EP3280831A1

EP3280831A1 - Method for nickel-free phosphating metal surfaces

Info

Publication number: EP3280831A1
Application number: EP16718613.9A
Authority: EP
Inventors: Olaf Dahlenburg; Frank Hollmann; Lisa SCHMEIER
Original assignee: Chemetall GmbH
Current assignee: Chemetall GmbH
Priority date: 2015-04-07
Filing date: 2016-04-07
Publication date: 2018-02-14
Anticipated expiration: 2036-04-07
Also published as: RU2018138295A; EP3280830B1; CN107735511A; JP2018512511A; WO2016162423A1; RU2017138446A; RU2748349C2; CN109312466A; EP3280830A1; US20180112314A1; BR112017021307B1; US20180334748A9; RU2017138445A; BR112018070593A2; RU2017138446A3; EP3280831B1; MX2017012917A; DE102016205814A1; US20180112313A1; JP2018510971A

Abstract

The invention relates to a method for, essentially, nickel-free phosphating a metal surface, in which a metal surface, optionally after cleaning and/or activating, is initially treated with an acidic aqueous phosphating composition which contains zinc ions, manganese ions and phosphate ions, is optionally rinsed and/or dried, and then is treated with an aqueous post-rinsing composition which comprises at least one type of metal ions selected from the group consisting of ions from molybdenum, copper, silver, gold, palladium, tin, antimony, titanium, zirconium and hafnium and/or at least one polymer selected from the group consisting of polymer classes of polyamines, polyethylenamines, polyanilines, polyimines, polyethylenimines, polythiophenes and polypryroles and to the mixtures and copolymerisates thereof. The invention also relates to the phosphating composition as well as to the post-rinsing composition which is essentially nickel-free.

Description

Process for nickel-free phosphating of metallic surfaces

The present invention relates to a process for essentially nickel-free phosphating of a metallic surface, a corresponding phosphating composition and a correspondingly phosphate-coated metallic surface.

From the prior art phosphate coatings on metallic surfaces are known. Such coatings serve to protect the corrosion of the metallic surfaces and also as adhesion promoters for subsequent paint layers. Such phosphate coatings are mainly used in the automotive industry and the general industry.

In addition to powder coatings and wet paints, the subsequent coating layers are above all cathodically deposited electrodeposition paints (KTL). Since during the deposition of KTL a current must flow between the metallic surface and the treatment bath, it is important to set a defined electrical conductivity of the phosphate coating in order to ensure efficient and homogeneous deposition.

Therefore, phosphate coatings are usually applied by means of a nickel-containing phosphating solution. The elementary or as alloying constituent, e.g. Zn / Ni, deposited nickel ensures a suitable conductivity of the coating in the subsequent electrodeposition coating.

However, nickel ions are no longer desirable as part of treatment solutions because of their high toxicity and environmental toxicity, and should therefore be avoided or at least reduced in content as much as possible. The use of nickel-free or low-nickel Phosphatierlosungen is known in principle. However, this is limited to certain substrates such as steel.

In the case of the aforementioned nickel-poor or nickel-free systems, moreover, given a given KTL deposition conditions, a non-optimal condition may result Substrate surface poor corrosion and paint adhesion values result.

The object of the present invention was therefore to provide a process with which metallic surfaces can be phosphated essentially nickel-free, with respect to their electrochemical properties, comparable or nearly comparable to the metallic surfaces which have been treated with nickel-containing phosphating solutions, and in particular the abovementioned Disadvantages of the prior art can be avoided.

This object is achieved by a method according to claim 1, a phosphating composition according to claim 21 and a phosphate-coated metallic surface according to claim 23.

In the method according to the invention for substantially nickel-free phosphating of a metallic surface, a metallic surface, optionally after purification and / or activation, is first treated with an acidic aqueous phosphating composition comprising zinc ions, manganese ions and phosphate ions, optionally rinsed and / or dried, and thereafter treated with an aqueous post-rinse composition comprising at least one type of metal ion selected from the group consisting of the ions of molybdenum, copper, silver, gold, palladium, tin, antimony, titanium, zirconium and hafnium and / or at least one polymer selected from the group consisting of the classes of polymers comprising polyamines, polyethyleneamines, polyanilines, polyimines, polyethylenimines, polythiophenes and polypryrenes and mixtures and copolymers thereof, wherein both the phosphating composition and the post-rinse composition are substantially nickel free. definitions:

On the one hand, an uncoated metallic surface, on the other hand, but also an already conversion coated metallic surface can be treated by the method according to the invention. If, in the following, a "metallic surface" is mentioned, therefore, an already conversion-coated metallic surface should always be included as well. For the purposes of the present invention, the term "aqueous composition" refers to a composition which comprises at least some, preferably predominantly water, as the solvent, and may comprise, in addition to dissolved constituents, also dispersed, ie emulsified and / or suspended constituents.

For the purposes of the present invention, "phosphate ions" are also to be understood as meaning hydrogenphosphate, dihydrogenphosphate and phosphoric acid, and pyrophosphoric acid and polyphosphoric acid as well as all their partially and completely deprotonated forms are to be included in the term "metal ion" in the context of the present invention either a metal cation or a complex cation Metal cation or a complex metal anion understood.

If a composition contains less than 0.3 g / l of nickel ions, it should be considered as "essentially nickel-free" for the purposes of the present invention.

The metallic surface is preferably steel, hot-dip galvanizing, electrolytic galvanizing, aluminum or their alloys such as Zn / Fe or Zn / Mg. The hot-dip galvanizing and the electrolytic galvanizing in each case are in particular such on steel. In particular, the metallic surface is at least partially galvanized.

The inventive method is particularly suitable for multi-metal applications.

If a metallic surface is to be coated, which is not a fresh hot-dip galvanizing, it is advantageous to clean the metallic surface before the treatment with the phosphating only in an aqueous cleaning composition, in particular to degrease. For this purpose, it is possible in particular to use an acidic, neutral, alkaline or strongly alkaline cleaning composition, but optionally also an acidic or neutral pickling composition.

