EP1606362A2

EP1606362A2 - Nitrogen-containing polymers for metal surface treatment

Info

Publication number: EP1606362A2
Application number: EP04720004A
Authority: EP
Inventors: Frank Dietsche; Helmut Witteler; Matthias KLÜGLEIN; Frank Klippel
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2003-03-13
Filing date: 2004-03-12
Publication date: 2005-12-21
Also published as: US20060162820A1; JP2006520852A; CA2518077A1; WO2004081128A2; US7879158B2; WO2004081128A3; BRPI0407941A; MXPA05008515A; CN1759152A; KR20050115901A; DE10310972A1; JP4357527B2

Abstract

The invention relates to a passivating layer on a metal surface, which can be obtained by bring the metal surface into contact with a composition consisting of a water-soluble, nitrogen-containing polymer; a surface whose structure consists of a metal surface and the inventive passivating layer; a method for forming a passivating layer on a metal surface; the use of a composition consisting of a water-soluble, nitrogen-containing polymer, for passivating a metal surface; and a structure on a metal surface, comprising an inventive passivating layer and other coats of lacquer.

Description

Polymers containing nitrogen for metal surface treatment

The present invention relates to a passivation layer on a metal surface which contains a nitrogen-containing polymer, a method for forming this passivation layer and the use of a composition comprising a water-soluble, nitrogen-containing polymer for passivation of a metal surface, a lacquer structure on a metal surface, comprising the passivation layer mentioned and a Painting and a method for forming this paint structure and a surface made up of a metal surface and the passivation layer according to the invention.

Metallic materials, especially iron and steel, are usually galvanized to protect them from corrosive environmental influences. The protection against corrosion of the zinc is based on the fact that it is even less noble than the metallic material and therefore initially only attracts the corrosive attack, ie it acts as a sacrificial layer. The metallic material itself remains intact as long as it is continuously covered with zinc and the mechanical functionality is retained over longer periods than with non-galvanized parts. The corrosive attack of such a zinc layer can in turn be delayed by applying a passivation layer. This is particularly the case with galvanized parts, both for parts that are subsequently painted and for those that are used without painting. Aluminum surfaces are also often provided with a passivation layer, especially if they are subsequently to be painted. The passivation layer delays the corrosive attack on the metal surface and at the same time serves to improve the adhesion of any lacquer layers to be applied. Instead of the term passivation layer, the term conversion layer is often used synonymously. So far, passivation layers have been obtained on zinc or aluminum surfaces, usually by immersing the workpiece to be protected in aqueous acidic solutions of CrO ₃ . The workpiece is protected against corrosion after immersion and drying. When immersed, part of the metal to be protected dissolves and immediately forms an oxidic film on the metal surface. This film is similar to the oxide film that is already present on many metals, but is denser and better adherent than this. This Cr (VI) treatment is optimal in terms of passivation. The time until white rust formation of an unpainted galvanized sheet is extended by Cr (VT) treatment from less than 1 hour to more than 100 hours.

In order to avoid the use of the extremely toxic and carcinogenic Cr (VI) compounds, passivation with the aid of acidic, aqueous solutions of Cr (III) salts is proposed in EP-A 0 907 762. Due to the application as a so-called "thick layer" with a thickness of 300 to 400 μm, these passivation layers offer excellent corrosion protection.

To avoid the use of heavy metals such as Cr (VI) and also Cr (III), the use of polymers is becoming increasingly important.

For example, DE-A 100 05 113 relates to an application solution which contains phosphoric acid and / or at least one fluoric acid of one or more elements from the group Zr, Ti, Hf and Si or their respective anions and a homo- or copolymer of vinylpyrrolidone and a process for the corrosion protection treatment a metal surface, the metal surface being brought into contact with a homo- or copolymer of vinylpyrrolidone. According to DE-A 100 05 113, known passivation agents based on fluorometalates of Zr, Ti, Hf or Si homo- or copolymers of vinylpyrrolidone are added to improve the corrosion protection.

JP-A 04231679 relates to anti-corrosion agents for surfaces made of copper or copper alloys, the copper surface being first treated with an alcoholic solution containing polyvinylimidazole and then with a solution containing a zinc salt. This treatment of corrosion protection werden- ^'and improves the heat resistance of the copper surface.

DE-A 44 09 306 relates to a method for modifying cleaned or chemically pretreated metal surfaces with aqueous solutions, organic polymers containing amino groups, in particular with polyvinylamines. The object of the present invention is to provide a passivation layer on a metal surface which meets the following requirements:

for many applications, even without subsequent painting, it must have a corrosion-inhibiting effect;

it must not deteriorate the paint adhesion, should preferably improve the paint adhesion, i.e. that the layer should generally not be hydrophobic;

it should be as thin as possible to ensure the dimensional accuracy of the passivated workpieces;

it must still have a corrosion-inhibiting effect even after tempering at temperatures of 120 ° C;

it should be color-neutral with respect to the base metal, but should, if possible, be recognizable by the eye in order to facilitate the detection of defects and to allow a simple distinction between passivated and non-passivated parts;

it should be able to be produced without complicated procedural steps.

It is in particular the object of the present invention to provide particularly thin passivation layers which already show excellent corrosion inhibition.

This object is achieved by a passivation layer on a metal surface, obtainable by bringing the metal surface into contact with a composition which contains a water-soluble, nitrogen-containing polymer, the polymer being a base and an aqueous solution of the polymer with the addition of one or more salts of the base metal forms a precipitate at pH <7.

The passivation layer according to the invention is characterized in that it already has an excellent corrosion-inhibiting effect in the form of a very thin layer. Any metal surface can generally be used as the metal surface. Suitable metal surfaces are generally technically customary materials selected from the group consisting of steel, cast iron, zinc, aluminum, magnesium and alloys of these metals with one another or with other alloy components. Zinc and aluminum as well as alloys of these metals with other alloy components are particularly preferred, a surface of zinc or zinc alloys generally being obtained by a galvanizing process of a metallic material such as iron or steel.

It is conceivable to use metal surfaces that are not pretreated. However, it is preferred that the metal surfaces have at least been cleaned prior to contacting the composition containing a water-soluble, nitrogen-containing polymer. The cleaning preferably includes degreasing the metal surface. Suitable cleaning or degreasing processes are known to the person skilled in the art.

The water-soluble, nitrogen-containing polymer (component A), which is a base and forms a precipitate in aqueous solution when one or more salts of the base metal are added at a pH <7, preferably contains vinylimidazole. The polymer particularly preferably contains> 50% by weight of vinylimidazole and optionally at least one further monomer. For the purposes of the present invention, the term polymer means both homopolymers and copolymers.

The polymer (component A) used according to the invention very particularly preferably contains the following components:

a)> 45% by weight to 100% by weight, preferably> 55% by weight, particularly preferably> 60% by weight of vinylimidazole as component Aa,

b) 0 to <50 wt .-%, preferably <40 wt .-%, particularly preferably <30 wt .-% N-vinyl lactams, other vinyl heteroaromatics, vinyl esters, Cr o-Ajkylacrylate or - methacrylates or a mixture of the monomers mentioned as Component Ab, c) 0 to 5% by weight, preferably <4% by weight, particularly preferably <3% by weight, of mono-ethylenically unsaturated monomers containing acid groups as component Ac.

N-vinyl lactams, for example N-vinyl caprolactam, N-vinyl pyrrolidone and N-vinyl piperidone, are suitable as component Ab, vinyl pyridines and vinyl pyridine N-oxides are suitable as further vinyl heteroaromatics, suitable vinyl esters are, for example, vinyl acetate and vinyl propionate and suitable C 1 -C 4] _. o-Alkyl (meth) acrylates are methyl, ethyl and butyl acrylate or the corresponding methacrylates.

As component Ab, preference is given to using N-vinylcaprolactam, N-vinylpyrrolidone and vinylpyridine.

Monoethylenically unsaturated compounds which contain at least one acid group, for example a carboxyl group, a sulfonic acid group or a phosphonic acid group, are suitable as component Ac. Compounds suitable as component Ac are, for example, acrylic acid, methacrylic acid, dimethacrylic acid, ethyl acrylic acid, crotonic acid, allylacetic acid and vinyl acetic acid. Furthermore, monoethylenically unsaturated dicarboxylic acids are suitable as component Ac, for example maleic acid, fumaric acid, itaconic acid, mesaconic acid, methylene malonic acid, citraconic acid, maleic anhydride, itaconic anhydride and methylene malonic anhydride, the anhydrides usually hydrolyzing to the corresponding dicarboxylic acids when introduced into water. Monomers containing sulfonic acid groups, for example 2-acrylamido-2-methylpropanesulfonic acid, (meth) acrylic acid-3-sulfopropyl ester, vinylsulfonic acid, methallylsulfonic acid and allylsulfonic acid, and monomers containing phosphonic acid groups, such as vinylphosphonic acid, can also be used as component Ac. The monomers mentioned as component Ac can be used either alone or as a mixture with one another.

Ac monomers selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, itaconic acid, 2-acrylarnido-2-methylpropanesulfonic acid, vinylsulfonic acid, acrylic or methacrylsulfonic acid 3-sulfopropyl ester and vinylphosphonic acid are preferably used as component Ac.

The monomers used as component Ac can either be in the form of the free acids or, which is preferred, in the form of their alkali metal, alkaline earth metal or Ammonium salts are used. Preferred alkali metal salts are sodium and potassium salts, preferred alkaline earth salts are magnesium and calcium salts.

In a very particularly preferred embodiment, the water-soluble, nitrogen-containing polymer is homopolyvinylimidazole, i.e. the polymer is composed of 100% by weight of N-vinylimidazole.

The weight average molecular weight (Mw) of the water-soluble, nitrogen-containing polymer used according to the invention is generally 1000 to 1,000,000 g / mol, preferably 10,000 to 150,000 g / mol. In the case of homopolyvinylimidazole used with very particular preference, this has a molecular weight of generally 5,000 to 200,000 g / mol. The molecular weight (Mw) was determined by means of gel permeation chromatography using a polystyrene standard.

Copolymers are generally to be understood as meaning those compounds which have at least 3 repeat units, preferably more than 10 repeat units.

The water-soluble, nitrogen-containing polymer used according to the invention can be produced in any manner known to the person skilled in the art. For example, one is

Production of the polymer by bulk polymerization, suspension polymerization,

Emulsion polymerization or solution polymerization, for example in toluene, water or ethanol. Furthermore, it is possible to prepare the water-soluble, nitrogen-containing polymer used according to the invention by precipitation polymerization from an organic solvent, such as alkanes or cycloalkanes, or in accordance with the process disclosed in DE-A 43 42 281.

The preferably used water-soluble, nitrogen-containing polymer, which is composed of> 50% by weight vinylimidazole and, if appropriate, at least one further monomer, and the very particularly preferably used homopolyvinylimidazole are preferably prepared by a process in accordance with the process disclosed in DE-A 43 42 281 ,

In a preferred embodiment of the present application, the metal surface is preferably brought into contact with a composition containing a) a water-soluble, nitrogen-containing polymer as defined above, as component A;

b) water or another solvent which is suitable for dissolving or dispersing, suspending or emulsifying the polymer (component A) as component B

c) optionally at least one surface-active compound, at least one emulsifier and / or at least one dispersant, as component C.

Component A

The water-soluble, nitrogen-containing polymer used as component A has already been defined above.

In the compositions used according to the invention, this polymer is generally used in an amount of 0.01 to 100 g / 1, preferably 0.01 to 70 g / 1, particularly preferably 0.01 to 50 g / 1, based on 1 1 each Composition used.

Component B

Component B is water or another solvent which is suitable for dissolving or dispersing, suspending or emulsifying the polymer (component A). In the context of the present text, a solvent is understood to mean a liquid matrix in which the various constituents of the composition according to the invention are present as finely as possible. Such a fine distribution can, for example in the sense of a molecularly disperse distribution, be a real solution of the ingredients in the solvent. However, the term "solvent" also includes liquid matrices in which the ingredients are distributed in the form of an emulsion or dispersion, i.e. do not form a molecularly disperse solution.

Examples of suitable solvents are water and water-miscible and water-immiscible solvents. Suitable water-miscible solvents are, for example, primary or secondary mono- or polyalcohols with 1 to about 6 C-

Atoms such as methanol, ethanol, propanol, isopropanol, n-butanol, iso-butanol, pentanol, Hexanol, cyclohexanol or glycerin. Also suitable as water-miscible solvents are low molecular weight ketones such as acetone or methyl ethyl ketone or ether alcohols such as diethylene glycol or triethyl glycol. Also suitable in the context of the present invention are solvents which are immiscible or only slightly miscible with water. These include, for example, ethers such as diethyl ether, dioxane or tetrahydrofuran, aromatic solvents such as toluene or xylene, halogenated solvents such as dichloromethane, chloroform or carbon tetrachloride and optionally substituted aliphatic solvents, which include, for example, the higher homologues of the abovementioned alcohols and ketones and paraffin hydrocarbons.

The solvents mentioned above can be used individually or as a mixture of two or more of the solvents mentioned. In a preferred embodiment of the present invention, water is used as the solvent, optionally in a mixture with one or more of the above-mentioned, preferably water-soluble solvents. If, within the scope of the present invention, a solvent is to be used which contains water and a water-immiscible solvent, the solvent can, for example, contain an emulsifier in order to enable an essentially stable W / O or O / W emulsion.

If the composition according to the invention contains a mixture of water and a further water-miscible solvent, the proportion of water in such a mixture is preferably at least about 30% by weight or more, for example at least about 40 or at least about 50% by weight. In the context of a particularly preferred embodiment of the present invention, the water content is at least about 75% by weight. Suitable combinations of water and water-miscible solvents are, for example, water / methanol, water / ethanol, water / propanol or water / isopropanol. A mixture of water and ethanol is preferred in the context of the present invention, the water content preferably being greater than about 75% by weight, for example greater than about 80 or about 85% by weight.

In the context of a preferred embodiment of the present invention, a composition according to the invention contains at least one solvent which has a water content of at least about 50% by weight.

Water is particularly preferably used as the solvent. The composition preferably used according to the invention as an aqueous solution generally has a pH of from 1 to 6, with narrower pH ranges being chosen depending on the substrate and type of application and the duration of action of the composition used according to the invention on the surface of the base metal. For example, the pH value for the treatment of bare metal surfaces is preferably set to the range from 2 to 6, for the treatment of aluminum surfaces preferably to the range from 2 to 4 and for the treatment of steel, zinc or galvanized steel preferably to the range from 3 to 6 5 a. Surfaces of a base metal that have already been pretreated and which, for example, carry a phosphate layer, are preferably brought into contact with a composition used according to the invention having a pH of 3.5 to 5.

The amount of water or another solvent depends on whether the composition according to the invention is a ready-to-use composition or a concentrate, and on the particular application. Basically, the quantity results from the concentrations of the individual components specified for the ready-to-use composition.

Component C

If appropriate, the composition according to the invention can additionally contain surface-active compounds, emulsifiers and / or dispersants. Suitable surface-active compounds are surfactants, which can be cationic, anionic, zwitterionic or nonionic. Suitable surfactants are, for example, alkyl and alkenyl alkoxylates of the R-EO _n / PO _{m type,} where R is generally linear or branched C ₆ -C ₃ o-alkyl radicals, preferably C ₈ -C ₂₀ -alkyl radicals and EO for an ethylene oxide unit and PO stands for a propylene oxide unit, where EO and PO can be arranged in any order and n and m are independently> 1 and <100, preferably> 3 and <50, for example E ulan®, Lutensol® and Plurafac® (der BASF), alkylphenol ethoxylates, EO / PO block copolymers (Pluronic®, from BASF), alkyl ether sulfates and alkyl ammonium salts, so-called quats.

The amount of these components in the composition according to the invention is generally 0.01-100 g / 1, preferably 0.1 to 20 g / 1. In a preferred embodiment, the composition used according to the invention contains, in addition to components A, B and optionally C:

d) at least one salt, an acid or a base based on transition metal cations, transition metal oxo anions, fluorometalates or

Lantanoids as component D, and / or

e) at least one acid selected from the group consisting of phosphoric acid, sulfuric acid, sulfonic acids, nitric acid, hydrofluoric acid and hydrochloric acid as

Component E and / or f) at least one further corrosion inhibitor as component F, and / or

g) compounds of Ce, Ni, Co, V, Fe, Zn, Zr, Ca, Mn, Mo, W, Cr and / or Bi as component G, and / or

h) further auxiliaries and additives as component H.

These compositions are suitable for passivating, in particular phosphating, the metal surfaces mentioned in the present application.

Component D

Suitable as component D are salts, acids and bases based on transition metal cations, transition metal oxo anions, fluorometalates or lanthanoids. Suitable transition metal cations are, in particular, fluorometalates of Ti (IV), Zr (IV), Hf (IV) and / or Si (IV), suitable lanthanides, in particular Ce. Tungsten and molybdates are also suitable.

Compositions according to the present application containing component D are particularly suitable for either a corrosion-protective layer on a

To deposit the metal surface or to reinforce the anti-corrosion effect of a corrosion layer already deposited on the metal surface. The Polymers used according to the invention (component A) have an excellent corrosion protection effect in the compositions according to the invention. In general, the use of component A in the compositions used according to the invention leads to such good corrosion protection properties that the addition of component D is not necessary. In a particularly preferred embodiment, compounds of component D are therefore not contained in the compositions used according to the invention.

The amount of component D is - if component D is contained in the compositions according to the invention - preferably 0.02 to 20 g / 1.

Component E

In addition to or instead of component D, the compositions according to the invention can also contain at least one acid selected from the group consisting of phosphoric acid, sulfuric acid, sulfonic acids such as methanesulfonic acid, vinylsulfonic acid, allylsulfonic acid, m-nitrobenzenesulfonic acid, naphthalenesulfonic acid and derivatives thereof, nitric acid, hydrofluoric acid and hydrochloric acid. The type of acid used depends on the type of treatment of the metal surface. For example, phosphoric acid is generally used in phosphating baths for phosphating steel surfaces. In this case, the composition used according to the invention is a phosphating solution. A distinction is made between so-called "non-layer-forming" phosphating solutions, which are solutions that have no divalent metals. Such "non-layer-forming" phosphating solutions are, for example, in the form of an iron phosphating solution. Do the phosphating solutions contain ions of divalent metals, e.g. B. zinc and / or manganese, the phosphating ^{solutions ■ are available} as so-called "forming" phosphating solutions. Compositions containing nitric acid according to the present application are particularly suitable for the surface treatment of zinc and its alloys, while hydrofluoric acid-containing compositions are particularly suitable for the surface treatment of aluminum and its alloys.

The amount of acid used can vary depending on the application. In general, if component E is contained in the compositions according to the invention, 0.2 to 200 g / 1, preferably 2 to 100 g / 1, of component E are used. Component F

In addition to or instead of components D and / or E, the compositions used according to the invention can contain at least one further corrosion inhibitor. Suitable corrosion inhibitors are selected from the group consisting of butynediol, benzotriazole, aldehydes, amine carboxylates, amino and nitrophenols, amino alcohols, aminobenzimidazole, aminoimidazolines, aminotriazole, benzimidazolamines, benzothiazoles, derivatives of benzotriazole, various boranol acid esters, such as boranol acid esters, with boronic acid amines such as boronic acid amines, such as boronic acid amines, such as boronic acid amines, such as boronic acid amines, such as boronic acid amines, such as boronic acid amines, such as boronic acid amines, such as boronic acid amines, such as boronic acid amines, such as boronic acid amines, such as boronic acid amines and carboxylic acid esters, , Quinoline derivatives, dibenzyl sulfoxide, dicarboxylic acids and their esters, diisobutenylsuccinic acid, dithiophosphonic acid, fatty amines and fatty acid amides, guanidine derivatives, urea and its derivatives, laurylpyridinium chloride, maleic acid amides, mercaptobenzimidazole, N-2-ethylaminosulfonamide, sodium-3-ethylaminosulfoneamine, sodium-3-ethylaminosulfonamide, neutralized phosphoric acid esters of alkyl alcohols and these phosphoric acid esters themselves, phosphoric acid esters of polyalkoxylates and here in particular of polyethylene glycol, polyetheramines, sulfonium ms salts, sulfonic acids such as methanesulfonic acid, thioethers, thioureas, thiuramide sulfides, cinnamic acid and their derivatives, zinc phosphates and silicates, zirconium phosphates and silicates.

Butynediol and benzotriazole are preferably used as further corrosion inhibitors.

The corrosion inhibitors, if they are used at all in the compositions, are used in an amount of generally 0.01 to 50 g / 1, preferably 0.1 to 20 g / 1, particularly preferably 1 to 10 g / 1.

Component G

In addition to or optionally instead of the components mentioned, compounds of Ce, Ni, Co, V, Fe, Zn, Zr, Ca, Mn, Mo, W, Cr and / or Bi can also be used. In general, the use of component A according to the invention in the compositions leads to such good corrosion protection properties that the addition of the compounds mentioned is not necessary. The compositions used according to the invention are preferably Cr (VI) -free, particularly preferably the compositions used according to the invention contain no compounds according to Component G. If the compounds mentioned (component G) are nevertheless used, preference is given to using compounds selected from Fe, Zή, Zr and Ca. The amount of these compounds in the compositions is - if these compounds are present at all - generally 0.01 to 100 g / 1, preferably 0.1 to 50 g / 1, particularly preferably 1 to 20 g / 1.

Component H

In addition to or instead of one or more of the components D to G listed, the compositions used according to the invention can contain further auxiliaries and additives. Suitable auxiliaries and additives include conductivity pigments or conductive fillers e.g. Iron phosphide, vanadium carbide, titanium nitride, carbon black, graphite, molybdenum disulfide or barium sulfate doped with tin or antimony, with iron phosphide being preferred. Such conductivity pigments or conductive fillers are added to the compositions used according to the invention to improve the weldability of the metal surfaces to be treated or to improve a subsequent coating with electrocoat materials. In addition, silica suspensions can be used, in particular when the compositions are used to treat aluminum-containing surfaces.

These additives are generally in finely divided form, i.e. their average particle diameters are generally 0.005 to 5 μm, preferably 0.05 to 2.5 μm. The amount of auxiliaries and additives is generally 0.1 to 50, preferably 2 to 35% by weight, based on the total mass of the compositions according to the invention.

The compositions used according to the invention may further contain additives to improve the forming behavior, for example wax-based derivatives based on natural or synthetic waxes, e.g. Waxes based on acrylic acid, polyethylene, polytetrafluoroethylene (PTFE) waxes or wax derivatives or paraffins and their oxidation products.

Depending on their field of application, the compositions used according to the invention can contain polymer dispersions based on styrene, 4-hydroxystyrene, butadiene, acrylic acid, acrylic acid esters, acrylic acid amides, acrylates, methacrylic acid, Contain methacrylic acid esters, methacrylic acid amides, methacrylates and derivatives of acrylamide. It is also possible that the compositions used according to the invention contain polyurethane dispersions and polyester urethane dispersions or polyurea dispersions.

Another group of compounds which can be present in the compositions used according to the invention are polyethylene glycols, polypropylene glycols, copolymers of ethylene oxide and copolymers of propylene oxide.

The compositions used according to the invention are used for passivation (conversion layer formation), in particular no-rinse conversion layer formation, that is to say processes with a reduced number of rinsing operations, for example on galvanized steel and aluminum. The passivation layer according to the invention is formed on the metal surface.

The compositions used according to the invention can optionally additionally contain a complexing agent as component I. Suitable complexing agents are e.g. Ethylenediaminetetraacetic acid (EDTA), ethylenediamine (ED), citric acid and salts of the compounds mentioned.

Furthermore, the compositions used according to the invention can optionally contain at least one acid or an alkali metal or alkaline earth metal salt of the corresponding acid, preferably selected from the group consisting of HNO ₃ , H ₂ SO ₄ , H ₃ PO ₄ , formic acid and acetic acid as component K. The acid is generally used in an amount of 0.5 to 700 g / 1, preferably 5 to 280 g / 1.

In addition to the components mentioned, the compositions used according to the invention can contain further additives as component L. Suitable additives are 1- (2-methylpyridinium) -2-ethylsulfobetaine, 1,1-dimethyl-2-propynyl-1-εumin, 1-pyridinium-2-ethylsulfobetaine, 1-pyridinium-2-hydroxy-3 - propylsulfobetaine, 1-pyridinium-3-propylsulfobetaine, 2,2'-dichlorodiethyl ether, 2,5-dimethyl-3-hexyne-2,5-diol, 2-butyne-l, 4-diol, 2-butyne-l , 4-diol ethoxylate, 2-butm-l, 4-dio_propoxylate, 3- (2-benzothiazolylthio) -l-propane-sulfonic acid Na salt, 3,3'-dithio-bis- (l-propane sulfonic acid) -Na- Salt, 3 [(aminoimino-methyl] thiol] -1-propanesulfonic acid, 3 - [(dimethylammo) -tMoxome ylthio] - 1-propansulfonic acid Na salt, 3- [Eώoxy-tMoxomemylthio] - l-propanesulfonic acid K salt, 3-chloro-2-hydroxy-1-propanesulfonic acid Na salt, 3-hexin-2,5-diol, 3-mercapto-1 - propane sulphonic acid Na salt, 4,4'-dihydroxydiphenyl sulfone, 4-mefhoxybenzaldehyde, aldehydes, alkylphenyl polyethylene oxide sulfopropyl ether K salts, alkyl polyethylene oxide sulfoproyl ether K salts such as tridecyl / pentadecyl polyethylene sulfonyl sulfonyl allyl ether kly salts salt, amidosulfonic acid, amine- and sodium-neutralized phosphoric acid esters of alkyl alcohols, amine carboxylates, amino and nitrophenols, amino alcohols, aminobenzimidazole, aminoimidazolines, aminotriazole, benzylacetoacetic acid methyl ester, benzylacetone, berizimidazolaniidene, benziazylphenolidine, benzothiazole bis, benziaziazole bis , Boric acid esters with various alkanolamines such as, for example, boric acid diethanolamine esters, carboxylic acids and their esters, carboxyethyl isoturonium betaine, quinoline derivatives, copolymers of ethylene and acrylic acid, copolymers of hnidazole and epichlorohydrin, copolymers of imidazole, morpholine and epichlorohydrin, copolymers of N, (dime thylarnino) propyl] urea and l, -Oxybis- [2-chloroethane], copolymers of n-butyl acrylate, acrylic acid and styrene, dibenzyl sulfoxide, dicarboxylic acids and their esters, diethylenetriaminepentaacetic acid and salts derived therefrom, Diisobutenylbemsteinsäure, Dmatriumemylenbisdithiocarbamat, dithiophosphonic acid, Ethylamidosulfonsäure, ethylenediaminetetraacetic and salts derived therefrom, ethylglycinediacetic acid and salts derived therefrom, ethylhexanolethoxylate, fatty amines and fatty acid amides, formaldehyde, glycerolethoxylate, guanidine derivatives, urea and its derivatives, hydroxyethyliminodiacetic acid and salts derived therefrom, imidazole, isopropylamidosulfonic acid, laurylimidylchloride, isulphonyl chloride, isopropyl amidyl chloride, isopropyl amidonyl chloride, isopropyl amidyl chloride, isopropyl amidyl chloride, isopropyl amidyl chloride, isopropyl amidyl chloride, isopropyl amidyl chloride, isopropyl amidyl chloride, isopropyl amidyl chloride, isulfonyl chloride, isopropyl amidyl chloride, isopropyl amidyl chloride, and isopropyl amidonyl chloride, isopropyl amidyl chloride, sulfonyl chloride, -Methosulfate, lauryl pyridinium chloride, maleic acid amides,

Mercaptobenzimidazole, methylamidosulfonic acid, N, N, N ', N'-tetrakis (2-hydroxypropyl) -emylenedi_unin, N, N-diethyl-2-propyne-l-amine, N, N-diethyl-4-amino-2-butyne -l-ol, N, N-dimethyl-2-propyne-l-amine, N-2-Emyexyl-3-aminosulfo-propionic acid, N-allyl-pyridinium chloride, Na salt of sulfated alkylphenol ethoxylates, sodium 2-ethylhexyl sulfate, Nicotinic acid, nitrilotriacetic acid and salts derived therefrom, nitrobenzenesulfonic acid sodium salt, N-methallylpyridmium chloride, ortho-chlorobenzaldehyde, phosphonium salts, phthalic acid amides, picolinic acid, polyeramine, polyethyleneimine, polyvinylimidazole, propargyl alcohol propanol, propanol alcohol propyl alcohol, propanol alcohol, propanol alcohol Propylene diamine tetraacetic acid and salts derived therefrom, pyrrole, quaternized polyvinylimidazole, reaction product from 2-butyne-1,4-diol and epichlorohydrin, reaction product from 2-butyne-1,4-diol and propane sultone, reaction product from saccharin and propane sultone, reaction product from alky l-ethoxylate / propoxylate with propane sultone, reaction product of polyethylene imine with propane sultone, reaction product of ß-naphthol ethoxylate / propoxylate with propane sultone, resorcinol ethoxylate, saccharin, ß-naphthol ethoxylate, ß-naphthol ethoxylate sulfate Na salt, Sulfonium salts, sulfonic acids such as methanesulfonic acid, thiodiglycol, Thiodiglykolethoxylat, thioethers, thioureas, Thiuramidsulfide, vinyl sulfonic acid sodium salt, cinnamic acid and its derivatives, zinc phosphates and silicates, zirconium and - silicates, hypophosphites (such as sodium hypophosphite), NaBH _4, Dimemylaminoboran, Diethylaminoboran , Hydrazine, formaldehyde, urotropin, palladium chloride, sodium stannate, HF _X BF ₃ , polyethylene glycols with a molecular weight of 100-1000000 g / mol, block copolymers of ethylene oxide and propylene oxide, for example Pluronic brands from BASF Aktiengesellschaft, Ludwigshafen / RJ .., and statistical copolymers of ethylene oxide and propylene oxide, in particular with molecular weights in the range 100-2000 g / mol.

In a very particularly preferred embodiment, the passivation layer according to the invention contains, apart from the water-soluble nitrogen-containing polymer, metal ions of the base metal, in particular aluminum and zinc or alloy metal ions of alloy metals with aluminum or zinc, no further metals. This means that the compositions used to produce the passivation layer contain no metals or metal compounds. Even without the addition of further metals or metal compounds, when using the water-soluble, nitrogen-containing polymers according to the present application, passivation layers are obtained which have excellent corrosion stability.

The layer thickness of the passivation layer according to the invention formed on the surface of a base metal is preferably <3 μm. The layer thickness is particularly preferably 0.01 to 3 μm, very particularly preferably 0.1 to 3 μm. The thickness of the layer is determined by differential weighing before and after the action of the composition used according to the invention on the metal surface, on the assumption that the layer has a specific density of 1 kg / 1. In the following, “layer thickness” is always understood to mean a size determined in this way, regardless of the specific density of the layer. These thin layers are sufficient to achieve excellent corrosion protection. Such thin layers ensure the dimensional accuracy of the passivated workpieces.

Another object of the present application is a surface made up of a metal surface and a passivation layer according to the present application. Suitable and preferably used metal surfaces and preferred embodiments of the passivation layer have already been mentioned above. Another object of the present application is a method for forming the passivation layer according to the invention on a metal surface, the metal surface being brought into contact with a composition as defined in accordance with the present application. Suitable compositions and preferred embodiments of suitable compositions have already been mentioned above. Suitable metal surfaces and preferred embodiments of the metal surfaces have also already been mentioned above.

The water-soluble, nitrogen-containing polymer used according to the invention can be present in solution, emulsion, suspension or as an aerosol in the process according to the invention. The polymer (component A) is preferably present in the compositions used in the process according to the invention in aqueous solution.

The type of application corresponds to the usual technical methods. The metal surface is preferably brought into contact with compositions used according to the invention by spraying the composition onto the metal surface or by dipping the metal surface into the composition. The particularly preferred application method used depends on the number, size and shape of the parts to be treated. Accordingly, the contacting is preferably carried out by means of a spraying, rolling or dipping process.

If the passivation layer according to the invention is applied to metal strips by phosphating, compositions according to the present application containing phosphoric acid as component E can be applied by a “roll-on” or “dry-in-place” or “no-rinse” method are, wherein the phosphating composition used according to the invention is applied to the metal strip and dried without rinsing, a polymer film being formed.

Another subject of the present application is a method comprising the steps:

a) optionally cleaning the metal surface to remove oils, greases and dirt, b) optionally washing with water, c) optionally pickling to remove rust or other oxides, d) optionally washing with water, e) contacting the metal surface with a composition containing a water-soluble, nitrogen-containing polymer, the polymer being a base and an aqueous solution of the polymer upon addition of one or more salts of the metal of the metal surface at a pH <7, a precipitate forms (component A), f) optionally washing with water, g) optionally aftertreatment.

The contacting of the metal surface with the water-soluble, nitrogen-containing polymer used according to the invention is the passivation step, in particular a phosphating step, which is carried out by methods known to the person skilled in the art. The passivation layer according to the invention is formed on the metal. If in step e)

After phosphating, post-treatment of the metal surface in g) with passivating additives is possible.

Preferred water-soluble, nitrogen-containing polymers (component A) have already been named above.

Washing with water takes place between the individual process steps in order to avoid contamination of the solution required for the subsequent step with components of the solution used in the previous step.

However, it is also conceivable to carry out processes according to the invention as a “no-rinse process”, i.e. without steps b), d) and f).

In the so-called "no-rinse" process, the composition used according to the invention is generally either sprayed onto the metal surface or transferred onto the surface by application rollers. This is followed by an exposure time which is generally in the range from 2 to 20 seconds, without further action Intermediate rinsing a drying of the composition used according to the invention, for example in a heated oven.

The steps of cleaning (step a)) and contacting the metal surface in the presence of the water-soluble, nitrogen-containing polymer (component A) (step e)) used according to the invention can also be carried out in one step, ie with a formulation which, in addition to the customary cleaning agents also contains the composition used according to the invention. The process according to the invention is generally carried out at a temperature of 5 to 100 ° C., preferably 10 to 80 ° C., particularly preferably 15 to 45 ° C.

Another object of the present application is the use of a composition containing a water-soluble, nitrogen-containing polymer, the polymer being a base and an aqueous solution of the polymer forming a precipitate when one or more salts of the metal on the metal surface are added at a pH <7 , for passivation of a metal surface. Compositions which are preferably used and polymers (component A) which are preferably used in the compositions have already been mentioned above. Metal surfaces which are preferably used and processes which are preferably carried out for passivating the metal surfaces have likewise already been mentioned above.

Following the method for forming a passivation layer on a metal surface, the metal surface provided with the passivation layer according to the invention can be provided with a varnish after the method steps a) to g). The painting is carried out according to methods known to those skilled in the art. For example, a powder coating or an electrolytic, in particular cathodic, dip coating can be used as the coating.

Another object of the present application is thus a lacquer build-up on a metal surface comprising at least one passivation layer X according to the invention and at least one lacquer layer, preferably several lacquer layers, as layer (s) Y.

The passivation layer and preferred embodiments of the passivation layer have already been mentioned above. Suitable layers of lacquer are known to the person skilled in the art.

The lacquer structure according to the invention can contain a multi-layer lacquer coating (several lacquer layers) with further layers. For example, a multi-layer coating can be constructed from at least one of the following layers, which can typically be arranged as follows:

• a pigmented and / or layer W provided with effect substances, • a layer Z selected from the group of primers, basecoat, primer, pigmented lacquer or lacquer provided with effect substances. Basically, all lacquers which are customary for these purposes and are known to the person skilled in the art are suitable as color and / or effect lacquers in the layer Z and / or W. These can be curable physically, thermally, with actinic radiation or thermally and with amine radiation (dual-cure). They can be conventional basecoats, waterborne basecoats, essentially solvent-free and water-free liquid basecoats (100% systems), essentially solvent-free and water-free solid basecoats (pigmented powder coatings) or essentially solvent-free pigmented powder coating dispersions (powder slurry basecoats). They can be thermally or DualCure-curable, and self- or externally cross-linking.

One or more, preferably 1 to 3, particularly preferably 1 to 2 and very particularly preferably a coloring and / or effect-imparting lacquer can be used in the layers.

Essentially solvent-free means that the coating material in question has a residual volatile solvent content of <2.0% by weight, preferably <1.5% by weight and particularly preferably <1.0% by weight. It is of particular advantage if the residual content is below the gas chromatographic detection limit.

Water-based paints such as those described in patent applications EP 0 089 497 AI, EP 0 256 540 AI, EP 0 260 447 AI, EP 0 297 576 AI, WO 96/12747, EP 0 523 610 AI, EP are particularly preferably used in the multi-layer coatings 0 228 003 AI, EP 0 397 806 AI, EP 0 574 417 AI, EP 0 531 510 AI, EP 0 581 211 AI, EP 0 708 788 AI, EP 0 593 454 AI, DE-A-43 28 092 AI, EP 0 299 148 AI, EP 0 394 737 AI, EP 0 590 484 AI, EP 0 234 362 AI, EP 0 234 361 AI, EP 0 543 817 AI, W095 / 14721, EP 0 521 928 AI, EP 0 522 420 AI, EP 0 522 419 AI, EP 0 649 865 AI, EP 0 536 712 AI, EP 0 596 460 AI, EP 0 596 461 AI, EP 0 584 818 AI, EP 0 669 356 AI, EP 0 634 431 AI, EP 0 678 536 AI, EP 0 354 261 AI, EP 0 424 705 AI, WO 97/49745, WO 97/49747, EP 0 401 565 AI or EP 0 817 684, column 5, lines 31 to 45, are known.

The color and / or effect coatings described above can be used not only for the production of color and / or effect base coatings, but also for color and / or effect combination effect layers. This is to be understood as a coating which fulfills at least two functions in a color and / or effect multi-layer coating. Functions of this type are, in particular, protection against corrosion, the imparting of adhesion, the absorption of mechanical energy and the coloring and / or effects. Above all, it serves Combination effect layer of the absorption of mechanical energy and the coloring and / or effect at the same time; it therefore fulfills the functions of a filler paint or stone chip protection primer and a base coat. The combination effect layer preferably also has a corrosion protection effect and / or an adhesion-promoting effect.

Typical thicknesses of the layer (W) and / or (Z) range from 0.1 to 2000 μm, preferably 0.5 to 1000 μm, particularly preferably from 1 to 500 μm, very particularly preferably from 1 to 250 μm and in particular from 10 up to 100 μm.

The lacquers which can be used in the multi-layer lacquers can contain coloring and / or effect pigments. All paint-typical pigments of organic or inorganic nature are suitable as color pigments. Examples of inorganic or organic color pigments are titanium dioxide, micronized titanium dioxide, iron oxide pigments, carbon black, azo pigments, phthalocyanine pigments, quinacridone and pyrrolopyrrole pigments.

The effect pigments are particularly characterized by a platelet-like structure. Examples of effect pigments are: metal pigments, e.g. made of aluminum, copper or other metals; Interference pigments, e.g. metal oxide coated metal pigments, e.g. titanium dioxide coated or mixed oxide coated aluminum, coated mica, e.g. titanium dioxide coated mica and graphite effect pigments. UV-curable pigments and, if appropriate, also fillers can advantageously be used, for example to improve the hardness. These are with radiation-curable compounds, e.g. acrylic functional silanes, coated pigments / fillers, which can thus be included in the radiation hardening process.

The paint structure according to the invention is generally carried out by a method comprising the steps:

a) formation of a passivation layer X according to a method for forming the passivation layer; b) painting the passivation layer,

manufactured.

A method for forming the passivation layer and preferred embodiments of this method have already been mentioned above. Suitable coating processes as step b) are known to the person skilled in the art. The following examples further illustrate the invention.

Examples

Comparative Examples:

Test sheets (galvanized steel, 20 μm zinc) were passivated using a passivation method mentioned in Table 1. The service life was determined in the salt spray test.

salt spray test

The result of a salt spray test in accordance with DIN 50021 serves as a measure of the corrosion-inhibiting effect. Depending on the type of corrosion damage observed, the service life in the corrosion test is defined differently.

If white spots generally form more than 1 mm in diameter (Zn or Al oxide, so-called white rust), the service life is specified as the time after which the damage pattern has reached rating grade 8 in DIN EN ISO 10289 from April 2001, Appendix B, page 19.

If black spots generally less than 1 mm in diameter (especially on zinc with a passivation layer) form before white rust spots form, the service life is indicated as the time after which the damage pattern has reached rating grade 8 in DIN EN ISO 10289 from April 2001, Appendix

A, page 9.

Table 1

The reagents mentioned in Table 2 are dissolved with the concentration C in 0.1% HNO ₃ . Test sheets (galvanized steel, 20 μm zinc) are immersed in the solution for 1 minute and dried by hanging overnight. The layer thickness D is partially determined by differential weighing. The service life is determined in the salt spray test.

differential weighing

The thickness of the layer is determined by differential weighing before and after the composition used according to the invention has acted on the metal surface and on the assumption that the layer has a specific density of 1 kg / l. In the following, “layer thickness” is always understood to mean a size determined in this way, regardless of the specific density of the layer.

Table 2

When comparing non-treated and treated (i.e. provided with a passivation layer according to the invention), a tripling of the service life in the corrosion test is understood as a reliable indication of the corrosion-inhibiting effect.

Immersion at a higher temperature (e.g. at 60 ° C) or in more concentrated solutions, even in nitric acid of a different concentration compared to the examples mentioned above, can further improve the service life in the corrosion test. An increase in the concentration of the polymer leads to an increase in the service life. The concentration of the polymer is preferably <5% by weight.

An aqueous zinc chloride solution forms a white, insoluble precipitate with aqueous polyvinylimidazole solution over wide concentration ranges, generally from as little as 0.5% by weight of the polymer.

* The K value is the Fikentscher constant for identifying the average molecular weight, cf. H.-G. Elias, Macromolecules Vol. 1, 5th Edition, Hüthig & Wepf Verlag, Basel 1990, page 99.

Claims

claims

1. Passivation layer on a metal surface obtainable by contacting the metal surface with a composition containing a water-soluble, nitrogen-containing polymer, the polymer being a base and an aqueous solution of the polymer upon addition of one or more salts of the metal to the metal surface at a pH - Value <7 forms a precipitation.

2. Passivation layer according to claim 1, characterized in that the water-soluble, nitrogen-containing polymer is composed of> 45% by weight of vinylimidazole and optionally at least one further monomer.

3. Passivation layer according to claim 2, characterized in that the water-soluble, nitrogen-containing polymer is homopolyvinylimidazole.

4. passivation layer according to one of claims 1 to 3, characterized in that the layer thickness of the passivation layer is <3 microns.

5. passivation layer according to claim 5, characterized in that the layer thickness is 0.01 to 3 microns.

6. Surface composed of a metal surface and a passivation layer according to one of claims 1 to 5.

7. A method of forming a passivation layer on a metal surface, the metal surface being brought into contact with a composition according to any one of claims 1 to 3.

8. The method according to claim 7, characterized in that the contacting is carried out by spraying, rolling, or dipping processes.

9. Use of a composition according to one of claims 1 to 3 for passivation of a metal surface.

10. Structure on a metal surface comprising a passivation layer X according to one of claims 1 to 5 and further lacquer layers Y

11. A method for forming a lacquer structure according to claim 11, comprising the steps of: a) forming a passivation layer X according to a method

Claim 7 or 8; b) painting the passivation layer.