Composition for phosphatizing of ferrous surfaces and method making use thereof

Abstract

The present invention relates to an acidic aqueous composition, which is free or essentially free of both fluoride anions and nickel cations, and which comprises at least constituents a1) to a5), which are different from one of another, namely phosphate anions as a1), nitrate anions as a2), zinc cations as a3), copper cations as a4), and magnesium cations as a5), a concentrate to produce said composition by dilution with water, a use of the composition for at least partial phosphatizing ferrous surfaces of substrates, a method of phosphatizing at least one ferrous surface of at least one substrate, the method comprising at least step 1), namely contacting the at least one ferrous surface at least in portion with the inventive aqueous acidic composition for phosphatizing the at least one surface, a substrate having at least one phosphatized surface and being obtainable by said method of phosphatizing, and a method of cold forming said substrate having at least one ferrous surface, the method comprises a step of subjecting said substrate having at least one phosphatized surface to a cold forming process.

Description

[0001] Composition for phosphatizing of ferrous surfaces and method making use thereof

[0002] The present invention relates to an acidic aqueous composition, which is free or essentially free of both fluoride anions and nickel cations, and which can be used as a phosphatizing composition in particular for substrates with ferrous surfaces, and to a method of phosphatizing such surfaces of substrates, the method comprising at least a step of contacting the at least one ferrous surface at least in portion with the inventive aqueous acidic composition.

[0003] Background of the invention

[0004] The use of phosphate coatings on metallic surfaces is known in the prior art. Such coatings serve as protection against corrosion of the metallic surfaces and, moreover, also as adhesion promoters for subsequent coating layers. Such phosphate coatings are, e.g., used in the automotive industry, but also in other industries as well. For example, phosphate coatings are often applied as first protection layers onto substrates such as ferrous substrates, which are subsequently subjected to a cold forming process in order to transform them into articles having a desired shape. In order to minimize the degree of deformation during this process, a lubricant such as a soap or oil or polymer composition is often further applied on top of the phosphate coatings.

[0005] In particular in the automotive industry, phosphate coatings are often applied by means of a nickel containing phosphatizing composition in order to ensure a sufficient electrical conductivity of for subsequent electrodeposition coatings to be applied on top. However, the use of nickel ions is no longer desirable because of their high toxicity and environmental toxicity and should therefore be avoided or at least reduced in their content as much as possible, e.g., in order to avoid any contaminations of the formed sludges during the phosphatizing methods. In addition, the known methods making use of compositions containing nickel ions, often require comparably long treatment times of, e.g., > 7 minutes, and comparably high temperatures of the baths made of the compositions of, e.g., > 60 °C, both being economically and ecologically disadvantageous. Further, often unwanted incrustations on heating pipes are observed. The use of nickel-free or low-nickel phosphatizing compositions is known in the prior art as well, for example, from WO 2004 / 099468 A1 and EP 0 613 964 A1 .

[0006] EP 0613964 A1 relates to a process comprising a step of applying to a ferrous material an aqueous acid phosphating solution, wherein said aqueous acid phosphating solution is free of nitrogen compounds including nitrate ions, inter alia contains zinc ions, magnesium ions, phosphate ions, fluoroborate ions, and chlorate ions, wherein a weight ratio of Zn:Mg:BF4 is from 1 :0.15:0.15 to 1 :1 : 1. The compositions of EP 0 613 964 A1 , hence, necessarily comprise fluoride ions at least in the form of fluoroborate. EP 0 613 964 A1 aims at facilitating the cold working of ferrous materials by a process, which does not give rise to waste water problems and results in a formation of firmly adhering coatings in a thickness, which is sufficient for cold-working operations. A disadvantage of the process according to EP 0 613 964 A1 , however, can be seen in that the amount of sludge formed during the process is comparably high, which is undesired, and that the sludge formed is comparably hard, which is disadvantageous with respect to the necessity of its subsequent disposal and the means for said disposal. In addition, the process of EP 0 613 964 A1 necessarily make use of fluoride ions, which is disadvantageous / undesirable in particular from an ecological point of view.

[0007] WO 2004 / 099468 A1 relates to a method for coating surfaces of metal objects with a composition containing an aqueous, acidic phosphate, said composition inter alia containing phosphate ions, zinc ions, optionally magnesium ions, and optionally calcium ions, wherein, however, at least 0.1 g / L of calcium or / and magnesium ions are present, optionally a complex fluoride MeF4 or / and MeFe (with Me = B, Si, Ti, Hf or / and Zr), and optionally fluoride ions, wherein, however, the total amount of complex fluoride and fluoride ions is at least 0.1 g / L, and to a composition as such. The compositions of WO 2004 / 099468 A1 , hence, necessarily comprise fluoride ions as such and / or in the form of complex fluorides. WO 2004 / 099468 A1 aims at providing a process for phosphating surfaces of metallic objects, which is suitable for forming phosphate layers for cold shaping, in which the content of sludge formed during the phosphating can be reduced noticeably as far as possible, without sacrificing profitability and industrial applicability. A disadvantage of the process according to WO 2004 / 099468 A1 can be seen in that although the amount of sludge formation may be reduced, the resulting sludge is, however, comparably hard, in particular when calcium ions are present in the compositions, which is disadvantageous with respect to the necessity of its subsequent disposal and the means for said disposal. In addition, the process of WO 2004 / 099468 A1 necessarily make use of fluoride ions, which is disadvantageous / undesirable in particular from an ecological point of view.

[0008] Thus, there is a need to be able to provide an efficient method of phosphatizing of ferrous substrates, which does not lead to the disadvantages observed, when using conventional phosphatizing compositions known in the prior art, in particular phosphatizing compositions containing nickel cations and / lor fluorides. In particular, there is a need to provide such a method, which allows an efficient method of phosphatizing of ferrous substrates to take place at comparably low temperatures with a sludge formation reduced to an extent as low as possible and with said sludge being as soft as possible.

