SK162698A3 - Zinc phosphating with integrated subsequent passivation - Google Patents

Abstract

A process for phosphating the surface of steel, galvanised or alloy-galvanised steel, aluminium and/or aluminium-magnesium alloys, in which the phosphating solution contains 0.2 to 3 g/l zinc ions, 3 to 50 g/l phosphate ions calculated as PO4, 0.001 to 4 g/l manganese ions, 0.001 to 0.5 g/l of one or more polymers selected from among polyethers, polycarboxylates, polymeric phosphonic acids, polymeric phosphino carboxylic acids and nitrogen-containing organic polymers and one or more accelerators. Preferred polymers are amino group-containing poly(vinyl phenol) derivatives.

Description

Method for phosphating metal surfaces

Technical field

The invention relates to a process for phosphating metal surfaces with aqueous, acidic phosphating solutions containing zinc, magnesium and phosphate ions and up to 0.5 g / l of organic polymers. Furthermore, the invention relates to the use of such methods as a preliminary preparation of a metal surface for subsequent painting, in particular for electrically applying a lacquer coating by dipping or powder coating. The method is applicable to the treatment of steel, galvanized or alloyed galvanized steel, aluminum, magnesium and aluminum alloys, alloyed or alloyed steel surfaces and bypasses the hitherto passivated post-rinsing.

BACKGROUND OF THE INVENTION

The aim of the metal phosphating is to create on the metal surface firmly adhered layers of metal phosphates which already improve corrosion resistance by themselves and in conjunction with lacquers or other organic coatings contribute to a significant increase in paint durability and wear resistance when exposed to corrosion. long ago known. Especially low-zinc phosphating processes in which the phosphating solutions contain a relatively low content of zinc ions, for example 0.5 to 2 g / l, are suitable for the preparation prior to painting, in particular before electrodeposition of the lacquer coating by dipping. An essential parameter in these low-zinc phosphating baths is the weight ratio of phosphate ions to zinc ions, which is typically greater than 8 and can reach values up to 30.

It has been shown that by the simultaneous use of other polyvalent cations in zinc phosphating baths, phosphate layers can be formed with significantly better corrosion protection and durability properties of the lacquer coating. For example, low-zinc processes with the addition of, for example, 0.5 to 1.5 g / l manganese ions and, for example, 0.3 to 2.0 g / l nickel ions, as well as the so-called three-cation methods for preparing metal surfaces prior to painting, e.g. by electrodeposition of lacquer coating by dipping of car bodies, they find wide application.

Since nickel and alternatively used cobalt have been classified as critical from a toxicological and wastewater point of view, there is a requirement for phosphating processes having similar qualities to the three-cation process but with substantially lower nickel and / or cobalt concentrations in the bath, and preferably without both of these metals.

From DE-A-20 49 350 a phosphating solution is known which contains as components 3 to 20 g / l of phosphate ions, 0.5 to 3 g / l of zinc ions, 0.003 to 0.7 g / l of cobalt ions, or 0.003 to 0.04 g / l of copper ions, or preferably 0.05 to 3 g / l of nickel ions, 1-8 g / l of magnesium ions, 0.01 to 0.25 g / l of nitrite ions and 3 g / l fluorine ions and / or 2 to 30 g / l chlorine ions. Accordingly, the process describes zinc-magnesium phosphating, wherein the phosphating solution additionally contains ions of a metal of the cobalt, copper, or preferably nickel group. Such zinc-magnesium phosphating could not be enforced in the art.

Patent application EP-B-18 841 describes a zinc phosphate solution catalysed by chlorates and nitrites containing, inter alia, 0.4 to 1 g / l of zinc ions, 5 to 40 g / l of phosphate ions as well as optionally at least 0.2 g / l l _; preferably 0.2 to 2 g / l of one or more ions of nickel, cobalt, calcium and manganese. Accordingly, the content of the optional manganese, nickel or cobalt is at least 0.2 g / l. In the embodiments, the nickel content is given in the range of 0.53 to 1.33 g / l.

Patent application EP-A-459 541 describes phosphatizing solutions which are substantially free of nickel and contain 0.2 to 4 g / l of manganese and 1 to 30 mg / l of copper in addition to zinc and phosphate. DE-A-42 10 513 discloses nickel-free phosphating solutions which contain, in addition to zinc and phosphate, 0.5 to 25 mg / l of copper ions as well as hydroxylamine as a catalyst. These phosphating solutions optionally also contain 0.15 to 5 g / l of manganese.

German Patent Application DE 196 06 017.6 discloses a reduced heavy metal phosphating solution containing 0.2 to 3 g / l of zinc ions, 1 to 150 mg / l of manganese ions and 1 to 30 mg / l of copper ions. This phosphating solution may optionally contain up to 50 mg / l of nickel ions and up to 100 mg / l of cobalt ions. Another optional component is lithium ions in amounts of 0.2 to 1.5 g / l.

German patent application DE 195 38 778.3 describes the weighting of phosphate layers by means of hydroxylamine as a catalyst. The use of hydroxy-3-ylamine and / or its compounds for influencing the shape of phosphate crystals is known from many publications. The patent application EP-A-315 059 discloses the particular effect of the use of hydroxylamine in phosphating baths that phosphate crystals on steel assume the desired columnar or knotted shape even when the zinc concentration in the phosphating bath exceeds the range usual for the low-zinc process. This allows the operation of phosphating baths with a zinc concentration of up to 2 g / l and a phosphate to zinc weight ratio of up to 3.7. Preferred cationic combinations in these phosphating baths are not detailed, but nickel has been used in all cases. Also, nitrates and nitric acid have been used in the patent examples, although the description discourages the presence of nitrates in larger amounts. The desired concentration of hydroxylamine is given in amounts of 0.5 to 50 g / l, preferably 1 to 10 g / l. The maximum concentration of hydroxylammonium sulfate in the patent examples is 5 g / l, which implies a hydroxylamine content of 2.08 g / l. (Hydroxylammonium sulfate contains 41.5 weight percent hydroxylamine.) The phosphating solution is sprayed onto the steel surface. The guide does not mention the soaking problems which lead to a significantly higher layer weight, which is undesirable as a basis for subsequent painting.

