depending on the workpiece to be processed, for example of natural origin (e.g. from organic materials such as walnut or coconut shells, wood, cherry pits, etc.), mineral origin (e.g. from silicates, oxides, etc.), and / or synthetic origin (e.g. from plastics). Furthermore, as already suggested, it is known that this vibration processing can be carried out dry or in the form of wet processing with the addition of a liquid processing medium such as water, which can be mixed with additives such as surfactants.

[0005] Instead of or in addition to the translational movement of the workpiece relative to the granule particles, the workpiece holders of known drag finishing machines are often rotationally driven, for example, by means of a suitable motor, to perform a rotational movement of the workpiece about its own axis, which leads to even more effective surface processing (see, for example, the aforementioned Patent Document 3). Furthermore, workpiece holders for drag finishing machines are known in which the clamping devices of the workpiece holder for removably fixing the workpiece are rotatably mounted and rotated via a shaft pivotally mounted within the workpiece holder. For this purpose, the workpiece holder has, for example, a planetary gear arrangement with a central sun gear that engages with planet gears that are in turn non-rotatingly connected to the drive shafts of the respective clamping devices and distributed around the circumference of the sun gear of the workpiece holder. Due to this combined translational movement (in the direction of rotation of the support or "plate" of the drag finishing machine) and rotational movement (about the axis of the respective clamping device or about the workpiece axis) of the clamping devices pivotally mounted on the workpiece holder together with the workpiece, the processing medium achieves a uniform processing quality in a shorter processing time than with purely translational movements.Furthermore, alternatively or additionally, the workpiece holder itself can likewise be pivotally fixed to the support of the drag finishing machine (see, for example, Patent Document 4).

[0006] Furthermore, conventional drag finishing methods for polishing or grinding metal workpieces of the aforementioned type have been further developed into electrochemical polishing methods, in which a metal workpiece is conductively connected to a positive electrode (anode) on the one hand and a plurality of granular particles filled with a liquid electrolyte is conductively connected to a negative electrode (cathode) on the other hand. A voltage is applied to both electrodes, and the workpiece is moved relative to the plurality of solid granular particles, for example, as described above. The surface quality of the machined workpiece can often be improved in this way, and electrochemical polishing is also a method of abrasive surface processing. When a voltage is applied to both electrodes from a voltage source, in addition to simply mechanically processing the metal workpiece's surface, a current flows due to the conductivity of the liquid electrolyte, thereby causing anodic dissolution of the metal workpiece's surface. In this case, these electrodes can be supplied with either a direct current voltage or a pulsed voltage. Typically, the workpiece is moved in an electrolyte solution to ensure the desired relative movement of the workpiece to the plurality of solid granular particles and to keep the concentration gradient formed on the workpiece's surface as low as possible. The selection of an appropriate liquid electrolyte is a key parameter here, and it has been found that some electrolytes that result in defect-free electropolishing of some metals have virtually no effect on other metals, or result in rough, jagged, or matte surfaces. Thus, traditionally, strong inorganic acids, particularly phosphoric and sulfuric acids that are miscible with alcohol, are used to electropolish aluminum and steel. For example, a mixture of phosphoric acid and alcohol is suitable for copper and brass.

[0007] Patent Document 5 describes a liquid electrolyte in the form of an electrolyte solvent for electrolytically polishing metal workpieces and a method for electrochemically polishing workpieces using such a liquid electrolyte solvent, where the electrolyte solvent contains alkylbenzenesulfonic acid or alkylbenzenesulfonate, i.e., a salt or derivative thereof, a petroleum fraction having 17 to 35 carbon atoms, and optionally a small amount of ethanolamine. Patent Document 6 discloses an improved liquid electrolyte solvent for electrochemically polishing metal workpieces, particularly those made of copper, zinc, silver, tin, gold, or alloys thereof, and a method for electrochemical polishing using such an electrolyte solvent, where the electrolyte solvent includes an ethoxylated alcohol, a sulfonic acid and / or sulfonate, an inorganic acid, a liquid hydrocarbon, and water.

