Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D17/00—Constructional parts, or assemblies thereof, of cells for electrolytic coating
  • C25D17/10—Electrodes, e.g. composition, counter electrode
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D17/00—Constructional parts, or assemblies thereof, of cells for electrolytic coating
  • C25D17/10—Electrodes, e.g. composition, counter electrode
  • C25D17/12—Shape or form
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D21/00—Processes for servicing or operating cells for electrolytic coating
  • C25D21/12—Process control or regulation

Definitions

• the present invention relates to a device and a method for controlling the effectiveness of a metal electrodeposition bath (containing in particular metal elements and adjuvants) and more particularly, although not exclusively, the thickness of the metal coating deposited on the parts. treated and the external appearance as shine.
• a metal electrodeposition bath containing in particular metal elements and adjuvants
• Hull cells see, for example, US Pat. No. 2,149,344. They comprise a tank containing the liquid metal electrodeposition bath to be deposited, respectively anodic and cathodic electrodes immersed in the bath and a current generator connecting the electrodes.
• the cathode electrode, on which the metal deposition coating is fixed, is in the form of a rectangular metal plate or the like, inclined with respect to the anode electrode so that the distance separating them varies progressively from one end to the other of the plate.
• the thickness of the deposited metal coating will progressively change along the inclined cathode plate and also the brightness of the latter. It is thus possible to study the influence of the current density on the amount of deposit (coating thickness, gloss, etc.) with fixed electrolysis conditions.
• Hull cell is intended for use in the laboratory, with a small tank without agitation of the bath.
• the inclined cathode plate can be replaced by a rotating metal cylinder whose rotation allows a non-zero relative speed between the cathode and the bath liquid.
• a device for controlling the characteristics of a metal bath which comprises, in a base and a cover of the device, an insulating substrate coated with segments or separate electrode sections in which circulate current to determine the thickness or mass of the coating deposited on the sections according to the current flowing through them.
• a device is of irregular shape and volume and is completely disposed in the bath, so it seems difficult to exploit for production tanks. It is more suitable for laboratory vessels.
• the object of the present invention is to overcome these various drawbacks and concerns a device and a method for controlling the efficiency of a metal electrodeposition bath whose design makes it possible, among other things, to scan a selected range of current densities with precision. , to give the actual current density at each point, to measure the deposited coating and to deduce the mass, thickness and gloss for a given current density, and to take into account the actual hydrodynamic conditions.
• the device for controlling the efficiency of a metal electrodeposition bath contained in a vessel is of the type comprising respectively anodic and cathodic electrodes connected to an electric current generator, said cathode electrode consisting of a plurality of individual test pieces adapted to be immersed in said metal plating bath and fed by a controllable power supply unit.
• This is connected to the current generator and comprises means for adjusting the current flowing through said cathode specimens so that in each of them circulates a determined current.
• the above device is remarkable in that the individual cathode specimens are suspended from a movable sample holder, disposed above the metal bath of the vessel to immerse substantially only the specimens in said bath.
• the deposition of a metal coating on each of the individual cathode specimens is simultaneously carried out during a single control by imposing distinct current densities thereon.
• distinct current densities thereon.
• different coatings corresponding to the current densities used are obtained.
• the effectiveness of the controlled bath in question can be accurately determined by the weight of the coating deposited for each specimen subjected directly to a specific current density, (in particular by weighing before and after the control) and, thus, determining the characteristics of thickness, gloss and others that are obtained for an imposed current density.
• the specimen holder is not only movable vertically for the immersion of the specimens but also horizontally, so that the horizontal displacement of the suspended specimens makes it possible to have a relative speed between the surface to be coated and the liquid metal bath, when checking it.
• the subsequent parts to be treated will be subjected to the current selected for obtaining thereon the desired coating whose thickness corresponds to a given corrosion resistance or a particular gloss.
• the device of the invention overcomes the previous disadvantages by covering, by the individual cathode test tubes, a determined and accurate range of current densities and by measuring the coating deposited on each individual test piece, proportional to the deposited metal mass from the bath as a function of the applied current density and representative of the efficiency of the bath under control.
• the part (s) to be treated are immersed in the bath at a given intensity corresponding to the thickness of the metal coating to be deposited.
• the control device can thus be used periodically to check the bath.
• the means for adjusting the current of the power supply unit are defined, for each cathode test tube, by a variable resistor connected on one side to the current generator and, on the other hand, side, to the corresponding cathode test tube. Note the simplicity of realization of the adjustment means ensuring the reliability of operation of the unit in use.
• each variable resistor and its corresponding cathode test piece an instrument for measuring the current passing through the test tube, in the form of an ammeter or the like.
