RU2797287C1 - Method and device for dry treatment of metal surfaces with electrically active solid particles - Google Patents

Abstract

FIELD: electrochemical processing of metal surfaces.

SUBSTANCE: invention is related to processing of metal surfaces in particular by polishing, and can be used in aeronautics, construction, automation, medicine, laser sintering and other fields of technology. The method of dry treatment of metal surfaces (1) by means of electrically active solid particles (9) includes the following steps: contact of said particles (9) with an electrode (3) of an electric power source (2), ejection of said particles (9) in the direction of the metal surface to be processing, transferring the electric charge of these particles to the metal surface to be processed. A device for dry treatment of metal surfaces (1) by means of electrically active solid particles (9) contains an electrical power source (2) with an electrode (3) that transfers an electric charge to electrically active solid particles (9), and a means for ejection of electrically active solid particles on the surface (1) to be processed.

EFFECT: providing the possibility of processing surfaces of large-sized elements, fixed elements without the need to place the surface in a container.

24 cl, 5 dwg

Description

OBJECT OF THE INVENTION

The object of the invention is a method for treating or polishing metal surfaces, characterized in that the ejection of electrically active solid particles on the part to be polished is carried out from an electrode connected to an electrical power source. This method allows dry polishing of metal surfaces without the need to place the surface to be treated in a container, which makes it possible to process surfaces that, due to their characteristics of size, location, etc., could not previously be processed, for example, large-sized elements, stationary elements and so on. This method has advantages and characteristics that demonstrate a significant novelty compared to the current state of the art.

The subject of the invention is also devices used for treating metal surfaces by ejecting electrically active solid particles from an electrode of an electrical power source onto the metal surface to be treated. These devices make it possible to process metal surfaces from a given distance without the need to place the surface inside the vessel. This makes it possible to process the surfaces of large-sized elements, stationary elements, and the like. These devices can be designed for handling large items with robotic arms, for use in chambers, for use as part of production lines, for use in mobile or stand-alone equipment. These devices are advantageous and represent a significant advance over the current state of the art, which is detailed below.

FIELD OF THE INVENTION

The scope of this invention is the industrial sector associated with the processing of metal surfaces. Namely, the industrial sector associated with the polishing of metal surfaces, with applications in areas such as aeronautics, construction, automation, medicine, laser sintering, among many other applications.

BACKGROUND OF THE INVENTION

Currently on the market are systems for polishing by ejection of abrasive particles onto the surface to be treated. The particles are forcefully driven in the direction of the surface, providing a polishing effect proportional to the impact force. Polishing systems by ejection of abrasive particles have a number of disadvantages. Polishing systems by ejection of abrasive particles cause insufficient uniformity of the surface to which they are applied, since the abrasive action is associated with pressure between the particles and the surface. Parts with a large contact surface are subjected to more abrasive action, which leads to a loss of sharpness of tops and edges. This limits their use in applications where precision or sharp edge retention is required. In addition, polishing systems by ejection of abrasive particles cause the same abrasive particles to be embedded in the metal surface, reducing the surface properties in terms of durability, chemical resistance and adhesion. It should also be noted that there are respiratory health risks associated with the use of these abrasive particle ejection polishing systems that use abrasive particles, both due to abrasive particles and dust and suspended microparticles generated during the process.

On the other hand, there are dry electropolishing systems disclosed in ES 2604830 (A1) as "a process for leveling and polishing metal by ion transport through free solids". This method is based on dipping and polishing the part to be processed in an environment consisting of solid particles capable of ion transport, while applying a potential between the part and the electrical counter electrode. This dry electropolishing system produces surfaces with low roughness and a mirror finish. In addition, this system does not significantly change the tops or corner edges of the object to be polished. Dry electropolishing systems have a number of disadvantages, among which are the fact that they are not suitable for working on large parts, such as aircraft wings, and the fact that they cannot be used for processing stationary elements, such as building elements, in among others.

The method of dry polishing metal surfaces by ejection of electrically active particles, which is the object of the present invention, is a significant advance, since it allows you to combine the mirror finish of the dry electropolishing system with the advantages of polishing by ejection of abrasive particles, expanding the scope of the former system and reducing the disadvantages of the latter. However, in order to achieve this goal, it is necessary in a non-obvious way to overcome several existing obstacles, such as the nature of the solid particles used, their compaction, or the type of electric current.

