Diethanolamine based oligomer comprising composition for use in chemical pretreatment of metallic substrates

Abstract

The present invention relates to an aqueous composition AC comprising besides water at least one of zirconium, titanium and hafnium cations as constituent(s) a1), and at least one diethanolamine based oligomer as constituent a2), which comprises repeating units of (CH2CH2NHCH2CH2O)n, with n = 2-9, or a concentrate, from which said aqueous composition AC is at least obtainable by dilution with water and, optionally, further, by pH adjustment, to a use of composition AC for providing or improving corrosion protection and / or adhesion, to a method of chemical pretreatment of at least one metallic surface of at least one substrate comprising at least step 1) i.e. contacting the at least one metallic surface of the at least one substrate at least in portion with the aqueous composition AC being suitable to form a coating film at least in portion onto said surface, to a method of coating an aforementioned chemically pretreated substrate, and to a coated substrate obtainable by said method.

Description

[0001] Chemetall GmbH 240142 WO01

[0002] Diethanolamine based oligomer comprising composition for use in chemical pretreatment of metallic substrates

[0003] The present invention relates to a chemical pretreatment composition and to a concentrate, from which said composition is obtainable, to a method of chemically pretreating metallic surfaces of substrates, to a chemically pretreated substrate obtainable by this method, to a use of the chemical pretreatment composition for providing or improving corrosion protection and / or adhesion, to a method of coating an aforementioned chemically pretreated substrate, and to a coated substrate obtainable by said method.

[0004] Background of the invention

[0005] Before substrates having metallic surfaces are being lacquered, i.e., before permanent coating layers are applied onto their surfaces, they are nowadays typically subjected to an anti-corrosive chemical pretreatment by using a suitable chemical pretreatment composition.

[0006] US 2022 / 0316084 A1 describes a method of performing pre-paint treatment of an automobile body, the method including performing an alkaline degreasing step, a first water-washing step, a chemical conversion treatment step, a second water-washing step, and a cationic electrodeposition painting step, in this order, wherein the chemical conversion treatment step is performed using an chemical conversion treatment agent including zirconium, free fluorine ions, an allylamine-diallylamine copolymer with a weight average molecular weight of 5000 to 100000, aluminum ions, nitrate ions each at a predetermined concentration; the allylamine-diallylamine copolymer forms an acid addition salt having an anionic counter ion, and the pKa of an acid thereof falls within the range of -3.7 to 4.8; and the content percentage of diallylamine is 80 mol % or more and 98 mol % or less.

[0007] US20010 / 045546 A1 discloses a method of preventing corrosion in pipelines comprising draining pipeline of all residual compounds, blowing through with nitrogen Chemetall GmbH 240142 WO01 and rinsing with a rinsing agent, characterized in that the rinsing agent is corrosion inhibiting. The rinsing agent comprises a fatty ester, rape seed oil, sunflower oil, polydiethanolamide, triethanol amine, one tall oil fatty acid, a polyether carboxylic acid, demineralized water and fatty alcohol polyglycol ester.

[0008] US 2016 / 083590 A1 relates to a surface treatment composition for coated steel sheet comprising an organic silicon compound (A), a hexafluorometallic acid (B), a urethane resin having one or more cationic groups (C), a vanadium compound (D) and an aqueous medium (E).

[0009] US 2013 / 023685 A1 relates to processes for preparing metal(IV) compounds which are suitable especially as catalysts for preparation of polyesters, polyurethanes and polysiloxanes.

[0010] WO 2018 / 050506 discloses pretreatment of a metallic surface including steel, galva nized steel, aluminum, an aluminum alloy, magnesium and / or a zinc-magnesium alloy, wherein the metallic surface is brought into contact with i) an acidic aqueous composition A which includes a1) at least one compound selected from the group consisting of titanium, zirconium and hafnium compounds, and with ii) an aqueous composition B which includes b1 ) at least one (meth)acrylate resin and b2) at least one phenol resin, where the metallic surface is brought into contact firstly with the composition A and then with the composition B and / or firstly with the composition B and then with the composition A and / or simultaneously with the composition A and the composition B.

[0011] Environmentally more adapted thin-film pretreatment systems are also well known in the prior art. These are, e.g., based on oxides of zirconium, titanium, cerium, molybdenum, vanadium, tungsten, or other transition metals, and are used as replacement for hazardous components, like chromium and nickel, which were used for decades in trivalent or hexavalent chromate as well as tri-cationic zinc phosphate coatings. In these terms especially zirconium and titanium got used in a wide range of pretreatment applications due to their high chemical stability under the conditions of oxygen or acidic corrosion. For example, aqueous solutions based on metal complex fluorides such as titanium and / or zirconium complex fluorides are used as such chemical pretreatment compositions in order to generate a conversion coating layer on the metallic surfaces of substrates. Optionally, these systems contain further Chemetall GmbH 240142 WO01 adhesion promotors or corrosion inhibitors such as organosilanes, organo- phosphonates or amino-functional alcohols. Together with the aforesaid inorganic compounds, these additives provide excellent adhesion to the metal surface as well as to a following organic coating such as, e.g., electrodeposition-, powder- or wetcoatings. Moreover, they can increase the barrier properties of the layer against the diffusion of corrosive ions against the diffusion and migration of corrosive species to or along the metal surface, which otherwise lead to inhibition of cathodic delamination during corrosive processes.

[0012] Even though prior art thin-film pretreatment systems often can provide a sufficient corrosion protection on metal substrates such as aluminum alloys, galvanized steels surfaces or zinc-magnesium alloys, they still suffer insufficient corrosion inhibition on steel surfaces, in particular in comparison to chromate or tricationic zinc phosphate conversion coatings. Moreover, prior art thin-film pretreatments often contain nitrogen oxide or phosphorous oxide containing anionic components (NxOyz; PxOyz') such as nitrates or phosphates, which may lead to eutrophication of water, if released in larger amounts to the environment. Due to this effect, the usage of nitrate and / or phosphate containing systems already faces legal restrictions in some countries, as, e.g., currently in China.

[0013] Thus, there is a need to provide chemical pretreatment compositions suitable for formation of thin permanent coating layers on metallic substrates including particularly ferrous substrates such as steel substrates or multi-metallic substrates including at least portions of steel, which compositions are less toxic and hazardous than prior art compositions, make use of easy accessible constituents, and which lead to at least the same, but preferably even to an improved, resistance to corrosion and / or water, and which at the same time also provide an excellent substrate adhesion and an excellent adhesion to any layers applied on top, compared to conventionally used aqueous coating compositions known in the prior art. Chemetall GmbH 240142 WO01

[0014] Problem

[0015] It has been therefore an objective underlying the present invention to provide chemical pretreatment compositions suitable for formation of thin permanent coating layers on metallic substrates including particularly ferrous substrates such as steel substrates or multi-metallic substrates including at least portions of steel, which compositions are less toxic and hazardous than prior art compositions, make use of easy accessible constituents, and which lead to at least the same, but preferably even to an improved, resistance to corrosion and / or water, and which at the same time also provide an excellent substrate adhesion and an excellent adhesion to any layers applied on top, compared to conventionally used aqueous coating compositions known in the prior art.

[0016] Solution

[0017] This objective has been solved by the subject-matter of the claims of the present application as well as by the preferred embodiments thereof disclosed in this specification, i.e. , by the subject matter described herein.

[0018] A first subject-matter of the present invention is an aqueous composition AC, wherein the aqueous composition AC comprises besides water at least one of zirconium, titanium and hafnium cations as constituent(s) a1 ), and at least one diethanolamine based oligomer as constituent a2), which comprises repeating units of (CH2CH2NHCH2CH2O)n, with n = 2-9, or a concentrate, from which said aqueous composition AC is at least obtainable by dilution with water and, optionally, further, by pH adjustment. Chemetall GmbH 240142 WO01

[0019] A further subject-matter of the present invention is a method of chemical pretreatment of at least one metallic surface of at least one substrate comprising at least step 1 ) and optionally one or more of steps 2) and 3), namely

[0020] 1) contacting the at least one metallic surface of the at least one substrate at least in portion with an aqueous composition AC being suitable to form a coating film at least in portion onto said surface comprising besides water at least one of zirconium, titanium and hafnium cations as constituent(s) a1), and at least one diethanolamine based oligomer as constituent a2), which comprises repeating units of (CH2CH2NHCH2CH2O)n, with n = 2-9, or a concentrate, from which said aqueous composition AC is at least obtainable by dilution with water and, optionally, further, by pH adjustment,

[0021] 2) optionally rinsing the coating film obtained after step 1) at least once with at least one aqueous rinsing composition ARC, which is different from aqueous composition AC, and

[0022] 3) optionally curing or drying the optionally rinsed coating film obtained after step 1) or 2) to give a cured or dried coating layer.

[0023] A further subject-matter of the present invention is a substrate, which is a chemically pretreated substrate being obtainable by the inventive method of chemical pretreatment as defined hereinbefore and hereinafter.

