NL8004294A - METHOD FOR CONTINUOUSLY CHECKING THE PRECIPITATION OF A METAL AND AN APPARATUS FOR USING THIS METHOD - Google Patents

Description

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Title: Method for continuously monitoring the precipitation of a metal and device for the application of this method.

The invention relates to a method and apparatus for continuously monitoring the electron deposition of metals and more particularly to a method for measuring the activation over potential of metal deposition and controlling the electrolyte cleaning and electron deposition processes. in response to deviations from recorded values of the cver potential from the desired values, and an apparatus for applying this method.

Electron deposition of metals, such as electrowinning, electro refining and electroplating, uses electrolytes containing impurities which, when these courts are present at certain critical concentrations, can be precipitated with the metal and thereby contaminate the precipitate or redissolve with a corresponding decrease in the efficiency of the metal deposition process In order to reduce the concentration of irritants in the electrolyte cleaning, certain processes can be used for electrolysis In addition to cleaning, one or more polarization additives may be added The electrolyte is added to help provide smooth and leveled deposits, and also to reduce the influence of residual impurities.

These polarization additives serve to change the polarization. The polarization can be changed by increasing or decreasing the concentration of a polarizing agent. The polarization can also be changed by decreasing or increasing the concentration of a depolarizing agent. These agents, both polarization as depolarizing agents, may be present in the electrolyte when it is supplied to the cells from the cleaning plant or may be substances, such as animal glue, which are added to the electrolyte for controlling the electron deposition process. the term "polarizing agents" includes agents of both the polarizing and depolarizing type. It is further noted that a particular substance will not always work in the same way in different processes. Therefore, a substance may be subject to a particular process. working as a polarizer, in another process, 800 4 2 94 2 using another metal as a depolarizing agent, or inactive in a third process. Similarly, it is known that contaminants "catalyze" the influence of the polarizing agents, therefore, certain tests 5 may be required to determine which polarizing agents are suitable for a particular process »

The procedures currently used to determine the purity of the electrolyte are based on chemical analyzes and determining current efficiencies as a measure of the performance. impurity content, while those for adding suitable polarizing agents are simply based on maintaining a constant concentration of agents in the electrolyte despite variations in the quality of the electrolyte. These processes lead to variations in the quality of the deposited metal and the efficiency of the electron deposition process.

The standard technique includes a number of references, which relate to methods of determining the influence of impurities and additives on electron deposition processes for metals and determining the purity of electrolyte solutions.

United States Patent 3,925,168 discloses a method and apparatus for determining the content of colloidal material, adhesive, or active curing agent in a copper electroplating bath by measuring the over-potential strain density relationships of solutions of varying known reactant content and comparing the results with that of a solution with a known galvanizing behavior and a known crude agent content. Canadian Patent 988,879 discloses a method of determining and controlling the cathode polarization voltage in relation to the current density of a lead refining electrolyte, wherein the slope of the polarization voltage current density curve is a measure of the amount of additives and wherein the effectiveness of additives is changed when the cathode polarization voltage reaches values outside the predetermined range of values.

A number of studies can be found in the published literature. 35 which relate to similar methods. For example, CL Mantell et al. (Trans. Met. Soc. Of ΑΙΜΕ, 236, 718 - 725, May 1966) have considered the utility of flow potential potential as an analytical tool for 800 4294 3 I * checking manganese electrowin solutions on metallic contaminants identified. Polarization curves which are trafficked with the formation of hydrogen have been found to be sensitive to metallic contaminants which affect the cathode surface and thereby alter the hydrogen voltage. ïï. S. Jennings et al

Metallurgical Transactions, U, 921-926, April 1973, a method for measuring cathode polarization curves of copper sulfate solutions containing varying amounts of additives by varying an applied voltage and recording the relationship between the voltage and the current density. 0. Vennesland et al. (Acta Chem. Scand.

- 27, 3, Sh6 - 850, 1973) Studied the influence of antimony, cobalt and beta-naphthol concentrations in a zinc sulfate electrolyte on the current-potential core frame by changing the cathode potential at a programmed rate, by changing the curves and compare the curves 15 'with a standard. TU Anderson et al., In Metallurgical Transactions B, 73, 333 - 338, September 1976, discuss a method for measuring the concentration of adhesive in a copper refining electrolyte by determining polarization scanning curves, which, by comparison, provide a measure of provide the adhesive concentration. In the U.S. patent-20 script h-1 hS. h-37, the use of a cyclic stress measurement to evaluate zinc and copper sulfate electrolytes is discussed.

Cyclic voltage diagrams, which include both the cathode deposition and the anode solution portions of the current-potential relationships, and polarization curves are recorded as a means of approximating the amounts of impurity and additives in zinc sulfate electrolyte.

This first group of references describes methods in which a metal is deposited on an electrode and where current or current density potential curves represent cathode polarization potentials with respect to varying currents and / or current densities.

T. R. Ingraham et al. In Can. With. Quarterly, 11.2, 1 * 51 - l * 5l *, 1972 a meter for measuring the quality of zinc electrolytes to measure the amount of cathodic hydrogen released during the electron deposition of zinc, and the current efficiency to indicate by comparing the weight of the precipitated zinc with both the amount of zinc expected and the hydrogen evolution rate. U.S. Pat. No. 9qa k k.013. ^ 12 describes a method of adhering to the purity of a cleaned zinc sulfate solution by exposing a sample of the solution to electrolysis, burning the gases formed, and internal to measure pressure in the combustion chamber, which is an indirect measure of the power efficiency. M. Maja et al. (J. Electrochem. Soc., 118 ', 9, 1538-1515, 1971) and P. Benvemiti et al. (La Metallurgia Italians, 6θ, 5, ^ -17 - ^ - 23, 1988} "describe methods for detecting contaminants and measuring the purity of zinc sulfate solutions by depositing zinc and then precipitating zinc 10 electrolytic pathway and establish a relationship between the calculated current level and the contamination level.

This second group of references relates to methods and devices for determining the electrolyte purity, wherein an electrolysis of solutions is used to determine the current efficiency, which is then related to the electrolyte purity.

U.S. Patent Application Serial No. 052,921 discloses a method of controlling a process for recovering zinc from a zinc sulfate electrowinning solution, wherein a potential, which is between electrodes in a test cell, contains a sample of the solution is applied, at a constant rate at a current with a value substantially equal to zero, is decreased, the decreasing potential is measured, ending the potential decrease at a value corresponding to the point at which zinc deposition begins, the activation overpotential is determined, the activation overpotential is related to the impurity concentration, and the process is set to obtain maximum zinc recovery.

Although in this method it is not necessary for the electrolysis solution to determine current efficiencies or to measure polarization potentials against varying currents or current densities, certain drawbacks still arise with this method. The process is not continuous, and it is necessary to determine the value of the activation excess potential for each sample by the applied potential each time until the value at which zinc deposition begins, and the current density from the value, which is substantially equal is to decrease to zero for a further small decrease in potential.

8004294 \ # 1 5

It has been found that it is unnecessary to reverse the applied potential. layers to determine the value of the activation excess potential. It has been determined that the activation over potential can be measured as a function of time at a controlled, low current and that the cleaning and electron striking processes can be controlled by correcting the amounts of reagents in response to deviations from recorded values of the overpotential to desired values. to return to the desired optimal values.

