WO2014076664A2

WO2014076664A2 - Surface treatment method, tank and machine implementing said method

Info

Publication number: WO2014076664A2
Application number: PCT/IB2013/060169
Authority: WO
Inventors: Emmanuel Turlot; Pierre Voumard
Original assignee: Cyklos Sa
Priority date: 2012-11-16
Filing date: 2013-11-15
Publication date: 2014-05-22
Also published as: WO2014076664A3; EP2733238A1

Abstract

A method for electrochemical surface treatment of metal parts by immersion in at least one treatment liquid contained in at least one treatment tank (1), and a tank and machine for carrying out this method, comprising at least one electrolytic step in which said parts are received on a rotary structure (3) provided with receiving means (15) and rotatably mounted iabout a horizontal shaft (5) inside said treatment tank (1), potential differences (V1, V2, V3) are established between said parts and a plurality of electrodes (C1, C'1; C2, C'2;C3, C'3) arranged in said treatment tank (1), said parts being supplied with current of opposite polarity to that of the electrode via said receiving means (15) and said rotary structure (3), and said parts are completely submerged in said treatment liquid by a rotational movement of said rotary structure (3) bringing them successively to face the electrodes (C1, C'1; C2, C'2;C3, C'3). In particular, the spatial distribution of the electrical fields between said parts and said electrodes can be controlled by implementing masking means (16, 17, 18, 19, 20, 21, 22, 23, 29) disposed inside said treatment tank (1). Figure

Description

Surface treatment process, tank and machine implementing the process

Field of the invention

The present invention relates to the field of processes and installations for electrochemical surface treatment of parts by immersing these parts in successive liquids contained in several processing tanks and transfers of parts between these tanks, and in particular the treatments by anodizing parts in aluminum. Examples of such treatments are anodizing or anodic passivation, porous anodization in an acidic medium, anodic dissolution, electrolytic polishing, hard or self-colored anodizing. Treatment liquids may include not only electrolytes, but also pre-treatment liquids, such as degreasing liquids, coloring liquids, clogging liquids and rinsing liquids.

The present invention more particularly relates to a method of electrochemical treatment of surfaces of metal parts by immersion in at least one treatment liquid contained in at least one treatment tank, comprising at least one electrolytic step in which said parts are housed on a rotating structure provided with housing means and mounted in rotation about a horizontal axis inside said treatment tank, potential differences are established between said parts and at least one electrode arranged in said treatment tank, said parts being fed in a current of opposite polarity to that of said electrode via said housing means and said rotary structure, and immersed completely said parts in said treatment liquid by a rotational movement of said rotary structure bringing them opposite said electrodes.

The present invention also relates to a surface treatment vessel of parts intended to implement a method as above, comprising a rotary structure, rotatably mounted inside said treatment tank around a bearing axis. horizontal rotation, said rotary structure comprising, at its periphery, at least one housing track parallel to the axis of rotation and provided with temporary fixing means, able to accommodate at least one part or a support of parts, maintained (e) temporarily in a determined position of the housing track during a said rotation by said fixing means.

State of the art

The most common aluminum surface treatment facilities operate in batch mode. Document DE 2 119 401 describes an example of this, in which motorized trucks equipped with moving arms travel over several treatment bins. The movable arms perform large vertical movements to plunge large loads of parts, suspended mobile carts, in successive bins and out of them. This type of installation has disadvantages:

when the parts to be treated have hollow parts, pockets of air may appear on certain parts of their surface during immersion in the treatment liquid, which leads to inhomogeneities of treatment, and thus to defects in quality of the parts; the volumes of the tanks, important, involve large quantities of liquid effluents pollutants to be reprocessed;

the vertical movements of the charges, as well as the large open area of these tanks, produce vapors and acid droplets in the atmosphere of the treatment unit, which implies powerful and expensive aeration and filtration systems.

Such installations can only operate within a plant specialized in surface treatments, complying with strict environmental safety standards. The parts must therefore be transported from the metallurgical plant, which has machined them, to the surface treatment plant, and from there to the user's site, resulting in significant packaging and transport costs.

US Patent 2,093,484 discloses a galvanizing device comprising a rotary drum of which a little less than the lower half dipped in a galvanizing bath. The drum carries electromagnets for temporarily fixing plates whose one face is intended to be galvanized. The plates are fed laterally to the drum and bent to contact the electromagnets, make a half-turn in the bath and are discharged laterally.

The patent application WO 2006/084973, the content of which is incorporated herein by reference, describes a continuous surface treatment plant consisting of several processing tanks of the defined type of inlet, each equipped with a motorized rotary drum. , whose axis of rotation is mounted horizontally so that the major part of the drum is immersed in a treatment liquid contained in the corresponding tank. Parts to be processed, especially if they are small, can be previously set up in batches on media in the form of cassettes, for example those described in patent EP 1 433 537, then transported by a conveying system for feeding each vessel with parts to be processed and to transport the parts further downstream. already processed. According to WO 2006/084973 this conveying system comprises two parallel conveyor chains, arranged on either side of the upper part of the tanks, the axes of the rotary drums being perpendicular to the two conveyor chains. The cassettes are transferred horizontally one after the other, alternately from one conveyor chain to another, after passing through a tank, where, carried by the drum, they undergo one or more rotations in the treatment liquid and a translation parallel to the axis of the drum. Each drum is rotated and fed with electric current via a flange. The current is transmitted by the drum to the parts to be treated. The rotations of the parts in the treatment liquids drive bubbles and air pockets that can be created by the immersion of the surface of the parts.

