DE102013107011A1 - Process for coating long Cu products with a metallic protective layer and a Cu long product provided with a metallic protective layer - Google Patents

Abstract

The invention makes it possible to optimally protect a Cu long product produced from a Cu material against corrosion by carrying out the following working steps: a) providing the Cu long product; b) cleaning and activating the surface of the Cu long product exclusively by chemical attack; c) drying the purified Cu long product and heating the Cu long product to a bath inlet temperature; d) hot-dip coating the Cu long product with a Zn-based metallic protective coating in a Zn-containing melt bath into which the Cu long product enters at the bath inlet temperature; e) optionally carried out thermal, chemical or mechanical aftertreatment of the Zn-coated hot-dip coated Cu long product.

Description

The invention relates to a method for coating long Cu products produced from a Cu material with a metallic protective layer.

Moreover, the invention relates to a provided with such a metallic protective layer Cu long product.

The "long products" to be coated in the context of the invention are predominantly rolled strips or sheets and blanks and blanks obtained therefrom, which are also referred to in the jargon as "flat products" due to their small thickness. In particular, the inventive method for processing so-called narrow band is suitable, the width of which is limited to a maximum of 600 mm. However, under long products processed according to the invention, wires, profiles or tubes made of Cu materials, which are suitable for being conveyed in a continuous pass through a coating installation, are also covered.

Due to their outstanding thermal and electrical conductivity, Cu-based materials are of particular importance in the field of electrical applications. In particular, this includes microelectronics and power engineering as well as all other electrical installations.

Although Cu is one of the nobler elements, environmental factors can also cause corrosion products on the surfaces of long products made of Cu materials. These can cause lasting damage to the structure and concomitant use properties of the Cu material.

Taking into account the currently high and tending to continue rising copper price thus resulting in corrosion a significant economic total damage. It is therefore looking for ways to protect semi-finished products, such as the Cu long products in question, made of components and other components made of Cu materials from corrosive deterioration. This applies in particular to components which are inevitably and permanently exposed to aggressive environmental influences. This includes the outdoor weathering, which are exposed in particular for conducting high electrical currents in plant construction used conductor tracks in practice.

Various attempts are known to improve the protection of Cu products by the application of a corrosion-resistant and the respective Cu substrate protective coating. An example of such a proposal is in the DD 155 437 A1 described possibility to provide Cu components by electrolytic coating with a chrome plating. In a similar way is in the DD 207 934 A1 It has been proposed to cover the Cu components with a nickel layer for protection against corrosion.

In the field of steel processing, it is also customary to provide a metallic protective layer from corrosion-sensitive steels or long-steel products or components intended for use in particularly aggressive environments. A particularly well-proven coating material are zinc and zinc alloys.

Various proposals have been made as to how copper-based products and components with a Zn coating can be protected from corrosion. Such a Zn coating can be deposited on a Cu substrate, for example, by virtue of the fact that the Cu substrate and a Zn donor are in direct contact as a solid in a tempered sodium hydroxide solution. Another possibility of producing a Zn coating on a body made of Cu material consists in a diffusion coating, in which first zinc, for example, applied as a suspension to the surface to be coated and then a heat treatment is carried out to remove the Zn from the suspension in the Cu substrate to diffuse. Examples of such an approach are in the DE 10 2008 020 576 A1 and the DE 10 2009 006 190 A1 described. It is likewise known that Cu components can be provided with a Zn protective layer in the sense of piece-wise galvanizing by brief immersion in a molten Zn bath. Finally, it has been attempted to subject Cu long products, according to the model of the usual in steel flat products hot dip galvanizing in a continuous process initially an annealing and then to pass through a Zn melt bath to provide it with the Zn coating.

It is to be understood in this context that, unless expressly stated otherwise, whenever Zn layer, Zn coating, Zn melt bath or the like is mentioned, It is always meant such layers, coatings, melt baths and the like, which may consist of pure zinc or a zinc alloy.

