DE60105653T2 - CONTINUOUS ELECTROLYTIC FURNING AND DECOMPOSITION OF UNLOCKED STEEL AND NON-STAINLESS STEEL - Google Patents

Abstract

Continuos electrolytic method in a neutral solution for the pickling and the descaling of carbon steels and stainless steels, in the presence of electrolysis current flow indirect effects, said current being AC or DC and having a frequency lower than 3 Hz, characterized in that the anodic treatment times and the cell currents are selected according to the formula: It=c+kI where: I is the current density crossing the cell; t is the anodic treatment time; c is the constant fraction of electric charge density outputted for the direct oxide change anodic reactions; and k is a time constant for the calculation of the fraction of electric charge density, proportional to the current density I (kI), outputted for the indirect anodic reactions linked to Oxygen development and to the consequent acidification at the steel/electrolytic solution interface (Carbon steels) or at the scale/electrolytic solution interface (stainless steels).

Description

The The present invention relates to the continuous pickling of hot rolled rolls unalloyed steel or carbon steel strip by an electrolytic Procedure in a neutral solution (pH in the range of 6.0 to 8.0). The present invention further relates to the field of continuous descaling of stainless ribbons or strips of steel for the removal of surface oxides, which were formed by the action of thermal treatments, comprising hot rolling and glow.

The Advantages of neutral electrolytic pickling and descaling processes in terms of conventional Procedures in acid baths are essentially the following: Use of non-hazardous, non-harmful and non-polluting pickling baths; easy treatment and recovery of residues; and increased Surface quality of the stained Materials.

It is known that the principal anodic reactions, which in theory can take place in a solution on the oxidized surface of hot-rolled carbon steel or unalloyed steel, can be schematized as follows: Fe + 2H ₂ O → Fe (OH) ₂ + 2H ⁺ + 2e ^- (0) H ₂ O → 2H ⁺ + ½O ₂ + 2e ^- (1) Fe ₃ O ₄ + 8H ⁺ → 3 Fe ³⁺ + 4H ₂ O + e ^- (2) Fe → Fe ³⁺ + 3e ^- (3)

The first reaction (0) is feasible only at a low electrode potential and is insignificant as a pickling reaction; it is essentially negligible for values of current density (I) exceeding a predetermined limit (I ₀ ).

Therefore, for I> I ₀ values, the second (1) and the third (2) reactions take place on the surface of the oxide-covered steel. The reaction (1) acidifies the metal-scale interface, whereas the reaction (2) converts the scale into a soluble compound by the effectiveness of the presence of the acidified interface. Therefore, these two reactions (1) and (2) constitute the essential mechanism of electrolytic pickling in a neutral solution.

To the Time of the complete resolution of the surface scale begins the anodic oxidation of the underlying metal, acc. the fourth reaction (3), occur until the equilibrium rate in the passivated state is achieved when the entire scale of the surface was removed (end of pickling treatment). Therefore, according to the electrolytic Beizmechanismuses, which by the second (1) and by the third (2) reaction is defined, the fourth reaction (3) insignificant.

Of course, to make the electric circuit, suitable auxiliary electrodes (also called counter electrodes) used on which the cathodic Reactions take place that allow the electrical neutrality the solution is maintained.

During the electrolytic pickling process in a neutral solution, the above-mentioned anodic reactions take place under control of the diffusion. This means that the reaction conditions depend on the diffusion of the reactants and on the reaction products through the boundary layer (flow), which in turn is determined by the dynamics of the fluid on the steel surface. Therefore, an increase in the turbulence of the solution at one of the interfaces can counteract effects on the attack rate against the scale, as it also increases the flow of hydrogen ions (H ⁺ ) leaving the acidified interface [Reaction (1) )].

Further, it is known from the Faraday laws of electrolysis, concerning the anodic dissolution, as well as cathodic deposition methods, that the amount of a substance obtained at the electrodes is proportional to the amount of electric charge passing through the electric circuit is directed. In particular, the amount of electric charge necessary to obtain a given amount of a substance to convert is constant, e.g. B. for one equivalent of any substance is a Faraday, ie 96.500 Coulomb required. The above is expressed by the following equation Q = I dead * t = constant where Q is the amount of electrical charge (in coulombs, C), I _{tot is} the applied electrical current (in amperes, A), and t is the electrolysis time (in seconds, sec).