[0009] Problem

[0010] It has been therefore an objective underlying the present invention to provide an efficient method of phosphatizing of ferrous substrates, which does not lead to the disadvantages observed, when using conventional phosphatizing compositions known in the prior art, in particular phosphatizing compositions containing nickel cations and / lor fluorides. In particular, it has been an objective to provide such a method, which allows an efficient method of phosphatizing of ferrous substrates to take place at comparably low temperatures with a sludge formation reduced to an extent as low as possible and with said sludge being as soft as possible.

[0011] Solution

[0012] This objective has been solved by the subject-matter of the claims of the present application as well as by the preferred embodiments thereof disclosed in this specification, i.e. , by the subject matter described herein.

[0013] A first subject-matter of the present invention is an acidic aqueous composition, which is free or essentially free of both fluoride anions and nickel cations, and which comprises at least constituents a1) to a5), which are different from one of another, namely phosphate anions as constituent a1 ), nitrate anions as constituent a2), zinc cations as constituent a3), preferably in an amount in a range of from 5 to 60 g / L, calculated as metal, and copper cations as constituent a4), wherein the composition further comprises magnesium cations as constituent a5).

[0014] A further subject-matter of the present invention is a concentrate to produce the inventive composition by dilution with water.

[0015] A further subject-matter of the present invention is a use of the inventive composition for at least partial phosphatizing ferrous surfaces of substrates.

[0016] A further subject-matter of the present invention is a method of phosphatizing at least one ferrous surface of at least one substrate, the method comprising at least step 1 ) and optionally also at least one of steps 2) and 3), namely

[0017] 1 ) contacting the at least one ferrous surface of the at least one substrate at least in portion with the inventive aqueous acidic composition for phosphatizing the at least one surface,

[0018] 2) optionally rinsing the phosphatized surface obtained after step 1 ) with water, and

[0019] 3) optionally drying the phosphatized surface obtained after step 1 ) or optional step 2).

[0020] A further subject-matter of the present invention is a substrate having at least one phosphatized surface, the substrate being obtainable by the inventive method of phosphatizing, wherein the phosphatized surface preferably is a surface bearing a phosphate layer having a coating weight in a range of from 3 to 15 g / m3, more preferably of from 4 to 12 g / m2, even more preferably of from 5 to 10 g / m3.

[0021] A further subject-matter of the present invention is a method of cold forming a substrate having at least one ferrous surface, characterized in that the method comprises a step of subjecting an inventive substrate having at least one phosphatized surface or an inventive substrate having at least one phosphatized surface obtainable from the inventive method of phosphatizing to a cold forming process, preferably by drawing, wherein prior to said cold forming process said substrate optionally has been subjected to a further step, wherein at least one lubricant has been applied at least in portion onto its phosphatized surface.

[0022] It has been in particular found that the inventive acidic aqueous composition can be efficiently used as a phosphatizing composition for phosphatizing ferrous surfaces of substrates. It has been found that by using the inventive acidic aqueous composition as a phosphatizing composition a sufficient pickling attack on the ferrous surfaces is achieved, without the need of using any fluoride anions as additional constituents therein, which is both ecologically and economically advantageous.

[0023] It has been surprisingly found that in particular the presence of magnesium cations in the composition allows to use phosphatizing baths obtainable from said composition of a comparably low temperature only, in particular of as low as 55 or 50 °C, during the phosphatizing step, which is advantageous both from an ecological and economic point of view. Further, less incrustation of the heating pipes of phosphatizing baths obtainable from the inventive compositions was observed, when using only the aforementioned comparably low temperature. It has been further surprisingly found that in particular the presence of magnesium cations in the composition enables applying comparably short contact times of the surfaces of the substrates to be phosphatized with the phosphatizing bath obtainable from said composition, in particular as short as 3 to 5 minutes only, which is advantageous both from an ecological and economic point of view.

[0024] Moreover, it has been in particular surprisingly found that in particular the presence of magnesium cations in the composition leads to an only comparably low sludge formation during phosphatizing, in particular compared to prior art phosphatizing processes: it has been found that the sludge volume can be reduced by at least 20 and up to 50 volume-%, compared to conventional phosphatizing processes. In addition, it has been further surprisingly found that the reduced amount of sludge, which is formed, is comparably soft and, hence, not hard, in particular compared to prior art phosphatizing processes. This is advantageous both from an ecological and economic point of view, since subsequent sludge disposal processes are facilitated in this manner. The softer the sludge, the lower is its volume, and the easier is the disposal of the sludge. In addition, it is easier to remove softer sludge from the heating pipes of phosphatizing baths obtainable from the inventive compositions than harder sludge, since in case of soft sludge this can be done, e.g., simply by compressed water spraying. When the sludge is hard, however, a higher force is necessary, and cleaning often is only possible by employing acids.

[0025] Further, it has been surprisingly found that no or at least significantly reduced incrustation of the heating pipes of phosphatizing baths obtainable from the inventive compositions was observed, in particular compared to phosphatizing processes of the prior art. As outlined hereinbefore, in case minor amounts of incrustations are observed, these can be removed by means of compressed water only, since the sludge incrustations present on the pipes have been formed from soft sludge only, and it is not necessary to use higher forces.

[0026] In addition, it has been found that the presence of magnesium cations in the composition allows to use phosphatizing baths obtainable from said composition having stabilized S-values (acid values). Hence, there is no need to reduce these values after bath makeup by addition of suitable constituents such as zinc carbonate as it is often necessary in prior art phosphatizing processes.

