EP4265804A2 - Method, installation and use of same in discontinuous galvanizing of pieces - Google Patents

Abstract

The present invention relates to a method and a system for galvanizing components, in particular metallic components, in discontinuous galvanizing, wherein before zinc is applied to the surface of the components in a zinc bath, at least one treatment of the component in a flux/wetting bath, flux bath and/or wetting bath takes place, in which bismuth is deposited on the surface of the at least one component. Furthermore, the invention also relates to the use of such a method and the components produced using such a method.

Description

Brief description of the invention

The present invention relates to a method, a system and their use for galvanizing components, in particular metallic components.

The process and the system are used in particular in piece galvanizing, in which individual parts are treated in baths, in the so-called dipping process, and these receive a surface treatment. This is referred to as discontinuous piece galvanizing or hot-dip galvanizing or hot-dip galvanizing. In contrast to this is strip galvanizing, which involves a continuous galvanizing process (DIN EN 10143 and DIN EN 10346).

With discontinuous piece galvanizing, which is regulated according to the DIN EN ISO 1461 standard, corrosion protection is generated using a melt pool of ≥ 98.0% by weight zinc (Zn) and other accompanying elements, which is based on the applied layer thickness. In some cases, this layer thickness can average several 100 µm (micrometers) thick. Known methods of piece galvanizing include chemical pretreatment in a degreasing bath, pickling bath and flux bath with rinsing baths in between, with the component surfaces being cleaned and/or pretreated of foreign substances in the individual baths. The rinsing baths in between have the task of avoiding or reducing the carryover of chemicals from the respective treatment bath into the next process step. After air drying or treatment in a drying oven (80°C to 120°C), a zinc surface is then applied, in which the component is placed in a zinc bath with liquid zinc (≥ 98.0 wt.% zinc (Zn); temperature from 440 to 460°C). During the subsequent outdoor weathering, the zinc surface applied to the component reacts with the components of the ambient air and forms a protective cover layer, the zinc carbonate layer (ZnCOs).

In contrast to discontinuous piece galvanizing, the component in the continuous galvanizing process has smaller zinc layer thicknesses of approximately 7 µm to 25 µm, which is due to other process techniques and as a result of the high throughput speed (up to 200 m/min) of the strip and thus a short reaction time between steel strip and zinc melt result. As a result, different protection periods arise between the two processes of continuous and discontinuous galvanizing due to the zinc layers.

Another difference between the continuous and the discontinuous process of the galvanizing process is the composition of the zinc bath melt due to the relevant standardization. While in discontinuous hot-dip galvanizing the zinc content in the bath melt must be ≥ 98% by weight, this is not the case in the continuous galvanizing process. Especially in recent decades, alloys with higher aluminum (Al) contents have been developed in the continuous galvanizing process, which lead to thinner, more ductile and more corrosion-resistant zinc layers due to a different phase formation and layer structure. This particularly includes the zinc-aluminum alloy, ZnAl5 alloy (Zn = 95% by weight, Al = 5% by weight), which is known under the trade name “Galfan”.

In the discontinuous hot-dip galvanizing process, referred to below as hot-dip galvanizing for the sake of simplicity, different alloy layers or alloy phases (Γ, δ1, ζ, η phase) are formed starting from the component base. Using the example of a steel component, these are layers or phases of zinc (Zn) and iron (Fe), such as Fig. 1 a) can be removed. The iron content in the individual phases decreases in the direction of the galvanizing layer on the component surface (Γ phase = 21-28% Fe, δ1 phase = 7-11.5% Fe, ζ phase = 6-6.2% Fe, η phase <0.08% Fe). Depending on the compactness of the δ1 phase, which acts as a diffusion barrier, the ζ phase above it can develop extremely and grow through to the surface; An η phase (pure zinc layer) is then hardly or not at all present. The layer formation, especially the δ1 and ζ phases, depends on the steel composition and forms differently depending on the Si and P content of the base material. Layer thicknesses > 150 µm can be created. Furthermore, the formation of the zinc layer is at the Hot-dip galvanizing depends on the immersion time or residence time within the zinc bath. The thickness of the layer tends to increase with increasing diving time.

In the continuous galvanizing process, a component surface that is almost free of contaminants is necessary in order to coat the component with a zinc (Zn) - aluminum (Al) alloy, preferably ZnAl5, since aluminum interacts with many substances on the component, as well as in the baths or can react with the intermediate products and the surface tension of the zinc melt increases. The resulting layer usually has a thickness of 7-25 µm (micrometers). The zinc layer and surface formed by the continuous galvanizing process has a different composition than that of hot-dip galvanizing due to the higher aluminum content and its effect in the layer structure. In particular, an iron-aluminum (FeAl) boundary layer forms directly on the steel base of the component, which prevents any further growth in layer thickness. Above this boundary layer, eutectic structures made up of the components aluminum and zinc can be found, usually in a ratio of 5% aluminum to 95% zinc, with cells with a higher zinc content also forming, such as Fig. 1 b) can be seen, regardless of the component, its steel composition and the residence time in the ZnAl5 melt. Unlike hot-dip galvanizing, the aluminum present in the zinc layer acts as a catalyst, which forms corresponding passive layers immediately after the galvanizing process. In addition, the zinc layer is not as brittle compared to the hot-dip galvanizing process and also allows for forming after galvanizing. The zinc layers produced by thin-film galvanizing are therefore thinner, more ductile, more stable and more corrosion-resistant than those produced by hot-dip galvanizing. Due to the fact that the ZnAl5 alloy (melting point at 382 °C, working temperature: 410 °C to 430 °C) uses a lower melt temperature and a higher drying oven temperature (150-250 °C) than hot-dip galvanizing , the temperature difference between the component and the melt is reduced, which means that the component and the surface are not subjected to as much stress and the risk of distortion and cracking due to the release of internal stresses is reduced. In has not yet been successful in practice.

Due to increasing optical requirements as well as the desire for more functional, thinner and more corrosion-resistant zinc layers and/or increasingly difficult conditions, such as more complex and difficult-to-remove input materials on the component surface, changes in steel production and steel composition, limit value reductions, restrictions in the input materials and/or Environmental protection, improved zinc surfaces as well as methods and / or devices that can generate such surfaces are needed.

Hot-dip galvanizing processes are also known that use a zinc/aluminum bath, as previously described for the continuous galvanizing process, for example in WO 2002/042512 A1 shown, however, such a process does not seem to reliably generate the required surface quality that can be used for all applications, since the galvanized surface structure increases with the complexity of the processing condition and geometry of the components due to the poorer wetting behavior and disturbances in the layer structure, the galvanizing layer and the Has galvanizing quality.

The object of the present invention is therefore to provide a method and a system which reduces or even solves the disadvantages of the prior art, in particular by subjecting the component surface to a preliminary treatment which enables the application of a zinc layer with a small thickness, preferably at Use of 5% by weight aluminum (Al) in the melt pool.

The present invention therefore relates to a method for galvanizing components, in particular metallic components, in discontinuous galvanizing, wherein before zinc is applied to the surface of the components in a zinc bath, preferably a zinc-aluminum alloy, such as ZnAl5 alloy, at least one treatment of the component takes place in a flux bath and / or wetting bath, in which bismuth is deposited on the surface of the at least one component.

In one aspect, the at least one component is immersed in the flux/wetting bath, which has the following flux/wetting agent composition: (a) 80% by weight to 98% by weight of ZnCl ₂ (zinc chloride), preferably 88% by weight ± 2% by weight ZnCl ₂ (zinc chloride); (b) 1 wt.% to 19 wt.% NH ₄ Cl (ammonium chloride), preferably 12 wt.% ± 2 wt.% NH ₄ Cl (ammonium chloride); and (c) 0.1 g/l to 4 g/l Bi ³⁺ , preferably 2 g/l ± 0.5 g/l Bi ³⁺ (bismuth ions), the weights being based on the flux/wetting agent and the sum of all components of the composition is 100% by weight, the flux/wetting bath also having a pH of ≤ 2.0, preferably pH ≤ 1, particularly preferably pH ≤ 0.5. In a preferred embodiment, the flux/wetting agent of the flux/wetting bath is in an aqueous solution and the total salt content within the bath is in the range from 100 to 650 g/l, preferably in the range from 250 to 450 g/l.

1. a) Vorflux und Hauptflux, wobei das Vorflux/Benetzungsbad eine Prozesslösung umfassend Bismut in Form von Bi³⁺ im Bereich von 0,1 g/l bis 10 g/l und einen pH-Wert von ≤ 2,0, vorzugsweise von pH ≤ 1,0, besonders bevorzugt von pH ≤ 0,5 aufweist und eine Benetzung der Bauteiloberfläche mit Bismut (Bi) bewirkt; und wobei das Hauptflux ZnCl₂ (Zinkchlorid) im Bereich von 80 Gew.% bis 98 Gew.%, vorzugsweise 88 Gew.% ± 2 Gew.% umfasst, und
   • NH₄Cl (Ammoniumchlorid) im Bereich von 1 Gew.% bis 19 Gew.%, vorzugsweise 12 Gew.% ± 2 Gew.%, wobei die Gewichtsangaben auf die Menge an ZnCl₂/NH₄Cl bezogen sind und die Summe dieser Bestandteile der Zusammensetzung 100 Gew.-% ergibt;
   • wobei ferner der pH-Wert des Hauptfluxbades bei einem pH-Wert von 0,5 bis pH 6, vorzugsweise bei pH ≤ 5, besonders bevorzugt bei pH 4 liegt; und/oder
2. b) Vorflux und Hauptflux, wobei
   • das Vorflux ein Benetzungsbad umfasst, dass eine Prozesslösung umfassend Bismut in Form von Bismutionen (Bi³⁺) im Bereich von 0,1 g/l bis 10 g/I; und
   • NH₄Cl (Ammoniumchlorid) im Bereich von 100 g/l bis 350 g/l aufweist; und
   • einen pH-Wert von ≤ 2,0, vorzugsweise von pH ≤ 1,0, besonders bevorzugt von pH ≤ 0,5 aufweist und eine Benetzung der Bauteiloberfläche mit Bismut (Bi) und NH₄Cl (Ammoniumchlorid) bewirkt; und wobei
   • das Hauptflux ZnCl₂ (Zinkchlorid) im Bereich von 80 Gew. % bis 98 Gew.%, vorzugsweise 88 Gew.% ± 2 Gew; und
   • NH₄Cl (Ammoniumchlorid) im Bereich von 1 Gew.% bis 19 Gew.%, vorzugsweise 12 Gew.% ± 2 Gew.%;
   • wobei die Gewichtsangaben auf die Menge ZnCl₂/NH₄Cl bezogen sind und die Summe dieser Bestandteile der Zusammensetzung 100 Gew.-% ergibt; und
   • wobei ferner der pH-Wert des Hauptfluxbades bei einem pH-Wert von 0,5 bis pH 6, vorzugsweise bei pH ≤ 5, besonders bevorzugt bei pH 4 liegt.

In one embodiment of the present invention, the flux/wetting bath, flux bath and/or wetting bath is divided into one or more steps, so that the individual steps within the process step of flux treatment and wetting can act individually on the surface of the at least one component, the steps of the process step of the flux/wetting treatment can be separated as follows:

1. a) Preflux and main flux, the preflux/wetting bath comprising a process solution comprising bismuth in the form of Bi ³⁺ in the range from 0.1 g/l to 10 g/l and a pH of ≤ 2.0, preferably pH ≤ 1.0, particularly preferably pH ≤ 0.5, and causes the component surface to be wetted with bismuth (Bi); and wherein the main flux comprises ZnCl ₂ (zinc chloride) in the range of 80% by weight to 98% by weight, preferably 88% by weight ± 2% by weight, and
   • NH ₄ Cl (ammonium chloride) in the range from 1 wt.% to 19 wt.%, preferably 12 wt.% ± 2 wt.%, whereby the weights refer to the amount ZnCl ₂ /NH ₄ Cl and the sum of these components of the composition results in 100% by weight;
   • furthermore, the pH value of the main flux bath is at a pH value of 0.5 to pH 6, preferably at pH ≤ 5, particularly preferably at pH 4; and or
2. b) pre-flux and main flux, where
   • the pre-flux comprises a wetting bath that contains a process solution comprising bismuth in the form of bismuth ions (Bi ³⁺ ) in the range from 0.1 g/l to 10 g/l; and
   • NH ₄ Cl (ammonium chloride) in the range of 100 g/l to 350 g/l; and
   • has a pH value of ≤ 2.0, preferably pH ≤ 1.0, particularly preferably pH ≤ 0.5 and causes the component surface to be wetted with bismuth (Bi) and NH ₄ Cl (ammonium chloride); and where
   • the main flux ZnCl ₂ (zinc chloride) in the range from 80% by weight to 98% by weight, preferably 88% by weight ± 2% by weight; and
   • NH ₄ Cl (ammonium chloride) in the range from 1 wt.% to 19 wt.%, preferably 12 wt.% ± 2 wt.%;
   • where the weight information is based on the amount of ZnCl ₂ /NH ₄ Cl and the sum of these components of the composition amounts to 100% by weight; and
   • furthermore, the pH value of the main flux bath is at a pH value of 0.5 to pH 6, preferably at pH ≤ 5, particularly preferably at pH 4.

