Surface finishing of containers

Abstract

An assembly for surface finishing, comprising: 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. Also, a method for surface finishing, a surface finished container, and a kit for surface finishing a container.

Description

[0001] SURFACE FINISHING OF CONTAINERS

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to the field of surface finishing. More particularly, the disclosure relates to surface finishing of containers.

[0004] BACKGROUND

[0005] For an adequate operation of certain objects, surfaces thereof may need to be surface finished so that the surfaces meet certain parameters, e.g., a particular shape, a limited rugosity, rounded edges, etc.

[0006] Containers, i.e., devices with one or more cavities therein for receiving substances or objects, require surface finishing of the parts forming the cavities so as to house such goods properly. Walls and / or a base delimiting the cavity may damage the housed goods, both when the goods are in the container for a short period of time and for longer periods of time. By way of example, friction and projecting parts on the surface of the cavity potentially abrade and break the goods. By way of another example, unpolished surfaces of the cavity potentially release particles of the walls into the cavity, which may mix with substances contained in the container, e.g., chemical contamination, organic decomposition, etc. These are possible problems that concern the housed goods.

[0007] Turning to the containers themselves, parts of the cavity that are not adequately surface finished may cause the deterioration of the containers, thereby shortening their useful life or requiring more frequent maintenance tasks, including, but not limited to, surface finishing for reconditioning of the containers and the cavities thereof. By way of example, stress corrosion cracking causes the formation of cracks, especially in harsh environments; the existence of recesses and valleys on walls and / or a base of the cavity makes the surface more prone to stress corrosion cracking. It is noted that surface finishing concave parts is oftentimes complex due to limitations of the process for applying a given surface finishing technique.

[0008] In addition to the foregoing problems, containers are particularly difficult to be surface finished due to what the surface finishing techniques entail. One of the most widely used techniques when it comes to surface finishing containers is acid baths. The handling of acids is typically exclusive to personnel and companies with special permits due to the hazardous nature of acids. But the use of acids also generates fumes and toxic particles that cause pollution and safety concerns; there might be spillage or leaks that suppose a potential risk to the environment and to human life. To avoid these undesired phenomena, the containers are immersed in acid pools. Hence, the containers usually must first be transported to facilities adapted for the use of acids, and then transported back to where they are used once they have been surface finished.

[0009] The dimensions of the containers, especially large ones, are also a limiting factor. Referring to the acid baths, this means that the acid pools shall have greater surface and volume than the container to be surface finished. The surface finishing technique employed must thus adapt to potentially great volumes. And when the surface finishing is to be conducted elsewhere from the premises where the containers are used, the transportation of larger containers becomes cumbersome and ineffective time-wise and energy-wise.

[0010] There is an interest in providing a way of surface finishing containers that alleviates or avoids the aforesaid problems.

[0011] SUMMARY

[0012] A first aspect relates to an assembly. The assembly comprises the container to be surface finished. The container includes at least one cavity defined by one or more surfaces such as, e.g., one or more walls and / or a base (in particular, inner wall(s) and / or an inner base), said surface(s) defining the shape of the cavity. The at least one cavity is adapted to hold a fluid that will be used for surface finishing the at least one surface of the cavity, i.e., the electrically conductive portion to be surface finished.

[0013] The assembly also comprises one, some or all devices or parts of a kit for surface finishing the container, for example but without limitation, a kit as disclosed in an aspect below. The kit comprises at least one electrically conductive device, an electric source with first and second poles, and, in some embodiments, at least one apparatus for providing relative motion between free solid bodies that are electrically conductive (e.g., electrolyte particles) as part of the fluid when arranged inside the cavity, and at least one surface of the container to be surface finished. In some cases, the assembly and the kit are configured to be connected to such at least one apparatus for providing the relative motion, which may be external to the assembly and the kit. The at least one surface is one or more surfaces defining the cavity, thus it can be part or the entirety of the surface(s) defining the cavity.

[0014] The at least one electrically conductive device is arranged at least partially inside the cavity of the container, and the electric source is configured to provide an electric potential difference between at least one surface of the one or more surfaces and the at least one electrically conductive device, thereby making it possible to conduct electropolishing for surface finishing the container. During most part or the entirety of the surface finishing, the at least one electrically conductive device does not contact the container or does not contact the at least one surface that has electrical potential to avoid short-circuits; to that end, the at least one electrically conductive device is preferably arranged in the cavity such that it does not contact the container or the at least one surface that has electrical potential. It may occur that, during the surface finishing, the at least one electrically conductive device comes into contact with the container or the at least one surface intermittently, although this is to be preferably avoided. The at least one surface may be flat, curved, regularly-shaped, irregularly-shaped, etc.

[0015] The electropolishing relies on the provision of electrically charged particles in the form of free conductive solid bodies, which are, for example, arranged in or are part of the fluid, so that it can produce ion transport and, therefore, exchange metal ions of the at least one surface of the container. For the electropolishing to be effective, there should be an electric potential difference between free conductive solid bodies and the at least one surface of the container. To this end, the container, or at least the surface thereof to be finished, should be electrically conductive and connected to a first pole, and the at least one electrically conductive device should be connected to a second pole, the latter making the electrically conductive particles to be also connected to the second pole and, consequently, producing the electric potential difference for the electropolishing. It is noted that the second pole is, in many cases, electrically opposite the first pole. Namely, the first and second poles provide the container and the electrolyte with a potential difference owing to, e.g., greater or lower electric potentials one and the other, and / or opposite electric potentials, and / or opposite electrical polarities. The electric potentials may not be the same continuously, for example, the connection of the container and the at least one electrically conductive device may be such that they are under an alternate current for changing potentials and / or polarities.

[0016] Upon contacting an electrically charged surface of the container, such electrically conductive particles of the electrolyte, when arranged in the fluid, exchange metal ions with the respective surface, thereby removing and / or depositing material therefrom and, thus, surface finishing it. The free conductive solid bodies are such that they are in contact one another or they are close one another even if they are apart so that an electrical bridge may be formed between the at least one electrically conductive device and the at least one surface of the container. The electrical bridge makes the metal ion exchange process particularly effective owing to the electrical circuit formed therebetween. In this sense, a density or amount or volume of conductive solid bodies, and a distance between the at least one electrically conductive device and the at least one surface of the container to be surface finished may be selected to form or enhance the formation of the electrical bridge (i.e. , greater packing factor of the electrically conductive particles to have a denser quantity of particles between the two ends of the electrical bridge to be formed).

