CZ389298A3 - Process of phosphate coating metal surfaces - 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

The invention relates to a process for phosphating metal surfaces with aqueous acidic phosphating solutions containing zinc, manganese and phosphate ions and up to 0.5 g / l of organic polymers. The invention further relates to the use of this method for the preparation of metal surfaces for subsequent painting, in particular by electrodeposition or powder painting. The method is applicable to the treatment of steel, galvanized steel or zinc alloy coated steel surfaces, aluminum, aluminum and magnesium alloy surfaces, aluminum steel or aluminum alloy coated steel, and does not employ the passivation rinsing necessary so far.

BACKGROUND OF THE INVENTION

The aim of metal phosphating is to provide a metal-phosphate bond on the metal surface, which in itself improves corrosion resistance, and in conjunction with lacquers and other organic layers contributes to a significant increase in paint adhesion and corrosion resistance under the surface corrosive stress. Such phosphating processes have long been known. Low-zinc phosphating processes are particularly suitable for the preparation prior to painting, in particular by electrodeposition coating, wherein the phosphating solutions have relatively low zinc ion contents, for example from 0.5 to 2 g / l. An essential parameter in these low-zinc phosphating baths is the weight ratio between phosphate and zinc ions, which is typically in the region of greater than 8 and can be as high as 30.

• ·

It has been shown that by using other polyvalent cations in zinc phosphating baths, layers can be obtained with significantly improved corrosion protection and better adhesion of the paint to the surface. For example, low-zinc phosphating baths with a wide range of additions of, for example, 0.5 to 1.5 g / l manganese ions and, for example, 0.3 to 2 g / l nickel ions are widely used as a so-called three-cation process for preparing metal surfaces for painting. for cathodic electrodeposition of automobile bodies.

Nickel and alternatively usable cobalt are classified as critical elements from a toxicological and wastewater point of view, and there is a need to develop a phosphating process having a similar level of performance to the tricationic process, but with significantly lower nickel and / or cobalt concentrations in the bath. without both of these metals.

DE-A-20 49 350 discloses a phosphating solution which contains as essential 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 up to 0.04 g / l copper ions or preferably 0.05 to 3 g / l nickel ions, 1 to 8 g / l magnesium ions, 0.01 to 0.25 g / l nitrite ions and 0.1 to 3 g / l of fluorine ions and / or 2 to 30 g / l of chlorine ions. Thus, the process describes zinc-magnesium phosphating, wherein the phosphating solution additionally contains one of cobalt, copper or preferably nickel ions. However, this type of zinc-magnesium phosphating could not be established in the art.

EP-B-18 841 discloses a zinc-containing phosphating solution with chlorate and nitrite ions as an accelerator comprising inter alia 0.4 to 1 g / l of zinc ions, 5 to 40 g / l of phosphate ions and optionally at least 0.2 g %, preferably 0.2 to 2 g / l of one or more ions selected from nickel, cobalt, calcium and manganese. According to this source, the content of optional magnesium, nickel or cobalt components is at least 0.2 g / l. Nickel contents of 0.53 and 1.33 g / l are given in the examples.

·· ··

EP-A-459 541 describes phosphatizing solutions which are substantially nickel-free and contain, in addition to zinc and phosphate, 0.2 to 4 g / l of manganese and 1 to 30 mg / l of copper. DE-A-42 10 513 discloses phosphating solutions which contain, in addition to zinc and phosphate, 0.5 to 25 mg / l of copper ions and hydroxylamine as an accelerator. These phosphating solutions may optionally contain in addition 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 also 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 an amount of between 0.2 and 1.5 g / l.

German patent application DE 195 38 778.3 describes the weight control of a layer of phosphate coatings using hydroxylamine as an accelerator. The use of hydroxylamine and / or its compounds for influencing the form of phosphate crystals is known from a number of publications. EP-A315 059 discloses, as a special effect, the use of hydroxylamine in phosphating baths that phosphate crystals of the desired columnar or knotted forms are formed on the steel even if the zinc concentration in the phosphating bath exceeds the range usual for the low-zinc process. As a result, it will be possible to use phosphating baths with zinc concentrations up to 2 g / l and with phosphate to zinc weight ratios up to 3.7. Preferred combinations of cations in these phosphating baths are not further discussed, but nickel is used in all cases. Similarly, nitrites and nitric acid are used in the examples, although the presence of nitrates in larger amounts is not recommended in the description. A suitable concentration of hydroxylamine is 0.5 to 50 g / l, preferably 1 to 10 g / l. The maximum concentration of hydroxylamine sulfate in the patent examples is 5 g / l, from which a hydroxylamine content of 2.08 g / l can be calculated. (Hydroxylamine sulphate contains

41.5% by weight of hydroxylamine.) The phosphating solution is applied to • 0

• * * 00 00 0 · 0 0 0 0 0 • 000 0 00 0 • ♦ 0000 0 000 000 • 0 0 0 0 steel surfaces by spraying. The document does not disclose problems in the soaking process which leads to phosphate layers with a considerably higher layer weight, which is not suitable as a basis for subsequent painting.

WO 93/03198 discloses the use of hydroxylamine as an accelerator in tricationic phosphating baths having 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 each, while maintaining the weight ratios set forth below zinc and other divalent cations. These baths further comprise 1 to 2.5 g / l of a hydroxylamine accelerator, which is to be understood as meaning hydroxylamine salt, preferably hydroxylamine sulfate. When converted to free hydroxylamine, hydroxylamine contents between 0.42 and 1.04 g / l are obtained.