[0008] Furthermore, in recent years, several electrolyte media have been proposed for electrochemical polishing of metal workpieces, which include, on the one hand, multiple polymer-based solid porous granular particles and, on the other hand, a liquid electrolyte made from a conductive hydrophilic liquid, particularly from the group of strong inorganic acids and sulfonic acids. However, in these cases, the liquid electrolyte is contained only within the pores of the granular particles, while other gas or air atmospheres are present within the void volumes of the multiple granular particles (see, for example, Patent Documents 7, 8, 9, 10, 11, and 12). Since current is induced only locally as a result of contact between each granular particle and the workpiece to be processed, surface processing of such workpieces is very time-consuming.

[0009] Patent Document 13 describes another electrolyte medium for electrochemical polishing of metal workpieces, which similarly includes a plurality of polymer-based, solid, porous granular particles on the one hand and a water-based liquid electrolyte on the other hand, housed in the pores of the granular particles. In this case, instead of a gas atmosphere present in the void volume of the granular particles, a non-conductive liquid, such as a silicone or hydrocarbon-based liquid, that is immiscible with the aqueous electrolyte is provided. The above comments regarding the gas atmosphere in the void volume of the granular particles apply as a disadvantage, and in addition, the preparation of the electrolyte medium has proven to be complicated. A similar electrolyte medium for electrochemical polishing of metal workpieces can be found in Patent Document 14, which includes a plurality of polymer-based, solid, porous granular particles on the other hand and a water- or dilute acid-based liquid electrolyte, which is absorbed in the pores of the granular particles. In this case, the non-conductive liquid, which is immiscible with the aqueous electrolyte, within the void volume of the granular particles, which may be, for example, silicone or hydrocarbon based, may be homogeneous or may form as the continuous phase of a "water-in-oil emulsion" in which multiple droplets of the aqueous electrolyte are emulsified as the dispersed phase. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] German Patent Invention No. 10204267C1 [Patent Document 2] German Utility Model No. 20005361U1 [Patent Document 3] German Patent Application Publication No. 102010052222A1 [Patent Document 4] German Utility Model No. 202009008070U1 [Patent Document 5] International Publication No. 2007 / 121999A2 Pamphlet [Patent Document 6] European Patent Invention No. 2646603B1 [Patent Document 7] International Publication No. 2017 / 186992A1 Brochure [Patent Document 8] International Publication No. 2019 / 145588A1 Brochure [Patent Document 9] International Publication No. 2020 / 099699A1 Brochure [Patent Document 10] International Publication No. 2020 / 174112A1 Brochure [Patent Document 11] International Publication No. 2020 / 099700A1 Brochure [Patent Document 12] International Publication No. 2021 / 156530A1 Brochure [Patent Document 13] ES (Spain) Patent Application Publication No. 2904576A1 [Patent Document 14] International Publication No. 2022 / 123096A1 Brochure Summary of the Invention [Problem to be solved by the invention]

[0011] The object of the present invention is to improve an electrolyte medium for electrochemical polishing of metal workpieces of the type mentioned in the introduction in a simple and cost-effective manner, so as to at least largely avoid the above-mentioned disadvantages and to ensure a defect-free surface quality of the electropolished workpiece and even to avoid local corrosion thereof, while shortening the surface treatment time and improving the efficiency of electropolishing. The present invention further relates to a method for electrochemically polishing metal workpieces of the type mentioned in the introduction using such an electrolyte medium. [Means for solving the problem]

[0012] A first part of this problem is solved by the present invention by providing an electrolyte medium for electrochemical polishing of a metal workpiece, the electrolyte medium comprising a plurality of solid granular particles and one liquid electrolyte, the liquid electrolyte comprising an emulsion, the emulsion comprising a continuous phase of at least one electrically conductive hydrophilic liquid and a dispersed phase emulsified in the continuous phase, the dispersed phase comprising at least one hydrophobic liquid that is immiscible with and has a lower electrical conductivity than the electrically conductive hydrophilic liquid.