[0027] Detailed description of the invention

[0028] The term “comprising” in the sense of the present invention, in connection for example with the aqueous acidic composition, preferably has the meaning of “consisting of”. With regard, e.g., to said composition it is possible - in addition to all mandatory constituents present therein, namely water and constituents a1 ) to a5) - for one or more of the further optional constituents identified hereinafter to be also included therein. All constituents may in each case be present in their preferred embodiments as identified below.

[0029] The proportions and amounts in wt.-% (% by weight) of any of the constituents given hereinafter, which are present in each of the aqueous acidic composition add up to 100 wt.-%, based in each case on the total weight of the aqueous acidic composition.

[0030] Aqueous acidic composition

[0031] A first subject-matter of the present invention is an acidic aqueous composition, which is free or essentially free of both fluoride anions and nickel cations, and which comprises at least constituents a1 ) to a5), which are different from one of another, namely phosphate anions as constituent a1 ), nitrate anions as constituent a2), zinc cations as constituent a3), and copper cations as constituent a4) wherein the composition further comprises magnesium cations as constituent a5). The composition is suitable for use as a phosphatizing (zinc phosphatizing) composition, in particular for ferrous substrates. The term “phosphatizing” and “phosphating” are used interchangeably herein.,

[0032] The aqueous composition is acidic, i.e. , has a pH value lower than, preferably lower than 6.5. Preferably, the composition has a pH value in a range of from 0.5 to 6.5, more preferably of from 0.8 to 6.0, still more preferably of from 1 .0 to 5.5 or 5.0, even more preferably of from 1 .2 to 4.5 or 4.0, still more preferably of from 1 .5 to 3.5 or 3.0, most preferably of from 1.7 to 3.0 or 2.8. Preferably, the pH value is measured at the operational temperature of a phosphatizing bath having been prepared from the composition, more preferably at a temperature in a range of from 40 to 70 °C, even more preferably of from 45 to 60 °C, yet more preferably of from 50 to 55 °C °C. The pH value can be adjusted by using sodium and / or potassium hydroxide and / or carbonate for alkaline adjustment, and can be in particular adjusted in case (further) acidic adjustment is needed by at least one inorganic acid such as phosphoric acid.

[0033] The term “aqueous” with respect to the aqueous acidic composition) in the sense of the present invention preferably means that the composition is a composition containing at least 50 wt.-%, preferably at least 60 wt.-%, more preferably at least 70 wt.-% in particular at least 80 wt.-%, most preferably at least 90 wt.-% of water, based on its total content of organic and inorganic solvents including water. Thus, the aqueous composition may contain at least one organic solvent besides water - however, in an amount lower than the amount of water present. Preferably, no organic solvent is present therein or at least no organic solvent has been added on purpose.

[0034] Preferably, the aqueous acidic composition contains at least 50 wt.-%, preferably at least 60 wt.-%, more preferably at least 70 wt.-% in particular at least 80 wt.-%, most preferably at least 90 wt.-% of water, in each case based on its total weight.

[0035] Preferably, the aqueous acidic composition has a temperature in a range of from 40 to 70 °C, preferably of from 45 to 60 °C, more preferably of from 50 to 55 °C. The aqueous acidic composition may be transformed into a bath containing it (phosphatizing bath). Hence, such bath is obtainable from said composition. The acidic aqueous composition is preferably used as a dip coat bath.

[0036] The acidic aqueous composition is free or essentially free of both fluoride anions and nickel cations. “Essentially free” in this context means that at least on purpose no fluoride anions and / or nickel cations are added, but it may not be ruled out that any of these may be present as impurities. The term “fluoride anions” in this context also includes complex fluorides such as tetrafluoroborates.

[0037] Preferably, the amount of fluoride anions present in the aqueous acidic composition does not exceed 2 g / L, more preferably does not exceed 1 g / L, even more preferably does not exceed 0.5 g / L, still more preferably does not exceed 0.2 g / L, yet more preferably does not exceed 0.1 g / L, most preferably is lower than 0.1 g / L, in each case calculated as F. Preferably, the amount of nickel cations present in the aqueous acidic composition does not exceed 2 g / L, more preferably does not exceed 1 g / L, even more preferably does not exceed 0.5 g / L, still more preferably does not exceed 0.2 g / L, yet more preferably does not exceed 0.1 g / L, even more preferably is lower than 0.1 g / L, most preferably is at most 0.05 g / L, e.g., is in a range of from 0 or 0.001 to 0.05 g / L, in each case calculated as metal. Preferably, the acidic aqueous composition is free or essentially free of boron, calculated as HBF4. “Essentially free” in this context means that at least on purpose no boron is added, but it may not be ruled out that it may be present as impurities. Preferably, the amount of boron present in the aqueous acidic composition does not exceed 2 g / L, more preferably does not exceed 1 g / L, even more preferably does not exceed 0.5 g / L, still more preferably does not exceed 0.2 g / L, yet more preferably does not exceed 0.1 g / L, most preferably is lower than 0.1 g / L, in each case calculated as HBF4.

[0038] The content of nickel cations as well as of all further cations and anions mentioned hereinbefore and hereinafter can be monitored and determined by the means of ICP- OES (optical emission spectroscopy with inductively coupled plasma). Said method is described in the ‘methods’ section. The content of fluoride anions, if present at all, is, however, determined by means of a fluoride electrode.

[0039] Preferably, the acidic aqueous composition is free or essentially free of calcium cations. “Essentially free” in this context means that at least on purpose no calcium cations are added, but it may not be ruled out that any of these may be present as impurities. Preferably, the amount of calcium cations present in the aqueous acidic composition does not exceed 1 g / L, calculated as metal. The presence of such cations may have a negative influence on the softness of the sludge and may in particular lead to a sludge, which is not soft.