In order to improve the corrosion protection by means of the phosphate layer, a so-called passivation after-rinse, also called after-passivation, is generally carried out. Baths containing chromic acid are still commonly used for this purpose. However, for reasons of working and environmental protection, there is pressure to replace these chromium-free passivation baths with chromium-free baths. For example, organic reactive solutions with complex-forming substituted poly (vinylphenols) are known for this purpose. Such compounds are described, for example, in DE-C-31 46 265. Particularly effective polymers of this type 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 EP-B-91 166, EP-B-319 016 and EP-B319 017. These polymers are also used within the scope of the present invention, so that the contents of the above four documents are expressly incorporated herein by reference. Further, the post-rinse passivation solutions may comprise amine-containing polymers in which the amine group is attached directly to the polymer chain without an aromatic ring spacer. These polymers, which can also be used in the present invention, are described in DE-A-44 09 306.

·· · I · ·

In conjunction with additional passivation rinses, the low-zinc phosphating baths now in use meet the corrosion protection requirements of the automotive industry. However, these methods have the disadvantage that an additional passivation rinse constitutes a further processing step, extends production time and increases the space requirement in the pretreatment line.

It is an object of the present invention to provide a phosphating solution which has sufficient anticorrosion properties required in the automotive industry and does not need to be used for an additional passivation rinse. This reduces the need for space in the pretreatment line and possibly also the production time.

The addition of polyacrylic acids to phosphate solutions is already known in the literature. For 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). Here, however, model zinc phosphate solutions are used for research, which differ considerably from those used today in practice: they contain higher amounts of zinc, on the other hand, the widely used manganese and, as a rule, the commonly used accelerator, are missing. Therefore, they cannot be a model for low zinc phosphating baths used in the present invention.

SUMMARY OF THE INVENTION

SUMMARY OF THE INVENTION The object of the present invention is to provide a method of phosphating metal surfaces of steel, galvanized steel or steel coated with zinc alloys and / or phosphating surfaces of aluminum, in which the metal surfaces are contacted by spraying or dipping for 3 s to 8 min s.

- 6 · a a 6 6 6 6 6 6 6 6 6 6 6 6 a 6 a a a

4 9 4

4944 4,444 4 44

Zinc-containing phosphating solution, characterized in that the phosphating bath contains

0.2 to 3 g / l of zinc ions 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 polyethers, polycarboxylates, polymeric phosphonic acids, polymeric phosphine carboxylic acids and nitrogen-containing organic polymers, and

one or more accelerators selected from

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 zinc concentration is preferably in the range between about 0.3 and about 2 g / l and especially between about 0.8 and about 1.6 g / l. Zinc contents in excess of 1.6 g / l, for example between 2 and 3 g / l, may bring some minor advantages to the process according to the invention, but may, on the other hand, increase sludge formation in the phosphating bath. Such zinc contents may be formed in the operated phosphating bath if additional zinc comes into solution as a result of etching when phosphating the galvanized surfaces. The content of nickel ions and / or cobalt ions in a concentration range of about 1 to about 50 mg / l in each case

-7 ···························· And about 5 to about 100 mg / l in the case of cobalt improves corrosion protection and paint adhesion in conjunction with as low a nitrate content of no more than about 0.5 g / l compared to phosphating baths which do not contain nickel or cobalt or have a nitrate content higher than 0,5 g / l. This makes it possible to achieve a suitable compromise between the performance of the phosphating bath on the one hand and the requirements for the treatment of rinse effluents on the other.

In a reduced heavy metal phosphating bath, the manganese content may range from about 0.001 to about 0.2 g / L. In other cases, conventional manganese contents are about 0.5 to about 1.5 g / L.

It is known from German patent application 195 00 927.4 that lithium ions improve the corrosion protection obtainable by zinc phosphating baths in the range of from about 0.2 to about 1.5 g / l. Lithium contents in the range of 0.2 to approximately

1.5 g / l and in particular from 0.4 to about 1 g / l have also proven advantageous with respect to the corrosion protection achieved in the phosphating process according to the invention with integrated additional passivation.

Of the aforementioned cations, which may be co-incorporated into the phosphate layer or at least positively affect the crystal growth of the phosphate layer, the phosphating baths typically comprise sodium, potassium and / or ammonium ions to adjust the free acid content. The term free acid is apparent to those skilled in the art of phosphating. The method chosen for the determination of free acid and total acid is set forth in the examples. Free acid and total acid are an important parameter in controlling phosphating baths because they have a large effect on the weight of the layer. The free acid content values useful in the present invention are 0 to 1.5 points in phosphating parts, up to

2.5 points in band phosphating and total acid content in the technologically usual range of about 15 to about 30 points.

• fl • fl • fl

For phosphating baths to be suitable for various substrates, it has become customary to add free and / or complex bound fluoride in amounts up to 2.5 g / l of total fluoride, of which up to 1 g / l of free fluoride. The presence of these amounts of fluorides is also advantageous for the phosphating baths of the invention. In the absence of fluoride, the aluminum content of the bath should not exceed 3 mg / l. In the presence of fluorine, higher aluminum contents are tolerated as a result of complexing, provided that the concentration of the non-complexed aluminum does not exceed 3 mg / l. The use of a fluorine-containing bath is therefore advantageous if the phosphated surfaces consist at least partially of aluminum or contain aluminum. In these cases, it is preferable not to use complex bound but only free fluoride, preferably at concentrations in the range of 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 accelerators. However, for phosphating steel surfaces it is necessary that the phosphating solution comprises one or more accelerators. These accelerators are common in the prior art as zinc phosphate bath components. Accelerators are substances which chemically bind hydrogen produced by acid etching on the metal surface by reducing themselves. Furthermore, the oxidizing accelerators have the effect that by etching the steel surfaces the released ferrous ions oxidize to trivalent iron, which can precipitate as ferric phosphate.

