Method for pre-treating metal substrate

Abstract

The present invention relates to a method of pre-treating a metal substrate comprising one or more cleaning steps 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 one or more chemical pretreatment steps selected from the group consisting of a 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 brought into contact with one or more chemical pretreatment compositions selected from the group consisting of a conversion treatment composition, a passivation treatment composition and a thin layer forming composition, performing chemical pretreatment to obtain a chemically pretreated base material; wherein i. And / or ii. Followed by one or more rinsing steps wherein at least one composition selected from the group consisting of a cleaning composition, a rinsing composition and a chemical pretreatment composition comprises one or more compounds of formula (I), the COOH groups of which can be fully or partially neutralized, in an amount of 0.8 to 200 mmol / L of the composition, and wherein one or more of the residues R1, R2, R3, R4 and R5 are selected from the group consisting of H, hydroxyl and alkyl. The invention further relates to a method for coating a metal substrate, in which the first step consists of the method for pre-treating the substrate according to the invention, in which, after the last rinsing step, one or more coating compositions are applied and cured. Furthermore, the present invention relates to the use of an aqueous composition comprising a compound of formula (I) and / or a salt thereof for the pretreatment of a metal substrate, the pretreatment comprising at least one of a cleaning step and a chemical pretreatment step; and further at least one rinsing step. # imgabs0 #

Description

[0001] The present invention relates to a method for pretreating metal substrates after cleaning and / or conversion coating of these substrates with one or more rinse compositions, and the use of these rinse compositions after cleaning and / or chemical pretreatment, in particular for preventing rust formation. The present invention further relates to a method for coating metal substrates, the first step of which is a pretreatment method according to the present invention. Background Art

[0002] During the production of metal sheets, impurities from the deformation process of the sheet (such as mill scale, oxide layers and drawing grease) are generated and must be removed before any permanent coating is applied to the sheet. In addition, after the production of such metal sheets intended to be coated with one or more coating compositions, an oxide layer is quickly formed at the surface of the bare sheet. For this reason, metal sheets are typically coated with anticorrosion oils by way of temporary anticorrosion protection immediately after production.

[0003] Therefore, before applying a high-quality coating to a metal substrate, the substrate must be thoroughly cleaned to remove the above-mentioned impurities, oils and greases to avoid the formation of defects in the final coating structure.

[0004] In high quality coating, cleaning of the sheet is followed by application of a chemical pretreatment composition (e.g., a conversion treatment composition or a thin layer forming composition) to the cleaned metal sheet to form a conversion coating to enhance the corrosion protection of such sheet. Such a step is prior to subsequent coating steps (e.g., electrodeposition coating, coating with a primer filler, basecoat and clearcoat or powder coating).

[0005] In order to avoid contamination of the chemical pretreatment composition with the cleaning composition used in the cleaning of the metal substrate, the metal substrate is rinsed with one or more rinsing compositions after the cleaning procedure and before the conversion coating process is carried out. Likewise, before any subsequent coating step (such as electrodeposition coating), the excess chemical pretreatment composition must be removed by rinsing the chemically pretreated substrate.

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

[0007] It is therefore an object of the present invention to avoid such rust formation during a method for pretreating a metal substrate.

[0008] In the prior art, formulations of rust inhibiting agents are described, most of which contain, inter alia, nitrogen- and / or phosphorus-containing compounds which are to be avoided, since nitrogen, in particular in the form of toxic nitrite ions, is known to have negative effects on health safety and the environment, and phosphorus-containing formulations are also known for their environmental problems.

[0009] However, many anti-rust formulations utilize harmful amounts of, for example, sodium nitrite or nitric acid, as proposed in CN 109112515A, wherein the rust inhibitor is a complex composition further comprising acetic acid, acrylic acid and stearic acid, polyethylene glycol, quartz sand, sodium (bi) carbonate, sodium benzoate and detergents (such as sodium lauryl sulfate and fatty alcohol sulfates), and less than 60 wt.-% of water. Similar compositions are disclosed, for example, in CN 109112516 A, but these compositions contain hydrochloric acid instead of nitric acid, and in fact chloride ions are known to cause corrosion. Other formulations (such as those described in CN 102181854) contain gluconates, triethanolamine, molybdates, aminophosphonic acid, sodium benzoate and nonionic surfactants.

[0010] Other metal corrosion inhibitors containing significant amounts of phosphoric acid or phosphoric acid salts, benzoic acid or benzoic acid salts, triethanolamine, and at least one selected from mercaptobenzothiazole and its salts, benzotriazole and toluenetriazole are known, for example, from US 4,219,433, which are used in cooling systems in contact with various metal parts. CN103602991 A describes another phosphate-containing corrosion inhibitor containing sodium hexametaphosphate, N-nitrosophenylhydroxylamine, benzoate, zinc salt and hexamethylenetetramine.

[0011] All of the above formulations contain various compounds that may adversely affect the coating of the metal substrate, and some of them even contain substances that are to be removed during one or more cleaning steps of the metal substrate. Therefore, these compositions are not intended to be used to prevent flash rust formation from occurring during or after cleaning, rinsing and / or chemical pretreatment of metal substrates.

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

[0013] However, the present invention contemplates the use of flash rust inhibiting functionality for a pretreatment step prior to completing additional coating steps with, for example, a primer filler composition, basecoat composition and / or clearcoat composition having flash rust inhibiting functionality; or with a powder coating.

[0014] The aim is to provide measures which have the lowest possible impact on the formulation of the subsequent organic coating composition. Thus, unlike the use as an additive in organic coatings, it should not be necessary to introduce the corrosion inhibitor directly into such organic coating compositions.

[0015] Furthermore, during the pretreatment of the metal substrate, preferably during and after the rinsing step of the metal surface pretreatment, flash rust formation should already be prevented.

[0016] Therefore, the main object of the present invention is to provide a method for pretreating a metal substrate, wherein the method comprises at least one cleaning, rinsing or chemical pretreatment step with a composition that does not contain nitrites that are harmful to health and the environment, and wherein the composition prevents or inhibits the formation of rust, especially flash rust, before applying a subsequent general coating composition. In addition, the composition, especially the rinsing composition, should not interfere with any subsequent steps, such as electrodeposition coating. In addition, such one or more compositions used in the method for pretreating a metal substrate should be easy to apply, cost-effective and easy to produce. Summary of the invention

[0017] Surprisingly, it has been found that the object of the present invention is achieved by providing a method for pretreating a metal substrate, the method comprising

[0018] 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 clean metal substrate; and / or, preferably as well as,

[0019] ii. one or more chemical pretreatment steps selected from a conversion treatment step, a passivation treatment step and a thin layer forming 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 conversion treatment composition, a passivation treatment composition and a thin layer forming composition to obtain a chemically pretreated substrate;

[0020] wherein i. and / or ii. are followed, preferably directly followed, by one or more rinsing steps, wherein at least one composition selected from the group consisting of a cleaning composition, a rinsing composition and a chemical pretreatment composition comprises one or more compounds of formula (I) in an amount of 0.8 to 200 mmol / L of the composition

[0021]

[0022] The COOH groups of the compounds may be completely or partially neutralized and the residue R 1 , R 2 , R 3 , R 4 and R 5 One or more of are independently selected from the group consisting of H, hydroxyl and alkyl.

[0023] Hereinafter, the above-mentioned method for pretreating a metal substrate and preferred embodiments thereof are referred to as "a method for pretreating a metal substrate according to the present invention".

[0024] Yet another subject of the present invention is a method for coating a metal substrate, which comprises the above-described method for pretreating a metal substrate according to the invention, wherein after the last rinsing step

[0025] iii. applying one or more coating compositions selected from the group consisting of a solid coating composition and a liquid coating composition to form one or more coating layers, each of the one or more coating layers being cured or uncured after application; and

[0026] iv. curing any coating layer or layers applied in step iii. that were not cured in step iii.

[0027] Hereinafter, the above-mentioned method for coating a metal substrate and preferred embodiments thereof are referred to as "a method for coating a metal substrate according to the present invention".