DISCLOSURE OF THE INVENTION

The method and apparatus for dry polishing metal surfaces by ejection of electrically active particles has a number of defining advantages and characteristics, which are detailed below.

The expression "electrically active solid particles" refers in this text to particles that can be electrically charged, that can conduct electricity, or both at the same time to a certain extent.

The expression "particle ejection" is understood herein in the broad sense of any method or system by which particles reach the treated surface, whether the driving force is gravity, fluid flow, compressed gas, electrostatic forces or centrifugal force, among others. .

The expression "electric power supply" in this document means any element capable of supplying electrical energy to electrically active solid particles. An electrical power source provides electrical energy to the solid particles. The electrical current supplied by the electrical power supply may be alternating, direct or pulsed current. Preferably, the electrical power supply includes a system that allows control of applied voltage and intensity.

The main steps that define the object of the method and device according to the invention are:

- Contact of the electrode of the electrical power source with electrically active solid particles;

- Ejection of electrically active solid particles of the device onto a metal surface.

Contact of electrically active solid particles with a metal surface.

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

- A set of electrically active solid particles;

- An electrical power source with an electrode that transfers an electrical charge to electrically active solid particles;

- Means for ejection of electrically active solid particles on the metal surface to be processed;

- Nozzle through which electrically active solid particles exit the device.

The interactions that exist between these minimal elements are as follows.

Electrically active particles come into contact with an electrode of an electrical power source, and it then transfers an electrical charge to them. From the electrode, the particles move towards the metal surface to be treated, where they come into contact with it and transfer some of the electrical energy. This contact causes a redox process on the metal surface, creating a polished effect. In FIG. 1 shows a drawing 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 made of non-conductive materials, such as plastic, that have undergone a plating process.

The transfer of electric charge from the electrode to the surface to be treated, through the flow of particles, to our knowledge, has not yet been described in the literature. Three possible mechanisms for the transfer of electric charge were comprehended, while these and many intermediate or derivative situations arise from them simultaneously:

1) due to the total charge of particles,

2) through electrical conduction through contact, and

3) due to electrical conductivity through a voltaic arc or ionized gas.

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

Depending on the controlled parameters of the system, the mechanism can be extended to other systems. Basically, these parameters are related to electricity, particle type, emission type and environment.

The mechanism of transfer of electric charge by particles with a total charge is enhanced under conditions of low compaction. Ideally, the particles are isolated from each other, that is, they do not have direct contact with each other. The energy density U that the particles can carry can be calculated from the dielectric constant ε _r of the particles and the applied electric field E.

For example, it has been experimentally proven that microporous gel particles of sulfonated polystyrene-divinylbenzene containing sulfuric acid at a level of 4%, having a diameter of 600 μm, give ε _r =1.10⋅10 ⁸ (measured at 100 Hz), which for an electric field, applied to 30 kV implies a stored energy density of 437 kJ m ^-1 . The same particles, when thrown onto a metal surface, produce an electrical discharge that does work on the surface. For example, when they are thrown onto a 316 stainless steel surface, they cause a noticeable current flow and a change in the visible surface.

This mechanism is facilitated by particles with a high dielectric constant and applied voltages, which provide a higher density of stored electrical energy and a high separation of particles, preventing discharge between them.

The mechanism for transferring electrical charge by electrical conduction through contact is preferable under conditions where continuous contact of the particles from the electrical power source to the surface to be treated is established. In this case, the electric current passes directly through the particles, so this mechanism is facilitated by particles with high electrical conductivity and high flux density. This mechanism provides relatively high current strengths, which allows you to process the part at a higher speed.

The mechanism of transfer of electric charge through discharges and voltaic arcs involves the transfer of electric charge from an electrical power source to the part through the particles and the medium between the particles. This means that the transfer of electrical charge occurs, at least in part, through the ionized gas. There are a number of possibilities that include avalanche-type discharges and corona-type discharges.

Although these discharges can occur in electrode-particle and particle-surface connections, they mainly occur between particles. This means that the medium between the particles and the distance between the particles are the parameters that have a great influence on the triggering of this mechanism.