Patent application WO 93/03198 discloses the use of hydroxylamine as a catalyst in three-cation phosphating baths with a zinc content of between 0.5 and 2 g / l and a nickel and manganese content of 0.2 to 1.5 g / l respectively, while still maintaining certain the weight ratios between zinc and other divalent cations. Furthermore, these baths contain 1 to 2.5 g / l of hydroxylamine catalyst, which is to be understood as meaning hydroxylamine salts, preferably hydroxylammonium sulfate. When converted to free hydroxylamine, the hydroxylamine content is assumed to be between 0.42 and 1.04 g / l.

In order to improve the corrosion protection by means of the phosphate layer, a so-called passive post-rinse, also called post-passivation, is also generally carried out in this process. Baths containing chromic acid are still commonly used for this purpose. However, for reasons of working and environmental protection, there is a tendency to replace these chromium-containing passivation baths with a chromium-free bath. Organic reactive bath solutions are known for this purpose

-4 with complex-acting substituted poly (vinylphenols). For example, such compounds are described in patent application DE-C-31 46 265. Particularly effective polymers of this kind contain amine substituents and can be obtained by Mannich reaction of poly (vinylphenols) with aldehydes and organic amines. Such polymers are described, for example, in patent applications EP-B-91 166, EP-B-319 016 and EP-B-319 017. Polymers of this kind are also used in the context of the present invention, so that the contents of the four documents are expressly incorporated of the present patent application. Furthermore, passivating rinse solutions can contain polymers containing amino groups in which the amino group is attached directly to the polymer chain without the presence of an aromatic ring. Such polymers which can also be used in the present invention are described in DE-A-44 09 306.

In conjunction with passive post-rinsing, the low-zinc phosphating baths currently used meet the corrosion protection requirements of the automotive industry. However, this method has the disadvantage that passive rinsing is a further step that extends the production time and increases the space requirement of the production line.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a phosphating solution which meets the automotive corrosion protection requirements of the automotive industry and in which passive rinsing can be omitted. This reduces the demands on the production line space and possibly also on production time.

It is already known from the literature that phosphating solutions contain polyacrylic acids. By way of example, J. I. Wragg, J. E. Chamberlain, L. Chann, H.W. White, T. Sugama, and S. Manalis: Characterization of polyacrylic acid modified zinc phosphate crystal conversion coatings, Journal of Applied Polymer Science, Vol. 50, 917-928 (1993). In this article, however, model zinc-containing phosphating solutions have been tested which differ significantly from those used in practice today: they contain a higher proportion of zinc, on the other hand, the widely used manganese as well as the currently used catalysts are missing. They are therefore not an example for low zinc phosphating solutions used in the present invention.

-5-Summary of the invention

The object is solved by a method of phosphating metal surfaces of steel, galvanized or alloyed with galvanized steel and / or aluminum, in which the metal surface is exposed to a zinc-containing phosphating solution by spraying or dipping for 3 seconds to 8 minutes. It contains

0.2 to 3 g / l of zinc ions, up to 50 g / l of phosphate ions calculated as PO ₄ ,

0.001 to 4 g / l of manganese ions,

0.001 to 0.5 g / l of one or more polymers selected from the group of polyethers, polycarboxylates, polymeric phosphonic acids, polymeric phosphinocarboxylic acids and organic nitrogen-containing polymers, and

one or more catalysts which may be

0.3 to 4 g / l of chlorate ions,

0.01 to 0.2 g / l nitrite ions,

0.05 to 2 g / l of m-nitrobenzenesulfonate ions,

0.05 to 2 g / l of m-nitrobenzoate ions,

0.05 to 2 g / l of p-nitrophenol,

0,005 to 0,15 g / l of hydrogen peroxide in free or bound form,

0.1 to 10 g / l of hydroxylamine in free or bound form,

0.1 to 10 g / l of reducing sugar.

The sugar concentration is preferably in the range of between about 0.3 and 2 g / l, and particularly between about 0.8 and 1.6 g / l. A zinc content above 1.6 g / l, for example between 2 and 3 g / l, has only minimal advantages for this process, but on the other hand it can increase the sludge content of the phosphating bath. Such a zinc content can occur in a working phosphating bath when additional zinc is additionally introduced into the phosphating bath when phosphating the galvanized surfaces. Nickel and / or cobalt ions in concentrations of about 1 to 50 mg / l of nickel and about 5 to 100 mg / l of cobalt in conjunction with as low a nitrate content of no more than about 0.5 g / improve corrosion protection and paint properties compared to phosphating pellets with no nickel or cobalt content or a nitrate content greater than 0,5 g / l. This achieves a suitable compromise between the performance of phosphating baths on the one hand and the requirements for post-rinse wastewater treatment on the other.

For low heavy metal phosphating baths, the manganese content may be in the range of about 0.001 to 0.2 g / l. Otherwise, the manganese content is in the range of about 0.5 to 1.5 g / l.

It is known from German patent application 195 00 927.4 that lithium ions in amounts of about 0.2 to 1.5 g / l improve the corrosion protection achievable with zinc-containing phosphating baths. The lithium content in amounts of 0.2 to about 1.5 g / l and in particular of about 0.4 to 1 g / l has a beneficial effect on the achieved corrosion protection also in the phosphating process according to the invention with integrated subsequent passivation.

In addition to the cations which are incorporated into the phosphate layer or which at least positively affect the crystalline growth of the phosphate layer, the phosphating baths typically contain sodium, potassium and / or ammonia ions to adjust the free acids. The term free acids is common to one skilled in the art of phosphating. The method of determining free acids as well as total acids selected in this work is shown in the Examples. Free acids and total acids are an important regulatory parameter for phosphating baths, as they have a large effect on the weight of the layer. The free acid values are between 0 and 1.5 points for partial phosphating, up to 2.5 points for band phosphating, and total acid values are between about 15 and 30 points in the technically conventional range, and are within the scope of the present invention.