[0013] From a manufacturing technology standpoint, the present invention further provides a method for electrochemical polishing of a metal workpiece to solve this problem, in which an electrolyte medium of the type described above is placed in a container and conductively connected to a cathode, a metal workpiece is conductively connected to an anode and immersed in the electrolyte medium in the container, and a voltage is applied to both electrodes to move the workpiece relative to a plurality of solid granular particles in the electrolyte medium.

[0014] Specifically, the liquid electrolyte of the electrolyte medium according to the present invention is formed as an "oil-in-water emulsion," in which the polar continuous phase of at least one electrically conductive hydrophilic (oleophobic) liquid represents the actual electrolyte, which serves to generate an electric current between an anode (positive electrode) connected to a metal workpiece and a cathode (negative electrode) connected to the electrolyte medium. The relatively high electrical conductivity of the electrolyte medium thus enables effective and time-efficient surface processing of metal workpieces with high surface quality and relatively low energy consumption. This is because the electrically conductive hydrophilic liquid present in the void volume of the solid granular particles, as the polar continuous phase of the liquid electrolyte, always ensures an electrically conductive connection between the workpiece, which is usually connected to the anode, and the cathode, just like the electrolyte solvent. The non-polar dispersed phase emulsified in the continuous phase (which contains at least one hydrophobic (lipophilic) liquid that is immiscible with the conductive hydrophilic liquid and has a lower electrical conductivity than the conductive hydrophilic liquid, and which may in particular be substantially non-conductive) serves, on the one hand, to effectively protect the metal workpiece even from localized corrosion during electrochemical surface processing; in this case, the hydrophobic liquid with low electrical conductivity or no electrical conductivity is finely dispersed in the conductive hydrophilic liquid of the continuous phase, so that it can be easily deposited on the surface of the workpiece to be processed during surface processing and exert an anti-corrosion protective effect. On the other hand, by varying the proportion of the hydrophobic liquid with low electrical conductivity or no electrical conductivity of the dispersed phase, the electrical conductivity and pH value of the electrolyte medium according to the invention can be adjusted.

[0015] In comparison with conventional electrolyte media, which contain a hydrophilic, conductive liquid on the one hand and a hydrophobic, non-conductive or low-electrical-conductivity liquid on the other hand as a single-phase solution, as in, for example, the above-mentioned Patent Documents 4 or 5, the electrolyte medium according to the present invention has the advantage that it can be used for the surface processing of workpieces made of practically any conductive metallic material, in which case the dispersed phase hydrophobic liquid with low or non-conductive electrical conductivity can provide more effective corrosion protection for the workpiece, while the continuous phase conductive hydrophilic liquid can have a high electrical conductivity, thereby ensuring efficient surface processing. Compared to an electrolyte medium in which a conductive hydrophilic liquid is contained solely within the pores of porous granular particles as an electrolyte and the void volume between the granular particles is filled with a non-conductive hydrophilic liquid that is immiscible with the conductive hydrophilic liquid (see Patent Document 13), and compared to an electrolyte medium in which a conductive hydrophilic liquid is contained solely within the pores of porous granular particles as an electrolyte and the void volume between the granular particles is filled with a so-called "water-in-oil emulsion" (in which the conductive hydrophilic liquid as a dispersed phase is contained in a non-conductive hydrophilic liquid as a continuous phase with which it is immiscible) (see Patent Document 14), the electrolyte medium according to the present invention not only offers the advantage of being easier to manufacture in terms of handling, but also of requiring less energy and ensuring significantly shorter processing times, since the conductive hydrophilic liquid in the continuous phase provides a smaller electrical resistance.

[0016] It should be noted here that the term "electrochemical polishing" in the sense of the present invention includes electrochemical smoothing as well as electrochemical brightening.

