KR20000016128A - Zinc phosphating with integrated subsequent passivation - Google Patents

Abstract

PURPOSE: A method for phosphorating a metal surface is provided to use an acid phosphate solution containing a zinc ion, a manganic ion, a phosphate ion, and less than 0.5 g/l of organic high molecules. CONSTITUTION: A process for phosphorating the surface of steel, galvanized or alloy-galvanized steel, aluminium and/or aluminium-magnesium alloys, in which the phosphorating 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

Continuous post-passivation zinc phosphate treatment

The present invention relates to a method of phosphating a metal surface using an acidic phosphate aqueous solution containing zinc ions, manganese ions, phosphate ions and up to 0.5 g / l organic polymer. The invention also relates to the use of this method as a pretreatment of metal surfaces for subsequent coatings, in particular for electrocoating or powder coating. This method can be used for the surface treatment of steel, zinc coated steel or zinc alloy coated steel, aluminum, aluminum-magnesium alloy, aluminum coated steel or aluminum alloy coated steel so that passivation has been required until now. Do not wash.

Phosphating of metals produces a layer of metal phosphate that adheres firmly to the metal surface, which alone improves corrosion resistance and is resistant to downward movement and paint adhesion during corrosive stresses in combination with paints or other organic coatings. Brings a significant increase in sex. Such phosphate treatments have long been known. Low-zinc phosphate treatments, in which the phosphate treatment liquid has a relatively low content, for example, 0.5 to 2 g / l zinc ions, are particularly suitable for pretreatment prior to coating, in particular before electrocoating. An important factor in these low-zinc phosphate treatment baths is the phosphate to zinc ion weight ratio, which can generally be above 8 and below 30.

It has been clarified that other polyvalent cations may be used in the zinc phosphate treatment bath to form a phosphate layer with markedly improved anticorrosive and paint adhesive properties. As an example, a low-zinc method which adds, for example, 0.5 to 1.5 g / l manganese ions and, for example, 0.3 to 2.0 g / l nickel ions, is used for pretreating metal surfaces for coating, for example, cathodic electrocoating of automobile bodies. It is widely applied as a so-called trication method.

Nickel and cobalt used as a substitute are classified as dangerous in terms of toxicity and wastewater treatment technology, while having similar performance levels to trication method, while at significantly lower concentrations of nickel and / or cobalt in the treatment bath, and preferably these two metals There is a need for a phosphate treatment that works without.

Phosphate ions 3 to 20 g / l, zinc ions 0.5 to 3 g / l, cobalt ions 0.003 to 0.7 g / l or copper ions 0.003 to 0.04 g / l from DE-A 20 49 350 or preferably nickel Phosphate treatment containing 0.05 to 3 g / l ions, 1 to 8 g / l magnesium ions, 0.01 to 0.25 g / l nitrite ions and 0.1 to 3 g / l fluoride ions and / or 2 to 30 g / l chloride Liquids are known. Therefore, this method is a zinc-magnesium phosphate treatment method in which the phosphate treatment liquid further contains one ion of metal cobalt, copper or, preferably, nickel. This zinc-magnesium phosphate treatment has not been successful in obtaining technical acceptance.

EP-B 18 841 is promoted by chlorate / nitrates, in particular zinc ions 0.4 to 1 g / l, phosphate ions 5 to 40 g / l, and optionally 0.2 g / at least one ion selected from nickel, cobalt, calcium and manganese Zinc phosphate treatment liquid containing 1 or more, preferably 0.2 to 2 g / l is described. Thus any manganese, nickel or cobalt content is at least 0.2 g / l. Nickel contents of 0.53 g / l and 1.33 g / l are given in the examples.

EP-A 459 541 describes phosphate treatment liquids that are substantially free of nickel and contain 0.2 to 4 g / l manganese and 1 to 30 mg / l copper in addition to zinc and phosphate. DE-A 42 10 513 discloses a nickel-free phosphate treatment solution containing 0.5 to 25 mg / l copper ions in addition to zinc and phosphate and hydroxylamine as promoter. These phosphate treatment solutions optionally further contain 0.15 to 5 g / l manganese.

German patent application DE 196 06 017.6 describes a phosphate treatment solution reduced by heavy metals containing 0.2 to 3 g / l zinc ions, 1 to 150 mg / l manganese ions and 1 to 30 mg / l copper ions. . This phosphate treatment liquid may optionally contain up to 50 mg / l of nickel ions and up to 100 mg / l of cobalt ions. 0.2 to 1.5 g / l amount of lithium ions is another optional component.

German patent application DE 195 38 778.3 describes the control of the layer weight in the phosphate layer using hydroxylamine as the promoter. The use of hydroxylamines and / or derivatives thereof that affect the phosphate crystal shape is known in many published patents. EP-A 315 059 is a particular effect of the use of hydroxylamine in phosphate treatment tanks, in which the phosphate crystals are still desired on the steel even if the zinc concentration in the phosphate treatment tank exceeds the usual range of low-zinc method. It mentions the fact that it is formed. It is therefore possible to operate phosphate treatment tanks with zinc concentrations below 2 g / l and to use low phosphate to zinc weight ratios of 3.7. Although not provided in more detail for the advantageous cation combinations in these phosphate treatment baths, nickel is used in all of the examples given in the patent. Although negatively described for the presence of large amounts of nitrate, nitrate and nitric acid are also used in the examples. The required hydroxylamine concentration is given as 0.5 to 50 g / l, preferably 1 to 10 g / l. In the examples the maximum concentration of hydroxylammonium sulfate is 5 g / l, from which the hydroxylamine content is calculated to be 2.08 g / l. (Hydroxyammonium sulfate contains 41.5% by weight of hydroxylamine.) The phosphate solution is applied to the steel surface by spraying. The document does not address the problems associated with the dipping process, producing a phosphate layer with a significantly higher layer weight and which is undesirable as a post-coating basis.