Patent Application WO 2008/035199, the content of which is incorporated herein by reference, discloses a parts surface treatment installation continuously the same type, constituted tanks similar drums to those described in WO 2006/084973 ^and a unique conveyor chain, horizontal and parallel to the axes of the drums, with horizontal transfer slides arranged between the tanks, with which are aligned the slides of the rotating drums when they arrive in their highest position, which emerges treatment liquid. An articulated system of rods and arms, arranged above these slides performs movements of va-and- horizontally to push the pieces or cassettes / brackets housing the parts, which are in the up position and to drive each cycle back and forth along the slides of the drums and transfer slides.

In the two continuous treatment plants described above, after the last rinse, the conveyor chain drives the treated parts to a drying tunnel arranged downstream of these facilities. The air leaving the drying tunnel is taken up by the air filtration system of the surface treatment plant. The elimination of large vertical displacements of parts above the tanks reduces the overall size of the installation and the generation of droplets and vapors, and thus reduces the power of the air filtration systems of the plant. processing unit.

Patent application WO 2010/125515, the content of which is incorporated herein by reference, also discloses a continuous metal surface treatment machine, comprising a plurality of contiguous tanks arranged in series and a piece transfer device similar to the device mentioned above. The tanks each comprise a rotatable structure that can accommodate the parts, or the supports housing the parts, mounted on a horizontal axis of rotation, the parts being immersed in the treatment liquid by the rotation of the rotary structure. In this machine the axes of rotation of the rotating structures of the series of tanks are integral in rotation and driven by a common drive device. The axis of rotation of the electrolytic treatment tank is electrically isolated from other axis parts, is connected to an electric generator by means of a rotating connector, and transfers the current to the rotating structure and parts. The downstream tank of the series is a steaming tank supplied with hot air. The machine is housed in a box comprising means for confining and reprocessing all the fluids emanating from the machine. In this way, the box constitutes a processing unit that can be installed and implemented in a plant that is not specialized in surface treatments, such as a metal parts forming plant that does not have effluent treatment equipment at the same time. standards required for an electrochemical plant.

By eliminating bubbles and air pockets from the surface of the parts, the three continuous installations described above make it possible to obtain a surface quality superior to that of installations operating in batch mode. The rotation of the parts driven by the drums brings them in variable orientations with respect to the electric field in the electrochemical treatment tank, hence a greater homogeneity of the treated surfaces. However, improvements in these installations are desirable in terms of productivity and the thicknesses of the layers that are desired to form on the surfaces of the parts.

In the case of anodizing process, at the time of the introduction of non-anodized parts into the electrolytic bath, the bare metal surface has a very low electrical resistance, which can induce very high electric currents. The voltage must therefore be limited as this may cause excessive heating of the surface of the part and the surrounding electrolyte, which hinders the start of the anodizing process by promoting a partial dissolution of the oxide. A voltage anodisation Therefore, the constant is limited with respect to the layer thicknesses that can be obtained during a fixed time treatment and with respect to the growth rate of the anodizing layer, hence the productivity.

During the anodization process, the growth of the oxide layer induces an increase in the electrical resistance between the cathode and the anode formed by the metal surface of the workpiece, thereby slowing down the process. This evolution can be compensated in an anodizing installation operating in batch mode, either with a current control, or by a programmed increase in the voltage, or with an increase in the current density over time. Such options are not applicable in a continuously operating facility.

Furthermore, when the parts to be treated are housed on a support which vehicles through a continuously operating installation such as those described above, it is desirable to house as many as possible on the same support to increase the productivity. But when the pieces are too close to each other, those placed on the periphery receive more current than those placed in the center, resulting in differences in the surface condition of the central parts and the marginal parts, which is unacceptable. .

The three documents summarized above do not disclose means for managing electrical currents as a function of time and do not disclose means for managing the spatial distribution of the current delivered to a batch of parts fixed on a support. A first object of the present invention is to provide a continuous process and an installation of the defined type of input, to obtain thicker anodizing layers than those obtained by the methods of the state of the art.

A second object of the present invention is to provide an installation of the defined type of input to manage, and in particular to vary the current that receives a part, respectively a batch of parts during a continuous electrochemical treatment .

A third object of the present invention and to provide a tank and a treatment facility of the defined type of input for processing batches of more rooms than the facilities described above, with equal processing time, without causing lack of homogeneity between parts.

A fourth object of the present invention is to avoid structural defects of the surface layers that can generate excessive local heating.