[0028] Another subject of the invention is the use of an aqueous composition for the pretreatment of a metal substrate, the aqueous composition containing a compound of the above formula (I) in an amount of 0.8 to 200 mmol per liter of composition, the COOH groups of which may be completely or partially neutralized, and in which the residue R 1 , R 2 , R 3 , R 4 and R 5 One or more of the above are independently selected from the group consisting of H, hydroxyl and alkyl, and the aqueous composition is selected from the group consisting of a cleaning composition, a rinsing composition and a chemical pretreatment composition.

[0029] In the following, the above-mentioned use and preferred embodiments thereof are denoted as "use according to the invention".

[0030] In the following sections, the present invention will be described in more detail. DETAILED DESCRIPTION

[0031] Hereinafter, terms used in the present invention are defined.

[0032] As used herein, the term "pre-treatment" or "pre-treating" is defined as follows: Lexikon "Lacke und Druckfarben [Varnishes and Inks]" (Publisher: Ulrich Zorll, Editor: Hans-Jürgen P. Adler-Stuttgart; New York: Thieme [Tieme Publishers], 1998; Terminology: The term "surface preparation" is used as defined in "Surface Preparation" on page 417.

[0033] On metal substrates, the first step of the surface treatment according to DIN 50902:1994-07 is a layer removal step which comprises one or more (chemical) cleaning steps with aqueous or nonaqueous cleaning compositions and is also referred to as "surface preparation step".

[0034] The term "chemical pretreatment" is used according to EN ISO 4618:2006 (E / F / D) (Term: 2.41 "Chemical pretreatment", which stands for any chemical process applied to a surface before the application of a coating material). According to this standard, for example, treatments that belong to conversion treatments (like chromating and phosphatizing) belong to chemical pretreatments and are therefore distinguished from the coating step, in which a coating material, i.e. a coating composition, such as a powder coating composition, an electrodeposition coating composition, an aqueous or non-aqueous liquid coating material, is applied.

[0035] In addition to typical conversion treatments such as chromating and phosphate treatments, chemical surface pretreatments can be accomplished with passivating compositions and film-forming compositions, as will be described in more detail below.

[0036] According to the above internationally valid definition of “pretreatment” of metal substrates, the pretreatment method according to the invention encompasses a surface preparation cleaning step and / or a chemical pretreatment step and in each case at least one rinsing step.

[0037] The term "metal substrate" encompasses any substrate having a surface comprising one or more pure metals and / or alloys according to the ordinary understanding of the term. If a substrate comprises regions of different metals, such a substrate is denoted herein as a "multi-metal substrate" as a subclass of a metal substrate.

[0038] The term "at least a portion of the metal substrate" means, according to the ordinary understanding of said term, that in some cases it may be desirable or sufficient to contact less than the entire surface of the substrate with the cleaning composition, rinsing composition and / or chemical pretreatment composition. If only a portion of the metal surface is contacted with the respective composition, it is typically the same portion for all steps of the method. However, it is generally desirable that the entire surface of the metal substrate is contacted with the respective composition or compositions.

[0039] The term "surface in contact with the substrate" encompasses any type of direct contact according to the ordinary understanding of the term.

[0040] The term "composition" means a substance consisting of one or more ingredients, typically more than one ingredient. However, for example, a "rinsing composition" may even consist of only water.

[0041] The term "aqueous" in combination with the term "composition" means that the volatile content of the composition, in which other ingredients can be dissolved or dispersed, mainly contains water or even consists of water. The water content, based on the total weight of such a composition, in particular in the case of an aqueous rinse-off composition, is preferably 97 wt.-% to 100 wt.-%, such as 97 wt.-% to 99.99 wt.-%, more preferably 98 wt.-% to 99.99 wt.-%, even more preferably 99 wt.-% to 99.98 wt.-%, and most preferably 99.50 wt.-% to 99.97 wt.-%.

[0042] The term "cleaning composition" defines a composition according to the ordinary understanding of the term that removes impurities from the surface of a metal substrate to be further processed (i.e., cleans the metal substrate), but does not permanently remain on the surface of the metal substrate. Thus, the term "cleaning composition" is different from the term "coating composition" because coating compositions are intended to remain permanently on the substrate.

[0043] The term "rinsing composition" defines a composition according to the ordinary understanding of the term which removes the excess portion of the composition which came 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 may be pure, such as deionized water.

[0044] As used herein, the term "chemical pretreatment composition" encompasses "conversion treatment composition," "passivation treatment composition," and "thin film forming composition."

[0045] The term "conversion treatment composition" defines a composition, according to the ordinary understanding of that term, which, if applied to a substrate metal, produces a surface layer containing compounds of the substrate metal (commonly referred to as a conversion coating) and environmental anions (ISO 2080:2008 (E / F), Terminology: 2.3 "Conversion treatment").

[0046] The pretreatment method according to the present invention

[0047] The method of pretreating a metal substrate according to the present invention provides a method of pretreating a metal substrate, in particular preventing or inhibiting the formation of flash rust.

[0048] The method comprises at least one or more cleaning steps in combination with one or more subsequent rinsing steps; or at least one or more chemical pretreatment steps in combination with one or more subsequent rinsing steps. Therefore, in the following, the compound of formula (I) which can be completely or partially neutralized, as well as the cleaning step and the chemical pretreatment step will first be described in more detail, and then the one or more rinsing steps will be described, because the rinsing step is carried out in the same way after the cleaning step and / or after the chemical pretreatment step.

[0049] Compounds having formula (I)

[0050] At least one composition selected from the group consisting of a cleaning composition, a rinsing composition and a chemical pretreatment composition contains one or more compounds having formula (I)

[0051]

[0052] The COOH groups of the compounds may be completely or partially neutralized and the residue R 1 , R 2 , R 3 , R 4 and R 5 One or more of are independently selected from the group consisting of H, hydroxyl and alkyl.

[0053] If reference is made hereinafter to compounds of formula (I), reference is to the compounds defined above as well as the preferred compounds of formula (I) as described below. The specified amounts and ranges of amounts are equally valid for the compounds of formula (I) defined above as well as the preferred compounds of formula (I) as described below.

[0054] Depending on the pH value of the cleaning compositions, rinsing compositions and chemical pretreatment compositions in which the compounds of formula (I) are employed, the COOH groups may be completely or partially neutralized. Independently of this, since the above compositions are typically and preferably aqueous compositions, at least some of the COOH groups are partially dissociated into COO - H + Group.

[0055] The term "neutralized" encompasses compounds or salts of formula (I) formed in situ due to the pH of the respective composition, but also compounds or salts of formula (I) formed prior to incorporation into the respective composition. Thus, the term "neutralized" encompasses any commercially available salt of an acidic compound of formula (I), i.e. a compound of formula (I) carrying a COOH group.

[0056] The compound of formula (I) and the fully or partially neutralized compound of formula (I) as present in the corresponding cleaning, rinsing or chemical pretreatment composition preferably has an aqueous solubility of at least 0.8 mmol / L in deionized water at a temperature of 20° C. Therefore, it is preferred that the compound of formula (I) and the fully or partially neutralized compound of formula (I) are completely soluble in the corresponding composition at a temperature of 20° C.

[0057] In the case of compounds of formula (I) substituted with OH and / or alkyl (ie, wherein R 1 , R2 , R 3 , R 4 and R 5 Among the compounds of formula (I) in which at least one of the radicals is OH and / or alkyl) and the corresponding fully or partially neutralized compounds of formula (I), those having not more than 3 radicals selected from OH and alkyl are preferred.

[0058] In the case of an alkyl group, even more preferred is R 1 , R 2 , R 3 , R 4 and R 5 Only 1 or 2 of the groups, most preferably R 1 , R 2 , R 3 , R 4 and R 5 Only one of the groups is an alkyl group.

[0059] If R 1 , R 2 , R 3 , R 4 and R 5 One or more of the groups is an alkyl group, and in view 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.

[0060] Most preferably, all of these R 1 , R 2 , R 3 , R 4 and R 5 The groups are all hydrogen. In this case, the compound of formula (I) is benzoic acid. The neutralized benzoic acid is in particular a salt thereof, preferably a water-soluble salt thereof.

