Method for pretreating a metal substrate

Abstract

The present invention relates to a method for pretreating a metal substrate, the method comprising one or more cleaning steps in which at least a portion of the surface of the metal substrate is contacted with one or more aqueous cleaning compositions to obtain a cleaned metal substrate, and / or one or more chemical pretreatment steps selected from a chemical conversion treatment step, a passivation treatment step and a thin layer forming step, in which at least a portion of the surface of the metal substrate is contacted with one or more chemical pretreatment compositions selected from a chemical conversion treatment composition, a passivation treatment composition and a thin layer forming composition to obtain a chemically pretreated substrate, wherein steps i. and / or ii. are followed by one or more rinsing steps, in which at least one composition selected from the cleaning composition, the rinsing composition and the chemical pretreatment composition contains a hydroxyl group represented by formula (I) in an amount of 0.8 to 200 mmol / L. [Formula 1] TIFF2025527793000008.tif4548 (wherein the COOH groups may be fully or partially neutralized and the residues R 1 , R 2 , R 3 , R 4 and R 5 wherein one or more of are independently selected from the group consisting of H, hydroxy groups and alkyl groups. The present invention further relates to a method for coating a metal substrate, the first step of which consists of pretreating the substrate according to the present invention, and after a final rinsing step, applying and curing one or more coating compositions. Furthermore, the present invention relates to the use of an aqueous composition comprising a compound of formula (I) and / or a salt thereof in the pretreatment of a metal substrate, the pretreatment comprising at least one of a washing step and a chemical pretreatment step, and further comprising at least one rinsing step.

Description

[Technical Field]

[0001] The present invention relates to a method for pretreating a metal substrate with one or more rinse compositions following cleaning and / or conversion coating of the substrate, and to a method for using a rinse composition following cleaning and / or chemical pretreatment, particularly to prevent rust formation. The present invention further relates to a method for coating a metal substrate, the first step of which is a pretreatment method according to the present invention. [Background technology]

[0002] During the manufacturing process of metal sheets, the deformation process of the sheet generates impurities, such as mill scale, oxide layers, and drawing grease, which must be removed before any permanent coating layer can be applied to the sheet. Furthermore, since such metal sheets are intended to be coated with one or more coating compositions, following their manufacture, an oxide layer rapidly forms on the surface of the raw sheet. For this reason, metal sheets are typically coated with anti-rust oil immediately after manufacture as a temporary anti-rust protection.

[0003] Therefore, before applying a high quality coating to a metal substrate, the substrate must be thoroughly cleaned to remove the aforementioned impurities, oils and greases to prevent defects from forming in the final coating structure.

[0004] In high quality coatings, following cleaning of the sheet, a chemical pretreatment composition, such as a conversion coating composition or a film-forming composition, is applied to the cleaned metal sheet to form a conversion coating layer to enhance corrosion protection of the sheet, prior to subsequent coating steps such as electrodeposition coating, coating with a primer filler, basecoat and clearcoat, or powder coating.

[0005] To avoid contamination of the chemical pretreatment composition with the cleaning composition used to clean the metal substrate, the metal substrate is rinsed with one or more rinse compositions following the cleaning procedure and before performing the conversion coating process. Similarly, excess chemical pretreatment composition must be removed by rinsing the chemically pretreated substrate prior to any subsequent coating step, such as electrodeposition coating.

[0006] It has been observed that after cleaning and / or chemical pretreatment, there is a risk of rust formation, in particular flash rust formation, during and / or immediately after the rinsing step.

[0007] The object of the present invention was therefore to avoid such rust formation during methods for pre-treatment of metal substrates.

[0008] The prior art describes rust inhibitor formulations, but most of the formulations contain, inter alia, nitrogen- and / or phosphorus-containing compounds which should be avoided, since nitrogen, especially in the form of toxic nitrite ions, is known to have adverse health and environmental effects, and phosphorus-containing formulations are also known for environmental problems.

[0009] Nevertheless, many rust-inhibiting formulations, such as those proposed in CN109112515A, use harmful amounts of sodium nitrite or nitric acid, and the rust inhibitors are elaborate compositions containing acetic acid, acrylic acid, and stearic acid, polyethylene glycol, quartz sand, sodium (bis)carbonate, sodium benzoate, and detergents such as sodium lauryl sulfate and fatty alcohol sulfates, and less than 60% by weight of water. A similar composition, such as that disclosed in CN109112516A, contains hydrochloric acid instead of nitric acid, and chloride ions are known to actually cause corrosion. Other formulations, such as those described in CN102181854, contain gluconates, triethanolamine, molybdate, aminophosphonic acid, sodium benzoate, and nonionic surfactants.

[0010] Further metal corrosion inhibitors containing a substantial amount of phosphoric acid or a phosphate, benzoic acid or a benzoate, triethanolamine, and at least one selected from mercaptobenzothiazole and its salts, benzotriazole, and tolyltriazole are known for use in cooling systems in contact with various metal parts, for example from US 4,219,433. Another phosphate-containing corrosion inhibitor containing sodium hexametaphosphate, N-nitrosophenylhydroxylamine, a benzoate, a zinc salt, and hexamethylenetetramine is described in CN 103602991A.

[0011] All of the above formulations contain various compounds that can adversely affect the coating of metal substrates, and some even contain materials that should be removed during the cleaning step(s) of the metal substrate. Thus, the compositions cannot be used to prevent flash rust formation that occurs during or after cleaning, rinsing, and / or chemical pretreatment of metal substrates.

[0012] It is commonly known that organic coating compositions, applied following a prior pretreatment, may contain rust inhibitors. As part of these organic coating compositions, these compounds become a permanent part of the cured coating layer and remain in the cured coating layer in either a reacted or free form.

[0013] However, the present invention is directed to the use of flash rust inhibition in a pretreatment step prior to further coating steps, which may be accomplished, for example, with a primer filler composition, basecoat composition and / or clearcoat composition having flash rust inhibition functionality, or with a powder coating.

[0014] The intention is to provide a method that will have as little effect as possible on the formulation of subsequent organic coating compositions, and thus, unlike their use as additives in organic coatings, there is no need to directly incorporate the corrosion inhibitor into such organic coating compositions.

[0015] Furthermore, flash rust formation is already prevented during and after the pretreatment process of the metal substrate, preferably the rinsing step of the metal surface pretreatment. [Prior art documents] [Patent documents]

[0016] [Patent Document 1] CN109112515A [Patent Document 2] CN109112516A [Patent Document 3] CN102181854 [Patent Document 4] US4,219,433 [Patent Document 5] CN103602991A Summary of the Invention [Problem to be solved by the invention]

[0017] Accordingly, a primary object of the present invention is to provide a method for pretreating a metal substrate, the method including at least one cleaning, rinsing, or chemical pretreatment step using a composition that is free of health- and environmentally harmful nitrites, and that prevents or inhibits the formation of rust, particularly flash rust, before a subsequent typical coating composition is applied. Furthermore, the composition, particularly the rinsing composition, does not interfere with any of the subsequent steps, such as electrodeposition coating. Furthermore, such composition(s) used in the method for pretreating a metal substrate should be easily applicable, cost-effective, and easy to manufacture. [Means for solving the problem]

[0018] Surprisingly, the object of the present invention is a method for pre-treatment of a metal substrate, comprising the following steps: i. one or more pretreatment steps selected from the group consisting of a cleaning step, wherein at least a portion of the surface of the metal substrate is contacted with one or more aqueous cleaning compositions to obtain a cleaned metal substrate; and / or preferably, ii. One or more chemical pretreatment steps selected from a chemical conversion treatment step, a passivation treatment step, and a thin layer formation step, in which at least a portion of the surface of the metal substrate is contacted with one or more chemical pretreatment compositions selected from a chemical conversion treatment composition, a passivation treatment composition, and a thin layer formation composition to obtain a chemically pretreated substrate. Including, Steps i. and / or ii. are preferably followed directly by one or more rinsing steps, in which at least one composition selected from cleaning compositions, rinsing compositions and chemical pretreatment compositions is present in an amount of 0.8 to 200 mmol / L of formula (I) [ka] wherein the COOH groups may be completely or partially neutralized and the residue R 1 , R 2 , R 3 , R 4 and R 5 are independently selected from the group consisting of H, a hydroxy group, and an alkyl group. a composition of one or more compounds of It has been found that this can be achieved by providing:

[0019] Hereinafter, the above-described method for pretreating a metal substrate and its preferred embodiment will be referred to as the "method for pretreating a metal substrate according to the present invention."

[0020] A further subject of the invention is a method for coating a metal substrate, comprising the method for pretreating a metal substrate according to the invention as described above, which comprises, after a final rinsing step, iii. applying one or more coating compositions selected from the group of solid coating compositions and liquid coating compositions to form one or more coating layers, each of which may or may not be cured after application; and iv. curing any one or more coating layers applied in step iii., whether or not cured in step iii.; Includes:

[0021] Hereinafter, the above-described method for coating a metal substrate and its preferred embodiments will be referred to as the "method for coating a metal substrate according to the present invention."