Summary of the invention

For this purpose, a first object of the invention is a method for the electrochemical surface treatment of metal parts by immersion in at least one treatment liquid contained in at least one treatment tank, comprising at least one electrolytic step in which one houses said parts on a rotating structure provided with housing means and mounted in rotation about a horizontal axis inside said treatment tank, differences in potential between said parts and at least one electrode arranged in the said treatment vessel, said parts being fed with currents of opposite polarity to that of said electrode via said housing means and said rotary structure, and these parts are completely immersed in said treatment liquid by a rotational movement of said rotary structure bringing them opposite said electrodes, in which method a number of electrodes at least equal to 2, fed at different electrical voltages, arranged in a plurality of treatment tanks or in a plurality of compartments of a tank comprising partitioning means, the values of the differences in potential and / or spatial distribution of the electric fields between said parts and said electrodes, and / or implementation of masking means arranged inside a said treatment tank.

According to one embodiment, the parts undergo a plurality of said electrolytic steps, said parts being brought successively opposite a plurality of pairs of said electrodes. In the case of anodization, the potential differences between said parts and said pairs of electrodes increase from one step to the next.

According to one embodiment a predetermined number of parts is placed beforehand on a support of parts, comprising at least one holding member adapted to immobilize each of said parts relative to said parts support, said parts support is introduced by conveying means in an immersion zone arranged in the upper part of said treatment tank and housed on said rotary structure, said piece support is driven by it in a rotational movement of one or more times 360 ° and brought to an output zone arranged in the upper part of said treatment tank, from which said parts support is extracted from said treatment tank.

According to one embodiment, said method is performed globally continuously and by successive displacements clocked.

According to one embodiment, during each clocked movement, the rotating structure marks a downtime when a workpiece support is facing an electrode. Preferably the stopping time has a duration longer than the duration of the rotational movement.

A second object of the invention is an application of a method such as above to anodizing aluminum parts or aluminum-based alloys.

A third object of the invention is a surface treatment vessel of parts intended to implement a method as defined above, comprising a rotating structure, mounted in rotation inside said treatment tank around a horizontal axis of rotation, said rotary structure comprising, at its periphery, at least one housing track parallel to the axis of rotation and provided with temporary fixing means, able to accommodate at least one part or a support of parts, temporarily held in a determined position of the housing track during a said rotation by said fixing means, said vessel comprising a plurality of electrodes, arranged upstream downstream in the direction of said axis of rotation, associated with a plurality of temporary fastening means and partitioning means disposed within said treatment vessel, providing compartments and insulation between an electrode upstream and a downstream electrode.

According to one embodiment, said treatment tank is segmented perpendicularly to the axis of rotation of said rotary structure into a plurality of compartments separated by partitions, and said rotary structure comprises in each compartment a wheel mounted centered on the axis. rotation and each compartment comprises a pair of electrodes mounted laterally on either side of a said wheel.

According to one embodiment, each wheel comprises four housing tracks arranged at 90 ° to each other, each housing track being aligned with a track of the adjacent compartments and said parts supports are housed by sliding with interlocking supports in a housing track when it is at the immersion zone, all of said housing tracks being parallel to the axis of the rotary structure.

According to embodiments, the treatment tank incorporates the masking means modifying the spatial distribution of the electric fields between the parts and the electrodes.

According to one embodiment, the treatment tank is equipped with a circulation system and reprocessing of the electrolyte common to the compartments of said tank.

According to one embodiment, the treatment tank, respectively each compartment of the tank, comprises perforated cathodes and the treatment liquid, after reprocessing, is reinjected towards the pieces, through said perforated cathodes, and in particular in the direction of the marginal portions of the workpiece supports.

According to one embodiment, the set of wheels is set to the same electrical potential as the axis of rotation of the rotary structure and the potential difference between a wheel and the pair of associated electrodes is adjustable to different values.

According to one embodiment, the electrodes arranged laterally extend downwardly from the tank, masking screens are interposed between the lower part of said electrodes and the rotary structure, said masking screens extend from one side to the other. lateral upper zone near said electrodes to a central lower zone near the bottom of the tank, leaving unmasked an area facing the lowest position that takes a housing track of the rotating structure to pass a part of the current by this unmasked area towards the housing track. This arrangement of screens leaving somehow a window in front of the lowest position of the parts carried by the rotating structure amounts to generating a virtual electrode in the bottom of the tank.

According to one embodiment, the lateral electrodes each consist of two separate vertically insulated parts, the upper part and the lower part of each of said lateral electrodes being at different electrical potentials.

According to one embodiment a housing track is bordered on both sides by a pair of longitudinal masking screens mounted on said rotary structure parallel to the axis of rotation and extending towards the two side electrodes.

According to one embodiment, a pair of transverse masking screens is mounted on the fixed structure of the tank perpendicular to the axis of rotation of the rotating structure, bordering a part or a support pieces by its front and rear , the geometries of said longitudinal masking screens and transverse masking screens being dimensioned so as not to prevent the functions in rotation and in translation of said vessel.

According to one embodiment, said part supports are lined with a lateral mask carried by said support.