[0040] Preferably, the acidic aqueous composition is free or essentially free of chrome cations. “Essentially free” in this context means that at least on purpose no chrome cations are added, but it may not be ruled out that any of such residues may be present as impurities. Preferably, the amount of chrome cations present in the aqueous acidic composition does not exceed 100 mg / L, calculated as metal.

[0041] Constituent a1) - phosphate anions

[0042] Preferably, the composition comprises phosphate anions as constituent a1 ) in an amount in a range of from 5 to 60 g / L, more preferably of from 6 to 50 g / L, even more preferably of from 7 to 48 g / L, still more preferably of from 8 to 40 g / L, yet more preferably of from 9 to 35 g / L, even more preferably of from 10 to 30 g / L, still more preferably of from 12 to 25 g / L, yet more preferably of from 14 to 20 g / L, in each case calculated as P2O5.

[0043] Phosphate anions can be, e.g., incorporated by using suitable phosphate anion sources such as phosphoric acid.

[0044] Phosphate anions can be present in a condensed form such as in case of pyrophosphates (diphosphates) and / or in a non-condensed form. In other words, mixtures of both forms can also be present. The term “phosphates” includes polyphosphates as well such as tripolyphosphates. In each case, their partially and completely deprotonated forms are preferably also included.

[0045] Constituent a2) - nitrate anions

[0046] Preferably, the composition comprises nitrate anions as constituent a2) in an amount in a range of from 10 to 100 g / L, more preferably of from 15 to 90 g / L, still more preferably of from 20 to 80 g / L, even more preferably of from 25 to 70 g / L, still more preferably of from 30 to 60 g / L, most preferably of from 35 to 50 g / L, in each case calculated as NO3.

[0047] Preferably, the amount of nitrate anions present in the composition as constituent a2) in g / L, calculated as NO3, exceeds the amount of phosphate anions present therein as constituent a1 ) in g / L, calculated as P2O5, more preferably in that the relative weight ratio of nitrate anions, calculated as NO3, and phosphate anions, calculated as P2O5, to each other is in a range of from 15:1 to 1 .1 : 1 , more preferably of from 10: 1 to 1 .2: 1 , even more preferably of from 7.5 to 1.3:1 , still more preferably of from 5.0 to 1.5:1 , yet more preferably of from 4:1 to 2:1 .

[0048] Nitrate anions can be, e.g., incorporated by using suitable nitrate anion sources such as nitric acid. Constituent a3) - zinc cations

[0049] Preferably, the composition comprises zinc cations as constituent a3) in an amount in a range of from 2.5 to 60 g / L, more preferably of from 5 to 50 g / L, even more preferably of from 7 to 40 g / L, still more preferably of from 10 to 30 g / L, yet more preferably of from 12 to 25 g / L, in each case calculated as metal. If the amount of zinc cations is too low, the phosphate layer formation can be disturbed because too much pickling takes place and / or due to a risk that iron phosphate or iron zinc (ZnFe) phosphate is deposited. If the amount of zinc cations is too high, solubility problems may occur, which may also have a negative effect on the deposition.

[0050] Preferably, the amount of zinc cations present in the composition as constituent a3) in g / L, calculated as metal, exceeds the amount of both magnesium cations present therein as constituent a5) and copper cations present therein as constituent a4) in g / L, calculated as metals.

[0051] Preferably, the relative weight ratio of zinc cations and magnesium cations (constituent a5)) to each other, in each case calculated as metal, is in a range of from 80:1 to 1.1 :1 , more preferably of from 70:1 to 1.2:1 , still more preferably of from 60:1 to 1.5: 1 , even more preferably of from 50:1 to 2:1 , yet more preferably of from 40:1 to 3:1 , still more preferably of from 35:1 to 4:1 , yet more preferably of from 30:1 to 5:1 , even more preferably of from 25:1 to 6:1 , most preferably of from 22:1 to 8:1.

[0052] Zinc cations can be, e.g., incorporated by using suitable zinc cation sources such as zinc carbonate, zinc oxide, zinc nitrate and / or zinc phosphate.

[0053] Constituent a4) - copper cations

[0054] Preferably, the composition comprises copper cations as constituent a4) in an amount in a range of from 0.5 to 100 ppm, more preferably of from 0.7 to 80 ppm, still more preferably of from 0.8 to 60 ppm, even more preferably of from 0.9 to 40 ppm, still preferably of from 1 to 30 ppm, even more preferably of from 3 to 25 ppm, yet more preferably of from 5 to 20 ppm, most preferably of from 7 to 18 ppm, in each case calculated as metal. It has been found that the presence of copper ions is advantageous since a reduced pickling attack during the phosphatizing has been observed when these ions are present. In addition, it has been found that the appearance of the resulting coat is improved.

[0055] Copper cations can be, e.g., incorporated by using suitable copper cation sources such as copper nitrate and / or copper hydroxycarbonate.

[0056] Constituent a5) - magnesium cations

[0057] Preferably, the composition comprises magnesium cations as constituent a5) in an amount in a range of from 0.1 to 6.0 g / L, more preferably of from 0.2 to 5.0 g / L, even more preferably of from 0.3 to 4.5 g / L, still more preferably of from 0.4 to 4.0 g / L, yet more preferably of from 0.5 to 3.5 g / L, even more preferably of from 0.6 to 3.0 g / L, still more preferably of from 0.7 to 2.5 g / L, yet more preferably of from 0.8 to 2.0 g / L, most preferably of from 1 .0 to 2.0 g / L, in each case calculated as metal.

[0058] Preferably, the amount of magnesium cations present in the composition as constituent a5) in g / L, calculated as metal, exceeds the amount of copper cations present therein as constituent a4) in g / L, calculated as metal.

