Electrolyte medium and method for electrochemical polishing of metal workpieces using such an electrolyte medium

Abstract

The invention relates to an electrolyte medium for electrochemical polishing of metal workpieces, which on the one hand contains a plurality of solid granulate particles and on the other hand contains a liquid electrolyte. According to the invention, the liquid electrolyte comprises an emulsion with a continuous phase of at least one electrically conductive hydrophilic liquid and, emulsified herein, a disperse phase of at least one hydrophobic liquid which is immiscible with the electrically conductive hydrophilic liquid and is less electrically conductive by comparison. The invention additionally relates to a method for electrochemical polishing of metal workpieces, wherein an electrolyte medium of the aforementioned kind is added to a container and electrically conductively connected to a cathode, the metal workpiece being electrically conductively connected to an anode and being dipped into the electrolyte medium located in the container, the electrodes being acted on by an electrical voltage and the workpiece being moved relative to the plurality of solid granulate particles of the electrolyte medium.

Description

[0001]Electrolyte medium and method for the electrochemical polishing of metallic workpieces using such an electrolyte medium. The invention relates to an electrolyte medium for the electrochemical polishing of metallic workpieces, which contains a plurality of solid granulate particles and a liquid electrolyte. The invention further relates to a method for the electrochemical polishing of metallic workpieces, wherein such an electrolyte medium is added to a container and electrically conductively connected to a cathode, wherein the metallic workpiece is electrically conductively connected to an anode and immersed in the electrolyte medium located in the container, wherein the electrodes are subjected to an electrical voltage and the workpiece is moved relative to the plurality of solid granulate particles of the electrolyte medium.For the surface treatment of workpieces, so-called drag finishing processes are known in which the workpiece is immersed in a bed of solid grinding or polishing granulate particles located in a container and is moved relative to the bed of granulate particles. Drag finishing machines are usually used here. These represent a special form of vibratory grinding machines in which the workpieces to be machined are releasably secured, for example, individually or to one or more clamping devices of a workpiece holder of the machine in order to polish or grind them as a result of the relative movement in relation to the bed of granulate particles. Such drag finishing machines often comprise a generally rotating part, essentially in the form of aA plate driven by a motor via a suitable gear, to which the workpiece holders are attached directly or indirectly, for example via lifting devices. This occurs particularly eccentrically with respect to the axis of rotation of the rotating part of the drag finishing machine. If this part - the so-called plate - of the drag finishing machine rotates, the workpiece holders attached to it describe a trajectory curve. The workpieces, carried by the clamping devices of the workpiece holders, are immersed in the container, which is filled with the bulk of the granulate particles, often with the addition of liquid processing media such as water, surfactants, etc. Due to the relative movement of the workpieces in relation to the granulate, their surface treatment takes place in the form of vibratory grinding. Such drag finishing machines are known, for example, from DE 102 04 267 C1, DE 20005 361 U1 or DE 102010 052 222 A1.Alternatively or additionally, the container holding the granulate particles can be moved relative to the workpieces, which are also moving, for example, rotating at least around their own axis, or even stationary, such as around its own axis and / or along a curved path, e.g., in the form of a circular path. If only the container is moving and the workpieces themselves do not perform any translational movement, this is also referred to as "plunge grinding" or "plunge polishing," a special form of drag finishing. Such machines, in which the workpiece holder supporting the workpiece is essentially stationary during surface treatment, are also referred to as dip finishing machines. The granulate particles can, in principle, be of a very different nature depending on the workpieces to be treated, e.g., of natural origin (e.g., organic material such as walnut or coconut shells, wood, cherry pits, etc.).), mineral origin (e.g. silicates, oxides, etc.) and / or synthetic origin (e.g. plastics). In addition, as already indicated, it is known to carry out vibratory finishing dry or - with the addition of a liquid processing medium, such as water, which may contain additives such as surfactants - in the form of wet processing. In order to ensure a rotary movement of the workpieces, such as around their own axis, as an alternative or in addition to a translational movement of the workpieces relative to the granulate particles, which leads to even more effective surface processing, the workpiece holders of known drag finishing machines are often rotationally driven, which can be achieved, for example, by means of suitable motors (see, for example, DE 102010 052 222 A1).In addition, workpiece holders for drag finishing machines are known, the clamping devices of which are rotatably mounted for releasably securing the workpieces and can be set in rotation via a shaft rotatably mounted in the workpiece holder. For this purpose, the workpiece holder has, for example, a planetary gear with a central sun gear, which engages with planetary gears, which in turn are non-rotatably connected to a support shaft of a respective clamping lock, which are arranged distributed around the circumference of the sun gear of the workpiece holder. Due to such a movement of the clamping devices rotatably mounted on the workpiece holder with the workpieces, which consists of a translational movement (in the direction of rotation of the support part or the "plate" of the drag finishing machine) and a rotational movement (around the axis of the respective clamping device oraround the workpiece axis), the processing medium achieves a uniform processing quality with shorter processing times compared to a purely translational movement. Furthermore, alternatively or additionally, the workpiece holder itself can be rotatably mounted on the support part of the drag finishing machine in a corresponding manner (cf., for example, DE 202009 008 070 U1). Furthermore, conventional drag finishing processes for polishing or grinding metallic workpieces of the aforementioned type have been further developed into electrochemical polishing processes in that, on the one hand, the metallic workpiece is electrically conductively connected to a positive electrode (anode), and, on the other hand, the granulate particles flooded with a liquid electrolyte are electrically conductively connected to a negative electrode (cathode). The electrodes are subjected to an electrical voltage and the workpiece, e.g.in the manner described above, relative to the majority of solid granulate particles. The surface quality of the machined workpieces can often be improved in this way, with such electrochemical polishing also representing an abrasive surface treatment process. If the electrodes are subjected to an electrical voltage by means of a voltage source, in addition to the purely mechanical surface treatment of the metallic workpieces, a current flow occurs due to the electrical conductivity of the liquid electrolyte, which ensures the superficial, anodic removal of the metallic workpieces. The electrodes can be supplied with either direct current or pulsed voltages.The workpieces are usually moved in the electrolyte solution to ensure the desired relative movement of the solution to the solid granulate particles and to keep any concentration gradient that develops on the surface of the workpieces as low as possible. The selection of a suitable liquid electrolyte is an important parameter here, although it has been shown that some electrolytes which lead to perfect electropolishing on one metal have virtually no effect on another or result in a rough, jagged or dull surface. For example, strong inorganic acids, particularly phosphoric acid and sulfuric acid, which may be mixed with alcohols, are conventionally used to electropolish aluminum and steel. A mixture of phosphoric acid and alcohols, for example, is suitable for copper and brass.WO 2007 / 121999 A2 describes a liquid electrolyte in the form of an electrolyte solution intended for electropolishing metallic workpieces and a method for electrochemically polishing workpieces by means of such a liquid electrolyte solution, wherein the electrolyte solution contains alkylbenzenesulfonic acid or alkylbenzenesulfonates, ie salts or derivatives thereof, a petroleum fraction having 17 to 35 carbon atoms and optionally small amounts of ethanolamine. EP 2646 603 B1 discloses an improved liquid electrolyte solution for the electrochemical polishing of metallic workpieces, in particular made of copper, zinc, silver, tin, gold or their alloys, as well as a method for electrochemical polishing using such an electrolyte solution, which contains ethoxylated alcohols, sulfonic acids and / or sulfonates, inorganic acids and liquid hydrocarbons as well as water.In addition, electrolyte media have recently been proposed for the electrochemical polishing of metallic workpieces, which, on the one hand, comprise a plurality of solid, porous, polymer-based granulate particles and, on the other hand, a liquid electrolyte made of an electrically conductive, hydrophilic liquid, in particular from the group of strong inorganic acids and sulfonic acids. However, the liquid electrolyte is exclusively absorbed in the pores of the granulate particles and a gas or air atmosphere is otherwise present in the hollow space of the granulate particles (cf., 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).However, due to the current flow induced only at specific points as a result of contact between a particular granulate particle and the workpiece to be machined, surface processing of the workpieces in this way is very time-consuming. ES 2904 576 A1 describes another electrolyte medium for the electrochemical polishing of metallic workpieces, which also comprises, on the one hand, a plurality of solid, porous, polymer-based granulate particles and, on the other hand, a liquid, water-based electrolyte absorbed in the pores of the granulate particles. Instead of a gas atmosphere present in the hollow volume of the granulate particles, a non-electrically conductive liquid, e.g., based on silicones or hydrocarbons, that is immiscible with the aqueous electrolyte is provided.With regard to the disadvantages, the above statement regarding the gas atmosphere in the hollow volume of the granulate particles applies, although the preparation of the electrolyte medium also proves to be complex. A similar electrolyte medium for the electrochemical polishing of metallic workpieces can be found in WO 2022 / 123096 A1, which, on the one hand, comprises a plurality of solid, porous, polymer-based granulate particles and, on the other hand, a liquid electrolyte based on water or diluted acids, which is absorbed into the pores of the granulate particles. The non-electrically conductive liquid, e.g. based on silicones or hydrocarbons, which is immiscible with the aqueous electrolyte and is not miscible with the aqueous electrolyte, in the void volume of the granulate particles, can in this case be either homogeneous or formed as a continuous phase of a "water-in-oil emulsion" in which droplets of the aqueous electrolyte are emulsified as a disperse phase.The invention is based on the object of developing an electrolyte medium for the electrochemical polishing of metallic workpieces of the type mentioned above in a simple and cost-effective manner, while at least largely avoiding the aforementioned disadvantages, in such a way that the surface treatment time is reduced and the efficiency of electropolishing is thus improved, while ensuring a perfect surface quality of the electropolished workpieces and avoiding even local corrosion of the same. It is further directed to a method for the electrochemical polishing of metallic workpieces of the type mentioned above using such an electrolyte medium.The first part of this object is achieved according to the invention in an electrolyte medium for the electrochemical polishing of metallic workpieces, which contains a plurality of solid granulate particles and a liquid electrolyte, in that the liquid electrolyte has an emulsion with a continuous phase of at least one electrically conductive, hydrophilic liquid and a disperse phase emulsified therein of at least one hydrophobic liquid which is immiscible with the electrically conductive, hydrophilic liquid and, in contrast, has a lower electrical conductivity.In terms of process engineering, the invention further provides a method for electrochemical polishing of metallic workpieces to achieve this object, wherein an electrolyte medium of the aforementioned type is added to a container and electrically conductively connected to a cathode, wherein the metallic workpiece is electrically conductively connected to an anode and immersed in the electrolyte medium located in the container, wherein the electrodes are subjected to an electrical voltage and the workpiece is moved relative to the plurality of solid granulate particles of the electrolyte medium.The liquid electrolyte of the electrolyte medium according to the invention is therefore formed from an "oil-in-water emulsion" whose - polar - continuous phase of at least one electrically conductive, hydrophilic (lipophobic) liquid represents the actual electrolyte, which serves to produce an electrical current flow between the anode (positive electrode) connected to the metallic workpiece and the cathode (negative electrode) connected to the electrolyte medium.In this way, due to the relatively high electrical conductivity of the electrolyte medium, effective and time-efficient surface treatment of the metallic workpieces with high surface quality and relatively low energy consumption is possible, since the electrically conductive, hydrophilic liquid present in the hollow volume of the solid granulate particles acts as a polar, continuous phase of the liquid electrolyte - similar to an electrolyte solution - and 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 disperse phase emulsified in the aforementioned continuous phase and consisting of at least one hydrophobic (lipophilic) liquid which is immiscible with the electrically conductive, hydrophilic liquid and has a lower electrical conductivity, and which in particular can also be substantially non-electrically conductive, serves on the one hand to effectively protect the metallic workpieces from even local corrosion during electrochemical surface treatment, wherein the less or non-electrically conductive, hydrophobic liquid, due to its finely dispersed distribution in the electrically conductive, hydrophilic liquid of the continuous phase, is able to deposit well on the surface of the workpieces being treated during surface treatment and to exert an anti-corrosive protective effect. On the other hand, the less ornon-electrically conductive, hydrophobic liquid of the disperse phase by varying its proportion to adjust the electrical conductivity and the pH of the electrolyte medium according to the invention. Compared to conventional electrolyte media, which contain, on the one hand, hydrophilic, electrically conductive liquids and, on the other hand, hydrophobic, electrically non-conductive or less conductive liquids, but as a single-phase solution, as is the case, for example, with WO 2007 / 121999 A2 or EP 2646 603 B1 mentioned above, the electrolyte medium according to the invention has the advantage that it can be used for surface treatment of workpieces made of practically any electrically conductive metal materials, wherein the less orA non-electrically conductive, hydrophobic liquid in the dispersed phase can offer the workpieces more effective corrosion protection, while the electrically conductive, hydrophilic liquid in the continuous phase can possess high electrical conductivity and thus ensures efficient surface treatment. Compared to an electrolyte medium in which the electrically conductive hydrophilic liquid, as the actual electrolyte, is absorbed exclusively in the pores of the porous granulate particles, and the void volume between the granulate particles is filled with an immiscible, electrically non-conductive hydrophilic liquid (cf. the above-cited ES 2904 576 A1) or with a "water-in-oil emulsion" of the electrically conductive hydrophilic liquid as the dispersed phase in the immiscible, electrically non-conductive hydrophilic liquid as the continuous phase (cf.The above-cited WO 2022 / 123096 A1) provides the electrolyte medium according to the invention with the advantage that, in addition to being easier to manufacture in terms of handling, it also ensures significantly shorter processing times with lower energy requirements, since the electrically conductive hydrophilic liquid of the continuous phase ensures lower electrical resistance. It should also be noted at this point that the term "electrochemical polishing" within the meaning of the present invention includes electrochemical smoothing and electrochemical brightening. The average droplet size of the hydrophobic liquid of the disperse phase of the emulsion of the liquid electrolyte can be adjusted within wide limits, in particular by the type and amount of suitable emulsifiers (see below).The emulsion can basically be a macroemulsion with an average droplet size of greater than about 1 µm up to about 1 mm, 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. The emulsion of the liquid electrolyte, which does not necessarily have to be essentially monodisperse, can be produced in a manner known as such, for example by introducing shear forces into the inhomogeneous mixture, e.g. by means of known rotor-stator systems, high-pressure emulsifiers or the like, by dispersing the inhomogeneous mixture using microporous membranes, etc.The electrically 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 from the group of alcohols, and / or water. Examples of advantageous alcohols include monohydric alcohols, such as phenoxyethanol, and in particular dihydric or polyhydric alcohols, such as glycols, in particular ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, propane-1,2,3-triol (glycerol), and the like, including mixtures thereof. To adjust the electrical conductivity and the pH, the electrically conductive, hydrophilic liquid of the continuous phase of the liquid electrolyte emulsion preferably further contains at least one acid. Examples of advantageous acids include both inorganic acids, such asSulfuric acid (H2SO4), sulfurous acid (H2SO4), hydrochloric acid (HCl), hydrofluoric acid (HF), phosphoric acid (H3PO4), nitric acid (HNO3), nitrous acid (HNO2) and the like, as well as organic acids such as oxalic acid (C2H2O4), citric acid (C6H8O7), sulfonic acids, preferably methanesulfonic acid (CH4O3S), ethanesulfonic acid (C2H6O3S), benzenesulfonic acid (C6H6O3S) including their sulfonates, and the like including mixtures thereof. The hydrophobic liquid of the disperse phase of the emulsion of the liquid electrolyte can preferably contain at least one liquid from the group of, in particular aliphatic, hydrocarbons and / or silicone oils. Examples of advantageous hydrocarbons include those having 10 to 20 carbon atoms, preferably having 12 to 16 carbon atoms, in particular in the form of alkanes including iso- and cycloalkanes and mixtures thereof.Examples of advantageous silicone oils include those having a viscosity between about 1 and about 2 x 10. 6cSt, in particular in the form of polydimethylsiloxanes. In an advantageous embodiment, the proportion of the disperse phase of the emulsion can be between approximately 15 mass% and approximately 70 mass%, in particular between approximately 25 mass% and approximately 60 mass%, for example between approximately 30 mass% and approximately 60 mass%, based on the total emulsion consisting of both continuous and disperse phases. In order to ensure a stable emulsion of the liquid electrolyte and in particular to prevent coalescence of the emulsified droplets of the disperse phase of the non- or slightly electrically conductive hydrophobic liquid in the continuous phase, the emulsion expediently further contains at least one emulsifier, in particular from the group of surfactants as surface-active substances.Examples of advantageous emulsifiers include those from the group of alkoxylated alcohols having at least 8 carbon atoms, in particular having at least 10 carbon atoms, such as ethoxylated iso- or n-tridecanol, secondary fatty alcohol ethoxylates (polyalkylene glycol ethers), (2-methoxymethylethoxy)propanol and the like, sulfonic acids having at least 8 carbon atoms, in particular having at least 10 carbon atoms, including their sulfonates, such as alkylsulfonic acids and sulfonates, preferably decane-, undecane-, dodecane- and tridecanesulfonic acid, alkylbenzenesulfonate, cumenesulfonate, sodium and potassium sulfonates, preferably sodium p-cumenesulfonate, potassium p-cumenesulfonate, etc., benzene-1,1-oxybis-tetrapropylene derivatives sulfonated (sodium salt) and the like, as well as Alaninates, such as sodium N-(2-carboxyethyl)-N-(2-ethylhexyl)-beta-alaninate and the like.The HLB value of the at least one emulsifier is advantageously between about 8 and about 18, in particular between about 9 and about 16. The above-mentioned amounts of the HLB value (hydrophilic-lipophilic balance) of the emulsifier, in particular in the form of surfactants, relate to the Griffin calculation method, according to which the HLB value is defined as follows:. where M l: Molar mass of the hydrophobic (lipophilic) portion of the emulsifier molecules; and M : Molar mass of the total emulsifier molecules. Emulsifiers in the form of surfactants, which form "oil-in-water" emulsions, generally have an HLB value of 8 to 18, whereby, according to the invention, an HLB value of 9 to 16 has proven particularly suitable for emulsifying relatively high volume fractions, e.g., greater than about 70 vol.%, of the disperse - hydrophobic or lipophilic - phase in the - electrically conductive, hydrophilic or lipophobic - continuous phase, thereby forming a highly concentrated emulsion. Furthermore, it is conceivable, for example, that the emulsion of the liquid electrolyte further contains at least one additive, in particular from the group of dyes, in order to make the (disperse / continuous) phases more visually recognizable, or optionally also the defoamer, for example.In principle, any known granulate particles known for polishing or grinding metallic workpieces, including those of the type mentioned above, can be considered as solid granulate particles for the electrolyte medium according to the invention. Granulate particles made of polymer materials have proven particularly advantageous in this regard, which have a lower hardness than mineral and metallic materials and in particular can have a rounded shape, preferably essentially spherical, and / or an average particle diameter between approximately 10 µm and approximately 5 mm, preferably between approximately 100 µm and approximately 1 mm.The polymer materials of the granulate particles should be advantageously acid-resistant, given the typically acidic environment of the liquid electrolyte emulsion (see also below), and advantageously oxidation-resistant, given the electrochemical polishing process. In an advantageous embodiment, the solid granulate particles can also be selected from the group of ion-exchange polymers, which are in principle any ion-exchange polymers, but preferably cationic ion-exchange polymers capable of absorbing metal ions released during the electrochemical polishing of the metallic workpieces. 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, and the like.Furthermore, the solid granulate particles can be compact or porous and / or gel exchangers, as is often the case with the aforementioned polymer materials due to their manufacturing process. If porous granulate particles are used, which usually contain residual water in the pores due to their manufacturing process, the residual water can mix with the (polar) continuous phase of the liquid electrolyte emulsion or dissolve in it virtually indefinitely.As already indicated, in an advantageous embodiment the liquid electrolyte has - 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 / or - an electrical 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 / 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. Furthermore, the volume ratio between the solid granulate particles and the emulsion of the liquid electrolyte should be selected such that the latter essentially completely fills the void volume of the granulate particles and a workpiece moving in the electrolyte medium relative to the granulate particles is essentially completely wetted by the emulsion of the liquid electrolyte.Thus, depending on the average particle diameter of the granulate particles, the volume ratio between the granulate particles and the emulsion of the liquid electrolyte can be, for example, between approximately 80 vol.