The invention also relates to a machine as defined at entry, comprising at least one tank having the above characteristics.

The subject of the invention is in particular such a machine, intended for the anodizing of aluminum parts, comprising from upstream to downstream

an oxidation tank intended to contain an electrolytic treatment liquid, for example sulfuric acid, said oxidation tank comprising several compartments each containing a pair of electrodes serving as cathode (s), in particular 2 cathodes arranged on both sides of the rotary structure of the treatment tank, said rotary structure serving as anode,

a rinsing tank intended to contain a rinsing liquid, for example water, a tank intended to carry out a finishing treatment, for example a clogging.

A machine having the characteristics mentioned above can be housed in a box comprising means for confining and reprocessing fluids emanating from said machine, inside said box.

Brief description of the figures

Other features and advantages of the invention will be apparent to those skilled in the art from the following description of embodiments, given by way of non-limiting examples, with reference to the accompanying drawings, in which:

- Figure 1 is a schematic view, from above, of a treatment tank according to the invention;

- Figure 2 is a perspective view of a cache;

- Figure 3 is a partial perspective view of a rotary structure;

- Figure 4 is a partial perspective view of a rotary structure;

- Figure 5 is a perspective view of a parts support surrounded by a cover;

- Figure 6 is a schematic vertical sectional view of a treatment tank;

FIG. 7 is a schematic view from above of the treatment tank of FIG. 6.

FIG. 8 is a partial schematic perspective view of a variant of the electrolyte circuit of a tank according to FIG. 1. Detailed description of execution modes

Figure 1 shows an electrolytic treatment tank 1 partitioned into three compartments by two vertical partitions 6 and 7. The three compartments may contain the same electrolyte, and in this case the partitions 6 and 7 are not necessarily sealed. Each compartment comprises a pair of electrodes C1, C ^' I, C2, C ^' 2, C3, C ^' 3 in the form of vertical metal plates arranged near the side walls of the tank 1. A gate 11 allowing the electric current to pass can be placed in front of each electrode to confine the bubbles that can form on its surface.

The vessel contains a rotating structure 3 comprising a horizontal axis 5 rotatably mounted on bearings 4,4 ^' , arranged in the upstream wall and the downstream wall of the tank, this axis passing through the partitions 6 and 7. At one of its ends , which protrudes from the wall of the electrolytic treatment tank, this shaft 5 carries a rotating connector 8, which is connected via contact pads 9 to a rectifier block, which constitutes the direct current supply of the tank 1, the electric current being transmitted to the workpieces via successively the axis 5, transverse plates 26, slides 15 and supports 27 described below.

The rotary structure 3 comprises a wheel 2 in each compartment. The structure of such wheels is illustrated in perspective by FIGS. 3 and 4. Each wheel 2 comprises two polygonal plates 26 mounted perpendicular to and on the axis 5. On the periphery of these plates 26 in transverse position are mounted housing tracks. 15 consisting of pairs of longitudinal rails, parallel to the axis of rotation, the dimensions and spacings of which are adapted to receive parts supports 27. In the embodiment illustrated in FIGS. 3 and 4, the polygonal plates 26 carry four pairs of slides arranged at 90 ° relative to each other. The transverse plates may have cutouts, not shown in the figures, to lighten the weight of the assembly of a rotary structure. As shown in Figure 1, each pair of slides of a wheel 2 of the electrolytic treatment tank 1 is aligned with a pair of slides of the other wheels, so as to allow the transfer of media from one wheel to the next by sliding along said housing tracks 15. The alignment of the positions of the slides is carried out at the mounting of the machine, which eliminates from the outset the subsequent problems of synchronization.

The slideways carry resilient fixing studs 28 whose positions and spacings correspond to the length of the supports and to the position of the two lateral electrodes Cl, C ^' I, resp.C2, C ^' 2, resp.C3, C ^' 3 each compartment of the treatment tank, thus allowing to retain the supports in a predetermined longitudinal position and precise on the slides during the rotational movements, so as to come in front of the electrodes, while allowing the sliding of the cassette supports under the action of a transfer device between two rotational movements.

In the context of a method of anodizing aluminum parts fixed on supports, the upstream compartment of the tank 1, which is filled for example with sulfuric acid, contains the first pair of metal plates Cl, C ^'I, arranged close to the side walls serving as cathodes of either side of the first wheel 2 of the rotating structure 3, the latter being supplied with electric current of opposite polarity to that of these electrodes. In this upstream compartment, a first potential difference VI is established between the pair of electrodes C1, C ^' I and the rotational structure 3 sufficiently moderate (10 - 20 volts) so as not to cause overheating. The intermediate compartment of the vessel 1 contains the second pair of metal plates C2, C ^' 2 as cathodes, arranged on either side of the second wheel of the rotary structure 3. There is established a second potential difference V2 between the pair of electrodes C2, C ^' 2 and the rotary structure 3. The downstream compartment of the vessel 1 contains the third pair of metal plates C3, C ^' 3 as cathodes, arranged on either side of the third wheel of the rotary structure 3. There is established a third potential difference V3 between the pair of electrodes C3, C ^' 3 and the rotary structure 3. For this type of anodizing treatment, the three differences in potential above are constant in time, obey the relation VI <V2 <V3 and are staggered between typically 20 volts and 80 volts.