• the device delivers the intensity by a direct reading and the actual current density at each point of the cathode test pieces is obtained by calculation or the ammeter is graduated in a particular way to display the density.
• the arrangement of the individual cathode test tubes is arbitrary in said bath, because of the large size of said production tank, not generating no or few "disturbances" between the cathode test tubes.
• the arrangement of individual cathode specimens could be established in the same horizontal plane in the metal bath, the cathodic specimens aligned in the horizontal plane can be regularly spaced from each other.
• the individual cathode specimens are dimensionally identical and have a disc shape.
• stirring means of the liquid metal bath are associated with the tank, especially when it is a production tank.
• two anode electrodes in the form of grids or preferably parallel plates between which are arranged cathode specimens.
• the invention also relates to the method of controlling the characteristics of a metal electroplating bath contained in a tank under the conditions of production of coated parts. It is remarkable in that it uses the control device as defined in one of the preceding claims, and that it comprises the steps of:
• efficiency curves are established for each controlled bath representative of the deposition rate as a function of the current density in each specimen, and, according to the efficiency curves obtained during the control of the test specimen. bath, is modified, if necessary, at least one of the parameters of the bath to deposit the coating on the parts under optimal production conditions.
• such a method and such a device can directly characterize the efficiency of a bath, whether new or in use, and can use the parameters established for the production of parts to be processed and avoid scrapping them, and also to be able to adapt to any type of tubs and / or baths of a workshop or other without difficulties.
• Figure 1 is a schematic cross sectional view of a control device of a metal electrodeposition bath, according to the invention.
• FIG. 2 is an enlarged view of one of said individual catheter specimens according to arrow F in FIG.
• Figure 3 shows the controllable power supply unit of each of the cathode test tubes of the device.
• Figures 4 and 5 show examples of efficiency curves of different baths, obtained from the control device and the implementation of the method according to the invention.
• the control device 1 diagrammatically shown in FIG. 1 is associated, in this example, with a production vessel 2 containing the liquid metal electrodeposition bath 3 whose effectiveness of its composition is to be verified according to certain operating characteristics. Indeed, from these, one can then adjust the production parameters to obtain the desired result on the parts to be treated, particularly with regard to mechanical properties, external appearance, etc., depending on the thickness deposited coating, depending on the current used.
• the metal bath is a platinum bath (Pt 2+ ions, Pt 4+ ) to which adjuvants are added, in order to deposit, by the passage of an electric current from a current generator 4 and circulating between respectively anodic and cathodic electrodes 6 immersed in the bath 3, a platinum coating on turbomachine blades or the like forming the cathode, and thus to improve their resistance vis-à-vis oxidation and corrosion.
• the control device could of course be associated with another type of tank, such as a laboratory tank.
• the anodic electrode 5 is defined by two anodes in the form of grids or metal plates 7, parallel in this representation, but not necessarily, and arranged vertically along two lateral and opposite sides 8 of FIG. tank.
• the cathode electrode 6, subsequently defined by the part or parts to be treated, is composed in the control device 1 of the invention by a plurality of individual cathode test tubes 9. Each of them will be subjected, as one will see it later, with a specific electric current and different from those circulating in the other specimens, so as to make deposits with distinct intensities on them and to measure the results of mass and, therefore, of thickness (one could also seek to obtain the same mass over a given range of intensities).
• the individual cathode specimens 9 are dimensionally identical and are, in this example, ten in number with a solid disc shape as shown in FIGS. 1 and 2. And they are immersed in the metal bath 3 having their disc perpendicular to the anodes and horizontally aligned. This provision is not an absolute necessity, as will be seen below. All of these specimens are suspended from a sample holder which is symbolized at 10 in FIG. 1 by respective links 13, and which is advantageously controllable so as, firstly, to move the specimens 9 horizontally to print a relative speed between the test pieces and the bath and to participate somewhat in the mixing of the bath 3 and, on the other hand, vertically to raise and lower the specimens 9 with respect to the liquid metal electrodeposition bath 3.
• the control device 1 comprises a controllable power supply unit 1 1 which is, on one side, connected to the current generator 4 and, from the In particular, as best seen in FIG. 3, the unit 11 includes means 12 for regulating the current which passes through the specimens to the desired value, which means 12 consist of There are as many variable electrical or electronic resistors 14 as there are individual cathode specimens 9.
• the set of these individual variable resistors 14, too, is connected on one side by a common connecting connector 15. to the current generator 4, while each of them is connected, on the other side, to the link 13 of the cathode electrode concerned by a connection connector 16.
• variable resistors 14 makes it possible to choose the intensity of current flowing through each of the specimens 9 and, therefore, the current density (intensity / surface of the specimen) studied for each specimen immersed in the metal bath.
• a current measuring instrument 17 from each resistor is provided, such as an ammeter which is connected in series between each variable resistor 14 and its cathode test specimen 9 in the unit 1 1.
• the control device 1 makes it possible to choose and cover a precise and important range of current densities to determine, from the characteristics of the metal electrodeposition bath 3, the efficiency of the latter.
• the ten cathode specimens 9 may be subjected to different intensities, for example from 1 to 10 amperes respectively, so as to record in real time the metallic deposition performed for each of the current densities and symbolized by the coating. R on magnified magnifying glass A of Figure 2.
• the method of the invention is implemented in a tank under real conditions of production with flow with agitation of the bath. And it consists in weighing the individual cathode specimens 9 before they are put in place on the specimen holder 1 1. Then, after mounting them suspended on the specimen holder, only the specimens 9 (with part of their connecting wire 13) of the device are immersed in the bath 3 of the tank by the descent of the specimen holder, and are subjected to the intensity of corresponding current and desired for each specimen, each intensity being read on the ammeter 17. It will be noted that the fact of only immersing the specimens in the bath added to their regular geometrical shape (thin disc) contributes to the accuracy and precision of the measures.
• the method thus makes it possible to define and be able to plot the efficiency curve of the electrodeposition bath concerned, that is to say the deposition rate (deposited mass) as a function of the current density applied to each specimen. Examples of such curves are shown in FIGS. 4 and 5, the abscissa axis representing the amperage (the current density) expressed in A / dm 2 and the ordinate axis representing the deposition rate expressed in g / dm 2 .h.
• the efficiency curves A and B of FIG. 4 make it possible to demonstrate the aging of the same metal bath over time with the decrease in the deposition rate which results therefrom.
• the implementation of the method allows the device 1 to record, by the specimens 9 immersed in the bath, the deposition rates according to the different intensities flowing in them, and that over a determined and desired intensity range, during the same control of the bath.
• the device delivers, by the test tubes (represented symbolically by squares on the curve) and the measurement readings that follow, the curve A of which the amperage will be chosen to obtain the desired coating thickness on the parts to be treated.
• the specimen 9A subjected to the associated current intensity provides a maximum deposition rate and this intensity can thus be chosen for the parts to be treated.
• the control of the efficiency of the bath makes it possible to know that the characteristics of the bath have changed and to be able to modify and intervene on the parameters concerned to maintain an optimal coating on the parts during the life of the bath. It can be seen that, on the curve B, the deposition rate is better for the specimen 9B subjected to a different intensity of the specimen 9A when the bath is new, which intensity can be chosen to treat the parts.
• the efficiency curves C and D of FIG. 5 show, by way of example, what can be obtained according to two baths with different compositions having, respectively, a pH of 4.2 +/- 0.3 and 6.5 +/- 0.3 and a temperature of 55 ° C +/- 2 ° C and 65 ° C +/- 2 ° C with standard production agitation.
• the deposition velocities obtained extend over a particularly large range
• the deposition rates are relatively close with the exception of the first test pieces subjected to lower intensities.
• the specimen concerned will be chosen to obtain the optimum deposition rate.
• the control device 1 in this example with a production tank, the specimen holder 10 and the controllable unit 1 1
• the parameters of the tank to obtain, on the part or the parts to be treated while immersed in the bath, the thickness of the selected coating corresponding to a given intensity.
• the control device 1 can not only serve to determine the effectiveness of a new bath, but also that of a bath in use, so as to periodically check its characteristics and, depending on the results of the control of efficiency, change the bath parameters to maintain the deposition conditions on the parts and ultimately have the same coatings, that is to say pieces reproducible to the identical.
• the method and the device make it possible to follow the evolution of the bath over time until its characteristics no longer correspond to the desired requirements.
• the time saved to perform these checks is important compared to previous devices and the time saving in production itself is also important.
• bath stirring means 18 are provided, such as a pump or the like, so that the homogenization thereof is good. assured.
• the specimens could be arranged in any way in the bath, instead of being aligned horizontally, and receive an identical coating.

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• Chemical & Material Sciences (AREA)
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• Chemical Kinetics & Catalysis (AREA)
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• Organic Chemistry (AREA)
• Automation & Control Theory (AREA)
• Electroplating Methods And Accessories (AREA)

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Citations (5)

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• 2010
  • 2010-03-31 FR FR1052373A patent/FR2958300B1/fr active Active
• 2011
  • 2011-03-30 RU RU2012145547/02A patent/RU2553161C2/ru active
  • 2011-03-30 WO PCT/FR2011/050715 patent/WO2011121240A1/fr active Application Filing
  • 2011-03-30 CN CN201180016583.1A patent/CN102822393B/zh active Active
  • 2011-03-30 CA CA2794579A patent/CA2794579A1/fr not_active Abandoned
  • 2011-03-30 EP EP11717696.6A patent/EP2553148B1/fr active Active
  • 2011-03-30 JP JP2013501914A patent/JP5764650B2/ja active Active
  • 2011-03-30 US US13/637,854 patent/US20130008797A1/en not_active Abandoned
  • 2011-03-30 BR BR112012024387A patent/BR112012024387A2/pt not_active IP Right Cessation

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