ES2754876A1 - DEVICE FOR THE DRY TREATMENT OF METALLIC SURFACES USING ELECTRICALLY ACTIVE SOLID PARTICLES (Machine-translation by Google Translate, not legally binding) - Google Patents

Abstract

Device for the dry treatment of metallic surfaces (1) by means of electrically active solid particles (9), comprising an electrical source (2) with an electrode (3) that transmits electric charge to the electrically active solid particles (9) and means for projecting electrically active solid particles onto the surface to be treated (1). Optionally, the electrical source (2) is connected to the surface to be treated (1), thus closing the electrical circuit. The propulsion of the electrically active solid particles (9) is preferably carried out only with the force of gravity, by means of a centrifugal system, by means of compressed gas or by a connecting rod-crank system or a worm gear system. The device can preferably be part of an in-line assembly, be a portable system or be inside a cabin (4). The device preferably comprises a delivery tank (7), a collection collector (6) and a particle recirculation system (5) (9) from the solid particle collection collector (6) to the delivery tank (7) . (Machine-translation by Google Translate, not legally binding)

Description

DESCRIPTION

DEVICE FOR DRY TREATMENT OF METALLIC SURFACES THROUGH ELECTRICALLY ACTIVE SOLID PARTICLES

OBJECT OF THE INVENTION

Objects of this invention are devices used to treat metal surfaces by projecting electrically active solid particles from an electrode from an electrical source to the metal surface to be treated. These devices allow metal surfaces to be treated at a certain distance without having to insert the surface into a tub. This allows the treatment of large element surfaces, immobile elements, etc. These devices can be designed to handle large elements using robotic arms, for use in booths, for online use in production lines, for use in portable or autonomous equipment. These devices have advantages and represent a notable advance over the current state of the art, which will be detailed below.

FIELD OF APPLICATION OF THE INVENTION

The present invention is framed in the field of metal surface treatment, with relevant implications in the sectors of construction, aeronautics, industrial, automotive, medicine, sintering and many others.

BACKGROUND OF THE INVENTION

Polishing systems are currently on the market by projecting abrasive particles onto the surface to be treated. The particles are forcefully propelled towards the surface, producing a Polishing effect proportional to the impact force. Polishing systems by projecting abrasive particles have a number of drawbacks. Polishing systems by abrasive particle projection cause a lack of homogeneity on the applied surface since abrasion is related to the pressure between the surface and the particles. The most exposed parts suffer more abrasive action, which generates a loss of definition of vertices and edges. This limits its application in cases that require precision or maintain the edge. Likewise, polishing systems by projection of abrasive particles cause inclusions of the same abrasive particles in the metallic surface, reducing the properties of the surface in terms of durability, chemical resistance and traction. Also noteworthy are the risks to respiratory health of these polishing systems by projection of abrasive particles that use abrasive particles, both for the abrasive particles, as well as for the dust and microparticles in suspension generated during the process.

On the other hand, there are the dry electropolishing systems described in ES2604830 (A1) as a "method for smoothing and polishing metals through the transport of ions by means of free solid bodies". This method is based on introducing and rubbing the part to be treated in a medium composed of solid particles capable of ionic transport while applying an electrical potential between the part and a counter electrode. This dry electropolishing system allows to obtain surfaces with a low roughness and specular finishes. Furthermore, this system does not substantially modify the vertices or edges of the object to be polished. Dry electropolishing systems have several drawbacks, among which stand out; the fact that it is impractical when it comes to polishing large parts, such as the wing of an airplane, and the fact that it cannot be applied to treat immovable elements, such as construction elements, among others.

The device for the dry polishing of metallic surfaces by means of the projection of electrically active solid particles object of the invention represents a notable advance since it allows to combine the specular finishes of the dry electropolishing system with the advantages of the system of polishing by means of particle projection abrasives, expanding the field of application of the former and reducing the inconvenience of the latter. However, in order to achieve this goal, it is necessary to overcome various obstacles present such as the nature of the solid particles to be used, their compaction or the type of electric current.