For each type and size of particles, there is a range of distances between particles at which this mechanism is triggered. Increasing the conductivity of the space between the particles increases the range of operating distances and provides a larger operating range. In a preferred embodiment, an element is added that promotes conduction between particles via voltaic arcs. These elements can be solid, liquid, ions, etc., and also use electromagnetic radiation.

In the case of liquid elements that promote conduction between particles by means of voltaic arcs, those that have the ability to generate microdroplets or aerosols are distinguished, increasing the conductivity of the medium between particles. There are also solid elements which promote conduction between particles by means of voltaic arcs which, through electrical transmission, generate micro- or nanoparticles in suspension, such as for example carbon derivatives, fiber-type carbon, graphite or finely divided carbon. Due to the passage of electricity, these carbon compounds increase their temperature and release volatile or suspended elements that facilitate the transmission of electricity. To create electrical bridges, it is also possible to add elements that promote conduction between particles by means of voltaic arcs, having the ability to hold an electrolytic liquid, such as, for example, a gel-type material, some of which are significantly larger than the average particle diameter, such as, for example, rods or cylinders. .

The generation of ions in the space between particles greatly increases the conduction between particles by means of voltaic arcs. It is possible to generate ions by means of ionizable or volatile substances, such as, for example, iodine, or by using electromagnetic radiation, either ionizing or non-ionizing. These various elements, which increase the conductivity of the space between the particles, can be used in combination with each other. They can be used in a mixture with electrically active particles, added at another point to improve the state of the environment, or they can be included in the composition of electrically active particles. Preferably, the particles can hold more liquid, in which case the vibrations and frictions in the process create microdroplets and aerosols between the particles, which change the conductivity of the system. Ultrasound can also be used to create microdroplets or spray systems. The use of electromagnetic radiation can increase the conductivity of the medium. The use of ionizing electromagnetic radiation, that is, ultraviolet, x-ray and gamma radiation, directly generates ions in the medium, which increases the conductivity of the collection of particles and gas between themselves. It is also possible to use electromagnetic non-ionizing radiation to increase the conductivity. For example, through the use of microwave radiation, plasma can be generated from particles, which increases the conductivity of the medium.

Electrical discharges occur more easily with alternating current than with direct current. For example, in the experiment, visible voltaic arcs are observed when using a direct current of 25 kV and higher. Under similar conditions, when using alternating current with a frequency of 50 Hz, voltaic arcs are observed at a voltage an order of magnitude lower than 2 kV.

To maintain a stable current flow with crown-type arcs, it is possible to increase the frequency of the alternating current even by several orders of magnitude, operate at voltages of the order of kilovolts, and also reduce the pressure of the medium.

An electrical power source provides the solid particles with electrical energy. The electrical current supplied by the electrical power supply may be alternating, direct or pulsed current. The electrical power supply preferably includes a system for controlling the applied voltage and intensity. Direct current is the current that produces the fastest effects on the surface, so in particle/surface systems that do not accumulate residue during the process, it is the preferred option. If a DC system produces surface buildup, you can improve results by using a current that supports polarity reversal. The most affordable way to obtain current with a change in polarity is to use alternating current. It can be directly used or rectified by means of diodes or other electroactive elements. A preferred alternative is to use an electric pulsed current power supply which allows the parameters of the applied pulses to be controlled, such as, for example, positive or negative voltages, duration of positive or negative pulses, duration of pauses, etc.

The electrical parameters applied by the electrical power supply determine the effect of the particles on the surface. The potential difference applied to create a polishing effect is in a large range from 1 V to 50 kV, and this is a feature that determines the mechanism of electrical transmission. The current supplied to the electrode can be direct, alternating or pulsed current. For example, a 30 kV direct current source with a pulsed ejection and without gravitational particle compaction, at a distance of 18 cm between the electrode and the surface to be processed, creates a polishing effect on the metal surface. Also, for example, a 30 V direct current source with a continuous gravitational ejection of particles and a seal, at a distance of 2 cm between the electrode and the surface to be treated, creates a polishing effect on the metal surface. So, for example, an alternating current source with a frequency of 50 Hz, up to 2 kV, with a pulsed ejection and without gravitational compaction of particles driven by air at a pressure of 5 bar, at a distance of 18 cm between the electrode and the surface to be treated, produces visible electric arcs and polishing effects on the metal surface. Qualitatively, in each of these examples, a higher proportion can be determined with respect to each of the electrical charge transfer mechanisms explained previously.