This configuration with a constant voltage in time for each compartment but increasing from one compartment to the next in the direction of travel of the parts is reflected for the parts by exposure to a voltage varying in stages during the anodizing process. As a result, the process according to the invention makes it possible to obtain anodizing layer thicknesses of the order of 60 microns, whereas with the same processing time under a single value of the voltage, it would be possible to obtain only layers of the order of 25 microns. In another aspect, for a given anodization layer thickness, for example 25 microns, the simultaneous treatment of parts under different voltage values makes it possible to reduce the total processing time, of a duration of the order of 40 minutes. at a duration of the order of 20 minutes.

In the method implementing the treatment tank 1 described above, the supports carrying the parts not yet treated, brought by a conveyor chain, are engaged in the pair of non-submerged slides of the upstream compartment, temporarily placed in the up position. of the rotary structure 3, each support being positioned longitudinally on the pair of upper slides through the transfer device cooperating with the elastic fastening studs 28 of the pair of slides. Each part is immersed in the tank 1, by making it, in the embodiment illustrated in FIG. 1, three complete rotations, that is to say one in each compartment, so that the air bubbles and air pockets that can be created inside the tank in contact with the parts with the liquid are removed, thus allowing the treatment liquid to treat the entire surface of the parts, making the treatment perfectly uniform.

The entire processing machine operates in sequences of synchronous and synchronous movements. After each rotation of 90 °, the rotating structure 3 marks a downtime. During this standstill, all the supports temporarily arranged in the high emergent position undergo a longitudinal translation whose length corresponds to the passage of a treatment station at the neighboring station, while the two supports located at the height of the axis 5 in each compartment are respectively immersed respectively in front of a cathode, and undergo electrolytic treatment. The cassette support located in the low position can be simply waiting but also benefit from the electrolytic treatment as will be described below. As illustrated in FIGS. 3 and 4, it is thus possible to make a complete rotation of 360 °, composed of four quarters of a turn, at each support between two translations, said support being immersed for almost three complete rotations in the liquid contained in the electrolytic treatment tank 1, with the exception of the upper portion of each rotation, where the support is momentarily out of the liquid to allow the introduction, advancement, transfer and removal of parts.

At each of the sequences, i.e. after each 90 ° rotation, a treated part carrier is transferred from the electrolytic processing tank 1 to a rotating structure of a rinsing tank (not shown in the figures). and then immersed in the rinsing liquid, following this process can be performed as described in WO 2010/125515.

The treatment tank 1 is equipped with a circulation system C of the electrolyte, allowing it to be cooled, filtered and regenerated continuously by adding fresh electrolyte from a tank. The installation may include a used electrolyte storage tank and a regeneration device thereof. As illustrated schematically in FIG. 1, the electrolyte is taken by overflow in an overflow on one side of the compartments of the tank 1, passes into the circulation / regeneration system C, the latter comprising at least one heat exchanger and a filter, not being illustrated in detail in FIG. 1. The electrolyte is reinjected via nozzles 10 into the bottom of the compartments. The arrangement of the overflow system and the distribution conduits of the electrolyte in the different compartments is optimized in order to render by construction the inter-compartmental ionic currents through the electrolyte much lower than the ionic currents flowing in the electrolyte between cathodes and anode of each of the compartments. This embodiment allows an advantageous configuration to a single segmented tank, the compartments of which share the axis of rotation, the mechanical drive, the power supply, 1 electrolyte and all the bath management elements.

In another embodiment, the processing machine comprises several, for example three independent electrolytic treatment tanks arranged in series and operating at different electrical voltages, each tank being equipped with a rotating structure and having its own power supply and its own electrolyte regeneration system. However, this mode of execution is less economical because it involves the multiplication of elements such as mechanical drives, power supplies, valves, pumps, etc.

When a coin carrier is positioned in front of a cathode the lines of the ion current between the coins and this cathode should ideally propagate as schematically illustrated in Figure 6 by the dotted arrows L1. But when the density of parts fixed on the same support becomes important this is no longer the case, the parts arranged on the edges receive more current than the parts arranged in the center of the support, which are partially hidden by their neighbors too close, resulting in a difference in speed of growth of the superficial layers between central parts and marginal parts.

In addition, when the density of the ion current between cathodes and part supports is high (400 A / m2) the temperature of the marginal pieces tends to become higher than that of the central parts, to the point of inducing parasitic phenomena, interfering with the formation of the surface layers of the marginal pieces. To counteract such local temperature rises, the invention proposes an embodiment of the circuit for circulating the electrolyte in each tank compartment, illustrated in FIG. 8. The electrolyte, after sampling by an overflow of the tank and cooling in a heat exchanger of the circuit C, is sent into two housings 30 disposed immediately behind the cathodes and in a housing 31 arranged at the bottom of the tank, facing the low stop position of the supports 27. The housings 30, 31 have a plurality of perforations on their faces directed towards the supports 27, aiming at producing an effect similar to a showerhead, these perforations being more numerous or of larger section at the periphery than in the central zone of the housings. The electrodes C4, C4 arranged in front of the perforated faces of the housings 30 also have perforations, corresponding to those of the housings, but much larger in size than the perforations of the housings to allow the flow of cooled electrolyte from the housings. In a variant of construction, the electrodes C4, C4 can serve as the front wall of the housings. The invention also proposes to remedy phenomena related to an unequal distribution of the ion current between marginal parts and central parts of the same support by correcting the spatial distribution of the ion current by means of masks.

According to an embodiment illustrated in FIG. 2, the tank 1 receives still masks 29. The mask 29 comprises a plate 12 made of insulating material intended to be arranged in the tank 1 in place of a grid 11 or between that and the corresponding wheel 2. The plate 12 has an opening whose shape corresponds to the shape of a support pieces, arranged facing the stop position of the support parts facing the cathode. This opening is surrounded by walls 13 perpendicular to the plate 12 on the side of this plate 12 facing the support of parts, forming a guide for channeling the ion current. The walls 13 carry a plate 14 on their end located on the part support side, which may be substantially parallel to the plate 12. This plate 14 has an opening whose shape and position also correspond to the shape and position of the parts support. The area of this opening of the plate 14 may be slightly smaller than that of the support parts, thus forming a diaphragm promoting the passage of ionic current to the central parts of the support, while the opening of the plate 12 may present an upper area. Those skilled in the art will observe that in this embodiment the mask 29 is interposed between the cathode and the parts carried by the support, but does not surround them.

According to another embodiment of the masking means, illustrated in FIG. 3, the masking means are in part carried by the wheel 2 and partly by the tank 1 itself. In this embodiment, the housing tracks 15 carry plates 16 parallel to the axis 5 and perpendicular to the plane formed by a pair of slides, so that a support 27 can slide and position itself between two plates 16. The tank receives masks comprising a pair of plates 17 vertical and perpendicular to the axis 5, arranged such that the plates 16 can pass between them, with sufficient clearance, during the rotation of the wheel 2. Between the pair of plates

17 is placed a diaphragm 18 similar to the diaphragm 14 described above. According to the respective dimensions of the tank 1, and the wheel 2, the diaphragm 18 can be carried by a structure similar to the assembly formed by the walls 13 and the plate 12 of the mask 29. During the rotation of the wheel 2 , the parts carried by the support 27 pass very close to the diaphragm 18 as is illustrated on the right part of FIG. 3. In the position of stop of the support 27 facing the cathode, the parts are surrounded on the four sides of the support by the plates 16 and 17 and face the diaphragm

18.

According to another embodiment of the masking means, illustrated in Figure 4, the masking means are partly carried by the wheel 2 and in part by each piece of support. Wheel 2 bears the same plates 16 as in the embodiment of FIG. 3. The parts support carries a pair of plates 19 on its transverse sides as well as a diaphragm 20 which connects them. Those skilled in the art will understand that the parts 19 and 20 are put in place on a support 27 just after placing the parts on the support and travel with it through the installation. The right part of Figure 4 shows the box thus formed by the combination of plates 16 carried by the wheel 2 and plates 19 and 20 carried by each support.

FIG. 5 illustrates that during a stopping time of the wheel 2, the configuration taken by the masking means described above, that is to say the parts 16, 17 and 18 of a On the other hand, the parts 16, 19 and 20, respectively, are substantially the same, and substantially cancel the lateral components of the ion current to which the parts would otherwise be exposed.

Figures 6 and 7 illustrate another embodiment of the spatial management of the electric current for valuing the downtime of a support parts facing the bottom of the tank. The placement of a cathode in the bottom of the tank is difficult because - the maintenance is difficult,

the gases, such as H 2, released at the cathode go spontaneously back to the parts,

- the fall of a room may create a short circuit. In this embodiment, a screen system provided with three openings is placed between two lateral cathodes C1, C ^' 1 and the wheel 2 rotating between them. In front of each cathode are placed a vertical plate 21 and a perpendicular wall 22, similar to the assembly formed by the plate 12 and the wall 13 of the mask 29 illustrated in FIG. 2. Instead of the diaphragms 14, a cylindrical screen 23, of which the axis coincides with the axis 5, is arranged around the submerged portion of the wheel 2. The screen 23 has two lateral openings 24 equivalent to the openings of the diaphragms 14 and a low opening 25 whose shape and position correspond to a support 27 in its low stop position facing the bottom of the tank. The ionic currents between cathodes and rotating structure are divided into two currents passing through the apertures 24, forming approximately between the upper portions of the cathodes C1, C ^' 1 and the two side-piece holders, the current lines of which are symbolized by the dashed arrows L1, and a current component passing through the 25, opening approximately between the lower portions of these same cathodes and the support of parts in the lower position, whose current lines are approximately symbolized by the dashed arrows L2. This arrangement creates a kind of "virtual cathode" at the bottom of the tank, which does not present the risks that would lead to the arrangement of a third physical cathode. Note that this virtual cathode does not emit hydrogen, the usual negative effects (trapping bubbles, increase the resistivity of the electrolyte) do not occur.

