MXPA01005464A

MXPA01005464A - Device and method to control steel pickling processes.

Info

Publication number: MXPA01005464A
Application number: MXPA01005464A
Authority: MX
Inventors: Sandro Fortunati
Original assignee: Henkel Kgaa
Priority date: 1998-12-02
Filing date: 1999-12-02
Publication date: 2002-07-02
Also published as: EP1141686B1; ITMI982612A1; ATE318408T1; DE69930001T2; CA2353387A1; JP2002531700A; IT1303814B1; DE69930001D1; ES2258863T3; EP1141686A1; WO2000033061A1

Abstract

A device and a method to control pickling processes are described, where the control device comprises means (C) to take a sample of the bath to be analysed; means (CA, D, EM) to analyse said sample in order to measure a number of parameters according to specific conductivity and potentiometric methodologies as well as the redox potential value of said samples and its temperature; restoring means, apt to calculate, according to the above measured values, the quantity of corrective chemicals to be added to the pickling bath in order to restore at the desired level the value of said parameters and to actuate at least a device to add into said pickling bath necessary quantities of correction chemicals. The parameters measured according to conductivity methodologies are the concentrations of sulphuric acid, of hydrofluoric acid, or of another inorganic acid; the parameters measured according to potentiometric methodologies are concentrations of bivalent and trivalent iron ions and of hydrogen peroxide and the corrective chemicals are sulphuric acid, hydrofluoric agent and an oxidising agent.

Description

DEVICE AND METHOD FOR CONTROLLING THE PROCESSES OF DEOXIDATION BY ACID BATH OF THE STEEL FIELD OF THE INVENTION The invention consists of a device and a method to control the processes for the deoxidation by acid bath for carbon steels, austenitic steels, ferritic and stainless martensitic steels, duplex steels and special alloys, in which said device handles automatically the formation of samples of the deoxidation baths by acid bath and analyzes the samples to define (according to the specific conductivity and the potentiometric methodologies) the critical parameters of the process and to restore the desired concentrations of the necessary chemicals in the deoxidation tanks for acid bath. This invention also allows the management of specific conditions of deoxidation by acid bath for the type of steel under treatment through the definition of operational procedures remotely activatable, automatically remembering and effecting the most suitable operating conditions for deoxidation by acid bath of the specific class of material under treatment. REF: 129148 , -I: .J¡.tji¿ *! Íac .. *. T .. *. isu aSyjaa- j > A¿_ »fe_ aat - A. -j a-Ji-l-i ..

STATE OF THE ART In the rolling, drawing, extrusion, heat treatment of steel products (such as plates, strips, tubes, rods) oxide layers are formed on the surface 5 thereof which must be removed so much. to obtain an adequate final appearance as well as to obtain passive and anticorrosive properties for the final product and to allow subsequent work. Said oxide surface layers are usually 10 remove by chemical treatment (deoxidation by acid bath) based on the exposure of the metal material to the action of one or more acid baths containing inorganic mineral acids (sulfuric, hydrochloric, nitric, hydrofluoric) alone or mixed together, at a dilution and temperature 15 suitable, followed by at least one final rinse of a water. For stainless steels, the usual processes of deoxidation by acid bath (either by immersion, spraying or turbulence) requires a mixture of nitric and hydrofluoric acids; such processes involve ecological problems 20 very serious due to the emission of reaction byproducts (extremely toxic nitrogen oxides) into the atmosphere as well as large amounts of nitrates in the waste water.

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Hence, during the recent past, a number of alternative "ecological" processes have been designed through the elimination of nitric acid. Among these processes, particularly effective on an industrial scale are those that use mixtures of sulfuric or hydrochloric acid, hydrofluoric acid and ferric ions, in which the adequate concentration of such ions in the deoxidation bath by acid bath is maintained through the addition of hydrogen dioxide. Some of these processes are described in the Italian patents 1,245,594 and 1,255,655 (corresponding to the North American US-A-5 345 383) and in the European patent application EP-A-0 769 575. In the technology of deoxidation or pickling by traditional acid bath, the process management usually includes an occasional control of the deoxidation or coating bath through the manual titration of the acidity or measurement of the conductivity of the solution and its content of iron (or total metals) through measurements of the density of the bathroom); It is also possible to measure the content of hydrofluoric acid by means of a specific, selective ion electrode. Some of these techniques have been used in the automation of unique operations in the processes of deoxidation by acid bath based on nitric acid of stainless steels. US Patent 4,060,717 (LECO Corp.) discloses the use of ion-selective electrodes for fluorine and hydrogen ions to measure the concentration of nitric acid (or other strong acids) and hydrofluoric acid in deoxidation or coating baths. Acid bath containing nitric and hydrofluoric acid; the electrical voltage data are combined by a control circuit and processed by a microprocessor to calculate the concentration of the two acids and the relevant adjustment of the concentrations. Japanese Patent 55040908 (NIPPON Steel Corp.) describes the determination of hydrofluoric acid and other strong acid (nitric, hydrochloric, sulfuric) through the determination with ion-selective electrons of the relevant anions after passing through the solution through of the ion exchange membranes, to adjust the acid concentrations. US Patent 5,286,368 (FOXBORO Corp.) measures the concentration of hydrofluoric acid in a mixture of nitric and hydrofluoric acids through the ability to form trivalent iron ion complexes towards tdi¿Íjit.k-I.J? -fait-A-. t », -k -mm ._.___ .mm" ^ * ¿c.íz¿L.iy ... HM ^ * m ... *. m, _ «._ .." .. ". ..._._ ", -_. «__J | t» J _. "I X fluorine ions, allowing to determine the concentration of the acids in the mixture. Japanese patent 072944509 (KAWASAKI Steel Corp.) measures the concentration of free hydrofluoric and nitric acids and that of iron ions in a deoxidation solution or acid bath pickling by iron ion concentration by an absorption method of the iron complex. iron salicylate, the concentration of free hydrofluoric acid by an absorptiometric method of fading the iron acetylacetone complex and the total concentration of the free acids by the titration method by neutralization, the concentration of the metric acid which is measured by subtracting the concentration of the hydrofluoric acid free from the total concentration of free acids Japanese patent 081660003 (MITSUBISHI Heavy Ind. Ltd.) refers to a method for continuously measuring the concentration of the iron ion in a deoxidation solution or pickling by acid bath. The continuous automatic handling of such processes of deoxidation by acid bath based on nitric acid, although they are better than an occasional manual or automatic control, carried out for example, a few times a day, is not essential Í .- «a¿a.t-¿y-y .._ y < a.iM., yit ^ .-. Ig-i-y. for the process in terms of quality of the treated material, due to the functional characteristics of such baths; particularly, in acid bath deoxidation of stainless steels, such baths usually have high concentrations of nitric acid (about 12-15%) and hydrofluoric acid concentrations of about 2-5%. The high concentrations of nitric acid ensure at the same time both a high acidity and an almost constant oxidation power, making it possible to handle the process through occasional additions of chemicals. In addition, the determination of the acid concentration is sufficient to have an adequate control of the deoxidation capacity by acid bath, of the bath. On the other hand, acid-free dehydration systems, free of nitric acid, such as those previously mentioned, find the oxidation properties of the system in the measurement of ferric ion concentration (Fe3") or better still in the control of the proportion of Fe3VFe ^ In this case, due to Id reaction of the deoxidation by acid bath (1) 2 Fe3"FeO - > 3Fe + (1) ¡^^^ ¿¡^ __ ^ * in a continuous process for the production of stainless steel strips or in high productivity automatic plants for the deoxidation by acid bath rods, the concentration of trivalent iron ions, the Fe3 + proportion / Fe2 + and hence the oxidation capacity of the solution tend to decrease rapidly, modifying continuously and drastically the behavior of the bath. The optimum conditions must therefore be adjusted continuously by means of oxidizing agents, such as hydrogen peroxide. In addition, the variation of trivalent iron concentration also indirectly influences the concentration of free acids present in the bath. For example, in an acid bath deoxidation system based on sulfuric acid, hydrofluoric acid and ferric salt mixtures, this influence is linked to the following preferred equilibrium: FeJ ++ nF "-> FeFn (3-n) -. Fe2 + + S042"- > FeS04 From here, during the oxidation / reduction reaction of the Fe3 + / Fe2 + pair the release of sulfuric acid and hydrofluoric acid respectively will occur from salts relevant complexes, thus modifying the composition of the bathroom. Process control through occasional analytical measurement, followed by large additions of chemicals to restore the best conditions of deoxidation in the bath, therefore also causes wide variations of the bath parameters with adverse consequences in the quality of the bath. product and the costs of the process. On the other hand, the frequent manual controls and the relevant adjustments of the composition, are time consuming and expensive, since this requires a large number of personnel to ensure a satisfactory control frequency (for example, an hourly control). The criticism of the processes of deoxidation by acid bath, free of nitric acid, is obviously linked to the total amount of iron dissolved per unit of time, to a number of deoxidation tanks per acid bath that are going to be controlled, to the number of materials that require different operating conditions and practical ability to verify frequent manual additions of acids in tanks.