[0022] A further subject of the present invention is the use of an aqueous composition for the pretreatment of metal substrates, which aqueous composition comprises a compound of formula (I) above, in which the COOH groups may be completely or partially neutralized and the residue R 1 , R 2 , R 3 , R 4 and R 5 wherein one or more of are independently selected from the group consisting of H, a hydroxy group, and an alkyl group, and the aqueous composition is selected from the group consisting of a cleaning composition, a rinse composition, and a chemical pretreatment composition.

[0023] Hereinafter, the above-described method of use and its preferred embodiments will be referred to as "the method of use according to the present invention."

[0024] The invention is described in more detail in the following sections. DETAILED DESCRIPTION OF THE INVENTION

[0025] The terms used in the present invention are defined below.

[0026] The terms "pretreatment" or "pretreating" as used herein are used in accordance with the term "surface pre-treatment" as defined in the Römpp Lexikon "Lacke und Druckfarben" (publisher: Ulrich Zorll, editor: Hans-Juergen P. Adler-Stuttgart; New York: Thieme, 1998; Terms: "Oberflaechenvorbehandlung" p. 417).

[0027] For metal substrates, according to DIN 50902:1994-07, the first step in surface treatment is a layer removal step, also called the "surface preparation step", which comprises one or more (chemical) cleaning steps using aqueous or non-aqueous cleaning compositions.

[0028] The term "chemical pretreatment" is used in accordance with EN ISO 4618:2006 (E / F / D) (term: 2.41 "chemical pretreatment", which denotes any chemical process applied to a surface prior to the application of a coating material). According to this standard, treatments such as chromate treatments and phosphate treatments, which belong to chemical conversion coatings, belong to chemical pretreatments and are therefore distinguished from coating processes in which a coating material, such as a coating composition, e.g., a powder coating composition, an electrodeposition coating composition, or an aqueous or non-aqueous liquid coating material, is applied.

[0029] In addition to typical conversion treatments, such as chromate and phosphate treatments, chemical surface pretreatment can be accomplished using passivating and film-forming compositions, which are described in more detail below.

[0030] In accordance with the above-mentioned internationally valid definition of "pretreatment" of metal substrates, the pretreatment method according to the invention comprises a surface preparation cleaning step and / or a chemical pretreatment step, and in each case at least one rinsing step.

[0031] The term "metallic substrate" encompasses any substrate having a surface comprising one or more pure metals and / or alloys, in accordance with the general understanding of the term. When a substrate comprises regions of different metals, the substrate is referred to herein as a "multi-metallic substrate," a subclass of metallic substrate.

[0032] The term "at least a portion of the metal substrate" means, in accordance with the common understanding of the term, that in some cases it is desirable to contact the surface of the substrate with the cleaning composition, the rinsing composition, and / or the chemical pretreatment composition not necessarily over the entire surface of the substrate, or that it is sufficient not to contact the entire surface of the substrate. When only a portion of the metal surface is contacted with each composition, it is typically the same portion for every step of the method. However, it is generally desirable to contact the entire surface of the metal substrate with each composition(s).

[0033] The term "contacting the surface of a substrate" encompasses any kind of direct contact, in accordance with the common understanding of the term.

[0034] The term "composition" refers to a substance that is composed of one or more material components, typically multiple material components. However, for example, a "rinse composition" may even consist solely of water.

[0035] The term "aqueous," in combination with the term "composition," means that the volatile content of the composition, in which other ingredients may be dissolved or dispersed, contains primarily or even consists of water. The water content of such compositions, particularly aqueous rinse compositions, relative to the total weight of the composition, is preferably 97% to 100%, for example 97% to 99.99%, more preferably 98% to 99.99%, even more preferably 99% to 99.98%, and most preferably 99.50 to 99.97% by weight.

[0036] The term "cleaning composition" defines, in accordance with the common understanding of the term, a composition that removes impurities from the surface of a metal substrate to be further processed, i.e., cleans the metal substrate, but does not remain permanently on the surface of the metal substrate. Thus, the term "cleaning composition" differs from the term "coating composition," since a coating composition is intended to remain permanently on the substrate.

[0037] The term "rinsing composition" defines, in accordance with the general understanding of the term, a composition that removes excess portions of a composition that has come into contact with the metal surface in the step immediately preceding the rinsing step in which the rinsing composition is used. In the simplest case, the rinsing composition can be pure, for example deionized water.

[0038] As used herein, the term "chemical pretreatment composition" encompasses "conversion treatment composition," "passivation treatment composition," and "film-forming composition."

[0039] The term "conversion treatment composition" defines, in accordance with the common understanding of the term, a composition which, when applied to a base metal, produces a surface layer containing compounds of the base metal (often called a conversion coating) and environmental anions (ISO 2080:2008(E / F), terminology: 2.3 "Conversion treatment").

[0040] Pretreatment method according to the present invention The method of pretreating a metal substrate according to the present invention provides a method of pretreating a metal substrate specifically to prevent or inhibit flash rust formation.

[0041] The method includes at least one combination of one or more washing steps with one or more subsequent rinsing steps, or at least one combination of one or more chemical pretreatment steps with one or more subsequent rinsing steps. Thus, hereinafter, the compound of formula (I), which may be fully or partially neutralized, and the washing and chemical pretreatment steps will be described in more detail first, and then the one or more rinsing steps will be described, since the rinsing steps may be performed following the washing steps and / or following the chemical pretreatment steps as well.

[0042] Compounds of formula (I) At least one composition selected from the cleaning composition, the rinsing composition, and the chemical pretreatment composition comprises a compound represented by formula (I): [ka] and containing one or more compounds of wherein the COOH groups may be completely or partially neutralized and the residue R 1 , R 2 , R 3 , R 4 and R 5 are independently selected from the group consisting of H, a hydroxy group, and an alkyl group.

[0043] In the following, when a compound of formula (I) is mentioned, it is understood to mean the compound defined above and the preferred compound of formula (I) described below. The amounts and ranges of amounts specified are equally valid for the compound of formula (I) defined above and the preferred compound of formula (I) described below.

[0044] Depending on the pH value of the cleaning, rinsing, and chemical pretreatment compositions in which the compounds of formula (I) are used, the COOH groups may be fully or partially neutralized. Regardless, the aforementioned compositions are typically and preferably aqueous compositions, so that at equilibrium, COOH groups are converted to COO - H + There is at least some partial dissociation into groups.

[0045] The term "neutralized" encompasses compounds or salts of formula (I) formed in situ depending on the pH value of the respective composition, but also compounds or salts of formula (I) formed prior to incorporation into the respective composition. Thus, the term "neutralized" includes salts of any commercially available acidic compounds of formula (I), i.e., compounds having a COOH group of formula (I).

[0046] The compound of formula (I) and the fully or partially neutralized compound of formula (I), as present in the respective cleaning, rinsing or chemical pretreatment compositions, preferably have an aqueous solubility in deionized water of at least 0.8 mmol / L at a temperature of 20° C. Thus, the compound of formula (I) and the fully or partially neutralized compound of formula (I) are preferably completely dissolved in the respective compositions at a temperature of 20° C.

[0047] OH and / or alkyl substituted compounds of formula (I), i.e., R 1 , R 2 , R 3 , R 4 and R 5 Among the compounds of formula (I) in which at least one of the groups is OH and / or an alkyl group, and the corresponding fully or partially neutralized compounds of formula (I), preference is given to compounds having up to three groups selected from OH and alkyl groups.

[0048] In the case of alkyl groups, from the viewpoint of water solubility, R 1 , R 2 , R 3 , R 4 and R 5 Only one or two of the groups, most preferably R 1 , R 2 , R 3 , R 4 and R 5 Even more preferably, only one of the groups is an alkyl group.

[0049] R 1 , R 2 , R 3 , R 4 and R5 If one or more of the groups is an alkyl group, from the standpoint of water solubility, it is preferred that the alkyl groups independently have 1 to 3, more preferably 1 or 2, and most preferably only 1 carbon atom.

[0050] Most preferably, R 1 , R 2 , R 3 , R 4 and R 5 All of the groups are hydrogen. In such a case, the compound of formula (I) is benzoic acid. Neutralized benzoic acids are particularly salts thereof, preferably water-soluble salts thereof.

[0051] Particularly preferred neutral species of the compounds of formula (I) are the alkali metal, ammonium and quaternary ammonium salts thereof.

[0052] Most preferred are the sodium, potassium, ammonium and tetramethylammonium salts of the compounds of formula (I), and especially preferred are the aforementioned salts of benzoic acid.