Due to the axis of rotation 5 which is above half the level of filling of the tank, the side cathodes can be extended towards the bottom of the tank so that their lower part is not completely masked , facilitating the passage of a current up to ^the opening 25 via a mask channeling L2 current lines to the bottom of the tank. This embodiment is advantageously combined with the homogenization masks illustrated by FIGS. 3-5 in that the "uncontrolled" propagation of current in the tank is voluntarily limited. The virtual cathode can be seen as an extension of the masks or as the modeling of the current lines not only near the supports but in the whole of the tank.

A development of this embodiment can consist in segmenting the lateral cathodes in two in a horizontal plane and feeding the lower part of these cathodes, which feeds the virtual electrode, at a higher voltage to compensate for voltage drops in the electrolyte induced by the passage of the current of the actual cathodes to the virtual cathode.

The machine comprising one or more processing tanks according to the invention comprises a transfer device synchronized with the drive device of the axis of the machine, comprising gripping members of the supports located in the up position on said rotary structures, said transfer device performing a simultaneous transfer movement of said supports in the high position, each support in the high position taking, under the effect of said transfer movement, the location occupied, before said transfer movement, the support in high position immediately downstream. This transfer device may be the same, or of the same type as the transfer devices described in the documents WO 2008/035199 and WO 2010/125515.

The machine can be housed in a box equipped with identical or similar functionalities to those described in WO 2010/125515. The bottom of the box may be a liquid retention tank of appropriate capacity. The box may contain a process liquid reservoir, a used process liquid reservoir, a rinsing fluid reservoir, and a used rinsing fluid reservoir. A device for the treatment of treatment liquids, housed inside the box may include at least one heat exchanger and a filter device. The device for the reprocessing of used liquids may comprise an evaporator which removes the used liquids by distillation and condensation. The box may also contain a gas washing station. Each support traversing the machine according to the invention performs a course that can be generally described as helical, although it is in fact made of a succession of rotations and translations. Moreover, the path of each medium consists of sequences clocked by these movements, but the overall process of processing a large number of media is to be considered as a continuous process. It is therefore possible to adjust the flow rates of the fluid, process liquid, rinse aid and airflow supplies to operate in an established steady state, the volumes and concentrations of the fluids in the entire series of fluids. remaining tanks constant. As a result, the quality of the treated parts remains perfectly constant. As a whole, the installation according to the invention produces only a small volume of discharges that can not be treated in situ, which allows its use in a plant that does not have the facilities of an electrochemical surface treatment plant.

The invention is not limited to the embodiments described and represented by way of examples above, but it comprises numerous technical variants as well as their combinations:

- Thus, Figures 3 and 4 illustrate a rotary structure with 4 support mounting positions. This number could be different. With, for example, only two fixing positions, each transverse plate can be replaced by two arms.

- The supports mentioned above are particularly suitable for the treatment of small parts. In the case of a processing unit of large but invariable parts, these can be attached directly to the rotating structure. Spatial management of the current can take into account the geometry of such parts.

- The axes of the rotating structures of two successive tanks can be connected by gears which solidarize in rotation without necessarily being aligned.

- The set of tanks can include several tanks built separately and then installed in series. It can also be achieved by means of a long vessel divided by partitions into a plurality of compartments with different functions.

- Such a tank may have a double wall serving as a retention tank in case of malfunction.

Claims

claims

A method for electrochemically treating the surface of metal parts by immersion in at least one treatment liquid contained in at least one treatment tank (1), comprising at least one electrolytic step in which said parts are housed on a rotating structure ( 3) provided with housing means (15) and rotatably mounted about a horizontal axis (5) inside said treatment vessel (1), a potential difference is established between said parts and at least one electrode arranged in said treatment tank (1), said parts being fed with current of opposite polarity to that of said electrode via said housing means (15) and said rotary structure

(3), and said pieces are immersed completely in said treatment liquid by a rotational movement of said rotary structure (3) bringing them opposite said electrode, characterized in that the method implements a plurality of electrodes (Cl, Cl, C2, C'2, C3, C'3) supplied with different electrical voltages

(VI, V2, V3), arranged in a plurality of treatment tanks or in a plurality of compartments of a treatment tank (1) comprising partitioning means (6, 7), each compartment comprising at least one said electrode .

2. Method according to claim 1, characterized in that the parts undergo a plurality of said electrolytic steps, that each treatment vessel or cell compartment comprises a pair of electrodes, said parts being brought successively opposite a plurality of pairs (Cl, Cl; C2, C2; C3, C'3; said electrodes.