The handling of the processes of deoxidation by acid bath for the stainless steels such as those previously mentioned for the plants of deoxidation by acid bath, continuous, of stainless steel strips or for automatic plants of high productivity for the processing of rods, have proved be critical for the quality of the final product; They are also not economical without the use of an automatic system for obtaining samples, control and dosage of reagents. The control device and the method according to the present invention require the use of analytical methods and with high specific capacity for an adequate handling of such processes. BRIEF DESCRIPTION OF THE INVENTION It is an object of the present invention a control device and a control method for baths of deoxidation by acid bath, free of nitric acid, comprising means for taking a sample from the bath to be analyzed; means to analyze the sample to ensure a number of parameters according to the specific conductivity methodologies (to find the concentration of hydrochloric acid, sulfuric acid or other strong inorganic acid) and potentiometric methodologies (for find the concentrations of trivalent and bivalent iron) as well as the measurement of the redox potential values of said sample and its temperature; restoration means, capable of calculating, according to the values measured above, the amount of correction chemicals (preferably hydrofluoric acid, sulfuric acid and an oxidizing agent) that must be added to the deoxidation bath or pickled by acid bath to restore the desired level the value of said parameters and actuate at least one device to add within said deoxidation or pickling bath the amounts of correction chemical. Preferably, the parameters measured are the concentration of the sulfuric acid, that of the hydrofluoric acid and those of the bivalent and trivalent iron ions. A further object of the present invention is a method for controlling the deoxidation baths or pickling by acid bath, free of nitric acid, which comprises the steps of: taking a sample from a deoxidation bath by acid bath; - measuring the concentration of said sample of a deoxidation bath by acid bath, of the acids, of the divalent iron ion and of the trivalent iron ion; - measuring the redox potential and the temperature of said sample of a deoxidation bath by acid bath; restore to the pre-set or pre-used levels the values of said concentrations measured in the deoxidation bath by acid bath, adding the calculated amount of the correction chemicals to the deoxidation bath by acid bath. BRIEF DESCRIPTION OF THE FIGURES The invention will now be described with reference to a non-limiting modality shown in the attached figures wherein: Figure 1 shows schematically a plant comprising an analysis device according to the invention; Figure 2 shows a simplified diagram of an analysis device according to the invention; Fig. 3 schematically shows the analysis vessel CA of Fig. 2, comprising a system for measuring conductivity and a preferred embodiment of the rinsing means of the vessel itself and the measuring electrode; Figure 4 schematically shows the analysis vessel CA of Figure 2, which comprises a potentiometric measuring system and a preferred embodiment of the rinsing means of the vessel itself and the measuring electrode. In the attached figures, the corresponding elements will be identified with the same reference. DETAILED DESCRIPTION OF THE INVENTION Figure 1 shows schematically a plant comprising an analysis device according to the invention, comprising: • a plurality of deoxidation tanks by acid bath V (VI,, Vn); • an analysis device A (later described with reference to the simplified diagram of figure 2) which, in the modality described here, includes a pair of analysis devices (Al, A2) that work simultaneously on different parameters; • a plurality of storage tanks S (SI, S2, S3) each containing a solution at a given concentration of one of the correction chemicals (a strong mineral acid, preferably sulfuric acid, hydrofluoric acid and an oxidizing agent, preferably but not necessarily hydrogen peroxide) that are going to be added to one of the V tanks; • a plurality of permanent recycling pipes, connecting the tanks V to the sampling inlets I (figure 2) of the analysis device A; • a plurality of pipes for feeding the correction chemicals, which connect the storage tanks S to the tanks V; • addition means that allow the analysis device A to control the addition to the tanks V of the correction chemicals contained in the storage or storage containers S. For simplicity, in figure 1 the components that are not of interest for the present description, such as valves, pumps, actuators, filtering and rinsing means, known per se, as well as others, if any, such as circuitry components, are omitted. The analysis device A comprises (FIG. 2) means for capturing, from a container V, a sample of the deoxidation or coating bath; means to analyze it to measure, according to the specific conductivity and potentiometric methodologies, the preset parameters (concentrations of strong mineral acid, for example acid sulfuric and hydrofluoric acid, as well as those of trivalent and bivalent iron), the redox potential and the temperature of the diluted sample; means for calculating the amounts of correction chemicals to be sent from the storage tanks S to the tanks V to adjust said parameters and means for driving the devices to the output of the storage tanks or tanks S to be sent to the bath deoxidation or pickling in the calculated amounts of said correction chemicals. Hereinafter, "sulfuric acids" will mean any strong mineral acid. Since the time required to measure the concentration of sulfuric and hydrofluoric acids is shorter than that needed to measure the concentration of iron ions (only a few minutes versus approximately 30 minutes), the analysis devices (Al, A2 ) are preferably divided, each specialized in only one of these analyzes (the measurement of sulfuric acid and hydrofluoric acid, respectively of the concentrations of iron ions). The analysis devices (Al, A2) can be managed by a high-level logic unit, not shown in the figures, which can be placed "in place" or a remote site, connected to the analysis devices (Al, A2) through bidirectional transmission means, known per se. Alternatively, said analysis devices (Al, A2) can be of the same model and comprise the analytical means suitable for measuring the concentration of both the acids (sulfuric and hydrofluoric) and the iron ions. In such a case, the device according to the invention would also work in the event of a malfunction of one of the analysis devices (Al, A2). Figure 2 shows a simplified diagram of an analysis device A (A1, A2) of figure 1 which comprises a combination relation: • a sampling module C, the sampling inputs of which I (II , ..., In) are connected in sequence to a permanent recycling pipe between the deoxidation or acid bathing tanks V (VI, ..., Vn; Figure 1) and the analysis device A; at least one storage tank (not shown) in which the sample of the bath to be analyzed is to be loaded, and are provided within the sampling module C; • a DR storage tank or container for the reagent, which contains the chemicals for analysis; • dosing means D (DI, D2) capable of extracting the quantities of chemicals necessary for the analysis and transferring them to the analysis vessel CA, part of the dosing means D are able to extract as low accuracy (from about 2 up to about 5%) high quantities of chemicals, the remaining dosing or measuring media are suitable for extracting with high accuracy (approximately 0.1%) small amounts of chemicals; in figure 2 the dosing or measuring means D with low and high accuracy are grouped respectively into two different functional units (DI, D2); • a CA analysis vessel, containing the measuring electrodes (generically called EM in FIG. 2), which receive from the sampling module C the sample of the bath to be analyzed, from the dosing means D or measuring the chemicals necessary for the analysis and from a storage tank W (not shown), the water (preferably having a conductivity less than 100 microsiemens) necessary to dilute the sample to a desired ratio; in figure 2 the elements are omitted additional (such as agitators) present in the CA analysis vessel, as they are not part of the present invention; • a UL logical unit, which controls and manages the analysis procedures, which acquires and elaborates the information from the EM measuring electrodes and the drive means to send the solutions of the correction chemicals contained in the deoxidation or pickling bath in the storage containers S (figure 1). In a preferred but not limiting embodiment, the dosing or measuring means of the functional unit DI are the peristaltic pumps with a constant supply, while the dosing or measuring means of the functional unit D2 are syringes in antacid material (for example PES) ) operated by an electric motor stepwise. Again in a preferred embodiment, the analysis device A also comprises means (hereinafter described with reference to FIGS. 3 and 4) allowing the CA analysis container and the EM measurement electrodes to be rinsed after each measurement with water and after a given number of measurements with a chemical solution (preferably but not necessarily hydrochloric acid at la '? & d.-AÁ'd ,, .. 10-20%), thus allowing the EM measuring electrodes to be maintained in optimum conditions, in order to have reliable analytical data, to minimize maintenance interventions and to highly improve the life of the electrodes. To ensure a constant quality of the final product, each type or family of materials to be deoxidized by an acid bath must be treated according to the characteristic parameters and standards (concentration of hydrofluoric and sulfuric acids, concentration of trivalent iron ions and bivalent, the ratio between trivalent and bivalent iron ions, the concentration of hydrogen peroxide, the temperature of the sample to be analyzed, and so on); in a preferred embodiment of the invention, the parameters that characterize each work stage as well as those that are related to the operation of the analysis device A, which will allow all the carrying out of different analyzes in the deoxidation or coating baths that are related to the specific work stages, they are grouped into operation procedures correlated in a unique way with the material itself and stored in the UL logical unit, which are re-obtained when they are necessary according to the material to be deoxidized or stripped with acid bath. - ^ a-iü-A ..., - «_ - _» -_-.... - ^ - ff tiirríiir iirfril Preferably but not necessarily, an operating procedure comprises at least the following information: • the order and the kind of analysis that will be done; • the pre-set values of the parameters for the deoxidation bath or pickling by acid bath; • the magnitude of the permissible deviations with respect to the preset values, beyond which the logic unit UL activates the means to send the solutions of the correction chemicals contained in the storage or storage containers to the deoxidation or pickling bath. S; • the proportions of the dilution with water in the CA analysis vessel of the sample of the deoxidation or pickling bath to be analyzed. The proper operation of the analysis device A can advantageously be checked periodically and automatically; for this purpose, in a preferred embodiment of the present invention, an additional operational auto-calibration procedure is stored in the UL logic unit which is activated after a given number of analyzes and comprises the functional steps of extracting from a container (preferably but not necessarily located in the reagent storage container DR) a fixed amount of a standard solution having a known composition, transferring it to the CA analysis vessel, analyzing it, comparing it with the analytical results obtained with the known composition and activating the signals of alarm if the deviation between the analytical results obtained and the known concentrations is greater than a desired value. According to a modality of the present mention, not shown in the figures, the UL logic unit can be connected to an operational center and / or a high-level logic unit, by means of which it can be controlled and operated; As mentioned above, this high-level logical unit can be placed "in situ" or remote. In particular, in each change of work activity, the central post operator may modify the operating procedure performed by one or more of the UL logical units, activating that which belongs to the activity to be initiated; the operator can also retrieve an operating procedure from one or more of the UL logical units, modify it and perform it by the UL logical units and / or add a new operating procedure by storing it in the UL logical units.

