EP3303652B1 - Pre-rinse containing a quaternary amine for conditioning prior to a conversion treatment - Google Patents

Description

The present invention relates to a multi-stage process for the corrosion-protective pretreatment of components made of metallic materials, wherein on a conditioning wet-chemical treatment with an aqueous composition (A) containing a salt of a quaternary amine, a further wet-chemical treatment based on water-soluble compounds of the elements Zr, Ti and / or Si follows, in the course of which a corresponding conversion of the surfaces of the metallic materials takes place, which provides a corrosion-protecting primer for additionally applied organic coatings.

The conversion treatment of metallic surfaces to provide a corrosion-protective coating based on aqueous compositions containing water-soluble compounds of the elements Zr, Ti and / or Si is a technical field extensively described in the patent literature. To improve the property profile of such conversion treatments in terms of corrosion protection and imparting sufficient paint adhesion, various variants of such metal pretreatment are known, which either aim at the composition of the conversion-causing agents or resort to further wet-chemical treatment steps in the immediate context of the conversion treatment.

The EP 1 455 002 A1 describes, for example, that it is advantageous for conversion treatment by means of previously described compositions which additionally contain fluoride ions as complexing agent and the metal surface-attracting agent, if for reducing the fluoride content in the conversion layer of the actual wet chemical treatment, an aqueous sink containing basic compounds immediately following or a drying step is downstream. Alternatively, the reduction of the fluoride content in the conversion layer serves to add certain cations selected from calcium, magnesium, zinc, copper or silicon-containing compounds to the surface conversion-inducing composition.

Concerning further adaptations of the procedure with the use of fluoride ions and water-soluble compounds of the elements Zr and / or Ti containing conversion treatment agents, US Pat WO 2011012443 A1 a downstream aqueous sink containing organic compounds having aromatic heterocycles with at least one nitrogen heteroatom.

The US 2010/222248 A1 and EP 2 253 741 A2 each disclose a multi-step process in which the metal surfaces are treated with an aqueous composition containing a salt of a quaternary organic amine selected from heterocycles having at least one quaternary nitrogen heteroatom, followed by a conversion treatment with an aqueous composition containing a titanium or a zirconium Connection.

Compared to this prior art, the object was to further standardize the anti-corrosive properties of conversion layers on different metal substrates obtainable by pretreatment with compositions of water-soluble compounds of the elements Zr, Ti and / or Si and in particular to improve the steel surfaces. Here, in particular, the average undermigration values in the corrosive delamination after coating layer build-up should be improved. In one aspect, the pretreatment for environmental health reasons should be largely without the presence of fluorides. A pretreatment method according to the present invention must, therefore, in order to realize this aspect, even in the absence of fluorides, a homogeneous and complete conversion of the so-called "free metal surface" so the degreased, purified and only the natural oxide layer having metal surface effect. Furthermore, under identical process conditions, a small variance in the conversion layer should result, ie a certain conversion can be reliably achieved in terms of process engineering. With regard to the application to various metal substrates in particular an optimal corrosion protection effect of such composite structures by means of a corresponding wet-chemical pretreatment is desired, which in addition to surfaces of the material iron and / or steel and surfaces of at least one of the materials zinc, galvanized steel and / or aluminum.

1. i) zumindest ein Teil der Oberflächen des Bauteils, die von den metallischen Werkstoffen gebildet werden, mit einer wässrigen Zusammensetzung (A) enthaltend ein gelöstes und/oder dispergiertes Salz eines quartären organischen Amins ("Konditionierung"), behandelt, und anschließend wird
2. ii) zumindest derselbe Teil der Oberflächen des Bauteils, die von den metallischen Werkstoffen gebildet werden, mit oder ohne dazwischenliegendem Spül- und/oder Trocknungsschritt mit einer wässrigen Zusammensetzung (B) enthaltend ein oder mehrere wasserlösliche Verbindungen der Elemente Zr, Ti und/oder Si ("Konversionsschichtbildung") in Kontakt gebracht.

This object is achieved by a multi-stage method according to claim 1. In the method for corrosion-protective pretreatment of at least partially made of metallic materials components is first

1. i) at least a part of the surfaces of the component formed by the metallic materials with an aqueous composition (A) containing a dissolved and / or dispersed salt of a quaternary organic Amines ("conditioning"), treated, and afterwards
2. ii) at least the same part of the surfaces of the component formed by the metallic materials, with or without intermediate rinsing and / or drying step with an aqueous composition (B) containing one or more water-soluble compounds of the elements Zr, Ti and / or Si ("Conversion layer formation") brought into contact.