The equation applies to any selection of I _tot or t, therefore the same effect is achievable if different different values of current I _{tot are applied} for respective electrolysis periods.

As is known, due to the high susceptibility of chromium to the Oxidation, the surface scale of thermally treated stainless steels clearly with chromium oxide enriched, which during the subsequent pickling in an acidic solution very difficult to remove.

In general, due to ecological reasons, in the pickling of stainless steels, mixtures of strong inorganic acids, ie HNO ₃ / HF solutions, or more recently, H ₂ SO ₄ / HF / H ₂ O ₂ solutions are used.

It However, before chemical pickling, to speed up the Method for removing the entire surface scale during the Production of stainless steels Descaling pretreatments performed. The effect of descaling is that the tinder is changing to simplify the subsequent removal of the same. The scale conditioning process for hot rolled stainless steel strips use mainly molten salt baths (thermochemical descaling) or electrolytic treatments.

A Type of thermochemical process currently used for descaling is used immersing in an oxidizing, molten Salt bath, which is suitable, the chromium oxides (or the mixed Chromium / iron oxides) in soluble to convert hexavalent chromium compounds.

electrolytic Descaling is a conventional one industrial process, which are carried out in acidic electrolytes can, as well as in neutral electrolytes, whereby the anion normally the sulphation is. Particularly attractive is the process of electrolytic Descaling in a neutral solution. Actually this kind of descaling when dissolving the scale is effective and the resolved one Tinder is made directly by precipitation out of the solution separated, without any residue treatment (eg by neutralization) would have to be performed. Of Further, no material is required in the construction of the system, the especially corrosion resistant is.

The principal anodic reactions of the change of the oxide scale which lead to the electrolytic scaling in a neutral solution can be represented as follows: H ₂ O → 2H ⁺ + ½O ₂ + 2e ^- (4) Cr ₂ O ₃ + 5H ₂ O → 2CrO ₄ ² + 10H ⁺ + 6e ^- (5)

Around make the electrolytic circuit, auxiliary electrodes (or counter electrodes) are used, on which the cathodic Develop reactions, and the electrical neutrality of the maintaining solution enable.

In the above-mentioned anodic reactions produce acidification of the scale / solution interface. This acidification determines the further dissolution of the scale according to the following reactions: Fe ₃ O ₄ + 8H ⁺ → 3 Fe ³⁺ + 4H ₂ O + e ^- (6) (NiO + 2H ⁺ → Ni ²⁺ + H ₂ O (7)

Of course, the reaction (7) relates to austenitic stainless steels since ferritic stainless steels do not contain significant amounts of nickel as an alloying metal. As a side effect of the dissolution of the iron and nickel oxides, a larger amount of Cr ₂ O _{3 is available} for anodization.

Therefore, the resulting electrolytic scaling mechanism in a neutral solution involves the anodic oxidation of chromium and the acidification of the interface, which causes the dissolution of the egg senoxid determined and, if present, the nickel oxide.

At the time of almost complete dissolution of the surface scale, the anodic reaction of the underlying metal begins to increase until the equilibrium ratio in the passivated state is reached according to the following schematic reaction: Me + nH ₂ O → MeO _n + 2nH ⁺ + 2ne ^- (8) where Me indicates the Fe-Cr-Ni alloy; subsequently only reactions (1) and (5) take place, but the latter takes place at a much slower rate with respect to the former.

During the electrolytic scaling process in a neutral solution, the entire reaction described above occurs under diffusion control. This means that the reaction conditions depend on the diffusion of the reactants and of the reaction products through the boundary layer, which in turn is determined by the dynamics of the fluid on the steel surface. Therefore, the increase of the vortex at the interface can cause opposite effects on the rate of attack on the scale as it also increases the flow of H ⁺ leaving the acidified interface [reaction (1)].