The analytical methods, which are used in the analysis of acid bath deoxidation baths, will now be described to better understand the described details, which are part of the present invention. a) Determination of the conductivity of hydrofluoric acid and sulfuric acid (or other strong acids with respect to hydrofluoric acid). This determination is based on the principle that, in an aqueous solution formed by a mixture of a weak acid such as hydrofluoric acid and a strong acid such as sulfuric acid, the conductivity of the solutions practically equivalent to that of the strong acid to the same concentration; the method also exploits (in a subsequent step to a first conductivity measurement of a bath sample properly diluted to measure the concentration of sulfuric acid) the high affinity of hydrofluoric acid for a metal cation present in the solution as a salt of known concentration . The anion of the salt more preferably comes from a strong acid (for example nitric or hydrochloric acid) so that the reaction formed by the fluorocomplexes of the metal cation and the hydrofluoric acid will generate a significant increase in the conductivity due to the formation of a quantity Ij- ^ a ^ - -i-áa ^ A.

Strongly dissociated acid equivalent, measured by a second conductivity measurement. For example: nHF + Fe (N03) 3 - > FeFnl3_n) + + n HN03 Such increase in conductivity, therefore, is proportional to the concentration of hydrofluoric acid which, after proper calibration, can be measured quantitatively. Such salts may, for example, be ferric nitrate, ferric chloride, aluminum nitrate, aluminum chloride; in a preferred embodiment of the invention a ferric nitrate * 9H20 solution is used, at a concentration of 750 g / 1. To ensure a sufficiently linear dependence of the conductivity of the acid concentration variation, the dilution of the sample should be carefully evaluated as a function of the concentration of the acids present in the bath to be analyzed; as a non-limiting example, for sulfuric acid concentrations up to 200 g / 1 and for hydrofluoric acid concentrations up to 60 g / 1, the dilution ratios from 1: 100 to 5: 100, and preferably 4: 100 , are considered acceptable.