[0017] The assembly and the electropolishing process associated therewith are configurable such that the conductive solid bodies contact the surface(s) of the container to be finished with more or less particles, and / or with more or less speed, and / or with larger or smaller footprint on the surface(s), each of which changes the dynamics of the electropolishing, in particular, the speed with which the electropolishing is conducted and / or how much material is removed.

[0018] While the free conductive solid bodies stay in contact with the surface of the container and the electrical connection exists, the particles may keep exchanging metal ions until they become saturated of metal ions, or until they have released all the metal ions they had, or until they lose their metal ion exchange capability owing to factors such as, e.g., loss of porosity of the particles, high temperature of the particles, etc. Continuous or sequential provision of free conductive solid bodies (in the form of electrolyte) into the fluid and / or continuous or sequential reconditioning of the solid bodies in the fluid allows having solid bodies in the fluid for repeated and, in some cases, continuous surface finishing, and do so alleviating any possible limited metal ion exchange capacity of the electrolyte particles as they reduce their efficacy over time.

[0019] In some embodiments, the assembly and the electropolishing process associated therewith are configurable such that electrically conductive solid particles are prevented from remaining static in direct contact with the surface being treated, as such static contact, regardless of electrical coupling, may result in detrimental effects, including corrosive marks due to local meniscus impregnation of liquid electrolyte. In some embodiments, fine-tuning of the assembly is applied to mitigate defects arising from this effect, particularly in the configurations according to the present disclosure where the container housing the solid bodies presents at least one surface to be treated, a scenario in which the described issue is more likely to occur.

[0020] Various strategies may be employed to address this challenge across different embodiments. In some embodiments, the solid particles contain a liquid electrolyte that is non-reactive with the surface material, such as non-acidic solutions based on deionized water retained by sulfonated PST-DVB strong cation exchange resins for the treatment of, e.g., stainless steel, where the acidity of the electrolyte is controlled to prevent degradation of the auto-passivation oxide layer. In some other embodiments, mechanisms or apparatuses for generating generalized motion among the solid bodies in contact with the surface are introduced, including, for example, one or more of: jets, motion brushes, pumps, or surface-oriented blades within the container. Such features help ensure that no static particles remain in contact with the surface, thereby preventing potential defects in the finishing process.

[0021] In the context of the present disclosure, surface finishing may encompass leading to a change in surface condition such as, e.g., roughness, waviness, gloss, oxides, surface tension, residual stresses, coatings, heterogeneities, dirt, substance attached to the surface, etc., on at least one surface of the container to be surface finished. Consequently, surface finishing may encompass one or more of: smoothing of the at least one surface, polishing of the at least one surface, precision finishing of the at least one surface, rounding of the at least one surface, deburring of the at least one surface, providing corrosion resistance to the at least one surface, electrodeposition of metallic ions, a change on the chemical composition on the metal surface, surface morphology or geometry modifications, residual stress relief, passivation or any change on the corrosive properties, surface tension modification, cleaning of the at least one surface, sterilization of the at least one surface, etc.

[0022] 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 WO 2017 / 186992 A1 , incorporated by reference in its entirety herein. 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 document, and in combination to aspects from WO 2022 / 123096 A1), incorporated by reference in its entirety herein, 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 non-significant electrical conductivity as below 10% of the total conductivity of the solid-particle based electrolyte.

[0023] In some embodiments, a solid-particle based electrolyte according to the present disclosure also includes, in addition to a plurality of electrically conductive solid particles, a plurality of abrasive particles, as disclosed in International Application No. PCT / ES2024 / 080378, incorporated by reference in its entirety herein. The present disclosure also includes, in some embodiments, a hybrid method for surface finishing at least one surface of a container by moving a combination of a plurality of electrically conductive particles and a plurality of abrasive particles relative to the surface(s) to be surface finished, and one or more particles of the plurality of electrically conductive particles comprising an electrolyte.

[0024] In some embodiments, one or more abrasive particles (e.g., one, some or all) of the plurality of abrasive particles 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 pap is a density of the abrasive particles, and presis a density of the electrically conductive particles or a resin thereof; and where MR = the particles (or resin thereof) including res the electrolyte; and where MR = where mapis a mass of the abrasive particles, and mresis a mass of the resin of the electrically conductive particles. 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.

[0025] 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.

[0026] In some embodiments, abrasive particles (synthetic and / or natural) of the plurality of abrasive particles 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).

[0027] In some embodiments, the abrasive composites typically comprise between 30% and 80% by weight of the abrasive powder and between 5% to 20% by weight of the charged polymer, any remaining percentage up to 100 % by weight, if necessary, consists of a solvent, such as water or alcohol, to form a stable colloidal suspension. The at least one abrasive composite particle varies in size from 2 nm to 500 nm, depending on the hardness and polishing requirements of the application. Densities of the abrasive composite particle(s) range from 2 to 7 g / cm3, and may be of, e.g., 2.6 g / cm3for abrasive composites comprising silica powder, 3.97 g / cm3for abrasive composites comprising alumina powder, and 5.6 g / cm3abrasive composites comprising for zirconium dioxide powder. The choice of a specific abrasive powder and / or charged polymer allows for tailored material properties and ultimately different removal rates. Some particular embodiments relate to abrasive composite particles with 60-70 wt.% silica combined with 10-20 wt.% PAA for semiconductor polishing, 50-65 wt.% alumina with 5-10 wt.% PDDA for hard substrates, and 40-60% cerium oxide with 5-15 wt.% PEI for optical glass polishing.

[0028] In some embodiments, the liquid retained by the solid particles is electrolytic, and its conductivity can be enhanced with acids or other agents, although in some embodiments of the disclosure the liquid also allows for reduced-acid or acid-free configurations, as in 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 composition of the fluid can be adjusted to include lubricating solids, which modify viscosity and provide additional control over the electropolishing process. In some other embodiments, the fluid may also consist of a gas, offering further flexibility in medium selection.

[0029] In the context of the present disclosure, the free conductive solid bodies, i.e., 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 be, e.g., ion exchange resins. The conductive solid bodies or particles have affinity to retain an amount of electrolytic solution, which provides them sufficient galvanic potential to react with a metallic surface in ionic exchange reactions.

[0030] In some embodiments, the assembly further comprises the fluid.

[0031] In some embodiments, the assembly or the fluid further comprises the free conductive solid bodies. In some embodiments, the fluid is an electrolytic fluid.

[0032] In some embodiments, the at least one electrically conductive device is apart from the at least one surface by a distance between 2 to 10 times a diameter of the electrolyte particles. In some embodiments, the distance is between 0.2 mm to 20 mm.

[0033] Such distances enable a more effective electric bridge between the at least one electrically conductive device and the at least one surface, and the flow of fluid between the device and the surface.

[0034] A more stable and continuous electric bridge increases the electropolishing rate since the electric potential difference should exist for the particles to exchange metal ions.

[0035] The flow of fluid makes that different particles come into contact with the surface(s) of the container. This not only makes it possible for less saturated particles to reach the surface, but also partially or completely saturated particles can get cooled down or withdrawn from the fluid for dispensing or recycling them. The metal ion exchange capacity of the solid bodies is also dependent on the temperature thereof, and the solid bodies get heated during the metal ion exchange process, therefore lowering their temperature is effective for increasing their capacity for further exchanging metal ions.

[0036] In some embodiments, the at least one electrically conductive device is apart from the at least one surface by a distance between 10 to 50 times a diameter of the electrolyte particles. In some embodiments, the distance is between 20 mm to 100 mm.

[0037] The surface finishing can also be effective at greater distances between the two poles considered for the surface finishing, especially if the electric potential difference between the two is greater. For example, if the voltage of the electric source providing the electric potential difference is increased, the speed at which the surface finishing is conducted generally increases; additionally or alternatively, the distance between the at least one electrically conductive device and the at least one surface may be larger with little or no influence on the speed of the surface finishing process.

[0038] In some embodiments, the at least one apparatus is configured to move the at least one electrically conductive device while arranged at least partially inside the cavity.

[0039] The motion of the at least one electrically conductive device causes the fluid to move, and so the free conductive solid bodies move relative to the at least one surface. Moreover, in some embodiments, the motion of the at least one electrically conductive device is used to control the electropolishing process as the electric potential difference provided depends on it. Thus, by rearranging the at least one electrically conductive device, so does the electric potential difference, and the dynamics of the electropolishing and / or the part of the volume of the assembly where electropolishing may be conducted changes as well. By way of example, a rotation of the at least one electrically conductive device, depending on the shape of the device, will cause the electropolishing to rotate as well, and so the potential surface(s) of the container to be surface finished will vary as the rotation occurs; in this way, the electropolishing may be conducted in a progressive manner, for example.

[0040] In some embodiments, the at least one electrically conductive device is fixed relative to the container.

[0041] In some embodiments, the at least one apparatus provides the relative motion between the free conductive solid bodies and the at least one surface by providing relative motion between the fluid and the at least one surface.

[0042] As the fluid includes the solid bodies, the motion of the fluid relative to the at least one surface causes the electropolishing process as well. The movement of the fluid relative to the at least one surface may be, for example, with shaking motion of the fluid and / or the container, fluid displacement, etc. To this end, the at least one apparatus comprises, for example, at least one vibrating apparatus, and / or at least one propeller, and / or at least one wave formation apparatus and / or at least one fluid motion generation apparatus, etc.

[0043] In some embodiments, the at least one electrically conductive device comprises a mesh that lets the fluid through. The mesh also lets the free conductive solid bodies through.

[0044] A mesh-like portion or device enables the provision of the electric potential difference and does not forbid the fluid from going through said portion or device, thereby providing more degrees of freedom for the motion of the solid bodies and the fluid.

[0045] By way of example, the mesh-like portion or device may have holes of any shape such as, but without limitation, rhomboidal, triangular, octahedric, etc., and the holes have a diameter between 0.10 cm2to 100 cm2.

[0046] In some embodiments, the at least one electrically conductive device comprises a solid member or body that, in some embodiments, does not let the fluid through. The solid member or body does not let the free conductive solid bodies through either. A solid portion or device limits the possible motion of the free conductive solid bodies and the fluid, which, in some cases, simplifies controlling the electropolishing process as there are fewer pathways that the conductive solid bodies may follow, especially if the solid portion or device does not let the fluid through.

[0047] In some embodiments, the at least one electrically conductive device is at least partially shaped resembling the cavity.

[0048] By reproducing the shape of the surface(s) defining the cavity, the at least one electrically conductive device may be separated from the at least one surface by a constant or substantially constant distance and allow the generation of the electric potential difference with different portions of the at least one surface.

[0049] In some embodiments, the at least one apparatus comprises a motor or a pump.

[0050] The motor or the pump moves the at least one electrically conductive device, and / or the free conductive solid bodies and the fluid, and / or the container.

[0051] In some embodiments, the at least one apparatus has no electrical connectivity with the fluid or the at least one electrically conductive device.

[0052] When the at least one apparatus has electrical connectivity, it may reduce the efficiency of the surface finishing as electric potential difference is provided by the at least one apparatus. The electrolyte particles thus do not form the electrical bridge in the form it is expected to, resulting in fewer conductive solid bodies causing the metal ion exchange from the at least one surface.

[0053] To this end, an electrical isolation device may be arranged on the at least one apparatus and / or electrically conductive device so as to reduce or block the transmission of the electric potential that the at least one electrically conductive device could provide to the at least one apparatus.

[0054] In some embodiments, the at least one apparatus is arranged to pump the free conductive solid bodies inside the cavity. In some embodiments, the at least one apparatus comprises a pump arranged to provide the free conductive solid bodies inside the cavity.

[0055] In some embodiments, the assembly or the at least one apparatus further comprises a device for reconditioning free conductive solid bodies temperature-wise and / or chemical composition-wise.

[0056] New free conductive solid bodies not yet present in the fluid, and / or reconditioned free conductive solid bodies can be pumped in the fluid for the electropolishing process. When reconditioned, the reconditioning device comprises means for cooling down the solid bodies, and / or means for changing the chemical composition of the solid bodies. Concerning the latter, the means may be adapted to remove and / or supply one or more predetermined chemical agents, and / or be adapted to produce a chemical reaction. The device for reconditioning is preferably coupled with the pump or a conduit through which the free conductive solid bodies are pumped.

[0057] The solid bodies are, in some embodiments, pumped towards the at least one surface and / or pumped proximate to the at least one surface to make the pumped solid bodies exchange metal ions.

[0058] In some embodiments, the at least one surface is at least one first surface, wherein at least one second surface of the one or more surfaces and / or a portion of the at least one first surface comprises electrically non-conductive paint or coating thereon.

[0059] The paint or coating is applied to particular surfaces or portions thereof that are not to be surface finished. As there is no electric potential difference between the conductive solid bodies and such portion or surface(s), no metal ion exchange takes place thereon.

[0060] In some embodiments, the assembly further comprises at least one pump for extracting free conductive solid bodies and / or the fluid from the cavity and / or introducing free conductive solid bodies and / or the fluid into the cavity.