[0059] Magnesium cations can be, e.g., incorporated by using suitable magnesium cation sources such as magnesium oxide.

[0060] Optional constituents

[0061] The composition may comprise one or more further cations and / or anions. Preferably, iron(ll) cations are present therein, more preferably in an amount in a range of from 0.1 to 8 g / L, even more preferably of from 0.2 to 6 g / L, still more preferably of from 0.3 to 4 g / L. Optionally, the composition may comprise manganese cations, e.g., in an amount of from 0 to 2 g / L. Preferably, the composition does not or essentially does not comprise any trivalent cations such as Al(lll) cations: the amount of such cations is preferably less than 100 mg / L. Concentrate

[0062] A further subject-matter of the present invention is a concentrate to produce the inventive aqueous acid composition by dilution with water. Optionally, the pH value of the resulting composition may be adjusted as well by use of at least one pH adjusting additive. The concentrate thus represents a master batch for producing the inventive aqueous acid composition.

[0063] All preferred embodiments described above herein in connection with the inventive aqueous acidic composition are also preferred embodiments of the inventive concentrate.

[0064] The concentrate used to produce the aqueous acidic composition typically contains the constituents of the aqueous acidic composition to be produced in the desired proportions, but at a higher concentration. Such concentrate is diluted with water to the desired concentrations of the constituents as disclosed hereinbefore to form the aqueous acidic composition. If necessary, the pH value of the aqueous acidic composition may be adjusted after dilution as well as outlined hereinbefore. Of course, it is also possible to further add any of the optional constituents of the aqueous acidic composition to the water used for dilution or to add any of the optional constituents after diluting the concentrate with water. It is, however, preferred that the concentrate already contains all necessary constituents.

[0065] Preferably, the concentrate is diluted with water in a weight ratio of 1 :5000 to 1 :10, more preferred 1 : 1000 to 1 : 10, most preferred in a ratio of 1 :300 to 1 : 10 and even more preferred 1 :150 to 1 :50 to produce the aqueous acidic inventive composition.

[0066] Use of the aqueous acidic composition

[0067] The inventive aqueous acidic composition can be used for at least partial phosphatizing ferrous surfaces of substrates. Hence, such a use is a further subject- matter of the present invention. All preferred embodiments described above herein in connection with the inventive aqueous acidic composition and the inventive concentrate are also preferred embodiments of the inventive use.

[0068] The substrate used has at least one ferrous surface. According at least one region of said surface has to be ferrous. Preferably, the substrate as such is metallic, i.e., is made of at least one metal and / or alloy thereof. The surface may consist of different regions comprising different metals and / or alloys thereof. Preferably, all regions, and more preferably, all surfaces of the substrates are ferrous. Even more preferably, the substrate as such is ferrous.

[0069] Preferably, the at least one ferrous surface of the substrate metal is selected from the group consisting of steel including cold rolled steel and hot rolled steel, as well as steel alloys, preferably steel alloys containing not more than 5 wt.-% of alloy ingredients such as Mn, Cr, B etc.

[0070] As substrates, e.g., strips, sheets, slugs, wires, wire coils, more complicated shaped parts, sleeves, profiles such as hollow or solid profiles, tubes, tube parts, discs, rods, bars or cylinders can be used.

[0071] Method of phosphatizing

[0072] A further subject-matter of the present invention is a method of phosphatizing at least one ferrous surface of at least one substrate, the method comprising at least step 1 ) and optionally also at least one of steps 2) and 3). The method may comprise one or more further additional optional steps including steps, which are performed prior to step 1 ). Since the surface to be phosphatized is ferrous, the method of phosphatizing can be regarded as an “ironside process”.

[0073] All preferred embodiments described above herein in connection with the inventive aqueous acidic composition, the inventive concentrate and the inventive use are also preferred embodiments of the inventive method. The same applies, of course, to the embodiments of the substrate as such as outlined hereinbefore in connection with the inventive use. Optional steps performed prior to step 1)

[0074] The at least one ferrous surface of the at least one substrate may be cleaned by means of an acidic, alkaline or pH-neutral cleaning composition and / or etched before contacting step 1 ). Prior to step 1 ) of the inventive one or more of the following optional steps can be performed, preferably in this order:

[0075] Step A): cleaning the surface of the substrate, preferably by making use of an alkaline or neutral, preferably alkaline, aqueous cleaning composition, and optionally subsequently rinsing the surface of the substrate, and / or

[0076] Step B): subjecting the surface of the substrate to acidic pickling, i.e. , etching, and optionally subsequently rinsing the surface of the substrate, and / or

[0077] Step C): activating the surface of the substrate by using an aqueous activating composition being different from the inventive aqueous acidic composition used in step 1 ).

[0078] Alternatively, optional steps A) and B) may be performed in one step. Preferably, both steps A) and B) are performed. Rinsing included in step A) is preferably performed with deionized water or tap water. Preferably, the acidic pickling according to step B) is performed by making use of hydrochloric acid, hydrofluoric acid, sulfuric acid, nitric acid, oxalic acid and / or phosphoric acid, more preferably hydrochloric acid. The activating composition used in optional step C) is used to deposit a plurality of ultrafine phosphate particles as seed crystals on the surface of the substrate used. These crystals help in the subsequent contacting step 1 ) to form a particular crystalline phosphate layer with the highest possible number of densely arranged fine phosphate crystals or a substantially closed phosphate layer on the surface. Thus, the activating composition used in optional step C) preferably contains a phosphate such as titanium phosphate and / or zinc phosphate, preferably zinc phosphate. Preferably, step C) is performed. An example of an aqueous activating composition that can be used in step C) and which is commercially available, is the product Gardolene® V 6526 from Chemetall GmbH.