In phosphating baths to be suitable for various substrates, it has become common for free and / or complex bound fluoride to be added in amounts up to 2.5 g / l of total fluoride, of which up to 1 g / free fluoride. The presence of such amounts of fluoride is also advantageous for the phosphating baths of the invention. In the presence of fluoride, the aluminum content of the bath should not exceed 3 mg / l. In the presence of fluoride, due to complexing, a higher aluminum content is tolerated as long as the concentration of non-complexed aluminum does not exceed 3 mg / l. The use of fluoride-containing baths is advantageous when the surfaces to be phosphated consist at least partly of aluminum. In these cases, it is preferable to use not complex bound but only free fluoride, preferably in concentrations ranging from 0.5 to 1.0 g / l.

For the phosphating of zinc surfaces, it would not be necessary for the phosphating baths to contain so-called catalysts. However, for phosphating steel surfaces, the phosphating solution needs to contain one or more catalysts. Such catalysts are common in the art as components of zinc phosphating baths. By these are meant the substances which chemically bind the hydrogen produced by the etching of metal surfaces by reducing themselves. In addition, the oxidation-acting catalysts have the effect of oxidizing the divalent iron ions released by etching from the steel surface into trivalent substances, so that they can appear as ferric phosphate.

The phosphating baths of the invention may contain one or more of the following components as a catalyst:

0.3 to 4 g / l of chlorate ions,

0.01 to 0.2 g / l nitrite ions,

0.05 to 2 g / l of m-nitrobenzenesulfonate ions,

0.05 to 2 g / l of m-nitrobenzoate ions,

0.05 to 2 g / l of p-nitrophenol,

0,005 to 0,15 g / l of hydrogen peroxide in free or bound form,

0.1 to 10 g / l of hydroxylamine in free or bound form,

0.1 to 10 g / l of reducing sugar.

When phosphating a galvanized steel, the phosphating solution needs to contain as little nitrates as possible. Nitrate concentrations of 0.5 g / l should not be exceeded as there is a risk of ulcers at higher nitrate concentrations. This means white, cratered defects in the phosphate layer. In addition, the galvanized surfaces deteriorate the paintability.

The use of nitrite as a catalyst leads to technically satisfactory results, especially on steel surfaces. However, for safety reasons (danger of nitrogen gases) it is recommended not to use nitrites as a catalyst. For the phosphating of galvanized surfaces, this is appropriate for technical reasons, since nitrites can form nitrates, which, as mentioned above, can lead to pustules and impaired paintability of the zinc surfaces.

For environmental reasons, hydrogen peroxide is preferred, and for technical reasons, because of the simplified formulation possibilities for additional dosing solutions, hydroxylamine as a catalyst is particularly preferred. However, the use of these two catalysts together is not recommended, since hydroxylamine decomposes under the influence of hydrogen peroxide. When hydrogen peroxide in free or bound form is used as a catalyst, concentrations of 0.005 to 0.02 g / l hydrogen peroxide are particularly preferred. The hydrogen peroxide can be added as such to the phosphating solution. However, it is also possible that hydrogen peroxide is used in bound form as compounds which liberate hydrogen peroxide in the phosphating bath by hydrolysis. Examples of such compounds are peroxo-salts such as perborate, perborate, perborate or perborate. Other sources of hydrogen peroxide are ionic peroxides such as alkali metal peroxides. A preferred embodiment of the invention consists in using a combination of chlorate ions and hydrogen peroxide in phosphating by the soaking process. In this embodiment, the concentration of chlorate may be, for example, in the range of 2 to 4 g / l and the concentration of hydrogen peroxide in the range of 10 to 50 ppm.

The use of reducing sugar as a catalyst is known from US-A-5,378,292. Within the scope of the present invention, it can be used in amounts between about 0.01 and 10 g / l, preferably in amounts between about 0.5 and 2.5. g / l. Examples of such sugars are galactose, mannose, and in particular glucose (dextrose).

A further preferred embodiment of the invention is the use of hydroxylamine as a catalyst. The hydroxylamine can be used as the free base, as the hydroxylamine complex, as the oxime, which represents the condensation product of the hydroxylamine with the ketone, or in the form of the hydroxylammonium salts. If free hydroxylamine is added to the phosphating bath or phosphating bath concentrate, then due to the acidic nature of these solutions, it will be abundantly present as a hydroxylammonium cation. When used as the hydroxylammonium salt, sulphates and phosphates are particularly preferred. In the case of phosphates, acid salts are preferred for better solubility. The hydroxylamine or its compounds are added to the phosphating bath in amounts such that the calculated free hydroxylamine concentration is between 0.1 and 10 g / l, preferably between 0.3 and 5 g / l. It is preferred that the phosphating baths contain hydroxylamine as the sole catalyst, or together with nitrate in the

-9maximum amount of 0.5 g / l. Accordingly, in a preferred embodiment, phosphating baths are used which do not contain any of the other catalysts, such as nitrite, oxoanions of halogens, peroxides or nitrobenzenesulfonate. A positive side effect is that the hydroxylamine concentration is above approximately

1.5 g / l reduce the risk of rust formation in under-soaked areas of phosphated parts.

When using a phosphating process on steel surfaces, iron in the form of divalent ions is dissolved. If the phosphating baths according to the invention do not contain any substances which are oxidative to the divalent iron, the divalent iron goes into the trivalent state solely as a result of air oxidation, so that it can appear as a trivalent iron phosphate. This is the case, for example, with hydroxylamine. Therefore, phosphate baths can produce a ferrous iron content which is significantly higher than that of the baths containing the oxidizing agent. In this sense, divalent iron concentrations are normally up to 50 ppm, while values up to 500 ppm may also occur in the short term during production. Such divalent iron concentrations are not detrimental to the phosphating process of the invention. When used in hard water, phosphating baths may also contain divalent magnesium and calcium cations that contribute to the hardness of the water at a total concentration of up to 7 mmol / l. Divalent magnesium or divalent calcium can also be added to the phosphating bath in amounts up to 2.5 g / L.

The weight ratio of phosphate ions to zinc ions in phosphating baths can be varied within wide limits as long as it is between 3.7 and 30. A weight ratio between 10 and 20 is particularly preferred. For the determination of the phosphate concentration, the entire phosphorus content of the phosphating bath will be considered as a form of PO ₄ ^3- phosphate ions. Accordingly, the known fact that, at pH values of phosphating baths, which are typically between about 3 and 3.6, only a very small portion of the phosphate is in fact in the form of triple negatively charged anions, is not taken into account when calculating the amounts. At these pH values, it is more likely that the phosphate will be present primarily as a single-charged dihydrophosphoric anion, along with minute amounts of undissociated phosphoric acid and double-negatively charged hydrophosphoric anions.

