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

Definitions

• the invention is based on an arrangement according to the preamble of claim 1. This is primarily intended for the field of electroplating, but also for other systems for the electrolytic treatment of workpieces, for example electrophoresis.
• the parts or workpieces to be treated usually form the cathode and are conductively connected to the cathode rail.
• the cathode rail usually forms the so-called product carrier.
• the anodes are connected to the two anode rails, which, like the workpieces, are located in the bathroom. The workpieces can be lowered into and removed from the bathroom using product carriers.
• the anode rails and the cathode rail are located outside the bath liquid, while the anodes connected to the anode rails and the workpieces connected to the cathode rail are located within the bath liquid.
• the anode rails and the cathode rail have a double function in that they must have sufficient mechanical stability to carry the anodes or the workpieces. They should also have sufficiently large cross sections with high conductivity for the supply and discharge of the usually very high electrolytic treatment currents. Even if the material copper has a very high electrical conductivity, it is generally not suitable for the production of such rails due to its susceptibility to corrosion and its low mechanical strength. For this reason, stainless steel is preferred in practice for reasons of contact security and mechanical strength. The disadvantage of a much lower conductivity than that of copper is accepted.
• a bath contains a number of so-called parallel cells with the workpieces to be treated electrolytically. Doing so will be even
• DE-OS 37 32 476.4 a method for equalizing the partial currents in an electrolytic bath is known, in order to improve the layer thickness distribution, passive series resistors have been introduced into the technologically conditioned partial circuits (cells) of the total electrolytic circuit, so that the series circuit thus formed Size of the partial currents were determined by the series resistors.
• no details are given about the number and arrangement of the anode and cathode rails. In particular, no technical teaching is given on where the respective currents are fed into the rails and where they emerge from the rails.
• Copper-conducting anode and cathode rails for example made of the mentioned stainless steel, with simple means and without substantial energy losses to ensure that the same cell voltage is effective on the individual workpieces of the cells of such a bath. This is one of the prerequisites for the desired material precipitation of approximately the same thickness on each workpiece.
• the combination of features a) and b 1 ) of the characterizing part of claim 1 is provided.
• the features of section a) have the effect that the passage of current through the anode rails in the feed direction from anode to anode is reduced, since part of this current is discharged into the bath with each anode.
• the current takes on the cathode rail in the same direction until it emerges on the other side of the bath from workpiece to workpiece, since a corresponding partial flow flows to it for each workpiece (cathode). If one considers this arrangement from one side of the bath, on which the feeds are located in the anode rails, to the other side of the bath, on which the current exit from the cathode rail is provided, this has assumed a constant cross section of each of the aforementioned rails, in this direction, the voltage drop per rail length is reduced on the anode rails and the voltage drop increases on the cathode rail. Both compensate at least partially. Added to this are the effects of characteristic b.).
• the anode rails and the cathode rail can thus consist of a material which is corrosion-resistant and poorly conductive with respect to copper, for example stainless steel.
• Section b contains an increase in cross-section or a reduction in cross-section of the rails, which corresponds approximately to the changing sizes of the currents in the rails and thus to approximately the same cell voltage as a result of the voltage drops in the individual subsections of the rails, which are caused by Ohm's law every cell of the bathroom leads.
• a further, subordinate and alternative solution to the aforementioned task and problem is the subject of claim 3. Also in this are the preamble and feature a) identical to those of claim 1 and claim 2.
• Characteristic b 3 is different. This also achieves equalization of the partial electrolyte currents of the individual cells and thus the goal of the task, but the disadvantages explained in reference to DE-OS P 37 32 476.4 are avoided. In addition, DE-OS P
• FIGS. 2 and 3 arrangements according to the invention
• Fig. 4 a basic representation of the voltage drops and voltages in a Stromver run as shown in FIGS. 2 and 3, but not taking into account the effects of features b 1 ), b 2 ) and b 3 ) of the claims,
• Fig. 7 a schematic representation of the currents
• FIGS. 1 and 4 show an arrangement according to the prior art with a rectifier 1 which supplies the direct voltage, two anode rails 2 and a cathode rail 3.
• the anode rails and the cathode rail are outside the bath liquid, while the anodes connected to the anode rails and workpieces connected to the cathode rail are located within the bath liquid.
• Anodes A 1 -A n and workpieces W 1 -W m are only indicated in principle in FIGS. 1 and 4. Otherwise, in the drawings, the anodes and the workpieces are symbolically captured or replaced by the sole representation of the anode rails and the cathode rail.
• FIGS. 2 and 3. 4 gives a basic illustration of the voltage relationships.
• the current is fed into the ends of the anode rails 2 from a respective right-hand side 4 ′ of the bath 4 from the direct current source 1
• the cross section Q K of the cathode rail 3 is larger than the respective cross section Q. of each of the anode rails 2.
• the ratio Q K : Q A should not be less than 1.7: 1, but can, as soon as it is economically justifiable is arbitrarily larger than 1.7: 1.
• a cross-sectional ratio of 2: 1 has been found to be particularly advantageous.
• the circuit arrangement is the same as in the example of FIG. 2.
• the difference is that the cross section of the anode rails 2 decreases from the feed points 8 in the further course of the current flow direction 12, i.e. the specific electrical resistance of the cross section of the anode rails increases in the direction 12.
• the arrangement on the cathode rail 3 is such that the cross sections of this rail increase in the direction of current flow 13, i.e. the specific electrical resistance of the cross-sections decreases in the direction 13, this idea of the invention is not limited to the step-like change of the cross-sections of the rails 2, 3 shown in FIG. 3, as is explained in more detail below from FIGS. 8 to 8d and their explanation will emerge.
• Fig. 4 shows schematically the anode rails 2 and
• Cells are named U z1V to U zmV or U z1R to U zmR .
• U z is the same for the distance A to B to be considered. By definition, it is U Bad V for the front of the goods and U Bad R for the back. Mathematically, this is expressed as follows
• U zmV U Bad V - ⁇ ⁇ 2V - ⁇ U 3V - ⁇ U n V;
• U z3V U Bad V - ⁇ U 2V - ⁇ U 3V - ⁇ U 3 ;
• U z 1V U Bad V - ⁇ U 1 - ⁇ U 2 - ⁇ U 3 ;
• the comparison variable is used to assess the effectiveness of the various rail arrangements introduced.
• the value is calculated from the maximum difference in cell voltages in relation to the minimum cell voltage.
• Q is the relative unevenness.
• the cross section Q K of the cathode rail is equal to the cross section Q A of each of the anode rails, a value for
• the invention also includes arrangements with deviating values, e.g. was exemplified with reference to FIGS. 2 and 5. There is also a significant improvement in value
• Rail length L the direction of the abscissa resulting from the above explanations for FIGS. 3 and 7 and in particular from the schematic resistance representation in FIG. 3.
• the anode rails 2 and the cathode rail 3 can be made of a stainless steel, e.g. a V2A steel.
• a stainless steel e.g. a V2A steel.
• the part of the system which carries out the respective contacting with the anode rail has a contact surface made of the same stainless steel, or is made overall of the same stainless steel.
• FIG. 8a to 8d in practice contain possible and advantageous embodiments of the design of the rails 2, 3 to achieve the different resistance values explained over the rail length.
• 8a shows that the rail is provided with a larger number of bores or other recesses 16 in the area of high resistance than in sections of lower resistance.
• FIG. 8b shows a rail which changes continuously in cross-section in its longitudinal direction
• FIGS. 8c and 8d show rail designs whose specific resistance value decreases in a stepped manner in the longitudinal direction of the rail (17).
• 8c is a rail which is in one piece
• FIG. 8d shows a rail composed of corresponding slats 18, 19.
• Especially the execution 8a are characterized by high mechanical stability.
• the longest, lower layer or lamella 18 in the drawing consists of a mechanically very strong stainless steel, while the shorter layers or lamellas 19 above are made of copper, ie made of a material with very high conductivity. It can also be seen that by changing the design of the aforementioned rail examples according to FIGS. 8a to 8d, the respectively desired resistance curve (resistance curve over rail length) according to FIG. 8 can be achieved.
• Resistance values are relatively small, so that voltage drops occur at them with the currents that occur, which are only in the millivolt range.
• These resistors are chosen so that, taking into account the voltage drops in the anode rails, the cathode rail and on the anodes and workpieces themselves, the respective cell voltages become equal to one another, or at least reach values that come very close to one another.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Electroplating Methods And Accessories (AREA)
• Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)

Applications Claiming Priority (2)

Publications (1)

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ID=6421306

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• 1990
  • 1990-12-22 DE DE19904041598 patent/DE4041598C1/de not_active Expired - Lifetime
• 1991
  • 1991-12-22 CA CA002099008A patent/CA2099008A1/en not_active Abandoned
  • 1991-12-22 WO PCT/DE1991/001013 patent/WO1992011401A1/de not_active Application Discontinuation
  • 1991-12-22 EP EP19920901291 patent/EP0563137A1/de not_active Withdrawn

Non-Patent Citations (1)

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