EP2771499B1 - Method for coating metallic surfaces with a multi-component aqueous composition - Google Patents

Description

The invention relates to a process for coating metallic surfaces with aqueous compositions, wherein in a pretreatment step a silane-based aqueous composition comprising at least one silane and / or a silicon-containing compound related thereto and optionally further components, without drying the coating e.g. is further treated at temperatures above 70 ° C by using at least one aqueous rinsing step after this pretreatment step and then an electrodeposition coating is carried out, wherein in the aqueous rinsing steps, at least in the last rinsing step, at least one surfactant is added.

The hitherto most frequently used methods for the treatment of metallic surfaces, in particular parts, band (coil) or band sections of at least one metallic material, or for the pretreatment of metallic surfaces prior to the painting of metallic surfaces are based on the one hand on the use of chromium ( VI) compounds optionally together with various additives or on the other hand on phosphates such as Zinc manganese nickel phosphates optionally together with various additives.

Due to the toxicological and ecological risks associated with chromate-containing processes or nickel-containing processes in particular, alternatives to these processes have been available for many years However, it has always been found that in many applications completely chromate-free or nickel-free processes do not fulfill 100% of the power spectrum or do not meet the desired safety. It is then attempted to keep the chromate contents or nickel contents as low as possible and as far as possible to replace Cr ⁶⁺ by Cr ³⁺ . In particular, in the automotive industry, for example, for the pretreatment of bodies before painting high-quality phosphating in use, which have kept the corrosion protection of automobiles to a high level of quality. Zinc manganese nickel phosphatings are usually used for this purpose. Despite many years of research and development, it has been unsuccessful for multi-metal applications, as is often the case in car bodies, where in Europe metallic surfaces of steel, galvanized steel and aluminum or aluminum alloys are typically pretreated in the same bath, without significant quality limitations to phosphatize. However, since nickel contents, even if they are comparatively low, are classified as toxicologically questionable in the foreseeable future, the question arises as to whether equivalent corrosion protection can be achieved with other chemical processes.

In particular, in the automotive industry, the first lacquer layer used is often an electrocoating with an electrodeposition coating (ETL), such as e.g. a cathodic electrodeposition paint (KTL) used. The compositions and conditions of use of electrocoating are known in principle.

The use of, for example, silanes / silanols in aqueous compositions for the preparation of siloxane / polysiloxane-rich corrosion-protective coatings is known in principle. For the sake of simplicity, silane / silanol / siloxane / polysiloxane is often referred to as silane in the following. These coatings have been proven, but the methods for coating with a predominantly silane in addition to solvent (s) containing aqueous composition sometimes difficult to apply. Not always, these coatings are formed with excellent properties. In addition, there may be problems here, to be able to sufficiently characterize the very thin transparent silane coatings on the metallic substrate and their defects with the naked eye or optical aids. The corrosion protection and the paint adhesion of the formed siloxane or / and polysiloxane-rich coatings are often, but not always high and sometimes not sufficiently high for certain applications even with suitable application. It requires further methods using at least one silane, which have a high process safety and a high quality of the coatings produced herewith, in particular with regard to corrosion resistance and paint adhesion.

In the design of silane-containing aqueous compositions, moreover, a small or large amount of addition of at least one component selected from the group of organic monomers, oligomers and polymers has been proven. In such compositions, the type and amount of silane addition is in part of critical importance for success. Usually, however, the addition amounts of silane for this purpose are comparatively low - usually only up to 5 wt .-% of all solids contents - and then act as a "coupling agent", the adhesion-promoting effect in particular between metallic substrate and paint and optionally between pigment and organic paint constituents should prevail, but subordinate partially also a low cross-linking effect can occur. Predominantly, very little silane additives are added to thermosetting resin systems.

In the case of the use of silane-containing solutions for coating metallic surfaces, it is hitherto known that the solutions containing essentially or predominantly silane and their derivatives are water-sensitive if the coatings have not been dried to a greater extent, so that rinsing the freshly coated, not yet dried coatings with water usually leads to deterioration of the coatings, for example by delamination, since they are not sufficiently rinsing. Obviously, the very thin oxide / hydroxide layers of the "natural" oxide skins of metallic surfaces are insufficient to keep freshly applied silane sufficiently adherent prior to throughdrying. Only when the coatings are, for example, 5 minutes at 80 ° C PMT (peak metal temperature), for example 25 minutes at 70 ° C PMT or more dried, these coatings are generally insensitive to water, since the condensation of silanes / silanols / Siloxanes / polysiloxanes is more advanced. The degree of drying associated with a condensation of the silanes / silanols / siloxanes / polysiloxanes and the rinse resistance of the siloxane / polysiloxane-containing coating will vary depending on the phase inventory, coating, and type of rinse.

Existing phosphating plants, in particular in the automotive industry for the purification and pretreatment, e.g. of bodies before painting require no drying system. But even without them, such a canal-like system is often well over a hundred meters long. In many cases, at the end of the line, where the finished phosphated bodies come out of the sewer, this system directly adjoins a system for coating with a cathodic dip paint (KTL), so that there is usually no space available for the additional construction of a drying system.

DE 102005015576 A1 describes the effects during pre-rinsing and / or rinsing before and after the silane pretreatment according to the invention mentioned therein. DE 20 17 327 A1 teaches a process in which on zinc-based metallic surfaces (a) the metal surfaces are treated with an aqueous conditioning liquid consisting of an aqueous solution of 1.5 to 10.0% by weight of sodium or potassium hydroxide together with at least 0.05% by weight each. % Iron ions and a masking agent for iron at a pH of at least 13 soaks, (b) the aqueous Rinsing conditioning fluid from the metal with water, (c) depositing a zinc phosphate conversion coating on the metal surface, and (d) electrophoretically depositing thereon a paint film.

When using an electrodeposition coating after a silane-based pretreatment, there was the problem, in particular in the automotive industry, of reducing the voltage of the electrodeposition coating in comparison with a sequence of processes using a zinc phosphate coating, because the comparatively thick zinc phosphate coatings cause a significantly higher electrical resistance in the electrodeposition bath. By using lower electrical voltages in the electrodeposition bath with a comparatively thin silane-based pretreatment coating With a comparatively low electrical resistance, there may be problems with the evenness, uniformity, and visual appearance of the applied electrodeposition paint, and with the paint coating just at the rear grip locations of intricately shaped metal parts.

The use of electrodeposition coating after a silane-based pretreatment has been a problem, especially in the automotive industry, to improve the quality of the electrodeposition coating, since in some situations it can be used on intricately shaped workpieces and constructions such as e.g. in housings and bodies is not sufficient to allow the same possible layer thicknesses of the electrodeposition coating outside and inside and thereby meet all other quality requirements for the paint.

It was therefore the object of proposing a process for aqueous compositions whose coatings have the most environmentally friendly chemical composition and ensure high corrosion resistance, including in multi-metal applications, such as steel and zinc-rich metallic surfaces and optionally also aluminum-rich metallic surfaces be treated or pretreated in the same bath, are suitable. It was also the task of proposing a sequence of processes from pre-treatment to electrocoating, in which the lowest possible low-quality coatings of silane-based pretreatment and electrodeposition coating can be applied in particular to bodies in the automotive series production. Furthermore, the object was to propose a method with silane-containing aqueous compositions, which can be implemented in existing systems of the automotive industry in principle and is particularly suitable for coating car bodies in the automotive industry. Here, a coating quality of the pretreatment coating and the electrodeposition coating is to be achieved on body surfaces, as in the high-quality corrosion-protective coatings of zinc manganese nickel phosphating is achieved in order not to endanger the quality standards.

It has now been found that the addition of at least one surfactant in the one rinse step when rinsing with water after the silane-based pretreatment or at least in the last of several rinse steps when rinsing with water after the silane-based pretreatment enables such a high homogenization of the electrodeposition coating in that a better encirclement of the electrodeposition coating and possibly also of the electric field occurs in the electrodeposition coating and that the layer thicknesses of the electrodeposition coating eg outside to inside e.g. be significantly evened out in a housing or in a body.

The addition of complex fluoride in the silane-based pretreatment helps to minimize or avoid impairments of the attachment of silane to the metallic surface, so that the rinsing can have little or no effect. A combination of at least two complex fluorides in the silane-based pretreatment composition, in particular of fluorotitanic acid and of fluorozirconic acid or salts thereof, also makes possible an extraordinary increase in the quality of the coatings.

It has been found that it is not only possible to rinse freshly applied and not yet dried and therefore not yet more strongly condensed coatings based on silane, but that this process sequence is even advantageous because the thus prepared and rinsed pretreatment coatings partially independent from the chemical composition of the aqueous silane-based (= silane / silanol / siloxane / polysiloxane or / and silane / silanol / siloxane) pretreatment composition may even have better corrosion protection and better paint adhesion. This contradicts earlier experiences, according to which rinsing a freshly applied and not much dried coating based on silane easily and often to a Impairment of layer quality, if not partial or isolated, leads to complete removal of the coating.

It has also been found that it is possible and advantageous to apply a lacquer such as an electrodeposition lacquer to silane-based, silane-based pretreatment coatings based on silane which have been freshly applied and not yet thoroughly dried and which may also have been flushed in this state to apply a varnish-like coating, a primer or an adhesive. The application of such compositions to silane-based wet films is advantageous because the coatings produced and rinsed in this way even have better corrosion protection and better paint adhesion, irrespective of the chemical composition of the aqueous bath.

It has now also been found that the use of an iron-containing aqueous composition prior to application of the silane-based pretreatment composition allows for increased tension in electrodeposition painting. Often, 5 to 15% higher voltages could be used. It was found that the wraparound created here was also improved by about 5 to 15% due to the increased stress.

1. a) mindestens eine Verbindung a) ausgewählt aus Silanen, Silanolen, Siloxanen und Polysiloxanen enthält, von denen mindestens eine dieser Verbindungen noch kondensieren kann, und
2. b) mindestens eine Titan-, Hafnium- oder/und Zirkonium-haltige Verbindung b) sowie
3. c) mindestens eine Art Kationen c) ausgewählt aus Kationen von Metallen der 1. bis 3. und 5. bis 8. Nebengruppe einschließlich Lanthaniden sowie der 2. Hauptgruppe des Periodensystems der Elemente oder/und mindestens eine entsprechende Verbindung c) oder/und
4. d) mindestens eine organische Verbindung d) enthält ausgewählt aus Monomeren, Oligomeren, Polymeren, Copolymeren und Blockcopolymeren,

wobei die mit der Vorbehandlungs-Zusammensetzung frisch aufgebrachte Beschichtung zumindest einmal mit Wasser gespült wird, wobei gegebenenfalls mindestens eine Wasserspülung einen Gehalt an Tensid aufweist, und
wobei nach dem Spülen mit Wasser eine Elektrotauchlack-Beschichtung aufgebracht wird,
wobei die mit dieser Zusammensetzung frisch aufgebrachte Beschichtung bis zu diesem Spülen nicht durchgetrocknet wird, so dass die mindestens eine kondensationsfähige Verbindung a) bis zum Spülen der Vorbehandlungs-Beschichtung mit Wasser oder/und bis zum Beschichten mit einem Elektrotauchlack nicht stark kondensiert oder/und
wobei die mit der Vorbehandlungs-Zusammensetzung frisch aufgebrachte Vorbehandlungs-Beschichtung bis zum Applizieren einer nachfolgenden Elektrotauchlack-Beschichtung nicht durchgetrocknet wird, so dass die mindestens eine kondensationsfähige Verbindung a) bis zum Applizieren der nachfolgenden Elektrotauchlack-Beschichtung nicht stark kondensiert und
wobei vor der Behandlung mit einer wässerigen Silan-basierten Vorbehandlungs-Zusammensetzung eine wässerige Behandlung mit einem Gehalt an wassergelöster Eisenverbindung durchgeführt wird.The object is achieved with a method for improving the encapsulation of an electrodeposition coating by coating metallic surfaces with a silane / silanol / siloxane / polysiloxane containing pretreatment composition, characterized in that this composition in addition to water and optionally in addition to at least one organic solvent or / and at least one pH-affecting substance

1. a) at least one compound a) selected from silanes, silanols, Siloxanes and polysiloxanes, of which at least one of these compounds can still condense, and
2. b) at least one titanium, hafnium or / and zirconium-containing compound b) and
3. c) at least one kind of cations c) selected from cations of metals of the 1st to 3rd and 5th to 8th subgroup including lanthanides and the 2nd main group of the Periodic Table of the Elements or / and at least one corresponding compound c) or / and
4. d) at least one organic compound d) selected from monomers, oligomers, polymers, copolymers and block copolymers,

wherein the freshly applied with the pretreatment composition coating is rinsed at least once with water, optionally at least one water rinse has a content of surfactant, and
wherein, after rinsing with water, an electrodeposition coating is applied,
wherein the coating freshly applied with this composition is not thoroughly dried until such rinsing, such that the at least one condensable compound a) does not strongly condense and / or until it has been rinsed with water and / or coated with an electrodeposition paint
wherein the pre-treatment coating freshly applied with the pretreatment composition is not dried through until application of a subsequent electrodeposition coating, such that the at least one condensable compound a) does not strongly condense until application of the subsequent electrodeposition coating and
wherein before the treatment with an aqueous silane-based pretreatment composition, an aqueous treatment containing a water-dissolved iron compound is carried out.

The object is also achieved with the use of the process according to the invention according to one of claims 1 to 21 coated metallic substrates in the automotive industry, for rail vehicles, in the aerospace industry, apparatus engineering, mechanical engineering, in the construction industry, in the furniture industry for the manufacture of crash barriers, lamps, profiles, panels or small parts, for the manufacture of bodies or body parts, of individual components, preassembled or connected elements, preferably in the automotive or aerospace industry, for the manufacture of appliances or installations, in particular household appliances , Control devices, test equipment or construction elements.

The object is further achieved by the use of an aqueous silane-based pretreatment composition in a coating process according to at least one of claims 1 to 22 for metallic substrates for improving the encapsulation of an electrodeposition coating, in which an aqueous silane-based composition according to at least one of claims 1 to 16 is contacted with a metallic substrate in which the coating newly applied with this composition is rinsed at least once with water, rinsing at least once with water containing surfactant, after rinsing with water an electrodeposition paint Coating is applied, wherein the freshly applied with this composition coating is not dried until this rinsing, so that the at least one condensable compound a) until rinsing the pretreatment coating with water or / and until coating m it is not strongly condensed with an electrodeposition paint and an aqueous treatment containing a water-dissolved iron compound is carried out prior to treatment with an aqueous silane-based pretreatment composition.

The object is finally achieved with the use of an aqueous silane-based pretreatment composition in a coating process according to at least one of claims 2 to 22 for metallic substrates to improve the application of an electrodeposition coating, wherein the substrates before the aqueous silane-based pretreatment at least once with an aqueous iron composition in which an aqueous silane-based composition according to any one of claims 2 to 16 is brought into contact with a metallic substrate, wherein the freshly applied with this composition coating at least once with water is rinsed, wherein optionally rinsed at least once with water containing a surfactant in which after rinsing with water, an electrodeposition coating is applied, wherein the pretreatment composition freshly applied Vorbehandlu ngs coating until application of a subsequent electrodeposition coating is not dried through, so that the at least one condensable compound a) is not strongly condensed until application of the subsequent electrodeposition coating and wherein prior to treatment with an aqueous silane-based pretreatment composition aqueous treatment with a content of water-dissolved iron compound is performed.

In one embodiment, a second conversion layer or / and a coating as a result of application of a rinsing solution can also be used in the middle of this process sequence. The second conversion layer or coating as a result of application of a rinsing solution is preferably an aqueous composition based on at least one silane / silanol / siloxane / polysiloxane, of at least one titanium, hafnium, zirconium, aluminum or / and boron-containing compound such as eg at least one complex fluoride, of at least one organic compound selected from monomers, oligomers, polymers, copolymers and block copolymers or / and of at least one Phosphorus and oxygen containing compound. In many embodiments, the concentration of the aqueous composition for the second conversion layer or the rinsing solution is generally lower than a comparable aqueous composition for the first conversion layer, namely the silane-based pretreatment coating according to the invention.

It is particularly advantageous if the freshly applied coating is first rinsed with water or with an aqueous solution before a subsequent coating is applied. In this case, the wet film of the silane-based pretreatment according to the invention can be rinsed without prior stronger drying of the wet film with water or / and with an aqueous composition which optionally contains surfactant. A subsequent coating can then be applied to this wet film in the not yet dried state. The rinsing of the wet film after the silane pretreatment is preferably carried out immediately after coating with the silane-containing aqueous composition, especially within one or two Minutes after coating with the silane pretreatment according to the invention, more preferably within 30 seconds or even within 10 seconds after this coating. When multiple water rinses are used, it is preferred that at least the last of these rinses have a content of at least one surfactant. Preferably, the electrodeposition paint is applied immediately after rinsing, especially within two or three minutes after rinsing the silane-based pretreatment coating, more preferably within 60 seconds or even within 20 seconds. The paint may in this case be in particular an electrodeposition paint or a water-containing wet paint. On the other hand, it can often happen, especially in industrial production, that the time from the end of rinsing with water until application of the electrodeposition paint is 1 to 120 minutes, but preferably only 2 to 60 or 3 to 40 or 4 to 20 minutes. It is then advantageous if, despite this waiting period, no stronger drying of the rinsed silane-based pretreatment coating occurs. It is then advantageous to take measures such that the rinsed silane-based pretreatment coatings do not dry through and, if possible, do not dry more, for example by using a wet-holding system, such as nozzles for spraying a water mist.

It is assumed that the at least one, still condensable silane / silanol / siloxane is even more chemically reactive and can react more intensively with the subsequently applied electrodeposition paint than an already thoroughly dried and thermally influenced strongly condensed silane / silanol / siloxane / polysiloxane. It is believed that even after a latency period of up to several hours, as long as no temperatures above 40 ° C. are used, the silane-based pretreatment coating dries out. The term "silane" is used here for silanes, silanols, siloxanes, polysiloxanes and their reaction products or derivatives, which are often also "silane" mixtures. The term "condensation" in the context of this application refers to all forms of crosslinking, further crosslinking and further chemical reactions of the silanes / silanols / siloxanes / polysiloxanes. Usually, this is based on an addition as silane, wherein the added at least one silane is often at least partially hydrolyzed, where it usually forms the first contact with water or moisture at least one silanol, formed from the at least one siloxane and later optionally also at least one polysiloxane will or can be. For the purposes of this application, the term "coating" refers to the coating formed with the aqueous composition, including the wet film, the dried film, the throughdried film, the elevated-temperature-dried film and the optionally thermally and / or irradiated further crosslinked film.

The aqueous silane-based pretreatment composition is an aqueous solution, an aqueous dispersion or / and an emulsion. Preferably, its pH is greater than 1.5 and less than 9, more preferably in the range of 2 to 7, most preferably in the range of 2.5 to 6.5, in particular in the range of 3 to 6. At a pH Value of eg 2.5 can significantly reduce the deposition of titanium or zirconium compounds, e.g. occur from the complex fluoride, which can be affected by slight reduction of the layer properties. At a pH of about 7, the complex fluoride contained in the bath may become unstable and precipitation may occur.

The aqueous silane-based pretreatment composition is particularly preferably at least one silane or / and at least one corresponding compound having at least one amino group, at least one urea group or / and at least one Ureido group (imino) added, since the coatings produced herewith often show a higher paint adhesion and / or a higher affinity to the subsequent electrodeposition coating layer. In particular, when using at least one silane or / and at least one corresponding compound having at least one such group, care must be taken that the condensation may be very rapid at pH values below 2. Preferably, the proportion of aminosilanes, ureidosilanes or / and silanes having at least one urea group or / and corresponding silanols, siloxanes and polysiloxanes can be increased in the sum of all types of compounds selected from silanes, silanols, siloxanes and polysiloxanes, more preferably above 20 , over 30 or over 40 wt .-% are calculated as the corresponding silanols, most preferably above 50, above 60, above 70 or above 80 wt .-% are and optionally even up to 90, up to 95 or up to 100 Wt .-% amount.

Preferably, the aqueous silane-based pretreatment composition has a silane / silanol / siloxane / polysiloxane content a) in the range of 0.005 to 80 g / L, calculated on the basis of the corresponding silanols. This content is particularly preferably in the range from 0.01 to 30 g / l, very particularly preferably in the range from 0.02 to 12 g / l, to 8 g / l or to 5 g / l, in particular in the range from 0, 05 to 3 g / L or in the range of 0.08 to 2 g / L or to 1 g / L. These content ranges relate in particular to bath compositions.

However, if a concentrate is used to prepare a corresponding bath composition, in particular by dilution with water and optionally by adding at least one further substance, it is advisable to separate, for example, a concentrate A containing silane / silanol / siloxane / polysiloxane a) to keep a concentrate B containing all or almost all other constituents and to bring these components together in the bathroom. Here can if appropriate, in each case at least one silane, silanol, siloxane and / or polysiloxane are also partly or wholly in the solid state, are added in the solid state and / or are added as dispersion or solution. However, the concentration ranges of the bath may have different salary ranges depending on the application.

The aqueous silane-based pretreatment composition particularly preferably contains at least one silane, silanol, siloxane or / and polysiloxane a) each having at least one group selected from acrylate groups, amino groups, succinic anhydride groups, carboxyl groups, epoxy groups, glycidoxy groups, hydroxy groups, ureido groups (Imino), isocyanato groups, methacrylate groups and / or urea groups per molecule, wherein also aminoalkyl groups, alkylaminoalkyl groups and / or alkylamino groups can occur. This composition particularly preferably contains at least one silane, silanol, siloxane or / and polysiloxane a) having at least two amino groups, at least three amino groups, at least four amino groups, at least five amino groups or / and at least six amino groups per molecule ,

The silanes, silanols, siloxanes or / and polysiloxanes in the aqueous silane-based pretreatment composition, or at least their compounds initially added to the aqueous composition, or at least a portion of them are preferably water-soluble. For the purposes of this application, the silanes are considered to be water-soluble if they have a solubility in water of at least 0.05 g / l, preferably of at least 0.1 g / l, at room temperature in the silane / silanol / siloxane / polysiloxane-containing composition. more preferably at least 0.2 g / L or at least 0.3 g / L. This does not mean that each of these silanes must have this minimum solubility, but that these minimum values are achieved on average. Preferably, in the aqueous silane-based pretreatment composition at least one silane / silanol / siloxane / polysiloxane is selected from fluorine-free silanes and the corresponding silanols / siloxanes / polysiloxanes each of at least one acyloxysilane, an alkoxysilane, a silane having at least one amino group such as an aminoalkylsilane, a silane having at least one succinic group and / or succinic anhydride group, a bis-silyl silane, a silane having at least one epoxy group such as a glycidoxysilane, a (meth) acrylato-silane, a multi-silyl-silane, a ureidosilane, a vinyl silane or / and at least one silanol or / and at least one siloxane or polysiloxane of chemically corresponding composition such as the abovementioned silanes. It contains at least one silane or / and (in each case) at least one monomeric, dimeric, oligomeric or / and polymeric silanol and / or (in each case) at least one monomeric, dimeric, oligomeric or / and polymeric siloxane, with oligomers also already including dimers and trimers. Particularly preferably, the at least one silane or the corresponding silanol / siloxane / polysiloxane has in each case at least one amino group, urea group or / and ureido group.

In particular, herein at least one silane and / or at least one corresponding silanol / siloxane / polysiloxane is contained or / and initially added selected from the group of or based on
(3,4-epoxyalkyl) trialkoxysilane,
(3,4-Epoxycycloalkyl) alkyltrialkoxysilane,
3-acryloxyalkyltrialkoxisilane,
3-Glycidoxyalkyltrialkoxysilan,
3-methacryloxyalkyltrialkoxysilane,
3- (trialkoxysilyl) alkylbernsteinsäuresilan,
4-amino-dialkylalkyltrialkoxysilan,
4-amino-dialkylalkylalkyldialkoxysilan,
Aminoalkylaminoalkyltrialkoxysilan,
Aminoalkylaminoalkylalkyldialkoxysilan,
aminoalkyl,
amine bis (trialkoxysilylalkyl),
Bis (trialkoxysilyl) ethane,
Gamma acryloxyalkyltrialkoxisilane,
Gamma-aminoalkyl,
Gamma methacryloxyalkyltrialkoxysilane,
(Gamma-trialkoxysilylalkyl) dialkylenetriamine,
Gamma Ureidoalkyltrialkoxysilan,
N-2-aminoalkyl-3-aminoproplyltrialkoxysilan,
N- (3-trialkoxysilylalkyl) alkylenediamine,
N-Alkylaminoisoalkyltrialkoxysilan,
N- (aminoalkyl) aminoalkylalkyldialkoxysilan,
N-beta- (aminoalkyl) -gamma-aminoalkyltrialkoxysilane,
N- (gamma-trialkoxysilylalkyl) dialkylenetriamine,
N-phenyl-aminoalkyltrialkoxysilane,
Poly (aminoalkyl) alkyldialkoxysilane,
Tris (3-trialkoxysilyl) alkylisocyanurat,
Ureidoalkyltrialkoxysilane and
Vinylacetoxysilane.

Particular preference is given here to containing at least one silane or / and at least one corresponding silanol / siloxane / polysiloxane or / and initially added selected from the group of or based on
(3,4-epoxybutyl) triethoxysilane,
(3,4-epoxybutyl) trimethoxysilane,
(3,4-epoxycyclohexyl) propyltriethoxysilane,
(3,4-epoxycyclohexyl) propyltrimethoxysilane,
3-acryloxypropyltriethoxysilane,
3-acryloxypropyltrimethoxysilane,
3-Aminopropylsilanetriol,
3-glycidoxypropyltriethoxysilane,
3-glycidoxypropyltrimethoxysilane,
3-methacryloxypropyltriethoxysilane,
3-methacryloxypropyltrimethoxysilane,
3- (triethoxysilyl) propylbernsteinsäuresilan,
Aminoethylaminopropylmethyldiethoxysilan,
aminoethylaminopropylmethyldimethoxysilane,
aminopropyltrialkoxysilane,
ethyltriethoxysilane beta- (3,4-epoxycyclohexyl)
ethyltrimethoxysilane beta- (3,4-epoxycyclohexyl)
methyltriethoxysilane beta- (3,4-epoxycyclohexyl)
methyltrimethoxysilane beta- (3,4-epoxycyclohexyl)
Bis-1,2- (triethoxysilyl) ethane,
1,2-bis (trimethoxysilyl) ethane,
Bis (triethoxysilylpropyl) amine,
Bis (trimethoxysilylpropyl) amine,
propyltriethoxysilane gamma- (3,4-epoxycyclohexyl)
Gamma (3,4-epoxycyclohexyl) propyltrimethoxysilane,
Gamma acryloxypropyltriethoxysilane,
Gamma acryloxypropyltrimethoxysilane
Gamma-aminopropyltriethoxysilane,
Gamma-aminopropyltrimethoxysilane,
Gamma Methacryloxypropyltriethoxysilane,
Gamma-methacryloxypropyltrimethoxysilane,
Gamma ureidopropyltrialkoxysilane,
N-2-aminoethyl-3-aminoproplyltriethoxysilan,
N-2-aminoethyl-3-aminoproplyltrimethoxysilan,
N-2-aminomethyl-3-aminoproplyltriethoxysilan,
N-2-aminomethyl-3-aminoproplyltrimethoxysilan,
N- (3- (trimethoxysilyl) propyl) ethylenediamine,
N-beta- (aminoethyl) -gamma-aminopropyltriethoxysilane,
N-beta- (aminoethyl) -gamma-aminopropyltrimethoxysilane,
N- (gamma-triethoxysilylpropyl) diethylenetriamine,
N- (gamma-trimethoxysilylpropyl) diethylenetriamine,
N- (gamma-triethoxysilylpropyl) dimethylenetriamine,
N- (gamma-trimethoxysilylpropyl) dimethylenetriamine,
Poly (aminoalkyl) ethyldialkoxysilan,
Poly (aminoalkyl) methyldialkoxysilan,
Tris (3- (triethoxysilyl) propyl) isocyanurate,
Tris (3- (trimethoxysilyl) propyl) isocyanurate,
Ureidopropyltrialkoxysilane and
Vinyltriacetoxysilane.

Optionally, in individual embodiments in the aqueous composition at least one silane / silanol / siloxane / polysiloxane containing a fluorine-containing group. Depending on the choice of silane compound (s), the hydrophilicity / hydrophobicity can be set purposefully.

Preferably, in some embodiments, at least one at least partially hydrolyzed, at least partially condensed silane / silanol / siloxane / polysiloxane is added to the aqueous silane-based pretreatment composition. In particular, when the aqueous composition is mixed together, at least one pre-hydrolyzed, pre-condensed silane / silanol / siloxane / polysiloxane may optionally be added in each case. Such an additive is particularly preferred.

In some embodiments, at least one silane / silanol / siloxane / polysiloxane at least substantially or / and completely hydrolyzed and / or at least substantially or / and completely condensed may be added to the aqueous silane-based pretreatment composition. In many embodiments, an unhydrolyzed silane binds poorer to the metallic surface than an at least partially hydrolyzed silane / silanol. A largely hydrolyzed and not or only slightly condensed silane / silanol / siloxane binds much better in many embodiments of the metallic surface than an at least partially hydrolyzed and largely condensed silane / silanol / siloxane / polysiloxane. A completely hydrolyzed and largely condensed silanol / siloxane / polysiloxane shows in many embodiments only a slight tendency to be chemically bound to the metallic surface.

In some embodiments, at least one silane that is multi-branched or / and has from three to twelve amino groups per molecule may be added to the aqueous silane-based pretreatment composition.

In some embodiments, the silane-based aqueous pretreatment composition may additionally or alternatively and / or silane (s) / silanol (s) be added with at least one siloxane or / and polysiloxane containing no or only a minor amount - e.g. less than 20 or less than 40% by weight of the sum of silane / silanol / siloxane / polysiloxane - of silanes / silanols. The siloxane or polysiloxane is preferably short-chain and is preferably applied by rollcoater treatment. If necessary, this will then have an effect on the coating due to greater hydrophobicity and higher blank corrosion protection.

Preferably, the aqueous silane-based pretreatment composition comprises at least two or even at least three compounds of titanium, hafnium and zirconium. These compounds may differ in their cations and / or in their anions. The aqueous composition, in particular the bath composition, preferably has a content of at least one complex fluoride b), more preferably at least two complex fluorides selected from complex fluorides of titanium, hafnium and zirconium. Preferably, their difference is not only in the nature of the complex. Preferably, the aqueous silane-based Pretreatment composition, in particular the bath composition, a content of compounds b) selected from compounds of titanium, hafnium and zirconium in the range of 0.01 to 50 g / L calculated as the sum of the corresponding metals. This content is particularly preferably in the range from 0.05 to 30 g / l, very particularly preferably in the range from 0.08 to 15 g / l, in particular in the range from 0.1 to 5 g / l.

Preferably, the aqueous silane-based pretreatment composition contains at least one complex fluoride, wherein the content of complex fluoride (s) is in particular in the range of 0.01 to 100 g / L calculated as the sum of the corresponding metal complex fluorides as MeF ₆ . The content is preferably in the range from 0.03 to 70 g / L, particularly preferably in the range from 0.06 to 40 g / L, very particularly preferably in the range from 1 to 10 g / L. The complex fluoride can be present in particular as MeF ₄ or / and as MeF ₆ , but also in other stages or intermediates. Advantageously, in many embodiments at least one titanium and at least one zirconium complex fluoride are present. In this case, it may be advantageous in many cases to have at least one MeF ₄ and at least one MeF ₆ complex in the composition at the same time, in particular at the same time a TiF ₆ and a ZrF ₄ complex. It may be advantageous to adjust these complex fluoride ratios already in the concentrate and to take over in this way in the bath.

Surprisingly, the individual complex fluorides do not interfere negatively when combined, but exhibit an unexpected positive enhancement effect. These complex fluoride-based additives appear to act in a similar or similar manner. If a combination of complex fluorides based on titanium and zirconium and not just a complex fluoride based only on titanium or only one based on zirconium is used, surprisingly, results are always noticeably better than with a single one of these additives. On the Surface deposits a complex fluoride based on titanium or zirconium probably as oxide or / and hydroxide.

It has surprisingly been found that a good multimetal treatment with a single aqueous composition is only possible when a complex fluoride has been used, and that a very good multimetal treatment with a single aqueous composition is only possible if at least two different complex fluorides are used such as those based on titanium and zirconium. The individual complex fluorides used in the most diverse experiments never showed results that were as good as for the combination of these two complex fluorides, regardless of which additives were added.

Alternatively to or in addition to at least one complex fluoride, a different type of titanium, hafnium and zirconium compound may also be added, for example, at least one hydroxycarbonate and / or at least one other water-soluble or slightly water-soluble compound, e.g. at least one nitrate and / or at least one carboxylate.

Preferably, only cations or corresponding compounds c) selected from the group of aluminum, barium, magnesium, calcium, indium, yttrium, lanthanum, cerium, vanadium, niobium, tantalum, molybdenum, tungsten, Lead, manganese, iron, cobalt, nickel, copper, silver, bismuth, tin and zinc, more preferably from the group of aluminum, magnesium, calcium, yttrium, lanthanum, cerium, vanadium, molybdenum, tungsten, manganese, iron, cobalt, Copper, bismuth, tin and zinc, if trace levels of less than 0.005 g / L in the bath composition except for copper and silver are excluded, calculated as metal. Very particular preference is given as cations and / or corresponding compounds c) in this case only types of cations or corresponding compounds selected from the group of magnesium, calcium, yttrium, lanthanum, cerium, manganese, iron, cobalt, copper, tin and zinc or selected from the group of calcium, yttrium, manganese, iron, cobalt, copper, tin and zinc, if from Trace levels of less than 0.005 g / L in the bath composition except for copper and silver, calculated as metal. Individual ones of these cations or compounds may also be preferred here in order to increase the conductivity of the respective coating or / and an interface in order to improve a connection to a coating or / and to produce similar cations in the aqueous silane-based pretreatment composition, to be used in at least one water rinse and / or in the electrodeposition paint.

On the other hand, it has surprisingly been found that cations of iron and zinc and therefore also the presence of corresponding compounds in the bath, which can increasingly contribute to the extraction of such ions from the metallic surface especially in acidic compositions, do not negatively affect the bath behavior in wide content ranges. effect the layer formation and the layer properties.

Preferably, the aqueous silane-based pretreatment composition, in particular the bath composition, has a content of cations and / or corresponding compounds c) in the range from 0.01 to 20 g / L, calculated as the sum of the metals. It is particularly preferably in the range from 0.03 to 15 g / L, very particularly preferably in the range from 0.06 to 10 g / L, in particular in the range from 0.1 to 6 g / L. Most preferably, the content of each individual type of cations or compounds c) in the aqueous silane-based pretreatment composition is in the range from 0.005 to 0.500 g / L, from 0.008 to 0.100 g / L or from 0.012 to 0.050 g / L is calculated as the metal, except for grades of cations of copper and silver, which may have a significant influence even in smaller quantities such as 0.001 to 0.030 g / L, where 1 ppm corresponds to 0.001 g / L. Depending on the nature of the cation or compound, the preferred levels in the aqueous silane-based pretreatment composition are of varying magnitude.

Preferably, the aqueous silane-based pretreatment composition contains at least one kind of cations selected from cations of cerium, chromium, iron, calcium, cobalt, copper, magnesium, manganese, molybdenum, nickel, niobium, tantalum, yttrium, zinc, tin and other lanthanides or / and at least one corresponding compound. In some embodiments, at least two, at least three, or at least four different types of cations are added, or at least three, at least four, or at least five different types of cations are found in the aqueous silane-based pretreatment composition. Cations of aluminum, iron, cobalt, copper, manganese, tin and zinc, 2.) Cations of cerium, iron, calcium, magnesium, manganese are particularly preferred in this case combinations of cations or their compounds selected from the group 1.) , Yttrium, zinc and tin, 3.) of cations of copper, manganese and zinc or 4.) of cations of aluminum, iron, calcium, copper, magnesium, manganese and zinc. Preferably, not all cations contained in the aqueous composition have not only been dissolved out of the metallic surface by the aqueous composition, but also at least partially or even substantially added to the aqueous composition. Therefore, a freshly prepared bath of certain cations or compounds may be free, which are released only from reactions with metallic materials or from reactions in the bath or arise.

The addition of manganese ions or of at least one manganese compound has surprisingly been found to be particularly advantageous. Although apparently no or almost no manganese compound is deposited on the metallic surface, this additive apparently promotes the Deposition of silane / silanol / siloxane / polysiloxane and thus significantly improves the properties of the coating. An addition of magnesium ions or at least one magnesium compound has unexpectedly been found to be advantageous, since this addition promotes the deposition of titanium and / or zirconium compounds, presumably as oxide and / or hydroxide, on the metallic surface and thus the properties of the coating clearly improved. A combined addition of magnesium and manganese leads in part to even further improved coatings. In contrast, addition of copper ions in the range of 0.001 to 0.030 g / L has been found to have a significant impact. An addition of indium or / and tin has proven particularly useful. With a higher content of calcium ions, care must be taken that no destabilization of a complex fluoride by formation of calcium fluoride occurs.

Preferably, the aqueous silane-based pretreatment composition contains at least one kind of cation or / and corresponding compounds selected from alkaline earth metal ions in the range of 0.01 to 50 g / L calculated as corresponding compounds, more preferably in the range of 0.03 to 35 g / L, most preferably in the range of 0.06 to 20 g / L, in particular in the range of 0.1 to 8 g / L or to 1.5 g / L. The alkaline earth metal ions or corresponding compounds may help to enhance the deposition of compounds based on titanium or / and zirconium, which is often advantageous in particular for increasing the corrosion resistance.

Preferably, the aqueous silane-based pretreatment composition contains at least one kind of cation selected from cations of aluminum, iron, cobalt, magnesium, manganese, nickel, yttrium, tin, zinc and lanthanides or / and at least one corresponding compound c) , in particular in the range of 0.01 to 20 g / L, calculated as the sum of the metals. It is particularly preferably in the range from 0.03 to 15 g / L, most preferably in the range from 0.06 to 10 g / L, in particular in the range of 0.020 to 6 g / L, from 0.040 to 1.5 g / L, from 0.060 to 0.700 g / L or from 0.080 to 0.400 g / L.

Preferably, the composition contains a content of at least one organic compound d) selected from monomers, oligomers, polymers, copolymers and block copolymers, in particular at least one compound based on acrylic, epoxy or / and urethane. In this case, additionally or alternatively, at least one organic compound having at least one silyl group can also be used. In some embodiments it is preferred to use such organic compounds with or without OH groups, amine groups, carboxylate groups, isocyanate groups and / or isocyanurate groups.

Preferably, the aqueous silane-based pretreatment composition contains a content of at least one organic compound d) selected from monomers, oligomers, polymers, copolymers and block copolymers in the range of 0.01 to 200 g / L calculated as a solid additive. The content is particularly preferably in the range from 0.03 to 120 g / L, very particularly preferably in the range from 0.06 to 60 g / L, in particular in the range from 0.1 to 20 g / L. Such organic compounds may help in some embodiments to even out the formation of the coating. These compounds may contribute to the formation of a more compact, denser, more chemically resistant or / and more water resistant coating compared to silane / silanol / siloxane / polysiloxane-based coatings, etc., without these compounds. Depending on the selection of the organic compound (s), the hydrophilicity / hydrophobicity can be set purposefully. However, a highly hydrophobic coating is problematic in some applications because of the required attachment of particular water-based paints. When using an additive of at least one organic compound may combine with compounds prove particularly advantageous with a certain functionality such as compounds based on amines / diamines / polyamines / urea / imines / diimines / polyimines or their derivatives, compounds based on particular capped isocyanates / isocyanurates / melamine compounds, compounds with carboxyl or / and hydroxyl groups such as carboxylates, long-chain sugar-like compounds such as (synthetic) starch, cellulose, saccharides, long-chain alcohols or / and derivatives thereof. Among the long-chain alcohols, in particular those having 4 to 20 C atoms are added, such as butanediol, butyl glycol, butyl diglycol, ethylene glycol monomethyl ether, ethylene glycol monomethyl ether, ethylene glycol monomethyl ether, ethylene glycol propyl ether, ethylene glycol hexyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether, diethylene glycol butyl ether, diethylene glycol hexyl ether or a propylene glycol ether such as propylene glycol monomethyl ether , Dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monobutyl ether, propylene glycol monopropyl ether, dipropylene glycol monopropyl ether, tripropylene glycol monopropyl ether, propylene glycol phenyl ether, trimethylpentanediol diisobutyrate, a polytetrahydrofuran, a polyether polyol and / or a polyester polyol.

The weight-based ratio of compounds based on silane / silanol / siloxane / polysiloxane calculated on the basis of the corresponding silanols to compounds based on organic polymers calculated as a solids addition in the composition is preferably in the range from 1: 0.05 to 1: 30, especially preferably in the range of 1: 0.1 to 1: 2, most preferably in the range of 1: 0.2 to 1: 20. In many embodiments, this ratio is in the range of 1: 0.25 to 1: 12, im Range of 1: 0.3 to 1: 8 or in the range of 1: 0.35 to 1: 5.

It has surprisingly been found that an addition, in particular of organic polymer and / or copolymer, the corrosion resistance in particular iron and steel significantly improved and thereby for a higher process reliability and consistently good coating properties is of particular advantage.

Optionally, the aqueous silane-based pretreatment composition contains a content of silicon-free compounds having at least one amino, urea or / and ureido group, in particular compounds of amine / diamine / polyamine / urea / imine / diimine / polyimine and their Derivatives, preferably in the range of 0.01 to 30 g / L calculated as the sum of the corresponding compounds. The content is particularly preferably in the range from 0.03 to 22 g / L, very particularly preferably in the range from 0.06 to 15 g / L, in particular in the range from 0.1 to 10 g / L. Preferably, at least one compound, e.g. Aminoguanidine, monoethanolamine, triethanolamine or / and a branched urea derivative with an alkyl radical added. An addition to, for example, aminoguanidine significantly improves the properties of the coatings according to the invention.

Optionally, the aqueous silane-based pretreatment composition contains a content of anions of nitrite and compounds having a nitro group, preferably in the range of 0.01 to 10 g / L calculated as the sum of the corresponding compounds. The content is particularly preferably in the range from 0.02 to 7.5 g / l, very particularly preferably in the range from 0.03 to 5 g / l, in particular in the range from 0.05 to 1 g / l. This substance is preferably added as nitrous acid HNO ₂ , as an alkali metal nitrite, as ammonium nitrite, as nitroguanidine or / and as paranitrotoluenesulphonic acid, in particular as sodium nitrite or / and nitroguanidine.

It has surprisingly been found that an addition, in particular of nitroguanidine, to the aqueous silane-based pretreatment composition makes the appearance of the coatings according to the invention very uniform and noticeably increases the coating quality. This has a very positive effect especially on "sensitive" metallic surfaces such as sandblasted iron or steel surfaces. Addition of nitroguanidine markedly improves the properties of the coatings according to the invention.

It has surprisingly been found that an addition of nitrite can significantly reduce the tendency to rust, especially of iron and steel surfaces.

Optionally, the aqueous silane-based pretreatment composition contains peroxide-based compounds such as hydrogen peroxide and / or at least one organic peroxide, preferably in the range of 0.005 to 5 g / L calculated as H ₂ O ₂ . The content is particularly preferably in the range from 0.006 to 3 g / l, very particularly preferably in the range from 0.008 to 2 g / l, in particular in the range from 0.01 to 1 g / l. In the presence of titanium, the bath often yields a titanium-peroxo complex which dyes the solution or dispersion in orange. However, this color is typically not in the coating, as this complex does not appear to be incorporated as such into the coating. Therefore, the color of the bath can be used to estimate the titanium content or peroxide content. Preferably, the substance is added as hydrogen peroxide.

It has been unexpectedly found that addition of hydrogen peroxide to the aqueous silane-based pretreatment composition of the invention improves the optical quality of the coated substrates.

Optionally, the aqueous silane-based pretreatment composition contains a content of phosphorus-containing compounds, preferably in the range of 0.01 to 20 g / L calculated as the sum of the phosphorus-containing compounds. Preferably, these compounds contain phosphorus and oxygen, especially as oxyanions and as corresponding compounds. The content is particularly preferably in the range from 0.05 to 18 g / L, very particularly preferably in the range from 0.1 to 15 g / L, in particular in the range from 0.2 to 12 g / L. Preferably, in each case as the substance d ₄ ) at least one orthophosphate, an oligomeric and / or polymeric phosphate and / or a phosphonate is added. The at least one orthophosphate and / or salts thereof and / or their esters may be, for example, in each case at least one alkali phosphate, iron, manganese or / and zinc-containing orthophosphate and / or at least one of their salts and / or esters. Instead or in addition, at least one metaphosphate, polyphosphate, pyrophosphate, triphosphate or / and their salts and / or their esters may also be added in each case. As the phosphonate, for example, at least one phosphonic acid such as at least one alkyl diphosphonic acid and / or its salts and / or its esters can be added in each case. The phosphorus-containing compounds of this substance group are not surfactants.

It has surprisingly been found that addition of orthophosphate to the aqueous silane-based pretreatment composition according to the invention significantly improves the quality of the coatings, in particular on electrolytically galvanized substrates.

It has also surprisingly been found that addition of phosphonate to the aqueous silane-based pretreatment composition of the present invention markedly improves the corrosion resistance of aluminum-rich surfaces, particularly at values in the CASS test.

Optionally, the aqueous silane-based pretreatment composition contains at least one kind of anions selected from carboxylates such as acetate, butyrate, citrate, formate, fumarate, glycolate, hydroxyacetate, lactate, laurate, maleate, malonate, oxalate, propionate, stearate, Tartrate or / and at least one corresponding, non-or / and only partially dissociated compound.

Optionally, the aqueous silane-based pretreatment composition contains a content of carboxylate anions and / or carboxylate compounds in the range of 0.01 to 30 g / L calculated as the sum of the corresponding compounds. The content is particularly preferably in the range from 0.05 to 15 g / L, very particularly preferably in the range from 0.1 to 8 g / L, in particular in the range from 0.3 to 3 g / L. At least one citrate, lactate, oxalate or / and tartrate can particularly preferably be added as carboxylate in each case. The addition of at least one carboxylate can help to complex a cation and to keep it more easily in solution, whereby a higher bath stability and controllability of the bath can be achieved. Surprisingly, it has been found that the binding of a silane to the metallic surface can be partially facilitated and improved by a carboxylate content.

Preferably, the aqueous silane-based pretreatment composition also contains a level of nitrate. Preferably contains a content of nitrate in the range of 0.01 to 20 g / L calculated as the sum of the corresponding compounds. The content is particularly preferably in the range from 0.03 to 12 g / l, very particularly preferably in the range from 0.06 to 8 g / l, in particular in the range from 0.1 to 5 g / l. Nitrate can help to even out the formation of the coating, especially on steel. If necessary, nitrite can convert, usually only partially, into nitrate. Nitrate may in particular be added as alkali metal nitrate, ammonium nitrate, heavy metal nitrate, as nitric acid and / or corresponding organic compound. The nitrate can significantly reduce the tendency to rust, especially on surfaces of steel and iron. Optionally, the nitrate may contribute to the formation of a defect-free coating or / and an exceptionally level coating which may be free of optically detectable marks.

The aqueous silane-based pretreatment composition preferably contains at least one kind of cation selected from alkali metal ions, ammonium ions and corresponding compounds, in particular potassium or / and sodium ions or at least one corresponding compound.

Optionally, the aqueous silane-based pretreatment composition contains a free fluoride content in the range of 0.001 to 3 g / L, calculated as F ^- . The content is preferably in the range from 0.01 to 1 g / l, particularly preferably in the range from 0.02 to 0.5 g / l, very particularly preferably in the range up to 0.1 g / l. It has been found that in many embodiments it is advantageous to have a low level of free fluoride in the bath because the bath can then be stabilized in many embodiments. Excessive free fluoride content can sometimes negatively affect the rate of deposition of cations. In addition, in many cases, non-dissociated or / and not complex-bound fluoride, in particular in the range of 0.001 to 0.3 g / L occur. Such an additive is preferably added in the form of hydrofluoric acid and / or its salts.

Preferably, the aqueous silane-based pretreatment composition contains at least one fluoride-containing compound and / or fluoride anions, calculated as F ^- and without the inclusion of complex fluorides, in particular at least one fluoride of an alkali fluoride (s), ammonium fluoride and / or Hydrofluoric acid, more preferably in the range of 0.001 to 12 g / L, most preferably in the range of 0.005 to 8 g / L, in particular in the range of 0.01 to 3 g / L. The fluoride ions or corresponding compounds can help to control the deposition of the metal ions on the metallic surface, so that, for example, the deposition of the at least one zirconium compound can be enhanced or reduced if necessary. Preferably, the weight ratio of the sum of complex fluorides calculated as the sum of the associated metals to the sum of the free Fluorides calculated as F ^- greater than 1: 1, more preferably greater than 3: 1, most preferably greater than 5: 1, more preferably greater than 10: 1.

In the process according to the invention, the aqueous silane-based pretreatment composition may contain at least one compound selected from alkoxides, carbonates, chelates, surfactants and additives, such as e.g. Biocides and / or defoamers.

As a catalyst for the hydrolysis of a silane, e.g. Acetic acid are added. The blunting of the pH of the bath can be carried out, for example, with ammonia / ammonium hydroxide, an alkali hydroxide or / and an amine-based compound such as e.g. Monoethanolamine occur while the pH of the bath is preferably lowered with acetic acid, hydroxyacetic acid and / or nitric acid. Such contents are among the pH-affecting substances.

The abovementioned contents or additives generally have a beneficial effect in the aqueous silane-based pretreatment compositions according to the invention in that they further improve the good properties of the inventive aqueous base composition comprising components a), b) and solvent (s). These additives usually work in the same way if only one titanium or only one zirconium compound or a combination of these is used. However, it has surprisingly been found that the combination of at least one titanium and at least one zirconium compound, in particular as complex fluorides, significantly improves the properties, in particular of the coatings produced therewith. The various additives thus surprisingly act as in a modular system and contribute to the optimization of the respective coating significantly. Especially when using a so-called multi-metal mix, as often in the pretreatment of bodies and in the treatment or pretreatment of various small parts or Assembly parts occurs, the aqueous silane-based pretreatment composition has proven very useful, since it can be specifically optimized with the various additives to the respective multi-metal mix and its characteristics and requirements.

In the process of the present invention, a mix of various metallic materials may be coated with the aqueous silane-based pretreatment composition in the same bath, e.g. in bodies or in different small parts. Here, for example, substrates with metallic surfaces selected from cast iron, steel, aluminum, aluminum alloys, magnesium alloys, zinc and zinc alloys in any mix can be coated simultaneously and / or sequentially according to the invention, wherein the substrates can be at least partially metallically coated and / or at least partially can consist of at least one metallic material.

Unless at least one other component or / and traces of other substances are present, the remainder is 1000 g / L of water or of water and at least one organic solvent such as e.g. Ethanol, methanol, isopropanol or dimethylformamide (DMF). Preferably, the content of organic solvents is particularly low or zero in most embodiments. Due to the hydrolysis of the at least one silane contained, a content in particular of at least one alcohol, e.g. Ethanol or / and methanol occur. It is particularly preferred to add no organic solvent.

Preferably, the aqueous silane-based pretreatment composition is free of or substantially free of all types of particles or particles larger than 0.02 micron mean diameter, which could be optionally added, for example, based on oxides such as SiO ₂ . It is also free from additives in some compositions organic monomers, oligomers, polymers, copolymers or / and block copolymers.

Only when the coatings made with the aqueous silane-based pretreatment composition, e.g. 5 minutes at 80 ° C PMT (peak-metal-temperature), e.g. 25 minutes at 70 ° C PMT or more dried, these coatings are usually insensitive to water, since the condensation of silanes / silanols / siloxanes / polysiloxanes has advanced more. The degree of drying associated with condensation and the resistance to fouling of the siloxane / polysiloxane-containing coating will vary depending on the phase inventory, coating, and type of rinse.

The applied siloxane / polysiloxane-containing coating is preferably applied fresh or / and may not or only slightly dry when rinsed. The coating is preferably rinsed within 20 seconds of application. Since the silane-containing aqueous composition when applied preferably has a temperature in the range of 10 to 50 ° C, more preferably in the range of 15 to 35 ° C, and also because the object to be coated preferably has a temperature in the range of 10 to 50 ° C. , more preferably in the range of 15 to 35 ° C, these temperatures are usually not so high and usually not so different that rapid drying of the wet film occurs.

Preferably, the aqueous silane-based pretreatment composition is poor, substantially free, or free of higher levels or levels of water-hardening agents, such as calcium contents above 1 g / L. Preferably, it is free or low in lead, cadmium, chromate, cobalt, nickel or / and other toxic heavy metals. Preferably, such substances are not intentionally added, but at least one heavy metal dissolved out of a metallic surface, for example, be introduced from another bath can and / or can occur as an impurity. Preferably, the composition is poor in, substantially free of, or wholly free of bromide, chloride, and iodide, as they may possibly contribute to corrosion.

The layer thickness of the coatings prepared with the aqueous silane-based pretreatment composition is preferably in the range of 0.005 to 0.3 .mu.m, more preferably in the range of 0.01 to 0.25 .mu.m, most preferably in the range of 0.02 to 0.2 μm, many at about 0.04 μm, at about 0.06 μm, at about 0.08 μm, at about 0.1 μm, at about 0.12 μm, at about 0.14 μm, at about 0.16 μm or about 0.18 μm. The organic monomer, oligomer, polymer, copolymer or / and block copolymer containing coatings are often somewhat thicker than those free or nearly free thereof.

Preferably, with the aqueous silane-based pretreatment composition, a coating is formed having a coating weight based on only the content of titanium and / or zirconium in the range of 1 to 200 mg / m ² calculated as elemental titanium. This layer weight is particularly preferably in the range from 5 to 150 mg / m ² , very particularly preferably in the range from 8 to 120 mg / m ² , in particular at about 10, about 20, about 30, about 40, about 50, about 60, about 70, about 80, about 90, about 100 or about 110 mg / m ² .

Preferably, with the aqueous silane-based pretreatment composition, a coating is formed having a coating weight which, based on only siloxanes / polysiloxanes, is in the range from 0.2 to 1000 mg / m ² calculated as the corresponding largely condensed polysiloxane. This layer weight is particularly preferably in the range from 2 to 200 mg / m ² , very particularly preferably in the range from 5 to 150 mg / m ² , in particular at about 10, about 20, about 30, about 40, about 50, about 60, about 70, about 80, about 90, about 100, about 110, about 120, about 130 or about 140 mg / m ² .

It has surprisingly been found that the quality of the silane-based pretreatment coating and the composition of the water for rinsing after the silane pretreatment have a significant effect on the quality of the subsequently applied electrodeposition coating and in some cases even on the subsequent coating layers.

When rinsing, the fluid used is preferably a liquid particle-free fluid, in particular water or a solution. The fluid is particularly preferably water of city water quality, a pure water quality such as fully demineralized water (deionized water) or a water quality with a content of eg at least one surfactant. A surfactant can cause homogenization of the wet film. The surfactant may be added to the water, which may also be an aqueous rinse solution, as surfactant mixture, wherein preferably an aqueous solution containing at least one surfactant and optionally also containing at least one additive such as at least one solubilizer, at least one surface-active substance such as a phosphonate, can be used on at least one of the electrodeposition coating and / or the electrodeposition coating substance. As a surfactant, it is obvious that basically any surfactant can be added, nonionic surfactants such as, for example, fatty alcohol polyglycol ethers being particularly preferred. It is advantageous in applications that can easily lead to foaming as in rinsing by spraying, low-foaming or little or almost non-foaming surfactants and / or surfactant-containing mixtures, which may additionally contain, for example, a defoamer and / or a solubilizer and individually or in combination have a low, very little or almost no tendency to foaming, for example in injection processes. In this case, the at least one surfactant can in principle be selected from the group of anionic, cationic, nonionic, amphoteric and other surfactants such as low-foam block copolymers. It may be advantageous to use a combination of at least two surfactants or at least three surfactants. Here, a combination of surfactants from different classes of surfactants can be selected, for example, one or two nonionic surfactants together with a cationic surfactant. At least two chemically different surfactants are particularly preferably selected from the nonionic surfactants. On the other hand, a combination of at least one surfactant per class selected from the classes of anionic, cationic, nonionic, amphoteric and other surfactants is particularly preferred, in particular a combination of at least one nonionic surfactant with at least one surfactant from a different surfactant class. On the other hand, only nonionic surfactants can be used in combination. Advantageously, the nonionic surfactants are selected from straight-chain ethoxylates and / or propoxylates and preferably those having alkyl groups of 8 to 18 carbon atoms. As far as surfactants are used with a cloud point, ie surfactants nonionic nature, it is advantageous that these surfactants are no longer above the cloud point in dissolved form in the washing medium of the washing process to minimize foaming, especially during spraying. Here, a mixture of an ethoxylated alkylamine together with at least one ethoxylated or ethoxylated-propoxylated alkyl alcohol to set a low foaming tendency be particularly advantageous. In particular, with a combination of surfactants simultaneously the wetting and defoaming properties such as the rinsing of the rinse water and low foaming can be optimized, but surprisingly also the same properties of electrocoating as visual impression of the electrodeposition coating such as unevenness and streaking, uniformity of the layer thicknesses of Electrocoating, Improvement of the Lackumgriffs in the electrocoating especially at hintergriffigen points to coating substrate and the avoidance of markings are favorably influenced. On the other hand, it is also possible to add at least one solubilizer, such as, for example, cumene sulfonate or a glycol, in particular a dipropylene glycol, a polyglycol, a polyacrylamide or / and a modified polyacrylamide, a biocide, a fungicide or / and a means for adjusting the pH. Value such as an amine or an inorganic or / and organic acid used in the rinse water. Therefore, a method is preferred in which an addition to the rinse water is used for rinsing the silane-based pretreatment coating, wherein the wetting and defoaming properties are simultaneously improved by the combination of at least two different surfactants and optionally further additives such as solubilizers. In the method according to the invention, an additive with a content of surfactant in the rinse water is used for rinsing the silane-based pretreatment coating, by means of which the properties of the electrodeposition coating and of the electrodeposition coating are advantageously influenced. Here, the electrocoated substrates, the aqueous silane-based pretreatment coating were rinsed with a surfactant-containing water, also showed a much better Lackumgriff than the non-surfactant-containing water rinsed electrocoated substrates.

The content of the surfactants in the rinse water for rinsing after the silane-based pretreatment is preferably in the range from 0.001 to 1.6 g / L, particularly preferably in the range from 0.01 to 1.0 g / L or from 0.05 to 0.6 g / L.

The fluid (= water for rinsing) preferably has a temperature in the range of 10 to 50 ° C, particularly preferably in the range of 15 to 35 ° C. It may be the objects coated with the wet film by immersion in a bath and / or in a liquid jet or film, through Spraying, by spraying or by a similar form of wetting in the liquid film and / or jet of a flushing ring. Preferably, the liquid jet or film does not enter the silane / silanol / siloxane / polysiloxane containing coating at a pressure above 2 bar.

As an alternative to the process sequence proposed so far, which is also based on the process sequence of the following Table 1, it is possible on the one hand to carry out a pre-rinsing or / and a first silane coating with an aqueous composition containing at least one prior to the silane-based pretreatment according to the invention Silane, at least one compound selected from fluoride-free compounds of titanium, hafnium, zirconium, aluminum and boron, at least one more dilute alkali such as NaOH and / or containing at least one complex fluoride, and / or at least one rinse after the aqueous silane pretreatment with an aqueous composition which not only contains water and which optionally contains at least one surfactant for equalizing the wet film.

In principle, any type of electrodeposition paint can be used as electrodeposition paint in the process according to the invention. In some embodiments, it may be advantageous to adapt the composition of the aqueous silane-based pretreatment or / and the composition of the water for rinsing after this pretreatment on the type of electrocoating used, especially with respect to the surfactant or surfactants used, which does not interfere with the Electrodeposition and affect the electrodeposition paint.

If necessary, the coatings prepared with the aqueous silane-based pretreatment composition according to the invention and then with an electrodeposition paint can then be coated with at least one primer, lacquer, adhesive or / and with a lacquer-like organic composition, where appropriate at least one of these further coatings is cured by heating and / or irradiation.

In addition to the process with the aqueous surfactant-containing rinse after the pretreatment with the silane-based composition, before the pretreatment with the silane-based composition, an aqueous treatment containing at least one water-dissolved iron compound may be carried out. This composition is preferably alkaline, in particular in a pH range of 9 to 14. This composition can be, for example, an alkaline cleaner which is used in at least one process stage and which has a content of at least one iron compound in at least one process stage. However, in another embodiment, this composition may also be free of some or all of the additives of a typical cleaner, for example, as an iron-containing aqueous rinse; this can then be used before, in between or after cleaning steps. When applied to metallic surfaces, this composition may in principle have a temperature> 0 ° C. and <100 ° C., in particular, as a cleaning composition, it may have a temperature in the range from 32 to 78 ° C. and particularly preferably in the range from 38 to 70 ° C or in the range of 40 to 60 ° C. The at least one iron compound is preferably at least one water-dissolved Fe ²⁺ compound or / and at least one water-soluble Fe ³⁺ compound. The total water-dissolved Fe content of the aqueous composition and the total Fe content of the aqueous composition are preferably in a range of 0.005 to 1 g / L. The contents of water-dissolved Fe ²⁺ compound are particularly preferably in the range from 0 to 0.5 g / L and the contents of water-dissolved Fe ³⁺ compound in the range from 0.003 to 0.5 g / L. The water-soluble Fe compounds may be added in particular as water-soluble salts such as sulfates and nitrates. Preferably, after cleaning at least once rinsed with water, in particular at least once with city water and at least once with deionized water.

Existing systems for the cleaning and phosphating of bodies before painting often have the following process stages shown in the middle column of Table 1. In the right-hand column, the process stages are reproduced, which have surprisingly been recommended in a shortened process sequence for the cleaning and silane coating of bodies. <u> Table 1: </ u> Typical sequence of phosphating process steps and recommended sequence for silane coating of bodies phosphating Silane coating Alkaline cleaning 1 heated heated Alkaline cleaning 2 heated heated Rinse 1 city water city water Rinse 2 city water VE water Activate very often, with Ti or Zn phosphate (Deleted) Rinse 3 Optional, if not activated before (Deleted) preparation Phosphate, heated Silane coating Rinse 4 city water VE water Rinse 5 VE water VE water after-rinse optional (Deleted) Rinse 6 VE water (Deleted) flushing ring optional (Deleted)

It has further surprisingly been found that it is not only possible to make coatings with certain solutions, which are not only based on silane, which are not only sufficiently rinsable against water, but even something else, even without a stronger drying of the freshly applied coating have better layer properties than comparable through-dried coatings. It appears that the less strongly dried, silane-based coatings are superior to a lacquer or lacquer-like composition, e.g. cathodic dip paint more reactive and thus have sufficient adhesion. This makes it possible to the previously considered as necessary drying step and u.U. Over 10 meters long drying channel to dispense.

Due to the decades of development of zinc manganese nickel phosphating of bodies, such phosphate coatings produced today are extremely high quality. Nevertheless, contrary to expectations, it was possible to achieve the same high-quality properties with the silane-containing coatings. With the method according to the invention it is surprisingly possible to carry out the pretreatment of bodies with silane-based solutions at relatively low levels of the aqueous compositions, without the Quality of the coatings. However, choosing significantly higher levels of the components of the bath increases the cost, while most of the time, the quality of the coatings produced thereby can not be increased.

With the method according to the invention, it is possible to reduce the pretreatment step from 3 to 5 minutes in phosphating to about 2 minutes when coating with silane-based coatings and to heating as in phosphating to temperatures often in the range of 50 to 60 ° C without. However, if the composition is lower, the bath temperature is preferably heated to temperatures in the range of 15 to 25 ° C.

With the method according to the invention, it is possible to carry out the pretreatment of bodies not only in shorter and significantly cheaper to operate plants, but also to operate much more environmentally friendly, since the amounts of sludge to be disposed of containing heavy metal can be reduced to a minimum and there water can be recycled and also because the water flow can be significantly reduced. Therefore, both the consumption of chemicals, as well as the expenses incurred in the treatment can be significantly reduced. This is because less than 1% of the amounts of sludge previously encountered in phosphating are related to the metallic surface to be coated, so that the expense of disposing of chemical waste is greatly reduced.

An addition of manganese to the aqueous silane-based pretreatment composition has surprisingly been found to be particularly advantageous: Although apparently no or almost no manganese compound is deposited on the metallic surface, the additive promotes the deposition of silane / silanol / siloxane / polysiloxane on the strong metallic surface. With the addition of nitroguanidine, it was surprisingly found that the appearance of the coated sheets is very uniform, especially on sensitive surfaces such as sandblasted iron or steel surfaces. An addition of nitrite has unexpectedly significantly reduced the potential for steel substrates. Surprisingly, it has been found that each additive having a significant positive effect, which is mentioned in this application, has an additive effect for improving the coating according to the invention: By selecting several additives similar to a modular system, the various properties, in particular of a multimetal system, can be further optimized.

It has surprisingly been found that a good multimetal treatment with a single aqueous composition is only possible when a complex fluoride has been used, and that a very good multimetal treatment with a single aqueous silane-based pretreatment composition is only possible if at least two different complex fluorides are used such as those based on titanium and zirconium. The individual complex fluorides used in the most diverse experiments never showed results that were as good as for the combination of these two complex fluorides, regardless of which additives were added.

It was not foreseeable that such a high quality improvement of aqueous silane-based pretreatment compositions containing silane / silanol / siloxane / polysiloxane would be possible. But even starting from aqueous compositions based on a silane and only one complex fluoride based on titanium or zirconium surprisingly turned out a significant increase in the quality level in all experiments.

It was also surprising that in the paint adhesion test, even on steel, there were rockfall marks of 1 or 2 when the process according to the invention applied a composition comprising at least one silane and at least one complex fluoride: steel has been found to be the most problematic material for watery Compositions based on a silane and only a complex fluoride based on titanium or zirconium, especially in the corrosion resistance, proven (see, for example, B 5).

In the case of aluminum and aluminum alloys, the CASS test is problematic according to experience, but it has also turned out to be significantly better than expected with the compositions according to the invention.

Examples and Comparative Examples:

The inventive examples (B) and the comparative examples (VB) described below are intended to explain the subject matter of the invention in more detail.

The aqueous bath compositions are prepared as mixtures according to Table 2 using pre-hydrolyzed silanes. They each contain a silane and optionally also low levels of at least one similar further silane, which is also simplistic silane and not silane / silanol / siloxane / polysiloxane is spoken of and usually being this variety of compounds, sometimes in larger numbers similar compounds, also pulls into the formation of the coating, so that there are often several similar compounds in the coating. Depending on the silane, prehydrolyzing may also take several days at room temperature with vigorous stirring, as long as the silanes to be used are not already prehydrolyzed. For prehydrolyzing the silane, the silane is added in excess to water and optionally catalysed with acetic acid. However, because of adjusting the pH, acetic acid was added only in some embodiments. In some embodiments, acetic acid is already included as a catalyst for the hydrolysis. Ethanol is formed during hydrolysis but is not added. The finished mixture is used fresh.

Then, at least 3 previously cleaned with an aqueous alkaline cleaner and with hot water and then rinsed with deionized water sheets are in each case per test of cold rolled steel (CRS), aluminum alloy Al6016 and from hot-dip galvanized or electrolytically galvanized steel or off (with Galvanneal ^® ZnFe layer on steel) with the appropriate treatment liquid on both sides at 25 ° C by spraying, dipping or Rollcoater treatment in contact. Immediately thereafter, the thus pretreated sheets are rinsed briefly with deionized water. The sheets of Comparative Examples are dried at 90 ° C PMT and then painted with a cathodic automotive dip paint (KTL). However, the sheets of the inventive examples are rinsed immediately after the aqueous silane-based pretreatment and immersed in the KTL bath immediately after rinsing. Afterwards, these sheets were provided with a complete, commercially used automotive paint finish (electrodeposition paint, filler, topcoat or clearcoat, total including KTL about 105 μm thickness of the layer package) and tested for their corrosion protection and their paint adhesion. The compositions and properties of the treatment baths as well as the properties of the coatings are summarized in Table 2.

The organofunctional silane A is an amino-functional trialkoxysilane and has one amino group per molecule. Like all of the silanes used in this case, it is largely or approximately completely hydrolyzed in the aqueous solution. The organofunctional silane B has one terminal amino group and one ureido group per molecule. The non-functional silane C is a bis-trialkoxysilane; the corresponding hydrolyzed molecule has up to 6 OH groups on two silicon atoms.

The complex fluorides of titanium or zirconium are used largely on the basis of a MeF _x complex such as MeF ₆ complex. Manganese and optionally low levels of at least one other cation, which is not mentioned in the table are added as metallic manganese of the respective complex fluoride solution and dissolved therein. This solution is mixed into the aqueous composition. If no complex fluoride is used, manganese nitrate is added. The silylated epoxy polymer has a low content of OH-- and isocyanate groups and is therefore subsequently also chemically crosslinkable at temperatures above 100 ° C.

The silanes contained in the aqueous composition - concentrate or / and bath - are monomers, oligomers, polymers, copolymers or / and reaction products with other components due to hydrolysis reactions, condensation reactions or / and further reactions. The reactions take place above all in the solution, during drying or optionally also during curing of the coating, in particular at temperatures above 70 ° C. All concentrates and baths were stable for over a week with no changes and no precipitation. No ethanol was added. Levels of ethanol in the compositions come only from chemical reactions.

The pH is adjusted in most examples and comparative examples, in the presence of at least one complex fluoride with ammonia, in other cases with an acid. All bathrooms show a good quality of the solution and almost always good bath stability. There are no precipitations in the baths. After coating with the silane-containing solution, in the examples according to the invention and in the comparative examples immediately following the aqueous silane-based pretreatment, rinsing is first carried out once with deionised water. The freshly applied wet film was not allowed to dry any more because it was rinsed within 5 seconds after the application of the silane-containing coating. Both the freshly coated substrate and the rinse water were at room temperature. To avoid the entry of substances of the pretreatment solution in the subsequent coating bath, was a rinse necessary. The freshly rinsed coated substrate was then immersed directly in the cathodic dip, so that no further drying could occur. The coated sheets of Comparative Examples, however, were dried immediately after rinsing at 120 ° C in a drying oven for 5 minutes, but the examples of the invention were coated without dipping immediately immediately afterwards with a cathodic dip paint by immersion.

The visual inspection of the coatings can only be significantly carried out on the coatings on steel due to the interference colors and allows the uniformity of the coating to be assessed. The coatings without any complex fluoride content are quite uneven. A coating with titanium and with zirconium complex fluoride has surprisingly been found to be significantly more uniform than if only one of these complex fluorides had been applied. Addition of nitroguanidine, nitrate or nitrite also improves the uniformity of the coating. Partly the layer thickness increases with the concentration of these substances. <u> Table 2: </ u> Compositions of baths in g / L based on solids contents, for silanes based on the weight of the hydrolyzed silanes; Residual content: water and usually a very small amount of ethanol; Process data and properties of the coatings Examples / VB VB 1 B1 VB 2 B2 VB 3 B 3 VB 4 B 4 VB 5 B 5 VB 6 B6 VB 7 B7 VB 8 B8 VB 9 B 9 Organofunkt. Silane A 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.1 0.1 0.3 0.3 0.2 0.2 0.2 0.2 H ₂ TiF ₆ as Ti - - 0.2 0.2 - - 0.2 0.2 0.2 0.2 0.1 0.1 0.3 0.3 0.2 0.2 0.2 0.2 H ₂ ZrF ₆ as Zr - - - - 0.2 0.2 0.2 0.2 0.2 0.2 0.1 0.1 0.3 0.3 0.4 0.4 0.2 0.2 Mn - - - - - - - - 0.3 0.3 - - - - 0.3 0.3 - - Silyl. Epoxy polymer - - - - - - - - - - - - - - - - 1.0 1.0 PH value 10.5 10.5 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 4 Coating weight mg / m ² of silanol and metal 10-20 10-20 20-50 20-50 20-50 20-50 20-50 20-50 20-60 20-60 10-40 10-40 30-80 30-80 30-80 30-80 50-100 50-100 Cross-cut BMW: Note stole 4 3 5 5 3 2 2 1 1 0 2 1 1 1 1 0 1 1 E-zinc on steel 3 3 4 3 4 3 1-2 1 1 0 1 1 1 1 1 1 0 0 Fire zinc on steel 2 2 4 3 4 3 1 0 0 0 1 0 0-1 0-1 0-1 0 0 0 Al 6016 2 2 2 2 2 2 1 1 1 0 2 1 1 1 1 0 1 1 Galvanneal ^® 1 1 1 1 2 1 1 0 1 0 1 0 0 0 0 0 0 0 10 cycles VDA mm infiltration: stole 8th 6 7 5 4 3 3 2.5 2 1 3.5 2 1.5 1.5 1.5 <1 2.5 2 E-zinc on steel 5 4 3 2.5 4 4 2 1 1 <1 3 1.5 1.5 1 1 <1 1 <1 Fire zinc on steel 4 4 2.5 2 3.5 3 <1 <1 <1 <1 1.5 1 1 1 1 <1 <1 <1 Galvanneal ^® 2 2 2 1 1.5 1.5 <1 0 <1 <1 1 1 <1 <1 <1 <1 0 0 Examples / VB VB 1 B 1 VB 2 B 2 VB 3 B 3 VB 4 B 4 VB 5 B 5 VB 6 B 6 VB 7 B 7 VB 8 B 8 VB 9 B9 Rockfall after VDA load, grade stole 5 5 4 4 4 3 2-3 1 1 1 2 2 2 1 1-2 1 1 0-1 E-zinc on steel 5 4 3 2 4 3 2 1 1 1 2 1 1-2 0 1 0 1 0-1 Fire zinc on steel 5 4 3 2 4 3 1 0 1 0 1 1 1 0 1 0 0 0 Galvanneal ^® 4 4 2 2 3 2 1-2 0 1 0 1 0-1 0 0 0 0 0 0 Salt spray test 1008 h: stole 7 6 4 4 3.5 3 2 1.5 1.5 <1 2.5 2 1.5 <1 1.5 <1 1 1 CASS test mm infiltration Al 6016 6 6 3.5 3 3.5 3 2.5 2.5 1.5 1 2.5 2 1.5 1 1.5 1 1.5 1

All of the examples, when considered as a whole, of the various metallic surfaces which have been coated, show a significant improvement in the properties of the aqueous silane-based composition compared to the respective comparative example, each time with the same bath composition followed by drying (as Comparative Example CE). and once without subsequent drying (as Inventive Example B) was applied. The examples given here are examples according to the invention, if they are used with this composition over the entire process flow to the electrodeposition coating on components using a Umgriffs.

It was surprising that this improvement, which brings only a limited improvement even with already good coating results, is systematically improved by the non-drying after application of the aqueous composition. Surprisingly, therefore, it is possible to achieve a significant improvement by non-drying which is nearly independent of the chemical composition of the aqueous bath. It was also surprising that this improvement occurred both in the solutions containing only silane, as well as in the silane and complex fluoride or optionally also containing manganese ions solutions. Therefore, it is considered that a similar continuous improvement from drying to non-drying also occurs in silane-based or silane-based complex fluoride-based solution solutions containing a variety of substances. The more different substances are contained and the higher their intrinsic contents are, the better the corrosion resistance and the paint adhesion can be, unless an optimum which may occur is exceeded.

The coating weight varies not only with the contents of the individual components of the aqueous solutions, but also with the type of the respective metallic surface being coated. By choosing the bath components and their Overall, a very significant improvement in corrosion resistance and paint adhesion can be achieved.

The bath compositions are all stable and easy to apply in the short time of use. There are no differences in behavior, visual impression and test results between the various examples and comparative examples that can be attributed to treatment conditions such as application by syringes, dipping or roller coater treatment. The resulting films are transparent and almost all are largely uniform. They show no coloring of the coating. The resulting films are transparent and almost all are largely uniform. The structure, the gloss and the color of the metallic surface appear only slightly changed by the coating. With a content of titanium or / and zirconium complex fluoride, iridescent layers are formed, in particular, on steel surfaces. The combination of several silanes has not yet resulted in any further significant improvement in the corrosion protection in the previous experiments; however, this can not be ruled out. In addition, a content of H ₃ AlF _{6 was} determined on aluminum-rich metallic surfaces due to corresponding reactions in the aqueous composition. However, the combination of two or three complex fluorides in the aqueous composition has surprisingly been extremely successful.

The layer thickness of the coatings produced in this way also depended on the type of application, which was initially varied in separate experiments, in the range from 0.01 to 0.16 μm, usually in the range from 0.02 to 0.12 μm at up to 0.08 microns, which was significantly larger with the addition of organic polymer.

Due to several decades of development of zinc manganese nickel phosphating of bodies, such phosphate coatings produced today are extremely high quality. Nevertheless, it was unexpectedly possible for the silane-containing aqueous compositions used for just a few years to achieve the same high-quality properties even with the silane-containing coatings, although greater efforts were required for this.

The corrosion protection grades are in the cross-cut test according to DIN EN ISO 2409 after storage for 40 hours in 5% NaCl solution according to BMW specification GS 90011 from 0 to 5, where 0 represents the best values. In the salt spray-condensation change test for 10 cycles according to the VDA-Prüfblatt 621-415 with varying corrosion load between salt spray test, condensation test and drying break the infiltration is measured from one side of the scratch and given in mm, the infiltration should be as small as possible. In the case of the rockfall test in accordance with DIN 55996-1, the coated sheets are bombarded with steel shot for 10 cycles following the above-mentioned VDA change test: the damage pattern is characterized by characteristic values from 0 to 5, with 0 indicating the best results. In the salt spray test in accordance with DIN 50021 SS, the coated sheets are exposed to a corrosive sodium chloride solution by spraying for up to 1008 hours; then the infiltration in mm is measured from the scratch, the scratch is made with a standardized stylus to the metallic surface and wherein the infiltration should be as small as possible. In the CASS test according to DIN 50021 CASS, the coated aluminum alloy sheets are exposed to a special corrosive atmosphere by spraying for over 504 hours; then the infiltration is measured in mm from the scratch, which should be as small as possible.

Further tests on bodywork elements have shown that the electrochemical conditions of the cathodic dip bath may possibly be slightly adapted to the different type of coating, but otherwise the excellent properties obtained in laboratory tests on sheets, even on body elements in the industrial environment transferable are.

In further experiments, the influence of additives to the rinse water was investigated.

All Examples and Comparative Examples B 10 to B 18 and VB 10 to VB 12 and VB15 to VB18 were wet-in-wet with or without surfactant additive for water rinse after aqueous silane-based pretreatment and before immersion in the same, used for a series used electrodeposition paint. The compositions of Examples and Comparative Examples B 10 to B 18 and VB 10 to VB 12 and VB15 to VB18 were prepared and used in the same manner as the other examples and comparative examples, except that in the second series only cold rolled steel ( CRS) and, in the third series, hot dip galvanized steel sheets were treated and that the panels treated with the silane containing composition were stored after flushing for 0.5 minutes for 30 minutes in room air at room temperature before being mixed with a commercially used cathodic Dipcoat (Electrocoating, e-coat, KTL) were dipped at 250V (2nd series) or 240V (3rd series).

However, it was a slightly different type of cold-rolled steel than the first series for the tests according to Table 2 (= 1st series). For Examples and Comparative Examples B 10 to B 14 and VB 10 to VB 12 (2nd series), however, a different electrodeposition paint was used than for Examples and Comparative Examples B 15 to B 18 and VB15 to VB18 (Series 3). For the latter, an electrocoating of generation 6 MC3 PPG was used. The layer thicknesses of the electrodeposition paint were measured using the VDA method.

The half-hour waiting period simulates the cycle time of such coated bodies to the introduction of the body in the KTL basin. Here, the silane-containing coatings dried somewhat, but not completely through. The silane pretreatment of these Examples and Comparative Examples is based on the composition of B 8 and VB 8 wherein in the third series aqueous silane-based pretreatment compositions as in B 8 and VB 8 were used but still 0.001 to 0.10 g / L Cu and 0.1 to 1 g / L Zn and possibly also traces of Al and small amounts of Fe contained. The pH was also adjusted to 4. The fully desalted water for rinsing was prepared in the inventive examples with an addition of at least one surfactant, wherein the surfactant or the surfactant mixture as aqueous Solution was added. The surfactant mixture A contains a nonionic surfactant based on a fatty alcohol polyglycol ether. The surfactant mixture B contains a different type of nonionic surfactant and a solubilizer. The surfactant mixture B proved to be particularly favorable for the rinsing of the rinse water. The surfactant mixture C contains a nonionic surfactant based on an alkylamine. The surfactant mixture D contains a nonionic surfactant and a cationic surfactant. The addition 1.) is a water-soluble diphosphonic acid with a longer alkyl chain. The addition 2.) is a water-soluble tin compound.

All KTL layers of a series were applied with the same tension, even if they differed significantly in the layer thicknesses. The KTL layers of the 2nd series were basically a bit too thick. The layer thicknesses were formed not only on the electrical conductivity of the pretreated substrate, but apparently also more on the quality of the remaining pretreatment layer, which apparently differed in their uniformity due to the different rinse compositions. The conditions were chosen so that inhomogeneities of the electrocoating paint were clearly visible and a differentiation of the quality of the cathodic electrocoating layer was possible.

The further investigations were carried out on pretreated, rinsed and KTL-coated sheets, but unlike the first series of examples and comparative examples without the further paint layers of a typical automotive paint system: The corrosion resistance was determined in the salt spray test according to DIN EN ISO 9227 over 1008 hours, the paint adhesion by Cross-hatching method according to a 240-hour constant climate test according to DIN EN ISO 6270-2 and according to DIN EN ISO 2409. For both methods of analysis, the smaller values are the better values.

On the one hand, there was a surprisingly strong correlation of the results with respect to corrosion resistance, paint adhesion, KTL layer thickness and assumed homogeneity of the KTL layer and a strong dependence of the results of rinses with and without surfactant. Additions to surfactant-containing rinsing waters are sometimes also another Improvement. It is believed that the homogeneity of the KTL layer is better, the lower the formed KTL layer thickness. Although the KTL layers of Examples B 13 and B 14 are the thinnest in this series, these coated sheets still have significantly better corrosion resistance than those with thicker KTL layers. Astonishingly strong is the differentiation of the quality of the lacquer adhesion, which leads over the entire possible width of the notes from 5 to 0.

It has surprisingly been found that the quality of the silane-based pretreatment coating and the composition of the water for rinsing after the silane pretreatment have a significant effect on the quality of the subsequently applied paint layers.

It was surprising that the addition of at least one surfactant even in spite of the relatively low surfactant content in the rinse water and as a result of a very thin, u.U. For example, monomolecular surfactant film has a strong effect on the subsequent electrodeposition coating and that the addition of at least one surfactant during rinse has a strong impact on the interface between silane pretreatment coating and electrodeposition coating as well as on the electrodeposition coating. The electrocoating paints selected in the 2nd and 3rd series are of particularly high quality and are known to be particularly uniformly processable.

Nevertheless, the unevennesses of the electrodeposition coating layer in Comparative Example CB 11a were so strong that it can be assumed that markings up to the top coat would be manifested in the subsequent coating with the subsequent coating layers typical in the automotive industry. On the other hand, it has been observed in similar work that formed in the coating of large-scale body elements during rinsing without a surfactant additive clearly visible streaks that can be avoided with an addition of surfactant. With the addition of surfactant in the rinse liquid, a smoother KTL layer could be produced, which in turn is responsible for the fact that even more uniform, smoother and poorer defect coating layers could be formed on the KTL layer. Amazingly, the Lackumgriff the electrocoating was significantly affected.

Because when rinsing after the silane pretreatment with water only inhomogeneities were observed in the subsequently applied electrocoating despite the sufficient, possibly repeated rinsing and at least once rinsing with deionized water again and again.

It was further determined in further, not shown in detail here experiments that basically any surfactant can be added, in particular nonionic surfactants are preferred, but it is beneficial in applications that can easily lead to foaming as in rinsing by spraying, low-foaming or little or almost non-foaming surfactants and / or surfactant-containing mixtures which may additionally contain, for example, a defoamer and / or a solubilizer and individually or in combination a low, a very low or almost no tendency to foaming eg have in injection processes. Advantageously, the nonionic surfactants are selected from straight-chain ethoxylates and / or propoxylates, preferably those having alkyl groups of 8 to 18 carbon atoms. The latter also includes the surfactants A, B and D. With such a combination of surfactants, the wetting and defoaming properties can be optimized at the same time, but also, surprisingly, several properties of the electrodeposition coating and electrodeposition coating can advantageously be influenced.

In particular on zinc-rich metallic substrates, the quality of the silane pretreatment and the type of rinsing with water had a great effect on the homogeneity or inhomogeneity of the electrocoating paint (e-coat, KTL) and, consequently, on the subsequent coats such as the base coat (Filler as color carrier) and the subsequent top coat (clear coat). In the case of rinsing water which contains no surfactant additive, it has been found that inhomogeneities in the electrodeposition paint such as streaks are scarcely avoidable. Streaks and other inhomogeneities as well as unevenness then lead in the consequence easily and often to plastic markings in the following lacquer layers. Basically, no plastic markings may occur on bodyworks for automobiles in the Base Coat or / and in the Top Coat, as these usually give rise to intensive mechanical reworking and repainting. If the paint layers When reworking eg by grinding to be worked off too much, for example, up to or in the metallic substrate, then in addition, a pretreatment before applying the first coat, eg a pretreatment composition based on at least one silane or on the basis of at least one silane a titanium or / and zirconium compound and / or with organic polymer. Such rework not only disturbs the workflow, but causes considerable costs, especially due to manual work.

When at least one surfactant was added to the rinse water and when normal work was done on the silane pretreatment, in none of the experiments did any inhomogeneities in the electrodeposition paint and plastic markings occur in any of the subsequent coats. As plastic markings are inhomogeneities in the topmost paint layer referred to, which become apparent in particular by differences in height of the paint surface with the naked eye more or less clearly visible. Only if the pretreatment composition itself was extraordinarily inhomogeneous, then under extreme conditions, even after rinsing with surfactant-containing rinse water, could significantly inhomogeneous electrodeposition coating layers occur and subsequently varnish layers with small markings.

Here, the electrocoated substrates, the aqueous silane-based pretreatment coating were rinsed with a surfactant-containing water, a much better Lackumgriff than the non-surfactant-containing water rinsed electrocoated substrates.

Advantageously, with the coating method according to the invention also those metallic components can be electrocoated with good results in which problems without the surfactant content in the water rinse and without the addition of an iron-containing treatment before the silane-based pretreatment occurred.

In addition to the process with the aqueous surfactant-containing rinse, before the pretreatment with the silane-based composition, an aqueous treatment containing a water-dissolved iron compound may be carried out.

In a new series of experiments was found in Examples 20 to 23 and in similar process variants compared to procedures with a water rinse without or with surfactant content, a further improvement of the application of the cathodic electrodeposition paint on zinc-containing metallic surfaces that in otherwise similar treatment and Treatment conditions as in the examples of Table 3 in which the electrodeposition coating at constant temperature and at a constant voltage, often by about 5 to 15% lower layer thickness. To clean the sheets prior to silane-based pretreatment, two-stage cleaning was used, using first a splash and then a dive. For two levels in Table 4, the left content refers to spraying and the right content to diving if different levels are used. As the electrodeposition coating layer in this process. by applying silane-based pretreatment compositions to lower stress compared to zinc phosphate-based pretreatments, the encapsulation of the electrodeposition coating layer is also correspondingly lower. Therefore, it is desirable to be able to use a higher voltage than, for example, 250 V, without exceeding a layer thickness of the dried and baked electrodeposition coating layer of, for example, 20 μm. In these examples, without the use of process steps according to the invention, a nominal layer thickness of the dried and baked electrodeposition coating layer resulted externally when using about 250 V in electrodeposition coating. Lowering this layer thickness despite the use of 250 V in the electrodeposition coating suggests the possibility of using higher voltages, which then also lead to a higher throwover. The herein added surfactant E is a nonionic surfactant based on an alkyl ethoxylate having an alkyl group and having an end group seal, wherein a content of cationic compound has also been added. The pH of the cleaner was in Range of 10 to 11. In the purification of Examples 20 to 23, a gluconate or / and a heptonate in the specified total amount was added as the complexing agent. In addition, the cleaner contained at least one alkali compound, which served to adjust the pH. Other variants, which are not listed in detail in Table 4, relate to optional additions of boric acid or silicate and the further variation of all contents of the cleaner, all of which process variants led to the same or the same results. In comparison with all of these examples according to the invention, neither an Fe-containing cleaning nor a surfactant-containing rinse was used in Comparative Example 19.

It has now been found that the use of an iron-containing aqueous composition prior to the application of the silane-based pretreatment composition enables increased electrodeposition stress for the preparation of a dried and baked electrodeposition paint layer of, for example, 20 μm. These were often by 5 to 15% higher voltages, for example, from 260 to 290 V, can be used. In this case it was also found that the wraparound generated here was also improved by about 5 to 15% due to the increased stress. Initial results also indicate improved lacquer adhesion and improved corrosion resistance for these variants according to the invention. <u> Table 4: Comparison of coating processes with and without Fe-containing additive in the two-stage cleaning and without and with the use of at least one surfactant in the rinse water to improve the electrodeposition coating Examples B / Comparative Example VB Addition in g / L (Cleaning: first spraying on the left / then dipping on the right) VB 19 B 20 B 21 B 22 B 23 Additives during cleaning: Surfactant E + cationic compound 2.0 / 3.0 2.0 / 3.0 2.0 / 3.0 2.0 / 3.0 5.0 / 8.0 Water-soluble Fe ²⁺ compound - - - sulfate - Amount of Fe ²⁺ additive 0 0 0 0,080 0 Water-soluble Fe ³⁺ compound - nitrate nitrate nitrate nitrate Amount of Fe ³⁺ additive 0 0.056 / 0.084 0.056 / 0.084 0.056 / 0.084 0.056 / 0.084 Carboxylic acid (s) -Zusatz 0 0.8 / 1.2 0.8 / 1.2 0.8 / 1.2 0.8 / 1.2 Additives to the rinse water: Total surfactant content in g / L 0 0 0.2 0 0 added surfactant - - e - - Visual impression of the drainage of the rinsing liquid on the silane-containing layer Good Good very well Good Good Visual impression of the silane-containing layer after rinsing Good Good Good Good Good Visual: Homogeneity of the KTL layer with respect to streaks strong streaks weak streaks weak streaks weak streaks weak streaks Visually: flatness of the cathodic electrocoat layer more uneven a bit uneven almost flat a bit uneven a bit uneven Avg. Layer thickness of the KTL outside, μm 19.5 17 16 16 18 Avg. Layer thickness of the KTL inside, μm 7 15 14 14 17 Layer thickness variations of the KTL Δd in μm between inside and outside as a measure of the wrap 12.5 2 2 2 1

Claims (24)

1. Process for improving the throwing power of an electrophoretic lacquer coating by coating metallic surfaces with a pretreatment composition containing silane/silanol/siloxane/polysiloxane, characterised in that this composition contains, in addition to water and optionally in addition to at least one organic solvent or/and at least one substance influencing the pH value,

   a) at least one compound a) selected from silanes, silanols, siloxanes and polysiloxanes, of which at least one of these compounds is still able to condense, and

   b) at least one titanium-containing, hafnium-containing, or/and zirconium-containing compound b) and also

   c) at least one type of cations c) selected from cations of metals of the 1st to 3rd and 5th to 8th subgroup, including lanthanides, and also from the 2nd main group of the periodic table of the elements, or/and at least one corresponding compound c), or/and

   d) at least one organic compound d) selected from monomers, oligomers, polymers, copolymers and block copolymers,
   wherein the coating freshly applied with the pretreatment composition is rinsed at least once with water, wherein optionally at least one water rinsing has a content of surfactant, and
   wherein after the rinsing with water an electrophoretic lacquer coating is applied,
   wherein the coating freshly applied with this composition is not thoroughly dried up until this rinsing, so that the at least one condensable compound a) does not strongly condense up until the rinsing of the pretreatment coating with water or/and up until the coating with an electrophoretic lacquer or/and
   wherein the pretreatment coating freshly applied with the pretreatment composition is not thoroughly dried up until the application of a subsequent electrophoretic lacquer coating, so that the at least one condensable compound a) does not strongly condense up until the application of the subsequent electrophoretic lacquer coating and
   characterised in that
   prior to the treatment with an aqueous silane-based pretreatment composition an aqueous treatment having a content of iron compound dissolved in water is carried out.
2. Process according to Claim 1, characterised in that the coating following the aqueous silane-based pretreatment is a second conversion layer or a coating as a consequence of application of an after-rinsing solution.
3. Process according to Claim 1 or 2, characterised in that the pH value of the aqueous silane-based pretreatment composition is more than 1.5 and less than 9.
4. Process according to one of the preceding claims, characterised in that the aqueous silane-based pretreatment composition has a content of silane/silanol/siloxane/ polysiloxane a) within the range from 0.005 to 80 g/L, calculated on the basis of the corresponding silanols.
5. Process according to one of the preceding claims, characterised in that the aqueous silane-based pretreatment composition contains at least one silane or/and the corresponding silanol/siloxane/polysiloxane with, in each instance, at least one amino group, urea group or/and ureido group.
6. Process according to one of the preceding claims, characterised in that the aqueous silane-based pretreatment composition has a content of at least one compound b) selected from titanium-containing, hafnium-containing and zirconium-containing compounds within the range from 0.01 to 50 g/L, calculated as the sum of the corresponding metals.
7. Process according to Claim 6, characterised in that the aqueous silane-based pretreatment composition has a content of at least one complex fluoride b) selected from complex fluorides of titanium, hafnium and zirconium.
8. Process according to Claim 7, characterised in that the aqueous silane-based pretreatment composition has at least one complex fluoride, wherein the content of complex fluoride(s) has within the range from 0.01 to 100 g/L, calculated as the sum of the corresponding metal-complex fluorides calculated as MeF₆.
9. Process according to one of the preceding claims, characterised in that the aqueous silane-based pretreatment composition contains at least one type of cations c) selected from cations of aluminium, cerium, iron, calcium, cobalt, copper, magnesium, manganese, molybdenum, nickel, niobium, tantalum, yttrium, zinc, tin and other lanthanides.
10. Process according to one of the preceding claims, characterised in that the aqueous silane-based pretreatment composition as cations or/and corresponding compounds c) in this regard only types of cations or corresponding compounds selected from the group of aluminium, magnesium, calcium, yttrium, lanthanum, cerium, manganese, iron, cobalt, copper, tin and zinc or selected from the group of aluminium, magnesium, calcium, yttrium, lanthanum, cerium, vanadium, molybdenum, tungsten, manganese, iron, cobalt, copper, bismuth, tin and zinc, if trace amounts of, in each instance, less than 0.005 g/L in the bath composition, with the exception of copper and silver, are disregarded, calculated as metal.
11. Process according to one of the preceding claims, characterised in that the aqueous silane-based pretreatment composition has a content of cations and corresponding compounds c) within the range from 0.01 to 20 g/L, calculated as the sum of the metals.
12. Process according to one of the preceding claims, characterised in that the aqueous silane-based pretreatment composition has a content of organic compounds d) within the range from 0.01 to 200 g/L, calculated as the sum of the corresponding compounds.
13. Process according to one of the preceding claims, characterised in that a mix of various metallic materials is coated with the aqueous silane-based pretreatment composition in the same bath.
14. Process according to one of the preceding claims, characterised in that with the aqueous silane-based pretreatment composition a coating is formed that, relative only to titanium or/and zirconium, lies within the range from 1 to 200 mg/m², calculated as titanium.
15. Process according to one of the preceding claims, characterised in that with the aqueous silane-based pretreatment composition a coating is formed having a layer weight which, relative only to siloxanes/polysiloxanes, lies within the range from 0.2 to 1000 mg/m², calculated as the corresponding largely condensed polysiloxane.
16. Process according to one of the preceding claims, characterised in that prior to the aqueous silane-based pretreatment coating according to one of the preceding claims a pre-rinsing or/and a first silane coating is also performed with an aqueous composition that contains at least one silane, at least one compound selected from fluoride-free compounds of titanium, hafnium, zirconium, aluminium and boron, at least one more strongly diluted alkali solution or/and at least one complex fluoride.
17. Process according to one of the preceding claims, characterised in that for the purpose of rinsing the silane-based pretreatment coating an additive is used having a content of surfactant in the rinsing water, by means of which the properties of the electrophoretic lacquering and of the electrophoretic lacquer coating are influenced advantageously.
18. Process according to one of the preceding claims, characterised in that for the purpose of rinsing the silane-based pretreatment coating an additive to the rinsing water is used in which the wetting and defoaming properties are improved at the same time through the combination of at least two different surfactants and optionally further additive substances such as solubilizers, for example.
19. Process according to one of the preceding claims, characterised in that after the aqueous silane-based pretreatment coating at least one rinsing is performed with an aqueous composition that contains not only water and that optionally contains at least one surfactant for homogenizing the wet film.
20. Process according to one of the preceding claims, characterised in that the coatings produced with an aqueous silane-based pretreatment composition and then with an electrophoretic lacquer are subsequently coated with at least one primer, lacquer, adhesive or/and with a lacquer-like organic composition, wherein optionally at least one of these further coatings is cured by being heated or/and irradiated.
21. Process according to one of the preceding claims, characterised in that prior to the treatment with an aqueous silane-based pretreatment composition an aqueous alkaline treatment having a content of at least one iron compound dissolved in water and optionally having a content of at least one complexing agent is carried out.
22. Use of the metallic substrates coated by the process according to one of the preceding claims in the automobile industry, for rail vehicles, in the aerospace industry, in apparatus construction, in mechanical engineering, in the construction industry, in the furniture industry, for the production of crash barriers, lamps, profiles, claddings or small parts, for the production of automobile bodies or bodywork parts, of individual components, pre-assembled or connected elements, preferentially in the automobile industry or aviation industry, for the production of appliances or installations, in particular of household appliances, monitoring devices, testing devices or structural elements.
23. Use of an aqueous silane-based pretreatment composition in a coating process according to at least one of Claims 1 to 21 for metallic substrates for the purpose of improving the throwing power of an electrophoretic lacquer coating, in which an aqueous silane-based composition according to at least one of Claims 1 to 15 is brought into contact with a metallic substrate, in which the coating freshly applied with this composition is rinsed with water at least once, wherein rinsing is effected at least once with water having a content of surfactant, in which after the rinsing with water an electrophoretic lacquer coating is applied, wherein the coating freshly applied with this composition is not thoroughly dried up until this rinsing, so that the at least one condensable compound a) does not strongly condense up until the rinsing of the pretreatment coating with water or/and up until the coating with an electrophoretic lacquer, and wherein prior to the treatment with an aqueous silane-based pretreatment composition an aqueous treatment having a content of iron compound dissolved in water is carried out.
24. Use of an aqueous silane-based pretreatment composition in a coating process according to at least one of Claims 1 to 21 for metallic substrates for the purpose of improving the throwing power of an electrophoretic lacquer coating, in which prior to the aqueous silane-based pretreatment the substrates are brought into contact at least once with an iron-containing aqueous composition, in which an aqueous silane-based composition according to at least one of Claims 1 to 15 is brought into contact with a metallic substrate, in which the coating freshly applied with this composition is rinsed with water at least once, wherein rinsing is optionally effected at least once with water having a content of surfactant, in which after the rinsing with water an electrophoretic lacquer coating is applied, wherein the pretreatment coating freshly applied with this pretreatment composition is not thoroughly dried up until the application of a subsequent electrophoretic lacquer coating, so that the at least one condensable compound a) does not strongly condense up until the application of the subsequent electrophoretic lacquer coating and wherein prior to the treatment with an aqueous silane-based pretreatment composition an aqueous treatment having a content of iron compound dissolved in water is carried out.