EP3967790A1 - Method and device for surface treatment - Google Patents

Abstract

The present invention relates to a method and a device for surface treatment, in particular for cleaning metallic surfaces using laminar flows.

Description

Summary of the Invention

The present invention relates to a method and a device for surface treatment, in particular for cleaning metallic surfaces using adjustable currents.

Objects or bodies made of metal are cleaned before possible surface treatments, for example electroplating, galvanizing or similar surface treatments, in order to remove particles and residues or impurities on the surface and to obtain surfaces free of impurities for a subsequent treatment of the metal object.

In the prior art, bodies are cleaned in appropriate baths, such as degreasing baths, and/or treated in pickling baths during cleaning. In both cleaning methods, the surface of the body is cleaned, for example by removing the adhering fat and/or oil in the degreasing on the one hand and other deposits such as rust and/or scale in the stain on the other. The baths are made up of basins into which the body to be treated is introduced and remains for a certain time until a corresponding cleaning or pickling result is achieved. In this so-called static cleaning or static pickling, the material surface is treated with little or no movement of the cleaning and/or pickling liquid. The static baths for cleaning and/or pickling usually include one or two positions for traverses with material. The cleaning speed is determined by the chemical composition, the substance concentration(s) of the cleaning solution and/or pickling solution and the temperature. The disadvantage of the static systems is that the cleaning and pickling process is very slow and there is no mass transfer in the boundary layer areas to be treated between the body (component) and the process liquid. The speed of pickling is increased in the prior art with the use of turbines by causing the pickling liquid to be in a turbulent state. The main disadvantage of the method shown is that the turbines used not only have significant dimensions, which the possible pickling positions in the Bath reduced, the pool is additionally divided to use the effects of the turbine, which in turn leads to a reduction in pool volume and pickling positions.

The object of the present invention is therefore to provide a method and a device which provide optimal surface treatment, in particular the cleaning of metal surfaces, without the disadvantages mentioned in the prior art, the reduced cleaning and/or pickling speed and the Loss of area within the process bath.

The present invention therefore relates to a method for the chemical surface treatment of bodies, in which an approximately laminar flow is generated within the liquid of at least one process tank for degreasing and/or pickling. In one embodiment, the stain is an iron and/or zinc stain. In one embodiment of the method according to the invention, the flow according to the invention swims around the body located in the at least one process tank. In one embodiment, the flooding of the body and the resulting movement at the boundary layer leads to the formation of a protective layer, a shift in the rest potential and/or a homogeneous cleaning surface.

In one embodiment, the approximately laminar flow within the liquid in at least one process basin for degreasing and/or pickling is generated by at least one flow pump arranged in the side area of the process basin for each direction of flow. In this case, only the at least one pump is active for one direction of flow, with the at least one pump being inactive for the other direction of flow. In a preferred embodiment, two or more interacting pumps are provided to generate a direction of flow in the process tank. In a particularly preferred embodiment, the pumps that work together are each arranged diagonally to one another on the opposite end faces of the process basin.

In the method according to the invention, the at least one flow pump, which generates an approximately laminar flow and in at least one Flooded body located process basin, in one embodiment, a rectifier.

In a further embodiment, the iron(II) ion content can be reduced and the iron(III) ion content increased during iron pickling by controllable regulation. In a preferred embodiment, the iron content in the process bath is regulated via a controllable supply of air and/or oxygen. In one embodiment, iron content and/or redox potential is monitored.

Furthermore, in one embodiment, monitoring and regulation of the suspended matter load and the temperature can be included. This monitoring and regulation can also contribute to further optimization of the degreasing process and/or pickling process.

In one embodiment of the present invention, a device for removing grease, oil and/or dirt is provided. This can include at least one overflow, one fat/oil separation unit and/or one filtration unit.

The present invention also relates to an associated device for the chemical surface treatment of bodies according to the method described above, comprising at least one process tank with process liquid and at least one pump per flow direction for producing an approximately laminar flow.

In one embodiment, the device has at least one degreasing bath and at least one pickling bath.

In one embodiment, at least one rinsing bath can also be provided. The rinsing bath reduces the entry of impurities into the subsequent processes, which means that such a bath can be interposed between each step, i.e. each process bath.

In a further embodiment, the device has a monitoring and regulation mechanism for determination, monitoring and/or regulation the temperature and/or concentrations of the substances contained in the process bath liquid.

In a further embodiment, the device comprises elements for removing fats, oils and/or contaminants. These elements can include at least an overflow, a fat/oil separation unit and/or a filtration unit.

The present invention is characterized by the embodiments in the claims and described in more detail by the statements in the following description and drawings.

Description of the drawings

1

Schematic representation of the degreasing process comprising a process bath (1) with an approximately laminar flow with an overflow (2) and separate containers (5, 6) for regeneration and disposal.

2

Schematic representation of the iron pickling process comprising a process bath (1) with an approximately laminar flow with an overflow (2) and separate containers (5, 11) for regeneration and disposal and addition of fresh acid.

3

Investigation of the weather resistance of bodies after pre-treatment.

4

Schematic representation of the course of flow with two interacting pumps in the basin. a) Representation of a clockwise (to the right) or b) counterclockwise (to the left) flow direction.

