Post-rinse pretreatment with aqueous compositions containing alkaline earth metal ions - Patent Application 20070122999

Abstract

The present invention relates to a method for pretreating at least one metal surface of a substrate, the method comprising at least steps 1 and 2, which comprise contacting at least one surface of the substrate with an acidic aqueous composition AAC to at least partially form a film on the surface, the acidic aqueous composition AAC containing at least fluoride anions, preferably in an amount ranging from 10 to 2000 mg / L calculated as fluorine, and further containing at least one metal cation selected from the group consisting of Ti, Zr, Hf, and mixtures thereof, and step 2, rinsing the film obtained after step 1 with an aqueous composition AC containing at least one alkaline earth metal ion different from the acidic aqueous composition AAC, before optional curing and / or drying of the film. The present invention also relates to methods for applying at least one coating film to at least one surface of a substrate that has undergone the pretreatment method, substrates obtainable by these methods, methods for using the aqueous composition AC for various purposes, and kits of parts containing the acidic aqueous composition AAC and the aqueous composition AC.

Description

[Technical Field]

[0001] The present invention relates in particular to a method for pretreating at least one surface of a substrate, the surface being at least partially made of at least one metal and / or its alloy, the method comprising the step of using a chemical pretreatment composition containing fluoride anions, followed by a post-rinsing step. Furthermore, the present invention relates to a method for applying at least one coating film, such as an electrodeposition coating film, onto the surface of a substrate pretreated according to the pretreatment method, and to a substrate obtainable by one of these methods. [Background technology]

[0002] Before a substrate having a metal surface is lacquered, i.e., before a permanent coating layer is applied to the surface, it is now commonly subjected to a rust-preventive and adhesion-promoting chemical pretreatment using an appropriate chemical pretreatment composition. Often, an aqueous solution based on a metal complex fluoride, such as a titanium and / or zirconium complex fluoride, is used as such a chemical pretreatment composition to produce a conversion coating layer on the metal surface of the substrate. As mentioned above, such a chemical pretreatment step is carried out before subsequent coating steps, such as an electrodeposition coating step, coating with a primer filler, base coat, and clear coat or powder coat. After subjecting the metal surface of the substrate to chemical pretreatment, the resulting conversion coating is often subsequently rinsed in a "post-rinse" step using deionized water to remove excess components of the chemical pretreatment composition. To further improve the rust-preventive properties of the conversion-treated surface of a metal substrate, particularly in the case of substrates made of cold-rolled steel (CRS), and to avoid flammable rust, it is known to use an alkaline aqueous composition or a nitrite-containing aqueous composition as a post-rinse composition instead of deionized water.

[0003] After chemical pretreatment, subsequent coating steps are usually carried out as previously described herein. In particular, when substrates intended for use in the automotive industry have undergone said chemical pretreatment, an electrodeposited coating layer is usually then applied over the converted surface for further protection against corrosion. Generally, there are anodic and cathodic depositable electrodeposited coating material (electrocoat) compositions, but cathodic depositable materials are the most important in industrial coatings, especially automotive coatings.

[0004] Depending on the chemical pretreatment method and parameters used, and also depending on the type of metal(s) on the metal surface of the substrate used, and particularly depending on the type and components of the chemical pretreatment composition used, undesirable surface defects / differences in the surface properties of the resulting conversion-treated substrate may be observed. These differences in the surface properties of the substrate may lead to differences in the application process when the electrodeposition coating material composition is subsequently applied to that surface. In particular, as a result of the different surface properties of the conversion-treated substrate, differences in the film build height ("mapping") of the electrodeposition coating film during application, excessive (too thick) electrodeposition coating layer thickness, and / or other cosmetic defects may occur and be observed. This is particularly true when the chemical pretreatment composition used contains fluoride, because fluoride contained in the conversion coating layer present on the metal surface may migrate into the applied electrocoat material and adversely affect the film build height, cause mapping, and / or cause the aforementioned cosmetic defects, especially if the metal surface, or at least a region of that surface, is in contact with the pretreatment composition for too long a period of time. The occurrence of different film build heights of electrocoat materials within a single layer is undesirable because these differences must be covered and smoothed by subsequently applied coating material compositions, such as primer coatings, to prevent telegraphing across the entire automotive coating surface. Such covering and / or smoothing often requires costly post-processing steps that must be performed manually, for example, by manual polishing, after the electrocoat material has already been applied. Similarly, the occurrence of the aforementioned appearance defects is undesirable, especially since they may remain visible even when additional coating layers, including topcoats, are applied. An excessively thick electrodeposited coating layer is also undesirable, as this can lead to unacceptable surface roughness of the layer, making it difficult to smoothly apply additional coating layers on top of it.

[0005] Therefore, there is a need to provide a chemical pretreatment method using a fluoride anion-containing chemical pretreatment composition that allows for the formation of a homogenous film build without mapping during application of a subsequently applied electrodeposition coating material onto the metal surface of the chemically pretreated substrate, and in particular without the occurrence of optical defects even if at least a portion of the surface of the substrate is in contact with the chemical pretreatment composition for too long a period of time. Summary of the Invention [Problem to be solved by the invention]

[0006] It is therefore an underlying object of the present invention to provide a chemical pretreatment method using a fluoride anion-containing chemical pretreatment composition that allows for the formation of a homogeneous film build during the application of a subsequently applied electrodeposition coating material onto the metal surface of the chemically pretreated substrate without mapping, and in particular without the occurrence of optical defects, even if at least a portion of the surface of the substrate is in contact with the chemical pretreatment composition for too long a period of time. [Means for solving the problem]

[0007] This object has been solved by the subject matter of the present claims and the preferred embodiments thereof disclosed herein, ie the subject matter described herein.

[0008] A first subject of the present invention is a method for pretreating at least one surface of a substrate, said surface being at least partially made of at least one metal and / or its alloy, the method comprising at least steps 1) and 2), namely 1) contacting at least one surface of a substrate, at least partially, with an acidic aqueous composition AAC to at least partially form a film on said surface, said acidic aqueous composition AAC containing at least fluoride anions, preferably in an amount ranging from 10 to 2000 mg / L calculated as fluorine, and more preferably at least one metal cation selected from the group consisting of titanium ions, zirconium ions, hafnium ions and mixtures thereof; and 2) rinsing the film obtained after step 1) with an aqueous composition AC (different from the acidic aqueous composition AAC) containing at least one alkaline earth metal ion, before any curing and / or drying of said film; Includes.

[0009] A further subject of the present invention is a method for applying at least one coating film onto at least one surface of a substrate, said method comprising at least steps 1) and 2) as defined herein and below, and further step 3), namely 3) applying a coating material composition comprising at least one film-forming polymer onto the optionally dried and / or optionally cured film, which film can be obtained, in turn, after carrying out a rinsing step 2) and, optionally, after further drying and / or curing of the film obtained after the rinsing step 2); Includes.

[0010] Preferably, the coating material composition applied in step 3) is an electrodepositable, preferably cathodically electrodepositable, coating material composition, and the at least one film-forming polymer present therein is preferably an electrodepositable, preferably cathodically electrodepositable, polymer.

[0011] A further subject of the present invention is a substrate obtainable by the inventive pretreatment method comprising at least steps 1) and 2), or by the inventive method of applying at least one coating film onto at least one surface of a substrate comprising at least steps 1) and 2), or by the inventive pretreatment method also comprising step 3).

[0012] A further subject of the present invention is the use of an aqueous composition AC as defined herein and hereinafter, For example, in relation to step 2) of the pretreatment method of the present invention, 1. A method of use for rinsing a film obtainable from at least partially applying an acidic aqueous and fluoride anion-containing composition, preferably an acidic aqueous composition AAC as defined herein and below, onto at least one surface of a substrate, for example in connection with step 1) of the pretreatment method of the present invention, said surface being at least partially made of at least one metal and / or alloy thereof, and rinsing being carried out before any curing and / or drying of said film, and / or 1. A method of use for at least partially reducing the fluoride content of a film obtainable from applying an acidic aqueous and fluoride anion-containing composition, preferably an acidic aqueous composition AAC as defined herein and hereinafter, at least partially onto at least one surface of a substrate, for example in connection with step 1) of the pretreatment method of the present invention, preferably by rinsing said film with an aqueous composition AC, preferably before any curing and / or drying of said film, wherein said surface is at least partially made of at least one metal and / or alloy thereof, and / or A method of use for improving the homogeneity of the film build and / or reducing the mapping of a coating film CF in at least one of its regions by rinsing said film with an aqueous composition AC, preferably before any curing and / or drying of said film and before application of a coating film CF, the coating film CF resulting from applying an electrodeposition coating material composition onto a cured or dried film, which in turn can be obtained from applying, at least in part, an acidic aqueous and fluoride anion-containing composition, preferably an acidic aqueous composition AAC as defined herein and below, for example in connection with step 1) of the pretreatment method of the present invention, onto at least one surface of a substrate, said surface being at least in part made of at least one metal and / or alloy thereof.

[0013] A further subject of the present invention is an acidic aqueous composition AAC, as defined herein and below, containing at least fluoride anions, for example in connection with step 1) of the pretreatment method of the present invention; and As defined herein and below, for example in connection with step 2) of the pretreatment method of the present invention, an aqueous composition AC containing at least one alkaline earth metal ion and different from the acidic aqueous composition AAC is provided. It is a kit of parts including:

[0014] Particularly surprisingly, it has been found that the pretreatment method of the present invention, despite the presence of fluoride anions in the chemical pretreatment composition used in step 1), allows for uniform film formation when applying a subsequently applied electrodeposition coating material onto the chemically pretreated metal surface of a substrate, regardless of the metal substrate material used. Unexpectedly, it has been found that, as a result of the chemical pretreatment step 1), undesirable film formation deviations (mapping) due to different surface properties of the substrate are not observed, or at least are significantly reduced, when and during application of the electrodeposition coating material composition onto the pretreated surface (which surface has previously undergone rinsing step 2). In particular, it has been found that this unexpected technical effect is particularly a result of the specific aqueous composition AC used as the rinsing composition in step 2) and the content of at least one alkaline earth metal ion present therein. It has been found that the presence of at least one alkaline earth metal ion in the rinse composition used in step 2) can reduce the amount of fluoride incorporated into the pretreated film (conversion film) obtained after step 1), and consequently can prevent or at least significantly reduce any adverse effects of fluoride anions on the electrocoat film build during electrocoat application. In particular, upon application of the electrocoat composition, such as by immersion of the pretreated substrate in an electrodeposition bath, less fluoride migration into the electrocoat film is observed, resulting in reduced electrical conductivity upon application of a voltage and, thus, advantageously, a thinner electrodeposited coating layer.

[0015] Furthermore, it has been found that the film build uniformity of the subsequently applied electrodeposition coating material composition is improved, and that the corrosion protection of the substrate is not adversely affected. Furthermore, it has been found that negative optical defects, such as the occurrence of runners, are not observed in the layer resulting from the subsequently applied electrodeposition coating material composition, particularly because the local high fluoride concentrations in the pretreatment obtained after step 1) are prevented by performing the rinsing step 2). Furthermore, it has been found that other properties of the layer resulting from the subsequently applied electrodeposition coating material composition, such as surface roughness, are likewise not adversely affected, and in particular, excessively high layer thicknesses can be avoided.

[0016] Furthermore, it has been surprisingly found that the aforementioned unexpected results are observed even when at least a portion of the surface of the substrate is in contact with the chemical pretreatment composition for an excessively long period of time. Thus, the method of the present invention overcomes the runner and mapping coating defects observed with conventional prior art chemical pretreatment methods, and enables the formation of a thinner, smoother layer of electrodeposited coating material. DETAILED DESCRIPTION OF THE INVENTION

[0017] The term "comprises" in the sense of the present invention preferably has the meaning "consisting of", for example in relation to compositions AC and AAC. For example, with respect to compositions AC and AAC, in addition to all essential components present therein, it is also possible for one or more of the further optional components specified below to be included therein. All components may in each case be present in their preferred embodiments, as specified below.

[0018] The percentages and amounts by weight (wt%) of any of the components shown below present in each composition are in each case based on the total weight of each composition and add up to 100 wt%.

[0019] Pretreatment method A first subject of the present invention is a method for pretreating at least one surface of a substrate, said surface being at least partially made of at least one metal and / or its alloy, said method comprising at least steps 1) and 2).

[0020] The term "pretreatment" as used herein is preferably used in accordance with the term "surface pretreatment" defined in the Römpp Lexikon "Lacke und Druckfarben" (Publisher: Ulrich Zorll, Editor: Hans-Juergen P. Adler-Stuttgart; New York: Thieme, 1998; term: "Oberflaechenvorbehandlung" page 417). For metal substrates or substrates with metal surfaces, according to DIN 50902:1994-07, the first step(s) of the surface treatment are often one or more (chemical) cleaning step(s) with aqueous or non-aqueous cleaning compositions (also referred to as "surface treatment step(s)").

[0021] The term "chemical pretreatment" is used in accordance with EN ISO 4618:2006 (E / F / D) (term: 2.41 "chemical pretreatment") to refer to a chemical process applied to a surface before applying a coating material. According to this standard, treatments such as chromite treatment and phosphating, which are encompassed by the term "chemical conversion treatment," belong to chemical pretreatment and are therefore distinct from the (subsequent) coating step in which a coating material, i.e., a coating composition, such as a powder coating composition, an electrodeposition coating composition, or an aqueous or non-aqueous liquid coating material, is applied. In addition to chemical conversion treatments such as chromite treatment and phosphating, chemical surface pretreatments can generally be achieved with passivating compositions and film-forming compositions, including aqueous fluoride anion-containing compositions such as composition AAC, which is primarily used as the chemical pretreatment composition in step 1).

[0022] In accordance with the above-mentioned internationally valid definition of the "pretreatment" of metal substrates, the pretreatment method according to the invention preferably comprises, in addition to the chemical pretreatment step 1) and the rinsing step 2), a surface preparation cleaning step. Preferably, the pretreatment method does not include a step involving treatment with chromium ions, such as Cr(VI) ions and / or Cr(III) ions. Preferably, chemical pretreatment step 1) is the only chemical pretreatment step of the pretreatment method. Thus, preferably, no other chemical pretreatment composition other than composition AAC is used.

[0023] Base material The substrate has at least one surface, which is at least partially made of at least one metal and / or alloy thereof, and therefore the substrate has at least one metallic surface.

[0024] Preferably, at least one surface of the substrate is at least partially made from at least one metal and / or alloy thereof, more preferably at least partially made from steel, preferably selected from the group consisting of bare steel, cold rolled steel (CRS), hot rolled steel, galvanized steel, such as hot dip galvanized steel (HDG), alloy galvanized steel and aluminized steel (e.g. Galvalume®, Galvannealed® or Galfan®), aluminum, aluminum alloys, such as aluminum magnesium alloy, aluminum magnesium silicon alloy, aluminum copper alloy, aluminum zinc alloy, aluminum zinc copper alloy, and zinc alloys, such as Zn / Mg alloy, Zn / Ni alloy, Zn / Mg / Al alloy.

[0025] Preferably, not only is at least one surface of the substrate metallic, but the substrate itself is metallic. The term "metallic substrate" encompasses any substrate having a surface comprising one or more pure metals and / or alloys thereof, in accordance with the general understanding of the term. When a substrate comprises regions of different metals, such a substrate is referred to herein as a "multi-metallic substrate," a subclass of metallic substrates.

[0026] Preferably, the substrate used is a conductive substrate, which is commonly used and known to those skilled in the art. The substrate can have any geometric shape and form, such as a coil or a sheet, and can also be used as an automobile part, including a wheel part, including an electric automobile part, such as a battery housing, and other workpieces. A particularly suitable substrate is a part of a production automobile body or a complete automobile body.

[0027] Optional process to be performed before process 1) Prior to step 1), one or more of the following optional steps may be performed in this order: Step A-1): cleaning the surface of the substrate and optionally rinsing it thereafter; Step B-1): A step of subjecting the surface of the substrate to acidic or alkaline pickling, i.e., etching, and then rinsing the surface of the substrate; Step C-1): contacting the surface of the substrate with an aqueous composition comprising at least one mineral acid (said aqueous composition is different from Compositions AC and AAC), or alternatively with an aqueous alkaline composition or a pH-neutral aqueous composition (each of these compositions is also different from Composition AC); and Step D-1): A step of rinsing the surface of the substrate obtained after contact in step C-1) and / or B-1).

[0028] Alternatively, steps A-1) and B-1) may be carried out in one step, which is preferred. Preferably, both steps A-1) and B-1) are carried out.

[0029] The optional step C-1) preferably serves to remove oxides, undesirable alloying elements, skins, brushing dust, etc. from the surface of the substrate, thereby further activating the surface for the subsequent conversion treatment in step 1).

[0030] Preferably, the at least one mineral acid of the composition in step C-1) is sulfuric acid and / or nitric acid, more preferably sulfuric acid.

[0031] The rinsing step D-1) and any rinsing that is part of step A-1) are preferably carried out using deionized water or tap water. Preferably, step D-1) is carried out using deionized water.

[0032] Step 1) and Composition AAC According to step 1) of the pretreatment method, at least one surface of a substrate is at least partially contacted with an acidic aqueous composition AAC containing at least fluoride anions to at least partially form a film on said surface. The acidic aqueous composition AAC represents a chemical pretreatment composition. By carrying out step 1), a conversion coating is formed on the surface of the substrate that has been contacted with the acidic aqueous composition AAC.

[0033] The term "at least partially" preferably means in this context, in accordance with the general understanding of the term, that in some cases it may be desirable or sufficient to contact less than the entire surface of the substrate with the chemical pretreatment composition AAC. If only a portion of the metal surface is contacted with the respective composition, it is typically the same portion in all steps of the method. However, it is generally desirable to contact the entire surface of the metal substrate with the respective composition.

[0034] The "contacting" according to step 1) can be a spraying, dipping or roll coating step. Composition AAC can also be applied manually by immersing the surface in water or by wiping or brushing. Spraying, dipping or roll coating are preferred.

[0035] The treatment time, i.e., the time during which the surface is in contact with the acidic aqueous composition AAC in step 1), is preferably 15 seconds to 20 minutes, more preferably 30 seconds to 10 minutes, and most preferably 45 seconds to 5 minutes, for example 1 minute to 3 minutes.

[0036] The temperature of the acidic aqueous composition AAC used in step 1) is preferably 5 to 50°C, more preferably 15 to 45°C, and most preferably 25 to 40°C.

[0037] The acidic aqueous composition AAC can be used as a dip-coat bath. However, as outlined above in connection with step 1), it can also be applied by virtually any conventional coating procedure, such as spray coating, roll coating, brushing, wiping, etc. Spraying and dipping are preferred.

[0038] The acidic aqueous composition AAC used in step 1) preferably does not contain chromium ions such as Cr(VI) and / or Cr(III) cations. The acidic aqueous composition AAC used in step 1) preferably does not contain phosphonate and / or phosphate anions.

[0039] In the sense of the present invention, the term "aqueous" in relation to the composition AAC used in the present invention preferably means that the composition AAC is a composition that contains at least 50% by weight, preferably at least 60% by weight, more preferably at least 70% by weight, particularly preferably at least 80% by weight, and most preferably at least 90% by weight of water, based on the total content of organic and inorganic solvents, including water. Thus, the composition AAC may contain at least one organic solvent in addition to water, but in an amount less than the amount of water present.

[0040] Preferably, the acidic aqueous composition AAC comprises at least 50% by weight, preferably at least 60% by weight, more preferably at least 70% by weight, particularly preferably at least 80% by weight, and most preferably at least 90% by weight of water, in each case based on its total weight.

[0041] The acidic aqueous composition AAC preferably has a pH value in the range of 0.5 to 6.5. The pH value is preferably measured at room temperature (23°C). The pH value of the acidic aqueous composition is more preferably in the range of 1.0 to 6.0, even more preferably in the range of 2.0 or 3.0 to 5.5. The pH can be adjusted, if necessary, preferably using nitric acid, aqueous ammonia, and / or sodium carbonate.

[0042] The total amount of all components (constituents) present in Composition AAC adds up to 100% by weight. Composition AAC can be a dispersion or a solution. Preferably, it is a solution.

[0043] Preferably, the acidic aqueous composition AAC contains fluoride anions in an amount, in each case calculated as fluorine, in the range of 10 to 2000 mg / L, more preferably in the range of 15 to 1500 mg / L, even more preferably in the range of 20 to 1000 mg / L, even more preferably in the range of 25 to 500 mg / L. As outlined below, complex fluorides, such as zirconium, titanium, and / or hafnium complexes formed with fluoride ions, are preferably present in the composition AAC, for example, by coordination of fluoride anions to zirconium, titanium, and / or hafnium cations in the presence of water. Alternatively, fluoride anions may be generated by adding other water-soluble fluoride compounds, such as fluorides (other than complex fluorides of Ti, Zr, and / or Hf) and hydrofluoric acid to the composition. The free fluoride content is determined using a fluoride ion sensitive electrode according to the method disclosed in the "Methods" section.

[0044] Preferably, the acidic aqueous composition AAC comprises at least one metal cation selected from the group consisting of titanium ions, zirconium ions and hafnium ions, and mixtures thereof, more preferably selected from the group consisting of titanium ions and zirconium ions, and mixtures thereof, and even more preferably selected from zirconium ions.

[0045] Preferably, the acidic aqueous composition AAC contains at least one organosilane, preferably in an amount of 5 to 1000 mg / L, more preferably 5 to 500 mg / L. Examples include (3-aminopropyl)trimethoxysilane, (3-aminopropyl)triethoxysilane, N-2-aminoethyl-3-aminopropyltrimethoxysilane, (3-mercaptopropyl)trimethoxysilane, (3-mercaptopropyl)triethoxysilane, (3-glycidyloxypropyl)trimethoxysilane and / or (3-glycidyloxypropyl)triethoxysilane, and / or vinyltrimethoxysilane. The organosilane is preferably present in its hydrolyzed form.

[0046] Preferably, the acidic aqueous composition AAC contains at least one metal cation selected from the group consisting of titanium, zirconium, and hafnium ions, and mixtures thereof, in an amount ranging from 5 to 2000 mg / L, more preferably from 7.5 to 1500 mg / L, even more preferably from 10 to 1000 mg / L, even more preferably from 15 to 500 mg / L, and even more preferably from 20 to 300 mg / L, calculated in each case as metal. Preferably, a precursor metal compound is used to generate the at least one metal cation. Preferably, the precursor metal compound is water-soluble. The solubility is determined at a temperature of 20°C and atmospheric pressure (1.013 bar). Particularly preferred zirconium, titanium, and / or hafnium compounds are complex fluorides of these metals. The term "complex fluoride" includes singly and multiply protonated forms, as well as deprotonated forms. Mixtures of such complex fluorides may also be used. Complex fluorides in the sense of the present invention are complexes of zirconium, titanium and / or hafnium formed with fluoride ions in the composition, for example by coordination of fluoride anions to zirconium, titanium and / or hafnium cations in the presence of water. The content of at least one metal cation can be monitored and determined by means of ICP-OES (Inductively Coupled Plasma Optical Emission Spectroscopy), which is described below in the "Methods" section.

[0047] Optionally, composition AAC may contain additional components, such as other metal cations (other than Ti, Zr, and / or Hf), and / or at least one water-soluble polymer, such as a water-soluble polymer having at least one functional group selected from acid groups, hydroxyl groups, and mixtures thereof. The solubility is measured at a temperature of 20°C and atmospheric pressure (1.013 bar). Preferably, the at least one water-soluble polymer is a homopolymer or copolymer obtainable from the polymerization of at least one ethylenically unsaturated monomer, wherein at least a portion of the monomers has at least one functional group selected from acid groups, hydroxyl groups, and mixtures thereof, more preferably a homopolymer or copolymer obtainable from the polymerization of at least one vinyl monomer and / or (meth)acrylic monomer, wherein at least a portion of the monomers has at least one functional group selected from acid groups, hydroxyl groups, and mixtures thereof.

[0048] Preferably, the conversion layer formed after drying or curing, preferably drying, step 1) (and subsequent rinsing step 2)) the film obtained has a coating mass determined by XRF (X-ray fluorescence spectroscopy) of: Calculated as metals, each ranges from 0.5 to 500 mg / m 2 , more preferably 1 to 400 mg / m 2 , and even more preferably 3 to 350 mg / m 2 , and even more preferably 5 to 300 mg / m 2 zirconium, titanium and / or hafnium ions, preferably zirconium and / or titanium ions, especially zirconium ions.

[0049] Step 2) and Composition AC According to step 2) of the pretreatment method, the film obtained after step 1) is rinsed with an aqueous composition AC, different from the acidic aqueous composition AAC, which comprises at least one alkaline earth metal ion, before any hardening and / or drying of said film.

[0050] The aqueous composition AC used in rinsing step 2) is preferably designated "rinsing composition", which preferably defines, in accordance with the common understanding of this term, a composition that removes the excess of the composition that was in contact with the metal surface in the step immediately preceding the rinsing step in which the rinsing composition is used, in this case the composition that was in contact with composition AAC in step 1).

[0051] Preferably, the at least one alkaline earth metal ion is present in the aqueous composition AC in an amount, in each case calculated as alkaline earth metal, in the range of 5 to 2000 ppm, more preferably 5 to 1500 ppm, even more preferably 5 to 1000 ppm, even more preferably 10 to 1000 ppm, even more preferably 15 to 800 ppm, even more preferably 20 to 750 ppm, even more preferably 25 to 600 ppm, even more preferably 35 to 500 ppm, even more preferably 45 to 400 ppm, even more preferably 50 to 300 or 250 ppm. ICP-OES can also be used to determine the amount.

[0052] Preferably, the at least one alkaline earth metal ion present in aqueous composition AC is selected from beryllium cations, magnesium cations, calcium cations, strontium cations, barium cations and mixtures thereof, more preferably selected from magnesium cations, calcium cations and mixtures thereof, and most preferably selected from magnesium cations.

[0053] Preferably, the aqueous composition AC can be obtained by dissolving at least one alkaline earth metal salt in water. Any suitable salt can be used. Exemplary salts are selected from alkaline earth metal nitrates, sulfates, acetates, and mixtures thereof. When acetates are used, the pH value of the aqueous composition AC is preferably adjusted by using at least one pH-adjusting compound or salt.

[0054] Preferably, aqueous composition AC is free or essentially free of fluoride anions.

[0055] Preferably, the aqueous composition AC comprises water in an amount of at least 80% by weight, more preferably at least 85% by weight, even more preferably at least 90% by weight, even more preferably at least 95% by weight, even more preferably at least 98% by weight, and even more preferably at least 99% by weight, in each case based on the total weight of the composition AC.

[0056] Preferably, the aqueous composition AC has a temperature in the range of 15 to 55°C, more preferably 17 to 50°C.

[0057] Optional step 2a) Optionally, step 2) can be followed by a further rinsing step, whereby the film obtained after step 2) is rinsed with water, preferably deionized water.

[0058] Optional step 2b) Optional step 2b) is drying and / or curing, preferably drying, the film obtained after step 3) or optionally after step 2a).

[0059] Drying and / or curing may be carried out in step 3) outlined below, for example, when a powder coating composition is applied as the coating material composition. However, step 2b) is optional, and therefore further method steps, such as step 3), can be carried out without drying and / or curing the film obtained after rinsing step 2). In particular, it is possible to apply a coating material composition, such as an electrodeposition coating material composition, to the wet film obtained after rinsing step 2) in step 3) outlined below.

[0060] The drying or curing step 2b) may preferably (if not carried out at all) be carried out, for example, at a temperature in the range from 15° C. to 100° C., more preferably from 18° C. to 95° C., in particular from 20° C. to 90° C. "Drying" in the sense of the present invention means physical drying, in particular by evaporation of water originally present in the composition(s) used, while "curing" further comprises a chemical reaction between at least two components originally present in the composition(s) and / or between at least one component originally present in the composition(s) and suitable functional groups present on the metal surface or in the conversion coating, for example if a water-soluble polymer is present in the composition AAC.

[0061] How to apply at least one coating film A further subject of the present invention is a method for applying at least one coating film onto at least one surface of a substrate, said method comprising at least steps 1) and 2) as defined herein and below, and further step 3), namely 3) applying a coating material composition comprising at least one film-forming polymer onto the optionally dried and / or optionally cured, preferably optionally dried, film, which film can be obtained after carrying out a rinsing step 2) and, optionally, after further drying and / or curing of the film obtained after the rinsing step 2); Includes.

[0062] All preferred embodiments described herein above in relation to the pretreatment method and its preferred embodiments are also preferred embodiments of the method for applying at least one coating film onto at least one surface of a substrate.

[0063] Preferably, the coating material composition applied in step 3) is an electrodepositable, preferably cathodically electrodepositable, coating material composition, wherein the at least one film-forming polymer present therein is preferably an electrodepositable, preferably cathodically electrodepositable, polymer. The substrate used is, of course, preferably a conductive substrate. Preferably, the coating material composition applied in step 3), such as an electrodepositable, preferably cathodically electrodepositable, coating material composition, is applied onto the wet film obtained after carrying out the rinsing step 2).

[0064] Electrodepositable coating (electrocoat) material compositions are coating materials that contain a binder, optionally containing a crosslinker, a pigment and / or filler, and often a polymer as an additive. Generally, there are anodically electrodepositable and cathodically electrodepositable electrocoat materials. Preferred cathodically electrodepositable materials are disclosed, for example, in EP 1 041 125 A1, DE 197 03 869 A1, and WO 91 / 09917 A2.

[0065] Preferably, the electrodeposition coating (electrocoat) material composition used is water-based.

[0066] As the cathodically electrodepositable polymer, any polymer capable of being electrodeposited cathodically is suitable. Preferred are poly(meth)acrylates, (meth)acrylate copolymers, and epoxide polymers. Most preferred are epoxide-amine adducts. For the purposes of the present invention, epoxide-amine adducts are reaction products of at least one epoxy resin with at least one amine. The epoxy resins used are more particularly those based on bisphenol A and / or its derivatives. The amines reacted with the epoxy resin are primary amines and / or secondary amines or their salts and / or tertiary amine salts. The at least one epoxide-amine adduct used is preferably a cationic, epoxide-based, and amine-modified resin.

[0067] At least one crosslinking agent may be present in the electrodeposition coating material composition, and the crosslinking agent is selected from the group consisting of blocked polyisocyanates, free polyisocyanates, amino resins, and mixtures thereof.

[0068] The term "blocked polyisocyanate" is known to those skilled in the art. Blocked polyisocyanates that can be used are polyisocyanates having at least two isocyanate groups (diisocyanates in the case of exactly two isocyanate groups), but preferably more than two, for example, 3 to 5 isocyanate groups, where the isocyanate groups are reacted so that the resulting blocked polyisocyanate is stable at room temperature, i.e., 18 to 23°C, but at elevated temperatures, such as ≥80°C, ≥110°C, ≥130°C, ≥140°C, ≥150°C, ≥160°C, ≥170°C, or ≥180°C, particularly with respect to hydroxyl groups and amino groups, e.g., primary and / or secondary amino groups, but reacts with conversion and formation of urethane and / or urea bonds, respectively.

[0069] Amino resins (aminoplast resins) are also known to those skilled in the art. The amino resins used are preferably melamine resins, more particularly melamine-formaldehyde resins, which are also known to those skilled in the art. However, it is preferred not to use amino resins such as melamine-formaldehyde resins as crosslinkers.

[0070] The electrodeposition coating material composition is preferably a one-component (1K) coating composition, and therefore preferably does not contain free polyisocyanate.

[0071] The electrodeposition coating material composition may contain at least one pigment and / or filler. The term "filler" is known to those skilled in the art, for example from DIN 55943 (dated October 2001). For the purposes of the present invention, a "filler" is preferably a component that is substantially, preferably completely, insoluble in the application medium, such as the electrodeposition coating material composition, and is used in particular to increase the volume. A "filler" in the sense of the present invention preferably has a refractive index different from that of a "pigment," the refractive index of the filler being <1.7. All conventional fillers and pigments can be used.

[0072] Step 3) is preferably carried out by immersing the substrate having the dried or cured, preferably dried, film obtained after step 2) in an electrodeposition coating bath containing the electrodeposition coating material composition, connecting the substrate as a cathode, and depositing a coating film CF obtained from the electrodeposition coating material composition on the substrate using a direct current, removing the coated substrate from the electrodeposition coating bath, and baking the coating film CF deposited on the substrate. The applied voltage is preferably in the range of 50 to 500 volts. The electrodeposition coating bath preferably has a bath temperature in the range of 20 to 45°C.

[0073] Substrates obtainable by a pretreatment method or by a method for applying at least one coating film A further subject of the present invention is a substrate obtainable by the inventive method for pretreatment comprising at least steps 1) and 2), or by the inventive method for pretreatment comprising at least steps 1) and 2), or by the inventive method for pretreatment as well as step 3), in which at least one coating film is applied onto at least one surface of the substrate.

[0074] All preferred embodiments described herein above in relation to the pretreatment method and the method of applying at least one coating film onto at least one surface of a substrate, and preferred embodiments thereof, are also preferred embodiments of the substrate of the present invention.

[0075] Method of using aqueous composition AC A further subject of the present invention is the use of an aqueous composition AC as defined herein and hereinafter, For example, in relation to step 2) of the pretreatment method of the present invention, 1. A method of use for rinsing a film obtainable from at least partially applying an acidic aqueous and fluoride anion-containing composition, preferably an acidic aqueous composition AAC as defined herein and below, onto at least one surface of a substrate, for example in connection with step 1) of the pretreatment method of the present invention, said surface being at least partially made of at least one metal and / or alloy thereof, and rinsing being carried out before any curing and / or drying of said film, and / or 1. A method of use for at least partially reducing the fluoride content of a film obtainable from applying an acidic aqueous and fluoride anion-containing composition, preferably an acidic aqueous composition AAC as defined herein and hereinafter, at least partially onto at least one surface of a substrate, for example in connection with step 1) of the pretreatment method of the present invention, preferably by rinsing said film with an aqueous composition AC, preferably before any curing and / or drying of said film, wherein said surface is at least partially made of at least one metal and / or alloy thereof, and / or A method of use for improving the homogeneity of the film build and / or reducing the mapping of a coating film CF in at least one of its regions by rinsing said film with an aqueous composition AC, preferably before any curing and / or drying of said film and before application of a coating film CF, the coating film CF resulting from applying an electrodeposition coating material composition onto a cured or dried film, which in turn can be obtained from applying, at least in part, an acidic aqueous and fluoride anion-containing composition, preferably an acidic aqueous composition AAC as defined herein and below, for example in connection with step 1) of the pretreatment method of the present invention, onto at least one surface of a substrate, said surface being at least in part made of at least one metal and / or alloy thereof.

[0076] All preferred embodiments described herein above in relation to the substrate of the present invention as well as the pretreatment method and the method of applying at least one coating film onto at least one surface of the substrate, and preferred embodiments thereof, are also preferred embodiments of the method of use of the present invention.

[0077] Kit of Parts A further subject of the present invention is an acidic aqueous composition AAC, as defined herein and below, containing at least fluoride anions, for example in connection with step 1) of the pretreatment method of the present invention; and As defined herein and below, for example in connection with step 2) of the pretreatment method of the present invention, an aqueous composition AC containing at least one alkaline earth metal ion and different from the acidic aqueous composition AAC is provided. The kit of parts includes, and preferably consists of, the above.

[0078] As used herein, the term "kit of parts" follows common usage and means at least two spatially separated components that are functionally integrated for intended use.

[0079] All preferred embodiments described herein above in relation to the pretreatment method and the method of applying at least one coating film onto at least one surface of a substrate, as well as the substrate of the invention and the method of use of the invention, and preferred embodiments thereof, are also preferred embodiments of the kit-of-parts of the invention.

[0080] method 1. Determination of fluoride content Free fluoride content is determined using a fluoride ion-selective electrode. The electrode is calibrated using at least three master solutions with known fluoride concentrations. The calibration process generates a calibration curve. The calibration curve is then used to determine the fluoride content.

[0081] 2. ICP-OES The amount of a specific element, such as zirconium, titanium, or hafnium, in a sample under analysis is determined using inductively coupled plasma optical emission spectroscopy (ICP-OES) in accordance with DIN EN ISO 11885 (dated September 1, 2009). The sample is thermally excited in an argon plasma generated by a radio-frequency magnetic field, and the light emitted by electronic transitions is visualized as spectral lines of the corresponding wavelengths and analyzed using an optical system. There is a linear relationship between the intensity of the emitted light and the concentration of the element in question. Prior to implementation, calibration measurements are performed using known element standards (reference standards) as a function of the specific sample under analysis. These calibrations can be used to determine the concentration of unknown solutions, such as titanium, zirconium, or hafnium.

[0082] 3. Coating mass XRF (X-ray fluorescence spectroscopy) is used to measure the coating mass of a particular element in a layer, such as a conversion coating layer, obtained by applying a chemical pretreatment composition to a substrate, in mg / m 2 Determined by unit.

[0083] 4.Paint thickness The paint thickness (dry film thickness) of the electrodeposition coating layer was measured in μm according to DIN EN ISO 2178:2016-11 using a Fischer Dualscope® MP20E-S tool. Each measured value represents the average of five measurements. Measuring the dry film thickness allows the film build and film build difference (mapping) to be determined. [Example]

[0084] The following examples further illustrate the present invention but are not to be construed as limiting its scope.

[0085] 1. Products and materials used As chemical pretreatment composition (CPC) a commercial product (Chemetall GmbH) was used, namely the product Oxsilan® 9835, which is an acidic aqueous composition containing, inter alia, fluoride anions and zirconium ions.

[0086] Different aqueous post-rinse compositions (comparative and inventive) were used: PRC1 (for comparison): deionized water; PRC2 (for comparison): aqueous alkaline composition (deionized water to which NaOH was added until the pH value reached 10); PRC3 (for comparison): an aqueous composition containing sodium nitrite (50 ppm, calculated as NO); and PRC4a to PRC4d (all according to the invention): aqueous compositions containing magnesium nitrate; PRC4a: 20 ppm calculated as Mg; PRC4b: 100 ppm calculated as Mg; PRC4c: 200 ppm calculated as Mg; PRC4d: 980 ppm calculated as Mg.

[0087] 2. Method (pre-treatment process, post-rinse, and electrocoating) A hot dip galvanized steel substrate (HDG substrate) was provided in the form of a metal panel.

[0088] The substrates were cleaned with a commercially available alkaline cleaner with a pH value of about 10.5 (by spray or immersion application at 55°C for about 1.5 minutes), followed by rinsing with tap water and then deionized water (30 seconds each).

[0089] For the subsequent contacting step, two different approaches were taken: Approach 1: A contacting step was carried out in which the entire surface of the substrate was contacted with the chemical pretreatment composition CPC described above in item 1. by immersion for 3 minutes. Thereafter, 50% of the surface area of ​​each substrate was contacted with the composition CPC by further immersion for an additional 3 minutes. Thus, 50% of the surface area of ​​each substrate was contacted with the composition CPC for a total of 6 minutes to simulate a longer treatment time, and the resulting respective surface areas are hereinafter referred to as "runner areas."

[0090] Approach 2: A contacting step was carried out in which the entire surface of the substrate was contacted by immersion with the chemical pretreatment composition CPC described above in item 1 for 3 minutes. Then, using a dropping funnel, the composition CPC was allowed to flow over a portion of the surface area of ​​the substrate for an additional 3 minutes. Each resulting surface area having a contact time of 6 minutes is hereinafter referred to as the "runner area."

[0091] The "runner areas" of the surface were areas that were contacted with the composition CPC in an uncontrolled manner for longer than planned to allow for observation of undesired mapping in these areas. The remaining surface area of ​​each substrate was contacted with the composition CPC for a total of 3 minutes.

[0092] The compositions (CPC) were in each case heated to 30° C. before application.

[0093] Following the contacting step according to Approach 1 or 2, a post-rinse step was carried out using either Composition PRC1, PRC2, PRC3, PRC4a, PRC4b, PRC4c, or PRC4d at ambient temperature (18-25°C) for 1 minute, thus post-rinsing the entire surface of all substrates.

[0094] The post-rinse step was followed by a final rinse with deionized water (30 seconds).

[0095] Next, a drying step was carried out using air blowing.

[0096] Finally, each of the resulting substrates was coated with a commercially available electrodeposition coating composition, namely, CathoGuard® 800. Electrodeposition was performed at a bath temperature of 31-33°C and a deposition voltage of 180-260 V (voltage ramp: 4 s, 30 s, or 60 s) for 2 min. The substrates were then baked at 175°C (substrate temperature) for 25 min.

[0097] 3. Investigating the properties of coated substrates 3.1 The total amount of F present in the layer formed by applying the chemical pretreatment composition CPC is expressed in mg / m according to the method defined in the "Methods" section. 2 of Zr (obtained from zirconium cations present in CPC) versus the total coating mass in mg / m 2 The Zr / F ratio was determined in the form of a quotient of the total amount of F (obtained from fluoride anions present in the CPC) of the total amount of F (obtained from fluoride anions present in the CPC) (hereinafter also referred to as "Zr / F-ratio"). A higher Zr / F-ratio indicates a more efficient reduction / removal of F from the layer, which is desirable. In Tables 1a and 1b shown below, the resulting Zr / F-ratios determined are summarized for both Approaches 1 and 2 described above in Section 2.

[0098] [Table 1]

[0099] As is apparent from Tables 1a and 1b, post-rinsing with any of PRC4a to PRC4d after chemical pretreatment with fluoride anion-containing composition CPC results in a reduction in the amount of F in the chemical pretreatment layer.

[0100] 3.2 Additionally, the paint thickness (dry film thickness) of the electrodeposited coating layer was determined in μm according to the method defined in the "Methods" section and is shown in Tables 1c and 1d. The effect of the type of post-rinse composition used on the paint thickness in the "runner areas" of the surface was investigated. The results are shown in Tables 1c and 1d. The respective paint thicknesses of the "non-runner areas" of the surface of the same panels are also shown in Tables 1c and 1d. It can be seen that the post-rinse treatment has only a small effect on the resulting electrodeposited coating thickness in the "non-runner areas," but a significant effect on the resulting electrodeposited coating thickness in the "runner areas." This ultimately results in a uniform difference in electrodeposited coating thickness between the "non-runner areas" and the "runner areas," which is desirable.

[0101] [Table 2]

[0102] As is evident from Tables 1c and 1d, chemical pretreatment with the fluoride anion-containing composition CPC followed by a post-rinse using any of PRC4a-PRC4d significantly reduces the paint thickness of the electrodeposited coating layer in the "runner area." A paint thickness difference of more than 1.5 μm between the "runner area" and the "non-runner area" (a difference in film build, and therefore undesirable mapping) is visually detectable even after topcoat application (applied subsequently to the application of the electrodeposited coating layer and, optionally, additional layers, such as a basecoat layer), as observed when any of PRC1-PRC3 is used instead. Furthermore, achieving a uniform and homogeneous film build requires additional sanding after the application of the electrodeposited coat, which is unacceptable. As is evident from Tables 1c and 1d, post-rinsing with deionized water (PRC1) or the use of conventional post-rinse compositions, such as the NaOH-containing composition (PRC2) or the sodium nitrite-containing composition (PRC3), is ineffective in this regard.

Claims

1. A method for pretreating at least one surface of a substrate, said surface being at least partially made of at least one metal and / or alloy thereof, the method comprising at least steps 1) and 2), namely 1) contacting at least a portion of the at least one surface of the substrate with an acidic aqueous composition AAC to at least partially form a film on the surface, the acidic aqueous composition AAC comprising at least fluoride anions in an amount in the range of 10 to 2000 mg / L, calculated as fluorine, and further comprising at least one metal cation selected from the group consisting of titanium ions, zirconium ions, hafnium ions, and mixtures thereof; and 2) rinsing the film obtained after step 1) with an aqueous composition AC containing at least one alkaline earth metal ion, different from said acidic aqueous composition AAC, before any curing and / or drying of said film. A method comprising:

2. 2. The method of claim 1, wherein the at least one alkaline earth metal ion is present in the aqueous composition AC in an amount in the range of from 5 to 2000 ppm, preferably from 5 to 1500 ppm, more preferably from 5 to 1000 ppm, even more preferably from 10 to 1000 ppm, even more preferably from 15 to 800 ppm, even more preferably from 20 to 750 ppm, even more preferably from 25 to 600 ppm, even more preferably from 35 to 500 ppm, even more preferably from 45 to 400 ppm, even more preferably from 50 to 300 or 250 ppm, in each case calculated as alkaline earth metal.

3. 3. The method according to claim 1 or 2, wherein the at least one alkaline earth metal ion present in the aqueous composition AC is selected from beryllium, magnesium, calcium, strontium, barium cations and mixtures thereof, preferably selected from beryllium, magnesium, strontium, barium cations and mixtures thereof, even more preferably selected from magnesium, calcium cations and mixtures thereof, and most preferably selected from magnesium cations.

4. 3. The method according to claim 1 or 2, wherein the aqueous composition AC is obtainable by dissolving at least one alkaline earth metal salt in water, said salt being preferably selected from alkaline earth metal nitrates, sulfates, acetates, and mixtures thereof.

5. 3. The method according to claim 1 or 2, wherein the aqueous composition AC comprises water in an amount of at least 80% by weight, preferably at least 85% by weight, more preferably at least 90% by weight, even more preferably at least 95% by weight, even more preferably at least 98% by weight, even more preferably at least 99% by weight, in each case based on the total weight of the composition AC.

6. 3. The method according to claim 1 or 2, wherein the acidic aqueous composition AAC comprises fluoride anions in an amount of 15 to 1500 mg / L, preferably 20 to 1000 mg / L, more preferably in the range of 25 to 500 mg / L, even more preferably in the range of 25 to 500 mg / L, in each case calculated as fluorine.

7. 3. The method according to claim 1 or 2, wherein the acidic aqueous composition AAC comprises at least one metal cation selected from the group consisting of titanium ions, zirconium ions, and mixtures thereof, preferably selected from zirconium ions.

8. 3. The method according to claim 1 or 2, wherein the acidic aqueous composition AAC comprises at least one metal cation selected from the group consisting of titanium ions, zirconium ions, hafnium ions, and mixtures thereof, in an amount in the range of 5 to 2000 mg / L, preferably 7.5 to 1500 mg / L, more preferably 10 to 1000 mg / L, even more preferably 15 to 500 mg / L, and even more preferably 20 to 300 mg / L, in each case calculated as the metal.

9. 3. The method according to claim 1 or 2, wherein the acidic aqueous composition AAC has a pH value in the range of 0.5 to 6.5, preferably 1.0 to 6.0, more preferably 2.0 or 3.0 to 5.

5.

10. 3. The method according to claim 1 or 2, wherein the rinsing step 2) is carried out for a time ranging from 10 seconds to 5 minutes, preferably from 20 seconds to 4.5 minutes, more preferably from 30 seconds to 4 minutes.

11. A method for applying at least one coating film onto at least one surface of a substrate, the method comprising at least steps 1) and 2) as defined in claim 1, and further step 3), i.e. 3) applying a coating material composition comprising at least one film-forming polymer onto the optionally dried and / or optionally cured film, which film can be obtained, in turn, after carrying out a rinsing step 2) and, optionally, after further drying and / or curing of the film obtained after the rinsing step 2); A method comprising:

12. 12. The method of claim 11, wherein the coating material composition is an electrodepositable, preferably cathodically electrodepositable, coating material composition, and the at least one film-forming polymer present therein is preferably an electrodepositable, more preferably a cathodically electrodepositable, polymer.

13. A substrate obtainable by the pretreatment method according to claim 1 or by the method according to claim 11.

14. of an aqueous composition AC as defined in claim 1, 1. A method of use for rinsing a film obtainable from applying, at least in part, an acidic aqueous and fluoride anion-containing composition, preferably the acidic aqueous composition AAC as defined in claim 1, onto at least one surface of a substrate, said surface being at least in part made of at least one metal and / or alloy thereof, and wherein rinsing is carried out before any curing and / or drying of said film, and / or 1. A method of use for at least partially reducing the fluoride content of a film obtainable from at least partially applying an acidic aqueous and fluoride anion-containing composition, preferably an acidic aqueous composition AAC as defined in claim 1, onto at least one surface of a substrate, by rinsing said film with the aqueous composition AC, preferably before any curing and / or drying of said film, wherein said surface is at least partially made of at least one metal and / or alloy thereof, and / or 1. A method of use for improving the homogeneity of the film build and / or reducing the mapping of a coating film CF in at least one of its regions by rinsing the film with an aqueous composition AC, preferably before any curing and / or drying of the film and before application of a coating film CF, wherein the coating film CF results from applying an electrodeposition coating material composition onto a cured or dried film, which cured or dried film is obtainable, in turn, from at least partially applying an acidic aqueous and fluoride anion-containing composition, preferably the acidic aqueous composition AAC as defined in claim 1, onto at least one surface of a substrate, said surface being at least partially made of at least one metal and / or alloy thereof.

15. an acidic aqueous composition AAC, as defined in claim 1, containing at least fluoride anions; and As defined in claim 1, for example in connection with step 2) of the pretreatment method of the present invention, an aqueous composition AC containing at least one alkaline earth metal ion and different from the acidic aqueous composition AAC is used. Kit of parts including.

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