Method for providing a coated object by particle coating

Abstract

The present disclosure relates to a coating method for providing an object of an electrically conductive material with a metal and / or a metal oxide coating, using a plurality of electrically conductive particles and at least one electric pulse, to electrically conductive particles for use in said coating method and a method for preparing the same, to a coated object obtainable by said coating method, and to a coated object having homogeneous morphology.

Description

[0001] METHOD FOR PROVIDING A COATED OBJECT BY PARTICLE COATING

[0002] TECHNICAL FIELD

[0003] The present disclosure is in the field of electrochemical coating and, in particular but without limitation, it relates to: a coating method, for providing an object of an electrically conductive material with a metal and / or a metal oxide coating, using a plurality of electrically conductive particles and at least one electric pulse; electrically conductive particles for use in a coating method; a method for preparing electrically conductive particles for use in coating methods; a coated object obtainable by a coating method; and a coated object having homogeneous morphology comprising, e.g., homogeneously distributed coating or coatings in terms of their thickness and amount of defects present therein.

[0004] BACKGROUND

[0005] Metal and metal oxide coatings are widely used to finish a wide range of products for numerous applications.

[0006] Electrochemical processes can be used for applying metal and metal oxide coatings to objects of an electrically conductive material. For instance, metal coatings may be applied by electroplating and metal oxides may be applied by anodizing electrically conductive materials. However, coating electrochemical processes traditionally involve the immersion of the objects to be treated in baths containing polluting and hazardous liquid electrolytes.

[0007] For instance, metal oxide coatings such as, e.g., anodized titanium, are widely used in a wide range of applications as in the aerospace, automotive and biomedical industries, among others. This is because in addition to the low density and high strength to weight ratio of the metal oxide coatings, anodic oxide layers present in the coatings (e.g., anodized titanium) may provide an improved wear and corrosion resistance as well as the possibility to obtain colored surfaces due to interference phenomena. All these features provided by the anodizing process add value to some metals, such as comprising titanium, copper, stainless steel, aluminium and aluminium alloys, extending its performance and enabling its use to further applications. However, anodizing processes, such as titanium anodizing and other anodizing processes, as aforesaid traditionally involve the immersion of the parts to be treated in baths containing polluting and hazardous liquid electrolytes. For that reason, there is an increasing focus on sustainable practices, with finishing methods that minimize environmental impact and use cleaner technologies.

[0008] Similarly, metal coatings are also of great interest to, e.g., improve the surface properties of an object such as corrosion and wear resistance, aesthetic finish, among others. Electroplating, also known as galvanizing or electrodeposition, is an electrochemical treatment of metal parts or metal surfaces to form a metal coating on a base part with the aim of modifying the surface properties of the part. Conventional electrodeposition is based on the reduction of metal cations in a liquid electrolytic medium on the surface of the object to be coated caused by the passage of an electric current, to form of a metal coating on the surface of the object, which is the one in contact with the liquid electrolyte.

[0009] Traditionally, once the electrodeposition process is finished, cleaning steps are generally required in which the already coated part must be washed to remove residues from the surface. Furthermore, the electrolytes used in conventional electrodeposition processes are highly polluting because they include metal cations, often media such as strong acids, cyanides, etc. as well as others chemical reagents used to increase the quality of the coating. Other liquids used to treat the piece in the process before and after electrodeposition also tend to be highly polluting. Consequently, handling these liquids poses a safety risk and environmental contamination.

[0010] On the other hand, electrodeposition processes usually generate coatings with thicknesses ranging from 1 to 50 microns. However, this thickness is not constant throughout the piece since non-homogeneous distributions of the coating are usually observed, with unequal thicknesses in different areas. The most exposed parts, that is, the outermost parts of the object being treated, receive more electrical density and consequently the degree of material deposition in the electrodeposition process is more accentuated, thus generating a thicker coating. This defect is especially visible on the edges and vertices of the object being treated by conventional electrodeposition where dendrites grow as a result of the edge effect.

[0011] Electrodeposition processes known to date further suffer from several limitations. On one hand their electrodeposition rate is limited by the formation of the Nernst diffusion layer, which is a well-known process by which, despite increasing the voltage, the speed of the process is limited by the mobility of the ions in the liquid medium. It would therefore be desirable to have an electrodeposition process that would prevent the formation of the Nernst diffusion layer. On the other hand, during electrodeposition the protons of the liquid electrolyte, usually aqueous, compete with the metal cations of the liquid electrolyte in the reduction process in an undesired secondary reaction whereby these protons are reduced to atomic hydrogen, which tends to diffuse into the metal and accumulate in intergranular spaces and defects in the metal. At these points, atomic hydrogen can recombine to form dihydrogen gas, increasing the fragility of the material and, for certain materials or alloys creating cracks and causing the material to break with almost no deformation reducing the lifetime of a desired workpiece of the coated material under servicelike working conditions. This process, known as hydrogen embrittlement, is one of the major concerns in the industry, especially in steel, titanium and copper. To correct this process, the pieces are usually treated with long processes in the oven with an intermediate and / or high temperature below the materials melting point to eliminate the hydrogen formed during conventional electrodeposition through solid state diffusion process. It would also be interesting to have an electrodeposition process that avoids the generation of atomic hydrogen.

[0012] Furthermore, industrial electrodeposition processes require high temperatures to be efficient, which entails an extra energy cost. It would be desirable to have an electrodeposition process that does not require high temperatures to be efficient.

[0013] Some known alternatives to electrodeposition include physical-chemical processes such as physical vacuum deposition (PVD) or chemical vacuum deposition (CVD) that are able to provide high-quality thin metal coating layers. However, in these processes, the deposition is carried out in vacuum, which makes the process difficult. Such processes are carried out with systems that are suitable on a laboratory scale but are not cost-effective and, thus, not applicable on an industrial scale. It would therefore be desirable to have an electrodeposition process that would allow high-quality thin layers to be obtained without the need to work in vacuum.

[0014] With an increasing focus on sustainable practices, there is a need for coating methods that minimize environmental impact and use cleaner technologies. Further, there is a need to have a coating process that overcomes the drawbacks and problems described above in respect of traditional electrochemical processes, such as anodizing and electrodeposition, for obtaining metal oxide and metal coatings.

[0015] Electrochemical processes using solid particles emerge as a new technology that reduces the use of hazardous mediums. For instance, international application published as WO 2022 / 184956 A1 describes a process of electrodeposition of a metal on a metal part by ionic transport by means of a set of free solid particles that retain a conductive solution that comprises metallic ions of the metal to be deposited and the electrolytic medium for electrodeposition of a metal on a metal part.

[0016] There is a need for improving such processes, e.g., to meet or even exceed results achieved by other electrochemical processes, and for extending their use to other electrochemical applications such as anodization. Providing processes that achieve one, more or all of the aforesaid challenges would be convenient.

[0017] SUMMARY

[0018] It has now been found that an object of an electrically conductive material may be provided with a metal and / or a metal oxide coating, using a plurality of electrically conductive particles and at least one electric pulse.

[0019] In particular, but without limitation, the present disclosure relates to a method for providing a coated object comprising: submerging an object comprising an electrically conductive material in a medium comprising a plurality of electrically conductive particles such that at least part of the surface of the object is in contact with the medium; and at least while the object is submerged: applying a voltage and / or a current to the object; and producing relative movement between the at least part of the surface and the plurality of electrically conductive particles in the medium; the object being electrically connected with a first pole of at least one electric source; the plurality of electrically conductive particles and / or the medium and / or a container containing the medium being electrically connected with a second pole of the at least one electric source; and applying the voltage and / or the current to the object comprises applying at least one electric pulse, whereby the object is provided with a metal and / or a metal oxide coating.

[0020] The use of an electric pulse, e.g., at least one electric pulse or one or more than one electric pulses, has been found to improve the coating process. As discussed in more detail below, not only the morphology of the coating has been found to improve but also the useful life of the particles has been increased, thereby being able to coat a higher number of objects, such as workpieces.

[0021] The present disclosure also relates to electrically conductive particles for use in said coating method and a method for preparing such electrically conductive particles. Such electrically conductive particles and media comprising the same may be referred to herein as dry electrolytes. The term dry electrolyte is used in contrast to liquid electrolytes to denote the presence of particles, e.g. free solid bodies, instead of working with liquid electrolyte solutions.

[0022] In particular, for metal coating, the electrically conductive particles may comprise a metal salt. The metal salt is preferably in a specific disposition, i.e., arrangement, which has been found to be particularly useful. The method of preparation disclosed provides the electrically conductive particles preferably with such specific disposition at least when the particles comprise the metal salt.

[0023] The present disclosure also relates to a coated object obtainable by a coating method such as, e.g., the previous coating method. In particular, coated objects obtainable by methods described herein have been advantageously found to have a homogeneous morphology. Particularly, metal coated objects, e.g., obtained by electroplating, have been found to comprise homogeneously distributed and highly compacted fine grains of deposited metal, and may display a reduced or non-existent edge effect. Metal oxide coated objects have also been shown to have a homogeneous morphology. Accordingly, the present disclosure also relates to a coated object having homogeneous morphology comprising homogeneously distributed and highly compacted fine grains of deposited metal and / or metal oxide. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] 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:

[0025] Figure 1A: Schematic representation of a time curve of the voltage (V) and / or current density (A / dm2) of a train of electric pulses, such as square wave pulses, in particular unipolar (direct current, DC) pulses, which may be preferably used in, e.g., an anodizing process, wherein: N represents the number of square pulses; topp represents the time during which no electricity is applied; tow represents the time during which electricity is applied; ti represents the time during which no electricity is applied but there is still current in the system; represents the time during which no electricity is applied and there is no current in the system and corresponds to the time between pulses; and t represents the time during which there is current in the system and corresponds to the duration of the pulse. Accordingly, topp = ti + t2; and t = toN + ti.

