EP2625310A1

EP2625310A1 - Method for passivating a metallic surface using a basic composition

Info

Publication number: EP2625310A1
Application number: EP11764545.7A
Authority: EP
Inventors: Achim Fessenbecker; Bernd Laubusch; Oihana Elizalde
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2010-10-05
Filing date: 2011-10-04
Publication date: 2013-08-14
Also published as: JP2013540204A; RU2013119807A; AU2011311640A1; KR20130116251A; BR112013008029A2; CN103237923A; WO2012045725A1

Abstract

A method for passivating a metallic surface by treating the surface with a basic aqueous composition containing a polymer comprising acid groups, a cationic crosslinker and a volatile basic compound makes possible a permanent passivation of sensitive metal surfaces.

Description

Method for passivating a metallic surface with a basic composition

description

The present invention relates to a method of passivating a metallic surface using an aqueous basic composition containing an acid group-comprising polymer, a cationic crosslinker and a volatile basic compound.

A further subject of the present invention is an aqueous, basic composition for the passivation of a metallic surface, wherein the composition contains an acid group-comprising polymer, a cationic crosslinker and a volatile basic compound. The invention also relates to the use of the composition for passivating a metal surface.

Likewise, the present invention relates to a coating on a metallic surface obtainable by the method according to the invention. Metallic materials, especially iron and steel, are usually galvanized to protect them from corrosive environmental influences. The corrosion protection of zinc is based on the fact that it is less noble than the metallic material itself and therefore first itself corroded. Since the zinc layer itself is also subject to corrosion (white rust), the corrosive attack on such a zinc layer is often delayed by applying a so-called passivation layer. The passivation layer is intended to delay the corrosive attack on the metal surface and at the same time serve to improve adhesion of paint layers that may be applied. Instead of the term passivation layer, the term conversion layer is often used interchangeably.

Passivation layers are applied, for example, to galvanized metal parts (e.g., galvanized or hot-galvanized substrates) which are subsequently painted. The application also takes place in those parts that are used without painting. Similarly, metallic surfaces of aluminum or aluminum alloys are often provided with a passivation layer, especially if they are to be subsequently painted.

For the production of flat, metallic workpieces, such as automotive parts, body parts, equipment panels, facade cladding, Deckenverkleidungen or window profiles, are used as raw material today usually long metal bands used, which are formed by suitable techniques to the desired moldings and / or assembled.

The corrosion protection treatment of such metallic materials is usually carried out in multi-stage processes. The surface of treated metals often has several different layers. Anti-corrosive treatment can be performed at various points in the manufacturing process. This can be both temporary corrosion protection as well as permanent corrosion protection. For example, temporary protection will only be used to store or transport the metallic workpiece, e.g. of the metal strip, applied and removed again before final processing.

Technically and economically of particular importance are tapes with a galvanized surface, in particular tapes of galvanized or hot-dip galvanized iron or iron alloys such. Stole. Also important are metal strips made of aluminum or aluminum alloys.

As a rule, one or more additional coating layers are applied to the passivated surface. They serve, for example, to protect the passivation layer and the metal from corrosive gases and / or liquids and / or from mechanical damage (such as rockfall). It can also serve aesthetic purposes. Coating layers are usually much thicker than passivation layers. Typical thicknesses for a layer of paint range from 4 μηι to 400 μηι.

In the prior art, passivation layers on zinc or aluminum surfaces were usually prepared by treating the workpiece to be protected with aqueous acid solutions of chromates (eg CrO ₃ ) or acidic aqueous solutions of Cr (III) salts (see EP-A 0 907 762).

In the presence of atmospheric oxygen, a thin layer of oxide usually forms on the surface of zinc or zinc alloys, aluminum or aluminum alloys, slowing down the corrosive attack on the underlying metal. Typically, in the passivation processes based on chromium compounds, this existing oxide film and a portion of the metal to be protected dissolves, and is at least partially incorporated into a film on the metal surface.

This film is similar to the naturally occurring oxide film and usually contains specifically introduced phosphate, heavy metals and / or fluorides. The resulting passivation or conversion layers are said to effectively protect the underlying metal from corrosive attack. More recently, passivation processes have also been developed, for example, for metal-coated steel sheets and piece goods (eg hot-dip galvanized steel) based on polymers as organic film formers. In this case, acidic aqueous solutions of various film-forming polymers, which have, for example, carboxyl, phosphoric acid and / or phosphonic acid groups, are used to form the passivation layer. After applying the acidic formulation, typically the metal surface (eg, zinc) is solubilized and polyvalent metal ions (eg, Zn ²⁺ ) are liberated. Typically, the pH increases near the metal surface. It usually comes to crosslinking and filming of the acidic polymers with the polyvalent metal ions.

Since the described passivation process using acidic polymers avoids the use of heavy metals such as chromium, these polymer-based passivation processes are becoming increasingly important. In the prior art, various mostly acidic passivation formulations are known, which generally contain a water-soluble, acid group-containing, film-forming polymer. Also, methods for passivation using these preparations have been described

DE-A 195 16 765 relates to a process for producing conversion coatings on surfaces of zinc or aluminum by treatment with an acidic solution containing an organic film former and aluminum ions in the form of a water-soluble complex with chelating carboxylic acids and phosphoric acids. Organic film formers are polymers containing carboxyl groups, in particular homopolymers and / or copolymers of acrylic and / or methacrylic acid.

WO 2004/074372 describes the passivation of metallic surfaces using copolymers containing acrylic acid and vinylphosphonic acid and / or maleic acid, it being possible for the passivation formulation to comprise further components.

WO 2008/012248 describes acidic formulations for passivating metallic surfaces containing co-polymers composed of monomethacrylic acid esters having hydrophobic groups (e.g., hydroxyethyl acetate), monomers having phosphonic acid groups (e.g., vinylphosphonic acid), and monomers having carboxyl groups (e.g., acrylic acid).

WO 2006/134116 describes a process for the passivation of metallic surfaces by treatment of the surface with an aqueous composition containing acid group-containing polymers and polyvalent cations such as zinc, calcium, magnesium or aluminum ions. WO 2006/134117 describes a process for the passivation of metallic surfaces by treatment of the surface with an aqueous composition containing acidic polymers with the addition of waxes (eg polyethylene waxes).

Such aqueous passivation solutions to improve corrosion protection are often applied to the galvanized steel strip directly after the galvanizing line (e.g., hot dip galvanizing). The order is usually done by means of rolling technology, for example, simple nip rolls or more technologically complex "roll coater" are used.

In the squeegee roll, which is technologically simple and inexpensive to produce, the pass-through solution is applied to the galvanized steel strip (for example, sprayed on) and then squeezed off by means of a roller. With the help of squeeze roller technology, only qualitatively insufficient, i. uneven passivation layers are obtained. If special demands are placed on the applied layers, the more complex and cost-intensive "roll-coater technique" is usually used, whereby the passivation solution is first applied to one or more rolls and then transferred to the steel strip Passivation layer can be obtained with a relatively uniform layer thickness.

The time required for film formation, i. The crosslinking of the acidic polymer is usually comparatively short. In the continuous passivation of a steel strip, from application of the formulation to the steel strip until the drying of the coated strip in the dryer, normally only a few seconds, typically e.g. 2 to 10 seconds.

WO 2009/047209 describes a continuous process for coating steel strips, wherein the passivation composition is first applied to a coating roll, doctored off and then transferred to the steel strip.

