ES2258863T3 - DEVICE AND PROCEDURE FOR CONTROLLING STEEL DECAPING PROCESSES. - Google Patents

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 procedure to control pickling processes of steel.

Field of the Invention

The present invention relates to a device and a procedure to control the processes of pickling for carbon steels, austenitic stainless steels, ferritic and martensitic, duplex steels and special alloys, in which said device automatically handles the samples of the pickling baths and the analysis of said samples in order to define (according to conductivity methodologies and specific potentiometric) critical process parameters and to restore the desired concentrations of the products Chemicals needed in pickling tanks. The invention also allows handling specific pickling conditions for the type of steel in treatment through the definition of procedures operations that can be activated remotely that revoke and perform automatically the most appropriate operating conditions for pickling the specific type of material in treatment.

State of the art

In lamination, wire drawing, extrusion, heat treatment of steel products (such as plates, bands, tubes, rods) oxide layers are formed on the surface of them that must be removed to get both a appropriate final appearance as well as passive properties and anticorrosive for the final product, and to allow a job additional.

Said surface oxide layers are removed usually by chemical treatment (pickling) based on the exposure of the metallic material to the action of one or more bathrooms of acid containing inorganic mineral acids (sulfuric, hydrochloric, nitric, hydrofluoric) alone or mixed with another, with an appropriate dilution and temperature, followed by at least one final rinse in water.

For stainless steels, the processes of usual pickling (either by immersion, spraying or turbulence) require a mixture of nitric and hydrofluoric acids; such processes involve very serious ecological problems due to the emission into the atmosphere of reaction by-products (oxides of extremely toxic nitrogen) as well as large amounts of nitrates to wastewater.

Therefore, during the recent past they have conceived several alternative "ecological" processes characterized by the elimination of nitric acid.

Among such processes, they are particularly industrially effective those who use acid mixtures sulfuric or hydrochloric, hydrofluoric acid and ferric ions, in the that the appropriate concentration of such ions in the pickling bath It is maintained through the addition of hydrogen dioxide. Some of processes of this type are described in Italian patents 1,245,594 and 1,255,655 (corresponding to the document US-A-5 345 383) and in the application for European patent EP-A-0 769 575.

In traditional pickling technology according to the patents mentioned above, process management usually includes occasional control of the pickling bath to through an acidity assessment or measurement of the Manual conductivity of the solution and its iron content (or of the total metals, through a density measurement of the bathroon); it is also possible to measure the acid content hydrofluoric using a selective ion electrode specific.

Some of these techniques have been used in the automation of individual operations in pickling processes based on nitric acid from stainless steels.

US Patent No. 4,060,717 (LECO Corp.) gives know the use of ion selective electrodes for ions of fluorine and hydrogen to measure the concentration of nitric acid (u other strong acid) and hydrofluoric acid in pickling baths that contain nitric and hydrofluoric acids; voltage data electrical collected by a control circuit are prepared by a microprocessor to calculate the concentration of the two acids and Adjust the relevant concentrations.

JP 55040908 (NIPPON Steel Corp.) patent gives to know the determination of hydrofluoric acid and other acid strong (nitric, hydrochloric, sulfuric) through the determination with ion selective ion electrodes relevant after passing the solution through membranes of ion exchange, in order to adjust the concentration of acids

US Patent No. 5,286,368 (FOXBORO Corp.) measures the concentration of hydrofluoric acid in a mixture of acids nitric and hydrofluoric through the complexation capacity of the trivalent iron ions with respect to fluorine ions, which allows to determine the concentration of acids in the mixture.

JP 072944509 (KAWASAKI Steel Corp.) measures the concentrations of hydrofluoric and nitric acids free and iron ion in a pickling solution measuring iron ion concentration by a procedure of absorptiometry with an iron salicylate complex, the concentration of free hydrofluoric acid by a procedure of attenuation absorptiometry with an acetylacetone complex of iron and the total concentration of free acids by a neutralization assessment procedure, measuring the concentration of free nitric acid by subtracting the concentration of free hydrofluoric acid from total acid concentration free.

JP 081660003 (MITSUBISHI Heavy Ind. Ltd.) refers to a procedure to continuously measure the iron ion concentration in a pickling solution.

Continuous automatic handling of pickling processes of this type based on nitric acid, although better than an occasional manual or automatic control, performed, for example, a few times a day, is not essential to the process in terms of quality of the treated material, for the functional characteristics of such baths; particularly, in the stripping of stainless steels, such baths usually have high concentrations of nitric acid (approximately 12 to 15%) and a concentration of hydrofluoric acid of approximately 2 to 5%. The high nitric acid concentration guarantees both high acidity and an almost constant oxidizing power, making it possible to manage the process through occasional additions of chemical products. In addition, the
The concentration of acid is sufficient to have adequate control of the capacity of pickling of the bath.

On the contrary, pickling systems free of nitric acid, such as those mentioned previously, they base the oxidizing properties of the system in the measurement of the concentration of ferric ions (Fe 3+), or better in the control of the Fe 3+ / Fe 2+ ratio.

In this case, by the reaction (1) of pickling

(1) 2 Fe 3+ + Fe0 \ rightarrow 3 \ Fe 2+

in a continuous process for the production of stainless steel bands or in automatic plants, high productivity for pickling rods, the concentration of trivalent iron ions, the reason Fe 3+ / Fe 2+ and therefore, the oxidizing capacity of the dissolution tend to decrease rapidly, continuously modifying and drastically the behavior of bathroom.

Therefore, the optimal conditions should continuously adjust by means of oxidizing agents, such as hydrogen peroxide.

In addition, the variation of the concentration of trivalent iron also indirectly influences concentration of the free acids present in the bath.

For example, in a pickling system based on sulfuric acid, hydrofluoric acid and mixtures of ferric salts, this influence is linked to the following balances preferred:

Fe 3+ + n \ F ^ - \ rightarrow FeF_ {n} {} ^ {(3-n) +}

F_ {e} {} 2+} + SO_ {4} {} ^ {2-} \ rightarrow FeSO_ {4}

Therefore, during the reaction of oxidation / reduction of the Fe3 + / Fe2 + torque will occur release of sulfuric acid and hydrofluoric acid respectively from the relevant complex salts, modifying this mode the composition of the bathroom.

A process control through measurements occasional analytics, followed by considerable additions of chemicals to restore the best conditions of pickling therefore results in very wide variations of Bathroom parameters with adverse consequences on the quality of the product and about the costs of the process.

On the other hand, frequent manual controls and the relevant composition adjustments are time consuming and they are expensive, since this requires a large number of staff to ensure a satisfactory control frequency (for example one control per hour).