From the Faraday laws of electrolysis, it is known that the anodic dissolution, as well as the cathodic deposition methods, is concerned that the amount of the substance obtained at the electrodes is proportional to the amount of electric charge which is passed through the electrolytic circuit , In particular, the amount of electric charge necessary to obtain (convert) a given amount of the substance is constant (for example, for one equivalent of any substance, a Faraday, ie, 96,500 coulombs is required). Therefore, for the electrolytic charge of a given amount of a substance, the associated current density is constant. Q = I dead · T = constant where Q is the amount of electrical charge (in coulombs, C), I _{tot is} the applied electrical current (in amperes, A) and t is the electrolysis time (in seconds, sec). This equation applies to any selection of I _tot or t, so that the same effect can be achieved if several different values of the current I _{tot are applied} for the respective electrolysis times t.

It has now been found that in the electrolytic pickling or descaling process in a neutral solution, the above-mentioned classical equation of electrolysis can lead to erroneous results. In fact, for a given amount of surface scale (provided the composition and structure of the scale oxides are constant) and for a given process, it can be observed that to achieve satisfactory pickling or descaling, ie complete conversion of the scale to 1 dm ² the oxidized steel surface should be applied at least 15 A for 40 seconds (carbon steels) and at least 10 A for 10 seconds (stainless steels) in the anodic treatment. In the event that it is desirable to apply other values of current density I (eg, 60 A / dm ² to speed up the process) to treat the same material (pickling / descaling), the new treatment time is not over calculates the classical equation of electrolysis, since operation at the highest current density would make the resulting value too short to ensure an efficient process.

Therefore is the information that comes from the classical equations of electrolysis is derivable to calculate the amount of electrical charge, which on the cells in a neutral electrolytic process must be created not suitable.

Therefore there is a requirement in this particular field for methods which in the presence of indirect effects of current flow, a correct selection of the aniodic treatment periods and the streams provides the cell, as well as the calculation of the dimensions the relevant descaling line and plant.

The present invention this requirement and provides additional Benefits available, which will become clear below.

In fact, an object of the present invention is a continuous electrolytic process in a neutral solution for pickling and descaling carbon steel or carbon steel and stainless steels according to claim 1.

The neutral saline solution It is preferably composed of sodium sulfate, in a concentration between 0.5 to 2.5 M, at a temperature in the range of 30 to 100 ° C.

In particular, it has been observed that in the case of DC electrolysis, satisfactory results can be obtained when the minimum amount of electric charge c is in the range of 200 to 1250 C / dm ² (unalloyed steels) and 40 to 200 c / dm ² (stainless steels ) and the time constant k is in the range of 2 to 25 seconds, preferably between 2 to 11 seconds for unalloyed steels and between 2 to 25 seconds for stainless steels.

The treatment time is in the range of 7 to 50 seconds for unalloyed steels and between 2 to 45 seconds for stainless steels. The current densities are in the range of 10 to 80 a / dm ² (unalloyed steels) and between 5 to 150 A / dm ² (stainless steels).

in the With regard to theoretical considerations, which are not reported here were, can the unpredictable results according to the invention are explained, considering the mechanism of electrolytic pickling, heterogeneous nature the same and the different effect of the electric current flow on the individual electrolytic pickling reactions. Therefore has it was found that the speed of the electrochemical Conversion reaction is less than proportional with respect to Increase in total cell current applied to the cell.

The practical consequence of this fact, as mentioned here, is that the electrolytic process does not work in a neutral solution according to the constancy the amount of electric charge delivered can be controlled as generally in the case of the electrolytic processes, which do not involve any indirect effects of current flow (in this case, the acidification the interface). The selection of treatment times at the anode and the cell currents should be carried out be taken into account by considering that the increase of the applied current should also increase the amount of electrical charge.

The Conditions which influence the neutral electrolytic process, should also be taken into account when setting up or executing the pickling lines concerned Be the functionality the process with different flow rates of should ensure to be processed strips or bands.