Reference List

1

Process bath or process basin

2

overflow

3

Surface skimmer (skimmer)

4

oil/fat concentrate

5

collection container

6

tranquilizer tank

7

Fresh/flush water/chemical supply

8th

pump

9

air supply

10

feed HCl

11

fresh acid container

12

Removal of stain

13

oil separation

14

Filter including pump

15

temperature control, concentration measurement unit; heat exchanger

Detailed description of the invention

The present invention relates to a method and a device for the surface treatment of material surfaces of bodies, with an approximately laminar flow profile being produced.

The term "approximately laminar" refers to a flow profile that runs laminar, but cannot run laminar in all areas due to the limited space in which the flow is generated. Areas in which the currents show changes over time are, for example, edges, corners and shadow areas caused by bodies within a basin. In confined spaces or shadowed areas, where the flow can be disturbed, turbulence can develop that does not allow a complete laminar flow. For this reason, the term "nearly laminar" flow describes that a laminar flow is produced by a pump, but due to the limited space, for example within a process tank, this generated laminar flow can only be approximately laminar, as it causes turbulent flows in some areas or flow shadows.

First of all, bodies can be all objects and objects that can undergo a surface treatment. Bodies of the present invention are in particular parts and constructions, such as stair constructions, building constructions, steel girders, gratings, crash barriers (guard rails), which are usually treated piecemeal.

The surface treatment includes the preparation and/or cleaning of the surface of the body for the following treatment, such as a wet/ Powder coating, application of metallic (protective) layers or other surface treatments. During cleaning, the surface of the body is cleaned in addition to the pre-treatment, for example by removing the adhering fat and/or oil in a degreasing process and/or further deposits such as rust and/or scale in the stain. The materials to be treated are preferably metallic materials and surfaces. In a preferred embodiment, the bodies are made of steel, galvanized steel, zinc, stainless steel and/or aluminum. In a particularly preferred embodiment, the bodies are made of steel or galvanized steel.

It is well known that turbulent movement of process liquids by bypass pumps or the supply of air, compressed air and/or liquid via floor pipes in iron pickling tanks can increase the pickling reaction rate and thus reduce the pickling time. The disadvantage of these systems, however, is that little or no liquid movement falls on the body parts located in the shadow of the flow. Another disadvantage of these systems is that, for example, large parts of the process basin are lost due to the large turbines used to generate turbulent flows. This leads to a reduced loading capacity of the tanks and/or to an enlargement of the tanks, which is associated with a higher use of chemicals and larger process rooms. The supply of air, compressed air and/or liquid into the pickling tank can also lead to foaming of the process liquid, which can have negative qualitative and system-specific effects. The disadvantage of the systems described is therefore not only the high energy consumption, but also the increased need for chemicals, process liquid and/or space. In addition, smooth movement of the stain is not provided by the prior art systems. Further disadvantages are the diffuse and non-controllable bath movements or flow alignments.

In order to achieve improved cleaning and/or pickling of the material and/or bodies in the process basins, an approximately laminar flow profile is created in the present invention. The almost laminar flow profile when degreasing the surfaces and/or pickling improves the degreasing performance as well the pickling process. In contrast to a turbulent flow profile, in laminar flows the liquid layers glide smoothly and evenly over one another, which means that no significant mixing processes occur. Such a flow flows around the body, ie the liquid moves symmetrically around the body, dividing in front of the middle of the body, flowing smoothly around the body and flowing back together after it. Due to the continuous flow of the liquid, a constant exchange is generated within the boundary layer between the body and the liquid, which leads to the removal of the "used" liquid and the supply of "fresh" liquid in the border area.

With the flow profile according to the invention, the entire volume of liquid in the process basin is moved, despite the body in the process basin (pretreatment, degreasing or pickling), as a result of which the liquid is completely circulated and homogenized. Due to the constantly changing boundary layers in the transition area between the material (component) and the process liquid, for example in the pre-treatment, degreasing or pickling bath, there is no saturation, since fresh process liquid is always transported to the material surface of the body in the bath. This improves the cleaning result compared to the prior art, such as example 2, 3 and can be found in Table 1. The at least one pump (8) per flow direction for generating the flow profile is attached to one side in the basin for surface cleaning of material surfaces of bodies, with only the pump or pumps for one flow direction being or being active. The flow profile is diverted at the end of the basin (end of the basin length), causing the flow direction of the process liquid to be clockwise (right-hand) or counter-clockwise (left-hand) compared to the cross-section of the basin, as in 4 shown. The direction of flow is preferably described to the movement of the process liquid within the basin in relation to the cross-section of the long side of the basin. In order to obtain a complete coverage of the basin with a unidirectional flow, two or more cooperating pumps (8) are used, supporting the same flow profile, for example "clockwise" as in Fig. 4 a) or 4 b). The two cooperating pumps (8) are preferably attached to the opposite end faces, with a first pump in the upper Area near the surface on the front side and which is arranged a second pump near the pool floor, such as in Figure 1, Figure 2 and 4 shown. The diagonal arrangement of the two cooperating pumps (8) leads to an increase in each direction of flow, for example the clockwise flow in the bath. However, several interacting pumps (8) can also be used per flow direction in order to maintain or reinforce the unidirectional flow profile, for example the clockwise flow profile, or to largely avoid flow shadows on bodies in the bath (1).