In galvanized metal surfaces, a certain proportion of aluminum is often present (for example, in a hot galvanizing about 0.2% Al to 99.8% Zn). Therefore, in passivation formulations which are described in the prior art, fluorides are frequently added as additives. Fluoride can act as a complexing agent in the acidic medium for the surface alumina (Al ₂ 0 ₃ ). Fluorides are undesirable because of their environmental properties (toxicity) and the resulting complex wastewater treatment. In the passivation process described in the prior art using an acidic, aqueous formulation based on acid group-containing polymers, the crosslinking of the acid group-containing polymer usually takes place from the inside to the outside (for example through zinc ions dissolved out on the metal surface), ie from the metal surface to the air / film layer interface. As a result, often an incompletely crosslinked topmost polymer layer is formed, which accordingly remains water-soluble. It can be replaced; the corrosion resistance decreases and the surface has an unfavorable appearance. For example, these poorly cross-linked passivation layers produce unfavorable stack-test results, which stack the coated metal surfaces, exposing the stacks to water for several days.

An object of the present invention is to provide compositions and methods for the treatment of metal surfaces which are suitable for forming a passivation layer on metal surfaces, wherein a continuous as possible cross-linked resistant passivation film layer is to be achieved. The passivation layers should also provide improved corrosion protection for the metal surface.

It is further an object of the present invention to provide a fluoride-free passivation composition.

The resulting passivation layer should be suitable both for workpieces that are subsequently painted, and for those that are used without painting. It should be noted in subsequent painting of the workpieces that adequate adhesion of the subsequent coating layer is ensured on the passivation layer. This means that the paint adhesion on the passivation layer should improve (or at least not deteriorate). The quality of the paint adhesion can be determined with the so-called grid-cut test (see also DIN ISO standard 2409) on a flat metal surface and / or on a defined dented metal surface. For this purpose, a fixed grid pattern is cut into the coating to the coated base. Then a defined tape is placed over the crosshatch and peeled off. The chipping of the coated grid elements is then visually evaluated and usually indicated on a scale from 0 to 5 by means of cross-hatch characteristics.

Furthermore, the appearance of polymer-containing passivation layers is important, with clear and transparent layers being desired. The optics can be affected by the so-called "chalking out". Here are the layers are no more completely clear and transparent, but have more or less non-transparent, white spots. "Chalking out" can easily be confused with white rust formation and can make quality control more difficult. Therefore, the passivation layers produced by the method according to the invention or by the composition according to the invention should have a clear, transparent appearance and a low tendency to chalk out.

It has surprisingly been found that a passivating, corrosion-protecting polymer layer forms on a metallic surface, in particular on metallic surfaces containing zinc and / or aluminum, if polymers comprising acidic groups in the form of their aqueous (clear), alkaline solution (in particular at pH 9 , 5 to 11) are applied to the metal surface, wherein in the solution at least one volatile base, in particular ammonia and at least one cationic crosslinker (eg polyvalent metal ions, especially Zn ²⁺ , and / or a polyamine) are included.

Very stable, continuously crosslinked passivation layers can be obtained with the method according to the invention, which in particular have good corrosion resistance in the so-called "stack test".

In addition, the passivation composition according to the invention is preferably free of heavy metal compounds, in particular chromium compounds, and fluorides. Under alkaline conditions, no additional complexing agent is needed to dissolve the alumina (Al ₂ O ₃ ) layer.

Further advantageous is the improved paint adhesion to the metallic surfaces coated with the method according to the invention compared to non-passivated metallic surfaces and / or passivation coatings of the prior art.

The film formation in the process according to the invention with the crosslinking of the acidic polymers with the cationic crosslinkers may be effected by a pH reduction, e.g. as a result of the evaporation of the volatile base, take place. In the strongly alkaline medium, the cationic crosslinkers are present in deprotonated form or as the salt of oxo and / or hydroxo acids (for example as zincate).

A pH decrease can result in the release of cationic charge (eg, Zn or polyammonium ions) and cross-linking with the deprotonated acidic groups of the film-forming polymer. The crosslinking can thus be carried out both from the outside inwards, ie starting from the phase boundary air / water film, and from the inside outwards, ie starting from the phase boundary. ze metal surface / water film done. The latter can be done by the alkaline dissolution of the metal, for example of Al and Zn, on the metallic surface with evolution of hydrogen and lowering of the pH. The crosslinking of hydrophobic, acrylate-containing polymer dispersions with polyvalent cations such as zinc ions and the addition of ammonia is known inter alia in the floor care sealant. No. 3,308,078 describes a composition for coating various surfaces comprising a polymer emulsion with an organic film former, ammonia and a metal-releasing complex.

The present invention relates to a method for passivating a metallic surface, in particular a metallic surface consisting essentially of one or more metals selected from the group consisting of zinc (Zn), aluminum (AI) and magnesium (Mg), in which a metallic surface comprising an aqueous composition comprising (or consisting of) the following components: at least one water-soluble, acidic group-comprising polymer (X), wherein the polymer (X) has at least 0.6 mole acid groups / 100 g polymer; in particular, the acidic groups are selected from carboxyl groups, sulfonic acid groups, phosphoric acid groups and / or and phosphonic acid groups; at least one volatile, basic compound (B), preferably selected from ammonia, Ci. ₆ alkylamines and Ci. ₆ alkanolamines; at least one cationic crosslinker selected from polyvalent metal ions (M) and cationic polymers (P), in particular cationic polyamines; at least one solvent (L) containing at least 80% by weight of water; optionally one or more surfactants (T); optionally further components (K); wherein the pH of the aqueous composition is in the range of 9 to 12, preferably in the range of 9.5 to 1 1. In particular, the present invention relates to a process for passivating metallic surfaces as described above, characterized in that a composition is used comprising (or consisting of): a) 10 to 40 wt .-% of at least one water-soluble, acidic groups Polymer (X), wherein the polymer (X) has at least 0.6 mol of acid groups / 100 g of polymer; b) 1 to 20 wt .-% of at least one volatile, basic compound

(B), preferably selected from ammonia, Ci_ ₆ alkylamines and Ci. ₆ alkanolamines; c) 0.01 to 25 wt .-% of at least one cationic crosslinker selected from polyvalent metal ions (M) (preferred

Mg ²⁺ , Ca ²⁺ , Zn ²⁺ , Mn ²⁺ , Fe ²⁺ , Cr ³⁺ , Al ³⁺ , Ti ⁴⁺ , Zr ⁴⁺ , Ce ³⁺ , Ce ⁴⁺ , particularly preferably Zn ²⁺ ) and cationic polymers (P), in particular cationic polyamines (in particular selected from tetraethylenepentamine, polyethyleneimines, polyethyleneimine derivatives, polyvinylamines and polyimidazoles, d) 20 to 89% by weight of at least one solvent (L) containing

at least 80 wt .-% water, e) optionally 0 to 3 wt .-% of at least one surfactant (T), f) optionally 0 to 30 wt .-% of at least one further component (K), wherein the pH of the aqueous Composition in the range of 9 to 12, preferably in the range of 9.5 to 1 1, is located.

The invention also relates to the formulations or compositions themselves and their preparation. To the polymer (X)

For passivation by means of the process according to the invention, an aqueous composition is used which comprises at least one water-soluble polymer (X) comprising acidic groups. The polymers (X) used may be homopolymers or copolymers. Mixtures of several different polymers can also be used.