The above-mentioned attempts to produce a Zn coating on Cu substrates require a finished molded component and are therefore not suitable for coating long products of the type of interest here. The coating of long products can be economically feasible only if the respective required work steps can be run through in a continuous sequence of the individual process steps. Although such a continuous process is in principle possible if the coating is carried out electrolytically. However, an electrolytic coating of Cu long products on an industrial scale entails high technical complexity and, concomitantly, high operating costs.

For the coating of steel strips in addition to the electrolytic coating and the hot dip galvanizing is known. It can be carried out both as piece galvanizing and continuously. Although the continuous hot-dip galvanizing has clear cost advantages compared to the piece galvanizing or the electrolytic coating. In hot-dip galvanizing, however, an annealing treatment must be performed in the process. This annealing treatment is typically carried out at at least 600 ° C under an H ₂ -N ₂ atmosphere to reduce oxides present on the surface of each long product to be coated, thereby activating the metal surface for subsequent Zn deposition.

If Cu materials are to be processed in this way, there is the problem that Cu is sensitive to the action of reducing, larger amounts of hydrogen-containing atmospheres from about 450 ° C. Thus, in the course of a conventionally carried out annealing, water can form, which remains trapped in the Cu material and leads to stresses after cooling. These stresses lead to cracks, through which the respective workpiece or long product becomes unusable. This phenomenon is also known in practice as the "hydrogen disease of Cu".

Against the background of the prior art explained above, the object of the invention was to provide a process which can be carried out industrially at low cost, with which it is possible to produce long products which are optimally protected against corrosion and consist of Cu materials. Likewise, a long Cu product made of Cu material should be given which has optimum corrosion resistance.

With regard to the method, this object has been achieved according to the invention in that, for coating a Cu long product consisting of a Cu material, the working steps specified in claim 1 are run through.

An abovementioned object according to the invention solving Cu long product is characterized accordingly by the features specified in claim 15.

Advantageous embodiments of the invention are specified in the dependent claims and are explained below as the general inventive concept in detail.

The invention is based on the idea of covering a long product made of a Cu material in the manner of a hot-dip coating method known in the field of coating flat steel products with a Zn coating.

In the process according to the invention, in contrast to the continuous hot-dip galvanizing processes customary in the field of steel processing, the surface cleaning and activation is not carried out by an annealing treatment, but exclusively by the use of chemical agents. This avoids the problems that occur when a long Cu product goes through a conventional hot dip galvanizing process.

• a) Bereitstellen des Cu-Langprodukts;
• b) ausschließlich durch chemischen Angriff erfolgendes Reinigen und Aktivieren der Oberfläche des Cu-Langprodukts;
• c) Trocknen des gereinigten Cu-Langprodukts und Erwärmen des Cu-Langprodukts auf eine Badeintrittstemperatur;
• d) Schmelztauchbeschichten des Cu-Langprodukts mit einem auf Zn basierenden metallischen Schutzüberzug in einem Zn-haltigen Schmelzenbad, in das das Cu-Langprodukt mit der Badeintrittstemperatur eintritt.
• e) Falls zur Einstellung einer bestimmten Oberflächenbeschaffenheit oder einer bestimmten Ausprägung der aufgebrachten Zn-Schicht gewünscht oder erforderlich, kann nach dem Schmelztauchbeschichten optional zusätzlich eine thermische, chemische oder mechanische Nachbehandlung des mit dem Zn-Überzug versehenen Cu-Langprodukts durchgeführt werden.

A method according to the invention for coating long Cu products produced from a Cu material with a metallic protective layer thus comprises, in accordance with the invention, the following steps performed in a continuous pass:

• a) providing the Cu long product;
• b) cleaning and activating the surface of the Cu long product exclusively by chemical attack;
• c) drying the purified Cu long product and heating the Cu long product to a bath inlet temperature;
• d) hot-dip coating the Cu long product with a Zn-based metallic protective coating in a Zn-containing melt bath into which the Cu long product enters at the bath inlet temperature.
• e) If it is desired or necessary to set a certain surface finish or a certain expression of the applied Zn layer, thermal, chemical or mechanical post-treatment of the Cu long product provided with the Zn coating may optionally additionally be carried out after the hot dip coating.