Another variable essential for obtaining reliable results (which must be handled by the logical unit UL of the analysis device A) is the temperature of the sample after dilution with water; in fact, in the industry the water temperature can vary considerably (usually between +5 and + 40 ° C) according to the temperature, the water source and the retention time in the storage tank W. It is apparent that a measure of the conductivity is significantly influenced by the temperature, and usually such a problem is overcome by means of an automatic compensation system incorporated in the measurement device; in the present case, the automatic compensation can correctly adjust only the effect on the first measurement of the conductivity (determination of the concentration of sulfuric acid) but on the second (determination of the concentration of hydrofluoric acid) made after the addition of the nitrate ferric as the composition of the solution changes and its dependence on temperature is, in fact, different before and after vision of ferric nitrate. This critical problem is solved with an analysis device A according to the invention, in which the unit UL logic takes into account the variation in conductivity due to the addition of a volume v3 of the ferric nitrate solution, depending on the temperature of the sample. The amount of ferric nitrate used during the titration should be such as to ensure complete complex formation of hydrofluoric acid; in the system considered, for the concentration of hydrofluoric acid less than 60 g / 1 the ratio between the volume v3 of a solution of ferric nitrate * 9H20 to 750 g / 1 and the volume vl in the sample of the bath must be greater than 0.5 and preferably 1. As a non-limiting example, the following operating procedure is given together with the relevant calculations for a sample dilution of 4: 100 by volume: • filling the CA analysis vessel, by means of the dosing means D2, with a given volume of water v2, which has a conductivity of less than 100 microsiemens to obtain a dilution ratio of 4: 100; • taking or collecting from the sampling module C (by means of the dosing means D2) a given volume vl of the sample of the deoxidation bath by acid bath to be analyzed; • start with the agitation of the solution; • measure the first conductivity (Lx); • add a given volume v3 = vl of a ferric nitrate solution ° 9H20 to 750 g / 1; • shake the solution and measure its temperature T; • measure the second conductivity (L2). The logical unit UL acquires the data Li, L2, T and automatically finds the concentration of the acids through the following calculations: • concentration of the sulfuric acid (g / 1): a.Li2 + bL? -c • concentration of the acid hydrofluoric (g / l): a? .d "+ b? .dC? where: a, b, c, ai, bi, Ci are coefficients of the quadratic equations, f = c2 + (c3.T), c2 and c3 are constants that depend on the amount of ferric nitrate * 9H2 added to the diluted sample before the second conductivity measurement In this example: a = 0.0066, b = 5.015, c = 6.98 ai = 0.0120, bi = 2.881 Ci = 3.81, c2 = 9.632, c3 = 0.297.

Figure 3 shows the characteristics of the CC conductivity cell, which specifies the form that minimizes the negative effects due to the high viscosity of the solution and facilitates the rinsing of the platinum measuring plates. Said DC conductivity cell comprises a hollow body B, in glass and having a substantially cylindrical shape, containing two EL black platinum plates; in the lower and upper parts of the hollow body B there are holes (Fl, F2) that allow the sample to be analyzed to circulate inside the hollow body B. Preferably, the hollow body B has a diameter of approximately 20 mm (and comprised of any shape between approximately 17 and 23 mm) and a height of approximately 40 mm (and in any way comprised between approximately 35 and 45 mm); the dimensions of the EL plates are approximately 10 X 5 mm (and in any case between approximately 8 X 12 mm and approximately 3 X 7 mm), the distance of the other signal is approximately 15 mm (and in any way between approximately 12 and 18 mm). To avoid polarization of the EL electrodes, the electrical measuring circuit (not shown) connected to the DC conductivity cell must work at high frequency (between 25 and 40 KHZ). B) Determination of bivalent iron The determination of bivalent iron can be carried out through potentiometric analysis, by titration with potassium permanganate according to the classical methodology. The operational sequence requires: • pouring a given volume of water v2 into the CA analysis vessel, through the TP overflow pipe, to obtain a dilution ratio > 1:50; • take from the sampling module C (by means of the dosing medium D2) a given volume vl of the sample of the deoxidation bath by treatment with acid, which is to be analyzed and the addition of said sample to the analysis vessel AC; • acidification of the sample of the deoxidation bath by acid bath, diluted, by means of the addition in the CA analysis vessel (by means of the DI dosing medium) of a given non-critical quantity of a solution of a strong acid, by example, a 1: 1 sulfuric acid solution by weight; • potentiometric titration, which has a preselected end point or an automatic search for the end point with a 0. potassium permanganate solution added to the analysis vessel by means of the dosing medium D2; • empty and rinse the CA analysis vessel. C) Determination of trivalent iron Trivalent iron is measured by iodometric titration, using, however, some specific attention to allow the use of an automatic device in obtaining reliable and reproducible results. Said determination requires the following sequence of operation: • pouring into the analysis vessel CA a given volume of water v2, through the overflow pipe TP, to obtain a dilution ratio > at 1:50; • take from the sampling module C (by means of the dosing means D2) a given volume vl of the sample of the deoxidation bath per acid bath to be analyzed and the addition of said sample to the CA analysis vessel; • initiate agitation; • adding to the CA analysis vessel (by means of the DI metering means) a given non-critical volume of a lanthanum nitrate solution has a known concentration; • wait for 30 seconds without agitation; • adding in the CA analysis vessel (by means of the DI metering means) a given non-critical volume of a hydrochloric acid solution at 1: 1 by volume; • add a non-critical volume of a potassium iodide solution, at a concentration of, for example, 1 kg / 1 to the analysis vessel CA (by means of the dosing means DI); • wait for 5 minutes without agitation; • initiate the agitation of the solution; • potentiometric titration with 0.1N sodium thiosulfate (added by means of the dosing means D2) of the iodine released by the reaction of trivalent iron with potassium iodide; • Empty and rinse the CA analysis vessel with water. For this automatic analysis, a more prominent aspect is the use of lanthanum nitrate; in fact, the addition of a salt that includes a cation capable of forming a complex with the Fluorine ion bound to the iron ion is essential for the quantitative analysis of the ferric ion through iodometric analysis. This analysis can be performed manually using a calcium chloride solution; however it has been proven that calcium chloride can not be used for the automatic titration of trivalent iron, due to the subsequent precipitation of calcium fluoride and calcium sulfate, which tends to continuously soil the electrodes in the CA analysis vessel. , resulting in significant errors and the maintenance of the complex. On the contrary, it was found that the salts of lanthanum can quantitatively release the ferric ion, generating precipitates in the form of powder and lanthanum fluoride that do not stick, thus allowing the automatic handling of the process with high reliability and with limited maintenance. This same result can be achieved by adding to the system a complexing agent for the iron ion, which however can be released quantitatively during the subsequent reaction with potassium iodide; Complexing agents such as EDTA can suitably serve this purpose.

The potentiometric system, illustrated schematically in Figure 4, comprises a measuring electrode E (inert to the working environment) immersed in the CA analysis vessel and a reference electrode R (preferably in glass, of the Ag / AgCl type) placed outside the CA analysis vessel and in contact with the solution under measurement through a salt bridge, comprising an electrolyte (contained in an SR tank) which is continuously passed through a porous SP septum placed at an extremity of a small plastic tube T. The continuous passage of the electrolyte through the SP septum is intended to cause electrical continuity; avoiding contact between the SP septum and the hydrofluoric acid of the deoxidation bath by acid bath and continuously renewing the electrolyte. In a preferred embodiment, the measuring electrode E is made of a body of antacid material which carries at one end a platinum P plate, one of whose surfaces, finished in the manner of a mirror, faces downwards, thus preventing the salts which are derived from the reaction products are deposited on the measuring surface of the plate P, soiling it. Advantageously, a 10% solution of glycerin can be added to the electrolyte (preferably 3M potassium chloride). (of another compatible product that has a viscosity at 20 ° C between 1.15 and 1.45 centipoise, inert with respect to the working environment and functionally equivalent) to improve the viscosity and reduce the flow velocity, thus allowing a better autonomy of the system potentiometric for a given volume of the SR tank. D) Determination of hydrogen peroxide The determination of free hydrogen peroxide in the processes of deoxidation with acid bath, free of nitric acid, such as those described here, is necessary in the treatment of ferritic and martensitic steels for the control of baths of finished / passivants used in general as the last operation before final rinsing; usually said oaxanes comprise sulfuric acid (20-60 g / 1), hydrogen peroxide (3-10 g / 1) and sometimes hydrofluoric acid. The analytical methodology and the operating sequence used for the determination of hydrogen peroxide are the same used for the determination of bivalent iron in the deoxidation baths by acid bath. e) Determination of the reduction-oxidation potential (redox) The device according to the invention measures, before the determination of bivalent iron, the redox potential 1 ?? i-i.1 -5-3 of the solution in the sample of the deoxidation bath or of the layering by dilute acid bath, using the potentiometric system already described; the value thus obtained is very close (+ - 20mv) to the redox potential measured in the bath before its dilution. The value obtained is compared with a range of values (usually between 200 and 550 mV) stored in the UL logical unit that is to be used as a first sign of the correct operation of the system; if the measurement value is outside that range, the UL logic unit of the analysis device A stops the analysis procedure and sends an alarm. The calibration of the potentiometric system is done at a given frequency (ie once a week) by measuring the redox potential in a standard solution of known potential (usually 468mV). As already mentioned, the logical unit UL of the analysis device 1 according to the present invention, after measuring the desired parameters in the sample of the deoxidation bath by acid bath under analysis, calculates the amount of each of the solutions or known concentrations of the correction chemicals (sulfuric acid, hydrofluoric acid and oxidizing agent) contained in the storage tank S, said chemicals are added in a timely manner to the deoxidation bath by acid bath to restore the ii, A --- t.Jafat t-if _rtμ? ri- | tá í -.- * ^ -...--- ^ ----.- »- ^^ ---- .. -l --- ti-i.-iJ desired composition values and trigger the media of addition (such as, for example, dosing pumps or electro-valves) at the outlet of the storage tanks S to send said calculated amounts of the correction chemicals to the deoxidation bath by acid bath. Having known the characteristics of the plant (volume of tank V, supply of each addition medium, pre-set concentration values for said correction chemicals, concentration of chemicals and so on) to have the correct amount of correction chemicals added to the bath of deoxidation by acid bath, the logic unit UL must calculate the period of activation of said addition means. The studies and experiments of these applicants showed that, to have again the desired values of the concentrations in the deoxidation bath by acid bath of sulfuric acid, hydrofluoric acid, trivalent iron ion and oxidizing reagent, the logical unit UL must actuate each of the addition means regulating the addition to the bath of deoxidation by acid bath, the solutions of sulfuric acid, hydrochloric acid and reagent oxidant, for a time S (in seconds) given by the following expression: S = K. (V0-vm) .vb / p in which: s = drive time (seconds); K = factor inversely proportional to the concentration of correction chemicals (1 / g); v0 = given concentration for the specific correction chemical (g / 1); v, -. = concentration of the specific correction chemical resulting from analysis (g / 1); vb = tank volume V; P = supply of the means of addition (1 / s). To obtain again the desired values the ratio R between the concentration of the trivalent and bivalent iron ions, the logic unit UL calculates the period of activation if (in seconds) of the addition means sending them to the bath of deoxidation by acid bath of the oxidizing reagent solution, by: • calculating B = A. R, in which A is the concentration (g / 1) of the bivalent iron ion that results from the titration with permanganate, R is the desired ratio between the and - ^ --....-.-and,? . i & > & .é, m, ¿; * ?: it¡ .fe. -. »« --- or-. * &? -. í concentration of, respectively, the trivalent and bivalent iron ions, and Bi is the theoretical concentration of the trivalent iron ion; • compare Bi with the measured B concentration of the trivalent iron ion (g / 1); • yes B > Bi (the measured concentration of the trivalent iron ions is greater than that of the divalent iron ions) the UL logical unit does not act; • yes B < Bi (the concentration of trivalent iron ions is lower than that measured) the logical unit UL calculates the period of activation if of the addition means regulating the addition to the deoxidation bath by acid bath of the oxidizing reagent solution, by means of the formula if = KK.C / p in which: s. = drive period (s); K = a factor inversely proportional to the concentration of the correction chemical (í / g), Ki = a factor proportional to the volume of the tank V (l); C = (B? -B) / R = amount of the divalent iron ion to be oxidized to restore the desired value of the iron ion concentration (g / 1); P = supply of the means of addition (1 / s).

Alternatively, the bath can be managed according to the ratio R between the trivalent iron ion and the bivalent iron according to the following calculation: • calculation of the total iron T = A + B where A is the concentration of Fe2 + obtained from the permanganometric analysis and B is the concentration of Fe3 + obtained from the iodomometric analysis. • calculation of R = B / A • compare R (proportion pre-sent) with Rl (preset ratio) • if R > Rl the logical unit UL does not make any addition of oxidizing product • if R < Rl the logical unit UL calculates the activation period if (in seconds) of the addition medium regulating the addition of the deoxidation bath by acid bath of the solution of the oxidant product according to the following formula if = K.Ki .C / p where C = A- [(A + B) / (R? +1)] = amount of bivalent iron to oxidize to restore the pre-sent R ratio to the pre-set Rx value SI = drive period (s) K = coefficient, inversely proportional to the tank volume V (1) P = supply of the addition means (1 / s). Figure 3 schematically shows an exploded view of the CA analysis vessel of Figure 2, which comprises a conductivity type measurement system and a preferred embodiment of the rinsing means of the CA analysis vessel and the measurement cell DC. In figure 3 it is possible to see: • the measuring cell of the conductivity CC used to measure the conductivity; • the CA analysis vessel; • TP, mobile overflow, the position of which (controlled by the UL logic unit) agrees to adjust the liquid level in the CA analysis vessel, and to empty the same container; • rinsing media (F, U) controlled by the UL logic unit, which allows rinsing of the CA analysis vessel and the cell that measures the conductivity CC. Figure 4 shows schematically an exploded view of the CA analysis vessel of Figure 2, comprising a potentiometric measurement system as well as a preferred embodiment, similar to that in Figure 3, of the rinsing means of the CA analysis vessel and the measurement electrons. Figure 4 shows: The potentiometric system, which comprises the measuring electrode E, the reference electrode R, placed outside the CA analysis vessel, and the salt bridge, which in turn comprises an electrolyte comprised in the tank SR, which passes continuously through a porous SP septum placed at one end of a small plastic tube T; • the CA analysis vessel; • TP mobile overflow, the position of which (controlled by the UL logic unit) agrees to adjust the liquid level in the CA analysis vessel and empty the same analysis vessel; • rinsing means (F, U) controlled by the UL logic unit, which allows the rinsing of the CA analysis vessel, the electrode end E and the porous SP septum. In the preferred embodiment shown in Figures 3 and 4, such rinsing means comprise a plurality of slots F positioned along the upper edge of the CA analysis vessel and a mouthpiece U suitable for rinsing ^ i ^ i * iiéM m *. t? tmsm «*»? ¿^ - ***. * - .. t Á. with a spray of water the end of the measuring electrode E and the porous septum SP, respectively the conductivity measuring cell CC; in figures 3 and 4, it is also possible to see the lid CP for the analysis vessel CA and the support means MS of the electrode E, the small tube T of the blood pressure system, the conductivity measuring cell CC and the small tubes ( not explicitly indicated in figures 3 and 4) that are connected to the dosing means D (Di, D2) with the CA analysis vessel, the CP cover and the support means MS will not be described, as they are known per se same and in any way do not belong to the present invention. Preferably, the CA analysis vessel, the measuring electrode E and the porous septum SP (respectively the CA analysis vessel and the conductivity measuring cell CC) are rinsed in water after each analysis and washed with a chemical solution after a given number of analysis. To rinse these components with water after each analysis, the UL logic unit performs the following steps in sequence: • completely empty the CA analysis vessel; • pouring a large amount of water into the CA analysis vessel through the slots F; • fill the CA analysis vessel with water until the tip of the electrode E and the porous septum SP are respectively immersed in the measuring cell of conductivity CC; • empty the CA analysis vessel; Then rinsing the tip of the electrode E and the porous septum SP, respectively in the conductivity measuring cell CC by spraying therein some water through the nozzle U; • empty the CA analysis vessel and prepare it for a subsequent analysis. To wash after a given number of analyzes with a chemical solution (preferably 10-20% hydrochloric acid) the CA analysis vessel, the electrode tip E and the porous SP septum (respectively the CA analysis vessel and the measurement cell of the conductivity CC), the UL logic unit fills the CA analysis vessel through the slots F to the tip of the electrode E and the porous septum SP, respectively, and is submerged in the conductivity measuring cell CC, socket a tank (preferably but not necessarily placed inside the reagent storage vessel DR) a quantity of the product (preferably hydrochloric acid) necessary for the chemical wash and sent to the CA analysis vessel; after a given period of time the UL logic unit empties the CA analysis vessel and rinses it with water, to remove any trace of the chemical solution. In addition, when not working, the CA analysis vessel is filled with water through the slots F and the nozzle U, to avoid any fouling and / or damage of the tip of the electrode E, the porous septum SP and the cell for measuring conductivity CC. It is possible for an expert to modify and improve, as suggested by ordinary experience and by natural technical evolution, the device for the control of the deoxidation baths by acid bath according to the present description, remaining within the scope of the invention. present invention. It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention. ñ? A, --a - and - i ---. aa -.- ii-. "Fa-», -.- t.jt-at ^ -? A-y ..- t ^^ .. t ^ aa_i_ y_j < * ... _ «« __. j ^. -y-f ^

Claims

CLAIMS Having described the invention as above, the contents of the following claims are claimed as property: 1. Control device for nitric acid-free acid bath de-oxidation baths, characterized in that it comprises means for taking a sample from the bath to be analyzed; means for analyzing the sample to measure a number of parameters according to the specific conductivity and potentiometric methodologies as well as to measure the potential reduction-oxidation value (redox) of said sample and its temperature; means for restoring, apt to calculate, according to the values measured above, the amount of correction chemicals that are to be added to the deoxidation bath by acid bath to restore the value of said parameters to the desired level and to actuate at least one device for adding within said deoxidation bath by acid bath the amounts of correction chemicals; further characterized in that the parameters measured are the concentrations of sulfuric acid, hydrofluoric acid and the bivalent and trivalent iron ions. Control device according to claim 1, characterized in that the restoration means introduce into the deoxidation bath by acid bath calculated amounts of solutions of the correction chemicals having a known concentration. Control device according to claim 2, characterized in that the correction chemicals are sulfuric acid, hydrofluoric acid and an oxidizing agent. 4. Control device according to claim 3, characterized in that the oxidizing agent is hydrogen peroxide. Control device according to claim 1, characterized in that it comprises at least one analysis device. Control device according to claim 5, characterized in that it comprises two analysis devices, operating simultaneously on different parameters. Control device according to claims 1, 3 and 6, characterized in that one of the analysis devices (A1, respectively A2) measures the concentrations in the deoxidation bath by acid bath of the sulfuric and hydrofluoric acids and adds acids sulfuric and hydrofluoric bath to the deoxidation bath by acid bath restore the given concentration levels, relevant, while the other analysis device (A2, respectively Al) measures the concentrations in the deoxidation bath by acid bath iron ions and adds oxidizing agent to the deoxidation bath by acid bath to restore the given value of the concentration of trivalent iron ions and / or the ratio between the trivalent and bivalent iron ions. Control device according to claim 7, characterized in that the analysis device comprises, in combination: a sampling module provided with inputs to take samples connected in sequence to the deoxidation tanks by acid bath to send at least a storage tank placed inside the sample module, a sample of the deoxidation bath by acid bath that is to be analyzed; a reagent storage, containing at least the tanks for the reagents used for the analysis of the sample of the deoxidation bath by acid bath; dosing means capable of extracting from the tanks in the storage of the reagent, given quantities of chemicals and transferring them to the analysis vessel; the analysis vessel, which contains the electrodes of $ LLMá ¡¡t, measurement used to analyze the sample of the deoxidation bath by acid bath, which receives from the sampling module the sample of the bath to be analyzed and from the means of dosing the chemicals necessary for the analysis; a logical unit that controls and handles the analysis procedures, which acquires and elaborates the information of the measuring electrodes and driving means to send the solutions containing the correction chemicals to the deoxidation bath by acid bath. Control device according to claim 8, characterized in that part of the dosing means are able to extract with high efficiency (from about 2 to about 5%) high amounts of chemicals and that the remaining dosing means are suitable for extracting with high accuracy (approximately 0.1%) small amounts of chemicals. Control device according to claim 9, characterized in that the dosing means having low accuracy and high accuracy are grouped respectively into two different units. 11. Control device according to claim 8, characterized in that it also comprises ..-... a-Aiy-i- *. < j means for sending to the analysis vessel water for rinsing the same vessel and the measuring electrodes and for diluting to the desired dilution ratio the sample of the deoxidation bath by acid bath contained within the analysis vessel. Control device according to claim 11, characterized in that the rinse and dilution water has a conductivity of less than 100 microsiemens. Control device according to claim 8, characterized in that each logic unit is connected to a central operating station and / or to a high-level logic unit, by means of which it is controlled and operated or directed. Control device according to claim 1, characterized in that the means for conducting conductivity measurements comprise a conductivity measuring cell provided at one of its ends with a hollow glass body and having a substantially cylindrical shape, which contains a pair of blackened platinum plates, in the lower and upper parts of said hollow body holes are provided that allow the ** "- * ^" ^ wf ^ sample to be analyzed, contained in the analysis vessel, to circulate inside the hollow body. Control device according to claim 14, characterized in that the hollow body has a diameter between 17 and 23 mm and a height comprised between 35 and 45 mm, the dimensions of the plates are between 8 X 12 m and 3 X 7 mm, the distance between them is between 12 and 18 mm. Control device according to claim 15, characterized in that the hollow body has a diameter of 20 mm and a height of 40 mm, the dimensions of the plates are 10 X 5 mm, the distance between them is 15 mm. Control device according to claim 1, characterized in that the means for performing the potentiometric measurements comprise a measurement electrode immersed in the analysis vessel and a reference electrode placed outside the analysis vessel, connected to the low solution measurement by a salt bridge constituted by an electrolyte that passes continuously through a porous septum placed in a tip of a small plastic tube. 18. Control device according to claim 17, characterized in that the electrolyte contains a product having a viscosity of between 1.15 and 1.45 centipoise at 20 ° C. Control device according to claim 18, characterized in that the electrolyte contains 10% glycerin. Control device according to claim 17, characterized in that the measuring electrode is constituted by a body of antacid material carrying on one of its ends a platinum plate having a finished surface in the form of a mirror that is facing down. Control device according to claim 8,14 and 17, characterized in that the analysis device also comprises means for chemically washing and rinsing with water the test vessel, the measuring electrode and the porous septum of the salt bridge, respectively the analysis vessel and the conductivity measuring cell, said means comprise at least slots positioned along the upper edge of the vessel and a nozzle capable of directing a flow of water on the end of the measuring electrode and on the .., -.- ¿. ^ --- ..-. ¿^^^ -, --... ^ 1 - ^^. - - ** - £ * - «• porous septum, respectively in the conductivity measuring cell. 22. Method for controlling deoxidation or nitrous acid-free acid bath baths, characterized in that it comprises at least the following steps: • taking a sample from a deoxidation bath by acid bath; • measure the concentration of the acids in the sample of a deoxidation bath by acid bath; • measure the concentration of the bivalent iron ion in said sample of a deoxidation bath by acid bath; • measure the concentration of the trivalent iron ion in said sample of a deoxidation bath by acid bath; • measure the oxidation reduction potential of said sample from a deoxidation bath by acid bath; • measure the temperature of said sample from a deoxidation bath by acid bath; • To restore to pre-set levels the values of the concentrations measured in said deoxidation bath by acid bath adding a calculated amount of correction chemicals to the deoxidation bath by acid bath. •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• 23. Method according to claim 22, characterized in that it also comprises the step of measuring the concentration of free hydrogen peroxide in the finishing / passivation baths used as the last operative operation before the final rinse in the treatment of ferritic and martensitic steels. Method according to claim 22, characterized in that the measurement of the concentration in said sample of a deoxidation bath by acid bath of the acids, comprises at least the following operations: • filling the analysis vessel, by means of the high precision dosing means, with a given volume of water having a conductivity of less than 100 microsiemens to obtain a given dilution ratio; • taking from a sampling module, by means of the high-precision dosing means, a given volume of the sample of the deoxidation bath per acid bath to be analyzed and inserting it into the analysis vessel; • shake the solution; • conduct a first conductivity measurement; • add a given volume of a ferritic nitrate solution in the analysis vessel.9H20; • shake the solution and measure its temperature; • conduct a second conductivity measurement; • Empty the analysis vessel. Method according to claim 24, characterized in that a solution of 750 g / 1 of ferric nitrate having the same volume as the sample of the deoxidation bath is added to the analytical vessel to be analyzed. Method according to claim 24, characterized in that the concentration as in the sample of a deoxidation bath by acid bath of sulfuric acid is calculated according to the following equation: wherein a, b, c, are coefficients of The quadratic equation and Li is the result of the first conductivity measurement. 27. The method according to claim 24, characterized in that the concentration in said sample of a deoxidation bath by acid bath of hydrofluoric acid is calculated according to the following equation: wherein: ai, bi, Ci, are coefficients of the quadratic equation; d = L2-L? -f; f = c2 + (c3 .T); Li and L2 are the results of the first and second conductivity measurements; c2, c3 are constants that depend on the amount of ferric nitrate.9H20 added to the analysis vessel. 28. Method according to claim 24; characterized in that the determination of the concentration of divalent iron ion in said sample of a deoxidation bath by acid bath is carried out by means of permanganometric titration. 29. Method according to claim 28, characterized in that the determination of the concentration of the divalent iron ion in said sample of a deoxidation bath by acid bath comprises at least the following operations: • filling the analysis vessel with a volume of water given to obtain a given dilution ratio; • take from the sample module, by means of the high-precision dosing means, a given volume of the deoxidation sample per acid bath to be analyzed and add it to the analysis vessel; • acidifying the sample of the deoxidation bath by acid bath, diluted, by adding in the analysis vessel, by means of the low precision dosing means, a given non-critical amount of a solution of a strong acid having a known concentration; • Potentiometric titration with a potassium permanganate solution of known concentration added to the analysis vessel by means of high precision dosing means, said potentiometric titration having a pre-sent end point or an automatic search of the end point; • Empty the analysis vessel. 