The criticality of free pickling processes of nitric acid is obviously linked to the total amount of dissolved iron per unit of time, to the number of tanks pickling to be controlled, to the number of materials that require different operating conditions and capacity practice to require frequent manual additions of acids to the tanks.

It was found that the management of the processes of pickling for stainless steels such as those mentioned previously for continuous pickling plants of stainless steel bands or for high productivity automatic plants for processing of rods, it was critical for the quality of the final product; too It may not be profitable without the use of an automatic system for sampling, control and dosage of reagents

The control device and the procedure according to the present invention require the use of a skill and specific analytical procedures for a proper management of such processes.

Summary of the invention

An objective of the present invention is provide a control device for free pickling baths  nitric acid comprising means for taking a sample of the bathroom to be analyzed; means to analyze said sample in order to measure several parameters according to methodologies of conductivity and specific potentiometers as well as to measure the value of the redox potential of said sample and its temperature; media of re-establishment, appropriate to calculate, according to the values Measured above, the amount of corrective chemicals which must be added to the pickling bath to restore until desired level the value of said parameters and to trigger at least a device for adding said pickling bath said amounts of corrective chemicals; in which said Measured parameters are the concentrations of sulfuric acid and of hydrofluoric acid measured according to conductivity methodologies specific and of the bivalent and trivalent iron ions measured according to specific potentiometric methodologies.

A further objective of the present invention is to provide a procedure to control pickling baths free of nitric acid, which comprises at least the stages following:

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take a sample of a bath of pickling

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measure according to methodologies of specific conductivity the concentration of sulfuric acid and hydrofluoric in said sample of a pickling bath;

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measure according to methodologies specific potentiometric iron ion concentration bivalent in said sample of a pickling bath;

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measure according to methodologies specific potentiometric iron ion concentration trivalent in said sample of a pickling bath;

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measure the redox potential of said sample of a pickling bath;

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measure the temperature of said sample of a pickling bath;

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reset to levels preset the values of these concentrations measured in said pickling bath by adding to the pickling bath the amount Calculated corrective chemicals.

List of figures

The invention will be described below. referring to a non-limiting embodiment represented in the attached figures in which:

Figure 1 schematically shows a plant comprising an analysis device according to the invention;

Figure 2 shows a simplified scheme of an analysis device according to the invention;

Figure 3 schematically shows the Analysis vessel CA of Figure 2, comprising a system of conductivity measurement and a preferred embodiment of the rinsing means of the container itself and the electrode of measurement;

Figure 4 schematically shows the Analysis vessel CA of Figure 2, comprising a system of potentiometric measurement and a preferred embodiment of the rinsing means of the container itself and the electrode of measurement.

In the attached figures, the elements corresponding will be identified with the same reference.

Detailed description of the invention

Figure 1 schematically shows a plant comprising an analysis device according to the invention, which understands:

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a plurality of tanks V of pickling (V1, ..., Vn);

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an analysis device A (described below with reference to the simplified scheme of Figure 2) that, in the embodiment described herein, includes a couple of analysis devices (A1, A2) that work simultaneously with different parameters;

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a plurality of deposits S (S1, S2, S3) each containing a solution with a given concentration of one of the corrective chemicals (a strong mineral acid, preferably sulfuric acid, acid hydrofluoric and an oxidizing agent, preferable but not necessarily hydrogen peroxide), which must be added to one of the tanks V;

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a plurality of pipes of permanent recirculation, which connect the V tanks to the inputs Sampling I (Figure 2) of device A of analysis;

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a plurality of pipes for feed the corrective chemicals, which connect the S deposits to V tanks;

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some means of addition that allow the analysis device A to control the addition to the V tanks of the corrective chemicals contained in the S. deposits

For simplicity, Figure 1 omits the components that are not interesting for the present description, such as valves, pumps, actuators, filtration media and clarified, known in themselves, as well as others, if they exist, circuit components

The analysis device A comprises (figure 2) means for taking a sample of the bath from a container V pickling a means to analyze it to measure, according specific conductivity and potentiometric methodologies, the preset parameters (sulfuric acid concentrations, and of hydrofluoric acid, as well as those of trivalent iron and bivalent), the redox potential and the temperature of said sample diluted means to calculate the quantities of chemicals correctors to be sent from the S deposits to the V tanks to adjust said parameters and means to drive the devices at the exit of the tanks S to send to the bathroom of pickling the calculated amounts of such chemicals concealers

Since the time needed to measure the Sulfuric and hydrofluoric acid concentration is shorter than necessary to measure the concentration of iron ions (only a few minutes versus approximately 30 minutes), the analysis devices (A1, A2) are preferably divided, each one being specialized in only one of said analyzes (measurement of sulfuric acid and hydrofluoric acid, respectively of iron ion concentrations).

The analysis devices (A1, A2) can managed by a higher level logical unit, not shown in the figures, which can be placed in place or in a remote site, connected to the analysis devices (A1, A2) to through bidirectional transmission means, known per se same.

Alternatively, said devices (A1, A2) of analysis can be of the same model and understand the means appropriate analytical to measure the concentration of both acids (sulfuric and hydrofluoric) such as iron ions.

In such a case, the device according to the invention could also work in case of a malfunction of one of the analysis devices (A1, A2).

Figure 2 shows a simplified scheme of an analysis device A (A1, A2) of Figure 1 comprising in combination relationship:

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a sampling module C, whose sampling inputs I (I1, ..., In) are connected in order to the permanent recirculation pipe between the tanks V (V1, ..., Vn; figure 1) pickling and device A of analysis; at least one deposit (not shown), in which the Sample of the bathroom to be analyzed, is provided within module C of sampling;

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a DR storage of reagents, which contains the chemicals for analysis;

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means D (D1, D2) of appropriate dosage to extract the quantities of products chemicals needed for analysis and to transfer them to the analysis vessel CA, being part of the means D of appropriate dosage to extract with a low accuracy (of about 2 to about 5%) high amounts of chemical products, the remaining dosage media being suitable for extraction with high precision (of approximately 0.1%) small amounts of chemicals; in figure 2 Dosing means D with low and high accuracy is grouped respectively into two functional units (D1, D2) different;

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an AC analysis vessel, which contains the measuring electrodes (so called generic EM in Figure 2), which they receive from the C module for making you show the sample of the bath to be analyzed, of the means D of dosing the chemicals needed for the analysis and of a reservoir W (not shown) water (preferably present a conductivity of less than 100 microsiemens) necessary to dilute said sample up to a desired dilution ratio; in figure 2 it omit additional elements (such as stirrers) present in the analysis CA container, which are not part of the present invention;

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a logical UL unit, which controls and manages the analysis procedures, obtains and elaborates the information from the EM measuring electrodes and the drive means to send the pickling bath the solutions of the corrective chemicals contained in the S deposits (figure 1).