[0026] Figure 1 B: Schematic representation of a time curve of the voltage (V) of a symmetric pulse, in particular bipolar (alternating current, AC) pulses, which may be preferably used in, e.g., an electroplating process, wherein N=1 symmetric pulse is depicted, T+represents the time during which electricity is applied on the cathode, also referred to as cathodic time or tcathode', T’ represents the time during which electricity is applied on the anode, also referred to as anodic time or tanOde', Tp+and Tp’ represent pause time, time during which no voltage is applied.

[0027] Figure 1C: Schematic representation of a time curve of the current density (A / dm2) of a train of electric pulses such as symmetric pulses, in particular bipolar (AC) pulses, which may be preferably used in, e.g., an electroplating process, wherein N=2 symmetric pulses are depicted. It can be seen that T+(= 40 ms) > T’ (= 2 ms).

[0028] Figure 2A: Graphic representation of the current intensity (A) measured at different voltages (V), using electrically conductive particles in an aqueous medium comprising of 0.81 wt.% of sulfuric acid with a DC with constant voltages as described for Comparative Example 1 .

[0029] Figure 2B: Graphic representation of the current intensity (A) measured at different voltages (V), using electrically conductive particles in an aqueous medium comprising 8 wt.% of sulfuric acid with a DC with constant voltages as described for Comparative Example 1.

[0030] Figure 3: Image of objects coated with a metal oxide coating using an anodizing process under the conditions of Comparative Example 1 at different voltages from 10V to 50V and the corresponding SEM micrographs showing the morphology of the surface of the coated objects.

[0031] Figure 4: Image of electrically conductive particles after 45 minutes of being used in a process for providing an object with a metal oxide coating using an anodizing process under the conditions of Comparative Example 1 at a voltage of 50 V.

[0032] Figure 5A: Image of a Focused Ion Beam (FIB)-cross section of a sulfonated styrene divinylbenzene electrically conductive particle before being employed in a method for providing a coated object as described herein.

[0033] Figure 5B: Image of a FIB-cross section of a sulfonated styrene divinylbenzene electrically conductive particle after being employed in a method for providing a coated object using DC at a constant voltage of 50 V for 45 minutes under the conditions of Comparative Example 1.

[0034] Figure 6: Graphic representation of the loss of weight % of the electrically conductive particles used in a method for providing a coated object as determined by thermogravimetry of particles prior to being used in a coating process (t = 0 min) and particles after being used for 15 minutes (t = 15min) and for 45 minutes (t = 15min) in a coating anodizing process using a DC under a constant voltage of 50 V under the conditions of Comparative Example 1.

[0035] Figure 7: Image of objects coated with a metal oxide coating using an anodizing process under the conditions of Example 1 at different voltages from 10 V to 110 V.

[0036] Figure 8: Image of objects coated with a metal coating using an electroplating process under the conditions of Example 2 at increasing times from 15 to 60 minutes.

[0037] Figure 9A: Image of a SEM micrograph of the microstructure of the surface of a metal coated object obtained using DC current using a constant current density under the conditions of Comparative Example 2 for 15 minutes.

[0038] Figure 9B: Image of a SEM micrograph of the microstructure of the surface of a metal coated object obtained using AC symmetrical pulses as represented in Figure 1C under the conditions of Example 2 for 15 minutes.

[0039] Figures 10A and 10B: Images of a SEM micrographs of the microstructure of the surface of a coated object obtained under de conditions of Comparative Example 2 with an image of the center of the object (Figure 10A) and an image of the edge of the object (Figure 10B).

[0040] Figures 11A and 11 B: Images of a SEM micrographs of the microstructure of the surface of a coated object obtained under the conditions of Example 2 with an image of the center of the object (Figure 11 A) and an image of the edge of the object (Figure 11 B).

[0041] Figures 12A and B: Images of a SEM micrographs of the microstructure of the surface of a coated object obtained under the conditions of Comparative Example 2 (Figure 12A) and Example 2 (Figure 12B).

[0042] Figure 13A: Graph of the measured coating thicknesses (as a function of applied current densities A / dm2) for different process times (15, 30, 45 and 60 minutes), according to Example 4.

[0043] Figure 13B: Images of objects coated according to Example 4 at different current densities (0.5, 1.0, 1.5 and 2.0 A / dm2) and different process times (15, 30, 45 and 60 minutes).

[0044] Figure 13C: Graph of the measured coating thicknesses (as a function of applied current densities A / dm2) for a process time of 30 minutes at 37 % of moisture at different stages of the electrolyte lifespan (dividing them into 1stand 2ndset of tests) according to Example 4.

[0045] Figures 14A-B and 15A-B: Images of objects coated according to Example 5 using mesoporous gel-type resins (Figure 14) and macroporous resins (Figure 15) using low acid concentrations (A) and high acid concentrations (B) at different times (5, 10, 15, 20 and 30 min).

[0046] Figures 16A and 16B: Images of objects coated according to Example 5 using (A) mesoporous gel-type resins and (B) macropororous resins at low acid concentrations (left) and high acid concentrations (right) at different current densities (0.5, 1 , 3 and 5 A / dm2).

[0047] Figures 17A-B and 18A-B: Images of a SEM micrographs of the microstructure of the surface of a coated object obtained under the conditions of Example 5 at current densities of 0.5 A / dm2(A) and 5 A / dm2(B) using macroporous resins (Figure 17) and gel-type mesoporous resins (Figure 18).

[0048] Figure 19: Images of SEM micrographs of the microstructure of the surface of a coated object obtained under the conditions of Example 6 showing the deposited copper structures at both the center (top images) and the edge (bottom images) of the substrate specimens using dry (right images) and liquid (left images) electrolytes.

[0049] Figures 20A and 20B: Images of objects coated according to Example 6 using dry electrolyte (Figure 20A) and liquid electrolyte (Figure 20B).

[0050] Figures 21 A and 21 B: Images of objects subjected to coating adhesion tests in accordance with LINE-EN ISO 2409 after coating according to Example 6 using dry electrolyte (Figure 21A) and liquid electrolyte (Figure 21 B).

[0051] Figures 22A and 22B: Images of SEM micrographs of objects coated according to Example 6 using dry electrolyte (Figure 22A) and liquid electrolyte (Figure 22B).

[0052] DETAILED DESCRIPTION

[0053] The present disclosure particularly relates, in an aspect and embodiments thereof, to a method for providing a coated object comprising: submerging an object of or comprising an electrically conductive material in a medium comprising a plurality of electrically conductive particles such that at least part of the surface of the object is in contact with the medium; and at least while the object is submerged: applying to the object a voltage and / or a current; and producing relative movement between the at least part of the surface and the plurality of electrically conductive particles in the medium.

[0054] The object is electrically connected with a first pole of at least one electric source. The electrically conductive particles and / or the medium containing, i.e., comprising the electrically conductive particles and / or a container containing the medium being electrically connected with a second pole of the at least one electric source. Applying the voltage and / or the current to the object comprises applying at least one electric pulse, whereby the object is provided with a metal and / or a metal oxide coating.

[0055] A method for providing a coated object as described herein comprises submerging an object of an electrically conductive material in a medium comprising a plurality of electrically conductive particles such that at least part of the surface of the object is in contact with the medium.

[0056] An object of an electrically conductive material suitable for a method described herein may be any object which has an electrically conductive material on its surface, or it is made of an electrically conductive material in its entirety. That is to say, in some embodiments, the object comprises, in at least one portion thereof, an electrically conductive material. An electrically conductive material is understood as a material which is capable of conducting charge carriers, such as ions or electrons. Preferably, the electric conductivity of the material is at least 10 pS / cm. An electrically conductive material is, in some embodiments, selected from, e.g., a metal, a metal alloy, an electrically conductive polymer, a ceramic material and composite material constituted by a conductive and non-conductive phase. The electrically conductive material is preferably a metal.

[0057] A metal is preferably selected from titanium (Ti), copper (Cu), nickel (Ni), cobalt (Co), chromium (Cr), aluminum (Al), silver (Ag), gold (Au), iron (Fe), and tungsten (W), and more preferably is selected from Ti, Cu, and Ni.

[0058] A metal alloy preferably comprises two or more of the metals previously mentioned, more preferably it is a metal alloy selected from titanium aluminum alloy (e.g., Ti6AI4V), an aluminum silicon alloy; a copper and zinc alloy (e.g., brass), an iron chromium alloy (such as stainless steel), an iron carbon alloy (iron carbide, cast iron and carbon steel alloy), carbides other than iron carbide (such as titanium carbide, tungsten carbide, zirconium carbide, and chromium carbide), yet more preferably it is an alloy selected from titanium aluminum alloy, brass and / or stainless steel.