[0061] Particularly preferred neutralizing substances for compounds of formula (I) are alkali metal salts, ammonium salts and quaternary ammonium salts thereof.

[0062] Most preferred are the sodium, potassium, ammonium and tetramethylammonium salts of the compound of formula (I), and particularly preferred are the above-mentioned benzoic acid salts.

[0063] i. One or more cleaning steps

[0064] In a first aspect of the pretreatment method according to the invention, the metal substrate is subjected to i. one or more cleaning steps, typically i. two or more cleaning steps, wherein at least a portion of the surface of the metal substrate or preferably the entire surface 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, if more than one cleaning composition is used, all cleaning compositions used are aqueous cleaning compositions.

[0065] The metal substrate to be used in the coating industry usually contains impurities on its surface, which can be physically or chemically attached to the metal surface of the metal substrate. Such impurities are especially used for the production and customization of oils and greases for 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 chemical pretreatment layer and coating formed subsequently. Such defects can, for example, lead to reduced adhesion of the coating to the metal substrate surface. Therefore, it is essential to clean the contaminated metal substrate before further use.

[0066] As used herein, the term metal substrate includes substrates of any shape, such as flat metal substrates (like simple plates or coils), as well as metal substrates with complex shapes (like automobile bodies or parts thereof). As used herein, the term "metal" includes pure metals and metal alloys as explained above. 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. Furthermore, the term "substrate" also includes preassembled metal parts, which are the same metal or alloy, or which are at least two different metals or alloys (multi-metal capability of the method).

[0067] The i. one or more steps of contacting the metal substrate with the cleaning composition can be carried out by any common cleaning procedure. Most preferably, spray cleaning and / or immersion cleaning are used. The temperature of the cleaning composition used in one or more i. cleaning steps is preferably in the range of 20°C to 70°C, more preferably 30°C to 65°C, and most preferably 40°C to 60°C, such as 45°C to 60°C. The duration of contact of the metal substrate with the cleaning composition is preferably in the range of 0.5 minutes to 15 minutes, more preferably 1 minute to 10 minutes, and most preferably 2 to 5 minutes.

[0068] Cleaning composition

[0069] In principle, all kinds of customary cleaning compositions 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 which the substrate comprises or consists of.

[0070] The cleaning composition is preferably aqueous and preferably has 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 below 6 at 20° C. are generally denoted as acidic cleaning compositions, while cleaning compositions having a pH value in the range of 6 to 8 at 20° C. are denoted as neutral, and those having a pH value in the range of greater than 8 to 12.5 at 20° C. are denoted as alkaline cleaning compositions. Independently 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 components.

[0071] Preferred acidic cleaning compositions have a pH within the above range and contain one or more ingredients selected from the group consisting of an inorganic acid (such as sulfuric acid), an organic acid, a complexing agent, a surfactant, and a fluoride.

[0072] Preferred neutral cleaning compositions have a pH value within the above range and contain one or more ingredients selected from the group consisting of a pH adjuster, an alkanolamine, a caustic, a surfactant, and a complexing agent.

[0073] Preferred alkaline cleaning compositions have a pH in the range of 8 to 12.5, more preferably 9 to 11, such as 10 to 11. Preferably the alkaline cleaning composition comprises one or more ingredients selected from the group consisting of: a pH adjuster, a caustic, a surfactant and a complexing agent.

[0074] Suitable cleaning compositions and / or water-dilutable concentrates thereof are available, for example, from Chemetall GmbH (Frankfurt, Germany) under the trade name Commercially available.

[0075] Since the typical ingredients of the cleaning composition and usually its rather extreme pH value negatively interfere with subsequent steps (such as chemical pretreatment), the one or more cleaning steps are preferably directly followed by one or more rinsing steps. The one or more rinsing steps after the one or more cleaning steps and the rinsing compositions used therein will be described below under the heading "Rinsing Step".

[0076] According to the method of the invention, in order to prevent or inhibit rust, in particular flash rust formation, during and after the cleaning process, at least one of the cleaning compositions is used, or if only one cleaning composition is used, the one cleaning composition may be supplemented with an amount of 0.8 to 200 mmol per liter of composition, preferably 1.0 to 150 mmol per liter of composition, more preferably 1.2 to 120 mmol per liter of composition, and even more preferably 1.6 to 50 mmol per liter of composition of one or more compounds of the above formula (I), wherein the COOH groups may be completely or partially neutralized, and wherein the residue R 1 , R 2 , R 3 , R 4 and R 5 One or more of are independently selected from the group consisting of H, hydroxyl and alkyl.

[0077] ii. One or more chemical pretreatment steps

[0078] In a second aspect of the pretreatment method according to the present invention, the metal substrate is subjected to ii. one or more chemical pretreatment steps, preferably ii. one pretreatment step, wherein at least a portion of the surface of the metal substrate or the entire surface is contacted with one or more chemical pretreatment compositions to obtain a chemically pretreated metal substrate. The metal substrate used in the one or more chemical pretreatment steps is the same as the metal substrate defined in the one or more cleaning steps.

[0079] The ii. one or more steps of contacting the metal substrate with the chemical pretreatment composition can be carried out by any common conversion treatment procedure, passivation treatment procedure and / or film forming procedure. Most preferred are spray application and / or immersion application, the latter being most preferred. The duration of contact of the metal substrate 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.

[0080] Typically, 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, even more preferably 20 to 50°C.

[0081] Within the above range, where the chemical pretreatment is film forming, the temperature preferably ranges from 10° C. to 50° C., more preferably from 15° C. to 45° C., and most preferably from 20° C. to 40° C., such as from 25° C. to 35° C. Using other chemical pretreatment compositions such as zinc phosphate based compositions, the temperature is preferably in the range of 20° C. to 60° C., and most preferably from 30° C. to 55° C., such as from 35° C. to 50° C.

[0082] Chemical pretreatment composition

[0083] Generally, any known chemical pretreatment composition as used in metal surface finishing may be used in ii. one or more chemical pretreatment steps of the method for pretreating a metal substrate according to the present invention.

[0084] The chemical pretreatment composition used in the present invention is preferably an acidic chemical pretreatment composition.

[0085] Preferably, the chemical pretreatment composition used in the method for coating according to the invention is selected from

[0086] a. Phosphate conversion treatment compositions, including layer-forming and non-layer-forming compositions. Examples of phosphate conversion treatment compositions are

[0087] i. Ni-containing and Ni-free zinc phosphate treatment compositions and trivalent cation phosphate treatment compositions, i.e., so-called "layer forming systems",

[0088] ii. compositions which form amorphous phosphate conversion coatings, i.e. so-called non-layer forming systems,

[0089] iii. a phosphate 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

[0090] iv. a composition for forming an amorphous iron phosphate conversion coating,

[0091] b. an organosilane-based film-forming composition comprising at least one organosilane and / or its hydrolysis product and / or its condensation product; and

[0092] c. a passivating composition comprising at least one compound selected from the group consisting of zirconium compounds, titanium compounds and hafnium compounds;

[0093] d. a passivation and thin film-forming composition comprising 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;

[0094] e. A passivating composition comprising at least one compound selected from the group of zirconium compounds, titanium compounds and hafnium compounds, and comprising 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 (especially (phosphonic acid-acrylic acid) copolymers), polyvinyl pyrrolidone and vinyl pyrrolidone copolymers, vinyl acetate copolymers (especially (vinyl alcohol-vinyl acetate) copolymers), ethoxylated polymers (e.g. polyethylene glycol and copolymers), and linear or branched poly(ethylene imine).

[0095] If a phosphate conversion treatment step, in particular a zinc phosphate treatment step or a trivalent cation phosphate treatment step, is carried out in ii., it is preferred that an additional activation step is carried out before ii. If carried out, the activation step is carried out by contacting the metal substrate with an activation composition before step ii. The contact is preferably carried out by dipping or spraying. Most preferably, the metal substrate is contacted by dipping application of the activation composition. The duration of the contact step with the activation composition is preferably in the range of 5 to 300 seconds, more preferably 10 to 200 seconds, and most preferably 20 to 90 seconds, such as 30 to 60 seconds. The activation composition or solution is, for example, available from Chemetall GmbH (Frankfurt, Germany) under the trademark If an activation step is carried out, the activation composition used therein preferably contains zinc phosphate crystals and / or titanium phosphate crystals, which promote the deposition of the phosphate conversion layer.