The method and apparatus of the present invention relates to the metal electro deposition test using electrolytes prepared for electro-galvanizing of metals used in metal recovery processes by electrowinning. or which are used in electron refining processes of metals. In many cases, the electron deposition processes include a cleaning process. The method and apparatus according to the invention can be used in the electron deposition processes for metals such as zinc, copper, lead, iron, cobalt, nickel, manganese, chromium, tin, cadmium, bisbuth, indium, silver, gold, rhodium and platinum.

When a metal ion-containing solution or electrolyte is exposed to a controlled, small current, which is supplied to electrodes, which are arranged in a test cell containing the electrolyte, and the current has a value sufficient to to cause deposition of metal on a suitable cathode, consisting of a material different from the metal being deposited, the value of the resulting potential represents the activation excess potential for the metal deposition on the suitable cathode. When the cathode is a movable cathode, values of the activation over potential can be measured and recorded and the electro deposition process of the metal can be controlled in response to the measured and recorded values of the activation over potential. An inch precipitate is defined in this context as the deposition of a metal that has just begun and is limited to a partial coating of the movable cathode surface by the metal. The measured values of the activation excess potential can be used as a direct measure of the contamination concentration (i.e. the efficiency of a cleaning process), the concentration of the polarization influencing

Ann *? 94 6 agent, and the concentration of the polarizing "affecting agent relative to the impurity concentration in the electrolyte in a process using the electron deposition of a metal comprising a cleaning process, in response to measured values of the 5 activation over potential, various changes are possible, either individually or in combination, the cleaning process can be adjusted; the concentration of the polarizing agent in the electrolyte can be adjusted, or the condensation of the polarizing agent in the electrolyte can be adjusted 10 to relative to the contaminant concentration; and the contaminant concentration can be adjusted to provide optimum efficiency and leveled metal deposition in the electron deposition process.

The invention therefore provides a method for re-15. gelling a process for the electron deposition of a metal using an electrolyte containing concentrations of impurities, the method comprising providing a test chain comprising a test cell, an electrolyte sample, a movable cathode with a surface which is attached to the electrolyte exposed, an anode and a reference electrode, with the electrodes immersed in the sample, a constant current source and measuring means electrically connected to the electrodes, with a small current applied to the electrodes in the test cell, which current is sufficient to cause an inchoate deposition of the metal on the cathode, the activation over-potential at the point of inchoate precipitation of the metal is measured, the activation over-potential is related to the concentration of impurities in the sample, and the process metal recovery is set to obtain optimum metal deposition n, where the inch precipitate is defined as the metal deposit which has just begun and is limited to a partial coating of the movable cathode surface by the metal.

In a second embodiment, the method comprises controlling a process for the electron deposition of a metal using an electrolyte containing concentrations of at least 1, the polarizing agent, measuring the activation excess potential according to said method, the measured activation excess. 8004294 I Λ Ί potential - is related to the concentration of the at least one polarizing agent in the sample, and concentration of the polarizing agent in the electrolyte is adjusted to obtain optimal efficiency and a gene -5 taught metal deposition in the electron deposition process, where an inch precipitate is defined as the deposition of a metal that has just begun and is limited to a partial coating of the movable cathode surface by the metal.

In a third embodiment, the method of controlling comprises a process for the electron deposition of a metal using an electrolyte, which contains impurity concentrations and at least one polarizing agent, measuring the activation excess potential according to said method , the measured activation excess potential is related to the concentration ratio between the contaminants and the at least one polarizing agent in the sample, and the concentration ratio in the electrolyte is adjusted to obtain optimum efficiency and leveled metal deposition in the electron deposition process wherein an inch precipitate is defined as the precipitate of a metal that has just started and is limited to a partial coating of the movable cathode surface by the metal.

An apparatus used in the method of measuring the activation overpotential of a metal comprises a test circuit, which includes a test cell, an electrolyte sample, a movable cathode, an anode, a reference electrode, constant current supply means and means for measuring the activation excess potential. The test cell consists of a small vessel with a circular, square or rectangular cross section, consisting of a suitable material, which preferably resists corrosion by the electrolyte and is large enough to accommodate a suitable electrolyte sample. If desired, the cell can be vented to remove formed gases. In the cell, means are present to allow continuous addition of electrolyte to and discharge of electrolyte from the test cell. The three electrodes are immersed in the electrolyte sample and are movably positioned in the cell at constant distances from each other.

The movable cathode consists of an electrically conductive material 800 42 94. 8 terial, that differs Tan. The metal which is deposited is suitable material to be used in the Bet electron deposition process of Bet metal to be deposited and which is compatible with Bet electrolyte used in the Bet process. The material.Tan the movable cathode can be the same as the material used for the cathode (nj in Bet electron deposition process, provided the material is different from Bet metal, which is deposited, for example, in Bet controlling an electron deposition process ,. using a sulfate-based electrolyte, such as in a process for depositing zinc, copper, manganese, nickel, cobalt, iron and cadmium, the movable cathode preferably from aluminum or a suitable aluminum alloy. a movable cathode of other available material such as, for example, titanium, iron, steel, stainless steel, nickel, lead, copper or the like, may be used in an electron deposition process, or use a movable flexible plastic electrode of a suitable electroconductive material.

The movable cathode has a constant area of its surface in contact with the electrolyte in the cell. It has been found that a surface area in contact with the electrolyte in the 2. 20 cell, m an area of about 0.1 to 1 cm gives particularly good results. The movable cathode preferably consists of a wire or strip which is present in and can move through a cathode holder.

The container surrounds the movable cathode subject to the constant surface area in contact with the electrolyte. Means 25 are provided to move the movable cathode intermittently or continuously through the cathode holder and thus in contact with the electrolyte. These members preferably include means for continuously moving the cathode at a constant speed. The use of a movable cathode in the form of a wire or strip has a number of advantages. Usually no special preparation of the cathode surface is required, wires or strips are readily available and inexpensive and test results are reproducible. The movable cathode does not need to be replaced and therefore allows intermittent or continuous operation. Most commercially available suitable wire or strip cat bottom materials are useful as long as they have a smooth and clean surface, good corrosion resistant properties in the electrolyte; be duetile enough to pass through the cathode holder 800 4 2 94 9. l "move, and elefcfcrocB.emis.cLe have properties that provide reproducible test results.

The anode consists of a suitable inert material, which allows gas gas resolution. For example, with a sulfate electrolyte 5, a suitable anode material is a lead-silver alloy. It has been found that with sulfate electrolytes, anodes made from a lead-silver alloy containing 0.75% silver must suffice and that with chloride-containing electrodes other than those containing concentrated hydrochloric acid, platinum will suffice. Other suitable inert materials for the anode include carbon and graphite. The reference electrode may be one of a number of suitable reference electrodes, such as, for example, a standard calomel electrode (SCE).

The three electrodes are electrically connected to a constant current source and means for measuring the activation excess potential.