The long Cu product provided in step a) may in principle be any kind of semi-finished or semi-finished products made of a Cu material, which are suitable because of their dimensions, in particular their much greater length compared to their width, to go through the individual stations of a method according to the invention in a continuous pass. Accordingly, the method according to the invention is particularly suitable for coating long Cu products which are unwound from coils and then pass through the respective coating system in such a way that in each case one section of the relevant long products is still in one station of the method, while another section already contains the section goes through the next step.

If the Cu long products processed according to the invention are present as strip material, the coating method according to the invention proves to be particularly economical. This is especially true when the Cu strip material is narrow bands. The coating of narrow copper strips has the advantage that it can be carried out particularly industrially on a large scale and the narrow strips are coated with coating metal even after their passage through the melt bath, even in the region of their edges. Accordingly, the coating applied according to the invention gives, in the case where the Cu long products processed according to the invention are in the form of Cu narrow bands, an optimum protection that completely encompasses the respective long product.

The procedure according to the invention for the coating of long Cu products can be carried out much more cost-effectively in comparison with a piece galvanizing or an electrolytic coating. In addition, Zn as a coating base is comparatively favorable with respect to Ni or Cr and also offers cathodic corrosion protection. The risk of hydrogen disease does not occur in the procedure according to the invention, since the inventive method manages completely without an annealing phase under a reducing atmosphere. As a result, it is consequently possible with the method according to the invention to produce a high quality Cu long product coated with a corrosion protection layer at minimized costs and high productivity.

The long Cu products processed according to the invention can be prepared from the Cu materials usually used for the production of such products. In addition to pure Cu, these include low-alloyed copper alloys or oxygen-containing copper alloys (E-Cu alloys), P-deoxidized oxygen-free copper alloys (SE-Cu, SW-Cu, SF-Cu alloys), non-deoxidized oxygen-free Cu alloys (OF-Cu alloys), including high-alloyed Cu alloys, such as Cu-Zn or Cu-Ni materials. In general, the Cu materials in question may have the following alloying elements in the amounts indicated below in each case (all content data in% by weight):
The Cu material of the inventively processed long products Cu contains in each case at least 50% Cu, wherein at Cu in the technical sense of pure Cu long products of the Cu content is up to 99.95% or more.

Zn up to 45%, Co up to 2%, Zr up to 0.5%, P up to 0.3%, Cd up to 1%, Mg in amounts of up to 5% and traces of W, Ta, Nb, V, Be and C may be present in the Cu material according to the invention processed long Cu products individually or in combination to increase the strength.

Likewise, up to 14% Al, up to 5% Fe, up to 10% Mn, up to 45% Ni, up to 2% Si, up to 8% Sn, in the Cu material of the inventively processed long Cu products carry up to 2% Cr and up to 5% Ag, either individually or in combination to give a high strength. At the same time, the corrosion resistance of the Cu material is improved by the single or combined presence of these elements.

Likewise, in order to improve the corrosion resistance, up to 0.05% As may be added in the Cu material of the long Cu products processed according to the invention.

By individual or combined Pb contents of up to 3.5% S contents of up to 0.1% and Te contents of up to 0.7%, the long products of the invention processed according to the invention can have improved machinability.

Oxygen may be present in the Cu material of the inventively processed long Cu products in levels of up to 0.04%, if not deoxidized copper is processed.

Of particular importance is the process step b) "cleaning and surface activation" of the inventive method. In this step, the surface of the Cu long product is cleaned and activated in such a way that in the subsequently passed coating bath a reactive wetting can take place through the Zn melt forming the coating bath.

Optimally, the Cu long product to be coated in step b) only passes through a flux bath. This surface treatment, also known as "fluxing" in the technical language, on the one hand causes the required cleaning and at the same time activates the Cu long product surface and on the other hand prevents reverse passivation of the activated surface until immersion in the coating bath. As a flux, also called "flux medium", in practice, an aqueous solution can be used which contains chloride, zinc, potassium and sodium and ammonium ions. Optionally, ions of the elements "Mg, Al, Fe, Mn, Mo, Ni, P, Si, Sr and Li" may also be present in the flux bath, so that the content of Mg ions is not more than 1.0 g / l and the content of the ions of the elements "Al, Fe, Mn, Mo, Ni, P, Si, Sr and Li" is not more than 10 mg / l.

Specifically, 210-250 g / l, in particular 230-250 g / l, chloride ions, 140-160 g / l zinc ions, 5-12 g / l, in particular 8 .mu.m, 210-250 g / l for the practical embodiment of the method according to the invention in the flux -12 g / l, ammonium ions and 30-40 g / l potassium ions to achieve the desired cleaning and activation effect.

At selected within these limits amounts of chloride, zinc and ammonium ions produced during the drying carried out after drying a ZnCl ₂ / NH ₄ Cl-salt mixture on the Cu surface. This forms by thermal cleavage during drying HCl, which ensures both activation against the Cu surface and against the upper slag of the coating. By inventively proposed dimensioning of the proportion of chloride and zinc ions is also avoided that already form in the liquid flux medium Chlorhydroxozinksäuren that would unnecessarily increase the Cu dissolution in Fluxmediumkessel.

The addition of potassium ions to the flux in the amounts provided by the invention stabilizes the flux against attack by or reaction with the Al of the coating bath. This reduces the development of smoke when immersing the Cu long product in the coating bath, which in turn has a positive effect on environmental and employee protection.

Optionally, in addition, the flux bath may contain, for example, 0.5-1.5 g / L of sodium ions, 0.5-1.5 g / L of calcium ions and up to 1 g / L of magnesium ions singly or in combination. Ca, Na and Mg, added together or alone, additionally enhance the effect of K and further reduce the surface tension of the flux. This improves the wetting of the surface of the Cu long product by the flux medium.

On the one hand to ensure optimum effectiveness of the flux and on the other hand to save energy, the temperature of the flux bath to 40-100 ° C, in particular 40-70 ° C, can be adjusted. The immersion time within which the Cu long product to be coated passes through the flux bath is typically 10-120 s in practice. A particularly good coating result is achieved when the pH of the flux is in the range of 4-4.5 and the flux has a density of 1.25-1.45 g / cm ³ .

In principle, the aim is to limit the purification and activation treatment in step b) to fluxing, since in this way media which are difficult to process and are contaminated with Cu are avoided. However, in the case where the surface of the Cu long product to be hot-dip coated in the manner of the present invention is heavily soiled, it may assist in cleaning and Activation may be required, the treatment in Flußmittelbad optionally an in-line heating stage upstream. In the course of such a pickling carried out prior to the fluxing, the long Cu product is passed through a heating medium, the immersion time also typically being 10-120 s. The mordant should be based on an acid (eg hydrochloric or sulfuric acid), which is tempered to 30-100 ° C, in particular 30-70 ° C, in order to achieve optimum surface cleaning with effective energy use. Excess acid is rinsed off after pickling and prior to fluxing through an aqueous medium over a period of 10-30 s, whereby the rinsing medium 30-100 ° C, especially 30-70 ° C, warm to achieve an optimum rinsing effect ,

In the course of step c), the previously cleaned and surface-activated long Cu product is not only dried, but also brought to the inlet temperature, with which it enters the subsequently passed melt bath. The minimum temperature should be so high that the flux medium entrained on the Cu surface from the flux bath is sufficiently dried to prevent wetting disturbances during the coating in the melt bath. At the same time, however, the drying temperature should not be too high to avoid burning off of the flux medium in the dryer, since premature burning off of the flux medium in the dryer leads to a lack of wetting of the Cu long product in the melt bath. As a particularly suitable temperature range for drying, it has therefore been found that the Cu long product is heated to a temperature of 100-230 ° C. The bath inlet temperature should be held during drying for at least 10 seconds to adequately heat the Cu substrate.

In hot dipping refinement, which is carried out as step d), the Cu long product heated to the bath inlet temperature is immersed in a molten Zn bath. The residence time in the coating bath is optimally 1-120 s in order to allow a reactive wetting, but at the same time to prevent excessive alloying of the coating and furthermore to keep the Cu dissolution in the coating bath as low as possible. To increase the process stability, a residence time in the coating bath of 1-60 s has proven to be ideal. For the same reasons, the coating bath should be heated to 430-530 ° C.

In addition to Zn and process- and production-related unavoidable impurities (in% by weight), the Zn-melt bath may contain 0.1-5.0% Al and up to 0.5% Fe. In addition, trace amounts of Mg, Si, Mn, Pb and rare earths may be present in the melt bath. If too little Al is present in the coating bath, no Al ₂ O ₃ "skin" forms on the coating bath, which promotes Zn slag formation. If, on the other hand, too much Al is present in the coating bath, Al-containing upper slag can increasingly form, which likewise worsens the coating result. Furthermore, too much Al in the coating bath increases the surface tension of the coating bath too much. For the coating of long Cu products of the type in question here, Al contents of the melt bath of up to 0.25% by weight have proven to be particularly suitable under these aspects.

The thickness of the Zn coating layer present on the Cu long product on exit from the melt bath is adjusted in a manner known per se to support weights of 50-600 g / m ² per belt side by means of stripping devices which have been proven in the prior art. 500 g / m ² per band side have been found to be particularly suitable.

As a result of the inventive procedure described above in its various variants, a long product obtained in accordance with the invention has a Cu core layer consisting of a Cu material and a Zn coating layer covering the core layer, which consists of Zn mixed crystal (n phase), in addition to Zn (in% by weight) up to 3.0% Cu, up to 1.0% Al and up to 1.0% Fe, wherein between the Zn coating layer and the Cu core layer, a Cu-Zn -Phase layer is present. The Al content of the coating layer comes from the proportion of Al, which is alloyed for procedural reasons the Zn coating bath used. The Cu content results from the fact that a part of the material of the Cu core layer is unavoidably dissolved in the coating bath during the immersion time. An Fe content of the coating may result from hot dip finishing of the Cu long product in a coating bath in which also flat steel products are hot dip coated. The existing between Cu substrate and Zn coating alloy layer of intermetallic Cu-Zn phases is at least partially opaque and is typically formed as a layer system. Al, Fe and impurities are only present in traces within this alloy layer. The presence of the alloy layer ensures good adhesion between the Cu core layer and the Zn coating, which ensures that the Zn coating adheres firmly to the Cu substrate even during a transformation of the long product.

The invention will be explained in more detail by means of exemplary embodiments. Show it:

1 a system for hot dip coating with the required for carrying out the method according to the invention and optionally additionally provided workstations;

2 the basic structure of a present on a surface of a Cu long product Zn coating;

3 a cross-sectional view of a long product with applied in accordance with the invention on a Cu core layer Zn coating;

4 a cross-sectional view of another long product with applied in accordance with the invention on a Cu core layer Zn coating.

The attachment 1 for hot dip coating of a copper long product P provided as a rolled strip and a coil C wound strip comprises a unwinding station in a line-sequential arrangement in the conveying direction F in-line 2 , a flux station 3 , a drying station 4 , a hot-dip station 5 and a coiler station 6 ,

Optionally, in the conveying direction F in front of the flux station 3 a pickling station 7 and one in the conveying direction F to the pickling station 7 but also in front of the Flux station 3 arranged rinsing station 8th be provided. Equally optional can be after the hot dipping station 5 a post-treatment station 9 connect.

In the unwinding station 2 the copper long product P to be coated is unwound from the respective coil C and, if the degree of soiling requires it, first passes through the pickling station 7 and the rinsing station 8th before entering the flux station 3 arrives. On the other hand, if the contamination of the Cu long product is within the normal range, the pickling station becomes 7 and the rinsing station 8th omitted or completely missing.

In the coating plant 1 For example, 17 trials have been made with rolled-up long products P, which have been produced from different Cu materials W1, W2, W3, W4, W5. The particular composition of the Cu materials W1-W5 is given in Table 1.

Provided that the respectively processed long Cu products P in the pickling station 7 pickled and in the rinsing station 8th For this purpose, a conventional hydrochloric acid based pickling bath heated to a temperature TB and passed through within a stimulus duration tB and demineralized water for flushing has been used, which has been heated to a temperature TS, the flushing being completed in each case in a flushing duration ts has been.

In the flux station 3 For example, the Cu long products P have passed through a flux bath, the four different flux-bath compositions F1-F4 listed in Table 2 having been investigated. The flux bath which has in each case passed through within a duration tF has in each case a temperature TF, a pH value F and a density rF.

In the drying station 4 the Cu long products have been dried and brought to the respective bath inlet temperature TE.

Subsequently, the Cu long products are in the hot dipping station 5 go through a melt bath maintained at a temperature TBad.

At the exit from the hot dip dipping station 5 is in the obtained long products LP, the thickness of the Zn coating Z on the originally in the plant 1 fed Cu long product formed Cu core layer K has been set in a conventional manner by means of a stripping device not shown here.

Table 3 summarizes the respectively set operating parameters for 17 tests.

For each of the 17 tests, the respective Cu material W1-W5, which consisted of the respectively processed Cu long product P, was in the Flux station 3 Fluxing bath F1-F4, the duration tF, in which the long Cu product has passed through the respective flux bath F1-F4, and the respective flux bath temperature TF, the respective pH value pH and the respective density rF of the respective flux bath F1 -F4 indicated.

Furthermore, in Table 3 the respective bath inlet temperature TE, in the column "bath" the composition of the respective melt bath and the temperature TBad of the respective melt bath are indicated.

Provided that the respectively processed long Cu products P in the pickling station 7 pickled and in the rinsing station 8th In addition, the respective temperature TB of the pickling agent, the pickling time tB, the temperature TS of the rinsing agent and the rinsing time tS are given in Table 3.

As in 2 schematically illustrates, in a coated according to the invention long product LP on the upper side of the Cu core layer K, a Zn coating Z is present, which formed on the Cu core layer K Cu-Zn alloy layer Cu-Zn and a Zn mixed crystal layer lying thereon ( η-phase) ZnM.

In the 3 reproduced cross-section representation has been obtained from the result of experiment 2 (only Flux treatment, no previous pickling and rinsing).

In the 4 reproduced cross-section representation, however, shows the result of the experiment 17, in which the examined Cu long product P has been pickled and rinsed before the fluxing.

A comparison of 3 and 4 shows that both process variants lead to approximately identical coatings. These also each have the covering layer ZnM of Zn mixed crystals (η phase) and an alloy layer Cu-Zn formed between the Cu core layer K and the covering layer ZnM.

For the obtained in the experiment 2 and in 3 shown Zn coating revealed a chemical analysis (EDX) that 1.5 wt .-% Cu, 0.2 wt .-% Al and 0.5 wt .-% Fe are dissolved in the Zn solid solution.

For the one obtained in experiment 17, in 4 As shown in the Zn coating, the chemical analysis (EDX) gave dissolved fractions of 1.7% by weight of Cu, 0.2% by weight of Al and 0.2% by weight of Fe.

In both embodiments, the Zn coating is connected to the Cu core layer K via the Cu-Zn alloy layer Cu-Zn. In both cases, this alloy layer is present as a layer system composed of a Cu-lean alloy layer Cu-Zn-1 and a Cu-rich alloy layer Cu-Zn-2. By means of X-ray diffractometric structural analysis (XRD), the upper alloy layer Cu-Zn-1 adjoining the outer layer ZnM could be deposited as CuZn ₆ (ε phase) and the second alloy layer Cu disposed between the first layer Cu-Zn-1 and the Cu core layer K. Zn-2 can be identified as Cu ₅ Zn ₈ (γ-phase).