[0053] i. Washing step(s) In a first embodiment of the pretreatment method according to the present invention, the metal substrate is subjected to i. one or more cleaning steps, typically i. two or more cleaning steps, in which at least a portion, or preferably the entire surface, of the metal substrate is contacted with one or more cleaning compositions, at least one of which is an aqueous cleaning composition, to obtain a cleaned metal substrate. Preferably, when multiple cleaning compositions are used, every cleaning composition used is an aqueous cleaning composition.

[0054] Metal substrates used in the coating industry often contain impurities on their surfaces, which are physically or chemically attached to the metal surface of the metal substrate. Such impurities include, among others, oils and greases used in the manufacture and customization of metal substrates, or oxidation products, such as metal oxides and / or hydroxides, present on the metal surface of the metal substrate. The presence of such impurities typically leads to defects in the subsequently formed chemical pretreatment layer and coating layer. Such defects can, for example, cause a decrease in the adhesion of the coating layer to the metal substrate surface. Therefore, cleaning of contaminated metal substrates is essential before further use.

[0055] The term "metal substrate" as used herein includes substrates of any shape, for example, flat metal substrates such as simple panels or coils, but also metal substrates of complex shapes, such as automobile bodies or parts thereof. The term "metal" as used herein includes the pure metals and metal alloys described above. Particularly preferred examples of metals and alloys are cold-rolled steel, galvanized steel, for example, hot-dip galvanized steel or electrolytic galvanized steel, and aluminum and its alloys. Particularly preferred substrates are cold-rolled steel and galvanized steel, for example, hot-dip galvanized steel. Furthermore, the term "substrate" also includes pre-assembled metal parts, where the metal parts are of the same metal or alloy, or the metal parts are of at least two different metals or alloys (multi-metal capability of the method).

[0056] The one or more steps of contacting the metal substrate with the cleaning composition can be carried out by any common cleaning procedure. Spray cleaning and / or immersion cleaning are most preferred. The temperature of the cleaning composition used in the one or more steps of cleaning is preferably in the range of 20 to 70°C, more preferably 30 to 65°C, and most preferably 40 to 60°C, for example, 45 to 60°C. The contact period of the metal substrate with the cleaning composition is preferably in the range of 0.5 to 15 minutes, more preferably 1 to 10 minutes, and most preferably 2 to 5 minutes.

[0057] Cleaning Composition In principle, any type of commonly used cleaning composition can be used in one or more cleaning steps in the pretreatment method according to the invention, depending on the type of impurities to be removed and the metal or alloy that the substrate comprises or consists of.

[0058] The cleaning compositions are preferably aqueous and preferably have a pH value in the range of 3.5 to 12.5 at 20° C. Cleaning compositions having a pH value in the range of 3.5 to less than 6 at 20° C. are generally designated as acidic cleaning compositions, while cleaning compositions having a pH value in the range of 6 to 8 at 20° C. are designated as neutral, and cleaning compositions having a pH value in the range of greater than 8 to 12.5 at 20° C. are designated as alkaline cleaning compositions. Regardless of its acidic, neutral, or alkaline pH value, the cleaning composition preferably does not contain nitrates or nitric acid, and even more preferably, the cleaning composition does not contain nitrates, nitric acid, and phosphorus-containing material components.

[0059] Preferred acidic cleaning compositions have a pH value in the above range and contain one or more ingredients selected from the group consisting of inorganic acids, such as sulfuric acid, organic acids, complexing agents, surfactants, and fluorides.

[0060] Preferred neutral cleaning compositions have a pH value within the above range and contain one or more ingredients selected from the group consisting of pH adjusters, alkanolamines, caustic agents, surfactants and complexing agents.

[0061] Preferred alkaline cleaning compositions have a pH value in the range of 8 to 12.5, more preferably 9 to 11, for example 10 to 11. Preferably, the alkaline cleaning composition comprises one or more ingredients selected from the group consisting of a pH adjuster, a caustic agent, a surfactant, and a complexing agent.

[0062] Suitable cleaning compositions and / or water-dilutable concentrates thereof are commercially available, for example, under the trade name Gardoclean® from Chemetall GmbH, Frankfurt, Germany.

[0063] Because typical ingredients of cleaning compositions, and often their rather extreme pH values, negatively interfere with subsequent steps, such as chemical pretreatment, the cleaning step(s) preferably follow directly with one or more rinsing steps. The one or more rinsing steps that follow the one or more cleaning steps, and the rinsing compositions used therein, are described below under the heading "Rinse Step."

[0064] According to the method of the present invention, at least one of the cleaning compositions, or if only one cleaning composition is used, one cleaning composition contains one or more of the above formula (I) (wherein the COOH groups may be completely or partially neutralized and the residue R 1 , R 2 , R 3 , R 4 and R 5 wherein one or more of the following are independently selected from the group consisting of H, a hydroxy group, and an alkyl group) to prevent or inhibit rust, particularly flash rust formation, during and following the cleaning procedure.

[0065] ii. Chemical pretreatment step(s) In a second embodiment of the pretreatment method according to the invention, the metal substrate is subjected to ii. one or more chemical pretreatment steps, preferably ii. one pretreatment step, in which at least a portion or the entire surface of the metal substrate is contacted with one or more chemical pretreatment compositions to obtain a chemically pretreated metal substrate. The metal substrate used in the chemical pretreatment step(s) is the same as that used in the cleaning step(s).

[0066] ii. The one or more steps of contacting the metal substrate with the chemical pretreatment composition can be carried out by any conventional conversion treatment procedure, passivation treatment procedure, and / or film formation procedure. Most preferred are spray application and / or immersion application, with the latter being most preferred. The period of time during which the metal substrate is contacted with the chemical pretreatment composition preferably ranges from 15 seconds to 8 minutes, more preferably from 1 minute to 5 minutes, and most preferably from 2 minutes to 4 minutes.

[0067] Generally, the temperature of the chemical pretreatment composition used in ii. one or more chemical pretreatment steps is preferably in the range of 10 to 60°C, more preferably 15 to 55°C, and even more preferably 20 to 50°C.

[0068] Within the aforementioned ranges, when the chemical pretreatment is thin film formation, the temperature is preferably in the range of 10 to 50° C., more preferably 15 to 45° C., and most preferably 20 to 40° C., for example, 25 to 35° C. When other chemical pretreatment compositions, such as zinc phosphate-based compositions, are used, the temperature is preferably in the range of 20 to 60° C., and most preferably 35 to 50° C., for example, 30 to 55° C.

[0069] Chemical Pretreatment Composition Generally, any known chemical pretreatment composition used in metal surface finishing can be used in ii. one or more chemical pretreatment steps of the method of pretreating a metal substrate according to the present invention.

[0070] The chemical pretreatment composition used in the present invention is preferably an acidic chemical pretreatment composition.

[0071] Preferably, the chemical pretreatment composition used in the coating method according to the present invention comprises: a. Phosphating conversion treatment compositions, including layer-forming and non-layer-forming compositions. Examples of phosphate conversion treatment compositions include: i. Ni-containing and Ni-free zinc phosphating compositions and tricationic phosphating compositions, i.e. so-called "layer forming systems"; ii. Compositions that form amorphous phosphate conversion coatings, i.e., so-called non-layer-forming systems; iii. A phosphate chemical conversion treatment composition containing zinc ions and at least one of manganese ions and nickel ions, including a Ti / Zn-based activation and an optional zirconium-based passivation; and iv. A composition that forms an amorphous iron phosphate conversion coating; b. an organosilane-based film-forming composition containing at least one organosilane and / or its hydrolysis product and / or its condensation product; and c. a passivation composition containing at least one compound selected from the group consisting of zirconium compounds, titanium compounds, and hafnium compounds; d. A passivating and film-forming composition containing at least one compound selected from the group consisting of zirconium compounds, titanium compounds and hafnium compounds, and containing at least one organosilane and / or its hydrolysis product and / or its condensation product; e. Passivation compositions containing at least one compound selected from the group consisting of zirconium compounds, titanium compounds, and hafnium compounds, and one or more polymers selected from the group consisting of poly(vinylphenol), poly(meth)acrylic acid, (meth)acrylic acid copolymers, maleic acid copolymers, phosphonic acid copolymers, particularly (phosphonic acid-acrylic acid) copolymers, polyvinylpyrrolidone and vinylpyrrolidone copolymers, vinyl acetate copolymers, particularly (vinyl alcohol-vinyl acetate) copolymers, ethoxylated polymers such as polyethylene glycol and copolymers, and linear or branched poly(ethyleneimine). is selected from.

