ES2472420A1 - Procedure to passivate a metal surface, and domestic appliance, in particular, domestic dishwashing machine with a wall part (Machine-translation by Google Translate, not legally binding) - Google Patents

Abstract

The invention relates to a method for passivating a metal surface (a), preferably a metal surface (a) of a wall part of a domestic dishwashing machine, in which an atmospheric plasma beam (26) is generated by electric discharge in a working gas, in which an acidic passivating agent (120) is introduced into the plasma beam (26), in which the plasma beam (26) containing the passivating agent (120) is applied to the surface metal (a), and in which, through the reaction of the passivating agent (120) acid with the metal surface (a), a passivating salt (118) is deposited on the metal surface (a). (Machine-translation by Google Translate, not legally binding)

Description

Procedure to passivate a metal surface, and domestic appliance, in particular, domestic dishwasher with a wall part.

The present invention relates to a method for passivating a metal surface, preferably a metal surface of a wall part of a household appliance, in particular, a metal surface of a wall part of a domestic dishwashing machine , in which a passivating agent is applied on the metal surface, preferably on the metal surface of a wall part of a household appliance, in particular, on the metal surface of a wall part of the machine domestic dishwasher

By "passivation" of a metal surface, preferably a metal surface of a wall part of a household appliance, in particular, a metal surface of a wall part of a domestic dishwashing machine, in the Context of this description is understood, for example, to apply a corrosion protective agent. A passivation may also comprise applying an agent to reduce friction during the processing of a metal workpiece. Similarly, the passivation of the metal surface, preferably of the metal surface of a wall part of a household appliance, in particular, the metal surface of a wall part of a domestic dishwashing machine , it can also mean reducing the electrical resistance, that is, an electrical insulation of the metal surface, preferably of the metal surface of a wall part of a household appliance, in particular, the metal surface of a part of wall of a domestic dishwasher machine.

An example of passivation of a metallic surface is phosphatation, in which, by means of chemical reactions of metallic surfaces with aqueous phosphate solutions, a so-called metal phosphate conversion layer is formed that adheres fixedly. Most of the time, phosphating is applied to steel, but it can also be used for galvanized or cadmium steels and aluminum. The main areas of application are protection against corrosion, adhesion, reduction of friction and wear, as well as electrical insulation.

In the phosphatation known from the prior art, the formation of the layer is caused by precipitation of poorly soluble salts of phosphoric acid, the so-called phosphates, of an aqueous solution. Depending on the type of solution, this may be layers of iron, zinc or manganese phosphate.

In non-layer phosphating, the metal cations participating in the layer formation come from the base material, while the metal cations of the phosphate solution do not participate in the layer composition.

In layer forming phosphatation, layer formation takes place by metal cations of the phosphate solution and, additionally, metal cations of the base material can be involved. The layer thicknesses reach between several hundred nanometers in the phosphating of iron, up to two micrometers and more in the phosphating of zinc and manganese.

The phosphate layer thus produced adheres very well on the substrate and, due to the microporous or microcapillary layer structure, allows a good anchorage for coatings that are subsequently applied. Additionally, the phosphate layer hinders subsurface oxidation at defective points of the coating. Phosphate layers alone provide a practical temporary protection against corrosion, which is often sufficient for storage before a next processing step. Similarly, applications are known in which a phosphating is used for permanent corrosion protection.

The phosphate layers also have good sliding properties, which has an advantageous effect, for example, in the case of cold forming of the steel. As a consequence of simple shear, zinc phosphate layers are preferably used here. In contrast, manganese phosphate layers are used to reduce the wear of sliding agents subjected to a high load.

The high electrical resistance of phosphate layers is used for at least partial electrical insulation. By way of example, the phosphate layer can be used to insulate them against each other with a thin separating layer in electric sheets for magnetic cores.

Likewise, a method is known to passivate a metallic surface in which, on metallic surfaces, complex salts of the chromic acid (chromates) are formed by the action of chromic acid. Such a procedure is called chromatation.

Also during chromatation, the base material of the metal surface is corroded. The dissolved metal ions of the base material are then incorporated into the chromate layer. The chromate layers thus obtained belong (similarly to the phosphate layers) to the passivating layers, that is, they are non-metallic inorganic protective layers. The most frequent function of chromate layers is corrosion protection. However, chromate layers can also be used for the generation of a primer for subsequent layers, as protection against oxidation (in silver), for reducing the visibility of fingerprints, or for modifying the appearance (brightness, color). Chromation procedures can be applied to aluminum, magnesium, silver, cadmium, and zinc.

It is common to all the procedures described above that can only be chemically carried out wet in a plurality of work steps by immersion baths. Therefore, the cost in equipment is considerable in the execution of the procedures. Likewise, the material cost is approximate, since a large part of the passivating agent used is not used.

In addition, delimitable surface areas of a workpiece cannot be treated separately, but the entire workpiece must always be chemically treated wet.

This problem arises especially in the manufacture of components that are composed of non-corrosive metal sheets, for example, by stainless steel sheets, and whose individual parts are joined together by heat welding. The weld seams that are generated are not resistant to corrosion in the same way as the metal sheet itself. Therefore, a separate corrosion protection is necessary as a measure of passivation only for the weld seam area. In case of chemical wet passivation, that is, for example phosphating, it is then necessary to chemically treat the entire component chemically.

As components, there may be mentioned here by way of example washing machine components, dishwashing machine components, tubular joints, and other components that come into contact with water during use.

In addition, precisely in smaller components, a chemical wet treatment with an acidic passivating agent is costly if it must be applied to a color or varnish coating as a bottom coat.

In addition, during chemical treatment by wet route precisely in smaller component structures, the problem arises in that, due to the effects of surface tension, the passivating agent is not supplied throughout the surface to cavities or notches . For this reason, holes on the surface originate here that may have a disadvantage in the subsequent use of the component.

Therefore, the present invention is based on the technical problem related to simplifying and configuring in a more effective manner the known process of the prior art for passivating a metal surface, preferably a metal surface of a wall portion of a domestic appliance, in particular, a metal surface of a wall part of a domestic dishwasher. Likewise, a domestic appliance comprising at least a part of the wall, which is composed, at least partially, of corrosion-resistant metal to a large extent, in particular stainless steel to a large extent, must be indicated.