The treatment times at the anode depend on the speed (v) of the pickling line and the total length of the electrodes (L) which impart anodic polarization to the strip to be processed. Therefore, the foregoing equation, which describes the amount of electrical charge delivered in a neutral solution during the electrolytic process, can be rewritten as follows I = c / (L / v - k)

Yet Another object of the present invention is the use of the electrolytic process described above, characterized that the width and the speed of the strip or band, the entire length the anodic electrode and therefore the length of the respective continuous neutral electrolytic pickling line of the discharged stream, chosen according to the above set and defined method according to the claims 4 and 8th.

The electrolytic treatment of steel strips is normally carried out in cells consisting of a pair of electrodes connected to opposite poles of the power supply, which alternately determine anodic and cathodic polarization sequences on the strip to be descaled. Since the descaling process requires only anodic polarization, the addition of the cathodic stage has the advantage that the electrochemical reactions take place directly on the strip without directly connecting the latter to the power supply; whereby the use of expensive carrier flow rolls can be avoided. Therefore, the total length (L) of the electrodes which exert the aniodic polarization on the strip is indicated by the sum of the unit length (L _a ) of the individual electrode units.

The cell may have a vertical or a horizontal structure, according to the criteria of Simplicity of the plant.

Furthermore, the neutral electrolytic treatment equation given in the present invention shows that there is an electrolysis time (k) which is not active for the treatment. This means that when designing a system for electrolytic treatment in a neutral solution for steel strips, it should be considered that the total treatment time (t) at the anode is greater than k T = L / v> k

In practice, the electrolytic descaling process is fractionated into a series of anodic and cathodic current pulses, with L = n * L a where L _{a is} the length of the individual anodic current pulses and n is the number of current pulses), the frequency (f) of each anodic current pulse should be f = v / L a <½ * n / k with factor 1/2 being introduced to account for the total treatment time (assuming symmetric cathodic current pulses).
For k _min = 2 sec and n _max = 12,
f _max <3 Hz is achieved.

This Limit of frequency for the electrolytic pickling in a neutral solution is with the reaction mechanisms interchangeable, which for the treatment was extended, the control of the electrified interface is included to the resolution to support the oxides. Are z. B. hot rolled, unalloyed steel strips under predetermined industrial conditions (with constant cooling method after rolling), the obtained scale shows almost constant composition and morphology, requiring a minimum amount of charge c requires to be pickled electrolytically, depending on the mechanical treatments for pre-pickling and breaking up the scale.

The electrolytic process in a neutral solution according to the present invention can also be carried out with alternating current, with a frequency smaller than 3 Hz, with total treatment periods and selected applied currents, for suitable values of c 'and k' according to the formula: It = c '+ k' × t

So far the present invention has not been briefly presented. Hereinafter will be described using the following examples and accompanying drawings, versions this discloses, by which the purpose, features, advantages and Application method of the invention should be made clear.

1 Fig. 12 shows the pattern of descaling, as a scale fraction P (t) / P _T converted as a function of duration, for initial scales P _T1 and P _T2 > P _T1 . The patterns were obtained using a descaling equation obtained with respect to the experimental observation of mass loss during the descaling process.

2 relates to the case where c = 70 C / dm ² and shows the four hyperbola branches with the parameters k, from bottom to top, corresponding to 1, 2, 3 and 4 seconds, with the asymptotes I = 0 A / dm ² and t = K sec.

example 1

A conventional low carbon steel with a heat roller scale mechanically pretreated by roller induced crushing (about 2.5% elongation) is subjected to the continuous electrolytic pickling process in a neutral solution according to the present invention. For this type of scale, it has been found that c equals 490 C / dm ² and k equals 3.7 sec. Furthermore, in order for the scale conversion reactions to take place, a current density I> I ₀ , with I ₀ = 10 A / dm ² , should be applied.

For a continuous neutral, electrolytic pickling line for 1.5 m wide strips, which evenly with 90 m / min and with 20 m / min at the beginning of the roll and at the end of the role, while the whole length (L) of the anodic electrode, and therefore the length of the pickling line or Plant, adjusted with respect to the current applied in the cell is, according to the provisions the equation of the neutral electrolytic pickling according to the present Invention.