[0096] Among these zinc phosphatizing compositions, Ni-containing compositions can be used. However, for environmental reasons, Ni-free zinc phosphatizing conversion compositions are preferred, which contain Zn ions and Mn ions. A further variant of the zinc phosphatizing conversion composition is the so-called trivalent cation phosphate conversion composition containing Zn, Mn and Ni ions. Phosphate conversion compositions are available, for example, from Chemetall GmbH (Frankfurt, Germany) under the trademark R (for zinc phosphate treatment) and Gardobond A (for amorphous phosphate products) are available.

[0097] The film-forming composition based on organosilane preferably contains at least one organosilane, such as aminosilane, the term "organosilane" including its hydrolysis products and condensation products, and optionally a compound selected from the group of zirconium compounds, titanium compounds and hafnium compounds. Such compositions are available, for example, from Chemetall GmbH (Frankfurt, Germany) under the trademark (like 9831, 9832, Oxsilan 9810 / 1 and Oxsilan 9810 / 3) are available to produce film layers.

[0098] The passivation treatment composition preferably contains at least one compound selected from the group of zirconium compounds, titanium compounds and hafnium compounds, more preferably fluorine complexes of titanium, zirconium and / or hafnium. Such a passivation treatment composition optionally contains one or more organosilanes, the term "organosilanes" including hydrolysis products and condensation products thereof.

[0099] Examples of the 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 are, for example GBX 2025 / 2.

[0100] Typically, any layer formed in one or more chemical pretreatment steps has a thickness typically less than 2 μm, such as preferably 50 nm to 2000 nm, more preferably 500 to 1500 nm for phosphate conversion treatments (such as iron and zinc phosphate treatments), and preferably 20 nm to 300 nm, more preferably 30 to 200 nm for thin film forming pretreatments.

[0101] According to the method of the invention, in order to prevent or inhibit rust formation, in particular flash rust formation, during and after the cleaning process, one or more chemical pretreatment compositions are used, or if only one chemical pretreatment composition is used, the one chemical pretreatment composition can be supplemented with an amount of 0.8 to 200 mmol per liter of composition, preferably 1.0 to 150 mmol per liter of composition, more preferably 1.2 to 120 mmol per liter of composition, and even more preferably 1.6 to 50 mmol per liter of composition of one or more compounds of the above formula (I), wherein the COOH groups may be completely or partially neutralized, and wherein the residue R 1 , R 2 , R 3 , R 4 and R 5 One or more of are independently selected from the group consisting of H, hydroxyl and alkyl.

[0102] One or more wash steps

[0103] One or more rinsing steps, preferably at least two rinsing steps, are performed to remove excess cleaning composition remaining on the surface of the metal substrate after i. performing one or more cleaning steps; and / or to remove excess chemical pretreatment composition remaining on the surface of the chemically pretreated metal substrate after ii. performing one or more chemical pretreatment steps.

[0104] The rinsing step is preferably carried out by spraying or immersion application, preferably immersion application, of a corresponding rinsing composition.

[0105] In principle, in both cases 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 the introduction of undesired substances.

[0106] However, if none of the i. one or more cleaning compositions or none of the ii. one or more chemical pretreatment compositions utilizes a corresponding composition supplemented with the above-defined amounts of one or more compounds of formula (I) (whose COOH groups may be partially or completely neutralized as defined above), then if only water is used as rinsing composition, it is observed in many cases that the cleaned and / or chemically pretreated metal substrates tend to form rust, in particular flash rust, on their surface. However, such rust formation or flash rust formation is generally detrimental to the formation of further coatings on the substrate and leads to defects, which again leads to reduced adhesion of the further coating and / or reduced corrosion protection.

[0107] One or more rinse compositions

[0108] As explained above, if at least one of the cleaning compositions and / or chemical pretreatment compositions used contains a corresponding amount of one or more compounds of formula (I) (whose COOH groups may be partially or completely neutralized as defined above), the rinsing composition as used in the rinsing step can be carried out with water or water containing a drag over from one or more previous steps of the pretreatment method according to the invention. If more than one rinsing step is carried out, the first rinsing step is preferably carried out with tap water as rinsing composition.

[0109] If a spray application is used in the first rinse step and tap water is used as the first rinse composition, such water, such as tap water, preferably has a relative humidity of 200 to 3500 μS / cm 2 , preferably 200 to 2500 μS / cm 2 Of course, water with a lower conductivity (such as deionized water) can also be used as the rinsing composition in the first rinsing step. Therefore, the rinsing composition can consist only of pure water. The conductivity is measured with a commercially available conductivity measuring device (WTW pH / Cond 340i; calibrated in a potassium chloride solution with a conductivity of 1.413 mS / cm at 25°C).

[0110] 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 further contain diluted ingredients from previous pre-treatment steps dragged into the immersion tank from the previously rinsed metal substrate (sheet), i.e. ingredients from one or more cleaning steps or one or more chemical pre-treatment steps.

[0111] If the first rinse composition is used for immersion rinsing, it typically has a pH in the range of 6 to 10 due to drag from the previous cleaning composition and / or chemical pretreatment composition, and therefore contains all the ingredients of the cleaning composition and / or chemical pretreatment composition in highly diluted form to preferably meet the above conductivity range. Of course, the first rinse step can also be carried out with deionized water.

[0112] Due to the drag from the first rinse composition, the second rinse composition preferably also has a pH in the range of 6 to 10, more preferably 6.5 to 9, and again 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.

[0113] Thus, from rinse step to rinse step, the drag will contain less of the ingredients contained in the cleaning composition and / or chemical pre-treatment composition.

[0114] Preferably, the last of these rinsing steps (which may be the first rinsing step in the case of only one rinsing step, but may also be the second or any further rinsing step) carried out after one or more cleaning steps and / or one or more chemical pretreatment steps is carried out by using a rinsing agent with a conductivity of less than 500 μS / cm 2 (e.g. 5 to 500 μS / cm 2 , more preferably 0 to 200 μS / cm 2 Of course, the last rinse step can also be performed with deionized water.

[0115] Flushing compositions containing corrosion inhibitors

[0116] According to the invention, if none of i. the one or more cleaning compositions or ii. the one or more chemical pretreatment compositions (if used) utilizes a composition supplemented with the above-defined amounts of benzoic acid and / or its above-described salts, it is necessary that at least one of the rinsing compositions used after the one or more cleaning steps and / or one of the rinsing compositions used after the one or more chemical pretreatment steps contains an amount of 0.8 to 200 mmol per liter of composition, preferably 1.0 to 150 mmol per liter of composition, more preferably 1.2 to 120 mmol per liter of composition, and even more preferably 1.6 to 50 mmol per liter of composition of one or more compounds of the above formula (I), wherein the COOH groups may be completely or partially neutralized, and wherein the residue R 1 , R 2 , R 3 , R 4 and R 5One or more of are independently selected from the group consisting of H, hydroxyl and alkyl. Most preferably, the upper limit of the above range is 34, 32, 30, 28, 26, 24 or 22 mmol per liter of flushing composition of one or more compounds of formula (I) above, wherein the COOH groups may be fully or partially neutralized, and wherein the residue R 1 , R 2 , R 3 , R 4 and R 5 One or more of are independently selected from the group consisting of H, hydroxyl and alkyl.

[0117] Apart from water and some possible drag-over from previous cleaning and / or chemical pretreatment steps and the above amounts of one or more compounds of formula (I) above, in which the COOH groups may be fully or partially neutralized, and optionally a pH regulator, the rinse composition is preferably not supplemented with any further ingredients.

[0118] However, if additional ingredients are present, the main ingredients (except the pH regulator) contained in the rinsing composition containing the corrosion inhibitor, in addition to water, are preferably one or more compounds of the above formula (I), wherein the COOH groups may be fully or partially neutralized. As the neutralized compound of formula (I), preferably, benzoic acid is used in neutralized form (such as sodium benzoate or potassium benzoate).

[0119] The preferred pH range for the flushing composition containing the corrosion inhibitor is 5 to 12, more preferably 6 to 11, and most preferably 7 to 10.

[0120] Most preferably, no nitrites and / or phosphorus-containing substances are intentionally employed in the rinsing composition comprising a corrosion inhibitor as used in the method for pretreatment of a metal substrate according to the present invention. However, if such substances are present in the cleaning and / or chemical pretreatment composition, it may happen that trace amounts of such substances are transferred to the rinsing composition used in the rinsing step due to some drag.

[0121] Typically, if nitrite is present in the rinse composition comprising one or more compounds of formula (I) above, wherein the COOH groups may be fully or partially neutralized, the amount of nitrite is less than 0.1 wt.-%, more preferably less than 0.01 wt.-%, and most preferably 0 wt.-%. Typically, if phosphorus-containing substances are present in the rinse composition comprising one or more compounds of formula (I) above, wherein the COOH groups may be fully or partially neutralized, the amount of phosphorus-containing substances is less than 0.1 wt.-%, more preferably less than 0.01 wt.-%, and most preferably 0 wt.-%.

[0122] It is highly surprising that the above-mentioned one or more compounds of formula (I) above, wherein the COOH groups may be fully or partially neutralized, act as effective flash rust inhibitors in rinsing solutions and that they act in particular in such small amounts. Surprisingly, highly diluted solutions of such compounds, which typically do not form permanent coatings, can be used to prevent flash rust. This is also true for cleaning compositions that are also not considered to stay permanently on the metal substrate, but also for layers formed by chemical pretreatments, which have very low, if any, ability to capture one or more compounds of formula (I) above, wherein the COOH groups may be fully or partially neutralized.

[0123] Preferred sequence of steps for a method of pretreating a metal substrate

[0124] Preferably (embodiment A), the method for pretreating a metal substrate according to the present invention comprises:

[0125] i. one or more pretreatment steps selected from the group consisting of cleaning steps, 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

[0126] ii. one or more chemical pretreatment steps selected from a conversion treatment step, a passivation treatment step and a thin layer forming 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 conversion treatment composition, a passivation treatment composition and a thin layer forming composition to obtain a chemically pretreated substrate,

[0127] wherein i. and ii. are followed by one or more rinsing steps, wherein at least one composition selected from a cleaning composition, a rinsing composition and a chemical pretreatment composition comprises one or more compounds of formula (I) as defined above in an amount of 0.8 to 200 mmol / L of the composition, wherein the COOH groups thereof may be fully or partially neutralized.

[0128] Further preferred (embodiment B) is that the method for pretreating a metal substrate according to the present invention comprises

[0129] 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

[0130] 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 to obtain a chemically pretreated substrate,

[0131] wherein i. and ii. are followed by one or more rinsing steps, wherein at least one composition selected from a cleaning composition, a rinsing composition and a chemical pretreatment composition comprises one or more compounds of formula (I) as defined above in an amount of 0.8 to 200 mmol / L of the composition, wherein the COOH groups thereof may be fully or partially neutralized.

[0132] Alternatively, further preferred (embodiment C) is that the method for pretreating a metal substrate according to the present invention comprises

[0133] 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; directly followed by

[0134] ii. one or more phosphate-free chemical pretreatment steps to obtain a chemically pretreated substrate,

[0135] wherein i. and ii. are followed by one or more rinsing steps, wherein at least one composition selected from a cleaning composition, a rinsing composition and a chemical pretreatment composition comprises one or more compounds of formula (I) as defined above in an amount of 0.8 to 200 mmol / L of the composition, wherein the COOH groups thereof may be fully or partially neutralized.

[0136] 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 amount of one or more compounds having the above formula (I), wherein the COOH groups may be fully or partially neutralized.

[0137] Even more preferably for any of the above embodiments A to C, at least one of the rinsing compositions after one or the last cleaning step, preferably the last rinsing composition after one or the last cleaning step, and / or at least one of the rinsing compositions after the chemical pretreatment step, preferably the last rinsing composition after one or more chemical pretreatment steps, before performing one or more activation steps in embodiment B or one or more chemical pretreatment steps in embodiments A to C contains the above-mentioned amount of one or more compounds of formula (I) above, wherein the COOH groups may be fully or partially neutralized.

[0138] In any of the above embodiments A to C, it is preferred that the above general or preferred amounts of the above one or more compounds of formula (I) above (in which the COOH groups may be fully or partially neutralized) are contained only in the rinse composition, preferably only in the last rinse composition, and most preferably only in the last rinse composition after the cleaning step, and optionally in the last rinse composition after the chemical pretreatment step.

[0139] Optionally, the metal substrate is dried after performing one or more rinsing steps. If the method of pretreating the metal substrate is performed directly before powder coating or coating with an aqueous coating composition or a solvent-based coating composition, it is preferred to first dry the pretreated metal substrate after the last rinsing step. However, if the electrodeposition coating is after the last rinsing step, it is typically not necessary to dry the pretreated metal substrate before electrodeposition coating, because electrodeposition coating is typically performed as an aqueous dip coating.

[0140] Method for coating a metal substrate

[0141] In the method for coating a metal substrate, the method for pretreating the metal substrate according to the invention is first carried out, after which one or more coating compositions selected from the group of solid coating compositions and liquid coating compositions are applied to form one or more coating layers, also referred to herein as paint coatings, in contrast to any layers that may have been formed in one or more chemical pretreatment steps. In addition, curing of the one or more coating compositions is carried out.

[0142] Therefore, a further subject of the present invention is a method for coating a metal substrate, which comprises

[0143] 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 clean metal substrate; and / or, preferably as well as,

[0144] ii. one or more chemical pretreatment steps selected from a conversion treatment step, a passivation treatment step and a thin layer forming 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 conversion treatment composition, a passivation treatment composition and a thin layer forming composition to obtain a chemically pretreated substrate;

[0145] wherein i. and / or ii. is directly followed by one or more rinsing steps, wherein at least one composition selected from the group consisting of cleaning compositions, rinsing compositions and chemical pretreatment compositions 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 one or more compounds of the above formula (I), wherein the COOH groups may be fully or partially neutralized, and wherein the residue R 1 , R 2 , R 3 , R 4 and R 5 One or more of are independently selected from the group consisting of H, hydroxyl and alkyl, wherein after the last rinsing step

[0146] iii. applying one or more coating compositions selected from the group consisting of a solid coating composition and a liquid coating composition to form one or more coating layers, each of the one or more coating layers being cured or uncured after application; and

[0147] iv. curing any coating layer or layers applied in step iii. that were not cured in step iii.

[0148] 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, but not limited to, the group of resins consisting of epoxy resins, mixtures of epoxy resins with polyester resins, mixtures of polyester resins with isocyanate components, poly(meth)acrylates and mixtures of polyesters with triglycidyl isocyanurate.

[0149] The liquid coating composition may be a one-component or two-component coating composition, an aqueous or non-aqueous coating composition. The non-aqueous coating composition may be a solvent-borne coating composition or a radiation-curable coating composition which is preferably solvent-free.

[0150] In particular, in automotive OEM coating, the following coating steps are performed in the following order: 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.

[0151] Therefore, a further subject of the present invention is a method for coating a metal substrate, which comprises

[0152] i. one or more cleaning steps, 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

[0153] ii. one or more chemical pretreatment steps, wherein at least a portion of the surface of the metal substrate is contacted with one or more chemical pretreatment compositions to obtain a chemically pretreated substrate;

[0154] wherein i. and / or ii. is directly followed by one or more rinsing steps, wherein at least one composition selected from the group consisting of cleaning compositions, rinsing compositions and chemical pretreatment compositions 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 one or more compounds of the above formula (I), wherein the COOH groups may be fully or partially neutralized, and wherein the residue R 1 , R 2 , R 3 , R 4 and R 5 One or more of are independently selected from the group consisting of H, hydroxyl and alkyl, wherein after the last rinsing step

[0155] 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 one or more coating layers thus formed, and

[0156] iv. curing any coating composition or compositions that were not cured in step iii.

[0157] Any preferred features and embodiments described above in connection with the method for treating a metal substrate are also preferred features and embodiments of the method for coating a metal substrate and are therefore not explicitly repeated in the following.

[0158] iii. One or more coating steps

[0159] After the pretreatment method according to the invention and in particular after any of the method embodiments A to C as described above, in particular in automotive OEM coating, an electrodeposition coating composition is preferably applied onto the only or last chemical pretreatment layer.

[0160] The electrodeposition coating composition is an aqueous coating composition, which is applied by dip coating, that is, the pickled, chemically pretreated metal substrate is immersed in a conductive aqueous electrodeposition coating composition, and a DC voltage is applied between the substrate and the counter electrode. The electrodeposition coating composition is an anode or cathode electrodeposition coating composition, preferably a cathode electrodeposition coating composition. The cathode electrodeposition coating composition is preferably selected from epoxy and poly (meth) acrylate electrodeposition coating compositions. They are applied according to the instructions of the coating manufacturer.

[0161] After forming the electrodeposition coating, the layer thus formed is preferably washed off and cured according to the coating manufacturer's instructions.

[0162] After the electrodeposition coating step, it is preferred to apply one or more other coating compositions. Such 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 may also be applied. Particularly preferred, at least one of a primer filler coating composition, a base coating composition and a clear coating composition is applied, most preferably in this order. If a plurality of coatings are formed (i.e., at least two coating compositions are applied), then application may be carried out in a wet-in-wet manner, and these coatings may be cured simultaneously afterwards. However, drying steps and / or curing steps may also be carried out between at least some or all of the application in the plurality of coating compositions.

[0163] Alternatively, a single powder coating composition or a single aqueous or a single non-aqueous coating composition may be applied with or without the application of an electrodeposition coating composition. In particular, if a powder coating composition is applied, it is recommended to first dry the rinsed and / or electrodeposition coated substrate.

[0164] iv.iii. Curing of one or more coatings

[0165] The conditions of the curing step depend on the coating composition applied after the method for pretreating a metal substrate according to the invention.

[0166] As used herein, the term "curing" encompasses any type of curing, preferably physical drying, radiation curing and thermal curing, wherein thermal curing preferably encompasses any curing mechanism by chemical crosslinking other than radiation curing. For example, the term thermal curing includes the curing of one-component compositions and two-component compositions. One-component compositions typically cure at temperatures above 100°C, for example in the range of 120°C to 200°C, while two-component compositions typically start to cure at room temperature, such as at a temperature of 20°C to 100°C, and are therefore typically not storage stable under ambient conditions.

[0167] The method for coating a metal substrate according to the invention provides good adhesion of the coating and corrosion resistance of the metal substrate.

[0168] Use according to the invention

[0169] A further subject of the invention is the use of an aqueous composition for the pretreatment of a metal substrate, the aqueous composition containing an amount of 0.8 to 200 mmol per liter of composition, preferably 1.0 to 150 mmol per liter of composition, more preferably 1.2 to 120 mmol per liter of composition, and even more preferably 1.6 to 50 mmol per liter of composition of one or more compounds of the above formula (I), wherein the COOH groups may be completely or partially neutralized, and wherein the residue R 1 , R 2 , R 3 , R 4 and R 5 One or more of are independently selected from the group consisting of H, hydroxyl and alkyl, the pretreatment comprises at least one of a cleaning step and a chemical pretreatment step; and at least one additional 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 selected from a cleaning composition and a rinsing composition, and most preferably the aqueous composition is a rinsing composition.

[0170] The use according to the invention provides for preventing or inhibiting rust formation, in particular flash rust formation, on metal substrates.

[0171] Hereinafter, the present invention will be further explained by providing working examples.

[0172] Examples

[0173] Testing of cleaned and rinsed substrates

[0174] Flash Rust Formation Test (FRF Test)

[0175] The flash rust laboratory scale simulation of steel plate as substrate was simulated according to two procedures. In procedure 1, sodium chloride was utilized as a flash rust formation accelerator, while in procedure 2, humidity exposure was applied to promote flash rust formation.

[0176] Procedure 1

[0177] In this process, cold rolled steel sheets (CRS sheets) are

[0178] (a) In the dipping application, 20 g / L GC S 5411 was used at 60 °C. GBA 7400 (alkaline builder and organic surfactant, a typical cleaning product provided by Chemetall Ltd.) cleans for 180 seconds;

[0179] (b) After this cleaning step, the plate was first rinsed with tap water for 15 seconds;

[0180] (c) After the first rinse, a second immersion rinse was performed with deionized water for 10 seconds; the deionized water was supplemented with the following before use: 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 (equal to ≈3.5 mmol / L) of sodium benzoate (Example A); or 200 ppm sodium chloride and 3000 mg / L (equal to ≈20.8 mmol / L) of sodium benzoate (Example B);

[0181] (d) After the second rinse, the substrate thus treated is air-dried.

[0182] Rust formation was assessed visually (brown stains due to flash rust formation).

[0183] The amount and intensity of flash rust formation was assessed visually and classified into 3 categories (Inhibited (no flash rust visible), Partially Inhibited (better than "Control 1 or 2" but still some rust visible), and No Inhibited (no difference from "Control 1 or 2")).

[0184] Furthermore, procedure 1 was repeated with different amounts of sodium benzoate in the second rinse of step (c), namely 0.1 g / L (equal to ≈0.7 mmol / L), 0.2 g / L (equal to ≈1.4 mmol / L), 0.3 g / L (equal to ≈2.1 mmol / L), 0.5 g / L (equal to ≈3.5 mmol / L) and 3 g / L (equal to ≈20.8 mmol / L) of sodium benzoate in deionized water, supplemented in each case with 200 ppm of sodium chloride. The results are shown in Table 1 in the Results section below.

[0185] Procedure 2

[0186] In this process, cold rolled steel sheets (size: 105 mm × 95 mm × 0.8 mm)

[0187] (a) Clean as in Procedure 1;

[0188] (b) Rinse as in Procedure 1 using the first dip rinse;

[0189] (c) after the first rinse, a second immersion rinse was performed with deionized water for 10 seconds; the deionized water was supplemented with the following before use: none (Control 2); or 40 mg / L of sodium nitrite (Comparative Example 2); or 500 mg / L (equal to ≈3.5 mmol / L) of sodium benzoate (Example C); or 3000 mg / L (equal to ≈20.8 mmol / L) of sodium benzoate (Example D);

[0190] (d) after the second rinse, the thus treated plate was centered and suspended in a vertical orientation in a closed cylindrical container (diameter: 125 mm; height: 280 mm) with the lowest of the four edges of the plate at a distance of approximately 1 cm above the surface of tempered tap water for 600 seconds to simulate high humidity;

[0191] (e) After step (d), drying the substrate by using compressed air.

[0192] Rust formation (brown stains due to flash rust formation) was assessed visually as described above for Procedure 1.

[0193] In addition, Procedure 2 was repeated with different amounts of sodium benzoate in the second rinse of step (c), namely, 0.1 g / L (equal to ≈0.7 mmol / L), 0.2 g / L (equal to ≈1.4 mmol / L), 0.3 g / L (equal to ≈2.1 mmol / L), 0.5 g / L (equal to ≈3.5 mmol / L), and 3 g / L (equal to ≈20.8 mmol / L) of sodium benzoate in deionized water. The results are shown in Table 1 in the Results section below.

[0194] Testing of cleaned, rinsed, surface prepared and further coated substrates

[0195] Sample preparation

[0196] Hot dip galvanized steel (HDG) panels and cold rolled steel (CRS) panels as indicated in Table 2 below were cleaned by immersion with an alkaline cleaner (containing 20 g / L GC 5345 and 3 g / L GBA H 7406; both commercially available from Chemetall GmbH) at a temperature of 60°C for 180 s, followed by a tap water rinse (first rinse) for 30 s.

[0197] The first rinse was followed by a second rinse as indicated in Table 2. The second rinse was performed for 30 s with deionized water (DI water) only (Comparative Example*) or deionized water supplemented with 0.5 g / L sodium benzoate (Invention).

[0198] After the second rinse, the substrates (plates) of Examples 2a*, 2b*, 3a*, 3b*, 5a*, 5b*, 6a and 6b were exposed to high humidity according to Procedure 2, step (d) above, and then dried according to Procedure 2, step (e).

[0199] After the second rinse with or without high humidity treatment, the panels were treated by immersion at 60° C. for 180 s in different chemical pretreatment baths as indicated in Table 2. In Examples 1a*, 1b*, 2a*, 2b*, 3a and 3b, OS 9832 was used for chemical pretreatment; in Examples 4a*, 4b*, 5a*, 5b*, 6a and 6b, GB X 2025 / 2 was used for chemical pretreatment.

[0200] After the chemical pretreatment, all samples were rinsed with deionized water for 30 s and then dried at a temperature of 120° C. for 30 s.

[0201] The pretreatment thus completed is followed by an electrodeposition coating composition (BASF 800) coated plate, and the electrodeposition coating composition was cured at 175°C for 20 minutes to produce an electrodeposition coating having a dry layer thickness of about 20±2 μm.

[0202] 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.

[0203] Neutral Salt Spray Test (NSS Test)

[0204] The NSS test is used to determine the corrosion resistance of a coating on a substrate. According to DIN EN ISO 9227 NSS (date: September 1, 2012), an NSS test is performed on a conductive substrate coated with a coating composition of the invention or a comparative coating composition. In this test, the analyzed sample is in a chamber in which there is continuous atomization with a 5% concentration of a common salt solution at a controlled pH in the range of 6.5 to 7.2 at a temperature of 35° C. for a duration of 1008 hours. The mist is deposited on the analyzed sample so that the sample is covered with a corrosive film of salt water. If the coating on the analyzed sample is notched to the substrate with a blade cut (Scratch Master 1 mm blade, 75 μm) before the NSS test of DIN EN ISO 9227 NSS, the level of subfilm corrosion (undercutting) of the sample can be studied according to DIN EN ISO 4628-8 (date: March 1, 2013), because the substrate corrodes along the notch line during the DIN EN ISO 9227 NSS test. The study was carried out after the NSS test had been carried out for a duration of 1008 hours. As a result of the progressive course of corrosion, the coating was more or less undercut during the test. The degree of undercutting in [mm] is a measure of the corrosion resistance of the coating. These values ​​are average values ​​of 3 plates. The results are shown in Table 2.

[0205] New VDA climate change test (new VDA test; VDA 233-102 test)

[0206] The new VDA test is used to determine the corrosion resistance of the coating on the substrate. According to DIN 55635 (May 2019), the conductive substrate coated with the coating composition of the present invention or the comparative coating composition is subjected to the new VDA test. Here, the alternating climate test is carried out in 6 cycles. Here, one cycle consists of a total of 168 hours (1 week) and covers three stages representing a 24-hour cycle time. The three stages are characterized as follows.

[0207] a) Salt spray stage (A): 3 hours of salt spray (1% NaCl solution; 35°C; 100% relative humidity)

[0208] b) Observation phase (B): 3 hours, 25°C, 70% relative humidity

[0209] c) Low temperature stage (C): 1 hour at -2.5°C; 6 hours at -15°C and 1 hour at -2°C; no relative humidity adjustment

[0210] The test cycle is formed by combining the three phases in the following order:

[0211] BACABBA

[0212] Before the alternating climate test was carried out, the corresponding coating on the investigated sample was scored with a blade notch to the substrate, thereby allowing the sub-film corrosion (bottoming) level of the sample to be studied according to DIN EN ISO 4628-8 (date: March 1, 2013), because the substrate corrodes along the scoring line during the alternating climate test. As a result of the progressive course of corrosion, the coating is more or less bottomed during the test. The bottoming degree in [mm] is a measure of the corrosion resistance of the coating. The average bottoming level described later in the results below represents the average of the individual values ​​of three to five different plates evaluated, wherein each individual value of the plate is in turn the average of the bottoming levels at 11 measuring points on the plate. The results are shown in Table 2.

[0213] Climate Change Test PV1210 (PV1210 Test)

[0214] The climate change test is used to determine the corrosion resistance of a coating on a substrate. The climate change test is carried out in 30 so-called cycles. Prior to the PV1210 test, the coating of the specimen to be tested is scored to the substrate with a knife notch (Scratch Master 1 mm blade, 75 μm) before the climate change test, and the extent of subfilm corrosion of the specimen can be tested according to DIN EN ISO 4628-8 (03-2013), since the substrate corrodes along the score line during the climate change test. As corrosion progresses, the coating is more or less wetted during the test. The extent of the undercut in [mm] is a measure of the resistance of the coating. The values ​​are average values ​​of 3 plates.

[0215] The alternating climate test PV 1210 is used to determine the corrosion resistance of coatings on substrates. The alternating climate test is carried out for a corresponding coated electrically conductive substrate consisting of hot-dip galvanized steel (HDG). Here, the alternating climate test is carried out in 30 cycles. Here, at 40±3° C. and at an atmospheric humidity of 100%, one cycle (24 hours) consists of a 4-hour salt spray test according to DIN EN ISO 9227 NSS (June 2017), a 4-hour storage according to DIN EN ISO 6270-2 (AHT method) of September 2005 (including cooling) and a 16-hour storage according to DIN EN ISO 6270-2 (AHT method) of September 2005 (including heating). After every 5 cycles, there is a 48-hour pause according to DIN EN ISO 6270-2 (AHT method) of September 2005 (including cooling). 30 cycles therefore correspond to a total duration of 42 days.

[0216] Before the alternating climate test was carried out, the corresponding coating on the investigated sample was scored with a blade notch to the substrate, thereby allowing the sub-film corrosion (bottoming) level of the sample to be studied according to DIN EN ISO 4628-8 (date: March 1, 2013), because the substrate corrodes along the scoring line during the alternating climate test. As a result of the progressive course of corrosion, the coating is more or less bottomed during the test. The bottoming degree in [mm] is a measure of the corrosion resistance of the coating. The average bottoming level described later in the results below represents the average of the individual values ​​of three to five different plates evaluated, wherein each individual value of the plate is in turn the average of the bottoming levels at 11 measuring points on the plate. The results are shown in Table 2.

[0217] result

[0218] The results of the FRF testing were visually evaluated as described above and are shown in Table 1 below.

[0219] Table 1

[0220]

[0221] At a concentration of 0.1 g / L (equal to ≈0.7 mmol / L) of sodium benzoate in deionized water, inhibition according to FRF Test Procedure 2 has been observed. At a concentration of 0.2 g / L (equal to ≈1.4 mmol / L) of sodium benzoate in deionized water, inhibition according to FRF Test Procedures 1 and 2 was observed. Concentrations of up to 3.0 g / L (equal to ≈20.8 mmol / L) of sodium benzoate in deionized water were tested without adverse effects. Therefore, even higher concentrations of the corrosion inhibitor are acceptable. Such concentrations, and even higher concentrations, are limited by process economics and the risk of excessive drag of sodium benzoate into the next step, which could affect the performance of subsequent steps.

[0222] Table 2

[0223]

[0224]

[0225] *Comparative Examples

[0226] 1 Procedure 2 Steps (d) and (e)

[0227] 2 OS 9832: 9832, an organosilane-based film-forming composition, commercially available from Chemetall GmbH

[0228] 3 GB X 2025 / 2: GB X 2025 / 2, containing a polymer-based passivation composition, commercially available from Chemetall GmbH

[0229] In Comparative Example 1a* / 1b*, no corrosion inhibitor was used, however, no exposure to high humidity (flash rust condition simulation) was performed. Therefore, the results in the corrosion test were good. In contrast, in Comparative Example 2a* / 2b*, the same procedure was performed, however with flash rust conditions simulation, and rather poor corrosion test results were observed. In Example 3a / 3b of the present invention, Comparative Example 2a* / 2b* was repeated, however, with the difference that in the second rinse, 0.5 g / L (i.e., approximately 3.5 mmol / L) of sodium benzoate was contained. The addition of sodium benzoate prevented the adverse effects of the flash rust simulation test.