[0072] When a phosphate chemical treatment step, particularly a zinc phosphate treatment step or a trication phosphate treatment step, is performed in step ii., it is preferable to perform an additional activation step prior to step ii. If performed, the activation step is carried out by contacting the metal substrate with an activating composition prior to step ii. The contact is preferably carried out by immersion or spraying. Most preferred is contacting the metal substrate with the activating composition by immersion application. The duration of the contact step with the activating composition is preferably in the range of 5 to 300 seconds, more preferably 10 to 200 seconds, and most preferably 20 to 90 seconds, for example 30 to 60 seconds. Activating compositions or solutions are available, for example, from Chemetall GmbH (Frankfurt, Germany) under the trade name Gardolene® V. When an activation step is performed, the activating composition used therein preferably contains zinc phosphate crystals and / or titanium phosphate crystals, which facilitate the deposition of the phosphate chemical layer.

[0073] Among zinc phosphate treatment compositions, Ni-containing compositions may be used. However, for environmental reasons, Ni-free zinc phosphate treatment conversion coating compositions containing Zn and Mn ions are preferred. A further variant of the zinc phosphate treatment conversion coating composition is the so-called tricationic phosphate treatment composition containing Zn, Mn, and Ni ions. Phosphate treatment conversion coating compositions are available, for example, from Chemetall GmbH (Frankfurt, Germany) under the trade names Gardobond® R for zinc phosphate treatments and Gardobond A for amorphous phosphate products.

[0074] The organosilane-based thin-film-forming composition preferably contains at least one organosilane, such as an aminosilane. The term "organosilane" includes its hydrolysis and condensation products, and optionally compounds selected from the group consisting of zirconium compounds, titanium compounds, and hafnium compounds. Such compositions are available for producing thin-film layers, for example, from Chemetall GmbH (Frankfurt, Germany) under the trade name Oxsilan®, such as Oxsilan® 9831, Oxsilan® 9832, Oxsilan® 9810 / 1, and Oxsilan® 9810 / 3.

[0075] The passivation composition preferably contains at least one compound selected from the group consisting of zirconium compounds, titanium compounds and hafnium compounds, more preferably fluorocomplexes of titanium, zirconium and / or hafnium. Such passivation compositions optionally contain one or more organosilanes, the term "organosilanes" including their hydrolysis and condensation products.

[0076] An example of a passivation treatment composition containing at least one compound selected from the group consisting of zirconium compounds, titanium compounds, and hafnium compounds, and containing one or more polymers, is Gardobond® GBX2025 / 2.

[0077] In general, any layer formed in the chemical pretreatment step(s) typically has a thickness of less than 2 μm, for example, phosphate chemical treatments such as iron phosphate treatment and zinc phosphate treatment, preferably 50 nm to 2000 nm, more preferably 500 to 1500 nm, and thin film pretreatments, preferably 20 nm to 300 nm, more preferably 30 to 200 nm.

[0078] According to the method of the present invention, one or more chemical pretreatment compositions, or if only one chemical pretreatment composition is used, one chemical pretreatment composition contains one or more compounds of formula (I) above, wherein the COOH groups may be fully or partially neutralized, and the residue R 1 , R 2 , R 3 , R 4 and R 5 wherein one or more of the following are independently selected from the group consisting of H, a hydroxy group, and an alkyl group) to prevent or inhibit rust, particularly flash rust formation, during and following the cleaning procedure.

[0079] Rinse process(es) One or more rinsing steps, preferably at least two rinsing steps, are performed to: i. remove excess cleaning composition remaining on the surface of the metal substrate after one or more cleaning steps have been performed; and / or ii. remove excess chemical pretreatment composition remaining on the surface of the chemically pretreated metal substrate after one or more chemical pretreatment steps have been performed.

[0080] The rinsing step is preferably carried out by spray or immersion application, preferably immersion application, of the respective rinsing composition.

[0081] In principle, in both cases of steps i. and ii., it is preferred to rinse the cleaned and / or chemically pretreated substrate with tap water and / or deionized water in order to avoid contamination with undesired substances.

[0082] However, it has been observed in many cases that when water alone is used as a rinse composition, the cleaned and / or chemically pretreated metal substrate is prone to rusting, particularly flash rust formation, on its surface unless either i. one of the one or more cleaning compositions or ii. one or more chemical pretreatment compositions are supplemented with the above-specified amount of one or more compounds of formula (I) (as defined above, wherein the COOH groups may be fully or partially neutralized), respectively. However, such rusting or flash rusting generally leads to defects that are detrimental to the formation of further coating layers on the substrate and also cause reduced adhesion and / or reduced corrosion protection of the further coating layers.

[0083] Rinse composition(s) As explained above, the rinse composition used in the rinse step can be carried out with water or water containing drag-over residues from the previous step(s) of the pretreatment method according to the invention, provided that at least one of the cleaning compositions and / or chemical pretreatment compositions used contains a respective amount of one or more compounds of formula (I) (as defined above, wherein the COOH groups may be fully or partially neutralized). If multiple rinse steps are carried out, the first rinse step is preferably carried out using tap water as the rinse composition.

[0084] In the first rinse step, if a spray is applied and tap water is used as the first rinse composition, the water, for example tap water, has a viscosity of 200 to 3500 μS / cm 2 , preferably 200 to 2500 μS / cm 2 The water preferably has a conductivity of 1.413 mS / cm. Of course, water with a lower conductivity, such as deionized water, can also be used as the rinse composition in the first rinse step. Thus, the rinse composition can consist of pure water alone. The conductivity is measured using a commercially available conductivity measuring device (WTW pH / Cond340i, calibrated with a potassium chloride solution with a conductivity of 1.413 mS / cm at 25°C).

[0085] If the first rinse composition is applied by immersion, the same rinse composition as used in the spray application can be used. However, if the metal substrate is rinsed in a continuous process, the rinse composition in the immersion tank will also contain diluted material components from the previous pretreatment step, i.e., from the cleaning step(s) or chemical pretreatment step(s), that have been drawn into the immersion tank from the previously rinsed metal substrate (plate).

[0086] When a first rinse composition is used for the soak rinse, this rinse composition typically has a pH value in the range of 6-10 due to residues from the previous cleaning composition and / or chemical pretreatment composition, and therefore contains all ingredients of the cleaning composition and / or chemical pretreatment composition in highly diluted form, preferably meeting the conductivity ranges described above. Of course, the first rinse step can also be performed with deionized water.

[0087] The second rinse composition also preferably has a pH value in the range of 6 to 10, more preferably 6.5 to 9, due to residues from the first rinse composition, and also contains all the ingredients of the first rinse composition, but further diluted with water. Of course, the second rinse step can also be carried out with deionized water.

[0088] Thus, as the rinsing process progresses, the residue will contain less and less of the ingredients contained in the cleaning composition and / or chemical pretreatment composition.

[0089] Preferably, the last rinse step (which may be the first rinse step if only one rinse step is performed, but may also be the second or any further rinse step) performed following the cleaning step(s) and / or chemical pretreatment step(s) has a saturation of 500 μS / cm 2 Less than, for example, 5 to 500 μS / cm 2 , more preferably 0 to 200 μS / cm 2 Of course, the final rinse step can also be performed with deionized water.

[0090] Rinse compositions containing corrosion inhibitors - Patent Application 20070122997 According to the present invention, if neither i. one of the one or more cleaning compositions nor ii. one or more chemical pretreatment compositions (if used) uses a composition supplemented with the above specified amounts of benzoic acid and / or said salts thereof, then at least one of the rinse compositions used following the cleaning step(s) and / or one of the rinse compositions used following the chemical pretreatment step(s) contains from 0.8 to 200 mmol per liter of composition, preferably from 1.0 to 150 mmol per liter of composition, more preferably from 1.2 to 120 mmol per liter of composition, and even more preferably from 1.6 to 50 mmol per liter of composition, of a compound of formula (I) above, wherein the COOH groups may be fully or partially neutralized and the residue R 1 , R 2 , R 3 , R 4 and R 5 wherein one or more of the COOH groups are independently selected from the group consisting of H, a hydroxy group, and an alkyl group. The most preferred upper limit of the range is 34, 32, 30, 28, 26, 24, or 22 mmol of one or more compounds of formula (I) above (wherein the COOH groups may be fully or partially neutralized) per liter of rinse composition.

[0091] water and possible residues from the preceding washing and / or chemical pretreatment steps, and the above formula (I) (wherein the COOH groups may be fully or partially neutralized and the residue R 1 , R 2 , R 3 , R 4 and R 5 wherein one or more of are independently selected from the group consisting of H, a hydroxy group, and an alkyl group), and optionally a pH adjuster, the rinse composition is preferably not supplemented with any further material components.

[0092] However, if further ingredients are included, the main ingredient, excluding the pH adjuster, contained in the corrosion inhibitor-containing rinse composition is preferably, in addition to water, one or more compounds of the above formula (I) (wherein the COOH group may be fully or partially neutralized). As the neutralized compound of formula (I), benzoic acid is preferably used in neutralized form, such as sodium benzoate or potassium benzoate.

[0093] The preferred pH range for rinse compositions containing corrosion inhibitors is 5-12, more preferably 6-11, and most preferably 7-10.