EXPLANATION OF THE INVENTION

Devices for the dry treatment of metal surfaces by projecting electrically active particles have a number of advantages and identifying characteristics, which are detailed below.

The term electrically active solid particles refers in this text to particles that can be electrically charged, that can conduct electricity, or both simultaneously characteristics to some extent.

The term particle projection is understood in this text in the broad sense of any method or system by which the particles reach the surface to be polished, regardless of whether the driving force has been gravity, the flow of a fluid, compressed gas , electrostatic forces or the centrifugal force among others.

The term "electrical source" is understood in this text as any element capable of delivering electrical energy to the electrically active solid particles. The electrical source provides electrical energy to solid particles. The electric current applied by the electrical source can be alternating, continuous or pulsed. Preferably, the electrical source includes a system that allows to control the applied voltage and intensity.

The devices of this invention allow the following essential steps to be carried out:

- Contact of an electrode of the electrical source with the electrically active solid particles.

- Projection of the electrically active solid particles from the device onto the metal surface

- Contact of the electrically active solid particles with the metallic surface

The minimum elements that define the device object of the invention are:

- A set of electrically active solid particles

- An electrical source with an electrode that transmits electrical charge to electrically active solid particles

- A means of projecting the electrically active solid particles onto the metal surface to be treated.

- A nozzle through which electrically active solid particles exit the device.

The interactions that occur between these minimum elements are as follows. Electrically active particles contact an electrode from the electrical source and this transmits an electrical charge to them. From the electrode, the particles move towards the metallic surface to be polished, where they contact and transmit part of the electrical energy. This contact generates redox processes on the metal surface producing a polishing effect. Figure 1 shows the design of a prototype as an example.

Due to the electrical nature of the process, the surface to be treated must be conductive, preferably metallic. This includes surfaces of non-conductive materials, such as plastics that have undergone a metallization process.

The transmission of the electrical charge from an electrode to the surface to be polished by means of a particle flow is not described to the best of our knowledge to date. Three possible electrical charge transmission mechanisms have been conceptualized, producing these and a variety of intermediate situations or derived from them simultaneously:

1) by net charge of particles

2) by electrical conductivity by contact

3) by electrical conductivity through electric arcs or ionized gas.

A schematic representation of these mechanisms can be seen in Figure 2.

Depending on controllable system parameters, one mechanism can be promoted over the others. Mainly, these parameters are electrical, the type of particles, the type of projection.

The mechanism of transmission of electrical charge by particles with net charge is favored in conditions of low compaction. In the ideal case the particles are isolated from each other, that is, without direct contact between them. The energy density that particles can transport, U, can be calculated from the dielectric constant of the particles £ r and the applied electric field E.

1 _

U = 2 £ 0 £ r E¿

For example, experimentally it has been proven that some sulfonated polystyrene-divinylbenzene macroporous gel particles containing 4% sulfuric acid, diameter 600 pm have an £ r = 1.10-108 (measured at 100 Hz) which for an applied electric field 30 kV implies a stored energy density of 437 kJ m-1. These same particles when projected on a metal surface produce an electric discharge that performs work on the surface. For example, when projected onto a 316 stainless steel surface they produce a detectable current flow and an appreciable surface modification.

This mechanism is favored by particles with a high dielectric constant and high applied voltages that allow a higher density of stored electrical energy, and a high separation of the particles that prevents them from discharging between them.

The electrical charge transmission mechanism by electrical conductivity by contact is favored under conditions in which a continuous contact of particles is established from the electrical source to the surface to be polished. In this case, an electric current is established directly through the particles, so this mechanism is favored by particles with a high electrical conductivity and high compaction of the flow. This mechanism produces comparatively high current intensities, which allows a faster treatment of the part.