The phosphating baths of the invention may contain one or more of the following components as an accelerator:

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, - · - · - · · · · · · · · · · · · · · · ··· · J ············································· · ·

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, it is essential that the phosphating solution contains as little nitrate as possible. Nitrate concentrations of 0.5 g / l should not be exceeded, as at higher nitrate concentrations there is a risk of so-called "staining" (Stippenbildung). These are white crater-like phosphate layer defects. In addition, the adhesion of varnishes on galvanized surfaces is affected.

The use of nitrite as an accelerator leads to technically satisfactory results, especially on steel surfaces. However, for safety reasons (danger of nitrous gases) it is advisable not to use nitrites as accelerators. This is also desirable for the phosphating of galvanized surfaces for technical reasons, since nitrite can form a nitrate, which, as mentioned previously, can lead to staining problems and reduced zinc paint adhesion.

Hydrogen peroxide is particularly preferred as an accelerator for environmental reasons, because of the simplified formation of additional dosage form hydroxylamine. However, the combined use of these accelerators cannot be recommended because hydroxylamine decomposes by the action of hydrogen peroxide. When hydrogen peroxide is used as the accelerator in free or bound form, concentrations of 0.005 to 0.02 g / l hydrogen peroxide are particularly preferred. Hydrogen peroxide can be added to the phosphating solution as such. However, it is also possible to use hydrogen peroxide in the bound form of compounds which liberate hydrogen peroxide in the phosphating bath by hydrolytic reactions. Examples of such compounds are peroxy salts, such as perborates, percarbonates, peroxosulfates or peroxodisulfates. Other sources of hydrogen peroxide are ionic peroxides, such as alkali metal peroxides. One preferred embodiment of the invention consists in using a combination of chlorate ions and hydrogen peroxide in the dip-phosphating process. In this embodiment, the concentration of chlorates may be, for example, in the range of 2 to 4 g / l, the concentration of hydrogen peroxide in the range of 10 to 50 ppm.

The use of reduced sugar as an accelerator is known from US-A-5,378,292. The sugars may be used in an amount of between about 0.01 and about 10 g / L in the present invention, preferably in an amount of between about 0.5 and about 2. 5 g / l. Examples of such sugars are galactose, mannose, and in particular glucose (dextrose).

Another preferred embodiment of the invention is the use of hydroxylamine as an accelerator. The hydroxylamine can be used as the free base, as the hydroxylamine complex, as the oxime, which is the condensation product of the hydroxylamine with the ketone, or in the form of the hydroxylammonium salts. Whether the free hydroxylamine is added to the phosphating bath or phosphating bath concentrate, it will occur largely as a hydroxylammonium cation due to the acidic nature of these solutions. Sulfates and phosphates are particularly suitable for use in the form of hydroxylammonium salts. In the case of phosphates, acid salts are preferred for their 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. Here, it is preferred that the phosphating baths contain hydroxylamine as the only accelerator, optionally with a maximum of 0.5 g / l nitrate. Therefore, in a preferred embodiment, phosphating baths are used which do not contain any of the other known accelerators such as nitrate, halogen oxoanions, peroxides or nitrobenzenesulfonates. As a positive side effect, hydroxylamine concentrations of greater than about 1.5 g / l prevent the risk of incision in poorly flooded locations of phosphated components.

4 4 4 4 4444 4 4444 4 4 4444 4

II ······· · · · · 4 4 «4 · 4 4 44

When the phosphating process is applied to steel surfaces, the iron passes into solution in the form of divalent ions. Since the phosphating baths of the invention do not contain any substances which would have a strong oxidative effect on the divalent iron ions, the divalent iron goes into a trivalent state mainly due to air oxidation, so that it can precipitate as ferric phosphate. This is the case, for example, with hydoxylamine. Consequently, divalent iron concentrations can be formed in the phosphating baths of the present invention which are significantly higher than those of the oxidizing baths. In this sense, divalent iron concentrations of up to 50 ppm are normal, and may rise briefly to 500 ppm during the process. Such phosphate iron concentrations are not detrimental to the phosphating methods of the invention. When using hard water, phosphating baths may contain Mg ²⁺ and Ca ²⁺ cations in a total concentration of up to 7 mmoi / l, which cause water hardness. It is also possible to add Mg ²⁺ and Ca ²⁺ in the phosphating baths in amounts up to

2.5 g / l.

The weight ratio of phosphate to zinc ions in phosphating baths can vary over a wide range if they are between 3.7 and 30. A weight ratio of between 10 and 20 is particularly preferred. To indicate the phosphate concentration, the total phosphorus content of the phosphating bath is considered as content present in the form of phosphate ions PO ₄ ³ -. In addition, when calculating the weight ratios, it is also noted that at the pH values of phosphating baths, which are usually in the range of about 3 to about 3.6, only a very small proportion of the phosphate is in the form of three negatively charged anions. Rather, at these pH values, it is expected that the phosphate is preferably in the form of a once negatively charged dihydrogen phosphate anion together with small amounts of undissociated phosphoric acid and twice negatively charged hydrogen phosphate anions.