An alkaline or strongly alkaline cleaning composition has proven to be particularly advantageous. The aqueous cleaning composition may optionally contain, in addition to at least one surfactant, a scaffold and / or other additives such as complexing agents. The use of an activating cleaner is also possible. After cleaning / pickling then takes place advantageously at least rinsing of the metallic surface with water, wherein the water optionally also dissolved in water additive such. As a nitrite or surfactant may be added.

Before treating the metallic surface with the phosphating composition, it is advantageous to treat the metallic surface with an activating composition. The activation composition serves to deposit a plurality of ultrafine phosphate particles as seed crystals on the metallic surface. These help in the subsequent process step, in contact with the phosphating - preferably without interim rinsing - form a particular crystalline phosphate layer with the highest possible number of densely arranged fine phosphate crystals or a substantially closed phosphate layer.

In particular, acidic or alkaline compositions based on titanium phosphate or zinc phosphate may be considered as activating compositions.

However, it can also be advantageous to add activating agents, in particular titanium phosphate or zinc phosphate, in the cleaning composition, ie to carry out purification and activation in one step.

The acidic aqueous phosphating composition includes zinc ions, manganese ions, and phosphate ions.

The phosphating composition may be obtained from a concentrate by dilution with a suitable solvent, preferably with water, by a factor of between 1 and 100, preferably between 5 and 50, and if necessary adding a pH modifying substance. The phosphating composition preferably comprises the following components in the following preferred and particularly preferred concentration ranges:

With regard to the manganese ions, however, a concentration in the range from 0.3 to 2.5 g / l has already been found to be advantageous with regard to the free fluoride, a concentration in the range from 10 to 250 mg / l.

The complex fluoride is preferably tetrafluoroborate (BF ^" ) and / or hexafluorosilicate (SiF ₆ ^{2 ~} ). Especially in the treatment of aluminum and / or galvanized material, a content of complex fluoride and single fluoride, for example sodium fluoride, in the phosphating composition advantageous.

Al ³⁺ is a bad poison in phosphating systems and can be removed from the system by complexation with fluoride, eg as cryolite. Complex fluorides are added to the bath as a "fluoride buffer", as otherwise the fluoride content quickly falls off and coating no longer takes place.Fluoride thus promotes the formation of the phosphate layer and thus indirectly also improves paint adhesion and corrosion protection.Complex fluoride also helps on galvanized material, errors In particular, in the treatment of aluminum, it is furthermore advantageous if the phosphating composition has a content of Fe (III), in which case a Fe (III) content in the range from 0.001 to 0.2 g / l, particularly preferably from 0.005 to 0.1 g / l and most preferably from 0.01 to 0.05 g / l.

In addition, the phosphating composition preferably contains at least one Accelerator selected from the group consisting of the following compounds in the following preferred and particularly preferred concentration ranges:

With regard to the nitroguanidine, however, a concentration in the range of 0.1 to 3.0 g / l has already been found to be advantageous with respect to the H2O2, a concentration in the range from 5 to 200 mg / l.

Most preferably, the at least one accelerator is H2O2. However, the phosphating composition preferably contains less than 1 g / l, more preferably less than 0.5 g / l, more preferably less than 0.1 g / l and most preferably less than 0.01 g / l of nitrate.

In particular, in the case of a galvanized surface, the nitrate in the phosphating composition causes an additional acceleration of the layer formation reaction, which leads to lower coating weights but, above all, reduces the incorporation of manganese into the crystal. However, if the manganese content of the phosphate coating is too low, this is at the expense of its alkali resistance.

Alkali resistance in turn plays a crucial role in subsequent cathodic electrodeposition. In this case, an electrolytic splitting of water occurs at the substrate surface: Hydroxide ions are formed. This causes the pH at the interface of the substrate to increase. It is true that only then can the electrocoating be agglomerated and separated. However, the increased pH can also damage the crystalline phosphate layer. The phosphating composition preferably has a temperature in the range of 30 to 55 ° C.

Furthermore, the phosphating composition can be characterized by the following preferred and particularly preferred parameter ranges:

With regard to the FS parameter, however, a value in the range of 0.2 to 2.5, with respect to the temperature such in the range of 30 to 55 ° C has already been found to be advantageous.

Here "FS" stands for free acid, "FS (verd.)" For free acid (diluted), "GSF" for total acid according to Fischer, "GS" for total acid and "S value" for acid value.

These parameters are determined as follows:

Free acid (FS):

To determine the free acid, 10 ml of the phosphating composition is pipetted into a suitable vessel, for example a 300 ml Erlenmeyer flask. If the phosphating composition contains complex fluorides, 2-3 g of potassium chloride are added to the sample. Then, using a pH meter and an electrode, it is titrated with 0.1 M NaOH to a pH of 3.6. The amount of 0.1 M NaOH consumed in ml per 10 ml of the phosphating composition gives the value of the free acid (FS) in points. Free acid (diluted) (FS (dil.)):

To determine the free acid (diluted), 10 ml of the phosphating composition are pipetted into a suitable vessel, for example into a 300 ml Erlenmeyer flask. Subsequently, 150 ml of deionized water added. Using a pH meter and an electrode, titrate with 0.1 M NaOH to a pH of 4.7. The consumed amount of 0.1 M NaOH in ml per 10 ml of the diluted phosphating composition gives the value of the free acid (diluted) (FS (dil.)) In points. About the difference to the free acid (FS) the content of complex fluoride can be determined. If this difference is multiplied by a factor of 0.36, the content of complex fluoride is SiF ₆ ^{2 ~} in g / l.