The electrode is a conductive element electrically connected to an electrical power source with which the particles come into contact before being ejected towards the surface to be treated. The shape of the existing electrode depends on the application or surface to be treated. In general, it is desirable to maximize the contact area of the particles with the electrode at the moments preceding their ejection. For example, the tube through which the particles circulate is connected to an output metal electrode, eg copper, in the form of a straightening cylinder. Thus, for example, in order to also process relatively flat plates or surfaces, the output electrode can be a "veil" type particle application system, which means a straight output channel. In a preferred embodiment, the electrode consists of a nozzle.

Electrically active solid particles can transfer an electrical charge from an electrical power source to the metal surface to be treated.

Solid particles preferably can hold liquid. This retained liquid can partially dissolve rust and salts generated by the passage of electric current, which improves the surface finish. The electrically active solids are preferably made from a polymer gel, as it provides a compromise between physical integrity and the ability to retain liquid in its structure. The electrically active particles are preferably a sulfonated polystyrene-divinylbenzene gel as they aid the process due to their ability to reversibly retain dissolved metal ions. The liquid held in the electrically active particles is preferably an aqueous acid solution, since most rust, hydroxide and metal salts are more soluble in an acidic environment. The aqueous acid solution preferably includes one or more strong acids (p/K _a <2). Due to their greater dissociation, they increase electrical transmission while improving the solubility of rust, hydroxides and metal salts, resulting in the best possible surface finish.

The process of transferring an electrical charge can cause a redox reaction on the metal surface, which can lead to the formation of metal rust on the surface. A good surface finish requires controlled removal of the resulting rust. Such surface rust can be removed, for example, by abrasive action or solvent action.

The removal of metallic rust from a surface by abrasion may be by the action of the same electrically active particles that act as abrasive particles. Rust can also be removed by exposure to non-electrically active abrasive particles. The impact of abrasive particles can be carried out simultaneously (abrasive particles and non-abrasive particles are released simultaneously) or alternately with the impact of electrically active particles. With this configuration, it would be a new dry electropolishing process combined with a sandblast type abrasive process.

Alternatively or additionally, the removal of surface rust can be carried out by means of a solvent action. The dissolution action can be performed with a particle-free liquid or with a liquid retained in the particles. The dissolving effect is preferably carried out by the liquid retained in the electrically active particles to ensure that the rust is dissolved at the same stage as it is formed.

The ejection of particles onto the metal surface requires an impulse force. In the simplest version, such an impulse is gravity.

This impulse is preferably provided by the controlled element. Such controlled element is preferably an impulse from a compressed gas. The use of pressurized gas provides the ability to control the speed and pressure of particles in contact with the surface, as well as to control the flow of particles and compaction.

In an alternative embodiment, the particles are ejected onto the metal surface by the impulse of a turbine which drives the particles by means of centrifugal force.

In an alternative embodiment, the particles are ejected onto the metal surface in an intermittent manner by means of the pulse of the crank system. This allows particles to be ejected in an intermittent manner with an easily adjustable system, both in terms of speed and volume of each ejection.

In an alternative embodiment, the particles are applied to the metal surface continuously by means of a screw conveyor impulse. This makes it possible to create a continuous and compact flow of particles, which contributes to the mechanism of transmission of electric current on contact.

The outflow of particles through the nozzle can be controlled using valves and timers to make it continuous or pulsed.

The method of ejecting particles to the surface can be adapted to the needs of the part to be processed. For example, if a flat surface needs to be treated as part of a production chain, a nozzle can be used that allows particles to be ejected to the surface in a curtain, which allows covering the entire surface width of the part that moves under the curtain.

In an alternative embodiment, the ejection may be carried out using an applicator hose nozzle through which the propelled particles must exit. Such application hoses may be configurable, for example, depending on the direction or size of the outlet nozzle. Such hoses can be moved in an automated way, for example, inside the ejection chamber, or they can be used manually on the surface to be treated. In case particles are ejected by means of compressed gas, these hoses may include an air dispersion element at the particle injection point at their end to compact the particles and maintain high conductivity.

The flow of particles exiting the nozzle can be adjusted using valves and timers to make it continuous or pulsed.