In a preferred embodiment but not limiting, the dosage means of the functional unit D1 are peristaltic pumps with a constant supply, while the Dosing means of the functional D2 unit are syringes in a antacid material (for example, PES) that are operated at through an electric stepper motor.

Once again in an embodiment preferred, the analysis device A also comprises media (described below herein with reference to figures 3 and 4) that allow to rinse with water the AC analysis vessel and EM measuring electrodes after each measurement and after a given number of measurements with a chemical solution (preferable but not necessarily acidic 10-20% hydrochloric), thus allowing keep the EM measuring electrodes in optimal conditions, to obtain reliable analytical data, to reduce to a minimum the maintenance interventions and to significantly improve the electrode life.

To guarantee a constant quality of final product, each type or family of materials that are going to pickling should be treated according to usual parameters and characteristic (concentration of hydrofluoric and sulfuric acids, concentration of trivalent and bivalent iron ions, ratio between trivalent and bivalent iron ions, peroxide concentration of hydrogen, temperature of the sample to be analyzed, etc.); In a preferred embodiment of the invention, the parameters that characterize each stage of work as well as those with respect to the operation of the analysis device A, all which allow different analyzes in bathrooms of pickling in relation to the specific work stage, they are grouped in biologically correlated operating procedures with the material itself and stored in the logical UL unit, which revoke when necessary according to the material that is going to pick up

Preferably but not necessarily, a operating procedure comprises at least the information next:

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the order and type of analysis what must be done;

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the default values of parameters for the pickling bath;

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the magnitude of the deviations admissible with respect to the preset values, beyond which the logical UL unit drives said means to send to the bathroom pickling solutions of corrective chemicals contained in deposits S,

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the reasons for dilution with water in the sample container CA of the pickling bath sample It will be analyzed.

Advantageously the proper operation of the analysis device A can be checked periodically and automatically; for this purpose, in an embodiment preferred of the present invention, in the logical UL unit stores an additional operational self-calibration procedure that it is activated after a given number of analyzes and includes the functional stages of extracting from a container (preferable but not necessarily located in the reagent DR storage) a fixed amount of a usual solution that has a known composition, to transfer it to the analysis vessel CA, to analyze it, to compare the analytical results obtained with the known composition and of activating alarm signals if the deviation between the analytical results obtained and the known concentrations is greater than a desired value.

According to an embodiment of the present invention, not shown in the figures, the logical UL unit can be connected to a central operating position and / or to a higher level logical unit, by means of which it can be controlled and operated; As indicated above, this higher level logical unit can be placed " in situ " or be remote.

In particular, at each change in the activity of operation, the operator of the central position can modify the operating procedure performed by one or more of the UL units logical, activating the pertaining to the activity that is going to to start the operator can also revoke from one or more of the logical UL units an operating procedure, modify it and result in it being done by the logical UL units and / or giving input to a new operating procedure by storing it in the logical UL units.

The analytical procedures, which are used in the analysis of pickling baths, they will be described below to better understand the details described, which are part of the present invention.

a) Determination of acid conductivity hydrofluoric and sulfuric acid

This determination is based on the principle of which, in an aqueous solution formed by a mixture of an acid weak such as hydrofluoric acid and a stronger acid such as sulfuric acid, the conductivity of the solution is practically equivalent to that of strong acid at the same concentration; he procedure is also taken advantage of (at a later stage than a first conductivity measurement in a bath sample duly diluted to measure the concentration of sulfuric acid) of the high affinity of hydrofluoric acid for a metal cation present in the solution as a salt of a concentration known. More preferably the salt anion comes from an acid strong (for example nitric or hydrochloric acid) so that the reaction that forms the fluorocomplexes of the metal cation and the hydrofluoric acid will generate a significant increase in conductivity due to the formation of an equivalent amount of Strong acid completely dissociated, measured by a second conductivity measurement.

For example:

n HF + Fe (NO 3) 3 → FeF_ {n} {} ^ {(3-n) +} + n \ HNO_ {3}

Therefore, an increase in the conductivity of this type is proportional to the concentration of hydrofluoric acid which, after proper calibration, can be measured quantitatively

Sales of this type can be, for example, ferric nitrate, ferric chloride, aluminum nitrate, aluminum; In a preferred embodiment of the invention, uses a solution of ferric nitrate * 9H2O, with a concentration of 750 g / l.

To ensure a dependency sufficiently linear conductivity of the variation of the concentration of acids, sample dilution should be carefully evaluated as a function of the concentration of acids present in the bath that will be analyzed; as a non-limiting example, for sulfuric acid concentrations of up to 200 g / l and for Hydrofluoric acid concentrations of up to 60 g / l, the reasons dilution from 1: 100 to 5: 100, and preferably 4: 100 They are considered acceptable.

Another essential variable for obtaining reliable results (which must be handled by the UL unit logic of the analysis device A) is the temperature of the sample after dilution with water; in fact, in the industry the water temperature may present considerable variations (usually between +5 and + 40 ° C) depending on the weather, the water source and retention time in tank W.

It is evident that a conductivity measurement It is greatly influenced by temperature, and usually such a problem is overcome by means of a system of automatic compensation incorporated in the measuring device; In the present case, automatic compensation can adjust correctly only the effect on the first measurement of the conductivity (determination of sulfuric acid concentration) but not on the second (determination of acid concentration hydrofluoric) performed after the addition of ferric nitrate, since the composition of the solution and its dependence on the temperature is, in fact, different before and after the addition of ferric nitrate

This critical problem is solved with a 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, which It depends on the temperature of the sample.

The amount of ferric nitrate used during the valuation must be such that it guarantees a complete complexation of hydrofluoric acid; in the system considered, for a hydrofluoric acid concentration less than 60 g / l the ratio between the volume v3 of a solution of ferric nitrate * 9H2O with 750 g / l and the volume v1 of the bath sample must be greater than 0.5 and preferably 1.

As a non-limiting example the following operating procedure is presented along with the calculations Relevant for a sample dilution of 4: 100 by volume:

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fill the CA container of analysis, by means of dosing means D2, with a volume v2  of given water, which has a conductivity of less than 100 microsiemens to obtain a dilution ratio of 4: 100;

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take from module C socket samples (by means of dosing means D2) a given volume v1 of the sample of the pickling bath to be analyzed;

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start stirring the dissolution;

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first measurement (L1) of the conductivity;

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adding a volume v3 = v1 given of a solution of ferric nitrate * 9H2O with 750 g / l;

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stir the solution and measure your temperature T;

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second measurement (L2) of the conductivity.