Total acid according to Fischer (GSF):

Following determination of the free acid (diluted), the dilute phosphating composition is titrated to pH 8.9 after addition of potassium oxalate solution using a pH meter and electrode with 0.1 M NaOH. The consumption of 0.1 M NaOH in ml per 10 ml of the diluted phosphating composition hereby gives the total Fischer acid (GSF) in points. If this value is multiplied by 0.71, the total content of phosphate ions is calculated as P2O ₅ (see W. Rausch: "The Phosphatization of Metals." Eugen G. Leuze-Verlag 2005, 3rd edition, pp. 332 ff) ,

Total Acid (GS):

The total acid (GS) is the sum of the divalent cations present as well as free and bound phosphoric acids (the latter being phosphates). It is determined by the consumption of 0.1 M NaOH using a pH meter and an electrode. For this purpose, 10 ml of the phosphating composition are pipetted into a suitable vessel, for example a 300 ml Erlenmeyer flask and diluted with 25 ml of deionized water. It is then titrated with 0.1 M NaOH to a pH of 9. The consumption in ml per 10 ml of the diluted phosphating composition corresponds to the total acid score (GS).

Acid value (S value):

The so-called acid value (S value) stands for the ratio FS: GSF and is obtained by dividing the value of the free acid (FS) by the value of the total acid according to Fischer (GSF).

Surprising was the further improvement of paint adhesion, especially on hot-dip galvanized surfaces, by setting an acid value in the range of 0.03 to 0.065, in particular in the range of 0.04 to 0.06.

It has surprisingly been found that especially in the case of steel or hot dip galvanizing as a metallic surface, a temperature of the phosphating of less than 45 ° C, preferably in the range between 35 and 45 ° C leads to further improved corrosion and paint adhesion values.

The phosphating composition is essentially nickel free. It preferably contains less than 0.1 g / l and more preferably less than 0.01 g / l of nickel ions. The treatment of the metallic surface with the phosphating composition is preferably carried out for 30 to 480, particularly preferably for 60 to 300 and very particularly preferably for 90 to 240 seconds, preferably by means of dipping or spraying.

By treating the metallic surface with the phosphating composition, depending on the surface being treated, the following preferred and particularly preferred zinc phosphate layer weights are obtained on the metallic surface (determined by X-ray fluorescence analysis (RFA)):

Preferably, the metallic surface is rinsed after treatment with the phosphating composition, more preferably rinsed with demineralized water or city water. Optionally, the metallic surface is dried prior to treatment with the post-rinse composition.

According to the inventive method is already with the Phosphatierzusammensetzung treated, ie phosphate-coated, metallic surface still treated with an aqueous Nachspülzusammensetzung.

The post-rinse composition can be obtained from a concentrate by dilution with a suitable solvent, preferably with water, by a factor of between 1 and 1000, preferably between 5 and 500, and if necessary adding a pH-modifying substance.

In one embodiment, the post-rinse composition contains at least one kind of metal ion selected from the group consisting of the ions of the following metals in the following preferred, most preferred and most preferred concentration ranges (all calculated as corresponding metal):

The metal ions contained in the rinsing solution separate either in the form of a salt which preferably contains the corresponding metal cation (eg molybdenum or tin) in at least two oxidation states - in particular in the form of an oxide hydroxide, a hydroxide, a spinel or a defect spinel - or elementally on the surface to be treated (eg copper, silver, gold or palladium).

In a preferred embodiment, the metal ions are molybdenum ions. These are preferred as molybdate, more preferably as Ammonium heptamolybdate and more preferably added as ammonium heptamolybdate x 7 H ₂ O the Nachspülzusammensetzung. The molybdenum ions can also be added as Nathummolybdat.

However, molybdenum ions, for example, may also be added to the post-rinse composition in the form of at least one molybdenum cation-containing salt, such as molybdenum chloride, and then oxidized to molybdate by a suitable oxidizing agent, for example by the accelerators described above. In such a case, the post-rinse composition itself contains a corresponding oxidizing agent. More preferably, the post-rinse composition contains molybdenum ions in combination with copper ions, tin ions or zirconium ions.

It particularly preferably contains molybdenum ions in combination with zirconium ions and optionally a polymer or copolymer, in particular selected from the group consisting of the polymer classes of polyamines, polyethyleneamines, polyanilines, polyimines, polyethyleneimines, polythiophenes and polypryrenes and mixtures and copolymers thereof and polyacrylic acid, wherein the content molybdenum ions and zirconium ions are each in the range of 10 to 500 mg / l (calculated as metal).

The content of molybdenum ions is preferably in the range from 20 to 225 mg / l, particularly preferably from 50 to 225 mg / l and very particularly preferably from 100 to 225 mg / l and the content of zirconium ions in the range from 50 to 300 mg / l. l, more preferably from 50 to 150 mg / l.

According to a further preferred embodiment, the metal ions are copper ions. Preferably, the rinsing solution then contains these in a concentration of 100 to 500 mg / l, more preferably from 150 to 225 mg / l.

According to a further embodiment, the rinse-off composition according to the invention comprises at least one polymer selected from the group consisting of the polymer classes of the polyamines, polyethyleneamines, polyanilines, polyimines, polyethyleneimines, polythiophenes and polypryrenes and also their mixtures and copolymers. The at least one polymer is preferably in a concentration in the range of 0.1 to 5 g / l, more preferably from 0.1 to 3 g / l, more preferably from 0.3 to 2 g / l and particularly preferably in the range from 0.5 to 1.5 g / l (calculated as pure polymer). The polymers used are preferably cationic polymers, in particular polyamines, polyethyleneamines, polyimines and / or polyethyleneimines. Particular preference is given to using a polyamine and / or polyimine, very particularly preferably a polyamine.

According to a third embodiment, the rinse-off composition according to the invention comprises at least one kind of metal ion selected from the group consisting of the ions of molybdenum, copper, silver, gold, palladium, tin, antimony, titanium, zirconium and hafnium and at least one polymer selected from the group consisting of the polymer classes of the polyamines, polyethyleneamines, polyanilines, polyimines, polyethylenimines, polythiophenes and polypryrenes and their mixtures and copolymers, in each case in the following preferred, particularly preferred and very particularly preferred concentration ranges (polymer calculated as pure polymer and metal ions calculated as the corresponding metal).

