Electrolyte medium and method for electrochemically polishing metal workpiece using same

Abstract

The invention relates to an electrolyte medium for the electrochemical polishing of metal workpieces, which electrolyte medium comprises, on the one hand, a plurality of solid particulate particles and, on the other hand, a liquid electrolyte. The invention proposes that the liquid electrolyte is an emulsion having a continuous phase consisting of at least one electrically conductive hydrophilic liquid and a dispersed phase consisting of at least one hydrophobic liquid that is immiscible with the electrically conductive hydrophilic liquid and has a lower conductivity than the hydrophilic liquid, emulsified in the continuous phase. The invention further relates to a method for electrochemically polishing a metal workpiece, in which an electrolyte medium of the above type is introduced into a container and connected to a cathode in an electrically conductive manner, in which the metal workpiece is connected to an anode in an electrically conductive manner and immersed in the electrolyte medium in the container, wherein a voltage is applied to the electrode and the workpiece is moved relative to the plurality of solid particulate particles of the electrolyte medium.

Description

Technical Field

[0001] The invention relates to an electrolyte medium for electrochemical polishing of a metal workpiece, comprising a plurality of solid granular particles and a liquid electrolyte. The invention also relates to a method for electrochemical polishing of a metal workpiece, wherein such an electrolyte medium is placed in a container and is electrically conductively connected to a cathode, wherein the metal workpiece is electrically conductively connected to an anode and immersed in the electrolyte medium in the container, wherein a voltage is applied to the electrodes and the workpiece is moved (moved) relative to the plurality of solid granular particles of the electrolyte medium. Background Art

[0002] For the surface treatment of metal workpieces, so-called drag polishing methods are known, in which the workpiece is immersed in a charge (Schüttung) of solid abrasive or polishing granular particles in a container and is moved relative to these particles in the charge of granular particles. In this process, drag polishers are usually used, which represent a special form of roller grinding machines, in which the workpiece to be treated is fixed, for example, individually or in a detachable manner, to one or more clamping devices of a workpiece holder of the machine, so that it is polished or ground due to the relative movement relative to the charge of granular particles. Such drag polishers often include a generally rotating part, which is basically in the form of a disc that is driven in rotation, for example, by means of an electric motor via a suitable gearbox, and to which the workpiece holder can be directly or indirectly, for example, via a lifting device. This fixing is particularly eccentric relative to the rotation axis of the rotating part of the drag polisher. If this part of the drag polisher, the so-called disc, rotates, the workpiece holder fixed thereto then describes a trajectory. The workpiece, which is supported by the clamping device of the workpiece holder, is immersed in a container with a charge consisting of granular particles, to which a liquid processing medium such as water, a surfactant, etc. is usually added, wherein due to the relative movement of the workpiece with respect to the particles, its surface treatment takes place in the form of a tumbling process. Such drag polishing machines are known, for example, from DE 102 04 267 C1, DE 20005 361 U1 or DE 102010 052 222.

[0003] As an alternative or in addition, the container for the granular particles can be moved relative to a workpiece that is also moving, for example rotating at least about its own axis, or a stationary workpiece, for example about its own axis and / or along a path (for example in the form of a circular path). If only the container is moved and the workpiece itself does not undergo a translational movement, this method is also called "immersion grinding" or "immersion polishing" as a special form of drag polishing, wherein such machines (in which the workpiece holder supporting the workpiece is essentially stationary during the surface treatment of the workpiece) are also called immersion polishing machines.

[0004] Depending on the workpiece to be processed, the granular particles can in principle be of various natures and can, for example, be of natural origin (e.g. from organic materials such as walnut shells, coconut shells, wood, cherry pits, etc.), of mineral origin (e.g. from silicates, oxides, etc.) and / or of synthetic origin (e.g. from plastics). Furthermore, as already mentioned, it is known that the tumbling process can be carried out dry or in wet form with the addition of a liquid process medium, for example water, which can be mixed with additives such as surfactants.