The organic polymers used according to the invention preferably have a molar mass (as determined, for example, by gel permeation chromatography) in the range of between about 500 and 50,000, especially between about 800 and 20,000.

Phosphating baths preferably contain organic polymers in a concentration of between about 0.01 and 0.1 g / l. At lower concentrations, the desired passivating effect is no longer manifested. Higher concentrations no longer substantially increase this effect and are therefore no longer economical.

Polymers useful in the present invention may belong to different chemical groups. However, they have in common that they have oxygen and / or nitrogen atoms in either the polymer chain or the side groups. The simplest polymers of this kind are polyalkylene glycols, for example polyethylene or polypropylene glycols, which preferably have a molar mass in the range of 500 to 10,000. Also suitable are polymeric carbonic acids such as homo- or copolymers of acrylic, methacrylic and maleic acids. Also suitable are polymeric phosphonic acids or polymeric phosphinocarboxylic acids. For example, mention may be made of polyphosphinocarboxylic acid, which may be understood as a copolymer of sodium hypophosphite and acrylic acid, and is commercially available as Belclene® 500 from FMC from the United Kingdom.

The organic polymers may further be selected from amino-containing homo- or copolymer compounds containing structural units of formula (I)

- CH ₂ - CH 1

N (I) / \

R ² CR ¹¹ II O as well as or consisting of hydrolysis products thereof, wherein R ¹ and R ² are the same or different and can replace hydrogen or alkyl of 1 to 6 carbon atoms such as methyl, ethyl, n-propyl , isopropyl, n-butyl, isobutyl, tert-butyl, amyl, nhexyl, isohexyl or diclohexyl.

A detailed list of polymers of this kind can be found in DE-A-44 09 306, the contents of which are hereby expressly incorporated in this publication. Special examples are the hydrolysis products of homo- and copolymers of N-vinylformamide, N-vinyl-N-methylformamide, N-vinyl acetamide, N-vinyl-N-methylacetamide, N-vinyl-N-ethylacetamide, N-vinylpropionamide and N-vinyl-N-methylpropionamide wherein N-vinylformamide is preferred for its very easy hydrolyzability. Suitable comonomers are monoethylenically unsaturated carbonic acids having 3 to 8 carbon atoms, as well as the water-soluble salts of these monomers.

These organic polymers can further be selected from poly-4-vinylphenol compounds of formula (II)

OH (II) (- CH - CH ₂ -) _n wherein n is a number between 5 and 100, x is independently hydrogen and / or CRR ¹ OH groups in which R and R ¹ are hydrogen, aliphatic and / or aromatic residues having 1 to 12 carbon atoms.

As a separate additional rinses, these polymers are disclosed in DE-C-31 According to the 46,265th of a particularly suitable poly-4-vinylphenol compounds wherein at least one x-CH ₂ OH. A process for their preparation is described in said document.

Particularly preferred are organic polymers which are selected from amino-containing homo- or copolymer compounds of at least one polymer which is selected from the group consisting of a), b), c) or d), wherein:

a) comprises a polymeric material wherein the unit is of the formula

where

R ¹ to R ³ are independently selected for each unit from the group consisting of hydrogen, C 1 -C 5 alkyl, or C 6 -C 18 aryl;

Y ¹ to Y ⁴ is selected independently for each unit from the group consisting of hydrogen, -CR ¹¹ R ⁵ OR ⁶ , -CH ₂ Cl, or one alkyl or aryl group of 1 to 18 carbon atoms-

or Z is R ⁷ R ⁹ R ⁷ R ⁹ I / I / - C - N or C ⁺ NR ¹⁰ I \ I \ R ⁸ R ¹⁰ R ⁸ R ¹²

however, at least one fraction of Y ¹ , Y ² , Y ³ or Y ^{4 of the} homo- or copolymer compound or material must be Z; R ⁵ to R ¹² are independently selected for each unit selected from the group consisting of hydrogen, alkyl, aryl, hydroxyalkyl, aminoalkyl, mercaptoalkyl, or phosphoalkyl;

R ¹² can also be -OH;

W ¹ is selected independently for each unit from the group consisting of hydrogen, acyl, acetyl, benzoyl; 3-allyloxy-2-hydroxypropyl; 3-benzyloxy-2-hydroxy-propyl; 3-butoxy-2-hydroxy-propyl; 3-alkyloxy-2-hydroxy-propyl; 2-hydroxyoctyl; 2-hydroxyalkyl; 2-hydroxy-2-phenylethyl; 2-hydroxy-2-alkyl-phenylethyl; benzyl; methyl; ethyl; propyl; alkyl; allyl; alkylbenzyl; haloalkyl; haloalkenyl; 2-chloropropenyl; sodium; potassium; tetraarylammonium; tetraalkylammonium; tetraalkylfosfónia;

- 13-tetraarylphosphonium or from the condensation product of ethylene oxide, propylene oxide or a mixture or copolymer thereof;

b) comprises a polymeric material with at least one unit of the formula

W ²

R ¹ where

R ¹ to R ² are independently selected for each unit from the group consisting of hydrogen, C 1 -C 5 alkyl, or C 6 -C 18 aryl;

Y ¹ to Y ³ is selected independently for each unit from the group consisting of hydrogen, -CR ⁴ R ⁵ OR ⁶ , -CH ₂ Cl, or one alkyl or aryl group having 1 to 18 carbon atoms or Z is

R ⁷ R ⁷ R ⁹ R ⁹

I / I / - C - N or - C ⁺ N ^- R ¹⁰

I \ I \

R ⁸ R ⁸ R ¹⁰ R ¹² but at least a fraction of ^{Y1, Y2} and ^Y3 of the final compound must be Z; R ⁴ to R ¹² are selected independently for each unit from the group consisting of hydrogen, alkyl, aryl, hydroxyalkyl, aminoalkyl, mercaptoalkyl or phosphoalkyl; R ¹² can also be -OH;

W ² is selected independently for each unit from the group consisting of hydrogen, acyl, acetyl, benzoyl; 3-allyloxy-2-hydroxypropyl; 3-benzyloxy-2-hydroxy-propyl; 3-alkyl-benzyloxy-2-hydroxy-propyl; 3-phenoxy-2-hydroxypropyl; 3-alkylphenoxy-2-hydroxypropyl; 3-butoxy-2-hydroxy-propyl; 3-alkyloxy-2-hydroxy-propyl; 2-hydroxy-14-octyl-; 2-hydroxyalkyl; 2-hydroxy-2-phenylethyl; 2-hydroxy-2-alkyl-phenylethyl; benzyl; methyl; ethyl; propyl; alkyl; allyl; alkylbenzyl; haloalkyl; haloalkenyl; 2-chloropropenyl or a condensation product of ethylene oxide, propylene oxide or a mixture thereof;

c) comprises a copolymer material in which at least a portion of the copolymer has a structure

R ¹ R ² and at least one fraction of said portion is polymerized with one or more monomers selected independently for each unit from the group consisting of acrylonitrile, methacrylonitrile, methyl acrylate, methyl methacrylate, vinyl acetate, vinyl methyl ketone, isopropenyl methyl ketone, acrylic acid, methacrylic acid , n-butyl methacrylate, styrene, m-bromostyrol, p-bromostyrol, pyridine, dialyldimethylammonium salts, 1,3-butadiene, n-butyl acrylate, tert-butylaminoethyl methacrylate, n-butyl methacrylate, tert-butyl methacrylate, n-butyl vinyl ether, tert-butyl vinyl ether chlorostyrol, o-chlorostyrol, p-chlorostyrol, n-decyl methacrylate, Ν, Ν-dialylmelamine, N, N-di-n-butylacrylamide, di-n-butyl maleate, di-n-butyl maleate, diethylaminoethyl methacrylate, diethylene glycol mono-diethyl ether, diethyl vinyl phosphate, vinyl phosphonic acid, diisobutyl maleate, diisopropylitaconate, diisopropyl maleate, dimethylfumarate, dimethylitaconate, dimethyl maleate t, di-n-nonyl fumarate, di-n-nonyl maleate, dioctyl fumarate, di-noctylitaconate, di-n-propylitaconate, N-dodecyl vinyl ether, acid ethyl fumarate, acid ethyl maleate, ethyl acrylate, ethyl methacrylate, ethyl methacrylate, N-ethyl ester, N-ethyl ester, 2-vinylpyridine, 5-ethyl-2-vinylpyridine-1-oxide, glycidyl acrylate, glycidyl methacrylate, nhexyl methacrylate, 2-hydroxyethyl methacrylate, isobutyl methacrylate, isobutylvinylether, methacrylate, isopropyl methacrylate, isopropyl methacrylate, isopropyl methacrylate, methacrylonitrile, N- 15-methylolacrylamide, N-methylolmethacrylamide, N-isobutoxymethylmethacrylamide, N-iso-butoxymethylmethacrylamide, N-alkyloxymethylmethacrylamide, N-alkyloxymethylmethacrylamide, N-vinylcaprolactam, methyl methyl acrylate, N-methylmethacrylate, N-methylmethacrylate, omethyl styrene, p-methyl styrene, 2-methyl-5-vinylpyridine, n-propyl methacrylate, sodium p-styrosulfonate, stearyl methacrylate, styrene, p-styrolsulfic acid New, p-styrene sulfonamide, vinyl bromide, 9-vinylcarbazole, vinyl chloride, vinylidene chloride, 1-vinyl naphthalene, 2vinylnaftalín, 2-vinylpyridine, 4-vinylpyridine, 2-vinylpyridine-N-oxide, 4-vinyl-pyrtmidín, Nvinylpyrolidon; and W ¹ , Y ¹ to Y ⁴ and R ¹ to R ³ are as described in (a);

d) comprises a condensation polymer of polymeric materials a), b) or c), condensing the condensable form a), b) or c) or a mixture thereof with another compound selected from the group consisting of phenols, tannins, Novolak resins , lignin compounds together with aldehydes, ketones or mixtures thereof to obtain a condensed resin product, wherein the condensed resin product by reacting Z at least a portion thereof by reacting the resin product with 1) an aldehyde or ketone, or 2) with a secondary amine further reacts to form the final an adduct which can react with an acid.

Methods for preparing such polymers are described in the above-mentioned applications EP-B-319 016 and EP-B-319 017. Polymers of this kind can be purchased from Henkel Corporation, Parker Amchen Division, USA, under the tradename Parcolene® 95C, Deoxylyte® 90A , 95A, 95AT, 100NC and TD-1355-CW.

Particular preference is given to those polymers in which at least one fraction of the organic polymer groups has a polyhydroxyalkylamine functionality which results from the condensation of an amine or ammonia with a ketose or aldose containing from 3 to 8 carbon atoms. The condensation products can be reduced to an amine.

Other examples of such polymers are the condensation products of polyvinylphenol with formaldehyde or paraformaldehyde and with a secondary organic amine. Preference is given here to starting from polyvinylphenols having a molar mass in the range of approximately 1000 to 10 000. Particularly preferred are those condensation products in which the secondary organic amine is either methylethanolamine or N-methylglucamine.

- 16V of the stated concentration ranges, organic polymers are stable in phosphating baths and no precipitation occurs. They also have no negative effect on the formation of layers, i.e. they do not cause passivation phenomena on the metal surface, which could prevent the growth of phosphate crystals.

The organic polymers can further be selected from substituted polyalkylene derivatives with building units

- (CR ¹ R ² ) _x -CR ³ Y wherein R ¹ , R ² , R ³ may independently be hydrogen or methyl or ethyl, x represents 1, 2, 3 or 4, and

Y represents a substituent that contains at least one nitrogen atom that is incorporated into an alkylamino group or into a mono- or polynuclear saturated or unsaturated heterocycle.