Mo 1 to 1000 mg / l 10 to 500 mg / l 20 to 225 mg / l

Cu 1 to 1000 mg / l 100 to 500 mg / l 150 to 225 mg / l

Ag 1 to 500 mg / l 5 to 300 mg / l 20 to 150 mg / l

Au 1 to 500 mg / l 10 to 300 mg / l 20 to 200 mg / l

Pd 1 to 200 mg / L 5 to 100 mg / L 15 to 60 mg / L

Sn 1 to 500 mg / l 2 to 200 mg / l 3 to 100 mg / l

Sb 1 to 500 mg / l 2 to 200 mg / l 3 to 100 mg / l

Ti 20 to 500 mg / l 50 to 300 mg / l 50 to 150 mg / l

Zr 20 to 500 mg / l 50 to 300 mg / l 50 to 150 mg / l

Hf 20 to 500 mg / l 50 to 300 mg / l 50 to 150 mg / l

Polymer 0.1 g / l to 3 g / l 0.3 g / l to 2 g / l 0.5 to 1.5 g / l According to a preferred embodiment, the at least one polymer is a cationic polymer, in particular a polyamine and / or polyimine, and the metal ions are copper ions, molybdenum ions and / or zirconium ions, in each case in the following preferred, particularly preferred and very particular preferred concentration ranges (polymer calculated as pure polymer and metal ions calculated as the corresponding metal).

The post-rinse composition comprises, in particular, when the metallic surface is aluminum or an aluminum alloy, preferably additionally 20 to 500 mg / l, more preferably 50 to 300 mg / l and particularly preferably 50 to 150 mg / l of Ti, Zr and / or Hf in complexed form (calculated as metal). These are preferably fluoro complexes. In addition, the post-rinse composition preferably comprises 10 to 500 mg / l, more preferably 15 to 100 mg / l, and most preferably 15 to 50 mg / l of free fluoride. More preferably, the post-rinse composition contains Zr in complexed form (calculated as metal) and at least one kind of metal ions selected from the group consisting of the ions of molybdenum, copper, silver, gold, palladium, tin and antimony, preferably molybdenum.

A post-rinse composition comprising Ti, Zr and / or Hf in complexed form preferably additionally contains at least one organosilane and / or at least one hydrolysis product thereof, ie an organosilanol, and / or at least one condensation product thereof, ie an organosiloxane / polyorganosiloxane, within a concentration range of 5 to 200 mg / l, more preferably from 10 to 100 mg / l, and particularly preferably from 20 to 80 mg / l (calculated as Si).

The at least one organosilane preferably has at least one amino group on. Particularly preferably it is one which can be hydrolyzed to an aminopropylsilanol and / or to 2-aminoethyl-3-amino-propyl-silanol and / or a bis (trimethoxysilylpropyl) amine.

The pH of the post-rinse composition is preferably in the acidic range, more preferably in the range of 3 to 5, particularly preferably in the range of 3.5 to 5.

Surprisingly, it has been found that lowering the pH promotes the deposition of molybdenum ions on the phosphate-coated metallic surface. In a rinsing solution containing molybdenum ions, therefore, the pH is preferably 3.5 to 4.5, and more preferably 3.5 to 4.0.

The post-rinse composition is essentially nickel free. It preferably contains less than 0.1 g / l and more preferably less than 0.01 g / l of nickel ions.

The post-rinse composition preferably has a temperature in the range of 15 to 40 ° C. The treatment of the metallic surface with the post-rinse composition is preferably carried out for 10 to 180, particularly preferably for 20 to 150 and very particularly preferably for 30 to 120 seconds, preferably by means of dipping or spraying.

The invention further relates to a phosphate-coated metallic surface, which is obtainable by the method according to the invention. By means of the method according to the invention, the electrical conductivity of the phosphate-coated metal surface can be adjusted in a targeted manner by producing defined pores in the phosphate layer. In this case, the conductivity may be either greater than, equal to, or smaller than that of a corresponding metal surface provided with a nickel-containing phosphate coating. The adjusted by the inventive method electrical conductivity of the phosphate-coated metal surface can be influenced by the variation of the concentration of a given metal ion or polymer in the rinse. On the phosphate-coated - as well as the Nachspülzusammensetzung treated - metallic surface can then cathodically deposited an electrodeposition paint and a paint system can be applied.

Optionally, the metallic surface is first rinsed after the treatment with the Nachspülzusammensetzung, preferably with deionized water, and optionally dried.

In the following, the present invention will be explained by non-limiting exemplary embodiments and comparative examples.

Comparative Example 1

A test plate of electrolytically galvanized steel (ZE) was prepared by means of a 1.3 g / l Zn, 1 g / l Mn, 13 g / l PO ₄ ^{3 "} (calculated as P ₂ O ₅ ), 3 g / l NO ₃ ^" and also 1 g / l nickel containing, 53 ° C hot Phosphatierlosung coated. No rinsing was done. Subsequently, the current density i in A / cm ^{2 was compared} with the vs. a voltage applied to silver / silver chloride (Ag / AgCl) electrode E is measured in V (see FIG. 1: ZE_Variation1 1_2: curve 3). The measurement was carried out by means of so-called linear sweep voltammetry (potential range: -1, 1 to -0.2 V _ref ; scan rate: 1 mV / s). In all examples and comparative examples, the measured current density i is dependent on the electrical conductivity of the conversion coating. The higher the measured current density i, the higher the electrical conductivity of the conversion coating. A direct measurement of the electrical conductivity in S / cm, as is possible in liquid media, can not be carried out in conversion coatings.