The logical UL unit acquires the data L_ {1}, L_ {2}, T and automatically finds the concentration of acids a through the following calculations:

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sulfuric acid concentration (g / l): a \ cdotL_ {1} 2 + b \ cdotL_ {1} -c

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acid concentration hydrofluoric (g / l): a_ {1} \ cdot \ delta2 + b_ {1} \ cdot \ delta-c_ {1}

in which:

a, b, c, a_ {1}, b_ {1}, c_ {1} are coefficients of quadratic equations;

\ delta = L_ {2} -L_ {1} - \ phi;

\ phi = c_ {2} + (c_ {3} \ cdotT);

c_ {2}, c_ {3} are constants that depend on the amount of ferric nitrate * 9H2 O added to the sample diluted before the second conductivity measurement.

In this example:

a = 0.0066; b = 5,015; c = 6.98

a1 = 0.0120; b1 = 2,881; c_ {1} = 3.81;

c2 = 9,632; c 3 = 0.297.

Figure 3 shows the characteristics of the DC conductivity cell, the specific shape of which minimizes the negative effects due to the high viscosity of the dissolution and facilitate rinsing of platinum plates measurement.

Said DC conductivity cell comprises a hollow body B, of glass and having a substantially shaped cylindrical, which contains two blackened platinum EL plates; in the lower and upper parts of the hollow body B there are holes (F1, F2) that allow the sample to be analyzed to circulate in the inside of the hollow body B.

Preferably, the hollow body B has a diameter of approximately 20 mm (and in any case, between approximately 17 and 23 mm) and a height of approximately 40 mm (and in any case, between approximately 35 and 45 mm); the EL plate dimensions are approximately 10 x 5 mm (and in In any case, between approximately 8 x 12 mm and approximately 3 x 7 mm), the distance between them being approximately 15 mm (and in any case, between approximately 12 and 18 mm).

To avoid electrode polarization EL, the electrical measurement circuit (not shown) connected to the DC conductivity cell must operate at a high frequency (between 25 and 40 kHz).

b) Determination of bivalent iron

The determination of bivalent iron can be carried out through a potentiometric analysis, by titration with potassium permanganate according to the methodology classic

The operational sequence requires:

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pour into the CA container of analysis a given volume v2 of water, through a TP tube of overflow, to obtain a dilution ratio ≥ 1:50;

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take from module C socket samples (by means of dosing means D2) a given volume v1 of the sample of the pickling bath to be analyzed, and the addition of said sample to the analysis vessel CA;

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acidification of the sample diluted pickling bath by adding to the CA container of analysis (by means of D1 dosing means) of an amount not given criticism of a solution of a strong acid, for example a 1: 1 sulfuric acid solution by weight;

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potentiometric titration, which presents a preset endpoint or automatic search of the endpoint with a solution of potassium permanganate of 0.1 N added to the analysis vessel CA by means D2 of dosage;

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empty and rinse the container CA analysis.

c) Determination of trivalent iron

Trivalent iron is measured by titration appliance, which nevertheless uses some specific attention to allow the use of an automatic device and obtain of reliable and reproducible results.

Such determination requires the sequence following operation:

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pour into the CA container of analysis a given volume v2 of water, through a TP tube of overflow, to obtain a dilution ratio ≥ 1:50;

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take from module C socket samples (by means of dosing means D2) a given volume v1 of the sample of the pickling bath to be analyzed, and the addition of said sample to the analysis vessel CA;

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start agitation;

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addition to the CA container of analysis (by means of dosing means D1) of a volume not critical given of a solution of lanthanum nitrate presenting a known concentration;

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wait for 30 s without shake;

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addition to the CA container of analysis (by means of dosing means D1) of a volume not critical given of a 1: 1 hydrochloric acid solution in volume;

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addition to the CA container of analysis (by means of dosing means D1) of a volume not given critic of a solution of potassium iodide, to a concentration for example of 1 kg / l;

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wait for 5 min. without shake;

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start stirring the dissolution;

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potentiometric titration with 0.1 N sodium thiosulfate (added by means D2 of dosage) of iodine released by the trivalent iron reaction with potassium iodide;

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empty and rinse with water the AC analysis vessel.

For this automatic analysis, one of the highlights are the use of lanthanum nitrate; from in fact, the addition of a salt that includes a cation that can complexing the fluorine ion bound to the iron ion is essential for the quantitative analysis of the ferric ion through the analysis appliance

The analysis can be performed manually using a solution of calcium chloride; however, it proved that calcium chloride cannot be used for automatic titration of trivalent iron, because of the subsequent precipitation of calcium fluoride and sulfate calcium, which tend to continuously dirty the electrodes in the CA container analysis, resulting in significant errors and A conservation of the complex. On the contrary, it was found that Lanthanum salts can quantitatively release the ferric ion, generating powdered and lanthanum fluoride precipitates that do not adhere, thus allowing automatic handling of processes with high reliability and very conservation limited

This same result can also be achieved. adding to the system a complexing agent for iron ion, which can nevertheless release it quantitatively during the subsequent reaction with potassium iodide; for this purpose they can complexing agents such as EDTA be suitable.

The potentiometric system, schematically illustrated in Figure 4, comprises a measuring electrode E (inert to the working environment) submerged in the analysis vessel CA and a reference electrode R (preferably glass, of the Ag / AgCl type) located outside of said analysis vessel CA and in contact with the measurement solution through a salt bridge, comprising an electrolyte (contained in an SR tank) that is arranged to continuously pass through a porous wall SP located at one end of a plastic T tube
small.

The continuous passage of the electrolyte through the SP wall aims to allow electrical continuity; avoid the contact between the wall SP and the hydrofluoric acid of the bath of pickling and continuously renew the electrolyte.

In a preferred embodiment, the measuring electrode E is manufactured from a body in a antacid material that supports at one of its ends a plate P of Platinum, one of whose surfaces, finished specularly, is orients down, thus preventing the salts that come from the reaction products are deposited on the measuring surface of plate P, making it dirty.

Advantageously, to the electrolyte (preferably 3M potassium chloride) a 10% solution of glycerin (from another compatible product that has a viscosity at 20ºC between 1.15 and 1.45 centipoise, inert with respect to the work environment and functionally equivalent) to improve the viscosity and reduce the flow rate, thus allowing better autonomy of the potentiometric system for a given volume of the SR tank.

d) Determination of hydrogen peroxide

The determination of free hydrogen peroxide in nitric acid free pickling processes such as described herein, it is necessary in the treatment of ferritic and martensitic steels for the control of the baths of finishing / passivation generally used as the last operation before the final rinse; usually said baths comprise sulfuric acid (20-60 g / l), hydrogen peroxide (3-10 g / l) and sometimes hydrofluoric acid.