[0005] In order to ensure a rotational movement of the workpiece, for example about its own axis, instead of or in addition to the translational movement of the workpiece relative to the granular particles (which leads to a more effective surface treatment), the workpiece holder of the known drag polishing machine is usually driven in rotation, which is achieved, for example, by a suitable electric motor (see, for example, DE 10 2010 052 222 A1). In addition, the following workpiece holder of the drag polishing machine is known, whose clamping device for removably fixing the workpiece is rotatably mounted and rotated by an axis rotatably mounted in the workpiece holder. For this purpose, the workpiece holder has, for example, a planetary gearbox with a central sun gear, which meshes with planetary gears, which in turn are connected to the bearing shafts of the corresponding clamping buckle (Spannverschluss) in a rotationally fixed manner, and the bearing shafts are distributed around the circumference of the sun gear of the workpiece holder. Due to this movement of the clamping device rotatably mounted on the workpiece holder and the workpiece, which consists of a translational movement (in the direction of rotation of the carrier part or "disc" of the drag polisher) and a rotational movement (about the axis of the corresponding clamping device or about the workpiece axis), a uniform processing quality can be achieved in a shorter processing time than with a pure translational movement by means of the processing medium. Furthermore, as an alternative or in addition, the workpiece holder itself can also be rotatably fastened to the carrier part of the drag polisher in a corresponding manner (see, for example, DE 202009 008 070 U1).

[0006] In addition, the conventional drag polishing method for polishing and grinding of metal workpieces of the above type has been further developed into an electrochemical polishing method, in which the metal workpiece is conductively connected to a positive electrode (anode) on the one hand, and the granular particles filled with a liquid electrolyte are conductively connected to a negative electrode (cathode) on the other hand, wherein a voltage is applied to the electrodes and the workpiece is moved relative to a plurality of solid granular particles, for example, in the above-mentioned manner. In this way, the surface quality of the treated workpiece can often be improved, wherein such electrochemical polishing also represents a method of removing surface treatment. If a voltage is applied to the electrodes by a power supply, in addition to the purely mechanical surface treatment, a current is also generated due to the conductivity of the liquid electrolyte, which leads to anodic corrosion of the surface of the metal workpiece. The electrodes can be powered with a DC voltage or a pulse voltage. Usually, the workpiece moves in an electrolyte solution to ensure the required relative movement thereof relative to the solid granular particles and to keep the concentration gradient formed at the workpiece surface as low as possible. The selection of a suitable liquid electrolyte is an important parameter in this process, wherein it has been shown that some electrolytes lead to a good electrochemical polishing effect for one metal, but have virtually no effect on another metal or lead to a rough, uneven or matte surface. For example, conventional electrochemical polishing for aluminum and steel uses strong mineral acids, especially phosphoric acid and sulfuric acid, which can be mixed with alcohols. For copper and brass, a mixture of phosphoric acid and alcohol is suitable.

[0007] WO 2007 / 121999 A2 describes a liquid electrolyte in the form of an electrolyte solution for electrochemical polishing of metal workpieces and a method for electrochemical polishing of workpieces by means of such a liquid electrolyte solution, wherein the electrolyte solution contains alkylbenzenesulfonic acid or alkylbenzenesulfonate (i.e., salts or derivatives thereof), a petroleum fraction having 17 to 35 carbon atoms and optionally a small amount of ethanolamine. In contrast, an improved liquid electrolyte solution for electrochemical polishing of metal workpieces, in particular workpieces made of copper, zinc, silver, tin, gold and alloys thereof, and a method for electrochemical polishing using an electrolyte solution of this type are known from EP 2646 603 B1, which contains an ethoxylated alcohol, a sulfonic acid and / or a sulfonate, an inorganic acid and a liquid hydrocarbon and water.

[0008] In addition, in recent years, an electrolyte medium has been proposed for electrochemical polishing of metal workpieces, which comprises, on the one hand, a plurality of solid porous granular particles based on polymers and, on the other hand, a liquid electrolyte consisting of a conductive hydrophilic liquid, in particular a strong mineral acid and a sulfonic acid, wherein the liquid electrolyte is only absorbed in the pores of the particles and the hollow volume of the granular particles is filled with gas or air (see, for example, WO 2017 / 186992 A1, WO 2019 / 145588 A1, WO 2020 / 099699 A1, WO 2020 / 174112 A1, WO 2020 / 099700 A1 or WO 2021 / 156530 A1). Since the current is only caused in a point-like manner by the contact of the corresponding granular particles with the workpiece to be treated, surface treatment of the workpiece in this way is very time-consuming.