In an embodiment with several pumps (8) per direction of flow, the pumps (8) are preferably arranged in the edge areas of the end faces of the elongated tanks. The opposite pumps for the opposite directions of flow are operated reversingly in order to generate a change in the direction of flow. In order to minimize flow shadows as far as possible and to obtain an optimal alignment of the flow profiles, two or more pumps (8) per flow direction are preferably positioned crossed on the front sides of the stretched tanks. The pumps (8) each located on one end are positioned in such a way that one pump is arranged in the upper area of the basin and the second pump (8) in the lower area of the basin, see for example Figures 1, 2 and 4 . Such an arrangement enables the formation of an opposite direction of flow. In order to avoid turbulence as far as possible and to produce an approximately laminar flow profile, in such an arrangement, as described above, the pumps (8) arranged diagonally and interacting with one another are active on the end faces. The pumps with an opposite flow direction are inactive.

By additionally reversing the pump operation, ie reversing the direction of rotation of the pumps (8), the flow shadows that form with bodies in the pool can be compensated for or prevented. The same can also be done by activating the pump operation crosswise, as explained above. With the aid of the described arrangement of the pumps and a reversal of the flow, targeted and controllable flow profiles can be generated that prevent saturation at the boundary layers of the body. A reversal of Flow direction is preferably delayed, ie only after the movement of the flow, for example "clockwise", for example Figure 4a ) has almost come to a standstill, the opposite flow formation "counterclockwise" takes place, as in Figure 4b ) shown. In one embodiment, the direction of flow is therefore changed within the at least one process bath. The change in flow direction can be accomplished by reversing the direction of rotation of the pumps (8) and/or by activating the opposite pumps (8) as discussed above. The duration of the different flow directions and/or the change of direction depends on the dimensions of the stretched process basin, its volume and/or the body in the process basin and the initial state of the components. In one embodiment, the duration of a flow direction is up to 20 minutes. In a preferred embodiment, the duration is up to 10 minutes, in a particularly preferred embodiment, the flow direction change takes place in up to 5 minutes. The basin shape of the process basin is stretched in one dimension, preferably the pool length is greater than the pool width. The flow profile according to the invention is deflected at the end of the pool (end of the length of the pool), as a result of which the approximately laminar flow profile is retained in the device according to the invention and the associated method.

The tanks for surface cleaning preferably do not require a separate inlet and/or outlet to produce the flow profile according to the invention. The pumps (8) are integrated directly into the tank, without having to carry out a costly remodeling of the tank and/or significantly reducing its volume.

The pumps (8) used to generate a flow according to the invention comprise at least one rectifier. The straightener makes it possible to create a laminar flow, in which the outflow velocity is equal to the flow velocity at the outlet of the pump (8). A high outflow speed with the straightener of the pump (8) enables the flow profile to be maintained even at a certain distance from the pump (8) without creating turbulence. At a certain distance, the flow profile therefore has approximately the same properties and approximately the same flow velocities as the flow at the outlet the pump (8). As previously explained, the term "approximately" indicates that in a confined or closed basin, the characteristics may vary slightly from the original flow due to deflections due to walls, bottom and/or other bodies, which however do not change the essential flow form, ie flow velocity, flow direction and/or flow form of the whole. Additional abrasion of the casing and/or rotor blades within the pumps can further increase the laminar flow profile and range of the flow. In one embodiment, the flow rate of the pump used is 2 m/s to 6 m/s, preferably 3.3 m/s. The range of the pumps (8) used in closed systems and one-sided assembly is in the range of 2 m to 20 m, preferably 2 m to 12 m, particularly preferably 9 m. The range in closed systems in two-sided assembly of the pumps ( crosswise, offset) is in the range of 2 m to 30 m, preferably 3 m to 25 m, particularly preferably 10 m to 18 m. The Reynolds number of the resulting flow profiles through the immersed components can be adjusted by the pump control. In a preferred embodiment, the Reynolds number can be controlled during the process. The Reynolds number in the tanks for producing a flow according to the invention depends on the characteristic length, the dynamic viscosity and density of the liquid and the flow velocity. In one embodiment, the Reynolds number in unequipped tanks is 2×10 ⁶ to 10×10 ⁶ .

In one embodiment, there is a heat exchanger (15) on and/or in the basin, which heats the process basin (1). In one embodiment, the flow can also be temporarily interrupted. During this so-called idle time, in which little or no flow is generated and the liquid is stationary or moving only slightly, the contaminants on the surface and/or the bottom of the tank can settle. In one embodiment, these contaminants, such as fats and/or oils on the liquid surface or other contaminants on the bottom of the basin, can be removed from the process basins by overflows, suitable suction devices, pumps and/or filters. Contaminants on the bottom of the tank are, for example, scale that has been detached in the form of hematite (Fe ₂ O ₃ ) or magnetite (Fe ₃ O ₄ ,), which accumulates and accumulates can collect at the bottom of the tank. A regeneration cycle can also be operated parallel to the actual production/cleaning cycle.

In one embodiment of the present invention, the chemical surface treatment flow is used in degreasing baths. The pools can have any shape. The process tanks preferably have a cuboid shape. The degreasing is preferably carried out as an alkaline hot degreasing. Through the use of laminar flow technology (8) in the degreasing bath, the demulsifying oils and/or fats cannot form and/or accumulate on the entire surface of the tank. In a preferred embodiment, in addition to the at least one pump for producing the flow (8) according to the invention, there is a heat exchanger (15) in the basin for each direction of flow, which heats the basin to a corresponding temperature. The temperature here is preferably 50-70.degree. C., particularly preferably 60.degree. The fats and/or oils accumulate due to the flow in the area of the narrow sides of the basin. The narrow sides of the pool are the front and/or back of the pool. These areas are usually not relevant to production, since there are heat exchangers (15) and/or overflows in these areas, which means that there is no product contact.