The technical problem described above is solved according to the invention by means of a process in which an atmospheric plasma beam is generated by electric discharge in a working gas, in which an acidic passivating agent is introduced into the plasma beam, in which the plasma beam containing the passivating agent is applied on the metal surface, preferably on the metal surface of the wall part of the household appliance, in particular, on the metal surface of the wall part of the domestic dishwashing machine, and in which, through the reaction of the acidic passivating agent with the metallic surface, preferably with the metallic surface of the wall part of the domestic appliance, in particular, with the metallic surface From the wall part of the domestic dishwasher machine, a passivating salt is deposited on the metal surface, preferably on the metal surface of the p wall art of the domestic appliance, in particular, on the metal surface of the wall portion of the domestic dishwasher machine.

Therefore, according to the invention it has been recognized that the application of the passivating agent by means of an atmospheric plasma beam takes advantage of many synergistic effects. Before explaining them, the sources of plasma and the properties of atmospheric plasma beams generated with them must first be explained.

By "plasma source" is meant a source for a plasma beam directed to the interior of a

Space area, where the shape of the plasma beam can be shaped round

or flat The plasma source can also generate a rotating plasma beam, a housing part, preferably the outlet opening, being made rotatably movable, and rotating about an axis during plasma generation. During the procedure of this plasma source, a wide strip of wider bands is treated along a surface.

The plasma source may have a plasma injector or several plasma injectors, arranged side by side, in the form of a plasma shower. The plasma source can have a clamp for positioning next to the movement device and power lines for the working gas and electrical voltage.

The electrical excitation of the working gas can occur with different frequencies, for example, in the microwave range in the order of, or above, 1 MHz, or in the frequency range between 1 and 100 kHz. The forms of the tension may vary between alternating voltages and pulsed continuous voltages, or be superimpositions thereof. The discharges are microwave discharges or high frequency spark discharges that can take the form of discharge arcs (arc discharges) or plume discharges. Like the frequency, the voltage amplitudes are adapted to the respective geometry of the plasma injector, and are, for example, in the range between 100 V and 10 kV. As a working gas, air is preferably used, together with which nitrogen, noble gases such as argon are also possible, also adding other gases such as hydrogen.

Such plasma sources can generate comparatively cold plasma beams with relatively high chemical excitation energy. The temperature of the beam decreases depending on the distance from the outlet opening, and is in the range below 300� C, preferably below 150� C and, preferably, below 100� C The high excitation energy of the working gas is produced by high frequency excitation in the excitation zone within the plasma source, in which only a small thermal stimulation occurs. Therefore, there is also talk of a non-thermal plasma. Through the choice of an appropriate working gas and the parameters of the electrical voltage, the temperature and activity of the plasma beam can be influenced.

The present procedure is not limited to the use of the plasma sources described above. Other plasma sources can also be used, by way of example with other excitation mechanisms, even if their plasma beams have other temperatures and lower plasma powers. Also with such known plasma sources the process according to the invention can be executed.

By way of example, from the EP 1 335 641 A1 pamphlet a method is known for the generation of an atmospheric plasma beam, that is, a plasma beam with an ambient pressure that is in the order of magnitude of the atmospheric pressure. Here, a working gas, first of all, air, nitrogen, protective gas (mixture of nitrogen and hydrogen), or a noble gas, especially argon or helium, is conducted through a channel, in which through a high voltage of A high frequency plasma beam is generated through an electric discharge, that is, a corona discharge and / or an arc discharge.

In EP 1 230 414 B1, a process for plasma polymerization by an atmospheric plasma beam is disclosed. In this method, a precursor material is incorporated into the plasma beam, stimulated there chemically and / or electronically, so that before, during,

or after deposition of the precursor stimulated on a surface, polymerization of the precursor is initiated.

According to the invention, the acidic passivating agent is now applied by means of an atmospheric plasma beam on the metallic surface to be passivated, preferably the metallic surface to be passivated from a wall part of a domestic appliance, in particular the metal surface to be passivated from a wall part of a domestic dishwashing machine, where, by reacting the acidic passivating agent with the metal surface, preferably the metal surface of a wall part of a domestic appliance, in In particular, the metal surface of a wall part of a domestic dishwashing machine, a passivating salt is deposited on the metal surface. In this way, more advantages are achieved.

On the one hand, by incorporating the passivating agent into the plasma beam, the excitation energy contained in the plasma beam is transmitted to the passivating agent without thereby causing a large increase in the temperature of the passivating agent.

On the other hand, the passivating agent is swirled with uniformity in the plasma beam by means of the often already rotating current and, therefore, when hitting the metal surface, preferably the metal surface of a wall part of a domestic appliance, in particular, the metal surface of a wall part of a domestic dishwasher machine, is distributed evenly. The swirling that originates in this way leads to an almost complete wetting of the surface, also in cavities and notches, also if they have small dimensions. The swirling of the plasma beam and the passivating agent in it transported further leads to the passivating agent not remaining on the surface being immediately evacuated again, and no further processing or cleaning is necessary.

Likewise, the application of the plasma beam on the surface causes a cleaning effect, so that, in the case of surfaces that are not too dirty, it is not necessary to perform a prior cleaning before applying the passivating agent. Only on dirtier surfaces that cannot be sufficiently cleaned by the plasma beam will a separate pre-cleaning be necessary. The number of working steps is therefore considerably reduced compared to the wet chemical process and, in multiple applications, a procedural step suffices for the passivation of the metal surface, preferably the metal surface Only one metal part of a wall of a household appliance, in particular, the metal surface of a wall part of a domestic dishwasher.

Another advantage is that, through the exposure of the metal surface, preferably the metal surface of a wall part of a household appliance, in particular, the metal surface of a wall part of a machine domestic dishwasher, to the plasma beam, does not cause any fouling of the metal surface, preferably the metal surface of a wall part of a household appliance, in particular, the metal surface of a wall part of a domestic dishwashing machine, as, for example, in the chemical wet process known from the prior art through prior immersion baths, or the like.