The method of ejecting the particles to the surface can be adapted to the requirements of the part to be polished. For example, if it is necessary to process a flat surface within the production chain, a nozzle can be used, which allows the particles to be ejected to the surface in the form of a curtain, which allows you to cover the width of the surface of the part moving under the curtain.

In an alternative embodiment, the ejection may be carried out using an applicator hose nozzle through which the propelled particles must exit. Such application hoses may be adjustable, for example, depending on the direction or size of the exiting nozzle. Such hoses can be moved in an automated way, for example, inside the ejection chamber, or they can be used manually on the surface to be polished. In case particles are ejected by means of compressed gas, these hoses may include an air dispersion element at the particle injection point at their end to compact the particles and maintain high conductivity.

The surface to be treated may be insulated, grounded or connected to an electrical power source. The surface to be treated is preferably connected to an electrode of an electrical power source. In this way, greater control over the applied potential difference is achieved and the current passing between the particle exit electrode and the surface to be treated can be measured.

The surface to be treated must be conductive. The surface to be treated is preferably metallic. This includes parts made of plastic materials having a metallized surface. Metals and alloys that can be machined include, but are not limited to, any type of cast iron, steel, chromium and 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 process large flat surfaces, large workpieces, stationary surfaces such as building structures, etc.

The electrical parameters applied to the electrical power supply determine the impact of the particles on the surface. The potential difference applied to obtain polishing effects is in a large range from 1 V to 50 kV, and this is a feature that determines the mechanism of electrical transmission. The current supplied to the electrode can be direct, alternating or pulsed current. For example, a 30 kV direct current source with pulsed particle ejection and no gravity seal at a distance of 18 cm between the electrode and the surface to be treated creates a polishing effect on the metal surface. Also, for example, a 30 V direct current source with a dense continuous gravitational ejection of particles at a distance of 2 cm between the electrode and the surface to be processed creates a polishing effect on the metal surface. So, for example, an alternating current source with a frequency of 50 Hz, up to 2 kV, with a pulsed ejection and without gravitational particle compaction, and driven by air at a pressure of 5 bar, at a distance of 18 cm between the electrode and the surface to be treated, creates visible electrical arcs and polishing effects on the metal surface. Qualitatively, for each of these examples, it is possible to determine a higher relative share for each of the electric charge transfer mechanisms.

Electrically active solid particles can transfer an electrical charge from an electrical power source to the metal surface to be treated. Solid particles preferably can hold liquid. This retained liquid can partially dissolve rust and salts generated by the passage of electric current, which improves the surface finish. The electrically active solids are preferably made from a polymer gel, as this provides a compromise between physical integrity and the ability to retain liquid in its structure. The electrically active particles are preferably a sulfonated polystyrene-divinylbenzene gel because they aid the process through their ability to reversibly retain dissolved metal ions. The liquid held in the electrically active particles is preferably an aqueous acid solution, since most rust, hydroxide and metal salts are more soluble in an acidic environment. The aqueous acid solution preferably includes one or more strong acids (pK _a <2). Due to their greater dissociation, they increase electrical transmission while improving the solubility of rust, hydroxides and metal salts, resulting in the best possible surface finish.

Other elements that improve the operation of the invention are:

- Preliminary container for feeding particles;

- Receiver for collecting particles. The receiver and the provisional container can be the same element;

- System for recycling particles from the receiver to the supply container, in case they are not the same element;

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

The device preferably comprises a solids feed container located prior to electrical contact and ejection. Such a container provides a constant supply of particles to the system and avoids stopping points.

Preferably, the device includes a receptacle for collecting solid particles after the particles hit the surface to be treated. Such a receiver is designed for each embodiment in a specific way and may take several forms, as seen in the examples. This element prevents particles from being scattered all over the place while still allowing the particles to be recycled.

In embodiments that enable this, the supply container and the receptacle are preferably the same element. This simplifies the design of the device and eliminates redundant elements, which reduces costs while maintaining the same functionality.

In the event that the supply container and the receiver are not the same element, a particle recycling system may exist between the solids collection container and the supply container. This system provides the ability to automatically reduce particles, thereby eliminating the need for human effort and increasing the level of automation.