[0059] An electrically conductive polymer is preferably selected from previously metallized polymers (comprising a metallic surface), intrinsically conductive polymers (ICPs) or conductive polymeric blends, e.g., a blend of a non-conductive polymer with an ICP or with a conductive filler such as carbon black or metallic particles, such as metallic nanoparticles. I PCs may be selected from, polyacetylene, PPy, polythiophene, poly(3,4-ethylenedioxythiophene) (PEDOT), and PANI. Other conductive polymers such as functionalized resins, e.g., functionalized with groups selected from amino, trimethylammonium, carboxylic acid, and / or sulphonic acid groups, may also be used including ionic exchange resins, in particular a resin selected from a polystyrene sulfonate (e.g. a sodium polystyrene sulfonate) resin, a polyacrylate resin with amino groups, or poly(2-acrylamido- 2-methyl-1 -propanesulfonic acid) resin (also known as polyAMPS), and polyethylene amine.

[0060] A ceramic material may comprise one or more ions of a metal, preferably a metal selected from the list of metals indicated above.

[0061] In several particular embodiments, the object is, e.g., a metallic object, or an object of an electrically conductive polymer, ceramic material or composite material constituted by a conductive and non-conductive phase. The object is, in some embodiments, selected from manufactured objects and, in particular, 3D printed objects, for example in the dentistry and jewelry sectors or sectors were a protective layer, e.g., to corrosion may be required or desirable. The object may include, e.g., anodized Ti-based dental prosthesis, coated with titanium oxide, and electroplated brass or stainless-steel jewelry parts coated with noble metals such as gold or silver.

[0062] For instance, the at least one surface of the object may comprise a metallic surface, and preferably the metallic surface comprises, e.g., a titanium aluminum alloy or an aluminum silicon alloy; an iron carbon alloy such as iron carbide, cast iron and carbon steel alloy; carbides other than iron carbide such as titanium carbide, tungsten carbide, zirconium carbide, and chromium carbide; and / or a copper and zinc alloy (e.g., brass).

[0063] Prior to electroplating, the object may be activated by polishing and / or cleaning. Activating may advantageously lead to modifying the surface of the object, thereby contributing to improving the subsequent coating and, in some instances, reducing or even eliminating the edge effect, otherwise observed for some objects. For instance, the object may be activated by degreasing (e.g., using Uniclean 251), pickling (e.g., using ammonium persulfate (in particular for brass objects), hydrochloric acid and / or sulfuric acid (in particular for stainless steel). Additionally, or alternatively, the object may be activated by sandblasting (e.g., using abrasive alumina (AI2O3) or other hard- and / or superhard particles, being these particles harder than the material to be treated).

[0064] A plurality of electrically conductive particles refers to two or more electrically conductive particles, for instance, but without limitation, up to millions of conductive electrically particles. The electrically conductive particles are preferably of one or more materials capable of retaining liquid, such as, for example, polymeric materials, mineral materials, ceramic materials, organic compounds, inorganic compounds, and materials of plant origin, and are preferably of a polymeric material. Electrically conductive particles of a polymeric material may simply be referred to herein as polymeric particles. Suitable polymeric materials may be, e.g., ion exchange resins.

[0065] The electric conductivity of the electrically conductive particles preferably is of at least 10 pS / cm, in particular at least 100 pS / cm, more in particular at least 1000 pS / cm. As a mode of example the electric conductivity of the electrically conductive particles may be of at most 20,000 pS / cm, in particular at most 10,000 pS / cm.

[0066] In some embodiments, in a method as described herein, some or all electrically conductive particles of the plurality of electrically conductive particles comprise a resin. The resin may be of a polymeric material.

[0067] In several embodiments, the electrically conductive particles are of a material selected from: strong and weakly acidic cationic resins, strong and weakly basic anion exchange resins and chelating resins, and more preferably are cationic exchange resins.

[0068] In several particular embodiments, the polymeric material of the resin is of a sulfonated divinylbenzene (S-DVB) and styrene copolymer, since it is a material resistant to acid and the oxidative action of the process as well as resistant to the applied electrical field. The polymeric material has the ability to act as an ion exchanger, which favors the extraction of metal from the surface to be surface finished (e.g., polished) by storing the ions.

[0069] Alternatively, the polymeric material of the resin is, in some embodiments, of a copolymer containing units derived from acrylic acid or methacrylic acid. Such copolymer includes derivatives with different functional groups such as acrylic acid, acrylamide, cyanoacrylate, alkyl acrylates, among others, and the corresponding methacrylate analogs.

[0070] In several particular embodiments, electrically conductive particles 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 acid or carboxylic acid groups. These acidic functional groups are especially useful 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. It may be preferred for the functional groups to be acidic groups and more preferably sulfonic acid groups.

[0071] Depending on the specific type of polymer and functional groups included, the exact composition of the electrically conductive, particles may vary and may be adjusted. As a mode of example, in several particular embodiments electrically conductive particles are of an ionexchange resin, preferably cationic ion-exchange resin that are preferably acid, for example but without limitation, polystyrene divinylbenzene also referred to as copolymer styrene- divinylbenzene (S-DVB), which may preferably be sulfonated (i.e. , comprise sulfonic groups).

[0072] Ion exchange resins suitable as electrically conductive particles as described herein may typically be available commercially. In a method as described herein, some or all electrically conductive particles of the plurality of electrically conductive particles may comprise water or an electrolyte. The electrically conductive particles may be regarded to encapsulate the water or the electrolyte. The surface of the electrically conductive particles may let the electrolyte escape, at least partially, upon the particle contacting a surface or another particle, and the surface may also let electrolyte on the surface of, e.g., the object to be coated, to be absorbed again into the particle.

[0073] In several embodiments, electrically conductive particles have a porous structure, which facilitates the exchange of fluids resulting in a faster process. Alternatively, the particles may have a gel-like structure. In this case the fluid exchange may be more restricted, which may result in a slower process, however, the particle-surface contact may be more defined, resulting in a more homogeneous coating, e.g., with a lower final roughness.

[0074] The electrically conductive particle may be of a porous material, whereby the electrolyte may be contained inside the porous of the material.

[0075] Preferably the particles may be porous, and may have a porosity selected from: microporosity, mesoporosity, macroporosity and fractal porosity. The particles may also be gellike, such as gel-like ion exchange particles.

[0076] Accordingly, in several embodiments in a method as described herein, the ion exchange resin particles: are selected from porous ion exchange particles, in particular, macroporous, mesoporous and / or microporous, preferably microporous ion exchange particles; and gel-like ion exchange particles; and / or comprise acidic, basic and / or chelating functional groups, preferably acidic groups and more preferably sulfonic acid groups; and preferably the ion exchange particles are sulfonated divinylbenzene (S-DVB) and styrene copolymer macroporous ion exchange resin particles.

[0077] Gel-like ion exchange particles may be preferred, in particular for use in, e.g., an electroplating process, as they have been found to contribute to a desired morphology of the coating together with a lower appearance deterioration when current density increases.

[0078] The shape of electrically conductive particles as described herein be polygonal, spheric and / or spheroid. Spheric and / or spheroid shapes may be preferred. However, also polygonal shapes present high interest to be able to coat complex shapes and / or geometries, like: 90° edges; etc.

[0079] Typically, the porous material is not saturated with the water or the electrolyte. Thereby, the water or the electrolyte may be released when in contact with, e.g., the surface of the object to be coated. In several embodiments, as aforesaid, electrically conductive particles comprise water. For instance, electrically conductive particles (such as ion exchange resins as defined above) may be hydrated with water. Hydration of the electrically conductive particles may have a hydration from 5 to 100 wt.%, in particular from 10 to 75 wt.% hydration and more in particular from 15 to 55 wt.% hydration, the % of hydration being defined as the weight amount of water over the total weight of the particle. A desired degree of hydration may be achieved by means known in the art, e.g. subjecting the dry particles (e.g., of ion exchange resins) to swelling in water until a desired degree of hydration is achieved, and / or subjecting hydrated particles to drying to achieve a desired degree of hydration.

[0080] In several embodiments, as aforesaid, electrically conductive particles comprise an electrolyte. 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. In some embodiments, the electrolyte is an acidic aqueous solution, e.g., an aqueous solution selected from an aqueous solution of sulfuric acid (H2SO4), sulfonic acids (e.g., methanesulfonic - MSA), phosphoric acid, nitric acid, carboxylic acids, citric acid, and hydrochloric acid. Preferably the electrolyte is an aqueous solution of sulfuric acid and / or MSA.

[0081] In several embodiments, electrically conductive particles comprise a combination of particles having different types of electrolytes (e.g., aqueous solutions of different acids). For instance, the electrically conductive particles may comprise particles comprising an aqueous solution of MSA and particles comprising an aqueous solution of H2SO4. Such particles may be used in a weight ratio from 1 :10 to 10:1 , in a particular example a ratio of MSA particles to H2SO4 particles of 8:2 may be used.

[0082] The total concentration of acids in the electrically conductive particles may be from 0.1 to 70 wt.% with respect to the total mass of the particles, in particular from 0.5 to 40 wt.%, and more in particular from 0.8 to 20 wt.%. In several particular embodiments, e.g., an acid concentration of about 17 wt.% is used. In several particular embodiments, the electrically conductive particles comprise both MSA and H2SO4. In several particular embodiments, the concentration of MSA in the electrically conductive particles is higher than the concentration of H2SO4. For instance, particles having about 17 wt.% of MSA may be used in combination with particles having about 0.8 % of H2SO4.

[0083] In some embodiments, the electrolyte is an ionic liquid or a conductive liquid polymer.

[0084] In a method for providing a coated object as described herein, the electrically conductive particles may preferably be ion exchange resin particles, preferably comprising a mixture of water and an acid, and the acid may more preferably be MSA and / or H2SO4. In several particular embodiments, the electrically conductive particles further comprise a metal salt and may preferably have an inner content of said mixture of water and an acid and, an outer content of said metal salt. Preferably, the salt is or comprises a salt of a metal cation selected from Cu, Ni, Cr, Au and Ag cation and / or an anion selected form sulfate and chloride anions, the anion may preferably be a sulfate anion. For instance, the salt may be selected from copper sulphate and nickel sulphate. Electrically conductive particles comprising a metal salt may be particularly used for providing an object with a metal coating, e.g., in an electroplating process.

[0085] A medium comprising a plurality of electrically conductive particles suitable for a method as described herein further comprises a fluid in some embodiments. A fluid may be electrically non-conductive or conductive. In several embodiments, the fluid is preferably non-conductive. The use of non-conductive fluids may advantageously result in the electrical conductivity of the coating system being, mostly or totally, due to the electrically conductive particles.

[0086] It is important to note there is no absolute lower limit that universally defines conductivity / non-conductivity; instead, the relevance of a material’s conductivity / non-conductivity may preferably be considered in context. Typically, a material may be regarded as not- significantly conductive if it exhibits a conductivity lower than 50% of that of the conductive reference material; more particularly, lower than 10%, and most particularly, lower than 1%. For example, if a particular embodiment is directed to electrically conductive free solid bodies with a conductivity of 10000 pS / cm, a non-significantly conductive comparative material would not necessarily need to have a conductivity below 10 pS / cm, but may have a conductivity, e.g., below 5000 pS / cm, more particularly below 1000 pS / cm, and most particularly below 100 pS / cm. This relative approach ensures meaningful comparison and functional distinction between conductive and non-conductive materials in the context of compositions, systems and methods described herein.

[0087] For instance, in some particular embodiments, an electrically non-conductive fluid has a conductivity of at most 1 pS / cm, in particular at most 0.5 pS / cm, and more in particular at most 0.1 pS / cm.

[0088] In a method as described herein the fluid of the medium may comprise a solvent, in several embodiments one or more solvents may be present. The solvent may be polar or nonpolar. The solvent may preferably be a polar solvent, and more preferably the polar solvent may be water. In several embodiments, the water of the polar solvent is deionized water. It has been found that deionized water may advantageously contribute to providing an electrically non-conductive fluid. A nonpolar solvent may be a nonpolar organic solvent, in particular selected from polyethylene glycol (PEG) and hydrocarbons, particular from C5 to C30 hydrocarbons, and more in particular from C6 to C16 hydrocarbons. Hydrocarbons may be aliphatic hydrocarbons and / or aromatic hydrocarbons and may preferably be aliphatic hydrocarbons. Aliphatic hydrocarbons may typically comprise less than 2% of aromatic groups. Preferably, hydrocarbons are selected from a mixture of aliphatic hydrocarbons, in particular a mixture of 012-015 aliphatic hydrocarbons. In several embodiments, the medium is an acidic aqueous solution (e.g., of sulfuric acid and / or MSA, preferably sulfuric acid), in particular an aqueous solution having an acid concentration from 0.1 to 20 wt.% relative to the mass of the water plus the acid in particular from 0.5 to 10 wt.%, and more in particular from 0.8 to 8 wt.%. In several particular embodiments, e.g., the medium has an acid concentration of about 0.8 wt.%, of about 5 % or of about 8 wt.%. An aqueous solution of sulfuric acid may be preferably used.

[0089] It has been surprisingly found that although the sulfuric acid content has a negligible effect on properties of the produced coating layers. A medium with a higher acid concentration (e.g. sulfuric acid content) may provide better performances of the coating process as such, reaching a constant intensity faster, and in terms of the product obtained, providing improved brightness and the color of the coating, in particular for a metal oxide coating obtained by an anodizing coating process.

[0090] The final acid concentration for the medium comprising the electrically conductive particles can be calculated from the addition of the acid present in the particles and the acid present in the medium.

[0091] In some embodiments of a method as described herein, submerging the object in the medium comprising the plurality of electrically conductive particles such that the at least one surface is in contact with the medium comprises, e.g., introducing the object into a container, such as a receptacle, a tray and a keg, comprising the medium comprising the plurality of electrically conductive particles. The container is, in some embodiments, provided with mixing means, e.g., selected from a stirrer, a rotator, a displacer, a shaker, a vibrator, a propeller.

[0092] Alternatively, submerging the object in the medium comprising the plurality of electrically conductive particles such that the at least one surface is in contact with the medium, comprises, in some embodiments, projecting a medium comprising the plurality of electrically conductive particles onto the object. Projecting the medium may be performed by, e.g., spraying the medium comprising the plurality of electrically conductive particles. Spraying may be performed using a sprayer.

[0093] In several embodiments, a method described herein comprises adding water to the medium comprising a plurality of electrically conductive particles. For instance, water may be added in between coating cycles in order to keep the quality of the electrolyte between in terms or relative humidity.

[0094] It has been found that adding water to the medium may contribute to keep stable the humidity of the electrolyte as well as enhance the working life of the electrically conductive particles and at the same time contribute to maintaining the quality of the coating and the efficiency of the coating method, as the conductivity of the electrically conductive particles is maintained. It has been surprisingly found that in a method described herein high temperatures are not necessary. For instance, submerging may be performed at a temperature from 10 to 90 °C, in particular from 12 to 75 °C, more in particular from 15 to 60 °C, and yet more in particular from 20 to 50 °C. Such temperatures were found to contribute to provide good brightness and roughness of the coated product. Higher temperatures were found to adversely affect the quality of the coated surface. Without being bound to any theory, the lower quality of the coating at higher temperatures may be attributed to the degradation of the electrically conductive particles at such higher temperatures.

[0095] In a method as described herein, current applied to the object may be selected from a direct current (DC), also referred to as unipolar current, and an alternating current (AC), also referred to as bipolar current.

[0096] As AC is a bipolar current, in a method as described herein the use of AC changes of the reaction taking place on the surface of the object being coated in the medium comprising the electrically conductive particles (from oxidation to reduction and vice versa). Accordingly, in absence of such a change in polarity, the use of DC may contribute to the efficiency of the coating method in that all or most of (i.e., a majority) the current is used for the targeted reaction (e.g., the reduction reaction for the formation of the metal coating in an electroplating process or the oxidation reaction by which the formation of the metal oxide coating takes place). Accordingly, in several embodiments, DC current is preferred. Nonetheless, in some other embodiments, AC current is preferred. In several embodiments, the formation of a metal oxide coating, e.g., through an anodizing process is preferably obtained using DC pulses.

[0097] In several embodiments, the formation of a metal coating, e.g., through an electroplating process is preferably obtained using AC pulses.

[0098] In a method as described herein, producing relative movement between the at least one surface and the plurality of electrically conductive particles in the medium may be achieved by moving one or both of the plurality of electrically conductive particles and the at least one surface. The relative movement may be attained by way of any motion, such as displacing, rotating, mixing, stirring, vibrating, shaking, spraying, propelling, sucking, etc.; a plurality of motion types may be combined simultaneously or sequentially to provide linear motion and / or rotational motion.

[0099] In a method as described herein, the object is electrically connected with a first pole of at least one electric source, e.g., a current generator, and the electrically conductive particles and / or the medium containing, i.e., comprising, the electrically conductive particles and / or a container containing the medium are electrically connected with a second pole of the at least one electric source. The connection to the poles may be by means known in the art. For instance, the object may be connected to the first pole (e.g., a positive pole) by means of a securing element, and the electrically conductive particles may be included in a container which is in contact electrically with the second pole (e.g., negative pole) of the one electric source, via the container directly or via a ring acting as a second pole. As a mode of example, reference may be made to the International Application No. PCT / ES2017 / 070247 (published as WO 2017 / 186992 A1). Alternatively, when submerging is performed by, e.g., projection, applying the voltage and / or the current to the object, may comprise connecting the second pole of the current generator opposite the first pole to a device that transmits the current to the electrically conductive particles, e.g. a beam of electrically conductive particles, supplied from a reservoir in combination with the medium comprising the same and the device projects the electrically conductive particles to the object, thereby closing the electrical circuit. As a mode of example, reference is made to the International Application No. PCT / ES2020 / 070499 (published as WO 2021 / 019121 A1) and Spanish Patent Application No. 202230989 (published as ES 2942541 A1).

[0100] In a method as described herein, applying the voltage and / or the current to the object comprises applying at least one electric pulse. In several embodiments, the voltage and / or current is applied from 1 to 120 min, in particular from 5 to 60 min.

[0101] The at least one electric pulse electric pulse may be applied under voltage control or under current density control. In several embodiments, the method for providing a coated object is an anodizing process in which the electric pulse is applied under voltage control. In several other embodiments, the method for providing the coated object is an electroplating process in which the electric pulse is applied under current control.