In one embodiment, an overflow (2) is provided on one or both of the narrow sides of the basin, ie the front and/or rear of the basin, or on all sides. The overflow (2) is preferably designed in such a way that contaminants located on the surface and/or on the bottom of the basin can be removed from the actual process bath, such as the degreasing bath. The overflow (2) can be individually adjustable mounted on the basin. The overflow (2) can also be coupled to a separate filtration circuit. This separate circuit makes it possible to extract and remove floating fats and/or oils that could interfere with the actual degreasing process in the process bath (1). The removal of the contaminants that can be settled on the ground can also be carried out using a pump circuit connected to the process circuit. The pump circuit can include any pump known in the art. The pump in the pump circuit is preferably a rotary piston pump, a rotary piston pump, a flap pump, a gear pump, an eccentric screw pump, a peristaltic pump, a pneumatic diaphragm pump and/or centrifugal pump. The pump is particularly preferably a centrifugal pump. In a preferred embodiment, the pump circuit has a filter (14). In one embodiment, the contaminants are separated on the floor in parallel with the actual production or cleaning cycle. Due to the intensive flow profiles, possible settleable contaminants are suspended on the bottom and can be removed by filtration. Appropriate cleaning prevents accumulation of sludge on the floor, which can have a disruptive effect on the cleaning result of the components. In an alternative embodiment, separation can also take place without the overflows and/or filtration described above, but with the aid of fat/oil separation devices, such as attachable and/or floating surface skimmer, so-called skimmer (3). Examples of oil separation devices are skimmers, ultrafiltration (crossflow), centrifuges, inclined plate clarifiers, decanters or osmosis units. However, the oil separating devices are not limited to the previous list, but can be any known separating devices. However, these grease and oil separation devices can also be used in addition to the overflows and/or filters. The overflow (2) and/or the oil separation device (13) are preferably installed on the opposite side of the heat exchanger (8) where the oil and/or fat creams accumulate. With the help of the current generated, which flows around the body to be treated from all sides, as well as the preferably intermediate downtimes and/or parallel regeneration times, an ideal degreasing result can be achieved and the degreasing times can be significantly reduced, which leads to a corresponding reduction in costs and an increase in throughput. The filtration and/or oil separation described above can take place during the idle times in which little or no bath movement is generated, or within the process in which the bath is moved by means of an approximately laminar flow. In a preferred embodiment, the oil is separated off during the idle times. If the pumps are arranged on one side, the overflow is preferably arranged opposite the pump. If the pumps are arranged on both sides in the basin, the arrangement of the overflow is irrelevant. The depth and/or height of the overflow is/are variable depending on the process basin. In a Embodiment has the at least one overflow a depth that is below the bath surface.

In one embodiment, continuous builder and surfactant additions can be incorporated into the bypass/filtration/oil separation loop. This avoids so-called sawtooth profiles in the bath composition and/or concentration of the process bath. Sawtooth profiles are constantly changing conditions in the bath composition and/or concentration that can strongly (negatively) affect the performance of the process baths. Possible builders are, for example, sodium hydroxide (NaOH) and/or potassium hydroxide (KOH). Surfactants for adjustment can include, for example, anionic, cationic and/or nonionic surfactants or mixtures thereof. However, builders and surfactants for use in the method shown and the associated device are not limited to the previous list, but can include all substances known in the prior art with these properties or combinations of these. With the help of the controlled additions, the cleaning or pickling result can also be checked.

In one embodiment, the process bath according to the invention is a demulsifying bath. In the demulsifying bath, splitting agents are introduced into the process tank if a certain oil/fat content is exceeded and/or there are splitting agents in the degreasing bath and/or the degreasing solution. In a preferred embodiment, the splitting agents are introduced into the basin (1) during periods of rest or standstill. This enables demulsifying and controlled oil/fat separation. The value of the oil and/or fat content in the basin is preferably below 3%. In a preferred embodiment, the oil and/or fat content in the process tank is below 1.5%. In a particularly preferred embodiment, the oil and/or fat content in the process tank is 0.3% to 0.5%. If this value is exceeded, a splitting agent, which can be an additive, is added to the process bath in the emulsifying bath (process liquid). The agent is preferably not added during the production process. The splitting agent can be any known means for separating oil and fat. Examples of such cleaving agents are, but are not limited to, mixtures of nonionic surfactants. In a preferred embodiment, it is a mixture of different fatty alcohols. In a particularly preferred embodiment, they are blends comprising alpha-alkyl-omega-hydroxypoly(oxypropylene) and/or poly(oxyethylene) polymers in which the alkyl chain contains at least 6 carbon atoms (C6) and ethoxylated propoxylated C12-14 alcohols.