The constant current source is connected to the anode and the movable cathode. The activation over potential measuring means measures the over potential on the movable cathode relative to the reference electrode. The measured activation excess potential can be recorded, for example, in a meter or other suitable reading instrument, or can be recorded in the form of a line as a function of time. The electrodes are fixed with respect to. mounted removably in the cell. It has been found that good results are obtained when the surface area of the movable cathode, which contacts the electrolyte, is kept at a constant distance of approximately U em from the surface of the anode and when the reference electrode is disposed between the cathode and the anode such that the end of the reference electrode is rigid about 1 cm from the surface area of the movable cathode in contact with the electrolyte, but does not cover this area. If desired, a membrane or semi-permeable membrane can be arranged in the test cell between the anode and the cathode to provide - separate anode and cathode compartments; the reference electrode is then housed in the cathode compartment.

Suitable means may be present to maintain the electrolyte in the cell at a suitable constant temperature. These members may be provided with controlled electrolyte heating / cooling means before it is supplied to the cell, or with a controlled 800 42 94 JO.

heating / cooling coil, which is the test cell is set up, or a bath. with constant temperature or the like,

In the process of the invention, a sample of electrolyte, which may consist of a base, an acid or a neutral material, and which may contain additives, which sample may be obtained from either an electrolyte cleaning process or a metal electro deposition process. , added to the test cell * To ensure achievable results, keep the sample in motion, for example by agitation or circulation. Preferably, the sample is moved. by continuously passing a small stream of electrolyte through the test cell. In this preferred embodiment, a sample of the electrolyte is continuously withdrawn from the cleaning or electron deposition process, passed through the test cell, and then returned to the respective process. Electrolyte, which is added to the cell, may be used at certain concentrations of the electrolyte components are adjusted, such as, for example, the metal and acid content, to minimize any variation in the test method, which may be caused by variations in component concentrations in the electrolyte.

When electrowinning zinc, both the zinc and acid concentration can be adjusted. A setting of the zinc level at 150 g / l can be used. The zinc concentration can also be adjusted to 55 g / l and the acid concentration to 150 g / l. Concentrations in the range of 1 g / l to 250 g / l zinc and 0 to 250 g / l sulfuric acid appear to be equally satisfactory when used in the test cell. When using a continuous sample flow, the excess electrolyte is removed from the cell by, for example, an overflow device.

The movable cathode is advanced through the cathode holder intermittently or continuously at a speed sufficient to permit an inchoate deposition of metal. Preferably, the movable cathode is continuously moved at a constant speed. The speed depends on the ratio between the cathode length and the cathode surface area, the current density value for an inchoate deposit, the surface area of the cathode exposed to the electrolyte, the fraction of the exposed cathode area, coated with deposited metal, and the weight of the deposited metal. The speed is also somewhat dependent on the degree of movement 8004294

φ X

IJ

From the electrolyte in the cell. Therefore, the speed at which the cathode is moved through the cathode holder and therefore through the electrolyte can vary over a range of values. At speeds lower than the minimum speed, the measured potential will be that of metal on that metal and not the activation potential of metal on the movable cathode. At rates that are several orders of magnitude greater than the minimum rate, such as, for example, a thousand times higher, the amount of metal deposited may be insufficient to obtain reliable and reproducible activation excess potential values.

10. Preferably, the speed at which the cathode is moved is about ten to five hundred times the minimum speed. The minimum speed can be calculated using the following formula: R, = S52i, «ft,. min xy where:

ie. . . . O

J a represents the cathode length surface area ratio m cm / cm; 2, b represents the current density, A / cm; 2c represents the free cathode area m cm; d represents the electrochemical equivalent for the metal being precipitated, g / Ah; x represents the fraction of the free cathode region to be coated with metal; and y represents the weight of the cured metal per unit of the cathode surface area, g / cm.

When the cathode is moved intermittently, the average speed of movement should be at least equal to the minimum speed of continuous movement, while the periods in which the cathode is stationary should not exceed the period leading to more than inch precipitation.

A small current is applied to the anode and the movable cathode to cause an inchoate deposition of metal on the cathode. Preferably, the small flow is controlled to have a constant value. The flow should be limited to small values which cause only an inch of precipitation. This is necessary to avoid the deposition of metal on previously deposited metal, thereby obtaining over potential values of a metal 8004294 12.

deposition on this metal instead of values of the desired activation overpotential of the metal deposition on the material of the movable cathode. Therefore, the deposition of too much metal should be avoided. Preferably, no more than about 10 to 30 degrees of the cathode surface in contact with the electrolyte should be covered with precipitated metal at any one time. Currents, expressed in current density, which cause an inchoate deposition on the cathode moving at the above speeds, should be at least 0.01 mA / cm. The strain densities with respect to the movable cathode, which will be discussed later, should be considered as referring to the free surface of the cathode. movable cathode. Below a current value, expressed as a current density, of 0.01 mA / em, special precautions are needed to obtain a reliable measurement. In practice, the current, expressed in the current density, should be in the range from 0.01 to U, 0.2 mA / cm. Values of the current, which are higher than the equivalent 2 current density of U, 0 mA / cm, require impractically large cathode velocities. Preferably, the current values, expressed in the 2 current density, are in the range from 0.1 to 0.1 U mA / cm. For an incho-copper copper precipitate at a current density of 0.005 mA / cm on a movable aluminum cathode, which has a length to surface ratio of 2.0 h, and a free area of 0.25 cm, of which 20% is coated with deposited copper and on which 7x10 g copper / cm is deposited, the minimum speed calculated from the above formula is about 0.20 em / h. Using the same values for the parameters, the minimum speed for lead is about 0.65 cm / h, for zinc about 0.21 cm / h and for manganese about 0.17 cm / h.

The temperature of the electrolyte, which is measured, can be kept constant. Changes in temperature affect the measured activation over potential, i.e., for example, a decreasing temperature increases the measured over potential. If desired, the cell and its contents. thereof set at and maintained at a suitable, controlled, constant temperature, which may be between 0 and 100 ° C and preferably between 20 ° and 75 ° C. If desired, the constant temperature may be approximately the same as the temperature of the electrolyte in the electron deposition and / or cleaning process, which process is involved. If the temperature is not kept constant at 800 4294 J3, the wairdeyan the actuation yoyer potential must be corrected for the temperature variations so that the results of the tests are comparative.

The activationoyer potential is used continuously or intermittently. 5 and recorded in the point of inch precipitation of metal on the movable cathode. For practical application of the method of the invention, the activation yer potential is expressed as the value of the measured over potential at a current, corresponding to a current density in the range of about 0.01 to 1 µ U, Q mA / em from the free cathode surface, preferably in the range of about 0.1 to 0.1 h mA / em. The activation excess potential is recorded in a suitable readout instrument or recorded as a function of time. The recorded values of the over potential are kept in a preferred range. This is done by making adjustments in the cleaning and electron deposition processes when the values of the over-potential deviate from the preferred range of values.