WO 93/03198 is hydroxyl as an accelerator while also maintaining the weight ratio between zinc and other divalent cations in a trication-phosphate treatment bath having a zinc content of 0.5 to 2 g / l and a nickel and manganese content of 0.2 to 1.5 g / l, respectively. The use of amines is disclosed. These treatment tanks also contain 1 to 2.5 g / l of "hydroxylamine promoter", wherein the hydroxylamine promoter according to the specification means a salt of hydroxylamine, preferably hydroxylamine sulfate. Calculating the amounts stated here as free hydroxylamine results in a hydroxylamine content of 0.42 to 1.04 g / l.

In general, in order to improve the anticorrosion made by the phosphate layer, so-called "passivation washing" (also called post-passivation) is actually carried out. Chromic acid containing treatment tanks are still widely used for this purpose. For industrial safety and environmental protection, these chromium-containing passivating tanks tend to be replaced by chrome-free baths. For this purpose, organic reaction bath liquids containing, for example, heterosubstituted poly (vinylphenol) are known. 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 (vinylphenol) with aldehydes and organic amines. Such polymers are described, for example, in EP-B 91 166, EP-B 319 016 and EP-B 319 017. Polymers of this type are also used for the purposes of the present invention and therefore these four substrates are used herein by reference. The passivating wash may also contain a polymer having an amino group, which is directly bonded to the polymer chain without the insertion of an aromatic ring. Likewise polymers of this type which can be used according to the invention are described in DE-A 44 09 306.

In combination with passivating washes, currently used low-zinc phosphate treatment tanks meet established standards for automobile construction. However, this process has the disadvantage that passivation cleaning is an individual treatment process that extends manufacturing time and increases the space requirements of the pretreatment line.

It is an object of the present invention to provide a phosphate treatment solution which satisfies the anticorrosive standards in the automotive industry and in which case passivation washing can be omitted. Therefore, the space required for the pretreatment line can be reduced and manufacturing time can be reduced.

The addition of polyacrylic acid to phosphate treatment liquids is already known from the literature. For example, J.I. Wragg, J.E. Chamberlain, L. Chann, H.W. The following papers by White, T. Sugama and S. Manalis are described: "Characterization of polyacrylic acid modified zinc phosphate crystal conversion coatings", Journal of Applied Polymer Science. of Applied Polymer Science), Vol. 50, 917-928 (1993). However, the zinc phosphate treatment solution model studied here is clearly different from what is currently used. They have a higher zinc content and, moreover, lack the widely used manganese and currently commonly used promoters. Therefore, they are not models for low-zinc phosphate treatment liquids used in accordance with the present invention.

The object is achieved by a phosphate treatment of a metal surface consisting of steel, zinc coated steel or zinc alloy coated steel and / or aluminum, wherein the metal surface is zinc-containing phosphate treatment by spraying or soaking for 3 seconds to 8 minutes. In contact with, the phosphate treatment solution contains:

Zinc ions 0.2-3 g / l,

Phosphate ions 3 to 50 g / l calculated as PO ₄ ,

Manganese ions 0.001-4 g / l,

0.001 to 0.5 g / l of at least one polymer selected from polyether, polycarboxylate, polymeric phosphonic acid, polymeric phosphinocarboxylic acid and nitrogen-containing organic polymer, and

One or more promoters selected from:

0.3-4 g / l chloride ions,

0.01 to 0.2 g / l nitrite ion,

m -nitrobenzene-sulfonic acid ion from 0.05 to 2 g / l,

m -nitrobenzoic acid ion 0.05 to 2 g / l,

p -nitrophenol 0.05 to 2 g / l,

Free or bound hydrogen peroxide 0.005 to 0.15 g / l,

0.1-10 g / l of free or bound hydroxylamine,

Reducing sugar from 0.1 to 10 g / l.

The zinc concentration is preferably about 0.3 to about 2 g / l, in particular about 0.8 to about 1.6 g / l. A zinc content of greater than 1.6 g / l, such as 2-3 g / l, has only a minor advantage in the process while increasing the amount of sludge produced in the phosphate treatment bath. If additional zinc enters the phosphate bath as a result of acid removal during phosphate treatment of the zinc coated surface, this zinc content can be set in the working phosphate bath. Nickel ions and / or cobalt ions in the concentration range of about 1 to about 50 mg / l nickel and about 5 to about 100 mg / l cobalt may, together with the lowest nitrate content (up to about 0.5 g / l), be nickel or Improves anticorrosion and paint adhesion as compared to phosphate treatment baths containing no cobalt or having a nitrate content of more than 0.5 g / l. Thus, there is a compromise between the performance of the phosphate treatment tank on the one hand and the requirements of the wastewater treatment technology on the other hand for the treatment of the wash water.

In phosphate treatment tanks reduced with heavy metals, the manganese content may be in the range from about 0.001 to about 0.2 g / l. Otherwise, a manganese content of about 0.5 to about 1.5 g / l is normal.

It is known from German Patent Application No. 195 00 927.4 that lithium ions in the quantitative range of about 0.2 to 1.5 g / l improve the anticorrosion obtainable using a zinc phosphate treatment bath. The lithium content in the quantitative range of 0.2 to about 1.5 g / l, in particular about 0.4 to about 1 g / l, also has a desirable effect on the anticorrosion obtainable in the continuous post-passivation phosphate treatment process according to the invention. In addition to the cations incorporated into the phosphate layer or at least having a desirable effect on crystal growth of the phosphate layer, the phosphate treatment bath generally further contains sodium ions, potassium ions and / or ammonium ions for free acid control. The concept of free acid is well known to those skilled in the art of phosphate treatment techniques. The method chosen in this document for measuring free acid and total acid is given in the Examples. Free acids and total acids are important control parameters for phosphate treatment baths because they have a significant effect on bed weight. Free acid values of 0 to 1.5 points for partial phosphate treatment, 2.5 points or less for continuous phosphate treatment and total acid values of about 15 to about 30 points are within the usual technical scope and are suitable for the present invention.

In phosphate treatment baths which should be suitable for different substrates, it is usually possible to add free fluorides and / or fluorides bound to complex compounds with a total amount of fluoride of 2.5 g / l or less (of which 1 g / l or less). It became. The presence of this amount of fluoride is also advantageous in the phosphate treatment bath according to the invention. In the absence of fluorides, the aluminum content of the treatment bath does not exceed 3 mg / l. In the presence of fluorides, due to the formation of complexes, higher Al contents are tolerated, provided that the concentration of uncomplexed Al does not exceed 3 mg / l. The use of fluoride-containing baths is therefore advantageous when the surface to be phosphated is at least partially made of aluminum or contains aluminum. In these cases, it is advantageous to use only free fluorides, preferably in a concentration of 0.5 to 1.0 g / l, without using fluorides bound to the complex.

In the phosphate treatment of the zinc surface, it is not absolutely necessary for the phosphate treatment tank to contain a so-called accelerator. However, it is essential for the phosphate treatment of the steel surface to contain more than one accelerator. These promoters are common in the prior art as components of zinc phosphate treatment baths. These are understood to include substances which themselves are chemically bonded to hydrogen formed by reduction as a result of the attack of acids on the metal surface. Oxidation promoters also have the effect of oxidizing iron (II) ions released by a corrosive attack on a steel surface to a trivalent state, so that they can precipitate out of iron (III) phosphate.

The phosphate treatment bath according to the invention may contain one or more of the following components as promoters:

0.3-4 g / l chloride ions,

0.01 to 0.2 g / l nitrite ion,

m -nitrobenzene sulfonic acid ion 0.05 to 2 g / l,

m -nitrobenzoic acid ion 0.05 to 2 g / l,

p -nitrophenol 0.05 to 2 g / l,

Free or bound hydrogen peroxide 0.005 to 0.15 g / l,

0.1-10 g / l of free or bound hydroxylamine,

Reducing sugar from 0.1 to 10 g / l.

In the phosphate treatment of zinc coated steel, it is essential that the phosphate treatment liquid contain as little nitrate as possible. Nitrate concentrations should not exceed 0.5 g / l, as there is a risk of so-called "pinholing" at higher nitrate concentrations. This means a white crater-like hole in the phosphate layer. Moreover, paint adhesion on the zinc coated surface is impaired.

The use of nitrite as an accelerator has a technically satisfactory effect, especially on steel surfaces. However, for industrial safety (risk of nitrogen gas release), it is preferred that there is no nitrite as an accelerator. Nitrate may be formed from nitrite in the phosphate treatment of the zinc-coated surface, and as described above, it is preferable that there is no technical reason as it may cause a problem of pinholes and reduce paint adhesion on zinc.

Particularly preferred promoters are hydroxylamines for technical reasons including the possibility of simple formulation for hydrogen peroxide and supplements for environmental friendliness. However, the combination of these two promoters is undesirable because hydroxylamine is degraded by hydrogen peroxide. When free or bound hydrogen peroxide is used as an accelerator, the hydrogen peroxide concentration is particularly preferably 0.005 to 0.02 g / l. Hydrogen peroxide can be added to the phosphate treatment liquid as it is. However, it is also possible to add bonded hydrogen peroxide as a compound that generates hydrogen peroxide by hydrolysis in a phosphate treatment tank. Examples of such compounds are per-salts, such as perborates, percarbonates, peroxosulfates or peroxodisulfates. Other suitable hydrogen peroxide sources are ionic peroxides such as alkali metal peroxides. Preferred embodiments of the invention include the use of a combination of chlorate ions and hydrogen peroxide in the phosphate treatment by dipping. In this embodiment, the concentration of chlorate may be, for example, 2 to 4 g / l and the concentration of hydrogen peroxide may be 10 to 50 ppm.

The use of reducing sugars as promoters is known from US-A 5 378 292. In the present invention, they are usable in amounts of about 0.01 to about 10 g / l, preferably about 0.5 to about 2.5 g / l. Examples of such sugars are galactose, mannose and, in particular, glucose (dextrose).

Another preferred embodiment of the present invention includes the use of hydroxylamine as promoter. Hydroxylamines can be used as free bases, hydroxylamine complexes, oximes (condensates of hydroxylamines and ketones), or in the form of hydroxylammonium salts. When free hydroxylamine is added to the phosphate bath or phosphate bath concentrate, due to the acidity of these solutions, most will be present in the form of hydroxylammonium cations. When used in the form of hydroxylammonium salts, sulfates and phosphates are particularly suitable. In the case of phosphates, acid salts are preferred because of their good solubility. The hydroxylamine or a compound thereof is added to the phosphate treatment tank in an amount such that the calculated concentration of free hydroxylamine is 0.1 to 10 g / l, preferably 0.3 to 5 g / l. It is preferred here that the phosphate treatment bath contains hydroxylamine as the only promoter and possibly together with nitrates up to 0.5 g / l. Thus, in a preferred embodiment, a phosphate treatment bath is used that contains no known promoters such as nitrite, oxo anion of halogen, peroxide or nitrobenzene-sulfonate. A positive side effect is that a hydroxylamine concentration of greater than about 1.5 g / l lowers the risk of rust in poorly submerged areas of the phosphated structure.

During phosphate treatment on the steel surface, iron passes through the solution in the form of iron (II) ions. If the present phosphate treatment tank does not contain a substance for oxidizing iron (II), the divalent iron can be converted to trivalent state alone as a result of oxidation in the atmosphere, and can precipitate as iron (II) phosphate. This is the case, for example, when hydroxylamine is used. Therefore, the iron (II) content that can be increased in the phosphate treatment tank is considerably larger than the iron content in the oxidant containing tank. In this case, iron (II) concentrations of up to 50 ppm are common, values of up to 500 ppm briefly during the manufacturing process are also possible. These iron (II) concentrations are not bad for the phosphate treatment method according to the present invention. When using hard water, the phosphate treatment bath may further contain hardness-producing cations Mg (II) and Ca (II) up to a total concentration of 7 mmol / l. Mg (II) or Ca (II) may also be added to the phosphate treatment bath in an amount up to 2.5 g / l.

The weight ratio of zinc ions to phosphate ions in the phosphate treatment tank can vary over a wide range, provided that it is between 3.7 and 30. Particular preference is given to a weight ratio of 10 to 20. To indicate the phosphate concentration, the total phosphorus content of the phosphate treatment bath is considered to be in the form of phosphate ion PO ₄ ^3- . Thus, in the weight ratio calculation, it does not take into account the fact that only a very small fraction of the phosphate is present in the form of a substantially trivalent negatively charged anion in the pH of the phosphate treatment tank, which is generally in the range of about 3 to about 3.6. At these pH values, phosphate is more likely to exist mostly as monovalent negatively charged dihydrogen phosphate anion, with small amounts of unsubstituted phosphoric acid and divalent negatively charged hydrogen phosphate anions.

The organic polymers used according to the invention preferably have a molecular weight of about 500 to about 50,000, in particular about 800 to about 20,000 (eg measurable by gel permeation chromatography).

The phosphate treatment bath preferably contains organic polymer at a concentration of about 0.01 to about 0.1 g / l. At lower concentrations, the required passivation effect is reduced. Higher concentrations do not in fact increase the effect and, as they increase, become uneconomical.

The polymers usable in accordance with the present invention may be circles of various chemical groups. However, what is common to these is that they have oxygen atoms and / or nitrogen atoms in the polymer chains or side groups. The simplest polymers of this type are polyalkylene glycols such as polyethylene glycol or polypropylene glycol, which preferably have a molecular weight of 500 to 10,000. Polymeric carboxylic acids such as homo- or co-polymers of acrylic acid, methacrylic acid and maleic acid are likewise suitable for polymeric phosphonic acids or polymeric phosphinocarboxylic acids. Examples include polyphosphinocarboxylic acid that can be interpreted as acrylic acid-sodium hypophosphite copolymer, and commercially available "Beclene ^(R) 500" manufactured by FMC, UK.

The organic polymer may also be selected from homo- or co-polymerized compounds and hydrolyzates thereof which consist of or contain structural units corresponding to formula (I) and which contain amino groups:

Wherein R ¹ and R ² are the same or different and are hydrogen or alkyl having 1 to 6 carbon atoms such as methyl, ethyl, n -propyl, isopropyl, n -butyl, isobutyl, t -butyl, amyl, n -hexyl , Isohexyl or dicyclohexyl may be indicated.)

A comprehensive list of such polymers can be found in DE-A 44 09 306 and used below. Specific examples include N-vinyl-formamide, N-vinyl-N-methyl-formamide, N-vinyl-acetamide, N-vinyl-N-methylacetamide, N-vinyl-N-ethylacetamide, N- It is a hydrolyzate of homo- or co-polymers of vinyl-propionamide and N-vinyl-N-methyl-propionamide, and N-vinylformamide is preferred because it is very easily hydrolyzable. Suitable comonomers are monoethylenically unsaturated carboxylic acids having 3 to 8 carbon atoms, and also water-soluble salts of these monomers.

The organic polymer may also be selected from poly-4-vinylphenol compounds corresponding to formula (II):

(In the formula,

n represents a number from 5 to 100,

x independently represents a hydrogen and / or CRR ₁ OH group, where R and R ₁ represent hydrogen, an aliphatic and / or aromatic group having 1 to 12 carbon atoms.)

These polymers are described as individual washes in DE-C 31 46 265. According to this specification, poly-4-vinylphenol compounds of the type in which at least one x represents CH ₂ OH are particularly suitable. The preparation method thereof is given in the above document.

Particular preference is given to using organic polymers selected from homo- or co-polymerizable compounds which contain an amino group and comprise at least one polymer selected from the group consisting of (a), (b), (c) or (d):

(a) consists of a polymeric material having at least one unit corresponding to the formula:

(In the formula:

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

Y ₁ to Y ₄ for each unit are independently selected from the group consisting of hydrogen, —CR ₁₁ R ₅ OR ₆ , —CH ₂ Cl or an alkyl or aryl group having 1 to 18 carbon atoms or Z of the formula:

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

R ₁₂ may also represent -O ^(-1) or -OH;

W ₁ for each unit is independently hydrogen, acyl group, acetyl group, benzoyl group; 3-allyloxy-2-hydroxy-propyl; 3-benzyloxy-2-hydroxy-propyl; 3-butoxy-2-hydroxy-propyl; 3-alkyloxy-2-hydroxy-propyl; 2-hydroxy-octyl; 2-hydroxy-alkyl; 2-hydroxy-2-phenylethyl; 2-hydroxy-2-alkyl-phenylethyl; benzyl; methyl; ethyl; profile; Alkyl; Allyl; Alkyl benzyl; Haloalkyl; Haloalkenyl; 2-chloropropenyl; salt; potassium; Tetraarylammonium; Tetraalkylammonium; Tetraalkylphosphonium; Tetraarylphosphonium or ethylene oxide, propylene oxide or mixtures or copolymers thereof;

b) consists of a polymeric material having at least one unit corresponding to the formula:

(In the formula,

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

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

However, at least one of Y ₁ , Y ₂ , or Y ₃ of the final compound must be Z; For each unit R ₄ to R ₁₂ are independently selected from the group consisting of hydrogen, alkyl, aryl, hydroxyalkyl, aminoalkyl, mercaptoalkyl or phosphoalkyl groups; R ₁₂ may also be -O ^(-) or -OH;

W ₂ for each unit is independently hydrogen, acyl group, acetyl group, benzoyl group; 3-allyloxy-2-hydroxy-propyl; 3-benzyloxy-2-hydroxy-propyl; 3-alkyl-benzyloxy-2-hydroxy-propyl; 3-phenoxy-2-hydroxy-propyl; 3-alkyl-phenoxy-2-hydroxy-propyl; 3-butoxy-2-hydroxy-propyl; 3-alkyloxy-2-hydroxy-propyl; 2-hydroxy-octyl; 2-hydroxy-alkyl; 2-hydroxy-2-phenylethyl; 2-hydroxy-2-alkyl-phenylethyl; benzyl; methyl; ethyl; profile; Alkyl; Allyl; Alkyl-benzyl; Haloalkyl; Haloalkenyl; 2-chloro-propenyl or a condensate of ethylene oxide, propylene oxide or mixtures thereof);

c) consists of a copolymer, wherein at least one part of the copolymer has the structure:

At least one portion of said portion is polymerized independently with at least one monomer selected from the group consisting of for each unit: acrylonitrile, methacrylonitrile, methyl acrylate, methyl methacrylate, vinyl acetate, vinyl methyl ketone Isopropenyl methyl ketone, acrylic acid, methacrylic acid, acrylamide, methacrylamide, n -amyl methacrylate, styrene, m -bromostyrene, p -bromostyrene, pyridine, diallyldimethylammonium salt, 1, 3-butadiene, n -butyl acrylate, t -butylaminoethyl methacrylate, n -butyl methacrylate, t -butyl methacrylate, n -butyl vinyl ether, t -butyl vinyl ether, m -chlorostyrene, o -chlorostyrene, p -chlorostyrene, n -decyl methacrylate, N, N-diallyl-melamine, N, N-di- n -butylacrylamide, di- n -butyl itaconate, di-n -Butyl male , Diethylaminoethyl methacrylate, diethylene glycol monovinyl ether, diethyl fumarate, diethyl itaconate, diethyl-vinyl phosphate, vinyl-phosphonic acid, diisobutyl maleate, diisopropyl itaconate , Diisopropyl maleate, dimethyl fumarate, dimethyl itaconate, dimethyl maleate, di- n -nonyl fumarate, di- n -nonyl maleate, dioctyl fumarate, di- n -octyl itaconate, Di- n -propyl itaconate, N-dodecyl vinyl ether, acid ethyl fumarate, acid ethyl maleate, ethyl acrylate, ethyl cinnamate, N-ethylmethacrylamide, ethyl methacrylate, ethyl vinyl ether, 5-ethyl-2-vinyl-pyridine, 5-ethyl-2-vinyl-pyridine-1 oxide, glycidyl acrylate, glycidyl methacrylate, n -hexyl methacrylate, 2-hydroxy-ethyl Metak Latex, 2-hydroxy-propyl methacrylate, isobutyl methacrylate, isobutyl vinyl ether, isoprene, isopropyl methacrylate, isopropyl vinyl ether, itaconic acid, lauryl methacrylate, N-methylolacrylic Amide, N-methylol-methacrylamide, N-isobutoxy-methylacrylamide, N-isobutoxy-methylmethacrylamide, N-alkyloxy-methylacrylamide, N-alkyloxy-methylmethacrylamide, N -Vinyl-caprolactam, N-methyl-methacrylamide, α-methyl-styrene, m -methyl-styrene, o -methylstyrene, p -methyl-styrene, 2-methyl-5-vinyl-pyridine, n- Propyl methacrylate, sodium p -styrene sulfonate, stearyl methacrylate, styrene, p -styrene sulfonic acid, p -styrene sulfonamide, vinyl bromide, 9-vinyl-carbazole, vinyl chloride, vinylidene chloride, 1- Vinyl-naphthalene, 2-vinylnaphthalene, 2-vinyl-pyridine, 4-vinyl- Naphthyridin-2-vinyl-pyridine N- oxide, 4-vinyl-pyrimidine, N- vinyl-pyrrolidone; And W ₁ , Y ₁ to Y ₄ and R ₁ to R ₃ are the same as those described for (a);

(d) consists of a condensation polymer of the polymer material (a), (b) or (c), and the condensable form of (a), (b), (c) or mixtures thereof is phenol, tannin, novolak resin And a second compound selected from the group consisting of lignin compounds and an aldehyde, a ketone or a mixture thereof, to condense to produce a condensation resin, which is then added to at least one portion thereof by adding "Z" 1) react with aldehydes or ketones, 2) secondary amines to form a final adduct that can react with acids.

Such polymer preparation methods are described in the already cited EP-B 319 016 and EP-B 319 017. Polymers of this type are the trademarks of Henkel Corporation, Parker Amschaft (Parcolene ( ^R) 95C, Deoxylyte ^(R) 90A, 95A, 95AT, 100NC and TD-1355-CW). Parker Amchen Division), USA.

Particularly preferred polymers in this connection are those in which at least one part of the Z groups of the organic polymer has a polyhydroxy-alkylamine functionality derived from the condensation of ketoses or aldoses with 3 to 8 carbon atoms with ammonia or amines. The condensate can be reduced to amine, if desired.

Other examples of such polymers are condensates of polyvinyl-phenol with formaldehyde or paraformaldehyde and condensates with secondary organic amines. Preference is given here to starting from polyvinylphenols having a molecular weight of about 1,000 to about 10,000. Particularly preferred condensates are those in which the secondary organic amine is selected from methylethanolamine and N-methylglucamine.

Within the concentration ranges mentioned above, the organic polymers in the phosphate treatment bath are stable and do not precipitate. They also do not adversely affect layer formation and thus do not result in passivation on the metal surface, for example, which can inhibit the growth of phosphate crystals.

The organic polymer may also be selected from substituted polyalkylene derivatives containing the following structural units:

(Wherein R ¹ , R ² , R ³ independently represent hydrogen or methyl or ethyl groups,

x represents 1, 2, 3 or 4, and

Y represents a substituent containing one or more nitrogen atoms and incorporated into an alkylamino group or a mononuclear or polynuclear saturated or unsaturated heterocyclic compound.).

Here, polymers in which R ¹ , R ² and R ³ each represent hydrogen are preferable. Preferably, x represents 1. Thus, substituted polyethylene is a particularly preferred polymer. Especially preferred are organic polymers containing one or more of the following structural units:

In another preferred embodiment, the organic polymer is a polymer sugar derivative containing an amino group. Examples thereof are chitosans, which may contain, for example, groups of the structure:

Regarding the pH of the phosphate treatment solution, several or more nitrogen atoms are added with protons and thus carrying a positive charge is applied to all nitrogen-containing organic polymers.