The formulation used according to the invention comprises preferably 10 to 40% by weight, preferably 15 to 35% by weight, more preferably 15 to 30% by weight and frequently 18 to 25% by weight of the polymer or polymers (X) , based on the amount of all components of the formulation (including the solvents).

For the purposes of this invention, the term "water-soluble" is to be understood as meaning that the polymer or polymers (X) used are homogeneously water-soluble, specifically in the amounts specified for the compositions.Preferably, the polymers (X) used should be continuous (unlimited) with water In particular, the polymers used should have a solubility of at least 50 g / l, preferably 100 g / l and more preferably at least 200 g / l in water at room temperature and pH 7. However, it should be noted that the solubility of the described Water-containing polymers (X) in water also depend on the pH value A polymer which has insufficient solubility for the intended use at a certain pH may still have sufficient solubility at another pH.

In particular, the polymers (X) used have at least 0.6 mol of acid groups / 100 g of the polymer. The polymers preferably have at least 0.9 mol acid groups / 100 g, more preferably at least 1 mol acid groups / 100 g and often even at least 1.2 mol acid groups / 100 g.

The acidic groups of the polymers (X) are as a rule selected from carboxyl groups, sulfonic acid groups, phosphoric acid groups and / or phosphonic acid groups. Preferably, the acidic groups are selected from carboxyl groups, phosphoric acid groups and phosphonic acid groups. The polymer (X) used is particularly preferably a copolymer (X1) composed of at least two different acid group-containing monomers, in particular of monomers containing carboxyl groups and of monomers containing phosphonic acid groups. Particularly preferred for carrying out the invention homo- or copolymers are used which comprise acrylic acid units and / or methacrylic acid units. In particular, the polymer (X) is one or more water-soluble copolymers (X1) synthesized from acrylic acid and / or methacrylic acid monomer units (M1) and various monoethylenically unsaturated monomers having acidic groups (M2). Optionally, OH-containing acrylic acid esters or methacrylic acid esters (M3) may also be present. Optionally, further monomers (M4) may be present as building blocks.

In a preferred embodiment of the invention, the water-soluble polymer (X) is a copolymer (X1) which is composed of (or contains) the following monomers:

M1: from 30 to 90% by weight of methacrylic acid and / or acrylic acid; M2: 10 to 70% by weight of at least one other monoethylenically unsaturated monomer other than (M1) which has one or more acidic groups (in particular monoethylenically unsaturated dicarboxylic acids having 4 to 7 carbon atoms, monoethylenically unsaturated phosphoric acids, monoethylenically unsaturated phosphonic acids, preferably monoethylenic unsaturated phosphonic acids) optionally M3: 0 to 40 wt .-% of at least one OH groups

Methacrylic acid ester and / or acrylic ester; optionally M4: 0 to 30 wt .-% of at least one further, of (M1), (M2) and

(M3) different ethylenically unsaturated monomer.

These percentages by weight relate to the sum (100% by weight) of all monomers in the copolymer (X1).

Furthermore, the preferred polymers (X) which comprise acidic groups described in WO 2009/047209 can be used in the context of the present invention. For the polymers (X) used in the process according to the invention, the embodiments described in WO 2009/047209 can be used with regard to the monomers (M 1), (M2), (M3) and (M4). The amount of acrylic acid and / or methacrylic acid (M 1) in the copolymer (X1) is from 30 to 90% by weight, preferably from 40 to 80% by weight and more preferably from 50 to 70% by weight, this statement referring to Sum of all monomers in the polymer is related. The amount of monomers (M2) in the copolymer (X1) is 10 to 70 wt .-%, preferably 20 to 60 wt .-%, and particularly preferably 30 to 50 wt .-%, each based on the sum of all monomers in the polymer ,

The monomer (M2) is at least one monoethylenically unsaturated monomer which is different from (M1) but copolymerizable with (M1) and which has one or more acidic groups, the acidic groups being selected from carboxyl groups, phosphoric acid groups and Groups, phosphonic acid groups or sulfonic acid groups. Several different monomers (M2) can be used.

With regard to the preferred embodiments of monomer (M2), reference is made to document WO 2009/047209.

Examples of such monomers (M2) include crotonic acid, vinylacetic acid, CC ₄ monoesters of monoethylenically unsaturated dicarboxylic acids, styrenesulfonic acid, vinylsulfonic acid, allylsulfonic acid, 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS), vinylphosphonic acid, monovinyl phosphoric acid, maleic acid, fumaric acid or itaconic acid. Vinylphosphonic acid is preferably used as monomer (M2).

In addition, the copolymer (X1) may optionally contain at least one acrylic acid ester having OH groups and / or methacrylic acid ester as the monomer building block (M3). Preference is given to monohydroxyacrylates and / or monohydroxymethacrylates. Preference is given to using hydroxyethyl acrylate as monomer (M3).

The amount of the monomers (M3) in the copolymer (X1) is 0 to 40% by weight, preferably 1 to 30% by weight. With regard to the further preferred embodiments of monomer (M3), reference is made to the document WO 2009/047209.

In addition to the monomers (M1), (M2), and optionally (M3), it is optionally possible to use from 0 to 30% by weight of at least one other ethylenically unsaturated monomer (M4) other than (M1), (M2) and (M3) become. In addition, preferably no other monomers are used. The monomers (M4) can serve to fine-tune the properties of the copolymer (X1). It is also possible to use several different monomers (M4). They are selected by a person skilled in the art according to the desired properties of the copolymer with the proviso that they must be copolymerizable with the monomers (M1), (M2) and (M3). They are preferably monoethylenically unsaturated monomers. In special cases, however, small amounts of monomers with several polymerizable groups can be used. As a result, the copolymer can be crosslinked to a small extent. Examples of suitable monomers (M4) include in particular aliphatic alkyl esters of (meth) acrylic acid, such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate or 2-ethylhexyl (meth) acrylate. Also suitable are vinyl or allyl ethers such as, for example, methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, 2-ethylhexyl vinyl ether, vinylcyclohexyl ether, vinyl 4-hydroxybutyl ether, decyl vinyl ether, 2- (diethylamino) ethyl-vinyl ether, 2- (di-n butyl-amino) ethyl vinyl ether or methyl diglycol vinyl ether or the corresponding allyl compounds. Also used may be vinyl esters such as vinyl acetate or vinyl propionate. It is also possible to use basic co-monomers, for example acrylamide and alkyl-substituted acrylamides.

Examples of crosslinking monomers include molecules having a plurality of ethylenically unsaturated groups, for example di (meth) acrylates such as ethylene glycol di (meth) acrylate or butanediol-1,4-di (meth) acrylate or poly (meth) acrylates such as trimethylolpropane tri (meth) acrylate or also di (meth) acrylates of oligo- or polyalkylene glycols, such as di-, tri- or tetraethylene glycol di (meth) acrylate. Further examples include vinyl (meth) acrylate or butanediol divinyl ether.

The term "(meth) acrylic" as used herein refers to either an acrylic group or a methacrylic group.

The amount of all monomers (M4) used together is 0 to 30 wt .-% based on the total amount of the monomers used. The amount is preferably 0 to 20 wt .-%, particularly preferably 0 to 10% wt .-%. If crosslinking monomers (M4) are present, their amount should generally not exceed 5%, preferably 2% by weight (based on the total amount of all monomers used for the process). It may for example be 10 ppm to 1 wt .-%.