Therefore, in the context of the invention it has been surprisingly shown that applying a passivating agent by means of an atmospheric plasma beam on a metal surface, preferably on a metal surface of a wall part of a domestic appliance, in In particular, on the metal surface of a wall part of a domestic dishwashing machine, it constitutes an effective alternative to the known wet chemical process.

Preferably, on the one hand, an aqueous phosphoric acid can be used as the passivating agent, and metal phosphate can be deposited on the metal surface, preferably on the metal surface of a wall part of a household appliance, in particular , on the metal surface of a wall part of a domestic dishwashing machine. On the other hand, as a passivating agent a chromic acid can be used, and metal chromate can be deposited on the metal surface, preferably on the metal surface of a wall part of a domestic appliance, in particular on the surface metal of a wall part of a domestic dishwasher machine. Likewise, citric acid or nitric acid can also be used as a passivating agent. In all cases, the link described above occurs between acidic anions and metal cations, as well as the formation of the respective metal salt, that is, phosphate, chromate, citrate, or nitrous salt. In this procedure there are mainly two positive effects.

On the one hand, the acid anion of phosphoric acid, chromic acid, citric acid or nitric acid is excited by the plasma beam itself, and brought to a reactive state without inducing a temperature to occur increased in excess of the acid fraction of the plasma beam. On the other hand, the metal surface itself, preferably the metal surface of a wall part of a domestic appliance, in particular, the metal surface of a wall part of a domestic dishwashing machine, is activated by the plasma beam, through which the reactivity of the metal surface is increased, preferably the metal surface of a wall part of a household appliance, in particular, the metal surface of a wall part of a domestic dishwashing machine, and the necessary metal cations are more easily generated during the chemical reaction with the acid anions. Accordingly, in the area of impact of the plasma beam on the metal surface, preferably on the metal surface of a wall part of a household appliance, in particular, on the metal surface of a wall part of a domestic dishwashing machine, the desired reaction and deposition of the metal salt occurs.

The reactivity of acid anions can also be adjusted especially through a corresponding modification of the plasma generation parameters. Through an appropriate choice of parameters, the treatment time by means of the plasma beam can be reduced. The treatment times thus achieved are markedly below the necessary treatment times in chemical wet procedures.

The acid passivating agent supplied to the plasma beam, that is, the aqueous acid solution, may or may not have metal ions. A chromatation can be carried out, for example, with sulfuric acid and sodium chromate. The chromic acid that originates with it then reacts with the surface. In the use of phosphoric acid as a passivating agent, it, on the other hand, does not contain metal ions. The reaction of the acid with the surface then leads, for example, to a metal chromate or a metal phosphate.

It has not yet been determined in detail what exact chemical and physical processes are developed during application to the plasma beam of a passivating agent. In any case, it has surprisingly turned out that the metal surfaces, preferably metal surfaces of a wall part of a household appliance, in particular metal surfaces of a wall part of a domestic dishwashing machine, exposed through The procedures described above have experienced sufficient passivation for industrial production.

Therefore, the preparation described below is provisional. In the process according to the invention, the acid is stimulated in the plasma before being applied, and thus reacts with the surface considerably faster. Also the cleaning and activation already described of the surface that take place at the same time have a positive impact on the reaction rate.

The classical chemical wet chromatoration usually consists of two essential steps. First, the oxide layer (aluminum hydroxide) is completely removed with sodium hydroxide solution. After rinsing with water, it is then immediately chromated. With the process according to the invention using the plasma, the removal of the oxide layer can be dispensed with. Therefore, the next passivation of the material takes place directly on the oxide layer.

As already stated above, phosphating can be carried out especially on steel and stainless steel, as well as on galvanized or cadmium-plated steels and aluminum. On the contrary, chromatation can be applied especially on aluminum, magnesium, silver, cadmium and zinc.

Another advantage of the procedure described above is that the application of passivation, by way of example, by phosphating, can be conducted in a directed manner over certain areas of the surface. Here, the weld seams between stainless steel sheets joined together are an example, which are commonly used for drums and interior linings of washing machines or dishwashing machines. Since the stainless steel sheets are already sufficiently protected against corrosion, but the weld seams are no longer sufficiently resistant to corrosion as a result of alterations of the structure within the material, only in the area of weld seams there is a need for subsequent passivation. Therefore, preferably the procedure described above is carried out in such a way that at least the weld bead between two metal surfaces, preferably between two metal surfaces of a wall part of a household appliance, in particular between two metallic surfaces of a wall part of a domestic dishwasher machine, be exposed to the plasma beam.

Preferably, the metal surface, preferably the metal surface of a wall part of a household appliance, in particular, the metal surface of a wall part of a domestic dishwashing machine, can be exposed to the beam of plasma during welding, or directly after welding. In this case, the thermal energy still accumulated in the weld bead and the adjacent metal can be used for greater reactivity of the metal surface, preferably the metal surface of a wall part of a household appliance, in particular , the metal surface of a wall part of a domestic dishwashing machine and, therefore, for greater effectiveness of passivation. Likewise, an application of the procedure described with a welding bead in the cooled state is also possible.

Together with the spatially delimited application of the plasma beam, by way of example, on a weld bead, the described process can also be carried out in such a way that the exposure of the metallic surface, preferably of the metallic surface of a wall part of a domestic appliance, in particular, the metal surface of a wall part of a domestic dishwashing machine, to the passivating agent is effected to generate a bottom layer for a next colored or varnished layer. In this case, a surface treatment is carried out, in particular, of the entire surface, of the metal surface, preferably of the metal surface of a wall part of a domestic appliance, in particular of the surface metal of a wall part of a domestic dishwasher machine. The subsequent coating with a paint or a varnish then leads to good adhesion and a durable coating. For such application, the rotating plasma injectors described above are especially suitable.

The passivating agent can be supplied to the plasma beam in a different way. Since the generation of the plasma beam from a working gas stream passes through different spatial areas starting from the discharge area, through the injector area, as well as the free beam outside the plasma source, the agent Passivator can be supplied to the plasma beam in each of these spatial areas.

Therefore, preferably, the passivating agent can be supplied in the discharge area to the originating plasma beam. In this case, the working gas is excited together with the passivating agent by electric discharge. The action of the discharge on the passivating agent is therefore very intense, and it depends on the type of passivating agent which is or is not appropriate for the direct action of the discharge.

