Surface finishing of complex geometries by turboflow

Abstract

An assembly for surface finishing, comprising: a container comprising at least one electrically conductive device arranged at least partially inside the container; an electric source providing an electric potential difference between at least one surface to be treated and the at least one electrically conductive device; and at least one apparatus for providing relative turbulent motion between free electrically charged conductive solid bodies of a fluid when arranged inside the container and the at least one surface for surface finishing the at least one surface by ion transport. Also, a method and solid-particle based electrolyte for surface finishing and a surface finished according to the described finishing system.

Description

[0001] SURFACE FINISHING OF COMPLEX GEOMETRIES BY TURBOFLOW

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to the field of surface finishing. More particularly, the disclosure relates to homogeneous surface finishing of parts with different sizes and shapes.

[0004] BACKGROUND

[0005] In the field of surface finishing, achieving a uniform, high-quality finish on parts of varying shapes and sizes presents a significant challenge. Surface finishing processes, such as polishing, are commonly used to improve the aesthetics, functionality, and durability of parts by creating smooth, defect-free surfaces. However, the diversity in geometries, contours, and dimensions of the parts being treated makes it difficult to utilize a single, flexible polishing system that can provide homogeneous results across different applications.

[0006] Traditional polishing methods often require specialized equipment, tools, or configurations for each type of part or application. For example, complex or irregular surfaces may demand custom tooling, while larger or smaller parts might necessitate different polishing media, techniques, or machines. This lack of versatility complicates the finishing process and increases production time and cost, as operators need to adjust or replace equipment for different tasks. Additionally, inconsistent surface finishes may result when the polishing system is not adequately adapted to the specific shape or size of the part, leading to quality issues such as uneven gloss, texture variations, or defects like scratches.

[0007] Traditional dry electropolishing methods that use electrically conductive solid bodies are effective in delivering good results in terms of surface finish and homogeneity. However, these methods lack flexibility and require specific fine-tuning and configurations for each application. This makes them less adaptable, especially when dealing with large parts or complex geometries. Their limitations become evident in scenarios where specialized setups are needed, often hindering their ability to provide efficient and consistent results across diverse shapes and sizes.

[0008] Given these challenges, there is a strong need in the market for a flexible surface finishing system based on dry electrolytes that can accommodate parts of various shapes and sizes while consistently delivering a homogeneous, mirror-like finish. This system should be adaptable enough to work on a wide range of materials and geometries without compromising on the quality of the surface finish. Such a system would provide manufacturers with greater efficiency, lower costs, and improved product quality, while reducing the need for multiple specialized tools or machines.

[0009] The present disclosure addresses this need by providing a system, method, or assembly designed to achieve uniform surface finishes, regardless of the geometry, dimensions, or material properties of the part and of at least one surface thereof to be treated. This system, method and assembly aim to offer a flexible, high-performance solution for surface finishing that ensures consistent results across a wide range of applications.

[0010] SUMMARY

[0011] The present disclosure provides an assembly and a method for surface finishing along with an electrolyte to carry out suitable for the assembly and the method that utilizes free electrically conductive solid bodies in an electrolytic medium, combined with turbulent motion, to achieve a uniform, high-quality surface finish. The disclosure addresses the need for a flexible surface finishing system capable of adapting to various part shapes and sizes, offering consistent results even for components presenting complex geometries.

[0012] In the context of the present disclosure, dry electrolytes, solid-particle based electrolyte, polishing medium, electrolytic medium and electrolytes based solid particles that are conductive because they retain an electrolyte liquid, these terms mean the same and will be used interchangeably along the description.

[0013] In the context of the present disclosure solid particles, conductive particles, solid electrolyte particles, solid bodies, electrically conductive free solid bodies, these terms mean the same and will be used interchangeably along the description.

[0014] In the context of the present disclosure a fluid, a fluid that includes solid particles, a medium, liquid medium, environment, liquid medium environment, surrounding liquid, a medium on the interstitial space or gaps, these terms mean the same and will be used interchangeably along the description.

[0015] In the context of the present disclosure, surface finishing may involve altering the condition of a surface, such as changes to roughness, waviness, gloss, presence of oxides, surface tension, residual stresses, coatings, heterogeneities, contaminants, or substances adhering to at least one surface of the container being treated. As a result, surface finishing may include, but is not limited to, processes such as smoothing, polishing, rounding, deburring, corrosion protection, electrodeposition of metallic ions, modifications in surface chemistry, surface morphology or geometry alterations, relieving residual stress, passivation, or any other alterations in corrosion properties, modification of surface tension, cleaning, and sterilization of the surface. In certain embodiments, the surface finishing process may be carried out through an electrochemical system employing solid particlebased electrolytes. In such configurations, the solid particle-based electrolyte comprises solid or semi-solid bodies that retain or encapsulate an electrolyte liquid, thereby making them galvanically active while maintaining structural integrity. The solid particles serve both as carriers of ionic species and as active agents in the electrochemical reactions occurring at the workpiece surface. The system can be configured such that the relative motion between the solid electrolyte particles and the workpiece surface facilitates localized electrochemical activity and mechanical action, allowing for precise control of surface modification.

[0016] For example, in electropolishing, the workpiece acts as the anode, and the solid particles are moved relative to the surface to promote uniform anodic dissolution, resulting in a smooth and bright finish. In deburring, a similar configuration is employed, but the process parameters are adjusted to increase the aggressiveness or abrasiveness of the particles; higher current densities may be used to concentrate the galvanic action on surface peaks, and controlled motion of the particles can be directed toward burrs for selective removal. In electrodeposition, the workpiece is configured as the cathode, and metallic ions from the solid electrolyte are reduced and deposited on the surface under the influence of the electric field. For passivation, the system parameters, such as applied voltage, current density, liquid electrolyte retained by the solid particles’ composition, and pH, are tuned according to the material being treated to form a stable, protective oxide or conversion layer, thus enhancing corrosion resistance.

[0017] The present disclosure relates to an advanced surface finishing method, solidparticle based electrolyte and assembly, capable of achieving a wide range of surface modifications, such as smoothing, polishing, precision finishing, deburring, rounding, and removing oxides or contaminants. This system allows for various enhancements, including changes in surface roughness, gloss, tension, and residual stresses, while also offering corrosion resistance, surface passivation, and chemical or morphological modifications. The disclosure is applicable to a wide range of surfaces, including those made from materials such as steel, stainless steel, copper, titanium, nickel, metal matrix composites and aluminum alloys.

[0018] A surface-treated part as described herein may encompass, without limitation, articles of any size, geometry, or functional application. Such parts may include structural or functional components such as tubular elements, stamped or molded pieces, sheet or laminar products, frames, housings, and assemblies employed in sectors including but not limited to transportation, construction, energy, consumer goods, and industrial manufacturing. Suitable materials may comprise metals and alloys (for example, aluminum, stainless steel, carbon steel, cast iron), as well as any other substrate capable of undergoing surface treatment. Particular examples include, without limitation, metallic tubes, stamping molds, automotive chassis, architectural panels, metallic furniture structures, machine tools, and industrial equipment. The scope further extends to any component where surface modification enhances durability, performance, or aesthetic value.

[0019] The disclosed aspects use free electrically conductive solid bodies suspended in a fluid, which are moved turbulently across the surface to be treated. These conductive particles, in several particular embodiments, are made from materials like polymeric ionexchange resins or other non ionically conductive substances, retain electrolytic solution, enabling them to engage in ionic exchange reactions with the metal surface.

[0020] It is within the scope of the present disclosure a method comprising arranging an electrolytic medium including at least a plurality of free electrically conductive solid bodies inside of a container. The method may also comprise arranging at least one electrically conductive device at least partially inside the container. The method may also comprise generating an electric potential difference between at least one surface to be treated and the at least one electrically conductive device. The method may also comprise generating a turbulence to the electrolytic medium in contact with the part to be treated, preferably with at least one surface thereof to be treated. The method may also comprise, while the electrolytic medium and the at least one electrically conductive device are both arranged inside the container, surface finishing the at least one surface to be treated by providing, at least by the turbulence, relative motion between at least some of the free electrically conductive solid bodies and the at least one surface so that at least some of the free electrically conductive solid bodies contact the at least one surface, thereby surface finishing the at least one surface.

[0021] As in some embodiments used herein, a turbulent flow refers to a fluid dynamic regime characterized by chaotic and vortical motion, typically quantified by the Reynolds number (Re), defined as Re = where p is the fluid density, II a characteristic velocity, L a characteristic length scale, and p the dynamic viscosity. In the context of the present invention, turbulent flow used in some embodiments correspond to Reynolds numbers in the range of about 102to 107, preferably from about 103to 106, and more preferably from about 5 103to 105. Within these ranges, the flow exhibits the irregular fluctuations, enhanced mixing, and energy cascade phenomena conventionally associated with turbulence, that ensures solving the problematics described in the background while ensuring a proper electrical connectivity of the system.

[0022] In some embodiments, the characterization and verification of turbulence conditions within the system may be performed in accordance with standardized methods, such as those defined in ISO 5167 (Measurement of fluid flow by means of pressure differential devices), ISO 4359 (Flow measurement in open channels), and ISO 5802 (Industrial fans, Performance testing using standardized ducts). These standards provide frameworks for determining flow rates, velocity profiles, and turbulence intensity in liquid or gas systems. In particular, the use of calibrated orifice plates, venturi tubes, or nozzles in accordance with ISO 5167 may allow accurate determination of Reynolds numbers in situ, while optical and anemometric techniques, such as particle image velocimetry (PIV) or laser Doppler velocimetry (LDV), may be used to assess the degree of turbulence and mixing efficiency within the container.

[0023] In the context of electrochemical surface finishing, employing solid particle-based electrolytes, monitoring the turbulence parameters according to the aforementioned ISO standards enables precise adjustment of hydrodynamic and electrochemical conditions. Proper control of the turbulence intensity ensures homogeneous distribution and motion of the conductive solid bodies, maintaining continuous galvanic contact between the electrolyte phase and the workpiece surface. This controlled interaction minimizes localized current density fluctuations, prevents particle agglomeration, and promotes uniform surface treatment, thereby enhancing the reproducibility and quality of the finishing process.

[0024] An assembly according to the present disclosure, in several particular embodiments, includes a container for housing both an electrolytic medium and at least one electrically conductive device, with an electric potential difference being applied between the device and a surface or part to be treated. The assembly includes at least one apparatus (also referred to as turbulence apparatus), which may include a gas outlet to introduce air, that enhances the motion of the conductive solid bodies, further ensuring thorough and even surface treatment. This combination of electric potential difference and turbulent motion provides a highly adaptable system that can be easily configured to accommodate different part geometries by simply arranging the part within the container, making the process efficient and versatile.

[0025] The turbulence generated within the container, in particular embodiments of the disclosure, is potentially enhanced by a fluid outlet, either gas or liquid, such as introducing air or non-conductive liquids, ensures efficient contact between the conductive particles and the surface, facilitating a homogeneous surface finish even on complex or large parts. In particular embodiments the outlet may be used to introduce conductive particles as well.

[0026] In several particular embodiments, an assembly according to the present disclosure, relates to a device for surface treating of internal cavities or containers, as disclosed on EP24382288.9, introduced here by reference. An assembly according to some embodiments includes a container comprising a cavity, the cavity being defined by one or more surfaces of the container; at least one electrically conductive device arranged at least partially inside the cavity; an electric source providing an electric potential difference between at least one surface of the one or more surfaces and the at least one electrically conductive device; and at least one apparatus for providing relative motion between free electrically conductive solid bodies of a fluid when arranged inside the cavity and the at least one surface for surface finishing the at least one surface.

[0027] The aspects of this disclosure thus offer a significant improvement over traditional surface finishing methods by providing a flexible, efficient solution for achieving mirror-like finishes on a wide range of parts, regardless of their shape or size, while maintaining uniformity and high-quality results.

[0028] A feature in several embodiments of the disclosure is the introduction of a turbulence element within the container, which generates a dynamic environment for the free electrically conductive solid bodies. This resulting turbulent motion ensures that the conductive particles are uniformly distributed and in continuous relative motion with respect to the surface being treated. It has been surprisingly found that turbulence facilitates the formation of optimal transient packing conditions for the electrically conductive bodies, ensuring that they effectively contact the surface to be polished while electrically charged and thereby exchanging ions. As a result, a homogeneous surface finish is achieved even on parts with intricate shapes or large dimensions.

