FR2462491A1 - METHOD FOR ADJUSTING THE ELECTROLYTIC DEPOSITION OF A METAL IN THE PRESENCE OF IMPURITIES - Google Patents

Abstract

THE INVENTION CONCERNS THE ADJUSTMENT OF ELECTROLYTIC METAL DEPOSIT OPERATIONS. IT RELATES TO A TUNING PROCEDURE ACCORDING TO WHICH AN ELECTROLYTE CURRENT CONSTANTLY FLOWS IN A TEST CELL IN WHICH THE ACTIVATION OVERVOLTAGE IS MEASURED BETWEEN A CATHODE AND A REFERENCE ELECTRODE, WITH A LOW CURRENT. THE ACTIVATION OVERVOLTAGE IS MEASURED AT THE TIME OF THE BEGINNING OF METAL DEPOSIT, AND ITS VALUE CORRESPONDS TO THE CONCENTRATION OF IMPURITIES AND THE CONCENTRATION OF POLARIZATION MODIFIER AGENTS WHICH MAY BE PRESENT. THE CONCENTRATION OF IMPURITIES OR THAT OF MODIFIER AGENTS IS REGULATED SO THAT THE ACTIVATION OVERVOLTAGE RETURNS TO AN OPTIMAL RANGE. APPLICATION TO THE SETTING OF METAL OBTAINING AND ELECTROLYTIC DEPOSIT OPERATIONS.

Description

The present invention relates to a method and apparatus for adjusting

  continuous electrolytic deposition of metals and more precisely a method for measuring the activation surge of a metal deposit and for adjusting the electrolyte purification and electroplating operations as a function of deviations from the recorded values overvoltage

  in relation to the desired values, and the invention relates

  also a device for the implementation of the

process.

  During electroplating operations

  than metals such as electrolytic

  electrolytic finishing and electrolytic deposition, electrolytes are used which contain impurities which, when their concentration exceeds certain critical values, can be deposited at the same time as

  metal and may therefore contaminate the deposit or provoke

  to put it into solution with a corresponding reduction

  of the metal deposition efficiency.

  perform purification operations, prior to electrolysis, to reduce the concentration of impurities in the electrolyte. In addition to purification, one can

  add one or more polarizing additives to the electri-

  trolyte so that they facilitate the formation of smooth, regular deposits and reduce the effects of

remaining impurities.

  These polarizing adjuvants cause a

  polarization definition. The latter can be

  modified by increasing or reducing the concentration

  an agent causing polarization. The polar

  may also be modified by reduction or increase

  tation of the concentration of an agent causing depolarization. These agents, both polarizing and depolarizing, may be present in the electrolyte transmitted to the cells by the purification plant, or they may be substances, such as a gelatin glue, which are added to the electrolyte so

  that they regulate the process of electrolytic deposition.

  It should be noted that the term "modifying agent"

  "polarization factor" refers to both types of agents causing both polarization and depolarization.It should also be noted that a given substance does not always act in the same way in different operations. the role of a polarizing agent in an operation,

  the role of a depolarizing agent in another opera-

  using a different metal or can be

  inactive in a third operation. In an analogous

  logue, we know that impurities can "catalyze"

  the effects of polarization modifying agents.

  Thus, we know that certain experiments can be

  before the decisive choice of modifying agents.

  polarization factors suitable for a given operation.

  The methods currently used for the determination of the purity of an electrolyte are based on chemical analyzes and the determination of the

  current yields, constituting a measure of the

  impurities, whereas those which

  The addition of suitable polarizing modifiers is simply a matter of maintaining a constant concentration of the agents in the electrolyte.

  despite variations in the quality of it. These

  give rise to variations in the quality of the

  deposited and the performance of the electronic filing

  lytic. There are already a number of references which relate to methods of determining the effects

  impurities and adjuvants on

  electrolytic deposit of metals, and determination of

  purity of the electrolyte solutions.

  The patent of the United States of America

  No. 3,925,168 discloses a method and apparatus for determining

  colloidal matter content, glue or active roughness agent, in a copper plating bath, by determining the relationship between overvoltage and current density in solutions with varying contents of known reagents, and comparing

  results with those of a solution with a

  known during the deposition and having a known content of active roughness agent. Canadian Patent No. 988,879 describes a method for determining and adjusting the cathodic polarization voltage as a function of the current density of a lead refining electrolyte,

  according to which the slope of the curve representing the

  polarization as a function of the density of

  is a measure of the amount of adjuvants, and

  the effectiveness of adjuvants is modified when the

  cathodic polarization reaches values that

  come out of a predetermined range.

  A number of literature studies relate to analogous processes. The article by C. L. Mantell et al in Trans. Met. Soc. of AIME, 236, 718-725, May 1966 shows the possibility of the use of current-potential curves as an analytical tool for the control of metallic impurities in the electrolytic solutions of manganese. This article shows that polarization curves corresponding to the evolution of hydrogen are sensitive to metallic impurities that affect the cathodic surface and thus modify the hydrogen overvoltage. The article by HS Jennings et al in Metallurgical Transactions, 4, 921 -926, April

  1973 describes a method for measuring polar curves.

  cathodic solution of copper sulphate solutions

  holding variable amounts of adjuvant, by variation

  applied voltage and by recording the

  between the voltage and the current density. The ar-

  article by O. Vennesland et al., in Acta Chem. Scand.

  27, 3, 846-850, 1973 describes the effects of

  antimony, cobalt and beta-naphthol in a zinc sulphate electrolyte, on the current-voltage curve, obtained by modifying the potential

  cathode, with a programmed speed, by recording

  curves and comparing them with a reference. The article by T.N. Anderson et al, in Metallurgical Transactions B, 7B, 333-338, September 1976 discloses a method of measuring the concentration of an adhesive in a copper refining electrolyte, by determining polarization scanning curves.

  which, by comparison, give a measure of the concentration

  glue. The patent of the United States of America

  No. 4 146 437 describes the use of a cyclic voltammetric technique for the evaluation of the quality of

  of electrolyte based on sulphates of copper and zinc.

  Cyclic voltammetric recordings, representing

  both the current-voltage relationships for the cathodic deposition and anodic dissolution portions, and polarization curves are noted and allow

  the approximate determination of the quantities of impure-

  and adjuvant-in sodium-based electrolytes

zinc fate.

  The first group of documents cited concerns processes in which a metal is deposited on an electrode and current-voltage or density curves

  current-voltage represent potentials of polarity

  cathodic reaction according to currents and / or

variable current densities.

  The article by T. R. Ingraham et al in Can.

  Met. Quarterly, 11, 2, 451-454, 1972 discloses a device

  measuring the quality of zinc electrolytes,

  to measure the amount of cathodic hydrogen

  during the electrolytic deposition of zinc and indi-

  the current efficiency by comparing the weight of zinc deposited with both the expected amount of zinc and the rate of evolution of hydrogen. U.S. Patent No. 4,013,412 discloses a method for controlling the purity of a solution

  purified zinc sulphate, by treatment of an

  during the electrolysis, by combustion of the evolved gases and by measurement of the internal pressure in the combustion chamber, constituting an indirect measure of the current efficiency. The articles

  of M. Maja et al in J. Electrochem. Soc., 118, 9, 1538-

  1540, 1971 and P. Benvenuti et al in La Metallurgia Italiana, 60, 5, 417-423, 1968 describe methods of detecting impurities and measuring the purity of

  zinc sulphate solutions by zinc deposition and then dis-

  electrolytic solution of deposited zinc and establishing a relationship between the calculated current yield

and the content of impurities.