[0079] Step 1) In step 1 ), the at least one ferrous surface of the at least one substrate is contacted at least in portion with the inventive aqueous acidic composition. A phosphate layer, i.e. , zinc phosphate layer is formed onto the portion of the surface contacted with the composition in step 1 ).

[0080] The treatment procedure according to step 1 ), i.e., the “contacting”, can, for example, include a spraying and a dip coating procedure. The composition can also be applied by flooding the surface or by roll coating or even manually by wiping or brushing. However, dipping is preferred. In this case, the substrate used is preferably dipped into a bath containing / obtainable from the inventive aqueous acidic composition.

[0081] Preferably, contacting step 1 ) is performed by dipping the at least one ferrous surface of the at least one substrate at least in portion into a bath containing / obtainable from the inventive aqueous acidic composition. The bath preferably has a temperature in a range of from 45 to 80 °C, more preferably of from 45 to 75 °C, even more preferably of from 50 to 70 °C, most preferably of from 50 to 65 °C or to 60 °C or to 55 °C. The treatment time, i.e., the period of time the surface is contacted with the aqueous acidic composition preferably does not exceed 10 minutes, more preferably is <8 minutes, even more preferably is <6 minutes, still more preferably does not exceed 5 minutes, yet more preferably is <4 minutes, most preferably does not exceeding 3 minutes.

[0082] Optional step 2)

[0083] Optionally, rinsing the phosphatized surface obtained after step 1 ) can be performed with water. Preferably, such rinsing is performed.

[0084] Optional step 3)

[0085] Optionally, drying the phosphatized surface obtained after step 1 ) or after optional step 2) can be performed. Preferably, such drying is performed.

[0086] The drying step 3) may be preferably performed, e.g., at a temperature in the range of 15 °C to 80 °C, more preferably at a temperature in the range of 18°C to 60 °C, in particular at a temperature in the range of 20 or 23 °C to 50 °C. Preferably, however, drying is simply performed at room temperature (15 to 23 °C) by air blowing. Substrate

[0087] A further subject-matter of the present invention is a substrate having at least one phosphatized surface, the substrate being obtainable by the method of phosphatizing described hereinbefore, wherein the phosphatized surface preferably is a surface bearing a phosphate layer having a coating weight in a range of from 3 to 15 g / m3, more preferably of from 4 to 12 g / m2, even more preferably of from 5 to 10 g / m3. The coating weight is determined by the method disclosed in the ‘methods’ section.

[0088] All preferred embodiments described above herein in connection with the inventive aqueous acidic composition, the inventive concentrate, the inventive use and the inventive method of phosphatizing are also preferred embodiments of the inventive substrate. The same applies, of course, to the embodiments of the substrate as such as outlined hereinbefore in connection with the inventive use.

[0089] Method of cold forming

[0090] A further subject-matter of the present invention is a method of cold forming a substrate having at least one ferrous surface, wherein method comprises a step of subjecting the inventive substrate having at least one phosphatized surface as defined hereinbefore or a substrate having at least one phosphatized surface obtainable from the inventive method described hereinbefore to a cold forming process, preferably by drawing, wherein prior to said cold forming process said substrate optionally has been subjected to a further step, wherein at least one lubricant has been applied at least in portion onto its phosphatized surface. Any kind of lubricant can be used for this purpose such as soaps, oils and / or polymer compositions.

[0091] All preferred embodiments described above herein in connection with the inventive aqueous acidic composition, the inventive concentrate, the inventive use, the inventive method of phosphatizing, and the inventive substrate are also preferred embodiments of the inventive method of cold forming. All possible cold forming processes known in the prior art can be carried out, in particular rolling such as thread rolling or beating, e.g. for nut or bolt blanks, drawing, in particular sliding drawing (tensile compression forming), e.g. of welded or seamless tubes, hollow sections, solid sections, wires or rods, e.g. during wire drawing or tube drawing, or deep-drawing, e.g. of strips or sheet metal, pressing such as cold extrusion (pressure forming), e.g. of hollow or solid bodies, stretch forming (forming to gauge block / final size) and / or cold upsetting, e.g. from wire sections to fasteners such as nuts.

[0092] The most common shaped bodies to be formed from the inventive substrates are strips, sheets, slugs, wires, wire coils, more complicated shaped parts, sleeves, profiles such as hollow or solid profiles, tubes, discs, discs, rods, bars or cylinders.

[0093] Preferably, the cold-formed substrate obtained after the cold forming process still bears at least part of the phosphate layer obtained after having performed step 1 ) and optionally step 3) of the inventive method of phosphatizing.

[0094] METHODS

[0095] 1. Acid (S), Free Acid (FA) and Fischer total acid (TAF)

[0096] The acid value (S-value) is the ratio FA:TAF and results from dividing the value of the free acid (FA) by the value of the total acid according to Fischer (TAF).

[0097] To determine the amount of free acid (FA), 10 ml of the phosphating composition is pipetted into a suitable vessel, for example a 300 ml Erlenmeyer flask. Then, using a pH meter and an electrode, it is titrated with 0.1 M NaOH to a pH of 3.8 to 4.2, in particular 4.0. The consumed amount of 0.1 M NaOH in ml per 10 ml of the phosphating composition gives the value of the free acid (FA) in points. To determine the amount of total acid according to Fischer (TAF) a dilute phosphating composition (10 ml of the phosphating composition are pipetted into a suitable vessel, for example into a 300 ml Erlenmeyer flask and subsequently, 150 ml of deionized water are added) is titrated to pH 8.7 after addition of potassium oxalate solution using a pH meter and an electrode with 0.1 M NaOH. The consumption of 0.1 M NaOH in ml per 10 ml of the diluted phosphating composition gives the total Fischer acid (TAF) in points.

