EP3011074A1

EP3011074A1 - Multi-step method for electrodeposition

Info

Publication number: EP3011074A1
Application number: EP14725124.3A
Authority: EP
Inventors: Nils BONGARTZ; Kirsten Agnes LILL; Ralf POSNER
Original assignee: Henkel AG and Co KGaA
Current assignee: Henkel AG and Co KGaA
Priority date: 2013-06-20
Filing date: 2014-05-16
Publication date: 2016-04-27
Anticipated expiration: 2034-05-16
Also published as: EP3011074B1; BR112015031240A2; JP2016527391A; ES2642271T3; US20160102405A1; KR102278974B1; US9382628B2; KR20160022309A; WO2014202294A1; CN105324517B; CN105324517A; JP6465871B2

Abstract

The subject matter of the present invention is a multi-step method for the anti-corrosive coating of metal components, in which method a reaction rinse is used after a conversion treatment before electrodepostion is carried out on the component. The conversion treatment includes first the deposition of a thin inorganic layer containing the elements Zr and/or Ti. The metal component is then treated with a reaction rinse containing a surface-active substance and is subsequently subjected to electrodeposition.

Description

Multi-stage process for electrocoating

The present invention is a multi-stage process for corrosion-protective coating of metallic components, in which a conversion treatment is followed by a reaction rinse, before a

Electrocoating of the component is performed. In this case, the conversion treatment initially involves the deposition of an inorganic thin layer containing the elements Zr and / or Ti. The metallic component is then aftertreated with a reaction rinse containing a surface-active substance and subsequently electrocoated.

The corrosion-protective coating of metallic components via a multi-stage process consisting of conversion treatment and the following

Electrocoating is a process that has been practiced for decades. From an economic point of view and due to ecological concerns, the automotive industry is endeavoring to replace the technically established conversion treatment by means of zinc phosphating by a resource-sparing and preferably equivalent pretreatment. In contrast to zinc phosphating, alternative concepts for conversion treatment often provide amorphous coatings with layer thicknesses in the nanometer range, in order to meet the desire for a less extensive pretreatment process.

WO 07/065645 discloses such a resource-conserving process for the anticorrosive coating of metallic substrates such as steel and galvanized steel comprising the process steps of the conversion treatment and subsequent dip-coating, wherein between the

Conversion treatment and electrocoating optionally a rinsing and / or drying step takes place. According to this teaching, a "wet-on-wet" process is preferred in which a drying step is omitted, and thus with a

Wet film provided metallic substrates are immediately electrocoated. The conversion treatment is carried out essentially by using chromium-free acidic aqueous compositions based on fluorocomplexes of the elements Zr and / or Ti. Naturally, thin conversion layers, as obtained, for example, in WO 07/065645, have a rather lower electrical layer resistance than the crystalline coatings of zinc phosphating, in which layer thicknesses of at least a few micrometers are provided. However, a high electrical sheet resistance is advantageous for those used in the established methods for corrosion-protective coating of automobile bodies

Electrocoating, as a high electrical resistance that

"Creeping in" the dip coating in cavity structures of

coated metallic component significantly improved. This typical

Coating behavior of electrocoating is referred to as

"Umgriffsverhalten", as it describes the encapsulation of the electrocoating in areas of the device with a low electric field density

Automotive industry is anxious to optimize the Umgriffsverhalten, so that either at the same immersion paint thickness in the exterior of a body deeper penetration of the dip in electrically shielded areas of the

Automotive body allows or with the same Umgriff a smaller

Dipping paint thickness outside of the body is required.

There is therefore a need for the previously described method for

To optimize corrosion-protective coating in such a way that a nearly equivalent Umgriffsverhalten results in the electrodeposition coating, without having to resort to conversion treatments on the type of phosphating.