Likewise, the passivating agent can be supplied downstream of the discharge area to the originated plasma beam. On the one hand, the passivating agent can be incorporated into the plasma beam current still within the plasma source, before the plasma beam is output from the plasma injector. On the other hand, the passivating agent can also be supplied to the plasma beam outside the plasma source. In the latter case, the passivating agent does not come into contact with the plasma source itself, or hardly does so, so that the influence on the pieces of the plasma source by the acid fraction can be minimized.

For a better distribution of the passivating agent, it can be advantageously incorporated by means of a sprayer, in particular a spray nozzle. With this, when the passivating agent is added to the working gas, or else, to the plasma beam, a fine and homogeneous distribution is achieved, which positively impacts until the moment of application of the plasma beam on the metal surface, preferably, the metal surface of a wall part of a household appliance, in particular, the metal surface of a wall part of a domestic dishwasher. However, the passivating agent can also be added to the plasma beam in another way.

The aforementioned technical problem is solved according to the invention in a domestic appliance, in particular a domestic dishwashing machine, in a domestic washing machine, in a domestic dryer, or the like, comprising at least one wall part, which is composed , at least partially, of corrosion-resistant metal to a large extent, in particular, stainless steel to a large extent, through that at least one metal surface of a wall part is provided with a passivating salt, at least by areas, preferably predominantly, especially completely, where the passivating salt is a product of a reaction of an acidic passivating agent, and applied by means of a plasma beam on the metal surface of the wall part, with the metal surface of the wall part.

In this, the advantages according to the invention mentioned above also result. Therefore, it has been especially recognized that the application of the passivating agent by means of an atmospheric plasma beam takes advantage of many synergistic effects.

With regard to constructive advantageous properties and / or related to the production technique, it can be advantageous if at least two of the wall parts are joined together, at least by areas, preferably predominantly, in particular, completely, by means of a weld joint, in particular, a weld bead, and if the weld joint, in particular, the weld bead, which joins together at least two wall parts, at least by areas, preferably predominantly, especially, completely, it is provided with a passivating salt, at least by areas, preferably predominantly, especially, completely. Thus, the surface of the weld joint is simplified and passivated here, in particular, the weld bead. The swirling already explained of the plasma beam leads to an almost complete wetting of the surface, also in cavities and notches, also if they have small dimensions. The swirling of the plasma beam and the passivating agent conveyed therein further leads to the passivating agent not remaining on the surface of the weld joint, in particular the welding bead, being immediately evacuated again, and not necessary. a processing

or subsequent cleaning of the weld joint, in particular of the weld bead.

So that the passivation of the weld joint, in particular, of the weld bead, can be configured effectively and effectively, this one, which joins at least two of the wall parts together, at least by areas , preferably predominantly, especially, completely, is provided with a passivating salt at least by areas, preferably predominantly, especially, completely, preferably also in an area on both sides with a respective area width of at least 3 mm., preferably, at least 5 mm., in particular, at least 10 mm.

Also, the at least one wall part, which is composed, at least partially, of corrosion-resistant metal to a large extent, in particular, stainless steel to a large extent, is preferably a part of a domestic dishwashing machine. comprising at least the following components and / or constructive groups: a washing tank for the accommodation of washing articles; means for supplying washing liquid to washing articles; a tank cover, composed, at least partially, of corrosion-resistant metal to a large extent, in particular, stainless steel to a large extent, as the upper part of the wash tank with two side walls, a cover wall, and a wall later; a wash basin as the base wall of the wash tank; a filling opening, locked with a door, for washing articles, next to the washing tank; and a frame piece with sealing function for washing liquid, at the end of the front side of the tank cover. As a consequence of the passivation according to the invention, the existing manufacturing process up to the moment of a domestic dishwashing machine can be significantly improved, in particular, of the at least one welding process in a domestic dishwashing machine, both from the point of technological and economic view, by way of example, as a result of a decrease in investment and / or commissioning costs, as well as a reduction in production times.

The passivating agent can again contain, on the one hand, a phosphoric acid, if necessary, diluted, so that the passivating salt and deposited on a metal surface comprises metal phosphate. On the other hand, the passivating agent may contain a chromatic acid, if necessary, diluted, so that the passivating salt and deposited on a metal surface comprises metal chromate. In both cases, the link described above occurs between acidic anions and metal cations, as well as the formation of the respective metal salt such as phosphate, or chromate.

Next, the invention is explained in more detail by means of embodiments, with reference to the attached drawing.

In the drawing they show

Fig. 1

a first exemplary embodiment of a device according to the invention for the passivation of a surface, in which a passivating agent is incorporated into the plasma beam in an area of the nozzle opening;

Fig 2

a second embodiment of a device according to the invention for the passivation of a surface, in which a passivating agent is incorporated into the plasma beam in an area of the discharge volume;

Fig. 3

a third exemplary embodiment of a device according to the invention for the passivation of a surface, in which a passivating agent is incorporated into the plasma beam in an area in front of the nozzle opening;

Fig. 4

a schematic perspective view of a washing tank of a domestic dishwashing machine according to the invention and loadable frontally, with rear wall removed; Y

Fig. 5

a schematic representation of a passivated weld joint whose surface has been treated by a device for the passivation of a surface according to the invention and represented in Figure 1.

Next, the execution of the process according to the invention is explained by means of three exemplary embodiments that differ in the area of the plasma nozzle in which the acidic passivating agent is supplied. Therefore, the same reference symbols indicate the same elements in the different embodiments.

Figure 1 shows a plasma source 2 and a feeding device 3. The plasma source 2 has a metal nozzle tube 4, which cynically narrows towards a nozzle opening 6. At the opposite end of the nozzle opening 6, the nozzle tube 4 has a torsion device 8 with an inlet 10 for a working gas, for example, for air or nitrogen gas. An intermediate wall 12 of the torsion device 8 has a crown of perforations 14 arranged obliquely in the perimetric direction, through which the working gas is twisted. The cynically narrowed downstream portion of the nozzle tube 4 is therefore traversed by the swirl-shaped working gas 16, the core of which runs along the longitudinal axis of the nozzle tube 4.