[0009] ES 2904 576 A1 describes another electrolyte medium for electrochemical polishing of metal workpieces, which likewise comprises, on the one hand, a plurality of solid porous granular particles based on polymers and, on the other hand, a liquid electrolyte based on water, which is absorbed in the pores of the granular particles. Instead of the gas present in the cavity volume of the granular particles, in this case, a liquid that is immiscible with the aqueous electrolyte and is non-conductive, for example a liquid based on silicone or hydrocarbons, is provided. With regard to the disadvantages, the above description of the gas in the cavity volume of the granular particles also applies, and the preparation of such an electrolyte medium is also more complicated. A similar electrolyte medium for electrochemical polishing of metal workpieces is described in WO 2022 / 123096 A1, which likewise comprises, on the one hand, a plurality of solid porous granular particles based on polymers and, on the other hand, a liquid electrolyte based on water or a diluted acid, which is absorbed in the pores of the granular particles. In this case, the aqueous electrolyte-immiscible, non-conductive liquid, such as a silicone or hydrocarbon-based liquid, in the void volume of the granular particles may be homogeneous or form the continuous phase of a "water-in-oil emulsion" in which droplets of the aqueous electrolyte are emulsified as a dispersed phase. Summary of the invention

[0010] The basic object of the present invention is to further develop an electrolyte medium for electrochemical polishing of metal workpieces of the above-mentioned type in a simple and cost-effective manner while avoiding the above-mentioned disadvantages to the greatest extent possible, so that the surface treatment time is reduced and the efficiency of electrochemical polishing is increased while ensuring the surface quality of the electrochemically polished workpiece is intact and even local corrosion is avoided. The invention also relates to a method for electrochemically polishing a metal workpiece of the above-mentioned type using such an electrolyte medium.

[0011] According to the present invention, the first part of the object is achieved in the case of an electrolyte medium for electrochemical polishing of a metal workpiece comprising a plurality of solid granular particles and a liquid electrolyte in the following manner: the liquid electrolyte is an emulsion having a continuous phase consisting of at least one electrically conductive hydrophilic liquid and a dispersed phase emulsified in the continuous phase consisting of at least one hydrophobic liquid that is immiscible with the electrically conductive hydrophilic liquid and has a lower electrical conductivity than the hydrophilic liquid.

[0012] From a process perspective, the present invention also proposes a method for electrochemical polishing of a metal workpiece to achieve this purpose, wherein an electrolyte medium of the above type is added to a container and conductively connected to a cathode, wherein the metal workpiece is conductively connected to an anode and immersed in the electrolyte medium in the container, wherein a voltage is applied to the electrodes, and the workpiece is moved relative to a plurality of solid granular particles of the electrolyte medium.

[0013] The liquid electrolyte of the electrolyte medium according to the invention thus consists of an "oil-in-water emulsion", whose polar continuous phase consisting of at least one electrically conductive hydrophilic (oleophobic) liquid represents the actual electrolyte for establishing an electric current between an anode (positive electrode) connected to the metal workpiece and a cathode (negative electrode) connected to the electrolyte medium. In this way, due to the relatively high electrical conductivity of the electrolyte medium, an effective and time-efficient surface treatment of the metal workpiece together with a high surface quality can be achieved at a relatively low energy consumption, since the presence of an electrically conductive hydrophilic liquid in the hollow volume of the solid granular particles, as the polar continuous phase of the liquid electrolyte, similar to the case of an electrolyte solution, always ensures an electrically conductive connection between the workpiece to be treated, which is usually in contact with the anode, and the cathode. The non-polar dispersed phase emulsified in the above-mentioned continuous phase consists of at least one hydrophobic (oleophilic) liquid that is immiscible with the conductive hydrophilic liquid and has a lower conductivity than the hydrophilic liquid, which liquid can also be substantially non-conductive, on the one hand effectively protecting the metal workpiece from even local corrosion during the electrochemical surface treatment process, wherein the low-conductive or non-conductive hydrophobic liquid is well deposited on the surface of the treated workpiece during the surface treatment due to its fine dispersion in the conductive hydrophilic liquid of the continuous phase and can produce an anti-corrosion protection effect. On the other hand, the low-conductive or non-conductive hydrophobic liquid of the dispersed phase can adjust the conductivity and pH value of the electrolyte medium according to the present invention by changing its fraction (ratio).