The mechanism of transmission of electric charge by discharges and electric arcs involves the transmission of electrical charge from the electrical source to the part through the particles and the medium between particles. That is, the transmission of electric charge takes place, at least partially, through ionized gas. There is a range of possibilities including avalanche-type discharges and corona discharges.

Although these discharges can occur electrode-particle and particle-surface mainly occur between particles. This implies that the medium between particles and the distance between particles are a parameter of great influence to trigger this mechanism.

For each type and size of particle there is a range of distances between particles in which this mechanism is triggered. Increasing the conductivity of the interparticle space increases the functional range of distances and allows more room for maneuver. In a preferred embodiment, an element is added that favors the conductivity between the particles by means of electric arcs. These elements can be, solids, liquids, ions, etc., as well as the use of electromagnetic radiation.

In the case of liquid elements that promote conductivity between particles by means of electric arcs, those that have the ability to generate microdroplets or aerosols stand out, increasing the conductivity of the medium between particles. There are also solid elements that promote conductivity between the particles by means of electric arcs that, due to electrical transmission, generate micro- or nano-particles in suspension, such as, for example, carbon derivatives such as carbon fibers, graphite, or micronized carbon. Due to the passage of electricity, these carbon compounds raise their temperature and generate volatiles or elements in suspension that favor electrical transmission. It is also possible to add elements that favor the conductivity between the particles by means of electric arcs with the capacity to retain electrolytic liquid, such as gel-like materials, with some dimension notably greater than the average diameter of the particles, such as bars or cylinders, to make electrical bridges.

The generation of ions in the space between particles considerably increases the conductivity between the particles by means of electric arcs. Ions can be generated by ionizable and volatile substances, such as iodine, or by the use of electromagnetic, ionizing or non-ionizing radiation. These different elements that increase the conductivity of the space between particles can be used in combination with each other. They can be used in admixture with the electrically active particles, added elsewhere to condition the medium, or they can be incorporated into the electrically active particles. Preferably, the particles can retain a certain amount of liquid, in which case the vibrations and friction of the process generate microdroplets and aerosols between the particles, which modifies the conductivity of the system. The use of ultrasound to generate microdroplets, or of nebulizer systems, is also possible. The use of electromagnetic radiation can increase the conductivity of the medium. The use of ionizing electromagnetic radiation, that is, ultraviolet, X-rays and y-rays, directly generates ions in the medium that increase the conductivity of the set of particles and gas between them. The use of non-ionizing electromagnetic radiation is also possible to increase conductivity. For example, by using microwave radiation it is possible to generate plasmas from particles that increase the conductivity of the medium.

Electric shock occurs more easily with alternating current than with direct current. For example, experimentally, visible arcs with direct current from 25 kV are observed.

Under identical conditions using alternating current at 50 Hz, arcs are observed at a voltage one order of magnitude less than 2 kV.

To maintain a stable current flow with corona arcs, you can increase the frequency of alternating current, even several orders of magnitude, work with voltages of the order of kilovolts, as well as reduce the pressure of the medium.

The electrical source supplies electrical energy to the solid particles. The electric current applied by the electrical source can be alternating, continuous or pulsed. Preferably, the electrical source includes a system that allows to control the applied voltage and intensity. Direct current is the one that produces the fastest effects on the surface, that is why in particle / surface systems that do not accumulate residues during the process, it is the preferred option. If the direct current system produces surface accumulations, it is possible to improve the results using current that contains polarity inversions. The most affordable way to obtain current with polarity reversals is to use alternating current. This can be used directly or rectified by diodes or other electroactive elements. A preferred alternative is the use of a pulsed current electrical source that allows controlling the applied pulse parameters, such as positive and negative voltages, positive and negative pulse duration, duration of pauses, etc.