With regard to the preferred embodiments of monomer (M4), reference is made to document WO 2009/047209. A preferred embodiment relates to the process described above, characterized in that the water-soluble polymer (X) is a copolymer (X1) which is composed of (or contains) the following monomers:

M1: 20 to 60% by weight of acrylic acid;

M2: 20 to 60% by weight of vinylphosphonic acid; M3: 1 to 40% by weight of hydroxyethyl acrylate.

The preparation of the polymers (X) or copolymers (X1) can be carried out by methods known to the person skilled in the art. The copolymers are preferably prepared by free-radical polymerization of the stated components (M1), (M2) and optionally (M3) and / or (M4) in aqueous solution. Details for carrying out a radical polymerization are known to the person skilled in the art. Production processes for the copolymers (X1) are described, for example, in WO 2006/021308 or in WO 2006/134116. The synthesized copolymers (X1) can be isolated from the aqueous solution by conventional methods known to those skilled in the art, for example by evaporation of the solution, spray drying, freeze drying or precipitation. The copolymers (X1) are preferably not isolated from the aqueous solution after the polymerization, but the resulting solutions of the copolymers are used (if appropriate after addition of further additives) as such for the process according to the invention. To facilitate such direct reuse, the amount of aqueous solvent used for the polymerization should be designed from the beginning so that the concentration of the polymer in the solvent is suitable for the application. It is also possible first to prepare a concentrate which is diluted to the desired concentration on site with water or optionally other solvents.

The molecular weight, in particular based on the weight-average molecular weight M _w , of the polymers (X) or copolymers (X1) used for the process according to the invention is determined by the person skilled in the art according to the desired application. For example, polymers having a molecular weight M _w of 3,000 to 1,000,000 g / mol can be used. Polymers having 5,000 g / mol to 500,000 g / mol, preferably 10,000 g / mol to 250,000 g / mol, particularly preferably 15,000 to 100,000 g / mol and very particularly preferably 20,000 to 75,000 g / mol, have proven particularly suitable. To the volatile, basic compound (B)

A volatile basic compound in the context of the present invention is to be understood as meaning a volatile inorganic or organic compound which reacts basicly in aqueous solution. As a measure of the volatility of the vapor pressure can be used.

In the present invention, a volatile basic compound (e.g., in aqueous solution) has a vapor pressure of greater than 0.01 kPa (20 ° C). More preferably, a volatile basic compound according to the present invention has a vapor pressure of more than 0.05 kPa (20 ° C), preferably more than 0, 1 kPa (20 ° C), preferably more than 0.5 kPa ( 20 ° C).

In the present invention, the following volatile basic compounds may be used: the primary, secondary and tertiary amines having a boiling point of 100 ° C. or less, such as ammonia (in the form of aqueous ammonia), monomethylamine, dimethylamine, trimethylamine, monopropylamine, Dipropylamine, tripropylamine and monopentylamine and the like.

In particular, it may be in the volatile basic compound (B) at least one compound selected from the group consisting of ammonia, CI_ ₄ alkylamines NEN (eg monomethylamine, dimethylamine, trimethylamine, ethylamine) and CI_ ₄ alkanolamines (eg, mono-, di and Triethanolamine, 1-aminopropan-2-ol); act. Preferably, ammonia is used as the volatile basic compound (B). The aqueous composition used according to the invention comprises 1 to 20% by weight, preferably 1 to 15% by weight, more preferably 1 to 10% by weight and most preferably 2 to 5% by weight of the volatile basic compound (B), based on the amount of all components of the aqueous composition (including the solvents).

The aqueous composition used in the process according to the invention has a pH in the range from 9 to 12, preferably in the range from 9.5 to 11. The pH of the aqueous composition depends on the type and concentration of the polymers (X) used and the volatile basic compound (B). The pH can still be influenced or adjusted by further basic or acidic components in the composition.

To the cationic crosslinker The aqueous composition used in the process according to the invention comprises at least one cationic compound which acts as a crosslinker for the acidic groups. can act comprehensive polymer (X). In particular, at least one polyvalent cation and / or at least one cationic polymer (P), in particular at least one cationic polyamine, can be used as the cationic crosslinker. In a preferred embodiment, the invention relates to a method described above, characterized in that the aqueous composition as cationic crosslinker at least one polyvalent metal ion (M) selected from the group consisting of Mg ²⁺ , Ca ²⁺ , Zn ²⁺ , Mn ²⁺ , Fe ²⁺ , Cr ³⁺ , Al ³⁺ , Ti ⁴⁺ , Zr ⁴⁺ , Ce ³⁺ and Ce ⁴⁺ , preferably Zn ²⁺ , Mg ²⁺ , Ca ²⁺ , Mn ²⁺ and Al ^{3 +} contains. It is preferably Zn ²⁺ and / or Mg ²⁺ and most preferably Zn ²⁺ .

The preparation next to it preferably does not comprise any further metal ions. The ions may be present as hydrated metal ions, but they may be in the form of dissolved compounds, for example as complex compounds. In particular, the ions may have complex bonds to the acidic groups of the polymer. If present, the amount of the polyvalent metal ions is selected from the group consisting of Zn ²⁺ , Mg ²⁺ , Ca ²⁺ , Mn ^2+, and Al ^3+: 0.01 wt% to 25 wt%, preferably 0.5 to 10% by weight and more preferably 1 to 5% by weight, in each case based on the total composition.

In particular, a polyamine is used as the cationic polymer (P). A polyamine or a polyamine compound in the context of the present invention is a saturated, open-chain or cyclic organic compound containing at least two (preferably at least five) amino groups, where the amino groups can be selected from primary, secondary and tertiary amino groups. Depending on the given conditions (pH value), the amino groups may be protonated and carry cationic charge.

In the process according to the invention, at least one polyamine is preferably selected from the group consisting of polyalkylimines (polyiminoalkylenes, eg polyethyleneimine PEI), alkoxylated polyethyleneimines, polyvinylimidazoles (polyvinylimidazoles), polyvinylamines and quaternized and / or alkoxylated derivatives of the abovementioned polyamines. In a further preferred embodiment, the invention relates to a process described above, characterized in that the aqueous composition contains as cationic crosslinker at least one cationic polymer (P) selected from polyethyleneimines, Polyethyleniminderivaten, polyvinylamines and polyvinylimidazoles. In particular, it is also possible to use alkoxylated, preferably ethoxylated and / or propoxylated polyamine compounds in the context of the present invention. In particular, alkoxylated polyamine compounds comprising 1 to 1000, preferably 1 to 100, preferably 1 to 50, preferably 1 to 10 alkoxy units can be used in the context of the present invention.

In particular, it is also possible to use quaternized polyamine compounds in the context of the present invention which have at least one quaternary ammonium group which is obtained in particular by substitution on the amino group with one or more radicals selected from C 1 -C ₆ -alkyl and benzyl can be obtained from the non-quaternized polyamine compound.

In the process according to the invention, the cationic crosslinker employed is preferably at least one polyamine (P) selected from the group consisting of polyalkylimines (polyimino-alkylenes, eg polyethyleneimines PEI), alkoxylated polyalkylimines (eg alkoxylated polyethyleneimines), quaternized polyalkylimines (eg quaternized polyethylenimines), polyvinylimidazoles (Polyimidazoles), quaternized polyvinylimidazoles, alkoxylated polyvinylimidazoles, polyvinylamines, quaternized polyvinylamines and alkoxylated polyvinylamines.

The cationic polymer (P) can be used in the aqueous composition used in the process according to the invention in an amount of from 0.01 to 25% by weight, in particular from 0.5 to 10% by weight, preferably from 2 to 10% by weight, more preferably 2 to 6 wt .-%, be contained.

In particular, as the cationic polymer (P), a polyalkylimine such as polyethyleneimine (PEI) or polypropyleneimine can be used. In a preferred embodiment, the aqueous composition contains at least one polyethyleneimine. Polyethyleneimines can be particularly described by the structural unit of the following general formula (P1)

wherein R ^a is selected from hydrogen, Ci _-6 alkyl, benzyl or a radical based on ethyleneimine such as - (CH ₂ CH ₂ NH) _n -H with rf 1 to 200 x is 4 to 20,000, preferably 4 to 1,000, preferably 4 to 300, preferably 4 to 100, particularly preferably 10 to 100, preferably 10 to 30.

The molecular weight of the polyethyleneimines used may be e.g. in the range from 100 to 800,000 g / mol, preferably in the range from 100 to 50,000 g / mol, preferably in the range from 500 to 10,000 g / mol, preferably in the range from 500 to 5,000 g / mol.

The data may relate in each case both to the number average molecular weight, to the weight average molecular weight, or to the viscosity average molecular weight, in particular the data relate to the number average molecular weight.

In particular, these may be branched polyethylenimines. Furthermore, the use of alkoxylated polyethylenimines (e.g., ethoxylated or propoxylated polyethylenimines), preferably with 2 to 20 alkoxy units, is possible.

In particular, polyvinylamines (P) can be used as the polyamine component. Polyvinylamines can be described in particular with reference to the structural unit of the general formula (P2)

-CH- CH-

I

N

(P2) where y is in particular an integer from 4 to 10,000, preferably from 10 to 5,000, particularly preferably from 10 to 1,000;

R ^b and R ^c are independently selected from hydrogen, CI_ ₆ alkyl and benzyl.

In particular, branched polyvinylamines are used in the context of the present invention.

The molecular weight of the polyvinylamines used is in particular in the range from 100 to 500,000 g / mol, preferably from 500 to 250,000 g / mol, preferably in the range from 1,000 to 250,000 g / mol. The data can refer in each case both to the number average molecular weight, to the weight average molecular weight, or to the viscosity average molecular weight, in particular the data relate to the number average molecular weight. In a further embodiment of the invention, polyvinylimidazoles can be used as the polyamine component (P). Polyvinylimidazoles can be described in particular by a structural unit of the general formula (P3):

in which z is in particular an integer from 4 to 10,000, preferably from 10 to 5,000, particularly preferably from 10 to 1,000

The molecular weight of the polyvinylimidazoles used is in particular in the range from 200 to 1,000,000 g / mol, preferably in the range from 1,000 to 500,000 g / mol, preferably in the range from 1,000 to 200,000 g / mol. The data may refer in each case both to the number average molecular weight, to the weight average molecular weight, or to the viscosity average molecular weight, in particular the data relate to the number average molecular weight.

In a preferred embodiment, the aqueous composition described above contains a quaternized polyvinylimidazole. In particular, a quaternization by addition of a Ci. ₆ alkyl radical and / or a benzyl radical on at least one of the nitrogen atom of the polyvinylimidazoles, in particular the quaternization can be carried out with a common methylating reagent (eg, methyl halides). It is also advantageous to use a combination of polyamine (P) and polyvalent metal ion (M) as a cationic crosslinker in the process described above.

In a further preferred embodiment, the aqueous composition used in the method described above contains as cationic crosslinker at least one polyamine (P) as described above in an amount of 0.01 to 25 wt .-%, (in particular from 0.5 to 10 wt. -%, preferably 2 to 10 wt .-%, particularly preferably 2 to 6 wt .-%) and at least one polyvalent metal ion selected from the group consisting of Mg ²⁺ , Ca ²⁺ , Zn ²⁺ , Mn ²⁺ , Fe ²⁺ , Cr ³⁺ , Al ³⁺ , Ti ⁴⁺ , Zr ⁴⁺ , Ce ³⁺ and Ce ⁴⁺ , (preferably Zn ²⁺ , Mg ²⁺ , Ca ²⁺ , Mn ²⁺ and Al ³⁺ ) in in an amount of 0.01 to 25% by weight, (preferably 0.5 to 10% by weight and particularly preferably 1 to 5% by weight). To the solvent (L)

As solvent (L) it is preferred to use exclusively water in the compositions. In addition to water, the solvent may comprise water-miscible organic solvents in small amounts. In particular, small amounts of organic solvents can be used, selected from monoalcohols such as methanol, ethanol or propanol, higher alcohols such as ethylene glycol or polyether polyols, ether alcohols such as butyl glycol or methoxypropanol and N-methylpyrrolidone. In general, the amount of water is at least 80% by weight (based on the total amount of solvent), preferably at least 90 wt .-% (based on the total amount of solvent) and often at least 95 wt .-% (based on the total amount on solvent).

The solvent is preferably contained in an amount of from 20 to 89% by weight in the above-described aqueous composition, preferably from 20 to 80% by weight, preferably from 20 to 70% by weight, preferably from 20 to 60% by weight. -%, preferably from 20 to 50 wt .-%.

To the surfactants (T)

A surfactant (T) may optionally contain in the aqueous composition used in the process according to the invention in an amount of 0 to 1% by weight, preferably 0 to 0.5% by weight. In particular, anionic, nonionic and / or cationic surfactants can be used.

In one embodiment of the invention, the above-described aqueous composition contains 0.1 to 2% by weight, preferably 0.1 to 0.8% by weight, of at least one surfactant selected from anionic, cationic and nonionic surfactants known to those skilled in the art is

The aqueous composition used in the process described above may optionally contain at least one surfactant (T), preferably selected from the group consisting of: i) alkoxylated alcohols, particularly alkoxylated (preferably ethoxylated) C comprising 2 to 14 alkylene oxide units ₍₆ -2O alcohols in particular ethoxy and / or propoxy units), for example hexanol ethoxylates ii) alkyl sulfates, in particular C ₈ -2o alkyl sulfates (for example 2-ethylhexyl sulfate, dodecyl sulfate) iii) sulfonates, in particular C ₈ - ₂ oAlkylsulfonate (eg dodecyl) iv) alkylaryl, especially C ₈ - ₂ oAlkylarylsulfate (eg Cumolsulfat) v) alkylarylsulfonates, in particular C ₈ -. ₂ oAlkylarylsulfonaten, for example alkyl benzene sulfonates (e.g., dodecylbenzene Sulfonates) vi) cationic surfactants, in particular C ₁₀ -16-alkyl-trimethylammonium salts. To the other components (K)

As further components, the above-described aqueous composition may contain at least one of the following components: a. Phosphate ions, in particular in an amount of 0 to 10 wt .-%, preferably from 0, 1 to 5 wt .-%;

b. Solubilizers (anionic, nonionic, cationic), in particular in an amount of 0 to 1 wt .-%;

c. organic crosslinkers; e.g. polyamines; also in its protonated form; in particular in an amount of 0 to 10% by weight;

d. Defoamers (e.g., silanes, modified silanes), especially in an amount of 0.001 to 0.1% by weight;

e. Deaerators (e.g., long chain alcohols), especially in an amount of 0.001 to 0.1% by weight;

f. Activators (e.g., nitrate, nitrobenzenesulfonate), especially in an amount of from 0 to 2% by weight, preferably from 0 to 0.5% by weight;

G. Hydrogen scavengers (eg, hydroxylammonium salts, hydrogen peroxide (H ₂ O ₂ ), nitrate), especially in an amount of from 0 to 2% by weight, preferably from 0 to 0.5% by weight;

H. Co-solvents (e.g., 2-ethylhexyl ethoxylate, butyl diglycol, propyl diglycol), especially in an amount of 0 to 5 weight percent, preferably from 0.1 to 2 weight percent; i. Anti-corrosive additives (for example nitrogen-containing heterocycles, phosphoric acid esters, organic mono-, di- and tricarboxylic acids), in particular in an amount of from 0.01 to 5% by weight, preferably from 0.1 to 2% by weight;

j. Complexing agents (e.g., aminoacetic acid derivatives, phosphonic acid derivatives), especially in an amount of from 0.01 to 5% by weight, preferably from 0.1 to 1% by weight.