[0017] The average droplet size of the hydrophobic liquid of the dispersed phase of the liquid electrolyte emulsion can be adjusted within a wide range, in particular by the type and amount of a suitable emulsifier (see below); i.e., these emulsions can essentially be macroemulsions with an average droplet size of more than about 1 μm and up to about 1 mm, microemulsions with an average droplet size of less than about 1 μm, or nanoemulsions with an average droplet size of less than about 100 nm. The liquid electrolyte emulsion does not necessarily have to be essentially monodisperse, but in this case, the emulsion can be produced in a manner known per se by introducing shear forces into the heterogeneous mixture, for example, by means of known rotor-stator systems, high-pressure emulsifiers, or by dispersing the heterogeneous mixture using a microporous membrane.

[0018] The conductive hydrophilic liquid of the continuous phase of the liquid electrolyte emulsion can preferably contain at least one liquid from the group of polar organic solvents, in particular alcohols, and / or water. Examples of advantageous alcohols include monohydric alcohols, such as phenoxyethanol, and in particular dihydric or higher alcohols, such as glycols, in particular ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, propane-1,2,3-triol (glycerol), and mixtures thereof.

[0019] The conductive hydrophilic liquid of the continuous phase of the liquid electrolyte emulsion preferably further contains at least one acid to adjust the electrical conductivity and pH value. Suitable acids include inorganic acids such as sulfuric acid (H2SO4), sulfurous acid (H2SO4), hydrochloric acid (HCl), hydrofluoric acid (HF), phosphoric acid (H3PO4), nitric acid (HNO3), and nitrous acid (HNO2), as well as organic acids such as oxalic acid (C2H2O4), citric acid (C6H8O7), sulfonic acids, preferably methanesulfonic acid (C4O3S), ethanesulfonic acid (C2H6O3S), benzenesulfonic acid (C6H6O3S), and sulfonates thereof, and mixtures thereof.

[0020] The hydrophobic liquid of the dispersed phase of the liquid electrolyte emulsion can preferably contain at least one liquid from the group of aliphatic hydrocarbons and / or silicone oils. Examples of advantageous hydrocarbons include hydrocarbons having 10 to 20 carbon atoms, preferably 12 to 16 carbon atoms, hydrocarbons in particular in the form of alkanes, including isoalkanes and cycloalkanes, and mixtures thereof. Preferred silicone oils include those having a viscosity of about 1 to about 2 x 10 6 and in particular those in the form of polydimethylsiloxane.

[0021] In an advantageous embodiment, the proportion of the dispersed phase in the emulsion can be from about 15% to about 70% by weight, in particular from about 25% to about 60% by weight, for example from about 30% to about 60% by weight, based on the total weight of the emulsion consisting of both the continuous and dispersed phases.

[0022] In order to ensure a stable emulsion of the liquid electrolyte and in particular to prevent the emulsified droplets of the dispersed phase of non-conductive or low-conductivity hydrophobic liquid from coalescing in the continuous phase, the emulsion advantageously further comprises at least one emulsifier, in particular an emulsifier from the group of surfactants, as surface-active substance.

[0023] Examples of advantageous emulsifiers are emulsifiers from the group of alkoxylated alcohols having at least 8 carbon atoms, in particular alkoxylated alcohols having at least 10 carbon atoms, such as ethoxylated iso- or n-tridecanol, secondary fatty alcohol ethoxylates (polyalkylene glycol ethers), (2-methoxymethylethoxy)propanol, etc., and emulsifiers from the group of sulfonic acids having at least 8 carbon atoms, in particular sulfonic acids having at least 10 carbon atoms, and sulfonates thereof, such as alkylsulfonic acids and alkylsulfones. Acid salts, preferably decane sulfonic acid, undecane sulfonic acid, dodecane sulfonic acid and tridecane sulfonic acid, alkylbenzene sulfonates, cumene sulfonates, sodium sulfonates and potassium sulfonates, preferably sodium-p-cumene sulfonate, potassium-p-cumene sulfonate, etc., benzene-1,1-oxybis-tetrapropylene derivative sulfonates (sodium salts), etc., and emulsifiers from the alanine salt group, for example sodium N-(2-carboxyethyl)-N-(2-ethylhexyl)-β-alaninate, etc.