[0094] Most preferably, no nitrites and / or phosphorus-containing materials are intentionally used in the rinse compositions containing corrosion inhibitors used in the method of pretreating a metal substrate according to the present invention. However, if such materials are included in the cleaning and / or chemical pretreatment compositions, any residue may cause trace amounts of such materials to migrate into the rinse compositions used in the rinsing step.

[0095] Typically, the amount of nitrite, if any, in a rinse composition containing one or more compounds of formula (I) above (wherein the COOH groups may be fully or partially neutralized), is less than 0.1 wt %, more preferably less than 0.01 wt %, and most preferably 0 wt %. Typically, the amount of phosphorus-containing material, if any, in a rinse composition containing one or more compounds of formula (I) above (wherein the COOH groups may be fully or partially neutralized), is less than 0.1 wt %, more preferably less than 0.01 wt %, and most preferably 0 wt %.

[0096] It was very surprising that one or more compounds of the above formula (I) (wherein the COOH group may be fully or partially neutralized) act as effective flash rust inhibitors in rinse solutions, and especially at such low concentrations. It was also surprising that highly diluted solutions of this compound, which typically do not form permanent coatings, are useful in preventing flash rust. The same applies to cleaning compositions that are not expected to remain permanently on metal substrates, but also to layers formed by chemical pretreatments that have very little, if any, ability to entangle one or more compounds of the above formula (I) (wherein the COOH group may be fully or partially neutralized).

[0097] Preferred Step Sequence for Pretreating a Metal Substrate The method for pretreating a metal substrate according to the present invention comprises the following steps: i. one or more pretreatment steps selected from the group consisting of a cleaning step, wherein at least a portion of the surface of the metal substrate is contacted with one or more aqueous cleaning compositions to obtain a cleaned metal substrate, followed by ii. One or more chemical pretreatment steps selected from a chemical conversion treatment step, a passivation treatment step, and a thin layer formation step, in which at least a portion of the surface of the metal substrate is contacted with one or more chemical pretreatment compositions selected from a chemical conversion treatment composition, a passivation treatment composition, and a thin layer formation composition to obtain a chemically pretreated substrate. (Embodiment A), Steps i. and / or ii. are followed by one or more rinsing steps, wherein at least one composition selected from cleaning compositions, rinsing compositions and chemical pretreatment compositions comprises one or more compounds of formula (I) as defined above, wherein the COOH groups may be fully or partially neutralized, in an amount of 0.8 to 200 mmol per liter of composition.

[0098] The method for pretreating a metal substrate according to the present invention comprises the following steps: i. one or more pretreatment steps selected from the group consisting of a cleaning step, wherein at least a portion of the surface of the metal substrate is contacted with one or more aqueous cleaning compositions to obtain a cleaned metal substrate, followed by one or more activation steps, followed by ii. one or more chemical pretreatment steps selected from a phosphate conversion treatment step, wherein at least a portion of the surface of the metal substrate is contacted with one or more chemical pretreatment compositions selected from a phosphate conversion treatment composition to obtain a chemically pretreated substrate; It is further preferred (embodiment B) that Steps i. and ii. are followed by one or more rinsing steps, wherein at least one composition selected from cleaning compositions, rinsing compositions and chemical pretreatment compositions comprises one or more compounds of formula (I) as defined above, wherein the COOH groups may be fully or partially neutralized, in an amount of 0.8 to 200 mmol per liter of composition.

[0099] Alternatively, the method for pretreating a metal substrate according to the present invention comprises the following steps: i. one or more pretreatment steps selected from the group consisting of a cleaning step, wherein at least a portion of the surface of the metal substrate is contacted with one or more aqueous cleaning compositions to obtain a cleaned metal substrate, followed directly by: ii. one or more phosphate-free chemical pretreatment steps to obtain a chemically pretreated substrate; It is further preferred (embodiment C) that the composition comprises: Steps i. and ii. are followed by one or more rinsing steps, wherein at least one composition selected from cleaning compositions, rinsing compositions and chemical pretreatment compositions comprises one or more compounds of formula (I) as defined above, wherein the COOH groups may be fully or partially neutralized, in an amount of 0.8 to 200 mmol per liter of composition.

[0100] For any of the above embodiments A to C, it is further preferred that at least one of the cleaning or rinsing compositions, preferably one of the rinsing compositions, contains the above amounts of one or more compounds of the above formula (I) (wherein the COOH groups may be fully or partially neutralized) described above.

[0101] Even more preferred for any of the above Embodiments A-C is that at least one of the rinse compositions following the first or last washing step, preferably the last rinse composition following the first or last washing step, and / or at least one of the rinse compositions following the chemical pretreatment step(s), preferably the last rinse composition following the chemical pretreatment step(s), before carrying out the activation step(s) in Embodiment B or the chemical pretreatment step(s) in Embodiments A-C, contains the above amounts of one or more compounds of the above formula (I) (wherein the COOH groups may be fully or partially neutralized) as described above.

[0102] In any of the foregoing embodiments A to C, it is preferred that the above-mentioned typical or preferred amounts of one or more compounds of the above-mentioned formula (I) (wherein the COOH groups may be fully or partially neutralized) are contained only in the rinse composition, preferably only in the final rinse composition, and most preferably only in the final rinse composition following a cleaning step, and optionally only in the final rinse composition following a chemical pretreatment step.

[0103] Drying the metal substrate after one or more rinsing steps is optional. If the method for pretreating the metal substrate is performed immediately before powder coating or coating with an aqueous or solvent-based coating composition, it is preferable to first dry the pretreated metal substrate after the final rinsing step. However, if electrodeposition coating follows the final rinsing step, it is typically not necessary to dry the pretreated metal substrate prior to electrodeposition coating, since this is typically performed as an aqueous dip coating.

[0104] Method for coating a metal substrate The method for coating a metal substrate first involves carrying out the method for pretreating a metal substrate according to the present invention, followed by applying one or more coating compositions selected from the group consisting of solid and liquid coating compositions to form one or more coating layers (also referred to herein as paint coating layers, as opposed to any layers that may be formed in the chemical pretreatment step(s)), followed by curing of the one or more coating compositions.

[0105] A further subject of the present invention is therefore a method for coating a metal substrate, said method comprising the following steps: i. one or more pretreatment steps selected from the group consisting of a cleaning step, wherein at least a portion of the surface of the metal substrate is contacted with one or more aqueous cleaning compositions to obtain a cleaned metal substrate; and / or preferably, ii. One or more chemical pretreatment steps selected from a chemical conversion treatment step, a passivation treatment step, and a thin layer formation step, in which at least a portion of the surface of the metal substrate is contacted with one or more chemical pretreatment compositions selected from a chemical conversion treatment composition, a passivation treatment composition, and a thin layer formation composition to obtain a chemically pretreated substrate. Including, Steps i. and / or ii. are directly followed by one or more rinsing steps, wherein at least one composition selected from cleaning compositions, rinsing compositions and chemical pretreatment compositions is / are provided with from 0.8 to 200 mmol per liter of composition, preferably from 1.0 to 150 mmol per liter of composition, more preferably from 1.2 to 120 mmol per liter of composition, and even more preferably from 1.6 to 50 mmol per liter of composition of a compound of formula (I) above, wherein the COOH groups may be completely or partially neutralized and the residue R 1 , R 2 , R 3 , R 4 and R 5 wherein one or more of the following compounds are independently selected from the group consisting of H, a hydroxy group, and an alkyl group; and after the final rinsing step, iii. applying one or more coating compositions selected from the group of solid coating compositions and liquid coating compositions to form one or more coating layers, each of which may or may not be cured after application; and iv. curing any one or more coating layers applied in step iii., whether or not cured in step iii.; Includes:

[0106] The solid coating composition is preferably a powder coating composition, most preferably selected from the group consisting of thermosetting resins. Preferably, the powder coating is selected from the group of resins consisting of, but not limited to, epoxy resins, mixtures of epoxy resins and polyester resins, mixtures of polyester resins and isocyanate components, poly(meth)acrylates, and mixtures of polyesters and triglycidyl isocyanurate.

[0107] The liquid coating composition can be a one-part or two-part coating composition, an aqueous or non-aqueous coating composition. The non-aqueous coating composition can be a solvent-based coating composition, or preferably a solventless radiation-curable coating composition.

[0108] Particularly in automotive OEM coatings, the following sequence of coating steps is carried out: applying an electrodeposition coating composition, applying one or more primer filler compositions, applying one or more basecoat compositions, and applying one or more clearcoat compositions, and curing the resulting coating layers.