1. a) Bismutionen (Bi3+) im Bereich von 0,1 g/l bis 10 g/l und einen pH-Wert von ≤ 2,0, vorzugsweise von pH ≤ 1,0, besonders bevorzugt von pH ≤ 0,5; oder
2. b) Bismutionen (Bi3+) im Bereich von 0,1 g/l bis 10 g/I; und
   NH₄Cl (Ammoniumchlorid) im Bereich von 100 g/l bis 350 g/l, behandelt wird;

wobei der pH-Wert der Prozesslösung bei ≤ 2,0, vorzugsweise bei pH ≤ 1,0, besonders bevorzugt bei pH ≤ 0,5 liegt.In a further aspect of the invention, the component is treated in a wetting bath upstream of the zinc bath, in which the component is treated with a process solution which has the following composition:

1. a) bismuth ions (Bi3+) in the range from 0.1 g/l to 10 g/l and a pH of ≤ 2.0, preferably pH ≤ 1.0, particularly preferably pH ≤ 0.5; or
2. b) bismuth ions (Bi3+) in the range from 0.1 g/l to 10 g/l; and
   NH ₄ Cl (ammonium chloride) in the range of 100 g/l to 350 g/l;

wherein the pH value of the process solution is ≤ 2.0, preferably at pH ≤ 1.0, particularly preferably at pH ≤ 0.5.

The bismuth (Bi) is used in the process liquid of the at least one process bath, preferably in the form of bismuth chloride (BiCl ₃ ), bismuth oxide (Bi ₂ O ₃ ), bismuth subcarbonate ((BiO) ₂ CO ₃ ) and/or bismuth granules (metal base).

In a preferred embodiment, the bath temperature of the flux/wetting bath, flux bath and/or wetting bath is also 30°C and 60°C, preferably between 40°C and 50°C. In addition, a pretreatment time in the flux/wetting bath, flux and/or wetting bath of preferably 10 seconds (sec) to 2 minutes (min), particularly preferably 20 seconds to 60 seconds is provided.

In one embodiment, the process solution within the flux/wetting bath, flux bath and/or wetting bath does not exceed a limit value of iron ions (Fe ^2+/3+ ) of 3 g/l to 10 g/l, particularly preferably ≤ 5 g/l .

In the method, in a further aspect, at least one rinsing process in a rinsing bath is upstream, downstream or interposed between the at least one flux/wetting bath, flux bath and/or wetting bath.

1. a) während des laufenden Betrieb aufbereitet, indem ein Volumen an Prozessflüssigkeit aus dem Flussmittel-/Benetzungsbad, Flussmittelbades und/oder Benetzungsbades entnommen wird und in einem separaten Becken mit Ammoniak (NH₃) und Wasserstoffperoxid (H₂O₂) bei einem pH- Wert von 2,0 bis 6,0, vorzugsweise von pH 3,5 bis 4,2 behandelt und aufbereitet wird; oder
2. b) entnommen und in einem ersten separaten Becken mit Ammoniak (NH₃) und einem pH-Wert von über 2, vorzugsweise zwischen 2,0 und 2,5, behandelt, und wobei das Filtrat im weiteren Schritt in einem zweiten separaten Becken mit Ammoniak (NH₃) und Wasserstoffperoxid (H₂O₂) bei einem pH-Wert 3,0 bis 6,0, vorzugsweise von 3,5 bis 4,2 behandelt wird.

Furthermore, in a further embodiment of the method of the present invention, the process solution is prepared within a process bath by means of at least one processing system and the process solution and/or components prepared from impurities are fed back to the process bath, such as the flux/wetting bath, flux bath and/or wetting bath . In the processing plant, part of the process liquid of the process bath is preferred

1. a) prepared during ongoing operation by removing a volume of process liquid from the flux/wetting bath, flux bath and/or wetting bath and storing it in a separate basin with ammonia (NH ₃ ) and hydrogen peroxide (H ₂ O ₂ ) at a pH Value of 2.0 to 6.0, preferably from pH 3.5 to 4.2 is treated and processed; or
2. b) removed and treated in a first separate basin with ammonia (NH ₃ ) and a pH value of over 2, preferably between 2.0 and 2.5, and the filtrate in the further step in a second separate basin Ammonia (NH ₃ ) and hydrogen peroxide (H ₂ O ₂ ) is treated at a pH of 3.0 to 6.0, preferably from 3.5 to 4.2.

In one aspect, the precipitation sludge within the at least one separate basin of the processing is collected and disposed of in at least one downstream filter press, the processed process liquid being returned to the process bath as a filtrate and/or the component obtained in the processing to the flux/wetting bath, flux bath and / or wetting bath is fed back in.

1. a) eine Entfettung der Bauteiloberfläche mittels mindestens eines Entfettungsbades, wobei das Entfettungsbad vorzugsweise ferner mindestens einen Regenerationskreislauf umfasst, in dem die Prozessflüssigkeit des Entfettungsbades aufbereitet wird;
2. b) einen Beizprozess, der in mindestens einem Beizbad erfolgt, wobei das Beizbad vorzugsweise ferner mindestens einen Regenerationskreislauf umfasst, in dem die Prozessflüssigkeit des Beizbades aufbereitet wird; und/oder
3. c) ein Spülen der Bauteiloberfläche mit einem oder mehreren Spülbädern, welche den Prozessbädern vorgeschaltet, zwischengeschaltet oder nachgeschaltet sind.

In one embodiment of the present invention, the flux/wetting treatment, flux bath and/or wetting bath are preceded by one or more process steps and/or process baths for cleaning the component, the at least one process step preferably comprising:

1. a) degreasing the component surface by means of at least one degreasing bath, the degreasing bath preferably further comprising at least one regeneration circuit in which the process liquid of the degreasing bath is prepared;
2. b) a pickling process which takes place in at least one pickling bath, the pickling bath preferably further comprising at least one regeneration circuit in which the process liquid of the pickling bath is prepared; and or
3. c) rinsing the component surface with one or more rinsing baths, which are connected upstream, intermediate or downstream of the process baths.

In one aspect of the present invention, the process liquid of the process steps in the process baths is moved to enable better cleaning of the component.

In one embodiment (i), the treatment of the component in the flux/wetting bath, flux bath and/or wetting bath is followed by one or more drying steps in the drying oven, with liquid residues on the component at a temperature between 100-230 ° C and a preferred residence time between 1 min and removed for 30 minutes; and/or (ii) one or more galvanizing steps are connected downstream, the zinc bath (7) containing 2% by weight to 10% by weight of aluminum (Al) and 90% by weight to 98% by weight of zinc (Zn), preferably 5% by weight ± 1% by weight of Al and 95% by weight ± 1% by weight of Zn and the residence time of the components in the zinc bath (7) is ≤ 10 minutes, preferably 5 minutes ± 1 minute at a temperature of 420 ° C ± 10 ° C.

Furthermore, according to a further aspect of the method, the at least one component can be cooled in at least one quenching bath and/or processed in at least one additional post-treatment step, preferably at least one further protective layer being applied to the component surface in the at least one post-treatment step.

• 88 Gew.% ± 2 Gew.% ZnCl₂ (Zinkchlorid);
• 12 Gew.% ± 2 Gew.% NH₄Cl (Ammoniumchlorid); und
• 2 g/l ± 0,5 g/l Bi³⁺ (Bismutionen);

wobei die Gewichtsangaben auf das Fluss-/Benetzungsmittel bezogen sind und die Summe aller Bestandteile der Zusammensetzung 100 Gew.-% ergibt, wobei ferner das Flussmittel-/Benetzungsbad einen pH-Wert ≤ 2,0, vorzugsweise von pH ≤ 1,0, besonders bevorzugt von pH ≤ 0,5 aufweist.The present invention also relates to a flux/wetting agent composition for galvanizing components, in particular metallic components in batch galvanizing, comprising the following composition:

• 88% by weight ± 2% by weight ZnCl ₂ (zinc chloride);
• 12% by weight ± 2% by weight NH ₄ Cl (ammonium chloride); and
• 2 g/l ± 0.5 g/l Bi ³⁺ (bismuth ions);

where the weight information is based on the flux/wetting agent and the sum of all components of the composition amounts to 100% by weight, furthermore the flux/wetting bath having a pH ≤ 2.0, preferably pH ≤ 1.0, especially preferably of pH ≤ 0.5.

• Bismut (Bi³⁺) im Bereich von 0,1 g/l bis 10 g/I; und
• NH₄Cl (Ammoniumchlorid) im Bereich von ≤ 350 g/l bei einen pH-Wert ≤ 2,0, vorzugsweise von pH ≤ 1,0, besonders bevorzugt von pH ≤ 0,5.

The invention further relates to a wetting agent composition for galvanizing components, in particular metallic components, comprising the following composition:

• Bismuth (Bi ³⁺ ) in the range from 0.1 g/l to 10 g/l; and
• NH ₄ Cl (ammonium chloride) in the range of ≤ 350 g/l at a pH ≤ 2.0, preferably pH ≤ 1.0, particularly preferably pH ≤ 0.5.

The invention further relates to a system for galvanizing components, in particular metallic components for discontinuous galvanizing, the system having at least one flux/wetting bath, flux bath and/or wetting bath has that is connected upstream of the zinc bath and in which bismuth is applied to the surface of the at least one component.

1. a) die folgende Flussmittel-/Benetzungsmittelzusammensetzung aufweist:
   • 80 Gew. % bis 98 Gew.% ZnCl₂ (Zinkchlorid), vorzugsweise 88 Gew.% ± 2 Gew.% ZnCl₂ (Zinkchlorid);
   • 1 Gew.% bis 19 Gew.% NH₄Cl (Ammoniumchlorid), 12 Gew.% ± 2 Gew.% NH₄Cl (Ammoniumchlorid); und
   • 0,1 g/l bis 4 g/l Bi³⁺ (Bismutionen), vorzugsweise 2 g/l ± 0,5 g/l Bi³⁺ (Bismutionen); wobei die Gewichtsangaben auf das Fluss-/Benetzungsmittel bezogen sind und die Summe aller Bestandteile der Zusammensetzung 100 Gew.-% ergibt, wobei ferner das Flussmittel-/Benetzungsbad einen pH-Wert von ≤ 2,0, bevorzugt von pH ≤ 1,0, besonders bevorzugt von ≤ 0,5 aufweist;
2. b) in wässriger Lösung vorliegt und der Gesamtsalzgehalt innerhalb des Bades im Bereich von 100 bis 650 g/l, bevorzugt im Bereich von 250 bis 450 g/l liegt;
3. c) in ein oder mehrere Schritte aufgeteilt sind, sodass die einzelnen Schritte innerhalb des Prozessschrittes der Flussmittelbehandlung und Benetzung einzeln auf die Oberfläche des mindestens einen Bauteils einwirken können, wobei das Flussmittel-/Benetzungsbad wie folgt aufgetrennt wird:
   1. i) Vorflux und Hauptflux, wobei das Vorflux ein Benetzungsbad umfasst, dass eine Prozesslösung umfassend Bi³⁺ (Bismutionen) im Bereich von 0,1 g/l bis 10 g/l und einen pH-Wert von ≤ 2,0, vorzugsweise von pH ≤ 1,0, besonders bevorzugt von pH ≤ 0,5 aufweist und eine Benetzung der Bauteiloberfläche mit Bismut (Bi) bewirkt; und wobei
      • das Hauptflux ZnCl₂ (Zinkchlorid) im Bereich von 80 Gew. % bis 98 Gew.%, vorzugsweise 88 Gew.% ± 2 Gew.% und
      • 1 Gew.% bis 19 Gew.% NH₄Cl (Ammoniumchlorid), vorzugsweise 12 Gew.% ± 2 Gew.% NH₄Cl (Ammoniumchlorid); und wobei die Gewichtsangaben auf die Menge ZnCl₂/NH₄Cl bezogen sind und die Summe dieser Bestandteile der Zusammensetzung 100 Gew.-% ergibt umfasst; und
      • wobei ferner der pH-Wert des Hauptfluxbades bei einem pH-Wert von 0,5 bis pH 6, vorzugsweise bei pH ≤ 5, besonders bevorzugt bei pH 4 liegt;
   2. ii) Vorflux und Hauptflux, wobei das Vorflux/Benetzungsbad eine Prozesslösung umfassend Bi³⁺ (Bismutionen) im Bereich von 0,1 g/l bis 10 g/l und
      • NH₄Cl (Ammoniumchlorid) im Bereich von 100 g/l bis 350 g/l aufweist; und
      • einen pH-Wert von ≤ 2,0, vorzugsweise von pH ≤ 1,0, besonders bevorzugt von pH ≤ 0,5 aufweist und eine Benetzung der Bauteiloberfläche mit Bismut (Bi) und NH₄Cl (Ammoniumchlorid) bewirkt; und
      • wobei das Hauptflux ZnCl₂ (Zinkchlorid) im Bereich von 80 Gew. % bis 98 Gew.%, vorzugsweise 88 Gew.% ± 2 Gew; und
      • NH₄Cl (Ammoniumchlorid) im Bereich von 1 Gew.% bis 19 Gew.%, vorzugsweise 12 Gew.% ± 2 Gew.%
      • umfasst; und wobei die Gewichtsangaben auf die Menge ZnCl₂/NH₄Cl bezogen sind und die Summe dieser Bestandteile der Zusammensetzung 100 Gew.-% ergibt; und
      • wobei ferner der pH-Wert des Hauptfluxbades bei einem pH-Wert von 0,5 bis pH 6, vorzugsweise bei pH ≤ 5, besonders bevorzugt bei pH 4 liegt.