In one embodiment, the flow profile according to the invention can also be used in iron pickling (Fe pickling). The mode of action and the structure correspond to that of the degreasing bath. In particular, the at least one basin for Fe pickling is preferably cuboid in shape, in which at least one pump (8) is arranged for each direction of flow in the area of one of the narrow sides of the basin. Heating the pools is optional due to the improved pickling effect. When heating the pools, in one embodiment, the pump can be located on the same side as a heat exchanger (15). If the pool is heated (15), the temperature of the iron pickling bath is between 15 °C and 45 °C. In a preferred embodiment, the temperature of the liquid in the basin is 20°C to 35°C. The narrow sides of the pool are the front and/or back of the pool. In a preferred embodiment, an overflow (2) is provided, with its structure and possible combinations being analogous to the overflow of the degreasing bath. The flow according to the invention and the corresponding circulation of the liquid comprising iron (Fe) in a hydrochloric acid (HCl) solution enables the additional absorption of oxygen (O ₂ ) from the air and thus contributes to an additional formation of iron(III) ions ( Fe ³⁺ ) at. The iron(III) ion concentration leads to an increase in the pickling performance. In one embodiment, an additional introduction of air or oxygen is provided. The air or oxygen is introduced using at least one ventilation system (9), which can preferably also be combined with the flow pump (8). A controllable, parallel air supply (9) enables additional formation of Fe ³⁺ and regulation of the pickling process. In a preferred embodiment, the at least one ventilation system (9) can therefore be controlled independently of the flow pump (8). With the help of this regulation, an optimal Fe ³⁺ production or regulation can take place within the tank. The optimum Fe ³⁺ content for the iron pickle in the bath is 0.1 g/l to 10 g/l, preferably 0.3 g/l to 8 g/l, particularly preferably 0.5 g/l to 5.0g/L. The pickling processes in the surface area known in the prior art show extreme and constantly changing stoichiometric conditions in the bath composition, the so-called sawtooth profile. Appropriate pickling is carried out using ideal pickling curves, ie content of iron and hydrochloric acid (HCl), with an increased HCl concentration of, for example, 170 g/L and a corresponding initial iron concentration of, for example, 70 g/L. Due to the removal of material from the surface of the body, the process bath (1) becomes enriched with iron over the course of its service life, while the HCl concentration is stoichiometrically reduced. Above a certain residual acid content, pickling becomes ineffective due to the required extended pickling time, which cannot be compensated for by corresponding temperature increases above a certain level. The old bath must then be disposed of accordingly and re-applied. The current in the iron/hydrochloric acid pickling tank, which can be combined with a controllable additional air supply (9), significantly reduces the hydrochloric acid concentration previously required. In one embodiment, the HCl concentration is 40 g/l to 100 g/l, preferably 50 g/l to 80 g/l. In one embodiment, the used acid is removed from the process tank (1) and fresh hydrochloric acid is added to the system. The removal of used acid and the addition of fresh acid can be carried out continuously or discontinuously. Fe pickling can therefore be run with an almost constant bath composition and concentration and therefore has no or a significantly reduced sawtooth profile compared to the prior art. In a preferred embodiment, the content of hydrochloric acid and/or iron(III) ions in the process bath (1) is monitored by suitable systems. The used acid and fresh acid are preferably stored in appropriate buffer stores/collecting containers (5, 11). With the help of the process listed above, the pickling times can be significantly reduced compared to the prior art. The degreasing and/or pickling times depend on various factors, such as the material, the processing condition and/or the degree of oxidation. In general, a reduction in the treatment time of 20% to 70% compared to the prior art can be observed, preferably by 30% to 50%. In the pickling tank, the flow profile created leads to an equilibrium between iron(III) ions and iron(II) ions in the process bath. The equilibrium created at the interface between the body and the liquid leads to the formation of a protective layer and/or generation of an optimal cleaning condition on the surface of the treated bodies, both of which lead to increased protection against corrosion, such as that 3 and can be found in Example 2.

The flow in the iron pickling tank, which can be combined with a controllable additional air supply (9), leads to the formation of a protective layer, a shift in the resting potential on the body and/or an ideal cleaning result, as well as a reduction in the number of crystallization nuclei due to the constant exchange of the liquid in the area of the boundary layer between liquid and corresponding body. This layer, shifting of the rest potential and/or improved removal of foreign bodies means that the body has little or no reoxidation products even after prolonged outdoor exposure, see example 2. 3 and Table 1. Subsequent process steps, such as the flux bath in the area of hot-dip galvanizing, are partly unnecessary due to the protective layer that is created. Preliminary data from the surface investigations using cross-sections of reference samples and samples from a pickling process according to the invention show, using the example of galvanizing, that the subsequent surface refinement is smoother, more compact and more uniform compared to the prior art. For example, in the case of the zinc coating, the bodies are free of blowholes and cracks using the method according to the invention, in contrast to the samples treated in standing pickles (stand pickling, pickling time of 30 minutes).

With iron pickling, due to the optimized flow profile, an equilibrium is formed at the boundary layer of bodies between iron(II) ions and iron(III) ions. The flow according to the invention enables the body in the process bath to be optimally wetted with process liquid, for example hydrochloric acid (hydrochloric acid, HCl) or other acid mixtures and/or oxidizing agents. In subsequent steps, such as rinsing or a flux bath, the iron(III) ions formed at the boundary layer form an iron(III) hydroxide layer which protectively surrounds the body, causing a shift in the resting potential and/or achieving a Optimum cleaning result with a low number of recrystallization nuclei on the component surface. These effects take place with a ratio of iron(III) ions and iron(II) ions (Fe ³⁺ /Fe ²⁺ ) in the process bath of 0.1% to 5%. In a preferred embodiment, the ratio of Fe ³⁺ /Fe ²⁺ is 0.2% to 3%, more preferably a ratio of 0.3 to 1.5%. Alternatively, a rinsing cycle can be switched on after pickling. This has low Fe and/or HCl content. The levels in an additional rinsing bath are below 5 g/L. In a preferred embodiment, the contents are ≦3 g/l, particularly preferably ≦1 g/l. This avoids the presence of a high proportion of iron or iron(II) ions and/or acid and reduces the carry-over into the subsequent processes. However, the method according to the invention and the associated device lead to an optimal result in the treatment of the surface even without a downstream rinsing device. This ideal cleaning reduces foreign bodies on the objects to a minimum. The reduction in foreign bodies and thus the corrosion-promoting elements leads to a significantly minimized oxidation of the treated bodies, see example 2, 3 and Tab. 1. This almost homogeneous surface also improves the subsequent processing of the body.