The components treated according to the present invention can be any arbitrarily shaped and configured spatial structures which originate from a fabrication process, in particular also semi-finished products such as strips, sheets, rods, tubes, etc., and composite structures joined together from the aforementioned semifinished products.

According to the invention, in the first step i) of the process according to the invention, a conditioning treatment with the aqueous composition (A) comprising the dissolved and / or dispersed salt of a quaternary organic amine is carried out ("conditioning"). This conditioning causes that in the course of the wet-chemical treatment with an aqueous composition (B) a sufficient and homogeneous coating layer with respect to the elements Zr, Ti and / or Si is achieved, so that a conversion of the metal surfaces of the component is effectively carried out, the one potentially good Lackhaftgrund provides. In particular, on steel surfaces is achieved in the course of the inventive method, a reproducible layer support with respect to the elements Zr, Ti and / or Si, which is the basis for effective suppression of corrosive infiltration of defects in an additionally applied lacquer coating.

A salt of a quaternary organic amine dissolved or dispersed in water in the meaning of the invention takes up an average particle diameter of less than 1 μm in the aqueous phase. The average particle diameter can be determined according to ISO 13320: 2009 by means of laser light diffraction from cumulative particle size distributions as a so-called D50 value directly in the aqueous composition (A) at 20 ° C.

The presence of quaternary organic amines according to claim 1 in an aqueous
Composition (A) in step i) increases the suitability of the conversion coating applied in step ii) to be a good paint adhesion base. A quaternary organic amine in the context of the present invention contains at least one nitrogen atom which has exclusively covalent bonds with carbon atoms and therefore possesses a permanent positive charge.

In the context of the present invention, it is preferred that the quaternary organic amines have a weight average molecular weight M _w of less than 5,000 g / mol.

mit den Resten R¹, R² und R³, die jeweils ausgewählt sind aus Wasserstoff, verzweigten oder unverzweigten Aliphaten mit nicht mehr als 6 Kohlenstoffatomen oder dem Rest -(CR⁴R⁴)_x-[Z(R⁴)_(p-1)-(CR⁴R⁴)_y]_n-Z(R⁴)_p, wobei Z jeweils ausgewählt ist aus Sauerstoff oder Stickstoff und p für den Fall, dass Z Stickstoff ist, den Wert 2 annimmt und anderenfalls gleich 1 ist und x und y jeweils natürliche Zahlen von 1 bis 4 und n ebenfalls eine natürliche Zahl von 0 bis 4 ist und R⁴ ausgewählt ist aus Wasserstoff oder verzweigten oder unverzweigten Aliphaten mit nicht mehr als 6 Kohlenstoffatomen, mit der Maßgabe, dass zumindest einer der Reste R² oder R³ nicht ausgewählt ist aus Wasserstoff;
mit Y als ringkonstituierenden divalenten Rest, der nicht mehr als 5 Brückenatome aufweist, wobei nicht mehr als ein von Kohlenstoffatomen verschiedenes Heterobrückenatom ausgewählt aus Sauerstoff, Stickstoff oder Schwefel Brückenatom sein kann und die Kohlenstoffatome wiederum unabhängig voneinander mit Resten R¹ oder solchen Resten substituiert vorliegen, über die eine Anellierung aromatischer Homocyclen mit nicht mehr als 6 Kohlenstoffatomen realisiert ist.According to the invention, the aqueous composition (A) contains a salt of a quaternary organic amine selected from heterocycles having at least one quaternary nitrogen heteroatom and the following structural formula (I):

with the radicals R ¹ , R ² and R ³ , which are each selected from hydrogen, branched or unbranched aliphatics having not more than 6 carbon atoms or the radical - (CR ⁴ R ⁴ ) _x - [Z (R ⁴ ) _{(p-) 1)} - (CR ⁴ R ⁴ ) _y ] _n -Z (R ⁴ ) _p , where Z is each selected from oxygen or nitrogen and p in the case where Z is nitrogen, takes the value 2 and otherwise equals 1, and x and y are each natural numbers from 1 to 4 and n is also a natural number from 0 to 4 and R ^{4 is} selected from hydrogen or branched or unbranched aliphatics having not more than 6 carbon atoms, with with the proviso that at least one of R ² or R ^{3 is} not selected from hydrogen;
with Y as the ring-constituting divalent radical having not more than 5 bridging atoms, wherein not more than one heterobuck atom other than carbon atoms selected from oxygen, nitrogen or sulfur may be bridging atom and the carbon atoms are again independently substituted with R ¹ or such radicals; via which an annulation of aromatic homocycles having not more than 6 carbon atoms is realized.

In principle, it has proven advantageous that the quaternary organic amine is represented by such heterocycles having the backbone of imidazole, imidazoline, pyrimidine, purine and / or quinazoline. Accordingly, in this connection, it is preferable that the heterocycle represented by the structural formula (I) as the ring-constituting divalent radical Y has such substituents selected from ethylene, ethenediyl, 1,3-propanediyl, 1,3-propenediyl, 1,4-butanediyl , 1,4-butenediyl, 1,4-butadienediyl, -CH = N-, -CH ₂ -NH-, (N, N-dimethylene) amine, (N-methylene-N-methyllylidene) amine, more preferably from ethenediyl , 1,4-butadienediyl, -C = N- or (N-methylene-N-methyllyliden) amine, most preferably from ethenediyl or -C = N- and particularly preferably from etendiyl, wherein each hydrogen covalently bonded to carbon atoms to be substituted may be replaced by the other representatives of the radical R ¹ according to the general structural formula (I).

Particularly advantageous are such quaternary organic amines have been found, which is selected from 1,2,3-trimethylimidazolium, 1-methyl-3-methylimidazolium, 1-ethyl-3-methylimidazolium, 1-isopropyl-3-methylimidazolium, 1-propyl 3-methylimidazolium, 1- (n-butyl) -3-methylimidazolium, 1- (isobutyl) -3-methylimidazolium, 1-methoxy-3-methylimidazolium, 1-ethoxy-3-methylimidazolium, 1-propoxy-3-methylimidazolium , more preferably 1,2,3-trimethylimidazolium.

According to the invention, it is generally advantageous if the proportion of the quaternary organic amine in the aqueous composition (A) is at least 0.05 g / kg, preferably at least 0.2 g / kg, more preferably at least 0.4 g / kg, but preferably is not greater than 5 g / kg, more preferably not greater than 10 g / kg.

Above 10 g / kg, even if the conditioning in step i) is followed by a rinsing step, no further suppression of corrosive delamination after paint build-up is observed, so that any amount of quaternary organic amine beyond this would be uneconomically used in the process according to the invention.

All counterions to the quaternary organic amine are generally all anions, in particular sulfates, nitrates, chlorides, carbonates and organic anions such as alkyl sulfates, alkyl sulfonates, alkyl phosphates and / or alkyl phosphonates.

Surprisingly, the presence of anions (K) has been selected from monoalkyl sulfates, monoalkyl sulfonates, dialkyl phosphates and / or dialkyl phosphonates preferably having not more than 5 carbon atoms, preferably monoalkyl sulfates and / or monoalkyl sulfonates preferably not more than 5 carbon atoms, most preferably methyl sulfate advantageous for a uniform conversion layer formation in step ii) of the method according to the invention, so that their additional presence is correspondingly preferred.

Consequently, the anions (K) are preferably at the same time the anionic constituent of the salt of the quaternary organic amine, so that the corresponding salt therewith is both source of the quaternary amine and source of the anion (K) and the ionic load in the aqueous composition (A ) can thus be reduced to a minimum. Suitable sources of the anions (K) are therefore in addition to the salts of the alkali and / or alkaline earth metals and the corresponding ammonium salts, in particular the corresponding salts of the previously described quaternary organic amines.

According to the invention, the proportion of anions (K) in the aqueous composition (A) is preferably at least 0.05 g / kg, more preferably at least 0.2 g / kg, particularly preferably at least 0.4 g / kg, but the proportion is preferably not greater than 5 g / kg, more preferably not greater than 3 g / kg, each calculated as the equivalent amount of SO ₄ based on the aqueous composition (A). Above 5 g / kg, even if the conditioning in step i) is followed by a rinsing step, no further increase or equalization of the conversion layer formation in step ii) causes, so that any amount beyond the conditioner would be used uneconomically in the process according to the invention.

The pH of the aqueous composition (A) in step i) can be chosen freely as far as possible and is usually in the range from 2 to 14, preferably above 3.0, more preferably above 4.0, particularly preferably above 5, 0, but preferably below 12.0, more preferably below 10.0, and most preferably below 8.0.

In addition, it may be advantageous for the treatment of components which have surfaces of the materials zinc and / or galvanized steel, that the aqueous composition (A) additionally contains an amount of iron ions, which in contact with the zinc surfaces there a thin coating layer causes iron and thus additionally contributes to the standardization of corrosion protection, which is accessible in the process according to the invention in particular for surfaces of the material iron. Such an icing can, according to the doctrine of WO 2008135478 A1 in an acidic medium, preferably in the presence of a reducing agent or according to the teaching of WO 2011098322 A1 in the alkaline medium, preferably in the presence of complexing agents and phosphate ions.

The aqueous composition (A) may contain further components according to the invention. In addition to the pH-regulating substances, these may also be surface-active compounds whose use in an aqueous composition (A) with a cleaning action is preferred.

However, in a preferred embodiment, the aqueous composition (A) contains less than 0.05 g / kg, preferably less than 0.01 g / kg, more preferably less than 0.001 g / kg of surface active compounds not composed of quaternary organic amines are so that the interaction of the surface-active compounds with the surfaces of the metallic materials of the component does not compete with that of the quaternary organic amine and thereby counteracts the respective desired technical effect.

mit M_l: Molmasse der lypophilen Gruppe des Niotensids; M: Molmasse des NiotensidsSurface-active compounds according to the present invention have an HLB value (hydrophilic-lipophilic balance) of less than 5 or more than 10. The HLB value is calculated using the following formula and can assume values from zero to 20 on the arbitrary scale: $$\mathrm{HLB}=20\cdot \left(1-{\mathrm{M}}_{\mathrm{I}}/\mathrm{M}\right)$$

with M _l : molecular weight of the lypophilic group of nonionic surfactant; M: molecular weight of the nonionic surfactant

Furthermore, it is preferred if the aqueous composition (A) in step i) of the process according to the invention is less than 0.5 g / kg, more preferably less than 0.1 g / kg, particularly preferably less than 0.05 g / kg of dissolved and / or dispersed organic polymers which are not quaternary organic amines. This ensures, as before, the presence of surface-active compounds that the interaction of such polymers with the surfaces of the metallic materials of the component does not compete with that of the conditioner or quaternary organic amines additionally present in a preferred embodiment of the present invention and thereby each desired technical effect is counteracted. An organic polymer dissolved or dispersed in this connection of the invention has a weight average molecular weight M _w of at least 5000 g / mol and in the aqueous phase has an average particle diameter of less than 1 μm. The average particle diameter can be determined according to ISO 13320: 2009 by means of laser light diffraction from cumulative particle size distributions as a so-called D50 value directly in an aqueous composition (A) at 20 ° C.

In a preferred method according to the invention, no conversion layer is produced on the surfaces of the metallic components in step i). Accordingly, the aqueous composition (A) does not contain any components in such an amount that it is capable of forming a conversion layer on a surface of a metallic material of the component during the period of time provided for the conditioning in step i). A conversion layer in the course of the conditioning in step i) of the method according to the invention is present when a cover layer is produced wet-chemically on the respective surface of the metallic material, the phosphates, oxides and / or hydroxides of elements of the titanium group, vanadium group and / or chromium group or phosphates of the elements calcium, iron and / or zinc in one Coating layer of at least 5 mg / m ² based on the respective sub-group element or of at least 50 mg / m ² drawn on the element phosphorus. The corresponding subgroup elements can be determined quantitatively by X-ray fluorescence analysis (XRF), while the layer coverage with respect to the element phosphorus can be determined quantitatively by pickling the surfaces of the metallic materials in aqueous 5% by weight CrO ₃ and subsequent atomic emission spectroscopy (ICP-OES).

In order to prevent the formation of a conversion layer on the surfaces of the metallic materials of the component, a method according to the invention is preferably characterized in that the aqueous composition (A) in step i) is less than 0.005 g / kg, particularly preferably less than 0.001 g / kg to water-soluble compounds of the elements Zr, Ti and / or Si based on the respective element, preferably less than 1 g / kg of water-soluble compounds of the elements Zn, Mn and Ca based on the respective element and / or preferably less than 0.05 g / kg, more preferably less than 0.01 g / kg of free fluoride determined with a fluoride-sensitive electrode at 20 ° C contains. In a further preferred embodiment, the total content of fluorides in the aqueous composition (A) is less than 0.05 g / kg, more preferably less than 0.02 g / kg, particularly preferably less than 0.01 g / kg. The total fluoride content (total fluoride) is determined in a TISAB-buffered aliquot of the aqueous composition (A) with a fluoride-sensitive electrode at 20 ° C (TISAB: "Total Lonic Strength Adjustment Buffer"), wherein the volume-related mixing ratio of buffer to aliquots of the aqueous composition (A) is 1: 1. The TISAB buffer is prepared by dissolving 58 g of NaCl, 1 g of sodium citrate and 50 ml of glacial acetic acid in 500 ml of deionized water (κ <1 μScm ^-1 ) and adjusting to pH 5.3 by 5N NaOH and making up to total volume of 1000 ml again with deionized water (κ <1 μScm ^-1 ).

In method step ii), an amount of active components sufficient to form a conversion layer should be present in the acidic aqueous composition (B). In this regard, it is advantageous if the aqueous composition (B) in step ii) preferably at least 0.01 g / kg, more preferably at least 0.05 g / kg, particularly preferably at least 0.1 g / kg of water-soluble compounds of the elements Zr , Ti or Si based on the respective element Zr, Ti or Si. In In this context, it should be noted that such compounds according to the present invention are considered to be water-soluble if their solubility in deionized water (κ <1μScm ^-1 ) is at least 1 g / L at 20 ° C.

For economic reasons, it is furthermore advantageous if the total proportion of these compounds, based on the elements Zr, Ti and Si, is preferably not greater than 0.5 g / kg, since higher contents usually do not further improve the corrosion-protecting properties of the conversion layer, but due to the higher deposition kinetics complicate the control of the coating layer with respect to these elements.

Due to the conditioning in step i) of the process according to the invention, fluorine-free water-soluble compounds of the elements Zr, Ti or Si in the aqueous composition (B) are also suitable for producing a sufficient conversion of the surfaces of the metallic materials of the component and are therefore preferred. Particularly preferred representatives are (NH ₄ ) ₂ Zr (OH) ₂ (CO ₃ ) ₂ , ZrO (NO ₃ ) ₂ or TiO (SO ₄ ) or silanes having at least one covalent Si-C bond.

As already stated, the use of complex fluorides and also free fluorides in step ii) for effecting the conversion of the surfaces of the metallic materials of the components can be dispensed with in the present inventive method due to the conditioning in step i). Accordingly, those methods are preferred according to the invention in which the proportion of free fluoride in the aqueous composition (B) with increasing preference is less than 0.05 g / kg, 0.01 g / kg, 0.001 g / kg and 0.0001 g / kg and most preferably no free fluoride is contained. Furthermore, in a preferred embodiment of the method according to the invention, the total proportion of fluorides (total fluoride) in the aqueous composition (B) with increasing preference is less than 0.05 g / kg, 0.02 g / kg, 0.01 g / kg, 0.001 g / kg and 0.0001 g / kg and most preferably no fluoride is included. The proportion of free fluoride and the total content of fluorides can be determined analogously to the procedure for determining the same parameters in the aqueous composition (A).

In combination with the conditioning in step i), the best results in terms of corrosion protection are achieved if copper ions are present in the aqueous composition (B) in step ii). In a particularly preferred embodiment of the process according to the invention, therefore, the aqueous composition (B) additionally contains water-soluble compounds which are a source of copper ions, preferably in the form of water-soluble salts, for example copper sulfate, copper nitrate and copper acetate. In this context, it should be noted that such compounds according to the present invention are considered to be water-soluble if their solubility in deionized water (κ <1μScm ^-1 ) is at least 1 g / L at 20 ° C.

The content of copper of water-soluble compounds in the aqueous composition (B) is preferably at least 0.001 g / kg, more preferably at least 0.005 g / kg. However, the content of copper ions is preferably not more than 0.1 g / kg, more preferably not more than 0.05 g / kg, otherwise the deposition of elemental copper begins to dominate over the conversion layer formation.

The pH of the aqueous composition (B) is preferably in the acidic range, more preferably in the range of 2.0 to 5.0, particularly preferably in the range of 2.5 to 3.5.

It is further preferred if the aqueous composition (B) contains nitrate ions as an accelerator of the conversion layer formation, wherein the proportion of nitrate ions is preferably at least 0.5 g / kg, but for reasons of economy preferably does not exceed 4 g / kg.

Surprisingly, the success of the invention occurs largely independently of the performance of one of the conditioning in step i) immediately following rinsing and / or drying step. Differences in the performance of the process caused by an intermediate rinsing step can be regularly absorbed by a moderate increase in the concentration of quaternary organic amine and the anions (K) contained in the aqueous composition (A). The general suitability of the method to solve the problem underlying the invention, in any case remains unaffected by the performance of a rinsing and / or drying step between steps i) and ii). However, in terms of process technology, it is preferable for step i) in a process according to the invention to be followed directly by a rinsing step to separate the active components in the individual treatment steps, wherein preferably no drying step takes place before step ii).

A rinsing step according to the invention is always the removal of water-soluble residues, not firmly adhering chemical compounds and loose solid particles from the component to be treated, which are removed from a previous wet-chemical treatment step with the adhesive on the component wet film, by means of a water-based liquid medium. The water-based liquid medium contains no chemical components that cause a significant surface coverage of the components made of metallic materials with subgroup elements, semi-metal elements or polymeric organic compounds. In any case, such a significant surface coverage is present when the liquid medium of the sink is depleted by at least 10 milligrams per square meter of the flushed surfaces, preferably by at least 1 milligram per square meter of the flushed surfaces, based on these components relative to the respective element or the respective polymeric organic compound without taking account of gains due to carryover and losses due to removal of wet films adhering to the component.

According to the invention, a drying step is any method step in which the provision and use of technical means is intended to dry the aqueous liquid film adhering to the surface of the component, in particular by supplying thermal energy or impressing an air flow.

The components that are treated in the method according to the invention, at least partially made of metallic materials. Preferred metallic materials for which an improvement in the properties of the conversion layer as a lacquer adhesion base is clearly evident are iron and alloys of iron, in particular steel. In this context, alloys of iron are materials which are formed by at least 50 at.% Of the respective material of iron atoms. On surfaces of iron and its alloys, a significant improvement in corrosion protection occurs in the corrosive infiltration of paint defects that even largely independent of whether immediately after the conditioning in step i) followed by a rinsing and / or drying step.

In the process according to the invention, step ii) is preferably followed by the application of an organic coating, especially a powder coating or dip coating, which in turn is preferably an electrodeposition paint. The electrodeposition coating preferably follows a rinsing step, but particularly preferably no drying step.

In a preferred embodiment of the method according to the invention, the component at least partially surfaces of the materials iron and / or steel, preferably at least 50%, more preferably at least 80% of the surface of the component, the surfaces of metallic materials, from surfaces of the materials iron and / or steel are formed.

In principle, however, composite structures and in particular components which, in addition to surfaces of the materials iron and / or steel, also have surfaces of the materials zinc and / or galvanized steel and aluminum, which may optionally be additionally phosphated, can be treated in the process according to the invention.

Furthermore, in the case where the component has surfaces of the materials zinc and / or galvanized steel, it is generally preferred that same surfaces be treated with a thin amorphous layer containing iron, so that the surfaces of these materials have an equally effective conditioning in step i ) of the method according to the invention, as is commonly found for the surfaces of the materials iron and / or steel. In this regard, a particularly effective icing of the surfaces of zinc and / or galvanized steel is disclosed in the published patent applications WO 2011098322 A1 and WO 2008135478 A1 each described as a wet-chemical process, which can be applied in an equivalent manner immediately before carrying out the process step i) according to the invention. In this respect, it is preferred for inventive method, in which the component comprises at least partially of the materials zinc and / or galvanized steel, that the surfaces of the component, which are made of these materials, an iron occupancy of at least 20 mg / m ² , however preferably not more than 150 mg / m ² .

EXAMPLES

In the following, steel sheets (CRS) are subjected to a multi-stage process for corrosion-protective pretreatment. The suitability of such pretreated and provided with a paint layer metal sheets to represent a good Lackhaftgrund is tested in a test according to DIN EN ISO 4628-8 for corrosive delamination.

1. (A) Alkalische Reinigung und Entfettung:
   Eintauchen des Bleches unter Rühren in einen alkalischen Reiniger zusammengesetzt aus 4 Gew.-%iger Ridoline® 2011 (Fa. Henkel) und 0,4 Gew.-%iger Ridosol® 1270 (Fa. Henkel) für 5 Minuten bei 56°C;
2. (B) Spüle mit Brauchwasser und anschließend mit entionisiertem Wasser (κ < 1µScm^-1) bei jeweils 20 °C;
3. (C) Konditionierung durch Eintauchen des Bleches für 1 Minute bei 35°C in eine Zusammensetzung enthaltend eine vorgegebene Menge eines "Konditionierers" in entionisertem Wasser (κ < 1µScm^-1) ohne weitere Zugabe pH-Wert verändernder Substanzen;
4. (D) ggf. Spüle mit entionisertem Wasser bei 20 °C (κ < 1µScm^-1)
5. (E) Konversionsbehandlung durch Eintauchen des Bleches für 3 Minuten bei 35 C in eine wässrige Zusammensetzung mit einem pH-Wert von ca. 2,6 enthaltend 1,6 g/kg an ZrO(NO₃)₂

The general procedure for pretreatment and coating consists of the successive obligatory and optional steps (A) - (E):

1. (A) Alkaline cleaning and degreasing:
   Immersion of the sheet with stirring in an alkaline cleaner composed of 4% by weight Ridoline® 2011 (Henkel) and 0.4% by weight Ridosol® 1270 (Henkel) for 5 minutes at 56 ° C .;
2. (B) rinse with service water and then with deionized water (κ <1μScm ^-1 ) at 20 ° C;
3. (C) conditioning by immersing the plate for 1 minute at 35 ° C in a composition containing a predetermined amount of a "conditioner" in deionized water (κ <1μScm ^-1 ) without further addition of pH-changing substances;
4. (D) if necessary, rinse with deionized water at 20 ° C (κ <1μScm ^-1 )
5. (E) Conversion treatment by immersing the sheet for 3 minutes at 35 ° C in an aqueous composition having a pH of about 2.6 containing 1.6 g / kg of ZrO (NO ₃ ) ₂

After the conversion treatment in process step (E), the respective sheet was first rinsed with deionized water (κ <1 μScm ^-1 ) at 20 ° C. and then coated with a cathodic dip coating and dried at 180 ° C. (dry layer thickness: 18-20 μm, CathoGuard ® 800 from BASF Coatings).

Table 1 below shows the various organic compounds used in the conditioning in step (C).

The composition C1 in Table 1 is not according to the invention. Tab. 1 Used compositions in conditioning conditioner Quantity in g / kg anion cation PH value C1 2 * - - 4.3 C2 2.5 chloride 1-ethyl-3-methylimidazolium 5.5 C3 2.5 methyl sulfate 1,2,3-trimethylimidazolium 7.5 * Polyvinyl pyrollidone (Mw ~ 160,000 g / mol)

It is clear that a steel coating in the range of 0-20 mg / m ² of zirconium can not be reproducibly produced on steel sheets when attempting a conversion treatment based on a fluoride-free composition in step (D) (entry 1). Likewise, conditioning on the basis of a pretreatment with an aqueous solution containing polyvinylpyrollidone (No. 2) fails because the conversion layer formation is neither increased nor reproducible overall. Only the addition of imidazolium salts causes a significant conversion of the steel surfaces, so that a usually sufficient coating thickness for a good corrosion protection and Lackhaftgrund in the range of 15-60 mg / m ^{2 is} easily achieved (# 3-4). If, in addition, methyl sulfate anion is contained, a strong acceleration of the conversion layer formation is also observed (entry 4).

The corrosion results and the associated process sequence are given in Table 2.

Examples No. 1 and No. 2 in Table 2 are not according to the invention. Tab. 2 Corrosion results on the corresponding pretreated and electrocoated sheets No. process sequence Corrosion ¹ U2 / mm Coating ² Zr mg / m ² 1 ABDE 3.3 10 ± 10 ^# 2 AB-C1-DE 3.3 6 ± 5 3 AB-C2-DE 2.5 15 ± 3 4 AB-C3-DE 2.2 57 ± 9 ¹ Corrosion on the cut in accordance with DIN EN ISO 4628-8, after removal from storage in the AC climate test VW in accordance with PV 12103
² Average and standard deviation over 5 plates, wherein the average value of 6 single measurements on the same plate was used for the coating of each individual plate and the determination in each case by means of X-ray fluorescence analyzer Niton® XL3t 900 (Thermo Fisher Scientific) with an analysis area of 50 mm ² was made.
# Mean and standard deviation over 62 sheets

Claims (13)

1. A multi-stage method for the anti-corrosion pretreatment of components made at least in part of metal materials, in which firstly

   i) at least part of the surfaces of the component that are made of the metal materials is brought into contact with an aqueous composition (A) containing a dissolved and/or dispersed salt of a quaternary organic amine selected from heterocycles comprising at least one quaternary nitrogen heteroatom and the following structural formula (I):

   

   having the functional groups R¹, R² and R³, which are each selected from hydrogen, branched or unbranched aliphatic compounds having no more than 6 carbon atoms or the functional group -(CR₄R₄)_x-[Z(R₄)_(p-1)-(CR₄R₄)_y]_n-Z(R₄)_p, wherein Z in each case is selected from oxygen or nitrogen and p assumes the value 2 if Z is nitrogen and otherwise is equal to 1, and x and y are each natural numbers from 1 to 4 and n is also a natural number from 0 to 4 and R₄ is selected from hydrogen or branched or unbranched aliphatic compounds having no more than 6 carbon atoms, with the proviso that at least one of the functional groups R² or R³ is not selected from hydrogen;
   having Y as a ring-constituting divalent functional group having no more than 5 bridge atoms, wherein it is not possible for more than one hetero-bridge atom which is different from carbon atoms and is selected from oxygen, nitrogen or sulfur to be a bridge atom, and the carbon atoms in turn are substituted, independently of one another, with functional groups R¹ or functional groups by means of which aromatic homocycles having no more than 6 carbon atoms are anellated,
   and subsequently

   ii) at least the same part of the surfaces of the component that are made of the metal materials is brought into contact with an aqueous composition (B) containing one or more water-soluble compounds of the elements Zr, Ti and/or Si.
2. The method according to claim 1, characterized in that the ring-constituting divalent functional group Y is selected from ethylene, ethenediyl, 1,3-propanediyl, 1,3-propenediyl, 1,4-butanediyl, 1,4-butenediyl, 1,4-butadienediyl, -CH=N-, -CH₂-NH-, (N,N-dimethylene)amine or (N-methylene-N-methylylidene)amine, preferably from ethenediyl, 1,4-butadienediyl, -C=N- or (N-methylene-N-methylylidene)amine, particularly preferably from ethenediyl or -C=N- and more particularly preferably from ethenediyl, it being possible in each case for hydrogen covalently bonded to carbon atoms to be substituted by the remaining representatives of a functional group R¹.
3. The method according to one or both of the preceding claims, characterized in that the quaternary organic amine is selected from 1,2,3-trimethylimidazolium, 1-methyl-3-methylimidazolium, 1-ethyl-3-methylimidazolium, 1-isopropyl-3-methylimidazolium, 1-propyl-3-methylimidazolium, 1-(n-butyl)-3-methylimidazolium, 1-(isobutyl)-3-methylimidazolium, 1-methoxy-3-methylimidazolium, 1-ethoxy-3-methylimidazolium, 1-propoxy-3-methylimidazolium, preferably from 1,2,3-trimethylimidazolium.
4. The method according to one or more of the preceding claims, characterized in that composition (A) in step i) additionally contains anions (K), which are selected from monoalkyl sulfates, monoalkyl sulfonates, dialkyl phosphates and/or dialkyl phosphonates having preferably no more than 5 carbon atoms, preferably from monoalkyl sulfates and/or monoalkyl sulfonates having preferably no more than 5 carbon atoms, particularly preferably from methyl sulfate.
5. The method according to one or more of the preceding claims, characterized in that the proportion of the quaternary organic amine in composition (A) is at least 0.05 g/kg, preferably at least 0.2 g/kg, particularly preferably at least 0.4 g/kg, but preferably no greater than 20 g/kg, particularly preferably no greater than 10 g/kg.
6. The method according to one or more of the preceding claims, characterized in that a conversion coating is not produced on the surfaces of the metal components in step i).
7. The method according to one or more of the preceding claims, characterized in that composition (A) contains less than 0.05 g/kg, preferably less than 0.01 g/kg, particularly preferably less than 0.001 g/kg, of surface-active compounds that are not composed of quaternary organic amines.
8. The method according to one or more of the preceding claims, characterized in that composition (B) in step ii) contains at least 0.01 g/kg, preferably at least 0.05 g/kg, particularly preferably at least 0.1 g/kg, of water-soluble compounds of the elements Zr, Ti or Si, based on the particular element.
9. The method according to one or more of the preceding claims, characterized in that composition (B) in step ii) contains less than 0.05 g/kg, preferably less than 0.01 g/kg, particularly preferably less than 0.001 g/kg, of free fluoride.
10. The method according to one or more of the preceding claims, characterized in that the total proportion of fluorides in composition (B) in step ii) is less than 0.05 g/kg, preferably less than 0.01 g/kg, particularly preferably less than 0.001 g/kg, and more particularly preferably less than 0.0001 g/kg.
11. The method according to one or more of the preceding claims, characterized in that before step i), the components are cleaned and degreased, preferably by being brought into contact with aqueous compositions containing surface-active compounds.
12. The method according to one or more of the preceding claims, characterized in that a rinsing step and preferably no drying step takes place between method steps i) and ii).
13. The method according to one or more of the preceding claims, characterized in that the component has, at least in part, surfaces made of the materials iron and/or steel, and preferably at least 50%, particularly preferably at least 80%, of the surface made of metal materials of the component is formed by surfaces made of the materials iron and/or steel.