[0109] A further subject of the present invention is therefore a method for coating a metal substrate, said method comprising the following steps: i. one or more pretreatment steps in which at least a portion of the surface of the metal substrate is contacted with one or more aqueous cleaning compositions to obtain a cleaned metal substrate; and / or ii. one or more chemical pretreatment steps, contacting at least a portion of the surface of the metal substrate with one or more chemical pretreatment compositions to obtain a chemically pretreated substrate; Including, Steps i. and / or ii. are directly followed by one or more rinsing steps, wherein at least one composition selected from cleaning compositions, rinsing compositions and chemical pretreatment compositions is / are provided with from 0.8 to 200 mmol per liter of composition, preferably from 1.0 to 150 mmol per liter of composition, more preferably from 1.2 to 120 mmol per liter of composition, and even more preferably from 1.6 to 50 mmol per liter of composition of a compound of formula (I) above, wherein the COOH groups may be completely or partially neutralized and the residue R 1 , R 2 , R 3 , R 4 and R 5 wherein one or more of the following compounds are independently selected from the group consisting of H, a hydroxy group, and an alkyl group; and after the final rinsing step, iii. forming one or more coating layers by performing one or more of the following coating steps: applying an electrodeposition coating composition, applying one or more primer filler compositions, applying one or more basecoat compositions, and applying one or more clearcoat compositions, and curing or not curing the coating layer(s) so formed; and iv. curing any one or more coating layers not cured in step iii; Includes:

[0110] Any of the preferred features and embodiments mentioned above in relation to the method for treating a metal substrate are also preferred features and embodiments of the method for coating a metal substrate and therefore will not be explicitly repeated herein below.

[0111] iii. Coating step(s) Following the pretreatment method according to the present invention, and optionally following method embodiments A to C described above, particularly in automotive OEM coatings, it is preferred to apply an electrodeposition coating composition over the only or final chemical pretreatment layer.

[0112] The electrodeposition coating composition is an aqueous coating composition that is applied by dip coating, i.e., by immersing a pickled, chemically pretreated metal substrate in the conductive aqueous electrodeposition coating composition and applying a voltage directly between the substrate and a counter electrode. The electrodeposition coating composition may be an anodic or cathodic electrodeposition coating composition, preferably a cathodic electrodeposition coating composition. The cathodic electrodeposition coating composition is preferably selected from epoxy-type and poly(meth)acrylate-type electrodeposition coating compositions. They are applied according to the coating manufacturer's specifications.

[0113] Following formation of the electrodeposited coating layer, the layer so formed is rinsed and cured, preferably according to the coating manufacturer's specifications.

[0114] Following the electrodeposition coating step, it is preferred to apply one or more additional coating compositions. Such additional coating compositions are preferably selected from water-based coating compositions, solvent-based coating compositions, or UV-curable coating compositions. However, so-called powder coating compositions can also be applied. Particularly preferred is the application of at least one of a primer filler coating composition, a base coat composition, and a clear coat composition, most preferably in this order. When multiple coating layers are formed (i.e., at least two coating compositions are applied), wet-in-wet application can be performed, and the coating layers can then be cured simultaneously. However, it is also possible to perform a drying and / or curing step between the application of at least some or all of the multiple coating compositions.

[0115] Alternatively, a single powder coating composition or a single aqueous or single non-aqueous coating composition can be applied, with or without the application of an electrodeposition coating composition. In particular, when applying a powder coating composition, it is desirable to first dry the rinsed and / or electrodeposition-coated substrate.

[0116] iv. iii. Curing of one or more coatings The conditions of the curing step depend on the coating composition applied subsequent to the method of pretreating a metal substrate according to the present invention.

[0117] As used herein, the term "curing" encompasses any type of curing, preferably physical drying, radiation curing, and thermal curing, with thermal curing preferably encompassing any curing mechanism that relies on chemical crosslinking other than radiation curing. For example, the term thermal curing includes the curing of one-part and two-part compositions. One-part compositions typically cure at temperatures above 100°C, e.g., in the range of 120-200°C, while two-part compositions typically begin to cure at room temperature, e.g., 20-100°C, and are therefore typically not storage stable under ambient conditions.

[0118] The method of coating a metal substrate according to the present invention provides good adhesion and corrosion resistance of the coating to the metal substrate.

[0119] Method of use according to the present invention A further subject of the present invention is the use of an aqueous composition for the pretreatment of metal substrates, which aqueous composition comprises from 0.8 to 200 mmol per liter of composition, preferably from 1.0 to 150 mmol per liter of composition, more preferably from 1.2 to 120 mmol per liter of composition, and even more preferably from 1.6 to 50 mmol per liter of composition of a compound of formula (I) as defined above, in which the COOH groups may be completely or partially neutralized and in which the residue R 1 , R 2 , R 3 , R 4 and R 5wherein one or more of are independently selected from the group consisting of H, a hydroxy group, and an alkyl group, and the pretreatment comprises at least one of a washing step and a chemical pretreatment step, and further at least one rinsing step. Preferably, the aqueous composition is selected from the group consisting of a cleaning composition, a rinsing composition, and a chemical pretreatment composition, preferably a cleaning composition and a rinsing composition, and most preferably, the aqueous composition is a rinsing composition.

[0120] The use according to the present invention provides for the prevention or inhibition of rust formation, particularly flash rust formation, on metal substrates.

[0121] The present invention will be further illustrated by the following examples. [Example]

[0122] Testing of washed and rinsed substrates Flash rust formation test (FRF test) Laboratory-scale simulations of flash rust on steel panel substrates were performed according to two procedures: Procedure 1 used sodium chloride as a flash rust accelerator, while Procedure 2 involved humidity exposure to accelerate flash rust formation.

[0123] Step 1 In this procedure, cold rolled steel panels (CRS panels) are (a) Cleaning by immersion application with 20 g / L GC S5411® / 3 g / L GBA7400 (alkaline builder and organic surfactant, a typical cleaning product from Chemetall GmbH) for 180 seconds at 60°C; (b) After this cleaning process, the panel is first rinsed with tap water for 15 seconds; (c) After the first rinse, a second immersion rinse was performed for 10 seconds with deionized water supplemented prior to use with 200 ppm sodium chloride and no inhibitor (Control 1), or 200 ppm sodium chloride and 40 mg / L sodium nitrite (Comparative Example 1), or 200 ppm sodium chloride and 500 mg / L (≈3.5 mmol / L) sodium benzoate (Example A), or 200 ppm sodium chloride and 3000 mg / L (≈20.8 mmol / L) sodium benzoate (Example B); (d) After the second rinse, the thus treated substrate was allowed to air dry.

[0124] Rust formation was assessed visually (brown stains due to flash rust formation).

[0125] The amount and intensity of flash rust formation was visually assessed and divided into three categories: inhibited (no visible flash rust), partially inhibited (better than "Control 1 or 2", but some rust spots still visible), and uninhibited (no difference from "Control 1 or 2").

[0126] Furthermore, procedure 1 was repeated in the second rinse step (c) with different amounts of sodium benzoate, namely 0.1 g / L (≈0.7 mmol / L), 0.2 g / L (≈1.4 mmol / L), 0.3 g / L (≈2.1 mmol / L), 0.5 g / L (≈3.5 mmol / L), and 3 g / L (≈20.8 mmol / L), dissolved in deionized water supplemented with 200 ppm sodium chloride in each case. The results are shown in Table 1 in the Results section below.

[0127] Step 2 In this procedure, a cold-rolled steel panel (dimensions: 105mm x 95mm x 0.8mm) is (a) Wash as in step 1, (b) Rinse with the first immersion rinse as in step 1; (c) After the first rinse, a second rinse was performed for 10 seconds with deionized water that was supplemented prior to use with either no additives (Control 2), 40 mg / L sodium nitrite (Comparative Example 2), 500 mg / L (≈3.5 mmol / L) sodium benzoate (Example C), or 3000 mg / L (≈20.8 mmol / L) sodium benzoate (Example D); (d) After the second rinse, the thus treated panel is suspended vertically in the center in a closed cylindrical container (125 mm diameter, 280 mm height) with the lowest of the four edges of the panel approximately 1 cm above the surface of the heated tap water for 600 seconds to simulate high humidity; (e) After step (d), the substrate was dried using compressed air.

[0128] Rust formation was assessed visually as in procedure 1 above (brown stains due to flash rust formation).

[0129] Additionally, Procedure 2 was repeated using different amounts of sodium benzoate in the second rinse step (c), namely 0.1 g / L (≈0.7 mmol / L), 0.2 g / L (≈1.4 mmol / L), 0.3 g / L (≈2.1 mmol / L), 0.5 g / L (≈3.5 mmol / L), and 3 g / L (≈20.8 mmol / L) of sodium benzoate in deionized water. The results are shown in Table 1 in the Results section below.

[0130] Testing of cleaned, rinsed, surface treated and further coated substrates Sample preparation The hot-dip galvanized steel (HDG) panels and cold-rolled steel (CRS) panels shown in Table 2 below were immersion cleaned in an alkaline cleaner (containing 20 g / L of GC5345 and 3 g / L of GBA H7406, both commercially available from Chemetall GmbH) for 180 seconds at a temperature of 60°C, followed by a tap water rinse (first rinse) for 30 seconds.