The system preferably has at least one flux/wetting bath

1. a) has the following flux/wetting agent composition:
   • 80% by weight to 98% by weight of ZnCl ₂ (zinc chloride), preferably 88% by weight ± 2% by weight of ZnCl ₂ (zinc chloride);
   • 1% by weight to 19% by weight NH ₄ Cl (ammonium chloride), 12% by weight ± 2% by weight NH ₄ Cl (ammonium chloride); and
   • 0.1 g/l to 4 g/l Bi ³⁺ (bismuth ions), preferably 2 g/l ± 0.5 g/l Bi ³⁺ (bismuth ions); where the weight information is based on the flux/wetting agent and the sum of all components of the composition amounts to 100% by weight, and furthermore the flux/wetting bath has a pH of ≤ 2.0, preferably pH ≤ 1.0, particularly preferably of ≤ 0.5;
2. b) is in aqueous solution and the total salt content within the bath is in the range from 100 to 650 g/l, preferably in the range from 250 to 450 g/l;
3. c) are divided into one or more steps, so that the individual steps within the process step of flux treatment and wetting can act individually on the surface of the at least one component, the flux/wetting bath being separated as follows:
   1. i) pre-flux and main flux, wherein the pre-flux comprises a wetting bath that has a process solution comprising Bi ³⁺ (bismuth ions) in the range from 0.1 g/l to 10 g/l and a pH of ≤ 2.0, preferably of pH ≤ 1.0, particularly preferably pH ≤ 0.5 and causes the component surface to be wetted with bismuth (Bi); and where
      • the main flux ZnCl ₂ (zinc chloride) in the range from 80% by weight to 98% by weight, preferably 88% by weight ± 2% by weight and
      • 1% by weight to 19% by weight of NH ₄ Cl (ammonium chloride), preferably 12% by weight ± 2% by weight of NH ₄ Cl (ammonium chloride); and where the weight information is based on the amount of ZnCl ₂ /NH ₄ Cl and the sum of these components of the composition comprises 100% by weight; and
      • furthermore, the pH value of the main flux bath is at a pH value of 0.5 to pH 6, preferably at pH ≤ 5, particularly preferably at pH 4;
   2. ii) pre-flux and main flux, wherein the pre-flux/wetting bath is a process solution comprising Bi ³⁺ (bismuth ions) in the range of 0.1 g/l to 10 g/l and
      • NH ₄ Cl (ammonium chloride) in the range of 100 g/l to 350 g/l; and
      • has a pH value of ≤ 2.0, preferably pH ≤ 1.0, particularly preferably pH ≤ 0.5 and causes the component surface to be wetted with bismuth (Bi) and NH ₄ Cl (ammonium chloride); and
      • wherein the main flux is ZnCl ₂ (zinc chloride) in the range from 80% by weight to 98% by weight, preferably 88% by weight ± 2% by weight; and
      • NH ₄ Cl (ammonium chloride) in the range from 1 wt.% to 19 wt.%, preferably 12 wt.% ± 2 wt.%
      • includes; and where the weight information is based on the amount of ZnCl ₂ /NH ₄ Cl and the sum of these components of the composition amounts to 100% by weight; and
      • furthermore, the pH value of the main flux bath is at a pH value of 0.5 to pH 6, preferably at pH ≤ 5, particularly preferably at pH 4.

1. a) Bismutionen (Bi³⁺) im Bereich von 0,1 g/l bis 10 g/l und einen pH-Wert von ≤ 2,0, vorzugsweise von pH ≤ 1,0, besonders bevorzugt von pH ≤ 0,5; oder
2. b) Bismutionen (Bi³⁺) im Bereich von 0,1 g/l bis 10 g/I; und
   • NH₄Cl (Ammoniumchlorid) im Bereich von 100 g/l bis 350 g/l, aufweist,
   • bei einem pH-Wert der Prozesslösung von ≤ 2,0, vorzugsweise von pH ≤ 1,0, besonders bevorzugt von pH ≤ 0,5,
   behandelt wird.

In one embodiment, the system comprises a wetting bath upstream of the zinc bath, in which the component is coated with a process solution

1. a) bismuth ions (Bi ³⁺ ) in the range from 0.1 g/l to 10 g/l and a pH of ≤ 2.0, preferably pH ≤ 1.0, particularly preferably pH ≤ 0.5; or
2. b) bismuth ions (Bi ³⁺ ) in the range from 0.1 g/l to 10 g/l; and
   • NH ₄ Cl (ammonium chloride) in the range from 100 g/l to 350 g/l,
   • at a pH value of the process solution of ≤ 2.0, preferably pH ≤ 1.0, particularly preferably pH ≤ 0.5,
   is treated.

In one aspect of the invention, at least one rinsing bath can be connected upstream, downstream or interposed between the at least one flux/wetting bath, flux bath and/or wetting bath in the system.

1. a) die Prozessflüssigkeit des Prozessbades während des laufenden Betrieb aufbereitet wird, wobei ein Volumen an Prozessflüssigkeit aus dem Flussmittel-/Benetzungsbades, Flussmittelbades und/oder Benetzungsbades (5) entnommen wird und mit Ammoniak (NH₃) und Wasserstoffperoxid (H₂O₂) bei einem pH- Wert von 2,0 bis 6,0, vorzugsweise von pH 3,5 bis 4,2 behandelt und aufbereitet wird; oder
2. b) die Prozessflüssigkeit aufbereitet wird, wobei ein Volumen der Prozessflüssigkeit aus dem Flussmittel-/Benetzungsbades, Flussmittelbades und/oder Benetzungsbades (5) entnommen wird und in einem ersten separaten Becken mit Ammoniak (NH₃) und einem pH-Wert von über 2, vorzugsweise zwischen 2,0 und 2,5 behandelt wird, und wobei das Filtrat im weiteren Schritt in einem zweiten separaten Becken mit Ammoniak (NH₃) und Wasserstoffperoxid (H₂O₂) bei einem pH-Wert von 3,5 bis 4,2 behandelt wird.

In one embodiment, the system additionally comprises at least one processing system, in which impurities or impurities from the process solution of the at least one process bath are reduced or removed within the at least processing system and the processed process solution and / or a processed component is fed back to the respective process bath. In a preferred embodiment, the processing system comprises at least one separate bath

1. a) the process liquid of the process bath is prepared during ongoing operation, a volume of process liquid being removed from the flux/wetting bath, flux bath and/or wetting bath (5) and mixed with ammonia (NH ₃ ) and hydrogen peroxide (H ₂ O ₂ ). is treated and processed at a pH of 2.0 to 6.0, preferably pH 3.5 to 4.2; or
2. b) the process liquid is prepared, a volume of the process liquid being removed from the flux/wetting bath, flux bath and/or wetting bath (5) and stored in a first separate basin with ammonia (NH ₃ ) and a pH value of over 2, is preferably treated between 2.0 and 2.5, and wherein the filtrate is treated in a further step in a second separate tank with ammonia (NH ₃ ) and hydrogen peroxide (H ₂ O ₂ ) at a pH of 3.5 to 4, 2 is treated.

1. a) ein Entfettungsbad zur Entfettung der Bauteiloberfläche;
2. b) ein Beizbad zum Beizen der Bauteils; und/oder
3. c) ein oder mehrere vorgeschaltete, zwischengeschaltete oder nachgeschaltete Spülbäder zum Spülen der Bauteiloberfläche.

In a further aspect, the flux/wetting bath, flux bath and/or wetting bath of the system is preceded by one or more process steps and/or process baths for cleaning the component. In a preferred embodiment, the at least one process bath upstream of the flux/wetting bath, flux bath and/or wetting bath comprises:

1. a) a degreasing bath for degreasing the component surface;
2. b) a pickling bath for pickling the component; and or
3. c) one or more upstream, intermediate or downstream rinsing baths for rinsing the component surface.

1. a) ein oder mehrere Trockenöfen zur Trocknung des Bauteils;
2. b) ein oder mehrere Verzinkungsbäder zur Verzinkung der Bauteiloberfläche;
3. c) mindestens einem Abschreckbad; und/oder
4. d) mindestens ein Nachbehandlungsbad, vorzugsweise zur Auftragung mindestens einer weiteren Schutzschicht auf der Bauteiloberfläche.

The system may further comprise, in a further aspect, one or more treatment steps corresponding to the flux/wetting bath, flux bath and/or wetting bath are connected downstream. These process steps preferably include

1. a) one or more drying ovens for drying the component;
2. b) one or more galvanizing baths for galvanizing the component surface;
3. c) at least one quenching bath; and or
4. d) at least one aftertreatment bath, preferably for applying at least one further protective layer to the component surface.

In addition, the present invention relates to the use of a previously described flux/wetting agent, flux and/or wetting agent in the previously described method and/or system as well as the use of the previously described method and/or system for galvanizing components, in particular metallic components in discontinuous galvanizing in a ZnAl5 melt.

Furthermore, the invention also relates to components produced according to the method described above.

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

Description of the drawings

Fig. 1

Representation of the alloy layers or alloy phases after discontinuous (a) and continuous (b) galvanizing on a metallic component.

Fig. 2

Schematic representation of the preferred structure of a system according to the invention with the individual process baths (1-8) and their regeneration circuits (shown below the baths).

• (1) Degreasing bath with alkaline hot degreasing, a bath rotation, a temperature ≥ 60°C; (2) At least one unheated rinsing bath containing city water, without bath agitation; (3) Pickling bath with ≤ 70-105 g/l HCl, ≥ 110-130 g/l iron (Fe) and bath rotation; (4) At least one unheated rinsing bath containing city water, without bath agitation; (5) Flux/wetting bath with (5.1) Common flux/wetting bath comprising 88 wt.% ZnCl ₂ (zinc chloride), 12 wt.% NH ₄ Cl (ammonium chloride), 2 g/l Bi ³⁺ (bismuth ions), a temperature of 40-50 ° C and a bath rotation; (5.2.1) Wetting bath comprising 0.1-10 g/l Bi ³⁺ (bismuth ions) at a temperature of 40-50°C and bath rotation; (5.2.2) Wetting bath comprising 0.1-10 g/l Bi ³⁺ (bismuth ions) and 100-350 g/l NH ₄ Cl (ammonium chloride) at a temperature of 40-50°C and bath rotation; (5.3) Separate flux/wetting bath with a pre-flux or wetting bath comprising 0.1-10 g/l Bi ³⁺ (bismuth ions) or comprising 0.1-10 g/l Bi ³⁺ (bismuth ions) and ≤ 350 g/ l NH ₄ Cl (ammonium chloride) at a temperature of 40-50 ° C and a bath rotation and a main flux comprising 88 wt.% ZnCl ₂ (zinc chloride), 12 wt.% NH ₄ Cl (ammonium chloride) at a temperature of 40-50 °C and a bath rotation; (6) Drying oven with a temperature of 100-230°C; (7) Zinc bath comprising a ZnAl5 melt comprising 5% by weight of Al and 95% by weight of Zn with a temperature of 410-430 ° C and, if necessary, bath rotation and overflow; (8) quenching and/or post-treatment bath and, if necessary, bath rotation and overflow;
• Component movement above the baths shown by arrows; Regeneration circuits arrows and schematic pools below the process baths; Bath movement (dashed line within the process baths)

Fig. 3

Schematic representation of the preferred structure of a flux/wetting bath, flux bath and/or wetting bath with processing system.