The electrical parameters applied by the electrical source determine the effects of the particles on the surface. The potential difference applied to produce polishing effects is in a wide range from 1 V to 50 kV and is an aspect that determines the electrical transmission mechanism. The current applied to the electrode can be continuous, alternating or pulsed. For example, a 30 kV direct current source with a pulsed, non-compact projection of particles by gravity, at a distance of 18 cm between electrode and surface to be polished, produces polishing effects on the metal surface. As for example also, a source of direct current at 30 V, with a projection of particles by compact and continuous gravity, at a distance of 2 cm between electrode and surface to be polished, produces polishing effects on the metallic surface. As for example also, a source of alternating current from 50 Hz to 2 kV, with a pulsed and non-compact projection of particles by gravity and driven by air at 5 bar, at a distance of 18 cm between electrode and surface to be polished, produces arcs Visible electrical and polishing effects on the metal surface. It is possible to qualitatively attribute to each of these examples a higher relative proportion of each of the electrical charge transmission mechanisms explained above.

The electrode is a conductive element electrically connected to the electrical source with which the particles contact before being projected towards the surface to be treated. The shape of the output electrode depends on the application or surface to be treated. In general, the aim is to maximize the contact area of the particles with the electrode in the moments prior to the projection. For example, a tube through which the particles circulate is connected to a tapering cylinder-shaped, eg, copper, metal outlet electrode. As for example also, to treat plates or relatively flat surfaces, the exit electrode can be a "curtain" system for applying particles, that is, a linear exit groove. In a preferred embodiment the electrode consists of the nozzle.

Electrically active solid particles can transmit electrical charge from the electrical source to the metal surface to be treated. Preferably, the solid particles can retain liquid. This retained liquid can partially dissolve the oxides and salts formed due to the passage of electric current, which improves the cleaning of the surface. Preferably, the electrically active solid particles are made of a polymer gel, as it offers a compromise between physical integrity and the ability to retain liquid in its structure. The electrically active particles are preferably sulfonated polystyrene-divinylbenzene gel because they favor the process due to their reversible ability to retain dissolved metal ions. Preferably, the liquid retained in the electrically active particles is an acidic aqueous solution since most oxides, hydroxides and metal salts are more soluble in an acidic medium. Preferably, the acidic aqueous solution includes one or more strong acids (pKa <2) due to its greater dissociation, increases electrical transmission while improving the solubility of oxides, hydroxides and metal salts, resulting in greater surface cleaning.

The electric charge transmission process can generate a redox reaction on the metal surface, which can lead to the formation of metal oxides on the surface. For a good surface finish, the controlled removal of the oxides formed is crucial. These surface oxides can be removed, for example, by an abrasive action or by a dissolving action.

The removal of metal oxides on the surface by abrasive action can be produced by the action of the same electrically active particles that act as abrasive particles. Oxides can also be removed by the action of non-electrically active abrasive particles. The action of the abrasive particles can be carried out simultaneously (both abrasive particles and non-abrasive particles are projected) or consecutively to the action of the electrically active particles. With this configuration, it would be a novel dry electropolishing process combined with a sandblasting abrasive process.

Alternatively or in addition, the removal of surface oxides can be carried out by a dissolving action. The dissolving action can be carried out by a free liquid or by liquid retained in the particles. Preferably the dissolving action is carried out by liquid retained in the electrically active particles to produce the dissolution of the oxides at the same stage as their formation.

The projection of particles onto the metal surface requires a driving force. In the simplest version, this momentum is the force of gravity.

This impulse is preferably provided by a controllable element. This controllable element is preferably the impulse of a compressed gas. The use of a gas under pressure allows to control the velocity and the pressure of the particle-surface contact, as well as to have control over the flow and compaction of the particles.

In an alternative embodiment, the particles are projected onto the metal surface by driving a turbine that drives the particles by centrifugal force.

In an alternative embodiment, the particles are projected onto the metal surface in a discontinuous manner by driving a connecting rod-crank system. This allows a projection of the particles in a discontinuous way with a highly configurable system regarding the speed and volume of each projection.

In an alternative embodiment, the particles are projected onto the metal surface continuously by driving a worm gear system. This allows a continuous flow to be created and compact particle, favoring the electrical transmission mechanism by contact.