An electrode 18 is centrally arranged next to the lower side of the intermediate wall 12, which coaxially penetrates the nozzle tube 4 in the direction of the narrowed section. The electrode 18 is electrically connected to the intermediate wall 12 and the remaining parts of the torsion device 8. The torsion device 8 is electrically insulated through a ceramic tube 20. The electrode 18 is applied a high frequency high voltage, which is generated by a transformer 22. The inlet 10 is connected through a flexible tube not shown with a source of work pressure gas with variable flow. The nozzle tube 4 is grounded. Through the applied voltage, a high frequency discharge in the form of a voltaic arc 24 is generated between the electrode 18 and the nozzle tube 4. The term "voltaic arc" is used here as a phenomenological description of the discharge, since that the discharge occurs in the form of a voltaic arc. The term “voltaic arc” is also used as a form of discharge in the continuous voltage discharges with essentially constant voltage values.

As a consequence of the helical current of the working gas, this voltaic arc 24 is channeled in a swirl core on the axis of the nozzle tube 4, so that it does not branch before the area of the nozzle opening 6 towards the wall of the nozzle tube 4. The working gas that rotates in the area of the eddy core and, thus, in the immediate surroundings of the voltaic arc 24, with high current velocity, comes into close contact with the voltaic arc 24 and , in this way, it is partly converted to the plasma state, so that an atmospheric plasma beam 26 leaves the plasma source 2 through the nozzle opening 6.

The feeding device 3 has a mixing tube 28 whose wall has at one point an opening 30, in which a sprayer 32 is inserted with exact adjustment. A feeder 34 for connecting the passivating agent 120 is connected to the sprayer 32, through which the passivating agent 120 reaches the sprayer 32, and there it is pulverized in a fine mist.

The passivating agent 120 protruding from the sprayer 32 arrives directly at the plasma beam 26, and is dragged with it in the direction of a metal surface A, preferably a metal surface A of a wall part of a household appliance 100, in Particularly a metal surface A of a wall part of a domestic dishwashing machine 100 (see also Figure 4 and Figure 5). The passivating agent 120 then strikes the metal surface A in the manner described above, so that a passivating layer B is formed. If, for example, a passivating agent 120 is used, for example, phosphoric acid, then a layer of Metal phosphate in passivating layer B.

The thickness of the passivating layer B may be different, and depends on the functional parameters. The thickness of the passivating layer B depends on, among other things, the amount of the passivating agent 120 incorporated in the plasma beam 26. In the case of dilute phosphoric acid, a value of approximately 50 g / h as application rate has advantageous result.

Figure 2 shows a second embodiment of a device for the passivation of a surface. The device has a plasma source 2, described above by means of Figure 1, for generating a plasma beam 26, as well as a feeding device 3.1 with a sprayer 32.1 in the area of the nozzle tube 4 that ends cynically. In this case, the passivating agent 120 is therefore incorporated in the area of the plasma source 2 in which the arc discharge is ignited and actuated. Also here, the wall of the nozzle tube 4 has at one point an opening 30.1, in which the sprayer

32.1 is introduced with exact adjustment. A feeder is connected to sprayer 32.1

34.1 for the supply of the passivating agent 120, through which the passivating agent 120 reaches the sprayer 32.1, and there it is pulverized in a fine mist.

The passivating agent 120 protruding from the sprayer 32 arrives directly at the plasma beam 26, and is dragged with it in the direction of a metal surface A, preferably a metal surface A of a wall part of a household appliance 100, in Particularly a metal surface A of a wall part of a domestic dishwashing machine 100 (see also Figures 4 and 5).

Figure 3 shows a third embodiment of a device for plasma passivation of a metal surface A. The device has a plasma source 2, described above by means of Figures 1 and 2, to generate a plasma beam 26, as well as a sprayer 32.2 arranged under the nozzle opening 6. A feeder 34.2 is connected to the sprayer 32.2, through which the passivating agent 120 reaches the sprayer 32.2, and there it is sprayed. The passivating agent 120 protruding from the sprayer 32.2 reaches the plasma beam 26 generated in the plasma source 2, and protruding from the nozzle opening 6, and continues to be transported with the plasma beam 26 in the direction of a metal surface A , preferably a metal surface A of a wall part of a household appliance 100, in particular a metal surface A of a wall part of a domestic dishwashing machine 100 (see also Figures 4 and 5).

In the figures 1 to 3 described, the plasma source 2 is moved in each case from right to left above the metal surface A, so that, in the width of the treatment width of the plasma beam 26, originates a passivation trail on the metal surface A. The passivation trail can be used to passivate a weld joint 122, in particular, a weld bead (see Figure 5). The passivation trace can also be used for a surface passivation of a metal surface A if the plasma source 2 is moved, if necessary, systematically above the entire metal surface A to be passivated

Figure 4 shows a schematic perspective representation of a washing tank 102 of a domestic dishwashing machine 100 according to the invention and front loadable. The domestic dishwasher machine shown is only an example for a household appliance 100, which could also be a household washing machine, a domestic dryer, a domestic washer-dryer, a microwave apparatus, a sterilizer, or the like.

The domestic dishwashing machine 100 shown comprises the washing tank 102 for housing washing articles, and means for supplying washing liquid to washing articles known to the person skilled in the art, but not represented for reasons of clarity, such as spray arms and spray nozzles. Also, it comprises a tank cover 104, composed, at least partially, of corrosion-resistant metal to a large extent, in particular, stainless steel to a large extent, as the upper part of the wash tank 102 with two side walls 106.L , 106.R, a cover wall 108, and a rear wall 110 removed. It also includes a wash basin 112 as the base wall 114 of the wash tank 102, a filling opening, closed with a door, known to the person skilled in the art, but not represented for reasons of clarity, for washing articles , next to the wash tank 102, and a frame piece with sealing function for washing liquid, by the end of the front side of the tank cover 104, known to the person skilled in the art, although not represented for reasons of clarity.

The two side walls 106.L, 106.R, the cover wall 108 and the rear wall 110 form the upper part of the wash tank 102 as part of the respective wall 116, and are composed, as already described. mentioned, at least partially, of corrosion-resistant metal to a large extent, in particular, stainless steel to a large extent.

