Aqueous acid leaching composition and its use

Abstract

The present invention relates to an aqueous composition having a pH value of 5-9 at 55° C., comprising at least one aminoorganophosphonic acid derivative of formula (I), wherein: the radicals R are independently CH 2 ‑PO(OR”) 2 , the groups R' are independently alkylene groups having 2-4 carbon atoms, and the groups R" are independently H, Na, K, Li or NH 4 ; and n is an integer of 0-4; and at least one water-soluble or water-dispersible copolymer selected from at least partially neutralized poly(meth)acrylic acid and polyvinylpyrrolidone; wherein the content of water is 80-99.5% by weight, based on the total weight of the composition. The present invention further relates to a concentrate for preparing the composition, a pickling method for pickling a metal substrate using the composition, a method for coating a metal substrate comprising the pickling method, and the use of the composition for pickling a metal substrate.

Description

[0001] The present invention relates to an aqueous neutral pickling composition for removing rust and scale in a process for pickling a metal substrate, and a concentrate for preparing the composition. The present invention further relates to the process and the use of the composition for pickling a metal surface. In addition, the present invention relates to a method for coating a metal substrate, in particular for improving corrosion protection.

[0002] background

[0003] Oxide layers and other residues not removed after heat treatment of the metal substrate often cause problems in the subsequent conversion coating step, resulting in reduced adhesion of subsequent coatings (especially coatings obtained by cathodic electrodeposition coating) and thus reduced corrosion protection.

[0004] Therefore, usually and especially in the automotive industry, aqueous cleaning and pickling solutions with rather extreme pH values ​​are used before conversion coating. A typical problem associated with highly acidic pickling solutions is the tendency to form rust films after rinsing the surface. In addition, when using highly acidic or highly alkaline compositions, more stringent occupational and industrial safety and transportation safety requirements must be observed. In addition, the pickling compositions are more aggressive to the metal substrates and equipment to be pickled.

[0005] In order to overcome such problems, more and more fluid, neutral rust and scale removal compositions suitable for ferrous and non-ferrous metals and alloys have been developed in recent years and can be used for dipping, immersion and spraying. They are suitable for removing oxide layers from metal surfaces that appear after thermal trimming, laser cutting and welding operations. Compared with pickling compositions based on inorganic acids or strong base compositions, the neutral pickling compositions have many advantages. In contrast to strong acids and strong bases, they are much easier to handle and the surface can usually be cleaned and pickled in one process step. Therefore, additional cleaning steps can usually be omitted.

[0006] In particular, neutral compositions based on phosphonic acids such as 1-hydroxyethane-1,1-diphosphonic acid or aminophosphonic acid are used for the above purpose, since they are known to be complexing agents even in a substantially neutral environment. The term "neutral" as used herein refers to an aqueous composition having a pH value of about 5-9 at 55°C, thus covering slightly acidic and slightly alkaline aqueous compositions.

[0007] On the other hand, phosphonates are generally not preferred when cleaning and pickling metal surfaces of different metal compositions. This is particularly important in the case of pickling of pre-assembled metal parts of different metal compositions, such as steel and galvanized steel in particular, when the same cleaning and pickling composition is used to clean and pickle metal substrates of different compositions either sequentially or simultaneously. This is because phosphonate-based cleaning and pickling solutions generally lack a balanced pickling weight loss for different substrates and have significantly different effects on the surface to be cleaned and pickled, depending on the type of metal or alloy.

[0008] WO 2013 / 156396A1 relates to improving the cleaning performance of protease-containing detergents or cleaning agents on protease-sensitive stains. These cleaning agents rely on active or protease. WO 2013 / 156396A1 discloses that it is well known that detergents containing proteases show improved cleaning performance when containing negatively charged polymers. However, in detergents containing a large amount of surfactants, their combination with negatively charged polymers becomes a problem. In order to overcome the related problems, specific phosphonates are added. Compared with the pickling composition of the present invention, the detergent concentrate disclosed in Example 1 of WO 2013 / 156396A1 contains a relatively low amount of water, while the detergent in the form of use contains more than 99.8% by weight of water. Since the purpose of these compositions is to clean textiles rather than pickling metal surfaces, their pH values ​​are neither optimized nor used to remove metal oxides from metal substrates.

[0009] Therefore, there is a continuing need for improved aqueous neutral compositions which provide improved, in particular balanced, pickling behavior when used on different substrates and which do not adversely affect the subsequent conversion coating process. In particular, the adhesion of subsequent coatings, such as electrodeposition coatings, fillers, basecoats and / or clearcoats, should not be deteriorated.

[0010] Overview

[0011] This need is met by providing an aqueous composition having a pH value of 5 to 9 at 55° C., said aqueous composition comprising at least one aminoorganophosphonic acid derivative of formula (I):

[0012]

[0013] in:

[0014] The groups R are independently CH 2 -PO(OR”) 2 ,

[0015] The radicals R' are independently alkylene radicals having 2 to 4 carbon atoms,

[0016] The groups R" are independently H, Na, K, Li or NH 4 ;and

[0017] n is an integer from 0 to 4;

[0018] and at least one water-soluble or water-dispersible copolymer selected from at least partially neutralized poly(meth)acrylic acid and polyvinylpyrrolidone;

[0019] The water content is 80-99.5% by weight, based on the total weight of the composition.

[0020] Hereinafter, the composition is referred to as "the composition of the present invention" or "the acid leaching composition of the present invention".

[0021] The invention further provides a concentrate comprising the ingredients of the composition of the invention in higher concentrations, which allows the composition of the invention to be prepared where required by dilution with a diluent comprising water and optionally an organic solvent and, if necessary, subsequent adjustment of the pH.

[0022] The present invention further provides a method for acid leaching a metal substrate comprising at least one step of contacting the metal substrate with a composition according to the present invention.

[0023] Hereinafter, this method is referred to as "the acid leaching method of the present invention".

[0024] Another object of the present invention is a method for coating a metal substrate, comprising at least:

[0025] (a) the acid leaching method of the present invention, followed by

[0026] (b) a step of coating the thus acid-impregnated metal substrate with a conversion coating composition, optionally followed by

[0027] (c) applying an electrodeposition coating composition; optionally followed by

[0028] (d) one or more steps of applying one or more further coating compositions.

[0029] Hereinafter, this method is referred to as "the coating method of the present invention".

[0030] Another subject of the invention is the use of the composition according to the invention for acid pickling of metal substrates.

[0031] Hereinafter, this use is referred to as "the use of the present invention".

[0032] Detailed Description

[0033] Compositions of the present invention

[0034] Since the composition of the present invention is an aqueous composition, the main component is water. Based on the total weight of the composition, the content of water is 80-99.5 wt %, more preferably 85-99 wt %, even more preferably 90-98.0 wt %, most preferably 95-97.5 wt %.