[0029] Said turbulent conditions contribute to an effective uniform adaptation of the obtained polishing result over the part to be treated, regardless of its shape and geometry. Turbulence in many configurations can break the electrical conductivity through the solid bodies while breaking the electrical bridges formed between cathode and anode, blocking the surface finishing process. However, adjusting the parameters of the assembly or method, some configurations enable the assembly or method to ensure the desired final surface result, such as the agitation power agitation, the proportion between electrically conductive solid bodies and non-conductive fluid, the liquid electrolyte and non-conductive fluid composition, the geometry and dimensions of the polishing tank.

[0030] In the present disclosure, turbulent motion is a step within the method of the present disclosure, resulting from dynamic conditions influenced by different factors, such as the proportion of solid to liquid phases, the degree of agitation, the viscosity of the fluid or the mixture, and / or the distance between electrodes of the given electrochemical cell. These factors individually and / or collectively determine the extent of turbulence and influence the transient packing factor of the electrically conductive solid particles under turbulence. The packing factor is further governed by the shape and size distribution of the particles, with specific thresholds beyond which direct particle-to-particle ohmic or electrical contact is disrupted, preventing a low probability for the establishment of continuous conductive pathways to carry out an effective surface finish, providing current densities below 0.1 A / m2.

[0031] The ratio of solid to liquid phases directly affects turbulence formation. A lower concentration of solid particles in the liquid enhances fluid mobility, increasing turbulence due to greater particle freedom and decreasing the current. Conversely, an excessively high solid concentration results in a denser suspension, suppressing turbulence by increasing interparticle interactions and restricting fluid movement and increasing the current. The solid-to-liquid ratio must be optimized to ensure turbulence is generated while maintaining sufficient current to ensure an effective electrochemical surface finishing. In a particular embodiment of the disclosure, the ratio in volume between the electrically conductive particles and the non-conductive fluid is 1 :10 to 2:1 , in particular from 1 :5 to 1 :1 , more in particular from 1 :2 to 1 : 1.

[0032] In some embodiments, agitation is used in combination with turbulence by preventing the formation of static regions where particles could settle. Higher agitation intensities enhance turbulence, breaking apart particle chains in detriment of the electrical conduction through a solid-phase bridge. If agitation is too low, static conductive paths may persist beyond the threshold for ensuring workable current densities, reducing the effectiveness of the surface finishing of the method or assembly and leaving excessive corrosive attacks or galvanic marks of the particles.

[0033] The viscosity of the fluid also influences both turbulence and the mobility of the conductive particles. Lower viscosity fluids allow for greater particle motion, increasing turbulence and reducing the likelihood of sustained conductive chains. Higher viscosity fluids, in contrast, dampen turbulence by restricting particle movement, potentially leading to localized areas of high packing density where prolonged conductive pathways could form. The selection of fluid viscosity is therefore another configurable variable to maintain the necessary dynamic conditions for transient packing factors. Some liquid environments where the solid bodies are allocated in particular embodiments of the present disclosure have a dynamics viscosity’s at 40°C of between 0.5 to 50 cP (i.e. , centipoise); in particular, between 15 to 30 cP; more in particular, between 20 to 26 cP.

[0034] The spacing between electrodes affects the electric field distribution and the movement of charged particles. A larger distance increases particle travel time and enhances dispersion, promoting turbulence and preventing sustained conductive paths. However, if the distance is too great, the effectiveness of the surface finishing of the method or assembly may be reduced due to insufficient interaction between the charged particles and the target surface. An optimal electrode spacing can be configured to balance turbulence generation and electrochemical efficiency. The optimal distance will depend on the agitation, the voltage applied, the frequency and / or electrical parameters used, as well as the diameter of the used solid particles. In some embodiments, the distance from the electrodes is from 10 to 10,000 times the average diameter of the solid particles, in particular from 50 to 1 ,000 times, more in particular from 100 to 500 times.

[0035] Depending on the voltage and current density used, the distance between the electrodes can be up to 100,000 times the average diameter of the solid particles.

[0036] The packing factor, which determines the likelihood of continuous conductive paths forming, is highly dependent on the shape and / or size distribution of the conductive solid particles. Different particle geometries exhibit distinct packing behaviors, influencing turbulence levels and the probability of conductive chains forming. Spherical particles typically exhibit a maximum random packing factor of around 0.64, with values below 0.50 minimizing the probability of a continuous conductive path due to frequent fluid gaps. Irregular or angular particles tend to interlock, potentially reaching a packing factor above 0.75 in densely packed conditions, though under turbulent conditions, values below 0.55 are more likely to prevent stable conductive pathways. Fibrous or elongated particles may align under shear forces, forming anisotropic structures with localized high packing factors, requiring values below 0.45 to disrupt conductive pathways.

[0037] By carefully selecting particle shape and controlling size distribution, the method or the assembly ensures that packing factors remain in an optimal range to ensure good turbulence and particle mobility while keeping a high processing speed.

[0038] For all features previously described and for practicality, in the present disclosure, turbulent motion may be understood as the ratio between the packing factor or density between the particles and environment taken under working conditions with respect to the one obtained at rest. A method for observing the correspondent ratio would be to use the m1Lfollowing formula: 0 = 7ffc; where m^orkcorresponds to the mass of a sample of one liter rest of the solid particle-based electrolyte taken underworking conditions and m^stthe mass of said solid particle-based electrolyte at rest maximizing the number of particles fitting inside a liter. In some embodiments, 0 ranges from 0.1 to 0.64, in particular from 0.2 to 0.6, more in particular from 0.3 to 0.5.

[0039] According to the present disclosure, working conditions preferably refer to the operational state of the system in which electrochemical and hydrodynamic parameters are actively controlled to induce surface treatment. Such conditions may include, but are not limited to, the establishment of an electric potential difference between the part being treated and a counter-electrode, generating a current flow that promotes ion transfer across the electrolyte medium; the induction of turbulent motion within the electrolytic medium, characterized by Reynolds numbers or 0 ranges within the ranges previously described; and the regulation of process variables such as temperature, pressure, electrolyte composition, and pH. Additional parameters (such as agitation intensity, gas injection rate, particle circulation speed, and voltage or current density) may be adjusted to achieve the desired balance between electrochemical reaction rate and mechanical surface interaction. In contrast, at rest conditions are preferably defined as those in which no significant electrical potential, current flow, or forced agitation is applied to the system, such that the electrolyte, particles, and treated surfaces remain substantially static and in thermodynamic equilibrium, with no intentional electrochemical reaction or material transfer taking place. The previous 0 applies for the case when the density of the solid particles is greater than the density of the fluid environment where they are allocated.

[0040] In some embodiments of the disclosure, the density of the solid particles is lower than the density of the fluid environment where they are allocated. In such cases, the above ranges described for 0 are not valid, instead the above ranges apply to the inverse value of 0, i.e. , the ranges apply to 0-1.

[0041] In some further embodiments of the disclosure, when the density of the conductive solid particles is lower than that of the surrounding liquid medium, the particles may remain suspended or even float at the upper regions of the container. In such cases, the effective turbulence and packing dynamics are better described by the inverse parameter 0“1, which reflects the relative buoyancy-driven distribution of the particles under agitation. Specific examples of this configuration include polymeric ion exchange resins such as styrene- divinylbenzene (S-DVB) copolymers in their hydrated form, having densities of approximately 1.01-1.10 g / cm3, dispersed within concentrated salt solutions or polyhydric alcohols (e.g., ethylene glycol or glycerol) having densities between 1.15 and 1.30 g / cm3. Likewise, expanded or porous polymer beads with densities below 1.0 g / cm3may float within aqueous solutions containing dissolved inorganic salts such as zinc sulfate, sodium tungstate, or lithium bromide. In some embodiments, hollow or microcellular polymeric conductive bodies are employed, exhibiting densities between 0.2 and 0.8 g / cm3, which when dispersed in higher-density ionic liquids (e.g., imidazolium-based ionic liquids with densities of 1.2-1 .4 g / cm3) remain buoyant and sustain turbulence at the liquid-gas interface. These combinations expand the operability of the method by allowing control of turbulence and packing factor behavior through the engineered density contrast between solid particles and the liquid medium.

[0042] In some embodiments of the disclosure, the movement, viscosity, and packing factor of the solid bodies are controlled by applying vibrations to different components of the system.

[0043] In several particular embodiments, the produced turbulence enhances the formation of an emulsion or a foam between the components of the non-conductive fluids and the solid bodies allowing the pass of current.

[0044] A solid particle-based electrolyte, according to some embodiments of the present disclosure, is constituted by at least a set of electrically conductive free particles retaining an electrolyte liquid to make them electrically conductive and a medium on its interstitial environment.

[0045] In the present disclosure, the term "free conductive solid bodies" refers to electrically conductive particles that may be composed of any non-conductive material capable of retaining liquid, such as polymeric materials, minerals, ceramics, organic or inorganic compounds, and materials of plant origin, with a preference for polymeric substances. These conductive particles may include ion exchange resins, which are capable of holding electrolytic solutions and have enough galvanic potential to react with metallic surfaces through ionic exchange.

[0046] In particular embodiments, the free conductive solid bodies may have various forms, including porous or gel-like structures, which enable efficient fluid exchange and greater precision in surface treatment. The particles may also include different functional groups, such as acidic or chelating groups, allowing for specific interaction with metal ions during the finishing process.

[0047] Some or all of the conductive particles, according to some embodiments, may be composed of materials such as strong or weak acidic cationic resins, basic anion exchange resins, or chelating resins, particularly cationic exchange resins, which facilitate metal ion exchange during surface finishing. In some cases, the particles are made from sulfonated divinylbenzene (S-DVB) and styrene copolymers, known for their resistance to acids and oxidative processes, or copolymers derived from acrylic or methacrylic acids, including functional derivatives with groups such as acrylic acid, acrylamide, or alkyl acrylates.

[0048] Conductive solid bodies may also feature functional groups, such as acidic, amino, or chelating groups, capable of capturing or retaining metal ions during processing. Acidic groups like sulfonic or carboxylic groups offer excellent chemical resistance and metal ion retention, while chelating groups, such as iminodiacetic or amino phosphonic groups, provide selectivity for transition metals.

[0049] The specific composition of the conductive particles may be adjusted, and in some embodiments, the particles are made from cationic resin derived from gel copolymer styrene-divinylbenzene (DVB), which may be sulfonated. These particles may encapsulate electrolytes liquids, with surfaces made of materials such as ion-exchange resins, allowing electrolyte liquid to be released or absorbed during surface finishing processes.

[0050] In some embodiments, the conductive particles have a porous structure that enhances fluid exchange and accelerates the process. Alternatively, some particles may have a gel-like structure that slows the process but improves surface contact, resulting in lower final roughness values.

[0051] The particles may take various shapes, including spherical, rhomboidal, pyramidal, cylindrical or broken or crushed particles. Any combination of different shapes is within the scope of the present disclosure.

[0052] Said previously described solid bodies may contain electrolytes liquids to make them electrically conductive, such as aqueous solutions of hydrofluoric acid (HF), sulfuric acid, sulfonic acids such as methanesulfonic acid (MSA), phosphoric acid, carboxylic acids, citric acid, hydrochloric acid, ionic liquids or deep eutectic solvents.

[0053] In some cases, the particles may contain different electrolytes liquids, such as MSA and sulfuric acid, in varying concentrations from 0.1 % to 70% by weight.

[0054] In some embodiments, the electrolyte liquid retained by the solid particles to make them conductive is an aqueous solution, such as water, such as tap water, drinking water, distilled water or in particular, deionized water.

[0055] In some embodiments, a solid particle-based electrolyte according to the present disclosure comprises a fluid included within the environment. Preferably the fluid medium is liquid and non-significantly conductive compared to the solid bodies, but other configurations are possible, such as including a gas, emulsions, etc. The conductivity of a liquid present on the environment according to some embodiments, can be enhanced with acids or other agents, though the disclosure also allows for reduced-acid or acid-free configurations. This reduces the environmental hazards associated with traditional acidbased surface finishing, making the process safer and more suitable for facilities that do not handle acids. Additionally, the fluid’s composition can be adjusted to include lubricating solids, enhancing the process by modifying the viscosity and providing further control over the electropolishing process.