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DD 155437 A1 [0007]
• DD 207934 A1 [0007]
• DE 102008020576 A1 [0009]
• DE 102009006190 A1 [0009]

Claims (17)

Process for coating a Cu long product produced from a Cu material with a metallic protective layer, comprising the following steps carried out in continuous flow: a) providing the Cu long product; b) cleaning and activating the surface of the Cu long product exclusively by chemical attack; c) drying the purified Cu long product and heating the Cu long product to a bath inlet temperature; d) hot-dip coating the Cu long product with a Zn-based metallic protective coating in a Zn-containing melt bath into which the Cu long product enters at the bath inlet temperature; e) optionally carried out thermal, chemical or mechanical aftertreatment of the Zn-coated hot-dip coated Cu long product. A method according to claim 1, characterized in that the Cu material in addition to production inevitable impurities (in wt .-%) Cu: at least 50% Zn: up to 45%; Al: up to 14%; As: up to 0.05%; Co: up to 2%; Fe: up to 5%; Mn: up to 10%; Ni: up to 45%; Pb: up to 3.5%; Si: up to 2%; Sn: up to 8%; Cr: up to 2%; Zr: up to 0.5%; P: up to 0.3%; S: up to 0.1%; Cd: up to 1%; O: up to 0.04%; Mg: up to 5%; Te: up to 0.7% Ag: up to 5% W, Ta, Nb, V, Be, C: in total up to 0.1%. Method according to one of the preceding claims, characterized in that the Cu long product in step b) passes through a flux bath. A method according to claim 3, characterized in that the flux bath is an aqueous solution is used, in addition to process and manufacturing-related impurities chloride, zinc, potassium, sodium and ammonium ions and optionally additionally ions of the elements "Mg, Al, Contains Fe, Mn, Mo, Ni, P, Si, Sr and Li "with the proviso that the content of Mg ions is not more than 1.0 g / l and the content of the ions of the elements" Al, Fe, Mn, Mo, Ni, P, Si, Sr and Li "are each not more than 10 mg / l. Method according to one of claims 3 or 4, characterized in that the temperature of the flux bath is 40-100 ° C. Method according to one of claims 3 to 5, characterized in that the pH of the flux bath is 4-4.5. Method according to one of claims 3 to 6, characterized in that the density of the flux bath is 1.25-1.45 g / cm ³ . A method according to claim 3 to 7, characterized in that the Cu long product in step b) is pickled before passing through the flux and rinsed after the pickling. A method according to claim 8, characterized in that the temperature of the media used for pickling and rinsing is in each case in the range of 30-100 ° C. Method according to one of the preceding claims, characterized in that the Cu long product is through-heated in the course of the drying carried out in step c) to a bath inlet temperature of 100-230 ° C. Method according to one of the preceding claims, characterized in that the residence time over which the long Cu product dwells in each case in the Zn melt bath is 1-120 s. Method according to one of the preceding claims, characterized in that the temperature of the melt bath is 430-530 ° C. Method according to one of the preceding claims, characterized in that the Zn melt bath in addition to Zn and process- and production-related unavoidable impurities (in wt .-%) 0.1-5.0% Al and up to 0.5% Fe. A method according to claim 12, characterized in that the Al content of the melt bath is at most 0.25 wt .-%. Method according to one of the preceding claims, characterized in that the long product is a Cu band. A method according to claim 15, characterized in that the width of the Cu-band is at most 600 mm. A long product having a Cu core layer made of a Cu material, having a Zn coating layer covering the core layer, and composed of Zn mixed crystal containing not only Zn (in wt%) but also 3.0% Cu, up to 1 , 0% Al and up to 1.0% Fe, and having a Cu-Zn phase layer present between the Zn coating layer and the Cu core layer.

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