[0102] In several embodiments, when the at least one electric pulse is applied under voltage control, the voltage of the at least one electric pulse preferably runs from 0 to up to 150 V, in particular from 0 to up to 140 V, more in particular from 0 to up to 130 V. For instance, before the start of the pulse the voltage may be 0 V or substantially 0 V, and at the point of the pulse with a maximum voltage the voltage may be up to 150 V or less, in particular up to 140 V or less, and more in particular up to 130 V or less. For instance, the maximum voltage of a pulse may be of at least 50 V, in particular at least 60 V and more in particular at least 90 V. It has been found that the use of electric pulses allows for the system to work at higher voltages that would be possible, with a continuous method, which when working at above 50 V leads to an important heating of the medium comprising the electrically conductive particles due to Joule effect, which produces an important temperature increase that promotes the dehydration and degradation of the electrolyte. The use of pulses has been found to allow the process to work at such voltages without suffering from these problems, locally decreasing the working temperature and increasing the lifetime of the electrically conductive particles.

[0103] In several embodiments, when the at least one electric pulse is applied under current density control, the current density of the at least one electric pulse preferably runs from at least -5 to up to 5 A / dm2, in particular from at least -4 to up to 4 A / dm2, more in particular from at least -3 to up to 3 A / dm2and yet more in particular from at least -2 to up to 2 A / dm2. It has been advantageously found that current densities within these ranges, and in particular up to 2 A / dm2contribute to minimizing the dehydration and damage of the electrically conductive particles, on one hand, and to achieving a higher shine of the coating, on the other hand. Without being bound to any theory, this could be attributable to the fact that these current intensities contribute to minimizing the dendritic structure of the coating.

[0104] Independently of the type of control, the maximum current density of the at least one electric pulse may be from 0.01 to 5.0 A / dm2, in particular from 0.05 to 4.5 A / dm2and more in particular from 0.25 to 4.0 A / dm2. Such maximum current densities advantageously contribute to optimization of the process and to increase effective lifetime of the electrically conductive particles used in the process. Furthermore, they have been found to contribute to achieving a good coating thickness (e.g., from 5 to 50 pm coating thickness), homogeneity and low density of defects (e.g., pores, cracks, etc.) in the coating. Higher current densities may lead to uncontrolled and undesired coating morphologies (such as an excessive dendritic growth).

[0105] In a method as described herein, the least one electric pulse may comprise from 1 to 104electric pulses, in particular from 2 to 103electric pulses, and more in particular from 3 to 102electric pulses, and yet more in particular from 4 to 75 electric pulses.

[0106] In a method as described herein, the least one electric pulse may preferably comprise more than one electric pulse. More than one electric pulse may be referred to as a train of electric pulses. When more than one electric pulse is used, the frequency of applying the more than one electric pulse may be from 0.05 to 30.0 Hz, in particular from 0.1 to 25.0 Hz, in particular from 0.15 to 10.0 Hz, more in particular from 0.2 to 5.0 Hz, and yet more in particular from 0.25 to 2.5 Hz. Such frequencies have been found to contribute to obtaining a homogeneous coating and to reduce the density of defects of the coatings, with the consequent increase on the quality and durability of the coating. Furthermore, the use of such frequencies and in particular lower frequencies, e.g., from 0.05 to 2.5 Hz, has been found to contribute to reducing the heating of the electrically conductive particles and the medium comprising the same. In several particular embodiments, it has been found that higher frequencies, e.g., from 2.5 to 30.0 Hz, may be suitably used with good results in particular for obtaining metal coatings, e.g., in an electroplating process. In several other embodiments it has been found that lower frequencies, e.g. from 0.05 to 2.5 Hz in particular about 0.8 Hz may be optimal for obtaining metal oxide coatings, e.g., in an anodizing process.

[0107] Using at least one electric pulse, in other words pulsing between two values of DC or AC instead of using the same value during the whole process, provides several advantages. For instance, the coating layers obtained may be more homogeneous as discussed in more detail below. At the same time, the medium containing the electrically conductive particles, or the particles themselves are not heated locally as much as if, e.g., a continuous DC current was used. Consequently, the electrically conductive particles do not degrade as much, increasing the durability thereof and also facilitating cleaning and regeneration of the particles, e.g., by facilitating the removal of metal ions, once they have reached the end of the useful life thereof.

[0108] An electric pulse or a train of electric pulses may be applied, e.g., using a square wave and referred to as square wave pulses. A schematic diagram of square wave formed pulses can be seen in Figure 1A, which provides a schematic representation of a time curve of the voltage (V) and / or current density (A / dm2) of a train of electric pulses, wherein: N represents the number of pulses; topp represents the time during which no electricity is applied; tow represents the time during which electricity is applied; ti represents the time during which no electricity is applied but there is still current in the system; represents the time during which no electricity is applied and there is no current in the system and corresponds to the time between pulses; and t represents the time during which there is current in the system and corresponds to the duration of the pulse. Accordingly, topp = ti + t2; and t = toN + ti.

[0109] In several embodiments, square wave pulses are used with DC current, also referred to as unipolar square wave pulses.

[0110] In several particular embodiments, square wave pulses, and more in particular unipolar square wave pulses, e.g., as illustrated in Figure 1A, are used in, e.g., an anodizing process for the formation of a metal oxide coating. In several particular embodiments, a pulse using square wave-formed at low frequency pulses is used whereby topp is often longer than t. The duration of pulses may vary, e.g., from 10 to 180 s, the current densities may vary from 2 to 20 A / dm2.

[0111] In several particular embodiments, symmetric wave pulses, e.g., as illustrated in Figure 1 B, are used, and more in particular bipolar symmetric wave pulses wave pulses using AC. In a symmetric pulse T+and T’ (also referred to the cathodic time and anodic time respectively) may be the same or may be different, for instance in several embodiments T+> T’ and in several alternative embodiments T+< T preferably T+> T’.

[0112] It may be preferred for AC to be used with symmetric wave pulses whereby the time of the pulse in the pole triggering the reaction of interest (e.g. reduction during the formation of a metal coating in an electroplating process or oxidation during the formation of a metal oxide coating in an anodizing process) may be longer than the time of the pulse in the pole triggering the contrary reaction. An example of a symmetric AC pulse with T+> T’ is shown in Figure 1C wherein T+= 40 ms and T’ = 2ms.

[0113] In several embodiments, a process (e.g., electroplating process, anodizing process, etc.) as described herein comprises one or more cycles, also referred to herein as coating cycles, reusing the medium comprising the electrically conductive particles to provide the coated object, in particular may comprise 1 to 100 cycles, more in particular from 2 to 50 cycles, yet more in particular from 5 to 30 cycles. However, it may be preferred for the coated object to be provided in a single cycle or only a few cycles, e.g., from 1 to 10 cycles.

[0114] In several embodiments, the medium comprising the electrically conductive particles are re-used in a subsequent coating cycle or in the coating of another object.

[0115] As described above, when re-using the medium comprising electrically conductive particles water may be added to the medium.

[0116] As described throughout the present disclosure, a coating method as described herein offers several advantages, and the coated objects may be used as such in their final application. Nonetheless, subsequent treatments may be applied, especially if so desired. For instance, when coating is used to provide an object with a metal coating such as copper, the coated object may be passivated, e.g., using an acidic solution such as a 20 second dip of the object into a 20% citric acid aqueous solution.

[0117] The present disclosure also relates, in an aspect and embodiments thereof, to electrically conductive particles for use in a coating method as described herein. The electrically conductive particles may have the same characteristics as described above. In particular, for metal coating, e.g., through an electroplating process, the electrically conductive particles may comprise a metal salt in a specific disposition which has been found to be particularly useful. The present disclosure also relates, in an aspect and embodiments thereof, to a method of preparation of electrically conductive particles that, in some embodiments, are provided with such specific disposition. The present disclosure also relates, in an aspect and embodiments thereof, to one or more (e.g., a plurality of) electrically conductive particles for use in a method such as, e.g., a method as described in an aspect and embodiments herein, in which

[0118] - the one or more electrically conductive particles are ion exchange resin particles that comprise:

[0119] • a mixture of water and an acid; and

[0120] • a metal salt; and

[0121] - the (one or more) ion exchange resin particles have an inner content of said mixture of water and an acid, and an outer content of said metal salt.

[0122] The acid preferably is, or comprises, MSA and / or H2SO4.

[0123] The metal salt preferably is, or comprises, a salt of a metal cation selected from copper, nickel, chromium, gold and silver cation and / or an anion selected from sulfate and chloride anions. The anion is preferably a sulfate anion.

[0124] The present disclosure also relates, in an aspect and embodiments thereof, to a method for preparing electrically conductive particles. In particular, the method may comprise providing ion exchange resin particles having a water content from 10 to 60 wt.%, in particular from 20 to 55 wt.%, more in particular from 30 to 50 wt.%, based on the total weight of the ion exchange resin particles.

[0125] The method may also comprise mixing the ion exchange resin particles with a mixture of water and an acid, preferably MSA and / or H2SO4, thereby providing partially swelled particles having an inner content of a mixture of water and an acid.

[0126] The method may also comprise mixing the partially swelled particles with an aqueous solution of a metal salt, thereby providing electrically conductive particles with an outer content of a metal salt. The metal salt is preferably a salt of a metal cation selected from copper, nickel, chromium, gold and silver cation and / or an anion selected from a sulfate and a chloride anion. The anion is preferably a sulfate anion.

[0127] Methods using dry electrolytes as described herein also pose a lower risk, of safety and environmental contamination than methods using, e.g., liquid electrolytes according to the prior art.

[0128] The present disclosure also relates, in an aspect and embodiments thereof, to a coated object obtainable by a coating method, such as a coating method as described herein.

[0129] In particular, coated objects obtainable by methods described herein have been advantageously found to have a homogeneous morphology. Particularly, metal coated objects, e.g., obtained by electroplating, have been found to comprise homogeneously distributed and highly compacted fine grains of deposited metal. Furthermore, the use of pulses has been found to drastically reduce the pore density of the coating and to reduce or even eliminate the edge effect observed when using other electroplating methods, thereby also contributing to the homogeneity of the coating obtained.

[0130] Metal oxide coated objects have also been shown to have a homogeneous morphology.

[0131] Accordingly, the present disclosure also relates, in an aspect and embodiments thereof, to a coated object having an electrically conductive core material and coating selected from a metal and / or metal oxide coating. The coating covers at least part of the surface of the core material of the object. The coating or coatings has a homogeneous morphology comprising, e.g., homogeneously distributed coating or coatings in terms of their thickness and amount of defects present, without being bound to any theory, probably owing to the formation of highly compacted fine grains of deposited metal and / or metal oxide, e.g., thanks to the solid-to-solid localized electrochemical action.

[0132] The morphology of the coating may be observed using, e.g., SEM and more in particular Field Emission SEM (FE-SEM),

[0133] In several embodiments, the coating may be homogeneous in that it has small differences in the thickness of the coating along the surface of the object covered by the coating, e.g., with differences in thickness from one point of the coating to another of at most 500 nm, depending on the thickness of the coating itself, and in particular from 1 to 200 nm and more in particular from 10 to 100 nm. For instance, for metal oxide coated objects differences may be observed of about 10 nm and for metal coated objects of about 100 nm. In percentage the thickness variation may be of at most 20%, in particular at most 18%, more in particular of at most 15%, yet more in particular at most 10%.

[0134] In several other embodiments, the coating may be regarded as highly compact in that it has a low-density of defects, e.g., the volume of defects of the coating may occupy less than 1% of the volume of the coating, in in particular from 0.1 to 0.5 %.

[0135] In a coated object as described herein the electrically conductive core material may be an electrically conductive material as described above for the coating method.

[0136] In several embodiments, the coating is a metal coating, preferably the metal of the coating is selected from copper, nickel, chromium, gold and silver. In several particular embodiments, the metal coating has an average thickness from 0.1 to 25 .m, in particular from 1 to 10 .m.

[0137] In several other embodiments, the coating is a metal oxide coating, preferably the metal oxide is selected from titanium oxide, copper oxide, and nickel oxide, and other oxides from metals of columns III, IV and V of the periodic table, preferably oxides of scandium, yttrium, zirconium, hafnium, vanadium and niobium. In several particular embodiments, the metal oxide coating has an average thickness from 0.002 to 200 nm, in particular from 0.005 to 150 nm, more in particular from 0.01 to 100 nm, yet more in particular 0.1 to 80 nm.

[0138] The average thickness and thickness variation of coatings of coated objects as described herein may be determined by means known in the art. Thickness may be determined using, e.g., a calowear test.

[0139] The coating of a coated object as described herein may have a surface with a roughness of less than 1 .m, in particular from 0.01 to 0.8 .m and more in particular from 0.1 to 0.6 .m. The surface area may be measured by White Light Interferometry (WLI).

[0140] The coating of a coated object as described herein may have a good corrosion resistance. The corrosion resistance may be expressed in terms of polarization resistance. The higher the polarization resistance the higher the corrosion resistance. In some embodiments, a coated object as described herein have, e.g., a polarization resistance equal to or greater than 10 kQ cm2, in particular greater than 100 kQ cm2. In particular, it has been found that objects provided with metal oxide coatings as described herein feature an increased Open Circuit Potential (OCP) and a reduced current during a potentiodynamic analysis, compared to, e.g., metal oxide coatings obtained by other methods, which are indicative of an improve corrosion resistance.

[0141] As indicated above, in several other embodiments, the coating may be regarded as highly compact in that it has a low-density of defects, e.g., the volume of defects of the coating may occupy less than 1% of the volume of the coating, in particular from 0.1 to 0.5 %. In terms of surface defects, a coated object as described herein may have a density of defects covering at most 30% of the total surface of the coating, in particular at most 20% more in particular at most 10% as determined by, e.g., at least five different scanning electron micrographs and quantification using an appropriate software such as an image processing program including Imaged (from the National Institutes of Health and the Laboratory for Optical and Computational Instrumentation (LOCI, University of Wisconsin).

[0142] Although some examples and embodiments may include a particular sequence of operations, the sequence may in some cases be altered without departing from the scope of the present disclosure.

[0143] 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.

[0144] Also, in this text, the term “embodiment” and “example” are used interchangeably to describe particular examples of aspects of the disclosure, but these terms should not be interpreted as excluding other examples and combinations of features of the disclosed aspects, which also fall within the scope of the present disclosure. In this sense, 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.

[0145] The present disclosure is further illustrated by the following examples without being limited thereto or thereby.

[0146] EXAMPLES

[0147] All examples were carried out using the following general process and components.

[0148] Several objects were subjected to coating by the following general method:

[0149] - holding the object with a moving arm and connecting the object to a pole of an electric source,

[0150] - connecting a container comprising particles in a medium to the opposite pole of the electric source whereby an electric current is applied to the system

[0151] - submerging the object into a container contained in a medium, whereby the object was completely covered by the particles, and

[0152] - moving the object inside of the particles thereby moving the particles relative to the object and allowing the contact of the particles with the surface of the object, for a specific amount of time; - the object was removed from the particles, to provide a surface treated object.

[0153] For metal oxide coating (Example 1 and Comparative Example 1) a mixture of particles sulfonated styrene divinylbenzene particles of 0.3 to 1.18 mm of diameter was used. The mixture contained:

[0154] - 2 kg of type A comprising an aqueous solution of sulfuric acid (with a sulfuric acid content of 4.12 wt.% with respect to the total weight of the particles of type A and 0.82 wt.% with respect to the total weight of particles of type A+B), and

[0155] - 8 kg of particles of type B comprising an aqueous solution of methanesulfonic acid (MSA) (with an MSA content of 20.34 wt.% with respect to a total weight of the particles of type B and 16.27 wt.% with respect to the total weight of particles of type A+B).

[0156] The medium comprising the electrically conductive particles was water comprising 0.81 or 8 wt.% of sulfuric acid for the lower and higher acid concentration medium respectively. The final acid concentration for the medium comprising the electrically conductive particles can be calculated from the addition of the acid present in the particles and the acid present in the medium.

[0157] For metal coating (Example 2, Comparative Example 2 and Example 4), 10 kg of sulfonated styrene divinylbenzene gel type particles were used as electrically conductive particles comprising an aqueous solution of sulfuric acid (5 wt. %) and 0.6 wt.% of copper sulphate salt. The medium comprising the electrically conductive particles was water comprising 5 wt.% of sulfuric acid.

[0158] Acid concentration effect

[0159] A preliminary experiment was performed to establish the most favorable acid concentration, whereby the aqueous medium comprising the electrically conductive particles had a sulfuric acid concentration of respectively 0.81 wt.% and 8 wt.% were tested applying DC using constant voltages ranging from 10 to 60V using DC about 2 minutes. The results are observed in Figure 2A for the lower acid concentration (of 0.81 wt.%) and in Figure 2B for the higher acid concentration (of 8 wt.%).

[0160] It can be seen from the figures that for all voltages (10 V, 20 V, 40 V, 50 V and 60 V) the current intensity becomes constant at about 38 seconds for the lower acid concentration (Figure 2A) and at about 8 seconds for the higher acid concentration (Figure 2B). It was also observed that the brightness of the pieces increased with the acid concentration (data not shown), denoting a more homogeneous coating.

[0161] In view of this the remaining experiments were carried out at the higher acid concentration (with an aqueous medium having 8 wt.% of sulfuric acid). Comparative Example 1 : Metal oxide coating (continuous anodizing process) Voltage effect

[0162] Cylinders of Ti6AI4V alloy were anodized by applying DC at constant voltages ranging from 0 to 60V at 5 volt intervals. Metal oxide coated samples obtained after 2 minutes at each voltage tested were photographed as a whole and SEM micrographs of their surfaces. The corresponding photographs are shown in Figure 3. It could be observed that colour range and appearance varied with the applied voltage. The colours observed were dull gold at 10V, copper like at 15V, deep purple at 20V, blue purple at 25V, dark blue at 30 V, lighter blue from 35 V onwards. In fact, the colour stabilized at 35 V, with no significant colour change with the increase of the voltage. No significant changes of the microstructure were observed either.

[0163] Particle evaluation

[0164] The particles used in the experiment were evaluated after 45 minutes of being submitted to DC at a constant voltage of 50 V.

[0165] A photograph of the particles is shown in Figure 4, wherein arrows show damaged particles (with loss of sphericity). This indicated that the use of DC at constant voltages was damaging to the electrically conductive particles, with consequence for the execution of the method and the coating results.

[0166] The surface of the particles was also compared to that of the particles before being used in such a process using Focused Ion Beam (FIB) imaging. Figures 5A and 5B respectively show images of a FIB-cross sections of an electrically conductive particle before and after being subjected to 45 minutes of being submitted to DC at a constant voltage of 50 V.