Fig. 4

Schematic representation of precipitation processes within the preparation.
(a) precipitation of bismuth (Bi) and iron or iron ions and return to the flux/wetting bath; (b) Separate precipitation of bismuth and iron or iron ions in two separate baths or basins together with return of the process liquid and/or the components into the flux/wetting bath, flux and/or wetting bath.

Fig. 5

Schematic representation of the preferred structure of a degreasing bath with alkaline hot degreasing with a regeneration circuit.

Fig. 6

Schematic representation of the preferred structure of a pickling bath with regeneration circuit and storage containers.

Reference symbol list

1

degreasing bath

2

Rinsing bath

3

Pickling bath

4

Rinsing bath

5

Flux/wetting bath

6

Drying oven

7

Zinc melt

8th

Quenching/post-treatment bath

9

regeneration cycle

10

overflow

11

Heating

12

reaction container

13

collection container

14

precipitation cycle

15

Calming container

Detailed description of the invention

The present invention relates to a method, a system and their use for galvanizing components, in particular metallic components in discontinuous galvanizing.

Hereinafter, the articles "a" and all derivatives thereof, as used herein, should generally be understood as "a/e/it or more" unless otherwise specified or apparent from the context as a singular form.

Where the terms "includes", "has", "possesses" and the like are used in the specification or claims, such terms are intended to be construed as the term "having" or "comprising", that is, not exhaustive except as is explicitly stated.

The term “bath” or “baths” used below generally refers to basins that can be filled with liquid, preferably process liquid, and into which a component can be embedded. For this reason, they are usually pools or baths that are open at the top. Although we generally speak of several baths, it can also be a basin or bath that is separated into individual sections that contain the respective process liquid. In such a case, the individual sections would each correspond to a bathroom.

As explained above, discontinuous galvanizing is a process in which one or more components undergo several process steps in the form of treatments in appropriate baths, with the result being that a zinc layer is applied to the component(s). Discontinuous galvanizing is also commonly referred to as hot-dip galvanizing, batch galvanizing and/or hot-dip galvanizing.

The term “component(s)” used in the method or system refers to metallic components of any kind, preferably components made of iron-containing or iron-based material, in particular components made of steel, such as blanks, sections, constructions and/or finished workpieces. The term “component” also includes groupings and/or combinations of components of different or the same type and/or different or the same material, which can undergo a common treatment in one or more process baths and/or steps. In some cases, these groupings can also be put together using suitable aids, such as trusses, goods carriers or similar devices.

In order to be able to generate a surface that is as pure and trouble-free as possible for galvanizing, the component is degreased, pickled and/or cleaned using known baths by transferring at least one component from one bath to the next, such as Fig. 2 can be found in numbers 1-4. These steps serve the holistic cleaning of components.

The crucial process step in the pretreatment of the at least one component, which allows a thin galvanizing layer within the usual discontinuous galvanizing process, is the treatment of the component in the flux/wetting bath, flux bath and/or wetting bath (5), the so-called "fluxing". In the following, a distinction is also made between the main flux and the pre-flux in the "flux(es)", with the component being wetted with bismuth and/or bismuth and NH ₄ Cl in the wetting bath or pre-flux, and the actual wetting in the main flux or flux bath Flux treatment with ZnCl ₂ /NH ₄ Cl or NH ₄ Cl alone is carried out on the surface. If both steps take place simultaneously in one bath, for the sake of simplicity it is referred to as a flux/wetting bath. If only bismuth alone or bismuth and NH ₄ Cl are used in a process bath, for the sake of simplicity it is referred to as a wetting bath, "pre-flux" or "wetting". In experiments related to the pretreatment of component surfaces, it was accidentally determined that by optimizing the flux/wetting bath, in particular the flux/wetting agent composition, flux composition and/or the wetting agent in combination with zinc alloys comprising aluminum, such as ZnAl5 alloys , high-quality surface coatings can be generated which have a thinner layer thickness of the zinc coating compared to usual hot-dip galvanizing and are nevertheless corrosion-resistant and malleable.

The process step of fluxing and/or wetting in the bath (5) can be carried out in one step or alternatively can be separated in order to achieve better wetting of the surface. The possible variants of the fluxing and/or wetting process step are described in more detail below.

• 80 Gew. % bis 98 Gew.% ZnCl₂ (Zinkchlorid);
• 1 Gew.% bis 19 Gew.% NH₄Cl (Ammoniumchlorid); und
• 0,1 g/l bis 4 g/l Bi³⁺ (Bismutionen),
• wobei die Gewichtsangaben auf das Fluss-/Benetzungsmittel bezogen sind und die Summe aller Bestandteile der Zusammensetzung 100 Gew.-% ergibt.

In one embodiment of the present invention, the fluxing and wetting takes place in a flux/wetting bath (5), as in the Fig. 2 , No. 5.1 is shown. In such a case, the at least one component is immersed in the flux/wetting bath (5), which has the following flux/wetting agent composition:

• 80% by weight to 98% by weight ZnCl ₂ (zinc chloride);
• 1% by weight to 19% by weight NH ₄ Cl (ammonium chloride); and
• 0.1 g/l to 4 g/l Bi ³⁺ (bismuth ions),
• where the weight information is based on the flux/wetting agent and the sum of all components of the composition is 100% by weight.

The pH value of the flux/wetting bath (5) is also particularly preferably pH ≤ 0.5, but at most 2.0.

• 88 Gew.% +/- 2 Gew.% ZnCl₂ (Zinkchlorid);
• 12 Gew.% +/- 2 Gew.% NH₄Cl (Ammoniumchlorid); und
• 2 g/l +/- 0,5 g/l Bi³⁺ (Bismutionen),
• auf, wobei die Gewichtsangaben auf das Fluss-/Benetzungsmittel bezogen sind und die Summe aller Bestandteile der Zusammensetzung 100 Gew.-% ergibt.

Studies of the surface of components after galvanization, which were subjected to pretreatment using the following composition of the flux/wetting bath (5), showed a surprisingly positive effect on the galvanizing layer, which had a lower thickness, formability and improved quality compared to the galvanizing layers, which were generated using the usual state-of-the-art hot-dip galvanizing processes. For this reason, the flux/wetting agent in a preferred embodiment

• 88% by weight +/- 2% by weight ZnCl ₂ (zinc chloride);
• 12% by weight +/- 2% by weight NH ₄ Cl (ammonium chloride); and
• 2 g/l +/- 0.5 g/l Bi ³⁺ (bismuth ions),
• on, whereby the weight information is based on the flux/wetting agent and the sum of all components of the composition is 100% by weight.

The pH value of the flux/wetting bath (5) is preferably pH ≤ 1.0, particularly preferably pH ≤ 0.5. The flux/wetting bath (5) is operated continuously at a maximum pH of 2.0, particularly preferably ≤0.5, which is adjusted using hydrochloric acid (HCl), preferably a dilute HCl solution. The pH value must be constantly below pH ≤ 2.0, otherwise the bismuth would precipitate. Due to the eutectic in the form of the NH ₄ Cl-ZnCl ₂ mixture and the bismuth (Bi), a fine pickling effect occurs in the zinc melt process step following the flux/wetting bath also a bismuth wetting in the boundary layer area of the component surface, which means that the resulting zinc coating has a high quality. Another advantage of the low pH value is that there is no formation of Fe ³⁺ (iron (III) ions) in the flux/wetting bath (5), which contribute to sludge sedimentation.

Due to the low pH value and the bath parameters, the bismuth is in the form of bismuth chloride (BiCl ₃ ). To adjust the bismuth content in the bath, in addition to bismuth chloride (BiCl ₃ ), bismuth oxide (Bi ₂ O ₃ ), bismuth subcarbonate ((BiO) ₂ CO ₃ ) or bismuth granules (metal base) can also be used, which then convert due to the acidic pH value.

The flux/wetting agent is preferably in an aqueous solution in the flux/wetting bath (5), the total salt content within the bath being in the range from 100 to 650 g/l, preferably in the range from 250 to 450 g/l. The total salt content includes the components NH ₄ Cl (ammonium chloride), and ZnCl ₂ (zinc chloride) and BiCl ₃ (bismuth chloride).

The bath temperature of the flux/wetting bath (5) is between 30°C and 60°C, preferably between 40°C and 50°C.

In order to achieve an optimal treatment surface for the zinc melt, which brings with it a fine pickling effect and wetting, a pretreatment time in the flux/wetting bath (5) is from 10 seconds (sec) to 2 minutes (min), preferably from 20 seconds to 60 sec, turned out to be beneficial.

In an alternative embodiment, the process step of the flux/wetting bath (5) is divided into one or more steps, so that the individual steps within the process step of flux treatment and wetting can have a better effect on the surface of the at least one component.

• 3 Fe → 3 Fe²⁺ + 6 e^- (Oxidation)
• 2 Bi³⁺ + 6 e^- → 2 Bi (Reduktion)
• Gesamtreaktion: 3 Fe + 2 Bi³⁺ →3Fe²⁺ + 2 Bi

In one aspect of the invention, the flux/wetting bath previously described is replaced by a bath, hereinafter referred to as a "wetting bath", such as Fig. 2 No. 5.2.1 is shown. The wetting bath includes: Bismuth (Bi ³⁺ ) in the range of 0.1 g/l to 10 g/l. To adjust the bismuth content, bismuth chloride (BiCl ₃ ), bismuth oxide (Bi ₂ O ₃ ), bismuth subcarbonate ((BiO) ₂ CO ₃ ) and/or bismuth granules (metal base) can also be used here. In order to be able to wet the component surface with bismuth, a pH value of pH ≤ 2.0, preferably pH ≤ 1.0, particularly preferably pH ≤ 0.5, is generated in the bath, whereby the pH is adjusted. Value preferably hydrochloric acid (HCl), particularly preferably dilute hydrochloric acid is used. In such a version, the components NH ₄ Cl (ammonium chloride) and ZnCl ₂ (zinc chloride) are not contained in the bath, which means that there is no fine pickling effect based on NH ₄ Cl-ZnCl ₂ in the following zinc melt (ZnAl5). Nevertheless, studies of the component surfaces treated in this way showed an improved zinc application, which has a smaller thickness and better functionality of the zinc layer. This is primarily attributed to the surprising effect of bismuth (Bi) deposited on the component surface in elemental or metallic form, which, due to its higher standard potential compared to the iron-containing surface of the component, is deposited on the component and forms a layer and/or point deposition which has a positive effect on the zinc layer that forms in the following galvanizing bath.

• 3 Fe → 3 Fe ²⁺ + 6 e ^- (oxidation)
• 2 Bi ³⁺ + 6 e ^- → 2 Bi (reduction)
• Overall reaction: 3 Fe + 2 Bi ³⁺ →3Fe ²⁺ + 2 Bi

• 0 g/l ZnCl₂ (Zinkchlorid);
• 100 g/l bis 350 g/l NH₄Cl (Ammoniumchlorid); und
• 0,1 g/l bis10 g/l Bismutionen (Bi³⁺).

In a further embodiment, NH ₄ Cl (ammonium chloride) can be added or generated directly and/or indirectly to the wetting bath, which only comprises bismuth as a composition component, as in the Fig. 2 No. 5.2.2 is shown. In this case, ZnCl ₂ (zinc chloride) is not added. The composition of the wetting bath therefore includes the following composition:

• 0 g/l ZnCl ₂ (zinc chloride);
• 100 g/l to 350 g/l NH ₄ Cl (ammonium chloride); and
• 0.1 g/l to 10 g/l bismuth ions (Bi ³⁺ ).

The ammonium chloride can also be produced through possible precipitation reactions, which means that it does not have to be added directly to the bath. The pH value is adjusted as in the previously described flux/wetting bath at a pH value of pH ≤ 2.0, preferably pH ≤ 1.0, particularly preferably pH ≤ 0.5 in the bath, for the adjustment the pH value is preferably carried out using hydrochloric acid (HCl), particularly preferably dilute hydrochloric acid (HCl). The iron ion content is ≤ 10.0 g/l, preferably ≤ 8.0 g/l, particularly preferably ≤ 5.0 g/l Fe ^2+/3+ (iron ions). In the present case, a fine pickling effect based on NH ₄ Cl (ammonium chloride) takes place in the ZnAl5 melt, ie the zinc bath, and the component surface is wetted with bismuth, which further improves the coating of the component surface with the zinc coating.