[0024] The HLB value of the at least one emulsifier is advantageously from about 8 to about 18, in particular from about 9 to about 16. In this case, the HLB value ( hydrophilic-lipophilic balance The above values ​​of hydrophilic-lipophilic balance (HLB) are based on the Griffin calculation method, according to which the HLB value is defined as follows: HLB = 20 × (1 − M1 / M) where: M1: the molar mass of the hydrophobic (lipophilic) part of the emulsifier molecule, and M: molar mass of all molecules of the emulsifier, is.

[0025] Generally, emulsifiers in the form of surfactants for forming "oil-in-water" emulsions have an HLB value of 8 to 18, with HLB values ​​of 9 to 16 according to the present invention being found to be particularly suitable for emulsifying a relatively high volume fraction, e.g., greater than about 70% by volume, of a hydrophobic or lipophilic dispersed phase in a conductive hydrophilic or lipophobic continuous phase to form highly concentrated emulsions.

[0026] It is further conceivable, for example, that the emulsion of the liquid electrolyte further contains at least one additive, in particular an additive from the group of dyes, to make the (dispersed / continuous) phase more easily visible, or possibly also an antifoaming agent.

[0027] The solid granular particles for the electrolyte medium according to the present invention can essentially be any known granular particles known for polishing or grinding metal workpieces, including those of the types described above. It has proven particularly advantageous if these granular particles are composed of polymeric materials, which are less hard than mineral and metal materials, have a rounded shape (preferably substantially spherical), and / or have an average particle size of about 10 μm to about 5 mm, preferably about 100 μm to about 1 mm. The polymeric materials of these granular particles should be acid-resistant in view of the typical acidic environment of the liquid electrolyte emulsion (see also below) and oxidation-resistant in view of the electrochemical polishing process. In an advantageous embodiment, these solid granular particles can also be selected from the group consisting of ion-exchange polymers, which can in principle be any ion-exchange polymer, but are preferably cationic ion-exchange polymers capable of absorbing metal ions released during the electrochemical polishing of metal workpieces. Examples of advantageous ion exchange polymers include copolymers of styrene with sulfonated ethylstyrene and / or sulfonated divinylbenzene, acrylic polymers containing acrylic acid and / or methacrylic acid units, and the like.

[0028] Furthermore, these solid granular particles can be dense or porous and / or gel-type ion exchange polymers, as is often the case with the aforementioned polymeric materials due to their manufacturing process. When porous granular particles are used, they typically have residual water within their pores due to the manufacturing process, but this residual water is miscible with or can dissolve virtually unlimitedly in the (polar) continuous phase of the liquid electrolyte emulsion.

[0029] As already indicated, this liquid electrolyte has the following properties in an advantageous embodiment: a pH value of about 1 to about 7, in particular about 2 to about 7, preferably about 3 to about 7, and / or Electrical conductivity of about 0.05 mS / cm to about 5 mS / cm, particularly about 0.1 mS / cm to about 3 mS / cm, preferably about 0.2 mS / cm to about 3 mS / cm, and / or Density: about 0.92 g / ml to about 1.04 g / ml, particularly about 0.96 g / ml to about 1.00 g / ml.

[0030] Furthermore, the volume ratio of the solid granular particles to the liquid electrolyte emulsion should be selected so that the liquid electrolyte emulsion almost completely fills the void volume of the granular particles and the workpiece moved relative to the granular particles in the electrolyte medium is almost completely wetted by the liquid electrolyte emulsion. Therefore, the volume ratio of the granular particles to the liquid electrolyte emulsion can be, for example, between about 80% by volume to about 20% by volume to about 40% by volume to about 60% by volume, particularly between about 75% by volume to about 25% by volume to about 45% by volume to about 65% by volume, depending on the average particle size of the granular particles.