The activation over potential has certain values for each metal depending on the electrolyte composition. Since each electrolyte composition can be cleaned to an optimum degree, has an optimal range of content of the polarizing agents and has an optimal range of the contents of polarizing agents relative to its impurity content, the activation excess potential will be similar manner have a range of values necessary to obtain the desired optimal results. Any of a number of suitable polarization-influencing agents of known type may be used in the electron deposition process of any metal. One of the most commonly used polarizing agents is an animal adhesive. It has been found that increasing impurity concentrations can lead to a decrease in the activation over-potential, while with increasing polarizing agent concentrations, the over-potential increases, while with increasing depolarizing agent concentrations, the oven potential decreases. If the value of the measured activation oven potential when cleaning the electrolyte is too small, the impurity concentration for an optimal metal recovery in the electron deposition process is too large. Therefore, depending on the electrolyte composition, the acti- 80042 94

Jlk suspension overpot one. indicator of the efficiency of the cleaning process and deviations from the optimum operation can be corrected by adjusting the cleaning process relative to values of the activation oven potential, thereby lowering the contaminant concentration. Insufficiently cleaned electrolyte can be further cleaned in an additional cleaning operation or by recirculation in the cleaning process. For example, in zinc electrowinning, a correction of the zinc dust cleaning process can be obtained by adjusting the temperature of the cleaning process, adjusting the duration of the cleaning process, increasing the amount of zinc dust used, or the amount of depolarizing agent, such as antimony, copper or arsenic, which is present in the electrolyte in ion form.

If the value of the activation excess potential measured for the electrolyte in the electrolyte deposition process is too low, the concentration of the polarizing agents in the electrolyte is insufficient to adequately control the cathode metal deposition or the impurity concentration is too high. large relative to the concentration of the polarizing agents. On the other hand, if the value is too high, the concentration of the polarizing agents is too high and consequently a decrease in efficiency and a rougher metal deposition gum occur. Therefore, depending on the composition of the electrolyte, the activation excess potential is an indicator of the efficiency of the electron-striking process and deviations from the optimal action can be corrected by changing the concentration or nature of the polarizing agents or by changing the concentration ratio between the polarizing agents and impurities in the electrolyte as necessary in relation to the activation potential values. A change in the concentration of the polarization-influencing agents can be suitably effected by increasing or decreasing the amount of addition of the polarization-influencing agents to the electrolyte. A decrease in the impurity concentration can be obtained by a more effective cleaning of the electrolyte before the electron deposition process.

In the case of the presence of too great a concentration of the polarization-influencing agents, a correction can also be made by adding an agent to the electrolyte which is opposite to the polarization agent. has influencing properties, and is sheeted in such a way that the ratio of impurities concentrations and the polarizing agents are sought on the correct level. Adding a depolarizing agent, if necessary, San on a Suitable means are effected by a controlled addition of a metal salt, which serves as a depolarizing agent, which addition leads to a correction of the ratio between the concentrations of the impurity and the polarizing agent. For example, 10 "in the electro-fins of zinc, antimony are added as ion depolarizing agents. '

The method according to the invention has a number of applications in processes for the electron deposition of metals. Therefore, the electrification can be used before, during and after the cleaning of the electrolyte and before, during and after the electron deposition of metal from the electrolyte.

For example, when cleaning a zinc sulfate electrolyte when electrowinning. zinc, the preferred methods are used to determine the degree of iron oxide removal and the degree of iron oxide removal from contaminants such as arsenic, antimony and germanium.

In the electron deposition process, the spray can be successfully used to determine the required amount of the polarization-influencing agents alone and in relation to the contaminant concentration, the required amount of contaminants in relation to the concentration of the polarizing agents, the need to adjust the electrolyte supply, or the electrolyte in the process, and the quality of the circulated electrolyte.

The invention will now be further elucidated with reference to a number of examples which are not to be taken in a limiting sense.

In these examples, rates of the activation potential were measured using a test cell with a sample volume of 500 ml. A volume of electrolyte was passed through the cell. Immersed in the electrolyte in the cell was a movable cathode, which cathode consisted of a wire which was housed in and could be advanced through a stationary cathode holder which was rigid in the cell 800 4 2 94 2 J6.

and exposing Q, 25 cm of the cathode to the electrolyte, an anode and an SCE, which was placed between, the cathode and the anode. free area-of the movable. cathode was spaced from the surface of the anode and 5 cm apart. The end of the SCE was spaced at a distance of 1 cm from the cathode, such that the end was not directly aligned between the anode and the free area of the cathode. The temperature of the electrolyte moving through the test cell was adjusted to the desired value. The anode and the movable cathode were connected to a constant current source, and the SCE and the cathode were connected to the activation over-potential measuring devices using a voltmeter with digital readout and a recording device. a constant current was stirred for an inch of precipitate of metal on the movable cathode and the values of the activation-15 'ring excess potential were measured and recorded. The fraction of the free cathode surface area covered with metal was 0.1.

Example ~ 1

This example illustrates the manner in which the activation crver potential measurements can be used to control the electron deposition of copper. The values of the activation excess potential were measured using a current corresponding to a current density of. 1.0 mA / cm. The cathode consisted of a wire of no.

1100 aluminum alloy with a diameter of 1.19 mm and a ratio of length to surface area of 2.51 cm / cm. The minimum speed of movement of the cathode through the electrolyte was calculated to be 1.09 cm / h. The cathode was advanced through the cathode holder at 160 cm / h. The anode was an anode consisting of lead and $ 0.75 silver. The electrolyte temperature was 50 ° C and the electrolyte flow rate was 660 ml / min. The values of the measured activator potential were recorded in a recording device.

The copper sulfate electrolyte contained 20 g / l copper and 150 g / l sulfuric acid, as well as varying amounts of added glue, chloride and antimony.

The electron deposition process was performed at a current density of HOO A / m for a period of 2 hours. After the precipitation time of 2 hours, the precipitate was analyzed for surface quality and its sensitivity. Ductivity was determined by the number of times, 8004294 η - that the precipitate could be bent through 180 ° before cracks occurred.

The amount of electrolyte additives, the average of the recorded values of the activation excess potential for each electrolyte composition and the qualities of the deposited copper are shown in Table 1 below.

Test Additions to the electrolyte Activation Ductility Nature of Ho. adhesive C1- Sb ion over potential l8o tube precipitation mg / 1 mg / 1 mg / 1 mV

Ho.

1 0 118 10 rough 2 2.5 - 122 T5 rough 3 5.0 - 132 Ifc smooth b 7.5 - 140 20 smooth 5 10 - 1b2 15 rough 6 20 150 16 rough 7 0 1 - 129 29 rough 8 0 10 1U0 25 raw 9 0 30 - 1 ^ -5 10 raw 10 5 1 1 ^ 0 6 smooth 11 T, 5 1 - 1 ^ 3 T raw 12 5 10 - 180 7 raw 13 5 30 - 182 10 raw 1¼ 0 - 300 118 12 raw 15 2.5 - 300 125 7 smooth 16 5 - 300 128 22 smooth 17 10 - 300 153 18 raw 18 20 - 300 16b 7 raw 19 0 10 300 lbo 25 raw 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 smooth 2b 5 30 20 180 16 smooth 800 4294 18

Results of test 1-6 show that the values of the activation overpotent increase substantially with increasing amounts of glue in the electrolyte. To obtain a smooth precipitate, the activation overpotential must be controlled in the area. of about 130 to 5 1 ^ 0 mV and the amount of adhesive in the electrolyte should be set when the measured value of the activation excess potential is outside this range.

The results of Runs 7-13 show that the presence of chloride in the electrolyte leads to crude precipitates which are in the 10-10. the presence of glue also makes it less ductile.

The results of the test 1 h - 18 show that when an electrolyte contains antimony and increasing amounts of glue, the values of the over potential increase, but that the results of the ductility test of the. precipitation become erratic. Chloride must also be present to correct this erratic behavior. As is apparent from the results of Runs 19-2h, the presence of about 10 mg / l chloride, as well as 5 mg / l glue, leads to smooth inductile deposits in the presence of antimony. In such a system, the values of the activation excess potential are about 180 mV, and the system can be controlled at about this value by properly adjusting the concentration of either glue, or chloride, or both.

Example 2

This example illustrates the manner in which the activation excess potential measurements can be used to control the manganese electron deposit. The values of the activation excess potential were measured under a current corresponding to a current density of 1.0 mA / cm. The cathode consisted of a wire of No. 1100 aluminum alloy with a diameter of 1.19 mm and a ratio between the length 2 and the surface area of 2.51 cm / cm. The minimum movement speed. The cathode through the electrolyte was calculated to be 0.92 cm / h. The cathode was advanced at a rate of 160 cm / h.

The anode consisted of an anode of lead and 0.75 # silver. The electrolyte temperature was 50 ° C and the electrolyte flow rate was 660 ml / min. The values of the measured activation excess potential were recorded in a recording device. The manganese sulfate electrolyte contained k5 g / l manganese sulfate, 135 g / l ammonium sulfate and 0.1 g / l sulfur diozyde, as well as the varying amounts of added glue, copper, nickel, 800 4794 zinc and antimony. The electrolyte bedroeg was 7.0. The electro-precipitation of manganese at a current density of 400 A / m requires the presence of 8 to 16 mg of glue per liter of pure electrolyte to obtain optimum flow efficiency and smooth deposits. 5 of the activation excess potential for the electrolyte with certain additives is shown in Table II below.

Table II

Additions to the electrolyte in mg / 1 Activation over potential adhesive Cu Ni 'Zn Sb in mV.

0 166 4 172

8 5 PM

'12 - - 179 16 - 183 20 190 2b - - 196 0 5 --- 155 0 1Q 151 16 10 - - - 151 o - 1 - - 16Ö 0 - 2 - - 166 16 - 2 183 16 10 2 158 0 0.5 - 168 0 - - 1 16k 16 - - 1 - 178 o - - - 1 166 0 10 '160' o 25 137 8 --- 25 139 20 - - 25 139 50 25 1 ^ 3 16 - - 1 1 172 16 - - 1 ισ i6k 800 4 2 94 20

From the tabulated results, "it appears that glue serves as a polarizing agent, that copper, zinc, and antiomone serve as depolarizing agents, and that nickel is essentially inactive. Thus, increasing amounts of glue increase the values of the activation excess potential, while copper, zinc and antimony have the opposite effect. The results also indicate that the optimum line levels in the pure electrolyte of 8 to 16 mg / l lead to values of the activation overpot ent ially in the region of Ijk to 183 mV and that the amount of glue should be increased when depolarizers (impurities - 10 gene) are present in small concentrations to return the activation excess potential values to within the desired range of 17 to 183. When impurity concentrations greater than a few mg / l are present the process for cleaning the electrolyte should be improved In this context, it also follows from the test results that the efficiency of the cleaning process can also be controlled in a favorable manner by measuring the activation potential of the electrolyte.

Example 3

This example illustrates the way in which the activation potential measurements can be used to control the electro deposition of nickel. The activation over potential values were measured at 55 ° C using a current corresponding to a current density of 1 mA / em. The cathode consisted of a wire of copper with a diameter of 1.19 mm and a ratio between the length and the surface area of 2.51 cm / cm. The minimum speed of movement of the cathode through the electrolyte was calculated at the value of 0.98 cm / h.

The cathode was advanced through the cathode holder at a rate of 160 cm / h. The anode consisted of lead 75% silver.

The electrolyte temperature was 55 ° C and the electrolyte flow rate was 660 ml / min. The values of the measured activation excess potential were recorded in a recording device. The electrolyte contained 50 g / l nickel as nickel sulfate, 10 g / l sulfuric acid, 90 g / l sodium chloride and 16 g / l boric acid, as well as varying amounts of glue and sodium lauryl sulfate. Sodium lauryl sulfate is a nickel electrowinning additive to prevent pitting in the deposited nickel, while glue is added as a leveling agent in electrogalvanizing nickel. The results are found in 800 4 2 94 21 in Table III below.

Table III

Additions to Let electrolyte in mg / l Activation over potential

in mV

sodium lauryl glue 5 sulfate

0 - TO

5 50 20 - kh 0 T0 - 5 8¼ 10 50 93

The results show that sodium lauryl sulfate acts as a depolarizing agent and, when present in increasing amounts, decreases the values of the activation excess potential, while glue serves as a polarizing agent and when the amount thereof increases, the values of the increase activation potential. The values of the activation excess potential. can be maintained at desired values by adjusting the concentration of the additive which changes polarization.

20 Example k

This example illustrates how the activation potential measurements can be used to control the electron deposition of lead. The activation excess potential values were measured using a current corresponding to a current density of 25 i +, 0 mA / cm. The cathode consisted of a copper wire with a diameter of 1.19 mm and a length to surface area ratio of 2.51 em / cm. The minimum speed of movement of the cathode through the electrolyte was calculated to be 13.8 cm / h. The cathode was advanced through the cathode holder at a rate of 160 cm / h. Anode 30 consisted of lead and 0.15% silver.

The temperature of the electrolyte was 100 ° C and the electrolyte flow rate was 660 ml / min. The values of the measured activation excess potential were recorded in a recording device. The lead silica fluoride electrolyte contained T5 g / l lead as lead silica fluoride, 90 g / l hydrofluoric acid, as well as varying amounts of ECA (Aloe extract), lignin sulfonate and sodium thiosulfate. The 8004294 22 electrolysis was carried out for 2b hours at 200 A / m 2 and at 100 ° C using Tan lead electrodes to obtain a lead deposit. The quality of the lead deposit was determined.

The additives to the electrolyte, the activation excess potential 5 and the nature of the lead deposition for each test are shown in Table IV below.

Table IV

Addition to the electrolyte Activation over potential Nature of the down ECA lignin Sodium impact mg / 1 sulfonate thiosulfate _mg / 1mg / L ..... .mV ___ ^ 0 Q 0 16 crude 0 b 0 35 crude 0.5 b 0 1 * 0 rough 1.0 1 * 0 1 * 3 rough 1.5 1 * 0 b6 smooth 15 2.0 k 0 52 smooth 3.0 b 0 58 rough 3.0 b 50 18 rough

From the results of Table IV, it appears that both ECA and lignin sulfonate act as polarizers and sodium thiosulfate acts as a depo-2Q brightener. In the lead electron deposition, the amount of lignin sulfonate is usually kept substantially constant, while the amount of ECA is adjusted to keep the activation excess potential in the desired range of 1 * 5 to 55 mV to obtain a smooth, leveled lead deposition. When the desired values of the activation excess potential are exceeded, sodium thiosulfate can be added to bring the value of the activation excess potential within the desired range.

These examples relate to the electrowinning of zinc.

The movable cathode consisted of a wire of 0.1 * 01 * 3 aluminum alloy 2q with a diameter of 1.19mm and a length to surface area ratio of 2.51cm / cm. The anode consisted of a lead-silver alloy containing 0.75 silver. The minimum cathode speed of movement was calculated to be a value of 1.0β cm / h. example 5 y. This example shows the influence of variations in the values of the 300 4 2 94 y - 23.

current supplied, expressed as current density, the cathode wire speed, the temperature of the electrolyte and the flow rate of the electrolyte. An amount of electrolyte was analyzed and adjusted to 55 g / 1 Zn and 150 g / 1 H 2 SO 2. The adjusted electrolyte "also contained 5 0.01 mg / 1 Sh, 0.03 mg / 1 Cu, 0.1 mg / l Co, 0.1 mg / 1 Egg, 0.005 mg / 1 Ge, 0.5 mg / 1 Cd, 30 mg / 1 Cl and 2 mg / 1 F. The adjusted electrolyte was continuously passed through the test cell and the activation excess potential was measured and recorded The results are tabulated in Table 7 below.

10 TABLE ΓΓΑ

Test Current— Speed Temperature Current Activation—

After. As a result of the movement of the electric speed, it is possible to transfer the catholyte of the material

mA / aa method ° C electrolyte mV

". ... cm / hr _ ml / min _ 55 0.1 60 30 668 10 56 1.0 60 30 668 75 57 1.0 180 '30 668 82 15 58 1.0 300 30 668 90 59 1.0 60 21 668 83 60 1.0 60 35 668 55 61 1.0 60 * 60 668 20 62 1.0 60 30 663 70 20 63 0Λ 60 30 668 35 6k 2.0 60 30 668 75 65 M 60 30 668 115

The results clearly indicate the influence of process variables and the need to use normalized conditions for practical application.

Example 6 _

This example shows the influence of varying amounts of antimony, germanium, cobalt and glue added to a set electrolyte with a composition as in Example 5. The activation over potential was measured using a current corresponding to a current density of 1.0 mA / cm 2, a cathode rate of 160 cm / h, an electrolyte temperature of 35 ° C and an electrolyte flow rate of 660 ml / min. The values of the measured activation excess potential were recorded in an x-y recorder. The results are found 8004294 2k in tabular form in Table V below. In this table, the values of the © potential represent the mean recorded values.

• 'TABLE V

Test Additions in mg / l Activation Over Potential

. , Uo. . .glue. .Sb. .Ge. .Co m / F

5 66 'oo 0 0 8o 6T 10 0 0 0 98 68 20 0 0 0 110 69 30 0 0' 0 120 T0 0 0.02 0 0 58 10 T1 10 '0.02 0 0 89 72 20 0.02 0 0 106 73 30 0.02 0 0 '109 7 ^' 0 0, Oil0 0 53 75 10 0.04 0 0 90 15 76 30 0.0ll0 '0 96 77 5 0.06 0 0 76 78 0 0.08 0 0 '50 79 10 0.08 0 0 78 80 30 0.08 0 0 83 20 81 0 0 'o, oil0 70 82 30 0 0.0i + 0 116 83 0 0.0il0 2.0 55 8il30 0.0il0 2.0 105

The results indicate that the increasing activation potential increases with increasing concentrations of glue and that the increasing activation potential of zinc decreases with increasing impurities concentrations.

"Example 7

This example illustrates that increasing concentrations of adhesive 2q are required to give good flow efficiency as increasing impurity concentrations are present in the electrolyte and that there are optimal areas for adhesive concentrations relative to impurity concentrations to provide the highest current efficiencies. -ten. Samples of a set electrolyte, as used in Example 2 ^ 6, to which varying amounts of glue and antimony and / or cobalt were charged 800 4 2 94 V.

Added as ealium antimony tartrate. respectively, cobalt sulfate, μπ were electrolysed in a cell at a current density at 100 A / m at 35 ° C for 2 h. The flow efficiencies for the zinc deposition were determined by determining the ratio between the weight of the precipitated zinc and the calculated weight, based on the total amount of current through the zinc precipitation cell. The results are shown in Table VI below.

• TABLE'VI

Test Adhesive added in mg / l 0 10 15 20 25 30 10 15 50 10 No. Sb added Co added Flow yields in% in mg / l added in mg / l. 85 0.01 0 88 92 91 90 89 88 8T 8j 85 86 0.03 0 T9 90 92 93 92 91 89 88 87 87 '0.05 0 56 86 90 92 93 93 92 91 88 15 -88' 0.07 0 1 + 3 72 81 85 89 92 93 92 89 89 '0.01 0.05 89 92 92 91 90 89 88 87 35 90' 0.01 2 88 92 92 92 92 9.1 91 90 89 91 0.01 5 65 87 92 92 92 92 92 92 91 92 0.01 5 * - 1 + 3 7l 82 82 81 79 77 75 20 93 0.03 0.05 80 90 92 93 93 91 90 88 86 9b 0.03 1 ho Jb 85 92 9¾ 93 92 91 89 95 0.03 5 - 58 Jb 87 92 9¾ 9b 93 90 96 0.03 5 * - - - lo 72 82 83 83 78 * 18 hours of precipitation.

From the tabulated results it appears that at each antimony concentration a correspondingly narrow range of adhesive concentrations was required to obtain the highest possible flow efficiency. The flow efficiency decreased with both too small and too large a glue concentration. Therefore, for each antimony concentration, there is a range of optimal adhesive concentrations. Likewise, when antimony and cobalt are present, adhesive additives are required to counteract the deleterious influence of these contaminants, and optimum adhesive concentrations exist for each antimony and cobalt concentration. Optimal adhesive concentrations were the same for 18 hour deposits as for 2 hours, but flow efficiencies were decreased. Example 8

Values, from the activation over potential for adhesives and contaminants 800 4 2 94. 26 settling concentrations obtained in tests, as indicated in Examples 5 and 6 and Tables IV and V, were combined with areas of maximum flow efficiencies for combinations of concentrations of glue and impurities obtained in tests, as indicated in 5 EXAMPLE 7 AND TABLE VI Hence, the areas below of values for optimum flow efficiency with respect to adhesive to impurity ratios were obtained as indicated by the values of the activation excess potential The areas are tabulated in Table VII below.

10 TABLE VII

Activation potential Range of flow efficiency in mV in% T5 75 - 83 8o 79 - 86 15 85 83-80 90 86 - 91 95 88 - 93 100. 90-9 ^ 105 90 - 9b 20 110 89 - 93 115 87-92 120 86 - 89 125 83 - 87

The numbers show that the highest ranges of current efficiency are obtained when the activation excess potential is held in the range of 90-115 mV measured at 35 ° C.

Example 9

This example illustrates that the activation over-potential measurements can be used to determine whether the correct adhesive concentration is present in the electrolyte relative to the deconcentration concentration and what changes in the adhesive concentration are required to optimize the zinc electrowinning process. Using the same electrolyte as in the previous examples, tests, as described in Example 6, were repeated, current efficiencies were determined. as for example 7 and the results were combined, as indicated in example 8. Using the results of the tests of this example, the required change in adhesive concentration in mg / 1 800 4294

2T

determined "when measured, sailing the activation excess potential in order to obtain the optimum flow efficiency in the electrolytic process. Information in Table VIII shows the program for controlling the electrolyte test of zinc by introducing 5 certain changes, in the glue concentration in the zinc electrolyte.

• TABLE VIII

Measured activation excess potential „. ,.

..... -18- * Required change in mV at 35 C · „.,. . . . ö ,, 0 J adhesive concentration m mg / l for optimum flow efficiency.

75 increase by 9 80 increase by 7 85 increase by 5 90 increase by 3 95 increase by 1 100 no change 105 no change '' 110 'decrease by 1 ^ 115' decrease by 3 120 decrease by 5 125 decrease by 7 130 decrease by 9

Example 10 20. ...

This example shows that the antimony m relation to measured values of the activation excess potential can be used to control the zinc electro-finding process at optimal current efficiency.

In a series of electrical find cells using an acidic zinc sulfate electrolyte of the adjusted composition, as indicated in Example 5, both glue and antimony were added.

Glue was added to the electrolyte at a constant rate of 200 mg / l, while antimony was normally added at a rate of 0.04 mg / l.

Using the electrolyte and the above additives 30. .

on glue and antimony, the activation over potential and the current efficiency were determined as in example 9. Optimal values for the current efficiency were obtained at activation over potentials of 100 to 105 mV. Using the results of these determinations, the anruy required changes in antimony concentrations in the electrolyte in mg / l he measured values of. the activation excess potential determined to obtain the optimum flow efficiency value in the electrolytic process. The control program can be found in Table 5 below.

TABLE IX

Measured activation over potential Required change in anticmoon-in mV concentration in mg / l for optimal flow efficiency.

85 decrease with 0.03 90 decrease with 0.02 95 decrease with 0.01 .100 no change 105 no change 110 increase with 0.01 115 increase with 0.02 120 increase with 0.03 · 15.

Example 11V

This example shows that the removal of impurities from a neutral zinc electrolyte by cementation with zinc dust can be controlled by activation over potential measurements. An impure electrolyte was subjected to a cleaning with varying amounts of zinc dust added to the electrolyte, the electrolyte containing previously added antimony as antimony potassium tartrate as varying amounts. The cementation was performed at 50 ° C with agitation and using a one-hour retention time. A stream of cleaned electrolyte was filtered and cooled to 35 ° C. The stream was then passed through the test cell to measure the activation excess potential. The purified electrolyte was analyzed to determine impurity concentrations. The results are tabulated in Table X below.

• TABLE X

_n Sb added Zinc Active- Impurities in a cleaned elec- J added in dust ring trolyte in mg / l mg / l added

enter tentally Cd Cu Co Hi Sb in g / l in mV

0.75 0 '3 ^ 200 3.5 1.6 1.8 0.75 0.75 0.5 21 U, 1 0.3 0.9 0.09 800 4294 29 0.75 1.0 6¾ 12 3., 0.3 0.5 0.05 0.75 1.5 7¾ 3.9 1.3 0.2 0.6 0.0¾ 0.75 2.0 J6 1.9 1.0 0.2 0, ¾ 0.03 0.75 2.5 86 0, ¾ 0.8 0.3 0.3 0.03 5 0.75 3.0 9¾ 0.3 0.6 0.2 0.2 0, 02 0.25 1.0 70 2.2 0.5 0.2 0.1 0.07 0.50 2.0 7¾ 2.2 0.6 0.1 0.1 0.03 1.00 * 2 0.085 0.6 0.6 0.1 0.1 0.02

Example 12 This example illustrates the manner in which the activation potential potential shades, such as those of Example 11, can be used to determine which process corrections must be made to control variables, such as zinc dust and antimony additives, in order to zinc cleanse of the electrolyte. The information in Table XI shows the program for controlling the zinc dust cleaning process by accomplishing certain. changes in zinc dust or antimony salt additions to the zinc electrolyte during purification, if the measured activation excess potential indicates that cleaning has not been completely completed.

TABLE XI

2o -

Measured activation Required additions over potential in mV for neutral zinc dust (g / 1) Sb (mg / l) electrolyte 80 0 o 75 0 0 70 0.3 0.1 25 65 0.6 0.2 60 - 0.9 0.3 55 1.2 Qik 50 1.5 0.5 ¾5 1.8 0.5 30 * <> 2'1 0.5 800 4 2 94

Claims (30)

1. Process for controlling a process for the electron-lane of a metal using an electrolyte containing concentrations of impurities "characterized in that a test chain is provided with a test cell, a sample of the electrolyte, a 5 "movable cathode with an area exposed to the electrolyte, an anode and a reference electrode, with the electrodes immersed in the sample, a constant current source and measuring means electrically connected to the electrodes connected to the electrodes in. a small current is applied to the test cell, which current is sufficient to cause an inchoate deposition of the metal on the cathode, the activation excess potential is measured at the point of inchoate precipitation of the metal, the measured activation excess potential being related to the impurity concentration in the sample, and the metal recovery process is set to obtain an optimum metal deposition, the inchate precipitation being defined as. the deposition of metal, which has just started and is limited to a partial coating of the movable cathode surface by the metal. 2. A method of controlling a process for the electron impact of a metal using an electrolyte containing concentrations of at least one polarization-influencing agent, characterized in that an electrolytic test circuit is provided, comprising a test cell, a sample of the electrolyte, a movable cathode having an area exposed to the electrolyte, an anode and a reference electrode, which electrodes are immersed in the sample, a constant current source and measuring means electrically the electrodes are connected, a small current is applied to the electrodes in the test cell, which current is sufficient to cause an inchoate deposition of the metal on the cathode, the activation excess potential becomes the point of inchoate deposition of the metal measured, the measured activation over-potential being related to a concentration of the at least one polarization-influencing agent part in the sample, and the concentration of the polarizing agent in the electrolyte is adjusted in order to obtain an optimum efficiency and a leveled metal deposition in the electron deposition process, whereby an inhate precipitate is defined as the deposition of metal, which has just begun and is limited to a partial coating of the movable cathode surface by the metal, 3. A method of controlling a process for the electron deposition of a metal using an electrolyte containing impurity concentrations and at least one polarization affecting agent, characterized in that an electrolytic test circuit having a test cell, a sample of the electrolyte, a moving 1Q. bare cathode having an area exposed to the electrolyte, an anode and a reference electrode, the electrodes being immersed in the sample, a constant current source, and measuring means electrically connected to the electrodes, the electrodes being electrodes are fed a small current into the test cell, which current is sufficient to cause an inchoate deposition of the metal on the cathode, the activation excess potential is measured at the point of the inchoate deposit of the metal, the measured activation excess potential is measured related to the concentration ratio between contaminants and the at least one, the polarization-affecting agent in the sample, and the concentration ratio in the electrolyte is adjusted to obtain optimum efficiency and leveled metal deposition in the electron deposition process, thereby providing an inchoate deposition defined as the deposition of metal which has just begun e n is limited to a partial coating of the movable cathode surface through the metal. Method according to claim 2 or 3, characterized in that the concentration of the polarization-influencing agents is adjusted by either increasing the amount of agent already present, Sf a second, the polarization-influencing agent having the opposite, adding the polarization-influencing characteristics to the already present polarization-influencing agent. A method according to claim 3, characterized in that the eonetration ratio is adjusted by changing the concentration of impurities in the electrolyte. The method according to claim 3, characterized in that the concentration ratio is adjusted by changing the concentration of the polarization-influencing agents in the electrolyte. 8 0 0 4 2 94 I; Method according to claim 6, characterized in that the concentration of the polarization-influencing agents is changed by either increasing the amount of agent already present, or by adding a second polarization-influencing agent with counter-5 added the polarization-influencing characteristics to the already present polarization-influencing agent. Method according to claim 1, 2 or 3, characterized in that the value of the current corresponds to a corresponding current density value in the range from 0.01 to 1.0 mA / cm, based on the free 10. area of the movable cathode. Method according to claim 1, 2 or 3, characterized in that the small current has a constant value. Method according to claim 1, 2 or 3, characterized in that the activation excess potential is measured continuously. Method according to claim 1, 2 or 3, characterized in that the activation excess potential is measured intermittently. Method according to claim 1, 2 "or 3, characterized in that the electrolyte sample is kept in motion. Method according to claim 1, 2 or 3, characterized in that the electrolyte sample is kept in motion by continuously passing an electrolyte current through the test cell. 11) -. Process according to claim 1, 2 or 3, characterized in that the value of the current which is sufficient to cause an inchoate precipitation of the metal is sufficient to cause not more than 10 to 30% of the surface area of the movable cathode exposed to the electrolyte is coated with deposited metal. Method according to claim 1, 2 or 3, characterized in that the movable cathode is moved at substantially constant speed. Method according to claim 1, 2 or 3, characterized in that the movable cathode is continuously advanced. IT Method according to claim 1, 2 or 3, characterized in that the movable cathode is advanced in an intermittent manner. 18. A method according to claim 1, 2 or 3, characterized in that the movable cathode is advanced through the electrolyte sample at a substantially constant speed, this substantially constant speed being at least equal to a minimum speed, determined by: 800 4 2 94 S. * "ABcd" min -: -, cm / η xy where ί a represents the ratio between the cathode length and the area-2 area in cm / cm; - 2 5. represents the current density in A / cm; e represents the free cathode surface in em; d represents the electrochemical equivalent of the metal deposited in g / Ah; x represents the fraction of the metal-clad cathode; 10 and y represents the weight of the deposited metal per unit of cathode surface area in g / em. Method according to claim 1, 2 or 3, characterized in that the Movable cathode is moved through the electrolyte sample at a substantially constant speed, said speed being in the range of ten to five hundred times the minimum speed, which minimum speed is determined by: S. = abcd, cm / h, mm - * * where: ^ 20. represents the ratio between the cathode length and the surface area in cm / em; 2 b represents the current density in A / cm; 2 e represents the free cathode area in cm; d represents the electrochemical equivalent of the metal being precipitated in g / Ah; x represents the fraction of the cathode which is coated with metal; and . y represents the weight of the deposited metal per unit of cathode surface area in g / cm. Method according to claim 1, 2 or 3, characterized in that the electrolyte in the test sample is kept at a substantially constant temperature and wherein the selected constant temperature is between 20 ° C and 75 ° C. 21. Method according to eonelusion 1, 2 or 3, characterized in that the electrolyte is a sulphate-based electrolyte, wherein the movable cathode in the test cell consists of a wire consisting of a material, 800 4 2 94 3 selected from aluminum. and suitable aluminum! egering and. 22. A method according to claim 1, 2 or 3, characterized in that the electrolyte is a sulphate-based electrolyte, wherein the movable cathode in the test cell consists of a strip consisting of a material selected from aluminum and cast aluminum alloys. Method according to claim 1, 2 or 3, characterized in that the electrodes are arranged in a fixed relationship relative to each other in the cell. 2k .. Method according to claim 1, 2 or 3, characterized in that the 10 'activation over-potential is measured by recording values of the activation over-potential as a function of time. Method according to claim 1, 2 or 3, characterized in that the metal is selected from zinc, copper, lead, iron, cobalt, nickel, manganese, chromium, tin, cadmium, bismuth, indium, silver, gold, rhodium and 15 platinum. A method according to claim 2 or 3, characterized in that the metal which is electrically deposited is selected from zinc, copper, manganese or nickel, the polarization-influencing agent consisting of animal glue. A method according to claim 1, 2 or 3, characterized in that the metal which is electrically deposited is selected from lead and nickel, the moving cathode consisting of a copper wire. 28. A method according to claim 1, 2 or 3, characterized in that the metal is selected from zinc, copper and manganese and the moving cathode 25 consists of a wire of a material selected from aluminum and aluminum alloys. 29. Method according to claim 5, characterized in that the metal which is deposited consists of zinc, the concentration ratio of which is adjusted by changing the concentration of antimony in the electrolyte. A method according to claim 6, characterized in that the metal that is precipitated is zinc, the concentration ratio of which is adjusted by changing the effective concentration of the polarization-affecting agent in the electrolyte. A method according to claim 30, characterized in that the polarization-influencing agent consists of animal glue. 32. A method according to claim 31, characterized in that the concentration is adjusted by adjusting the concentration of glue to a value at which the activation crer potential is measured at a temperature between 25 ° C and 40 ° C. C, is in the range from 70 to 150 millivolts, the activation crer potential being measured at a value of a small constant current, corresponding to a current density. In the range from 0.01 to 4.0 A / cm, based on the free surface, the movable cathode 33. Method according to claim 32, characterized in that the value of the current density concerned is in the range from 0.1 10 to 0.4 A / cm 2. A method according to claim 3, characterized in that the concentration concentration in the electrolyte is adjusted by changing the concentration of the impurities and at the same time changing the concentration of the at least one polarizing agent. A method according to claim 32 or 33, characterized in that the concentration of glue is increased when the measured value of the activation over-potential decreases below about 70 mV, the concentration of glue being decreased when the measured value of the activation over-potential . until drilling 150 mV increases. 36. A method according to claim 5, characterized in that the metal which is deposited consists of zinc, the polarization affecting agent consists of animal glue, and the impurity consists of dissolved antimony, the ratio of eonentration being reduced. set by setting the concentration of antimony to a value, where the activation over potential, measured at a temperature between 25 ° C and 40 ° C, is in the range of 70 to 150 millivolts, and where the activation over potential is measured at a value of a small, constant current, corresponding to a current density in the range 0.01 to 4.0 A / cm, based on the free surface 30 of the movable cathode. Method according to claim 36, characterized in that the value of the relevant current density is in the range from 0.1 2 to 0.4 A / em. Method according to claim 32 or 33, characterized in that the concentration of antimony is increased when the measured value of the activation over-potential decreases below about 70 mV and the 800 4294 concentration of antimony is decreased when the measured value of the activation over-potential until "rises above 15'0 mV. 800 4294