[0014] Compared to conventional electrolyte media, which comprise a hydrophilic conductive liquid on the one hand and a hydrophobic, non-conductive or less conductive liquid on the other hand, but as a single-phase solution, as is the case, for example, with WO 2007 / 121999 A2 or EP 2646 603 B1 mentioned at the outset of this document, the electrolyte medium according to the invention has the following advantages: it can be used for the surface treatment of workpieces made of almost any conductive metallic material, wherein the low-conductive or non-conductive hydrophobic liquid in the dispersed phase can provide more effective corrosion protection for the workpiece, while the conductive hydrophilic liquid in the continuous phase can have a high conductivity and thus ensure efficient surface treatment. Compared to electrolyte media in which the conductive hydrophilic liquid as the actual electrolyte is only absorbed in the pores of the porous granular particles and the void volume between the granular particles has an immiscible non-conductive hydrophilic liquid (see the aforementioned ES 2904 576 A1) or even an "oil-in-water emulsion" with a conductive hydrophilic liquid as a dispersed phase in an immiscible non-conductive hydrophilic liquid as a continuous phase (see the aforementioned WO 2022 / 123096 A1), the electrolyte medium according to the invention offers the following advantages: in addition to being easier to manufacture in terms of processing technology, it can, in particular, significantly shorten processing times and reduce energy consumption, since the conductive hydrophilic liquid in the continuous phase ensures lower resistance.

[0015] Furthermore, it should be pointed out that, in the sense of the present invention, the term "electrochemical polishing" includes electrochemical smoothing and electrochemical brightening.

[0016] The average droplet size of the hydrophobic liquid of the dispersed phase of the emulsion of the liquid electrolyte can be adjusted within a wide range, in particular by the type and amount of suitable emulsifiers (see below), that is, the emulsion can be essentially a macroemulsion with an average droplet size of more than about 1 µm to about 1 mm, or a microemulsion with an average droplet size of less than about 1 µm, or a nanoemulsion with an average droplet size of less than about 100 nm. Emulsions of liquid electrolytes that do not necessarily have to be essentially monodisperse can be produced in the known manner, for example by applying shear forces to the inhomogeneous mixture, for example by means of known rotor-stator systems, high-pressure emulsifiers, etc., or by dispersing the inhomogeneous mixture using microporous membranes, etc.

[0017] The conductive hydrophilic liquid of the continuous phase of the emulsion of the liquid electrolyte may preferably contain at least one liquid from the group of polar organic solvents, in particular the group of alcohols, and / or water. Examples of preferred alcohols include monohydric alcohols, such as phenoxyethanol, and in particular dihydric or polyhydric alcohols, such as ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, propane-1,2,3-triol (glycerol), etc., including mixtures thereof.

[0018] In order to adjust the conductivity and pH value, the conductive hydrophilic liquid of the continuous phase of the emulsion of the liquid electrolyte also preferably contains at least one acid. Examples of preferred acids include inorganic acids such as sulfuric acid (H2SO4), sulfurous acid (H2SO3), hydrochloric acid (HCl), hydrofluoric acid (HF), phosphoric acid (H3PO4), nitric acid (HNO3), nitrous acid (HNO2), etc.; and organic acids such as oxalic acid (C2H2O4), citric acid (C6H8O7), sulfonic acid, preferably methanesulfonic acid (CH4O3S), ethanesulfonic acid (C2H6O3S), benzenesulfonic acid (C6H6O3S) and its sulfonate, etc., including mixtures thereof.

[0019] The hydrophobic liquid of the dispersed phase of the emulsion of the liquid electrolyte preferably comprises at least one liquid from the group of hydrocarbons, in particular aliphatic, and / or silicone oils. Examples of preferred hydrocarbons include those having 10 to 20 carbon atoms, preferably 12 to 16 carbon atoms, in particular in the form of alkanes, alkanes including isoalkanes and cycloalkanes, and mixtures thereof. Preferred exemplary silicone oils include those having a carbon number in the range of about 1 to about 2×10 6 Silicone oils of viscosity between cSt, in particular in the form of polydimethylsiloxane.

[0020] In a preferred embodiment, it can be provided that the fraction of the dispersed phase of the emulsion is between about 15% by mass and about 70% by mass, in particular between about 25% by mass and about 60% by mass, for example between about 30% by mass and about 60% by mass, based on the entire emulsion consisting of both the continuous phase and the dispersed phase.

[0021] In order to ensure a stable emulsion of the liquid electrolyte and in particular to prevent the emulsified droplets of the dispersed phase of the non-conductive or low-conductive hydrophobic liquid from coalescing in the continuous phase, the emulsion should appropriately contain at least one emulsifier, in particular from the group of surfactants as surface-active substances.

[0022] Examples of preferred emulsifiers include those from the following groups: alkoxylated alcohols having at least 8 carbon atoms, in particular at least 10 carbon atoms, such as ethoxylated isotridecyl alcohol or n-tridecyl alcohol, secondary fatty alcohol ethoxylates (polyalkyl glycol ethers), (2-methoxymethylethoxy)propanol, etc.; sulfonic acids and sulfonates thereof having at least 8 carbon atoms, in particular at least 10 carbon atoms, such as alkylsulfonic acids and sulfonates thereof, preferably decane, undecane, dodecane and tridecanesulfonic acid, alkylbenzenesulfonates, isopropylbenzenesulfonates, sodium and potassium sulfonates, preferably sodium p-isopropylbenzenesulfonate, potassium p-isopropylbenzenesulfonate, etc., sulfonated benzene-1,1-oxybistetrapropyl derivatives (sodium salts), etc.; and alanine salts, such as sodium N-(2-carboxyethyl)-N-(2-ethylhexyl)-β-alaninate, etc.

[0023] The HLB value of the at least one emulsifier is suitably between about 8 and about 18, in particular between about 9 and about 16. The abovementioned amounts for the HLB value (hydrophile-lipophile balance) of an emulsifier, in particular in the form of a surfactant, relate here to the calculation method according to Griffin, according to which the HLB value is defined as follows:

[0024]

[0025] Where M1: the molar mass of the hydrophobic (lipophilic) part of the emulsifier molecule; and

[0026] M: molar mass of the entire molecule of the emulsifier.

[0027] Emulsifiers in the form of surfactants that usually form "oil-in-water" emulsions have an HLB value of 8 to 18, wherein according to the present invention, an HLB value of 9 to 16 has proven to be particularly suitable for emulsifying a relatively high volume fraction, for example greater than about 70% by volume, of a hydrophobic or oleophilic dispersed phase in a conductive hydrophilic or oleophobic continuous phase, thereby forming a highly concentrated emulsion.

[0028] Furthermore, it is conceivable, for example, that the emulsion of the liquid electrolyte also contains at least one additive, in particular from the group of dyes, in order to make the (dispersed / continuous) phase visually more recognizable, or optionally, for example, also a defoamer.

[0029] For the electrolyte medium according to the invention, in principle any known solid granular particles for polishing and grinding of metal workpieces can be used, including those of the above-mentioned type. Here, in particular granular particles made of polymer materials have proven to be advantageous, which have a lower hardness than mineral and metal materials and can be particularly round in shape, preferably substantially spherical, and / or have an average particle size between about 10µm and about 5 mm, preferably between about 100µm and about 1 mm. The polymer material of the granular particles should have good acid resistance in view of the usually acidic environment of the emulsion of the liquid electrolyte (see below) and should have good oxidation resistance in view of the electrochemical polishing process. In a preferred embodiment, the solid granular particles can also be selected from the group of ion exchange polymers, wherein it can in principle be any ion exchange polymer, but preferably a cation exchange polymer, which is able to absorb the released metal ions during the electrochemical polishing of the metal workpiece. Examples of advantageous ion exchange polymers include copolymers of styrene with sulfonated ethylstyrene and / or with sulfonated divinylbenzene, acrylic resins with acrylic acid and / or methacrylic acid units, etc.

[0030] Furthermore, the solid granular particles can be dense or also porous and / or gel exchangers, as is often the case with the above-mentioned polymer materials during the manufacturing process. If porous granular particles are used which usually have residual water in the pores due to the manufacturing process, the residual water can mix with the (polar) continuous phase of the emulsion of the liquid electrolyte or dissolve almost infinitely therein.

[0031] As previously mentioned, in an advantageous embodiment, the liquid electrolyte has

[0032] a pH value between about 1 and about 7, in particular between about 2 and about 7, preferably between about 3 and about 7; and

[0033] a conductivity between about 0.05 mS / cm and about 5 mS / cm, in particular between about 0.1 mS / cm and about 3 mS / cm, preferably between about 0.2 mS / cm and about 3 mS / cm; and

[0034] A density between about 0.92 g / ml and about 1.04 g / ml, in particular between about 0.96 g / ml and about 1.00 g / ml.

[0035] In addition, the volume ratio between the solid granular particles and the emulsion of the liquid electrolyte should be selected so that the liquid electrolyte can substantially completely fill the cavity volume of the granular particles, and the workpiece moving relative to the granular particles in the electrolyte medium can be substantially completely wetted by the emulsion of the liquid electrolyte. For example, depending on the average particle size of the granular particles, the volume ratio between the granular particles and the emulsion of the liquid electrolyte can be between about 80 volume % to 20 volume % to about 40 volume % to 60 volume %, in particular between about 75 volume % to 25 volume % to about 45 volume % to 65 volume %.

[0036] In the method for electrochemical polishing of a metal workpiece according to the present invention, an electrolyte medium of the above type is added to a container and electrically connected to a cathode, wherein the metal workpiece is electrically connected to an anode and immersed in the electrolyte medium in the container, wherein a voltage is applied to the electrodes, and the workpiece is moved relative to a plurality of solid granular particles of the electrolyte medium, and the relative movement of the workpiece relative to the solid granular particles can be carried out in any known manner, such as the manner commonly used in conventional drag-type or immersion polishing methods. With regard to this relative movement of the workpiece relative to the solid granular particles during the surface treatment process, for example, the following manners may be used:

[0037] Rotational movement of the workpiece and / or the container, in particular a rotational movement substantially about an axis of symmetry of the workpiece and / or the container; and / or

[0038] a translational movement of the workpiece relative to the container, in particular substantially in the form of a trajectory; and / or

[0039] Vibration excitation of the workpiece and / or container, for example by ultrasound, piezoelectric drives, unbalanced drives (eccentric drives), etc.

[0040] In order to prevent damage to the workpieces due to collisions with one another and / or with the walls of the container, it is advantageous to clamp the metal workpieces on workpiece holders which are movable relative to the container and which also allow for easy electrical contacting of the (corresponding) workpieces.

[0041] Advantageously, provision can also be made for the emulsion of the electrolyte medium, in particular its continuous phase, to be selected to be chemically and electrochemically inert with respect to the metallic material of the workpiece to be electrochemically polished. DETAILED DESCRIPTION

[0042] The following are specific embodiments of the electrolyte medium according to the present invention, which are only used for illustration and do not constitute a limitation to the present invention:

[0043] Embodiment 1:

[0044] (a) Granular particles :

[0045] 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;

[0046] (b) Electrolytes :

[0047] Continuous phase (hydrophilic, conductive):

[0048] 49% by mass of ethylene glycol and glycerol as polar solvents,

[0049] 11% by mass of benzenesulfonic acid, C10-C13-secondary alkyl derivatives as acid;

[0050] Dispersed phase (hydrophobic, non-conductive):

[0051] 32% by mass of aliphatic hydrocarbon mixture in the form of C12 to C16 alkanes, isoalkanes and cycloalkanes;

[0052] Emulsifier (surfactant):

[0053] 7% by mass of alcohol ethoxylates, such as ethoxylated isotridecanol and secondary alcohol ethoxylates;

[0054] additive:

[0055] 1 mass% defoamer.

[0056] Embodiment 2:

[0057] (a) Granular particles :

[0058] 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;

[0059] (b) Electrolytes :

[0060] Continuous phase (hydrophilic, conductive):

[0061] 19 mass% ethylene glycol as polar solvent,

[0062] 10% by mass of an alkylsulfonic acid, such as methanesulfonic acid as the acid;

[0063] Dispersed phase (hydrophobic, non-conductive):

[0064] 61% by mass of a mixture of aliphatic hydrocarbons in the form of C12 to C16 alkanes, isoalkanes and cycloalkanes;

[0065] Emulsifiers (surfactants):

[0066] 10% by mass of alcohol ethoxylate, for example ethoxylated isotridecanol.

[0067] Embodiment 3:

[0068] (a) Granular particles :

[0069] 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;

[0070] (b) Electrolytes :

[0071] Continuous phase (hydrophilic, conductive):

[0072] 23 mass% ethylene glycol and water as polar solvents,

[0073] 5% by mass of alkylsulfonic acid, for example C10 to C13 sulfonic acid as acid,

[0074] 4 mass% inorganic acid;

[0075] Dispersed phase (hydrophobic, non-conductive):

[0076] 58% by mass of aliphatic hydrocarbon mixture in the form of C12 to C16 alkanes, isoalkanes and cycloalkanes;

[0077] Emulsifiers (surfactants):

[0078] 10% by mass alcohol ethoxylate, such as ethoxylated isotridecanol

Claims

1. Electrolyte medium for electrochemical polishing of metal workpieces, comprising (a) a plurality of solid granular particles, and (b) liquid electrolyte, It is characterized in that The liquid electrolyte is an emulsion having a continuous phase composed of at least one conductive hydrophilic liquid and a dispersed phase composed of at least one hydrophobic liquid immiscible with the conductive hydrophilic liquid and having lower conductivity than the hydrophilic liquid, emulsified in the continuous phase.

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

3. The electrolyte medium according to claim 1 or 2, characterized in that The electrically conductive, hydrophilic liquid of the continuous phase of the emulsion further comprises at least one acid.

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

5. The electrolyte medium according to any one of claims 1 to 4, characterized in that The fraction of the dispersed phase of the emulsion is between 15% and 70% by mass, in particular between 25% and 60% by mass, based on the total emulsion.

6. The electrolyte medium according to any one of claims 1 to 5, characterized in that The emulsion further comprises at least one emulsifier, in particular an emulsifier from the group of surfactants.

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

8. The electrolyte medium according to claim 6 or 7, characterized in that The at least one emulsifier has an HLB value of between 8 and 18, in particular between 9 and 16.

9. The electrolyte medium according to any one of claims 1 to 8, characterized in that The solid granular particles are made of polymer material, in particular ion exchange polymer.

10. The electrolyte medium according to any one of claims 1 to 9, characterized in that The solid granular particles are porous and / or gel exchangers.

11. The electrolyte medium according to any one of claims 1 to 10, characterized in that The liquid electrolyte has: a pH value between about 1 and about 7, in particular between about 2 and about 7; and / or A conductivity between about 0.05 mS / cm and about 5 mS / cm, in particular between about 0.1 mS / cm and about 3 mS / cm; and / or A density between about 0.92 g / ml and about 1.04 g / ml, in particular between about 0.96 g / ml and about 1.00 g / ml.

12. A method for electrochemically polishing a metal workpiece, wherein the electrolyte medium according to any one of claims 1 to 11 is added to a container and electrically connected to a cathode, wherein the metal workpiece is electrically connected to an anode and immersed in the electrolyte medium in the container, wherein a voltage is applied to the electrodes and the workpiece is moved relative to a plurality of solid granular particles of the electrolyte medium.

13. The method according to claim 12, characterized in that The relative movement of the metal workpiece relative to the electrolyte medium in the container is performed by at least one of the following relative movements: a rotational movement of the workpiece and / or the container, in particular a rotational movement substantially about an axis of symmetry of the workpiece and / or the container, translational motion of the workpiece relative to the container, and Vibration excitation of workpieces and / or containers.

14. The method according to claim 12 or 13, characterized in that The metal workpiece is clamped on a workpiece holder which is movable relative to the container.

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

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