· • ry 9 9 99 9 9 9 9 9 9 9 9 9 9 9 9 9999 9 9 99 99 9

- i z - ······ ♦ · · · · · · · · · · · · · · ·

The organic polymers of the invention preferably have molecular weights (as determined, for example, by gel permeation chromatography) in the range of about 500 to about 50,000, especially about 800 to about 20,000.

The phosphating baths contain organic polymers preferably at a concentration between about 0.01 and about 0.1 g / l. At lower concentrations, the desired passivating effect occurs to a lesser extent. Higher concentrations no longer significantly increase the effect and are therefore uneconomical.

Polymers used in the context of the invention may belong to different groups of chemical substances. However, they have in common that they carry oxygen atoms and / or nitrogen atoms either in the polymer chain or in the side groups. The simplest polymers of this type are polyalkylene glycols, for example polyethylene or polypropylene glycol, which preferably have a molecular weight ranging from 500 to 10,000. Polymeric carboxylic acids, such as homo- or copolymers of acrylic, methacrylic and maleic acids, are equally suitable. Also suitable are polymeric phosphonic acids or polymeric phosphinocarboxylic acids. For example, polyphosphinocarboxylic acids which may be viewed as copolymers of acrylic acid and sodium hypophosphite are commercially available as Belclene® 500 from FMC Corporation, UK.

Further, the organic polymers may be selected from amino-containing homo- or copolymer compounds containing structural units of formula (I) - CH 2 - CH -

R2 3

(I)

Or their hydrolysis products, or consisting thereof, wherein R ¹ and R ² may be the same or different and may be hydrogen or C 1 -C 6 alkyl. , for example methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, amyl, n-hexyl, isohexyl or dicyclohexyl.

A detailed list of such polymers can be found in DE-A44 09 306, the contents of which are hereby incorporated by reference. Particularly preferred are the hydrolytic 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 vinyl formamide is preferred for its very easy hydrolyzability. Suitable comonomers are monoethylenically unsaturated carboxylic acids having 3 to 8 carbon atoms and the water-soluble salts of these monomers.

Organic polymers selected from poly-4-vinylphenol compounds of formula (II) may also be used,

wherein n is a number between 5 and 100, x are independently hydrogen and / or CRR 10 OH-, wherein R and R 1 are hydrogen, aliphatic and / or aromatic radicals having 1 to 12 carbon atoms.

DE-C-31 46 263. These polymers are described as separate after-rinse solutions.

Poly-4-vinylphenol compounds in which it is at least 1 x = CH 2 OH. A process for their preparation is described in said document.

Particularly preferred are organic polymers selected from amino-containing homo- or copolymer compounds containing at least one polymer selected from the group consisting of:

(a), (b), (c) or (d), where:

a) comprises a polymeric material comprising at least one

Rl «2 where:

R! to R 3 are selected for each unit independently from: hydrogen, C 1 -C 5 alkyl or C 6 -C 18 aryl;

Y 1 to Y 4 are selected for each unit independently from the group: hydrogen, -CR 11 R ₅ OR 5, -CH ₂ Cl or an alkyl or aryl group of 1 to 18 carbon atoms, or Z:

or '7 ~ ”8, R ₉ /

N - R ₁₀ ^X wherein R _i2, however, at least part of the groups Y-ι, Y _2, Y 3 or Y ₄ homo- or copolymeric compound or a homo- or copolymer material must be Z; R ₅ and R ₂ is selected independently for each unit that

- groups 15 are hydrogen, alkyl, aryl, hydroxyalkyl, aminoalkyl, mercaptoalkyl or phosphoalkyl; R ₁₂ may also be or OH;

W 1 is independently selected for each unit from hydrogen, acyl, acetyl, benzoyl; 3-allyloxy-2-hydroxypropyl; 3-benzyloxy-2-hydroxypropyl; 3-butoxy-2-hydroxypropyl; 3-alkyloxy-2-hydroxypropyl; 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; tetraalkylphosphonium; tetraarylphosphonium or the 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:

where: Rj

R 1 to R ₂ is independently selected for each unit from hydrogen, C 1 -C 5 alkyl or C 6 -C 18 aryl;

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

• ·

• «• · · · ·

- 17 • ·

but at least part of the groups _Y2, or Y3 of the end product must be Z; R ₄ to R ₁₂ is independently selected for each unit of hydrogen, alkyl, aryl, hydroxyalkyl, aminoalkyl, mercaptoalkyl or phosphoalkyl; R ₁₂ can also be O ^{( 1)} or -OH;

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

(c) means a copolymer material, where at least part of the copolymers have the structure:

3.

R1 and at least a portion of said portion is polymerized with one or more monomers selected independently for each unit of acrylonitrile, methacrylonitrile, methyl acrylate, methyl methacrylate, vinyl acetate, vinyl methyl ketone, isopropenyl methyl ketone, acid.