The amount of additional components (K) in the sum should not exceed 30% by weight, in particular not more than 20% by weight, preferably not more than 10% by weight and especially preferably not more than 5% by weight. % (in each case based on the total composition). If metal ions or metal compounds are present, they are preferably compositions which contain no chromium compounds. Furthermore, preferably no metal fluorides or complex metal fluorides should be present. The passivation according to the invention is therefore preferably a chromium-free passivation, more preferably a chromium- and fluoride-free passivation.

The aqueous compositions used according to the invention can be obtained by mixing the components.

As the metal surface to be treated, any metal surface can generally be used, in particular surfaces of base metal. It can be, for example, surfaces containing essentially iron, iron alloys, steel, zinc (Zn), Zn alloys, aluminum (Al) or Al alloys, tin (Sn) and Sn alloys, magnesium (Mg). or Mg alloys act. The steels can be both low-alloyed and high-alloyed steels. Often the metal surface is aluminum or aluminum alloys, or zinc or zinc alloys, with a surface of zinc or zinc alloys generally being obtained by a galvanizing process of a metallic material such as iron or steel.

The inventive method is particularly suitable for passivation of metallic surfaces of Zn, Zn alloys, Al or Al alloys. These may be the surfaces of bodies or workpieces consisting entirely of the said metals or alloys. However, they may also be the surfaces of Zn, Zn alloy, Al or Al alloy coated bodies, which bodies may be made of other materials such as other metals, alloys, polymers or composites. In particular, it may be the surface of galvanized iron or steel. The term "galvanized" also includes coating with a zinc alloy, in particular hot dip galvanizing with Zn-Al alloys and electrolytic galvanizing with Zn-Ni, Zn-Fe, Zn / Mn and Zn / Co alloys.

The present invention preferably relates to a method for passivating a metallic surface, characterized in that the metallic surface is surfaces consisting essentially of one or more metals selected from the group consisting of zinc (Zn), aluminum (AI) and magnesium (Mg). Zn or Al alloys are known to the person skilled in the art. Depending on the desired application, the skilled person will select the type and amount of alloying components.

Typical further constituents of zinc alloys include in particular Al, Mg, Pb, Si, Mg, Sn, Cu and Cd. It may also be Al / Zn alloys in which Al and Zn are present in approximately the same amount. The coatings may be substantially homogeneous coatings or even coatings having concentration gradients. For example, it can be galvanized steel, which was additionally vapor-deposited with Mg. As a result, a Zn / Mg alloy can form on the surface. Typical further constituents of aluminum alloys are in particular Mg, Mn, Si, Zn, Cr, Zr, Cu and Ti.

In a preferred embodiment of the method is the surface of a band metal, preferably made of aluminum or an aluminum alloy or iron or steel, in particular strips of electrolytically galvanized or hot-galvanized steel.

Often it is the surface of moldings which are obtainable by processing operations such as cutting, forming and / or joining from the mentioned tape fall. Examples are automobile bodies or parts thereof, truck bodies, linings for household appliances (such as washing machines, dishwashers, dryers, gas and electric stoves, microwave ovens, freezers or refrigerators), covers for technical equipment or devices (such as machines, control cabinets, computer cases or the - same), architectural elements (such as wall parts, façade elements, ceiling elements, windows or door profiles or partitions), furniture made of metallic materials (such as metal cabinets or metal shelves).

The metallic surfaces to be treated may also have thin oxidic, hydroxidic and / or carbonic surface layers or layers of similar construction. Such layers usually self-form on metallic surfaces in contact with the atmosphere, and are included in the term "metallic surface". In a preferred embodiment, the process relates to a continuous process for the passivation of galvanized steel strips in a coil coating plant following the galvanizing (eg electrolytic galvanizing or Feuerverzin- kung). With the method according to the invention, one-sided or two-sided galvanized steel strips can be passivated. Galvanized steel strips have a thickness of 0.2 to 0.3 mm and widths of 0.5 to 2.5 m. Galvanized steel strips are commercially available for a variety of applications. The person skilled in the art selects a suitable steel strip depending on the intended use. In general, the known strip coating systems based on, for example, squeeze-roll technology or roll-coater technology can be used to carry out the process according to the invention. Suitable plants are described, for example, in WO 2009/047209. The method according to the invention for the passivation of galvanized steel strips is preferably carried out by means of a continuous method using squeeze rolls. For this purpose, the galvanized steel strip is moved by means of drive rollers. The passivation composition is sprayed, for example by means of a spray station on the steel strip and forms a wet film. By means of one or more squeezing rollers, excess passivation composition is squeezed off. The result is a thin, damp film, which can then be dried in a dryer.

The steel belts can typically be driven through the plant at a speed of 80 to 200 m / min, preferably 50 to 150 m / min. The treatment time can be determined by the person skilled in the art according to the desired properties of the passivation layer and other factors. In continuous processes, it is advantageous that the maximum time between application of the aqueous composition to the metallic surface of the steel strip and the drying of the film is 1 to 60 seconds.

In the method according to the invention described above, the metallic surface may be brought into contact with the aqueous composition, in particular by spraying, dipping or rolling.

In a preferred embodiment, the method of passivation of a metallic surface described above comprises the following steps: i) optionally cleaning the metallic surface to remove oils, fats, dirt and / or oxide films; ii) optionally washing the metallic surface with water; iii) contacting a metallic surface with an aqueous composition as described above; wherein the aqueous composition is in

Form of a wet film is applied to the surface; iv) drying the wet film obtained in step iii), preferably at temperatures in the range of 20 to 250 ° C; v) optionally after-treatment of the passivated surface.

In a preferred embodiment, the invention relates to a method as described above, characterized in that the aqueous composition is applied to the metallic surface in the form of a wet film, wherein the aqueous composition is in an application weight in the range of 0.3 to 2 g / m ² , preferably 0.3 to 1 g / m ² , in particular 0.4 to 0.8 g / m ² (based on the sum of the solids of the aqueous composition) is applied to the metallic surface. The passivation layers obtainable by the described process according to the invention preferably have a layer thickness in the range of 1 to 3 μm, preferably 1 to 2 μm and an application weight in the range from 0.3 to 2 g / m ² , preferably 0.3 to 1 g / m ² , particularly preferably 0.4 to 0.8 g / m ² (based on the sum of the solids of the aqueous composition).

