EP2118337A1

EP2118337A1 - Method for the anti-corrosive treatment of metal substrates

Info

Publication number: EP2118337A1
Application number: EP07856691A
Authority: EP
Inventors: Michael Dornbusch
Original assignee: BASF Coatings GmbH
Current assignee: BASF Coatings GmbH
Priority date: 2007-03-15
Filing date: 2007-12-13
Publication date: 2009-11-18
Also published as: US20100098842A1; CN101636525A; WO2008110195A1; JP2010521583A; DE102007012406A1

Abstract

The invention relates to a method for the anti-corrosive treatment of metal substrates in which, in a first step (I), the substrate is coated by deenergized dipping in an aqueous bath of an anti-corrosive agent K1 having a pH value between 1 and 5, comprising at least one compound with a lanthanide metal as a cation and/or a d-element metal, with the exception of chromium, as a cation and/or a d-element metallate, with the exception of metallates comprising chromium, as an anion, and at least one acid with oxidation capacity, with the exception of acids having phosphorus or chromium, wherein a conversion is brought about on the surface of the substrate and, in a final step (III), an additional coating is performed by the precipitation of a cathodic electro-dipcoat.

Description

Process for corrosion protection equipment of metallic substrates

Processes and coating compositions for the electroless corrosion protection coating of various metal substrates, in particular by autophore-dipcoating, are known. They offer the advantage of the simpler and cheaper process as well as the shorter process time. In particular, cavities in or edges on the substrates to be coated can be better coated with the electroless methods than with methods in which the application of electrical voltages is necessary.

Recently, the development of chromium-free autophoretic coating compositions has been sought which ensure a very good corrosion protection comparable to chromium-containing coating compositions. In this case, coating compositions containing salts of the lanthanide and the d-elements and an organic film-forming component turned out to be particularly suitable.

However, the autophoretic coating compositions described, for example, in WO-A-99/29927, WO-A-96/10461 and DE-A-37 27 382 have as disadvantages the tendency of the metal ions formed from the substrate to migrate through the deposited corrosion protection layer and the use of ecologically critical substances, in particular fluorides, on.

DE-A-10 2005 023 728 and DE-A-10 2005 023 729 describe coating compositions which excellently solve the aforementioned problems of metal ion migration and the use of ecologically critical substances. In particular, the two-stage process for corrosion protection equipment of metallic substrates described in DE-A-10 2005 023 728, in which in a first stage the substrate is immersed in a bath of a corrosion inhibitor K, which causes a conversion on the substrate surface and in a second stage the substrate treated according to step (a) is immersed in a bath of an aqueous coating composition comprising a water-dispersible and / or water-soluble polymer P with covalently bonded ligands which form chelates with the metal ions liberated upon corrosion of the substrate and / or the substrate surface , as well as with crosslinking functional groups B, which can form covalent bonds with themselves, with further complementary functional groups B 'of the polymer P and / or with further functional groups B and / or B' on crosslinking agents V, has proven to be particular proved suitable.

For special applications, in particular in the automotive industry, however, the anticorrosive coatings on purely autophoretic basis have proved to be insufficient, since the corrosion protection, especially after impact stress can not fully meet the high requirements.

In WO-A-01/46495 the combination of a 2-stage pretreatment of metal substrates is described, which in the first stage, a pretreatment with a coating agent containing a compound of elements of the group MIb, IVb and / or lanthanides, and in a second Stage, the pretreatment with a coating composition comprising a reaction product of an epoxy-functional compound with phosphorus-, amine- and / or sulfur-containing compounds, with a subsequent lead-free electrodeposition coating. The coating produced in this way should combine good corrosion protection with a high degree of eco friendliness. However, fluorine-containing compounds which are ecologically critical are preferably used in the first pretreatment stage. Task and solution

In the light of the aforementioned prior art, it was the object of the invention to find an ecologically largely harmless process for anti-corrosion protection, in particular in the automotive sector, which can be applied to the substrate to be protected by means of a technically simple process. In particular, the process should be feasible without fluoride-containing substances. Furthermore, the method according to the invention should in particular lead to anticorrosive layers which largely prevent the migration of the metal ions formed from the substrate and which are deposited well on edges and in cavities of the substrate. Furthermore, the influence of foreign metal ions should be kept as low as possible and an effective corrosion protection can be achieved with comparatively low use of material. Furthermore, the method should provide corrosion protection layers which develop effective protection for as many different metal substrates as possible and are largely independent of the redox potential of the substrate to be coated.

In the light of the above objects, a process for corrosion protection equipment of metallic substrates was surprisingly found comprising as a first stage (I) a current-free pretreatment with an aqueous corrosion inhibitor K1, containing at least one compound (A1) with a lanthanide metal as a cation and / or a d Element metal with the exception of chromium as cation and / or a d-element metalate with the exception of chromium-containing metallates as anion and (A2) at least one acid capable of oxidation with the exception of phosphorous and / or chromium-containing acids, summarizes, preferably as a second stage (II), a further current-free pretreatment with an aqueous corrosion inhibitor K2, which a water-dispersible and / or water-soluble polymer P with covalently bonded ligands L, which form chelates with the metal ions liberated upon corrosion of the substrate and / or with the substrate surface, and with crosslinking functional groups B, which contain themselves, with further functional groups B 'of the polymer P and / or with other functional groups B and / or B' to crosslinkers V can form covalent bonds contains, and as the final stage (III) a further coating by deposition of an electrodeposition paint.

Description of the invention

The first stage (I) of the process according to the invention

In the first stage (I) of the process according to the invention, the aqueous anticorrosive agent K1 described below is applied to the metallic substrate without electricity. Current-free means in this case the absence of electrical currents by applying an electrical voltage.

Prior to the application of the aqueous corrosion inhibitor K1, the substrate is purified in a preferred embodiment of the invention, in particular oily and greasy residues, preferably detergents and / or alkaline cleaning agents are used. In a further preferred embodiment of the invention, cleaning with detergents and / or alkaline cleaning agents is followed by rinsing again with water before application of the coating composition according to the invention. In order to remove deposits and / or chemically modified, in particular oxidized, layers on the surface of the substrate, in a further preferred embodiment of the invention prior to the final rinsing step, a mechanical cleaning of the surface, for example with grinding media, and / or a chemical removal of the surface layers, for example with deoxidizing cleaning agents.