Preferred are those polymers in which R ^{@ 1} , R @ ² , R @ ³ are hydrogen. Preferably x is 1. Accordingly, polymers which are substituted polyethylenes are particularly preferred. Organic polymers which contain one or more of the following building units are particularly preferred:

-CH ₂ ^- ₂ of -CHÍh

_-CH2-CH

In a further preferred embodiment, the organic polymers are polymeric derivatives of amino-containing sugars. Examples are chitosans, which may include, for example, the following building groups:

HOH ₂ C

HO h ₂

For all nitrogen-containing organic polymers, at pH values of the phosphating solution, at least a portion of the nitrogen atoms are protonated and therefore bear a positive charge.

Phosphating solutions are generally operated in the form of aqueous concentrates, which are adjusted on site by adding water to the process concentration. For stabilization reasons, these concentrates may contain an excess of free phosphoric acid, so that when diluted to a bath concentration, the free acid value is first too high or the pH value is too low. Addition of alkaline substances such as sodium hydroxide, sodium carbonate or ammonia reduces the free acid value to the desired level. Furthermore, it is known that during use of phosphating baths, the free acid content may increase over time by the consumption of cation-forming layers and possibly also by decomposition reactions of the catacyser. In these cases, the free acid value must be reset from time to time to the desired level. This means that the content of alkali metal ions or ammonium ions in the phosphating baths can vary widely and can increase unilaterally during the use of the phosphating baths by neutralizing the free acid. Accordingly, the weight ratio of alkali metal ions and / or ammonium ions to, for example, zinc ions may be very low in freshly prepared phosphating baths, for example less than 0.5, and in extreme cases may be up to 0. During use of the bath, the ratio will usually increase, so that the ratio will be greater than 1 and can reach 10 or more. Low-zinc phosphating baths generally require the addition of alkali metal ions or ammonium ions in order to adjust the free acid to the required range at the desired PO ₄ ³ ": Zn> 8 weight ratio. By analogy, it is also possible to consider ratios in amounts of alkali metal ions and / or ammonium ions to other bath components, for example phosphate ions.

In lithium-containing phosphating baths, it is advantageous to avoid the use of sodium compounds to adjust the free acid, since too high sodium concentrations suppress the beneficial effect of lithium on corrosion protection. In this case, basic lithium compounds are preferably used to adjust the free acid. Potassium compounds are also suitable, if desired.

Basically, it does not matter in which form the cation-forming or affecting layers are introduced into the phosphating baths. However, nitrates should not be used so that the upper limit of the nitrate content is not exceeded. Preferably, metal ions are used in the form of compounds which do not enrich the phosphating solution with foreign ions. It is therefore most preferred to use metals in the form of their oxides or carbonates. Lithium can also be used as sulfate.

The phosphating solutions according to the invention are suitable for the phosphating of steel surfaces, galvanized or alloyed with galvanized steel, aluminum, alloyed or alloyed steel, as well as aluminum-magnesium alloys. The term aluminum encompasses technically common aluminum alloys, such as, for example, Al2O5.5Si1.4. These materials, as is increasingly common in the automotive industry, may also be present at the same time.

The body parts can also be made of the aforementioned material, for example after the Bonazink® process. In this case, the base material is first chromated or phosphated and then covered with an organic resin. The phosphating process of the invention then results in phosphating at the damaged areas of the treated layer or on the untreated back surfaces.

The method is suitable for use in dipping, spraying or dip / spray combinations. It can be used in particular in the automotive industry, where normal treatment times are between 1 and 8 minutes, in particular between 2 and 5 minutes. Use in strip phosphating in steel mills where treatment times are between 3 and 12 seconds is also possible. When used in band phosphating, it is recommended that the bath concentrations be set to the upper half of the range preferred by the present invention. For example, the zinc content may be in the range of 1.5 to 2.5 g / l and the free acid content may be in the range of

1.5 to 2.5 points. Galvanized steel, in particular electrolytically galvanized steel, is particularly suitable as a substrate for strip phosphating.

As is common in the prior art for other phosphating baths, suitable bath temperatures are in the range of between 30 and 70 ° C independently of the field of application, with temperatures between 45 and 60 ° C being preferred.

The phosphating process according to the invention is intended, in particular, for treating said metal surfaces prior to painting, e.g. It is also suitable as a pretreatment prior to powder coating, as is used, for example, in the case of household electrical appliances. This phosphating method is to be considered as a sub-step in the technically conventional pre-treatment chain. In this chain, phosphating is usually preceded by steps such as purification / degreasing, partial rinsing, and activation, wherein activation is usually accomplished using titanium phosphate-containing activating means.

EXAMPLES

The phosphating method according to the invention as well as the comparative method have been tested on ST 1405 steel sheets used in the automotive industry. The following soaking process, which is customary in bodywork, was carried out:

1. Purification with alkaline cleaner (Ridoline ® 1501, Henkel KGaA), 2% in tap water, 55 ° C, 4 minutes.

2. Rinse with tap water, room temperature, 1 minute.

3. Activation with titanium phosphate activation agent (Fixodine® 950, Henkel KGaA), 0.1% in fully desalinated water, room temperature, 1 minute.

4. Phosphating with phosphating baths having the following composition:

1.0 g / l Zn ²⁺

1.0 g / l Mn ²⁺

0.1 g / l Fe ²⁺ g / l PO ₄ ³

0.95 g / l SiF ₆ ² 0.2 g / l F “

1.7 g / l (NH ₃ OH) ₂ SO ₄ Polymer according to the table.

In addition to the cations mentioned, the nitrate-free phosphate baths contained sodium ions as needed to adjust the free acid.

The free acid was 0.9 points, the total acid was 23 points; The pH was 3.35. The free acid point number is understood to mean

-20 consumption of 0.1 N sodium hydroxide in ml to titrate 10 ml of bath solution to pH 3.6. By analogue, the total acid point number indicates the consumption in ml up to a pH of 8.2.

5. Rinse with desalinated water.

and

6. Drying with compressed air.

The weight per area (weight of the layer) was determined by dissolving in a 5% solution of chromic acid according to DIN 50942. It is given in the table.

Phosphated test sheets were coated with BASF cathodic dipping (FT 85-7042). The corrosion protection effect was tested in the alternating climatic test according to VDA 621-415 for 9 cycles. As a result, the damage to the paint in the cracks (half the crack width) is shown in the table.