[0031] In a method according to the present invention for electrochemical polishing of a metal workpiece, an electrolyte medium of the type described above is placed in a container and conductively connected to a cathode, a metal workpiece is conductively connected to an anode and immersed in the electrolyte medium in the container, and a voltage is applied to both electrodes to move the workpiece relative to a plurality of solid granular particles of the electrolyte medium, wherein the relative movement of the metal workpiece relative to the solid granular particles can be performed in any known manner, for example, as known in conventional drag or immersion finishing processes. Thus, the relative movement of the workpiece relative to the solid granular particles during surface processing can be, for example, Rotational movements of the workpiece and / or the container, in particular rotational movements of the workpiece and / or the container substantially around one axis of symmetry, and / or a translational movement of the workpiece relative to the container, in particular in the form of an approximately curved trajectory, and / or Vibration excitation of the workpiece and / or vessel, for example by means of ultrasound, piezoelectric actuators, eccentric rotary drives, etc.

[0032] Furthermore, in order to avoid damage to the workpieces due to multiple workpieces colliding with each other and / or the walls of the container, it is advantageous for the metal workpieces to be clamped in a workpiece holder that is movable relative to the container, and which also allows easy electrical contact of the (each) workpiece.

[0033] Furthermore, it is advantageous if the electrolyte medium emulsion, and particularly its continuous phase, is selected to be chemically and electrochemically inert to the metallic material of the workpiece being electropolished.

[0034] The following are embodiments of electrolyte media according to the present invention, which serve for illustrative purposes only and are not intended to limit the present invention.

[0035] Example 1: (a) Granular particles:Porous polymer particles having an average particle size of about 500 μm and / or about 1 mm, which are made of an ion exchange resin based on a copolymer of styrene and sulfonated ethylstyrene; (b) Electrolytes: Continuous phase (hydrophilic, conductive): 49% by weight of ethylene glycol and glycerol as polar solvents, 11% by mass of benzenesulfonic acid as an acid, C10-C13-sec-alkyl derivatives, Dispersed phase (hydrophobic, non-conductive): 32% by weight of a mixture of aliphatic hydrocarbons in the form of C12 to C16 alkanes, isoalkanes and cycloalkanes, Emulsifier (surfactant): 7% by weight of alcohol ethoxylates, such as ethoxylated iso-tridecanol and secondary alcohol ethoxylates, Additives: 1% by weight antifoaming agent.

[0036] Example 2: (a) Granular particles: porous polymer particles having an average particle size of about 500 μm and / or about 1 mm, consisting of an ion exchange resin based on a copolymer of styrene and sulfonated ethylstyrene; (b) Electrolytes: Continuous phase (hydrophilic, conductive): 19% by mass of ethylene glycol as a polar solvent, 10% by weight of alkylsulfonic acids as acids, for example methanesulfonic acid; Dispersed phase (hydrophobic, non-conductive): 61% by mass of a mixture of aliphatic hydrocarbons in the form of C12 to C16 alkanes, isoalkanes and cycloalkanes, Emulsifier (surfactant): 10% by weight of alcohol ethoxylates, for example ethoxylated isotridecanol.

[0037] Example 3: (a) Granular particles: porous polymer particles having an average particle size of about 500 μm and / or about 1 mm, consisting of an ion exchange resin based on a copolymer of styrene and sulfonated ethylstyrene; (b) Electrolytes: Continuous phase (hydrophilic, conductive): 23% by weight of ethylene glycol and water as polar solvents, 5% by mass of an alkylsulfonic acid as an acid, such as a C10 to C13 sulfonic acid; 4% by mass inorganic acid, Dispersed phase (hydrophobic, non-conductive): 58% by mass of aliphatic hydrocarbon mixture in the form of C12 to C16 alkanes, isoalkanes and cycloalkanes, Emulsifier (surfactant): 10% by weight of alcohol ethoxylates, such as ethoxylated iso-tridecanol.