[0024] A further subject-matter of the present invention is a use of the aqueous composition AC wherein the aqueous composition AC comprises besides water at least one of zirconium, titanium and hafnium cations as constituent(s) a1), and at least one diethanolamine based oligomer as constituent a2), which comprises repeating units of (CH2CH2NHCH2CH2O)n, with n = 2-9, or of a concentrate, from which said aqueous composition AC is at least obtainable by dilution with water and, optionally, further, by pH adjustment for providing or improving corrosion resistance of metallic surfaces of substrates and / or for providing or improving adhesion of metallic surfaces of substrates to one or more further coating layers present thereon. Chemetall GmbH 240142 WO01

[0025] A further subject-matter of the present invention is a method of coating of at least one chemically pretreated metallic surface of at least one substrate, wherein chemical pretreatment of the at least one metallic surface has been carried out according to the inventive method of chemical pretreatment as defined hereinbefore and hereinafter, the method of coating further comprising at least step 4), namely

[0026] 4) applying at least one coating material composition comprising at least one filmforming polymer and / or resin onto the optionally rinsed film obtained after step 1 ) or 2) as defined hereinbefore and hereinafter or onto the dried or cured, preferably dried, film, which in turn is obtainable from drying or curing the film obtainable from optional step 3) as defined hereinbefore and hereinafter.

[0027] A further subject-matter of the present invention is a substrate, which is a coated substrate being obtainable by the inventive method of coating as defined hereinbefore and hereinafter.

[0028] It has been in particular surprisingly found that composition AC can be used as chemical pretreatment composition, which is suitable for forming a thin permanent coating layer such as a conversion coating layer on metallic substrates including particularly ferrous substrates such as steel substrates or multi-metallic substrates including at least portions of steel.

[0029] Moreover, it has been in particular surprisingly found that composition AC can be effectively used as chemical pretreatment composition in a chemical pretreatment method and that the chemically pretreated substrates as such or chemically pretreated substrates bearing further coating layers such as an electrodeposition coating layer, show an excellent corrosion resistance. It has been in particular surprisingly found in this regard, that this effect is a result of the presence of at least one diethanolamine based oligomer as constituent a2) in composition AC. Chemetall GmbH 240142 WO01

[0030] Further, it has been in particular surprisingly found that composition AC can be effectively used as chemical pretreatment composition in a chemical pretreatment method and that the chemically pretreated substrates show an excellent substrate adhesion and, in addition, an excellent adhesion to any layers applied on top, in particular to an electrodeposition coating layer applied on top of the chemical pretreatment layer. It has been in particular surprisingly found in this regard, that this effect is a result of the presence of the at least one diethanolamine based oligomer as constituent a2) in composition AC.

[0031] In addition, it has been found that the aforementioned surprising effects as far as corrosion resistance and adhesion are concerned, can be observed on various kinds of metallic surfaces, not only on aluminum alloys, but also on steel including zinc- coated (galvanized) steel. Therefore, it has been surprisingly found that composition AC can be effectively used not only for forming conversion layers on steel, but also on multi-metallic substrates.

[0032] Detailed description of the invention

[0033] The term “comprising” in the sense of the present invention, in connection for example with the inventively used or inventive aqueous composition AC, preferably has the meaning of “consisting of”. With regard, e.g., to said composition referred to hereinbefore, it is possible - in addition to all mandatory constituents present therein - for one or more of the further optional constituents identified hereinafter to be also included therein. All constituents may in each case be present in their preferred embodiments as identified below.

[0034] The proportions and amounts in wt.-% (% by weight) of any of the constituents given hereinafter, which are present in each of the compositions add up to 100 wt.-%, based in each case on the total weight of the respective composition. Chemetall GmbH 240142 WO01

[0035] Pretreatment method including chemical pretreatment step 1)

[0036] A subject-matter of the present invention is a method of chemical pretreatment of at least one metallic surface of at least one substrate comprising at least step 1) and optionally one or more of steps 2) and 3) as described hereinbefore and hereinafter. The method may comprise further steps performed prior to step 1 ) and / or after each of steps 1), 2) and 3).

[0037] Chemical pretreatment is a term known by a person skilled in the art and in particular is part of a pretreatment method.

[0038] The term “pretreatment” as used herein is preferably used in accordance with the term “surface pretreatment” as defined in Rdmpp Lexikon “Lacke und Druckfarben” (Publisher: Ulrich Zorll, Editor: Hans-Jurgen P. Adler - Stuttgart; New York: Thieme, 1998; term: “Oberflachenvorbehandlung” page 417). On metallic substrates or substrates having metallic surfaces, according to DIN 50902: 1994-07, the first step(s) of a surface treatment is / are often one or more (chemical) cleaning step(s) with aqueous or non-aqueous cleaning compositions (also called “surface preparation step”). Consequently, as it will be outlined hereinafter, the method may comprise one or more further optional steps performed prior to step 1 ).

[0039] The term “chemical pretreatment” is used in accordance with EN ISO 4618:2006 (E / F / D) (term: 2.41 “chemical pre-treatment”), which represents any chemical process applied to a surface prior to the application of a coating material. According to this standard, e.g., treatments like chromatizing (chromating) and phosphatizing and oxalating, which can be subsumed under the term “conversion treatment”, belong to the chemical pretreatment and thus are to be distinguished from (subsequent) coating steps, wherein coating materials, i.e., coating compositions such as powder coating compositions, electrodeposition coating compositions, aqueous or non-aqueous liquid coating materials are applied. Besides conversion treatments such as chromatizing (chromating) and phosphating, the chemical surface pretreatment may be achieved Chemetall GmbH 240142 WO01 with passivation compositions and thin-film forming compositions in general, including the aqueous composition AC, which is mandatorily used as chemical pretreatment composition in step 1). Hence, step 1) of the method represents a chemical pretreatment step and the aqueous composition AC used therein represents a chemical pretreatment composition.

[0040] In accordance with the above internationally valid definitions of a “pretreatment” of metallic substrates, the pretreatment method according to the present invention preferably encompasses surface preparing cleaning steps besides the chemical pretreatment step 1).

[0041] Preferably, the pretreatment method does not contain any step involving any treatment with chromium ions such as Cr(VI) ions and / or Cr(lll) ions.

[0042] Preferably, the chemical pretreatment step 1) is the only chemical pretreatment step of the pretreatment method. Hence, preferably, other chemical pretreatment compositions than the aqueous composition AC applied in step 1) are not used.

[0043] Preferably, the film obtained after step 1) or after optional steps 2) and / or 3) has a coating weight in a range of from 0.5 to 500 mg / m2, more preferably of from 1 to 400 mg / m2, even more preferably of from 2 to 350 mg / m2, determined in each case as tracer element(s) such as Ti, Zr and / or Si via XRF measurements according to the method disclosed in the ‘method’ section. Preferably, the cured or dried coating layer obtained after optional step 3) preferably has a dry film thickness below 0.5 pm.

[0044] Substrate

[0045] The substrate used in step 1 ) contains at least one metallic surface. The term “metallic surface” in the sense of the present invention preferably means that the surface of the substrate used is at least partially made of at least one metal, i.e. , that at least one Chemetall GmbH 240142 WO01 region of said surface is made of at least one metal and / or alloy thereof. Preferably, the overall surface of the substrate is made of at least one metal and / or alloy thereof, more preferably, the whole substrate is made of at least one metal and / or alloy thereof, i.e., the substrate consists of at least one metal and / or alloy thereof. If a substrate comprises areas of different metals, such substrate is herein denoted as “multi-metallic substrate” as a subclass of metallic substrates. Such multi-metallic substrates can be subjected to step 1) of the chemical pretreatment method and can be coated in the same treatment bath

[0046] The at least one metallic surface of the substrate may be optionally pre-coated, but preferably is not pre-coated.

[0047] Preferably, the substrate used is an electrically conductive substrate, which is used customarily and known to the skilled person. The substrate can have all sorts of geometry and shape such as coils, foils and sheets as well as represent parts such as automotive parts including vehicle parts such as wheel parts. Particularly suitable substrates are parts of vehicle bodies or complete bodies of automobiles for production.

[0048] Preferably, the at least one surface of the substrate is at least partially made of at least one metal and / or alloy thereof, more preferably is made at least partially of at least one of steel, steel alloys, aluminum, aluminum alloys, zinc, zinc alloys including zinc magnesium alloys, and mixtures thereof, even more preferably is made at least partially of at least one of steel and steel alloys. Examples of steel and / or steel alloys are bare steel, cold rolled steel (CRS), hot rolled steel (HRS), galvanized steel (zinc plated steel) such as hot dip galvanized steel (HDG), electrolytically galvanized steel (EG), alloy galvanized steel and aluminized steel such as, for example, Galvalume®, Galvannealed® or Galfan®, as well as steel coated at least in portion with at least one kind of zinc-aluminum-magnesium alloy (ZM). Examples of aluminum alloys are aluminum magnesium alloys, aluminum magnesium silicon alloys, aluminum copper Chemetall GmbH 240142 WO01 alloys, aluminum zinc alloys, and aluminum zinc copper alloys. Examples of zinc alloys are Zn / Mg alloys and Zn / Ni alloys as well as Zn / Mg / AI alloys.

[0049] Optional steps performed prior to step 1)

[0050] As mentioned hereinbefore and in accordance with the above internationally valid definition of a “pretreatment” of metallic substrates, the pretreatment method according to the present invention preferably encompasses surface preparing cleaning steps besides the chemical pretreatment step 1).

[0051] Prior to step 1) one or more of the following optional steps can be performed in this order:

[0052] Step A-1 ): cleaning and optionally subsequently rinsing the surface of the substrate,

[0053] Step B-1): subjecting the surface of the substrate to acidic or alkaline pickling, i.e., etching, and subsequently rinsing the surface of the substrate,

[0054] Step C-1): contacting the surface of the substrate with an aqueous composition comprising at least one mineral acid, said aqueous composition being different from compositions AC and ARC or alternatively with an aqueous alkaline composition or pH- neutral aqueous composition, each of these compositions being also different compositions AC and ARC, and

[0055] Step D-1): rinsing the surface of the substrate obtained after the contact according to step C-1) and / or B-1).

[0056] Alternatively, steps A-1) and B-1) may be performed in one step, which is preferred. Preferably, both steps A-1) and B-1 ) are performed. Optional step C-1) preferably serves to remove oxides, undesired alloy components, the skin, brushing dust etc. from the surface of the substrate and to thereby activate the surface for the subsequent Chemetall GmbH 240142 WO01 conversion treatment in step 1). 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.

[0057] Rinsing step D-1) and the optional rinsing being part of step A-1) are preferably performed by using deionized water or tap water. Preferably, step D-1) is performed by using deionized water.

[0058] Step l )

[0059] According to step 1) the at least one metallic surface of the at least one substrate is contacted at least in portion with an aqueous composition AC being suitable to form a coating film at least in portion onto said surface. Aqueous composition AC represents a chemical pretreatment composition. By performing step 1) a conversion film (or conversion coating film or passivation film) is formed on the surface of the substrate, which has been in contact with the aqueous composition AC.

[0060] The term “at least in portion” preferably means in this context, in accordance with the general understanding of said term, that in some cases it might be desired or sufficient to contact not the whole surface of the substrate with the chemical pretreatment composition AC. If only part of the metallic surface is contacted with the respective composition, it is typically the same part for all steps of the method. However, generally, it is desired to contact the whole surface of the metallic substrate with the respective compositions.

[0061] The “contacting” according to step 1) can be a spraying, a dipping (immersing) or a roll coating (rolling) step. The composition AC can also be applied by flooding the surface or even manually by wiping or brushing. Preferred is spraying, or dipping.

[0062] The treatment time, i.e. , the period of time the surface is contacted with the aqueous composition AC in step 1), is preferably from 1 seconds to 20 minutes, more preferably Chemetall GmbH 240142 WO01 from 15 or 30 seconds to 10 minutes, and most preferably 45 seconds to 5 minutes, as for example 1 to 3 minutes.

[0063] The temperature of the aqueous composition AC used in step 1 ) is preferably of from 5 to 50 °C, more preferably of from 15 to 45 °C or to 40 °C and most preferably from 25 to 35 °C.

[0064] The aqueous composition AC can be used as a dip coat bath. However, it can also be applied by virtually any conventional coating procedure like, e.g., spray coating, roll coating, brushing, wiping etc. as outlined above in connection with step 1). Spraying and dipping are preferred.

[0065] Preferably, the film obtainable after step 1) - preferably after drying according to optional step 3) - has a coating weight determined by XRF (X-ray fluorescence spectroscopy) of 0.5 to 500 mg / m2, more preferably 1 to 400 mg / m2, even more preferably 2 to 350 mg / m2, still more preferably 3 to 300 mg / m2, of silicon, zirconium, titanium and / or hafnium ions, each calculated as metal or element.

[0066] Aqueous composition AC used in step 1)

[0067] The aqueous composition AC comprises, besides water, at least constituents a1) and a2), which are different from one of another. At least one of zirconium, titanium and hafnium cations is present as constituent(s) a1), and at least one diethanolamine based oligomer as constituent a2) is present as constituent a2). The aqueous composition AC used in step 1 ) represents a “pretreatment composition” or “chemical pretreatment composition” or “composition for the conversion coating”. Chemetall GmbH 240142 WO01

[0068] Preferably, the aqueous composition AC is an aqueous acidic composition, more preferably has a pH value in a range of from 0.1 to <7.0, still more preferably of from 0.5 to 6.5, even more preferably of from 1 .0 to 6.0, yet more preferably of from 1 .5 or 2.0 or 5.5, still more preferably of from 2.5 or 3.0 to 5.25, most preferably of from 3.5 or 4.0 to 5.0. The pH value can be in particular adjusted by using a suitable pH adjusting constituent, in particular sodium and / or potassium hydroxide and / or sodium and / or potassium and / or ammonium carbonate for alkaline adjustment, or can be in particular adjusted in case acidic adjustment is needed by at least one inorganic acid such as phosphoric and / or sulfuric and / or boric acid and / or nitric acid and / or by at least one organic acid such as methyl sulfonic acid.

[0069] The aqueous composition AC can be a dispersion or solution. Preferably, it is a solution. Solubility is determined at a temperature of 20°C and atmospheric pressure (1.013 bar).

[0070] Preferably, the aqueous composition AC used in step 1) has a temperature in a range of from 5 to 50 °C, more preferably of from 15 to 45 °C or to 40 °C and most preferably from 25 to 35 °C.

[0071] The aqueous composition AC used in step 1) is preferably free or essentially free of any chromium ions such as Cr(VI) cations and / or Cr(lll) cations, more preferably is free of chromium ions or comprises a maximum amount of chromium ions of <10 mg / L, calculated as metal, and / or is preferably free or essentially free of any nickel ions such as Ni(ll) cations and / or Ni(lll) cations, more preferably is free of nickel ions or comprises a maximum amount of nickel ions of <10 mg / L, calculated as metal, and / or is preferably free or essentially free of any boron ions such as B(lll) cations and / or B(IV) cations, more preferably is free of boron ions or comprises a maximum amount of boron ions of <10 mg / L, calculated as boron, and / or is preferably free or essentially free of any nitrate anions, more preferably is free of nitrate anions or comprises a maximum amount of nitrate anions of <10 mg / L, calculated as nitrate, and / or is preferably Chemetall GmbH 240142 WO01 free or essentially free of any phosphate anions, more preferably is free of phosphate anions or comprises a maximum amount of phosphate anions of <10 mg / L, calculated as phosphate.

[0072] “Essentially free” in this context means in each case that at least on purpose none of the aforementioned constituents is added, but it may not be ruled out that any residues of any of the constituents may be present as impurities and / or may be present in amounts being naturally present in water.

[0073] The term “aqueous” with respect to the aqueous composition AC used in step 1) in the sense of the present invention preferably means that the composition is a composition containing at least 50 wt.-%, preferably at least 60 wt.-%, more preferably at least 70 wt.-% in particular at least 80 wt.-%, most preferably at least 90 wt.-% of water, based on its total content of organic and inorganic solvents including water. Thus, the aqueous composition may contain at least one organic solvent besides water - however, in an amount lower than the amount of water present. Preferably, the aqueous composition AC does not or essentially does not contain any organic solvent(s).

[0074] Preferably, the aqueous composition AC contains at least 50 wt.-%, preferably at least 60 wt.-%, more preferably at least 70 wt.-% in particular at least 80 wt.-%, most preferably at least 90 wt.-% of water, in each case based on its total weight.

[0075] Preferably, the aqueous composition AC is free or is essentially free of organic solvents. “Essentially free” in this context means that at least on purpose organic solvents are not added, but it may not be ruled out that any of these may be present as impurities. Preferably, the amount of organic solvent(s) present in the aqueous composition AC does not exceed 5 wt.-%, yet more preferably does not exceed 2.5 wt. %, even more preferably is lower than 2.0 wt.-%, most preferably is at most 1 .0 wt. % or at most 0.5 wt.-% or at most 0.1 wt.-%, in each case based on the total weight of the composition. Chemetall GmbH 240142 WO01

[0076] Constituent a1)

[0077] At least one of zirconium, titanium and hafnium cations, preferably at least one of zirconium and titanium cations, more preferably at least zirconium cations, is present as constituent(s) a1) in the aqueous composition AC.

[0078] Preferably, the aqueous composition AC comprises the at least one of zirconium, titanium and hafnium cations in an amount in a range of from 1 or 5 to 4 000 mg / L, more preferably of from 7.5 to 2 000 mg / L, even more preferably of from 10 to 1 500 mg / L, still more preferably of from 12.5 to 1 000 mg / L, yet more preferably of from 15 to 750 mg / L, even more preferably of from 20 to 500 mg / L in each case calculated as metal.

[0079] Preferably, a precursor metal compound is used to generate the at least one metal cation being present in composition AC as constituent a1). Preferably, the precursor metal compound is water-soluble. Solubility is determined at a temperature of 20°C and atmospheric pressure (1.013 bar). Particularly preferred zirconium, titanium and / or hafnium compounds for use as precursor compounds are the complex fluorides of these metals. The term “complex fluoride” includes the single and multiple protonated forms as well as the deprotonated forms. It is also possible to use mixtures of such complex fluorides. Complex fluorides in the sense of the present invention are complexes of metal cations such as zirconium, titanium and / or hafnium cations formed with fluoride ions in the composition, e.g., by coordination of fluoride anions to zirconium, titanium and / or hafnium cations in the presence of water. In case complex fluorides of at least one of zirconium, titanium and / or hafnium cations have been used as precursor compounds, the aqueous composition further comprises fluoride anions as constituent a3).

[0080] Additionally, or alternatively, zirconium can also be added in form of zirconyl compounds as, e.g., zirconyl nitrate, zirconyl acetate, zirconium carbonate and / or Chemetall GmbH 240142 WO01 zirconium nitrate, the latter one being particularly preferred, in particular when the aqueous composition is acidic. The same applies to titanium and hafnium.

[0081] The content of the at least one metal cation a1) can be monitored and determined by the means of ICP-OES (optical emission spectroscopy with inductively coupled plasma). Said method is described hereinafter in the ‘method’ section.

[0082] Constituent a2)

[0083] At least one diethanolamine based oligomer is present as constituent a2) in the aqueous composition AC.

[0084] The precursor for the diethanolamine based oligomer as constituent a2) is Diethanolamine with the formula HN(CH2CH2OH)2 and contains a secondary amine and two hydroxyl groups. The synthesis of the diethanolamine based oligomer is described below. The formed diethanolamine based oligomer has a high soluble property at different pH ranges. This is necessary when the metallic surface is brought into contact with a solution that contains the constituents a1). In this composition the metallic surface needs to be acidic etched in the aqueous solution in order to initiate the conversion coating process. The addition of the diethanolamine based oligomer a2) improves the properties of the coatings formed, in particular of the adhesion property and corrosion protection.

[0085] Preferably, the at least one diethanolamine based oligomer is present in composition AC an amount in a range of from 1 to 500 000 mg / L, more preferably of from 2 to 300 000 mg / L, even more preferably of from 3 to 200000 mg / L, still more preferably of from 4 to 100 000 mg / L, yet more preferably of from 5 to 50 000 mg / L, even more preferably of from 6 to 20 000 mg / L, yet more preferably of from 7 to 15 000 mg / L, even more preferably of from 7.5 to 10 000 mg / L, yet more preferably of from 8 to 5 000 mg / L, still more preferably of from 9 to 2 500 mg / L or to 2 000 mg / L, yet more preferably of from 10 to 1 000 mg / L, most preferably of from 15 or 20 to 500 mg / L.

[0086] Preferably, the at least one diethanolamine based oligomer being present as constituent a2) in composition AC has a weight average molecular weight in a range of from 200 to 300 000 g / mol or to 20 000 g / mol, more preferably of from 500 to 200 Chemetall GmbH 240142 WO01

[0087] 000 g / mol on to 15 000 g / mol, even more preferably of from 1 000 to 100 000 g / mol or to 10 000 g / mol, still more preferably of from 1 200 to 75 000 g / mol or to 6000 g / mol,

[0088] The at least one diethanolamine based oligomer as constituent a2) in composition AC comprises repeating units of (CH2CH2NHCH2CH2O)n, with n = 2-9.

[0089] Each oligomer is denoted by a specific suffix, indicating the number of repeating units it contains, such as dimer, trimer, tetramer, pentamer, and hexamer. The utilization of these different oligomers allows for a versatile and tailored approach to meet the specific requirements of the invention. Series of diethanolamine based oligomers or polyether from diethanolamine could be synthesized by using a suitable catalyst. The catalysts used for the syntheses of (CH2CH2NHCH2CH2O)3, (CH2CH2NHCH2CH2O)s, (CH2CH2NHCH2CH2O)6, (CH2CH2NHCH2CH2O)7, (CH2CH2NHCH2CH2O)8, and (CH2CH2NHCH2CH2O)9 were CaCI2, H3PO4 / AcOH, H3PO4, NaOH, AI2(SO4)3 / AcOH, and Al2(SO4)3, respectively. The diethanolamine based oligomers as constituent a2) used in the present invention were made in house by H3PO4catalyst. Diethanolamine was polymerized under different reaction times to form diethanolamine based oligomers a2) of controlled molecular weight. For the experimental procedure it is referred to Journal of Colloid and Interface Science 284, 2005, pp. 167-175. Further also refer is made to Russian Journal of Organic Chemistry, 2013, Vol. 49, No. 7, pp. 949-967. Therefore, the diethanolamine based oligomers can also be expressed as reaction products of diethanolamine with the catalyst as described above and preferably H3PO4is used as the catalyst.

[0090] The inventively used diethanolamine based oligomer comprises preferably repeating units of (CH2CH2NHCH2CH2O)n, with n = 2-9. It is intended here that a pure oligomer, which means with only one n with n = 2, 3, 4, 5, 6, 7, 8, or 9 is used, but further all combinations thereof shall be also encompassed. Further one inventively used diethanolamine based oligomer is preferable with a Mw of around 1500 g / mol, comprising next to the monomer, a mixture of diethanolamine based oligomer with n = 2-4.

[0091] Optional constituent a3) Chemetall GmbH 240142 WO01

[0092] Preferably, the aqueous composition AC further comprises fluoride anions including complex fluoride anions as constituent a3), preferably in an amount in a range of from 5 or 10 to 2 000 mg / L, more preferably of from 15 to 1 500 mg / L, even more preferably of from 20 to 1 000 mg / L, still more preferably of from 25 to 500 or to 200 mg / L, in each case calculated as fluorine. Preferably, the complex fluorides contain zirconium.

[0093] Preferably, the aqueous composition AC comprises fluoride anions being present therein as complex fluoride anions as constituent a3), which are preferably coordinated to at least one of zirconium, titanium and hafnium cations in the presence of water, more preferably at least one of zirconium and titanium cations, still more preferably zirconium cations, being also present in the composition as constituent(s) a1), more preferably in an amount of from 1 or 50 mg / L to 4 000 mg / L, still more preferably of from 10 or 100 mg / L to 2 000 or to 1 500 mg / L, yet more preferably in an amount of from 50 or 100 mg / L to 500 or 250 mg / L, calculated in each case as H2MF6 with M = Zr, Ti and / or Hf. Alternatively, fluoride anions being present as constituent a3) may be generated by adding other water-soluble fluorine compounds, e.g., fluorides (other than complex fluorides of Ti, Zr and / or Hf) as well as hydrofluoric acid to the composition. The free fluoride content is determined by means of a fluoride ion sensitive electrode according to the method disclosed in the ‘methods’ section.

[0094] Optional constituent a4)

[0095] Optionally and preferably, the aqueous composition AC further comprises at least one organosilane and / or a hydrolysis and / or condensation product thereof as constituent(s) a4), preferably in an amount in a range of from 0 or 5 to 20 000 or to 15 000 mg / L, more preferably of from 0 or 10 to 10 000 or to 5 000 mg / L, even more preferably of from 0 or 15 to 1 000 or to 500 mg / L, still more preferably of from 0 or 20 to 250 or to 200 mg / L, in each case calculated as elemental silicon. Chemetall GmbH 240142 WO01

[0096] The term “organosilanes” includes, e.g., organoalkoxysilanes and organosilanols. Examples of hydrolysis and / or condensation products of organosilanes are organosiloxanes and polyorganosiloxanes as well as polyorganosilanols. For the purpose of this invention, “polyorganosiloxanes” are preferably understood to mean those compounds which can be condensed from at least two organosilanols and do not form a polydimethylsiloxane. The term “organo” in “organosilane” preferably means that at least one organic group is present, which is connected directly to a silicon atom via a carbon atom and can consequently not be subjected to hydrolysis.

[0097] Preferably, optional constituent a4) has at least one functional group selected from (meth)acrylate groups, alkylaminoalkyl groups, alkylamino groups, alkyltetrasulfide groups, amino groups, aminoalkyl groups, carboxyl groups, epoxy groups, glycidoxy groups, hydroxyl groups, isocyanato groups, mercaptoalkyl groups, succinic anhydride groups, imido groups, imino groups, and / or ureido groups (urea groups).

[0098] Examples of organosilanes are, e.g., (3-aminopropyl)trimethoxysilane, (3- aminopropyl)triethoxysilane, bis (trimethoxysilylpropyl) amine, bis (triethoxysilylpropyl) amine, N-2-aminoethyl-3-aminopropyltrimethoxysilane, (3- butylaminopropyl)trimethoxysilan, bis(3-triethoxysilylpropyl)disulfide, bis(3- triethoxysilylpropyl)tetrasulfide), bis(3-trimethoxysilylpropyl)disulfide, bis(3- trimethoxysilylpropyl)tetrasulfide), 1 ,2-bis(triethoxysilyl)ethane, (3- mercaptopropyl)trimethoxysilane, (3-mercaptopropyl)triethoxysilane, (3- methylaminopropyl)triethoxysilan, (3-methylaminopropyl)trimethoxysilan, (3- glycidyloxypropyl)trimethoxysilane and / or (3-glycidyloxypropyl)triethoxysilane, and / or vinyltrimethoxysilane. The organosilane is preferably present in a hydrolyzed form thereof.

[0099] Preferably, the aqueous composition AC comprises at least one organosilane and / or a hydrolysis and / or condensation product thereof as constituent(s) a4) with at least one amino group, urea group, imido group, imino group and / or ureido group per organosilane unit, more preferably with at least one or more such as at least two amino Chemetall GmbH 240142 WO01 groups per organosilane unit. Particularly preferred is 2-aminoethyl-3- aminopropyltrimethoxysilane, 2-aminoethyl-3-aminopropyltriethoxysilane, bis (trimethoxysilylpropyl) amine and / or bis (triethoxysilylpropyl) amine.

[0100] Further optional constituents including optional constituents a5) and a6)

[0101] Optionally, the aqueous composition AC further comprises at least one kind of metal cations selected from the group of cations of metals of the 1 st to 3rd subgroup (copper, zinc and scandium groups) and 5th to 8th subgroup (vanadium, manganese and iron groups) of the periodic table of the elements including the lanthanides as well as the 2nd main group of the periodic table of the elements (alkaline earth metal group), lithium and bismuth and / or tin. More preferably the aqueous composition AC further optionally comprises at least one kind of metal cations selected from the group consisting of cations of cerium and other lanthanides, chromium, iron, calcium, cobalt, copper, magnesium, manganese, molybdenum, nickel, niobium, tantalum, yttrium, vanadium, lithium, bismuth, zinc and tin, and mixtures thereof. Most preferred are copper and / or zinc cations.

[0102] Optionally and preferably, the aqueous composition AC further comprises zinc cations as constituent a5), preferably in an amount in a range of from 0 or 5 to 5 000 mg / L, more preferably of from 0 or 10 to 2 500 mg / L, even more preferably of from 0 or 25 to 1 000 or to 500 mg / L, in each case calculated as metal, and / or copper cations as constituent a6), preferably in an amount in a range of from 0 or 0,5 to 1 000 mg / L, more preferably of from 0 or 0,5 to 500 mg / L, even more preferably of from 0 or 0,5 to 100 mg / L, still more preferably of from 0 or 0,5 to 50 mg / L, in each case calculated as metal.

[0103] Optionally, the aqueous composition AC further comprises at least one pH-value adjusting constituent, preferably selected from the group consisting of nitric acid, sulfuric acid, methanesulfonic acid, acetic acid, aqueous ammonia, sodium hydroxide and sodium carbonate, wherein methanesulfonic acid and sodium carbonate are Chemetall GmbH 240142 WO01 preferred. Depending on the pH value of the aqueous composition, the above constituent can be present in their fully or partially deprotonated form or in protonated forms.

[0104] Optionally, the aqueous composition AC further comprises at least one organic solvent, preferably selected from the group consisting of methanol, ethanol, ethylene glycol n- butyl ether, ethylene glycol n-propyl ether, propylene glycol n-propyl ether, propylene glycol n-butyl ether and mixtures thereof. Methanol and ethanol can be, e.g., present as reaction products of the organosilane hydrolysis.

[0105] Optionally, the aqueous composition AC further comprises at least one organic acid, preferably at least one organic acid having at least two carboxylic acid groups and / or at least one organic acid having at least one carboxylic acid groups and at least one further functional group having at least one donor atom such an OH-group, e.g., lactic acid, in particular when the aqueous composition is alkaline. The presence of such a compound may be helpful for stabilization of the at least one metal cation being present in the composition as a1) such as Zr cations.

[0106] The aqueous composition may further comprise at least one of the following constituents: one or more waxes, one or more wetting agents and one or more defoamers and / or rheology additives.

[0107] Optionally, the aqueous composition AC may comprise at least one water-soluble polymer different from constituent a2) such as a water-soluble polymer having at least one kind of functional groups selected from acid groups, hydroxyl groups, and mixtures thereof. Preferably, the at least one water-soluble polymer if present is a homopolymer or copolymer obtainable from polymerization of at least one kind of ethylenically unsaturated monomers, wherein at least part of said monomers bear at least one kind of functional groups selected from acid groups, hydroxyl groups, and mixtures thereof, more preferably is a homopolymer or copolymer obtainable from polymerization of at least one kind of vinyl monomers and / or (meth)acrylic monomers, wherein at least part Chemetall GmbH 240142 WO01 of said monomers bear at least one kind of functional groups selected from acid groups, hydroxyl groups, and mixtures thereof.

[0108] Optional step 2)

[0109] In optional step 2) the film obtained after step 1 ) is rinsed at least once with at least one aqueous rinsing composition ARC, which is different from aqueous composition AC. Preferably, composition ARC consists or essentially consists of water only. The term “rinsing” preferably means, in accordance with the general understanding of this term, a removal of excessive parts of the aqueous composition AC, which was contacted with the surface in the step directly preceding the optional rinsing step.

[0110] Tap water and / or deionized water can be used for rinsing in optional step 2). As outlined hereinbefore, optional step 2) can be performed more than once. It is hence possible, e.g., to perform a rinsing in step 2) once with tap water followed by rinsing with deionized water or vice versa.

[0111] Optional step 3)

[0112] In optional step 3) the film obtained after step 1 ) or after optional step 2) is dried or cured to give a cured or dried coating layer.

[0113] Drying and / or curing may be performed in particular, when in a step 4) as outlined hereinafter, a coating material composition is subsequently applied. However, step 3) is only optional and, hence, further method steps such as step 4) may be carried out without drying and / or curing the film obtained after having performed step 1 ) or rinsing step 2). In particular it is possible to apply a coating material composition such as an electrodeposition coating material composition in a step 4) as outlined hereinafter onto a wet film obtained after having performed step 1 ) or rinsing step 2). Chemetall GmbH 240142 WO01

[0114] The drying or curing step 3) may be preferably performed (if performed at all), e.g., at a temperature in the range of 15°C to 180°C, more preferably at a temperature in the range of 25°C to 150°C, in particular at a temperature in the range of 50°C to 130°C. “Drying” in the sense of the present invention means physical drying by evaporation of in particular water originally present in the composition(s) used, whereas “curing” further includes a chemical reaction between at least two constituents originally present in the composition(s) and / or between at least one constituent originally present in the composition(s) and a suitable functional group present on the metallic surface or in the conversion film, e.g., due to the presence of polymer a2) in composition AC. Once a film is dried, the resulting product can be regarded as a layer.

[0115] Preferably, a conversion layer formed after drying or curing, preferably drying, the film obtainable after step 3), has a coating weight determined by XRF (X-ray fluorescence spectroscopy) of: 0.5 to 500 mg / m2, more preferably of from 1 to 400 mg / m2, even more preferably of from 2 to 350 mg / m2, determined in each case as tracer element(s) such as Ti, Zr and / or Si via XRF measurements.

[0116] Preferably, the dry layer thickness of a conversion layer formed after drying or curing, preferably drying, the film obtainable after step 3), is below 0.5 pm. Preferably, the obtained cured or dried coating layer obtained after step 3) has a dry film thickness in a range of from 1 nm to <500 nm, more preferably of from 10 nm to 250 nm, in particular of from 80 to 150 nm.

[0117] Substrate obtainable by chemical pretreatment method

[0118] A further subject-matter of the present invention is a substrate, which is a chemically pretreated substrate being obtainable by the inventive method of chemical pretreatment as defined hereinbefore and hereinafter. Chemetall GmbH 240142 WO01

[0119] All preferred embodiments described above herein in connection with the chemical pretreatment method and preferred embodiments thereof are also preferred embodiments of the substrate obtainable by this method.

[0120] Aqueous composition AC

[0121] A subject-matter of the present invention is an aqueous composition AC as defined hereinbefore and hereinafter in connection with step 1) and as used in step 1) of the chemical pretreatment method comprising besides water at least one of zirconium, titanium and hafnium cations as constituent(s) a1 ), and at least one diethanolamine based oligomer as constituent a2).

[0122] All preferred embodiments described above herein in connection with the inventive chemical pretreatment method, the substrate obtainable therefrom, and preferred embodiments thereof are also preferred embodiments of the inventive composition AC.

[0123] Concentrate

[0124] A further subject-matter of the present invention is a concentrate, from which the aqueous composition AC is at least obtainable by dilution with water and, optionally, further, by pH adjustment.

[0125] All preferred embodiments described above herein in connection with the inventive chemical pretreatment method, the substrate obtainable therefrom, and the inventive composition AC, and preferred embodiments thereof are also preferred embodiments of the inventive concentrate.

[0126] The concentrate used to produce the aqueous composition AC typically contains the constituents of the aqueous composition AC to be produced in the desired proportions, but at a higher concentration. Such concentrate is diluted with water to the desired Chemetall GmbH 240142 WO01 concentrations of the constituents as disclosed hereinbefore to form composition AC. If necessary, the pH value of the composition may be adjusted after dilution as well as outlined hereinbefore. Of course, it is also possible to further add any of the optional constituents of the composition to the water used for dilution or to add any of the optional or some of the necessary constituents after diluting the concentrate with water. It is, however, preferred that the concentrate already contains all necessary constituents.

[0127] Preferably, the aqueous composition AC is obtainable from a concentrate by dilution with water, preferably with deionized water, such that the concentrate is present in the composition after dilution in an amount of from 5 to 60 g / L, more preferably 10 to 40 g / L, even more preferably of from 15 to 30 g / L, based on the total weight of the composition (obtained after dilution of the concentrate).

[0128] Preferably, the concentrate is diluted with water in a weight ratio of 1 :5000 to 1 :10, more preferred 1 : 1000 to 1 : 10, most preferred in a ratio of 1 :300 to 1 : 10 and even more preferred 1 : 150 to 1 :50 to produce the composition AC.

[0129] Preferably, composition AC can be prepared from a concentrate by dilution of the concentrate with water.

[0130] Use

[0131] A further subject-matter of the present invention is a use of the aqueous composition AC described hereinbefore or hereinafter for providing or improving corrosion resistance of metallic surfaces of substrates and / or for providing or improving adhesion of metallic surfaces of substrates to one or more further coating layers present thereon. Chemetall GmbH 240142 WO01

[0132] All preferred embodiments described above herein in connection with the inventive chemical pretreatment method, the substrate obtainable therefrom, the inventive composition AC, and the concentrate, and preferred embodiments thereof are also preferred embodiments of the inventive use.

[0133] Coating method

[0134] A further subject-matter of the present invention is a method of coating of at least one chemically pretreated metallic surface of at least one substrate, wherein chemical pretreatment of the at least one metallic surface has been carried out according to the inventive method of chemical pretreatment as defined hereinbefore and hereinafter, the method of coating further comprising at least step 4), namely

[0135] 4) applying at least one coating material composition comprising at least one filmforming polymer and / or resin onto the optionally rinsed film obtained after step 1 ) or 2) as defined hereinbefore and hereinafter or onto the dried or cured, preferably dried, film, which in turn is obtainable from drying or curing the film obtainable from optional step 3) as defined hereinbefore and hereinafter.

[0136] The method of coating according to the present invention comprises at least step 4) and is performed after having carried out the inventive chemical pretreatment method as defined hereinbefore and hereinafter. The method of coating may, however, comprises one or more further additional optional steps.

[0137] All preferred embodiments described above herein in connection with the inventive chemical pretreatment method, the substrate obtainable therefrom, the inventive composition AC, the concentrate and the inventive use, and preferred embodiments thereof are also preferred embodiments of the inventive coating method. Chemetall GmbH 240142 WO01

[0138] The coating material composition used in step 4) is different from each of compositions AC, and ARC.

[0139] The coating material composition can be, e.g., an electrodeposition coating composition, a primer coating composition, a basecoat composition, or a topcoat including a clearcoat composition. It is, of course, possible to apply more than one composition subsequently to form a multilayer coating system, which is conventionally used, e.g., in the automotive industry.

[0140] Preferably, the coating material composition applied in step 4) is an electro- depositable, preferably a cathodically depositable, coating material composition, wherein the at least one film-forming polymer and / or resin present therein preferably is an electro-depositable, preferably a cathodically depositable, polymer.

[0141] Substrate obtainable by coating method

[0142] A further subject-matter of the present invention is a substrate, which is a coated substrate being obtainable by the inventive method of coating as defined hereinbefore and hereinafter.

[0143] All preferred embodiments described above herein in connection with the inventive chemical pretreatment method, the substrate obtainable therefrom, the inventive composition AC, the concentrate, the inventive use, and inventive coating method, and preferred embodiments thereof are also preferred embodiments of the inventive coated substrate. Chemetall GmbH 240142 WO01

[0144] METHODS

[0145] 1. Free fluoride content determination

[0146] The free fluoride content is determined by means of a fluoride ion selective electrode. The electrode is calibrated using at least three master solutions with known fluoride concentrations. The calibration process results in the building of calibration curve. Then the fluoride content is determined by using of the curve.

[0147] 2. ICP-OES

[0148] The amounts of certain elements in a sample under analysis, such as of zirconium, titanium, hafnium etc., is determined using inductively coupled plasma atomicemission spectrometry (ICP-OES) according to DIN EN ISO 11885 (date: September 1 , 2009). A sample is subjected to thermal excitation in an argon plasma generated by a high- frequency field, and the light emitted due to electron transitions becomes visible as a spectral line of the corresponding wavelength and is analyzed using an optical system. There is a linear relation between the intensity of the light emitted and the concentration of the element in question. Prior to implementation, using known element standards (reference standards), the calibration measurements are carried out as a function of the particular sample under analysis. These calibrations can be used to determine concentrations of unknown solutions such as the concentration of the amount of titanium, zirconium and hafnium.

[0149] 3. Coating weight

[0150] XRF (X-ray fluorescence spectroscopy) is used for determining the coating weight in mg / m2of certain (tracer) element(s) such as Ti, Zr and / or Si in a layer such as the conversion layer resulting from applying the chemical pretreatment composition to a substrate. Chemetall GmbH 240142 WO01

[0151] 4. Copper catalyzed acetic acid salt spray (CASS) mist testing to DIN EN ISO 9227

[0152] The copper catalyzed acetic acid salt spray mist test is used for determining the corrosion resistance of a coating on a substrate and has been used for aluminum and / or aluminum alloys. The samples have been scratched all the way down parallel to the longitudinal side. In accordance with DIN EN ISO 9227 (07-2017) the samples under analysis are in a chamber in which there is continuous misting of a 5% strength common salt solution, the salt solution being admixed with acetic acid and copper chloride, at a temperature of 50 °C over a duration of 504 hours with controlled pH. The spray mist deposits on the samples under analysis, covering them with a corrosive film of salt water. The samples were then investigated for their level of undermining (creepage) in accordance with DIN EN ISO 4628-8 (03-2013), since the substrate corrodes along the score line during the CASS mist test.

[0153] 5. Neutral Salt Spray test: Neutral Salt Spray Test DIN EN ISO 9227 (NSS test) method

[0154] The panels are in a chamber in which a 5% saline solution with a controlled pH value is continuously nebulized at a temperature of 35 ° C for 1008 hours. The mist is deposited on the test objects and covers them with a corrosive film of salt water. Then, they were washed with deionized water, and further dried at ordinary temperature. Subsequently, the corrosion attack on the tested material system is then assessed visually or using electrical and microscopic methods.

[0155] 6. pH measurements pH measurements were done using the device “WTW pH 330 i” with the following pH electrode: “SI Analytics BlueLine 28 pH”. The calibration was done with three buffer solutions (traceable to SRM from NIST and PTB) with the following pH values: 4, 7, 10. Chemetall GmbH 240142 WO01

[0156] 7. GMW 14872: Cyclic Corrosion test

[0157] GMW 14872 is a test standard developed by General Motors (GM) that specifies the requirements for conducting the Cyclic Corrosion test. The Cyclic Corrosion test is designed to simulate real-world environmental conditions that can accelerate the corrosion process. It involves subjecting test specimens to a series of alternating cycles of different corrosive environments, including salt spray (5% sodium chloride solution), humidity (100%), and dry conditions (room temperature). The samples have been scratched all the way down parallel to the longitudinal side. The test cycles are repeated for 30 cycles.

[0158] 8. Hot salt water resistance test: Honda 5100Z-TR0, 6.5 test method.

[0159] Humidity Test DIN EN ISO 6270-2 CH test method. The panels should be X scratched and then immersed into a 5 mass % NaCI solution at 55° C. for 240 hours. Then, they were washed with tap water, and further dried at ordinary temperature. Subsequently, the creepage and the percentage of the total area of blister occurred on the general surface of an electrodeposition coating was measured following DIN EN ISO 4628-8 and DIN EN ISO 4628-2.

[0160] 9. Cross hatch adhesion 240 hours test

[0161] Cross Hatch Adhesion Test determines a coating’s ability to resist separation from a substrate. The test is performed by cutting a lattice pattern in the coating, applying a piece of pressure-sensitive tape over the coating, and removing it swiftly to determine how much coating is removed from the surface. Condition the panels immediately prior to testing at a temperature of 23 ± 2°Cand a relative humidity of (50 ± 5)% for 240 hours (Required for laboratory testing in accordance with ISO 2409). The test results can be used in accordance with DIN EN ISO 4628-2 (07-2016) and DIN EN ISO 2409 (12-2020).

[0162] 10. Cyclic Corrosion Test (168 h = 5 cycles): PV 1210 Test Chemetall GmbH 240142 WO01

[0163] This standard specifies a test method to determine the corrosion resistance of automotive bodies, assemblies and components. It is cyclic in nature, i.e.; test specimens are exposed to changing climates over time. Test specimens are placed in an enclosed chamber and exposed to a changing climate that comprises of the following 3 part repeating cycle. 4.0 hours exposure to salt spray according to DIN 50 021 -SS. followed by 4.0 hours exposure to an ambient climate according to DIN 50 014-23 / 50-2. followed by 16.0 hours exposure to a condensing water climate according to DIN 50 017-KK. This 24 hour cycle is repeated for 5 days (nominally Monday to Friday). This is then followed by 48 hours (nominally a weekend) exposure to an ambient climate according to DIN 50 014-23 / 50-2, before the entire cycle repeats. The samples were then investigated fortheir level of undermining (creepage) in accordance with DIN EN ISO 4628-8 (03-2013).

[0164] 11. Stone chip testing according to DIN EN ISO 20567-1 (multi-impact test)

[0165] The primary goal of this test is to evaluate the durability and protective qualities of surface coatings when subjected to repeated impacts by small stones or similar objects. The results help manufacturers understand how well their coatings can withstand real-world conditions. The test requires a specialized apparatus that typically consists of a device that can launch stones at a specified speed and angle towards the coated test samples. The apparatus must be calibrated to ensure consistent and repeatable results. The specimens used for testing are usually coated panels or surfaces that are representative of the materials used in vehicles or other applications. The dimensions and preparation of these specimens must adhere to the standards set forth in the DIN EN ISO 20567-1 . The results of the test are evaluated based on the extent of damage observed on the coated surfaces. The degree of damage is classified using predefined criteria, which may include: number and size of chips; depth of scratches or cracks and adhesion loss of the coating.

[0166] 12. Filiform Corrosion Test DIN EN ISO 4623-2 (12-2016)

[0167] The primary goal of the filiform corrosion test is to assess the susceptibility of a coated surface to filiform corrosion, which is characterized by the formation of filament-like Chemetall GmbH 240142 WO01 corrosion patterns that can develop under the coating, leading to aesthetic and functional degradation. The test specimens are prepared according to the specific requirements of the standard, ensuring that the coatings are applied uniformly and cured properly. The specimens are subjected to specific pre-treatment conditions, which may involve exposure to a controlled atmosphere or pre-soaking in a saline solution to simulate environmental conditions conducive to corrosion. The specimens are then placed in a testing chamber that maintains a controlled humidity level (typically around 100% relative humidity) and temperature (usually at 40°C) to accelerate the corrosion process. The specimens are exposed to these conditions for a specified period, usually ranging from several hours to several days, depending on the requirements of the test. After the exposure period, the specimens are examined for signs of filiform corrosion. The evaluation criteria include the length and number of filiform corrosion threads formed under the coating.

[0168] 13. Cyclic Corrosion Test, Cycle B (DIN EN ISO 11997-1, 01-2018), (7 days = 1 cycles)

[0169] The purpose of this test is to provide an accelerated test procedure for the assessment of the corrosion behavior of components and of the corrosion protection provided by coating systems. The test method is based on real corrosive conditions and delivers differentiated results for a large number of uses in automotive applications. Test specimens are placed in an enclosed chamber, and positioned at an angle of 65° to 75° to the horizontal with the side to be tested uppermost. The salt spray phase is performed with a 1 % solution of sodium chloride, (pH 6.5 to 7.1) and falls out onto the specimens at a rate of 2.0 to 4.0ml / 80cm2 / hour. A full test cycle lasts 7 days and consists of: Cycles B is multi step cycles consisting of varying degrees of temperature from -15°C to +50°C and humidity values of between 50% and 95%. The results are evaluated based on DIN EN ISO 4628-8 (03-2013) and DIN EN ISO 20567-1 (07- 2017).

[0170] EXAMPLES

[0171] The following examples further illustrate the invention but are not to be construed as limiting its scope.

[0172] Example 1 Chemetall GmbH 240142 WO01

[0173] Three kinds of substrates were used, namely a hot-dip galvanized steel substrate (HDG substrate), a cold rolled steel substrate (CRS substrate) and an aluminum alloy substrate (AA6014S substrate). Each of the substrates were cleaned by making use of a commercially available phosphate free alkali cleaner having a pH value of about 10.8 at 60 °C for about 3 minutes. Then, spray rinsing with tap water and subsequent spray rinsing with deionized water was performed (for 30 seconds each at ambient temperature). A contacting step was then carried out, wherein the overall surface of each of the substrates was contacted with the composition for the conversion coating described below for 3 minutes by immersion at 30 °C in order to form a conversion coating film onto the surface of each of the substrates.

[0174] For the conversion coating the commercial product GardoTP 9906 (Chemetall.; includes fluoride, and a zirconium compound) and the respective corrosion-inhibition diethanolamine based oligomer with a Mwof 1218 g / mol were added to a 100 L batch in such an amount as to result in a zirconium concentration of 100 mg / L and a diethanolamine based oligomer concentration of 200 mg I L. The diethanolamine based oligomer was synthesized as described above under section Constituent a2). The bath temperature was adjusted to 30 ° C. The pH and the free fluoride content were adjusted through addition of diluted sodium bicarbonate solution to pH = 4.8 and 30-40 mg / L free fluoride. Further, 0,5 mg / L copper cations were added to the bath, calculated as metal and if the Zr weight was not high enough, then it was necessary to add more Cu and the amount has been adjusted to 8-10 mg / L. Before the throughput of substrates, the finished bath was aged for at least 12 hours to obtain a chemical equilibrium. The conversion treatment was carried out for 180 seconds with moderate stirring, followed by rinsing with tap water and demineralized water for 30 seconds at ambient temperature. Following the rinsing steps, a drying step was performed by warm air drying for 8 minutes in an oven at 120 °C air temperature. As a reference for corrosion protection testing a commercial thinfilm pretreatment system Oxsilan®9832 was used, containing H2ZrFe, organosilanes and copper.

[0175] The layer weights (SG) in mg I m2on the pretreated substrates were determined by X- ray fluorescence analysis (XRF).

[0176] Finally, a commercially available electrodeposition (ED) coating material (Cathoguard® 800) was applied on the conversion coated surface of the substrates and baked at 175 Chemetall GmbH 240142 WO01

[0177] °C for 25 minutes. The dry layer thickness of the ED coating was in a range of from 20 pm and 25 pm.

[0178] Further the same procedure described above has been applied, but with a diethanolamine based oligomer concentration of 500 mg in the bath. Further, 0,5 mg / L copper cations were added to the bath, calculated as metal and if the Zr weight was not high enough, then it was necessary to add more Cu and the amount has been adjusted to 15 mg / L. Table 1. Results of diethanolamine based oligomers, Zr-based thinfilm pretreatment systems after ED-coating and hot salt water resistance test in 240 h, on CRS, HDG and AA6014s. Reference is a commercially available thinfilm pretreatment system Oxsilan®9832 based on zirconium and silane.

[0179] Table 1 Chemetall GmbH 240142 WO01

[0180] Example 2

[0181] Two kinds of substrates were used, a cold rolled steel substrate (CRS substrate) and an aluminum alloy substrate (AA6014S substrate). Each of the substrates were cleaned by making use of a commercially available phosphate free alkali cleaner having a pH value of about 10.8 at 60 °C for about 3 minutes. Then, spray rinsing with tap water and subsequent spray rinsing with deionized water was performed (for 30 seconds each at ambient temperature). A contacting step was then carried out, wherein the overall surface of each of the substrates was contacted with the composition for the conversion coating described below for 3 minutes by immersion at 30 °C in order to form a conversion coating film onto the surface of each of the substrates.

[0182] For the conversion coating the commercial product GardoTP 9906 (Chemetall.; includes fluoride, and a zirconium compound) and the respective corrosion-inhibition diethanolamine based oligomer with a Mwof 4853 g / mol were added to a 100 L batch in such an amount as to result in a zirconium concentration of 200 mg / L and a diethanolamine based oligomer concentration of 200 mg I L. The diethanolamine based oligomer was synthesized as described above under section Constituent a2). The bath temperature was adjusted to 30 ° C. The pH and the free fluoride content were adjusted through addition of diluted sodium bicarbonate solution to pH = 4.8 and 30-40 mg / L free fluoride. Further, 0,5 mg / L copper cations were added to the bath, calculated as metal and if the Zr weight was not high enough, then it was necessary to add more Cu and the amount has been adjusted to 8-10 mg / L. Before the throughput of substrates, the finished bath was aged for at least 12 hours to obtain a chemical equilibrium. The conversion treatment was carried out for 180 seconds with moderate stirring, followed by rinsing with tap water and demineralized water for 30 seconds at ambient temperature. Following the rinsing steps, a drying step was performed by warm air drying for 8 minutes in an oven at 120 °C air temperature. As a reference for corrosion protection testing a commercial thinfilm pretreatment system Oxsilan®9832 was used, containing H2ZrFe, organosilanes and copper. Chemetall GmbH 240142 WO01

[0183] The layer weights (SG) in mg I m2on the pretreated substrates were determined by X- ray fluorescence analysis (XRF).

[0184] Finally, a commercially available electrodeposition (ED) coating material (Cathoguard® 800) was applied on the conversion coated surface of the substrates and baked at 175 °C for 25 minutes. The dry layer thickness of the ED coating was in a range of from 20 pm and 25 pm.

[0185] Table 2. Results of diethanolamine based oligomers, Zr-based thinfilm pretreatment systems after ED-coating and neutral salt spray test, GMW14872 cyclic corrosion test on CRS, and salt spray test on AA6014s. Reference is a commercially available thinfilm pretreatment system Oxsilan®9832 based on zirconium and silane.

[0186] Example 3

[0187] Three kinds of substrates were used, namely a hot-dip galvanized steel substrate (HDG substrate), a cold rolled steel substrate (CRS substrate) and an aluminum alloy substrate (AA6014S substrate). Each of the substrates were cleaned by making use of a commercially available phosphate free alkali cleaner having a pH value of about 10.8 at 60 °C for about 3 minutes. Then, spray rinsing with tap water and subsequent spray rinsing with deionized water was performed (for 30 seconds each at ambient Chemetall GmbH 240142 WO01 temperature). A contacting step was then carried out, wherein the overall surface of each of the substrates was contacted with the composition for the conversion coating described below for 3 minutes by immersion at 30 °C in order to form a conversion coating film onto the surface of each of the substrates.

[0188] For the conversion coating the commercial product GardoTP 9906 (Chemetall.; includes fluoride, and a zirconium compound) and the respective corrosion-inhibition diethanolamine based oligomer (PDA) with Mw=1218 g / mol were added to a 100 L batch in such an amount as to result in a zirconium concentration of 100 mg / L and a diethanolamine based oligomer concentration was 20 mg / L. The diethanolamine based oligomer was synthesized as described above under section Constituent a2). The bath temperature was adjusted to 30 ° C. The pH and the free fluoride content were adjusted through addition of diluted sodium bicarbonate solution to pH = 4.8 and 30-40 mg / L free fluoride. Further, 0,5 mg / L copper cations were added to the bath, calculated as metal and if the Zr weight was not high enough, then it was necessary to add more Cu and the amount has been adjusted to 4 mg / L. Before the throughput of substrates, the finished bath was aged for at least 12 hours to obtain a chemical equilibrium. The conversion treatment was carried out for 180 seconds with moderate stirring, followed by rinsing with tap water and demineralized water for 30 seconds at ambient temperature. Following the rinsing steps, a drying step was performed by warm air drying for 8 minutes in an oven at 120 °C air temperature. As a reference A for corrosion protection testing a commercial thinfilm pretreatment system Oxsilan®9832 was used, containing H2ZrFe, organosilanes and copper. Reference B is a commercially available thinfilm pretreatment system Oxsilan®9832 without organic components silane.

[0189] The layer weights (SG) in mg I m2on the pretreated substrates were determined by X- ray fluorescence analysis (XRF).

[0190] Finally, a commercially available electrodeposition (ED) coating material (Cathoguard® 800) was applied on the conversion coated surface of the substrates and baked at 175 °C for 25 minutes. The dry layer thickness of the ED coating was in a range of from 20 pm and 25 pm. Chemetall GmbH 240142 WO01

[0191] Further the same procedure described above has been applied, but with a diethanolamine based oligomer concentration of 50, 100, 200, 500 mg / L, respectively, in the bath. Further, 0,5 mg / L copper cations were added to the bath, calculated as metal and if the Zr weight was not high enough, then it was necessary to add more Cu and the amount has been adjusted to 8-10 mg / L.

[0192] Table 3. Results of diethanolamine based oligomers, Zr-based thinfilm pretreatment systems after ED-coating and cross hatch test in 240 h, on CRS, HDG and AA6014s. OS 9832 is reference A, which is a commercially available thinfilm pretreatment system Oxsilan®9832 based on zirconium and silane. OS 9832 w / o Si is reference B, which is a commercially available thinfilm pretreatment system Oxsilan®9832 without organic components silane.

[0193] Table 4. Results of diethanolamine based oligomers, Zr-based thinfilm pretreatment systems after ED-coating and hot salt water resistance test in 240 h, on CRS, HDG and AA6014s. OS 9832 is reference A, which is a commercially available thinfilm pretreatment system Oxsilan®9832 based on zirconium and silane. OS 9832 w / o Si is reference B, which is a commercially available thinfilm pretreatment system Oxsilan®9832 without organic components silane. Chemetall GmbH 240142 WO01

[0194] Table 5. Results of diethanolamine based oligomers, Zr-based thinfilm pretreatment systems after ED-coating plus Daimler black and Cyclic Corrosion Test PV1210 (02- 2016), on CRS and HDG. OS 9832 is reference A, which is a commercially available thinfilm pretreatment system Oxsilan®9832 based on zirconium and silane. OS 9832 w / o Si is reference B, which is a commercially available thinfilm pretreatment system Oxsilan®9832 without organic components silane. Chemetall GmbH 240142 WO01

[0195] Table 6. Results of diethanolamine based oligomers, Zr-based thinfilm pretreatment systems after ED-coating plus Daimler black and Filiform Corrosion Test DIN EN ISO 4623-2 (12-2016) and CASS test DIN EN ISO 9227 (03-2023), on AA6014S. OS 9832 is reference A, which is a commercially available thinfilm pretreatment system Oxsilan®9832 based on zirconium and silane. OS 9832 w / o Si is reference B, which is a commercially available thinfilm pretreatment system Oxsilan®9832 without organic components silane.

[0196] Table 7. Results of diethanolamine based oligomers, Zr-based thinfilm pretreatment systems after ED-coating plus Daimler black and Cyclic Cor. Test, Cycle B DIN EN ISO 11997-1 (01 -2018), on CRS and HDG. OS 9832 is reference A, which is a commercially available thinfilm pretreatment system Oxsilan®9832 based on zirconium and silane. OS 9832 w / o Si is reference B, which is a commercially available thinfilm pretreatment system Oxsilan®9832 without organic components silane. Chemetall GmbH 240142W001

Claims

Chemetall GmbH 240142 WO01CLAIMS1 . An aqueous composition AC characterized in that the aqueous composition AC comprises besides water at least one of zirconium, titanium and hafnium cations as constituent(s) a1), and at least one diethanolamine based oligomer as constituent a2), which comprises repeating units of (CH2CH2NHCH2CH2O)n, with n = 2-9, or a concentrate, from which said aqueous composition AC is at least obtainable by dilution with water and, optionally, further, by pH adjustment.

2. A method of chemical pretreatment of at least one metallic surface of at least one substrate characterized in that it comprises at least step 1) and optionally one or more of steps 2) and 3), namely1) contacting the at least one metallic surface of the at least one substrate at least in portion with an aqueous composition AC being suitable to form a coating film at least in portion onto said surface comprising besides water at least one of zirconium, titanium and hafnium cations as constituent(s) a1), and at least one diethanolamine based oligomer as constituent a2), which comprises repeating units of (CH2CH2NHCH2CH2O)n, with n = 2-9, or a concentrate, from which said aqueous composition AC is at least obtainable by dilution with water and, optionally, further, by pH adjustment,2) optionally rinsing the coating film obtained after step 1 ) at least once with at least one aqueous rinsing composition ARC, which is different from aqueous composition AC, and3) optionally curing or drying the optionally rinsed coating film obtained after step 1) or 2) to give a cured or dried coating layer.

3. The method according to claim 2, characterized in that the at least one diethanolamine based oligomer is present as constituent a2) in composition AC in an amount in a range of from 1 to 500 000 mg / L, more preferably of from 2 to 300 000 mg / L, even more preferably of from 3 to 200 000 mg / L, still more preferably of from 4 to 100 000 mg / L, yet more preferably of from 5 to 50 000 mg / L, even more preferably of from 6 to 20 000 mg / L, yet more preferablyChemetall GmbH 240142 WO01 of from 7 to 15 000 mg / L, even more preferably of from 7.5 to 10 000 mg / L, yet more preferably of from 8 to 5 000 mg / L, still more preferably of from 9 to 2 500 mg / L or to 2 000 mg / L, yet more preferably of from 10 to 1 000 mg / L, most preferably of from 15 or 20 to 500 mg / L.

4. The method according to claim 2 - 3, characterized in that the at least one diethanolamine based oligomer as constituent a2) in composition AC has a weight average molecular weight in a range of from 200 to 300 000 g / mol or to 20 000 g / mol, more preferably of from 500 to 200 000 g / mol or to 15 000 g / mol, even more preferably of from 1 000 to 100 000 g / mol or to 10 000 g / mol, still more preferably of from 1 200 to 75 000 g / mol or to 6000 g / mol.

5. The method according to one or more of the preceding claims 2 - 4, characterized in that the aqueous composition AC comprises the at least one of zirconium, titanium and hafnium cations in an amount in a range of from 1 or 5 to 4 000 mg / L, more preferably of from 7.5 to 2 000 mg / L, even more preferably of from 10 to 1 500 mg / L, still more preferably of from 12.5 to 1 000 mg / L, yet more preferably of from 15 to 750 mg / L, even more preferably of from 20 to 500 mg / L in each case calculated as metal.

6. The method according to one or more of the preceding claims 2 - 5, characterized in that the aqueous composition AC is an aqueous acidic composition, preferably has a pH value in a range of from 0.1 to <7.0, more preferably of from 0.5 to 6.5, even more preferably of from 1 .0 to 6.0, yet more preferably of from 1.5 or 2.0 or 5.5, still more preferably of from 2.5 or 3.0 to 5.25, most preferably of from 3.5 or 4.0 to 5.0.

7. The method according to one or more of the preceding claims 2 - 6, characterized in that the aqueous composition AC further comprises fluoride anions including complex fluoride anions as constituent a3), preferably in an amount in a range of from 5 or 10 to 2 000 mg / L, more preferably of from 15 to 1 500 mg / L, even more preferably of from 20 to 1 000 mg / L, still more preferably of from 25 to 500 or to 200 mg / L, in each case calculated as fluorine.Chemetall GmbH 240142 WO018. The method according to claim 7, characterized in that the aqueous composition AC comprises fluoride anions being present therein as complex fluoride anions as constituent a3), which are preferably coordinated to at least one of zirconium, titanium and hafnium cations being also present in the composition as constituent(s) a1), more preferably in an amount of from 1 or 50 mg / L to 4 000 mg / L, still more preferably of from 10 or 100 mg / L to 2 000 or to 1 500 mg / L, yet more preferably in an amount of from 50 or 100 mg / L to 500 or 250 mg / L, calculated in each case as H2MF6 with M = Zr, Ti and / or Hf.

9. The method according to one or more of the preceding claims 2 - 8, characterized in that the aqueous composition AC further comprises at least one organosilane and / or a hydrolysis and / or condensation product thereof as constituent(s) a4), preferably in an amount in a range of from 0 or 5 to 20 000 or to 15 000 mg / L, more preferably of from 0 or 10 to 10 000 or to 5 000 mg / L, even more preferably of from 0 or 15 to 1 000 or to 500 mg / L, still more preferably of from 0 or 20 to 250 or to 200 mg / L, in each case calculated as elemental silicon, and / or zinc cations as constituent a5), preferably in an amount in a range of from 0 or 5 to 5 000 mg / L, more preferably of from 0 or 10 to 2 500 mg / L, even more preferably of from 0 or 25 to 1 000 or to 500 mg / L, in each case calculated as metal, and / or copper cations as constituent a6), preferably in an amount in a range of from 0 or 0,5 to 1 000 mg / L, more preferably of from 0 or 0,5 to 500 mg / L, even more preferably of from 0 or 0,5 to 100 mg / L, still more preferably of from 0 or 0,5 to 50 mg / L, in each case calculated as metal.

10. The method according to one or more of the preceding claims 2 - 9, characterized in that step 3) is performed and that the cured or dried coating layer obtained after step 3) preferably has a dry film thickness below 0.5 pm and / or in that the cured or dried coating layer obtained after step 3) preferably has a coating weight in a range of from 0.5 to 500 mg / m2, more preferably of from 1 to 400 mg / m2, even more preferably of from 2 to 350 mg / m2, determined in each case as tracer element(s) such as Ti, Zr and / or Si via XRF measurements.Chemetall GmbH 240142 WO0111. The method according to one or more of the preceding claims 2 - 10, characterized in that the at least one metallic surface of the at least one substrate is made at least partially of at least one of steel, steel alloys, aluminum, aluminum alloys, zinc, zinc alloys including zinc magnesium alloys, and mixtures thereof, preferably is made at least partially of at least one of steel and steel alloys.

12. A method of coating of at least one chemically pretreated metallic surface of at least one substrate, wherein chemical pretreatment of the at least one metallic surface has been carried out according to the method as defined in one or more of claims 2 to 10, the method of coating further comprising at least step 4), namely4) applying at least one coating material composition comprising at least one film-forming polymer and / or resin onto the optionally rinsed film obtained after step 1) or 2) as defined in claim 2 or onto the dried or cured, preferably dried, film, which in turn is obtainable from drying or curing the film obtainable from optional step 3) as defined in claim 2 or 10.

13. A use of the aqueous composition AC according to claim 1 for providing or improving corrosion resistance of metallic surfaces of substrates and / or for providing or improving adhesion of metallic surfaces of substrates to one or more further coating layers present thereon.

14. A substrate, which is a chemically pretreated substrate being obtainable by the method according to one or more of claims 2 to 11 , or a coated substrate being obtainable by the method according to claim 12.

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