In a further aspect, the present invention relates to a composition for passivating a metallic surface comprising: a) from 10 to 40% by weight of at least one water-soluble, acid group-containing polymer (X), wherein the polymer (X) is at least 0.6 mol of acid groups / 100 g of polymer, and wherein preferred acid groups are carboxyl groups and phosphonic acid groups; b) 1 to 20% by weight of at least one volatile basic compound (B) selected from ammonia, C 1-4 -alkylamines and C 1-4 -alkanolamines; c) 0.01 to 25 wt .-% of at least one cationic crosslinker selected from polyvalent metal ions (M) and cationic polyamines (P) d) 20 to 89 wt .-% of at least one solvent (L) containing

at least 80% by weight of water; e) optionally 0 to 3 wt .-% of at least one surfactant (T), f) optionally 0 to 30 wt .-% of at least one further component (K); the composition having a pH in the range of 9 to 12, preferably in the range of 9.5 to 11.

In a preferred embodiment, the invention is directed to a composition (in particular an aqueous composition) for passivating a me-metallic surface containing a) 10 to 40 wt .-% of at least one water-soluble, acidic

Group-comprising polymer (X), wherein the polymer (X) has at least 0.6 mol of acid groups / 100 g of polymer, and wherein the polymer (X) in particular has carboxyl groups and phosphonic acid groups; b) 1 to 20% by weight of ammonia; c) from 0.5 to 5% by weight, of at least one polyamine (P) selected from polyethyleneimines, polyethylenimine derivatives, polyvinylamines and polyvinylimidazoles; d) from 20 to 89% by weight of at least one solvent (L) containing at least 80% by weight of water; e) optionally 0.01 to 25 wt .-% of at least one polyvalent metal ion

(M) selected from Mg ²⁺ , Ca ²⁺ , Zn ²⁺ , Mn ²⁺ , Fe ²⁺ , Cr ³⁺ , Al ³⁺ , Ti ⁴⁺ , Zr ⁴⁺ and Ce ³⁺ ; f) optionally 0 to 3 wt .-% of at least one surfactant (T); the composition having a pH in the range of 9 to 12, preferably in the range of 9.5 to 11.

For the components mentioned (polymer (X), volatile base (B), polyamine (P), metal ion (M), surfactant (T), solvent (L), other components (K)) apply the next above in connection with the inventive method mentioned preferred embodiments.

The present invention is further directed to the use of the above-described composition for passivating a metallic surface, in particular a metallic surface consisting essentially of one or more metals selected from the group consisting of zinc (Zn), aluminum (AI) and magnesium (Mg), especially of galvanized steel. In particular, the invention relates to the use of the above-described composition for passivating a galvanized steel strip in a continuous process.

A further subject of the present invention is a coating on a metallic surface obtainable by bringing the metallic surface into contact with an aqueous composition comprising the following components: a) at least one water-soluble polymer comprising acidic groups (X), wherein the polymer (X) at least 0.6 mol of acid groups / 100 g of polymer; b) at least one volatile, basic compound (B), c) at least one cationic crosslinker selected from polyvalent metal ions (M) and cationic polymers (P); d) at least one solvent (L) containing at least 80% by weight of water; e) optionally a surfactant (T); f) optionally further components (K); wherein the pH of the aqueous composition is in the range of 9 to 12, preferably in the range of 9.5 to 11.

For the abovementioned components (polymer (X), volatile base (B), cationic polymer (P), metal ion (M), surfactant (T), solvent (L), further components (K)), see above Connection with the method according to the invention said preferred embodiments.

In particular, the invention is directed to a coating described above, characterized in that the coating additionally comprises one or more coating The present invention will be further illustrated by the following experimental examples.

Example 1 :

In each case, aqueous solutions of an acid group-containing polymer (polymer X) of about 50% by weight of acrylic acid (monomer M1), about 30% by weight of vinylphosphonic acid (monomer M2), about 20% by weight of hydroxyethyl acrylate (monomer M3 ) prepared as described in WO 2008/612248.

There were starting formulations of about 20 wt.% Of the acidic group comprising polymer (polymer (X)), optionally 85% phosphoric acid (H ₃ P0 ₄ ) and zinc oxide (ZnO), by dissolving or dispersing the components in water and mixing the components. The exact amounts (in wt .-%) of the components of the starting formulation are summarized in Table 1.

The various starting formulations were adjusted to a pH of about 10.5 by adding ammonia (volatile basic compound B). Furthermore, in some formulations, a polyethyleneimine having an average molecular weight of 2,000 g / mol was additionally added as a cationic crosslinker. In formulation V4, a surfactant and a defoamer (modified silane) were additionally used. As reference C1, a hot-dip galvanized sheet without passivation was used. The following formulations V1 to V4 were prepared as indicated in Table 1.

Table 1: Coating formulations

Example 2:

Using the compositions described in Example 1, coated hot-dip galvanized steel test panels (Gardobond OE H DG 3, 105 x 190 mm) were prepared.

As a pretreatment, the test panels were immersed in a mildly alkaline cleaning solution (Surtech 133, Surtech) for about 30 seconds, rinsed immediately with demineralized water and then dried with nitrogen. The cleaned sheets were immersed at room temperature for 1 second (s) in the formulations listed in Table 1, squeezed off with a roller system and dried for 12 s at 160 ° C in a drying oven. The peak metal temperature (PMT) during drying did not exceed 50 ° C.

The coated test panels thus obtained were tested for corrosion resistance. The salt spray test, the condensed water climate test (KWT) and the stack test were carried out as described in Example 3.

The test results are summarized in Table 2.

Table 2: Test results for corrosion resistance

X1 V1 V2 V3 V4

Reference pH - - 10.5 10.4 10.5 10 solution

Overlay [g / m ² ] 0 0.8 0.8 0.8 0.8

24h 0 6 9 10 10

Salt spray test 48h - 3 7 8 9

DIN ISO 9227 72h - 0 3 5 6

96h - - 0 0 3

KWT 21 4 4 2 1 1

Zyk¬

DIN ISO 6270-2 len 1 day 4 0 0 0 0

Stacktest 7 days - 3 2 1 1

14 days - 4 4 4 3

Appearance Solution Clear Clear Clear Clear

It turns out that coatings with the compositions according to the invention had a significantly better corrosion resistance in all test methods compared to test panels which were coated with a comparative solution.

Example 3

To evaluate the passivation layer, the test procedures described below and summarized in Table 2 were carried out. a) salt spray test (DIN EN ISO 9227)

The quality of the corrosion protection of the test panels coated according to Example 2 was evaluated in the neutral salt spray test in accordance with DIN EN ISO 9227 by assigning evaluation numbers of 0 to 10 according to specified standards.

The rating number or rating is a measure of the occurrence of white rust on the sheet. The higher the rating, the lower the amount of corroded area [%] and the better the corrosion protection. The evaluation numbers were assigned in accordance with Table 3. An average of 5 sheets was formed:

Table 3: Evaluation scheme salt spray test

Corroded area

rating number

[%]

no error 10

0 <A <0, 1 9

0.1 <A <0.25 8

0.25 <A <0.5 7

0.5 <A <1, 0 6 1, 0 <A <2.5 5

2.5 <A <5.0 4

5.0 <A <10 3

10 <A <25 2

25 <A <50 1

50 <A 0

Condensation Exchange Climate Test KWT (DIN EN ISO 6270-2)

Furthermore, the sheets were tested in the condensate exchange test "KWT" in accordance with DIN EN ISO 6270-2. This consists of one or more climatic cycles, each with two test sections.