In the present case, therefore, the current density i measured in the case of a nickel-containing conversion coating always serves as a reference point for statements about the electrical conductivity of a given conversion coating.

The indication "1 E" in FIGS. 1 to 4 always stands for "10". For example, "1 E-4" accordingly means "1 (T".

Comparative Example 2

A test plate according to Comparative Example 1 was obtained by means of a nickel-free, 1.3 g / l Zn, 1 g / l Mn, 16 g / l PO ₄ ^{3 "} (calculated as P ₂ O ₅ ) and 2 g / l NO ₃ ^" , Coated 53 ° C warm Phosphatierlosung without rinsing and then the current density i over the voltage E according to Comparative Example 1 measured (see Fig. 1. ZE_Variation1_1: curve 1, ZE_Variation1_3: curve 2).

As can be seen from FIG. 1, the resting potential of the nickel-free system (Comparative Example 2) is shifted to the left compared to that of the nickel-containing system (Comparative Example 1). Also, the electrical conductivity is lower: The "arms" of the curve 1 and the curve 2 are respectively below the curve 3, ie towards lower current densities. Comparative Example 3

A test plate according to Comparative Example 1 was coated by means of a nickel-free phosphating solution according to Comparative Example 2. Subsequently, the thus coated test plate was treated with a rinsing solution containing about 120 mg / l ZrF ₆ ^{2 ~} (calculated as Zr) with a pH of about 4. The current density i across the voltage E was measured according to Comparative Example 1 (see FIG. 2. ZE_Variation6_1: curve 1; ZE_Variation6_2: curve 2). Comparing with Comparative Example 1 (FIG. 2: ZE_Variation1 1_2: curve 3). As can be seen from FIG. 2, the resting potential of the nickel-free system when using a ZrF ₆ ^2- containing rinsing solution (Comparative Example 3) compared to that of the nickel-containing system (FIG. Comparative Example 1) shifted to the left. The electrical conductivity is lower in the nickel-free system mentioned (see the comments on Comparative Example 2). example 1

A test plate according to Comparative Example 1 was coated by means of a nickel-free phosphating solution according to Comparative Example 2. Subsequently, the test plate coated in this way was treated with a rinsing solution containing about 220 mg / l copper ions and having a pH of about 4. The current density i across the voltage E was measured according to Comparative Example 1 (see FIG. 3. ZE_Variation2_1: curve 1; ZE_Variation2_2: curve 2). Compared again with Comparative Example 1 (FIG. 3: ZE_Variation1 1_2: curve 3).

As can be seen from FIG. 3, the resting potential of the nickel-free system when using a rinsing solution containing copper ions (Example 1) corresponds to that of the nickel-containing system (Comparative Example 1). The conductivity of this nickel-free system is slightly increased over that of the nickel-containing system.

Example 2

A test plate according to Comparative Example 1 was coated by means of a nickel-free phosphating solution according to Comparative Example 2. Subsequently, the thus coated test plate was treated with a rinsing solution, which was about 1 g / l (calculated on the pure polymer) electrically conductive polyamine (Lupamin® 9030, manufacturer BASF) contained a pH of about 4 had. The current density i across the voltage E was measured according to Comparative Example 1 (see FIG. 4. ZE_Variation3_1: curve 1; ZE_Variation3_2: curve 2). Comparison is made with Comparative Example 1 (FIG. 4: ZE_Variation1 1_2: curve 3).

As can be seen from FIG. 4, the quiescent potential of the nickel-free system when using an after-rinsing solution containing an electrically conductive polymer (Example 2) corresponds to that of the nickel-containing system (Comparative Example 1). The electrical conductivity of the nickel-free system is somewhat reduced compared to the nickel-containing system.

Comparative Example 4

A test plate of hot-dip galvanized steel (EA) was coated by means of a 1 g / l nickel-containing phosphating solution according to Comparative Example 1. Subsequently, the thus-coated test plate was treated with a rinsing solution containing about 120 mg / l ZrF ₆ ^{2 ~} (calculated as Zr) with a pH of about 4, and then the current density i in A / cm ^{2 was} compared with the voltage. a voltage applied to silver / silver chloride (Ag / AgCl) electrode E was measured in V (see FIG. 5: EA 173: curve 1). The measurement was carried out by means of so-called linear sweep voltammetry. Comparative Example 5

A test plate according to Comparative Example 4 was coated by means of a nickel-free and nitrate-free, 1, 2 g / l Zn, 1 g / l Mn and 16 g / l PO ^{3 "} (calculated as P2O ₅ ) containing 35 ° C warm phosphating without rinsing and then the current density i is measured via the voltage E according to Comparative Example 3 (see Fig. 5. EA 167: curve 3, EA 167 2: curve 2).

As can be seen from FIG. 5, the resting potential of the nickel-free system (Comparative Example 5) is shifted to the right compared to that of the nickel-containing system (Comparative Example 4). The electrical conductivity is significantly lower in the case of the nickel-containing system, which is attributable to the passivation by means of the rinsing solution containing ZrF ₆ ^{2 ~} . Example 3

A test plate according to Comparative Example 4 was coated by means of a nickel-free phosphating solution according to Comparative Example 2. Subsequently, the thus coated test plate was treated with a rinsing solution containing about 120 mg / l ZrF ₆ ^{2 ~} (calculated as Zr) and 220 mg / l molybdenum ions with a pH of about 4. The current density i over the voltage E was measured according to Comparative Example 1 (see Fig. 6. EA 178: curve 3, EA 178 2: curve 2). Comparison is made with Comparative Example 3 (FIG. 6: EA 173: curve 1).