The aqueous corrosion inhibitor K1 has a pH of between 1 and 5 and contains at least one compound (A1) with a lanthanide metal as cation and / or a d-element metal with the exception of chromium as cation and / or a d-element metal. Elemental metalate with the exception of chromium-containing metalates as anion and (A2) at least one oxidation-capable acid with the exception of phosphorus-containing and / or chromium-containing acids.

The compound (A1) is preferably very soluble in water. Particular preference is given to compounds (A1) [cation] n [anion] m (with n, m> = 1) having a solubility product LP = [cation] " ^* [anion] ^m >^10'8 * mol ^{(n + m)} / L ^{(n + m)} , most preferably compounds (A1) with a solubility product LP> 10 ^"6 * mol ^{(n + m)} / l ^{(n + m)} . In a very particularly preferred embodiment of the invention, the concentration of the compounds (A1) in the anticorrosive agent 10 ^"1 to 10 ^{" 4} ITiOl / !, in particular 5 * 10 ^"1 to 10 ^{" 3} mol / l.

The compound (A1) may have as its cationic component lanthanide metal cations and / or d-metal cations. Preferred lanthanide metal cations are lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium and / or dysprosium cations. Very particular preference is given to lanthanum, cerium and praseodymium cations. The lanthanide metal cations can be present in monovalent, trivalent and / or trivalent oxidation state, the trivalent oxidation state being preferred. Preferred d-metal cations are titanium, vanadium, manganese, yttrium, zirconium, niobium, molybdenum, tungsten, cobalt, ruthenium, rhodium, palladium, osmium and / or iridium cations. Excluded as d-element cation is the chromium cation in all oxidation states. Very particular preference is given to vanadium, manganese, tungsten, molybdenum and / or yttrium cations. The d-element cations can be present in one to six valent oxidation state, with a three to six-valent oxidation state being preferred.

The anions forming the compounds (A1) with the lanthanide metal cations and / or d-element cations are preferably selected in such a way that the abovementioned conditions for the solubility product LP are given. Anions of oxidizing acids of the elements of VI., VII. And VIII. Subgroup of the Periodic Table of the Elements and anions of oxidizing acids of the elements of V. and VI are preferred. Main group of the Periodic Table of the Elements with the exception of anions of oxidizing acids of phosphorus and chromium are used, such as preferably nitrates, nitrites, sulfites and / or sulfates. Further possible as anions are halides except fluorides.

In a further preferred embodiment of the invention, the lanthanide metal cations and / or d-element cations of the compounds (A1) can also be present as complexes with monodentate and / or polydentate potentially anionic ligands. Preferred ligands are optionally functionalized terpyridines, optionally functionalized ureas and / or thioureas, optionally functionalized amines and / or polyamines, in particular EDTA, imines, in particular imin-functionalized pyridines, organosulfur compounds, in particular optionally functionalized thiols, thiocarboxylic acids, thioaldehydes, Thioketone, dithiocarbamates, sulfonamides, thiamides and particularly preferably sulfonates, optionally functionalized organoboron compounds, in particular boric acid esters, optionally functionalized polyalcohols, in particular carbohydrates and derivatives thereof and chitosans, optionally functionalized acids, in particular di- and / or oligofunctional acids, if appropriate functionalized carbenes, acetylacetonates, optionally functionalized acetylenes, optionally functionalized carboxylic acids, in particular carboxylic acids which are ionic and / or keto dinatively bound to metal centers, as well as phytic acid and its derivatives.

Very particular preference is given as ligands phytic acid, their derivatives and sulfonates, which are optionally functionalized.

In a particularly preferred embodiment of the invention, the compounds (A1) contain d-element metallates as anions, which together with the d-element cations or also alone can form the compound (A1). Preferred d-elements for the metallates are vanadium, manganese, zirconium, niobium, molybdenum and / or tungsten. Very particular preference is given to vanadium, manganese, tungsten and / or molybdenum. Excluded as d-element metalate are chromates in all oxidation states. Particularly preferred d-element metalates are oxo anions, in particular tungstates, permanganates, vanadates and / or molybdates.

If the d-element metallates form the compound (A1) alone, that is to say without lanthanide metal cations and / or d-metal cations, then the preferred solubility product LP of such compounds is as described above. Preferred cations of such compounds (A1) are ammonium ions which are optionally substituted by organic radicals, phosphonium ions and / or sulfonium ions, alkali metal cations, in particular lithium, sodium and / or potassium, alkaline earth metal cations, in particular magnesium and / or calcium. Particularly preferred are the optionally substituted with organic radicals ammonium ions and the alkali metal cations, which ensure a particularly high solubility product LP of the compound (A1).

As component (A2) of the corrosion protection agent K1, at least one acid capable of oxidation is used in such a way that the pH of the corrosion protection agent is between 1 and 5, preferably between 2 and 4. Preferred acids (A2) are selected from Group of oxidizing mineral acids, such as in particular nitric acid, nitrous acid, sulfuric acid and / or sulfurous acid. To adjust the pH, if necessary, a buffer medium can be used, such as salts of medium-strong bases and weak acids, in particular ammonium acetate.

As the continuous phase, water is used for the corrosion inhibitor K1, preferably deionized and / or distilled water.

The substrate pretreated as above is contacted with the anticorrosion agent K1. This is preferably done by immersing or pulling through the substrate in or by a bath containing the corrosion inhibitor K1. The residence times of the substrate in the anticorrosion agent K1 are preferably 1 second to 10 minutes, preferably 10 seconds to 8 minutes, and more preferably 30 seconds to 6 minutes. The temperature of the bath containing the corrosion inhibitor K1 is preferably between 25 and 90 ^° C., preferably between 30 and 80 ^° C., more preferably between 35 and 70 ^° C.

The wet film thickness of the layer produced with the coating agent K1 after autodeposition is between 5 and 900 nm, preferably between 15 and 750 nm, particularly preferably between 25 and 600 nm.

After the treatment of the substrate with the coating agent K1 and before the final electrodeposition coating drying of the layer of the coating K1 can be carried out at temperatures between about 30 and 200 ⁰ C, in particular between 100 and 180 ⁰ C, wherein the drying apparatus for the advantageous Effect of the coating composition of the invention can be considered largely uncritical. Particularly preferably, the layer of coating agent K1 is flashed off before the final electrodeposition coating or, if appropriate, before the preferred application of the corrosion inhibitor K2, ie for a period of 30 seconds to 30 minutes, preferably for a period of 1 minute to 25 minutes, temperatures between 25 and 120 ⁰ C, preferably between 30 and 90 ⁰ C exposed.

The preferred second stage (II) of the process according to the invention

The aqueous anticorrosive agent K2 according to the invention, which in a preferred embodiment of the invention is applied to the layer of corrosion inhibitor K1 applied in the first stage (I) of the process according to the invention, contains polymers P which carry ligands L which react with those in the corrosion of the Substrate released metal ions form chelates, and carry the crosslinking functional groups B, which can form covalent bonds with itself and / or with other functional groups B ', which may optionally be part of additional crosslinking V.

For the purposes of the invention, water-dispersible or water-soluble means that the polymers P in the aqueous phase form aggregates with an average particle diameter of <50, preferably <35 nm and particularly preferably <20 nanometers or are dissolved in a molecularly disperse manner. Thus, such aggregates differ significantly in their average particle diameter of dispersion particles, as described for example in DE-A-37 27 382 or WO-A-96/10461. Molecular dispersions of dissolved polymers P generally have molecular weights of <100,000, preferably <50,000, more preferably <20,000 daltons.

The size of the aggregates consisting of polymer P is in a conventional manner by introducing hydrophilic groups HG am Polymer P accomplished. The number of hydrophilic groups HG on the polymer P depends on the solvation capacity and the steric accessibility of the groups HG and can also be set by a person skilled in the art in a manner known per se. Preferred hydrophilic groups HG on the polymer P are ionic groups such as in particular sulfate, sulfonate, sulfonium, phosphate, phosphonate, phosphonium, ammonium and / or carboxylate groups and nonionic groups, in particular hydroxyl, primary, secondary and / or tertiary amine, amide and / or oligo- or polyalkoxy substituents, such as preferably ethoxylated or propoxylated substituents, which may be etherified with further groups. The hydrophilic groups HG may be identical to the ligands L and / or crosslinking functional groups B and B 'described below. The number of hydrophilic groups HG on the polymer P depends on the solvation capacity and the steric accessibility of the groups HG and can also be set by a person skilled in the art in a manner known per se.

In a further preferred embodiment of the invention, the abovementioned hydrophilic groups HG form a gradient in their concentration along the polymer backbone. The gradient is defined by a slope in the spatial concentration of the hydrophilic groups along the polymer backbone. Polymers P thus constructed are capable of forming micelles in the aqueous medium and have a surface activity on the surface of the substrate to be coated, that is, the interfacial energy of the coating composition according to the invention on the surface to be coated is reduced.

The gradient is preferably generated by suitable arrangement of monomeric units which make up the polymer and which hydrophilic groups and / or groups with which hydrophilic groups HG can be generated, are produced in a manner known per se. As polymer backbone of the polymers P it is generally possible to use any desired polymers, preferably those having molecular weights of from 1,000 to 50,000 daltons, more preferably having molecular weights of from 2,000 to 20,000 daltons. The polymer backbone used are preferably polyolefins or poly (meth) acrylates, polyurethanes, polyalkyleneimines, polyvinylamines, polyalkyleneamines, polyethers, polyesters and polyalcohols which are in particular partially acetalated and / or partially esterified. The polymers P can be linear, branched and / or dendritic. Very particularly preferred polymer backbones are polyalkyleneimines, polyvinylamines, polyalcohols, poly (meth) acrylates and hyperbranched polymers, as described, for example, in WO-A-01/46296.

The polymers P are preferably stable to hydrolysis in the acidic pH range, in particular at pH values <5, particularly preferably at pH values <3.

Suitable ligands L are all groups or compounds which can form chelates with the metal ions released upon corrosion of the substrate. Preference is given to mono- and / or polydentate potentially anionic ligands. Particularly preferred ligands are L.

optionally functionalized ureas and / or thioureas, especially acylthioureas such as

benzoylthiourea,

optionally functionalized amines and / or polyamines, in particular EDTA,

optionally functionalized amides, in particular carboxylic acid amides

Imines and imides, in particular imin-functionalized pyridines, Oximes, preferably 1,2-dioximes such as functionalized diacetyldioxime,

Organosulfur compounds, such as, in particular, optionally functionalized thiols such as thioethanol, thiocarboxylic acids, thio-aldehydes, thioketones, dithiocarbamates, sulfonamides, thioamides and particularly preferably sulfonates,

Organophosphorus compounds, in particular phosphates, more preferably phosphoric acid esters of (meth) acrylates, and also phosphonates, particularly preferably vinylphosphonic acid and hydroxy-, amino- and amido-functionalized phosphonates,

optionally functionalized organoboron compounds, in particular boric acid esters,

optionally functionalized polyalcohols, in particular carbohydrates and derivatives thereof, and chitosans, optionally functionalized acids, in particular di- and / or oligofunctional acids, or optionally functionalized (poly) carboxylic acids, in particular carboxylic acids, which are bonded to metal centers ionically and / or coordinately preferably (poly) methacrylates having acid groups or di- or oligofunctional acids,

optionally functionalized carbenes,

Acetylacetonates,

- optionally functionalized acetylenes, as well

- phytic acid and its derivatives.

Suitable crosslinking functional groups B on the polymer P are those which can form covalent bonds with themselves and / or with complementary functional groups B '. The covalent bonds are preferably formed thermally and / or by the action of radiation. Particularly preferably, the covalent bonds are formed thermally. The crosslinking functional Groups B and B 'cause the formation of an intermolecular network between the molecules of polymer P. Under the action of radiation crosslinking functional groups B and B', respectively, have activatable bonds, such as carbon-hydrogen, carbon-carbon, carbon Oxygen, carbon-nitrogen, carbon-phosphorus or carbon-silicon single or double bonds. In this case, carbon-carbon double bonds are particularly advantageous. Particularly suitable carbon-carbon double bonds as groups B are

- Particularly preferably (meth) acrylate groups

- Ethyl acrylate groups

- vinyl ether and vinyl ester groups

- crotonate and cinnamate groups - allyl groups

- dicyclopentadienyl groups

- norbornyl and isoprenyl groups

- Isopropenyl or butenyl groups.

Thermally crosslinking functional groups B can form covalent bonds with themselves or preferably with complementary crosslinking functional groups B ¹ under the influence of thermal energy. Particularly suitable thermal crosslinking functional groups B and B 'are

- Particularly preferably hydroxyl groups

Mercapto and amino groups,

Aldehyde groups, azide groups,

Acid groups, in particular carboxylic acid groups, Acid anhydride groups, in particular carboxylic anhydride groups,

Acid ester groups, in particular carboxylic acid ester groups,

Ether groups, more preferably carbamate groups,

- urea groups,

- epoxide groups,

Particularly preferably isocyanate groups, which are very particularly preferably reacted with blocking agents which deblockieren at the stoving temperatures of the coating compositions of the invention and / or are incorporated without deblocking in the forming network.

Particularly preferred combinations of thermally crosslinking groups B and complementary groups B 'are:

Hydroxyl groups with isocyanate and / or carbamate groups,

Amino groups with isocyanate and / or carbamate groups,

- Carboxylic acid groups with epoxide groups.

Particularly preferred polymers P having a gradient of the hydrophilic groups along the polymer backbone contain copolymers PM, which can be prepared by single-stage or multistage radical copolymerization in an aqueous medium

a) olefinically unsaturated monomers (a1) and (a2), wherein (a1) in each case at least one monomer from the group consisting of oiefinisch unsaturated monomers (a11) having at least one hydrophilic group HG, olefinically unsaturated monomers (a12) having at least one Ligand group L and olefinically unsaturated monomers (a13) having at least one crosslinking group B. and

b) at least one olefinically unsaturated monomer of the general formula I which is different from the olefinically unsaturated monomers (a1) and (a2)

R ¹ R ² C = CR ³ R ⁴ (I),

wherein the radicals R ¹ , R ² , R ³ and R ^{4 are} each independently hydrogen or substituted or unsubstituted alkyl, cycloalkyl, alkylcycloalkyl, cycloalkylalkyl, aryl, alkylaryl, cycloalkylaryl, arylalkyl or arylcycloalkyl radicals with the proviso that at least two of the variables R ¹ , R ² , R ³ and R ^{4 are} substituted or unsubstituted aryl, arylalkyl or arylcycloalkyl radicals, in particular substituted or unsubstituted aryl radicals.

Suitable hydrophilic monomers (a11) contain at least one hydrophilic group (HG) which, as described above, preferably from the group consisting of sulfate, sulfonate, sulfonium, phosphate, phosphonate, phosphonium, ammonium and / or or carboxylate groups and hydroxyl, primary, secondary and / or tertiary amine, amide and / or oligo- or polyalkoxy substituents, such as preferably ethoxylated or propoxylated substituents, which may be etherified with further groups. Examples of suitable hydrophilic monomers (a11) are acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid, maleic acid, fumaric acid or itaconic acid and salts thereof, preferably acrylic acid and methacrylic acid, olefinically unsaturated sulfonic, sulfuric, phosphoric or Phosphonic acids, their salts and / or their partial esters. Also suitable are olefinically unsaturated sulfonium and phosphonium compounds. Also very suitable are monomers (a11) which carry at least one hydroxyl group or hydroxymethylamino group per molecule and are essentially free from acid groups, such as in particular hydroxyalkyl esters of alpha, beta-olefinically unsaturated carboxylic acids, such as hydroxyalkyl esters of acrylic acid, methacrylic acid and ethacrylic acid, in which Hydroxyalkyl group contains up to 20 carbon atoms, preferably 2-hydroxyethyl, 2-hydroxypropyl, 3-hydroxypropyl, 3-hydroxybutyl, 4-hydroxybutyl acrylate, methacrylate, formaldehyde adducts of aminoalkyl esters of alpha, beta-olefinically unsaturated carboxylic acids and of alpha , beta-unsaturated carboxylic acid amides, such as N-methylol and N, N-dimethylol aminoethyl acrylate, - aminoethyl methacrylate, -acrylamide and -methacrylamide. Suitable amine-ring-containing monomers (a1) are: 2-aminoethyl acrylate and methacrylate, N-methyl- and N, N-dimethyl-aminoethyl acrylate, or allylamine. As monomers containing amide groups (a11) are preferred amino de of alpha, beta-olefinically unsaturated carboxylic acids such as (meth) acrylamide, preferably N-methyl - or N ₁ N-dimethyl (meth) acrylamide, are used. As ethoxylated or propoxylated monomers (a11) it is preferred to use acrylic and / or methacrylic acid esters of polyethylene oxide and / or polypropylene oxide units whose chain length is preferably between 2 and 20 ethylene oxide or propylene oxide building blocks. When selecting the hydrophilic monomers (a11) care should be taken to avoid the formation of insoluble salts and polyelectrolyte complexes.

Examples of suitable monomers (a12) are olefinically unsaturated monomers which have the above-described ligands L as substituents. Examples of suitable monomers (a12) are esters and / or the amides of acrylic acid, methacrylic acid, ethacrylic acid, cro- tonic acid, maleic acid, fumaric acid or itaconic acid, in particular of acrylic and / or methacrylic acid, which have the ligands L in the ester and / or amide radical. Preferred ligands L are optionally functionalized urea and / or thiourea subtituents, optionally functionalized amine and / or polyamine subtynes, imine and imide substituents, in particular imin-functionalized pyridines, oxime substituents, preferably 1,2-dioximes such as functionalized diacetyldioxime, Organosulfur substituents, in particular derivable from optionally functionalized thiols such as thioethanol, thiocarboxylic acids, thioaldehydes, thioketones, dithiocarbamates, sulfonamides, thioamides and particularly preferably sulfonates, organophosphorus substituents, in particular derivable from phosphates, more preferably phosphoric acid esters of (meth) acrylates, and phosphonates, vinylphosphonic acids and hydroxy-, amino- and amido-functionalized phosphonates, optionally functionalized organoboron substituents, in particular derivable from boric acid esters, optionally functionalized polyalcohol substituents - tuenten, such as in particular derivable from carbohydrates and derivatives thereof and chitosans, optionally functionalized acid substituents, in particular derivable from di- and / or oligofunctional acids, or optionally functionalized (poly) carboxylic acids, in particular carboxylic acids, the ionic and / or coordinative can be bonded to metal centers, preferably (poly) methacrylates with acid groups or di- or oligofunctional acids, substituents with optionally functionalized carbenes, acetylacetonates, optionally functionalized acetylenes, and phytic acids and derivatives thereof.

Examples of suitable monomers (a13) are olefinically unsaturated monomers which have the above-described crosslinking groups B and B 'as substituents. Examples of suitable monomers (a13) are esters and / or the amides of acrylic acid, methacrylic acid, ethacrylic acid, crotonic acid, maleic acid, fumaric acid or itaconic acid, in particular of acrylic and / or methacrylic acid, which have the crosslinking groups B in the ester and / or amide radical. Particularly preferred hydroxylating groups B and B 'are hydroxyl groups, and also, for example, mercapto and amino groups, aldehyde groups, azide groups, acid groups, in particular carboxylic acid groups, acid anhydride groups, in particular carboxylic anhydride groups, acid ester groups, especially carboxylic acid ester groups, ether groups, more preferably carbamate groups, for example urea groups. Epoxide groups, and particularly preferably isocyanate groups, which are very particularly preferably reacted with blocking agents which unblock at the stoving temperatures of the coating compositions of the invention and / or are incorporated without deblocking in the forming network.

The monomers (a11) are arranged in the polymer PM in such a way that the already described gradient of the hydrophilic groups HG results along the polymer main chain. This is generally due to the specific copolymerization parameters of the different monomers (a11), (a12), (a13), (a2) and (b) in the aqueous reaction medium. The aforementioned monomers (a12) and (a13) are preferably randomly arranged along the main polymer chain. From the above performance of the exemplified monomers (a11), (a12) and (a13) it is apparent that the hydrophilic groups HG, the ligands L and the crosslinking groups B can be partially or completely identical. In this case, then also the ligands L and the crosslinking functional groups B usually have a gradient along the polymer main chain.

Examples of preferred olefinically unsaturated comonomers (a2) are (1) substantially acid group-free esters of olefinically unsaturated acids, such as (meth) acrylic acid, crotonic acid, ethacrylic acid, vinylphosphonic acid or vinylsulfonic acid alkyl or cycloalkyl esters having up to 20 carbon atoms in the alkyl radical, in particular methyl, ethyl, propyl , n-butyl, sec-butyl, hexyl,

Ethylhexyl, stearyl and lauryl, cyclohexyl (meth) acrylate;

(2) vinyl esters of alpha-branched monocarboxylic acids having 5 to 18 carbon atoms in the molecule, such as the vinyl esters of Versatic® acid sold under the trademark VeoVa®; such as

(3) vinylaromatic hydrocarbons, such as styrene, vinyltoluene or alpha-alkylstyrenes, especially alpha-methylstyrene;

For the preparation of the copolymers PM reference is made to the teachings of DE-A-198 58 708, DE-A-102 06 983 and DE-A-102 56 226.

As crosslinkers V with groups B and / or B 'thermally and / or by radiation-crosslinking groups, in principle all crosslinkers known to the person skilled in the art are suitable. Preference is given to low molecular weight or oligomeric crosslinkers V having a molecular weight of <20,000 daltons, more preferably <10,000 daltons. The backbone of the crosslinker V carrying the crosslinking groups B and / or B 'can be linear, branched and / or hyperbranched. Preference is given to branched and / or hyperbranched structures, in particular those as described, for example, in WO-A-01/46296. The crosslinkers V are preferably stable to hydrolysis in the acidic pH range, in particular at pH values <5, particularly preferably at pH values <3.

Particularly preferred crosslinkers V carry the above-described crosslinking groups B and / or B ', which are crosslinking with the crosslinking Groups of the polymer P react under the formation of covalent bonds. Very particular preference is given to crosslinkers V with groups B and / or B 'that crosslink thermally and, if appropriate, additionally by the action of radiation. In a further particularly preferred embodiment of the invention, the crosslinkers V carry in addition to the crosslinking groups B and / or B 'ligands L', which may be identical to and / or different from the ligands L of the polymer P. Particularly suitable crosslinking functional groups B and B 'for the crosslinkers V are:

- in particular hydroxyl groups,

- especially aldehyde groups,

Azide groups, acid anhydride groups, in particular carboxylic anhydride groups,

Carbamate groups,

- urea groups,

in particular isocyanate groups which are very particularly preferably reacted with blocking agents which deblock at the stoving temperatures of the coating compositions of the invention and / or are incorporated into the forming network without deblocking,

(Meth) acrylate groups, - vinyl groups

or combinations thereof.

Very particularly preferred crosslinkers V are branched and / or hyperbranched polyisocyanates which are at least partially blocked and additionally carry ligands L '. As the continuous phase, water is used for the coating agent K2, preferably deionized and / or distilled water. As a further preferred component, at least one acid capable of oxidation is used in such a way that the pH of the coating agent K2 is preferably between 1 and 5, preferably between 2 and 4. Particularly preferred acids are selected from the group of oxidizing mineral acids, in particular nitric acid, nitrous acid, sulfuric acid and / or sulfurous acid. To adjust the pH, if necessary, a buffer medium can be used, such as, for example, salts of medium-strength bases and weak acids, in particular ammonium acetate.

In a further preferred embodiment of the invention, the coating agent K2 contains at least one component KOS, which reduces the surface tension of the coating agent according to the invention during the autodeposition on the substrate surface and / or during the subsequent drying step. The component KOS can be selected from the group of anionic, cationic and nonionic surface-active substances. Amphiphilic substances, which may be low molecular weight, oligomeric and / or polymeric, are preferably used. By "amphiphilic" it is to be understood that the substances have a hydrophilic and a hydrophobic structural component. "Low molecular weight" means that the average molecular weights of the surface-active component KOS are up to 2000 daltons, particularly preferably up to 1000 daltons. "oligomer" means that the surface-active component KOS has about 2 to 30, preferably 3 to 15, preferably repeating components and has an average molecular weight between about 200 and 4000 daltons, preferably between about 500 and 3000 daltons, and under "polymer" in that the surface-active component KOS has more than 10 preferably repeating building blocks and an average molecular weight of more than 500 daltons. preferably more than 1000 daltons. The surface-active component KOS is different from the polymer P according to the invention.

As the surface-active component KOS, alkylcarboxylic acid and its salts, alpha-omega-dicarboxylic acids and their salts, alpha-omega-dialcohols, alpha-omega-diamines and -amides and their salts, alkylsulfonic acids and their salts are preferred as low-molecular substances Salts and alkylphosphoric acids and alkylphosphonic acids and their salts used. As oligomeric and / or polymeric surface-active substances it is preferred to use polyalkylene glycols, polyvinyl lactams, such as, for example, polyvinylpyrrolidone and polyvinyl caprolactam, polyvinylimidazoles, polyvinyl alcohols and polyvinyl acetate. Adhesive and / or 1, 6-hexanediol are very particularly preferred as surface-active component KOS as low-molecular substances and poly (oligo) ethylene glycols and / or poly (oligo) propylene glycols as oligomeric and / or polymeric substances. The proportion of the surface-active substance KOS in the coating agent K2 is preferably between 10 ^-4 and 5% by weight, preferably between 10 ² and 2% by weight, based on the coating agent K 2.

In a particularly preferred embodiment of the invention, the coating agent K2 additionally contains a salt (S) which has lanthanide metal cations and / or d-metal cations as the cationic constituent. Preferred lanthanide metal cations are lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium and / or dysprosium cations. Very particular preference is given to lanthanum, cerium and praseodymium cations. The lanthanide metal cations can be present in mono-, di- and / or trivalent oxidation state, the trivalent oxidation state being preferred. Preferred d-metal cations are titanium, vanadium, manganese, yttrium, zirconium, niobium, molybdenum, tungsten, cobalt, ruthenium, rhodium, palladium, osmium and / or iridium cations. Excluded as d-element cation is the chromium cation in all oxidation states. Very particular preference is given to vanadium, manganese, tungsten, molybdenum and / or yttrium cations. The d-element cations can be present in one to six valent oxidation state, with a three to six valent oxidation state being preferred.

In a very particularly preferred embodiment of the invention, the lanthanide metal cations and / or d-element cations of the salt (S) can also be present as complexes with monodentate and / or polydentate potentially anionic ligands. Preferred ligands are optionally functionalized terpyridines, optionally functionalized ureas and / or thioureas, optionally functionalized amines and / or polyamines, in particular EDTA, imines, in particular imin-functionalized pyridines, organosulfur compounds, in particular optionally functionalized thiols, thiocarboxylic acids, thioaldehydes, Thioketone, dithiocarbamates, sulfonamides, thioamides and particularly preferably sulfonates, optionally functionalized organoboron compounds, in particular boric acid esters, optionally functionalized polyalcohols, in particular carbohydrates and derivatives thereof and chitosans, optionally functionalized acids, in particular di- and / or oligofunctional acids, if appropriate functionalized carbenes, acetylacetonates, optionally functionalized acetylenes, optionally functionalized carboxylic acids, in particular carboxylic acids, which are ionic and / or koodi can be bound natively to metal centers, and phytic acid and their derivatives.

In the preferred second step (II) of the process, the substrates coated with the anticorrosion agent K1 are coated with the coating agent K2. In this case, the substrate coated with the anticorrosive agent K1 can be dried or flashed off before application of the anticorrosion agent K2 as described above. Preferably, the coating closes with the corrosion inhibitor K2 directly to the coating with the anticorrosion agent K1, wherein after the application of the anticorrosive K1 preferably rinsed with preferably distilled water and blown dry with air, preferably with an inert gas, for example with nitrogen. The coating is preferably carried out by immersing or pulling through the coated substrate in or through a bath containing the coating agent K2. The residence times of the substrate in the coating agent K2 are preferably 1 second to 15 minutes, preferably 10 seconds to 10 minutes and more preferably 30 seconds to 8 minutes. The temperature of the bath containing the coating composition according to the invention is preferably between 20 and 90 ^° C., preferably between 25 and 80 ^° C., more preferably between 30 and 70 ^° C.

The wet film thickness of the layer produced with the coating agent K2 after autodeposition is between 5 and 1500 nm, preferably between 15 and 1250, particularly preferably between 25 and 1000 nm.

After the treatment of the substrate with the coating agent K2 and before the final electrocoating, drying of the composite of substrate and the layers of the coating agent K1 and the coating agent K2 at temperatures between about 30 and 200 ⁰ C, in particular between 100 and 180 ^0th C carried out, wherein the drying apparatus for the advantageous effect of the coating composition according to the invention can be considered largely uncritical.

Most preferably, the composite of coating agent K1 and coating agent K2 is flashed off before the final electrodeposition coating, that is to say for a period of 30 seconds to 30 minutes, preferably for a period of 1 minute Temperatures between 25 and 120 ⁰ C, preferably between 30 and 90 ⁰ C exposed to 25 minutes.

The final electrodeposition coating (III) of the coating method according to the invention

For the electrodeposition coating carried out in stage (III), in principle all cathodic electrodeposition coatings are suitable. It is preferred to use cathodically depositable electrodeposition paints which meet high ecological standards, such as, in particular, electrodeposition paints free of lead or chromium-containing anti-corrosive pigments, as described, for example, in EP-A-0 528 853.

As binders for the cathodically depositable electrodeposition paints, preference is given to using amine-modified epoxy resins in combination with crosslinkers, as described, for example, in DE-A-35 18 770, DE-A-35 18 732, EP-AO 102 501, DE-A-27 01 002, US-A-4,104,147, EP-A-004,090, EP-A-012463, US-A-4,031,050, US-A-3,922,253, US-A-4,101,486, US-A-4,038,232 and US -A-4,017,438.

The electrodeposition coatings can be applied without problems to the layers deposited according to step (I) or step (II). The parameters for the electrophoretic deposition of electrodeposition coatings correspond to the technologically common parameters.

The layered composites prepared in the sequence of stages (I) and (III) or stages (I), (II) and (III) are generally at temperatures of 130 to 200 ⁰ C, preferably at temperatures of 150 to 180 ⁰ C. , burned for a period of 15 to 60 minutes, preferably for a period of 15 to 30 minutes. Intensive crosslinking of the electrodeposition coating layer applied in step (III) and the layer of coating composition K2 applied in the preferred step (II) are carried out here. Surprisingly, the electrodeposition coating adheres excellently to the layers deposited according to stage (I) or stage (II). In addition, the laminates have outstanding resistance to impact stress.

The resistance to corrosion is excellent and meets the requirements of the automotive industry to a high degree.

The layers applied in accordance with stage (III) can be used to apply, in particular, the layers customary in automotive OEM finishing, in the sequence of filler, basecoat and clearcoat, in a manner known per se.

Surprisingly, the process according to the invention can be used on a wide range of substrates and is largely independent of the redox potential of the substrate. Preferred substrate materials are zinc, iron, magnesium and aluminum, and their alloys, wherein the aforementioned metals are preferably present in the alloys to at least 20 wt .-%. Preferably, the substrates are formed as sheets, as used for example in the automotive industry, the construction industry and the mechanical engineering industry.

The examples given below are intended to further illustrate the invention. Examples

Production Example 1a: Preparation of the First Tank with the Corrosion Inhibitor K1 1.77 g (0.01 mol) of ammonium molybdate tetrahydrate (A1) are dissolved in one liter of water. The solution is adjusted to pH = 2.5 using nitric acid (A2). Optionally, it is counter-buffered to adjust the aforementioned pH with aqueous ammonia solution.

Preparation Example 2a Synthesis of the Polymer Component P for the Anti-Corrosive K2

There are 5g (6.25 * 10 ^"3 mol) of a polyethyleneimine having an average molecular weight Mw = 800 g / mol (Lupasol FG from BASF AG, ratio of primary: secondary: tertiary amino groups (pst): 1: 0, 9: 0.5) in 100 g of ethanol under a nitrogen atmosphere, and 10.7 g (0.066 mol) of benzoylisothiocyanate dissolved in 86 g of ethanol are added over 45 minutes at 75 ^° C. The mixture is stirred for a further 4 hours at this temperature and set the product without further purification.

Preparation Example 2b Synthesis of Crosslinker V Containing Salt S for Corrosion Inhibitor K2

3.1 g (0.008 mol) of cerium (III) chloride heptahydrate in 50 ml of water are initially taken. A solution of 4.1 g (0.025 mol) of 4-hydroxycinnamic acid and 1 g (0.025 mol) of sodium hydroxide solution in 50 ml of water is prepared and brought to pH = 7.9 with hydrochloric acid. This solution is added slowly to the cerium solution, so that the pH of the cerium solution does not rise above 6. The precipitate is washed with ethanol and water. 1.7 g (0.003 mol) of this cerium complex are mixed with 9.1 g (2.5% NCO content) of a branched polyisocyanate blocked with dimethylpyrazole at 75% (Bayhydur VP LS 2319 from Bayer AG). in 80.1 g of ethyl acetate and 0.7 g of an OH-functional dipropylenetriamine (Jeffcat ZR 50 Fa. Huntsmann) for 5 hours at 4O ⁰ C reacted. The product is used without further purification.

Production Example 3: Production of the Second Basin with the Corrosion Inhibitor K2

In one liter of water in each case 3 g of the polymer component P are dissolved according to Example 2a and 2g of the crosslinker V according to Example 2b. The solution is adjusted to pH = 2.5 by means of nitric acid. Optionally, counter-buffered to adjust the aforementioned pH with aqueous ammonia solution.

Example 4 Coating of the Substrate with the Corrosion Inhibitor K1 (Stage I) and Corrosion Inhibitor K2 (Stage II)

The substrate (sheet of galvanized steel) is cleaned for 5 minutes at 55 ° C in a cleaning solution (Ridoline C72 Fa. Henkel) and then rinsed with distilled water.

Subsequently, the rinsed with distilled water plate immediately immersed at 45 ° C for 4 minutes in the first basin of the corrosion inhibitor K1 according to Example 1a. Thereafter, the coated sheet is rinsed with distilled water and blown dry with nitrogen. Immediately thereafter, the sheets are immersed for 5 minutes at 35 ° C. in the second basin of the corrosion inhibitor according to the invention according to Example 3a. It forms a non-visible to opalescent layer in the λ / 4 range of visible light. Thereafter, the coated sheet is rinsed with distilled water and blown dry with nitrogen. The sheet is then flashed for 2.5 minutes at 80 ⁰ C.

Example 5 Coating of the Sheet Coated According to Example 4 with a Cathodic Electrocoat (Stage III)

The coated and conditioned sheet according to Example 4 is treated with a commercially available lead-free cathodic electrodeposition paint (Cathode guard ® 500 from BASF Coatings AG) at a bath temperature of 32 ° C and a deposition time of 120 seconds, and thereafter cured for 20 minutes at 175 ⁰ C. The thickness of the deposited and cured layer of cathodic electrodeposition paint is 19 to 20 μm.

As a reference, a sheet coated with a commercially available phosphating agent (Gardobond 26S W42 MBZE3 from Chemetall) is also coated and cured with the above-mentioned lead-free electrodeposition paint according to the above-mentioned conditions. The thickness of the deposited and cured layer of cathodic electrodeposition paint is also 19 to 20 microns.

Example 6: Rapid corrosion test with Harrison solution on the substrates coated according to Example 5 A Harrison solution (5 g NaCl + 35 g (NH ₄ ) ₂ SO ₄ ) in 1000 ml demineralized water is used. As substrates here steel, galvanized steel or zinc alloys can be used. On the coated with the above-mentioned layer samples (6 ^* 6 cm) is a plastic cylinder with a diameter of 48 mm and a height of 6 cm with an adhesive: Scrintec 600 silicone adhesive transparent, RTV 1 k oxime system (Ralicks, 46459 Rees) glued to the surface. In this cylinder, 70 ml of Harrison solution are added. With these samples, an electrochemical impedance measurement (EIS) in a 2-electrode arrangement of 1 MHz to 10OmHz with an amplitude of 1 mV and open potential is performed with a platinum network as the counter electrode.

The samples prepared in this way are weathered for a total of 20 cycles in a temperature range from 25 ^° C. to 73 ^° C. so that the maximum and the minimum temperature are run through within one hour. After this, the now dry cylinder is again filled with 30 ml Harrison solution, after 10 minutes residence time this solution is used to determine the possibly during weathering ions by means of ICP-OES (Inductively Coupled Plasma - Optical Emission Spectrometry). Subsequently, 70 ml of Harris solution is again introduced into the cylinder and a renewed EIS measurement is carried out. After the EIS measurement, a renewed weathering is carried out by the rapid test and then again taken an ICP-OES sample and made a further EIS measurement. The measurement is verified by a double determination.

Evaluation of the corrosion test: a) ICP-OES data of the immersion solution

The ICP-OES data are normalized to the area of the samples. These data give a linear progression. Due to the linearity of the corrosion kinetics, the different coatings can be compared by the slopes of the graph. The ICP-OES data represent the resolution of the substrate per area and time and are therefore a direct measure of the corrosion rate that is possible with a particular coating.

b) EIS measurements

The EIS measurements can also be used to measure the corrosion kinetics. By measurement at the defect, this is detected electrochemically, ie the oxide layer of the substrate is determined. Assuming that the same oxide growth is to be expected under the same weathering conditions, the capacitance is set according to: ε ' _n 0ε ⁰ J "A

C =

a measure of the area of the exposed substrate, and this in turn is a measure of the corrosion rate. The larger the capacity or its square root, the greater the corrosion rate. The square root of this capacity is approximately linear to the reciprocal infiltration of a VDA-KWT test, so these values can be used as a measure of corrosion protection.

Evaluation of the corrosion test:

Results of the corrosion test

Substrate square root of the capacity

Galvanized steel sheet

Phosphatization 26S W42 MBZE3 (Chemetall) and Cathoguard® 500 0.00172

Galvanized steel sheet coated according to Example 4 and Cathoguard® 500 0.00163

The results of the corrosion tests show the improvement of the corrosion protection by the coating composition of the invention over a commercial corrosion inhibitor (phosphating).

Claims

claims:

1. A method for corrosion protection equipment of metallic substrates, characterized in that

(I) in a first stage, the substrate is coated by electroless immersion in an aqueous bath of a corrosion inhibitor K1 having a pH of between 1 and 5, containing at least (A1) a compound with a lanthanide metal as cation and / or d Element metal with the exception of chromium as cation and / or a d-element metalate with the exception of chromium-containing metalates as anion and (A2) at least one acid capable of oxidation with the exception of phosphorus-containing and / or chromium-containing acids, wherein Conversion is effected on the substrate surface and

(III) in a final step, a further coating is carried out by deposition of a cathodic electrodeposition paint.

2. The method according to claim 1, characterized in that the lanthanide metal and / or d-element cations containing compound (A1) has at least one component which is selected from the group of anions oxidizing acids of the elements of VI., VII. And VIII. Subgroup, the elements of the V. and VI. Main group of the Periodic Table of the Elements, with the exception of anions phosphorus and / or chromium-containing

Acids, the halides, with the exception of fluoride, and the tentiell anionic complexing mono- and / or polydentate ligands.

3. The method according to claim 2, characterized in that at least one component of the compound (A1) is a d-element

Metalate, in particular tungstate, permanganate, vanadate and / or molybdate.

4. The method according to any one of claims 1 to 3, characterized in that the acid (A2) is selected from the group of

Nitric acid, nitrous acid, sulfuric acid and / or sulphurous acid.

5. The method according to any one of claims 1 to 4, characterized in that between step (I) and the final stage

(III) of the process, a further coating step (II) takes place, in which the substrate is immersed in a bath of an aqueous corrosion inhibitor K2 stream-free, wherein K2 at least one water-dispersible and / or water-soluble polymer P containing covalently bound ligands L, which with the at form the chelates released from the corrosion of the substrate metal and / or the substrate surface, as well as with crosslinking functional groups B which adhere to themselves, with further complementary functional groups B 'of the polymer P and / or with further functional groups B and / or B'

Crosslinkers V can form covalent bonds.

6. Vefahren according to claim 5, characterized in that the aqueous corrosion inhibitor K2 additionally contains a salt (S) containing, as a cationic constituent Lanthanidmetallkatio- nen and / or d-metal cations.

7. Vefahren according to claim 6, characterized in that the lanthanide metal cations and / or d-metal cations of the salt (S) are present as complexes with mono- and / or polydentate ligands.

8. The method according to claim 5 to 7, characterized in that the crosslinkers V have covalently bound ligands L '.

9. The method according to any one of claims 5 to 8, characterized in that the ligands L are selected from the group

Ureas, amines, amides, imines, imides, pyridines, organo-sulfur compounds, organophosphorus compounds, organoboron compounds, oximes, acetylacetonates, polyalcohols, acids, phytic acids, acetylenes and / or carbenes.

10. The method according to any one of claims 5 to 9, characterized in that the polymer P has as polymer backbone one or more building blocks selected from the group consisting of polyesters, polyacrylates, polyurethanes, polyolefins, polyalcohols, polyvinyl ethers, polyvinylamines and polyalkyleneimine.

11. The method according to any one of claims 1 to 10, characterized in that in step (I) the residence time of the substrate in the aqueous bath of the corrosion inhibitor K1 is 1 second to 10 minutes and the temperature of the aqueous bath containing the corrosion inhibitor K1, between 25 and 90 ⁰ C.

12. The method according to any one of claims 5 to 11, characterized in that in step (II) the residence time of the substrate in the aqueous bath of the corrosion inhibitor K2 1 second to 15 minutes and the temperature of the aqueous bath containing the corrosion inhibitor K2 between 25 and 90 ⁰ C is located.

13. The method according to any one of claims 5 to 12, characterized in that the thickness of the layer produced in step (II) with the coating agent K2 after autophoretic application is between 5 and 1500 nm.

14. The method according to any one of claims 1 to 4, characterized in that in step (I) the layer of coating agent K1 before the final stage (III) for a period of 30 seconds to 30 minutes, temperatures between 25 and

120 ⁰ C, is suspended.

15. The method according to any one of claims 1 to 4 and 14, characterized in that the thickness of the layer produced in step (I) with the coating K1 layer after autophoretic application is between 5 and 900 nm.

16. The method according to any one of claims 5 to 15, characterized in that in step (II) the composite of coating K1 and coating K2 before the final stage (III) for a period of 30 seconds to 30 minutes, temperatures between 25 and 120 ⁰ C, is suspended.

17. The method according to any one of claims 1 to16, characterized in that after application of the electrocoating the

Layer composite during a period of 15 to 60 minutes, temperatures of 120 to 200 ⁰ C is exposed.

18. The method according to any one of claims 1 to 17, characterized in that the substrate contains at least 20 wt .-% of a metal selected from the group consisting of Fe, Al and / or Zn on the surface to be coated.