  This second group of documents relates to methods and apparatus for determining purity

  electrolyte, using the electrolysis of

  for the determination of the current efficiency

  is then connected to the purity of the electrolyte.

  U.S. Patent Application No. 052,921, filed June 26, 1979, discloses a method for controlling a process for separating zinc from a solution of zinc sulfate for electrolysis, comprising

  the reduction of a potential applied between electro-

  placed in a test cell containing a sample of

  of solution, with a constant speed towards a current intensity of almost zero, the measurement of the

  decreasing potential, stopping the reduction of the

  to a value corresponding to the moment at which the

  zinc starts to settle, the determination of

  activation voltage, determining the relationship between the activation overvoltage and the concentration of impurities, and setting the obtaining operation

  electrolytic so that the separation of zinc is op-

  timale. Although the method described in this patent application no longer requires the electrolysis of a solution for the determination of current yields or for the measurement of the polarization potentials as a function of currents or of variable current densities, it presents

  still several disadvantages. This process is not

  tinu and it requires the determination of the value of the activation overvoltage for each sample, by reduction each time of the applied potential until the value at which the zinc begins to settle is reached, and the density current moves away

  its value is practically zero for a small reduction

additional potential.

  According to the invention, it can be seen that the reduction

  applied potential is not necessary in order to

  determining the value of the power surge

  tion. Thus, according to the invention, it can be seen that

  activation voltage can be measured as a function of time, at a low current set intensity, and that

  purification and electrolysis

  can be adjusted by correcting the reagent quantities according to the differences between the recorded values of the overvoltage and the desired values,

  so that the values become optimal again.

  The method and apparatus according to the invention is

  apply to electrolytic deposition operations of

  which employ electrolytes prepared for the electrolytic coating of metals, which are used in metal separation operations by electrolytic obtaining, or which are used in

  electrolytic refining of metals.

  In many cases, electronic filing operations

  lytic include a purification operation. The method and apparatus according to the invention can be used in the electrolytic deposition of metals such as zinc, copper, lead, iron, cobalt, nickel, manganese, chromium, tin , cadmium, bismuth, indium, silver, gold, rhodium

and platinum.

  When a solution containing metal ions

  or an electrolyte is subjected to a controlled low current applied to electrodes placed

  in a test cell containing the electrolyte and

  that the current has a value sufficient for it to provoke

  that a metal deposit on a suitable cathode

  formed of a material other than the deposited metal, the value of the resulting potential represents the surge

  activation of the metal deposit on the cathode

  nable. When the cathode is mobile, values of the

  activation surge can be measured and recorded

  and the electrolytic deposition operation of the

  It can be set according to the measured values and

  registered overvoltage activation. In the pasture-

  memory, the term "beginning deposit" means the deposit of a metal which has just begun and

  limited to the partial recovery of the area of the

  mobile thode by the metal. Measured values for activation surge can be used as a direct measure of impurity concentration

  (ie the effectiveness of a purification operation

  cation), the concentration of a

  polarization, and the concentration of such a

  polarization modifier with respect to the concentration of impurities in the electrolyte, in a

  electrolytic deposition of a metal which comprises an

  purification. Depending on the values measured for the activation overvoltage, several modifications are possible, either separately or in combination:

  the purification operation can be adjusted, the con-

  The polarization modifier may be set in the electrolyte, or the concentration of the polarization modifier in the electrolyte may be adjusted in relation to the concentration of impurities, and the concentration of the impurities may be adjusted to that the yield is optimal and that the

  metal deposits formed during the electrolysis

tick be smooth.

  Thus, the invention relates to a method for controlling an electrolytic deposition operation of a metal employing an electrolyte containing impurities, said method comprising the establishment of a test circuit comprising a cell of an electrolytic sample, a moving cathode having a surface exposed to the electrolyte, an anode and a reference electrode, the electrodes being immersed in the sample, a constant current source and

  a measuring device electrically connected to electri-

  trodes, the application of a current of low intensity to the electrodes placed in the test cell, this intensity being sufficient for it to provoke the deposition

  beginning of the metal on the cathode, the measurement of the

  activation voltage at the time of deposit starting from

  tal, the determination of the relationship between the activation overvoltage and the concentration of impurities in the sample, and the setting of the separation operation

  metal so that it settles optimally.

  In a second embodiment, the method

  includes the setting of an electroplating operation

  than a metal, using an electrolyte containing

  at least one polarization modifying agent, this

  method comprising measuring the activation overvoltage by the method described above, determining the relationship between the measured activation overvoltage and the concentration of the modifying agent or agents.

  polarization modifiers present in the sample

  lon, and the adjustment of the concentration of this

  in the electrolyte so that the yield is optimal and the metal deposits are smooth,

  during electrolytic deposition.

  In a third embodiment, the method comprises setting a

  d5pôt. electrolytic: of a metal with a

  trolyte which contains impurities and at least one polarization modifying agent, the method comprising measuring the activation overvoltage according to the method described above, determining the relationship between the measured activation overvoltage and the ratio of the concentrations of the impurities and the agent (s)

  polarization modifiers present in the sample

  lon, and adjusting this ratio of concentrations in the electrolyte so that the deposition efficiency is optimal and that the metal deposits are smooth, during the

electrolytic deposition.

  The apparatus used for the method of measuring the activation surge of a metal comprises a test circuit which comprises a test cell, a

  electrolyte sample, a moving cathode, an anode

  of a reference electrode, a power supply with

  constant and a device for measuring the activation surge. The test cell is a small vessel of circular, square or rectangular cross section, made of a suitable material and preferably resistant to corrosion by the electrolyte while being large enough

  to contain a suitable sample of the electrolyte

  you. If necessary, the cell can be ventilated so that the gas that emerges can escape. A device,

  placed in the cell makes it possible to add and

  continuous evacuation of the electrolyte from the cell

  test. The three electrodes are immersed in the

  electrolyte sample and are placed amo

  in the cell, at constant distances from

each other.

  The moving cathode is formed of an electrically conductive material other than the deposited metal,

  this material can be used during the opera-

  electrolytic deposition of the deposited metal and being

  compatible with the electrolyte used in this operation.

  tion. The material of the moving cathode may be the same as that of the cathode or cathodes used during the electroplating operation, provided that this material is different from the deposited metal. By

  example, when setting up electronic filing operations

  trolytic using a sulfate-based electrolyte, for example in deposition operations of zinc, copper, manganese, nickel, cobalt, iron and cadmium, the moving cathode is advantageously formed of aluminum or a suitable alloy of aluminum. Where appropriate, a moving cathode formed of other materials, for example titanium, iron, steel, stainless steel, nickel, lead, copper or the like, may

  be used in an electroplating operation.

  One can also use a flexible and mobile electrode

  of a plastics material having a suitable conductivity

corn.