[0061] The fluid and the electrolyte may be renewed over time, or initially supplied into the cavity, for example without requiring manual intervention.

[0062] In some embodiments, the container is a container according to an aspect below.

[0063] Another aspect relates to a method. The method comprises, e.g.: arranging a fluid inside a cavity of a container; arranging at least one electrically conductive device at least partially inside the cavity; generating an electric potential difference between at least one surface of the container and the at least one electrically conductive device; and surface finishing the at least one surface of the container by providing relative motion between the fluid or free conductive solid bodies thereof and the at least one surface.

[0064] The fluid, which includes an electrically conductive particles in the form of free conductive solid bodies, has at least some particles therein come into contact with the at least one surface while the fluid and the at least one electrically conductive device are both arranged inside the cavity, thereby surface finishing the at least one surface. The electric potential difference between the particles and the at least one surface causes electropolishing.

[0065] The cavity is defined by one or more surfaces of the container, which includes the at least one surface to be surface finished. That is to say, the at least one surface is an electrically conductive part to be surface finished. The at least one electrically conductive device preferably does not contact the container or the at least one surface that has electrical potential during part or the entirety of the surface finishing to avoid short-circuits.

[0066] In some embodiments, the method further comprises manufacturing the container.

[0067] The container, which may comprise or be made of an electrically conductive material (such as, but without limitation, steel, stainless steel, cast iron alloy, cupper alloy, titanium alloy, scalmalloy (e.g., brass, alpaca, etc.), nickel alloy, cobalt-chromium alloy, aluminum alloy, or a combination thereof), once manufactured is surface finished. The container may be manufactured in any form known in the art, for example, casting, injection molding, stamping, etc.

[0068] In some embodiments, the method is carried out with or on an assembly as described above.

[0069] In some embodiments, the at least one electrically conductive device is apart from the at least one surface by a distance between 2 to 50 times a diameter of the free conductive solid bodies during part or an entirety of the surface finishing. In some embodiments, the distance is between 2 to 10 times the diameter, and / or between 10 to 50 times the diameter. In some embodiments, the distance is between 0.2 mm to 20 mm and / or between 20 mm and 100 mm.

[0070] In some embodiments, the surface finishing comprises moving the at least one electrically conductive device while arranged at least partially inside the cavity.

[0071] In some embodiments, the method further comprises arranging an electrical isolation device between the at least one apparatus and one or more of: the at least one electrically conductive device and the fluid.

[0072] In some embodiments, the at least one surface is at least one first surface, and the method further comprises painting or coating, with electrically non-conductive paint or coating, at least one second surface of the one or more surfaces and / or a portion of the at least one first surface.

[0073] In some embodiments, the arranging of the fluid comprises arranging the free conductive solid bodies and / or the fluid in the cavity. In some embodiments, the arranging comprises pouring electrolyte and / or the fluid in the cavity.

[0074] In some embodiments, the surface finishing comprises pumping, with the at least one apparatus, the free conductive solid bodies and / or the fluid in the cavity.

[0075] In some embodiments, the method further comprises pumping, with at least one pump, the free conductive solid bodies and / or the fluid out from the cavity.

[0076] In some embodiments, the method further comprises reconditioning at least some free conductive solid bodies temperature-wise and / or chemical composition-wise.

[0077] In some embodiments, the method does not comprise immersing the container in a pool, in particular a pool with the fluid.

[0078] In some embodiments, the surface finishing is carried out at premises where the container has been used for receiving at least one substance or at least one object.

[0079] In some embodiments, the container is a container according to an aspect below.

[0080] In some embodiments, after the surface finishing, the at least one surface has a skewness (Rsk) equal to or less than 0.

[0081] In some embodiments, after the surface finishing, the at least one surface has a reduced peak height (Rpk) between 8.5 and 16.5, the endpoints being included in the range.

[0082] Such Rsk and / or Rpk values make the at least one surface more protected against stress corrosion cracking whereby chloride anions can produce cracks or extend cracks in valleys or recesses on the at least one surface. Therefore, with lower attained Rsk and / or Rpk values there are fewer smaller valleys or recesses present on the at least one surface that could lead to stress corrosion cracking.

[0083] In some embodiments, after the surface finishing, the at least one surface has a surface roughness (Ra) equal to or less than 1 .0 pm, more particularly equal to or less than 0.5 pm.

[0084] In some embodiments, after the surface finishing, the at least one surface has a surface roughness ratio between 5.0 and 6.5, the endpoints being included in the range. The surface roughness ratio is calculated as the difference between the tallest peak and the deepest valley (Rz) divided by the surface roughness (Ra).

[0085] Another aspect relates to a container surface finished with a method as previously described. That is to say, the container has at least one surface that has been surface finished with the method.

[0086] In some embodiments, the container and / or a cavity thereof has a volume equal to or greater than 100 cm3.

[0087] In some embodiments, the container and / or a cavity thereof has a volume equal to or smaller than 5000 m3.

[0088] In some embodiments, the container is one of: a tube, an oil and / or gas pipe, a barrel (e.g., a petrol barrel), a mold for injection, a mold for stamping, or a ship container.

[0089] In some embodiments, the at least one surface of the container comprises or is made of one of the following: steel, stainless steel, cast iron alloy, cupper alloy, titanium alloy, scalmalloy (e.g., brass, alpaca, etc.), nickel alloy, cobalt-chromium alloy, aluminum alloy, or a combination thereof.

[0090] In some embodiments, the at least one surface has a skewness (Rsk) equal to or less than 0.

[0091] In some embodiments, the at least one surface has a surface roughness Ra equal to or less than 0.1 pm.

[0092] Another aspect relates to a kit for surface finishing a container. The kit comprises, e.g.: a fluid comprising a plurality of free electrically conductive solid bodies; at least one electrically conductive device; and an electric source having a first pole adapted for connection with at least one surface of the container to provide a first electric potential thereto, and a second pole connected to the at least one electrically conductive device to provide a second electric potential thereto.

[0093] The kit is preferably configured to be connected with, or comprises, at least one apparatus for providing relative motion between at least some free electrically conductive solid bodies of the fluid when arranged inside a cavity of the container and the at least one surface of the container.

[0094] In some embodiments of any one of the aspects above, the fluid has a minority (i.e. , below 50.0%) of acid in total weight of the fluid, the fluid being with or without an electrolyte of the free conductive solid bodies.

[0095] In some embodiments of any one of the aspects above, the fluid without the free conductive solid bodies comprises acid in a concentration such that an electrical conductivity of the fluid without the acid decreases less than 10% with respect to the electrical conductivity of the fluid with the acid and without the free conductive solid bodies.

[0096] In some embodiments of any one of the aspects above, the fluid without the free conductive solid bodies comprises acid in a concentration such that an electrical conductivity of the fluid increases less than 10% with respect to the electrical conductivity of the fluid without the acid and without the free conductive solid bodies.

[0097] In some embodiments, the fluid does not comprise acid.

[0098] The assembly allows the surface finishing of the container without having to transport the latter to facilities where acid may be handled safely since the fluid has less than 50% of its total weight in acid agents, in some cases below 10%, and in some cases below 1 %. In some cases, the fluid does not have acid agents.

[0099] The lack or the reduced quantity of acid agents makes the assembly suitable for any or many facilities, even those which might not be adequate for handling acids, which, in turn, makes the transportation of the containers to other locations unnecessary. Namely, the surface finishing can be conducted at the same premises where the container usually is. Vapors, fumes and other particles caused by the surface finishing by large quantities of acids are also alleviated or avoided altogether. Such particles include, in some cases, those deposited on the finished at least one surface and which damage it. When the number of particles on the at least one surface is excessive, neutralization or passivation of the at least one surface is generally required to increase the useful life of the container.

[0100] In some embodiments of any one of the aspects above, the fluid comprises a liquid. In some embodiments, the fluid comprises a gas.

[0101] The fluid, which is a medium (e.g., an electrolytic medium) that serves as a moderating fluid for the free conductive solid bodies, comprises as majority thereof (i.e., 50.0% or more) liquid and / or gas (e.g., air, oxygen, etc.). The fluid thus allows the electrolyte and, particularly, the free conductive solid bodies thereof to move relative to the at least one surface for electropolishing such that an electric potential difference between the electrolyte particles and the at least one surface is present. In this sense, the fluid provides a physical medium with viscosity and aerodynamics such that there is an effective motion and recirculation of the medium (and, thus, fluid with electrolyte) inside the container. Namely, the fluid, together with the relative motion effected, influences the establishment of the electric bridge for the electric potential difference.

[0102] A liquid fluid, or a fluid with a majority in liquid form aids in the cooling down of free conductive solid bodies as they heat up during the electropolishing due to ohmic effects.

[0103] In some embodiments of any one of the aspects above, the fluid comprises a lubricating solid.

[0104] The lubricating solid modifies a viscosity of the fluid and / or a viscosity on the at least one surface, thereby enabling additional control parameters of the electropolishing.

[0105] In some embodiments of any one of the aspects above, the fluid is electrically conductive.

[0106] The conductivity of the medium due to the conductivity of the fluid favors the reduction of the time taken for the surface finishing to conclude if compared with a same configuration but with a less conductive or non-conductive fluid. The conductivity of the fluid increases the electrical field and the number of electrical paths generated between the two conductive ends, i.e., the at least one electrically conductive device and the at least one surface. In this sense, the distance between the two conductive ends, namely between the two poles of the surface finishing process, may be considered as being virtually smaller as the electrical bridges formed therebetween are formed more frequently and / or more reliably.

[0107] The precision with which the surface finishing is conducted may become lower than for configurations in which the fluid is less conductive or non-conductive. Particularly, a parameter (or parameters) used to quantify the result of the surface finishing, for example, a roughness value, a thickness of a deposited layer, etc., may be greater than in those other configurations.

[0108] By way of example, roughness values Ra and Rz generally used in the field may attain values of 0.20 pm and 0.60 pm, respectively, whereas configurations with less conductive fluids could attain values below the aforementioned ones.

[0109] In some embodiments of any one of the aspects above, a galvanic capacity of the electrically conductive fluid is equal to or smaller than a galvanic capacity of the electrolyte.

[0110] When the conductive fluid has such galvanic capacity, the precision of the surface finishing might become greater, thereby attaining greater dimensional tolerance. The surface finishing may also reduce the number of vapors and the pollution generated during the surface finishing.

[0111] By way of examples, roughness values Ra and Rz may attain values of 0.10 pm and 0.30 pm, respectively. In some embodiments of any one of the aspects above, the fluid is electrically non- conductive. For example, the fluid has an electrical conductivity of 1.0 pS crn-1or lower, in particular 0.5 pS crn"1or lower, more in particular 0.1 pS crn"1or lower.

[0112] The surface finishing is mostly or completely influenced by the action of the electrolyte within the free conductive solid bodies, thereby increasing the level of control and, thus, precision of the surface finishing process since it depends more on the action of the electrolyte. In turn, the precision of the surface finishing can be increased, and achieve so with an even lower generation of vapors and pollution, not only to the environment but also to the surface that is surface finished as fewer undesired particles become attached or remain on the treated surface.

[0113] By way of example, roughness values Ra and Rz may attain values below 0.10 pm and 0.3 pm, respectively, for example between 0.03 and 0.10 pm in the case of Ra, and between 0.10 and 0.30 in the case of Rz.

[0114] It will be noted that all the aforesaid Ra and Rz values are just exemplary values for a particular surface finishing treatment; in this regard, other values could likewise be provided for other surface finishing treatments, for example, deburring of the at least one surface, providing corrosion resistance to the at least one surface, etc.

[0115] In some embodiments of any one of the aspects above, at least some (thus, some or all) free conductive solid bodies are of or comprise a material selected from: strong and weakly acidic cationic resins, strong and weakly basic anion exchange resins and chelating resins, and in particular cationic exchange resins, as such resins contribute to exchange metal ions in surface finishing processes.

[0116] In some embodiments of any one of the aspects above, at least some free conductive solid bodies are of polymeric material are of a sulfonated divinylbenzene S-DVB and styrene copolymer, since it is a material resistant to acid and the oxidative action of the process. Such material has the ability to act as an ion exchanger.

[0117] Alternatively, the polymeric material particles are of a copolymer containing units derived from acrylic acid or methacrylic acid. This includes derivatives with different functional groups such as acrylic acid, acrylamide, cyanoacrylate, alkyl acrylates, among others, and the corresponding methacrylate analogs.

[0118] In some embodiments of any one of the aspects above, at least some free conductive solid bodies are of polymeric materials including functional groups that are capable of capturing or retaining the metal ions generated during the process, such as acid, amino, or chelating groups. These functional groups can be of the acidic type, such as sulfonic or carboxylic groups. These acidic functional groups are especially useful in this application as they have good chemical resistance and are capable of retaining a wide variety of metal ions. It is also possible to use functional groups that are of the chelating type such as, for example, iminodiacetic, aminophosphonic, polyamine, 2-picolylamine, thiourea, amidoxime, isothiouronium, bispicolilamine, among others. These chelating groups have a high selectivity over the transition metals versus alkali or alkaline earth metals, which allows them to be more flexible in the formulation and does not require the use of distilled water.

[0119] Depending on the specific type of polymer and functional groups included, the exact composition of the free conductive solid bodies may vary and may be adjusted. As a mode of example, in some embodiments, the free conductive solid bodies are of a cationic resin of a gel copolymer styrene-divinylbenzene (DVB), which in some cases is sulfonated.

[0120] The free conductive solid bodies may have at least a surface thereof that encapsulates the electrolyte, and such surface may be of a particular material such as, for example but without limitation, an ion-exchange resin, preferably cationic ion-exchange resin that is preferably acid, for example but without limitation, polystyrene divinylbenzene. The encapsulating surface may let the electrolyte escape, at least partially, upon the particle contacting a surface or another particle, and it may also let electrolyte on the surface of, e.g., the container to be surface finished, to be absorbed again into the particle.

[0121] In some embodiments of any one of the aspects above, at least some free conductive solid bodies have a porous structure, which facilitates the exchange of fluids resulting in a faster process. Alternatively, the bodies have, in some embodiments, a gellike structure. In such cases, the fluid exchange is more restricted, which results in a slower process, however, the particle-surface contact is more defined, resulting in a lower final roughness when such surface finishing is sought.

[0122] The free solid conductive bodies are, in some cases, of a porous material, whereby the electrolyte is contained inside the porous of the material. In some examples, the particles are porous, and the porosity is selected from: microporosity, mesoporosity, macroporosity and fractal porosity. Typically, the porous material is not saturated with the electrolyte. Thereby, the electrolyte is typically released when in contact with the surface of to be surface finished. The function of the electrolyte is twofold: on the one hand, it conducts electricity, and on the other, it dissolves the oxides that are formed on the surface to be treated.

[0123] A shape of free conductive solid bodies as described herein may preferably be spheric or spheroid.

[0124] In some embodiments of any one of the aspects above, the electrolyte is an acidic aqueous solution, e.g., an aqueous solution of hydrofluoric acid (HF), sulfuric acid, sulfonic acids (e.g., methanesulfonic acid, MSA), phosphoric acid, carboxylic acids, citric acid, and hydrochloric acid. In some examples, the electrolyte is or comprises an aqueous solution of sulfuric acid or MSA. In some embodiments of any one of the aspects above, at least some free conductive solid bodies comprise a combination of bodies having different types of electrolyte (e.g., aqueous solutions of different acids), For instance, the free conductive solid bodies comprise solid bodies comprising an aqueous solution of MSA and solid bodies comprising an aqueous solution of sulfuric acid.

[0125] The total concentration of the acids in the electrolyte is, in some cases, from 0.1 to 70 wt.% with respect to the total mass of water therein plus the acid, in particular from 1 to 40 wt.%. In some cases, the acid concentration is from 1 % and 10 wt.% relative to the mass of the water plus the acid.

[0126] In particular, an HF solution such as, e.g., a 90 to 99% water, H2O, and 10 to 1 % HF, by weight of acid to the total weight of water and acid is used in some cases. As another example, an aqueous solution of sulfuric acid having, e.g., a 75 to 99% water, H2O, and 25 to 1 % of sulfuric acid, in particular 10 to 1 % of sulfuric acid, by weight of acid to the total weight of water and acid is used in some cases. Similarly, an aqueous solution of methanesulfonic acid (MSA) having, e.g., a 60 to 99% water, H2O, and 40 to 1 % of MSA, in particular from 10 to 1 % of MSA, by weight of acid to the total weight of water and acid is used in some cases.

[0127] In some embodiments of any one of the aspects above, at least some free conductive solid bodies are dry electropolishing solid bodies.

[0128] BRIEF DESCRIPTION OF THE DRAWINGS

[0129] 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 figures:

[0130] Figure 1 shows an assembly in accordance with some embodiments.

[0131] Figure 2 shows an assembly in accordance with some embodiments.

[0132] Figure 3 shows an assembly in accordance with some embodiments.

[0133] Figure 4 shows an assembly in accordance with some embodiments.

[0134] Figure 5 shows an assembly in accordance with some embodiments.

[0135] Figure 6 shows an assembly in accordance with some embodiments.

[0136] Figure 7 shows an assembly in accordance with some embodiments.

[0137] Figures 8A-8B show an assembly in accordance with some embodiments.

[0138] Figure 9 shows an assembly in accordance with some embodiments.

[0139] Figure 10 shows an assembly in accordance with some embodiments.

[0140] Figure 11 shows an assembly in accordance with some embodiments. DETAILED DESCRIPTION

[0141] Figure 1 shows an assembly in accordance with some embodiments.

[0142] The assembly 100 includes a container 1 with one or more surfaces 30. At least one surface 31 of the surfaces 30 on the inside are such that a cavity 35 is formed. The cavity 35 serves as a receptacle, for substances and / or goods to be contained in the container 1 , and for a physical medium for surface finishing the container 1 . Part or the entirety of the at least one surface 31 is to be surface finished.

[0143] The assembly 100 includes at least one electrically conductive device 4 at least partially introduced in the cavity 35, and at least partially immersed in fluid 6 when such fluid 6 is comprised by or arranged in the assembly 1. The fluid 6, which may be liquid and / or gas, and optionally include a lubricating solid (not illustrated), includes, at least during the surface finishing, free electrically conductive solid bodies 40, e.g., electrolyte particles.

[0144] 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 is connected with or comprises an electric source 45, such as a power source with a first pole 46 and a second pole 47, e.g., an anode and a cathode, respectively, or vice versa. More in particular, the at least one surface 31 is electrically connected with the first pole 46, and the at least one electrically conductive device 4 is electrically connected with the second pole 47. In particular embodiments, the polarity of first 46 and second 47 poles of the power source 45 is inverted at least once, in some cases is periodically inversed and reversed within all process optionally presenting a duty cycle between each inversion.

[0145] The assembly 100 includes or can be connected with at least one apparatus 7 for producing a relative movement between the fluid 6 and the at least one surface 31 so that the solid bodies 40 may come into contact with the at least one surface 31 and then move around in the fluid 6. In this example, the at least one apparatus 7 is a motor coupled with the at least one electrically conductive device 4, the latter moving, in this case, rotating owing to the action of the motor.

[0146] As it can be appreciated, the at least one electrically conductive device 4 is preferably arranged such that it does not contact the at least one surface 31 , nor the container 1 , to avoid short-circuiting the two, and there is rather a distance D between the two. The distance D is, in some cases, between 2 to 50 times the diameter of the solid bodies 40. Further, an electrical isolator 29 is optionally arranged between the at least one electrically conductive device 4 and the at least one apparatus 7 to likewise avoid shortcircuiting the two.

[0147] In this example, the at least one electrically conductive device 4 is a single propeller, but in other examples it could be more than one propeller, and / or be other type of devices and / or have other shapes.

[0148] Figure 2 shows an assembly 100 in accordance with some embodiments.

[0149] 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.

[0150] Further, the at least one apparatus 7, which may be part of the assembly 100 or not, includes a motor and a propeller at least partially immersed in the fluid 6.

[0151] Figure 3 shows an assembly 100 in accordance with some embodiments.

[0152] The assembly 100 includes the at least one electrically conductive device 4 at least partially shaped according to the shape of the cavity 35 and at a distance from the at least one surface 31. The assembly 100 also includes a receptacle 3 with a porous membrane on one or more sides thereof that lets fluid 6 pass through, and in some cases also free electrically conductive solid bodies 40 pass through. In some other cases, a receptacle 3 with a porous membrane prevents the free electrically conductive solid bodies 40 and / or at least part of the fluid 6 pass through, thereby generating an increase and decrease of pressure to the solid bodies 40 surface finishing the at least one surface 31 during fluid 6 inlet and outlet cycles. The receptacle 3 may be coupled with a conduit 5 for recirculating and / or pumping fluid 6 and / or solid bodies 40. For example, in some cases, free electrically conductive solid bodies 40 are pumped into the fluid 6 through the conduit 5 into the receptacle 3, which in turn lets the solid bodies 40 reach parts in the cavity 35 beyond the receptacle 3. Also, in some cases, fluid 6 is extracted through the conduit 5 and reconditioned or recycled. Likewise, the conduit 5 may be coupled with a pump that pumps a fluid, such as the fluid 6, to produce or increase the motion of the fluid 6 within the cavity 35.

[0153] The electric source 45 is electrically connected with the at least one surface 31 and the electrically conductive device 4 to produce an electric potential difference.

[0154] The assembly 100 may also include a cover 2 for controlling the fluid 6, especially that it does not escape the container 1 nor lets people reach the cavity 35.

[0155] Figure 4 shows an assembly 100 in accordance with some embodiments.

[0156] The assembly 100 includes the at least one apparatus 7 for producing a relative movement between the fluid 6 and / or solid bodies 40 and the at least one surface 31 in the form of a mechanical agitator. In this example, the mechanical agitator has a number of solid bodies coupled therewith for moving volumes of fluid 6 as the mechanical agitator is actuated with, e.g., a motor of the at least one apparatus 7. The distances D between the electrically conductive device 4 and the surfaces 31 of the container 1 may be adjusted and / or varied between different portions of the electrically conductive device 4 and the portions of the surfaces 30 closest thereto may not be constant, i.e., the distance D is variable.

[0157] Figure 5 shows an assembly 100 in accordance with some embodiments.

[0158] The assembly 100 includes the at least one apparatus for producing a relative movement between the fluid 6 and / or solid bodies 40 and the at least one surface 31 in the form of an ultrasound generator 9. The ultrasound generator 9 may be coupled with an axis 8 that receives an electrical connection for powering the ultrasound generator 9 and, optionally, for controlling the operation of the ultrasound generator 9, e.g., via controller commands. Ultrasounds provided by the ultrasound generator 9 produce displacement of volumes of fluid 6 and solid bodies 40.

[0159] Figure 6 shows an assembly 100 in accordance with some embodiments.

[0160] The assembly 100 includes the at least one apparatus for producing a relative movement between the fluid 6 and / or solid bodies 40 and the at least one surface 31 in the form of a vibrating apparatus. The vibrating apparatus includes a vibrator 11 . The vibrating apparatus optionally includes one or more of: a supporting base 10 for the container 1 to make the supporting base 10 to vibrate and, in turn, make the container 1 to vibrate; one or more vibration absorbers and / or one or more elastic devices 12 (e.g., springs, silent-blocks, air pillows, etc.); and / or a supporting structure 13 to support the assembly 100. The one or more elastic devices 12 are preferably adapted to tune or allow tuning of the vibration exerted by the vibrator 11 , for example to make the fluid 6 and / or solid bodies 40 vibrate at a frequency that enhances the motion of the fluid 6 and / or solid bodies 40, such as, but not limited to, a resonant frequency. The supporting structure 13 may be any surface that can hold the assembly 100, for example, the floor of premises.

[0161] Figure 7 shows an assembly 100 in accordance with some embodiments.

[0162] The assembly 100 includes the at least one apparatus for producing a relative movement between the fluid 6 and / or solid bodies 40 and the at least one surface 31 in the form of a fluid projection apparatus. The fluid projection apparatus includes at least one nozzle 14 electrically coupled with the electric source 45 for providing an electric potential difference with respect to the at least one surface 31 to be surface finished. The at least one nozzle 14 projects fluid 6 and / or solid bodies 40 to the at least one surface 31 from a distance D.

[0163] The fluid projection apparatus may also include a pump 15, preferably a pump configured to adjust pressure and flow, and / or a fluid intake 16 for delivering fluid 6 already in the cavity 35 towards the at least one nozzle 14, for example with the aid of the pump 15, if any. This arrangement allows the projection of fluid 6 already in the cavity 35, thereby easing the process and reducing the volume of new fluid 6 or free electrically conductive solid bodies thereof to be pumped into the assembly 100.

[0164] Figures 8A-8B show an assembly 100 in accordance with some embodiments.

[0165] The assembly 100 includes the at least one apparatus for producing a relative movement between the fluid 6 and the at least one surface 31 in the form of a rotating apparatus 17 (e.g., a turbine) that, in turn, includes at least one brush 18 coupled therewith. The rotating apparatus 17 is arranged such that it can move, e.g., rotate about an axis 26, such as an excentric axis. The movement may be provided for, example, by the action of a motor (not illustrated) of the at least one apparatus. The rotating apparatus 17 is electrically connected with the electric source 45 to provide the electric potential difference with respect to the at least one surface 31 to be surface finished. The at least one brush 18, which in some cases contact(s) the at least one surface 31 , is electrically non-conductive, and it lets the fluid 6 and the bodies thereof flow therewithin so that the bodies move, especially towards the surface(s) 31 to be surface finished owing to the motion imparted by the rotating apparatus 17. With the at least one brush 18, the motion of the bodies can be controlled, in particular in what regards pressure and direction, to have the bodies reach the surface(s) 31 and, thus, reduce the possibility of having the fluid 6 substantially motionless. The rotating apparatus 17 or the at least one brush 18 may also include a mechanical device for pushing the fluid 6 within the at least one brush 18 towards the at least one surface 31 .

[0166] Figure 9 shows an assembly 100 in accordance with some embodiments.

[0167] The assembly 100 includes the at least one apparatus for producing a relative movement between the fluid 6 and the at least one surface 31 in the form of a conduit 19 for delivering a fluid into the cavity 35.

[0168] In some cases, the delivered fluid is a fluid different from the medium fluid 6 that includes free electrically conductive solid bodies. By way of example, the fluid is air. The delivered fluid may cause the formation of particles or bubbles 20 of the delivered fluid in the medium fluid 6. Such particles or bubbles 20 typically produce motion of the medium fluid 6 in addition to the motion imparted to the medium fluid 6 due to the fluid pumping.

[0169] In some other cases, the delivered fluid is the medium fluid 6, which is pumped inside the cavity 35 such that the motion the medium fluid 6 has due to the pumping produces the relative motion.

[0170] Figure 10 shows an assembly 100 in accordance with some embodiments.

[0171] The assembly 100 includes the at least one apparatus for producing a relative movement between the fluid 6 and the at least one surface 31 in the form of an apparatus 27 for subjecting the container 1 to oscillations and / or vibrations in one or more directions 21 , 22, 23. The apparatus 27 may shake the container 1 in a controlled manner to produce the oscillations and / or vibrations. Figure 11 shows an assembly 100 in accordance with some embodiments.

[0172] The assembly 100 includes the at least one apparatus for producing a relative movement between the fluid 6 and the at least one surface 31 in the form of a piston apparatus 24. The piston apparatus includes a first chamber 24a for a first fluid (e.g., air) that actuates a compressing piston as first fluid is received and expelled through conduits coupled with the first chamber 24a. A second chamber 24b holds a second fluid (e.g., hydrogen sulfide) that presses against and gets mixed with the medium fluid 6 as a result of the compression exerted by the compressing piston.

[0173] 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.

[0174] 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.

Claims

CLAIMS1. An assembly for surface finishing, comprising: a container comprising a cavity, the cavity being defined by one or more surfaces to be treated 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.

2. The assembly of claim 1 , wherein the at least one electrically conductive device is apart from the at least one surface by a distance between 0.2 mm and 100 mm.

3. The assembly of any one of the preceding claims, wherein the at least one apparatus is configured to move the at least one electrically conductive device while arranged at least partially inside the cavity.

4. The assembly of any one of the preceding claims, wherein the at least one apparatus provides the relative motion between the free electrically conductive solid bodies and the at least one surface by providing relative motion between the fluid and the at least one surface.

5. The assembly of any one of the preceding claims, wherein the at least one electrically conductive device comprises a mesh that lets the free electrically conductive solid bodies through.

6. The assembly of any one of the preceding claims, wherein the at least one electrically conductive device comprises a solid body that does not let the free electrically conductive solid bodies through.

7. The assembly of any one of the preceding claims, wherein the at least one apparatus comprises a motor or a pump.

8. The assembly of any one of the preceding claims, wherein the at least one apparatus has no electrical connectivity with the fluid or the at least one electrically conductive device.

9. The assembly of any one of the preceding claims, wherein the at least one apparatus is arranged to pump the free electrically conductive solid bodies inside the cavity, or comprises a pump arranged to provide the free electrically conductive solid bodies inside the cavity.

10. The assembly of any one of the preceding claims, wherein the at least one surface is at least one first surface, wherein at least one second surface of the one or more surfaces and / or a portion of the at least one first surface comprises electrically non-conductive paint or coating thereon.11 . The assembly of any one of the preceding claims, further comprising the fluid.

12. The assembly of any one of the preceding claims, further comprising the free electrically conductive solid bodies.

13. The assembly of any one of the preceding claims, wherein a first pole of the electric source is connected with the container and a second pole of the electric source is or is connected with the at least one electrically conductive device.

14. A method comprising: arranging a fluid inside a cavity of a container, the cavity being defined by one or more surfaces of the container, the fluid including at least a plurality of free electrically conductive solid bodies; arranging at least one electrically conductive device at least partially inside the cavity; generating an electric potential between at least one surface of the container and the at least one electrically conductive device; and while the fluid and the at least one electrically conductive device are both arranged inside the cavity, surface finishing the at least one surface of the container by providing 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.

15. The method of claim 13, further comprising manufacturing the container.

16. The method of any one of the preceding claims, wherein the at least one electrically conductive device is apart from the at least one surface by a distance between 0.20 mm and 100.0 mm at least during part of the surface finishing.

17. The method of any one of the preceding claims, wherein the surface finishing comprises moving the at least one electrically conductive device while arranged at least partially inside the cavity.

18. The method of any one of the preceding claims, further comprising arranging an electrical isolation device between the at least one apparatus and one or more of: the at least one electrically conductive device and the fluid.

19. The method of any one of the preceding claims, wherein the surface finishing comprises pumping, with the at least one apparatus, the free electrically conductive solid bodies and / or the fluid in the cavity; and / or the method further comprises pumping, with at least one pump, the free electrically conductive solid bodies and / or the fluid out from the cavity.

20. The method of any one of the preceding claims, wherein the at least one surface is at least one first surface, and wherein the method further comprises painting or coating, with electrically non-conductive paint or coating, at least one second surface of the one or more surfaces and / or a portion of the at least one first surface.21 . The method of any one of the preceding claims, wherein the method is carried out with or on an assembly according to any one of claims 1-13.

22. A container surface finished with a method according to any one of claims 14-21.

23. The assembly of any one of claims 1-13, the method of any one of claims 14-21 or the container of claim 22, wherein the container and / or a cavity thereof has a volume equal to or greater than 100 cm3.

24. The assembly of any one of claims 1-13 and 23, the method of any one of claims 14-21 and 23 or the container of any one of claims 22-23, wherein the container and / or a cavity thereof has a volume equal to or smaller than 5000 m3.

25. A kit for surface finishing a container, comprising: a fluid comprising a plurality of free electrically conductive solid bodies; at least one electrically conductive device; and an electric source having a first pole adapted for connection with at least one surface of the container to provide a first electric potential thereto, and a second pole connected tothe at least one electrically conductive device to provide a second electric potential thereto; wherein the kit is configured to be connected with, or comprises, at least one apparatus for providing relative motion between at least some free electrically conductive solid bodies of the fluid when arranged inside a cavity of the container and the at least one surface of the container.

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