As can be seen Fig. 6, corresponds to the rest potential of the nickel-free system in the use of a ZrF ₆ ^{2 ~} and molybdenum ion-containing rinsing solution (Example 3) that of the nickel-containing system (Comparative Example 4). By adding molybdenum ions (Example 3) to the post-rinse solution containing ZrF ₆ ^{2 ~} (Comparative Example 4), it was possible to markedly increase the conductivity at the substrate surface. Test plates according to Comparative Examples 1 to 3 (VB1 to VB3) and Examples 1 and 2 (B1 and B2) were coated after phosphating with a cathodic electrodeposition paint and a standard autobillack construction (filler, basecoat, clearcoat) and then a cross-cut test according to DIN EN ISO 2409 subjected. In each case, 3 panels were tested before and after exposure to condensation for 240 hours (DIN EN ISO 6270-2 CH). The corresponding results can be found in Table 1. A grating cut result of 0 is the best, and one of 5 the worst value. Values of 0 and 1 are comparable good values.

Table 1

Tab. 1 reveals the poor results of VB2 and in particular VB3 in each case after loading, while B1 (copper ions) and B2 (electrically conductive polyamine) give good - VB1 (nickel-containing phosphating) at least comparable results.

Comparative Example 6

A test plate of hot-dip galvanized steel (EA) was prepared by means of a 1, 1 g / l Zn, 1 g / l Mn, 13.5 g / l PO ₄ ^{3 "} (calculated as P ₂ O ₅ ), 3 g / l NO ₃ ^" And also 1 g / l nickel-containing, 53 ° C warm Phosphatierlosung nitritbeschleunigt (about 90 mg / l nitrite) coated. Subsequently, the thus coated test plate was treated with a rinsing solution containing about 120 mg / l ZrF ₆ ^{2 ~} (calculated as Zr) with a pH of about 4.

Comparative Example 7

A test panel according to Comparative Example 6 was prepared by means of a nickel-free, 1, 1 g / l Zn, 1 g / l Mn, 17 g / l PO ₄ ^{3 "} (calculated as P ₂ O ₅ ) and 0.5 g / l NO ₃ ^" containing 35 ° C warm Phosphatierlosung nitrite accelerated (about 90 mg / l nitrite) coated. Subsequently, the thus coated test plate was treated with a rinsing solution containing about 120 mg / l ZrF ₆ ^{2 ~} (calculated as Zr) and 220 mg / l molybdenum ions with a pH of about 4.

Example 4

A test plate according to Comparative Example 6 was obtained by means of a nickel- and nitrate-free, 1, 1 g / l Zn, 1 g / l Mn and 17 g / l PO ₄ ^{3 "} (calculated as P2O ₅ ), 35 ° C warm Phosphatierlösung nitrite-accelerated (about 90 mg / l nitrite) coated. Subsequently, the thus coated test plate was treated with a rinsing solution containing about 120 mg / l ZrF ₆ ^{2 ~} (calculated as Zr) and 220 mg / l molybdenum ions with a pH of about 4. Comparative Example 8

A test panel according to Comparative Example 6 was prepared by means of a nickel-free, 1, 1 g / l Zn, 1 g / l Mn, 17 g / l PO ₄ ^{3 "} (calculated as P ₂ O ₅ ) and 0.5 g / l NO ₃ ^" containing 35 ° C warm phosphating accelerated peroxide (about 80 mg / l H2O2) coated. Subsequently, the thus coated test plate was treated with a rinsing solution containing about 120 mg / l ZrF ₆ ^{2 ~} (calculated as Zr) and 220 mg / l molybdenum ions with a pH of about 4.

Example 5

A test plate according to Comparative Example 6 was peroxide-accelerated by means of a nickel-free and nitrate-free, 1.3 g / l Zn, 1 g / l Mn and 17 g / l PO ₄ ³ (calculated as P2O ₅ ) containing 35 ° C phosphating solution ( 80 mg / l H2O2), followed by the test plate coated with a rinsing solution containing about 120 mg / l ZrF ₆ ^{2 ~} (calculated as Zr) and 220 mg / l molybdenum ions with a pH of about 4 treated.

Test plates according to Comparative Examples 6 to 8 (VB6 to VB8) and Examples 4 and 5 (B4 and B5) were coated after phosphating with a cathodic electrodeposition paint and a standard autobillack construction (filler, basecoat, clearcoat) and then a cross-cut test according to DIN EN ISO 2409 subjected. In each case, 3 panels were tested before and after exposure to condensation for 240 hours (DIN EN ISO 6270-2 CH). The corresponding results can be found in Tab. 2. Table 2

Table 2 shows the poor results of VB7 (nitrite accelerated) and VB8 (peroxide accelerated) compared to VB6, while B4 (nitrite accelerated) and B5 (peroxide accelerated) give good - VB6 (nickel phosphating) comparable results.

Comparative Example 9

Example 6

A test plate according to Comparative Example 9 was peroxide-accelerated by means of a nickel-free and nitrate-free, 1 g / l Zn, 1 g / l Mn and 17 g / l PO ₄ ³ (calculated as P2O ₅ ), 35 ° C phosphating solution ( 80 mg / l H2O2), followed by the test plate coated with a rinsing solution containing about 120 mg / l ZrF ₆ ^{2 ~} (calculated as Zr) and 220 mg / l molybdenum ions with a pH of about 4 treated.

Comparative Example 10

A test plate of bare steel was prepared by means of a 1, 1 g / l Zn, 1 g / l Mn, 13.5 g / l PO ₄ ^{3 "} (calculated as P ₂ O ₅ ), 3 g / l NO ₃ ^" and 1 g / l nickel, 53 ° C hot Phosphatierlosung nitritbeschleunigt (about 90 mg / l nitrite) coated. Subsequently, the thus coated test plate was treated with a rinsing solution containing about 120 mg / l ZrF ₆ ^{2 ~} (calculated as Zr) with a pH of about 4. Example 7

A test plate according to Comparative Example 10 was peroxide-accelerated by means of a nickel-free and nitrate-free, 1 g / l Zn, 1 g / l Mn and 17 g / l PO ₄ ³ (calculated as P2O ₅ ), 35 ° C phosphating solution ( 80 mg / l H2O2), followed by the test plate coated with a rinsing solution containing about 120 mg / l ZrF ₆ ^{2 ~} (calculated as Zr) and 220 mg / l molybdenum ions with a pH of about 4 treated.