In a further embodiment, the flow in the process tank (1) can also be used in zinc pickling. With the help of the optimal liquid movement in the zinc pickling through the flow and an optional control of the suspended matter load and/or temperature, an optimal pickling result can be achieved that reduces the pickling times from the prior art by at least 20-70%, preferably by 30% to 50% . The stoichiometric ratios and processes are analogous to Fe pickling. Here only Fe is replaced by Zn. In the state of the art, zinc pickling also has an extreme sawtooth profile. The bath concentration is, for example, 160 g/l HCl and 0 g/l Zn. Over the course of the service life and interim discontinuous additions of fresh acid, the bath is enriched with Zn, while the HCl concentration is reduced stoichiometrically. Above a certain residual acid content, pickling is also ineffective here and the bath has to be disposed of and made up again. The flow according to the invention considerably reduces the concentration of hydrochloric acid previously required. In one embodiment, the HCl concentration is 30 g/l to 80 g/l, preferably 40 g/l to 70 g/l. In contrast to Fe pickling, no additional air is fed into the process bath (1) for zinc pickling, as this would lead to increased foam formation and oxidation of zinc (Zn) is not possible. The process bath (1) of the zinc pickling includes the following ingredients: zinc (Zn) and hydrochloric acid (HCl). The zinc concentration in the process liquid is preferably a zinc (Zn)/iron (Fe) ratio of 8:1. As in the previous process bath (1), in one embodiment the used acid can be removed from the process bath (1) and added by a discontinuous or continuous addition of fresh acid. The zinc pickles can thus be run almost constantly in their bath composition and concentration, analogously to the iron pickles, and therefore have no sawtooth profile or a significantly reduced sawtooth profile compared to the prior art. With the help of the permanently reduced HCl content of the tanks, the potential for hydrogen storage in the material decreases, which leads to embrittlement of the metal (hydrogen embrittlement) and, in the worst case, to brittle fracture. The hydrogen embrittlement described above can occur in any pickling process, ie for example when pickling iron and zinc, and is significantly reduced by the process described.

In one embodiment, the process tank for zinc pickling includes at least one overflow, preferably two overflows, as already described above, due to the formation of foam. In order to reduce the increased formation of foam during zinc pickling and to prevent overfoaming and/or sloshing, additional nozzles can be provided. These nozzles are arranged above the overflows and/or at or on the surrounding pool edges and spray liquid, preferably a process solution (here: zinc pickling), onto the foam that forms. This has the advantage that foam formation is reduced and the bath level of the process bath does not have to be further reduced. Furthermore, no air supply is necessary.

With the help of flow technology (8) in the process baths for the pre-treatment of surfaces of bodies, the pre-treatment of the bodies can not only be shortened, but also the number of process baths previously required can be reduced. Furthermore, previously known process sequences can be modified and/or varied. This leads to a significant cost reduction as well as a reduction in the use of chemicals and/or downstream feedstocks and a corresponding increase in production. In the case of surface pre-treatment, for example in hot-dip galvanizing, 6 to 8 pre-treatment tanks with iron pickling are provided in the prior art. the Flow profiles according to the invention in the method and/or device in the process bath (1) allow a reduction of these to 3 to 4 basins. In one embodiment, the method using laminar flow technology enables a reduction in the process baths for surface treatment by at least 30%, preferably by at least 50%. By reducing the pickling bath surfaces, lowering the HCl concentrations and, if necessary, using a suitable emission inhibitor, the HCl emissions in the corresponding pre-treatment areas/plants are significantly reduced. In a preferred embodiment, the emission is less than 1 mg/m ³ HCl. The previous use of acid scrubbers is no longer necessary. On the contrary, with the continued use of an acid scrubber, the relevant emission values at the chimney outlet would be higher than with the use of a wind deflector fan. When acid scrubbers are used, the values are ≦9 mg/m ³ , preferably ≦7 mg/m ³ , particularly preferably ≦5 mg/m ³ HCl. These values are further reduced by replacing them with known wind deflector fans and/or additional fresh air supply. The emission values can be reduced to ≦4 mg/m ³ HCl (wind deflector fan exit), preferably ≦2 mg/m ³ HCl (wind deflector ventilator exit), particularly preferably to ≦1 mg/m ³ HCl (wind deflector ventilator exit). The reduction of the hydrochloric acid concentration through the laminar flow technology in the process baths leads to the fact that the developments in emission protection, which replaced the earlier wind deflector fans by the use of an encapsulation with an acid scrubber, are reversed again, since an acid scrubber is technically less effective and economically more expensive.

With the help of the method according to the invention and the associated device, waste materials and input materials are reduced to a minimum and an optimal degreasing and pickling result is achieved, which ensures an optimized wetting condition that can meet the constantly increasing optical demands of the end user/customer. The method according to the invention and the associated device also make it possible to dispense with any subsequent process baths, as a result of which a potential accident relevance is reduced.

The present invention therefore also relates to a device comprising at least one degreasing bath and at least one bath for pickling, wherein at least one of Process baths includes a flow device for generating a flow profile according to the invention. The device can also contain at least one rinsing bath. In a preferred embodiment, each process bath has at least one pump per flow direction for laminar flow generation, with the pumps being located within the basin and arranged in the side area. Within the basin means here the arrangement of the pumps in the process basin in direct contact with the process liquid, ie within the process liquid. The process baths can have any shape, but the baths preferably have a cuboid shape with at least one pump for generating the laminar flow on the end faces. As already explained above with regard to the method, the two or more pumps (8) for the laminar flow can be attached on one side in the tank or on two opposite sides in the tank for surface modification of material surfaces of bodies. In a preferred embodiment, two or more pumps are arranged in the basin for each direction of flow. Here, one of the cooperating pumps (8) is located on one of the two front sides, i.e. one pump is arranged on both narrow sides of the process tank, so that a flow direction is formed, i.e. either "clockwise" or "counterclockwise" compared to the Cross section of the bath. In order to obtain a flow or direction of flow in the same direction, the two cooperating pumps are preferably attached to opposite end faces, with the one first pump being arranged diagonally in height to the one second pump on the opposite end face. This arrangement does not change the direction of flow, e.g. "clockwise", but maintains and/or increases the direction of flow already present without changing the direction of flow, e.g. "counterclockwise" in the cross-section of the basin, see example Fig. 4 b) . In one embodiment, several pumps that work together can also be arranged for each direction of flow. In a further embodiment, in addition to the cooperating pumps (8), oppositely located pumps (8) can also be present which reverse the direction of flow, such as the Fig. 4 a) and b) can be seen. This change in flow direction, for example from right to left (in cross-section), makes it possible to minimize flow shadows through bodies. In this embodiment, respectively only the pump (8) active for one flow direction or the pumps (8) acting together for one flow direction, ie the pumps (8) which support the same flow direction. The at least one pump (8) for the opposite flow direction is inactive during this time. In a preferred embodiment, at least two pumps (8) are arranged in the tank for each direction of flow, with the pumps that interact in each case being arranged diagonally to one another on the opposite end side, as for example in Figures 1 and 2 shown. The at least two interacting pumps (8) that generate a flow with the same flow direction, for example "clockwise", for example Fig. 4 a) , are preferably active simultaneously. In the case of several pumps (8) for the same direction of flow, however, only some of these can be in operation.

The pumps for generating the flow according to the invention are designed in such a way that the Reynolds number can be variably adjusted. The Reynolds number in the tanks for producing a flow according to the invention depends on the characteristic length, the dynamic viscosity and density of the liquid and the flow velocity. In one embodiment, the Reynolds number in unequipped tanks is 2-10×10 ⁶ .

As already described above with regard to the method, in one embodiment the device can have units for monitoring, determining and regulating parameters such as temperature, pH value, substance concentrations, etc. In a preferred embodiment, the process baths for degreasing and/or pickling have monitoring mechanisms and control mechanisms that are used to determine, monitor and/or control the temperature and/or concentrations of the substances contained in the process bath liquid. In a particularly preferred embodiment, the temperature and the iron ion content in the process basin of the iron pickling are determined. The iron(III) ion content in the at least one process bath for iron pickling should be 0.1 g/l to 10 g/l, preferably 0.3 g/l to 8 g/l, particularly preferably 0.5 g /L to 5.0 g/L and/or a ratio of Fe( ³⁺ )/Fe( ²⁺ ) of 0.1 to 5%, preferably 0.2 to 3%, particularly preferably 0.3 to 1 .5%.

In a further embodiment, the device comprises a device for removing fats, oils and/or contaminants from the at least one process tank. As already described in the method, the overflow and regeneration circuit can have different configurations and variations, as presented above. In a preferred embodiment, when the at least one pump is mounted on one side, the overflow is located on one of the two end faces of the process tank opposite the heat exchanger. At least one oil separation device can also be present in addition to or instead of the overflow. Possible oil separation devices are, for example, the elements described above.

In certain pools that tend to increase foam formation, nozzles can be arranged on the overflows and/or on or on the surrounding pool edges to reduce it, into which, through suitable inflow lines, liquid is pumped, which is pumped by means of the nozzles onto the forming Foam is distributed and reduces its formation.

These and other embodiments of the present invention are disclosed in, and are encompassed by, the specification and examples. Additional literature on known materials, methods and applications that can be used in accordance with the present invention can be retrieved from public libraries and databases, for example using electronic devices. A more complete understanding of the invention can be obtained by reference to the following examples, which are provided for the purpose of illustration and are not intended to limit the scope of the invention.

examples Example 1: Process for the ideal pre-treatment of surfaces

The process steps of the optimized surface pretreatment of metallic bodies, preferably made of steel, include the steps of degreasing (a); the rinsing (b), whereby a carryover of the solution from (a) into the following process steps is prevented; iron pickling (c); a further rinsing process (b); and optionally a subsequent zinc pickling and/or a flux bath (d). The degreasing stage (a) serves to remove organic impurities. through the in 1 The degreasing method shown, together with the device with laminar flow, enables almost complete removal of organic substances, in particular fat and oils. Unlike stationary or turbulent baths, the laminar flow in the process bath (1) washes around the body and thus reaches all parts of the body. The fat and/or oil separated from the body can be removed from the bath through an overflow (2) on the process bath (1) and thus increase the effectiveness of the degreasing. The separated fat and/or oil can be removed as in 1 shown also be collected in a container (5). The container (6) is a settling container that only has a reduced/decelerated movement and/or flow, so that the fat and/or oil settles on the surface and can be separated as a concentrate by a surface skimmer (3), for example a disc skimmer. This is collected in a corresponding collection container (5) for disposal. The cleaned process liquid remaining in the container (6) can be returned to the process tank (1) through an additional line. Possible settleable soil substances can be removed by filtration (14). This regeneration circuit enables an optimized defatting of the body as well as a return of the process liquid into the process tank (1), whereby less chemical input is used.

In the subsequent pickling stage (c), which follows the rinsing process (b), oxidic impurities on the body surface are removed, with the removal taking place in an acidic process bath. In the iron pickling agents described in the prior art, 6 to 8 iron pickling baths are generally required to remove the impurities from the bodies. in the in 2 illustrated method according to the invention with laminar flow technology (8) is im Process tank (1) being washed around by the moving liquid and leads to an optimal pickling result, whereby only 3 to 4 pickling baths are used. An additional supply of air or oxygen (O ₂ ) (9) on the liquid surface and/or the pump (8) leads to an increase in the Fe ³⁺ concentration in the process liquid in the basin (1), which causes an improved pickling effect . Any oil and/or fat that can settle on the surface of the liquid during pickling can also be removed from the process tank through an overflow (2) and/or other oil separator (13). The system for separating oil or fat from the process bath can be analogous to the system in degreasing (a). As in 2 is shown, the iron pickle can also be removed from the process liquid in the form of used pickle (12) and stored in a collection container (5). Parallel to the withdrawal, fresh acid can be introduced into the process bath from a storage container (11).

In the prior art, for example in the hot-dip galvanizing process, bodies that are to receive a zinc coating also go through an additional flux bath (d) as a pretreatment stage. The purpose of this bath is to protect the bodies from flash rust/corrosion on the way to the drying process and the actual zinc coating process (see zinc melt). Due to the optimal degreasing and/or iron pickling using laminar flow technology, treatment of the body for further surface modification is unnecessary, simple rinsing (b) is sufficient in the method according to the invention to keep the concentration of impurities to be introduced into the subsequent processes low, so that these not lead to a loss of quality in further treatment.

Example 2 Surface treated by the method according to the invention

In aging tests in which pretreated metal bodies were exposed to the weather for different lengths of time, clear differences in the degree of corrosion could be determined. For this purpose, bodies treated according to the state of the art (reference: stand stain; pickling time 90 minutes) and bodies treated by the laminar pre-treatment system for 5, 10, 15 or 30 minutes were compared with one another. The conditions were 1.2 g/L Fe ³⁺ ± 0.5 g/L Fe ³⁺ . Again 3 and Table 1, bodies that were degreased and pickled using the laminar process showed a significantly lower reoxidation process in outdoor weathering than bodies that were pretreated with the methods known in the prior art. Severe corrosion of the bodies that had been pretreated for 90 minutes (reference sample) using the prior-art method could already be determined shortly after outdoor weathering, in contrast to the bodies that had been treated for 5 minutes, 10 minutes, 15 minutes, or 30 minutes were treated with the method according to the invention. As can be seen from the experiment in Table 1, with the aid of the method and the device according to the ^invention , all ^disruptive Contamination is removed from the body and a protective layer, a shift in the resting potential and/or an ideal, almost impurity-free surface condition is created, which largely prevents or minimizes a reoxidation process. Tab. 1 Corrosion statistics for outdoor exposure 5 mins 10 mins 15 minutes 30 min Reference (90 mins) day 1 ++ + + - +++ day 21 +++ +++ ++ + +++ - No visible corrosion
+ Slight corrosion
++ Medium corrosion
+++ Severe corrosion

Claims (10)

Process for the chemical surface treatment of bodies, wherein an approximately laminar flow within the liquid in at least one process tank (1) for degreasing and/or pickling is generated by at least one flow pump (8) arranged in the side area of the process tank (1) in each direction of flow, wherein only the at least one pump (8) is active for one direction of flow. The method of claim 1, wherein the at least one flow pump includes a rectifier. Method according to Claim 1 or 2, in which at least two interacting pumps (8) are arranged in the process tank (1) to generate a direction of flow, preferably in which the interacting pumps (8) are arranged diagonally on opposite end faces of the process tank (1) in relation to one another . Method according to any one of claims 1 to 3, wherein the flow creates an equilibrium at the boundary layer between body and liquid, which forms a protective layer and/or creates an optimal cleaning state on the surface of the bodies treated. The method according to any one of claims 1 to 4, wherein during iron pickling by a controllable regulation of the iron (II) ion content can be reduced and the iron (III) ion content can be increased, the regulation of the iron content in the process bath preferably via a controllable air and / or oxygen supply takes place. A method according to any one of claims 1 to 5, wherein a) monitoring of temperature, pH value and/or substance concentrations; b) regulation of the temperature, the pH value and/or the substance concentrations; and or c) an overflow, a fat/oil separation unit and/or a filtration is included. Device for the chemical surface treatment of bodies according to the method according to one of Claims 1 to 6, comprising at least one process tank with process liquid and one pump per flow direction for producing an approximately laminar flow. The device of claim 7, wherein the device a) at least one degreasing bath; and b) at least one pickling bath,
includes. Apparatus according to claim 7 or 8, wherein the apparatus a) monitoring of temperature, pH value and/or substance concentrations; b) regulation of the temperature, the pH value and/or the substance concentrations; and or c) at least one overflow, one fat/oil separation unit and/or one filtration
includes. A device according to any one of claims 7 to 9, wherein the device comprises at least one rinsing bath.

Images