[0056] In some embodiments, a “non-significantly conductive” fluid is understood as a medium whose intrinsic electrical conductivity is substantially lower than that of the solid conductive bodies or of a conventional liquid electrolyte. Specifically, the fluid without conductive particles may contain dissolved or suspended ionic species in such concentrations that its electrical conductivity is equal to or below approximately 10% of that exhibited by a fluid containing both a liquid electrolyte and conductive particles. In certain embodiments, the fluid may be substantially free of electrolyte liquid, such as acids or salts, or may contain only trace amounts thereof. In alternative configurations, the fluid without conductive particles may present a conductivity between about 1 % and 99% of that of the corresponding electrolyte-containing medium, preferably between 10% and 50%, and more preferably between 25% and 35%. The fluid composition may therefore contain less than 10% by weight of liquid electrolyte, in some cases below 5%, or even less than 1 %, and may, in certain embodiments, be entirely acid-free. This definition allows for safe operation of the system without the need for specialized acid-handling facilities, while maintaining adequate electrochemical functionality when used in conjunction with the conductive solid particles.

[0057] The fluid without conductive particles may contain certain amounts of liquid electrolyte in a concentration such that its electrical conductivity decreases to equal or below 10% compared to the fluid with liquid electrolyte and the conductive particles. In some instances, the fluid may be entirely free of electrolyte liquid, such as an acid. In some embodiments, the fluid without conductive particles presents a conductivity of between 1 - 99% of that of the fluid with liquid electrolyte and the conductive particles, in particular, between 10 - 50 %, more in particular between 25 - 35 %.

[0058] The method or the assembly allows surface finishing without requiring transport of the container to facilities capable of handling acids, as the fluid contains less than 10%, in some cases below 5%, or even less than 1 %by weight of liquid electrolyte, such as acids. In certain cases, the fluid is completely acid-free.

[0059] The absence or reduced presence of acid agents renders the method or the assembly suitable for use in various facilities, even those not designed for handling acids, thus eliminating the need to transport containers to specialized locations. Surface finishing can therefore be performed on-site, reducing the production of harmful vapors, fumes, or particles typically generated by large amounts of acid. Such particles, when excessive, often require neutralization or passivation of the treated surface to extend the surface to be treated lifespan.

[0060] In some embodiments, the fluid on the medium consists of a liquid, while in others it may be a gas. The fluid serves as a medium that facilitates the movement of conductive solid bodies relative to the surface, creating an electrical potential difference between the electrolyte particles and the surface to be treated. The fluid's viscosity and aerodynamics ensure effective motion and recirculation inside the container, thus aiding the electropolishing process. When in liquid form, the fluid also helps cool down the conductive particles during electropolishing due to heat generated by ohmic effects, such as joule effect.

[0061] A medium on the interstitial gaps between the free solid particles in a solid-particle based electrolyte according to the present invention, can include non-conductive fluids, which may include hydrocarbons such as mineral oils, paraffins, or silicone oils, more specifically, a mixture of aliphatic hydrocarbons with a carbon chain between 12-15 C containing less than 2% of aromatic groups. Other non-conductive fluids, such as certain synthetic oils and inert gases, are also utilized in some embodiments depending on the application. Additionally, various elements are incorporated, in some embodiments, into the solid-particle based electrolyte to further enhance its functionality. These may include surfactants to reduce surface tension, abrasive particles to aid in material removal during polishing, or moderator particles to control the polishing rate and prevent excessive wear or damage to the material being treated. In particular embodiments, other components that are included on the interstitial space between solid bodies are one or more of: fatty acids, glycols, sulfoxides, ionic liquids, deep eutectic solvents, phenols and fatty alcohols.

[0062] In some embodiments, medium on the interstitial gaps between the free solid particles comprises an oil, such as, e.g., a mixture of aliphatic hydrocarbons with a carbon chain between 12-16 C.

[0063] In some embodiments, the fluid includes a lubricating solid that adjusts the viscosity of the fluid and / or the surface, allowing greater control over the electropolishing process.

[0064] The maximum turbulence and / or motion applied to the solid-particle based electrolyte and to the solid bodies depends on different factors, such as the desired results and the composition of the solid-particle based electrolyte. Increasing the turbulence increases the homogeneity of the solid-particle based electrolyte packing factor distribution through space and motion of a particle, resulting on higher isotropic electrolytic conditions all over the tank, triggering a higher homogeneity obtained over the surfaces to be treated. However, increasing the turbulence while increasing the velocity of the conductive solid particles, decreases the average number of contacts between them within a certain timelaps, which can act in detriment of the surface finishing speed.

[0065] The mentioned decrease on the current of the process while increasing the agitation or turbulence supplied to the polishing medium can be adjusted by modifying the solidparticle based electrolyte. In some embodiments, increasing the proportion of conductive solution comprised in the medium of a solid-particle based electrolyte including an emulsion within the interstitial space of the solid particles, increases the channels under which the particles can transmit the charge, allowing for the pass of current. Adjusting the surfactants nature and content used, also allows to control the surface tension between the constitutive phases, which can be used to enlarge the meniscus of conductive solution, or solvent capable to transport the charged spices between particles and the surface to be treated, connecting two particles and / or the particles with the surface to be treated, and though preventing the blockage of current. In some configurations mentioned above, it is possible to increase the surface treatment speed increasing the turbulence of the system while adjusting the solid-particle based electrolyte composition.

[0066] In some embodiments, a possible method to overcome the decrease of current during an increase in turbulent conditions, according to the present disclosure, consists of increasing the time under which an isolated free solid body keeps a previously established charge. When the plurality of solid bodies, according to some embodiments, is made from porous materials, such as ion-exchange resins, these resins may feature functional groups like sulfonic or carboxylic groups for metal ion retention, or chelating groups for selective interaction with transition metals. The functional groups, together with the degree of crosslinking, determine the resin’s ion exchange capacity (IEC), which is a parameter that determines its performance as an impedance. Varying the IEC changes the dielectric constant of the ion exchange resin and thereby affecting to its reactance. This effect can be configured together with the frequency of the electrical pulses used, as higher frequencies present higher current efficiency over capacitive reactance’s. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] To complete the description and in order to provide for a better understanding of the disclosure, a set of drawings is provided. Said drawings form an integral part of the description and illustrate embodiments of the disclosure, which should not be interpreted as restricting the scope of the disclosure, but just as examples of how the disclosure can be carried out. The drawings comprise the following figure:

[0068] Figure 1 shows an assembly in accordance with some embodiments.

[0069] Figures 2A and 2B show an assembly in accordance with some embodiments for surface treating inner surfaces.

[0070] Figure 3 shows an assembly in accordance with some embodiments including a temperature control system.

[0071] Figure 4 shows an assembly in accordance with some embodiments.

[0072] Figure 5 shows an assembly in accordance with some embodiments.

[0073] DETAILED DESCRIPTION

[0074] A first aspect of the present disclosure includes, in preferred embodiments, a method for finishing a surface comprising: arranging an electrolytic medium including at least a plurality of free electrically conductive solid bodies inside of a container; arranging at least one electrically conductive device at least partially inside the container; generating an electric potential between at least one surface to be treated and the at least one electrically conductive device; generating a turbulence to the electrolytic medium in contact to the part to be treated; while the electrolytic medium and the at least one electrically conductive device are both arranged inside the container, surface finishing the at least one surface to be treated by providing relative motion between at least some of the free electrically charged conductive solid bodies and the at least one surface so that at least some of the free electrically conductive solid bodies contact the at least one surface, thereby surface finishing the at least one surface.

[0075] In some particular embodiments of the disclosure, turbulence within the particlebased electrolyte may be generated by any suitable mechanical, hydraulic, pneumatic, or electromagnetic means, including but not limited to a turbine, pump, impeller, propeller, jet nozzle, diffuser, oscillating element, vibrating membrane, ultrasonic transducer, rotating stirrer, mechanical agitator, flow-restricting orifice, baffle arrangement, vortex generator, acoustic excitation, or combinations thereof. A solid-particle based electrolyte according to the present disclosure refers to an electrolyte including a first plurality of solid particles retaining a liquid electrolyte making them electrically conductive, as in the introduced by reference International Application No. PCT / ES2017 / 070247 (published as WO 2017 / 186992 A1). The environment allocated on an interstitial space between the solid bodies can include either a gas a solid and liquid medium, or any possible combination of said mentioned aspects, as mentioned on the previously referenced application, and in combination to aspects from the introduced by reference International Application No. PCT / ES2021 / 070864 (published as WO 2022 / 123096 A1), in which a moderation fluid is present on the interstitial space between the solid bodies is to be understood as any fluid, either gas, liquid, superfluid or any other possible fluid presenting a non-significant electrical conductivity of that presented by the electrically conductive solid particles, preventing them to short-circuit the system and preventing the ion for being significantly carried out by the free solid bodies. A nonsignificant electrical conductivity as below 10% of the total conductivity of the solid-particle based electrolyte.

[0076] In some embodiments, a solid-particle based electrolyte according to the present disclosure includes in addition to the first plurality a second plurality of abrasive particles, as mentioned in the International Application No. PCT / ES2024 / 080378 introduced here by reference. The present disclosure includes a hybrid method for surface finishing at least one surface of an object by moving a combination of a first plurality of electrically conductive particles and a second plurality of abrasive particles relative to the object, the object being electrically connected to a first pole of at least one electrical source and the electrolytic medium being electrically connected to a second pole of the at least one electrical source, and one or more particles of the first plurality of particles electrically conductive comprising an electrolyte liquid.

[0077] The term "free electrically conductive solid bodies" refers to electrically conductive particles that may be made from non-conductive materials capable of retaining liquid making them ionically conductive, such as polymers, minerals, ceramics, organic compounds, or even plant-derived materials, with a preference for polymeric substances. In particular, ion-exchange resins that hold electrolytic solutions are used to facilitate ionic exchange reactions with metallic surfaces.

[0078] The ratio between the electrically conductive particles and the non-conductive fluid has an effect on the turbulence, packing factor and the conductivity of the electrolytic medium under work conditions. In a particular embodiment of the disclosure, the ratio in volume between the electrically conductive particles and the non-conductive fluid is 1 :10 to 2:1 , in particular from 1 :5 to 1 :1 , more in particular from 1 :2 to 1 :1.

[0079] In some embodiments, the electrolyte liquid of one or more (e.g., one, some, all) electrically conductive particles of the first plurality of electrically conductive particles is inside the electrically conductive particles.

[0080] Liquid retention in the electrically conductive particles can occur due to porosity of the material or due to molecular structure such as a gel-like structure. Possible retention mechanisms within the scope of the present disclosure include: permeation, absorption, adsorption, retention in the interlaminar space.

[0081] The electrically conductive particles may be of any material capable of retaining liquid, such as, for example, polymeric materials, mineral, ceramic, organic compounds, inorganic compounds, of plant origin, and are preferably of polymeric material. Electrically conductive particles of a polymeric material may simply be referred to herein as polymeric particles.

[0082] Suitable polymeric materials may be, e.g., ion exchange resins.

[0083] In some embodiments, the electrolyte liquid is contained within one or more electrically conductive particles. Liquid retention in these particles may occur due to the porosity of the material or the molecular structure, such as a gel-like structure. Various retention mechanisms, including permeation, absorption, adsorption, and retention in the interlaminar space, are contemplated within the present disclosure.

[0084] The present disclosure encompasses embodiments wherein ion exchange resins are categorized based on their ionization properties, which are influenced by their pKa values. Strong ion-exchange resins may remain fully ionized across a wide pH range, whereas weak ion-exchange resins may exhibit ionization depending on the pH. Resins having a pKa up to 3 may be considered strong acid cation (SAC) resins, such as sulfonated polystyrene resins, while resins with a pKa of 4.5 to 6 may be categorized as weak acid cation (WAC) resins, such as poly(methacrylic acid).

[0085] In some embodiments, the resins include SAC resins such as styrene- divinylbenzene with sulfonic acid groups, which may remain fully ionized in acidic environments. Examples of such resins may include poly(perfluorosulfonic acid) and sulfonated phenolic polymers, which may provide high efficiency in acidic and neutral conditions. In some embodiments, the resins comprise WAC resins, such as poly(acrylic acid), may contain carboxylic acid groups with a pKa of 4.5 to 6.0, making them suitable for moderately acidic environments. An example of such a resin is crosslinked poly(acrylic acid- co-divinylbenzene).