In the first section, the test specimens are exposed for 8 hours at a temperature of 40 ° C and a relative humidity of 100%, in the second section at a temperature of 18-28 ° C at a humidity of less than 100% (ambient conditions). The duration of a cycle is 24 hours. The optical assessment of the samples was carried out according to the following criteria as the mean value of 3 sheets: no chalking

easy chalking out

medium chalking

strong chalking

very strong chalking The resistance of the test panels coated as described above were compared in a so-called stack test "stack test" against each other.

For this purpose, three coated plates were divided in the middle, wetted with 5 ml of distilled water and placed each other with the test pages. The test was carried out in a climatic change chamber, where the stacks ("stacks") were weighted with a 5 kg weight and subjected to a defined number of cycles (DIN EN ISO 6270-2, AHT).

The evaluation of the corrosion was carried out as an average of 3 sheets according to the following evaluation scheme:

0 = no change vis-à-vis fresh metal sheet visually in order 1 = beginning whitening / chalking (0- 20% of the surface white)

2 = distinct whitening / chalking and starting white rust (20-50% of the area white)

3 = strong whitening / chalking (50-80% of the area white)

4 = completely corroded (80-100% of the area white) d) Determination of the weight

The determination of the coating weight was determined gravimetrically by measuring the difference in tare before and after coating in the demagnetized and dry state of the test sheets. The tare is then converted to the area of the respective sheet and expressed in [g / m ² ].

Claims

claims

A process for passivating a metallic surface comprising contacting a metallic surface with an aqueous composition containing the following components: at least one water-soluble polymer comprising acidic groups (X) wherein the polymer (X) is at least 0.6 mol Acid groups / 100 g of polymer; at least one volatile basic compound (B); at least one cationic crosslinker selected from polyvalent metal ions (M) and cationic polymers (P); at least one solvent (L) containing at least 80% by weight of water; optionally one or more surfactants (T); optionally further components (K); wherein the pH of the aqueous composition is in the range of 9 to 12.

A method according to claim 1, characterized in that a composition is used comprising: a) 10 to 40 wt .-% of at least one water-soluble polymer comprising acidic groups (X), wherein the polymer (X) at least 0.6 mol acid groups / 100 g comprises polymer; b) 1 to 20 wt .-% of at least one volatile, basic compound (B); c) 0.01 to 25% by weight of at least one cationic crosslinker selected from polyvalent metal ions (M) and cationic polymers (P); d) 20 to 89 wt .-% of at least one solvent (L) containing at least 80 wt .-% water, e) optionally 0 to 3 wt .-% of at least one surfactant (T), f) optionally 0 to 30 wt. -% of at least one other component (K). wherein the pH of the aqueous composition is in the range of 9 to 12.

3. The method according to any one of claims 1 or 2, characterized in that the aqueous composition as cationic crosslinker at least one polyvalent metal ion (M) selected from Mg ²⁺ , Ca ²⁺ , Zn ²⁺ , Mn ²⁺ , Fe ²⁺ , Cr ³⁺ , Al ³⁺ , Ti ⁴⁺ , Zr ⁴⁺ , Ce ³⁺ and Ce ⁴⁺ .

4. The method according to any one of claims 1 to 3, characterized in that the aqueous composition contains as cationic crosslinker at least one cationic polymer (P) selected from polyethyleneimines, Polyethyleniminderivaten, polyvinylamines and polyvinylimidazoles.

5. The method according to any one of claims 1 to 4, characterized in that the composition contains 0, 1 to 2 wt.%, Preferably 0, 1 to 0.8 wt.% Of at least one surfactant (T).

Process according to any one of Claims 1 to 5, characterized in that the water-soluble polymer (X) is a copolymer (X1) composed of the following monomers:

M1: from 30 to 90% by weight of methacrylic acid and / or acrylic acid;

M2: 10 to 70% by weight of at least one other monoethylenically unsaturated monomer other than (M1) which has one or more acidic groups;

optionally M3: 0 to 40% by weight of at least one OH group

Methacrylic acid ester and / or acrylic ester; optionally M4: 0 to 30 wt .-% of at least one other, from (M1), (M2) or

(M3) different ethylenically unsaturated monomer.

7. The method according to any one of claims 1 to 6, characterized in that it is the water-soluble polymer (X) is a copolymer which is composed of the following monomers: M1: 20 to 60 wt .-% acrylic acid;

M2: 20 to 60% by weight of vinylphosphonic acid;

M3: 1 to 40% by weight of hydroxyethyl acrylate.

A process according to any one of claims 1 to 7, characterized in that the aqueous composition is applied to the metallic surface in the form of a wet film, and wherein the aqueous composition has an application weight in the range of 0.3 to 2 g / m ² the metallic surface is applied.

9. A composition for passivating a metallic surface comprising a) from 10 to 40% by weight of at least one water-soluble, acid group-comprising polymer (X), wherein the polymer

(X) has at least 0.6 mol of acid groups / 100 g of polymer; b) 1 to 20 wt .-% of at least one volatile basic conjunction (B) selected from ammonia, amines CI_ ₄ alkyl and CI_ ₄ alkanolamines; c) 0.01 to 25 wt .-% of at least one cationic crosslinker selected from polyvalent metal ions (M) and cationic polymers (P) d) 20 to 89 wt .-% of at least one solvent (L), containing at least 80 wt .-% Water; e) optionally 0 to 3 wt .-% of at least one surfactant (T); f) optionally 0 to 30 wt .-% of at least one further component (K); wherein the aqueous composition has a pH in the range of 9 to 12.

10. The composition according to claim 9 comprising a) 10 to 40 wt .-% of at least one water-soluble, acidic

Group-comprising polymer (X), wherein the polymer (X) has at least 0.6 mol of acid groups / 100 g of polymer; b) 1 to 20% by weight of ammonia; d) from 0.5 to 5% by weight of at least one cationic polymer (P) selected from polyethyleneimines, polyethylenimine derivatives, polyvinylamines and polyvinylimidazoles; c2) optionally 0.01 to 25 wt .-% of at least one polyvalent metal ion

(M) selected from Mg ²⁺ , Ca ²⁺ , Zn ²⁺ , Mn ²⁺ , Fe ²⁺ , Cr ³⁺ , Al ³⁺ , Ti ⁴⁺ , Zr ⁴⁺ and Ce ³⁺ ; d) from 20 to 89% by weight of at least one solvent (L) containing at least 80% by weight of water; e) optionally 0 to 3 wt .-% of at least one surfactant (T); f) optionally 0 to 30 wt .-% of at least one further component (K); wherein the pH of the aqueous composition is in the range of 9 to 12.

Use of a composition according to one of claims 9 or 10 for the passivation of a metallic surface.

Coating on a metallic surface obtainable by contacting a metallic surface with an aqueous composition comprising the following components: a) at least one water-soluble polymer comprising acidic groups (X), wherein the polymer (X) has at least 0.6 mol of acid groups / 100 g comprises polymer; b) at least one volatile, basic compound (B);

c) at least one cationic crosslinker selected from polyvalent metal ions (M) and cationic polymers (P);

d) at least one solvent (L) containing at least 80% by weight of water; e) optionally a surfactant (T);

f) optionally further components (K), wherein the pH of the aqueous composition is in the range of 9 to 12.