% to 20 vol.% up to approximately 40 vol.% to 60 vol.%, in particular between approximately 75 vol.% to 25 vol.% up to approximately 45 vol.% to 65 vol.%.In the method according to the invention for the electrochemical polishing of metallic workpieces, according to which an electrolyte medium of the type described above is added to a container and electrically conductively connected to a cathode, wherein the metallic workpiece is electrically conductively connected to an anode and immersed in the electrolyte medium located in the container, wherein the electrodes are subjected to an electrical voltage and the workpiece is moved relative to the plurality of solid granulate particles of the electrolyte medium, the relative movement of the metallic workpiece with respect to the solid granulate particles can take place in any known manner, as is known, for example, in conventional drag or immersion finishing processes.As far as such a relative movement of the workpiece with respect to the solid granulate particles during surface treatment is concerned, this can therefore be, for example, - a rotational movement of the workpiece and / or the container, in particular substantially around an axis of symmetry of the workpiece and / or the container; and / or - a translational movement of the workpiece with respect to the container, in particular substantially in the form of a trajectory curve; and / or - a vibration excitation of the workpiece and / or the container, e.g. by means of ultrasound, piezo actuators, unbalance drives or the like.Furthermore, to avoid damage to the workpieces caused by collisions with each other and / or the container wall, it may be advantageous if the metallic workpiece is clamped to a workpiece holder that is movable relative to the container and also allows for easy electrical contact with the (respective) workpiece. Furthermore, it may advantageously be provided that the emulsion of the electrolyte medium, in particular its continuous phase, is selected to be chemically and electrochemically inert with respect to the metallic material of the workpiece to be electropolished.The following are exemplary embodiments of electrolyte media according to the invention, which serve merely as illustrations and do not limit the invention: Example 1: (a) Granulate particles: porous polymer particles with an average particle diameter of approximately 500 µm and / or approximately 1 mm made of ion exchange resin based on copolymers of styrene and sulfonated ethylstyrene; (b) Electrolyte: Continuous phase (hydrophilic, electrically conductive): - 49 mass% ethylene glycol and glycerol as polar solvents, - 11 mass% benzenesulfonic acid, C10-C13 sec-alkyl derivatives as acid; Disperse phase (hydrophobic, not electrically conductive): - 32 mass% aliphatic hydrocarbon mixture in the form of C12 to C16 alkanes, isoalkanes and cycloalkanes; Emulsifier (surfactant): - 7 mass% alcohol ethoxylates, e.g. ethoxylated iso-tridecanol and secondary alcohol ethoxylates; Additives: - 1 mass% defoamer.Example 2: (a) Granule particles: porous polymer particles with an average particle diameter of approximately 500 µm and / or approximately 1 mm made from ion exchange resin based on copolymers of styrene and sulfonated ethylstyrene; (b) Electrolyte: Continuous phase (hydrophilic, electrically conductive): - 19 mass% ethylene glycol as polar solvent, - 10 mass% alkylsulfonic acid, e.g. methanesulfonic acid, as acid; Disperse phase (hydrophobic, not electrically conductive): - 61 mass% aliphatic hydrocarbon mixture in the form of C12 to C16 alkanes, isoalkanes and cycloalkanes; Emulsifier (surfactant): - 10 mass% alcohol ethoxylates, e.g. ethoxylated isotridecanol. Example 3: (a) Granule particles: porous polymer particles with an average particle diameter of approximately 500 µm and / or approximately 1 mm made of ion exchange resin based on copolymers of styrene and sulfonated ethylstyrene; (b) Electrolyte: continuous phase (hydrophilic, electrically conductive): - 23 mass.-% ethylene glycol and water as polar solvents; - 5 mass% alkylsulfonic acid, e.g. C10- to C13-sulfonic acids, as acid; - 4 mass% inorganic acid; Disperse phase (hydrophobic, not electrically conductive): - 58 mass% aliphatic hydrocarbon mixture in the form of C12- to C16-alkanes, iso-alkanes and cycloalkanes; Emulsifier (surfactant): - 10 mass% alcohol ethoxylates, e.g. ethoxylated iso-tridecanol.

Claims

Patent claims 1. An electrolyte medium for electrochemically polishing metallic workpieces, comprising: (a) a plurality of solid granulate particles and (b) a liquid electrolyte, characterized in that the liquid electrolyte comprises an emulsion with a continuous phase of at least one electrically conductive, hydrophilic liquid and a disperse phase emulsified therein of at least one hydrophobic liquid that is immiscible with the electrically conductive, hydrophilic liquid and, in contrast, has a lower electrical conductivity.

2. An electrolyte medium according to claim 1, characterized in that the electrically 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.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 contains at least one acid.

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

5. Electrolyte medium according to one of claims 1 to 4, characterized in that the proportion of the disperse phase of the emulsion is between 15% by mass and 70% by mass, in particular between 25% by mass and 60% by mass, based on the entire emulsion.

6. Electrolyte medium according to one of claims 1 to 5, characterized in that the emulsion further contains at least one emulsifier, in particular from the group of surfactants.

7. 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, sulfonic acids having at least 8 carbon atoms, sulfonates and alaninates.

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.Electrolyte medium according to one of claims 1 to 8, characterized in that the solid granulate particles are made of polymer materials, in particular from the group of ion-exchanging polymers.

10. Electrolyte medium according to one of claims 1 to 9, characterized in that the solid granulate particles. porous and / or gel exchangers.

11. The electrolyte medium according to one of claims 1 to 10, characterized in that the liquid electrolyte has - a pH value between 1 and 7, in particular between 2 and 7; and / or - an electrical conductivity between 0.05 mS / cm and 5 mS / cm, in particular between 0.1 mS / cm and 3 mS / cm; and / or - a density between 0.92 g / ml and 1.04 g / ml, in particular between 0.96 g / ml and 1.00 g / ml. 12.A method for the electrochemical polishing of metallic workpieces, wherein the electrolyte medium according to one of claims 1 to 11 is applied to a container and electrically conductively connected to a cathode, wherein the metallic workpiece is electrically conductively connected to an anode and immersed in the electrolyte medium located in the container, wherein the electrodes are subjected to an electrical voltage and the workpiece is moved relative to the plurality of solid granulate particles of the electrolyte medium.

13. The method according to claim 12, characterized in that the relative movement of the metallic workpiece with respect to the electrolyte medium located in the container is achieved by at least one relative movement from the group - rotational movement of the workpiece and / or the container, in particular substantially about an axis of symmetry of the workpiece and / or the container;. - translational movement of the workpiece relative to the container; and - vibration excitation of the workpiece and / or the container.

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

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

Images