With regard to the information from the equation which is taken into account, the current density (I) applied to the electrolytic loading cell as a function of the length of the (L) anode and the rate (v) of the pickling line in column 3 given in Table 1; in column 4 the electric charge density (Q), and in column 5 the total current (I _tot ) which is output, calculated by multiplying the current density for the anodic electrode surface as indicated. As a result, at the steady speed of 90 m / min, the electric charge density (Q) which is given off for the electrolytic pickling increases as the length of the anodic electrode decreases. Accordingly, the applied total current increases (I _tot ).

Table 1

In column 6 the current I _tot °, which is calculated according to the classical law of electrolysis (I _tot ° = I ° * S = 490 * v / L * S), is given. Accordingly, neglecting the method according to the present invention, the sizing of the power supply current and the speed of the pickling line are equal, insufficient to ensure complete pickling with a reduction in the length of the plant.

Of Further, it is taught from Table 1 that a lower-level operation Speed (20 m / min) the use of an entire anodic Length includes which 16 m does not exceed so that the condition I> I ° is not fulfilled. This is achieved by the electrodes and the power supply is sectioned to only one area, regardless of the total length of the Anodes, which are arranged in the cells.

Example 2

A silicon (3% Si) steel for magnetic inserts with hot rolling scales mechanically pretreated by in-line shot peening is subjected to the continuous neutral electrolytic pickling process according to the first invention. Since the shot peening device causes a partial removal of the scale whose unit is inversely proportional to the speed of the pickling line, it has been found that for this material c ₁ = 525 C / dm ² , where v = 20 m / min, c ₂ = 680 C / dm ² , where v = 40 m / min; where k = 3.1 sec in both cases; Further, a current density I> 15 A / dm ^{2 should be} applied for the scale conversion reactions to take place.

For a continuous neutral electrolytic pickling line for 1.2 m wide strips or strips operated at 40 and 60 m / min, the total length (L) of the anodic electrode and therefore the length of the pickling line with respect to the Cell applied current, as determined the equation of the continuously neutral electrolytic license according to the invention.

in the With regard to the information from the equation in question, are the Current density (I), which to the electrolytic Beizzelle as a Function of the length (L) of the anodic electrode and the speed (V) of the pickling line applied as indicated in Table 2, as well as other relevant quantities.

Table 2

That is, it is confirmed that at equal speeds, the length of the anodic electrode decreases as the electric charge (Q) to be delivered increases for the electrolytic pickling. Accordingly, the applied total current increases (I _tot ). With the speed of 20 m / min, the actual length of the anode should not exceed 12 m, so that the current density does not become too low (I <I ₀ ). From this it is clear that the pickling plant for the material in question could easily be dimensioned with a length of the anodic electrode of 10 to 14 m.

Also in that case However, the structure of the electrolytic pickling plant according to the classical laws electrolysis to sub-assessment led the power supply.

Example 3

The process according to the present invention is applied to the descaling of conventional hot rolled steels, with a mechanical descaling pretreatment as in Example 1 (scale with c = 490 C / dm ² , k = 3.7 sec and I ₀ = 10 A / dm ² ).

The pickling line, comprising an entire length L of the anodic electrode = 24 m (band or strip width = 1.5 m) should be suitable at a speed in the range of 60 to 120 m / min to be operated. In Table 3, the current densities are (I), which are connected to the electrolytic Beizzelle as a function of Length (L) applied to the anodic electrode and the speed (v) of the pickling line are shown. Table 3 also covers all others Quantities indicated.

Table 3

the would result if the invention disclosed herein were not considered, the Dimensioning the current of the power supply clearly insufficient have been to the descaling with an increase in speed the pickling line sure.

Example 4

The method according to the present invention is applied to conventional hot-rolled steels with mechanical descaling pretreatment as in Example 1 (scale with c = 490 C / dm ² , k = 3.7 sec and I ₀ = 10 A / dm ² ).