Now, a metal surface 116.O of a wall part 116 is provided with a passivating salt 118, at least by areas, preferably predominantly, especially, completely, where the passivating salt 118 is a product of a reaction of an acidic passivating agent 120, and applied by means of a plasma beam 26 (see Figures 1 to 3) on the metal surface 116.O, with the metal surface 116.O. The passivating salt 118 then forms a passivating layer B (see Figures 1 to 3).

In addition, the two side walls 106.L, 106.R of the upper part of the wash tank 102 are provided in each case with a weld joint 122, in particular, a weld bead. The respective weld joint 122 runs horizontally along the corresponding side wall 106.L, 106.R, and may be provided with a passivating salt 118 at least by areas, preferably predominantly, especially, completely. The solder joints 122 indicated have only exemplary characteristics; in principle, they can be provided at any point of the wash tank 102, in particular of the tank cover 104.

Figure 5 shows a schematic representation of a passivated weld joint 122, in particular, a passivated weld bead, whose surface 122.O has been treated by a device for the passivation of a metal surface A according to the invention. , and depicted in figure 1 (see figures 1 to 3).

Thus, two of the wall parts 116.1, 116.2, especially of the mentioned wall parts of a domestic dishwashing machine 100, are joined together, at least by areas, preferably predominantly, in particular, completely, by a weld joint 122. The weld joint 122, which joins each other at least by areas, preferably predominantly, especially, completely the two wall parts 116.1, 116.2, is provided with a passivating salt 118, at least by areas, preferably predominantly, especially completely. The passivating salt 118 then forms a passivating layer B.

The weld joint 122 shown, which joins the two wall portions 116.1, 116.2 together, at least by areas, preferably predominantly, especially, completely, is provided with a passivating salt 118, at least by areas , preferably predominantly, especially, completely, also in an area 122.1, 122.2 on both sides with a respective area width 122.B1, 122.B2 of at least 3 mm., preferably, of at least 5 mm., especially, at least 10 mm. The area 122.1, 122.2 on both sides preferably extends specularly inverted with respect to a weld joint 122, in particular, with respect to its center line 122.M.

The plasma source 2 is moved in the direction of the depth T (arrow) above the metal surface A, so that at the depth of the plasma beam 26 a passivation trace is generated on the metal surface TO.

The passivating agent 120 used in the figures contains a phosphoric acid, if any, diluted, and the passivating salt and deposited on a metal surface comprises metal phosphate. Alternatively, the passivating agent 120 may contain a chromatic acid, citric acid, or nitric acid, where appropriate, diluted, and the passivating salt and deposited on a metal surface may comprise metal chromate, metal citrate or salt. metallic nitrous

The embodiments and improvements of the invention set forth above and / or described in dependent claims may, except in cases of univocal dependencies or inconsistencies, be applied separately, or also in any combination with one another.

In summary, it is ensured that, by means of the invention, a method known in the state of the art for passivating a metal surface, preferably, a metal surface of a wall part of a domestic appliance, in particular a metallic surface of a wall part of a domestic dishwasher machine, is perfected in such a way that it has a simplified and more effective configuration.

List of reference symbols

2 Plasma source 3 Power device

3.1 Feed device 4 Nozzle tube 6 Nozzle opening 8 Torsion device 10 Inlet 12 Intermediate wall 14 Perforation 16 Swirl 18 Electrode 20 Ceramic tube 22 Transformer 24 Voltaic arc 26 Plasma beam 28 Mixer tube 30 Opening

30.1 Opening 32 Sprayer

32.1 Sprayer

32.2 Sprayer 34 Feeder

34.1 Feeder

34.2 Feeder

100 Domestic appliance; domestic dishwasher machine 102 Wash tank 104 Tank cover

106.L Side wall

106.R Side wall 108 Cover wall 110 Back wall 112 Wash basin 114 Base wall 116 Wall part

116.1 Wall part

116.2 Wall part

116.O Metal surface 118 Passivating salt 120 Passivating agent 122 Welding joint

122.1 area 122.B1 Area width

122.2 area 122.B2 Area width

122.M Centerline

122.O Surface

A Metallic surface B Passive layer T Depth direction (arrow)

Claims (16)

1. Procedure for passivating a metal surface (A), preferably a metal surface (A) of a wall part of a household appliance, in particular a metal surface (A) of a wall part of a domestic dishwashing machine, in which an atmospheric plasma beam (26) is generated by electric discharge in a working gas, into which an acidic passivating agent (120) is introduced into the plasma beam (26), in the which plasma beam (26) containing the passivating agent (120) is applied on the metal surface (A), preferably on the metal surface (A) of the wall part (116; 116.1, 116.2) of the domestic appliance (100), in particular, on the metal surface (A) of the wall portion (116; 116.1, 116.2) of the domestic dishwasher (100), and in which, through the reaction of the passivating agent (120) acidic with the metal surface (A), preferably with the metal surface (A) of the wall portion (116; 116.1, 116.2) of the domestic appliance (100), in particular, with the metal surface Metal (A) of the wall part (116; 116.1, 116.2) of the domestic dishwashing machine (100), a passivating salt (118) is deposited on the metal surface (A), preferably on the metal surface lica (A) of the wall part (116; 116.1, 116.2) of the domestic appliance (100), in particular, on the metal surface (A) of the wall part (116; 116.1, 116.2) of the machine domestic dishwasher (100).

2.

Process according to claim 1, in which a phosphoric acid is used as the passivating agent (120), if necessary, and metal phosphate is deposited on the metal surface (A), preferably on the metal surface Metal (A) of the wall part (116; 116.1, 116.2) of the household appliance (100), in particular, on the metal surface (A) of the wall part (116; 116.1, 116.2) of the domestic dishwasher machine (100).

3.

Process according to claim 1, in which as a passivating agent (120) a chromic acid is used, if necessary, diluted, and metal chromate is deposited on the metal surface (A), preferably on the metal surface Metal (A) of the wall part (116; 116.1, 116.2) of the household appliance (100), in particular, on the metal surface (A) of the wall part (116; 116.1, 116.2) of the domestic dishwasher machine (100).

Four.

Method according to one of claims 1 to 3, in which the metal surface (A), preferably the metal surface (A) of the wall part (116; 116.1, 116.2) of the domestic appliance (100), in particular, the metal surface (A) of the wall part (116; 116.1, 116.2) of the domestic dishwashing machine (100), has a weld joint (122), in particular, a welding bead, and at least the weld joint (122), in particular, the weld bead, is exposed to the plasma beam (26).

5.

Method according to claim 4, in which the metal surface (A), preferably the metal surface (A) of the wall part (116; 116.1, 116.2) of the domestic appliance (100), in particular, the The metal surface (A) of the wall portion (116; 116.1, 116.2) of the domestic dishwasher (100) is exposed to the plasma beam (26) during welding, or directly after welding.

6.

Method according to one of claims 1 to 3, in which the exposure of the metal surface (A), preferably of the metal surface (A) of the wall part (116; 116.1, 116.2) of the domestic appliance (100), in particular, of the metallic surface

(A) of the wall part (116; 116.1, 116.2) of the domestic dishwashing machine (100), to the passivating agent (120) is effected to generate a bottom layer for a next colored or varnished layer.

7.

Method according to one of claims 1 to 6, in which the passivating agent

(120) is supplied in the discharge area to the plasma beam (26) that originates.

8.

Method according to one of claims 1 to 6, in which the passivating agent

(120) is supplied downstream of the discharge area to the originated plasma beam (26).

9.

Method according to claim 7 or 8, in which the passivating agent (120) is introduced by means of a sprayer (32; 32.1, 32.2), in particular, a spray nozzle.

10.

Domestic appliance (100), in particular, domestic dishwashing machine, domestic washing machine, domestic dryer, or the like, comprising at least one wall part (116; 116.1, 116.2), which is composed, at least partially, of Corrosion-resistant metal to a large extent, in particular, stainless steel to a large extent, characterized in that at least one metal surface (A) of a wall part (116; 116.1, 116.2) is provided with a passivating salt ( 118), at least by areas, preferably predominantly, especially, completely, where the passivating salt (118) is a product of a reaction of an acidic passivating agent (120), and applied by means of a plasma beam (26 ) on the metal surface (A) of the wall part (116; 116.1, 116.2), with the metal surface (A) of the wall part (116; 116.1, 116.2).

eleven.

Domestic appliance (100) according to claim 10, characterized in that at least two of the wall parts (116.1, 116.2) are joined together, at least by areas, preferably predominantly, especially, completely, by a weld joint (122), especially a weld bead, and because the weld joint (122), in particular, the weld bead, which joins at least two of the wall parts (116.1, 116.2), at least by areas, preferably predominantly, especially, completely, is provided with a passivating salt (118), at least by areas, preferably predominantly, especially, completely.

12.

Domestic appliance (100) according to claim 11, characterized in that the solder joint (122), in particular, the weld bead, which joins at least two wall parts (116.1, 116.2), at least by areas, preferably predominantly, especially, completely, is provided with a passivating salt (118), at least by areas, preferably predominantly, especially, completely, also in an area (122.1, 122.2) on both sides with a respective area width (122.B1, 122.B2) of at least 3 mm., preferably, of at least 5 mm., in particular, of at least 10 mm.

13.

Domestic appliance (100) according to claim 10, 11 and 12, characterized in that at least one wall part (116; 116.1, 116.2), which is composed, at least partially, of corrosion-resistant metal to a large extent, In particular, stainless steel is, to a large extent, a part of a domestic dishwashing machine (100) comprising at least the following components and / or constructive groups: a washing tank (102) for housing washing items; means for supplying washing liquid to washing articles; a tank cover (104), composed, at least partially, of corrosion-resistant metal to a large extent, in particular, stainless steel to a large extent, as the upper part of the wash tank (102) with two side walls (106. L, 106.R), a cover wall (108), and a rear wall (110); a wash basin (112) as the base wall (114) of the wash tank (102); a filling opening, locked with a door, for washing articles, next to the washing tank (102); and a piece of

frame with sealing function for washing liquid, at the end of the front side of the tank cover (104).

14.

Domestic appliance (100) according to one of claims 10 to 13, characterized

5 because the passivating agent (120) contains a phosphoric acid, if necessary, diluted, and because the passivating salt and deposited on a metal surface (A) comprises metal phosphate. 15. Domestic appliance (100) according to one of claims 10 to 13, characterized 10 because the passivating agent (120) contains a chromatic acid, if necessary, diluted, and because the passivating salt and deposited on a metal surface (A) comprises metal chromate. SPANISH OFFICE OF THE PATENTS AND BRAND Application No.: 201232053 SPAIN Date of submission of the application: 28.12.2012 Priority Date: REPORT ON THE STATE OF THE TECHNIQUE 51 Int. Cl.: See Additional Sheet RELEVANT DOCUMENTS

Category

56 Documents cited Claims Affected

X

EP 2460595 A2 (INNOVENT EV) 06.06.2012, page 3, paragraph [27] - page 4, paragraph [33]. one

X

WO 2006134118 A1 (BASF AG) 21.12.2006, page 4, lines 11-29; page 5, lines 24-37; page 9, line 12 - page 11, line 23; page 18, line 11 - page 19, line 38. 10,13-15

X

WO 2006134117 A1 (BASF AG.) 21.12.2006, page 4, lines 1-41; page 5, lines 28-37; page 6, line 4 - page 8, line 15; page 18, line 19 - page 20, line 2; page 20, line 33 - page 21, line 26. 10,13-15

X

WO 2006134116 A1 (BASF AG) 21.12.2006, page 3, line 36 - page 4, line 38; page 5, lines 29-31; page 6, line 1 - page 8, line 11; page 14, line 33 - page 15, line 41; page 16, lines 13-61; page 18, lines 1-34. 10,13-15

X

EP 0653502 A2 (NIHON PARKERIZING) 17.05.1995, page 3, line 28 - page 4, line 10; page 4, lines 39-47. 1,2,6-9

Y

3

X

US 5858465 A (HUNT ANDREW TYE) 12.01.1999, column 5, lines 20-40; column 7, line 56 - column 8, line 64. 1,2,6-9