[0086] In some embodiments, electrically conductive particles incorporate chelating resins containing functional groups such as iminodiacetic acid and aminophosphonic acid, which are capable of forming stable chelates with metal ions. These embodiments facilitate selective metal recovery even in the presence of competing ions. Examples of such resins may include crosslinked iminodiacetic acid-functionalized resins and thiourea- functionalized styrene-divinylbenzene resins. An example of a suitable chelating resin is poly(styrene-divinylbenzene) functionalized with aminophosphonic groups.

[0087] Additional embodiments of the present disclosure feature strong base anion (SBA) resins incorporating quaternary ammonium groups that remain fully ionized in neutral to highly alkaline environments, rendering them suitable for removing or recovering strong acid anions. An example of such a resin is crosslinked poly(styrene-divinylbenzene) functionalized with trimethylammonium groups. Alternatively, weak base anion (WBA) resins with amine functional groups may be employed in certain embodiments, such as poly(styrene-divinylbenzene) with tertiary amine groups, effectively absorbing weak acid anions in moderately acidic to neutral pH environments.

[0088] In further embodiments, electrically conductive particles comprise or consist of sulfonated divinylbenzene-styrene copolymers, such as sulfonated styrene-divinylbenzene resins, which exhibit resistance to acidic and oxidative conditions. Alternatively, copolymers of acrylic acid or methacrylic acid, including derivatives with different functional groups such as acrylic acid-co-acrylamide copolymers, may be utilized to enhance ion capture capabilities. These polymeric materials may include acid, amino, or chelating functional groups to optimize metal ion retention.

[0089] Various embodiments include electrically conductive particles with porous structures, such as macroporous poly(styrene-divinylbenzene), which facilitate fluid exchange and contribute to process efficiency. In alternative embodiments, a gel-like structure, such as poly(acrylamide) gel resins, is employed to regulate fluid movement, ensuring precise polishing outcomes. The particles may be spherical or spheroid in shape, designed to release the electrolyte liquid upon contact with a surface and to reabsorb the electrolyte liquid as needed.

[0090] Typically, the porous material is not saturated with the electrolyte liquid. Thereby, the electrolyte liquid is typically released when in contact with the surface of the object to be surface finished.

[0091] These conductive particles, in several embodiments, are made from materials like polymeric ion-exchange resins or other substances that retain the electrolytic solution, enabling ionic exchange reactions with the metal surface. The vibrations ensure efficient contact between the conductive particles and the surface, facilitating a homogeneous surface finish even on complex or large parts.

[0092] In some embodiments, the liquid retained by the solid particles is electrolytic, and its conductivity can be enhanced with acids or other agents, although the disclosure also allows for reduced-acid or acid-free configurations, reference made on the International Application No. PCT / ES2022 / 070649 (published as WO 2023 / 067214 A1), where acid-free configuration using electrically conductive solid bodies are used for polishing composite materials, such as metal matrix composite materials. This reduces environmental hazards typical of acid-based surface finishing, making the process safer and more suitable for facilities that do not handle acids. The fluid’s composition can be adjusted to include lubricating solids, which modify viscosity and provide additional control over the electropolishing process. In some other embodiments, the fluid consists of a gas, offering further flexibility in fluid medium selection.

[0093] The disclosure also provides, in some embodiments, the use of free conductive solid bodies in various forms, such as microporous or gel-like structures, which enhance fluid exchange and provide precise surface treatment. These particles may contain functional groups, such as acidic or chelating groups, allowing for specific interaction with metal ions during polishing. In some particular embodiments, the solid bodies comprise an ion exchange resin, which can be cationic or anionic, strong or week, depending on the application.

[0094] The system supports different liquid electrolytes, including aqueous solutions of sulfuric acid, sulfonic acids, such as methanesulfonic acid (MSA), phosphoric acids, ionic liquids, deep eutectic solvents, inorganic or organic salt solutions or other electropolishing agents, giving the user flexibility in choosing from any preexisting liquid electrolyte.

[0095] In some embodiments, the conductive particles encapsulate liquid electrolytes such as, e.g., aqueous solutions of acids like hydrofluoric, sulfuric, methanesulfonic, phosphoric, or citric acids. In some embodiments, these particles contain different liquid electrolytes in concentrations ranging from 0.1 % to 70% by weight, depending on the specific surface finishing requirements. The porous or gel-like structures of these particles enhance fluid exchange and surface contact, leading to improved control over surface roughness and other finishing parameters. In some cases, to alleviate or overcome the decrease of current during an increase in turbulent conditions, according to the present disclosure, I EC of the ion exchange resin is varied, and thereby affecting to its reactance, and adjusting the frequency of the polishing parameters.

[0096] In particular, strong acid cation (SAC) resins, which are used in some embodiments, with an Ion Exchange Capacity (IEC) ranging from 1.8 to 2.5 eq / L typically offer robust ion exchange ability and maintain performance across a broad pH range, ideal for acidic conditions. These resins generally exhibit dielectric constants between 5 and 20, owing to their high ionic content and strong water affinity.

[0097] For weak acid cation (WAC) resins, which are used on some other embodiments, the IEC typically ranges from 1.0 to 1.8 eq / L, and their effectiveness is pH-dependent, performing best in moderately acidic to neutral environments. These resins typically have dielectric constants between 3 and 15, reflecting their lower ionic content and reduced water absorption. Similarly, strong base anion (SBA) resins, which are used on some embodiments, with an I EC of 0.9 to 1 .5 eq / L and weak base anion (WBA) resins, which are used on some other embodiments, with an I EC of 1 .0 to 1.4 eq / L offer effective ion exchange in neutral to alkaline environments. SBA resins generally exhibit dielectric constants between 4 and 16, while WBA resins typically range from 3 to 12. The dielectric constants of these resins are influenced by their ionic content and hydration levels, with higher values typically correlating with higher I EC.

[0098] Increasing the ion exchange capacity of a resin results in a higher dielectric constant, as higher ionic content and water retention improve the resin's polarizability. This enhancement increases the resin's ability to withstand higher turbulent conditions, making it more viable in such environments. Ion exchange resins comprised in a first plurality of the present disclosure may have an I EC ranging from 0.1 to 5 eq / L, particularly between 1.5 and 3 eq / L, and more specifically between 1.7 and 2.5 eq / L. These resins would exhibit dielectric constants in the range of 4 to 20, depending on the specific resin type. These properties contribute to the resin's resilience under variable turbulent conditions, improving the performance and efficiency of the method described in the disclosure.

[0099] The crosslinking degree of the ion exchange resin further influences its osmotic pressure and the ability of the particle to establish transient liquid bridges or menisci under turbulent conditions. Resins with lower crosslinking levels exhibit reduced osmotic pressure, favoring the release of sufficient liquid from within the particle to form a liquid meniscus capable of connecting with adjacent particles over a certain time under turbulence. However, while lower crosslinking enhances liquid release, the resulting meniscus is weaker and less stable. Conversely, higher crosslinking degrees increase osmotic pressure, reducing the amount of liquid released and thereby limiting meniscus formation, yet providing stronger and more resilient menisci when they occur. The configuration of crosslinking, therefore, provides a controllable parameter to balance the probability and strength of particle connection through transient liquid menisci in dynamic environments.

[0100] The degree of crosslinking of the ion exchange resins employed in the present disclosure may be configured to tailor the balance between osmotic pressure, swelling, and liquid retention. In some embodiments, the crosslinking degree, expressed as the proportion of divinylbenzene or equivalent crosslinking agent in the resin matrix, ranges from 1% to 25% by weight, preferably from 2% to 15%, and more preferably from 4% to 10%. Lower crosslinking levels within these ranges favor greater liquid uptake and swelling, thereby enhancing the probability of transient meniscus formation under turbulence, while higher crosslinking levels reduce swelling and liquid release but provide increased mechanical integrity and thermal stability.

[0101] In particular embodiments, ion exchange resins with higher ion exchange capacity values, such as nuclear grade resins with I EC values approaching the upper limit of 5 eq / L, are employed. Such resins exhibit high ionic content and strong water retention, leading to elevated dielectric constants and improved stability under turbulent conditions. Non-limiting examples of suitable high-capacity resins include highly sulfonated styrene-divinylbenzene (S-DVB) copolymers, perfluorinated sulfonic acid resins such as Nation®, and specialty nuclear-grade cationic exchange resins with I EC values of 4 to 5 eq / L. These materials demonstrate particular advantages in demanding electrochemical finishing applications, where both resilience against turbulence and the capacity to maintain controlled ionic pathways are required.

[0102] The ion exchange capacity (I EC) of the resins can likewise be adjusted depending on the application requirements. In some embodiments, resins present an I EC between 0.1 and 5 eq / L, in particular between 1.0 and 4.0 eq / L, and more preferably between 1.5 and 3.0 eq / L. Resins with moderate I EC values ensure balanced polarizability and osmotic response, whereas high-capacity resins, such as nuclear grade cationic exchange resins with I EC values of 4.0 to 5.0 eq / L, provide enhanced water retention, higher dielectric constants, and robustness under severe turbulent conditions.

[0103] The swelling degree of the resins is further dependent on the type of counter-ion associated with the active groups. For instance, hydrogen- and lithium-form resins typically exhibit higher swelling factors due to the smaller ionic radii and stronger hydration shells of H+and Li+, whereas sodium- and potassium-form resins demonstrate intermediate swelling behavior. In contrast, larger or multivalent ions, such as calcium, magnesium, or transition metal ions, reduce swelling by imposing stronger electrostatic binding within the polymer matrix. In certain embodiments, the swelling volume change may range from 5% to 80% relative to the dry resin volume, more particularly from 20% to 60%, depending on the ion form and crosslinking degree. This tunability of swelling provides an additional parameter for controlling the transient packing factor, osmotic release, and stability of menisci formation under turbulent electrochemical finishing conditions.

[0104] Conductive particles may have various shapes, including spherical, rhomboidal, pyramidal, or cylindrical, and different dimensions depending on the desired final result. In particular embodiments the diameter of a spherical shape is between 0,05 and 50 mm, preferably between 0,1 and 10 mm, more in particular between 0,3- and 1 ,5-mm. Crushed particles may also be used, which can lead to higher packing factors and facility for surface treating difficult-to-reach areas, such as small radius cavities.

[0105] In some embodiments, big particles, bigger than a spherical particle of 50 mm diameter, are added to increase the inertia of the system ensuring the desired mobility. These particles may adopt different shapes depending on the application and system configuration to ensure the desired effect. In some embodiments, the particles are ionically conductive to prevent current blockage, in others non-conductive. Other parameters and its combinations, such as density, friction coefficient, surface roughness, surface energy can be selected for providing the desired mobility to the system.

[0106] In some embodiments, the conductive particles are composed by various shapes which can be used to increase the surfaces connecting the solid bodies. This increase on the surface connection results on a higher ion transport capacity and can also have an impact on the reactant behavior of the solid-particle based electrolyte, which in combination to a fine-tuning of the used electrical parameters, such as voltage and frequency, can be used to enhance the pass of current.

[0107] In particular embodiments, a second plurality of abrasive particles is added to the first plurality of electrically conductive solid particles in order to obtain a hybrid mechanoelectrochemical surface treatment.

[0108] In some embodiments, a maximum size of one or more abrasive particles of the at least one abrasive particle is between 0.1 mm and 25.0 mm, preferably between 0.5 mm and 15.0 mm, more preferably between 0.75 mm and 10 mm, and yet more preferably between 1 mm and 5 mm.

[0109] In some embodiments, one or more abrasive particles (e.g., one, some or all) of the at least one abrasive particle have a density ratio DR fulfilling the following: 7 > DR > 0.7, and / or a mass ratio MR fulfilling the following: 2 > MR > 0.2; where DR = where papis a density of the abrasive particles, a density of the electrically conductive particles or a resin thereof; and where the particles (or resin thereof) including the electrolyte liquid; and where MR = mapis a mass of the abrasive particles, and mresis a mass of the resin of the electrically conductive particles.

[0110] As a mode of example, the density of abrasive particles pap) may be from 2.5 to 5.5 g / cm3, in particular from 3.0 to 5.0 g / cm3, yet more in particular from 3.5 to 4.5 g / cm3.

[0111] The hardness of abrasive particles may be from 3 to 10 in the mohs scale, in particular from 5 to 9.75 mohs, more in particular from 6 to 9.5 mohs, and yet more in particular from 7.5 to 9.25 mohs.