Claims

1. 1. An electrolyte medium for electrochemical polishing of a metal workpiece, comprising: (a) a plurality of solid granular particles; (b) one liquid electrolyte; In an electrolyte medium comprising the liquid electrolyte comprises an emulsion; the emulsion comprises a continuous phase comprising at least one conductive hydrophilic liquid and a dispersed phase emulsified within the continuous phase; the dispersed phase comprises at least one hydrophobic liquid that is immiscible with and has a lower electrical conductivity than the conductive hydrophilic liquid; An electrolyte medium characterized by:

2. Electrolyte medium according to claim 1, characterized in that the conductive hydrophilic liquid of the continuous phase of the emulsion contains at least one liquid from the group of polar organic solvents, in particular from the group of alcohols, and / or water.

3. 3. The electrolyte medium according to claim 1, wherein the conductive hydrophilic liquid of the continuous phase of the emulsion further contains at least one acid.

4. Electrolyte medium according to any one of claims 1 to 3, characterized in that the hydrophobic liquid of the dispersed phase of the emulsion contains at least one liquid, in particular from the group of aliphatic hydrocarbons and / or from the group of silicone oils.

5. 5. The electrolyte medium according to claim 1, wherein the proportion of the dispersed phase of the emulsion in relation to the total amount of the emulsion is between 15% and 70% by weight, in particular between 25% and 60% by weight.

6. 6. The electrolyte medium according to claim 1, wherein the emulsion further comprises at least one emulsifier, in particular an emulsifier from the group of surfactants.

7. 7. The electrolyte medium according to claim 6, characterized in that the emulsion contains at least one emulsifier from the group of alkoxylated alcohols having at least 8 carbon atoms, the group of sulfonic acids having at least 8 carbon atoms, the group of sulfonates, and the group of alanine salts.

8. 8. Electrolyte medium according to claim 6 or 7, characterized in that the HLB value of the at least one emulsifier is between 8 and 18, in particular between 9 and 16.

9. 9. The electrolyte medium according to claim 1, wherein the solid granular particles are formed from the group of polymer materials, in particular ion-exchange polymers.

10. 10. The electrolyte medium according to claim 1, wherein the solid granular particles are porous and / or gel-type ion exchange polymers.

11. The liquid electrolyte is a pH value of 1 to 7, in particular 2 to 7; and / or an electrical conductivity of 0.05 mS / cm to 5 mS / cm, in particular 0.1 mS / cm to 3 mS / cm, and / or a density of 0.92 g / ml to 1.04 g / ml, in particular 0.96 g / ml to 1.00 g / ml; 11. The electrolyte medium according to claim 1, characterized in that it has the following characteristic values:

12. 12. A method for electrochemically polishing a metal workpiece, comprising: placing the electrolyte medium of any one of claims 1 to 11 in a container and conductively connecting it to a cathode; conductively connecting the metal workpiece to an anode and immersing it in the electrolyte medium in the container; applying a voltage to both electrodes; and moving the workpiece relative to a plurality of solid granular particles in the electrolyte medium.

13. Relative movement of the metal workpiece with respect to the electrolyte medium within the vessel, a rotational movement of the workpiece and / or the container, in particular a rotational movement of the workpiece and / or the container substantially about one axis of symmetry; - translational movement of the workpiece relative to the container; and - vibration excitation of the workpiece and / or the vessel; 13. The method of claim 12, wherein the method is performed by relative movement of at least one of the group.

14. 14. A method according to claim 12 or 13, wherein the metal workpiece is clamped to a workpiece holder which is movable relative to the container.

15. 15. The method according to any one of claims 12 to 14, characterized in that the emulsion of the electrolyte medium, in particular its continuous phase, is selected so as to be chemically and electrochemically inert towards the metallic material of the workpiece to be electropolished.

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