[0098] 2. Phosphate points (PP)

[0099] PP is the sum of FA and TAF. It is, however, determined by the following method: 5 ml of the phosphating solution is pipetted into an Erlenmeyer flask and diluted with 50 ml of distilled water. Then, 25 ml of a 30 wt.-% potassium oxalate solution as well as 10 - 15 drops of phenolphthalein are added. Next, the resulting solution is titrated with. Titrate with a 0.1 M sodium hydroxide solution to a color change from colorless to red (at pH 8.7). The consumption of ml of the sodium hydroxide solution multiplied by factor 2 indicates the phosphate points.

[0100] 3. Coating weight of phosphate layer

[0101] The coating weight is measured by gravimetry. A phosphatized test panel is weighted before and after removal of the coating and the weight loss is measured. The coating is removed by dissolving it into a sodium hydroxide solution further containing complex ions. For this, the panel is immersed in said solution for 5 minutes at 70 °C, then rinsed with water and dried by air blowing. The panel is weighted again afterwards, the weight loss measured and the coating weight determined accordingly taking into account the known surface of the panel.

[0102] 4. ICP-OES The amount of certain elements in a sample under analysis is determined using inductively coupled plasma atomic emission spectrometry (ICP-OES) according to DIN EN ISO 11885 (date: September 1 , 2009).

[0103] EXAMPLES

[0104] The following examples further illustrate the invention but are not to be construed as limiting its scope.

[0105] 1. Phosphatizing compositions

[0106] 1.1 An aqueous acidic phosphatizing composition IPC1 (inventive example) being free of fluoride and being nickel-free has been prepared from deionized water, phosphoric acid, nitric acid, and suitable sources of zinc, copper and magnesium cations. The constituents of said starting composition are displayed in Table 1. IPC1 has a pH value in a range of from 1 .8 to 2.6. The S value was determined to be 0.33. The phosphate points (PP) were determined to be 30.

[0107] Table 1 - IPC1

[0108] 1.2 An aqueous acidic phosphatizing composition CPC1 (comparative example) has been prepared in a similar manner as IPC1. However, as no magnesium cations source has been used for its preparation, no magnesium cations were present therein.

[0109] 2. Phosphatizing method

[0110] As metal workpieces the following ferrous substrates were used: a) Cold rolled steel (CRS); substrate S1 (panels), b) Hot rolled steel (HRS); substrate S2 (panels), and c) Steel alloys with less than 5 wt.-% of alloy ingredients; substrate S3 (wires and tubes) Each of the workpieces was cleaned by dipping into a cleaning bath prepared from a 50 g / L aqueous cleaning solution of Gardoclean® S5165 available from Chemetall GmbH and 5 g / L of GBA H7375 also available from Chemetall GmbH at 65 °C for 10 minutes and then rinsed with cold tap water for 1 minute. Afterwards, the surface- purified workpieces were then pickled by using a 15 wt.-% HCI solution for 1 to 20 minutes, depending on the substrate used, at room temperature and subsequently rinsed by cold tap water for 1 minute. The workpieces were then activated by Gardolene® V6526 available from Chemetall GmbH at room temperature for 1 minute by dipping the workpieces into a corresponding bath. Then, the workpieces were dipped into a bath containing either IPC1 or CPC1 at temperatures in a range of from 50 to 60°C for 3 to 10 minutes, and subsequently rinsed by cold tap water (twice). Finally, the workpieces obtained were dried with pressed air at room temperature.

[0111] 3. Investigation of the phosphatized substrates, the working equipment and the sludge formed during the phosphatizing method

[0112] 3.1 The coating weights of the phosphatizing layers present on the surfaces of each of the phosphatized substrates were determined and were found to be in a range of from 6 to 8 g / m3.

[0113] 3.2 No or only minor amounts of incrustation on the surface of the heating pipes of each phosphatizing bath were found.

[0114] 3.3 Only a low amount of sludge formation of only soft sludge (less volume compared to harder sludge) was found in all cases.

[0115] 3.4 It was found that the use of composition IPC1 (Mg cations containing) allowed working at lower bath temperatures of only 50 to 55 °C (energy saving) and shorter treatment times of only 3 to 5 minutes (also energy saving) compared to use of CPC1 (not containing Mg cations). A coating weight in a range of from 6 to 8 g / m3as outlined above in 3.1 was determined in case of using IPC1 already at bath temperatures of 50 to 55 °C after 3 to 5 minutes, whereas in case of using CPC1 said coating weight was only achieved after 7 to 10 minutes treatment time at 57 to 60 °C. In addition, it was found that the presence of Mg cations in IPC1 allows stabilization of the S-value such that no additional constituents for lowering this value after bath makeup have to be added.

Claims

CLAIMS1 . An acidic aqueous composition, which is free or essentially free of both fluoride anions and nickel cations, and which comprises at least constituents a1 ) to a5), which are different from one of another, namely phosphate anions as constituent a1 ), nitrate anions as constituent a2), zinc cations as constituent a3) in an amount in a range of from 5 to 60 g / L, calculated as metal, and copper cations as constituent a4), wherein the composition further comprises magnesium cations as constituent a5).

2. The composition according claim 1 , characterized in that it comprises magnesium cations as constituent a5) in an amount in a range of from 0.1 to 6.0 g / L, preferably of from 0.2 to 5.0 g / L, more preferably of from 0.3 to 4.5 g / L, still more preferably of from 0.4 to 4.0 g / L, yet more preferably of from 0.5 to 3.5 g / L, even more preferably of from 0.6 to 3.0 g / L, still more preferably of from 0.7 to 2.5 g / L, yet more preferably of from 0.8 to 2.0 g / L, most preferably of from 1 .0 to 2.0 g / L, in each case calculated as metal.