[0230] Comparison of inventive example 3a with comparative example 2a* clearly shows that the presence of 0.5 g / L (i.e., approximately 3.5 mmol / L) of sodium benzoate in the second rinse composition significantly improves the corrosion resistance of the hot-dip galvanized steel panels (HDG panels) thus treated and pretreated with OS 9832 in the VDA 233-102 test, with the depth of undercutting of inventive sample 3a being only 0.6 mm compared to 1.9 mm for comparative example 2a*.

[0231] Comparison of Example 3b of the present invention with Comparative Example 2b* clearly shows that the presence of 0.5 g / L (i.e., approximately 3.5 mmol / L) of sodium benzoate in the second rinse composition also significantly improves the corrosion resistance of the cold rolled steel sheets (CRS sheets) thus treated and pretreated with OS 9832. In the NSS test, the depth of the pitting of Sample 3b of the present invention was only 1.3 mm compared to 3.2 mm for Comparative Example 2b*, in the PV1210 test, the depth of the pitting of Sample 3b of the present invention was only 0.8 mm compared to 2.5 mm for Comparative Example 2b*, and in the VDA 233-102 test, the depth of the pitting of Sample 3b of the present invention was only 2.1 mm compared to 4.7 mm for Comparative Example 2b*.

[0232] Furthermore, Inventive Example 3b and Comparative Example 2b* were exposed to high humidity. While Inventive Example 3b had no visible flash rust formation, Comparative Example 2b* showed strong flash rust formation.

[0233] The results are even more impressive when comparing Inventive Examples 6a and 6b to Comparative Examples 5a* and 5b*, and especially when comparing Inventive Example 6b to Comparative Example 5b*.

[0234] Comparison of the inventive example 6a with the comparative example 5a* clearly shows that the presence of 0.5 g / L (i.e., approximately 3.5 mmol / L) of sodium benzoate in the second rinse composition significantly improves the corrosion resistance of the hot-dip galvanized steel sheet (HDG sheet) as treated and pretreated with GB X 2025 / 2 in the VDA 233-102 test, with the depth of undercutting of the inventive sample 6a being only 0.5 mm compared to 1.7 mm for the comparative example 5a*.

[0235] Comparison of Example 6b of the present invention with Comparative Example 5b* clearly shows that the presence of 0.5 g / L (i.e., about 3.5 mmol / L) of sodium benzoate in the second rinse composition also significantly improves the corrosion resistance of the cold rolled steel sheets (CRS sheets) treated as such and pretreated with GB X 2025 / 2. In the NSS test, the depth of the inventive sample 6b was only 1.3 mm compared to 3.0 mm for Comparative Example 5b*, in the PV1210 test, the depth of the inventive sample 6b was only 0.8 mm compared to 2.7 mm for Comparative Example 5b*, and in the VDA 233-102 test, the depth of the inventive sample 6b was only 2.5 mm compared to 4.5 mm for Comparative Example 5b*.

[0236] Although the specimen used in Inventive Example 6b was exposed to high humidity, no visible flash rusting was observed, whereas Comparative Example 5b*, which was exposed to high humidity, showed intense flash rusting formation.

Claims

1. A method for pretreating a metal substrate, the method comprising: 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 conversion treatment step, a passivation treatment step and a thin layer forming 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 conversion treatment composition, a passivation treatment composition and a thin layer forming composition to obtain a chemically pretreated substrate; wherein i. and / or ii. are followed by one or more flushing steps, characterized in that At least one flushing composition is used, which comprises water in an amount ranging from 97 wt.-% to 99.99 wt.-% and one or more compounds of formula (I) in an amount ranging from 0.8 to 200 mmol / L of the composition The COOH groups of the compounds may be completely or partially neutralized and the residue R 1 , R 2 , R 3 , R 4 and R 5 One or more of are independently selected from the group consisting of H, hydroxyl and alkyl.

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

3. The method for pretreating a metal substrate according to claim 1, comprising: i. one or more cleaning steps; This is followed by one or more activation steps, followed by 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, wherein i. and ii. are followed by one or more washing steps.

4. The method for pretreating a metal substrate according to claim 1, comprising: i. One or more cleaning steps; followed directly by ii. one or more phosphate-free chemical pretreatment steps, wherein i. and ii. are followed by one or more washing steps.

5. A method for pretreating a metal substrate according to any one or more of claims 1 to 4, wherein: The one or more compounds of formula (I) as defined in claim 1 are contained in at least one of the wash-off compositions.

6. A method for pretreating a metal substrate according to any one or more of claims 1 to 5, 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 the corresponding composition.

7. A method for pretreating a metal substrate according to any one or more of claims 1 to 6, wherein: In the one or more compounds of formula (I), the residue R 1 , R 2 , R 3 , R 4 and R 5 is H; and the COOH groups are fully or partially neutralized in the form of their alkali metal salts, ammonium salts and / or quaternary ammonium salts.

8. A method for pretreating a metal substrate according to any one or more of claims 1 to 7, wherein: The one or more rinsing steps are performed with one or more rinsing compositions having a pH value in the range of 6 to 10.

9. A method for pretreating a metal substrate according to any one or more of claims 1 to 8, wherein: The chemical pretreatment composition is selected from a. A layer-forming phosphate conversion treatment composition and / or a non-layer-forming phosphate conversion treatment composition, which is preferably selected from the group consisting of: i. Ni-containing and Ni-free zinc phosphatizing compositions and trivalent cation phosphatizing compositions, ii. a composition for forming an amorphous phosphate conversion coating, iii. A phosphate 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; as well as iv. forming an amorphous iron phosphate conversion coating composition; b. an organosilane-based film-forming composition comprising at least one organosilane and / or its hydrolysis product and / or its condensation product; c. a passivating composition comprising at least one compound selected from the group consisting of zirconium compounds, titanium compounds and hafnium compounds; d. a passivation and thin film-forming composition comprising 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. A passivating composition comprising at least one compound selected from the group of zirconium compounds, titanium compounds and hafnium compounds, and comprising 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, in particular (phosphonic acid-acrylic acid) copolymers, polyvinylpyrrolidone and vinylpyrrolidone copolymers, vinyl acetate copolymers, in particular (vinyl alcohol-vinyl acetate) copolymers, ethoxylated polymers such as polyethylene glycol and copolymers, and linear or branched poly(ethyleneimine).

10. The method for pretreating a metal substrate according to any one or more of claims 1 to 9, characterized in that The contacting of the metal substrate with the 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 a contact temperature in the range of 10°C to 60°C.

11. A metal substrate obtainable by a process according to any one or more of claims 1 to 10.

12. A method for coating a metal substrate, wherein: The metal substrate is treated by the method for pretreating a metal substrate according to claim 1, and After the last rinse step, iii. applying one or more coating compositions selected from the group consisting of a solid coating composition and a liquid coating composition to form one or more coating layers, each of the one or more coating layers being cured or uncured after application; and iv. curing any coating layer or layers applied in step iii. that were not cured in step iii.

13. The method for 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, aqueous one-component or two-component compositions, solvent-borne one-component or two-component compositions and radiation-curable coating compositions.

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

15. Use of an aqueous composition for pretreating a metal substrate, the aqueous composition comprising 97 wt.-% to 99.9 wt.-% of water and one or more compounds of formula (I) in an amount of 0.8 to 200 mmol / L of the composition The COOH groups of the compounds may be completely or partially neutralized and the residue R 1 , R 2 , R 3 , R 4 and R 5 One or more of the above are independently selected from the group consisting of H, hydroxyl and alkyl, the pretreatment comprising at least one of a cleaning step and a chemical pretreatment step; and at least one additional rinsing step.

16. Use according to claim 15 for preventing or inhibiting the formation of flash rust on the metal substrate.

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