Acrylic, methacrylic acid, acrylamide, methacrylamide, namylmethacrylate, styrene, m-bromostyrene, p-bromostyrene, p-bromostyrene, pyridine, diallyldimethylammonium salts, 1, 3-butadiene, n-butyl acrylate, t-butylaminoethyl methacrylate, n-butyl methacrylate, tert-butyl methacrylate, n-butyl vinyl ether, tert-butyl vinyl ether, m-chlorostyrene, o-chlorostyrene, pchlorstyrene, n-decylmethacrylate, diallyme, me, N, N-di-butylacrylamide, di-n-butylitaconate, di-n-butyl maleate, diethylaminoethyl methacrylate, diethylene glycol monovinyl ether, diethylfumarate, diethylitaconate, diethylvinyl phosphate, vinylphosphonic acid, diisobutyl maleate dimethyl, diisoproitate, diisoproitate, , di-n-nonyl maleate, dioctyl fumarate, di-n-octylitaconate, di-propylitaconate, N-dodecyl vinyl ether, acid ethyl fumarate, acid ethyl maleate, ethyl acrylate, ethyl cinnamate, N-ethyl methacrylamide, e thylmethacrylate, ethylvinyl ether, 5-ethyl-2-vinylpyridine, 5-ethyl-2-vinylpyridin-1-oxide, glycidyl acrylate, glycidyl methacrylate, nhexyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, isobutyl methacrylate, isobutyl methacrylate, isobutyl methacrylate , methacrylamide, methacrylic acid, methacrylonitrile, N-methylolacrylamide, N-methylolmethacrylamide, Nizobutoxymethylacrylamide, N-isobutoxymethylmethacrylamide, Nalkyloxymethylacrylamide, N-alkyloxymethylmethacrylamide, Nvinylcaprolactam, 2-methyl-5-vinylpyridine, n-propyl methacrylate, sodium p-styrene sulfonate, stearyl methacrylate, styrene, p-styrene sulfonic acid, pstyrenesulfonamide, vinyl bromide, 9-vinylcarbazole, vinyl chloride, vinylidene chloride, 1-vinylnaphthalene, 2-vinylnaphthalene, 2-vinylnaphthalene, 2-vinylnaphthalene, 2-vinylpyridine-N-oxide, 4-vinylpyrimidine, Nv inylpyrrolidone; and W 1, Y 1 -Y 4 and R 1 -R 3 are as defined in a);

• ·

- 18 I · 4> · t · 4 ► 4 · * ·

d) means a condensation polymer of polymeric materials a), b) or c), wherein the condensable form a), b), c) or a mixture thereof is condensed with a second compound selected from: phenols, tannins, novolak resins, lignin compounds together with aldehydes, ketones or mixtures thereof to produce a condensed resin product, wherein the condensed resin product further reacts by adding Z to at least a portion thereof by reacting the resin product with 1) an aldehyde or ketone, 2) a secondary amine to form a final adduct that can react with an acid .

Methods for making these polymers are described in EP-B-319 016 and EP-B-319 017. The polymers are available from Henkel Corporation, Parker Amchen Division, USA under the tradenames Parcolene (R) 95C, Deoxylyte (R) 90A, 95A, 95AT, 100NC and TD-1355-CW.

Particular preference is given to those polymers in which at least one part of the organic polymer groups has a polyhydroxyalkylamine functional group which is derived from the condensation of an amine or ammonia with a ketose or aldose having from 3 to 8 carbon atoms. The condensation products can be reduced to the amine, if necessary.

Other examples of such polymers are the condensation products of polyvinylphenol with formaldehyde or paraformaldehyde and a secondary organic amine. Preference is given here to starting from polyvinylphenols having a molecular weight in the range from about 1000 to about 10,000. Particularly preferred are those condensation products in which the secondary organic amine is selected from methylethanolamine and N-methyl glucamine.

Within the stated concentration ranges, organic polymers are stable in phosphating baths and do not lead to the formation of precipitates. They also have no negative effect on the formation of the layer, nor do they lead to, for example, passivation on the metal surface, which could prevent the growth of phosphate crystals.

Further, the organic polymers may be selected from substituted polyalkylene derivatives containing building units

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

Y represents a substituent containing at least one nitrogen atom which is built into an alkylamino group or a saturated or unsaturated mono- or polynuclear heterocycle.

2

Preference is given to those polymers in which the groups R, R, R ³ are each hydrogen. Preferably x = 1. Accordingly, polymers which are substituted with polyethylenes are particularly preferred. Organic polymers containing one or more of the following building units are particularly preferred.

In another preferred embodiment, the amino-containing organic polymers are sugar derivatives. Examples are chitosans, which may contain, for example, the following building group:

· «··

l) · · ·

I · · · · · · · · · · · · · · · · ·

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

The phosphating baths are usually supplied in the form of aqueous concentrates, which are adjusted to concentrations suitable for on-site use by the addition of water. For stability reasons, these concentrates may contain an excess of free phosphoric acid, so that when diluted to a bath concentration, the free acid value is initially too high or the pH value is too low. Addition of alkali such as sodium hydroxide, sodium carbonate or ammonia reduces the free acid value to the desired range. Furthermore, it is known that the free acid content may increase over time as the phosphating bath is used, due to the consumption of layer-forming cations and possibly due to decomposition reactions of the accelerators. In these cases, it is desirable to occasionally adjust the free acid content by adding alkali to the desired range. This means that the contents of the alkali metal or ammonium ions in the phosphating bath can fluctuate within wide limits, and when using the phosphating bath, their concentration can still increase as a result of damping the free acid. Thus, the weight ratio of alkali metal and / or ammonium ions to, for example, zinc ions can be very low in fresh phosphating baths, for example <0.5, and in extreme cases even 0, while in bath usage conditions it usually increases so that the ratio can be > 1 up to 10 or more. Low-zinc phosphating baths typically require the addition of alkali metal or ammonium ions in order to

it was possible to adjust the free acid content to the desired range at the desired PO ₄ ': Zn> 8 weight ratio. Similarly:

• · ·

The weight ratios of alkali metal ions and / or ammonium ions to other bath components, for example phosphate ions, may also be envisaged.