The flow of particles out through the nozzle can be controlled by valves and timers to make it continuous or pulsed.

The shape of the projection of the particles on the surface can be adapted to the needs of the part to be polished. For example, in case you want to process a flat surface within a manufacturing chain, you can use a nozzle that allows the projection of particles in the form of a curtain on the surface that allows the entire width of the surface of the moving part to be covered. under the curtain.

In an alternative embodiment, the spraying can be carried out using an application hose shaped nozzle from which the driven particles would exit. These application hoses can be configurable, for example, in the direction or size of the outlet hole. These hoses can be moved automatically for example within a spray booth, or they can be used manually against the surface to be polished. In the event that the projection of the particles takes place by means of compressed gas, these hoses can incorporate in their final section an air dissipating element at the point of delivery of the particles to compact the particles and maintain a high conductivity.

The flow of particles out through the nozzle can be controlled by valves and timers to make it continuous or pulsed.

The shape of the projection of the particles on the surface can be adapted to the needs of the part to be polished. For example, in case you want to process a flat surface within a manufacturing chain, you can use a nozzle that allows the projection of curtain-shaped particles on the surface that allows to cover the entire width of the surface of the piece that moves under the curtain.

In an alternative embodiment, the spraying can be carried out using an application hose shaped nozzle from which the driven particles would exit. These application hoses can be configurable, for example, in the direction or size of the outlet hole. These hoses can be moved automatically for example within a spray booth, or they can be used manually against the surface to be polished. In the event that the projection of the particles takes place by means of compressed gas, these hoses can incorporate in their final section an air dissipating element at the point of delivery of the particles to compact the particles and maintain a high conductivity.

The surface to be treated can be isolated, connected to an earth connection or to the electrical source. Preferably the surface to be treated is connected to the electrical source by means of an electrode from the electrical source. In this way, a greater control of the applied potential difference is obtained and it is possible to measure the step current between the particle's output electrode and the surface to be treated.

The surface to be treated must be conductive. The surface to be treated is preferably metallic. This includes pieces of plastic materials with a surface that has been metallized. Treatable metals and alloys include, but are not limited to, all types of irons and steels, chrome-cobalt alloys, nickel, and nickel alloys, such as nitinol, zinc, and zinc alloys, such as Zamak, aluminum, and alloys, titanium and alloys, copper and alloys, tungsten carbide, etc.

The versatility of this system makes it possible to treat large flat surfaces, large parts, surfaces that are immovable, such as construction structures, etc.

The electrical parameters applied by the electrical source determine the effects of the particles on the surface. The potential difference applied to produce polishing effects is in a wide range from 1 V to 50 kV and is an aspect that determines the electrical transmission mechanism. The current applied to the electrode can be continuous, alternating or pulsed. For example, a 30 kV direct current source, with a pulsed and non-compacted projection of particles by gravity, at a distance of 18 cm between electrode and surface to be polished produces polishing effects on the metal surface. As for example also, a source of direct current at 30 V, with a projection of particles by compact and continuous gravity, at a distance of 2 cm between electrode and surface to be polished, produces polishing effects on the metallic surface. As for example also, a source of alternating current from 50 Hz to 2 kV, with a pulsed and non-compact projection of particles by gravity and driven by air at 5 bar, at a distance of 18 cm between electrode and surface to be polished, produces arcs Visible electrical and polishing effects on the metal surface. It is possible to qualitatively attribute to each of these examples a higher relative proportion of each of the electrical charge transmission mechanisms explained above.

Electrically active solid particles can transmit electrical charge from the electrical source to the metal surface to be treated. Preferably, the solid particles can retain liquid. This retained liquid can partially dissolve the oxides and salts formed due to the passage of electric current, which improves the cleaning of the surface. The electrically active solid particles are preferably made of a polymer gel, as it offers a compromise between physical integrity and the ability to retain liquid in its structure. The electrically active particles are preferably sulfonated polystyrene-divinylbenzene gel because they favor the process due to their reversible ability to retain dissolved metal ions. Preferably, the liquid retained in the electrically active particles is an acidic aqueous solution since most oxides, hydroxides and metal salts are more soluble in an acidic medium. Preferably, the acidic aqueous solution includes one or more strong acids ( pK ^to <2) due to its greater dissociation, increase electrical transmission while improving the solubility of oxides, hydroxides and metal salts, resulting in greater surface cleaning .