Method according to one of the preceding claims, characterized in that a predetermined number of parts placed beforehand on a support (27) of parts comprising at least one holding member (28) adapted to immobilize each of said parts relative to the said support (27) of parts are introduced into an immersion zone arranged in the upper part of a treatment tank (1) or a tank compartment and housed on said rotary structure (3), that said support (27) of parts is driven by the latter in a rotational movement of one or more times 360 ° and brought to an outlet zone arranged in the upper part of said treatment tank or said compartment, from which said parts support is extracted from said treatment tank or said compartment, and in that said process is carried out continuously and by clocked displacements, said rotary structure (3) marking a time-out when said support ( 27) located opposite a said electrode (Cl, Cl, C2, C 2, C3, C'3).

Method according to one of the preceding claims, characterized in that a control of the spatial distribution of the electric fields between said parts and said electrodes is carried out.

Method according to one of the preceding claims, characterized in that masking means (16, 17, 18, 19, 20, 21, 22, 23, 29) arranged inside a said treatment tank. Application of a method according to one of the preceding claims to anodization of aluminum or aluminum-based alloy parts, the potential differences (VI, V2, V3) between said parts and said pairs of increasing electrodes from one step to the next.

Cuvette for surface treatment of parts intended to implement a method according to one of the preceding claims, comprising a rotating structure (3) rotatably mounted inside said treatment tank (1) around a axis (5) of horizontal rotation, said rotary structure comprising, at its periphery, at least one housing track (15) parallel to the axis of rotation (5) and provided with temporary fixing means (28), suitable for housing at least one part or a support (27) of parts, held temporarily in a determined position of the housing track during a said rotation by said fixing means (28), characterized in that said vessel comprises a plurality electrodes (C1, C1; C2, C'2; C3, C'3), arranged upstream to downstream in the direction of said axis of rotation associated with a plurality of temporary fixing means (28) and means for partition (6, 7) arranged inside said tank (1) of treatment providing compartments and electrical insulation between an electrode upstream and a downstream electrode.

Treatment vessel according to claim 7, characterized in that said treatment vessel (1) is segmented perpendicularly to the axis of rotation of said rotary structure (3) in a plurality of compartments separated by partitions (6, 7), said rotary structure comprises in each compartment a wheel (2) mounted centered on the axis of rotation and that each compartment comprises a pair of electrodes (C1, C1; C2, C'2; C3, C'3) mounted laterally on either side of a said wheel (2).

9. Treatment tank according to one of claims 7 to 8, characterized in that the set of wheels (2) is at the same electrical potential as the axis of rotation (5) of the rotating structure and that the difference potential between a wheel (2) and the associated electrode or electrode pair (Cl, Cl; C2, C'2; C3, C'3; C4, CM) is adjustable to different values.

10. Processing tank according to one of claims 7-9, characterized in that each wheel (2) comprises four housing tracks (15) arranged at 90 ° from each other, each housing track being aligned with a track adjacent compartments, and that said supports (27) of parts are slidably accommodated with each support (27) in a track (15) housing when it is at the level of the immersion zone, all of said housing tracks being parallel to the axis of the rotary structure.

11. Processing tank according to one of claims 7 to 10, characterized by the presence of masking means (16, 17, 18, 19, 20, 21, 22, 23, 29) modifying the spatial distribution of the electric fields between said parts and said electrodes.

Treatment tank according to one of claims 7 to 11, characterized in that the laterally arranged electrodes extend downwards from the tank, whereby masking screens (21, 22, 23) are interposed between the lower part of said electrodes and the rotary structure, said masking screens (23) extend from a lateral upper zone near said electrodes to a central lower zone near the bottom of the tank, leaving unmasked an area (25) facing the lowest position taken by a housing track of the rotating structure for generating an ion current through said unmasked area (25) towards said housing track.

13. Processing tank according to claim 12, characterized in that the lateral electrodes consist of two vertically separate parts, the upper part and the lower part of each of said lateral electrodes being at different electrical potentials.

Processing vessel according to any one of claims 7 to 13, characterized in that said housing track (15) is bordered on either side by a pair of longitudinal masking screens (16) mounted on said rotating structure parallel to the axis of rotation (5) and extending towards the two side electrodes.

Processing vessel according to claim 14, characterized by a pair of transverse masking screens (17) mounted on the fixed structure of the vessel perpendicular to the axis of rotation of the rotating structure, bordering a workpiece or support of parts (27) by its front and rear, the geometries of said longitudinal masking screens (16) and screens of transverse masks (17) being dimensioned so as not to prevent the functions in rotation and in translation of said vessel.

16. Processing tank according to one of claims 7 to 15, receiving parts supports, characterized in that said parts supports are lined with a lateral support mask.

17. Processing tank according to one of claims 7 to 16, characterized in that said treatment tank is equipped with a circulation system (C) and reprocessing of the electrolyte common to the compartments of said tank.

18. Treatment tank according to claim 17, characterized in that said treatment tank comprises perforated electrodes (C4, CM) and in that the treatment liquid, after reprocessing, is reinjected via perforated housings (30) in the direction of parts, through said perforated electrodes, and in particular towards the marginal portions of the part supports.

19. Surface treatment machine comprising one or more treatment tanks (1) according to one of claims 7 to 18.