In lithium-containing phosphating baths, sodium compounds are preferably not used for adjusting the free acid content, since too high sodium concentrations suppress the beneficial effect of lithium on corrosion protection. In this case, lithium is preferably used to adjust the free acid. Potassium compounds may also be used.

In principle, it does not matter in which form the cation-forming or layer-forming cations are supplied to the phosphating baths. However, it is preferable not to use nitrates in order not to exceed the preferred upper limit of their content. Preferably, metal ions are used in the form of those compounds which do not introduce any foreign ions into the phosphating bath. Therefore, it is preferable to use metals in the form of oxides or carbonates. Lithium can also be used in the form of sulfate.

The phosphating baths according to the invention are suitable for phosphating surfaces of steel, galvanized steel or steel coated with zinc alloys, surfaces of aluminum, aluminum steel or steel coated with aluminum alloys and aluminum-magnesium alloys. The term "aluminum" also includes technically common aluminum alloys, such as AIMgO, 5Si1,4.

These materials can also be processed side by side, as is increasingly common in the automotive industry.

The body parts can also be composed of a material already treated, such as is obtained, for example, by the Bonazink® process. The base material is first chromated or phosphated and then coated with an organic resin. The phosphating process of the present invention then results in the phosphating of damaged areas of these previously formed layers or untreated back portions.

- 22 · · · · · · · · · · · · · · · · · · · · · · · · · · ·

Λ ·. · · · · · · · · · · · · · · · · · · ·

The process is suitable for use in a dipping, spraying and spraying / dipping process. In particular, it can be used in the automotive industry where treatment times of between 1 and 8 minutes, in particular 2 to 5 minutes, are usual. However, it is also possible to use strip phosphating in steel mills where the treatment time is between 3 and 12 s. When using a strip phosphating process, it is advisable to adjust the bath concentrations to the upper half of the preferred ranges according to the invention. For example, the zinc content may be in the range of 1.5 to 2.5 g / l and the free acid content in the range of 1.5 to 2.5 points. Especially galvanized steel, in particular electrolytically galvanized steel, is suitable as a substrate for strip phosphating.

As is customary with other prior art phosphating baths, bath temperatures of between 30 and 70 ° C are suitable, with a temperature range of between 43 and 60 ° C being preferred.

The phosphating process of the invention is intended to treat said metal surfaces prior to painting, for example, prior to cathodic electrocoating, as is common in the automotive industry. They are further suitable as a pretreatment prior to powder coating, for example used for household articles. Phosphating should be regarded as a sub-step in a conventional technical processing chain. In this chain, phosphating is usually preceded by the steps of purification / degreasing, intermediate rinse and activation, the activation usually taking place by means of an activating agent containing titanium phosphate.

DETAILED DESCRIPTION OF THE INVENTION

The phosphating processes of the present invention, as well as comparative examples, have been tested on St 1405 steel sheets used in the automotive industry. In this case, the method customary in the manufacture of bodies in the dipping process was used:

- 23 1. Cleaning with alkaline detergent (Ridoline® 1501, Henkel KGaA), 2% solution in city water, 55 ° C, 4 minutes.

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

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

4. Phosphating with phosphating baths of 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 table.

In addition to the cations mentioned above, the nitrate-free phosphate baths contained sodium ions to adjust the free acid if necessary.

The free acid concentration at the points was 0.9, total acid 23; the pH was 3.35. The number of free acid points refers to the consumption of 0.1 N sodium hydroxide needed to titrate 10 ml of bath solution to a pH of 3.6. Analogously, the amount of bound acid points indicates the consumption of 0.1 N sodium hydroxide for titration of 10 ml bath solution to pH 8.2.

5. Rinse with desalinated water.

6. Compressed air drying.

The weight per area ("layer weight") was determined according to DIN 50942 by leaching in 5% chromic acid and is shown in the table.

Phosphated test sheets were coated with BASF FT 85-7042 cathodic dip lacquer. Corrosion tests were carried out according to the VDA test with variable climate 621-415 in 9 cycles. As a result, the table shows the penetration of corrosion under the varnish on the scratch (half scratch width).

Table: Phosphating baths and phosphating results

Nr. Polymer (concentration) Layer weight (g / m ² ) Penetration under lacquer (U / 2 mm) Srovn.1 without 3.7 1.9 Ex. 1 polyethylene glycol mol. weight 1000, 10 ppm 3.2 1.7 Ex. 2 as Example 1, 50 ppm 3.9 1.5 Ex. 3 TD-1355-CW 3000 * ^} 10 ppm 3.5 1.5 Ex. 4 jako příkl. 3, 50 ppm 3.8 1.3 Ex. 5 TD-1355-CW 8600 ** ^} 10 ppm 3.7 1.4 Ex. 6 jako příkl. 5, 50 ppm 3.2 1.1

*) Reaction product of the Mannich reaction of polyvinylphenol (molecular weight 3000, determined by gel permeation chromatography) with paraformaldehyde and glucamine (Parker Amchen, USA) **) As above, molecular weight of polyvinylphenol: 8600.