[0167] The dehydration of the particles was also evaluated by measuring the weight loss of the particles at different time intervals. In particular, Figure 6 shows a graphic representation of the loss of weight % of the electrically conductive particles used in a method for providing a coated object as determined by thermogravimetry of particles prior to being used in a coating process (t = 0 min) and particles at different processing times, i.e., after being used for 15 minutes (t = 15min) and for 45 minutes (t = 15min) in a coating anodizing process using a DC under a constant voltage of 50 V. As it can be observed the peak corresponding to the loss of water peak (at around 100°C), is lower with increased processing time, which is an indication that the particles had loss an increasing amount of water with processing time. The peak at around 300°C which corresponds to the acid content, does not vary significantly with processing time whereas the peaks between 400 and 500°C show variation with increasing time which can be attributed to the increased degradation of the particles with processing time.

[0168] Example 1 : Metal oxide (pulse anodizing process) Several sheets of a Ti6AI4V alloy were provided with a metal oxide coating by anodizing applying DC pulses at voltages ranging from 0 to 110V at a frequency of 0.4 Hz, with a tonand toff of 0.5 and 2 s respectively during an effective time of 2 minutes, that corresponds to a total time of 10 minutes (20% duty cycle).

[0169] The results obtained at different voltages (10 V, 30 V, 50 V, 90 V and 110 V) are shown in Figure 7. At all the voltages the coating obtained had a thickness of 60 nm which was very homogeneous. Further the coated object had different colors depending on the voltage used ranging from dull gold at 10V, dark blue at 30 V, light sky blue at 50 V, light green at 70 V, gold at 90 V and intense gold at 110 V.

[0170] The defects observed on the particles and the dehydration under the conditions of comparative experiment 1 were minimized or were not observed at all when pulses of DC were used even if working at voltages higher than 50 V (data not shown).

[0171] Comparative Example 2: Metal oxide coating (continuous anodizing process)

[0172] A brass alloy sample was electroplated by applying DC at a constant current density of 2 A / dm2for 15 minutes.

[0173] Example 2: Metal coating (pulse electroplating process)

[0174] A brass alloy has been electroplated by applying AC pulses at current densities ranging from -2 to +2 A / dm2at a frequency of 25 Hz, with a cadhodic (T) and anodic (T+) pulse durations of 40 and 2 ms respectively during 15 minutes, with an effective electroplating time of 3 minutes for the total of 15 minutes of the process (80% duty cycle).

[0175] Example 3: Evaluation of the Edge effect and porosity and continuity of the coating

[0176] The objects metal coated under the conditions of Comparative Example 2 and Example 2, were evaluated in more detail to observe the edge effect, which is the difference of the morphology of the coating depending on the part of the object that it is being coated.

[0177] The results are shown in figures 10 and 11 for Comparative Example 2 and Example 2 and respectively, with a SEM image of the center of the pieces (figures 10A and 11A) and a SEM image for the edge of the pieces (figures 10B and 11 B). As it can be observed the edge effect is much more marked for the Comparative Example 2 (Figure 10), using a DC with a constant current density, than for Example 2 (Figure 11) wherein AC pulses are used.

[0178] The porosity and continuity of the coating was also looked at. Figure 12 shows SEM images of brass alloys electroplated using a constant DC current according to Comparative Example 2 (Figure 12A) and using AC pulses according to Example 2 (Figure 12B), demonstrating the effect of process parameters, in particular the application of pulses, to obtain a non-porous, continuous microstructure during electroplating and to achieve coatings with improved continuity and minimal porosity. In particular, the use of AC pulses (duty cycles) has shown to enhance the electroplating performance. Whereas the use of constant DC current results in coating with a porous-like structure (exhibited on SEM image of Figure 12A), the use of a pulsed current including duty cycles results in a coating with a more continuous and less porous structure (exhibited on the SEM image of Figure 12B). Without being bound to any theory, it is believed that this improvement may be attributed to a reduction in the Joule effect during plating, thereby improving deposition consistency and also extending the lifetime of the electrolyte (e.g., by diminishing the thermal degradation of the electrolyte). All in all, by applying at least one electric pulse, a the deposited coating exhibited an improved, homogeneous microstructure across the surface of the treated object.

[0179] Example 4: current density comparison

[0180] In order to evaluate the relevance of controlling moisture content in the electrically conductive particles and / or the medium comprising the same, referred to herein also as dry electrolytes, during electroplating on the consistency of the deposition performance, electroplating was carried out using free solid bodies presenting a moisture content carefully adjusted and maintained at 37% being grams of water with respect to grams of partially hydrated free solid bodies. The 37% moisture content was determined by thermogravimetric measurements and was maintained by adding water to the system, when required. The plating current densities applied were 0.5 A / dm2, 1.0 A / dm2, 1.5 A / dm2, 2.0 A / dm2, and 2.5 A / dm2. For each current density, plating durations of 15, 30, 45, and 60 minutes were tested. Moisture content was verified following each interval and water was replenished as required.

[0181] Initial analysis indicated that water loss from the particles or medium, which increased with the increase of the current densities applied, led to performance deterioration in plating, which is attributed to at least one of the following mechanisms:

[0182] 1 . evaporation of water,

[0183] 2. water consumption due to side reactions at the cathode, and

[0184] 3. water consumption at the inert anode, such as stainless steel.

[0185] Figure 13A shows the measured coating thicknesses (as a function of applied current densities A / dm2) for different process times (15, 30, 45 and 60 minutes). The maximum coating thickness for a given time was observed at a current density of 1.5 A / dm2. At higher current densities, a decrease in thickness was noted, which was attributed to the dilution effect resulting from water addition — leading to a decrease in the conductivity of the electrolyte medium from an initial value of 17.3 mS / cm to 11.7 mS / cm.

[0186] Figure 13B shows the appearance of the coated samples at different current densities (0.5, 1.0, 1.5 and 2.0 A / dm2) and different process times (15, 30, 45 and 60 minutes). In all cases, visual assessment indicated acceptable surface finishes, with no significant macroscopic defects.

[0187] To further investigate the role of medium conductivity, Figure 13C compares coating thickness at 30 minutes of plating time using different current densities. Two sets of experiments were conducted. The first set of tests was performed under moisture-controlled conditions (37% moisture content), as described above by addition of water when the moisture of the free solid bodies dropped below 37% (1stset of tests curve with squares in figure 13C). The second set of tests was performed with the same free solid bodies at the end of the first set of tests, in a second cycle of use, also under moisture control at 37% by addition of water (2ndset of tests, curve with circular dots in figure 13C). As it can be observed from figure 13C The second set of tests (curve with circular dots) showed significantly reduced thickness values compared to the first set (curve with squares), indicating a somewhat ageing of the system after a first cycle of use. However, it was observed that upon addition of the solution acting as electrolyte (of the electrically conductive free solid bodies: aqueous solution of sulfuric acid (5 wt. %) and 0.6 wt.% of copper sulphate salt), the performance of the process (tested again at 1.0 and 1.5 current densities) was restored and the thickness of the coating obtained was very similar to that obtained with the first set of tests (electrolyte addition curve with triangles in figure 13C). The recovered performance indicated that it may be preferred to jointly control both the moisture content and the ionic conductivity of the medium to improve or optimize plating efficiency.

[0188] Example 5: Gel VS Macro porous particle coating comparison

[0189] This example addresses the influence of the pore size of sulfonated polystyrene- divinylbenzene (PST-DVB) resin particles and acid concentration on the coating quality.

[0190] Figures 14 and 15 show pictures of coated metal parts using mesoporous gel-type resins (Figure 14) and macroporous resins (Figure 15) using low acid concentrations (A), using aqueous acid solutions having an acid concentration lower than 10 wt.%, such as 5 wt.%, and high acid concentrations (B) using aqueous acid solutions having an acid concentration higher than 10 wt.% such as 15 wt.%, the weight % corresponding to weight of acid with respect to weight of solution at different times (5, 10, 15, 20 and 30 min), the higher the time the higher the number of cycles. It was observed that particles with larger pore sizes (i.e. , macroporous structures) required higher acid concentrations in the electrolyte medium to maintain coating performance across multiple cycles. Conversely, particles with smaller pore sizes (i.e., mesoporous or gel-type structures) allowed for the use of lower acid concentrations without detrimental effects on performance. Additionally, the effect of current density was analyzed. High acid concentrations enabled the application of higher current densities while still producing compact, non-porous metal coatings. Figure 16 shows pictures of coated metal parts using (A) mesoporous gel-type resins and (B) macropororous resins at low acid concentrations (left) and high acid concentrations (right) at different current densities (0.5, 1 , 3 and 5 A / dm2).

[0191] Figures 17 and 18 provide scanning electron microscope (SEM) images comparing two representative samples at current densities of 0.5 A / dm2(A) and 5 A / dm2(B) using macroporous resins (Figure 17) and gel-type mesoporous resins (Figure 18). Lower current densities (A) resulted a continuous, dense, and non-porous coating, whereas higher current densities (B) resulted in coatings with a higher porosity and lower-adherence.

[0192] Furthermore, it was established that even when operating at higher current densities (approximately 5 A / dm2), the use of gel-type (mesoporous) particles (Figure 18B) mitigated the formation of large pores more effectively than macroporous particles (Figure 17B). The structure of the deposited metal was found to be influenced both by the particle morphology and the current density, but the effect on porosity appeared to be more markedly influenced by the porosity of the resin. Gel particles consistently yielded finer microstructures regardless of applied current.

[0193] Example 6: Comparison of dry electrolyte VS liquid electrolyte coating

[0194] This example compares the morphology and performance of copper coatings deposited using dry electrolytes versus conventional liquid electrolytes.

