Electrodeposition coating composition containing lamp black pigment

Abstract

The present invention relates to a cathodically depositable aqueous electrodeposition coating composition comprising at least one cathodically depositable polymer (a) and at least one carbon black pigment (b), wherein the at least one carbon black pigment (b) has a number-based median primary particle size (d) of at least 50 nm and at most 200 nm. N,50％ ); a method for at least partially coating a conductive substrate by a cathodic electrodeposition coating method, which comprises at least steps (1) to (5), including the step (1) of at least partially immersing the substrate in an electrodeposition coating bath comprising the electrodeposition coating composition of the present invention; a conductive substrate at least partially coated with the baked electrodeposition coating composition of the present invention and / or obtainable by the method of the present invention; and use of the carbon black pigment (b) for improving corrosion protection and / or film formation uniformity.

Description

[0001] The present invention relates to an aqueous cathodically depositable electrodeposition coating material composition comprising at least one cathodically depositable polymer (a) and at least one carbon black pigment (b), wherein the at least one carbon black pigment (b) has a number basis median primary particle size (d) of at least 50 nm and at most 200 nm. N,50％ ); a method for at least partially coating a conductive substrate by cathodic electrodeposition coating, comprising at least steps (1) to (5), comprising step (1) of at least partially immersing the substrate in an electrodeposition coating bath comprising the electrodeposition coating composition of the present invention; a conductive substrate coated with the electrodeposition coating composition of the present invention which is at least partially baked and / or obtainable by the method of the present invention; and use of the carbon black pigment (b) for improving corrosion protection and / or film build uniformity. Background of the Invention

[0003] In the automotive industry, metal components used in manufacturing often have to be protected against corrosion. The requirements for the corrosion control to be achieved are very stringent, especially since manufacturers often offer a warranty against rust perforation for many years. Such corrosion control is usually achieved by coating the component or the substrate used to manufacture the component with at least one coating suitable for the purpose.

[0004] In order to ensure the necessary corrosion control, it is conventional practice to apply an electrodeposition coating on a metal substrate, which substrate may have been pretreated by phosphatizing and / or by other types of pretreatment methods. Electrodeposition coatings (electrophoretic coatings) are coatings containing polymers (optionally containing crosslinking agents) as binders, pigments and / or fillers and general additives. There are usually electrophoretic coatings (electrocoat materials) that can be deposited anodically and cathodically. For example, WO 2006 / 117189 A1 discloses an anodic electrodeposition coating composition that contains, in particular, metallic effect pigments. However, cathodically depositable materials are most important in industrial coatings, especially in automotive finishing. In cathodic electrodeposition coating, the substrate to be coated is immersed in an electrocoating bath and connected as a cathode. The bath has an anode as a counter electrode. The particles of the electrophoretic coating are stabilized with a positive charge and deposited on the cathode to form a coating film. After deposition, the coated substrate is removed from the electrocoating bath and baked, ie, thermally cures the coating film.

[0005] Cathodically depositable electrophoretic coatings are known from the prior art, for example from EP 1 041 125 A1, DE 19703 869 A1 and WO 91 / 09917 A2. Furthermore, coating compositions which generally comprise an effective corrosion-inhibiting amount of carbon pigments are disclosed in WO 2004 / 065498 A2.

[0006] The metal substrates used in the automotive industry that must be protected from corrosion are typically a variety of different metal substrates, such as bare steel, phosphated steel and / or steel substrates that have been pretreated by at least one other pretreatment method. In addition, these various different metal substrates are often additionally or alternatively mechanically pretreated, such as by a sanding process, depending on the desired surface properties. When the electrodeposition coating is applied to their surface, the difference in the material surface properties of the substrate may lead to differences in the application process, because due to the different material / surface properties of the substrate, differences in film build heights may result. It is not desirable to have these different film build heights, because these differences need to be covered and leveled by the coating (such as primer coating) applied subsequently to prevent exposure to the surface of the entire automotive coating. Such covering and / or leveling (levelling out) usually requires a cost-intensive post-processing process that must be performed manually.

[0007] Therefore, it is necessary to provide an electrodeposition coating that can achieve uniform film formation during application of the electrodeposition coating to the optionally pretreated surface of the substrate, regardless of the substrate material used and / or the pretreatment method used to pretreat the substrate material, without impairing the corrosion protection properties.

[0008] question

[0009] It is therefore an object of the present invention to provide an electrodeposition coating which is capable of achieving uniform film formation during its application onto various optionally pretreated surfaces of a metal substrate, regardless of the substrate material used and / or the pretreatment method used.

[0010] Solution

[0011] This object is solved by the subject-matter of the claims of the present application and by its preferred embodiments disclosed in the present description, ie by the subject-matter described herein.

[0012] The first subject of the present invention is a cathodically depositable aqueous electrodeposition coating composition comprising

[0013] (a) at least one cathodically depositable polymer and

[0014] (b) at least one carbon black pigment,

[0015] wherein the at least one carbon black pigment (b) has a number-based median primary particle size (d) of at least 50 nm and at most 200 nm N,50％ )'s lamp black paint.

[0016] Another subject of the present invention is a method for at least partially coating an electrically conductive substrate by cathodic electrodeposition coating, comprising at least steps (1) to (5), namely

[0017] (1) immersing at least part of a conductive substrate into an electrodeposition coating bath containing the electrodeposition coating composition of the present invention,

[0018] (2) connecting the substrate as a cathode,

[0019] (3) depositing a coating film obtained from the electrodeposition coating composition on a substrate using direct current,

[0020] (4) removing the coated substrate from the electrodeposition coating bath, and

[0021] (5) Baking the coating film deposited on the substrate.

[0022] Another subject of the present invention is an electrically conductive substrate coated with an at least partially baked electrodeposition coating composition of the invention and / or obtainable by the process of the invention.

[0023] Another subject of the present invention is the use of the at least one carbon black pigment (b) as defined above and in the description below for improving the corrosion protection of conductive substrates with baked coating films obtained from cathodically depositable aqueous electrodeposition coating compositions which - in addition to the at least one carbon black pigment (b) - also comprise at least one cathodically depositable polymer (a) and / or for improving the uniformity of film formation and / or for reducing mapping of coating films obtained from cathodically depositable aqueous electrodeposition coating compositions which - in addition to the at least one carbon black pigment (b) - also comprise at least one cathodically depositable polymer (a).

[0024] It has been surprisingly found that the electrodeposition coating composition of the present invention is able to achieve uniform film formation during its application to the optionally pretreated surface of the substrate, independently of the substrate material used and / or its optional previous pretreatment. Thus, it has been unexpectedly found that when the electrodeposition coating composition of the present invention is applied to these substrates (e.g., bare steel and phosphated steel substrates), no undesirable film formation deviations caused by the different surface properties of the substrate are observed or at least significantly reduced. In particular, it has been found that this unexpected technical effect is attributed to the specific pigment (b) present in the coating composition. This is surprising because carbon black pigments are usually incorporated into the electrodeposition coating composition only to provide the overall gray color of the resulting electrodeposition coating film.

[0025] Furthermore, it has surprisingly been found that - in addition to the improved uniformity of the film formation - the corrosion protection of the substrate is additionally improved. Furthermore, it has been found that other properties of the resulting electrodeposited film, such as surface roughness, are not negatively affected.

[0026] In particular, it has been found that only when using the specific carbon black pigments (b) defined above (i.e. having a number-based median primary particle size (d N,50％ The above advantages and technical effects are only observed when using other carbon black pigments, such as furnace black pigments or lamp black pigments that do not meet the number-based median primary particle size standards specified above. As is apparent from the experimental section of this article, such advantages and effects are not achieved when using other carbon black pigments, such as furnace black pigments or lamp black pigments that do not meet the number-based median primary particle size standards specified above. DETAILED DESCRIPTION OF THE INVENTION

[0028] In the sense of the present invention, the term "comprising" with respect to, for example, the electrodeposition coating composition of the present invention preferably has the meaning of "consisting of". With respect to the electrodeposition coating composition of the present invention, it is possible that, in addition to components (a), (b) and water, one or more additional components specified below and optionally contained in the electrodeposition coating composition of the present invention are also included therein. All components may each be present in their preferred embodiments as specified below.

[0029] Electrodeposition coating composition of the present invention

[0030] The cathodically depositable aqueous electrodeposition coating composition of the present invention (hereinafter also referred to as the electrodeposition coating composition of the present invention) comprises at least components (a), (b) and water. The terms "electrodeposition coating composition" and "electrodeposition coating composition" as used herein are interchangeable.

[0031] The cathodically depositable aqueous electrodeposition coating composition of the present invention is suitable for at least partially coating a conductive substrate with an electrodeposition coating composition, meaning that it is suitable for at least partially being applied to a substrate surface of a conductive substrate, such application giving an electrodeposition coating film on the substrate surface.

[0032] The cathodically depositable electrodeposition coating composition of the invention is aqueous. With respect to the electrodeposition coating composition of the invention, the term "aqueous" is preferably understood for the purposes of the invention to mean water, as a solvent and / or as a diluent, present as the main component of all solvents and / or diluents present in the electrodeposition coating composition, preferably present in an amount of at least 35% by weight, based on the total weight of the electrodeposition coating composition of the invention. Organic solvents may additionally be present in smaller proportions, preferably in an amount of <20% by weight.

[0033] The electrodeposition coating composition of the present invention preferably comprises a water fraction of at least 40% by weight, more preferably at least 50% by weight, even more preferably at least 60% by weight, even more preferably at least 65% by weight, in particular at least 70% by weight, most preferably at least 75% by weight, in each case based on the total weight of the electrodeposition coating composition.

[0034] The electrodeposition coating composition of the invention preferably comprises an organic solvent fraction of <10% by weight, more preferably in the range of 0 to <10% by weight, very preferably in the range of 0 to <7.5% by weight or 0 to <5% by weight or 0 to 2% by weight, in each case based on the total weight of the electrodeposition coating composition. Examples of such organic solvents include heterocyclic, aliphatic or aromatic hydrocarbons, monohydric or polyhydric alcohols, in particular methanol and / or ethanol, ethers, esters, ketones and amides, for example N-methylpyrrolidone, N-ethylpyrrolidone, dimethylformamide, toluene, xylene, butanol, ethylene glycol, propylene glycol and butyl glycol ether and their acetates, butyl diethylene glycol, diethylene glycol dimethyl ether, cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone, acetone, isophorone or mixtures thereof.

[0035] The solids content of the electrodeposition coating composition of the invention is preferably in the range of 5 to 35% by weight, more preferably 7.5 to 30% by weight, very preferably 10 to 27.5% by weight, more particularly 12.5 to 25% by weight, most preferably 15 to 22.5% by weight or 15 to 20% by weight, in each case based on the total weight of the electrodeposition coating composition. The solids content, in other words the non-volatile matter, is determined according to the method described below.

[0036] The electrodeposition coating composition of the present invention preferably has a pH in the range of 2.0 to 10.0, more preferably in the range of 2.5 to 9.5 or in the range of 2.5 to 9.0, very preferably in the range of 3.0 to 8.5 or in the range of 3.0 to 8.0, more particularly in the range of 2.5 to 7.5 or in the range of 3.5 to 7.0, particularly preferably in the range of 4.0 to 6.5, most preferably in the range of 3.5 to 6.5 or 5.0 to 6.0.

[0037] The electrodeposition coating composition comprises component (a) in an amount of preferably 15 to 85% by weight, more preferably 20 to 80% by weight, very preferably 25 to 77.5% by weight, more particularly 30 to 75% by weight or 35 to 75% by weight, most preferably 40 to 70% by weight or 45 to 70% by weight or 50 to 70% by weight, in each case based on the total solid content of the electrodeposition coating composition. Alternatively, the electrodeposition coating composition of the present invention comprises component (a) in an amount of preferably 1 to 40% by weight, more preferably 2.5 to 37.5% by weight, very preferably 4 to 35% by weight, more particularly 5.5 to 32.5% by weight, most preferably 7 to 30% by weight or 8 to 25% by weight, in each case based on the total weight of the electrodeposition coating composition.

[0038] The electrodeposition coating composition comprises component (b) in an amount of preferably 0.005 to 4.0% by weight, more preferably 0.007 to 2.5% by weight, very preferably 0.010 to 1.5% by weight, more particularly 0.015 to 1.0% by weight, most preferably 0.020 to 0.5% by weight or 0.025 to 0.1% by weight, in each case based on the total weight of the electrodeposition coating composition.

[0039] The electrodeposition coating composition comprises component (b) in an amount of preferably 0.050 to 5.0 wt. %, more preferably 0.060 to 4.0 wt. %, very preferably 0.070 to 3.0 wt. %, more particularly 0.080 to 2.0 wt. %, still more preferably 0.09 to 1.5 wt. %, still more preferably 0.10 to 1.0 wt. %, most preferably 0.12 to 0.75 wt. % or 0.13 to 0.5 wt. %, in each case based on the total solids content of the electrodeposition coating composition.

[0040] In the case where the electrodeposition coating composition of the present invention additionally comprises at least one crosslinking agent component (c), the component (c) is preferably present in an amount of 5 to 45% by weight, more preferably 6 to 42.5% by weight, very preferably 7 to 40% by weight, more particularly 8 to 37.5% by weight or 9 to 35% by weight, most preferably 10 to 35% by weight, particularly preferably 15 to 35% by weight, in each case based on the total solid content of the electrodeposition coating composition. Alternatively, in the case where the electrodeposition coating composition of the present invention additionally comprises at least one crosslinking agent component (c), the component (c) is preferably present in an amount of 0.5 to 30% by weight, more preferably 1 to 25% by weight, very preferably 1.5 to 20% by weight, more particularly 2 to 17.5% by weight, most preferably 2.5 to 15% by weight, particularly preferably 3 to 10% by weight, in each case based on the total weight of the electrodeposition coating composition.

[0041] The electrodeposition coating composition of the present invention preferably contains no component having an ethylenically unsaturated double bond. More specifically, both components (a) and (c) of the electrodeposition coating composition of the present invention contain no ethylenically unsaturated double bond.

[0042] The fractions in weight % of all components (a), (b) and water contained in the electrodeposition coating composition of the present invention and additional components which may be present as component (c) add up to 100 weight % of the total weight of the electrodeposition coating composition.

[0043] The relative weight ratios of components (a) and (c) (if component (c) is present) to each other in the electrodeposition coating composition are preferably in the range of 5:1 to 1.1:1, more preferably in the range of 4.5:1 to 1.1:1, very preferably in the range of 4:1 to 1.2:1, more particularly in the range of 3:1 to 1.5:1.

[0044] Component (a)

[0045] Component (a) is at least one cathodically depositable polymer which preferably acts as at least one binder in the electrodeposition coating composition of the present invention. At the same time, component (a) may also act as a grinding resin as outlined in more detail below.

[0046] Any polymer is suitable as binder and thus as component (a) as long as it is cathodically depositable. Preference is given to poly(meth)acrylates, (meth)acrylate copolymers and epoxide polymers.

[0047] Component (a) of the electrodeposition coating composition of the present invention preferably comprises and / or is at least one epoxide-amine adduct.

[0048] For the purposes of the present invention, epoxy-amine adducts are the reaction products of at least one epoxy resin and at least one amine. The epoxy resins used are more particularly those based on bisphenol A and / or its derivatives. The amines reacted with the epoxy resins are primary and / or secondary amines or their salts and / or salts of tertiary amines.

[0049] The at least one epoxy-amine adduct used as component (a) is preferably a cationic, epoxide-based and amine-modified resin. The preparation of such cationic, amine-modified epoxy resins is known and described, for example, in DE 35 18 732, DE 35 18 770, EP 0 004 090, EP 0 012 463, EP 0 961 797 B1 and EP 0 505 445 B1. Cationic, epoxy-based, amine-modified resins are preferably understood to be the reaction product of at least one polyepoxide having preferably two or more, for example three epoxy groups and at least one amine, preferably at least one primary and / or secondary amine. Particularly preferred polyepoxides are polyglycidyl ethers of polyphenols made from polyphenols and epihalohydrins. The polyphenols used may in particular be bisphenol A and / or bisphenol F. Other suitable polyepoxides are polyols, for example polyglycidyl ethers of ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,4-propylene glycol, 1,5-pentanediol, 1,2,6-hexanetriol, glycerol and 2,2-bis(4-hydroxycyclohexyl)propane. The polyepoxides used may also be modified polyepoxides. Modified polyepoxides are understood to be those polyepoxides in which some of the reactive functional groups have been reacted with at least one modifying compound. Examples of such modifying compounds are as follows:

[0050] i) carboxyl-containing compounds, such as saturated or unsaturated monocarboxylic acids (e.g. benzoic acid, linseed oil fatty acid, 2-ethylhexanoic acid, Versatic acid), aliphatic, cycloaliphatic and / or aromatic dicarboxylic acids of various chain lengths (e.g. adipic acid, sebacic acid, isophthalic acid or dimerized fatty acids), hydroxyalkylcarboxylic acids (e.g. lactic acid, dimethylolpropionic acid) and carboxyl-containing polyesters, or

[0051] ii) amino group-containing compounds, such as diethylamine or ethylhexylamine or diamines having secondary amino groups, for example N,N′-dialkylalkylenediamines, such as dimethylethylenediamine, N,N′-dialkylpolyoxyalkyleneamines, such as N,N′-dimethylpolyoxypropylenediamine, cyanoalkylated alkylenediamines, such as bis-N,N′-cyanoethylethylenediamine, cyanoalkylated polyoxyalkyleneamines, such as bis-N,N′-cyanoethylpolyoxypropylenediamine, polyaminoamides, such as Versamides, in particular amino-terminated reaction products of diamines (for example hexamethylenediamine), polycarboxylic acids (especially dimerized fatty acids) and monocarboxylic acids (more especially fatty acids), or reaction products of 1 mol of diaminohexane with 2 mol of monoglycidyl ethers or monoglycidyl esters, in particular glycidyl esters of α-branched fatty acids (for example Versatic acid), or

[0052] iii) hydroxyl-containing compounds such as neopentyl glycol, bisethoxylated neopentyl glycol, neopentyl glycol hydroxypivalate, dimethylhydantoin-N,N′-diethanol, hexane-1,6-diol, hexane-2,5-diol, 1,4-bis(hydroxymethyl)cyclohexane, 1,1-isopropylidenebis(p-phenoxy)-2-propanol, trimethylolpropane, pentaerythritol or amino alcohols such as triethanolamine, methyldiethanolamine or hydroxyl-containing alkylketimines such as aminomethylpropane-1,3-diol methylisobutylketimines or tris(hydroxymethyl)aminomethanecyclohexanoneketimines, and polyglycol ethers, polyester polyols, polyether polyols, polycaprolactone polyols, polycaprolactam polyols of various functionalities and molecular weights, or

[0053] iv) Saturated or unsaturated fatty acid methyl esters esterified with the hydroxyl groups of epoxy resins in the presence of sodium methoxide.

[0054] Examples of amines that can be used to prepare component (a) are mono- and dialkylamines, such as methylamine, ethylamine, propylamine, butylamine, dimethylamine, diethylamine, dipropylamine, methylbutylamine, alkanolamines, such as methylethanolamine or diethanolamine, dialkylaminoalkylamines, such as dimethylaminoethylamine, diethylaminopropylamine or dimethylaminopropylamine. The amines that can be used may also include other functional groups, as long as they do not interfere with the reaction of the amine with the epoxy groups of the optionally modified polyepoxide, and do not cause gelation of the reaction mixture. Secondary amines are preferably used. The charge required for water dilutability and electrodeposition can be generated by protonation with a water-soluble acid (e.g., boric acid, formic acid, acetic acid, lactic acid; preferably acetic acid and / or formic acid). Another way to introduce cationic groups into the optionally modified polyepoxide is to react the epoxy groups of the polyepoxide with amine salts.

[0055] Epoxy-amine adducts which can be used as component (a) are preferably reaction products of epoxy resins based on bisphenol A with primary and / or secondary amines or their salts and / or salts of tertiary amines.

[0056] Component (b)

[0057] The electrodeposition coating composition of the present invention comprises at least one carbon black pigment as component (b), which is a lamp black pigment.

[0058] The term "pigment" is known to the skilled person, for example, from DIN 55943 (date: October 2001). "Pigment" in the sense of the present invention preferably refers to a component in powder or flake form which is substantially, preferably completely insoluble in its surrounding medium (e.g. the electrodeposition coating composition of the present invention). Pigments are preferably colorants and / or substances which can act as pigments due to their magnetic, electrical and / or electromagnetic properties. The pigment preferably differs from the "filler" in its refractive index, the refractive index of the pigment being ≥ 1.7.

[0059] Carbon black pigment is usually made by the thermal decomposition of hydrocarbons (liquid and gaseous hydrocarbons) under controlled conditions, i.e., by an oxidative pyrolysis process, most often by the incomplete combustion of raw materials. The most common source of raw materials for the production of carbon black is a heavy hydrocarbon stream derived from coal or crude oil processing, which is referred to as carbon black oil (CBO). CBO is usually mainly containing polycyclic aromatic hydrocarbon feedstock oil. Natural gas, coal tar distillates (carbochemical oils) or residual oil made by catalytic cracking of petroleum fractions and olefins made by thermal cracking of naphtha or gas oil (petrochemical oil) are the key sources of this raw material. The production method is different based on the arrangement of heat and decomposition stage. Filter the obtained carbon black product (such as lamp black, gas black or furnace black) from the exhaust gas of production process. Manufacturing method includes furnace method, gas method, lamp method and thermal carbon black method.

[0060] More than 98% of the world's annual carbon black production is achieved through the furnace black process. The furnace black process is continuous and uses liquid and gaseous hydrocarbons as raw materials. The heated liquid raw material is sprayed into a heat source generated by the combustion of natural gas or fuel oil and preheated air. Since it is carried out at extremely high temperatures, the reaction is confined to a refractory-lined furnace. After the carbon black is formed, the process mixture is quenched by injecting water. This also prevents any unwanted secondary reactions. The gas loaded with carbon black then passes through a heat exchanger for further cooling while heating the preheated air required for process combustion. Bag filters separate carbon black particles from the gas stream. The gases produced by this reaction are combustible and in most cases are burned in a boiler to generate steam and / or electricity, or alternatively burned (flared). The carbon black collected by the filter has an extremely low bulk density, and depending on the application, it is usually pelletized or further densified for further processing.

[0061] The gas black process uses vaporized oil as a feedstock. The oil is heated and the resulting vapor is carried by hydrogen-rich gas into a tube equipped with multiple burners. The individual particles impact the surface of a water-cooled drum. A portion of the resulting carbon black is deposited on the rolls, the remainder enters a filter system. The two carbon black streams are then combined. Subsequent processing is similar to the furnace black process. The thermal black process for producing carbon black is a semi-batch process that uses natural gas as the most common feedstock, although higher hydrocarbon oils can also be used. It involves the thermal decomposition of the feedstock in a refractory-lined vessel, which decomposes the natural gas into carbon black and hydrogen.

[0062] Lamp black is a specialty carbon black made by incomplete combustion of carbon black oil similar to the furnace black process, except that the combustion is carried out in large open shallow vessels. Lamp black is the oldest industrial-scale carbon black production process still in use. Lamp black pigments (b) are produced by this process.

[0063] Preferably, the electrodeposition coating composition of the present invention does not contain any furnace black, gas black and / or thermal black pigment. In addition, preferably, the at least one pigment (b) is the only lamp black carbon black pigment present in the electrodeposition coating composition of the present invention. In particular, the at least one pigment (b) is the only carbon black pigment present in the electrodeposition coating composition of the present invention.

[0064] The at least one carbon black pigment (b) has a number-based median primary particle size (d) of at least 50 nm and at most 200 nm. N,50％ ). Term quantity base median particle size (d N,50％ ) are parameters known to those skilled in the art. The characteristic variable marked with a lowercase letter "d" is the percentile (50%) of the cumulative distribution curve, where the 50% percentile corresponds to the median. The index "N" relates to the number-based distribution.

[0065] Preferably, the at least one carbon black pigment (b) has a number-based median primary particle size (d ) of at least 75 nm and at most 150 nm, more preferably at least 80 nm and at most 120 nm, even more preferably at least 85 nm and at most 110 nm, in particular at least 90 nm and at most 105 nm. N,50％ ).

[0066] Preferably, the at least one carbon black pigment (b) has an average primary particle size of at least 50 nm and at most 200 nm, more preferably at least 60 nm and at most 175 nm, even more preferably at least 70 nm and at most 160 nm, even more preferably at least 80 nm and at most 150 nm, even more preferably at least 85 nm and at most 140 nm, in particular at least 90 nm and at most 130 nm, most preferably at least 95 nm and at most 125 nm.

[0067] Preferably, the at least one carbon black pigment (b) has a primary particle size of 5 nm to 600 nm, wherein 5 nm is the minimum measured primary particle size and 600 nm is the maximum measured primary particle size.

[0068] For the purposes of the present invention, the number basis median primary particle size (d N,50％ ), average primary particle size and primary particle size, in particular the minimum and maximum values ​​of the primary particle size. The measurement methods are described below in the "Methods" section.

[0069] Preferably, the at least one carbon black pigment (b) has a pH value in the range of >6 to 10. Lamp black pigments suitable as component (b) are commercially available.

[0070] Preferably, the at least one carbon black pigment (b) contains not more than 50 ppm, more preferably not more than 30 ppm, even more preferably not more than 20 ppm, in particular not more than 10 ppm, most preferably not more than 4 ppm of sulfur in the water-soluble fraction obtained from the at least one carbon black pigment (b), as measured by ICP-OES according to DIN EN ISO 11885:2009-09. The measurement method is described below in the "Methods" section.

[0071] Component (b) is preferably incorporated into the electrodeposition coating composition in the form of a pigment paste. In addition to the pigment (b), other pigments and / or fillers each different from the pigment (b) may also be present and preferably present in the pigment paste. Such a paste generally contains at least one polymer used as a grinding resin. Therefore, preferably, at least one such polymer used as a grinding resin is included in the electrodeposition coating composition of the present invention. It is possible that the at least one polymer (a) used as a binder in the electrodeposition coating composition may also serve as a grinding resin in the pigment paste. The grinding resin in question is preferably an epoxy-amine adduct that may correspond to component (a) and / or may be included under the definition of component (a) as outlined above. The polymer used as a grinding resin preferably has a structural unit that interacts with the surface of the pigment. The grinding resin therefore preferably has the effect of an emulsifier. In many cases, a quaternary ammonium compound is incorporated to improve the properties of the grinding resin. The pigment is preferably ground together with the grinding resin, i.e., ground to form a pigment paste. Grinding is conventionally performed using a standard mill. In order to produce a finished electrodeposition coating composition, this paste is mixed with the remaining ingredients. The use of pigment pastes advantageously allows greater flexibility in electrodeposition coatings, since the pigment and binder of the electrodeposition coating composition can be easily adapted to the requirements of the practice at any time via the amount of pigment paste.

[0072] If the electrodeposition coating composition of the invention comprises at least one polymer which is different from polymer (a) and which serves as a grinding resin, the polymer is preferably contained in the electrodeposition coating composition in an amount of 0.5 to 10% by weight, more preferably 0.5 to 7.5% by weight and very preferably 0.75 to 5% by weight, in each case based on the total weight of the electrodeposition coating composition.

[0073] Preferably, the coating composition of the present invention is obtainable by mixing a pigment slurry comprising at least the at least one carbon black pigment (b) with a mixture comprising at least water and a polymer (a).

[0074] In case the at least one pigment (b) is incorporated into a pigment slurry - which may contain one or more further pigments and / or fillers each different from the pigment (b) as component (d) - and the pigment slurry is used as a precursor for preparing the electrodeposition coating composition of the invention, the pigment slurry preferably contains component (b) in an amount of 0.10 to 10.0% by weight, more preferably 0.15 to 7.5% by weight, very preferably 0.20 to 5.0% by weight, more particularly 0.25 to 3.5% by weight, even more preferably 0.30 to 2.0% by weight, even more preferably 0.35 to 1.5% by weight, most preferably 0.35 to 1.0% by weight, in each case based on the total weight of the pigment slurry. Preferably, the at least one pigment (b) is the only carbon black pigment present in the pigment slurry.

[0075] Optional component (c)

[0076] At least one crosslinking agent may be present in the electrodeposition coating composition as component (c) selected from blocked polyisocyanates, free polyisocyanates, amino resins and mixtures thereof. Component (c) is different from component (a).

[0077] The term "blocked polyisocyanate" is known to the skilled person. Useful blocked polyisocyanates are polyisocyanates having at least two isocyanate groups (in the case of exactly two isocyanate groups, diisocyanates), but preferably having more than two, for example 3 to 5 isocyanate groups, wherein the isocyanate groups have been reacted so that the blocked polyisocyanate formed is stable at room temperature, i.e. at temperatures of 18 to 23° C., in particular toward hydroxyl groups and amino groups, such as primary and / or secondary amino groups, but reacts at elevated temperatures, for example at ≥80° C., ≥110° C., ≥130° C., ≥140° C., ≥150° C., ≥160° C., ≥170° C., or ≥180° C. and therewith converts and forms urethane and / or urea bonds, respectively.

[0078] In the preparation of blocked polyisocyanates, it is possible to use any desired organic polyisocyanates suitable for crosslinking. The isocyanates used are preferably (hetero)aliphatic, (hetero)alicyclic, (hetero)aromatic or (hetero)aliphatic-(hetero)aromatic isocyanates. Preferred polyisocyanates are those containing 2 to 36, in particular 6 to 15, carbon atoms. Preferred examples are ethylene 1,2-ethylene diisocyanate (ethylene 1,2-ethylene diisocyanate. diisocyanate), tetramethylene 1,4-diisocyanate, hexamethylene 1,6-diisocyanate (HDI), 2,2,4(2,4,4)-trimethylhexamethylene 1,6-diisocyanate (TMDI), diphenylmethane diisocyanate (MDI), 1,9-diisocyanato-5-methylnonane, 1,8-diisocyanato-2,4-dimethyloctane, 1,12-dodecane diisocyanate, ω,ω′-diisocyanato dipropyl ether, cyclobutene 1,3-diisocyanate, cyclohexane 1,3- and 1,4-diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate ester, IPDI), 1,4-diisocyanatomethyl-2,3,5,6-tetramethylcyclohexane, decahydro-8-methyl (1,4-methylenenaphthalene-2 ​​(or 3), 5-yl dimethylene diisocyanate, hexahydro-4,7-methyleneindan-1 (or 2), 5 (or 6)-yl dimethylene diisocyanate, hexahydro-4,7-methyleneindan-1 (or 2), 5 (or 6)-yl diisocyanate, hexahydro-4,7-methyleneindan-1 (or 2), 5 (or 6)-yl diisocyanate, hexahydrotoluene 2,4- and / or 2,6-diisocyanate (H6-TDI), 2,4- and / or 2,6-toluene diisocyanate (TDI), perhydrodiphenylmethane 2,4′-diisocyanate, perhydrodiphenylmethane 4,4′-diisocyanate (H 12 MDI), 4,4′-diisocyanato-3,3′,5,5′-tetramethyldicyclohexylmethane, 4,4′-diisocyanato-2,2′,3,3′,5,5′,6,6′-octamethyldicyclohexylmethane, ω,ω′-diisocyanato-1,4-diethylbenzene, 1,4-diisocyanatomethyl-2,3,5,6-tetramethylbenzene, 2-methyl-1,5-diisocyanatopentane (MPDI), 2-ethyl-1,4-diisocyanatobutane, 1,10-decane diisocyanate, 1,5-hexane diisocyanate, 1,3-methylcyclohexane diisocyanate, 1,4-methylcyclohexane diisocyanate, 2,5(2,6)-bis(isocyanatomethyl)bicyclo[2.2.1]heptane (NBDI), and any mixtures of these compounds. It is also possible to use polyisocyanates of higher isocyanate functionality. Examples are hexamethylene diisocyanate and isophorone diisocyanate, more particularly the corresponding isocyanurates. It is also possible to use mixtures of polyisocyanates.

[0079] For blocking polyisocyanates, it is preferred to use any desired suitable aliphatic, alicyclic or aromatic alkyl monoalcohols. Examples thereof are aliphatic alcohols such as methyl, ethyl, chloroethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, 3,3,5-trimethylhexyl, decyl and dodecyl alcohols; alicyclic alcohols such as cyclopentanol and cyclohexanol; aromatic alkyl alcohols such as benzyl alcohol and methylbenzyl alcohol. Similarly, suitable diols such as ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol and / or polyols can also be used to block polyisocyanates. Other suitable blocking agents are hydroxylamines such as ethanolamine, oximes such as methyl ethyl ketone oxime, acetone oxime and cyclohexanone oxime, and amines such as dibutylamine and diisopropylamine.

[0080] Tris(alkoxycarbonylamino)-1,3,5-triazines (TACT) are likewise known to the skilled person. The use of tris(alkoxycarbonylamino)-1,3,5-triazines as crosslinkers in coating compositions is known. For example, DE 197 12 940 A1 describes the use of such crosslinkers in basecoat materials. U.S. Pat. No. 5,084,541 describes the preparation of corresponding compounds which can be used as component (c). For the purposes of the present invention, such triazines are covered by the term "blocked polyisocyanates".

[0081] Amino resins (aminoplast resins) are likewise known to the skilled person. The amino resins used are preferably melamine resins, more particularly melamine-formaldehyde resins, which are likewise known to the skilled person. However, amino resins such as melamine-formaldehyde resins are preferably not used as crosslinkers (c). The electrodeposition coating composition of the invention is therefore preferably free of amino resins such as melamine-formaldehyde resins.

[0082] The electrodeposition coating composition of the present invention is preferably used as a one-component (1K) coating composition. Therefore, the electrodeposition coating composition of the present invention preferably does not contain free polyisocyanate.

[0083] Optional component (d)

[0084] The electrodeposition coating composition of the present invention may contain at least one pigment other than the at least one carbon black pigment used as component (b) and / or may contain at least one filler as an optional component (d).

[0085] The term "filler" is known to the skilled person, for example, from DIN 55943 (date: October 2001). A "filler" for the purposes of the present invention is preferably a component which is substantially, preferably completely, insoluble in the application medium (e.g. the electrodeposition coating composition of the present invention) and which serves in particular to increase the volume. A "filler" in the sense of the present invention preferably differs from a "pigment" in its refractive index, the refractive index of the filler being <1.7.

[0086] Any conventional filler known to the skilled person can be used as optional component (d). Examples of suitable fillers are kaolin, dolomite, calcite, chalk, calcium sulfate, barium sulfate, graphite, silicates, such as magnesium silicate, especially the corresponding phyllosilicates, such as hectorite, bentonite, montmorillonite, talc and / or mica, silicon dioxide, especially fumed silica, hydroxides such as aluminum hydroxide or magnesium hydroxide, or organic fillers such as textile fibers, cellulose fibers, polyethylene fibers or polymer powders; for further details, reference is made to Lexikon Lacke und Druckfarben, Georg Thieme Verlag, 1998, pp. 250 et seq., “Fillers”.

[0087] Any conventional pigment known to the technician can be used as optional component (d), as long as it is different from pigment (b). Examples of suitable pigments are inorganic and organic coloring pigments. Examples of suitable inorganic coloring pigments are white pigments, such as titanium dioxide, zinc white, zinc sulfide or zinc lithopone; black pigments, such as carbon black (but preferably not using other carbon black pigments except pigment (b)) of non-pigment (b), iron manganese black or spinel black; color pigments, such as chromium oxide, chromium oxide hydrate green (chromium oxide hydrate green), cobalt green or ultramarine green, cobalt blue, ultramarine blue or manganese blue, ultramarine violet or cobalt violet and manganese violet, red iron oxide, cadmium sulfide selenide, molybdenum chrome red or ultramarine red; brown iron oxide, mixed brown, spinel phase and corundum phase or chrome orange; or yellow iron oxide, nickel titanium yellow, chrome titanium yellow, cadmium sulfide, cadmium sulfide zinc, chrome yellow or bismuth vanadate. Other inorganic coloring pigments are silicon dioxide, aluminum oxide, hydrated aluminum oxide, especially boehmite, titanium dioxide, zirconium oxide, cerium oxide and mixtures thereof. The example of suitable organic coloring pigment is monoazo pigment, disazo pigment, anthraquinone pigment, benzimidazole pigment, quinacridone pigment, quinophthalone pigment, diketopyrrolopyrrole pigment, dioxazine pigment, indanthrone pigment, isoindoline pigment, isoindolinone pigment, azomethine pigment, thioindigo pigment, metal complex pigment, perinone pigment, perylene pigment, phthalocyanine pigment or nigrosine.

[0088] Component (d) - similar to component (b) - is preferably incorporated into the electrodeposition coating composition in the form of a pigment paste and / or filler paste. It is possible and preferred that a pigment paste can be used which contains both pigment (b) and one or more other pigments and / or fillers as component (d) each different from pigment (b). Such a paste generally contains at least one polymer used as a grinding resin. Therefore, preferably, at least one such polymer used as a grinding resin is included in the electrodeposition coating composition of the present invention. The at least one polymer (a) used as a binder in the electrodeposition coating composition is likely to also serve as a grinding resin in the pigment paste. The grinding resin in question is preferably an epoxy-amine adduct that may correspond to component (a) and / or can be included under the definition of component (a) as outlined above. The polymer used as a grinding resin preferably has structural units that interact with the surface of the pigment. The grinding resin therefore preferably has the effect of an emulsifier. In many cases, a quaternary ammonium compound is incorporated to improve the properties of the grinding resin. The pigment is preferably ground together with the grinding resin to form a pigment paste. In order to produce a finished electrodeposition coating composition, this paste is mixed with the remaining ingredients. The use of pigment pastes advantageously allows greater flexibility in electrodeposition coatings, since the pigment and binder of the electrodeposition coating composition can be easily adapted to the requirements of the practice at any time via the amount of pigment paste.

[0089] Further optional components

[0090] The electrodeposition coating composition of the present invention may contain at least one catalyst, such as a metal-containing catalyst as component (e). However, in a preferred embodiment, the electrodeposition coating composition of the present invention does not include a catalyst, such as a metal-containing catalyst. The catalyst optionally included is preferably a bismuth-containing catalyst. It is particularly preferred that a bismuth-containing catalyst be used, such as bismuth (III) oxide, basic bismuth (III) oxide, bismuth (III) hydroxide, bismuth (III) carbonate, bismuth (III) nitrate, bismuth (III) oxynitrate (basic bismuth (III) nitrate), bismuth (III) salicylate and / or bismuth (III) subsalicylate (bismuth (III) subsalicylate) and mixtures thereof. Particularly preferred are water-insoluble bismuth-containing catalysts. More particularly preferred is bismuth (III) subnitrate. The electrodeposition coating composition of the present invention preferably contains at least one bismuth-containing catalyst in an amount such that the bismuth (III) content, calculated as bismuth metal and based on the total weight of the electrodeposition coating of the present invention, is 10 ppm to 20 000 ppm. The amount of bismuth, calculated as metal, can be determined by means of inductively coupled plasma-atomic emission spectroscopy (ICP-OES) in accordance with DIN EN ISO 11885 (date: September 2009).

[0091] Depending on the desired application, the electrodeposition coating composition of the present invention may contain one or more commonly used additional additives as one or more optional components (f). Component (f) is different from any of components (a) to (e). These additives are preferably selected from wetting agents, emulsifiers, dispersants, surface active compounds such as surfactants, flow control aids, solubilizers, defoamers, rheological aids, antioxidants, stabilizers, preferably heat stabilizers, processing stabilizers and ultraviolet and / or light stabilizers, tougheners, plasticizers and mixtures of the above additives. The additive content can vary widely depending on the intended use. Based on the total weight of the electrodeposition coating composition of the present invention, the additive content is preferably in the range of 0.1 to 20.0% by weight, more preferably 0.1 to 15.0% by weight, very preferably 0.1 to 10.0% by weight, especially preferably 0.1 to 5.0% by weight, and more particularly in the range of 0.1 to 2.5% by weight.

[0092] Electrocoating method

[0093] Another subject of the present invention is a method for at least partially coating an electrically conductive substrate by cathodic electrodeposition coating, comprising at least steps (1) to (5), namely

[0094] (1) at least partially immersing a conductive substrate into an electrodeposition coating bath comprising the electrodeposition coating composition according to any one of claims 1 to 9,

[0095] (2) connecting the substrate as a cathode,

[0096] (3) depositing a coating film obtained from the electrodeposition coating composition on a substrate using direct current,

[0097] (4) removing the coated substrate from the electrodeposition coating bath, and

[0098] (5) Baking the coating film deposited on the substrate.

[0099] All preferred embodiments described above with respect to the electrodeposition coating composition of the present invention are also preferred embodiments related to the above-mentioned method of the present invention for at least partially coating a conductive substrate by a cathodic electrodeposition coating process using such an electrodeposition coating composition.

[0100] The method of the invention is particularly suitable for electrodeposition coating of automobile bodies or parts thereof, including respective metal substrates. Thus, preferably the substrate is an automobile body or parts thereof.

[0101] All electrically conductive substrates which are conventionally used and known to the skilled person are suitable as electrically conductive substrates for use according to the invention. The electrically conductive substrate for use according to the invention is preferably a metal substrate, more preferably selected from steel, preferably steel selected from bare steel, cold rolled steel (CRS), hot rolled steel, galvanized steel such as hot dip galvanized steel (HDG), alloy galvanized steel (e.g. Galvalume, Galvannealed or Galfan) and aluminized steel, aluminum and magnesium; and Zn / Mg alloys and Zn / Ni alloys. Particularly suitable substrates are parts of a vehicle body for production or the entire vehicle body.

[0102] Before the respective conductive substrate is used in step (1) of the process according to the invention, it is preferably cleaned and / or degreased.

[0103] The conductive substrate used according to the invention is preferably a pretreated substrate, for example with at least one metal phosphate, such as zinc phosphate. This pretreatment by phosphating, which is usually carried out after the substrate has been cleaned and before the electrodeposition coating of the substrate in step (1), is a customary pretreatment step in particular in the automotive industry. However, pretreatment methods other than phosphating are also possible, for example thin-film pretreatment based on zirconium oxide.

[0104] In the implementation of steps (1), (2) and (3) of the method of the present invention, the electrodeposition coating composition of the present invention is cathode deposited on the substrate area immersed in the bath in step (1). In step (2), the substrate is connected as a cathode and a voltage is applied between the substrate and at least one counter electrode located in the deposition bath and separated from it by an anion exchange membrane that is permeable to anions, for example. The counter electrode acts as an anode accordingly. When the current passes between the anode and the cathode, a firmly attached coating film is deposited on the cathode, i.e., on the immersed part of the substrate. The voltage applied here is preferably in the range of 50 to 500 volts. When steps (1), (2) and (3) of the method of the present invention are implemented, the electrodeposition coating bath preferably has a bath temperature of 20 to 45° C.

[0105] The baking temperature in step (5) is preferably in the range of 120 to 210°C, more preferably 120 to 205°C, very preferably 120 to 200°C, more particularly 125 to 195°C or 125°C to 190°C, most preferably 130 to 185°C or 140 to 180°C.

[0106] After step (5) of the method of the present invention has been carried out, one or more additional coatings may be applied to the baked coating film obtained after step (5). For example, a primer and / or filler may be applied, followed by a basecoat and a clearcoat.

[0107] Therefore, the method of the present invention preferably comprises at least one additional step (6), namely

[0108] (6) at least one additional coating composition different from the composition applied in step (1) is at least partially applied to the baked coating film obtained after step (5).

[0109] Base

[0110] Another subject of the invention is an electrically conductive substrate at least partially coated with a baked electrodeposition coating according to the invention. The baked coating corresponds to the baked coating film obtained after step (5) of the process according to the invention.

[0111] All preferred embodiments described above with respect to the electrodeposition coating composition of the invention and the process of the invention are also preferred embodiments in connection with the above-mentioned at least partially coated substrate of the invention.

[0112] use

[0113] Another subject of the present invention is the use of at least one carbon black pigment (b) as defined above for improving the corrosion protection of conductive substrates bearing baked coating films obtained from cathodically depositable aqueous electrodeposition coating compositions which - in addition to the at least one carbon black pigment (b) - also comprise at least one cathodically depositable polymer (a) and / or for improving the uniformity of film formation and / or for reducing mapping of coating films obtained from cathodically depositable aqueous electrodeposition coating compositions which - in addition to the at least one carbon black pigment (b) - also comprise at least one cathodically depositable polymer (a) .

[0114] Preferably, the cathodically depositable aqueous electrodeposition coating composition is the cathodically depositable aqueous electrodeposition coating composition of the present invention.

[0115] All preferred embodiments described above with respect to the electrodeposition coating composition of the invention, the process of the invention and the at least partially coated substrate of the invention are also preferred embodiments in connection with the above-mentioned use.

[0116] method

[0117] 1. Determination of non-volatile matter

[0118] The non-volatile matter (solids or solid content) is determined according to DIN EN ISO 3251 (date: June 2019). This involves weighing 1 gram of sample into a pre-dried aluminum pan and drying the pan with the sample in a drying cabinet at 180° C. for 30 minutes, cooling in a desiccator and then weighing again. The residue calculated relative to the total amount of sample used corresponds to the non-volatile matter.

[0119] 2. Analysis of Water-Soluble Components of Carbon Black Pigments Using ICP-OES

[0120] Inductively coupled plasma-atomic emission spectroscopy (ICP-OES) according to DIN EN ISO 11885 (date: September 2009) is used to study the water-soluble components of carbon black pigments (such as the carbon black pigment (b) used according to the present invention) and to determine the amount of unwanted elements / ions present therein, such as Na, K.Cl, S and Si. The sample for ICP-OES measurement is as follows and prepared according to DIN 19529 (date: December 2015): 10 grams of carbon black pigment are weighed into a 250 ml PE spiral container and mixed with 80 ml of deionized water. The conductivity of the deionized water is determined in advance. Subsequently, the sample is eluted at 22 rpm using an overhead shaker for 24 hours. 20 ml of the resulting suspension is centrifuged and the aqueous component is purified through a 0.45 μm glass material (frit). The resulting aqueous component is then analyzed by ICP-OES. The SpectroBlue device of Spectro Company is used for ICP-OES measurement.

[0121] 3. Number-based median primary particle size of carbon black pigment

[0122] The number base median primary particle size and the average primary particle size, and the minimum and maximum particle sizes were determined by transmission electron microscopy (TEM). The microscope and device Tecnai G 20 of FEI company were used for TEM measurement. The bright field image mode at 200kV was used for TEM measurement. The magnification of the microscope was calibrated according to ISO 29301:2010. The magnification was selected in a way that the smallest particle observed was imaged on at least 10 pixels. The sample for TEM measurement was prepared as follows: a carbon black pigment (e.g., carbon black pigment (b) used according to the present invention) of a spoon tip (spatulatip) was placed on a first microscope slide, and then a drop of deionized water was added. With the help of a second microscope slide, the resulting mixture was rubbed. Then one slide was removed and the resulting rubbed film was transferred to a sample carrier. The sample carrier was a 20nm thick carbon foil on a 3mm copper mesh. The sample was then analyzed by TEM. The recorded TEM images were automatically evaluated. The ImageJ-PluginParticleSizer software developed within the framework of NanoDefine was used for evaluation.

[0123] 4. VDA climate change test (DIN EN ISO 11997-1:2018-01)

[0124] This climate change test is used to determine the corrosion resistance of a coating on a substrate. The climate change test is carried out in 5 or 10 so-called cycles.

[0125] If the coating of the sample to be tested is scored to the substrate with a knife cut before the climate change test, the sample can be tested for the extent of under-film corrosion according to DIN EN ISO 4628-8 (03-2013), because the substrate corrodes along the score line during the climate change test. As the corrosion progresses, the coating is more or less penetrated during the test. The degree of undermining in [mm] is a measure of the corrosion resistance of the coating.

[0126] 5. Salt spray test

[0127] The corrosion resistance of the coatings was determined by a salt spray test. The coated substrates under investigation were subjected to a salt spray test according to DIN EN ISO 9227 NSS (date: September 2012). The samples under investigation were placed in a chamber in which a mist was generated at a temperature of 35° C. - continuously over a duration of 504 hours or 1008 hours - from a 5% strength sodium chloride solution with a controlled pH of 6.5 to 7.2. This mist was deposited on the sample under investigation and covered it with a film of corrosive salt water.

[0128] If the coating on the specimen under investigation is scratched to the substrate with a blade incision before the salt spray test according to DIN EN ISO 9227 NSS, the extent of corrosive undermining of the specimen can be investigated according to DIN EN ISO 4628-8 (03-2013), because the substrate corrodes along the scratch line during the salt spray test according to DIN EN ISO 9227 NSS. Due to the progressive corrosion process, the coating is undermined to a greater or lesser extent during the test. The extent of undermining in [mm] is a measure of the corrosion resistance of the coating.

[0129] 7. Film formation and Uneven film formation (mapping)

[0130] The film build is determined according to DIN EN ISO 2178:2016-11. This method is also used to determine differences in film build (mapping).

[0131] 8. Surface roughness

[0132] Surface roughness is determined according to DIN EN 10049:2014-03. Example

[0133] The following examples further illustrate the present invention but should not be construed as limiting the scope thereof.

[0134] 1. Preparation of pigment slurry

[0135] 1.1 Pigment paste P1 used according to the invention

[0136] The following ingredients listed in Table 1a below were mixed with one another in this order in a dissolver. This was then ground using a standard mill to obtain the pigment slurry P1 used according to the invention.

[0137] Table 1a: Composition of pigment paste P1

[0138] Element Amount [wt.-%] Grinding resin 41.0 Deionized water 8.1 additive 0.5 Carbon Black Pigment CB1 0.8 catalyst 4.0 White pigment 21.0 filler 24.6

[0139] As is evident from Table 1c depicted below in item 1.3, CB1 is the pigment CB1 used according to the invention. An epoxy-amine adduct has been used as grinding resin. All additives and other ingredients present in P1 are commercial products. Pigment paste P1 has a solids content of 66.6% by weight.

[0140] 1.2 Comparison of pigment pastes P2 to P4

[0141] The pigment pastes used for comparison were prepared in the same manner as described in item 1.1, except that instead of the pigment CB1 used according to the invention, the pigment CB2 was used in P2, CB3 in P3 and CB4 in P4.

[0142] The compositions of pigment pastes P2, P3 and P4 are summarized in Table 1b.

[0143] Table 1b: Composition of pigment pastes P2, P3 and P4

[0144]

[0145]

[0146] As is apparent from Table 1c depicted below in item 1.3, CB2, CB3 and CB4 are each carbon black pigments which are not used according to the invention. Epoxy-amine adducts have been used as grinding resins. All additives and other ingredients present in P2 to P4 are commercial products. Except for the carbon black pigment, the same ingredients as in the case of pigment paste P1 are used. Pigment paste P2 has a solid content of 66.3% by weight. Pigment paste P3 has a solid content of 66.0% by weight. Pigment paste P4 has a solid content of 67.3% by weight.

[0147] 1.3 As is apparent from Table 1c depicted below, CB1 is a pigment CB1 used according to the invention, while CB2 to CB3 are lamp black pigments not used according to the invention, since they exhibit a number-based median primary particle size of less than 50 nm. CB4 is also a carbon black pigment not used according to the invention, since it is a furnace black pigment (Cabot Corporation). 120) and additionally having a number basis median primary particle size of less than 50 nm.

[0148] Table 1c: Number basis median primary particle size

[0149]

[0150] 1.4 Further properties of the pigments CB1 to CB4 are shown in Tables 1d and 1e.

[0151] Table 1d: Further particle size measurement results

[0152]

[0153]

[0154] Table 1e: Analysis of water-soluble components of CB1 to CB4 by using ICP-OES

[0155]

[0156] “-“=Not detected

[0157] 2. Preparation of electrodeposition coating composition

[0158] 2.1 Preparation of the water-based coating composition I1 of the present invention

[0159] The following components listed in the following Table 2a were mixed with each other in this order, and the electrodeposition coating material I1 of the present invention was obtained.

[0160] Table 2a: Composition of electrodeposition coating I1

[0161] Element Amount [parts by weight] Water-based binder and crosslinker dispersions 2 668 Deionized water 2 451 Pigment paste P1 380

[0162] Aqueous binder and crosslinker dispersions are commercial products available from BASF Coatings GmbH, Germany ( 800) having a solids content of 38% by weight and containing an epoxy-amine adduct and a blocked polyisocyanate. The epoxy-amine adduct is different from the epoxy-amine adduct used as grinding resin for preparing pigment paste P1.

[0163] 2.2 Preparation of comparative aqueous coating compositions C2 to C4

[0164] A comparative aqueous coating composition was prepared in the same manner as described in item 2.1, except that instead of the pigment paste P1 used according to the invention, pigment pastes P2, P3 and P4 were used.

[0165] The compositions of coating compositions C2 to C4 are summarized in Table 2b.

[0166] Table 2b: Composition of electrodeposition coatings C2, C3 and C4

[0167]

[0168] Aqueous binder and crosslinker dispersions are commercial products available from BASF Coatings GmbH, Germany ( 800) having a solids content of 38% by weight and containing an epoxy-amine adduct and a blocked polyisocyanate. The epoxy-amine adduct is different from the epoxy-amine adduct used as grinding resin for preparing pigment pastes P2 to P4.

[0169] 3. Electrodeposition coating of substrates

[0170] Coating films obtained from electrodeposition coating compositions I1 and C2 to C4 were deposited on cathodically connected test panels at a deposition voltage of 200-380 V and a coating bath temperature of 28-36° C. within 2 minutes and thereafter baked at a substrate temperature of 150 to 190° C. for 15 minutes.

[0171] As test panels, different substrates were used, namely substrate S1 (bare steel) and S2 (with phosphatizing composition) ( GB26S 6800 OC) pre-treated steel substrate), S3 (with phosphating composition ( GB26S 6800 OG) pre-treated galvanized steel substrate) and S4 (pre-treated with thin film method ( 9831 W OC) pre-treated bare steel substrate).

[0172] In the case of phosphatized substrates S2 and S3, a deposition voltage of 220-260 V and a coating bath temperature of 32° C. were used. Baking was performed in an oven at an oven temperature of 175° C. for 25 minutes. In the case of substrates S1 and S4, a deposition voltage of 180-240 V and a coating bath temperature of 32° C. were used. Baking was performed in an oven at an oven temperature of 175° C. for 25 minutes.

[0173] 4. Study of the properties of coated substrates

[0174] 4.1 Film build

[0175] The film formation of coated substrates S1, S2 and S3 was measured.

[0176] The film formation was determined according to DIN EN ISO 2178:2016-11 by measuring the dry layer thickness of the electrodeposited coatings obtained on the various substrates. The results are summarized in Table 4a.

[0177] Table 4a: Film Formation

[0178]

[0179] "-" = Not determined

[0180] 4.2 Uneven film formation (Mapping)

[0181] In different experimental runs, the mapping observed for the coated substrates S1 and S3 (difference in film build (Δ)) was investigated. The results are summarized in Table 4b. For each composition I1, C2, C3 and C4, the same and specific application conditions on the substrates S1 and S3 were selected to be adjusted to achieve a film build of about 20 μm on S3, so as to be able to make a direct comparison with regard to the occurrence of mapping. The application on each substrate S1 and S3 was carried out successively.

[0182] Table 4b: Difference in film formation (Δ)

[0183]

[0184] 4.3 Corrosion protection (salt spray test)

[0185] The coated substrates S1 (504h) and S4 (1008h) were subjected to a salt spray test (NSS). The results are summarized in Table 4c.

[0186] Table 4c: Undercut after NSS

[0187] Example / Comparative Example Bottom corrosion after 504 or 1008 h NSS [mm] I1 on S1 (the present invention) 1.2 I1 on S4 (invention) 0.7 C2 on S1 (comparison) 2.3 C2 on S4 (comparison) - C3 on S1 (comparison) 2.6 C3 on S4 (comparison) - C4 on S1 (comparison) 3.2 C4 on S4 (comparison) 1.2

[0188] "-" = Not determined

[0189] 4.4 Corrosion protection (VDA)

[0190] The coated substrates S2 (10 cycles) and S4 (10 cycles) were subjected to a VDA test (VDA). The results are summarized in Table 4d.

[0191] Table 4d: Undercut after VDA

[0192]

[0193]

[0194] "-" = Not determined

Claims

1. A cathodic-depositable aqueous electrodeposition coating composition comprising (a) at least one cathodically depositable polymer and (b) at least one carbon black pigment, Wherein the at least one carbon black pigment is a lamp black pigment having a number-based median primary particle size of at least 50 nm and at most 200 nm.

2. The coating composition according to claim 1, characterized in that The at least one carbon black pigment has a number-based median primary particle size of at least 75 nm and at most 150 nm.

3. The coating composition according to claim 1, characterized in that The at least one carbon black pigment has an average primary particle size of at least 50 nm and at most 200 nm.

4. The coating composition according to claim 2, characterized in that The at least one carbon black pigment has an average primary particle size of at least 50 nm and at most 200 nm.

5. The coating composition according to claim 1, characterized in that The at least one carbon black pigment has an average primary particle size of at least 75 nm and at most 150 nm.

6. The coating composition according to claim 2, characterized in that The at least one carbon black pigment has an average primary particle size of at least 75 nm and at most 150 nm.

7. The coating composition according to any one of claims 1 to 6, characterized in that The at least one carbon black pigment has a primary particle size in the range of 5 nm to 600 nm.

8. The coating composition according to any one of claims 1 to 6, characterized in that The at least one carbon black pigment contains not more than 50 ppm of sulfur in the water-soluble fraction obtained therefrom, as measured by ICP-OES in accordance with DIN EN ISO 11885:2009-09.

9. The coating composition according to claim 7, characterized in that The at least one carbon black pigment contains not more than 50 ppm of sulfur in the water-soluble fraction obtained therefrom, as measured by ICP-OES in accordance with DIN EN ISO 11885:2009-09.

10. A coating composition according to any one of claims 1 to 6 and 9, characterized in that It is obtained by mixing a pigment slurry comprising at least said at least one carbon black pigment with a mixture comprising at least water and said cathodically depositable polymer.

11. The coating composition according to claim 8, characterized in that It is obtained by mixing a pigment slurry comprising at least said at least one carbon black pigment with a mixture comprising at least water and said cathodically depositable polymer.

12. A coating composition according to any one of claims 1 to 6, 9, 11, characterized in that The at least one carbon black pigment is the only carbon black pigment present in the electrodeposition coating composition.

13. The coating composition according to claim 11, characterized in that The at least one carbon black pigment is the only carbon black pigment present in the electrodeposition coating composition.

14. A coating composition according to any one of claims 1 to 6, 9, 11, 13, characterized in that The at least one carbon black pigment is present in the electrodeposition coating composition in an amount of 0.005 to 4.0 wt % based on the total weight of the electrodeposition coating composition and / or in an amount of 0.050 to 5.0 wt % based on the total solid content of the electrodeposition coating composition.

15. The coating composition according to claim 12, characterized in that The at least one carbon black pigment is present in the electrodeposition coating composition in an amount of 0.005 to 4.0 wt % based on the total weight of the electrodeposition coating composition and / or in an amount of 0.050 to 5.0 wt % based on the total solid content of the electrodeposition coating composition.

16. A coating composition according to any one of claims 1 to 6, 9, 11, 13, 15, characterized in that At least one epoxy-amine adduct is present as the at least one cathodically depositable polymer.

17. The coating composition according to claim 14, characterized in that At least one epoxy-amine adduct is present as the at least one cathodically depositable polymer.

18. A coating composition according to any one of claims 1 to 6, 9, 11, 13, 15, 17, characterized in that At least one epoxy-amine adduct is present as at least one cathodically depositable polymer, which is the reaction product of at least one epoxy resin based on bisphenol A with at least one primary and / or secondary amine and / or salt thereof and / or at least one tertiary amine salt.

19. The coating composition according to claim 16, characterized in that At least one epoxy-amine adduct is present as at least one cathodically depositable polymer, which is the reaction product of at least one epoxy resin based on bisphenol A with at least one primary and / or secondary amine and / or salt thereof and / or at least one tertiary amine salt.

20. A coating composition according to any one of claims 1 to 6, 9, 11, 13, 15, 17, 19, characterized in that At least one crosslinking agent is present in the electrodeposition coating composition as component (c) and is selected from blocked polyisocyanates, free polyisocyanates, amino resins and mixtures thereof.

21. The coating composition according to claim 18, characterized in that At least one crosslinking agent is present in the electrodeposition coating composition as component (c) and is selected from blocked polyisocyanates, free polyisocyanates, amino resins and mixtures thereof.

22. A method for at least partially coating a conductive substrate by cathodic electrodeposition coating, comprising at least steps (1) to (5), namely (1) at least partially immersing a conductive substrate into an electrodeposition coating bath containing the electrodeposition coating composition according to any one of claims 1 to 21, (2) connecting the substrate as a cathode, (3) depositing a coating film obtained from the electrodeposition coating composition on a substrate using direct current, (4) removing the coated substrate from the electrodeposition coating bath, and (5) Baking the coating film deposited on the substrate.

23. The method according to claim 22, characterized in that comprises at least one additional step (6), namely (6) at least one additional coating composition different from the composition applied in step (1) is at least partially applied to the baked coating film obtained after step (5).

24. An electrically conductive substrate coated with the electrodeposition coating composition according to any one of claims 1 to 21 in at least partially baked form and / or obtained by the process according to claim 22 or 23.

25. Use of at least one carbon black pigment as defined in any one of claims 1 to 15 for improving the corrosion protection of conductive substrates with baked coating films obtained from a cathodically depositable aqueous electrodeposition coating composition comprising, in addition to the at least one carbon black pigment, at least one cathodically depositable polymer and / or for improving the uniformity of film formation and / or for reducing film formation unevenness of coating films obtained from a cathodically depositable aqueous electrodeposition coating composition comprising, in addition to the at least one carbon black pigment, at least one cathodically depositable polymer.

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