Represented by:

0 0 0 0 0 0 0 0 0

AAl - ý /

0 · ·

0 0 *

0 0 · • 0 0 0 0 0 0 0 0

0 0 0

Claims (16)

A method for phosphating metal surfaces of steel, galvanized steel, zinc-alloy coated steel, aluminum surfaces and / or hi-magnesium alloys, in which metal surfaces are contacted by spraying or dipping for a period of between 3 seconds and 8 minutes with a phosphating solution containing zinc, characterized in that the phosphating solution comprises: 0.2 to 3 g / l of zinc ions, 3 to 50 g / l phosphate ions, calculated as PO4, 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 phosphine carboxylic acids, nitrogen-containing organic polymers and poly-4-vinylphenoic compounds of formula I wherein n is a number between 5 and 100, x being independently hydrogen and / or CRR1OH-, in which R and R1 are hydrogen, aliphatic and / or aromatic radicals having 1 to 12 carbon atoms, and one or more accelerators selected from - 26 0,05 to 2 g / l of m-nitrobenzoate ions, 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 no more than 0.5 g / l of nitrate and the weight ratio of phosphate ions to zinc ions is between 3.7 and 30. Method according to claim 1, characterized in that the phosphating solution additionally contains 1 to 50 mg / l of nickel ions and / or 5 to 100 mg / l of cobalt ions. Method according to any one of claims 1 and 2, characterized in that the phosphating solution additionally contains 0.2 to 1.5 g / l of lithium ions. Method according to one of claims 1 to 3, characterized in that the phosphating solution additionally contains fluoride in an amount of up to 2.5 g / l of total fluoride, of which up to 1 g / l of free fluoride, always calculated as F. Process according to any one of claims 1 to 4, characterized in that the phosphating solution contains, as accelerator, 0.1 to 10 g / l of hydroxylamine in free or bound form. Process according to any one of claims 1 to 5, characterized in that the phosphating solution contains organic polymers in a concentration between 0.01 and 0.1 g / l. - 27 • · · · · Process according to one of Claims 1 to 6, characterized in that the organic polymers are selected from homo- or copolymer compounds containing structural units of the general formula (II) - ch ₂ - ch - N / \ R ² C - R * and their hydrolytic products, or consisting of said compounds, wherein R ¹ and R ² are the same or different and may be hydrogen or C 1 -C 6 alkyl. The process according to any one of claims 1 to 6, wherein the organic polymers are selected from amine-containing homo- or copolymer compounds comprising at least one polymer selected from a), b), c) or d), wherein: (a) comprises a polymeric material containing at least one unit of the formula: Ri - 28 ··· ··· · · · ··· where: R ₁ to R 3 are selected for each unit independently from: hydrogen, C 1 -C 5 alkyl or C 6 -C 18 aryl; Y ₁ to Y ₄ are selected for each unit independently from: hydrogen, -CR 11 R ₅ OR 6, -CH ₂ Cl or alkyl or aryl of 1 to 18 carbon atoms, or Z: or y ^R 9 Νς- RLO ^Xr 12 however, at least a part of the groups Y1 _Y2, Y3 or Y4 of the homo- or copolymeric compound or a homo- or copolymer material must be Z; R ₅ to R ₁₂ are selected independently for each unit from the group: hydrogen, alkyl, aryl, hydroxyalkyl, aminoalkyl, mercaptoalkyl or phosphoalkyl; R 12 can also be -O ^{( 1)} or -OH; Ni is selected independently for each unit from: hydrogen, acyl, acetyl, benzoyl; 3-allyloxy-2-hydroxypropyl; 3-benzyloxy-2-hydroxypropyl; 3-butoxy-2-hydroxypropyl; 3-alkyloxy-2-hydroxypropyl; 2-hydroxyoctyl; 2hydroxyalkyl; 2-hydroxy-2-phenylethyl; 2-hydroxy-2-alkylphenylethyl; benzyl; methyl; ethyl; propyl; alkyl; allyl; alkylbenzyl; haloalkyl; haloalkenyl; 2-chloropropenyl; sodium; potassium; tetraarylammonium; tetraalkylammonium; tetraalkylphosphonium; tetraarylphosphonium or the condensation product of ethylene oxide, propylene oxide or a mixture or copolymer thereof; - 29 • ΦΦφφφφφ · · · · · · φφφ · φ · · φ · φ · (b) comprises a polymeric material containing at least one unit of the formula: where: R 1 to R ₂ are independently selected from the group: hydrogen, C 1 -C 5 alkyl or C 6 -C 18 aryl; Ά to Y ₃ are independently selected for each unit from: hydrogen, -CR 4 R ₅ OR 6, -CH ₂ Cl or alkyl or aryl of 1 to 18 carbon atoms, or Z: * 7 / ^R 9 N-R 10 ^X R 12 wherein, however, at least a portion of the groups Y 1 Y ₂ or Y _{3 of the} final compound must be Z; R ₄ to R ₁₂ are selected for each unit independently from: hydrogen, alkyl, aryl, hydroxyalkyl, aminoalkyl, mercaptoalkyl or phosphoalkyl; R ₁₂ can also be -OH; • to ·· • to - 30 to · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · W 2 is selected independently for each unit from the group: hydrogen, acyl, acetyl, benzoyl; 3-allyloxy-2-hydroxypropyl; 3-benzyloxy-2-hydroxypropyl; 3-alkylbenzyloxy-2-hydroxypropyl; 3-phenoxy-2-hydroxypropyl; 3-alkylphenoxy-2-hydroxypropyl; 3-butoxy-2-hydroxypropyl; 3-alkyloxy-2-hydroxypropyl; 