The Entzunderungsanlage consists of 12 cells, each having a uniform length L _a = 2 m, with a total L = 24 m (strip = 1.5 m) have; the former should be able to operate at a speed in the range of 40 to 120 m / min, according to the two different process control electronics: In one case (see Table 4a) with the electronics of the maximized use of power from individual power supplies ( ie, a number of cells proportional to the speed of the pickling line) and in the other case (see Table 4b) with constant use of all cells (ie, use of a jump density proportional to the speed of the pickling line). The data obtained are given in the following Tables 4a and 4b.

Table 4a

Table 4b

The Equation of continuously neutral electrolytic pickling according to the invention shows that the two process control electronics are not equivalent are, since overall less pickling stream is necessary, if the operation was carried out while maximizing the number of cells used.

The classical equation of electrolysis would not have allowed to understand the difference between the control electronics, it would be rather if the necessary power for the pickling has been determined under.

Example 5

A neutral electrolytic pickling plant, used in a combined Pickling annealing line for cold rolled stainless steel strips, operated with a total length L of Anodic electrode = 4 m and strip = 1.25 m suitable for a change the speed of treatment from 20 to 70 m / min to the fore after a constancy of the thermal cycle at different Thicknesses of stainless steel tire to be considered.

According to the descaling equation, the direct current density (I) applied to the electrolytic stirring cell with changes in the speed (v) of the pickling line is shown in column 2 of Table 5; in column 3 the density (Q) of the electric charge and in column 4 the total current to be delivered (I _tot ) calculated by multiplying the current density for the anodic electrode surface as indicated.

Table 5

In column 5, the current I _tot ° is obtained by the classical law of electrolysis (I _tot ° = I ° * S = 70 * v / L * S). If, consequently, the knowledge according to the invention is not taken into account, the dimensioning of the current of the power supply would have been clearly insufficient to ensure descaling with an increase in the speed of the pickling line.

Example 6

A neutral electrolytic descaling unit, operated with the same speed range (20-70 m / min) according to example 5, and with a larger overall Electrode length, corresponding to L = 5.12 m (bandwidth = 1.25 m) is taken into account. The operational parameters of this plant, calculated using the descaling equation according to the invention, are given in Table 6.

Comparing this case with Example 5, the laws of electrolysis would show the same pattern of total current (I _tot °) with an increase in pickling line speed. Accordingly, the descaling equation according to the invention shows the need for lower currents, the speeds being identical, with respect to the previous case.

Table 6

Also in this situation would the structure or the execution according to the known Laws of electrolysis to undershoot the power supply to lead.

Example 7

A neutral electrolytic scaling plant, operated with a entire length L of the anodic electrode = 8 m (strip width = 1.25 m), which capable of the treatment speed of 60 to 120 m / min to change, will be checked. The operational parameters of this plant calculated by the scaling equation according to the invention are shown in Table 7.

Table 7

Also this case confirms that the design of the power supply according to the classical laws of Electrolysis would have been significantly flawed, by mistake to the other operational speeds of the pickling lines.

Example 8

The case of a neutral electrolytic descaling unit consisting of four cells, each measuring the length of the anodic electrode L _a = 2 m, for a total of L = 8 m (strip width = 1.25 m) is checked.

The Power distribution was as a function of the speed of the pickling line already observed in Example 7. Assuming that the plant could also be operated with only three cells (eg for operational reasons, failure etc.) and therefore with L = 6 m, are the Entzunderungsströme to be applied in Table 8 indicated.

Table 8

Of the Operation with three cells, with an increase in speed at a surplus demand of Total current results, a fact which in terms of the classical laws of electrolysis could not have been foreseen would.

Example 9

This is the case of a neutral electrolytic descaling unit consisting of n = 6 cells of uniform length L _{a of} the anode = 1 m and L = 6 m (strip = 1.25 m) operated in the one case (see Table 9a), with process control electronics maximizing the use of power from individual power supplies (ie, using a number of cells proportional to the speed of the pickling line) and in the other case (see Table 9b) with the constant use of all cells (ie Use of a current density proportional to the speed of the pickling line).