[0112] In some embodiments, the hardness of a particle is not abrasive if presents an equal or lower hardness than the surface being treated. For example, in the case of polishing stainless steel, it generally exhibits a hardness of approximately 150-600 HV (Vickers), corresponding to about 5-6 on the Mohs scale. Accordingly, particles having a hardness below or equal to this range, such as talc (Mohs 1), calcite (Mohs 3), or polymer-based particulates, are classified as non-abrasive with respect to SSL. Conversely, a particle is considered abrasive when its hardness exceeds that of the SSL surface, for example quartz (Mohs 7), corundum (Mohs 9), or diamond (Mohs 10), as such particles are capable of producing wear or surface damage under operational conditions.

[0113] The geometry of abrasive particles may typically include edges, owing to their surface and / or their shape. For instance, abrasive particles may be prismatic, e.g., of triangular base or another geometrical base; cylindric; cubic; rhombic; pyramidal; conic; and / or spheric.

[0114] The material of a second plurality of abrasive particles may be synthetic (i.e., manufactured) and / or natural (i.e., naturally sourced, e.g., mined minerals). In some embodiments, the abrasive particles are preferably synthetic abrasive particles. Some natural abrasive particles (e.g., zirconia alumina, diamond dust, etc.) may also be manufactured, and synthetic versions of naturally sourced abrasive particles may be preferred due to difficult availability and higher costs of the naturally sourced abrasive particles. Additionally, or alternatively, synthetic particles may be preferred as they may be more effective as abrasives, since they may be free of impurities that natural abrasive particles may comprise.

[0115] In some embodiments, abrasive particles (synthetic and / or natural) of the at least one abrasive particle are selected from alumina (aluminum (III) oxide: AI2O3), e.g., in the form of corundum, emery (impure corundum), and ceramic aluminum oxide, including white AI2O3, brown AI2O3 and gray AI2O3; zirconia (zirconium dioxide); zirconia alumina (a combination of aluminum (III) oxide and zirconium dioxide); iron(lll) oxide (e.g., ceramic iron oxide); borazon (cubic boron nitride or CBN); boron carbide; glass powder; steel abrasive; silicon carbide (carborundum); calcite (calcium carbonate); diamond dust; novaculite; pumice; sand; garnet; sandstone; rotten stone (Tripoli); powdered feldspar; staurolite; and slag (a by-product of processes for smelting ores and recycling metals, comprising a mixture of metal oxides and silicon dioxide).

[0116] In some embodiments, the at least one abrasive particle comprises the second plurality of abrasive particles comprising more than one type of abrasive particles, e.g., two, three or more different types of abrasive particles.

[0117] A solid particle-based electrolyte according to the present disclosure, in some embodiments, includes a medium on its environment. The medium is a fluid that may comprise gas and / or liquid, e.g., air, water, aqueous solutions, non-conductive liquids etc.

[0118] A gas medium, such as air, may be advantageously used to facilitate processing, as no liquid needs to be added and then removed from the system and the surface treated objects.

[0119] A liquid medium may be advantageously used to modulate the properties of the system. A liquid medium may be referred to as a moderator liquid. If a liquid medium is used the composition of the liquid medium may vary greatly and may be adjusted to specific objects to be surface treated, and / or specific first plurality of electrically conductive particles and at least one abrasive particle.

[0120] A non-conductive liquid, as described herein, is a fluid that when being at rest at room temperature does not significantly conduct electrical current. A non-conductive fluid may typically be immiscible in the liquid electrolyte contained in the solid electrolyte particles. In this way, a non-conductive fluid may contribute to keeping the liquid electrolyte inside the electrically conductive particles, whereas the non-conductive fluid is kept outside the same. In some cases, the non-conductive liquid is miscible, such as water, DMSO, Propylene Carbonate, Ionic liquids, DES, or it is a partially miscible liquid. Without being bound to any theory with regards to a non-conductive liquid, by covering the surface of the object to be surface treated, may contribute to one or more of, e.g.:

[0121] Surface protection against localized acid attacks;

[0122] Reduction of atmospheric oxidation;

[0123] Greater control over the electrochemical process;

[0124] Higher selectivity in the peaks; and / or

[0125] Final finish with lower roughness.

[0126] A non-conductive liquid may be selected from hydrocarbons, organic solvents, water immiscible solvents, organic compounds, essential oils, silicone and silicone oils, and fluorinated solvents, and emulsions, among others. They can be used alone or in combination with each other.

[0127] Hydrocarbons may be particularly selected from C5-C30 hydrocarbons, more in particular from C6-C16 hydrocarbons.

[0128] Water immiscible solvents and organic compounds may be selected from, for example, aliphatic alcohols like 1 -octanol, organic carbonates like propylene carbonate, ethylene carbonate, among others.

[0129] Silicones and silicone oils as described herein, are understood to be those oligomers, polymers, cycles or other structures that include O- Si bonds in their main chain. Silicone oils may include dimethylsiloxane units -OSi(Me2)- as well as cyclic ones such as hexamethylcyclotrisiloxane, in particular polydimethylsiloxanes may be used.

[0130] Fluorinated solvents are understood as solvents that incorporate at least one fluorine atom in their chemical structure and may include fluorinated and perfluorinated fluids.

[0131] Emulsions may typically be a non-conductive non-polar continuous phase containing conductive polar solution micelle, typically water-in-oil type emulsions (w / o). The conductive polar solution of micelles may have the same composition as the liquid electrolyte of the electrically conductive particles. As the non-polar continuous phase is non- conductive, the emulsion at rest without solid electrolyte particles is non-conductive. As a mode of example, an emulsion-based non-conductive liquid may comprise:

[0132] - A non-conductive liquid such as a non-conductive liquid mentioned above; - A conductive solution as a dispersed polar phase;

[0133] Optionally, surfactants to stabilize the emulsion.

[0134] The first plurality of electrically conductive particles and the at least one abrasive particle (in some embodiments in which abrasive particles are provided) may be, e.g., dispersed in the electrolytic medium or sedimented in the electrolytic medium. Generally, when the particles and the object are moved relatively to each other the first plurality of particles and the at least one abrasive particle will be dispersed in the electrolytic medium. This may be achieved as described above by way of any motion, such as displacing, rotating, mixing, stirring, vibrating, shaking, spraying, etc.

[0135] The medium can be selected to improve the effectiveness of the combination of the two types of particles.

[0136] In some embodiments, the medium makes the combination to be in dry suspension, e.g., when a liquid such as a, e.g., moderator liquid is used as the fluid medium, or makes the combination to be dry, wherein a gas is used as the fluid medium.

[0137] In particular embodiments, as described on the International Application No. PCT / EP2025 / 052440, introduced here by reference, wherein the electrolytic medium further comprises a fluid, the fluid comprises an organic compound comprising hydrophilic groups such as a fatty acid, an alcohol and other organic compounds comprising sulfonic, sulfate, sulfone or thiol groups, nitro or nitrate groups, phosphate groups, or amine groups, in particular a fatty acid and / or an alcohol.

[0138] An organic compound comprising hydrophilic groups may be an organic compound comprising a carboxyl group (such as a fatty acid) and / or a hydroxyl group (such as an alcohol). The fatty acid may be selected from 03 to C50 fatty acids, e.g., 04 to 050 fatty acids in particular from 06 to 030 fatty acids, more in particular from 08 to 028 fatty acids. The alcohol may be selected from a 02 to 050 alcohol, in particular a 02 to 010 alcohol, comprising one or more hydroxyl groups. In particular, the alcohol may be a glycol, comprising two hydroxyl groups and may preferably be ethylene glycol. The alcohol may also be a fatty alcohol such as from 04 to 050 fatty alcohols, in particular from 06 to 030 fatty alcohols and more in particular from 08 to 028 fatty alcohols.

[0139] Organic compounds comprising sulfonic, sulfate, sulfone or thiol groups may be selected from sulfonic acids, such as alkylbenzene sulfonic acids and their salts, including sodium dodecylbenzenesulfonate (SDBS) and sodium toluenesulfonate; and sulfate esters and their salts, such as sodium lauryl sulfate (SLS) and ammonium SLS.

[0140] Organic compounds comprising nitro or nitrate groups may be selected from alkyl nitrates, and nitroalkanes, including nitromethane or nitroethane.

[0141] Organic compounds comprising phosphate groups may be selected from aryl phosphates such as triphenyl phosphate (TPP), tricresyl phosphate (TCP); alkyl phosphates such as diethyl phosphate or tributyl phosphate; and phosphate esters such as monoalkyl or dialkyl phosphate esters.

[0142] Organic compounds comprising amine groups may be selected from primary amines such as ethylamine and propylamine; secondary amines such as diethylamine and dipropylamine), and tertiary amines (e.g., triethylamine and tributylamine). In some embodiments the organic compound comprising hydrophilic groups is a fatty acid and / or an alcohol.

[0143] In some other embodiments, the organic compound comprising hydrophilic groups is an organic compound comprising sulfonic, sulfate, sulfone or thiol groups, nitro or nitrate groups, phosphate groups, or amine groups.

[0144] A fluid in a medium of a method or assembly as described herein may be electrically non-conductive or conductive. In several preferred embodiments, the fluid is non- conductive. The use of non-conductive fluids may advantageously result in the electrical conductivity of the surface polishing system being due to, mostly or totally, the electrically conductive particles. For instance, according to some embodiments, an electrically non- conductive fluid may have a conductivity of at most 1000 pS / cm, in particular at most 50 pS / cm, and more in particular at most 10 pS / cm.

[0145] It has been found that the presence of an organic compound comprising hydrophilic groups such as a fatty acid and / or an alcohol as described herein may contribute to the fluid to being non-conductive or conductive depending on the form of the organic compound comprising hydrophilic groups, for instance, whether is a fatty acid or an alcohol or the form of the fatty acid, e.g., if used in neutral form or as a salt, and / or the presence of other components in the fluid that may contribute to the conductivity or the non-conductivity of the fluid.

[0146] An organic compound comprising hydrophilic groups as used herein has the meaning commonly used in the art. In particular, it is an organic compound, such as a hydrocarbon, that has one or more hydrophilic groups, also referred to as polar groups, such as a carboxyl, a hydroxyl group, sulfonic, sulfate, sulfone or thiol groups, nitro or nitrate groups, phosphate groups, or amine groups, in particular a carboxyl or a hydroxyl group. The organic compound may also have both a hydrophilic and a hydrophobic (lipophilic) group or region. For instance, fatty acids have a polar head (the carboxyl group) that is hydrophilic and an apolar tail that defines a hydrophobic region. Similarly, glycols such as ethylene glycol and other alcohols such as fatty alcohols, have polar groups (e.g., hydroxyl groups) and apolar groups or regions (e.g., the hydrocarbon parts) each defining hydrophilic and hydrophobic regions. Similarly organic compounds comprising sulfonic, sulfate, sulfone or thiol groups, nitro or nitrate groups, phosphate groups, or amine groups, in addition to these hydrophilic groups may also have hydrophobic groups or regions (e.g., hydrocarbon parts).

[0147] Fatty acids as used herein has the meaning commonly used in the art. In particular, a fatty acid is understood by a person skilled in the art a carboxylic acid consisting of a hydrocarbon chain and a terminal carboxyl group. Fatty acids may be naturally occurring or derived from naturally occurring products such as fatty acids derived from esters in fats and oils. Fatty acids may also be synthetic.

[0148] Organic compounds comprising carboxyl groups are compounds known in the art having one or more -COOH groups, in their neutral form or ionic form (e.g., used as a salt), preferably comprising one carboxyl group, such as fatty acids. Fatty acids for surface finishing an object may be used, e.g., in a method as described herein in their neutral form or a salt, e.g. of an alkali or an alkaline earth metal ion. For instance, a fatty acid salt may be selected from a sodium, potassium, calcium and magnesium fatty acid salt.

[0149] Organic compounds comprising hydroxyl groups are compounds known in the art having one or more -OH groups, preferably comprising one or two carboxyl groups, such as alcohols and mono- or di-alcohols. Alcohols as used herein has the meaning commonly used in the art. In particular, alcohols are hydrocarbons comprising one or more hydroxyl groups as described above, and may be particularly be selected from glycols (such as ethylene glycol) and fatty alcohols (which are similar to fatty acids in that they have a hydrocarbon chain and a terminal hydroxyl group, instead of a carboxyl group of the fatty acids).

[0150] Organic compounds comprising sulfonic, sulfate, sulfone or thiol groups are compounds known in the art, having one or more -S(=O)2-OH groups (also represented as -SO3H) or -OS(=O)2-OH, -S(=O)2-, or -SH, respectively, in their neutral form or ionic form used as, e.g., a salt, preferably comprising one sulfonic, sulfate, sulfone or thiol group. Sulfonic or sulfate groups may be particularly preferred.

[0151] Organic compounds comprising nitro or nitrate groups are compounds known in the art, having one or more -NO2 or -ONO2 groups respectively, preferably comprising one nitro or nitrate group.

[0152] Organic compounds comprising phosphate groups are compounds known in the art, having one or more -OP(=O)O2H2 groups, in their neutral form or ionic form, e.g., used as a salt, preferably comprising one phosphate group

[0153] Organic compounds comprising amine groups are compounds known in the art, and may typically be primary, secondary or tertiary amines, having one or more -NH2, -NH-R or -NR2 groups respectively, in their neutral form or ionic form, e.g., used as a salt.

[0154] Said particular organic compounds comprising hydrophilic groups have been found to work particularly well to modulate surface finishing processes, ensuring better control over the resulting surface quality, compared to other compounds that may also be used in a method as described herein but may not work so well such as ketones, amide groups, or carboxylic acids other than fatty acids (e.g., nitrobenzoic acid).

[0155] Organic compounds comprising hydrophilic groups as described herein can exhibit a wide range of structural diversity, which may influence their functionality within the system and ultimately their effects in the surface finishing method. While linear aliphatic compounds comprising said hydrophilic groups may be typically used, cyclic structures also hold significant potential as effective agents in this context. Cyclic organic compounds comprising hydrophilic groups may offer unique advantages, such as improved stability or specific interaction patterns with the surface being treated. Examples of such compounds include sugars like fructose, glucose, and sucrose, which contain hydroxyl groups and can form protective layers through their unique chemical interactions with the surface of the object to be surface treated (e.g. a metal surface). In a method as described herein, it is notable that organic compounds comprising hydrophilic groups (acting as control, modulating and / or protective agents) may be used as such and have an effect as such or may also derive from a precursor or may have a different effect upon transformation within the system during the execution of the method. For instance, certain compounds, such as sugars (e.g., fructose) may as such have an effect as a compound comprising hydroxyl groups but may also undergo transformations during the process, yielding derivatives like levulinic acid that continue to contribute to the system’s protective functionality. Similarly, esters can undergo hydrolysis, releasing carboxylic acids and alcohols (e.g., glycols) that play a role in maintaining surface integrity and uniformity during electropolishing.

[0156] Combinations of organic compounds comprising hydrophilic groups have also been found to work particularly well. In some embodiments, a combination of a fatty acid and an alcohol is used. Fatty acids and / or alcohols (e.g., glycols such as ethylene glycol) may also be used in combination with organic compounds comprising sulfonic, sulfate, sulfone or thiol groups, nitro or nitrate groups, phosphate groups; and / or amine groups. In some embodiments, alcohols (e.g., glycols such as ethylene glycol) are used, preferably in particular combination with organic compounds comprising sulfonic, sulfate, sulfone or thiol groups (e.g. dodecyl benzene sulfonic acid and / or petroleum sulfonic acids or salts thereof). In some other embodiments, fatty acids (e.g., oleic acid) are used in particular combination with organic compounds comprising sulfonic, sulfate, sulfone or thiol groups (e.g. dodecyl benzene sulfonic acid and / or petroleum sulfonic acids or salts thereof). In some embodiments, alcohols (e.g., glycols) are used in combination with organic compounds comprising nitro or nitrate groups. In some embodiments, fatty acids and / or alcohols (e.g., glycols such as ethylene glycol) are used in combination with organic compounds comprising phosphate groups. In some embodiments, organic compounds comprising amine groups are used in combination with fatty acids, alcohols and / or organic compounds comprising phosphate groups.

[0157] A second aspect of the present disclosure includes an apparatus or an assembly to carry out the previously defined method.

[0158] Figure 1 shows an assembly in accordance with some embodiments, describing an assembly for surface finishing, comprising: a container (63) comprising at least one electrically conductive device (65) at least partially arranged inside the container (63); an electric source (61) providing an electric potential difference between at least one surface (62) to be treated and the at least one electrically conductive device (64); and at least one apparatus (66) for providing turbulent relative motion between a fluid (64), in particular of free electrically conductive solid bodies within the fluid (64), when the fluid (64) is arranged inside the container and the at least one surface for surface finishing the at least one surface.

[0159] Said assembly as represented in Figure 1 , the apparatus for providing turbulent relative motion includes a fluid outlet (67) to include a fluid, in some cases a gas, such as e.g., air, to the generated turbulence. The inclusion of a gas through the fluid outlet (67), in some embodiments, is configured to apply a controlled pressure to the particles under conditions of static or near-static motion, thereby imparting sufficient kinetic energy to overcome initial resistance and initiate relative movement, ultimately facilitating the establishment of a turbulent flow. This arrangement has been found to reliably enhance particle mobility and promote consistent turbulence within the assembly.

[0160] In particular embodiments, the at least one apparatus (66) for providing turbulent motion includes a turbine, an impeller or a similar device, but it can be any other possible system. A turbine can be configured to a speed of between 10 - 200 RPM, particularly between 30 - 100 RPM, and more in particular between 50 - 70 RPM. In some embodiments, said at least one apparatus (66) for providing turbulent motion is electrically coupled to a current generator for providing electrically charged particles guided to the part to be treated, increasing the charge transmission efficiency to the surface being treated. The depth of the at least one apparatus (66) within the electrolyte, particularly the electrolyte surface level, can be adjusted in order to control the turbulence. In a particular embodiment, the at least one apparatus (66) is located at the bottom of a receptacle of the container (63), in others between a depth of 50 % and 90 % with respect to the height of the surface, more in particular between 70 % and 80%.

[0161] The selection of the value of RPM and the depth will be configured depending on the compromise between the achieved level of turbulence and the proper electrical connectivity. In several particular embodiments, the combination of the values provided above have provided successful results for delivering uniform surface treatment of the part, homogeneous in terms of final roughness reduction and final shiny aspect

[0162] The defined ranges of rotational speed (RPM) and immersion depth of the turbulence-generating apparatus establish an optimized working window that enables precise control over both hydrodynamic and electrochemical conditions within the system. In the specific configuration tested (comprising a 10,000 L cubic container as shown in Fig. 1 and a solid particle-based electrolyte according to Example 1 filling the entire volume) the selected ranges of 10-200 RPM and 50-90 % immersion depth, particularly between 50- 70 RPM and 70-80 % depth, have proven effective for treating stainless steel (SSL) tubes of approximately 5 cm diameter and 5 m length, including parts with complex curvatures and internal geometries. Under these operating conditions, the process achieved a reduction in surface roughness from Ra = 1-2 pm to Ra = 0.5-0.1 pm, yielding a uniform, glossy finish over the entire surface. Adjusting the rotational speed allows regulation of the turbulence intensity and therefore of the rate of particle-surface interaction: higher RPM values generally promote increased local turbulence and enhanced mass and charge transfer, resulting in finer surface finishes, whereas lower speeds favor selective or less aggressive treatments. Similarly, varying the immersion depth of the turbulence apparatus permits control over the turbulence distribution and flow pattern inside the container, thereby influencing the uniformity and selectivity of the surface modification. The ability to fine-tune these parameters within the disclosed ranges provides the skilled person with an effective means to adapt the process to different geometries, materials, and desired surface outcomes, ensuring reproducible and controllable electrochemical surface finishing.

[0163] In particular embodiments, the at least one apparatus (66) for providing turbulent motion includes a fluid outlet (67), such as gas outlet e.g. air, in a particular embodiment is used to decompactify the solid bodies, making them more susceptible for agitation and for maintaining the turbulent conditions. In some other embodiments, the gas outlet (67) is used to add gas, such as air, to the formed emulsion or foam because of the turbulence, modifying the conductivity and surface treatment performance of the dry electrolyte. In some different embodiments the fluid outlet (67) is a liquid outlet, that may introduce the same liquid used as a liquid medium present on the environment of the solid-particle based electrolyte, or it may introduce another liquid with different properties, such as temperature, pressure or chemical composition. In some embodiments the liquid expelled by the fluid outlet may include solid particles, either conductive or non-conductive. In some cases, the introduced liquid includes a second plurality of abrasive particles.

[0164] In particular embodiments, an assembly according to the present disclosure, includes an open container (63) at atmospheric pressure.

[0165] In other embodiments, an assembly according to the present disclosure, includes a closed tank. In some embodiments, the closed tank comprises a hermetic tank including a system with means for adjusting the pressure during the working conditions. Increasing the pressure can increase the processing speed and the current of the process, as particles releases more conductive liquid upon contacts, allowing for more aggressive treatments; whereas decreasing the pressure increases the mobility of the solid bodies and allowing for higher turbulent configurations.

[0166] In particular embodiments, a hermetic tank does not leave any space for a gas, such as air, and the full deposit is filled by the solid-particle based electrolyte and its liquid medium occupying the totality of its environment.

[0167] In particular embodiments the part being surface treated is a cavity (35) that part of a container or receptacle (63) that holds a solid-particle based electrolyte.

[0168] In particular embodiments, as described in EP24382288.9, where an internal cavity or an inner surface of a container is at least part of the surface to be polished, turbulent motion is provided to enhance the surface finishing process. As illustrated in Figure 2A, an assembly (100) in accordance with some embodiments includes a container (1) with one or more surfaces (30). At least one surface (31) on the inside forms a cavity (35), which serves as a receptacle for substances and / or goods contained in the container (1 ) and as a physical electrolytic medium for surface finishing. Part or the entirety of at least one surface (31) is to be surface finished.

[0169] As illustrated on Figure 2B, the assembly (100) includes at least one electrically conductive device (4), which is at least partially introduced into the cavity (35) and immersed in fluid (6) when such fluid is present in the assembly (100). The fluid (6), which may be liquid and / or gas and optionally include a lubricating solid, contains free electrically conductive solid bodies (40), such as electrolyte particles, at least during the surface finishing process. The assembly (100) is configured to generate an electric potential difference between the electrically conductive device (4) and the at least one surface (31). For example, the assembly (100) includes or is connected to an electric source (45) with electrodes providing a first pole (46) and a second pole (47), such as an anode and a cathode, respectively, or vice versa. In particular, the at least one surface (31) is electrically connected to the first pole (46), while the at least one electrically conductive device (4) is connected to the second pole (47).

[0170] Furthermore, the assembly (100) includes or can be connected to at least one apparatus (7) for producing turbulent relative movement between the fluid (6) and the at least one surface (31), ensuring that the solid bodies (40) come into contact with the at least one surface (31) and move within the fluid (6). In this example, the at least one apparatus (7) is a motor coupled to the electrically conductive device (4), which moves, specifically rotates, due to the motor's action.

[0171] To prevent short-circuiting, the at least one electrically conductive device (4) is preferably positioned such that it does not contact the at least one surface (31) or the container (1), maintaining a distance D between them. In some cases, this distance D ranges from 2 to 50 times the diameter of the solid bodies 40. Additionally, an electrical insulator (29) may be arranged between the at least one electrically conductive device (4) and the at least one apparatus (7) to further prevent short-circuiting.

[0172] In this example, the at least one electrically conductive device (4) is a single propeller, though in other embodiments, it may include multiple propellers, alternative devices, or different shapes.

[0173] Figure 2B shows an assembly 100 in accordance with some embodiments.

[0174] Like in the embodiments of Figure 1 , the assembly (100) includes the container (1), the fluid (6) and the at least one electrically conductive device (4). In these embodiments, however, the at least one electrically conductive device (4) is at least partially shaped according to the shape of the cavity (35) and at a distance from the at least one surface (31), thereby making it possible to continuously surface finish different portions of the cavity (35) in a substantially homogeneous manner.

[0175] Further, the at least one apparatus (7), which may be part of the assembly or not, includes a motor and a propeller at least partially immersed in the fluid (6).

[0176] As represented on Figure 3, in particular embodiments, an assembly according to the present disclosure, includes a refrigeration system adapted to one apparatus for providing turbulent motion including a fluid outlet, as specified in the International Application No. PCT / ES2017 / 070247 (published as WO 2017 / 186992 A1), introduced by reference, which comprises a method and equipment for controlling the temperature of particles in polishing processes using solid particles and / or solid particles containing an electrolyte liquid in a liquid environment. The method includes: a step of absorbing liquid (5) from a container (3) where particles (2) are located; a step of thermally adjusting the liquid (4); and a step of reintroducing the thermally adjusted liquid (4) into the tank or container to control the temperature of the particles. The equipment comprises a duct circuit (10) with an inlet (101) and an outlet (102) in the container, a suction pump (11), a filter (12) with a mesh that prevents particle passage, and a heat exchanger. In particular, for an efficient temperature adjustment, the inlet and outlet devices can be oriented for selecting the most efficient thermal adjustment areas within the container, such as an area of a surface to be polished.

[0177] In some embodiments, a method described herein and / or the surface finishing step is carried out at a temperature from room temperature (e.g., from 10°C to 25°C) to 80°C, in particular from 30°C to 60°C and more in particular from 40°C to 50°C. These temperatures may advantageously contribute to reducing the time of the surface treatment to obtain a desired final roughness. In some present embodiments, means for generating wave pressure within the solidparticle based electrolyte are included to guide the particles into contact with the surface to be treated while maintaining the turbulent motion. In some cases, these means include vibratory systems, while in others, a diaphragm membrane is utilized to direct the vibrations effectively.

[0178] The vibration mechanisms that can be integrated into this embodiment are described in EP24383288.8, introduced by reference, which discloses an assembly and method for surface finishing. This system comprises a container that includes at least one electrically conductive device, acting as a first electrode, at least partially arranged inside the container. An electric source generates a potential difference between at least one surface to be treated — partially arranged within the container and acting as a second electrode — and the at least one electrically conductive device. These electrodes are connected through a solid- particle-based electrolyte that enables ion exchange between the surface to be treated and the electrolyte liquid when current is applied. Additionally, at least one device is adapted with means for generating vibrations, thereby inducing relative motion between the solid- particle-based electrolyte and the surface to be treated.

[0179] In some of these embodiments, a vibration is included along with a turbulence according to the present disclosure, and a method for finishing a surface comprises: arranging a solid-particle based electrolyte (4) inside of a container (3); immersing within said electrolyte (4) at least part of an electrically conductive (5) and at least part of a surface to be treated (2); applying an electrical potential difference between said electrically conductive (5), and a surface to be treated (2), by connecting them to an electric source (1), generating an ion transport between the surface to be treated and said solid-particle based electrolyte (4) when current is applied; providing at least a vibration, e.g., to the electropolishing system (6, 7, 8, 9), and thereby inducing a relative motion between the solid-particle based electrolyte (4) and the at least one surface to be treated (2).

[0180] These embodiments including vibrations are particularly suited for applications requiring the finishing of complex internal geometries, such as conical or tubular parts used in the pharmaceutical industry and extends to complex shapes like those found in internal barrels, where controlled vibrational patterns can precisely polish interior surfaces

[0181] In several embodiments, the assembly includes a container that houses both the electrolytic medium and at least one electrically conductive device, with an electric potential applied between the device and the part being polished. Vibrational energy enhances the movement of the solid bodies, ensuring thorough and even surface treatment. This combination of electrical potential and vibration provides a highly adaptable system that can easily be adjusted to accommodate different part geometries by modifying the vibration parameters, making the process efficient, versatile, and capable of delivering superior results.

[0182] The generated vibrations can be applied directly to the solid bodies, to the medium in which they are suspended, to the part being polished, or to various points within the processing receptacle, depending on the specific polishing or cleaning requirements. In several embodiments, where the vibration source has been positioned at the bottom of the receptacle, results on an efficient vibration transmission to the surface of the part. However, other configurations are also possible to optimize cavitation effects, such as placing the vibration source on the part holder, on the receptacle sidewalls, or in a combination of bottom and side positions. This flexibility enables precise control over the frictional interaction between the solid bodies and the surface, enhancing their adaptability to complex geometries. By fine-tuning the amplitude and frequency of the vibrations, the system adjusts the mobility and packing density of the solid bodies, ensuring thorough and uniform coverage across the surface. This approach yields consistent, high-quality polishing results, particularly in hard-to-reach areas like concave surfaces or inner channels, where traditional methods often fall short.

[0183] Figure 4 shows an assembly in accordance with some embodiments. Some embodiments include means for holding (401 , 402, 408) a component, which in some embodiments is heavy and / or big, being surface treated. Said embodiments may comprise a structure (401) that provides with sufficient mechanical resistance to ensure that the part being treated is well secured and controlled when arranged within a container (403) with a solid-particle based electrolyte (404). Particular embodiments include fixing means (402) to secure and connect said structure (401) with the component being treated. In some embodiments the fixing means include an electrically conductive device to electrically couple the part being treated and an electric source (406). Several embodiments incorporate means to arrange and remove (408) the component being treated inside the pool (403), such as a moving platform (408) that enables the motion of the structure (401) when the fixing means (402) hold the component in the upper position.

[0184] The power supply (406) generates a potential difference between the component being treated and the cathodes (409), enabling an ion transport guided through a solidparticle based electrolyte (404), under turbulent conditions, connecting them bough.

[0185] Some embodiments of the disclosure include one or more turbulence generators (405), such as impellers arranged along the pool (403), delivering turbulences to the solidparticle based electrolyte (404).

[0186] Embodiments according to Figure 4 include a control station where an operator can interact and configure the different parameters of the process. Figure 5 shows an assembly in accordance with some embodiments. In the embodiments described herein, the part being treated (501) present a complex and non- uniform geometry.

[0187] In order to generate a turbulent motion adapted to the geometry of the part being treated, embodiments described herein include a set of lateral motors (502) and frontal motors (503), adapted to a turbulence element, either lateral (504) or frontal (505), such as an impeller that in some cases comprise alternate blades.

[0188] Particular embodiments illustrated on Figure 5 incorporate separate motors (502, 503) adapted to each turbulence elements (504, 505) that allows for an independent motion and synchronization between them. This synchronization allows for guiding the resulting turbulence jet into the specific surface of the part being treated in the desired direction, achieving high precision on controlling the final surface finish.

[0189] As illustrated in Figure 5, the use of independently driven lateral motors (502) and frontal motors (503), each coupled to their respective turbulence elements (504, 505), provides the possibility of finely controlling the fluid dynamics around the part being treated (501). Unlike static or non-synchronized systems, which tend to create repetitive or stagnant flow patterns that cause particles to repeatedly strike the same surface region, often producing localized wear, scratches, or polishing defects, the independent actuation and synchronization of the turbulence elements enable dynamic adjustment of both the intensity and the direction of the turbulent jet. By carefully controlling motor rotation speeds, phases, and relative orientations, the operator or automated system can effectively “steer” the turbulence across the complex geometry of the part. In practice, this means that turbulence can be guided to sweep across concave areas, sharp edges, or recessed cavities, ensuring that conductive particles make uniform contact with the entire surface. This controlled sweeping action not only minimizes the risk of uneven finishing or surface defects but also enhances overall precision, reproducibility, and quality of the electrochemical treatment.

[0190] In some embodiments, the assembly comprises a cavity located between the first inner wall (506), which retains the solid particle-based electrolyte, and the external wall (507). This cavity may serve as a thermal management layer, allowing the introduction of a fluid medium to regulate the working temperature of the system. Depending on the specific application, the fluid within the cavity may be a gas, such as air, nitrogen, argon, or carbon dioxide, or a liquid, such as water, glycol, oil, or other heat-transfer fluids. The choice of fluid can be selected according to desired thermal conductivity, heat capacity, or chemical compatibility with the container.

[0191] In particular embodiments, the cavity may be filled with a circulating coolant, for example chilled water or a water-glycol mixture, connected to a conditioning circuit as illustrated in Figure 3. Such a circuit may include pumps, heat exchangers, temperature sensors, and feedback controls, enabling active heating or cooling of the process environment. In alternative embodiments, the cavity may be filled with air or another inert gas, either under static conditions to provide thermal insulation or under dynamic conditions by flowing the gas through the cavity to remove heat generated during operation.

[0192] In some further embodiments, the cavity contains specialized fluids to achieve dual functionality, such as dielectric oils that not only regulate temperature but also provide electrical insulation, or phase-change materials that absorb heat peaks during transient operation. In yet some other embodiments, the cavity is maintained under partial vacuum to minimize thermal conduction and thus stabilize the system against rapid temperature fluctuations.

[0193] The cavity may also be partitioned into separate zones, each independently connected to a conditioning circuit, allowing for localized heating or cooling in specific regions of the assembly. For example, one section of the cavity may circulate warm water to prevent condensation, while another section circulates chilled water to dissipate heat near the electrodes. By combining different fluids, flow regimes (static, laminar, turbulent), and circuit configurations (open-loop, closed-loop, single-pass, or recirculating), the cavity provides a versatile means of precisely controlling thermal conditions of the solid-particle based electrolyte and the part being treated.

[0194] Another aspect refers to a solid particle-based electrolyte useable, for example, in a method or with an assembly according to the present disclosure. The solid-particle based electrolyte comprises a plurality of free electrically conductive solid bodies comprising ion exchange resins configured to retain an electrolyte liquid; and a fluid medium occupying interstitial spaces of the solid bodies. The fluid medium contains less than 10% by weight of a liquid electrolyte, in some cases less than 5% by weight of the liquid electrolyte, and in some cases less than 1 % by weight of the liquid electrolyte.

[0195] In some embodiments, the fluid medium of the solid-particle based electrolyte is acid free.

[0196] In some embodiments, the solid-particle based electrolyte comprises a plurality of abrasive particles.

[0197] Another aspect refers to a system comprising an assembly according to the present disclosure, and the surface to be treated. In some embodiments, the system comprises a part in turn comprising said surface to be treated.

[0198] In this text, the term “includes”, “comprises” and derivations thereof (such as “including”, “comprising”, etc.) should not be understood in an excluding sense, that is, these terms should not be interpreted as excluding the possibility that what is described and defined may include further elements, steps, etc.

[0199] On the other hand, the disclosure is obviously not limited to the specific embodiment(s) described herein, but also encompasses any variations that may be considered by any person skilled in the art (for example, as regards the choice of materials, dimensions, components, configuration, etc.), within the general scope of the invention as defined in the claims.

[0200] EXAMPLES

[0201] Example 1

[0202] The present example has been operated by assemblies in accordance with some embodiments, such as, e.g., the assembly represented on Figure 1.

[0203] The solid-particle based electrolyte used comprises, o 50 % in volume (300 L) of electrically conductive particles made of:

[0204] • 98 % wt. of spherical particles with a heterogeneous particle size distribution ranging between 0.3 - 1.1 mm in diameter of sulfonated gel styrene divinylbenzene particles in an acid format after being dried up to get a constant moisture of 35 - 45 wt. % with respect to the total weight of the solid bodies. In some embodiments an heterogeneous distribution means a bimodal or a gaussian particle size distribution.

[0205] • 2 % of methanesulfonic acid at a concentration of 70% wt. o 50 % in volume (300 L) of a non-conductive fluid made of:

[0206] • 73.8 % wt. of hydroseal: a mixture of aliphatic hydrocarbons with a carbon chain between 12-15 C containing less than 2% of aromatic groups.

[0207] • 1 .48 % wt. of ethoxylated alcohol with an ethoxylation of 2,5 mol and 10 carbons.

[0208] • 22.14 % wt. of water

[0209] • 1 .85 of methanesulfonic acid at a concentration of 70% wt.

[0210] • 0.74 % wt. of sodium natural sulfonate.

[0211] In this particular embodiment the container (63) is a cube of a size of 2m. In other possible configurations of the disclosure, the container adopts other shapes and sizes.

[0212] The depth under which the apparatus for providing turbulent relative motion (6) between free electrically conductive solid bodies within a fluid (64) is allocated is 1 m.

[0213] The apparatus for providing turbulent relative motion (66) between free electrically conductive solid bodies within a fluid (64), consisting on an impeller at 50 RPM.

[0214] The polished part in the example is a blade of 20 cm of diameter, made out of stainless steel. The used parameters are a DC at 30 V, with a current of 5 A. After a polishing process of 30 min, the roughness has been decreased homogeneously from Ra = 1 pm to a Ra = 0,3 pm, achieving a mirror finish.

[0215] In some different embodiments of the disclosure, other electrical parameters or polarities are used to achieve the desired result.

[0216] Example 2

[0217] The present example has been operated by assemblies in accordance with some embodiments, such as, e.g., the assembly represented on Figure 1.

[0218] The solid-particle based electrolyte used comprises: o 61 % in volume of electrically conductive particles made of:

[0219] • 98.14 % wt. of spherical particles of sulfonated gel styrene- divinylbenzene resin, in an acid format, having a heterogeneous particle size distribution ranging between 0.3 - 1.1 mm in diameter. The particles are conditioned to reach a constant moisture content of 35 - 45 wt.% with respect to the total weight of the solid bodies. In some embodiments, a heterogeneous distribution refers to a bimodal or Gaussian particle size distribution.

[0220] • 1 .86 % wt. of methanesulfonic acid (MSA) at 70 % wt. concentration, incorporated to activate the surface of the solid particles and enhance ionic exchange within the solid matrix. o 39 % in volume of a non-conductive fluid made of:

[0221] • 43.81 % wt. of hydroseal, a mixture of aliphatic hydrocarbons with a carbon chain between Ci2-Ci5and containing less than 2 % of aromatic groups.

[0222] • 0.65 % wt. of DBS-type surfactant (such as dodecylbenzenesulfonate or an equivalent ethoxylated surfactant).

[0223] • 7.73 % wt. of water, providing limited ionic conductivity and assisting in wetting of the solid particles.

[0224] • 36.21 % wt. of oleic acid, acting as a lubricating and viscositymodifying agent to stabilize the suspension and improve process control during surface finishing.

[0225] • 11.60 % wt. of methanesulfonic acid (MSA, 70 % wt.), dispersed in the liquid phase to enhance charge transfer and maintain the overall acidity required for controlled electrochemical activity.

[0226] In this particular embodiment, the container (63) is cubic with a capacity of 5, 0001- In other possible configurations of the disclosure, the container adopts other shapes and sizes. The depth under which the apparatus for providing turbulent relative motion (6) between free electrically conductive solid bodies within a fluid (64) is allocated is 0.7 m.

[0227] The apparatus for providing turbulent relative motion (66) between free electrically conductive solid bodies within a fluid, consisting on an impeller of 33 cm diameter with a rotation configured to be at 800 RPM

[0228] The polished part in the example consists on a car chassis stamping mold of a nodular grey cast iron alloy with an exposed surface of about 0.1 m2. The used electrical parameters are 55V with an anodic pulse of 1s, cathodic pulse of 2s with a duty cycle of 100 ms between each polarity switch, achieving 17 A during the anodic pulse and 17 A during the cathodic pulse. After a polishing process of 540 min, the roughness has been decreased homogeneously from Rz = 60 pm to a Ra = 10 pm, achieving a mirror finish.

[0229] In some different embodiments of the disclosure, other electrical parameters or polarities are used to achieve the desired result.

[0230] Example 3

[0231] The present example has been operated by assemblies in accordance with some embodiments, such as, e.g., the assembly represented on Figure 5.

[0232] The solid-particle based electrolyte used comprises: o 69 % in volume of electrically conductive particles made of:

[0233] • 96.5 % wt. of spherical particles with a heterogeneous particle size distribution ranging between 0.3 - 1.1 mm in diameter of sulfonated gel styrene divinylbenzene particles in an acid format after being dried up to get a constant moisture of 50 wt. % with respect to the total weight of the solid bodies. In some embodiments a heterogeneous distribution means a bimodal or a gaussian particle size distribution.

[0234] • 3.5 % of deionized water o 31 % in volume of a non-conductive fluid made of:

[0235] • 74.5 % wt. of hydroseal: a mixture of aliphatic hydrocarbons with a carbon chain between 12-15 C containing less than 2% of aromatic groups.

[0236] • 9.96 % wt. of octanoic acid of 98% wt.

[0237] • 14.92 % wt. of deionized water.

[0238] • 0.55 % of dodecylbenzenesulfonic acid

[0239] • 0.07 % wt. of sodium natural sulfonate.

[0240] • 0.5 % wt of ricin oleic acid.

[0241] In this particular embodiment the container capacity is of 3,600 L (1 x 1.2 x 3 m). In other possible configurations of the disclosure, the container has other shapes and / or sizes.

[0242] The depth under which the apparatus for providing turbulent relative motion between free electrically conductive solid bodies within a fluid, is allocated is 0.6 m.

[0243] The apparatus for providing turbulent relative motion (503) between free electrically conductive solid bodies within a fluid, consisting on a motor set at 1700 RMP linked to an impeller of 40 cm of diameter, the impeller’s (502) rotation was configured to be at 300 RPM and with alternate direction from the one of the neighbors to provide with the proper turbulence (i.e. , clockwise - counterclockwise synchronized configuration).

[0244] The polished part in the example consists on a car bumper made out of Stainless steel AISI 430 with an exposed surface of about 4.5 m2. The used electrical parameters are 40V with an anodic pulse of 1s, cathodic pulse of 2s with a duty cycle of 100 ms between each polarity switch, achieving 75 A during the anodic pulse and 95 A during the cathodic pulse. After a polishing process of 420 min, the roughness has been decreased homogeneously from Ra = 0.5 pm to a Ra = 0,1 pm, achieving a mirror finish. In some different embodiments of the disclosure, other electrical parameters or polarities are used to achieve the desired result.

Claims

CLAIMS1. An assembly for surface finishing, comprising: a container comprising at least one electrically conductive device at least partially arranged inside the container; an electric source configured to provide an electric potential difference between at least one surface to be treated and the at least one electrically conductive device; and at least one apparatus configured to provide turbulent relative motion between free electrically conductive solid bodies of electrolytic medium when arranged inside the container and the at least one surface for surface finishing the at least one surface.

2. An assembly according to claim 1 , wherein the at least one apparatus comprises a fluid outlet to include a gas to a generated turbulence.

3. An assembly according to claim 2, further comprising a gas.

4. An assembly according to any one of claims 2-3, wherein the gas comprises air.

5. An assembly according to any one of the preceding claims, further comprising the electrolytic medium with the electrically conductive solid bodies arranged in the container.

6. An assembly according to claim 5, wherein a ratio in volume between the electrically conductive solid particles and non-conductive fluid of the electrolytic medium is between 1 :10 and 2:1 , preferably between 1 :5 and 1 :1 , more preferably between 1 :2 and 1 :1.

7. An assembly according to any of claims 5 to 6, wherein non-conductive fluid of the electrolytic medium has a dynamic viscosity at 40 °C in the range of 0.5 to 50 cP, preferably 15 to 30 cP, more preferably 20 to 26 cP.

10. An assembly according to any of claims 5 to 7, wherein the electric source comprises electrodes, wherein a distance between the electrodes is from 10 to 10,000 times an average diameter of the free electrically conductive solid particles, preferably from 50 to 1 ,000 times, more preferably from 100 to 500 times.11 . An assembly according to any of claims 5 to 10, wherein the free electrically conductive solid bodies are ion exchange resins selected from cationic resins, anionic resins, chelating resins, sulfonated divinylbenzene-styrene copolymers, acrylic resins, or methacrylic resins.

12. An assembly according to any of claims 5 to 11 , wherein the electrically conductive solid bodies have an ion exchange capacity between 0.1 and 5 eq / L, preferably between 1 .5 and 3 eq / L, more preferably between 1.7 and 2.5 eq / L.

13. An assembly according to any of the preceding claims, wherein the at least one apparatus is configured to provide the turbulent relative motion so that the turbulent relative motion produces an emulsion or foam between the electrolytic medium and the free electrically conductive solid bodies.

14. An assembly according to any of the preceding claims, wherein the electrolytic medium comprises a plurality of abrasive particles configured to provide hybrid mechanoelectrochemical surface treatment.

15. An assembly according to any of the preceding claims, wherein the turbulent motion of the solid-particle based electrolyte is characterized by a packing ratio 0 defined as the ratio between an apparent density of the conductive particles and the electrolytic medium, under working conditions, and the apparent density of the system at rest, wherein 0 ranges from 0.1 to 0.64, preferably from 0.2 to 0.6, and more preferably from 0.3 to 0.5, when a density of the free electrically conductive solid bodies is greater than a density of the electrolytic medium.

16. An assembly according to any of the preceding claims, wherein the turbulent motion of the free electrically conductive solid bodies is characterized by a packing ratio 0 defined as the ratio between an apparent density of the conductive particles and the electrolytic medium under working conditions and the apparent density of the system at rest, wherein 0“1ranges from 1.5 to 10, preferably from 2.0 to 5.0, and more preferably from 2.2 to 3.3, when a density of the free electrically conductive solid bodies is lower than a density of the electrolytic medium.

17. An assembly according to any of the preceding claims, wherein the at least one apparatus comprises at least one of a turbine, pump, impeller, propeller, jet nozzle, diffuser, oscillating element, vibrating membrane, ultrasonic transducer, rotating stirrer, mechanical agitator, flow-restricting orifice, baffle arrangement, vortex generator, or acoustic excitation device.

18. A method for finishing a surface comprising:arranging an electrolytic medium including at least a plurality of free electrically conductive solid bodies inside of a container; arranging at least one electrically conductive device at least partially inside the container; generating an electric potential difference between at least one surface to be treated and the at least one electrically conductive device; generating a turbulence to the electrolytic medium in contact with the at least one surface to be treated; while the electrolytic medium and the at least one electrically conductive device are both arranged inside the container, surface finishing the at least one surface to be treated by providing, at least by the turbulence, relative motion between at least some of the free electrically conductive solid bodies and the at least one surface so that at least some of the free electrically conductive solid bodies contact the at least one surface.

19. A method according to claim 18, wherein a gas is comprised in the generated turbulence.

20. A method according to claim 19, wherein the gas comprises air.

21. A method according to any of claims 18 to 20, wherein a ratio in volume between the free electrically conductive solid bodies and non-conductive fluid of the electrolytic medium is between 1 :10 and 2:1 , preferably between 1 :5 and 1 :1 , more preferably between 1 :2 and 1 :1.

22. A method according to any of claims 18 to 21 , wherein non-conductive fluid of the electrolytic medium has a dynamic viscosity at 40 °C in the range of 0.5 to 50 cP, preferably 15 to 30 cP, more preferably 20 to 26 cP.

23. A method according to any of claims 18 to 22, wherein turbulence is generated by applying mechanical, hydraulic, pneumatic, acoustic, or electromagnetic agitation.

24. A method according to any of claims 18 to 23, wherein the turbulence is generated by vibration applied to the container or to electrodes for generating the electric potential difference.

25. A method according to any of claims 18 to 24, wherein the turbulence produces an emulsion or foam between the fluid and the free electrically conductive solid bodies.

26. A method according to any of claims 18 to 25, wherein the electrolytic medium further includes a plurality of abrasive particles for providing hybrid mechano-electrochemical surface finishing.

27. A method according to any of claims 18 to 26, wherein the turbulence is characterized by a packing ratio 0 defined as the ratio between an apparent density of the particle-fluid system under working conditions and the apparent density of the system at rest, wherein 0 ranges from 0.1 to 0.64, preferably from 0.2 to 0.6, and more preferably from 0.3 to 0.5, when the density of the free electrically conductive solid bodies is greater than the density of the electrolytic medium.

28. A method according to any of claims 18 to 26, wherein the turbulence is characterized by a packing ratio 0 defined as the ratio between an apparent density of the particle-fluid system under working conditions and the apparent density of the system at rest, wherein 0“1ranges from 1.5 to 10, preferably from 2.0 to 5.0, and more preferably from 2.2 to 3.3, when the density of the free electrically conductive solid bodies is lower than the density of the electrolytic medium.

29. A solid particle-based electrolyte, comprising: a plurality of free electrically conductive solid bodies comprising ion exchange resins configured to retain an electrolyte liquid; and a fluid medium occupying interstitial spaces of the solid bodies, wherein the fluid medium contains less than 10% by weight of a liquid electrolyte.

30. A solid particle-based electrolyte according to claim 29, wherein the fluid medium contains less than 5% by weight of the liquid electrolyte, more preferably less than 1 %.

31. A solid particle-based electrolyte according to any of claims 29 to 30, wherein the fluid medium is acid free.

32. Use of a solid particle-based electrolyte according to any of claims 29 to 31 in an assembly according to any of claims 1 to 17, or in a method according to any of claims 18 to 28.

33. A system comprising an assembly according to any of claims 1 to 17, and the surface to be treated.

34. A system according to claim 33, comprising a part, wherein the part comprises the surface to be treated.

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