[0195] SEM micrographs (Figure 19) show the deposited copper structures at both the center (top images) and the edge (bottom images) of the substrate specimens using dry (right images) and liquid (left images) electrolytes. It was observed that coatings obtained using dry electrolytes exhibited finer grain structures and more uniform morphologies in both regions. These results were consistent across samples and indicated improved coherence and compactness of the copper layers.

[0196] Electroplating was also conducted under identical pulse parameters using both types of electrolytes. The conditions were as follows:

[0197] • Frequency: 25 Hz

[0198] • Duty cycle: 80%

[0199] • Cathodic current density: +2 A / dm2

[0200] • Anodic current density: -2 A / dm2

[0201] • Total plating time: 20 minutes

[0202] These parameters were identified as optimized conditions for dry electrolyte systems. The results confirmed that bipolar pulsing at these conditions provided very fine and homogeneous copper deposits, significantly reducing edge effects typically observed in continuous processes.

[0203] A summary of results is shown in Table 1 for treatments using electroconductive particles (A) and liquid electrolytes (B). Table 1 : Dry electrolyte vs liquid electrolyte treatments

[0204] Both electrolyte types (dry, left column and liquid, right column of Table 1) produced clear and bright deposits with similar layer thicknesses (considering standard deviation, Figures 20A and 20B). Surface roughness was higher in samples produced with liquid electrolytes, though not significantly. Coating adhesion in both cases was excellent, classified as category 0 in accordance with LINE-EN ISO 2409 (Figures 21A and 21 B). The morphology of the surface of the treated parts was clearly improved using dry electrolytes as displayed by the corresponding SEM micrographs (Figures 22A and 22B). As can be observed on the SEM micrographs, 22A presents a less porous and more compact structure of the coated surface than that of 22B. This results on a better adhesion and higher mechanical resistance of the final coated surface, making it beneficial for particular applications where high mechanical adherence of the coated surface are required, such as wear-resistance applications.

[0205] From a resource, efficiency and safety perspective, the use of dry electrolytes resulted in a reduction of water consumption by 58.68%. However, electricity consumption increased by approximately 19.51 %. These figures may vary in practical settings depending on equipment efficiency. Importantly, the dry electrolyte process required fewer protective measures due to the absence of toxic vapors, eliminating the mandatory use of masks, as they pose a lower risk of safety and environmental contamination. Both processes could be performed at room temperature without the need for additional ventilation or extraction systems.

Claims

1. CLAIMS1 . A method for providing a coated object comprising: submerging an object comprising an electrically conductive material in a medium comprising a plurality of electrically conductive particles such that at least part of the surface of the object is in contact with the medium; and at least while the object is submerged:- applying a voltage and / or a current to the object; and- producing relative movement between the at least part of the surface and the plurality of electrically conductive particles in the medium; wherein the object is electrically connected with a first pole of at least one electric source; wherein the plurality of electrically conductive particles and / or the medium and / or a container containing the medium is electrically connected with a second pole of the at least one electric source; and wherein applying the voltage and / or the current to the object comprises applying at least one electric pulse, whereby the object is provided with a metal and / or a metal oxide coating.

2. The method of claim 1 , wherein the at least one electric pulse is applied: under voltage control; or under current density control.

3. The method of claim 2, wherein the at least one electric pulse is applied under voltage control, and the voltage of the at least one electric pulse runs from 0 to up to 150 V, in particular from 0 to up to 140 V, more in particular from 0 to up to 130 V.

4. The method of claim 2, wherein the at least one electric pulse is applied under current density control, and a current density of the at least one electric pulse runs from at least -5 to up to 5 A / dm2, in particular from at least -4 to up to 4 A / dm2, more in particular from at least -3 to up to 3 A / dm2and yet more in particular from at least -2 to up to 2 A / dm2.

5. The method of any one of the preceding claims, wherein a maximum current density of the at least one electric pulse is from 0.01 to 5.0 A / dm2, in particular from 0.05 to 4.5 A / dm2and more in particular from 0.25 to 4.0 A / dm2.

6. The method of any one of the preceding claims, wherein the least one electric pulse comprises from 1 to 104electric pulses, in particular from 2 to 103electric pulses, and more in particular from 3 to 102electric pulses, and yet more in particular from 4 to 75 electric pulses.

7. The method of any one of the preceding claims, wherein the at least one electric pulsecomprises a plurality of electric pulses and, optionally, a frequency of application of the plurality of electric pulses is from 0.05 to 30.0 Hz, in particular from 0.1 to 25.0 Hz, in particular from 0.15 to 10.0 Hz, more in particular from 0.2 to 5.0 Hz, and yet more in particular from 0.25 to 2.5 Hz.

8. The method of any one of the preceding claims, wherein the particles of the plurality of electrically conductive particles are ion exchange resin particles, preferably comprising a mixture of water and an acid, and more preferably the acid is methane sulfonic acid and / or sulfuric acid.

9. The method of claim 8, wherein the particles of the plurality of electrically conductive particles further comprise a metal salt, and preferably have an inner content of said mixture of water and an acid and, an outer content of said metal salt, preferably a salt of a metal cation selected from copper, nickel, chromium, gold and silver cation and / or an anion selected form sulfate and chloride anions, preferably the anion is a sulfate anion.

10. The method of any one of claims 8-9, wherein the ion exchange resin particles: are selected from porous ion exchange particles, in particular, macroporous, mesoporous and / or microporous, preferably microporous ion exchange particles; and gel-like ion exchange particles; and / or comprise acidic, basic and / or chelating functional groups, preferably acidic groups and more preferably sulfonic acid groups; wherein the ion exchange particles are preferably sulfonated divinylbenzene (S-DVB) and styrene copolymer macroporous ion exchange resin particles.11 . The method of any one of the preceding claims, wherein the submerging is performed at a temperature from 10 to 90 °C, in particular from 15 to 75 °C, more in particular from 20 to 60 °C.

12. The method of any one of the preceding claims, further comprising adding water to the medium comprising the plurality of electrically conductive particles.

13. One or more electrically conductive particles for use in the method of any one of claims 1- 12, wherein: each particle of the one or more electrically conductive particles is an ion exchange resin particle comprising:- a mixture of water and an acid, and preferably the acid is methane sulfonic acid and / or sulfuric acid; and- a metal salt preferably a salt of a metal cation selected from copper, nickel, chromium, gold and silver cation and / or an anion selected form sulfate and chlorideanions, preferably the anion is a sulfate anion; and each ion exchange resin particle having an inner content of said mixture of water and an acid, and an outer content of said metal salt.

14. A method for preparing one or more electrically conductive particles for use in the method of any one of claims 1-12, comprising: providing ion exchange resin particles having a water content from 10 to 60 wt.%, in particular from 20 to 55 wt.%, more in particular from 30 to 50 wt.%, based on a total weight of the ion exchange resin particles; mixing the ion exchange resin particles with a mixture of water and an acid, preferably methane sulfonic acid and / or sulfuric acid, thereby providing partially swelled particles having an inner content of a mixture of water and an acid; and mixing the partially swelled particles with an aqueous solution of a metal salt, thereby providing electrically conductive particles with an outer content of a metal salt, preferably a salt of a metal cation selected from copper, nickel, chromium, gold and silver cation and / or an anion selected form a sulfate and a chloride anion, preferably the anion being a sulfate anion.

15. Use of the method of any one of claims 1-12 to coat an object.

16. A coated object obtainable by the method of any one of claims 1-12.

17. A coated object comprising an electrically conductive core material and a coating selected from a metal and / or metal oxide coating, the coating covering at least part of the surface of the core material of the object, wherein the coating has a homogeneous morphology comprising homogeneously distributed and highly compacted fine grains of deposited metal and / or metal oxide.

18. The coated object of any one of claims 16-17, wherein the coating is a metal coating, preferably the metal of the coating is selected from copper, nickel, chromium, gold and silver.

19. The coated object of any one of claims 16-18, wherein the coating has: an average thickness from 0.1 to 25 mm, in particular from 1 to 10 mm; and / or a thickness variation of at most 20%, in particular at most 18%, more in particular of at most 15%, yet more in particular at most 10%.

20. The coated object of any one of claims 16-19, wherein the coating is a metal oxide coating, preferably the metal oxide is selected from titanium oxide, copper oxide, and nickel oxide, and other oxides from metals of columns III, IV and V of the periodic table, preferably oxides ofscandium, yttrium, zirconium, hafnium, vanadium and niobium.21 . The coated object of claim 20, wherein the coating has: an average thickness from 0.002 to 200 nm, in particular from 0.005 to 150 nm, more in particular from 0.01 to 100 nm, yet more in particular 0.1 to 80 nm; and / or a thickness variation of at most 20%, in particular at most 18%, more in particular of at most 15%, yet more in particular at most 10%.

22. The coated object of any one of claims 17-21 , wherein the electrically conductive core material is selected from: a metal, preferably a metal selected from titanium, copper, and nickel; a metal alloy, preferably a metal alloy selected from brass and / or stainless steel; and an electrically conductive polymer, preferably previously metallized polymers, intrinsically conductive polymers, conductive polymeric blends and other conductive polymers, in particular resins functionalized with groups selected from amino, trimethylammonium, carboxylic acid, and / or sulphonic acid groups.

23. The coated object of any one of claims 17-22, wherein the coating has a surface with a roughness of less than 1 .m, in particular from 0.01 to 0.8 .m and more in particular from 0.1 to 0.6 |im.

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