• 80 Gew. % bis 98 Gew.% ZnCl₂ (Zinkchlorid), besonders bevorzugt 88 Gew.% +/- 2 Gew.% ZnCl₂ (Zinkchlorid);
• 1 Gew.% bis 19 Gew.% NH₄Cl (Ammoniumchlorid), besonders bevorzugt 12 Gew.% +/- 2 Gew.% NH₄Cl (Ammoniumchlorid),
• wobei die Gewichtsangaben auf die Menge ZnCl₂/NH₄Cl bezogen sind und die Summe dieser Bestandteile der Zusammensetzung 100 Gew.-% ergibt. Der pH-Wert des Hauptfluxbades liegt in der Regel bei einem pH-Wert von 0,5 bis pH 6, vorzugsweise bei pH ≤ 5, besonders bevorzugt bei pH 4. Der pH- Wert wird dabei wie zuvor zu den Bädern beschrieben eingestellt. Der Eisenionenanteil liegt bei <_ 10,0 g/l, vorzugsweise bei ≤ 8,0 g/l, besonders bevorzugt bei ≤ 5,0 g/l Fe^2+/3+ (Eisen).

In a further embodiment of the present invention, the process step is carried out within the flux/wetting bath (5), as in the Fig. 2 No. 5.3, separated in order to improve the respective effects of the individual chemical processes within the process step on the component surface. In such a preferred arrangement of the flux/wetting bath, the component surface is first wetted in the pre-flux or wetting bath with bismuth (Bi ³⁺ ) in the range from 0.1 g/l to 10 g/l, the bismuth content in the bath being determined by the Addition of bismuth chloride (BiCl ₃ ), bismuth oxide (Bi ₂ O ₃ ), bismuth subcarbonate ((BiO) ₂ CO ₃ ) and/or bismuth granules (metal base) is adjusted. In order to obtain a deposition of the bismuth on the component surface, as mentioned above, a pH value of pH ≤ 2.0, preferably of pH ≤ 1.0, particularly preferably of pH ≤ 0.5, is generated in the bath, which is preferably by Hydrochloric acid (HCl), particularly preferably dilute hydrochloric acid (HCl), is adjusted. The wetting bath or pre-flux can also include the direct and/or indirect addition and/or production of NH ₄ Cl (ammonium chloride), so that in addition to the bismuth, the component surface is also wetted with NH ₄ Cl (ammonium chloride). When using ammonium chloride in the wetting bath, 100-350 g/l NH ₄ Cl is preferably used in the wetting bath. Following the pre-flux bath, the component is further treated in the so-called main flux. The main flux preferably has the following composition:

• 80% by weight to 98% by weight of ZnCl ₂ (zinc chloride), particularly preferably 88% by weight +/- 2% by weight of ZnCl ₂ (zinc chloride);
• 1% by weight to 19% by weight of NH ₄ Cl (ammonium chloride), particularly preferably 12% by weight +/- 2% by weight of NH ₄ Cl (ammonium chloride),
• where the weight information is based on the amount of ZnCl ₂ /NH ₄ Cl and the sum of these components of the composition is 100% by weight. The pH value of the main flux bath is generally at a pH value of 0.5 to pH 6, preferably at pH ≤ 5, particularly preferably at pH 4. The pH value is adjusted as described above for the baths. The iron ion content is <_ 10.0 g/l, preferably ≤ 8.0 g/l, particularly preferably ≤ 5.0 g/l Fe ^2+/3+ (iron).

Experimental studies have surprisingly shown that the metallic, elemental bismuth deposited on the component surface in the pre-flux or wetting bath is not washed off or rinsed off in the subsequent main flux and/or intermediate rinsing steps. Consequently, improved wetting and cleaning of the component surface is achieved, which is essential for a thinner zinc application. Due to such a treatment in the pre-flux or wetting bath and an optional subsequent main flux, high-quality zinc layers could be generated after the zinc bath, which had high corrosion resistance despite the low layer thickness. The zinc coatings developed in this way had the quality characteristics of longevity and flexibility, which are particularly important in the automotive industry. A further advantage of such an arrangement is that bismuth is not present in the main flux, which is the case in the flux baths known in the prior art when using bismuth.

In one embodiment, in addition to the baths, ie flux/wetting bath (5). Fig. 2 , No. 5.1, according to the wetting bath Fig. 2 No. 5.2.1, the wetting bath with ammonium chloride Fig. 2 No. 5.2.2, and/or the separate flux and wetting bath Fig. 2 No. 5.3, one or more rinsing baths must be connected upstream and/or downstream in order to prevent or reduce the carryover of the chemicals, components and/or substances formed within the respective baths and to compensate for the carryover and/or evaporation losses.

In the process step of flux/wetting treatment, flux and/or wetting treatment (5), Fig. 2 No. 5.1, 5.2.1, 5.2.2 and/or 5.3, this may result in a Accumulation of contaminants can occur, such as iron ions (Fe ^2+/3+ ), which disrupt and/or influence the process flow. This accumulation of contaminants can be remedied in one aspect by reapplying the respective bath. This should always be done when the concentration of the contaminant has exceeded a limit range. For iron ions (Fe ^2+/3+ ), this is preferably a limit value of 3 g/l to 10 g/l, particularly preferably ≤ 5 g/l.

However, in one embodiment of the present invention, the baths include at least one processing system that removes the impurities from the baths and reprocesses the process liquid and/or certain components. In the at least one flux/wetting bath (5) or the separate processes, the at least one processing system is used to separate iron so that the baths can be in operation for a longer period of time without new preparation. The process bath is set up in such a way that an overflow is arranged on at least one edge region of the respective bath. When using a heat exchanger and/or a heater in the bathroom, this overflow is preferably located on the opposite end face of the bathroom. The overflow and/or the bath directly can be connected to a filter press for the regeneration process, which is used to separate suspended matter/sludge. Due to the suspended matter/sludge separation in a separate compartment, the process in the flux bath and/or wetting bath is not disturbed by this. After contaminants have been separated, the process liquid can then be fed back into the process bath.

In a further aspect, in addition to the separation of the impurities, in particular the separation of suspended matter/sludge using the overflow and/or from the bath directly, the process liquid can also or alternatively be processed in the flux/wetting bath, flux bath and/or wetting bath (5), like in the Fig. 4 is executed. One or more precipitation variants can be used in the processing, for example in the Fig. 4 a) and b) are shown. In a first precipitation variant, which is under the Fig. 4 a) is shown, the process bath, ie the flux/wetting bath (5), Fig. 2 , No. 5.1-5.3, processed in batch operation, ie during ongoing operation. This ensures that the impurities, such as iron ions (Fe ^2+/3+ ), are continuously removed from the bath. This involves a certain volume of process liquid removed from the respective bath and fed to a separate bath, basin and/or container or separate area. This so-called batch volume can contain a different amount of the process liquid depending on the bath volume, but the amount is selected such that the process in the bath is not disturbed by the removal of the process liquid. In a preferred embodiment it is an amount of ≤ 1 m ³ process liquid. In the separate basin, hereinafter referred to as precipitation bath 1, the process liquid is treated and prepared, with ammonia (NH ₃ ) and hydrogen peroxide (H ₂ O ₂ ) at a pH of 2.0 to 6.0, preferably pH 3.5 to 4.2, are added until bismuth and/or iron precipitation can no longer be observed. Alternatively, the precipitation process can also take place over a defined period of time. Bismuth precipitation can usually be observed at a pH value above 2. Iron (Fe) precipitates at a pH value above 3. The iron (II) (Fe ²⁺ ) present in the process liquid, which is present as iron chloride (FeCl ₂ ), is oxidized using hydrogen peroxide (H ₂ O ₂ ) and converted into iron (III) (Fe ³⁺ ), in the form of filterable iron(III) hydroxide (Fe(OH) ₃ ). Bismuth and iron components are simultaneously precipitated in a precipitation bath and removed from the process liquid in a downstream filter press. The precipitation sludge produced in the filter press is preferably collected and disposed of. The filtrate is added to the process bath (step 5.1-5.3, Fig. 2 ) is recycled, with the high pH and bismuth deficits generated by the precipitation process being compensated for before recycling, during recycling and/or in the process bath itself. Here, the pH value is brought back to a pH value of less than 2, preferably ≤ 0.5, using preferably diluted hydrochloric acid (HCl), and the bismuth concentration is brought back to the desired value, preferably ≤ 2.0 g/l bismuth, by appropriate addition , set.

In a second precipitation variant, which is below Fig. 4 b) is shown, as in the first precipitation variant, the process liquid of the flux/wetting bath, flux bath and/or wetting bath (5), Fig. 2 , No. 5.1-5.3, processed in batch operation. The batch volume is further treated in separate baths. Unlike the first precipitation variant, bismuth is first precipitated, which is carried out by adding ammonia (NH ₃ ) and preferably a pH value of over 2, preferably between 2.0 and 2.5. The one generated by the precipitation Suspension is passed through a filter press and the bismuth, which is then in the form of bismuth sludge or bismuth filter cake, is separated in this and can be used as a recovered component in the process, such as the process bath of steps 5.1 to 5.3 ( Fig. 2 ) can be reused. The filtrate, ie the remaining liquid, is further treated in a further step, which preferably takes place in another basin or separate area, in order to achieve separation of iron. In this step, the pH of the bath is raised to a preferred pH of 3.5 to 4.2, preferably using ammonia (NH ₃ ). The ammonia (NH ₃ ) and hydrogen peroxide (H ₂ 0 ₂ ) are then added alternately until the iron components have been precipitated in the remaining liquid. The iron(II) (Fe ²⁺ ), which is formed by the process and is present in the form of iron chloride (FeCl ₂ ), is converted into iron(III) (Fe ³⁺ ), in the form of hydrogen peroxide (H ₂ 0 ₂ ). of iron(III) hydroxide (Fe(OH) ₃ ), which is passed through another filter press and separated as iron hydroxide sludge. The sludge formed can be disposed of. The resulting filtrate, which now consists of a cleaned process liquid, can be fed to the at least one process bath in accordance with precipitation variant 1. The advantage of such a precipitation variant is that the components are separated from each other separately from the "used" process liquid, which makes it possible to reuse the components.

Alternatively or in addition to the precipitation variants described above, the at least one process bath, in particular the flux/wetting bath (5), flux and/or wetting bath, can also be prepared by using two identical baths, with only one bath being active. In such a precipitation variant, the active bath does not necessarily have to be subject to a previously described variant of processing, which requires continuous removal. On the contrary, the active bath remains in use until the interference limit concentration of the interfering substances exceeds a certain range. In the case of the iron content in the process liquid, the limit would be over 2 g/l, preferably at 3.5 g/l, particularly preferably over 5 g/l of iron or iron ions in the process bath. If the limit value is exceeded by suitable means, which can be automatic measurements or manual measurements, the bath becomes one of those listed above precipitation processes, Fig. 4 , switched on. The precipitation process is carried out until there is a reduced concentration of contaminants in the process bath. With regard to the iron and/or the iron ions, the concentration is less than 5 g/l, preferably less than 3 g/l, particularly preferably less than 0.5 g/l. During the preparation of the first bath, the previously inactive second process bath is active and is operated until a contaminant limit value is exceeded in it too. The change between the at least one active and one inactive process bath is preferably carried out continuously.

The aforementioned preparation processes of the process liquid in the flux/wetting bath (5), flux bath and/or wetting bath, have been described with regard to an exact number of baths or additional areas. However, the number of baths in the individual precipitation variants and/or active/inactive baths can vary, so that several baths or areas can be available for each of the baths or areas specified above.

In the case of a separate wetting bath, as described below Fig. 2 , No. 5.2.1 or 5.3, in which the component is only treated with bismuth itself, the limit concentration of contaminants is usually not reached or is only reached after a long standing time, in particular with one or more preceding cleaning steps, such as at least one rinsing bath , this in Fig. 2 , No. 4 is shown. In such a case, the wetting bath is therefore preferably completely disposed of and re-applied.

In a further embodiment of the present invention, the flux/wetting bath (5), flux bath and/or wetting bath can be preceded by one or more process steps and/or baths which improve the cleaning condition of the component surface for the subsequent galvanizing step and thus produce an improved zinc coating layer.