Other elements that improve the operation of the invention are:

- A prior deposit for delivery of particles.

- A collector for collecting the particles. The collector and the pre-tank can be the same element.

- A particle recirculation system from the collector to the delivery tank, if they are not the same element.

- Vibrators at the points of storage or circulation of the particles to facilitate their transport, as well as transmitting vibration to the surface to be treated.

Preferably, the device comprises a solid particle delivery tank prior to electrical contact and spraying. This tank ensures the delivery of particles to the system constantly and avoids downtime.

Preferably, the device comprises a collector for collecting solid particles once they have hit the surface to be polished. This collector is designed for each realization so specific and can adopt various conformations, as can be seen in the examples. This element prevents the dispersion of particles everywhere and at the same time allows the recirculation of particles.

In the embodiments that allow it, preferably the delivery tank and the collection collector are the same element. This allows to simplify the design of the device and avoid redundancy of elements, which results in lower costs while maintaining the same functionality.

In the event that the delivery tank and the collection collector are not the same element, there may be a particle recirculation system between the collection collector and the solid particle delivery tank. This system allows the reuse of particles automatically, thus avoiding the necessary human effort and improving the degree of automation.

The device preferably comprises a vibrator or vibrators that vibrate the particles to facilitate their movement. Said vibrator may preferably be located in the delivery tank and / or in the collection collector. The movement of a granular material such as the particles used in this process can form locks through arcs. The use of vibrators in the tanks and circulation tubes significantly reduces the formation of arches which prevents blockages at the circulation points.

Consequently, the following steps are identified that improve the method object of the invention are:

- Recirculation of particles from the collection collector to the delivery tank, if they are not the same element.

- Vibration of electrically active solid particles

This novel technology is conceived with a wide variety of possible end applications. As an example and without limitation purposes, some of the possible applications are presented. An application is in individual polishing units to polish large structural parts, such as the wing of an airplane to improve its aerodynamics. A final application is its use in continuous in-line processes to treat metal surfaces after production or as a previous step to other treatments.

Another final application is in autonomous portable polishing devices.

DESCRIPTION OF THE DRAWINGS

Figure 1. Exemplary design of the device that executes the polishing method object of the invention.

Figure 2A. Schemes of the electricity transmission mechanism between the electrical source and the metallic surface by means of a net charge on the particles.

Figure 2B. Schemes of the electricity transmission mechanism between the electrical source and the metallic surface by means of electrical conductivity by contact.

Figure 3C. Schematics of the electricity transmission mechanism between the electrical source and the metallic surface by means of electrical conductivity through electric arcs.

Figure 3. Diagram of a device for online surface treatment

Figure 4. Diagram of a portable device for surface treatment

Figure 5. Diagram of a device with a cabin for surface treatment

PREFERRED EMBODIMENTS OF THE INVENTION

Below are several exemplary cases without limitation purpose.

Realization 1

The device consists of a delivery tank (7) for particles (9) whose outlet is connected to a copper tube that acts as an electrode (3), in turn connected to an electrical source (2). The particles (9) fall continuously by gravity to the surface to be treated (1), which is connected to the electrical source (2) through the counter-electrode. The particles (9) fall, after contact with the piece, to a collection collector (6) for their subsequent recirculation by means of a recirculation system (5). Both the particle delivery tank (7) and the collection collector (6) have a vibrator (8). A schematic representation is found in Figure 1.