  The moving cathode has a surface of constant extent in contact with the electrolyte placed in the cell. An area of contact with the electrolyte of the cell of about 0.1 is determined.

  and 1 cm2 gives excellent results. The cathode

  bile is preferably a wire or a strip placed in a cathodic support and moving in it.The support surrounds the moving cathode except at the surface

  constant which is in contact with the electrolyte. A disc

  positive ensures the displacement of the moving cathode by

  intermittently or continuously in its support and in

  sequence in contact with the electrolyte. Preferably,

  this device allows the continuous movement of the body

  constant speed thode. The use of a cathode

  mobile web or strip has a certain

  a number of advantages. No special preparation

  the surface of the cathode is usually not

  necessary, the wire or the tape is easily available

  at a low price, and the results of the tests are

  producible. The moving cathode does not have to be replaced

  and thus allows intermittent operation

  or continuous. Most cathodic materials suitable for

  commercially available yarns or webs are useful to the extent that they are

  surfaces that are sufficiently smooth and clean,

  sufficient corrosion resistance in the electrolyte, sufficient ductility so that it can be displaced in the cathodic support, and electrochemical characteristics that allow reproducible results to be obtained during the tests. The anode is formed of a suitable inert material which allows the release of gases. For example,

  in a sulphate-based electrolyte, an anode material

  A suitable alloy is a lead-silver alloy. We build

  according to the invention that in the electrolytes to

  sulphate base, anodes formed of a lead-lead alloy

  silver containing 0.75% of silver give satisfaction and that in electrolytes containing chlorides,

  other than those containing hydrochloric acid -

  that concentrated, the platinum gives satisfaction. Other materials of inertia suitable for the formation of the anode are carbon and graphite. The reference electrode may be any of a number of suitable reference electrodes such as by

  example a normal calomel electrode.

  The three electrodes are electrically connected

  a constant current source and a device for measuring the activation overvoltage. The constant current source is connected to the anode and the cathode

  mobile. The device for measuring the overvoltage of

  tivation measures the overvoltage on the moving cathode by

  relative to the reference electrode. The overvoltage

  for example, can be read on a device

  or any other instrument giving a proper reading or it can be recorded as a plot as a function of time. The electrodes are arranged in the cell in a fixed position

  compared to others, while being removable. We build

  that we obtain good results according to the invention

  when the surface of the moving cathode which is

  tact of the electrolyte remains at a fixed distance of

  4 cm from the surface of the anode, when the electro-

  of reference is placed between the cathode and the anode t462491 and when the reference electrode is placed between

  the cathode and the anode so that the end of the

  the reference electrode is disposed rigidly at a distance of about 1 cm from the disengaged surface of the moving cathode, in contact with the electrolyte, but without it covering this surface. If necessary, a diaphragm or a semi-permeable membrane may be

  placed in the test cell between the anode and the

  thode so that separate anode and cathode compartments are delimited; the reference electrode is

  then placed in the cathode compartment.

  A suitable device can be used to maintain the temperature of the cell electrolyte at a suitable constant value. Such a device may include an adjustable electrolyte heating and cooling device, mounted

  before the entry of electrolyte from the cell, or a

  Adjustable pentin heating and cooling

  in the test cell, or a temperature bath

constant or the like.

  According to the method of the invention, a sample

an electrolyte which may be basic, neutral or acidic and which may contain adjuvants, obtainable

  following an operation to purify the elec-

  trolyte or an electrolytic deposition operation of a

  metal, is introduced into the test cell. The exchanged

  tillon is kept moving for example by stirring

  tion or circulation, so that the results are

  producible. The sample is preferably maintained

  in motion by continuous circulation of a small cou-

  electrolyte in the test cell. In this

  advantageous embodiment, a sample of

  trolyte is removed constantly during the purification or electrolytic deposition operation, circulates in

  the test cell and is then sent back to the

  corresponding ration. The electrolyte introduced into the cell can be adjusted so that certain concentrations of the electrolyte ingredients, for example the metal and acid contents, can be adjusted and allow

  minimizing variations in the process of

  which may be due to variations in

  ingredients in the electrolyte.

  For example, during the electro-

  lytic zinc, the concentrations of the

  zinc and acid at a time. For example, we can

  reduce the concentration of zinc to 150 g / l. In a

  the zinc concentration can be adjusted to 55 g / l

  and that of the acid at 150 g / l. Concentrations

  between 1 and 250 g / l for zinc and between 0 and

  250 g / i for sulfuric acid also give

  Satisfaction in the test cell. When using

  sample flow, the electrolyte

  excess is removed from the cell for example by

  tucking. The moving cathode advances into the cathode holder intermittently or continuously at a

  sufficient speed to allow for the joint filing

  leading to metal. Preferably, the moving cathode advances continuously at a constant speed. This velocity is dependent on the ratio of cathode length to surface area, current density value causing early deposition, cathode surface exposed to the electrolyte, exposed surface area fraction. by the deposited metal, and the weight of the deposited metal. The speed depends

  also to a certain extent the importance of

  electrolyte in the cell. Thus, the

  The displacement rate of the cathode in its support and consequently in the electrolyte can vary over a whole range. For speeds lower than the minimum value of the range, the overvoltage measured is that of the metal on this metal and is not a surge

  activating the metal on the moving cathode. At vi

  corresponding to multiples of several

  10 times the minimum speed, for example for a speed 1000 times greater, the amount of deposited metal may not be sufficient for the values obtained

  for the activation surge are reliable and reproduce

  ductile. Preferably, the displacement speed of the cathode is from 10 to 500 times the minimum speed.

  This minimum speed can be calculated using the following formula: R = abcd min xy where R is the minimum speed in cm / h, a is the ratio of the length to the cathodic surface exPosed, in cm / cm, b represents the current density in A / cm2, c represents the exposed surface of

  cathode in cm2, d represents the electrochemical equivalent

  that deposited metal, in g / Ah, x represents the fraction of the exposed cathodic surface covered by the metal, and y represents the weight of deposited metal per cathodic surface unit, in g / cm

  When the cathode is moved intermittently

  the average speed of movement must be at

  less than the minimum speed of continuous movement

  while the periods during which Catholic

  are fixed must not exceed those which

  a larger deposit than a beginning deposit.

  A low intensity current is applied to the anode and the moving cathode so that it causes

  a deposit starting metal on the cathode. Befor-

  This low intensity current is set to a constant value. Intensity should be limited to

  low values that only cause a

  Cant. This characteristic is necessary so that the metal can not be deposited on already deposited metal, because the values obtained for the overvoltage would be the deposit of the metal on itself and not the desired surge of activation of the metal deposit.

  on the matter of the moving cathode. So, the deposit -

  too much metal should be avoided.

  Preferably, about 10 to 30% of the cathodic surface

  that in contact with the electrolyte must be covered

  at any time by the deposited metal. The inten-

  Current densities, expressed as a current density, which cause a deposit beginning on a cathode moving at a previously indicated rate, should be at least 0.01 mA / cm 2. Densities of

  current at the moving cathode as indicated by

  in the following, should be considered in

  the exposed surface of the moving cathode. Au-

  below a value of 0.01 mA / cm of current intensity, expressed as a current density, special precautions may be necessary

  to obtain reliable measurements. In practice, the

  the current density, expressed as the current density, shall be between 0.01 and 4.0 mA / cm Values greater than an equivalent density of

  current of 4.0 mA / cm2 require deceleration speeds

  placement of the cathode too high to be used

  in practice. Intensities, expressed as a current density, are preferably in the range of 0.1 to 0.4 mA / cm. For example, in the case of the beginning deposit of copper at a current density of

  current of 0.4 mA / cm, on a moving aluminum cathode

  nium having a ratio of its length to its surface of 2.4 cm / cm2, the exposed surface being 0.25 cm2 of which% is covered with deposited copper and on which 7.10 3 g / cm2 of copper is deposited, the minimum speed ,

  calculated using the preceding formula, is

  viron 0,20 cm / h. For the same parameter values, the minimum speed is about 0.65 cm / h for lead, about 0.21 cm / h for zinc and about

0.17 cm / h for manganese.

  The temperature of the electrolyte being measured can be maintained at a constant value. The

  variations in temperature have an effect on the

  measured activation voltage, a reduction in the temperature

  for example, an increase in the measured overvoltage. Where appropriate, the cell and its

  contents are set and maintained at a constant temperature

  controlled suitable aunt which may be between 0 and 100 ° C and preferably between 20 and 75 ° C. Where appropriate, the constant temperature may be approximately

  the same as that of the electrolyte used in the

  electrolytic deposit and / or during

  as appropriate. When the temperature is not maintained at a constant value, the value of the activation overvoltage must be corrected for temperature variations so that the results

trials are comparable.

  The activation surge is measured

  continuously or intermittently, and it is recorded

  at the time of the deposit of the metal on the

  mobile thode. When practicing the method of the invention in practice, the activation overvoltage is expressed as the overvoltage value measured at a current intensity corresponding to a current density of between approximately 0.01 and 4, 0 mA / cm 2 exposed cathode surface, preferably for a value between 0.1 and 0.4 mA / cm 2. The activation overvoltage is read on a suitable instrument or it can be recorded as a function of time. The recorded values of the overvoltage are maintained in an advantageous range. This characteristic is obtained by adjusting the purification operations and

  electrolytic deposition when the values of the

  voltage deviate from the advantageous range.

  The activation surge has a value

  special for each metal according to the composition of the electrolyte. Since each electrolyte composition can be purified to an optimum value, has an optimal range of polarization-modifying agent contents and has an optimum range of ratios of modifying agent contents to

  impurities, the activation surge has

  log a range of values needed for

  results are optimal. Any one can be used

  many suitable polarization modifying agents known in the art, during the deposition

  electrolytic of each metal. One of the modifying agents

  polarization factors most commonly used

  is a gelatin glue. It is determined that the increase

  concentration of impurities may cause a reduction in the activation surge while increasing concentrations of polarizing agents

  increases surge and increases in

  de-polarizing agents reduces overvoltage.

  When the measured value of the activation overvoltage, during the electrolysis purification, is too low, the concentration of the impurities is too high for the separation of the metal to be optimal during electroplating. Thus, depending on the composition of the electrolyte, the activation overvoltage indicates the efficiency of the purification operation, and the deviations from an optimal operation can be corrected by adjusting the purification operation according to the values activation overvoltage,

  so that the concentration of the impurities is reduced.

  An insufficiently purified electrolyte may undergo

  additional purification during a sup-

  additional purification or recirculation in the purification plant. For example, when electrolytically obtaining zinc, the correction of the purification operation by zinc dust can

  be carried out by adjusting the temperature of the

  ration of purification, or the duration of this operation.

  by increasing the amount of dust

  zinc used or by increasing the amount

  depolarizing agent, such as antimony, copper or arsenic present in ionic form in the electrolyte. When the value of the activation overvoltage measured for the electrolyte during the electrodeposition operation is too low, the concentration

  polarization modifying agents, in the electri-

  trolyte, is not sufficient for the proper setting of cathodic deposition of metal, or the concentration of impurities

  is too high compared to that of modifying agents

  ers. On the other hand, when the value is too high, the concentration of the polarization modifying agents is too high and the yield is reduced, the metal deposit formed being rough. So, depending on the concentration of the electrolyte, the surge

  activation is an indicator of the performance of the opera-

  electrolytic deposition and the deviations from

  optimal functioning can be corrected

  concentration or nature of agents

  polarization modifiers or by changing the ratio

  the concentration of the modifying agents and the impurities in the electrolyte in the necessary direction

  indicated by the values of the activation overvoltage.

  The variation in the concentration of modifying agents

  polarization devices can be carried out in any

  suitable, for example by increasing or re-

  the speed of addition of modifying agents

  in the electrolyte. A reduction in the concentration

  impurity may be ensured by

  more efficient cation of the electrolyte before the deposit

  electrolytic. In the presence of an ex-

  cessation of polarization modifying agents, a correction can also be made by addition to

  the electrolyte of an agent having different characteristics

  polarization modification

  to ensure that the ratio of the concentrations of

  and modifying agents have the value

  venable. The addition of a depolarizing agent, if appropriate, may conveniently be effected by the controlled addition of a metal salt which acts as a depolarizing agent, such addition causing the correction of the ratio of the concentrations of the impurities to the depolarizing agents.

  polarization. For example, when obtaining electrolyte

  zinc, ionic antimony can be added as a depolarizing agent. The process according to the invention has a number of applications in the electrolytic deposition of metals. Thus, it can be used before, during and after the purification of the electrolyte and before, during and after the deposition

  electrolytic metal from the electrolyte.

  For example, during the purification of a zinc sulfate electrolyte used for electrolytic zinc production, the process can be

  used to determine the importance of the

  removal of iron oxide, and the importance of

  removal by iron oxides of such impurities

  as arsenic, antimony and germanium.

  In an electroplating operation, the process can be advantageously used for

  determination of the necessary quantity of

  polarization modifiers, alone or as a function of

  the concentration of impurities, the quantity required

  of impurities as a function of the concentration of

  polarization modifiers,

  of the introduced electrolyte or electro-

  lyte used, and the quality of the electrolyte re-

cycle.

  The following description relates to examples

  implementation of the invention given for illustrative

and not limiting.

  In the following examples, the values of

  activation surge are measured with one

  test lule with a sample volume of 500 cm3.

  A determined volume of electrolyte circulates in the cell. A movable cathode formed of a wire advancing in a fixed cathodic support, arranged to

-

  remains in the cell so that 0.25 cm 2 of the cathode is exposed to the electrolyte, an anode and a normal calomel electrode placed between the cathode and the anode, are immersed in the electrolyte placed in the cell. The exposed surface of the mobile cathode is 4 cm from the surface of the anode and the tip of the normal calomel electrode is 1 cm from the surface of the anode.

  the cathode so that its tip is not directly

  aligned between the anode and the exposed surface of

  the cathode. The temperature of the electrolyte which circulates

  in the test cell is set to the desired value. The anode and the moving cathode are connected to a constant current source, and the normal calomel electrode and the cathode are connected to the activation overvoltage measuring device, comprising a

  voltmeter giving a digital reading and recording

  Treur. A current of constant current is applied to cause a deposition of metal on the moving cathode, and the values of the activation overvoltage are measured and recorded. The exposed cathodic surface fraction covered by the metal is

equal to 0.4.

EXAMPLE 1

  This example shows how the activation overvoltage measurements can be used for adjusting the electrolytic deposition of copper. Activation overvoltage values are measured with a current whose intensity corresponds to a current density of 1.0 mA / cm 2. The cathode is 1119 mm diameter aluminum alloy wire, having a ratio of its length to the surface of-2.51 cm / cm. The calculated minimum speed of displacement of the

  cathode in the electrolyte is 1.09 cm / h. The cap

  thode circulates in the cathodic support at a speed of 160 cm / h. The anode is made of lead containing 0.75% silver. The electrolyte temperature is 500C and its flow rate is 660 cm 3 / min. A recorder 246t491

  keeps the values of the activation overvoltage me-

  sured. The copper sulphate electrolyte con-

  holds 20 g / l of copper and 150 g / l of sulfuric acid, as well as varying amounts of glue, chloride and antimony that are added.

  The electrolytic deposition operation is carried out

  killed at a current density of 400 A / m2 for a period of 24 hours. After this deposition period, the quality of the surface and the ductility of the deposit are analyzed. Ductility is determined in the form of

  number of folds of the depot at 1800 before he presented

  you're cracking. The amounts of adjuvant in the

  the electrolyte, the average of the values recorded for the

  activation surge for each composition of

  the electrolyte, and the qualities of the deposited electro-

  lytically appear in Table I. Test 1

A10 6

Additions to trolyte

glue C1-

mg / l mg / l

0 -

2,5 -

, 0 -

7,5 -

-

-

BOARD

elec-

ions Sb mg / 1 I Surge

of activators

  tion, mV Ductility number of bends to 7 0 1 - 129 29 rough

8 0 10 - 140 25 "

9 0 30 - 145 10 "

  5 1 - 140 6 smooth 11 7,5 1 - 143 7 rough

12 5 10 - 180 7

13 5 30 - 182 10 "

  14 0 - 300 118 12 rough 2.5 - 300 125 7 smooth

16 5 - 300 128 22 "

17 10 - 300 153 18 rough

18 20 - 300 164 7 "

  19 0 10 300 140 25 rough 20 5 10 300 178 23 smooth 21 30 10 300 203 11 rough 22 5 1 300 136 11 smooth

23 5 30 300 181 13 "

24 5 30 20 180 16 "

  The results of tests 1 to 6 show that the values of the activation surge increase

  when the quantity of glue present in the electro-

  lyte increases. The activation overvoltage should be set between approximately 130 and 140 mV and the amount of

  glue present in the electrolyte must be adjusted when

  that the measured value of the activation overvoltage is outside this range so that the formed deposit

be smooth.

Nature

of the de-

  The results of tests 7 to 13 show that the presence of chloride in the electrolyte causes the formation of rusty deposits which, in the presence of glue

  added, also become less ductile.

  The results of tests 14 to 18 show that, when an electrolyte contains antimony and

  increasing amounts of glue, the value of the

  voltage increases, but the results of the deposit ductility test become erratic. The correction

  this erratic behavior requires the presence

  mixed with a chloride. As indicated by the results of tests 19 to 24, the presence of approximately 10 mg / l of chloride with 5 mg / l of glue ensures the formation of smooth and ductile deposits in the presence of antimony. For

  such a system, the values of the overvoltage of

  approximately 180 mV, and this value can be adjusted by fine-tuning

  glue, chloride or both.

EXAMPLE 2

  This example shows how the activation surge measurements can be used for the

  adjustment of the electrolytic deposition of manganese. The values

  their activation overvoltage are measured for a current corresponding to a current density of 1.0 mA / cm. The cathode is an aluminum alloy wire

  No. 1100 of 1.19 mm diameter having a long-term

  area / area of 2.51 cm / cm2. The minimum speed

  The displacement abutment of the cathode in the electrolyte is 0.92 cm / h. The cathode advances at a speed of 160 cm / h. The anode is made of lead containing 0.75% silver. The temperature of the electrolyte is 50 ° C. and its flow rate is 660 cm / min. A recorder keeps

  the measured values of the activation overvoltage.

  The electrolyte based on manganese sulphate contains 45 g / l of manganese sulphate, 135 g / l of ammonium sulphate and 0.1 g / l of sulfur dioxide, as well as variable amounts of glue, of copper, nickel, zinc and antimony. The pH of the electrolyte is equal

  at 7.0. The electrolytic deposition of manganese has a density

  current of 400 A / m2 And requires the presence of 8 to 16 mg / l of glue in the purified electrolyte so that the deposits are smooth and give an optimal yield.

  badly running. The values of the power surge

  in the case of the electrolyte which has undergone

  The specific requirements are shown in Table II.

Cu glue additions

0 -

4 -

8 -

* 12 -

-

24 -

TABLE II

  Electrolyte in Sl Ni Zn Sb Activation overvoltage mV -

0 5

0 10

16 10

- 1

2 - -

- - 0,5 -

_- - 1

_- - 1

- - - 1

- - - 10

_ _ - 25

_ _ - 25

_ _ - 25

- - - 25

- - 1 1

- - 1 10

16

0

16

246Q491

  It is noted from the results of the table that glue acts as a polarizing agent, that copper, zinc and antimony play the role.

  denolarizing agents and that nickel is practically

  inactive. Thus, increasing amounts of adhesive have the effect of increasing the values of the activation surge while the copper, the zinc

  and antimony have the opposite effect. The results

  Also, the optimal concentrations of glue in the purified electrolyte, between 8 and 16 mg / l, give the activation surge of values between 174 and 183 mV, and that the amount of glue must

  to be increased when depolarizing agents (impure-

  are present at low concentrations, so that the activation potential

  within the desired range of 174 to 183 mV. Lors-

  that the concentration of impurities exceeds a few milligrams / liter, the operation of purification of the electrolyte must be accentuated. In this respect, the test results also show that the effectiveness

  purification can be advantageously controlled

  also by measuring the power surge

electrolyte.

EXAMPLE 3

  This example shows how the activation surge measurements can be used

  for the adjustment of electrolytic deposition of nickel.

  The values of the activation overvoltage are measured

  at 550C, with a current corresponding to a den-

  1 mA / cm. The cathode is a 1.19 mm diameter copper wire with a length / area ratio

  2.51 cm / cm. The calculated minimum speed of movement

  The cathode in the electrolyte is 0.98 cm / hr.

  The cathode advances in the support cathodiquezà a vi-

  capacity of 160 cm / h. The anode is made of lead

0.75% silver.

  The temperature of the electrolyte is 550C and its flow rate of 660 cm / min. A recorder keeps

  the measured values of the activation overvoltage.

  The electrolyte contains 50 g / l of nickel in the form of nickel sulphate, 40 g / l of sulfuric acid, 90 g / l of sodium chloride and 16 g / l of boric acid, as well as variable amounts of glue. and sodium lauryl sulphate. The latter substance is an adjuvant used during electrolytic nickel production to prevent the formation of pits in the deposited nickel, and the glue is added during the electrolytic coating of nickel in the form of a coating agent. equalization. The results appear in the

Table III.

TABLE III

  Additions to the electrolyte in mg / l

  glue laurylsufate tion, mV sodium

0 70

50

20 44

- 0 70

84

93

  The results show that sodium lauryl sulphate behaves as a depolarizing agent and, when present in increasing amounts, reduces the values of the activation surge, and that the

  glue acts as a polarizing agent and that,

  as its quantities increase, the values of the

  activation voltage increase. This overvoltage can be maintained at the desired values by setting the

  Adjuvant concentration that modifies the polarization.

EXAMPLE 4

  This example shows how the activation overvoltage measurements can be used for setting lead electroplating. The values of the activation overvoltage are measured with a current corresponding to a current density of 4.0 mA / cm 2. The cathode is a copper wire

  1.19 mm in diameter with a length / over-

  face of 2.51 cm / cm. The calculated minimum speed of displacement of the cathode in the electrolyte is 13.8 cm / h. The cathode advances in its support to a

  speed of 160 cm / h. The anode is made of lead

holding 0.75% money.

  The temperature of the electrolyte is 40 C

  and its flow rate of 660 cm3 / min. A recorder

  ve the measured values of the activation overvoltage.

  An electrolyte based on lead fluosilicate

  holds 75 g / 1 of lead in fluosilicate form, 90 g / l

  of fluosilicic acid and varying amounts of

  aloe extract (ECA), lignin-suleDnate

  and sodium thiosulfate. Electrolysis is effected

  killed for 24 hours at 200 A / m2 and at 40 C, using massive lead electrodes, so that it forms

  a lead deposit. The quality of this deposit is determined.

  Table IV shows the additions made

  in the electrolyte, the activation surge and

  the nature of the lead deposit for each test.

TABLE IV

  Additions to the electrolyte Surge Nature of ECA lighine-thiosulfadtivation deposition mg / 1 sulphonate te of SOMV mg / 1 dium, mg / 1 0 0 0 16 rough

0 4 0 35 "

0.5 4 0 40

1.0 4 0 43 "

1.5 4 0 46 Smooth

2.0 4 0 52

3.0 4 0 58 rough

3.0 4 50 18 "

  The results in Table IV show that

  Aloe extract and lianine-sulfonate

  both carry polarizing agents while the

  Sodium thiosulfate behaves as a depolarizing agent.

  In the electroless deposition of lead, the amount of lignin sulphonate is usually maintained at a substantially constant value, while the amount of aloe extract is adjusted so that the activation surge is maintained in the desirable range of 45 and 55 mV so that the lead deposit is smooth and even. When the desired values of

  the activation surge are exceeded, the thiosul-

  sodium fate can be added so that the value of

  this surge returns to the desired range.

  These examples concern the electro-

  lytic zinc. The moving cathode is a No. 4043 aluminum alloy wire 1.19 mm in diameter having a length / area ratio of 2.51 cm / cm. The anode is

  formed of lead-silver alloy containing 0.75% silver.

  The calculated maximum speed of movement of the car

thode is 1.06 cm / h.

EXAMPLE 5

  This example shows the effects of changes in the values of the applied current, expressed as a current density, the speed of the cathode wire,

  the temperature of the electrolyte and the flow rate thereof.

  A certain quantity of the electrolyte of the plant is analyzed and adjusted to 55 g / l of Zn and 150 g / l of H 2 SO 4. The regulated electrolyte also contains 0.01 mg / l of Sb, 0.03. mg / l Cu, 0.1 mg / l Co, 0.1 mg / l Ni, 0.005 mg / l Ge, 0.5 mg / l Cd, 30 mg / l Cl and 2 mg / i of F. The electrolyte thus set flows continuously in the test cell and the surge

  activation is measured and recorded as described.

  The results are collated in Table IVA.

TABLE IVA

  Density of current mA / cm2 0.1 1.0 1.0 1.0 1.0 1.0 1.0 1.0 0, 1 2.0 4.0 Speed of the

cathode

bile, cm / h Temperature

of electricity

trolyte, C Flow rate

electro-

  lyte, cm3 / min Activation surge mV, Test n w a '0 * The results clearly show the effect of

  parameters on the process and the need for

  standardized conditions in the practical application of

tick.

EXAMPLE 6

  This example shows the effects of varying amounts of added antimony, germanium, cobalt and glue for adjusting the electrolyte having

  the composition indicated in Example 5. The overexposure

  activation voltage is measured with a current

  corresponds to a current density of 1.0 mA / cm, a

  cathodic speed of 160 cm / h, a temperature of

  350C electrolyte and an electrolyte flow rate of

  660 cm 3 / min. An x-y recorder keeps track of

  their measured overvoltage activation. The re-

  The results are shown in Table V. In this

  overvoltage values represent the average value-

not recorded.

Additions Trial,

TABLE V

in mg / l.

  n Adhesive Sb Ge Co Overvoltage activation, mV

66 0 0 0

67 10 0 0

68 20 0 0

69 30 0 0

0 0.02 0

71 10 0.02 0

72 20 0.02 0

73 30 0.02 0

74 0 0.04 0

0.04 0

76 30 0.04 0

77 5 0.06 0

78 0 0.08 0

79 10 0.08 0

30 0.08 0

81 0 0 0.04

82 30 0 0.04

83 0 0.04 084 30 0.04 0

The results i

0 80

0 98

0 110

0 120

0 58

0 89

0 106

0 109

0 53

o 90

0 96

0 76

0 50

0 78

0 83

0 70

0 116

2.0 55

2,0,105

  state that an increase in the concentration of the adhesive causes an increase in the activation surge, and that an increase in the concentrations of the impurities reduces the overvoltage

zinc activation.

EXAMPLE 7

  This example shows that the concentration of

  glue must be increased so that the

  rant is good when increasing concentrations of impurities are present in the electrolyte, and that there are optimal ranges of glue concentration with respect to the concentrations of impurities so that

  the current efficiencies are as high as possible.

  Electrolytic samples of electrolyte from the properly regulated plant are electrolyzed,

Z462491

  - used in Example 6, after addition of variable amounts of glue and antimony and / or cobalt, in the form of antimony and potassium tartrate and cobalt sulfate respectively, in a cell, for a density of current of 400 A / m2, at 35 C and for 24 hours. The current efficiencies of the zinc deposit are determined from the ratio of the weight of zinc deposited to the weight calculated from the total amount of the current flowing in the cell to

  zinc deposit. The results appear in the table

Bleau VI.

TABLE VI

  Assay Adhesive added in mg / 10 15: -20 Sb added Co added in mg / 1 in mg / l yields

30 40 45 50

while running. %

89

94

  * Depot 0.01 0.03 0.05 0.07 0.01 0.01 0.01 0.01 0.03 0.03 0.03 0.03 48 hours The ri o0 0.05 * 0, 05 *

88 92 91 90 89 88 87 87 85

79 90 92 93 92 91 89 88 87

56 86 90 92 93 93 92 91 88

43 72 81 85 89 92 93 92 89

89 92 92 91 90 89 88 87 85

88 92 92 92 92 91 91 90 89

87 92 92 92 92 92 92 91

- 43 74 82 82 81 79 77 75

90 92 93 93 91 90 88 86

74 85 92 94 93 92 91 89

- 58 74 87 92 94 94 93 90

- - - 40 72 828383 78

  Table results clearly show

  for each concentration of antimony, the concentration

  glue must be within a range

  corresponding scale so that the yields in terms of

  the highest possible. These current efficiencies decrease when the concentrations are too low as well as when they are too high. Thus, there is a range of concentrations

  optimal glue for each concentration of antimony.

  Likewise, in the presence of antimony and cobalt, the additions of glue must compensate for the harmful effects of these impurities and there are

  optimal concentrations of glue for each concentration

  antimony and cobalt. These optimal glue concentrations are the same for 48-hour and 24-hour deposits, but current efficiencies have decreased.

EXAMPLE 8

  The values of the activation overvoltage,

  for concentrations of glue and impurities ob-

  during the tests of Examples 5 and 6 and

  Table IV and V are combined with the ranges of

  Maximum current levels for combinations of glue and impurity concentrations obtained during the tests as shown in Example 7 and Table VI. Thus, we obtain the following ranges

  values corresponding to the optimal performance in terms

  rant, depending on the ratios of the concentrations of glue and impurities as indicated by the values of the activation overvoltage. The beaches are in

Table VII.

TABLE VII

  Activation overvoltage Current efficiency range,%

mV _ _._.

75-83

79-86

83-89

86-91

95-88-93

90-94

90-94

89-93

87-92

120-86-89

83-87

  We observe from the values of the table t462491

  that the highest ranges of yields in terms of

  corresponding to the maintenance of the surge of ac--

  between 90 and 115 mV when measured at 350C.

EXAMPLE 9

* This example shows that the activation overvoltage measurements can be used for

  determination of the presence of a concentration

  in the electrolyte, relative to the concentration of impurities, and what changes in

  concentration of glue is necessary for the operation

  electrolytic zinc production is optimal.

  The tests described in Example 6 are repeated with

  the same electrolyte as in the previous examples

  teeth, and the current yields are determined as described in Example 7 and the results are combined.

  as described in Example 8. The variation is determined

  the glue concentration in mg / l, using the test results in this example, for the measured values of the activation overvoltage so that the current yield during the electrolytic operation gives a value of optimal. The results in Table VIII show the adjustment program of

  the operation of obtaining electrolytic zinc, cor-

  corresponding to specified changes in the concentration

  glue in the zinc electrolyte.

TABLE VIII

  Overvoltage activation - Necessary modification of the con-

  measured at 350 ° C, glue centering, in mg / l for mV that the current efficiency is _ optimal increase of 9 increase of 7 increase of 5 increase of 3 95 increase of 1 unchanged without change - reduction of 1 reduction of 3 120 reduction of 5 reduction of 7 reduction of 9

EXAMPLE 10

  This example shows that antimony can be

  used for the setting of the elec-

  trolytic zinc at optimal current efficiency,

  according to the measured values of the overvoltage of

vation.

  We add both glue and anti-

  monk in a series of cells for obtaining electricity

  lytic by use of an acidic electrolyte containing zinc sulphate, having the regulated composition indicated in Example 5. The adhesive is added to the electrolyte at a constant rate of 20 mg / l while the antimony

  is normally added at a rate of 0.04 mg / l.

  Activation overvoltages and current efficiencies as described in Example 9 are determined using the above-mentioned electrolyte and additions.

  glue and antimony. Optimal values are obtained

  current yields for surges

  activation from 100 to 105 mV. Variations are determined

  required concentrations of antimony in the electrolyte, in mg / l, for the measured values of the activation overvoltage, giving the optimum value

  in current output during the elec-

  trolytic, using the results of these determinations.

  The adjustment program is shown in Table IX.

TABLE IX

  Overvoltage activation - Necessary modification of the con-

  measurement, mV concentration of antimony, in mg / l, so that the current efficiency

be optimal.

  85 reduction of 0.03 reduction of 0.02 reduction of 0.01 without change without change 110 increase of 0.01 increase of 0.02 increase of 0.03

EXAMPLE 11

  This example shows that the removal of impu-

  of a neutral electrolyte based on zinc, by pre-

  cipitation with zinc powder, may be

  controlled by measurements of the activation surge.

  The impure electrolyte of the plant is purified

  by varying amounts of

  added to the electrolyte which contains anterior

  additionally added antimony

  form of antimony tartrate and potassium. The pre-

  The precipitation is carried out at 500 ° C. with stirring, with a residence time of one hour. We filter and cool

  at 350C a stream of purified electrolyte. We circulate

  Run this current in the test cell to measure the activation surge. The electrolyte is analyzed

  purified to determine the concentrations of

  purities. The results are shown in Table X.

PAINTINGS

  Sb added, mg / 1 0.75 0.75 0.75 0.75 0.75 0.75 0.75 0.25 0.50 1.00 Zinc powder added, g / l 0.5 1.0 1.5 2.0 2.5 3.0 2.0 2.0 2.0

Overvoltage

  tivation, mV Impurities in the purified electrolyte, mg / 1 Cd Cu Co Ni Sb 3, 9 1.9 0.4 0.3 2.2 2.2 0.6 3.5 4.1 3.4 1, 3 1.0 0.8 0.6 0.5 0.6 0.6 1.6 0.3 0.3 0.2 0.2 0.3 0.2 0.2 0.1 0.1 1 , 8 0.9 0.5 0.6 0.4 0.3 0.2 0.1 0.1 0.1 0, 75 0.09 0.05 0.04 0.03 0.03 0.02 0.07 0.03 0.02 w -JN No o -B

EXAMPLE 12

  This example shows how the measurements of the activation surge, for example of the type obtained

  in example 11, can be used for the de-

  termination of the corrections that must be made for the adjustment of parameters such as additions

  of antimony and zinc dust, with a view to

  the purification of the electrolyte by

  the zinc powder. The data in Table XI indicate

  the program for adjusting the purifica-

  cation with zinc powder, including

  specified additions of zinc powder or antimony salt to the zinc electrolyte,

  during purification, when the power surge

  Measured value indicates that the purification is not complete.

TABLE XI

  Activation surge Additions measured nose for neutral lyte electro powder, mV7 zinc, g / l

0

0

0.3

0.6

60 0.9

1.2

1.5

1.8

2.1

  : esses of Sb, mg / i o 0.1 0.2 0.3 0.4 0.5 0.5 0.5

Claims (29)

  1. A method for controlling an electrolytic deposition operation of a metal, with an electrolyte containing impurities, said method being characterized in that it comprises the establishment of a test circuit comprising a cell test, an electrolyte sample, a moving cathode having a surface exposed to the electrolyte, an anode and a   reference, the electrodes being immersed in the   sample, a source of constant current and a   positive measurement electrically connected to the electrodes,   the application of a low-intensity current to electri-   placed in the test cell, the intensity of the current being sufficient to cause a deposit   beginning of the metal on the cathode, the measurement of the   activating voltage at the onset of metal deposition, the measured activation surge being related to the concentration of impurities in the sample, and the setting of the metal separation operation to   metal deposition is optimal,   "corresponding to the time when metal deposition has just started and is limited to   partial of the surface of the cathode mobile by the metal.   2. Method for controlling an electrolytic deposition operation of a metal, with an electrolite   containing at least one polarizing modifier   the method being characterized in that it comprises   the establishment of a combined electrolytic test circuit   taking a test cell, a sample of electro-   lyte, a moving cathode having an electrolyte-exposed surface, an anode and a reference electrode, the electrodes being immersed in the sample, a   constant current source and a device for   electrically connected to the electrodes, the application of a low current to the electrodes placed in the test cell, the intensity of the current being sufficient for it to cause a deposit starting from   metal on the cathode, measurement of the voltage surge   during the deposit of the metal, the   measured overvoltage of activation being related to the   centering the at least one polarizing modifier present in the sample,   and adjusting the concentration of the modifying agents   polarization indicators in the electrolyte so that   the yield is optimal and the metallic deposits   be equalized during the electrolytic deposition process, the "starting deposit" corresponding to the moment when the   metal deposit has just started and is limited -   partial overlap of the cathode surface mobile by the metal.   3. Method for controlling an electrolytic deposition operation of a metal with an electrolyte   containing impurities and at least one modifying agent   polarization detector, said method being characterized in that it comprises establishing an electrolytic test circuit containing a test cell, an electrolyte sample, a moving cathode having a surface exposed to the electrolyte, an anode and a reference electrode, the electrodes being immersed in the sample, a constant current source and a measuring device electrically connected to the   electrodes, the application of a low current of   tensity at the electrodes placed in the cell of   sai, the intensity of the current being sufficient for   causes it depositing the metal starting on the cathode, measuring the activation overvoltage at the time of the   beginning deposit of metal, the measured overvoltage of   tivation being related to the ratio of the concentrations of impurities and polarization modifiers   present in the sample, and the setting of this ratio   concentration in the electrolyte so that it is optimal and the metallic deposits formed during electroplating are equalized, the "starting deposit" corresponding to the moment when the deposit   metal has just started and is limited to a   partial coverage of the surface of the moving cathode by the metal.   4. Method according to one of claims 2 and   3, characterized in that the concentration of the agents   polarization factor is adjusted by   tion of the quantity of agent already present or by   of a second polarization modifier   whose characteristics of modification of the Polish   are opposed to those of the modifying agent. already present.   5. Method according to claim 3, characterized in that said concentration ratio is adjusted by changing the concentration of impurities in the electrolyte.   6. Process according to claim 3, characterized in that said concentration ratio is regulated by   modification of the concentration of modifying agents   polarization in the electrolyte.   7. Process according to claim 6, characterized in that the concentration of the modifying agents of   polarization is modified by increasing the quantity   already existing agent or by addition of a second   polarization modifying agent whose characteristics   polarization change ticks are opposite   to those of the modifying agent already present.   8. Process according to any one of the claims   1 to 3, characterized in that the intensity of the   rant corresponds to a current density of   0.01 and 4.0 mA / cm of exposed surface of the mobile thode.   9. Process according to any one of the claims   1 to 3, characterized in that the low current   intensity has a constant intensity.   10. Process according to any one of the claims   1 to 3, characterized in that the overvoltage of   tivation is measured continuously or intermittently tence.   11. Process according to any one of the claims   1 to 3, characterized in that the sample of   the electrolyte is kept in motion, in particular by continuous circulation of an electrolyte stream in the test cell.   12. Process according to any one of the claims   1 to 3, characterized in that the intensity of the   which is sufficient for it to cause a starting deposit of the metal, has a value sufficient for at most 30% of the surface of the moving cathode   exposed to the electrolyte overlap with deposited metal.   13. Process according to any one of the claims   1 to 3, characterized in that the moving cathode advances at a substantially constant speed, so that continuous or intermittent.   14. Process according to any one of the claims   1 to 3, characterized in that the moving cathode advances in the electrolyte sample at a substantially constant speed which is at least equal to a minimum speed R min, expressed in cm / h, given by the formula R. _abcd min xy where a represents the ratio of the length to   the surface of the cathode, expressed in cm / cm 2, b represents   the current density, expressed in A / cm,   has the exposed cathode surface, in cm2, d represents   the electrochemical equivalent of the deposited metal, in g / Ah, x represents the cathode fraction covered by the metal, and represents the weight of deposited metal   per unit of cathode area, in g / cm, this   substantially constant pitch being advantageously   between 10 and 500 times the minimum speed.   15. Process according to any one of the claims   1 to 3, characterized in that the electrolyte placed in the test cell is maintained at a substantially constant temperature, and this constant temperature is between 20 and 75aC.   16. Process according to any one of the claims   1 to 3, characterized in that the electrolyte is sulfate-based, and the moving cathode placed in the test cell is in the form of a wire or a strip.   of a subject selected from the group that includes   minium and suitable alloys of aluminum.   17. Process according to any one of the claims   1 to 3, characterized in that the electrodes are placed in the cell in a fixed position, compared to others.   18. Process according to any one of the claims   1 to 3, characterized in that the measurement of   activation voltage is performed by recording values of the activation overvoltage based time.   19. Process according to any one of the claims   1 to 3, characterized in that the metal is selected from the group consisting of zinc, copper, lead, iron, cobalt, nickel, manganese, chromium, tin, cadmium, bismuth, indium,   silver, gold, rhodium and platinum.   20. Method according to one of claims 2 and   3, characterized in that the deposited electrolytic metal   is selected from the group that includes zinc,   copper, manganese and nickel, and the modifying agent   polarization is a gelatin glue.   21. Process according to any one of the claims   1 to 3, characterized in that the electrolytically deposited metal is selected from the group consisting of lead and nickel, and the moving cathode is formed of a copper wire.   22. Process according to any one of the claims   1 to 3, characterized in that the metal is selected from the group consisting of zinc, copper and   manganese, and the moving cathode is a thread of a   chosen in the group that includes aluminum 2462491 | and its alloys.   23. The method of claim 5, characterized in that the deposited metal is zinc, and said concentration ratio is adjusted by changing the concentration of antimony in the electrolyte. 24. The method of claim 6, characterized in that the deposited metal is zinc, and said concentration ratio is adjusted by changing the   effective concentration of pH-modifying agent   in the electrolyte, this modifying agent   being advantageously a gelatin glue.   25. The method of claim 24, characterized in that said concentration ratio is adjusted by adjusting the concentration of the adhesive to a value for which the measured activation overvoltage   at a temperature between 25 and 40 ° C is   between 70 and 150 mV, and the activation surge   is measured for a low intensity current corresponding to   at a current density of between 0.01 and 4.0 A / cm 2 and preferably between 0.1 and 0.4 A / cm 2 of   exposed surface of the moving cathode.   26. Process according to claim 3, characterized   in that said ratio of concentrations in the elec-   trolyte is regulated by simultaneous modification of the concentration of the impurities and the concentration of   minus a polarizing modifier.   27. The method of claim 25, characterized   in that the concentration of the glue is increased when   that the measured value of the activation overvoltage decreases below about 70 mV, and is reduced when the measured value of the activation overvoltage exceeds 150 mV.   28. Process according to claim 5, characterized   in that the deposited metal is zinc, the modifying agent   polarization is a gelatin glue, and   the impurity is formed of dissolved antimony, the said   port of concentration being adjusted by adjusting the concentration of antimony to a value at which the   activation overvoltage measured at a   between 25 and 400C is between 70 and 150 mV, this activation overvoltage being measured with a constant current of low intensity corresponding to a current density of between 0.01 and 4.0 A / cm 2, preferably between 0, 1 and 0.4 A / cm 2 of area exposed of the moving cathode.   29. The method of claim 25, characterized in that the concentration of antimony is increased when the measured value of the activation surge.   falls below about 70 mV, and is reduced when   that the measured value of the activation overvoltage de- passes 150 mV.