Comparative Example 11

A test plate of electrolytically galvanized steel (ZE) was prepared by means of a 1, 1 g / l Zn, 1 g / l Mn, 13.5 g / l PO ₄ ^{3 "} (calculated as P ₂ O ₅ ), 3 g / l NO ₃ ^" and also 1 g / l nickel, 53 ° C warm Phosphatierlosung nitritbeschleunigt (about 90 mg / l nitrite) coated. Subsequently, the thus coated test plate was treated with a rinsing solution containing about 120 mg / l ZrF ₆ ^{2 ~} (calculated as Zr) with a pH of about 4.

Example 8

A test plate according to Comparative Example 1 1 was peroxide-accelerated by means of a nickel- and nitrate-free, 1, 1 g / l Zn, 1 g / l Mn and 17 g / l PO ₄ ^{3 "} (calculated as P2O ₅ ) containing 35 ° C warm Phosphatierlosung 80 mg / l H2O2) and the test plate thus coated was treated with a rinsing solution containing about 120 mg / l ZrF ₆ ^{2 ~} (calculated as Zr) and 220 mg / l molybdenum ions with a pH of ca. 4 treated.

Test plates according to Comparative Examples 9 to 1 1 (VB9 to VB1 1) and Examples 6 to 8 (B6 to B8) were coated after phosphating with a cathodic electrodeposition paint and a standard autobillack construction (filler, basecoat, clearcoat) and that at VB6 to VB8 , B4 and B5 previously described cross-hatch test. The results are summarized in Tab. 3. In addition, said test plates were subjected to a VDA test (VDA 621-415), wherein the paint infiltration (U) was determined in mm and the paint peeling after rockfall (DIN EN ISO 20567-1, Verf. C) was determined. A result of 0 is the best, one of 5 is the worst value after the fall of the stone. A value up to 1, 5 is to be regarded as a good value. The results are also summarized in Tab. 3.

Table 3

Table 3 shows the good results which can be achieved with the nickel-free process according to the invention both on hot-dip galvanized steel (B6) and on bare steel (B7) and on electrolytically galvanized steel (B8). These are comparable to the nickel-containing process (compare B6 with VB9, B7 with VB10 and B8 with VB1 1).

Comparative Example 12

Example 9

A test plate according to Comparative Example 12 was by means of a nickel and nitrate-free, 1 g / l Zn, 1 g / l Mn and 17 g / l PO ₄ ^{3 "} (calculated as P2O ₅ ), 35 ° C warm phosphating peroxidized accelerated (about 80 mg / l H2O2) the so-coated test plate was treated with a rinsing solution containing about 120 mg / l ZrF ₆ ^{2 ~} (calculated as Zr) and 220 mg / l molybdenum ions with a pH of about 4.

Example 10

A test plate according to Comparative Example 12 was peroxide-accelerated by means of a nickel- and nitrate-free, 1, 2 g / l Zn, 1 g / l Mn and 13 g / l PO ^{3 "} (calculated as P2O ₅ ) containing 45 ° C phosphating (approx Subsequently, the test plate thus coated was treated with a rinsing solution containing about 120 mg / l ZrF ₆ ^{2 ~} (calculated as Zr) and 220 mg / l molybdenum ions with a pH of about 4 ,

Comparative Example 13

A test plate made of bare steel was nitrite-accelerated by means of a phosphating solution according to Comparative Example 12 (about 90 mg / l nitrite). Subsequently, the thus coated test plate was treated with a rinsing solution containing about 120 mg / l ZrF ₆ ^{2 ~} (calculated as Zr) with a pH of about 4.

Example 11

A test plate according to Comparative Example 13 was peroxide-accelerated by means of a phosphating solution according to Example 9 (about 80 mg / l H2O2) coated. Subsequently, the thus coated test plate was treated with a rinsing solution containing about 120 mg / l ZrF ₆ ^{2 ~} (calculated as Zr) and 220 mg / l molybdenum ions with a pH of about 4.

Example 12

A test plate according to Comparative Example 13 was peroxide-accelerated by means of a phosphating solution according to Example 10 (about 50 mg / l H2O2) coated. Subsequently, the thus coated test plate was treated with a rinsing solution containing about 120 mg / l ZrF ₆ ^{2 ~} (calculated as Zr) and 220 mg / l molybdenum ions with a pH of about 4. Comparative Example 14

A test plate of AA6014 S was coated with nitrite (about 90 mg / l nitrite) by means of a phosphating solution according to comparative example 12. Subsequently, the thus coated test plate was treated with a rinsing solution containing about 120 mg / l ZrF ₆ ^{2 ~} (calculated as Zr) with a pH of about 4.

Example 13

A test plate according to Comparative Example 14 was peroxide-accelerated by means of a phosphating solution according to Example 9 (about 80 mg / l H2O2) coated. Subsequently, the thus coated test plate was treated with a rinsing solution containing about 120 mg / l ZrF ₆ ^{2 ~} (calculated as Zr) and 220 mg / l molybdenum ions with a pH of about 4.

Example 14

A test plate according to Comparative Example 14 was peroxide-accelerated by means of a phosphating solution according to Example 10 (about 50 mg / l H2O2) coated. Subsequently, the thus coated test plate was treated with a rinsing solution containing about 120 mg / l ZrF ₆ ^{2 ~} (calculated as Zr) and 220 mg / l molybdenum ions with a pH of about 4.

Test plates according to Comparative Examples 12 to 14 (VB12 to VB14) and Examples 9 to 14 (B9 to B14) were coated after phosphating with a cathodic electrodeposition paint and a standard auto paint finish (filler, basecoat, clearcoat).

The test plates of Comparative Examples 12 and 13 (VB12 and VB13) and Examples 9 to 12 (B9 to B12) were subjected to the VDA test described above. The results are summarized in Tab. 4. The test plates of Comparative Example 14 (VB14) and Examples 13 and 14 (B13 and B14), however, were subjected to a 240-hour CASS test according to DIN EN ISO 9227. The results are summarized in Tab. 5. Table 4

Example 15

A hot dip galvanized steel (EA) test panel was heated to 35 ° C. using a nickel and nitrate-free, 1.1 g / l Zn, 1 g / l Mn and 17 g / l PO ₄ ³ (calculated as P2O ₅ ) 80 mg / l H2O2), the acid value of the phosphatizing solution was adjusted to 0.07, and the test plate thus coated was treated with about 120 mg / l ZrF ₆ ^{2 ~} (calculated as Zr) and 220 Mg / l rinsing solution containing molybdenum ions with a pH of about 4 treated.

Example 16

A test plate of hot-dip galvanized steel (EA) was by means of a 35 ° C phosphatizing solution containing nickel and nitrate, 1, 1 g / l Zn, 1 g / l Mn and 17 g / l PO ^{3 "} (calculated as P2O ₅ ) 80 mg / l H2O2), the acid value of the phosphating solution was adjusted to 0.05, and the test plate thus coated was then treated with about 120 mg / l ZrF ₆ ^{2 ~} (calculated as Zr). and rinsing solution containing 220 mg / 1 molybdenum ions having a pH of about 4 treated.

Test panels according to Examples 15 and 16 (B15 and B16) were coated after phosphating with a cathodic electrodeposition paint and a standard autobillack construction (filler, basecoat, clearcoat) and then - as described above - a cross-cut test before and after loading for 240 hours with condensed water subjected. The results are summarized in Tab. 6.

Tab. 6 shows that the grating cut results can be significantly improved after loading with condensed water by lowering the acid value (B16).

Claims

claims

1 . Process for essentially nickel-free phosphating of a metallic surface, characterized in that a metallic surface, optionally after purification and / or activation, is first treated with an acidic aqueous phosphating composition comprising zinc ions, manganese ions and phosphate ions, optionally rinsed and / or dried, and thereafter treated with an aqueous post-rinse composition which selects at least one type of metal ion selected from the group consisting of the ions of molybdenum, copper, silver, gold, palladium, tin, antimony, titanium, zirconium and hafnium and / or at least one polymer from the group consisting of the classes of polymers comprising polyamines, polyethyleneamines, polyanilines, polyimines, polyethylenimines, polythiophenes and polypryrenes and mixtures and copolymers thereof, wherein both the phosphating composition and the final rinsing composition are substantially non-reactive l are free.

2. The method according to claim 1, characterized in that the metallic surface is at least partially galvanized.

3. Process according to claim 1 or 2, characterized in that the phosphating composition calculates 0.3 to 3.0 g / l of zinc ions, 0.3 to 2.0 g / l of manganese ions and 8 to 25 g / l of phosphate ions (calculated as P2O ₅ ).

A method according to any one of the preceding claims, characterized in that the phosphating composition comprises from 30 to 250 mg / L of free fluoride.

A process according to any one of the preceding claims, characterized in that the phosphating composition comprises from 0.5 to 3 g / l of complex fluoride.

6. The method according to claim 5, characterized in that it is the complex fluoride to tetrafluoroborate (BF ^" ) and / or hexafluorosilicate (SiF ₆ ^{2 ~} ) is.

7. The method according to any one of the preceding claims, characterized in that the phosphating composition has a content of Fe (III).

8. The method according to any one of the preceding claims, characterized in that the phosphating contains at least one accelerator selected from the group consisting of nitroguanidine, H ₂ O ₂ , nitrite and hydroxylamine.

9. The method according to claim 8, characterized in that it is at least one accelerator to H ₂ O ₂ .

10. The method according to any one of the preceding claims, characterized in that the phosphating composition contains less than 1 g / l, preferably less than 0.5 g / l of nitrate.

A process according to any one of the preceding claims, characterized in that the phosphating composition is a free acid in the range 0.3 to 2.0, a free acid (diluted) in the range 0.5 to 8, a total Fischer acid in the range from 12 to 28, a total acid in the range of 12 to 45 and an acid value in the range of 0.01 to 0.2.

12. The method according to any one of the preceding claims, characterized in that the phosphating composition has an acid value in the range of 0.03 to 0.065.

13. The method according to any one of the preceding claims, characterized in that the phosphating composition has a temperature in the range of 30 to 50 ° C, preferably in the range between 35 and 45 ° C.

14. The method according to any one of the preceding claims, characterized in that the post-rinse composition comprises molybdenum ions.

A method according to claim 14, characterized in that the post-rinse composition comprises molybdenum ions and zirconium ions.

A process according to claim 15, characterized in that the post-rinse composition comprises 20 to 225 mg / L of molybdenum ions and 50 to 300 mg / L of zirconium ions.

17. The method according to any one of claims 14 to 16, characterized in that the pH of Nachspülzusammensetzung 3.5 to 4.5, preferably 3.5 to 4.0.

18. The method according to any one of the preceding claims, characterized in that the Nachspülzusammensetzung comprises copper ions.

A method according to claim 18, characterized in that the post-rinse composition comprises from 100 to 500 mg / l of copper ions.

20. The method according to any one of the preceding claims, characterized in that the Nachspülzusammensetzung comprises a polyamine and / or polyimine.

21. Acidic aqueous phosphating composition for substantially nickel-free phosphating of a metallic surface according to any one of the preceding claims.

22. Concentrate from which a phosphating composition according to claim 21 is obtainable by diluting with a suitable solvent by a factor between 1 and 100 and if necessary adding a pH modifying substance.

23. A phosphate-coated metallic surface, characterized in that it is obtainable by a process according to any one of claims 1 to 20.