[0035] The composition of the present invention may also contain a small amount of one or more organic solvents, which are preferably miscible with or soluble in water. Based on the total weight of the composition of the present invention, their amount is preferably 10 wt % or less, more preferably less than 5 wt %, even more preferably less than 3 wt % or less than 1 wt %. Most preferably, the only solvent used in the composition of the present invention is water.

[0036] The composition of the present invention is preferably an aqueous solution or an aqueous dispersion, most preferably an aqueous solution.

[0037] When used to pickle different metal substrates, the compositions of the present invention generally provide a more balanced pickling. By measuring the pickling weight loss, the extent of pickling of different substrates can be compared. Pickling weight loss is the loss of material during the pickling process, expressed in g / m 2 This amount should not be too low, which would indicate insufficient pickling, nor too high, which would indicate too rough a surface preparation and therefore increase the risk of damaging the substrate surface, resulting in an uneven surface and thus poor adhesion of subsequent coatings.

[0038] Sufficient acid leaching weight loss is preferably from about 0.5 g / m 2 Initially, preferably no more than about 2.5 g / m 2 , therefore, exceptions to this range may be acceptable depending on the desired application. When comparing the difference in pickling weight loss (Δpwl) of different metal substrates pickled with the same pickling composition, it is preferred that the difference be no greater than about 0.6 g / m 2 , even more preferably not more than 0.4 g / m 2 , most preferably not more than 0.3 or 0.2 g / m 2 When the acid leaching is carried out, a balanced acid leaching is generally obtained. The acid leaching weight loss, in particular the above values ​​and (Δpwl) are determined as described in the experimental part of the present application. The above acid leaching weight loss values ​​and Δpwl values ​​are preferably applicable to CRS (cold rolled steel) and HDG (hot dip galvanized steel) and a comparison of the two. However, the acid leaching composition of the present invention is also applicable to other substrates. Aminoorganophosphonic acid derivatives of formula (I)

[0039] The composition of the present invention comprises at least one aminoorganophosphonic acid derivative of formula (I):

[0040]

[0041] in:

[0042] The groups R are independently CH 2-PO(OR”) 2 ,

[0043] The radicals R' are independently alkylene radicals having 2 to 4 carbon atoms,

[0044] The groups R" are independently H, Na, K, Li or NH 4 ;and

[0045] n is an integer from 0 to 4;

[0046] Preferably, the composition according to the invention comprises at least two different aminoorganophosphonic acid derivatives of formula (I) having different values ​​for n.

[0047] It is particularly surprising that the organophosphonic acid derivatives of formula (I) which if used alone lead to unacceptably high acid leaching losses can be used in the compositions of the invention, but when used in admixture with at least one water-soluble or water-dispersible copolymer as defined above provide more balanced acid leaching results.

[0048] In order to provide an aqueous composition of the present invention having a pH of 5 to 9 at 55°C, if a free acid is used, it may be necessary to neutralize the CH groups of the free acid. 2 -PO(OH) 2 At least some of the acidic hydrogen atoms present in the aminophosphonic acid are oxidized to form an alkali or ammonium salt of the aminoorganic phosphonic acid. This is preferably done in situ, i.e. by using KOH, NaOH, LiOH and / or NH 4 OH, particularly preferably the pH adjustment is carried out using aqueous solutions of these bases in an already aqueous composition. However, it is also possible to prepare the salts in advance and dissolve them in the aqueous medium. Most preferably, R" is independently selected from H, K and Na.

[0049] In formula (I), it is further preferred that R' is an alkylene group having 2 or 3 carbon atoms, and most preferably R' is CH 2 CH 2 .

[0050] Furthermore, n is preferably an integer of 0-3, even more preferably n=0, 1 or 2, and most preferably 0 or 1.

[0051] Although all definitions of R, R', R", and n are independently combinable, it is particularly preferred that the radicals R are independently CH 2 -PO(OR”) 2 , the groups R' are independently an alkylene group having 2 or 3 carbon atoms, the groups R" are independently H, Na or K; and n is an integer of 0-3.

[0052] Most preferably, the groups R are independently CH 2 -PO(OR”) 2, the groups R' are independently CH 2 CH 2 , the groups R" are independently H, Na or K; n is 0, 1 or 2, more preferably n=0 or 1.

[0053] An example of a particularly preferred aminophosphonic acid and its salt is aminotri(methylenephosphonic acid) (ie, R=CH 2 -PO(OH) 2 , R'=CH 2 CH 2 and n=0), ethylenediaminetetrakis(methylenephosphonic acid) (ie R=CH 2 -PO(OH) 2 , R'=CH 2 CH 2 and n = 1) and diethylenetriamine penta(methylenephosphonic acid) (i.e. R = CH 2 -PO(OH) 2 , R'=CH 2 CH 2 and n=2) and Li, K, Na and ammonium salts thereof. Among these exemplary salts of aminophosphonic acid, sodium and / or potassium salts are preferred.

[0054] It has generally been found that particularly balanced acid leaching is observed when at least two different aminophosphonic acid derivatives of the formula (I) are used and the different values ​​of n do not differ by more than 2, preferably by more than 1. Thus, if two different amino acid derivatives of the formula (I) are used, preferably Δn=1 or 2, preferably Δn=1.

[0055] Water-soluble or water-dispersible copolymers

[0056] As used herein, the term "copolymer" refers to a polymer composed of at least two different monomers, preferably two different monomers or three different monomers (terpolymer).

[0057] At least partially neutralized poly(meth)acrylic acid

[0058] The term "poly(meth)acrylic acid" as used herein and in general terms encompasses "polyacrylic acid", "polymethacrylic acid" and "poly(acrylic acid / methacrylic acid)".

[0059] Preferably, the at least partially neutralized poly(meth)acrylic acid is a (meth)acrylic acid-maleic acid copolymer. In particular, the at least partially neutralized poly(meth)acrylic acid is an at least partially neutralized polymer polymerized from a mixture comprising (meth)acrylate, maleic acid and / or its anhydride and optionally a carboxyl-free monoethylenically unsaturated monomer.

[0060] If no other non-carboxyl-containing monoethylenically unsaturated monomers are copolymerized, the (meth)acrylic acid-maleic acid copolymer is preferably an alternating copolymer and preferably has a molar ratio of acrylic acid to maleic acid of 50:50.

[0061] Typically, these copolymers are prepared by free-radical polymerization. Since the monomers used in their synthesis carry only one polymerizable group, namely a monoethylenically unsaturated group, the copolymers are linear copolymers.

[0062] Preferably, the weight average molecular weight Mw of the copolymer determined by gel permeation chromatography (GPC) is 15,000-100,000 g / mol, more preferably 20,000-90,000 g / mol, even more preferably 30,000-80,000 g / mol, for example 50,000-70,000 g / mol. GPC can be carried out according to DIN 55672-3:2016-03. Such products are for example sold under the trade name Commercially available from BASF SE, Ludwigshafen, Germany.

[0063] It is also possible to use copolymers which differ from the above-mentioned (meth)acrylic acid-maleic acid copolymers only in that preferably 0-10 mol%, more preferably 1-8 mol%, and most preferably 1-5 mol% of the combined amount of (meth)acrylic acid ester and maleic acid is replaced by a third monoethylenically unsaturated monomer selected from a group not containing carboxyl groups but preferably containing hydrophilic groups, such as acrylic acid ester or methacrylic acid ester. The above-mentioned weight average molecular weight ranges also apply to these copolymers.

[0064] Polyvinylpyrrolidone

[0065] In addition to the at least partially neutralized poly(meth)acrylic acid, a water-soluble or water-dispersible polyvinylpyrrolidone can be combined with the aminoorganophosphonic acid derivative of formula (I) in order to obtain a balanced pickling effect.

[0066] Preferred polyvinylpyrrolidone copolymers are vinyl acetate-vinylpyrrolidone copolymers. In particular, polyvinylpyrrolidone is preferably polymerized from a mixture of vinylpyrrolidone and vinyl acetate and optionally other monoethylenically unsaturated monomers.

[0067] The vinyl acetate-pyrrolidone copolymer is preferably a random copolymer, preferably having a molar ratio of vinyl acetate to vinyl pyrrolidone of 30:70 to 70:30, more preferably 30:70 to 60:40, even more preferably 30:70 to 50:50, for example 40:60.

[0068] Typically, these copolymers are prepared by free radical polymerization. Since the monomers used in their synthesis carry only one polymerizable group, the copolymers are linear copolymers.

[0069] Preferably, the weight average molecular weight Mw of the copolymer determined by gel permeation chromatography (GPC) is 15,000-100,000 g / mol, more preferably 20,000-90,000 g / mol, even more preferably 30,000-80,000 g / mol, for example 50,000-70,000 g / mol. GPC can be carried out according to DIN 55672-3: 2016-03. The polydispersity Mw of the copolymer w / M n Preferably it is 3-7, more preferably 4-6.

[0070] Copolymers which differ from the above-mentioned vinyl acetate-vinyl pyrrolidone copolymers only in that preferably 0-10 mol%, more preferably 1-8 mol%, and most preferably 1-5 mol% of the combined amount of vinyl acetate and vinyl pyrrolidone is replaced by a third monoethylenically unsaturated monomer selected from vinyl monomers, acrylic acid ester monomers, and methacrylic acid monomers may also be used. The above-mentioned weight average molecular weight ranges also apply to these copolymers.

[0071] pH

[0072] The aqueous composition of the present invention has a pH value (measured at 55° C.) of 5-9, preferably 5.5-8.5, more preferably 6.0-8.0, most preferably 6.5-7.5.

[0073] Amount of aminoorganic phosphonic acid derivative and water-soluble or water-dispersible copolymer

[0074] The composition of the invention must contain at least one aminoorganophosphonic acid derivative of the formula (I).

[0075] The amount of all aminoorganophosphonic acid derivatives of formula (I) is preferably 0.2-5.0 wt %, more preferably 0.3-3.0 wt %, most preferably 0.4-2.8 wt %, based on the total weight of the composition of the present invention and as free acid (i.e. R=CH 2 -PO(OH) 2 )calculate.

[0076] The amount of all water-soluble or water-dispersible copolymers (calculated as free acid in the case of partially neutralized poly(meth)acrylic acid and defined as used in the composition of the present invention) is preferably from 0.05 to 2.0% by weight, more preferably from 0.10 to 1.0% by weight, most preferably from 0.15 to 0.5% by weight, based on the total weight of the composition of the present invention.

[0077] All weight % ranges used throughout this specification apply not only to the broadest definition of the respective ingredient, but also to any other preferred embodiments of that ingredient.

[0078] The combined amount of all aminoorganic phosphonic acid derivatives of formula (I) and all water-soluble or water-dispersible copolymers (calculated as free acid in the case of partially neutralized poly(meth)acrylic acid and defined as used in the composition of the invention) contained in the composition of the invention is preferably 0.25-7.0 wt. %, more preferably 0.3-3.0 wt. %, even more preferably 0.4-1.5 wt. %, most preferably 0.5-1.0 wt. %, based on the total weight of the composition of the invention, calculated as free acid in the case of aminoorganic phosphonic acid derivatives of formula (I) and as free acid (COOH) in the case of at least partially neutralized poly(meth)acrylic acid.

[0079] Weight ratio of amino organic phosphonic acid derivative to water-soluble or water-dispersible copolymer

[0080] The weight ratio of the sum of the aminoorganic phosphonic acids of formula (I) to the sum of the water-soluble or water-dispersible copolymers defined in the composition of the present invention is preferably from 1:1 to 30:1, more preferably from 1:1 to 10:1, even more preferably from 1:1 to 5:1, most preferably from 1:1 to 3:1.

[0081] Other Ingredients

[0082] The composition of the present invention may also contain other ingredients such as additives, which are necessarily different from the aminoorganophosphonic acid derivatives of formula (I) and the water-soluble or water-dispersible copolymers defined for the composition of the present invention. The other ingredients are also different from water and organic solvents.

[0083] If present, such additives generally do not interfere with the pickling effect provided by the compositions of the invention, but rather enhance other properties, such as increased shelf life through the addition of preservatives; or a general cleaning or degreasing effect, such as through the addition of surfactants, preferably nonionic surfactants.

[0084] Unlike household cleaning compositions (eg detergents, especially laundry detergents), the compositions of the present invention do not contain proteases, preferably no enzymes at all, since acid leaching is significantly different from enzymatic cleavage reactions, eg cleavage of protein-based soils and / or stains.

[0085] Preferably, the total amount of other ingredients other than the aminoorganic phosphonic acid derivative of formula (I) and the water-soluble or water-dispersible copolymer defined for the composition of the present invention is less than 50% by weight, more preferably less than 40% by weight, even more preferably less than 30% by weight or less than 20% by weight, for example less than 10% by weight, based on the combined amount of the ingredients consisting of the other ingredients, the aminoorganic phosphonic acid derivative of formula (I) and the water-soluble or water-dispersible copolymer defined for the composition of the present invention.

[0086] Preferably, the composition of the present invention contains no other pickling agents or metal ion chelating agents besides the aminoorganophosphonic acid derivative of formula (I) and the water-soluble or water-dispersible copolymer as defined for the composition of the present invention.

[0087] The concentrate of the present invention

[0088] The present invention further relates to a concentrate comprising a liquid medium consisting of water and / or an organic solvent; an aminoorganic phosphonic acid derivative of formula (I) and a water-soluble or water-dispersible copolymer as defined for the composition of the present invention; and any other ingredients of the composition of the present invention. The sum of the amounts of the aminoorganic phosphonic acid derivative of formula (I), the water-soluble or water-dispersible copolymer as defined for the composition of the present invention and the optional other ingredients is preferably 10-90% by weight, more preferably 20-90% by weight, even more preferably 30-90% by weight or 40-90% by weight, and most preferably 50-90% by weight, based on the total weight of the concentrate.

[0089] The concentrate of the present invention is most preferably free of proteases, preferably free of enzymes.

[0090] The concentrate allows the preparation of the composition of the invention when desired, by diluting with a diluent comprising water and optionally an organic solvent and, if necessary, subsequently adjusting the pH to 5-9, preferably 5.5-8.5, more preferably 6.0-8.0, most preferably 6.5-7.5 at 55° C. The concentrate is preferably an aqueous concentrate.

[0091] Preferably, the dilution ratio is from 1:1 (concentrate volume: diluent volume) to 1:50, more preferably from 1:2 to 1:10, most preferably from 1:3 to 1:5.

[0092] Use of the concentrate reduces the need for large storage volumes and facilitates transportation to the point of use.

[0093] Acid leaching method of the present invention

[0094] The acid leaching process of the present invention comprises at least one step of contacting a metal substrate with a composition of the present invention.

[0095] Metal substrate

[0096] The term "metal substrate" as used herein includes substrates of any shape, for example flat metal substrates such as simple plates or coils, but also metal substrates with complex shapes, such as automobile bodies or parts thereof. The term "metal" as used herein includes pure metals and metal alloys. Particularly preferred examples of metals and alloys are cold rolled steel, galvanized steel (such as hot dip galvanized steel or electrolytic galvanized steel) and aluminum and its alloys. Particularly preferred substrates are cold rolled steel and galvanized steel, such as hot dip galvanized steel. In addition, the term "substrate" also includes preassembled metal parts, which are made of the same metal or alloy, or which are made of at least two different metals or alloys (multi-metal capability of the method). Contact of the metal substrate with the composition of the invention

[0097] The step of contacting the metal substrate with the composition of the present invention is preferably a step selected from the following steps:

[0098] (a) immersing a metal substrate in the composition of the present invention,

[0099] (b) immersing a metal substrate with the composition of the present invention; and

[0100] (c) Spraying a metal substrate with the composition of the present invention.

[0101] The composition may be agitated, such as by stirring or the like, while in contact with the metal substrate.

[0102] The metal substrate is preferably contacted with the composition of the present invention for a period of time of 1 to 15 minutes, more preferably 3 to 12 minutes, and most preferably 5 to 10 minutes.

[0103] The temperature of the composition of the present invention during the step of contacting the metal substrate is preferably 20-70°C, more preferably 30-65°C, most preferably 40-60°C, such as 50-60°C.

[0104] In view of maintaining the temperature of the present composition within the above range and optimizing the contact area of ​​the substrate during contact, it is most preferred to contact the metal substrate by immersing the metal substrate in the present composition.

[0105] Optional other steps of the acid leaching method of the present invention

[0106] The acid leaching method of the present invention may comprise one or more steps carried out prior to the at least one step of contacting the metal substrate with the composition of the present invention.

[0107] It should be emphasized that the optional further steps described below are not necessarily the only optional steps possible in the pickling method of the present invention. If desired, in addition to the preferred optional steps, any other cleaning, rinsing and / or drying steps may also be implemented.

[0108] In particular, the pickling process may comprise, prior to said at least one step (iv) of contacting the metal substrate with the composition of the invention, at least one cleaning step (i), preferably followed by at least one rinsing step (ii), even more preferably followed by two rinsing steps (ii) and (iii).

[0109] Therefore, the preferred acid leaching method of the present invention comprises

[0110] (i) a step of contacting the metal substrate with a cleaning composition, optionally followed by

[0111] (ii) a step of rinsing the metal substrate with a first rinse composition, optionally followed by

[0112] (iii) a step of rinsing the metal substrate with a second rinse composition, followed by (iv) a step of contacting the metal substrate with a composition of the present invention.

[0113] The step (i) of contacting the metal substrate with the cleaning composition can be carried out in the same manner as the step of contacting the metal substrate with the composition of the present invention, except that a cleaning composition is used instead of the composition of the present invention. Most preferred is spray cleaning and / or immersion cleaning. The temperature of the cleaning composition used in step (i) is preferably 20-70°C, more preferably 30-65°C, most preferably 40-60°C, for example 45-60°C. The time for which the metal substrate is in contact with the cleaning composition is preferably 0.5-15 minutes, more preferably 1-10 minutes, and most preferably 3-5 minutes.

[0114] The cleaning composition preferably has an alkaline pH of 8-12, more preferably 9-11, for example 10-11 and preferably comprises at least one of a base, a phosphonate, a surfactant and a complexing agent.

[0115] Suitable cleaning agents are available, for example, from Chemetall GmbH (Frankfurt, Germany) under the trade name Commercially available.

[0116] The rinsing steps (ii) and (iii) are preferably carried out by spraying or dipping, preferably dipping in a corresponding rinsing composition. The rinsing composition is generally water or, if dipping is chosen, water containing diluted components of the preceding treatment step due to the unavoidable drag from the preceding bath.

[0117] The first rinse composition preferably has a pH of 9-12 as it is dragged from the previous cleaning composition, and preferably comprises all the ingredients of the cleaning composition, but diluted with water.

[0118] As drawn from the first rinse composition, the second rinse composition preferably has a pH of 8-11, and preferably comprises all the ingredients of the first rinse composition, but diluted with water.

[0119] The rinsing step can also be performed with water alone, especially in laboratory-scale experiments.

[0120] The above-described sequence of steps (i) to (iv) is also a preferred embodiment of step (a) of the coating process according to the invention.

[0121] The acid leaching process of the present invention may further comprise one or more steps after the at least one step of contacting the metal substrate with the composition of the present invention (iv), ie one or more rinsing steps (v) to (vii).

[0122] Therefore, the preferred acid leaching method of the present invention may also include:

[0123] (iv) a step of contacting a metal substrate with the composition of the present invention, followed by

[0124] (v) a step of rinsing the metal substrate with a third rinse composition, optionally followed by (vi) a step of rinsing the metal substrate with a fourth rinse composition, optionally followed by (vii) a step of rinsing the metal substrate with a fifth rinse composition.

[0125] The rinsing steps (v), (vi) and (vii) are preferably carried out by spraying or dipping the corresponding rinsing composition. The rinsing composition may consist only of water, but is usually a water-diluted composition from the previous steps due to drag from the previous steps. If the pickling process according to the invention is carried out continuously, it is particularly preferred to carry out the rinsing steps (v) to (vii). In this case, if the pickling is carried out on an iron-containing metal substrate, an accumulation of iron compounds will occur in the pickling composition. The iron compounds can be rinsed off in each rinsing step.

[0126] The sequence of steps (iv) to (vii) described above is also a preferred embodiment of step (a) of the coating method of the present invention.

[0127] In order to keep the iron compounds in solution, the third cleaning composition preferably has an acidic pH of 1-3, and preferably further comprises the ingredients of the previous pickling composition, but diluted with water.

[0128] To avoid rust film formation after the acid rinse, the fourth rinse composition preferably has an alkaline pH of 9-12 and preferably contains caustic and a complexing agent. Rust film may particularly form if the acid leaching process is run as a continuous process and the process is interrupted and / or the time between steps is too long.

[0129] If the pickling process of the invention is followed in particular by a phosphate conversion coating step, it is preferred that the fifth rinse composition has a pH of 9-10 and contains the ingredients of the fourth rinse composition due to drag, but diluted with water.

[0130] Typically, an activation step is performed before the phosphate conversion coating step, and before the conversion coating step, preferably, the pH value of the rinse composition is neither too high nor too low. Therefore, it is particularly preferred that the pH value of the fifth rinse solution is within the above-mentioned slightly alkaline or neutral range. Particularly preferably, rinsing is performed with water in step (vii).

[0131] Of course, all steps before the step of contacting the metal substrate with the composition of the present invention and steps after the step of contacting the metal substrate with the composition of the present invention may be performed in combination in the acid leaching method of the present invention.

[0132] In this case, the acid leaching method of the present invention preferably comprises:

[0133] (i) a step of contacting the metal substrate with a cleaning composition, optionally followed by

[0134] (ii) a step of rinsing the metal substrate with a first rinse composition, optionally followed by

[0135] (iii) a step of rinsing the metal substrate with a second rinse composition, followed by

[0136] (iv) a step of contacting a metal substrate with the composition of the present invention, followed by

[0137] (v) a step of rinsing the metal substrate with a third rinse composition, optionally followed by (vi) a step of rinsing the metal substrate with a fourth rinse composition, optionally followed by (vii) a step of rinsing the metal substrate with a fifth rinse composition.

[0138] The cleaning compositions, rinse compositions and compositions of the invention are as defined above. The above described sequence of steps (i) to (vii) is also a preferred embodiment of step (a) of the coating process of the invention.

[0139] Coating method of the present invention

[0140] There is further provided a method for coating a metal substrate comprising at least:

[0141] (a) the acid leaching method of the present invention, followed by

[0142] (b) a step of coating the metal substrate thus treated with a conversion coating composition to obtain a conversion coating,

[0143] Optionally followed by

[0144] (c) applying an electrodeposition coating composition to obtain an electrodeposition coating; optionally followed by

[0145] (d) one or more steps of applying one or more further coating compositions to obtain one or more further coating layers.

[0146] It should be emphasized that the steps of the coating method of the present invention as described above are not necessarily the only steps possible in the coating method of the present invention. If necessary, in addition to the above steps, any other rinsing, drying and / or curing steps can also be implemented.

[0147] Therefore, preferably there is at least one rinsing step (b") after step (b) and before step (c). It is also preferred that there is at least one rinsing step (c') followed by a curing step (c") after step (c).

[0148] Preferably, the coating obtained by the coating method of the present invention is a multilayer coating. Even more preferably, the coating obtained by the coating method of the present invention is a coating comprising a conversion coating, an electrodeposition coating and preferably at least one other coating.

[0149] Step (a)

[0150] Therefore, as a pretreatment step, the coating method of the present invention comprises at least step (a), ie the acid leaching method of the present invention, in particular at least step (iv) of the acid leaching method of the present invention.

[0151] More preferably, step (a) contained in the coating method of the present invention comprises steps (iv), (v), (vi) and (vii) of the pickling method of the present invention.

[0152] Even more preferably, step (a) comprised in the coating method of the present invention comprises steps (i) to (vii) of the pickling method of the present invention.

[0153] Step (b)

[0154] Generally, any known conversion coating composition may be used in step (b) of the coating method of the present invention.

[0155] The conversion coating composition used in the present invention is preferably an acidic conversion coating composition.

[0156] Preferably, the conversion coating composition used in the coating method of the present invention is selected from: i. phosphate conversion coating compositions, such as Ni-containing and Ni-free zinc phosphating compositions and trication phosphating compositions, wherein the phosphate conversion coating composition comprises zinc ions and at least one of manganese ions and nickel ions,

[0157] ii. an organosilane-based conversion coating composition comprising at least one organosilane and / or its hydrolysis products and / or condensation products; and

[0158] iii. A passivating conversion coating composition comprising at least one compound selected from the group consisting of zirconium compounds, titanium compounds and hafnium compounds.

[0159] If a phosphate conversion step, in particular a zinc phosphating step or a trication phosphating step, is implemented as step (b), an additional activation step (a') is preferably implemented after step (a) and before step (b). If implemented, the activation step (a') is carried out by contacting the metal substrate with an activation composition after step (a) and before step (b). The contact is preferably carried out by dipping, immersing or spraying, as described for contacting the metal substrate with the composition of the present invention. Most preferably, the metal substrate is contacted by dipping the activation composition. The time of contact with the activation composition is preferably 5-300 seconds, more preferably 10-200 seconds, most preferably 20-90 seconds, for example 30-60 seconds. For example, the activation composition or solution can be, for example, produced by Chemetall GmbH (Frankfurt, Germany) under the trade name V and ZL was purchased commercially.

[0160] If an activation step is carried out, the activation composition used therein preferably comprises zinc phosphate crystals and / or titanium phosphate crystals, which assist the deposition of the phosphate conversion layer.

[0161] If a phosphate conversion step, in particular a zinc phosphating step or a trication phosphating step, is carried out as step (b), an additional passivation step (b') is preferably carried out after step (b) and before step (c). The passivating composition can be obtained, for example, from Chemetall GmbH (Frankfurt, Germany) under the trade name D was purchased commercially.

[0162] Among the zinc phosphating compositions, Ni-containing compositions may be used. However, for environmental reasons, Ni-free zinc phosphating conversion coating compositions are preferred, which contain Zn ions and Mn ions. Another variant of the zinc phosphating conversion coating composition is the so-called tricationic phosphate conversion coating composition containing Zn, Mn and Ni ions. Phosphate conversion coating compositions are available, for example, from Chemetall GmbH (Frankfurt, Germany) under the trade name Commercially available.

[0163] The organosilane-based conversion coating composition preferably comprises at least one organosilane, the term "organosilane" including its hydrolysis products and condensation products, and optionally a compound selected from zirconium compounds, titanium compounds and hafnium compounds. Such compositions can be obtained, for example, from Chemetall GmbH (Frankfurt, Germany) under the trade name Commercially available, it is used to prepare thin film systems.

[0164] The passivating conversion coating composition preferably comprises at least one compound selected from zirconium compounds, titanium compounds and hafnium compounds, more preferably fluorine complexes of titanium, zirconium and / or hafnium. The conversion coating composition optionally comprises one or more organosilanes, the term "organosilanes" including hydrolysis products and condensation products thereof.

[0165] Step (c)

[0166] In step (c), an electrodeposition coating composition is applied to the conversion coating formed in step (b). The electrodeposition coating composition is an aqueous coating composition applied by dipping, i.e., immersing the acid-dipped, conversion-coated metal substrate in a conductive aqueous electrodeposition coating composition and applying a DC voltage between the substrate and a counter electrode.

[0167] The electrodeposition coating composition is an anodic or cathodic electrodeposition coating composition, preferably a cathodic electrodeposition coating composition.

[0168] The cathodic electrodeposition coating compositions are preferably selected from epoxy-type and poly(meth)acrylate-type electrodeposition coating compositions. They are applied according to the coating manufacturer's instructions.

[0169] After step (c), the electrodeposited coating formed is preferably rinsed (step (step (c')) and cured (step (c")) according to the coating manufacturer's instructions.

[0170] One or more steps (d)

[0171] After the electrodeposition coating step (c), preferably one or more other coating compositions are applied. The other coating compositions are preferably selected from water-based coating compositions, solvent-based coating compositions or UV-curing coating compositions. However, so-called powder coating compositions can also be used.

[0172] It is particularly preferred to apply at least one of a filler coating composition, a basecoat composition and a clearcoat composition. If multiple coatings (i.e. at least two coating compositions) are applied, the application can be carried out wet-on-wet and the coatings can then be cured simultaneously. However, a drying step and / or a curing step can also be carried out during the application of at least some or all of the multiple coating compositions that may be used in step (d).

[0173] The method of coating a metal substrate of the present invention provides a well-adherent, corrosion-resistant coating, preferably a multi-layer coating.

[0174] Uses of the present invention

[0175] The present invention further provides the use of the composition of the present invention for acid leaching a metal substrate, wherein the metal substrate is a metal substrate as described above.

[0176] If applied to different metal substrates, the composition and its use provide a balanced and mild, but sufficiently high pickling to allow pickling of different metal substrates successively with the same pickling composition or, if desired, in the form of preassembled parts comprising different metal substrates.

[0177] Hereinafter, the present invention will be further explained by providing working examples. Example

[0178] Testing Procedure

[0179] Determination of weight loss by acid leaching

[0180] Two plates made of CRS (cold rolled steel) and HDG (hot dip galvanized steel) were weighed before being treated with an acid pickling solution.

[0181] After pickling, all panels were rinsed with deionized water, dried and weighed. In each case, the weight loss caused by treatment with the pickling solution (i.e., pickling weight loss) represents the removal of material. In each case, the average of three panels was calculated.

[0182] The weight loss of acid leaching should preferably not exceed 2.5g / m 2 , as surface defects may occur, resulting in poor adhesion of any subsequent coating. In addition, the acid leaching weight loss should preferably not be less than 0.5g / m 2 , because otherwise the pickling may not be sufficient.

[0183] If the difference in weight loss between CRS and HDG after acid leaching is 0.6 g / m 2 or less, and the acid leaching weight loss of both materials is 0.5-2.5g / m 2 , a balanced acid leaching weight loss of a specific acid leaching composition can be achieved.

[0184] Determination of conversion coating weight

[0185] The weight of the conversion layer on the acid-impregnated and zinc-phosphated metal substrates was determined by XRF analysis and expressed in g / m 2 Indicates that as P 2 O 5 calculate.

[0186] For acid-etched and zinc-phosphated metal substrates, if the conversion layer weight of CRS does not exceed 4.0 g / m 2 , the conversion layer weight of HDG does not exceed 3.5g / m 2 , the conversion layer weight is considered good.

[0187] Acid leaching The weight of the conversion layer on the treated metal substrate was determined by XRF analysis and expressed in mg / m 2 Indicates that it is calculated as Zr.

[0188] In acid leaching In the case of metal substrates treated with 9832, if the conversion layer weight of CRS does not exceed 150g / m 2 , the weight of the conversion layer of HDG does not exceed 150g / m 2 , the conversion layer weight is considered good.

[0189] Cross-hatch adhesion test

[0190] Cross-hatch adhesion testing was performed on acid-coated conversion-coated and electrodeposition-coated metal substrates in accordance with DIN EN ISO 2409.

[0191] If no delamination is observed, the result is rated "0" and complete delamination is rated "5". All other delamination ratings are between "0" and "5". Acceptable delamination ratings are "0" or "1". The result is the average of the two panels.

[0192] Electrochemical delamination test

[0193] Electrochemical delamination testing was performed on acid dipped conversion coated and electrodeposition coated metal substrates according to BMW's current AA-0175 standard.

[0194] Delamination is measured in millimeters [mm]. Acceptable delamination is less than 2 mm. The results are the average of two panels.

[0195] Preparation Example

[0196] Acid leaching of metal substrates

[0197] Acid leaching to determine the acid leaching weight loss

[0198] use Panels made of CRS (cold rolled steel) and HDG (hot dip galvanized steel) were spray cleaned for 3 minutes and dip cleaned for 5 minutes with an aqueous solution of S5411 (20 g / L; pH 10.5) at a temperature of 55° C. The panels were then rinsed with water containing the drag ingredients of the previous composition (cleaner bath).

[0199] In each case, two panels were immersed for 10 minutes in a bath containing one of the inventive pickling compositions I1 and I2; or one of the comparative pickling compositions C1, C2 or C3 (see Table 1). The compositions were aqueous solutions of compounds A, B or C (comparative); or aqueous solutions of inventive mixtures of compounds A and B (I1) and B, C and E (I2), as shown in Table 1. The temperature of the bath was 55° C. The panels were rotated at a rate of 250 rpm.

[0200] Table 1

[0201]

[0202] 1 Adjusted by adding 50 wt % KOH aqueous solution;

[0203] A: A copolymer based on acrylic acid, maleic acid and a carboxyl-free hydrophilic ethylenically unsaturated monomer;

[0204] B: Compound of formula (I), R=CH 2 -PO(OH) 2 , R'=CH 2 CH 2 , n = 0;

[0205] C: Compound of formula (I), R=CH 2 -PO(OH) 2 , R'=CH 2 CH 2 , n = 1;

[0206] D: vinyl acetate-vinyl pyrrolidone (40:60) copolymer (molar ratio).

[0207] After the panels were pickled, they were removed from the bath and rinsed with water containing some drag from the previous step. The panels so pickled were dried and used to determine the pickling weight loss according to the above procedure.

[0208] Acid leaching as pretreatment before coating step

[0209] The other panels made of CRS and HDG were cleaned and rinsed as described above and then immersed in a bath containing one of the pickling compositions shown in Table 2 for 5 minutes and 10 minutes, respectively. The pickling composition was an aqueous solution of the invention of a mixture of the corresponding amounts of compounds B and C (I3) and A and E (I4). The bath temperature was 55° C. and stirred at a rate of 250 rpm.

[0210] Table 2

[0211]

[0212] 1 Adjustment was performed by adding aqueous KOH solution;

[0213] A: Copolymer based on acrylic acid, maleic acid and carboxyl-free monomers;

[0214] B: Compound of formula (I), R=CH 2 -PO(OH) 2 , R'=CH 2 CH 2 , n = 0;

[0215] E: Compound of formula (I), R=CH 2 -PO(OH) 2 , R'=CH 2 CH 2 , n=2.

[0216] Prior to conversion coating, the thus acid-impregnated panels are first rinsed with slightly acidic water and then with alkaline water, and then the thus acid-impregnated metal substrates are used in a wet manner prior to carrying out conversion coating.

[0217] Conversion coating of acid-etched metal substrates

[0218] In each case, acid-impregnated panels made of CRS and HDG (impregnated with the acid-impregnating compositions of Table 2) were coated with either a zinc phosphate-based conversion coating composition (available from Chemetall GmbH, Frankfurt, Germany) or a silane-based conversion coating composition ( 9832, available from Chemetall GmbH, Frankfurt, Germany).

[0219] Zinc phosphate conversion coating

[0220] The plate was immersed in 1 g / L of V 6559 solution for 30-60 seconds V 6559 (commercially available from Chemetall GmbH, Frankfurt, Germany) activated panels to be coated with the zinc phosphate conversion coating composition.

[0221] Zinc phosphating is performed by heating the activated panels at 55°C. The coating was carried out by dipping in 24T (commercially available from Chemetall GmbH, Frankfurt, Germany) for 3 minutes.

[0222] Subsequently, the plate was immersed in 2.1 g / L of D68000 / 8 (pH 4.3) solution for 30 seconds Panels coated with the zinc phosphate conversion coating composition were passivated with TU-T® D 6800 / 8 (commercially available from Chemetall GmbH, Frankfurt, Germany).

[0223] Silane-based conversion coating

[0224] The panels to be coated with the silane-based conversion coating composition were neither activated prior to conversion coating nor passivated after conversion coating.

[0225] To prepare the conversion coating, the acid-soaked panels were heated at 32°C in a Conversion coating composition ( 9832) for 3 minutes.

[0226] After conversion coating and prior to electrodeposition coating, the conversion coated acid dipped metal substrate was rinsed with deionized water.

[0227] The panels thus conversion coated were subjected to conversion layer weight determination as described above.

[0228] Electrodeposition coating of conversion coated acid-impregnated metal substrates

[0229] Commercially available from BASF Coatings GmbH (Münster Hiltrup, Germany) The conversion coated acid dipped CRS panels were electrodeposited with the 800 electrodeposition coating composition.

[0230] The thus electrodeposition coated panels were rinsed and dried in an oven at 175°C for 15 minutes to a final thickness of 18-22 μm and then subjected to cross-hatch and electrochemical delamination tests as described above.

[0231] Test Results

[0232] Table 3 below shows the results of acid leaching weight loss measurements and confirms that the mixture of the present invention exhibits mild but sufficient acid leaching, with the acid leaching weight losses of CRS and HDG both being between 0.7 and 0.9 g / m 2 range, and only 0.1g / m 2 Excellent acid leaching weight loss balance.

[0233] In contrast, when an acid leaching solution containing only polymer (C1) or only aminoorganophosphonic acid derivative (C3) of formula (I) was used, insufficient acid leaching was shown, or in the case of C2, aggressive acid leaching of HDG was caused accompanied by uneven acid leaching.

[0234] Table 3

[0235]

[0236] The results shown in Table 4 below reflect the weight of the zinc phosphate conversion layer obtained on CRS and HDG panels pickled for 5 and 10 minutes, respectively, in g / m 2 As P 2 O 5 The target value of CRS is preferably 4 g / m 2 or lower, the target value of HDG is preferably lower than 3.5 g / m 2 , which was observed in all cases when acid soaked for 5 and 10 minutes.

[0237] Table 4

[0238]

[0239] The results shown in Table 5 below reflect the results obtained on CRS and HDG panels pickled for 5 and 10 minutes, respectively. 9832 Weight of conversion layer, g / m 2 The target values ​​of CRS and HDG are preferably less than 150 g / m 2 , which was observed in all cases when acid soaked for 5 and 10 minutes.

[0240] Table 5

[0241]

[0242] Table 6 shows the results of application, rinsing, drying and curing. Before 800 cathode electrodeposition coating, the CRS plates were acid-immersed for 5 minutes and 10 minutes respectively. Cross-hatch adhesion test results obtained for conversion coating of 9832. As shown in all examples, no adhesion failure was observed for any sample.

[0243] Table 6

[0244]

[0245] Table 7 shows the CRS / Results of the electrochemical delamination test of 9832.

[0246] Table 7

[0247]

[0248] Thus, Tables 6 and 7 show that the coatings applied to the acid-impregnated metal substrates of the present invention have perfect adhesion in the cross-hatch adhesion test and the electrochemical delamination test. A good delamination value is a value of <2.0 mm. Both samples showed very good values ​​of less than 1 mm.

Claims

1. An aqueous composition having a pH value of 5 to 9 at 55° C., comprising at least one aminoorganophosphonic acid derivative of formula (I): in: The groups R are independently CH 2 -PO(OR”) 2 , The radicals R' are independently alkylene radicals having 2 to 4 carbon atoms, The groups R" are independently H, Na, K, Li or NH 4 ;and n is an integer from 0 to 4; and at least one water-soluble or water-dispersible copolymer selected from at least partially neutralized poly(meth)acrylic acid and polyvinylpyrrolidone; The water content is 80-99.5% by weight, based on the total weight of the composition.

2. The aqueous composition according to claim 1, wherein R' is CH 2 CH 2 , R" is selected from H, K and Na; n is 0, 1 or 2.

3. The aqueous composition of claim 1, wherein the at least partially neutralized poly(meth)acrylic acid is an at least partially neutralized polymer obtained by polymerization of a mixture comprising (meth)acrylic acid, maleic acid and / or its anhydride and optionally carboxyl-free monoethylenically unsaturated monomers; and the polyvinylpyrrolidone is obtained by polymerization of a mixture of vinylpyrrolidone and vinyl acetate and optionally other monoethylenically unsaturated monomers.

4. The aqueous composition of claim 2, wherein the at least partially neutralized poly(meth)acrylic acid is an at least partially neutralized polymer obtained by polymerization of a mixture comprising (meth)acrylic acid, maleic acid and / or its anhydride and optionally non-carboxyl monoethylenically unsaturated monomers; and the polyvinylpyrrolidone is obtained by polymerization of a mixture of vinylpyrrolidone and vinyl acetate and optionally other monoethylenically unsaturated monomers.

5. The aqueous composition according to claim 3, wherein the at least partially neutralized poly(meth)acrylic acid is a polymer comprising (meth)acrylic acid and maleic acid, and 0-10 mol% of the combined amount of (meth)acrylic acid and maleic acid is replaced by a third monoethylenically unsaturated monomer selected from the group consisting of a non-carboxyl group, and / or the at least partially neutralized poly(meth)acrylic acid has a weight average molecular weight of 15,000-100,000 g / mol as determined by gel permeation chromatography; and / or wherein the polyvinyl pyrrolidone is a random polymer, wherein the molar ratio of vinyl acetate to vinyl pyrrolidone is from 30:70 to 70:30, and 0-10 mol% of the combined amount of vinyl acetate and vinyl pyrrolidone is replaced by a third monoethylenically unsaturated monomer selected from vinyl monomers, acrylate monomers and methacrylate monomers; and / or the polyvinyl pyrrolidone has a weight average molecular weight of 15,000-100,000 g / mol as determined by gel permeation chromatography.

6. The aqueous composition according to claim 4, wherein the at least partially neutralized poly(meth)acrylic acid is a polymer comprising (meth)acrylic acid and maleic acid, and 0-10 mol% of the combined amount of (meth)acrylic acid and maleic acid is replaced by a third monoethylenically unsaturated monomer selected from the group consisting of a non-carboxyl group, and / or the at least partially neutralized poly(meth)acrylic acid has a weight average molecular weight of 15,000-100,000 g / mol as determined by gel permeation chromatography; and / or wherein the polyvinyl pyrrolidone is a random polymer, wherein the molar ratio of vinyl acetate to vinyl pyrrolidone is from 30:70 to 70:30, and 0-10 mol% of the combined amount of vinyl acetate and vinyl pyrrolidone is replaced by a third monoethylenically unsaturated monomer selected from vinyl monomers, acrylate monomers and methacrylate monomers; and / or the polyvinyl pyrrolidone has a weight average molecular weight of 15,000-100,000 g / mol as determined by gel permeation chromatography.

7. The aqueous composition according to any one of claims 1 to 6, having a pH value of 6.0 to 8.

0.

8. An aqueous composition according to any one of claims 1 to 6, wherein the amount of all aminoorganophosphonic acid derivatives of formula (I) is 0.2-5.0 wt %, based on the total weight of the composition and calculated as free acid; and / or The amount of all water-soluble or water-dispersible copolymers, calculated as free acids in the case of partially neutralized poly(meth)acrylic acid, is from 0.05 to 2.0% by weight, based on the total weight of the composition.

9. The aqueous composition according to claim 7, wherein the amount of all aminoorganophosphonic acid derivatives of formula (I) is 0.2-5.0 wt %, based on the total weight of the composition and calculated as free acid; and / or The amount of all water-soluble or water-dispersible copolymers, calculated as free acids in the case of partially neutralized poly(meth)acrylic acid, is from 0.05 to 2.0% by weight, based on the total weight of the composition.

10. An aqueous composition according to any one of claims 1 to 6, wherein the total amount of other ingredients other than the aminoorganophosphonic acid derivative of formula (I) and other than the water-soluble or water-dispersible copolymer calculated as the free acid in the case of partially neutralized poly(meth)acrylic acid is less than 50% by weight of the combined amount of the other ingredients, the aminoorganophosphonic acid derivative of formula (I) and the water-soluble or water-dispersible copolymer calculated as the free acid in the case of partially neutralized poly(meth)acrylic acid.

11. The aqueous composition according to claim 9, wherein the total amount of other ingredients other than the aminoorganophosphonic acid derivative of formula (I) and other than the water-soluble or water-dispersible copolymer calculated as the free acid in the case of partially neutralized poly(meth)acrylic acid is less than 50% by weight of the combined amount of the other ingredients, the aminoorganophosphonic acid derivative of formula (I) and the water-soluble or water-dispersible copolymer calculated as the free acid in the case of partially neutralized poly(meth)acrylic acid.

12. The aqueous composition according to any one of claims 1 to 6, which is free of proteases.

13. The aqueous composition of claim 11, which is free of proteases.

14. A method for acid leaching a metal substrate, comprising at least one step of contacting the metal substrate with an aqueous composition according to any one of claims 1 to 13.

15. The method for acid leaching a metal substrate according to claim 14, wherein include: (i) a step of contacting the metal substrate with a cleaning composition, optionally followed by (ii) a step of rinsing the metal substrate with a first rinse composition, optionally followed by (iii) a step of rinsing the metal substrate with a second rinse composition, followed by (iv) a step of contacting a metal substrate with an aqueous composition according to any one of claims 1 to 13, followed by (v) a step of rinsing the metal substrate with a third rinse composition, optionally followed by (vi) a step of rinsing the metal substrate with a fourth rinse composition, optionally followed by (vii) A step of rinsing the metal substrate with a fifth rinsing composition.

16. A method for acid leaching a metal substrate according to claim 14 or 15, wherein the metal substrate is selected from steel, aluminum and alloys thereof.

17. A method for acid pickling a metal substrate according to claim 14 or 15, wherein the metal substrate is selected from galvanized steel.

18. A method for coating a metal substrate, comprising at least include: (a) a method of acid-dipping a metal substrate according to any one of claims 14 to 17, followed by (b) a step of coating the acid-dipping metal substrate with a conversion coating composition, optionally followed by (c) a step of applying an electrodeposition coating composition, optionally followed by (d) one or more steps of applying one or more further coating compositions.

19. The method of coating a metal substrate according to claim 18, wherein the conversion coating composition used in step (b) is selected from the group consisting of: i. a phosphate conversion coating composition comprising at least one of manganese ions and nickel ions and zinc ions, ii. an organosilane-based conversion coating composition comprising at least one organosilane and / or its hydrolysis product and / or its condensation product; and iii. a passivating conversion coating composition comprising at least one compound selected from the group consisting of zirconium compounds, titanium compounds and hafnium compounds; and In the case of using a phosphate conversion coating composition, before carrying out step (b), the acid-impregnated metal substrate obtained in step (a) is contacted with an activation composition comprising zinc phosphate crystals and / or titanium phosphate crystals; and In case of using a phosphate conversion coating composition, the conversion-coated metal substrate obtained in step (b) is contacted with a passivating composition comprising at least one compound selected from zirconium compounds, titanium compounds and hafnium compounds.

20. The method for coating a metal substrate according to claim 18, wherein the electrodeposition coating composition used in step (c) is selected from anodic and cathodic electrodeposition coating compositions; and in the case of using a cathodic electrodeposition coating composition, the cathodic electrodeposition coating composition is selected from epoxy-type electrodeposition coating compositions and poly(meth)acrylate-type electrodeposition coatings; and after step (c), the electrodeposition coating is dried and cured.

21. A method for coating a metal substrate according to claim 19, wherein the electrodeposition coating composition used in step (c) is selected from anodic and cathodic electrodeposition coating compositions; and in the case of using a cathodic electrodeposition coating composition, the cathodic electrodeposition coating composition is selected from epoxy-type electrodeposition coating compositions and poly(meth)acrylate-type electrodeposition coatings; and after step (c), the electrodeposition coating is dried and cured.

22. The method for coating a metal substrate according to any one of claims 18 to 21, wherein the other coating composition used in step (d) is selected from a filler composition, a basecoat composition and a clearcoat composition.

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