In an exemplary case, the particles (9) used are sulfonated polystyrene-divinylbenzene macroporous gel particles loaded with an electrolyte solution containing 4% sulfuric acid. This prototype has been tested with different types of electric current: continuous from 1 to 60 V; toggles from 50 Hz to 50,000 Hz from 0 to 220 V.

The polishing method for treating a 316 steel surface with different types of electric current has been tested with these parameters: it continues up to 35 kV, it alternates at 50 Hz up to 15 kV.

The direct current results show a linear behavior of the intensity with respect to the potential difference. It is observed that after an effective 5 min treatment at 30 kV there is a reduction of R ^a from 0.37 to 0.34 pm in the area most exposed to the flow of particles.

The results using 50 Hz alternating current show linear behavior in the range of 0 to 5 kV. Increasing the voltage from this point does not produce an increase in proportional current. This effect clearly indicates a change of mechanism in the transmission of the electrical charge.

Device for online surface treatment

It consists of a device for online surface treatment. A schematic representation is found in Figure 3. In this example, without limitation, it is designed to treat metal plates. The device includes an electrical source (3), a “curtain” system for applying the particles (9), a conveyor system for the plate to be treated and a recirculation system (5) that collects the particles and deposits them in the delivery tank (7).

The metal plate to be treated is located on a conveyor belt provided with vibration and connected to the electrical source. At one point along the conveyor belt there is a curtain type particle projector (9). The linear applicator produces a linear projection of particles (9) on the surface to be treated (1) that covers the entire width of the plate to be treated. The plate travels through the particle curtain at a suitable speed that provides the treatment time to obtain the desired finishes. The curtain type particle projector includes a vibrator (8) to facilitate the flow of the particles. In the exit slot of the particles there is a metallic element, connected to the negative pole of the power supply that acts as an electrode (3). The particles contact this electrode (3) before reaching the surface to be treated (1). A recirculation system (5) is applied near the contact point, which sucks the particles after having contacted the surface and deposits them in the delivery tank (7).

Portable device for surface treatment

It consists of a portable device for surface treatment (1). A schematic representation is found in Figure 4. This device facilitates its joint transportation, such as, for example, with wheels. The device includes a compressor and a compressed air tank, an electrical source (2), a delivery tank (7) for particles and a recirculation system (5).

The device can be connected to a power outlet, alternatively it can include a sufficient electric accumulator that provides the energy. The delivery tank (7) particles (9) in its lower part has an outlet to the particle delivery hose, the tank can be provided with a vibrator (8) to facilitate the flow of particles (9). The particles (9) are propelled through the application hose by means of compressed air bar coming from the compressor. The necessary pressure depends on the length and placement of the application hose, a pressure between 3 and 10 bar provides good results. The application hose ends in a diffuser that allows the exit of part of the air, forcing the compaction of the particles (9). The output of the particles occurs through, or in contact with, an electrode (3), which can be an element of, for example, copper, 316 stainless steel or titanium iridium, connected to the electrical source (2) , preferably to the positive pole, preferably with an ammeter to monitor the intensity. The application electrode (3) is located at a distance of between 0.5 and 10 cm from the surface, so that there is a flow of particles between the electrode and the surface to produce a current flow. The final part of the particle outlet is included within a collection collector (6) that is very close to or in contact with the surface to be treated (1). This particle collection collector (6) is connected to a recirculation system (5) comprising a second hose provided with aspiration, which collects the particles from the collection collector (6) after their contact with the surface and directs them back to the delivery tank (7) particles. The surface to be treated (1) is connected to the electrical source (1) by, for example, an electrical clamp preferably to the positive pole. To polish surfaces not accessible by an operator or to improve precision, the system may include the use of a robotic arm.

The design of the system is designed to occupy a compact volume and contains elements, such as wheels or sliding elements, that make it portable.

The applied current depends on the composition of the surface to be treated and the particles (9) used. For example, to treat a 316 steel surface good results are obtained using sulfonated polystyrene-divinylbenzene particles containing 4% sulfuric acid with a continuous current of 12V.

Cabin surface treatment device

It consists of a device for the treatment of surfaces (1) in a closed cabin (4). A schematic representation is found in Figure 5. The device includes an electrical source (2), one or more electrically active particles outlets (9) with electrodes (3), a system for anchoring the pieces to be polished, a cabin (4) closed for treatment and a recirculation system (5) that sucks the particles from the collection collector (6), which in this example also acts as a delivery tank (7), towards the particle outlets.

The metal parts to be polished are placed on racks inside the cabin by means of suitable anchors, so that they are connected to the electrical source (2). The cabin (4) is provided with several particle outlets connected in its final section to electrodes (3). The projection of the particles (9) occurs through the use of compressed air, preferably in a range of 2 to 10 Bar, preferably between 4 and 6 bar.

The bottom of the cabin (4), which acts as a collection collector (6) while acting as a delivery tank (7), has an inclination and the particles (9) are collected by a recirculation system (5) that transports them to the particle exits.

The applied electric current depends on several factors such as the type of material, the total area to be processed, the distance between the particle exit point and the surface. For example, to polish 316 steel 4 cm apart a total area of 25 cm2.

Claims (14)

claims Device for the dry treatment of metallic surfaces (1) by means of electrically active solid particles (9) characterized in that it comprises an electrical source (2) with an electrode (3) that transmits electric charge to the electrically active solid particles (9) and means for projecting electrically active solid particles onto the surface to be treated (1). 2. Device for the dry treatment of metal surfaces (1) by means of electrically active solid particles (9) according to claim 1, characterized in that the electrical source (2) is connected to the surface to be treated (1), thus closing the electrical circuit. Device for the dry treatment of metallic surfaces (1) by means of electrically active solid particles (9) according to any of the preceding claims, characterized in that the propulsion of the electrically active solid particles (9) is carried out only with the force of gravity. Device for the dry treatment of metal surfaces (1) by means of electrically active solid particles (9) according to any of claims 1-2, characterized in that the propulsion of the electrically active solid particles (9) is carried out by means of a centrifugal system. 5. Device for the dry treatment of metallic surfaces (1) by means of electrically active solid particles (9) according to any of claims 1-2, characterized in that the propulsion of the electrically active solid particles (9) is carried out by means of compressed gas. Device for the dry treatment of metallic surfaces (1) by means of electrically active solid particles (9) according to any of claims 1-23, characterized in that the propulsion of the electrically active solid particles (9) is carried out by means of a connecting rod system. crank or worm gear system. Device for the dry treatment of metallic surfaces (1) by means of electrically active solid particles (9) according to any of the preceding claims, characterized in that it forms part of an in-line assembly. Device for the dry treatment of metallic surfaces (1) by means of electrically active solid particles (9) according to any of claims 1-6, characterized in that it is a portable system. 9. Device for the dry treatment of metallic surfaces (1) by means of electrically active solid particles (9) according to any of claims 1-6, characterized in that the device and the surface to be treated (1) are inside a cabin (4) . Device for the dry treatment of metallic surfaces (1) by means of electrically active solid particles (9) according to any of the preceding claims, characterized in that the device comprises a delivery tank (7) of solid particles (9) prior to contact with the electrode (3). Device for the dry treatment of metallic surfaces (1) by means of electrically active solid particles (9) according to any of the preceding claims, characterized in that the device comprises a collector (6) for solid particles (9) once they have impacted against the surface to be treated (1). Device for the dry treatment of metallic surfaces (1) by means of electrically active solid particles (9), claim 10, characterized in that the device comprises a system for recirculating (5) the particles (9) from the collection collector (6) of solid particles to the delivery tank (7). 13. Device for the dry treatment of metal surfaces (1) by means of electrically active solid particles (9), any one of the preceding claims, characterized in that the device comprises a vibrator (8). Device for the dry treatment of metallic surfaces (1) by means of electrically active solid particles (9), any one of the preceding claims, characterized in that the particle delivery device comprises a diffuser.