2-hydroxyoctyl; 2-hydroxylalkyl; 2-hydroxy-2-phenylethyl; 2-hydroxy-2-alkyl-phenylethyl; benzyl; methyl; ethyl; propyl; alkyl; allyl; alkylbenzyl; haloalkyl; haloalkenyl; 2-chloropropenyl or the condensation product of ethylene oxide, propylene oxide or mixtures thereof; (c) means: a copolymer material, wherein at least a portion of the copolymer has a "/" structure 12 and at least a portion of said moieties are polymerized with one or more monomers independently selected for each unit from acrylonitrile, methacrylonitrile, methyl acrylate, methyl methacrylate, vinyl acetate, vinylmethylketone, isopropenylmethylketone, acrylic acid, methacrylic acid, acrylamide, methacrylamide, n -amyl methacrylate, styrene, m-bromostyrene, p-bromostyrene, pyridine, diallyldimethylammonium salts, 1,3-butadiene, n-butyl acrylate, tert-butylaminoethyl methacrylate, n-butylmethacrylate, tert-butylmethacrylate, n-butylvinyl ether, tert-butylvinyl ether, tert-butylvinyl ether, tert-butylvinyl ether , o-chlorostyrene, p-chlorostyrene, n-decyl methacrylate, - 31 • 1 · 1 Ν, Ν-diallylmelamine, N, N-di-n-butyl acrylamide, di-n-butylitaconate, di-n-butyl maleate, diethylaminoethyl methacrylate, diethylene glycol monovinyl ether, diethyl fumarate, diethylitaconate, diethylvinyl phosphate, diisophosphonate, diisophosphonic acid, , dimethyl maleate, di-n-nonyl fumarate, di-nonyl maleate, dioctyl fumarate, di-n-octylitaconate, di-propylitaconate, N-dodecyl vinyl ether, acid ethyl fumarate, acid ethyl maleate, ethyl acrylate, ethyl cinnamate, ethyl ethyl methacrylate, N-ethyl methacrylate, 2-vinylpyridine, 5-ethyl-2-vinylpyridine-1-oxide, glycidyl acrylate, glycidyl methacrylate, nhexylmethakrylát, 2-hydroxyethyl methacrylate, 2hydroxypropylmethakrylát, isobutyl, izobutylvinylether, isoprene, izoproylmethakrylát, izoproylvinylether, itaconic acid, lauryl methacrylate, methacrylamide, methacrylic acid, methacrylonitrile, Nmethylolakrylamid , N-methylolmethacrylam id, Nizobutoxymethylacrylamide, N-isobutoxymethyimethacrylamide, N-alkyloxymethylacrylamide, N-alkyloxymethylmethacrylamide, Nvinylcaprolactam, methyl acrylate, N-methylmethacrylamide, amethylstyrene, m-methylstyrene, m-methylstyrene, n-methylstyrene, n-methylstyrene, n-methylstyrene, n-methylstyrene, n-methylstyrene, sodium styrene sulfonate, stearyl dimethacrylate, styrene, styrene sulfonic acid, p-styrene sulfonamide, vinyl bromide, 9-vinylcarbazole, vinyl chloride, vinylidene chloride, 1-vinylnaphthalene, 2-vinylnaphthalene, 2-vinylpyridine, 4-vinylpyridine, 4-vinylpyridine, 4-vinylpyridine, 4-vinylpyridine, vinylpyrrolidone; and W 1, Y 1 -Y 4 and R 1 -R 4 are as described in a); d) means a condensation polymer of a), b) or c), wherein the condensable form a), b), c) or a mixture thereof is condensed with a second compound selected from: phenols, tannins, novolak resins, compounds - 32 ·· · f · f · f · f · f · f · f · f · f · f · f · f · f · f · f · f · f · f · f · f · f · f · f · f · f · f · f · f · f · f · f · f · f · Lignin, together with aldehydes, ketones or mixtures thereof, to produce their condensation resin product, wherein the condensation resin product is then further reacted by adding Z to at least a portion of the resin product with 1) an aldehyde or ketone, 2) a secondary amine to form a final adduct that can react with the acid. 9. The process of claim 8 wherein at least a portion of the organic polymer moieties comprise a polyhydroxyalkylamine functionality derived from the condensation of an amine or ammonia with a ketose or aldose containing from 3 to 8 carbon atoms. The process according to claim 8, wherein the organic polymer is a condensation product of polyvinylphenol having a molecular weight of 1000 to 10,000 with formaldehyde or paraformaldehyde and a secondary organic amine. 11. The process of claim 10 wherein the secondary organic amine is selected from methylethanolamine and N-methylglucamine. Process according to any one of claims 1 to 8, characterized in that the organic polymers are selected from substituted polyalkylene derivatives. - (CR ¹ R ² ) _x -CR ³ Y - 33 9 9 9 9 # 9 9 9 9 9 9 9 9 9 · 9 9 9 9 · ···· · 999 999 9 9 9 9 99 99 99 9 99 99 wherein R ¹ , R ² , R ³ independently represent a hydrogen atom or a methyl or ethyl group, x = 1, 2, 3 or 4 and Y represents a substituent containing at least one nitrogen atom that is built into an alkylamino or mono- or polynuclear saturated or unsaturated heterocycles. The method according to claim 12, characterized in that R ¹ , R ² , R ³ are each hydrogen and ax = 1. Process according to claim 12 or 13, characterized in that the organic polymers comprise one or more of the following building units: Process according to any one of claims 1 to 6, characterized in that the organic polymers are polymeric derivatives of amine-containing sugar. The method of claim 15, wherein the polymer sugar derivatives comprise the following building groups: