Electrolyte solution

Abstract

An electrolyte solution is provided for electrochemical processing. The electrolyte solution includes a substantially anhydrous ionic solvent, an ionizable material in the form of an inorganic salt, and a viscosity modifier. The electrolyte has a viscosity in the range of 1 to 50 mPa.s at 20°C.

Description

Technical Field

[0001] The present disclosure relates to electrolyte solutions and electrochemical machining processes.

Background Art

[0002] Electrochemical machining, such as electrochemical jet machining, is a process for selectively machining the surface of a workpiece. This is done by applying a voltage between a part of an electrochemical machining apparatus, such as a nozzle, and the surface to be machined while supplying a jet or spray of electrolyte towards the surface from the nozzle. By this machining method, the surface can be machined by an electrochemical reaction such that the surface can be machined as long as the surface material is conductive. This machining process enables roughening and, for example, improves the bondability / adhesion of parts or surface coatings. This machining can modify the optical and / or tribological properties of the surface and can also polish the material surface.

[0003] In electrochemical processing techniques, a processing medium (i.e., an electrolyte solution) is required to enable ion migration. This ion migration enables material to be added to or removed from the target surface.

[0004] These processing media have conventionally been aqueous electrolytes. However, these pose a problem when used in some electrochemical machining processes because they form a passivated surface on some metals and alloys such as titanium and steel during the electrochemical machining process. This can lead to a decrease in machining accuracy and a decrease in the ability to texture their surfaces in a repetitive manner.

[0005] Existing non-aqueous electrolyte solutions typically have a high viscosity and are used in tank-type electrochemical machining systems. Such electrolyte solutions are not suitable for being sprayed towards the surface of the workpiece because of their high viscosity. These conventional non-aqueous electrolyte solutions have been limited to applications such as metal deposition and metal polishing because the conductivity of these solutions is generally low (deposition and polishing require only low current density levels compared to electrochemical machining processes).

Summary of the Invention

[0006] This technology aims to overcome or at least mitigate one or more problems related to the prior art.

[0007] A first aspect is an electrolyte solution for electrochemical machining treatment, the electrolyte solution comprising a substantially anhydrous ionic solvent, an ionizing material in the form of an inorganic salt, and a viscosity modifier, and providing an electrolyte solution having a viscosity in the range of 1 to 50 mPa·s at 20 °C.

[0008] The viscosity modifier may include an aqueous inorganic salt solution.

[0009] The viscosity modifier may be a concentrated aqueous inorganic salt solution.

[0010] The viscosity modifier may be a saturated aqueous inorganic salt solution.

[0011] The concentration of the saturated solution may be at or near the saturation point of the aqueous inorganic salt solution. The concentration of the aqueous inorganic salt solution may generally be at the saturation point.

[0012] The concentration of the aqueous inorganic salt solution may be in the range of 80 - 100% of the concentrated solution. The concentration of the aqueous inorganic salt solution may be in the range of 90 - 100% of the concentrated solution. The concentration of the aqueous inorganic salt solution may be in the range of 95 - 100% of the concentrated solution.

[0013] The aqueous inorganic salt solution may have a molar concentration in the range of 0.1 M to 5 M. The aqueous inorganic salt solution may have a molar concentration in the range of 1 M to 5 M.

[0014] The concentration of the viscosity modifier in the aqueous electrolyte solution may be less than 50% by weight. Optionally, the concentration of the viscosity modifier in the aqueous electrolyte solution is in the range of 20 - 40% by weight, for example, about 30% by weight.

[0015] The concentration of the substantially anhydrous ionic solvent can be at least 50% by weight, optionally at least 60% by weight, for example, about 70% by weight.

[0016] The ionizing material can comprise a compound of the formula MX. M can be Na + , K + , Ca 2+ , Mg 2+ , Cu 2+ and Zn 2+ or can be selected from these combinations. X can be F - , Cl - , Br - , I - , NO3 - and SO4 2- or can be selected from these combinations.

[0017] The substantially anhydrous ionic solvent can contain a polyol.

[0018] The substantially anhydrous ionic solvent can be selected from ethylene glycol, glycerol, methanol, ethanol, 1-propanol, 2-propanol, and / or propylene glycol.

[0019] The substantially anhydrous ionic solvent can be selected from ethylene glycol and / or glycerol.

[0020] The substantially anhydrous ionic solvent can contain a quaternary ammonium salt.

[0021] The quaternary ammonium salt can be selected from one or more of choline chloride, tetraethylammonium chloride, and / or tetramethylammonium chloride.

[0022] The substantially anhydrous solvent can be a deep eutectic solvent containing ethylene glycol and choline chloride.

[0023] The substantially anhydrous ionic solvent can have a ratio of choline chloride to ethylene glycol in the range of 1:2 to 1:5.

[0024] The substantially anhydrous ionic solvent can have a ratio of choline chloride to ethylene glycol of about 1:3.

[0025] The pH of the electrolyte solution can be in the range of 5 to 9.

[0026] The electrolyte solution can have a viscosity in the range of 5 to 30 mPa·s at 20°C. Optionally, the electrolyte solution has a viscosity in the range of 10 to 15 mPa·s at 20°C.

[0027] The electrolyte solution can have a conductivity of at least 10 mS / cm.

[0028] The electrolyte solution can have a conductivity in the range of 10 mS / cm to 40 mS / cm. Optionally, the electrolyte solution has a conductivity in the range of 20 mS / cm to 30 mS / cm.

[0029] A second aspect provides an electrochemical machining process for machining the surface of a workpiece using an electrochemical machining apparatus comprising a nozzle configured to supply an injection of an electrolyte solution towards the surface of the workpiece, the electrochemical machining process comprising the steps of: supplying an injection of any of the above electrolyte solutions from the nozzle of the electrochemical machining apparatus towards the surface of the workpiece; and applying a charge to the nozzle of the electrochemical machining apparatus and to the surface of the workpiece such that the nozzle and the surface define the first and second electrodes of an electrolytic cell.

[0030] The process can apply a current density in the range of 400 A / cm 2 to the following current density, optionally 150 A / cm 2 and below, optionally 100 A / cm 2 and below, for example, 25 to 100 A / cm 2 .

[0031] Embodiments will now be described with reference to the accompanying drawings.

Brief Description of the Drawings

[0032]

Figure 1

Figure 2

Mode for Carrying Out the Invention

[0033] The present teachings relate to electrolyte solutions for the electrochemical machining, polishing, and / or etching of metals.

[0034] The electrolyte solution can be discharged (e.g., sprayed) from a nozzle toward the surface of the workpiece and has a sufficiently high electrolytic conductivity to transmit a “high” current (e.g., greater than 1 A) through the nozzle. The nozzle can be, for example, a circular nozzle of 1 mm. In an alternative configuration, the nozzle can be configured as a substantially rectangular nozzle having, for example, a width of at least 5 mm or 10 mm and a depth of about 0.2 mm. It should be understood that the size and geometry of the nozzle can be varied to suit the application.

[0035] It has been found that the electrolyte solution of the present teachings produces little passivation of the metal surface (e.g., titanium, titanium alloy, steel, iron, etc.) during electrochemical machining, thereby enabling the production of a visually smooth machined surface when compared to a water-salt electrolyte.

[0036] One embodiment of the electrolyte solution is for use in a substantially anhydrous ionic solvent, an ionizing material in the form of an organic salt, and a viscosity modifier.

[0037] The electrolyte solution has a viscosity in the range of 1 to 50 mPa·s at 20°C. The electrolyte solution can have a viscosity in the range of 5 to 40 mPa·s at 20°C, often in the range of 5 to 30 mPa·s at 20°C, often in the range of 5 to 20 mPa·s at 20°C, often in the range of 10 to 15 mPa·s at 20°C, often in the range of 15 to 20 mPa·s at 20°C.

[0038] A substantially anhydrous ionic solvent can be regarded as an anhydrous solvent. A substantially anhydrous solvent can include a solvent having a small amount of water. For example, a substantially anhydrous solvent can contain up to 1 wt% of water, often up to 0.5 wt% of water, for example, up to 0.1 wt% of water (i.e., in the range of 0 - 1 wt%, often 0.01 - 0.5 wt%, or 0.05 - 0.1 wt%).

[0039] A substantially anhydrous ionic solvent can be a polyol. Polyols that are particularly suitable for use in an electrochemical machining electrolyte solution are ethylene glycol and glycerol or a combination thereof.

[0040] In one embodiment, the substantially anhydrous solvent contains ethylene glycol. Since the viscosity of ethylene glycol at room temperature is lower than that of other possible solvents, ethylene glycol can be more easily sprayed towards the surface of the workpiece. The substantially anhydrous solvent can contain one or more of glycerol, methanol, ethanol, 1 - propanol, 2 - propanol, and / or propylene glycol.

[0041] In other embodiments, the substantially anhydrous solvent contains a combination of ethylene glycol and glycerol. The ratio of ethylene glycol to glycerol can be about 50:50 by weight%, often 70:30 by weight%, often 90:10 by weight%, often 95:5 by weight%.

[0042] A substantially anhydrous ionic solvent can further contain a quaternary ammonium salt. The inclusion of a quaternary ammonium salt in a substantially anhydrous solvent has been found to improve the solubility of the salt in the substantially anhydrous solvent.

[0043] A substantially anhydrous ionic solvent can contain one or more of choline chloride, tetraethylammonium chloride, and / or tetramethylammonium chloride.

[0044] The substantially anhydrous ionic solvent may include a combination of ethylene glycol and choline chloride. That is, the substantially anhydrous ionic solvent may be a deep eutectic solvent.

[0045] The substantially anhydrous ionic solvent may contain a ratio of polyol to quaternary ammonium salt in the range of 1:2 to 1:5. In many cases, the ratio of polyol to quaternary ammonium salt is in the range of 1:3 to 1:4, and in many cases it is 1:3 to 1:4. The substantially anhydrous ionic solvent has a ratio of polyol to quaternary ammonium salt of about 1:3, but in many cases, this ratio can be 1:2, 1:4 or 1:5 or a ratio in between.

[0046] The substantially anhydrous ionic solvent may have a ratio of choline chloride to ethylene glycol in the range of 1:2 to 1:5. In many cases, the ratio of choline chloride to ethylene glycol is in the range of 1:3 to 1:4, and in many cases it is 1:3 to 1:4. The substantially anhydrous ionic solvent has a ratio of choline chloride to ethylene glycol of about 1:3, but in many cases, this ratio can be 1:2, 1:4 or 1:5 or a ratio in between. [Table 1]

[0047] Table 1 shows the conductivity of various compositions of the substantially anhydrous ionic solvent. It was found that the conductivity of the substantially anhydrous ionic solvent is too low for effective processing of the surface of the workpiece in electrochemical jet machining.

[0048] The electrolyte solution for the electrochemically machined surface also contains an ionized material in the form of an inorganic salt. The addition of an inorganic salt to the electrolyte solution increases its conductivity and thus helps to promote ion transfer during electrochemical machining.

[0049] The electrolyte solution contains a viscosity modifier. This is provided to keep the viscosity of the electrolyte solution within a specific range in order to facilitate the spraying of the electrolyte solution towards the surface of the workpiece (for example, from the nozzle of an electrochemical machining device). In an embodiment, the electrolyte solution has a viscosity in a predetermined range of 1 to 50 mPa·s at 20 °C.

[0050] The viscosity modifier consists of an aqueous-salt solution. By using an aqueous-salt solution as the viscosity modifier, it has been found that while the viscosity of the electrolyte solution decreases, the concentration of the ionized material in the electrolyte solution increases (and thus the conductivity of the solution increases).

[0051] The ionized material in the electrolyte solution includes an inorganic salt compound of the formula MX. M is selected from Na + , K + , Ca 2+ , Mg 2+ , Cu 2+ and Zn 2+ or a combination thereof. X is selected from F - , Cl - , Br - , I - , NO 3- and SO4 2- or a combination thereof. M is often a Group I metal such as Na + or K + , and X is often a halogen such as F - , Cl - , Br - , I - .

[0052] The aqueous-salt solution in the electrolyte solution is a concentrated solution. The concentration of the saturated solution is at or near the saturation point of the aqueous inorganic salt solution. It should be understood that the saturation point of the aqueous-salt solution may depend on the salt used.

[0053] The concentration of the aqueous inorganic salt solution can be in the range of 80 - 100% of the concentrated solution, often in the range of 90 - 100% of the concentrated solution, and often in the range of 95 - 100% of the concentrated solution. In other words, the concentration of the aqueous inorganic salt solution can be in the range of 80 - 100% of the concentration point of the aqueous inorganic salt solution, often in the range of 90 - 100% of the concentration point of the aqueous inorganic salt solution, and often in the range of 95 - 100% of the concentration point of the aqueous inorganic salt solution.

[0054] By defining the concentration of the viscosity modifier at or near the saturation point, the water content of the electrolyte solution can be minimized while maximizing the concentration of the salt in the electrolyte solution. Also, by using the aqueous solution concentration at or near the saturation point (e.g., below it), a stable solution is provided in which precipitation of the salt from the solution is prevented / minimized. This enables the salt solution to maintain a stable state during storage. This also helps prevent the introduction of useless fine particles in the solution that can be harmful to the injection of the electrolyte solution.

[0055] In one configuration, the water - salt solution in the electrolyte solution has a molar concentration in the range of 0.1M - 5M, often in the range of 1M - 5M. Often, the molar concentration can be, for example, in the range of 1M - 4M. The molar concentration can be about 3M (e.g., in the range of 2.5M - 3.5M or 2.9M - 3.1M), but often the molar concentration is 1M, often 2M, often 4M, or often 5M.

[0056] As described above, when aqueous electrolyte solutions are used in some electrochemical processing treatments, they can be a problem because they form a passive surface on some metals and alloys such as titanium and steel during the electrochemical processing. Therefore, even when a water - salt viscosity modifier is used in the electrolyte solution, the water content of the electrolyte solution should be limited in order to be considered substantially anhydrous.

[0057] The concentration of the viscosity modifier in the electrolyte solution (and thereby the concentration of water in the electrolyte solution) is generally less than 50% by weight. In other words, the concentration of the water-salt solution in the electrolyte solution is generally less than 50% by weight. In some embodiments, the concentration of the viscosity modifier in the electrolyte solution can be in the range of 0 to 50% by weight, often 0.1 to 50% by weight, often 1 to 50% by weight, often 10 to 50% by weight, and often 20 to 50% by weight.

[0058] It has been found that electrochemical processing carried out using an electrolyte containing more than 50% by weight of the viscosity modifier begins to face problems associated with conventional water-salt electrolyte solutions.

[0059] Often, the concentration of the viscosity modifier in the electrolyte solution (and thereby the concentration of water in the electrolyte solution) is less than 40% by weight. In other words, the concentration of the water-salt solution in the electrolyte solution is less than 40% by weight. In some embodiments, the concentration of the viscosity modifier in the electrolyte solution can be in the range of 0 to 40% by weight, often 0.1 to 40% by weight, often 1 to 40% by weight, often 10 to 40% by weight, and often 20 to 40% by weight.

[0060] Often, the concentration of the viscosity modifier in the electrolyte solution (and thereby the concentration of water in the electrolyte solution) is less than 30% by weight. In other words, the concentration of the water-salt solution in the electrolyte solution is less than 30% by weight. In some embodiments, the concentration of the viscosity modifier in the electrolyte solution can be in the range of 0 to 30% by weight, often 0.1 to 30% by weight, often 1 to 30% by weight, often 10 to 30% by weight, and often 20 to 30% by weight.

[0061] Often, the concentration of the viscosity modifier in the electrolyte solution (and thereby the concentration of water in the electrolyte solution) is less than 20% by weight. In other words, the concentration of the water-salt solution in the electrolyte solution is less than 20% by weight. In some embodiments, the concentration of the viscosity modifier in the electrolyte solution can be in the range of 0 to 20% by weight, often 0.1 to 20% by weight, often 1 to 20% by weight, and often 10 to 20% by weight.

[0062] In many cases, the concentration of the viscosity modifier in the electrolyte solution (and thus the concentration of water in the electrolyte solution) is less than 10 wt%. In other words, the concentration of the water-salt solution in the electrolyte solution is less than 10 wt%. In some embodiments, the concentration of the viscosity modifier in the electrolyte solution can be in the range of 0 to 10 wt%, often 0.1 to 10 wt%, often 1 to 10 wt%, often 5 to 10 wt%.

[0063] When the electrolyte solution is defined in terms of the weight percentage of the viscosity modifier, it should be understood that the remainder of the electrolyte solution is provided substantially by the anhydrous ionic solvent and the ionized material.

[0064] The concentration of the substantially anhydrous ionic solvent can be at least 50 wt%, often at least 60 wt%, often at least 70 wt%, often at least 75 wt%, often at least 80 wt%.

[0065] The concentration of the substantially anhydrous ionic solvent can be at least 50 wt%. In other words, the concentration of the substantially anhydrous ionic solvent can be in the range of 50 to 99 wt%, often 50 to 95 wt%, often 50 to 90 wt%, often 50 to 80 wt%, often 50 to 70 wt%, often 50 to 60 wt%.

[0066] The concentration of the substantially anhydrous ionic solvent can be at least 60 wt%. In other words, the concentration of the substantially anhydrous ionic solvent can be in the range of 60 to 99 wt%, often 60 to 95 wt%, often 60 to 90 wt%, often 60 to 80 wt%, often 60 to 70 wt%.

[0067] The concentration of the substantially anhydrous ionic solvent can be at least 70 wt%. In other words, the concentration of the substantially anhydrous ionic solvent can be in the range of 70 to 99 wt%, often 70 to 95 wt%, often 70 to 90 wt%, often 70 to 80 wt%.

[0068] The concentration of the substantially anhydrous ionic solvent can be at least 80% by weight. In other words, the concentration of the substantially anhydrous ionic solvent can be in the range of 80 to 99% by weight, often in the range of 80 to 95% by weight, and often in the range of 80 to 90% by weight.

[0069] The concentration of the substantially anhydrous ionic solvent can be at least 90% by weight. In other words, the concentration of the substantially anhydrous ionic solvent can be in the range of 90 to 99% by weight, often in the range of 90 to 95% by weight.

[0070] The conductivity of these electrolyte solutions is related to i) the amount of dissolved inorganic salts and ii) the viscosity. The addition of ionized materials in the aqueous viscosity modifier to the electrolyte solution increases the room-temperature electrolyte conductivity of the electrolyte solution by i) increasing the dissolved salt content and ii) decreasing the viscosity. It should be understood that increasing the temperature of the electrolyte solution decreases the viscosity and increases the conductivity. Therefore, increasing the temperature enables a reduction in the viscosity modifier and enables a reduction in the amount of water added to the electrolyte solution to obtain equivalent conductivity / viscosity.

[0071] For suitability for electrochemical jet machining processes, the electrolyte solution can usefully have a high conductivity. The electrolyte solution generally has a conductivity of at least 10 mS / cm, often in the range of 10 mS / cm to 80 mS / cm, often in the range of 10 mS / cm to 70 mS / cm, often in the range of 10 mS / cm to 60 mS / cm, often in the range of 10 mS / cm to 50 mS / cm, often in the range of 10 mS / cm to 40 mS / cm, often in the range of 15 mS / cm to 35 mS / cm, and often in the range of 20 mS / cm to 30 mS / cm.

[0072] To maintain the sustainability of electrochemical spraying / processing of the surface of a workpiece in an industrial environment, the electrolyte should not be a strongly toxic and / or strongly acidic / alkaline solution for it to be useful. This also makes it possible to maintain the electrolyte solution as a solution with a low environmental load. The electrolyte may be substantially neutral. In other words, the pH of the electrolyte solution can be in the range of 5 to 9 or 6 to 8.

Example

[0073] Table 2 shows the conductivity of various compositions of a substantially anhydrous ionic solvent. To increase the conductivity of the substantially anhydrous ionic solvent, an ionizing material was added to the substantially anhydrous ionic solvent consisting of a choline chloride:ethylene glycol solution in a ratio of 1:3.

[0074] A viscosity modifier containing an aqueous sodium chloride solution with a concentration of 4M was added to the choline chloride:ethylene glycol solution. The concentration of the viscosity modifier was varied from 0 wt% to 10 wt%, 20 wt%, 30 wt%, 40 wt% and 50 wt%. Table 2 shows the conductivity of the electrolyte solution with the varied concentration of the viscosity modifier.

Table 2

[0075] A viscosity modifier consisting of an aqueous sodium chloride solution with a concentration of 4M was added to the choline chloride:ethylene glycol solution. The concentration of the viscosity modifier was varied in 10 wt% increments from 0 wt% to 100 wt%. Table 3 shows the viscosity at room temperature of the electrolyte solution with the varied concentration of the viscosity modifier.

Table 3

Example

[0076] A further example of an electrolyte solution for electrochemical processing has the following relative concentrations. Ethylene glycol: 40% by weight, choline chloride: 30% by weight, viscosity modifier: 30% (consisting of 24.3% by weight of water and 5.7% by weight of sodium chloride)

[0077] This electrolyte solution has been found to be particularly advantageous when machining a titanium surface.

Example

[0078] A further example of an electrolyte solution for electrochemical machining processes has the following relative concentrations. A substantially anhydrous ionic solvent comprising ethylene glycol in the range of 50 - 55% by weight and choline chloride in the range of 40 - 45% by weight

[0079] The electrolyte solution may further comprise a viscosity modifier in the form of an aqueous inorganic salt solution. The aqueous inorganic salt solution may be in the range of 0.1% - 50% by weight.

[0080] The salt may be sodium nitrate. Sodium nitrate may be up to 5% (in the range of 0.1 - 5% by weight) of the electrolyte solution.

[0081] Referring to FIGS. 1 and 2, an electrochemical machining apparatus 10 for performing an electrochemical machining process on the surface 12 of a workpiece is shown.

[0082] The electrochemical machining apparatus 10 includes a base unit 14 and a hand-held machining unit 16. The base unit 14 and the machining unit 16 are connected via an umbilical cord 18 through which the base unit 14 can supply power and electrolyte to the machining unit 16.

[0083] The machining unit 16 is designed to be operated manually (as shown in FIG. 1) or as part of an automated process or remotely.

[0084] Referring to FIG. 2, the machining unit 16 is shown positioned on the surface 12 of the workpiece.

[0085] The processing unit 16 includes a housing 22. A nozzle 24 is positioned within the housing 22, and the nozzle 24 is configured to supply an electrolyte jet 26 towards the surface 12 of the workpiece. In this configuration, the nozzle defines an area of 1 mm 2 , but it should be understood that the nozzle area can be changed to suit the application. As shown, the housing 22 is configured to define an enclosed working space when positioned relative to the surface 12 of the workpiece.