The device preferably includes a vibrator or vibrators which cause the particles to vibrate to facilitate their movement. Said vibrator may preferably be located in the supply container and/or in the receiver. The movement of granular material, which is the particles used in this process, can form blockages in the form of arches. The use of vibrators in compartments and circulation channels greatly reduces arching, which prevents clogging at circulation points.

Therefore, the following steps are defined that will improve the object of the method according to this invention:

- recirculation of particles from the collection receptacle to the supply container, in case they are not the same element;

- performing vibration of electrically active solid particles.

This new technology has been developed with a wide range of possible end uses in mind. For example, with and without intent to limit, some uses are presented. The application lies in the polishing of individual components for the processing of large structural parts, for example, the wing of an aircraft, to improve its aerodynamics. Its end use is in continuous in-line processes for the treatment of metal surfaces after they have been fabricated, or as a pre-stage before other treatments.

Another end use is polishing stand-alone mobile units.

BRIEF DESCRIPTION OF THE DRAWINGS

In FIG. 1 is an exemplary drawing of a device implementing a polishing method according to an aspect of the invention.

In FIG. 2A shows the mechanism for transferring electricity between an electrical power source and a metal surface through the net charge of the particles.

In FIG. 2B shows the mechanism for transferring electricity between an electricity source and a metal surface by electrical conduction by contact.

In FIG. 3C shows the mechanism for transferring electricity between an electrical power source and a metal surface by electrical conduction through voltaic arcs.

In FIG. 3 shows a device for in-line surface treatment.

In FIG. 4 shows a mobile surface treatment device.

In FIG. 5 shows a device with a surface treatment chamber.

PREFERRED EMBODIMENTS FOR CARRYING OUT THE INVENTION

Below are a few exemplary options without any intent to limit.

Embodiment 1

The device comprises a supply container (7) for particles (9), the outlet of which is connected to a copper tube acting as an electrode (3), in turn connected to an electrical power source (2). Particles (9) continuously fall under the action of gravity down onto the surface (1) to be treated, which is connected to the electrical power source (2) by means of a counter electrode. After contact with the part, the particles (9) enter the receiver (6) for collection for their subsequent recycling through the recycling system (5). Both the supply container (7) for particles and the receiver (6) have a vibrator (8). A schematic representation can be seen in Fig. 1.

In an exemplary case, the particles (9) used are microporous sulfonated polystyrene-divinylbenzene gel particles filled with an electrolyte solution which contains 4% sulfuric acid. This prototype has been tested with different types of electrical current: DC 1 to 60 V, AC 50 Hz to 50,000 Hz, 0 to 220 V.

With these parameters, the polishing method for surface treatment of steel 316 was confirmed by various types of electric current: DC up to 35kV, AC 50Hz up to 15kV.

DC results show a linear dependence of the intensity on the potential difference. It is noted that after treatment for 5 minutes, operating at 30 kV, there is a decrease in R _a from 0.37 to 0.34 μm in the area most affected by the particle flow.

The results of using 50 Hz alternating current show a linear characteristic in the range from 0 to 5 kV. Increasing the voltage from this point does not increase the proportional intensity. This effect clearly indicates a change in the mechanism of electric charge transfer.

Linear surfacing device

It consists of a device for in-line surface treatment. A schematic representation is shown in FIG. 3. In this example, without limiting the purpose, it is for processing metal plates. The device includes an electrical power source (3), a curtain-type particle application system (9), a transfer system for a plate to be processed, and a recirculation system (5) that collects particles and stores them in a supply container (7).

The metal plate to be processed is located on a conveyor belt provided with vibration and connected to an electrical power source. At one point of the conveyor belt path there is a device for curtain-like particle ejection (9). The linear feeder produces a linear ejection of particles (9) onto the surface (1) to be processed, covering the entire width of the plate to be processed. The wafer moves through the curtain of particles at the proper speed which gives it the processing time to obtain the expected finish. The device for curtain ejection of particles includes a vibrator (8) to ensure the flow of particles. In the slots through which the particles exit, there is a metal element connected to the negative pole of the supply source, which acts as an electrode (3). The particles come into contact with the electrode (3) before reaching the surface (1) to be treated. Near the point of contact, a recirculation system (5) is applied, which sucks up the particles after their contact with the surface and stores them in the supply container (7).

Mobile Surface Treatment Unit

It consists of a mobile device for surface treatment (1). A schematic representation is shown in FIG. 4. This device facilitates joint transportation, for example, using wheels. The device includes a compressor and a compressed air blower, an electric power source (2), a supply container (7) for supplying particles, and a recirculation system (5).

The device may be connected to a plug, alternatively it may include a rechargeable battery sufficient to provide power. The supply container (7) for particles (9) at the bottom has an outlet to the hose for supplying particles, the container can be equipped with a vibrator (8) to ensure the flow of particles (9). Particles (9) are moved along the supply hose by means of compressed air coming from the compressor. The required pressure depends on the length and location of the supply hose, pressures between 3 and 10 bar provide good results. The supply hose ends with a diffuser, which allows some of the air to escape, causing the particles (9) to condense. The exit of particles occurs through or in contact with an electrode (3), which can be an element made, for example, of copper, stainless steel 316 or irradiated titanium, connected to an electrical power source (2), preferably to the positive pole, preferably with an ammeter to control the intensity. The deposition electrode (3) is located at a distance of 0.5 to 10 cm from the surface, so that a stream of particles occurs between the electrode and the surface to ensure the passage of current. The particle exit end is included inside a collection receptacle (6) which is located very close to or in contact with the surface (1) to be treated. The receptacle (6) for collecting these particles is connected to a recirculation system (5) which contains a second hose equipped with a suction device that collects particles from the receptacle (6) after their contact with the surface and again ejects them into the supply container (7) for particles . The surface (1) to be processed is connected to the electrical power supply (1) by means of, for example, an electrical clamp, preferably on the positive pole. To polish worker inaccessible surfaces or improve reliability, the system may include the use of a robotic arm.

The design of the system is designed to occupy a compact volume, and it contains elements such as, for example, wheels or sliding elements, which make it suitable for carrying.

The applied current depends on the composition of the surface to be treated and the particles used (9). For example, for surface treatment of steel 316, good results are achieved using particles of sulfonated polystyrene-divinylbenzene containing sulfuric acid in an amount of 4% at a constant current of 12V.

Surface treatment device in a chamber It consists of a surface treatment device (1) in a closed chamber (4). A schematic representation can be seen in Fig. 5. The device includes an electrical power source (2), one or more outputs of electrically active particles (9) with electrodes (3), a system for fixing parts to be polished, a closed chamber (4) for processing and a recirculation system (5) , which sucks particles from the receptacle (6), which in this example also acts as a pressure feed container (7), towards the particle outlets.

The metal parts to be polished are placed on frames inside the chamber by means of suitable fasteners in such a way that they are connected to an electrical power source (2). The chamber (4) is provided with several particle outlets connected at their end to electrodes (3). The particles (9) are ejected by means of compressed air, preferably in the range of 2 to 10 bar, preferably 4 to 6 bar.

The lower part of the chamber (4), which acts as a collection receptacle (6) as well as a supply container (7), is sloped and the particles (9) are collected by a recirculation system (5) which transports them to the particle outlets.

The applied electric current depends on several factors such as the type of material, the total area to be treated, the distance between the exit point of the particles and the surface. For example, to polish 316 steel at a distance of 4 cm, the total area is 25 cm ² .

Claims (27)