Phosphate treatment tanks generally function in the form of an aqueous concentrate, which is adjusted to the concentration to be used by adding water in situ. These concentrates may contain excess free phosphoric acid for stability reasons, so the value of the free acid is initially very high and the pH is very low upon treatment tank concentration dilution. The value of the free acid can be lowered to the required range by adding an alkali such as sodium hydroxide, sodium carbonate or ammonia. The free acid content can increase over time as a result of the consumption of layer-forming cations and possibly the decomposition reaction of the promoter when the phosphate treatment bath is in use. In this case, the value of the free acid sometimes needs to be readjusted to the required range by addition of alkali. This means that the alkali metal or ammonium ion content in the phosphate treatment tank can fluctuate over a wide range, and during the period that the phosphate treatment tank is in use, the free acid tends to increase due to dealkalization. Thus, for example, the alkali metal ions and / or ammonium ions to zinc ion weight ratios are very low for freshly prepared phosphate treatment tanks, for example, may be less than 0.05 and even zero in the extreme, while in general the resulting time for the treatment tank maintenance process. As it elapses, the ratio exceeds 1 and the value can reach 10 or more. Typically, low-zinc phosphate treatment tanks need to add alkali metal ions or ammonium ions to adjust the free acid to the range required at the required weight ratio (PO ₄ ³ : Zn is greater than 8). The ratio of alkali metal and / or ammonium ions to other components of the treatment bath, such as phosphate ions, can also be similarly described.

In the case of lithium-containing phosphate treatment baths, it is desirable to avoid using sodium compounds to control the free acid because the beneficial effects of lithium on anticorrosive are hampered by excessively high sodium concentrations. In this case, a basic lithium compound is preferably used for free acid control. Otherwise, potassium compounds are also suitable.

In principle, the form in which cations which generate or affect the layers are introduced into the phosphate treatment bath is not critical. However, nitrates should be avoided in order not to exceed the desired upper limit of nitrate content. The metal ion is preferably used in the form of a compound which does not introduce any other ions into the phosphate treatment liquid. For this reason it is most advantageous to use metals in the form of oxides or carbonates. Lithium can also be used as the sulfate.

The phosphate treatment tank according to the present invention is suitable for the phosphate treatment of the surface consisting of steel, zinc coated steel or zinc alloy coated steel, aluminum, aluminum coated steel or aluminum alloy coated steel, and aluminum-magnesium alloy. The term “aluminum” here includes aluminum alloys common in the art, such as AlMg _0.5 Si _1.4 . The materials, which are becoming increasingly common in automobile manufacturing, can also be juxtaposed.

In this regard, the vehicle body fabrication part can also be made of a material that has already been pretreated, such as occurs in the Bonanzink process, for example. Here, the substrate material is first chrome plated or phosphated and then coated with an organic resin. Subsequently, the phosphate treatment is performed on the damaged part or the untreated back side of the pretreatment layer according to the present invention. The method is suitable for application by dipping, spraying or spraying / dipping. The method can be used in particular for automobile construction, with a treatment time of 1 to 8 minutes, in particular 2 to 5 minutes. However, it can also be used for continuous phosphate treatment in steel mills and the treatment time is 3 to 12 seconds. When using the continuous phosphate treatment method, it is preferable in each case to adjust the treatment tank concentration within the upper half of the preferred range according to the invention. For example, the zinc content can be 1.5 to 2.5 g / l and the free acid content can be 1.5 to 2.5 points. Zinc coated steel and electroplated steel are particularly suitable as substrates for continuous phosphate treatment.

As is also common in other known phosphate treatment baths, suitable treatment bath temperatures are 30 to 70 ° C., preferably 45 to 60 ° C. temperature range, regardless of the application.

The phosphate treatment method according to the invention is particularly for the treatment of the metal surface prior to coating, for example prior to cathodic electrocoating as is customary in automobile construction. It is also suitable as a pretreatment prior to powder coating, for example as used in household utensils. Phosphate treatment should be considered as an individual process in a typical industrial pretreatment chain. In this chain, processes involving washing and degreasing, intermediate washing and activation are preceded by the phosphate treatment process and activation is generally carried out using an active agent containing titanium phosphate.

The phosphate treatment and comparative method according to the invention is tested on steel sheet ST 1405 used in automobile construction. The immersion method carried out follows the following procedure which is common in automobile body construction:

1. Wash with alkaline cleaner (Ridoline ^(R) 1501, Henkel KGaA), 2% batch in tap water, 55 ° C., 4 min.

2. Wash with tap water, room temperature 1 min.

3. Activated using titanium phosphate containing activator (Fixodine ^(R) 950, Henkel), 0.1% batch in demineralized water, room temperature, 1 min.

4. Phosphating using a phosphate treatment tank of the following composition:

Zn ²⁺ 1.0 g / l

Mn ²⁺ 1.0 g / l

Fe ²⁺ 0.1 g / l

PO ₄ ^3- 14 g / l

SiF ₆ ^2- 0.95 g / l

F ^- 0.2 g / l

(NH ₃ OH) ₂ SO ₄ 1.7 g / l

Polymer of Table 1.

In addition to the cations listed above, the nitrate-free phosphate treatment bath contains sodium ions, if necessary, for free acid control.

The free acid score is 0.9 and the total acid score is 23; pH is 3.35. The score of free acid means the consumption (ml) of 0.1 N sodium hydroxide solution required to titrate 10 ml of the treatment bath solution until a pH value of 3.6 is obtained. Similarly, the total acid score indicates the consumption (ml) before obtaining a pH value of 8.2.

5. Wash with demineralized water

6. Blow drying using compressed air

Mass per unit surface (“layer weight”) is measured by dissolving in a 5% chromic acid solution according to DIN 50942. This is shown in Table 1.

Phosphated test plates are coated with BASF Cathodic Immersion Paint (FT 85-7042). Anticorrosive activity is tested for 9 cycles in a cross-climate test with VDA 621-415. The results are included in Table 1 as creepage leaks in scribes.

Phosphate Treatment Tank and Phosphate Treatment Results number Polymer (concentration) Layer weight (g / m ² ) Creepage leakage (U / 2, mm) Comparative Example 1 No polymer 3.7 1.9 Example 1 Polyethylene glycol molecular weight 1000, 10 ppm 3.2 1.7 Example 2 50 ppm equivalent to Example 1 3.9 1.5 Example 3 TD-1355-CW 3000 ^*) 10 ppm 3.5 1.5 Example 4 50 ppm equivalent to Example 3 3.8 1.3 Example 5 TD-1355-CW 8600 ^**) 10 ppm 3.7 1.4 Example 6 50 ppm equivalent to Example 5 3.2 1.1 ^(*) Mannich reaction product of paraformaldehyde and glucamine (Parker Ambank, USA) and polyvinyl-phenol (molecular weight 3000, measured by gel permeation chromatography) ^(**) Molecular weight of polyvinylphenol : 8600.

Claims (20)

In the phosphate treatment of a metal surface consisting of steel, zinc coated steel or zinc alloy coated steel, aluminum and / or aluminum-magnesium alloy, the metal surface is contacted with zinc-containing phosphate treatment by spraying or dipping for 3 seconds to 8 minutes. The phosphate treatment method characterized in that the phosphate treatment liquid contains: Zinc ions 0.2-3 g / l, Phosphate ions 3 to 50 g / l calculated as PO ₄ , Manganese ions 0.001-4 g / l, 0.01 to 0.5 g / l of at least one polymer selected from polyethers, polycarboxylates, polymeric phosphonic acids, polymeric phosphinocarboxylic acids and nitrogen-containing organic polymers And One or more promoters selected from: 0.3-4 g / l chloride ions, 0.01 to 0.2 g / l nitrite ion, m -nitrobenzene-sulfonic acid ion from 0.05 to 2 g / l, m -nitrobenzoic acid ion 0.05 to 2 g / l, p -nitrophenol 0.05 to 2 g / l, 0.005 to 0.15 g / l of free or bound hydrogen peroxide, 0.1-10 g / l of free or bound hydroxylamine, Reducing sugar from 0.1 to 10 g / l. The phosphate treatment method according to claim 1, wherein the phosphate treatment liquid further contains 1 to 50 mg / l of nickel ions and / or 5 to 100 mg / l of cobalt ions. The phosphate treatment method according to claim 1 or 2, wherein the phosphate treatment liquid further contains 0.2 to 1.5 g / l of lithium ions. The phosphate treatment liquid according to any one of claims 1 to 3, further comprising fluoride in an amount of 2.5 g / l or less (1 g / l or less free fluoride, each calculated as F ⁻ ) of the total fluoride. Phosphate Treatment. The phosphate treatment method according to any one of claims 1 to 4, wherein the phosphate treatment liquid contains 5 to 150 mg / l of free or bound hydrogen peroxide as an accelerator. The phosphate treatment method according to any one of claims 1 to 4, wherein the phosphate treatment solution contains 0.1 to 10 g / l of hydroxyl or free amine as an accelerator. The phosphate treatment method according to any one of claims 1 to 6, wherein the phosphate treatment liquid contains 0.5 g / l or less of nitrate. The phosphate treatment method according to any one of claims 1 to 7, wherein the phosphate treatment liquid contains an organic polymer having a concentration of 0.01 to 0.1 g / l. The phosphate treatment method according to any one of claims 1 to 8, wherein the organic polymer is a polyalkylene glycol having a molecular weight of 500 to 10,000. The phosphate salt according to any one of claims 1 to 8, wherein the organic polymer contains an amino group and is selected from homopolymerized or copolymerized compounds consisting of or containing structural units and hydrolyzates thereof corresponding to the following general formula (I). conduct: [Formula I] (Wherein R ¹ and R ² are the same or different and may represent hydrogen or alkyl having 1 to 6 carbon atoms.) The phosphate treatment method according to any one of claims 1 to 8, wherein the organic polymer is selected from poly-4-vinylphenol compounds represented by the following general formula (II): [Formula II] (In the formula, n represents a number from 5 to 100, x independently represents a hydrogen and / or CRR ₁ OH group, where R and R ₁ represent hydrogen, an aliphatic and / or aromatic group having 1 to 12 carbon atoms.) The homopolymer according to any one of claims 1 to 8, wherein the organic polymer contains an amino group and comprises at least one polymer selected from the group consisting of (a), (b), (c) or (d). Phosphate treatment selected from polymerization or copolymerization compounds: (a) consists of a polymeric material having at least one unit corresponding to the formula: (In the formula, R ₁ to R ₃ for each unit are independently selected from the group consisting of hydrogen, an alkyl group of 1 to 5 carbon atoms or an aryl group of 6 to 18 carbon atoms; Y ₁ to Y ₄ for each unit are independently selected from the group consisting of hydrogen, CR ₁₁ R ₅ OR ₆ , -CH ₂ Cl or an alkyl or aryl group having 1 to 18 carbon atoms or Z of the formula: However, at least one of the Y ₁ , Y ₂ , Y ₃ or Y ₄ of the homopolymerized or copolymerized compound or material must be Z; R ₅ to R ₁₂ for each unit are independently selected from the group consisting of hydrogen, alkyl, aryl, hydroxyalkyl, aminoalkyl, mercaptoalkyl or phosphoalkyl groups; R ₁₂ may also represent -O ^(-1) or -OH; W ₁ for each unit is independently hydrogen, acyl group, acetyl group, benzoyl group; 3-allyloxy-2-hydroxy-propyl; 3-benzyloxy-2-hydroxy-propyl; 3-butoxy-2-hydroxy-propyl; 3-alkyloxy-2-hydroxy-propyl; 2-hydroxy-octyl; 2-hydroxy-alkyl; 2-hydroxy-2-phenylethyl; 2-hydroxy-2-alkyl-phenylethyl; benzyl; methyl; ethyl; profile; Alkyl; Allyl; Alkyl-benzyl; Haloalkyl; Haloalkenyl; 2-chloropropenyl; salt; potassium; Tetra-arylammonium; Tetra-alkylammonium; Tetra-alkylphosphonium; Tetra-arylphosphonium or ethylene oxide, propylene oxide or mixtures or copolymers thereof; b) consists of a polymeric material having at least one unit corresponding to the formula: (In the formula, R ₁ to R ₂ for each unit are independently selected from the group consisting of hydrogen, an alkyl group of 1 to 5 carbon atoms or an aryl group of 6 to 18 carbon atoms; Y ₁ to Y ₃ for each unit are independently selected from the group consisting of hydrogen, —CR ₄ R ₅ OR ₆ , —CH ₂ Cl or an alkyl or aryl group having 1 to 18 carbon atoms or Z of the formula: However, at least one of Y ₁ , Y ₂ , or Y ₃ of the final compound must be Z; For each unit R ₄ to R ₁₂ are independently selected from the group consisting of hydrogen, alkyl, aryl, hydroxy-alkyl, amino-alkyl, mercapto-alkyl or phospho-alkyl groups; R ₁₂ may also represent -O ^(-1) or -OH; W ₂ for each unit is independently hydrogen, acyl group, acetyl group, benzoyl group; 3-allyloxy-2-hydroxy-propyl; 3-benzyloxy-2-hydroxy-propyl; 3-alkyl-benzyloxy-2-hydroxy-propyl; 3-phenoxy-2-hydroxy-propyl; 3-alkyl-phenoxy-2-hydroxy-propyl; 3-butoxy-2-hydroxy-propyl; 3-alkyloxy-2-hydroxy-propyl; 2-hydroxy-octyl; 2-hydroxy-alkyl; 2-hydroxy-2-phenylethyl; 2-hydroxy-2-alkyl-phenylethyl; benzyl; methyl; ethyl; profile; Alkyl; Allyl; Alkyl-benzyl; Haloalkyl; Haloalkenyl; 2-chloro-propenyl or a condensate of ethylene oxide, propylene oxide or mixtures thereof; c) consists of a copolymer, wherein at least one portion of the copolymer has the structure At least one portion of said portion is polymerized independently with at least one monomer selected from the group consisting of for each unit: acrylonitrile, methacrylonitrile, methyl acrylate, methyl methacrylate, vinyl acetate, vinyl methyl ketone , Isopropenyl methyl ketone, acrylic acid, methacrylic acid, acrylamide, methacrylamide, n-amyl methacrylate, styrene, m -bromostyrene, p -bromostyrene, pyridine, diallyl-dimethylammonium salt, 1 , 3-butadiene, n -butylacrylate, t -butylaminoethyl methacrylate, n -butyl methacrylate, t -butyl methacrylate, n -butyl vinyl ether, t -butyl vinyl ether, m -chlorostyrene , o -chlorostyrene, p -chloro-styrene, n -decyl methacrylate, N, N-diallyl-melamine, N, N-di- n -butylacrylamide, di- n -butylitaconate, di -n-butyl male , Diethylamino-ethyl methacrylate, diethylene glycol monovinyl ether, diethyl fumarate, diethyl itaconate, diethyl-vinyl phosphate, vinyl-phosphonic acid, diisobutyl maleate, diisopropyl itac Nitrate, diisopropyl maleate, dimethyl fumarate, dimethyl itaconate, dimethyl maleate, di- n -nonyl fumarate, di- n -nonyl maleate, dioctyl fumarate, di- n -octyl itaconate , Di- n -propyl itaconate, N-dodecyl vinyl ether, acid ethyl fumarate, acid ethyl maleate, ethyl acrylate, ethyl cinnamate, N-ethyl-methacrylamide, ethyl methacrylate, ethyl vinyl Ether, 5-ethyl-2-vinyl-pyridine, 5-ethyl-2-vinyl-pyridine-1 oxide, glycidyl acrylate, glycidyl methacrylate, n -hexyl methacrylate, 2-hydroxy Ethyl meta Relate, 2-hydroxy-propyl methacrylate, isobutyl methacrylate, isobutyl vinyl ether, isoprene, isopropyl methacrylate, isopropyl vinyl ether, itaconic acid, lauryl methacrylate, N-methylol Acrylamide, N-methylol-methacrylamide, N-isobutoxy-ethylacrylamide, N-isobutoxy-methyl-methacrylamide, N-alkyloxy-methylacrylamide, N-alkyloxy-methyl-methacryl Amide, N-vinyl-caprolactam, N-methyl-methacrylamide, α-methylstyrene, m -methyl-styrene, o -methyl-styrene, p -methyl-styrene, 2-methyl-5-vinyl-pyridine , n -propyl methacrylate, sodium p -styrene sulfonate, stearyl methacrylate, styrene, p -styrene sulfonic acid, p -styrenesulfonamide, vinyl bromide, 9-vinyl-carbazole, vinyl chloride, vinylidene chloride , 1-vinyl-naphthalene, 2-vinyl-naphthalene, 2-vinyl-pyridine, 4-bi -Pyridine, 2-vinyl-pyridine N- oxide, 4-vinyl-pyrimidine, N- vinyl-pyrrolidone; And W ₁ , Y ₁ to Y ₄ and R ₁ to R ₃ are the same as those described for (a); (d) consists of condensed polymers made from polymers (a), (b) or (c), and the condensable forms of (a), (b), (c) or mixtures thereof are phenol, tannin, novolac A second compound selected from the group consisting of resins, lignin compounds, and aldehydes, ketones, or mixtures thereof, to condense to produce a condensation resin, which is then added to at least one portion thereof by addition of " Z " React with 1) aldehyde or ketone, and 2) secondary amine to form the final adduct which can react with acid. 13. The method of claim 12 wherein at least one portion of the organopolymer Z group has a polyhydroxy-alkylamine functionality derived from the condensation of a ketose or aldose with an amine or ammonia with 3 to 8 carbon atoms. 13. The method of claim 12 wherein the organic polymer is a condensation product of polyvinyl-phenol having a molecular weight of about 1,000 to about 10,000 with formaldehyde or paraformaldehyde and secondary organic amines. 15. The method of claim 14, wherein the secondary organic amine is selected from methylethanolamine and N-methylglucamine. The phosphate treatment method according to any one of claims 1 to 8, wherein the organic polymer is selected from substituted polyalkylene derivatives of the general formula: (Wherein R ¹ , R ² , R ³ independently represent hydrogen or methyl or ethyl groups, x represents 1, 2, 3, or 4, and Y represents a substituent containing at least one nitrogen atom and incorporated into an alkylamino group or a mononuclear or multinuclear saturated or unsaturated heterocyclic compound.) The phosphate treatment method according to claim 16, wherein R ¹ , R ² , and R ³ each represent hydrogen and x represents 1. 18. The phosphate treatment method according to claim 16 or 17, wherein the organic polymer contains at least one unit of the formula: The phosphate treatment method according to any one of claims 1 to 8, wherein the organic polymer is a high molecular sugar derivative containing an amino group. The phosphate treatment method according to claim 19, wherein the high molecular sugar derivative contains a group represented by the following formula.