The analytical methodology and the sequence Operational used for the determination of hydrogen peroxide  they are the same as those used for iron determination bivalent in pickling bathrooms.

e) Determination of redox potential

The device according to the invention measures, before the determination of bivalent iron, the redox potential of the dissolution in the sample of the diluted pickling bath used by the potentiometric system already described; the value obtained in this way It is very close (± 20 mV) to the redox potential measured in the bath before dilution.

The value obtained is compared with a range of values (usually between 200 and 550 mV) stored in the logical UL unit to be used as a first signal of the correct operation of the system; if the measured value is found outside of said range, the logical UL unit of device A Scan stops the scan procedure and sends an alarm. The potentiometric system calibration is carried out at a given frequency (say, once a week) by measuring of the redox potential in a usual solution with a potential known (usually 468 mV).

As already mentioned, the logical UL unit of an analysis device 1 according to the present invention, after measure the desired parameters in the sample of the pickling bath in analysis, calculate the amount of each of the solutions with a known concentration of corrective chemicals (sulfuric acid, hydrofluoric acid and oxidizing agent) contained in tanks S, said chemicals being added from a timely way to the pickling bath to restore the values of the desired composition and drives addition means (such as, by example, pumps or dosing solenoid valves) at the outlet of the deposits S to send said quantities to the pickling bath Calculated corrective chemicals.

Knowing the characteristics of the plant (volume of tank V, supply of each means of addition, values concentration levels for these chemicals correctors, concentration of said chemicals, etc.) to present the correct amount of chemicals correctors added to the pickling bath, the logical UL unit only must calculate the period of operation of said means of addition.

The studies and experiments of these Applicants showed that, to return the desired values to  concentrations in the sulfuric acid pickling bath, of acid hydrofluoric, trivalent iron ion and oxidizing reagent, the logical UL unit must drive each of the means of addition which regulate the addition to the pickling bath of the solutions of sulfuric acid, hydrofluoric acid and oxidizing reagent, during a period of time s (in seconds) given by the following expression:

s = K \ cdot (v_ {0} - v_ {m}) \ cdot v_ {b} / p

in the that:

s = drive time (seconds);

K = factor inversely proportional to the concentration of the corrective chemicals (l / g);

v_ {0} = concentration given for the product specific corrective chemical (g / l);

v_ {m} = concentration of said product specific corrective chemical resulting from the analysis (g / l);

V_ {b} = volume of tank V;

p = supply of the means of addition (l / s).

To return the R ratio to the desired value, enter the concentration of trivalent and bivalent iron ions, the UL logical unit calculates the drive period s1 (in seconds) of the addition means that send the pickling bath the oxidant reagent solution:

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calculating B_ {1} = A \ cdotR, in which A is the concentration (g / l) of the bivalent iron ion resulting from permanganate titration, R is the desired ratio between the concentration of, respectively, iron ions trivalent and bivalent, and B1 is the theoretical concentration of trivalent iron ion;

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comparing B_ {1} with the measured B concentration of trivalent iron ion (g / l);

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if B? B_ {1} (the measured concentration of trivalent iron ions is greater than that of the bivalent iron), the logical UL unit does not act

?

if B <B_ {1} (the concentration of trivalent iron ions is lower than the measurement), the logical UL unit calculates the period s1 of activation of the addition means that regulate the addition to the stripping bath of the oxidant reagent solution, by means of the formula

s1 = K \ cdot \ K_ {1} \ \ cdot C / p

in the that:

s_ {1} = drive period (s);

K = factor inversely proportional to the concentration of the corrective chemicals (i / g);

K_ {1} = factor proportional to the volume V of tank (l);

C = (B_ {1} -B) / R = amount of bivalent iron ion that must be oxidized to restore value desired for iron ion concentration (g / l);

p = supply of the means of addition (l / s).

Alternatively the bathroom can be handled in function of the ratio R between trivalent iron and iron bivalent according to the following calculation:

?

Total iron calculation T = A + B

where A is the concentration of Fe 2+ obtained from the permanganometric analysis and B is the Fe 3+ concentration obtained from the analysis appliance

?

calculation R = B / A

?

compare R (real ratio) with R1 (preset reason)

?

if R> R1, the UL unit logic does not make any oxidant product addition

?

if R <R1, the UL unit Logic calculates the drive period s1 (in seconds) of the addition means regulating the addition to the pickling bath of the oxidizing product solution according to the following formula

s1 = K \ cdot \ K_ {1} \ \ cdot C / p

in the that

C = A - [(A + B) / (R1 +1)] = amount of iron bivalent that must be oxidized to reestablish the real R ratio up to the default R_ {1}

s_ {1} = drive period (s)

K = coefficient, inversely proportional to tank volume V (I)

P = supply of the means of addition (I / s).

Figure 3 schematically shows a view in exploded view of the analysis vessel CA of Figure 2, comprising a measurement system of the conductivity type and a preferred embodiment of the rinse means of the AC container of Analysis and measuring cell CC.

In figure 3 it is possible to observe:

?

the DC cell measuring the conductivity used for the conductivity measurement;

?

the AC vessel of analysis;

?

the overflow TP, mobile, whose position (controlled by the logical UL unit) allows set the level of liquid in the analysis vessel CA, and empty the same container;

?

means (F, U) for rinsing controlled by the logical UL unit, which allow rinsing of the AC analysis vessel and the DC cell measuring the conductivity.

Figure 4 schematically shows a view in exploded view of the analysis vessel CA of Figure 2, comprising a potentiometric measurement system as well as a preferred embodiment, similar to that of Figure 3, of the means of rinsing of the AC analysis vessel and the electrodes of measurement.

In figure 4 it can be seen:

?

the potentiometric system, which comprises the measuring electrode E, the reference electrode R, located outside the CA analysis vessel, and the salt bridge that in turn it comprises an electrolyte contained in the SR tank, which continuously passes through a porous SP wall located in a end of a small plastic T-tube;

?

the AC vessel of analysis;

?

the mobile overflow TP, whose position (controlled by the logical UL unit) allows set the level of liquid in the analysis vessel CA, and empty the same analysis vessel;

?

means (F, U) for rinsing controlled by the logical UL unit, which allow rinsing of the AC analysis vessel, electrode E end and wall Porous SP

In the preferred embodiment shown in Figures 3 and 4, such rinsing means comprise a plurality of grooves F located along the upper edge of the AC analysis vessel and a suitable U nozzle to clarify with a water spray the end of the measuring electrode E and the porous wall SP, respectively the measuring cell CC of the conductivity; in figures 3 and 4, the CP cover for the analysis vessel CA and the MS media that support electrode E, the small tube T of the system potentiometric, DC cell conductivity measurement and small tubes (not explicitly indicated in figures 3 and 4) that connect the dosing means D (D1, D2) with the AC analysis vessel; the CP cover and the MS support media, since they know themselves and in everything case, they do not belong to the present invention.

Preferably, the analysis vessel CA, the measuring electrode E and the porous wall SP (respectively the AC analysis vessel and the DC cell measuring the conductivity) rinse with water after each analysis and wash with a chemical solution after a given number of analysis.

To rinse said components with water afterwards of each analysis, the logical UL unit performs in order the following stages:

?

completely empty the AC analysis vessel;

?

pour into said AC container of analysis a considerable amount of water through the slots F;

?

fill the CA container of analysis with water until the tip of electrode E and the wall SP porous, respectively the conductivity measuring cell CC are submerged;

?

empty the AC container of analysis;

?

further clarify the tip of electrode E and the porous wall SP, respectively cell CC of conductivity measurement by spraying some water on them through the mouthpiece U;

?

empty the AC container of analysis and prepare it for further analysis.

To wash the analysis vessel AC after of a given number of analyzes with a chemical solution (preferably 10-20% hydrochloric acid), the AC analysis vessel, electrode tip E and wall SP porous (respectively the AC analysis vessel and the CC cell of conductivity measurement), the logical UL unit fills the AC analysis vessel with water through slots F up to that the tip of electrode E and the porous wall, respectively the DC cell conductivity measurement are submerged, socket a tank (preferred but not necessarily located within the DR reagent storage) a quantity of product (preferably hydrochloric acid) necessary for said washing chemical and sends it to the CA analysis vessel; after a period of time given the logical UL unit empties the AC container of analysis and rinse it with water, to remove any trace of the chemical dissolution

Also, when it is not running, the AC 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 electrode E, the porous wall SP, and the DC cell of conductivity measurement.

For an expert it is possible to modify and improve, as common experience and technical development suggests natural, the device for the control of pickling baths according to the present description, without thereby departing from the scope of The present invention.

Claims (48)

1. Control device for pickling baths free of nitric acid comprising means for taking a sample of the bathroom to be analyzed; a means to analyze said sample in order to measure several parameters according to specific conductivity and potentiometric methodologies as well how to measure the redox potential value of said sample and its temperature; means of restoring, appropriate for calculate, according to the previous measured values, the amount of corrective chemicals that must be added to the bath pickling in order to reset the value to the desired level of said parameters and to drive at least one device for add said quantities of products to said pickling bath corrective chemicals; in which said measured parameters are the Sulfuric acid and hydrofluoric acid concentrations measured according to specific conductivity methodologies and iron ions bivalent and trivalent measures according to potentiometric methodologies specific. 2. Control device according to claim 1, characterized in that said restoring means introduce the calculated amounts of solutions of said corrective chemicals into the stripping bath having a known concentration. 3. 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 said oxidizing agent is hydrogen peroxide. 5. Control device according to claim 1, characterized in that it comprises at least one analysis device (A). 6. Control device according to claim 5, characterized in that it comprises two analysis devices (A1, A2) that work simultaneously with different parameters. 7. 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 pickling bath of sulfuric and hydrofluoric acids and adds sulfuric and hydrofluoric acids to the bath of pickling in order to restore the relevant concentration levels given, while the other analysis device (A2, respectively A1) measures the concentrations in the pickling bath of the iron ions and adds an oxidizing agent to the pickling bath to restore the given value of the trivalent iron ion concentration and / or the ratio between the trivalent and bivalent iron ions. 8. Control device according to claim 7, characterized in that the analysis device (A) comprises in combination: a sampling module (C) provided with sample inlets (1) connected in order to tanks of pickling (V) to send at least one deposit located inside the sampling module (C), a sample of the pickling bath to be analyzed; a reagent storage (DR), containing at least the reagent tanks used for the analysis of said sample of the pickling bath; appropriate dosage means (D) for extracting from said tanks in the reagent storage (DR) given amounts of chemicals and transferring them to an analysis vessel (CA); containing the analysis vessel (CA) the measuring electrodes (EM) used to analyze the sample of the pickling bath, which receives from the sampling module (C) the sample of the bath to be analyzed and the dosing means (D) the chemicals needed for the analysis; A logical unit (UL) that controls and manages the analysis procedures, acquires and processes the information from the measuring electrodes (EM) and the actuation means to send the solutions containing the corrective chemicals to the pickling bath. 9. Control device according to claim 8, characterized in that part of the dosing means (D) is suitable for extracting with high precision (from about 2 to about 5%) high amounts of chemicals, and because the means Remaining dosages are suitable for extracting with small precision (approximately 0.1%) small amounts of chemicals. 10. Control device according to claim 9, characterized in that said dosing means (D) having a low precision and high precision are grouped respectively into two different units (D1, D2). 11. Control device according to claim 8, characterized in that it also comprises means for sending water to the analysis vessel (CA) to rinse the same vessel (CA) and the measuring electrodes (EM) and to dilute the bath sample of pickling contained in the analysis vessel (CA) up to the desired dilution ratio. 12. Control device according to claim 11, characterized in that the water for rinsing and dilution has a conductivity of less than 100 microsiemens. 13. Control device according to claim 8, characterized in that each logical unit (UL) is connected to a central operating position and / or to a higher level logical unit, by which it can be controlled and operated. 14. Control device according to claim 1, characterized in that said means for carrying out the conductivity measurements comprise a conductivity measuring cell (CC) provided at one of its ends with a hollow glass body (B) and having a substantially cylindrical shape, which contains a pair of blackened platinum plates (EL), holes (F1, F2) being provided in the lower and upper parts of said hollow body (B) that allow the sample to be analyzed, contained in the analysis vessel (CA), circulate inside the hollow body (B). 15. Control device according to claim 14, characterized in that the hollow body (B) has a diameter between 17 and 23 mm and a height between 35 and 45 mm, the dimensions of the plates (EL) being comprised between 8 x 12 mm and 3 x 7 mm, the distance between one and the other between 12 and 18 mm. 16. Control device according to claim 15, characterized in that the hollow body (B) has a diameter of 20 mm and a height of 40 mm, the dimensions of the plates (EL) being 10 x 5 mm, the distance being one to another 15 mm. 17. Control device according to claim 1, characterized in that said means for performing the potentiometric measurements comprise a measuring electrode (E) immersed in the analysis vessel (CA) and a reference electrode (R) located outside the analysis vessel (CA), connected to the measurement solution through a salt bridge consisting of an electrolyte that is continuously passed through a porous wall (SP) located at one end of a small plastic tube (T). 18. Control device according to claim 17, characterized in that the electrolyte contains a product having a viscosity between 1.15 and 1.45 centipoise at 20 ° C. 19. Control device according to claim 18, characterized in that the electrolyte contains 10% glycerin. 20. Control device according to claim 17, characterized in that the measuring electrode (E) is constituted by a body in an antacid material that supports at one of its ends a platinum plate (P) having a surface with oriented specular finish down. 21. Control device according to claims 8, 14 and 17, characterized in that the analysis device (A) also comprises means for chemically washing and rinsing the analysis vessel (CA), measuring electrode (E) and water with water. the porous wall (SP) of the salt bridge, respectively the analysis vessel (CA) and the conductivity measuring cell (CC), said means comprising at least some grooves (F) located along the upper edge of the vessel ( CA) and a nozzle (U) suitable for directing a flow of water on the end of the measuring electrode (E) and on the porous wall (SP), respectively on the conductivity measuring cell (CC). 22. Procedure to control baths of free pickling of nitric acid, comprising at least following stages:

?

take a sample of a bath of pickling

?

measure according to methodologies of specific conductivity the concentration of sulfuric acid and hydrofluoric in said sample of a pickling bath;

?

measure according to methodologies specific potentiometric iron ion concentration bivalent in said sample of a pickling bath;

?

measure according to methodologies specific potentiometric iron ion concentration trivalent in said sample of a pickling bath;

?

measure the redox potential of said sample of a pickling bath;

?

measure the temperature of said sample of a pickling bath;

?

reset to levels preset the values of these concentrations measured in said pickling bath by adding to the pickling bath the amount Calculated corrective chemicals.

23. A 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 operating operation before final rinsing in the treatment of ferritic and martensitic steels. 24. Method according to claim 22, characterized in that the measurement of the concentration in said sample of a sulfuric acid and hydrofluoric acid pickling bath according to specific conductivity methodologies comprises at least the following operations:

?

fill the analysis vessel (CA), by means of high precision dosing means (D2), with a given volume of water that has a lower conductivity at 100 microsiemens to obtain a given dilution ratio;

?

take from a socket module (C) of samples, by means of high dosage means (D2) precision, a given volume of the sample of the pickling bath that goes to be analyzed and introduced into the analysis vessel (AC);

?

stir the solution;

?

perform a first measurement of conductivity (L1);

?

add to analysis vessel (CA) a given volume of a solution of ferric nitrate * 9 H2O;

?

stir the solution and measure your temperature (T);

?

perform a second measurement of conductivity (L2);

?

empty the analysis vessel (AC).

25. Method according to claim 24, characterized in that a solution of 750 g / l of ferric nitrate having the same volume as the sample of the pickling bath to be analyzed is added to the analysis vessel (CA). 26. A method according to claim 24, characterized in that the concentration (as) in said sample of a sulfuric acid pickling bath is calculated according to the following equation: as = a \ cdot L_ {2} + b \ Ld {1} - C in which a, b, c are coefficients of the quadratic equation and L_ {1} is the result of the first measurement of conductivity. 27. Method according to claim 24, characterized in that the concentration (af) in said sample of a hydrofluoric acid pickling bath is calculated according to the following equation: af = a_ {1} \ cdot \ delta2 + b_ {1} \ cdot \ delta - c_ {1} in which: a_ {1}, b_ {1}, c_ {1} are coefficients of the quadratic equation; \ delta = L_ {2} –L_ {1} - \ phi; \ phi = c_ {2} + (c_ {3} \ cdot T); L_ {1} and L_ {2} are the results of the first and second conductivity measurement; c_ {2}, c_ {3} are constants that depend on the amount of ferric nitrate * 9 H 2 O added to the analysis vessel (AC). 28. Method according to claim 24, characterized in that the determination according to specific potentiometric methodologies of the concentration of the bivalent iron ion in said sample of a pickling bath is carried out by permanganometric titration. 29. Method according to claim 28, characterized in that the determination according to specific potentiometric methodologies of the concentration of the bivalent iron ion in said sample of a pickling bath comprises at least the following operations:

?

fill the analysis vessel (CA) with a given volume of water to obtain a ratio of dilution given;

?

take from the module (C) of samples, by means of high dosage means (D2) precision, a given volume of the pickling bath sample that goes to be analyzed, and add it to the analysis vessel (CA);

?

acidify the bath sample diluted pickling by adding in the test vessel (CA), by means of low precision dosing means (D1), of a given non-critical amount of a strong acid solution which has a known concentration;

?

potentiometric titration with a solution of potassium permanganate of a concentration known added to the analysis vessel (CA) by means (D2) High precision dosing presenting such assessment potentiometric a real endpoint or an automatic search of the final point;

?

empty the analysis vessel (AC).

30. The method according to claim 22, characterized in that the determination according to specific potentiometric methodologies of the concentration of the trivalent iron ion in said sample of a pickling bath is carried out by means of a household evaluation. Method according to claim 30, characterized in that the determination according to specific potentiometric methodologies of the concentration of the trivalent iron ion in said sample of a pickling bath comprises at least the following operations:

?

fill the analysis vessel (CA) with a given volume of water, to obtain a dilution ratio Dadaist;

?

take from the module (C) of samples, by means of high dosage means (D2) precision, a given volume of the pickling bath sample that goes to be analyzed, and adding said bath sample to the container of analysis (CA);

?

start agitation;

?

add to analysis vessel (CA), by means of low precision dosing means (D1), a given non-critical volume of a solution, at a concentration known, of a salt of an element, that when reacting with the sulfuric and hydrofluoric acids, form soluble or precipitated salts that can be easily removed;

?

wait for a period of given time without stirring;

?

add to analysis vessel (CA), by means of low precision dosing means (D1), a given non-critical volume of a solution of hydrochloric acid at a known concentration;

?

add to analysis vessel (CA), by means of low precision dosing means (D1), a given non-critical volume of a potassium iodide solution of a known concentration;

?

wait for a given period of time without stirring;

?

stir the solution;

?

potentiometric titration with sodium thiosulfate at a known concentration, added by high precision dosing means (D2) of iodine released by the reaction of trivalent iron with iodide of potassium;

?

empty the analysis vessel (AC).

32. Method according to claim 31, characterized in that the salt of an element which, when reacting with sulfuric and hydrofluoric acids, forms soluble and precipitated salts that can be easily removed is lanthanum nitrate. 33. A method according to claims 29 or 31, characterized in that said volume of water is filled in the analysis vessel (CA) through an overflow tube incorporated in the analysis vessel (CA). 34. Method according to claim 22, characterized in that the determination of the redox potential of said sample of a pickling bath is carried out before the determination of the concentration of bivalent iron, because the value obtained in this way of the redox potential is compared with a range of values given and because if the measured value is outside this range the analysis procedure is stopped and an alarm signal is generated. 35. Method according to claim 23, characterized in that the determination of free hydrogen peroxide comprises at least the following operations:

?

fill the analysis vessel (CA) with a given volume of water to obtain a dilution ratio Dadaist;

?

take from the module (C) of samples, by means of high dosage means (D2) precision, a given volume of the pickling bath sample that goes to be analyzed, and add it to the analysis vessel (CA);

?

acidify the bath sample from diluted pickling by adding in the test vessel (CA), by means of low precision dosing means (D1), of a given non-critical amount of a strong acid from a known concentration;

?

potentiometric titration with a solution of potassium permanganate of a concentration known added to the analysis vessel (CA) by means (D2) High precision dosing presenting such assessment potentiometric a real endpoint or an automatic search of the final point;

?

empty the analysis vessel (AC).

36. A method according to claim 22, characterized in that it also comprises, after each analysis, a water rinse operation of the analysis vessel (CA), of the means for performing the potentiometric measurements and of the conductivity measuring cell; The analysis vessel (CA), the means for performing potentiometric measurements, the conductivity measuring cell and the conductivity measuring cell after a given number of analysis are chemically washed. 37. Method according to claim 36, characterized in that said rinse with water comprises at least the following operations:

?

completely empty the analysis vessel (CA);

?

pour into said container of analysis (CA) a large amount of water through the slots (F) located along the upper edge of the container analysis (CA);

?

fill said container with water of analysis (CA) until submerging the tip of said means to perform potentiometric measurements and the measuring cell of the conductivity;

?

empty the analysis vessel (AC);

?

further clarify the tip of said means for performing potentiometric measurements and the conductivity measuring cell, spraying on them a little water through a nozzle (U) located on the analysis vessel (CA);

?

empty the analysis vessel (CA) and prepare it for further analysis.

38. Method according to claims 36 and 37, characterized in that the chemical washing comprises at least the following operations:

?

fill the container with water analysis (CA) through the slots (F) located around the upper edge of the analysis vessel (CA) until the tip of said means to perform potentiometric measurements and the conductivity measurement cell;

?

take from a tank the amount of the product necessary to obtain the chemical wash solution and send the latter to said analysis vessel (CA);

?

after a period of time given, empty the analysis vessel (CA) and rinse with water to remove any trace of the chemical solution of washed.

39. Method according to claim 38, characterized in that said chemical washing is carried out with hydrochloric acid at between 10 and 20%. 40. Method according to claim 38, characterized in that the quantity of the product necessary to produce the chemical washing solution is extracted from a tank located in the reagent storage (DR). 41. A method according to claim 22, characterized in that when it is not in operation, the analysis vessel (CA) is filled with water through slots (F) located along the upper edge of the analysis vessel (CA) and through a nozzle (U) located inside said container. 42. Method according to claim 22, characterized in that the concentrations in the stripping bath of sulfuric acid, hydrofluoric acid, trivalent iron ions and oxidizing product are returned to the desired values by activating each of the media of dosage that regulate the addition in the pickling bath of the corresponding corrective chemicals for a period of time (s) given by the following formula s = K \ cdot (v_ {0} - v_ {m}) \ cdot v_ {b} / p in the that: s = drive time; K = factor inversely proportional to the concentration of the corrective chemicals; v_ {0} = concentration given for the product specific corrective chemical; v_ {m} = concentration of said product specific corrective chemical resulting from the analysis; V_ {b} = tank volume; p = supply of the means of addition. 43. Method according to claim 22, characterized in that the ratio R between the concentrations of the trivalent iron ion and the bivalent iron ion in the pickling bath is returned to the desired value by the following operations:

?

calculate B_ {1} = A \ cdotR in which A is the concentration of the bivalent iron ion that results of the permanganate titration, R is the desired ratio between the concentration of, respectively, the trivalent iron ions and bivalent, and B1 is the theoretical concentration of iron ion trivalent;

?

compare B_ {1} with the measured B concentration of trivalent iron ion;

?

if B \ Bq {1}, I don't know actuate the dosing means (D2) that regulate the entrance to the pickling bath of an oxidizing product;

?

if B <B_ {1}, they are activated the means (D2) of dosage that regulate the entrance to the bathroom of pickling of an oxidizing product for a period of time (s1) expressed by the formula

s1 = K \ cdot K_ {1} \ cdot C / p in the that: s_ {1} = drive period; K = factor inversely proportional to the concentration of the corrective chemicals; K_ {1} = factor proportional to the volume of tank; C = (B_ {1} -B) / R = amount of bivalent iron ion that must be oxidized to restore value desired 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 the trivalent iron and bivalent iron ion in the pickling bath is returned to the desired value by the following operations:

?

Total iron calculation T = A + B wherein A is the concentration of Fe 2+ obtained from the permanganometric analysis and B is the concentration of Fe 3+ obtained from the household analysis.

?

calculation of R = B / A

?

compare R (real ratio) with R1 (preset reason)

?

if R> R1 the logical UL unit does not make any oxidant product addition

?

if R <R1 the logical UL unit calculates the period s1 of activation (in seconds) of the media of addition that regulate the addition to the pickling bath of the oxidizing product solution according to the following formula

s1 = K \ cdot K_ {1} \ cdot C / p in the that C = A - [(A + B) / (R1 +1)] = amount of iron bivalent that must be oxidized to reestablish the real R ratio up to the default R_ {1} s_ {1} = drive period (s) K = coefficient, inversely proportional to tank volume V (I) P = supply of the means of addition (I / s). 45. Method according to claim 22, characterized in that the logical unit (UL) handles the pickling bath by means of one of the operating procedures loaded in its memory and comprising a plurality of parameters that characterize a specific operation and the working parameters of the analysis device to analyze the pickling bath associated with said specific operation. 46. Method according to claim 45, characterized in that each of the operating procedures comprises at least the following information:

?

order and type of analysis that they must be done;

?

values given for parameters to be examined in the pickling bath;

?

magnitude of deviation admissible with respect to these given values, beyond which logical unit (UL) drives the dosing means (D) to send the chemical products to the pickling bath concealers;

?

water dilution ratios of the sample of the pickling bath to be analyzed.

47. Method according to claim 45, characterized in that the logical unit (UL) also performs an activated self-calibration operating procedure after a given number of analyzes, comprising the following steps:

?

take from a container a given amount of a solution that has a composition (CA) known and analyze it;

?

transfer said solution to analysis vessel (CA);

?

compare the values obtained by analysis with those expected;

?

activate alarms if 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 located in a reagent storage (DR).