Table 9a

Table 9b

The two process control electronics are not equivalent, since a total of less total descaling current is necessary when operating carried out is going to maximize the number of cells used. In In this case, there is also an undervaluation of the Entzunderungsstromes through the classical equation of electrolysis.

To the method described above, one skilled in the art, the implementation further and possible Needs, Various other modifications and variants cause Vari, the however, all are within the scope of the present invention, as by the attached claims Are defined.

Claims (10)

A continuous electrolytic process in a neutral solution for pickling and descaling mild steel and stainless steel in the presence of indirect effects of electrolysis current flow, the current being direct or alternating current, at a frequency of less than 3 Hz, the duration the anodic treatment, when the desired cell current is applied, and the cell current, when the desired treatment time is employed, are selected according to the formula: It = c + kI where: - I is the current density passing through the cell, - t is the duration of the anodic treatment, - c is the constant fraction of the electric charge density released for the direct oxide exchange reactions at the anode. - k is the time constant for calculating the electric charge density fraction, proportional to the current density I (kI) emitted for the indirect reactions at the anode, associated with the evolution of oxygen and the subsequent acidification at the steel / electrolytic solution interface of unalloyed steel and at the interface between scale / solution for stainless steels; the constants c and k are known for each type of steel and scale. Continuous electrolytic process in one neutral solution in the presence of indirect effects of the electrolysis current flow, wherein the current is direct or alternating current, with a frequency less than 3 Hz, according to the claim 1, wherein the neutral solution consisting essentially of sodium sulfate, in a concentration from 0.5 to 2.5 M, one stands, in a concentration of 0.5 to 2.5 M, at a temperature in the range of 30 to 100 ° C. A continuous electrolytic process in a neutral solution for pickling unalloyed steel in the presence of indirect effects of electrolysis current flow according to claim 1 or 2, wherein the amount of electric charge c is in the range of 200 to 1250 C / dm ² and the time constant k in the Range of 2 to 11 seconds for treatment times at the anode in the range of 7 to 50 seconds and current densities in the range of 10 to 80 A / dm ² . Use of a continuous electrolytic process in a neutral solution for pickling unalloyed steel in the presence of indirect effects of the electrolysis current flow, the current being direct or alternating current, having a frequency of less than 3 Hz, according to one of claims 1 to 3 characterized in that, in adjusting the width of the strip to be milled, the speed v of the strip to be picked and the cell current I, the total length of the anodic electrode and therefore the length L of the continuous pickling line concerned are defined by the formula becomes: I = c / (L / v - k) which is the formula of claim 1, transformed by replacing the time t by the ratio L / v. Use according to claim 4, wherein a control logic for the Method is used, which involves the use of a number of cells proportional to the speed of the pickling line and the use of the maximum available Provides power. Use according to claim 4, wherein a control logic for the Method is used, which is the constant use of a number of cells and the use of a Storm Density proportional to the speed of the pickling line provides. A continuous electrolytic process in a neutral solution for pickling stainless steel in the presence of indirect effects of electrolysis current flow according to claim 1 or 2, wherein the amount of electric charge c is in the range of 40 to 200 C / dm ² and the time constant K in the Range of 2 to 25 seconds for treatment times at the anode in the range of 2 to 45 seconds and current densities in the range of 5 to 150 A / dm ² . Use of a continuous electrolytic process in a neutral solution for pickling unalloyed steel in the presence of indirect effects of electrolysis current flow, the current being direct or alternating current, with a frequency of less than 3 Hz, according to one of claims 1, 2 or 7 characterized in that, in adjusting the width of the strip to be milled, the speed v 'of the strip to be picked and the cell current I', the total length of the anodic electrode and therefore the length L 'of the continuous electrolytic element concerned pickling line is defined by the formula: I '= c' / (L '/ v' - k ') which is the formula of claim 1, transformed by replacing the time t 'by the ratio L' / v '. Use according to claim 8, wherein a control logic for the Method is used, which involves the use of a number of cells proportional to the speed of the pickling line and the use of the maximum available Provides power. Use according to claim 9, wherein a control logic for the Method is used, which is the constant use of a number of cells and the use of a Storm Density proportional to the speed of the pickling line provides.