Y

3

Y

FR 853144 A (GILBERT) 11.03.1940, page 1, lines 32-37; page 4, lines 80-86; page 5, lines 27-54. 3

TO

EP 2194162 A2 (INNOVENT EV) 09.06.2010, column 3, paragraphs [13-14]; columns 3, paragraph 16 - column 4, paragraphs [25]. 1-8

TO

US 2009 061184 A1 (JAWOROVSKI) 07.10.2010, page 1, paragraph [14] - page 2, paragraph [17]; page 2, paragraphs [20-21]; page 3, paragraph 28. one

TO

WO 2010112914 A1 (KERONITE INTERNAT LTD) 07.10.2010, the whole document. one

Category of the documents cited X: of particular relevance Y: of particular relevance combined with other / s of the same category A: reflects the state of the art O: refers to unwritten disclosure P: published between the priority date and the submission of the application E: previous document, but published after the date of submission of the application

This report has been prepared • for all claims • for claims no:

Date of realization of the report 27.03.2014

Examiner A. Rua Aguete Page 1/4

REPORT OF THE STATE OF THE TECHNIQUE Application number: 201232053 CLASSIFICATION OBJECT OF THE APPLICATION C23C4 / 10 (2006.01) C23C8 / 36 (2006.01) D06F39 / 12 (2006.01) D06F58 / 20 (2006.01) C23C4 / 12 (2006.01) A47L15 / 42 (2006.01) D06F49 / 00 (2006.01) D06F37 / 26 (2006.01) Minimum documentation sought (classification system followed by classification symbols) A47L, C23C, D06F Electronic databases consulted during the search (name of the database and, if possible, search terms used) INVENTIONS, EPODOC State of the Art Report Page 2/4  WRITTEN OPINION Application number: 201232053 Date of Completion of Written Opinion: 03.23.2014 Statement

Novelty (Art. 6.1 LP 11/1986)

Claims Claims 2-9.11-15 1.10 IF NOT

Inventive activity (Art. 8.1 LP11 / 1986)

Claims Claims 11-12 1-10, 13-15 IF NOT

The application is considered to comply with the industrial application requirement. This requirement was evaluated during the formal and technical examination phase of the application (Article 31.2 Law 11/1986).  Opinion Base.- This opinion has been made on the basis of the patent application as published. State of the Art Report Page 3/4  WRITTEN OPINION Application number: 201232053 1. Documents considered.- The documents belonging to the state of the art taken into consideration for the realization of this opinion are listed below.

Document

Publication or Identification Number publication date

D01

EP 0653502 A2 (NIHON PARKERIZING) 05/17/1995

D02

US 5858465 A (HUNT ANDREW TYE) 12.01.1999

D03

FR 853144 A (GILBERT) 11.03.1940

D04

EP 2194162 A2 (INNOVENT EV) 06.09.2010

D05

US 2009 061184 A1 (JAWOROVSKI) 10.07.2010

D06

WO 2010112914 A1 (KERONITE INTERNAT LTD) 10.07.2010

D07

WO 2006134118 A1 (BASF AG) 21.12.0021

D08

WO 2006134117 A1 (BASF AG) 21.12.2006

D09

WO 2006134116 A1 (BASF AG) 21.12.2006

2. Statement motivated according to articles 29.6 and 29.7 of the Regulations for the execution of Law 11/1986, of March 20, on Patents on novelty and inventive activity; quotes and explanations in support of this statement The object of the invention is a method to passivate a metal surface by application on said surface of a plasma beam generated by electric discharge in a working gas in which the passivating agent is introduced into said plasma beam and as a consequence of the reaction that takes place between the acidic passivating agent and said metal surface, a passivating salt is deposited on the metal surface. An object of the invention is also a domestic appliance comprising a wall part composed of corrosion-resistant metal with a protective layer of passive salt. Document D1 (EP 0653502) discloses a method for passivating a metal surface, for example a surface of zinc-coated steel, in which an atmospheric plasma beam is generated by electric discharge in a gas working, in which an acidic passivating agent is introduced into the plasma beam that is applied on the surface metallic, producing a deposition of a passivating salt on said surface. (See page 4, lines 39-47). Document D2 discloses a similar procedure for the passivation of a metallic surface by deposition of a passivating layer on said surface by the action of an atmospheric plasma beam. (See column 2, lines 2945). The terms preferably and in particular in the characterizing part of claims 1-6 and 10-13 do not produce any limitation on the scope of the claims. Therefore, in view of what is disclosed in D1 and D2, the object of the invention set forth in claim 1 is not new. (Art. 6 LP). Claims 2-3 and 6-9 refer to features that are either common in the state of the art or that for an expert in the field they do not require the exercise of any inventive activity. (See for Reiv. 3, document D3, p. 1, lines 32-32; p. 4, lines 80-86): p. 5, lines 27-54: for Reiv. 6-9, see for example document D2, fig. 1A-1C, paragraph 5, lines 20-40; paragraph 11, lines 36-50; paragraph 12, lines 29-52). The object of the invention of claims 4 and 5 is about features widely known in the state of the technique or obvious to an expert in the field. On the other hand, household appliances that comprise a wall part, which at least in part is composed of metal corrosion resistant, such as steel, in which at least one metal surface of a wall part is provided with a passivating salt, they are widely known in the state of the art. (See for example, documents D7-D9). As it is a product claim, in this case the manufacturing method thereof is not limiting in the measure that does not affect the essential characteristics thereof, therefore, the object of the invention included in the Claim 10 is not new considering the state of the known art. (Art. 6 LP). Claims 13-15 refer to features that are deduced directly from documents D7 to D9, as is the case of claim 14 or is it usual features in the state of the art or that for a Those skilled in the art do not require the exercise of any inventive activity, in the case of claims 13 and 15. Accordingly, claims 2 to 9 and 13 to 15 of the application lack inventive activity (Art. 8 LP). On the other hand, neither the documents D1 to D9 cited or any relevant combination thereof reveals an apparatus domestic in which the welding cord that joins two wall parts together is provided with a passivating salt. Therefore, the invention as set forth in claims 11 and 12 of the application is new and is considered to be It implies inventive activity. (Art. 6 and 8 LP). State of the Art Report Page 4/4