Table: Phosphating baths and phosphating results

Number Polymer (concentration) Layer weight (g / m ² ) Damage paint (U / 2 mm) Control 1 without polymer 3.7 1.9 Example 1 polyethylene glycol, molar mass 1000, 10 ppm 3.2 1.7 Example 2 as Example 1, 50 ppm 3.9 1.5 Example 3 TD-1355-CW 3000 ^? 10 ppm 3.5 1.5 Example 4 as Example 3, 50 ppm 3.8 1.3 Example 5 TD-1355-CW 8600 ^Ί 10 ppm 3.7 1.4 Example 6 as Example 5, 50 ppm 3.2 1.1

The Mannich reaction product of polyvinylphenol (molar mass 3000, determined by gel permeation chromatography) with paraformaldehyde and glucamine (Parker Amchen, USA) * ^w) as above, molar mass of polyvinylphenol 8600.

«GIG-W

Claims (13)

Method for phosphating metal surfaces of steel, galvanized or alloyed with galvanized steel, aluminum and / or aluminum-magnesium alloys, in which the metal surfaces are sprayed or soaked for a period of from 3 seconds up to 8 minutes with a zinc-containing phosphating solution characterized in that the phosphating solution comprises: 0.2 to 3 g / l of zinc ions, 3 to 50 g / l phosphate ions calculated on PO ₄ , 0.001 to 4 g / l of manganese ions, 0.001 to 0.5 g / l of one or more polymers selected from polycarboxylates, polymeric phosphonic acids, polymeric phosphinocarboxylic acids, nitrogen-containing organic polymers and poly-4-vinylphenol compounds of formula II wherein n is a number between 5 and 100, x is independently hydrogen and / or CRR ¹ OH group in which R and R ¹ are hydrogen, aliphatic and / or aromatic radicals having 1 to 12 carbon atoms, as well as one or more catalysts selected from 0.05 to 2 g / l of m-nitrobenzocathion, 0.05 to 2 g / l of p-nitrophenol, 0.1 to 10 g / l of hydroxylamine in free or bound form, 0.1 to 10 g / l of reducing sugar, wherein the phosphating solution contains not more than 0.5 g / l of nitrate and the weight ratio of phosphate ions to zinc ions is in the range 3.7 to 30. Method according to claim 1, characterized in that the phosphating solution contains 1 to 50 mg / l of nickel ions and / or 5 to 100 mg / l of cobalt ions. -223. Process according to one or both of Claims 1 and 2, characterized in that the phosphating solution contains 0.2 to 1.5 g / l of lithium ions. Method according to one or more of claims 1 to 3, characterized in that the phosphating solution contains fluoride in amounts of up to 2.5 g / l of total fluoride, of which up to 1 g / l of free fluoride, recalculated as F. Process according to one or more of Claims 1 to 4, characterized in that the phosphating solution contains, as a catalyst, 0.1 to 10 g / l of hydroxylamine in free or bound form. Process according to one or more of Claims 1 to 5, characterized in that the phosphating solution contains organic polymers in concentrations between 0.01 and 0.1 g / l. Process according to one or more of Claims 1 to 6, characterized in that the organic polymers are chosen from homo- or copolymer compounds containing amino groups containing structural units of the general formula (I). _CH2 -CHI N (I) / \ R ² C - R ¹¹ II ⁰ ', or their hydrolysis products, or consisting thereof, wherein R ¹ and R ² are the same or different and may be hydrogen or alkyl of 1 to 6 carbon atoms. Process according to one or more of Claims 1 to 6, characterized in that the organic polymers are selected from homo- or copolymeric amino-containing compounds, comprising at least one polymer selected from the group consisting of; (c) or (d), where (a) comprises a polymeric material having at least one unit of the formula W ¹ : R ¹ R I οι R ² where R ¹ to R ³ are independently selected for each unit from the group consisting of hydrogen, C 1 -C 5 alkyl, or C 6 -C 18 aryl; Y ¹ to Y ⁴ are independently selected for each unit from the group consisting of hydrogen, -CR ¹¹ R ⁵ OR ⁶ , -CH 2 Cl or one alkyl or aryl group having 1 to 18 carbon atoms or Z is R ⁷ R ^and or R ^a R ⁷ I C I R ^{8 s +} DB but at least a fraction of Y ^1, Y ^2, Y ³ or Y ⁴ homo- or copolymer compound or material must be Z; R ⁵ to R ¹² are independently selected for each unit selected from the group consisting of hydrogen, alkyl, aryl, hydroxyalkyl, aminoalkyl, mercaptoalkyl, or phosphoalkyl; R ¹² can also be -OH; W ¹ is selected independently for each unit from the group consisting of hydrogen, acyl, acetyl, benzoyl; 3-allyloxy-2-hydroxypropyl; 3-benzyloxy-2-hydroxy-propyl; -243-butoxy-2-hydroxy-propyl; 3-alkyloxy-2-hydroxy-propyl; 2-hydroxyoctyl; 2hydroxyalkyl-; 2-hydroxy-2-phenylethyl; 2-hydroxy-2-alkyl-phenylethyl; benzyl; methyl; ethyl; propyl; alkyl; allyl; alkylbenzyl; haloalkyl; haloalkenyl; 2chlórpropenyl groups; sodium; potassium; tetraarylammonium; tetraalkylammonium; tetraalkylfosfónia; tetraarylphosphonium or a condensation product of ethylene oxide, propylene oxide or a mixture or copolymer thereof; (b) includes a polymeric material with at least one unit of the formula: W ^{2 R2} - Cl R ¹ where R ¹ to R ² are independently selected for each unit from the group consisting of hydrogen, C 1 -C 5 alkyl, or C 6 -C 18 aryl; Y ¹ to Y ³ are independently selected for each unit from the group consisting of hydrogen, -CR ⁴ R ⁵ OR ⁶ , -CH ₂ Cl or one alkyl or aryl group having 1 to 18 carbon atoms or Z is R ⁷ R ⁷ R ⁹ R ⁹ I / I / _ C - N or - C - ⁺ NR ¹⁰ I \ I \ R ⁸ R ⁸ R ¹⁰ R ¹² but at least a fraction of ^{Y1, Y2} and ^Y3 of the final compound must be Z; R ⁴ to R ¹² are selected independently for each unit of the group consisting of hydrogen, -25alkyl-, aryl-, hydroxyalkyl-, aminoalkyl-, mercaptoalkyl- or phosphoalkyl groups; R ¹² can also be -O ⁽¹¹⁾ or -OH; W ² is selected independently for each unit from the group consisting of hydrogen, acyl, acetyl, benzoyl; 3-allyloxy-2-hydroxypropyl; 3-benzyloxy-2-hydroxy-propyl; 3-alkyl-benzyloxy-2-hydroxy-propyl; 3-phenoxy-2-hydroxypropyl; 3-alkylphenoxy-2-hydroxy-propyl; 3-butoxy-2-hydroxy-propyl; 3-alkyloxy-2-hydroxy-propyl; 2hydroxyoktyl-; 2-hydroxyalkyl; 2-hydroxy-2-phenylethyl; 2-hydroxy-2-alkyl-fenyIetyl-; benzyl; methyl; ethyl; propyl; alkyl; allyl; alkylbenzyl; haloalkyl; halogénalkenyI-; 2-chloropropenyl or a condensation product of ethylene oxide, propylene oxide or a mixture thereof; c) comprises a copolymer material in which at least a portion of the copolymer has a structure R ¹ R ² and at least one fraction of said portion is polymerized with one or more monomers selected independently for each unit from the group consisting of acrylonitrile, methacrylonitrile, methyl acrylate, methyl methacrylate, vinyl acetate, vinyl methyl ketone, isopropenyl methyl ketone, acrylic acid, methacrylic acid, acrylamid , n-amyl methacrylate, styrene, m-bromostyrol, p-bromostyrol, pyridine, dialyldimethylammonium salts, 1,3-butadiene, n-butyl acrylate, tert-butylaminoethyl methacrylate, n-butyl methacrylate, tert-butyl methacrylate, n-butyl vinyl ether, tert-butyl vinyl ether, tert-butyl vinyl ether m-chlorostyrol, chlorostyrol, p-chlorostyrol, n-decylmethacrylate, Ν, Ν-dialylmelamine, N, N-di-butylacrylamide, di-n-butylitaconate, di-n-butyl maleate, diethylaminoethyl methacrylate, diethylene glycol mono-mono, diethylitaconate, diethylvinyl phosphate, vinylphosphonic acid, di-isobutyl maleate, diisopropylitaconate, diisopropyl maleate, dimethyl fu-26marate, dimethylitaconate, dimethyl maleate eate, di-n-nonyl fumarate, di-n-nonyl maleate, dioctyl fumarate, di-n-octyl itaconate, di-n-propylitaconate, N-dodecyl vinyl ether, acid ethyl fumarate, acid ethyl maleate, ethyl acrylate, ethyl methacrylate, ethyl cinnamate, ethyl cinnamate, ethyl cinnamate ethylvinyl ether, 5-ethyl-2-vinylpyridine, 5-ethyl-2-vinylpyridine-1-oxide, glycidyl acrylate, glycidyl methacrylate, n-hexyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, isobutyl methacrylate, isobutylvinyl, isobutylvinyl isopropyl vinyl ether, itaconic acid, lauryl methacrylate, methacrylamide, methacrylic acid, methacrylonitrile, N-methyl-olacrylamide, N-methylolmethacrylamide, N-isobutoxymethylmethacrylamide, N-iso-butoxymethylmethacrylamide, N-alkyloxymethyl, N-alkyloxymethyl, N-alkyloxymethyl methyl acrylate, N-methylmethacrylamide, α-methylstyrol, m-methylstyrrole, o-methylstyrol, p-methylstyrol, 2-methyl-5-vinylpyridine, n-propyl methacrylate, sodium p-styrene sulfonate, stearyl methacrylate, styrene, psic acid tyrolsulfonic, p-styrene-sulfonamide, vinyl bromide, 9-vinylcarbazole, vinyl chloride, vinylidene chloride, 1-vinyl-naphthaline, 2-vinylnaphthaline, 2-vinylpyridine, 4-vinylpyridine, 2-vinylpyridine-N-oxide, 4-vinyl- pyrimidine, N-vinylpyrrolidone; and W ¹ , Y ¹ to Y ⁴ and R ¹ to R ³ are as defined in (a); d) comprises a condensation polymer of polymeric materials a), b) or c) condensing the condensable form a), b), c) or a mixture thereof with another compound selected from the group consisting of phenols, tannins, Novolak resins , lignin compounds together with aldehydes, ketones or mixtures thereof to obtain a condensed resin product, wherein the condensed resin product by reacting Z at least a portion thereof by reacting the resin product with 1) an aldehyde or ketone, or 2) with a secondary amine further reacts to form the final adduct which can react with ^acidic! Lina. The process according to claim 8, characterized in that at least one fraction of the groups of organic polymers has a polyhydroxyalkylamine functionality that results from the condensation of an amine or ammonia with a ketose or aldose having 3 to 8 carbon atoms. -2710. The process of claim 8, wherein the organic polymer is a condensation product of polyvinylphenol having a molar mass in the range of 1000 to 10,000 with formaldehyde or paraformaldehyde and a secondary organic amine. The process of claim 10, wherein the secondary organic amine is either methylethanolamine or N-methylglucamine. Process according to one or more of claims 1 to 8, characterized in that the organic polymers are selected from substituted polyalkylene derivatives. - (CR ¹ R ² ) _x -CR ³ wherein R ¹ , R ² , R ³ may independently be hydrogen or a methyl or ethyl group, x represents 1, 2, 3 or 4, and Y represents a substituent containing at least one nitrogen atom which is incorporated into an alkylamino group or into a mono- or multinuclic saturated or unsaturated heterocycle. 13. The method of claim 12, characterized uj whether account is characterized in that R ^1, R ^2, R ³ are hydrogen and x = first A method according to claim 12 or 13, characterized in that. organic polymers contain one or more of the following building units: NH -2815. Process according to one or more of claims 1 to 6, characterized in that the organic polymers are polymeric derivatives of sugars containing amino groups. Method according to claim 15, characterized in that the polymeric sugar derivatives comprise the following building groups: