EP1692201A1

EP1692201A1 - Functionalised phenol-aldehyde resin and method for treating metallic surfaces

Info

Publication number: EP1692201A1
Application number: EP04820579A
Authority: EP
Inventors: Alina Monica Koch; Heike Quellhorst; Olaf Lammerschop; Patrick Droniou; Michael Kux
Original assignee: Henkel AG and Co KGaA
Current assignee: Henkel AG and Co KGaA
Priority date: 2003-12-11
Filing date: 2004-10-30
Publication date: 2006-08-23
Also published as: JP4890261B2; JP2007514023A; WO2005061570A1; US20070017603A1; DE10358309A1

Abstract

The invention relates to a phenol-aldehyde resin containing the following constituents: a phenolic constituent without carboxyl groups, aromatic hydroxycarboxylic acid, and imidazole. The invention also relates to a method for producing one such resin, to the use thereof for the anti-corrosion treatment of bare metallic surfaces or metallic surfaces provided with a conversion layer; to an aqueous treatment solution for treating bare metallic surfaces or metallic surfaces provided with a conversion layer, said solution containing at least one inventive phenol-aldehyde resin; and to metallic strips, metallic parts or objects containing metallic parts, at least one surface thereof having been treated using one such method.

Description

"Functionalized phenol-aldehyde resin and method for treating metal surfaces"

The present invention relates to a new functionalized phenol-aldehyde resin and the use of this or related resins for the anti-corrosion treatment of metal surfaces. These can be bare metal surfaces, that is to say those that have not yet been pretreated, or metal surfaces that already have a corrosion-protective conversion layer. A special feature of the corrosion protection treatment is that no toxic chromium has to be used.

Components made of metal sheets, such as vehicle bodies, housings for household appliances or metal furniture, can be assembled from metal sheets that do not yet have a permanently corrosion-protective coating. In a process sequence comprising several stages, a permanently corrosion-protective coating consisting of a conversion layer and a lacquer layer can be produced after the metallic components have been assembled. A well-known example of this is the process sequence of phosphating and painting, as is common in automobile construction, for example. The actual phosphating is only one step in a treatment sequence which, in addition to cleaning and rinsing stages, usually includes activation before phosphating, actual phosphating and often post-passivation after phosphating. This is followed by several painting stages. The pretreatment before painting thus requires several treatment steps, which in turn make a correspondingly extensive and therefore costly pretreatment system necessary. In addition, heavy metal-containing wastes are generated during phosphating, which have to be disposed of in a costly manner.

In addition to phosphating, other methods are known for producing a so-called conversion layer, which protects the metal underneath from corrosion and which is a primer for a subsequent coating layer. A "conversion layer" is understood to mean a layer on a metal surface which is formed by "conversion treatment" under the action of a "conversion solution" and which contains both elements from the metal surface and from the conversion solution. Typical examples are phosphate layers or chromate layers. In addition to phosphating and chromating processes, other processes for conversion treatment are known, for example with conversion solutions based on complex fluorides of boron, silicon, titanium or zircon. These complex fluorides are mostly used together with organic polymers. Examples of such conversion treatments are given in DE-A-101 31 723 and the literature cited therein. However, none of these alternative processes has so far been able to displace phosphating as a pretreatment before painting in automotive engineering.

There is extensive state-of-the-art technology for the deposition of corrosion-protective layers on bare metal surfaces to increase corrosion protection. Here are some examples:

US Pat. No. 5,129,967 discloses treatment baths for a no-rinse treatment (referred to there as "dried in place conversion coating") of aluminum, comprising a) 10 to 16 g / l of polyacrylic acid or its homopolymers, b) 12 to 19 g / l hexafluorozirconic acid, c) 0.17 to 0.3 g / l hydrofluoric acid and d) up to 0.6 g / l hexafluorotitanic acid.

EP-B-8 942 discloses treatment solutions containing a) 0.5 to 10 g / l polyacrylic acid or an ester thereof and b) 0.2 to 8 g / l on at least one of the compounds ^ ZrFg, ^ TiFg and ^ SiFg, the pH of the solution being below 3.5,

US-A-4 992 116 describes treatment baths for the conversion treatment of aluminum with pH values between about 2.5 and 5, which contain at least three components: a) phosphate ions in the concentration range between 1.1x10 ^" ^ to 5.3x10 ^" ^ mol / l corresponding to 1 to 500 mg / l, b) 1, 1x10 ^{* 5} to 1, 3x10 ^"3 mol / l of a fluoric acid of an element from the group Zr, Ti, Hf and Si (corresponding to depending on the element 1, 6 to 380 mg / l) and c) 0.26 to 20 g / l of a polyphenol compound, obtainable by reacting poly (vinylphenol) with aldehydes and organic amines in the form of a Mannich Reaction. Open-chain amines, in particular polyhydroxyalkylamines, are used as amines.

WO 92/07973 teaches a chromium-free treatment process for aluminum, the essential components in acidic aqueous solution being 0.01 to about 18% by weight of H ₂ ZrF ₆ and 0.01 to about 10% by weight of a 3- (NC _{1 -4} alkyl-N-2-hydroxyethylaminomethyl) _-4 -hydroxystyrene polymer used. Optional components are 0.05 to 10% by weight of dispersed SiO ₂ , 0.06 to 0.6% by weight of a solvent for the polymer, as well as surfactant.

WO 97/31135 discloses a solution for rinsing conversion-treated metal surfaces which contain compounds, for example hexafluoro complexes, of Ti, Zr or Hf and a phenolic resin. The phenolic resin can have differently substituted phenols. The molar mass of the resin is in the range 100 to 1000.

US 6 419 731 discloses a solution for the conversion treatment of aluminum, which contains a zirconium compound, fluoride ions and a water-soluble resin, wherein the water-soluble resin can be a phenolic resin, among others.

US Pat. No. 5,246,507 also relates to an agent for treating metal surfaces, which contains metal compounds, which can be selected, for example, from compounds of Ti, Zr and Hf, and an organic polymer. The polymer can be, for example, a condensation product of formaldehyde with phenol and a phenolic carboxylic acid.

US 5 846 917 describes phenolic imidazolines which can be obtained by a condensation reaction of hydrocarbyl polyaminophenols with carbonyl compounds. They are primarily used as antioxidants. It is expected that they also have a corrosion-inhibiting and passivating activity. Structurally, these polymers differ from phenolic resins in that they do not contain any alkylene-bridged phenolic units.

Japanese Patent Application Publication No. 59-157110 (cited here from Patent Abstracts of Japan) discloses phenolic resins containing an imidazole ring. The use of these resins is seen as a component in heat-resistant adhesives, for example for copper-containing laminates, printed circuit boards or the like. The Derwent paper with the "acquisition number"("AN") 1999-018521 contains a summary of the Japanese document JP 10287859. Accordingly, phenolic adhesives of the resol resin type are produced which additionally contain imidazole. The adhesives are used to manufacture plywood or veneer.

Phenol-aldehyde condensation products, in particular phenol-formaldehyde condensation products, have long been known under the name phenolic resins, phenoplasts, novolaks, resols, resitols or resites. For their manufacture and properties, reference is made, for example, to the keywords mentioned in Römpps Chemie Lexikon.

The object of the present invention is to provide new polymers of the phenolic resin type which can be used in particular in aqueous solution or emulsion for the surface treatment of bare metal surfaces or metal surfaces which already have a conversion layer. The treatment of the metal surfaces with the polymers is intended to improve corrosion protection and / or the adhesion of a subsequently applied lacquer or an adhesive to the metal surface.

In a first aspect, the invention relates to a phenol-aldehyde resin which contains as components a phenolic component without a carboxyl group, aromatic hydroxycarbonic acid and imidazole.

A “phenol-aldehyde resin” is understood to mean in particular a phenol-formaldehyde resin. Instead of the formaldehyde or in a mixture with it, however, other aldehydes such as furfural can also be used. The phenolic component is primarily phenol itself It is preferred that at least 50%, preferably at least 90% of the phenolic component is phenol, and instead of or together with phenol, other aromatic hydroxy compounds such as alkyl or aryl-substituted phenols such as cresols, polyhydric phenols can be used as the phenolic component such as pyrocatechol, resorcinol or hydroquinone, trihydric phenols (pyrogallol, phloroglucin, hydroxyhydroquinone) or fused phenols such as For example, α- and β-naphthol or alkyl-bridged diphenols such as bisphenol A can be used.

By definition, the aromatic hydroxycarboxylic acid has an aromatic ring system to which at least one hydroxyl group and at least one carboxylic acid group are bonded. The simplest examples of this are the positional isomers of hydroxybenzoic acid such as salicylic acid and m- or p-hydroxybenzoic acid. The aromatic ring system can carry further substituents such as, for example, alkyl groups, nitro groups, amino groups or also further hydroxyl or carboxylic acid groups. The aromatic hydroxycarboxylic acid can also have a condensed aromatic ring system and, for example, be one of the positional isomers of hydroxynaphthoic acid. An example of an aromatic hydroxycarboxylic acid with more than one carboxyl group is hydroxyphthalic acid. When “aromatic hydroxycarboxylic acid” is used in the context of this disclosure, this always includes the fact that mixtures of different acids can also be present. The aromatic hydroxycarboxylic acid is preferably selected from hydroxybenzoic acids, in particular from salicylic acid and p-hydroxybenzoic acid.

“Imidazole” is preferably understood to mean the base body itself. However, the round body can in particular bear substituents on the C atoms. These substituents can represent a further aromatic ring system, as is the case, for example, in benzimidazole.

With regard to the molar ratios of the individual constituents in the phenol-adehyde resin, it is preferred to select the molar ratio of phenolic component: aromatic hydroxycarboxylic acid and the molar ratio of phenolic component: imidazole in each case and independently of one another such that the proportion of the phenolic component in the resin is at least so is as large as the proportion of the aromatic hydroxycarboxylic acid or the proportion of imidazole, but is preferably greater than this proportion in each case. In particular, it is preferred to select the molar ratio of phenolic component: aromatic hydroxycarboxylic acid and the molar ratio of phenolic component: imidazole in each case and independently of one another such that it is in the range from 1: 1 to 100: 1. Of course, the two molar ratios can be approximately the same or different. The molar ratios are particularly preferably selected such that a molar ratio of aromatic hydroxycarboxylic acid: imidazole results which is in the range from 100: 1 to 1: 100, in particular in the range from 10: 1 to 1:10. A molar ratio in the range from 1: 1 to 10: 1 is particularly preferred.

The phenol-aldehyde resin is preferably constructed in such a way that it consists of at least 50%, preferably at least 90%, of the phenolic component, aromatic hydroxycarboxylic acid and imidazole and the bridging alkylene groups derived from the aldehyde component (when using formaldehyde: methylene groups). The further constituents of the polymer can, for example, be aromatic aminocarboxylic acids such as, in particular, aminobenzoic acids instead of the aromatic hydroxycarboxylic acid or other aromatic or aliphatic heterocycles instead of the imidazole. Again, a resin is preferred, the phenolic component of which consists of at least 50%, preferably at least 90% and in particular completely of the basic body phenol, the aromatic hydroxycarboxylic acid of which is at least 50%, preferably at least 90% and in particular entirely of a hydroxybenzoic acid (in particular Salicylic acid) and its imidazole component consists of at least 50%, preferably at least 90% and in particular completely of the basic body imidazole itself. Particularly preferred is a phenol-aldehyde resin which consists entirely of phenol, hydroxybenzoic acid (especially salicylic acid), imidazole and the bridging alkylene groups (especially methylene groups). The average molar mass of the phenol-aldehyde resin (which can be determined, for example, by gel permeation chromatography using a polyethylene glycol standard) is preferably at least 500, in particular at least 1000 and preferably at most 50,000, in particular at most 10,000.

The general process for the preparation of phenol-aldehyde resins by condensation of a phenol with an adehyde in aqueous solution is generally known and can be found in textbooks and chemical encyclopedias. The phenol-Adehyd resins described above, with its at least 3 aromatic components can be prepared for example by offset, an aqueous solution containing the phenolic component, aromatic hydroxycarboxylic acid and imidazole with an aqueous aldehyde and at a temperature between 40 ^C C and the Boiling point mixed for a period in the range of 10 minutes to 10 hours. For example, this solution can be boiled under reflux, which can already be sufficient mixing. Otherwise the mixing can be done by stirring or shaking. This manufacturing method forms a further aspect of the present invention. A more specific production process in the context of this invention is that a) in a first step, an aqueous solution of a phenol-aldehyde resin with bound aromatic hydroxycarbon acids is prepared, and b) in a second step, with imidazole and then with aqueous aldehyde solution and at a temperature mixed between 40 ° C and the boiling point for a period in the range of 10 minutes to 10 hours.

Here, too, the solution can be mixed by boiling at reflux, by stirring or by shaking, both in the first stages a) and in the second stage b).

In this preparation, the concentration of the organic compounds in the aqueous reaction solution is preferably selected so that at the end of the reaction an aqueous solution of the phenol-aldehyde resin is obtained which has a solids content of resin in the range from 10 to 50% by weight , In the sense of the intended use of the resin for the treatment of metal surfaces, it is not necessary to further process this solution. Rather, it can be marketed directly as such and used to prepare the treatment solution described below by diluting it with water or to supplement this treatment solution with an active ingredient.

In a further aspect, the present invention relates to the use of a phenol-aldehyde resin described above or a mixture of two or more of such resins for the corrosion-protective treatment of bare metal surfaces or those already provided with a conversion layer. The metal surfaces are preferably selected from surfaces of steel, galvanized or alloy galvanized steel, aluminized steel, zinc, aluminum, magnesium or alloys which consist of at least 50 atomic percent zinc, aluminum or magnesium. As a conversion layer, the metal surfaces can have, for example: an anodizing layer, a phosphating layer such as can be produced using a layer-forming or non-layer-forming phosphating process, or a coating based on fluorocomplexes of, for example, B, Si, Ti, Zr, Hf, as used for example in the literature cited in the introduction.

Furthermore, the present invention relates to a method for the corrosion-protective treatment of bare metal or metal layers already provided with a conversion layer. Surfaces in which the metal surfaces are brought into contact with an aqueous treatment solution which contains one or more phenol-aldehyde resin (s), at least one phenol-aldehyde resin containing imidazole and preferably a phenol-aldehyde resin after one or more of claims 1 to 7.

Typical metal surfaces for this have been mentioned above. The metal surfaces can be completely bare or completely covered with a conversion layer. However, it can also be metal surfaces of complex components, such as automobile bodies, which consist partly of bare and partly conversion-coated metal parts. Then, with the method according to the invention, a corrosion protection layer is produced on the bare metal parts and the corrosion protection effect of the conversion-treated metal surfaces is improved. Furthermore, there may be metal surfaces, some of which already have an organic coating, but which are damaged at individual points such as cut edges, grinding points or welding points, so that here again there are areas of a bare metal surface. Such relationships occur, for example, when complex components such as automobile bodies or household appliances are at least partially assembled from pre-coated metal sheets.

According to the invention, the minimum condition is that at least one phenol-aldehyde resin is present which has at least bound imidazole, but not necessarily also the aromatic hydroxycarboxylic acid. For such phenol-aldehyde resins with incorporated imidazole, but without incorporated aromatic hydroxycarboxylic acid, the preferred embodiments described above apply accordingly in terms of components and molar ratios. However, it is preferred to bring the metal surfaces into contact with an aqueous treatment solution which contains at least one phenol-aldehyde resin described above from the 3 components mentioned, as is characterized in particular in claims 1 to 7.

The aqueous treatment solution preferably contains at least 5 and in particular at least 20 mg / l, but preferably at most 2000, in particular at most 200 mg / l of phenol-aldehyde resin which contains bound imidazole and preferably a phenol-aldehyde resin after one or more of claims 1 to 7. At lower contents, the anti-corrosive effect diminishes. Even higher levels can deteriorate the corrosion protection again or are at least uneconomical. The aqueous treatment solution preferably has a pH in the range from at least 1.5, in particular from at least 1.8 up to a maximum of 6.0, in particular up to a maximum of 4.5. At lower pH values, the pickling attack increasingly attacks the metal. At higher pH values, the layer formation and thus the corrosion-protecting effect deteriorates increasingly.

The temperature of the treatment solution is preferably in the range from 20 to 60 ° C. and in particular in the range from 25 to 40 ° C. The preferred contact time of the metal surface with the treatment solution is preferably in the range from 5 to 240 seconds, in particular in the range from 30 to 200 seconds. The metal surface can be brought into contact with the treatment solution in the usual way, for example by immersing it in the treatment solution, by spraying it with the treatment solution or by combinations thereof or by rolling the treatment solution on.

When using the method for the aftertreatment of metal surfaces that already have a conversion layer, the conversion layer can be produced immediately before the aftertreatment according to the invention and can therefore still be moist. It can be rinsed with water between the generation of the conversion layer and the aftertreatment according to the invention. However, this can also be avoided. Secondly, however, a longer period of time may elapse between the generation of the conversion layer and the aftertreatment according to the invention. This is the case, for example, when components such as, for example, automobile bodies or household appliances are assembled from pre-phosphated steel and then aftertreated with the treatment method according to the present invention. A cleaning step can be provided between the conversion treatment and the aftertreatment according to the invention.

In addition to the phenol-aldehyde resin, the aqueous treatment solution preferably contains one or more compounds of elements of the 4th main or subgroup of the periodic table, in particular of Si, Ti and / or Zr. A treatment solution is preferably used which contains a total of at least 0.01 g / l, in particular at least 0.025 g / l, and up to 10 g / l, in particular up to 1 g / l, especially up to 0.5 g / l Ti and / or Zr and / or Si ions and at least such an amount of fluoride contains that the atomic ratio Ti to F and / or Zr to F and / or -Si to is in the range from 1: 1 to 1: 6.

The Ti, Zr and / or Si ions mentioned can be used completely in the form of hexafluoro complexes such as, for example, hexafluoro acids or their salts which are water-soluble in the concentration range mentioned, such as sodium salts. In this case, the atomic ratio is 1: 6. However, complex compounds can also be used in which less than six fluoride ions are each connected to the central elements Ti, Zr or Si. These can form automatically in the treatment solution if both hexafluoro complexes of at least one of the central elements Ti, Zr or Si and at least one further compound of one of these central elements are added to it. Examples of such further compounds are nitrates, carbonates, hydroxides and / or oxides of the same or another of the three central elements mentioned. For example, the treatment solution may contain hexafluorozirconate ions as well as (preferably colloidal) silica (SiO ₂ ) or its reaction products. Unreacted silica can be suspended in the treatment solution.

Such a treatment solution can also be obtained by using hydrofluoric acid or its (optionally acidic) salts together with those compounds of Ti, Zr and / or Si which can form fluorocomplexes with them. Examples are the nitrates, carbonates, hydroxides and / or oxides already mentioned. It is preferred to use a total of such an amount of Ti, Zr and / or Si as the central metal and such an amount of fluoride that the atomic ratio of central metal to fluoride is less than or equal to 1: 2, in particular less than or equal to 1: 3. The atomic ratio can also be less than 1 to 6 if the treatment solution contains more fluoride, for example in the form of hydrofluoric acid or its salts, than is required stoichiometrically to form the hexafluoro complexes of the central metals Ti, Zr and / or Si.

Depending on the substrate, the aqueous solution can additionally contain 0.001 to 2, preferably 0.005 to 0.5 g / l ions of one or more of the metals Mn, Ce, Li, V, W, Mo, Mg, Zn, Co and Ni. For environmental reasons, however, attempts will be made to avoid using Co and Ni. These additional metal ions can further improve the corrosion protection effect and paint adhesion. Due to the pickling attack on the metal surfaces, the treatment solutions in practical operation will additionally contain metal ions which have been removed from the metal surface. Besides that already mentioned zinc, these can in particular be iron and aluminum. Their concentrations can likewise be in the range from 0.001 to 2, in particular in the range from 0.005 to 0.5 g / l. It can be advantageous in the treatment of aluminum surfaces in particular to add aluminum ions in the concentration range mentioned in the form of soluble aluminum compounds to the treatment solution from the outset. The same applies to the addition of zinc ions, for example as nitrate salt, in the treatment of galvanized substrates with the treatment solution.

Furthermore, the aqueous solution can additionally contain 0.001 to 1.5, preferably 0.1 to 1 g / l phosphoric acid, phosphorous acid, phosphonic acid and / or in each case their anions and / or in each case their esters. Esters should be selected so that they are water-soluble or water-dispersible. These additives also improve corrosion protection and paint adhesion. However, according to the basic idea of the present invention, care should be taken not to choose such a combination of additives which leads to the formation of a crystalline zinc-containing phosphate layer. Because this would lead to a conventional zinc phosphate layer, which is known in the prior art and only brings about a sufficient corrosion protection effect if the technically customary steps of activation and post-passivation are also carried out. However, this more complex process sequence is to be avoided in the context of the present invention. For example, this is achieved in that the treatment solution does not simultaneously contain zinc and / or manganese in concentrations above 0.3 g / l and phosphoric acid or phosphate ions in concentrations above 3 g / l.

However, it is advantageous if the aqueous solution also contains one or more components which are known in the technical field of phosphating as so-called phosphating accelerators. This is particularly the case when the treatment solution is used to treat bare metal surfaces. In phosphating, such accelerators have the main task of preventing the formation of bubbles of elemental hydrogen on the metal surface. This effect is also called the depolarization effect. As with conventional phosphating, this also results in the process according to the invention that the conversion layer is formed more quickly and that it is formed more uniformly. Accordingly, it is preferred that the aqueous solution one or more phosphating accelerators selected from 0.05 to 2 g / l m-nitrobenzenesulfonate ions, 0.1 to 10 g / l hydroxylamine in free or bound form, 0.05 to 2 g / l m-nitrobenzoate ions, 0.05 to 2 g / l p-nitrophenol, 1 to 70 mg / l hydrogen peroxide in free or bound form, 0.05 to 10 g / l organic N-oxides 0 , 1 to 3 g / l nitroguanidine contains 1 to 500 mg / l nitrite ion 0.5 to 5 g / l chlorate ion.

The method according to the invention is generally integrated into a technical treatment sequence which usually begins with the cleaning of the parts to be treated. These can be bare metal parts which are coated with a surface layer due to the treatment method according to the invention, which improves corrosion protection and the adhesion of an organic coating subsequently applied. The treatment with the treatment solution according to the invention can be the only treatment step that produces such a surface layer. However, the method according to the invention can also be used to improve corrosion protection and paint adhesion on metal surfaces that already have a conversion layer. This may have already been applied by the manufacturer of the strip material, so that a long time may have passed between the first conversion treatment and the use of the treatment method according to the invention. However, the conversion layer can also be carried out as an aftertreatment step immediately before the method according to the invention is used. Between the individual treatment steps and also after the method according to the invention has been used, water is generally rinsed one to more times. Desalinated water is preferably provided as the last rinse after using the method according to the invention.

Subsequently, the metal surfaces treated with the method according to the invention are generally coated with a further layer based on organic polymers. This can be, for example, a single or multi-layer lacquer. For example, this can be the paint structure customary in automobile construction, the metal next layer of which is currently usually a cathodic electrocoat. However, a powder coating can also be applied as a coating, as is sufficient, for example, for the field of household appliances, metal furniture and the like. Furthermore, the surface layer produced with the treatment method according to the invention on the metal surfaces can serve as an adhesive base for an adhesive bond. In this In this case, the treated metal surface is coated with an adhesive. Metal parts can be glued together, metal parts with glass or with plastic parts or with rubber. For example, the method can serve as a pretreatment for a rubber-metal composite.

A special possible application for the method according to the invention is explained below:

In principle, it would be economically and ecologically advantageous to manufacture metallic components from material already coated by the manufacturer of the metal strips and only to clean and paint them after assembly. Waste associated with the pretreatment would then be centralized at the manufacturers of the metal strips and not widely distributed among the processors of the metal strips. Accordingly, pre-coated metal strips are already on the market. On the one hand, these can be pre-phosphated, ie they have a phosphate layer, but they do not have any other coating based on organic polymers. In the automotive and household appliance industry, metal strips are also increasingly being processed, which are already provided with a corrosion protection layer by the manufacturer of the strips. Such materials are known for example under the names Granocoat ^R , Ourasteel ^R , Bonazinc ^R and Durazinc ^R. They have a thin organic coating over a conversion layer, for example a chromating or phosphating layer. The organic coating consists of polymer systems such as epoxy or polyurethane resins, polyamides and polyacrylates. Solid additives such as silica, zinc dust and soot improve the corrosion protection and, due to their electrical conductivity, allow the metal parts coated with layers of a thickness of about 0.3 to about 10 μm, preferably up to about 5 μm, to be electrically welded and electrolytically painted. The substrate materials are usually coated in a two-stage process, in which the inorganic conversion layer is first produced and then the organic polymer film is applied in a second treatment stage. Further information can be found in DE-A-10022075 and the literature cited therein.

Metal sheets provided with a coating based on organic polymers in the belt process are therefore already being used in part in the construction of vehicle bodies, household appliances and furnishings. The most stringent requirements in terms of corrosion protection and liability are one in automotive engineering subsequently applied lacquers, since vehicles are exposed to the most severe corrosion. At present, no vehicle bodies are made exclusively from organically pre-coated metal sheets. Rather, this material is used together with non-pre-coated metal sheets for the vehicle bodies. The assembled bodies therefore currently still go through the usual pretreatment process before painting, ie they are subjected to the complex process sequence of phosphating.

In principle, the phosphating process could be replaced by a less complex pretreatment process if the vehicle bodies were made exclusively from organically precoated metal substrates. To do this, however, the problem must be solved that when assembling bodies made of organically pre-coated metal sheets, there are inevitably places where the organic pre-coating is damaged or missing. This is the case, for example, at cut edges, at welding points and at ground points.

For reasons of better corrosion protection, organically precoated metal substrates are often used in vehicle construction in which electrolytically galvanized or hot-dip galvanized steel is used as the metal substrate. In the case of such organically coated metal substrates, however, the locations mentioned with a damaged organic layer are particularly difficult to treat, since they differ from the conventional metal surfaces with regard to their electrochemical potentials and their chemical reactivity. In such damaged areas, both the steel substrate (i.e. iron) and the zinc coating are usually exposed. There may be a high local area ratio of steel (iron) to zinc, for example a ratio of> 9: 1. This is particularly the case with cut edges which represent a cross section through the coated steel substrate. The corrosion conditions at these border areas, which combine zinc and iron, differ from the other conditions on the homogeneous surface. Depending on the local ratio of zinc to iron at the exposed metal sites, there is a different electrochemical potential between the potentials of zinc and iron. Furthermore, when the bodies are machined, there are ground areas that have special conditions and thus special electrochemical potentials. Because the grinding process creates an activated interface of steel (iron) with finely divided reactive zinc. Another aspect of the present invention now lies in a method for producing a component containing painted metal parts, wherein a) metal sheets (preferably made of galvanized steel), which carry a coating based on organic polymers, are cut and / or punched and / or reshaped and the metal parts obtained in this way are joined together to produce the component, areas of the metal surface of the sheet being produced which are not covered by the coating based on organic polymers; b) cleans the assembled component, c) brings the cleaned assembled component into contact with a chromium-free acidic aqueous treatment solution, which creates a passivation layer on the areas of the metal surface created in sub-step a) that are not covered by the coating based on organic polymers , which does not represent a zinc phosphate layer, the aqueous treatment solution containing one or more phenol-aldehyde resin ^), at least one phenol-aldehyde resin having bound aromatic hydroxycarboxylic acids and / or bound imidazole and preferably a phenol-aldehyde resin according to one or represents several of claims 1 to 7, d) if desired, but not necessarily, rinsing the component treated in sub-step c) one or more times with water and e) coating it with a lacquer layer.

For the treatment solution to be used preferably in step c), the above-mentioned features apply accordingly, as summarized in one or more of claims 13 to 16. Sub-step c) is preferably the only treatment step after sub-step a) which creates a passivation layer on the areas of the metal surface which are produced in sub-step a) and which are not covered by the coating based on organic polymers.

This special method can be used in particular if all metal parts of the component consist exclusively of the sheets made of galvanized steel, which have a coating based on organic polymers, during the implementation of sub-steps b) to e).

All metal parts of the component can accordingly consist of organically precoated metal, in particular of galvanized steel. In addition to these metal parts, however, the component can also contain plastic components, as can be the case, for example, in automobile construction. For the production of, for example, a vehicle body 1 «series, the metallic components made of organically precoated material can be joined together with plastic parts.

The term "galvanized steel" includes hot-dip galvanized steels and electrolytically galvanized steels. Alloy-galvanized steels are also included, in which the coating can consist, for example, of a zinc-nickel alloy or a zinc-aluminum alloy. After galvanizing, the steels can be tempered so that an iron-zinc alloy forms at the interface between steel and zinc.

The joining of the sheets to form the component in sub-step a) can be carried out according to the usual methods known in the prior art, for example by gluing, flanging, riveting, flanging and / or welding, in particular by means of electric welding. In addition to cutting and / or punching in sub-step a), joining by welding due to the associated damage to the coating based on organic polymers leads to the creation of further locations on the component which are not covered by the coating based on organic polymers. These are also passivated in sub-step c), as are bare metal areas that result from grinding.

This embodiment of the method according to the invention is particularly suitable for the production of components with organically precoated sheets which have a coating based on organic polymers with a thickness in the range from 1 to 10 μm, the coating additionally containing electrically conductive particles in addition to the organic polymers. Due to these characteristics of the organic coating, the components can be joined together by electric welding. Examples of such coatings are contained in DE-A-19748764, DE-A-199 51 113, DE-A-10022075 and in the literature cited therein. As mentioned above, metal strips with such coatings are commercially available under different trade names.

The passivation layer produced in sub-step c) should therefore not constitute a conventional zinc phosphate layer, since according to the present task ee, a shorter and thus more economical sequence of processes should be used compared to zinc phosphating. A zinc phosphate layer does not form if the treatment solution does not contain at least 0.3 g / l zinc ions and at least 3 g / l phosphate ions (as phosphoric acid or any protolysis step thereof) at the same time. In sub-step c), the assembled component can be brought into contact with the acidic aqueous treatment solution in different ways, for example by immersing it in the treatment solution or by spraying it with the treatment solution. After this step, you can rinse with water, but need not. I.e. the process can be used as a "rinse" or as a "no-rinse" process.

Here, the treatment according to sub-step c) preferably does not represent a re-passivation of a previous main conversion layer formation, but is the only treatment step after the assembly of the components, which creates a passivation layer on the bare metal areas.

In particular, this sequence of processes can be used in the production of vehicle bodies, household appliances, pieces of furniture, or a part thereof in each case.

In another aspect, the present invention also relates to an aqueous treatment solution for the treatment of bare metal surfaces or metal surfaces having a conversion layer, the at least one phenol-aldehyde resin characterized in more detail above according to one or more of claims 1 to 7 or a mixture of two or more contains such resins. For the preferred composition of this treatment solution, the features mentioned above apply accordingly, as summarized in one or more of claims 13 to 16.

Finally, the present invention also relates to a metal strip, a metal part or an object containing metal parts, characterized in that at least one surface of the metal strip or the metal parts has been treated with the method described in detail above according to one or more of claims 12 to 17. As described above, the metal parts can have a coating based on organic polymers on the treated surfaces, for example they can be painted or glued.

embodiments

Abbreviations: 1S

s = seconds; min = minutes; h = hours; d = days

Demineralized water = demineralized water; SS = salt spray test; CRS = cold rolled steel,

Ridoline® and Ridosol® are alkaline cleaners from the applicant

syntheses:

The proportions of the resin components are understood as molar ratios

1. Production of phenol-salicylic acid-formaldehyde resins a. Phenol-salicylic acid-formaldehyde resin (phenol / salicylic acid 3: 1): In a three-necked flask with reflux condenser and stirrer, a solution of 20 g phenol, 9.78 g salicylic acid and 37.8 g 30% sodium hydroxide solution is prepared at 80 ° C , After the phenol has completely dissolved, 23.3 g of a 36.5% strength formaldehyde solution are added via a dropping funnel within 30 minutes. The solution is then heated to 95 ° C. and stirred for 6 h. Solids content: 42.4% b. Phenol-salicylic acid-formaldehyde resin (phenol / salicylic acid 1: 1) A solution of 10 g phenol, 14.68 g salicylic acid and 28.3 g 30% sodium hydroxide solution is prepared at 80 ° C. in a three-necked flask with reflux condenser and stirrer. After the phenol has completely dissolved, 17.5 g of a 36.5% strength formaldehyde solution are added via a dropping funnel within 30 minutes. The solution is then heated to 95 ° C. and stirred for 6 h. Solids content: 42.2% c. Imidazole-modified phenol-salicylic acid-formaldehyde resin (phenol / salicylic acid 3: 1; 0.5 imidazole) A solution consisting of 44.5 g phenol-salicylic acid-formaldehyde resin (phenol / salicylic acid 3: 1; see La.) And 3.62 g imidazole at 80 ° C. After the starting materials have been completely dissolved, 3.8 g of 36.5% formaldehyde solution in 10 g of water are added over a period of 15 min via a dropping funnel. Then the solution is at 95 ° C heated and stirred for 6 h. Solids content: 40.6% of theory Imidazole-modified phenol-salicylic acid-formaldehyde resin (phenol / salicylic acid 1: 1; 0.5 imidazole) A solution consisting of 39.5 g of phenol-salicylic acid-formaldehyde resin (phenol / salicylic acid 1: 1; see 1.b.) and 1.81 g imidazole at 80 ° C. After the starting materials have completely dissolved, 1.89 g of 36.5% strength formaldehyde solution in 10 g of water are added over a period of 15 minutes via a dropping funnel. The solution is then heated to 95 ° C. and stirred for 6 h. Solids content: 36.5% e. Imidazole-modified phenol-salicylic acid-formaldehyde resin (phenol / salicylic acid 1: 1; 0.33 imidazole) A solution consisting of 39.5 g phenol-salicylic acid-formaldehyde resin (phenol / salicylic acid 1: 1; see 1.b.) and 1.21 g imidazole at 80 ° C. After the starting materials have been completely dissolved, 1.26 g of 36.5% formaldehyde solution in 10 g of water are added over a period of 15 min via a dropping funnel. The solution is then heated to 95 ° C. and stirred for 6 h. Solids content: 35.0% f. Imidazole-modified phenol-salicylic acid-formaldehyde resin (phenol / salicylic acid 1: 1; 0.25 imidazole) A solution consisting of 39.5 g phenol-salicylic acid-formaldehyde resin (phenol / salicylic acid 1: 1; see 1.b.) and 0.9 g imidazole at 80 ° C. After the starting materials have been completely dissolved, 0.95 g of 36.5% formaldehyde solution in 10 g of water are added over a period of 15 minutes via a dropping funnel. The solution is then heated to 95 ° C. and stirred for 6 h. Solids content: 35.3% provision of phenol-formaldehyde resins a. Phenol-formaldehyde resin In a three-necked flask with reflux condenser and stirrer, a solution of 20 g phenol and 28.3 g 30% sodium hydroxide solution is prepared at 80 ° C. After the phenol has completely dissolved, 15.1 g of a 36.5% formaldehyde solution are added via a dropping funnel within 30 minutes. The solution is then heated to 95 ° C. and stirred for 6 h. Solids content: 43.3% b. Imidazole-modified phenol-formaldehyde resin (0.25 imidazole) In a three-necked flask with reflux condenser and stirrer, a solution consisting of 10 g phenol-formaldehyde resin (see 2.a.) and 0.46 g imidazole at 80 ° C manufactured. After the starting materials have been completely dissolved, 0.48 g of 36.5% strength formaldehyde solution in 25 g of water is added over a period of 15 minutes via a dropping funnel. The solution is then heated to 95 ° C. and stirred for 6 h. Solids content: 10.3% c. Imidazole-modified phenol-formaldehyde resin (0.5 imidazole) In a three-necked flask with reflux condenser and stirrer, a solution consisting of 10.2 g phenol-formaldehyde resin (see 2.a.) and 1.25 g imidazole at 80 ° C. After the starting materials have been completely dissolved, 1.31 g of 36.5% formaldehyde solution in 25 g of water are added over a period of 15 min via a dropping funnel. The solution is then heated to 95 ° C. and stirred for 6 h. Solids content: 13.4% of theory Imidazole-modified phenol-formaldehyde resin (1 imidazole) A solution consisting of 10 g phenol-formaldehyde resin (see 2.a.) and 1.84 g imidazole at 80 ° C. is prepared in a three-necked flask with reflux condenser and stirrer. After the starting materials have completely dissolved, 1.93 g of 36.5% formaldehyde solution in 25 g of water are added over a period of 15 min via a dropping funnel. The solution is then heated to 95 ^° C. and stirred for 6 h. Solids content: 13.0% 2. Application of the new polymers for the conversion treatment Example 1: Conversion process with modified resins

Substrate: CRS

Process sequence (diving application):

1. Cleaning: Ridoline 1570, 2%; Ridosol 1237, 0.3%; 5 min; 55 ° C

2. Rinse water

3. Rinse deionized water

4. Conversion treatment: 180 s; 30 ° C with one of the following bath preparations ZrF ₆ ^{2 "} corresponding to 150 mg / l Zr, polymer (according to Table 1: 37 mg / l solids content); pH 4.0

5. Rinse deionized water

6. Drying: compressed air

7. Painting: polyester PES 5807 / RAL 5009 GL (TIGC-free), company IGP); approx. 60-80 μm

Corrosion test:

Neutral salt spray test SS DIN 50021, 21 d

Comment on the evaluation of the results: The infiltration values on the cut were determined from one side of the cut (according to the standard). In some test series, comparative example 1b with Sokalan® HP 56 was used as the reference system. This corresponded to a relative corrosion protection of 1. In each corrosion test series, such “reference sheets” were also tested in order to obtain comparability between different test series. Systems with a better corrosion protection than the reference system have a relative corrosion protection (“Rel. Corrosion protection”) <1, those with a worse> 1. In other test series, the extent of the paint infiltration is given directly. This can be seen from the table headers. Tab. 1 Examples 1, Comparative Example 1

Example 2, Comparative Example 1a: Pretreatment with non-carboxylic acid-modified phenol-formaldehyde resins

Substrate: CRS process sequence (immersion application): 1. Cleaning: Ridoline 1570, 2%; Ridosol 1237, 0.3%; 5 min; 55 ° C 2. Rinse water 3. Rinse deionized water 4. Conversion treatment: 180 s; 30 ° C with one of the following bath batches ZrF ₆ ^{2 "} corresponding to 150 mg / l Zr; polymer (according to Table 2: 37 mg / l solids content); pH 4.0 5. Rinse deionized water 6. Drying: compressed air 7. Painting : Polyester PES 5807 / RAL 5009 GL (TIGC-free), company IGP); approx. 60-80 μm

Corrosion test: Neutral salt spray test DIN 50021 SS, 21 d Tab. 2 Example 2 (phenol-formaldehyde-imidazole resins), comparative example 1a (phenol-formaldehyde resins without imidazole)

Comparative Example 1b pretreatment with homo- and copolymers of polyvinylpyrrolidone (when using Sokalan® HP 56 ³⁾ : reference system for “relative corrosion protection”)

Substrate: CRS process sequence (immersion application): 1. Cleaning: Ridoline 1570, 2%; Ridosol 1237, 0.3%; 5 min; 55 ° C 2. Rinse water 3. Rinse deionized water 4. Conversion treatment: 180 s; 30 ° C with one of the following bath preparations ZrF ₆ ^{2 "} corresponding to 150 mg / l Zr; polymer (according to Table 3: 37 mg / l solids content); pH 4.0 5. Rinse deionized water 6. Drying: compressed air 7. Painting : Polyester PES 5807 / RAL 5009 GL (TIGC-free), company IGP); approx. 60-80 μm

Corrosion test: Neutral salt spray test DIN 50021 SS, 21 d Tab. 3 Comparative Example 1 b

¹⁾ Polyvinyl pyrrolidone. Manufacturer: BASF; CAS-No. 9003-39-8

²⁾ N-vinylcaprolactam-1-vinyl-2-pyrrolidone copolymer. Manufacturer: BASF; CAS-No. 51987-

20-3

³⁾ Vinyl imidazole-vinyl pyrrolidone copolymer. Manufacturer: BASF; CAS-No. 117197-37-2; was used as the standard system here

Comparative Example 1c: Iron Phosphating Pretreatment was carried out using a standard method from the applicant. Was painted with polyester PES 5807 / RAL 5009 GL (TIGC-free), company IGP); approx. 60-80 μm (as above). Relative corrosion protection> 1

Comparative Example 1d: Dication-zinc phosphating Pretreatment was carried out using a standard method from the applicant. Was painted with polyester PES 5807 / RAL 5009 GL (TIGC-free), company IGP); approx. 60-80 μm (as above). Relative corrosion protection <1

Example 3: Conversion process with modified resins at different pH values

Polymer: phenol-salicylic acid-formaldehyde grafted with 0.5 part of imidazole based on phenol (ratio of phenol / salicylic acid 1: 1) Substrate: CRS

Process sequence (immersion application): 1. Cleaning: Ridoline 1570, 2%; Ridosol 1237, 0.3%; 5 min; 55 ° C 2. Rinse water 3. Rinse deionized water 4. Conversion treatment: 180 s; 30 ° C with one of the following bath approaches ZrF ₆ ^{2 "} corresponding to 150 mg / l Zr; Tab. 4 (37 mg / l solids content polymer) 5. Rinse deionized water 6. Drying: compressed air 7. Painting: polyester PES 5807 / RAL 5009 GL (TIGC-free), company IGP); approx. 60-80 μm

Tab. 4 Example 3

Example 4: Conversion process with resin: phenol-formaldehyde grafted with 0.25 part of imidazole based on phenol; different pH values.

Substrate: CRS process sequence (immersion application): 1. Cleaning: Ridoline 1570, 2%; Ridosol 1237, 0.3%; 5 min; 55 ° C 2. Rinse water 3. Rinse deionized water 4. Conversion treatment: 180 s; 30 ° C with one of the following bath preparations ZrF ₆ ^{2 "} corresponding to 150 mg / l Zr; Tab. 5 (37 mg / l solids content polymer [phenol-formaldehyde resin x 0.25 imidazole] 5. Rinse deionized water 6. Drying: compressed air 7. Painting: polyester PES 5807 / RAL 5009 GL (TIGC-free), company IGP); approx. 60-80 μm

Tab. 5 Example 4

Example 5: Conversion process based on a combination of H ₂ ZrF ₆ and SiO ₂ at different pH values; Painting: powder coating or cationic electrocoating (= KTL)

Polymer: phenol-salicylic acid-formaldehyde grafted with 0.5 part of imidazole based on phenol (ratio of phenol / salicylic acid 1: 1)

Substrate: CRS process sequence (immersion application): 1. Cleaning: Ridoline 1570, 2%; Ridosol 1237, 0.3%; 5 min; 55 ° C 2. Rinse water 3. Rinse deionized water 4. Conversion treatment: 180 s; 30 ° C with one of the following bath preparations ZrF ₆ ^{2 "} corresponding to 150 mg / l Zr; addition of SiO ₂ according to Tab. 6 (37 mg / l solids content polymer) 5. Rinse deionized water 6. Drying: compressed air 7. Painting: polyester PES 5807 / RAL 5009 GL (TIGC-free), IGP); approx. 60-80 μm; or KTL from BASF Coatings, Cathoguard 310 (lead-free, approx. 20 μm) Tab. 6 Example 5

Comparative Example 3: Conversion Process with Polyvinylpyrrolidone / Polyvinylimidazole Copolymer (Sokalan® HP56)

Substrate: CRS process sequence (immersion application): 1. Cleaning: Ridoline 1570, 2%; Ridosol 1237, 0.3%; 5 min; 55 ° C 2. Rinse water 3. Rinse deionized water 4. Conversion treatment: 180 s; 30 ° C with ZrF ₆ ^{2 '} corresponding to 150 mg / l Zr; (37 mg / l solids content polymer) 5. Rinsing VE water 6. Drying: compressed air 7. Painting: polyester PES 5807 / RAL 5009 GL (TIGC-free), company IGP); approx. 60-80 μm; or KTL from BASF Coatings, Cathoguard 310 (lead-free, approx. 20 μm) Example 6: Conversion process based on H ₂ ZrF ₆ with different amounts of polymer

Substrate: CRS

Process sequence (immersion application): 1. Cleaning: Ridoline 1570, 2%; Ridosol 1237, 0.3%; 5 min; 55 ° C 2. Rinse water 3. Rinse deionized water 4. Conversion treatment: 180 s; 30 ° C with one of the following bath preparations ZrF ₆ ^{2 '} corresponding to 150 mg / l Zr; Addition of polymer according to Table 7; pH 1, 8 5. Rinsing VE water 6. Drying: compressed air 7. Painting: polyester PES 5807 / RAL 5009 GL (TIGC-free), company IGP); approx. 60-80 μm

Tab. 7 Example 6 and Comparative Examples 4a and 4b

Comparative Example 4b: Conversion Process with Polyvinylpyrrolidone / Polyvinylimidazole Copolymer (Sokalan® HP56J

Substrate: CRS

Process sequence (immersion application): 1. Cleaning: Ridoline 1570, 2%; Ridosol 1237, 0.3%; 5 min; 55 ° C 2. Rinse water 3. Rinse deionized water 4. Conversion treatment: 180 s; 30 ° C with ZrF ₆ ^{2 "} corresponding to 150 mg / l Zr, pH 4.0 5. Rinse deionized water 6. Drying: compressed air 7. Painting: polyester PES 5807 / RAL 5009 GL (TIGC-free), company IGP)

Claims

claims

1. Phenol-aldehyde resin which contains a phenolic component without carboxyl group, aromatic hydroxycarboxylic acid and imidazole as components.

2. phenol-aldehyde resin according to claim 1, characterized in that the molar ratio of phenolic component: aromatic hydroxycarboxylic acid and the molar ratio of phenolic component: imidazole is in each case in the range from 1: 1 to 100: 1.

3. phenol-aldehyde resin according to claim 2, characterized in that the molar ratio of aromatic hydroxycarboxylic acid: imidazole is in the range from 10: 1 to 1: 100.

4. phenol-aldehyde resin according to one or more of claims 1 to 3, characterized in that at least 50%, preferably at least 90% of the phenolic component is phenol.

5. phenol-aldehyde resin according to one or more of claims 1 to 4, characterized in that the aromatic hydroxycarboxylic acid is selected from hydroxybenzoic acids, in particular from salicylic acid and p-hydroxybenzoic acid.

6. phenol-aldehyde resin according to one or more of claims 1 to 5, characterized in that it consists of at least 50%, preferably at least 90% of the phenolic component, aromatic hydroxycarboxylic acids and imidazole and the bridging alkylene groups.

7. phenol-aldehyde resin according to one or more of claims 1 to 6, characterized in that it has an average molecular weight of at least 500, in particular at least 1000, and at most 50,000, in particular at most 10,000.

8. A process for producing a phenol-aldehyde resin according to one or more of claims 1 to 7 by preparing an aqueous solution which phenolic component, aromatic hydroxycarboxylic acid and imidazole contains, mixed with aqueous aldehyde solution and mixed at a temperature between 40 ° C and the boiling point for a period in the range of 10 minutes to 10 hours.

9. A process for the preparation of a phenol-aldehyde resin according to one or more of claims 1 to 7, by a) in a first step producing an aqueous solution of a phenol-aldehyde resin with bound aromatic hydroxycarbon acids and b) in a second step Imidazole and then mixed with aqueous aldehyde solution and mixed at a temperature between 40 ° C and the boiling point for a period in the range of 10 minutes to 10 hours

10. The method according to claim 8 or 9, characterized in that the concentrations of the organic compounds in the aqueous reaction solution are selected so that an aqueous solution of the phenol-aldehyde resin according to one or more of claims 1 to 7 is obtained, which one Solids content in the range of 10 to 50 wt .-%.

11. Use of phenol-aldehyde resins according to one or more of claims 1 to 7 for the corrosion-protective treatment of bare or metal surfaces provided with a conversion layer.

12. A method for the corrosion-protecting treatment of bare or provided with a conversion layer metal surfaces, wherein the metal surfaces are brought into contact with an aqueous treatment solution which contains one or more phenol-aldehyde resin (s), characterized in that at least one phenol-aldehyde Contains resin-bound imidazole and preferably represents a phenol-aldehyde resin according to one or more of claims 1 to 7.

13. The method according to claim 12, characterized in that the aqueous treatment solution contains at least 5, preferably at least 20 and up to 2,000, preferably up to 200 mg / l of phenol-aldehyde resin which contains bound imidazole and preferably a phenol-aldehyde Resin after one or more of claims 1 to 7.

14. The method according to one or both of claims 12 and 13, characterized in that the aqueous treatment solution has a pH in the range from at least 1.5, preferably from at least 1.8 to a maximum of 6, preferably to a maximum of 4.5.

15. The method according to one or more of claims 12 to 14, characterized in that the aqueous treatment solution additionally contains one or more compounds of elements of the fourth main or subgroup of the periodic table, preferably of Si, Ti and / or Zr.

16. The method according to one or more of claims 12 to 15, characterized in that the aqueous treatment solution additionally contains fluoride ions.

17. A process for producing a component containing painted metal parts, wherein a) metal sheets which have a coating based on organic polymers are cut and / or punched and / or shaped and the metal parts obtained thereby are joined to produce the component, areas the metal surface of the sheet, which is not covered by the coating based on organic polymers; b) cleans the assembled component, c) brings the cleaned assembled component into contact with a chromium-free acidic aqueous treatment solution, which creates a passivation layer on the areas of the metal surface created in sub-step a) that are not covered by the coating based on organic polymers , which is not a zinc phosphate layer, wherein the aqueous treatment solution contains one or more phenol-aldehyde resin (s), at least one phenol-aldehyde resin having bound aromatic hydroxycarboxylic acids and / or bound imidazole and preferably one phenol-aldehyde resin after one or more of claims 1 to 7, d) if desired, but not necessarily rinsing the component treated in sub-step c) one or more times with water and e) coated with a layer of lacquer.

18. Aqueous treatment solution for the treatment of bare metal surfaces or a conversion layer which contains one or more phenol-aldehyde resin (s) according to one or more of claims 1 to 7.

19. A metal strip, metal part or metal part containing object, characterized in that at least one surface of the metal strip or metal parts has been treated with a method according to one or more of claims 12 to 17.