EP 1 455 002 A1 discloses in a related context a

Conversion treatment by means of a chromium-free acidic aqueous

Composition containing fluorocomplexes of Zr and / or Ti, wherein after the conversion treatment and before the electrodeposition coating different

Post-treatment steps are proposed to reduce the proportion of water-soluble fluorides in the conversion layer and thus to improve the corrosion protection after electrocoating. As more effective

Post-treatment step, among other things, an intermediate sink with an alkaline aqueous solution is proposed. However, the focus of this prior art is the corrosive infiltration of the coated metallic

To improve component, and less so, the conversion treatment using a chromium-free acidic aqueous composition containing fluorocomplexes of the elements Zr and / or Ti with the requirements of a likewise

Balancing resource-saving or optimized electrocoating. According to WO 07/065645, an intermediate sink may also be effected before the electrodeposition coating and after the conversion treatment, it being possible to use aqueous solutions containing water-soluble compounds of the elements Co, Ni, Sn, Cu, Ti and Zr or water-soluble or water-dispersible organic polymers.

In the present case, in the light of this state of the art, the object is to optimize the known process sequence of corrosion-protective pretreatment and subsequent electrocoating in such a way that on the one hand realizes savings in the coating material in the electrodeposition coating and on the other hand components with complex geometries can be satisfactorily electrocoated.

This object is achieved by a multi-stage method for

corrosion-protective coating of the surfaces of a metallic component, in which the surface of the metallic component is subjected to a conversion treatment by contacting with an acidic aqueous composition comprising water-soluble compounds of the elements zirconium and / or titanium, as a result of which a coating of zirconium and / or or titanium of at least 10 mg / m ^{2 is} generated directly on the surface of the metallic component, this conversion treatment with or without intermediate rinsing and / or drying step following a reaction rinse, wherein the reaction rinse by contacting the conversion treated surface of the metallic Component having an aqueous composition containing at least one surface-active substance, and then the thus treated

Surface of the metallic component with or without intervening rinsing and / or drying step is electrocoated.

"Conversion treatment" in the sense of the present invention is any

wet-chemical pretreatment of a metal surface, as a result of which metal elements of the wet-chemical pretreatment dissolved in water become analytically measurable constituents of such a surface coating which do not have any effect on the surface

Substantially natural oxide layer of the conversion treated metal.

"Surface-active substances" in the context of the present invention are organic compounds composed of a hydrophilic and at least a lipophilic molecular constituent or a lipophilic and at least one hydrophilic molecular constituent, wherein the molecular weight of the

surface-active substance does not exceed 2000 g / mol.

"Electrocoating" in the context of the present invention is each brought about by applying an external voltage source to the metallic component

Deposition of an organic coating from an aqueous phase containing the paint.

A "rinsing step" in the sense of the present invention refers to a process that is intended solely for the immediate purpose of active components

preceding wet-chemical treatment step, which are present dissolved in a wet film adhering to the component, as far as possible to be removed from the surface of the component by means of a rinsing solution, without the active components to be removed being replaced by others. Active components in this context are constituents contained in a liquid phase which cause an analytically detectable coating of the metal surfaces of the component with elemental constituents of the active components.

A "drying step" in the context of the present invention refers to a process in which the surfaces of the metallic component having a wet film are to be dried with the aid of technical measures.

The layer coating of zirconium and / or titanium can be determined directly after the conversion treatment by means of X-ray fluorescence analysis method (RFA) after rinsing with deionized water (κ <Ι μεοητ ¹ ) and subsequent drying of the component.

In the process of the invention, the corrosion-protective pretreated and post-treated in the reaction rinse metallic components in the

Electrodeposition coating with constant wringing a smaller layer thickness of the dipping paint or at a constant immersion coating thickness improved Umgriffsverhalten. Accordingly, a comparatively resource-saving operation is ensured in the electrocoating and the

Electrocoating complex metal components with cavity-like

Structures improved. The proportion of surface-active substances in the reaction rinse is preferably at least 20 ppm, more preferably at least 50 ppm. If these preferred minimum levels of surfactants are undercut, there will be a significant decrease in wrap-around with otherwise identical electrocoating parameters that is no longer acceptable for certain complex geometry applications and components. Above 1 wt .-% of surface-active substances, a further improvement of Umgriffs regularly not observed, so that for reasons of economy preferably not more than 1 wt .-% of surface-active substances in the reaction rinse of the inventive method are included.

The term "ppm" stands for "parts per million" and in the context of the present invention refers to the mass of the respective composition so that 1 ppm corresponds to a proportion of 1 mg of the respective substance per kilogram of the respective composition.

The surface-active substances in the reaction rinse of the process according to the invention can be selected from anionic surfactants, cationic surfactants,

zwitterionic surfactants and nonionic surfactants, wherein the use of nonionic surfactants is preferred in the reaction rinse, inter alia, because of their good compatibility with the bath constituents of the electrodeposition coating. Compatibility here is to be understood as the absence of precipitates in the dip-coating bath. These

Compatibility of surface-active substances with bath constituents of

Electrocoating is to be considered, as the lugging of

Ingredients from the reaction rinse in the electrodeposition coating can not be completely prevented especially in the anti-corrosive coating strong-consuming components.

Furthermore, it has been found that nonionic surfactants are components of

Reaction sink affect the Umgriffsverhalten the dip paint comparatively more positive. In this connection, preference is generally given to those nonionic surfactants whose HLB value (hydrophilic-lipophilic balance) is at least 8, more preferably at least 10, particularly preferably at least 12, but

more preferably not more than 18, particularly preferably not more than 16.

The HLB value is used for the quantitative classification of nonionic surfactants according to their internal molecular structure, with a breakdown of the nonionic surfactant into a lipophilic and a hydrophilic group. The HLB value according to The present invention is calculated according to the following formula and can assume values of zero to 20 on the arbitrary scale:

with Mi: molar mass of the lypophilic group of nonionic surfactant

M: molecular weight of the nonionic surfactant

Substantially, such nonionic surfactants are preferred in the reaction rinse of the process according to the invention for further improving the encasing of the dip coating, which are selected from alkoxylated alkyl alcohols, alkoxylated fatty amines and / or alkylpolyglycosides, particularly preferably from alkoxylated alkyl alcohols and / or alkoxylated fatty amines, particularly preferably from alkoxylated alkyl alcohols. The alkoxylated alkyl alcohols and / or alkoxylated fatty amines are preferably end-capped, particularly preferably having an alkyl group which in turn preferably has not more than 8 carbon atoms, more preferably not more than 4 carbon atoms.

Particular preference is given to those alkoxylated alkyl alcohols and / or alkoxylated fatty amines as nonionic surfactants in the reaction rinse of the process according to the invention which are ethoxylated and / or propoxylated, the number of alkylene oxide units preferably not being greater than 20, particularly preferably not greater than 16. but more preferably at least 4, more preferably at least 8.

With regard to the lipophilic constituent of the aforementioned nonionic surfactants, those alkoxylated alkyl alcohols and / or alkoxylated fatty amines are preferred as nonionic surfactants in the reaction rinse of the process according to the invention whose alkyl group is saturated and preferably unbranched, the number of carbon atoms in the alkyl group preferably not being smaller than 6, more preferably not less than 10, but preferably not greater than 24, more preferably not greater than 20.

Overall, it is shown that longer-chain nonionic surfactants are preferable for improving the Umgriffsverhaltens means of the reaction rinse, so that in a Another preferred embodiment of the process according to the invention are those alkoxylated alkyl alcohols and / or alkoxylated fatty amines, in particular the alkoxylated alkyl alcohols, whose lipophilic alkyl group comprises at least 10 carbon atoms, more preferably at least 12 carbon atoms, wherein the longest carbon chain in the alkyl group of at least 8th

Carbon atoms and an HLB value is realized in the range of 12 to 16 realized.

Preferred representatives of the alkoxylated alkyl alcohols are in inventive

Method selected, for example

four to eight times ethoxylated or propoxylated C6-C12 fatty alcohols, eight to sixteen times ethoxylated C12-C18 fatty alcohols, six to fourteen-fold propoxylated C12-C18 fatty alcohols, four to eight times ethoxy and propoxylated C12-C18 fatty alcohols, which in turn are methyl, Butyl or benzyl end-capped may be present.

For the reaction rinses of the process according to the invention, the pH is preferably not below 4, more preferably not below 6, in order to minimize the pickling attack on the coating produced in the conversion treatment by an acid reaction rinse. Conversely, the

Reaction rinses preferably have no pH above 12, more preferably above 10. For the abovementioned reaction rinses which contain nonionic surfactants, the pH in a preferred embodiment of the process according to the invention is to be adjusted to neutral (pH 7) to alkaline, the pH again preferably not being above 12, more preferably not above 1 , particularly preferably should not be above 10, but preferably at least 7, more preferably at least 8. The adjustment of the alkaline pH causes in the presence of nonionic surfactants a significant improvement of the Umgriffs in subsequent electrocoating, especially if between the conversion treatment and reaction rinse no rinsing step, more preferably neither a rinsing step nor a drying step. The adjustment of the pH of the reaction rinse is preferably carried out via a

Buffer system, making the entry of components of acidic aqueous

Composition from the conversion treatment in the Nachspüle does not lead to a shift in the pH outside the optimal range. In a particularly preferred embodiment of the method according to the invention, therefore, after the conversion treatment and before the reaction rinse on a be dispensed with additional rinsing step. The use of a buffer system also facilitates the bath control, since a re-dosing of the pH-stabilizing substances has to be done only moderately and occasionally. In a preferred embodiment of the method according to the invention contains

Reaction rinse the buffer system at least in such an amount that at an entry of a Val acid, the pH does not change by more than 0.5, preferably not more than 1, 0 units, but preferably such amounts of buffer are not exceeded for which the reaction rinse assumes an electrical conductivity of more than 1.0 mScnr ¹ , preferably of more than 0.5 mScnr ¹ . A preferred buffer system is a carbonate-bicarbonate buffer system (for example Na ₂ C0 ₃ / NaHC0 ₃ ).

The "pH" in the present invention refers to the negative decadic logarithm of the activity of the hydronium ions at 25 ° C.

It has been found that the positive influence of the reaction rinse on the immersion of the dipping paint is weakened by the additional presence of layer-forming active components and sometimes fails completely. This applies in particular to those active components which are capable of forming thin amorphous phosphate layers. In a preferred embodiment of the method according to the invention, the aqueous composition of the

Therefore reaction sink less than 1 g / kg, more preferably less than 0, 1 g / kg, most preferably less than 0.01 g / kg dissolved in water phosphates calculated as P0. ₄

The layer-forming active components which cause worsening of the wraparound also include water-soluble compounds of certain metal elements, which usually cause a conversion of the metal surface.

Accordingly, in a further preferred embodiment of the

process according to the invention that the aqueous composition of the reaction rinse less than 20 ppm, more preferably less than 10 ppm, more preferably less than 1 ppm of water-soluble compounds of elements of subgroups HIB, IVB, VIB and / or the element vanadium based on the respective Contains element, wherein preferably less than 20 ppm of these water-soluble compounds are contained in total based on said elements. The same applies to the presence of silanes which are present in the reaction rinse of the process according to the invention preferably in an amount of less than 0.005 g / l, more preferably less than 0.002 g / l, particularly preferably less than 0.001 g / l are calculated based on the corresponding silanols.

"Silanes" in the context of this invention include silanes, silanols, siloxanes,

Polysiloxanes and their reaction products or derivatives. The reaction products are in particular condensation and hydrolysis products in the aqueous medium to understand.

Furthermore, disadvantageous for the Umgriffsverhalten the dip in the

The process according to the invention can be the presence of such layer-forming active components in the reaction rinse, which cause the deposition of a metallic phase upon contact with the metallic component. Accordingly, in a further preferred embodiment of the process according to the invention, it is preferred that the aqueous composition of the reaction solution is less than 50 ppm, preferably less than 10 ppm, more preferably less than 5 ppm of water-soluble compounds of the elements Co, Ni, Cu and / or Sn contains on the respective element, wherein preferably less than 50 ppm in total of these water-soluble compounds are contained based on said elements.

The conversion treatment preceding the reaction rinse takes place in a process which is preferred according to the invention with such acidic aqueous

Compositions containing fluoro acids of the elements zirconium and / or titanium and their salts and hydrolysis products. Hydrolysis products are

for example, those compounds in which fluoride ions on the central atom are partially substituted by hydroxide ions.

Surprisingly, it has been found that the reaction rinse for such processes according to the invention, in which a phosphate layer is produced in the conversion treatment, produces a substantially lower effect with regard to the improvement of the encapsulation in the subsequent electrodeposition coating. According to the invention, it is therefore preferred that the acidic aqueous composition for the conversion treatment does not produce a phosphate layer with a layer coverage of at least 0.2 g / m ^2, based on P0 _4, on the metallic component. To ensure this, the acidic aqueous composition should

Conversion treatment preferably less than 1 g / kg in total, especially preferably a total of less than 0.1 g / kg of phosphates dissolved in water, calculated as P0 ₄ .

It has also been found that the presence of copper ions in the acidic aqueous composition of the conversion treatment, which is usually in small amounts to the conversion bath to accelerate the conversion

Conversion layer formation based on the elements zirconium and / or titanium is added, can affect the application of the spray process adversely affect the effectiveness of the method according to the invention. It is therefore preferred that the acidic conversion conversion composition in such processes according to the invention in which the conversion treatment is effected by spraying has a total of less than 50 ppm, more preferably less than 10 ppm, most preferably less than 1 ppm of copper dissolved in water. Contains ions. Overall, for inventive method that the molar ratio of the total proportion of water-soluble compounds of zirconium and / or titanium based on the respective elements zirconium and titanium to the total content of water-soluble compounds of the elements Co, Ni, Cu and / or Sn based on the respective elements Co, Ni, Cu and / or Sn in the conversion bath is preferably not less than 0.6, more preferably not less than 1.0.

Furthermore, it has already been found that the presence in the reaction rinse can be disadvantageous for the process according to the invention. Accordingly, preference is given to those processes in which the introduction of silanes into the reaction rinse is largely prevented. This can be done, for example, by the acidic composition not being a silane-based composition in the conversion treatment. In preferred method according to the invention, the acidic composition in the conversion treatment contains a total of less than 0.005 g / l, more preferably less than 0.002 g / l, particularly preferably less than 0.001 g / l of silanes calculated on the basis of the corresponding silanols.

The type of application of both the acidic aqueous composition in the conversion treatment and the reaction rinse is freely selectable under conventional application methods. Thus, the aqueous compositions of the method according to the invention can be brought into contact with the metallic component either by spraying or by immersion. A rinsing and / or drying step can be intermediately interposed between the reaction rinse and the subsequent electrocoating. The advantage of the method according to the invention is that contained in the reaction rinse in a preferred embodiment according to the invention

Nonionic surfactants exert no adverse effect on the electrodeposition coating, so that can be dispensed with an intermediate rinsing step to remove the surface-active substances in adhering to the component wet film before electrocoating. In a preferred embodiment of the

According to the method of the invention, the metallic component can therefore be electrocoated after the reaction rinse without intervening rinsing step.

Furthermore, it has been found in the process according to the invention that drying of the component immediately after the reaction rinse or drying of the component immediately after a rinsing step subsequent to the reaction rinse is not necessary for an improved reattachment behavior in the following

Dipcoating is, so that the present method in terms of its

Single steps completely "wet-in-wet" - ie without will-be-craving

Drying step - can be performed.

Accordingly, it is preferred according to the invention if, after the reaction rinse and before the electrodeposition coating, no drying step takes place in which the drying takes place above a temperature of 40 ° C., and preferably no drying step takes place at all.

The corrosion-protected coated metallic component in the method according to the invention is preferably selected from aluminum, zinc, iron, steel and / or galvanized steel. The method according to the invention is particularly suitable for improving the encircling of an immersion paint on surfaces of steel and / or galvanized steel.

EXAMPLES

All experiments were carried out with cold rolled steel sheets (CRS). The following basic process was used for all of the following

Examples applied:

1) Alkaline cleaning:

To prepare the alkaline cleaner, the bath is filled with service water, 3% Ridoline® 1574 and 0.3% Ridosol® 1270 (each Henkel AG & Co. KGaA) added and the pH adjusted to pH 1 1 by slow addition of a phosphate solution.

Injection pressure: 1 bar

Temperature: 50 - 60 ° C

Treatment time: 120 seconds

2) deionised water sink

Injection pressure: 1 bar

Temperature: room temperature ° C

Treatment time: 30-60 seconds

3) conversion treatment

4) reaction rinse

5) demineralized water sink (κ <1 μεοητ ¹ )

Injection pressure: 1 bar

Temperature: room temperature ° C

Treatment time: 30-60 seconds

6) Cathodic dip coating (CathoPrime®, BASF Coatings AG):

It was added to 2573 g of deionized water, 690 g of pigment paste GV81 -0001 and 1760 g of binder GY80-0640 (each BASF Coatings AG) with stirring. The deposition was carried out at 30 ° C bath temperature potentiostatic for a total of 105 seconds at a voltage of 160 V. This

Separation voltage was set within 15 seconds by means of a corresponding potential ramp. The determination of

Coating layer thickness was carried out after curing of the dip coating for 25 min at 180 ° C by means of a coating thickness gauge (DUALSCOPE® FMP40, Helmut Fischer GmbH). In order to explain the effect of the reaction rinse on the dipping paint thickness and the wraparound, two pairs of sheets were prepared, one each

Reference sheet pair only the treatment steps 1 -3, 5 and 6 passes. The changes in dip paint thickness and wrap around refer to the corresponding values of the reference plate pair.

In order to determine the throw-over of the electrodeposition paint, two sheets were assembled by means of a plastic frame and tape into a device, wherein the distance of the inner sheet surfaces was 4 mm. The electrodeposition paint could penetrate only through a lower opening between the two inner surfaces of the sheet metal in the enclosed by the sheets and the plastic spacer inner volume. This device was stirred in the above

Electrocoating bath brought and switched as a cathode. Compared to the outer metal surfaces, a stainless steel anode was arranged in parallel at a distance of 10 cm, the cathode to anode area ratio being 5: 1.

Example B1:

The conversion bath contained 270 ppm H ₂ ZrF ₆ , 60 ppm ZrO (NO 2) 2 and 300 ppm HNO ₃ . The pH was adjusted to pH 4.5 by addition of aqueous ammoniacal solution. The conversion treatment was carried out at 40 ° C bath temperature for 60 seconds by spraying at a pressure of 1 bar.

The reaction rinse was carried out with a solution of 750 ppm 2,4,7,9-tetramethyl-5-decyne-4,7-diol in demineralized water for 60 seconds at 20 ° C by immersion.

Example B2:

Conversion treatment as in Example 1.

The reaction rinse was carried out with 200 ppm of butyl end-capped 4- to 5-tuply ethoxylated octanol (C8, 4-5 EO, butyl, HLB value 14) in deionized water for 60 seconds at 20 ° C. by immersion.

Example B3:

Conversion treatment as in Example 1, but at a bath temperature of 20 ° C.

The reaction rinse was carried out with a solution of 20 ppm of butyl end-capped 10-times ethoxylated C12-C18 fatty alcohols (C12-C18, 10 EO, butyl, HLB value 13.3-15) in demineralized water for 60 seconds at 20.degree by spraying at an injection pressure of 1 bar. Example B4:

Conversion treatment as in Example 1, but at a bath temperature of 20 ° C.

The reaction rinse was carried out for 60 seconds at 20 ° C. by spraying at an injection pressure of 1 bar with a solution of 100 ppm of butyl end-capped 10-times ethoxylated C12-C18 fatty alcohols (C12-C18, 10 EO, butyl, HLB value 13, 3-15) and 5 wt .-% of a buffer system consisting of 0.2 mol / L Na ₂ C0 ₃ and 0.2 mol / L NaHCOs in deionized water (pH 9.7).

Example B5:

Conversion treatment as in Example 1, but at a bath temperature of 20 ° C.

The reaction rinse was carried out for 60 seconds at 20 ° C. by spraying at an injection pressure of 1 bar with a solution of 100 ppm of butyl end-capped 10-times ethoxylated C12-C18 fatty alcohols (C12-C18, 10 EO, butyl, HLB value 13, 3-15) at a pH of 7.8.

Example B6:

The conversion bath contained 340 ppm H ₂ ZrF ₆ , 15 ppm Cu (NO 2) 2 and 4 ppm HF. The pH was adjusted to pH 4.0 by addition of aqueous ammoniacal solution. The conversion treatment was carried out at 20 ° C bath temperature for

120 seconds in the dipping process.

The reaction rinse was carried out with a solution of 1000 ppm of butyl end-capped 10-times ethoxylated C12-C18 fatty alcohols (C12-C18, 10EO, butyl, HLB value 13.3-15) in demineralized water for 120 seconds at 20 ° C by immersion.

Example B7:

Conversion treatment as in Example 1, but at a bath temperature of 20 ° C.

The reaction sink effected with a solution of 67 ppm butyl-sealed end group 10-tuply ethoxylated C12-C18 fatty alcohols (C12-C18, 10 EO, butyl; HLB value from 13.3 to 15) and 27 ppm H ₂ ZrF ₆ in VE - Water for 60 seconds at 20 ° C by spraying at an injection pressure of 1 bar.

Comparative Example CB1: To prepare a Eisenphosphatierlösung a bath was filled with deionized water, 2 wt .-% Duridine 7760 (Henkel AG & Co. KGaA) was added, the pH adjusted by slow addition of sodium hydroxide solution to pH 4.5. The sheet was then sprayed from the bath at a temperature of 50 ° C for 1 10 seconds at an injection pressure of 1 bar with the iron phosphating solution. The layer weight of iron phosphate was 0.5 g / m ² determined as P0. ₄

The reaction rinse was carried out with a solution of 1000 ppm of butyl end-capped 10-times ethoxylated C12-C18 fatty alcohols (C12-C18, 10 EO, butyl, HLB value 13.3-15) in deionised water for 60 seconds at 20.degree by immersion.

Table 1 summarizes the values for the electrodeposition paint thickness and the throw-over for the exemplary embodiments described above.

It can be seen for each of the examples B1-B6 according to the invention that the dipping paint thickness could always be significantly reduced and improved wraparound realized at the same time (Table 1). Thus, the object of the present invention, which consists on the one hand to realize savings in terms of the coating material in the electrodeposition coating and on the other hand be able to satisfactorily electrocoating components with more complex geometries, solved in full. Furthermore, it can be seen that the geminal nonionic surfactant of Example B1, in comparison with the linear amphiphiles of Examples B2-B6

Umgriffsverbesserung and the desired reduction in dip paint thickness falls slightly. A comparison of Examples B2 and B4 shows that the longer-chain end-capped ethoxylated fatty alcohol (B4) gives the best results and, in particular, surprisingly improves the drug behavior. The effect of nonionic surfactants is also strictly selective for the previous one

Conversion treatment as shown in Comparative Example VB1, in which the reaction rinse of an iron-phosphated sheet metal surface to none

Improvement in Umgriff and dip paint thickness leads. Also beyond the nonionic surfactant as an active component composition of

Reaction rinse is decisive for the success of the method according to the invention. Thus, example B7 shows that the additional presence of

Active components from the stage of the conversion treatment is disadvantageous and at higher concentrations of these active components (here: H ₂ ZrF ₆ ) even a significant deterioration in Umgriffsverhalten and in terms of Tauchlackdicke occurs. Also in this context, it is therefore advantageous that the Reaction rinse is buffered alkaline as in Example B4, so that in a running coating system a transfer of Konversionsbadbestandteilen in the reaction rinse by scooping components there only leads to precipitation of the compounds of the elements Zr and / or Ti and not to a deterioration in performance. In addition, in alkaline buffered reaction rinses, as compared to neutral to slightly alkaline reaction rinses, improvement in varnish coverage can be observed, as can be seen by comparing Examples B4 and B5.

Tab. 1

The absolute values were measured on the outer sides of the plate pairs facing the anode (in each case averaged over 5 layer thickness measurements). The respective absolute value corresponds to the longest visible extent of the dip coating on the insides of the plate pair

Claims

claims:

1. A method for corrosion-protective coating of the surfaces of a metallic component, wherein the surface of the metallic component of a conversion treatment by contacting with an acidic aqueous composition containing water-soluble compounds of zirconium and / or titanium is subjected, as a result, a layer support zirconium and / or titanium of at least 10 mg / m ² directly on the

Surface of the metallic component is produced, characterized in that this conversion treatment with or without intermediate rinsing and / or drying step follows a reaction rinse, wherein the reaction rinse by contacting the conversion-treated surface of the metallic component with an aqueous composition containing at least one surface-active Substance takes place, and then the thus treated surface of the metallic component with or without intervening rinsing and / or drying step is electrocoated.

2. The method according to claim 1, characterized in that the

surfactant is selected from nonionic surfactants.

3. The method according to claim 2, characterized in that the nonionic surfactants have an HLB value of at least 8, preferably of at least 10, more preferably of at least 12, but preferably not more than 18, more preferably not more than 16.

4. The method according to one or both of the preceding claims 2 and 3, characterized in that the nonionic surfactant is selected from alkoxylated alkyl alcohols and / or alkoxylated fatty amines which are preferably endgruppenverschlossen, particularly preferably endgruppenverschlossen with an alkyl group, preferably not more than 8th

Having carbon atoms, more preferably not more than 4 carbon atoms.

5. The method according to claim 4, characterized in that the

alkoxylated alkyl alcohols and / or fatty amines ethoxylated and / or propoxylated, wherein the number of alkylene oxide units in total is not greater than 20, preferably not greater than 16, but is preferably at least 4, more preferably at least 8.

6. The method according to one or both of claims 4 and 5, characterized

in that the alkyl group of the alkoxylated alkyl alcohol and / or alkoxylated fatty amine is saturated and preferably unbranched, wherein the number of carbon atoms in the alkyl group is not less than 6, preferably not less than 10, but not more than 24, preferably not is greater than 20.

7. The method according to one or more of the preceding claims, characterized in that the proportion of surface-active substances in the reaction rinse above 20 ppm, preferably above 50 ppm, but preferably not above 1 wt .-%.

8. The method according to one or more of the preceding claims, characterized in that the aqueous composition of the reaction rinse less than 1 g / kg, preferably less than 0, 1 g / kg, more preferably less than 0.01 g / kg of in water dissolved phosphates calculated as P0 ₄ contains.

9. The method according to one or more of the preceding claims, characterized in that the aqueous composition of the reaction rinse less than 20 ppm, preferably less than 10 ppm, more preferably less than 1 ppm of water-soluble compounds of elements of subgroups HIB, IVB, VIB and / or of the element contains vanadium based on the respective element, wherein preferably less than 20 ppm of these water-soluble compounds are contained in total based on the elements mentioned.

10. The method according to one or more of the preceding claims, characterized in that the aqueous composition of the reaction rinse less than 50 ppm, preferably less than 10 ppm, more preferably less than 5 ppm of water-soluble compounds of the elements Co, Ni, Cu and / or Contains Sn based on the respective element, wherein a total of preferably less than 50 ppm of these water-soluble compounds based on said elements are included.

1 1. A method according to one or more of the preceding claims 2 to 10, characterized in that the aqueous composition of

Reaction rinse has a pH which is not less than 7, preferably not less than 8, and preferably not more than 12, more preferably not more than 1 1, particularly preferably not more than 10.

12. The method according to one or more of the preceding claims, characterized in that no rinsing step, preferably neither a rinsing step nor a drying step takes place between the conversion treatment and the reaction rinse.

13. The method according to one or more of the preceding claims, characterized in that the water-soluble compounds of the elements zirconium and / or titanium in the acidic aqueous composition

Conversion treatment are selected from fluoro acids of the elements zirconium and / or titanium and their salts.

14. The method according to one or more of the preceding claims, characterized in that the acidic aqueous composition for

Conversion treatment no phosphate layer with a layer thickness of at least 0.2 g / m ² based on P0 ₄ generated.

15. The method according to one or more of the preceding claims, characterized in that the acidic aqueous composition for

Conversion treatment less than 0.005 g / l, preferably less than 0.002 g / l, more preferably less than 0.001 g / l calculated on silanes based on the respective silanols.

16. The method according to one or more of the preceding claims, characterized in that after the reaction rinse and before the

Electrocoating no drying step takes place.

17. The method according to one or more of the preceding claims, characterized in that the metallic component at least partially

Surfaces of steel and / or galvanized steel.