WO2005061761A1

WO2005061761A1 - Two-stage conversion treatment

Info

Publication number: WO2005061761A1
Application number: PCT/EP2004/012323
Authority: WO
Inventors: Alina Monica Koch; Marian Pawlik; Heike Quellhorst; Patrick Droniou
Original assignee: Henkel Kommanditgesellschaft Auf Aktien
Priority date: 2003-12-11
Filing date: 2004-10-30
Publication date: 2005-07-07
Also published as: US20070017602A1; CA2548975A1; CN1890404A; DE10358310A1; EP1692325A1

Abstract

The invention relates to a method for the two-stage corrosion prevention treatment of metallic surfaces. According to the inventive method, (a) in a first step, the metallic surface is brought into contact with a chromium-free first aqueous solution having a pH value of between 1.5 and 5, and containing a total of at least 0.01 g/l and up to 10 g/l Ti and/or Si ions, and at least a quantity of fluoride such that the atomic ratio Ti to F and/or Zr to F and/or Si to F is between 1: 1 and 1: 6, and then (b) in a second step, the metallic surface is brought into contact with a chromium-free second aqueous solution having a pH value between 1.5 and 5, containing a total of at least 0.01 g/l and up to 10 g/l Ti and/or Zr and/or Si ions, and at least a quantity of fluoride such that the atom ratio Ti to F and/or Zr to F and/or Si to F is between 1: 1 and 1: 6, and additionally containing such a quantity of soluble anions of oxoacids of molybdenum and/or wolfram in the oxidation stage VI, that the entire concentration of molybdenum and/or wolfram, calculated as MoO42- and/or WO42-, is between 5 and 1500 mg/l.

Description

"Two-step conversion treatment"

The invention is in the field of anti-corrosion treatment of metal surfaces, for example vehicle bodies or household appliances. A corrosion-protective layer is created on ferrous surfaces such as steel surfaces and / or on selected non-ferrous surfaces such as zinc or zinc alloys (e.g. galvanized or alloy-galvanized steel), aluminum, magnesium or their alloys. This improves corrosion protection and adhesion of an applied layer based on organic polymers, such as a varnish or an adhesive. A special feature of the invention 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 term "conversion treatment" means that components of the treatment solution react chemically with the metal surface, which creates a corrosion protection layer in which both components of the treatment solution and metal atoms from the metal surface are incorporated.

Vehicle bodies such as automobile bodies are currently assembled from steel and / or other metallic materials such as galvanized steel or aluminum. After assembling, the bodies are cleaned and subjected to a conversion treatment before painting to achieve adequate corrosion protection and sufficient paint adhesion. The bodies are then painted, nowadays usually by cathodic electro-painting. A similar process can be carried out by household appliances containing metallic components such as refrigerators, freezers, washing machines, spin dryers, stoves, microwave ovens or even metallic furniture be subjected. Due to the lower requirements for corrosion protection for such objects, they are usually coated with a powder coating after the conversion treatment.

Phosphating is widespread as a conversion treatment in household appliances. In the case of vehicle bodies, the conversion treatment takes place exclusively as so-called "layer-forming" zinc phosphating. For this purpose, the vehicle bodies are brought into contact with an aqueous solution with a pH of about 2.5 to about 3.8, which contains about 0.3 to 2 g / 1 zinc ions and about 10 to about 20 g / l phosphate ions. Frequently, these phosphating solutions additionally contain about 0.3 to 2 g / l of manganese ions and often nickel or copper ions. This treatment creates a layer of crystalline zinc iron phosphates on steel surfaces and a layer of crystalline zinc phosphates on zinc or aluminum surfaces.

The actual phosphating step is accompanied by additional steps so that these crystalline zinc-containing phosphate layers have a sufficient effect for corrosion protection and paint adhesion. For example, the metal surfaces are first cleaned - usually in several stages - before phosphating and then activated. For the activation step, the metal surfaces are brought into contact with a solution which mainly contains secondary alkali metal phosphates and suspended colloidal titanium phosphates. This step must be checked very carefully to ensure that the subsequent phosphating is of sufficient quality. In particular, the activation baths use up comparatively quickly in comparison to phosphating baths, so that they have to be renewed in short time intervals of a few days to a few weeks. The monitoring and care of the activation baths therefore represents a significant part of the care and monitoring effort for a phosphating line.

The actual phosphating step is regularly followed by a so-called post-passivation. This post-passivation closes the remaining pores in the crystalline phosphate layer and improves corrosion protection and paint adhesion. For this purpose, the phosphated metal surfaces are brought into contact with an aqueous solution, which can contain different components. Post-passivation solutions based on hexavalent chromium, complex fluorides of titanium and / or zircon, and reactive are currently in practical use Polymers of vinylphenol derivatives or copper ions. These post-passivation baths must also be checked and adjusted regularly.

Conversion treatment in the form of phosphating usually requires, in addition to cleaning, at least 3 treatment baths for activation, phosphating and post-passivation, all of which have to be checked regularly and, if necessary, readjusted or renewed. These at least 3 required baths and the additional rinsing baths between them lead to a high space requirement and investment costs and thus increase the costs for the production of vehicle bodies and household appliances. In addition, waste containing heavy metals arises during the phosphating process, which has 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. For example, this can be achieved 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. This also applies to the teachings of the following three documents:

A treatment solution for producing a conversion layer on bare metal surfaces is known from US Pat. No. 6,193,815, which has the following components: a) 0.01 to 5 parts by weight of dissolved phosphate ions, b) 0.1 to 2 parts by weight of titanium ions, c) 0.05 to 5 Parts by weight of fluoride ions and d) 0.01 to 2 parts by weight of a water-soluble accelerator, which can be, for example, a combination of nitric acid and ammonium heptamolybdate.

It is obvious that the titanium ions and the fluoride ions react with one another to form fluorocomplexes or can be used directly as fluorocomplexes. According to exemplary embodiments, tungsten can also be used as an accelerator in addition to heptamolybdate. This treatment solution is especially suitable for the treatment of aluminum surfaces. WO 03/078682 discloses a method for producing a conversion layer on a metallic surface by treatment with an aqueous solution with the following components: a) a source of tungsten ions and b) a soluble material that contains zircon. The surface is then dried and / or baked. Examples of suitable zirconium compounds are hexafluorozirconic acid and its salts.

US 5449415 describes a "no rinse" conversion process for cold-rolled steel in particular, "no rinse" means that the treatment solution is not rinsed off after application, but is dried directly. This treatment solution contains as essential components: a) an anionic component, which can be, for example, a fluorocomplex of titanium or zircon, b) a cationic component selected from the metals Co, Mg, Mn, Zn, Ni, Sn, Cu, Zr, Fe and Sr, c) a sufficient amount of acid to adjust the pH in the range of 0.5 to 5, d) oxo anions of phosphorus or phosphonate anions, e) an organic polymer.

This solution preferably additionally contains a further component selected from tungsten, molybdate, silicon tungstate and silicon molybdate.

The above-mentioned examples of conversion solutions which contain complex fluorides of titanium or zircon represent conversion solutions for producing conversion layers on bare metal surfaces. However, it is also known to use solutions of complex fluorides of titanium or zircon for the passivating aftertreatment of phosphate layers.

The present invention has as its object the process chain z. B. to make automobile production more economical and ecological. On the one hand, the formation of wastes containing heavy metals should be avoided, in particular wastes which contain toxic heavy metals such as chromium or nickel. On the other hand, the process sequence should be shortened compared to the usual phosphating. On the one hand, this shortens the length of the production line and, on the other hand, it reduces the number of rinsing steps required, which leads to water savings. Nevertheless, a conversion layer are produced which correspond in their quality with regard to corrosion protection and paint adhesion to a conventional phosphating layer.

The present invention relates to a method for two-stage corrosion protection treatment of metal surfaces, the metal surfaces a) being brought into contact in a first step with a chromium-free first aqueous solution with a pH in the range from 1.5 to 5, which is at least 0 in total .01 g / l, preferably at least 0.025 g / l, and up to 10 g / l, preferably up to 1 g / l, in particular up to 0.5 g / l Ti and / or Zr and / or Si Contains ions and at least such an amount of fluoride that the atomic ratio Ti to F and / or Zr to F and / or Si to F is in the range from 1: 1 to 1: 6, and thereafter, with or without intermediate rinsing with water, b) in a second step in contact with a chromium-free second aqueous solution with a pH in the range from 1.5 to 5, the total of at least 0.01 g / l, preferably at least 0.025 g / l, and up to 10 g / l, preferably up to 1 g / l, in particular up to 0.5 g / l Ti and / or Zr and / or Si ions and at least such an amount of fluoride that the atomic ratio Ti to F and / or Zr to F and / or Si to F is in the range from 1: 1 to 1: 6, and additionally such an amount of soluble anions of oxo acids of molybdenum and / or tungsten in oxidation state VI contains that the total concentration of molybdenum and / or tungsten, calculated as MoO ₄ ^{2 "} and / or WO ₄ ^2" , is in the range from 5 to 1500 mg / l.

Of course, this two-stage process sequence is part of the longer treatment chain in the manufacture of painted metal objects such as automobile bodies, household appliances and the like. In this treatment chain, the assembled components are first cleaned and rinsed before they are subjected to the two-stage conversion treatment according to the invention. Water can be rinsed between the two sub-steps a) and b) of the two-stage process according to the invention, but need not. After the second step b), one or more rinses are generally carried out with water, the last rinsing step preferably being carried out with demineralized water. Then the object can be painted. If the requirements for corrosion protection are low, such as for household appliances, this can be done with a powder coating. In order to cope with the higher corrosion protection requirements of automobile construction, it is preferable to apply the currently technically customary multilayer paint structure, the layer closest to the metal of which is usually a cathodic electrocoat. However, the process sequence according to the invention is not only capable of to prepare the metal surfaces for painting, but it can also serve as a basis for gluing.

Sub-steps a) and b) are the only steps (apart from the usual rinsing steps) that have to be carried out between cleaning the parts and applying a layer based on organic polymers such as a varnish or an adhesive for the conversion treatment of the metal surfaces. Additional activation, such as in the case of phosphating, or a further post-pass step is not necessary.

The two-stage process sequence according to the invention can also be used for the passivation of bare metal spots which arise when the components, such as, for example, the automobile bodies, are completely assembled from pre-coated material. The following considerations apply here:

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 , Durasteel ^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 become. Further information can be found in DE-A-100 22 075 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. In the automotive industry, the strictest requirements regarding corrosion protection and adhesion of a subsequently applied paint are made, since vehicles are exposed to the most severe corrosion stresses. 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, i. H. 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 creates 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.

The two-stage treatment sequence according to the invention is suitable for producing a sufficient passivation layer for further painting at the problem areas mentioned, where the organic precoating is damaged or missing entirely.

Therefore, a special aspect of the present invention consists in a method for producing a component containing painted metal parts, wherein

I) Sheets of metal that carry a coating based on organic polymers, cut and / or punch and / or form and assemble the metal parts thus obtained for the production of the component, thereby creating areas of the metal surface of the sheet that are not covered by the coating organic polymers are covered;

II) cleans the assembled component,

III) the cleaned, assembled component is subjected to a sequence of processes which produces a passivation layer on the regions of the metal surface which are formed in sub-step I) and which are not covered by the coating based on organic polymers, which is not a zinc phosphate layer, the regions of the metal surface of the Sheets which are not covered by the coating based on organic polymers a) in a first step are in contact with a chromium-free first aqueous solution with a pH in the range from 1.5 to 5, which in total is at least 0.01 g / l, preferably at least 0.025 g / l, and up to 10 g / l, preferably up to 1 g / l, in particular up to 0.5 g / l of Ti and / or Zr and / or Si ions and at least one contains such an amount of fluoride that the atomic ratio Ti to F and / or Zr to F and / or Si to F is in the range from 1: 1 to 1: 6, and thereafter, with or without intermediate rinsing with water, b) in one second step in contact with a chrome-free second aqueous solution with a pH in the range from 1.5 to 5, the total of at least 0.01 g / l, preferably at least 0.025 g / l, and up to 10 g / l, preferably up to 1 g / l, in particular up to 0.5 g / l Ti and or Zr and / or Si ions and at least one contains such an amount of fluoride that the atomic ratio Ti to F and / or Zr to F and / or Si to F is in the range from 1: 1 to 1: 6, and which additionally contains such an amount of soluble anions of oxo acids of molybdenum and / or tungsten in oxidation state VI contains that the total concentration of molybdenum and / or tungsten, calculated as MoO ₄ ^{2 "} and / or WO ^2" , is in the range from 5 to 1500 mg / l

IV) if desired, but not necessarily, rinsing the component treated in sub-step c) one or more times with water and

V) coated with a layer of lacquer.

The further explanations apply both to the general aspect of the present invention according to claim 1 and to its specific application according to claim 2:

In contrast to the second aqueous solution used in sub-step b), the first aqueous solution in sub-step a) preferably contains no compounds of molybdenum or tungsten. Their use has no technical advantage here and would therefore be uneconomical. However, it would not be technically disadvantageous.

Both in sub-step a) and in sub-step b), an aqueous treatment solution is used, the total of at least 0.01 g / l, preferably at least 0.025 g / l, and up to 10 g / l, preferably up to 1 g / l, in particular up to 0.5 g / l of Ti and / or Zr and / or Si ions and at least such an amount of fluoride that the atomic ratio Ti to F and / or Zr to F and / or Si to F is in the range from 1: 1 to 1: 6, and which may additionally contain at least 0.005 g / l, preferably at least 0.01 g / l, and up to 20 g / l, preferably up to 1 g / l, of organic polymers got to. 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 each of which less than six fluoride ions are 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. For example, the atomic ratio can be as small as 1 to 12 or 1:18 or even lower if an appropriate excess of fluoride is used, ie twice or three times or even more than that which is necessary for the complete formation of the hexafluoro complexes.

In step a), treatment solutions can be used which contain combinations of ingredients known in the prior art, for example, according to US Pat. No. 5,129,967, a treatment solution which contains at least the following components in water: a) polyacrylic acid or its homopolymers, b) Hexafluorozirconic acid, c) 0.17 to 0.3 g / l hydrofluoric acid and d) up to 0.6 g / l hexafluorotitanic acid,

according to EP-B-8942, a treatment solution containing a) polyacrylic acid or an ester thereof and b) at least one of the compounds H ₂ ZrFg, H ₂ TiFg and ^ SiFg, the pH of the solution being below 3.5,

(further polymers which can be used in similar treatment baths are listed in WO 02/20652),

according to US-A-4 992 116 a treatment solution with pH values between € 2.5 and 5, which contains at least three components: a) phosphate ions in the concentration range between 1.1x10 ^"5 to 5.3x10 ^" ^ mol / l, corresponding to 1 to 500 mg / l, b) at least one fluoric acid of an element from the group Zr, Ti, and Si and c) a polyphenol compound, obtainable by reacting poly (vinylphenol) with aldehydes and organic amines,

according to WO 92/07973 a treatment solution which as essential components in acidic aqueous solution ^ ZrFg and a 3- (N-C ^ alkyl-N-2-hydroxyethylaminomethyl) -

Contains 4-hydroxystyrene polymer.

In sub-step a) it is also possible to use treatment solutions in which the organic polymers are selected from homopolymers and copolymers of vinylpyrrolidone. Treatment solutions of this type are described in DE-A-100 05 113 and DE-A-101 31 723. If a treatment solution which contains copolymers of vinylpyrrolidone is accordingly used in the process according to the invention, these copolymers may contain one or more other monomers in addition to vinylpyrrolidone. They can therefore be present, for example, as copolymers of two components or as copolymers of three components (= terpolymers). Mixtures of homo- and two-component copolymers, homo- and terpolymers or two-component copolymers and terpolymers can also be used.

Suitable homopolymers or copolymers of vinylpyrrolidone are, for example, the polymers listed in Table 1 or the polymers of the monomers listed therein. Copolymers of vinyl pyrrolidone with monomers having caprolactam or imidazole groups are particularly preferred.

Table 1: Examples of homo- or copolymers of vinyl pyrrolidone

If the treatment solution in sub-step a) contains organic polymers, these are preferably present in concentrations of at least 0.005 g / l, in particular at least 0.01 g / l, and up to 20 g / l, in particular up to 1 g / l.

In contrast, the treatment solution for sub-step b) is preferably free of organic polymers. Their use in sub-step b) is possible without disadvantage, but it also brings no significant technical advantage and is therefore uneconomical.

In sub-step b), the formulation “soluble anions of oxo acids of molybdenum and / or tungsten in oxidation state VI” means that the compounds, as a rule salts, which contain the anions mentioned, among those described in this disclosure conditions with regard to concentrations, pH values and temperatures are soluble in the treatment solution. The person skilled in the art is aware that under the conditions mentioned in the treatment solution, the anions of the oxo acids of molybdenum and / or tungsten in oxidation state VI can certainly be in a different form than they were introduced. Decisive for this are the pH-dependent protolysis equilibria of the respective anions. Some of these can be present as free anions, but depending on the pH they can also be in partially or completely protonated form. It is also known to the person skilled in the art that, depending on the temperature, pH value and concentration, the anions mentioned tend to condense or hydrolytically cleave. The position of the corresponding equilibria is also decisive for this. For example, the anions of the oxo acids of molybdenum and / or tungsten in oxidation state VI can be introduced in the form of the orthometalates, metametalates, parametalates, polymetalates such as, in particular, heptametalates or as heteropolymetalates. The term "metallates" here means the molybdates or the tungstates. They are preferably used as salts with cations such as sodium, potassium, lithium, calcium, cerium, barium, magnesium, strontium, ammonium or as corresponding acids.

The metal surfaces which can be treated with the method according to the invention 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 , Different metal surfaces can also be present side by side, as is increasingly the case in automobile construction. The method according to the invention shows its advantages particularly in the treatment of steel. For these surfaces in particular, there has so far been no suitable process other than phosphating to meet the high corrosion protection and paint adhesion requirements in vehicle construction. When used on steel surfaces, however, the method according to the invention leads to properties with regard to corrosion protection and paint adhesion which are comparable to those of a technically advanced phosphating.

Both the first and the second treatment solution can contain metal ions which have been removed from the surfaces to be treated. These are in particular iron, zinc and / or aluminum ions. These can be present, for example, in concentrations between 0.001 and 1 g / l, in particular between 0.005 and 0.5 g / l. The second aqueous solution can additionally contain complexing agents, for example in amounts of 0.01 to 10 g / l, in particular 0.05 to 5 g / l. With smaller quantities, the technical advantage is increasingly lost. Larger quantities have no further advantage and are therefore uneconomical. However, they don't bother either. The complexing agents can be selected, for example, from chelating anions of hydroxycarboxylic acids or from polybasic carboxylic acids such as lactate, oxalate, citrate, tartrate or gluconate. Acetylacetonate is also suitable as a complexing agent. Other suitable complexing agents are amino, imino or nitrilocarboxylic acids such as, for example, ethylenediaminetetraacetic acid or nitrilotriacetic acid or their anions. Polybasic phosphonates, phosphonocarboxylates or amino, imino or nitriloalkylene phosphonates are also suitable as complexing agents. Examples are 1-hydroxyethane-1, 1-diphosphonic acid, nitrilotri (methylenephosphonic acid), phosphonobutanetricarboxylic acid and other phosphonic acids known to those skilled in the art with similar properties.

The first and / or the second treatment solution preferably has a pH of at least 1.5, in particular at least 1.7, and up to 5, preferably up to 4. The pH values of the first and second treatment solution can of course be different. It is preferred in particular for the second aqueous solution that it contains buffer substances for the pH range mentioned.

As mentioned above, the presence of organic polymers in the second aqueous solution has no significant technical advantage. For economic reasons, it is therefore preferred that it contains no more than 5 mg / l of organic polymers.

Treatment parameters can be selected to carry out sub-step a), as mentioned in the literature cited for this purpose. This applies in particular to the temperature of the first aqueous solution, the contact time with the metal surface and the type of application. In the second step b), the metal surfaces are brought into contact with the aqueous solution, preferably for a period in the range from 5 seconds to 10 minutes, in particular from 10 seconds to 1 minute. As is technically common, this can be done by immersing the metal surfaces in the treatment solution, by spraying with the treatment solution or by combinations thereof. The temperature of the second aqueous solution is preferably at least 20 ° C., in particular at least 30 ° C., and preferably not more than 60 ° C., in particular not more than 50 ° C. At lower temperatures, the treatment becomes less effective. Temperatures higher than the upper limits mentioned do not harm, but are not necessary and are therefore economically disadvantageous due to the increased energy requirement.

embodiments

Abbreviations:

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

Demineralized water = demineralized water; CASS = copper accelerated salt spray test

EG = electrolytically galvanized steel, CRS = cold-rolled steel

KTL = cathodic electrocoat

Ridoline® and Ridosol® are alkaline cleaners from the applicant.

Sokalan® HP 56 is a vinylimidazole-vinylpyrrolidone copolymer (from BASF), CAS no

117197-37-2.

Molybdate was introduced as the ammonium salt.

If necessary, pH values were down with nitric acid, up with

Ammonia solution or adjusted with sodium carbonate solution.

Example 1 :

Rinse after conversion treatment with H ₂ ZrFβ / Sokalan HP56

Substrate: aluminum AA 6016 Process sequence (spray application):

1. Cleaning: Ridoline 7163 CF, 1.5%; Ridosol 550 CF, 0.15%; 80 s; 55 ° C

2. Rinse hot water

3. Rinse deionized water

4. conversion treatment: 108 s; 30 ° C; pH 3.8 Bath composition: H ₂ ZrF ₆ acid (corresponding to 150 mg / l Zr) and Sokalan HP 56 (corresponding to 40 mg / l solid) 5. Reactive sink 40 s, 30 ° C; pH 1.8 bath composition: H ₂ ZrF _β- acid (corresponding to 50 mg / l Zr) and molybdate (corresponding to 500 mg / l MoO ₄ ^{2 "} ) 6. Rinse deionized water 7. Drying: compressed air 8. Painting: KTL Cathoguard 310, from BASF; Layer thickness approx. 20 μm

Corrosion test: aluminum DIN 50021 CASS, 10 d; Infiltration at the Ritz

Comparative Example 1: Conversion treatment with H ₂ ZrFe / Sokalan HP56 without rinsing

Substrate: aluminum AA 6016 Process sequence (spray application):

1. Cleaning: Ridoline 7163 CF, 1.5%; Ridosol 550 CF, 0.15%; 80 s; 55 ° C

2. Rinse hot water

3. Rinse deionized water

4. conversion treatment: 108 s; 30 ° C; pH 3.8 Bath composition: H ₂ ZrF ₆ acid (corresponding to 150 mg / l Zr) and Sokalan HP 56 corresponding to 40 mg / l

5. Rinse deionized water

6. Drying: compressed air

7. Painting: KTL Cathoguard 310, from BASF; Layer thickness approx. 20 μm

Corrosion test: aluminum DIN 50021 CASS, 10 d; Infiltration at the Ritz

Tab. 1. Results of test series 1

Example 2: MoO ^ ZrFe sink after conversion treatment with H ₂ ZrFe / Sokalan HP56

Substrate: EG

Process sequence (diving application):

1. Cleaning: Ridoline 1570, 3%; Ridosol 1237, 0.3%; 7 min; 55 ° C

2. Rinse hot water

3. Rinse deionized water

4. Conversion treatment: 180 s; 30 ° C; pH 3.8; with the bath mixture H ₂ ZrF ₆ acid (corresponding to 150 mg / l) and Sokalan HP 56 (corresponding to 37 mg / l solids content)

5. Rinse deionized water

6. Reactive sink 30 s, 30 ° C; pH 1.8 Bath composition: H ₂ ZrF ₆ acid (corresponding to 50 mg / l Zr) and molybdate (corresponding to 500 mg / l MoO ₄ ^{2 "} )

7. Rinse deionized water

8. Drying: compressed air

9. Painting: KTL Cathoguard 310, from BASF; Layer thickness approx. 20 μm

Comparative Example 2: Conversion treatment with H ₂ ZrFe / Sokalan HP56 without rinsing

Substrate: EG

Process sequence (diving application):

1. Cleaning: Ridoline 1570, 3%; Ridosol 1237, 0.3%; 7 min; 55 ° C

2. Rinse hot water

3. Rinse deionized water

5. Rinse deionized water

6. Drying: compressed air

7. Painting: KTL Cathoguard 310, from BASF; Layer thickness approx. 20 μm Paint adhesion test:

EG salt water storage test (5% NaCI solution, 40 ° C, 6 d; rock fall according to VDA 621-427 before and after)

Tab. 2: Results of test series 2

Examples 3a and 3b: MoO ^ ZrFe sink after conversion treatment with H ₂ ZrFe / Sokalan HP56

Substrate: EG process sequence (immersion application): 1. Cleaning: Ridoline 1570, 3%; Ridosol 1237, 0.3%; 7 min; 55 ° C 2. Rinse of industrial water 3. Rinse of deionized water 4. Conversion treatment: 180 s; 30 ° C; pH 3.8, with the bath mixture H ₂ ZrF ₆ acid (corresponding to 150 mg / l) and Sokalan HP 56 (corresponding to 37 mg / l solids content) 5. Rinse deionized water 6. Reactive rinse 60 s, 30 ° C; pH 1.8 Bath composition: H ₂ ZrF ₆ acid (corresponding to 50 mg / l Zr), MoO ₄ ^{2 '} according to the table (example 3a and 3b) 7. Rinse deionized water 8. Drying: compressed air 9. Painting: KTL Cathoguard 310, Fa BASF; Layer thickness approx. 20 μm and full structure (automotive quality) Comparative example 3a: conversion treatment with H ₂ ZrFe / Sokalan HP56 without rinsing

Substrate: EG

Process sequence (diving application):

1. Cleaning: Ridoline 1570, 3%; Ridosol 1237, 0.3%; 7 min; 55 ° C

2. Rinse hot water

3. Rinse deionized water

4. Conversion treatment: 180 s; 30 ° C; pH 3.8; with the bath mixture H ₂ ZrF ₆ acid (corresponding to 150 mg / l) (Sokalan HP 56, corresponding to 37 mg / l solids content)

5. Rinse deionized water

6. Drying: compressed air

7. Painting: KTL Cathoguard 310, from BASF; Layer thickness approx. 20 μm and full structure (automotive quality)

Comparative Examples 3b and 3c: MoO ₄ sink (without ZrF ₆ ) after conversion treatment with HzZrFe / Sokalan HP56

1. Cleaning: Ridoline 1570, 3%; Ridosol 1237, 0.3%; 7 min; 55 ° C

2. Rinse hot water

3. Rinse deionized water

4. Conversion treatment: 180 s; 30 ° C; pH 3.8 with the bath mixture H ₂ ZrF ₆ acid (corresponding to 150 mg / l) and Sokalan HP 56 (corresponding to 37 mg / l solids content)

5. Rinse deionized water

6. Reactive sink 60 s, 30 ° C; pH 1.8 bath composition: MoO ^{2 "} according to Table 3

7. Rinse deionized water

8. Drying: compressed air

9. Painting: KTL Cathoguard 310, from BASF; Layer thickness approx. 20 μm and full structure (automotive quality) Paint adhesion tests

EG Alternating climate test VDA 621 -415, 70 d; Rockfall according to VDA 621-427 before and after

Tab. 3: Results of test series 3

Example 4:

Sink with different pH after conversion treatment with H ₂ ZrFe / Sokalan HP56

Substrate: EG process sequence (spray application): 1. Cleaning: Ridoline 7163 CF, 1.5%; Ridosol 550 CF, 0.15%; 80 s; 55 ° C 2. Rinse of industrial water 3. Rinse of demineralized water 4. Conversion treatment: 108 s; 30 ° C; pH 3.8 Bath composition: H ₂ ZrF ₆ acid (corresponding to 150 mg / l Zr) and Sokalan HP 56 (corresponding to 37 mg / l solid) 5. Reactive sink 40 s, 30 ° C; Bath composition: H ₂ ZrF ₆ acid (corresponding to 50 mg / l Zr) and molybdate (corresponding to 500 mg / l MoO ₄ ^{2 "} ); pH values adjusted according to Table 4

6. Rinse deionized water

7. Drying: compressed air

8. Painting: KTL Cathoguard 310, from BASF; Layer thickness approx. 20 μm

Paint adhesion test:

EG salt water storage test (5% NaCI solution, 40 ° C, 6 d; rockfall according to VDA 621-427 before and after)

Comparative Example 4: Conversion Treatment With

HP56 without rinsing

Substrate: EG

Process sequence (spray application):

1. Cleaning: Ridoline 7163 CF, 1.5%; Ridosol 550 CF, 0.15%; 80 s; 55 ° C

2. Rinse hot water

3. Rinse deionized water

4. conversion treatment: 108 s; 30 ° C; Bath composition: H ₂ ZrF _e acid (corresponding to 150 mg / l Zr) and Sokalan HP 56 corresponding to 40 mg / l

5. Rinse deionized water

6. Drying: compressed air

7. Painting: KTL Cathoguard 310, from BASF; Layer thickness approx. 20 μm

Paint adhesion test:

EG salt water storage test (5% NaCI solution, 40 ° C, 6 d; rockfall according to VDA 621-427 before and after) Tab. 4: Results of test series 4

Example 5: Process used as post-rinse after conversion treatment

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; pH 4.0; Bath composition: H ₂ ZrF _β- acid (corresponding to 150 mg / l Zr) and 40 mg / l polymer (phenol-salicylic acid-formaldehyde resin grafted with 0.5 part imidazole based on phenol (ratio phenol / salicylic acid 1: 1)) 5. Rinse deionized water 6. Reactive rinse 60 s, 30 ° C; Bath composition: H ₂ ZrF ₆ acid (corresponding to 50 mg / l Zr) and molybdate (corresponding to 500 mg / l MoO ₄ ^{2 '} ); pH 2.8 7. Sink VE water 8. Drying: compressed air 9. Painting: polyester PES 5807 / RAL 5009 GL (TIGC-free), company IGP); approx. 60-80 μm Comparative Example 5a: Conversion process as 5 without reactive rinsing

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; pH 3.0; Bath composition: H ₂ ZrF ₆ acid (corresponding to 150 mg / l Zr) and 40 mg / l polymer (phenol-salicylic acid-formaldehyde resin grafted with 0.5 part imidazole based on phenol (ratio phenol / salicylic acid 1: 1)) 5. Sink VE water 6. Drying: compressed air 7. Painting: polyester PES 5807 / RAL 5009 GL (TIGC-free), company IGP); approx. 60-80 μm

Comparative Example 5b: Rinse from 5 used as a conversion bath

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; Bath composition: H ₂ ZrF _β- acid (corresponding to 50 mg / l Zr) and molybdate (corresponding to 500 mg / l MoO ₄ ^{2 "} ); pH 2.8

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 5

Claims

claims

1. A process for the two-stage corrosion protection treatment of metal surfaces, the metal surfaces a) being brought into contact in a first step with a chromium-free first aqueous solution with a pH in the range from 1.5 to 5, which in total is at least 0.01 g / l, preferably at least 0.025 g / l, and up to 10 g / l, preferably up to 1 g / l, in particular up to 0.5 g / l Ti and / or Zr and / or Si ions and at least one contains such an amount of fluoride that the atomic ratio Ti to F and / or Zr to F and / or Si to F is in the range from 1: 1 to 1: 6, and thereafter, with or without intermediate rinsing with water, b) in one second step in contact with a chromium-free second aqueous solution with a pH in the range from 1.5 to 5, the total of at least 0.01 g / l, preferably at least 0.025 g / l, and up to 10 g / l, preferably up to 1 g / l, in particular up to 0.5 g / l Ti and / or Zr and / or Si ions and at least one such amount e of fluoride contains that the atomic ratio Ti to F and / or Zr to F and / or Si to F is in the range from 1: 1 to 1: 6, and additionally such a quantity of soluble anions of oxo acids of molybdenum and / or Tungsten in oxidation state VI contains that the total concentration of molybdenum and / or tungsten, calculated as MoO ₄ ^{2 "} and / or WO ₄ ^2" , is in the range from 5 to 1500 mg / l.

2. A process for producing a component containing painted metal parts, wherein I) metal sheets which have a coating based on organic polymers are cut and / or punched and / or formed 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; II) cleans the assembled component, IM) subjects the cleaned assembled component to a sequence of processes which produces a passivation layer on the areas of the metal surface which are formed in sub-step I) and which are not covered by the coating based on organic polymers, which is not a zinc phosphate layer, taking the areas of the metal surface of the sheet that are not on the coating Based on organic polymers are covered a) in a first step with a chromium-free first aqueous solution with a pH in the range from 1.5 to 5, which in total at least 0.01 g / l, preferably at least 0.025 g / l , and up to 10 g / l, preferably up to 1 g / l, in particular up to 0.5 g / l Ti and / or Zr and / or Si ions and at least such an amount of fluoride that the Atomic ratio Ti to F and / or Zr to F and / or Si to F is in the range from 1: 1 to 1: 6, and then, with or without intermediate rinsing with water, b) in a second step with a chromium-free second aqueous solution in contact with a pH in the range from 1.5 to 5, the total of at least 0.01 g / l, preferably at least 0.025 g / l, and up to 10 g / l, preferably up to 1 g / l, contains in particular up to 0.5 g / l of Ti and / or Zr and / or Si ions and at least such an amount of fluoride that the atomic ratio Ti to F and / or Zr to F u nd / or Si to F is in the range from 1: 1 to 1: 6, and which additionally contains such an amount of soluble anions of oxo acids of molybdenum and / or tungsten in oxidation state VI that the total concentration of molybdenum and / or tungsten, calculated as MoO ^{2 '} and / or WO ^{2 "} , is in the range from 5 to 1500 mg / l, IV) if desired, but not necessarily rinsing the component treated in sub-step c) one or more times with water and V) with a lacquer layer coated.

3. The method according to one or both of claims 1 and 2, characterized in that the metal surfaces are selected from surfaces of steel, galvanized or alloy galvanized steel, aluminized steel, zinc, aluminum, magnesium or alloys which are at least 50 atomic percent zinc, Aluminum or magnesium exist.

4. The method according to one or more of claims 1 to 3, characterized in that the first aqueous solution additionally at least 0.005 g / l, preferably at least 0.01 g / l, and up to 20 g / l, preferably up to 1 g / l contains organic polymers.

5. The method according to one or more of claims 1 to 4, characterized in that the second aqueous solution additionally contains complexing agents.

6. The method according to one or more of claims 1 to 5, characterized in that the first and / or the second aqueous solution has a pH of at least 1.5, preferably at least 1.7, and up to 5, preferably to to have 4.

7. The method according to one or more of claims 1 to 6, characterized in that the second aqueous solution additionally contains buffer substances for the pH range 1.5 to 5.

8. The method according to one or more of claims 1 to 6, characterized in that the second aqueous solution contains no more than 5 mg / l organic polymers.

9. The method according to one or more of claims 1 to 7, characterized in that the metal surfaces in the second step b) for a period in the range from 5 seconds to 10 minutes, preferably 10 seconds to one minute in contact with the second aqueous solution brings.

10. The method according to claim 8, characterized in that the second aqueous solution has a temperature of at least 20 ° C, preferably at least 30 ° C, and not more than 60 ° C, preferably not more than 50 ° C.