3. The composition according to claim 1 or 2, characterized in that it comprises copper cations as constituent a4) in an amount in a range of from 0.5 to 100 ppm, preferably of from 0.7 to 80 ppm, more preferably of from 0.8 to 60 ppm, even more preferably of from 0.9 to 40 ppm, still preferably of from 1 to 30 ppm, even more preferably of from 3 to 25 ppm, yet more preferably of from 5 to 20 ppm, most preferably of from 7 to 18 ppm, in each case calculated as metal.

4. The composition according to one or more of the preceding claims, characterized in that it comprises zinc cations as constituent a3) in an amount in a range of from 5 to 50 g / L, preferably of from 7 to 40 g / L, more preferably offrom 10 to 30 g / L, yet more preferably of from 12 to 25 g / L, in each case calculated as metal.

5. The composition according to one or more of the preceding claims, characterized in that the amount of magnesium cations present therein as constituent a5) in g / L, calculated as metal, exceeds the amount of copper cations present therein as constituent a4) in g / L, calculated as metal, and / or in that the amount of zinc cations present therein as constituent a3) in g / L, calculated as metal, exceeds the amount of both magnesium cations present therein as constituent a5) and copper cations present therein as constituent a4) in g / L, calculated as metals.

6. The composition according to one or more of the preceding claims, characterized in that the relative weight ratio of zinc cations and magnesium cations to each other, in each case calculated as metal, is in a range of from 80:1 to 1.1 :1 , preferably of from 70:1 to 1.2:1 , more preferably of from 60:1 to 1.5:1 , even more preferably of from 50:1 to 2:1 , yet more preferably of from 40:1 to 3:1 , still more preferably of from 35:1 to 4:1 , yet more preferably of from 30:1 to 5:1 , even more preferably of from 25:1 to 6:1 , most preferably of from 22:1 to 8:1.

7. The composition according to one or more of the preceding claims, characterized in that it comprises phosphate anions as constituent a1 ) in an amount in a range of from 5 to 60 g / L, preferably of from 6 to 50 g / L, more preferably of from 7 to 48 g / L, still more preferably of from 8 to 40 g / L, yet more preferably of from 9 to 35 g / L, even more preferably of from 10 to 30 g / L, still more preferably of from 12 to 25 g / L, yet more preferably of from 14 to 20 g / L, in each case calculated as P2O5, and / or nitrate anions as constituent a2) in an amount in a range of from 10 to 100 g / L, preferably of from 15 to 90 g / L, more preferably of from 20 to 80 g / L, even morepreferably of from 25 to 70 g / L, still more preferably of from 30 to 60 g / L, most preferably of from 35 to 50 g / L, in each case calculated as NO3.

8. The composition according to one or more of the preceding claims, characterized in that the amount of nitrate anions present therein as constituent a2) in g / L, calculated as NO3, exceeds the amount of phosphate anions present therein as constituent a1 ) in g / L, calculated as P2O5, preferably in that the relative weight ratio of nitrate anions, calculated as NO3, and phosphate anions, calculated as P2O5, to each other is in a range of from 15:1 to 1.1 :1 , preferably of from 10:1 to 1.2:1 , more preferably of from 7.5 to 1.3:1 , still more preferably of from 5.0 to 1.5:1 , yet more preferably of from 4:1 to 2:1.

9. The composition according to one or more of the preceding claims, characterized in that it has a pH value in a range of from 0.5 to 6.5, preferably of from 0.8 to 6.0, more preferably of from 1 .0 to 5.5 or 5.0, even more preferably of from 1.2 to 4.5 or 4.0, still more preferably of from 1.5 to 3.5 or 3.0, most preferably of from 1 .7 to 3.0 or 2.8.

10. A concentrate to produce the composition according to one or more of the preceding claims by dilution with water.

11. A use of the composition according to one or more of claims 1 to 9 for at least partial phosphatizing ferrous surfaces of substrates.

12. A method of phosphatizing at least one ferrous surface of at least one substrate, the method comprising at least step 1 ) and optionally also at least one of steps 2) and 3), namely1 ) contacting the at least one ferrous surface of the at least one substrate at least in portion with the aqueous acidic composition as defined in one or more of claims 1 to 9 for phosphatizing the at least one surface,2) optionally rinsing the phosphatized surface obtained after step 1 ) with water, and3) optionally drying the phosphatized surface obtained after step 1 ) or optional step 2).

13. The method according to claim 12, characterized in that contacting step 1 ) is performed by dipping the at least one ferrous surface of the at least one substrate at least in portion into a bath obtainable from the aqueous acidic composition as defined in one or more of claims 1 to 9, preferably for a period of not exceeding 10 minutes, more preferably <8 minutes, even more preferably <6 minutes, still more preferably not exceeding 5 minutes, yet more preferably <4 minutes, most preferably not exceeding 3 minutes, wherein the bath preferably has a temperature in a range of from 45 to 80 °C, preferably of from 45 to 75 °C, more preferably of from 50 to 70 °C, most preferably of from 50 to 65 °C or to 60 °C or to 55 °C.

14. A substrate having at least one phosphatized surface, the substrate being obtainable by the method according to claim 12 or 13, wherein the phosphatized surface preferably is a surface bearing a phosphate layer having a coating weight in a range of from 3 to 15 g / m3, more preferably of from 4 to 12 g / m2, even more preferably of from 5 to 10 g / m3.

15. A method of cold forming a substrate having at least one ferrous surface, characterized in that the method comprises a step of subjecting the substrate having at least one phosphatized surface according to claim 14 or a substrate having at least one phosphatized surface obtainable from the method according to claim 12 or 13 to a cold forming process, preferably by drawing, wherein prior to said cold forming process said substrate optionally has been subjected to a further step, wherein at least one lubricant has been applied at least in portion onto its phosphatized surface.

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