1. Method for dry treatment of metal surfaces (1) by means of electrically active solid particles (9), characterized in that it includes the following steps: - contact of said particles (9) with electrode (3) of electric power source (2), - ejection of said particles (9) towards the metal surface to be processed, - transferring the electric charge of said particles to the metal surface to be processed. 2. The method of dry treatment of metal surfaces (1) with electrically active solid particles (9) according to claim 1, characterized in that the transfer of electricity between the electric power source (2) and the metal surface (1) during the ejection step is ensured by the total the charge of these particles (9). 3. The method of dry treatment of metal surfaces (1) by means of electrically active solid particles (9) according to claim 1, characterized in that the transfer of electricity between the electrical power source (2) and the metal surface (1) during the ejection step is ensured by electrical conduction by contact. 4. The method of dry treatment of metal surfaces (1) by means of electrically active solid particles (9) according to claim 1, characterized in that the transfer of electricity between the electric power source (2) and the metal surface (1) during the ejection step is ensured by electrical conduction through voltaic arcs. 5. Method for dry treatment of metal surfaces (1) with electrically active solid particles (9) according to any one of the preceding claims, characterized in that the current supplied to the electrode is constant. 6. The method of dry processing of metal surfaces (1) by means of electrically active solid particles (9) according to any of the previous paragraphs. 1-4, characterized in that the current supplied to the electrode (3) is a current that contains positive sections and negative sections. 7. The method of dry treatment of metal surfaces (1) by means of electrically active solid particles (9) according to claim 4, characterized in that in the medium between said particles (9) there is a conductive element that increases the conductivity between said particles by means of voltaic arcs. 8. Method for dry treatment of metal surfaces (1) by means of electrically active solid particles (9) according to claim 7, characterized in that the element that promotes conduction between said particles (9) by means of voltaic arcs is a derivative of carbon, iodine, talc, gel cylinders and/or rods. 9. The method of dry processing of metal surfaces (1) by means of electrically active solid particles (9) according to claim 7, characterized in that the element that promotes conduction between said particles (9) by means of voltaic arcs is a source of ionizing radiation (ultraviolet, X-ray and gamma rays), non-ionizing radiation source (microwaves), nebulizer and aerosol generator and/or ultrasound source. 10. Method for dry treatment of metal surfaces (1) with electrically active solid particles (9) according to any one of the preceding claims, characterized in that it includes the step of using abrasive particles simultaneously or alternately with said electrically active particles. 11. A device for dry processing of metal surfaces (1) by means of electrically active solid particles (9), characterized in that it contains an electrical power source (2) with an electrode (3), which transfers an electric charge to electrically active solid particles (9), and means for ejecting electrically active solid particles onto the surface (1) to be treated. 12. A device for dry processing of metal surfaces (1) by means of electrically active solid particles (9) according to claim 11, characterized in that the electrical power source (2) is connected to the surface (1) to be processed, thereby closing the electrical circuit. 13. Device for dry processing of metal surfaces (1) by means of electrically active solid particles (9) according to any one of paragraphs. 11, 12, characterized in that the promotion of electrically active solid particles (9) is provided only by gravity. 14. Device for dry processing of metal surfaces (1) by means of electrically active solid particles (9) according to any one of paragraphs. 11, 12, characterized in that the promotion of electrically active solid particles (9) is provided by means of a centrifugal system. 15. Device for dry processing of metal surfaces (1) by means of electrically active solid particles (9) according to any one of paragraphs. 11, 12, characterized in that the promotion of electrically active solid particles (9) is provided by compressed gas. 16. Device for dry processing of metal surfaces (1) by means of electrically active solid particles (9) according to any one of paragraphs. 11, 12, characterized in that the promotion of electrically active solid particles (9) is provided by means of a crank system or a system of screw conveyors. 17. Device for dry processing of metal surfaces (1) by means of electrically active solid particles (9) according to any one of paragraphs. 11-16, characterized in that it forms part of a flow assembly. 18. Device for dry processing of metal surfaces (1) by means of electrically active solid particles (9) according to any one of paragraphs. 1-16, characterized in that it is a mobile system. 19. Device for dry processing of metal surfaces (1) by electrically active solid particles (9) according to any one of paragraphs. 11-16, characterized in that the device and the surface (1) to be processed are inside the chamber (4). 20. Device for dry processing of metal surfaces (1) by electrically active solid particles (9) according to any one of paragraphs. 11-19, characterized in that the device contains a supply container (7) for solid particles (9) located before contact with the electrode (3). 21. Device for dry processing of metal surfaces (1) by electrically active solid particles (9) according to any one of paragraphs. 11-20, characterized in that the device contains a receiver (6) for collecting said solid particles (9) after their collision with the surface (1) to be treated. 22. A device for dry processing of metal surfaces (1) by means of electrically active solid particles (9) according to claim 20, characterized in that the device contains a system (5) for recycling said particles (9) from a receiver (6) for collecting solid particles into feed container (7). 23. Device for dry processing of metal surfaces (1) by means of electrically active solid particles (9) according to any one of paragraphs. 11-22, characterized in that the device contains a vibrator (8). 24. Device for dry processing of metal surfaces (1) by electrically active solid particles (9) according to any one of paragraphs. 11-23, characterized in that the said particle output device contains a diffuser.

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