30. Method according to claim 22, characterized in that the determination of the concentration of trivalent iron in said sample of a deoxidation bath by acid bath is performed by iodometric titration. 31. Method of compliance with claim 30, characterized in that the determination of the concentration of trivalent iron ion in said sample of a deoxidation bath by acid bath comprises at least the following operations: • filling the analysis vessel with a given volume of water, to obtain a proportion of given dilution; • taking from the sample module, by means of the high-precision dosing means, a given volume of the sample of the deoxidation bath per acid bath to be analyzed and adding said sample of the bath to an analysis vessel; • initiate agitation; • adding, within the analytical vessel, by means of the low-precision metering means, a given non-critical volume of a solution, at a known concentration of a salt of an element which reacts with the sulfuric and hydrofluoric acids, and forms soluble or precipitated salts that can be easily removed; • wait for a given period of time without shaking; • adding to the analysis vessel, by means of the low-precision dosing means, a given non-critical volume of a hydrochloric acid solution at a known concentration; • adding a given non-critical volume of a potassium iodide solution, at a known concentration, into the analysis vessel by means of the low-precision dosing means; • wait for a given period of time, without shaking; • shake the solution; • Potentiometrically titrated with sodium thiosulfate of known concentration, added by means of high precision dosing media, of the iodine released by the reaction of trivalent iron with potassium iodide; • Empty the analysis vessel. 32. Method according to claim 31, characterized in that the salt of an element from which it reacts with the sulfuric and hydrofluoric acids, forms soluble salts and precipitates that can be easily removed which is the lanthanum nitrate. 33. Method according to claim 29 or 31, characterized in that the volume of water is filled into the analysis vessel through an overflow tube incorporated in the analysis vessel. 34. Method according to claim 22, characterized in that the determination of the oxidation reduction potential of said sample of a deoxidation bath by acid bath is done before the determination of the bivalent iron concentration, in that the value thus obtained of the oxidation reduction potential is compared with a range of given values and in that if the measured value is out of range the analysis procedure is stopped and an alarm signal is generated. 35. Method according to claim 23, characterized between the determination of the free hydrogen peroxide at least comprises the following operations: • filling the analysis vessel with a given volume of water to obtain a given dilution ratio; • take from the sampling module, by means of the high-precision dosing means, a given volume of the sample of the deoxidation bath per acid bath to be analyzed and add it into the analysis vessel; Acidifying the deoxidation bath sample by acid bath, diluted, by adding in the test vessel, by means of the low precision dosing means, a given non-critical amount of a strong acid of a known concentration; • Potentiometric titration with a solution of potassium permanganate 15 of known concentration added to the analytical vessel by means of the high precision metering means, said potentiometric titration having a present end point or an automatic search of the end point; • Empty the analysis vessel. 36. Method according to claim 22, characterized in that it also comprises, after each analysis, a rinsing operation with water from the container "! - *» •. * ». of analysis, of the means to make the potentiometric measurements and of the conductivity measurement cell; the analytical vessel, the means for making the potentiometric measurements, the cell for measuring the conductivity and the cell for measuring the conductivity are chemically washed after a given number of analyzes. 37. Method according to claim 36, characterized in that the rinsing with water comprises at least the following operations: • completely emptying the analysis vessel; • pour a large amount of water into the analysis vessel through the slots placed along the upper edge of the analysis vessel; • filling said analytical vessel with water up to the tip of said means to make the potentiometric measurements and the immersed conductivity measurement cell; • empty the analysis vessel; • further rinsing the tip of said means for making the potentiometric measurements and the conductivity measuring cell, by sprinkling some water therethrough through a nozzle placed in the analysis vessel; • empty the analysis vessel and prepare it for subsequent analysis. 38. Method according to claim 36 and 37, characterized in that the chemical washing comprises at least the following operations: • filling the analysis vessel with water through the slots placed around the upper edge of the analysis vessel, until the point of said means for making the potentiometric measurements and the conductivity measurement cell immersed; • take from a tank the amount of product necessary to obtain the chemical wash solution and send it later to the analysis vessel; • After a given period of time, empty the analysis vessel and rinse it with water to remove any trace of the chemical solution from the wash. 39. Method according to claim 38, characterized in that the chemical washing is done with 10-20% hydrochloric acid. 40. Method according to claim 38, characterized in that the amount of the product necessary to make the chemical wash solution is extracted from a tank placed in the reagent storage tank. ¿^^ a ^^ Í 41. Method according to claim 22, characterized in that when not working, the analysis vessel is filled with water through the slots placed along the upper edge of the analysis vessel and through a nozzle placed inside said vessel . 42. Method according to claim 22, characterized in that the concentrations in the bath of deoxidation by acid bath, sulfuric acid, hydrofluoric acid, trivalent iron ions and oxidant product are returned to the desired values by activating each of the dosing means regulating the addition in the deoxidation bath by acid bath of the corresponding correction chemicals for a period of time given by the following formula: s = K. (v- - v). vD / p in which: s = drive time; K = factor inversely proportional to the concentration of the correction chemicals; v0 = given concentration for the specific correction chemical; Vp- = concentration of the specific correction chemical that. it results from the analysis; Í .-. Á-Á2k .. AM.Í, M ..-.- * b¿-. v = volume of the tank; P = supply of the means of addition. 43. Method according to claim 22, characterized in that the ratio R between the concentrations of trivalent iron ion and the divalent iron ion in the bath of deoxidation by acid bath is returned to the level of the desired value by means of of the following operations: • calculate Bi = AR 10 in which A is the concentration of the bivalent iron ion that results from the titration with permanganate, R is the desired ratio between the concentration of, respectively, the trivalent and bivalent iron ions and Bi is the theoretical concentration of the trivalent iron ion; 15 • compare B-. with the measured concentration B of the trivalent iron ion; • yes B > Bi, do not operate the dosing means that regulate the entrance to the deoxidation bath by acid bath of an oxidizing product; 20 • yes B < Bl, activate the dosing media that regulate the entry to the deoxidation bath by acid bath of an oxidizing product for a period of time expressed by the formula in which: Yes = drive period; K = factor inversely proportional to the concentration of the corrective chemicals; Ki = factor proportional to the volume of the tank; C = (Bi-B) / R = amount of bivalent iron ion to be oxidized to restore the desired value of iron ion concentration; P = supply of the means of addition. 44. Method according to claim 22, characterized in that the ratio R between the concentrations of trivalent iron ion and divalent iron ion in the bath of deoxidation by acid bath is returned to the desired value by means of the operations following: • calculation of total iron T = A + B where A is the concentration of Fe2 ^ obtained from the permanganometric analysis and B is the concentration of Fe3 + obtained from the iodometric analysis. • calculation of R = B / A • compare R (pre-sent relation) with Rl (prefixed relationship) • if R >; Rl the logical unit UL does not make any addition of the oxidant product • if R < Rl the logical unit UL calculates the period of activation of the addition means regulating the addition to the bath of deoxidation by acid bath of the solution of the product according to the following formula: where C = A- [(A + B) / (R? +1)] = amount of bivalent iron to be oxidized to restore the present ratio R relative to the predetermined value R_ si = drive period K = coefficient, inversely proportional to the volume of the tank VP = supply of the addition media. 45. Method according to claim 22, characterized in that the logic unit handles or administers the deoxidation bath by acid bath by means of one of the operating procedures loaded in its memory and comprising a plurality of parameters that characterize a specific operation of the working parameters of the analysis device to analyze the deoxidation bath by acid bath associated with the specific operation. t ~ ^. ^ ¿. ". Íy ^ .Í.-É * ^ 46. Method according to claim 45, characterized in that each of the operating procedures comprises at least the following information: • order and kind of analysis to be performed; • given values for the parameters under examination in the deoxidation bath by acid bath; • magnitude of the permissible deviation with respect to the given values, beyond which the logic unit drives the dosing means to send the correction chemicals to the deoxidation bath by acid bath; • proportions of dilution with water of the sample of the deoxidation bath by acid bath that is going to be analyzed. 47. Method according to claim 45, characterized in that the logic unit also performs an activated self-calibration operating procedure after a given number of analysis, comprising the steps of: • taking from a container a given quantity of a solution having a known composition and analyzing it; • transfer this solution to the analysis vessel; • compare the values obtained from the analysis with the expected ones; • activate the alarms if the deviations between the measured and expected values are higher than a given amount. 48. Method according to claim 47, characterized in that the solution with the known composition is taken from a container placed in a reagent storage device or container. ,? fSÜtP-í l-í-.yAri.'J -.,. -., r-¿-.¿