[0086] The electrochemical machining apparatus 10 is configured to apply an electric charge to the nozzle 24 and the surface 12. Thus, the nozzle 24 and the surface 12 correspond to the first and second electrodes of the electrolytic cell. In an alternative configuration, the processing unit 16 may include an additional electrode independent of the nozzle, and the electrochemical machining apparatus may be configured to apply an electric charge to the additional electrode and the surface 12.

[0087] The electrochemical machining apparatus 10 is intended to be used by an operator who performs an electrochemical machining process to machine the surface of the workpiece. The machining process may include i) supplying an electrolyte solution jet from the nozzle of the electrochemical machining apparatus towards the surface of the workpiece according to any of the above, and ii) applying an electric charge to the nozzle of the electrochemical machining apparatus and applying an electric charge to the surface of the workpiece such that the nozzle and the said surface define the first and second electrodes of the electrolytic cell.

[0088] The electrochemical machining process may apply a current density of 400 A / cm 2 or less. The electrochemical machining process may apply a current density of 150 A / cm 2 or less. In many cases, the electrochemical machining process is from 10 A / cm 2 to 400 A / cm 2 , often from 10 A / cm 2 to 150 A / cm 2 , often from 10 A / cm 2 to 100 A / cm 2 , often from 25 A / cm 2 to 100 A / cm 2 , often from 25 A / cm2 ~75 A / cm 2 and often 40 A / cm 2 ~60 A / cm 2 in the range, often about 50 A / cm 2 of current density can be applied.

[0089] Conventionally, reducing the current density would result in a deterioration of the surface quality of the machined surface. On the other hand, by using the electrolyte solution as described above in the electrochemical machining process, it has been found that a visually smooth polished surface can be obtained by applying a current density of 50 A / cm 2 .

[0090] The electrochemical machining apparatus can be configured to apply a potential of less than 500 V. Often, the electrochemical machining apparatus can apply a potential in the range of 1 V to 500 V.

[0091] By supplying the electrolyte through the nozzle 24 and spraying it towards the surface 12, material removal and deposition are realized. When a potential is applied between the nozzle 24 and the surface 12, anodic dissolution of the surface 12 or deposition onto the surface 12 is brought about.

[0092] In the operation of the first mode, a negative charge is applied to the nozzle 24 and a positive charge is applied to the surface 12. In the operation of this first mode, the apparatus 10 etches the surface 12 to modify its topography. In the operation of the second mode, a positive charge is applied to the nozzle 24 and a negative charge is applied to the surface 12. In the operation of this second mode, materials (for example, silica particles or additive coatings that enable surface functionalization, etc.) can be deposited onto the surface 12, which modifies its surface topography.

[0093] Nozzle 24 is disposed within housing 22 so as to be spaced apart from surface 12 during use. The distance between electrode (nozzle) 24 and workpiece surface 12 (i.e., the electrode gap) affects the treatment of surface 12. Nozzle 24 is movable within housing 22 such that the distance between nozzle 24 and surface 12 can be adjusted to suit a particular machining operation.

[0094] To enable application of charge to nozzle 24 and surface 12, base unit 14 includes a power source 32 for supplying power to machining unit 16 via umbilical cord 18. It should be understood that power source 32 may include one or more batteries for supplying power to machining unit 16 or may be connectable to an external power source.

[0095] Although the electrochemical jet treatment of a material surface has been described with reference to the electrochemical machining apparatus shown in FIGS. 1 and 2, it should be understood that the electrolyte solution described above can be utilized in any suitable electrochemical machining apparatus configured to supply an injection of electrolyte solution towards the surface.

[0096] Although the teachings have been described with reference to one or more embodiments, it should be understood that various changes or modifications can be made without departing from the scope of the invention as defined in the claims that follow.

Claims

1. An electrolyte solution for electrochemical machining treatment, A substantially anhydrous ionic solvent, and An ionizing material in the form of an inorganic salt, and A viscosity modifier, and comprising The substantially anhydrous ionic solvent contains up to 1% by weight of water, The viscosity modifier contains an aqueous inorganic salt solution, The electrolyte solution having a viscosity in the range of 5 to 30 mPa·s at 20 °C.

2. The electrolyte solution according to claim 1, wherein the aqueous inorganic salt solution has a molar concentration in the range of 0.1 M to 5 M.

3. The electrolyte solution according to claim 1 or 2, wherein the concentration of the viscosity modifier in the electrolyte solution is less than 50% by weight, and optionally, the concentration of the viscosity modifier in the electrolyte solution is in the range of 20 to 40% by weight, for example, about 30% by weight.

4. The electrolyte solution according to any one of claims 1 to 3, wherein the concentration of the substantially anhydrous ionic solvent is at least 50% by weight, optionally at least 60% by weight, for example, about 70% by weight.

5. The ionizing material contains a compound of the formula MX, where M is Na ＋ , K ＋ , Ca ２＋ , Mg ２＋ , Cu ２＋ and Zn ２＋ or a combination thereof, and X is F － , Cl － , Br － , I － , NO ３ － and SO ４ ２－ or a combination thereof, the electrolyte solution according to any one of claims 1 to 4.

6. The substantially anhydrous ionic solvent contains a polyol, and optionally, the substantially anhydrous solvent is selected from ethylene glycol, glycerol, methanol, ethanol, 1-propanol, 2-propanol, and / or propylene glycol. The electrolyte solution according to any one of claims 1 to 5.

7. The substantially anhydrous ionic solvent is selected from ethylene glycol and / or glycerol. The electrolyte solution according to claim 6.

8. The substantially anhydrous ionic solvent contains a quaternary ammonium salt, and optionally, the quaternary ammonium salt is selected from one or more of choline chloride, tetraethylammonium chloride, and / or tetramethylammonium chloride. The electrolyte solution according to any one of claims 1 to 7.

9. The substantially anhydrous ionic solvent is a deep eutectic solvent containing ethylene glycol and choline chloride. The electrolyte solution according to any one of claims 1 to 8.

10. The substantially anhydrous ionic solvent has a ratio of choline chloride to ethylene glycol in the range of 1:2 to 1:5, and optionally, the substantially anhydrous ionic solvent has a ratio of choline chloride to ethylene glycol of about 1:

3. The electrolyte solution according to claim 9.

11. The pH of the electrolyte solution is in the range of 5 to 9. The electrolyte solution according to any one of claims 1 to 10.

12. The electrolyte solution has a viscosity in the range of 10 to 15 mPa·s at 20°C. The electrolyte solution according to any one of claims 1 to 11.

13. The electrolyte solution has a conductivity of at least 10 mS / cm. The electrolyte solution according to any one of claims 1 to 12.

14. The electrolyte solution has a conductivity in the range of 10 mS / cm to 40 mS / cm, and optionally, the electrolyte solution has a conductivity in the range of 20 mS / cm to 30 mS / cm, the electrolyte solution according to claim 13.

15. An electrochemical machining process for machining the surface of a workpiece using an electrochemical machining apparatus comprising a nozzle configured to supply an injection of an electrolyte solution towards the surface of the workpiece, supplying an injection of the electrolyte solution according to any one of claims 1 to 14 from a nozzle of the electrochemical machining apparatus towards the surface of the workpiece; applying a charge to the nozzle of the electrochemical machining apparatus and applying a charge to the surface of the workpiece such that the nozzle and the surface define the first and second electrodes of an electrolytic cell; An electrochemical machining process comprising.

16. The process applies a current density of 400 A / cm ２ or less, optionally 150 A / cm ２ or less, optionally 100 A / cm ２ or less, for example, in the range of 25 to 100 A / cm ２ The electrochemical machining process according to claim 15.

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