[0131] The first rinse was followed by a second rinse as shown in Table 2. The second rinse was performed for 30 seconds with deionized water (DI water) alone (Comparative Example*) or with deionized water supplemented with 0.5 g / L sodium benzoate (Inventive Example).

[0132] Following the second rinse, the substrates (panels) of Examples 2a*, 2b*, 3a*, 3b*, 5a*, 5b*, 6a and 6b were exposed to high humidity according to step (d) of Procedure 2 above, and then dried according to step (e) of Procedure 2.

[0133] After the second rinse, the panels, with or without high humidity treatment, were immersion treated for 180 seconds at a temperature of 60°C in various chemical pretreatment baths as shown in Table 2. For Examples 1a*, 1b*, 2a*, 2b*, 3a and 3b, the chemical pretreatment was carried out with OS9832, and for Examples 4a*, 4b*, 5a*, 5b*, 6a and 6b, the chemical pretreatment was carried out with GB X2025 / 2.

[0134] After chemical pretreatment, all samples were washed with deionized water for 30 seconds and then dried at a temperature of 120° C. for 30 seconds.

[0135] Following this completed pretreatment, the panels were coated with an electrodeposition coating composition (BASF Cathoguard® 800) and cured at 175°C for 20 minutes to give an electrodeposition coating layer with a dry thickness of approximately 20±2 μm.

[0136] The test specimens thus obtained were tested in the natural salt spray test, the VDA new climate change test, and the climate change test PV1210, which are described in detail below.

[0137] Neutral salt spray test (NSS test) The NSS test was used to measure the corrosion resistance of coatings on substrates. According to DIN EN ISO 9227 NSS (dated September 1, 2012), the NSS test was performed on conductive substrates coated with the coating composition of the present invention or the comparative coating composition. In this test, the sample to be analyzed is placed in a chamber that continuously mists the sample with a 5% strength common salt solution at a temperature of 35°C for a period of 1008 hours, with the pH controlled between 6.5 and 7.2. The mist deposits on the sample under analysis, covering it with a corrosion film of saltwater. Prior to the NSS test according to DIN EN ISO 9227 NSS, the coating of the sample to be analyzed is scored with a blade (Scratch Master 1 mm blade, 75 μm) down to the substrate, and the degree of underfilm corrosion (erosion) of the sample can be determined according to DIN EN ISO 4628-8 (dated March 1, 2013). This is because the substrate corrodes along the score line during the DIN EN ISO 9227 NSS test. This investigation is carried out after the NSS test has been carried out for a period of 1008 hours. As a result of the corrosion progression, the coating is more or less eroded during the test. The degree of erosion [mm] is a measure of the resistance of the coating to corrosion. The values ​​are average values ​​for three panels. The results are shown in Table 2.

[0138] VDA New Climate Change Test (VDA New Test, VDA233-102 Test) The VDA New Test was used to measure the corrosion resistance of coatings on substrates. In accordance with DIN 55635 (May 2019), the VDA New Test was performed on conductive substrates coated with the coating composition of the present invention or the comparative coating composition. The climatic test here was performed in six cycles. One cycle here consisted of a total of 168 hours (one week) and included three stages, each representing a 24-hour cycle time. The characteristics of the three stages were as follows: a) Salt spray stage (A): 3 hours of salt spray mist (1% NaCl aqueous solution, 35°C, relative humidity 100) b) Observation stage (B): 3 hours at 25°C and 70% relative humidity c) Low temperature stage (C): 1 hour at -2.5°C, 6 hours at -15°C, and 1 hour at -2°C, without relative humidity adjustment The test cycle consisted of three stages combined in the following order: BACABBA.

[0139] Prior to the climatic testing, each coating on the investigated specimens was scored with a blade down to the substrate, allowing the level of sub-film corrosion (erosion) of the investigated specimens to be assessed according to DIN EN ISO 4628-8 (dated March 1, 2013). During the climatic testing, the substrate corrodes along the score line. As a result of the corrosion process, the coating is eroded to a greater or lesser extent during the test. The degree of erosion [mm] is a measure of the coating's resistance to corrosion. The average erosion level reported in the results below represents the average of the individual values ​​evaluated on three to five different panels, and the individual value for a panel is the average erosion level at 11 measurement points on the panel. The results are shown in Table 2.

[0140] Climate Change Test PV1210 (PV1210 Test) This climatic test was used to determine the corrosion resistance of a coating on a substrate. The climatic test was carried out over 30 so-called cycles. Prior to the PV1210 test, the coating of the test specimen was scored with a blade (Scratch Master 1 mm blade, 75 μm) down to the substrate. The climatic test was then carried out. During the climatic test, the substrate corroded along the score, allowing the extent of undercoat corrosion of the specimen to be tested in accordance with DIN EN ISO 4628-8 (03-2013). As corrosion progresses, the coating is more or less penetrated during the test. The extent of corrosion [mm] is an indicator of the corrosion resistance of the coating. The values ​​are average values ​​for three panels.

[0141] The PV1210 climate test was used to measure the corrosion resistance of coatings on substrates. The climate test was performed on a correspondingly coated conductive substrate consisting of hot-dip galvanized steel (HDG). The climate test consisted of 30 cycles. One cycle (24 hours) consisted of a 4-hour salt spray mist test according to DIN EN ISO 9227 NSS (June 2017), a 4-hour storage period including cooling according to DIN EN ISO 6270-2 (AHT method) of September 2005, and a 16-hour storage period including heating at 40 ± 3°C and 100% atmospheric humidity according to DIN EN ISO 6270-2, AHT method of September 2005. Every 5 cycles included a 48-hour break including cooling according to DIN EN ISO 6270-2, AHT method of September 2005. Therefore, the 30 cycles corresponded to a total of 42 days.

[0142] Prior to the climatic testing, each coating on the investigated samples was scored with a blade down to the substrate, allowing the level of subsurface corrosion (erosion) of the investigated samples to be assessed according to DIN EN ISO 4628-8 (dated March 1, 2013). During the climatic testing, the substrate corrodes along the score line. As a result of the corrosion process, the coating is eroded to a greater or lesser extent during the test. The degree of erosion [mm] is a measure of the coating's resistance to corrosion. The average erosion level reported in the results below represents the average of the individual values ​​evaluated on three to five different panels, and the individual value for a panel is the average erosion level at 11 measurement points on the panel. The results are shown in Table 2.

[0143] result The results of the FRF test were visually evaluated as described above and are shown in Table 1 below.

[0144] [Table 1]

[0145] Inhibition according to FRF Test Procedure 2 was already observed at a sodium benzoate concentration of 0.1 g / L (≈0.7 mmol / L) in deionized water. Inhibition according to FRF Test Procedures 1 and 2 was observed at a sodium benzoate concentration of 0.2 g / L (≈1.4 mmol / L) in deionized water. Concentrations up to 3.0 g / L (≈20.8 mmol / L) of sodium benzoate in deionized water were tested without any detrimental effects. Thus, much higher concentrations of corrosion inhibitor are acceptable. Even at these higher concentrations, the concentration is limited by process economics and the risk of excessive sodium benzoate being drawn into the next step, potentially affecting its performance.

[0146] [Table 2]

[0147] *Comparative example 1 Steps (d) and (e) of Procedure 2 2 OS9832: Oxsilan® 9832, an organosilane-based film-forming composition commercially available from Chemetall GmbH 3 GB X2025 / 2: Gardobond® GB X2025 / 2 polymer-based passivation composition, commercially available from Chemetall GmbH.

[0148] In Comparative Examples 1a* / 1b*, no corrosion inhibitor was used, and exposure to high humidity (simulating flash rust conditions) was not performed. Therefore, the corrosion test results were good. In contrast, in Comparative Examples 2a* / 2b*, the same procedure was followed, but flash rust conditions were simulated, and significantly poorer corrosion test results were observed. In Inventive Examples 3a / 3b, Comparative Examples 2a* / 2b* were repeated, except that the second rinse contained 0.5 g / L, or approximately 3.5 mmol / L, of sodium benzoate. The addition of sodium benzoate prevented the adverse effects of the flash rust simulation test.

[0149] Comparing Inventive Example 3a with Comparative Example 2a*, it is clear that the presence of 0.5 g / L, i.e., about 3.5 mmol / L, of sodium benzoate in the second rinse composition significantly improved the corrosion resistance of OS9832 pretreated hot-dip galvanized steel panels (HDG panels) treated in this manner in the VDA 233-102 test, with the extent of corrosion being only 0.6 mm for Inventive Example 3a compared to 1.9 mm for Comparative Example 2a*.

[0150] A comparison of Inventive Example 3b with Comparative Example 2b* revealed that the presence of 0.5 g / L, or about 3.5 mmol / L, of sodium benzoate in the second rinse composition also significantly improved the corrosion resistance of OS9832-pretreated cold-rolled steel panels (CRS panels) treated in this manner. In the NSS test, the extent of corrosion was only 1.3 mm for Inventive Sample 3b compared to 3.2 mm for Comparative Example 2b*; in the PV1210 test, the extent of corrosion was only 0.8 mm for Inventive Sample 3b compared to 2.5 mm for Comparative Example 2b*; and in the VDA233-102 test, the extent of corrosion was only 2.1 mm for Inventive Sample 3b compared to 4.7 mm for Comparative Example 2b*.

[0151] Furthermore, Inventive Example 3b and Comparative Example 2b* were exposed to high humidity. Inventive Example 3b, no visible flash rust was formed, but Comparative Example 2b* showed strong flash rust formation.

[0152] The results were even more impressive when comparing inventive examples 6a and 6b with comparative examples 5a* and 5b*, and especially when comparing inventive example 6b with comparative example 5b*.

[0153] Comparing Inventive Example 6a with Comparative Example 5a*, it is clear that the presence of 0.5 g / L, i.e. about 3.5 mmol / L, of sodium benzoate in the second rinse composition significantly improved the corrosion resistance of the GB X2025 / 2 pretreated hot-dip galvanized steel panels (HDG panels) treated in this way in the VDA 233-102 test, with the extent of corrosion being only 0.5 mm for Inventive Example 6a compared to 1.7 mm for Comparative Example 5a*.

[0154] A comparison of Inventive Example 6b and Comparative Example 5b* revealed that the presence of 0.5 g / L, i.e., about 3.5 mmol / L, of sodium benzoate in the second rinse composition significantly improved the corrosion resistance of GB X2025 / 2 pretreated cold-rolled steel panels (CRS panels) treated in this manner in the VDA 233-102 test: in the NSS test, the extent of corrosion was only 1.3 mm for Inventive Example 6b compared to 3.0 mm for Comparative Example 5b*; in the PV1210 test, the extent of corrosion was only 0.8 mm for Inventive Example 6b compared to 2.7 mm for Comparative Example 5b*; and in the VDA 233-102 test, the extent of corrosion was only 2.5 mm for Inventive Example 6b compared to 4.5 mm for Comparative Example 5b*.

[0155] Although the sample used in Inventive Example 6b was exposed to high humidity, no visible flash rust was observed, whereas in Comparative Example 5b*, which was exposed to high humidity, the occurrence of strong flash rust was observed.

Claims

1. 1. A method for pretreating a metal substrate, comprising the steps of: i. one or more pretreatment steps selected from the group consisting of a cleaning step, wherein at least a portion of the surface of the metal substrate is contacted with one or more aqueous cleaning compositions to obtain a cleaned metal substrate; and / or ii. One or more chemical pretreatment steps selected from a chemical conversion treatment step, a passivation treatment step, and a thin layer formation step, in which at least a portion of the surface of the metal substrate is contacted with one or more chemical pretreatment compositions selected from a chemical conversion treatment composition, a passivation treatment composition, and a thin layer formation composition to obtain a chemically pretreated substrate. Including, Steps i. and / or ii. are followed by one or more rinsing steps, using at least one rinsing composition comprising water in the range of 97% to 99.9% by weight and a compound of formula (I) in an amount of 0.8 to 200 mmol / L of said composition. 【Chemical 1】 wherein the COOH groups may be completely or partially neutralized and the residue R １ , R ２ , R ３ , R ４ and R ５ are independently selected from the group consisting of H, a hydroxy group, and an alkyl group. a composition comprising one or more compounds of method.

2. i. one or more washing steps, followed by ii. One or more chemical pretreatment steps wherein steps i. and ii. are followed by one or more rinsing steps; The method of pretreating a metal substrate according to claim 1 .

3. i. one or more washing steps; followed by one or more activation steps, ii. One or more chemical pretreatment steps selected from phosphate conversion treatment steps, wherein at least a portion of the surface of the metal substrate is contacted with one or more chemical pretreatment compositions selected from phosphate conversion treatment compositions. Including, Steps i. and ii. are followed by one or more rinsing steps; The method of pretreating a metal substrate according to claim 1 .

4. i. one or more washing steps, followed directly by ii. One or more phosphate-free chemical pretreatment steps Including, Steps i. and ii. are followed by one or more rinsing steps; The method of pretreating a metal substrate according to claim 1 .

5. 3. The method of claim 1 or 2, wherein one or more compounds of formula (I) as defined in claim 1 are included in at least one of the rinse compositions.

6. 3. The method of pretreating a metal substrate according to claim 1 or 2, wherein the one or more compounds of formula (I) as defined in claim 1 are present in at least one composition selected from a cleaning composition, a rinsing composition, and a chemical pretreatment composition in an amount of 1.0 to 150 mmol per liter of each composition.

7. In one or more compounds of formula (I) above, the residue R １ , R ２ , R ３ , R ４ and R ５ 3. The method for pretreating a metal substrate according to claim 1 or 2, wherein is H and the COOH groups are completely or partially neutralized in the form of their alkali metal, ammonium and / or quaternary ammonium salts.

8. 3. The method of claim 1 or 2, wherein the one or more rinsing steps are performed using one or more rinsing compositions having a pH value in the range of 6-10.

9. The chemical pretreatment composition comprises one of the following: a. A layer-forming phosphate conversion treatment composition and / or a non-layer-forming phosphate conversion treatment composition, preferably i. Ni-containing and Ni-free zinc phosphate treatment compositions and tricationic phosphate treatment compositions; ii. A composition that forms an amorphous phosphate conversion coating; iii. A phosphate chemical conversion treatment composition containing zinc ions and at least one of manganese ions and nickel ions, including a Ti / Zn-based activation and an optional zirconium-based passivation; and iv. Compositions that form amorphous iron phosphate conversion coatings a layer-forming phosphate conversion treatment composition and / or a non-layer-forming phosphate conversion treatment composition selected from the group consisting of: b. an organosilane-based film-forming composition containing at least one organosilane and / or its hydrolysis product and / or its condensation product; and c. a passivation composition containing at least one compound selected from the group consisting of zirconium compounds, titanium compounds, and hafnium compounds; d. A passivating and film-forming composition containing at least one compound selected from the group consisting of zirconium compounds, titanium compounds, and hafnium compounds, and containing at least one organosilane and / or its hydrolysis product and / or its condensation product; e. Passivation compositions containing at least one compound selected from the group consisting of zirconium compounds, titanium compounds, and hafnium compounds, and one or more polymers selected from the group consisting of poly(vinylphenol), poly(meth)acrylic acid, (meth)acrylic acid copolymers, maleic acid copolymers, phosphonic acid copolymers, particularly (phosphonic acid-acrylic acid) copolymers, polyvinylpyrrolidone and vinylpyrrolidone copolymers, vinyl acetate copolymers, particularly (vinyl alcohol-vinyl acetate) copolymers, ethoxylated polymers such as polyethylene glycol and copolymers, and linear or branched poly(ethyleneimine). Selected from: The method for pretreating a metal substrate according to claim 1 or 2.

10. 3. The method of pretreating a metal substrate according to claim 1 or 2, characterized in that contacting the metal substrate with one or more chemical pretreatment compositions is carried out by spray application and / or immersion application for a contact time of 15 seconds to 8 minutes and at a contact temperature in the range of 10 to 60°C.

11. A metal substrate obtainable by the method according to claim 1 or 2.

12. 10. A method for coating a metal substrate, comprising treating the metal substrate with the method for pretreating a metal substrate according to claim 1; After the final rinse step, iii. applying one or more coating compositions selected from the group consisting of solid coating compositions and liquid coating compositions to form one or more coating layers, with or without curing each of the one or more coating layers after application; and iv. curing any one or more coating layers applied in step iii., whether cured or uncured in step iii.; The method includes:

13. 13. The method of coating a metal substrate according to claim 12, wherein in step iii, the one or more coating compositions are selected from the group consisting of powder coating compositions, waterborne one- or two-part compositions, solvent-based one- or two-part compositions, and radiation-curable coating compositions.

14. A coated metal substrate obtainable according to claim 12 or 13.

15. 1. A method for using an aqueous composition in the pretreatment of a metal substrate, the aqueous composition comprising 97 to 99.9% by weight of water and an aqueous solution of formula (I) in an amount of 0.8 to 200 mmol / L of the composition. 【Chemistry 2】 wherein the COOH groups may be completely or partially neutralized and the residue R １ , R ２ , R ３ , R ４ and R ５ wherein one or more of the following are independently selected from the group consisting of H, a hydroxy group and an alkyl group, and said pretreatment comprises at least one of a washing step and a chemical pretreatment step, and further at least one rinsing step.

16. 16. The use of claim 15 for preventing or inhibiting flash rust formation on said metal substrate.

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