The at least one further process step preferably comprises at least one degreasing bath (1). In the at least one degreasing bath (1), which is shown schematically in the Fig. 2 , No. 1 as well as the Fig. 5 is shown, the component surface is freed from fats and / or oils by treating it using alkaline hot degreasing at preferably over 60 ° C. Here you can An emulsifying (= oils/fats in solution) or demulsifying (= oils/fats floating) procedure, based on the surfactant composition, can be used. The total treatment time in the at least one degreasing bath (1), depending on the oil and/or grease load on the component surface, is between 2 minutes and 60 minutes, preferably between 5 minutes and 20 minutes. The at least one degreasing bath (1) can be in one Aspect have an overflow that surrounds the basin and / or is arranged on at least one side of the bath. If a heat exchanger and/or a heater is used in the degreasing bath (1), the overflow is preferably arranged on the opposite side of the pool. In one aspect of the present invention, creaming oils and/or fats can be separated in the overflow itself and/or at least one calming tank connected to it or to the degreasing bath (1). This is done, for example, using a bag filter and/or belt filter, but other devices can also be used for this purpose. The settling tank, the overflow and/or the process basin in the degreasing bath (1) itself can also be followed by a filter press for separating suspended matter/sludge, in which the aforementioned impurities are filtered, and the degreasing bath (1), Fig. 2 , Number 1; Fig. 5 a filtered and/or purified process liquid is fed back in. At least one rinsing bath (2) can be connected downstream of the degreasing bath (1).

In a further aspect, the system and/or the method include a pickling process that can take place in at least one pickling bath (3), such as Fig. 2 , No. 3 and Fig. 6 is shown. Possible baths and process sequences that can be used in pickling are, for example, the European registration EP3483304A1 refer to. For the removal of, among other things, rust and scale in the pickling bath (3), preferably two to 8 pickling baths (3), particularly preferably four to six pickling baths (3), are used, all or only some of which can be active. The pickling time is between 5 minutes and 240 minutes, preferably between 10 minutes and 180 minutes, particularly preferably between 15 minutes and 120 minutes, depending on the rusting state of the component surface and/or the degree of scale. The pickling process preferably takes place in a temperature range of 15 ° C up to 40°C, preferably between 20-30°C. In order to increase the pickling effect and promote the formation of passive layers on the component surface, the formation of iron (III) ions in the Pickling bath can be increased. This is preferably done by additionally introducing air, in particular oxygen, into the process bath. The air can be introduced using common systems, such as, but not limited to, air blowers, air pumps, including hoses or pipe distribution systems with corresponding outlet openings and/or using bath circulation or bath movement. With the help of this, the content of iron (III) ions (Fe ³⁺ ) can be increased to up to 5.0 g/l, with preferably 0.5 -1.5 g/l Fe ³⁺ being achieved in the process liquid . The Fe ³⁺ reduces, among other things, hydrogen embrittlement and/or hydrogen storage in the components, which means that during the galvanizing process (step 7, Fig. 2 ) a reduction in hydrogen outgassing can be observed, which results in improved galvanizing layers (Zn-Al layers) which have a reduced formation of, for example, voids and/or cracks.

2 FeCl ₃ + H ₂ → 2 FeCl ₂ + 2 HCl

The at least one pickling bath (3) can further comprise at least one overflow which surrounds all side areas of the basin or only parts thereof. This overflow is preferably arranged on the opposite side of the heat exchanger and/or the bath heater if one is in operation. Each individual pickling bath (3) or the baths together can, in one aspect, comprise an individual and/or a common regeneration circuit in which the process liquid is regenerated and fed back into the at least one process bath. The composition of the at least one pickling bath (3) can in principle have any Fe/HCl ratio, but this is preferably 70 g/l hydrochloric acid (HCl) and 200 g/l iron (Fe), preferably 105 g/l HCl and 110 g/l Fe. If the components' concentrations fall below 70 g/l HCl and above 130 g/l iron (Fe), the respective process liquid of the respective bath is disposed of or partially disposed of and reconstituted. For the regeneration circuit of the pickling bath (3), the process bath itself and/or the overflow is connected to one or more stabilization tanks. Contaminants such as fats, oils or other contaminants that were on the component surface can be removed from these settling containers using suitable measures such as skimming and/or filters. The at least one settling tank, overflow and / or the at least one process bath of the pickle is further in one A filter press is installed downstream, which is intended to separate suspended matter/sludge. Due to the separation of the dirt and/or impurities in the regeneration circuit, the process liquid can be fed back into the pickling bath, which can delay or even prevent a new batch or partial batch of the bath.

With the help of continuous and/or discontinuous preparation and/or partial disposal and/or regeneration of the process liquid within the pickling, the bath condition remains almost constant, which, among other things, prevents or reduces saw number profiles and minimizes the use of chemicals within the baths.

As described above, one or more rinsing baths (2, 4) between the individual process baths can be between the at least one degreasing bath (1), the at least one pickling bath (3), the at least one flux/wetting bath, wetting bath and/or flux bath (5). (1, 3, 5) can be interposed to prevent the chemicals from the individual baths from being carried over into the next process step. Furthermore, the use of the at least one rinsing bath is intended to compensate for possible evaporation and/or carryover losses from the upstream process bath. The rinsing liquid of the at least one rinsing bath (2, 4) preferably comprises unheated water, whereby the respective city water can be used. Due to the fact that iron and/or iron ions are present in the flux/wetting bath (5), flux bath and/or wetting bath of step 5 ( Fig. 2 ) and/or the galvanizing bath (7) of step 7 ( Fig. 2 ) have a disruptive effect on the formation of the zinc layer, preferably at least two rinsing baths are used in particular before the flux/wetting bath (5), flux bath and/or wetting bath, which have a maximum interference limit concentration of less than/equal to (≤) 10 g/l iron / iron ions, preferably ≤ 8 g / l iron / iron ions, particularly preferably ≤ 5 g / l iron / iron ions.

Each of the previous process steps ( Fig. 1 , Nos. 1-5) can be carried out within a so-called standing bath. In such a case, the process liquid in the respective baths is not moved. Investigations of the However, the component surface after cleaning and/or galvanizing has shown that in particular the movement of the process liquid within the steps degreasing bath (1), pickling bath (3) and flux/wetting bath (5) ( Fig. 2 ), flux bath and/or wetting bath have contributed to an improved surface coating. For this reason, in a preferred aspect, in the at least previously mentioned process steps of degreasing, pickling and flux treatment and wetting, a bath movement is generated by at least one pump, preferably a bath circulation according to that in the European patent application EP3483304A1 described procedure takes place. Here, one or more pumps are used to form a laminar flow, which can preferably form a flow change, ie the reversal of the bath rotation. This can be achieved by two pumps that generate different flow directions and are operated alternately or by pumps that can change the flow direction by reversing the direction of rotation. Due to the bath movement, the process liquid in the area of the component surface is regularly exchanged, which means that there is no saturation or enrichment in the boundary layer area between the component surface (substrate) and the components of the process solution. The bath rotation with or without changing the flow direction can be carried out using pumps with and without rectifiers, which are arranged inside or outside the bath. A combination of several variants is also possible.

Is the pretreatment, ie cleaning of the component surface after steps 1-5 ( Fig. 2 ) is completed, then in one embodiment the component is dried in a further step in the drying oven (6) in order to free the surface of liquid residues, such as Fig. 2 , No. 6 can be found. Circulating air is preferably generated by radial and/or axial fans, with the temperature in the oven being between 100 and 230 °C. The residence time of the component in the drying oven (6) is between 1 minute and 60 minutes, preferably between 5 minutes and 30 minutes, depending on the liquid load on the component.

In a further aspect of the present invention, the component is treated in a zinc bath (7) after cleaning and, if necessary, drying. The zinc bath (7), which is in Fig. 2 Step 7 is shown includes 2 wt.% to 10 wt.% aluminum (Al) and 90% by weight to 98% by weight of zinc (Zn), preferably 5% by weight ± 1% by weight of Al and 95% by weight ± 1% by weight of Zn. However, the zinc bath (7) may also contain traces of other accompanying elements. As a rule, the residence time of the components in the ZnAl5 melt, ie the galvanizing bath (7), in order to obtain an optimal galvanizing layer, is ≤ 10 minutes, preferably 5 min ± 1 min, at a melting temperature of 420 ° C ± 10 ° C In order to avoid an accumulation of aluminum and/or aluminum compounds, such as iron-aluminum compounds, on the zinc bath surface, which can lead to quality losses, such as spots, in one aspect, additional melt bath circulation can be carried out using suitable pumps and/or overflows.

The galvanizing step (7) ( Fig. 2 ) in a further embodiment, at least one quenching bath (8) can be connected downstream, through which the components are cooled after galvanizing, and / or at least one additional after-treatment step (8), such as passivation and / or sealing, in which at least one Another protective layer can be applied to increase corrosion protection. These optional steps after the actual galvanizing are preferably carried out, like the previous steps, in a dipping process in which the component is immersed in a basin or bath. In addition, the at least one additional bath in the optional step can also have a bath circulation device, as previously described for cleaning steps 1-5 ( Fig. 2 ).

In the at least one quenching bath (8), the components are cooled and any remaining ash residues, in particular chlorides from the flux/wetting bath (5), flux bath and/or wetting bath, are rinsed off. In order to avoid corrosion products on the component surface and/or to avoid attack of the galvanizing layer applied to the component surface, the quenching bath is replaced at a chloride content ≥ 300 mg/l, preferably ≥ 250 mg/l, particularly preferably ≥ 200 mg/l. Alternatively, in one embodiment, the enriched process liquid of the quenching bath (8) can be used to compensate for the evaporation/carryover losses in the flux/wetting bath (5), flux bath and/or wetting bath of the pretreatment.

Here, the liquid of the quenching bath (8) can be filtered, for example using suitable filters, and one of steps 5 ( Fig. 2 , Fig. 3 ) are supplied.

In addition to the quenching bath (8), a passivation/sealing bath after galvanizing (7) ( Fig. 2 ) or after a quenching bath (8), which can be a chemical passivation, for example using chromium salts, an inorganic sealing using, for example, silicates and / or an organic sealing, such as polymers. During chemical passivation, the passivating agent reacts with the surface of the galvanized component by forming a corresponding conversion layer. In contrast, with inorganic and organic sealing, an additional layer is applied to the already galvanized surface. The layers applied within the passivation and/or sealing on the component surface have a layer thickness of less than 5 µm, preferably less than 3 µm, particularly preferably ≤ 1 µm (micrometers). The process liquid of the passivation bath and/or sealing bath is preferably continuously filtered in a bypass using suitable filters, such as a candle filter. If a limit value within the process liquid required for the passivation bath and/or sealing bath is exceeded, the respective process liquid is (partially) disposed of and reconstituted.

In the individual process steps 1-8 ( Fig. 2 ), which are carried out in the system of the present invention, carry-over into the subsequent process or processes can occur due to carry-over of individual chemicals from the previous processes and/or removal from the component surface, whereby the respective subsequent process step or steps May contain traces of chemicals that have been previously used. Furthermore, the rinsing baths as well as the evaporation and carryover losses mean that small amounts of other components, ions, metals and/or salts can be found in the individual process baths due to the use of drinking water, which can have a different composition . However, these are negligible for the effect and/or the individual process steps.

The present invention further relates to the use of the flux/wetting process, the system comprising one or more process baths (1-8; Fig. 2 ) and/or the process for galvanizing in the coating of iron-based components, preferably using a zinc-aluminum alloy, particularly preferably a ZnAl5 alloy.

Furthermore, the invention also relates to components that have been treated with the flux/wetting process or the method described above.

These and other embodiments of the present invention are disclosed in and are encompassed by the specification and examples. Further literature on any of the known materials, methods and applications that can be used in accordance with the present invention can be accessed 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 purposes of illustration and are not intended to limit the scope of the invention.

Examples Example 1: Preferred embodiment of a system for galvanizing a component surface

In the Fig. 2 A hot-dip galvanizing system is shown, which includes a greasing process in a degreasing bath, Fig. 2 , Number 1; a pickling process in the pickling bath, Fig. 2 , No. 3; a flux treatment and/or wetting in a flux/wetting bath, Fig. 2 , No. 5; a drying step in the drying oven, Fig. 2 , No. 6; galvanizing in zinc melt, Fig. 2 , No. 7; and optionally includes an additional step of quenching in the quenching bath (8) and/or passivation/sealing in the aftertreatment bath (8). Between the individual pretreatment steps before galvanizing, at least one rinsing bath (2, 4) is preferably arranged in each process step (1, 3 and/or 5), which preferably comprises unheated water and is intended to prevent the previous process step from being carried over into the subsequent process step; Fig. 2 . The arrows above the process baths within the Fig. 2 characterize the course of the component within the system, ie the flow of goods.

Bath circulation preferably takes place in the process baths 1, 3, 5, 7 and/or 8, with the respective process bath having at least one pump with which the process liquid can be moved. In one aspect, a regular rotation reversal of the process liquid should preferably be formed, which is formed by the reversing operation of the pump and/or at least two pumps which can form a reverse flow and are active in opposite directions. The corresponding bath circulation is indicated by the dashed arrows within the respective process baths Fig. 2 marked.

In addition, the process baths, in particular the at least one degreasing bath (1, Fig. 2 as well as Fig. 5 ), which has at least one pickling bath (2; Fig. 2 , Fig. 6 ), the at least one flux/wetting bath (5; Fig. 2 , Fig. 3 ), flux bath and/or wetting bath, and/or the additional quenching and/or post-treatment bath (8; Fig. 2 ) have a regeneration circuit that regenerates the respective process liquids of the respective bath and returns them to the corresponding process bath for reuse. The Regeneration cycle is within the Fig. 2 shown under the corresponding process baths.

In the preferred embodiment, alkaline hot degreasing is used in the degreasing bath (1), which has temperatures of over 60 ° C.

The following parameters are used in the pickle (3) to further clean the component: ≤ 70-105 g/l HCl; ≥ 110 -130 g/l Fe; 20-30°C.

The flux/wetting bath (5) can be designed in different variants, which are described in steps 5.1, 5.2.1, 5.2.2 and 5.3 of Fig. 2 are shown.

In variant 5.1 of the flux/wetting bath (5), this has the following composition: 88% by weight ZnCl ₂ (zinc chloride), 12% by weight NH ₄ Cl (ammonium chloride) and 2 g/l Bi ³⁺ (bismuth ions) , at a temperature of 40-50°C.

This is only followed by wetting with bismuth in a wetting bath Fig.2 No. 5.2.1, the bath has the following composition: 0.1 g/l - 10g/lg/l Bi ³⁺ (bismuth ions), at a temperature of 40-50°C.

In a further embodiment, 5.2.2, the wetting bath can also comprise ammonium chloride (NH ₄ Cl) in addition to bismuth. In such a case, the bath has the following composition: 100-350 g/l NH ₄ Cl (ammonium chloride) and 0.1 g/l -10 g/l Bi ³⁺ (bismuth ions), at a temperature of 40-50 °C.

Alternatively, the flux/wetting bath (5) can also include a pre-flux or wetting bath and a pre-flux or main flux, as can be seen in 5.3. Here, the component is wetted with bismuth in a wetting bath or pre-flux, with the process liquid in the bath having the following composition: 0.1 g/l 10 g/lg/l Bi ³⁺ (bismuth ions) or 0.1 g/l - 10 g/l Bi ³⁺ (bismuth ions) and ≤ 350 g/l NH ₄ Cl (ammonium chloride), at a temperature of 40-50°C. The downstream main flux then has the following composition: 88% by weight ZnCl ₂ (zinc chloride) and 12% by weight NH ₄ Cl (ammonium chloride), at a temperature of 40 up to 50°C. As an alternative to the main flux, only a bath comprising ammonium chloride can be connected downstream, without the addition of ZnCl ₂ .

After surface cleaning, a drying step (6) can be provided in the drying oven before galvanizing, the drying oven preferably having a temperature of 100 to 230 ° C.

The subsequent galvanizing bath, also called zinc melt (7), has the following composition: 5% by weight of Al and 95% by weight of Zn, at a bath temperature of 410-430°C, which is also referred to as a ZnAl5 alloy bath.

Example 2: Treatment in a flux/wetting bath, flux bath and/or wetting bath (5)

In order to substantiate the preliminary results of the improved discontinuous aluminum-containing piece galvanizing using an upstream flux/wetting bath, flux bath and/or wetting bath (5), further series of tests were carried out in which, in addition to the sequence of treatments, the compositions and/or conditions were changed.

For the test series, 10 cm long square profile specimens made of Sebisty steel with extreme signs of deep rust were used. Due to their hollow space, they should also reflect the effects of galvanizing or pretreatment on three-dimensional bodies or the behavior of the hollow space. The extreme deep rust phenomena were generated by outdoor weathering of the test specimen over a longer period of time, which was preferably at least 365 days. Before the test specimens were treated in a flux/wetting bath, flux bath and/or wetting bath, they were cleaned as usual, first in a degreasing bath, a pickling bath and several intermediate rinsing cycles. The alkaline hot degreasing was carried out at a temperature of 60 ° C and a residence time of the test piece of 10 minutes. The iron stain in which the test piece was immersed was operated at room temperature with a residence time of the test piece of 60 minutes.

The results of the test series indicated that within the thin-film galvanizing in the ZnAl5 alloy bath, no significant change in the galvanizing layer thickness could be determined in the different pretreatment steps, i.e. sequence of the pre-flux, wetting bath and/or flux bath, but there were significant changes with regard to the galvanizing layer formed Differences in quality in the optical and haptic areas.

In contrast to flux compositions without bismuth, both the test specimens that were subjected to a pretreatment in a flux/wetting bath containing bismuth alone and those that were treated in a wetting bath containing bismuth with a subsequent flux bath or pre-flux comprising only ammoinium chloride (NH ₄ Cl). , an improved surface structure after galvanizing. This improved surface structure had significantly fewer pimples, streaks, scales, scales and/or other irregularities than the surfaces with the commonly used flux compositions.

Although improvements in surface quality in terms of adhesion, homogeneity of the galvanizing and the surface could already be observed at pH values below 2.0, the series of tests showed that at pH values above 0.5 the bismuth The compositions of the wetting bath, pre-flux or the flux/wetting bath still partially failed and poorer galvanizing surfaces were formed on the components. In tests with a pH value of less than 0.5, the surface of the test specimens showed a further improvement in the homogeneity of the galvanizing layer compared to the tests above a pH value of 0.5 and below a pH value of 2.0, whereby only a smaller number of streaks, pimples and/or similar irregularities could be detected. The test specimens showed no differences in the galvanizing quality between pH values of 0.20 and 0.50. Above a pH value of 2.0, the bismuth was almost completely precipitated, meaning no improvements in surface quality were observed.

In contrast to the combination bath, ie wetting/flux bath, comprising ZnCl ₂ , NH ₄ Cl and a Bi component, such as bismuth itself or a bismuth compound, the treatment of the test specimens before the actual flux treatment with bismuth as a wetting agent and, if necessary, additional ammonium chloride Surprisingly, there is a further improvement in the surface after galvanizing the test specimen. This had almost no pimples and showed a homogeneous surface structure of the galvanizing layer.

After treatment in a wetting bath or pre-flux comprising bismuth or bismuth and ammonium chloride (NH ₄ Cl) at pH values of less than 0.5, the test specimens, which are intended to represent components, had a black coating, which was metallic Bismuth deposition acted. With the subsequent main flux/flux bath, this resulted in a homogeneous surface structure after galvanizing.

Interestingly, a sole preflux/wetting bath comprising ammonium chloride (NH ₄ Cl) and bismuth compound without zinc chloride and without a subsequent flux treatment also led to an improvement in surface quality compared to the standard methods in which a flux bath always contains the components zinc chloride (ZnCl ₂ ) and ammonium chloride (NH ₄ Cl).

In addition, it was surprisingly found that the drying temperature in the drying oven after treatment in the ammonium chloride (NH ₄ Cl)-containing pre-flux/wetting bath, comprising the sole components ammonium chloride (NH ₄ Cl) and/or bismuth, should not exceed 150 ° C, since otherwise incorrect surface galvanization or no homogeneous surface was achieved.

Table 1 below shows the conditions, components and process sequences of the preferred embodiments of the baths. Table 1 Preferred combinations and conditions determined based on the test series Pre-flux/wetting bath: 200-350 g/l NH ₄ Cl; 0.5-2 g/l Bi, pH = 0.20-0.30; Temperature (T) = 45 °C; Dwell time (VZ) = 60 sec. T _{drying oven} = 110-150°C Wetting bath: 0.5-2 g/l Bi, pH = 0.20-0.30; T = room temperature (RT); VZ = 60 sec. Pre-flux: 200-350 g/l NH ₄ Cl, no ZnCl ₂ , pH = 4.0; T = 45 °C, VZ = 60 sec. T _{drying oven} = 11 0-1 50 °C Wetting bath: 0.5-2 g/l Bi; pH = 0.20-0.30; T = RT; VZ = 60 sec. Flux bath: 350 g/l ZnCl ₂ ; 50 g/l NH ₄ Cl; pH = 4.0; T = 45°C; VZ = 60 sec. T _{drying oven} = 225 °C Flux/wetting bath: 350 g/l ZnCl ₂ ; 50 g/l NH ₄ Cl; 0.5-2 g/l Bi, pH = 0.25-0.5; T = 45°C; VZ = 60 sec. T _{drying oven} = 225 °C Flux/wetting bath: 50 g/l ZnCl ₂ , 350 g/l NH ₄ Cl, 0.5-2 g/l Bi, pH = 0.25-0.5; T = 45°C; VZ = 60 sec. T _{drying oven} = 1 50-225 °C Wetting bath: 0.5-2 g/l Bi; pH = 0.20-0.30; T = RT; VZ = 60 sec. Flux bath: 50 g/l ZnCl ₂ , 350 g/l NH ₄ Cl; pH = 4.0; T = 45°C; VZ = 60 sec. T _{drying oven} = 1 50-225 °C

The series of tests carried out as well as other preliminary tests showed that the concentration of the bismuth compound(s) as well as the pH value of the bismuth-containing bath or the concentration of the depositable bismuth ions were decisive for the quality of the zinc coating and the bath combinations listed in Table 1 and Pretreatments achieved improved surfaces in the ZnAl5 melt compared to the previously described and used combination flux baths, which always included zinc chloride and ammonium chloride. Initial results indicate that this improved surface is achieved after galvanization by the sub-deposition of bismuth on the component surface during pretreatment.

Claims (18)

Method for galvanizing components, in particular metallic components in discontinuous galvanizing, wherein before zinc is applied to the surface of the components in a zinc bath (7), at least one treatment of the component in a flux/wetting bath, flux bath and/or wetting bath ( 5) takes place, in which bismuth is deposited on the surface of the at least one component, with a concentration of 0.1 g/l to 4 g/l Bi ³⁺ , preferably 2 g/l ± 0.5 g/l Bi ^{3 +} (bismuth ions) is included in at least one bath at a pH value of less than 2.0. Method according to claim 1, wherein the at least one component is immersed in the flux/wetting bath (5), the flux/wetting agent of the flux/wetting bath (5) a) has the following composition: (i) 80% by weight to 98% by weight ZnCl ₂ (zinc chloride), preferably 88% by weight ± 2% by weight ZnCl ₂ (zinc chloride); (ii) 1 wt% to 19 wt% NH ₄ Cl (ammonium chloride), preferably 12 wt% ± 2 wt% NH ₄ Cl (ammonium chloride); and (iii) 0.1 g/l to 4 g/l Bi ³⁺ , preferably 2 g/l ± 0.5 g/l Bi ³⁺ (bismuth ions); where the weight information is based on the flux/wetting agent and the sum of all components of the composition is 100% by weight, b) has a pH of ≤ 2.0, preferably ≤ 1.0, particularly preferably ≤ 0.5; c) is present in aqueous solution and the total salt content within the bath (5) is in the range from 100 to 650 g/l, preferably in the range from 250 to 450 g/l. Method according to claim 1, wherein the flux/wetting bath (5) is divided into one or more steps, so that the individual steps within the process step of flux treatment and wetting can act individually on the surface of the at least one component, the steps of the process step of Flux and wetting treatment can be separated as follows: a) Preflux and main flux, the preflux comprising a wetting bath that contains a process solution comprising bismuth in the form of Bi ³⁺ in the range from 0.1 g/l to 10 g/l and a pH of ≤ 2.0, preferably of pH ≤ 1.0, particularly preferably of pH ≤ 0.5 and causes the component surface to be wetted with bismuth (Bi); and wherein the main flux is ZnCl ₂ (zinc chloride) in the range from 80% by weight to 98% by weight, preferably 88% by weight ± 2% by weight, and NH ₄ Cl (ammonium chloride) in the range from 1% by weight to 19% by weight, preferably 12% by weight ± 2% by weight, the weights being based on the amount of ZnCl ₂ /NH ₄ Cl and the sum of these Components of the composition make up 100% by weight; furthermore, the pH value of the main flux bath is at a pH value of 0.5 to pH 6, preferably at pH ≤ 5, particularly preferably at pH 4; and or b) pre-flux and main flux, where the pre-flux comprises a wetting bath that contains a process solution comprising bismuth in the form of bismuth ions (Bi ³⁺ ) in the range from 0.1 g/l to 10 g/l; and NH ₄ Cl (ammonium chloride) in the range from 100 g/l to 350 g/l; and has a pH value of ≤ 2.0, preferably pH ≤ 1.0, particularly preferably pH ≤ 0.5 and causes the component surface to be wetted with bismuth (Bi) and NH ₄ Cl (ammonium chloride); and where the main flux ZnCl ₂ (zinc chloride) in the range from 80% by weight to 98% by weight, preferably 88% by weight ± 2% by weight; and NH ₄ Cl (ammonium chloride) in the range of 1 wt% to 19 wt%, preferably 12 wt% ± 2 wt%; where the weight information is based on the amount of ZnCl ₂ /NH ₄ Cl and the sum of these components of the composition amounts to 100% by weight; and furthermore, the pH value of the main flux bath is at a pH value of 0.5 to pH 6, preferably at pH ≤ 5, particularly preferably at pH 4. Method according to claim 1, wherein the component is treated in a wetting bath upstream of the zinc bath (7), in which the component is coated with a process solution a) bismuth ions (Bi ³⁺ ) in the range from 0.1 g/l to 10 g/l and a pH of ≤ 2.0, preferably pH ≤ 1.0, particularly preferably pH ≤ 0.5; or b) bismuth ions (Bi ³⁺ ) in the range from 0.1 g/l to 10 g/l; and NH ₄ Cl (ammonium chloride) in the range of 100 g/l to 350 g/l, is treated; wherein the pH value of the process solution is ≤ 2.0, preferably at pH ≤ 1.0, particularly preferably at pH ≤ 0.5. Method according to one of claims 1 to 4, wherein a) Bismuth (Bi) in the form of bismuth chloride (BiCl ₃ ), bismuth oxide (Bi ₂ O ₃ ), bismuth subcarbonate ((BiO) ₂ CO ₃ ) and/or bismuth granules (metal base) in the flux/wetting bath, flux bath and/or Wetting bath (5) is used; b) the bath temperature of the flux/wetting bath, flux bath and/or wetting bath (5) is 30°C and 60°C, preferably between 40°C to 50°C; c) the pretreatment time in the flux/wetting bath, flux and/or wetting bath (5) is 10 seconds (sec) to 2 minutes (min), preferably 20 seconds to 60 seconds; d) at least one rinsing process in a rinsing bath is upstream, downstream or interposed between the at least one flux/wetting bath, flux bath and/or wetting bath (5); e) the process solution within the flux/wetting bath, flux bath and/or wetting bath (5) has a limit value of iron ions (Fe ^2+/3+ ) of 3 g/l to 10 g/l, particularly preferably 5 g/l, does not exceed; and or f) the process solution is prepared within the flux/wetting bath, flux bath and/or wetting bath (5) by means of at least one processing system and the processed process solution and/or component is fed back to the flux/wetting bath, flux bath and/or wetting bath (5). Method according to claim 5, wherein in the processing plant a) the process liquid of the process bath is prepared during ongoing operation by removing a volume of process liquid from the flux/wetting bath, flux bath and/or wetting bath (5) and storing it in a separate basin with ammonia (NH ₃ ) and hydrogen peroxide (H ₂ O ₂ ) is treated and processed at a pH of 2.0 to 6.0, preferably from pH 3.5 to 4.2; or b) the process liquid is prepared, a volume of the process liquid being removed from the flux/wetting bath, flux bath and/or wetting bath (5) and stored in a first separate basin with ammonia (NH ₃ ) and a pH value of over 2, is preferably treated between 2.0 and 2.5, and wherein the filtrate is treated in a further step in a second separate tank with ammonia (NH ₃ ) and hydrogen peroxide (H ₂ O ₂ ) at a pH of 3.5 to 4, 2 is treated. Method according to claim 5 or 6, wherein the resulting precipitation sludge is collected and disposed of in a filter press downstream of the at least one separate basin and the processed process liquid is returned to the process bath as a filtrate and / or the component obtained in the processing is returned to the flux/wetting bath, flux bath and / or wetting bath (5) is fed back in. Method according to one of claims 1 to 7, wherein the flux/wetting bath (5), flux bath and/or wetting bath is preceded by one or more process steps and/or process baths for cleaning the component, the at least one process step preferably comprising: a) degreasing the component surface by means of at least one degreasing bath (1), the degreasing bath (1) preferably further comprising at least one regeneration circuit in which the process liquid of the degreasing bath (1) is prepared; b) a pickling process which takes place in at least one pickling bath (3), the pickling bath (3) preferably further comprising at least one regeneration circuit in which the process liquid of the pickling bath (3) is prepared; and or c) rinsing the component surface with one or more rinsing baths, which are connected upstream, intermediate or downstream of the process baths (1, 3, 5). Method according to one of claims 1 to 8, wherein the flux/wetting bath (5), flux bath and/or wetting bath a) one or more drying steps are followed in the drying oven (6), with liquid residues on the component being removed at a temperature between 100-230 ° C and a preferred residence time between 1 minute and 30 minutes; and or b) one or more galvanizing steps are followed, the zinc bath (7) containing 2% by weight to 10% by weight of aluminum (Al) and 90% by weight to 98% by weight of zinc (Zn), preferably 5% by weight ± 1% by weight of Al and 95% by weight ±1% by weight of Zn and the residence time of the components in the zinc bath (7) is ≤ 10 minutes, preferably 5 minutes ± 1 minute at a temperature of 420 ° C ± 10 ° C lies. Flux/wetting agent composition for galvanizing components, in particular metallic components in batch galvanizing, comprising the following composition: 88% by weight ± 2% by weight ZnCl ₂ (zinc chloride); 12% by weight ± 2% by weight NH ₄ Cl (ammonium chloride); and 2 g/l ± 0.5 g/l Bi ³⁺ (bismuth ions); where the weight information is based on the flux/wetting agent and the sum of all components of the composition amounts to 100% by weight, furthermore the flux/wetting bath having a pH ≤ 2.0, preferably pH ≤ 1.0, especially preferably of pH ≤ 0.5. System for galvanizing components, in particular metallic components in discontinuous galvanizing, the system having at least one flux/wetting bath, flux bath and/or wetting bath (5) that is connected upstream of the zinc bath (7) and in which the surface of the at least Bismuth is applied to a component, the at least one bath having a concentration of 0.1 g/l to 4 g/l Bi ³⁺ (bismuth ions) and a pH value below 2.0. Plant according to claim 11, wherein the at least one flux/wetting bath (5) a) has the following flux/wetting agent composition: 80% by weight to 98% by weight of ZnCl ₂ (zinc chloride), preferably 88% by weight ± 2% by weight of ZnCl ₂ (zinc chloride); 1% by weight to 19% by weight NH ₄ Cl (ammonium chloride), 12% by weight ± 2% by weight NH ₄ Cl (ammonium chloride); and 0.1 g/l to 4 g/l Bi ³⁺ (bismuth ions), preferably 2 g/l ± 0.5 g/l Bi ³⁺ (bismuth ions); wherein the weight information is based on the flux/wetting agent and the sum of all components of the composition amounts to 100% by weight, and furthermore the flux/wetting bath (5) has a pH of ≤ 2.0, preferably pH ≤ 1 .0, particularly preferably ≤ 0.5; b) is in aqueous solution and the total salt content within the bath (5) is in the range from 100 to 650 g/l, preferably in the range from 250 to 450 g/l; c) are divided into one or more steps, so that the individual steps within the process step of flux treatment and wetting can act individually on the surface of the at least one component, the flux/wetting bath (5) being separated as follows: i) pre-flux and main flux, wherein the pre-flux comprises a wetting bath that has a process solution comprising Bi ³⁺ (bismuth ions) in the range from 0.1 g/l to 10 g/l and a pH of ≤ 2.0, preferably of pH ≤ 1.0, particularly preferably pH ≤ 0.5 and causes the component surface to be wetted with bismuth (Bi); and wherein the main flux is ZnCl ₂ (zinc chloride) in the range of 80% by weight to 98% by weight, preferably 88% by weight ± 2% by weight; and 1% by weight to 19% by weight of NH ₄ Cl (ammonium chloride), 12% by weight ± 2% by weight of NH ₄ Cl (ammonium chloride); and where the weight information is based on the amount of ZnCl ₂ /NH ₄ Cl and the sum of these components of the composition comprises 100% by weight; and furthermore, the pH value of the main flux bath is at a pH value of 0.5 to pH 6, preferably at pH ≤ 5, particularly preferably at pH 4; ii) pre-flux and main flux, wherein the pre-flux comprises a wetting bath that contains a process solution comprising Bi ³⁺ (bismuth ions) in the range of 0.1 g/l to 10 g/l; and NH ₄ Cl (ammonium chloride) in the range from 100 g/l to 350 g/l; and has a pH value of ≤ 2.0, preferably pH ≤ 1.0, particularly preferably pH ≤ 0.5 and causes the component surface to be wetted with bismuth (Bi) and NH ₄ Cl (ammonium chloride); and wherein the main flux is ZnCl ₂ (zinc chloride) in the range from 80% by weight to 98% by weight, preferably 88% by weight ± 2% by weight; and NH ₄ Cl (ammonium chloride) in the range from 1 wt.% to 19 wt.%, preferably 12 wt.% ± 2 wt.% includes; and where the weight information is based on the amount of ZnCl ₂ /NH ₄ Cl and the sum of these components of the composition amounts to 100% by weight; and furthermore, the pH value of the main flux bath is at a pH value of 0.5 to pH 6, preferably at pH ≤ 5, particularly preferably at pH 4. Plant according to claim 11, wherein the plant comprises a wetting bath upstream of the zinc bath (7), in which the component is coated with a process solution a) bismuth ions (Bi ³⁺ ) in the range from 0.1 g/l to 10 g/l; or b) bismuth ions (Bi ³⁺ ) in the range from 0.1 g/l to 10 g/l; and
NH ₄ Cl (ammonium chloride) in the range from 100 g/l to 350 g/l; wherein the pH value of the process solution is ≤ 2.0, preferably at pH ≤ 1.0, particularly preferably at pH ≤ 0.5. Plant according to one of claims 11 to 13, wherein a) at least one rinsing bath is connected upstream, downstream or interposed between the at least one flux/wetting bath, flux bath and/or wetting bath (5); b) contaminants from the process solution of the at least one process bath (5) are reduced or removed within at least one processing system and the processed process solution is fed back to the respective process bath (5), the processing system preferably comprising at least one separate bath, in which (i) the process liquid of the process bath is prepared during ongoing operation, a volume of process liquid being removed from the flux/wetting bath, flux bath and/or wetting bath (5) and mixed with ammonia (NH ₃ ) and hydrogen peroxide (H ₂ O ₂ ) is treated and processed at a pH of 2.0 to 6.0, preferably pH 3.5 to 4.2; or (ii) the process liquid is prepared, with a volume of the process liquid being removed from the flux/wetting bath, flux bath and/or wetting bath (5) and stored in a first separate basin with ammonia (NH ₃ ) and a pH value of over 2 , preferably between 2.0 and 2.5, and wherein the filtrate is treated in a further step in a second separate tank with ammonia (NH ₃ ) and hydrogen peroxide (H ₂ O ₂ ) at a pH of 3.5 to 4 ,2 is treated; Plant according to one of claims 11 to 14, wherein a) the flux/wetting bath (5), flux bath and/or wetting bath is preceded by one or more process steps and/or process baths for cleaning the component, the at least one process bath preferably comprising: (i) a degreasing bath (1) for degreasing the component surface; (ii) a pickling bath (3) for pickling the component; and or (iii) one or more upstream, intermediate or downstream rinsing baths for rinsing the component surface;
and or b) the flux/wetting bath (5) is followed by one or more process steps, which include the following steps: (i) one or more drying ovens (6) for drying the component; (ii) one or more galvanizing baths (7) for galvanizing the component surface; (iii) at least one quenching bath; and or (iv) at least one aftertreatment bath, preferably for applying at least one further protective layer to the component surface. Use of the method according to one of claims 1-9, the system according to one of claims 11 to 15 for galvanizing components, in particular metallic components in discontinuous galvanizing and / or a zinc-aluminum alloy. Component produced by the method according to one of claims 1 to 9. Wetting agent composition for galvanizing components, in particular metallic components in batch galvanizing, comprising the following composition: Bismuth (Bi ³⁺ ) in the range from 0.1 g/l to 10 g/l; and NH ₄ Cl (ammonium chloride) in the range of ≤ 350 g/l and has a pH value ≤ 2.0, preferably pH ≤ 1.0, particularly preferably pH ≤ 0.5.

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